Outcomes of obese and nonobese patients undergoing revision total hip arthroplasty.код для вставкиСкачать
Arthritis & Rheumatism (Arthritis Care & Research) Vol. 59, No. 5, May 15, 2008, pp 738 –745 DOI 10.1002/art.23562 © 2008, American College of Rheumatology ORIGINAL ARTICLE Outcomes of Obese and Nonobese Patients Undergoing Revision Total Hip Arthroplasty ANNE LÜBBEKE,1 KAREL G. M. MOONS,2 GUIDO GARAVAGLIA,1 AND PIERRE HOFFMEYER1 Objective. To evaluate the effect of obesity on the incidence of adverse events (surgical site infection, dislocation, re-revision, or >1 adverse event), functional outcome, residual pain, and patient satisfaction after revision total hip arthroplasty (THA). Methods. We conducted a university hospital-based prospective cohort study including 52 obese and 152 nonobese patients with revision THA performed between 1996 and 2006. We used incidence rates, rate ratios, and hazard ratios (HRs) to compare the incidence of events in obese and nonobese patients and in 4 body mass index (BMI) categories (<25, 25–29.9, 30 –34.9, >35). Functional outcome and pain were measured 5 years postoperative using the Harris Hip Score. Results. The incidence rate for >1 complication increased with rising BMI (1.8, 3.4, 10.3, and 17.9 cases/100 personyears). The increase was small between normal and overweight patients (adjusted HR 1.5, 95% conﬁdence interval [95% CI] 0.5, 4.7), signiﬁcantly greater with BMI 30 –34.9 (adjusted HR 4.5, 95% CI 1.4, 14.0), and most evident with BMI >35 (adjusted HR 10.9, 95% CI 2.9, 41.1). The adjusted HR for surgical site infection (obese versus nonobese) was 4.1 (95% CI 1.1, 15.0) and for dislocation 3.5 (95% CI 1.3, 9.3). Eighty patients had a followup visit at 5 years. Obese patients had moderately lower functional results and higher levels of residual pain, but patient satisfaction was almost similar. Conclusion. Revision THA is technically challenging, particularly in obese patients, probably due to more difﬁcult anatomic conditions. We found an increased risk of adverse events, notably surgical site infection and dislocation in these patients. INTRODUCTION Obesity has been associated with a higher prevalence of symptomatic osteoarthritis of the hip and a subsequent increase in total hip arthroplasty (THA) procedures (1– 6). Interestingly, a recent large population-based study (6) did not ﬁnd an increase in revision procedures among obese patients post primary THA. Prosthetic joint infections, dislocations, and revisions are rare but serious complications after primary THA. There are conﬂicting results in the current literature concerning the inﬂuence of obesity on the occurrence of these complications. A number of studies found an increase in perioperative morbidity (7–9) and complications such as infections or dislocations associated with obesity (8,10 – 13), whereas others have reported no differences (14 – 1 Anne Lübbeke, MD, DSc, Guido Garavaglia, MD, Pierre Hoffmeyer, MD: Geneva University Hospital, Geneva, Switzerland; 2Karel G. M. Moons, PhD: Julius Center for Health Sciences and Primary Care, University Medical Center, Utrecht, The Netherlands. Address correspondence to Anne Lübbeke, MD, DSc, Orthopaedic Surgery Service, Geneva University Hospital, 24, Rue Micheli-du-Crest, 1211 Geneva 14, Switzerland. E-mail: firstname.lastname@example.org. Submitted for publication March 16, 2007; accepted in revised form November 7, 2007. 738 18). The literature concerning the inﬂuence of obesity on revision for aseptic loosening is also inconclusive, which has partially been related to differences in activity level (15,16,18 –23). However, functional outcome and patient satisfaction after THA have been considered comparable or only slightly lower in obese compared with nonobese patients (11,13,17,24). In comparison with primary hip arthroplasty, revision hip arthroplasty is a prolonged intervention resulting in more extensive tissue damage and is associated with more short- and long-term complications, as well as a higher mortality rate (25–29). The intervention is considered to be technically challenging, particularly in obese patients probably because of more difﬁcult anatomic conditions. Only a few studies, notably with short-term followup, have reported on the inﬂuence of obesity on outcomes after revision THA (12,30,31). There is even less literature concerning the effect of obesity on functional outcomes and satisfaction after revision surgery (32,33). The aim of this study was ﬁrst to evaluate the association between obesity and the incidence of main complications (in particular, surgical site infection, dislocation, and re-revision) after revision THA up to 5 years postoperatively. Also, we aimed to determine whether functional outcome, pain, and patient satisfaction at 5 years differed Effect of Obesity on Revision THA 739 Table 1. Patient distribution* No. Total number of revision THAs performed Patients excluded because of bilateral revision Number of eligible revision patients Patients with missing BMI Total number of patients included Patients due for 5-year visit Patients who had died Lost to followup Unable to attend 5-year visit Patients who completed 5-year followup 214 9 205 1 204 110 15 8 7 80 * THA ⫽ total hip arthroplasty; BMI ⫽ body mass index. between obese and nonobese patients who underwent revision THA. PATIENTS AND METHODS Study design and patient population. We undertook a prospective etiologic cohort study including all consecutive patients who underwent a revision THA at the university orthopedic department of the only public hospital for the urban and surrounding rural population between March 26, 1996 and July 31, 2006. Overall, 300 –350 primary and 25–30 revision THAs were done annually. Revisions were performed by senior orthopedic surgeons. We excluded re-revisions from this study. Study followup extended through October 31, 2006. For those patients who underwent bilateral revisions during the study period (n ⫽ 9), only the ﬁrst revision THA was included in order to allow for an analysis on the patient level. A total of 205 patients were eligible. One patient was excluded due to missing weight and height information, leaving 204 patients (Table 1). All patients received antibiotic and thrombosis prophylaxis, and the procedures were performed in ultraclean air laminar ﬂow operating rooms using hooded gowns. Gentamicin-loaded bone cement was used in cases with cemented implants. Exposure and outcome variables. The exposure (etiologic factor) of interest was obesity deﬁned as a BMI ⱖ30 kg/m2, in keeping with previous studies (12,13,30,32,34). The association between BMI and the primary outcome was also examined using 4 BMI categories (⬍25, 25–29.9, 30 –34.9, and ⱖ35). The primary outcome was the incidence of adverse events including the occurrence of ⱖ1 of the following during the followup period: surgical site infection (prosthetic joint and/or superﬁcial infection), dislocation (ﬁrst event), or re-revision for any cause. Prosthetic joint infection was diagnosed according to the criteria by Zimmerli et al (35), and internationally recognized criteria (12) were used for the inclusion of superﬁcial infections. Secondary outcomes were functional status, pain, and patient satisfaction (all continuous variables) 5 years after revision surgery. The Harris Hip Score (HHS; a physicianassessed, hip-speciﬁc clinical score evaluating the do- mains of pain, function, deformity, and motion) (36) was used to measure functional status. Scores range from 0 (worst) to 100 (best). The pain item of the HHS, consisting of a 6-grade response scale (none, slight/occasional, mild, moderate, marked, serious limitation/totally disabling pain) and rated numerically from 0 to 44 (no pain ⫽ 44), was used to deﬁne the pain outcome. The HHS is the most widely used physician-assessed hip score in orthopedic surgery (37,38). The total score and the pain subscore have shown high reliability and validity (38 – 40). Patient satisfaction was measured using a 0 –10 visual analog scale, where 10 ⫽ best. In the estimation of the association between obesity and the primary (and secondary) outcomes, the following potential confounders were assessed preoperatively: 1) age; 2) sex; 3) indication for revision deﬁned as a 7-category variable (aseptic loosening of cup, stem, or both; septic loosening; recurrent dislocation; periprosthetic fracture; technical error) as well as dichotomized variable (aseptic loosening versus all other indications for revision); and 4) surgery of the index hip prior to primary THA. The following clinical scores were also preoperatively assessed: the Merle d’Aubigné score, the Charnley classiﬁcation grade, and the American Society of Anesthesiologists (ASA) score. The Merle d’Aubigné score (41) is a hip-speciﬁc, physician-assessed clinical score evaluating pain, function, and motion on a scale from 0 to 6 (best, total score 18). The score has been used by orthopedic surgeons to evaluate hip arthroplasties for more than 50 years, and it highly correlates with the HHS (Spearman’s correlation coefﬁcient 0.81– 0.82) (42,43). The Charnley classiﬁcation (44) comprises 3 grades: 1 hip affected and the other normal (grade A), both hips affected (grade B), and multiple-joint disease or other disabilities leading to difﬁculties in ambulation (grade C). The ASA score is obtained from the anesthesia report and evaluated as a binary variable (1–2 versus 3– 4). It is a physical status classiﬁcation system aimed at grading the patient in relation to his physical preoperative status. The ASA 6-point scale ranges from a healthy patient to a patient with an extreme systemic disorder that is an imminent threat to life. The Merle d’Aubigné score was used preoperatively from March 1996 to June 2003. Complete score information was available for 30 (76.9%) of 39 obese patients and for 88 (76.5%) of 115 nonobese patients operated on during that time period. Four patients had a missing ASA score. The following information related to the revision surgery was assessed: 1) surgical approach without or with (yes/no) use of trochanteric/proximal-femoral osteotomy indicated in cases where greater femoral and/or acetabular exposure was needed; 2) use of an acetabular ring in case of insufﬁcient acetabular bone (yes/no); 3) femoral head size in millimeters; 4) cementing of stem and/or cup (yes/ no); and 5) operation time in minutes. Data collection. Patient weight and height were