Alteration in Articular Structure of Knee Joints in the Progression of Contractures after Spinal Cord Injury, pp. 397-426
Authors: Hideki Moriyama and Yoshiko Tobimatsu
Abstract: Joint contractures after spinal cord injuries (SCI) remain a prevalent and significant complication. Contractures after SCI have been suggested to have developmental factors associated with muscle tone. On the other hand, in patients with SCI, joints in the lower extremity are unloaded and restricted in movement. Therefore, the alterations of the periarticular connective tissue and the articular cartilage have been described in relation to the results obtained on animal models with the suppression of mechanical forces produced experimentally. The objective of this study was to clarify the relationship between the muscular and articular factors leading to contractures after SCI and to identify the changes in the periarticular connective tissue and the articular cartilage during contracture formation. Fifty-two female Wistar rats that underwent a spinal cord transection were assessed at 3, 5, 7, 14, 21, 56, 70, 84, 112 or 168 days postinjury. Knee joint motion was measured for flexion and extension. Myotomy of the transarticular muscles was then performed and range of motion was measured again. These procedures allowed isolation of the muscular and articular factors of contractures. The periarticular connective tissue and the articular cartilage of the knee joint were assessed with histological, histomorphometric, and immunohistochemical analyses. Knee flexion contractures progressed for 14 days after SCI, regardless of changes in muscle tone. The restriction in motion progressed during the first 84 days and plateaued thereafter. Both the muscles and the intra-articular tissues contributed to the progression of the contracture. In particular, the muscular factors were greater than the articular factors in extension angular displacement in which the range of motion was restricted. Histological results showed a disarranged posterior capsule in the SCI knees with the flexion contracture. Cartilage thickness of SCI knees decreased at apposed regions and increased at unapposed regions. SCI decreased the number of chondrocytes, especially at unapposed regions. Matrix staining decreased at apposed regions. This study defined the time course that contracture progression was more rapid in the early stage after SCI and stabilized in the later stage of injury. Based on our findings of contractures in SCI, in addition to the changes of the intra-articular tissues, more attention should be directed to the changes of the muscles. A disarranged capsule may lead to joint stiffness. The alteration of the periarticular connective tissue and the articular cartilage after SCI would not be explained only by either a suppression of mechanical forces or an influence through nerve tissues.