Endocrine/Metabolic Disorders and Crystal-induced Diseases

A. Scheurecker and J. Kramer

6 Endocrine/Metabolic Disorders and Crystal-induced Diseases

Osteomalacia and Rickets

Definition

Osteomalacia and rickets both are characterized by inadequate calcification of newly formed bone matrix with accumulation of osteoid. In rickets, there is additional involvement of the growth plate.

Pathology

causes:

– deficiency in active form of vitamin

– impaired vitamin D metabolism

– calcium deficiency

– impaired phosphate metabolism

– gastrointestinal malabsorption

inadequate or delayed osteoid mineralization in compact and cancellous bone

rickets: disorganization in the growth plate and adjacent metaphysis

Clinical Signs

bone pain

muscular weakness and adynamia

skeletal deformity (bellshaped thorax, fish vertebrae, rachitic rosary, varus or valgus deformity of knee)

Diagnostic Evaluation

(→ primary method of choice)

Recommended Radiography Projections

standard projections of the knee joint in two planes

Findings

rickets:

– widening of the growth plate

– diminished density on the metaphyseal side of the growth plate

– widening and “cupping” of the metaphysis

– disorganization and fraying of metaphyseal cancellous bone

– deossification and indistinct margin of epiphyseal ossification centers

– abnormal curvatures (saber tibia)

osteomalacia:

– diminished bone density and indistinct fine bone structure (ground-glass appearance), thinning of compact bone

– thickening of long tubular bones from sub periosteal osteoid deposition

– Looser zones of transformation

(→ complementary method for osteomalacia)

^99mTc whole body scan is positive at typical (osteomalacia) Looser zones

Role of Imaging

identification of abnormal bone density and structure

identification of Looser zones

demonstrate typical changes in rickets involving the growth plate, metaphysis, and ossification centers

Basic Treatment Strategies

vitamin D replacement

UV irradiation

normalization of serum phosphate and serum calcium levels

Osteoporosis

Definition

Osteoporosis involves a decrease in bone mass, structural changes to bone tissue and deteriorating osseous functions that lead to an increased risk of fracture.

Pathology

bone atrophy, predominantly caused by pathologically increasing bone loss with normal new bone formation (exception: senile osteoporosis)

thinning and rarification of trabeculae

thinning of cortical bone

Generalized Osteoporosis

Role of Imaging

identification of abnormal bone density and structure

identification of pathologic fractures

Pathology

primary osteoporosis:

– type I osteoporosis:

postmenopausal osteoporosis

– type II osteoporosis:

senile osteoporosis

– idiopathic osteoporosis:

juvenile, presenile

secondary osteoporosis:

– endocrine

– calcium deficiency related to malabsorption

– inactivity induced atrophy

– hereditary disorders (e.g., osteogenesis imperfecta)

– rheumatic diseases

– drug-induced (cortisone, antacids)

Clinical Signs

pain only with fracture (trauma usually inadequate)

Diagnostic Evaluation

Recommended Radiography Projections

standard projections

Findings

more prominent trabecular pattern due to loss of cancellous bone

thinning of cortical bone

muscle and ligament insertions clearly standing out

important: impossible to quantify osteoporosis

only as supplementary diagnostic procedure for complicated or occult fractures

Basic Treatment Strategies

drug therapy depending on cause of osteoporosis

avoid trauma

minimization of risk factors (poor diet, nicotine, lack of activity)

Regional Osteoporosis

Inactivity-induced Osteoporosis

Pathology

venous stasis due to failure of muscle pump

active hyperemia from nerve damage

Diagnostic Evaluation (Figs. 6.1, 6.2)

(→ method of choice)

Findings

homogenous or bandlike decreases in bone density affecting the metaphysis or appearing in patches

Fig. 6.1a,b Inactivity-induced osteoporosis.

Conventional radiograph, AP, and lateral: mixed homogeneous and patchy decreases in bone density with clear trabecular pattern and cortical thinning as a result of inactivity following trauma.

Fig. 6.2 a–c Inactivity-induced osteoporosis.

Coarse, strandlike subchondral bone structure and patchy areas of high signal.

a MRI sagittal section, T1.

b MRI coronal section, T1.

c MRI sagittal section, STIR.

Regional Migratory (Transient) Osteoporosis

Pathology

very rapidly developing osteoporosis of the joint

self-limiting and reversible

migratory character: after abatement, attack of further joints, generally next closest

no history of trauma or immobilization

Clinical Signs

localized pain and swelling

Diagnostic Evaluation

Findings

moderate osteopenia

certain segments may be more heavily involved (e.g., medial femoral condyle)

Recommended Sequences

short tau inversion recovery (STIR)

Findings

high-signal bone marrow edema (Fig. 6.3)

Fig. 6.3a,b Transient regional osteoporosis.

a MRI coronal section, T1 SE: diffuse hypointensity in the medial femoral condyle.

b MRI coronal section, STIR sequence: diffuse high signal bone marrow edema in the medial femoral condyle.

Aggressive Regional Osteoporosis

Pathology

rapidly progressing patchy osteoporosis

osteoclastic bone resorption caused by active or passive hyperemia

Clinical Signs

nonspecific pain

posttraumatic or with trophic disorders (e.g., lymphedema)

Diagnostic Evaluation

(→ method of choice)

Recommended Radiography Projections

knee joint in two planes with adjacent parts of lower and upper leg

Findings

frayed cortical bone with subperiosteal and endosteal osteolytic lesions (appearance comparable to metastasis)

only as a supplemental procedure to exclude presence of blastoma

Sudeck Atrophy (Reflex Sympathetic Dystrophy Syndrome)

Role of Imaging

identification of abnormal density and structure of cortical and cancellous bone

exclusion of arthritis if intra-articular erosions absent

in Sudeck atrophy, evaluation of soft tissue changes according to stage

Pathology

microcirculation disorder resulting from dysfunctional sympathetic vasoconstrictor neurons

trophic disorder involving bone and periarticular soft tissue structures

stages in disease course:

– stage I-early stage: soft tissue edema

– stage II-acute stage: decrease in bone density, bone resorption in cortical and cancellous bone, marked inflammatory dystrophic soft tissue swelling

– stage III-healing stage: resolution of soft tissue swelling and decrease in bone density with coarse strandlike cancellous bone structure

– stage IV-defect stage: soft tissue atrophy and moderate loss of bone density with coarsening of cancellous architecture

Clinical Signs

painful swelling and hypersensitivity