obtained at the preoperative entrance examination, just before surgery. Information about the potential confounding 740 Lübbeke et al Table 2. Distribution of baseline characteristics among obese and nonobese patients* Female Male Age at operation, mean ⫾ SD years Age, years ⬍50 50–59 60–69 70–79 ⱖ80 Reason for revision Aseptic loosening total Stem loosening Cup loosening Septic loosening Recurrent dislocation Periprosthetic fracture Technical error Merle d’Aubigné score, mean ⫾ SD‡ ASA score 1–2 3–4 Missing Surgery prior to primary THA Charnley classiﬁcation A B C Hip contralateral Normal Affected unoperated Operated BMI <30 (n ⴝ 152) BMI >30 (n ⴝ 52) 88 (57.9) 64 (42.1) 72.5 ⫾ 11.8 26 (50.0) 26 (50.0) 68.7 ⫾ 9.9 8 (5.2) 13 (8.6) 32 (21.1) 56 (36.8) 43 (28.3) 2 (3.8) 5 (9.6) 14 (26.9) 28 (53.9) 3 (5.8) 73 (48.0) 19 (12.5) 17 (11.2) 19 (12.5) 12 (7.9) 7 (4.6) 5 (3.3) 10.5 ⫾ 2.3 16 (30.8) 13 (25.0) 2 (3.8) 7 (13.5) 7 (13.5) 3 (5.8) 4 (7.6) 10.1 ⫾ 2.2 98 (64.5) 51 (33.6) 3 (1.9) 8 (5.3) 22 (42.3) 29 (55.8) 1 (1.9) 3 (5.8) 60 (39.5) 52 (34.2) 40 (26.3) 6 (11.5) 18 (34.6) 28 (53.9) 74 (48.7) 12 (7.9) 66 (43.4) 22 (42.3) 5 (9.6) 25 (48.1) RR (95% CI) Mean difference (95% CI)† 1.2 (0.9, 1.7) 3.7 (0.1, 7.4) 0.4 (⫺0.6, 1.3) 1.7 (1.2, 2.3) 2.0 (1.4, 3.0)§ * Values are the number (percentage) unless indicated otherwise. BMI ⫽ body mass index; RR ⫽ relative risk; 95% CI ⫽ 95% conﬁdence interval; ASA ⫽ American Society of Anesthesiologists; THA ⫽ total hip arthroplasty. † F or continuous variables. ‡ Used preoperatively from March 1996 to June 2003. Complete score information was available for 30 (77%) of 39 obese patients and 88 (77%) of 115 nonobese patients operated on during that time period. § Charnley classiﬁcation grade C compared with grade A and B combined. variables and the surgical intervention was systematically documented by the operating surgeon on speciﬁcally designed data collection forms. The data were checked by a trained medical secretary and 1 of the investigators (AL). We retrieved information regarding primary outcome events from each patient. We contacted all participants who were 5 years postoperative for a followup visit that included a clinical and radiologic examination. Information about the occurrence of the primary outcome events since the intervention, which were not treated at our institution, was obtained either during the followup visit or, for all those who were unable to join the followup visit, by phone. Followup examinations were completed by 2 trained physicians who had not performed the operations. Statistical analysis. The distribution of preoperative baseline characteristics (potential confounders) and technique- and implant-related variables was examined for obese and nonobese patients. To assess the association between obesity and the primary outcome, we calculated person-times from the date of operation until the ﬁrst occurrence of any of the above deﬁned events, death, end of the study (October 31, 2006), or loss to followup. Then we estimated the crude incidence rate and crude incidence rate ratio (IRR) with their 95% conﬁdence intervals (95% CIs). We repeated the analyses after stratiﬁcation for age, sex, ASA score, Charnley classiﬁcation grade, and indication for revision (dichotomized) to identify possible confounding or effect modiﬁcation using 2 BMI groups, with the nonobese group as the reference group. Moreover, we employed Cox proportional hazards analysis and presented adjusted hazard ratios (HRs). The proportional hazards assumption was checked by examining graphs of the log minus log survival functions. The analyses above were performed for any ﬁrst primary outcome event, and then repeated for the separate events if data allowed for it. Due to the small numbers of primary outcome events, we adjusted only for the most important confounders, which were ASA score for surgical site infection, and age and ASA score for dislocation. No adjustment was made for the outcome re-revision as only 8 patients had this event. Additionally, incidence rates and IRRs for the ﬁrst primary Effect of Obesity on Revision THA 741 Table 3. Incidence rates for each of the adverse events across obese and nonobese patients* Complication (1 event) Cases Person-years Incidence rate† Surgical site infection Cases Person-years Incidence rate† Dislocation Cases Person-years Incidence rate† Re-revision Cases Person-years Incidence rate† BMI <30 (n ⴝ 152) BMI >30 (n ⴝ 52) Unadjusted IRR (95% CI) Adjusted HR (95% CI) 13 516 2.5 17 145 11.7 4.7 (2.3, 9.6) 4.0 (1.8, 8.9)‡ 4 543 0.7 6 177 3.4 4.6 (1.3, 16.4) 4.1 (1.1, 15.0)§ 10 519 1.9 10 167 6.0 3.1 (1.3, 7.5) 3.5 (1.3, 9.3)¶ 4 543 0.7 4 195 2.0 2.8 (0.7, 11.1) - * BMI ⫽ body mass index; IRR ⫽ incidence rate ratio; 95% CI ⫽ 95% conﬁdence interval; HR ⫽ hazard ratio. † Cases/100 person-years. ‡ Complication (1 event of any primary outcome) adjusted for age, sex, and American Society of Anesthesiologists (ASA) score. § Surgical site infection (including superﬁcial and deep infection) adjusted for ASA score. ¶ Dislocation adjusted for age and ASA score using Cox proportional hazards models. outcome event were assessed across the 4 BMI categories (⬍25, 25–29.9, 30 –34.9, and ⱖ35) with the normal weight