Abstract
INTRODUCTION:
Short femoral stems are receiving increasing attention for less invasive total hip replacement (THR). The purpose of this study is to report our initial experience with a short modular femoral (SMF) stem at a minimum two-year follow up.
METHODS:
Twenty-six primary total hip arthroplasties (THAs) using the SMF stem were performed between August 2009 and January 2010. Patients were evaluated clinically with Harris Hip Score (HHS) and radiographically up to two years. Radiographs were analyzed to determine the degree of stem migration from its initial postoperative position. These parameters were compared to those of a cohort of 54 patients implanted with a monolithic tapered wedge stem from the same manufacturer over the same time period.
RESULTS:
There were three early revisions of the femoral component for thigh pain in the SMF group, and one revision for CoCr allergy, with improvement in HHS from 60 to 89. Radiographically, 20 of 26 stems (76%) migrated into varus in the first six weeks. Of these, eight patients (29.6%) reported moderate to severe thigh pain. Radiographic evidence of isolated lateral cortical hypertrophy at the stem tip was seen in 46% of study patients, and evidence of osteointegration was seen in all cases by one year. Between one and two years post op the pain had resolved in four patients not revised. It was persistent in one patient. Comparative analysis with the control group demonstrated no significant difference in stem subsidence, but a significantly greater varus shift in coronal-plane angulation (Mean 4.3°, SD 3.8° vs. Mean 1.0°, SD 1.1°; p < 0.0001). Mean HHS was lower in the SMF group (85.2 vs. 91.4; p < 0.01) at last follow up.
DISCUSSION AND CONCLUSION:
The SMF stem demonstrated a tendency towards migration into a varus position where the lateral stem touches the lateral cortex of the femur, with resulting relatively higher incidence of thigh pain and early aseptic revision.
