The influence of body mass index on outcome of open arthrolysis for post-traumatic elbow stiffness

ARTICLE IN PRESS J Shoulder Elbow Surg (2017) ■■, ■■–■■

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ORIGINAL ARTICLE

The influence of body mass index on outcome of open arthrolysis for post-traumatic elbow stiffness Wei Zheng, MD, Shuai Chen, MD, Jialin Song, MD, Jiazhi Liu, MD, Cunyi Fan, MD, PhD* Department of Orthopaedics, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, China Background: Being overweight has become a serious public health concern in China. Higher body mass index has been proven to be associated with poor outcome after orthopedic surgery. The purpose of this study was to examine the effect of being overweight on functional outcomes and complications after open arthrolysis for post-traumatic elbow stiffness. Methods: We performed a retrospective study including 122 patients with post-traumatic elbow stiffness undergoing arthrolysis, including 84 in the normal weight group and 38 in the overweight group. Demographic data, surgical data, and data on preoperative and postoperative functional performance and complications were obtained. Results: Demographic data and disease characteristics were comparable between the 2 groups at baseline. All patients showed significant improvement after elbow arthrolysis. Postoperatively, the range of motion and Mayo Elbow Performance Score of the normal weight group were significantly better than those of the overweight group. Sixteen patients developed postoperative complications. No significant differences in complication rates between the 2 groups were found. Conclusions: Most patients showed satisfactory functional outcomes after arthrolysis. The postoperative functional outcomes of the overweight group were inferior to those of the normal weight group to a certain extent. This study underlines the importance of detailed rehabilitation instructions in patients with higher body mass index. Level of evidence: Level III; Retrospective Cohort Design; Treatment Study © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved. Keywords: Post-traumatic elbow stiffness; arthrolysis; body mass index; overweight; functional performance; postoperative complications

Wei Zheng, Shuai Chen, and Jialin Song contributed equally to the manuscript. The Ethics Committee of our hospital concluded that no approval of the committee was necessary because of the retrospective design of the study. All patients signed informed consent to collect, file, and use the data. *Reprint requests: Cunyi Fan, MD, Department of Orthopaedics, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, 600 Yishan Road, Shanghai 200233, China. E-mail address: [email protected] (C. Fan).

Currently, being overweight and obesity have become a major public health concern worldwide. In 2008, 1.46 billion adults worldwide had a body mass index (BMI) of ≥25 kg/ m2, and one-third of them were classified as obese.6 According to the Working Group on Obesity in China criteria, obesity prevalence approximately tripled from 3.75% to 11.3% among Chinese adults from 1991 to 2011.17,34 As reported by extensive studies, being overweight and obesity are associated with

1058-2746/$ - see front matter © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved. http://dx.doi.org/10.1016/j.jse.2016.12.065

ARTICLE IN PRESS 2 longer hospital stays and negative functional outcomes after orthopedic procedures, such as total joint arthroplasty and arthroscopy; they have also been correlated with increased perioperative and postoperative complications, including greater infection rates, increased need for revision surgery, and difficulty in achieving fracture union.1,11,13,23,31 Moreover, several other studies found negative results on comparing nonobese and obese patients.16,27,28 Elbow stiffness is a common complication after elbow trauma or surgery, with an incidence ranging from 5% to 40%.20,22,29 It is generally defined as elbow range of motion (ROM) ≤100°, and a loss of 50° of motion results in an 80% functional loss in daily living and work-related activities.22 Post-traumatic elbow contractures can be the result of intrinsic or extrinsic causes, including long-term immobilization, soft tissue contracture, intra-articular block, and heterotopic ossification formation.18,19 Both nonsurgical and surgical methods are used to treat post-traumatic elbow stiffness. Currently, when conservative treatment fails to improve functional outcomes, open arthrolysis, which has been proven effective with a relatively low incidence of complications, is employed.9,14,24 Several studies have focused on the influence of BMI on elbow surgery. Golden et al reported that increased BMI in healthy children is negatively correlated with ROM of the elbow joint.7 Previous studies also demonstrated the adverse effects of obesity on functional outcomes and postoperative complications after various elbow operations, including arthroplasty, arthroscopy, and open reduction and internal fixation (ORIF).2,5,8,32,33 The goal of this retrospective study was to compare the functional outcomes and postoperative complications between overweight and normal weight patients with post-traumatic elbow stiffness after they have undergone arthrolysis. Given the evidence that increased BMI is a predisposing factor for increased complications and adverse functional outcomes after different orthopedic procedures, we hypothesized that being overweight would have a similar negative effect on outcomes after elbow arthrolysis.

