Fatty infiltration of gastrocnemius-soleus muscle complex: Considerations for myosteatosis rehabilitation.

Although previous studies have reported fatty infiltration of the gastrocnemius-soleus complex, little is known about the volumetric distribution and patterns of fatty infiltration. The purpose of this anatomical study was to document and quantify the frequency, distribution, and pattern of fatty infiltration of the gastrocnemius-soleus complex. One hundred formalin-embalmed specimens (mean age 78.1 ± 12.3 years; 48F/52M) were serially dissected to document the frequency, distribution, and pattern of fatty infiltration in the medial and lateral heads of gastrocnemius and soleus muscles. Fatty infiltration was found in 23% of specimens, 13 unilaterally (8F/5M) and 10 (5M/5F) bilaterally. The fatty infiltration process was observed to begin medially from the medial aspect of the medial head of gastrocnemius and medial margin of soleus and then progressed laterally throughout the medial head of gastrocnemius and the marginal, anterior, and posterior soleus. The lateral head of gastrocnemius remained primarily muscular in all specimens. Microscopically, the pattern of infiltration was demonstrated as intramuscular with intact aponeuroses, and septa. The remaining endo-, peri-, and epimysium preserved the overall contour of the gastrocnemius-soleus complex, even in cases of significant fatty replacement. Since the external contour of the calf is preserved, the presence of fatty infiltration may be underdiagnosed in the clinic without imaging. Myosteatosis is associated with gait and balance challenges in the elderly, which can impact quality of life and result in increased risk of falling. The findings of the study have implications in the rehabilitation management of elderly patients with sarcopenia and myosteatosis.

The 3D muscle morphology and intramuscular innervation of the digital bellies of flexor digitorum profundus: Clinical implications for botulinum toxin injection sites.

Spasticity of flexor digitorum profundus is frequently managed with botulinum toxin injections. Knowledge of the 3D morphology and intramuscular innervation of the digital bellies of flexor digitorum profundus is necessary to optimize the injections. The purpose of this study was to digitize and model in 3D the contractile and connective tissue elements of flexor digitorum profundus to determine muscle morphology, model and map the intramuscular innervation and propose sites for botulinum toxin injection. Fiber bundles (FBs)/aponeuroses and intramuscular nerve branches were dissected and digitized in 12 formalin embalmed cadaveric specimens. Cartesian coordinate data were reconstructed into 3D models as in situ to visualize and compare the muscle morphology and intramuscular innervation patterns of the bellies of flexor digitorum profundus. The 3rd, 4th and 5th digital bellies were superficial to the 2nd digital belly and located adjacent to each other in all specimens. Each digital belly had distinct intramuscular innervation patterns. The 2nd digital belly received intramuscular branches from the anterior interosseus nerve (AIN). The superior half of the 3rd digital belly was innervated intramuscularly by the ulnar nerve (n = 4) or by both the anterior interosseus and ulnar nerves (n = 1). The inferior half of the belly received dual innervation from the anterior interosseus and ulnar nerves in 2 specimens, or exclusively from the AIN (n = 2) or the ulnar nerve (n = 1). The 4th digital belly was innervated by intramuscular branches of the ulnar nerve. One main branch, after coursing through the 4th digital belly, entered the lateral aspect of the 5th digital belly and arborized intramuscularly. The morphology of the FBs, aponeuroses and intramuscular innervation of the digital bellies of FDP were mapped and modelled volumetrically in 3D as in situ. Previous studies were not volumetric nor identified the course of the intramuscular nerve branches within each digital belly. Based on the intramuscular innervation of each of the digital bellies, one possible optimized botulinum toxin injection location was proposed. This injection location, at the junction of the superior and middle thirds of the forearm, would be located in dense nerve terminal zones of the anterior interosseus and ulnar nerves. Future anatomical and clinical investigations are necessary to evaluate the efficacy of these anatomical findings in the management of spasticity.

Quantification of needle angles for lumbar medial branch denervation targeting the posterior half of the superior articular process: an osteological study.

