Morbidly Obese vs Nonobese Aseptic Revision Total Hip Arthroplasty: Surprisingly Similar Outcomes

    Morbidly Obese vs Non-Obese Aseptic Revision Total Hip Arthroplasty: Surprisingly Similar Outcomes Chad D. Watts MD, Matthew T. Houdek MD, Eric R. Wagner MD, David G. Lewallen MD, Tad M. Mabry MD PII: DOI: Reference:

S0883-5403(15)00790-1 doi: 10.1016/j.arth.2015.08.036 YARTH 54688

To appear in:

Journal of Arthroplasty

Received date: Revised date: Accepted date:

10 April 2015 9 August 2015 10 August 2015

Please cite this article as: Watts Chad D., Houdek Matthew T., Wagner Eric R., Lewallen David G., Mabry Tad M., Morbidly Obese vs Non-Obese Aseptic Revision Total Hip Arthroplasty: Surprisingly Similar Outcomes, Journal of Arthroplasty (2015), doi: 10.1016/j.arth.2015.08.036

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Morbidly Obese vs Non-Obese Aseptic Revision Total Hip Arthroplasty: Surprisingly Similar Outcomes [email protected]

Matthew T. Houdek, MD

[email protected]

Eric R. Wagner, MD

[email protected]

David G. Lewallen, MD

[email protected]

Tad M. Mabry, MD*

[email protected]

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Chad D. Watts, MD

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Department of Orthopedic Surgery, Mayo Clinic 200 First Street SW

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Rochester, MN 55905

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Phone: (507) 284-4051

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Fax: (507) 266-4234

The institution of all authors has received funding from Zimmer (Warsaw, IN, USA), Stryker (Mahwah, NJ, USA), DePuy (Warsaw, IN, USA), and Biomet (Warsaw, IN, USA). One or more of the authors consults for Zimmer (DGL). IRB #14-001561 *Corresponding author

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Morbidly Obese vs Non-Obese Aseptic Revision Total Hip Arthroplasty: Surprisingly Similar Outcomes

Abstract

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Background: Morbid obesity (body mass index [BMI] ≥ 40 kg/m2) has been associated with

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increased risk of complications following primary total hip arthroplasty (THA), but there is little data regarding the outcomes of aseptic revision THA in these patients. The aims of this study

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were to compare the outcomes between matched cohorts of morbidly obese and non-obese (BMI

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<30 kg/m2) patients undergoing first-time aseptic revision THA. Methods: We performed a retrospective matched cohort analysis of all morbidly obese patients

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who underwent a first-time aseptic revision THA at our institution with at least four years of

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clinical followup (n=123). These patients were matched 1:1 with a cohort of 123 non-obese patients using sex, age (±2 years), and date of revision surgery (±3 years). Implant and patient

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outcomes were obtained from our institution’s total joint registry and the medical record. Results: The overall incidence and risk of complication, reoperation, and re-revision were similar in each group, though the type of complications varied between groups. Morbidly obese patients were more likely to dislocate (OR 3.3, p=0.03), but were less likely to develop polyethylene wear (OR 0.1, p=0.04) and aseptic loosening (OR 0.3, p=0.03). Harris hip scores improved following surgery in both groups (p<0.001). Conclusions: We were surprised to find similar complications, failures, and clinical outcomes when comparing matched morbidly obese and non-obese patients undergoing aseptic revision

ACCEPTED MANUSCRIPT THA. Quality outcome measures such as hospital readmissions and short-term medical

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complications were not addressed by this study and could be the basis for future studies.

Level of Evidence: Level III, Prognostic Study

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Key Words: morbid obesity; revision hip arthroplasty; aseptic

ACCEPTED MANUSCRIPT Introduction Obesity has rapidly become a global epidemic which now affects over one-third of

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American adults and more than 500 million people worldwide [1, 2]. Obesity has been linked

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with the development of hip osteoarthritis and the need for total hip arthroplasty in younger patients [3-5]. This trend is particularly worrisome for the healthcare system because of the

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increased complications and need for revision associated with primary THA in these patients [6-

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11].

