Page 195 - Reconstructive Techniques in Musculoskeletal Tumor Surgery

All complications of soft tissue and instability (Henderson type 1) were managed without implant removal. Few studies speci ed the incidence of complications of soft tissue and instability; however, our results (6%) are comparable with those recently reported by others (7% – 9%)8, 25. Pala et al8 noted that type 1 complications were more frequent in primary than in revision reconstructions (10% versus 4%). Although with the numbers we had we could not demonstrate an association between having a previous reconstruction or an extra-articular resection, it is plausible that soft tissue problems occur more often in previously operated sites and after more extensive resections as a result of scarring and restricted exibility of surrounding soft tissues. The most common type 1 complication in a large study on KMFTR and HMRS knee replacements (Stryker, Newbury, UK) was patellar tendon rupture with an overall incidence of 5%14. We did not observe any patellar tendon ruptures. We attribute this to the use of the attachment tube. The tube allows for ingrowth of the extensor apparatus and apparently ensures reliable, long-lasting xation26.
Aseptic loosening (Henderson type 2) occurred in 12% of the primary reconstructions. This is comparable with most long-term follow-up studies (table
3). The high risk of loosening of megaprostheses around the knee has been
ascribed to many factors, including the torque acting on the stems and the long
lever arm associated with greater resection length25, 27. We could not demonstrate
an in uence of resection length in the current series. HA coating appeared to
decrease the risk of loosening of uncemented distal femoral replacements. Pala et
al reported a comparable rate (6%) for uncemented HA-coated GMRS prostheses
(Stryker, Rutherford, NJ, USA), although their follow-up was substantially shorter 9 (table 3). Satisfactory rates of loosening (0%–8%) have also been reported for
cemented custom-made implants with HA collars (Stanmore Implants Worldwide,
Elstree, UK)5, 6, 28. Although loosening may occur as late as 25 years after cemented
xation5, 6, 16, it is unlikely to occur after bony ingrowth of a HA-coated implant has
taken place29. A prerequisite for ingrowth is primary stability; relative motion of
more than 150 μm between bone and stem is critical for adequate xation30. Blunn
et al29 reported on a series of uncemented tumor implants (Stanmore Implants Worldwide) and noted that subperiosteal cortical bone loss occurred at the mid-
stem level. This process, however, stabilized, and none of their implants was revised
as a result. We did not observe this as a reason for revision.
Like most modern tumor prostheses, the implants used in our study had a rotating hinge (table 3). Authors postulated that rotating hinges reduce the risk
MUTARS knee replacement
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