BACKGROUND: Lumbar medial branch radiofrequency ablation (RFA) is a common intervention to manage chronic axial low back pain originating from the facet joints. A more parasagittal approach targeting the posterior half of the lateral neck of superior articular process (SAP) was previously proposed. However, specific needle angles to achieve parallel placement at this target site have not been investigated. OBJECTIVE: To quantify and compare the needle angles, on posterior and lateral views, to achieve parallel placement of electrodes along the medial branch at the posterior half of the lateral neck of SAP at each lumbar vertebral level (L1-L5) and sacrum. DESIGN: Osteological Study. METHODS: Twelve disarticulated lumbosacral spines (n = 72 individual bones) were used in this study. Needles were placed along the periosteum of the posterior half of the lateral neck of SAP, bilaterally and photographed. Mean needle angles for each vertebral level (L1-L5) and sacrum were quantified, and statistical differences were analyzed. RESULTS: The posterior view provided the degrees of lateral displacement from the parasagittal plane (abduction angle), while the lateral view provided the degrees of declination (cranial-to-caudal angle) of the needle. Mean needle angles at each level varied, ranging from 5.63 ± 5.76° to 14.50 ± 14.24° (abduction angle, posterior view) and 40.17 ± 7.32° to 64.10 ± 9.73° (cranial-to-caudal angle, lateral view). In posterior view, a < 10-degree needle angle interval was most frequently identified (57.0% of needle placements). In lateral view, the 40-50-degree (L1-L2), 50-60-degree (L3-L5), and 60-70-degree (sacrum) needle angle intervals occurred most frequently (54.2%, 50.0%, and 41.7% of needle placements, respectively). CONCLUSIONS: Targeting the posterior half of the lateral neck of SAP required <10-degree angulation from parasagittal plane in majority of cases. However, variability of needle angles suggests a standard "one-size-fits-all" approach may not be the optimal technique.

Quantification of Needle Angles for Traditional Lumbar Medial Branch Radiofrequency Ablation: An Osteological Study.

BACKGROUND: Clinical outcomes following lumbar medial branch radiofrequency ablation (RFA) have been inconsistent. One possible reason is less-than-optimal placement of the electrode along the medial branch at the lateral neck of superior articular process (SAP). Needle angles that define optimal placement (i.e., parallel to the medial branch) may be helpful for consistent technical performance of RFA. Despite its importance, there is a lack of anatomical studies that quantify RFA needle placement angles. OBJECTIVE: To quantify and compare needle angles to achieve parallel placement along the medial branch as it courses on the middle two-quarters of the lateral neck of the SAP at the L1-L5 vertebrae. DESIGN: Osteological Study. METHODS: Ten lumbar vertebral columns were used in this study. Needles were placed along the periosteum of the middle two-quarters of the lateral neck of SAP. Mean needle angles for L1-L5 were quantified and compared using posterior (n = 100) and lateral (n = 100) photographs. RESULTS: Mean needle angles varied ranging from 29.29 ± 17.82° to 47.22 ± 16.27° lateral to the parasagittal plane (posterior view) and 33.53 ± 10.23° to 49.19 ± 10.69° caudal to the superior vertebral endplate (lateral view). Significant differences in mean angles were found between: L1/L3 (P = .008), L1/L4 (P = .003), and L1/L5 (P = .040) in the posterior view and L1/L3 (P = .042), L1/L4 (P < .001), L1/L5 (P < .001), L2/L4 (P = .004), and L2/L5 (P = .004) in lateral view. CONCLUSIONS: Variability of needle angles suggest a standard "one-size-fits-all" approach may not be the optimal technique. Future research is necessary to determine optimal patient-specific needle angles from a more detailed and granular analysis of fluoroscopic landmarks.

Typical m. triceps surae morphology and architecture measurement from 0 to 18 years: A narrative review.

