Abstract
Many two-part fractures of the proximal humerus are treated conservatively due to the frequent failure of internal fixation. The current investigation examines the biomechanical properties of a unique plate versus a standard plate for internal fixation of proximal humerus fractures. The unique plate employs screws that thread into the plate, creating a multi-planer, fixed angle device. A cadaveric model was developed that relied on the rotator cuff musculature as the primary deforming force. The locking plate displayed significantly greater holding power on the humeral head (p=0.007). This may lead to more consistent results in two-part fractures treated with internal fixation.
The current investigation evaluates a unique plate designed to treat fractures of the proximal humerus. The plate employs screws that thread into the plate creating a fixed angle device. This plate was tested versus a standard cloverleaf plate.
The locking plate displayed greater holding power on the humeral head in the model tested. This may lead to decreased failure rates in two-part fractures treated with internal fixation.
Many two-part fractures of the proximal humerus are treated conservatively due to the frequent failure of common internal fixation modalities. This is done with the acceptance of possible non-union and loss of function. A more reliable method for stable internal fixation is therefore desirable.
A significant difference was found (p=0.007) with the locking plate displaying greater holding capability on the humeral head.
Eight pairs of preserved, cadaveric humeri were dissected and plated with either the locking plate or standard cloverleaf plate followed by an osteotomy at the surgical neck. A servo-hydraulic testing machine was then used to pull on the rotator cuff musculature until failure was achieved. Failure of the plate-head interface was reached in five of the eight pairs. Previous biomechanical studies have not taken into account the clinical mode of failure when testing internal fixation modalities for proximal humerus fractures. The current study has reproduced failure into varus by relying on the rotator cuff musculature as the primary deforming force.
Funding: All implants donated by Synthes, Canada
Correspondence should be addressed to Cynthia Vezina, Communications Manager, COA, 4150-360 Ste. Catherine St. West, Westmount, QC H3Z 2Y5, Canada
