Lateral Femoral Shaft Research Articles

Load Sharing in the Femur Using Strut Allografts: A Biomechanical Study.

BackgroundFemoral strut allografts are used in revision hip arthroplasty for management of bone loss associated with implant failure or periprosthetic fractures. They have also been used to treat unremitting thigh pain in well-fixed cementless femoral stems, to address the differential in structural stiffness between the stem and femoral shaft. Our study used an in vitro biomechanical model to measure the effect of placement of allografts on femoral strains, to determine their load-sharing capacity.Material and methodsThree rosette strain gauges were applied to the femoral surface of each of 6 cadaveric femurs, at the stem tip level on anterior, medial, and lateral cortices. After stem implantation, cortical strut allografts were applied to the lateral femoral shaft and secured with 4 Dall-Miles cables. A fourth gauge was placed on the midpoint of the allograft. Strains were recorded in the intact femur, then the implanted femur with and without the allograft under simulated physiologic loading in a load frame.ResultsReduction in distal femoral principal strains, between 12% and 59%, was seen in all cortices following placement of the allograft. Under axial loading, 30% of the strain in the lateral cortex was borne by the allograft. Greater reductions in strain, by as much as 59%, occurred under axial load and torque.ConclusionThe results of this biomechanical model indicate that by placement of an allograft, cortical strains can be reduced to levels approaching those in an intact femur, supporting this technique for treatment of unremitting thigh pain in well-fixed prostheses.

Proximal external femoral torsion increases lateral femoral shaft bowing: a study based on 3D CT reconstruction models.

Femoral bowing influences the genesis and management of knee osteoarthritis (OA). The aim of this study was to investigate the relationship between the femoral torsion angle (FTA) and femoral bowing angle (FBA) in a southern Chinese population. It was hypothesized that a greater FTA would lead to a greater lateral FBA. A total of 381 lower extremities from 381 osteoarthritic patients (298 women, 83 men; 201 left, 180 right; mean age 66.5 ± 8.9years) were retrospectively reviewed. Age, sex, body mass index (BMI), side, height, femoral length (FL), hip-knee-ankle angle (HKA) and FTA were set as FBA-related factors. The three-dimensional (3D) FBA, the angle between the anatomical axis of the proximal femur and the anatomical axis of the distal femur in the plane they form, and its projection on the coronal (lateral FBA) and sagittal (anterior FBA) planes were measured on 3D computed tomography (CT) models. The correlation of the 3D, lateral and anterior FBAs with each of the FBA-related factors was explored using multiple linear regression analysis. The correlation between the FBA and FTA was explored and verified after using propensity score matching to control for the other FBA-related factors. The mean lateral and anterior FBAs were 5.5°, with 53.5% greater than 5°, and 12.7°, with 70.3% greater than 11°, respectively. 3D FBA was positively correlated with age (Std.Co = 0.113, P < 0.05) and HKA (Std.Co = 0.129, P < 0.05). Lateral FBA was positively correlated with age (Std.Co = 0.118, P < 0.05), female sex (Std.Co = 0.206, P < 0.05), HKA (Std.Co = 0.184, P < 0.05) and FL (Std.Co = 0.220, P < 0.05). Anterior FBA was positively correlated with age (Std.Co = 0.108, P < 0.05) and male sex (Std.Co = 0.108, P < 0.05). When the related factors were balanced between the two groups (NS), FTA did not significantly affect 3D FBA or anterior FBA (NS), while FTA was positively correlated with lateral FBA (Std.Co = 0.165, P < 0.05). External torsion of the proximal femur increases the lateral FBA by twisting a partial anterior FBA into a lateral FBA, especially in the female population. If a patient is found to have a large lateral FBA preoperatively, one should be alert to the possibility of a concomitant large FTA, as there are implications for femoral orthopedics, TKA and patellofemoral pressure distribution. III.

Femoral Bowing and Femoral Neck-Shaft Angle Evaluation Can Reduce Atypical Femoral Fractures in Osteoporotic Patients: A Scientific Report.

