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

Proximal humerus fractures account for 4% to 5% of all fractures.¹ These fractures occur most frequently in the elderly—patients older than 60 years sustain 71% of these injuries²—and in females.^1,3 Given an aging population, this incidence is predicted to increase 3-fold over the next 30 years.⁴ There is much debate regarding management of acute, displaced proximal humerus fractures. A recent Cochrane Review of published outcomes of operative and nonoperative treatment of displaced proximal humerus fractures found insufficient evidence supporting either modality, though surgery was associated with additional procedures.⁵ A review of 1000 proximal humerus fractures found that 49% had less than 1 cm of displacement of the major fragments or angulation of less than 45°.³ Other authors have reported similar findings.^6,7 Although the incidence of proximal humerus fractures has remained stable over the past decade, from 1999 to 2005 there was a 25% relative increase in surgical management, including a relative increase of 29% in open reduction and internal fixation (ORIF) versus a 20% increase in arthroplasty.¹

Locking plates have consistently demonstrated biomechanical superiority over other forms of fixation in osteoporotic bone.^8-11 Egol and colleagues⁸ found that osteoporotic bone limited the torque of fixation to values less than what is required for adequate frictional force between the plate and the bone. This problem can be overcome with fixed-angle devices, such as locked plates.⁹ Compared with locked nail constructs, proximal humerus locking plates have demonstrated superiority in torsion, loading, and varus bending.^10,11 Compared with blade plates, proximal humerus locking plates exhibited increased stiffness and torsional fatigue resistance.¹² In a randomized clinical trial, Olerud and colleagues¹³ reported superior functional results with locking plate fixation compared with nonoperative treatment of displaced 3-part fractures in elderly patients with 2-year follow-up, though these clinical results were not supported by others.¹⁴ Two recent case–control studies comparing functional outcomes for 3- and 4-part fractures with follow-up of more than 2 years revealed higher Constant scores after locked plating compared with hemiarthroplasty, though complications were higher with locked plates.^15,16 Adoption of locked proximal humerus plating has been correlated with good clinical outcomes and union rates, though this has been accompanied by a higher rate of reoperation.⁷ Reoperation rates from 1999 to 2005 increased both in the immediate postoperative period (odds ratio, 3.36) and at 1 year (odds ratio, 3.90).¹

Complications of Locked Plating

Regardless of fixation type, reduced humeral head bone mass and quality may lead to implant loosening, fracture redisplacement, and, ultimately, poor outcomes. Baseline osteoporosis may predict likelihood of fixation failure.¹⁷ Multiple studies have reported on the implant-related complications associated with locking plate fixation—most commonly, intra-articular screw penetration, postoperative fracture displacement, and avascular necrosis (AVN)^18-24 (Figure 1). A meta-analysis of 12 studies with a total of 514 proximal humerus fractures treated with locking plate fixation showed an overall complication rate of 49% and a 13.8% reoperation rate.²⁵ The most common indication for reoperation involved intra-articular screw perforation. The most common complications were varus malunion (16%), osteonecrosis (10%), intra-articular screw penetration (8%), subacromial impingement (6%), and infection (4%).

Suboptimal intraoperative fracture reduction, specifically with residual varus, has been correlated with loss of fracture fixation. In a series of 153 fractures, loss of fixation occurred in 13.7% of cases, with the leading risk factor being varus malreduction.¹⁹ Failure rates were 30.4% and 11% when the head shaft angle was less than 120° and when it was 120° or more, respectively. Solberg and colleagues¹⁶ found that initial postoperative varus angulation of more than 20° resulted in universal loss of fixation. Conversion of these cases to hemiarthroplasty resulted in poor outcomes. Preoperative fracture alignment may also predict fixation failure.²² In one series, initial varus angulation healed with a mean 16° varus and a Constant score of 63, whereas initial valgus alignment healed with 6° varus and a Constant score of 71.²² Complications occurred in fractures that were initially in varus 79% of the time and initially in valgus 19% of the time. Screw perforation has been associated with loss of reduction 44% of the time.²⁰

In an analysis of locking plate constructs revised after early (<4 weeks) failure in 8 patients with osteoporosis, Micic and colleagues²¹ found implant pullout leading to varus malalignment. All cases lacked medial support and subchondral screw purchase; 3 were initially malreduced. Owsley and Gorczyca²³ retrospectively reviewed 53 cases of displaced proximal humerus fractures treated with locked plating. Despite the high rate of radiographic union, 36% developed complications, including screw cutout (23%), varus displacement of more than 10° (25%), and AVN (4%); 13% required revision. These complications disproportionately affected patients older than 60 years (57%) and negatively affected functional outcomes.