Magnetic resonance imaging of musculoskeletal disorders in pregnancy

Abstract

Pregnancy, childbirth, and breastfeeding may result in various musculoskeletal (MSK) disorders. Many changes occurring during pregnancy can be related to MSK disorders, leading to stress on skeletal bones and joints, in particular overload on the lumbar spine and pelvic girdle; moreover during pregnancy, increased levels of relaxin, a polypeptide hormone produced by the corpus luteum and decidua, lead to greater ligamentous laxity particularly in the joints of the pelvis, resulting in widening of the symphysis pubis and sacroiliac joints, and to increased motion of the pelvic joints, inflammation, and reduced stability of the pelvis. Diagnosis of MSK disorders is mostly clinical; however, imaging is required for differential diagnosis. Currently, the use of MRI is reserved for the investigation of pain in pregnancy where there is a strong suspicion of abnormality such as the presence of neurological signs and in case of focal inflammatory signs suggesting osteomyelitis, pathologic bone infiltration or neurologic symptoms, and cauda equina syndrome to rule out lumbar disk herniation or other compressive conditions. Typical MSK conditions are low back pain and pelvic girdle pain syndrome, coccygodynia, and osteitis condensans ilii. Major changes occur in maternal calcium homeostasis during pregnancy and breastfeeding affecting bone mineral density. Pregnancy could be a risk factor for developing a new onset or worsening of a preexisting osteoporosis and thus leading to increased risk of stress fractures, frequently involving the sacrum or the femoral head. Hip disorders are a possible cause of significant clinical impairment during pregnancy. Peculiar pictures to be considered include transient osteoporosis, stress fractures, and osteonecrosis of the femoral head. Neural disorders can also affect pregnancy, most commonly carpal tunnel syndrome; other less frequent syndromes include meralgia paresthetica, obturator neuropathy, and postpartum foot drop. MRI is the modality of choice to investigate MSK disorders in pregnancy owing to the lack of ionizing radiation and because it can show signs of very early stage disease. Even if imaging features of these conditions are shared by those occurring in general population, radiologists should be aware of such disorders, as they require most often imaging than in the past.