B.W. Schreurs, J.J.C. Arts, P. Buma, and N. Verdonschot reply:
We thank Mr. Board for his interest in our paper and for giving us the
opportunity to provide information about our treatment of bone allografts. We
agree that this is a clinically relevant and important topic.
We started to perform bone impaction grafting on the acetabular side in
1979, and from the beginning we never washed the grafts. Hence, all of our
long-term reports of the results of procedures on the acetabular side are
based on unwashed fresh-frozen morsellized bone
allografts6. When we
began the current study on femoral bone impaction grafting in 1991, we
continued that practice and so the bone grafts used in this femoral study were
not washed.
We agree with Mr. Board that washing of morsellized bone improves the
resistance to subsidence after femoral bone impaction
grafting1. Others
showed increased mechanical properties and better interparticle stability
after washing of grafts in laboratory
models7-9.
Also, in clinical models, washing has seemed to improve initial cup
stability2,10.
Other potential advantages of washing bone chips are the reduction of the
bacterial contamination grade and the improvement of the incorporation of
these
allografts3,11.
A theoretic negative aspect of washing could be the loss of biologically
active factors that are released from the bone during the morsellization
process. However, we have not found this adverse effect in several
experiments.
We would stress that more important than washing or not washing the bone
chips is the need to carefully remove all soft tissue and cartilage before
milling the femoral head. The presence of cartilage remnants will adversely
affect the mechanical properties of the
construct8. A human
biopsy study showed that these cartilage remnants are not incorporated into
new bone and can be found intact many years after the original surgical
procedure12.
We used the Novio Magus bone mill. The dimensions of bone chips used on the
femoral side are, for technical reasons, small, and we prefer chips between 2
and 5 mm. In the more proximal areas, such as the calcar region, larger chips
can be used, which may be beneficial for stem stability.
In light of our very satisfactory long-term results with use of unwashed
grafts both on the acetabular and the femoral side, we currently continue that
practice. We acknowledge, however, that there is evidence that washing is
beneficial for immediate stability, longer-term incorporation, and reducing
the risk of infection.