The double crush syndrome: a common occurrence in cyclists with ulnar nerve neuropathy-a case-control study.

OBJECTIVE: To evaluate the incidence of double crush syndrome in the upper limbs of cyclists with clinical diagnosis of ulnar nerve neuropathy.
DESIGN: Case-control study.
SETTING: Outpatient clinics and university setting. PARTICIPANTS: Consecutive sampling of 70 cyclists (140 upper limbs) with a mean age of 36 years (+/-11.3). Seventy-two upper limbs were excluded, leaving 40 upper limbs with a clinical diagnosis of ulnar nerve neuropathy [ULNN (+)] and 28 without symptoms of ulnar nerve neuropathy [ULNN (-)]. ASSESSMENT: Cyclists were examined clinically for the presence of proximal dysfunction using the following testing (independent variables): (1) thoracic outlet syndrome provocation testing: elevated arm stress test and modified Cyriax release test; (2) presence of an elevated first rib: cervical rotation lateral flexion test; and (3) presence of proximal symptoms: reports of neck pain and shoulder pain. MAIN OUTCOME MEASUREMENTS: The upper limbs of cyclists were categorized into 2 groups (dependent variable)-ULNN (+) and ULNN (-)-based on history, symptoms, motor, sensory, and provocative clinical testing.
RESULTS: A significantly greater number of upper limbs of cyclists with ULNN (+) presented with positive provocative testing for thoracic outlet syndrome (elevated arm stress test P = 0.005; modified Cyriax release test P = 0.002) than did the upper limbs of cyclists with ULNN (-). The likelihood for the presence of neck pain, shoulder pain, and an elevated first rib was 3, 5, and 12 times greater, respectively, in the ULNN (+) than the ULNN (-) group.
CONCLUSION: A statistically significant greater number of the upper limbs of cyclists with clinical diagnosis of ulnar nerve neuropathy presented with proximal dysfunctions suggestive of double crush syndrome.