Patellofemoral Update
Isolate patellofemoral osteoarthritis is a relatively common condition. In a radiographic study of patients older than 40 years who had painful knees, Davies and colleagues noted that the prevalence of patellofemoral osteoarthritis (PFO) was 9% (19 of 206 knees).
McAlindon and colleagues found the presence of isolated patellofemoral degeneration in 12% of men and 26% of women in patients with knee pain who were older than 55 years. In patients older than 55 years without knee pain, the prevalence was 5% in both men and women. They concluded from this study that PFO is common, associated with disability, occurs in the absence of tibiofemoral disease, and can no longer be omitted from future studies of the osteoarthritis of the knee joint.
Theory
The theory is that untreated lateral patellar compression syndrome or persistent lateral patellar tracking leads to lateral retinacular shortening, medial retinaculum strain, lateral patellar facet compression and ultimately, lateral facet articular cartilage damage and osteophyte formation. The end-stage syndrome is characterized by deep anterior/lateral knee pain, crepitation and mechanical symptoms. The physical exam findings include: negative passive patellar tilt, crepitus, lateral facet tenderness and lateral patellar tilting, joint space narrowing, and sometimes patellar subluxation on the Merchant radiographs.
After a failed course of physical therapy, bracing, taping and injections, the surgical options include: arthroscopic chondroplasty, subchondral drilling, lateral facetectomy, cartilage transplantation, distal patellar realignment with a tibial tubercle osteotomy, patellectomy, patellar replacement or total knee replacement. These surgical options have mixed marginal and good published results. It may be the only option after a severe open patella fracture, but there is a high morbidity associated with a patellectomy because of the reduction of the lever arm, subsequent strength deficit and the potential to compromise future reconstructive surgery.
Lateral facetectomy study
Lateral facetectomy is supported by many studies because of its simplicity, ability to address the symptomatic osteophyte and perform a simultaneous lateral retinacular release. The study by Wetzel and Bellemans was a retrospective study of 155 patients (168 knees) who were treated with a partial lateral facetectomy for symptomatic PFO. Average patient age was 57.3 years and average follow-up was 10.9 years. An associate lateral retinacular release was performed in 78.6% of the cases.
Failure time was defined as the time from the facetectomy to another surgery. During the follow-up period, Wetzel and Bellemans found that 62 knees (36.9%) had failed. Additionally, 60 knees underwent a total knee arthroplasty, one patient underwent a patellofemoral replacement, and one patient had a patellectomy. Average time to reoperation in the failure group was 8 years. At final follow-up, good or fair results were found in 79 of the 106 knees that had not failed, corresponding to 47% of the original group.
Short-term and long-term studies have shown that lateral facetectomy can significantly improve the symptoms of PFO. This study showed beneficial effects of this procedure continued to be present in nearly half of the patients at greater than 10-year follow-up. Another long-term study by Lopez-Franco and colleagues showed similar benefits.
Decreased pain
Why does a lateral facetectomy work? It probably decreases pain because of multiple reasons. First, the engaging, symptomatic osteophyte is removed, which can improve the mechanical symptoms. Second, by removing the osteophyte and/or doing a concurrent lateral retinacular release, the lateral retinaculum is lengthened and can improve patellar tilt, tracking and decrease the patellofemoral contact forces. Third, denervation of the lateral retinaculum may diminish some of the pain.
There are concerns with a lateral facetectomy. Decrease in patellar bone stock may compromise a future patellar replacement. Over-resection of the lateral facet may lead to alterations in the patellar contact forces and an increase or progression of symptoms. Inadequate cauterization of the superior lateral geniculate artery may lead to a postoperative hemarthrosis and subsequent quadriceps weakness or shutdown, or return to the operating room for evacuation of the hematoma. A lateral facetectomy does not address patellar subluxation or mal-tracking. Additional surgery, such as a tibial tubercle osteotomy, may be done in conjunction with the facetectomy to improve tracking.
An isolated lateral facetectomy is not the correct surgery for everyone with symptomatic PFO. I caution the surgeon to cherry pick the patients for this procedure. The patients who most likely will benefit from a lateral facetectomy are the patients who have isolated symptomatic PFO, with isolated lateral facet arthritis, lateral patellofemoral joint space narrowing, and a lateral facet and/or lateral trochlear osteophyte. These patients should have no significant patellar subluxation on their Merchant view and no history of a patellar dislocation, as these factors seem to affect the outcome scores. Consideration of concomitant tibial tubercle realignment may be necessary to improve patellar tracking and to unload the articular cartilage.
References:
Davies AP. The radiologic prevalence of patellofemoral osteoarthritis. Clin Orthop Relat Res. 2002;(402):206-212.
Jones RE. Arthroscopic facetectomy for severe isolated patellofemoral arthrosis.Orthopedics. 2008;31(9):917-919.
Lopez-Franco. Knee. 2013;doi:10.1016/j.knee.2013.08.006.
McAlindon TE. Radiographic patterns of osteoarthritis of the knee joint in the community: the importance of the patellofemoral joint. Ann Rheum Dis. 1992;51(7):844-849.
Paulos LE. Arthroscopy. 2008;doi:10.1016/j.arthro.2007.12.004.
Wetzel T. Knee. 2012; doi:10.1016/j.knee.2011.04.005.
Yercan HS. The treatment of patellofemoral osteoarthritis with partial lateral facetectomy. Clin Orthop Relat Res. 2005;(436):14-19.
- Robin V. West, MD, is an associate professor, University of Pittsburgh, UPMC Sports Medicine, Department of Orthopaedics, 3200 South Water St., Pittsburgh, PA 15203; email: westrv@upmc.edu.
- Disclosure: West has no relevant financial disclosures.
