Review of ultrasound-guided labeling: exploring its potential in teaching cadaveric ligaments during anatomical dissection courses.

Objectives: This scoping review aimed to give an overview of the existing literature about ultrasound-guided labeling techniques of human cadaver ligaments and tried to work out the possibilities of integrating ultrasound into dissection courses. Methods: A literature review was carried out on the 3rd of January 2023, with relevant studies discovered in the following databases: MEDLINE, EMBASE, CENTRAL, BIOSIS Previews and Web of Science Core Collection. Grey literature was also considered. The reference lists of all relevant papers were scanned. Only ultrasound studies on human cadaver ligaments were included. The included studies' general characteristics and ultrasound-guided approaches to label the ligaments were taken from them and examined. Results: The search found 8899 matches, but only 96 of them met the criteria. The transverse carpal ligament (15.62%) and the annular pulleys (19.79%) were the ligaments that had received the greatest research attention. Twenty-three studies are included in the methodological analysis. Both the marking substrate and the injected volume were diverse. Although 65% of the included studies achieved 100% accuracy using the ultrasound directed labeling approaches. Conclusions: Ultrasound-guided labeling techniques achieve a high accuracy. Therefore, this methodology could be a potential teaching tool for students during the dissection course. But caution is advised in drawing general conclusions because of the small sample sizes and different methodologies in the studies. Future larger-scale research is necessary.

Fat quantification in the sacroiliac joint syndesmosis: a new semi-automatic volumetric approach.

Fat is physiologically embedded within the interosseous ligaments in the posterior part of the sacroiliac joint (PSIJ). This composite of fat and ligaments is hypothesized to serve a shock-absorbing, stabilizing function for the sacroiliac joint and the lumbopelvic transition region. Using a novel Python-based software (VolSEQ), total PSIJ volume and fat volume were computed semi-automatically. Differences within the cohort and the viability of the program for the quantification of fat in routine computed tomography (CT) scans were assessed. In 37 CT scans of heathy individuals, the PSIJ were first manually segmented as a region of interest in OSIRIX. Within VolSEQ, 'fat' Hounsfield units (- 150 to - 50 HU) are selected and the DICOM file of the patient scan and associated region of interest file from OSIRIX were imported and the pixel sub volumes were then automatically computed. Volume comparisons were made between sexes, sides and ages (≤ 30, 31-64 and > 65 years). PSIJ volumes in both software (VolSeq vs. OSIRIX) were non-different (both 9.7 ± 2.8cm3; p = 0.9). Total PSIJ volume (p = 0.3) and fat volume (p = 0.7) between sexes were non-different. A significant difference in total PSIJ volume between sexes (p < 0.01) but not in fat volume (p = 0.3) was found only in the ≥ 65 years cohort. Fat volume within the PSIJ remains unchanged throughout life. PSIJ volume is sex-dependent after 65 years. VolSEQ is a viable and user-friendly method for sub-volume quantification of tissues in CT.

Undergraduate medical student perceptions and learning outcomes related to anatomy training using Thiel- and ethanol-glycerin-embalmed tissues.

Anatomical dissection is known to serve as an integral tool in teaching gross anatomy, including postgraduate training. A variety of embalming techniques exist, resulting in different haptic and optical tissue properties. This study aimed to objectify learning outcomes and medical student perceptions related to the use of two widely used embalming techniques, namely Thiel and ethanol-glycerin embalming. Between 2020 and 2022, first- and second-year medical students enrolled in the course on topographic anatomy participated in this study. Objective structured practical examinations were carried out for the head, neck, thorax, abdomen, pelvis, and extremity regions following regional dissection just before the oral examinations began. Six to ten numbered tags were marked in prosections of each region in Thiel- and ethanol-glycerin-embalmed specimens. Following the examinations, the students were surveyed regarding the suitability of the two embalming techniques with respect to preservation, colorfastness, tissue pliability, and the suitability in preparing for their anatomy examinations. Consistently higher scores were achieved for the thoracic and abdominal regions in ethanol-glycerin-embalmed specimens when compared to Thiel. No benefit was found for Thiel-embalmed upper or lower extremities. Tissues embalmed with ethanol-glycerin were rated higher for preservation and suitability to achieve the learning objectives, tissue pliability was rated higher for Thiel-embalmed tissues. Ethanol-glycerin embalming appears to offer certain advantages for undergraduate students in recognizing visceral structures, which may align with students' ideas on tissue suitability for their learning. Consequently, the benefits reported for Thiel embalming for postgraduate study unlikely reflect its suitability for novices.

