Περίληψη:
Background: Despite improvements in the design and manufacturing of the
components used in total knee arthroplasty, wear of the polyethylene
bearing remains a potential source of failure. One theoretical advantage
of modular tibial implants is that, when the components are well fixed,
patients with wear or instability of the tibial insert can be treated
with isolated polyethylene exchange. The aim of this study was to assess
the results of isolated tibial insert exchange during revision surgery
in a relatively large, consecutive group of patients.
Methods: From 1985 through 1997, we performed fifty-six isolated tibial
insert exchanges in fifty-five patients (twenty-nine men [one man had
bilateral revision] and twenty-six women; mean age, sixty-six years)
primarily because of wear or instability. Patients with loosening of any
of the components, a history of infection, severe stiffness of the knee,
recognized malposition of any component, or problems with the extensor
mechanism were excluded. Twelve knees had had one, two, or three prior
revisions. The duration of follow-up averaged 8.3 years (range, 1.6 to
16.2 years) after the index arthroplasty and 4.6 years (range, two to
fourteen years) after the revision.
Results: The mean Knee Society knee and function scores improved from 56
and 50.9 points prior to the revision to 76 and 59 points at the time of
final follow-up. Fourteen (25%) of the fifty-six knees subsequently
required rerevision at a mean of only three years (range, 0.5 to 6.8
years) after the tibial insert exchange. The cumulative survival rate at
5.5 years was 63.5% (95% confidence interval, +/-14.4%, with nineteen
patients remaining at risk). Of the twenty-seven knees with preoperative
instability, eight were rerevised and another four were considered
failures because of severe pain. Of the twenty-four knees that were
treated with the index revision because of wear of the insert, five were
rerevised. In addition, one extremity in this group was amputated above
the knee as a result of chronic osteomyelitis of the ankle concomitant
with chronic pain at the site of the total knee arthroplasty and another
two inserts were considered failures because of severe pain.
Conclusions: Isolated tibial insert exchange led to a surprisingly high
rate of early failure. Tibial insert exchange as an isolated method of
total knee revision should therefore be undertaken with caution even in
circumstances for which the modular insert was designed and believed to
be of greatest value.
Συγγραφείς:
Babis, GC
Trousdale, RT
Morrey, BF