Assessment of cartilage regeneration in initial and second-look arthroscopy following low tibial osteotomy for varus osteoarthritis of the ankle.

Abstract

The cover of cartilaginous defects in patients with varus osteoarthritis (OA) of the ankle in the medial compartment (medial gutter, talar dome, and tibial plafond) after low tibial osteotomy has only been reported in a few studies. There has also been little description of the distribution of the defects and the risk factors for persistent defects after surgery. The aim of this study was to report the degree and distribution of cartilage repair after low tibial osteotomy, and their association with postoperative outcomes in these patients. We retrospectively reviewed 24 patients (27 ankles) who underwent low tibial osteotomy for OA of the ankle. There were eight males and 16 females. Their mean age was 70.8 years (55 to 79), and the mean follow-up was 29.1 months (14 to 60). Clinical assessments included the Japanese Society for Surgery of the Foot (JSSF) ankle/hindfoot scale score and a visual analogue scale (VAS) score for pain. Radiological assessments included the Takakura-Tanaka classification, tibial anterior surface angle, talar tilt angle, tibiomedial malleolar angle (TMMA), tibial lateral surface angle, and mechanical ankle joint axis point. The condition of the cartilage was evaluated using the modified Outerbridge classification at the initial and second-look arthroscopies. The mean JSSF scale and VAS sores and all radiological parameters improved significantly postoperatively. At the initial arthroscopy, grade 4 cartilage defects were most common in the medial gutter (26 of 27 ankles; 96%), followed by the anteromedial talar dome (talar zone 1) (20 of 27 ankles; 74%). At the second-look arthroscopy, grade 4 defects were absent in the medial gutter but remained in ten of 20 ankles (50%) of those initially in talar zone 1. The modified Outerbridge grade in talar zone 1 at second-look arthroscopy correlated positively with postoperative VAS (<i>R</i> = 0.48). Pre- and postoperative TMMA (cutoff values: 43.1° and 31.4°) and postoperative VAS scores were significantly higher in patients in whom there was not cartilage repair in talar zone 1 than in those in whom there was cartilage repair (preoperative TMMA, p = 0.004; postoperative TMMA, p = 0.015; postoperative VAS score, p = 0.026), while the postoperative mechanical ankle joint axis point (cutoff value: 80.7%) was significantly smaller (p = 0.041). Second-look arthroscopy after low tibial osteotomy revealed good cartilage repair in the medial gutter, but it was poor in the anteromedial talar dome and associated with persistent postoperative pain. A large pre- and postoperative TMMA and medial deviation of the postoperative axis of loading may inhibit cartilage repair in these patients.