Superior Gluteal Nerve Anatomy and Its Injuries: Aiming for a More Secure Surgical Approach of the Pelvic Region.

Because most of the recognized causes of superior gluteal nerve (SGN) injury are iatrogenic, detailed knowledge of the anatomy of the SGN is crucial to prevent its injury associated with surgical procedures. This study aims to describe the precise location of SGN or its branches at the greater sciatic foramen, measure the distances of these neural structures to palpable bony landmarks, and evaluate the possible correlation between these parameters and pelvis size. Twenty human cadaveric hemipelvises were studied. After dissection to expose the SGN or its branches at the greater sciatic foramen, the distances from these neural structures to the greater trochanter (GT), to the anterior superior iliac spine (ASIS), to the posterior superior iliac spine (PSIS), to the ischial tuberosity (IT), and to the greater sciatic notch apex were measured. We found that at the greater sciatic foramen, the SGN emerges as a common trunk in 75% of hemipelvises, and already divided in its superior and inferior branches in 25% of hemipelvises. When the SGN exits the pelvis as a common trunk, it does so, in most cases, in contact with the bone at the apex of the greater sciatic notch or superior to the level of the apex. The median distance from the SGN at the greater sciatic notch to the PSIS, ASIS, GT and IT is 7.6 cm, 10.9 cm, 7.5 cm and 10.8 cm, respectively. We found a positive correlation between some of the analyzed parameters and the size of the pelvis. The anatomical data of this study may serve as pivotal guides during orthopedic pelvic surgery, contributing to minimize SNG iatrogenic lesions with significant implications in the patient's quality of life.

Proximal femur geometry: a major predictor of proximal femur fracture subtypes.

INTRODUCTION: Proximal femur geometry (PFG) represents an important risk factor for the occurrence of hip fractures. There are currently few studies regarding the correlation between PFG and the occurrence of a specific fracture subtype, and those that exist have small cohorts and present with different methodologies and contradictory results. Therefore, there is no consensus in the literature regarding this topic. The present study aimed to establish the contribution of the PFG in the occurrence of different subtypes of proximal femur fractures (PFF): intertrochanteric, neck and subtrochanteric. METHODS: Analysis of 1022 plain anteroposterior pelvic radiographs of patients consecutively admitted to the emergency room of a Level 1 Trauma Centre between 2013 and 2019 after low energy trauma who presented with PFF and underwent surgical treatment. Patients were analysed considering age, gender and subtype of PFF (intertrochanteric, neck or subtrochanteric). Radiological parameters including cervicodiaphyseal angle (CDA), horizontal offset (HO), femoral neck width (FNW), femoral neck length (FNL), great trochanter-pubic symphysis distance (GTPSD), acetabular teardrop distance (ATD) and width of the intertrochanteric region (WIR) were measured and compared between the different subtypes of fractures (7154 measurements). Statistical analysis was conducted recurring to absolute measurements and measurements ratios. The correlation was assessed using t-test. RESULTS: There were statistically significant differences in proximal femur geometry between the different subtypes of fractures. Patients presenting with femoral neck fractures had greater CDA (132.5 ± 6.9 vs. 130.0 ± 7.3; p < 0.001) and lower HO (45.8 ± 7.4 vs. 49.0 ± 8.0; p < 0.001), HO/ATD (0.34 ± 0.068 vs. 0.37 ± 0.072; p < 0.001) and HO/GTPSD (0.26 ± 0.049 vs. 0.28 ± 0.039; p < 0.001) than patients with intertrochanteric/subtrochanteric fractures. CONCLUSIONS: PFG represents an important contributor to the occurrence of different fracture subtypes. Femoral neck fractures are associated with greater CDA and lower HO, HO/ATD and HO/GTPSD when compared to intertrochanteric or subtrochanteric fractures.

Deep gluteal space anatomy and its relationship with deep gluteal pain syndromes.

INTRODUCTION: Increasing interest has been seen in understanding the anatomy and biomechanics involved in the Deep Gluteal Syndrome, therefore the main objective of our paper was to define the anatomy of the deep gluteal space concerning the important osseous, muscular and neurological structures. METHODS: 12 cadaveric models (24 hemipelvises) were used. We proceeded with classical anatomic dissection and evaluated numerous osseous, musculotendinous and neurologic structures and their relationships. We also determined the femoral anteversion and neck-shaft angles. RESULTS: We found that 15.4% of lower limbs examined presented variations in the sciatic nerve (SN) emergence, and this was significantly longer in men. The distance from the SN to the trochanteric region was also significantly lower in males.The average ischiofemoral distance (IFD) was 2.5 ± 1.3 cm, at the same time that the structures comprised in that space showed superior areas, such as the quadratus femoris (QF) with 5.0 ± 1.1 cm and the SN with 1.4 ± 0.3 cm widths.Besides that, we also evaluated the distance from the SN to the lesser trochanter (LT) and the ischial tuberosity (IT), in the ischiofemoral space, reaching average values of 1.1 ± 0.7 cm and 1.5 ± 0.6 cm respectively.Regarding the relationship between the proximal hamstring insertion, we verified that the LT was at an average distance of 1.6 ± 1.1 cm, that the SN was only 0.2 ± 0.3 cm lateral to it, and the PN is just 2.6 ± 1.2 cm proximal to it. CONCLUSIONS: Our study confirmed the extreme variation in the SN origin that can contribute to the Piriformis syndrome. The IFD obtained in our study showed that this distance was small for the structures contained in this space.The proximal hamstring insertion showed a significantly more extended footprint in males, which puts the pudendal nerve (PN) at higher risk of iatrogenic injury.

