Aseptic Loosening of implants is caused by osteolysis. It is most significant factor limiting longevity of THA. Revision for loosening is 4x higher than next leading cause (dislocation at 13.6%), and its particularly problematic in younger patients [2]. Osteolysis is bone resorption caused by the body’s response to particulate debris generated as the THA implant wears out. Motion between any two components of the prosthesis (ie the femoral head and the acetabuluar liner, the head-neck junction of the femoral stem, or the liner and shell of the acetabulum) generates debris that floats around the joint. This debris stimulates a host response. Particles of metal, poly, or cement can all cause osteolysis, albeit different types of reaction. Osteolysis is important because it leads to implant loosening and/or periprosthetic fractures. While osteolysis is the primary cause of loosening, infection must be part of the differential diagnosis. Historical Perspective: Osteolysis was first described by Harris in 1976 and it was attributed to “cement disease” [3], because it was observed around the femoral component, and this was what started the drive for cementless implants. Yet after significant R&D, and development of cementless implants, osteolysis was still seen around the implants [4], and the histology was similar between cemented [5] and cementless implants [6]. Surgeons then looked for another cause of osteolysis and recognized that it was produced by wear particles. STAGES OF OSTEOLYSIS 1) Debris production (ie poly wear) is the initial stage (we talk about metal debris in a separate section because it behaves totally differently, see section). Particulate debris in THA is produced by Abrasive and Adhesive wear (whereas the TKA produces delaminating wear: small fissures form within the poly). ▪ Adhesive wear is two surfaces bonding together causing the softer material to “peel” off as a thin film onto the harder surface during motion. Volumetric wear is a specific type of adhesive wear, and it occurs as the femoral head articulates with the cup liner, and the amount of wear is proportional to the femoral head radius squared (therefore larger femoral head = more wear..this is why the initial Charnley implants, which used conventional poly, used a size 22 femoral head). Linear wear is caused by focused stress on a isolated part of the poly due to abnormal loading. ▪ Abrasive wear occurs when a harder surface (which is never completely smooth) cuts or ploughs through a softer surface, like a cheese grater. Both cause particle formation. Most wear occurs superiorly in the cup (or at the rim in cases of impingement). The conventional PE wear from articulating with a Cobalt-chrome head is 0.10 mm/year. The ultramolecular weight poly (UMWPE, also known as highly-crosslinked poly) wear is about 0.02 mm/year. What is the difference between conventional and UMWPE?

1. OSTEOLYSIS AND LOOSENING
OF THA IMPLANTS
PRESENTED BY- DR VASU
MODERATOR- DR ANURAG SIR
PIMS UDAIPUR

2. THA Aseptic Loosening is a macrophage-induced inflammatory
response that results in bone loss and implant loosening in the absence
of an infection.
Steps in the process-
1.prosthesis micromotion- leading to wearing of
implant surface
2.particulate debris formation
3.macrophage activated osteolysis

3. wear and osteolysis basic science
Wear and Osteolysis are the commonest cause of aseptic loosening in Total
Hip Arthroplasty (THA), requiring revision.
traditionally it was called the Cement Disease, it has been agreed that other
particles, e.g, metal debris, polyethylene wear particles, and bone fragments, are
equally active in generating bone resorbing materials through an inflammatory
process.

4. Maloney, Smith, and Schmalzried examined the
membranes from failed cementless femoral
components with electron microscopy and
automated particle analysis and found that –
-Macrophages are the predominant cell line
involved in the response to particulate
debris. Surface interaction between
macrophages and wear debris can incite an
inflammatory response whether phagocytosis
occurs or not. Multiple cytokines and
chemokines are produced as a result of this
interaction. These mediators
ultimately result in bone loss by activation of
osteoclast production and inhibition of
osteoblast formation from mesenchymal stem
cells

6. Osteolysis has been reported in association with numerous loose and
well-fixed cemented and cementless components of several designs.
Increased fluid pressure and implant motion may play a role, the final
pathway is effected by the host response to particulate debris of all
types.
It is now recognized that particles of metal, cement, and polyethylene
can produce periprosthetic osteolysis, either alone or in concert.
Osteolysis also has been reported in conjunction with metal-on-metal
and ceramic-on-ceramic bearing surfaces.

7. segments of the femoral and acetabular components that are
not contiguous with the articulating surfaces still may come in
contact with joint fluid.
Schmalzried, Jasty, and Harris described these areas of access
as the “effective joint space,” which is defined by the intimacy
of contact between the implants and bone.

