Morphological characteristics of the cubital tunnel as indication for anterior interosseous nerve supercharge end-to-side transfer in treating advanced cubital tunnel syndrome.

Background: Cubital tunnel syndrome (CuTS) is a prevalent compressive neuropathy addressed through various treatments, including the anterior interosseous nerve (AIN) supercharge end-to-side (SETS) transfer for advanced CuTS. Decision to add AIN-SETS is based on various indicators and protocols, but deciding on the appropriate method for borderline cases can be challenging. Therefore, this study aims to non-invasively examine the cubital tunnel anatomy of patients using CT scans and compare the findings with existing indicators and measurements, to determine if they can serve as supplementary indicators to aid in treatment decisions.

Hypothesis: The bony cubital tunnel volume is correlated to other traditional indicators and can be used as an additional indication for deciding whether to perform AIN-SETS in treating advanced CuTS.

Patients and methods: This is a single-center retrospective cohort study from South Korea, including 91 patients aged 20-70 years with CuTS. Participants were classified into Group A (n = 43), who underwent both cubital tunnel release (CuTR) and AIN-SETS, and Group B (n = 48), who underwent only CuTR. Preoperative elbow CT data were analyzed for cubital tunnel morphology analysis, with follow-up assessments such as grip strength and electromyography/ nerve conduction velocity (EMG/NCV) tests at 3, 6, and 12 months postoperatively.

Results: Group A and B showed no significant differences in demographic parameters, except for a longer disease duration in Group A (p = 0.032). Group A had a smaller cubital tunnel volume (CTV) compared to Group B (1150.6 ± 52.8 mm³ vs. 1173.5 ± 56.2 mm³, p = 0.014) and a smaller cross-sectional area (40.9 ± 10.2 mm² vs. 45.1 ± 11.7 mm², p = 0.033). Pearson correlation analysis revealed statistically significant positive correlations between CTV measurements and pre-operative grip strength, as well as EMG results, a key indicator for AIN-SETS (R² = 0.48, 0.23, p = 0.01).

Discussion: Measuring the cubital tunnel anatomy using CT can aid in determining the treatment approach for advanced CuTS patients and assist in deciding whether to perform AIN-SETS surgery, serving as a supplementary indicator for cases at the borderline limits of other indicators. Future research may be necessary to establish control groups without symptoms and determine appropriate cut-off values.

Level of evidence: IV.