Screw placement may eliminate iatrogenic extensor tendon-related complications

BOSTON – Iatrogenic extensor tendon-related complications can be eliminated through the use of screws that do not violate the dorsal cortex during volar plate fixation of distal radius fractures, according to a study presented here.

Jeffrey A. Greenberg, MD, presented his group’s findings at the 2010 Annual Meeting of the American Society for Surgery of the Hand.

Greenberg’s model of an extra-articular distal radius fracture demonstrated that screws can be placed 75% of the distance to the dorsal cortex and still withstand activity-related loads on the distal radius without sacrificing support of the subchondral bone.

A cadaveric study

Jeffrey A. Greenberg

Greenberg and his team examined nine fresh-frozen cadaveric radii, determining bone mineral density (BMD) and separating the radii into three groups, with each group having a similar mean BMD.

The specimens were osteotomized to simulate extra-articular fractures with metaphyseal comminution. They were then stabilized using volar locking plates and divided into three groups that differed by the length of the screws placed in their distal fragments. The groups consisted of those whose screws were placed 75% of the distance to the dorsal cortex (group 1), to the dorsal cortex (group 2), or bicortically (group 3). The investigators axial loaded each specimen to failure.

Exceeding documented evidence

The mean load to failure was 947N for group 1, 780N for group 2 and 1062N for group 3, with “no significant difference” found among the groups. All of the specimens failed in the distal fragment, and eight of the nine failed in more than one aspect.

Seven of the specimens had broken screws in the distal fragment, seven had bent screws in the distal fragment and five fractured through the lunate fossa. Two of the specimens had shaft fractures.

“This model supports using the volar-locked plating technique in which screws are placed short of the dorsal cortex,” Greenberg concluded. “Fixed-angle screws placed 75% of the distance to the dorsal cortex were able to support loads of at least 570N, which surpasses forces generated by gentle wrist active range of motion. Utilizing this technique should eliminate all iatrogenic extensor tendon injuries.”

Reference:
Greenberg JA, Izadi K. The effect of screw length on fracture stability in volar plating of distal radius fractures. Paper #48. Presented at the 2010 Annual Meeting of the American Society for Surgery of the Hand. Oct. 7-9, 2010. Boston, Mass.

I think we all know that — even under the best of circumstances — it can be difficult to tell whether a screw has really perforated the irregular dorsal cortex or the distal radius, so this paper comes as reassurance suggesting that we can safely err on using shorter screws that do not penetrate the dorsal cortex.

You chose with this scenario to appropriately test this model with a gap, but also chose a method which stressed these specimens by load to failure rather than by failure with cyclical loading, so perhaps I have one bias — cyclical loading might have been more appropriate.

— Hill Hastings II, MD
American Society for Surgery of the Hand Moderator

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