Surgery for Obesity and Related Diseases 10 (2014) 335–339

Integrated health article

Total weight loss associated with increased physical activity after bariatric surgery may increase the need for total joint arthroplasty David Trofa, B.A.a, Eric L. Smith, M.D.a,*, Vivek Shah, M.D.a, Scott Shikora, M.D.b a Department of Orthopaedics, Boston, Massachusetts Brigham and Women’s Hospital, Boston, Massachusetts Received September 15, 2013; accepted September 19, 2013 b

Abstract

Background: Retrospectively, our institution noticed an increased number of patients undergoing total joint arthroplasty (TJA) after bariatric surgery. Considering that bariatric surgery is a proven modality to reduce osteoarthritic pain, we sought to identify a reason some patients may later require TJA. The objective of this study was to investigate the hypothesis that rapid or increased weight loss after bariatric surgery may be a risk factor for TJA. Methods: Weight loss parameters were retrospectively assessed in 15 bariatric surgery patients who subsequently received a primary TJA and compared with matched bariatric controls. Results: Patients who required a TJA lost 27.9% more of their body mass index (BMI) compared with controls (P ¼ .049). Furthermore, patients who underwent TJA 25–48 months postbariatric surgery lost 78.2% more of their BMI compared with controls (P o .001). Total knee arthroplasty patients lost 43.9% more of their BMI compared with controls (P ¼ .02), and the difference in BMI change for total hip arthroplasty patients was not significant versus controls. Conclusion: These results contradict the tenant that weight loss is universally protective against arthritis and merit larger prospective investigations. (Surg Obes Relat Dis 2014;10:335-339.) r 2014 American Society for Metabolic and Bariatric Surgery. All rights reserved.

Keywords:

Rapid weight loss; Bariatric surgery; Total knee arthroplasty; Total hip arthroplasty

Obesity, defined as body mass index (BMI) Z30 kg/m2, is a well-documented independent risk factor for the development and progression of hip and knee osteoarthritis [1–5]. In fact, various population studies have shown a direct correlation between the increased incidence of obesity in the United States and knee osteoarthritis [6]. As such, obesity is also a risk factor for total joint arthroplasty (TJA). One large scale study using data from 54,406 total hip and knee patients’ reports that the risk for total knee arthroplasty (TKA) and total hip arthroplasty (THA) is 3.2 and 1.92, respectively, times higher in patients with a BMI of 30–34.9 kg/m2 compared with individuals with a BMI of 25 kg/m2 and less [3]. The risk of TKA and THA is 32.73 and 8.56 higher, respectively, in patients with * Correspondence: Eric Smith, M.D., Department of Orthopaedics, 800 Washington Street, Tufts Medical Center #306, Boston, MA 02111. E-mail: [email protected]

BMI 440 kg/m2. In addition, obese patients require THA at significantly younger ages compared with nonobese patients [7]. Because obesity has proven to be a significant risk factor for knee and hip arthritis, numerous investigations have assessed the outcomes and complications of TJA in this patient population. Interestingly, the literature presents conflicting results. For instance, some studies have found higher rates of complications, such as deep vein thrombosis, superficial wound complications, joint infection, and early prosthetic failure, with TJA in obese patients, suggesting that orthopaedic surgeons may be discouraged from operating on such patients until adequate weight loss is achieved [8–12]. However, other analyses have been unable to associate an increased incidence of prosthetic failure or complication rate due to obesity [7,13–18] and conclude that the advantages of improved functionality and quality of life may outweigh the associated risks of TJA [19].

1550-7289/14/$ – see front matter r 2014 American Society for Metabolic and Bariatric Surgery. All rights reserved. http://dx.doi.org/10.1016/j.soard.2013.09.011

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D. Trofa et al. / Surgery for Obesity and Related Diseases 10 (2014) 335–339

Because some orthopaedic surgeons may not operate on morbidly obese patients, weight reduction surgery has been recommended to assist patients in decreasing their BMI before TJA. In 2008, 4220,000 bariatric surgery operations were performed in the United States. Currently, the laparoscopic Roux-en-Y gastric bypass is the most commonly performed surgery and is considered the gold standard bariatric operation [20]; however, laparoscopic adjustable gastric banding and sleeve gastrectomy are accepted procedures performed regularly worldwide. Although weight loss after bariatric surgery is highly variable between patients, most procedures have an expected excess weight loss (EWL) Z50% [21]. A previous small retrospective case series found that TJA in 14 patients who had previous bariatric surgery had an excellent outcome [22]. The investigators noted that 7 of the patients were already planning a TJA at the time of bariatric surgery, but they did not examine what risk factors predisposed the other patients to later require a TJA. The purpose of our study was to examine weight loss associated with bariatric surgery as a possible risk factor for developing end stage osteoarthritis. To accomplish this goal we compared weight loss in patients treated surgically for obesity that subsequently needed a TJA with matched bariatric controls who did not require a TJA. Methods After approval from the Institutional Review Board, the 2007–2009 total joint database at a single medical center was cross-referenced with the 2000–2009 database of bariatric surgery patients at the same institution. The total

