Synthetic Femur Models Research Articles

Multiplanar Semicircular New-Generation Implant System Developed for Proximal Femur Periprosthetic Fractures: A Biomechanical Study

Background and Objectives: The study aimed to evaluate a newly designed semicircular implant for the fixation of Vancouver Type B1 periprosthetic femoral fractures (PFFs) in total hip arthroplasty (THA) patients. To determine its strength and clinical applicability, the new implant was compared biomechanically with conventional fixation methods, such as lateral locking plate fixation and a plate combined with cerclage wires. Materials and Methods: Fifteen synthetic femur models were used in this biomechanical study. A Vancouver Type B1 periprosthetic fracture was simulated by osteotomy 5 mm distal to the femoral stem. The models were divided into three groups: Group I (lateral locking plate fixation), Group II (lateral locking plate with cerclage wires), and Group III (new semicircular implant system). All fixation methods were subjected to axial loading, lateral bending, and torsional force testing using an MTS biomechanical testing device. Failure load and displacement were measured to assess stability. Results: The semicircular implant (Group III) demonstrated a significantly higher failure load (778.8 ± 74.089 N) compared to the lateral plate (Group I: 467 ± 68.165 N) and plate with cerclage wires (Group II: 652.4 ± 65.474 N; p < 0.001). The new implant also exhibited superior stability under axial, lateral bending, and torsional forces. The failure load for Group III was more robust, with fractures occurring at the screw level rather than plate or screw detachment. Conclusions: Compared to traditional fixation methods, the newly designed semicircular implant demonstrated superior biomechanical performance in stabilizing Vancouver Type B1 periprosthetic femoral fractures. It withstood higher physiological loads, offered better structural stability, and could be an alternative to existing fixation systems in clinical practice. Further studies, including cadaveric and in vivo trials, are recommended to confirm these results and assess the long-term clinical outcomes.

Population-specific femur models: A step towards improved osteosynthetic biomechanical testing in orthopaedics

BackgroundBiomechanical testing using synthetic bone surrogates has become a standard method for evaluating osteosynthesis techniques. However, these surrogates often fail to account for population-specific variations in bone anatomy and mechanical properties, leading to limitations in predicting clinical outcomes. This study addresses this gap by developing and validating a population-specific synthetic femur model for older women of European ethnicity, incorporating variations in geometry and mechanics observed in this demographic. MethodsThe femur model was developed using a statistical shaping algorithm and 3D models from women aged 75 to 85 years. Synthetic femora were fabricated using polyurethane, enriched with fillers and additives to mimic osteoporotic bone characteristics. Mechanical testing, including axial compression, four-point bending, and torsion, was performed on synthetic femora and were validated against human osteoporotic femora. FindingsThe synthetic femora demonstrated comparable mechanical properties to human osteoporotic femora, particularly in flexural and torsional rigidity. Axial stiffness was slightly lower in the synthetic femora but remained within the range of literature values. Statistical analysis revealed significant differences between synthetic and human bones in certain parameters, highlighting the need for population-specific models. InterpretationThe developed synthetic femur model offers a promising solution for addressing the limitations of current bone surrogates in biomechanical testing. By incorporating population-specific characteristics these models provide a more accurate representation of human bone, improving the validity of biomechanical evaluations and potentially leading to more equitable treatment outcomes in orthopaedics. Further research is warranted to explore the applicability of these models across different populations and anatomical sites.

Efficacy of poller screw in addition to lag screw in the treatment of intertrochanteric fractures with proximal femoral nail: a biomechanical evaluation.

