vendex and Tibial-Fractures

Peak reverse torque (PRT) is a valid method to evaluate implants' secondary stability in the healing bone. The secondary stability is achieved by the implant over time and it has been positively correlated with the implants' osseointegration level. In other words, peak reverse torque is the force required to break the bone-implant interface. The purpose of this study was to compare the peak reverse torque for the self-tapping and non-self-tapping screws used in a dynamic compression plate-screw-bone construct after 60 days of loading when used to stabilize 2.5-cm defects in the tibia of goats. The second objective was to compare the peak removal torque of the screws placed in the different positions to evaluate the impact of construct biomechanics on implants osseointegration.. In total, 176 non-self-tapping screws and 66 self-tapping screws were used to fix the 8-holes dynamic compression plates to the bones. The screws were placed in the tibiae from proximal (position sites 1,2, 3) to distal (position sites 4,5,6) and were removed 60 days post-implantation. The animals remained weight-bearing throughout the study period. The screws placed in the proximal diaphysis had significantly less peak reverse torque than screws placed in the distal diaphysis in both groups (p < 0.05). The peak reverse torque resistance was also significantly less for the non-self-tapping screws as compared with the self-tapping screws (p < 0.05). The intracortical fractures in the trans-cortex occurred significantly more frequently during the placement of non-self-tapping screws (p < 0.05) as compared with self-tapping screws (p < 0.05).. Based on these results, we concluded that self-tapping screws may be expected to maintain a more stable bone-implant interface during the first 60 days of loading as compared with non-self-tapping screws. This should be a consideration for orthopedic surgeons and scientists using bone plates to stabilize non-load sharing fractures when a stable plate-screw-bone interface is needed to ensure prolonged stability.

Topics: Animals; Bone Plates; Bone Screws; Female; Goats; Tibia; Tibial Fractures; Torque

The objective of this study was to compare the torsional stability of diaphyseal long bone fractures fixed with either a Fixion nail (DiscOTech, Monroe Township, NJ) or a standard locked Zimmer M/DN locked nail (Zimmer, Warsaw, IN).. Two fracture models were used to evaluate the bone-implant constructs. A transverse osteotomy was created in all tibiae, and a spiral fracture was created in all humeri. Paired specimens were randomly assigned to receive either a Fixion or Zimmer M/DN locked nail. Each implanted construct was cyclically loaded in torsion, and construct stiffness for each fracture type and each bone computed from the resulting load-displacement curves.. Performance of the Fixon nail in the tibial transverse model was variable: 2 of 10 implanted constructs failed during testing, and average construct stiffness was significantly greater for the Zimmer nail. No significant difference was found between the stiffness of the Zimmer M/DN and Fixion implanted humeral constructs either with or without the interlock.. Fracture type significantly affected the performance of the Fixion nail. Our results suggest that the Fixion nail is most suitable for use in fractures where torsional loads across the fracture site are shared between the nail and the bony ends of the fracture, as in a spiral fracture.

Topics: Biomechanical Phenomena; Bone Nails; Equipment Design; Fracture Fixation, Intramedullary; Humans; Humeral Fractures; Rotation; Tibial Fractures; Torque; Torsion Abnormality

On the basis of a six-degree-of-freedom adjustable fracture reduction hexapod external fixator, a system which can be used for measuring axial and shear forces as well as torsion and bending moments in the fixator in vivo was developed. In a pilot study on 9 patients (7 fresh fractures and 2 osteotomies of the tibia), the load in the fixator during the healing process was measured after 2, 4, 8 and 12 weeks and at fixator removal. The measured values enabled both the type of fracture to be determined as well as the monitoring of the healing process. In well-reduced type A3 fractures small axial (direction of the bone axis) forces were found in the fixator. A2, B2 and C3 fractures showed distinct axial forces, which decreased during the healing process, according to an increasing load transfer over the bone. Bending moments in the fixator showed good correspondence with the clinical healing process, except in the case of a C3 fracture. A combination of bending moment and axial force proved to be particularly suitable to assess fracture healing. In transverse fractures, the well-known resorption phenomenon of bone in the fracture gap at approximately 4 weeks was detected by the system. Compared with other external fixator load measurements in vivo, the hexapod offers the advantage of being able to measure all forces and moments in the fixator separately and with a relatively simple mechanical arrangement. In our opinion, it will be possible to control fracture healing using this system, thereby minimizing radiation exposure from radiographs. Furthermore, the measurement system is a step towards the development of external fixator systems that enable automatic adjustments of the callus mechanical situation ("automatic dynamization") and inform the patients about the optimal weight bearing of their extremity ("intelligent fixator").

