Proximal Humerus Fractures: Comprehensive Guide to Epidemiology, Classification, & Surgical Anatomy

Comprehensive Introduction and Patho-Epidemiology

Proximal humerus fractures represent a significant and expanding challenge within orthopedic traumatology, accounting for approximately five to six percent of all adult fractures. As the global population ages, the incidence of these injuries continues to rise in a near-exponential fashion, cementing their status as the third most common osteoporotic fracture in the elderly, trailing only proximal femur and distal radius fractures. The management of these injuries requires a profound understanding of patient-specific physiological demands, local osseous biology, and complex regional biomechanics. While a substantial majority of these fractures are minimally displaced and amenable to conservative management, the subset of complex, displaced, or comminuted fractures demands rigorous surgical decision-making to optimize functional outcomes and mitigate debilitating complications.

The patho-epidemiology of proximal humerus fractures demonstrates a classic bimodal distribution, a hallmark of many long-bone metaphyseal fractures. In the younger demographic, typically males in their second to fourth decades of life, these fractures are predominantly the result of high-energy trauma, such as motor vehicle collisions, falls from significant heights, or forceful athletic injuries. These high-energy mechanisms often result in severe soft tissue disruption, marked displacement, and a higher incidence of concomitant neurovascular injuries or polytrauma. Conversely, the second and much larger peak occurs in the elderly population, particularly post-menopausal females, where low-energy mechanisms—most commonly a fall from a standing height onto an outstretched hand—precipitate the fracture due to underlying osteopenia or frank osteoporosis. In this older cohort, the compromised microarchitecture of the cancellous bone within the humeral head and metaphyseal region dictates not only the fracture pattern but also the biomechanical limitations of internal fixation.

Classification of these fractures is paramount for both prognostic stratification and surgical planning. The Neer classification system, introduced in 1970, remains the most widely utilized and universally understood framework among orthopedic surgeons. Neer’s system is fundamentally based on the anatomical relationship of four key segments: the articular segment (humeral head), the greater tuberosity, the lesser tuberosity, and the humeral shaft. A segment is only considered a distinct "part" if it is displaced by more than one centimeter or angulated by more than 45 degrees relative to its native anatomical position. Therefore, a severely comminuted fracture with minimal displacement may still be classified as a "one-part" fracture. The AO/OTA classification system offers a more morphological approach, categorizing fractures into unifocal extra-articular (Type A), bifocal extra-articular (Type B), and articular (Type C) lesions, providing a high degree of detail useful for research but often deemed overly cumbersome for rapid clinical communication.

The economic and societal burden of proximal humerus fractures cannot be overstated. In the elderly, the loss of upper extremity independence translates directly to an inability to perform activities of daily living (ADLs), often precipitating a transition from independent living to assisted care facilities. The evolution of management strategies over the past two decades reflects an ongoing attempt to balance the risks of surgical intervention against the profound morbidity of a dysfunctional shoulder. While open reduction and internal fixation (ORIF) with anatomically contoured locking plates revolutionized the treatment of these fractures in the early 2000s, the unacceptably high failure rates in osteoporotic bone have recently driven a paradigm shift toward shoulder arthroplasty—specifically, reverse total shoulder arthroplasty (rTSA)—as the definitive management for complex fracture patterns in the geriatric population.

Detailed Surgical Anatomy and Biomechanics

A masterful command of the surgical anatomy and regional biomechanics is the foundational prerequisite for the successful operative management of proximal humerus fractures. The proximal humerus is defined by the articular surface, the anatomical neck, the surgical neck, and the greater and lesser tuberosities. The anatomical neck represents the true junction between the articular cartilage and the metaphyseal bone, and fractures through this region carry a profoundly high risk of avascular necrosis (AVN) due to the disruption of intraosseous vascular anastomoses. The surgical neck, located distal to the tuberosities, is the most frequent site of fracture. The bicipital groove (intertubercular sulcus) lies between the greater and lesser tuberosities, housing the long head of the biceps tendon, which serves as an indispensable surgical landmark for identifying the anatomical interval between the tuberosities during complex reconstructions.

