Optimal fixation of oblique scaphoid fractures: a cadaver model.
OBJECTIVE
Acute scaphoid fractures are commonly fixed with headless cannulated screws positioned in the center of the proximal fragment. Central placement of the screw may be difficult and may violate the scaphotrapezial joint. We hypothesize that placement of the screw through the scaphoid tuberosity will achieve perpendicular fixation of an oblique waist fracture and result in more stable fixation than a screw in the center of the proximal fragment.


METHODS
We designed oblique osteotomies for 8 matched pairs of cadaver scaphoids and fixed each specimen with a headless cannulated screw. In 1 specimen, we positioned the screw at the center of the proximal fragment; we placed its matched pair perpendicular to the fracture. The perpendicular screw was directed through the scaphoid tuberosity. We placed the specimen under the increasing load of a pneumatically driven plunger. We compared stiffness, load, distance at failure, and mechanism of failure between the central and perpendicular screw groups.


RESULTS
We found no difference between groups. Stiffness was identical in both groups (131 N/mm) and load to failure was similar (central screw, 137 N vs perpendicular screw, 148 N).


CONCLUSIONS
In this biomechanical model of an unstable scaphoid fracture, we found that similar stability of fixation had been achieved with a screw perpendicular to the fracture plane with entry through the tuberosity, compared with a screw in a central position in the proximal fragment. This study suggests that placing the screw through the tuberosity, perpendicular to a short oblique fracture, will not impair fixation stability.


CONCLUSIONS
Percutaneous fixation of scaphoid fractures has become popular although it is technically challenging. An easier distal approach through the tuberosity, without violating the scaphotrapezial joint, may not impair the fixation stability of an oblique fracture.
Department of Orthopaedic Surgery, Hadassah-Hebrew University Medical Center, Kiryat Hadassah, POB 12000, Jerusalem 91120, Israel. shail@hadassah.org.il
Shai
S
Luria
Lado
L
Lenart
Borut
B
Lenart
Eran
E
Peleg
Matej
M
Kastelec
D001696:Biomechanical Phenomena; D001863:Bone Screws; D002102:Cadaver; D005593:Fracture Fixation, Internal / Q000295:instrumentation / Q000379:methods*; D050723:Fractures, Bone / Q000601:surgery*; D006801:Humans; D010027:Osteotomy; D021361:Scaphoid Bone / Q000601:surgery*; D013314:Stress, Mechanical