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

Objective 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. Indications Isolated retropatellar contained cartilage defect size >2.5 cm(2). Age 3 degrees, kissing lesions. Surgical technique Two-stage procedure: At initial arthroscopy, chondrocytes were harvested. At the second stage, the patient was positioned prone and the leg with a thigh tourniquet was fixed in a leg holder. Removal of table extension below the knee and support of foot in sling to prevent knee hyperextension. Placement of 2 lateral portals. Lesion visualized and debrided, followed by aspiration of intra-articular fluid. A loop, placed posterior to the patellar ligament using a lasso, was used to suspend a weight to expand the patellofemoral space. The lesion was then dried using a sponge. NOVOCART (R) Inject (TETEC, Reutlingen, Germany) administered onto the defect. Gel was allowed to solidify for 15 min and operation was completed. Postoperative management Knee locked in extension using a brace for 6 weeks. Continuous passive motion applied and incrementally increased until full range of motion (ROM) at week 6. Weight-bearing as tolerated was allowed with the knee in extension. Routine clinical follow-up after 3, 6 and 12 months. Results Mean age of the 5 patients 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 a Kujala 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 a translating 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