Implant Selection for
Femoral Revision Arthroplasty
Allan E. Gross, M.D.,
F.R.C.S.(C) Head, Division of
Orthopaedic Surgery Mount Sinai Hospital Professor of Surgery,
Department of Surgery University of Toronto Toronto, Ontario The surgeon's choice of implant for the femur during revision hip
arthroplasty depends primarily on the remaining femoral bone stock. This can be pre-determined to a degree by
routine antero-posterior and lateral x-rays, but the final decision is made
at surgery after removal of the existing implant, and close inspection of the
remaining femoral bone stock. This
may require intr-operative x-rays. The
remaining bone stock may be classified as: Type
I - No significant loss of bone stock. Metaphysis and diaphysis are structurally
intact. Example - a loose cementless
implant. Type
II - Contained bone loss where the metaphysis
and or the diaphysis are intact but weakened by cortical thinning and
ballooning. Example - a failed
cementless or cemented stem with osteolysis. Type
III - Uncontained loss of bone which is
circumferential (segmental) but less than 5 cms in length. The defect involves the calcar and the
lesser trochanter. Example - a failed
femoral implant with segmental loss of bone extending below the level of the
lesser trochanter, but does not extend into the diaphysis. Type
IV - Uncontained loss of bone greater than 5
cms in length. This is
circumferential (segmental) loss of bone extending into the diaphysis. Example - the multiple revised femoral
implant. Bone stock is the most important factor in
deciding on the surgeon's choice of implant but there are other factors to
consider: i) whether patient is high
or low demand which depends on: a)
age b)
height and weight c)
lifestyle & previous disease d)
multiple joint disease ii) previous infection iii) status of soft tissues iv) leg length discrepancy Of
these additional factors, the most important in selecting the femoral implant
is whether the patient is high or low demand, and whether or not there was
previous infection. For example, if
the patient is elderly and low demand, then a long stem cemented implant is
suitable because further revisions do not have to be anticipated. If the patient is younger and or higher
demand, then further revisions have to be anticipated and a cemented long
stem femoral component should not be performed. Also in high demand patients techniques that restore bone stock
are desirable. If there was previous
infection then it is better not to use a technique that involves bone
grafting or inserting a component that is going to be difficult to remove if
the infection recurs. Bone grafting
can be done in an infected hip if necessary, but the revision must be staged. Table
VI Femoral Defects and
Reconstructive Options
|
