Intraoperative measurement of pressure adjacent to the ulnar nerve in patients with cubital tunnel syndrome

Purpose: Little is known about whether the pressure adjacent to the ulnar nerve actually is increased in patients with cubital tunnel syndrome or if it is a causative factor. We measured the pressure adjacent to the ulnar nerve in patients with cubital tunnel syndrome during surgery and verified whether or not there was an association with patient age, duration of the disease, motor nerve conduction velocity, and severity of the ulnar nerve neuropathy. Methods: Eight elbows in 8 patients with an average age of 62 years were treated surgically and the extraneural pressures within the cubital tunnel were measured during surgery by using a fiberoptic microtransducer. Pressure was measured 3 times with the elbow fully extended and then 3 times with the elbow flexed 130 degrees. The transducers were placed at 1, 2, and 3 cm distal to the proximal edge of the Osborne ligament. The severity of the neuropathy was evaluated according to Akahori's classification. The ulnar nerve palsy was graded as stage III in 5 patients and as stage IV in 3 patients. Results: The average pressures within the cubital tunnel at 1, 2, and 3 cm distal to the proximal edge of the cubital tunnel retinaculum with the elbow flexed were 105, 29, and 18 mm Hg, respectively. The pressures at I and 2 cm distal to the proximal edge of the cubital tunnel retinaculum were significantly higher in elbow flexion than in elbow extension. There was also a positive correlation between the pressure and patient age but this was not significant The pressures correlated significantly with the stage of ulnar nerve neuropathy, motor nerve conduction velocity, and disease duration Conclusions: The extraneural pressure within the cubital tunnel actually was increased in the patients and compression of the ulnar nerve might be a causative factor of cubital tunnel syndrome.