Abstract
INTRODUCTION
In Total Knee Arthroplasty (TKA), the neutral overall limb alignment (NOLA), i.e. the mechanical alignment of the lower limb within 0°±3°, is targeted for achieving good clinical/functional results. The kinematic overall limb alignment (KOLA), which uses the axis through the centres of the femur posterior condyles modelled as cylinders, represents a novel approach for achieving better soft tissue balance.
Patient-specific instrumentation (PSI) is nowadays offered as an effective technology in TKA to obtain better lower limb alignments than those via conventional guides (CON). Although relevant results are still inconsistent, the benefits claimed include shorter operative time, reduced surgical instrumentation, and accurate preoperative planning.
The aim of this study was to report the preliminary clinical and radiological results of TKA patients operated via NOLA-PSI and KOLA-PSI. Comparisons between them and with the results obtained via NOLA-CON were performed.
PATIENTS AND METHODS
A four-centre randomised study on 144 patients has been designed to assess these three techniques. In each centre, 36 patients are planned to be operated, 12 per technique. Currently, in our centre 18 patients have been operated so far: 6 via NOLA-CON (Group A), 3 via NOLA-PSI (Group B), and 9 via KOLA-PSI (Group C). All patients were implanted with a cruciate-retaining TKA (Triathlon®, Stryker®-Orthopaedics, Mahwah, NJ-USA) with patella resurfacing, those in PSI groups according to Otismed® imaging protocol. This includes pre-operative MRI scans at the hip, knee and ankle joints. Clinical evaluations were performed pre-operatively, at 45 days, and 3, 6 and 12 months post-operatively using the knee and functional IKSS (International Knee Society Score). At 45 days post-operatively a weight-bearing long leg radiograph was performed to measure possible differences between planned and implanted component alignment in patients operated via NOLA groups (A and B) and via KOLA group (C).
RESULTS
The post-operative knee and functional scores at the most recent follow-up in NOLA groups (A and B) were 78±19 (minimum÷maximum, 51÷95) and 80±23 (45÷100), respectively; in group C these were 91±12 (65÷100) and 89±15 (60÷100).
The mean alignment of the mechanical axis in the coronal plane in NOLA-CON (group A) was 1.5° in varus, the 20% being larger than 3° and considered as outliers. In the PSI groups (B and C), the mean absolute difference with respect to the planned alignment was 0.7°, without outliers.
Only one complication was observed (group B), where a manipulation was necessary two months after TKA due to small knee motion range.
DISCUSSION
The present results in PSI showed good accuracy and reproducibility of the planned alignments with respect to those achieved during surgery. Particularly, KOLA showed better clinical/functional results, without soft tissue release; the 25% of the remaining patients had medial or lateral structure release.
KOLA seems the ideal reference in TKA, though it does not reflect normal morphology. However, lower limb alignment larger than 3° has been estimated in an important fraction of the normal adult population.
In conclusion these preliminary results revealed a good efficacy of the examined PSI, in general, and better clinical results via KOLA.
