The impact of leg length discrepancy after total hip arthroplasty on function and quality of life in Chinese

doi:10.21203/rs.3.rs-3324915/v1

Background

Postoperative leg length discrepancy (LLD) has been reported as an important factor for Chinese patients' satisfaction after total hip arthroplasty (THA). This study investigated the impact of postoperative LLD on function and quality of life in Chinese patients.

Methods

Patients who underwent primary unilateral THA with a single prosthesis were identified from our hospital. The patients were divided into two groups according to postoperative LLD: a small LLD group(LLD༜9 mm) and a large LLD group (LLD ≥ 10 mm). The Harris hip score (HHS) and the 12-item Short-Form health survey (SF-12) were used to compare the two groups. Multivariate logistic regression was used to identify potential risk factors associated with postoperative LLD.

Results

A total of 147 patients were included, with a mean follow-up of 6.22 ± 1.66 years. Of these patients, 119 had a small LLD (< 9 mm) and 28 had a large LLD (≥ 10 mm), and the average postoperative LLD was 6.48 ± 5.18mm. There were no significant differences between the two groups for HHS and SF-12 physical component score (PCS), but the SF-12 mental component score (MCS) was significantly lower in the large LLD group than the small LLD group (P = 0.008). Patient height was found to be an important risk factor for postoperative LLD (OR 0.909, 95% CI [0.843–0.979], P < 0.05).

Conclusions

Postoperative LLD does not affect hip function after THA in Chinese patients; however, large LLDs of over 10 mm may lead to decreased quality of life. Low height of patients was identified as a risk factor for postoperative LLD.

leg length discrepancy

total hip arthroplasty

quality of life

Total hip arthroplasty (THA) is an effective intervention for the treatment of persistent pain and disability related to different hip disorders ^[1]. However, there is a wide range of reported dissatisfaction rates among patients postoperatively, ranging from 3.3–16.3% in various studies ^[2–6]. A recent report demonstrated 8.1% dissatisfaction rate among Chinese patients, and it was suggested that postoperative leg length discrepancy (LLD) was significantly associated with the level of patient satisfaction ^[7].

Postoperative LLD has been identified as one of the most common complications after THA, resulting in patient dissatisfaction, pain and gait disturbances ^[8], and even litigation against orthopaedic surgeons ^[9]. The general consensus amongst clinicians is that a postoperative lower limb discrepancy of less than 10 mm is usually acceptable ^[10]. Despite this, there is yet no consensus regarding the impact of postoperative LLD (≥ 10 mm) on hip function and quality of life.

The objective of this study was to investigate the influence of LLD after THA on hip function and quality of life of Chinese patients. Our hypothesis was that postoperative LLD contributes to poor function and quality of life in patients who underwent THA, while our null hypothesis assumed that postoperative LLD had no effect on these outcomes.

With the approval of our hospital's institutional review board, we retrospectively reviewed a consecutive series of 174 patients who underwent primary unilateral THA with a single anatomic cementless stem (Ribbed Hip System, Waldemar Link, Hamburg, Germany) between October 2009 and October 2016. All THA procedures were performed by one of two experienced surgeons (Wang and Chen) under epidural anaesthesia, with the patient in the lateral decubitus position and utilizing the posterolateral approach. Preoperative templating was performed in all cases. After hip reduction, the operated limb was mirrored parallel to the contralateral limb, and intraoperative LLD was assessed by palpation of the patellar tip and heel and by assessment of soft tissue tension.

Inclusion criteria were as follows: age ≥ 18 years, available full-length anteroposterior radiograph, no history of lumbar spine surgery, no contralateral THA during follow-up, minimum follow-up of 3 years. Exclusion criteria consisted of developmental dysplasia of the hip, previous spinal, pelvic or lower limb injuries/fractures.

Patients were divided into two groups according to the radiological result of the postoperative LLD: the small LLD group, in which the operated leg was shortened or lengthened within 9 mm compared with the contralateral side, and the large LLD group, in which the operated leg was shortened or lengthened more than 10 mm compared with the contralateral side.