Bisphosphonates (BPs) are the mainstay of osteoporosis treatment due to their safety and efficacy. There is evidence that BPs medication may be complicated by atypical femoral fractures (AFFs). Prolonged administration of BPs is even more strongly associated with AFFs. AFF is a relatively rare complication of BPs when taking into account the huge population worldwide that benefits from this pharmacotherapy. AFF is, however, a serious complication of BPs treatment, which includes prolonged healing time and high revision rate when operative treatment is required. Less frequently, AFFs occur even without BPs administration, while these fractures have all the characteristics of “stress” or “insufficiency” fractures. The critical point of view in AFFs pathogenesis seems to be not only the biology of cortical bone, but also the mechanical issue. It has been proven that BPs, glucocorticoids and proton pump inhibitors (PPIs) can cause bone turnover suppression and affect the biological parameter of AFFs pathogenesis. Specific mechanical femoral bone properties predispose to AFFs pathogenesis. Several studies have already reported that increased femoral bowing > 5.250 degrees or decreased femoral neck-shaft angle <125 degrees, are associated with increased risk for diaphyseal and subtrochanteric AFFs respectively, regardless of BPs uptake. If these two parameters are simultaneously present, the probability for AFFs occurrence increases dramatically. Our scientific report, which is based on the current evidence about AFFs, is that if both femoral bowing angle and femoral neck-shaft angle are evaluated before BPs administration, this intervention may reduce the incidence of AFFs. Thus, in cases with excessive lateral femoral shaft bowing or very small femoral neck-shaft angle, the prescription of another anti-osteoporotic treatment than BPs should be recommended. If, however, BPs can’t be avoided, clinicians should be aware of the fact that long-term administration may be implicated with AFFs occurrence. In these cases, short term BPs administration with timely drug holiday between three and five years may be reasonable. Finally, roentgenographic evaluation of both femurs every six months and medical reference in case of any emerging thigh pain are also logical interventions to prevent and reduce AFFs.

Patellofemoral Pain in Adolescents: Understanding Patellofemoral Morphology and Its Relationship to Maltracking

Background: Developing bone is highly adaptable and, as such, is susceptible to pathological shape deformation. Thus, it is imperative to quantify if changes in patellofemoral morphology are associated with adolescent-onset patellofemoral pain, as a pathway to improve our understanding of this pain’s etiology. Purpose: To quantify and compare patellofemoral morphology in adolescent patients with patellofemoral pain with matched healthy adolescent controls and determine if a relationship exists between patellofemoral shape and kinematics (measured during active flexion-extension). Study Design: Cross-sectional study; Level of evidence, 3. Methods: Using 3-dimensional static magnetic resonance images acquired during a previous study, we measured patellar, trochlear, and lateral patellar width; trochlear and patellar depth; Wiberg index; patellar-height ratio; lateral trochlear inclination; cartilage length; and lateral femoral shaft length. Student t test was used to compare shape parameters between adolescents with patellofemoral pain and controls. Pearson correlations and stepwise linear regression models were used to explore the relationship among morphology, kinematics (medial-lateral shift/tilt), and pain. Results: Relative to controls, adolescents with patellofemoral pain had larger sulci (mean ± SD, 6.6 ± 0.7 vs 6.0 ± 1.1 mm; 95% CI, 0.6 mm; P = .043; d = 0.66), lateral patellar width (23.1 ± 2.4 vs 21.4 ± 2.6 mm; 95% CI, 1.6 mm; P = .033; d = 0.70), and patella-trochlear width ratio (1.2 ± 0.1 vs 1.1 ± 0.1; 95% CI, 0.1; P < .001; d = 1.26). Shape correlated with kinematics in both cohorts and in the entire population. In the patellofemoral pain group, lateral shaft length (r = 0.518; P = .019), Wiberg index (r = 0.477; P = .033), and patellar-height ratio (r = −0.582; P = .007) were correlated with medial shift. A moderate correlation existed between patellar-height ratio and lateral patellar tilt (r = 0.527; P = .017). Half of the variation in patellar shift in the patellofemoral pain cohort was explained by the patellar-height ratio and Wiberg index (R2 = 0.487; P = .003). Linear correlations with pain were not found. Conclusion: This study provides direct evidence that patellofemoral morphology is altered and influences maltracking in adolescents with patellofemoral pain, highlighting the multifactorial etiology of this pain. Neither morphology nor kinematics (measured during active flexion-extension) correlated with pain. Both increases and decreases in these parameters likely lead to pain, negating a direct linear correlation.

Surgical Hip Dislocation for Exposure of the Posterior Column.

