van Aalst, Michiel J.H. PT, MSc; Oosterhof, Jan PT, PhD; Nijhuis-van der Sanden, Maria W.G. PT, PhD; Schreurs, B. Wim MD, PhD
Total hip arthroplasty (THA) is a highly cost-effective procedure1–3 resulting in substantial and sustained pain relief, improvement in physical function, and enhanced health-related quality-of-life.4–10 Current local clinical rehabilitation protocols are typically aimed at a quick discharge from the hospital. Nevertheless, the discharge may be delayed for several reasons, including postoperative complications and delayed functional recovery, with a negative influence on patient satisfaction and patient flow. Furthermore, the number of hip arthroplasties will increase based on demographic data and increasing patient-driven demand for this type of surgery. To reduce the risks of delayed functional recovery after surgery, preoperative training is recommended,11,12 and it is important to identify the patients at high risk for delayed recovery.13 Patient characteristics sensitive to preoperative training interventions are especially needed.
In previous studies, a number of factors have been shown to increase the length of hospital stay (LOS) after THA: increased age,14–18 female sex,14–17 increased body mass index (BMI),19,20 presence of comorbidity,16 and smoking.19–21 Nonetheless, these factors are not or hardly sensitive to specific preoperative training interventions.
Recently, Dall et al.14 demonstrated that a lower preoperative combined Harris Hip Score (HHS) function and activity score was an independent predictor of an extended LOS after THA. However, aiming at preoperative training interventions, it is important to know which physical function characteristics are at risk for delayed functional recovery.
The aim of the present study was to identify independent preoperative hip function characteristics that are predictive of an extended LOS after primary THA and that might also be sensitive to preoperative intervention. For this purpose, a retrospective chart analysis was conducted on available prospectively collected data of patients who underwent unilateral primary elective cemented THA during a 4-yr period.
MATERIALS AND METHODS
Patients who underwent a cemented THA between January 2005 and January 2009 were selected from the data bank of the department of orthopedic surgery. Exclusion criteria were THA for secondary osteoarthritis caused by rheumatic diseases, THA for proximal femoral fractures, and all THAs in which a reconstruction was performed with acetabular bone impaction grafting. Furthermore, patients who had a contralateral hip implant or surgery within 1 yr before surgery were also excluded. Thus, 158 patients were included with 158 hip implantations. The local Committee on Research Involving Human Subjects approved this study.
Individual patient characteristics included demographic, clinical, and comorbidity factors and were obtained from the medical dossiers. The collected demographic factors were sex, age, height, body weight, and BMI. The clinical factors were obtained from the hospital discharge summary for each patient and included indication for THA, American Society of Anesthesiologists Physical Status Classification, type of anesthesia (general or regional), date of operation, date of discharge, and discharge destination. Destinations at discharge included the categories home, nursing home, or rehabilitation hospital. Collected comorbidity factors were preexisting cardiovascular disease (coronary artery disease, myocardial infarction, congestive heart failure, valvular heart disease, arrhythmia, peripheral vascular disease, thrombophlebitis, thromboembolic disease, hypertension, transient ischemic attack, and stroke), pulmonary disease (chronic obstructive pulmonary disease and asthma), diabetes mellitus, and other preexisting medical problems that required medical treatment (e.g., hypothyroidism or hyperthyroidism). Furthermore, preoperative HHS and Oxford Hip Questionnaire (OHQ) data were collected. Visual analog scales (VASs) were obtained for pain at rest and pain during physical activity on a scale from “no pain” (0 mm) to “unbearable pain” (100 mm). All scores were administered at the outpatient department, approximately 1 mo before surgery according to the preoperative consultation protocol.
To obtain information on potentially predictive factors that might be sensitive to preoperative intervention, those items concerning hip strength and mobility were extracted from the HHS and the OHQ. Selected factors from the HHS included the items limping, the need to use a walking aid, the ability to use public transport, and range of hip motion. Range of hip motion was defined as the summation of degrees of flexion, abduction, adduction, external rotation, and internal rotation. Selected factors from the OHQ included the use of (public) transport and stairs. Subsequently, the scores of the selected items from the HHS and the OHQ were dichotomized. HHS “limping” was classified as yes (slight, moderate, or severe) or no (none); HHS “support” was classified as “no use of walking aid” (none) or “else” (cane for long walks, cane most of the time, one crutch, two canes, two crutches, or not able to walk); HHS “enter public transportation” was classified as yes or no; and OHQ “public transport” and OHQ “stairs” were classified as “difficult” (with moderate difficulty, with extreme difficulty, or not able to do) or “not” (easily or with little difficulty).