Topics: Equipment Design; Equipment Failure Analysis; External Fixators; Fracture Healing; Humans; Physical Examination; Pilot Projects; Stress, Mechanical; Tibial Fractures; Torque; Transducers; Weight-Bearing

This work was to investigate potential roles of HMGB1-mediated ERK pathway in the healing process of bone fracture. Rat tibial fracture models were established and divided into control (rats with normal saline), HMGB1 (rats with HMGB1), and HMGB1+ PD98059 groups (rats with HMGB1 and 1 mg/kg of ERK1/2 inhibitor PD98059) with 30 rats per each. The healing of rats' fracture was observed by X-ray films, the morphological changes of bone fractures by HE staining, the callus formation by micro-CT and biomechanical test, and the expression of osteogenesis-related genes, HMGB1 and ERK-related proteins by qRT-PCR and Western blot. Rats in the HMGB1 group was increased in X-ray scores, peak torque, torsional stiffness, and the bone volume fraction (bone volume/total volume, BV/TV); meanwhile, those rats presented elevations in osteogenesis-related genes and HMGB1 expressions, as well as p-ERK/ERK ratio. However, rats in the HMGB1+ PD98059 group was significantly reduced in X-ray score, peak torque, torsional stiffness, and BV/TV, as well as the expression of osteogenesis-related genes and the ratio of p-ERK/ERK, as compared to those from HMGB1 group. HMGB1 could promote the expressions of osteogenesis-related genes and accelerate the healing process of fracture via activation of the ERK signaling pathway.

Topics: Animals; Biomechanical Phenomena; Disease Models, Animal; Enzyme Activation; Fracture Healing; Gene Expression Regulation; HMGB1 Protein; Male; MAP Kinase Signaling System; Osteogenesis; Rats, Sprague-Dawley; Tibial Fractures; Torque; X-Ray Microtomography; X-Rays

Heightened local inflammation due to muscle trauma or disease is associated with impaired bone regeneration.. We hypothesized that FK506, an FDA approved immunomodulatory compound with neurotrophic and osteogenic effects, will rescue the early phase of fracture healing which is impaired by concomitant muscle trauma in male (~4 months old) Lewis rats. FK506 (1 mg/kg; i.p.) or saline was administered systemically for 14 days after an endogenously healing tibia osteotomy was created and fixed with an intermedullary pin, and the overlying tibialis anterior (TA) muscle was either left uninjured or incurred volumetric muscle loss injury (6 mm full thickness biopsy from middle third of the muscle).. The salient observations of this study were that 1) concomitant TA muscle trauma impaired recovery of tibia mechanical properties 28 days post-injury, 2) FK506 administration rescued the recovery of tibia mechanical properties in the presence of concomitant TA muscle trauma but did not augment mechanical recovery of an isolated osteotomy (no muscle trauma), 3) T lymphocytes and macrophage presence within the traumatized musculature were heightened by trauma and attenuated by FK506 3 days post-injury, and 4) T lymphocyte but not macrophage presence within the fracture callus were attenuated by FK506 at 14 days post-injury. FK506 did not improve TA muscle isometric torque production CONCLUSION: Collectively, these findings support the administration of FK506 to ameliorate healing of fractures with severe muscle trauma comorbidity. The results suggest one potential mechanism of action is a reduction in local T lymphocytes within the injured musculoskeletal tissue, though other mechanisms to include direct osteogenic effects of FK506 require further investigation.

Topics: Adaptive Immunity; Animals; Biopsy; Bone Nails; Bone Regeneration; Bony Callus; Disease Models, Animal; Fracture Fixation, Intramedullary; Fracture Healing; Humans; Immunity, Innate; Immunosuppressive Agents; Macrophages; Male; Muscle, Skeletal; Muscular Diseases; Osteotomy; Rats; Rats, Inbred Lew; Soft Tissue Injuries; T-Lymphocytes; Tacrolimus; Tibial Fractures; Torque

According to Fraser's description, ipsilateral femoral and tibial diaphyseal fractures are characterised as type I floating knee and have a better prognosis than fractures with joint involvement (type II). There are few reports of functional and muscle strength in these patients. The objective of this study was to evaluate the functional and isokinetic muscle strength of patients with type I floating knee undergoing femoral and tibial internal fixation.. Patients with type I floating knee undergoing concomitant femoral and tibial internal fixation were invited for clinical evaluation. The parameters evaluated included the following: Karlstrom and Olerud score; Lysholm score; isokinetic thigh and hip muscle evaluation; knee range of motion; pain level; investigation of associated knee injuries by clinical evaluation and MRI; and types of complications.. Twenty-one patients were included in the study; 11 of these were clinically evaluated, with a mean follow-up of 23.9 months. Six patients had an acceptable result according to the Karlstrom criteria, whereas eight patients had a poor result based on the Lysholm scale. The peak torque deficit was 61% for knee extensors, 37% for flexors and -9% for hip abductors. The mean pain level was 5.9. Three patients had a partial anterior cruciate ligament (ACL) injury; one patient had a posterior cruciate ligament (PCL) injury; and three patients had a meniscal injury. There were four cases of tibial or femoral nonunion at one year and two cases of chronic osteomyelitis.. Patients with type I floating knee had unsatisfactory functional results, significant knee extensor and flexor muscle strength deficits and a significant rate of complications at the two-year follow-up.