Surgical hip dislocation is performed for safe and efficient management of acetabular fractures predominantly involving the posterior column. The dislocation of the femoral head allows for direct visualization of the hip joint during fracture treatment. The patient is placed in the lateral decubitus position with sterile preparation and draping of the ipsilateral leg to allow for dislocation. The skin incision is straight and centered over the greater trochanter. After the skin incision, the interval between the gluteus maximus and medius muscles is developed. The sciatic nerve is identified, and special attention to the course of the medial circumflex femoral artery is given during dissection of the piriformis and triceps coxae muscles (obturator internus and superior and inferior gemelli muscles). The latter are incised 2 cm posterior to their insertion on the posterior aspect of the greater trochanter. The vastus lateralis muscle belly is elevated from the lateral femoral shaft, and a trochanteric osteotomy is performed. The trochanteric medallion is rotated 90°, and the gluteus minimus muscle is released from the capsule. After complete exposure of the hip capsule, a z-shaped capsulotomy is performed whereby any injury to the posterior capsular attachments of a posterior wall fragment is avoided. The posterior column and the greater and lesser sciatic notches are exposed, with the sciatic nerve under protection. The femoral head is dislocated either anteriorly or posteriorly to obtain direct visualization of the hip. Reduction begins at the articular surface, in cases of marginal impaction, and proceeds to the posterior wall and/or posterior column and the anterior column, when involved. For fixation, 3.5-mm cortical screws acting as positioning or lag screws and reconstruction plates are used. The capsule is sutured, the trochanteric fragment is reduced anatomically and stabilized with two 3.5-mm cortical screws, the piriformis and triceps coxae muscles are sutured, and a layered closure is performed. The Kocher-Langenbeck approach might be used instead. Surgical hip dislocation facilitates assessment of cartilage damage at the acetabulum, marginal impaction, labral tears and femoral head lesions, removal or reinsertion of free intra-articular fracture fragments, direct visualization of the accuracy of reduction, and verification of extra-articular screw placement.

Femoral implant screwed on the lateral femoral shaft

Femoral implant screwed on the lateral femoral shaft

Femoral shaft strains during daily activities: Implications for atypical femoral fractures

BackgroundAtypical femoral fractures are low-energy fractures initiating in the lateral femoral shaft. We hypothesized that atypical femoral fracture onset is associated with daily femoral strain patterns. We examined femoral shaft strains during daily activities. MethodsWe analyzed earlier calculations of femoral strain during walking, sitting and rising from a chair, stair ascent, stair descent, stepping up, and squatting based on anatomically consistent musculoskeletal and finite-element models from a single donor and motion recordings from a body-matched volunteer. Femoral strains in the femoral shaft were extracted for the different activities and compared. The dependency between femoral strains in the lateral shaft and kinetic parameters was studied using multi-parametric linear regression analysis. FindingsTensile strain in the lateral femoral shaft varied from 327με (squatting) to 2004με (walking). Walking and stair descent imposed tensile loading on the lateral shaft, whereas the other activities mainly imposed tensile loads on the anterior shaft. The multi-parametric linear regression showed a moderately strong correlation between tensile strains in the lateral shaft and the motion kinetic (joint moments and ground reaction force) in the proximal (R2=0.60) and the distal shaft (R2=0.46). InterpretationBone regions subjected to tensile strains are associated with atypical femoral fractures. Walking is the daily activity that induces the highest tensile strain in the lateral femoral shaft. The kinetics of motion explains 46%–50% of the tensile strain variation in the lateral shaft, whereas the unexplained part is likely to be attributed to the way joint moments are decomposed into muscle forces.

Focus on pertrochanteric fractures.

Extramedullary fixation using the sliding hip screw has been the mainstay and gold standard in the fixation of pertrochanteric femoral fractures. However, there has been a dramatic shift in treatment over a relatively short period of time, as orthopaedic surgeons have extensively left this faithful device. Cephalomedullary nails presented promising biomechanical results and seem superior to plates simply by the design of the implant. Intramedullary nails have a shorter lever arm compared to plates, attached to the lateral femoral shaft, and thereby decrease the risk of implant failure. Some surgeons advocate that stabilizing pertrochanteric fractures with intramedullary nailing takes less time, is minimally invasive with reduced blood loss compared to compression hip screws. In the treatment of pertrochanteric fractures, clinical studies have not been supportive for any of these claims.

