Introduction. Quadriceps performance following total knee arthroplasty (TKA) is a critical factor in patient satisfaction that can be significantly affected by implant design (Greene, 2008). The objective of this study was to compare quadriceps efficiency (QE) following TKA with a medial-pivot system (EVOLUTION®, MicroPort Orthopedics Inc., Arlington, TN, USA) to non-implanted control measurements. Methods. Five cadaveric leg specimens with no prior surgeries, deformities, or disease were obtained. Each was placed in a custom closed chain device and loaded to simulate a heel-up squat from full-extension to deep flexion (approximately 115°) and back to full extension. Quadriceps force (FQ) and ground reaction force (FZ) were measured, and the ratio of the two was calculated as the quadriceps load factor (QLF). QFLs are inversely related to QE, with higher QFLs representing reduced efficiency. Each specimen was then implanted with a medial-pivot implant by a board certified orthopedic surgeon and force measurements were repeated. Mean pre- (represents control values) and post-implantation QFLs were compared to determine any differences in QE throughout the range of motion. Results. Mean QFLs were not statistically different for pre- and post-implantation measurements throughout loading (Figure 1). QE was increased in the post-implantation measurements compared to pre-implantation between approximately 80° and 115° flexion and reduced between 5° and 80°. The mean peak post-implantation QFL was 5% less than that measured pre-implantation. Discussion. Quadriceps muscles were least efficient during peak flexion (80°–115°) when FQ was highest during both pre- and post-implantation measurements. The similar QE seen between the pre- and post-implantation measurements for most of the range of motion could be a result of the system design, which seeks to mimic the kinematics of the normal knee (Schmidt, 2003). The observed nearly-linear change in the FQ through 75° is likely due to the combination of the medial spherical radius and the conformity of the medial tibial insert socket that provides a constant moment arm on which the extensor mechanism can act. The primary driver of decreasing efficiency of the extensor mechanism is the increasing moment arm of the load with increasing flexion. The second increase in FQ in deep flexion (>110°) for the implanted measurements is likely due to the smaller closing radius on the femoral component in this range. These preliminary data have the potential to be significant clinically in that decreased QE may result in increased quadriceps forces manifesting in anterior knee pain or patient fatigue. Additionally, increased QE may play a role in rehabilitation and return to activities of daily living. The current results show the medial-pivot system may increase QE during peak flexion and does not significantly reduce QE during midflexion when compared to control. In-vivo testing is needed to confirm if these results translate to clinical practice

Quadriceps tendon ruptures are a rare but debilitating injury resulting in loss of knee extension necessitating surgical intervention. Currently, multiple different surgical techniques and rehabilitation programs are utilized by surgeons. Researchers have been unable to determine the best surgical technique with respect to function and complication rate; certain techniques are more cost-effective than others. Early vs. late motion rehabilitation programs are utilized; recent evidence suggests that less aggressive initial rehabilitation may lead to decreased extensor lag and fewer additional surgeries. The goal of our study is to determine the treatment practices of orthopaedic surgeons across Canada. Our study was completed anonymously via . SurveyMonkey.com. (Palo Alto, California). Based on current literature, a 26-question survey was distributed. E-mail invitations were be sent to all members of the Canadian Orthopaedic Association. Participation is voluntary. Currently, 104 surveys have been completed. 78% of respondents utilize transosseous drill holes, 13% utilize suture anchors and 9% utilize a combined surgical technique. The majority of surgeons begin range of motion (ROM) at 2 weeks (42%) or 6 weeks (24%); ROM is then commonly progressed in a step-wise fashion at 2-week intervals (58%). Approximately half of respondents have performed revision surgery for quadriceps re-rupture. Surgical management of quadriceps tendon ruptures is fairly consistent amongst Canadian orthopaedic surgeons. However, wide variation exists regarding rehabilitation, favoring early initiation and progression of ROM despite some evidence recommending a longer period of immobilization

