COXA VARA AND VALGA, HIP BIOMECHANICS, DEVELOPMENTAL COXA VARA

1. COXA VARA
AND
COXA VALGA
PRESENTER: DR. KISAN NEPALI

2. Content
• Introduction
• Development of neck shaft angle
• Related biomechanics
• Biomechanics changes in coxa valga and coxa vara
• Coxa valga
• Coxa vara
• Developmental coxa vara

3. Introduction: Neck shaft angle
• Varies according to age.
• Freedom of motion.
• Deviation in either ways alter force relationship and
biomechanics of hip joint.
• Understanding balance of force and moments to
estimate effects of alteration.

4. Development of Neck shaft angle
Crescentic cartilage column Trochanteric epiphysis Greater Trochanter
Cervical epiphysis Neck and head

5. • Progressive weight bearing
• Muscular force
Fig: development of Neck shaft angle

6. In adult ,
NSA: 120
Range: 115-140
Decrease in Neck shaft angle below normal: Coxa Vara
Increase in Neck shaft angle above normal: Coxa Valga

7. Biomechanics
• Effort
• Load
• Fulcrum: Hip joint
Abductor
tension
Body weight
Resultant joint force
Effort X Effort arm= load X Load arm

8. W= 2/3
OF TBW
W= 1/3
OF TBW
W= 1/3
OF TBW
LL= (1/6+1/6) OF TBW
=2/6 OF TBW
=1/3 OF TBW
DOUBLE LEG STANCE

9. 3W W
---X--- -------3X-------
Effort X Effort arm= load X Load arm
SINGLE LEG STANCE

10. Effect of NSA on loading
Ref: Biomechanics of normal and diseased hip

11. Effect of NSA on stress on proximal femur
Ref: Biomechanics of normal
and diseased hip

12. Effect of neck length on proximal femur
Ref: Biomechanics of normal and diseased hip

13. Articular congruency
Ref: Biomechanics of normal and diseased hip

14. Summary
• Coxa vara reduces the load supported by the hip joint and the upper
end of the femur, but greatly increases the stressing of the femoral
neck.
• Inversely, coxa valga augments the load supported by the hip and neck
but reduce the stressing of the femoral neck. Stressed in pure
compression and either slightly or not at all in shearing.

15. Coxa valga
• Infants valgus to varus ( 148 to 120) under the influence of the abductor force and
walking.
• Most of this correction actually occurs by the time children are 2 to 3 years of age.
• The direct cause of the coxa valga is the abnormal force on the proximal femoral
growth plate.

16. Causes of coxa valga
• Bilateral
• Neuromuscular disorders, e.g. cerebral palsy
• often have concurrent femoral anteversion
• Skeletal dysplasias, e.g. Turner syndrome, mucopolysaccharidoses
• Medical condition: Rickets
• Unilateral
• Trauma causing growth plate arrest

17. Clinical feature
• Generally asymptomatic in infants.
• Older kids and adult:
• Pain
• Limit mobility of hip
• LL discrepancy
• Walking difficulty

18. Treatment
• In many cases, is a symptom of another medical condition.
• No need of treatment as long as acetabulum shows adequate development
• When required, Varus derotation osteotomy and angled blade-plate fixation
is effective.
• Osteotomy is done at intertrochanteric or subtrochanteric level.

19. Coxa vara: Classification
• CONGENITAL FEMORAL DEFICIENCY
WITH COXA VARA
• DEVELOPMENTAL COXA VARA
• Isolated (may be bilateral)
• Associated with a skeletal
dysplasia
• Cleidocranial dysostosis
• Metaphyseal dysostosis
• Other skeletal dysplasias
. ACQUIRED COXA VARA
• Slipped capital femoral epiphysis
• Sequela of avascular necrosis of the
femoral epiphysis
• Legg-Calvé-Perthes disease
• Traumatic coxa vara
• Femoral neck fracture
• Traumatic hip dislocation
• Sequela of reduction for
developmental dysplasia of the hip
• Septic necrosis
• Other causes of avascular
necrosis of the immature
femoral head
• Coxa vara associated with pathologic
bone disorders
• Osteogenesis imperfecta
• Fibrous dysplasia
• Renal osteodystrophy
• Osteopetrosis
• Other bone-softening
• conditions affecting the femoral
neck

20. Congenital Coxa Vara
• Present at birth
• Extremely rare
• a/w:
• Proximal femoral focal deficiency
• Fibular hemimelia
• Anomalies in other part of body: cleidocrainal dysostosis

21. Developmental Coxa Vara
• Often B/L
• progressive decrease in the femoral neck shaft angle
• shortening of the affected lower limb
• Presence of defect in the medial part of the neck

22. Epidemiology
• Incidence: 1: 25000 live birth in Scandinavian population
• M:F=1:1
• Unilateral to bilateral cases in between 1:2 and 3:1
• Bilateral cases more likely to be a/w a generalized skeletal dysplasia

23. Pathoanatomy
• Primary defect in endochondral ossification of the medial part of the
femoral neck.
• Dystrophic bone along medial inferior aspect of femoral neck.
• Fatigues with weight bearing
• Progressive varus deformity.