The quantification of 3D-trabecular architecture of the fourth cervical vertebra using CT osteoabsorptiometry and micro-CT.

BACKGROUND: Bone functional adaptation rationalises the inhomogeneous morphology found in bone. By means of computed tomography osteoabsorptiometry and micro-computed tomography, the mineralisation of the subchondral endplates and trabecular microstructure of vertebral bodies can be assessed to visualise the chronic loading conditions bone endures over time. In this study, we determined cancellous and compartment-specific trabecular architecture in the cervical vertebra to aid with successful integration of orthopaedic implants. METHODS: We examined the micro-computed tomography scans of seven prospectively healthy C4 vertebrae, evaluated their microstructure parameters (bone volume fraction (BV/TV), bone surface density (BS/BV), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), trabecular number per volume (Tb.N), connectivity density (Conn.D), structure model index (SMI), and degree of anisotropy (DA), and compared the trabecular architecture in twelve predefined volumes of interest: the cranial and caudal 0-10%, 10-15%, and 25-50% in both the ventral and dorsal half. Using computed tomography osteoabsorptiometry, the subchondral bone mineralisation of the subchondral endplates of nine C4 vertebrae was also evaluated. RESULTS: Highest mineralisation is located dorsally at the endplates. Tb.Sp and Tb.N were the only two parameters that displayed significant differences in averaged values of VOI. Nonetheless, distinct, consistent ventral-dorsal modulations were seen in matched sample ventral-dorsal comparison in the BV/TV, BS/BV, and SMI overall levels, as well as in Tb.Th in the three caudal levels. To simplify, the vertebra was split into ventral-cranial, dorsal-cranial, ventral-caudal, and dorsal-caudal equal quarters. The ventral quarters display lower BV/TV, respectively, higher BS/BV and SMI than their sample paired dorsal quarters. The ventral-cranial quarter shows the lowest BV/TV and the highest BS/BV and SMI, describing spacious cancellous bone with rod-like trabeculae. In contrast, the dorsal-caudal quarter exhibits the highest BV/TV and Tb.Th and the lowest BS/BV and SMI, illustrating thicker, denser, and more plate-like trabeculae. The dorsal-cranial and ventral-caudal quarters are comparable and represent intermediate characteristics. CONCLUSIONS: CT-OAM and µCT demonstrate the interdependence of compact and trabecular bone in response to long-term loading conditions. Results show highest mineralisation in the dorso-caudal part of the C4 vertebra. Recommended placement of orthopaedic implants should be positioned dorsally with screws anchored in the dorsal-caudal region.

Influence of size and shape of the auricular surfaces on subchondral bone density distribution in the sacroiliac joint.