Topics: Adult; Female; Femoral Fractures; Follow-Up Studies; Fracture Fixation, Internal; Humans; Joint Instability; Knee Joint; Magnetic Resonance Imaging; Male; Middle Aged; Muscle Strength; Prognosis; Range of Motion, Articular; Retrospective Studies; Tibial Fractures; Torque; Treatment Outcome; Young Adult

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

Although the posteromedial fragment in tibial plateau fractures is often considered unstable, biomechanical evidence supporting this view is lacking. We aimed to evaluate the stability of the fragment in a cadaver model. Our hypothesis was that under the expected small axial force during rehabilitation and the combined effects of this force with shear force, internal rotation torque, and varus moment, the most common posteromedial tibial fragment morphology could maintain stability in early flexion.. Axial compression force alone or combined with posterior shear, internal rotation torque, or varus moment was applied to the femurs of 5 fresh cadaveric knees. A Tekscan pressure mapping system was used to measure pressure and contact area between the femoral condyles, meniscus, and tibial plateau. A Microscribe 3D digitizer was used to define the 3-dimensional positions of the femur and tibia. A 10-mm and then a 20-mm osteotomy was created with a saw at an angle of 30 degrees in the axial plane with respect to the tangent of the posterior tibial plateau and 75 degrees in the sagittal plane, representing a typical posteromedial fracture fragment. At each flexion angle (15, 30, 60, 90, and 120 degrees) and loading condition (axial compression only, compression with shear force, torque, and varus moment), distal displacement of the medial femoral condyle and the tibial fracture fragments was determined.. For the 10-mm fragment, medial femoral condyle displacement was little affected up to approximately 30-degree flexion, after which it increased. For the 20-mm fragment, there was progressive medial femoral condyle displacement with increasing flexion from baseline. However, for the 10- and 20-mm fragments themselves, displacements were noted at every flexion angle, starting at 1.7 mm inferior displacement with 15 degrees of flexion and internal rotation torque and up to 10.2 mm displacement with 90 degrees of flexion and varus bending moment.. In this cadaveric model of a posteromedial tibial plateau fracture, both fracture fragments studied displaced with knee flexion, even at low flexion angles. Although such fragments may initially seem nondisplaced after injury, posteromedial fragments similar to these tested are likely to displace during knee range of motion exercises in non-weight-bearing conditions.

Topics: Biomechanical Phenomena; Cadaver; Fracture Fixation; Humans; Joint Instability; Knee Joint; Osteotomy; Rotation; Tibial Fractures; Torque; Weight-Bearing

The expression of transforming growth factor-beta 1 (TGF-β1) inside the callus cells of diabetic rats and the impact of insulin therapy on its expression and biomechanics was investigated. The rats were randomly divided as follows: an insulin therapy group (IT), a diabetic model group (DM), and a non-diabetic control group (NC). Bone specimens from each group were extracted at different times for immunohistochemical observation of the expression of TGF-β1. Concurrently, the destruction torque and torsional stiffness were detected at different times. One to four weeks after fracture, TGF-β1 was widely expressed in fractured callus cells and periosteal proliferating cells, while the expression inside diabetic cells was significantly reduced. The expression of TGF-β1 decreased over the first 68 weeks, and the mature bone cells never expressed TGF-β1. The destruction torque (Nm) detected in the 6th week revealed that there was a statistically significant difference between the DM, NC, and IT groups (P < 0.01). In conclusion, TGF-β1 expression was significantly reduced inside the callus cells of diabetic rats. Insulin therapy increased TGF-β1 expression inside the callus cells of diabetic rats and improved the biomechanical characteristics of the callus.

Topics: Animals; Bony Callus; Cell Proliferation; Diabetes Mellitus, Experimental; Fracture Healing; Gene Expression; Hardness; Hypoglycemic Agents; Insulin; Male; Periosteum; Rats; Rats, Wistar; Tibial Fractures; Torque; Transforming Growth Factor beta1

Using human cadaver specimens, we investigated the role of supplementary fibular plating in the treatment of distal tibial fractures using an intramedullary nail. Fibular plating is thought to improve stability in these situations, but has been reported to have increased soft-tissue complications and to impair union of the fracture. We proposed that multidirectional locking screws provide adequate stability, making additional fibular plating unnecessary. A distal tibiofibular osteotomy model performed on matched fresh-frozen lower limb specimens was stabilised with reamed nails using conventional biplanar distal locking (CDL) or multidirectional distal locking (MDL) options with and without fibular plating. Rotational stiffness was assessed under a constant axial force of 150 N and a superimposed torque of ± 5 Nm. Total movement, and neutral zone and fracture gap movement were analysed. In the CDL group, fibular plating improved stiffness at the tibial fracture site, albeit to a small degree (p = 0.013). In the MDL group additional fibular plating did not increase the stiffness. The MDL nail without fibular plating was significantly more stable than the CDL nail with an additional fibular plate (p = 0.008). These findings suggest that additional fibular plating does not improve stability if a multidirectional distal locking intramedullary nail is used, and is therefore unnecessary if not needed to aid reduction.

