**1. Introduction**

Proximal humerus fractures (PHF) account for approximately 6% of all fractures [1]. The so-called head-split fracture describes a rare phenomenon (accounting for less than 5% of all PHF) that results from fracture lines traversing the articular surface of the humeral head [2]. This occurs when the impaction force of trauma acts in a vertical direction against the glenoid or acromion, such that shearing forces lead to humeral head cleavage.

This type of fracture was originally diagnosed by a double shadow visible on plain anteroposterior (AP) radiographs, although it was usually regarded as a subtype of posterior dislocation fractures because of its rare occurrence [3–5]. Furthermore, the double shadow sign was easily missed on plain AP views of three patients in the first consecutive series including eight PHF patients [4]. Chesser et al. recommended the need for additional axillary radiographs and computed tomography (CT) scans to thoroughly diagnose these rare ye<sup>t</sup> devastating fractures, which require early treatment to restore shoulder function [6]. If the pelican sign is detected on axillary views, a type II head-split fracture is diagnosed.

**Citation:** Imiolczyk, J.-P.; Brunner, U.; Imiolczyk, T.; Freislederer, F.; Endell, D.; Scheibel, M. Reverse Shoulder Arthroplasty for Proximal Humerus Head-Split Fractures—

A Retrospective Cohort Study. *J. Clin. Med.* **2022**, *11*, 2835. https://doi.org/ 10.3390/jcm11102835

Academic Editor: Patrick Joel Denard

Received: 15 April 2022 Accepted: 12 May 2022 Published: 17 May 2022

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**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

The first arc represents the lesser tuberosity and the second arc a part of the articular surface which remained attached to the lesser tuberosity [2,7].

Therefore, a most recent attempt has been made to classify these specific fractures on CT scans by Scheibel et al. [7]. With the extension of CT for diagnosis or surgery planning, the event of fracture lines through the articular face can be diagnosed far better than on two-dimensional radiographs.

Head-split PHF were first described in young male patients with high-energy trauma (i.e., a bicycle, motor or car accident) or epileptic seizures, where open reduction and internal fixation (ORIF) was considered the adequate treatment solution whenever closed reduction was not possible [6]. While these patients usually have good bone quality and the best potential for revascularization, it is important that these fractures are surgically fixed early after trauma in order to lower the risk of avascular necrosis and potential cartilage and joint degeneration [5,6,8]. Head-split fractures have also been reported in older, mainly female, patients involved in low-energy trauma (i.e., a simple fall from height) who typically have poorer bone quality and limited regenerative potential [2,7]. Conservative treatment for these particular fractures that are often misdiagnosed on plain radiographs has shown unsatisfactory results; in this instance, hemiarthroplasty (HA) was considered as a salvage procedure [6].

Reverse shoulder arthroplasty (RSA) has proven a reliable treatment option for severely displaced three- or four-part PHF in the older population, which offers encouraging mid-term results regarding pain loss, good return in range of motion and good functional outcome [9–14]. While ORIF and HA are both associated with high rates of complications (50% and 100%, respectively), and often followed by consecutive revision surgery, RSA may present as a potential treatment option even for relatively young patients aged below 70 years [15].

Given the sparse knowledge on the ideal treatment for this particular PHF and the accompanying high complication rates after HA and ORIF, the aim of this study was to evaluate clinical and radiological results as well as occurrence of complications in a unique consecutive series of head-split PHF patients treated with RSA.

#### **2. Materials and Methods**
