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Introduction:

The proximal interphalangeal joint of the finger is swollen either on one or both sides when the joint is sprained or dislocated. The cause of this swelling is not known anatomically. We studied the collateral ligaments with ultrasonography to determine if the collateral ligaments are enlarged in thickness.

Materials & Methods

30 cases of proximal interphalangeal joint injury were examined with ultrasound and collateral ligament thickness was measured. 100 healthy digits with no history of trauma or other pathology affecting the interphalangeal joint were examined to measure the collateral ligament thickness. Sonosite Edge II was used for the sonographic evaluation and measurement of the collateral ligament of the healthy and injured digits. Exclusion criteria was presence of - rheumatoid arthritis, gout, Diabetes and infection.

Results

Collateral ligaments of proximal interphalangeal joint of injured digit were twice as thick as the contralateral unaffected healthy collateral ligament of proximal interphalangeal joint. We found wide range of thickness of collateral ligament of proximal interphalangeal joint in healthy digits which can be as thin as 0.6 mm to 1.7 mm with average thickness being 1 mm. Average thickness of injured collateral ligament after sprain or dislocation of the joint was 2 mm (range 1.1 mm to 2.6 mm)

Conclusions

We found that comparison of collateral ligament thickness of injured and contralateral healthy digit to be useful when looking for collateral ligament injury of proximal interphalangeal joint after sprain or dislocation of the joint using ultrasonography. We established a normal range of thickness of healthy collateral ligament using ultrasonography for comparison. Although the range of thickness of normal collateral ligament overlaps with range of thickness measurement of the abnormal collateral ligament, it is the comparison with the contralateral healthy collateral ligament that is useful.