Abstract
Purpose
Locking plates are widely used in clinical practice for the surgical treatment of complex proximal humerus fractures, especially in osteoporotic bone. The aim of this study is to assess the biomechanical influence of the infero-medial locking screws on maintaining reduction of the fragments in a proximal humerus fracture.
Materials & Methods
A standard 3-part proximal humerus fracture was created in fourth generation humerus saw bones. Each specimen was anatomically reduced and secured with a PHILOS locking plate. Eleven of the specimens had infero-medial locking screws inserted, and 11 specimens did not. Each humerus sawbone underwent cyclical loading at 532N, as previous studies showed this was the maximum force at the glenohumeral joint. The absolute inter-fragmentary motion was recorded using an infra-red motion analysis device. Each specimen was then loaded to failure.
Results
The fixation of a 3-part proximal humerus fracture with the insertion of the infero-medial locking screws had significantly less inter-fragmentary motion at 250, 500, 750 and 1000 cycles, when compared to a similar fracture pattern without this strategically placed screw (P< 0.001). In both groups at each 250 cycle increment there was a significant increase in the overall fracture fragment movement (P< 0.01). The load to failure in the group with the infero-medial screws was also significantly more (P< 0.001). The median load of 1159N was required for construct failure compared to 1452N in the group without the inferomedial screws.
Conclusion
This study supports the importance of anatomical reduction and adequate support of the medial column on maintaining fracture reduction of proximal humerus fractures. The key placement of the infero-medial locking screws is of significant importance in creating a solid construct for proximal humerus fracture healing. This may reduce implant complications such as screw perforations or the possible loss of reduction of fracture fragments.
