Factors influencing knee valgus alignment in Crowe type IV hip dysplasia after total hip arthroplasty

Background Valgus deformity of the knee remains a complaint after total hip arthroplasty (THA) among some patients with Crowe type IV hip dysplasia. We aimed to identify the knee alignment in these patients before and after surgery, and to explore the factors contributing to postoperative knee valgus alignment. Materials and methods We retrospectively reviewed a series of Crowe type IV patients who received THA between February 2010 and May 2019 in our hospital. The patients’ medical data were collected from the hospital information system. On both preoperative and postoperative full limb length standing radiographs, the following parameters were measured: hip–knee–ankle angle (HKA), mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle, anatomical tibiofemoral angle, anatomical lateral distal femoral angle, femoral neck-shaft angle, pelvic obliquity, limb length, height and lateral distance of hip center, and femoral offset. Univariate and multivariate binary logistic regression were used to identify the factors influencing postoperative knee valgus alignment. Results A total of 64 Crowe type IV patients (87 hips) were included in the study. Overall, HKA improved from 176.54 ± 3.52° preoperatively to 179.45 ± 4.31° at the last follow-up. Those hips were subdivided into non-valgus group (≥ 177.0°, n = 65) and valgus group (< 177.0°, n = 22) according to postoperative HKA. Only postoperative mLDFA was a significant factor in the multivariate regression model. Conclusions The postoperative mLDFA is a major factor related to knee valgus alignment after THA, which combines the preoperative anatomy and surgical reconstruction. Other factors previously published were found to have no significance. Level of evidence III.

QUANTIFICATION OF NEURAL ELEMENTS IN POSTERIOR CRUCIATE LIGAMENT: COMPARISON BETWEEN HEALTHY KNEES AND WITH PRIMARY OSTEOARTHROSIS

ABSTRACT Objective: To quantify the neural elements in the posterior cruciate ligament (PCL) in healthy knees and with primary osteoarthrosis (OA). Methods: In two groups with OA, one of cadavers and another of individuals, the area of neural elements identified in histological sections of PCL with anti-S100 immunohistochemistry was quantified. Results: The overall mean area of the neural elements was 0.96% ± 0.67%, with the value in the cadaver group of 1.02% ± 0.67% and in the OA group of 0.80% ± 0.64%, with a significant statistically difference (p = 0.001). No correlation was observed between neural element quantification and the age of the individuals (p > 0.05). There was no difference in the quantification of neural elements between the sexes in the cadaver group (p = 0.766), but in the OA group there was a statistically significant reduction in males (p = 0.003). Also, in the osteoarthrosis group there was no difference in the quantification of neural elements in the knees with varus or valgus alignment (p = 0.847). Conclusion: There was a decrease in neural element quantification in PCL of individuals affected by OA in relation to non-arthritic individuals, with this quantification not related to age or with the axis of the lower limb. However, this quantification is not related to age or the axis of the lower limb. Level of Evidence III, Case control study.

Energy Absorption Strategies in the Lower Extremities during Double-Leg Landings in Knee Valgus Alignment

Landing with the knee in a valgus position may alter energy absorption strategies in the lower extremities and increase mechanical stress on the knee joint. We compared the energy absorption strategies in the lower extremities during valgus and varus landings. Seventeen females were divided into valgus and varus groups. Lower extremity kinetic data were obtained during drop jumps, using a three-dimensional motion analysis system. Negative mechanical work in the lower extremities were calculated during landing. The valgus group exhibited significantly more negative mechanical work at the knee, and less negative mechanical work at the hip, compared with the varus group. However, there was no difference in the negative mechanical work at the ankle between the two groups. Findings suggest that an increased valgus landing reduces the contribution of the hip to energy absorption and is associated with a reciprocal increased contribution by the knee. Hence a knee valgus landing position may be a key biomechanical factor that increases energy absorption in the knee, thereby increasing the risk of injury. Results further indicate that this can be prevented by adopting a knee varus position on landing, which facilitates absorption of the mechanical load at the hip, rather than at the knee.

