A methodological approach for collecting simultaneous measures of muscle, aponeurosis, and tendon behaviour during dynamic contractions.

Skeletal muscles and the tendons that attach them to bone are structurally complex and deform non-uniformly during contraction. While these tissue deformations dictate force production during movement, our understanding of this behaviour is limited due to challenges in obtaining complete measures of the constituent structures. To address these challenges, we present an approach for simultaneously measuring muscle, fascicle, aponeurosis, and tendon behaviour using sonomicrometry. To evaluate this methodology, we conducted isometric and dynamic contractions in in situ rabbit medial gastrocnemius. We found comparable patterns of strain in the muscle belly, fascicle, aponeurosis, and tendon during the isometric trials to those published in the literature. For the dynamic contractions, we found that our measures using this method were consistent across all animals and aligned well with our theoretical understanding of muscle-tendon unit behaviour. Thus, this method provides a means to fully capture the complex behaviour of muscle-tendon units across contraction types.

Biceps femoris long head muscle and aponeurosis geometry in males with and without a history of hamstring strain injury.

OBJECTIVES: Hamstring strain injuries (HSIs) commonly affect the proximal biceps femoris long head (BFlh) musculotendinous junction. Biomechanical modeling suggests narrow proximal BFlh aponeuroses and large muscle-to-aponeurosis width ratios increase localized tissue strains and presumably risk of HSI. This study aimed to determine if BFlh muscle and proximal aponeurosis geometry differed between limbs with and without a history of HSI. METHODS: Twenty-six recreationally active males with (n = 13) and without (n = 13) a history of unilateral HSI in the last 24 months underwent magnetic resonance imaging of both thighs. BFlh muscle and proximal aponeurosis cross-sectional areas, length, volume, and interface area between muscle and aponeurosis were extracted. Previously injured limbs were compared to uninjured contralateral and control limbs for discrete variables and ratios, and along the relative length of tissues using statistical parametric mapping. RESULTS: Previously injured limbs displayed significantly smaller muscle-to-aponeurosis volume ratios (p = 0.029, Wilcoxon effect size (ES) = 0.43) and larger proximal BFlh aponeurosis volumes (p = 0.019, ES = 0.46) than control limbs with no history of HSI. No significant differences were found between previously injured and uninjured contralateral limbs for any outcome measure (p = 0.216-1.000, ES = 0.01-0.36). CONCLUSIONS: Aponeurosis geometry differed between limbs with and without a history of HSI. The significantly larger BFlh proximal aponeuroses and smaller muscle-to-aponeurosis volume ratios in previously injured limbs could alter the strain experienced in muscle adjacent to the musculotendinous junction during active lengthening. Future research is required to determine if geometric differences influence the risk of re-injury and whether they can be altered via targeted training.

A Modified Algorithm-Based Levator Aponeurectomy in Mild to Moderate Congenital Blepharoptosis.

BACKGROUND: Levator aponeurectomy is a common operation for mild to moderate blepharoptosis. The accuracy of ptosis correction relied on intraoperative judgement when patients were under local anesthesia. For patients who must receive the operation under general anesthesia, it would be an issue to determine how much length of levator aponeurosis to shorten. To solve this issue, we collected data from patients who underwent the operation under local anesthesia and concluded an algorithm. METHODS: This single-center, prospective bivariate regression study allocated patients of mild to moderate congenital blepharoptosis who received levator aponeurectomy under local anesthesia. Preoperative MRD1 and levator function, intraoperative amount of levator aponeurotic shortening, and postoperative MRD1 were measured. The follow-up period was right after the operation. RESULTS: Twenty-nine patients were included in this trial. Two subjects exited because of not receiving allocated operation and data of the other 27 subjects (including 34 eyelids) were analyzed. A scatter diagram was drawn where x axis referred to levator function and y axis referred to the ratio of the amount of shortening of levator aponeurosis over the height of MRD1 correction. Linear regression showed y = - 0.2717*x + 5.026, R2 = 0.8553. CONCLUSION: A modified algorithm to predict the amount of shortening of levator aponeurosis based on levator function and height of ptosis correction was concluded with better accuracy and clinical feasibility. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Musculoaponeurotic architecture of the human masseter muscle: an in vivo ultrasonographic study of architectural changes during mandibular protrusion and lateral excursions.

