Reducing Postoperative Fracture Displacement After Locked Plating of Proximal Humerus Fractures: Current Concepts

Augmentation Techniques

Despite its reported complications, proximal humerus locked plating remains the most widely used type of fixation.¹ Advancements in locking plate design, improved understanding of fixation principles, and adoption of techniques augmenting proximal humerus locking plate fixation, particularly in osteoporotic bone, have reduced postoperative complications (Table 1).

Rotator Cuff Sutures

A widely adopted technique for neutralizing rotator cuff–deforming forces, which theoretically can cause fracture displacement, is incorporation of heavy nonabsorbable sutures. These sutures are placed through the rotator cuff–tuberosity junction and tied down after being passed through the plate. Obtaining and maintaining tuberosity reduction are essential in achieving good functional outcomes after fixation. In addition, tension band sutures may be particularly useful in the setting of initial varus deformity.²⁶

Although clinical use of these sutures is common, biomechanical studies of their adjunctive contribution to fracture stability are lacking.²⁷ The rotator cuff musculature has a maximal contractile force of 3.5 kg/cm².²⁸ Ricchetti and colleagues²⁹ described a technique that involves using a locked plate and tagging the rotator cuff with heavy nonabsorbable sutures. Selective traction on the sutures can help obtain and maintain fracture reduction. Multiple studies have reported on suture use with locked plating for proximal humerus fractures.^29-34 Badman and colleagues³⁰ retrospectively reviewed 81 cases of metaphyseal defects or medial comminution treated with locked plating, rotator cuff sutures, and structural allograft. All cases healed within 6 months after surgery. The incidence of screw cutout was 3.7%, the incidence of AVN was 6.2%, and the incidence of varus collapse was 6%. A cadaveric study that used specimens (mean age, 77 years) with a simulated 3-part proximal humerus fracture treated with a locked plate both with and without cerclage sutures found no difference in interfragmentary motion between the groups.²⁷ The authors concluded that additive sutures are not required for anatomically reduced fractures. Multiple sutures may counteract the deforming forces that act on bony segments that cannot be adequately maintained with screws, such as an osteoporotic greater tuberosity.

Medial Column Restoration

The importance of reducing and maintaining the medial calcar to provide biomechanical support for a laterally placed plate has been recognized.^26,34-37 Gardner and colleagues²⁶ suggested that medial support was achieved if the medial cortex was anatomically reduced, if the proximal fragment was impacted laterally onto the shaft, or if 1 or more inferomedial screws were placed. Cases that did not achieve medial support developed significantly more humeral head subsidence (5.8 mm vs 1.2 mm) and screw penetration. Krappinger and colleagues³⁶ found that factors leading to fixation failure included age, local bone mineral density, anatomical reduction, and restoration of the medial cortical support. The authors concluded that anatomical reduction and restoration of the medial cortex were important in minimizing mechanical loads at the bone–implant interface. Biomechanically, Lescheid and colleagues³⁷ found that the most stable construct was anatomical reduction with medial cortical contact. In the setting of comminution, however, it may be preferable to intentionally perform varus malreduction to achieve medial contact than to achieve anatomical reduction with a fracture gap. Badman and colleagues³⁰ found that the incidence of screw penetration was 6% in patients with an intact medial calcar versus 29% in patients without medial support. In a retrospective analysis of patients treated with a locking plate and suture augmentation, Jung and colleagues³⁵ concluded that restoring medial support was the most reliable factor in the prevention of loss of reduction with or without screw perforation. Last, Solberg and colleagues¹⁶ reported better clinical outcomes when the length of the metaphyseal segment attached to the articular fragment was more than 2 mm. A length of less than 2 mm was predictive of developing AVN.

Use of Bone Void Fillers

Allograft. Allograft is cancellous or corticocancellous chips or tricortical graft used as osteoconductive filler for metaphyseal defects.³⁸ An increasingly popular technique involves using an endosteal fibular allograft strut to indirectly reduce the fracture and help support the medial calcar.^39-42 Hettrich and colleagues⁴⁰ reported on radiographic outcomes of displaced proximal humerus fractures with medial comminution treated with a locked plate and an endosteal fibular allograft or semitubular plate. The reduction was maintained in 96% of cases; there was 1 varus collapse. There were no cases of implant failure, screw perforation, or AVN. Other authors have also reported on successful use of fibular allograft in conjunction with a locked plate; the rate of reduction loss was low, and there were no cases of screw cutout or intra-articular screw penetration.^30,41,42 These clinical outcomes are supported by results of biomechanical studies of the added benefit of intramedullary fibular allograft.^43-46 Mathison and colleagues⁴³ reported that a construct with fibular allograft and a locking plate increased the failure load by 1.72 times and the stiffness by 3.84 times compared with a control group of locking plate only. Bae and colleagues⁴⁶ found significantly higher maximum failure load and construct stiffness with no varus collapse in specimens prepared with locked plate and fibular strut augmentation compared with a control group.