A Retrospective Cohort Analysis and Review of the Literature

• Updated on: 2018-04-03
• Read original article here

Arm wrestling can result in significant injuries such as fractures to the humeral shaft, medial epicondyle of the humerus, radius, and scapular neck and nonfracture injuries such as rupture of the subscapularis tendon. Although the incidence of these fractures is likely underreported in the literature, arm wrestling has gained popularity in the United States, with major networks televising competitions. Although a variety of injuries can occur, the most commonly sustained is the humeral shaft fracture. As early as 1905, Ashhurst reported on 23 cases of these types of fractures. Since then, injuries sustained by this mechanism have been reported worldwide. However, only 2 studies with a total of 12 patients from the United States have been published. Furthermore, although there have been several biomechanical studies describing the mechanism behind this fracture pattern, little has been reported on clinical and radiographic outcomes.

The current study aimed to (1) characterize a series of consecutive humeral shaft fractures that occurred secondary to arm wrestling and (2) compare clinical and radiographic outcomes of these patients with those of other patients with a similar fracture pattern but a different injury mechanism following a similar treatment protocol.

This study received institutional review board approval. The authors retrospectively reviewed a prospectively collected humeral shaft fracture database maintained by their institution for the period 2009 to 2017. During this period, 93 patients presented to their clinic with an acute closed humeral shaft fracture. All patients were initially managed with a coaptation splint and converted to a Sarmiento functional brace at 2 weeks after injury (Figure 1). All patients presenting with a closed, isolated, low-energy humeral shaft fracture were treated using a similar algorithm, which included close clinical follow-up and physiotherapy for elbow and shoulder range of motion with active biceps and triceps strengthening. At each follow-up visit, the fracture site was evaluated for mobility and the level of pain was recorded. Radiographs, including anteroposterior and transthoracic lateral of the humerus, were obtained to assess for fracture union, which was determined by the presence of bridging callus and loss of the fracture line. Nine (10%) of the patients had sustained their fractures secondary to torsional failure of bone during an arm wrestling match (AW group) (Figure 2). The clinical and radiographic outcomes of these 9 patients were compared with those of the 84 non-arm wrestling patients who sustained their fractures through other means, most commonly low-energy falls, and were also treated nonoperatively (NAW group) (Figure 3). Patient with a fracture sustained while arm wrestling. Anteroposterior (A, C) and lateral (B, D) radiographs obtained at initial presentation (A, B) and at final follow-up (C, D). Patient with a fracture not sustained while arm wrestling. Anteroposterior (A, C) and lateral (B, D) radiographs at initial presentation (A, B) and at final follow-up (C, D). At each follow-up visit, the shoulder and elbow of the affected extremity were assessed for range of motion and these values were recorded. At the final follow-up visit, the degree of angulation of the humerus, as seen on both anteroposterior and lateral radiographs, was recorded. These results were then compared with those of the 84 patients who sustained humeral shaft fractures that were also managed nonoperatively. A Student's t test was used to compare the cohorts.

The mean age of the 9 AW patients was 31.62±5.75 years. They had a mean body mass index of 26.59±9.53 kg/m. The patients were followed for a mean of 20.4 weeks (range, 12–52 weeks). Although 2 of the patients reported a history of smoking cigarettes, none of the patients reported that they were currently using tobacco products. Fractures occurred in the dominant arm of 6 patients (66.7%). Fracture type was assessed as external rotation spiral pattern occurring in the distal portion of the humerus in all cases (Figure 1). One patient (11.1%) presented with a radial nerve palsy. No other neurovascular complications were observed. The AW patients' fractures were classified as healed at a mean of 13.6 weeks (range, 10–20 weeks) (95% confidence interval [CI], 11.5–15.6). With the use of the most recent radiographs available, the mean angulation was 15.1° (95% CI, 12.0°–18.2°) on the anteroposterior view and 8.9° (95% CI, 3.7°–14.1°) on the lateral view. At the patient's final follow-up visit, the flexion–extension arcs of the elbow and the shoulder were recorded. The mean elbow flexion was 141.1° (95% CI, 134.4°–147.8°), and the mean shoulder forward elevation was 168.8° (95% CI, 153.3°–184.2°). In the NAW group, patients were followed for a mean of 36.1 weeks (range, 8–64 weeks). The mean age at presentation was 48.12±19.73 years, which was significantly higher than that of the AW group (P=.01). The mean body mass index of 25.56±6.06 kg/m was not significantly different from that of the AW group (P=.52). Within this group, 9 patients used tobacco products on a regular basis and 11 patients reported a history of using tobacco products. Seven patients (8.3%) in this cohort presented with a radial nerve palsy. The mean time to union was 18.4 weeks (95% CI, 16.8–20.1), which was 5 weeks longer than in the AW group (P=.05). At the final follow-up visit, the mean forward elevation was 155.3° (95% CI, 147.9°–162.6°) and the mean elbow flexion was 133.0° (95% CI, 127.8°–138.2°). On radiographic examination, these patients had a mean angulation of 12.8° (95% CI, 10.9°–14.7°) on the anteroposterior view and 8.8° (95% CI, 7.17°–10.4°) on the lateral view. On comparison of these clinical results between the AW group and the NAW group, no significant differences were seen for forward elevation, elbow flexion, anteroposterior angulation, and lateral angulation (P=.26, .85, .90, and .50, respectively) (Table).

