vendex and Fractures--Bone

Operative treatment for middle-third clavicle fractures has been increasing as recent data has demonstrated growing patient dissatisfaction and functional deficits after non-operative management. A controlled biomechanical comparison of the characteristics of locked intramedullary (IM) fixation versus superior pre-contoured plating for fracture repair and hardware removal is warranted. Therefore, the purpose of the present study was to investigate potential differences between these devices in a biomechanical model.. Thirty fourth-generation composite clavicles were randomized to one of five groups with 6 specimens each and tested in a random order. The groups tested were intact, repair with plate, repair with IM device, plate removal, and IM device removal. The lateral end of the clavicles was loaded to failure at a rate of 60 mm/min in a cantilever bending setup. Failure mechanism, energy (J), and torque (Nm) at the site of failure were recorded.. Failure torque of the intact clavicle (mean ± standard deviation) was 36.5 ± 7.3 Nm. Failure torques of the IM repair (21.5 ± 9.0 Nm) and plate repair (18.2 ± 1.6 Nm) were not significantly different (n.s.) but were significantly less than the intact group (P < 0.05). Failure torque following IM device removal (30.2 ± 6.5 Nm) was significantly greater than plate removal (12.9 ± 2.0 Nm) (P < 0.05). No significant differences were observed between the intact and IM device removal groups (n.s.).. The results of the current study demonstrate that IM and plate devices provide similar repair strength for middle-third clavicle fractures. However, testing of the hardware removal groups found the IM device removal group to be significantly stronger than the plate removal group.

Topics: Biomechanical Phenomena; Bone Plates; Bone Screws; Clavicle; Device Removal; Fracture Fixation, Internal; Fracture Fixation, Intramedullary; Fractures, Bone; Humans; Internal Fixators; Torque

 The aim of this study was to determine the effect of a unicortical defect at either the mid-diaphysis (MD) or distal metaphysis (DM) on the torsional properties of tibiae in an.  Thirty-eight tibiae from 19 skeletally mature female New Zealand White rabbits were assigned to one of three groups; Group 1: intact, Group 2: MD defect and Group 3: DM defect. Defects were created using a 1.6 mm Ellis pin. Pure torsion was applied to each sample and peak torque and angular displacement recorded..  All tibiae fractured in a spiral configuration. Fracture lines involved the defect in 33% of the MD samples and 0% of the DM samples. No differences were detected for peak torque and stiffness between groups. However, energy (mean ± standard deviation) was significantly reduced (.  Defects placed in the MD significantly reduced energy and angle in comparison to intact samples. No significant difference in peak torque or stiffness was observed between groups. If canine tibiae were similarly affected, our findings suggest jig pin placement in the DM to have a lesser effect on the torsional properties of the tibiae.

Topics: Animals; Biomechanical Phenomena; Diaphyses; Dog Diseases; Dogs; Female; Fractures, Bone; Osteotomy; Rabbits; Tibia; Torque

The long-term performance of the quadriceps femoris muscle and physical function following surgical repair of a lower extremity fracture remains largely undefined. The purpose of this study was to investigate between-limb differences in quadriceps performance 12 months after surgical fixation of a lower extremity fracture. It was hypothesized that the injured limb would be significantly weaker, have a lower rate of torque development (RTD), and that there would be a reduced step-down performance compared to the uninjured limb 12 months after surgery. Additionally, this study sought to identify demographic, surgical, and psychological factors associated with poor quadriceps function 12 months after surgery.. Quadriceps performance was measured bilaterally in 95 participants (49 female), aged 42 (SD = 14.5) years, 12 months after surgical fixation of a lower extremity fracture. Isometric quadriceps strength and RTD were quantified using isometric dynamometry, and a timed step-down test was used to evaluate quadriceps performance. Independent predictor variables from the time of surgery were extracted from participants' medical records. Kinesiophobia was screened at the time of testing. Wilcoxon signed-rank tests and linear regression analyses were used to assess between-limb differences in quadriceps performance and to determine factors associated with quadriceps performance 12 months after surgery.. Significant between-limb differences in each measure of quadriceps performance were identified (peak torque involved: 1.37 [0.71] Nm × kg-1; uninvolved: 1.87 [0.74] Nm × kg-1; RTD involved: 4.16 [2.75] Nm × kg-1 × s-1; uninvolved: 6.10 [3.02] Nm × kg-1 × × -1; and single-leg step-downs involved: 12.6 [5.0]; uninvolved: 21.7 [14.8]). Female biological sex, external fixation, and kinesiophobia at 12 months were associated with reduced after-surgery quadriceps performance outcomes.. Quadriceps performance is impaired 12 months after surgical repair of a lower extremity fracture, particularly in female participants, in cases requiring external fixation, and in those with higher kinesiophobia 12 months after surgery.. Because long-term quadriceps weakness negatively impacts functional mobility, targeted strengthening should be emphasized after surgical repair of lower extremity fracture.

Topics: Anterior Cruciate Ligament Injuries; Anterior Cruciate Ligament Reconstruction; Female; Fractures, Bone; Humans; Lower Extremity; Muscle Strength; Quadriceps Muscle; Torque

Recently, biodegradable implants made from magnesium (Mg) alloys have been developed to obviate the need for later implant removal. Mg-based cannulated compression screws (CCS) are ideal for intramedullary screw (IMS) fixation of metacarpal fractures. The present study aimed at investigating the torque acting on Mg-based CCS at failure and at intramedullary metacarpal insertion. The devices were CE certified Magnezix 2.7 and 3.2 mm CCSs (Syntellix®, Hannover, Germany). Torque at failure was measured in a synthetic bone model using a standardized polyurethane foam block. In a second assessment, insertional torque was measured in ten cadaveric metacarpal bones. Mean torque at failure for the 2.7 mm and 3.2 mm CCSs was 42.8 Ncm (±1.9 Ncm) and 63.0 Ncm (±2.2 Ncm), respectively. In the human cadaver model, the torque distribution curve at metacarpal insertion showed three peaks. The highest reached 53.6% of the lowest torque at failure measured in the synthetic bone model for the 3.2 CCS (31.4 vs. 58.6 Ncm). The mean difference between peak torque at metacarpal insertion and torque at failure was 38.3 Ncm (99% CI [33.6, 43.0 Ncm], p < 0.0001). In terms of torque load, Mg-based CCSs are suitable for IMS fixation of metacarpal fractures. Biodegradable implants may represent an important improvement of this treatment method; confirmation by in-vivo studies is needed.

Topics: Biomechanical Phenomena; Bone Screws; Fracture Fixation, Internal; Fractures, Bone; Humans; Magnesium; Metacarpal Bones; Torque

To determine the influence of screw head diameter on equine condylar fracture fixation with 5.5 mm cortical screws.. Ex vivo, biomechanical study, blinded, matched-pair design.. Fifteen pairs of equine third metacarpal (MC3) bones.. Lateral condylar fractures were simulated by parasagittal osteotomies and repaired pairwise by 2 × 5.5 mm cortical screws of 8 mm (standard) or 10 mm (modified) head diameter. Interfragmentary compression at maximum screw insertion torque was measured. The instrumented specimens were pairwise stratified for biomechanical testing under the following modalities (n = 5): (1) screw insertion torque to failure, (2) quasi-static axial load to failure, and (3) cyclic axial load to 2 mm displacement followed by failure. Tests (1) and (2) were analyzed for yield, maximum, and failure torque/angle and load/displacement, respectively. Number of cycles to 2 mm displacement and failure was assessed from test (3).. Maximum insertion torque was greater, and failure angle smaller, when constructs repaired with modified screws were tested (8.1 ± 0.5 vs. 7.4 ± 0.5 Nm; P = .0047 and 550 ± 104 vs. 1130 ± 230; P = .008). Axial yield (7118 ± 707 vs. 5740 ± 2267 N; P = .043) and failure load (12 347 ± 3359 vs. 8695 ± 2277 N; P = .043) were greater for specimens repaired with modified screws. No difference was detected between constructs in the number of cycles to 2 mm displacement.. Condylar MC3 osteotomies repaired with modified 5.5 mm cortical screws sustained greater maximal hand torque insertion, smaller insertion failure angle and 1.4 fold greater quasi-static failure forces than constructs repaired with standard 5.5 mm screws.. Use of modified screws with larger heads may improve the fixation of condylar fractures in horses. These results provide evidence to justify clinical evaluation in horses undergoing fracture repair.

