The ischial tuberosity, commonly referred to as the “sit bone,” is a thick, rounded part of the pelvic bone that bears the majority of the body’s weight when a person is seated. A pressure ulcer, also known as a pressure injury, is localized damage to the skin and underlying soft tissue, often occurring over bony prominences. This damage results from prolonged pressure or pressure combined with a sliding force called shear, which cuts off blood flow to the affected area. Pressure ulcers over the ischial tuberosity are highly prevalent among individuals with limited mobility who spend extended periods in a chair or wheelchair.
Why the Ischial Tuberosity is Vulnerable
The anatomy of the ischial tuberosity makes it particularly susceptible to pressure injury because it functions as a high peak pressure point. When an individual sits, the weight of the torso is concentrated onto the small surface area of these bony projections, creating intense compressive forces. This sustained pressure occludes blood vessels, depriving soft tissue, particularly muscle, of oxygen and nutrients. This deprivation can lead to tissue damage in as little as two hours.
Shear is another mechanical force that occurs when the skin remains stationary against the seating surface while the underlying bone shifts, such as when a person slouches or slides forward in a chair. This motion stretches and bends the blood vessels, further impeding circulation and increasing damage potential. The deep muscle tissue adjacent to the bone is more sensitive to ischemia than the skin’s surface, meaning severe injury often begins deep inside the body, making early detection difficult. Individuals with impaired sensation, such as those with spinal cord injuries or neuropathy, are at a greater risk because they cannot feel the discomfort that prompts a change in position.
Identifying the Stages of Ulcer Development
Recognizing the progression of tissue damage is important for seeking prompt intervention. The initial sign of injury is often a change in the skin’s appearance, which remains intact but shows a persistent area of redness or discoloration. This discoloration is known as non-blanchable erythema because it does not turn pale when pressed. This early stage may also feel warmer, cooler, firmer, or softer than the surrounding healthy tissue.
Stage Descriptions
The stages of pressure ulcer development are defined by the depth of tissue damage:
- Stage 2: Involves partial-thickness loss of skin, appearing as a shallow, open ulcer with a red-pink wound bed or an intact or ruptured serum-filled blister.
- Stage 3: Involves full-thickness tissue loss, extending into the subcutaneous fat layer. The wound may resemble a crater, but bone, tendon, or muscle are not yet visible.
- Stage 4: The most severe stage involves full-thickness tissue loss with exposed structures, where bone, tendon, or muscle are visible or palpable within the wound bed. This deep damage often includes undermining and tunneling, which are channels extending from the wound’s surface.
A separate concern is Deep Tissue Injury (DTI), which presents as a purple or maroon area of discolored intact skin or a blood-filled blister. DTI signals damage to the deep soft tissue from pressure or shear. This type of injury can rapidly progress to a severe open wound.
Proactive Prevention Techniques
Preventing pressure ulcers relies on a comprehensive strategy focused on managing pressure, maintaining skin integrity, and ensuring proper nutrition. Pressure redistribution is achieved using specialized support surfaces, such as air, gel, or high-density foam cushions designed for seating or mattresses for bedridden individuals. The correct cushion must allow the body to immerse and be enveloped, maximizing the contact area. This effectively spreads the load away from the bony prominence.
Pressure Management
Regular repositioning is the most direct way to relieve sustained pressure and must be scheduled consistently. Wheelchair users should perform a pressure relief maneuver, such as a weight shift or full lift off the seat, every 15 to 30 minutes for at least 30 seconds to allow for tissue reperfusion. Bedridden individuals require a turning schedule, typically repositioned every one to two hours. They should be positioned at a 30-degree angle when lying on their side to avoid direct pressure on the hip bone.
Skin Integrity and Nutrition
Meticulous skin inspection, performed at least twice daily, is necessary to identify subtle changes like non-blanchable redness before they worsen. Skin hygiene requires gentle cleansing and moisturizing to maintain the skin’s barrier function, while managing moisture from incontinence or perspiration is necessary to prevent skin breakdown. Proper nutritional support, particularly adequate protein and calorie intake, is important for maintaining tissue health.
Treatment and Healing Protocols
Once an ischial tuberosity pressure ulcer has formed, the immediate action is to completely off-load the affected area, which typically means eliminating sitting on that side entirely. For established wounds, treatment centers on cleaning the wound bed and protecting it from further injury or infection. Dressings are selected based on the wound’s characteristics, such as the amount of drainage or the presence of dead tissue. This maintains a moist environment that encourages healing.
Infection control is a serious concern, as pressure ulcers can lead to complications like osteomyelitis, which is infection of the underlying bone. Signs of infection, such as increased redness, warmth, pus, or a foul odor, require immediate medical evaluation and often treatment with antibiotics. Debridement, the removal of non-viable or dead tissue (slough or eschar), is performed to clear the wound bed. This promotes the growth of healthy tissue and reduces the risk of infection.
For deep or non-healing ulcers, advanced therapies or surgical intervention may be required. This may involve vacuum-assisted closure (negative pressure wound therapy) to prepare the wound bed, followed by reconstructive surgery using skin or muscle flaps. After healing, the return to sitting must be gradual and closely monitored to prevent recurrence.