What Is an Impacted Fracture? Causes and Treatment

An impacted fracture is a break where the broken ends of the bone are driven into each other rather than separating apart. Instead of a clean gap between fragments, the pieces compress together and interlock, sometimes telescoping one into the other. This makes impacted fractures distinct from most other breaks, and it also makes them surprisingly easy to miss on initial imaging. The compressed bone ends can provide a degree of built-in stability, which changes the treatment calculus considerably, but that stability is not always reliable.

How an Impacted Fracture Happens

The defining force behind an impacted fracture is compression along the bone’s long axis. When a load pushes straight through the length of a bone, rather than bending or twisting it, the pieces tend to crumple into each other instead of flying apart. A fall onto an outstretched hand drives force up through the wrist and forearm. A fall directly onto the shoulder compresses the top of the upper arm bone downward. A stumble that lands your full weight on one leg sends a shock straight up through the hip. In each case, the energy travels along the bone like a car crashing into a wall, and the bone collapses inward at its weakest point.

Experimental work confirms this pattern. When bones are subjected to axial loading during impact, the resulting fracture is shaped differently than fractures from sideways or bending forces. The number of fracture lines becomes less dependent on the direction of the blow and more dependent on the sheer compressive energy involved.¹ Cadaveric studies on the proximal radius, for example, show that axial compression produces characteristic fracture shapes when the bone fails under the load.²

This is why impacted fractures are especially common in falls. Young, healthy people can sustain them after high-energy impacts like car accidents or sports collisions. But older adults with weaker bones can get impacted fractures from something as ordinary as a stumble at home, because the spongy bone in the hip, shoulder, and wrist is already soft enough to compress under relatively modest force.

Why Osteoporosis Makes These Fractures More Likely

Impacted fractures have a strong relationship with osteoporosis, the condition where bones become porous and fragile over time. The spongy interior of bones, especially near joints, loses density with age. That interior is precisely where impacted fractures happen, because the thin lattice of bone tissue collapses more easily when it is already thinned out. The lifetime risk of a fragility fracture is around 50% in Caucasian women and about 20% in men, and impacted fractures of the hip, shoulder, and wrist are among the most typical types.³

This is not to say that only older adults get impacted fractures. A skier who crashes and catches their weight on one hand, or a football player who takes a direct hit to the top of the shoulder, can absolutely sustain one regardless of bone density. But the frequency goes up sharply in people whose bones are already compromised, and those patients tend to get impacted fractures from less dramatic injuries.

Where Impacted Fractures Show Up Most Often

Three areas of the body account for the vast majority of impacted fractures: the hip, the shoulder, and the wrist. Each has its own clinical quirks.

The Hip

An impacted hip fracture usually occurs at the femoral neck, the narrow bridge of bone connecting the ball of the hip joint to the shaft of the thighbone. In a valgus-impacted fracture, the ball portion gets driven slightly upward and outward into the surrounding bone, creating what surgeons call a Garden type I fracture. The bone fragments remain engaged with each other, which is why some patients with these fractures can actually still walk, albeit with pain, leading to delayed diagnosis.

Despite that apparent stability, things can go wrong. Several studies have noted that when the femoral neck is tilted more than about 20 degrees on a lateral X-ray, the risk of the fracture shifting later climbs significantly.⁴ The best treatment for these fractures, whether screws, a partial hip replacement, or something else entirely, remains genuinely controversial, and the debate has not settled.⁵

The Shoulder

Impacted fractures of the proximal humerus, the top of the upper arm bone near the shoulder, are also common. Research looking at the patterns of these fractures found that the overwhelming majority followed one of a few predictable shapes. Posteromedial impaction, sometimes called varus impaction, was by far the most frequent pattern, occurring in over half of cases. Lateral or valgus impaction accounted for about 14%. The direction of the impaction turns out to matter quite a bit for recovery: lateral impaction fractures tended to have worse outcomes than other patterns.⁶

The Wrist

Falling onto an outstretched hand commonly produces impacted fractures of the distal radius, the larger forearm bone at the wrist. The force of impact can push bone fragments into the joint surface, creating what are called impacted articular fragments. These are clinically significant because they can disrupt the smooth surface needed for the wrist joint to move properly. Imaging studies have shown that these impacted central articular fragments are a recognized feature of intra-articular distal radius fractures.⁷ The complexity of treating these fractures increases when the pieces are pushed deep enough that they need to be “disimpacted,” or pried back up into their original position, before fixation.⁸

Why These Fractures Are Easy to Miss

One of the more frustrating aspects of impacted fractures is that standard X-rays can fail to show them clearly. Because the bone ends are jammed together rather than separated, there may be no obvious gap or displacement visible on a plain film. A patient might have a genuine fracture and a nearly normal-looking X-ray.