The authors investigated the outcomes of patients with humeral shaft fractures sustained while arm wrestling and compared these patients with patients with all other humeral shaft fractures managed nonoperatively. Their analysis indicates that these patients have similar range of motion and radiographic changes after nonsurgical management. Furthermore, AW patients had shorter times to radiographic union than NAW patients. This difference may be the result of AW patients being significantly younger and sustaining less soft tissue damage because of the spiral nature of the fracture and the rotational mechanism of injury. In adults, fractures sustained from arm wrestling that have been reported have been uniformly spiral. The fracture has been reported to be located at the junction of the middle and lower third or the lower third in 83% of cases, the middle third in 16% of cases, and the upper third in only 1% of cases. The current study had similar results, with all of the fractures occurring in the distal portion of the humerus. Radial nerve palsy occurred in 1 (11.1%) of the current patients and in 10% to 23% of the cases in the literature. Several studies have attempted to explain this fracture pattern based on humerus morphology. Pedrazzini et al attributed the characteristic fracture site to an unfavorable ratio of the inner-to-outer diameter and a low mineral density in the distal third of the bone. Similarly, Marks et al suggested that the spiral structure of the humerus combined with the rotational nature of the sport account for the characteristic fracture pattern. Kruczynski et al used the finite element method to show that the forces generated by the acting muscles predominately exert stress on this distal portion of the bone 11.5 cm above the elbow on the medial–posterior side. In children, the resulting injury is an avulsion of the medial epicondyle, which can be attributed to a weak point in the humerus created by the growth plate. Thus, the structure of the humerus explains the fracture location but not the mechanism of injury. Most of these fractures have been reported to occur in males, with only 9 cases involving females appearing in the literature and 2 additional cases involving females reported in the current study. As both the literature and the current study have shown, the fractures are not a result of the isometric tension generated by the muscles because they may occur in females, the elderly, and children. Thus, intrinsic muscle torsion alone does not adequately explain the injury. Instead, these factors combined with the forces generated by the opponent better describe the mechanism of injury. The moment of fracture occurs as the participant is attempting to counteract the increased force of external rotation on his or her arm generated by the opponent. To achieve this, a strong internal rotation is generated at the shoulder by the pectoralis major, latissimus dorsi, teres major, and subscapularis. Creating this strong opposing force with the elbow fixed augments the eccentric contraction from the force generated by the opponent acting on the humerus as a lever arm. Because of the mechanical properties of the bone discussed above, this leads to a rotational failure of the mid to distal portion of the humerus, causing the fracture. Similar injuries due to rotational failure have been reported as a result of a throwing motion. These torsional injuries have been associated with throwing javelins, baseballs, and hand grenades. In these cases, the pattern of injury was similarly a spiral fracture located in the distal one-third of the humerus. One limitation of this study was that it lacked a functional scoring tool such as the Disabilities of the Arm, Shoulder and Hand score, which would have allowed for a more complete assessment. Nevertheless, this study represents the first to report on both the clinical and the radiographic outcomes following this type of musculoskeletal trauma. Furthermore, this investigation represents the first instance in which the outcomes of these patients were compared with those of other patients with humeral shaft fractures. Outcomes following nonoperative management of this injury were good in every patient the authors encountered. Even for patients with displaced fractures or butterfly fragments, the use of a closed reduction with a functional brace achieved union in all cases. Although there was an increased angulation of the humerus on both the anteroposterior and the lateral views, the range of motion of the elbow and the shoulder returned to normal values. Furthermore, these outcomes did not differ from those of patients who sustained humeral shaft fractures by other mechanisms. These results indicate that operative management of these types of fractures is not indicated, regardless of position of fracture and high-energy mechanism of injury.

Fractures sustained while arm wrestling are typically spiral type fractures in the distal portion of the humerus. These injuries are the result of a rotational failure of the humerus when attempting to counteract eccentric external rotation of the arm with internal rotation. This oppositional contraction, compounded by the spiral nature of the bone and weaker distal third, makes the humerus prone to spiral fractures in this area. Favorable radiographic and clinical outcomes are to be expected with nonoperative management. Although some angulation of the humerus on both the anteroposterior and the lateral views is to be expected, generally no loss of motion occurs in the elbow and the shoulder. Furthermore, these types of fractures heal quicker than fractures of the humeral shaft sustained by other mechanisms and have comparable outcomes.