[Revision of unconstrained total knee arthroplasty - a technical analysis]

Total knee arthroplasty (TKA) revisions are increasing due to the rising numbers of primary cases, younger patients and an aging population. The technical demand of these procedures is incomparable higher than in primary cases. Also the expectable clinical results are inferior. Measures to improve the clinical results are desireable. PATIENTS/MATERIAL: 203 unconstrained knee arthroplasties were explanted in 2009 in a single centre. In 150 cases those were TKAs. Fractures were excluded. These cases were analysed with special attention to the reason for the failure. Clinical and radiological data were included.

Survival of revised implants was in the mean 55 months (range: 0,5-125 months). In 46 cases components showed an aseptic loosening (30.7 %), 37 TKAs were unstable (24.7 %), in 26 cases stiffness was detected (17.3 %), and nine misplaced TKA components (five femoral, two tibial, two combined; total 6 %) as well as three broken inlays (2 %) were encountered. In 25 cases deep infection was observed (16.7 %) and four patients complained of an unspecific anterior knee pain (2.6 %). Three TKAs were removed for a two-staged procedure. In five cases an inlay exchange was performed and in another five cases a conversion from cruciate retaining to posterior stabilised state was performed. In 60 cases a rotating hinged TKA was implanted (40 %) and in 42 a pure hinge (28 %). In 45 cases a condylar constrained TKA system (CCK, 30 %) was used. Range of movement increased with the procedure. Plain radiographs were inferior in detecting all loosening in advance.

This study demonstrated that in more than one third of the cases the revision could have been avoided and was due to technical errors during the primary procedure. Infection and arthrofibrosis were besides unspecific complaints less often observed than is described in the literature. This study supports the high demand on the technical issues during the primary procedure which should be conducted by experienced surgeons. Registry data from Germany should allow the provision of more specific information in the future.