Proximal humerus fractures are the third most common fractures in the elderly and are increasing in frequency as the population ages.³ Most are nondisplaced and can be adequately treated without surgery. Fifteen to twenty percent of these fractures require surgical intervention because of significant displacement.¹³ Many techniques of internal fixation have been described and the results are varied. The introduction of locking plate technology has fostered a renewed interest in treating displaced proximal humerus fractures with plate osteosynthesis.²³ Three- and four-part fractures commonly treated with hemiarthroplasty in the past can now be reconstructed with joint preserving techniques.¹⁵,²⁴ Although locking plates provide advantages over traditional plate and screw fixation, the use of locking technology alone does not ensure a good outcome, and high rates of complications have been reported in some series.¹,¹⁷ With an increasing number of proximal humerus fractures and expanding indications for joint preserving surgery, shoulder surgeons will increasingly face the complications of failed attempts at open reduction and internal fixation (ORIF).

Proximal humeral nonunion is neither common nor rare. Nonoperative treatment results in nonunion in 1% to 12% of patients.⁸,²⁰,²⁸ Following ORIF, rates of 0% to 25% have been reported.¹⁷,²¹,²²,²⁶ There is no universally accepted definition of what constitutes a nonunion, but failure to heal 6 months after a fracture is an acceptable timeline to consider intervention. No evidence of healing callus by 3 months should raise suspicion that a delayed union or nonunion is developing. Treatment of this problem is challenging. Surgery is complicated by distorted anatomy, disuse osteopenia, soft tissue contracture, scar formation, and bone resorption. Norris et al. noted that “all the reconstructive and rehabilitative skill of the experienced shoulder surgeon are necessary” to achieve optimal results.¹⁶ In young patients with adequate bone remaining and preserved articular cartilage and rotator cuff, ORIF with bone grafting can be considered. In elderly patients lacking bone or with significantly impaired healing capacity, symptomatic nonunion may be best treated with arthroplasty.⁷ This chapter reviews the evaluation of proximal humeral nonunions and arthroplasty treatment options.

Causes of nonunion can be divided into factors related to the patient, the fracture, and the initial method of treatment.²⁹ Although these divisions are arbitrary, they can help guide an organized approach to patient assessment. One should recognize, however, that nonunions typically result from a combination of factors leading to a suboptimal micro-environment in which optimal strain is not achieved, and fracture healing cannot result.¹⁸

Patient-specific factors that can contribute to nonunion include metabolic bone diseases, medications, alcohol abuse, tobacco use, nutritional deficiencies, and comorbidities.²⁷ Although not all of these can be corrected preoperatively, recognition is an important step in patient evaluation. Osteoporosis is often cited as a cause of nonunion but low bone mass by itself does not inherently compromise healing. Osteoporosis is often associated with osteomalacia or vitamin D deficiency, however, which may impair fracture healing
and is potentially correctable.⁴ This is an especially important consideration in patients with comorbid conditions of the kidney and liver where vitamin D activation occurs. Cooperation with the patient’s internist to evaluate and treat deficiency is useful. Collaboration with other medical specialists is also important to optimize the management of comorbidities. Healy et al. noted that the 16 of 25 patients in their series with significant medical illnesses all had unsatisfactory results.¹⁰ Changing medications that interfere with bone healing such as glucocorticoids, antiepileptics, and nonsteroidal anti-inflammatory agents should also be considered. Tobacco use has been associated with impaired bone healing. Rose et al. reported 4 nonunions out of just 16 patients with proximal humeral fractures treated with locking plates.²¹ Three of these failures were attributed to heavy smoking. Although cessation of tobacco use is an admirable goal and should be encouraged, it is rarely accomplished sufficiently early to affect an improvement in healing biology. Recognition of alcohol abuse may also be a critical determinant in treatment. If a patient cannot comply with postoperative precautions and rehabilitation because of alcohol impairment, surgery is contraindicated.

The unique anatomy of the shoulder and the fracture pattern can also contribute to nonunion formation. Entrapment of the biceps, deltoid, and rotator cuff within the fracture site has each been described. Communication of the fracture with synovial fluid is a proposed cause of nonunion and the significant bony resorption in proximal fractures.¹⁴ Nonunion occurs most frequently at the surgical neck. The transition from the predominantly cancellous bone of the proximal humeral metaphysis to the cortical diaphyseal bone has been suggested as a potential reason for this. The constant distractive force of gravity on the arm is also another factor which may lead to nonunion at this site. Surgical neck nonunion is also more likely if there is glenohumeral stiffness, such as from preexisting osteoarthritis, because motion preferentially occurs at the fracture site rather than at the stiff joint (Fig. 28-1).

Treatment methods can compromise fracture healing in several ways. With nonoperative treatment, fracture alignment must be protected by minimizing the deforming pull of the muscular attachments. If the arm is not splinted appropriately, the pectoralis major will pull the shaft anteriorly, and the head will be displaced through the pull of the rotator cuff. With exaggerated displacement and insufficient bony contact, nonunion will result. The arm should be immobilized across the front of the body, with the elbow anterior to the midline in the coronal plane. This will neutralize the muscular forces across the fracture site. Improper immobilization, such as use of a hanging arm cast, can also produce traction across the fracture site. Neer considered excessive traction from hanging cast treatment a common etiology of nonunion in his 50 reported cases.¹⁴

Operative treatment can result in nonunion if there is extensive stripping of the soft tissue attachments to bone, inadequate or excessive fixation, or a malreduction resulting in fracture distraction. If range of motion exercises are started prematurely, they can also contribute to fixation failure and nonunion. The upper extremity should move as a unit before any therapy is begun.

The symptoms of proximal humeral nonunion can vary considerably. Although many patients will report severe pain and functional loss, a significant percentage may be minimally symptomatic.⁸ The amount of pain and functional loss must be carefully assessed and is the sole basis for intervention. For patients with little pain, and the ability to reach their head, opposite axilla, and perineum, nonoperative treatment is appropriate given the substantial risk of complications associated with surgery. Significant pain and dysfunction warrant surgical treatment.