Abstract
Background: Neurogenic claudication secondary to lumbar stenosis is often cited by overweight and obese patients as a factor limiting their ability to lose weight. Many patients believe that they will be able to increase their activity and subsequently lose weight following relief of symptoms. The objective of this study was to evaluate weight loss in overweight and obese patients who obtained substantial pain relief after lumbar decompression surgery for spinal stenosis.
Methods: Changes in the body weight and body mass index of overweight and obese patients after lumbar decompression surgery were assessed at a mean of 34.4 months postoperatively. Sixty-three patients (thirty-seven men and twenty-six women with a mean age of 53.4 years) were included in the study. Preoperative and postoperative body weight and body mass indices were calculated, and Zurich Claudication Questionnaire (ZCQ) Symptom Severity and Physical Function scores were obtained.
Results: The ZCQ Symptom Severity and Physical Function scores significantly improved, by a mean of 56.4% and 53.0%, respectively. At the time of follow-up, both the mean body weight and the mean body mass index significantly increased, by 2.48 kg and 0.83 kg/m2, respectively. Overall, 35% of the patients gained =5% of their preoperative body weight, 6% of the patients lost =5% of their preoperative body weight, and 59% remained within 5% of their preoperative body weight.
Conclusions: The majority of overweight and obese patients maintain or increase their body weight and body mass index following successful lumbar decompression surgery. Substantial relief of symptoms and functional improvements do not appear to help overweight or obese patients to lose weight. This suggests that obesity is an independent disease and not simply a function of symptomatic spinal stenosis, and patients should be counseled regarding these expectations.
Level of Evidence: Prognostic Level II. See Instructions to Authors for a complete description of levels of evidence.
The prevalence of overweight and obese individuals in the United States continues to increase at alarming rates1-4. Current estimates are that, in the United States, 65.7% of individuals are overweight and 32.9% of individuals are obese3,4. Overweight and obese patients with neurogenic claudication secondary to lumbar stenosis often cite their debilitating symptoms as a factor limiting their ability to lose weight. Such symptoms may limit the activity and mobility of these patients, theoretically inhibiting weight loss and potentially promoting weight gain. Patients often believe that, after successful treatment of their symptoms, they will regain the ability to resume more vigorous activities and thereby lose weight. To our knowledge, however, this has not been previously reported in the literature.
The objective of this study was to assess, at the time of intermediate-term follow-up, weight changes in overweight and obese patients who had successful resolution of symptoms after lumbar decompression surgery.
The records of all overweight and obese patients who had undergone primary lumbar decompression for treatment of lumbar spinal stenosis by two of the authors (H.H.B. and C.G.F.) from January 2003 to June 2005 were r etrospectively reviewed. Institutional review board approval was obtained prior to data collection. We classified patients as overweight or obese on the basis of their body mass index5,6, which was calculated by dividing the patient's weight in kilograms by the squared value of his or her height in meters. Patients were classified preoperatively as overweight if their body mass index was 25.1 to 29.9 kg/m2, obese if it was 30 to 34.9 kg/m2, and morbidly obese if it was =35 kg/m2. Strict inclusion and exclusion criteria were established in order to minimize any potential confounding variables that could have an adverse effect on a patient's ability to lose weight.
Patient Inclusion Criteria
To be included in the study, patients had to have had chronic neurogenic claudication symptoms such as severe buttock and/or lower-limb pain for a minimum of six months prior to surgery; a primary lumbar decompressive procedure, with or without arthrodesis; an age between thirty-five and sixty-five years old at the time of surgery; and good to excellent satisfaction with the surgical outcome as determined with the Zurich Claudication Questionnaire (ZCQ)7,8. All patients were followed for a minimum of two years, and the maximum duration of follow-up was 4.3 years.
Patient Exclusion Criteria
No specific upper limit for body weight or body mass index was defined to establish patients as inappropriate candidates for surgery when the decision whether to proceed with a lumbar decompression procedure was being made; that decision was left to the discretion of the attending surgeon. Patients with a preoperative body mass index of =25 kg/m2 were not considered in this review. Patients were also excluded if they were discovered, during our retrospective review, to have had a preoperative or postoperative major medical comorbidity that could be functionally limiting (major cardiopulmonary disease, a stroke-induced neurologic deficit, severe psychiatric disease, debilitating hip or knee arthritis, prior pathological involvement of the cervical or thoracic spine, or oncologic disease), any medical comorbidity that was deemed uncontrolled, missing clinical data, any subsequent major surgical procedure, or any surgical complication in the short or intermediate term following the lumbar decompression. Additionally, patients who had been lost to follow-up or were determined to have had a poor surgical result or a poor functional status, including those with continued back and lower-limb pain, continued narcotic dependence, or continued neurologic deficits, were excluded.
