Early Experience with a Modern Generation Knee System: Average 2 Years’ Follow-up

Abstract

Arthritis in the knee is a leading cause of pain and disability with total knee arthroplasty (TKA) often the treatment of choice after failure of more conservative treatments. TKA has been demonstrated to be one of the most successful procedures performed. However, despite the good long-term survivorship rates, patient satisfaction is still an issue post TKA with over 20% of patients exhibiting patient dissatisfaction most commonly due to anterior knee pain (over 18-28% patients) and mediolateral or varus-valgus instability. Recent studies have demonstrated that collateral ligament strains are altered post TKA which may lead to laxity and/or tightness of the ligaments resulting in patient discomfort, pain, stiffness and/or instability post TKA. As a result, it may be beneficial to ensure ligamentous strains after TKA are similar or close to the native situation. The purpose of this study was to evaluate the clinical and radiographic results of the Unity Knee™ Total Knee System (Corin Ltd, Cirencester, UK), a modern generation, single-radius total knee replacement (TKR) and its accompanying instrumentation which is designed to help maintain proper ligament balance and restore the medial jointline. A total of 89 knees (89 patients) were implanted with the device in a single surgeon series. All patients were assessed using the American Knee Society Score (AKSS), the Oxford Knee Score (OKS), and radiographs. There was 1 revision due to infection and Kaplan-Meier survivorship was 98.9% at 2 years. The mean AKSS knee score for the total cohort was 87.1 ± 7.98 and the mean Oxford Knee score was 45.89 + 3.69. Radiographic review found no signs of radiographic failure in any of the knees. This study demonstrates good survivorship, clinical, and radiographic results at 2 years for this TKR.

Comparison of Functional Outcomes of Total Knee Arthroplasty Using Two Different Single Radius Implants

“…Our results indicated significant improvements in all clinical outcomes of the first 78 CR patients in a single surgeon series. Our results are similar to those recently reported by Paszicsnyek indicating good survivorship and positive clinical outcome of this implant [14]. In that study, the author investigated the functional outcome of the TKA by using Unity and indicated significant improvement in the outcomes measured by American Knee Society Score, Oxford Knee score and radiographic measurements.…”

“…Traditionally, knee prosthetics with multi-radius design over the femoral component have been used; however, recent development of single-radius knee implants have shown improvements in both mechanical and clinical functions of the knee after TKA [8,13,14,18,[26][27][28][29][30]. In these implants, the biomechanical functions are improved by lengthening the extensor moment arm, providing longer distal and posterior axis, and by maintaining the isometry of the rotation and force distribution throughout the range of motion resulting in less patellar load [7,8,31,32].…”

“…This implant maintains the medial joint axis throughout full range of motion. This design concept helps with isometry of MCL loading and movement after TKA [14].…”

“…In a very recent study by Paszicsnyek, clinical outcomes of 89 patients treated by TKA using Unity knee implants with a posterior stabilizing approach (PS) were evaluated [14]. The authors indicated positive survivorship, clinical and performance improvements, and no radiographic failure.…”