Abstract
Dislocation of the polyethylene-rotating platform is a recognised complication of LCS knee arthroplasty.
We report ten cases of rotating platform dislocation out of 2151 primary total knee arthroplasties (0.5%) performed to date in our unit.
Of the ten cases (3 male: 7 female), six patients had a preoperative valgus deformity, two had a varus deformity and the remaining two patients were in neutral alignment, although the wear was predominantly within the lateral compartment. Two patients also had a previous patellectomy on the side of the platform spinout.
Of the ten cases, six patients were symptomatic as a result of their platform dislocation. The remaining four patients were asymptomatic and mobilising without any difficulty. In these patients, the dislocated platform was diagnosed on x-ray at outpatient review. Time to detection of the platform dislocation ranged from six days to two years.
Three patients required revision of their original insert to a larger, deeper dish insert. Three were managed by open reduction of the original insert. Of the remaining patients, one was managed successfully by closed reduction, one required an arthrodesis and one had the tibial insert cemented to the tibial tray. All patients at latest review have a functional and stable knee joint.
In conclusion, we feel that surgical error was to blame for the majority of our ten cases. Furthermore, we emphasise the importance of producing equal and balanced flexion and extension gaps at the time of knee arthroplasty in order to prevent mobile bearing dislocation. A novel technique for reducing a dislocated rotating platform is also described.
The abstracts were prepared by Mr R. B. Smith. Correspondence should be addressed to him at the British Orthopaedic Association, Royal College of Surgeons, 35-43 Lincoln’s Inn Fields, London WC2A 3PN.
