Autologous Chondrocyte Implantation "Segmental-Sandwich" Technique for Deep Osteochondral Defects in the Knee: Clinical Outcomes and Correlation With Magnetic Resonance Imaging Findings

Abstract

Background: Symptomatic osteochondral defects are difficult to manage, especially in patients with deep (>8-10 mm) empty defects. The restoration of articular congruence is crucial to avoid the progression to osteoarthritis (OA).

Purpose: To describe the autologous chondrocyte implantation (ACI) "segmental-sandwich" technique for restoration of the osteochondral unit and to evaluate midterm outcomes in patients treated with this procedure. Correlations between magnetic resonance imaging (MRI) and radiographic findings with outcomes were assessed.

Study design: Case series; Level of evidence, 4.

Methods: Outcomes were evaluated for a consecutive cohort of 15 patients with symptomatic deep (>8 mm) osteochondral lesions who underwent autologous bone grafting plus the ACI segmental-sandwich technique performed by a single surgeon between 2003 and 2011. Patients with a minimum 2-year follow-up were included. All patients completed validated clinical outcome scales and a patient satisfaction survey. The Kellgren-Lawrence (K-L) grade was assessed for the progression to OA. The repair site was evaluated with the MOCART (magnetic resonance observation of cartilage repair tissue) score. Filling and tissue characteristics of the bone defect were analyzed with MRI.

Results: All patients (mean age at surgery, 31.0 ± 9.1 years) were available for follow-up (mean follow-up, 7.8 ± 3.0 years; range, 2-15 years). The mean chondral lesion size was 6.0 ± 3.5 cm² (range, 1.5-13.5 cm²), with a mean bone defect area of 1.7 cm² (27%-40% of overall surface area treated by ACI) and depth of 1.0 cm. All patients had successful clinical outcomes, and all functional scores improved significantly (P < .05). Patients reported a very high satisfaction rate (93%). The K-L grade demonstrated no significant progression to OA over a mean follow-up of 4.7 years. For 12 patients with MRI results available, the mean MOCART score at a mean of 3.3 years was 64.2 ± 19.9, with complete or near-complete (≥75% of defect volume) chondral defect filling (83%) and complete integration to adjacent cartilage (83%). Bone defects were completely filled in 83% of patients.

Conclusion: The ACI segmental-sandwich technique provides significant functional improvements at midterm follow-up and excellent survival rates. This unique treatment allows for the resurfacing of cartilage defects and the repair of underlying segmental bone lesions.

Keywords: articular; autologous bone graft; autologous chondrocyte implantation; cartilage; osteochondral lesion; osteochondral unit.

Figure 1.

Autologous chondrocyte implantation segmental-sandwich technique. (A) Osteochondral defect: the bone defect is smaller than the overlying chondral defect. (B) Preparation of the bone defect: a high-speed bur, usually 8 mm in diameter, removed all subchondral sclerotic bone back to healthy-appearing spongy bone. Then, a 3 mm–diameter bur undermined the subchondral bone to secure the membrane when it was glued to the graft with overlying gentle pressure. (C) Fibrin glue was applied over the bone graft, and the membrane was secured. The second membrane was then sutured to the surface with the tourniquet down and with a dry defect bed. The cultured chondrocytes were then injected into the sealed cavity. The bone grafted area was smaller than the overlying chondral defect.

Figure 2.

Intraoperative photographs and postoperative magnetic resonance imaging (MRI). A 22-year-old male football player who underwent prior treatment of a medial femoral condyle (MFC) defect with a fresh osteochondral allograft that failed by resorption and collapse of the allograft. (A) Debrided defect of the MFC with osseous deficiency from removal of the allograft and extension of chondral degeneration around it, producing a segmental bone defect of the surface chondral area. (B) Osseous defect bone grafted with autologous cancellous bone to the level of the adjacent subchondral bone. (C) The osseous bone grafted area was then covered with fibrin glue and a membrane, the area was covered with a neural patty, and the tourniquet was let down. The overall area was then covered with a second membrane that was sutured and filled with cells. (D) Coronal view (T1-weighted) showing complete osseous defect filling (black arrow) and complete chondral defect filling with a congruent articular surface (white arrow) at 6 months postoperatively. (E) Sagittal view showing complete chondral defect filling (over the bone grafted [black arrows] and non–bone grafted [white arrows] areas). This case was included in the present study; however, the MRI results were excluded, as postoperative MRI was performed at 6 months postoperatively and did not meet the inclusion criteria of MRI evaluations (>1 year after index surgery).

Figure 3.

Modified Cincinnati Knee Rating System: overall condition.