Evidence of trochlear dysplasia in femoral component designs

The study aimed to compare trochlear profiles of various total knee arthroplasty (TKA) models to anatomic profiles observed in healthy and pathologic knees and to evaluate trochlear designs against radiologic indicators for PF disorders and trochlear dysplasia.

The trochlear profiles of 14 different TKA models were digitized using a coordinate measurement machine at various flexion angles (0°, 15°, 30° and 45°) to deduce the following variables: sulcus angle, trochlear groove orientation, height of lateral facet, and mediolateral groove position. The effect of externally rotating the femoral component on those variables was simulated.

The sulcus angle was greater than the indicators for trochlear dysplasia of 144° in 11 implants at 45° flexion, and in 13 implants at 30° flexion. The lateral facet height was less than average anatomic values of 5 mm in eight specimens through the entire range of early flexion (0°-30°). The trochlear groove was oriented laterally in 13 specimens (3.3°-11.7°) and was vertical in one specimen (0.3°). Applying an external rotation up to 6° resulted in noticeable lateral translation of the trochlear groove and facets, but negligible posterior translation.

The study presented a detailed description of previously overlooked TKA design parameters and revealed that some femoral components exhibit characteristics of trochlear dysplasia. The clinical relevance of this descriptive study is that surgeons should be aware of such design limitations to improve choice of implant for patients with history of PF disorders and to adapt surgical techniques as necessary to optimize PF tracking.

Case-control study, Level III.