The aim of this review was to report on the imaging modalities used to assess morphological and architectural properties of the m. triceps surae muscle in typically developing children, and the available reliability analyses. Scopus and MEDLINE (Pubmed) were searched systematically for all original articles published up to September 2020 measuring morphological and architectural properties of the m. triceps surae in typically developing children (18 years or under). Thirty eligible studies were included in this analysis, measuring fibre bundle length (FBL) (n = 11), pennation angle (PA) (n = 10), muscle volume (MV) (n = 16) and physiological cross-sectional area (PCSA) (n = 4). Three primary imaging modalities were utilised to assess these architectural parameters in vivo: two-dimensional ultrasound (2DUS; n = 12), three-dimensional ultrasound (3DUS; n = 9) and magnetic resonance imaging (MRI; n = 6). The mean age of participants ranged from 1.4 years to 18 years old. There was an apparent increase in m. gastrocnemius medialis MV and pCSA with age; however, no trend was evident with FBL or PA. Analysis of correlations of muscle variables with age was limited by a lack of longitudinal data and methodological variations between studies affecting outcomes. Only five studies evaluated the reliability of the methods. Imaging methodologies such as MRI and US may provide valuable insight into the development of skeletal muscle from childhood to adulthood; however, variations in methodological approaches can significantly influence outcomes. Researchers wishing to develop a model of typical muscle development should carry out longitudinal architectural assessment of all muscles comprising the m. triceps surae utilising a consistent approach that minimises confounding errors.

Ultrasound-Guided Gluteal Fascial Plane Block for the Treatment of Chronic Refractory Greater Trochanteric Pain Syndrome - Technique Description and Anatomical Correlation Study.

INTRODUCTION: Greater trochanteric pain syndrome may often mimic pain generated from other sources. However, it is most commonly caused by gluteus medius and gluteus minimus tendinopathy or tear. The purpose of this technical report was to: 1) describe the ultrasound-guided fascial plane block technique targeting the superior gluteal nerve in the plane between gluteus medius/gluteus minimus to treat moderate-to-severe, chronic, refractory greater trochanteric pain syndrome; 2) anatomically correlate the procedure with cadaveric dissections demonstrating the structures being imaged and the tissues along the needle trajectory; 3) demonstrate the feasibility of the technique with serial dissection of one cadaveric specimen following injection with color dye. TECHNIQUE DESCRIPTION: The ultrasound-guided fascial plane block targeting the superior gluteal nerve to treat moderate-to-severe, chronic, refractory greater trochanteric pain syndrome has been outlined with supporting ultrasound scans and anatomical dissections. The cadaveric dissections are correlated to the ultrasound scans of a healthy volunteer and provide visualization of the tissues in the needle trajectory. The feasibility study in a cadaveric specimen showed adequate stain of the superior gluteal nerve without spread to the piriformis muscle belly, the sciatic nerve, or the inferior gluteal nerve. CONCLUSIONS: This ultrasound-guided fascial plane block is a feasible option for blocking the superior gluteal nerve without inadvertent involvement of the sciatic and inferior gluteal nerves. Further randomized controlled clinical trials are necessary to assess the clinical efficacy of the gluteus medius/gluteus minimus fascial plane block to treat moderate-to-severe, chronic, refractory greater trochanteric pain syndrome.

Anatomical Study of the Innervation of Triangular Fibrocartilage Complex and Distal Radioulnar and Radiocarpal Joints: Implications for Denervation.

