Metabolic Bone Diseases and Spondylitis Quiz

Soft Tissue and Bone Disorders

• Metabolic bone disease: the third most common endocrine disorder after diabetes and thyroid conditions. It covers a wide spectrum of bone disorders often involving mineral irregularities like calcium, phosphorus, and magnesium or vitamin D deficiencies. Common types include osteoporosis, rickets/osteomalacia, fluorosis, and primary hyperparathyroidism (PHPT). Less common types include Paget disease, tumor-induced osteomalacia, fibrous dysplasia, and osteogenesis imperfecta.
• Developmental dysplasia of the hip: a common developmental process occurring in utero or during the first year of life. Involves malposition of the hip joint which can cause instability in the neonatal hip. Three levels of severity exist: unstable hip dysplasia, subluxation, and complete dislocation.
• Scoliosis: an abnormal lateral curvature of the spine. Classifications include idiopathic (unknown cause), osteopathic (spinal disease), and myopathic (muscle weakness), and neuropathic (central nervous system disorder).
• Ankylosing spondylitis: an autoimmune inflammatory arthropathy impacting axial skeleton, sacroiliac joints, apophyseal joints, costovertebral joints, and intervertebral discs. It can progress to fibrosis, calcification, and ossification, often resulting in joint fusion.
• Pathophysiology of tendon, ligament, and cartilage injury and healing: details on how tendons, ligaments, and cartilage are injured and heal.
• Heterotopic ossification: bone formation in non-osseous tissues (ectopic). Risk factors include serious traumatic injuries (e.g., fractures, surgery, spinal cord injury, burns, amputations), pre-existing HO, and certain disorders like hypertrophic osteoarthritis, ankylosing spondylitis (AS), and diffuse idiopathic skeletal hyperostosis .
• Ehlers-Danlos Syndrome (EDS): inherited disorders affecting connective tissue. Classic features include joint hypermobility (leading to dislocations, subluxations, and sprains), skin hyperextensibility, and tissue fragility (affecting healing). There are 13 different subtypes. Vascular EDS is often life-threatening due to vascular hemorrhage.
• Adhesive Capsulitis (Frozen Shoulder): characterized by painful, gradual loss of shoulder range of motion, either spontaneous or trauma-related. Symptoms result from inflammatory and fibrotic changes in the shoulder capsule and bursa. Natural history involves gradual return to function over 15-18 months. Treatment typically includes non-surgical options for pain management and regaining motion.

Osteomalacia

• Definition: softening of the bone caused by insufficient mineralization of the bone matrix (osteoid) laid down by osteoblasts. The problem lies in impaired bone tissue construction.
• Pathogenesis: osteoid fails to mineralize, reducing bone strength. This makes the bone softer and more prone to bending.
• Pathogenesis of osteomalacia (continued): undermineralized regions of bone appear as radiolucent (light-absorbing) strips on X-rays. Osteoid seams with reduced mineral content are visible. Osteomalacia can be misdiagnosed as osteoporosis.
• Pathogenesis of osteomalacia (continued): insufficient intestinal calcium absorption (reduced calcium availability, impaired vitamin D, and vitamin D metabolism), and increased renal phosphorus loss (problems with kidney disorders or tumors interfering with phosphorus reabsorption).

Risk factors for osteomalacia

• Older adults: calcium and vitamin D deficiency, reduced sunlight exposure, and intestinal malabsorption issues.
• Medications: excessive antacids (causing phosphate deficiency), and aluminum hydroxide (binding with phosphate and preventing GI absorption).
• Chronic medical conditions: hyperparathyroidism, chronic renal failure, and renal tubular defects.

Clinical manifestations of osteomalacia

• Bone pain: often intensified with exercise. Chronic pain can develop.
• Bone scan report: osteomalacia is often misdiagnosed as osteoporosis. Undermineralized areas (osteoid) can be detected histologically (via bone biopsy) and radiographically (from X-rays or other imaging).
• Clinical manifestations of osteomalacia (continued): softening of bones and muscle weakness can lead to alterations in bone structure, postural deformities, and an elevated risk of fractures. Long bone bowing is often observed.

Paget's Disease

• Definition: a localized disorder of bone remodeling, characterized by excessive osteoclast activity (bone resorption), followed by imperfect osteoblast activity (bone repair). "Pagetic osteoclasts" are found at affected sites, thus causing disorganized bone tissue.
• Etiology: cause is unknown, although 15-30% of cases have positive family history. Viral and genetic factors are possible causes (e.g., paramyxoviral infection, mutations in CSF-1 gene, RANK gene and PML gene). A strong correlation exists with geographic location (e.g., Europe, North America, Australia, and New Zealand).
• Etiology (continued): accelerated bone resorption (osteoclasts) slows bone repair (osteoblasts), resulting in fibrous tissue replacing normal bone. Unorganized bone structure makes fractures more likely.
• Pathology: regions of accelerated bone formation may not be adequately mineralized, resulting in widened osteoid seams. Commonly affected areas include the pelvis, spine, femurs, and skull. The bone condition can be either monostotic (one bone affected) or polyostotic (multiple bones affected). Complications include osteoarthritis and neurologic issues.
• Pathology (continued): trabecular bone is replaced with coarse, irregular, thickened trabeculae. Cortical bone is irregularly thickened and rough, sometimes showing pits.
• Clinical manifestations: skeletal deformity, bowing of long bones, excessive skull enlargement. Other symptoms may include hearing loss and severe headaches, and bone pain might not appear until late in the disease. Affected bone areas might feel warm from hypervascularity.

Ehlers-Danlos Syndrome

• Definition: a group of inherited connective tissue disorders. There are 13 subtypes.
• Characteristics: joint hypermobility (dislocations, subluxations, sprains), skin hyperextensibility, and tissue fragility (poor wound healing).
• Prevalence: hypermobility type (hEDS) is the most common subtype, found in 1 in 3000 – 5000 people.
• Diagnostic criteria: the Brighton scale (9-point scale) evaluates joint laxity to aid diagnosis.
• Treatment: no specific treatment exists, but management addresses individual symptoms. If vascular complications arise, cardiac work-ups are necessary and management of pain, high blood pressure, and cholesterol is important.

Adhesive Capsulitis

• Definition: also known as "frozen shoulder", marked by painful gradual loss of shoulder range of motion. This loss can be spontaneous or injury-related.
• Symptoms: inflammatory/fibrotic changes in the shoulder capsule/bursa, causing reduced capsule volume and the development of adhesions.
• Natural history: gradual return to function over 15-18 months, although 20%-50% experience lasting limitations.
• Proposed sequence of alterations: involves nerve dysfunction, repetitive strain injury, trauma, previous surgery, impingement, and rotator cuff degeneration. This chain of events leads to a pro-inflammatory environment, triggering substance P, cytokines, and neuropeptide release. Growth factors promote fibroblast activity, while altered MMP and TIMP levels contribute to scar tissue contractures.
• Treatment: non-surgical interventions manage pain and increase range of motion (MUA and capsulotomy, when necessary).

Test your knowledge on various aspects of metabolic bone diseases and conditions like ankylosing spondylitis. This quiz covers key concepts such as symptoms, pharmacological management, and complications associated with these disorders. Prepare to delve into pathology and clinical presentations relevant to bone health.