Personalised 3D Printed high tibial osteotomy achieves a high level of accuracy: ‘IDEAL’ preclinical stage evaluation of a novel patient specific system

Patient-specific implants combined with 3D-printed drilling guides for corrective osteotomies of multiplanar tibial and femoral shaft malunions leads to more accurate corrections

PURPOSE

The aim of this study was to evaluate the feasibility of using patient-specific implants (PSI) for complex shaft corrective osteotomies in multiplanar deformities of long bones in the lower extremities. Additionally, it aimed to investigate the added value of these implants by quantifying surgical accuracy on postoperative CT, comparing their outcomes to two commonly used techniques: 3D virtual visualizations and 3D-printed surgical guides.

METHODS

Six tibial and femoral shaft corrective osteotomies were planned and performed on three Thiel embalmed human specimen. Depending on the specimen a different respective technique was used; 1) '3D Visualization' using 3D virtual plan preoperatively and free-hand corrective osteotomy techniques with standard manually contoured plates; 2) '3D guided' utilizing 3D surgical guides and manually contouring of conventional implant; and 3)'3D PSI' utilizing a 3D surgical guide with a patient-specific implant. Accuracy of the corrections was assessed through measurements for varus/valgus angulation, ante/recurvation, rotation and osteotomy plane error as quantified on postoperative CT-scans.

RESULTS

Twelve corrective osteotomies were performed. For, the median difference between the surgical plan and postoperative CT assessment was 3.4°, 4.6°, and 2.2° for the '3D visualization', '3D guided', and '3D PSI' methods respectively. Regarding ante/recurvation, the differences were 3.8°, 43.8°, and 1.2°, respectively. For rotation, the differences were 11.9°, 18.7°, and 3.5°, respectively. Discrepancies between planned and executed levels of osteotomy plane were 6.2 mm, 3.2 mm, and 1.4 mm, respectively.

CONCLUSION

PSIs with 3D-printed drilling guides for complex multiplanar corrective osteotomies of femoral and tibial shaft malunions is feasible and achieves accurate corrections. This technique enables precise determination of the osteotomy plane, guides correction in all three planes, and ensures satisfactory implant fitting; thus accurately translating the virtual surgical plan into clinical practice. The 3D PSI method is beneficial for complex cases with significant multiplanar deformities in bone anatomy, particularly with rotational malalignment.

A simple formula to control posterior tibial slope during proximal tibial osteotomies

BACKGROUND

High tibial osteotomy surgery is a widely successful joint-preserving procedure which alters the hip-knee-ankle axis which can delay the progression of osteoarthritis; however, conventional osteotomy surgical procedures do not adequately control the posterior tibial slope. This study aimed to determine the key variables influencing posterior tibial slope during high tibial osteotomy and provide a simple means of implementing the findings during pre-operative planning.

METHODS

A virtual cohort of twenty-eight proximal tibia geometries of knee osteoarthritis patients was used in the study. Firstly, absolute posterior tibial slope values were contrasted using anatomical and posterior mechanical axis measurement approaches. Secondly, the influence of variables affecting posterior tibial slope change during osteotomy surgery was investigated using 3D preoperative planning surgical simulation and analytical modelling.

FINDINGS

There was a poor correlation (R2 = 0.38) between the different clinical measurements of posterior tibial slope; with an average of 7.0 ± 1.3° and 14.8 ± 2.2° respectively. An analytical solution for the change in posterior tibial slope was derived based on the hinge axis angle and the osteotomy opening angle. For three different opening angles (6°, 9° and 12°) and seven different hinge axis orientations (-30° to +30°), the results obtained were identical for the analytical model and the 3D preoperative planning.

INTERPRETATION

This study determined that the key variables affecting posterior tibial slope during high tibial osteotomy are the osteotomy opening angle and the hinge axis orientation. The derived formula provides a simple means of determining the change in posterior tibial slope resulting from a particular surgical approach.