PURPOSE: Open and percutaneous denervation is an emerging technique for joint pain. This study investigated the course and distribution of the articular branches innervating the triangular fibrocartilage complex (TFCC), distal radioulnar joint (DRUJ), and radiocarpal joint (RCJ) relative to bony and soft tissue landmarks to guide wrist denervation procedures. METHODS: Fourteen formalin-embalmed specimens were serially dissected to expose the origin, course, and distribution of articular branches innervating the TFCC, DRUJ, and RCJ. Bony and soft tissue landmarks to localize each articular branch were documented and visualized on a 3-dimensional reconstruction of the bones of the distal forearm and hand. RESULTS: The TFCC was innervated by articular branches from the posterior interosseus nerve (10 of 14 specimens), dorsal cutaneous branch of the ulnar nerve (14 of 14 specimens), palmar cutaneous branch of the ulnar nerve (12 of 14 specimens), and medial antebrachial cutaneous nerve (9 of 14 specimens). The DRUJ was innervated by the posterior interosseus nerve (9 of 14 specimens) and anterior interosseus nerve (14 of 14 specimens). The RCJ was innervated by the posterior interosseus nerve (14 of 14 specimens), superficial branch of the radial nerve (5 of 14 specimens), lateral antebrachial cutaneous nerve (14 of 14 specimens), and palmar cutaneous branch of the median nerve (10 of 14 specimens). CONCLUSIONS: Multiple nerves were found to innervate the TFCC, DRUJ, and RCJ. The relationship of anatomical landmarks to specific articular branches supplying the TFCC, DRUJ, and RCJ can inform selective denervation procedures based on the structural origin of pain. CLINICAL RELEVANCE: The detailed documentation of the spatial relationship of the nerve supply to the wrist provides clinicians with the anatomical basis to optimize current, and develop new denervation protocols to manage chronic wrist pain.

Parametric Multi-Scale Modeling of the Zygomaticus Major and Minor: Implications for Facial Reanimation.

ABSTRACT: Facial paralysis can severely impact functionality and mental health. Facial reanimation surgery can improve facial symmetry and movement. Zygomaticus minor (Zmin) and zygomaticus major (Zmaj) are 2 important perioral muscles, that function to elevate the upper lip, contributing to the formation of a smile. The objective of this study was to analyze the morphology in three-dimensional (3D) and quantify architectural parameters of Zmin and Zmaj. In ten formalin-embalmed specimens, Zmin and Zmaj were serially dissected and digitized at the fiber bundle level. The 2 muscles were modeled in 3D to construct high fidelity models. The 3D models were used to assess muscle morphology and quantify architectural parameters including mean fiber bundle length, physiological cross-sectional area, and line of action. Zygomaticus minor fiber bundles were oriented horizontally or slightly obliquely and had a muscular attachment to the medial modiolus. Zygomaticus minor was found to either have no partitions or medial and lateral partitions. Specimens with partitions were divided into type 1 and type 2. Type 1 consisted of a medial partition with fiber bundles attaching to the zygomatic bone at the inferior margin of the orbit. The type 2 medial partition attached to the lateral margin of the orbit to attach to the zygomatic bone. Zygomaticus major had obliquely oriented fiber bundles with most specimens having inferior and superior partitions attaching to the inferior aspect of the zygomatic bone. Zygomaticus major was found to have a greater mean fiber bundle length and physiological cross-sectional area than Zmin. The direction of the line of action of Zmin and Zmaj was closely related to fiber bundle arrangement. Detailed 3D anatomical understanding of Zmin and Zmaj, at the fiber bundle level, is critical for reconstructive surgeons performing dynamic facial reanimation. This data can be used to assist with selecting the ideal donor site for reconstruction.

Muscle architecture of vastus medialis obliquus and longus and its functional implications: A three-dimensional investigation.

Vastus medialis (VM) has two partitions, longus (VML), and obliquus (VMO), which have been implicated in knee pathologies. However, muscle architecture of VMO and VML has not been documented volumetrically. The aims of this study were to determine and compare the muscle architecture of VMO and VML in three-dimensional (3D) space, and to elucidate their relative functional capabilities. Twelve embalmed specimens were used in this study. Each specimen was serially dissected, digitized (Microscribe™ MX), and modeled in 3D (Autodesk Maya®). Architectural parameters: fiber bundle length (FBL), proximal (PPA)/distal (DPA) pennation angle, and physiological cross-sectional area (PCSA) were compared using descriptive statistics/t-tests. Sarcomere lengths (SLs) were measured and compared from six biopsy sites of VM. VMO and VML were found to have superficial and deep parts based on fiber bundle attachments to aponeuroses, medial patellar retinaculum, and adductor magnus tendon. The superficial part of VMO was further subdivided into superior and inferior partitions. Architecturally, VMO was found to have significantly shorter mean FBL, greater mean PPA and DPA, and smaller mean PCSA than VML. VML was found to be connected to the fascia lata by thin fascial bands, not present in VMO. SLs of VMO and VML were comparable. VMO and VML are architecturally and functionally distinct, as evidenced by marked differences in their musculoaponeurotic geometry, attachment sites, and architectural parameters. VMO likely contributes greater to medial patellar stabilization, whereas VML, with a larger relative excursion and force-generating capability, to the extension of the knee. Clin. Anat. 32:515-523, 2019. © 2019 Wiley Periodicals, Inc.

