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Letter to the Editor

Pre-operative psoas muscle mass and post-operative gait speed following total hip arthroplasty for osteoarthritis

Hidetaka Wakabayashi1,*, Naoko Watanabe1, Mami Anraku2, Hideyuki Oritsu1, Yoshitaka Shimizu1

Article first published online: 7 JUL 2015

DOI: 10.1002/jcsm.12046

How to Cite

Wakabayashi, H., Watanabe, N., Anraku, M., Oritsu, H., and Shimizu, Y. (2015) Pre-operative psoas muscle mass and post-operative gait speed following total hip arthroplasty for osteoarthritis. Journal of Cachexia, Sarcopenia and Muscle, doi: 10.1002/jcsm.12046.

Author Information

1
Department of Rehabilitation Medicine, Yokohama City University Medical Center, Yokohama City, Japan
2
Department of Radiation, Yokohama City University Medical Center, Yokohama City, Japan

*Correspondence to: Hidetaka Wakabayashi, Department of Rehabilitation Medicine, Yokohama City University Medical Center, 4-57 Urafune-chou, Minami Ward, Yokohama City 232-0024, Japan: Tel: +81-45-261-5656, Fax: +81-45-253-9955, Email: noventurenoglory@gmail.com


Muscle volumes of the gluteus medius, gluteus maximus, and tensor faciae latae assessed by a computed tomography (CT) scan were greater in men than women and not different between the left and the right side after total hip arthroplasty (THA).[1] Body mass index, sex, age,[2] and ambulatory status[3] affected functional outcome after THA. However, the effects of psoas muscle mass and muscle quality on functional outcomes after THA are unknown. The purpose of this study was to investigate the association between pre-operative psoas muscle mass, muscle quality assessed by a pelvic CT scan, and post-operative gait speed following THA.

A retrospective cohort study was conducted on 135 consecutive hip osteoarthritis patients who received unilateral THA (right/left: 83/52). We measured psoas muscle area (PMA) and psoas muscle attenuation (PMT in Hounsfield Units) by pre-operative (median 32 days) pelvic CT to assess the hip joint at the level of the fourth lumbar vertebra using Slice-O-Matic software (v.5.0; Tomovision, Magog, Quebec, Canada). Post-operative gait speed was measured by a 10 m walk test at discharge.

Body mass index, PMA, skeletal muscle index (SMI) calculated by PMA/body height2 (cm2/m2), and PMT were larger in men, and post-operative gait speed was faster (Table 1). PMA, SMI, and PMT were larger in the contralateral non-operated (NOP) side (Table 2). A significant association was found between post-operative gait speed, PMA, SMI, PMT on the NOP side, and age (Table 3).

Table 1. Baseline characteristics and statistical analysis between men and women
 Total N = 135Men N = 11Women N = 124P value
  1. BMI, body mass index; HU, Hounsfield Unit; PMA, psoas muscle area; PMT, psoas muscle attenuation; SD, standard deviation; SMI, skeletal muscle index.
  2. at-test, b Mann–Whitney U-test.
Age, years, mean ± SD67 ± 1065 ± 968 ± 100.392a
BMI, kg/m2, mean ± SD24.0 ± 3.926.6 ± 4.823.8 ± 3.70.021a
Post-operative length of stay, median (interquartile range)18 (16–22)18 (15–19)18 (16–22)0.250b
PMA, cm2, mean ± SD12.10 ± 3.9720.44 ± 6.1911.36 ± 2.700.001a
SMI, cm2/m2, mean ± SD5.23 ± 1.547.94 ± 2.434.99 ± 1.180.002a
PMT, HU, mean ± SD36.2 ± 9.442.0 ± 10.635.7 ± 9.20.032a
Postoperative gait speed, m/s, median (interquartile range)0.67 (0.50–0.87)0.94 (0.67–1.20)0.66 (0.46–0.83)0.012b
Table 2. Statistical analysis of psoas muscle between the total hip arthroplasty side and the contralateral non-operated side: t-test
 THANOPP value
  1. HU, Hounsfield Unit; NOP, contralateral non-operated side; PMA, psoas muscle area; PMT, psoas muscle attenuation; SD, standard deviation; SMI, skeletal muscle index; THA, total hip arthroplasty side.
PMA, cm2, mean ± SD5.34 ± 2.006.76 ± 2.33<0.001
SMI, cm2/m2, mean ± SD2.31 ± 0.802.92 ± 0.91<0.001
PMT, HU, mean ± SD34.6 ± 10.640.4 ± 9.1<0.001
Table 3. Gait speed, psoas muscle mass, and muscle quality: Spearman rank correlation
 PMA THAPMA NOPSMI THASMI NOPPMT THAPMT NOPAgeBMI
  • * means P value < 0.05.
  • BMI, body mass index; HU, Hounsfield Unit; NOP, contralateral non-operated side; PMA, psoas muscle area; PMT: psoas muscle attenuation; SMI, skeletal muscle index; THA, total hip arthroplasty side.
Gait speed0.1400.381*0.0040.249*0.0720.249*−0.440*−0.108
PMA THA 0.458*0.946*0.409*0.359*0.175*−0.0720.273*
PMA NOP  0.354*0.932*0.0680.354*−0.191*0.250*
SMI THA   0.408*0.376*0.1350.0550.263*
SMI NOP    0.0910.325*−0.0580.256*
PMT THA     0.581*−0.142−0.258*
PMT NOP      −0.230*−0.253*
Age       −0.054

A stepwise multiple linear regression analysis of post-operative gait speed adjusted by age, sex, post-operative length of stay, SMI, and PMT on the NOP side revealed that age, postoperative length of stay, and SMI were independently associated with post-operative gait speed (gait speed = 0.070 × SMI on the NOP side − 0.011 × age − 0.006 × post-operative length of stay + 1.322, p < 0.001, R2 = 0.255). In contrast, PMT on the NOP side was not independently associated with post-operative gait speed.

Skeletal muscle index on the NOP side was independently associated with postoperative gait speed. Core muscle size measured as the psoas area from the CT scan provides a good measure of overall muscle mass and sarcopenia.[4] Psoas muscle mass on the NOP side rather than the THA side seems to reflect overall muscle mass, because psoas muscle mass on the THA side is regionally affected by severe osteoarthritis. As sarcopenia often occurs in rehabilitation settings, rehabilitation nutrition as a combination of both rehabilitation and nutrition care management for sarcopenia with osteoarthritis may improve functional outcome after THA.[5]

In conclusion, pre-operative psoas muscle mass on the NOP side is independently associated with post-operative gait speed following THA for osteoarthritis. A pre-operative pelvic CT scan of the hip joint can be useful to assess psoas muscle mass and to predict the post-operative functional outcome following THA.

Acknowledgments

The authors have complied with the guidelines of ethical authorship and publishing as stated in the Journal of Cachexia, Sarcopenia, and Muscle 2010;1: 7–8 (von Haehling S., Morley J. E., Coats A. J., and Anker S. D.). This work was supported by a research Grant-in-Aid for Scientific Research C (no. 25350611) from the Ministry of Education, Science, Culture, Sports, Science, and Technology of Japan. The ethics committee of the Yokohama City University Medical Center approved the study. This study has been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments.

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