joint database consisted of 525 patients, and the bariatric database consisted of 5,000 patients. Patients who had been treated surgically for obesity and later had a primary TJA were identified. We obtained the following data on the patients: age, sex, BMI before bariatric surgery, BMI before primary arthroplasty, type of arthroplasty, type of bariatric surgery, and length of time between surgeries (Table 1). Only patients with a preexisting diagnosis of arthritis at the time of bariatric surgery were included in the study. Patients who did not lose at least 10% of their original BMI between surgeries were excluded from the study. Fifteen patients matched our selection criteria. To identify a time period postbariatric surgery when patients may be most at risk for symptomatic osteoarthritic pain, we subdivided our cohort into 3 groups based on the length of time between gastric bypass and primary TJA. Patients in groups 1, 2, and 3 had TJA 0–24 months, 25–48 months, and Z49 months after bariatric surgery, respectively. Patients were also analyzed based on the type of arthroplasty, hip or knee, performed. Control gastric bypass patients were matched to our cohort by sex, age (⫾2 years), and diagnosis of arthritis at the time of their bariatric surgery. Among the available controls for each TJA patient, the 3 with the longest length of follow-up were selected to ensure a follow-up period equal to the time between bariatric surgery and TJA of the patients. Two controls did not lose 10% of their original BMI and were eliminated from the study. Thirty-7 controls matched our selection criteria. In the bariatric surgery literature there are numerous ways to report and compare weight loss outcomes postbariatric surgery. These include changes in BMI [23], percentage of

Table 1 Patient characteristics Patient

Age (years)/ gender

Type of arthroplasty

Type of bariatric surgery

BMI at bypass (kg/m2)

BMI at TJA (kg/m2)

Decrease in BMI (kg/m2)

Time between surgeries (mo)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 AVG

32/F 50/M 56/M 59/F 51/F 39/F 45/F 47/F 59/F 58/F 53/F 31/F 54/F 44/F 49/F 48.4

L TKA R TKA, R TKA, R TKA R TKA L TKA R TKA, R TKA R TKA, L THA R THA, R THA R THA L THA R THA, –

Roux-en-Y Roux-en-Y Roux-en-Y Lap Band Roux-en-Y Roux-en-Y Roux-en-Y Roux-en-Y Roux-en-Y Roux-en-Y Roux-en-Y Roux-en-Y Roux-en-Y Roux-en-Y Roux-en-Y –

57.8 60.7 51.0 44.5 53.3 66.0 61.7 39.8 46.8 39.2 48.0 57.7 40.0 54.9 56.8 51.9

22.4 43.0 36.3 24.7 26.3 30.2 40.0 31.6 35.8 22.7 35.9 41.6 33.3 37.2 35.0 33.1

35.4 17.7 14.7 19.8 27.0 35.8 21.7 8.2 11.0 16.5 12.1 16.1 6.7 17.7 21.8 18.8

92 108 17 37 36 31 43 79 11 92 19 27 4 7 33 42.4

L TKA L TKA

L TKA L TKA L THA

L THA

(61.3%) (29.2%) (28.8%) (44.5%) (50.7%) (54.2%) (35.2%) (20.6%) (23.4%) (42.1%) (25.3%) (27.9%) (16.9%) (32.2%) (38.4%) (35.4%)

AVG ¼ average; BMI ¼ body mass index; F ¼ female; L ¼ left; M ¼ male; R ¼ right; THA ¼ total hip arthroplasty; TJA ¼ total joint arthroplasty; TKA ¼ total knee arthroplasty.

Rapid Weight Loss Associated with Joint Arthroplasty / Surgery for Obesity and Related Diseases 10 (2014) 335–339

total weight loss, percentage of excess weight loss (%EWL), and percentage of excess BMI loss (%EBMIL): %EWL ¼ ðpreoperative weight–current weightÞ= ðpreoperative weight–ideal weightÞ  100

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Diego, CA). Statistical significance was determined using Student’s two-tailed t test, and significance was set at P r .05. Results

%EBMIL ¼ ðpreoperative BMI–current BMIÞ= ðpreoperative BMI–25Þ  100

Patient characteristics (Table 1)