LOS was defined as the full number of days between the date of surgery and the date of discharge from the hospital.
Discharge criteria for going home were (1) independent transfer from supine to sit and from sit to stand, (2) safe mobilization with the aid of one or two crutches, and (3) climbing stairs independently and safely. If these criteria could not be met within a reasonable period (aiming at a hospital LOS of 1 wk), the patients were referred to a nursing home or an external rehabilitation center. The decision to discharge the THA patients to the home environment, to a nursing home, or to an external rehabilitation center was eventually made by the physician in dialogue with the physical therapist, the nursing staff, the patient, and the patient’s family.
All hip prostheses were implanted according to a standardized surgical technique. A posterolateral approach without trochanteric osteotomy was used in all hips. In all THA patients, a conventional acetabular full polyethylene Exeter Contemporary cup was cemented, predominantly with an inner diameter of 28 mm and, in some cases, with an inner diameter of 32 mm in combination with a cemented femoral Exeter stem (Stryker Howmedica, Newbury, UK). All THA patients received antibiotic prophylaxis consisting of 2 g of cefazolin intravenously just before surgery. Postoperatively, nonsteroidal anti-inflammatory drugs were used for 7 days to prevent heterotopic ossification. The patients with a contraindication for nonsteroidal anti-inflammatory drugs were treated by one dose of radiation therapy. All patients received thrombosis prophylaxis with low–molecular-weight heparin for 6 wks.
During hospitalization, all patients had physical therapy according to a standard protocol. On the first postoperative day, the therapy was focused on isometric strengthening and increasing the range of hip motion. On the second postoperative day, the THA patients were mobilized with a walking aid under supervision of a physical therapist to train transfers and ambulation.
To identify preoperative patient characteristics that are predictive of an extended LOS after THA, the THA patients were divided into two groups according to the median LOS used as a cutoff. Univariate associations between preoperative patient characteristics and LOS were determined using two-tailed unpaired Student’s t tests or χ2 tests when appropriate. A multivariate logistic regression analysis was conducted to determine the predictors associated with an extended LOS, including potential confounding factors. The first step in the regression procedure was to determine a model containing only the potential confounding variables (age, sex, BMI, presence of comorbidity [yes or no], and VAS pain at rest and during movement). Subsequently, the selected dichotomized preoperative HHS and OHQ variables were added to the logistic regression equation one at a time using the criterion of reducing the −2 log likelihood error for the included variables. After each variable was entered separately, it was checked for a significant association with LOS, adjusted for the potential confounding factors. Nonsignificant variables were not used in the final regression model, whereas variables significantly associated with LOS were added together with the confounding factors to the regression analysis to fit a model to obtain estimates for each predictive factor in the presence of all of the other covariates. Classification accuracy of the regression model was tested with the area under the receiver operating characteristic curve. A P value of less than 0.05 was considered to indicate statistical significance.
One hundred sixty-seven patients fulfilled the inclusion criteria. Nine patients (three men and six women; mean [SD] age, 70.2 [7.8] yrs; median [range] LOS, 6.0 [3–12] days) were excluded from further analysis; for five patients, BMI was not known; for three patients, pain intensity scores were missing; and for one patient, the OHQ scores were not available. Therefore, the study cohort consisted of 158 THA patients. Seventy-seven THA patients (49%) had surgery using general anesthesia. Eighty-one (51%) had surgery with spinal/epidural anesthesia. Eighty-eight THA patients (56%) had at least one relevant comorbid condition, and 21 patients (13%) had multiple (two or more) comorbidities. For further subject characteristics, see Table 1.
The mean (SD) LOS in the hospital surgical unit was 7.5 (4.4) days (median [range], 6.0 [3–41] days). Overall, 76 THA patients (48 %) had an LOS of more than 6 days. For the THA patients with an LOS of more than 6 days, the mean (SD) LOS was 10.3 (5.0) days (median [range], 8.0 [7–41] days); for those with an LOS of 6 days or less, the mean (SD) LOS was 4.8 (1.0) days (median [range], 5.0 [3–6] days). One hundred forty-nine THA patients (94.3%) were discharged to the home environment; seven (4.4%), to a nursing home; and two (1.3%), to an external rehabilitation center.
