Introduction
Proximal Humerus fractures make up 4-5% of all fractures. They are common in the older osteoporotic individuals secondary to low energy trauma such as a fall from standing but are also seen in younger patients after a high energy trauma such as a motor vehicle accident or fall from a height.
Anatomy
Range of motion through the shoulder girdle involves the glenohumeral, scapulothoracic, acromioclavicular and sternoclavicular joint. The glenohumeral joint is a complex array of bone and soft tissue structures. The joint has few bony restraints and relies heavily on soft tissue constraints (dynamic and static) for stability and thus allows the shoulder a maximal range of motion.
Neer described the proximal humerus as having four parts: 1) humeral head, 2) greater tuberosity, 3) lesser tuberosity, and 4) humeral shaft. The humeral head articulates with the glenoid and included the anatomic neck where the shoulder capsule attaches. The greater tuberosity is the attachment point of the supraspinatus, infraspinatus and teres minor. The lesser tuberosity is the attachment point of the subscapularis. The humeral shaft articulates with the rest of the proximal humerus at the surgical neck.
The arcuate artery, a continuation of the ascending branch of the anterior humeral circumflex artery, is the main blood supply to the humeral head and if disrupted can cause avascular necrosis.
Classification
The Neer classification of proximal humerus fractures is the most widely used system. The basis of the classification system is anatomy and the relatively predictable fracture cleavage lines through the proximal humerus. Fractures most predictable occur between the four anatomic parts of the proximal humerus: 1) anatomic neck fracture (between humeral head and rest of proximal humerus), 2) surgical neck fracture (between humeral shaft and remaining proximal humerus), 3) greater tuberosity, 4) lesser tuberosity. Neer classified proximal humerus fractures as either: one part, two part, three part or four part depending on the number of the above fracture lines seen on X-ray.
Proximal humerus fractures should also be classified on displacement. Displacement of a fragment greater than 1 cm or angulation greater than 45 degrees is considered displaced.
Lastly, the humeral head should be noted as located or dislocated. Two-part lesser tuberosity fracture are often associated with posterior dislocations. Two-part greater tuberosity fractures are often associated with anterior dislocations.
Radiographs
Anteroposterior, lateral (aka: scapular Y) and axillary X-rays of the shoulder make up the trauma series and must all be obtained to adequately evaluate proximal humerus fractures. The most common missed diagnosis in orthopeadics is a posterior shoulder dislocation because an axillary view was not obtained on initial evaluation.
Presentation
The typical patient will be an older female after a fall onto the shoulder or outstretched arm with a painful shoulder, swelling, ecchymosis, and refusal to range the shoulder.
Physical exam should include a thorough neurovascular evaluation because of the close proximity of the neurovascular bundle to the glenohumeral joint. Also, cervical spine pain can radiate to the shoulder and thus a cervical spine exam is imperative.
Treatment
Minimally displaced proximal humerus fractures can be treated with a short course of immobilization with a collar and cuff sling or shoulder immobilizer and early range of motion exercises.
Displaced proximal humerus fractures are best treated with closed or open reduction and percutaneous or internal fixation. With more comminuted fracture patterns or those concerning for AVN of the humeral head a shoulder arthroplasty may be the most appropriate course of action.
Dislocation must be reduced on an urgent basis for risk of humeral head avascular necrosis.
Complications
Avascular Necrosis
Nonunion
Malunion
Neurovascular injury
Decreased range of motion
