Medial opening wedge high tibial osteotomy: more than ten years of experience with Puddu plate technique supports its indication.

PURPOSE: To describe the short-term and long-term results of patients who underwent a medial opening wedge high tibial osteotomy (MOW-HTO) for unicompartmental medial knee joint osteoarthritis. METHODS: A retrospective review was conducted of patients with MOW-HTO using a Puddu plate®, with more than ten year follow-up. The degree of correction, initial chondral damage, number of meniscal lesions, preoperative and 1-year postoperative functional scale scores (IKDC and Lysholm), and arthroplasty conversion rates at the ten year follow-up were registered. We assumed early indication when patients underwent the operation before they were 40 years old and delayed ≥ 40. Functional outcomes were analyzed by adjusting for pre-operative values. Fisher's exact test was used to study the association between the arthroplasty conversion rates and the timing of indication. RESULTS: Fifty-five patients were included, 37 of whom were male (67%). Twenty-nine patients had early indications for surgery (53%). All patients completed ten year follow-up. All patients improved IKDC (p < 0.01) and Lysholm (p < 0.01) scores compared to their presurgical scores at the one year post-operative evaluation. We had six minor complications, none requiring revision surgery. We had three conversions to arthroplasty, all in the late indication group, not statistically significant different. Linear regression showed that early indication was associated with a higher IKDC score when adjusting for the Outerbridge chondral damage score, the number of meniscal lesions, and sex (p < 0.01). CONCLUSION: All patients improved functional scores one year after surgery. Early indication (i.e., younger than 40 years of age) was independently associated with better functional outcomes than late indication at one year follow-up.

The effects of a valgus collapse knee position on in vivo ACL elongation.

There are conflicting data regarding what motions increase ACL injury risk. More specifically, the mechanical role of valgus collapse positions during ACL injury remains controversial. Our objective was to evaluate ACL elongation in a model that mimics knee movements thought to occur during ACL injury. Eight healthy male subjects were imaged using MR and biplanar fluoroscopy to measure the in vivo elongation of the ACL and its functional bundles during three static knee positions: full extension, 30° of flexion, and a position intended to mimic a valgus collapse position described in the literature. For this study, the valgus collapse position consisted of 30° of knee flexion, internal rotation of the hip, and 10° of external tibial rotation. ACL length decreased significantly from full extension (30.2 ± 2.6 mm) to 30° of flexion (27.1 ± 2.2 mm). ACL length further decreased in the valgus collapse position (25.6 ± 2.4 mm). Both functional bundles of the ACL followed similar trends with regards to decreases in length in each of the three positions. Since strain would follow patterns of ACL length, landing on an extended knee may be a more relevant risk factor for ACL injuries than the valgus collapse position in males. Future studies should evaluate the effects of dynamic motion patterns on in vivo ACL strains.

Measurement of in vivo anterior cruciate ligament strain during dynamic jump landing.

Despite recent attention in the literature, anterior cruciate ligament (ACL) injury mechanisms are controversial and incidence rates remain high. One explanation is limited data on in vivo ACL strain during high-risk, dynamic movements. The objective of this study was to quantify ACL strain during jump landing. Marker-based motion analysis techniques were integrated with fluoroscopic and magnetic resonance (MR) imaging techniques to measure dynamic ACL strain non-invasively. First, eight subjects' knees were imaged using MR. From these images, the cortical bone and ACL attachment sites of the tibia and femur were outlined to create 3D models. Subjects underwent motion analysis while jump landing using reflective markers placed directly on the skin around the knee. Next, biplanar fluoroscopic images were taken with the markers in place so that the relative positions of each marker to the underlying bone could be quantified. Numerical optimization allowed jumping kinematics to be superimposed on the knee model, thus reproducing the dynamic in vivo joint motion. ACL length, knee flexion, and ground reaction force were measured. During jump landing, average ACL strain peaked 55±14 ms (mean and 95% confidence interval) prior to ground impact, when knee flexion angles were lowest. The peak ACL strain, measured relative to its length during MR imaging, was 12±7%. The observed trends were consistent with previously described neuromuscular patterns. Unrestricted by field of view or low sampling rate, this novel approach provides a means to measure kinematic patterns that elevate ACL strains and that provide new insights into ACL injury mechanisms.