Fixed angle locking plates for proximal humeral fracture fixation

Incidence of avascular necrosis following biceps tenodesis during proximal humerus open reduction and internal fixation

Avascular necrosis (AVN) may occur in up to 77% of proximal humeral fractures and can cause fixation failure. Risk factors include fracture position, calcar length and medial hinge integrity. We routinely perform intra-articular biceps tenotomy with tenodesis at the level of pectoralis major to facilitate fragment identification and potentially ameliorate post-operative pain relief. Concern exists that tenotomising the biceps damages the adjacent arcuate artery, potentially increasing the rate of AVN. The purpose of this study was to evaluate whether biceps tenodesis is associated with an increased risk of radiographically evident humeral head AVN. 61 fractures surgically treated over a 52-month period were retrospectively reviewed and radiographically assessed in accordance with Neer’s classification, calcar-length and medial hinge integrity. 40, 20 and 1 were four-, three- and two-part fractures respectively. 37 had a calcar-length less than 8mm and 26 suffered loss of the medial hinge. The median radiographic follow-up was 23 months. There was radiographic evidence of humeral head AVN in only one case, comparing favourably to rates quoted in current literature. In our experience, intra-articular biceps tenotomy with the deltopectoral approach was thus not associated with a significantly increased risk of humeral head AVN, even in complex four-part fractures.

PROXIMAL HUMERUS FRACTURE WITH LOCKING PLATE: FUNCTIONAL AND RADIOGRAPHIC RESULTS

OBJECTIVE

To correlate the functional outcome and radiographic indices of proximal humerus fractures treated with locking plate.

METHODS

Seventy patients with proximal humerus fractures treated with locking plate, with mean follow-up of 30 months. These patients were analyzed for the score of the University of California, Los Angeles (UCLA) for the operated shoulder, range of motion measurements and radiography of both shoulders. After that, a graphical correlation was established between the radiographic measurements and the functional outcomes.

RESULTS

78% good and excellent results according to the UCLA score, with mean130° elevation; 45° lateral rotation; and thumb-T10 medial rotation. The type of fracture according to the Neer classification and age had a significant correlation with the range of motion. An association was found between the lowest mean elevation and the UCLA score when the neck-shaft angle variation in the antero-posterior plane was greater than 15° varus (p <0.001).

CONCLUSION

The variation of the neck-shaft angle measurement in the anteroposterior plane showed significant correlation with the range of motion and can be one of the predictors of functional results in proximal humerus fractures treated with locking plate. Level of evidence III, Retrospective Study.

Biomechanical comparison of screw-based zones of a spatial subchondral support plate for proximal humerus fractures

Stabilisation of proximal humerus fractures remains a surgical challenge. Spatial subchondral support (S3) plate promises to overcome common complications associated with conventional proximal humerus plates. This study compared the biomechanical performance of S3 plate with a fixed-angle hybrid blade (Equinoxe Fx) plate and a conventional fixed-angle locking plate (PHILOS). The effects of removal of different S3 plate screws on the humeral stability were also investigated. A total of 20 synthetic left humeri were osteotomised transversely at the surgical neck to simulate a two-part fracture and were each treated with an S3 plate. Head screws were divided into three zones based on their distance from the fracture site. Specimens were divided into four equal groups where one group acted as a control with all screws and three groups had one of the screw zones missing. With humeral head fixed, humeral shaft was first displaced 5 mm in extension, flexion, valgus and varus direction (elastic testing) and then until 30 mm varus displacement (plastic testing). Load-displacement data were recorded to determine construct stiffness in elastic tests and assess specimens' varus stability under plastic testing. Removal of the screw nearest to the fracture site led to a 20.71% drop in mean elastic varus bending stiffness. Removal of the two inferomedial screw above it resulted in a larger drop. The proximal screw pair had the largest contribution to extension and flexion bending stiffness. Varus stiffness of S3 plate constructs was higher than PHILOS and Fx plate constructs. Stability of humeri treated with S3 plate depends on screws' number, orientation and location. Varus stiffness of S3 plate construct (10.54 N/mm) was higher than that of PHILOS (6.61 N/mm) and Fx (7.59 N/mm) plate constructs. We attribute this to S3 plates' thicker cross section, the 135° inclination of its screws with respect to the humeral shaft and the availability of pegs for subchondral support.

Biomechanical comparison of screw-based zoning of PHILOS and Fx proximal humerus plates

Background

Treatment of proximal humerus fractures with locking plates is associated with complications. We aimed to compare the biomechanical effects of removing screws and blade of a fixed angle locking plate and hybrid blade plate, on a two-part fracture model.