The most common type of failure in treating intertrochanteric fractures with proximal femoral nails is cut-out due to varus collapse. We aim to evaluate the effect of the poller screw applied to the proximal fragment and the lag screw on varus collapse and stability in intertrochanteric fractures. An unstable intertrochanteric fracture model without medial support was simulated in 20 synthetic femur models. In the poller screw group, in addition to the lag screw, pole screws were applied to the proximal fragment superior and inferior to the lag screw. In the progressive cyclic loading test, starting from 100 N, the loading was increased by 50 N in each cycle, and the test was continued until the maximum load at which failure occurred as a result of conditioning cycles and progressive cyclic loading tests, stiffness, type of failure, force at failure, lag screw displacement, and varus collapse were recorded. The average stiffness was found to be 124.705 N/mm in the poller screw group and 102.77 N/mm in the control group (P < 0.001). The maximum load to failure was 1897.10 N in the poller screw group and 1475.20 N in the control group (P < 0.001). The average displacement of the lag screw within the femoral head was 0.85mm in the poller screw group and 3.60mm in the control group (P < 0.001). As a result, it has been shown that poller screws applied around the lag screw increase fixation stiffness and reduce varus collapse.

Intercalary reconstruction of long bones by massive allograft: Comparison of construct stability ensured by three different host-graft junctions and two types of fixations in a synthetic femur model.

An intercalary segmental allograft is an option for limb salvage in bone tumours. Stable and congruent intercalary reconstructions are a prerequisite for achieving host-graft union. However, a too rigid fixation could increase the risk of late complications correlated with negative bone remodelling. This study compared the reconstruction stiffness achieved by three different host-graft junctions, namely, end-to-end, modified step-cut, and taper. A low-stiffness bone plate was used as the fixation method, except for the taper junction where a low-stiffness intramedullary nail was also used to investigate the effects of different types of fixation on construct stiffness. Composite femora were tested under four loading conditions to determine coronal and sagittal bending stiffness, as well as torsional stiffness in opposite directions. Stiffness values were expressed as a percentage of intact host bone stiffness (%IBS). While a reduction of coronal bending stiffness was found with taper junctions (76%IBS) compared with the high values ensured by end-to-end (96%IBS) and modified step-cut junctions (92%IBS), taper junctions significantly increased stiffness under sagittal bending and torsion in intra- and extra-direction: end-to-end 29%IBS, 7%IBS, 7%IBS, modified step-cut 38%IBS, 20%IBS, 21%IBS, and taper junction 52%IBS, 55%IBS, 56%IBS, respectively. Construct stiffness with taper junctions was decreased by 11–41%IBS by replacing the bone plate with an intramedullary nail. Taper junctions can be an alternative to achieve intercalary reconstructions with more homogeneous and, in three out of four loading conditions, significantly higher construct stability without increasing bone plate stiffness. The risk of instability under high torsional loads increases when taper junctions are associated with a low-stiffness intramedullary nail.

Biomechanical comparison of four different fixation methods in the management of Pauwels type III femoral neck fractures: Is there a clear winner?

BackgroundCannulated screws augmented with the medial buttress plate could confer greater biomechanical stability and higher union rates than the screw fixation alone for treating young patients with Pauwels type III femoral neck fractures (FNFs). No study has evaluated the effects of distal bicortical screw fixation and biomechanical properties of buttress plate augmentation under simultaneous vertical and rotational forces, physiologically acting on the hip joint. This study aimed to compare the biomechanical properties of four methods of three cannulated screw fixation under the combined axial and torsional loading in a synthetic femur model of type III FNF. MethodsTwenty-four third-generation composite femora were divided into four groups (6 femora in each group) based on the screw fixation configuration: inverted triangle configuration (Group A), Pauwels' configuration (Group B), inverted triangle configuration combined with medial buttress plate using distal unicortical (Group C), and distal bicortical screw placement (Group D). A Pauwels type III FNF was simulated on the sawbones. Each model was subjected to the combined axial and torsional cyclic loading and subsequently tested to failure. ResultSignificant differences were determined in axial stiffness (AS) among the four groups (p = 0.024), whereas there was no significant difference in torsional stiffness (p = 0.147). The mean AS was higher in group D (639.5 ± 86.2 N/mm) than in group A (430.6 ± 94.8 N/mm), group B (426.2 ± 41.9 N/mm), and group C (451.2 ± 156.7 N/mm). Failure forces (FFs) were significantly different among four groups (p = 0.007), while there was no considerable difference in failure moment values (p = 0.555). The mean FF was significantly higher in group D (1307.1 ± 96.4 N) than in group A (1076.9 ± 371.2 N) and group B (1075.5 ± 348.3 N) (p = 0.014 and p = 0.018, respectively). There was no significant difference in the mean FF between groups D and C. ConclusionRegardless of the medial plate use, multiple cannulated systems could provide similar biomechanical results regarding torsional stiffness and failure moments. Bicortical placement of the most distal screw in medial buttress plate application could improve axial stability but not significantly affect the rotational stability of the inverted triangle screw fixation system in managing type III FNFs.

