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Osteonecrosis of the Shoulder
synonyms: avascular necrosis, AVN, osteonecrosis
Shoulder AVN ICD-9:
- 733.41(shoulder), 733.40(unspecified), 733.49(other)
Shoulder AVN Etiology / Epidemiology / Natural History
- Most commonly adults 20-50yrs old
- Etiology: EtOH or prolonged high dose steriods. Other risk factors: sickle cell, dysbarism, Gaucher's disease, trauma, high-dose radiation, thrombophilia, protein S & C defiencies, hypofibrinolysis.
- Thought to be due to altered circulating lipids and coagulation mechanisms.
- Marrow death occurs 6-12 hrs after ischemia, radiographic changes appear after 3 months, articular collapse within 6-12 months in 80% of patients with clinical AVN.
Shoulder AVN Anatomy
Shoulder AVN Clinical Evaluation
Shoulder AVN Xray / Diagnositc Tests
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- MRI: If suspected but not seen or if only in one shoulder MRI is indicated. MRI sensitivity and specificiaty=95% for early AVN. Not good for estimating the extent of lesion.
- CT is the best technique to determine area of bone death.
- Bone scans are sensitive but have large number of false positives and have no advantage over MRI
- Evaluation should include lipid levels and possible screening for decreased levels of protein C and S and antithrombin III and increased levles of plasminogen activatoter inhibitor-1.
Shoulder AVN Classification / Treatment
Cruess RL, CORR 1978;86-93
ARCO Staging (Association for Research on Osseous Circulation) ARCO News 1992;4:41
- Stage 0-Bone biopsy demonstrates AVN. All other tests normal. Generally treated non-operatively
- Stage I-Bone scan or MRI positive. Lesions subdivided based on location (medial, central and lateral) and percentage of head involvement. Ia=<15% involvement; Ib=15-30%; Ic=>30%. Treatment: consider core decompression in young patients or Alendronate 70mg weekly (Lai KA, JBJS 2005;87A:2155).
- Stage II-Xray=osteoclerosis, cystic , osteopenia or mottled femoral head without collapse or acetabular involvement. Bone Scan/MF+RI=lesions subdivived based on location (medial, central and lateral) and percentage of head involvement. IIa=<15% involvement; IIb=15-30%; IIc=>30%. Treatment: core decompression for IIa sclerotic disease in young patients.
- Stage III-Xray=crescent sign; lesions subdivided based on location (medial, central and lateral) and percentage of head involvement. IIIa=<15% involvement or <2mm depression of head; IIIb=15-30% or 2-4mm depression; IIIc=>30% or >4mm depression. Treatment: Osteotomy vs vascularized fibula vs resurfacing vs THA.
- Stage IV-Xray=flattened particular surface, joint space narrowing, acetabular changes, osteophytes. Treatment: arthrodesis vs THA
- Ficat based on plain radiographs. Stage I=symptomatic hip,no xray change. Stage II, xray= patchy areas that are radiolucent and radiodense. Stage III=“crescent sign”=subchondral collapse. Stage IV=articular surface collapse.
- U of Pennslvania system (Steinberg). 0-normal MRI, XRAY, bone scan.1-abnormal MRI\bone scan .2-sclerotic\cystic changes on xray. 3-crescent sign. 4-flattened femoral head. 5-joint narrowing. 6-advanced DJD
Shoulder AVN Treatment Options
- Avoid chronic steriod use, correct lipid and coagulation abnormalities.
- conservative tx/ resticted activity usually ineffective.
- Electrical stimulation -some studies have shown benefit from pulsing electromagnetic fields applied externally for hip AVN. further study needed
- Alendronate 70mg weekly (hip AVN) (Lai KA, JBJS 2005;87A:2155).
- Core Decompression (Dines JS, Arthroscopy 2007;23:103e1), (Laporte DM, CORR 1998:254:60
- Surface Replacement (Copeland S, JBJS 2006;88:900)
- Hemiarthroplasty
- TSA
- 5 10 16
- Hemiarthroplasty vs TSA: no difference in outcome or ROM between hemiarthroplasty and TSA. Complication rate is significantly higher with TSA
(22%) than with hemiarthroplasty (8%). TSA should be reserve for stage V osteonecrosis. (Feeley BT, JSES 2008;17:689).
Shoulder AVN Associated Injuries / Differential Diagnosis
Shoulder AVN Complications
- Humeral head collapse
- Arthritis
- Pain
Shoulder AVN Follow-up Care
- Dependent on stage and treatment.
Shoulder AVN Review References
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