Transient Osteoporosis of the Hip

Other Names

• Transient osteoporosis of the hip (TOH)
• Primary bone marrow edema syndrome (BMES)
• Primary TOH
• Secondary TOH
• Transitory Demineralization of the Hip
• Transient Marrow Edema Syndrome
• Bone Marrow Edema (BME)
• Transient Regional Osteoporosis
• Regional Osteoporosis
• Algodystrophy
• Regional migratory osteoporosis

Pathophysiology

• General
  • Typically considered to be benign and self-limiting
  • In women, typically seen in the last trimester of pregnancy
• Some type of insult initiates the process, typically idiopathic
  • This leads to leading to an increase in bone turnover, venous hypertension, and/or microfracture causing edema
• 3 stage hypothesis
  • Stage 1: acute onset hip pain is due to edema (insult often unknown)
  • Stage 2: involves increased resorption and demineralization of the bone
  • Stage 3: the resolution of the process clinically and by radiograph
• The cause of hip pain is not always clear, proposed etiologies include
  • Increased intraosseous pressure
  • Venous hypertension
  • Increased focal bone turnover
  • Microfracture
  • Periosteal irritation
• Uncommon, can progress to ischemic injury to the femoral head and Avascular Necrosis
  • Distinguishing between TOH and early AVN is challenging clinically and radiographically
  • Also unclear if TOH represents early AVN or is a separate clinical entity
  • Some authors suggest TOH represents an abortive syndrome of the AVN pathway

Causes

• Most commonly idiopathic
  • May be primary vs secondary, challenging to distinguish
  • Proposed insults leading to TOH include trauma, infection, inflammation, degenerative process, ischemic injury, neoplasia, surgery, drugs, metabolic, and neurologic disorders
  • Compression of the Obturator Nerve
• Pathologic Fracture
• Avascular Necrosis of the Hip
• Pregnancy, particularly 3rd trimester
  • Note that estrogen is elevated in pregnancy
• Alcohol use
• Tobacco Use Disorder
• History of corticosteroid use
• Abnormal vascularity
• Drug use
• Inflammation
• Metabolic derangement
• Mechanical injury
• Neurologic deficit
• Osteogenesis Imperfecta^[7]
• Osteoporosis
  • Not entirely clear if this is truely a risk factor
• Hypothyroidism^[8]
• Hypophosphotemia^[9]

Differential Diagnosis

• Fractures And Dislocations
  • Pelvic Fracture
  • Hip Fracture
  • Acetabular Fracture
  • Femoral Neck Stress Fracture
  • Pelvic Stress Fracture
  • Hip Dislocation

• Arthropathies
  • Osteitis Pubis
  • Avascular Necrosis of the Hip
  • Hip Osteoarthritis
  • Femoroacetabular Impingement
  • Transient Osteoporosis of the Hip

• Muscle and Tendon Injuries
  • Hip Flexor Tendonitis
  • Piriformis Syndrome
  • Hamstring Strain
  • Proximal Hamstring Tendinopathy
  • Adductor Strain
  • Greater Trochanteric Pain Syndrome

• Bursopathies
  • Iliopsoas Bursitis
  • Ischial Bursitis

• Ligament Injuries
  • Acetabular Labrum Tear

• Neuropathies
  • Meralgia Paresthetica

• Other
  • Snapping Hip Syndrome
  • Septic Arthritis
  • Gout
  • Leg Length Discrepancy
• Pediatric Pathology
  • Transient Synovitis of the Hip
  • Developmental Dysplasia of the Hip (DDH)
  • Legg-Calve-Perthes Disease
  • Slipped Capital Femoral Epiphysis (SCFE)
  • Avulsion Fractures of the Ilium (Iliac Crest, ASIS, AIIS)
  • Ischial Tuberostiy Avulsion Fracture
  • Avulsion Fractures of the Trochanters (Greater, Lesser)
  • Apophysitis of the Ilium (Iliac Crest, ASIS, AIIS)

Diagnosis

• History
  • Pain of TOH usually starts spontaneously
  • Pain presentation may vary from insidious vague pain with antalgic gait
  • Less commonly, may result in more severe progressive pain leading to immobility and hospitalization
• Physical Exam: Physical Exam Hip
• Special Tests

Radiographs

• Standard Radiographs Hip
  • Screening tool
• Early Findings (first 3-6 weeks from symptom onset)
  • Typically normal
• Later findings (after the first 3-6 weeks)
  • Eventually will see diffuse osteopenia of the femoral head, sometimes bilateral
  • Periarticular demineralization
  • Absence of subchondral changes

MRI

• Preferred imaging modality for suspected TOH
  • Sensitive enough to detect TOH up to 48 hours after onset^[10]
• Findings
  • Intermediate signal sequences on T1-weighted image
  • High signal intensity on T2-weighted images
  • Hyper intensity on contrast-enhanced images
  • Delayed peak enhancement of edematous marrow is particularly characteristic of TOH
• Characteristics of TOH^[11]
  • The homogenous pattern of enhancement with no clear border
  • Diffuse pattern of edema with no focal defect, typically located at femoral head, sometimes neck
  • The presence of an irregular band of low signal intensity due to stress fracture
  • Absence of subchondral changes
  • Findings are often accompanied by joint effusion

Bone Scintigraphy

• Radionucleotide uptake occurs in all 3 phases of TOH
  • Lasts for up to 4 weeks after resolution of symptoms^[12]

Treatment

Prognosis

• Typically resolves in 6 months (range 2-12 months) with conservative therapy^[13]
• Core decompression therapy vs conservative therapy
  • Does not appear to improve outcomes compared to medical therapy^[3]
  • Note that data is limited to case reports
• Progression to Avascular Necrosis of the Hip
  • Limited data does makes prognostication challenging

Nonoperative

• First line treatment
  • Goal: Prevent microfractures, relieve pain
• Minimizing weight-bearing activities and relative rest
• Using Crutches or Wheelchair if needed
• Hot packs
• Ultrasound therapy
• Bisphosphonates
  • IV pamidronate showed an average clinical recovery of 2 months, compared to a historical control recovery of 6 months^[14]
  • However, alendronate oral therapy in 8 cases shows an average clinical recovery of 6 months
• Calcitonin
  • In 6 cases shows a shortened mean clinical recovery of 4.7 months
• Teriparatide
  • Case reports of benefit^[15]
• Combination therapy
  • Combination of calcitonin and bisphosphonate therapy, zoledronate, or teriparatide in different reports shows almost a 1 month recovery time^[16][17]
• Corticosteroids including Prednisolone, Deflazacort have been used
• Special Population: Pregnant women
  • Many of the above drugs are not safe or approved in pregnancy or in women who are breastfeeding
  • Consider Calcium, Vitamin D supplements in these patients

Operative

• Indications
  • Progression to AVN
• Technique
  • Core Decompression +/- bone grafting
  • Total Hip Arthroplasty
  • Rotational Osteotomy
  • Curettage and Bone Grafting
  • Vascularized Free-fibula Transfer
  • Total Hip Resurfacing
  • Hip Arthrodesis