Prone-positioned knee arthroscopy for isolated retropatellar cartilage defects with gel-type autologous chondrocyte implantation.

Abstract

Treatment of isolated retropatellar cartilage defects using current gel-type regenerative methods requires settlement of the gel to the underlying subchondral bone under gravity; thus, prone positioned arthroscopy is used. Isolated retropatellar contained cartilage defect size >2.5 cm2. Age <40years, epiphyseal closure, cartilage defect grade3/4 (International Cartilage Repair Society). Cartilage defects at medial or lateral femorotibial compartments, at the trochlea, with degenerative genesis, rheumatoid arthritis, local infection, patellar malalignment, patellofemoral dysplasia, knee instability, knee malalignment >3°, kissing lesions. Two-stage procedure: At initial arthroscopy, chondrocytes were harvested. At the second stage, the patient was positioned prone and the leg with athigh tourniquet was fixed in aleg holder. Removal of table extension below the knee and support of foot in sling to prevent knee hyperextension. Placement of 2lateral portals. Lesion visualized and debrided, followed by aspiration of intra-articular fluid. Aloop, placed posterior to the patellar ligament using alasso, was used to suspend aweight to expand the patellofemoral space. The lesion was then dried using asponge. NOVOCART® Inject (TETEC, Reutlingen, Germany) administered onto the defect. Gel was allowed to solidify for15 min and operation was completed. Knee locked in extension using abrace for 6weeks. Continuous passive motion applied and incrementally increased until full range of motion (ROM) at week6. Weight-bearing as tolerated was allowed with the knee in extension. Routine clinical follow-up after 3, 6 and 12months. Mean age of the 5patients was 23 ± 6 (range 14-30) years; mean follow-up time after surgery 28 ± 7 (range 20-40) months. All patients returned to full activity without residual knee ROM restriction. Clinical examination at the latest follow-up revealed aKujala score of 90 ± 12 points and Lysholm score of 95 ± 5 points. MRI showed filled cartilage defects in all patients. Mocart score was 63 ± 7 points. Cartilage was inhomogeneous and hyperintense at the repaired site. Quantitative measurement of the patella mobility of the operated knee under atranslating force of 10 N showed medial and lateral displacements of 21 ± 5 and 15 ± 2 mm and on the healthy side 22 ± 5 and 19 ± 3 mm, respectively.