Correlation of tibial component size and rotation with outcomes after total knee arthroplasty
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KNEE ARTHROPLASTY
Correlation of tibial component size and rotation with outcomes after total knee arthroplasty Antonio Klasan1 · Joshua G. Twiggs2 · Brett A. Fritsch1 · Brad P. Miles2 · Thomas J. Heyse3 · Michael Solomon4 · David A. Parker1 Received: 10 February 2020 / Accepted: 15 July 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Introduction Tibial component design and positioning contribute more to patient satisfaction than previously realized. A surgeon needs to decide on the size and rotation, bearing in mind that coverage should be as high as possible, whilst malrotation and overhang should be avoided. No study investigates the impact of each of these components on clinical outcomes in a single cohort. Materials and methods This is a retrospective analysis of 1-year postoperative outcomes measured with the Knee Injury and Osteoarthritis Outcome (KOOS) Score, as well as a previously validated rotational CT protocol. Coverage, rotation from Insall’s axis, and overhang of an asymmetric tibial baseplate were measured, and positive and negative correlations to clinical outcomes were calculated. Results A total of 499 knees were analyzed. Patient average age was 68.4 years. Rotation within 7° internal and 5° external from Insall’s axis was a “safe zone”. Mean coverage was 76%. A total of 429 knees (94%) had a coverage of at least 70% and 102 knees (22%) greater than 80%. Overhang was detected in 23% of the cohort. Increased coverage was correlated to increased KOOS score and overhang correlated with a decreased KOOS score (p = 0.008). Conclusions This study demonstrates the individual role of three aspects of tibial component implantation properties in postoperative pain and short-term functional outcomes. Upsizing to the point of overhang with rotational tolerance of 7° internal and 3° external to Insall’s axis demonstrates best patient reported outcomes. Overhang decreases the clinical outcome by the same margin as loss of 16% of coverage. Keywords Total knee arthroplasty · Tibial component · Coverage · Overhang · Rotation · Patient reported outcomes
Introduction Total knee arthroplasty (TKA) is the treatment of choice for advanced knee osteoarthritis. The number of procedures increases yearly [1], but the patient satisfaction has remained at the same level for a number of years, in spite of advancements in implant design and techniques [2]. Pain has been identified as the main reason for dissatisfaction [2]. * Antonio Klasan [email protected] 1
Sydney Orthopaedic Research Institute, Level 1, The Gallery, 445 Victoria Ave, Chatswood, NSW 2067, Australia
2
360 Knee Systems, Sydney, NSW, Australia
3
Red Cross Hospital, Frankfurt, Germany
4
Sydney Orthopaedic Specialists, Randwick, NSW, Australia
There is a growing number of studies suggesting that tibial component design and tibial implantation properties are an important factor of patient satisfaction and postoperative pain. Nicoll and Rowley found a strong correlation of implant malrotation with pain,
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