Background: long term survivorship in total knee arthroplasty is significantly dependant on prosthesis alignment, several studies have correlated poor outcome with malalignment of the components. The debate on the optimal system for femoral alignment is now largely resolved, but there is still controversy about whether intramedullary or extramedullary systems are better for the tibial side.

Objecives :  is to determine whether intramedullary or extramedullary tibial alignment guide is better for accurate sagital tibial prosthesis alignment in total knee replacement arthroplasty.

Patients and methods: Of 65 patients recruited, only 48 patients (55 knees) were met the inclusion criteria of this study (32 female and 16 male) with an average age of 62.2 years ranging from 57 to 70 years who had attended the outpatient clinic in medical city-orthopedic and trauma consultation unit and private work, during the period from October 2010 till March 2012. All patients were diagnosed to have severe osteoarthritis of their knees and we performed total knee replacement arthroplasty for them. Patients were divided into two groups, group A, were 22 patients (25 knees) in which we used intramedullary alignment guide for the preparation of proximal tibia, and group B, were 26 patients (30 knees) in which we used extramedullary alignment guide for the preparation of the proximal tibia. Three months postoperatively, a standing long leg proper lateral plain X-ray (digital software) was taken and the sagital tibial slope was measured for each case.

Results: Accurate alignment of sagital posterior slope of tibial prosthesis was found in 80% (20 out of 25 knees) in group A, and in 43.3% (13 out of 30 knees) in group B.By using Student t test, the P value was less than 0.001 which was very significant.

Conclusion: we concluded that the intramedullary tibial alignment guide is statistically more accurate than extramedullary tibial alignment guide, in the sagital positioning of the tibial component.