Methods

Forty-five synthetic humeri were divided into nine groups where four were implanted with a hybrid blade plate and the remaining with locking plate, to treat a two-part surgical neck fracture. Plates’ head screws and blades were divided into zones based on their distance from fracture site. Two groups acted as a control for each plate and the remaining seven had either a vacant zone or blade swapped with screws. For elastic cantilever bending, humeral head was fixed and the shaft was displaced 5 mm in extension, flexion, valgus and varus direction. Specimens were further loaded in varus direction to investigate their plastic behaviour.

Results

In both plates, removal of inferomedial screws or blade led to a significantly larger drop in varus construct stiffness than other zones. In blade plate, insertion of screws in place of blade significantly increased the mean extension, flexion valgus and varus bending stiffness (24.458%/16.623%/19.493%/14.137%). In locking plate, removal of screw zones proximal to the inferomedial screws reduced extension and flexion bending stiffness by 26–33%.

Conclusions

Although medial support improved varus stability, two inferomedial screws were more effective than blade. Proximal screws are important for extension and flexion. Mechanical consequences of screw removal should be considered when deciding the number and choice of screws and blade in clinic.

Electronic supplementary material

The online version of this article (10.1186/s12891-018-2185-5) contains supplementary material, which is available to authorized users.

Biomechanical analysis of plate systems for proximal humerus fractures: a systematic literature review

BACKGROUND

Proximal humerus fractures are the third most common in the human body but their management remains controversial. Open reduction and internal fixation with plates is one of the leading modes of operative treatment for these fractures. The development of technologies and techniques for these plates, during the recent decades, promise a bright future for their clinical use. A comprehensive review of in vitro biomechanical studies is needed for the comparison of plates' mechanical performance and the testing methodologies. This will not only guide clinicians with plate selection but also with the design of future in vitro biomechanical studies. This review was aimed to systematically categorise and review the in vitro biomechanical studies of these plates based on their protocols and discuss their results. The technologies and techniques investigated in these studies were categorised and compared to reach a census where possible.

METHODS AND RESULTS

Web of Science and Scopus database search yielded 62 studies. Out of these, 51 performed axial loading, torsion, bending and/or combined bending and axial loading while 11 simulated complex glenohumeral movements by using tendons. Loading conditions and set-up, failure criteria and performance parameters, as well as results for each study, were reviewed. Only two studies tested four-part fracture model while the rest investigated two- and three-part fractures. In ten studies, synthetic humeri were tested instead of cadaveric ones. In addition to load-displacement data, three-dimensional motion analysis systems, digital image correlation and acoustic emission testing have been used for measurement.

CONCLUSIONS

Overall, PHILOS was the most tested plate and locking plates demonstrated better mechanical performance than non-locking ones. Conflicting results have been published for their comparison with non-locking blade plates and polyaxial locking screws. Augmentation with cement [calcium phosphate or poly(methyl methacrylate)] or allografts (fibular and femoral head) was found to improve bone-plate constructs' mechanical performance. Controversy still lies over the use of rigid and semi-rigid implants and the insertion of inferomedial screws for calcar region support. This review will guide the design of in vitro and in silico biomechanical tests and also supplement the study of clinical literature.

Outcomes evaluation of locking plate osteosynthesis in displaced fractures of the proximal humerus

Objective

To evaluate functional outcomes, radiographic findings and complications of proximal humeral fractures treated with locking plates and to determine prognostic factors for successful clinical outcomes.

Methods

Forty patients undergoing internal fixation of fractures of the proximal humerus with the Philos^® plate were included in the study. The surgeries were performed between 2004 and 2011 and the patients underwent radiographic and clinical evaluation, by Constant–Murley and Dash score. Outcomes were analyzed by use of multivariate regression with several different variables.

Results

Patients were on average of 61.8 ± 16.28 years, and most were female (70%). The Constant–Murley score was 72.03 ± 14.01 and Dash score was 24.96 ± 19.99. The postoperative radiographs showed a head-shaft angle of 135.43° ± 11.82. Regression analysis showed that the patient's age and the Hertel classification influenced the Constant–Murley scale (p = 0.0049 and 0.012, respectively). Other prognostic criteria such as Neer and AO classification, head-shaft angle, the presence of metaphyseal comminution and extension of the humeral metaphyseal fragment showed no effect on prognosis. Complications occurred in four patients (10%).

Conclusion

The fixation with the Philos^® plate provided good clinical and radiographic results in fractures of the proximal humerus, with a low complication rate. Patient's age and Hertel classification were defined as prognostic factors that led to worse functional outcomes.