Most previous studies investigating autograft options (quadriceps, hamstring, bone-patella-tendon-bone) in primary anterior cruciate ligament (ACL) reconstruction are confounded by concomitant knee injuries. This study aims to investigate the differences in patient reported outcome measures and revision rates for quadriceps tendon in comparison with hamstring tendon and bone-patella-tendon-bone autografts. We use a cohort of patients who have had primary ACL reconstruction without concomitant knee injuries. All patients from the New Zealand ACL Registry who underwent a primary arthroscopic ACL reconstruction with minimum 2 year follow-up were considered for the study. Patients who had associated ipsilateral knee injuries, previous knee surgery, or open procedures were excluded. The primary outcome was Knee Injury and Osteoarthritis Outcome Score (KOOS) and MARX scores at 2 years post-surgery. Secondary outcomes were all-cause revision and time to revision with a total follow-up period of 8 years (time since inception of the registry). 2581 patients were included in the study; 1917 hamstring tendon, 557 bone-patella-tendon-bone, and 107 quadriceps tendon. At 2 years, no significant difference in MARX scores were found between the three groups (2y mean score; 7.36 hamstring, 7.85 bone-patella-tendon-bone, 8.05 quadriceps, P = 0.195). Further, no significant difference in KOOS scores were found between the three groups; with the exception of hamstring performing better than bone-patella-tendon-bone in the KOOS sports and recreation sub-score (2y mean score; 79.2 hamstring, 73.9 bone-patella-tendon-bone, P < 0.001). Similar revision rates were reported between all autograft groups (mean revision rate per 100 component years; 1.05 hamstring, 0.80 bone-patella-tendon-bone, 1.68 quadriceps, P = 0.083). Autograft revision rates were independent of age and gender variables. Quadriceps tendon is a comparable autograft choice to the status quo for primary ACL reconstruction without concomitant knee injury. Further research is required to quantify the long-term outcomes for quadriceps tendon use

Quadriceps moment arm is one of the factors determining quadriceps force. Total knee arthroplasty designs with larger quadriceps moment arms should generate less quadriceps and patellofemoral forces. A study was conducted to measure knee kinematics, quadriceps and patellofemoral forces in two knee designs with differing centers of rotation. In addition, the effect of a central dome-shaped versus a medialized patella component was determined. Six human cadaver knees were tested before implantation and after sequential implantation with two posterior cruciate retaining designs: Scorpio and Control. The quadriceps moment arm of the Scorpio design was 1 cm longer than that of the Control design. Knee kinematics was measured with an eletromagnetic tracking device while the knee was put through dynamic simulated stair climbing under peak flexion moments of 40 N-m. Quadriceps tension and patellofemoral compressive and shear forces were measured for both conditions and for the central and medialized patella components. The normal unimplanted condition showed increasing rollback with flexion while both implanted conditions displayed relatively less rollback. Overall, quadriceps tension was highest in the unimplanted condition and lowest in the Scorpio condition. The Scorpio design showed a 10-20% reduction in quadriceps tension at angles greater than 40° when compared to the Control design. Patellofemoral forces were also significantly reduced in the Scorpio design when compared to Control. There were no differences noted between the central and medialized patella component. The Scorpio design, with its more posterior center of rotation, reduced quadriceps tension and patellofemoral forces. Reduced quadriceps forces may facilitate postoperative rehabilitation and activities such as stair climbing. Reduction in patellofemoral forces could reduce patellar complications such as anterior knee pain, component wear and loosening. These results are currently undergoing validation with a prospective clinical study