Vastus Lateralis Transfer for Severe Hip Abductor Deficiency: A Salvage Procedure

Abductor muscle deficiency can be a debilitating problem following hip arthroplasty surgery. We report outcomes of a novel method of abductor muscle function reconstruction surgery in patients with chronic, irreparable gluteus medius and minimus defects. Four consecutive patients who underwent our method of abductor reconstruction surgery were retrospectively reviewed. All patients had severe pain and positive Trendelenberg gait before surgery. the vastus lateralis (VL) muscle was raised on its neurovascular pedicle and transferred 12-14 centimetres by proximal translation. The proximal portion of VL was reattached via bony anchors to the external surface of the iliac wing just below the iliac crest. The distal portion of VL reattached to the lateral femoral shaft, lateral intermuscular septum, and the fascia of vastus intermedius. Average follow-up was 10 months (range 7-15 months). Three of the four patients report dramatic improvement in pain as measured by the visual analogue pain scale. The same three patients report being "extremely satisfied" with the pain relief achieved and "extremely satisfied" with the operation overall. Two patients reported being "extremely satisfied" with improvements in walking. Hip abduction power improved in all patients but to varying degrees. The results show that our method of VL transfer may be a viable option for patients with severe abductor deficiency. Modest but clinically relevant early results are seen.

Relationship between shaft bowing in the femur and tibia and bone mineral density in women with varus knee osteoarthritis

s / Osteoarthritis and Cartilage 20 (2012) S54–S296 S219 Figure 3. Predicted versus true rotation for the 6 pelvises under study.Ă 433 RELATIONSHIP BETWEEN SHAFT BOWING IN THE FEMUR AND TIBIA AND BONE MINERAL DENSITY IN WOMEN WITH VARUS KNEE OSTEOARTHRITIS Y. Akamatsu , N. Mitsugi , H. Kobayashi , K. Kumagai , Y. Kusayama , T. Saito . Yokohama City Univ. Sch. of Med., Yokohama, Japan; Yokohama City Univ. Med. Ctr., Yokohama, Japan Purpose: Anterior and lateral shaft bowing of the femur and tibia in patients with varus knee osteoarthritis (OA) results in malalignment of the whole lower extremity, when the preoperative planning in total knee arthroplasty or high tibial osteotomy is performed on the knee radiograph. Previous studies reported that femoral shaft bowing in women was different from that in men. To our knowledge, no studies investigating the relationship between shaft bowing in the femur and tibia and bone mineral density (BMD) have been reported. We hypothesized that anterior and lateral shaft bowing in the femur and tibia was related with age, body mass index (BMI), and BMD in women with varus knee OA. The main aim of our study was to assess the relationship between anterior and lateral shaft bowing in the femur and tibia and BMD in women with varus knee OA. Methods: We enrolled 52 women between April 2010 and March 2011 at our institution. All patients had symptomatic primary varus knee OA. Anteroposterior and lateral whole leg radiographs were taken with the patients in a standing position. Femoral and tibial shaft was divided into five equal parts. In the coronal and sagittal planes, anterior and lateral shaft bowing of the femur and tibia were defined as the angulations between midlines drawn in the second and forth parts from the proximal femur and tibia. The Kellgren and Lawrence grades were grade 2 in 3 knees, grade 3 in 7 knees, and grade 4 in 42 knees. Limb alignment was expressed as the femorotibial angle (FTA) obtained from the anteroposterior radiograph. BMD values were measured in L2-L4 vertebrae and the femoral neck using a QDR-4500 (Hologic Inc., Bedford, MA, USA). The lumbar spine and femoral neck BMDs were analyzed using standard software. BMI was calculated as an index of obesity. Data are expressed as means and standard deviation. Significance was set at p < 0.05. We used Pearson's correlation coefficients to investigate the relationship between two continuous variables (bowing, age, BMI, and BMDs). Results: Mean age and BMI were 72.4 8.9 years and 26.6 4.4 kg/m2, respectively. Mean FTA was 183.6 3.4 degree. Anterior femoral Anterior and lateral bowing in the femoral and tibial shaft and multivariate factors. Variables Anterior femoral bowing Lateral femor Age 0.317 (p1⁄40.022) 0.156 (p1⁄40. Body mass index 0.109 (p1⁄40.442) 0.045 (p1⁄40.75 Lumbar spine BMD 0.160 (p1⁄40.258) 0.252 (p1⁄40. Femoral neck BMD 0.345 (p1⁄40.012) 0.076 (p1⁄40. shaft bowing was positively correlated with age and negatively correlated with femoral neck BMD (r 1⁄4 0.317, p 1⁄4 0.022, and r 1⁄4 0.345, p 1⁄4 0.012, respectively). Lateral femoral shaft bowing was not related with multivariate factors. Anterior tibial shaft bowing demonstrated a positive correlation with BMI (r 1⁄4 0.283, p 1⁄4 0.042). Lateral tibial shaft bowing was positively correlated with age and negatively correlated with femoral neck BMD (r 1⁄4 0.364, p 1⁄4 0.008, and r 1⁄4 0.293, p 1⁄4 0.035, respectively). Conclusions: Karakas and Harma stated that anterior femoral shaft bowing was related with age. Our results showed that anterior femoral shaft bowing was correlated with age and femoral neck BMD. Contrary to our expectation, lateral femoral shaft bowing was not related with femoral neck BMD. Only anterior tibial shaft bowing was affected by BMI. Also, the relationship between anterior tibial shaft bowing and lumbar spine BMD might be associated with degenerative changes of the lumbar spine. Lateral tibial shaft bowing was correlated with age and femoral neck BMD, although anterior tibial shaft bowing was not related with femoral neck BMD. In Japanese, these results in the tibia might be associated with congenital tibia vara. The results from our small number of patients should be considered preliminary. However, if shaft bowing in the femur and tibia were related with BMD, the use of medication for osteoporosis might be a proper conservative approach to treatment. 434 DOES ANKLE CARTILAGE ADAPT TO STRONG ALTERATIONS IN LOADING ENVIRONMENT AFTER TRANSPLANTATION TO THE KNEE (VAN NEES ROTATIONPLASTY)? S. Maschek , F. Eckstein , W. Wirth , G. Gradl , C. Kirchhoff , K. Wortler , R. von Eisenhart-Rothe . 1 Paracelsus Med. Univ., Salzburg, Austria; Chondrometrics GmbH, Ainring, Germany; 3 Technical Univ.,

