Talking the talk

Clinical image

AP radiograph of avascular necrosis of the femoral head. Source: Wikimedia Commons — Mikael Häggström, M.D.; CC0 1.0. Image binary is embedded locally in this package; original source and licence are retained.

Key points

• AP view of pelvis with both hips showing diffuse sclerosis with increased density in the superolateral aspect of both hips suggestive of AVN. I would like to see frog leg lateral view
  • To see crescent sign suggestive of subchondral fracture

AVN

• Osteonecrosis of the femoral head due to interruption of blood supply leading to ischaema and cell death
• Etiology
  • Steroid
  • Smoking
  • Alcohol
  • Idiopathic

AS IT GRIPS 3 C

• Alcohol
• Steroid
• Idiopathic
• Trauma
• Gaucher
• Rheumatoid
• Infection
• Pregnancy
• Smoking
• CRS/Chemo/Caisson

Pathology

• Related to underlying ethiology that alters the blood flow
• Five vascular areas that can be involved are
  • Extra osseous arterial most important
    • Trauma/vasculitis/spasm
  • Intra osseous Arterial due to circulating micro emboli
    • Fat embolism/Caesson/SCD
  • Extra osseous extravascular
    • Capsular tamponade
  • Intra osseous extravascular
    • Fat cell hypertrophy (steroid)
    • Abnormal cells (Goucher)
  • Intera osseous venous
    • stasis in SCD/Fat cells
• Clotting abnormalities

Steroid AVN

• Fat cell hypertrophy
• Increased fat cell content
• Fat embolism
• Endothelial and smooth muscle cell damage
• Primary osteocyte death
• 10-30% of AVN, m/c atraumatic cause

• 2g prednisone > 2 months

Classification

• Ficat and Arlet with hungerfold modification
  • 0: preclinical: Suspected disease in C/L hip
  • 1: Pre radiographic: MRI shows double line sign/bone scan
  • 2: Precollapse : Osteopenia, Sclerosis, cyst and cresent sign
  • 3: Collapse: Flat head
  • 4: OA with deformed head

Steinberg

• 7 stages

• 0: Histology

• 1:abnormal bone scan/MRI

• 2:Sclerosis, cyst

• 3:Cresent sign with out flattening

• 4: Flattening

• 5: OA

• 6:Advance OA

• <15%

• 15-30%

• 30%

Others

• ARCO: Association research Circulation Osseous)
• University of pennsylvania
• Mitchell MRI classification

Kerboull Necrotic angle

• Necrotic angle is measured in AP and Frog lateral

• 200 degree: poor result with bone preservation

Management

• Goal is to
  • relieve pain
  • prevent deformity
  • preserve function
• Based on
  • Precollapse or not
  • Necrotic segment
  • Femoral head depression
  • Acetabular involvement

Non surgical

• Collapse occurs in 80% patients with pain with in 4 years
• Pharmacological
  • Alendronate: Agarvala et al , JBJS 2009, 2% failure in 1, 8% in 2 and 33% in stage 3
  • Iloprost: vasodilator
  • Statins: pro osteoblastic and anti adipogenic
  • Electrical stimulation: experimental
  • Hyperbaric O2: reversal of cellular ischemia

Stage 1 and 2

• Core decompression: relieve pressure, increase vascularity and healing
  • 2/3 good result (Mont et al)
• Tantalum rod insertion: no donor site morb, structural supp, osteointegration
  • 15 % failure rate
• VFG/non VFG
• Medical: Bisphosphonates, Anticoagulants, Vasodilators, Lipid lowering agents
• Stem cells: one stage or two stage
• Trapdoor
• Muscle pedicle BG

VFG

• McKee indications
  • <45
  • 2mm or less collapse
  • etiology withdrawn
  • no contracture
  • joint supple
• Advantages: support subchondral bone and provide blood supply for revascularistion
• compli: Gaskill
  • Donor site: Great toe contracture , weakness, pain sensory deficit
  • Graft site: Pin migration, HO, Infection, Fracture, DVT

2 and 3

• Trapdoor: Mont et al 73% excellent result in 5 years
• Osteotomy
  • Attempts to shift the involved part medially
  • Angular: varus/valgus
  • Rotational: Sugioka
  • Indications
    • Young <45
    • Kerboull <200
    • No joint narrowing
    • Unilateral
    • Traumatic/idiopathic

Arthroplasty

• Bipolar Hemi: elderly
• Hybrid THA
• Uncemented THA:
  • Cheung et al in Hip Int, 2015: 117 AVN, age 51 mean, >95 % survival in 19 years
  • SCD, Goucher, CKD, Trauma, NOF # higher revision rate
• Cemented
  • Historically poor result
  • Steinberg 96% survival with 2nd gen cementing
  • Kim: No difference in result with hybrid and uncemented

Choice of THA

• < 55 years
  • Uncemented THA CoC
    • 6.35% revision in 10 year MoP
    • 4.5% revision for CoP
    • 3.5% revision for CoC
  • Cemented THA CoP
    • 7.5 % revision MoP
    • 3.5% revision CoP
  • Non controversial answer (Kim comparison, Steinberg)
    • Cemented Forced closed Femoral stem with at least 2nd gen cementing
    • Ceramic head
    • Highly cross linked poly

CoC

• Hard, wear resistant and wettable
  • Better lubrication
  • Decreased wear
  • Catastrophic Fracture, Squeaking, chipping during insertion

Asymtomatic ON

• Necrosis in MRI Kim et al
  • Small (<30% head involved): 5% disease progression
  • Medium (30-50%): 45%
  • Large(>50%):85%