What Is the Proximal Humerus and How Are Fractures Treated?

The proximal humerus is the upper end of the arm bone, the part that forms the ball of the ball-and-socket shoulder joint. It matters most in clinical practice because it breaks frequently: proximal humerus fractures rank among the three most common fractures in older adults, and the region’s unusual blood supply, complex muscle attachments, and proximity to major nerves make treatment decisions anything but straightforward. Whether you have been told you have one of these fractures, are recovering from shoulder surgery, or simply want to understand why the top of the arm bone gets so much attention in orthopedics, the anatomy of this region explains almost everything about how injuries happen and how they heal.

What Makes Up the Proximal Humerus

The proximal humerus has four main parts that surgeons think of as separate “segments” because each can break off independently. The humeral head is the smooth, rounded ball that sits in the shallow socket of the shoulder blade. Flanking it are two bony bumps called the greater tuberosity (on the outer side) and the lesser tuberosity (on the front). Between them lies a groove where the biceps tendon runs. Below these structures is the surgical neck, a slightly narrower zone where the bone transitions into the shaft. The rotator cuff tendons attach directly to the tuberosities, which is why a fracture through that area can drag muscle attachments apart and complicate healing.

The shape of the tuberosities themselves influences shoulder health even before a fracture occurs. Research comparing shoulders with intact rotator cuffs to those with torn cuffs found that the angle of the middle facet of the greater tuberosity differed between the two groups, averaging about 36 degrees in intact shoulders versus roughly 31 degrees in torn ones. A flatter angle on the greater tuberosity may reduce the downward pull the infraspinatus muscle exerts on the humeral head, making impingement beneath the bony arch above the shoulder more likely.¹

Blood Supply and Why It Matters

One of the trickiest aspects of the proximal humerus is its blood supply. For decades, surgeons assumed the anterior humeral circumflex artery was the dominant feeder of the humeral head. More recent work overturned that view. A study using contrast injection in cadavers found that the posterior humeral circumflex artery actually provides about 64% of the blood to the humeral head, while the anterior artery contributes roughly 36%.² Detailed imaging of the intraosseous branch of the anterior artery has also shown that blood flow within the greater tuberosity runs in a medial direction and concentrates toward the lower part of the humeral head. The anterior-superior and superior-medial zones of the head receive little direct perfusion, creating a high-risk zone for avascular necrosis when fractures disrupt the remaining blood supply.³

This vascular anatomy has direct surgical consequences. When a fracture-dislocation disrupts both circumflex arteries, the humeral head can lose its blood supply entirely. A small study of fracture-dislocations found that when surgery was delayed, every patient developed avascular necrosis, compared with a 20% rate in those operated on within the first two days.⁴ This is why surgeons treat certain displaced fracture-dislocations as time-sensitive injuries.

Who Fractures the Proximal Humerus and Why

These fractures overwhelmingly affect older adults, especially postmenopausal women, and the biggest predictor is bone density. The Dubbo Osteoporosis Epidemiology Study found that low bone mineral density at the hip was the primary independent risk factor for proximal humerus fractures in both men and women, roughly doubling the risk.⁵ But bone fragility alone does not tell the whole story. The EPIDOS study, which followed thousands of older women, identified a cluster of fall-related risk factors including previous falls, low physical activity, impaired balance, and lower limb pain. These fall-related factors were especially predictive in women who already had osteoporosis, essentially compounding the risk of weak bone with the likelihood of hitting the ground.⁶

In younger adults, proximal humerus fractures typically require higher-energy trauma such as a fall from height, a motor vehicle collision, or a sports injury. In children and adolescents, these fractures account for a small proportion of pediatric fractures, and the presence of the growth plate adds a layer of complexity and also an advantage: younger bones remodel, meaning the body can reshape a displaced fracture over time as the child grows.⁷

Diagnosing and Classifying These Fractures

Standard X-rays remain the first-line imaging for a suspected proximal humerus fracture, but they have limits. CT scans allow significantly better assessment of the fracture pattern, regardless of how many fragments are present.⁸ Three-dimensional CT reconstructions and even 3D-printed models of the fracture have shown improved reliability for certain evaluations, though among experienced surgeons and senior residents, the jump from 2D to 3D CT did not significantly improve agreement on fracture classification.⁹

The classification issue itself is a known weak spot in this field. The Neer classification, the system most widely used to describe how many parts of the proximal humerus have broken apart, has surprisingly poor agreement between observers. A large survey of orthopedic shoulder surgeons found only fair interobserver reliability, with a kappa value of about 0.30.¹⁰ In plain terms, two experienced shoulder surgeons looking at the same fracture images disagree about the classification a substantial portion of the time. This unreliability has real consequences because treatment recommendations often hinge on which “type” of Neer fracture a surgeon sees.

