Tendones peroneos: una revisión contemporánea / Peroneal tendons. Contemporary update

La patología de peroneos es compleja y frecuentemente subdiagnosticada. El conocimiento detallado de la anatomía, biomecánica y fisiopatología es fundamental para realizar un correcto diagnóstico y tratamiento. El objetivo de este artículo es revisar la información más actualizada sobre la patología de los tendones peroneos (tendinopatía, inestabilidad y rotura).

Pathology of the peroneal tendons is complex and often underdiagnosed. Knowledge of anatomy, biomechanics, and physiopathology is necessary for diagnosing and treating this condition. The objective of this article is to review the most updated information regarding peroneal tendon pathology (tendinopathy, dislocation/subluxation, and tears), which may help managing patients with lateral pain of the foot and ankle.

Tendon Healing in a Mouse Model of Loeys-Dietz Syndrome: Controlled Study Using a Patellar Tendon Transection Model.

BACKGROUND: Loeys-Dietz syndrome (LDS) is a rare autosomal-dominant connective tissue disorder caused by genetic mutations in the transforming growth factor-ß (TGFß) signaling pathway. In addition to vascular malformations, patients with LDS commonly present with bone and tendon abnormalities, including joint laxity. While TGFß signaling dysregulation has been implicated in many of these clinical manifestations, the degree to which it influences the tendinopathy and tendon healing issues in LDS has not been determined. METHODS: Wound healing after patellar tendon transection was compared between wild-type (WT) and Tgfbr2-mutant (LDS) mice (7 mice per group). In all mice, the right patellar tendon was transected at midsubstance, while the left was untouched to serve as a control. Mice were euthanized 6 weeks after surgery. Tendon specimens were harvested for histopathologic grading according to a previously validated scoring metric, and gene expression levels of Mmp2, Tgfb2, and other TGFß-signaling genes were assayed. Between-group comparisons were made using 1-way analysis of variance with post hoc Tukey honestly significant difference testing. RESULTS: Expression levels of assayed genes were similar between LDS and WT tendons at baseline; however, at 6 weeks after patellar tendon transection, LDS tendons showed sustained elevations in Mmp2 and Tgfb2 compared with baseline values; these elevations were not seen in normal tendons undergoing the same treatments. Histologically, untreated LDS tendons had significantly greater cellularity and cell rounding compared with untreated WT tendons, and both WT and LDS tendons had significantly worse histologic scores after surgery. CONCLUSION: We present the first mechanistic insight into the effect of LDS on tendons and tendon healing. The morphologic differences between LDS and WT tendons at baseline may help explain the increased risk of tendon/ligament dysfunction in patients with LDS, and the differential healing response to injury in LDS may account for the delayed healing and weaker repair tissue. LEVEL OF EVIDENCE: Level V.

A Hyperglycemic Microenvironment Inhibits Tendon-to-Bone Healing through the let-7b-5p/CFTR Pathway.

BACKGROUND: Tendon-to-bone healing is a difficult process in treatment of rotator cuff tear (RCT). In addition, diabetes is an important risk factor for poor tendon-to-bone healing. Therefore, we investigated the specific mechanisms through which diabetes affects tendon-to-bone healing by regulating the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR). METHODS: Tendon-derived stem cells (TDSCs) were extracted from rats after which their proliferative capacities were evaluated by the MTT assay. The expression levels of CFTR and tendon-related markers were determined by qRT-PCR. Then, bioinformatics analyses and dual luciferase reporter gene assays were used to identify miRNAs with the ability to bind CFTR mRNA. Finally, CFTR was overexpressed in TDSCs to validate the specific mechanisms through which the high glucose microenvironment inhibits tendon-to-bone healing. RESULTS: The high glucose microenvironment downregulated mRNA expression levels of tendon-related markers and CFTR in TDSCs cultured with different glucose concentrations. Additionally, bioinformatics analyses revealed that let-7b-5p may be regulated by the high glucose microenvironment and can regulate CFTR levels. Moreover, a dual luciferase reporter gene assay was used to confirm that let-7b-5p targets and binds CFTR mRNA. Additional experiments also confirmed that overexpressed CFTR effectively reversed the negative effects of the hyperglycaemic microenvironment and upregulation of let-7b-5p on TDSC proliferation and differentiation. These findings imply that the hyperglycemic microenvironment inhibits CFTR transcription and, consequently, proliferation and differentiation of TDSCs in vitro by upregulating let-7b-5p. CONCLUSIONS: A hyperglycemic microenvironment inhibits TDSC proliferation in vitro via the let-7b-5p/CFTR pathway, and this is a potential mechanism in diabetes-induced poor tendon-to-bone healing.

