Aseptic loosening is the most common cause of total knee arthroplasty failure. It occurs without infection and is associated with osteolysis and inflammation. Wear particles from the prosthetic components are phagocytosed by macrophages, triggering a biological response that leads to bone resorption around the implant. This causes loosening. Diagnosis involves imaging to detect osteolysis and loosening. Treatment is revision surgery, with goals of restoring joint alignment and stability. Prevention relies on surgical technique to minimize wear particle production and ensure adequate cement penetration for fixation.

1. Aseptic Loosening In TKA
Dr. Mohammad.Z.Arshad
Fellow in Arthroplasty
Sunshine Hospital

2. OVERVIEW
• Introduction
• Causes of failure
• History
• Definition
• Pathogenesis
• Diagnosis
• Modern Knee Society Radiographic Evaluation System
• Treatment
• Principles Of Revision TKA

3. INTRODUCTION
• TKA by almost any measure is extremely
successful at relieving pain and restoring function
for patients with knee arthritis.
• General studies show the incidence of revision for
any reason to be 3% or less at 5 and 10 yrs.

4. Causes Of Knee Arthroplasty Failure
• Infection
• Aseptic loosening and wear-Sharkey et al
highlighted aseptic loosening as the most
common cause, at 39.9% of all revision TKAs.
• Arthrofibrosis
• Instability

5. History
• Harris et al ascribed the localized bone resorption,
and subsequent component loosening, seen in
artificial joints to “cement disease” .
• They felt that particles of cement were somehow
related to the loss of bone seen around artificial
joints.
• This idea lead to cementless implants, which are
commonly used in hip arthroplasty today.
• However, when cementless implants showed similar
patterns of bone loss and loosening, it became clear
that the explanation was far more complicated.

6. History
• Schmalzried et al in 1992 showed that
small polyethylene particles were
present in macrophages in the
periprosthetic region, particularly at the
prosthesis/cement and bone interface.
• The implication was that all areas of the
prosthesis that could be exposed to
joint fluid were susceptible to
osteoclast-mediated bone resorption.

7. Definition
• Aseptic loosening refers to the failure
of joint prostheses without the
presence of mechanical cause or
infection. It is often associated
with osteolysis (bone resorption) and
an inflammatory cellular response
within the joint.

8. Causes
• Implant factors - fixation type, implant design, use of constraint, and wear
debris from metal, cement, or polyethylene.
• Surgical factors - joint malalignment and ligamentous imbalance, surgical and
cement technique.
• Patient factors - osteoporosis, stress shielding, high BMI.

9. Pathogenesis
• Osteolysis represents a histiocytic
response to wear debris.
Steps in the process include:-
• Particulate debris formation
• Macrophage activated osteolysis
• Prosthesis micromotion
• Particulate debris dissemination

10. Step 1: Particulate Debris Formation
Wear leads to particulate debris formation
Types of wear:-
• Adhesive wear-microscopically PE sticks to prosthesis and debris gets pulled off
• Abrasive wear- cheese grater effect of prosthesis scraping off particles
• Third body wear- particles in joint space cause abrasion and wear
• Volumetric wear- main determinant of number of particles created
• Linear wear- is measured by the distance the prosthesis has penetrated into the liner

11. Step 2: Macrophage Activated
Osteoclastogenesis and Osteolysis
• macrophage releases osteolytic factors(cytokines) including
- TNF-alpha
- TGF-beta
- 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 enhances RANK and RANKL
activation
• An increase in production of RANK and RANKL gene transcripts
leads to osteolysis
Macrophage activation
macrophage recruitment
Increase TNF-alpha
increases RANK
RANKL mediated bone
resorption
Osteolysis

12. Step 3: Prosthesis Micromotion
• Osteolysis surrounding the prosthesis leads to micromotion
o micromotion leads to increase particle wear and further prosthesis
loosening
o N-telopeptide urine level is a marker for bone turnover and are elevated in
osteolysis

13. Step 4: Debris Dissemination
• Increase in hydrostatic pressure leads to dissemination of debris into effective
joint space.
o increased hydrostatic pressure is the result of inflammatory response
o dissemination of debris into effective joint space further propagates
osteolysis.

