To determine the effect of altering tibial slope on the two-year range of motion (ROM) of patients undergoing condylar total knee replacements (TKR).

A single surgeon performed 74 primary cemented posterior stabilised tri-compartmental TKR’s on 56 patients (19 male, 37 female) with mean age of 67.1 years, height 66.7in., weight 187.4 lb, and BMI 29.58 kg/m2. 51 had osteoarthritis, and five had rheumatoid arthritis. A standard surgical technique was employed utilising flexion axis localisation to position the femoral components. Patients were followed for two years minimum using outcome measures and x-rays. Knees where tibial slope was restored to a degree angle equal to, or slightly greater than, their pre-op slope (group 1) were compared to knees where tibial slope was decreased (group 2).

The average 2 year post-op ROM in Group 1 was significantly greater than that of Group 2 (129.3 degrees vs. 120.5 degrees, p=.001). The average pre-op to post-op increase in ROM in Group 1 was significantly greater than Group 2 (38.1 degrees vs.27.7 degrees, p=.003). Correlational analysis revealed that restoration of pre-op tibial slope was the primary determinant of post-op ROM, followed by pre-op ROM, then weight and BMI (each to significance of p< 0.05).

Restoration of tibial slope clearly produced increased ROM in this study. Using one standard slope cut for every tibia may prevent many patients from achieving their maximum potential ROM.