Staged medial opening wedge high tibial osteotomy for bilateral varus gonarthrosis: biomechanical and clinical outcomes.

PURPOSE: (1) To evaluate the effect of staged bilateral medial opening wedge high tibial osteotomy (HTO) on established biomechanical risk factors for disease progression and on validated measures of pain and function and (2) To compare outcomes in patients having the second surgery staged within or beyond 12 months of the first surgery. METHODS: Thirty-seven patients with bilateral varus alignment and medial compartment osteoarthritis underwent staged bilateral medial opening wedge HTO (21 within and 16 beyond 12 months). Patients underwent full-limb standing anteroposterior radiographs to determine frontal plane alignment (mechanical axis angle) and three-dimensional gait analysis to estimate the distribution of load across the tibiofemoral compartments (external knee adduction moment). Patients also completed the Knee Injury and Osteoarthritis Outcomes Scores (KOOS), the Lower Extremity Functional Scale, the Short Form Health Survey and the six-minute walk test (6MWT). Patients (both limbs) were evaluated before and approximately 6, 12 and 24 months after each surgery. RESULTS: There were statistically and clinically significant changes in both limbs that were of similar magnitudes and that remained relatively stable over time postoperatively. Mean (95% CI) improvements in outcomes were as follows. Mechanical axis angle: 9.4° (8.4°, 10.4°) (i.e. average change of both limbs), peak knee adduction moment: -1.7%BW*Ht (-2.1, -1.4 %BW*Ht) (i.e. average change of both limbs), 6MWT: 36.7 m (19.4, 54.0 m), SF-12 Physical Component Summary: 12.0 (8.5, 15.5) and KOOS Pain: 25.4 (19.6, 31.2). Other than the shorter time period to reach maximum benefit of both surgeries, there were no remarkable differences at final assessment between patients having surgeries staged within or beyond 12 months. CONCLUSIONS: The present findings demonstrate that patients with bilateral varus gonarthrosis experience marked improvements in established biomechanical risk factors for disease progression bilaterally (mechanical axis angles and external knee adduction moments), as well as clinically important improvements in patient-important outcomes, after staged medial opening wedge HTO. Current findings suggest no difference in outcomes for patients who have the second surgery staged within or beyond 12 months of the first surgery. LEVEL OF EVIDENCE: IV.

Comparison of Gait Characteristics Between Patients With Nontraumatic and Posttraumatic Medial Knee Osteoarthritis.

OBJECTIVE: To compare knee kinematics and kinetics during walking in patients with posttraumatic versus nontraumatic medial compartment knee osteoarthritis (OA). METHODS: Participants with medial compartment knee OA were classified as nontraumatic (n = 122) or posttraumatic (n = 93) based on evidence of previous anterior cruciate ligament tear, confirmed arthroscopically. Kellgren/Lawrence severity scores and mechanical axis angle (MAA) were determined from radiographs. Knee flexion and adduction angles and external moments were calculated from gait analysis using a 3-dimensional optical motion capture system and force plate. Peak values were identified and principal component (PC) analysis determined waveform characteristics (PC scores). Linear regression models examined whether the OA group (posttraumatic or nontraumatic) predicted peak values and PC scores after controlling for age, gait speed, and severity. Models were repeated with and without controlling for MAA. RESULTS: The knee OA group was a significant predictor of peak knee adduction angles (P = 0.04) and moments (P = 0.05). Similarly, it was a significant predictor for some knee adduction angle (P = 0.02 to 0.64) and moment (P = 0.02 to 0.25) PC scores. The nontraumatic OA group had higher adduction angles and moments. There were no significant relationships between OA group and knee flexion angles and moments. After controlling for MAA, only one significant relationship remained between knee adduction moment shape characteristics and OA group. CONCLUSION: Frontal plane knee kinematics and kinetics during walking differ between patients with posttraumatic versus nontraumatic medial compartment knee OA, with posttraumatic OA showing relatively decreased adduction.