Bone-patellar tendon-bone autografts, hamstring autografts or allografts are widely used grafts for ACL revision surgeries. Also use of quadriceps autograft for both primary and revision ACL surgeries is in an increasing popularity due to its biomechanical superior properties and less donor site morbidity. However, although several fixation techniques and devices for quadriceps tendon graft fixation on femoral side have been reported, literature lacks about biomechanical studies comparing properties of these different fixation techniques and devices. We aimed to investigate whether there is a difference between the fixation techniques of quadriceps tendon graft by using different fixation techniques and devices on the femoral side in terms of stiffness and amount of slippage in the tunnel. Full-thickness central parts of quadriceps tendons from paired knees of twenty five calf knees were fixed through a 10mm x 25mm tunnel in twenty five paired sheep femurs. Quadriceps tendon patellar side with soft tissue ending fixed with four different fixation devices (adjustable suspensory system (group 1), absorbable interference screw (group 2), titanium interference screw (group 3) and adjustable suspensory system + absorbable interference screw (group 4)) and quadriceps tendon with a patellar bone plug fixed with a titanium interference screw (group 5) were tested in a servohydraulic materials testing machine. 10 samples were included in each group. After applying a preload of 10 N, a cyclic force was applied for 20 cycles from 10N to 110N at a 1 hertz frequency. Amount of slippage in the tunnel was calculated as the difference measured in millimeters between length at 10 N after 20 cycles and starting length at 10 N (Graph 1). To determine the stiffness, a single load-to-failure cycle was performed at a strain rate of 20 mm/min as the last step (Figure 1). Rupture of the graft was not seen in any of the samples. Median values of amount of slippage in the tunnel were 6,41mm, 5,99mm, 3,01mm, 4,83mm, and 3,94mm respectively. Median values of maximum load at failure were 464N, 160N, 350N, 350N and 389N respectively. Amount of slippage in the tunnel was highest in the group 1 and was lowest in the group 3 (p<0.001). Group 1 was found to be most resistant group against load-to-failure test and group 2 was the weakest (p<0.001). However inter-group analyses between group 3 and 5 revealed that, although group 3 had the least slippage in the tunnel, group 5 was better in terms of stiffness, but there was no statistically significant difference (p=0,124 and 0,119 respectively). There was a significant difference between group 2 and 3 in both amount of slippage in the tunnel and stiffness (p=0,001 and 0.028 respectively)(Table 1). Our study revealed that, although quadriceps graft with a bone plug fixed with metal interference screws is widely presumed to be a stable fixation technique, there was no significant difference in terms of stiffness when compared with quadriceps graft with soft tissue ending fixed with a metal interference screw. Although adjustable suspensory device group was the best in the terms of resistance against load-to-failure, it was the worst in terms of amount of slippage from the tunnel. Thus, if a suspensory device is to be used, it must be kept in mind that a strong 20 cycles of intra-operative tension force must be applied to prevent further slippage of the graft in the tunnel which can result in failure of reconstruction. For any figures or tables, please contact the authors directly

Introduction: The goals of TKR are restoration of the mechanical axis, joint line and Q –angle. Reproduction of the offset of the extensor mechanism during arthroplasty is less well understood. The lever arm of the extensor mechanism is primarily affected by femoral component position, patella tracking and overall patellar thickness. Changing this lever arm alters quadriceps muscle and patellofemoral joint reaction force. Some TKR designs purposefully aim to increase this offset in order to reduce PFJ contact pressures. Overstuffing the PFJ will however adversely affect outcome. The aims of this study were to measure and compare the pre and postoperative quadriceps lever arm and its effect on function in a consecutive series of patients undergoing TKR. Methods: Fifty consecutive patients who had an LCS TKR without patellar resurfacing by a single surgeon were reviewed. Patient demographics were recorded. We measured the pre and post-operative quadriceps lever arm using comparable lateral radiographs and digital imaging software. Functional outcome in these patients was determined using the American Knee Society Score pre and 6-months post-operatively. Patients were specifically questioned regarding the presence or absence of anterior knee pain. Results: Quadriceps lever arm was on average 6 mm greater post-operatively than pre-op but this difference was not significant [t-test]. The functional outcome in these patients was independent of any change in quadriceps lever arm. Conclusions Reproduction of normal biomechanics is essential in order to optimise outcome from TKR. Using the LCS system, there is a small but insignificant increase in the quadriceps moment arm. We have not found that this has any bearing on functional outcome in these patients

