Application of natural orifice transluminal endoscopic surgery with ENDOCRAB system for stomach perforation model: ex vivo porcine study.

Iatrogenic stomach perforation is a detrimental, irreversible, and fatal condition. Traditional surgery and endoscopic suturing clips and devices have been introduced to seal holes and prevent sepsis and disease progression. However, the development of endoscopic devices for perforations remains challenging, with no standard device available. This study investigates the superficial layer approximation strengths of the newly designed ENDOCRAB system for gastric wall defects. Thirty porcine stomachs were prepared ex vivo for the perforation model and distributed equally into three groups: ENDOCRAB system, Through-the-Scope Clip (TTSC), and hand suturing (HS). Both ENDOCRAB and TTSC achieved mucosal-submucosal layer apposition, whereas HS allowed a full-thickness layer. Their air leakage pressure and procedural duration were measured. The analysis of air-leakage pressure demonstrated comparable suture strength between ENDOCRAB (118.5 ± 41.7 mmHg) and HS (127.4 ± 30.2 mmHg, P = 0.812), but inferior strength with TTSC (73.6 ± 21.6 mmHg, P = 0.012). HS achieved the shortest procedural duration, whereas ENDOCRAB and TTSC showed no significant differences. The ENDOCRAB system showed significantly greater strength than the TTSC, was comparable to HS in strength, and required a procedural duration similar to that of the TTSC. Furthermore, long-term in vivo experiments and histological evaluations are essential.

Alterations in articular cartilage T2 star relaxation time following mechanical disorders: in vivo canine supraspinatus tendon resection models.

BACKGROUND: The role of altered joint mechanics on cartilage degeneration in in vivo models has not been studied successfully due to a lack of pre-injury information. We aimed 1) to develop an accurate in vivo canine model to measure the changes in joint loading and T2 star (T2*) relaxation time before and after unilateral supraspinatus tendon resections, and 2) to find the relationship between regional variations in articular cartilage loading patterns and T2* relaxation time distributions. METHODS: Rigid markers were implanted in the scapula and humerus of tested dogs. The movement of the shoulder bones were measured by a motion tracking system during normal gaits. In vivo cartilage contact strain was measured by aligning 3D shoulder models with the motion tracking data. Articular cartilage T2* relaxation times were measured by quantitative MRI scans. Articular cartilage contact strain and T2* relaxation time were compared in the shoulders before and 3 months after the supraspinatus tendon resections. RESULTS: Excellent accuracy and reproducibility were found in our in vivo contact strain measurements with less than 1% errors. Changes in articular cartilage contact strain exhibited similar patterns with the changes in the T2* relaxation time after resection surgeries. Regional changes in the articular cartilage T2* relaxation time exhibited positive correlations with regional contact strain variations 3 months after the supraspinatus resection surgeries. CONCLUSION: This is the first study to measure in vivo articular cartilage contact strains with high accuracy and reproducibility. Positive correlations between contact strain and T2* relaxation time suggest that the articular cartilage extracellular matrix may responds to mechanical changes in local areas.

Threshold-based quantification of fatty degeneration in the supraspinatus muscle on MRI as an alternative method to Goutallier classification and single-voxel MR spectroscopy.

BACKGROUND: Conventional fat quantification methods for rotator cuff muscles have various limitations, such as inconsistent reliabilities of the Goutallier grades and need for advanced techniques in quantitative MRI sequences. We aimed to examine a threshold-based fat quantification method in the supraspinatus muscle on standard T1-weighted MR images and compare the threshold-based method with Goutallier grades and MR spectroscopy. METHODS: We retrospectively examined 38 symptomatic patients, who underwent T1 and T2-weighted fast spin-echo MR imaging and a single voxel spin-echo MR spectroscopy. The supraspinatus muscle and fossa were manually segmented in T1-weighted sagittal images and clustering-based thresholding was applied to quantify the fat fractions in the segmented areas using custom MATLAB software. Threshold-based fat fractions were compared with the Goutallier grades and MR spectroscopy fat/water ratios. A one-way analysis of variance and Pearson correlation were tested in the MATLAB software. RESULTS: Inter-observer reliability of threshold-based fat fractions for the supraspinatus muscle and fossa were 0.977 and 0.990 respectively, whereas the reliability of the Goutallier grading was 0.798. Threshold-based fat fractions in the supraspinatus fossa were significantly different between various Goutallier grades (one-way ANOVA, p < 0.001). Threshold-based fat fractions in the supraspinatus muscle strongly correlated with the MR spectroscopy fat/water ratio (Pearson correlation R-square = 0.83). CONCLUSIONS: Threshold-based fat quantification on standard T1-weighted MR images was highly reliable and produced comparable results to conventional Goutallier grades and MR spectroscopy fat/water ratios and could serve as an alternative method for accurate fat quantification in rotator cuff muscles.

Role of the acetabular labrum on articular cartilage consolidation patterns.

Damage to the acetabular labrum has been associated with cartilage degeneration. Because conventional pressure measurement devices were unable to examine the sealing function of the acetabular labrum on cartilage contact mechanics, we used an image-based computational method to examine how labrectomy affects articular cartilage contact area and strain patterns in porcine hips. Cyclically loaded hip samples were continuously imaged in a CT scanner every 3 min to trace the positions of the femur and acetabulum. Image-based displacement-controlled finite element analysis was used to calculate articular cartilage contact area and nominal strain at different time points. No changes in cartilage contact area were found after labrectomy. Compared to the labrum intact condition, average nominal strain in labrectomized hips was elevated at early time points after load application. The areas of 'high' strain in labrectomized hips were found to be increased by approximately 7% after 30 min of cyclic loading, while the changes in the areas of 'low' strain were minimal. Our result showed that changes in articular cartilage strain following labrectomy were concentrated on locally overloaded areas where the degenerative process of articular cartilage may be initiated.

Physeal cartilage exhibits rapid consolidation and recovery in intact knees that are physiologically loaded.

The growth plate (physis) is responsible for long bone growth through endochondral ossification, a process which can be mechanically modulated. However, our understanding of the detailed mechanical behavior of physeal cartilage occurring in vivo is limited. In this study, we aimed to quantify the time-dependent deformational behavior of physeal cartilage in intact knees under physiologically realistic dynamic loading, and compare physeal cartilage deformation with articular cartilage deformation. A 4.7 T MRI scanner continuously scanned a knee joint in the sagittal plane through the central load-bearing region of the medial compartment every 2.5 min while a realistic cyclic loading was applied. A custom auto-segmentation program was developed to delineate complex physeal cartilage boundaries. Physeal volume changes at each time step were calculated. The new auto-segmentation was found to be reproducible with COV of the volume measurements being less than 0.5%. Time-constants of physeal cartilage consolidation (1.31±0.74 min) and recovery (1.63±0.70 min) were significantly smaller than the values (5.53±1.78/17.71±13.88 min for consolidation/recovery) in articular cartilage (P<0.05). The rapid consolidation and recovery of physeal cartilage may due to a relatively free metaphyseal fluid boundary which would allow rapid fluid exchange with the adjacent cancellous bone. This may impair the generation of hydrostatic pressure in the cartilage matrix when the physis is under chronic compressive loading, and may be related to the premature ossification of the growth plate under such conditions. Research on the growth plate fluid exchange may provide a more comprehensive understanding of mechanisms and disorders of long bone growth.