Eugenol-Preconditioned Mesenchymal Stem Cell-Derived Extracellular Vesicles Promote Antioxidant Capacity of Tendon Stem Cells In Vitro and In Vivo.

Tendon stem cells (TSCs) are often exposed to oxidative stress at tendon injury sites, which impairs their physiological effect as well as therapeutic application. Recently, extracellular vesicles (EVs) derived from bone marrow mesenchymal stem cells (BMSCs) were shown to mediate cell protection and survival under stress conditions. The function of BMSC-EVs may be affected by pretreatment with various factors such as eugenol (EUG)-a powerful antioxidant. In our previous study, we found that H2O2 significantly impaired TSC proliferation and tenogenic differentiation capabilities. Apoptosis and intracellular ROS accumulation in TSCs were induced by H2O2. However, such H2O2-induced damage was prevented by treatment with EUG-BMSC-EVs. Furthermore, EUG-BMSC-EVs activated the Nrf2/HO-1 pathway to counteract H2O2-induced damage in TSCs. In a rat patellar tendon injury model, the ROS level was significantly higher than that in the normal tendon and TSCs not pretreated showed a poor therapeutic effect. However, EUG-BMSC-EV-pretreated TSCs significantly improved tenogenesis and matrix regeneration during tendon healing. Additionally, the EUG-BMSC-EV group had a significantly improved fiber arrangement. Overall, EUG-BMSC-EVs protected TSCs against oxidative stress and enhanced their functions in tendon injury. These findings provide a basis for potential clinical use of EUG-BMSC-EVs as a new therapeutic vehicle to facilitate TSC therapies for tendon regeneration.

Extracorporeal Shockwave Therapy With a Modified Technique on Tendon and Ligament for Knee Osteoarthritis: A Randomized Controlled Trial.

BACKGROUND: There have been no definitive guidelines on the treatment method and specific points in the body. PURPOSE: The aim of the study was to investigate the effects of extracorporeal shockwave therapy on treating the main tendons and ligaments of knee osteoarthritis. METHOD: A total of 36 patients with knee osteoarthritis were enrolled in trial and organized into two groups: 3-wk extracorporeal shockwave therapy for the intervention group and 3-wk sham extracorporeal shockwave therapy for control group. Both groups received the same physical therapies: (1) transcutaneous electrical nerve stimulation, (2) magnetic field treatment, and (3) quadricep muscle strength training. Evaluation was performed before the start of treatment, at third week after the start of treatment, and 1 wk after the end of treatment. The study used randomized controlled trials (level of evidence, 1). RESULT: Eextracorporeal shockwave therapy group had significant improvement in WOMAC pain score, physical function, and total score (mean difference = -2.8, P < 0.001; -5.1, P = 0.02; -8.3, P = 0.004, respectively), Visual Analog Scale score (mean difference = -2.3, P < 0.001), and the distance of 6-min walk test (mean difference = 28.7, P = 0.01) in the 1 wk after the end of treatment. Statistical significance in WOMAC pain, physical function, and total scores (mean difference = -3.0, P = 0.001; -5.6, P = 0.02; -9.3, P = 0.004, respectively) and Visual Analog Scale score (mean difference = -1.2, P = 0.027) was observed between the extracorporeal shockwave therapy group and control group. CONCLUSIONS: Extracorporeal shockwave therapy for the tendons and ligaments has clinical benefits for pain and physical function improvement in knee osteoarthritis. In addition, improvement in physical performance was observed in the short-term follow-up.

Circular RNA PVT1 inhibits tendon stem/progenitor cell senescence by sponging microRNA-199a-5p.

Tendon stem/progenitor cell (TSPC) senescence can lead to age-dependent tendon maladies and undermines both tendon repair and replacement capacity in humans. The mechanisms underlying TSPC senescence and sensitivity to adverse factors are complicated. In this study, we analyzed involvement of the circular RNA (circRNA) PVT1 (circPVT1) in TSPC senescence. circPVT1 expression was found to be significantly diminished in human TSPCs under prolonged in vitro culture. Accordingly, circPVT1 knockdown promoted senescence progression and suppressed self renewal, migration, and tenogenic differentiation of TSPCs. Furthermore, we found that circPVT1 directly targets microRNA (miR)-199a-5p thereby attenuating its negative regulation of SIRT1 expression. Either miR-199a-5p inhibition or SIRT1 overexpression attenuated the senescence-boosting effect of circPVT1 knockdown, implying that circPVT1 suppresses TSPC senescence in part by upregulating the miR-199a-5p-SIRT1 signaling axis. Our findings conclusively explain the major roles of circPVT1 in TSPC senescence regulation; circPVT1 is a novel potential therapeutic target for reducing tendon senescence.

