Diagnostic Evaluation of Musculoskeletal Function

Diagnostic Evaluation

IMAGING PROCEDURES

X-ray Studies

X-ray studies are important in evaluating patients with muscu-loskeletal disorders. Bone x-rays determine bone density, texture, erosion, and changes in bone relationships. Multiple x-rays are needed for full assessment of the structure being examined. X-ray study of the cortex of the bone reveals any widening, narrowing, or signs of irregularity. Joint x-rays reveal fluid, irregularity, spur formation, narrowing, and changes in the joint structure. After being positioned for the study, the patient must remain still while the x-rays are taken.

Computed Tomography

A computed tomography (CT) scan shows in detail a specific plane of involved bone and can reveal tumors of the soft tissue or injuries to the ligaments or tendons. It is used to identify the lo-cation and extent of fractures in areas that are difficult to evalu-ate (eg, acetabulum). CT studies, which may be performed with or without the use of contrast agents, last about 1 hour. The pa-tient must remain still during the procedure.

Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) is a noninvasive imaging tech-nique that uses magnetic fields, radio waves, and computers to demonstrate abnormalities (ie, tumors or narrowing of tissue path-ways through bone) of soft tissues such as muscle, tendon, cartilage, nerve, and fat. Because an electromagnet is used, patients with any metal implants, clips, or pacemakers are not candidates for MRI.

To enhance visualization of anatomic structures, contrast media may be injected intravenously. During the procedure, the patient needs to lie still for 1 to 2 hours and will hear a rhythmic knocking sound. Patients who experience claustrophobia may be unable to tolerate the confinement of closed MRI equipment without sedation. Open MRI systems are available, but they use lower-intensity magnetic fields, which reduces the quality of the imaging; repeated imaging may be required. Advantages of open MRI include increased patient comfort, reduced problems with claustrophobic patients, and reduced noise.

Arthrography

Arthrography is useful in identifying acute or chronic tears of the joint capsule or supporting ligaments of the knee, shoulder, ankle, hip, or wrist. A radiopaque substance or air is injected into the joint cavity to outline soft tissue structures and the contour of the joint. The joint is put through its range of motion to dis-tribute the contrast agent while a series of x-rays is obtained. If a tear is present, the contrast agent leaks out of the joint and is ev-ident on the x-ray image.

After an arthrogram, the joint is usually rested for 12 hours, and a compression elastic bandage is applied as prescribed. In ad-dition, the nurse provides comfort measures (mild analgesia, ice) as appropriate. The nurse should explain to the patient that it is normal to experience clicking or crackling in the joint for a day or two after the procedure, until the contrast agent or air is absorbed.

Nursing Interventions

Before the patient undergoes an imaging study, the nurse should assess for conditions that may require special consideration dur-ing the study or that may be contraindications to the study (eg, pregnancy; claustrophobia; inability to tolerate required po-sitioning due to age, debility, or disability; metal implants). It is essential that the patient remove all jewelry, hair clips, hearing aids, and other metal before having an MRI. If contrast agents will be used for CT scan, MRI, or arthrography, the nurse should carefully assess the patient for possible allergy.

Bone Densitometry

Bone densitometry is used to estimate bone mineral density (BMD). This can be done through the use of x-rays or ultrasound. Dual-energy x-ray absorptiometry (DEXA) determines bone min-eral density at the wrist, hip, or spine to estimate the extent of osteoporosis and to monitor a patient’s response to treatment for osteoporosis. Bone sonometry (ultrasound) measures heel bone quantity and quality and is used to estimate BMD and the risk of fracture for people with osteoporosis. Bone density sonography iscost-effective, readily available screening tool for diagnosing osteoporosis and predicting a person’s risk for fracture.

NUCLEAR STUDIES

Bone Scan

A bone scan is performed to detect metastatic and primary bone tumors, osteomyelitis, certain fractures, and aseptic necrosis. A bone-seeking radioisotope is injected intravenously. The scan is performed 2 to 3 hours after the injection. At this point, distribu-tion and concentration of the isotope in the bone are determined. The degree of nuclide uptake is related to the metabolism of the bone. An increased uptake of isotope is seen in primary skeletal disease (osteosarcoma), metastatic bone disease, inflammatory skeletal disease (osteomyelitis), and certain types of fractures.

NURSING INTERVENTIONS

Before the patient undergoes a bone scan, the nurse should inquire about possible allergy to the radioisotope and should assess for any condition that would contraindicate performing the procedure (eg, pregnancy). In addition, it is important to encourage the patient to drink plenty of fluids to help distribute and eliminate the isotope. Before the scan, the nurse asks the patient to empty the bladder, because a full bladder interferes with scanning of the pelvic bones.

