According to our results, all the patients treated with plating for more than two-fragments PHFs reported good functional outcome and a reduced pain. Deltopectoral and transdeltoid approaches are commonly performed for the implant. The most common investigated plate is the PHILOS.
There is no common consensus among the orthopedic surgeons, and several treatment algorithms for the proximal humerus fractures have been proposed [14]; moreover, numerous articles reported dissonant results in the mid-term functional outcome, when compared surgical and nonsurgical treatments [21–23], but higher complication rates after surgical procedures have been shown [2, 6, 14].
The surgical approach is still debated: the most commons are the deltopectoral and the transdeltoid. The proximal humerus has a rich, but vulnerable blood supply, which must be carefully protected during open reduction. Avascular necrosis of the humeral head represents a complication, due to vascular traumatic damage [24].
In each included study, both approaches were found valid for shoulder pain and functional outcomes. Bockmann et al. [19] analyzed and compared the approaches and found similar score values and complication rate. At the same time, the sample had a small size, a short follow-up and number of patients lost to follow-up. Most cases of complications in the deltopectoral group were represented loosening of the plate in the shaft [19, 25]. On the other hand, in the deltopectoral approach, the substantial soft tissue dissection, including the deltoid muscle partial release and retraction, the humeral manipulation to access the lateral aspect of the humerus and vascular damage during plating and dissection, represent the main literature controversies [14, 25], despite anatomic exposure is performed under the intact deltoid muscles as a functional unit [9]. In the MIPO technique, the deltoid splitting approach provides a direct access to the lateral aspect of the proximal humerus; therefore, the plate could be placed more easily than with the deltopectoral approach [9].
Similarly, the most proper implant type is not already defined, and the use of locking or non-locking screws is widely debated. Locking screws have threaded heads, that lock into the plate’s screw holes to create an angular stable fixation. While the conventional non-locking screws rely on the bone-plate interface for stability, locking screws are reliant on the bone-screw interface instead, resulting in theoretically lower friction [26]. The two types of screws failure modes are different. Toggling, loosening or the pulling out are the more common causes of failure for the non-locking plates, while the pullout or failing of all screws are common in of locking plates [27]. Locking plates advantages including excellent elastic stiffness and good fatigue behaviour under axial compression and larger stiffness than blade plates in the cyclic external rotation [28]. Non-locking plates constructs in 20° of abduction have been proven greater stiffness than locking plate [28, 29]. In order to assess the result of Polyaxial and monoaxial locking screws, Philos and NCB plates were compared in three studies [30–32]: it has been proven that Philos plate needed more numerous, but thinner screws to report similar NCB plate performances under axial compression [28]. At the same time, the use of monoaxial screws could cause a significant number of complications, due to the perforation of screws through the humeral head [28].
The overall rate for complications after internal fixation of PHFs is documented in the recent literature as between 10% and 34% [26]. In osteoporotic bone several implants have been developed, to enhance the clinical outcome and avoid complications [19, 25]. According to biomechanical studies, fixation with CFR-PEEK plates was documented similar or superior in screws and plate connection stability. The plate has been proved to allow more minimal movements at the fracture site than fixation with titanium plates. In addition, CRF-PEEK is a radiolucent material, offering the advantage of easier intraoperative and postoperative radiographic assessment of the fracture situation [14]. Ziegler et al. [14] in their study evidenced several CFR-PEEK plates benefits, including intraoperative fluoroscopic visibility of the fracture fragments and the absence of screw-to-plate cold fusion, associated to easier plate removal [14]. In addition, the polyaxial locking self-tapping screws allow for correct screw placement in the parts of the humeral head with high bone mineral density [14]. On another hand, Röderer G et al. [10] highlighted that NCB system in an osteoporotic PHF model, providing higher survival rate when exposed to cyclic torsional loading and more strength in this anatomical region.
Another common complication is the loss of reduction, often caused by the high stiffness of the locking plate or the underestimation of the regional bone density differences [32]. Posterior and superior region of the humeral head purchase significantly better bone quality compared to the anterior aspect of the humeral head, suggesting that the best screw fixation might be achieved in the cranio-central and posterior-medial aspect of the humeral head [32]. Secondary displacement, screw cut-out and osteonecrosis were observed more frequently if not at least one screw was purchased in the superoposterior region [18, 32]. For these reasons, as suggested by Zi-zhang Liu and colleagues, the augmentation of minimally invasive injectable calcium sulfate implant (MIIG) can enhance the healing rate and decrease the incidence of fixation loosening, delayed fracture healing and fracture displacement. It has minor disadvantages than iliac grafts, polymethacrylic acid bone cement and calcium phosphate cements [15].
Main limits of this study were the heterogenous of the scores considered to assess the patient functional outcome and the paucity of prospective randomized comparative studies, in comparison to studies results. We extensively searched and identified all relevant plating in PHFs articles. Therefore, risk of bias assessment showed moderate overall risk which could influence our analysis.