Objective: The objective of this study is to evaluate the role of quadriceps tightness in patients with patellar symptoms. Material and methods: We evaluated 64 patients (12 men and 52 women) diagnosed of patellar malalignment, chondromalacia, patellar pain, patellar subluxation... in 100 knees. We defined 2 groups according the presence or not of imaging disorders: Group A (48 knees) with normal x-ray and CT-scan; group B (52 knees) with malalignment in x-ray or CT-scan. In both groups we evaluated quadriceps tightness by placing the patient prone and passively bringing the heels toward buttock. Average distance between heels/buttock (HBD) was 9.1 cm. in both groups before treatment and none presented HBD = 0 cm. Treatment consisted in passive quadriceps stretches after warm-up. Results: After 11 rehabilitation sessions (range: 9–12), average HBD was 2.5 cm. in group A and 3.6 cm. in group B. HBD = 0 cm. was present in 32/48 knees in group A and 12/52 knees in group B. With a follow-up of 36–48 months, patients with HBD = 0 and values of HBD similar to values after treatment were present in both groups. After follow-up, pain was reported in 4/36 patients in group A and 20/28 in group B. Conclusions: Quadriceps tightness is always present in patients with patellar symptoms and it is a valuable and reproducible sign. Passive quadriceps stretches are highly effective in patients with normal imaging tests and can be useful before surgery in patients with patellar malalignment

Patients with advanced osteoarthritis tend to have limited range of motion; the purpose of this in vivo anatomical study is to identify the anatomical structures responsible for limited knee movement in patients with osteoarthritis. Forty-two quadriceps releases were performed in patients who had TKA. The releases were carried out utilising subvastus approach and just before proceeding with the knee replacement surgery. The ranges of motion were documented before and after the release using digital photography and lateral portable X-ray. No bony resection was done, and no ligament release was performed. Quadriceps excursion was also studied under fluoroscopy in six volunteers throughout the range of movement. The quadriceps release improved the range of motion in all patients; at least 135 degrees of flexion were obtained. The improvements were more dramatic in patients who had previous surgeries. The average of improvement in knee flexion after the release was 36 degrees. The presence of osteophytes or gross deformity did not influence the degree of improvement. The fluoroscopy study has shown that the average excursion of quadriceps muscle from 0 to 145 degrees is 7 cm. The excursion per degree varies throughout the range of motion; it is more per degree near full flexion and extension than around 90 degrees of flexion. The limited excursion of the quadriceps muscle is the main limiting factor to full knee flexion. Other pathological changes such as osteophytes, surface pathology, posterior capsule and the cruciate ligaments play very limited roles