Topics: Bone Nails; Bone Plates; Cadaver; Fibula; Fracture Fixation, Intramedullary; Humans; Prosthesis Design; Rotation; Stress, Mechanical; Tibial Fractures; Torque

The aim of the study was to evaluate the knee joint function in adolescent patients following operative treatment - fixation via arthroscopic or open surgery (arthrotomy), due to tibial eminence fractures. 28 patients, aged from 7 to 16 years, treated operatively between 1994-2009 in four orthopeadic centres underwent evaluation. Evaluation was performed 12-180 months following surgery. Patients were divided into two groups depending on the operative treatment received. Group A consisted of 14 patients who underwent arthroscopic reduction and stabilization. Group B consisted of 14 patients who were treated by open reduction (artrothomy) and stabilization. The results of clinical and radiological examinations and isokinetic tests used in the evaluation declared that operative treatment due to tibial eminence fracture, regardless of surgical method used, does not significantly disrupt knee joint function resulting in a slight weakening of knee joint extensor muscle strength.

Topics: Adolescent; Adult; Female; Humans; Knee Joint; Male; Muscle Contraction; Muscle Strength; Muscle, Skeletal; Postural Balance; Range of Motion, Articular; Recovery of Function; Reproducibility of Results; Sensitivity and Specificity; Tibial Fractures; Torque; Treatment Outcome

Displaced medial malleolus fractures require surgical repair because of the critical role the structure plays in normal joint function. Various approaches exist, but options are limited for small fragment fractures. This study compared repair with the Medial Malleolar Sled fixation system (Trimed, Inc, Valencia, CA) to lag screws in 2 modes of biomechanical loading in a cadaveric model.. A Müller type B medial malleolus fracture was simulated on matched pairs of cadaveric lower extremities and repaired with the sled or 2 cancellous lag screws. Tibial distraction (tension, n = 10) or internal rotation (torsion, n = 11) was applied. Fragment movement was measured in the sagittal (tension and torsion) and transverse (torsion-only) planes. Fragment movement at 1 mm and 2 mm (clinical malunion) of gapping during tension and at 2, 4, 6, and 8 N-m during torsion was analyzed via paired t tests.. In tension, the load at the 2-mm gap was statistically lower for screws (P = .026). Opening angle was statistically larger for the sled at the 1-mm (P = .0004) and 2-mm (P = .008) gap. In torsion, gapping was statistically lower for the sled (ranging from P = .0013 at 4 N-m to P = .0187 at 8 N-m). No differences were detected for opening angle or transverse plane movement.. The sled appeared stronger in tension and as effective as lag screws in torsion. The sled may be a viable option for fractures too small for 4.0- or 3.5-mm lag screws.. The sled may be suitable in applications where a tension band would normally be considered and may provide stronger fixation in osteoporotic bone compared with lag screw fixation.

Topics: Adult; Aged; Ankle Injuries; Biomechanical Phenomena; Bone Density; Bone Screws; Bone Wires; Cadaver; Female; Fluoroscopy; Fracture Fixation, Internal; Humans; Male; Middle Aged; Tibial Fractures; Torque

To better understand the mechanisms underlying spiral fracture we would like to carry out biomechanical tests of long bones loaded in torsion to failure. A device was fabricated to perform torsional tests of long bones using a single-axis linear actuator. The principal operation of the device was to transform the vertical displacement of a material testing machine's linear actuator into rotational movement using a spur gear and rack system. Accuracy and precision of the device were quantified using cast-acrylic rods with known torque-rotation behavior. Cadaveric experimentation was used to replicate a clinically relevant spiral fracture in eleven human proximal tibiae; strain-gage data were recorded for a single specimen. The device had an experimental error of less than 0.2 Nm and was repeatable to within 0.3%. Strain gage data were in line with those expected from pure torsion and the cadaveric tibiae illustrated spiral fractures at ultimate torque and rotation values of 130.6 +/- 53.2 Nm and 8.3 +/- 1.5 degrees, respectively. Ultimate torque was highly correlated with DXA assessed bone mineral density (r = 0.87; p < 0.00 1). The device presented is applicable to any torsional testing of long bone when only a single-axis linear actuator is available.

