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ROCHESTER, Minn., April 11 -- A simple test of ulnar fovea tenderness that led to discovery of a common type of ligament injury may ease diagnosis of unexplained wrist pain, researchers found.

A positive test was defined as exquisite pain on physical examination of the "soft spot" at the junction of the ulnar bone and hand, reported Richard A. Berger, M.D., Ph.D., of the Mayo Clinic here, and colleagues.

It indicated a lengthwise tear in the ulnotriquetral ligament or complete ligament rupture with 86.5% specificity and 95.2% sensitivity compared with wrist arthroscopy, they reported in the April issue of the American Journal of Hand Surgery.

Their case series of 272 consecutive patients is the first to describe a split-tear ligament injury, they wrote.

Dr. Berger, who has a split-tear injury himself from pushing a heavy crate down a flight of stairs, discovered the new type of ligament injury one day during arthroscopy when he poked his finger where the patient said the pain was and saw "the ligament opened up like a book."

"I'd been seeing it all along but I didn't know what I was looking at," he said, because it had never been described before.

Since then, he has discovered the injury to be the cause of 30% to 40% of ulnar-sided wrist pain in his practice, he said.

Foveal ligament disruption, in which the whole ligament complex unattaches from the ulna, is most often caused by high torque injuries from skiing or falls. Split tears may be from lower energy, repetitive torque injuries such as from bowling or golf, Dr. Berger speculated.

He and colleagues reviewed records of the 272 consecutive patients (53.7% male, median age 33.7) who underwent wrist arthroscopy from 1998 to 2003. Those with clearly abnormal wrist anatomy prior to arthroscopy were excluded.

Most patients had a history of trauma (75.4%) and the majority had ulnar-sided wrist pain (55.1%).

All patients had the ulnar fovea test results documented prior to arthroscopy. For the test, the examiner pressed his thumb into the ulnar fovea between the ulnar styloid process and flexor carpi ulnaris tendon between the volar surface of the ulnar head and pisiform with the forearm in neutral rotation.

The test was positive if the patient said it replicated the character and location of their pain compared with the test on the contralateral side.

The findings were:

• Of 156 patients (57.4%) positive for ulnar fovea tenderness, there were 139 true positives and 17 false positives for foveal disruptions or ulnotriquetral ligament injuries or both by arthroscopy.

• Of the 116 negative for ulnar fovea tenderness, arthroscopy indicated seven false negatives and 109 true negatives.

• 95.2% sensitivity of the test in detecting foveal disruptions or ulnotriquetral ligament injuries or both (95% confidence interval 90% to 98%).

• 86.5% specificity of the test in detecting foveal disruptions or ulnotriquetral ligament injuries or both (95% CI 79% to 92%).

To distinguish foveal disruption from ulnotriquetral ligament injury, the examiner checked stability of the distal radioulnar joint. Instability was defined as subjectively measured asymmetry of radius translation as the forearm is rotated.

"Ulnotriquetral ligament injuries are typically associated with a stable distal radioulnar joint and foveal disruptions are associated with an unstable distal radioulnar joint," the researchers wrote.

In the study, 40.9% of patients had joint instability and all but two of these were positive for ulnar fovea tenderness. Relatively few patients without joint instability were positive on the ulnar fovea test (30.4%). The majority of these (34 of 49) had injuries of the ulnotriquetral ligament.

The investigators briefly discussed therapy by closure of the longitudinal split tears with sutures arthroscopically.

A study of the efficacy of this approach for the relatively young patient group is ongoing. But Dr. Bergen hinted that this simple suturing approach followed by six weeks of immobilization then rehabilitation has "a very high percentage of success" for symptomatic relief whereas immobilization alone does not.

This anecdotal evidence suggests that the split tear is likely the pathology for the symptoms, though it remains unclear "why an injury like this hurts," Dr. Bergen said, except that the ligament contains nerve tissue.

The researchers said their findings only establish diagnostic utility of the test for patients symptomatic despite appropriate nonsurgical interventions, without other evidence of pathology, "for whom wrist arthroscopy would be the next logical step in the diagnostic workup," they wrote.

"This study does not establish the clinical importance" of ulnotriquetral ligament split tears, they added.

However, in Dr. Bergen's practice, "if a patient is symptomatic and has a positive fovea sign, then I'm thinking of taking them to surgery just on the basis of that sign," he said.

The researchers reported no conflicts of interest.

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