Using univariate analysis, the THA patients who required an LOS of more than 6 days were more likely to be older (P < 0.001), to have one or more comorbid conditions (P = 0.008), to have used a walking aid preoperatively (P = 0.002), and to have had trouble with climbing stairs preoperatively (P < 0.001) compared with the THA patients who required an LOS of 6 days or less. The complete results of the univariate analysis are shown in Table 2.
The final multivariate model included the factors sex, age, BMI, presence of comorbidity, preoperative pain at rest, preoperative pain during movement, preoperative HHS support, and preoperative OHQ stairs (classification accuracy of 76%). There was no significant association between LOS and age, sex, BMI, and presence of comorbidity. Logistic regression analysis revealed a significant independent association between the preoperative need to use a walking aid and LOS (P = 0.04) and between the preoperative ability to climb stairs and LOS (P = 0.007). The THA patients who preoperatively had used a walking aid had an 18.5% increased chance of requiring an LOS of more than 6 days compared with those who did not need to use a walking aid preoperatively (odds ratio [OR], 2.15; 95% confidence interval, 1.03–4.50). The THA patients who preoperatively were not able to climb stairs or who had moderate to extreme difficulty in climbing stairs had a 23.6% increased chance of requiring an LOS of more than 6 days compared with those who experienced very little trouble or no trouble at all with climbing stairs preoperatively (OR, 2.74; 95% confidence interval, 1.31–5.74). The complete results of the final multivariate model are shown in Table 3.
The primary aim of the present study was to identify independent specific physical function characteristics that may be sensitive for preoperative training intervention and that are predictive of an extended LOS after primary elective THA. The THA patients who preoperatively had difficulties climbing stairs and those who used a walking aid preoperatively had a considerably increased chance of requiring an extended LOS. The latter finding is consistent with previously described results of Husted et al.,16 who reported that preoperative use of a walking aid was associated with an increased LOS in individuals who were admitted for hip and knee replacement surgery.
In this study, the mean hospital LOS was 7.5 days, and 94.3% of the patients were discharged home. This LOS is slightly shorter than the LOS of the studies of Hayes et al.22 (9.5 days and 98% of the patients were discharged home) and Dall et al.14 (8.1 days and 92% of the patients were discharged home). However, in the United States, the mean hospital LOS for primary THA declined from 9.1 days in 1992 to 3.7 days in 2008, and the proportion of patients discharged home declined from 68.0% to 48.2%.23 These differences may be explained by differences in factors driving LOS; in this study, functional milestones were used aiming at discharge to home, similar to the studies of Hayes et al.,22 Dall et al.,14 and Husted et al.16 In the United States, the reduction in hospital LOS is accompanied by a significant reduction in the proportion of patients discharged directly home and a significant increase in the proportion of patients discharged to postacute care facilities.23 Therefore, the findings of this study to reduce hospital LOS may not be directly applicable in the United States; however, because the authors used functional milestones aiming at discharge to home, these predictors of hospital LOS may identify patients at risk for a delayed recovery of physical functioning after primary THA.
There was no significant independent association between LOS and age, sex, BMI, presence of comorbidity, and preoperative pain at rest or during movement. When comparing these findings with the results of two larger studies14,16 with similar discharge criteria, the results on BMI and comorbidity are in agreement with both these studies, although the results on age and sex do not seem to match with their findings. However, Husted et al.16 found ORs for age (OR, 1.02) and sex (OR, 0.6) as predictors for LOS, which are quite similar to the findings of this study (OR, 1.03 and 0.63, respectively). Therefore, the negative findings could be explained by the difference in size of the study population and thus in a lack of power of this study. However, a 10-yr increase in age would provide an independent 6.5% increase in LOS, which is of minor value. Presumably, concerning functional recovery, muscle strength largely determines the predictive value of increased age.24
Both predictors for LOS—the preoperative use of a walking aid and difficulty managing stairs—may be explained by the loss of hip muscle strength. Patients with hip osteoarthritis are frequently reported to have reduced hip muscle strength25 compared with control individuals26–28 or compared with the less severely affected side.26 Hip muscle weakness in osteoarthritis has been suggested to be caused by disuse atrophy as a result of pain-related arthrogenous inhibition of muscle function and reflex inhibition of muscles moving the affected joints.29–31 Consequently, both these disabilities may serve as an important target for preoperative training, for example, by improving muscle strength and therefore reducing LOS; however, this hypothesis needs further proof. For reasons described above in the current study, analyses were controlled for pain intensity at rest and during movement 1 mo before surgery; however, both pain qualities did not significantly contribute in predicting LOS; therefore, pain approximately 4 wks before surgery is not predictive of LOS. However, earlier long-standing pain could have induced muscle weakness.
