Modified Macroscopic Soft Tissue Injury (Modified MASTI) Classification for Bone and Soft Tissue Integrity in Cruciate Retaining Total Knee Arthroplasty.

Background: The purpose of this study was to develop a 'modified macroscopic soft tissue injury (MASTI) classification' for cruciate retaining (CR) total knee arthroplasty (TKA), and compare the iatrogenic injury of robotic-arm assisted (RA) TKA and conventional jig-based (CJ) TKA using it. Methods: 100 symptomatic knee osteoarthritis patients were chosen of which fifty received RA TKA, whereas fifty received CJ TKA. Posterior cruciate ligament (PCL), soft tissue envelope and bone resection surfaces were assessed during operation and scores allotted for each. The overall score was then graded to form the classification. Results: The classification had a high inter-observer reliability. RA TKA patients had significantly better PCL scores, soft tissue injury scores, bony injury scores, and modified MASTI grades, and had decreased chances and extent of soft tissue release for coronal balancing. Lesser degree of constitutional varus and sagittal plane deformity, and lower BMI have been found to be associated with better soft tissue preservation and better-modified MASTI grades. Conclusion: The 'modified MASTI classification' is a validated and reliable system to serve as a universal tool and platform for recording and grading iatrogenic bone and soft tissue injury during CR TKA. Using this classification, RA TKA is found to be less invasive and inflicts lesser extent of iatrogenic injuries when compared to CJ TKA. This classification can also be used as a parameter for evaluating the outcome of bone and soft tissue injuries and soft tissue releases to short- and long-term functional outcomes of patients, complications and longevity of implants. Supplementary Information: The online version contains supplementary material available at 10.1007/s43465-025-01343-3.