A Longitudinal Study of Subchondral Plate and Trabecular Bone in Followed up for 54 Months Cruciate-deficient Dogs with Osteoarthritis

From the Orthopaedic Research Laboratories, Section of Orthopaedics, Department of Surgery, the Multipurpose Arthritis and Musculoskeletal Disease Center, and the Division of Rheumatology, Department of Internal Medicine, University of Michigan, Ann Arbor; and the Rheumatology Division, Department of Medicine, the Multipurpose Arthritis and Musculoskeletal Disease Center, and the Specialized Center of Research in Osteoarthritis, Indiana University School of Medicine, Indianapolis. Supported in part by NIH grants AR-01793, AR-20557, AR-38406, AR-39250, and AR-20582. D. K. Dedrick, MD: Orthopaedic Research Laboratories, Section of Orthopaedics, Department of Surgery, Multipurpose Arthritis and Musculoskeletal Disease Center, and Division of Rheumatology, Department of Internal Medicine, University of Michigan; S. A. Goldstein, PhD: Orthopaedic Research Laboratories, Section of Orthopaedics, Department of Surgery, Multipurpose Arthritis and Musculoskeletal Disease Center, University of Michigan; K . D. Brandt, MD: Rheumatology Division, Department of Medicine, Multipurpose Arthritis and Musculoskeletal Disease Center, and Specialized Center of Research in Osteoarthritis, Indiana University School of Medicine; B. L. O’Connor, PhD: Rheumatology Division, Department of Medicine, Multipurpose Arthritis and Musculoskeletal Disease Center, and Specialized Center of Research in Osteoarthritis, Indiana University School of Medicine; R. W. Goulet, MS: Orthopaedic Research Laboratories, Section of Orthopaedics, Department of Surgery, Multipurpose Arthritis and Musculoskeletal Disease Center, University of Michigan; M. Albrecht, BS: Rheumatology Division, Department of Medicine, Multipurpose Arthritis and Musculoskeletal Disease Center, and Specialized Center of Research in Osteoarthritis, Indiana University School of Medicine. Address reprint requests to Dale K. Dedrick, MD, Orthopaedic Research Laboratory, GO161 N.I.B., University of Michigan, 400 North Ingalls, Ann Arbor, MI 48109-0486. Submitted for publication May 5 , 1992; accepted in revised form February 9, 1993. were analyzed with microscopic computed tomography (micro-CT) at a resolution of 60 pm, and biochemical and morphologic changes in the femoral articular cartilage were assessed. Results. At 3 months and 18 months after ACLT, the articular cartilage in the unstable knee showed histologic changes typical of early OA and increased water content and uronic acid concentration; by 54 months, full-thickness ulceration had developed. Micro-CT analysis showed a loss of trabecular bone in the unstable knee, compared with the contralateral knee, at all time points. Al. both 18 and 54 months, the differences in trabecular thickness and surface-tovolume ratio were greater than at 3 months. Although the mean subchondral plale thickness, especially in the medial aspect of the medial tibial plateau, was greater in the OA knee than in the contralateral knee 18 months and 54 months after ACLI‘, these differences were not statistically significant; however, the difference was significantly greater at 54 months than at 3 months. Conclusion. Thickening of the subchondral bone is not required for the development of cartilage changes of OA in this model. The bony changes that develop after ACLT, however, could result in abnormal transmission of stress to the overlying cartilage and thereby contribute to the progression of cartilage degeneration.