14. Small particles
Inflammatory response
Particles <1um phagocytosed by macrophages
Stimulate Osteoclasts
Resorb bone around prosthesis
Process + other factors
Loosening of implant

15. Factors
• Factors affecting wear rate of polyethylene in TKA
- patients < 50 year old implying demand or activity level of patient
- motion between modular tibial insert and metal tray (i.e., backside wear)
- Sterilization method (gamma radiation should be followed by remelting in o2 free
environment destroying remaining free radicals)
- manufacturing method (machining > compression molding)
- thickness < 6mm more stress on component more wear (Barret et al
recommends above 8 to 10 poly)

16. Factors
• Presence of third-body debris-
roughness of femoral component
counterface
• Alignment and stability of the TKA
-malalignment causes asymmetric
loading causes early loosening
-more frequent with varus rather
than valgus malalignment

17. Collier et al found that
• Failure to correct hip-knee-ankle alignment at
TKA will continue the pathologic wear state.
• Placing a TKA in 5 degrees more varus could
lead to 0.11 to 0.14 mm/year more
polyethylene wear.
• Less varus alignment decreased the amount of
medial tibial polyethylene wear 2 to 3 times.
• The ideal alignment after TKA would have a
mechanical axis of zero.
Malalignment
Increased Wear
Aseptic Loosening

18. Diagnosis
• Symptoms
o pain:
-localized to the tissues around the loose components
o swelling:
-due to irritation of loose component causing proliferation of synovium & increased fluid production
o knocking of knees
• Aggravating factors
-weightbearing
-often activity related

19. Diagnosis
• Physical examination
o May have minimal pain with ROM
o Increased pain with weight bearing
o May or may not be any instability
o Presence of clinical malalignment is nearly pathognomonic
• Serum labs
o ESR normal
o CRP normal
o Any elevation should prompt aspiration of the knee
• Excluding infection is very critical before a thorough evaluation of aseptic loosening

20. Imaging
• AP X-Rays
- tibial osteolysis readily visible on AP
- femoral osteolysis may be difficult to detect
on AP as lesions are typically located in
posterior condyles and are obscured by the
femoral component
• Oblique X-Rays
- often more helpful for identifying femoral
osteolysis.
• Findings
- radiolucent line around implant or cement
strongly suggestive
- change in position of the implant
-varus or valgus subsidence of tibial component

21. Imaging
• Radiographically, fixation of cemented
TKA may be assessed by radiolucent
lines (RLLs), defined as radiolucent
intervals between either the implant
and the cement, or the cement and the
underlying bone.
• A few previous studies suggest that the
presence of a nonprogressive RLL is not
predictive of aseptic failure.

22. Imaging
• However, Kajetanek et al in their
study found a positive correlation
between the presence of an RLL and
surgical revision for aseptic loosening.

23. Modern Knee Society Radiographic
Evaluation System
• A modern system was developed, approved by the Knee Society
members, which ensured proper radiographic documentation of
coronal and sagittal implant alignment, fixation interface
integrity with respect to radiolucent lines and osteolysis to
document precise deficiency locations.
• The documentation of lucent lines should be graded as “partial”
or “complete” with respect to the zone denoted on the
schematic images and regions of osteolysis should be
documented in millimetres in the zone locations.
• This evaluation system remains descriptive rather than predictive
or prognostic in its current scope and form.

24. MKSRES Implant Zone Classification : Tibial Component
• Tibial Component AP View:
• Zone 1: medial baseplate
• Zone 2: lateral baseplate
• Zone 3: central keel/stem region (“M” and
“L” designate the respective regions of the
central keel)
• Zone 4: Revision TKA Stem Extension (“M”
and “L” designate the respective regions of
the stem extension)
• Zone 5: inferior aspect of tibial keel/stem
Fig. 3. (A) Coronal radiographic schematic
of keeled and two-peg implants with zones
for documentation of radiolucent lines and
osteolysis.

25. MKSRES Implant Zone Classification : Tibial Component
• Tibial Component Lateral View:
• Zone 1: anterior baseplate
• Zone 2: posterior baseplate
• Zone 3: central keel/stem/peg fixation
region (“A” and “P” designate the respective
regions of the central keel)
• Zone 4: Revision TKA Stem Extension (“A”
and “P” designate the respective regions of
the stem extension)
• • Zone 5: inferior aspect of tibial keel/stem
Fig. 3. (B) sagittal radiographic schematic of keeled and
two-peg implants with zones for documentation of
radiolucent lines and osteolysis.

