Osteoarthritis (OA) of the hip is a major cause of restricted locomotor activity and functional disability.1,2 Total hip replacement (THR) is a valuable procedure for the management of end-stage arthritis and is effective in improving quality of life and physical function and alleviating pain.3,4
Limb length discrepancy (LLD) is an adverse outcome of THR.5,6 There are 2 types of LLD—apparent and true. Apparent LLD is pelvic obliquity, which occurs after THR because of tight hip abductors and usually resolves within 6 months with abductor stretching. In contrast, true LLD reflects unequal bone length (eg, due to bone loss, growth alteration, and subsidence).4,6 Love and Wright7 reported an 18% incidence of limb lengthening greater than 1.5 cm after unilateral THR, with 6% of patients treated with a shoe lift on the nonoperated leg. A similar study by Woo and Morrey8 found an average lengthening of 1 cm in a series of 333 cases. Although LLD as much as 2 cm is common among the normal population,3,5 discrepancies after THR may lead to patient dissatisfaction and functional impairment.
While a large number of participants are satisfied with their pain relief and improved function after THR, LLD arising from either lengthened or shortened femur after THR is a significant source of patient dissatisfaction.5–9,10 Lengthening of the leg can contribute to the development of nerve palsy, specifically of the sciatic nerve palsy, leading to functional limitations. Discrepancies in limb length have also been associated with alterations in gait, chronic low back pain, and chronic hip pain. Hence, LLD after THR has been a leading cause of litigation and may lead to revision surgery.6 Even relatively minor differences in leg length can be detected by patients and may impact satisfaction with surgery, especially when patients are required to wear a lift in the contralateral shoe to correct the discrepancy.5–7,11,12
Most studies of LLD after THR have focused on methods to minimize the problem or techniques to assess true leg length differences. Few studies have examined the long-term influence of LLD on satisfaction and function. The purpose of this study was to determine whether perceived LLD influences function and satisfaction 6 years after primary THR, adjusting for other predictors of functional status and patient satisfaction.
MATERIALS AND METHODS
This article summarizes the results of a secondary data analysis of a large cohort that has been described previously.13,14 The parent study used Medicare claims data to identify participants in the US Medicare population, aged 65 years and older, who underwent elective primary THR between July 1, 1995, and June 30, 1996.14 Participants with diagnostic codes indicating infection, cancer, hemiarthroplasty, fracture, and/or dislocation of the hip or femur and those who underwent bilateral and revision surgeries were excluded from the analysis because these individuals were likely to have outcomes that differed from those undergoing elective THR. Trained abstractors reviewed the medical records.14
Medicare claims data provided information about patient characteristics, such as age, gender, and race. Medical record data included a patient's primary diagnosis (OA, rheumatoid arthritis, or avascular necrosis), other relevant medical comorbidities (Charlson comorbidity index), and type of fixation (cemented, uncemented, or hybrid). Participants provided information on their educational background, which was categorized as either less than a college education or at least some college education. Participants also provided information about weight and height, which were used to calculate body mass index (BMI; weight in kilograms divided by height in meters squared), and 2 items addressing fear of falling and fall history.
Of the 926 participants with 3-year follow-up data, 638 completed a questionnaire that addressed level of perceived LLD, function, and satisfaction 6 years after surgery. The 6-year time frame was selected as it represented a midpoint after surgery and would provide information on longer-term results of surgery. The questionnaire included a single item asking whether the patient perceived a difference in leg length and used a 3-level response (feels same length, feels slightly uneven, and feels severely uneven). We combined the last 2 responses to produce a binary variable indicating whether patient perceived any LLD. Hip function was assessed by using the patient-administered version of the Harris Hip Score questionnaire, a validated 9-item disease-specific measure of pain and functional status.15 These items use an ordinal response set. The items are summed and converted to a 0 to 100 scale. A score of less than 70 indicates poor outcome, 70 to 79 fair, 80 to 89 good, and 90 to 100 excellent.15,16 We chose the Harris Hip Score to evaluate function after THR, as it is reliable, valid, and responsive and has been widely used to evaluate hip function after THR.15,16
Satisfaction with surgery was assessed by using a previously validated Satisfaction scale.13,14 This scale consisted of 4 independent questions addressing satisfaction with pain relief, ability to do house and yard work, ability to participate in recreational activities, and overall results of surgery. Each item had 4 responses (very satisfied, somewhat satisfied, somewhat dissatisfied, and very dissatisfied), which were summed. The Satisfaction scale was transformed to a 0 to 100 scale, wherein 0 indicated least satisfaction and 100 indicated maximum satisfaction.14
SPSS version 14.0 was used to conduct the analyses.17 Univariate analyses were conducted to describe sample characteristics. Associations between the dichotomized primary LLD variable and the dependent variables (total scores of Satisfaction, Harris Hip function) were conducted by using Wilcoxon tests because of the skewed nature of the data.