A Novel Fluoroscopic View for Improved Assessment of the Safety of the Posterosuperior Screw in Femoral Neck Fracture Fixation.

The purpose of the present study was to determine specific fluoroscopic views of the femoral neck to accurately identify partially extraosseous ("in-out-in"; IOI) placement of the posterosuperior screw for fixation of femoral neck fractures. A 3.2-mm guide pin was placed in the posterosuperior aspect of 2 synthetic femur models: 1 entirely intraosseous and 1 IOI. Sequential fluoroscopic images were made at 5° intervals in order to identify which fluoroscopic projections identified IOI guide pin placement. These images were utilized to inform screw placement and assessment in the second phase of the study, which involved the use of cadaveric specimens. In Phase II, the posterosuperior screw of the inverted triangle was placed in 10 cadaveric specimens with use of a standard posteroanterior fluoroscopic view and 1 of 2 lateral views, either (1) neck in line with the shaft, i.e., 0° lateral; or (2) a -15° rollunder view. The final fluoroscopic views (i.e., the posteroanterior and multiple lateral and oblique views) were randomized and blinded for review by 10 orthopaedic residents and 5 attending orthopaedic traumatologists. Specimens were stripped of soft tissue and inspected for screw perforation. Overall accuracy of respondents was 68.8%, with no difference between the attending traumatologists (71.8%) and resident surgeons (67.4%; p = 0.173). Interobserver reliability was moderate (κ = 0.496). Dissection identified that 4 (40%) of 10 screws were extraosseous. All of the extraosseous screws were placed with use of the 0° lateral view. The -15° rollunder lateral view was the most sensitive (81.7%) and specific (92.2%) view for identifying IOI screw placement. Surgeons often utilize the standard posteroanterior and 0° lateral fluoroscopic views to safely place screws; however, many of these screws are IOI. The addition of a -15° rollunder lateral view significantly improved identification of IOI screws in the posterosuperior femoral neck. Unidentified IOI screw placement may result in damage to the blood supply of the femoral head.

Biomechanical comparison of medial sustainable nail and proximal femoral nail antirotation in the treatment of an unstable intertrochanteric fracture.

AimsRestoration of proximal medial femoral support is the keystone in the treatment of intertrochanteric fractures. None of the available implants are effective in constructing the medial femoral support. Medial sustainable nail (MSN-II) is a novel cephalomedullary nail designed for this. In this study, biomechanical difference between MSN-II and proximal femoral nail anti-rotation (PFNA-II) was compared to determine whether or not MSN-II can effectively reconstruct the medial femoral support.MethodsA total of 36 synthetic femur models with simulated intertrochanteric fractures without medial support (AO/OTA 31-A2.3) were assigned to two groups with 18 specimens each for stabilization with MSN-II or PFNA-II. Each group was further divided into three subgroups of six specimens according to different experimental conditions respectively as follows: axial loading test; static torsional test; and cyclic loading test.ResultsThe mean axial stiffness, vertical displacement, and maximum failure load of MSN-II were 258.47 N/mm (SD 42.27), 2.99 mm (SD 0.56), and 4,886 N (SD 525.31), respectively, while those of PFNA-II were 170.28 N/mm (SD 64.63), 4.86 mm (SD 1.66), and 3,870.87 N (SD 552.21), respectively. The mean torsional stiffness and failure torque of MSN-II were 1.72 N m/° (SD 0.61) and 16.54 N m (SD 7.06), respectively, while those of PFNA-II were 0.61 N m/° (SD 0.39) and 6.6 N m (SD 6.65), respectively. The displacement of MSN-II in each cycle point was less than that of PFNA-II in cyclic loading test. Significantly higher stiffness and less displacement were detected in the MSN-II group (p < 0.05).ConclusionThe biomechanical performance of MSN-II was better than that of PFNA-II, suggesting that MSN-II may provide more effective mechanical support in the treatment of unstable intertrochanteric fractures.Cite this article: Bone Joint Res 2020;9(12):840–847.