26. MKSRES Implant Zone Classification : Femoral Component
• Femoral Component Lateral and AP View
• Zone 1: anterior flange
• Zone 2: posterior flange
• Zone 3: central box/peg/distal fixation region (“A” and “P”
designate the respective chamfers if visible)
• Zone 4: Revision TKA Stem Extension (“M” and “L”
designate
the respective regions of the stem extension on the AP
view; “A” and “P” designate the respective regions of the
stem extension on the lateral view
Fig. 4. (C) Coronal and (D) sagittal radiographic schematic of revision femoral implants that
have stem extensions with zones for documentation of radiolucent lines and osteolysis.
Radiolucent lines should be denoted and documented as “partial” or “complete” and osteolysis
documented in millimeters.
(C) Sagittal plane radiographic schematic
of femoral implant with zones denoted
for documentation radiolucent
lines and osteolysis

27. MKSRES Implant Zone Classification : Patellar Component
• Patella Component Patellofemoral View:
• Zone 1: medial
• Zone 2: lateral
• Zone 3: central peg/baseplate region (“M” and “L” designate the
respective regions on the merchant view, whereas “S” and “I”
designate the superior and inferior regions on the lateral view)
• Patella bone thickness is measured and noted.
Fig. 5. Patellofemoral radiographic view schematic
denoting patella bone thickness, measured in
millimeters.
. (D) Patellofemoral view radiographic schematic of multi- or
single peg patella implant with zones denoted for
documentation radiolucent lines and osteolysis. Radiolucent
lines should be denoted and documented as “partial” or
“complete” and osteolysis documented in millimeters.

28. IMAGING
• CT Scan & MRI
- viable options for assessing larger
osteolytic lesions to aid in
preoperative planning
• Tc Bone scan
• Differential
- Periprosthetic Joint Infection.
• Most accurate test for diagnosis of
aseptic loosening in tka was SPECT/CT
ARTHROGRAPHY

29. Treatment
• Non-Operative
- observation
• Indications
-stable implant with minimal symptoms
• Operative
- Revision TKA
• Indications
- pain due to aseptic loosening
- pain with evidence of osteolysis
- extensive osteolysis that would compromise revision surgery in the future.

30. Treatment
 Contraindications for revision :-
 Systemic infection
 Charcot arthropathy
 Neuromuscular disorders
 Poor medical condition
 Previous operative details – type of implant , company ,size, any complications of index surgery

31. Principles Of Revision TKA
 Identification of mechanism of failure
 Preoperative planning
 Obtain adequate exposure
 Extraction of components with minimal bone loss
 Bone defect management
 Joint line restoration and selection of appropriate revision component
 Obtain ligamentous and joint stability and flexion and extension gap balancing
 Rehabilitation

32. Techniques To Enhance Exposure
• Tibial tubercle osteotomy
• Femoral peel
• Medial epicondylar osteotomy
• Quadriceps myocutaneous flap

33. Joint Line Restoration And Ligament
Balancing
• Definition- joint line is the articulating surface
of the femoral component in extension, flexion
and all points in between.
• Importance
• Jl elevation of more than 4 mm- more
patellofemoral problems
• Jl elevation of more than 8mm – unfavourable
outcome of tkr

34. Joint Line References
• Medial femoral epicondlyle joint line -
30mm
• Lateral femoral epicondyle – 27mm
• One finger below the inferior pole of
patella
• One finger above the head of fibula –
15mm
• 12-16mm distal to femoral attachment
of pcl
• Old meniscal scar
• Adductor tubercle joint line

35. Joint Line References
• Adductor ratio
• Ratio between atjl and femoral width
• Constant value of 0.52
• No variation with sex
• Most accurate method of
reconstructing Joint line

36. Obtain Ligamentous And Joint Stability
• 3 step approach
 Recreate tibia
 Recreate the femur and rebuild flexion space
 Recreate extension space

37. Take Home Message
• Hampton et al used each zone of MKSRES and measured for
its minimum cement penetration depth. The number of zones
with minimum penetration depth less than 2 mm used as the
final variable.
• RLLs were then observed for at the Implant Cement interface
and at the Bone Cement interface. The summed length of RLLs
on the AP and lateral radiographs was divided by the summed
surface area of the readable IC interface on AP and lateral
radiographs.
• Radiographic indicators of poor cement mantle quality in a
newly postoperative TKA appear to correlate with later failure
by aseptic loosening.
• They suggest that surgeons remain focused on performing
meticulous cementing technique in order to reduce the risk of
later aseptic TKA failure.