Evaluation of subsidence, chondrocyte survival and graft incorporation following autologous osteochondral transplantation.

PURPOSE: The aim of this study was to evaluate subsidence tendency, surface congruency, chondrocyte survival and plug incorporation after osteochondral transplantation in an animal model. The potential benefit of precise seating of the transplanted osteochondral plug on the recipient subchondral host bone ('bottoming') on these parameters was assessed in particular. METHODS: In 18 goats, two osteochondral autografts were harvested from the trochlea of the ipsilateral knee joint and inserted press-fit in a standardized articular cartilage defect in the medial femoral condyle. In half of the goats, the transplanted plugs were matched exactly to the depth of the recipient hole (bottomed plugs; n = 9), whereas in the other half of the goats, a gap of 2 mm was left between the plugs and the recipient bottom (unbottomed plugs; n = 9). After 6 weeks, all transplants were evaluated on gross morphology, subsidence, histology, and chondrocyte vitality. RESULTS: The macroscopic morphology scored significantly higher for surface congruency in bottomed plugs as compared to unbottomed reconstructions (P = 0.04). However, no differences in histological subsidence scoring between bottomed and unbottomed plugs were found. The transplanted articular cartilage of both bottomed and unbottomed plugs was vital. Only at the edges some matrix destaining, chondrocyte death and cluster formation was observed. At the subchondral bone level, active remodeling occurred, whereas integration at the cartilaginous surface of the osteochondral plugs failed to occur. Subchondral cysts were found in both groups. CONCLUSIONS: In this animal model, subsidence tendency was significantly lower after 'bottomed' versus 'unbottomed' osteochondral transplants on gross appearance, whereas for histological scoring no significant differences were encountered. Since the clinical outcome may be negatively influenced by subsidence, the use of 'bottomed' grafts is recommended for osteochondral transplantation in patients.

Osteochondral autograft transplantation for osteochondritis dissecans of the knee. Preliminary results of a prospective case series.

To evaluate the short-term outcome of osteochondritis dissecans (OCD) treated with mosaic osteochondral autograft transplantation (OAT), 7 male patients (mean age 33.4) with 8 OCD lesions on the lateral border of the medial femoral condyle were prospectively followed. Patients were evaluated by the International Knee Documention Committee (IKDC) score and the Knee injury and Osteoarthritis Outcome Score (KOOS) questionnaires preoperatively, at 6 months and 1 year after surgery. MRI evaluation using the modified Sanders score was performed at 1-year follow-up. The IKDC subjective score and all subscales of the KOOS improved significantly. MRI evaluation showed good surface congruency, no oedema or protuberance of the osteocartilaginous cylinders, good similarity of cartilage thickness and a non-complete osseous integration. With the small numbers of patients available, no correlation could be found between MRI findings, percentage of defect coverage and patient satisfaction. Mosaic OAT appeared in this study as a valid treatment option in selected cartilage defects. OCD lesions improved significantly following osteochondral transplantation. The limitations of this technique are the number and size of the plugs needed to repair the defect. Future research should focus on identifying the appropriate choice of operative treatment for well defined subtypes of articular cartilage lesions, rather than searching for one superior technique for all.

Bone scintigraphy after osteochondral autograft transplantation in the knee: 13 patients followed for 4 years.

BACKGROUND AND PURPOSE: Autologous osteochondral transplantation (OCT) is an established method of treating articular cartilage defects in the knee. However, the potential for donor site morbidity remains a concern. Both the restoration of the original cartilage defect and the evolution of the donor site defects can be evaluated by bone scintigraphy. Thus, we performed a prospective bone scintigraphic evaluation in patients who were treated with OCT. PATIENTS AND METHODS: In 13 patients with a symptomatic articular cartilage defect, bone scintigraphies were obtained preoperatively, 1 year after osteochondral transplantation, and finally at an average follow-up of 4 (2.5-5.5) years. The evolution of scintigraphic activity was evaluated for both the recipient and the donor site. Parallel, clinical scoring was performed using the Lysholm knee scoring scale, the Cincinnati knee rating system, and the Tegner activity score. RESULTS: The bone scintigraphic uptake was elevated at the involved femoral condyle preoperatively, and gradually decreased to normal levels in 7 of 11 cases. The originally normal uptake at the trochlea increased 1 year after transplantation. Then, a gradual decrease in uptake occurred again at this donor site to remain elevated at the final scintigraphy. A correlation was found between elevated scintigraphic activity and the presence of retropatellar crepitus. The mean Lysholm and Cincinnati scores had increased 1 year after transplantation. The mean Tegner score had increased 3 years after transplantation. INTERPRETATION: Elevated bone scintigraphic activity from an osteochondral lesion in the knee can be restored with OCT. However, increased scintigraphic activity is introduced at the donor site, which becomes reduced with longer follow-up. The use of fairly large osteochondral plugs appears to correlate with retropatellar crepitus and increased scintigraphic activity, and is not therefore recommended.

A cadaveric analysis of contact stress restoration after osteochondral transplantation of a cylindrical cartilage defect.

Osteochondral transplantation is a successful treatment for full-thickness cartilage defects, which without treatment would lead to early osteoarthritis. Restoration of surface congruency and stability of the reconstruction may be jeopardized by early mobilization. To investigate the biomechanical effectiveness of osteochondral transplantation, we performed a standardized osteochondral transplantation in eight intact human cadaver knees, using three cylindrical plugs on a full-thickness cartilage defect, bottomed on one condyle, unbottomed on the contralateral condyle. Surface pressure measurements with Tekscan pressure transducers were performed after five conditions. In the presence of a defect the border contact pressure of the articular cartilage defect significantly increased to 192% as compared to the initially intact joint surface. This was partially restored with osteochondral transplantation (mosaicplasty), as the rim stress subsequently decreased to 135% of the preoperative value. Following weight bearing motion two out of eight unbottomed mosaicplasties showed subsidence of the plugs according to Tekscan measurements. This study demonstrates that a three-plug mosaicplasty is effective in restoring the increased border contact pressure of a cartilage defect, which may postpone the development of early osteoarthritis. Unbottomed mosaicplasties may be more susceptible for subsidence below flush level after (unintended) weight bearing motion.

Press-fit stability of an osteochondral autograft: Influence of different plug length and perfect depth alignment.

BACKGROUND: Osteochondral autologous transplantation is used for the treatment of full-thickness articular cartilage lesions of a joint. Press-fit stability is an important factor for good survival of the transplanted plugs. MATERIAL AND METHODS: 36 plugs of three different lengths were transplanted in fresh-frozen human knees. On one condyle, 3 plugs were exactly matched to the depth of the recipient site ("bottomed" plugs) and on the opposite condyle 3 plugs were 5 mm shorter than the depth of the recipient site ("unbottomed" plugs). Plugs were left protruding and then pushed in until flush, and then to 2 mm below flush level, using a loading apparatus. RESULTS: Longer plugs needed higher forces to begin displacement. At flush level, bottomed plugs needed significantly higher forces than unbottomed plugs to become displaced below flush level (mean forces of 404 N and 131 N, respectively). Shorter bottomed plugs required higher forces than longer bottomed ones. INTERPRETATION: Bottomed plugs generally provide much more stability than unbottomed ones. Short bottomed plugs are more stable than long bottomed plugs. Thus, in clinical practice it is advisable to use short bottomed plugs. If, however, unbottomed plugs are still chosen, the longer the plug the higher the resulting stability will be because of higher frictional forces.