Concomitant hook of hamate fractures in patients with scaphoid fracture: more common than you might think

Abstract

Objective: The scaphoid is the most commonly fractured carpal bone. The presence of a concomitant hook of hamate fracture is of particular relevance given that it is often occult on routine wrist/scaphoid radiographs and that hook of hamate fractures are prone to symptomatic non-union, resulting in chronic ulnar wrist pain. Prompt diagnosis and immobilisation/fixation may minimise such complications. Our study is aimed at assessing the frequency of concomitant hook of hamate fractures in patients with scaphoid fractures.

Methods: Hook of hamate fracture is often occult on wrist/scaphoid radiographs. Hence, we identified all 2,568 CT and MRI studies performed to investigate scaphoid fracture at our institution from April 2005 to March 2016. Three hundred and twelve out of 2,568 cases were confirmed to have a scaphoid fracture. Images were then retrospectively reviewed by a Consultant Musculoskeletal Radiologist and Musculoskeletal Radiologist Trainee to assess for the presence of concomitant hook of hamate fracture and, if present, whether this was identified on initial reporting.

Results: Concomitant hook of hamate fracture was identified in 10.3% of cases (32 out of 312, 30 on CT, 2 on MRI); most were minimally/non-displaced. Sixty percent of fractures identified on CT were missed on the initial review (18 out of 30). Both cases identified on MRI had been initially reported.

Conclusion: Scaphoid fracture is associated with higher than expected rates of concomitant hook of hamate fracture. Given the potential morbidity associated with hook of hamate fracture, this should be considered a review area when investigating scaphoid injury. These fractures are often minimally displaced, hence easily overlooked on CT. MRI may therefore be superior when investigating radiographically occult scaphoid fractures.

Keywords: Fracture; Hamate; Hook of hamate; Scaphoid.

Fig. 1

A 24-year-old man with fracture of the right scaphoid and concomitant hook of hamate fracture (CT performed 3 months after initial injury). a Axial CT bone window shows the subtle non-displaced fracture line across the hook of hamate waist (arrow), also seen in b at a slightly more distal level. Minimally and non-displaced hook of hamate fractures are often most conspicuous on axial images followed by c sagittal reformats. Note the marginal sclerosis in a–c suggestive of fracture healing. Interval CT 4 months later (not shown) confirmed a healed hook of hamate fracture. d Coronal reconstruction demonstrates the poorly healing distal pole scaphoid fracture with some sclerosis of the proximal component

Fig. 2

A 24-year-old man with fracture of the left scaphoid and concomitant hook of hamate fracture involving the tip of the hamate hook (CT performed 2 weeks after the initial injury). a Coronal CT reconstruction shows the minimally displaced fracture of the proximal pole of the scaphoid with some resorption of the fracture margins. b Axial CT image shows the subtle non-displaced concomitant fracture of the left hook of hamate tip (arrow), which is easily overlooked if not actively sought

Fig. 3

A 21-year-old man with fracture of the left scaphoid and concomitant hook of hamate fracture. a Sagittal STIR shows significant marrow oedema involving the hook and body of the hamate, which is easily discernible compared with the low signal observed in the other imaged bones. A low signal fracture line is seen across the base of the hook of hamate (arrow). b Hook of hamate fracture on axial T1 and c corresponding axial STIR sequences, both demonstrating obvious marrow signal abnormality, although the displaced fracture line is more conspicuous on T1. d Coronal STIR sequences easily demonstrate marked oedema with angulated fracture of the distal scaphoid pole (dashed arrow), but also draw attention to marked marrow oedema of the hook of hamate (arrow). As is generally the rule with MRI of most fractures, bony abnormality was most notable on the fluid-sensitive sequences due to marrow oedema, although the fracture line was most conspicuous on T1