Materials and methods Patients and data collection A retrospective study on prospectively collected data of all patients treated with elbow arthrolysis combined with hinged external fixation between September 2013 and December 2014 was conducted. The inclusion criteria were as follows: (1) skeletal maturity, (2) post-traumatic elbow stiffness with total arc of flexion and extension ≤100°, and (3) minimum follow-up of 12 months. The exclusion criteria were as follows: (1) history of burn injury or central nervous system injury, (2) associated nonunion or malunion of the elbow joint, (3) severe articular damage requiring joint arthroplasty, (4) receiving other elbow ORIF or second arthrolysis during the follow-up period, and (5) unwillingness to participate in the study. All operations were performed by the same senior surgeon.

W. Zheng et al. Preoperative demographics, including age, sex, height, weight, current smoking history, and comorbidities, were recorded. According to World Health Organization criteria, obesity can be classified by BMI, the body weight in kilograms divided by the height in meters squared. All the participants were classified according to their BMI as follows: normal weight (BMI < 25 kg/m 2 ) and overweight (BMI ≥ 25 kg/m2). The following baseline clinical data were also collected: disease duration, diseased side, original injury type, treatment history, ROM, visual analog scale (VAS) score for pain, and Mayo Elbow Performance Score (MEPS). Original injury type included distal humerus fractures, radial head fractures, olecranon fractures, coronoid fractures, elbow dislocations, Monteggia injuries, terrible triad injuries (radial head fracture and coronoid fracture, combined with an ulnohumeral dislocation), and floating elbow fractures (concomitant fractures of both the forearm and the distal humerus). Motion of the diseased elbow was assessed by a goniometer to measure flexion, extension, pronation, and supination. The MEPS is widely used to evaluate patients’ elbow function; it includes four subscales, namely, pain, ROM, stability, and activity of daily living. The questionnaire generates an overall score ranging from 0 to 100, which can be classified into 4 groups: excellent, 91 to 100; good, 81 to 90; fair, 71 to 80; and poor, 0 to 70. The following information related to the operation was also assessed: operative time, type of anesthesia, number of anchors used for surgical fixation, blood transfusion, and intraoperative complications (including intraoperative fracture and nerve injury). At follow-up, postoperative complications, including infection, elbow instability, and nerve complications, were evaluated. Clinical evaluation, ROM of the elbow joint, MEPS, ΔROM (postoperative ROM − preoperative ROM), and ΔMEPS (postoperative MEPS − preoperative MEPS) were also assessed. All the clinical assessments were performed by authors W.Z., S.C., and J.L.

Surgical technique Operations were performed under axillary block or general anesthesia. The approach was chosen on the basis of the previous surgical approach and location of disease. In general, patients underwent arthrolysis by a combined lateral and medial approach. An extended Kocher approach was applied on the lateral side to release the anterior part of the elbow. To release the posterior part of the elbow, we applied a medial incision posterior to the medial epicondyle. Subsequently, the posterior band of the medial collateral ligament and posterior capsule were released, and bone impediments or scar tissues were removed under direct visualization. If patients had undergone previous surgery by the posterior approach, the approach was commonly performed along the previous scar. After soft tissue flap elevation, the same procedures as those in the medial and lateral approach were performed. During the operation, the anterior part of the medial collateral ligament and ulnar bundle of the lateral collateral ligament were preserved for elbow stability. Subcutaneous anterior transposition of the ulnar nerve was performed for all patients with the medial approach. Atraumatic sutures were applied to reattach the ligaments. Finally, a hinged external fixation was applied, with 2 nails each on the humerus and ulna.

Postoperative treatment Postoperative rehabilitation was standardized for all patients. After surgery, patients were prescribed 200 mg of celecoxib once daily

ARTICLE IN PRESS Influence of BMI on elbow arthrolysis for approximately 4 to 6 weeks to prevent heterotopic ossification. Patients were instructed to perform cycling exercises, which involved flexion and extension, after surgery under the protection of a hinged external fixator. The exercises were performed 4 times daily for 30 minutes each time during the first postoperative week. The length of exercise was gradually increased to 1 hour in the ensuing weeks. The hinged external fixator was removed 6 weeks postoperatively.

Statistical analysis The subjects’ characteristics were described as proportions for qualitative data and means (standard deviation) for quantitative data. Oneway analysis of variance was used to compare continuous data, whereas Pearson χ2 analysis was used to compare the categorical data. Linear regression analyses were used to determine the relationship between BMI and postoperative outcomes (postoperative ROM, MEPS, and change in ROM and MEPS). For all analysis, P ≤ .05 was considered statistically significant. All the statistical analyses were performed using SPSS version 19.0 (IBM, Armonk, NY, USA).

