Cementless fixation in TKA remains controversial because of less predictable osseointegration and difficulty interpreting fixation interfaces. Radiolucent zone analysis (RLZ) of plain radiographs is the only practical method of evaluating the fixation interface.

Methods: This study evaluated 567 consecutive primary LCS mobile-bearing TKA with in-depth RLZ analysis of all cases by one author (T.K.). Mean follow-up was 5.7 years (2.0-14.9), mean age 69 years (70% females). Diagnosis included 8.3% rheumatoids. The same porocoated femoral and patella components were utilized. Tibial components included a 3-fin (ACL/PCL-retaining) or tapered-cone design (PCL-retaining/substituting). Bone treatment included generous use of autograft: cortico-cancellous struts for slope-off deformities and soft bone, morselized impaction for central zones, slurry to achieve interference fit.

Results: Good/excellent results were 94.7% with 4 fixation failures. Sequential RLZ of six patellar, four femoral, six tibial zones revealed: 1). Minimal femoral/patella lucencies---no failures; 2) Tibial tapered cone (n = 523) had one (0.2%) failure. Lucencies of 1–2 mm (usually isolated) were noted in 2% medial, lateral, posterior and 4% anterior/central zones, all of which remained stable; 3).Tibial 3-fin tibial design (n = 44) had 3 failures (6.8%) with RLZ > 2mm in multiple zones.

Conclusion: Cementless fixation with LCS porocoat pros-thesis was successful in all femoral/patellar and 99% of the tibial-cone design. The 3-fin design had multiple RLZ and a higher failure rate (not recommended). RLZ analysis with plain X-rays (over time) is a practical method of evaluating cementless fixation and correlates with clinical outcomes in our study.