Original Communications
Biomechanical evaluation of flexor tendon function after hamate hook excision*,**

https://doi.org/10.1053/jhsu.2003.50005Get rights and content

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.)

Section snippets

Materials and methods

Eight normal, fresh-frozen cadaver forearms were fixed on a specially designed frame (Fig. 1).

. Cadaveric forearm specimens were fixed on a custom frame assembly. Tendons were loaded with 5 lb or 10 lb of weight and small, ring, and long finger flexor tendon forces were measured with a load cell and connected to a recorder as shown.

The wrist and the hand were secured to the frame platform by 3-mm K-wires passed through the radius and distal metacarpal shafts of the thumb and small finger

Results

Reductions in flexor tendon forces were found after hamate hook excision when the flexor tendons were loaded with 5-lb (2.26 N) and 10-lb (5.33 N) forces (Table 1).

. Reductions in flexor tendon force after hamate hook excision

Empty Cell5-lb (2.26 N) Force10 lb (5.33 N) Force
Small finger8% to 12%7% to 9%
Ring finger11% to 20%11% to 20%
Long finger12% to 16%12% to 16%
The changes of the flexor tendon forces varied with the wrist positions and with the individual fingers tested (Tables 2, 3; Figs. 4, 5).

.

Discussion

Hamate hook fractures in athletes may be divided into direct and indirect injuries.6 Direct mechanisms of injury include acute impingement on the hamate hook by a handle such as that of a bat, racket, or golf club, and the indirect mechanism refers to shearing fractures of the hamate hook base by flexor tendons contracting forcefully as they move ulnarly in a power grip.6 Patients usually present late and complain of increasing pain at the dorsal and ulnar aspects of the hand with use of the

Acknowledgements

The authors would like to thank Janice Hepler, Executive director of Medical Education & Research Institute, Memphis, TN, and Richard Smith, Assistant Professor, Orthopedic Research Laboratory, for their contributions.

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No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.

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Reprint requests: James H. Calandruccio, MD, Editorial Department, Campbell Foundation, 1211 Union Ave, Suite 510, Memphis, TN 38104.

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