Evaluation of bone impingement prediction in pre-operative planning for shoulder arthroplasty.

In shoulder arthroplasty, malpositioning of prostheses often leads to reduced postoperative range of motion (ROM) and complications such as impingement, loosening, and dislocation. Furthermore, the risk of impingement complications increases when reverse total prostheses are used. For this purpose a pre-operative planning system was developed that enables surgeons to perform a virtual shoulder replacement procedure. The present authors' pre-operative planning system simulates patient-specific bone-determined ROM meant to reduce the risk of impingement complications and to improve the ROM of patients undergoing shoulder replacement surgery. This paper describes a validation experiment with the purpose of ratifying the clinical applicability and usefulness of the ROM simulation module for shoulder replacement surgery. The experiment was performed on cadaveric shoulders. A data connection was set up between the software environment and an existing intra-operative guidance system to track the relative positions of the bones. This allowed the patient-specific surface models to be visualized within the software for the position and alignment of the tracked bones. For both shoulders, ROM measurements were recorded and tagged with relevant information such as the type of prosthesis and the type of movement that was performed. The observed ROM and occurrences of impingement were compared with the simulated equivalents. The median deviation between observed impingement angles and simulated impingement angles was -0.30 degrees with an interquartile range of 5.20 degrees (from -3.40 degrees to 1.80 degrees). It was concluded that the ROM simulator is sufficiently accurate to fulfil its role as a supportive instrument for orthopaedic surgeons during shoulder replacement surgery.