The Impact of Hyaluronic Acid on Tendon Physiology and Its Clinical Application in Tendinopathies.

The physical-chemical, structural, hydrodynamic, and biological properties of hyaluronic acid within tendons are still poorly investigated. Medical history and clinical applications of hyaluronic acid for tendinopathies are still debated. In general, the properties of hyaluronic acid depend on several factors including molecular weight. Several preclinical and clinical experiences show a good efficacy and safety profile of hyaluronic acid, despite the absence of consensus in the literature regarding the classification according to molecular weight. In in vitro and preclinical studies, hyaluronic acid has shown physical-chemical properties, such as biocompatibility, mucoadhesivity, hygroscopicity, and viscoelasticity, useful to contribute to tendon healing. Additionally, in clinical studies, hyaluronic acid has been used with promising results in different tendinopathies. In this narrative review, findings encourage the clinical application of HA in tendinopathies such as rotator cuff, epicondylitis, Achilles, and patellar tendinopathy.

Absent pyramidal eminence and stapedial tendon associated with congenital stapes footplate fixation: Intraoperative and radiographic findings.

OBJECTIVE: Report an association between congenital stapes footplate fixation (CSFF) and radiological absence of the pyramidal eminence and stapedial tendon. PATIENTS: Children and adults with intraoperatively confirmed CSFF and an absent stapedial tendon. INTERVENTIONS: Computed tomography (CT); exploratory tympanotomy with stapedotomy. MAIN OUTCOME MEASURES: Absence of a pyramidal eminence and stapedial tendon aperture identified on preoperative CT that was confirmed intraoperatively. RESULTS: Eight patients with intraoperative confirmation of CSFF and absent stapedial tendon were retrospectively identified. The average preoperative bone conduction and air conduction pure tone averages were 19.6 dB (SD 15.6 dB) and 55.9 dB (SD 23.6 dB), respectively. The average air-bone gap was 36.3 dB (SD 17.9 dB) preoperatively. In the seven patients who underwent preoperative CT, all were consistently identified to have an absent or hypoplastic pyramidal eminence and absent stapedial tendon aperture at the pyramidal eminence. In six cases, the stapedial footplate appeared normal, while in one case the footplate appeared abnormal which correlated with severe facial nerve prolapse observed intraoperatively. All eight cases underwent exploratory tympanotomy and demonstrated intraoperative stapes footplate fixation, absent stapedial tendon and either absent or hypoplastic pyramidal eminence, which correlated with preoperative CT findings. CONCLUSIONS: This study identifies a clinically pragmatic association between an absent pyramidal eminence identified on high-resolution CT and the diagnosis of CSFF. In a condition that otherwise generally lacks distinctive radiological features, the absence of a pyramidal eminence on CT in a patient with nonprogressive, congenital conductive hearing loss may strengthen clinical suspicion for CSFF.

The Subtle Cavovarus Foot Deformity: The Nonneurologic Form of Cavus Foot Deformity.

Conditions of ankle instability, peroneal tendon tears, and stress fractures of the lateral metatarsals are commonly encountered in a clinical foot and ankle practice. Evaluation of the supporting foot structure is critical to prevent failure of index procedures. The prominence of the subtle cavus foot is now a recognized entity and must be properly diagnosed and addressed surgically.

Brown syndrome: clinical features and results of superior oblique tenotomy / Síndrome de Brown: quadro clínico e resultados da tenectomia do oblíquo superior

ABSTRACT Purpose: This study was conducted to further define the specific clinical characteristics of patients with Brown syndrome and evaluate the outcomes of superior oblique tenotomy in its surgical management. Methods: A retrospective analysis of the medical charts of 45 patients with Brown syndrome was performed, which revealed that 11 patients underwent superior oblique tenotomy due to abnormal head posture and/or hypotropia and 1 patient underwent bilateral superior oblique tendon elongation with a silicone band due to abnormal head posture. In the last patient, silicone bands were removed at the postoperative 3rd month due to the lack of improvement in the abnormal head posture and the limitation of elevation in adduction. Simultaneous horizontal rectus muscle surgery was performed in four patients. Results: There was a predominance of female gender, right eye, congenital form, unilaterality, A-pattern, and an abnormal head posture type with a combination of chin up and head tilting. Bilateral form was observed only in female patients. Amblyopia was detected in two patients. Among patients aged >5 years, 40% had reduced stereopsis. Abnormal head posture was found in 60% of patients. More than half of them were diagnosed with a vertical and/or horizontal deviation. Tenotomy procedure eliminated the abnormal head posture in all patients and significantly improved the mean limitation of elevation in adduction and hypotropia (p=0.001, p=0.012). Two patients developed inferior oblique overaction in the operated eye. There was complete spontaneous resolution in two patients. Conclusions: The clinical features of patients with Brown syndrome in our study are considerably consistent with those of previous reports. The present study demonstrated the effectiveness of superior oblique tenotomy with less overcorrection in the surgical treatment of Brown syndrome.(AU)

