vendex and Femoral-Neck-Fractures

Orthopaedic implants can be introduced in clinical practice if equivalency to an already approved implant can be demonstrated. A preclinical laboratory test can in theory provide the required evidence. Due to the lack of consensus on the optimum design of biomechanical experiments, setups vary considerably. This review aims to make femoral neck fracture models more accessible for evaluation to orthopaedic surgeons without any particular background in biomechanics. Additionally, the clinical relevance of the different setups is discussed.. This is a narrative review based on a non-systematic search in PubMed, Scopus and Cochrane.. Biomechanical femoral neck fracture experiments should aim at optimizing the recreation of the in vivo situation. The bone quality of the experimental femurs should resemble the hip fracture population, hence cadaveric bones should be preferred to the available synthetic replica. The fracture geometry must be carefully selected to avoid bias. The load applied to the specimen should result in forces within the range of in vivo measured values and the magnitude should be related to the actual weight of the donor. A well designed biomechanical experiment can prevent harmful devices from being introduced in clinical practice, however, positive results can never exclude the necessity of subsequent clinical studies.

Topics: Biomechanical Phenomena; Cadaver; Compressive Strength; Female; Femoral Neck Fractures; Femur; Humans; Male; Models, Anatomic; Torque; Weight-Bearing

To evaluate axial fracture obliquity and posterior inferior comminution in vertically oriented femoral neck fractures (FNFs) in the physiologically young patient. A biomechanical investigation was designed to evaluate the impact of these fracture elements on torque to failure using cannulated screw (CS) and sliding hip screw fixation.. Four Pauwels III FNF models were established in synthetic femurs: (1) vertically oriented in the coronal plane (COR), (2) coronal plane with axial obliquity (AX), (3) coronal plane with posterior inferior comminution (CCOM), and (4) coronal plane with axial obliquity and posterior inferior comminution (ACOM). In each group (n = 10), specimens were fixed using either 3 CSs or a sliding hip screw with supplemental antirotation screw (SHS). Quasistatic cyclic ramp-loading to failure was performed using a custom testing jig combining axial preloading and torsional ramp-loading. The primary outcome was torque to failure, defined as angular displacement ≥5 degrees.. In the CS group, torque to failure was 40.2 ± 2.6 Nm, 35.0 ± 1.4 Nm, 29.8 ± 1.5 Nm, and 31.8 ± 2.2 Nm for the COR, AX, CCOM, and ACOM fracture groups, respectively (P < 0.05). In the SHS group, torque to failure was 28.6 ± 1.3 Nm, 24.2 ± 1.4 Nm, 21.4 ± 1.2 Nm, and 21.0 ± 0.9 Nm for the COR, AX, CCOM, and ACOM fracture groups, respectively (P < 0.05). In both constructs, groups with posterior inferior comminution demonstrated significantly lower torque to failure compared to the COR group (P < 0.05). The CS construct demonstrated higher torque to failure in all groups when compared to the SHS construct (P < 0.01).. Posterior inferior comminution significantly affects torque to failure in vertically oriented FNFs. Three peripherally placed CSs may resist combined axial and torsional loading better than a sliding hip screw construct.

Topics: Biomechanical Phenomena; Femoral Fractures; Femoral Neck Fractures; Fracture Fixation, Internal; Fractures, Comminuted; Humans; Torque

This study evaluated whether patients with a left-sided femoral neck fracture (FNF) treated with a sliding hip screw (SHS) had a higher implant failure rate than patients treated for a right-sided FNF. This was performed to determine the clinical relevance of the clockwise rotational torque of the femoral neck lag screw in a SHS, in relation to the rotational stability of left and right-sided FNFs after fixation.. Data were derived from the FAITH trial and Dutch Hip Fracture Audit (DHFA). Patients with a FNF, aged ≥50, treated with a SHS, with at least 3-month follow-up data available, were included. Implant failure was analyzed in a multivariable logistic regression model adjusted for age, sex, fracture displacement, prefracture living setting and functional mobility, and American Society for Anesthesiologists Class.. One thousand seven hundred fifty patients were included, of which 944 (53.9%) had a left-sided and 806 (46.1%) a right-sided FNF. Implant failure occurred in 60 cases (3.4%), of which 31 were left-sided and 29 right-sided. No association between fracture side and implant failure was found [odds ratio (OR) for left vs. right 0.89, 95% confidence interval (CI) 0.52-1.52]. Female sex (OR 3.02, CI: 1.62-6.10), using a mobility aid (OR 2.02, CI 1.01-3.96) and a displaced fracture (OR 2.51, CI: 1.44-4.42), were associated with implant failure.. This study could not substantiate the hypothesis that the biomechanics of the clockwise screw rotation of the SHS contributes to an increased risk of implant failure in left-sided FNFs compared with right-sided fractures.. Therapeutic Level II.See Instructions for Authors for a complete description of levels of evidence.

