Surgical exposure for open reduction and internal fixation of multifragmentary and displaced proximal humerus fractures can be extremely challenging. Typically the greater tuberosity displaces proximally and posteriorly and the lesser tuberosity displaces medially when fractured. The humeral head fragment may be relatively small if an anatomic neck fracture is present or may be larger if the fracture is through the surgical neck.
The workhorse surgical approach to the proximal humerus, the deltopectoral approach, is an anterior approach and has been applied to locked plating of proximal humerus fractures. However, there are distinct disadvantages to this exposure. The large deltoid muscle mass often requires vigorous retraction or partial release to expose the intertuberosity fracture line, the lateral plating zone posterior to the bicipital groove, and the posteriorly displaced greater tuberosity fragment. Retraction and release are often coupled with internal rotation of the provisionally stabilized fracture, which can displace tenuously reduced fragments.
The anterolateral acromial approach uses the muscular interval between the anterior and the middle heads of the deltoid, along the avascular raphe. The incision begins just proximal to the anterolateral corner of the acromion and extends distally down the lateral aspect of the arm, ending just proximal to the deltoid tuberosity. Importantly, the humeral shaft is often displaced anteriorly due to the pull of the pectoralis major, which can affect cutaneous landmarks for the incision. The deltoid fascia is thin and relatively superficial in this region, even in obese patients. Once the fascial level is identified, the raphe should be sought as a visible stripe between the muscle fibers. Often anterior and posterior palpation is the best method to identify the indentation of this interval. The interval is then divided, exposing the bursa deep to the deltoid. The split should be extended proximally until the edge of the acromion is clearly palpated.
Critical to performing this exposure safely is identification of the crossing anterior motor branch of the axillary nerve, approximately 65 mm from the edge of the acromion. It is helpful to mark this on the skin before incision to provide an estimation of where it will be encountered in the deep dissection. The nerve can either be approached directly from superficial to deep or once the proximal split is large enough, a finger can be placed distally and used to palpate the band-like structure on the undersurface of the deep deltoid. If a low surgical neck fracture line is present, care should be taken to ensure the nerve is not entrapped at the fracture site. If the fracture lines are all proximal to the nerve, the nerve need not be fully dissected. After palpation and protection, the plate can be reliably inserted along the humeral shaft deep to the nerve once reduction is complete.
Once the nerve is identified, multiple aspects of the reduction and the implant application are greatly facilitated. The bursa should be definitively incised next. The periosteum can then be elevated off of the edges of the tuberosity fracture lines to aid in reduction assessment. Sutures can be placed in the rotator cuff attachments to mobilize the tuberosities and secure them to each other. Significantly displaced lesser tuberosity fragments require careful retraction of the anterior deltoid to minimize stretch on the nerve. However, this is always possible through this approach.
Elevators, K-wire joysticks, and sutures can be used to manipulate the humeral head fragment. By accessing the cancellous bone of the fragment, an elevator can be used to “pull” the head fragment back onto the shaft, focusing on the medial hinge fracture position, in varus fractures. Conversely, in valgus-type patterns, the lateral aspect of the head can be “propped up,” so it is facing the glenoid. Provisional K-wires should be placed so as to not obstruct the anticipated plate position as much as possible. If a fibular strut allograft is planned, this can be inserted into the shaft by gentle lateral traction on the shaft and it can then be gently tamped, so that it obliquely contacts the inferior humeral head. When a fracture dislocation of the humeral head is present, the cancellous surface can similarly be accessed, multiple threaded K-wires placed, and the head can be easily manipulated back into the glenoid. In this situation, if the head fragment is juxta-thoracic, a computed tomographic angiogram is recommended to ensure the vessels are not entrapped by the head fragment. If there is any question, a deltopectoral approach is recommended to provide extensile vascular access, should it be necessary if vascular injury occurs with head manipulation.
Overall, this approach is very useful for all aspects of reduction and plating of proximal humerus fractures and has become the preferred surgical approach for nearly all proximal humerus fracture patterns.