Historically, orthopedic dogma dictated that the ascending branch of the anterior circumflex humeral artery (often referred to as the arcuate artery of Laing) was the primary and most critical blood supply to the humeral head. However, modern cadaveric and advanced perfusion studies have fundamentally redefined our understanding of this vascular network. Landmark investigations by Brooks et al. and Hettrich et al. have conclusively demonstrated that the posterior circumflex humeral artery (PCHA) provides the predominant vascular supply—accounting for approximately 64% of the blood flow to the humeral head. The PCHA supplies the critical inferomedial and central portions of the articular segment. Consequently, surgical approaches and reduction techniques must meticulously avoid iatrogenic injury to the posterior and inferior capsular structures to preserve this vital perfusion. The anterior circumflex humeral artery, while still important for the supply of the greater tuberosity and anterior structures, is no longer considered the sole arbiter of humeral head viability.

The displacement of fracture fragments in the proximal humerus is predictably dictated by the powerful deforming forces of the attaching musculature. The greater tuberosity serves as the insertion site for the superior and posterior rotator cuff—namely, the supraspinatus, infraspinatus, and teres minor. When fractured, the greater tuberosity is classically pulled superiorly and posteriorly, leading to subacromial impingement and loss of external rotation if left unreduced. The lesser tuberosity is the insertion site for the subscapularis; a displaced lesser tuberosity fragment is pulled medially, disrupting the anterior mechanical block to instability and severely compromising internal rotation. The pectoralis major, inserting on the lateral lip of the bicipital groove on the humeral shaft, exerts a massive medializing and anteriorizing force on the distal shaft fragment. Finally, the deltoid muscle contributes to the proximal migration of the humeral shaft. Understanding these vectorial forces is essential for executing provisional reduction maneuvers and determining the placement of neutralizing fixation.

Predicting the risk of humeral head ischemia is a critical component of anatomical assessment. Hertel’s radiographic criteria provide a highly reliable framework for anticipating avascular necrosis following proximal humerus fractures. The most significant predictors of ischemia include a metaphyseal head extension (calcar length) of less than 8 millimeters, a disrupted medial hinge with greater than 2 millimeters of displacement, and the presence of an anatomical neck fracture. When all three of these criteria are present, the positive predictive value for ischemia approaches 97%. Recognizing these anatomical disruptions pre-operatively allows the surgeon to intelligently counsel the patient and pivot the surgical plan from osteosynthesis to arthroplasty when the biological environment is deemed unsalvageable.

Exhaustive Indications and Contraindications

The decision-making matrix for proximal humerus fractures is notoriously complex, requiring the surgeon to synthesize patient-specific variables (chronological and physiological age, bone mineral density, functional demands, medical comorbidities) with fracture-specific variables (Neer classification, degree of comminution, head split presence, tuberosity displacement, and Hertel criteria). There is no universally applicable algorithm; rather, treatment must be highly individualized.

Non-operative management remains the gold standard for the vast majority (approximately 80%) of proximal humerus fractures. Minimally displaced fractures, defined strictly by Neer's criteria (<1cm displacement, <45 degrees angulation), predictably heal with conservative care, yielding excellent functional outcomes. Furthermore, non-operative management is frequently indicated even in significantly displaced fractures if the patient is a low-demand, frail elderly individual with severe medical comorbidities that preclude safe anesthesia, or in patients with profound cognitive impairment (e.g., advanced dementia) who cannot comply with strict post-operative rehabilitation protocols. In these scenarios, the goal shifts from anatomical restoration to pain control and the achievement of a functional, albeit limited, "pseudo-articulation."

Operative intervention is strongly indicated for displaced two-, three-, and four-part fractures in physiologically young and active patients where the preservation of native joint mechanics is paramount. Open reduction and internal fixation (ORIF) with a locking plate construct is the workhorse procedure for these scenarios. Operative management is also indicated for open fractures, fractures associated with progressive neurovascular compromise, and pathological fractures. In the elderly population with complex three- or four-part fractures, particularly those with poor bone stock, head-split components, or high risk of AVN, primary arthroplasty is indicated. While hemiarthroplasty was historically the procedure of choice, the unpredictable healing of the tuberosities around the prosthesis often led to catastrophic functional failures (anterosuperior escape). Consequently, reverse total shoulder arthroplasty (rTSA) has largely supplanted hemiarthroplasty, as it relies on the deltoid rather than the rotator cuff for elevation, providing more reliable functional outcomes even in the setting of tuberosity nonunion or resorption.

