2.3.3. Radiological Evaluation

All patients followed an identical radiological assessment: anterior–posterior and lateral weight-bearing radiographs, a long-leg view of the lower limbs, and a Merchant view [16] of the patellofemoral joint. These assessments were performed in all patients, preoperatively and at six months, one year and every two years. All radiographs were reviewed by an orthopaedic surgeon who was not part of the surgical team and blinded to the clinical outcome results: the reviewing surgeon evaluated the pre-operative arthritic stage following the Kellgren–Lawrence (K-L) scale [17] and assessed post-operative results according to the Knee Society Roentgenographic evaluation system (KSS) for radiolucency, femorotibial alignment, and evidence of loosening, wear, and osteolysis [13].

Femoral mechanical axis, tibial mechanical axis, hip–knee–ankle angle, mechanical axis of the lower limb and anatomical axis were measured with the Paley method [18] before surgery, and post-operatively in all cases. From the sagittal perspective, the tibial slope was calculated using the posterior tibial cortex as a reference [19]. The degrees of variation after surgery in the mechanical axis (D mechanical axis) and slope (D slope) were kept under consideration to assess if greater changes could influence the clinical results and patient’s satisfaction. Patients with a post-operative mechanical axis, with a discordance of +/−3° from the mean range, were considered outliers.

The review of the hospital database, the phone interview and the follow-up x-rays were used to identify the rate of infection and mechanical failures that occurred. A flow chart of the materials and methods used is provided in Figure 1.

Flow chart describing study demographics and methodology.