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Images
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
            • most studies show a return to full activity at 6 weeks 
          • 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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