Contraindications to surgical intervention must be strictly respected to avoid devastating iatrogenic complications. Absolute contraindications include active local or systemic infection, severe medical instability precluding anesthesia, and the presence of a paralyzed, functionless extremity (e.g., complete brachial plexus avulsion). Relative contraindications include severe osteopenia where hardware purchase is deemed impossible, non-compliance due to psychiatric or cognitive disorders, and long-standing neglected fractures where soft tissue contractures preclude anatomical reduction without unacceptable neurovascular tension.

Indications and Contraindications Summary

Pre-Operative Planning, Templating, and Patient Positioning

Thorough pre-operative planning is the cornerstone of successful surgical execution. The radiographic evaluation must begin with a complete, high-quality trauma series of the shoulder, which includes a true anteroposterior (Grashey) view, a Scapular Y view, and an axillary lateral view. The axillary lateral is absolutely non-negotiable, as it is the only view that reliably demonstrates the relationship of the humeral head to the glenoid (ruling out occult dislocations) and allows for the assessment of lesser tuberosity displacement. In patients whose pain precludes the abduction required for a standard axillary view, a Velpeau axillary view (taken with the patient in a sling, leaning obliquely backward over the cassette) provides an adequate alternative.

Advanced imaging via Computed Tomography (CT) is highly recommended for all complex fracture patterns being considered for operative intervention. A CT scan with 3-dimensional surface rendering provides unparalleled visualization of articular head-split components, the exact degree of tuberosity comminution, and the presence of an intact medial calcar hinge. This information is critical for differentiating between fracture patterns amenable to osteosynthesis and those requiring primary arthroplasty. Furthermore, CT imaging allows the surgeon to assess the local bone mineral density and the volume of the humeral head, which dictates the type and length of screws required for adequate purchase.

Digital templating should be performed routinely. Utilizing the uninjured contralateral shoulder as a reference, the surgeon can estimate the native neck-shaft angle, the appropriate height for plate placement, and the anticipated trajectory of the critical calcar screws. Templating also aids in anticipating the need for structural allografts (e.g., fibular strut grafts) in cases of severe medial comminution or metaphyseal voids, which mechanically augment the medial column and prevent catastrophic varus collapse.

Patient positioning is a critical step that directly influences the ease of reduction and fluoroscopic visualization. The beach chair position is overwhelmingly preferred by most shoulder surgeons. The patient is placed in a semi-upright position (approximately 45 to 60 degrees), with the hips and knees slightly flexed to prevent sciatic nerve tension. The operative arm must be completely free to allow for unrestricted manipulation, extension, and rotation. A specialized shoulder positioner or a pneumatic arm holder is highly advantageous. The beach chair position utilizes gravity to assist in reducing the proximally migrated shaft fragment and allows for seamless conversion to an arthroplasty approach if intraoperative findings dictate a change in plan. However, the anesthesia team must maintain vigilant hemodynamic monitoring, as the upright posture increases the risk of cerebral hypoperfusion events. The fluoroscopy (C-arm) unit should be brought in from the head of the bed or the contralateral side, ensuring that orthogonal views can be obtained without compromising the sterile field or requiring awkward maneuvering of the injured extremity.

Step-by-Step Surgical Approach and Fixation Technique

The standard deltopectoral approach remains the most versatile and widely utilized surgical corridor for the management of proximal humerus fractures. It provides extensile exposure to the glenohumeral joint, the tuberosities, and the humeral shaft while exploiting a true internervous plane between the deltoid (axillary nerve) and the pectoralis major (medial and lateral pectoral nerves).

The incision begins at the tip of the coracoid process and extends distally and laterally toward the deltoid tuberosity, following the path of the cephalic vein. The cephalic vein serves as the visual sentinel for the deltopectoral interval. While historically debated, modern consensus favors retracting the vein laterally with the deltoid muscle to preserve its primary venous tributaries, though medial retraction is acceptable if local anatomy dictates. Once the interval is developed, the clavipectoral fascia is incised lateral to the conjoined tendon (coracobrachialis and short head of the biceps). The conjoined tendon is retracted medially, taking meticulous care to avoid aggressive traction that could result in a neuropraxia to the musculocutaneous nerve, which enters the muscle belly proximally.

Deep dissection reveals the subdeltoid and subacromial bursae, which are excised to expose the fracture hematoma. The long head of the biceps tendon is identified within the bicipital groove; this structure is the "Rosetta Stone" of proximal humeral anatomy, definitively separating the greater tuberosity (posterior/lateral) from the lesser tuberosity (anterior/medial). In highly comminuted fractures, the biceps tendon may be incarcerated within the fracture site and must be carefully extricated.

