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Association of bone health by calcaneal quantitative ultrasound with quadriceps strength and function one year after unilateral total knee arthroplasty
∗Corresponding author: Yoshinori Hiyama. y.hiyama.cj@juntendo.ac.jp
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Received: ,
Accepted: ,
This article was originally published by Reed Elsevier India Pvt. Ltd. and was migrated to Scientific Scholar after the change of Publisher.
Abstract
Abstract
Although total knee arthroplasty (TKA) effectively improves knee pain and functional decline due to knee osteoarthritis, hip fractures are more likely to occur in the first year after surgery. Bone mineral density (BMD) measured by dual-energy X-ray absorptiometry (DXA) decreases in the first year after TKA, but it is not clear whether BMD measured by quantitative ultrasound (QUS) also shows a decrease. This study aimed to evaluate the change in QUS parameters before and 1 year after TKA and to investigate the association of QUS parameters with quadriceps strength and function 1 year after TKA.
This prospective cohort study included 30 patients scheduled for their unilateral TKA. We assessed BMD using QUS before and 1 year after surgery. Quadriceps strength was assessed using a hand-held dynamometer, and function was assessed using a self-reported questionnaire. A linear mixed model estimated the mean difference in QUS parameters before and 1 year after TKA. A general linear model was also used to examine the association of QUS parameters with quadriceps strength and self-reported function at 1 year after surgery.
We found no significant decrease in the QUS parameters on either the surgical or non-surgical side at 1 year postoperatively compared to preoperatively. The QUS parameters were not associated with quadriceps strength or self-reported function on either the surgical or non-surgical side at 1 year postoperatively.
QUS alone may not be sufficient to detect changes in BMD from before surgery to 1 year after TKA. Clinicians should evaluate BMD preoperatively to identify patients at high risk for hip fractures and develop a program to prevent postoperative hip fractures.
Level 3, Cohort study.
Keywords
Bone mineral density
Quantitative ultrasound
Total knee arthroplasty
Fracture risk
1 Introduction
Total knee arthroplasty (TKA) is a widely performed procedure for end-stage knee osteoarthritis (OA) and effectively improves knee pain and functional decline associated with knee OA.1 However, in the first year after TKA surgery, there is an increased likelihood of hip fractures,2–4 with a 26 % higher risk compared to individuals without TKA2 and a 46 % increased risk compared to the last year before surgery.2 Hip fractures not only lead to high mortality rates5 but also significantly impact the health of older adults, with over 60 % unable to regain their pre-fracture levels of daily living and mobility function.6
Bone mineral density (BMD) is one of the most important predictors of hip fracture risk. The mainstream BMD measurement is dual-energy X-ray absorptiometry (DXA), and a 1 standard deviation decrease in BMD increases the risk of hip fracture by up to 2.6 times.7 After TKA, BMD has been reported to decrease rapidly by 15 % in the first 6 months postoperatively, with no recovery observed by 2 years.8 This decrease in BMD among TKA patients exceeds the age-related decrease.9,10
Recently, quantitative ultrasound (QUS) has gained popularity as a cost-effective method to assess BMD as a pre-screening test for DXA,11 given its meaningful correlation with DXA11 and its ability to predict hip fractures.12,13 In Japan, the number of facilities with DXA increased 2.8-fold in the 15 years from 1996 to 2011, while the number of facilities with QUS increased 10.1-fold to 7,893, with a growing capacity for BMD pre-screening. A previous study reported that patients undergoing staged bilateral TKA showed improvement in QUS parameters compared to preoperative levels after 5 years.14 However, there is a lack of data on QUS assessment in the first year after TKA, a period when the prevalence of hip fractures is high. Understanding the change in QUS parameters before and after TKA can facilitate the adoption of BMD pre-screening using QUS in post-TKA patients to identify those at high risk for hip fractures.
A previous cross-sectional study has demonstrated that low BMD, as assessed by QUS, is associated with poor quadriceps strength and function,15,16 while a previous longitudinal study has indicated that declines in quadriceps strength increase the risk of declining BMD,17 suggesting a link between quadriceps strength, function, and BMD. However, it remains uncertain whether BMD is also associated with quadriceps strength and function after TKA surgery. Postoperatively, quadriceps strength significantly decreases compared to the non-operated side at 3 and 6 months postoperatively.18 However, 1 year after surgery, it strengthens beyond preoperative levels, no longer differing from the non-operated side.18 Functional improvement is also observed within the first year after TKA, surpassing preoperative levels 1 year after surgery.1 Postoperative rehabilitation aims to enhance quadriceps strength and function. An association with BMD would indicate that postoperative rehabilitation should further promote these aspects, while the lack of association would suggest the need for updates to include BMD improvement.
