Trochlear Thickness and Its Effect on the Outcomes of Total Knee Arthroplasty

Total knee arthroplasty is the gold standard treatment for advanced knee osteoarthritis. In spite of the great advance in the prosthesis design, surgical techniques and rehabilitation programs, only 85% (75% to 92%) of patients with total knee arthroplasty are satisfied with their operations and 30% develops patellofemoral complications. Patellofemoral complications after TKR are usually caused by multiple factors related to surgical technique (e.g., implant positioning and sizing, soft-tissue balancing, patellar resurfacing, etc.) and implant design (e.g., trochlear thickness, sagittal curvature, patellar component shape).

Numerous biomechanical studies suggest that patellofemoral tracking is not always restored to physiological values, because the prosthetic trochlea may differ from the native trochlea.

Theoretically decreasing of contact area distance of trochlea might increase the contact pressure in the patellofemoral joint. The increased contact pressure will elevate the stress in the subchondral bone of the patellofemoral joint, which is hypothesized to be a cause of patellofemoral pain.

A mechanical experiment was performed in an attempt to analyze the influence of thickening of the patella on the knee extension movement. The measurement show that anterior advancement of the extensor apparatus at the level of the patella gives a mechanical advantage, enabling the quadriceps to extend the knee with the use of less force. so increase thickness of patella affects the quadriceps function but no study has been shown the effect of trochlear thickness on quadriceps or patellofemoral joint.

Nonetheless, no study has been con-ducted to investigate the thickness of the trochlear groove and its effect on the outcome of TKR, So many people has different measurements of trochlear thickness which may affect PFJ so knowing of native trochlear thickness in patients with KNEE OA can affect the outcomes of total knee arthroplasty.

Preoperative and postoperative radiography (CT scan) can provide an adequate measurement of trochlear thickness which will help in understanding more about PFJ and its effect in the total knee replacement.

Inclusion criteria

• Advanced knee osteoarthritis in which total knee arthroplasty is indicated

Exclusion criteria

• Revision total knee arthroplasty
• Previous osteotomy around the knee
• Post traumatic knee arthritis
• Inflammatory knee arthritis