CHAPTER 9-LUMBAR SPINE, SACRUM, & COCCYX: RADIOGRAPHIC POSITIONING & PATHOLOGY

PEDIATRIC APPLICATIONS:

2 Primary Concerns Are Pt. Motion & Safety: >Short Exposure Time helps reduce motion. Communication: >Clear, simple instructions & distraction techniques such as toys or stuffed animals. Immobilization: Technical Factors: >Vary w/pt size, use of short exposure times, associated w/high mA is recommended to reduce the risk of pt. motion.

NUCLEAR MEDICINE TECHNOLOGY:

A Radiopharmaceutical-tagged tracer element is injected that concentrates in areas of increased bone activity, demonstrating a hot spot on the NM img. Commonly, pt.'s at risk or are symptomatic for skeletal metastases undergo a bone scan (pt.'s w/multiple myeloma are an exception to this). The vertebral column is a common site of skeletal metastases. Inflammatory conditions, Paget's Disease, Neoplastic Processes, & Osteomyelitis may also be dem. on the bone scan.

SPINA BIFIDA:

A congenital condition in which the posterior aspects of the vertebrae fail to develop, exposing part of the spinal cord. This condition varies greatly in severity & occurs most often at L5. Common Imaging Procedures: >Prenatal US; PA & Lateral Spine; CT or MRI Radiographic Appearance: >Open posterior vertebra, exposure of part of spinal cord.

PATIENT POSITION:

AP Projections of L-Spine: are obtained w/knees & hips flexed, reduces the lumbar curvature (lordosis), brings back closer to table & lumbar vertebral column more parallel to IR, also flexing knees allows for greater pt comfort. >Incorrect Position: when lower limbs are extended, tips the pelvis forward slightly, exaggerating the lumbar curvature.

HNP-HERNIATED NUCLEUS PULPOSUS (HERNIATED LUMBAR DISK):

Also known as a Herniated Lumbar Disk "Slipped Disk", usually due to trauma or improper lifting. The soft inner part of the intervertebral disk (nucleus pulposus) protrudes thru the fibrous outer layer, pressing on the spinal cord or nerves. Occurs most frequently at L4-L5 lvls, causing Sciatica (an irritation of the sciatic nerve that passes down the posterior leg). Plain radiographs do not dem. this condition but can be used to rule other pathologic processes, such as neoplasia & spondylolisthesis. Common Imaging Procedures: >AP/Lateral L-Spine; CT, MRI Radiographic Appearance: >Possible Narrowing of the Intervertebral Disk Spaces.

ANKYLOSING SPONDYLITIS-BAMBOO SPINE:

An inflammatory condition that begins in the SI joints & progresses up the vertebral column. The spine may become completely rigid as the intervertebral & costovertebral joints fuse. Most common in men in their 30's & no cause is known. Most Common Imaging Procedure: >AP/Lateral L-Spine, SI Joints; Nuclear Medicine Bone Scan. Radiographic Appearance: >Vertebral Column Becoming Fused, Appearance of Piece of Bamboo; Anterior Longitudinal Ligaments Calcifying.

CLINICAL INDICATIONS-PATHOLOGY:

Ankylosing Spondylitis Fractures: >Compression Fractures >Chance Fractures Herniated Nucleus Pulposus-HNP Lordosis Metastases: >Osteolytic >Osteoblastic >Combination Osteolytic & Osteoblastic Scoliosis Spina Bifida Spondylolisthesis Spondylolysis

GERIATRIC APPLICATIONS:

Communication & Comfort: >Sensory Loss (eyesight & hearing) associated w/aging may result in the need for additional assistance, time, & patience in achieving the required positioning. Pt.'s may have fear of falling & recumbent position may be more comfortable. >Pt.'s w/exaggerated kyphosis may be more comfortable if put in an erect position. Technical Factors: >Osteoporosis common in older pt's, kV or mAs may require a decrease. >May have difficulty holding still or tremors to reduce the risk of motion use short exp. times associated w/higher mA.

POSITIONING CONSIDERATIONS:

Gonadal Shielding PA vs. AP Medium to High kV Lead Mat on Table Top SID 40-46" (102-117cm) AP L-Spine: Leg Position

GONADAL SHIELDING:

Gonadal Shielding Should Always Be Used On Males: of reproductive age for L-spine, sacrum, & coccyx radiographs. Shield should be placed w/top edge of shield at the lower margin of the symphysis pubis.

REDUCE SCATTER:

Increasing kV & Lowering mAs: >Reduces pt dose but, increases the energy of the scatter radiation more likely to reach the IR & produce FOG, which tends to degrade the radiographic img. Close Collimation: w/high kV technique to limit the amnt of scatter radiation reaching the IR. Use Lead Mat on Table Top For Lateral Projections-Absorbs Scatter.

BONE DENSITOMETRY:

Is a noninvasive measurement of bone mass. The L-Spine is an area that is often assessed in a bone density study. Is accurate to w/in 1% & the radiation skin dose is very low. Conventional radiography does not detect bone loss until bone mas has been reduced by atleast 30%.

