Does patellofemoral geometry in TKA affect patellar position in mid-flexion?

Abstract

Comparative study, Level III.

Differences between native and prosthetic knees in terms of cross-sectional morphology of the femoral trochlea: a study based on three-dimensional models and virtual total knee arthroplasty

“…The discrepancies between the native and prosthetic knees in terms of sulcus height (H) values, which are exemplified in Fig. 2, may be related to different positioning of the patella following TKA; as the position of the patella determines the lever arm of the extensor mechanism, such inappropriate design of the prosthetic components is likely to influence quadriceps efficiency as well as joint reaction forces and contact levels on the femoral trochlea or condyles [11]. Such differences might also cause the component to become anteriorly displaced, as evident in the higher sulcus height (H) values noted for the 0 and 90° cross-sections.…”

“…In the 0° cross-section, the PRF is relatively small, and thus the decrease in lateral tilt angle (α) has little effect on the PRF vector or the stability of the patella. However, recent studies revealed that quadriceps forces are highest between 70 and 110° [11, 20, 21]. In the 45° cross-section (67.5° of knee flexion), the PRF is relatively high, and thus the decrease in lateral tilt angle (α) might result in a decrease in the PRF vector and subsequent patellar instability.…”

“…In the 45° cross-section (67.5° of knee flexion), the PRF is relatively high, and thus the decrease in lateral tilt angle (α) might result in a decrease in the PRF vector and subsequent patellar instability. In the 90° cross-section (135° knee flexion), even though the lateral tilt angle (α) in the MP component is higher than that noted in the native knee, the patella transits over the intercondylar notch [11, 22, 23], and it is the retinacula, rather than the bony structure, that might serve as the main factor maintaining patellar stability. As the patella tilts laterally from 0 to 75° of knee flexion [24], the contact area is mainly on the lateral side; however, the medial tilt (β) might affect patellar tilting during knee flexion, together with the sulcus angle, and does not represent the main factor regulating patellar motion in the 0 and 45° cross sections.…”

“…Previous evidence of trochlear dysplasia in the design of the femoral component was obtained based on 14 digital TKA models, but these findings were not evaluated in the context of the clinical outcomes achieved with the evaluated implants [7]. Saffarini et al [11] highlighted the influence of patellofemoral geometry on mid-flexion kinematics after comparing two different knee components (HLS Noetos® and KneeTec®). In their simulation study, Varadarajan et al [6] also measured the trochlear geometry before and after TKA, but did not discuss the effect of TKA on patellar motion and soft-tissue changes.…”

Does patellofemoral congruence following total knee arthroplasty correlate with pain or function? Intraoperative arthroscopic assessment of 30 cases

“…While patellar morphology is often associated with excessive tilt, Wiberg type C being most predisposed (23,24), it does not necessarily correlate with patellar subluxation or osteosclerosis (22,25), and pressure distribution data cannot be extrapolated to conclude on AKP or clinical outcomes. Moreover, most studies of patellar congruence are either radiographic, and therefore represent limited static data with inconsistent reliability (26), or intra-operative with the joint capsule open and therefore under non-physiological conditions (27).…”