A sacral decubitus ulcer is a pressure injury, a wound caused by sustained pressure on the skin and soft tissue over the sacrum (the triangular bone at the base of your spine). It forms when lying on your back for extended periods compresses the tissue between the bone and the surface beneath you, cutting off blood flow and causing the tissue to break down and die. These wounds are also called pressure ulcers, pressure injuries, or bedsores, and the sacrum is one of the three most common sites where they develop.
How Pressure Creates the Wound
The sacrum sits close to the skin’s surface with relatively little fat or muscle cushioning it. When you lie on your back, your body weight presses the skin and underlying tissue against that bony prominence. If that pressure continues without relief, the tiny blood vessels feeding the tissue get squeezed shut. Without blood flow, the cells stop receiving oxygen and nutrients, and the tissue begins to die. This process, called ischemia, is the core mechanism behind every pressure ulcer.
Pressure alone isn’t the whole story. Shear forces also contribute. When the head of a hospital bed is raised, for example, your body tends to slide downward while the skin over the sacrum stays in place, stretching and distorting the tissue layers beneath. Friction from bedding and moisture from sweat or incontinence further weaken the skin’s integrity. Fecal incontinence is a specific and significant risk factor for sacral ulcers because it exposes already-vulnerable skin to both moisture and bacteria.
Stages of Tissue Damage
The National Pressure Injury Advisory Panel classifies these wounds into stages based on how deep the damage extends. Understanding the stage helps clarify how serious the injury is and what tissue has been affected.
Stage 1: The skin is still intact, but there’s a patch of redness that doesn’t turn white when you press on it (called non-blanchable erythema). This discoloration signals that tissue damage has already begun beneath the surface. People who develop this early sign are significantly more likely to progress to a more severe ulcer within 28 days if nothing changes.
Stage 2: The outer layers of skin have broken open. You may see a shallow, pink or red wound bed, or an intact or ruptured blister filled with clear fluid. This is partial-thickness skin loss, meaning the damage hasn’t reached the deeper fat layer yet.
Stage 3: The wound now extends through the full thickness of the skin into the subcutaneous fat beneath it, but hasn’t crossed the tough connective tissue (fascia) that covers the muscle. You may see dead tissue in the wound, and it can produce a noticeable odor. Because the sacrum has a moderate layer of subcutaneous fat, Stage 3 sacral ulcers can be deceptively deep.
Stage 4: This is the most severe stage. The wound extends through the fascia, and muscle, tendon, or even bone may be visible or directly involved. Stage 4 sacral ulcers can create large cavities of tissue loss and carry the highest risk of serious complications.
Two additional categories exist. An unstageable pressure injury is one where dead tissue or a thick, dark scab (eschar) covers the wound bed, making it impossible to tell how deep the damage goes. A deep tissue pressure injury appears as a persistent, deep purple or maroon discoloration, sometimes resembling a blood blister, that signals damage in the deeper layers even though the surface skin may still be intact. These can evolve rapidly into open wounds or, in some cases, resolve without tissue loss.
Who Is Most at Risk
The people most vulnerable to sacral pressure ulcers are those who cannot reposition themselves. This includes patients with spinal cord injuries, people recovering from surgery, those in intensive care, and elderly individuals with limited mobility. A widely used clinical tool evaluates six factors to predict a patient’s risk: their ability to sense discomfort from pressure, how physically active they are, how well they can shift their own body position, their nutritional status, how much moisture their skin is exposed to, and the degree of friction and shear their skin endures.
In hospital settings, these injuries are common. Prevalence rates in intensive care units have been reported at around 16.6%, though the range varies enormously depending on the facility and region, from under 1% to over 80% in some studies. In long-term care facilities, rates generally fall between 2.3% and 23.9%. About 75% of all pressure injuries occur around the pelvic area, with the sacrum, the bony points you sit on (ischial tuberosities), and the outer hip bone (greater trochanter) being the primary sites.
Complications of Advanced Sacral Ulcers
One of the most feared complications of a Stage 4 sacral ulcer is osteomyelitis, an infection of the underlying bone. Because the sacrum can become exposed in deep wounds, it seems logical that bone infection would be nearly universal in these cases. But biopsy studies tell a different story. In one study, only 17% of patients with Stage 4 sacral ulcers (where bone was exposed) had confirmed bone infection on biopsy. Another found that more than half of autopsy specimens from patients with advanced sacral ulcers showed no detectable bone infection at all. When osteomyelitis was present, it tended to be superficial and localized rather than widespread. Researchers have suggested that the systemic symptoms often attributed to bone infection, like fever, may actually be driven by the extensive soft tissue infection surrounding the wound.
Other complications include bacterial infection of the wound itself (which can progress to sepsis), chronic pain, and prolonged hospitalization. Large sacral ulcers can take months to heal and sometimes require surgical reconstruction.
How Sacral Ulcers Are Managed
Treatment depends entirely on the stage. Early-stage injuries focus on removing the source of pressure through repositioning, specialized mattresses, and protecting the skin from moisture and friction. For wounds with dead or damaged tissue, that tissue typically needs to be removed to allow healing. This process, called debridement, can take several forms: surgical removal with instruments for heavily infected wounds, enzyme-based treatments that chemically dissolve dead tissue, moisture-retentive dressings that let the body’s own immune system break down debris, or even medical-grade maggots that selectively consume necrotic tissue while leaving healthy tissue intact.
One important exception: if a sacral ulcer has a dry, stable, firmly attached scab with no signs of infection underneath (no redness, warmth, or drainage), that scab is generally left alone rather than removed. It acts as a natural biological cover.
For Stage 3 and Stage 4 sacral ulcers, healing is a long process. Nutritional support plays a major role since the body needs adequate protein and calories to rebuild tissue. Wound dressings are selected to maintain a moist healing environment, manage drainage, and protect against further contamination. When wounds are too large or deep to close on their own, surgical options like tissue flap procedures may be considered, where nearby muscle and skin are moved to cover the defect.