Distal Radius Fractures: Does Obesity Affect Fracture Pattern, Treatment, and Functional Outcomes?

Abstract

Background: Distal radius fractures (DRFs) are 16% of fractures treated by orthopedic surgeons. Obesity’s influence on DRF complexity has not been studied. This study was undertaken to determine if body mass index (BMI) affects DRF pattern, treatment, and functional outcomes. Methods: Part 1 was a retrospective review of patients who sustained a DRF after a fall from standing height with no prior reduction or treatment. Radiographs were classified as “simple” or “complex.” Part 2 consisted of contacting patients from Part 1 and obtaining a Quick Disabilities of the Arm, Shoulder and Hand (QuickDASH) score. Retrospective review also identified patients who failed initial nonoperative treatment. Fracture pattern, failure of nonoperative treatment, and QuickDASH scores were compared with BMI at the time of injury. Results: For Part 1, 130 patients (132 wrists) were identified. Average age was 57 years, 77% were female, and average BMI was 28.2 kg/m². Each point increase in BMI increased the chance of having a complex DRF (odds ratio = 1.07). Part 2 identified 50 patients who completed a QuickDASH at an average of 4.6 years after injury. Those with a BMI <25 kg/m² (n = 15) had an average QuickDASH score of 37; patients with a BMI ≥25 kg/m² (n = 35) had an average QuickDASH score of 18. Increasing BMI was suggestive of a lower QuickDASH score (P = .08). No significant difference was found with respect to BMI and failure of nonoperative treatment. Conclusions: A higher BMI increases the odds of a complex DRF. Despite more complex fractures, overweight patients may experience less disability after sustaining a DRF.

Introduction

Distal radius fractures (DRFs) have an incidence greater than 640 000 annually in the United States.³ Current recommendations have been provided by the American Academy of Orthopaedic Surgeons but do not identify body habitus or obesity in their algorithm for treatment of DRFs.¹¹ Despite addressing many issues surrounding the treatment of this relatively common injury, the guidelines make no mention of the role obesity might play in initial evaluation or outcomes.

The incidence of obesity as documented by the Centers for Disease Control and Prevention grows annually, and the effect on patients’ health is studied in many arenas. The effects of obesity in the orthopedic literature have been variable. For example, obesity has been shown to increase the odds of suffering an ankle fracture. However, Strauss et al determined that, in ankle fractures at 2 years from injury, “the presence of obesity did not affect the incidence of complications, the time to fracture union or the level of function.”¹⁸

Obesity has been shown to convey increased risks in other orthopedic surgeries. For example, the American Association of Hip and Knee Surgeons’ work group found that patients with a body mass index (BMI) >30 kg/m² are at increased risk of perioperative complications after undergoing knee replacement surgery and that “as BMI increases (>40) . . . functional improvement becomes less and/or occurs more gradually.”²¹ Tucker et al found that antegrade femoral nailing in obese patients took much longer than nonobese patients but found that if a different technique was utilized (retrograde nailing), then the procedure could be done in a time similar to nonobese patients.¹⁹

In the hand literature, it is commonly accepted that referral for treatment of osteoporosis after DRF and pharmacologic intervention in the setting of osteoporosis does decrease risk of future fragility fractures (including DRF).^9,16 There are cross-sectional studies that have shown that obesity is protective against wrist fractures,^4,10,12-14 while others have shown that BMI does not affect incidence of wrist fractures.^7,15 Our study did not try to add to the debatable incidence of DRF as this topic has been exhaustively reviewed. This study instead delineated the characteristics of DRFs in obese patients, detected if they fail nonoperative treatment with greater frequency, and identified patient reported outcomes relative to BMI using the validated Quick Disabilities of the Arm, Shoulder and Hand (QuickDASH) score.⁸

Materials and Methods

After institutional review board approval, the medical records of all adult patients treated by the senior author (J.R.) for a DRF between 2008 and 2014 were retrospectively reviewed. To be included in the review, adult patients had to have a documented fall from standing height, be less than 1 week from the date of injury, have a BMI documented within 1 year of the injury, and have acceptable radiographs prior to receiving any treatment (ie, attempted reduction, surgery, or attempt at nonoperative treatment).

Part 1 of this study consisted of a retrospective review of the initial radiographs and medical records prior to any reduction or treatment. Fractures were then classified by the AO/OTA (Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association) system and categorized by a single observer as simple (AO group 23-A) or complex (AO group 23-B, 23-C, open fractures, or ipsilateral upper extremity fracture). The BMI of the patient was blinded during classification of the fracture; the main variable was BMI. The association of BMI and having a simple or complex fracture was evaluated using a smoothing spline and plotted to demonstrate the odds ratio (OR) as a function of BMI. Chart review also identified patients who failed initial attempts at nonoperative treatment which was usually due to a loss of reduction during immobilization.

Part 2 of this study prospectively collected QuickDASH scores after 3 attempts were made to contact the 130 patients (132 wrists) identified in Part 1 of the study. The association of BMI and QuickDASH score was then evaluated using common ranges of BMI (<18; 18-24.99 [healthy weight]; 25-29.99; 30-34.99; 35-39.99; and >40 kg/m²). The significance level was set at .05.

