HOOK OF HAMATE FRACTURE

Definition:  The hamate bone had a volar extension referred to as a hook.  Fractures to the hook of hamate comprise 2-4% of all carpal fractures.^1,2 They are often associated with a delayed diagnosis.^2,4

Mechanism of Injury:
1) Repetitive stress from holding a golf club/hockey stick/baseball bat/racquet against the hypothenar eminence.  The movement of the head of the equipment against the hypothenar eminence runs back and forth over the hook of hamate. ^1,2,3,4 
2) Trauma – a direct blow to the hook of hamate causing fracture, such as a fall onto an outstretched hand.

Differential Diagnosis:  TFCC tear, Hamate contusion, Guyon’s Canal/Ulnar Canal syndrome, ECU tenosynovitis/tendinosis, Pisiform fracture/contusion.

Exam:

Inspection – Swelling, ecchymosis

Palpation – Tenderness over pisiform, hook of hamate, palpate flexor carpi ulnaris tendon as well as it inserts on to the pisiform and hamate. Neurovascular examination, in particular ulnar artery and nerve distribution.^2,3

AROM – will be normal.

AROM v. Resistance – Pain with grip, may have associated weakness as well. Pain with flexion of wrist versus resistance.

PROM – May have pain with extension of wrist.

Special Tests: Allen test – rule out ulnar artery thrombosis.²

Investigations:

Imaging:  Xray – AP, lateral, oblique and include carpal tunnel view to assess hook.^1,2

US – may be able to further assess Flexor Carpi Ulnaris tendon.

CT – if high suspicion of fracture of hook of hamate and initial xrays normal, consider CT/MRI. CT is the most reliable diagnostic study for hook of hamate.4

MRI – can also be used to identify hook of hamate fracture.

Management:

Conservative treatment: Cast immobilization of 4^th/5^th MCPs along with a thumb spica to decrease motion of hook for 6-8 weeks.² If unsuccessful see surgical.

Surgical: Excision of the hook through fracture site is associated with earlier return to sports.^1,2,3,4 Even if painless non-union, excision is recommended to reduce risk of tendon rupture and/or neurovascular damage of ulnar vessels.²

Return To Sport: 8 weeks to return to sport with excision of hook if acute treatment within 2 weeks.²

Dr. Neil Dilworth (June 4, 2014)

References

1. Bachoura A, Wroblewski A, Jacoby S, Osterman AL, Culp RW Hook of hamate fractures in competitive baseball players. Hand (2013) 8:302-307

2. Bracker MD 5-Minute Sports Medicine Consult 2^nd Edition Lippincott Williams & Wilkins Philadelphia, PA 2001

3. Casa DJ, Davis BA, St. Pierre P, Sallis RE, Wilder RP, O’Connor FG ACSM’s Sports Medicine: A comprehensive Review Lippincott Williams & Wilkins Philadelphia, PA 2013.

4. Thorne, Charles H.; Chung, Kevin C.; Gosain, Arun K.; Gurtner, Geoffrey C.; Mehrara, Babak J.; Rubin, Peter J.; Spear, Scott L. Grabb and Smith’s Plastic Surgery
Lippincott Williams & Wilkins, Philadelphia, PA 2014.