Fracture reduction begins with control of the tuberosities. Heavy, non-absorbable, braided sutures (e.g., #5 FiberWire or equivalent) are passed through the bone-tendon junction of the supraspinatus/infraspinatus (greater tuberosity) and the subscapularis (lesser tuberosity). These "tag sutures" serve a dual purpose: they allow the surgeon to manipulate and reduce the tuberosities out of the joint space, and they will ultimately be tied through the plate to neutralize the rotator cuff's deforming forces. The humeral head is then reduced onto the metaphyseal shaft. Restoration of the medial cortical hinge (the calcar) is the most critical biomechanical step in preventing post-operative varus collapse. If the medial column is severely comminuted, an intramedullary fibular strut allograft should be impacted into the humeral shaft to provide rigid medial support.

Fixation is typically achieved using an anatomically pre-contoured proximal humeral locking plate. The plate must be positioned meticulously: it should sit just lateral to the bicipital groove (to avoid injuring the ascending branch of the anterior circumflex humeral artery and the biceps tendon) and approximately 5 to 8 millimeters distal to the superior tip of the greater tuberosity. Placing the plate too high guarantees subacromial impingement during shoulder elevation. Provisional fixation is achieved with K-wires. Locking screws are then sequentially placed into the humeral head. The placement of inferomedial "calcar screws" is strictly mandatory; these screws must engage the dense bone of the inferior quadrant of the humeral head to act as a mechanical buttress against the massive varus forces exerted by the deltoid and pectoralis major. Finally, the previously placed tuberosity sutures are passed through dedicated suture holes in the plate and tied securely, creating a tension-band effect that compresses the tuberosities against the shaft and plate.

Complications, Incidence Rates, and Salvage Management

Despite advancements in implant technology and surgical technique, the operative management of proximal humerus fractures is fraught with a high complication profile, particularly in the osteoporotic elderly population. The surgeon must be acutely aware of these potential pitfalls, aggressively work to prevent them during the index procedure, and possess the technical armamentarium to manage them when they occur.

Mechanical failure, specifically varus collapse and secondary screw cutout, represents the most frequent complication following ORIF. As the humeral head collapses into varus under the deforming pull of the musculature, the rigid locking screws do not back out; instead, they perforate the articular cartilage and impinge upon the glenoid, causing rapid and devastating chondrolysis. This complication is directly correlated with the failure to restore medial calcar support or the omission of inferomedial calcar screws. Salvage of screw cutout typically requires hardware removal and, depending on the degree of articular damage, conversion to a hemiarthroplasty or rTSA.

Avascular necrosis (AVN) of the humeral head is a biologically driven complication resulting from the disruption of the posterior circumflex humeral artery and intraosseous anastomoses. The incidence of AVN is highly variable, ranging from less than 5% in two-part fractures to over 30% in complex four-part fractures or anatomical neck fractures. Interestingly, not all cases of radiographic AVN translate to poor clinical outcomes; partial head necrosis may be surprisingly well-tolerated if the articular geometry remains relatively spherical. However, symptomatic AVN with subchondral collapse necessitates surgical salvage, uniformly via shoulder arthroplasty.

Neurologic injuries are relatively common, with the axillary nerve being the most frequently injured structure due to its proximity to the inferior capsule and its course around the surgical neck. Most axillary nerve deficits are traction neuropraxias sustained at the time of injury and resolve spontaneously within 3 to 6 months. Iatrogenic injury can occur from aggressive retraction or errant drill placement during lateral plate application. Post-operative stiffness (adhesive capsulitis) is nearly universal to some degree; hence, early passive motion is critical.

Complications, Incidence, and Salvage Matrix

Phased Post-Operative Rehabilitation Protocols

The success of surgical intervention in proximal humerus fractures is inextricably linked to a rigorously structured, phased post-operative rehabilitation protocol. The overarching goal of rehabilitation is to navigate the delicate biological tightrope between protecting the fragile osteosynthesis construct to allow for bony union and preventing the severe, functionally limiting adhesive capsulitis that plagues the shoulder joint following trauma. Communication between the orthopedic surgeon and the physical therapist must be explicit, detailing bone quality, the rigidity of fixation, and the status of the tuberosity repairs.