3 Table I

Demographic and clinical characteristics of patients

Characteristics

Normal weight (BMI < 25)

Overweight (BMI ≥ 25)

No. of patients Age (years) Male BMI (kg/m2) Tobacco use Disease duration (months) Diseased side Right Left Previous elbow ORIF Comorbidities Follow-up time (months)

84 35 ± 12 51 (61) 21.69 ± 2.01 12 (14) 35 ± 53

38 38 ± 13 .183 30 (79) .048 26.90 ± 1.19 <.001 7 (18) .560 26 ± 51 .419 .177 24 (63) 14 (37) 26 (68) .449 4 .784 19 ± 5 .294

42 (50) 42 (50) 63 (75) 6 20 ± 4

P value

BMI, body mass index; ORIF, open reduction and internal fixation. Categorical variables are presented as number (%). Continuous variables are presented as mean ± standard deviation.

Results Table II

A total of 133 patients with post-traumatic elbow stiffness underwent elbow arthrolysis in our hospital during the study period; 9 patients were lost to follow-up and 2 patients refused to participate in the study. Consequently, 122 patients (81 men and 41 women) who underwent elbow arthrolysis combined with hinged external fixation were included in this study. The average follow-up duration for all the patients was 19 months (range, 12-29 months). The average age of the patients was 35 ± 12 years in the normal weight group and 38 ± 13 years in the overweight group. The normal weight group had 51 male patients and 33 female patients; the overweight group had 30 male patients and 8 female patients. The average BMI in the normal weight and overweight groups was 21.69 and 26.90, respectively (P < .001) (Table I). One patient in the overweight group was considered clinically obese, with a BMI ≥ 30 kg/m2. Detailed types of original injury are shown in Table II. The operative time in the overweight group (162 ± 51 minutes) was similar to that in the normal weight group (166 ± 47 minutes). Forty-one normal weight and 18 overweight patients received general anesthesia (P = .883) (Table III). For surgical fixation, 1.37 anchors per person were used in the normal weight group and 1.26 anchors per person were used in the overweight group (P = .363). Two normal weight patients received 1 unit of packed red blood cells, and 1 overweight patient received 2 units. No intraoperative complications in both groups were observed. Preoperatively, overweight patients had motion of elbow (extension, flexion, pronation, supination, ROM), VAS score, and MEPS similar to those in the normal weight group (Table IV). Postoperative extension, flexion, and ROM were better in the normal weight than in the overweight group (P = .006, .030, and .004, respectively). Significant improvements in ROM (69° ± 30°) for all the patients were observed

Comparison of original injury type

Characteristics

Normal weight (BMI < 25)

Overweight (BMI ≥ 25)

Total number Distal humeral fracture Radial head fracture Olecranon fracture Coronoid fracture Terrible triad injury of elbow Monteggia fracture Elbow dislocation Floating elbow fracture

84 28 15 13 4 4 2 6 12

38 13 5 8 2 3 1 3 3

BMI, body mass index.

postoperatively; however, the ΔROM in the overweight group (59° ± 27°) was inferior to that in the normal weight group (74° ± 31°) (P = .017). Postoperatively, 18 overweight (47%) and 18 normal weight (21%) patients had a ROM ≤100° (P = .004). For all the patients, the mean VAS score for pain decreased from 2.5 ± 2.0 (preoperatively) to 0.7 ± 1.4 (at the follow-up) (P < .001). Postoperatively, the VAS scores were significantly higher in the overweight group (1.2 ± 1.6) than in the normal weight group (0.5 ± 1.2) (P = .019). All the patients showed remarkable improvement in MEPS from 60 ± 11 (preoperatively) to 94 ± 8 (postoperatively) (P < .001). Postoperatively, the normal weight group had a higher MEPS (95 ± 7 points) than the overweight group (90 ± 10 points) (P = .004). However, the ΔMEPS between the normal weight (31 ± 12) and overweight (35 ± 12) group was not significantly different (P = .146). According to the MEPS classification, 21% of overweight patients reported less satisfactory outcomes, including 2 with poor and 6 with fair outcomes, which was higher than the data in the normal weight group (5%, 4 with fair outcomes) (P = .014).

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W. Zheng et al. Table III

Operative characteristics

Characteristics

Table V

Normal Overweight P weight (BMI ≥ 25) value (BMI < 25)

Operative time (minutes) 166 ± 47 General anesthesia 41 (49) No. of anchors used for fixation 0 8 1 37 2 39 Blood transfusion 2 (3) Intraoperative complications 0

162 ± 51 18 (47)

7 14 17 1 (2) 0

.721 .883 .363

1.000

BMI, body mass index. Categorical variables are presented as number (%). Continuous variables are presented as mean ± standard deviation.

