Background: The purpose of this study was to assess the clinical and patient-reported outcomes of primary total hip arthroplasty in super-obese patients (those with a body mass index [BMI] of ≥50 kg/m2) compared with a matched group of patients who had a normal BMI (<30 kg/m2). A secondary objective was to assess patients’ experiences in finding a treating surgeon.
Methods: Forty-eight hips in forty-five patients who had a minimum BMI of 50 kg/m2 and who had undergone a primary total hip arthroplasty at one of four high-volume institutions between 2001 and 2010 were reviewed. This included twenty-six women and nineteen men who had a mean age of fifty-four years (range, thirty-six to seventy-one years) and who were followed for a mean time of six years (range, four to twelve years). These patients were compared in a 1:3 ratio with a non-obese matched group (those with a BMI of <30 kg/m2) of 135 patients who had undergone total hip arthroplasty during the same time period by the same surgeons. The outcomes evaluated included implant survivorship, complication rates, Harris hip scores, 36-item Short-Form (SF)-36 questionnaires, University of California Los Angeles (UCLA) activity scores, and patient experience in finding a treating surgeon.
Results: The super-obese group had a 4.5 times higher odds ratio of undergoing a revision when compared with the matching group (p = 0.06); the overall implant survivorship was 89.6% for the super-obese group and 97.8% for the matching group. The super-obese group also had a significantly higher odds ratio (7.7) of complications compared with the matching group (p = 0.017). The super-obese group also had significantly lower mean values for the Harris hip score (82 points for the super-obese group compared with 91 points for the matched group; p = 0.002), the SF-36 Physical Component Summary score (39 points for the super-obese group and 49 points for the matched group; p = 0.001), the SF-36 Mental Component Summary scores (46 points for the super-obese group and 58 points for the matched group; p = 0.001), and the UCLA activity score (3.9 points for the super-obese group compared with 6.2 points for the matched group; p = 0.001). Compared with the matched group, super-obese patients were evaluated by a larger number of orthopaedic surgeons prior to undergoing total hip arthroplasty.
Conclusions: The clinical and patient-reported outcomes of primary total hip arthroplasty were lower in the super-obese patients. These patients also faced challenges in finding surgeons who would perform their procedure. Super-obese patients may benefit from counseling with their treating surgeon to set realistic expectations with regard to the outcomes of their procedure.
Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.
Obesity is a global epidemic and the leading cause of preventable death worldwide, with an increasing incidence and prevalence in adults and children1,2. It is associated with higher medical comorbidities, and surgical interventions in obese patients may be associated with more difficult procedures and more intraoperative and postoperative complications. In addition, the risk of requiring a primary total hip arthroplasty at an earlier age3 may increase in obese and morbidly obese patients4,5, as some reports have shown a positive correlation between obesity and degenerative hip disease6-9. For these reasons, it has been suggested that obesity is one of the most serious public health problems of the twenty-first century2.
Total hip arthroplasty is a successful and cost-effective procedure for treating degenerative hip disease, in terms of improving pain and increasing function. However, obese patients may face challenges in finding orthopaedic surgeons to perform their hip arthroplasty because of the fear of higher complications, inferior clinical outcomes, and longer and more difficult operations with no increases in reimbursement. Studies have shown increased complications after hip arthroplasty, including prolonged wound drainage, increased blood loss10, increased deep venous thromboses11, increased length of stay, and higher superficial or deep infection rates in obese patients (those with a body mass index [BMI] of >30 kg/m2) and morbidly obese patients (those with a BMI of >40 kg/m2)12,13. There are not many data available on the outcomes of lower-extremity total joint arthroplasty in super-obese patients (those with a BMI of >50 kg/m2 or more than about 225% overweight)14-19, which may partly be due to the reluctance of orthopaedic surgeons to perform this procedure in this patient population.
In our practice, we observed higher rates of hip arthroplasty revisions and complications in super-obese patients and thus hypothesized that these patients might achieve worse clinical outcomes. We undertook this study to evaluate the clinical and patient-reported outcomes of this procedure in this patient population compared with a matched group of patients who were not obese (those with a BMI <30 kg/m2). For both groups, we evaluated the overall implant survivorship, clinical outcomes measured by Harris hip scores, medical and surgical complications, Short Form (SF)-36 Health Surveys, University of California Los Angeles (UCLA) activity scores, and patient experience in finding a treating orthopaedic surgeon.
