ISAKOS: 2019 Congress in Cancun, Mexico
ISAKOS

2019 ISAKOS Biennial Congress ePoster #945

 

What is the Optimal Indication for Kinematically Aligned Total Knee Arthroplasty to Maximize the Effectiveness of Natural Joint Line Concept?

Yasuo Niki, MD, PhD, Tokyo JAPAN
Kengo Harato, MD, PhD, Tokyo JAPAN
Shu Kobayashi, MD, PhD, Tokyo JAPAN
Takeo Nagura, MD, PhD, Tokyo JAPAN
Masaya Nakamura, MD, PhD, Tokyo JAPAN
Morio Matsumoto, MD, PhD, Tokyo JAPAN

Keio University, School of Medicine, Department of Orthopaedic Surgery, Tokyo, JAPAN

FDA Status Cleared

Summary

Possible indications for Kinematically aligned TKA are patients with around 65 year-old, male, lower BMI and higher activity preoperatively, which might maximize the effectiveness of natural joint line concept.

Abstract

Purpose

Controversy does exist as to whether KA-TKA (KA-TKA) is indicated for all patients or what is the optimal indication for KA-TKA to maximize the effectiveness of natural joint line concept. We developed patient reported outcome composite measure for patient satisfaction and function, which consisted of Knee Society Score (KSS) 2011, pain DETECT score (PDS), and pain catastrophizing scale (PCS). The purpose of this study was to evaluate and compare patient reported outcome of KA-TKA with mechanically aligned TKA (MA-TKA), using our newly developed composite measure. Based on these data, we enlighten the group of patients who should undergo KA-TKA rather than MA-TKA, which might lead to establishment of surgical indication for KA-TKA.

Methods

The study enrolled 139 patients who underwent KA-TKA using portable navigation system (OrthAlign Inc,) due to end-stage rheumatoid arthritis or osteoarthritis. All patients were followed-up at least 2 years. The same number of the patients undergoing MA-TKA using the same navigation system were selected by propensity matching and served as controls. All TKAs were performed by a single surgeon (Y.N.). The implants used were NexGen LPS-FLEX or CR-FLEX (Zimmer-Biomet). At 2 years postoperatively, the data of KSS 2011, PCS, and PDS were collected. In statistical analysis, principle component analysis narrowed down two clinically important components according to the amount of each eigenvalue. These two components reflected patient satisfaction and function after TKA. The composite scores of patient satisfaction and function were calculated by multiplying individual score and corresponding factor loadings. The resulting composite scores were a mean of zero and a standard deviation of one. Based on the scatter plot of the two composite score, characteristics of patients with KA-TKA were compared with those of MA-TKA.

Results

Preoperative patient characteristics of KA- and MA-TKA groups were similar, suggesting successful matching. Scatter plot of the both composite scores for patient satisfaction and function exhibited neither floor nor ceiling effects. The composite function score was significantly higher in KA-TKA group than in MA-TKA group (p<0.01), whereas the composite satisfaction score was comparable between the two groups. The scatter plot of the two scores also indicated that KA-TKA group included characteristic patient group (n=41) exhibiting higher function score and relatively lower satisfaction score (Fig.1). When such 41 patients were assessed in detail and compared with whole patients (n=485) (Table 2), they were younger (65 years old on average) and had higher KSS total activity score preoperatively, and achieved higher total and advanced activity scores, postoperatively.

Conclusions

Functional activity after KA-TKA was better, whereas patient satisfaction was comparable with MA-TKA. We noticed a certain patient group in KA-TKA (about 30%) exhibiting higher function and moderate satisfaction, postoperatively. Such well-functioning TKA patients were characterized by around 65 year-old male with lower BMI and had higher activity preoperatively. Such patient group exerted maximum effects of kinematic alignment concept and might be a possible indication for KA-TKA.