Summary

In the first-operated knees, greater improvement in ambulatory function was measured due to lower preoperative conditions, compared to the opposite knee, although similar outcomes in muscle strength, ambulatory function, and KSS and 2011 KSS scores were obtained for the first- and second-operated knees.

Abstract

Introduction

Simultaneous or staged total knee arthroplasty (TKA) is available as a treatment modality for patients with bilateral knee osteoarthritis. Concerns have been raised regarding the difference in outcomes between the first and contralateral knee in patients treated with staged bilateral TKA. Few studies have focused on functional recovery, such as muscle strength and walking ability, and patient satisfaction using patient-reported outcomes for comparison. This study aimed to compare knee function and patient-reported outcomes between first- and second-operated knees and to evaluate the effect of the time between surgeries on the recovery of the second TKA.

Materials And Methods

In this retrospective study 56 patients who underwent staged primary TKA due to osteoarthritis were included. The average age at the time of the first TKA was 74.2 years (standard deviation [SD] = 7.7 years). The average height and weight were 151.5 cm (SD = 8.6 cm) and 61.5 kg (SD = 12.4 kg), respectively. The average time between the first and second TKA was 14.9 months (SD = 14.9 months). Due to the variability of the time between surgeries, patients were divided based on the time between surgeries between TKA.
For muscle strength evaluation, knee joint extension and flexion muscle strengths were measured during isometric contraction for 3 s in the open kinetic chain. For ambulatory function, the timed up and go (TUG) test and 10 meters walking time (10 m WT) were conducted. Knee scoring was conducted using the Knee Society Score (KSS) and the new KSS (2011 KSS). All measurements were performed before surgery, one month after surgery, and one year after surgery.

Results

In the preoperative measurements, the first-operated knees showed inferior TUG test (p = 0.003), and 10 m WT (p = 0.030) KSS knee score (p = 0.010), 2011 KSS symptoms (p < 0.001), and 2011 KSS satisfaction (p = 0.014). In addition, varus deformity in the hip-knee-ankle angle was larger in the knees that underwent the first operation (p = 0.045). No significant differences between the first- and second-operated knees in muscle strength, ambulatory function, and KSS and 2011 KSS were observed at one month and one year after surgery.
Regarding the amount of improvement in each value before and after surgery, greater improvement was observed in the KSS knee (p = 0.021) and function score (p = 0.004) and 2011 KSS functional activities (p = 0.008) one month after surgery in the first-operated knees. The improvement in 2011 KSS symptoms (p = 0.013) was greater one year after surgery.
In the sub-analysis to detect the differences among the time between surgeries, preoperative ambulatory function, KSS, and 2011 KSS were not significantly different. There were no significant differences in the improvement in ambulatory function, KSS, and 2011 KSS at one month and at one year.

Discussion

In the first-operated knees, greater improvement in ambulatory function was measured due to lower preoperative conditions, compared to the opposite knee, although similar outcomes in muscle strength, ambulatory function, and KSS and 2011 KSS scores were obtained for the first- and second-operated knees. The time between surgeries seems not to affect the rate of recovery of the second knee.