A Biomechanical Comparison of Trochanteric Versus Piriformis Reconstruction Nails for Femoral Neck Fracture Prophylaxis.

To compare piriformis fossa to greater trochanteric entry cephalomedullary implants in an evaluation of femoral neck load to failure when the device is used for femoral shaft fractures with prophylaxis of an associated femoral neck fracture. Thirty fourth-generation synthetic femur models were separated into 5 groups: intact femora, entry sites alone at the piriformis fossa or greater trochanter, and piriformis fossa and greater trochanteric entry sites after the insertion of a cephalomedullary nail. Each model was mechanically loaded with a flat plate against the superior femoral head along the mechanical axis and load to failure was recorded. Mean load to failure was 5487 ± 376 N in the intact femur, 3126 ± 387 N in the piriformis fossa entry site group, 3772 ± 558 N in the piriformis entry nail, 5332 ± 292 N for the greater trochanteric entry site, and 5406 ± 801 N for the greater trochanteric nail group. Both piriformis groups were significantly lower compared with the intact group. Both greater trochanteric groups were similar to the intact group and were statistically higher than the piriformis groups. A piriformis fossa entry site with or without an intramedullary implant weakens the femoral neck in load to failure testing. A greater trochanteric entry yields a load to failure equivalent to that of an intact femoral neck. Instrumentation with a greater trochanteric cephalomedullary nail is significantly stronger than a piriformis fossa cephalomedullary nail during axial loading in a composite femur model.

Sequential fluoroscopic rollover images reliably identify "in-out-in" posterosuperior screws during percutaneous fixation of femoral neck fractures.

Percutaneous screws placed into the posterosuperior femoral neck are frequently extraosseous or "in-out-in" (IOI). These IOI screws are not readily identifiable on anteroposterior (AP) and lateral fluoroscopic images. The purpose of this study was to examine the ability of surgeons to identify IOI guide pins using sequential fluoroscopic rollover images. A 3.2-mm guide pin was placed into the posterosuperior quadrant of eleven synthetic femur models. Five samples were "all-in" (AI), and six were IOI. Sequential fluoroscopic rollover images were obtained starting with an AP image, then images at 10-degree rollover intervals ending with a direct lateral image. Images were reviewed in a blinded fashion by five attending orthopedic trauma surgeons and 20 resident surgeons to determine whether guide pins were AI or IOI. Accuracy, interobserver reliability, sensitivity, and specificity were assessed. The overall accuracy of responses was 86% with no difference between attending trauma surgeons and residents (p = 0.5). The sensitivity and specificity for an IOI guide pin were 98.0% and 71.2%, respectively. Interobserver reliability among surgeons was good (κ = 0.703). The use of the sequential fluoroscopic rollover images after placement of the posterosuperior guide pin into the femoral neck was highly sensitive for detecting an IOI position. The 40-degree rollover image was the best view to evaluate the proximity of the guide pin to the posterior cortex.