category (⬍25) as the reference group. We used Cox proportional hazards analysis to adjust for age, sex, and ASA score. The Kaplan-Meier approach was employed to estimate the one minus survival function (cumulative incidence function). To assess the association between obesity and the secondary outcomes, we calculated mean scores (with SDs) and the (crude) mean differences with 95% CIs for obese and nonobese patients using the unpaired Student’s t-test. We repeated the analyses after stratiﬁcation for age, sex, Charnley classiﬁcation grade, ASA score, and indication for revision. Multivariable linear modeling was used to adjust the effect of BMI on all 3 secondary outcomes for age, sex, preoperative function and pain, ASA score, and Charnley classiﬁcation grade. RESULTS Among the 204 patients, 114 were women and 90 were men, with a mean age of 71.6 years (range 32–94 years) and a mean BMI of 26.7 (range 15– 44). Twenty-ﬁve percent (n ⫽ 52) of the revisions were performed in patients with a BMI ⱖ30. Table 2 presents the distribution of the baseline characteristics (potential confounders) across obese and nonobese patients. The 2 groups mainly differed with respect to age, ASA score, Charnley classiﬁcation grade, and indication for revision. Obese participants were younger, more often classiﬁed as Charnley grade C, and had higher ASA scores. Moreover, they were revised for aseptic loosening less often overall (less loosening of the cup or of both components, more stem loosening), but more often for recurrent dislocation or technical error. In obese patients the revision was performed, on average, 92 months after the primary hip THA, compared with 125 months in nonobese patients (mean difference 33 months, 95% CI 9, 58). The 2 groups did not signiﬁcantly differ with respect to the use of osteotomy. A trochanteric or proximal femoral osteotomy was performed in 31 (60%) obese patients and 79 (52%) nonobese patients. In the obese group, an acetabular ring was used in 17 (43%) of the 40 revisions involving a cup replacement as compared with 89 (66%) of 134 cup replacements in the nonobese group. In the large majority of patients, a 28-mm head was chosen, except for 3 cases from each group with a 22-mm or a 32-mm head. A cemented cup was inserted in 67% of obese patients versus 80% of nonobese patients, and a cemented stem in 83% versus 74%. The groups did not differ with respect to operation time (209 versus 210 minutes). Primary outcomes. The followup period for the primary outcome ranged from 3 to 74 months. During followup, 3 (5.8%) of 52 obese patients and 22 (14.5%) of 152 nonobese patients had died, and 4 (7.7%) obese and 6 (3.9%) nonobese patients were lost to followup. Obese patients contributed a mean ⫾ SD of 33 ⫾ 25 person-months, and nonobese patients contributed a mean ⫾ SD of 41 ⫾ 21 person-months. Overall, 20 complications occurred in 17 (33%) of 52 obese patients compared with 18 events in 13 (9%) of 152 nonobese patients. Surgical site infections were reported in 6 (11.5%) obese patients (3 superﬁcial, 3 prosthetic joint) and 4 (2.6%) 742 Lübbeke et al Table 4. Occurrence of ﬁrst primary outcome event (surgical site infection, dislocation, or re-revision) according to 4 BMI categories* BMI Cases Person-years Incidence rate† Unadjusted IRR (95% CI) Adjusted HR (95% CI)‡ <25 (n ⴝ 83) 25–29.9 (n ⴝ 69) 30–34.9 (n ⴝ 41) >35 (n ⴝ 11) 5 281 1.8 1.0 (Ref.) 1.0 (Ref.) 8 235 3.4 1.9 (0.6, 5.8) 1.5 (0.5, 4.7) 12 117 10.3 5.8 (2.0, 16.4) 4.5 (1.4, 14.0) 5 28 17.9 10.0 (2.9, 34.7) 10.9 (2.9, 41.1) * BMI ⫽ body mass index; IRR ⫽ incidence rate ratio; HR ⫽ hazard ratio; 95% CI ⫽ 95% conﬁdence interval. † Cases/100 person-years. ‡ Adjusted for age, sex, and American Society of Anesthesiologists score using Cox proportional hazards models. nonobese patients (1 superﬁcial, 3 prosthetic joint). The crude incidence rate was 4.6 times higher in obese patients (Table 3). After adjustment for ASA score, the adjusted HR was 4.1 (95% CI 1.1, 15.0). After stratiﬁcation for sex, we observed a higher incidence rate of infection in obese versus nonobese women (IRR 15.5, 95% CI 1.7, 138.8) but no signiﬁcant increase in obese versus nonobese men (IRR 2.0, 95% CI 0.3, 12.2). Dislocation was observed in 10 (19.2%) obese patients and 10 (6.6%) nonobese patients. The crude incidence rate was 3.1 times higher in obese individuals. After adjustment for age and ASA score, the adjusted HR was 3.5 (95% CI 1.3, 9.3). Eight re-revisions were undertaken, with 4 re-revisions in each group (7.7% versus 2.6%). In each group, 2 re-revisions were performed for septic loosening; 1 for recurrent dislocation and 1 for early aseptic loosening of the cup. The crude incidence rate of re-revision for any cause was 2.8 times higher in obese patients (95% CI 0.7, 11.1). Loss of ﬁxation of the trochanteric osteotomy was observed in 5 (17.2%) obese patients and 5 (9.3%) nonobese patients. The incidence rate for the occurrence of ⱖ1 adverse event increased with rising BMI (Table 4 and Figure 1). This increase was small between normal and overweight patients (adjusted HR 1.5), but it became signiﬁcantly greater in the group with a BMI 30 –34.9 (adjusted HR 4.5) and was most evident in the group with a BMI