Measurement of Leg Length Discrepancy

The measurement of LLD was performed on the first postoperative full-length anteroposterior radiographs, as described by Du et al. ^[11]. All radiographs were imported into image analysis software (Orthocrat TraumaCad v2.0, USA) and magnification was corrected for the diameter of an artificial femoral head (Fig. 1). The length of the lower limb was defined as the distance from the teardrop to the centre of the ankle joint (Fig. 2). To assess the LLD, the difference in length between the two sides was recorded^[12], regardless of whether the surgical side was shorter or longer than the non-surgical side. In order to ensure objectivity, an independent examiner carried out the radiological measurement on each patient three times.

Assessment of functional outcome and quality of life

Patients' functional outcomes and quality of life were assessed using a telephone questionnaire, which included a joint-specific questionnaire ( Harris hip score; HHS) ^[13] and a general health questionnaire (12-item Short-Form Health Survey; SF-12, with scores for physical component score and mental component score; PCS and MCS respectively) ^[14].

Statistical analysis

Statistical analysis was carried out using the SPSS for Windows version 18.0 (SPSS Inc., Chicago, IL, USA). Demographic data were represented as mean and standard deviation (SD). The distributions of continuous variables were captured using the Kolmogorov-Smirnov test. For the follow-up time, HHS and PCS variables which were not normally distributed were compared between two groups through a Mann-Whitney U test. Variables with normal distributions had their contrasts between same groups examined using Student's t-test. The chi-squared test was applied to analysed classified variables. Logistic regression model by the "Forward: LR" method was used to carry out multivariate analysis. All analyses applied were conduced under two-tailed conditions and P values less than 0.05 were reported as statistically significant.

A total of 174 consecutive patients were included in the study. Of these, 147 (84.5%) had a complete set of results available: 64 female and 83 male. The mean preoperative weight was 67.82 ± 14.03 kg (range 42–107 kg), and mean height 166.35 ± 8.66 cm (range 147–188 cm). The mean age at time of surgery was 46.97 ± 12.07 years (range 18–70 years), and the mean follow-up time 6.22 ± 1.66 years (range 3.1–11.1 years). Preoperative diagnoses consisted of osteoarthritis (OA) in 35 (23.81%), rheumatoid arthritis (RA) in 4 (2.72%), ankylosing spondylitis (AS) in 15 (10.20%), osteonecrosis of the femoral head (ONFH) in 76 (51.70%), and femoral neck fracture (FNF) in 17 (11.56%) (Table 1). In 10 patients, the limb was shortened on the operative side, while 137 patients had equal length or lengthening (Fig. 3). The mean postoperative LLD was 6.48 ± 5.18 mm (ranging from a shortening of 6 mm to a lengthening of 26 mm), with 119 patients (80.95%) falling within the small LLD group, and 28 patients (19.05%) in the large LLD group.

Comparisons of postoperative HHS and SF-12 PCS between the two groups showed no statistically significant differences (P > 0.05). However, the SF-12 MCS of the large LLD group was significantly lower than those of the small LLD group (47.74 ± 6.75 vs. 50.67 ± 4.70, P = 0.008) (Table 1). Moreover, the mean height of the large LLD group was smaller than that of the small LLD group (163.43 ± 6.17 mm vs. 167.03 ± 9.03 mm, P = 0.047, respectively) (Table 1).

When other patient factors were compared (weight, sex, diagnosis, BMI, age at surgery, age at follow-up, and follow-up time) between the two groups, there were no statistically significant differences (P > 0.05). Accordingly, after adjusting for the influence of preoperative patient characteristics (i.e., weight, sex, diagnosis, BMI, and age at surgery), multivariate logistic regression analysis revealed that patient height was a risk factor for postoperative LLD of more than 10 mm (OR 0.909, 95% CI 0.843–0.979, P < 0.05) (Table 2).

