The effects of rasp oversize on the clinical and radiographic outcomes of total hip arthroplasty with a collared satin-finished composite-beam cemented stem

Abstract Background This study aimed to compare the clinical and radiographic outcomes of using two different oversized rasps in total hip arthroplasty (THA) with a composite-beam cemented stem (DCM-J). Methods A consecutive series of 105 hips underwent hybrid THA using the DCM-J stem between 2006 and 2010. Among the patients with a minimum 10-year follow-up, a 1.5-mm oversized rasp was used in 38 hips (group S), while a 0.5-mm oversized rasp was used in 36 hips (group M). The Japanese Orthopaedic Association (JOA) hip score and radiographic findings were evaluated, including cement mantle thickness, stress shielding, and cortical hypertrophy Results The JOA hip score was significantly improved postoperatively with 100% of the implant survival rate in both groups when septic loosening was excluded. Radiographic assessment performed immediately postoperatively revealed that the cement mantle thickness was significantly larger in group M than group S in Gruen zone 1 but did not differ between groups in zones 2–7. Stress shielding was significantly more frequent in group M than group S at 2 years (p=0.011), 5 years (p=0.012), and ≥10 years postoperatively (p=0.038). Cortical hypertrophy appeared in a time-dependent manner; however, the prevalence did not significantly differ between groups at final follow-up at a mean of 11.7 years (range 10–14 years) postoperatively. Conclusions The DCM-J stem achieved good clinical results in both groups. Stress shielding was significantly more frequent in THA using the 0.5-mm rasp than the 1.5-mm rasp, indicating that sufficient cement mantle room should be prepared for the cemented stem.