Tibial alignment technique and its influence on clinical and functional outcomes following total knee arthroplasty

Restoration of neutral mechanical axis is thought to influence implant survival and function in Total Knee Arthroplasty (TKA). There is no consensus whether Intramedullary (IM) or Extramedullary (EM) tibial alignment technique is superior to achieve this outcome. Study aims to evaluate functional and radiological outcome of TKA using the EM and IM technique.

A retrospective study of 400 primary TKA (314 patients) was performed. 200 knees were studied in each IM and EM group, which were matched. Functional assessment was performed using Oxford Knee Score (OKS) and Tibial component alignment measured in coronal and sagittal radiographs.

The average coronal and sagittal alignment of the tibial component in IM group was 89.16° and 88°, whereas in EM group, these were 88.1° and 88.5° respectively. The adjusted mean difference change in Pre and Post-operative OKS in IM group compared to EM group was 0.5 (p = 0.52). There was no statistically significant difference in the complications between the two groups. Subgroup analysis of patients with BMI >35 showed predictable coronal tibial alignment with IM technique with fewer outliers.

Intramedullary tibial alignment is associated with fewer outliers compared to the extramedullary technique particularly in patients with a BMI over 35.