Anatomical Comparison of Radiofrequency Ablation Techniques for Sacroiliac Joint Pain.

Objective: To compare the percentage of sacral lateral branches (LBs) that would be captured if lesions were created by seven current sacroiliac joint (SIJ) radiofrequency ablation (RFA) techniques: three monopolar and four bipolar. Design: Cadaveric fluoroscopy study. Setting: Anatomy and surgical skills laboratories. Subjects: Forty cadaveric SIJs. Methods: LBs were exposed, radiopaque wires were sutured to LBs, and anterior-posterior fluoroscopic images through the S1 superior endplate were obtained. Lesions that would be created by 17 versions of seven current SIJ RFA techniques were mapped on the fluoroscopic images. These 17 versions were compared: 1) percentage of LBs that would be captured; 2) percentage of SIJ specimens in which 100% of LBs would be captured; and 3) percentage of LBs that would not be captured at each level (S1-S4). Results: Both the mean LB and 100% capture rates were greater for the bipolar techniques (93.4-99.7% and 62.5-97.5%, respectively) than for the monopolar techniques (49.6-99.1% and 2.5-92.5%, respectively) evaluated. For the bipolar techniques, 1.5-29.2% of LBs would not be captured at S1 and 0% at S2-S4 vs 0-29.2% at S1-S4 for the cooled monopolar techniques vs 36.9-100% at S1-S4 for the conventional monopolar technique. Conclusions: The findings suggest that, if lesions were created, the RFA needle placement locations of the bipolar techniques evaluated may be capable of capturing all LBs, but those of the current monopolar techniques evaluated may not. Future in vivo imaging studies are required to compare the lesion morphology generated by different SIJ RFA techniques and correlate the findings with clinical outcomes.

Diffusion-Tensor Imaging Versus Digitization in Reconstructing the Masseter Architecture.

Accurate characterization of the craniomaxillofacial (CMF) skeleton using finite element (FE) modeling requires representation of complex geometries, heterogeneous material distributions, and physiological loading. Musculature in CMF FE models are often modeled with simple link elements that do not account for fiber bundles (FBs) and their differential activation. Magnetic resonance (MR) diffusion-tensor imaging (DTI) enables reconstruction of the three-dimensional (3D) FB arrangement within a muscle. However, 3D quantitative validation of DTI-generated FBs is limited. This study compares 3D FB arrangement in terms of pennation angle (PA) and fiber bundle length (FBL) generated through DTI in a human masseter to manual digitization. CT, MR-proton density, and MR-DTI images were acquired from a single cadaveric specimen. Bone and masseter surfaces were reconstructed from CT and MR-proton density images, respectively. PA and FBL were estimated from FBs reconstructed from MR-DTI images using a streamline tracking (STT) algorithm (n = 193) and FBs identified through manual digitization (n = 181) and compared using the Mann-Whitney test. DTI-derived PAs did not differ from the digitized data (p = 0.411), suggesting that MR-DTI can be used to simulate FB orientation and the directionality of transmitted forces. Conversely, a significant difference was observed in FBL (p < 0.01) which may have resulted due to the tractography stopping criterion leading to early tract termination and greater length variability. Overall, this study demonstrated that DTI can yield muscle FB orientation data suitable to representative directionality of physiologic muscle loading in patient-specific CMF FE modeling.

Examining the effect of self-explanation on cognitive integration of basic and clinical sciences in novices.