The utility of %EWL has been challenged, because its calculation is based on an ideal weight from an outdated weight table [24–26]. Similarly, the equation for %EBMIL assumes that the ideal outcome for any bariatric operation is a BMI of 25 kg/m2. This is an incredibly challenging target for bariatric patients with high initial BMIs, particularly those who are super-obese (defined as BMI 450 kg/m2) [27]. In an attempt to create a measurement that would allow for a more accurate outcome comparison between bariatric patients, Baltasar et al. analyzed the initial and final BMIs of 7,410 patients 3 years postbariatric surgery and created a formula to calculate %EBMIL using a patient’s predicted BMI (PBMI) instead of a BMI of 25 kg/m2. The PBMI was intended to represent a realistic outcome based on preoperative BMI and the type of bariatric operation performed: %EBMIL ¼ ðpreoperative BMI–current BMIÞ= ðpreoperative BMI–PBMIÞ  100 *PBMI for gastric bypass: ðpreoperative BMI  :43Þ þ10:23 *PBMI for gastric banding: ðpreoperative BMI  :43Þ þ 16:97 ½27 In our study, BMI values for each patient and control were graphed over time and compared. Changes in control BMIs were calculated for the length of time equal to the time between patient surgeries. The rate of BMI change over time was assessed using a linear regression analysis to create a best-fit line for each patient and control BMI curve. %EBMIL also was calculated using the standard method as well as with PBMI. Statistical analyses were performed using GraphPad Prism version 5.02 for Windows (GraphPad Software, San

Of the 15 patients identified, 13 were female and 2 were male, with an average age of 48.4 years. The average BMI at the time of bariatric surgery was 51.9 kg/m2, and the average length of time between bariatric surgery and primary TJA was 42.4 months. Only 1 patient had a laparoscopic gastric banding procedure; all other patients and controls underwent Roux-en-Y gastric bypass. There were 13 TKAs performed in 9 patients and 8 THAs performed in 6 patients. The rate of bilateral TJA operations in this cohort was 40%. Weight loss comparisons (Table 2) The average patient BMI at the time of TJA was 33.1 kg/ m2, which represents an 18.8 kg/m2 (35.4%) decrease in BMI from the time of bariatric surgery. Matched gastric bypass controls lost an average 14.7 kg/m2 (29.7%) of their BMI in an identical time period, from an initial BMI of 49.4 kg/m2 to 34.7 kg/m2. Thus, compared with controls, patients who underwent a primary TJA lost 27.9% (P ¼ .049) more of their original BMI. The average patient bestfit slope showed a rate of change of –0.70 kg/m2/mo compared with –0.62 kg/m2/mo for controls (P ¼ .68). When calculating %EBMIL using BMI of 25 kg/m2 as an outcome goal, the average excess BMI loss in patients was 70.2% compared with 63.3% of controls (P ¼ .32). The % EBMIL using PBMI was 102.7% compared with 83.5% of controls (P ¼ .07). Subgroup analysis based on the time between surgeries showed significant changes in BMI for group 2, but not groups 1 or 3. Patients of group 2 lost 23.7 kg/m2 (41.8%) of their initial BMI compared with 13.3 kg/m2 (28.6%) of controls (P o .001). Thus, patients in group 2 lost 78.2% more of their BMI versus controls at a significantly elevated rate, –0.60 kg/m2/mo versus –0.28 kg/m2/mo (P o .001).

Table 2 Weight loss comparisons Group

1 2 3 TKA THA All

Decrease in BMI (kg/m2)

Rate of BMI loss (kg/m2/mo)

%EBMIL using BMI 25 kg/m2

%EBMIL using PBMI

Patients

Controls

P value

Patients

Controls

P value

Patients

Controls

P value

Patients

Controls

P value

12.5 23.7 19.5 21.3 15.2 18.8

14.7 13.3 17.5 14.8 14.6 14.7

0.47 o 0.001* 0.69 0.02* 0.86 0.049*

–1.29 –0.60 –0.10 –0.52 –0.97 –0.70

–1.33 –0.28 –0.07 –0.34 –1.04 –0.62

0.92 o 0.001* 0.72 0.25 0.86 0.68

52.7 % 76.9% 82.3% 73.7% 65.1% 70.3%

58.1% 64.8% 68.5% 62.8% 64.1% 63.3%

0.65 0.19 0.42 0.19 0.94 0.32

70.6% 126.1% 107.6% 114.0% 85.7% 102.7%

78.0% 83.4% 92.0% 83.3% 83.8% 83.5%

0.62 0.02* 0.47 0.03* 0.90 0.07

BMI ¼ body mass index; mo ¼ month; PBMI ¼ predicted body mass index; TKA ¼ total knee arthroplasty; THA ¼ total hip arthroplasty; %EBMIL ¼ percentage of excess body mass index. * P r .05.

