PCL 7- INVESTIGATION OF HIP PAIN

Plain Radiography

~Plain radiographs of the hip and pelvis should be ordered as the first diagnostic test for patients with hip pain.

~Plain radiographs can delineate the alignment, bone mineralization, articular cartilage, and soft tissue.

~Alignment abnormality may indicate a fracture, a dislocation, or secondary causes of osteoarthritis such as congenital dislocation of the hip or slipped capital femoral epiphysis.

~Bone mineralization indicates osteoporosis or osteopenia as the underlying cause of pain.

~ An anteroposterior pelvic radiograph and a "frog-leg" lateral hip radiograph may reveal fractures, provide a better view of the anterolateral femoral head, and help evaluate for osteonecrosis.

~For patients in the later stages of osteonecrosis, radiographs show a break in the cortex and a rim sign (a subcortical black lucent line) characteristic of femoral head collapse.

~ A 40-degree cephalad anteroposterior view is useful for elucidating subtle femoral neck and pubic fractures.

~ On plain radiographs, joint-space narrowing is indicative of articular cartilage loss, spurs or osteophytes are indicative of arthritic change, segmental radiolucency or sclerotic changes of the femoral head are indicative of avascular necrosis, calcifications are indicative of synovial chondromatosis, and soft-tissue calcification is indicative of calcific tendinitis.



Arthrography

~Arthrography, which involves obtaining images after a contrast agent has been injected into the hip, is a useful tool for showing labral abnormalities, especially when it is performed in conjunction with magnetic resonance imaging (MRI).

~Magnetic resonance arthrography is the most sensitive and specific test for labral tear of the hip. Injection with local anesthetic agents during the arthrogram can be a powerful tool for the diagnosis of hip abnormalities: if the injection does not
reduce the pain (however transiently), other diagnoses should be ruled out.

~Arthrography continues to have a role in the diagnosis of infection and loosening of the prosthesis in the patient with a painful total joint arthroplasty.



Computed Tomography

~Computed tomography (CT) of the hip and pelvis is most useful in the assessment of fractures, particularly complex fractures. Pelvic and acetabular fractures, osseous sequelae of hip dislocation, and intra-articular osseous fragments are better visualized by CT than by plain radiographs.

~CT also is useful in characterizing calcifications secondary to tumor matrix within bone or soft tissue or to ossification, and CT is the best modality for imaging cortical bone.



Magnetic Resonance Imaging

~MRI provides excellent visualization of medullary bone and soft tissues.

~The diagnosis of osteonecrosis of the femoral head is made earlier by MRI than by any other technique, including bone scintigraphy, CT, and plain radiographs.

~MRI also is the method of choice for the diagnosis of occult hip fracture in the elderly, and despite its expense, can be cost-effective for this purpose.

~MRI is the most accurate method for the diagnosis of stress fractures around the hip and pelvis, and it is the best test for the diagnosis of transient osteonecrosis of the hip.

~It is also the most valuable test for the staging of bony and soft tissue tumors around the hip.

~MRI is frequently helpful in documenting synovitis of the hip joint by revealing effusion (eg, in pigmented villonodular synovitis).

~Magnetic resonance arthrography is useful in defining labral abnormalities.



Electromyography and Nerve Conduction Velocity Studies

Electromyography and nerve conduction velocity studies are used in the differential diagnosis of hip pain to evaluate referred lumbosacral plexopathies and to assess local nerve entrapment or nerve damage from trauma, surgery, or other disease states.



Injections

~Differential block of the hip joint can be a valuable adjunct in differentiating the source of intra-articular hip joint pain.

~This procedure is best undertaken in the fluoroscopy suite, with arthrography used to confirm the location of the injection.

~The technique may be particularly useful in distinguishing intra-articular hip abnormalities from referred lumbosacral radiculopathy and possible soft-tissue conditions.

~Dye injection along the iliopsoas tendon sheath under fluoroscopy sometimes reveals the snapping of the iliopsoas tendon over the pelvic brim, and when accompanied by lidocaine or corticosteroid injection, may help prove that the tendon condition is the pain generator.



SOURCE: Ilksen Gurkan, MD, & Simon Mears, MD, PhD, Current Rheumatology Diagnosis and Treatment,Chapter 11: The Patient with Hip Pain