Topics: Animals; Biomechanical Phenomena; Bone Screws; Cadaver; Fracture Fixation; Fracture Fixation, Internal; Fractures, Bone; Horse Diseases; Horses; Torque

The etiology of bone refractures after screw removal can be attributed to residual drill hole defects. This biomechanical study compared the torsional strength of bones containing various sized cortical drill defects in a tibia model.. Bicortical drill hole defects of 3 mm, 4 mm, and 5 mm diameters were tested in 26 composite tibias versus intact controls without a drill defect. Each tibia was secured in alignment with the rotational axis of a materials testing system and the proximal end rotated internally at a rate of 1 deg./s until mechanical failure.. All defect test groups were significantly lower (P < 0.01) in torque-to-failure than the intact group (82.80 ± 3.70 Nm). The 4 mm drill hole group was characterized by a significantly lower (P = 0.021) torque-to-failure (51.00 ± 3.27 Nm) when compared to the 3 mm drill hole (59.00 ± 5.48 Nm) group, but not different than the 5 mm hole group (55.71 ± 5.71 Nm). All bones failed through spiral fractures, bones with defects also exhibited posterior butterfly fragments.. All the tested drill hole sizes in this study significantly reduced the torque-to-failure from intact by a range of 28.4% to 38.4%, in agreement with previous similar studies. The 5 mm drill hole represented a 22.7% diameter defect, the 4 mm drill hole a 18.2% diameter defect, and the 3 mm drill hole a 13.6% diameter defect. Clinicians should be cognizant of this diminution of long bone strength after a residual bone defect in their creation and management of patient rehabilitation programs.

Topics: Biomechanical Phenomena; Bone and Bones; Bone Screws; Fractures, Bone; Humans; Tibia; Torque

Pedicle screw fixation is one of the most common procedures used in spinal fusion surgery. The screw loosening is a major concern, which may be caused by broken pedicles. In vitro pullout tests or insertion torque are the main approaches for assessing the stability of the screw; however, direct evidence was lacking for clinical human spines. Here, we aim to provide a model that can predict the pullout strengths of pedicle screws in various pedicle conditions from X-ray images. A weighted embedded bone volume (EBV) model is proposed for pullout strengths prediction by considering the bone heterogeneity and confinement of the screw. We showed that the pullout strength is proportional to the EBV for homogeneous bone and the weighted EBV for layered composite bone. The proposed weighted EBV model is validated with in vitro Sawbones® pullout experiments. The results show that the model has better accuracy than the simple EBV model, with a coefficient of determination of 0.94. The proposed weighted EBV model can help assess the stability of a pedicle screw in a broken pedicle by simply examining 2D X-ray images.

Topics: Biomechanical Phenomena; Fractures, Bone; Humans; Pedicle Screws; Spinal Fusion; Torque; X-Rays

Bone screws are used in orthopaedic procedures to fix implants and stabilise fractures. These procedures require care, as improperly torquing the screws can lead to implant failure or tissue damage, potentially requiring revision surgery or causing further disability. It was proposed that automated torque-limit identification may allow clinical decision support to control the screw torque, and lead to improved patient outcomes. This work extends a previous model of the screw insertion process to model complex thread geometries used for bone screws; consideration was made for the variable material properties and behaviours of bone to allow further tuning in the future. The new model was simulated and compared with the original model. The model was found to be in rough agreement with the earlier model, but was distinct, and could model thread features that the earlier model could not, such as the fillets and curves on the bone screw profile. The new model shows promise in modelling the more advanced thread geometries of bone screws with higher accuracy.Clinical relevance: This work extends a self tapping screw model to support complex thread shapes, as common in bone screws, allowing more accurate modelling of the clinically relevant geometries.

Topics: Bone and Bones; Bone Screws; Fractures, Bone; Humans; Torque

Topics: Animal Welfare; Animals; Biomechanical Phenomena; Cadaver; Cattle; Fractures, Bone; Tail; Torque

Lag screw osteosynthesis in odontoid fractures shows a high rate of pseudarthrosis. Biomechanical properties may play a role with insufficient fragment compression or unnoticed screw stripping. A biomechanical comparison of different constructed lag-screws was carried out and the biomechanical properties determined.. Two identical compression screws with different pilot holes (1.25 and 2.5 mm), a double-threaded screw and one sleeve-nut-screw were tested on artificial bone (Sawbone, densities 10-30pcf). Fragment compression and torque were continuously measured using thin-film force sensors (Flexiforce A201, Tekscan) and torque sensors (PCE-TM 80, PCE GmbH).. The lowest compression reached the double-threaded screw. Compression and sleeve-nut-screw achieved 214-298% and 325-546%, respectively, of the compression force of double-threaded-screw, depending on the test material. The pilot hole optimization led to a significant improvement in compression only in the densest test material. Screw stripping took place significantly later with increasing density of the test material on all screws. In compression screws this was done at a screw rotation of 180-270°, in sleeve nut screw at 270-720° and in double-threaded screws at 300-600° after reaching the maximum compression.. Double-threaded screw is robust against screw stripping, but achieves only low fragment compression. The classic compression screws achieve better compression, but are sensitive to screw stripping. Sleeve-nut screw is superior in compression and as robust as double-threaded screw against screw stripping. Whether the better biomechanical properties lead to a reduction in pseudarthrosis must be proven in clinical trials.

Topics: Biomechanical Phenomena; Bone Screws; Fracture Fixation, Internal; Fractures, Bone; Humans; Mechanical Phenomena; Odontoid Process; Pressure; Torque

We hypothesised that intercarpal K-wire fixation of adjacent carpal bones would reduce torque and lever force within a fractured scaphoid bone.. In eight cadaver wrists, a scaphoid osteotomy was stabilised using a locking nail, which also functioned as a sensor to measure isometric torque and lever forces between the fragments. The wrist was moved through 80% of full range of motion (ROM) to generate torque and force within the scaphoid. Testing was performed with and without loading of the wrist and K-wire stabilisation of the adjacent carpal bones.. Average torque and lever force values were 49.6 ± 25.1 Nmm and 3.5 ± 0.9 N during extension and 41 ± 26.7 Nmm and 8.1 ± 2.8 N during flexion. Torque and lever force did not depend on scaphoid size, individual wrist ROM, or deviations of the sensor versus the anatomic axis. K-wire fixation did not produce significant changes in average torque and lever force values except with wrist radial abduction (P = 0.0485). Other than wrist extension, torque direction was not predictable.. In unstable scaphoid fractures, we suggest securing rotational stability with selected implants for functional postoperative care. Wrist ROM within 20% extension and radial abduction to 50% flexion limit torque and lever force exacerbation between scaphoid fragments.