Although multiple studies have described the outcomes of primary THA in obese

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patients, there is limited data regarding the outcomes of aseptic revision THA in these patients [12]. The aims of this study were to compare the 1) complications, 2) survival free of

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reoperation or repeat revision, 3) risk factors for failure, and 4) clinical outcome scores between

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matched cohorts of morbidly obese (BMI ≥ 40 kg/m2) and non-obese (BMI <30 kg/m2) patients

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undergoing first-time aseptic revision THA.

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Patients and Methods

After obtaining approval from our Institutional Review Board, we conducted a singlecenter, retrospective, 1:1 matched cohort analysis. Our institutional total joint registry, which prospectively captures survival data and patient outcomes, was used to identify 4,223 index revision THAs performed for aseptic reasons over a 20-year period (1987-2007), including 165 in patients with morbid obesity and 2,771 in patients with BMI <30 kg/m2. Patients were excluded if there was any history of ipsilateral hip revision or periprosthetic infection (PJI). PJI, which was defined using the Musculoskeletal Infection Society criteria [13], was excluded in all hips prior to revision using serum inflammatory markers and aspiration when clinically

ACCEPTED MANUSCRIPT indicated. We then only considered patients with minimum of 5-year followup, which was available for 75% of patients with morbid obesity and 76% of patients with BMI < 30 kg/m2

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(p=0.83). All (n=123) knees meeting criteria in patients with morbid obesity were included and

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matched with a cohort of 123 patients with BMI <30 kg/m2 using sex, age (± 2 years), and date of revision THA (± 3 years). Authors were blinded to patient outcomes at the time of group

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matching.

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There were 123 patients in each group, with each group consisting of 75 (61.0%) females. The mean age was 59 (range, 25-86) years in the morbidly obese group and 59 (range,

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27-86) years in the non-obese group. There were more diabetics in the morbidly obese group (24% vs. 5%, p < 0.001), but similar numbers of rheumatoids (11% vs 11%, p=0.99) and

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smokers (11% vs 11%, p=0.99). The most common reason for revision was aseptic loosening in

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each group, and similar components were revised in each group (Table 1). Mean head size was 30 mm (range, 22-44 mm) in the morbidly obese group and 30 mm (range, 22-40 mm) in the

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non-obese group (Table 1). Mean follow-up was 8.4 years (range, 5-20 years) and 8.8 years

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(range, 5-20 years) for the morbidly obese and non-obese groups, respectively (p=0.34). All outcomes were analyzed using appropriate summary statistics, including 95% confidence intervals, where appropriate. Baseline covariates were assessed to evaluate homogeneity between groups and compared using chi-square tests or logistic regression (for categorical outcomes), or two-sample tests or Wilcoxon rank-sum tests (for outcomes measured on a continuous scale) as applicable. Kaplan-Meier estimates were used to assess survival and compared using log-rank tests. Risk analysis was performed using Cox multivariate analysis. All statistical tests were two-sided and the threshold for statistical significance was set at α = 0.05.

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Results

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Complications

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The proportion of patients who experienced at least one complication was similar in each group, but the type of complications varied between groups. In the morbidly obese group, 49

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(40%) patients sustained at least one complication, compared with 50 (41%) patients in the non-

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obese group (p=0.99). The most common complication in both groups was intraoperative or postoperative femur fracture (18% morbidly obese vs 23% non-obese, OR 0.74, p=0.43).

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Morbidly obese patients were more likely to sustain at least one dislocation postoperatively (12% vs 4%, OR 3.28, p=0.03), but were less likely to encounter polyethylene wear (0.8% vs 6.5%,

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OR 0.12, p=0.04) or aseptic loosening (3% vs 11%, OR 0.26, p=0.03). There were no major

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differences in the risk of PJI (p=0.21), heterotopic ossification (p=0.21), venous thromboembolism (p=0.99), hematoma (p=0.99), delayed wound healing (p=0.99), osteolysis

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(p=0.68), or nerve palsy (p=0.62) between groups (Table 2).

