Factors Influencing Outcomes after Ulnar Nerve Stability-Based Surgery for Cubital Tunnel Syndrome: A Prospective Cohort Study

Abstract

Purpose: Simple decompression of the ulnar nerve has outcomes similar to anterior transposition for cubital tunnel syndrome; however, there is no consensus on the proper technique for patients with an unstable ulnar nerve. We hypothesized that 1) simple decompression or anterior ulnar nerve transposition, depending on nerve stability, would be effective for cubital tunnel syndrome and that 2) there would be determining factors of the clinical outcome at two years.

Materials and methods: Forty-one patients with cubital tunnel syndrome underwent simple decompression (n=30) or anterior transposition (n=11) according to an assessment of intra-operative ulnar nerve stability. Clinical outcome was assessed using grip and pinch strength, two-point discrimination, the mean of the disabilities of arm, shoulder, and hand (DASH) survey, and the modified Bishop Scale.

Results: Preoperatively, two patients were rated as mild, another 20 as moderate, and the remaining 19 as severe according to the Dellon Scale. At 2 years after operation, mean grip/pinch strength increased significantly from 19.4/3.2 kg to 31.1/4.1 kg, respectively. Two-point discrimination improved from 6.0 mm to 3.2 mm. The DASH score improved from 31.0 to 14.5. All but one patient scored good or excellent according to the modified Bishop Scale. Correlations were found between the DASH score at two years and age, pre-operative grip strength, and two-point discrimination.

Conclusion: An ulnar nerve stability-based approach to surgery selection for cubital tunnel syndrome was effective based on 2-year follow-up data. Older age, worse preoperative grip strength, and worse two-point discrimination were associated with worse outcomes at 2 years.

Keywords: Cubital tunnel syndrome; anterior transposition; prognostic factor; simple decompression; ulnar nerve stability-based surgery.

Fig. 1. While viewing the proximal compressing structures of the ulnar nerve using a long nasal speculum, the brachial fascia and arcade of Struthers (^*) were released under direct visualization.

Fig. 2. After releasing Osborne's ligament, a distal cavity was created between the subcutaneous tissue and Osborne's fascia. A short nasal speculum was introduced to clearly visualize Osborne's fascia and the deep flexor pronator aponeurosis.

Fig. 3. If the ulnar nerve was considered unstable, the nerve was transposed anteriorly, and a fascial sling raised from the underlying muscle fascia was created to prevent slippage of the nerve after transposition.