Biomechanical in vitro assessment of fixed angle plating using a new concept of locking for the treatment of osteoporotic proximal humerus fractures

Abstract

Locked plating attempts to improve mechanical stability via better anchorage of the screws in the bone. In 22 paired osteoporotic humeri an AO/ASIF 11-B 1 fracture was created. Locked and conventional plating using the same device of the latest generation was performed. Torsional loading around three axes (x = varus/valgus, y = flexion/ extension, z = axial rotation) with an increasing moment (2, 3.5, 5 and 7.5 N·m) was applied. Interfragmentary motion within the locked group was lower for all three axes with higher cumulative survival rates (p<0.05). The typical mode of failure was loss of fixation in the humeral head occurring earlier in the conventional group. The locking mechanism investigated provides more ultimate strength in an osteoporotic proximal humerus fracture model. Correlation with BMD suggests that this device may especially be suitable for use in osteoporotic bone.

The clinical benefit of medial support screws in locking plating of proximal humerus fractures: a prospective randomized study

“…Although satisfactory results can be achieved with non-operative treatment in 80% of proximal humerus fractures [3], surgical intervention is generally accepted in some unstable fractures, especially in displaced and osteoporotic cases, for the high nonunion rate of 5-23% with conservative treatment [2]. Recent studies have noted that locking plates can provide adequate mechanical support and thus have shown superior outcomes over other means of fixation methods in these patients [4,5]. Also, various devastating complications have been addressed by using locking plating, such as varus displacement of humeral head, loss of fixation and nonunion, which may occur frequently in comminuted and unstable fractures involving the medial supporting structures [1,2,6].…”

Retrograde nailing versus locking plate osteosynthesis of proximal humeral fractures: a biomechanical study

“…Foruria et al 6 and Roderer et al 19 proved in their biomechanical studies on cadaveric proximal humeri that locking plates possess superior biomechanical properties under rotational load compared with locked intramedullary nails. Comparing their results with those from a former biomechanical study from our research laboratory, we expected the locking plate to be superior for torsional loading.…”

Use of Locking Plates in Orthopaedic Trauma Surgery

“…In poor-quality bone, nonlocking screws may strip prior to generating sufficient compressive force between plate and bone. Locking constructs are not as dependent on bone quality to provide stability 2 , and they have been shown to maintain stability in osteoporotic bone better than nonlocking constructs 1 .…”

“…These fractures demand a fixedangle construct to avoid loss of reduction 1 . Partially because of their ease of application, locking plates have essentially supplanted other fixed-angle constructs such as the blade plate and dynamic condylar screw.…”