Summary

The pre-operative CT-based OTS hip system results in implant size accuracy of 100% within a margin of ±1 size.

Abstract

In total hip arthroplasty (THA), utilizing pre-operative planning contributes to minimizing surgical complications, enhances the accuracy of the surgery, and reduces implant inventory and costs.
Ortoma Treatment Solution (OTSTM) is a novel orthopedic surgical platform that utilizes CT imaging with AI-based algorithms to automate several critical aspects of THA. It contains three modules - pre-operative planning, navigation during surgery, and follow-up analysis. The main objective of this study was to assess the precision of the OTS hip pre-operative planning module in determining the correct implant size, specifically evaluating whether the implant size chosen with the planning tool accurately matches the actual implant size utilized during surgery.
The surgeries for this study included 32 patients (mean age 59 years, 7 females) with primary osteoarthritis of the hip who underwent total hip replacement from March 2020 to May 2023 with an uncemented Pinnacle cup and Corail stems (Pinnacle®, Corail®, DePuy Synthes, Warsaw, IN, USA). Inclusion criteria were patients eligible for THA and the exclusion criteria were patients younger than 18 years old, patients with previous hip surgery, or fractures at the treatment side.
Before surgery a pre-op CT scanning of the patients was performed. The CT protocol used for the Philips Brilliance 64-slice scanner was a kVp of 120 kV, a tube current of 30 Eff mAs, 0.6-1 mm increments, 1.110 pitch, and a rotation time of 0.4 seconds. Slice acquisition was done in 64 x 0.625 mm. The effective dose received per scan was below 2 mSv.
THA was performed using a posterior surgical approach with implantation technique according to the manufacturer’s instructions and protocol. One experienced surgeon performed all the surgeries. For all the patients, OTS hip planning was used for pre-op planning.
One patient was excluded from the evaluation because the patient had severe Legg-Calve-Perthes disease. It is observed that the patient had advanced developed osteoarthritis with an enlargement and lateralisation of the femoral head. In addition, the acetabulum was shallow and steep without a clearly defined acetabulum rim.
The findings indicate that:
- For the cup implant, 30 out of 31 cases achieved an exact match (96.8%). In one case, the implant used during surgery was one size smaller than the one chosen during pre-operative planning.
- For the stem implant, 28 out of 31 cases achieved an exact match (90.3%). In three cases, there was a discrepancy of ±1 size between the implant used during surgery and pre-operative planning.
- For the head implant, 30 out of 31 cases achieved an exact match (96.8%). In one case, there was a discrepancy of +1 size between the implant used during surgery and pre-operative planning.
The results show that the pre-operative CT-based OTS hip system is precise, achieving an exact match for cup and head implant sizes in over 96.8% of the cases, whereas the stem implant reached an exact match in more than 90.3% of the cases. Additionally, using a pre-operative CT-based OTS hip system results in implant size accuracy of 100% within a margin of ±1 size.