Search

Purpose: To determine if trochlear morphology in healthy knees depends on sex and ethnicity, and to compare it to off-the-shelf 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 quantified for each knee and for 10 total knee arthroplasty (TKA) models. Univariable regression analyses were performed to determine associations of the five trochlear parameters with sex and ethnicity. Interquartile ranges (IQR) of native trochlear parameters were compared to the trochlear parameters of 10 off-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 off-the-shelf TKA prostheses., Conclusions: The findings suggest that thresholds used in the diagnosis of patellofemoral instability should be adapted to patient sex and ethnicity, and that standard off-the-shelf TKA may not restore native trochlear parameters in all patients., Level of Evidence: III, retrospective comparative.

Purpose: Unexplained pain and stiffness after total knee arthroplasty (TKA) often result from mismatch between implant geometry and knee morphology, which depends on patient size, sex, and ethnicity. This study aimed to determine whether size, sex, or ethnicity are independently associated with distal femoral morphology in healthy Caucasian and Asian knees, and to compare anatomic ratios to those of commercially available TKA implants., Methods: Two series of computed tomography (CT) angiograms from France (264 knees) and China (259 knees) were used to digitize osteometric landmarks at the level of the femoral epicondyles, to measure anteroposterior (AP) and mediolateral (ML) dimensions at the anterior, posterior, medial, and lateral zones. The aspect (ML/AP), trapezoidicity (MLp/MLa), and asymmetry (APl/APm) ratios, as well as the sulcus angle were calculated and compared to those of 9 TKA models. Multivariable analyses were performed to determine whether anatomic ratios were independently associated with sex, origin, or size., Results: Multivariable analyses revealed that, independently from size, female knees were narrower (β = - 0.03; p < 0.001) and more asymmetric (β = 0.02; p < 0.001), while Chinese knees were more trapezoidal (β = 0.04; p = 0.002) and asymmetric (β = 0.02; p < 0.001) with shallower trochleae (β = 6.4°; p < 0.001). Compared to native knees, most implants were too wide, and many of the recent models too 'trapezoidal'. Most prosthetic trochleae were too shallow compared to French knees, but within the third quartile of Chinese knees., Conclusions: The morphology of the distal femur depends on sex and ethnicity independently from size. The wide spectrum of morphotypes observed cannot be covered by 'off-the-shelf' TKA models, and until customized implants become more accessible, prosthetic overhang, and under-coverage remain inevitable., Level of Evidence: III, Retrospective comparative study.