Primary Osteoarthritis of the Hip

Definition

  • Degeneration of the tissues of the hip joint, including hyaline cartilage, fibrocartilage, bone & synovium

Prevalence

  • 3% to 6% in the Caucasian population
  • Asian, black, & East Indian populations have very low prevalence of hip Osteoarthritis

Types

  • Primary osteoarthritis (Osteoarthritis) of the hip (90%)
    • a diagnosis made by exclusion
  • Secondary osteoarthritis of hip
    • osteonecrosis, trauma, sepsis, or rheumatoid arthritis
    • congenital hip disease & slipped capital femoral epiphysis

Aetiology

  • Genetic
    • Family studies from Sweden, Britain, & the United States show ↑ rates of hip Osteoarthritis in first-degree relatives of the index patient when compared with the normal population
    • low prevalence of hip Osteoarthritis in Asian & black populations in their native countries; the low incidence of total joint replacement for primary Osteoarthritis in Asian, black, & Hispanic populations in North America; & the familial association of hip Osteoarthritis in Caucasians all suggest that genetic factors may be involved in the occurrence of this disease
    • Rate of THRCaucasians 75 per 100,000 persons
      • blacks had half the incidence
      • Asians had only one tenth.
  • Location
    • incidence of Osteoarthritis was not related to latitude or longitude
  • Body Weight
    • Osteoarthritis of the knee has been shown to be consistently related to obesity
    • Hip Osteoarthritis: controversial
    • no relationship between body weight or body-mass index & the occurrence of hip Osteoarthritis. However, other studies have shown an ↑ risk of Osteoarthritis of the hip in obese individuals
  • Occupational Factors
    • Occupations requiring heavy lifting, farming, & elite sports activity are associated with ↑ rates of hip Osteoarthritis
    • ? exacerbate hereditary predisposition to Osteoarthritis of the hip
      • work
        • physical demands of work have been estimated to account for 40% of cases of hip Osteoarthritis
      • carrying heavy loads
      • farmers
      • track, field, & racket sports soccer players
  • Other Anatomic Considerations
    • DDH
    • acetabular abnormality
    • femoral anteversion
      • not shown

Predisposing Anatomic Abnormalities

  • Hip dysplasia
    • If primary Osteoarthritis of the hip is due to a subtle dysplasia, it should be seen frequently in Japanese persons, with their extremely high rate of dysplasia; however, primary Osteoarthritis is rare in that population
    • incidence of DDH in Caucasians is 0.5%. If Osteoarthritis developed in all children with DDH, this would account for only one eighth of the cases of Osteoarthritis in the Caucasian population
    • In summary, when controlled studies of acetabular measurements are done & the rates of DDH & Osteoarthritis for each racial subgroup are considered, DDH accounts for only a small percentage (5% to 10%) of hip Osteoarthritis in Caucasians
  • clinical SUFE in the adolescent occurs in only 1 of every 800 boys (an incidence of only 0.125%)
    • Anatomically normal femora accounted for more than 80% of the Osteoarthritis in their series
    • Furthermore, although there is little primary Osteoarthritis in the black & Polynesian populations, as well as a low incidence of THR performed because of Osteoarthritis, these populations have two to four times the rate of SUFE in Caucasians.

Grading

  • Kellgren’s grading system was used to characterise the degree of hip arthritis
    • absent (grade 0)
    • doubtful (grade 1)
    • minimal (grade 2)
    • moderate (grade 3)
    • severe (grade 4).

References

JAAOS

Contribution

Phong Tran