Pathophysiology of atypical femoral fractures and osteonecrosis of the jaw

In recent years, atypical femoral fractures and osteonecrosis of the jaw have emerged as potential complications of long-term bisphosphonate therapy; osteonecrosis of the jaw has also been reported in patients receiving high doses of denosumab. The pathophysiology of both conditions is poorly defined, and the underlying mechanisms are likely to differ. The initiation of atypical fractures in the lateral femoral shaft suggests that reduced tensile strength, possibly secondary to alterations in the material properties of bone resulting from low bone turnover, may be an important pathogenetic factor. Osteonecrosis of the jaw is characterised by infection, inflammation, bone resorption and bone necrosis, but the sequence in which these occur has not been established. However, the observation that bone resorption occurs in close proximity to microbial structures suggests that infection may be the most important trigger, often as a result of dental disease. Other possible pathogenetic factors include suppression of bone turnover, altered immune status and adverse effects of bisphosphonates on the oral mucosa.

The influence of soft tissue release on the tension around hip joint through posterolateral hip approach.

Objective To investigate the influence of selective soft tissue release on the tension around hip joint through posterolateral approach, and to ascertain the sequence of soft tissue release in total hip arthroplasty. Methods Five fresh frozen cadavers with ten intact lower extremities were used in the study. All the pelves of cadavers were fixed on the operating table by a special designed fixer on a lateral position. Femoral supracondylar bone traction was employed for axial traction. The force for traction was 15 kg. Posterolateral approach was used for exposure and two sequences for soft tissue release were studied. One Kirschner wire was fixed at the bone near the anterior superior iliac spine, and the wire was perpendicu-lar to the operating table. Another Kirschner wire was fixed into the bone at lateral femoral shaft. The two Kirschner wires were parallel to each other. The distance between the two Kirschner wires was measured be-fore and after each soft tissue structure release. Results There were no significant changes of the distance measured before and after applying traction alone, releasing external rotation muscles, opening the posterior capsule and releasing the gluteus maximus insertion. There were significant changes of distance measured before and after resection of femoral head, release of tensor fasciae latae and/or iliotibial band, excision of anterior capsule, and release of iliopsoas tendon had. The average lengthened distance was 1.5 mm (range, 1-3 mm) after resection of femoral head, and 8.0 mm (range, 2-19 mm) after release of tensor fasciae latae and/or iliotibial band, 5.5 mm (range, 1-13 mm) after excision of anterior capsule, and 1.8 mm (range, 1-3 mm) after release of iliopsoas tendon respectively. The distance lengthened after both release of tensor fasci-ae latae (and/or iliotibial band) and excision of anterior capsule was the most significant, average 13.5 mm (range, 11-20 mm). Conclusion Release of anterior capsule, tensor fasciae latae and/or iliotibial band, and iliopsoas tendon will decrease the soft tissue tension around hip joint. Among all the soft tissue structures we investigated, the anterior capsule and tensor fasciae latae (iliotibial band) make the most effective result. To maintain the soft tissue tension around hip joint depends on different structures working together, releasing one structure alone may not obtain the optimal result. Careful evaluation of tension of tensor fasciae latae and iliotibial band can help avoiding the limb length discrepancy during hip arthroplasty surgery. Key words: Hip joint; Arthroplasty, replacement, hip; Cadaver