OBJECTIVE: The present study evaluated the in vivo musculoaponeurotic architecture of the superficial head (SH) of the masseter muscle (MM) of asymptomatic participants in excursive mandibular movements compared to the relaxed state as examined with ultrasonography. It was hypothesized that the mean fiber bundle length (FBL) and mean height of the aponeurosis (HA) of the laminae of the SH would differ significantly between the relaxed state and protrusion, ipsilateral excursion, and contralateral excursion. STUDY DESIGN: The MM was studied volumetrically in 12 female and 12 male asymptomatic participants bilaterally by using ultrasound imaging. Mean FBL and HA in protrusion and ipsilateral and contralateral excursion were compared to these values in the relaxed state using paired t tests (P < .05). The intraclass correlation coefficient was used to assess intraexaminer reliability. RESULTS: The SH exhibited multiple laminae. Fiber bundles were found to attach to bone and the superior and inferior aponeuroses. Mean FBL was significantly shorter and mean HA significantly longer in protrusion and the excursions than in the relaxed state although the pattern of altered laminae and aponeuroses differed among the mandibular movements. Intraexaminer reliability was excellent. CONCLUSION: Specific changes in mean FBL and mean HA suggest differential contraction of the SH of the MM based on laminar morphology. These findings provide a baseline to investigate musculoaponeurotic changes in patients with myogenic masseter muscle pain.

Assessing site-specificity of the biomechanical properties of hamstring aponeuroses using MyotonPRO: A cadaveric study.

BACKGROUND: Hamstring muscles are the most frequently reported sites of muscle strain injuries, especially near the bi-articular muscles' myotendinous junction, where aponeurosis provides a connective tissue network linking muscle fibers to the tendon. This study aimed to investigate the reliability and site-specific differences of hamstring aponeuroses under different conditions (formalin and urea) using MyotonPRO. METHODS: Eight hamstring muscle groups were dissected from four human cadavers (two males and two females) aged 83-93 years. Measurements of the mechanical properties of the aponeuroses from the superficial and deep regions of biceps femoris long head, semitendinosus, and semimembranosus (after formalin solution immersion) were done using MyotonPRO (intra-rater reliability was examined within a 24-h interval), following which the hamstring aponeuroses were measured using a similar procedure after urea solution immersion. FINDINGS: Test-retest (intra-rater) results revealed that the MyotonPRO measurement of tone, stiffness, relaxation, and creep of cadaveric aponeuroses presented good to excellent reliability (ICC: 0.86 to 0.98). There were no significant differences in tone, stiffness, elasticity, relaxation, and creep among the six sites of hamstring aponeuroses under both formalin and urea conditions. Significant differences between formalin and urea conditions were found in the tone, stiffness, relaxation, and creep of hamstring aponeuroses (P < 0.05). INTERPRETATION: These results suggested that the biomechanical properties of hamstring aponeuroses showed homogeneity between the sites using MyotonPRO. Urea solution could potentially neutralize the effect of formalin on the biomechanical properties of cadaveric muscle-aponeurosis-tendon units. The present findings might influence the design of subsequent cadaveric studies on hamstring muscle strains.

Congenital ptosis with aponeurotic maldevelopment: clinical and surgical perspectives : Aponeurotic maldevelopment in congenital ptosis.

PURPOSE: Levator muscle dystrophy has been commonly accused being the main pathology of congenital ptosis, nevertheless, few reports drew attention to the existence of congenital aponeurotic defects. This study aims at highlighting the detailed clinical and surgical features of aponeurotic maldevelopment together with the efficacy of simple aponeurosis repair. METHODS: This is a retrospective nonrandomised study including patients with congenital ptosis who underwent levator muscle surgery throughout 4 years. Patients' records were reviewed for the preoperative clinical assessment and photographs, intraoperative recorded data, and videos as well as postoperative data and photographs. RESULTS: Twenty-seven eyes of 22 patients (9.4%) out of 287 eyes were recorded to have absent levator muscle at its typical anatomical insertion site intraoperatively. The mean preoperative MRD1 was (0.44 ± 1.17 mm). The mean levator function was 8.56 ± 3.89 mm, with higher-than-normal crease position (mean value 10.07 ± 1.62 mm). 25 eyes of included cases (92.6%) showed total absence of the levator aponeurosis edge which only was revealed after cutting through the orbital septal covering of the preaponeurotic fat. CONCLUSION: Congenital aponeurotic defect is an established yet under reported entity of congenital ptosis with reproducible characteristic intraoperative findings. Simple aponeurosis repair could achieve ptosis correction in such cases.