The purpose of this study was to evaluate the change in QUS parameters before and 1 year after TKA and investigate its association with quadriceps strength and function 1 year after TKA. We hypothesised that the QUS parameter would also decrease at 1 year after TKA compared to preoperative values, as observed in previous studies using DXA,8–10 and that the QUS parameter would be associated with quadriceps strength and function at 1 year after TKA.
2 Methods
2.1 Design, setting, and participants
This prospective cohort study consecutively recruited patients scheduled for their first unilateral knee arthroplasty from February 2017 to January 2018. Patients with the following diseases or impairments were excluded: stroke, neuromuscular disorders, cognitive impairment, cardiovascular disease, respiratory disease, or musculoskeletal disorder, except for contralateral knee OA. This study has the Institutional Review Board approval (Number: E16HS-017). Informed consent was obtained from all participants prior to participation. The sample size calculation was not pre-specified because we aimed to discover the association of bone health with quadriceps strength and self-reported function 1 year after TKA.19 All assessments were performed 1 month preoperatively and 1 year postoperatively.
2.2 QUS assessment
For all participants, calcaneal bone status was assessed using a QUS device (A 1000 EXP II, GE Healthcare, Tokyo, Japan) by the same examiner (RT), who instructed the participant to sit in a chair with a handrail, rested, and then took measurements of both heels. Measurement takes approximately 10 s to complete, eliminating any loss of measurement accuracy due to foot movement. Broadband ultrasound attenuation (BUA, dB/MHz) and speed of sound (SOS, m/s) were measured by the QUS device. The stiffness index (SI) is automatically calculated from BUA and SOS according to the following formula and recorded in the QUS device: SI (%) = (0.67 × BUA) + (0.28 × SOS) − 420.20 The examiner extracted the stiffness index of all participants recorded on the QUS device as analysis data.
2.3 Quadriceps strength
Quadriceps strength was also assessed by the same experienced examiner (RT) using a hand-held dynamometer (μTas F1; Anima, Tokyo, Japan). Participants were instructed to sit with their knees flexed at 70°, and the attachment was placed on the front of the lower leg. The lever arm length was defined as the distance between the knee joint and the attachment of the dynamometer. After some submaximal practice, maximum isometric force was measured twice for approximately 3 s with verbal encouragement, with a rest period of approximately 30 s between measurements. All measurements were taken from the nonoperative side. Quadriceps strength was determined by multiplying the greater of the two measurements by the lever arm length and normalizing for body weight.
2.4 Knee pain and function
A Japanese self-reported questionnaire21 based on the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC)22,23 was used to assess knee pain and function. Like the original WOMAC, the questionnaire consists of 17 items on knee function and five items on pain. Each item was scored on a five-point Likert scale. The pain was assessed independently for each knee. For both the components of knee function and pain, the total score ranged from 0 to 100, with higher scores indicating better function or less pain, respectively. To avoid differences due to different explainers, the same examiner (RT) who performed the QUS assessment and measurement of quadriceps strength explained the self-reported questionnaire to all participants.
2.5 Covariates
Covariates such as age, sex, and body mass index (BMI) were collected from the medical records. The severity of knee OA was graded by an experienced physician using the Kellgren-Lawrence radiographic grading system.24
2.6 Statistical analysis
All analyses, including QUS assessment, quadriceps strength measurement, knee pain and function evaluation, and covariates, were performed by a single author (YH) using Stata/BE version 17 (Stata Corp., College Station, TX, USA). We performed complete case analyses because patients with missing data were few. For patient characteristics, means and standard deviations were used to describe continuous variables that were normally distributed, and numbers and proportions were used to describe categorical variables. For the first analysis, we estimated the mean difference in SI before and after surgery using a linear mixed model with adjustment for age and BMI. Time points were considered fixed factors, while individual participants were considered random factors. For the second analysis, we examined whether SI was associated with quadriceps strength and self-reported function scores, with adjustments for age, sex, contralateral knee OA severity, self-reported pain score, and preoperative SI using a general linear model. Finally, we performed two sensitivity analyses to ensure that our results are robust. We estimated the mean differences in SI before and after surgery only in women since nearly three-quarters of the participants were women, and sex differences could affect the results. Additionally, we examined whether SI was associated with quadriceps strength and self-reported function scores only in women, with adjustments for age, contralateral knee OA severity, self-reported pain score, and preoperative SI using a general linear model. For all analyses, p < 0.05 was defined as statistical significance.
