hematemesis, confusion, aspiration pneumonia, and death. Sixty-five percent of the patients received at least one blood transfusion. Harris hip scores improved ...
The Journal of Arthroplasty Vol. 23 No. 7 2008
Total Hip Arthroplasty in the Underweight Daniel T. Alfonso, MD,* R. Damani Howell, MD,* Glinys Caceres, MD,* Peter Kozlowski, BA,* and Paul E. Di Cesare, MD y
Abstract: The outcomes of 20 patients diagnosed with osteoarthritis or rheumatoid arthritis with body mass index less than 18.5 (considered underweight) who received total hip arthroplasty at a single institution were reviewed. Surgical complications in the first 30 days after surgery included 1 prolonged surgical site drainage and 3 posterior dislocations. Two patients experienced medical complications that included hematemesis, confusion, aspiration pneumonia, and death. Sixty-five percent of the patients received at least one blood transfusion. Harris hip scores improved from 35 to 81 (P b .05) at an average of 6.1 years (2-10.1 years) of follow-up. Total hip arthroplasty is effective in patients who are underweight; however, they appear to be at an increased risk of dislocation and blood transfusion. Key words: total hip arthroplasty, underweight, total joint arthroplasty. © 2008 Elsevier Inc. All rights reserved.
of patients with hip osteoarthritis or rheumatoid arthritis who are underweight (BMI, b18.5) and undergo hip arthroplasty surgery.
The general medical and surgical complications associated with obesity have received much attention in the literature. Previous studies have found that an increase in body mass index (BMI) is associated with increased operative time, venous thromboembolic events, superficial and deep wound infection, blood loss, and aseptic loosening [1-4]. In the general population in the United States, Schoenborn et al [7] estimated that 2.3% are underweight, and Flegel et al [5] found that being underweight leads to more than 33 000 excess deaths per year. Despite the health risks that being underweight pose, to the best of our knowledge, there is no study in the literature reporting on the medical and surgical complications and outcomes
Material and Methods Between January 1, 1998, and December 31, 2004, 20 total hip arthroplasties were performed in 20 patients of 4358 primary total hip arthroplasties, all performed at the author's institution. Incidence of underweight patients (BMI, b18.5 kg/m2) receiving total hip arthroplasty with a diagnosis of osteoarthritis or rheumatoid arthritis was 0.5%. Indications for surgery, preoperative Harris hip scores, medical history, postoperative surgical and medical complications, transfusion requirements, and date of discharge from the hospital were recorded. Follow-up surveys were used to determine clinical outcomes. The institutional review board approved this retrospective study.
From the *Department of Orthopaedic Surgery, Musculoskeletal Research Center, NYU-Hospital for Joint Diseases, New York, New York; and yDepartment of Orthopaedic Surgery, U.C. Davis Medical Center, Sacramento, California. Submitted March 12, 2007; accepted September 6, 2007. No benefits or funds were received in support of the study. Reprint requests: Paul E. Di Cesare, MD, Department of Orthopaedic Surgery, UC Davis Medical Center, 4860 Y Street, Suite 3800, Sacramento, CA 95817. © 2008 Elsevier Inc. All rights reserved. 0883-5403/08/2307-0002$34.00/0 doi:10.1016/j.arth.2007.09.008
Demographics The study population consisted of 13 female and 7 male patients. The preoperative medical conditions are listed in Table 1. The preoperative
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THA in the Underweight Alfonso et al Table 1. Preoperative Medical Conditions Cardiac Hypertension Coronary artery disease Hypercholesterolemia Atrial fibrillation Arrhythmia Aortic stenosis History of myocardial infarction History of Endocarditis Pulmonary Chronic obstructive pulmonary disease Gastrointestinal Gastritis Irritable bowel syndrome Hematologic Anemia Endocrinologic Hypothyroidism Dermatologic Psoriasis Eczema Other History of sarcoma Glaucoma Deaf/mute HIV Depression Endometriosis
8 5 4 2 2 1 1 1 1 1 1 2 3 1 1 1 1 1 1 1 1
diagnosis was osteoarthritis in 15 patients and rheumatoid arthritis in 5 patients; no patients had developmental dysplasia of the hip. Twelve total hip arthroplasties were left sided. All patients received a hybrid total hip arthroplasty (cemented femoral component and an uncemented acetabular component) through a posterior approach by 7 different surgeons. The mean age of the patients was 68 years (35-81 years). No patient had a history of dementia or other neurologic condition or a diagnosed eating disorder. The mean BMI was 17.4 kg/m2 (16.2-18.4 kg/m2). Postoperatively, all patients received deep venous thrombosis (DVT) prophylaxis based upon surgeon preference (12 patients received low molecular weight heparin, 5 patients received aspirin and serial compressive devices, and 3 patients received Coumadin). Patients also received prophylactic antibiotics, 18 of the patients received 24 hours of cefazolin, and 2 patients who were penicillin allergic received 24 hours of clindamycin.
