The effects of temperature on the viscoelastic properties of the rabbit medial collateral ligament.

There are disparate views on the effects of temperature on the mechanical properties of ligaments and tendons. We attempted to resolve the inconsistencies by testing the medial collateral ligaments of twelve, three-month old New Zealand white rabbits in both elastic-dominated and viscous-dominated tests between 25 degrees C and 55 degrees C. We found that in elastic-dominated monotonic loading, the loading portions of the load-extension curves were mathematically similar. Differences could be accounted for through a base-line shift of the origin caused by additional relaxation and thermal contraction/expansion of the apparatus and specimen. In tests where the viscous component of behavior was manifest, we found results similar to those of other investigators. Thus we conclude that in assessing the effects of temperature on the mechanical properties of tissues it is important to account for both temperature and initial positions of the apparatus and specimen, and to consider the effects of both relaxation and thermal contraction/expansion.

Production of catabolin by synovium from an experimental model of osteoarthritis.

Catabolic factors from synovium, or catabolins, may be important in the pathogenesis of osteoarthritis. The synovial production of catabolin in osteoarthritis was studied using the experimental model of osteoarthritis induced by section of the anterior cruciate ligament. At 1, 4, and 32 weeks after operation, the synovium was harvested, cultured, and the synovial conditioned medium assayed for catabolic activity. The synovial conditioned medium from the operated joints was significantly more capable of inducing cartilage destruction (p less than 0.05) than was the synovial conditioned medium from the unoperated knees. However, when the results were expressed relative to the weight of synovium, the differences were not significant. These results suggest that the increased production of catabolic synovial factors in early experimental osteoarthritis is probably a result of the synovial hypertrophy.

Closed reduction of dislocations of the lower cervical spine.

Dislocation of the lower cervical spine (C3-T1) is associated with a high incidence of neurologic injury. Attempted closed reduction by skeletal traction with weights ranging up to 50 lb (23 kg) is considered standard care in North America, although these attempts are often unsuccessful. This retrospective review, over a 6-year span, of 39 patients with dislocations and facet locks of the lower cervical spine treated with closed reduction showed that 35 (90%) were successful. Recommended weight was exceeded in 22 patients (63%) with no deteriorations in neurologic status. If patients are monitored radiologically and neurologically throughout traction, up to 70% of body weight can be used safely. An algorithm for treatment is provided.

Magnetic resonance imaging of osteoarthritis: correlation with gross pathology using an experimental model.

Conventional radiography has several limitations in the study of osteoarthritis (OA): changes occur late, they are restricted to bone, and they do not correlate well with the patient's symptoms. Magnetic resonance imaging (MRI) can visualize with great detail the soft tissue changes in and around joints. We have obtained MR images of knees using an experimental model of OA in order to study the early changes of OA, to correlate the images with the gross pathology, and to compare MR images with radiographs. The changes on MRI correlated with the gross pathological changes as assessed by Kendall's rank correlation test as follows: meniscal changes, tau = 0.58 (p less than 0.01); osteophytes, tau = 0.59 (p less than 0.05); capsular fibrosis, tau = 0.55 (p less than 0.05); and overall, tau = 0.68 (p less than 0.001). Abnormalities were evident on MRI as early as 4 weeks after the onset of the disease, which is 8 weeks before they appear on radiographs. Thus, MRI can show changes in OA earlier than radiography can, and the images correlate with the gross pathology.

Sacral fractures: classification and neurologic implications.

Sacral fractures can be classified, for diagnostic purposes, into three categories: 1) the sacral fracture which occurs in conjunction with a pelvic fracture, 2) the isolated sacral fracture of the lower segments; and 3) the isolated sacral fracture of the upper segments. The frequency of each type of fracture decreases from (1) to (3), but the neurologic implications increase. However, treatment for the three types should be conservative, since neurologic deficit at this level tends to improve spontaneously.