An Affordable Knee Arthroscopy Simulator

Abstract: Introduction: The objective of this study is to describe a model of knee arthroscopy simulator that is affordable, low-cost and easily reproducible, aiming to enable the diffusion of more effective active teaching and training methodologies. Methods: For the creation of the arthroscopic camera, an endoscopic camera for mobile phones and computers model SXT-5.0M manufactured by KKMOON were used. The camera was introduced in a metal tube, which was coupled to a set of three 20 mm PVC hydraulic connectors to simulate the handle and sleeve of the arthroscope. The camera has a resolution of 1280 x 720 pixels and is equipped with six built-in white LED lamps, simulating and eliminating the need to use an additional light source. The knee model was developed using a PVC pipe fixed on a wooden support, to which synthetic femur and tibia models were affixed. Four three-centimeter diameter holes, compatible with the standard arthroscopic portals, were made in the body of the PVC pipe. For the menisci, a model was made out of modeling clay (Corfix®), until the anatomical structures were close to the real ones. The model consists of both menisci and the intercondylar eminence, simulating the proximal tibial articular surface. The model made out of modeling clay was the basis for the production of a thin Crystal Polyester Resin mold. Using the resin mold, the meniscal models were made of Silicone Rubber Type II, widely used in industry and crafts. Results: A functional and reproducible simulator was obtained, consisting of a knee model and an arthroscopic camera. The simulator works adequately adapted to a TV, monitor or computer, and allows the simulation of diagnostic procedures, meniscectomy and meniscoplasty. Conclusion: It is possible to develop a knee arthroscopy simulator, with components available in local and electronic commerce, at a cost of approximately R$ 300.

An Affordable Knee Arthroscopy Simulator

Abstract: Introduction: The objective of this study is to describe a model of knee arthroscopy simulator that is affordable, low-cost and easily reproducible, aiming to enable the diffusion of more effective active teaching and training methodologies. Methods: For the creation of the arthroscopic camera, an endoscopic camera for mobile phones and computers model SXT-5.0M manufactured by KKMOON were used. The camera was introduced in a metal tube, which was coupled to a set of three 20 mm PVC hydraulic connectors to simulate the handle and sleeve of the arthroscope. The camera has a resolution of 1280 x 720 pixels and is equipped with six built-in white LED lamps, simulating and eliminating the need to use an additional light source. The knee model was developed using a PVC pipe fixed on a wooden support, to which synthetic femur and tibia models were affixed. Four three-centimeter diameter holes, compatible with the standard arthroscopic portals, were made in the body of the PVC pipe. For the menisci, a model was made out of modeling clay (Corfix®), until the anatomical structures were close to the real ones. The model consists of both menisci and the intercondylar eminence, simulating the proximal tibial articular surface. The model made out of modeling clay was the basis for the production of a thin Crystal Polyester Resin mold. Using the resin mold, the meniscal models were made of Silicone Rubber Type II, widely used in industry and crafts. Results: A functional and reproducible simulator was obtained, consisting of a knee model and an arthroscopic camera. The simulator works adequately adapted to a TV, monitor or computer, and allows the simulation of diagnostic procedures, meniscectomy and meniscoplasty. Conclusion: It is possible to develop a knee arthroscopy simulator, with components available in local and electronic commerce, at a cost of approximately R$ 300.

Retrograde Stainless Steel Flexible Nails Have Superior Resistance to Bending in Distal Third Femoral Shaft Fractures.

