Notas / Notes - Active Congress.......

MIÉRCOLES / WEDNESDAY
86
tapered, highly polished, non-collared device. Advocates of
these devices state that subsidence does not automatically
lead to clinical loosening because the stem’s so-called “selftightening
geometry” allows re-stabilization within the cement
mantle as subsidence occurs. Subsidence of the wedgeshaped
stem may also provide a beneficial compressive load
to the bone graft. However, other authors have raised concerns
about the supposed benign nature of stem subsidence, and
impaction allografting has been succesfully performed using
stems that resist subsidence, including those with a rough
surface finish and precoating.
Impaction allografting is one of the more technically demanding
types of femoral reconstruction, and the frequency of complications
in reported series reflects this. Dislocation rates typically
range from 3-6 percent, and infection rates are similar;
most re-operations have been performed for periprosthetic
fracture management, though hardware-related trochanteric
bursitis and recurrent dislocation also have required surgery.
However, the incidence of greater trochanteric osteotomy nonunion
seems high with impaction grafting, ranging from 33-
50%. This may be related to compromised proximal bone stock
or the presence of cement interposed in the osteotomy site.
Femoral fracture and perforation of the cortex were amongst
the most common and potentially destructive complications
in early reports; the incidence ranging from 5-24 % with
higher rates in series that selected patients for impaction
grafting based on femoral bone-stock deficiency. Intra-operative
fracture usually occurs during the vigorous impaction
process required to obtain a stable neo-endosteum; re-inforcement
of the cortical shell, either with cortical strut grafting
or synthetic mesh should be performed if the integrity of the
cortex is in question. Intra-operative perforation of the femoral
shaft typically occurs during cement removal, and if recognized,
is easily treated with cortical strut allografts. Postoperative
fracture of the femur may occur about the stem tip
or more proximally; it may be related to unrecognized femoral
perforation, non-displaced fracture at surgery, or unappreciated
areas of osteolysis. The use of longer implants to bypass
such defects has been strongly recommended.
Recent reports on longer term follow up are now available
and encouraging. In the JBJS (2006) Sloof and colleagues
reported on 33 consecutive cases at a mean of 10.4 years.
There was one unrecognized intraoperative fracture, which
healed following nonoperative treatment. There were three
postoperative femoral fractures, all through cortical defects
at the level of the tip of the prostheses. All fractures healed
after plate fixation, and all femoral implants were left in situ.
No re-revisions were required. The average subsidence of
the stem within the cement mantle was 3 mm; seven stems
migrated 5 mm. The average Harris hip score improved to
85 points (68 -100) with a survival rate of 100%.
In the 2006 Journal of Arthroplasty Capello reported on 48
impaction graftings revision using a bead-blasted chrome
cobalt stem with minimum 6 1/2-year follow-up. There were
only 2 failures due to aseptic loosening of the femoral component
(4%). But a total of 22 total complications with overall
failure rate of 21% was noted.
A Scandinavian series (Acta Ortho 2006) reviewing only the
most severe bone deficiency cases (21 hips Endo-Klinik
classification grade III or IV with 4 having a preoperative
fracture). No femoral re-revisions had been necessary after
a mean follow-up of 60 (41-85) months. The mean Harris
Hip Score improved by 39 points to 78 points. 2 fractures
occurred postoperatively, 1 of which needed reoperation with
osteosynthesis. 1 patient needed a closed reduction after
dislocation. 4 stems showed significant subsidence (> 10
mm) in the follow-up radiographs.
The 2003 series reported in the JBJS by Ling’s group reported
on all patients from one centre who had undergone surgery
more than five years previously. This included 207 patients
with 226 hips operated on by 32 different surgeons. 33
patients (35 functioning hip)s died and 1 was lost to followup.
Two (1%) developed early postoperative infection. 12
stems underwent a further surgical procedure for aseptic
failure, ten were for femoral fracture and two for loosening.
Survivorship with any further femoral operation as the endpoint
was 90.5% (confidence intervals, 82 to 98) and using
femoral reoperation for symptomatic aseptic loosening as
the endpoint, the survivorship was 99.1% (confidence intervals,
96 to 100) at 10 to 11 years.
An important limitation to consider when comparing clinical
reports on this technique is the impressive number of variables
that may impact on outcome in a femoral revision using impaction
allografting. Two series using similar implants and
similar inclusion criteria may still differ with respect to cement
(technique, type, viscosity), allograft (source, consistency,
pretreatment with radiation or freeze-drying), surgical approach,
and aftercare, to name a but a few potentially important
factors. The effects of most of these variables have on results
in this especially complex technique have yet to be described.
However, nearly every clinical series of impaction grafting
has inferred histological healing or incorporation of the cancellous
allograft from plain radiographs. The largest series
of biopsies following impaction grafting demonstrated
histological bone healing in all cases.
While initial series reported were, in general, performed with
less than ideal instruments, and with implants that were not
designed to meet the needs of all revision cases, more recent
improvements in instrumentation and therefore surgical
technique, as well a larger variety of stem types have helped
reduce the incidence of complications. However, due to the
excellent long term results and ease of performance extensively
coated cementless stems and the common use of
extended trochanteric osteotomies the technique is used
more rarely now then when it was first introduced in most of
North America. It does however remain a useful technique
in specific cases of massive bone loss and patulous canals
which would require massive cementless stems.