Total Knee Replacement Reasons for Failure

1. Why Do TKRs Fail
Sureshan Sivananthan MD FRCS (Tr&Orth)
CONSULTANT ORTHOPAEDIC SURGEON

2. Why do TKRs Fail?

3. Failed TKR
Patient
Surgeon
Device

4.  The outcome of TKA is influenced by multiple
interconnected factors, including patient selection,
implant design, and surgical technique.
 Total knee arthroplasty has been shown to be highly
successful, with patient satisfaction rates reported from
85% to 95% with low rates of failure, but if failure
occurs, its impact is significant

5. Outcomes of TKR
 In 2003, 402,000 primary total knee and 32,000
revision TKAs were performed in the United States.
 The number of total knee revisions is expected to
double by 2015.
 Understanding current failure mechanisms of primary
TKA will be critical to help manage a potentially
overwhelming TKA revision burden.
Kurtz et al. JBJS(A). 2007;89(4):780-85

6. Rates of Failure
 Long-term studies have demonstrated excellent
survivorship rates for TKA. 4–6
 Rand and Bryan reported failure rates of condylar total
knee prostheses implanted at the Mayo Clinic over a
20-year period and demonstrated 91% survivorship at
10 years and 78% at 20 years
Rand JA Orthop Clin North Am. 1982;13(1):201-
212

7.  Survivorship of patients older than 70 years at the
time of surgery also increased to 94% at 10 years.
 Other factors that were attributed to increased
survivorship were cruciate retaining and non-modular
tibial designs
Ranawat CS. CORR. 1989;(248):27-33
Rand JA. JBJS(A). 2003;85(2):259-65
Scuderi GR. JBJS(B).1989;71(5):798-803

9. Reasons for Failure
 Sharkey et al retrospectively reviewed reasons for 212
revisions over a 3-year period from 1997 to 2000
Sharkey PF. CORR.2002;(404):7-13

10.  Failures were subdivided into early (<2 years) and
late (>2 years), with 55% falling into the early group

11.  The most common reason for failure in the early group
was infection, comprising 25%.
 Polyethylene wear and aseptic loosening were more
common in the late group comprising >70% of all late
revisions combined.
 The early group also demonstrated a surprisingly high
rate of aseptic loosening of 16.9%, which points to
surgical technique as a major contributing factor to early
revision

12.  Fehring et al retrospectively reported reasons for
revision of 440 total knees due to early failure.
Fehring TK. CORR.2001;(392):315-318

13.  64% of revisions fell into this early failure group.
 Infection (38%).
 Instability (26%)
 Failure of cementless fixation (13%).
 Indicate room for improvement in surgical technique

14. Why and When do Knees
Fail in 2015
 Infection, aseptic loosening, instability, and
patellofemoral complications.
 Infection is the commonest Reason
 Instability is the second commonest reason
 Aseptic Loosening is third

15. Wear
 When materials are in contact with each other and
undergo relative motion, wear occurs.
 Type 1 and 4 wear in TKR

16. Polyethylene in TKR
 Compared to THR, TKRs have decreased conformity
which results in substantially increased contact
stresses on the Polyethylene Bearing.
 Predominant wear mechanism in TKR are
 Subsurface delamination
 Pitting
 Fatigue Cracking
 Wear particles are twice as large as in THR

17. Polyethylene in TKR
 Should we use XLPE ?
 (1) the material properties of XLPE reduce adhesive and abrasive wear,
but not the risk of crack propagation, deformation, pitting, and
delamination found in TKR;
 (2) wear-induced osteolysis in TKR has not been found to be a major
cause of failure at long-term follow-up;
 (3) mid-term follow-up studies show no difference in any recorded
outcome measure between conventional PE and XLPE; and
 (4) XLPE is two to four times the cost of conventional PE without an
improvement in clinical or radiographic outcomes.
 Conventional compression-molded polyethylene with its outstanding
long-term results should remain the material of choice in TKR.

18. Undersurface Wear
 Improved Lock Mechanism

19. TKR Materials
 Metal Component Relatively Unchanged for 35 years
 Poly component has changed from un crosslinked to
highly cross linked to medium cross linked.
 Improvements in Lock Mechanism have resulted in
lesser micromotion and reduced failure of poly.
 Improvements in Conformity of Design

20. How can we Improve
 Reducing “Wear”
 Oxinium
 Ceramic Bearing
 Improved Design
 More conforming, Increased “footprint” on poly
 Better Lock Mechanism
 Better Fixation Methods
 Vacuum Cement Mixing
 Tibial Stem Design