When Surgery Is Not Needed

A large proportion of proximal humerus fractures are minimally displaced, meaning the fragments have not shifted far from their normal position. These generally heal well without surgery. One prospective study of conservatively managed fractures found that at one year, the average functional score on the injured shoulder was only about 8 points lower than on the healthy side, and the risk of delayed healing or nonunion was around 7%.¹¹

Even for displaced fractures in older adults, the case for surgery is weaker than many people expect. A systematic review and meta-analysis combining data from both randomized trials and observational studies found no difference in functional outcomes between surgical and nonsurgical treatment, while reoperations were more common in the surgical group. The authors recommended nonoperative treatment as the default for the typical patient over 65 with a displaced proximal humerus fracture.¹² This does not mean surgery is never appropriate in this age group, but it does mean that a sling, pain management, and early rehabilitation are often enough.

Plates, Nails, and Choosing Between Them

When a fracture is displaced enough to warrant fixation, surgeons have two main options: a locking plate applied to the outside of the bone through an open incision, or an intramedullary nail inserted down the center of the bone through a smaller entry point near the top of the shoulder. Both techniques have passionate proponents, and the evidence suggests neither is clearly superior overall. A systematic review and meta-analysis found no significant differences between nails and plates in functional scores, pain levels, range of motion, complication rates, or reoperation rates at six or twelve months.¹³ A review of the comparative literature reached a similar conclusion, noting that some studies found plates slightly better for external rotation while others found nails biomechanically superior for unstable fractures, ultimately suggesting that fracture pattern and implant design matter more than the broad category of fixation.¹⁴

Locking plates are well studied, and so are their complications. A large pooled analysis of over 3,400 fractures treated with locking plates found that the most common complication was screws penetrating into the joint (about 10% of cases), followed by the humeral head collapsing into a tilted position (about 7%), and avascular necrosis (about 5%). Roughly one in seven patients needed another operation.¹⁵ Longer-term follow-up paints a sobering picture: one prospective study at six years found that avascular necrosis developed in about a fifth of patients and post-traumatic arthritis in about a third, and roughly a third required reoperation.¹⁶ Augmenting fixation with a fibular strut graft placed inside the bone canal has shown promise for improving stability, with one series reporting that all patients achieved bony union and near-normal motion at one year.¹⁷

When Joint Replacement Is the Better Option

For severely comminuted fractures, especially three- and four-part fractures in older patients where the humeral head is unlikely to survive or where fixation would be unreliable, joint replacement becomes the preferred strategy. The two main choices are hemiarthroplasty, which replaces only the ball, and reverse total shoulder arthroplasty, which flips the ball-and-socket relationship so the deltoid muscle rather than the rotator cuff drives shoulder movement.

Reverse shoulder arthroplasty has increasingly won this contest. A randomized trial in patients aged 70 and older with displaced three- and four-part fractures found that the reverse group achieved a mean functional score about 11 points higher than the hemiarthroplasty group, along with markedly better overhead reach and satisfaction.¹⁸ Another randomized trial confirmed significantly higher functional scores and better forward elevation and abduction with the reverse design, and also highlighted a critical difference: in the hemiarthroplasty group, when the tuberosities failed to heal, functional outcomes dropped sharply, whereas outcomes after reverse arthroplasty were less dependent on tuberosity healing.¹⁹ A systematic review noted that reverse arthroplasty did produce better forward flexion but slightly less external rotation, and had a higher rate of clinical complications alongside a lower revision rate compared with hemiarthroplasty.²⁰

A cost-utility analysis reinforced the clinical findings, concluding that reverse arthroplasty was consistently more effective and less costly than either locking plate fixation or hemiarthroplasty in elderly patients, while nonoperative care remained the cheapest option but yielded the fewest quality-adjusted life years.²¹ A separate economic evaluation alongside a large randomized trial found that surgery in general accumulated about £1,758 more in costs per patient than nonoperative care, with no improvement in quality of life, and had less than a 10% probability of being cost-effective.²²

Getting the Tuberosities to Heal

When a reverse shoulder arthroplasty is performed for a fracture, the surgeon typically reattaches the tuberosity fragments around the prosthesis using sutures. Whether those fragments heal in position turns out to matter a great deal. A systematic review and meta-analysis of 21 studies found that anatomic healing of the greater tuberosity after reverse arthroplasty led to significantly better abduction, forward elevation, and external rotation.²³ A separate meta-analysis confirmed that healed tuberosities were associated with higher forward flexion, external rotation, internal rotation, and Constant scores.²⁴ One clinical series using a 135-degree prosthesis design achieved an 82% tuberosity healing rate and found that patients with healed tuberosities achieved dramatically better abduction, flexion, external rotation, and satisfaction compared with those whose tuberosities did not heal.²⁵ Achieving tuberosity healing is one of the main technical challenges of fracture arthroplasty, and prosthesis design continues to evolve to improve it.