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Incidence and Survivorship

We found no difference in the incidence or survivorship free of reoperation or re-revision between groups. In the morbidly obese group, 15 (12%) patients required a reoperation, whereas 22 (18%) of non-obese patients underwent at least one reoperation (HR 1.5, p=0.27). Reasons for reoperation included PJI (n=5), aseptic loosening (n=5), periprosthetic femur fracture (n=4), instability (n=2), and wound complications (n=2) in the morbidly obese group, compared with aseptic loosening (n=13), periprosthetic femur fracture (n=6), instability (n=3), osteolysis (n=2), wound complications (n=2), and PJI (n=2) in the non-obese group. Likewise, a similar number of morbidly obese patients underwent re-revision compared with non-obese patients (10% vs

ACCEPTED MANUSCRIPT 13%, HR 1.4, p=0.37). Reasons for re-revision included aseptic loosening (n=5), instability (n=3), periprosthetic femur fracture (n=2), and PJI (n=1) in the morbidly obese group, compared

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with aseptic loosening (n=13), instability (n=2), and osteolysis (n=1) in the non-obese group.

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Patient survivals, free of reoperation and revision, were similar between groups at 5-, 10-, and 15-years (Fig. 1).

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Predictive Risk Factors

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Using multivariate analysis, we did not find morbid obesity, age ≥ 60 years, sex, diabetes, rheumatoid arthritis, or tobacco use to be predictive of complication, reoperation, or repeat

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revision (Table 3). Clinical Outcome Scores

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Harris hip scores were similar between groups prior to revision (50 ± 16 vs 53 ± 13,

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p=0.14). Patients in both groups improved significantly following surgery (p<0.001). Nonobese patients had significantly better scores than the morbidly obese group at two and five

Discussion

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years, but similar scores at ten and fifteen years (Table 4).

Given the rapidly expanding prevalence of obesity and the high rate of complications following primary THA in this patient population, a dramatic increase in the number of obese patients necessitating revision THA is anticipated [3-5]. Recognizing and understanding the risks and outcomes of these patients will be important considerations in management. Several studies outline the risks associated between obesity and primary THA [6-10], but little has been published regarding the outcomes of revision THA in obese patients. Houdek et al. previously reported on the outcomes of morbidly obese patients undergoing two-stage revision THA for

ACCEPTED MANUSCRIPT infection [14], and Pulos et al. recently published short-term complications in patients with BMI ≥ 35 kg/m2 undergoing revision THA for any reason (septic or aseptic) [12], but the outcomes of

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septic and aseptic revisions are not necessarily comparable [15-17]. Limited literature exists

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analyzing the outcomes following aseptic revision THA in obese patients. We found that morbidly obese patients (BMI ≥ 40 kg/m2) experienced similar complications, reoperations, and

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re-revisions when compared to a matched cohort of non-obese (BMI < 30 kg/m2) patients.

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In this study, the incidence of complication was roughly 40% in each group, which is compatible with previous studies reporting 30-75% complications following revision THA [18].

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Though our groups had similar rates of overall complication, we found that morbidly obese patients had an increased risk of dislocation. While obesity has previously been linked with hip

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instability [9, 10, 19-22] and infection [12, 19, 20] these findings are not universal [23-25].

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Interestingly, our study showed that morbidly obese patients actually had a lower risk of aseptic loosening and polyethylene wear. In the only other review of revision THA in obese

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patients, Pulos et al. did not find any difference in the rate of loosening or polyethylene wear,

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possibly due to relatively short follow-up time (mean of 36 months) [12]. We propose that these findings may be related to varying levels of activity between morbidly obese and non-obese groups.

In addition to similar complication rates, we found that non-obese patients were just as likely to require reoperation and re-revision as the morbidly obese patients. Our respective implant survival rates at ten and twenty years were 87% and 62% in the morbidly obese patients, compared with 88% and 45% in the non-obese patients. While there is no data for direct comparison regarding aseptic revision THA in obese patients, these implant survival rates are

ACCEPTED MANUSCRIPT strikingly better than those reported for morbidly obese patients following two-stage revision THA for infection (ten year survival of 56%) [14].

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Although revision total hip arthroplasty is effective in restoring function and decreasing

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pain in patients with failed total hip arthroplasty [26-28], obesity has been associated with lower clinical outcome scores when compared to non-obese patients [21]. In our study, patients in both

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groups experienced improvement in symptoms postoperatively, with no difference in scores at

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ten and fifteen years, which demonstrates that morbidly obese patients do benefit from surgery. This study is not without limitations worthy of consideration. Foremost, although our

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data was prospectively collected, the data was examined retrospectively. Because of this, it is possible that important differences existed between the morbidly obese and non-obese groups.