Mechanical Ptosis by Medial Upper Eyelid Fat Prolapse.

Common symptoms of medial fat pad prolapse may include a noticeable bulge in the inner corner of the upper eyelid, puffiness, and a tired or aged appearance. In some cases, this condition may contribute to mechanical ptosis. However, mechanical ptosis caused by medial upper eyelid fat prolapse has not been reported previously. The purpose of the current study is to report the author's experience of successful treatment of ptosis caused by medial upper eyelid fat prolapse in a 67-year-old woman. The patient complained of slowly aggravating asymmetric upper eyelids starting from 5 years ago. At the time of her visit, she had to use her left forehead to open her eyes, making her left eyebrow upwardly positioned. This condition might be related to medial upper eyelid fat prolapse-related mechanical ptosis. The author explored her left upper eyelid with a 9 mm height incision. The author found a substantial amount of medial fat herniation and levator aponeurosis tear. After fat pad removal, the author fixed the levator aponeurosis tear with nylon 6-0, and transdermal sutures were done. The patient was happy with esthetically pleasing results 2 months after the initial surgery. The author successfully treated this rare condition with basic principles, such as fat removal, levator aponeurosis repair, and transdermal sutures.

Influence of muscle length on the three-dimensional architecture and aponeurosis dimensions of rabbit calf muscles.

The function of a muscle is highly dependent on its architecture, which is characterized by the length, pennation, and curvature of the fascicles, and the geometry of the aponeuroses. During in vivo function, muscles regularly undergo changes in length, thereby altering their architecture. During passive muscle lengthening, fascicle length (FL) generally increases and the angle of fascicle pennation (FP) and the fascicle curvature (FC) decrease, while the aponeuroses increase in length but decrease in width. Muscles are differently structured, making their change during muscle lengthening complex and multifaceted. To obtain comprehensive data on architectural changes in muscles during passive length, the present study determined the three-dimensional fascicle geometry of rabbit M. gastrocnemius medialis (GM), M. gastrocnemius lateralis (GL), and M. plantaris (PLA). For this purpose, the left and right legs of three rabbits were histologically fixed at targeted ankle joint angles of 95° (short muscle length [SML]) and 60° (long muscle length [LML]), respectively, and the fascicles were tracked by manual three-dimensional digitization. In a second set of experiments, the GM aponeurosis dimensions of ten legs from five rabbits were determined at varying muscle lengths via optical marker tracking. The GM consisted of a uni-pennated compartment, whereas the GL and PLA contained multiple compartments of differently pennated fascicles. In the LML compared to the SML, the GM, GL, and PLA had on average a 41%, 29%, and 41% increased fascicle length, and a 30%, 25%, and 33% decrease in fascicle pennation and a 32%, 11%, and 35% decrease in fascicle curvature, respectively. Architectural properties were also differentiated among the different compartments of the PLA and GL, allowing for a more detailed description of their fascicle structure and changes. It was shown that the compartments change differently with muscle length. It was also shown that for each degree of ankle joint angle reduction, the proximal GM aponeurosis length increased by 0.11%, the aponeurosis width decreased by 0.22%, and the area was decreased by 0.20%. The data provided improve our understanding of muscles and can be used to develop and validate muscle models.

Orbital septum attachment site on the levator aponeurosis sling for mild congenital blepharoptosis.