It has been shown that retrograde titanium flexible intramedullary nails (Ti FIN) provide superior resistance to bending compared to antegrade Ti FIN in distal femur fractures. The purpose of this study was to compare resistance to torsional and bending forces of stainless steel (SS) FIN, with or without a locking screw, and Ti FIN in distal third femoral shaft fractures. We hypothesize that locked retrograde SS FIN will demonstrate greater resistance to both bending and torsional forces. Thirty adolescent synthetic femur models were used to simulate transverse distal femoral fractures at either 60 mm or 90 mm proximal to the distal femoral physis. The femurs were instrumented with antegrade Ti FIN, antegrade SS FIN, retrograde Ti FIN, retrograde SS FIN, or retrograde locked SS FIN. Three models for each construct at both osteotomy levels were tested. Models were analyzed to determine maximum resistance to bending and torsion. In fractures 60 mm from the physis, retrograde SS FIN demonstrated statistically superior resistance to bending when compared with both antegrade and retrograde Ti FIN (P=0.001 and 0.008, respectively) and antegrade SS FIN (P=0.0001). Locked SS constructs showed a trend towards greater resistance to bending forces when compared with unlocked constructs (P>0.05). No significant difference was seen in resistance to bending when fractures were 90 mm proximal to the distal femoral physis between the five groups. No significant differences were observed in resistance to torsion in either the proximal or distal fracture models, regardless of construct type. Retrograde SS FIN confer significantly greater resistance to bending forces for fractures 60 mm proximal to the distal femoral physis compared with Ti FIN or antegrade entry SS FIN. In fractures 90 mm from the physis, no differences were noted in our model. Our results support the use of retrograde SS nails in the pediatric patient with distal femoral shaft fractures. Level II-comparative biomechanical study.

Are piriformis reconstruction implants ideal for prophylactic femoral neck fixation?

ObjectivesProphylactic femoral neck fixation may be performed in the setting of geriatric diaphyseal femur fracture, pathologic or impending atypical femur fractures. Fixation constructs often utilize cephalomedullary implants with one or two proximal interlocking screws into the femoral head/neck. Variations in proximal femoral anatomy and implant design can interfere with the placement of two screws in the femoral head and neck. Our objective was to assess the strength of piriformis entry reconstruction implants with one versus two proximal interlock screws for prophylactic femoral neck fixation. MethodsThirty fourth generation synthetic femur models were separated into 5 groups. The control group was an intact femur, and the second group was an intact femur with an entry hole in the piriformis fossa. The remaining groups had an intramedullary nail placed with either 0, 1, or 2 screws placed into the femoral head and neck. Each femur was mechanically loaded along the mechanical axis through the femoral head. Load to failure and failure displacement were recorded. ResultsMean load to failure was 5583 ± 543 N in the intact femur. Constructs with 2 screws had a significantly higher mean load to failure (3223 ± 474 N) compared to one screw constructs (2368 ± 280 N). All of the experimental groups remained significantly lower than the intact femur model (p < 0.05). ConclusionOur results demonstrate that piriformis entry reconstruction implants have a significantly lower load to failure compared to an intact femur irrespective of screw construct. Further studies are needed to investigate this potential iatrogenic weakening.

Evaluating the use of an electronic inclinometer in correcting rotational disorders of the hip in children

BackgroundFemoral derotation osteotomies are commonly performed to correct rotational disorders of the hip in children. Surgical correction is typically assessed visually with the use of a goniometer or osteotomy template, but these methods have been shown to be inaccurate. In this study, we aimed to determine the accuracy of an electronic inclinometer in performing derotation osteotomies of 2 different magnitudes in comparison to commonly used visual techniques. MethodsWe performed derotation osteotomies of 15°and 30° in a synthetic femur model using a goniometer, triangle osteotomy template, and electronic inclinometer. The degree of derotation was assessed by computed tomography (CT) and measured by a musculoskeletal radiologist. Statistical analyses included descriptive statistics, as well as t-test, analysis of variance (ANOVA), and Fisher’s exact test to determine differences between osteotomy techniques. ResultsWe performed 40 proximal femoral derotation osteotomies. The mean difference from the planned derotation was 5.9° for the goniometer technique, 3.8° for the osteotomy triangle technique, and 3.2° for the electronic inclinometer technique (p-value = 0.048). There was no difference between the techniques for 15° derotation osteotomies (p-value = 0.28); however, there was a trend towards significance for 30° derotation osteotomies (p-value = 0.07). Fewer osteotomies had a difference greater than 3° from the planned derotation using the electronic inclinometer technique (p-value = 0.04). ConclusionsThe accuracy of derotation osteotomies can be improved with the use of an electronic inclinometer. This technology has the potential to improve surgical technique, minimize surgical error, and possibly improve patient outcomes.

