Functional safe zone. Safe zone

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2 Functional safe zone Every patient moves differently 1, and the amount of pelvic rotation through functional activities should be accounted for with total hip replacement. Pelvic tilt can change significantly through daily activities 2,3 ; the arc of pelvic motion has Safe zone been shown to be as great as 70 through sit to stand activities 1, changing the functional orientation of the implant. No safe zone has ever accounted for this. Cup inclination ( ) Cup anteversion ( ) OPS is designed to optimally orientate a cup within a safe zone, and for the cup to remain within that safe zone as the pelvis rotates throughout functional activity.

3 The arc of pelvic motion has been shown to be as great as 70 through sit to stand activities 1 DiGioia CORR 2006

4 Overview Every patient moves differently 1 and their total hip replacement should be optimised to account for this. The orientation of the acetabular cup is one of the most important factors under the surgeon s control 4, and acetabular cup orientation has a significant effect on device performance, including patient outcomes, impingement, edge loading, bearing wear, osteolysis and loosening 5,6. There remains two key issues with THR today: 1 2 What is the target for a well orientated cup? Are we able to achieve that orientation? 1 Implant orientation Clinical issue Safe zones There have been various attempts to define a safe zone for the orientation of an acetabular cup, and increasing evidence to suggest that one generic zone is not applicable 7,8,9,10,11. Clinical solution Pelvic tilt Pelvic tilt is an important consideration for a patient s physiological profile, and the arc of pelvic motion in some patients can be as mobile as 70 and in others as stiff as 5 during functional activities 1,12. This can have significant impact on the functional orientation of the acetabular cup. What is the optimal cup orientation for an individual patient? OPS is a state-of-the-art technology platform that delivers potential target orientations unique for each individual. These target orientations are calculated from a dynamic pre-operative functional simulation, which accounts for the patient s physiological profile throughout a range of daily activities.

5 2 Delivery Clinical issue Intra-operative tools It is inherently difficult to position the cup during surgery and achieving a target position is a considerable challenge in THR. It has been shown that up to 50% of surgeries miss the intended orientation 13 and the chance of hitting a target to within 5 can be as low as 21.5% 14. Clinical solution How is the optimised position delivered during surgery? Once the target orientation for a specific patient has been decided, a unique guide is produced for the individual. The planned orientation is built into the axis of the guide which is used intraoperatively with a simple laser system to allow the surgeon to deliver on the planned cup orientation.

6 Reference: 1. DiGioia AM, Hafez MA, Jaramaz B, Levison TJ, Moody JE, Functional pelvic orientation measured from lateral standing and sitting radiographs. Clin Orthop Relat Res 453: Ishida T, Inaba Y, Kobayashi N, Iwamoto N, Yukizawa Y, Choe H, Saito T. Changes in pelvic tilt following total hip arthroplasty. Journal of Orthopaedic Science. 2011; Au J, Perriman DM, Neeman TM, Smith PN. Standing or supine x-rays after total hip replacement - when is the safe zone not safe? Hip International Echeverri S, Leyvraz P, Zambelli P, et al. Reliable acetabular cup orientation with a new gravity-assisted guidance system. J Arthroplasty 2006; 21(3): Meftah M, Yadav A, Wong AC, Ranawat AS, Ranawat CS. A novel method for accurate and reproducible functional cup positioning in total hip arthroplasty. J. Arthroplasty 2013; Aug:28(7): Harrison C, Thomson AI, Cutts S, Rowe PJ, Riches PE, Research synthesis of recommended acetabular cup orientations for total hip arthroplasty. J. Arthroplasty Yoon Y, Hodgson AJ, Tonetti J, et al. Resolving inconsistencies in defining the target orientation for the acetabular cup angles in total hip arthroplasty. Clin Biomech 2008; 23: McCollum DE, Gray WJ. Dislocation after total hip arthroplasty. Causes and prevention. Clin Orthop Relat Res 1990; 261: Harris W. Advances in surgical technique for total hip replacement: without and with osteotomy of the greater trochanter. Clin Orthop Relat Res 1990; 146: Pedersen DR, Callaghan JJ, Brown TD. Activity-dependence of the safe zone for impingement versus dislocation avoidance. Med Eng Phys 2005; 27: Lewinnek GE, Lewis JL, Tarr R, Compere CL, Zimmerman JR. Dislocations after total hip-replacement arthroplasties. J Bone Joint Surg [AM] 1978; Mar:60-A;2 12. SA, Yeung E, Jackson MP, Rajaratnam S, Martell JM, Walter WL, Zicat BA, Walter WK. The role of patient factors and implant position in squeaking of ceramic-on-ceramic total hip replacements. J Bone Joint Surg 2011; Apr: 93-B,4 13. Callanan MC, Jarrett B, Bragdon CR, Zurakowski D, Rubash HE, Freiberg AA, Malchau H. Risk factors for cup malpositioning quality improvement through a joint registry at a tertiary hospital. Clin Orthop Relat Res 2011; 469: Bosker BH, Verheyen CCPM, Horstmann WG, Tulp NJA. Poor accuracy of freehand cup positioning during total hip arthroplasty. Arch Orthop Trauma Surg 2007; 127: Get the full picture. Scan to view the OPS introductory video Corin P No. I1328 Rev0 05/2015 ECR 13891