PURPOSE: This study aimed to investigate the value of the orbital septum attachment site on the levator aponeurosis (OSASLA) sling in correcting mild congenital blepharoptosis. METHODS: A total of 60 patients (92 eyes) with mild congenital blepharoptosis (levator function ≥ 8 mm) were treated in our hospital from January to October 2021, and relevant data of these patients were collected. All patients underwent OSASLA sling for ptosis correction. The distances from the superior tarsal border to the OSASLA were measured. The primary outcome was the number of postoperative changes in the marginal reflex distance 1 (MRD1). Pearson's correlation coefficient between the distance from the superior tarsal border to the OSASLA and the height of the upper eyelid elevated was analyzed. RESULTS: Fifty-eight patients (89 eyes) successfully underwent OSASLA sling surgery. The preoperative MRD1 was 1.4-3.6 mm (mean 2.1 ± 0.5 mm), and the postoperative MRD1 was 3.4-5.0 mm (mean 3.7 ± 0.6 mm). The distance from the superior tarsal border to the OSASLA sling was significantly and positively correlated with the height of the upper eyelid elevation (r = 0.7328, P < 0.0001). The eyelid margin positions of the patients did not regress substantially during 6-18 months of follow-up. CONCLUSIONS: Compared with the shortening of levator palpebrae superioris (LPS) and pleating of LPS, the OSASLA sling is a less invasive, more effective, and easy-operating surgery for mild congenital blepharoptosis.

Tarsal Buckling and Entropion after Levator Aponeurosis Advancement in Patients with Floppy Eyelid Syndrome.

Two patients with floppy eyelid syndrome presented with severe eye pain and foreign body sensation after recent levator aponeurosis advancement. The examination in both patients was notable for entropion of the upper eyelid, and upper lid eversion revealed deformity of the tarsus in both patients. Surgical revision with full-thickness horizontal tarsotomy and limited excision of the abnormal tarsus corrected the deformity. The authors propose a mechanism for this phenomenon and a modification of surgical technique that may prevent this complication.

Comparisons of the Fusion Point of Orbital Septum and Levator Aponeurosis in Patients with and Without Mild Ptosis.

OBJECTIVE: By comparing the position of the fusion point between the oriental orbital septum and the levator aponeurosis of the upper eyelid in Asian without and with mild ptosis, this study explores the relationship between the fusion point and mild ptosis, providing scientific basis for better utilizing the orbital septum to correct mild ptosis. METHODS: In this study, the outpatients who underwent double eyelid blepharoplasty with incision method in the plastic laser cosmetology department of Hunan Provincial People's Hospital from October 2018 to April 2019 were divided into the normal group and the mild ptosis group. The position of the fusion part of the orbital septum and the aponeurosis of the levator palpebrae superioris was observed in the two groups. There are three types of this position: the height of the fusion part is greater than the width of the tarsal plate, the height of the fusion part is equal to the width of the tarsal plate, and the height of the fusion part is less than the width of the tarsal plate. After the fusion part was exposed during the operation, the width of tarsal plate and the height of fusion part were measured with a scale. The difference of the location of fusion part between the two groups was analyzed. RESULTS: The tarsal plate width was 11.061 ± 0.635 mm in the normal group and 11.062 ± 0.675 mm in the mild ptosis group. There was no significant difference in tarsal plate width between normal group and mild ptosis group (t = 0.645, p = 0.16). The height of the fusion part was 11.032 ± 0.646 mm in the normal group and 11.645 ± 0.429 mm in the mild ptosis group. The fusion position of mild ptosis group was higher than that of normal group (t = 3.769, P < 0.05). There was significant difference in the distribution of fusion site between the two groups (x2 =38.00, P < 0.0001). CONCLUSION: The height of aponeurosis fusion of orbital septum and levator palpebrae superioris in mild ptosis group was higher than that in normal group, which may be the cause of mild ptosis. It is suggested that the appropriate treatment of orbital septum in clinical operation may be effective in the treatment of mild blepharoptosis. LEVEL OF EVIDENCE III: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors https://www.springer.com/00266 .

Outer Fascia of Orbicularis Oculi Muscle (OFOOM)-Orbicularis (OOM)-Aponeurosis Fixation Approach in Double-Eyelid Blepharoplasty Revision.

