Abstract
Introduction
Primary fixation in uncemented Total Hip Replacement (THR) is achieved by implanting an appropriately sized stem. Last year, in our pilot study, we classified undersizing & reported the incidence of subsidence & radiolucent lines (RLL) in undersized uncemented stems. Now we report on a larger cohort of patients, reporting undersizing and its association with radiolucent lines and subsidence. Secondarily we report on the effect of using a collar, patients' BMI, and in a smaller group the five-year failure rate.
Methods
A retrospective review of electronic records of 1337 cases who underwent THR using the Corail stem was carried out. 1204 (Collared 1042, Uncollared 162) had a minimum follow up of 1 year, 693 of those had a follow up of at least 5 years. Radiological review was carried out by 2 independent investigators.
Results
19.77% stems were undersized. There was significantly higher incidence of subsidence & RLL in undersized stems with more than 1 year follow up. There no significant increase in incidence of RLL in those with BMI greater than 30 (16.88% vs 18.81%). Analysis of undersized collared stems demonstrated that even in this sub group undersizing is associated with increased incidence of RLL (P 0.00001) & subsidence (P 0.0003). A five year follow up, the revision rate for aseptic loosening of stem was 3.09% in undersized stems & 0.29% in appropriately sized stems (P 0.06)
Conclusions
Our study indicates undersizing of uncemented stems is associated with poorer radiological outcomes & there's a trend of higher revision rate at 5 year follow up. This reinforces the importance of implanting appropriately sized stem, as undersizing can potentially compromise stem survival in uncemented total hip arthroplasty.