Table IV

Preoperative and postoperative clinical evaluation

Characteristics

Normal weight (BMI < 25)

Preoperative, mean ± SD Extension (°) 35 ± 18 Flexion (°) 77 ± 28 Pronation (°) 44 ± 30 Supination (°) 60 ± 35 Range of motion (°) 42 ± 29 VAS 2.5 ± 2.1 MEPS 61 ± 12 Postoperative, mean ± SD Extension (°) 9 ± 10 Flexion (°) 124 ± 15 Pronation (°) 64 ± 21 Supination (°) 77 ± 18 Range of motion (°) 115 ± 21 VAS 0.5 ± 1.2 MEPS 95 ± 7

Overweight (BMI ≥ 25)

P value

33 ± 15 77 ± 26 45 ± 29 60 ± 34 44 ± 22 2.5 ± 2.0 59 ± 10

.634 .968 .902 .912 .699 .913 .426

15 ± 11 118 ± 15 61 ± 25 71 ± 25 103 ± 20 1.2 ± 1.6 90 ± 10

.006** .030* .468 .156 .004** .019* .004**

BMI, body mass index; SD, standard deviation; MEPS, Mayo Elbow Performance Score; VAS, visual analog scale. * P < .05. ** P < .01.

To demonstrate whether BMI affected postoperative outcomes, we included BMI, age, and sex in a multivariable linear regression analysis. We found that when age and sex were controlled, a BMI increase of 1 was associated with a decrease in postoperative ROM by 2° (P = .002), postoperative MEPS by 0.73 (P = .004), and ΔROM by 2° (P = .031). Moreover, a higher BMI was not significantly related to ΔMEPS (P = .136) after controlling for demographic variables. Overall, 16 of the 122 patients (13.1%) developed postoperative complications (Table V). One patient (1.2%) in the normal weight group and 2 patients (5.3%) in the overweight group developed a postoperative wound infection, and all of them received formal débridement of the wound. Seven

The distribution of postoperative complications

Characteristics

Normal weight (BMI < 25)

Overweight (BMI ≥ 25)

P value

Total number Infection New onset or exacerbation of nerve symptoms Instability

10 1 7

6 2 4

.765 .229 .960

2

0

1.000

patients (8.3%) in the normal weight group presented with new onset or exacerbation of nerve symptoms, including 5 with ulnar nerve symptoms, 1 with medial nerve symptoms, and 1 with radial and medial nerve symptoms. In addition, 1 patient with ulnar nerve symptoms underwent reoperation for ulnar nerve decompression. Four patients (10.5%) in the overweight group developed new onset of ulnar nerve symptoms, and none of them underwent reoperation. Furthermore, in the normal weight group, 2 patients (2.4%) had elbow instability problems, including 1 with moderate instability (<10° of varus-valgus laxity) and 1 with gross instability (≥10° of varus-valgus laxity). One year after arthrolysis, the patient with gross instability underwent further surgery to reconstruct the elbow ligament. No overweight patients presented with elbow instability.

Discussion The prevalence of being overweight has become a major public health issue. A higher BMI is associated with an increased incidence of various medical comorbidities, including diabetes mellitus, cardiovascular disease, and hypertension, and it is likely to increase the risk of postoperative medical and surgical complications. Recently, the influence of being overweight and obesity on lower extremity surgery has received great attention, and several studies have proved negative effects of higher BMI on postoperative functional outcomes and complication rates.1,11,13,16,23,28 Moreover, researchers have started to study the association between being overweight/obesity and clinical outcomes after upper extremity surgery, which in turn led to conflicting conclusions. Some suggest that increased BMI is associated with inferior functional performance and increased complication rates,2,5,8,31-33 whereas others have shown no differences between different BMI levels.10,15,21 To our knowledge, our study is the first to examine the effect of being overweight on the clinical outcomes and complications after open arthrolysis in patients with post-traumatic elbow stiffness. We hypothesized that a higher BMI would negatively affect postoperative functional performance based on ROM, VAS score, MEPS, and complication rates. Furthermore, several studies showed that a higher BMI is associated with increased rates of diabetes mellitus, cardiovascular disease, and hypertension, and these comorbidities potentially influence research findings. Nevertheless, the over-

