Similar outcome with a new anteverted or a straight standard stem: a randomized study of 72 total hip arthroplasties evaluated with clinical variables, radiostereometry, and DXA up to 2 years

Abstract

Background and purpose — The anatomical uncemented stem, SP-CL (Static Physiologicus – CementLess), designed to facilitate insertion and to avoid stress concentration at solitary contact points, has been on the market since 2014 but is not well documented. We studied its clinical performance, migration, and associated bone remodeling in a randomized controlled trial, with the Corail stem as control.

Patients and methods — 79 patients (80 hips) were primarily recruited and 71 patients (72 hips, 36 SP-CL, 36 Corail) attended the last follow-up at 2 years. The Oxford Hip Score (OHS) was the primary outcome. In addition, we assessed stem migration, changes in bone mineral density, and development of radiolucencies by RSA, DXA, and conventional radiography.

Results — At 2 years Oxford Hip Score was similar between the SP-CL and Corail stem. At 2 years the SP-CL stems showed a median distal migration of 0.23 mm (–0.1 to 5.2) and the Corail stems of 0.11 mm (–0.4 to 4.4). The SP-CL stems showed slightly more loss of bone mineral density in Gruen region 7 (p = 0.003).

Interpretation — We found no difference in clinical results between the SP-CL and the well-documented Corail stem. The same stem stability was reached between 1 and 2 years postoperatively for both stems. As a next step we think that the SP-CL stem should be studied in a multi-center setting, before being accepted for general use.