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We identified more diabetics in the morbidly obese group, and were able to control for this

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difference with multivariate risk analysis, but there are likely other comorbidities that are inherently different between groups, which were not directly accounted for in this study.

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Furthermore, our study was performed at a single institution by multiple different surgeons,

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without standardized reconstruction methods or techniques. Additional factors such as medical complications, implant costs, and hospital readmissions may also be different for the morbidly obese population, but these factors require a much larger study population and were not directly addressed by our study. In conclusion, while caring for patients with morbid obesity and hip arthritis remains challenging, we were surprised to find similar complications, failures, and clinical outcomes when comparing matched morbidly obese and non-obese patients following aseptic revision THA. Though we are in favor of educating and optimizing the morbidly obese patients prior to surgery, these findings argue that operative intervention should not be withheld on the basis of

ACCEPTED MANUSCRIPT morbid obesity, especially in the setting of a failed THA. These results should be interpreted with caution, however, as most of the existing literature regarding revision hip and knee

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arthroplasty in morbidly obese patients is much less favorable [12, 14, 29, 30]. Furthermore, our

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findings do not quantify outcomes such as hospital readmissions, urinary tract infections, deep venous thromboses, and other factors which affect quality reports, reimbursement, and

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potentially access to care. Such outcomes could be the basis for future studies.

ACCEPTED MANUSCRIPT Fig 1. Kaplan-Meier Estimates showed that morbidly obese and non-obese patients had similar survival free of complication, reoperation, and revision. A) Survival free of complication was 66% (58-75%) vs

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61% (53-70%) at five years, 56% (46-67%) vs 51% (40-61%) at ten years, and 52% (40-64%) vs 44% (31-

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57%) at fifteen years for the morbidly obese and non-obese groups, respectively (p=0.21). B) Survival free of reoperation was 95% (86-100%) vs 94% (90-98%) at five years, 84% (75-92%) vs 83% (74-91%) at

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ten years, and 80% (68-91%) at fifteen years for the morbidly obese and non-obese groups, respectively

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(p=-.27). C) Survival free of repeat revision was 99% (98-100%) vs 100% at five years, 87% (78-96%) vs 88 (80-96%) at ten years, and 83% (71-94%) vs 68% (53-83%) at fifteen years for the morbidly obese and

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non-obese groups, respectively (p=0.29).

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Joint Surg Am. 2012 May 2;94(9):794-800. 7. Friedman RJ, Hess S, Berkowitz SD, Homering M. Complication rates after hip or knee arthroplasty in morbidly obese patients. Clin Orthop Relat Res. 2013 Oct;471(10):3358-66. 8. Haverkamp D, Klinkenbijl MN, Somford MP, Albers GH, van der Vis HM. Obesity in total hip arthroplasty--does it really matter? A meta-analysis. Acta Orthop. 2011 Aug;82(4):417-22. 9. Jamsen E, Nevalainen P, Eskelinen A, Huotari K, Kalliovalkama J, Moilanen T. Obesity, diabetes, and preoperative hyperglycemia as predictors of periprosthetic joint infection: a single-center analysis of 7181 primary hip and knee replacements for osteoarthritis. J Bone Joint Surg Am. 2012 Jul 18;94(14):e101.

ACCEPTED MANUSCRIPT 10. Ong KL, Kurtz SM, Lau E, Bozic KJ, Berry DJ, Parvizi J. Prosthetic joint infection risk after total hip arthroplasty in the Medicare population. J Arthroplasty. 2009 Sep;24(6 Suppl):105-9.

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11. Vasarhelyi EM, MacDonald SJ. The influence of obesity on total joint arthroplasty. J Bone Joint Surg

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13. Parvizi J, Zmistowski B, Berbari EF, Bauer TW, Springer BD, Della Valle CJ, et al. New definition for periprosthetic joint infection: from the Workgroup of the Musculoskeletal Infection Society. Clinical

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14. Houdek MT, Wagner ER, Watts CD, Osmon DR, Hanssen AD, Lewallen DG, Mabry TM. Morbid

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obesity: a significant risk factor for failure of two-stage revision total hip arthroplasty for infection. The Journal of bone and joint surgery American volume. 2015 Feb 18;97(4):326-32.