3 Results
We included 30 patients who met the criteria to participate in this study and excluded one patient without SI data out of 30 patients. Finally, we included 29 patients in the analyses. The mean age was 74.3 years (standard deviation, 6.5 years), and almost three-quarters (72.4 %) were women (Table 1). All 29 patients had contralateral knee OA (grade 2: 27.6 %; grade 3: 55.2 %; and grade 4: 17.2 %).
| Total | ||
| N = 29 | ||
| Age, years | 74.3 | (6.5) |
| Women, n (%) | 21 | (72.4 %) |
| BMI, kg/m2 | 25.5 | (3.8) |
| X-ray grade, n (%) | ||
| Surgical side | ||
| Grade 1 | 0 | (0 %) |
| Grade 2 | 8 | (27.6 %) |
| Grade 3 | 15 | (51.7 %) |
| Grade 4 | 6 | (20.7 %) |
| Non-surgical side | ||
| Grade 1 | 0 | (0 %) |
| Grade 2 | 8 | (27.6 %) |
| Grade 3 | 16 | (55.2 %) |
| Grade 4 | 5 | (17.2 %) |
Table 2 shows SI, quadriceps strength, and self-reported pain and function preoperatively and postoperatively. We found no significant decrease in SI on either the surgical (mean difference, 0.14; 95 % confidence interval [CI], −2.24–2.51) or non-surgical side (mean difference, −1.09; 95 % CI −4.22–2.03) at 1 year postoperatively compared to preoperatively. SI was not associated with quadriceps strength or self-reported function on either the surgical (quadriceps strength; mean difference, 1.24; 95%CI −3.84–6.39; self-reported function; mean difference, −0.19; 95%CI, −0.41–0.11) or non-surgical side (quadriceps strength; mean difference, 9.26; 95%CI −0.92–19.4; self-reported function; mean difference, −0.17; 95%CI, −0.62–0.29) at 1 year after TKA. However, the postoperative SI was associated with preoperative SI on both the surgical side (mean difference, 0.89; 95%CI, 0.66–1.12) and the non-surgical side (mean difference, 0.89; 95%CI, 0.53–1.26).
| Preoperative | Postoperative | |||||
| Total (N = 29) | Men (N = 8) | Women (N = 21) | Total (N = 29) | Men (N = 8) | Women (N = 21) | |
| Stiffness index, % | ||||||
| Surgical side | 68.9 (13.7) | 83.1 (12.1) | 63.5 (10.0) | 69.4 (14.2) | 84.6 (10.0) | 63.3 (10.6) |
| Non-surgical side | 71.4 (13.4) | 86.1 (12.1) | 65.8 (9.1) | 70.6 (16.3) | 86.8 (16.9) | 64.2 (10.9) |
| Quadriceps strength, Nm/kg | ||||||
| Surgical side | 0.63 (0.29) | 0.81 (0.34) | 0.57 (0.25) | 0.94 (0.57) | 1.01 (0.60) | 0.90 (0.57) |
| Non-surgical side | 0.79 (0.31) | 0.92 (0.49) | 0.74 (0.21) | 0.88 (0.43) | 0.95 (0.40) | 0.84 (0.45) |
| Self-reported pain, points | ||||||
| Surgical side | 61.4 (26.1) | 63.1(27.9) | 60.8 (26.0) | 91.6 (11.7) | 91.3 (10.3) | 91.7 (12.6) |
| Non-surgical side | 63.3 (26.3) | 63.1(27.9) | 64.0 (26.4) | 88.4 (17.6) | 91.3 (12.8) | 87.1 (19.5) |
| Self-reported function, points | 61.9 (19.3) | 66.9 (17.1) | 60.4 (20.1) | 89.1 (14.0) | 93.2 (8.1) | 87.3 (15.8) |
Sensitivity analysis in women showed no significant decrease in SI on the surgical side (mean difference, −0.41; 95%CI −3.50–2.68) or non-surgical side (mean difference, −1.81; 95%CI −4.84–1.22) at 1 year after TKA compared to prior to surgery. Additionally, the general linear model, including only women, demonstrated that the SI was not associated with quadriceps strength or self-reported function on both the surgical side (quadriceps strength; mean difference, 0.018; 95%CI −6.99–7.03; self-reported function; mean difference, −0.004; 95%CI, −0.32–0.31) and non-surgical side (quadriceps strength; mean difference, 1.90; 95%CI, −6.08 to 9.89; self-reported function; mean difference, −0.028; 95%CI, −0.42–0.37). However, similar to the primary analysis, the postoperative SI was associated with preoperative SI on both the surgical side (mean difference, 0.72; 95%CI, 0.34–1.10) and non-surgical side (mean difference, 0.90; 95%CI, 0.33–1.47).
4 Discussion
In this study, we observed no decrease in calcaneal QUS parameters from before surgery to 1 year after TKA surgery. In addition, bone health at 1 year after TKA was not associated with quadriceps strength or self-reported function but with preoperative bone health. Sensitivity analyses confirmed the robustness of our results.
