High failure rates for patellofemoral osteoarthritis surgery

Orthopaedic surgeons have expressed alarm about high revision rates with patellofemoral arthroplasty (PFA) for the treatment of isolated patellofemoral osteoarthritis.

Registry figures show ten year revision rates of over 27%, which is three times greater than revision rates seen with total knee arthroplasty, according to a new multinational study led by Australian investigators.

Although much less commonly performed than TKA,  the high failure rates with PFA are cause for concern because the procedure is often done in younger people, say the study authors led by Dr Peter Lorimer of the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR), Adelaide.

The high revision rates are equivalent to those seen with metal-on-metal conventional hip replacement that led to such devices and procedures being abandoned, they write in Clinical Orthopaedics and Related Research.

In their article they note that isolated patellofemoral arthritis is relatively uncommon, and PFA accounts for only about 1% of primary knee replacements. Since the number of PFA cases in national registries is low, they combined figures from eight countries to analyse outcomes for 6784 PFAs.

The mean age of patients undergoing PFA was between 50-60 years in the registries, and 95% of procedures were done for OA.

The combined data showed a consistent pattern of  high rate of revision rates with  PFA, with the 5-year cumulative percent revision ranging from 8.0% to 18.1%.

The ten year revision rate exceeded 20% in two large registries, including Australian figures that showed PFA revision was required in 26.6% of patients. BY way of comparison, the registry data showed that TKA survivorship was less than 3% at 2 years and less than 6% at 10 years. Most PFAs (83%) were revised to a TKA.

The most common reason for revision was disease progression (42%), ongoing pain (17%) and implant loosening or lysis (14%).

The study investigators said this suggested that “appropriate patient selection for this procedure may be of greater importance than implantation technique or prosthesis durability.”

“Although there may be potential functional benefits from PFA, these findings of consistent and alarmingly high rates of revision should create concern, particularly as this procedure is often used in younger patients,” they concluded.

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