Several studies have shown that cognitive integration of basic and clinical sciences supports diagnostic reasoning in novices; however, there has been limited exploration of the ways in which educators can translate this model of mental activity into sound instructional strategies. The use of self-explanation during learning has the potential to promote and support the development of integrated knowledge by encouraging novices to elaborate on the causal relationship between clinical features and basic science mechanisms. To explore the effect of this strategy, we compared diagnostic efficacy of teaching students (n = 71) the clinical features of four musculoskeletal pathologies using either (1) integrated causal basic science descriptions (BaSci group); (2) integrated causal basic science descriptions combined with self-explanation prompts (SE group); (3) basic science mechanisms segregated from the clinical features (SG group). All participants completed a diagnostic accuracy test immediately after learning and 1-week later. The results showed that the BaSci group performed significantly better compared to the SE (p = 0.019) and SG groups (p = 0.004); however, no difference was observed between the SE and SG groups (p = 0.91). We hypothesize that the structure of the self-explanation task may not have supported the development of a holistic conceptual understanding of each disease. These findings suggest that integration strategies need to be carefully structured and applied in ways that support the holistic story created by integrated basic science instruction in order to foster conceptual coherence and to capitalize on the benefits of cognition integration.

Evaluation of clinically relevant landmarks of the marginal mandibular branch of the facial nerve: A three-dimensional study with application to avoiding facial nerve palsy.

Injury to the marginal mandibular branch of the facial nerve (MMN) during surgery often results in poor functional and cosmetic outcomes. A line two finger breadths or 2 cm inferior to the border of the mandible is commonly used in planning neck incisions to avoid injury to the MMN. The purpose was to compare the two finger breadth/2 cm landmarks in predicting MMN course, and their accuracy/reliability. Thirty-one cadaveric specimens were scanned to obtain 3D surface topography (FARO® scanner). Four independent raters pinned the inferior border of the mandible and a two finger breadth line and 2cm line below. The location of each pin was digitized (Microscribe™). A preauricular flap was raised, and MMN branches were digitized and modelled (Geomagic®/Maya®) enabling quantification of the accuracy of these landmarks. The location of the two-finger breadth line was variable, spanning 25-51 mm below the inferior border of the mandible (ICC = 0.10). The most inferior MMN branch did not pass below the two-finger breadth line in any specimen, but a narrow clearance zone (≤5 mm) was found in two. In contrast, in 7/31 specimens, the most inferior MMN branch coursed below the 2 cm line and would be at risk of injury. It was concluded that an incision two finger breadths below the inferior border of the mandible could provide safer access than the 2 cm line. After an incision has been placed using the two finger-breadth landmark, caution must be exercised during dissection as branches of the MMN may lie only a few millimeters superior to the incision.

Neuromuscular partitioning of subscapularis based on intramuscular nerve distribution patterns: implications for botulinum toxin injections.

Subscapularis muscle spasticity is commonly treated with botulinum toxin injections; however, there are challenges in determining optimal injection sites within the muscle. The purpose of this study was to document the intramuscular innervation patterns of the subscapularis (1) to determine how the muscle is neuromuscularly partitioned and (2) to identify a strategy for botulinum toxin injection based on neuromuscular partitioning. In 50 formalin-embalmed cadaveric specimens, the extramuscular and intramuscular innervation was (1) serially dissected, digitized, and reconstructed in 3 dimensions (n=7); or (2) serially dissected and photographed (n=43). Intramuscular innervation patterns were compared among specimens to identify neuromuscular partitions. Variation was observed in the number (2-5) and origin of extramuscular nerve branches to the subscapularis. Despite variation in extramuscular innervation, the intramuscular innervation was consistent. Based on intramuscular innervation patterns, the subscapularis had 3 neuromuscular partitions (superior, middle, inferior) in 78% of specimens, and 2 partitions (superior, inferior) in 22% of specimens. The superior and middle partitions were most commonly innervated by branch(es) from the posterior cord, and the inferior partition by branch(es) from the axillary nerve. Injection of botulinum toxin into each partition may help to optimize results in the treatment of shoulder spasticity, and may be achieved by a combination of medial and inferior approaches. Clinical studies are required to determine whether the combination approach is more effective than any single approach and whether the number of partitions injected correlates with clinical outcomes.