ⱖ35 (adjusted HR 10.9), although the width of the 95% CI increased due to the low patient number in this latter group. Adjustment was performed for age, sex, and ASA score. Further adjustment for indication for revision and Charnley classiﬁcation grade did not substantially change the results. Secondary outcomes. Five years after revision, 31 obese and 79 nonobese patients were due for followup. Among the obese group, 2 (6.5%) patients had died, 3 (9.7%) were lost to followup, and 2 (6.5%) were unable to attend. Of the nonobese patients, 13 (16.5%) had died, 5 (6.3%) were lost to followup, and 5 (6.3%) were unable to attend. Of those still alive, 24 (82.8%) obese patients and 56 (84.8%) nonobese patients were seen at the 5-year visit. The mean ⫾ SD time to followup was 57 ⫾ 8 months. Five years postoperatively, obesity was associated with moderately lower functional status (HHS) and a lower pain subscore, which remained after adjustment for age, sex, preoperative function and pain (Merle d’Aubigné score), ASA score, and Charnley classiﬁcation grade (Table 5). The association with patient satisfaction was less evident, after adjustment the 95% CI included 0. DISCUSSION The primary aim of this study was to determine whether obesity was associated with a higher incidence of major events in patients undergoing revision THA. We found signiﬁcantly more events, notably surgical site infections and dislocations, in obese patients. Secondarily, we found moderately lower results on the HHS but almost similar satisfaction in obese patients 5 years postoperatively. In comparison with primary THA, revision surgery is associated with greater soft tissue damage and prolonged Figure 1. Cumulative incidence (one minus survival function) of ﬁrst primary outcome event (surgical site infection, dislocation, or re-revision) in normal weight (body mass index [BMI] ⬍25), overweight (BMI 25–29.9), obese (BMI 30 –34.9), and highly obese (BMI ⱖ35) patients after revision total hip arthroplasty using the Kaplan-Meier approach. Effect of Obesity on Revision THA 743 Table 5. Harris hip score (HHS), pain, and patient satisfaction at 5 years for obese and nonobese patients* BMI, mean ⴞ SD HHS HHS pain Satisfaction Difference, mean (95% CI) <30 (n ⴝ 56) >30 (n ⴝ 24) Unadjusted Adjusted† Adjusted‡ 82.8 ⫾ 14.7 39.2 ⫾ 7.2 8.2 ⫾ 1.8 71.4 ⫾ 17.0 33.9 ⫾ 9.6 7.2 ⫾ 2.7 11.4 (3.9, 18.9) 5.3 (0.8, 9.7) 1.0 (⫺0.2, 2.3) 9.2 (2.0, 16.7) 5.0 (0.9, 9.1) 0.8 (⫺0.3, 1.9) 8.9 (1.9, 15.9) 5.4 (1.1, 9.8) 1.1 (⫺0.1, 2.3) * Values are the mean ⫾ SD unless otherwise indicated. BMI ⫽ body mass index; 95% CI ⫽ 95% conﬁdence interval. † Adjusted for age, sex, and Charnley classiﬁcation grade (all 80 patients included in analysis). ‡ Adjusted for age at operation, sex, preoperative Merle d’Aubigné score, American Society of Anesthesiologists (ASA) score, and Charnley classiﬁcation grade. Due to missing values on preoperative Merle d’Aubigné score and ASA score, only 66 patients could be included for adjustment. operation time, which may explain the increased incidence of superﬁcial and deep infections after revision. Larger soft tissue dissection and subsequent increased muscle weakness in revision THA might be one of the responsible factors for higher dislocation rates (45). In turn, obesity has been associated with higher rates of wound healing complications (46) and higher morbidity. Furthermore, in obese patients the intervention can be more technically challenging with respect to exposure, implant positioning, and soft tissue closure (47). Literature about the inﬂuence of obesity on the occurrence of adverse events after revision THA is sparse. Most studies have reported on small patient groups and short followup periods. Perka et al (31), in a retrospective study including 229 patients of whom 31 had a BMI ⱖ30, found no increase in perioperative morbidity and mortality within 90 days. Another study (12) evaluated the risk of surgical site infection after revision according to 3 BMI categories. The authors did not observe an increase in infection in obese patients during the study followup, which was limited to the in-hospital postoperative period. In contrast, a recent matched cohort study (30) reported a much higher risk of dislocation (relative risk 6.3) in morbidly obese patients as compared with a group of normal-weight and overweight patients 12 to 28 months after revision THA. The mean age of their patients was 57 years, compared with 72 years in our study. All patients were operated upon by 1 experienced surgeon. The even higher relative risk for dislocation in obese patients in their study might be due to the low dislocation rate (3%) in their young, nonobese patients. In a previous study evaluating the effect of obesity on complications after primary THA, we observed a 4-times higher rate of infection similar to our current ﬁndings. The only difference is that in the present study, we included both superﬁcial and prosthetic infections (11). However, the increase in dislocation due to obesity was less important after primary THA in that study than it was in this study (2 times versus 3 times higher). Our ﬁndings are also in accordance with several other studies reporting on increased postoperative