Updated: 5/11/2021

Hook of Hamate Fracture

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https://upload.orthobullets.com/topic/6035/images/33_moved.JPG
https://upload.orthobullets.com/topic/6035/images/hamate_golf.jpg
https://upload.orthobullets.com/topic/6035/images/hamate_baseball.jpg
https://upload.orthobullets.com/topic/6035/images/carpals.jpg
https://upload.orthobullets.com/topic/6035/images/hamate_lat.jpg
https://upload.orthobullets.com/topic/6035/images/hamate_anatomy.jpg
  • Summary
    • Hook of hamate fractures are rare, often missed, injuries generally as a result of a direct blow to the hamate bone most commonly seen in athletes.
    • Diagnosis is confirmed with either a radiographic carpal tunnel view or CT scan.
    • Treatment is either observation, surgical excision, or surgical fixation depending on the severity of the symptoms and activity demands of the patient.
  • Epidemiology
    • Incidence
      • 2-4% of carpal fractures
    • Demographics
      • more common in males (2:1 ratio)
    • Location
      • hamate body
      • hook of hamate (this topic)
    • Risk factors
      • often seen in athletes in sports requiring gripping
        • golf
        • baseball
        • hockey
  • Etiology
    • Pathophysiology
      • mechanism of injury
        • typically caused by a direct blow to the volar proximal palm
          • grounding a golf club
          • checking a baseball bat
        • falling on outstretched hand
    • Associated conditions
      • bipartite hamate
        • will have smooth cortical surfaces
      • small finger/ring finger flexor tendonitis or tendon rupture
      • ulnar neuropathy in Guyon's canal
        • often motor only (deep branch)
      • ipsilateral carpal bone fracture
  • Anatomy
    • Hamate
      • osteology
        • carpal bone that is distal and radial to the pisiform
        • articulates with
          • fourth and fifth metacarpals
          • capitate
          • triquetrum
      • hook of hamate
        • forms part of Guyon's canal, which is formed by
          • roof - superficial palmar carpal ligament
          • floor - deep flexor retinaculum, hypothenar muscles
          • ulnar border - pisiform and pisohamate ligament
          • radial border - hook of hamate
        • one of the palpable attachments of the flexor retinaculum
        • deep motor branch of ulnar nerve lies under the hook
      • blood supply
        • vessels enter the hamate base via a radial and ulnar foramina to supply the hook of the hamate
          • ulnar vessel is absent in 29% of patients
            • absent ulnar vessel considered the reason for high non-union rate of hook of hamate fractures
  • Classification
    • Milch Classification
      Type I
      Hook of hamate fx (most common)
         Type I-I
         Avulsion
         Type I-II
         Middle of hook
         Type I-III
         Base of hook
      Type II
      Body of hamate fx
         Type IIA
         Coronal
         Type IIB
         Transverse
  • Presentation
    • History
      • commonly a delay in diagnosis
        • average of 4 weeks from injury to diagnosis
    • Symptoms
      • ulnar-sided wrist pain
        • most common complaint
      • hypothenar pain
      • pain with activities requiring tight grip
    • Physical examination
      • motion
        • limitation in ulnar deviation
        • decreased grip strength
      • neurovascular exam
        • paresthesia in ulnar nerve distribution
          • positive tinel's over Guyon's canal may be present
        • motor weakness in intrinsics
      • provocative maneuver
        • tenderness over the hook of hamate
          • most common finding (80% sensitivity)
        • hook of hamate pull test
          • hand held in ulnar deviation as patient flexes DIP joints of the ulnar 2 digits against resistance
            • the flexor tendons act as a deforming force on the fracture site, positive test elicits pain
            • 70% sensitivity
        • pain with dorsoulnar deviation of wrist
  • Imaging
    • Radiographs
      • recommended views
        • PA and lateral of wrist
          • 10% sensitivity
        • carpal tunnel view
          • best radiograph to see hook of hamate fracture
          • 40% sensitivity
      • findings
        • PA view
          • absence of eye sign or cortical ring
            • normally produced by intact hook
    • CT
      • indications
        • establish diagnosis if radiographs are negative
      • findings
        • may see sclerotic fx line in chronic injuries 
      • 92% sensitivity
        • can be missed if nondisplaced and if CT cuts greater than 1 mm
    • MRI
      • indications
        • most accurate method of diagnosis in cases of high-clinical suspicion
          • 100% sensitivity
  • Treatment
    • Nonoperative
      • immobilization 6 weeks
        • indications
          • majority of nondisplaced acute hook of hamate fractures
        • outcomes
          • high-levels of non-union (40-50%)
          • majority of patients are pain-free and have full ROM despite non-union
    • Operative
      • excision
        • indications
          • symptomatic chronic hook of hamate fractures with non-union
          • hook of hamate fractures with ulnar neuritis
          • high-level athletes
        • outcomes
          • surgical treatment of choice
          • fastest recovery and return to play noted for athletes who wish for prompt return to play
          • some studies show decreased small finger FDP tendon strength by 10-15% with excision
            • excision leads to 5 mm of ulnar displacement of small finger FDP tendon
      • ORIF
        • indications
          • acute and significantly displaced fractures in patient's unable to tolerate reduction in grip strength
        • outcomes
          • small case series have shown nearly 100% union rate
          • theoretically improved grip strength compared to excision
  • technique
    • Immobilization
      • short arm ulnar gutter cast
    • Excision 
      • approach
        • modified volar wrist incision in lined with the ulnar border of ring finger
      • technique
        • release of the guyon canal generally also performed
        • hook should be removed subperiosteally to avoid damage to motor branch of ulnar nerve
    • ORIF
      • approach
        • see above
      • technique
        • small-fragment headless compression or countersunk screws
          • screws need to be countersunk to prevent irritation of the deep motor branch of the ulnar nerve
        • in cases of ulnar neuritis
          • neurolysis of deep motor branch of ulnar nerve is recommended.
  • Complications
    • Non-union
      • incidence (most common)
        • 50% rate of non-union
      • risk factors
        • considered natural course of fracture given fracture site motion and poor blood supply
    • Ulnar nerve neuritis in Guyon's canal
      • incidence
        • 20% rate of ulnar neuropathy
      • treatment
        • hook of hamate excision
    • Closed rupture of the flexor tendons to the small finger
      • incidence
        • very rare (only case reports)
    • Weakened grip strength
      • risk factors
        • excision of large hook of hamate fractures
  • Prognosis
    • High non-union rate with conservative management (up to 50%)
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Questions (9)
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(OBQ11.130) A 24-year-old racquetball player presents after accidentally striking his racket against the wall during a match three months ago. He is tender to palpation over the hypothenar mass, and his pain is aggrevated by grasping. A radiograph and CT scan of his wrist are shown in Figures A and B. Which of the following treatment methods has been definitively shown in the literature to have a favorable outcome, and a high chance to return to pre-injury activities in patients with this injury?