Distribution, course, and spatial relationships of the saphenous nerve: A 3D neuroanatomical map for nerve stimulation.

The overall objective of this study was to construct a 3D neuroanatomical map of the saphenous nerve based on cartesian coordinate data to define its course in 3D space relative to bony and soft tissue landmarks. Ten lower limb embalmed specimens were meticulously dissected, digitized, laser scanned, and modelled in 3D. The course of the main branches, number of collateral branches, and relationship of saphenous nerve to the great saphenous vein were defined and quantified using the high-fidelity 3D models. In 60% of specimens, the saphenous nerve was found to have three branches in the leg, infrapatellar, anterior, and posterior. In 40% of specimens, the posterior branch was absent. Three landmarks were found to consistently localize the anterior branch: the medial border of tibia at the level of the tibial tuberosity, the medial border of tibia at the level of the mid-point of leg, and the mid-point of the anterior border of the medial malleolus. The posterior branch, when present, had variable branching patterns but did not extend as far distally as the medial malleolus in any specimen. Anatomically, the anterior and posterior branches at the level of the tibial tuberosity could be most advantageous for nerve stimulation due to their close proximity to the bifurcation of the saphenous nerve where the branches are larger and more readily localizable than distally. Additionally, the tibial tuberosity is a prominent landmark that can be easily identified in most individuals and could be used to localize the anterior and posterior branch using ultrasound or other imaging modalities. These findings will enable implementation of highly realistic computational models that can be used to simulate saphenous nerve stimulation using percutaneous and implanted devices.

Imaging of the acetabular labrum.

The evaluation and proposed relevance of acetabular labral tears has rapidly evolved over the last decade due to the recognition of femoroacetabular impingement, an increase in the number of surgical options, and improved imaging of the hip with MR arthrography and 3-T MR protocols. The acetabular labrum, stabilizing the hip joint, provides a seal, enhancing fluid lubrication, maintains synovial pressure, and prevents direct contact of the articular surfaces. The labrum takes on a weightbearing role at the extremes of motion with excessive forces seen in a great number of athletic activities thought to contribute to tearing. Approximately 25% of labral tears are not associated with any specific injury or traumatic event with the underlying etiology thought to be repetitive microtrauma. This article reviews the anatomy of the acetabular labrum and discusses the five most commonly occurring etiologies of labral tears: trauma, femoroacetabular impingement, hip hypermobility, dysplasia, and degeneration. We also review the surgical and MR classification of labral tears and describe potential pitfalls in image interpretation.

Evidence for the functional compartmentalization of the temporalis muscle: a 3-dimensional study of innervation.

PURPOSE: The temporalis muscle is commonly used for functional transfer. It is architecturally complex, but few studies have examined its intramuscular innervation and none has used 3-dimensional modeling techniques. Understanding neuromuscular compartmentalization may allow the design of local muscle transfers to minimize donor-site morbidity. The purpose of the present study was to document the intramuscular innervation patterns throughout the volume of the temporalis muscle and define functional units within the muscle. MATERIALS AND METHODS: In 10 formalin-embalmed cadaveric specimens, the foramen ovale was exposed and the branches of the mandibular nerve were identified. Each branch was digitized in short segments extramuscularly and intramuscularly. Three-dimensional models were reconstructed from the digitized data using Maya software, and the innervation patterns were documented. RESULTS: The temporalis muscle was found to have superior and inferior parts that were further grouped by innervation into regions, with each receiving its innervation from 1 primary nerve. The nerves originated directly from the mandibular nerve, except in 3 specimens, where the posterior deep temporal nerve arose from the masseteric nerve. CONCLUSION: These results provide a detailed mapping of innervation patterns and suggest there are at least 5 functional compartments. Each of these has the capacity for selective activation, 3 of which have clinical value. These findings may allow for decreased donor-site morbidity and more functionally sophisticated designs in clinical practice.