Topics: Equipment Design; Equipment Failure Analysis; Fractures, Closed; Humans; Physical Stimulation; Robotics; Tibial Fractures; Torque

Topics: Bone Screws; Device Removal; Fractures, Ununited; Humans; Male; Middle Aged; Prosthesis Failure; Tibial Fractures; Titanium; Torque

Valgus bending of the knee is promoted as an anterior cruciate ligament injury mechanism and is associated with a characteristic "footprint" of bone bruising. The hypothesis of this study was that during ligamentous failure caused by valgus bending of the knee, high tibiofemoral contact pressures induce acute osteochondral microdamage.. Four knee pairs were loaded in valgus bending until gross injury with or without a tibiofemoral compression pre-load. The peak valgus moment and resultant motions of the knee joint were recorded. Pressure sensitive film documented the magnitude and location of tibiofemoral contact. Cartilage fissures were documented on the tibial plateau, and microcracks in subchondral bone were documented from micro-computed tomography scans.. Injuries were to the anterior cruciate ligament in three knees and the medial collateral ligament in seven knees. The mean (standard deviation) peak bending moment at failure was 107 (64)Nm. Valgus bending produced regions of contact on the lateral tibial plateau with average maximum pressures of approximately 30 (8)MPa. Cartilage fissures and subchondral bone microcracks were observed in these regions of high contact pressure.. Combined valgus bending and tibiofemoral compression produce slightly higher contact pressures, but do not alter the gross injury pattern from isolated valgus bending experiments. Athletes who sustain a severe valgus knee bending moment, may be at risk of acute osteochondral damage especially if the loading mechanism occurs with a significant tibiofemoral compression component.

Topics: Adult; Cadaver; Compressive Strength; Fractures, Cartilage; Humans; Knee Injuries; Knee Joint; Male; Pressure; Radiography; Rupture; Tibial Fractures; Torque; Weight-Bearing

Valgus bending and shearing of the knee have been identified as primary mechanisms of injuries in a lateral loading environment applicable to pedestrian-car collisions. Previous studies have reported on the structural response of the knee joint to pure valgus bending and lateral shearing, as well as the estimated injury thresholds for the knee bending angle and shear displacement based on experimental tests. However, epidemiological studies indicate that most knee injuries are due to the combined effects of bending and shear loading. Therefore, characterization of knee stiffness for combined loading and the associated injury tolerances is necessary for developing vehicle countermeasures to mitigate pedestrian injuries. Isolated knee joint specimens (n=40) from postmortem human subjects were tested in valgus bending at a loading rate representative of a pedestrian-car impact. The effect of lateral shear force combined with the bending moment on the stiffness response and the injury tolerances of the knee was concurrently evaluated. In addition to the knee moment-angle response, the bending angle and shear displacement corresponding to the first instance of primary ligament failure were determined in each test. The failure displacements were subsequently used to estimate an injury threshold function based on a simplified analytical model of the knee. The validity of the determined injury threshold function was subsequently verified using a finite element model. Post-test necropsy of the knees indicated medial collateral ligament injury consistent with the clinical injuries observed in pedestrian victims. The moment-angle response in valgus bending was determined at quasistatic and dynamic loading rates and compared to previously published test data. The peak bending moment values scaled to an average adult male showed no significant change with variation in the superimposed shear load. An injury threshold function for the knee in terms of bending angle and shear displacement was determined by performing regression analysis on the experimental data. The threshold values of the bending angle (16.2 deg) and shear displacement (25.2 mm) estimated from the injury threshold function were in agreement with previously published knee injury threshold data. The continuous knee injury function expressed in terms of bending angle and shear displacement enabled injury prediction for combined loading conditions such as those observed in pedestrian-car collisions.

Topics: Accidents, Traffic; Aged; Cadaver; Elasticity; Female; Humans; Knee; Knee Injuries; Knee Joint; Ligaments, Articular; Male; Middle Aged; Models, Biological; Movement; Range of Motion, Articular; Rupture; Stress, Mechanical; Tibial Fractures; Torque; Weight-Bearing

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

Recently developed inflatable nails avoid reaming and interlocking screws in tibial fractures and reflect a new principle for stabilization of long bone fractures. We asked if the bending stiffness, rotational rigidity, or play (looseness of rotation) differed between an inflatable versus large-diameter reamed interlocked nails, and whether the maximal torque to failure of the two bone-implant constructs differed. In a cadaveric model, we compared the biomechanical properties with those of an interlocked nail in eight pairs of fractured tibial bones. Bending stiffness, rotational rigidity, play (looseness in rotation), and torsional strength within 20 degrees rotation were investigated using a biaxial servohydraulic testing system. For all biomechanical variables, we found a large interindividual variance between the pairs attributable to bone quality (osteoporosis) for both fixation methods. The inflatable nail had a higher bending stiffness, with a mean difference of 58 N/mm, and a lower torsional strength, with a mean difference of 13.5 Nm, compared with the locked nail. During torsional testing we noted slippage between the inflatable nail and bone. We observed no differences in play or rotational rigidity. Given the lower torsional strength we recommend caution with weightbearing until there are signs of fracture consolidation.