CT scans are considerably more sensitive. In a study comparing X-ray to CT for wrist injuries, X-rays caught radius fractures about 95% of the time, but their sensitivity dropped sharply for smaller carpal bones and for fractures extending into the joint space, where it fell to around 75%.⁹ For knee injuries, X-ray sensitivity for features like fracture lines reaching the joint surface was 78% or less.¹⁰ The practical takeaway is that if you have significant pain after a fall and the initial X-ray looks “fine,” a CT or MRI might still be warranted, particularly for the hip and wrist where impacted fractures commonly hide.

For impacted hip fractures, MRI is often the follow-up of choice when X-rays are equivocal. It can reveal bone marrow edema, swelling inside the bone itself, that confirms a fracture even when the cortex looks intact on X-ray. Many older patients with hip pain after a fall end up getting an MRI specifically because the suspicion of an occult impacted fracture is high.

Treatment Depends on Stability

The key question with any impacted fracture is whether the interlocked fragments will stay put or whether they are likely to shift. A stable impacted fracture, where the bone ends are firmly engaged and well-aligned, can sometimes heal without surgery. An unstable one, or one where the joint surface is disrupted, usually requires an operation.

Non-Operative Management

For certain impacted hip fractures, non-operative treatment with controlled weight-bearing has shown reasonable results. In one large study of Garden I hip fractures managed without surgery, secondary displacement occurred in about 30% of patients, typically within the first few weeks. Avascular necrosis of the femoral head, where the bone dies from lost blood supply, developed in roughly 4% of cases.¹¹ A separate study comparing non-operative treatment with partial weight-bearing against screw fixation found no difference in failure rates between the two approaches, with comparable complication rates and functional outcomes.¹²

That said, the 30% displacement rate without surgery is not trivial. A fracture that shifts typically requires emergency surgery that is more complex than a planned fixation would have been. So the decision is often a trade-off: accept a one-in-three chance of needing surgery later, or go ahead and fix it now while conditions are more controlled. The patient’s age, overall health, bone quality, and willingness to restrict weight-bearing all factor in.

Surgical Options

When surgery is needed, the approach depends on the location and severity of the fracture. For impacted hip fractures, options range from percutaneous screw fixation, where a few screws are placed through small incisions to pin the bone in place, to partial or total hip replacement in cases where the fracture pattern or bone quality makes fixation unreliable.

For impacted fractures near joint surfaces, like the wrist or the acetabulum (hip socket), surgeons often need to disimpact the fragments first. This means carefully separating the compressed pieces and restoring the joint surface to its normal shape before securing everything with plates, screws, or pins. The void left behind after disimpaction is typically filled with bone graft to provide structural support.¹³ Getting the joint surface smooth again matters enormously, because even a small step-off in the cartilage surface can accelerate arthritis down the line.

How Impacted Fractures Heal

Impacted fractures almost always occur in cancellous bone, the spongy, lattice-like bone found near joints. This type of bone heals through a different mechanism than the dense shaft of a long bone. Instead of forming a large callus, the bulky lump of new bone that wraps around a mid-shaft fracture, cancellous bone heals through a more direct process. New bone forms within the marrow spaces between the existing lattice, filling in the damaged area from the inside out. This happens because the spongy interior has a rich blood supply that feeds the healing process efficiently.¹⁴

Research has characterized this as “inter-trabecular bone formation,” where new bone arises freely in the marrow, likely from local stem cells, and remains confined to a few millimeters around the injury site.¹⁵ Because impacted fracture fragments are already in contact with each other, the distance new bone needs to bridge is minimal, which generally supports faster healing compared to fractures where the pieces have pulled apart. However, “faster” is relative. Most impacted fractures still take six to twelve weeks to heal enough for normal activity, and full remodeling of the bone takes months longer.

