Morphometric analysis of anatomical implant forms for minimally invasive acetabular fracture osteosynthesis

Significantly reducing the presurgical preparation time for anterior pelvic fracture surgery by faster creating patient-specific curved plates

BACKGROUND

To shorten the preoperative preparation time, reconstruction plates were designed using the computed tomography (CT)-based three-dimensional (3D) medical imaging surgical planning software OOOPDS. In addition, 3D printing was used to generate curved plates for anterior pelvic fracture surgeries.

METHODS

This study analyzed two groups with the same 21 patients who underwent surgery for traumatic anterior pelvic ring fractures. In Group 1, the direct reconstruction plates were preoperatively contoured according to the anatomical 3D-printed pelvic model. In Group 2, the fixation plates were contoured according to the 3D printed plate templates, which were created based on the simulated plate templates by the OOOPDS software. The processing time, including the 3D printing time for the pelvic models in Group 1, the 3D printing time for the fixation plate templates in Group 2, and the pre-contouring time for the plates in both groups, was recorded.

RESULTS

The mean time of pre-contouring for the curved reconstruction plates in Group 2 was significantly less than in Group 1 (-55 min; P < 0.01). The mean time of 3D printing for the 3D plate template model in Group 2 was significantly less than that for the 3D pelvic model in Group 1 (-869 min; P < 0.01). Experimental results showed that the printing time for the plate pre-contouring and the 3D plate templates could be effectively reduced by approximately 93% and 90%, respectively.

CONCLUSION

This method can shorten the preoperative preparation time significantly.

Artificial intelligence and CT-based 3D statistical modeling to assess transsacral corridors and plan implant positioning

Transsacral corridors at levels S1 and S2 represent complex osseous spaces allowing percutaneous fixation of non- or minimally-displaced fragility fractures of the sacrum. To safely place transsacral implants, they must be completely intraosseous. However, standard radiographs and CT do not properly demonstrate the corridor's intricate configuration. Our goal was to facilitate the three-dimensional assessment of transsacral corridors using artificial intelligence and the planning of transsacral implant positioning. In total, 100 pelvic CTs (49 women, mean age: 58.6 ± SD 14.8 years; 51 men, mean age: 60.7 ± SD 13 years) were used to compute a 3D statistical model of the pelvic ring. On the basis of morphologic features (=predictors) and principal components scores (=response), regression learners were interactively trained, validated, and tuned to predict/sample personalized 3D pelvic models. They were matched via thin-plate spline transformation to a series of 20 pelvic CTs with fragility fractures of the sacrum (18 women and 2 men, age: 69-9.5 years, mean age: 78.65 ± SD 8.4 years). These models demonstrated the availability, dimension, cross-section, and symmetry of transsacral corridors S1 and S2, as well as the planned implant position, dimension, axes, and entry and exit points. The complete intraosseous pathway was controlled in CT reconstructions. We succeeded to establish a workflow determining transsacral corridors S1 and S2 using artificial intelligence and 3D statistical modeling.

Symmetry Matching of the Medial Acetabular Surface-A Quantitative Analysis in View of Patient-Specific Implants

OBJECTIVE

To quantify intrapelvic surface symmetry in reference to a preshaped suprapectineal acetabular implant.

METHODS

In this cross-sectional study, an anatomically preshaped acetabular fracture implant was fitted on 3D surface models of 516 pelvises from a preexisting bone database using a software tool for automated implant fitting (SOMA, Stryker Orthopaedic Modeling and Analytics) of a CAD model of the implant. The distances between bone and the reference implant were measured at 2310 reference points for each hemipelvis.

RESULTS

The average distance between the left hemipelvis and the plate was 1.98 mm (median, 10% percentile: 1.45, 90% percentile: 2.78) and 2.0 mm (median, 10% percentile: 1.45, 90% percentile: 2.92) between the right hemipelvis and the plate. There was no significant difference between the 2 hemipelvises (median absolute pairwise delta: 0.25 mm; 10% percentile: 0.04, 90% percentile: 0.82; Wilcoxon, P = 0.064).

CONCLUSIONS

With regard to the periacetabular surface of the inner pelvis, the pelvis can be considered sufficiently symmetric for using the mirrored contralateral hemipelvis as a template for patient-specific implants in acetabular fracture fixation.

[Interspinous spacers and disc herniation. Geomorphometric and clinical study of 71 cases treated by L4-L5 microdiscectomy associated to spacer placement]

OBJECTIVE

A controversial indication of interspinous spacers is their use as a complement to discectomy. At the present time, there is no solid clinical evidence of effectiveness of that association, which might result from variability in spacer positioning, restricting its correct biomechanical actions. In this study our goal was to identify and analyse the variability in the placement of an interspinous spacer, and to investigate its relationship with the clinical results.

MATERIALS AND METHODS

We performed a retrospective study on X-ray films from 71 patients suffering from disc herniation in L4-L5 who underwent surgery in our hospital, consisting of: microdiscectomy and biomed interspinous spacer implantation. The geomorphometric techniques used to analyse the data were procrustes superimposition and principal components analysis. We compared the clinical results (using the Herron and Turner scale), segmental lordosis and surgical distraction with the geomorphometric parameters.

RESULTS

Significant morphological variability was found in the implant position showing cephalo-caudal translation and clockwise-counterclockwise rotations. This variability did not correlate with clinical results. A relationship with anatomical features (lordosis) and additional surgical distraction was identified. A different morphology of implant-segment configuration was identified in cases with recurrence of disc herniation.

CONCLUSIONS

Geometric morphometrics allowed identifying high variability in the final placement of interspinous spacers. Nevertheless, it seems not to be related to the clinical outcome, depending rather on the degree of lordosis and distraction. Some differences in segment-implant morphology were identified in cases with recurrences. To assess the effectiveness of spacers, larger studies including morphological and clinical variables are required.