PANCE Blueprint Musculoskeletal (8%)

Avascular necrosis (Lecture)

Patient will present as → a 49-year-old female with progressive left hip pain and limp which has become progressively worse over 13 months. Her past medical history is significant for heterozygous sickle cell anemia and she is has been under hydroxyurea treatment for about 20+ years. She is on no other medication and denies alcohol or tobacco use. The pain is localized to the groin, lateral hip, and buttocks and she reports a sudden increase in pain about two months ago after her last sickle cell crisis. Physical exam reveals a left hip with painful restriction of ROM and a limp. Right hip has mild symptoms. An MRI is performed with results seen here.

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Avascular necrosis is a disease that results from the temporary or permanent loss of blood supply to the bone. When blood supply is cut off, the bone tissue dies and the bone collapses. If avascular necrosis happens near a joint, the joint surface may collapse

  • AVN of this hip will start as an insidious onset of a dull ache or throbbing localized to the groin, lateral hip, or buttocks associated with weight-bearing activities that progresses to pain at rest and night pain
  • Think trauma, steroid use, or sickle cell
  • Additional risk factors include SLE, hypercoagulable states, irradiation, hematologic diseases (leukemia, lymphoma), and adysbaric disorders (decompression sickness, "the bends")
  • In children AVN is known as Legg-Calve' Perthes disease - will present with persistent pain and a limp in children ages 2-11 years old with a peak incidence of 4-8 years of age
  • Besides the hip, the areas likely to be affected are the shoulder, knee, hand, and foot
  • Osteonecrosis is a more general and inclusive term often used interchangeably with avascular necrosis and is now preferable

MRI is the study of choice for early detection - order when radiographs are negative, and osteonecrosis is still suspected

  • Bone scintigraphy is also quite sensitive (~85%) and is the second option after MRI. It is a choice when multiple sites of involvement must be assessed in patients with risk factors, such as sickle cell disease
  • Radiographs for suspected hip AVN => AP hip, frog-lateral of the hip, AP and lateral of the contralateral hip

Treatment may be conservative (anti-inflammatory, analgesia, and reduced/non-weight bearing) or may eventually need joint replacement

  • Bisphosphonates - indicated for precollapse AVN
  • Core decompression is a surgical procedure that involves surgical drilling into the area of dead bone near the joint. This reduces pressure, allows for increased blood flow, and slows or stops bone and/or joint destruction

Question 1
Identification of hip fracture and initiation of treatment is imperative to avoid such complications as avascular necrosis (AVN). Which of the following groups are most at risk for AVN?
A
Children and adolescents
B
Teenagers
C
Adults in middle age
D
The elderly
Question 1 Explanation: 
AVN is more common in patients in the pediatric and adolescent age groups. This outcome is due to the precarious nature of the blood supply to the subchondral region of the femoral head, which does not stabilize until years after skeletal maturity, after which collateral flow develops.
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Disorders of the hip (PEARLS) (Prev Lesson)
(Next Lesson) Developmental Dysplasia of the Hip (ReelDx)
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