Associations between ulnar nerve strain and accompanying conditions in patients with cubital tunnel syndrome

Pathophysiology of cubital tunnel syndrome (CubTS) is still controversial. Ulnar nerve strain at the elbow was measured intraoperatively in 13 patients with CubTS before simple decompression. The patients were divided into three groups according to their accompanying conditions: compression/adhesion, idiopathic, and relaxation groups. The mean ulnar nerve strain was 43.5 ± 30.0%, 25.5 ± 14.8%, and 9.0 ± 5.0% in the compression/adhesion, idiopathic, and relaxation groups respectively. The mean ulnar nerve strains in patients with McGowan's classification grades I, II, and III were 18.0 ± 4.2%, 27.1 ± 22.7%, and 33.7 ± 24.7%, respectively. The Jonckheere-Terpstra test showed that there were significant reductions in the ulnar nerve strain among the first three groups, but not in the three groups according to McGowan's classification. Our results suggest that the pathophysiology, not disease severity, of CubTS may be explained at least in part by the presence of ulnar nerve strain.