Sagittal Band Injuries

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Sagittal band injuries result from acute direct trauma or chronic, repetitive microtrauma, and typically occur in boxers.

Pathology

Intact sagittal band (A) and sagittal band tear with subluxation of extensor tendon (B). ET: extensor tendon; FR: flexor tendon; SB: sagittal band.

At the dorsal aspect of the MCPJ the extensor tendons are stabilised by the extensor hood and particularly by the sagittal band during flexion and extension of the fingers.

Since the sagittal band prevents deviation of the extensor tendon during flexion and bowstringing during MCP joint hyperextension, injury to the sagittal band causes extensor tendon dislocation.

The most frequent location of this injury is the third finger. The site of the tear may affect whether the extensor tendon is displaced towards the radial or ulnar side. Although the most frequent site of disruption is the radial sagittal band, such that the extensor tendon dislocates in an ulnar direction, radial subluxation can occur with forced valgus injury. Since the second and fifth fingers have two tendons per finger, they may displace in different directions, one to the radial side and the other to the ulnar side.

Imaging

Ultrasound demonstrates irregular thickening of the abnormal sagittal band with hypoechogenicity. The extensor tendon can appear normal or can become swollen with loss of the fibrillar pattern, suggestive of a partial tear. On dynamic examination, the extensor tendon can be subluxed or dislocated during finger flexion in the transverse plane.

References

Part or all of this article or section is derived from Current status of ultrasonography of the finger by Seun Ah Lee et al, used under CC-BY-NC