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The %EBMIL calculated using PBMI for group 2 was 126.1% compared with 83.4% for controls (P ¼ .02). No difference was identified in %EBMIL calculated using an ideal goal BMI of 25 kg/m2. The change in BMI for THA patients was similar to controls, 15.2 kg/m2 versus 14.6 kg/m2 (P ¼ .86). On the other hand, TKA patients lost 43.9% more BMI compared with controls (P ¼ .02), but not at a significantly elevated rate (P ¼ .25). The %EBMIL of TKA patients calculated with using PBMI was 114.0% compared with 83.3% of controls (P ¼ .03), but no difference was identified when calculated using the ideal BMI of 25 kg/m2. Discussion The obesity epidemic is an ever-increasing concern, particularly because high BMI can have deleterious effects on morbidity and mortality. Individuals who are obese have higher incidences of coronary artery disease, hypertension, hyperlipidemia, cholelithiasis, cancer, and diabetes [28]. Previous investigations have shown that weight loss is protective against osteoarthritis. For instance, in a study of 3617 women over an average follow-up of 7.28 years obese women were found to have an increased risk of arthritis; however, obese women who lost 410% of their weight were at no increased risk of developing arthritis compared with women with BMIs between 19–21 kg/m2 [29]. Similarly, the protective effects of weight loss were illustrated by the Framingham Study, which showed that a decrease in BMI of 2 units or more over 10 years decreased the odds for developing osteoarthritis by 450% [30]. Despite these results, the amount and rate of weight loss described by these studies is much lower than what is expected after bariatric procedures. In the current work, rapid weight loss was assessed as a possible risk factor and contributor to the progression of symptomatic osteoarthritis leading to TJA. Because all patients included in this study were diagnosed with osteoarthritis before their bariatric procedure, we are not proposing that rapid weight loss is causative to joint degeneration; however, we believe that it may play a significant role in the progression of osteoarthritis in this patient population. Our key finding is that bariatric patients who required a TJA lost significantly more of their BMI compared with their counterparts who did not receive a new hip or knee. Considering these data, we believe that some bariatric patients who, after losing weight due to the restrictive and malabsorptive effects of their surgery, subsequently engage in a more active lifestyle, placing additional stress on joints already damaged from chronic obesity. This hypothesis is supported by the recent work of Edwards et al. which examined the Western Ontario and McMaster Universities Index of Osteoarthritis and Knee Osteoarthritis Outcomes Score of 24 patients postbariatric surgery [6]. All variables examined were significantly improved at 6 and 12 months

after bariatric surgery, including physical function and active participation in sports. Although increased activity and weight loss should be encouraged in patients to help protect against co-morbid conditions such as high cholesterol, diabetes, hypertension, and cardiovascular disease, the long-term effects of increased exercise levels on bariatric patients’ joints are unknown. The present study identified a 25–48-month timeframe during which postbariatric surgery patients are most likely to have lost a substantial amount of their BMI at an elevated rate; this may represent a period when bariatric patients should avoid high impact activities to reduce the risk of a future TJA. The limitations of this study relate to the weaknesses of retrospective investigations as well as the lack of standardization for reporting weight loss outcomes. Furthermore, we were limited by the small patient population studied, despite the hundreds of thousands of bariatric surgeries and total joint arthroplasty surgeries performed per year. Despite this, we were able to use simple, reproducible outcome measurements that have been used in previous investigations to detect a difference in weight loss between our study groups. To our knowledge, this is the first report to consider the rapid weight loss associated with bariatric surgery as a possible risk factor for the progression of osteoarthritis requiring arthroplasty. As such, the findings of this study would be enhanced by a prospective investigation of a large group of gastric bypass patients with consistent follow-ups to document changes in BMI, nutritional status, and activity level to elucidate risk factors that may lead to the development of symptomatic end stage osteoarthritis. Disclosures Scott Shikora discloses commercial interests including salary received as Editor-in-Chief of Obesity Surgery Journal, stock options received from GI Gynamics, and honoraria received from Baxter Healthcare Company and EnteroMedics. Eric L. Smith discloses commercial interests including consultancy fees received from Omni Life Science and Depuy and research support from Stryker Orthopaedics and Depuy. The other authors have no commercial associations that might be a conflict of interest in relation to this article. References [1] Gandhi R, Razak F, Mahomed NN. Ethnic differences in the relationship between obesity and joint pain and function in a joint arthroplasty population. J Rheumatol 2008;35:1874–7. [2] Hochberg MC, Lethbridge-Cejku M, Scott WW Jr., Reichle R, Plato CC, Tobin JD. The association of body weight, body fatness and body fat distribution with osteoarthritis of the knee: data from the Baltimore Longitudinal Study of Aging. J Rheumatol 1995;22: 488–93. [3] Bourne R, Mukhi S, Zhu N, Keresteci M, Marin M. Role of obesity on the risk for total hip or knee arthroplasty. Clin Orthop Relat Res 2007;465:185–8.

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Total weight loss associated with increased physical activity after bariatric surgery may increase the need for total joint arthroplasty.

Retrospectively, our institution noticed an increased number of patients undergoing total joint arthroplasty (TJA) after bariatric surgery. Considerin...
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