[Effectiveness comparison of different tibial intramedullary nail guide rod in total knee arthroplasty]

To compare the effectiveness of the traditional center of tibial plateau as the entry point and digital technology in the design of intramedullary tibial nail point positioning method in total knee arthroplasty (TKA).

Between October 2011 and October 2012, 60 cases undergoing unilateral TKA and meeting the selection criteria were randomly divided into 2 groups: in group A (30 cases), the tibial plateau center as the entry point of tibial intramedullary positioning was used; in group B (30 cases), Mimics 10.01 software to simulate the guide rod point of tibial intramedullary positioning was used. There was no significant difference in gender, age, etiology, disease duration, sides, and preoperative knee range of motion, Hospital for Special Surgery (HSS) score, and Western Ontario and McMaster University Osteoarthritis Index (WOMAC) between 2 groups (P > 0.05). Postoperative X-ray films were taken to measure the tibiofemoral angle and tibial angle; knee range of motion, and HSS and WOMAC scores were used to assess the activity of knee.

The entry point of group B was located in front of the center of tibial plateau, which was inconsistent with the traditional entry point. The incision healed by first intention in all patients of 2 groups. The patients were followed up 6 to 12 months (mean, 8.6 months). The X-ray measurement at 1 week after operation showed no significant difference in tibiofemoral angle between 2 groups (t = -6.65, P = 0.72), but the anteroposterior and lateral tibial angles of group A were significantly lower than those of group B (P < 0.05). The knee range of motion, HSS score, and WOMAC score of 2 groups were significantly higher at 3 and 6 months after operation when compared with preoperative values (P < 0.05), and the values at 6 months were significantly increased than those at 3 months after operation (P < 0.05). HSS score and WOMAC score had no significant difference between 2 groups at 3 months after operation (P > 0.05), but the scores of group B were significantly higher than those of group A at 6 months (P < 0.05). The knee range of motion of group B was significantly better than that of group A at 3 months after operation (t = 2.13, P = 0.04), but no significant difference was found between 2 groups at 6 months (t = 0.58, P = 0.56).

Compared with the traditional intramedullary guide rod insertion point positioning, digital individualized design of entry point positioning has the advantages of more accurate lower limb force line, better recovery of knee function, and earlier 90 degrees activities, but the long-term effectiveness needs further observation.