An alternative design of locked percutaneous device for skeletal extension through skin

A skeletal extension bar (SEB) through the skin may be involved with many treatments of orthopedic diseases. A new locked percutaneous device (LPD), LPD-III, was designed for the SEB not only to allow the skin to bind onto the SEB, similarly to the LPD, but also to allow the skin binding to shift up or down the SEB while the body changes weight. Two designs of LPD-III were tried. The LPD-III-F was made from a formation of nylon hooks, fixed directly onto the SEB surface. Soft tissue can lock and shift onto the hook formation naturally. The LPD-III-S was made by attaching a stainless steel spring as a single row of rings on a nylon sleeve. Tissue can lock through the spring rings and the nylon sleeve can be manually shifted on the SEB to follow the change of thickness of soft tissue. The SEB is a stainless steel bar implanted in the sheep ilium through the skin and buttock. Two sheep were employed, both implanted with a SEB with LPD-III-F in one ilium and another SEB with LPD-III-S in the other ilium. Our experiment demonstrates that: first, both designs, LPD-III-F and LPD-III-S, function well as a skin junction shifting device; second, the LPD-III-F has abilities to re-bind the skin that not only repair damaged binding junction but also shift the skin binding up to overcome skin downgrowth; and third, powerful evidence certifies again that the mechanical connection exists in LPD.