Extra- and intramuscular innervation of the masseter: Implications for facial reanimation.

PURPOSE: Irreversible facial paralysis results in significant functional impairment. The motor nerve to the masseter is a reconstructive option, but despite its clinical importance, there are few parametric anatomic studies of the masseteric nerve. The purpose of this study was to investigate the extra- and intramuscular innervation of the masseter in 3D to determine the relationship of the nerve to the muscle heads and identify landmarks to aid identification. MATERIALS AND METHODS: The nerve was dissected throughout its entire course in eight formalin-embalmed cadaveric specimens (mean age 84.9 ± 12.2 years). The nerve was digitized at 1-2 mm intervals using a MicroScribe™ digitizer and modeled in 3D in Autodesk® Maya®. RESULTS: Two or three extramuscular nerves were found to enter the deep head (DH) of the masseter: one main "primary" nerve (n = 8) and one (n = 4) or two (n = 4) smaller primary nerve(s). The main primary nerve supplied both the deep and superficial heads, whereas the smaller primary nerve(s) only supplied the DH. Surgical landmarks for masseter nerve localization were quantified. CONCLUSIONS: Comprehensive mapping of the innervation of the masseter muscle throughout its volume revealed neural partitioning that could provide a basis for safety planning for muscle flaps and donor nerve identification and explain why masseter functional loss is not incurred by donor nerve sacrifice. Quantified landmarks correlate to previous studies and support the constant anatomy of this nerve. Our results provide a basis to optimize surgical approaches for donor nerve and muscle flap surgery.

Dissection, digitization, and three-dimensional modelling: a high-fidelity anatomical visualization and imaging technology.

Technological advances have enabled the development of a novel technique of dissection, digitization and three-dimensional modelling of skeletal muscle and other tissues including neurovascular structures as in situ over the last 25 years. Meticulous serial dissection followed by digitization is used to collect Cartesian coordinate data of the contractile and connective tissue elements throughout the entire muscle volume. The Cartesian coordinate can then be used to construct high-fidelity three-dimensional models that capture the spatial arrangement of the contractile and connective tissue elements as in situ enabling detailed studies of the arrangement of the fiber bundles and their attachment sites to aponeuroses, tendon, and bone. In the laboratory, we have concurrently developed a computational methodology to quantify architectural parameters, including fiber bundle length, pennation angle, volume, physiological cross-sectional area in three-dimensional space. In this paper, a flexor digitorum superficialis specimen will be used to demonstrate the high-fidelity outcomes of dissection, digitization, and three-dimensional modelling. This three-step methodology provides a unique opportunity to study muscle architecture in three dimensions, as in situ. Knowledge translation from the anatomy laboratory to the clinical setting has been highly successful.

Measuring Shear Wave Velocity in Adult Skeletal Muscle with Ultrasound 2-D Shear Wave Elastography: A Scoping Review.

Ultrasound 2-D shear wave elastography (US 2D-SWE) is a non-invasive, cost-effective tool for quantifying tissue stiffness. Amidst growing interest in US 2D-SWE for musculoskeletal research, it has been recommended that shear wave velocity (SWV) should be reported instead of elastic moduli to avoid introducing unwanted error into the data. This scoping review examined the evolving use of US 2D-SWE to measure SWV in skeletal muscle and identified strengths and weaknesses to guide future research. We searched electronic databases and key review reference lists to identify articles published between January 2000 and May 2021. Two reviewers assessed the eligibility of records during title/abstract and full-text screening, and one reviewer extracted and coded the data. Sixty-six studies met the eligibility criteria, of which 58 were published in 2017 or later. We found a striking lack of consensus regarding the effects of age and sex on skeletal muscle SWV, and widely variable reliability values. Substantial differences in methodology between studies suggest a pressing need for developing standardized, validated scanning protocols. This scoping review illustrates the breadth of application for US 2D-SWE in musculoskeletal research, and the data synthesis exposed several notable inconsistencies and gaps in current literature that warrant consideration in future studies.