Background:. Total knee replacement (TKR) is a frequent and effective surgery for knee osteoarthritis. Postoperative pain is under concern and can be relieved by different methods, including femoral nerve block (FNB). The efficacy of FNB on pain relief was associated with the absence of clinical impact when measured with the range of motion (ROM). Recent studies suggest that the quadriceps strength is the best indicator of functional recovery after TKR. The goal of this study is to compare the quadriceps strength recovery after TKR according to the kind of analgesia (patient control analgesia (PCA) with or without FNB) Hypothesis: the FNB delays the QSR at short and mid-term follow-up. Methods:. Prospective randomized trial with single-blind assessment involving 135 patients admitted for TKR in an academic center. Randomization into one of the three following groups: A) Continuous FNB 48h + PCA B) Single-shot FNB and PCA C) PCA alone. Groups were comparable for demographic and surgical data. The FNB was realised and controlled (electric stimulation) by an expert anesthesiologist before the surgery. Follow-up standardised in all groups with blinded assessors. Quadriceps strength measured with a validated dynamometer at 6 weeks, 6 and 12 months. Secondary outcomes included clinical evaluation (ROM, pain, stability) and functional scores (SF-36 v2, WOMAC). Multivariate analysis (Kruskal-Wallis, Mann-Whitney) for main outcomes and Spearman factor for correlation. Sample size calculated for alpha 5% and study power 80%. Results:. 111 patients available for 6 weeks follow-up (A-B-C:40-38-33) and 104 (36-36-32) at 6 and 12 months. Two patients in group B excluded for direct fall in the first postoperative week with extensor mechanism rupture and peri-prosthetic femoral fracture. QSR is significantly decreased in patients with FNB at all times (mean, 95% IC): 6 weeks (A 51.3%, 44.1–58.5; B 62.2%, 55.2–69.2; C 77.4%, 70.7–84.1; p < 0,05), 6 months (A 65.4%, 57.9–72.9; B 82.1%, 74.2–90; C 95.7%, 88.5–102.9; p < 0,05) and 12 months (A 87.8%, 82.1–93.5; B 97.8%, 89–106.6; C 104.8%, 96.1–113.5; p < 0,05). No significant difference between continuous or single-shot FNB. Higher ROM in group C at all times (p 6 weeks = 0,046; p 6 months = 0,159; p 12 months = 0,026). No correlation between ROM and QSR (rho = 0,07; p = 0,23). Better functional results in the group C at all times (p < 0,05), with good correlation to QSR (rho = 0,177; p = 0,032). Slight difference in analgesic effect of FNB (p = 0,14). Conclusion:. Femoral nerve block has a negative influence on QSR at short and mid-term follow-up and delays the rehabilitation after TKR. QSR is actually the most sensitive indicator of functional recovery after TKR and is better related to functional tests than ROM. This can explain the harmlessness of FNB in previous studies. FNB should not yet be recommended for analgesia after TKR

Quadriceps femoris muscle (QFM) weakness is associated with the development of knee osteoarthritis (OA). Neuromusclar electrical stimulation (NMES) circumvents neural inhibition causing muscle contraction, however there is little reported data demonstrating its role in knee OA. Our aim was to evaluate the effectiveness of a NMES program in patients with knee OA. Sixteen patients (10 women, 6 men) with severe knee OA were randomised into control (n=6) or intervention (n=10) groups. These were similar in terms of age (64.8 ± 11.0 vs. 64.6 ± 7.6; mean ± SD) and BMI (31.8 ± 6.11 vs.30.7 ± 2.9). NMES was applied using a garment-based stimulator for 20 min/day, 5 d/wk for 8 weeks. Isokinetic and isometric QFM strength were determined at baseline, and weeks 2, 5, and 8 using a dynomometer. Functional assessments involved a 25 metre timed walk test (TWT), timed stair-climb test (SCT), and timed chair-rise test (CRT) at baseline and week 8. Subjects recorded NMES session duration in a log book while the device also recorded total treatment time. Function significantly improved in the NMES group as determined by the timed SCT (p< 0.01) and the timed CRT (p< 0.01) at week 8 compared to week 0. Isometric QFM strength was significantly higher in the NMES group at weeks 2, 5 and 8 than week 0. Compared to week 0, isokinetic hamstring strength increased significantly in the NMES group at week 2, week 5 and week 8 while isokinetic QFM strength increased at week 5 (p< 0.05) and week 8 (p< 0.01). Patient recorded compliance was 99.5% (range, 97.1%–100%) and overall usage recorded on the stimulator was 96.1% ± 13.2. The use of a portable home-based NMES program produced significant QFM strength gain with associated improvement in function in patients with severe knee OA. Compliance was excellent overall