To measure the effect of perceived LLD on individual items from the Function and Satisfaction scales, we collapsed the Likert Response scales into binary variables. We dichotomized satisfaction with score less than 80, indicating less than full satisfaction and score of 80 and greater, indicating full satisfaction on the basis of the verbal anchors of the Likert scale in the questionnaire. That is, a score greater than 80 indicated, on average, that the patient was very satisfied. Harris Hip Score was dichotomized with score of 70 or less, indicating poor function. Logistic regression was used to examine independent effect of perceived LLD on satisfaction after THR and poor function (Harris Hip Score), adjusting for age, gender, BMI, Charlson comorbidity index, level of education, type of fixation (cemented vs uncemented or hybrid), and Western Ontario and McMaster Universities pain subscale. Forward and backward stepwise regressions were used to confirm the stability of the model.
A total of 638 participants met our inclusion criteria (mean age, 72 years [SD = 5]). Seventy-four percent of participants were between 65 and 76 years of age at the time of surgery, 31% were living alone, and more than half (62%) were women. Ninety-eight percent were white and 89% had a primary diagnosis of OA. Almost 23% of the participants had a BMI greater than 30 kg/m2; 17% participants had 2 or more comorbidities (Table 1). The most prevalent comorbidities were high blood pressure (52%) and asthma/bronchitis (12.5%). Sixty-one percent of the participants had a hybrid type of prosthesis (cemented femur, uncemented acetabulum). Thirteen percent participants were on medications for pain and discomfort, and 10% were on anti-inflammatory drugs. Twenty-one percent of our participants were college graduates.
Thirty-two percent of participants perceived an LLD and 68% did not. We found that median function (Harris Hip) score was 83 among those who perceived an LLD compared with a score of 92 among those who did not perceive an LLD (P < .001). The median satisfaction score was 92 among those who perceived an LLD compared with a score of 100 among those did not perceive an LLD (P < .001).
Bivariate analysis was used to examine the association between LLD and select functional items from the Harris Hip scale and the 2 fall-related questions. Crude odds ratios (OR) showed that participants who perceived LLD were 3 times more likely than those who did not report LLD to report a limp (OR, 3.05; 95% confidence interval [CI], 2.1-4.3), twice as likely to use assistive devices (OR, 1.98; 95% CI, 1.4-2.9), and 21/2 times more likely to use a banister while climbing stairs (OR, 2.5; 95% CI, 1.7-3.5). Participants with LLD were also more than twice as likely to report fear of falling (OR, 2.45; 95% CI, 1.64-3.6) and 1.92 times more likely to fall (OR, 1.92; 95% CI, 1.27-2.9).
We also examined the association between LLD and select aspects of satisfaction with surgery. In bivariate analyses, participants who perceived LLD were almost 3 times as likely as those who did not report LLD to be less than fully satisfied with relief of pain (OR, 2.93; 95% CI, 1.16-7.40), nearly 4 times more likely to be less than fully satisfied with their ability to do housework (OR, 3.89; 95% CI, 2.01-7.53), 3 times more likely to be less than fully satisfied with their ability to do recreational activity (OR, 3.21; 95% CI, 1.90-5.43), and 4 times more likely overall to be fully satisfied with the results after surgery (OR, 4.44; 95% CI, 1.96-10.07).
Logistic regression was used to identify the independent effects of LLD on functional status and satisfaction with surgery. The principal outcome variables were summary scores for functional status (the Harris Hip Score, dichotomized at 70, which indicated poor function) and satisfaction with the results of surgery (dichotomized at 80, which indicated being less than fully satisfied). Bivariate associations are shown in Table 2.
Next, we examined the independent effect of LLD on the outcomes, adjusting for significant bivariate associations. Participants who perceived LLD were 2 times more likely to report poor function (OR, 2.00; 95% CI, 1.85-3.36). Other predictors of poor function included pain in the index hip (OR, 15.04; 95% CI, 7.51-30.11) and less than high school education (OR, 1.40; 95% CI, 1.07-1.83). With respect to satisfaction, participants who perceived LLD were 2 times more likely to be less than fully satisfied with surgical results (OR, 2.24; 95% CI, 1.40-3.70), and participants who reported pain were 12 times more likely to be less than fully satisfied (OR, 13.39; 95% CI, 6.91-26.00).
