An excellent 5-year survival rate despite a high incidence of distal femoral cortical hypertrophy in a short hip stem

Although reported results on short stems sound very promising, the occurrence of distal femoral cortical hypertrophy is often observed. The aim of the present study was to report 5-year survival data of a commercially available trochanter sparing short stem and investigate the clinical impact of distal femoral cortical hypertrophy on the outcome.

123 total hip arthroplasties were performed on 120 patients from April 2008 to May 2010 (mean age 62, range 29–89 years; 71 hips from male patients, 58%). Clinical and radiological data were collected preoperative, at 6 weeks, 1, 2, 3, and 5 years postoperative to assess the outcome. Radiographs taken immediately postoperative as well as 1 and 5 years postoperative were used to identify and assess cortical hypertrophy.

1 stem had to be revised due to aseptic loosening, resulting in a Kaplan-Meier survival analysis with endpoint for stem revision of 99.2% (95% Confidence Interval 94.1–99.9) at 5 years. 96 radiological and 95 clinical follow-ups were analysed 5 years postoperative. 68 (71%) hips showed distal femoral cortical hypertrophy after 5 years. The average Harris Hip Score and Oxford Hip Score improved 33 (standard deviation (SD) 15.1, range 2–70), 18 (SD 12.1, range -10–43) points, respectively. Overall 16% of the patients reported thigh pain, unrelated to the presence of cortical hypertrophy.

This short stem shows an excellent 5-year survival rate and good clinical outcome despite a high incidence of cortical hypertrophy. However, the question of the mechanism of load transfer arises.