911 C OPYRIGHT Ó 2015
BY
T HE J OURNAL
OF
B ONE
AND J OINT
S URGERY, I NCORPORATED
Weight Changes After Total Hip or Knee Arthroplasty Prevalence, Predictors, and Effects on Outcomes Michael P. Ast, MD, Matthew P. Abdel, MD, Yuo-yu Lee, MS, Stephen Lyman, PhD, Allison V. Ruel, BA, and Geoffrey H. Westrich, MD Investigation performed at the Division of Adult Reconstruction and Joint Replacement Service, Department of Orthopedic Surgery, Hospital for Special Surgery, Weill Cornell Medical College of Cornell University, New York, NY
Background: Conflicting evidence exists with regard to weight loss after total hip arthroplasty or total knee arthroplasty. The purposes of this study were to determine whether patients lose weight after total hip arthroplasty or total knee arthroplasty, whether there are predictors of weight change after total hip arthroplasty or total knee arthroplasty, and whether weight changes after total hip arthroplasty or total knee arthroplasty affect patient-reported outcomes. Methods: Using our institutional registry, we evaluated the two-year change in self-reported body mass indices for all patients who underwent elective, unilateral total hip arthroplasty or total knee arthroplasty for osteoarthritis. A 5% change in body mass index was considered clinically meaningful. Patient-reported outcomes were compared between patients who underwent total hip arthroplasty and those who underwent total knee arthroplasty and between obesity classes, on the basis of whether patients gained, lost, or maintained weight. Results: We reviewed 3893 total hip arthroplasties and 3036 total knee arthroplasties. Of the patients who underwent total joint arthroplasty, 73% (2850 patients) in the total hip arthroplasty group and 69% (2090 patients) in the total knee arthroplasty group demonstrated no change in body mass index. Patients who underwent total knee arthroplasty were more likely to lose weight than patients who underwent total hip arthroplasty. Increasing preoperative obesity correlated with a greater likelihood of weight loss. Patients who underwent total knee arthroplasty and lost weight demonstrated better clinical outcome scores, but weight gain in general was associated with inferior clinical outcomes. Greater body mass index, total knee arthroplasty, and female sex were significant predictors of weight loss (p < 0.05). Better preoperative functional status was significantly associated with a lower likelihood of weight gain (p < 0.05). Conclusions: Most patients maintained their body mass index after total hip arthroplasty or total knee arthroplasty. Female patients, patients with higher preoperative body mass index, and those who underwent total knee arthroplasty were more likely to lose weight after surgery. Level of Evidence: Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.
Peer Review: This article was reviewed by the Editor-in-Chief and one Deputy Editor, and it underwent blinded review by two or more outside experts. It was also reviewed by an expert in methodology and statistics. The Deputy Editor reviewed each revision of the article, and it underwent a final review by the Editor-in-Chief prior to publication. Final corrections and clarifications occurred during one or more exchanges between the author(s) and copyeditors.
O
besity in patients undergoing total joint arthroplasty has been demonstrated to be associated with increased risks of revision1, infection2,3, blood loss4, venous thromboembolism5, and overall direct costs6. Recently, a workgroup of the American Association of Hip and Knee Surgeons (AAHKS) Evidence Based Committee investigated the effects of obesity on total joint arthroplasty7. That group demonstrated that obesity
presented several areas of concern for patients undergoing total joint arthroplasty. The serious consequences of obesity on total joint arthroplasty have led some surgeons to recommend delaying total joint arthroplasty in favor of weight loss surgery to decrease the prevalence of perioperative complications8. Although studies have demonstrated the effects of obesity on total joint arthroplasty, conflicting evidence exists with regard
Disclosure: One or more of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of an aspect of this work. In addition, one or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. No author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.