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15. Assmann G, Kasch R, Maher CG, Hofer A, Barz T, Merk H, et al. Comparison of health care costs

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between aseptic and two stage septic hip revision. J Arthroplasty. 2014 Oct;29(10):1925-31. 16. Choi HR, Beecher B, Bedair H. Mortality after septic versus aseptic revision total hip arthroplasty: a

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matched-cohort study. J Arthroplasty. 2013 Sep;28(8 Suppl):56-8. 17. Romano CL, Romano D, Logoluso N, Meani E. Septic versus aseptic hip revision: how different? J Orthop Traumatol. 2010 Sep;11(3):167-74. 18. Thomasson E, Guingand O, Terracher R, Mazel C. Perioperative complications in revision hip surgery. Ortop Traumatol Rehabil. 2001 Jan-Mar;3(1):38-40. 19. Chee YH, Teoh KH, Sabnis BM, Ballantyne JA, Brenkel IJ. Total hip replacement in morbidly obese patients with osteoarthritis: results of a prospectively matched study. J Bone Joint Surg Br. 2010 Aug;92(8):1066-71.

ACCEPTED MANUSCRIPT 20. 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 Dec;453:142-6.

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21. Lubbeke A, Moons KG, Garavaglia G, Hoffmeyer P. Outcomes of obese and nonobese patients

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undergoing revision total hip arthroplasty. Arthritis Rheum. 2008 May 15;59(5):738-45. 22. Elson LC, Barr CJ, Chandran SE, Hansen VJ, Malchau H, Kwon YM. Are morbidly obese patients

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undergoing total hip arthroplasty at an increased risk for component malpositioning? J Arthroplasty.

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2013 Sep;28(8 Suppl):41-4.

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Bone Joint Surg Br. 2008 Apr;90(4):424-9.

24. Lehman DE, Capello WN, Feinberg JR. Total hip arthroplasty without cement in obese patients. A

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minimum two-year clinical and radiographic follow-up study. J Bone Joint Surg Am. 1994 Jun;76(6):85462.

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25. McLaughlin JR, Lee KR. The outcome of total hip replacement in obese and non-obese patients at

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10- to 18-years. J Bone Joint Surg Br. 2006 Oct;88(10):1286-92. 26. Adelani MA, Crook K, Barrack RL, Maloney WJ, Clohisy JC. What is the prognosis of revision total hip

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arthroplasty in patients 55 years and younger? Clin Orthop Relat Res. 2014 May;472(5):1518-25. 27. Mahomed NN, Barrett JA, Katz JN, Phillips CB, Losina E, Lew RA, Guadagnoli E, Harris WH, Poss R, Baron JA. Rates and outcomes of primary and revision total hip replacement in the United States medicare population. J Bone Joint Surg Am. 2003 Jan;85-A(1):27-32. 28. Saleh KJ, Celebrezze M, Kassim R, Dykes DC, Gioe TJ, Callaghan JJ, Salvati EA. Functional outcome after revision hip arthroplasty: a metaanalysis. Clin Orthop Relat Res. 2003 Nov(416):254-64. 29. Watts CD, Wagner ER, Houdek MT, Lewallen DG, Mabry TM. Morbid obesity: increased risk of failure after aseptic revision TKA. Clin Orthop Relat Res (in press).

ACCEPTED MANUSCRIPT 30. Watts CD, Wagner ER, Houdek MT, Osmon DR, Hanssen AD, Lewallen DG, Mabry TM. Morbid obesity: a significant risk factor for failure of two-stage revision total knee arthroplasty for infection. The

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Journal of bone and joint surgery American volume. 2014 Sep 17;96(18):e154.

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Figure 1

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Morbidly Obese

Non-Obese

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Patients

75 (61%)

75 (61%)

0.99

Age (yrs.)