QID: 3553
FIGURES:
1

Activity restriction and continued monitoring

4%

(154/4272)

2

Open reduction and internal fixation

4%

(164/4272)

3

Casting for 6 weeks, followed by physical therapy

6%

(267/4272)

4

Corticosteroid injection and immediate return to play

0%

(16/4272)

5

Surgical excision

85%

(3648/4272)

L 1 C

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(OBQ08.23) A professional baseball player develops acute hand pain after fouling off a pitch. He is tender over the hypothenar eminence and has paresthesias in the ring and small fingers. Which radiographic view is most likely to reveal the pathology?

QID: 409
1

PA wrist

2%

(59/3585)

2

AP wrist in ulnar deviation

4%

(154/3585)

3

Lateral wrist

5%

(169/3585)

4

Carpal tunnel

88%

(3165/3585)

5

Scaphoid

1%

(18/3585)

L 1 C

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(SBQ07SM.40) A 44-year-old man presents with ulnar-sided right wrist pain and mild constant tingling in the fourth and fifth digits after injuring his wrist while playing golf. Although pain and function have improved with conservative treatment 6 months following the injury, he still reports difficulty with his golf game. Which of the following should initially be obtained in this patient to aide in the diagnosis?

QID: 1425
1

Bone scan of the wrist and hand

1%

(19/3392)

2

EMG study of the affected extremity

17%

(584/3392)

3

Carpal tunnel view radiograph

74%

(2501/3392)

4

CT scan of the distal forearm and wrist

4%

(126/3392)

5

Contrast enhanced magnetic resonance angiogram

4%

(139/3392)

L 2 C

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(OBQ04.21) A 24-year-old professional baseball outfielder reports persistent pain in the hypothenar region when batting for the past year. His CT scan is shown in Figure A. What is the recommended treatment?

QID: 132
FIGURES:
1

pisiform excision

2%

(43/2789)

2

hook of hamate excision

92%

(2559/2789)

3

carpal tunnel release

0%

(7/2789)

4

decompression of Guyon's canal

1%

(16/2789)

5

open reduction and internal fixation

5%

(144/2789)

L 1 D

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