Topics: Biomechanical Phenomena; Bone Wires; Cadaver; Carpal Bones; Fracture Fixation, Internal; Fractures, Bone; Humans; Osteotomy; Range of Motion, Articular; Scaphoid Bone; Torque; Wrist

A new locking-screw technology, the Variable Fixation Locking Screw (VFLS; Biomech Innovations), was developed with the aim of promoting secondary fracture-healing. The VFLS features a resorbable sleeve that progressively decreases its mechanical properties and mass during the fracture-healing time. In this study, we investigated whether the VFLS can provide rigid as well as progressive dynamic fixation.. The interfragmentary stability provided by the VFLS was tested in a simulated fracture-gap model and compared with that provided by standard locking or by a combination of both technologies under compression and torsional loading. Tests were performed with an intact sleeve (initial condition) and after its chemical dissolution. An optical measurement system was used to characterize interfragmentary movements.. The axial stiffness did not differ significantly among groups in the initial condition. Sleeve resorption significantly decreased construct stiffness. The torsional stiffness of the samples instrumented with the VFLS was lower than that of the control group. The degradation of the sleeve resulted in a significant increase in axial displacement recorded at both the cis and trans cortices. In samples featuring combined technologies, this increase was about 12% to 20% at the trans cortex and about 50% to 60% at the cis cortex. In samples featuring VFLS technology only, this increase was about 20% to 37% at the trans cortex and about 70% to 125% at the cis cortex.. The initial stability offered by the VFLS is equivalent to that of standard locking-screw technology. The resorption of the degradable sleeve leads to effective and reproducible fracture-gap dynamization, progressively varying the way the fracture gap is strained and the magnitude of the strain.. The VFLS provides rigid and progressive dynamic fixation in vitro. Such variable stability might have beneficial effects in terms of triggering and boosting secondary fracture-healing.

Topics: Biomechanical Phenomena; Bone Plates; Bone Screws; Bone Substitutes; Fracture Fixation, Internal; Fracture Healing; Fractures, Bone; Humans; Time Factors; Torque; Torsion, Mechanical

The assessment of dental implant performance is dominated by the concept of mechanical stability. Primary stability is defined as the capacity of a bone-implant structure to bear loads without occurrence of excessive damage and loosening. In order to achieve the highest primary stability, dental implants are inserted into bone using a press-fit procedure. Pre- and postoperative evaluation of primary stability using implantation torque and resonance frequency analysis are valid approaches but do not allow the systematic comparison of different protocols in similar situations. The aim of this research is to develop and validate an explicit, micro-finite element (μFE) methodology to study the effect of different amounts of initial press-fit on implantation torque and initial stiffness of a dental implant. Ten bovine trabecular bone samples were prepared that cover a wide range of bone volume fraction. A dental implant was inserted using two implantation protocols named soft (small initial drilled hole) and dense (increased initial drilled hole). The implantation torque was measured and the stiffness was calculated using an infinitesimal off-axis loading. Finite element simulations of the implant insertion and subsequent loading were performed on micro-computed tomography (μCT) reconstructions of the samples using an explicit solver. Bone was defined as an elasto-plastic material with von Mises yield criteria and hardening. Element deletion was triggered by a threshold in cumulated plastic strains. A sensitivity analysis was performed on friction, hardening and fracture strain to provide a better insight into the effects of these parameters on the results. The implantation torque required for the soft protocol was higher compared to the dense approach in both experiment and simulation due to the higher amount of bone compaction in the first approach. Interestingly, stiffness did not show a significant dependency on the drilling protocol in both experiment and simulation. In conclusion, the explicit microFE methodology developed in this study was able to capture the outcome of two drilling protocols in terms of torque and stiffness and represents a powerful tool to explore the effect of different parameters on primary stability of dental implants.

Topics: Animals; Cancellous Bone; Cattle; Dental Implants; Finite Element Analysis; Fractures, Bone; Stress, Mechanical; Torque; Weight-Bearing; X-Ray Microtomography

Modeling of cortical bone response and failure is critical for the prediction of Crash Induced Injuries (CII) using advanced finite element (FE) Human Body Models (HBM). Although cortical bone is anisotropic and asymmetric in tension and compression, current HBM often utilize simple isotropic, symmetric, elastic-plastic constitutive models. In this study, a 50th percentile male femur FE model was used to quantify the effect of asymmetry and anisotropy in three-point bending and axial torsion. A complete set of cortical bone mechanical properties was identified from a literature review, and the femur model was used to investigate the importance of material asymmetry and anisotropy on the failure load/moment, failure displacement/rotation and fracture pattern. All models were able to predict failure load in bending, since this was dominated by the cortical bone material tensile response. However, only the orthotropic model was able to predict the torsional response and failure moment. Only the orthotropic model predicted the fracture initiation location and fracture pattern in bending, and the fracture initiation location in torsion; however, the anticipated spiral fracture pattern was not predicted by the models for torsional loading. The results demonstrated that asymmetry did not significantly improve the prediction capability, and that orthotropic material model with the identified material properties was able to predict the kinetics and kinematics for both three-point bending and axial torsion. This will help to provide an improved method for modeling hard tissue response and failure in full HBM.

Topics: Anisotropy; Cortical Bone; Femur; Finite Element Analysis; Fractures, Bone; Humans; Materials Testing; Mechanical Phenomena; Models, Biological; Rotation; Torque

Eccentric training is an established training method in competitive sports. It has been used effectively to improve muscle strength during rehabilitation after cruciate ligament reconstruction. However, it is still uncertain whether or not eccentric training contributes to successful rehabilitation after apophysis fractures. A fourteen-year-old soccer player, forward position, presents with an apophysis avulsion located at the right spina iliaca anterior inferior. After completing an early rehabilitation phase and isokinetic concentric strength development, the patient starts an eccentric training programme eight weeks after the injury, including training on an isokinetic dynamometer (Biodex) for four weeks, followed by a four-week eccentric ergometer training (Eccentron). Before and after each eccentric training phase, isokinetic maximum strength tests of the knee extensors and flexors are performed with angular velocities of 60 degrees per second (°/sec.), 180°/sec. and 240°/sec. In response to the eight-week eccentric rehabilitation program, maximum torque increases in all angular velocities in the injured (60°/sec. + 14.4 %; 180°/sec. + 8.8 %; 240°/sec. + 6.3 %) and the uninjured leg (60°/sec. + 15.6 %; 180°/sec. + 1.9 %; 240°/sec. + 8.1 %) between the first and the last test. Furthermore, neuromuscular coordination has improved during the eccentric training sessions. This case study demonstrates that controlled eccentric training in the open and closed kinetic chain increases coordination and strength of the trained muscles and therefore should be regarded as a valuable contribution toward a safe return to sport after apophysis fractures.. Exzentrisches Training ist eine etablierte Krafttrainingsmethode im Leistungssport. Sie wird auch schon erfolgreich zur Kraftverbesserung in der Rehabilitation bei Kreuzbandplastiken eingesetzt. Allerdings ist noch nicht klar, ob exzentrisches Training auch nach Apophysenfrakturen zu einer erfolgreichen Rehabilitation beitragen kann. Ein 14-jähriger Stürmer wird mit einer Apophysenfraktur an der rechten Spina iliaca anterior inferior vorstellig. Nach einer frühen Rehaphase und einem isokinetisch-konzentrischen Kraftaufbau beginnt der Patient acht Wochen nach der Verletzung mit einem vierwöchigen exzentrischen Trainingsprogramm auf einem isokinetischen Dynamometer (Biodex), gefolgt von einem vierwöchigen exzentrischen Ergometertraining (Eccentron). Vor und nach jeder exzentrischen Trainingsphase werden isokinetische Maximalkrafttests der Kniestrecker und -beuger bei Winkelgeschwindigkeiten von 60 Grad pro Sekunde (°/sek), 180°/sek und 240°/sek durchgeführt. Durch das insgesamt achtwöchige exzentrische Rehabilitationsprogramm kann das maximale Drehmoment des Patienten bei allen Winkelgeschwindigkeiten im verletzen (60°/sek + 14,4 %; 180°/sek + 8,8 %; 240°/sek + 6,3 %) aber auch im unverletzten Bein (60°/sek + 15,6 %; 180°/sek + 1,9 %; 240°/sek + 8,1 %) zwischen erster und letzter Testung erhöht werden. Zudem zeigte sich eine Verbesserung der neuromuskulären Koordination während der exzentrischen Trainingseinheiten. Diese Einzelfallstudie zeigt, dass kontrolliertes exzentrisches Training in der offenen und geschlossenen kinetischen Kette sowohl die Koordinations- als auch die Kraftfähigkeit der trainierten Muskulatur verbessert und somit einen wertvollen Beitrag zu einem sicheren Return-to-Sport nach Apophysenfrakturen leisten kann.