Ordinary Cannulated Compression Screws or Headless Cannulated Compression Screws? A Synthetic Bone Biomechanical Research in the Internal Fixation of Vertical Femoral Neck Fracture.

Purpose The purpose of this study is to verify whether the headless cannulated compression screw (HCCS) has higher biomechanical stability than the ordinary cannulated compression screw (OCCS) in the treatment of vertical femoral neck fractures. Materials and Methods 30 synthetic femur models were equally divided into 2 groups, with 50°, 60°, and 70° Pauwels angle of femoral neck fracture, under 3D printed guiding plates and C-arm fluoroscopic guidance. The femur molds were fixed with three parallel OCCSs as OCCS group and three parallel HCCSs as HCCS group. All specimens were tested for compressive strength and maximum load to failure with a loading rate of 2 mm/min. Results The result showed that there was no significant difference with the compressive strength in the Pauwels angle of 50° and 60°. However, we observed that the maximum load to failure with the Pauwels angle of 50°, 60°, and 70° and the compressive strength with 70° of HCCS group showed better performance than the OCCS group. Conclusion HCCS performs with better biomechanical stability than OCCS in the treatment of vertical femoral neck fracture, especially with the Pauwels angle of 70°.

Biomechanical comparison of oblique and step-cut osteotomies used in total hip arthroplasty with femoral shortening

Various types of shortening osteotomies and prosthesis are used for femoral reconstruction in total hip arthroplasty of the high hip dislocation. This biomechanical study investigates whether step-cut osteotomies result in better stability than oblique osteotomies and cylindrical femoral stems enhance stability of the osteotomy more than conical stems, and which osteotomy and prosthesis type maintain the stability better after cyclical loading. Oblique and step-cut shortening osteotomies were compared under axial and rotational forces, using synthetic femur models and conical or cylindrical femoral prostheses. The models underwent cyclic loading for 10,000 cycles at 3Hz (100-1000N axial bending or 0.5-10Nm torque). After the completion of cyclic loading, the models were loaded until failure. Stiffness values before and after cyclical loading, and failure loads were the outcome parameters. Relative displacements at the osteotomy sites were also measured using 3-Dimensions Digital Imaging Correlation System. The mean failure load was significantly higher in conical prosthesis groups under axial forces. In torsion tests, the mean stiffness of conical prosthesis groups after cyclical loading was higher in oblique osteotomies. The other parameters were similar between the groups. According to the results of the study, although some individual statistically significant parameters were obtained, step-cut osteotomies, which are technically challenging procedures, were not found biomechanically superior to oblique osteotomies, with neither conical nor cylindrical prostheses.

Biomechanical Comparison of 2 Different Femoral Stems in the Shortening Osteotomy of the High-Riding Hip

BackgroundWe hypothesized that a rectangular cross-sectional femoral stem may produce more initial stability of the transverse subtrochanteric femoral shortening osteotomy rather than a circular cross-sectional stem. MethodsTwenty, fourth-generation, synthetic femur models were inserted with either circular or rectangular cross-sectional femoral stems after 3 cm of transverse subtrochanteric shortening. Half of the models were tested with axial bending and the other half with torsional loads. After the femora underwent cyclic loading, they were loaded until failure. Outcome parameters were stiffness values before and after cyclical loading, failure loads/torques, and displacements at the osteotomy sites. ResultsIn axial bending tests, the results were not significantly different between the groups. Under rotational forces, the mean stiffness value before cyclical loading and failure torque of the cylindrical stems was significantly higher than that of rectangular cross-sectional stems (11.8 ± 1.2 vs 7.1 ± 2.8 Nm/degree; P = .009 and 136.9 ± 60.2 vs 27.1 ± 17.5 Nm; P = .027 Nm, respectively). The mean amounts of displacements at the osteotomy sites were not significantly different between the groups in any direction in both axial and rotational tests. ConclusionsAccording to the results of the study, using straight, cylindrical femoral stems can increase rotational stability of the transverse osteotomy more than the rectangular cross-sectional stems although the latter one has the advantages of rectangular geometrical design.