SCOLIOSIS:

Is lateral curvature of the vertebral column that usually occurs w/some rotation of the vertebra. It involves the thoracic & lumbar regions. Common Imaging Procedures: >Erect PA-AP & Lateral Spine Radiographic Appearance: >Lateral Curvature of Vertebral Column.

MRI-MAGNETIC RESONANCE IMAGING:

Is superior for the evaluation of soft tissue structures of the L-spine; spinal cord & intervertebral disk spaces.

LOWER SPINE TOPOGRAPHIC LANDMARKS:

Level A: >Corresponds to superior margin of symphysis pubis. The prominence of the greater trochanter at same lvl. Level B: >ASIS at S1-2 lvl. (1st or 2nd sacral segment). Level C: >Most superior portion of iliac crest same lvl. as junction of L4-5 vertebrae. Level D: >Lowest margin of ribs or Lower Costal Margin at lvl. of L2-3. Level E: >Xiphoid Tip at lvl. of T9-10.

COMPRESSION FRACTURES:

May be due a trauma, osteoporosis, or metastatic disease. The superior and inferior surfaces of the vertebral body are driven together, producing a wedge-shaped vertebra. Common Imaging Procedure: >AP/Lateral L-Spine; CT Radiographic Appearance: >Anterior Wedging of Vertebrae; Loss of Body Height. Exp. Factor Adjustment: >None or Slight Decrease depending on severity

METASTASES-OSTEOLYTIC-OSTEOBLASTIC-COMBINATION OF BOTH:

Metastases: are primary malignant neoplasms that spread to distant sites via blood & lymphatics. >Osteolytic: destructive lesions w/irregular margins. >Osteoblastic: proliferative bony lesions of increased density. >Combination Osteolytic & Osteoblastic: moth-eaten appearance of bone resulting from the mix of destructive & blastic lesions. Common Imaging Procedures: >Bone Scan; AP/Lateral of Spine Radiographic Appearance-Dependent on Lesion Type: >Destructive-irregular margins & decreased density. >Osteoblastic Lesions: increased density. >Combination: moth-eaten appearance Exposure Factor: >None or Increase or Decrease; depending on type of lesion & stage of pathologic process.

MYELOGRAPHY:

Requires injection of contrast medium into the sub-arachnoid space via a Lumbar or Cervical puncture to visualize the soft tissue structures of the spinal canal. Lesions of the spinal canal, nerve roots, & intervertebral disks are dem. The increase in availability of CT & MRI greatly reduced the number of myelograms performed.

CHANCE FRACTURES:

Results from a hyperflexion force that causes fx thru the vertebral body & posterior elements (spinous process, pedicles, facets, transverse processes). Pt.'s wearing lap type seat belts are at risk bc these belts act as a fulcrum during sudden deceleration. Common Imaging Procedure: >AP/Lateral L-Spine; CT Radiographic Appearance: >Fx thru Vertebral Body & Posterior Elements

PA VS. AP PROJECTIONS:

The PA or Prone Position: places L-Spine in natural curvature so that the intervertebral disk spaces are almost parallel to the divergent x-ray beam. This position also opens up & provides better visualization of the margins of the intervertebral disk spaces. >PA for Females: is a lower ovarian dose 25%-30% less dose compared to the AP. Disadvantage to PA: increases the OID of the L-Spine, results in magnification unsharpness, especially for pt w/large abdomen.

SPONDYLOLYSIS:

The dissolution of a vertebra, such as from aplasia (lack of development) of the vertebral arch & separation of the pars interarticularis of the vertebra. On the oblique projection, the neck of the scottie dog appears broken. Most common at L4 or L5. Common Imaging Procedure: >AP/Lateral/Oblique Views of Spine; CT Radiographic Appearance: >Defect in the Pars Interarticularis (Scottie dog appearing to wear a collar).

SPONDYLOLISTHESIS:

The forward movement of 1 vertebra in relation to another. Commonly due to a developmental defect in the pars interarticularis or may result from spondylolysis or severe osteoarthritis. Most common at L5-S1 but also occurs at L4-L5 & severe cases require a spinal fusion. Common Imaging Procedures: >AP/Lateral L-Spine; CT Radiographic Appearance: >Forward slipping of 1 vertebra in relation to another.

LORDOSIS:

The normal concave curvature of the L-spine or an abnormal or exaggerated concave lumbar curvature. This condition may result from pregnancy, obesity, poor posture, rickets, or TB of the spine. A Lateral projection will best dem. the extent of lordosis. Common Imaging Procedures: >Lateral L-spine, Scoliosis Series, including erect PA-AP & Lateral Radiographic Appearance: >Normal concave lumbar curvature or abnormal or exaggerated lumbar curvature.

CT-COMPUTED TOMOGRAPHY:

Used for the presence & extent of fx's, disk disease, & neoplastic disease.

EXPOSURE FACTORS:

To ensure that the beam passes thru the Intervertebral Disk Spaces: >Use a radiolucent sponge under the pt.'s waist to ensure the spine is parallel w/IR. SID 40-46" (102-117cm) Grid Medium to High kV Ranges