Conway CuTS Scale Predicts Impairment Better Than Traditional Scales After Cubital Tunnel Syndrome Surgery

Chrissa McClellan, MD

A retrospective study of patients who underwent surgery for cubital tunnel syndrome (CTS) revealed that a recently developed scale, the Conway CuTS scale, has a higher sensitivity in detecting impairment levels compared with more widely used scales such as the Zeidman scale. Despite these promising findings, the authors noted that further work with larger samples is warranted to better understand the new scale’s predictive value of surgery outcomes.¹

Presented at the 2024 American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) Annual Meeting, held October 15-18, in Savannah, Georgia, the study included 52 patients who underwent surgery for CTS. Before surgery, the Conway scale was shown to be better at identifying mild impairment in patients who were considered normal on the Zeidman scale (9 cases). While the correlation between the 2 scales and the DeltaPROMIS scores wasn’t statistically significant, the Conway scale seemed to have a higher ability to predict outcomes compared with the Zeidman scale (P = 0.3 vs P = 0.6).

The newly developed Conway scale defines mild impairment as an ulnar motor nerve conduction velocity (UMNCV) across the elbow <50 m/s using the 3 cm inching technique; moderate impairment as UMNCV<50 m/s with the standard 10 cm technique; and severe impairment as UMNCV<50 m/s with the standard 10 cm technique, along with decreased amplitudes and/or EMG changes. Led by Chrissa McClellan, MD, a physical medicine and rehabilitation specialist at the University of Missouri, each patient had preoperative electrodiagnostic data, acquired with the Zeidman and Conway scales, as well as PROMIS scores.

In the study, the PROMIS scores were significantly improved through surgery, from a mean of 35.3 (SD, –8.2) to 39.6 (SD, –10.9; delta, 4.3 [SD, –10.7]; P = .006). Overall, the study authors concluded that the Conway scale may be a better method to identify impairment in this population than other previously, more traditional scales.

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CTS happens when the ulnar nerve, which passes through the cubital tunnel on the inside of the elbow, becomes inflamed, swollen, and irritated. This syndrome can occur when a person bends the elbows often, leans on their elbow a lot, or has an injury to the area. Additionally, arthritis, bone spurs, and previous fractures or dislocations of the elbow can also cause CTS. CTS is typically diagnosed through a complete medical history and physical exam; however, there are other diagnostic tests that include nerve conduction, electromyogram, and x-ray.

The Conway scale has been often used with athletes to evaluate the success of procedures like ulnar nerve transposition, taking into account factors like pain, grip strength, and ability to return to their previous activity level. A recently published 2022 study described the clinical outcomes of competitive baseball pitchers with hypertrophic sublime tubercles who underwent ulnar collateral ligament (UCL) reconstruction. The analysis, which featured 10 players, had clinical history, preoperative imaging, intraoperative findings during UCLR, and postoperative outcomes measured with the Conway scale.²

The average follow-up time was 20.4 months (range: 3–38). Three patients (patients 8, 9, and 10) were less than a year post-UCLR, so their final outcomes on the Conway scale were not yet determined. Among the remaining seven patients, six successfully returned to pitching at or above their previous level, achieving excellent outcomes on the Conway scale. One patient (patient 1) could not return to his prior level of play in minor league baseball, resulting in a fair outcome. No patients reported lingering symptoms or showed signs of instability during postoperative exams. Additionally, there were no cases of recurrent sublime tubercle hypertrophy on follow-up X-rays.

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REFERENCES
1. McClellan C, Drymalski M, Farmer H, Cirstea C, Gill B. Predicting surgical outcomes for cubital tunnel syndrome with the Conway scale: a pilot study. Presented at: 2024 AANEM meeting; October 15-18; Savannah, GA. ABSTRACT 225
2. Vaswani R, Fu MC, Dines JS, et al. Hypertrophy of the sublime tubercle in elbow ulnar collateral ligament injuries: a case series of baseball pitchers undergoing ulnar collateral ligament reconstruction with short-term follow-up. JSES Rev Rep Tech. 2022;2(4):513-519. doi:10.1016/j.xrrt.2022.06.003