Determination of Leg Alignment in Hip Osteoarthritis Patients with the EOS® System and the Effect on External Joint Moments during Gait

The present study considered the entire leg alignment and links static parameters to the external joint moments during gait in patients with hip osteoarthritis. Eighteen patients with unilateral hip osteoarthritis were measured using the EOS® system. Clinical leg alignment and femoral parameters were extracted from the 3D reconstruction of the EOS images. A 3D gait analysis was performed and external knee and hip adduction moments were computed and compared to 18 healthy controls in the same age group. The knee adduction moments of the involved leg were strongly correlated to the femoral offset and the varus/valgus alignment. These parameters alone explained over 50% of the variance in the knee adduction moments. Adding the pelvic drop of the contralateral side increased the model of femoral offset and varus/valgus alignment and explained 78% of the knee adduction moment during the first half of the stance phase. The hip adduction moments were best associated with the hip kinematics and not the leg alignment.

Computed Tomography-Based Patient-Specific Instrumentation Loses Accuracy with Significant Varus Preoperative Misalignment

Patient-specific instrumentation (PSI) has been introduced to simplify and make total knee arthroplasty (TKA) surgery more precise, effective, and efficient. We performed this study to determine whether the postoperative coronal alignment is related to preoperative deformity when computed tomography (CT)-based PSI is used for TKA surgery, and how the PSI approach compares with deformity correction obtained with conventional instrumentation. We analyzed pre-and post-operative full length standing hip-knee-ankle (HKA) X-rays of the lower limb in both groups using a convention > 180 degrees for valgus alignment and < 180 degrees for varus alignment. For the PSI group, the mean (± SD) pre-operative HKA angle was 172.09 degrees varus (± 6.69 degrees) with a maximum varus alignment of 21.5 degrees (HKA 158.5) and a maximum valgus alignment of 14.0 degrees. The mean post-operative HKA was 179.43 degrees varus (± 2.32 degrees) with a maximum varus alignment of seven degrees and a maximum valgus alignment of six degrees. There has been a weak correlation among the values of the pre- and postoperative HKA angle. The adjusted odds ratio (aOR) of postoperative alignment outside the range of 180 ± 3 degrees was significantly higher with a preoperative varus misalignment of 15 degrees or more (aOR: 4.18; 95% confidence interval: 1.35–12.96; p = 0.013). In the control group (conventional instrumentation), this loss of accuracy occurs with preoperative misalignment of 10 degrees. Preoperative misalignment below 15 degrees appears to present minimal influence on postoperative alignment when a CT-based PSI system is used. The CT-based PSI tends to lose accuracy with preoperative varus misalignment over 15 degrees.

The Effect of Osseous Valgus Alignment and Posteromedial Ligament Complex Deficiency on ACL Graft Forces: Risk Factors for Failure of ACL Reconstruction

Aims and Objectives: Dynamic valgus moments are known risk factors for ACL (re-)injuries. However, the association between osseous valgus alignment and ACL stress is not fully understood. The aim of the present study was to biomechanically investigate the influence of osseous valgus alignment, with and without deficiency of the medial collateral ligament and posterior oblique ligament (= posteromedial ligament complex; PMC), on ACL-graft forces under axial load. Additionally, it was investigated whether PMC reconstruction alone, correction osteotomy alone or a combination of both procedures were capable to decrease ACL-graft forces. Materials and Methods: The native ACL was dissected and ACL reconstruction was performed on ten cadaveric knee joints. A lateral distal femur osteotomy was done to adjust for three different alignment conditions according to the position where the axial weight bearing line (WBL) dissected the tibial plateau (% from medial to lateral): straight leg (50%), medium valgus (85%) and high-grade valgus (115%). Each alignment condition was tested with the PMC intact, deficient and reconstructed. The specimens were placed in a testing rig in 15° of knee flexion with the tibia fixed and the femur mobile on an X-Y-table. Axial loads of 400 N were applied and changes of ACL-graft forces (via an attached load-cell) and dynamic valgus angle (DVA) (via 3D motion tracking) were recorded. Results: In the PMC intact state, lateralization of the WBL to 85% and to 115% led to significantly increased ACL graft forces (85% vs. 50%: 96.1 ± 25.0 N vs. 63.7 ± 22.0 N, p=0.010; 115% vs. 50%: 109.9 ± 24.5 N vs. 63.7 ± 22.0 N; p<0.001) and DVA (85% vs. 50%: 2.0 ± 1.2° vs. 0.0 ± 0.8°, p=0.027; 115% vs. 50%: 2.1 ± 1.3° vs. 0.0 ± 0.8°; p=0.027). Dissection of the PMC led to a significant increase of ACL graft forces and DVAs at 85% and 115% valgus alignment (p<0.001), but not at 50% alignment. In valgus aligned knees (85%) with additional PMC deficiency, reconstruction of the PMC alone was able to significantly decrease ACL graft forces (85% deficient vs. 85% reconstructed: 158.0 ± 47.3 N vs. 112.1 ± 28.8 N; p<0.001) and DVA (85% deficient vs. 85% reconstructed: 7.4 ± 4.0° vs. 3.0 ± 2.0°; p<0.001). However, alignment correction alone was significantly more effective in reducing ACL graft forces (85% reconstructed vs. 50% deficient: 112.1 ± 28.8 N vs. 81.5 ± 23.8 N, p<0.001) and DVA (85% reconstructed vs. 50% deficient: 3.0 ± 2.0° vs. 0.81.0°; p=0.010). These relations were similar for high grade valgus alignment (115%). Conclusion: Osseous valgus alignment led to significantly increased ACL graft forces and DVA under axial joint compression, which was even further enhanced, when the PMC was deficient. In the valgus aligned and PMC deficient knee, correction to a straight leg axis was significantly more effective in decreasing forces on the ACL graft than reconstruction of the PMC.

