Three-Dimensional Morphological Study on the Effectiveness of Expanded Polytetrafluoroethylene Prosthesis in the Paranasal Augmentation

BACKGROUND

The paranasal depression is a common facial feature of Oriental populations. One of the most wildly used method to improve it was paranasal augmentation using expanded polytetrafluoroethylene (ePTFE). The effectiveness of it should be tested by three-dimensional morphological measurements.

METHODS

Patients who underwent paranasal augmentation using ePTFE between January 2017 and December 2022 were recruited in the study. The preoperative and postoperative clinical variables and three-dimensional measurement of patients were also collected. The satisfaction outcome were assessed.

RESULTS

By establishing a coordinate system based on the Frankfurt plane, 16 landmarks including nasal alar crest, subnasal point, upper lip, pogonion, glabella, sub-cheek, orbitale, tragion in left and right side of faces were marked. Five segments, 4 ratios, and 3 angles were measured based on it. The significant increase of segments, ratios, and angles indicated that paranasal augmentation could increase the protrusion of paranasal area, both in absolute value and relative proportion. The significant decrease of other data indicated that the protrusion difference between paranasal base and upper lip, forehead, and chin, respectively, were shortened after surgery. The average size of implant was 6.54 ± 1.02 mm, and the average increase of paranasal height was 4.38 ± 1.04 mm postoperatively. This indicates that two-thirds of its height will ultimately be reflected effectively in the sagittal elevation of the paranasal base.

CONCLUSIONS

Paranasal augmentation using ePTFE could effectively increase paranasal height and improve subunits relationships, and the ePTFE prosthesis should be designed and carve considering the 1/3 loss of height after implantation.

LEVEL OF EVIDENCE III

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The risk of violating the posterior malleolar fracture when nailing the ipsilateral concomitant spiral distal tibial fracture

Background

For a distal tibial spiral fracture combined with a non-displaced posterior malleolar fragment (PMF), we proposed a hypothesis that the treating surgeon could assess the size of the PMF to determine the need for stabilizing that structure first before rodding the tibia.

Materials and methods

Fifty 3-D models (22 females) of combined distal tibial and posterior malleolar fractures from one trauma center were reconstructed. In each case, a virtual tibial intramedullary nail (vIM nail) with three distal anteroposterior (AP) locking screws (S₁₃, S₁₅ and S₃₇, the number indicating the distance from the screw to the nail tip) were inserted into the center of the tibial canal and ended on top of the distal tibial physeal scar. Contact between the screws and the PMF was defined as causing PMF displacement. The relationship between PMF secondary displacement and traumatic anatomic factors (the fragment area and height of the PMF) was explored. Then, the parameters were justified by analyzing intraoperative radiographs of 35 cases treated by nail with single locking screw (S₁₅) design.

Results

In the analog experiment, multiple logistic regression analysis revealed that the height of the PMF could confidently predict the risk of fragment displacement (S₁₃: odds ratio [OR] 1.18, 95% confidence interval [CI] 1.06–1.32; S₁₅: OR 1.15, 95% CI 1.05–1.27). Regarding the height of the PMF, the receiver operating characteristic established a cut-off value of 31.2 mm for preliminary fixation of the fragment with 88.89% sensitivity and 88.89% specificity. In the operation group the nail stopped on the top of distal tibial physeal scar, no PMF secondary displacement occurred when the PMF height was less than 31.2 mm. However, the incidence of secondary displacement was 93.33% when the height of the PMF exceeded 31.2 mm.

Conclusion

When the distal tibial physeal scare was set as the limit of nail insertion depth, the height of the PMF could be used as a reliable reference predicting the risk of PMF secondary displacement caused by distal anteroposterior locking screw.

Glenoid morphology and the safe zone for protecting the suprascapular nerve during baseplate fixation in reverse shoulder arthroplasty

PURPOSE

The purpose of this study was to investigate glenoid morphology and define the safe zone for protecting the suprascapular nerve baseplate screw during baseplate fixation in reverse shoulder arthroplasty (RSA) in a Chinese population.

