Abstract
In high-demand situations, modern thinking and experience in total hip arthroplasty (THA) favours the uncemented press-fit cup over its cemented counterpart. Before its regular use in 1996, a high-demand cemented stem was designed for use as a short revision stem with a press-fit cup, with or without impaction bone grafting, in active people, especially those over 55 years.
Conceptually, a collarless double-tapered highly polished design was preferred. The clip-on hollow centraliser was designed for 5-mm subsidence. The valgus stem, with cement superior to the shoulder, limited upward pistoning in the cement sleeve, creating less debris. The stiff upper and flexible distal part resulted in a decreased contribution from shear and an increased contribution from compression in load transfer from prosthesis to cement. Three sizes are available: G1, G2 and G3. A straight type is presently being developed for smaller patients with congenital dysplasia of the hip.
The stem, made by (Thornton Heavy Engineering Sheffield, United Kingdom), from Rex 734 stainless steel to ISO-2002 standards, tapers 10 mm to 12 mm (6°). All tolerances are adequate to handle Inox or Ceramic heads.
From April 1996 to December 2002, 278 stems were implanted in Dr Weber’s practice. The first 172 hip operations (168 patients) were studied. The mean age was 58.6 years. There were 137 primary hips and 25 revisions.
The mean follow-up period was 4.5 years (3 to 7). Three patients died with the prosthesis in situ. Two reoperations were done: one cup was revised for recurrent dislocation and one fracture below the step was successfully plated. Only three cases of subsidence were documented, all of them less than 3 mm. To date there have been no stem revisions.
The prosthesis, together with the stainless steel head and cross-linked cup, can be regarded as cost-effective and can be used routinely, as a high-demand prosthesis with press-fit cup, or as a short-revision prosthesis.
The abstracts were prepared by Professor M.B.E. Sweet. Correspondence should be addressed to him at PO Box 47363, Parklands, Johannesburg 2121, South Africa.
