Purpose
To compare lag versus nonlag screw fixation for long oblique proximal phalanx (P1)
fractures in a cadaveric model of finger motion via the flexor and extensor tendons.
Methods
We simulated long oblique P1 fractures with a 45° oblique cut in the index, middle,
and ring fingers of 4 matched pairs of cadaveric hands for a total of 24 simulated
fractures. Fractures were stabilized using 1 of 3 techniques: two 1.5-mm fully threaded
bicortical screws using a lag technique, two 1.5-mm fully threaded bicortical nonlag
screws, or 2 crossed 1.14-mm K-wires as a separate control. The fixation method was
randomized for each of the 3 fractures per matched-pair hand, with each fixation being
used in each hand and 8 total P1 fractures per fixation group. Hands were mounted
to a custom frame where a computer-controlled, motor-driven, linear actuator powered
movement of the flexor and extensor tendons. All fingers underwent 2,000 full flexion
and extension cycles. Maximum interfragmentary displacement was continuously measured
using a differential variable reluctance transducer. Our primary outcome was the difference
in the mean P1 fragment displacement between lag and nonlag screw fixation at 2,000
cycles.
Results
The observed differences in mean displacement between lag and nonlag screw fixation
were not statistically significant throughout all time points. A two one-sided test
procedure for paired samples confirmed statistical equivalence in the fragment displacement
between these fixation methods at all time points, including the primary end point
of 2,000 cycles.
Conclusions
Nonlag screws provided equivalent biomechanical stability to lag screws for simulated
long oblique P1 fractures during cyclic testing in this cadaveric model.
Clinical relevance
Fixation of long oblique P1 fractures with nonlag screws has the potential to simplify
treatment without sacrificing fracture stability during immediate postoperative range
of motion.
Key words
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Article info
Publication history
Published online: July 08, 2021
Accepted:
June 2,
2021
Received:
June 16,
2020
Footnotes
No benefits in any form have been received or will be received related directly or indirectly to the subject of this article.
Identification
Copyright
© 2022 by the American Society for Surgery of the Hand. All rights reserved.