Topics: Bone Nails; Cadaver; Elasticity; Equipment Failure Analysis; Fracture Fixation, Internal; Humans; Prosthesis Design; Prosthesis Failure; Radiography; Rotation; Stress, Mechanical; Tibial Fractures; Torque; Weight-Bearing

The effect of an intact fibula on rotational stability after a distal tibial fracture has, to the best of our knowledge, not been clearly defined. We designed a cadaver study to clarify our clinical impression that fixation of the fibula with a plate increases rotational stability of distal tibial fractures fixed with a Russell-Taylor intramedullary nail.. Seven matched pairs of embalmed human cadaveric legs and sixteen fresh-frozen human cadaveric legs, including one matched pair, were tested. To simulate fractures, 5-mm transverse segmental defects were created at the same level in the tibia and fibula, 7 cm proximal to the ankle joint in each bone. The tibia was stabilized with a 9-mm Russell-Taylor intramedullary nail that was statically locked with two proximal and two distal screws. Each specimen was tested without fibular fixation as well as with fibular fixation with a six-hole semitubular plate. A biaxial mechanical testing machine was used in torque control mode with an initial axial load of 53 to 71 N applied to the tibial condyle. Angular displacement was measured in 0.56-N-m torque increments to a maximal torque of 4.52 N-m (40 in-lb).. Initially, significantly less displacement (p < or = 0.05) was produced in the specimens with fibular plate fixation than in those without fibular plate fixation. The difference in angular displacement between the specimens treated with and without plate fixation was established at the first torque data point measured but did not increase as the torque was increased. No significant difference in the rotational stiffness was found between the specimens treated with and without plate fixation after measurement of the second torque data point (between 1.68 and 4.48 N-m).. Fibular plate fixation increased the initial rotational stability after distal tibial fracture compared with that provided by tibial intramedullary nailing alone. However, there was no difference in rotational structural stiffness between the specimens treated with and without plate fixation as applied torque was increased.

Topics: Aged; Aged, 80 and over; Ankle Injuries; Ankle Joint; Biomechanical Phenomena; Bone Plates; Bone Screws; Cadaver; Female; Fibula; Fracture Fixation, Internal; Fracture Fixation, Intramedullary; Humans; Joint Instability; Male; Models, Anatomic; Tibial Fractures; Torque

Interfragmentary movements affect the quality and quantity of callus formation. The mounting plane of monolateral external fixators may give direction to those movements. Therefore, the aim of this study was to determine the influence of the fixator mounting plane on the process of fracture healing. Identically configured fixators were mounted either medially or anteromedially on the tibiae of sheep. Interfragmentary movements and ground reaction forces were evaluated in vivo during a nine week period. Histomorphological and biomechanical parameters described the bone healing processes. Changing only the mounting plane led to a modification of interfragmentary movements in the initial healing phase. The difference in interfragmentary movements between the groups was only significant during the first post-operative period. However, these initial differences in mechanical conditions influenced callus tissue formation significantly. The group with the anteromedially mounted fixator, initially showing significantly more interfragmentary movements, ended up with a significantly smaller callus diameter and a significantly higher callus stiffness as a result of advanced fracture healing. This demonstrates that the initial phase of healing is sensitive to mechanical conditions and influences the course of healing. Therefore, initial mechanical stability of an osteosynthesis should be considered an important factor in clinical fracture treatment.

Topics: Animals; Bony Callus; External Fixators; Female; Fracture Healing; Sheep; Stress, Mechanical; Tibial Fractures; Torque; Torsion Abnormality; Weight-Bearing

This study tested the hypothesis that interfragmentary axial movement of transverse diaphyseal osteotomies would result in improved fracture healing compared to interfragmentary shear movement. Ten skeletally mature merino sheep underwent a middiaphyseal osteotomy of the right tibia, stabilized by external fixation with an interfragmentary gap of 3 mm. A custom made external fixator allowed either pure axial (n=5) or pure shear movement (n=5) of 1.5 mm amplitude during locomotion by the animals. The movement of the osteotomy gap was monitored weekly in two sheep by an extensometer temporarily attached to the fixator. After 8 weeks the sheep were killed, and healing of the osteotomies was evaluated by radiography, biomechanical testing, and undecalcified histology. Shear movement considerably delayed the healing of diaphyseal osteotomies. Bridging of the osteotomy fragments occurred in all osteotomies in the axial group (100%), while in the shear group only three osteotomies (60%) were partially bridged. Peripheral callus formation in the shear group was reduced by 36% compared to the axial group (p<0.05). In the axial group bone formation was considerably larger at the peripheral callus and in between the osteotomy gaps but not in the intramedullary area. The larger peripheral callus and excess in bone tissue at the level of the gap resulted in a more than three times larger mechanical rigidity for the axial than for the shear group (p<0.05). In summary, fixation that allows excessive shear movement significantly delayed the healing of diaphyseal osteotomies compared to healing under axial movement of the same magnitude.

