Experimental lead arthropathy: an animal model.

BACKGROUND: We previously demonstrated short-term effects of intra-articular lead on joint structures in an animal model. We now present histopathologic findings in animals studied over a more extended period. METHODS: Twelve female New Zealand White rabbits had identical lead or stainless steel pellets, or a sham arthrotomy (without implant) inserted in both front knees. The rabbits were killed 4 at a time at 6, 10, and 14 weeks after implantation, and the knee joint structures were evaluated histologically for changes in the synovium, articular cartilage, and meniscus. RESULTS: Histology of the tibial articular surface, femoral articular surface, medial meniscus, lateral meniscus, and synovium showed greater signs of degeneration in the knees with lead implants than controls at all time periods. CONCLUSION: Intrasynovial lead, which does not undergo fibrous encapsulation, has been linked to lead intoxication. Clinical and experimental reports support removal of lead bodies from articular areas in an attempt reduce or slow the degeneration of affected joints. Nonmechanical effects of lead on intraarticular structures may lead to degenerative changes

Histology of the extensor retinaculum of the wrist and the ankle.

The extensor retinaculum of the wrist has been used for reconstruction of the annular pulleys of the flexor sheath. We examined the histologic structure of the extensor retinaculum and tendon sheath of the wrist and ankle in cadaveric specimens using hematoxylin-eosin and Verhoeff-van Gieson stains to detect elastin and alcian blue to detect hyaluronic acid, comparing the structure with that described previously for the annular pulleys. Three distinct layers are identified in the retinaculums of both the ankle and wrist: the inner gliding layer, with hyaluronic acid-secreting cells, shows isolated chondroid metaplasia; the thick middle layer contains collagen bundles, fibroblasts, and interspersed elastin fibers; and the outer layer consists of loose connective tissue containing vascular channels. This basic 3-layered histologic composition of the extensor retinaculum is carried in anatomic pulleys throughout the body and appears to represent an adaptive mechanism to provide both a smooth gliding surface as well as the mechanical strength to prevent tendon bowstringing. Given the same histologic structure as the annular pulleys, the extensor retinaculum is a reasonable biologic replacement for the reconstruction of deficient annular pulleys. Likewise, the extensor retinaculum of the ankle could be used to reconstruct a deficient retinaculum of the wrist.