Materials and Methods
We reviewed the database of all patients who had undergone a primary total hip arthroplasty by four experienced fellowship-trained adult joint reconstructive surgeons (M.A.M., S.F.H., P.M.B., and A.L.M.) at one of four high-volume institutions to determine the number of patients who had a BMI of at least 50 kg/m2 (super-obese). Three super-obese patients identified in the database were lost to follow-up after their second-year visit. Although none of these patients had required a revision procedure and all had achieved Harris hip scores of >80 points, they were not included in our study as we had attempted to evaluate the minimum four-year follow-up results for all patients. The remaining forty-eight hips in forty-five patients who had undergone a primary total hip arthroplasty between 2001 and 2010 and who had a minimum of four years of follow-up were identified and were included in this study. All medical records, including preoperative and postoperative studies, admission and discharge summaries, clinic visits, and radiographic studies were reviewed. This included twenty-six women and eighteen men at a mean age of fifty-four years (range, thirty-six to seventy-one years) and a mean BMI of 55 kg/m2 (range, 50 to 65 kg/m2) who were followed for a mean duration of six years (range, four to twelve years) (Table I). Six additional patients who had follow-up of less than two years were not included in this study. The underlying cause of hip disease was end-stage osteoarthritis in thirty-nine patients and osteonecrosis in six patients. The most common comorbidities in these patients included hypertension and cardiovascular disease (72%), hypercholesterolemia (70%), diabetes (61%), gastrointestinal conditions (38%), and psychiatric conditions (27%). We did not have any specific contraindication for hip arthroplasty for super-obese patients with regard to their BMI. All patients had undergone routine preoperative optimization and medical and cardiac clearance when necessary by their primary care physicians. The procedure in eleven patients was delayed from three to twelve weeks due to medical optimization. None of the patients had undergone a bariatric surgical procedure for weight reduction prior to the total hip arthroplasty. A portion of the data from some of these patients (n = 23) at an earlier follow-up was previously reported16. The databases used in our study are clinical databases that are collected prospectively in our centers. All data are collected during periodic scheduled office visits as well as patient surveys. Appropriate institutional review board approval for the study of these patients was obtained from all institutions.
The super-obese patients were compared (at a 1:3 ratio) with a matched group of 135 patients (144 hips) who were not obese (BMI, <30 kg/m2) and who underwent a primary total hip arthroplasty by the same surgeons and during the same time period. Groups were matched by mean age (within one year), sex (exact ratio), procedure (unilateral compared with bilateral), follow-up time (within six months), preoperative Harris hip score (within 2 points), and type of hip disease (osteoarthritis compared with osteonecrosis). Outcomes evaluated included implant survivorship, complication rates, Harris hip scores, Short-Form (SF)-36 questionnaires, and University of California, Los Angeles (UCLA) activity scores, as well as patient experience in finding a treating surgeon.
In the super-obese group, forty-one total hip arthroplasties were performed through an anterolateral approach and seven total hip arthroplasties were performed through a posterior approach. There were no significant differences in the type of surgical approach between the super-obese and the matched group (nine posterior approaches and 126 anterolateral approaches; p = 0.82). All patients in both groups had received an Accolade femoral component prosthesis (Stryker) with a Trident acetabular component (Stryker). The acetabular prostheses were porous-coated and were implanted using a press-fit technique with or without screws. The femoral prosthetic component was a proximally porous-coated stem with a modular head and was implanted using a press-fit cementless technique.
All procedures were performed under general anesthesia. All patients received 2 g of intravenous cefazolin antibiotic thirty minutes prior to initiation of the procedure. This was followed by two additional doses every eight hours for a total of twenty-four hours of coverage. Similar postoperative rehabilitation protocols were used for all patients, with no special techniques for super-obese patients. These protocols included bed rest during the day of the procedure, followed by physical therapy, activities with weight-bearing as tolerated to improve function, and range-of-motion activities from postoperative day 1.
Patients returned for follow-up visits at approximately six weeks, three months, six months, twelve months, and then yearly thereafter. Clinical evaluation was based on the Harris hip scoring system20. At the initial follow-up visits, patients were examined thoroughly and were assessed for any surgical complications such as prolonged wound drainage (persistent drainage from the incision site during follow-up visits), hematoma formation, superficial infection (cellulitis over the incision site) or deep infection (deep periprosthetic infection), deep venous thrombosis, or pulmonary embolism. All patients were followed by means of preoperative and postoperative Harris hip scores and UCLA activity scores. All patients also were followed by postoperative SF-36 Health Survey questionnaires to evaluate general physical and mental health status after total hip arthroplasty.
During each postoperative visit, anteroposterior and lateral views of the hips were obtained, and implants were evaluated radiographically by the senior authors for any periprosthetic fractures, progressive radiolucencies of the femoral component according to the Gruen zones21, acetabular component progressive radiolucencies according to the DeLee and Charnley zones22, implant subsidences, or component failures. Revisions were defined as a change of the femoral or acetabular components for any septic or aseptic reasons, including osteolysis, component malalignment, or implant loosening.