59 (25-86)

59 (27-86)

0.85

BMI (kg/m2)

44 (40-67)

25 (15-30)

<0.001

101 (50-245)

106 (55-244)

0.34

14 (11%)

14 (11%)

0.99

14 (11%)

13 (11%)

0.99

30 (24%)

6 (5%)

<0.001

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Gender: Females

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Follow up (mos)

Current Smoker

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Diabetes Mellitus

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Rheumatoid

Reason for Revision

0.77 78 (63%)

73 (59%)

Osteolysis

32 (26%)

37 (30%)

Instability

13 (11%)

13 (11%)

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Aseptic loosening

Components Revised

0.94

Liner

12 (10%)

12 (10%)

Femur

49 (40%)

48 (39%)

Cup

35 (29%)

39 (32%)

Femur and cup

27 (22%)

24 (20%)

Head Size <28 mm

P-value

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Variable

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Table 1: Comparison of Patient Characteristics Between Groups

0.98 11 (9%)

11 (9%)

ACCEPTED MANUSCRIPT 97 (79%)

98 (80%)

>32 mm

15 (12%)

14 (11%)

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28-32 mm

ACCEPTED MANUSCRIPT Table 2: Comparison of Complications Between Groups Non-Obese

Odds Ratio (95% CI)

P-value

Infection

5 (4.1%)

1 (0.8%)

5.17 (0.60-44.91)

0.213

Fracture

22 (17.9%)

28 (22.8%)

0.74 (0.40-1.38)

0.428

Dislocation

15 (12.2%)

5 (4.1%)

3.28 (1.15-9.32)

0.033

Heterotopic ossification

5 (4.1%)

1 (0.8%)

5.17 (0.60-44.91)

0.213

Polyethylene wear

1 (0.8%)

8 (6.5%)

0.12 (0.02-0.98)

0.036

Venous thromboembolism

3 (2.4%)

3 (2.4%)

1.00 (0.20-5.05)

0.999

Aseptic loosening

4 (3.3%)

14 (11.4%)

0.26 (0.08-0.82)

0.025

Hematoma

2 (1.6%)

1 (0.8%)

2.02 (0.18-22.53)

0.999

Delayed wound healing

6 (4.9%)

5 (4.1%)

1.21 (0.36-4.08)

0.999

Osteolysis

2 (1.6%)

4 (3.3%)

0.49 (0.09-2.74)

0.684

Nerve palsy

3 (2.4%)

1 (0.8%)

3.05 (0.31-29.73)

0.622

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Morbidly Obese

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Complication

ACCEPTED MANUSCRIPT Table 3: Cox Multivariate Analysis of Risk Factors Complication

Reoperation

Re-Revision

0.94 (0.6-1.4)

1.47 (0.7-3.0)

1.44 (0.7-3.4)

p=0.74

p=0.27

p=0.37

1.19 (0.8-1.8)

1.05 (0.5-2.1)

0.91 (0.5-2.6)

p=0.38

p=0.88

p=0.82

1.57 (0.8-3.1)

2.20 (0.9-4.9)

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Morbid Obesity

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Age ≥60 years

p=0.70

p=0.20

p=0.06

1.12 (0.3-3.1)

0.39 (0.02-2.0)

p=0.08

p=0.84

p=0.30

0.73 (0.4-1.3)

2.34 (0.9-5.1)

1.80 (0.5-4.9)

p=0.33

p=0.07

p=0.32

0.87 (0.4-1.6)

0.35 (0.01-1.2)

0.39 (0.02-1.9)

p=0.35

p=0.28

1.58 (0.9-2.5)

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Diabetic

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Rheumatoid

Smoker

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1.08 (0.7-1.6) Male

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Variable

p=0.67

ACCEPTED MANUSCRIPT Table 4: Clinical Outcome Data Non-Obese

Preoperative

49.6 (±16.3)

52.5 (±13.0)

2 year follow-up

77.0 (±15.2)

83.9 (±18.9)

0.017

5 year follow-up

72.5 (±18.3)

78.8 (±21.7)

0.027

10 year follow-up

70.6 (±18.3)

15 year follow-up

72.7 (±15.9)

RI P

SC

NU

ED PT CE AC

T

Morbidly Obese

MA

Harris Hip Score

P-value 0.138

76.7 (±24.0)

0.150

76.1 (±16.8)

0.767