Radiographic evaluation of tibial component alignment in total knee arthroplasty following extramedullary and intramedullary tibial referencing

Background: Long term survivorship of total knee arthroplasty (TKA) is significantly dependant on prostheses alignment. The debate on optimal referencing for femoral component is largely resolved with Intra-medullary jigs reproducing superior alignment. However there is still a contention about whether intramedullary or extramedullary jigs are better for tibial referencing. This study aims to compare the accuracy of tibial component alignment in TKA using intramedullary and extramedullary tibial referencing jigs.Methods: Between December 2012 and September 2014, 66 primary conventional cemented TKAs were performed using Nexgen-LPS Flex (Zimmer) implants in 55 patients, 50-80 y old (mean 65.54 y) with osteoarthritis/rheumatoid arthritis. Intramedullary and extramedullary tibial referencing was used in alternate patients undergoing TKA after excluding patients with BMI >35 kg/m2, knee deformity >150,excessive tibial bowing, previous fractures/surgeries/retained metalwork around knee. Postoperatively, tibial component alignment (TCA) in coronal plane was assessed using AP radiograph of leg. A 3º cutoff from neutral mechanical axis (i.e., 90o±3o) was considered acceptable.Results: The intramedullary group (n=33) had 4 outliers (TCA >93º or <87º) whereas the extramedullary group (n=33) had 7 outliers (p=0.511). The difference in mean TCA between intramedullary and extramedullary groups was not statistically significant [90.70±2.43 and 90.55±2.17 (p=0.790)]. There were no significant per-operative/post-operative complications in either group.Conclusions: We conclude that both intramedullary and extramedullary tibial referencing guides can be used to achieve desired tibial component alignment (90±3º) in TKA. However the surgeon should appreciate the benefits and deficiencies of either types of tibial referencing and use whichever is suited in a particular case.