A bone survey is a specific type of diagnostic imaging that provides a comprehensive look at the entire skeletal structure. This systematic examination assesses the health, integrity, and structure of nearly every bone in the body. It is typically used when a medical condition is suspected to affect multiple parts of the skeleton, rather than just an isolated area. The survey provides detailed images that help physicians identify widespread changes, such as fractures, lesions, or bone density alterations, indicative of systemic diseases or injuries.
What is a Skeletal Survey and How is it Different from a Bone Scan?
A skeletal survey, also called a bone survey, is a series of plain film X-ray images taken of the entire body. The procedure captures standardized projections of the skull, spine, chest, pelvis, and all four limbs to systematically cover the skeleton. This technique visualizes structural abnormalities, such as fractures, areas of bone loss (lytic lesions), or abnormal bone shape, providing a static picture of the bone’s physical structure.
The skeletal survey differs significantly from a nuclear medicine bone scan, which is a functional imaging test. A bone scan involves injecting a radioactive tracer, such as Technetium-99m, into the bloodstream. This tracer accumulates in areas of high bone turnover, indicating increased metabolic activity.
Because a bone scan detects metabolic activity, it is highly sensitive to abnormalities like early stress fractures, infections, or metastatic disease. However, this sensitivity lacks specificity, as many conditions, including arthritis, can cause a “hot spot.” In contrast, the skeletal survey provides anatomical detail, allowing physicians to characterize the specific appearance of a lesion, such as the “punched-out” holes seen in multiple myeloma. For conditions like multiple myeloma, which may not show increased bone turnover, the skeletal survey is often the preferred diagnostic tool.
Key Medical Conditions Requiring a Bone Survey
The bone survey is reserved for medical situations concerning widespread skeletal involvement. One frequent application in adults is the diagnosis and monitoring of multiple myeloma, a cancer of the plasma cells in the bone marrow. This condition often causes destructive lytic lesions, which appear as distinct areas of bone destruction on the X-ray images. The survey determines the extent of the disease throughout the skeleton, aiding in staging and treatment planning.
The skeletal survey also assesses metastatic disease, which is cancer that has spread to the bone. Although a bone scan is generally more sensitive for detecting early metastases, the skeletal survey is useful for evaluating the specific appearance of known lesions. It is also preferred when the primary cancer causes purely lytic, destructive changes that a bone scan might miss. Cancers like breast, prostate, or lung cancer frequently metastasize to the spine, pelvis, and ribs, which are systematically imaged during the procedure.
A particularly important use of the skeletal survey is evaluating suspected non-accidental trauma, especially in infants and young children under two years old. Children with suspected physical abuse may have occult injuries, which are fractures that are not clinically obvious or are in different stages of healing. The standardized, comprehensive nature of the survey ensures thorough examination of common sites for abuse-related fractures, such as the ribs and the ends of long bones.
The procedure is also routinely used to diagnose and follow congenital skeletal abnormalities, known as skeletal dysplasias. These are genetic disorders causing abnormal development of cartilage and bone, leading to issues with bone shape and growth. Metabolic bone disorders, such as rickets, which affect bone mineralization, can also be assessed. In these cases, a modified or limited survey may be utilized, focusing on metabolically active areas like the wrists and knees.
The Bone Survey Procedure and Safety Considerations
The bone survey is performed in a radiology department by a trained technologist. It is non-invasive, requiring no injection or special patient preparation beyond wearing comfortable clothing. The procedure involves taking a specific, standardized set of X-ray images, typically 15 to over 20 individual pictures, to ensure complete coverage of the body. The technologist carefully positions the patient for each image, which may involve standing, sitting, or lying on the imaging table.
The total examination duration is usually between 30 and 60 minutes, depending on the number of images and the patient’s ability to cooperate with positioning. The X-ray machine is operated from an adjacent control room, and the technologist steps out briefly for each exposure. The process is designed to be efficient while maintaining the high quality necessary for accurate diagnosis.
Exposure to ionizing radiation is a common concern with any X-ray procedure. While the bone survey involves radiation, the effective dose is considered low compared to the diagnostic value provided. For instance, the estimated effective dose for a skeletal survey in an infant is typically 0.2 to 0.6 millisieverts (mSv), comparable to about one month of natural background radiation exposure.
The principle of “as low as reasonably achievable” (ALARA) is followed to minimize the radiation dose without compromising image quality. For conditions like cancer or suspected non-accidental trauma, the benefits of obtaining a definitive diagnosis and guiding immediate treatment outweigh the minimal risk of this low-dose radiation exposure. Physicians carefully weigh this risk-benefit ratio, ensuring the test is only ordered when medically necessary.