The CLS system. Theoretical concept and results.

The CLS femoral prosthesis is a titanium stem designed as a 3-dimensional taper for press-fit implantation. The distal part of the prosthesis is intentionally made small so that it will not fill the intramedullary canal in the proximal diaphysis. The surface is bead blasted and has no bone ingrowth surface. Ribs in the proximal part of the prosthesis are designed to minimize rotational migration. The CLS acetabular component is a 6-sided expanding cup intended for implant with press-fit stabilization. This article emphasizes indications for use of the CLS, and it includes a brief report on clinical and radiographical results. Data from a review of the first 300 CLS stems implanted from 1983 to 1985 with an 82-month average follow-up suggested that neither bone ingrowth nor distal fit and fill are necessary for stable secondary fixation of an uncemented stem.