BACKGROUND: Incisional double-eyelid blepharoplasty is the main surgical technique to obtain an artificial crease. Postoperative complications decrease patients' satisfaction, and patients with prominent depressed groove and persistent pretarsal swelling (sausage phenomenon) usually need revision surgery. To resolve the sausage phenomenon after blepharoplasty, we adopt Outer Fascia of Orbicularis Oculi Muscle (OFOOM)-Orbicularis (OOM)-Aponeurosis Fixation Approach to create natural double eyelids. METHODS: We included 68 patients in the study. The inclusion criteria for revision surgery were as follows: (1) pretarsal OOM remained after primary surgery, (2) prominent depressed surgical scar/groove and persistent pretarsal bulge (sausage phenomenon), (3) postsurgical abnormally wide crease. The surgical procedure involved releasing the pretarsal OOM, forming OFOOM-OOM flap, and OFOOM-OOM flap fixed with aponeurosis. Outcome observations were assessed using the FACE-Q questionnaire, and the follow-up period ranged from 6 to 36 months (mean=18 months). RESULTS: The depressed groove and pretarsal bulge showed significant improvements, and FACE-Q scores of the 68 patients before surgery (mean scores=66) compared with those after surgery (mean scores=90) were significantly different (P<0.01). Four patients with palpebral fold asymmetry and two patients with shallow eyelids received revision surgery, and patients were satisfied with the secondary surgery effects. Six patients presented with unnatural curves of folds and revision surgery alleviated these situations. CONCLUSIONS: Outer Fascia of Orbicularis Oculi Muscle (OFOOM)-Orbicularis (OOM)-Aponeurosis Fixation Approach is an effective way to resolve the sausage phenomenon. The OFOOM-OOM flap is a reliable and flexible structure to create natural double eyelids. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

A Retrospective study of anatomical differences in levator aponeurosis angle and length in East-Asian blepharoplasty.

This study aimed to analyze the anatomical differences in levator aponeurosis angle and length between both sides in double eyelidplasty in East Asians. The retrospective study included patients with mild blepharoptosis who underwent upper blepharoplasty with levator aponeurosis. In the study, 140 patients were enrolled, 126 females and 14 males, with an age range of 16-73 years. The mean levator aponeurosis angle was 19.2 ± 2.9° on the right and 17.0 ± 3.8° on the left, which was significantly different (95% CI, p < 0.001). The mean length was 24.1 mm on the right and 23.2 mm on the left, a difference that was also statistically significant (95% CI, p < 0.001). The relationship between the dominant eye and levator aponeurosis prominence was also investigated, although there was no apparent correlation. Within the limitations of the study, it seems that this is the first study of the anatomical differences of the levator aponeurosis between both sides, leading to a greater predictability of surgery to maximize postoperative symmetry.

Both gastrocnemius aponeurosis flaps and semitendinosus tendon grafts are effective in the treatment of chronic Achilles tendon ruptures - a systematic review.

INTRODUCTION: A chronic Achilles tendon rupture (ATR) is defined as an ATR that has been left untreated for more than four weeks following rupture. This systematic review aims to summarize the outcomes of chronic ATR treated using either a gastrocnemius aponeurosis flap or semitendinosus tendon graft. METHODS: A systematic search was conducted in three databases (PubMed, Scopus and Cochrane), for studies describing outcomes after surgical treatment of chronic ATR using gastrocnemius aponeurosis flaps or semitendinosus tendon grafts with more than 10 patients included. The studies were assessed for quality and risk of bias using the Methodological Items used to assess risk of bias in Non-Randomized Studies (MINORS). RESULTS: Out of the 818 studies identified with the initial search, a total of 36 studies with 763 individual patients were included in this systematic review. Gastrocnemius aponeurosis flap was used in 21 and semitendinosus tendon graft was used in 13 of the studies. The mean (SD) postoperative Achilles tendon Total Rupture Score (ATRS) for patients treated with a gastrocnemius aponeurosis flap was 83 (14) points and the mean (SD) American Orthopaedic Foot and Ankle Score (AOFAS) was 96 (1.7) points compared with ATRS 88 (6.9) points and AOFAS 92 (5.6) points for patients treated with a semitendinosus tendon graft. The included studies generally had low-quality according to MINORS, with a median of 8 (range 2-13) for all studies. CONCLUSION: Both gastrocnemius aponeurosis flaps and semitendinosus tendon grafts give acceptable results with minimal complications and are valid methods for treating chronic ATR. The main difference is more wound healing complications in patients treated with a gastrocnemius aponeurosis flap and more sural nerve injuries in patients treated with a semitendinosus grafts. The current literature on the subject is of mainly low quality and the absence of a patient-related outcome measure validated for chronic ATR makes comparisons between studies difficult. LEVEL OF EVIDENCE: Level IV.

Chronic changes in muscle architecture and aponeurosis structure following calf muscle strain injuries.