complications in obese patients after primary THA (7,8,12,13). Two of these studies found higher rates of postoperative infections (8,12). Stickles et al (13) evaluated 1-year orthopedic complication rates according to 5 BMI categories (⬍25, 25–29, 30 –34, 35–39, and ⱖ40) using univariate analyses, and they found a signiﬁcant increase with rising BMI, similar to what we observed in our data. A few studies reported similar short-term (orthopedic) complication rates (14 –18), but their numbers of patients, and as a consequence their numbers of adverse events, were small. Literature about pain and function after revision THA is lacking. Lower functional results (on the HHS score) in obese patients undergoing revision THA have been reported in 2 studies at 3 and 5 years postoperative (32,33). In contrast to the present study, those analyses were unadjusted. Davis et al (48) analyzed predictors of pain and functional outcomes 2 years after revision THA using the Western Ontario and McMaster Universities Osteoarthritis Index, and they emphasized the importance of preoperative pain and function for the 2-year results. However, they did not include BMI among their predictors. Previous studies have reported that obesity was associated with greater pain and disability in patients with hip or knee osteoarthritis (49,50). However, we found similar preoperative Merle d’Aubigné scores (10.5 in nonobese versus 10.1 in obese patients) together with signiﬁcant differences in Charnley classiﬁcation grades between the 2 groups. Part of the explanation for this could be that the function domain, which we expect to mainly be related to disability, counts only for one-third of the total Merle d’Aubigné score. An additional subscore analysis of our data revealed that the difference of 0.4 points on the preoperative Merle d’Aubigné score between obese and nonobese patients was mostly due to lower function subscores in the obese group. With respect to the pain issue, we are unable to provide a clear reason why obese and nonobese patients did not differ at baseline in our study. This prospective, hospital-based study compared the occurrence of several main adverse events in addition to pain, functional outcome, and patient satisfaction 5 years postoperatively in obese and nonobese patients undergoing ﬁrst revision THA. To our knowledge, the followup period was longer than in any previous study. Analyses were performed for 2 and 4 BMI categories. We used incidence rates and Cox proportional hazards analysis to account for patient differences in length of followup and censoring, and to adjust for baseline differences (confounding) across BMI categories. Data collection and clinical followup were standardized, and the clinical assessment was performed by 2 independent surgeons in order to avoid observer bias. The study has several weaknesses. First, it was limited by the relatively small number of adverse events resulting in large conﬁdence intervals. For the same reason, we were unable to adjust for all potentially confounding factors. 744 Lübbeke et al However, adjustment for several confounders was made for the combined complications, and for the complications infection and dislocation alone we adjusted for the most important confounders. Second, obese and nonobese patients differed by several baseline characteristics, which could be due to differences in the adverse events following primary THA and/or differential selection at the time of indication for primary or revision arthroplasty. Because 2 different clinical scores evaluating pain, function, and mobility were used at baseline and at followup, we were unable to analyze score differences. No information on intraoperative bone quality was available, but reports have shown that obese subjects tend to have greater bone mineral density and a lower risk of hip fractures (51–53). In addition, the need for an acetabular ring indicating insufﬁcient acetabular bone stock was higher in the nonobese group, and severity of revision based on bone stock loss was not found to be signiﬁcantly related to pain and function in the study by Davis et al. Finally, our study was conducted at 1 large academic center; however, baseline characteristics and indications for revisions did not substantially differ from descriptions of other hospital- or community-based revision cohorts in the literature (30,54 –56). Further studies including a larger number of patients are needed to assess external validity and to evaluate the extent to which different techniques and implants can inﬂuence the results. Revision THA is a technically-challenging intervention, particularly in obese patients, probably because of more difﬁcult anatomical conditions. Our results revealed that obesity was associated with higher event rates; notably, surgical site infection and dislocation. Furthermore, we found moderately lower HHS with higher levels of pain 5 years postoperative. Surgeons, patients, and referring physicians should be aware of an increased risk of adverse events in this patient group. Further studies are necessary to evaluate whether changes in medical preparation, surgical technique, and implant choice can help reduce the adverse event rate in obese patients undergoing revision THA. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. ACKNOWLEDGMENT 16. The authors would like to thank Richard Stern, MD for his helpful comments. 17. AUTHOR CONTRIBUTIONS 18. Dr. Lübbeke had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Study design. Lübbeke, Moons, Hoffmeyer. Acquisition of data. Lübbeke, Garavaglia. Analysis and interpretation of data. Lübbeke, Moons. Manuscript preparation. Lübbeke, Moons. Statistical analysis. Lübbeke, Moons. 19. 20. 21. REFERENCES 1. Felson DT. An update on the pathogenesis and epidemiology of osteoarthritis. Radiol Clin North Am 2004;42:1–9. 2. Flugsrud GB, Nordsletten L, Espehaug B, Havelin LI, Engeland A, Meyer HE. The impact of body mass index on later 22. 23. total hip arthroplasty for primary osteoarthritis: a cohort study in 1.2 million persons. Arthritis Rheum 2006;54:802–7. Karlson EW, Mandl LA, Aweh GN, Sangha O, Liang MH, Grodstein F. Total hip replacement due to osteoarthritis: the importance of age, obesity, and other modiﬁable risk factors. Am J Med 2003;114:93– 8. Lievense AM, Bierma-Zeinstra SM, Verhagen AP, van Baar ME, Verhaar JA, Koes BW. Inﬂuence of obesity on the development of osteoarthritis of the hip: a systematic review. Rheumatology (Oxford) 2002;41:1155– 62. Oliveria SA, Felson DT, Cirillo PA, Reed JI, Walker AM. Body weight, body mass index, and incident symptomatic osteoarthritis of the hand, hip, and knee. Epidemiology 1999;10: 161– 6. Wendelboe AM, Hegmann KT, Biggs JJ, Cox CM, Portmann AJ, Gildea JH, et al. Relationships between body mass indices and surgical replacements of knee and hip joints. Am J Prev Med 2003;25:290 –5. Jain NB, Guller U, Pietrobon R, Bond TK, Higgins LD. Comorbidities increase complication rates in patients having arthroplasty. Clin Orthop Relat Res 2005;435:232– 8. Namba RS, Paxton L, Fithian DC, Stone ML. Obesity and perioperative morbidity in total hip and total knee arthroplasty patients. J Arthroplasty 2005;20:46 –50. Sadr Azodi O, Bellocco R, Eriksson K, Adami J. The impact of tobacco use and body mass index on the length of stay in hospital and the risk of postoperative complications among patients undergoing total hip replacement. J Bone Joint Surg Br 2006;88:1316 –20. Eveillard M, Mertl P, Canarelli B, Lavenne J, Fave MH, Eb F, et al. Risk of deep infection in ﬁrst-intention total hip replacement: evaluation concerning a continuous series of 790 cases. Presse Med 2001;30:1868 –75. In French. Lubbeke A, Stern R, Garavaglia G, Zurcher L, Hoffmeyer P. Differences in outcomes of obese women and men undergoing primary total hip arthroplasty. Arthritis Rheum 2007;57:327– 34. Ridgeway S, Wilson J, Charlet A, Kafatos G, Pearson A, Coello R. Infection of the surgical site after arthroplasty of the hip. J Bone Joint Surg Br 2005;87:844 –50. Stickles B, Phillips L, Brox WT, Owens B, Lanzer WL. Deﬁning the relationship between obesity and total joint arthroplasty. Obes Res 2001;9:219 –23. Ibrahim T, Hobson S, Beiri A, Esler CN. No inﬂuence of body mass index on early outcome following total hip arthroplasty. Int Orthop 2005;29:359 – 61. Lehman DE, Capello WN, Feinberg JR. Total hip arthroplasty without cement in obese patients: a minimum 2-year clinical and radiographic followup study. J Bone Joint Surg Am 1994; 76:854 – 62. McLaughlin JR, Lee KR. The outcome of total hip replacement in obese and nonobese patients at 10 to 18 years. J Bone Joint Surg Br 2006;88:1286 –92. Moran M, Walmsley P, Gray A, Brenkel IJ. Does body mass index affect the early outcome of primary total hip arthroplasty? J Arthroplasty 2005;20:866 –9. Soballe K, Christensen F, Luxhoj T. Hip replacement in obese patients. Acta Orthop Scand 1987;58:223–5. Espehaug B, Havelin LI, Engesaeter LB, Langeland N, Vollset SE. Patient-related risk factors for early revision of total hip replacements: a population register-based case– control study of 674 revised hips. Acta Orthop Scand 1997;68:207–15. McClung CD, Zahiri CA, Higa JK, Amstutz HC, Schmalzried TP. Relationship between body mass index and activity in hip or knee arthroplasty patients. J Orthop Res 2000;18:35–9. Munger P, Roder C, Ackermann-Liebrich U, Busato A. Patient-related risk factors leading to aseptic stem loosening in total hip arthroplasty: a case– control study of 5,035 patients. Acta Orthop 2006;77:567–74. Raut VV, Kay P, Siney PD, Wroblewski BM. Factors affecting socket ﬁxation after cemented revision. Int Orthop 1997;21: 83– 6. Surin VV, Sundholm K. Survival of patients and prostheses Effect of Obesity on Revision THA 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. after total hip arthroplasty. Clin Orthop Relat Res 1983;177: 148 –53. Chan CL, Villar RN. Obesity and quality of life after primary hip arthroplasty. J Bone Joint Surg Br 1996;78:78 – 81. Lie SA, Havelin LI, Furnes ON, Engesaeter LB, Vollset SE. Failure rates for 4,762 revision total hip arthroplasties in the Norwegian Arthroplasty Register. J Bone Joint Surg Br 2004; 86:504 –9. Mahomed N, Katz JN. Revision total hip arthroplasty: indications and outcomes [review]. Arthritis Rheum 1996;39:1939 – 50. Mahomed NN, Barrett JA, Katz JN, Phillips CB, Losina E, Lew RA, et al. Rates and outcomes of primary and revision total hip replacement in