Topics: Adolescent; Bone and Bones; Ergometry; Exercise Therapy; Fractures, Bone; Humans; Leg Injuries; Male; Muscle Strength Dynamometer; Pelvic Bones; Soccer; Torque

This biomechanical study compared the torsional strength and stiffness of a locking compression plate with all locking versus nonlocking screws and examined the effect of placing a locking unicortical or nonlocking bicortical screw nearest the fracture gap in a synthetic bone model.. Synthetic bone models simulating a diaphyseal fracture without anatomic reduction were tested using four screw configurations: all bicortical locking (ABL), all bicortical nonlocking (ABN), a hybrid construct with a bicortical nonlocking screw nearest the fracture gap (BN), and a unicortical locking screw placed nearest the fracture gap (UL). Torsional stiffness, rotation and torque at failure were compared via ANOVA and post hoc pairwise comparisons (p < 0.05). ABN and BN had the highest stiffness (p < 0.01) with ABL greater than UL (p < 0.01). Rotation at failure was greatest for ABL (p < 0.01) with UL greater than ABN (p < 0.05). Unicortical locking screws nearest the fracture gap decreased stiffness, without significantly affecting torque or rotation at failure. Construct stiffness was found to exist in a very narrow range of 0.9-1.2 N m/deg with standard deviations of 0.1 N m/deg in all cases. The results of this study support the use of nonlocking screws in a hybrid construct to increase torsional stiffness.

Topics: Biomechanical Phenomena; Bone and Bones; Bone Plates; Bone Screws; Fracture Fixation, Internal; Fractures, Bone; Humans; Materials Testing; Models, Biological; Torque

Radiological features alone do not allow the discrimination between accidental paediatric long bone fractures or those sustained by child abuse. Therefore, there is a clinical need to elucidate the mechanisms behind each fracture to provide a forensic biomechanical tool for the vulnerable child. Four-point bending and torsional loading tests were conducted at more than one strain rate for the first time on immature bone, using a specimen-specific alignment system, to characterise structural behaviour at para-physiological strain rates. The bones behaved linearly to the point of fracture in all cases and transverse, oblique, and spiral fracture patterns were consistently reproduced. The results showed that there was a significant difference in bending stiffness between transverse and oblique fractures in four-point bending. For torsional loading, spiral fractures were produced in all cases with a significant difference in the energy and obliquity to fracture. Multiple or comminuted fractures were seen only in bones that failed at a higher stress or torque for both loading types. This demonstrates the differentiation of fracture patterns at different strain rates for the first time for immature bones, which may be used to match the case history given of a child and the fracture produced.

Topics: Biomechanical Phenomena; Child; Child Abuse; Forensic Medicine; Fractures, Bone; Humans; Stress, Mechanical; Torque

Transforming growth factor beta 1 (TGF-β1) and bone morphogenetic protein-2 (BMP-2) are important regulators of bone repair and regeneration. In this study, we examined whether TGF-β1 and BMP-2 expressions were delayed during bone healing in type 1 diabetes mellitus. Tibial fractures were created in 95 diabetic and 95 control adult male Wistar rats of 10 weeks of age. At 1, 2, 3, 4, and 5 weeks after fracture induction, five rats were sacrificed from each group. The expressions of TGF-β1 and BMP2 in the fractured tibias were measured by immunohistochemistry and quantitative reverse-transcription polymerase chain reaction, weekly for the first 5 weeks post-fracture. Mechanical parameters (bending rigidity, torsional rigidity, destruction torque) of the healing bones were also assessed at 3, 4, and 5 weeks post-fracture, after the rats were sacrificed. The bending rigidity, torsional rigidity and destruction torque of the two groups increased continuously during the healing process. The diabetes group had lower mean values for bending rigidity, torsional rigidity and destruction torque compared with the control group (P<0.05). TGF-β1 and BMP-2 expression were significantly lower (P<0.05) in the control group than in the diabetes group at postoperative weeks 1, 2, and 3. Peak levels of TGF-β1 and BMP-2 expression were delayed by 1 week in the diabetes group compared with the control group. Our results demonstrate that there was a delayed recovery in the biomechanical function of the fractured bones in diabetic rats. This delay may be associated with a delayed expression of the growth factors TGF-β1 and BMP-2.

Topics: Animals; Biomechanical Phenomena; Bone Morphogenetic Protein 2; Bony Callus; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 1; Fracture Healing; Fractures, Bone; Immunohistochemistry; Male; Rats, Wistar; Real-Time Polymerase Chain Reaction; Tibial Fractures; Time Factors; Torque; Transforming Growth Factor beta1

The purpose of this study is to define the function of the pronator quadratus muscle after plating of a distal radius fracture using anterior (volar) approach. Fourteen cases with volar plating after for a distal radius fracture were included in the study. Sixteen healthy volunteers were selected to determine the effect of dominant arm on pronation torque of the forearm for the control group. Biodex System 4 PRO (Biodex Medical Systems Inc., New York) torque meter was used for pronation torque measurement. In healthy volunteer group, there was no statistically significant difference in mean pronation torque values between the dominant arm and nondominant arms. The mean loss of pronator strength was 18.5 % and the mean loss of pronator durability was 12.9 % indicating a pronator insufficiency in the cases operated by a volar approach compared to uninjured forearm. Two patients among the operated group, who had further strengthening exercises beyond their own rehabilitation regimes, had improved pronator torque compared to uninjured forearm. In conclusion, the results of this study indicate that following volar plating of distal radius fractures, there is a significant loss in pronator strength of the forearm. As the two of the patients had improved pronator strength of their operated forearm, further rehabilitation regimes should be considered to prevent pronator weakness following volar plating for distal radius fractures.