Sixty-three patients were included in this study. Thirty-seven were men and twenty-six were women. The average age (and standard deviation) at the time of the lumbar decompression procedure was 53.4 ± 8.1 years (range, 36.3 to 64.9 years). The average preoperative patient weight was 92.3 ± 16.2 kg (range, 63.5 to 136.1 kg), and the average patient height was 1.7 ± 0.1 m (range, 1.5 to 2.0 m). The average body mass index was 31.0 ± 4.7 kg/m2 (range, 25.1 to 47.0 kg/m2). Preoperatively, thirty-two patients were classified as overweight, with a mean body mass index of 27.7 ± 1.6 kg/m2; seventeen were classified as obese, with a mean body mass index of 31.2 ± 0.9 kg/m2; and fourteen were classified as morbidly obese, with a mean body mass index of 38.4 ± 3.2 kg/m2.
Following lumbar decompression, all patients were referred for formal physical therapy. At our institution, the initial physical therapy regimen was started while the patient was in the hospital and consisted of generalized mobilization, flexibility exercises for the lower limbs, and active-assisted walking. The physical therapy regimen was typically advanced at six weeks to include generalized aerobic conditioning, core strengthening, lower-limb strengthening, and education and training regarding body mechanics. Patients who underwent an arthrodesis procedure in addition to the lumbar decompression were restricted from considerable forward bending and lifting for approximately three months after the surgery. Preoperatively and postoperatively, all overweight and obese patients were encouraged to enter and participate in a weight loss program that included nutritional and physical education. Although enrollment in a weight loss program of the patient's choice was encouraged, it was not mandated or specifically monitored.
The preoperative body weight, body mass index, and available demographic data were collected from the medical record of each patient at the initiation of this study. The orthopaedic and general medical records were analyzed to identify our aforementioned inclusion and exclusion criteria. The preoperative height and weight were obtained from the medical record. Patients were typically weighed while wearing their clothing, without shoes. Information to determine the preoperative and postoperative ZCQ scores was obtained in a telephone interview in the postoperative period. Preoperative scores were determined on the basis of the patients' recollection of the severity of their preoperative symptoms and their level of physical function, and postoperative scores represented the patients' perception of their current status. ZCQ Symptom Severity questions asked about pain severity, duration, and location in addition to whether numbness, muscle weakness, or balance problems were present. ZCQ Physical Function questions asked whether walking ability was restricted to the household, restricted to short outdoor excursions, or unrestricted. No ZCQ score was determined on the basis of information extracted from the medical record.
If the patient had had a two to 4.3-year follow-up visit in our orthopaedic clinic, or if a medical evaluation had been completed within three weeks prior to our telephone interview, then the weight recorded at the examination was utilized in the study. Otherwise, the patient was asked during the telephone interview to stand on his or her home scale and report the reading to the interviewer. No generalized or approximate weight ranges were accepted from any patient.
Statistical Methods
A linear regression analysis was utilized to compare the preoperative and follow-up body weights. A paired Student t test and a one-way analysis of variance were performed to analyze any difference in the mean body weight or body mass index following the lumbar decompression surgery.
The clinical outcomes of each patient were also retrospectively reviewed. A paired Student t test was performed to analyze differences between the preoperative and postoperative ZCQ Symptom Severity domain scores and between the preoperative and postoperative ZCQ Physical Function domain scores. A linear regression analysis was utilized to assess whether the extent of improvement in both the Symptom Severity and Physical Function scores was associated with the percent change in body weight of each patient. The level of significance was considered to be p = 0.05.
Of 127 patients between the ages of thirty-five and sixty-five years who had undergone a primary lumbar decompression with or without arthrodesis at our institution, sixty-three met the inclusion criteria. The indication for lumbar decompression was chronic symptomatic spinal stenosis in all sixty-three patients, and all had had failure of nonoperative medical management prior to the lumbar decompression surgery. All patients underwent a laminectomy and bilateral medial facetectomy. Twenty-nine patients underwent a one-level decompression; twenty-five, a two-level decompression; six, a three-level decompression; and three, a four-level decompression. In addition to the lumbar decompression, arthrodesis was performed for spondylolisthesis in eighteen patients (at one level in nine, at two levels in eight, and at three levels in one). No patient in this study had made a preoperative or postoperative Workers' Compensation or disability claim. Only fourteen patients were noted to have continued smoking cigarettes after the lumbar decompression, and the typical quantity was one pack per day.
