Scaphoid Fractures: Is a Single Screw Enough?
Stephanie A. Kwan, DO1, Tiffany N Bridges, DO1, Levi Buchan, DO1, Ashkan Sedigh, BS2, Richard Tosti, MD2, Justin Kistler, MD2, Amir R Kachooei, MD3 and Michael Rivlin, MD2, (1)Jefferson Health - New Jersey, Stratford, NJ, (2)Rothman Orthopaedic Institute, Philadelphia, PA, (3)AdventHealth, Rothman Orthopedic Institute, Orlando, FL
The tenuous blood supply of the scaphoid predisposes the carpus to nonunion following fracture. Therefore, certain fractures are managed surgically, typically with a headless compression screw (HCS). Postoperatively there still remains a risk of nonunion and a single HCS may still permit rotation. The purpose of this study was to assess in vitro the biomechanical stability of a single HCS construct in the treatment of displaced scaphoid waist fractures. We hypothesized that one HCS would not provide rotational stability of the fracture.
The scaphoids of 8 fresh frozen cadavers were included. Two k-wires were placed perpendicular to the scaphoid and then cut flush to serve as markers for rotation (Figure 1). An osteotomy was created at the level of the scaphoid waist between the markers. Radiographs were taken of the wrist at end range of motion (ROM). Images were reviewed by two different observers, if the wires were not parallel, this was deemed to demonstrate rotation (Figure 2). An HCS was then advanced across the reduced fracture site. The specimen was rotated until one pin was orthogonal and if the wires were not parallel this was deemed to demonstrate rotation. In a separate limb of the investigation, to quantify native rotation moment (without fixation) within the scaphoid a sensor was affixed to the osteotomized scaphoid. The wrist was then taken through full ROM and rotation was recorded via the sensor connected microprocessor.
Six measurements were collected for each specimen in flexion, extension, pronation, supination, radial deviation, and ulnar deviation after the osteotomy and again after fixation. The radiographs after osteotomy demonstrated rotation at the osteotomy site in all specimens in flexion (8/8), extension (7/8), pronation (8/8), radial deviation (8/8), and ulnar deviation (8/8) with the exception of supination (4/8). The radiographs after fixation with an HCS demonstrated rotation in all ROM for all specimens with the exception of flexion for one specimen. Interfragmentary (or internal scaphoid) rotation was found to be 23-30° during flexion/extension, 18-24° during supination/pronation, and 28-35° during ulnar/radial deviation around the central axis.
A single HCS appears fails to prevent fragment relative rotation at the fracture site in all tested specimens. Internal angular tension is observed within the scaphoid and rotation of 20-30 degrees is noted around the central axis during simulated range of motion. Surgeons may consider the use of additional fixation to a single HCS to provide additional stability.
Scaphoid AAHS 2024, Figure 2.png
Scaphoid AAHS 2024, Figure 1.png
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