Topics: Adult; Bone Plates; Case-Control Studies; Female; Forearm; Fracture Fixation, Internal; Fractures, Bone; Humans; Male; Middle Aged; Muscle Strength; Muscle, Skeletal; Pronation; Radius; Torque

In practice, the surgeon must rely on screw position (insertion depth) and tactile feedback from the screwdriver (insertion torque) to gauge compression. In this study, we identified the relationship between interfragmentary compression and these 2 factors.. The Acutrak Standard, Acutrak Mini, Synthes 3.0, and Herbert-Whipple implants were tested using a polyurethane foam scaphoid model. A specialized testing jig simultaneously measured compression force, insertion torque, and insertion depth at half-screw-turn intervals until failure occurred.. The peak compression occurs at an insertion depth of -3.1 mm, -2.8 mm, 0.9 mm, and 1.5 mm for the Acutrak Mini, Acutrak Standard, Herbert-Whipple, and Synthes screws respectively (insertion depth is positive when the screw is proud above the bone and negative when buried). The compression and insertion torque at a depth of -2 mm were found to be 113 ± 18 N and 0.348 ± 0.052 Nm for the Acutrak Standard, 104 ± 15 N and 0.175 ± 0.008 Nm for the Acutrak Mini, 78 ± 9 N and 0.245 ± 0.006 Nm for the Herbert-Whipple, and 67 ± 2N, 0.233 ± 0.010 Nm for the Synthes headless compression screws.. All 4 screws generated a sizable amount of compression (> 60 N) over a wide range of insertion depths. The compression at the commonly recommended insertion depth of -2 mm was not significantly different between screws; thus, implant selection should not be based on compression profile alone. Conically shaped screws (Acutrak) generated their peak compression when they were fully buried in the foam whereas the shanked screws (Synthes and Herbert-Whipple) reached peak compression before they were fully inserted. Because insertion torque correlated poorly with compression, surgeons should avoid using tactile judgment of torque as a proxy for compression.. Knowledge of the insertion profile may improve our understanding of the implants, provide a better basis for comparing screws, and enable the surgeon to optimize compression.

Topics: Bone Screws; Compressive Strength; Equipment Design; Fracture Fixation, Internal; Fractures, Bone; Humans; Materials Testing; Scaphoid Bone; Torque

Connexin 43 (Cx43) is the most abundant gap junction protein in bone and is required for osteoblastic differentiation and bone homeostasis. During fracture healing, Cx43 is abundantly expressed in osteoblasts and osteocytes, while Cx43 deficiency impairs bone formation and healing. In the present study we selectively deleted Cx43 in the osteoblastic lineage from immature osteoblasts through osteocytes and tested the hypothesis that Cx43 deficiency results in delayed osteoblastic differentiation and impaired restoration of biomechanical properties due to attenuated β-catenin expression relative to wild type littermates. Here we show that Cx43 deficiency results in alterations in the mineralization and remodeling phases of healing. In Cx43 deficient fractures the mineralization phase is marked by delayed expression of osteogenic genes. Additionally, the decrease in the RankL/Opg ratio, osteoclast number and osteoclast size suggest decreased osteoclast bone resorption and remodeling. These changes in healing result in functional deficits as shown by a decrease in ultimate torque at failure. Consistent with these impairments in healing, β-catenin expression is attenuated in Cx43 deficient fractures at 14 and 21 days, while Sclerostin (Sost) expression, a negative regulator of bone formation is increased in Cx43cKO fractures at 21 days, as is GSK-3β, a key component of the β-catenin proteasomal degradation complex. Furthermore, we show that alterations in healing in Cx43 deficient fractures can be rescued by inhibiting GSK-3β activity using Lithium Chloride (LiCl). Treatment of Cx43 deficient mice with LiCl restores both normal bone formation and mechanical properties relative to LiCl treated WT fractures. This study suggests that Cx43 is a potential therapeutic target to enhance fracture healing and identifies a previously unknown role for Cx43 in regulating β-catenin expression and thus bone formation during fracture repair.

Topics: Adaptor Proteins, Signal Transducing; Animals; beta Catenin; Biomechanical Phenomena; Bony Callus; Calcification, Physiologic; Connexin 43; Female; Femur; Fracture Healing; Fractures, Bone; Gene Expression Regulation; Glycogen Synthase Kinase 3; Glycogen Synthase Kinase 3 beta; Glycoproteins; Intercellular Signaling Peptides and Proteins; Lithium Chloride; Mice; Mice, Knockout; Osteoblasts; Osteocytes; Osteoprotegerin; RANK Ligand; Signal Transduction; Torque

The purpose of this study was to study the potential of novel biodegradable PCL bone cement to improve bone screw fixation strength in osteoporotic bone.. The biomechanical properties of bone cement (ε-polycaprolactone, PCL) and fixation strength were studied using biomechanical tests and bone screws fixed in an osteoporotic bone model. Removal torques and pullout strengths were assessed for cortical, self-tapping, and cancellous screws inserted in the osteoporotic bone model (polyurethane foam blocks with polycarbonate plate) with and without PCL bone cement. Open cell and cellular rigid foam blocks with a density of 0.12 g/cm3 were used in this model.. Removal torques were significantly (more than six-fold) improved with bone cement for cancellous screws. Furthermore, the bone cement improved pullout strengths three to 12 times over depending on the screw and model material.. Biodegradable bone cement turned out to be a very potential material to stabilize screw fixation in osteoporotic bone. The results warrant further research before safe clinical use, especially to clarify clinically relevant factors using real osteoporotic bone under human body conditions and dynamic fatigue testing for long-term performance.

Topics: Biocompatible Materials; Bone Cements; Bone Screws; Compressive Strength; Elastic Modulus; Fractures, Bone; Humans; Materials Testing; Models, Biological; Polyesters; Torque

Operative fixation of displaced mid-shaft clavicle fractures has been shown to improve the functional outcomes and decrease the likelihood of non-union; however, little is known about the need for locking screws versus traditional screws. We, therefore, evaluated the strength of unicortical locked plating versus traditional bicortical non-locking fixation methods.. Ten matched pairs of fresh, frozen cadaver clavicle specimens were obliquely osteotomized through the mid-shaft to represent the most common fracture pattern. After randomization, the clavicles were repaired using pre-contoured plates with either standard bicortical non-locking screws or unicortical locking screws. The constructs were then potted in cement and tested on a MTS machine using a custom gimble and evaluated for load to failure and axial and rotational stiffness.. There was no significant difference between the constructs in terms of axial stiffness (locking 688.3 ± 306.2 N/mm, non-locking 674.5 ± 613.0 N/mm; p = 0.77) or load to failure (locking 720.1 ± 232.0 N, non-locking 664.8 ± 167.5 N; p = 0.46). However, rotational stiffness varied significantly (locking 1.70 ± 0.91 N-m/mm, non-locking 2.49 ± 0.78 N-m/mm, p = 0.049) with bicortical non-locking constructs exhibiting higher torque values.. Unicortical fixation using pre-contoured plates and locking screws has a similar biomechanical profile compared to gold standard non-locked bicortical screws in cyclic axial compression and axial load to failure. Non-locking constructs were stiffer under rotational testing. This technique may provide a suitable biomechanical environment for bony healing. This may also improve the safety of clavicle plating by protecting infraclavicular structures from injury during drilling or screw penetration as it obviates the need for bicortical fixation.