BACKGROUND: Muscle strain injuries in the human calf muscles are frequent sports injuries with high recurrence. Potential structural and functional changes in the medial head of the musculus gastrocnemius (GM) and the associated aponeurosis are not well documented. PURPOSE: To test whether a GM muscle strain injury affects muscle fascicle length, pennation angle, and the morphology of the deep aponeurosis at rest and during muscle contraction long time after the injury. Additionally, electromyography (EMG) of the GM and the soleus muscle during a unilateral heel rise was measured in the injured and uninjured calf. METHODS: GM fascicle length, pennation angle, and aponeurosis thickness was analyzed on dynamic ultrasonography (US) recordings in 10 participants with a chronic calf strain. In addition, US images taken across the distal portion and mid-belly of the GM were analyzed at three different ankle positions. EMG recordings were obtained during a unilateral heel rise. RESULTS: The pennation angle of the injured distal GM was significantly larger compared to the uninjured GM in the contracted, but not the relaxed state. Pennation angle increased more in the injured compared to the uninjured GM during contraction. Fascicle length was shorter in the most distal portion of the injured GM. Fascicles at the distal portion of the injured GM showed a pronounced curvilinear shape as the muscle contracted and the aponeurosis was enlarged in the injured compared to the uninjured GM. The ratio between GM and soleus EMG activity showed a significantly higher relative soleus activity in the injured compared to the healthy calf. CONCLUSION: The greater change in pennation angle and curvilinear fascicle shape during contraction suggest that a long-term consequence after a muscle strain injury is that some muscle fibers at the distal GM are not actively engaged. The significantly enlarged aponeurosis indicates a substantial and long-lasting connective tissue involvement following strain injuries.

Sex differences in the kinematics and kinetics of the foot and plantar aponeurosis during drop-jump.

Plantar fasciitis is one of the most common musculoskeletal injuries in runners and jumpers, with a higher incidence in females. However, mechanisms underlying sex-associated differences in its incidence remain unclear. This study investigated the possible differences in landing and jumping kinematics and kinetics of the foot between sexes during drop-jump activities. Twenty-six participants, including 13 males and 13 females, performed drop-jumps from a platform onto force plates. Nineteen trials including ten males and nine females were selected for inverse dynamics analysis. The patterns of stretch and tensile force generated by the plantar aponeurosis (PA) were estimated using a multi-segment foot model incorporating the PA. Our results demonstrated that dorsiflexion, angular velocity, and normalized plantarflexion moment of the midtarsal joint right after the heel landed on the floor were significantly larger in females than in males. Consequently, the PA strain rate and tensile stress tended to be larger in females than in males. Such differences in the kinematics and kinetics of the foot and the PA between sexes could potentially lead to a higher prevalence of foot injuries such as plantar fasciitis in females.

Aponeurosis structure-function properties: Evidence of heterogeneity and implications for muscle function.

Aponeurosis is a sheath-like connective tissue that aids in force transmission from muscle to tendon and can be found throughout the musculoskeletal system. The key role of aponeurosis in muscle-tendon unit mechanics is clouded by a lack of understanding of aponeurosis structure-function properties. This work aimed to determine the heterogeneous material properties of porcine triceps brachii aponeurosis tissue with materials testing and evaluate heterogeneous aponeurosis microstructure with scanning electron microscopy. We found that aponeurosis may exhibit more microstructural collagen waviness in the insertion region (near the tendon) compared to the transition region (near the muscle midbelly) (1.20 versus 1.12, p = 0.055), which and a less stiff stress-strain response in the insertion versus transition regions (p < 0.05). We also showed that different assumptions of aponeurosis heterogeneity, specifically variations in elastic modulus with location can alter the stiffness (by more than 10x) and strain (by approximately 10% muscle fiber strain) of a finite element model of muscle and aponeurosis. Collectively, these results suggest that aponeurosis heterogeneity could be due to variations in tissue microstructure and that different approaches to modeling tissue heterogeneity alters the behavior of computational models of muscle-tendon units. STATEMENT OF SIGNIFICANCE: Aponeurosis is a connective tissue found in many muscle tendon units that aids in force transmission, yet little is known about the specific material properties of aponeurosis. This work aimed to determine how the properties of aponeurosis tissue varied with location. We found that aponeurosis exhibits more microstructural waviness near the tendon compared to near the muscle midbelly, which was associated with differences in tissue stiffness. We also showed that different variations in aponeurosis modulus (stiffness) can alter the stiffness and stretch of a computer model of muscle tissue. These results show that assuming uniform aponeurosis structure and modulus, which is common, may lead to inaccurate models of the musculoskeletal system.

