Abstract
Introduction
Acetabular cup lucency predicts cup survival. The relationship of subchondral plate removal and cup survival is unclear. Using data from a prospective study conducted between January 1999 and January 2002 we investigated the role of subchondral plate removal in cemented acetabular cup survival at five years.
Methods
A number of cemented cups were implanted using antero-lateral and posterior approaches.1400 cups were inserted. 935 cups (67%) were followed up at 5 years and acetabular radiolucency (AR) recorded.
Results
F: M ratio was 1.88. The mean age was 66 (range 23–94). 325 cups had AR. AR was commonest in zone 1 (274). 126 cups has AR isolated to zone 1 only. AR ranged from 1–3 mm. Bone surface was clean and dry in 780 cases. High viscosity cement was used in 1391cases. Simplex was the commonest cement used (749) followed by CMW1 (347). Conventional UHMWPE acetabular liner was used in 755 and “Duration” in 644 patients. 719 Exeter cups and 363 flanged cups were inserted. Acetabular roof was decorticated in 844 and cement pressurised in 1269 cups. AR was more common if cement was not pressurised (52/78 not pressurised vs 268/850 pressurised, p=0.000), if subchondral plate was removed (219/561, p=0.002), and if Simplex or CMW1 was used instead of Palacos (p=0.000). AR after subchondral plate removal was equally common in the young and the older patients (>65 years). There was no difference in cup (p=0.55) or pressuriser type (p= 0.45) between those with or without AR. In a logistic regression model only cement pressurisation and type of cement used were predictive of AR (n=895, p=0.000). Subchondral bone removal became insignificant (p=0.443).
Discussion
AR was only affected by cement pressurisation and type of cement used. Subchondral plate removal did not prove likely to affect 5 year cup survival.
