Can elbow extension be used as a test of clinically significant injury?

ABSTRACT

Background. The objective of this study was to evaluate whether a simple test of full elbow extension was a reliable indicator of bone/joint injury at the elbow joint.

Methods. In this prospective study, patients with acute elbow injuries were asked to fully extend the injured elbow. Radiologists blinded to the results of the extension test interpreted the radiographs.

Results. Of 114 patients with acute elbow injury entered into the study, 110 underwent radiographic evaluation. Inability to extend the elbow was found in 37 of 38 patients with bone injury. Only 1 of 54 patients who were able to fully extend the elbow was found to have bone/joint injury. The sensitivity and specificity of the elbow-extension test for identification of bone/joint injury was 97% and 69%, respectively.

Conclusions. The elbow-extension test can be used as a sensitive clinical screening test for patients with acute elbow injuries.

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IN THE CURRENT CLIMATE of managed care and rationing of health care resources, several studies have been undertaken in an attempt to reduce the number of radiologic tests used to evaluate bone injuries of various anatomic sites. (1, 2) Rules for making clinical decisions, such as the Ottawa ankle and knee rules, have been validated in clinical practice and have led to a decrease in unnecessary radiographs. (3, 4) To date, only 1 published report has studied a patient's ability to extend the injured elbow as an indicator of the presence or absence of significant injury. (5) Since most of the patients in that study were less than 20 years old, the applicability of the elbow-extension test to the adult population remains unclear. The objective of this study was to analyze whether the elbow-extension test could be used as a sensitive screening test in determining bone/joint injury at the elbow joint.

MATERIALS AND METHODS

This prospective study was conducted from December 1, 1996, to November 30, 1997, in an urban emergency department (ED) with an annual census of 48,000 patients. The department supports a fully accredited emergency medicine residency program, and the hospital serves as the primary teaching hospital for the medical school. The study site's institutional review board approved the study.

All patients over the age of 14 years presenting to the ED with an acute (less than 24 hours old) elbow injury were included in the study. Patients with altered mental status due to concomitant central nervous system injury or drug intoxication were excluded from the study. During the clinical evaluation, the examining physician completed a brief study data sheet and assessed the seated patient's ability to actively extend and lock the injured elbow with the arm in a supine position. The inability to actively extend the elbow fully was defined as a positive test. A comparison test on the unaffected elbow was done in patients with a positive test. Information collected on the data sheet included the mechanism of injury and the perceived need for radiographs, in addition to the results of the elbow-extension test. The data sheet was completed before obtaining radiographs; the need for radiographs was left to the discretion of the examining physician.

The examining physician interpreted the radiographs. The official radiology reading was done by an attending radiologist blinded to all clinical information, including the results of the elbow-extension test; this official reading was used to determine the presence or absence of bone/joint injury. Bone/joint injury was defined as a fracture, dislocation, or joint effusion; joint effusions were included because they have been associated with occult bone injuries. (6,7)

Information from the data sheets was compared with the official radiology reading. Sensitivity, specificity, and positive and negative predictive values, along with their 95% confidence intervals (CI), were calculated for the elbow-extension test. (8)

RESULTS

During the study period, 114 patients with acute elbow injuries were enrolled in the study. Review of ED logs did not identify any patients with a primary complaint of elbow injury who were not enrolled. No victims of multiple trauma were enrolled. There were 53 males and 61 females, with a mean age of 37 years (range, 16 to 76 years). All 114 patients had study data forms completed; 110 patients had elbow radiographs done. The patients in the study population presented between 30 minutes and 22.5 hours after the injury occurred (median, 3.75 hours after injury). The 4 patients who did not have radiographs done were excluded from analysis; however, all 4 were able to fully extend the injured elbow, and chart review failed to identify subsequent ED or clinic visits for elbow pain.

Bone/joint injury was identified in 38 patients (Table 1). Mechanisms of injury for these patients included direct blow (30 patients), hyperextension (7 patients), and crush injury (1 patient). There were no discrepancies between the preliminary ED reading and the final radiology reading.

The clinical performance of the elbow-extension test is shown in Table 2. The single false-negative test (patient with a bone injury who could fully extend the elbow) occurred in a patient with a nondisplaced radial-head fracture.

DISCUSSION

This study was designed to evaluate whether radiographically significant elbow injuries could be predicted based on the patient's ability to fully extend the affected elbow. The test was easy to perform in the ED and proved to be sensitive, though not specific in predicting bone injury. In this study's adult population, our sensitivity of 97.3% and specificity of 69.4% were similar to the findings of Hawksworth and Freeland, (5) who reported a sensitivity of 90.7% and a specificity of 69.5%.

