Title:Changes in Scaphoid and Lunate Position and Loading at Two Wrist Pushup Positions
VOLUME: 16 ISSUE: 3
Author(s):Frederick W. Werner*, Emily R. Tucci, Brett T. Daly and Brian J. Harley
Affiliation:Department of Orthopedic Surgery, SUNY Upstate Medical University, Syracuse, New York, Department of Orthopedic Surgery, SUNY Upstate Medical University, Syracuse, New York, Department of Orthopedic Surgery, SUNY Upstate Medical University, Syracuse, New York, Department of Orthopedic Surgery, SUNY Upstate Medical University, Syracuse, New York
Keywords:Scaphoid, lunate, carpal kinematics, scapholunate interosseous ligament, pushup, positions.
Abstract:
Background: Scapholunate interosseous ligament (SLIL) injury following a fall on an
outstretched hand may lead to carpal instability and in some cases require long-term rehabilitation
following repair. Rehabilitation, especially in athletes, may include pushups, but little is known as
to what type of pushup may be safer.
Objective: To determine biomechanical differences between two pushup positions (neutral or extended).
Methods: Six fresh cadaver wrists with pre-existing SLIL damage were uni-axially loaded in neutral
and extension in order to simulate two different pushup styles. The motions of the scaphoid and
lunate in relation to the radius were measured. The dorsal, proximal, and volar insertion sites of the
SLIL were identified and, using the collected kinematic data, gap distances were calculated for
each site.
Results: Gap distance between the proximal SLIL insertion points was significantly greater in neutral
than in extension. There was a trend that the dorsal and volar SLIL insertion points were also
greater in neutral than in extension. After the wrist was extended 90o, the scaphoid extended 70.1o
and the lunate extended 28.6o compared to their positions with the wrist in neutral.
Conclusion: The larger gap distances between the scaphoid and lunate in neutral suggest that a
neutral style pushup could put higher forces on a wrist with pre-existing SLIL damage and may
thus hinder recovery for a person with a repaired SLIL. A pushup in extension, in these injured
wrists, may be less detrimental.
