Femoral component rotation in patellofemoral joint replacement.

Patellofemoral joint replacement is a successful treatment option for isolated patellofemoral osteoarthritis. The short and mid-term outcomes are related to malposition and unexplained pain.
The ‘Zimmer Gender-Solutions Patello-Femoral Joint (PFJ) System’ is a third generation, asymmetrical patellofemoral joint prosthesis. The surgical technique is highly reproducible although assessment of correct rotational alignment remains difficult. The ‘Surgical Technique’ brochure suggests using Whiteside’s line or the transepicondylar axis. In practice the lower leg axis as described by Clark et al. is used (Clark et al. 2012).
At present, no studies have been performed that demonstrate the actual amount of rotation achieved with the Zimmer prosthesis or other prosthetic designs. Considering the importance of avoiding malposition, further study is needed.
We hypothesize that the CT-based (actual) femoral component rotation is 3 to 6 degrees external relative to the transepicondylar axis. Furthermore, we hypothesize that the short-term (less than 2 years) clinical outcomes of the Zimmer patellofemoral prosthesis are related to the actual amount of femoral component rotation.

(1) When using the lower leg axis as a reference, the CT-based femoral component rotation with Zimmer Gender-Solutions patellofemoral joint replacement is 3 to 6 degrees external relative to the transepicondylar axis.



(2) The short-term (less than 2 years) clinical outcomes of Zimmer patellofemoral joint replacement are related to the actual amount of femoral component rotation.

(1) Preoperative: clinical (KOOS) and radiological assessment, screening, informed consent;

(2) Patellofemoral joint replacement;

(3) 1-3 days post-surgery: CT assessment of femoral component rotation;

(4) 1 year post-surgery: clinical (KOOS) and radiological assessment.

Zimmer Gender-Solutions patellofemoral joint replacement.