The Effect of Intramedullary vs Extramedullary Tibial Guides on the Alignment of Lower Extremity and Functional Outcomes Following Total Knee Arthroplasty: A Randomized Clinical Trial

Document Type : RESEARCH PAPER


Joint Reconstruction Research Center, Tehran University of Medical Sciences, Tehran, Iran


Objectives: Total knee arthroplasty (TKA) has been known as a definitive treatment for advanced knee 
osteoarthritis. Both intramedullary (IM) and extramedullary (EM) tibial guides have been used to restore 
the desired extremity alignment. However, controversy exists regarding the superiority of either 
technique We aimed to compare the functional outcomes and accuracy of IM and EM tibial guides in 
providing neutral alignment after TKA.
Methods: In a randomized, double-blinded clinical trial, we studied 98 patients undergoing primary TKA in two 
groups of IM and EM. We measured the medial proximal tibial angle (MPTA), varus angle (VA), and joint-line 
convergence angle with normal ranges of 90°±3°, 0-2°, and 0±3°, respectively, on a three-joint alignment view after 
three months. We also assessed the functional outcomes at the last follow-up. Finally, we compared these outcomes 
between the two groups. 
Results: Eighty-four patients (IM=42, EM=42) were included in the final analysis (16 males, 68 females, mean age: 
63.9±8.6 years, mean follow-up: 13±2.9 months). The mean postoperative (post-op) alignment angles showed no 
significant difference, although MPTA outliers were significantly more frequent in the EM group (26.2% vs. 9.5% in 
IM, P=0.04). None of the functional outcomes showed a significant difference between the two groups. However, 
the mean increase in knee range of motion (ROM) was significantly higher in the knees with VAs within ±3° of neutral 
than those outside this range (30.8 vs. 27.4, respectively, P=0.039).
Conclusion: We conclude that both techniques were not different regarding the mean alignment angles and 
functional outcomes. However, fewer MPTA outliers can be seen with the IM technique. A post-op mechanical axis 
within ±3° of neutral can result in a more ROM increase after one year. 
 Level of evidence: I


Main Subjects

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