The association between cubital tunnel morphology and ulnar neuropathy in patients with elbow osteoarthritis

BackgroundMorphologic changes in the cubital tunnel during elbow motion in patients with elbow osteoarthritis have not been examined in vivo. We examined changes in cubital tunnel morphology during elbow motion and characteristics of medial osteophyte development to elucidate whether cubital tunnel area and medial osteophyte size are factors contributing to cubital tunnel syndrome in patients with elbow osteoarthritis.MethodsWe performed computed tomography of 13 primary osteoarthritic elbows in patients with cubital tunnel syndrome (group A) and 25 primary osteoarthritic elbows in patients without cubital tunnel syndrome (group B) at full extension, 90° of flexion, and full flexion. Cubital tunnel area, humeral and ulnar osteophyte area, and proportion of osteophytes within the cubital tunnel were analyzed at each position.ResultsHumeral osteophytes and osteophyte proportion within the cubital tunnel were larger at full flexion (24.7 mm2 and 49.9% in group A; 18.7 mm2 and 39% in group B) and 90° of elbow flexion (20.3 mm2 and 45.3% in group A; 10.2 mm2 and 30.2% in group B) than at full extension (9.0 mm2 and 31.3% in group A; 2.3 mm2 and 12.5% in group B). These parameters were significantly greater in group A than in group B at full extension and 90° of flexion.ConclusionsThe effect of medial osteophytes on the ulnar nerve, especially on the humeral side, rather than narrowing of the cubital tunnel, may be a causative factor for cubital tunnel syndrome with elbow osteoarthritis.