Impact of the Weightbearing Line on Cartilage Regeneration of the Medial Knee Compartment after Open-Wedge High Tibial Osteotomy, Based on Second-Look Arthroscopy

OBJECTIVE: Cartilage regeneration is multifactorial. This study aimed to optimize the biomechanical factor of weightbearing loading allowing for cartilage regeneration and elucidate the association between cartilage regeneration and clinical outcomes after medial open-wedge high tibial osteotomy (OWHTO). DESIGN: This was a retrospective, observational study of 142 patients who underwent OWHTO and subsequently underwent second-look arthroscopic assessment at a single orthopedic surgery center in Japan. Clinical and radiographic outcomes were compared between patients with (group R) and without (group D) cartilage regeneration, measured using the International Cartilage Repair Society grading system and the macroscopic staging system at the time second-look arthroscopy was performed. A receiver operating characteristic curve analysis was used to determine the optimal weightbearing line ratio (WBLR) for cartilage regeneration. RESULTS: Group R included 82 knees, and group D 60 knees. The WBLR was higher in group R (60.9% ± 6.7%) than in group D (55.6% ± 7.6%) (P < 0.001) and was associated with a greater improvement in clinical outcomes, namely the Lysholm scale score and all subscales of the Knee Injury and Osteoarthritis Outcome Score (P < 0.01). The WBLR predicted cartilage regeneration with an odds ratio of 1.11 (P = 0.001) and an area under the curve of 0.718, for a WBLR value of 62%. CONCLUSIONS: A WBLR of 62% was associated with cartilage regeneration after OWHTO and high patient-reported clinical outcomes.