Topics: Aged; Biomechanical Phenomena; Bone Plates; Bone Screws; Cadaver; Clavicle; Fracture Fixation, Internal; Fractures, Bone; Humans; Middle Aged; Random Allocation; Torque

Implant surface characterization and biomechanical testing were made to evaluate the effect of different surface treatments along with different implant bulk configurations expressed as biomechanical fixation at early implantation times. Three implant surfaces, namely bioactive ceramic electrodeposition (ED), alumina-blasted/acid etched (AB/AE), and resorbable blasting media (RBM) were fabricated in three implant macrogeometries (cylindrical, small chamber, and large chamber). All combinations between surface and bulk configurations were placed in the radii of beagle dogs (n=18), which were euthanized 14 and 40 days after surgery (n=9 animals per time in vivo). The implants were subjected to torque to interface fracture. Effects of time, surface, and macrogeometry on torque to interface fracture were evaluated by a GLM at 95% level of significance. The results showed a significant increase in torque as time elapsed in vivo (p<0.001), and that the ED surface presented significantly higher values compared to AB/AE and RBM (p<0.001) at both times. The small chamber only presented a significantly higher biomechanical fixation compared to other geometries at 40 days in vivo (p=0.02). Biomechanical fixation at 14 and 40 days was affected by implant surface treatment, whereas implant design only affected results at 40 days in vivo.

Topics: Animals; Biomechanical Phenomena; Dogs; Fracture Fixation, Internal; Fractures, Bone; Male; Mechanical Phenomena; Prostheses and Implants; Radius; Surface Properties; Time Factors; Torque

Numerous studies on the mechanisms of ankle injury deal with injuries to the syndesmosis and anterior ligamentous structures but a previous sectioning study also describes the important role of the posterior talofibular ligament (PTaFL) in the ankle's resistance to external rotation of the foot. It was hypothesized that failure level external rotation of the foot would lead to injury of the PTaFL. Ten ankles were tested by externally rotating the foot until gross injury. Two different frequencies of rotation were used in this study, 0.5 Hz and 2 Hz. The mean failure torque of the ankles was 69.5+/-11.7 Nm with a mean failure angle of 40.7+/-7.3 degrees . No effects of rotation frequency or flexion angle were noted. The most commonly injured structure was the PTaFL. Visible damage to the syndesmosis only occurred in combination with fibular fracture in these experiments. The constraint of the subtalar joint in the current study may have affected the mechanics of the foot and led to the resultant strain in the PTaFL. In the real world, talus rotations may be affected by athletic footwear that may influence the location and potential for an ankle injury under external rotation of the foot.

Topics: Adult; Ankle; Ankle Injuries; Ankle Joint; Biomechanical Phenomena; Cadaver; Fibula; Foot; Fractures, Bone; Humans; Lateral Ligament, Ankle; Male; Middle Aged; Rotation; Subtalar Joint; Talus; Torque

This study evaluated healing of equine metatarsal osteotomies and ostectomies in response to percutaneous injection of adenoviral (Ad) bone morphogenetic protein (BMP)-2, Ad-BMP-6, or beta-galactosidase protein vector control (Ad-LacZ) administered 14 days after surgery. Radiographic and quantitative computed tomographic assessment of bone formation indicated greater and earlier mineralized callus in both the osteotomies and ostectomies of the metatarsi injected with Ad-BMP-2 or Ad-BMP-6. Peak torque to failure and torsional stiffness were greater in osteotomies treated with Ad-BMP-2 than Ad-BMP-6, and both Ad-BMP-2- and Ad-BMP-6-treated osteotomies were greater than Ad-LacZ or untreated osteotomies. Gene expression of ostectomy mineralized callus 8 weeks after surgery indicated upregulation of genes related to osteogenesis compared to intact metatarsal bone. Expression of transforming growth factor beta-1, cathepsin H, and gelsolin-like capping protein were greater in Ad-BMP-2- and Ad-BMP-6-treated callus compared to Ad-LacZ-treated or untreated callus. Evidence of tissue biodistribution of adenovirus in distant organs was not identified by quantitative PCR, despite increased serum antiadenoviral vector antibody. This study demonstrated a greater relative potency of Ad-BMP-2 over Ad-BMP-6 in accelerating osteotomy healing when administered in this regimen, although both genes were effective at increasing bone at both osteotomy and ostectomy sites.

Topics: Adenoviridae; Animals; Biomechanical Phenomena; Bone Morphogenetic Protein 2; Bone Morphogenetic Protein 6; Bone Morphogenetic Proteins; Bony Callus; Disease Models, Animal; Fracture Healing; Fractures, Bone; Gene Expression Regulation; Gene Transfer Techniques; Genetic Therapy; Horses; Humans; Lac Operon; Metatarsal Bones; Oligonucleotide Array Sequence Analysis; Osteogenesis; Osteotomy; Tomography, X-Ray Computed; Torque; Torsion, Mechanical; Transforming Growth Factor beta

Distal third tibia fractures have classically been treated with standard plating, but intramedullary (IM) nailing has gained popularity. Owing to the lack of interference fit of the nail in the metaphyseal bone of the distal tibia, it may be beneficial to add rigid plating of the fibula to augment the overall stability of fracture fixation in this area. This study sought to assess the biomechanical effect of adding a fibular plate to standard IM nailing in the treatment of distal third tibia and fibula fractures.. Eight cadaveric tibia specimens were used. Tibial fixation consisted of a solid titanium nail locked with 3 screws distally and 2 proximally, and fibular fixation consisted of a 3.5 mm low-contact dynamic compression plate. A section of tibia and fibula was removed. Testing was accomplished with an MTS machine. Each leg was tested 3 times; with and without a fibular plate and with a repetition of the initial test condition. Vertical displacements were tested with an axial load up to 500 N, and angular rotation was tested with torques up to 5 N*m.. The difference in axial rotation was the only statistically significant finding (p = 0.003), with fibular fixation resulting in 1.1 degrees less rotation through the osteotomy site (17.96 degrees v. 19.10 degrees ). Over 35% of this rotational displacement occurred at the nail-locking bolt interface with the application of small torsional forces.. Fibular plating in addition to tibial IM fixation of distal third tibia and fibula fractures leads to slightly increased resistance to torsional forces. This small improvement may not be clinically relevant.

Topics: Bone Plates; Cadaver; Fibula; Fracture Fixation, Intramedullary; Fractures, Bone; Humans; Materials Testing; Rotation; Stress, Mechanical; Tibial Fractures; Torque

Proximal femur fractures are of main concern for elderly and especially osteoporotic patients. Despite advanced implant modifications and surgical techniques, serious mechanical complication rates between 4-18% are found in conventional osteosyntheses of proximal femur fractures. Clinical complications such as the rotation of the femoral head and the cut-out phenomenon of the fracture fixation bolt are often diagnosed during post-operative treatments. Therefore, efforts in new intramedulary techniques focus on the load bearing characteristics of the implant by developing new geometries to improve the implant-tissue interface. The objective of this investigation was to analyse the osteosynthesis/femur head interaction of two commonly used osteosyntheses, one with a helical blade and the other one with a screw design under different loading conditions. For the comparative investigation the helical blade of the Proximal Femur Nail Antirotation was investigated versus the screw system of the Dynamic Hip Screw. After implantation in a femoral head the loads for rotational overwinding of the implants were analysed. Pull-out forces with suppressed rotation were investigated with analysis of the influence of the previous overwinding. All investigations were performed on human femoral heads taken of patients with average age of 70.3+/-11.8. The bone mineral densities of the human specimens were detected by QCT-scans (average BMD: 338.9+/- 61.3$\\frac[\\mathit[mg]][\\mathit[cm];[3]]$) Prior to cadaveric testing the experimental set-up was validated and special influences were analysed by the use of synthetic foam blocks (Sawbone). The helical blade showed a significant higher torque for the rotation of the femoral head compared to the screw system. The pull-out forces of the blade were substantially lower than of the comparative screw. Taken together the helical blade showed a higher potential of rotational stability, but after a rotation the lower pull-out forces demonstrate a higher degree of damage to the femoral head.