Topics: Bone Screws; Female; Femoral Neck Fractures; Fracture Fixation, Internal; Hip Fractures; Humans; Torque

The purpose of this study is to determine the biomechanical properties of the bicortical off-axis screw fixation for stabilizing of Pauwels III femoral neck fractures compared with other fixation methods.. Eighteen synthetic femurs (Sawbones Pacific Research Laboratories, Vashon, WA) were divided into three groups. The osteotomy was made vertically to mimic the Pauwels type III femoral neck fracture. Group A (n = 6) was fixed with traditional inverted triangle cannulated screws. Group B (n = 6) was fixed with a unicortical off-axis screw and two parallel cannulated screws. Group C (n = 6) was fixed with a bicortical off-axis screw and two parallel cannulated screws. Each group was tested with a nondestructive axial compression test at a 7° of valgus followed with 1000 cycles of cyclic loading test from 100 N to 1000 N. Finally, a destructive axial compression test was applied until catastrophic failure.. The average axial stiffness from group A to group C was 856.5, 934, and 1340 N/mm, respectively. The average ultimate failure load from group A to group C was 2612.7, 2508.8, and 3706 N, respectively. Group C exhibited significantly greater axial stiffness and a higher ultimate failure load than the other two groups (P < 0.05). Regarding the interfragmental displacement, the values from group A to group C were 0.41, 0.83, 0.36, respectively, and group B exhibited significantly larger fracture gap formation after the cyclic loading test.. The results of this biomechanical study show statistically significant increases in axial stiffness and ultimate failure load for the off-axis screw placed in bicortical fashion. Once the off-axis screw was positioned unicortically, the largest fracture diastasis was observed as compared to the other two methods.

Topics: Artificial Organs; Biomechanical Phenomena; Bone and Bones; Bone Screws; Femoral Neck Fractures; Fracture Fixation, Internal; Humans; Materials Testing; Models, Biological; Simulation Training; Stress, Mechanical; Torque

In undisplaced femoral neck fractures, internal fixation remains the main treatment, with mechanical failure as a frequent complication. As torsional stable fixation promotes femoral neck fracture healing, the Hansson Pinloc® System with a plate interlocking pins, was developed from the original hook pins. Since its effect on torsional stability is undocumented, the novel implant was compared with the original configurations.. Forty-two proximal femur models custom made of two blocks of polyurethane foam were tested. The medial block simulated the cancellous head, while the lateral was laminated with a glass fiber filled epoxy sheet simulating trochanteric cortical bone. Two hollow metal cylinders with a circumferential ball bearing in between mimicked the neck, with a perpendicular fracture in the middle. Fractures were fixated by two or three independent pins or by five configurations involving the interlocking plate (two pins with an optional peg in a small plate, or three pins in a small, medium or large plate). Six torsional tests were performed on each configuration to calculate torsional stiffness, torque at failure and failure energy.. The novel configurations improved parameters up to an average of 12.0 (stiffness), 19.3 (torque) and 19.9 (energy) times higher than the original two pins (P < 0.001). The plate, its size and its triangular configuration improved all parameters (P = 0.03), the plate being most effective, also preventing permanent failure (P < 0.001).. The novel plate design with its pin configuration enhanced torsional stability. To reveal clinical relevance a clinical study is planned.

Topics: Biomechanical Phenomena; Bone Nails; Bone Plates; Cancellous Bone; Cortical Bone; Femoral Neck Fractures; Femur Neck; Fracture Fixation, Internal; Humans; Materials Testing; Models, Biological; Prosthesis Design; Prosthesis Failure; Rotation; Torque

The purpose of this study was to evaluate the maximum insertion torque of cancellous bone screws in osteoporotic proximal femurs with and without the use of washers.. Eight matched pairs of osteoporotic fresh-frozen human cadaveric femurs (age >70 years, all female) were used. Two screws were inserted in each femur either with or without a washer, and maximum insertion torque was measured using a 50 N·m torque transducer. The testing was performed using a customized device, which allowed the torque transducer to apply a constant axial force and rate of rotation to the screws.. In 14 of 16 paired trials, the maximum screw insertion torque was higher when a washer was used. The average maximum torque with a washer was 5.1 N·m compared with 3.1 N·m without a washer (P < 0.01).. The addition of washers increased the maximum insertion torque of cancellous screws in the proximal femur by 65% in this study. Washers prevent the screw heads from penetrating the lateral cortex at low insertion torque loads, and thereby provide for an improved purchase of the screws in the femoral head with a higher maximum insertion torque. We advocate for routine washer use and encourage future clinical studies to further understand the correlation between their use and improved outcomes in this patient population.