METHODS

Shoulder computed tomography (CT) scans from 56 subjects were retrospectively reviewed. Three-dimensional (3D) reconstruction was performed using Mimics software, and corresponding bony references were used to evaluate glenoid morphology. To standardize evaluation, the coronal scapular plane was defined. Safe fixation distances and screw placements were investigated by constructing a simulated cutting plane of the baseplate during RSA.

RESULTS

Mean glenoid height was 35.83 ± 2.95 mm, and width was 27.32 ± 2.78 mm, with significant sexual dimorphism (p < 0.01). According to the cutting plane morphology, the average baseplate radius was 13.84 ± 1.34 mm. The distances from the suprascapular notch and from two bony reference points at the base of the scapular spine to the cutting plane were 30.27 ± 2.77 mm, 18.39 ± 1.67 mm and 16.52 ± 1.52 mm, respectively, with a gender-related difference. Based on the clock face indication system, the danger zone caused by the suprascapular nerve projection was oriented between the two o'clock and eight o'clock positions in reference to the right shoulder.

CONCLUSIONS

Glenoid size and the safe zone for screw fixation during RSA were characterized in a Chinese population. Careful consideration of baseplate fixation and avoidance of suprascapular nerve injury are important for improved clinical outcome.

Predicting anatomical landmarks and bone morphology of the femur using local region matching

PURPOSE

Anatomical landmarks and bony features are frequently used in biomechanical and surgical applications. The purpose of this study was to develop a local region matching-based anatomical landmark prediction method.

METHODS

A reference femur model with anatomical landmarks and a surface division map was prepared. Initial registration between the reference femur model and a target femur model was performed in three-dimensional Cartesian space, and closest point pairs were determined by the initial surface correspondence. The models were mapped to unit spheres through spherical parameterization. Spherical registration using the closest point pairs in the spherical parametric space enabled the application of a division map from the reference model to the target model. The reference and target models were divided into local regions defined in the division map, and the corresponding regions were again registered in Cartesian space. Anatomical landmarks in the local regions were identified in the target model.

RESULTS

The accuracy of the proposed method was tested for anatomical landmarks marked by a clinician on 35 femoral models. The effectiveness of local region matching was demonstrated by automatic measurements of the femoral neck-shaft angle. The average prediction error for all eight anatomical landmarks of the femur was 2.74 (±1.78) mm. The average of the predicted neck-shaft angle for our Korean subjects was 126.41° (±4.92°), which was comparable to previous studies in Japanese and Chinese populations.

CONCLUSION

Anatomical landmarks and features could be accurately predicted using the proposed local region matching method. This method offers robustness and accuracy in determining anatomical bony landmarks and bone morphology for clinical and biomechanical applications.

Morphological measurements of the posterior surface of the normal proximal tibia in a healthy Chinese population

BACKGROUND

To measure and calculate the morphological parameters and determine the anatomical characteristics of the posterior surface of the proximal tibia in a healthy Chinese population.

METHODS

A total of 150 volunteers with normal knees were enrolled. The parameters in the multi-slice spiral computed tomography (MSCT) three-dimensional (3-D) reconstruction images were measured and calculated by two independent qualified observers. The differences and correlation were investigated. The intraclass correlation coefficient (ICC) was used to assess inter-observer reliability.

RESULTS

The posterior margin of the tibial plateau is presented as two superior arc-shapes. The central angles of these arcs were 118°±14° (medial) and 106°±20° (lateral). The radii of these arcs both showed a skewed distribution. The median radii of the arcs were 22 mm in the medial and 20mm in the lateral. There were two significant angles present in the sagittal plane of the posterior cortex of the proximal tibia. The first angles were 39°±7° (medial) and 47°±7° (lateral). The second angles were 39°±4° (medial) and 41°±5° (lateral). Significant differences were observed in the central angles and the first angles but not in the second angles between the medial and lateral. There were no significant differences between different gender groups, and between left and right limbs. All of these parameters exhibited excellent to moderate ICC.

CONCLUSION

Due to the varying anatomic morphology between the postero-medial and postero-lateral surface of the proximal tibia, the internal fixation implants of these two parts should be designed differently.