ENDOSCOPIC STUDIES

Arthroscopy

Arthroscopy is a procedure that allows direct visualization of a joint to diagnose joint disorders. Treatment of tears, defects, and disease processes may be performed through the arthroscope. The procedure is carried out in the operating room under sterile con-ditions; injection of a local anesthetic into the joint or general anesthesia is used. A large-bore needle is inserted, and the joint is distended with saline. The arthroscope is introduced, and joint structures, synovium, and articular surfaces are visualized. After the procedure, the puncture wound is closed with adhesive strips or sutures and covered with a sterile dressing. Complications are rare but may include infection, hemarthrosis, neurovascular com-promise, thrombophlebitis, stiffness, effusion, adhesions, and delayed wound healing.

NURSING INTERVENTIONS

The joint is wrapped with a compression dressing to control swelling. In addition, ice may be applied to control edema and dis-comfort. Frequently, the joint is kept extended and elevated to re-duce swelling. It is important to monitor neurovascular function. The nurse administers prescribed analgesics to control discomfort. The nurse should explain when the patient can resume activity and what weight-bearing limits to follow, as prescribed by the ortho-pedic surgeon. The nurse also explains to the patient and family the symptoms (eg, swelling, numbness, cool skin) to watch for in order to determine whether complications are occurring and the importance of notifying the physician of these observations. The physician’s prescription for analgesic medication is also explained.

OTHER STUDIES

Arthrocentesis

Arthrocentesis (joint aspiration) is carried out to obtain synovial fluid for purposes of examination or to relieve pain due to effu-sion. Examination of synovial fluid is helpful in the diagnosis of septic arthritis and other inflammatory arthropathies and reveals the presence of hemarthrosis (bleeding into the joint cavity), which suggests trauma or a bleeding disorder. Normally, synovial fluid is clear, pale, straw-colored, and scanty in volume. Using aseptic technique, the physician inserts a needle into the joint and aspirates fluid. Anti-inflammatory medications may be injected into the joint. A sterile dressing is applied after aspiration. There is a risk for infection after this procedure.

Electromyography

Electromyography (EMG) provides information about the elec-trical potential of the muscles and the nerves leading to them. The test is done to evaluate muscle weakness, pain, and disability. The purpose of the procedure is to determine any abnormality of function and to differentiate muscle and nerve problems. Needle electrodes are inserted into selected muscles, and responses to electrical stimuli are recorded on an oscilloscope. Warm com-presses may relieve residual discomfort after the study.

Biopsy

Biopsy may be performed to determine the structure and com-position of bone marrow, bone, muscle, or synovium to help di-agnose specific diseases. The nurse monitors the biopsy site for edema, bleeding, pain, and infection. Ice is applied as prescribed to control bleeding and edema. In addition, analgesics are ad-ministered as prescribed for comfort.

LABORATORY STUDIES

Examination of the patient’s blood and urine can provide infor-mation about a primary musculoskeletal problem (eg, Paget’s disease), a developing complication (eg, infection), the baseline

for instituting therapy (eg, anticoagulant therapy), or the re-sponse to therapy. The complete blood count includes the hemoglobin level (which is frequently lower after bleeding asso-ciated with trauma and surgery) and the white blood cell count (which is elevated in acute infections, trauma, acute hemorrhage, and tissue necrosis). Before surgery, coagulation studies are per-formed to detect bleeding tendencies (because bone is very vas-cular tissue).

Blood chemistry studies provide data about a wide variety of musculoskeletal conditions. Serum calcium levels are altered in patients with osteomalacia, parathyroid function, Paget’s disease, metastatic bone tumors, or prolonged immobilization. Serum phosphorus levels are inversely related to calcium levels and are diminished in osteomalacia associated with malabsorption syn-drome. Acid phosphatase is elevated in Paget’s disease and met-astatic cancer. Alkaline phosphatase is elevated during early fracture healing and in diseases with increased osteoblastic ac-tivity (eg, metastatic bone tumors). Bone metabolism may be evaluated through thyroid studies and determination of calci-tonin, parathyroid hormone, and vitamin D levels. Serum enzyme levels of creatine kinase and aspartate aminotransferase become elevated with muscle damage. Aldolase is elevated in muscle dis-eases (eg, muscular dystrophy, skeletal muscle necrosis). Serum osteocalcin (bone GLA protein) indicates the rate of bone turnover. Urine calcium levels increase with bone destruction (eg, parathyroid dysfunction, metastatic bone tumors, multiple myeloma).

Specific serum biochemical markers can be used to provide in-formation about bone formation; these include bone-specific alka-line phosphatase and osteocalcin from osteoblasts, and procollagen 1 carboxyterminal propeptide and procollagen 1 aminotermi-nal propeptide from the bone matrix. Specific serum biochemical markers that provide information about bone resorption include tartrate-resistant acid phosphatase and bone sialoprotein from osteoclasts, and aminoterminal telopeptide of type 1 collagen and carboxyterminal telopeptide of type 1 collagen from bone matrix. Biochemical markers of bone resorption in the urine include pyridi-noline and deoxypyridinoline crosslinks, aminoterminal telopeptide of type 1 collagen, and hydroxyproline from collagen degradation from bone matrix (Koopman, 2001; Woitge & Seibel, 2001).