ANALYSIS OF 10-YEAR SURVIVAL RATES FOR 100 CEMENTLESS BALGRIST STEMS IN PRIMARY TOTAL HIP PROSTHESES

Abstract

Introduction and Objectives: At present, cementless cups offer a reliable alternative for survival of total hip prostheses (THP). This study analyzes the clinical and radiographic results obtained using the Balgrist conical stem cup in patients with an average follow-up time of 10 years.

Materials and Methods: This is a study of 100 cement-less THP (Balgrist cups, SL stems) implanted between June 1991 and February 1995 in 93 patients (7 bilateral). Patients were 55% male and 45% female, with an average age of 58.5 years (20–74). Diagnoses were 72% coxarthrosis, 13% avascular necrosis, 5% fractures, 4% rheumatism, 2% Perthes disease, 2% dysplasia, and 2% post-infection sequelae. Two deaths occurred during the follow-up period (unrelated to THP). No cases were lost. Average follow-up time was 10 years (range: 8–12 years). Clinical evaluation was done using the Merle D’Aubigné scale as modified by Kramer and Maichl, to numerically evaluate degree of pain and walking capacity. Radiographic evaluation included determining radiolucent lines, sclerosis, osteolysis in the Lee and Chanley zones, stem subsidence, heterotopic ossification, and deterioration of polyethylene. Survival analysis was done according to Kaplan-Meier at 10 years using prosthetic revision as the endpoint.

Results: Clinical evaluation based on the modified Merle D’Aubigné scale was as follows: 81% very good results, 2% good, 3% satisfactory, 2% fair, and 11% poor (this last group included revision THP). Radiographic evaluation showed Zone I sclerotic lines in 4%, zone II lines in 1%, and zone I radiolucency in 2%. These lines did not correlate with cup migration. There were 28% of patients with heterotopic ossification, 3 cases with poly-ethylene deterioration, and 4 cases with migration. Survival analysis revealed 7 revisions: 4 of the cup, one due to pain from malpositioning (vertical cup), 2 for ring breakage and pain, one for ring breakage without pain, 2 THP due to septic loosening (Staphylococcus epider-midis), and one stem head revision. All of this resulted in 10–year survival rates of 92% (0.92 +/− 0.06; p< 0.05) for THP and 93% (0.93 +/−0.06; p< 0.05) for the Balgrist cup.

Discussion and Conclusions: Compared with other cementless cups, the Balgrist cup has a high survival rate. Both clinical and radiographic results obtained in this study are similar to other studies published on the use of this same type of cup.