The sacroiliac auricular surface has a variable morphology and size. The impact of such variations on subchondral mineralization distribution has not been investigated. Sixty-nine datasets were subjected to CT-osteoabsorptiometry for the qualitative visualization of chronic loading conditions of the subchondral bone plate using color-mapped densitograms based on Hounsfield Units in CT. Auricular surface morphologies were classified into three types based on posterior angle size: Type 1: >160°, Type 2: 130-160° and Type 3: <130°. Auricular surface size was categorized based on the mean value (15.4 cm2 ) separating the group into 'small' and 'large' joint surfaces. Subchondral bone density patterns were qualitatively classified into four color patterns: two marginal patterns (M1 and M2) and two non-marginal patterns (N1 and N2) and each iliac and sacral surface was subsequently categorized. 'Marginal' meant that 60-70% of the surface was less mineralized compared with the highly dense regions and vice versa for the 'non-marginal' patterns. M1 had anterior border mineralization and M2 had mineralization scattered around the borders. N1 had mineralization spread over the whole superior region, N2 had mineralization spread over the superior and anterior regions. Auricular surface area averaged 15.4 ± 3.6 cm2 , with a tendency for males to have larger joint surfaces. Type 2 was the most common (75%) and type 3 the least common morphology (9%). M1 was the most common pattern (62% of surfaces) by sex (males 60%, females 64%) with the anterior border as the densest region in all three morphologies. Sacra have a majority of surfaces with patterns from the marginal group (98%). Ilia have mineralization concentrated at the anterior border (patterns M1 and N2 combined: 83%). Load distribution differences related to auricular surface morphology seems to have little effect on long-term stress-related bone adaptation visualized with CT-osteoabsorptiometry. Higher iliac side mineralization was observed in larger joint surfaces and age-related morphomechanical size alterations were seen in males.

Auricular surface morphology and surface area does not influence subchondral bone density distribution in the dysfunctional sacroiliac joint.

The subchondral lamella of the sacroiliac auricular surface is morphologically inconsistent. Its morpho-mechanical relationship with dysfunction (SIJD) remains unstudied. Here, the iliac and sacral subchondral bone mineralization is compared between morphological subtypes and in large and small surfaces, in SIJD joints and controls. CT datasets from 29 patients with bilateral or unilateral SIJD were subjected to CT-osteoabsorptiometry. Surface areas and posterior angles were calculated and surfaces were classified by size: small (<15 cm3 ) and large (≥15 cm3 ), and morphological types: 1 (>160°), 2 (130°-160°), and 3 (<130°). Mineralization patterns were identified: two marginal (M1 and M2) and two non-marginal (N1 and N2). Each sacral and iliac surface was subsequently classified. Dysfunctional cohort area averaged 15.0 ± 2.4 cm2 (males 16.2 ± 2.5 cm2 , females 13.7 ± 1.6 cm2 ). No age correlations with surface area were found nor mean Hounsfield Unit differences when comparing sizes, sexes or morphology-type. Controls and dysfunctional cohort comparison revealed differences in female sacra (p = 0.02) and small sacra (p = 0.03). There was low-conformity in marginal and non-marginal patterns, 26% for contralateral non-dysfunctional joints, and 46% for dysfunctional joints. The majority of painful joints was of type 2 morphology (59%), equally distributed between small (49%) and large joints (51%). Larger joints had the highest frequency of dysfunctional joints (72%). Auricular surface morphology seems to have little impact on pain-related subchondral lamella adaptation in SIJD. Larger joints may be predisposed to the onset of pain due to the weakening of the extracapsular structures. Dysfunctional joints reflect common conformity patterns of sacral-apex mineralization with corresponding superior corner iliac mineralization.

Fat Is Consistently Present within the Plantar Muscular Space of the Human Foot-An Anatomical Study.

Background and Objectives: The foot comprises of active contractile and passive connective tissue components, which help maintain stability and facilitate movement during gait. The role of age- or pathology-related degeneration and the presence of fat within muscles in foot function and pain remains unclear. The existence of fat has to date not been quantified or compared between individuals according to age, sex, side or subregion. Materials and Methods: 18 cadaveric feet (mean age 79 years) were sectioned sagittally and photographed bilaterally. Fat in the plantar muscular space of the foot (PMSF) was quantified through the previously validated manual fat quantification method, which involved observing photographs of each section and identifying regions using OsiriX. Fat volume and percentage was calculated using a modified Cavalieri's method. Results: All feet had fat located within the PMSF, averaging 25.8% (range, 16.5-39.4%) of the total PMSF volume. The presence of fat was further confirmed with plastination and confocal microscopy. Conclusions: These findings suggest that fat within the PMSF is a consistent but highly variable finding in elderly cohorts. Fat within the foot muscles may need to be considered a norm when comparing healthy and non-healthy subjects, and for therapeutic interventions to the foot. Further work is required to understand in detail the morphological and mechanical presence of fat in the foot, and compare these findings with pathological cohorts, such as sarcopenia. Additionally, future work should investigate if fat may compensate for the degeneration of the intrinsic muscles of the foot, with implications for both the use of orthotics and pain management.

