Aseptic loosening total hip arthroplasty.

1. ASEPTIC LOOSENING
OF
THA
PRESENTER: DR.IMRAN ALI

2. A good prosthesis is important

4.  Although success rates for total hip
arthroplasty (THA) now approach 97%,
osteolysis and aseptic loosening continue to
plague surgeons.
 Reported prosthetic failure rates due to these
complications are as high as 20%.1
1Sinha RK, Shanbhag AS, Maloney WJ, Hasselman CT, Rubash HE.
Osteolysis: Cause and Effect, Instructional Course Lectures, Volume
47. Rosemont, Ill: American Academy of Orthopaedic Surgeons Press;
1998: 307-320.

5.  When cemented femoral components were the
predominant types of prostheses used, as
many as 12% of patients demonstrated
symptomatic loosening, and as many as 20%
required revision surgery.[2]
 2 Aseptic loosening in THA. In: American Academy of Orthopaedic
Surgeons. Adult Reconstruction Orthopaedic Knowledge Update.
Rosemont, Ill: American Academy of Orthopaedic Surgeons Press;
1996: 147-156.

6. Osteolysis
 is the end result of a biologic process that
begins when the number of wear particles
generated in the joint space overwhelms the
capsule's capacity to clear them.

7. Osteolysis
 Steps in osteolysis:
 particulate debris formation
 Access of these particles to periprosthetic bone
 macrophage activated osteolysis
 prosthesis micromotion
 particulate debris dissemination

8. osteoclast osteoblast interaction
cytokines/
chemokine
s
MACROPHAGESDEBRIS
phagocytosis
inhibit

9. Sources of particulate debris
1. Wear
 Mechanisms of wear
 A. Adhesion:
 microscopically PE sticks to prosthesis and debris gets pulled off
 B. Abrasion:
 C. Third body wear particles in joint space cause
abrasion and wear
 D. Micro Fatigue
2. Corrosion: electrochemical reaction

10. wear rates by material
 Non-cross linked UHMWPE
 wear rate is 0.1-0.2 mm/yr
 Ceramic bearings
 lowest wear rates of any bearing combination
 (0.5 to 2.5 µ per component per year)
 Ceramic-on-polyethylene,
 ranging from 0 to 150 µ.
 Metal-on-metal produces smaller wear
particles as well as lower wear rates
 (ranging from 2.5 to 5.0 µ per year)

12. Modes of wear
 1. Motion between 2 surfaces designed for
motion
 2. Primary bearing surface against an non
intended bearing surface
 i.e. femoral head against acetabular shell when liner has
worn out
 3. Interposed third body particles i.e. bone or
cement
 4. Two non bearing surfaces together i.e. back
sided fretting, morse taper fretting, screws

14. Loosening of THA
components
 With Cemented THAs, the acetabulum is the first
component to fail from loosening.
 With cementless hips, the femoral component
loosens more often as a result of osteolysis.
 Loosening occurs at implant-cement interface in
femoral component, while at bone-cement interface
in acetabulum.

15. Zones of loosening
 Femoral component
Seven Gruen zones
 Acetabular component
Three Delee and Charnley
zones

16. Gruen 7 zones
of femur
•Zone 1
•Debonding
•Zone 4
•Subsidence
•Zone 7
•Fragmentation of
cement

18. Barrack grading

20. Delee and
Charnley
acetabular
zones

21. Harris grading
Cemented Femoral loosening;
Radiographic
 Definite loosening
 Stem failure – fracture/deformation
 Cement mantle fracture esp zone 4
 Radiolucency >1mm
 Changes in stem position- usually varus position
 Pistoning effect
 Probable loosening
 Continous radioluscent line at bone-cement interface
 Endosteal cavitation-linear and focal osteolysis
 Possible loosening
 Radioluscent lines at bone-cement interface 50-100%

22. Harris grading
 1. Possible
 Bone-cement
lucency < 50% total
 may be due to poor
cementing technique

23. Harris grading
 2. Probable
 Cement-implant
radiolucent line
>2mm wide
 - progressive

24.  3. Definite
 Cement fracture(zone 4)
 Femoral stem fracture
 Radiolucency >2 mm
 Greun zone 1> debonding
 New lucency cement -
implant interface
 Stem migration,/ varus
 Pistoning effect

27. Mechanism of stem failure
A. Subsidence/Pistoning
 1-2 mm normal in first year
 > 5 mm abnormal
 Quantified by measuring distance against a
fixed landmark e.g tip of greater troch, tear
drop

28. Subsidence

29. Mechanism of stem failure
 B. Medial midstem
pivot
 Medial migration of the
proximal stem in
association with lateral
displacement of the
distal stem tip