24. Pathoanatomy
Studies reports
• Defects in cartilage production and secondary metaphyseal bone formation
• Cartilage cell no. reduced
• Not well organized in regular column
• Adjacent metaphyseal bone osteoporotic and infiltrated with nest of cartilage
cells.
• Acetabulum: decreased volume
• Femoral head: small
• Femoral neck: shorter
• Physis: wider

25. Biomechanics

26. Compression and tensile force in normal and abnormal hip

27. Effects of decrease neck shaft angle

28. Effect of shortened femoral neck

29. Clinical Features
• Does not manifest until after birth and usually not until walking age
• Painless limp
• Abductor weakness
• LL discrepancy
• Painless but easy fatigability or aching pain around the gluteal muscles after
prolonged exercise
• Trendelenberg gait, B/L: waddling gait.

30. On examination:
• GT more prominent and proximal
• Limitation of abduction and internal rotation
• Trendelenburg test positive
• Shortening in u/l cases (seldom exceeds 3cm at skeletal maturity, even in
untreated patients)
• Evidence of skeletal dysplasia

31. Radiographic findings:
• Decreased NSA of the affected
hip
• More vertical orientation of
physeal plate
• Short neck
• Abnormal bony fragment
inferolateral to the physeal
plate and contained in inverted
Y shaped lucency
• Acetabular dysplasia

32. Quantification of varus deformity
1. Neck –shaft angle
2. Head shaft angle
3. Helgenreiner-Epiphyseal angle (H-E angle)

33. Helgenreiner – Epiphyseal angel (H-E) angle
• Normal : 0-25 (avg: 16)
• Prognostic value of H-E angle
• >60 degree: deformity invariably progress
and need surgical correction.
• <45 degree: stable or improves
• 45 and 59 degree : indeterminate

34. Natural history
• Increase tensile force on superior femoral neck
• Progressive varus deformity
• Stress-fracture related non union of femoral neck
• Premature degenerative arthritis changes
Does is occur in all cases?
• Weinstein et al.
• Determining factor
• H-E angle (60,60-45,45)

35. Treatment
• No cause- no cure
• Aimed at preventing secondary deformities.
• Goals of treatment
• Correction of the varus angulation into a more normal physiological range
• Changing the loading characteristics seen by femoral from shear to compression
• Correction of limb length inequality
• Reestablishment of a proper abductor muscle length-tension relation.

36. Nonsurgical
• H-E angle of <45 degree and are asymptomatic
• Assess for evidence of skeletal dysplasia
• LL inequality
• Periodic radiographic assessment to assess deformity till maturity.
• HE angle between 45-60 degree
• Serial radiographs to assess for progression
• For symptomatic limp, Trendelenburg gait, or progressive deformity surgery is done.

37. Operative
• Indication of surgery
• HE angle of 60 degree or greater
• Neck shaft angle less than 110 degree
• Symptomatic limp
• Trendelenburg gait
• Progressive deformity

38. Surgery
• Corrective valgus osteotomies
• intertrochanteric or
• subtrochanteric level
• To rotate the proximal femoral physis from a vertical to horizontal position (convert
shear force into compressive force)
• To allow remodeling and normal ossification to occur
• Restore hip abductor function.

39. Timing of surgery
Two problem
• Early: weak fixation
• Late : acetabular dysplasia become permanent
• As soon as bony development is deemed adequate (usually 4-5 years)

40. Osteotomy
• Intertrochanteric osteotomy
• Langenskiold Valgus producing osteotomy
• Pauwel osteotomy
• Subtrochanteric osteotomy
• Borden Osteotomy

41. Pawel’s valgus osteotomy
• Cuneiform Y-shaped intertrochanteric osteotomy

42. Borden and colleagues
• The blade of a blade plate of appropriate size with an angle of 140 degree is inserted into the neck parallel to the long axis of the femoral neck.

43. Wagner fixation
• Performed with a bifurcated plate driven through
the intramedullary surface of the proximal
fragment and secured to the distal fragment with
screws.

44. After treatment :
• A spica cast can be worn until union is complete.
• Cast can be removed at 8-12 wks
• Implant removal after 1-2 years following healing of osteotomy

45. Complication:
• Recurrence
• 30-70%
• Development of coxa valga
• Mc: intertrochanteric osteotomy
• Premature epiphyseal plate closure
• Avascular necrosis
• Degenerative changes
• Others: LLD, Pseudoarthrosis, trochanteric overgrowth.

46. Summary
• NSA is very crucial for facilitating hip ROM.
• Any deviation has severe impact on hip biomechanics.
• Developmental coxa vara has characteristic clinical and radiological finding.
• The first step in treating development coxa vara is to find out any other possible cause for this
condition(Table)
• Once diagnosed, child follow up every 4 to 6 month and radiograph evaluated for H-E angle,
symptomatic limp or Trendelenburg gait.
• Valgus producing osteotomy with appropriate rotational osteotomy is preferred treatment.

47. References
• Biomechanics of normal and diseased hip
• Campbell’s operative orthopedics, 14th edition
• Tachdjian's Pediatric Orthopaedics 6th Ed
• lovell and winter's pediatric orthopedics 8th edition
• Related article
• Internet