Patient-related risk factors leading to aseptic stem loosening in total hip arthroplasty: a case-control study of 5,035 patients.
BACKGROUND
We hypothesized that certain patient characteristics have different effects on the risk of early stem loosening in total hip arthroplasty (THA). We therefore conducted a case-control study using register-database records with the aim of identifying patient-specific risk factors associated with radiographic signs of aseptic loosening of the femoral component in THA.


METHODS
Data were derived from a multinational European registry and were collected over a period of 25 years. 725 cases with radiographic signs of stem loosening were identified and matched to 4,310 controls without any signs of loosening. Matching criteria were type of implant, size of head, date of operation, center of primary intervention, and follow-up time. The risk factors analyzed were age at operation, sex, diagnosis and previous ipsilateral operations, height, weight, body mass index and mobility based on the Charnley classification.


RESULTS
Women showed significantly lower risk of radiographic loosening than men (odds ratio (OR) 0.64). Age was also a strong factor: risk decreased by 1.8% for each additional year of age at the time of surgery. Height and weight were not associated with risk of loosening. A higher body mass index, however, increased the risk of stem loosening to a significant extent (OR 1.03) per additional unit of BMI. Charnley Class B, indicating restricted mobility, was associated with lower risk of loosening (OR 0.78).


CONCLUSIONS
An increased activity level, as seen in younger patients and those with unrestricted mobility, is an important factor in the etiology of stem loosening. If combined with high BMI, the risk of stem loosening within 10 years is even higher. A younger person should not be denied the benefits of a total hip arthroplasty but must accept that the risk of future failure is increased.
Münger
Peter
P
Maurice E. Müller Research Centre in Orthopaedic Surgery, University of Bern. Switzerland.
Röder
Christoph
C
Ackermann-Liebrich
Ursula
U
Busato
André
A
D000328:Adult; D000367:Age Factors; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D015992:Body Mass Index; D016022:Case-Control Studies; D005260:Female; D005500:Follow-Up Studies; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000601:surgery; D011475:Prosthesis Failure; D012042:Registries; D012086:Reoperation; D012307:Risk Factors; D012737:Sex Factors