the United States Medicare population. J Bone Joint Surg Am 2003;85A:27–32. Pellicci PM, Wilson PD Jr, Sledge CB, Salvati EA, Ranawat CS, Poss R, et al. Long-term results of revision total hip replacement: a followup report. J Bone Joint Surg Am 1985; 67:513– 6. Saleh KJ, Celebrezze M, Kassim R, Dykes DC, Gioe TJ, Callaghan JJ, et al. Functional outcome after revision hip arthroplasty: a meta-analysis. Clin Orthop Relat Res 2003;416: 254 – 64. Kim Y, Morshed S, Joseph T, Bozic K, Ries MD. Clinical impact of obesity on stability following revision total hip arthroplasty. Clin Orthop Relat Res 2006;453:142– 6. Perka C, Labs K, Muschik M, Buttgereit F. The inﬂuence of obesity on perioperative morbidity and mortality in revision total hip arthroplasty. Arch Orthop Trauma Surg 2000;120: 267–71. Katz JN, Phillips CB, Baron JA, Fossel AH, Mahomed NN, Barrett J, et al. Association of hospital and surgeon volume of total hip replacement with functional status and satisfaction 3 years following surgery. Arthritis Rheum 2003;48:560 – 8. Lubbeke A, Katz JN, Perneger TV, Hoffmeyer P. Primary and revision hip arthroplasty: 5-year outcomes and inﬂuence of age and comorbidity. J Rheumatol 2007;34:394 – 400. World Health Organization. Obesity: preventing and managing the global epidemic. Report of a WHO consultation. Geneva: WHO; 1997. Zimmerli W, Trampuz A, Ochsner PE. Prosthetic-joint infections. N Engl J Med 2004;351:1645–54. Harris WH. Traumatic arthritis of the hip after dislocation and acetabular fractures: treatment by mold arthroplasty. An endresult study using a new method of result evaluation. J Bone Joint Surg Am 1969;51:737–55. Mahomed NN, Arndt DC, McGrory BJ, Harris WH. The Harris hip score: comparison of patient self-report with surgeon assessment. J Arthroplasty 2001;16:575– 80. Soderman P, Malchau H. Is the Harris hip score system useful to study the outcome of total hip replacement? Clin Orthop Relat Res 2001;384:189 –97. McGrory BJ, Freiberg AA, Shinar AA, Harris WH. Correlation of measured range of hip motion following total hip arthroplasty and responses to a questionnaire. J Arthroplasty 1996; 11:565–71. McGrory BJ, Harris WH. Can the Western Ontario and Mc- 745 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. Master Universities (WOMAC) osteoarthritis index be used to evaluate different hip joints in the same patient? J Arthroplasty 1996;11:841– 4. Merle D’Aubigne R. Functional results of arthroplasty of the hip. Acta Orthop Belg 1953;19:81–103. Bryant MJ, Kernohan WG, Nixon JR, Mollan RA. A statistical analysis of hip scores. J Bone Joint Surg Br 1993;75:705–9. Ovre S, Sandvik L, Madsen JE, Roise O. Comparison of distribution, agreement and correlation between the original and modiﬁed Merle d’Aubigné-Postel Score and the Harris hip score after acetabular fracture treatment: moderate agreement, high ceiling effect and excellent correlation in 450 patients. Acta Orthop 2005;76:796 – 802. Charnley J. Numerical grading of clinical results. In: Low friction arthroplasty of the hip: theory and practice. Berlin: Springer-Verlag; 1979. p. 20 – 4. Alberton GM, High WA, Morrey BF. Dislocation after revision total hip arthroplasty: an analysis of risk factors and treatment options. J Bone Joint Surg Am 2002;84-A:1788 –92. Thomas EJ, Goldman L, Mangione CM, Marcantonio ER, Cook EF, Ludwig L, et al. Body mass index as a correlate of postoperative complications and resource utilization. Am J Med 1997;102:277– 83. Della Valle CJ. Total hip arthroplasty in obese patients. In: Lieberman JR, Berry DJ, editors. Advanced reconstruction: hip. Rosemont, IL: American Academy of Orthopedic Surgeons; 2006. Davis AM, Agnidis Z, Badley E, Kiss A, Waddell JP, Gross AE. Predictors of functional outcome 2 years following revision hip arthroplasty. J Bone Joint Surg Am 2006;88:685–91. Cimmino MA, Sarzi-Puttini P, Scarpa R, Caporali R, Parazzini F, Zaninelli A, et al. Clinical presentation of osteoarthritis in general practice: determinants of pain in Italian patients in the AMICA study. Semin Arthritis Rheum 2005;35:17–23. Marks R. Obesity proﬁles with knee osteoarthritis: correlation with pain, disability, disease progression. Obesity (Silver Spring) 2007;15:1867–74. Felson DT, Zhang Y, Hannan MT, Anderson JJ. Effects of weight and body mass index on bone mineral density in men and women: the Framingham study. J Bone Miner Res 1993; 8:567–73. Gruen T. A simple assessment of bone quality prior to hip arthroplasty: cortical index revisited. Acta Orthop Belg 1997;63 Suppl 1:20 –7. Langlois JA, Mussolino ME, Visser M, Looker AC, Harris T, Madans J. Weight loss from maximum body weight among middle-aged and older white women and the risk of hip fracture: the NHANES I epidemiologic followup study. Osteoporos Int 2001;12:763– 8. Khatod M, Barber T, Paxton E, Namba R, Fithian D. An analysis of the risk of hip dislocation with a contemporary total joint registry. Clin Orthop Relat Res 2006;447:19 –23. Lachiewicz PF, Soileau ES. Changing indications for revision total hip arthroplasty. J Surg Orthop Adv 2005;14:82– 4. Malchau H, Herberts P, Ahnfelt L. Prognosis of total hip replacement in Sweden: followup of 92,675 operations performed 1978 –1990. Acta Orthop Scand 1993;64:497–506.