3D accuracy and clinical outcomes of corrective osteotomies with patient-specific instruments in complex upper extremity deformities: an approach for investigation and correlation
Authors: Delbrück Heide , Weber David Christian , Eschweiler Jörg , Hildebrand Frank 
Published: October 2022

Abstract
Background
Corrective osteotomies of the upper extremities with patient-specific instruments (PSIs) are increasingly used. In this context, the concordance between planning and postoperative 3D radiographs as well as the association between 3D accuracy and clinical outcome has rarely been evaluated. In this pilot study, we aimed to investigate our clinical mid-term outcome and 3D accuracy as well as their possible correlation, including identifying aspects critical to reaching optimal correction results.

Methods
From October 2018 to January 2020, we used PSIs for 12 corrective osteotomies of the upper extremity in 11 bones of 8 patients (congenital or posttraumatic deformities in 2 elbows, 3 forearms, 3 distal radii). In follow-up examination (10–25 months postoperatively), patient satisfaction, grip strength, ROM, VAS, and DASH were evaluated. Three-dimensional radiological accuracy was determined with 3D-reconstructed postoperative CT scans. With the software tool “Part Comparison” of Mimics® Innovation Suite Software/Materialise, surface differences of pre-planned and postoperative 3D models were compared.

Results
Compared to the preoperative situation pain and function were better at follow-up: The average VAS score significantly decreased from 6.5 ± 4.1 cm preoperatively to 2.3 ± 2.6 cm at the follow-up time point (p = 0.008). The average DASH score significantly improved, from 48.4 ± 30.9 to 27.0 ± 25.2 (p = 0.015). In the part comparison analysis “planned vs postoperative comparison”, significantly more points in percent (= 3D accuracy) were in a −3 mm to 3 mm interval than in the “preoperative vs planned comparison” (87.3 ± 13.8% vs 48.9 ± 16.6%, p = 0.004). After surgery, the maximum deviation value over all cases was 4.5 ± 1.1 mm, and the minimum deviation value was − 4.5 ± 1.2 mm vs preoperatively 12.9 ± 6.2 mm (p = 0.004) and − 7.2 ± 2.1 mm (p = 0.02), respectively. Clinically, in all cases with higher accuracy (> 90%), an improvement of either DASH or VAS or both of > 60% to the preoperative values occurred. There was a significant correlation between accuracy (%) and ΔVAS (p = 0.004). There were no method-related complications.

Conclusions
Our data after PSI-based corrective osteotomy in complex deformities of the upper extremity in a limited number of cases indicate a positive correlation between 3D accuracy and clinical outcomes. Examination of 3D accuracy to analyse sources of error in the hole procedure from initial CT scan to end of surgery even in patients with not fully satisfactory clinical results is required for further development of the method to achieve optimal correction results with nearly 100% congruence between the planned and postoperative 3D bone position.
Trial registration This retrospective study was registered in the Center for Translational & Clinical Research Aachen (CTC-A) with the number 20-514 on November 20, 2021