The findings of this study may have important implications for future studies regarding the selection of patients who may benefit from preoperative physical therapy.
The retrospective design of this study may be considered a weak point, although the data of the patients who underwent unilateral primary elective cemented THA in a 4-yr period were collected prospectively. However, this design ensures independent data collection and determination of LOS because of the fact that at the time of gathering these data, the aim of this study was not yet known. The authors assume that a strong point of this study is the large group of patients who underwent the same standardized surgery for primary THA following the same protocol during hospital stay, using clear discharge criteria. However, the results of this study may be limited for THA with cemented implants because of the fact that patients with uncemented stems may have a delayed functional recovery because of restricted weight bearing during walking.
The use of one dichotomous variable for all different comorbidities, assuming similar effect on physical function, may have limitations. However, in a large study predicting LOS, Dall et al.14 found no significant effect of diabetes, ischemic heart disease, or other medical comorbidities when analyzed as separate variables. Possibly, the use of an index of comorbid diseases that impair physical function, for example, as developed by Groll et al.,32 would have been more appropriate.
For logistic reasons, some patients may not have visited the research assistants (students) for assessment of physical function (HHS and OHQ score) and pain, which, at the authors’ outpatient clinic, is the standard procedure for patients indicated for total hip and knee replacement arthroplasty. However, the authors have no information about these missing data.
This study demonstrated that the THA patients who preoperatively had difficulties climbing stairs and those who were preoperatively required to use a walking aid showed a considerably increased chance to require an extended LOS, while controlling for known possible confounders. These findings may help to identify patients who are at risk for an increased LOS after primary THA and who may benefit from preoperative physical training.
1. Faulkner A, Kennedy LG, Baxter K, et al. Effectiveness of hip prostheses in primary total hip replacement: A critical review of evidence and an economic model. Health Technol Assess. 1998; 2: 1–133
2. Fortin PR, Penrod JR, Clarke AE, et al. Timing of total joint replacement affects clinical outcomes among patients with osteoarthritis of the hip or knee. Arthritis Rheum. 2002; 46: 3327–30
3. Lavernia CJ, Drakeford MK, Tsao AK, et al. Revision and primary hip and knee arthroplasty. A cost analysis. Clin Orthop Relat Res. 1995; 311: 136–41
4. Bachmeier CJ, March LM, Cross MJ, et al. A comparison of outcomes in osteoarthritis patients undergoing total hip and knee replacement surgery. Osteoarthritis Cartilage. 2001; 9: 137–46
5. Fitzpatrick R, Morris R, Hajat S, et al. The value of short and simple measures to assess outcomes for patients of total hip replacement surgery. Qual Health Care. 2000; 9: 146–50
6. Hirvonen J, Blom M, Tuominen U, et al. Health-related quality of life in patients waiting for major joint replacement. A comparison between patients and population controls. Health Qual Life Outcomes. 2006; 4: 3
7. Montin L, Leino-Kilpi H, Suominen T, et al. A systematic review of empirical studies between 1966 and 2005 of patient outcomes of total hip arthroplasty and related factors. J Clin Nurs. 2008; 17: 40–5
8. Nilsdotter AK, Aurell Y, Siosteen AK, et al. Radiographic stage of osteoarthritis or sex of the patient does not predict one year outcome after total hip arthroplasty. Ann Rheum Dis. 2001; 60: 228–32
9. Ostendorf M, Buskens E, van Stel H, et al. Waiting for total hip arthroplasty: Avoidable loss in quality time and preventable deterioration. J Arthroplasty. 2004; 19: 302–9
