Working Diagnosis:
Sagittal band injury

Treatment:
The boxer was treated conservatively with a volar splint for two weeks and then transitioned to a brace that limited MCP flexion to 30 degrees for an additional four weeks.

Outcome:
Our boxer elected to do his own rehabilitation program with his trainer and was back to training with punching 3-4 weeks after coming out of the MCP flexion brace. He has successfully boxed since then.

Author's Comments:
This boxer had a type II sagittal band injury according to the Ryan and Murray Classification. The sagittal band is dorsal to the extensor tendon hood and is the primary lateral stabilizer to the extensor tendon overlying the metacarpophalangeal joint. This case was challenging in that we had a boxer coming for an evaluation of what would be considered a chronic injury (more than one week). Because our boxer saw two providers prior to the diagnosis of a sagittal band injury, he did not understand the importance of appropriate splinting and was started late on continuous splitting. Fortunately, he had a good functional outcome.

Editor's Comments:
Sagittal band injuries are relatively uncommon and are sometimes referred to as a boxer's knuckle. The sagittal band is part of the dorsal hood, a structure that acts to stabilize the extensor digitorum communis tendon as it crosses the metacarpophalangeal (MCP) joint. Sagittal band injuries can occur from a fall or direct blow, causing compressive trauma to the MCP joint. Patients present with pain and sometimes swelling of the affected MCP joint.
The Rayan and Murray classification system describes three types of sagittal band injuries. Type I is a contusion of the retinacular tissue without a tear. Type II is associated with extensor tendon subluxation. Type III is associated with extensor tendon dislocation. X-rays of the hand should be performed to rule out a fracture or dislocation, and an MRI can help confirm the diagnosis of a sagittal band injury.
Most acute sagittal band injuries can be managed conservatively with an orthosis that maintains MCP extension. Some may consider acute surgical management for high level athletes but in general, surgery is reserved for chronic injuries or those who have failed a course of conservative management.

References:
Kleinhenz BP, Adams BD. Closed Sagittal Band Injury of the Metacarpophalangeal Joint. J Am Acad Orthopaedic Surgeons. 2015;23(7):415-423.

Macknet D, Evans P. (2020, February 20). Sagittal Band Rupture. Orthobullets. https://www.orthobullets.com/hand/6029/sagittal-band-rupture.

Roh YH, Hong SW, Gong HS, et al. Prognostic Factors for the Nonsurgically Treated Sagittal Band Injuries of the Metacarpophalangeal Joint. J Hand Surg Am. 2019;44:896.e2-897.e5.

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