How Gender, Age, Bone Strength Predict TKA Failures

Watch outcomes of total knee arthroplasty (TKA) most closely for women in the postmenopausal age group. Artificial knees are most likely to need replacement in women between the ages of 65 and 74, according to a new study reported at the American Academy of Orthopaedic Surgeons meeting in New Orleans.

Based on records from the Nationwide Impatient Sample for 301,718 patients who had revision surgery between 2006 and 2010, the study found that infection (25%) and mechanical loosening (18%) of these prostheses were the most common reasons for their repacement.

More than 60% of these patients had a moderate severity of illness score, reported Kevin Bozic MD of the University of California San Francisco, making comorbidities another risk factor for revision.

Whether or not a woman is using bisphosphonates may have an important impact on the need for revision surgery, to judge from another large retrospective study. Looking at more than 34,000 records of primary TKA procedures done in California in the decade between 2001 and 2011, and commparing them with information from an osteoporosis screening database, Monti Khatod MD and coworkers from Kaiser Permanente discovered a strong effect for the anti-osteoporosis medication.

Aming the nearly 20% of women taking bisphosphonates who had knee replacement, fewer than 1% had to have revision surgery. But 2.7% of those not on bisphosphonates needed their TKA procedures redone

This correlation did not hold, however, for women younger than 65 years of age who had a normal DEXA scan. In this group, the overall adjusted risk of peri-prosthetic fractures was nearly four times higher than average.

Before prescribing bisphosphonates for a patient younger than 65 who is anticipating knee replacement, order a DEXA scan, concludes their report. If the scan is normal, don't start bisphosphonates.