Proximal humerus fractures

Proximal humeral fractures treated with a low-profile plate with enhanced fixation properties

BACKGROUND

Our purpose was to evaluate the clinical and radiographic outcomes of proximal humeral fractures treated with a new generation plating system and compare results with a meta-analysis of recent literature.

METHODS

Between 2014 and 2017, 93 patients (18 males, 75 females) with proximal humerus fractures were treated with open reduction and internal fixation (ORIF) using a Pantera® Plate. These low-profile plates are anatomically shaped and include "cross-elements" that form a three-dimensional scaffold in bone to enhance fixation stability. According to Neer classification, there were 24 two-part fractures, 49 three-part fractures and 20 four-part fractures (4 with dislocated heads). X-rays and Constant Shoulder Scores (CSS) were used to evaluate healing, complications, and clinical outcomes. Results were compared with a meta-analysis of similar studies reported in literature over the last 10 years.

RESULTS

Eighty-three patients with a minimum follow-up of 2 years had a mean CSS of 72 (53-90) graded as excellent for 23 patients (28%), good for 35 (42%), fair for 14 (17%), and poor for 11 (13%). Fractures healed without complication in 75 (91%) patients. Eight (9%) complications were observed, i.e., three avascular necrosis of the humeral head, one case of implant loosening, two cases of subacromial impingement and two superficial infections. There was no significant correlation between Neer fracture stage and patient outcome (p = 0.257). Compared to the literature, this method had a lower complication grade (p = 0.03), though it did not significantly differ in its clinical outcomes (p = 0.08).

CONCLUSIONS

The investigated plating system includes design features that can potentially increase utility for ORIF of proximal humeral fractures. While the complication profile was signficantly less than reported in the literature for standard proximal humerus plates, clinical outcomes were similar. Further studies will be required to better understand the role of plate design on treatment of these challenging fractures.

LEVEL OF EVIDENCE

IV, therapeutic study.

Investigating gender and ethnicity differences in proximal humeral morphology using a statistical shape model

Morphological variability in the shoulder influences the joint biomechanics and is an important consideration in arthroplasty and implant design. The objectives of this study were to quantify cortical and cancellous proximal humeral morphology and to assess whether shape variation was influenced by gender and ethnicity, with the overarching goal of informing implant design and treatment. A statistical shape model of the proximal humeral cortical and cancellous regions was developed for a training set of 84 subjects of both genders and different ethnicities. Cortical and cancellous bone geometries were reconstructed from CT scans, meshed with triangular elements, and registered to a template. Principal component analysis was applied to quantify modes of variation. Anatomical measurements were computed on the registered geometries to assess correlation with modes of variation. Parallel analysis identified six significant modes of variation, which accounted for 93% of variation in the training set and described scaling (Mode 1), inclination of the head (Modes 2 and 5), and shape of the greater tuberosity and neck region (Modes 3, 4, and 6). Size differences as described by Mode 1 were statistically significant for gender and ethnicity, where female and Asian subjects were smaller than male and Caucasian subjects, respectively; however, differences in other modes were not significant. Cortical thickness of the shaft after normalization by outer diameter was significantly larger for Asian subjects compared to Caucasian subjects. The statistical shape model quantified cortical and cancellous humeral morphology considering gender and ethnicity, providing descriptive data to support surgical planning, and implant design. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:3043-3052, 2018.

The anterolateral approach to the proximal humerus for nonunions and delayed unions

Nonunions of proximal humerus fractures can be disabling as a result of pain, deformity and instability, and are often found in geriatric patients with poor bone quality. There are relatively few studies examining the treatment of nonunions of the proximal third of the humerus and the ideal treatment and surgical approach remains unclear. This case series reports the successful use of the anterolateral acromial approach for treatment of the symptomatic proximal third humerus nonunions in a geriatric group of patients with clear challenges as a result of patient comorbidities and bone quality.

Biomechanical analysis of proximal humeral fixation using locking plate fixation with an intramedullary fibular allograft

BACKGROUND

Loss of locking plate fixation has been reported in proximal humeral fractures, particularly in older patients with poor bone density. In such fractures, the medial support between the humeral head and shaft is occasionally missing, resulting in varus collapse of the construct. A biomechanical study was performed to understand the behaviour of the interface of these fractures fixed with a locking plate fixation with and without augmentation. The augmentation consisted of an intramedullary fibular allograft (bone peg) that has been reported for use in these fractures.