Subchondral Bone Changes Following Sacroiliac Joint Arthrodesis - A Morpho-mechanical Assessment of Surgical Treatment of the Painful Joint.

BACKGROUND: Sacroiliac joint arthrodesis is an ultima ratio treatment option for sacroiliac joint dysfunction. Fusion drastically reduces sacroiliac joint movement providing long-lasting pain-relief associated with tension-relief to the innervated sacroiliac joint structures involved in force closure. OBJECTIVES: To display the bone mineralization distribution patterns of the subchondral bone plate in 3 distinct regions (superior, anterior, and inferior) of the sacral and iliac counterparts of the sacroiliac joint pre- and post-sacroiliac joint arthrodesis and compare patterns of sacroiliac joint dysfunction post-sacroiliac joint fusion with sacroiliac joint dysfunction pre- arthrodesis patterns and those from healthy controls. STUDY DESIGN: An observational study. SETTING: The research took place at the University of Basel, Switzerland, where the specific image analysis program (Analyze, v7.4, Biomedical Imaging Resources, Mayo Foundation, Rochester, NY, USA) was made available. METHODS: Mineralization densitograms of 18 sacroiliac joint dysfunction patients pre- and post-sacroiliac joint arthrodesis (>= 6, >= 12, and >= 24 months post-surgery) were obtained using computed tomography osteoabsorptiometry. For each patient, pre- vs. post-surgery statistical comparisons were undertaken, using the Hounsfield unit values derived from the subchondral mineralization of superior, anterior, and inferior regions on the iliac and sacral auricular surfaces. Post-operative values were also compared to those from a healthy control cohort (n = 39). RESULTS: In the pre-operative cohort at all 3 follow-up times, the superior iliac region showed significantly higher Hounsfield unit values than the corresponding sacral region (P < 0.01). Mineralization comparisons were similar for the sacrum and ilium in the anterior and inferior regions at all follow-up points (P > 0.5) with no surgery-related changes. Sacral density increased significantly in the post-operative state; not observed on the ilium. Post-operative sacroiliac joints showed a significantly increased mineralization in the superior sacrum after >= 6 months (P < 0.05), not replicated after >= 12 nor >= 24 months. Further comparison of post-operative scans versus healthy controls revealed significantly increased mineralization in the superior sacral region at (>=) 6, 12, and 24 months (P < 0.01), likely related to bone grafting, and in the anterior and inferior regions in post-operative scans at >= 12 and >= 24 months follow-up (P < 0.05). LIMITATIONS: The given study is limited in sample size. Post-operative computed tomography scans had screws which may have left artifacts or partial volume effects on the surfaces. Healthy controls were different patients to the sacroiliac joint dysfunction and post-operative cohorts. Both cohorts were age-matched but this comparison did not take into account potential population differences. Size differences in the regions may have also been an influencing factor of the results as the regions were based on the size and shape of the articular surface. CONCLUSIONS: Sacroiliac joint arthrodesis results in an increased morpho-mechanical conformity in the anterior and inferior sacrum and reflects variable morpho-mechanical density patterns compared to the healthy state due to permanent alterations in the kinematics of the posterior pelvis.

Subchondral bone strength of the sacroiliac joint-a combined approach using computed tomography osteoabsorptiometry (CT-OAM) imaging and biomechanical validation.