ARTICLE IN PRESS Influence of BMI on elbow arthrolysis weight group in our study showed no increase in the rates of medical comorbidities compared with the normal weight group at baseline. Moreover, researchers have examined the clinical outcomes among overweight and obese patients undergoing upper extremity surgery, including total elbow/ shoulder arthroplasty, elbow/shoulder arthroscopy, and ORIF of elbow fracture. Warrender et al31 recently reported increased operative time and average length of stay in obese patients undergoing arthroscopic rotator cuff repairs. However, London et al15 showed that no statistically significant differences in anesthesia type and duration of surgery existed between obese and nonobese groups after elbow, forearm, and hand operations. In this study, we found no differences in type of anesthesia, operative time, anchors used, and transfusion rate between the overweight and normal weight groups as well. In addition, with detailed perioperative examination, perioperative medical management, and meticulous nursing, no intraoperative complications occurred in either group. All these data showed that open arthrolysis combined with hinged external fixation is still a safe procedure for overweight patients. In our study, most of the patients gained a significant improvement in ROM, which was similar to that in previous studies.14,24,30 Several studies showed that a higher BMI negatively influenced ROM and the results of related questionnaires after upper extremity surgery.31 One study in a healthy pediatric population also demonstrated that increased BMI was negatively correlated with ROM of the elbow joint.7 Salazar et al25 reviewed the clinical records of 39 patients treated operatively for heterotopic ossification of the elbow and found that obesity adversely influenced the ROM from preoperatively to postoperatively. In this study, we demonstrated that elbow ROM of overweight patients was inferior to that of normal weight patients after elbow arthrolysis. Although the overweight group showed a remarkable improvement in ROM after surgery, 18 patients (47%) still had a ROM ≤100°, which was higher than that in the normal weight group (21%). Increased soft tissue around the elbow may be a potential mechanical reason. Similarly, although VAS scores improved significantly in both BMI groups at followup, comparison between the groups revealed that the overweight group had a significantly poorer postoperative VAS score for pain, which was consistent with previous studies.12,22 According to the MEPS, a comprehensive evaluation index, the normal weight group had a significantly higher satisfactory proportion (95%) than the overweight group (79%) postoperatively. Thus, overweight patients should be counseled preoperatively that their postoperative expectations should be tempered. Regardless of the difference between groups postoperatively, the overall trend in our study shows that elbow arthrolysis offers a significant improvement in the pain and functional performance in both BMI groups. Griffin et al8 recently reported that a higher BMI was associated with an increased incidence of local and systemic complications after total elbow arthroplasty. Werner et al32,33 also noted significantly increased rates of infection, nerve injury, and stiffness after elbow surgery in obese patients.

5 However, London et al15 demonstrated comparable complication rates between morbidly obese and nonobese patients undergoing elbow, forearm, and hand surgery. In our study, 11 patients (9.0%) developed new onset of ulnar nerve symptoms after elbow arthrolysis, and the ulnar nerve was the most commonly involved (9 cases), which was consistent with previous studies.3,4,26 Moreover, no significant differences in nerve complication rates between the normal weight and overweight cohorts were observed (8.3% vs. 10.5%). In addition, postoperative infection (3 cases) was uncommon; all cases improved after formal débridement. A systematic review involving 810 patients also reported a low overall infection rate (1.6% ± 0.9%) after elbow arthrolysis,3 which was similar to the result of our study (2.5%). We found that the overweight group had roughly quadruple the incidence (5.3%) of postoperative infection compared with the normal weight group (1.2%). However, because of the sample size, differences in infection rates between the 2 groups were not significant. Two patients with normal BMI developed elbow instability after surgery, which could be attributed to the lack of sufficient capsule and tendon overlapping the diseased elbow. This study has several limitations. First, this is a retrospective study, with all the potential drawbacks inherent in the study design, and a prospective study is required to demonstrate the effect of BMI on clinical outcomes. Second, the sample size is relatively small, and we lacked sufficient power to assess the difference in complications between groups. Moreover, in the overweight group, only 1 patient was medically classified as obese. To further explore the association between obesity or morbid obesity and postoperative rehabilitation, further studies with a larger sample size are needed.

Conclusions This study reports new data concerning the association of BMI and clinical outcomes after open arthrolysis in patients with post-traumatic elbow stiffness. Although most patients showed significant improvements after surgery, the postoperative functional outcomes of the overweight patients were inferior to those of the normal weight patients to a certain extent. Our study also showed that patients with different BMI levels had comparable postoperative complication rates. In addition, further prospective studies including a larger sample size, longer follow-up duration, and more evaluation indicators are needed to validate the results of this study further.

Disclaimer The authors, their immediate families, and any research foundations with which they are affiliated have not received any financial payments or other benefits from any commercial entity related to the subject of this article.

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W. Zheng et al.

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