Abstract
Objectives: The study investigates the impact of posterior proximal tibia offset (PPTO) and posterior tibial slope (PTS) on tibial baseplate positioning in total knee replacement (TKR) and determines the effect of intraoperative PTS adjustment on preventing posterior cortex impingement.
Materials and methods: A prospective, single-center study was conducted on 100 patients indicated for primary TKR and having appropriate true lateral knee X-rays with a radiographic marker. However, patients with extra-articular deformity, neuromuscular disorders, revision TKR, or inadequate X-rays were excluded from the study. Preoperative X-rays were analyzed using Bone Ninja software to measure PPTO, %PPTO, and impingement point (IP). Cases were divided into two groups based on the tibial slope given using intramedullary zig: 3° (group A) and 0° (group B). Postoperative X-rays measured the IP to assess baseplate positioning. Data from 50 MAKO robotic cases was analyzed to determine the average PTS in Indian cases.
Results: Group A had an average PPTO of 10.14 mm and %PPTO of 18.41%, with postoperative IP line towards anterior cortex in 52% of cases. Group B had an average PPTO of 11.12 mm and %PPTO of 19.12%, with postoperative IP line towards the posterior cortex in 94% of cases. A
strong negative correlation (r = −0.75 for group A and r = −0.87 for group B) was observed between %PPTO and IP. The Chi-square test yields a Chi-square value of 32.484, and a p-value of 0.0000, indicating a highly significant difference in the distribution of postoperative IP categories
between the two groups. The average medial and lateral tibial slopes in Indian cases were found to be 11.85° and 8.97°, respectively.
Conclusion: This study underscores the importance of preoperative assessment of tibial morphology and intraoperative adjustments to mitigate risks associated with PPTO, emphasizing the need for individualized surgical strategies with advanced technology like robot/navigation to
achieve optimal results in knee arthroplasty.