30. Mechanism of stem failure
 Calcar pivot
 Either medial or
lateral movement of
the distal tip of the
embedded stem
with reasonable
support proximally

31. Mechanism of stem failure
 Distal pivot/bending
cantilever
 - distal fix strong, but
proximally loose
 - breakdown of
proximal cement

33. Are all radioluscent line due to
loosening?
 Radiolucent lines btn femoral cortex and cement
 Cancellous bone not completely removed during sx
 Normal age related expansion of femoral canal assoc
cortical thinning.1
 Medullary canal expands at 0.33mm/yr
 Cortical thickness decrease by 0.15mm/yr
 No surrounding sclerotic line
 1. Poss et al study

34. Technical problems that
contribute to stem loosening
 Failure to remove adequate cancellous bone
medially
 Inadequate quantity of cement
 Thin column cracks easily
 Tip of stem should be supported by a plug of cement
 Presence of voids in cement
 Poor mixing, injecting, pressurizing technique,
 Blood, bone fragments ion cement( laminations)
 Failure to prevent stem motion while cement is
hardening
 Failure to position component in neutral or mildly
valgus position

35. Cementless
femoral
components

36. Engh classification
Types based on presence of radiolucent lines (RLL)
 I. Stable bony ingrowth
 Take one year to see
 A. Spot welds at end of porous coating
 B. Absence of RLL next to porous coating
 - may have RLL next to non porous coated areas
 C. Calcar atrophy secondary to stress
shielding

37. Stable bony ingrowth
Spot welds Stress shielding

38. Stable fibrous ingrowth
 A. No spot welds
 B. Parallel
sclerotic lines /
 RLL about porous
coating
 C. No migration


39. Unstable fibrous ingrowth
 A. Component migration
 B. Progressive increase
RLL
 - divergent RLL
 C. Pedestal formation
(bony hypertrophy at tip)

40. Cemented Acetabular loosening;
radiographic features
 Bone-cement lucency >2mm and/or progressive
 Medial migration and protrusion of cement and cup
 Change in inclination of cup >50
 Eccentric PE wear of the cup
 Fracture of cup and/or cement(rare)

41. Technical problems during sx
leading to cup loosening
 Inadequate support of the cup by bone & cement
 Insufficient bone stock
 Acetabullum not reamed deeply enough
 Failure to remove all cartilage, loose bone fragments, fibous
tissue and blood
 Failure to make sufficient no of holes in acetabulum to secure
good cement-bone bon
 Failure to pressurize cement, distribute cement
 Movementt of cup or cement mantle while cement is hardening
 Malpositioning of cup

42. Uncemented Acetabular Component
 Concepts
 Bone ingrowth into component averages only
12%
 - even with 84% bone contact
 Non continuous radiolucent lines
 commonly found in press fit acetabular
components
 are often not progressive

43. Radiographic signs of ingrowth
fixation

 Moore et al CORR 2006
 - 3 or more 97% stable
 - 2 or less, 83% unstable

44. Radiographic signs of ingrowth
fixation
Five signs
 - absence of
radiolucent lines
 - presence of a
superolateral
buttress
 inferomedial
buttress
 - medial bone
stress-shielding

45. Radiographic signs of
loosening
 5 signs
 - radiolucent lines that
appear after two years
 - progression of radiolucent
lines after two years
 - radiolucent lines in all
three zones
 - radiolucent lines 2 mm or
wider in any zone
 - migration > 2mm

46. Engh Classification
I. Stable bony
ingrowth
 A No RLL
 B One RLL zone
1/2
 C RLL zones 1 & 2

47.  II Stable fibrous
ingrowth
 - <2mm zone 3

III Unstable fibrous
ingrowth
 - >2mm RLL in zone
3

49. Diagnosis
 History
 Pain on wt bearing –groin, buttock or thigh
 Typically ‘start-up’ pain
 Pain relieved by rest, aggravated by hip rotation
 Physical exam
 Antalgic gait
 Limb length discrepancy
 Investigations
 Laboratory
 R/O infection
 Imaging
 Progressive radiolucency
 Migration of implant

50. Treatment
 Asymptomatic patient
Radiographic loosening often appears
be4 symptoms
More frequent follow-up
Revision surgery if bone destruction is
progressive
 Symptomatic patient
Revision surgery

51. Indications for surgery
 Symptomatic patient
 Loose implants
 Large lytic lesions
 Progressive osteolysis even if no
symptoms

52. Revision Total Hip
Arthroplasty
 cementless components are generally
preferred in revision settings.
 The bone sclerotic and does not provide
optimal conditions for cement interdigitation
 only the loose components need to be
revised
 If implant remains stable despite
osteolysis, bone grafting of the defects
with retention of the implant is
recommended