The Isolation, Culture, and Cryopreservation of Human Rectus Sheath Fibroblasts.

The vast majority of pelvic and intra-abdominal surgery is undertaken through at least one incision, through either the linea alba or the rectus sheath. These connective tissue layers are formed from the aponeuroses of the rectus muscles (anterior and posterior rectus sheath) and are vital for the structural integrity of the abdominal wall. Poor healing of these connective tissues after surgery can lead to significant morbidity for patients, who can develop unsightly and painful incisional hernias. Fibroblasts within the rectus sheath are responsible for laying down and remodeling collagen during the healing process after surgery. Despite their importance for this healing process, such cells have not been studied in vitro. In order to carry out such work, researchers must first be able to isolate these cells from human tissue and culture them successfully so they may be used for experimentation. This article provides an extensive and detailed protocol for the isolation, culture, cryopreservation, and thawing of human rectus sheath fibroblasts (RSFs). In our hands, this protocol develops confluent cultures of primary fibroblasts within 2 weeks, and sufficient cultures ready for freezing and storage after a further 2 to 4 weeks. © 2023 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol: Collagenase digestion of human rectus sheath and isolation of RSFs Alternate Protocol: Collagenase digestion of human rectus sheath and isolation of RSFs, digestion in flask Support Protocol: Cryopreservation and thawing of human RSFs.

Bifurcated distal biceps brachii tendon coexisting with separated bicipital aponeurosis: a complex variational case report.

Variations appearing in biceps brachii muscle are common with accessory head, different origins, variant insertion, and different pattern of nerve innervation. However, variations appearing in both origin and insertion, and with other anomalous morphology at the same time are seldom. Here we report a complex variational case on the right arm of a 91-year-old Japanese female cadaver. The complex variations included (1) the biceps brachii muscle bifurcated at its distal ending; (2) the long head had its own tendon, which divided into two parts, i.e., a lateral part fused into the fascia between the brachioradialis and extensor carpi brevis, and a medial part attached to the radius about one centimeter ahead of the radial tuberosity; (3) the short head had an accessory origin from the shoulder capsule; (4) the bicipital aponeurosis was of two parts with an anterior superior layer formed by the long head and a posterior deep one formed by the short head; (5) the musculocutaneous nerve was especially underdeveloped that only innervated the coracobrachialis; (6) the existence of communicating branch between the musculocutaneous and median nerves, and the median nerve issued muscular branches to the biceps brachii and brachialis muscles, and (7) the brachioradial muscle had two accessory muscular bundles that originated from the fascia of the brachial muscle (proximal one) and from the bicipital aponeurosis (distal one).

Regional differences in the mechanical properties of the plantar aponeurosis.

The plantar aponeurosis functions to support the foot arch during weight bearing. Accurate anatomy and material properties are critical in developing analytical and computational models of this tissue. We determined the cross-sectional areas and material properties of four regions of the plantar aponeurosis: the proximal middle and distal middle portions of the tissue and the medial (to the first ray) and lateral (to the fifth ray) regions. Bone-plantar aponeurosis-bone specimens were harvested from fifteen cadaveric feet. Cross-sectional areas were measured using molding, casting, and sectioning methods. Mechanical testing was performed using displacement control triangle waves (0.5, 1, 2, 5, and 10 Hz) loaded to physiologic tension by estimating from body weight and area ratio of the region. Five specimens were tested for each region. Regional deformations were recorded by a high-speed video camera. There were overall differences in cross-sectional areas and biomechanical behavior across regions. The stress-strain responses are non-linear and mainly elastic (energy loss 3.6% to 7.2%). Moduli at the proximal middle and distal middle regions (400 and 522 MPa) were significantly higher than the medial and lateral regions (225 and 242 MPa). The effect of frequency on biomechanical outcomes was small (e.g., 3.5% change in modulus), except for energy loss (107% increase as frequency increased from 0.5 to 10 Hz). These results indicate that the plantar aponeurosis tensile response is non-linear, nearly elastic, and frequency independent. The cross-sectional area and material properties differ by region, and we suggest that such differences be included to accurately model this structure.