Design of Kinematic Connectors for Microstructured Materials Produced by Additive Manufacturing.

The main characteristic of materials with a functional gradient is the progressive composition or the structure variation across its geometry. This results in the properties variation in one or more specific directions, according to the functional application requirements. Cellular structure flexibility in tailoring properties is employed frequently to design functionally-graded materials. Topology optimisation methods are powerful tools to functionally graded materials design with cellular structure geometry, although continuity between adjacent unit-cells in gradient directions remains a restriction. It is mandatory to attain a manufacturable part to guarantee the connectedness between adjoining microstructures, namely by ensuring that the solid regions on the microstructure's borders i.e., kinematic connectors) match the neighboring cells that share the same boundary. This study assesses the kinematic connectors generated by imposing local density restrictions in the initial design domain (i.e., nucleation) between topologically optimised representative unit-cells. Several kinematic connector examples are presented for two representatives unit-cells topology optimised for maximum bulk and shear moduli with different volume fractions restrictions and graduated Young's modulus. Experimental mechanical tests (compression) were performed, and comparison studies were carried out between experimental and numerical Young's modulus. The results for the single maximum bulk for the mean values for experimental compressive Young's modulus (Ex¯) with 60%Vf show a deviation of 9.15%. The single maximum shear for the experimental compressive Young's modulus mean values (Ex¯) with 60%Vf, exhibit a deviation of 11.73%. For graded structures, the experimental mean values of compressive Young's moduli (Ex¯), compared with predicted total Young's moduli (ESe), show a deviation of 6.96 for the bulk graded structure. The main results show that the single type representative unit-cell experimental Young's modulus with higher volume fraction presents a minor deviation compared with homogenized data. Both (i.e., bulk and shear moduli) graded microstructures show continuity between adjacent cells. The proposed method proved to be suitable for generating kinematic connections for the design of shear and bulk graduated microstructured materials.

Assessment of the Dimensional and Geometric Precision of Micro-Details Produced by Material Jetting.

Additive Manufacturing (AM) technology has been increasing its penetration not only for the production of prototypes and validation models, but also for final parts. This technology allows producing parts with almost no geometry restrictions, even on a micro-scale. However, the micro-Detail (mD) measurement of complex parts remains an open field of investigation. To be able to develop all the potential that this technology offers, it is necessary to quantify a process's precision limitations, repeatability, and reproducibility. New design methodologies focus on optimization, designing microstructured parts with a complex material distribution. These methodologies are based on mathematical formulations, whose numerical models assume the model discretization through volumetric unitary elements (voxels) with explicit dimensions and geometries. The accuracy of these models in predicting the behavior of the pieces is influenced by the fidelity of the object's physical reproduction. Despite that the Material Jetting (MJ) process makes it possible to produce complex parts, it is crucial to experimentally establish the minimum dimensional and geometric limits to produce parts with mDs. This work aims to support designers and engineers in selecting the most appropriate scale to produce parts discretized by hexahedral meshes (cubes). This study evaluated the dimensional and geometric precision of MJ equipment in the production of mDs (cubes) comparing the nominal design dimensions. A Sample Test (ST) with different sizes of mDs was modeled and produced. The dimensional and geometric precision of the mDs were quantified concerning the nominal value and the calculated deviations. From the tests performed, it was possible to conclude that: (i) more than 90% of all analyzed mDs exhibit three dimensions (xyz) higher than the nominal ones; (ii) for micro-details smaller than 423 µm, they show a distorted geometry, and below 212 µm, printing fails.

Coracoid morphology and humeral version as risk factors for subscapularis tears.

BACKGROUND: The pathophysiology of subscapularis (SS) lesions is still relatively unknown despite recent interest in predictive factors for SS tears. Our goal was to determine the influence of the coracoid morphology and humeral version on SS tears. METHODS: This was a retrospective, controlled, single-blinded study. We analyzed 232 shoulders with SS lesions confirmed by magnetic resonance imaging. The coracoid proximal length, coracoid distal length (CLD), and coracoid total length were measured. The coracoid length ratio, coracoid angle (CA), and humeral version were also evaluated. RESULTS: We found that greater humeral retroversion was progressively related to more serious SS injuries, with values of -28.6° ± 19.5° and -51.0° ± 11.1° in the normal SS group and tear group, respectively (P < .001). The same tendency was shown for the CA, with values of 123.8° ± 11.1° in the control group vs. 97.4° ± 10.1° in the tear group (P < .001). Greater CLD, coracoid total length, and coracoid length ratio were also associated with an increased risk of SS tears (P < .001). The CA and CLD represented the best predictors of SS tears, presenting areas under the receiver operating characteristic curve of 90.0% and 89.0%, respectively. CONCLUSIONS: This article is the first to study the influence of different parameters of the coracoid process morphology and humeral version on SS tears. We proved that humeral version and coracoid morphology were important risk factors for SS pathology and could accurately predict these lesions. Finally, our study was the first to create a classification system to divide coracoids according to their morphology and relative risk of associated SS tears.