Hook of the Hamate: The Spectrum of Often Missed Pathologic Findings

Abstract

Objective: The purposes of this article are to review hook of the hamate anatomy, describe the imaging features of the spectrum of pathologic conditions, and discuss the pearls and pitfalls of imaging for clinical decision making for pathologic entities affecting the hook of the hamate.

Conclusion: Knowledge of the anatomy, imaging appearance, and clinical management of hook of the hamate abnormalities is important for radiologists in guiding the care of patients with ulnar-sided wrist symptoms.

Keywords: bipartite; coalition; delay in diagnosis; fracture; hamate; hook of the hamate; wrist.

Fig. 1. 31-year-old man with normal wrist

A, Axial proton density–weighted MR image shows body of hamate (HB), capitate (C), small-finger flexor tendons (F), hook of hamate (HH), ulnar nerve and branches (1), ulnar artery (2), ulnar vein (3), flexor retinaculum (4), and median nerve (5). B, Carpal tunnel view radiograph shows hook of hamate (HH) and pisiform (P).

Fig. 2. Two patients with sports-related hook of hamate fractures

A, 21-year-old male baseball player with acute medial wrist pain while batting in game. Carpal tunnel radiograph shows acute nondisplaced transverse fracture (arrow) at base of hook. B, 21-year-old male lacrosse player with gradual onset of wrist discomfort over several weeks without blunt trauma. Axial CT image shows nondisplaced transverse stress fracture (arrow) near base of hook.

Fig. 3. 22-year-old man injured in dirt bike accident

A, Axial CT image shows acute nondisplaced transverse fracture at tip of hook (black arrow) and nondisplaced vertical fracture of hamate body (white arrow). B, Coronal CT image shows extent of acute hamate body fracture (arrow).

Fig. 4. Type 1 and type 2 hook of hamate fractures

A, 63-year-old man after fall 6 weeks earlier. Sagittal CT image shows partially healed type 1 transverse fracture at tip of hook (arrow). B, 53-year-old man after acute blunt trauma. Axial CT image shows chronic nonunion of type 2 transverse fracture at middle portion of hook (arrow), which was incidental finding in evaluation of acute displaced comminuted fractures at bases of fourth and fifth metacarpals. C and D, 61-year-old woman with chronic wrist pain. Axial proton density–weighted (C) and sagittal T1-weighted (D) MR images show chronic nonunion of type 2 transverse fracture (arrow).

Fig. 5. Type 3 hook of hamate fractures

A–C, 45-year-old man after falling down steps 5 weeks earlier. Posteroanterior radiograph (A) shows focal lucency (black arrow) at hamate and subtle overlap of hook with fourth carpometacarpal joint. Incidental lunotriquetral coalition is also present (white arrow). Axial T2-weighted fat-saturated (B) and sagittal T1-weighted (C) MR images show displaced type 3 transverse fracture at base of hook (arrow) with associated bone marrow edema and adjacent soft-tissue edema. Type 3 hook of hamate fractures. D, 56-year-old man after recent motor vehicle collision. Axial CT image shows acute displaced comminuted type 3 fracture of hook (arrow).

Fig. 5. Type 3 hook of hamate fractures

A–C, 45-year-old man after falling down steps 5 weeks earlier. Posteroanterior radiograph (A) shows focal lucency (black arrow) at hamate and subtle overlap of hook with fourth carpometacarpal joint. Incidental lunotriquetral coalition is also present (white arrow). Axial T2-weighted fat-saturated (B) and sagittal T1-weighted (C) MR images show displaced type 3 transverse fracture at base of hook (arrow) with associated bone marrow edema and adjacent soft-tissue edema. Type 3 hook of hamate fractures. D, 56-year-old man after recent motor vehicle collision. Axial CT image shows acute displaced comminuted type 3 fracture of hook (arrow).

Fig. 6. 27-year-old man after fall from bicycle

A–C, Two contiguous sagittal CT images (A and B) and axial CT image (C) show acutely displaced hook of hamate transverse fracture (black arrow) in association with acute displaced oblique fracture of distal radius (white arrow, A and B).

Fig. 7. Bipartite hook of hamate

A, 67-year-old man with acute wrist pain after fall from standing. Sagittal CT image shows displaced comminuted fracture (black arrow) at base of fourth metacarpal. Os hamuli proprium (white arrow) is incidental finding. Ossicle and adjacent hamate have rounded well-defined margins. B and C, 41-year-old man after motorcycle collision. Sagittal CT image (B) shows bipartite hook of hamate (arrow). Axial CT image (C) shows acute displaced avulsion fracture of os hamuli proprium (arrow).

Fig. 8. Two patients with pisiform-hamate coalition

A–C, 21-year-old man after motor vehicle collision. Lateral radiograph of wrist (A) shows acute displaced comminuted distal ulnar shaft fracture. Osseous body (white arrow) was initially thought to represent anterior capitate dislocation. However, capitate was soon thereafter properly identified in its normal anatomic position (black arrow). Sagittal conventional (B) and sagittal volume-rendered (C) CT images show complete osseous fusion of hamate (asterisk) and pisiform (arrow). (A and C adapted from presentation at Radiological Society of North America 2013 annual meeting, Chicago, IL) D, 25-year-old woman 2 days after fall. Posteroanterior radiograph shows pisiform-hamate coalition (black arrow) and lunotriquetral coalition (white arrow). (Adapted from presentation at Radiological Society of North America 2013 annual meeting, Chicago, IL)

Fig. 9. 75-year-old man with wrist sepsis that developed during long-term IV antibiotic treatment of blood culture–positive methicillin-sensitive Staphylococcus aureus and mitral valve endocarditis

A, Posteroanterior radiograph obtained at hospital admission shows no signs of infection. B, Posteroanterior radiograph 5 weeks after hospital admission shows interval development of erosions (arrows), global joint space loss, and diffuse osteopenia at carpus. C and D, Sagittal T1-weighted (C) and axial T2-weighted fat-saturated (D) MR images 5 weeks after hospital admission show abnormal marrow signal intensity, compatible with reactive bone marrow edema or osteomyelitis, involving hook of hamate (arrow), body of hamate, capitate, and trapezoid bones. Synovitis of carpus and carpal tunnel flexor tendon compartment is also present.

Fig. 10. 63-year-old man with chronic wrist pain and inability to flex small finger

A and B, Axial (A) and sagittal (B) CT images show ovoid lytic lesion with adjacent sclerosis centered in hook of hamate (arrow) with thin cortical defect along radial aspect of hook. Surgical exploration 1 month later revealed small-finger flexor tendon tear. After surgical resection of hook, pathologic analysis showed lytic mass to be posttraumatic inflammatory cyst in setting of hook of hamate fracture nonunion.