Ischemic Osteonecrosis Ischemic Osteonecrosis (More accurate term) aka avascular necrosis AVN: this term describes subarticular (subchondral) bone death Intramedullary bone infarct: depicts osteonecrosis within the medullary cavity of the bone (above x-ray image) Causes: m/c: trauma, systemic corticosteroids, diabetes, vasculitis in SLE. The list is long. Other vital causes: Sickle cell disease, Gaucher disease, alcohol, caisson disease, SCFE, LCP, etc. Pathology: ischemia and bone infarct with resultant devitalized center surrounded by ischemia and edema with normal bone on the outer periphery (MRI double line sign) Sub-articular necrotic bone eventually collapses and fragments leading to progressive bone and cartilage destruction and rapidly progressing DJD Early Dx often missed but crucial to prevent severe DJD M/C Sites Hips, shoulders, talus, scaphoid bone. Many peripheral idiopathic AVN sites are known by their eponyms (e.g., Kienbock aka AVN of the lunate bone, Preisier aka scaphoid AVN) Radiography is insensitive to early AVN and may only present as subtle osteopenia Some of the early appreciable rad features are increased patchy bone sclerosis followed by sub-articular bone collapse or "crescent sign" signifying stage-3 on Ficat classification (above) Earliest detection and early intervention can be achieved by MRI (most sensitive modality) If MRI contraindicated or unavailable, 2nd most sensitive modality is radionuclide bone scan (scintigraphy) X-ray and CT scanning are of equal value Coronal MRI Slice Fluid sensitive, sensitive coronal MRI slice revealing bill ischemic osteonecrosis of the femoral head MRI findings: l Tc99-MMDP Radionuclide Bone Bone scan reveals a central area of photopenia (cold spot) d/t necrotic fragment surrounded by increased osteoblastic activity as increased uptake of Tc-99 MDP in the right hip The patient is a 30-year-old female with breast cancer and chemotherapy treatment who suddenly presented with right hip pain Radiographic Progression of AVN Later stages present with articular collapse, subarticular cysts, increased patchy sclerosis and complete flattening of the femoral head with resultant severe DJD. Rx: THA Management Early imaging Dx with MRI or bone scintigraphy is essential Referral to the Orthopedic surgeon Core decompression (above) can be used to revascularize the affected bone during earlier stages but produces mixed results Delayed changes of AVN: THA as IN severe DJD cases B/L THA B/L THA in the patient with ischemic osteonecrosis of the right and later left hip When B/L hip AVN is present, typically consider systemic causes (corticosteroids, diabetes) Inflammatory Arthritis Affecting the Hip Consider common systemic inflammatory condition such as RA and AS/EnA Hip RA may develop in 30% of patients with RA Key features to DDx inflammatory arthritis vs. DJD is symmetrical/uniform aka concentric joint loss often leading to axial migration and Protrusion Acetabule in advanced cases Key element between RA vs. AS: the presence of RA bone erosion w/o productive bone changes or enthesitis in AS d/t inflammatory subperiosteal bone proliferation, whiskering/fluffy periostitis (collar-type enthesitis circumferentially affecting head-neck junction) Dx: Hx, PE, labs: CRP, RH, anti-CCP Ab (RA) CRP, HLA-B27, RF- (AS) Septic Arthritis Gonococcal infections, iatrogenic causes, I.V. drug use, and some others Routes: hematogenous, adjacent spread, direct inoculation (e.g., iatrogenic) Clinically: pain and reduced ROM presented as monoarthritis, generalized signs/symptoms. CBC, ESR, CRP changes. ARthrocentesis and culture are crucial M/C pathogen Staph. Aureus & Neisseria Gonorrhea 1st step: radiography, often unrewarding in the early stage. Later (4-10 days) indistinctness of the white cortical line at the femoral articular epiphysis, loss of joint space, effusion as a widening of the medial joint area (Waldenstrom sign) MRI - best at early DX: T1, T2, STIR, T1+C may help with early. Early I.V. antibiotics crucial to prevent rapid joint destruction Slipped Capital Femoral Epiphysis (SCFE) Important to diagnose but easily missed potentially leading to Ischemic Osteonecrosis of the femoral head aka AVN Presents typically in overweight children (more often boys), age over 8 years. Greater incidence in African-American boys 1st step: radiography, especially look for a widened physeal growth plate (so-called pre-slip). Later, slip and disturbed Klein's line (above image). MRI - best modality for early Dx and early intervention The frog lateral view often demonstrates the medial slip better than the AP view Clinically Limping Child or Adolescent M>F (10-18 years). African-Americans are at greater risk. 20% of cases of SCFE are B/L. Complications: AVN >>DJD Radiography: AP pelvis, spot, and frog leg may reveal slippage as Klein line failed to cross through the lateral aspect of the femoral head Additional features: physis may appear widened MRI w/o gad is required for the earliest Dx and prevention of complications (AVN) Normal and Abnormal Klein Line Consistent with SCFE. The physis is also widened. Dx: SCFE Urgent referral to the Pediatric Orthopedic surgeon Subtle Changes in Left Hip Note suspected subtle changes in the left hip that may require MR examination to confirm the Dx Delay in care may result in significant complications Perthes' Disease aka Legg-Calves-Perthes Disease (LCP) Refers to Osteochondritis of the femoral head with osteonecrosis likely d/t disturbed vascularization of the femoral head Presents typically in children (more often boys) aged under 8 years as atraumatic "limping child." 15% may have B/L Perthe's Imaging steps: 1st step x-radiography, followed by MRI especially in stage 1 (early) w/o x-ray abnormalities Unspecific signs: joint effusion with Waldenstrome sign+ (>2-mm increase in medial joint space compared to the opposite side). Past approach: Fluoroscopic Arthrography (replaced by MRI) Pathologic-Radiologic Correlation: in well-established cases, the femoral head characteristically becomes sclerotic, flattened and fragmented due to avascular necrosis (AVN). Later on, an occasional Coxa Magna changes may develop (>10% femoral head enlargement) Management: symptoms control, bracing. Boys at younger ate show better prognosis d/t more immaturity and better chances of bone/cartilage repair mechanisms. In advanced cases, operative care: osteotomy, hip arthroplasty in adulthood if advanced DJD develops Common Neoplasms & Other Conditions Affecting Hip/Pelvis M/C hip & pelvis neoplasms in adults: bone metastasis ( above far left), 2nd m/c Multiple Myeloma (M/C primary bone malignancy in adults). Tips: remember Red Marrow distribution. Less frequent: Chondrosarcoma Paget's disease of bone (above-bottom left image) is m/c detected in the pelvis and Femurs Children and young adults 'limping child' benign neoplasms: Fibrous Dysplasia (above middle image), Solitary Bone Cyst (21%), Osteoid Osteoma, Chondroblastoma. Malignant pediatric neoplasms: m/c Ewing Sarcoma (above middle right and bottom images) vs. Osteosarcoma. >2y.o-consider Neuroblastoma Imaging: 1st step: radiography followed by MRI are most appropriate. If Mets are suspected: Tc99 bone scintigraphy is most sensitive Multiple Myeloma Multiple Myeloma in a 75-y.o male (AP pelvis view) Chondrosarcoma in a 60-y.o male (axial and coronal reconstructed CT+C slices in the bone window) Hip Pelvis Arthritis & Neoplasms