Medial elbow stability assessment after ultrasound-guided ulnar collateral ligament transection in a cadaveric model: ultrasound versus stress radiography

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Background

The ulnar collateral ligament (UCL), consisting of 3 bundles, is the primary medial restraint in the elbow. Recent research has demonstrated that ultrasound is an effective modality to evaluate the medial elbow, whereas stress radiography is standard practice in the measurement of medial elbow laxity. This study (1) compared dynamic ultrasound (USD) with stress radiography in the evaluation of UCL insufficiency and (2) further evaluated the contribution of the anterior bundle of the UCL to medial elbow stability.

Methods

Stress radiographs and USD were used to obtain coronal plane measurements of the medial joint space of 16 cadaveric elbows before and after USD-guided isolated transection of the anterior bundle of the UCL. Measurements were performed with and without a valgus stress applied to the elbows, and gapping of the ulnohumeral joint space was documented.

Results

Transection of the anterior bundle of the UCL resulted in 1.5 mm and 1.7 mm of additional gapping in the ulnohumeral joint as measured with stress radiographs and USD, respectively. No differences were recorded in the ulnohumeral gapping measurements between stress radiography and USD.

Conclusions

The lack of difference between measurements reveals USD is as reliable as stress radiography in evaluating the medial ulnohumeral joint space and continuity of the UCL while eliminating radiation exposure and minimizing cost of the diagnostic examination. The increase in ulnohumeral gapping with isolated transection of the anterior bundle of the UCL demonstrates its significant contribution to medial elbow stability.

Section snippets

Specimens

The study evaluated 8 paired (16 total), fresh frozen cadaveric upper extremity specimens, extending from the first rib to the finger tips, based on an a priori power analysis calculation (2 tailed, 1 − β = 0.80 and α = 0.05) to detect a significant difference between 2 imaging modalities, USD and XR. The specimens were stored at −20°C and thawed to room temperature before use. The donors were a mean age of 77.0 years (range, 68-85 years) at the time of death, and arm dominance was not

Results

Means and standard deviations of the XR and US measurements for NS, ST, Cut, stress opening, cut opening, and UCL transection stress difference are presented in Table I. Significant differences were observed between XR and USD in NS (t15 = −5.90, P < .001), ST (t15 = −4.47, P < .001), and cut (t15 = −3.15, P = .007). There was no difference between the XR and USD measurements in stress opening (U = 108.0, P = .451), in which the average stress opening was 1.6 mm when using both imaging

Discussion

Despite advances in prevention and treatment of elbow injuries in throwing athletes, the incidence and disability due to these injuries continues to rise.11, 29 Surgical treatments have proven to be reliable over time, but the decision to operate or not operate on an injured athlete remains difficult. Precise evaluation of the structural integrity of the UCL ligament is central to the process. XR and USD have both been successfully used to evaluate the UCL, although no studies to date have

Conclusion

There were no significant differences between XR and USD in the evaluation of medial elbow laxity in this cadaveric study. These findings support the use of USD as a preferred method of evaluation of medial elbow instability in the throwing athlete. USD gives a fast, comprehensive evaluation of the UCL in both static and dynamic states while minimizing cost and eliminating radiation exposure to the patient. Isolated sectioning of the anterior bundle of the UCL resulted in 1.7 mm of increased

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.

Acknowledgments

The authors thank Drew Skidmore for his assistance with data collection.

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