Results The mean length of stay was 6.7 days (range, 413 days). Two patients experienced medical complications. One 85-year-old female with a diagnosis of osteoarthritis had an episode of hematemesis and postoperative confusion. Her comorbid conditions included coronary artery disease, hypothyroidism, gastritis, anemia, and sarcoma. A second 67-year-
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old male patient with a diagnosis of osteoarthritis sustained aspiration pneumonia leading to intubation and death. His comorbid conditions included chronic obstructive pulmonary disease and hypertension. There were 4 operative complications in the first 30 days after surgery. The same patient who sustained aspiration pneumonia also had prolonged wound drainage as well as a posterior dislocation. In addition, 2 other patients had postoperative posterior dislocations. The 3 posterior dislocations occurred on postoperative day 6, 13, and 28. Of the 3 dislocations, 1 patient had rheumatoid arthritis and the other 2 had osteoarthritis. All 3 hip dislocations were reduced using closed methods with conscious sedation. There were no subsequent dislocations in these 3 patients. There were no DVT or pulmonary embolism in our cohort. With the exception of the one dislocation that occurred in a patient with rheumatoid arthritis, all other complications occurred in patients with a diagnosis of osteoarthritis. Thirteen of 20 patients received at least one packed red blood cell transfusion. The mean number of transfusions for patients receiving a transfusion was 2 U (range, 1-5 U). The mean preoperative hematocrit was 36% and was lowest on postoperative day 2 at 27.6%. The decision to transfuse was made by monitoring the hemoglobin level. Institutional guidelines for postoperative transfusion were a combination of hemoglobin of b9 g/dL and clinical symptoms of anemia or prior cardiac history; however, the ultimate decision of whether or not to transfuse was at the discretion of the attending surgeon. The mean preoperative Harris hip score was 35 (range, 16-53). With the exception of the one patient who died in the perioperative period, all patients were alive at follow-up. At a mean of 6.1 years (2-10.1 years) of follow-up, the remaining 19 patients had a statistically significant improvement of their mean Harris hip score to 81 (range, 61-97; P b .05).
Discussion In the United States, where obesity has become an epidemic, less is known about the medical sequelae of being underweight and undergoing orthopedic surgery. According to the Third National Health and Nutrition Survey, the age-adjusted prevalence of obesity in the United States increased from 22.9% in the period from 1988 to 1994 to 30.5% in the period from 1999 to 2000 [6]. In 1999, the prevalence of being underweight in the United States was 2.3%
958 The Journal of Arthroplasty Vol. 23 No. 7 October 2008 [7]. The reason for the abundance of literature on obesity and total joint arthroplasty, and the paucity of literature on being underweight and total joint arthroplasty is most likely because of the higher prevalence of obesity and the alarming rise in prevalence of obesity. The prevalence of being underweight is reported to be 2.3% of the population, which differed from the total cohort of 0.5% for our total hip patients. Although numerous population-based studies have shown no increase in the incidence of hip osteoarthritis with obesity, the literature is lacking on a potential protective basis of a low BMI or being underweight [8,9]. However, being underweight has been linked to increased morbidity and mortality compared with having a BMI within the healthy range (18.525 kg/m2 ) for age groups from adolescents to elderly [5,10,11]. Having a BMI of less than 18.5 may be a normal physiologic state or may be a symptom of a medical condition. The differential diagnosis includes neoplastic disorders, inflammatory disorders (rheumatoid arthritis, sclerosing cholangitis), psychiatric disorders (anorexia nervosa, neurosis), infectious etiologies (Lyme disease, tuberculosis), and genetic disorders (Klinefelter's disease, Marfan's disease) [12]. The differential diagnosis of medical conditions that may have thinness as a symptom is extensive. For most of our patients, a specific diagnosis explaining the patients' BMI could not be explained, but 5 patients had rheumatoid arthritis, 1 patient had irritable bowel syndrome, 1 had gastritis, and 1 was diagnosed with depression. A low BMI may be a reflection of a state of malnourishment where the body has fewer reserves, cannot react to stress appropriately, and may have a crippled immune system [13]. Musculoskeletal sequelae of being underweight include less muscle mass, less soft tissue, and greater likelihood of osteoporosis [13,14]. Rates of dislocation after primary total hip arthroplasty is approximately 1% to 3% [15-18]. Although the reported dislocation rate varies depending on a number of factors [19], none of the patients in this cohort had a history of prior hip surgery, neurologic or psychiatric illness, or developmental dysplasia of the hip. All hip surgery in this study was performed though a posterior approach. Although some authors found no difference in dislocation rates between a posterior approach to the hip and other approaches, other authors found increased rates between 4% and 6.5% [15,20,21]. In our cohort, 15% of patients sustained posterior dislocations in the perioperative period, which is higher than the highest percentage quoted in the
literature for posterior approach alone. A weakness in this study is that the 20 total hip arthroplasties were performed by 7 different surgeons who all used slightly different technique. There are a number of possible reasons why patients who are underweight have a higher dislocation rate. Underweight patients have reduced muscle mass as compared with normal or overweight patients and therefore may lack the normal soft tissue tension across the hip joint that promotes stability. Also, in comparison to patients who are obese, patients who are underweight have decreased soft tissue mass and therefore do not have the same constraints on range of motion, which may account for the increased rates of instability in this patient cohort. In our series, 65% of patients received at least 1 U of packed red blood cells. In contrast, in the series of 9482 patients with a mean age of 66.6 years who underwent total hip or total knee arthroplasty studied by Bierbaum et al [22], 4409 (46%) received a blood transfusion in the perioperative period. The decision to transfuse was made at a higher hematocrit level that is normally accepted today in both our cohort and the Bierbaum cohort, so the higher rate of transfusion in our patient population may be related to their underweight status. The reason for the increased transfusion rate may be because patients who are underweight have less blood reserve and become symptomatic at higher hematocrits. Indeed, Nelson et al [23] demonstrated that a 100-kg patient could tolerate twice as much blood loss compared with a 50-kg patient before the hematocrit would drop from 40% to below 21%. The Harris hip score significantly improved, demonstrating the benefit of total hip arthroplasty in underweight patients. Because Harris hip scores mainly represent patients' pain, function, and activity, it is a good measure of patients' overall satisfaction of the procedure. Despite a high dislocation rate and high transfusion rate, total hip arthroplasty remains a successful procedure in underweight patients.
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