The most clinically useful findings of this study were the high sensitivity and negative predictive values. Given a 35% prevalence of bone injury, it appears that plain radiographs of the elbow can be safely deferred in patients who are able to fully extend the injured elbow. Since one of our patients with a nondisplaced radial-head fracture was able to fully extend, it may be prudent to carefully examine the radial head and consider radiographs in patients with an appropriate mechanism for this injury, even if they can fully extend the elbow.

Use of the elbow-extension test to exclude the need for radiographs in our study population would have reduced radiographic evaluation by nearly 50%. If our findings can be validated in other settings, the potential savings would be substantial.

Limitations of this study included a relatively small sample size and the failure to obtain radiographs on every patient. The 4 patients who did not have imaging presented less than 4 hours after injury. It is possible that hemarthrosis could have developed later in these and other early presenters; whether the development of delayed hemarthrosis would convert some negative tests to positive cannot be determined by this study. This study did not determine whether the inability to fully extend was due to highly developed arm-flexor musculature, as might be seen in trained athletes, nor did the study address the issue of patient expectations regarding the performance of radiographs.

The presumption that a joint effusion in the setting of acute injury indicates chondral or osteochondral injury is widely accepted but not invariably correct. (9) It is possible that patients with underlying diseases causing elbow effusions (such as rheumatoid arthritis) were included in the study population. These patients might bias the results.

Future studies should apply the elbow-extension test prospectively and follow the clinical course of patients who did not undergo radiographs to determine whether significant injuries are missed. Patient satisfaction assessments to determine acceptability of this approach would be useful.

CONCLUSIONS

The elbow-extension test can be used as a sensitive clinical screening test for patients with acute elbow injuries. The elbow-extension test may allow clinicians to forego ordering plain radiographs in adult patients with acute elbow injuries. Patients who can fully extend the affected elbow may be safely treated without the aid of plain radiographs.

TABLE 1.

Types of Elbow Injury

Injury                 No. of Patients

Olecranon fracture            6
Coronoid fracture             5
Radial-head fracture         17
Capitellum fracture           3
Epicondyle fracture           1
Posterior dislocation         2
Joint effusion                4

  Total                      38
TABLE 2

Clinical Performance of the Elbow-Extension Test

                      Bone Injury          No Bone Injury

Unable to Extend           37                    22
 (positive test)
Able to Extend             1                     50
 (negative test)
                  Sensitivity = 97.3%   Specificity = 69.4%
                  (95% CI = 84.6-99.9)  (95% CI = 57.3-79.5)
                  PPV = 62.7%           NPV = 98.0%
                  (95% CI = 49.1-74.7)  (95% CI = 88.2-99.9)

CI = Confidence interval,

PPV = positive predictive value,

NPV = negative predictive value.

References

(1.) Gleadhill DNS, Thomson JY, Simms P: Can more efficient use be made of x-ray examinations in the accident and emergency department? BMJ 1987; 294:943-947

(2.) McConnochie KM, Roghmann KJ, Pasternack J, et al: Prediction rules for selective radiographic assessment of extremity injuries in children and adolescents. Pediatrics 1990; 86:45-57

(3.) Stiell IG, McKnight RD, Greenberg OH, et al: Implementation of the Ottawa ankle rules. JAMA 1994; 271:827-832

(4.) Stiell IG, wells GA, Hoag RH, et al: Implementation of the Ottawa knee rule for the use of radiography in acute knee injuries. JAMA 1997; 278:2075-2079

(5.) Hawksworth CRE, Freeland P: Inability to fully extend the injured elbow: an indicator of significant injury. Arch Emerg Med 1991; 8:253-256

(6.) Manns RA, Lee JR: Critical evaluation of the radial-head capitellum view in acute elbow with an effusion. Clin Radiol 1990; 42:433-436

(7.) Alexander JE, Holder JC: Fat pad signs in the diagnosis of subtle fractures. Am Fam Physician 1988; 37:93-102

(8.) Fenn Buderer NM: Statistical methodology: incorporating the prevalence of disease into the sample size calculation for sensitivity and specificity. Acad Emerg Med 1996; 3:895-899

(9.) Murphy WA, Siegel MJ: Elbow fat pads with new signs extended differential diagnosis. Radiology 1977; 124:659-665

RELATED ARTICLE: KEY POINTS

* Patients who can fully extend and lock an acutely injured elbow with the arm in supination are unlikely to have radiographic evidence of elbow injury.

* The elbow-extension test may be less reliable in patients with radial-head fractures.

* This study did not assess the reliability for the test in patients with multiple injuries.

From the Department of Emergency Medicine, University of Missouri-Kansas City School of Medicine, Truman Medical Center, Kansas City, Mo.

Reprint requests to Robert A. Schwab, MD, Truman Medical Center, Department of Emergency Medicine, 2301 Holmes St, Kansas City, MO 64108.