Sexual and ethnic polymorphism result in considerable mismatch between native trochlear geometry and off-the-shelf TKA prostheses

Abstract

Purpose To determine if trochlear morphology in healthy knees depends on sex and ethnicity, and to compare it to of-theshelf TKA prostheses. Methods Three retrospective series of CT angiograms from France (female, 124; male, 135), China (female, 122; male, 137) and South Africa (female, 21; male, 62) were used to digitize osseous landmarks at the level of the femoral epicondyles. Sulcus angle, trochlear rotation, lateral trochlear inclination, trochlear asymmetry ratio, and trochlear depth index were quantiied for each knee and for 10 total knee arthroplasty (TKA) models. Univariable regression analyses were performed to determine associations of the ive trochlear parameters with sex and ethnicity. Interquartile ranges (IQR) of native trochlear parameters were compared to the trochlear parameters of 10 of-the-shelf TKA prostheses. Results Compared to French knees, Chinese knees had greater sulcus angle (β = 6.3°, p < 0.001), trochlear rotation (β = 0.8°, p = 0.004) and trochlear depth index (β = 1.60, p < 0.001). Conversely, South African knees had greater trochlear rotation (β = 1.9°, p < 0.001) and lateral trochlear inclination (β = 3.7°, p < 0.001). Female knees had smaller trochlear asymmetry ratios (β = − 0.03, p = 0.05) but greater trochlear rotation angles (β = 0.7, p = 0.005). Considerable mismatches in trochlear morphology were revealed between native knees and of-the-shelf TKA prostheses. Conclusions The indings suggest that thresholds used in the diagnosis of patellofemoral instability should be adapted to patient sex and ethnicity, and that standard of-the-shelf TKA may not restore native trochlear parameters in all patients. Level of evidence III, retrospective comparative.

Personalisation and customisation in total knee arthroplasty: the paradox of custom knee implants

“…This parameter‐tool duality increases the potential to address multiple challenges simultaneously while remaining compatible with different personalisation strategies and other assistive technologies [25]. Furthermore, custom implants offer three features that are rarely attainable when using off‐the‐shelf implants, which are not designed to be implanted in variable positions: Optimisation of bone‐implant fit: the implanted components are designed to follow the contours of the resected bone surfaces, thus avoiding any prosthetic over‐ or under‐coverage, and hence minimizing the risks of soft‐tissue impingements [1, 2, 15]; Decoupling of the patellofemoral compartment from the tibiofemoral compartment: the trochlear groove can be oriented to optimise patellofemoral kinematics independently from the femoral condyles that should be aligned to optimise tibiofemoral kinematics, which eliminates the need for external rotation of the femoral component [14, 19, 22, 24]; Restoration of native condylar curvature: the sphericity or ‘ovoidicity’ of prosthetic condyles can be adjusted to match the unique anatomy of the individual, to maintain equal ligament tensions throughout the range of knee flexion [6, 27]. …”

“…(1) Optimisation of bone-implant it: the implanted components are designed to follow the contours of the resected bone surfaces, thus avoiding any prosthetic or under-coverage, and hence minimizing the risks of soft-tissue impingements [1,2,15]; Decoupling of the patellofemoral compartment from the tibiofemoral compartment: the trochlear groove can be oriented to optimise patellofemoral kinematics independently from the femoral condyles that should be aligned to optimise tibiofemoral kinematics, which eliminates the need for external rotation of the femoral component [14,19,22,24];…”

Controversy: supporting patellar resurfacing in total knee arthroplasty – do it

“…Recent studies published by Saffarini et al 20 , 21 and Kuo 22 show that even the so-called patellar friendly implants are not able to restore normal morphology of the anterior femur. Using a patellar implant may therefore help to better match the two components.…”

Biomechanical and Clinical Effect of Patient-Specific or Customized Knee Implants: A Review

“…Moreover, the prostheses of conventional TKA cannot cover the wide spectrum of ethnic tibiofemoral morphotypes [25]. Mismatch in the angles of the sulcus between the native knees and prostheses has been proved, however, it is not clear to what extent this is true for other patellofemoral ratios [25,26]. In recent studies, it was shown that four of the five measured trochlear morphometric parameters relied significantly on ethnicity, whereas only two of the measured parameters relied on gender [26].…”

“…Mismatch in the angles of the sulcus between the native knees and prostheses has been proved, however, it is not clear to what extent this is true for other patellofemoral ratios [25,26]. In recent studies, it was shown that four of the five measured trochlear morphometric parameters relied significantly on ethnicity, whereas only two of the measured parameters relied on gender [26]. Such research, including anatomical analysis, provides standards for the suitable design of femur and tibia components, taking into account gender or patient-specific differences in the Asian population [24,[27][28][29][30][31].…”