Introduction

Several patient reported outcome measures have been used to assess improvement in the quality of life following total knee arthroplasty (TKA). Sleep quality is critical aspect of quality of life. However, there is paucity of studies evaluating the sleep quality and knee function following TKA during the first postoperative year.

Aims: The primary objective of our study was to evaluate the sleep quality and knee function in patients undergoing unilateral and bilateral TKA using the Pittsburgh Sleep Quality Index (PSQI) and Knee Society Score (KSS) respectively. The secondary objective was to study the correlation between the two aforementioned outcome measures over the course of first postoperative year following TKA.

Methods

107 patients (female - 76 / male - 31) with a mean age of 64.63 years (±7.50) who underwent 168 TKA (unilateral - 45 / bilateral staged - 89 / bilateral simultaneous - 34) between June 2018 to October 2018 were included in the study. All procedures were performed by a single surgeon using a cemented posterior-stabilised implant without patella resurfacing. Prospective global PQSI score and KSS were recorded 1 week preoperatively, weekly upto the sixth postoperative week and at 1 year postoperatively. Body mass index (BMI) and Charlson comorbidity index (CCI) were recorded during preoperative assessment.

Results

Mean(±SD) BMI and CCI were 28.45(±4.64) and 2.48(±0.93) respectively. Mean(±SD) preoperative global PSQI score of 1.98(±0.97) increased to 13.48(±3.36) in the first postoperative week (p<0.001) and high global PSQI scores were noted during all the six weeks following TKA (p<0.001) whereas at the first postoperative year, global PSQI score reduced to 2.10(±1.15) (p=0.15). Mean(±SD) preoperative KSS of 52.00(±9.98) increased to 71.67(±6.58) and 85.49(±4.67) at the sixth week and the first postoperative year respectively (p<0.001). Preoperative KSS had moderate correlation with preoperative global PSQI score of patients with unilateral TKA (r=0.40), simultaneous bilateral TKA (r=0.43) and staged bilateral TKA (r=0.39) (p<0.001). Strong correlation was noted between the preoperative global PSQI score and the six week postoperative KSS of patients with unilateral TKA (r=0.59), simultaneous bilateral TKA (r=0.60) and staged bilateral TKA (r=0.59) (p<0.001). However, low correlation was noted between preoperative global PSQI score and KSS at first postoperative year (r=0.10, p=0.19) following TKA. Similar correlation findings were noted between the postoperative global PSQI score at six weeks and postoperative KSS at the six weeks and at one year following TKA.

Conclusion(s): Patients undergoing unilateral, bilateral staged and bilateral simultaneous TKA experience changes in sleep quality but report an overall improvement in knee function during the first postoperative year. Sleep quality (assessed using global PSQI score) has moderate to strong correlation with knee function in the early postoperative period (upto six weeks) beyond which there is a low correlation with knee function thereby suggesting a transient phenomenon. Hence patients undergoing TKA can be appropriately counselled regarding the variation in sleep quality in the postoperative period and reassured accordingly