Bone mineral density distribution patterns at the sacroiliac joint (SIJ) may reflect long-term adaptation patterns to the loading the joint endures. This study aims to display bone mineralisation patterns of the articular SIJ subchondral lamella using computed tomography (CT) osteoabsorptiometry and mechanical indenting, to determine whether a relationship exists between mineralisation and mechanical strength. Twenty hemipelves were CT-scanned before osteoabsorptiometry densitograms were derived. Each articular side of eleven SIJs was mechanically indented following a 10-mm grid scheme. The sacral surface displayed lower Hounsfield unit (HU) values (≤ 700 HU) than the iliac side (> 700 HU). The apex, superior corner and borders yielded the highest HU scores (> 700 HU). Penetration strength was significantly higher on the iliac side (p < 0.04). Mineral density correlated positively with penetration strength of the subchondral bone layer (p < 0.05). No correlations were found between the HU values, nor between penetration strength of corresponding sides of the same SIJ in the majority of cases (p > 0.05). The iliac subchondral lamella is mechanically denser than the sacral aspect. The non-correlation between density and bone strength of articulating sides indicates biomechanical non-conformity. Loading throughout the SIJ may follow a complex distribution pattern involving the surrounding soft tissues, suspending the sacrum between the ilia.

Quantification of fat in the posterior sacroiliac joint region applying a semi-automated segmentation method.

BACKGROUND AND OBJECTIVE: Fat within the posterior sacroiliac joint region (PSIJ) is thought to compensate for the incongruent surfaces of the sacrum and ilium posteriorly. Knowledge on the presence of fat in the SIJ could provide useful information about joint physiology and clinical kinematic implications of its presence. This study aimed at quantifying fat within the PSIJ, using a semi-automated method, and to compare the results to a manual segmentation method based on data from frozen cadaveric sections and computed tomography (CT). The results may provide a quicker and more objective method for fat volume quantification. METHODS: Seventy-eight cadaveric hemipelves were used. Frozen sections were obtained and photographed and CT data obtained from subsamples. A MATLAB routine was deployed to assess fat in the serial sections and CT scans, using masks derived from color thresholds and Hounsfield units, respectively. Regions of interest were created to isolate the PSIJ region before fat volume was computed. A Friedman test was used for the comparison between all masks and the manual method, a Kruskall-Wallis test for comparing the CT results with all masks and the manual method and Bland-Altman plots were used to express the result differences of these methods. RESULTS: PSIJ fat volume averaged 3.9 ± 2.2, 4.9 ± 2.5, 3.7 ± 2.3 and 7.2 ± 7.3 cm3 for masks 1 (fat mask), 2 (no-fat mask), 3 ('control' fat mask) and CT, respectively. All masks and the CT fat volume were significantly different to the manual segmentation method (p<0.01). Mask 2 differed significantly from masks 1 and 3 (both p<0.01). Bland-Altman plots yielded differences in the measurements between the various methods. CONCLUSIONS: Manual segmentation of PSIJ fat volume may result in a relative underestimation of the total fat compared to semi-automated or CT-based methods, as fat might not be sufficiently distinguished from surrounding structures. However, the CT-based method resulted in vastly higher variation in the results and warrants further study. The semi-automated approach to quantify fat based on color thresholds presented here is more investigator-independent, time efficient and applicable to CT scans, which provides opportunity to use this technique on various tissue types in vivo.

Quantification of fat in the posterior sacroiliac joint region: fat volume is sex and age dependant.

