From 2005 to 2010, 62 patients (25 male and 38 female patients) with a mean age of 56 years (range, 40–82 years) with clinical and electrophysiological evidence of ulnar nerve entrapment were included in this study. The mean duration of symptoms before surgery was 17 months (range, 4–48 months). The right side was involved in 39 patients and the left in 23. The dominant side was affected in 2 patients.

The patients had persistent pain and progressive motor and sensory deficits, despite conservative treatment. All the patients had persistent pain and progressive numbness radiating along the ulnar aspect of the forearm to the little and ring fingers. Tinel’s sign at the elbow was also present in all the patients. Some patients presented with weakness or atrophy of the flexor carpi ulnaris and flexor digiti minimi profundus. Significant cervical spine and shoulder diseases were excluded by clinical examination and magnetic resonance imaging (MRI), as necessary. Patients with serious acute forearm injury and brachial plexus injury were also excluded from the study. All the patients were carefully examined clinically by the authors, and were diagnosed with cubital tunnel syndrome by electrodiagnostic testing and ultrasonography.

To avoid inter-observer bias, ultrasonographic examination of the ulnar nerve in all patients was performed by the same radiologist (who is well trained in ultrasonographic studies of the peripheral nerves in the arm), who was blinded to the clinical and electrodiagnostic data.

Ultrasonography was performed with a Philips iU 22 scanner (Eindhoven, The Netherlands) and a 7–12 MHz linear array transducer. Ultrasonographic examinations of the ulnar nerve were carried out in the region of the cubital tunnel at the level of the medial epicondyle. Measurements were repeated at 2 cm proximal to the medial epicondyle of the humerus to 2 cm distal to the epicondyle, where the nerve entered the flexor carpi ulnaris muscle, both with the elbow in full extension and in full flexion at 90°. The diameter of the ulnar nerve was determined within the echogenic rim surrounding the nerve as described before [6–8]. The maximal diameter of the ulnar nerve (MDU) was measured in longitudinal views (Fig. 1) and the range of the hypoechoic area around the nerve was also observed (Fig. 1). The cross-sectional area (CSA) was also measured on transverse scans by drawing a best-fitting ellipsoid over the ulnar nerve (Fig. 2).

All of the procedures were performed by the corresponding author, Professor Doctor Wenchuan Zhang. The technique originally described by Eaton et al. [13] was utilized in all patients. All the anterior subcutaneous transposition procedures were performed under brachial plexus block and a tourniquet was placed high on the brachium. The medial epicondyle is marked as a reference point on the elbow, which is flexed to 45°. At a point 1 to 1.5 cm anterior to the medial epicondyle, a second mark is made to indicate where the fascial sling will be sutured to the deep dermis, because once the incision is made the skin retracts, distorting the reference points. A curvilinear 10-cm incision is made midway between the epicondyle and the olecranon, along the sulcus for the ulnar nerve. The skin, with superficial and deep fascia, is cut. In the deep layer of subcutaneous tissue, one or more branches of the medial brachial and antebrachial cutaneous nerves are variably located, and they must be preserved during the blunt dissection. The ulnar nerve is readily palpable proximal to the cubital tunnel, where it lies posterior to the medial intermuscular septum. After the cubital tunnel was dissected, five common entrapment sites, including the arcade of Struthers, the medial intermuscular septum, Osborne’s ligament, and the fascial origins of the flexor digitorum superficialis and flexor carpi ulnaris (FCU), were decompressed [4], and then the ulnar nerve was identified in the arm.

Wherever possible, concomitant vessels and branches of the ulnar nerve were preserved [5]. As the nerve is dissected distally, care must be taken to retain the accompanying longitudinal venae comitantes, thereby preserving critical longitudinal blood supply to the nerve, especially since certain small segmental vessels must be sacrificed to allow for anterior transposition of the nerve. The isolated ulnar nerve was transposed underneath the subcutaneous tissue. Finally, a fascial relaxing suture was used to make a subcutaneous bed for the nerve, and the skin was closed successively with 3-0 nonabsorbable sutures.