Biomechanical comparison of semi-rigid pediatric locking nail versus titanium elastic nails in a femur fracture model.

BackgroundThe treatment for length-unstable diaphyseal femur fractures among school-age children is commonly intramedullary elastic nails, with or without end caps. Another possible treatment is the semi-rigid pediatric locking nail (PLN). The purpose of this biomechanical study was to assess the stability of a length-unstable oblique midshaft fracture in a synthetic femur model stabilized with different combinations of intramedullary elastic nails and with a PLN.MethodsTwenty-four femur models with an intramedullary canal diameter of 10.0 mm were used. Three groups with various combinations of titanium elastic nails (TEN) with end caps and one group with a PLN were tested. An oblique midshaft fracture was created, and the models underwent compression, rotation, flexion/extension, and a varus/valgus test, with 50 and 100 % of the forces generated during walking in corresponding planes.ResultsWe present the results [median (range)] from 100 % loading during walking. In axial compression, the PLN was less shortened than the combination with two 4.0-mm TEN [by 4.4 (3.4–5.4) mm vs. 5.2 (4.8–6.6) mm, respectively; p = 0.030]. No difference was found in shortening between the PLN and the four 3.0-mm TEN [by 7.0 (3.3–8.4) mm; p = 0.065]. The two 3.0-mm TEN did not withstand the maximum shortening of 10.0 mm. In external rotation, the PLN rotated 12.0° (7.0–16.4°) while the TEN models displaced more than the maximum of 20.0°. No model withstood a maximal rotation of 20.0° internal rotation. In the four-point bending test, in the coronal and the sagittal plane, all combinations except the two 3.0-mm TEN in extension withstood the maximum angulation of 20.0°.ConclusionsPLN provides the greatest stability in all planes compared to TEN models with end caps, even though the difference from the two 4.0-mm or four 3.0-mm TEN models was small.

Tunnel Intersection in Combined Anatomic Reconstruction of the ACL and Posterolateral Corner

Femoral tunnel intersection in combined anterior cruciate ligament and posterolateral corner reconstruction has been reported to be high. The purpose of this study was to examine the risk of intersection between an anatomic femoral anterior cruciate ligament tunnel created with a retrograde reaming device and femoral lateral collateral ligament reconstruction tunnels of varying trajectory in a synthetic femur model.

Accuracy study of new computer-assisted orthopedic surgery software

PurposeThe new computerized system is based on image analysis and designed to aid in orthopedic surgeries by virtual trajectory of the guide wire, intra-operative planning and various measurements. Validation of the accuracy and safety of any computer-aided surgery system is essential before implementing it clinically. We examined the accuracy of guide-wire length and angle measurements and fusion of multiple adjacent images (panoramic view image, PVI®) of the new software. MethodsThis is a 2-part study. Part I: twenty guide wires were drilled to various depths in a synthetic femur model and the results obtained by the software measurements were compared with manual measurements by a caliper and a depth gauge. Part II: a sawbone femur shaft was osteotomized and various inclinations of >10° to the varus or valgus angles were tested. The manually obtained measurements of angles and lengths were compared to the new computerized system software PVI. ResultsThere was a significant positive linear correlation between all groups of the computerized length and the control measurements (r>0.983, p<0.01). There was no significant difference among different distances, angles or positions from the image intensifier. There was a significant positive linear correlation between the angle and length measurement on the PVI and the control measurement (r>0.993, p<0.01). ConclusionsThe new computerized software has high reliability in performing measurements of length using an aiming, positioning and referring device intra-operatively.