Unciform bone

Abstract: A technique of bone grafting the ununited hook of the hamate is presented as an alternative to simple excision of the nonunion fragment. The procedure was successful in four patients. The advantages of preserving the hook of the hamate for the pulley effect on the flexor profundi are discussed.

Abstract: Purpose: Hamate hook fractures are uncommon injuries for which treatment is controversial. Excision of the hamate hook is considered to be the preferred method of treatment but the effects of hamate excision are not clearly delineated. The purpose of this study was to determine what effect, if any, excision of the hamate has on flexor tendon function. Method: The biomechanical effects of hamate hook excision on flexor tendon function were studied in fresh cadaveric forearm specimens with wrists fixed in 3 positions (neutral, 30° extension, 30° extension with 30° ulnar deviation). Flexor tendon force, flexor tendon excursion, and flexor tendon shift were evaluated. Results: Flexor tendon force decreased after hamate hook excision (11% in neutral, 14% in 30° extension, and 15% in 30° extension with 30° ulnar deviation). The flexor profundus tendons had a 7- to 11-mm increase in proximal tendon excursion after hamate hook excision depending on the position of the wrist, and the flexor profundus tendons of the small finger shifted 4 to 5 mm in ulnar direction. Conclusions: The hamate hook provides some biomechanical advantage for flexor tendon function and cadaveric changes in tendon force after its excision suggest that power grip may be decreased after hamate hook excision. (J Hand Surg 2003;28A:138–143. Copyright © 2003 by the American Society for Surgery of the Hand.)

Abstract: A clinical impression of avascular changes in the hook of the hamate after fracture led to this study of the pattern and size of the hamate hook vascular foramina. It appears that vessels enter the hamate hook at primarily two sites. The radial base foramina are large and always present, while the ulnar tip foramina are small and absent in 29% of specimens. In these hamates, fracture at the hook base could potentially compromise blood supply to the hook fragment, and this may be a factor in hamate hook nonunion.

Abstract: Type II lunate bones have an "extra" facet that articulates with the hamate bone, which frequently leads to arthritis. Because the only prior studies, to our knowledge, on this common and clinically significant variant involved dissection of cadavers, we performed an MR imaging study of the type II lunate.We retrospectively reviewed MR images obtained at 1.5 T of 186 wrists for frequency of type II lunates, size of the extra facet, amount of hamatolunate apposition, and presence of hamate subchondral edema. Of the 186 wrists, 28 also had correlation with findings on wrist arthroscopy.One hundred seven wrists (57.5%) had type II lunates with an average extra facet size of 4.6 mm (range, 1.2-12.0 mm). Apposition (articulation) of the extra lunate facet with the hamate averaged 77.4% (range, 0-100%). Hamate edema was seen in only nine wrists (4.8%), all of which had type II lunates. Arthroscopic evidence of focal hamate chondromalacia and MR imaging evidence of marrow edema were seen in six of these nine wri...