Nerve Injuries Around the Proximal Humerus

The axillary nerve wraps around the surgical neck of the humerus at close range, and the suprascapular nerve runs nearby as well. Many patients do not realize that nerve damage is common with these fractures. An electromyography study of 143 patients found nerve injuries in about two-thirds of them. The axillary nerve was affected in 58% and the suprascapular nerve in 48%, and combinations of nerve injuries were frequent. Displaced fractures carried a higher rate of nerve damage (about 82%) than nondisplaced fractures (about 59%). The reassuring finding was that nerve function and muscle strength recovered in all patients, though recovery could take a long time.²⁶ Numbness over the outer shoulder or difficulty raising the arm after a fracture may reflect axillary nerve involvement rather than just pain or stiffness.

Rehabilitation and Early Movement

There is a natural temptation to keep a fractured shoulder completely still until the bone heals, but the evidence favors moving sooner rather than later. A randomized trial comparing immediate mobilization to conventional immobilization followed by physiotherapy in patients with impacted, nonoperatively treated fractures found that the early-movement group had significantly better functional scores and less pain at six weeks and three months, with no increase in fracture displacement or healing problems.²⁷ A more recent meta-analysis of randomized trials confirmed a statistically significant advantage for early mobilization in combined function scores at three months, though the difference became less clear at later time points, and complication rates were similar between groups.²⁸ A separate systematic review found that early mobilization resulted in slightly better Constant Shoulder Scores but noted the difference was not large enough to be considered clinically meaningful on its own; it did not lead to more complications.²⁹

The practical takeaway is that for stable, nonoperatively managed fractures, gentle pendulum exercises and guided motion started within the first week or two appear safe and help restore function faster, even if the long-term endpoint is similar. Stiffness is one of the most common complaints after proximal humerus fractures, and early movement helps prevent it without jeopardizing bone healing.

The Pediatric Situation

Proximal humerus fractures in children follow different rules. Because the growth plate near the top of the humerus contributes most of the bone’s longitudinal growth, younger children have enormous remodeling capacity. A fracture that would require surgery in an adult can straighten itself out in a growing child. A systematic review of pediatric outcomes found favorable results for minimally displaced fractures regardless of treatment method, and for children under 10, outcomes were generally good even with significant displacement.³⁰ The debate heats up for adolescents, particularly those close to skeletal maturity, who have less remodeling potential and may need surgical reduction if the fracture is badly displaced.

Cement Augmentation for Osteoporotic Bone

Weak bone is the reason many of these fractures happen in the first place, and it is also the reason fixation can fail. Screws placed into osteoporotic bone may loosen, back out, or cut through the soft cancellous bone of the humeral head. One approach to this problem is injecting bone cement through cannulated screws after plate fixation. The cement spreads between the spongy bone trabeculae around each screw tip, creating a root-like complex that anchors the hardware more firmly. This technique has been shown to increase screw-bone interface strength, reduce the incidence of screw loosening and pull-out, and lower the risk of humeral head collapse.³¹ Various cement types and augmentation strategies have been described, including polymethyl methacrylate and calcium phosphate cement, and the technique is gaining traction as the population ages and the proportion of osteoporotic fractures rises.³²

Tumors and Reconstruction After Resection

Beyond fractures, the proximal humerus is a relatively common site for bone tumors, both primary cancers and metastases from cancers elsewhere. When a tumor requires wide surgical removal of the proximal humerus, reconstruction is challenging because you are replacing not just bone but the attachment points for the rotator cuff and deltoid. Options include allograft bone from a donor, a custom metal prosthesis (megaprosthesis), a reverse total shoulder prosthesis, or composite constructs that combine donor bone with a prosthesis.³³ Reverse total shoulder arthroplasty has become increasingly popular in this setting, especially when the rotator cuff must be sacrificed during tumor removal, because the reverse design relies on the deltoid rather than the cuff for overhead function.³⁴

A systematic review of reconstruction methods found that functional scores were broadly similar across prosthetic options, with patients generally limited to about 45 to 90 degrees of active abduction. Reoperation rates were lowest with autograft arthrodesis (about 11%) and megaprosthesis (about 10%), and highest with osteoarticular allograft (about 34%). When the rotator cuff was removed but the deltoid and axillary nerve were preserved, reverse arthroplasty provided the best active forward flexion and abduction among the available options.³⁵

What the Proximal Humerus Reveals About Human Evolution

The shape of the proximal humerus carries a surprising amount of evolutionary information. A three-dimensional analysis of the proximal humeral shape across living great apes, modern humans, and the early hominin Australopithecus afarensis found significant morphological differences that track with each species’ way of moving. Modern humans have a distinctly different proximal humerus from all the great apes, reflecting our complete commitment to upright walking and our abandonment of arm-based locomotion. The 3.2-million-year-old A. afarensis, despite being bipedal on the ground, had a proximal humerus more closely resembling an orangutan’s than a modern human’s, suggesting that its forelimbs were still functionally involved in climbing or hanging from branches even as its legs had already adapted for walking upright.³⁶ The proximal humerus, in other words, is a fossil record of how we gradually gave up the trees.