Topics: Animals; Bony Callus; Compressive Strength; Disease Models, Animal; External Fixators; Female; Fracture Fixation; Fracture Healing; Radiography; Shear Strength; Sheep; Tibia; Tibial Fractures; Torque

To improve mechanical performance, a prototype tibial locking screw with two components was developed for the current study: a both-ends-threaded screw with a smooth shank and a small set screw inserted obliquely through the cap of the both-ends-threaded screw. The bending strength and holding power of this prototype screw were compared with that of five commercially available tibial locking screws: Synthes, Howmedica, Richards, Osteo AG, and Zimmer. To test bending strength, the screws were inserted into a polyethylene tube and loaded at their midpoint to simulate a three-point bending test. Single-loading yielding strength and cyclic-loading fatigue life then were measured. To test holding power, the screws were inserted into polyurethane foam tubes, and stripping torque and pushout strength were measured. The results showed that the yielding strength and the fatigue life were related closely to the inner diameter of the fully threaded screws. The stripping torque reflected the pushout strength, which also was estimated by the formula D[0.5 + 0.57735 (D - d)/2p] (D, outer diameter; d, inner diameter; p, pitch). Even though, among all of the tested screws, the prototype had the smallest outer diameter at its middle, it had the highest fatigue strength, and simultaneously preserved its high bone-holding power. A clinical trial using this prototype screw is warranted, one in which the difficult surgical technique of inserting the set screws should be investigated.

Topics: Bone Screws; Equipment Design; Fracture Fixation, Internal; Humans; Reproducibility of Results; Tensile Strength; Tibial Fractures; Torque

To evaluate whether coating AO/ASIF screws with osteoconductive materials can improve bone-screw fixation.. Ninety-six AO/ASIF 4.5-millimeter cortical screws were divided into four paired groups and implanted in the femurs and tibiae of six sheep: Group A = standard stainless steel screws; Group B = stainless steel screws coated with highly crystalline hydroxyapatite; Group C = stainless steel screws coated with low crystalline hydroxyapatite; Group D = titanium screws coated with titanium. The screws were implanted according to the standard AO technique to an insertion torque of 2,000 Newton-millimeters. Sheep were killed at one, three, and twelve months after surgery.. Extraction torque was measured on six screws from each group selected at random at time of each euthanization. Morphologic analysis of the bone-screw interface was performed on the remaining screws.. At each euthanization the extraction torque of Group A was lower than that of the other groups (p < 0.0001). At three and twelve months the extraction torque of Group B was higher than that of Group D (p = 0.002). Morphologic results showed extensive bone-screw gap in Group A. Optimal osteointegration was observed in Groups B and C. Osteointegration of Group D was higher than that of Group A and lower than that of Groups B and C.. It was demonstrated that AO/ASIF screws coated with osteoconductive materials achieve optimal fixation strength, even in the early phase. This fixation strength was significantly higher than that of the standard screws.

Topics: Animals; Biomechanical Phenomena; Bone Screws; Coated Materials, Biocompatible; Disease Models, Animal; Durapatite; Female; Femoral Fractures; Fracture Fixation; Fracture Healing; Random Allocation; Sheep; Tensile Strength; Tibial Fractures; Titanium; Torque

Pin tract infection is a common complication of external fixation. An antiinfective external fixator pin might help to reduce the incidence of pin tract infection and improve pin fixation.. Stainless steel and titanium external fixator pins, with and without a lipid stabilized hydroxyapatite/chlorhexidine coating, were evaluated in a goat model. Two pins contaminated with an identifiable Staphylococcus aureus strain were inserted into each tibia of 12 goats. The pin sites were examined daily. On day 14, the animals were killed, and the pin tips cultured. Insertion and extraction torques were measured.. Infection developed in 100% of uncoated pins, whereas coated pins demonstrated 4.2% infected, 12.5% colonized, and the remainder, 83.3%, had no growth (p < 0.01). Pin coating decreased the percent loss of fixation torque over uncoated pins (p = 0.04).. These results demonstrate that the lipid stabilized hydroxyapatite/chlorhexidine coating was successful in decreasing infection and improving fixation of external fixator pins.

