THE PATELLAR CUT MATTERS: AN ANALYSIS OF PATELLOFEMORAL ARTHROPLASTY BIOMECHANICS

O. Dandridge; A. Garner; A. Amis; J. Cobb; R. Van Arkel

doi:10.1302/1358-992X.2022.7.083

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Knee

THE PATELLAR CUT MATTERS: AN ANALYSIS OF PATELLOFEMORAL ARTHROPLASTY BIOMECHANICS

The British Association for Surgery of the Knee (BASK) May 2022 Meeting, Newport, Wales, 17–18 May 2022.

O. Dandridge
A. Garner
A. Amis
J. Cobb
R. Van Arkel

THE PATELLAR CUT MATTERS: AN ANALYSIS OF PATELLOFEMORAL ARTHROPLASTY BIOMECHANICS

Dandridge O, Garner A, Amis A, Cobb J, Arkel RV. THE PATELLAR CUT MATTERS: AN ANALYSIS OF PATELLOFEMORAL ARTHROPLASTY BIOMECHANICS. Orthop Procs. 2022;104-B(SUPP_7):83-83. doi:10.1302/1358-992X.2022.7.083

Dandridge, O., et al. “THE PATELLAR CUT MATTERS: AN ANALYSIS OF PATELLOFEMORAL ARTHROPLASTY BIOMECHANICS.” Orthopaedic Proceedings, vol. 104-B, no. SUPP_7, 2022, pp. 83-83., https://doi.org/10.1302/1358-992X.2022.7.083

Dandridge, O., Garner, A., Amis, A., Cobb, J., & Arkel, R. V. (2022). THE PATELLAR CUT MATTERS: AN ANALYSIS OF PATELLOFEMORAL ARTHROPLASTY BIOMECHANICS. Orthopaedic Proceedings, 104-B(SUPP_7), 83-83. https://doi.org/10.1302/1358-992X.2022.7.083

Dandridge, O., Garner, A., Amis, A., Cobb, J. and Arkel, R. V. (2022) “THE PATELLAR CUT MATTERS: AN ANALYSIS OF PATELLOFEMORAL ARTHROPLASTY BIOMECHANICS.” Orthopaedic Proceedings, 104-B(SUPP_7), pp. 83-83. Available at: https://doi.org/10.1302/1358-992X.2022.7.083

Dandridge, O., A. Garner, A. Amis, J. Cobb, and R. Van Arkel. “THE PATELLAR CUT MATTERS: AN ANALYSIS OF PATELLOFEMORAL ARTHROPLASTY BIOMECHANICS.” Orthopaedic Proceedings 104-B, no. SUPP_7 (2022): 83-83. https://doi.org/10.1302/1358-992X.2022.7.083

Dandridge O, Garner A, Amis A, Cobb J, Arkel RV. THE PATELLAR CUT MATTERS: AN ANALYSIS OF PATELLOFEMORAL ARTHROPLASTY BIOMECHANICS. Orthop Procs. 2022 Jul 1;104-B(SUPP_7):83-83. https://doi.org/10.1302/1358-992X.2022.7.083

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Abstract

Patellofemoral Arthroplasty (PFA) is an alternative to TKA for patellofemoral osteoarthritis that preserves tibiofemoral compartments. It is unknown how implant positioning affects biomechanics, especially regarding the patella. This study analysed biomechanical effects of femoral and patellar component position, hypothesising femoral positioning is more important.

Nine cadaveric knees were studied using a repeated-measures protocol. Knees were tested intact, then after PFA implanted in various positions: neutral (as-planned), patellar over/understuffing (±2mm), patellar tilt, patellar flexion, femoral rotation, and femoral tilt (all ±6°). Arthroplasties were implemented with CT-designed patient-specific instrumentation. Anterior femoral cuts referenced Whiteside's line and all femoral positions ensured smooth condyle-to-component transition. Knee extension moments, medial patellofemoral ligament (MPFL) length-change, and tibiofemoral and patellofemoral kinematics were measured under physiological muscle loading. Data were analysed with one-dimensional statistical parametric mapping (Bonferroni-Holm corrected).

PFA changed knee function, altering extension moments (p<0.001) and patellofemoral kinematics (p<0.05), but not tibiofemoral kinematics. Patellar component positioning affected patellofemoral kinematics: over/understuffing influenced patellar anterior translation and the patellar tendon moment arm (p<0.001). Medially tilted patellar cuts produced lateral patellar tilt (p<0.001) and vice versa. A similar inverse effect occurred with extended/flexed patellar cuts, causing patellar flexion and extension (p<0.001), respectively. Of all variants, only extending the patellar cut produced near-native extension moments throughout. Conversely, the only femoral effect was MPFL length change between medially/laterally rotated components.

PFA can restore native knee biomechanics. Provided anterior femoral cuts are controlled and smooth condyle-to-component transition assured, patellar position affects biomechanics more than femoral, contradicting the hypothesis.