Results

Part 1 of the study identified 130 patients (132 wrists) who met the inclusion criteria. The average age of the cohort at injury was 57 years old (18-98 years), 77% female with an average BMI of 28.2 kg/m² (range, 14-51 kg/m²). Of the 132 wrists evaluated, 51 were classified as simple and 81 were classified as complex. When the type of fracture (simple or complex) was analyzed in comparison with BMI (Figure 1), it was found that each point increase in BMI increased the chance of having a complex DRF by an OR of 1.07 (P < .05). For example, a patient with a BMI of 35 kg/m² is at higher risk of sustaining a complex fracture compared with a patient with a BMI of 25 kg/m² by an OR of 2.11. Age was not found to be a confounding variable in this analysis. Contrary to our initial hypothesis, no statistical relationship with BMI was found to identify which patients were at increased risk of failing nonoperative treatment (16 of 132 wrists).

Figure 1.

Odds of sustaining a simple vs complex fracture.

Note. The y-axis is the percentage of patients that sustained either a simple or complex fracture. BMI = body mass index; Simple = AO group 23-A; Complex = AO group 23-B and 23-C or any open injury or ipsilateral upper extremity fracture.

Part 2 of this study resulted in contact with 50 (50 wrists) of the previously mentioned 130 patients from Part 1. Average age of those who completed the QuickDASH score was 58 years (range, 34-83 years), 82% female with an average BMI of 29.3 kg/m² (18.5-50 kg/m²). On average, patients completed the QuickDASH questionnaire 4.6 years (range, 22-73 months) after their injury. Fifteen patients with a BMI <25 kg/m² were identified with an average QuickDASH score of 37, while the 35 patients with a BMI that was ≥25 kg/m² were found to have less disability with an average QuickDASH score of 18 (Figure 2). While not statistically significant, an increasing BMI was suggestive of a lower QuickDASH score (P = .08) even when controlling for the type of fracture (simple vs complex). No difference was found in the rates of those who failed initial attempts at nonoperative treatment between the 2 groups (2 of the 15 [13%] patients with BMI ≥25 kg/m², 5 of 35 [14%] patients with BMI <25 kg/m²).

Figure 2.

Average QuickDASH score for those with a BMI < 25 kg/m² (n = 15) or ≥ 25 kg/m² (n = 35).

Note. QuickDASH = Quick Disabilities of the Arm, Shoulder and Hand; BMI = body mass index.

Discussion

DRFs as they relate to the epidemic of obesity were examined in a study by Chiu and Robinovitch on impact forces during a fall onto an outstretched hand; the study showed that greater mass intuitively resulted in greater force across the wrist at low-level falls.² Obesity appears to be protective against forearm osteopenia,⁶ and authors have furthermore proposed different mechanisms to explain the relationship between adipose and bone.^1,5,17 However, to our knowledge, there have not been any studies evaluating fracture characteristics and treatment outcomes as they relate to BMI.

This study is limited innately by its retrospective nature. Furthermore, it was underpowered to detect any factors that lead to failure of nonoperative treatment which would be useful information in clinical practice. Likewise, while the data suggest that an increasing BMI can mean less disability, there was not sufficient power to reach significance (P = .08). Another limitation of this study was the high rate of patients treated operatively (112 of the 132 wrists [85%] in Part 1, 45 of the 50 wrists [90%] in Part 2) which we believe is due to the tertiary referral setting but could also represent treatment bias. This study does not identify why an overweight patient perceives less disability compared with a healthy weight patient with the same fracture type. Activity level of the different patients may lead to their perception of disability in a way that is not fully explained with a tool like the QuickDASH score.

We also recognize that, for Part 1 of the study, we compared fracture pattern on a continuum of BMI while in Part 2 of the study, we made the somewhat arbitrary grouping of those with a BMI <25 kg/m² compared with those with a BMI of ≥25 kg/m². This design was due to the relatively low number of patients (n = 50) in Part 2 of the study. We believe that a more ideal analysis of complications would be when outcomes are compared with BMI as a continuous variable. We do not believe there is any practical recommendation that can be given to a patient with a BMI of 24.9 kg/m² (healthy weight) vs a patient with a BMI of 25.1 kg/m² (overweight).

One of the strengths of this study was the evaluation of fracture patterns in comparison with BMI as a continuous variable, specifically, the finding that every 1-point increase in BMI can result in more complex DRFs (OR = 1.07). While counseling patients to lose weight to get to a specific BMI is helpful in setting goals, it may not be the most accurate way of describing disease characteristics or the risk of complications that exist with increasing weight.

More specific risk stratification has been sought in many areas of orthopedics. A 2016 article in the hip arthroplasty literature addressed this shortcoming in traditional reporting when they evaluated the “risk of complications and implant survival according to BMI as a continuous variable.”²⁰ In that study, they used a BMI range of 27 to 32 kg/m² as a reference because of the stable rate of implant revision or removal and were then able to identify “a 3% increased risk of implant revision or removal per unit of BMI for a BMI of >32 kg/m² (HR, 1.03; p=0.002).” Such data will allow clinicians to provide more accurate assessment of risk to patients and may also be tied to reimbursement and/or insurance premiums.

In conclusion, we were unable to identify BMI as a risk factor for failing nonoperative treatment. Our data suggest that an increasing BMI may result in less perceived disability. Finally, while it may not change clinical practice, it is notable that increasing BMI does lead to more complex DRFs.