Intro: Quadriceps rupture following total knee arthroplasty is a devastating injury. Early operative repair is necessary to maintain the integrity of the extensor. Postoperative rehabilitation usually involves a prolonged period of immobilisation to allow the repair to consolidate. This immobilisation can cause irreversible stiffness in the patient with a total knee replacement. We present a method of rehabilitation to allow early range of motion. Case Report: A 57 year old gentleman presented with bilateral tri-compartmental osteoarthritis, he had no other significant medical history. Bilateral synchronous total knee replacements were performed and the early post operative was unremarkable. The patient fell whilst mobilising indoors at home during the fifth post operative week and sustained rapid hyperflexion injures to both knees. Ultrasound scans of the knees demonstrated bilateral discontinuities of the quadriceps mechanisms and a large fluid collection filling the defect. The patient returned to the operating where a direct repair was achieved. Post operatively the patient was rested in bilateral cylinder casts until the sutures were removed at two weeks. For two week periods the knees were then mobilised in a hinged cast brace allowing 0–30, 0–60 and 0–90 degrees making the total time in cast 8 weeks. At the time of removal of the casts the patient had 110 degrees of flexion in the right leg and 85 degrees of flexion in the left. At six months postoperatively the patient flexes freely to over 100 degrees. Conclusion: Bilateral quadriceps ruptures in a relatively young patient can be managed with early repair and an aggressive rehabilitation regime. This case suggests that is possible to achieve a satisfactory outcome although the input required is significant

Introduction & aims: Quadriceps muscle wasting is common in patients with osteoarthritis (OA) of the hip and knee. Previous studies,using ultrasound and performing biopsies, have demonstrated quadriceps muscle fibre atrophy. Thigh girth measurements are quoted in textbooks as a means of quantitatively assessing muscle bulk. This study has looked at these measurements in patients with hip and knee OA to see if these measurements are useful. Method: 87 patients (mean age 62, range 36–87) with a diagnosis of OA were seen in the pre-assessment clinic. 47 were awaiting total hip replacement (THR) and 40 were awaiting total knee replacement (TKR).All were awaiting primary arthroplasty and had not had previous joint surgery. Thigh girth measurements were taken at 2 points corresponding with one-third and two-thirds of the length between the anterior superior iliac spine and the tibial tuberosity. These measurements were taken for both thighs. The observed differences were analysed with normal probability plots and paired Student’s t-tests. Results: No significant difference in thigh girth could be detected in patients awaiting total knee replacement. Girth was significantly reduced in the thigh on the side of planned THR. This difference was apparent when measured both proximally and distally. Conclusion: Measurements of thigh girth were not useful indicators of quadriceps wasting in patients awaiting TKR. Patients awaiting THR should have thigh girth measured, those with reduced thigh girth on the side of planned arthroplasty may have quadriceps atrophy and can then be referred for physiotherapy prior to surgery

Introduction

Anterior cruciate ligament (ACL) injuries represent a significant burden of disease to the orthopaedic surgeon and often necessitate surgical reconstruction in the presence of instability. The hamstring graft has traditionally been used to reconstruct the ACL but the quadriceps tendon (QT) graft has gained popularity due to its relatively low donor site morbidity.

Background: Quadriceps femoris muscle (QFM) weakness has been implicated in the development of knee osteoarthritis (OA) as well as predicting functional ability after TKA. Preoperative strengthening (prehabilitation) may be facilitated by applying neuromuscular electrical stimulation (NMES) to the affected QFM using a garment-based portable stimulator. Methods: Single blind, randomised control efficacy study with NMES applied to the affected QFM for 20 min, 5 days a week, for 8 weeks pre-TKA. Isokinetic and isometric strength was assessed at baseline, week 2, week 5 and immediately pre-op. Function was assessed using a 25 metre timed walk test (TWT), timed stair-climb test (SCT), and timed chair-rise test (CRT) at baseline and pre-op. Results: 13 patients (8 women and 5 men) scheduled for TKA for knee OA were recruited and randomised into a control (n=5) or intervention (n=8) group. Groups were similar in terms of age (65.5 ± 6.8 vs. 61.8 ± 9.0; mean ± SD) and BMI (29.7 ± 2.1 vs.33.2 ± 5.6). There was an improvement in SCT (p< 0.01) and CRT (p< 0.01) in the NMES group at week 8 compared to week 0. Isokinetic hamstring strength and isometric QFM strength increased significantly at weeks 2, 5 and 8 compared to baseline whereas isokinetic QFM strength only increased at week 5 (p< 0.05) and week 8 (p< 0.01) compared to baseline. Conclusion: The use of a portable home-based NMES program for 8 weeks results in significant strength gains with associated improvements in function in patients scheduled for TKA for knee OA