Postoperative LLD is often considered a problem after THA and remains a surgical challenge in the current era. Many surgeons have attempted to validate methods to minimize disparities based on preoperative template measurement and intraoperative measurement methods ^{[8, 15, 16]}. However, possible risk factors for postoperative LLD after THA have yet to be identified. Studies have reported that patients with smaller body dimensions (BMI < 26 kg/m² and height < 175 mm) are more likely to report subjective LLD for a given objective LLD, regardless of sex or age ^[17]. This study showed that multivariate logistic regression analysis revealed patient height as the only risk factor for postoperative LLD (≥ 10 mm) in Chinese patients. Because of ethnic differences, this may explain why there was a difference from previous findings. Furthermore, cementless femoral stem design has been found to have a significant impact on postoperative LLD because of its complex three-dimensional geometry ^[18]. It has been reported that proximal femur anatomy and femoral stem design were only significant factors in univariate analysis for a recent study regarding postoperative LLD after THA, whereas low-volume surgeon was the only independent risk factor in multivariate analysis ^[19], prompting us to choose a single prosthesis type in this study in order to avoid any confounding caused by different prosthesis types. Similarly, the two surgeons who performed the THA procedures in this study were both senior surgeons, each performing over 100 operations per year.

Patient-perceived leg length discrepancy (PP-LLD) refers to a situation in which patients feel uncomfortable with the length of their legs despite having minimal or no anatomic inequality. Numerous studies have documented that 30%-42% of patients may experience PP-LLD after THA, although there is reportedly no correlation between this sensation and actual anatomical LLD ^{[20, 21]}. The feeling normally decreases during postoperative recovery, often guided by doctors through counselling and rehabilitation at 3 months or even 1 year after surgery ^{[22, 23]}. As the interval of follow up for the patients in this study was relatively long, further studies should be conducted in order to explore whether PP-LLD affects the medium- and long-term outcome of quality of life for those patients.

In the review of relevant literature, it was reported that there was no statistical association between LLD and functional outcomes after THA ^{[24, 25]}. The data collected from patients participating in this study also failed to show significant differences between postoperative HHS scores of the two groups - a result consistent with other related research reports.

Various scoring methods are employed to address the relationship between LLD and quality of life in previous studies. White et al. followed 200 patients with THA prospectively, and concluded that there was no statistically significant link between LLD and SF-36 (Medical Outcomes Study Short-Form 36-Item Health Survey) scores ^[25]. Pakpianpairoj studied 151 patients and suggested that only PP-LLD poses an effect on quality of life when measured using the EQ-5D assessment; moreover, as time progresses, this effect appears to diminish ^[22]. Wylde et al. argued that there was no such effect on WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index) scores either ^[26]. Conversely, Fujimaki et al. reported that a whole-leg LLD of ≥ 5 mm could reduce patients' quality of life according to both SF-36 and WOMAC scores^[2]. In this study, the SF-12 MCS score of the large LLD group was noticeably lower than the small LLD group, and their difference was greater than the minimal clinically important difference (MCID) of 3 reported previously among Chinese patients^[27]. We believe that large LLD (≥ 10 mm) undoubtedly affects mental health quality of life post-THA. Possible reasons may include the reason that different primary conditions behind THA, osteonecrosis of the femoral head in Chinese case versus primarily osteoarthritis in western countries, and the lower tolerable threshold of postoperative LLD due to shorter average height in our population.

This study does carry some limitations. As it was retrospective with a small sample size and held within a single center. Also, only 10 patients (6.80%) experienced limb shortening, making difficult to distinguish the difference between limb shortening and lengthening. Therefore, larger sample sizes across multiple centers are needed in future studies.

Although LLD does not affect hip function after THA in Chinese patients, a large LLD of greater than 10 mm could significantly impact patient's quality of life and psychological well-being. Additionally, short stature is identified as a risk factor for developing a postoperative LLD. Therefore, the surgeon should strive to reduce the likelihood of a postoperative LLD as much as possible, particularly in patients of short stature.