Topics: Animals; Anti-Infective Agents, Local; Bone Nails; Chi-Square Distribution; Chlorhexidine; Coated Materials, Biocompatible; Device Removal; Disease Models, Animal; Durapatite; External Fixators; Fracture Fixation; Goats; Male; Stainless Steel; Staphylococcal Infections; Statistics, Nonparametric; Tibial Fractures; Titanium; Torque

Epidemiology revealed that diaphyseal fractures of the tibia affect young people, particularly young men; no increase was noticed for the elderly. This indicates that osteoporosis does not lead to increased bone fragility. Obviously, this is a biomechanical enigma. Torque measurements were carried out on human cadaveric tibiae and revealed a great correlation between the polar moment of inertia of the cortical bone at the tibial isthmus and the ultimate torque at failure (r = 0.83) and a lesser correlation between the cross-sectional density at the isthmus and the torque at failure (r = 0.57). Therefore, the size is more important than the degree of osteoporosis. We can speculate that endosteal resorption due to osteoporosis is compensated for by periosteal apposition and therefore does not lead to bone weakness.

Topics: Age Factors; Aged; Biomechanical Phenomena; Bone Density; Diaphyses; Humans; Male; Osteoporosis; Research Design; Tibia; Tibial Fractures; Tomography, X-Ray Computed; Torque; Torsion Abnormality

To evaluate the effects of two bioceramics on bone regeneration during repair of segmental bone defects, Biocoral and tricalcium phosphate cylinders were implanted in osteotomized sheep tibial defects 16 mm in length and followed up for 16 weeks. In comparison with the TCP-implanted defect, a significant increment in area and density of external callus was quantified radiomorphometrically at 3 weeks, and a marked increase in maximal torque capacity, maximal angle of deformation and absorption of energy was demonstrated mechanically in the Biocoral-implanted tibia at 16 weeks after implantation. Better bone integration with the substratum was microscopically observed in Biocoral cylinders. With good osteointegration and biomechanical-performance, Biocoral seems to be superior to TCP in repair of segmental defects in weight-bearing limbs.

Topics: Animals; Bone Substitutes; Calcium Phosphates; Ceramics; Female; Fracture Healing; Microscopy, Electron, Scanning; Prostheses and Implants; Radiography; Sheep; Tibial Fractures; Torque

The isokinetic performance of thigh muscles was evaluated in 37 patients at an average of 7 years after sustaining a fracture of the tibial plateau. The mean torque deficit in the quadriceps of the injured limb was an average of 15% at a speed of 60 degrees/s and 16% at 180 degrees/s, while the corresponding deficits in the hamstrings were 3% and 8%. The radiological appearance of the injured knee correlated significantly to the quadriceps deficit at both speeds. Limited knee movement and thigh atrophy also correlated with the deficit at the lower speed. The strength deficit tended to decrease during follow-up. A multiple step-wise regression analysis showed that the radiological result, length of follow-up and thigh atrophy accounted for 47% of the variation in loss of quadriceps strength. At the higher speed, the functional result was associated with the deficit in quadriceps strength, and older patients had greater deficits than younger. Regression analysis indicated that the radiological and functional result accounted for 31% of the variation in quadriceps strength. Anatomical restoration of the tibial plateau and good muscle rehabilitation are important in obtaining good long term results after this fracture.

Topics: Adolescent; Adult; Analysis of Variance; Biomechanical Phenomena; Female; Follow-Up Studies; Humans; Isometric Contraction; Kinetics; Male; Middle Aged; Muscle, Skeletal; Regression Analysis; Thigh; Tibial Fractures; Torque

Based upon magnetic resonance scans of five human tibiae a three-dimensional finite element model using eight nodal isoparametric elements was developed to analyze the biomechanical properties of fracture fixation by an unreamed interlocking nail. Tension phenomena and bone implant translations occurring in the borderlines of the fracture zone, bone-implant interface, and the fixation site of the interlocking screws were analyzed with the help of link elements. The proximal fracture segment was fixed with a link element so as to produce exclusively translatory shifts corresponding to the vector of the load applied. Under condition of static load F = 500 N or axial torsion MT = 15 Nm the biomechanical properties of a nailed horizontal fracture (42-A3), a three fragment lesion (42-B2), and a comminuted midshaft fracture (42-C3) were evaluated. On condition of axial load maximum dislocations of 0.1549 mm are induced in the direction of the x-axis due to the asymmetric geometry of the human tibia which promotes medially directed translations. Independent from the fracture type present a homogenous tension profile was calculated for the whole tibia diaphysis with a sigmaEQV ranging from 24.18 to 121.14 MPa due to the relative low elastic modulus of the cortical bone compared to material characteristics of the implant. However, application of a torsional moment MT = 15 Nm induces significantly increased tension maxima in the nail-interlocking screw interface with a sigmaEQV = 7, 626 MPa. Maximum translatory movements ux = 12.59 mm and uy = 23.53 mm in the x and y plane indicate that these load conditions bear a high risk of an implant failure.

Topics: Biomechanical Phenomena; Bone Nails; Bone Screws; Computer Simulation; Elasticity; Equipment Design; Equipment Failure; Fracture Fixation, Intramedullary; Fractures, Comminuted; Humans; Magnetic Resonance Imaging; Mathematics; Models, Biological; Stress, Mechanical; Surface Properties; Tibia; Tibial Fractures; Torque