Abstract
Introduction
Length of hospital stay in Japan is 20 to 30 days, which is much longer than United States. Reasons of such differences are utilization of a national insurance system in Japan, and more than 90 % of patients are discharged to home. The purpose of the current study was to investigate inpatient recovery process during relaxed standing, and to clarify the appropriate length of hospital stay following TKA.
Methods
Thirty patients (25 Females and 5 Males) with knee osteoarthritis, 67 to 84 years old (mean 75), participated. All the subjects provided informed consent and the study was approved by our institution. The subjects were asked to step on the two scales and perform relaxed standing, placing each foot on each scale independently. Evaluations were divided into two categories; subjective and objective components. Subjective component was based on pain level, and objective component consisted of vertical knee force and knee flexion angle during relaxed standing. Namely, subjective pain level on TKA side, vertical knee forces (%BW) on TKA side, and knee flexion angles (degrees) on TKA side during relaxed standing, were examined. Each evaluation was done twice. Data evaluations were done pre- and post-operatively. Postoperative evaluations were done daily from postoperative day 3 to 21. Pain level, vertical knee force, and knee flexion angle were evaluated using visual analog scale (100 mm), same type of two scales, and goniometer, respectively. Vertical knee force (%BW) was defined as the ratio of weight bearing on TKA side to body weight in our study.
An average value of two trials was calculated. Values of preoperative measurements were used as controls. Statistical difference between the data was evaluated using two-tailed repeated-measures of analysis of variance. After a significant P value (< 0.05) was determined, a post hoc Bonferroni correction was performed to compare selected mean values, and P-values of < 0.05 was considered as significant.
Results
Changes of subjective component (Fig. 1)
Preoperative pain score was 69.1. After TKA, pain level became maximum on postoperative day 3. Thereafter, pain gradually decreased, and on postoperative day 8, pain score was significantly smaller than preoperative score.
Changes of objective component (Fig. 2, 3)
Preoperative vertical knee force was 43.5 (%BW). Similarly, after TKA, it became minimum on postoperative day 3. Thereafter, knee force gradually increased, and on postoperative day 17, knee force was significantly larger than preoperative force.
Preoperative knee flexion angle was 15.6 (degrees). After TKA, knee flexion angle during standing became maximum on postoperative day 4. Thereafter, subjects could gradually extend the knee, and on postoperative day 16, it was smaller than preoperative angle.
Discussion
According to the previous study, standing is a most frequent activity during weight bearing in patient's daily life after joint replacement surgery. After TKA, significant pain reduction was observed from postoperative day 8, and objective knee condition became stable from postoperative day 16 or 17. Thus, hospital stay at least for 16 to 17 day after