J Bone Joint Surg Am. 2015;97:911-9
d
http://dx.doi.org/10.2106/JBJS.N.00232
912 TH E JO U R NA L O F B O N E & JO I N T SU RG E RY J B J S . O RG V O LU M E 97-A N U M B E R 11 J U N E 3, 2 015 d
d
W E I G H T C H A N G E S A F T E R T O TA L H I P
OR
KNEE ARTHROPLASTY
d
TABLE I Characteristics of Patients Who Had Undergone Total Hip Arthroplasty (N = 3893) Characteristic
No. of Patients
Weight category Normal weight (BMI of 18.50 to 24.99 kg/m2)
1196 (30.7%)
Overweight (BMI of 25.00 to 29.99 kg/m2) Obese class I (BMI of 30.00 to 34.99 kg/m2)
1599 (41.1%) 742 (19.1%)
Obese class II (BMI of 35.00 to 39.99 kg/m2)
252 (6.5%)
Obese class III (BMI of ‡40.00 kg/m2)
104 (2.7%)
Demographics Female sex
1876 (48.2%)
Race White
3627 (93.2%)
Asian
21 (0.5%)
Black Hispanic
118 (3.0%) 101 (2.6%)
Other
26 (0.7%)
Education High school or less
404 (10.4%)
Some college or college graduate
1881 (48.3%)
Master’s, professional, or doctoral degree
1552 (39.9%)
Unspecified
56 (1.4%)
Insurance Medicaid (any patient with Medicaid) Medicare (any patient with Medicare but no Medicaid)
40 (1.0%) 1824 (46.9%)
Commercial only (without Medicaid or Medicare)
2002 (51.4%)
Self-pay (no other insurance listed)
14 (0.4%)
Unspecified
13 (0.3%)
Charlson-Deyo Comorbidity Index 0 1 to 2
3115 (80.0%) 688 (17.7%)
‡3
77 (2.0%)
Unspecified
13 (0.3%)
Laterality Right Left
2102 (54.0%) 1791 (46.0%)
First surgery of a staged bilateral arthroplasty No Yes
to whether patients lose weight after total hip arthroplasty or after total knee arthroplasty. A recent meta-analysis by Inacio et al.9 showed that small studies exist demonstrating both weight loss and weight gain after total hip arthroplasty or total knee arthroplasty, but most are underpowered. Furthermore, studies that demonstrated weight change after arthroplasty did not evaluate whether any predictors of such change exist. To our knowledge, no studies have examined whether weight change after total hip arthroplasty or after total knee arthroplasty was associated with a difference in clinical outcomes. The goals of our study were to determine if patients truly lose weight after total hip arthroplasty or total knee arthroplasty,
3888 (99.9%) 5 (0.1%)
if there are predictors of weight change after total hip arthroplasty or total knee arthroplasty, and if weight changes after total hip arthroplasty or total knee arthroplasty affect patient-reported outcomes. We hypothesized that most patients would maintain their weight postoperatively; however, heavier patients would be more likely to lose weight. Further, we believed that preoperative activity level would be predictive of weight change after total hip arthroplasty or total knee arthroplasty, but no other demographic variations would predict weight change. Finally, we hypothesized that those patients who were able to lose a clinically meaningful amount of weight postoperatively would have improved patientreported outcomes.