RESUMO Objetivo: Definir mais detalhadamente as características clínicas específicas de pacientes com síndrome de Brown e avaliar os resultados da tenectomia do músculo oblíquo superior no manejo cirúrgico da síndrome de Brown. Métodos: Prontuários de 45 pacientes com síndrome de Brown foram analisados retrospectivamente. Onze pacientes submetidos à tenectomia do músculo oblíquo superior devido a postura anormal da cabeça ou a hipotropia e um paciente submetido ao alongamento bilateral do tendão do oblíquo superior com uma faixa de silicone devido a postura anormal da cabeça. Neste último paciente, a faixa de silicone foi removida no terceiro mês pós-operatório devido à ausência de melhora na postura anormal da cabeça e à limitação da elevação em adução. Quatro pacientes submeteram-se simultaneamente à cirurgia do músculo reto horizontal. Resultados: Houve predominância de sexo feminino, olho direito, forma congênita, acometimento unilateral, padrão em "A" e um tipo de postura anormal da cabeça combinando queixo elevado e inclinação da cabeça. A forma bilateral foi vista apenas em pacientes do sexo feminino. Foi constatada ambliopia em 2 pacientes. Dentre os pacientes acima de 5 anos de idade, 40% tinham estereopsia reduzida. Postura anormal da cabeça estava presente em 60% dos pacientes. Mais da metade dos pacientes foi diagnosticada com um desvio vertical, horizontal ou ambos. O procedimento de tenectomia eliminou a postura anormal da cabeça em todos os pacientes e melhorou significativamente a limitação média da elevação em adução e a hipotropia (p=0,001 e p=0,012). Dois pacientes desenvolveram hiperação do músculo oblíquo inferior no olho operado. Resolução completa ocorreu espontaneamente em 2 pacientes. Conclusões: O quadro clínico dos pacientes com síndrome de Brown no nosso estudo é bastante consistente com os relatos iniciais na literatura. Este estudo mostrou a eficácia da tenectomia do oblíquo superior, com menor hipercorreção no tratamento cirúrgico da síndrome de Brown.(AU)

Risk Factors for Anterior Tibial Tendon Pathology.

BACKGROUND: Though the tibialis anterior (TA) serves a vital role in ankle dorsiflexion, there is little information regarding risk factors and demographic information that might predispose one to tendinopathy or rupture. This study investigates the features of patients in a single institution who presented with either TA tendinopathy or rupture. The circumstances surrounding rupture were also noted. METHODS: ICD-9/10 codes were used to find patients who presented with TA pathology to 2 foot and ankle surgeons at 1 academic medical center from 2011 to 2018. Patient characteristics were noted, including age, sex, body mass index, and the presence of a gastrocnemius equinus contracture. Characteristics of patients with traumatic and atraumatic ruptures were compared. RESULTS: Ninety-four patients presented between 2011 and 2018 (79 cases of tendinopathy and 15 ruptures). The average patient age was 56 years, and the ratio of women to men was 74:20 (3.7:1). With regard to those who experienced rupture, there were 2 ruptures directly related to athletic activity (traumatic), whereas 13 ruptures were found on examination with no overt history of injury (atraumatic). The average age for patients with traumatic ruptures was 39 years compared with 73 years for those with atraumatic rupture (P < .05). CONCLUSION: This study investigates the features of patients in a single institution who presented with TA pathology. With regard to tendon ruptures, traumatic ruptures tend to occur in younger patients, whereas older patients are more likely to suffer atraumatic ruptures. Nonoperative treatment often appears to be effective for TA pathology. LEVEL OF EVIDENCE: Level III, retrospective comparative series.

The effect of the platelet-rich plasma and ozone therapy on tendon-to-bone healing in the rabbit rotator cuff repair model.