All data were recorded using an Excel spreadsheet (Microsoft). Statistical analyses were performed by using the Fisher exact test and the Student t test to compare the implant survivorship, clinical outcomes, and complication rates between the two groups. A p value of <0.05 was used as a threshold for significance.
Source of Funding
No funding was received in support of this work.
The super-obese group had a significantly higher odds ratio, 4.5 times (95% confidence interval [95% CI], 1.2 to 26 times; p = 0.06), of undergoing a revision procedure for any septic or aseptic reason compared with the matched group. Overall septic and aseptic implant survivorship in the super-obese group was 89.6%, with five patients undergoing revision; one had a revision for stem loosening (at nine months), two had a revision for acetabular component loosening (at nineteen and at 128 months), and two had a two-stage revision for deep periprosthetic infection (at three and at seven months after the index arthroplasty). In the matched group, survivorship was 97.8%, with three patients undergoing revision of the acetabular component with no periprosthetic infections. All patients who had undergone revision surgery achieved Harris hip scores of >75 points at a minimum twelve-month follow-up.
The mean Harris hip scores in the super-obese patients had significantly improved compared with their preoperative scores (p = 0.01); however, at the time of the latest follow-up, their mean postoperative scores were significantly lower (p = 0.002) for the super-obese patients compared with the matched group. In the super-obese group, the mean Harris hip scores had improved from 39 points (range, 26 to 48 points) preoperatively to 82 points (range, 68 to 94 points) postoperatively. In the matched group, the Harris hip scores had improved from a mean score of 41 points (range, 26 to 48 points) preoperatively to 91 points (range, 74 to 100 points) postoperatively (Table I).
The super-obese group had a higher odds ratio of surgical complications (odds ratio, 7.7 [95% CI, 1.4 to 42]; p = 0.017) compared with the matched group. In the super-obese group, there were no intraoperative complications. However, two patients had early postoperative wound complications, including persistent wound drainage, which were successfully treated with surgical irrigation and debridement. One patient developed a superficial hip abscess due to a suture granuloma and was successfully treated with excision and drainage. Another patient had a superficial skin infection that was successfully treated nonoperatively with oral antibiotics. Two patients developed deep periprosthetic infections that required revisions. In the matched group, there were no intraoperative complications; however, one patient developed a wound hematoma that was treated with irrigation and debridement. All patients with surgical complications achieved Harris hips scores of >75 points at a minimum two-year follow-up.
The mean postoperative SF-36 scores were significantly lower (p = 0.001) in the super-obese patients compared with the matched group. In the super-obese group, the mean postoperative scores were 39 points (range, 22 to 46 points) for the SF-36 Physical Component Summary (PCS) and 46 points (range, 23 to 66 points) for the SF-36 Mental Component Summary (MCS). In the matched group, the mean postoperative scores improved to 49 points (range, 32 to 68 points) for the SF-36 PCS and 58 points (range, 36 to 67 points) for the SF-36 MCS and were significantly higher (p = 0.001) than those in the super-obese group.
The mean postoperative UCLA activity scores were significantly lower (p = 0.001) in the super-obese patients compared with the matched group. In the super-obese group, the mean UCLA activity score had improved from 2.2 points (range, 2 to 3 points) preoperatively to 3.9 points (range, 2 to 6 points) at the time of the latest follow-up. In the matched group, the mean UCLA activity score had improved from approximately 3.5 points (range, 2 to 4 points) preoperatively to 6.2 points (range, 3 to 8 points) at the time of the latest follow-up.
Super-obese patients had faced significant challenges (p = 0.01) in finding an orthopaedic surgeon who would perform their primary total hip arthroplasty. Super-obese patients had seen a mean of 2.5 previous orthopaedic surgeons (range, one to four previous surgeons) who had refused to perform the procedure prior to the patients being referred to our institutions. This was significantly higher (p = 0.01) than in the matched group, who had not often seen a previous surgeon (mean, 0.5 previous surgeon [range, zero to one previous surgeon]).
Obesity is a worldwide challenge and the number of patients who have a higher BMI has increased during the past two decades, with higher projections for the future. With such increases in the prevalence of obesity, the incidence and prevalence of super-obesity (BMI of >50 kg/m2) and super-super-obesity (BMI of >60 kg/m2) may also increase. According to the National Institutes of Health (NIH), an increase of approximately 20% above “ideal body weight” is the point at which weight-related health problems may appear. However, super-obese patients exceed their estimated ideal body weight by approximately 225%. Therefore, future orthopaedic surgeons may encounter a higher percentage of patients who have an extreme BMI who may need to undergo arthroplasties because obesity is also an independent risk factor for degenerative joint disease. To our knowledge, outcomes of arthroplasties have not been widely reported in the super-obese patient population. The purpose of this study was to evaluate the clinical and patient-reported outcomes of primary total hip arthroplasty in super-obese patients compared with a matched group of patients who had a normal-weight BMI. Although we found overall acceptable outcomes in the super-obese patients, these patients had lower implant survivorships, Harris hip scores, UCLA activity scores, and SF-36 scores and higher overall complications compared with the matched group.