913 TH E JO U R NA L O F B O N E & JO I N T SU RG E RY J B J S . O RG V O LU M E 97-A N U M B E R 11 J U N E 3, 2 015 d
d
W E I G H T C H A N G E S A F T E R T O TA L H I P
OR
KNEE ARTHROPLASTY
d
TABLE II Multinomial Logistic Regression Results Examining the Predictors for Weight Loss or Gain After Total Hip Arthroplasty Parameter
BMI Loss of >5%*†
P Value‡
BMI Gain of >5%*†
P Value‡
Weight category§ Overweight compared with normal weight
1.76 (1.10 to 2.83)
0.019
0.58 (0.40 to 0.85)
0.0057
Obese class I compared with normal weight Obese class II compared with normal weight
5.60 (3.45 to 9.10) 6.23 (3.48 to 11.16)
5%*†
P Value‡
Overweight compared with normal weight
2.16 (1.50 to 3.10)
BY
T HE J OURNAL
OF
B ONE
AND J OINT
S URGERY, I NCORPORATED
Weight Changes After Total Hip or Knee Arthroplasty Prevalence, Predictors, and Effects on Outcomes Michael P. Ast, MD, Matthew P. Abdel, MD, Yuo-yu Lee, MS, Stephen Lyman, PhD, Allison V. Ruel, BA, and Geoffrey H. Westrich, MD Investigation performed at the Division of Adult Reconstruction and Joint Replacement Service, Department of Orthopedic Surgery, Hospital for Special Surgery, Weill Cornell Medical College of Cornell University, New York, NY
Background: Conflicting evidence exists with regard to weight loss after total hip arthroplasty or total knee arthroplasty. The purposes of this study were to determine whether patients lose weight after total hip arthroplasty or total knee arthroplasty, whether there are predictors of weight change after total hip arthroplasty or total knee arthroplasty, and whether weight changes after total hip arthroplasty or total knee arthroplasty affect patient-reported outcomes. Methods: Using our institutional registry, we evaluated the two-year change in self-reported body mass indices for all patients who underwent elective, unilateral total hip arthroplasty or total knee arthroplasty for osteoarthritis. A 5% change in body mass index was considered clinically meaningful. Patient-reported outcomes were compared between patients who underwent total hip arthroplasty and those who underwent total knee arthroplasty and between obesity classes, on the basis of whether patients gained, lost, or maintained weight. Results: We reviewed 3893 total hip arthroplasties and 3036 total knee arthroplasties. Of the patients who underwent total joint arthroplasty, 73% (2850 patients) in the total hip arthroplasty group and 69% (2090 patients) in the total knee arthroplasty group demonstrated no change in body mass index. Patients who underwent total knee arthroplasty were more likely to lose weight than patients who underwent total hip arthroplasty. Increasing preoperative obesity correlated with a greater likelihood of weight loss. Patients who underwent total knee arthroplasty and lost weight demonstrated better clinical outcome scores, but weight gain in general was associated with inferior clinical outcomes. Greater body mass index, total knee arthroplasty, and female sex were significant predictors of weight loss (p < 0.05). Better preoperative functional status was significantly associated with a lower likelihood of weight gain (p < 0.05). Conclusions: Most patients maintained their body mass index after total hip arthroplasty or total knee arthroplasty. Female patients, patients with higher preoperative body mass index, and those who underwent total knee arthroplasty were more likely to lose weight after surgery. Level of Evidence: Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.
Peer Review: This article was reviewed by the Editor-in-Chief and one Deputy Editor, and it underwent blinded review by two or more outside experts. It was also reviewed by an expert in methodology and statistics. The Deputy Editor reviewed each revision of the article, and it underwent a final review by the Editor-in-Chief prior to publication. Final corrections and clarifications occurred during one or more exchanges between the author(s) and copyeditors.
O
besity in patients undergoing total joint arthroplasty has been demonstrated to be associated with increased risks of revision1, infection2,3, blood loss4, venous thromboembolism5, and overall direct costs6. Recently, a workgroup of the American Association of Hip and Knee Surgeons (AAHKS) Evidence Based Committee investigated the effects of obesity on total joint arthroplasty7. That group demonstrated that obesity
presented several areas of concern for patients undergoing total joint arthroplasty. The serious consequences of obesity on total joint arthroplasty have led some surgeons to recommend delaying total joint arthroplasty in favor of weight loss surgery to decrease the prevalence of perioperative complications8. Although studies have demonstrated the effects of obesity on total joint arthroplasty, conflicting evidence exists with regard
Disclosure: One or more of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of an aspect of this work. In addition, one or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. No author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.
