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 Recurrence after excision incidence very rare (few case reports only) risk factors high level baseball players who continue playing years after excision prevention extraperiosteal excision Prognosis High non-union rate with conservative management (up to 50%)