Summary

Differences in acute postoperative pain, sleep status, and functional recovery between TKA and UKA were investigated. Postoperative pain and PCA consumption were lower and ROM was greater in UKA, but there was no difference in sleep status.

Abstract

Introduction

Postoperative pain can cause sleep disturbances, and sleep disturbances can enhance pain. Although multimodal analgesia is widely used for postoperative pain, few studies have focused on postoperative pain and sleep. Poor sleep may discourage rehabilitation and impede functional recovery.
The purpose of this study is to clarify the differences in acute postoperative pain, sleep state and functional recovery between total knee arthroplasty (TKA) and unicompartmental knee arthroplasty (UKA), and to observe the relationship between surgical invasion and sleep status.

Methods

This was a single-center, prospective, observational study approved by the IRB authorities, and informed consent was obtained from patients prior to participation.
Seventy consecutive patients who underwent arthroplasty at our institution were included in the study. Pain and sleep status were assessed on the day of admission, the day of surgery, and on postoperative days 1, 2, 3 and 7. Pain was assessed by visual analogue scale (VAS) and consumption of fentanyl PCA was assessed. Sleep status was evaluated with a mattress-type actigraphy without a direct sensor including bioelectrodes attached to the human body. Sleep efficacy and body movement frequency were evaluated as indices of sleep status. Sleep efficacy was defined as the ratio of actual sleep time to total bedtime. Functional recovery was assessed at knee range of motion on postoperative days 2 and 7.

Results

SECTION:
There were no differences in preoperative VAS pain scores and sleep status between TKA and UKA.
Mean VAS pain scores on the day of surgery were 25.3 vs. 21.1 for TKA and UKA, respectively. The number of body movements and sleep effect were 26.2 vs. 28.6, 85% vs. 84%, respectively.
VAS pain scores on postoperative day 1 were significantly lower in UKA (18.8) compared to TKA (27.7). The number of body movements and sleep effectiveness were 28.5 vs. 24.2 and 81.2 vs. 82.0%, respectively.
On postoperative day 2, the VAS pain score was 37.2 vs. 32.4, and the number of body movements and sleep effect were 27.0 vs. 26.6 and 78.2 vs. 75.6%, respectively. The range of motion of the knee was 89.4 degrees of flexion for TKA and 96.1 degrees for UKA, with UKA having a greater range of motion. Extension was 12.2 and 9.4 degrees, respectively.
PCA fentanyl consumption was significantly lower in UKA (140.3 µg) compared to TKA (162.0 µg).
VAS pain scores on postoperative day 3 were significantly lower in UKA (29.4) compared to TKA (56.8). Body movement frequency and sleep efficiency were 28.0 vs. 28.9 and 76.3 vs. 70.0%, respectively.
On postoperative day 7, the VAS pain score was 25.8 vs. 27.5, and the number of body movements and sleep efficiency were 27.5 vs. 34.5 and 74.5 vs. 71.9%, respectively. The range of motion of the knee was 104.6 degrees of flexion for TKA and 116.2 degrees for UKA, with UKA having a greater range of motion. Extension was 6.0 and 3.4 degrees, respectively.

Discussion

In this study, we investigated postoperative pain, sleep status and functional recovery in TKA and UKA; UKA had smaller VAS pain scores, less PCA fentanyl consumption, less postoperative pain and greater range of motion. Regarding sleep status, we expected that less pain would lead to less body movement and better sleep efficiency, but in fact there was no difference in the number of body movements or sleep efficiency. TKA, which is generally considered more invasive than UKA, affected pain and functional recovery but not sleep state. It was considered necessary to explore further factors.

ACKNOWLEDGEMENTS: Japan Society for the Promotion of Science (JSPS) KAKENHI (19K18486).