Biomechanical evaluation of hybrid double plate osteosynthesis using a locking plate and an inverted third tubular plate for the treatment of proximal humeral fractures

Abstract

BackgroundTreating proximal humerus fractures can be challenging because of large metaphyseal defects that conceal anatomical landmarks. In such cases, medial cortical support with, for example, calcar screws, is mandatory. Nevertheless, varus dislocations and implant failures in patients with impaired bone quality persist. Thus, the need for effective treatment of these patients exists. Hybrid double plate osteosynthesis was introduced as an alternative, yielding similar results as calcar screws. However, a biomechanical comparison of the stability of these two techniques is pending.MethodsCadaveric humeral specimens were treated with plate osteosynthesis and calcar screws (group 1, n = 9) or hybrid double plate osteosynthesis (group 2, n = 9) using a proximal humerus fracture model with a two-part fracture. Displacement, stiffness, failure mode, and ultimate load were examined biomechanically in a cyclic compressive-loading scenario.ResultsAlthough the hybrid double plate osteosynthesis (group 2) tended to confer higher stiffnesses than the medial support screws at higher cycles (group 1), this trend was below the level of significance. The displacement revealed non-significantly lower values for group 1 as compared with group 2 for cycles 50 and 2000, but at 5000 cycles, group 2 offered non-significantly lower displacement values than group 1. The ultimate load tended to be non-significantly higher in the hybrid double plate osteosynthesis group (group 2: 1342±369 N, group 1: 855±408 N). Both groups yielded similar failure rates, with the majority of failures in group 2 being gap closures (n = 8), whereas those in group 1 being plate dislocations (n = 4).ConclusionsThe use of an additive plate osteosynthesis in the region of the bicipital groove may be a potential alternative to the previously-established method of using calcar screws. The biomechanical data obtained in this study suggests that hybrid double plate osteosynthesis is as rigid and robust as calcar screws.

Biomechanical behavior of three types of fixation in the two-part proximal humerus fracture without medial cortical support

“…The advantages of this hardware include affordability, low profile, better adaptation to the surface, and the ability to place screws at various angles in order to avoid contact with the screws from the lateral locking plate, which have a fixed angle. Theopold et al also demonstrated that the use of a second plate alters load distribution [5]. In their experiment, they used an inverted non-locked one-third tubular plate in the bicipital groove.…”

“…Varus reduction and insufficient bone stock contribute to the high number of cases in which surgery is unsuccessful [1]. Recently several authors have called attention to the lack of medial support as an important risk factor for surgical failure [2–5]. Krappinger et al indicated age >63 years, bone mineral density levels <95 mg/cm 3 , non-anatomic reduction, and failure to restore cortical medical support as risk factors for post-osteosynthesis failure [4].…”

“…Adequate mechanical support in the inferomedial region of the proximal humerus has been suggested as an influential factor in preventing complications related to fixation of unstable fractures with locking plates [5–9]. Jung et al reported a significant reduction in the number of complications in a series of 62 patients (63 fractures) when medial support was restored, even when osteoporosis was present [8].…”

“…Theopold et al evaluated the situation of large metaphyseal medial cortical defect using humerus fracture model with a two-part fracture in a biomechanical comparison of the stability of two techniques: (1) plate osteosynthesis and calcar screws and (2) hybrid double plate osteosynthesis [5]. They observed that hybrid double plate osteosynthesis tended to confer higher stiffnesses and ultimate load than the medial support screws, although this trend was below the level of significance for both variables.…”

“…They observed that hybrid double plate osteosynthesis tended to confer higher stiffnesses and ultimate load than the medial support screws, although this trend was below the level of significance for both variables. Despite the potential criticism of an additional plate osteosynthesis in the region of the bicipital groove, it was demonstrated that a second plate alters load distribution, fulfilling the additional benefits of a medial support screw [5]. Wanner et al suggested the use of two non-locking plates, one on the anteromedial face and the other on the lateral face of the proximal region of the humerus, and presented a low complication rate and very positive results (88% excellent or satisfactory) [10].…”