Complications Worth Knowing About

The built-in stability of an impacted fracture is genuinely helpful, but it does not eliminate the risks that come with any fracture near a major joint. For impacted femoral neck fractures treated with screw fixation, one study found a reoperation rate of about 15% and a major complication rate of roughly 17%. Those major complications included avascular necrosis, collapse into a worse position, the screws cutting through the bone, nonunion, deep infection, and blood collections requiring surgical drainage.¹⁶

Avascular necrosis is a particular worry with impacted hip fractures. The femoral head gets its blood supply through a few vulnerable vessels that travel along the femoral neck. Even a fracture that looks stable can disrupt those vessels enough that parts of the bone die months later, sometimes requiring a hip replacement even after the fracture itself has healed.

For impacted fractures involving a joint surface, the long-term concern is post-traumatic arthritis. Even with surgical restoration of the joint surface, the cartilage damage sustained during the initial impact can lead to progressive wear and pain over the following years. This is especially relevant for younger patients with decades of joint use ahead of them.

What Recovery Looks Like

Rehabilitation after an impacted fracture depends on the location and the treatment approach. For non-operative impacted hip fractures, the first several weeks typically involve restricted weight-bearing, often with a walker or crutches, to protect the fracture while it heals. Gradual progression to full weight-bearing follows as X-rays confirm healing. For impacted shoulder fractures, early gentle range-of-motion exercises help prevent the shoulder from stiffening, while avoiding loads that could displace the fracture.

Structured physical therapy plays a significant role in recovery regardless of the specific fracture. Early mobilization and tailored rehabilitation protocols have been shown to be important for achieving good functional outcomes after fractures, particularly in patients recovering from surgery.¹⁷ For older adults recovering from hip fractures, physical therapy is not just about rebuilding strength; it is about relearning confidence in movement. Fear of falling is remarkably common after a hip fracture, affecting roughly 60% of patients a month after the injury and still present in nearly half at three months. For patients who had good physical function before their fracture, that fear was associated with worse recovery outcomes.¹⁸ Addressing that psychological barrier is as much a part of rehabilitation as the physical exercises.

Impacted Fractures in Children

Children are not immune to impacted fractures, and their growing bones add an extra layer of concern. The growth plates, the soft cartilage zones near the ends of children’s long bones, are vulnerable to compression injuries. If an impacted fracture extends into or through a growth plate, it can disrupt the normal growth process. A review of growth plate injuries in children found that while most had good functional outcomes, some developed complications including limb-length differences, angular deformities, and premature closure of the growth plate itself.¹⁹

The good news is that children’s bones heal faster than adults’ bones, and their remodeling capacity is impressive. A mild impacted fracture in a child may correct some degree of angulation on its own as the bone grows. But any impacted fracture near a growth plate in a child deserves close follow-up, often with repeat imaging over months, to catch growth disturbances early while they can still be managed.

Reducing the Risk of Fragility Fractures

Because so many impacted fractures are fragility fractures tied to osteoporosis, prevention strategies are worth understanding. The current clinical approach combines medication with lifestyle measures. Antiresorptive drugs like bisphosphonates and denosumab are the most widely used osteoporosis medications, and they reduce the risk of vertebral fractures by 40 to 70%, non-vertebral fractures by 25 to 40%, and hip fractures by 40 to 53% in postmenopausal women with osteoporosis.²⁰

Beyond medication, the prevention toolkit includes adequate calcium and vitamin D intake, weight-bearing and resistance exercise, avoidance of smoking and heavy alcohol use, and fall prevention strategies.²¹ Fall prevention is sometimes underappreciated. It includes practical steps like removing trip hazards at home, improving lighting, wearing proper footwear, addressing vision problems, and reviewing medications that cause dizziness. For older adults, the most impactful fracture prevention measure is often the simplest: not falling in the first place.

Bone density screening, typically with a DEXA scan, is recommended for women over 65 and men over 70, as well as for younger adults with specific risk factors. Identifying osteoporosis before a fracture occurs creates the opportunity to start treatment and potentially avoid the cascade of complications that comes with a hip, shoulder, or wrist fracture. Given that an impacted fracture is often the first clinical sign of weakened bone, one fracture should trigger an evaluation to prevent the next.