Fat is appreciated as a structural component of synovial joints. It may serve a shock-absorbing function for the incongruent surfaces, vessels and ligaments, but has not been investigated in the posterior sacroiliac joint (PSIJ). Sixty-six cadaveric hemipelves were serially-sectioned and photographed. The amount of visible fat in the PSIJ was quantified using a modified version of Cavalieri's method. Total volume, fat volume and fat percentage of the PSIJ were calculated in predefined sub-regions. Fat is consistently present in the PSIJ (1.9 ± 1.3 cm3). Fat volume correlates with the PSIJ total volume (p < 0.0001; r = 0.73) and age (p = 0.024; r = 0.24), and is smaller in males (1.4 ± 0.8 cm3) than females (2.4 ± 1.5 cm3). Fat volumes in the middle and inferior sub-regions of the PSIJ show side- (p < 0.0001) and sex-differences (p = 0.013 females, middle sub-region). Age and PSIJ total volume correlate between sexes in various sub-regions (p = 0.05 females superior sub-region; males inferior sub-region). Fat percentage differs between sexes and sub-regions (p = 0.018 females, superior sub-region) but is independent of age and sides. The presence of fat within the PSIJ is a normal finding and shows sex-dependant and age-related differences. It is unclear whether fat is linked to age-related degeneration or has a shock-absorbing role in stress- and load-dissipation in the PSIJ.

A Systematic Review of the Normal Sacroiliac Joint Anatomy and Adjacent Tissues for Pain Physicians.

BACKGROUND: The sacroiliac joint (SIJ) forms a complex joint and has shown to be underappreciated in its involvement with lower back pain. Research efforts have intensified on SIJ anatomy and biomechanics because of its predisposing position to pain and dysfunction in individuals suffering from lower back discomfort. Previous work has focused on SIJ anatomy including bone and joint structure, innervation, as well as biomechanics and the treatment of SIJ pain. However, to date, no review exists describing the range of 'normal' anatomic features of the SIJ. OBJECTIVES: To describe the normal appearance of the SIJ and adjacent tissues, as opposed to 'abnormal' conditions involving SIJ morphology. It will also identify key areas that require further study because of lacking information or disagreement. STUDY DESIGN: A systematic literature review. SETTING: The research took place at the University of Otago, New Zealand. All published research on 'normal SIJ anatomy' available from MEDLINE, OVID, Scopus, Web of Science, PubMed, and Science Direct were included, available until December 2018, in English, French, and German. Subject areas included bony landmarks, joint type, bone morphology, ligamentous attachments, muscular and fascial relationships, blood supply, fatty infiltration, and morphologic variation. METHODS: Articles met the selection criteria if they contained specific information on SIJ anatomy, including bone morphology and architecture, ligaments, muscle attachments, innervation, vasculature, and the presence of fat. Biomechanics and kinematics related keywords were used as the literature often couples these with the anatomy. Keywords of individual articles were named as 'structures of interest.' RESULTS: A total of 88 primary and 101 secondary articles were identified in the time frame from 1851 to 2018. Primary articles provided quantitative data and detailed anatomic descriptions. Secondary articles did not focus specifically on the anatomy of the SIJ. Although research appeared to be in general agreement on bony landmarks, joint type, myofascial attachments, vasculature, and innervation of the SIJ, there was only part consensus on ligament attachments and cartilage structure. Information regarding bone density of the articulating surfaces of the SIJ is lacking. Despite its potential clinical significance, fatty infiltration within the joint lacks research to date. LIMITATIONS: Only the given databases were used for the initial search. Keyword combinations used for this review may not have been inclusive of all articles relevant to the SIJ. Work in languages other than the ones listed or work that is not available via the internet may be missing. CONCLUSIONS: This study provides an overview of normal SIJ structures, including all neuromusculoskeletal elements related to the joint. There is a lack of knowledge on the SIJ ligaments warranting further investigation. Furthermore, there are discrepancies in relation to the nomenclature, layers, attachment sites, and on the topographical relationships between ligamentous tissues and nerves. Subsequent studies on the quantification of fat and bone density in the SIJ have been suggested. These could be useful radiologic parameters to assess the condition of the joint clinically. This review may provide insight into the clinical signs and abnormal biomechanical features of the joint for the purposes of treating SIJ pain. KEY WORDS: Bone density, bony landmarks, fat infiltration, innervation, ligaments morphology, muscles, sacroiliac joint, vasculature.