There were several limitations of this study, including the small sample size. Also, this was not a prospective study, which could have further reduced any potential biases. Furthermore, the senior authors have extended experience performing arthroplasties in patients who have a high BMI. Thus, our results may not be representative of true clinical outcomes of total hip arthroplasty in super-obese patients. Outcomes may also be different at longer-term follow-ups. Psychiatric diseases have been demonstrated to have effects on patient-reported outcomes; however, they were not evaluated in our study. Medical complications were not evaluated or compared between the two groups. Nevertheless, we believe that our results are valuable because there is a paucity of studies showing outcomes of primary total hip arthroplasty in this patient population. Further studies with longer follow-up are needed to better evaluate the outcomes of these patients.
Only a few prior studies have evaluated the outcomes of primary total hip arthroplasty in super-obese patients (Table II)15,17,18,19. Arsoy et al.18 compared the results of forty-two primary total hip arthroplasties in forty super-obese patients (mean BMI, 53 kg/m2 [range, 50 to 64 kg/m2]) with those in a matched group of patients (1:2) who had a mean BMI of 26 kg/m2. At a mean follow-up of forty-eight months (range, three to 126 months), the mean Harris hip score in the super-obese group had improved from 35 points preoperatively to 75 points postoperatively (p < 0.001), and this was significantly lower (p < 0.01) than the postoperative score of 89 points in the matched group. Twenty-four super-obese patients had at least one complication, which included at least one major complication in eleven patients and at least one minor complication in fourteen patients. The most common surgical complications were superficial wound infection (23.8%), fracture (7%), dislocation (7%), deep infection (2.4%), aseptic loosening (2.4%), and nerve palsy (2.4%). When compared with the matched group, the super-obese patients had an increased risk of overall complications (hazard ratio, 5.6 [95% CI, 2.8 to 11.0]). Rajgopal et al.17 compared thirty-nine total hip arthroplasties in thirty super-obese patients with two matched groups of class-I obese patients (BMI of 30 to 34.9 kg/m2) and normal-weight patients (BMI of 18.5 to 24.9 kg/m2), each with thirty-nine total hip arthroplasties in thirty-nine patients. At a mean follow-up of 4.2 years (range, 2.0 to 11.7 years), they reported that super-obese patients experienced longer hospital stays and higher rates of major complications and readmissions than normal-weight patients and class-I obese patients. Although super-obese patients demonstrated reduced preoperative and postoperative satisfaction scores, there was no significant difference in improvement in the score with respect to the Harris hip score or the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). In addition, they reported six readmissions requiring reoperation in the super-obese group, comprising four wound irrigation and debridements, one revision for periprosthetic fracture, and one revision for dislocation. In the class-I obese patients, there were two readmissions, but no readmissions among the normal-weight patients. These outcomes are in agreement with our findings with regard to higher revision and higher complication rates in super-obese patients compared with non-obese patients.
In summary, although super-obese patients have achieved significant improvement in various clinical and patient-reported metrics compared with their preoperative status, we found lower clinical outcome scores, a higher revision rate, and higher complications in super-obese patients compared with the matched group at a mean follow-up of six years (minimum, four years). Also, these patients faced challenges finding surgeons who would perform their procedure, potentially because of the more demanding procedure and fear of higher complications and inferior outcomes. Based on these findings, we believe that total hip arthroplasty may have lower overall outcomes in super-obese patients, although the procedure can still result in acceptable outcomes for relief of pain and improved function in this patient population. Super-obese patients may benefit from a discussion with their orthopaedic surgeons to develop realistic expectations about the potential outcomes and complications of their arthroplasty.
Investigation performed at the Sinai Hospital of Baltimore, Baltimore, Maryland; Department of Orthopaedic Surgery, Seton Hall University of Health and Medical Sciences, South Orange, New Jersey; Mount Sinai Beth Israel, New York, NY; Department of Orthopaedic Surgery, University of Louisville, Louisville, Kentucky; and Bonutti Clinic, Effingham, Illinois
A commentary by Raymond Paul Robinson, MD, is linked to the online version of this article at jbjs.org.
Disclosure: None 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 any aspect of this work. 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. Also, one or more of the authors has had another relationship, or has engaged in another activity, 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.
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