Extramedullary Guide Alignment Is not Affected by Obesity in Primary Total Knee Arthroplasty

Coronal alignment of the tibial implant correlates with survivorship of total knee arthroplasty (TKA), especially in obese patients. The purpose of this study was to determine if obesity affects coronal plane alignment of the tibial component when utilizing standard extramedullary tibial guide instrumentation during primary TKA. A retrospective review from June 2017 to February 2018 identified 142 patients (162 primary TKAs). There were 88 patients (100 knees) with body mass index (BMI) < 35 kg/m2 and 54 patients (62 knees) with BMI ≥ 35.0 kg/m2. The cohorts did not differ in age (p = 0.37), gender (p = 0.61), or Charlson's comorbidity index (p = 0.54). Four independent reviewers measured the angle between the base of the tibial component and the mechanical axis of the tibia on the anteroposterior view of long-leg film at first postoperative clinic visit. Outliers were defined as patients with greater than 5 degrees of varus or valgus alignment (n = 0). Reoperations and complications were recorded to 90 days postoperatively. There was no significant difference in mean tibial coronal alignment between the two groups (control alignment 90.8 ± 1.2 degree versus obese alignment 90.8 ± 1.2 degree, p = 0.91). There was no difference in varus versus valgus alignment (p = 0.19). There was no difference in the number of outliers (two in each group, p = 0.73). There was no difference in rate of reoperation (p = 1.0) or complication (p = 0.51). Obesity did not affect coronal plane alignment of the tibial component when using an extramedullary guide during primary TKA in our population.

Lower-Extremity Energy Absorption During Side-Step Maneuvers in Females With Knee Valgus Alignment

Context: Excessive knee valgus on landing can cause anterior cruciate ligament injury. Therefore, knee valgus alignment may show characteristic energy absorption patterns during landings with lateral movement that impose greater impact forces on the knee joint compared with landings in other alignments. Objective: To investigate the energy absorption strategy in lower-extremities during side steps in females with knee valgus alignment. Design: Controlled laboratory study. Setting: University research laboratory. Participants: A total of 34 female college students participated in this experiment. Interventions: Participants performed single-leg drop vertical jump and side steps. All participants were divided into valgus (n = 13), neutral (n = 9), and varus (n = 12) groups according to knee position during landing in single-leg drop vertical jumps. Main Outcome Measures: Lower-extremity joint angles, moments, and negative works were calculated during landing in side steps, and 1-way analysis of variance and post hoc tests were used to determine between-group differences. Results: Negative works of hip extensors, knee abductors, and ankle plantar flexors during landing in side steps were significantly smaller in the valgus than in the varus group; however, negative work of the knee extensors was significantly greater in the valgus group than in varus group. Conclusions: The findings of this study indicated that landing with knee valgus induced the characteristic energy absorption strategy in the lower-extremity. Knee extensors contributed more to energy absorption when landing in knee valgus than in knee varus alignment. Learning to land in knee varus alignment might reduce the impact on the knee joint by increasing the energy absorption capacities of hip extensors, knee abductors, and ankle plantar flexors.