Low GS (＜26 kg for men and ＜16 kg for women in the dominant hand) is associated with poor nutritional status, low levels of fitness, and a range of adverse outcomes including limited functional activities, disability, prolonged LOS, as well as even mortality[8-10]. The extent of these effects on patient-reported outcome measure (PROM), postoperative complications, and unplanned readmissions following primary THA is unclear. In this study, through conducting a prospective case-control design, we concluded that low GS before THA is a significant risk factor for increased LOS, unplanned hospital readmissions, worse PROM, and postoperative complications.
A number of previous studies have examined the predictive role of low GS for the clinical outcomes following orthopedic surgery [15-19]. For instance, Shen et al. reported patients with high preoperative GS to display a better surgical outcome in terms of disability and health status six months after spine surgery . Selakovic et al. showed multivariate regression analysis adjusted for age and gender revealed that grip weakness was an independent predictor of worse functional outcome at 3 and 6 months after hip fracture for both genders and in all age populations. Similarly, Hershkovitz et al. suggested that grip strength is independently associated with rehabilitation outcome in post-acute frail hip fracture patients . A few studies have also investigated the predictive role of low GS in arthroplasty patients. Hashimoto et al. have investigated the effects of preoperative GS on stair ascent and descent ability in patients undergoing total knee arthroplasty. In another study, Shyam et al. examined this simple GS test may be highly beneficial preoperatively in identifying those patients likely to require longer inpatient stays and therefore those who would benefit from early nutritional intervention and focussed physiotherapy on a cohort of total hip and total knee arthroplasty patients. Similar to our study, they chose to measure the GS in patients who planned to undergo THA in the pre-admission clinic and reported similar findings to our study about the LOS, with an average delay in-hospital stay of 5 days in low GS cohort compared to the normal GS (12.2 ± 3.1 vs.7.2± 3.8). However, unlike in our study, Hashimoto et al. and Shyam et al. did not investigate whether there existed a statistically significant difference in PROM and postoperative complications between the two cohorts.
Our study further corroborated previous findings [16,18-20] about the patient characteristics associated with low GS in this population undergoing primary THA. As expected, there were significant differences in preoperative characteristics between the low GS and normal GS cohorts. Patients with low GS, were more likely to be female, older, have a lower BMI and higher ASA score. Also, these patients were more likely to have increased rates of pressure sore before THA, preoperative albumin < 3.5 g/dL, and perioperative blood transfusion rate. This meant patients with low GS experienced worse nutritional status and limitations in mobility. Multivariate analysis was utilized to demonstrate that even when accounting for these differences in preoperative characteristics, low GS patients remained at risk for 90-day postoperative major complications after THA. The statistically significant variables in the univariate analysis in Table 1 were treated as potential confounders and analyzed in the multivariate analysis.
Low GS was present in 31.9% in men and 48.1% in women of the total primary THA patients in this study. This percentage is higher than 5% in men and 18% in women aged 65 years and above in multiple populations (Europe/North America, South America, Middle East, Africa, South East Asia, South Asia, and China) , and 18.0% and 38.4% in Australian men and women, respectively . The reason for the difference in reported prevalence about low GS could be related to the race and the selection of the studied population. Our population, who is based on the patients undergoing THA in Asia, may have worse overall muscle strength and function compared to the general elderly population. When considering such a considerable percentage, these equate to significant effects on the over 600,000 primary THAs performed annually . Low GS patients were more likely to have a worse functional outcome and quality of life reflected by HHS and SF-12 scores. Besides, they were nearly seven times (OR, 7.11) as likely to had a higher risk of experiencing a major complication within 90 days of surgery, which in this study included myocardial infarction, postoperative mortality, sepsis, stroke, PJI, and death, after controlling for confounding variables. Limitations in mobility, reflected by the GS, may explain the high risk for these complications and other adverse outcomes, including pressure sore after THA, respiratory complications, urinary tract infection, and DVT. Of note, despite no statistically significant difference in dislocation after THA between two cohorts, the percentage in the low GS cohort is nearly 3.6 times than that in normal GS cohort (6.1 vs. 1.7, p=0.082). This could mean GS has a close association with the function of the abductor muscle group.
Our findings have certain implications. First, there is an ongoing urgent need to identify THA patients at increased risk for worse outcomes. Identifying this population of patients allows for the initiation of prevention and specific intervention to avoid the debilitating consequences of THA. Especially for patients undergoing THA due to hip fracture, other methods measuring muscle strength such as gait speed and muscle mass cannot be assessed before surgery. Instead, GS measurement is simple enough to be applied in the clinical setting. Therefore, confirmation of the prognostic value of HGS assessed in the THA setting is very significant. To the best of our knowledge, this is the first study to evaluate the role of HGS in predicting the clinical outcomes following THA for both gender and all ages. Second, muscle weakness, reflected by GS, is a modifiable risk factor that can be improved. It has been well known that strengthening exercises, especially for patients undergoing a selective operation, had positive effects on various outcomes after THA . Therefore, GS measurement before THA could be considered in the design for individualized treatment plans to improve functional recovery.
Our study has several limitations. First, the sample size was relatively small. Patients were collected only from one single center. Second, analyzed complications in this study are limited to medical complications 90 days postoperatively. Therefore, we do not have data on delayed complications or orthopedic-specific perioperative complications. Third, despite being discussed, there are significant differences in preoperative characteristics between the cohorts. The multivariate analysis attempts to account for these differences; however, there remains a risk that the analysis missed important confounding factors not included in the model. Therefore, the potential confounding effects of these factors on grip strength could not be determined. Lastly, we are also completely aware of the fact that our GS measurement method is different from the standardized approach advocated by the American Society of Hand Therapists (ASHT), where the subjects are tested in a seated position . GS was measured before THA in the supine position, since we noticed that it is unrealistic for a portion of patients, such as those with hip fracture, to complete the GS test in a seated position. Measuring GS after THA in a seated position would definitely be a more standardized way to assess muscle strength. However, we have standardized the way to measure GS in all the included patients, and this approach was also used by other authors [16, 24, 25]. Consequently, it is reasonable to assume that measuring GS in the supine position is an appropriate way to assess function.