Kyphoplasty treats painful vertebral compression fractures (VCFs), often caused by osteoporosis. This minimally invasive surgery involves injecting bone cement, polymethylmethacrylate (PMMA), into the fractured vertebra to stabilize it and restore height. Although kyphoplasty is generally safe, a known complication is the unintended leakage of this cement beyond the treated bone. Recognizing the symptoms of cement leakage is important, as it can lead to serious complications involving the spinal nerves or circulatory system.
The Mechanism of Cement Leakage
The synthetic polymer cement used in kyphoplasty is initially a low-viscosity paste, allowing it to flow into the cracks within the fractured bone. Leakage occurs when this material escapes the vertebral body through breaches in the bone wall, such as fracture lines. The pressure applied during the injection process can push the cement out, particularly if the material has not yet achieved a thicker consistency.
Cement leakage can occur into several anatomical areas surrounding the spine, which determines the type of symptoms a patient may experience. The most concerning pathways are the spinal canal, where nerve tissue resides, and the paravertebral veins, which connect directly to the circulatory system. Leakage into surrounding soft tissues is also common, though it rarely causes clinical symptoms. Kyphoplasty uses a balloon to create a cavity before injection, which is intended to reduce the risk of leakage, but it does not eliminate the possibility.
Symptoms of Nerve Compression
Leakage of PMMA cement into the spinal canal or the intervertebral foramen (the openings where nerves exit the spine) results in direct pressure on the spinal cord or nerve roots. This mechanical compression causes new or worsening neurological symptoms post-procedure. The most frequent sign is the onset of new, sharp, or radiating pain, known as radiculopathy, which travels from the back down into the arms, chest, or legs. This new pain often feels different from the original fracture pain.
Direct pressure on the nerve roots manifests as sensory and motor deficits in the extremities. Patients may report numbness, a prickling sensation, or tingling (paresthesia) in the areas supplied by the compressed nerve. In severe instances, cement compression can lead to motor weakness, causing difficulty lifting the foot, gripping objects, or moving the affected limbs.
Leakage into the lower lumbar spine may result in Cauda Equina Syndrome, a medical emergency characterized by the compression of the bundle of nerves at the base of the spinal cord. Specific symptoms include difficulty with bladder or bowel control, such as urinary retention or incontinence. A loss of sensation in the saddle area (inner thighs, buttocks, and perineum), known as saddle anesthesia, is a hallmark sign of this severe nerve compression.
Signs of Vascular and Pulmonary Involvement
A less common but potentially life-threatening complication is the extravasation of PMMA into the paravertebral venous plexus. These veins lack valves and connect directly to the inferior vena cava, providing a pathway for the cement to travel to the heart and lungs. If cement fragments reach the pulmonary vasculature, the condition is referred to as Pulmonary Cement Embolism (PCE).
Many cases of PCE are asymptomatic and only discovered incidentally on post-operative imaging. The most common sign of a symptomatic cement embolism is the sudden onset of shortness of breath (dyspnea), which may occur hours to months after the kyphoplasty. Patients may also experience sharp chest pain that worsens with deep breathing.
The body’s response to the blockage involves changes in heart and respiratory function. A rapid heart rate (tachycardia) may be noted as the heart attempts to compensate for the reduced oxygen exchange in the lungs. In severe cases, the patient may exhibit hypoxemia, a measurable drop in the blood’s oxygen saturation level. These systemic symptoms are distinct from localized neurological deficits and require immediate attention.
Urgent Response and Patient Safety
Patients who have undergone kyphoplasty should be observant for new symptoms in the days and weeks following the procedure. If new back pain, radiating limb pain, numbness, or weakness develops, it should be reported to the treating physician promptly. Early evaluation determines if the symptoms correlate with cement leakage.
Certain symptoms signal a medical emergency requiring immediate attention, such as calling emergency services. These include the sudden onset of significant difficulty breathing, persistent or crushing chest pain, or any loss of bladder or bowel control. Diagnostic imaging, typically a CT scan, is the standard method used to confirm the presence and location of the cement leakage. This imaging guides medical professionals in managing the complication.