DISCUSSION AND CONCLUSIONS
We have examined the prevalence of self-reported LLD in a population-based cohort of patients surveyed 6 years after elective primary THR and found that 32% of participants perceived a LLD. Patients who reported LLD were twice as likely to report worse function and were twice as likely to report less than complete satisfaction with surgery. This rate of LLD is consistent with prior literature, which reports that radiographically documented LLD varies on average between 1 and 16 mm and perceived LLD varies between 6% and 32%.5,7
Long-term effects of LLD on function and satisfaction of patients after unilateral primary THR are not well understood. Edeen et al18 interviewed and examined 68 patients who had undergone THR to determine the clinical significance of LLD after THR on patient satisfaction, use of orthoses, and presence of gait abnormalities. Edeen et al18 reported that more than half of the patients with postoperative limb length inequality were bothered by their LLD. In addition, the magnitude of LLD was found to be correlated with awareness of inequality, abnormal gait, use of ambulatory assistive devices, need for a shoe lift, and prior leg length inequality. In 1978, Williamson and Reckling19 found that 27% of patients with postoperative lengthening had complaints about their leg discrepancy and required a shoe lift. Turula et al20 reported that 6% of patients who had undergone THR were subjectively aware (of the LLD) and had a marked limp with a lengthening greater than 1.4 cm. The authors concluded that a large limb inequality may contribute to low back pain, limp, and mechanical loosening of prosthesis.20 While some studies reported poorer outcomes in patients whose leg lengths were significantly worse than those of patients who considered their operated leg to be of equal length,5–21,22 White and Dougall10 reported that there was no correlation between the occurrence of LLD after THR and functional outcomes and patient satisfaction.
Konyves and Bannister5 assessed LLD and function by using the Oxford Hip Score, a clinician-focused outcome measure, in patients before THR and 3 and 12 months after THR. They found that patients who perceived true lengthening reported poorer function (18% worse) at 12 months compared with those who perceived equal leg length. In our cohort, participants who perceived LLD had a median score of 83 on the Harris Hip scale and 92 on the Satisfaction scale compared with median scores of 92 on the Harris Hip and 100 on the Satisfaction scale in the participants who did not perceive a LLD. These differences are clinically important15–16,23 and document a statistically significant relation between perceived LLD, function, and satisfaction. Hence, participants who perceived LLD had poor function and were less satisfied 6 years after unilateral THR compared with those who did not perceive LLD.
The THR is performed to reestablish unassisted gait with functional independence and pain relief. In our study, participants were 3 times more likely to report a limp if they had the perception of LLD. These patients also reported the need for assistive devices and environmental assistance (use of banisters) for ambulating and ascending and descending stairs. Patients were also less satisfied with their pain relief and ability to do their household and recreational activities because of a perceived LLD.
One of the leading causes of patient dissatisfaction after THR is a limp.5–7,21 A limp can be caused by a loosening of the implants, mechanical problems (heterotrophic ossification, abductor disturbance, etc), biologic problems (sepsis, neuromuscular imbalance, contractures, etc), and extra pelvic causes, such as degenerative pathology in the spine, knee, and ankle. An important cause of postoperative limp is LLD. Consistent with the findings of this study, Edeen et al18 found a noticeable limp in almost 41% participants with leg length inequality. Moreover, these participants had greater leg length inequality and required an assisted device. The results of our regression analyses illustrated that perceived LLD remained a strong predictor of function and satisfaction after adjusting for other covariates. Among the predictors of poor function, hip pain was the most important, with an adjusted OR of 15, reinforcing the fact that an increased level of hip pain is related to decreased function. Pain also remained the most significant predictor of less than full satisfaction with surgery (adjusted OR, 13), followed by perceived LLD with an adjusted OR of 2.24.
There are limitations of this study. Radiographs were not available to confirm the existence of LLD. However, the intent of the study was to describe the impact of patient-perceived LLD, not true LLD, on function and satisfaction. Also, while patients reported the presence of a LLD, there was no way to determine which leg was longer, though data suggest that the operated leg is often the longer limb.5 There was no information available regarding current use of a heel lift. Thus, the impact of a heel lift on function could not be determined.
The study has several strengths. This is a large prospective cohort of patients who have undergone a primary THR. The measures used are well validated and responsive. Of particular importance is the fact that the primary outcomes are specific to hip disorders and, in the case of the Satisfaction scale, designed specifically for patients after THR. The functional outcome measure is a patient-oriented measure versus a clinician-oriented measure and thus, aligns well with the purpose of this study to assess patient's perspective of LLD and its impact on outcomes.
In conclusion, participants who perceived LLD reported poor function. These patients were more likely to report difficulty in gait, as noted by their reports of limping while walking and were more likely to report the use of an assistive device or external support while climbing stairs. These patients were more likely to be less than fully satisfied with pain relief, with ability to engage in activities of daily living, and with ability to engage in recreational activities. Regardless of whether limb length inequality is clinically or radiographically measured, perceived LLD influences function and satisfaction up to 6 years after surgery. These results suggest the need for providers to assess patient perspectives regarding LLD and to address these concerns in the clinical encounter and with interventions such as training to promote equal weight distribution among the limbs. Further studies should be conducted to determine whether interventions such as equal weight distribution training will reduce the perception of LLD to improve function and satisfaction after surgery.
This study was funded by NIH K24 AR 02123 and NIH P60 AR 48872.
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function; limb length discrepancy; satisfaction