Topics: Aged; Biomechanical Phenomena; Bone Density; Bone Nails; Bone Screws; Cadaver; Female; Femur; Femur Head; Fracture Fixation, Internal; Fractures, Bone; Humans; Male; Torque; Weight-Bearing

Shoulder stabilization is of utmost importance in upper extremity reanimation following paralysis from devastating brachial plexus injuries. The purpose of this report is to present the authors' experience with suprascapular nerve reconstruction in 118 cases of adult brachial plexus lesions. Outcomes were analyzed in relation to various factors, including patient age, denervation time, donor nerve used, and functional restoration achieved in the supraspinatus versus the infraspinatus muscles.. The medical records of 118 adult patients operated on by a single surgeon between 1978 and 2002 who had suprascapular nerve reconstruction were reviewed; 102 patients had adequate follow-up. Direct neurotization of the suprascapular nerve was carried out in 78 patients, while in 40 patients, interposition nerve grafts were used. In 80 patients, the distal spinal accessory was used as the motor donor nerve for suprascapular nerve neurotization, while in 10 patients, other extraplexus motor donors were used. In 28 patients, intraplexus motor donors were used to reinnervate the suprascapular nerve.. Results were good or excellent in 79 percent of the patients for the supraspinatus muscle and in 55 percent for the infraspinatus. There was a statistically significant difference between direct spinal accessory to suprascapular nerve neurotization and accessory to suprascapular via a nerve graft. Early surgery and less than 6 months of denervation time yielded significantly better results than late surgery and more than 6 months of delay in the treatment.. Suprascapular nerve neurotization is a high priority in upper limb reanimation for restoration of glenohumeral joint stability, shoulder abduction, and external rotation. Concomitant neurotization of the axillary nerve yields improved outcomes in shoulder abduction function. The best results are seen when direct neurotization of the suprascapular nerve is performed within 6 months from the injury.

Topics: Accessory Nerve; Accidents, Traffic; Adolescent; Adult; Aged; Axilla; Biomechanical Phenomena; Brachial Plexus; Child; Clavicle; Denervation; Female; Football; Fractures, Bone; Humans; Joint Instability; Male; Middle Aged; Muscle, Skeletal; Nerve Transfer; Radiculopathy; Recovery of Function; Retrospective Studies; Rotation; Shoulder Joint; Torque

To compare variables for screw insertion, pushout strength, and failure modes for a headless tapered compression screw inserted in standard and oversize holes in a simulated lateral condylar fracture model.. 6 pairs of third metacarpal bones from horse cadavers.. Simulated lateral condylar fractures were created, reduced, and stabilized with a headless tapered compression screw by use of a standard or oversize hole. Torque, work, and time for drilling, tapping, and screw insertion were measured during site preparation and screw implantation. Axial load and displacement were measured during screw pushout. Effects of drill hole size on variables for screw insertion and screw pushout were assessed by use of Wilcoxon tests.. Drill time was 59% greater for oversize holes than for standard holes. Variables for tapping (mean maximum torque, total work, positive work, and time) were 42%, 70%, 73%, and 58% less, respectively, for oversize holes, compared with standard holes. Variables for screw pushout testing (mean yield load, failure load, failure displacement, and failure energy) were 40%, 40%, 47%, and 71% less, respectively, for oversize holes, compared with standard holes. Screws could not be completely inserted in 1 standard and 2 oversize holes.. Enlarging the diameter of the drill hole facilitated tapping but decreased overall holding strength of screws. Therefore, holes with a standard diameter are recommended for implantation of variable pitch screws whenever possible. During implantation, care should be taken to ensure that screw threads follow tapped bone threads.

Topics: Animals; Bone Screws; Cadaver; Forelimb; Fractures, Bone; Horse Diseases; Horses; Metacarpal Bones; Torque

Muscle atrophy is clearly related to a loss of muscle torque, but the reduction in muscle size cannot entirely account for the decrease in muscle torque. Reduced neural input to muscle has been proposed to account for much of the remaining torque deficits after disuse or immobilization. The purpose of this investigation was to assess the relative contributions of voluntary muscle activation failure and muscle atrophy to loss of plantarflexor muscle torque after immobilization. Nine subjects (ages 19-23) years with unilateral ankle malleolar fractures were treated by open reduction-internal fixation and 7 weeks of cast immobilization. Subjects participated in 10 weeks of rehabilitation that focused on both strength and endurance of the plantarflexors. Magnetic resonance imaging, isometric plantarflexor muscle torque and activation (interpolated twitch technique) measurements were performed at 0, 5, and 10 weeks of rehabilitation. Following immobilization, voluntary muscle activation (56.8 +/- 16.3%), maximal cross-sectional area (CSA) (35.3 +/- 7.6 cm(2)), and peak torque (26.2 +/- 12.7 N-m) were all significantly decreased ( p < 0.0056) compared to the uninvolved limb (98.0 +/- 2.3%, 48.0 +/- 6.8 cm(2), and 105.2 +/- 27.0 N-m, respectively). During 10 weeks of rehabilitation, muscle activation alone accounted for 56.1% of the variance in torque ( p < 0.01) and muscle CSA alone accounted for 35.5% of the variance in torque ( p < 0.01). Together, CSA and muscle activation accounted for 61.5% of the variance in torque ( p < 0.01). The greatest gains in muscle activation were made during the first 5 weeks of rehabilitation. Both increases in voluntary muscle activation and muscle hypertrophy contributed to the recovery in muscle strength following immobilization, with large gains in activation during the first 5 weeks of rehabilitation. In contrast, muscle CSA showed fairly comparable gains throughout both the early and later phase of rehabilitation.

Topics: Adult; Ankle Injuries; Ankle Joint; Female; Fractures, Bone; Humans; Immobilization; Magnetic Resonance Imaging; Male; Muscle Contraction; Muscle, Skeletal; Muscular Atrophy; Torque

Neuromuscular electrical stimulation (NMES) could simulate physiological muscle functions known to be associated with the normal bone healing process. The object of the present study was to evaluate the effect of NMES on fracture healing, using an animal model. Thirty rabbits received unilateral, transverse, mid-tibial, 3-mm gapped osteotomies that were stabilized with double-bar external fixators. The femoral vein was ligated to induce venous stasis. From the fourth post-operative day, the study group was treated with 1 h daily of NMES for four weeks, while the control group was treated without NMES. For NMES, two surface electrodes were used: one above the patellar tendon and another around the lateral thigh. Callus area and mineral content at the osteotomy gap were measured, biweekly, using computerized tomographic examinations. Biomechanical properties of healing were evaluated with a torsion test, eight weeks after the index operation. Osteotomies treated with NMES exhibited 31% (p=0.01) higher mineral content and 27% (p=0.009) larger callus area than control osteotomies at eight weeks. The maximum torque, torsional stiffness, angular displacement at maximum torque, and energy required to failure of specimens in the study group were 62% (p=0.006), 29% (p=0.03), 34.6% (p=0.008), and 124% (p<0.0001) higher, respectively, than those in the control group at eight weeks. The results of the present study demonstrated that the use of NMES can enhance callus development and mineralization, with the consequent improvement in biomechanical properties of the healing bone.

