The success of total knee replacement (TKR) depends
on optimal soft-tissue balancing, among many other factors. The
objective of this study is to correlate post-operative anteroposterior
(AP) translation of a posterior cruciate ligament-retaining TKR
with clinical outcome at two years. In total 100 patients were divided
into three groups based on their AP translation as measured by the
KT-1000 arthrometer. Group 1 patients had AP translation <
5
mm, Group 2 had AP translation from 5 mm to 10 mm, and Group 3 had
AP translation >
10 mm. Outcome assessment included range of movement
of the knee, the presence of flexion contractures, hyperextension,
knee mechanical axes and functional outcome using the Knee Society
score, Oxford knee score and the Short-Form 36 questionnaire. At two years, patients in Group 2 reported significantly better
Oxford knee scores than the other groups (p = 0.045). A positive
correlation between range of movement and AP translation was noted,
with patients in group 3 having the greatest range of movement (mean
flexion: 117.9° (106° to 130°)) (p <
0.001). However, significantly
more patients in Group 3 developed hyperextension >
10° (p = 0.01). In this study, the best outcome for cruciate-ligament retaining
TKR was achieved in patients with an AP translation of 5 mm to 10
mm.
We performed a prospective, randomised controlled trial of unicompartmental knee arthroplasty comparing the performance of the Acrobot system with conventional surgery. A total of 27 patients (28 knees) awaiting unicompartmental knee arthroplasty were randomly allocated to have the operation performed conventionally or with the assistance of the Acrobot. The primary outcome measurement was the angle of tibiofemoral alignment in the coronal plane, measured by CT. Other secondary parameters were evaluated and are reported. All of the Acrobot group had tibiofemoral alignment in the coronal plane within 2° of the planned position, while only 40% of the conventional group achieved this level of accuracy. While the operations took longer, no adverse effects were noted, and there was a trend towards improvement in performance with increasing accuracy based on the Western Ontario and McMaster Universities Osteoarthritis Index and American Knee Society scores at six weeks and three months. The Acrobot device allows the surgeon to reproduce a pre-operative plan more reliably than is possible using conventional techniques which may have clinical advantages.