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

BACKGROUND

Morphologic 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.

METHODS

We 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.

RESULTS

Humeral osteophytes and osteophyte proportion within the cubital tunnel were larger at full flexion (24.7 mm(2) and 49.9% in group A; 18.7 mm(2) and 39% in group B) and 90° of elbow flexion (20.3 mm(2) and 45.3% in group A; 10.2 mm(2) and 30.2% in group B) than at full extension (9.0 mm(2) and 31.3% in group A; 2.3 mm(2) 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.

CONCLUSIONS

The 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.