Topics: Animals; Bone Density; Bony Callus; Disease Models, Animal; Electric Stimulation Therapy; Female; Fracture Healing; Fractures, Bone; Osteogenesis; Osteotomy; Rabbits; Radiography; Stress, Mechanical; Tibia; Time Factors; Torque; Torsion Abnormality

INTRODUCTION/ PURPOSE: The widespread occurrence of muscular atrophy during immobilization and its reversal presents an important challenge to rehabilitation medicine. We used 3D-magnetic resonance imaging (MRI) in patients with surgically-stabilized ankle mortise fractures to quantify changes in plantarflexor and dorsiflexor muscle size during immobilization and rehabilitation, as well as to evaluate changes in force generating capacity (specific torque).. Twenty-individuals participated in a 10 wk rehabilitation program after 7 wk of immobilization. MRIs were acquired at baseline, 2, and 7 wk of immobilization, and at 5 and 10 wk of rehabilitation. Isometric plantarflexor muscle strength testing was performed at 0, 5, and 10 wk of rehabilitation.. Dorsiflexors and plantarflexors atrophied 18.9% and 24.4% respectively, the majority of which occurred during the first 2 wk of immobilization (dorsiflexors: 9.6%; plantarflexors: 14.1%). Likewise, more than 50% of hypertrophy during rehabilitation occurred within the first 5 wk of rehabilitation for both the dorsiflexors (12.9%) and plantarflexors (13.2%), when compared to the total amount of hypertrophy over 10 wk of rehabilitation (dorsiflexors: 17.6%, plantarflexors: 22.5%). There were no significant differences in hypertrophy or atrophy of the dorsiflexor or plantarflexor muscles, despite a rehabilitation emphasis on the plantarflexors. Patients had significantly lower plantarflexor specific torque (torque/CSA) than healthy, control subjects immediately after cast immobilization, which did not return to normal after 10 wk of rehabilitation (P < 0.05).. Our investigation of the consequences of limb immobilization on rehabilitation outcomes in patients can be applied directly to optimizing rehabilitation programs. Although muscle hypertrophy occurred early during rehabilitation, plantarflexor muscle function (specific torque) should remain the focus of rehabilitation programs because although CSA recovered quickly, specific torque still lagged behind that of control subjects.

Topics: Adaptation, Physiological; Adult; Ankle Injuries; Case-Control Studies; Female; Fractures, Bone; Humans; Hypertrophy; Imaging, Three-Dimensional; Immobilization; Isometric Contraction; Magnetic Resonance Imaging; Male; Middle Aged; Muscle, Skeletal; Muscular Atrophy; Time Factors; Torque

Intramedullary screws frequently are used for fixation of Jones fractures of the fifth metarsal. While the ability of intramedullary screw fixation in fifth metatarsals to resist bending and tensile forces is well known, the ability to withstand torsion has not been studied. This paper compares the torsional stiffness of Jones fractures treated with 6.5-mm short- threaded intramedullary screws to those treated with 5.0-mm cannulated short-threaded intramedullary screws.. Nine fresh-frozen, matched pairs of cadaver fifth metatarsals had an acute Jones fracture simulated with an osteotomy. They were stabilized with intramedullary screws and then loaded to failure.. The torsional stiffness of the metatarsals fixed with the 6.5-mm did not differ significantly from that using 5.0-mm screws. However, to achieve stability, the 5.0-mm screw had to be long enough to reach the metatarsal head and neck. This tended to straighten the normally curved fifth metatarsal bone and caused lateral gapping at the fracture site.. Both 5.0-mm or 6.5-mm screws provide equal torsional rigidity, but 5.0-mm screws may need to be longer, which could potentially straighten the fifth metatarsal shaft in patients who have a curved fifth metatarsal.

Topics: Aged; Aged, 80 and over; Biomechanical Phenomena; Bone Screws; Cadaver; Female; Fracture Fixation, Intramedullary; Fractures, Bone; Humans; Male; Metatarsal Bones; Middle Aged; Torque

Stainless steel wires (Kirschner's wires) have been used for over 60 years to fix internally a wide range of osteotomies and fractures in bones. Fixclips (Corifix, Cirencester, UK) shaped like winged washers have been used to clamp pairs of K wires of diameters ranging from 0.8 to 3.0 mm to standard orthopaedic screws and to fix bones internally in more than 400 patients. The system has proved to be biologically and mechanically very effective. This paper describes the design and some biomechanical test results of the Fixclip. Preliminary strength tests conducted using a Hounsfield Tensometer show that the pull-out force, reflecting the grip of the clip on the wire, is dependent on the wire size and, throughout the clinically relevant range, increases linearly with increasing screw torque. Changing the surface finish of the clip did not confer any advantage over the existing polished clip in terms of grip strength.

Topics: Bone Screws; Bone Wires; Equipment Failure Analysis; Fracture Fixation, Internal; Fracture Healing; Fractures, Bone; Friction; Humans; Osteotomy; Reproducibility of Results; Sensitivity and Specificity; Surface Properties; Tensile Strength; Torque

This study describes the metabolic, morphologic, neurologic, and functional adaptations observed in the plantar flexors during 8 weeks of lower leg immobilization and 10 weeks of physical therapy following ankle surgery. A combination of magnetic resonance imaging and spectroscopy, isokinetic and isometric muscle testing, and simple functional tests revealed many adaptive changes due to immobilization, including atrophy, loss of muscle strength, reduced central activation, increase in fatigue resistance, and an increase in inorganic phosphate content. After 10 weeks of physical therapy all alterations were reversed, with the exception of a remaining 5.5% deficit in total muscle cross-sectional area.

Topics: Adult; Ankle Injuries; Atrophy; Bed Rest; Casts, Surgical; Fractures, Bone; Humans; Isometric Contraction; Isotonic Contraction; Longitudinal Studies; Magnetic Resonance Imaging; Magnetic Resonance Spectroscopy; Male; Motor Activity; Muscle, Skeletal; Physical Therapy Modalities; Torque; Walking

Rational treatment of ankle fractures requires knowledge of the extent of bone and soft tissue injury. Although the Lauge-Hansen classification attempts to do this by relating specific fracture patterns to injury mechanism, the experimental underpinning for this classification has not been reexamined rigorously using modern experimental methods. This study examines the hypothesis that the clinically occurring supination and external rotation injury pattern does not result from the mechanism described by Lauge-Hansen. Thirty-two anatomic specimen ankles were mounted on an MTS machine for combined axial loading with external rotation to failure testing. A foot plate supinated the foot 25 degrees. Testing was performed with the ankle at neutral, 25 degrees plantar flexed, 10 degrees to 15 degrees dorsiflexed, and in 6 degrees to 8 degrees leg valgus. Pure supination and external rotation with the ankle in neutral did not result in the Lauge-Hansen supination and external rotation type fractures. This outcome was not altered if the ankle specimens initially were placed in plantar flexion or dorsiflexion. The addition of a valgus load, which pushes the talus laterally against the fibula, resulted in the classic Lauge-Hansen supination and external rotation type fracture. All specimens had an isolated lateral injury or a lateral injury that preceded medial injury.

Topics: Aged; Aged, 80 and over; Ankle Injuries; Cadaver; Fibula; Foot; Fractures, Bone; Humans; Ligaments, Articular; Middle Aged; Muscle Contraction; Pliability; Range of Motion, Articular; Rotation; Rupture; Soft Tissue Injuries; Stress, Mechanical; Supination; Tendon Injuries; Tibia; Torque; Video Recording