RESUMO
OBJECTIVE: The articular cartilage of autologous osteochondral grafts is typically different in structure and function from local host cartilage and thereby presents a remodeling challenge. The hypothesis of this study was that properties of the articular cartilage of trochlear autografts and adjacent femoral condyle are associated with the 3-D geometrical match between grafted and contralateral joints at 6 and 12 months after surgery. DESIGN: Autografts were transferred unilaterally from the lateral trochlea (LT) to the medial femoral condyle (MFC) in adult Spanish goats. Operated and contralateral Non-Operated joints were harvested at 6 and 12 months, and analyzed by indentation testing, micro-computed tomography, and histology to compare (1) histological indices of repair, (2) 3-D structure (articular surface deviation, bone-cartilage interface deviation, cartilage thickness), (3) indentation stiffness, and (4) correlations between stiffness and 3-D structure. RESULTS: Cartilage deterioration was present in grafts at 6 months and more severe at 12 months. Cartilage thickness and normalized stiffness of Operated MFC were lower than Non-Operated MFC within the graft and proximal adjacent host regions. Operated MFC articular surfaces were recessed relative to Non-Operated MFC and exhibited lower cartilage stiffness with increasing recession. Sites with large bone-cartilage interface deviations, both proud and recessed, were associated with recessed articular surfaces and low cartilage stiffness. CONCLUSION: The effectiveness of cartilage repair by osteochondral grafting is associated with the match of 3-D cartilage and bone geometry to the native osteochondral structure.
RESUMO
Current treatments for damaged articular cartilage (i.e., shaving the articular surface, perforation or abrasion of the subchondral bone, and resurfacing with periosteal and perichondrial resurfacing) often produce fibrocartilage, or hyaline-appearing repair that is not sustained over time (Henche 1967, Ligament and Articular Cartilage Injuries. Springer-Verlag, New York, NY, pp. 157-164; Insall 1974, Clin. Orthop. 101: 61-67; Mitchell and Shepard 1976, J. Bone Joint Surg. [Am.] 58: 230-233; O'Driscoll et al. 1986, J. Bone Joint Surg. [Am.] 68: 1017-1035; 1989, Trans. Orthop. Res. Soc. 14: 145; Kim et al. 1991, J. Bone Joint Surg. [Am.] 73: 1301-1315). Autologous chondrocyte transplantation, although promising, requires two surgeries, has site-dependent and patient age limitations, and has unknown long-term donor site morbidity (Brittberg et al. 1994, N Engl. J. Med. 331: 889-895; Minas 2003, Orthopedics 26: 945-947; Peterson et al. 2003, J. Bone Joint Surg. Am. 85-A(Suppl. 2): S17-S24). Osteochondral allografts remain a widely used method of articular resurfacing to delay arthritic progression. The present study compared the histological response to four types of osteochondral implants in a rabbit model: autograft, frozen, freeze-dried, and fresh implants. Specimens implanted in the femoral groove were harvested at 6 and 12 weeks. Results showed similar restoration of the joint surface regardless of implant type, with a trend toward better repair at the later timepoint. As has been observed in other studies (Frenkel et al. 1997, J. Bone Joint Surg. 79B: 281-286; Toolan et al. 1998, J. Biomed. Mater. Res. 41: 244-250), each group in this study had at least one specimen in which a healthy-appearing surface on the implant was not well-integrated with host tissues. Although the differences were not statistically significant, freeze-dried implants at both timepoints had the best histological scores. The osteochondral grafts tested successfully restored the gross joint surface and congruity. At 12 weeks, no significant differences were observed between the various allografts and autologous osteochondral grafts.