Anthropometry of the Human Scaphoid

LETTERS TO THE EDITOR

Anthropometry of the Human Scaphoid To the Editor: We read with great interest the paper by Heinzelmann, Archer, and Bindra on their analysis of morphometric data of the human scaphoid.1 We would like to congratulate the authors on their work. However, it is our view that their conclusion must be interpreted with caution. The authors conclude that, allowing 2-mm countersinking of the screw, the usual screw length will be 27 mm for males and 23 mm for females. These values may be of importance for the old type of screws because of their differential pitch. With the new generation of screws (eg, the Twin-Fix from Stryker, Kompressor [KMI, Carlsbad, CA], new Synthes Scaphoid screw), the compression achieved at the fracture side is independent of the length of the screw. We would like to advise hand surgeons wanting to use a screw of more than 24 mm in length for male patients or 22 mm for female patients to reconsider their calculation. The working length of the screw in the scaphoid is important, but it is not necessary to introduce the longest screw possible, at the risk of making it too long and damaging the joint surface. The most common technical error during fixation of scaphoid fractures, in particular with a percutaneous technique, is still the insertion of a screw that is too long. Marcel F. Meek, MD, PhD Carlos Heras-Palou, MD, PhD Pulvertaft Hand Centre Derby United Kingdom

In Reply: We would like to thank Dr. Meek and Dr. HerasPalou for reading our article and for their comments. We agree with their observation that insertion of a screw that is too long can damage articular surfaces on either side of the scaphoid. Dr. Meek and Dr. Heras-Palou have stated that insertion of the longest screw possible is not necessary; however, a recent biomechanical study suggests that a longer screw provides significantly greater stability (p ⬍ .01).1 Additionally, a microarchitectural study of the scaphoid in our laboratory suggests that the most dense cancellous bone for screw purchase is located at the proximal and distal poles of the bone (Bindra et al, presented at the Meeting of the International Federation of Societies for Surgery of the Hand, 2004). Although it is possible that different screw designs may achieve compression with shorter screws, we do believe that a screw that engages the dense bone at the two poles of the scaphoid may offer maximum stability. The cadaveric measurements we have provided in our paper are to be used as a guide only—it remains critical for the surgeon to accurately measure the length of the screw track prior to screw insertion. Andrew D. Heinzelmann, MD Graeme Archer, MD Orthopaedic Surgery Department University of Arkansas for Medical Sciences Little Rock, AR Randy R. Bindra, MD Department of Orthopaedic Surgery and Rehabilitation Loyola University Medical Center Maywood, IL

doi:10.1016/j.jhsa.2007.11.014

doi:10.1016/j.jhsa.2007.11.015

REFERENCE

REFERENCE

1.Heinzelmann AD, Archer G, Bindra RR. Anthropometry of the human scaphoid. J Hand Surg 2007;32A:1005–1008.

1.Dodds SD, Panjabi MM, Slade JF III. Screw fixation of scaphoid fractures: a biomechanical assessment of screw length and screw augmentation. J Hand Surg 2006;31A:405– 413.

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