8. Osteolysis represents a histiocytic response to wear debris.
Steps in the process include-
1.particulate debris formation
2.macrophage activated osteolysis
3.prosthesis micromotion
4.particulate debris dissemination

9. Step 1: particulate debris formation
Types of wear
1.adhesive wear
most important in osteolytic process
microscopically PE sticks to prosthesis and debris gets pulled off
2.abrasive wear
cheese grater effect of prosthesis scraping off particles
3.third body wear
particles in joint space cause abrasion and wear
4.volumetric wear
main determinant of number of particles created
directly related to square of the radius of the head
volumetric wear more or less creates a cylinder
head size is most important factor in predicting particles generated
5.linear wear
is measured by the distance the prosthesis has penetrated into the liner

10. Wear leads to particulate debris formation
wear rates by material
1.Polyethylene -non-cross linked UHMWPE wear rate is 0.1-0.2 mm/yr
linear wear rates greater than 0.1 mm/yr has been associated with osteolysis and subsequent
component loosening
highly-cross linked UHMWPE (Ultra-high-molecular-weight polyethylene) generates smaller
wear particles and is more resistant to wear (but has reduced mechanical properties
compared to conventional non-highly cross-linked)
factors increasing wear in THA-
thickness < 6mm
malalignment of components
patients < 50 yo
men
higher activity level
femoral head size between 22 and 46mm in diameter does not influence wear rates of
UHMWPE

11. 2.Ceramics
• ceramic bearings have the lowest wear rates of any bearing
combination (0.5 to 2.5 µ per component per year)
• ceramic-on-polyethylene bearings have varied, ranging from 0 to
150 µ.
• has a unique complication of stripe wear occurring from lift-off
separation of the head gait
• recurrent dislocations or incidental contact of femoral head with
metallic shell can cause "lead pencil-like" markings that lead to
increased femoral head roughness and polyethylene wear rates

12. 3.metals
• metal-on-metal produces smaller wear particles as well as
lower wear rates than those for metal-on-polyethylene
bearings (ranging from 2.5 to 5.0 µ per year)
• titanium used for bearing surfaces has a high failure rate
because of a poor resistance to wear and notch sensitivity.
• metal-on-metal wear stimulates lymphocytes
• metal-on-metal serum ion levels greater with cup
abduction angle >55 degrees and smaller component size

13. Step 2: macrophage activated osteoclastogenesis and osteolysis
Macrophage activation
results in macrophage activation and further macrophage recruitment
macrophage releases osteolytic factors (cytokines) including -
TNF- alpha
osteoclast activating factor
oxide radicals
hydrogen peroxide
acid phosphatase
interleukins (Il-1, IL-6)
prostaglandins
Osteoclast activation and osteolysis
increase of TNF- alpha increases RANK
increase of VEGF with UHMWPE inhances RANK and RANKL activation
RANKL mediated bone resorption
an increase in production of RANK and RANKL gene transcripts leads to osteolysis

14. Step 3: prosthesis micromotion
Step 4: debris dissemination
• Increase in hydrostatic pressure leads to dissemination of debris
into effective joint space as a result of inflammatory response
• dissemination of debris into effective joint space further
propagates osteolysis

18. LOOSENING
Femoral and acetabular loosening are some of the most serious long-term
complications of THA and commonly lead to revision.
In all patients suspected of having loosening of one or both components, the
possibility of infection must be considered.
LOOSENING can be- SEPTIC or ASEPTIC
CEMENTED or UNCEMENTED IMPLANT

22. CEMENTED FEMORAL COMPONENTS
1.Radiolucency between the superolateral one third of the stem (Gruen zone 1)
and the adjacent cement mantle, indicating debonding of the stem from the
cement and possible early stem deformation.
2.Radiolucency between the cement mantle and surrounding bone.
3.Subsidence of the stem alone or in combination with the surrounding cement
mantle.
4. Change of the femoral stem into a more varus position
5. Fragmentation of the cement, especially between the superomedial aspect of the stem
and the femoral neck (Gruen zone 7)
6. Fracture of the cement mantle, most commonly near the tip of the stem (Gruen zone 4)
7. Deformation of the stem
8. Fracture of the stem
Points suggestive of loosening of femoral component

23. The following are technical problems that contribute to stem loosening:
1. Failure to remove the soft cancellous bone from the medial surface of the femoral
neck;
2. Failure to provide a cement mantle of adequate thickness around the entire stem
3. Removal of all trabecular bone from the canal, leaving a smooth surface with no
capacity for cement intrusion or failure to roughen areas of smooth neocortex that
surrounded previous implants
4. Inadequate quantity of cement and failure to keep the bolus of cement intact to
avoid lamination.
5. Failure to pressurize the cement, resulting in inadequate flow of cement into the
interstices of the bone.
6. Failure to prevent stem motion while the cement is hardening.
7. Failure to position the component in a neutral alignment (centralized) within the
femoral canal
8. The presence of voids in the cement as a result of poor mixing or injecting technique

24. Barrack, Mulroy, and Harris described a grading system
for the femoral component cement mantle.
Grade C and D mantles have been associated with increased risk of loosening,
as reported by Malik et al. and Chambers et al.

25. 1.Complete filling of the medullary canal without radiolucencies (“white-out”) is termed
grade A.
2. Slight radiolucency at the bone-cement interface (<50%) is grade B.
3. Lucency surrounding 50% to 99% of the interface or any cement mantle defect
constitutes grade C.
4.Complete lucency on any projection or a defect of the mantle at the tip of the stem is
considered grade D.