We hypothesised that calcaneal QUS-measured BMD would decrease at 1 year after TKA compared to preoperatively, as several previous studies have indicated a correlation between calcaneal QUS and femoral BMD measured by DXA.11,25,26 Additionally, femoral BMD measured by DXA has been reported to decrease 1 year after TKA compared to preoperative levels.8–10 However, the results of our present study contradict this hypothesis, suggesting that calcaneal QUS-measured BMD does not decrease at 1 year after TKA. This finding implies that QUS alone may not suffice to detect changes in BMD in the first year after TKA and should be complemented by DXA.
However, in this study, the SI on both the surgical and non-surgical sides in women was lower than that observed in individuals with hip fractures in previous studies,13 both preoperatively and postoperatively. In contrast, the SI in men closely resembled those without hip fractures.13 These findings suggest that QUS measurements, both before and after TKA, have the potential to identify individuals at high risk of hip fractures. Consequently, more healthcare facilities should incorporate QUS assessments for hip fracture risk before and after TKA, given that QUS is a cost-effective alternative to DXA and the availability of QUS installations is rising. Screening strategies with QUS prior to DXA were highly cost-effective compared to direct screening with DXA in women aged 65–74 years but less cost-effective in men of a similar age.27 Therefore, pre-screening with QUS in women before and after TKA may also offer cost-effectiveness benefits.
In addition, our study demonstrated a significant association between lower QUS parameters after TKA and lower QUS parameters before TKA. This suggests that clinicians can identify patients at high risk for hip fracture after TKA preoperatively. To mitigate hip fracture risk, it may be imperative to implement preventive programs aligning with the recommendations of the National Osteoporosis Guideline group, which includes ensuring sufficient dietary calcium and vitamin D intake, moderating alcohol consumption, avoiding smoking, and incorporating regular weight-bearing and muscle strengthening exercises to prevent fragility fractures.28 Future research should focus on developing preoperative programs to mitigate the risk of postoperative hip fractures in patients undergoing TKA.
Furthermore, our study found no significant association between the QUS parameter and quadriceps strength or self-reported function 1 year after TKA surgery. In general, postoperative rehabilitation after TKA surgery aims to improve quadriceps weakness and functional decline to facilitate a return to activities of daily living. However, our results suggest that standard postoperative rehabilitation interventions aimed at addressing quadriceps weakness and functional decline may not impact the QUS parameter. Therefore, postoperative rehabilitation programs should be updated to not only address quadriceps weakness and functional decline but also target hip fracture risk as indicated by the QUS parameter.
The present study has several strengths. First, it is the first study to evaluate BMD using QUS 1 year after TKA. Given the increasing number of QUS installations, the dissemination of BMD pre-screening through QUS is anticipated to expand for both pre- and post-TKA patients in the future. Second, the consistency of results was enhanced as the same experienced examiner conducted QUS measurements, quadriceps strength assessments, and provided explanations for the self-reported questionnaire, thereby reducing variability in the results. Third, the robustness of our results was supported by the sensitivity analyses. Nevertheless, our study also has some limitations, and the results should be interpreted cautiously. The primary limitation includes a limited sample size, which is particularly insufficient to explore potential differences in bone health between women and men. Second, all participants in this study had contralateral knee OA, which may limit the generalizability of our findings to a broader population of knee OA patients. However, most patients undergoing TKA have OA in the contralateral knee.29 Third, the covariates we adjusted for in our analyses may not be sufficient. For example, we did not account for nutritional status, including vitamin D and calcium intake, or smoking, which could potentially affect BMD.
5 Conclusions
This study focuses on the impact of TKA on bone health, particularly the potential decrease in BMD in the first year after surgery. Using calcaneal QUS, the researchers found that BMD did not significantly decrease in TKA patients during this period. However, QUS measurements were effective in identifying individuals at high risk of hip fractures both before and after surgery, especially in women. The study highlights the potential of QUS as a cost-effective tool for assessing hip fracture risk and suggests the need for updated rehabilitation programs to address both functional improvement and bone health in TKA patients.
Use of AI tool
No AI tool has been used.
Declaration of competing interest
The authors declare no conflict of interest.
Ethical statement
This study was approved by the Ethics Committee of Tokyo University of Technology, Japan (Number: E16HS-017).
Funding
This work was supported by JSPS KAKENHI Grant Number JP16K21439.
Informed consent statement
Informed consent was obtained from all participants involved in the study. The study is in accordance with the ethical standards of the 1964 Helsinki declaration and its late amendments.
CRediT authorship contribution statement
Yoshinori Hiyama: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Project administration, Writing – original draft, Writing – review & editing. Ryo Takahashi: Conceptualization, Data curation, Investigation, Writing – review & editing. Tomoya Tanaka: Conceptualization, Writing – review & editing. Sadaya Misaki: Conceptualization, Writing – review & editing, all authors have read and agreed to the published version of the manuscript.
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