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PREOPERATIVE PLANNING OF REVISION TOTAL KNEE ARTHROPLASTY J.J. Prosser, D.O.

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PREOPERATIVE PLANNING OF REVISION TOTAL KNEE ARTHROPLASTY J.J. Prosser, D.O. Introduction Of the 200,000 TKAs performed in the U.S. in 1996, 50,000(1/4) were ... – PowerPoint PPT presentation

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Title: PREOPERATIVE PLANNING OF REVISION TOTAL KNEE ARTHROPLASTY J.J. Prosser, D.O.


1
PREOPERATIVE PLANNING OF REVISION TOTAL KNEE
ARTHROPLASTY J.J. Prosser, D.O.
2
Introduction
  • Of the 200,000 TKAs performed in the U.S. in
    1996, 50,000(1/4) were performed in patients
    under 65y/o
  • 20,000 revision TKAs in 1996 alone
  • More and more individuals at risk for implant
    failure

3
Implant Failure
  • 2 causes of implant failure
  • 1.aseptic loosening
  • 2.wear related osteolysis

4
Implant Failure continued
  • Both result in loss of periprosthetic bone
  • Stability of revision implant depends on quantity
    and quality of metaphyseal bone
  • ID bone defects on prerevision radiographs is a
    crucial part of preoperative planning

5
Goals
  • Shorten the learning curve of the implant system
  • Appropriate size- fracture vs. loosening
  • Correction of leg length discrepancies
  • Correct during surgery
  • Formulate alternative plans if procedure of
    choice can not be performed - special equipment
    on standby

6
Results
  • Proficient preoperative planning leads to a
    reduction in surgical time
  • It minimizes or eliminates the need for repeated
    steps

7
Planning X-Rays
  • Radiographs of good quality
  • Known magnification

8
Radiographs of Good Quality
  • AP and lateral
  • AP
  • Must include sufficient amount of proximal femur
    for templating
  • Must provide a scale for magnification
  • Proper rotation- internal rotation of the hip
    until the head and neck are parallel with the
    cassette

9
Rotational Error
  • Degree of error in sizing is a function of the
    rotational distortion
  • Closer to an ideal AP projection less error in
    templating

10
Leg Length Discrepancy
  • Draw a line at the level of the ischial
    tuberosities
  • Relationship between this line and the lesser
    trochanter allows for assessment
  • Measure and record any discrepancies

11
Template of the Acetabulum
  • Position template so that the center of the
    prosthesis reproduces the center of rotation of
    the head
  • Typically the inferior margin of the acetabulum
    lies at the level of the obturator foramen

12
Sizing of the Acetabulum
  • Implant should contact as much of the acetabular
    bone as possible
  • Do not remove excessive amount of subchondral
    bone
  • Medial position should be at the tear drop
  • Eccentricities can be managed with bone grafting
    or eccentric cement mantles

13
Position of the Acetabular Component
  • 15 degrees of anteversion
  • measured as the largest distance of the cup
    opening on the AP centered on the cup
  • 40 degrees of inclination
  • measured as the angle between the longitudinal
    axis of the cup opening and the tear drop line

14
Template of the Femur
  • Must allow for cement mantle with cemented
    arthroplasties
  • Size and location of mantle are discretion of the
    surgeon
  • Press fit must fill the proximal canal
  • Size determined by template that best fits the
    upper femur

15
Head and Neck Size
  • No leg length discrepancy
  • superimpose the center of the prosthetic head and
    femoral head to the acetabular center of the hip
  • Leg length discrepancy
  • distance from the acetabular center to the
    femoral center should equal the discrepancy

16
Type and Size of the Femoral Component
  • Determined by adjusting medial side of the
    component to medial wall of the canal
  • The trochanteric line of the template is placed
    at the apex of the greater trochanter
  • Size determines the amount of offset
  • Larger the prosthesis the larger the offset

17
Neck Resection
  • Template will indicate the neck resection level
  • easily measured from the proximal aspect of the
    lesser trochanter
  • reproduced in surgery with adequate exposure
  • can also utilize the relationship between the tip
    of the greater trochanter and the prosthetic
    femoral head
  • Any measurements must be done with a ruler whose
    scale is magnified the same amount as the x-ray

18
Completed Template
  • Line B to C leg length discrepancy
  • Point D center of the acetabulum
  • Point E center of femoral head
  • Line F intended level of resection

19
Final Planning
  • Most templates include a magnified scale
  • Lateral x-ray templating done in a similar
    fashion
  • Size of the medullary plug can be determined by
    measuring the canal at the level of the stem
  • Templating the non-operative side in complicated
    revision cases is often helpful to assess the
    need for special equipment or bone graft

20
Checking the Plan
  • Fitting of trial components and instrumentation
  • In uncemented THAs criteria for the tightness of
    the stem
  • apply predetermined rotation and extraction
    forces
  • Postoperative x-rays
  • compare components, cuts, and leg length to preop
    plan
  • check acetabular placement and orientation as
    well as fit of the femoral stem

21
Summary
  • Preoperative planning is a necessary first step
  • Shorten learning curve of prosthetic system
  • Minimize intraoperative guess work
  • Decrease surgical time
  • Allows for precision and reproduceability

22
Eggli S, Pisan M, Muller ME
  • The value of preoperative planning for total hip
    arthroplasty.
  • JBJS. 1998 May80(3)382-390.

23
History
  • Both Charnley and Muller emphasized the
    importance of preop radiographs in deciding the
    type and size of prosthesis, in achieving the
    correct position and orientation of the
    components, in equalizing leg length and in
    reducing intraoperative complications

24
Study
  • 100 consecutive patients
  • THR secondary to idiopathic OA from 1985-1988
  • 45 men and 55 women
  • Mean age of 66

25
Three basic steps
  • Appropriate type and size of prosthesis
  • 3 neck lengths
  • Anatomic position and orientation of the
    acetabular component
  • 40 degrees of inclination
  • 15 degrees of anteversion
  • Restoration of leg lengths

26
Results
  • Stem- 98 type
  • 92 size
  • Acetabulum- 100 type
  • 90 size
  • Leg length- 0.9 preop
  • 0.3 postop

27
Discussion
  • Used cemented femoral component in 90 of cases
  • More pre and post op agreement

28
Knight JL, Atwater RD.
  • Preoperative planning for total hip arthroplasty.
    Quantitating its utility and precision.
  • J Arthroplasty. 19927 Suppl403-409.

29
Study
  • 110 primary THA
  • Cemented and uncemented

30
Results
  • Preop estimate of magnification differed from
    actual magnification
  • Preop bone morphology did not correlate with type
    of femoral stem fixation
  • Preop estimate
  • Acetabular cups- 62
  • Cemented stem- 78
  • Cementless- 42
  • Leg length equalization
  • 70

31
Discussion
  • Surgeons need better methods to estimate bone
    morphology and magnification from preop
    radiographs
  • Preop planning may not reduce intraoperative
    complications
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