J Bone Joint Surg Am. 2015;97:911-9
d
http://dx.doi.org/10.2106/JBJS.N.00232
912 TH E JO U R NA L O F B O N E & JO I N T SU RG E RY J B J S . O RG V O LU M E 97-A N U M B E R 11 J U N E 3, 2 015 d
d
W E I G H T C H A N G E S A F T E R T O TA L H I P
OR
KNEE ARTHROPLASTY
d
TABLE I Characteristics of Patients Who Had Undergone Total Hip Arthroplasty (N = 3893) Characteristic
No. of Patients
Weight category Normal weight (BMI of 18.50 to 24.99 kg/m2)
1196 (30.7%)
Overweight (BMI of 25.00 to 29.99 kg/m2) Obese class I (BMI of 30.00 to 34.99 kg/m2)
1599 (41.1%) 742 (19.1%)
Obese class II (BMI of 35.00 to 39.99 kg/m2)
252 (6.5%)
Obese class III (BMI of ‡40.00 kg/m2)
104 (2.7%)
Demographics Female sex
1876 (48.2%)
Race White
3627 (93.2%)
Asian
21 (0.5%)
Black Hispanic
118 (3.0%) 101 (2.6%)
Other
26 (0.7%)
Education High school or less
404 (10.4%)
Some college or college graduate
1881 (48.3%)
Master’s, professional, or doctoral degree
1552 (39.9%)
Unspecified
56 (1.4%)
Insurance Medicaid (any patient with Medicaid) Medicare (any patient with Medicare but no Medicaid)
40 (1.0%) 1824 (46.9%)
Commercial only (without Medicaid or Medicare)
2002 (51.4%)
Self-pay (no other insurance listed)
14 (0.4%)
Unspecified
13 (0.3%)
Charlson-Deyo Comorbidity Index 0 1 to 2
3115 (80.0%) 688 (17.7%)
‡3
77 (2.0%)
Unspecified
13 (0.3%)
Laterality Right Left
2102 (54.0%) 1791 (46.0%)
First surgery of a staged bilateral arthroplasty No Yes
to whether patients lose weight after total hip arthroplasty or after total knee arthroplasty. A recent meta-analysis by Inacio et al.9 showed that small studies exist demonstrating both weight loss and weight gain after total hip arthroplasty or total knee arthroplasty, but most are underpowered. Furthermore, studies that demonstrated weight change after arthroplasty did not evaluate whether any predictors of such change exist. To our knowledge, no studies have examined whether weight change after total hip arthroplasty or after total knee arthroplasty was associated with a difference in clinical outcomes. The goals of our study were to determine if patients truly lose weight after total hip arthroplasty or total knee arthroplasty,
3888 (99.9%) 5 (0.1%)
if there are predictors of weight change after total hip arthroplasty or total knee arthroplasty, and if weight changes after total hip arthroplasty or total knee arthroplasty affect patient-reported outcomes. We hypothesized that most patients would maintain their weight postoperatively; however, heavier patients would be more likely to lose weight. Further, we believed that preoperative activity level would be predictive of weight change after total hip arthroplasty or total knee arthroplasty, but no other demographic variations would predict weight change. Finally, we hypothesized that those patients who were able to lose a clinically meaningful amount of weight postoperatively would have improved patientreported outcomes.
913 TH E JO U R NA L O F B O N E & JO I N T SU RG E RY J B J S . O RG V O LU M E 97-A N U M B E R 11 J U N E 3, 2 015 d
d
W E I G H T C H A N G E S A F T E R T O TA L H I P
OR
KNEE ARTHROPLASTY
d
TABLE II Multinomial Logistic Regression Results Examining the Predictors for Weight Loss or Gain After Total Hip Arthroplasty Parameter
BMI Loss of >5%*†
P Value‡
BMI Gain of >5%*†
P Value‡
Weight category§ Overweight compared with normal weight
1.76 (1.10 to 2.83)
0.019
0.58 (0.40 to 0.85)
0.0057
Obese class I compared with normal weight Obese class II compared with normal weight
5.60 (3.45 to 9.10) 6.23 (3.48 to 11.16)
5%*†
P Value‡
Overweight compared with normal weight
2.16 (1.50 to 3.10)
