The ‘jumbo’ acetabular component is now commonly
used in acetabular revision surgery where there is extensive bone
loss. It offers high surface contact, permits weight bearing over
a large area of the pelvis, the need for bone grafting is reduced
and it is usually possible to restore centre of rotation of the
hip. Disadvantages of its use include a technique in which bone
structure may not be restored, a risk of excessive posterior bone
loss during reaming, an obligation to employ screw fixation, limited
bone ingrowth with late failure and high hip centre, leading to increased
risk of dislocation. Contraindications include unaddressed pelvic
dissociation, inability to implant the component with a rim fit,
and an inability to achieve screw fixation. Use in acetabulae with
<
50% bone stock has also been questioned. Published results
have been encouraging in the first decade, with late failures predominantly because
of polyethylene wear and aseptic loosening. Dislocation is the most
common complication of jumbo acetabular revisions, with an incidence
of approximately 10%, and often mandates revision. Based on published results,
a hemispherical component with an enhanced porous coating, highly
cross-linked polyethylene, and a large femoral head appears to represent
the optimum tribology for jumbo acetabular revisions. Cite this article:
Metaphyseal bone loss is common with revision
total knee replacement (RTKR). Using the Anderson Orthopaedic Research
Institute (AORI) classification, type 2-B and type 3 defects usually
require large metal blocks, bulk structural allograft or highly
porous metal cones. Tibial and femoral trabecular metal metaphyseal
cones are a unique solution for large bone defects. These cones
substitute for bone loss, improve metaphyseal fixation, help correct
malalignment, restore the joint line and may permit use of a shorter
stem. The technique for insertion involves sculpturing of the remaining
bone with a high speed burr and rasp, followed by press-fit of the
cone into the metaphysis. The fixation and osteoconductive properties
of the porous cone outer surface allow ingrowth and encourage long-term
biological fixation. The revision knee component is then cemented
into the porous cone inner surface, which provides superior fixation
compared with cementing into native but deficient metaphyseal bone.
The advantages of the cone compared with allograft include: technical
ease, biological fixation, no resorption, and possibly a lower risk
of infection. The disadvantages include: difficult extraction and
relatively short-term follow-up. Several studies using cones report
promising short-term results for the reconstruction of large bone
defects in RTKR. Cite this article:
