Bone Deficiency in Primary Total Knee Arthroplasty - PowerPoint PPT Presentation


PPT – Bone Deficiency in Primary Total Knee Arthroplasty PowerPoint presentation | free to view - id: 5d569c-ZWQxM


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation

Bone Deficiency in Primary Total Knee Arthroplasty


Introduction numerous etiologies exist for presence of bone defects at time of TKA axial ... premature radiolucent lines at augmentation-bone interface ... – PowerPoint PPT presentation

Number of Views:448
Avg rating:3.0/5.0
Slides: 23
Provided by: KHAWAJ7


Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Bone Deficiency in Primary Total Knee Arthroplasty

Bone Deficiency in Primary Total Knee Arthroplasty
  • Douglas Dennis, M.D.
  • Reviewed by K. Ikram, D.O.
  • Jan. 11, 2000

  • numerous etiologies exist for presence of bone
    defects at time of TKA
  • axial malalignment
  • trauma
  • previous osteotomy
  • prior TKA
  • defects must be localized and classified as
    central or peripheral

  • varus deformities charac. assoc. with posteromed.
  • valgus assoc. with central lateral defect
  • defects present following HTO
  • bone defects most frequently occur in prox. tibia

  • Goals of reconstruction of bone defects
  • preservation of host bone
  • restoration of anatomic jt. line
  • axial alignment
  • ligamentous stability
  • flex-ext. space symmetry and balance
  • secure implant fixation

  • various surgical options available for handling
    such defects including
  • thicker osseous resection
  • shifting the component away from the defect
  • filling the defect with methylmethacrylate (with
    or without screw augmentation)
  • modular prosthetic augmentation

  • use of custom-designed components
  • bone graft (auto vs. allograft)
  • purpose of this report is to review the various
    treatment options including indications and
    clinical results of each tx. method.

Increased Bone Resection
  • thicker tibial resection to base of defect should
    be reserved for shall defects
  • lt 5 mm medially or lt 10 mm laterally
  • numerous studies show reduction in strength with
    more distal resection
  • lessens osseous support of tibial comp.
  • also may lead use of smaller tibial comp., has
    dec. surface area, leading to inc. unit loading
  • should be limited to pts. of advanced age in
    which revision TKA is unlikely.

Component Shifting
  • shifting tibial component medial or lat. away
    from defect may eliminate or reduce the size of
    the defect
  • if shift medially, create a relative
    lateralization of tibial tubercle which may
    result in pat.-fem. instab.
  • a smaller tibial comp. often required again
    diminishing surface area therefore inc. unit load

Cement and Screws
  • filling defects with cement alone is simple and
    efficient but premature radiolucent lines often
  • large mass of cement creates risk of thermal
    necrosis and often difficult to pressurize
  • net shrinkage of 2 as cement polymerizes
  • both math. and biomech. analyses show inf.
    implant support when using this technique
  • Lotke reported success in 58/59 pts at 7 yr f/u
    if bone defect lt 20 mm involved lt 50 of tib.

  • addition of screws to reinforce strength of
    cement in tx. deficiencies of mod. defects of
    5-10 mm thickness.
  • has same disadv. of cement alone (difficulty of
    pressurization, shrinkage, etc.)
  • Ritter reported on 47 cases and observed no
    prosthetic loosening or failures at 6 yrs f/u.

Modular Prosthetic Augmentation
  • early designs were angular in shape and limited
    to tibial component
  • current designs include angular hemi-plateau and
    full plateaus wedges and rectangulat block shapes
    with variable thicknesses
  • also, distal and post. fem. comp. augmentations
  • repairing defects with these prosthetics allow
    immediate support with satisfactory load transfer

  • no risk of disease transmission, malunion,
    nonunion, or resorption.
  • however, size and shape are limited so difficult
    to use with large, irreg. defects.
  • due to modular attachment, potential for debris
    generation and osteolysis is created.

  • controversy regarding choice of ang. wedge vs.
    rectangular block augmentations persists
  • angular wedges preserve more host bone
  • rect. augmentations are more biomech. stable
    owing to reduced shear loads at bone-aug.

  • defect bed is often sclerotic and should be
    predrilled to enhance cement pressurization and
    interdigitization into host bone.
  • failure to pre-drill often leads to premature
    radiolucent lines at augmentation-bone interface
  • in cases of large defects, defects with osseous
    fragmenation, or marked obesity, use a diaphyseal
    engaging stem to protect and offload the osseous
    defect and reconstruction.

Custom Components
  • similar advantages to the use of modular
  • however, a new modular interface is not created
    so dec. risk of debris-induced osteolysis
  • numerous disadvantages
  • manufacturing delays
  • high costs
  • often poorly fits

  • indications limited to pts who have bone defects
    that cannot be managed effectively with modular
    augmentation and are not good candidates for bone

Bone Graft
  • offers advantage of bone stock restoration for
    further revisions and ability to contour bone
    graft to fit defect without resection of host
  • cost effective, especially if autologous
  • provides more physiologic load transfer if union
  • disadvantages include malunion, nonunion, late
    collapse, and disease transmission.

  • meticulous surgice technique required for optimum
  • minimum resection of sclerotic bone to create a
    healthy cancellous interface enhance union
  • geometric shaping of host defect and bone graft
    enhance mech. interlock, graft stability, and
    surface contact area available for healing.
  • rigid fixation of bone graft is mandatory to
    assure graft union

  • as with prosthetic augmentation, if underlying
    host bed is weakened, addition of
    diaphyseal-engaging stem is warranted to reduce
    loads on graft during incorporation.
  • excellent short term results noted with success
    rates gt 90.

  • numerous options exist for management of minor
    bone defects assoc. with primary TKA
  • biomech. studies show filling defects with cement
    results in inf. load transfer under eccentric
    loading conditions
  • rectangular augmentations may be superior to
    angular wedges owing to reduction in shear
    stresses at fixation interface

  • bone graft favored for cavitary defects, massive
    bone loss, and in younger pts in whom additional
    revision surgery is likely
  • prosthetic augmentations favored in peripheral
    defects of moderate size in more elderly pts.
  • preoperative planning is key when dealing with
    any kind of bony defects.

(No Transcript)