Comparison of Two Methods of Patellar Resurfacing in Total Knee Arthroplasty

Comparison of Two Methods of Patellar Resurfacing in Total Knee Arthroplasty.A Prospective, Randomized, Double-blind Study

The aim of this prospective, randomized study was to compare the clinical and radiological results of "free-hand" technique and "resection guide" technique for preparing patella during total knee arthroplasty.

With improved surgical techniques and implant designs, patella resurfacing has been favored by increasing surgeons. When performing the resection, several principles such as restoring the original patellar thickness, avoiding over or under resection must be complied in order to achieve satisfactory outcomes.This study was conducted to compared the outcomes of two commonly adopted methods for performing patellar resection in total knee arthroplasty. One hundred patients with osteoarthritis were recruited in the clinical trial using Nexgen Legacy Posterior Stabilized-Flex prosthesis. Patients were randomized to receive "free-hand" technique and "resection guide" technique when performing patellar resection in total knee arthroplasty. Patients were evaluated preoperatively and at follow-up visits conducted at twelve months, at twenty-four months. Clinical outcome was assessed and compared with use of the visual analogue pain scale (VAS), range of motion, Knee Society Score (KSS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and the Short Form-36 (SF-36). Patellar alignment was assessed before surgery and at each follow-up by measuring the patellar tilt (PT) and lateral patellar displacement (PD). Prosthetic position and leg alignment were also compared between the two groups.

Patellar resurfacing with freehand technique:Using freehand technique for patella preparation during total knee arthroplasty.

Patellar resurfacing with resection guide technique: Using patellar resection guide technique for patella preparation during total knee arthroplasty.

The patellar tilt is the angle between the transverse axis of the patella and The patellar tilt is the angle between the transverse axis of the patella and the anterior intercondylar line.The PT was assessed by a blinded observer using 30° skyline radiographs.

The Knee Society's Knee Scoring System (KSS) has served as a simple, objective way to measure a patient's functional ability before and after total knee arthroplasty (TKA).Scale Name:score scale range:0~100,and a higher values represent a better outcome.

The Western Ontario and McMaster Universities (WOMAC) Osteoarthritis (OA) Index is a tested questionnaire to assess symptoms and physical functional disability in patients with OA of the knee.Scale Name:score scale range:0~100,and a lesser values represent a better outcome.

The SF-36 is a multi-purpose, short-form health survey with only 36 questions. It yields an 8-scale profile of functional health and well-being scores as well as psychometrically-based physical and mental health summary measures and a preference-based health utility index. A higher values represent a better outcome.

Radiographic evaluation:The measurements were made by a blinded observer, in accordance with the principles stipulated by the Knee Society, by using computer-generated data derived from the digital radiographs.

Radiographic evaluation:The following parameters were measured: the coronal femoral component angle (α; angle between femoral shaft and transcondylar line of the femoral component); coronal tibial component angle (β; angle between the mechanical axis of the tibia and tibial base plate); sagittal femoral component angle (γ; angle of femoral component flexion); and sagittal tibial component angle (δ; posterior slope angle of the tibial component).

The patellar displacement is the lateral displacement of the median ridge of the patella from the intercondylar sulcus of the femur.The PD was assessed by a blinded observer using 30° skyline radiographs.

Inclusion Criteria: diagnosis of primary osteoarthritis of the knee, with Ahlbäck grade of ≥2 (symptoms persisting after conservative treatment for at least 3 months) knees with <20° varus or <15° valgus deformity patellar thickness is more than 21mm Exclusion Criteria: restricted motion (flexion contracture of >25°) patella alta (Insall-Salvati ratio of <0.6) history of previous knee surgery

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