The majority of patients (71%) had either no additional medical condition (thirty-one patients) or only one additional medical condition (fourteen patients). Sixteen patients (25%) had two medical comorbidities, one patient (2%) had three, and one patient (2%) had four. The most common medical comorbidity was hypertension (twenty-three patients), followed by depression (seven) and diabetes mellitus (six). All medical comorbidities were well controlled with pharmacologic therapy, and the patients' physical function and mobility were not limited by these conditions.
The average duration of follow-up (and standard deviation) was 34.4 ± 8.0 months (range, twenty-four to 51.3 months). There was a significant linear correlation between the weight at the time of follow-up and the preoperative weight of each patient (r2 = 0.92, p < 0.001) (Fig. 1). At the time of follow-up, the average patient body weight had increased significantly by 2.48 kg (p = 0.001), from 92.3 ± 16.1 kg to 94.8 ± 18.3 kg. In addition, the average body mass index had increased significantly by 0.83 kg/m2 (p = 0.001), from 31.0 ± 4.7 kg/m2 to 31.8 ± 5.6 kg/m2. Overall, twenty-two patients (35%) gained =5% of their preoperative body weight, four patients (6%) lost =5% of their preoperative body weight, and thirty-seven patients (59%) remained within 5% of their preoperative body weight.
With the number of patients available, subgroup analysis did not reveal a significant difference in the average change in body weight (p = 0.2) or body mass index (p = 0.15) among patients considered overweight, obese, or morbidly obese. The average increases in the body weight and body mass index were 1.8 ± 4.7 kg and 0.6 ± 1.5 kg/m2, respectively, in the overweight subgroup; 2.0 ± 3.7 kg and 0.6 ± 1.4 kg/m2 in the obese subgroup; and 4.8 ± 8.0 kg and 1.7 ± 2.8 kg/m2 in the morbidly obese subgroup. The average gain in body weight was 2.2% in the overweight subgroup, 2.0% in the obese subgroup, and 4.1% in the morbidly obese subgroup. The average percent change in body weight was also not significantly different among subgroups (p = 0.51).
Comparison of the preoperative and follow-up ZCQ scores for each patient demonstrated a significant improvement in both the Symptom Severity domain and the Physical Function domain. The average Symptom Severity score improved from 24.2 ± 3.3 points (range, 17 to 33 points) preoperatively to 10.6 + 3.9 points (range, 7 to 27 points) at the time of follow-up (p < 0.001). (A lower score indicated improvement.) A Symptom Severity score of 24 points typified a patient with severe back and lower-limb pain and moderate-to-severe lower-extremity muscle weakness and numbness, whereas a score of 10 points typified a patient with mild back pain once a week and no lower-extremity muscle weakness or numbness. The average Physical Function score also improved, from 14.0 ± 2.4 points (range, 8 to 20 points) preoperatively to 6.5 ± 2.2 points (range, 5 to 13 points) at the time of follow-up (p < 0.001). A physical function score of 14 points typified a patient who could walk about the household comfortably but was able to walk less than two blocks outdoors and avoided walking outdoors, whereas a score of 6 points typified a patient who could walk an unrestricted distance comfortably. There was a mean improvement of 56.4% in the Symptom Severity domain and 53.0% in the Physical Function domain. Despite the overall improvement in the symptom scores, we found only a minimal, negative trend, which was not significant, when we compared a patient's level of improvement in the ZCQ Symptom Severity score and the percent change in body weight (Fig. 2). Similarly, although there was an overall improvement in each patient's ZCQ Physical Function domain score, we found only a minimal, negative trend, which was not significant, when we compared this score with each patient's percent change in body weight (Fig. 3).