30. ACCORDING TO GRUEN ET AL. MODES OF STEM FAILURE CAN BE-
1.SUBSIDENCE/PISTONING
2.MEDIAL MID STEM PIVOT
3.CALCAR PIVOT
4.DISTAL PIVOT OR BENDING CANTELEVER

40. CEMENTLESS FEMORAL COMPONENTS
Engh et al. proposed a simple classification system for uncemented
femoral component fixation based on radiographic
inspection. Fixation is classified as
(1) bone ingrowth,
(2) stable fibrous fixation,
(3) unstable

41. Fixation by bone ingrowth is defined as an implant with no
subsidence and minimal or no radiopaque line formation
around the stem.

42. A. Cortical hypertrophy may be present at the distal end of the
porous surface, and “spot welds” may be evident between the
stem and endosteum.
B. Variable degrees of proximal stress shielding can be seen

44. 2.
An implant is considered to have stable fibrous ingrowth when no progressive
migration occurs, but an extensive radiopaque line forms around the stem.
These lines surround the stem in parallel fashion and are separated from the
stem by a radiolucent space 1 mm wide.
The femoral cortex shows no signs of local hypertrophy, suggesting that the
surrounding shell of bone has a uniform load-carrying function

47. 3. UNSTABLE FIBROUS INGROWTH
An unstable implant is defined as one with definite evidence of progressive
subsidence or migration within the canal and is at least partially surrounded by
divergent radiopaque lines that are more widely separated from the stem at its
extremities.
Increased cortical density and thickening typically occur beneath the collar (if
present) and at the end of the stem, indicating regions of local loading and lack
of uniform stress transfer.

49. Subsidence of a cementless femoral component early in the
postoperative course may allow the stem to attain
a more stable position within the femoral canal.
Bone ingrowth may still occur, and early subsidence is still
compatible with durable implant fixation.
Subsidence seen months or years after surgery implies that the
implant fixation is unstable.

50. ACETABULAR LOOSENING
Serial radiographs should be inspected for changes in the acetabular
bone, the component itself, and the three zones of the
bone-implant interface

51. femoral loosening commonly occurs at the stem-cement interface BUT
acetabular loosening rarely occurs at the cup-cement interface
Schmalzried et al. determined that the process is initiated at the periphery
of the cup and progresses toward the dome. This finding explains the
frequent appearance of early radiolucencies at the periphery of the
implant that later involve all three zones. The mechanical stability of the
implant is determined by the overall degree of bone resorption at the
cement
CEMENTED ACETABULAR COMPONENTS

52. Changes in the pelvis and acetabular component that can be
observed in serial radiographs include the following:
1. Absorption of bone from around part or all of the cement mantle and an increase in the
width of the area of absorption, which is especially significant if more than 2 mm wide and
progressive 6 months or more after surgery.
2. Wear of the cup, as indicated by a decrease in the distance between the surface of the
head and the periphery of the
cup.
3. Fracture of the cup and cement (both rare).
4. A radiolucency 2 mm wide with or without a surrounding fine line of density, which
may develop in one or more of the three zones around the cement mass in the pelvis.
5.Change in the inclination >5 degree

54. It is generally agreed that the acetabular component is loose if a
radiolucency of 2 mm or more in width is present in all three
zones.
Hodgkinson, Shelley, and Wroblewski stated that When two zones of
the bone-cement interface showed radiolucency, 71% were loose,
and only 7% were unstable when demarcation was present only in
one zone
A change in the position of the cup in inclination, anteversion, or
retroversion, as seen on the anteroposterior radiograph, is definite
evidence of loosening.

56. Engh, Griffin, and Marx classified these components as
stable
probably unstable when progressive radiolucencies are
present, and
definitely unstable when measurable migration occurs.
Loosening of cementless, porous-coated acetabular
components is an uncommon finding with follow-up of 10 years.

57. When femoral or pelvic osteolysis has been detected, more frequent follow-up is
advisable. Radiographs should be made at 6- to 12-month intervals. Loose
implants and large lytic lesions are clear indications for surgery. Progressive
osteolysis is another cause for reoperation, even in the absence of symptoms.
Options for treatment of acetabular osteolysis around a well-fixed
cementless component include liner and femoral head exchange alone,
liner and head exchange combined with bone grafting of osteolytic
lesions, and complete acetabular revision of the liner and modular shell
with or without bone grafting. Isolated liner and head exchange has the
advantage of a simpler procedure and retention of well-fixed
components that should minimize iatrogenic bone loss.

58. Narkbunnam et al. developed a scoring system to help determine acetabular component
loosening in the setting of osteolysis based on the location and size of lytic lesions in the
three Delee and Charnley zones. With increasing diameter of osteolysis, thickness of
radiolucencies, and number of zones involved, the chances of implant loosening increase