Introduction

Patellofemoral instability is one of the most common presentations to a children's orthopaedic clinic. Recurrent patellar dislocations and instability episodes are painful, disabling and increase the risk of irreversible chondral damage. The medial patellofemoral ligament is the primary static stabiliser to prevent lateral dislocation of the patella and is almost always torn or attenuated in these cases. Reconstruction of this ligament is commonly performed using autologous hamstring tendon however there has been some interest recently in use of quadriceps tendon as a graft. Children with patellar instability also present unique challenges due to the small size of the patella and the presence of open growth plates which may require adaptations to the common techniques.

Abstract

Introduction

Chronic ruptures of the quadriceps tendon after total knee arthroplasty (TKA) are rare but are a devastating complication. The objective of this study was to validate the use of fresh frozen total fresh quadriceps tendon allografts for quadriceps tendon reconstruction. The hypothesis of this work was that the graft was functional in more than 67% of cases, a higher percentage than the results of conventional treatments.

Abstract

Abstract

To explain the knee kinematics, the vector of the quadriceps muscle, the primary extensor, is important and the relationship of the quadriceps vector (QV) to other kinematic and anatomic axes will help in understanding the knee.

Knee kinematics is important for understanding knee diseases and is critical for positioning total knee arthroplasty components. The relationship of the quadriceps to knee has not been fully elucidated. Three-dimensional imaging now makes it possible to construct a computer based solid model of the quadriceps and to calculate the vector of the muscle as individual parts and as a whole. Two studies are presented, one American and one Japanese subjects.

Using CT data from subjects who had CT for reasons other than lower extremity pathology (American) or specifically for the study (Japanese), 3-D models of each quadriceps component (vastus medialis, intermedius, lateralis and rectus femoris) were generated. Using principal component analysis for direction and volume for length, a vector for each muscle was constructed and addition of the vectors gave the QV. Three anatomic axes were defined: Anatomic Axis (AA) – long axis of the shaft of the femur; Mechanical Axis (MA) center of the femoral head to the center of the trochlear and the Spherical Axis (SA) – a line from the geometric center of the head of the femur to the geometric center of the medial condyle of the femur at the knee.

Fourteen American cases (mean age 39.1, 9 male 5 female) and 40 Japanese subjects (mean age 29.1, 21 male, 19 female) were evaluated. In all subjects the quadriceps vector at the level of the center of the femoral head was anterolateral to the center of the femoral head. The position of the QV was more lateral in Japanese compared to Americans; and, in Japanese, the vector was more lateral and posterior for women than for men. In both study populations, the QV was most closely aligned with the SA as compared to the AA or the MA.

The vector representing the quadriceps pull, originating at the top of the patella, progresses proximally toward the neck (not the head) of the femur. With the femur in anatomic position in the coronal plane, the vector crosses the femoral neck lateral to the femoral head approximately at the midpoint of the neck. While there were significant differences between the passing point of the vector based on sex and ethnicity, the QV vector most closely parallels the SA (< 1° different) for all subjects in this study. The relationship of the SA to the kinematic flexion axis (KFS) of the knee is being evaluated with the hypothesis that the relationship is 90°. If this is correct, the SA may prove a robust axis to which to align total knee arthroplasty.

We conclude that the QV as calculated progresses from the top of the patella to the mid-femoral neck and the SA is most closely parallel to this vector.