Temporal changes in sleep quality and knee function following primary total knee arthroplasty: a prospective study

Purpose Several patient-reported outcome measures (PROMs) have been used to assess improvement in the quality of life following total knee arthroplasty (TKA). However, there is paucity of studies evaluating the sleep quality and knee function following TKA. The primary aim of our study was to evaluate the sleep quality and knee function in primary TKA patients using the Pittsburgh Sleep Quality Index (PSQI) and Knee Society Score (KSS), respectively. The secondary aim was to assess the correlation between the two outcome measures over the course of first post-operative year following TKA. Methods One hundred sixty-eight patients (female-140/male-28) with mean age of 64.63 years (+/- 7.50) who underwent 168 primary unilateral TKA using a cemented posterior-stabilised implant without patella resurfacing between June 2018 and October 2018 were included in the study. Global PSQI and KSS were recorded pre-operatively and post-operatively weekly up to six weeks and at one year. Body mass index (BMI) and Charlson comorbidity index (CCI) were recorded during pre-operative assessment. Results Mean(+/- SD) BMI and CCI were 28.45(+/- 4.64) and 2.48(+/- 0.93), respectively. Pre-operative global PSQI of 1.98(+/- 0.97) increased to 13.48(+/- 3.36) in the first post-operative week (p < 0.001) and remained high during all the six weeks following TKA (p < 0.001), whereas at the first post-operative year, it reduced to 2.10(+/- 1.15) (p = 0.15). Pre-operative KSS of 52.00(+/- 9.98) increased to 71.67(+/- 6.58) and 85.49(+/- 4.67) at 6 weeks and the first post-operative year respectively (p < 0.001). Pre-operative global PSQI had moderate correlation with pre-operative KSS (r = 0.39) (p < 0.001). Strong correlation was noted between pre-operative global PSQI and six week post-operative KSS (r = 0.47) (p < 0.001). Low correlation was noted between pre-operative global PSQI and KSS at the first post-operative year (r = 0.10, p = 0.19) following TKA. Multiple regression analysis revealed age, CCI, and pre-operative range of motion as independent predictors of global PSQI. Conclusions Patients undergoing TKA experience changes in sleep quality but report an overall improvement in knee function during the first post-operative year. Sleep quality has moderate to strong correlation with knee function in the early post-operative period 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 post-operative period and reassured accordingly.