Phase I: Maximum Protection and Early Passive Motion (Weeks 0 to 4)
Immediately post-operatively, the patient is placed in a clinical sling or shoulder immobilizer. The primary objective during this phase is the protection of the fracture site and the mitigation of post-operative edema. Strict avoidance of any active range of motion (ROM) of the shoulder is mandatory to prevent the rotator cuff from exerting catastrophic pull-out forces on the tuberosity fixation. However, to prevent distal edema and stiffness, active ROM of the elbow, wrist, and hand is initiated on post-operative day one. Gentle, gravity-dependent pendulum exercises (Codman exercises) are permitted. By week two, formal passive range of motion (PROM) in forward elevation and external rotation (limited to 30 degrees to protect the subscapularis repair) is initiated by the therapist.

Phase II: Active-Assisted and Early Active Motion (Weeks 4 to 8)
Progression to Phase II is contingent upon radiographic evidence of early callus formation and clinical stability of the fracture site. The sling is gradually weaned and discontinued. The patient transitions from passive to active-assisted range of motion (AAROM) utilizing pulleys, cane exercises, and wall-walks. As the fracture consolidates, typically around week 6, true active range of motion (AROM) is initiated. The focus shifts to re-establishing neuromuscular control of the periscapular stabilizers (serratus anterior, rhomboids, trapezius) to prevent compensatory scapulothoracic hiking, which is a common maladaptive movement pattern following shoulder trauma.

Phase III: Strengthening and Functional Return (Weeks 8 to 12+)
Once radiographic union is confirmed—usually between 8 and 10 weeks—the patient enters the strengthening phase. Isotonic and isometric strengthening of the rotator cuff and deltoid musculature begins using resistance bands and light weights. The physical therapist focuses on optimizing glenohumeral kinematics and restoring endurance. Advanced proprioceptive exercises and sport-specific or occupation-specific training are introduced late in this phase. Patients must be counseled that maximal medical improvement following a complex proximal humerus fracture may take up to 12 to 18 months, and some permanent deficit in extreme overhead elevation or terminal rotation is a common, expected outcome.

Summary of Landmark Literature and Clinical Guidelines

The evolution of proximal humerus fracture management is deeply rooted in several landmark publications that have continuously challenged and refined orthopedic dogma.

Charles Neer’s seminal 1970 publication in the Journal of Bone and Joint Surgery fundamentally established the modern anatomical classification system. By defining fractures based on the displacement of the four major anatomical segments rather than mere fracture lines, Neer provided a prognostic framework that remains the global standard half a century later. His work also highlighted the high rate of AVN associated with four-part fractures, laying the groundwork for early prosthetic replacement strategies.

In 2004, Hertel et al. published a critical study in the Journal of Shoulder and Elbow Surgery that revolutionized the prediction of humeral head ischemia. By meticulously analyzing perfusion patterns and radiographic parameters, Hertel established that the length of the metaphyseal head extension (calcar length) and the integrity of the medial hinge are the most powerful predictors of post-traumatic ischemia. This paper is required reading for all orthopedic trainees, as it directly informs the intraoperative decision to attempt joint-preserving ORIF versus proceeding to primary arthroplasty.

The management of displaced proximal humerus fractures in the elderly was profoundly disrupted by the publication of the PROFHER (Proximal Fracture of the Humerus Evaluation by Randomisation) trial in JAMA in 2015. This large, multicenter randomized controlled trial compared surgical intervention (predominantly ORIF and hemiarthroplasty) with non-surgical management for displaced two-, three-, and four-part fractures in patients over the age of 65. The study concluded that there was no significant difference in patient-reported clinical outcomes or quality of life between the surgical and non-surgical groups at two years. While heavily debated and criticized for its heterogeneous surgical techniques and inclusion criteria, the PROFHER trial forced the orthopedic community to critically re-evaluate the indications for surgery in the elderly, reinforcing the validity of conservative management for a substantial portion of this demographic.

Most recently, the literature has been dominated by the shift toward reverse total shoulder arthroplasty (rTSA) for complex fractures in the geriatric population. Landmark outcome studies by Boileau, Sirveaux, and others have demonstrated that rTSA provides more predictable pain relief and functional elevation compared to hemiarthroplasty or ORIF in osteoporotic bone, largely because it circumvents the reliance on tuberosity healing for overhead function. Current clinical guidelines from the American Academy of Orthopaedic Surgeons (AAOS) reflect this literature, strongly supporting non-operative management for minimally displaced fractures, ORIF for young patients with reconstructable patterns, and rTSA as the arthroplasty of choice for non-reconstructable fractures in the elderly.