Topics: Aged; Biomechanical Phenomena; Bone Screws; Cadaver; Female; Femoral Neck Fractures; Femur; Fracture Fixation, Internal; Humans; Internal Fixators; Osteoporosis; Torque

Fragility hip fractures are increasingly common and hemiarthroplasty is one of the standard treatments. Although a common surgery, it should be performed with great caution because of the poor premorbid and bone quality in this demographic. Intra-operative fractures can occur while attempting press fit of the femoral implant. However; vigilance often steps down once the implant is secured and the hip reduced. This case report reminds surgeons that a large amount of torque can be transmitted during intra-operative positioning, such as during an attempt of hip dislocation. This torque, in addition to the risk factor of osteoporotic bone, can result in iatrogenic fractures. Published literature regarding management of an intra-operative fracture while the prosthetic hip is still reduced is lacking. The authors propose that temporary prophylactic cerclage wiring is a prudent and safe procedure prior to hip dislocation.

Topics: Aged, 80 and over; Bone Wires; Female; Femoral Neck Fractures; Hemiarthroplasty; Hip Dislocation; Humans; Intraoperative Complications; Male; Osteoporotic Fractures; Periprosthetic Fractures; Prosthesis Failure; Risk Factors; Torque

To analyze the extent of postoperative hip abductor insufficiency in primary total hip arthroplasty (THA) patients undergoing anterolateral minimally invasive (ALMI) approach, and to investigate whether the clinical outcomes are more favorable in femoral neck fracture (FNF) patients than in non-femoral neck fracture (nFNF) patients.. A total of 48 patients were enrolled in this study. Each patient underwent a clinical examination preoperatively and 6, 12, 24 and 48 weeks postoperatively. The abductor torque, Trendelenburg's sign, gait velocity, Harris hip score, Oxford hip score, Westren Ontario and McMaster Universities (WOMAC) score and visual analog scale pain score were recorded. Statistical evaluation was performed with SPSS software version 18.0. The significance level was set at P<0.05.. The abductor torque of the operated hip and the recovery ratio showed a gradual improving tendency from 6 weeks postoperatively until the last follow-up. Gait velocity, Harris hip score, Oxford hip score and WOMAC score improved significantly after the operation until 24 weeks postoperatively. In the FNF group, the abductor torque of the operated side and the recovery ratio were significantly higher than in nFNF group at 6 weeks postoperatively, however, as time passed, this trend tended to disappear.. This study demonstrates that patients can obtain good abductor strength and function in the early postoperative period and the hip abductor function of patients who suffer from hip osteoarthritis, rheumatoid arthritis, avascular necrosis of the femoral head could be significantly improved following ALMI THA.

Topics: Aged; Arthroplasty, Replacement, Hip; Femoral Neck Fractures; Hip; Humans; Middle Aged; Minimally Invasive Surgical Procedures; Muscle Strength; Muscle, Skeletal; Prospective Studies; Recovery of Function; Torque

The aim of this study was to compare the biomechanical properties of minimal invasive sliding antirotator compressive hip screw (MIS-A-CHS), and multiple cannulated screws (CS) on a Pauwels type 3 femoral neck fracture model.. A Pauwels type 3 vertical femoral neck fractures was created on 12 third-generation proximal femur models which were divided into two equal groups. The fracture was fixed with three CS in the first group, and MIS-A-CHS in the second group. The axial and rotational stiffness and maximum compression effect were compared between the groups.. The axial and rotational stiffness and maximum compression were significantly higher in MIS-A-CHS group (912.5 N, 540 N and 10.2 N/m, respectively) than the CS group (627.5 N, 380 N, and 3.9 N/m, respectively).. MIS-A-CHS appears to be a more secure fixation method in Pauwels type 3 femoral neck fractures than the CS.

