Modern total knee arthroplasty designs do not reliably replicate anterior femoral morphology

Abstract

Purpose Biomechanical studies suggest that PF tracking is not reliably restored to physiological values in TKA despite surgical technique optimization. A clinical observation is that current TKA designs may not replicate anterior femoral offset. The aim was to examine the intraoperative resection thicknesses of the anterior femoral condyles during TKA and correlate these findings relative to modern prostheses. Methods This was a retrospective analysis of 199 patients who underwent 233 TKAs using a single implant design with measured anterior femoral condylar resection thicknesses. The aim was to restore posterior condylar offset whilst minimizing overstuffing of the anterior compartment of the knee by choosing the smallest prosthesis to allow for the maximal anterior resection as close to the cortex without inducing notching. Prosthetic measurements from 7 commonly used TKAs were collected by analysis of 3D models of median sized explants. Results An average of 7.9 mm (SD 2.5 mm, range 2–16.5 mm) and 11.5 mm (SD 2.5 mm, range 2–21 mm) was resected from the medial and lateral aspects of the anterior femur, respectively. The average anterior flange thickness for the prosthesis data set was 6.6 mm (SD 0.6 mm, range 6.1–7.9 mm) medially and 7.6 mm (SD 0.7 mm, range 6.8–9.0 mm) laterally. Comparison across patients who received the median prosthesis size of 5 (SD 1.3, range 2–8) was inadequately restored by 1.4 mm (p < 0.00001) medially and 3.4 mm (p < 0.00001) laterally. Conclusion Host anatomy is not routinely restored during TKA. The surgical teaching to aim for an anterior femoral osteotomy close to the anterior cortex will result in understuffing of the PFJ and based on current prosthesis designs, the risk of overstuffing is not as significant as once believed. Future prostheses and surgical techniques should aim to restore not only posterior femoral but also anterior femoral offset. Level of evidence IV, Case series.

Alignment philosophy influences trochlea recreation in total knee arthroplasty: a comparative study using image-based robotic technology

“…Modern arthroplasty data demonstrate more than 15% of patients suffer from clinically significant patellofemoral dysfunction following TKA even when the patella is resurfaced [ 4 ]. The behaviour of the patella is largely dictated by the position of the trochlea which in TKA is a product of femoral component design and positioning [ 5 ]. Restoring constitutional trochlea anatomy may lead to more physiologic patellofemoral kinematics and improve function of the extensor mechanism following TKA.…”

Functional Alignment Philosophy in Total Knee Arthroplasty – Rationale and technique for the varus morphotype using a CT based robotic platform and individualized planning

“…Modern implant designs do not account for the wide variety of distal femoral anatomy seen in the normal population [ 35 , 36 ]. Furthermore, the variability between AP and mediolateral dimensions in the femur or the medial and lateral tibial plateaus may lead to the imperfect matching of implant sizing to the patient’s anatomy [ 37 ].…”

Patella resurfacing during total knee arthroplasty is cost-effective and has lower re-operation rates compared to non-resurfacing

“…The patella-friendly TKA and the un-resurfaced patellae aim to reduce anterior knee pain and improve patellofemoral tracking. However, these modernised designs have not been successful in restoring normal morphology [ 27 , 28 ].…”