Acknowledgments

We are grateful to all patients who participated in this study.

Author contributions

WG and ZW contributed to the conception of the study; ZW and JC performed the operation; WG and XL performed the data analyses and wrote the manuscript; JC helped perform the analysis with constructive discussions.

Funding

This research did not receive any speciﬁc grant from funding agencies in the public, commercial, or not-for-proﬁt sectors.

Availability of data and materials

The analyzed dataset in this study is available from the frst author on reasonable request.

Ethics approval and consent to participate

This study was approved by ethics committee of Army Medical Center, Iran (No. 5300789). All methods were carried out in accordance with the Declaration of Helsinki and relevant regulations.

Consent for publication

Not applicable.

Competing interests

The author declares that they have no competing interests

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Table.1. Association of postoperative LLD with characteristics of the patients

Variables	Total (n=147)	Postoperative LLD		P values
Variables	Total (n=147)	Small LLD < 9mm (n=119)	Large LLD ≥10mm (n=28)	P values
Weight (kg)	67.82±14.03	67.99±13.93	67.09±14.66	0.761
Height (cm)	166.35±8.66	167.03±9.03	163.43±6.17	0.047
Gender				0.234
Male	83 (56.46)	70 (58.82)	13 (46.43)
Female	64 (43.54)	49 (41.18)	15 (53.57)
Diagnosis				0.668
AS	15 (10.2)	11 (9.24)	4 (14.29)
ONFH	76 (51.7)	60 (50.42)	16 (57.14)
FNF	17 (11.56)	15 (12.61)	2 (7.14)
OA	35 (23.81)	29 (24.37)	6 (21.43)
RA	4 (2.72)	4 (3.36)	0 (0)
Age of surgery (years)	46.97±12.07	47.24±11.85	45.82±13.11	0.579
BMI (kg/m²)	24.42±4.21	24.25±3.84	25.14±5.54	0.318
Age of follow-up (years)	53.24±12.27	53.5±12.05	52.14±13.36	0.599
Follow-up time (years)				0.569
25% quartile	4.84	4.77	4.91
50% quartile	5.88	5.79	6.28
75% quartile	7.34	7.38	7.0325
HHS				0.060
25% quartile	87.8	87.9	82.175
50% quartile	92.8	93.5	90.25
75% quartile	96.6	96.6	94.8
MCS	50.11±5.25	50.74±4.70	47.67±6.75	0.008
PCS				0.437
25% quartile	42.36	42.44	40.7925
50% quartile	46.01	46.01	44.88
75% quartile	48.86	48.86	49.87

Values given as mean ± SD or N (%). Bold values indicate statistical signiﬁcance (P <.05).

BM (BMI=Body Mass Index, MCS=mental component score, PCS=physical component score)

Table.2. Logistic regression analysis to identify the risk factors for postoperative LLD.

Characteristics	OR	95%CI	P values
Gender	0.377	0.101-1.41	0.147
Weight	0.707	0.435-1.15	0.163
Height	0.909	0.843-0.979	0.012
Diagnosis			0.786
ONFH	1.769	0.271-11.536	0.551
FNF	1.185	0.1-13.986	0.893
OA	0.823	0.112-6.053	0.848
RA	1.251	0.357-4.384	0.726
AS	0.944	0.854-1.044	0.263
Age of surgery (years)	1.172	0.329-4.176	0.806
BMI (kg/m²)	2.698	0.73-9.974	0.137

No competing interests reported.

The impact of leg length discrepancy after total hip arthroplasty on function and quality of life in Chinese

Status:

Version 1

Abstract

Background

Methods

Results

Conclusions

Figures

Introduction

Patients and Methods

Measurement of Leg Length Discrepancy

Assessment of functional outcome and quality of life

Statistical analysis

Results

Discussion

Conclusion

Declarations

References

Tables

Additional Declarations

Status:

Version 1