Patellofemoral arthroplasty for patellofemoral OA improved alignment, knee function
Patellofemoral arthroplasty yielded significant improvements in patellofemoral alignment and knee function among patients with patellofemoral osteoarthritis with trochlear dysplasia, according to results.
Researchers preoperatively and postoperatively assessed patellar tilt, congruence angle, Blackburne-Peel ratio, tibial tuberosity-trochlear groove (TT-TG) distance and lateral trochlear inclination for changes in patellofemoral alignment in 35 patients with patellofemoral OA and trochlear dysplasia who underwent patellofemoral arthroplasty between January 2014 and March 2018. Researchers also assessed patient reported functional outcomes using the Oxford Knee Score (OKS).
During a mean follow-up of 24 months, researchers found excellent intraclass correlation coefficients for all measurements, as well as significant postoperative improvement in patellofemoral alignment and knee function. Results showed a decrease in patellar tilt from approximately 23.3° preoperatively to 6.4° postoperatively and in congruence angle from approximately 32.3° preoperatively to 10.2° postoperatively. Lateral trochlear inclination increased from approximately 8.3° preoperatively to 16° postoperatively, while the TT-TG distance decreased from approximately 18.2 mm preoperatively to 11.5 mm postoperatively, according to results.
Researchers noted no significant postoperative change in Blackburne-Peel ratio. However, researchers found improvements in the average OKS from 19.5 preoperatively to 29.2 at 6 months postoperatively, to 37.9 at 1 year postoperatively and to 39.1 at final follow-up. During the short-term follow-up, no patient developed patellofemoral malalignment or prosthesis loosening, according to results.
Perspective
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There is no doubt that patellofemoral arthroplasty is effective for pain relief and improved function in patients with isolated patellofemoral arthritis, but it is an arthroplasty. Correction of the parameters that the authors include is predictable given proper surgical technique and alignment. Was joint preservation surgery, such as osteotomy, cartilage restoration or tibial tubercle transfer considered, particularly in younger patients? These also work well and avoid risks of late component wear or loosening.
Patellofemoral arthroplasty is a great alternative for older patients, but joint preservation must be considered, particularly in younger patients. Patient age and activity level must always enter into the decision-making process.
I admit my bias, but anteromedialization of the tibial tubercle is consistently successful for lateral patellofemoral arthritis long term, with minimum 15-year follow-up as shown by Klinge and colleagues, and in patients who are older than 50 years, as shown by Carofino and colleagues. Always weigh the relative risks and benefits carefully.
References:
Carofino BC, et al. J Knee Surgery. 2008; doi:10.1055/s-0030-1247803.
Klinge SA, et al. Arthroscopy. 2019;doi:10.1016/j.arthro.2019.02.030.
Perspective
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Patellofemoral arthroplasty has been increasingly shown to be an excellent option in patients suffering from isolated anterior compartment OA. Despite favorable outcomes, however, patellar malalignment remains a significant source of short-term failure. The authors of this study evaluated the changes in patellofemoral congruence after isolated patellofemoral arthroplasty in those patients with trochlear dysplasia in the context of localized anterior compartment OA.
The results of the study show, albeit at short-term follow-up of approximately 2 years, that parameters including patellar tilt, TT-TG distance, lateral trochlear inclination and congruence angle can all improve after a well done arthroplasty. Additionally, no prosthesis loosening was observed, nor revision due to instability or pain. The small number of patients (n=35) in the study can be reflective of the difficulties in indicating the correct patient for this procedure. The surgeons appropriately excluded any patient with cartilage degeneration in the tibiofemoral compartments. Additionally, 17% of the patient cohort required either a concomitant medial patellofemoral ligament reconstruction or lateral retinacular release, underscoring the importance of appropriate soft tissue balancing even in the context of a bony resurfacing procedure. Patellofemoral arthroplasty surgeons should remain cognizant of the many bony and soft tissue factors that contribute to patellar tracking.
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