10. Tubach F, Ravaud P, Baron G, et al. Evaluation of clinically relevant changes in patient reported outcomes in knee and hip osteoarthritis: The minimal clinically important improvement. Ann Rheum Dis. 2005; 64: 29–33
11. Coudeyre E, Jardin C, Givron P, et al. Could preoperative rehabilitation modify postoperative outcomes after total hip and knee arthroplasty? Elaboration of French clinical practice guidelines. Ann Readapt Med Phys. 2007; 50: 189–97
12. Vukomanovic A, Popovic Z, Durovic A, et al. The effects of short-term preoperative physical therapy and education on early functional recovery of patients younger than 70 undergoing total hip arthroplasty. Vojnosanit Pregl. 2008; 65: 291–7
13. Valkenet K, van de Port IG, Dronkers JJ, et al. The effects of preoperative exercise therapy on postoperative outcome: A systematic review. Clin Rehabil. 2010; 25: 99–111
14. Dall GF, Ohly NE, Ballantyne JA, et al. The influence of pre-operative factors on the length of in-patient stay following primary total hip replacement for osteoarthritis: A multivariate analysis of 2302 patients. J Bone Joint Surg Br. 2009; 91: 434–40
15. Forrest G, Fuchs M, Gutierrez A, et al. Factors affecting length of stay and need for rehabilitation after hip and knee arthroplasty. J Arthroplasty. 1998; 13: 186–90
16. Husted H, Holm G, Jacobsen S.: Predictors of length of stay and patient satisfaction after hip and knee replacement surgery: Fast-track experience in 712 patients. Acta Orthop. 2008; 79: 168–73
17. Vincent HK, Alfano AP, Lee L, et al. Sex and age effects on outcomes of total hip arthroplasty after inpatient rehabilitation. Arch Phys Med Rehabil. 2006; 87: 461–7
18. Weber EW, Slappendel R, Prins MH, et al. Perioperative blood transfusions and delayed wound healing after hip replacement surgery: Effects on duration of hospitalization. Anesth Analg. 2005; 100: 1416–21
19. Sadr Azodi O, Bellocco R, Eriksson K, et al. The impact of tobacco use and body mass index on the length of stay in hospital and the risk of post-operative complications among patients undergoing total hip replacement. J Bone Joint Surg Br. 2006; 88: 1316–20
20. Vincent HK, Weng JP, Vincent KR.: Effect of obesity on inpatient rehabilitation outcomes after total hip arthroplasty. Obesity (Silver Spring). 2007; 15: 522–30
21. Moller AM, Pedersen T, Villebro N, et al. Effect of smoking on early complications after elective orthopaedic surgery. J Bone Joint Surg Br. 2003; 85: 178–81
22. Hayes JH, Cleary R, Gillespie WJ, et al. Are clinical and patient assessed outcomes affected by reducing length of hospital stay for total hip arthroplasty? J Arthroplasty. 2000; 15: 448–52
23. Cram P, Lu X, Kaboli PJ, et al. Clinical characteristics and outcomes of Medicare patients undergoing total hip arthroplasty, 1991-2008. JAMA. 2011; 305: 1560–7
24. Bortz WM II.: A conceptual framework of frailty: A review. J Gerontol A Biol Sci Med Sci. 2002; 57: M283–8
25. Wang T, Ackland T, Hall S, et al. Functional recovery and timing of hospital discharge after primary total hip arthroplasty. Aust N Z J Surg. 1998; 68: 580–3
26. Arokoski MH, Arokoski JP, Haara M, et al. Hip muscle strength and muscle cross sectional area in men with and without hip osteoarthritis. J Rheumatol. 2002; 29: 2185–95
27. Gilbey HJ, Ackland TR, Wang AW, et al. Exercise improves early functional recovery after total hip arthroplasty. Clin Orthop Relat Res. 2003; 408: 193–200
28. Rasch A, Dalen N, Berg HE.: Test methods to detect hip and knee muscle weakness and gait disturbance in patients with hip osteoarthritis. Arch Phys Med Rehabil. 2005; 86: 2371–6
29. Hurley MV.: The role of muscle weakness in the pathogenesis of osteoarthritis. Rheum Dis Clin North Am. 1999; 25: 283–98,
30. O’Reilly S, Jones A, Doherty M.: Muscle weakness in osteoarthritis. Curr Opin Rheumatol. 1997; 9: 259–62
31. O’Reilly SC, Jones A, Muir KR, et al. Quadriceps weakness in knee osteoarthritis: The effect on pain and disability. Ann Rheum Dis. 1998; 57: 588–94
32. Groll DL, To T, Bombardier C, et al. The development of a comorbidity index with physical function as the outcome. J Clin Epidemiol. 2005; 58: 595–602