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Patellofemoral knee replacement effective when following strict indication criteria
Researchers find that patellofemoral arthritis occurs in 8% of patients with knee OA.
Data on more than 400 patellofemoral knee arthroplasties with the Avon prosthesis show good device survivorship but high rates of radiographic arthritic disease progression.
“It is important to establish the correct diagnosis and then refine it with stricter indications for arthroplasty,” said Christopher E. Ackroyd, FRCS, of the Avon Orthopaedic Centre in Bristol, England, at the British Orthopaedic Association Annual Congress in Glasgow. “Perhaps in the beginning we were not quite as strict as we should have been with regard to disease progression.”
Ackroyd’s group has performed patellofemoral knee replacements for 18 years, initially with the Lubinus prosthesis. However, maltracking and instability led to excessive wear and disease progression in the tibiofemoral joint, and they discontinued its use. Since 1996, they have used the Avon [Stryker] prosthesis, and have now performed 444 implants as a part of a prospective cohort study.
Device survivorship
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Image: Ackroyd CE |
Survivorship and functional outcomes have been “satisfactory” in patients with at least 5 years follow-up, Ackroyd said. “The survivorship for disease progression at 5 years was 95.8%, and there were no cases of failure of the prosthesis itself. Disease progression was the problem.”
Researchers reported 28 cases (7%) of symptomatic progression of arthritic disease in the medial or lateral tibio-femoral compartments causing recurrent joint pain. However, evidence of radiographic progression of the disease process occurred in up to 20% of patients. “Perhaps it is inevitable,” Ackroyd said.
Ackroyd discussed 12 cases of persistent, unexplained pain. Three possible causes have surfaced, including: an extended anterior saggital cut leading to overstuffing; insufficient external rotation; and oversizing of the femoral component leading to medial or lateral retinacular impingement. Furthermore, two patients with patella alta required distalization of the tibial tubercle.
Ackroyd said that retinacular impingement might be difficult to diagnose. “The implication is that there is excessive pressure in the retinaculum causing discomfort and pain on that side.” Resizing or repositioning the femoral component can eliminate the pain.
Revision to TKR
Ackroyd said if revision to total knee replacement (TKR) was eventually required, they found it to be straightforward. Among this patient cohort, 37 (8%) required revision.
The most important part of patellofemoral arthroplasty: patient selection. Avoid patients over the age of 70 and those with any deformity, he said. Ackroyd also noted that they have slowly extended the indications to include younger patients, down to the age of 30 years. If a patient has evidence of significant arthritic disease, physicians should consider other options.
“Patellofemoral arthritis occurs in about 8% of patients with osteoarthritis of the knee,” Ackroyd said. “So it is not that rare of a condition.”
For more information:
- Ackroyd CE, Newman JH, Eldrige JDJ, et al. Lessons learned from 18 years experience with isolated patellofemoral arthroplasty. Presented at the British Orthopaedic Association Annual Congress. Sept. 27-29, 2006. Glasgow.
- Dr. Ackroyd has a financial interest in the product mentioned in the article.