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 login to view 2 more bullets 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 login to view 3 more bullets hook of hamate forms part of Guyon's canal, which is formed by login to view 4 more bullets 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 login to view 2 more bullets 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 login to view 1 more bullet motor weakness in intrinsics provocative maneuver tenderness over the hook of hamate login to view 1 more bullet hook of hamate pull test login to view 3 more bullets pain with dorsoulnar deviation of wrist Imaging Radiographs recommended views PA and lateral of wrist login to view 1 more bullet carpal tunnel view login to view 2 more bullets findings PA view login to view 2 more bullets 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 login to view 1 more bullet Treatment Nonoperative immobilization 6 weeks indications login to view 1 more bullet outcomes login to view 2 more bullets Operative excision indications login to view 3 more bullets outcomes login to view 5 more bullets ORIF indications login to view 1 more bullet outcomes login to view 2 more bullets 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 login to view 1 more bullet in cases of ulnar neuritis login to view 1 more bullet 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%)