OSTEONECROSIS OF HEAD OF FEMUR

• Dfn: It refers to the death of osteocytes with subsequent structural changes leading to femoral head collapse & secondary arthrits of hip joint.
• Etiology/Causes: I) Idiopathic– most common
  II)Local– trauma, dysplasia, post-radiation,
  III)Systemic– 1)arterial disease, 2) Gauchers ds, 3)Sickle Cell  ds, 4)Liver cirrhosis, 5)Pancreatitis, 6) SLE, 7)Amyloidosis
  IV)Acquired- a)Drugs- Phenytoin, Steroid; b) Alcohol, c)Dysbarism(Cassion’s ds), d) Renal transplant
• PATHOPHYSIOLOGY:
     >Loss of cell-viability(cell necrosis)
     >Invasion of marrow space of dead bone by proliferating capillaries.
     >Invasion of dead bone by mesenchymal cells   >Differentiation of mesenchymal cells to oteoblast   >New bone formation
     >Early remodelling of repaired cancellous bone
    >Late remodelling
     >Resorption of subchondral bone + Invasion of articular cartilage

SIGNS/SYMPTOMS:

 

• B/L-50%
• Pain in groin- anteromedial
• Sectoral sign +nt → collapse of head
• Restriction of Abduction/Internal rotation
• Limping Gait   

INVESTIGATION:

• X-Ray– changes detected only after 2-6 months
• Bone Scan-early detection
• MRI– within 48 hours→ “Double line” sign, pathognomic

 

CLASSIFICATION

• Ficat-Arlet
• Steinberg
• Marcus
• Arco
• Pittsburg

Pittsburgh  Classification
			PLAIN  RADIOGRAPHIC
			FINDINGS
STAGE		MRI  FINDINGS	STRUCTURE	CONTOUR
I		Abnormal	Normal	Normal
	A	<30%	—	—
	B	>30%	—	—
II		Abnormal	Abnormal	Normal
	A	<30%	<30%	—
	B	>30%	>30%	—
III		Abnormal	Abnormal	Abnormal
	A	<30%	<30%	<2  mm
	B	>30%	>30%	>2  mm

 

Ficat  and  Arlet  Classification  of  Osteonecrosis  of  the  Femoral  Head
STAGE	SYMPTOMS	RADIOGRAPHY	BONE  SCAN	PATHOLOGICAL FINDINGS	BIOPSY
0	None	Normal	Decreased uptake?
1	None/mild	Normal	Cold spot onfemoral head	Infarction of        weight-bearing portion of femoral head	Abundant dead marrow cells, osteoblasts, osteogenic  cells
2	Mild	Density change in femoral head	Increased uptake	Spontaneous repair of infarcted area	New bone deposited between necrotic trabeculae
2A		Sclerosis or cysts, normal joint line, normal head contour	Increased uptake
2B		Flattening (crescent sign)
3	Mild to moderate	Loss of sphericity, collapse	Increased uptake	Subchondral fracture, collapse, compaction & fragmentation of necrotic segment	Dead bone trabeculae & marrow cells on both sides of fracture line
4	Moderate to severe	Joint space narrowing, acetabular changes	Increased uptake	Osteoarthritic changes	Degenerative change in acetabular cartilage

 

MITCHELL  CLASSIFICATION (MRI findings)
A	Central Osteonecrosis – signal similar to Fat
B	-signal similar to Blood
C	-signal similar to Fluid
D	-signal similar to Fibrous tissue

 

 

Management:-

Stage 0– Rest, Bisphosphonate, Vitamin-C, Reassurance

Stage 1– Core decompression, Electrical stimulation, BMP, Bone-Graft ( Vascularized/Non-vascularized)

Stage 2A– Core decompression with Phemister bone graft; Transtrochanteric osteotomy; Muscle-pedicle grafting

Stage 2B– if (a)<30% head involved;(b)<45 year age;(c)Unilateral:- 1.Transtrochanteric osteotomy, 2.Sugioka’s rotational osteotomy, 3.Intertrochanteric osteotomy.

– if >30% head involved:- Resufacing Arthroplasty

Stage 3– Osteotomies; Resurfacing Arthroplasty (if >30% head involved, >2mm collapse)

Stage 4– Hip Arthrodesis; Girdlestone Resection; Arthroplasty ( THR, Resurfacing Arthroplasty)

 

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