Topics: Biomechanical Phenomena; Bone Screws; Comparative Effectiveness Research; Equipment Failure Analysis; Femoral Neck Fractures; Fracture Fixation, Internal; Hip Joint; Humans; Materials Testing; Models, Anatomic; Torque; Weight-Bearing

Fourth generation composite femurs (4GCFs, models #3406 and #3403) simulate femurs of males <80 years with good bone quality. Since most hip fractures occur in old women with fragile bones, concern is raised regarding the use of standard 4GCFs in biomechanical experiments. In this study the stability of hip fracture fixations in 4GCFs was compared to human cadaver femurs (HCFs) selected to represent patients with hip fractures. Ten 4GCFs (Sawbones, Pacific Research Laboratories, Inc., Vashon, WA, USA) were compared to 24 HCFs from seven females and five males >60 years. Proximal femur anthropometric measurements were noted. Strain gauge rosettes were attached and femurs were mounted in a hip simulator applying a combined subject-specific axial load and torque. Baseline measurements of resistance to deformation were recorded. Standardized femoral neck fractures were surgically stabilized before the constructs were subjected to 20,000 load-cycles. An optical motion tracking system measured relative movements. Median (95% CI) head fragment migration was 0.8mm (0.4 to 1.1) in the 4GCF group versus 2.2mm (1.5 to 4.6) in the cadaver group (p=0.001). This difference in fracture stability could not be explained by observed differences in femoral anthropometry or potential overloading of 4GCFs. 4GCFs failed with fracture-patterns different from those observed in cadavers. To conclude, standard 4GCFs provide unrealistically stable bone-implant constructs and fail with fractures not observed in cadavers. Until a validated osteopenic or osteoporotic composite femur model is provided, standard 4GCFs should only be used when representing the biomechanical properties of young healthy femurs.

Topics: Aged; Biomechanical Phenomena; Cadaver; Female; Femoral Neck Fractures; Femur; Fracture Fixation, Internal; Hip Fractures; Humans; Male; Materials Testing; Middle Aged; Models, Anatomic; Motion; Torque

Internal fixation of fractures using plates and screws is a common method of treatment. Occasionally the internal fixation fails prior to fracture healing. This often requires revision surgery. Determining the force that internal fixation needs to withstand postoperatively would enable this force to be applied intraoperatively as a test to predict successful fixation. The purpose of the present paper was to determine the minimum stripping torque needed to predict successful internal fixation strength.. The pull-out strength and stripping torque relationships of 4.5-mm cortical bone screws in Sawbones polyurethane foam were determined. Screw forces were directly measured using an LCM load cell washer on a model intertrochanteric neck of femur fracture fixed with 135 degrees 4-hole pin and plate loaded to single leg stance conditions. Additionally a 135 degrees 4-hole pin and plate was mounted on foam blocks and loaded until failure of the shaft screws from the foam occurred. Predicted stripping torque/yield load was determined.. Pull-out strength and stripping torque of 4.5-mm cortical bone screws in polyurethane foam have a high degree of linear correlation R(2) = 0.95. Direct measurement of shaft screw forces at single leg stance conditions were 585-686 N. This correlated with a stripping torque of 0.9 Nm. Load to yield testing at single leg stance conditions corresponded to a stripping torque of 1.8 Nm.. Withstanding 0.9-1.8 Nm of torque during insertion of the femoral shaft screws of a 135 degrees 4-hole pin and plate predicts that the construct will successfully withstand single leg stance.

Topics: Bone Nails; Bone Plates; Equipment Failure Analysis; Femoral Neck Fractures; Fracture Fixation, Internal; Humans; Torque

Displacement of internally fixed femoral neck fractures due to implant migration is a common problem. This in vitro study was performed to compare maximum torque and holding power for five different implants.. Synthetic porous material with low, medium or high density was used to simulate cancellous bone. The tested implants included three conventional screws (AO, Olmed, Hansson), one screw with threads and a barb (Hybrid), and a pin with a hook (LIH).. The Hansson screw provided higher maximum torque in low and medium density blocks when compared with the other implants (p < 0.0001) followed by LIH, Hybrid, Olmed, and AO. For high-density blocks there was no significant difference between Hansson and Hybrid screws, both with significantly higher torque than the other implants. The maximal pullout in low-density blocks differed significantly between all five implants with the Hansson screw providing the highest holding power. For medium and high-density blocks the conventional screws had significantly higher pullout resistance compared with the Hybrid and LIH.. The in vitro model used seemed to provide reproducible and clinically relevant results. There was a good correlation between material density and holding power for all implants. Screws inserted without predrilling provided higher maximal torque while maximal pull out load seemed less affected by predrilling being used or not.

Topics: Bone Density; Bone Screws; Femoral Neck Fractures; Fracture Fixation, Internal; Humans; Torque