Femoral neck geometry and hip fracture risk: the Geelong osteoporosis study

To determine the relationship between femoral neck geometry and the risk of hip fracture in post-menopausal Caucasian women, we conducted a retrospective study comparing the femoral neck dimensions of 62 hip fracture cases to those of 608 randomly selected controls. Measurements were made from dual-energy X-ray absorptiometry scans (Lunar DPX-L), using the manufacturer's ruler function, and included: hip axis length (HAL), femoral neck axis length (FNAL), femoral neck width (FNW), femoral shaft width (FSW), medial femoral shaft cortical thickness (FSCT(med)), and lateral femoral shaft cortical thickness (FSCT(lat)). The fracture group was older (median age 78.3 years vs 73.8 years), lighter (median weight 59.9 kg vs 64.5 kg), and, after adjustment for age, taller (mean height 158.7+/-0.8 cm vs 156.7+/-0.2 cm) than the controls. Furthermore, bone mineral density was lower in this group (0.682+/-0.016 g/cm(2) vs 0.791+/-0.006 g/cm(2)). After adjustment for age, bone mineral content (BMC) or height, hip fracture patients had greater FNW (up to 6.6%) and FSW (up to 6.3%) than did the controls. Each standard deviation increase in FNW and FSW was associated with a 1.7-fold (95% CI 1.3-2.3) and a 2.4-fold (95% CI 1.8-3.2) increase in the fracture risk, respectively. BMC-adjusted FNAL was greater in the fracture group (+2.1%) than in the controls, while the age-adjusted FSCT(med) was reduced (-7.2%). There was a trend towards longer HAL (up to 2.1%) after adjustment for age or BMC, and thinner age-adjusted FSCT(lat) (-1.7%) in fracture patients that did not reach statistical significance. In multivariate analysis, the risk of hip fracture was predicted by the combination of age, FNW, FSW, BMC and FSCT(med). HAL was not analyzed because of the small number of HAL measurements among fracture cases. We conclude that post-menopausal women with hip fractures have wider femoral necks and shafts, thinner femoral cortices and longer femoral neck axis lengths than do women with no fractures. Alteration in hip geometry is associated with the risk of hip fracture.

Iliotibial band tenodesis: a new strategy for attachment.

We investigated the changes in distance between Gerdy's tubercle on the tibia and points on the posterior two thirds of the lateral surface of the lateral femoral condyle and adjacent lateral femoral shaft in 15 cadaveric knees. A three-dimensional digitizer was used to quantify motion of the knee during flexion ranging from full extension to 120 degrees of flexion. Four load states were applied: internal, external, and neutral rotation, and quadriceps muscles loads based on one third of values in the literature for maximal isometric quadriceps muscles moments. The femoral location most isometric to Gerdy's tubercle was found to be strongly influenced by the load state. A 1.0 cm wide iliotibial band tenodesis was modelled by five straight lines arising from Gerdy's tubercle and attaching to a simulated washer at the junction of the lateral femoral condyle and shaft. Using this model and the motion data obtained from the cadavers, we investigated the effects of quadriceps muscles loading and external rotation of the knee on changes in the distances between these tibial and femoral attachments for each of the five lines. A 180 degrees twist modelled into the tenodesis significantly reduced the range of changes in distance (difference between the largest and smallest changes in distance among the lines for a given angle of flexion) for both of these load states. Therefore, a 180 degrees twist in the tenodesis can enhance isometry among the fibers of the tenodesis. This implies that a 180 degrees twist can enhance load sharing among the fibers of the tenodesis and, therefore, enhance the overall strength of the tenodesis.