American Association for Hand Surgery

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Evaluation of Antegrade Intramedullary Compression Screw Fixation of Metacarpal Shaft Fractures in a Cadaver Model
Don Hoang, MD, MHS1, Catphuong L Vu, MD, MPH1 and Jerry I Huang, MD2, (1)University of Washington, Seattle, WA, (2)Department of Orthopaedics and Sports Medicine, University of Washington Medical Center, Seattle, WA

INTRODUCTION: For displaced metacarpal shaft fractures, a number of surgical fixation options exist including the use of intramedullary Kirschner wires, plates and screws, and most recently intramedullary headless compression screws (IMHCS). IMHCS fixation has been unanimously performed in a retrograde manner. We present our study evaluating a novel approach to IMHCS of metacarpal shaft fractures through an antegrade approach in a cadaver model.

MATERIALS & METHODS: We performed antegrade placement of IMHCS in 10 cadaver hands in each of the thumb through small metacarpals for a total of 50 samples. Transverse and short oblique fractures were created followed by fracture reduction and fixation through a 5-6 mm incision over the dorsal wrist under fluoroscopic imaging. Appropriate screw widths and diameters were used based on parameters found in a previous CT study evaluating metacarpals shaft canal diameters. We evaluated for adequate fracture reduction and fixation with fluoroscopy, for extensor mechanism violation and performed measurements of carpometacarpal joint violation. We also determined the placement of the guidewire on the metacarpal head relative to the dorsal cortex.  

RESULTS: Table 1 depicts our composite results. In each of the fifty metacarpals, we achieved successful fracture reduction and fixation (Figure 1) without violation of the extensor mechanism at the wrist. Our retrograde guidewire entry point through the metacarpal head was found on average to be 4.2 to 4.7mm volar to the dorsal cortex. The actual area of CMC joint violation with IMHCS placement was found to be less than 1% for the thumb, middle, ring and the largest in the index CMC joint at close to 5% (Figure 2).


CONCLUSIONS: We have found that placement of the screw through an antegrade approach can be performed effectively for proximal and midshaft metacarpal fractures involving any of the five hand metacarpals. There is minimal violation of the articular surfaces of the trapezium, capitate, and hamate for the thumb, middle, and ring metacarpals, with the most involvement with antegrade IMHCS fixation of the index metacarpal shaft. This approach successfully avoids defect creation in the extensor tendon, sagittal band, and the cartilaginous articular surface of the metacarpal head at the metacarpophalangeal joint from a retrograde approach. In this cadaveric study, the approach can be done through a minimally invasive 6 mm incision.






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