Overweight and obese patients who are considering lumbar decompression surgery for treatment of symptoms of neurogenic claudication are often encouraged to lose weight prior to surgery in order to minimize the risks of perioperative and postoperative complications. Olsen et al. demonstrated that morbid obesity is a risk factor for surgical site infection following lumbar laminectomy and arthrodesis9. Additionally, Patel et al. showed a positive linear correlation between increasing body mass index and substantial postoperative complications that could affect the patient's overall outcome10. Despite these known risks, patients often cite difficulties in losing weight secondary to radiating buttock and lower-limb pain from chronic lumbar stenosis. Furthermore, patients often believe that relief of the symptoms following surgery will aid them in their attempts to lose weight. The results of this study indicate that even when lumbar decompression surgery has a good or excellent outcome, overweight and obese patients do not lose weight and many actually have an increase in their body weight and body mass index. Only 6% of the overweight and obese patients in our study lost =5% of their preoperative body weight.
The finding that patients do not lose weight after the resolution of preoperative symptoms has been described following lower-extremity total joint replacement11-14. Potential confounding factors such as notably advanced patient age were not addressed in these previous reports, and those factors may have had an effect on the ability of these patients to mobilize after the joint replacement. Furthermore, we are not aware of any studies of weight loss following successful total knee or hip replacement in a highly functional patient population.
Obesity is a complex, multifactorial condition. Various physical and emotional factors probably affect the ability to lose weight. Using our inclusion and exclusion criteria, we attempted to select the optimal situation and environment for an overweight or obese patient to lose weight postoperatively. A middle-aged patient population without functionally limiting medical comorbidities is an ideal cohort who would, at least theoretically, be able to increase their activity and mobility following surgery. This selected cohort of patients had also not undergone any additional major surgical procedures and did not have any surgical complications. In addition, the patients were completely or almost completely satisfied with the results of the operation. We excluded all patients who were not satisfied in order to limit new or continued symptoms as a possible cause of limited mobility and function. Furthermore, this cohort of satisfied patients had significantly improved Symptom Severity and Physical Function scores on the ZCQ. An intermediate-term follow-up of more than two years (twenty-four months) but less than 4.3 years (51.3 months) was deemed necessary, not only to provide enough time for rehabilitation after the surgery and for the patients to attempt to lose weight, but also to minimize the potential effect of other confounding variables such as advancing age.
This study had some limitations. It was a retrospective review of a nonrandomized patient population. Also, the relatively small size of the study population may have influenced the results, although our strict selection criteria were purposefully designed to minimize obvious causes of potential inactivity by the overweight and obese patients, including notably advanced age, major medical comorbidities, complications associated with the lumbar decompression procedure, and fair or poor outcomes of the operation. We understand that, despite the use of these criteria, there may have been unidentified factors leading to patient inactivity. Another potential limitation of this study is that an unknown number of severely obese patients may have been denied surgery secondary to their overall body habitus and health state. Because a specific upper limit for weight or the body mass index was not initially defined, information on patients who may have been denied surgery for this reason was not available.
In addition to utilizing the ZCQ, we could have assessed the patients' activity levels by evaluating the duration of time that they needed to return to their previous work status. Although this information was not available for review for the majority of the patients in this study, it is important to note that no patient had made a Workers' Compensation or disability claim. Workers' Compensation claims have been shown to be associated with a patient's inability to return to work following lumbar spine surgery, regardless of whether a neurologic deficit was present15.
Our method of obtaining the preoperative and postoperative weights of each patient was also not ideal. We would have preferred each patient to have been weighed, while he or she was undressed, on the same scale at each of their preoperative and postoperative visits; however, this was not logistically possibly at our institution. Obtaining an in-office, intermediate postoperative patient weight was also difficult, as the majority of patients had no symptoms or functional limitations at six months and therefore did not always return for routinely scheduled follow-up visits. To account for this inherent variability, instead of using a nominal weight value we considered a patient's weight to have changed only when the difference was =5% of the preoperative weight. According to this criterion, only 6% of the overweight and obese patients actually lost weight despite a successful outcome after lumbar decompression, while 35% of the patients gained weight.
Although our patients were encouraged to participate in a weight loss program, their compliance and progress were not specifically controlled for in this study. The patient's motivation to lose weight was also not specifically evaluated preoperatively; therefore, its influence could not be assessed. Despite these limitations, all overweight and obese patients who gained weight expressed, in their postoperative interview, disappointment with their current body weight and noted that they were still having difficulty losing weight. 
The results of this study indicate that most overweight and obese patients either maintain or gain weight following successful lumbar decompression surgery. Weight loss following resolution of lower-extremity claudication symptoms may be an unrealistic expectation for patients. Patients should be counseled preoperatively and encouraged to participate in a weight reduction program before and after undergoing lumbar decompression surgery.
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