METHODS

Six embalmed pairs of specimens were utilized; each pair of specimens had one humerus repaired with the locking plate fixation, and the other humerus repaired with the plate fixation and bone peg. The constructs were tested in bending to determine the relative movement between the humeral head and the shaft under bending loads, and the failure loads of both constructs. Digital Imaging Correlation was used to determine the relative movement.

FINDINGS

The bone peg increased the failure load of the constructs by 1.72 (SD 0.54) times (P=0.02). The relative movement was measured by comparing the initial stiffness of both constructs. Initial stiffness of the construct was increased 3.84 (SD 1.92) times (P=0.005) with the use of the bone peg.

INTERPRETATION

The intramedullary bone peg significantly decreases the relative movement at the interface. Further studies are needed to accurately determine the effect this reduction has on the healing process, and overall clinical result.

Age- and sex-related changes of humeral head microarchitecture: histomorphometric analysis of 60 human specimens

Fractures of the humeral head are frequent and will further increase due to demographic changes. Prior to operative fracture treatment, the regional differences of bone quality, especially of elderly people, have to be carefully considered to assure stable implant fixation. However, conclusive data concerning the variation of histomorphometric parameters are still lacking. Consequently, the purpose of this study was to analyze the age- and sex-related changes in bone microarchitecture. For that reason, 60 proximal humeri were harvested from patients at autopsy. Twelve regions of interest (ROI) were defined for each centered coronar humeral head slice and the specimens were subjected to radiographic, histological, and histomorphometric analyses. We could demonstrate that in contrast to men, women over 60 years of age had a significant age-related decrease in bone mass. The most prominent decrease was observed in the region of the greater tuberosity, which represents an osteoporotic fracture site. The most superior and medially located part of the centered coronar humeral head slice showed, independent from age and sex, the highest bone mass and can therefore be considered as the best location for subchondral screw placement. Taken together, our study revealed distinct sex-related changes of the humeral head bone microarchitecture with aging, which should be considered in implant positioning.

Injuries to the proximal humerus

Five to seven percent of all fractures involve the humerus, with most occurring in ladies over the age of 60 who have osteoporosis. and suffer fractures after a simple fall. In younger individuals such fractures result from high energy injuries (road traffic accidents). Around 75% are non-displaced fractures according to Neer's classification and can be treated non-operatively. The remaining 25% require surgical intervention based on the understanding of the anatomy of the proximal, the mechanism of the injury and the quality of the patient's bone. The displaced fractures may lead to avascular necrosis, osteoarthritis, pseudoarthrosis, and reduced motion and function. Involvement of the specialist is needed at an early stage in order to restore the limb functionality and the quality of life.

Biomechanical analysis of plate osteosynthesis systems for proximal humerus fractures

OBJECTIVES

To biomechanically assess five proximal, humeral, fracture-plate-fixation systems.

METHODS

Surgical neck fractures, with and without cortical contact, were created in 25 fresh-frozen cadaveric humeri. Five methods of plate fixation were used for repair: construct A [an eight-hole, low contact dynamic compression (LCDC) plate contoured into a blade shape, supported by one, 70-mm-long, 4.5-mm-diameter cortical screw acting as a truss], construct B (a 10-hole LCDC plate arrangement identical to construct A, but using one, 70-mm-long, 3.5-mm-diameter cortical screw as a truss), construct C [a five-hole dynamic compression (DC) blade plate with one, 6.5-mm-diameter cancellous screw], construct D (a five-hole T-plate supported by three, 6.5-mm-diameter cancellous screws), and construct E (a five-hole cloverleaf plate supported by five, 4-mm-diameter cancellous screws). Plates were posterior to the bicipital groove, 10 mm distal to the greater tuberosity tip, on the lateral aspect of the humeral shaft. Screw fixation was done using standard AO compression plating techniques. Stiffness of constructs was measured in bending and axial compression. Locked plates were not assessed.

RESULTS

For cortical contact [abduction of 20 degrees (P=0.02), flexion of 20 degrees (P=0.02), flexion of 90 degrees (P=0.005)] and no cortical contact [flexion of 90 degrees (P=0.0001)], construct A was significantly stiffer than other constructs. For no cortical contact in abduction of 90 degrees (P=0.05), construct A was significantly stiffer than other constructs.

CONCLUSIONS

Construct A was significantly stiffer than other constructs.