BACKGROUND: The aim of this study is to histologically and biomechanically investigate the effects of local PRP and ozone therapy (O2O3) on tendon-to-bone healing in a rabbit model of the supraspinatus tendon tear. METHODS: Four groups were formed to have seven rabbits in each group: repair, R; repair + PRP, RP; repair + ozone, RO; and repair + PRP + ozone, RPO. The supraspinatus tendon was detached by sharp dissection from the footprint and an acute tear pattern was created. Thereafter, tendon repair was performed with the transosseous technique. In the RP group, PRP, and in the RPO group, PRP + O2O3 mixture was injected to the tendon repair site. In the RO group, O2O3 gas mixture was injected into subacromial space three times a week for a total of 4 weeks. The study was ended at postoperative 6th week. RESULTS: When compared with the R group, a statistically significant increase was observed in the biomechanical strength of the RP and RPO groups. The highest increase in biomechanical strength was detected in the RPO group. The histology of the RO and RPO groups showed better collagen fiber continuity and orientation than the R and RP groups. CONCLUSIONS: The results obtained from this study show that the ozonized PRP can be used as biological support to increase tendon-to-bone healing. However, these results need to be supported by clinical studies.

Wrist Contracture Caused by Adhesion of the Extensor Carpi Radialis Tendon after Distal Radius Fracture: A Case Report.

Although distal radius fractures are common, wrist contracture caused by an extra-articular lesion after a distal radius fracture is seldom reported. We report a rare case of wrist contracture caused by adhesion of extensor carpi radialis brevis (ECRB) tendon after distal radius fracture. The patient was successfully treated with tenolysis of the ECRB tendon.

Tendon release reduced joint stiffness with unaltered leg stiffness during gait in spastic diplegic cerebral palsy.

Biomechanical deviations at individual joints are often identified by gait analysis of patients with cerebral palsy (CP). Analysis of the control of joint and leg stiffness of the locomotor system during gait in children with spastic diplegic CP has been used to reveal their control strategy, but the differences between before and after surgery remain unknown. The current study aimed to bridge the gap by comparing the leg stiffness-both skeletal and muscular components-and associated joint stiffness during gait in 12 healthy controls and 12 children with spastic diplegic CP before and after tendon release surgery (TRS). Each subject walked at a self-selected pace on a 10-meter walkway while their kinematic and forceplate data were measured to calculate the stiffness-related variables during loading response, mid-stance, terminal stance, and pre-swing. The CP group altered the stiffness of the lower limb joints and decreased the demand on the muscular components while maintaining an unaltered leg stiffness during stance phase after the TRS. The TRS surgery improved the joint and leg stiffness control during gait, although residual deficits and associated deviations still remained. It is suggested that the stiffness-related variables be included in future clinical gait analysis for a more complete assessment of gait in children with CP.

Muscle-tendon unit in children with cerebral palsy.

Muscle-tendon unit surgery for correction of deformities and movement dysfunction in children with cerebral palsy (CP) is fairly complicated. An understanding of basic muscle-tendon unit properties and their adaptation to both CP and surgery are important to develop advances in this field. In this review, we provide information to therapists, surgeons, and scientists regarding the short- and long-term adaptations of the muscle-tendon unit. Surgical releases, lengthening, and transpositions are discussed, as are some of the tissue, cellular, and molecular adaptations. What this paper adds Muscle strength, tone, and control must be considered in surgical interventions for cerebral palsy (CP). Muscle-tendon unit lengthening causes significant and lasting weakness requiring prolonged rehabilitation. Sarcomere length increases in CP muscle may be one of the underlying causes of muscle weakness. Muscle satellite cells are decreased and epigenetically modified in a way that may limit muscle growth in CP.

Navicular Syndrome-related changes to collagen proportion of different cross-sections of the flexor tendons in equine distal forelimb.

The aim of this study was to quantify the distribution of aligned and non-aligned collagen in cross-sections of the superficial digital flexor tendon (SDFT) and deep digital flexor tendon (DDFT) in different levels of the distal forelimb of equines diagnosed with NS (Navicular Syndrome). Sixty equine forelimbs were collected. Was compared two groups (NA, Not affected vs. NS-group) by t-Student. Diagnosis of NS was based on clinical and lameness examination, diagnostic analgesia and radiological findings. The proportion of aligned and non-aligned collagens at 2 levels for the SDFT and 3 levels for the DDFT were measured by histochemical stains. The amount of aligned and non-aligned collagen in tendons were calculated using Colour-Based Segmentation function. Regarding collagen, there were significant differences in the amount of aligned collagen (NA: 21.2 ± 1.31; NS-group: 12.2 ± 4.67; p = 0.0026) and non-aligned collagen (NA: 21.8 ± 2.22; NS: 25.1 ± 1.73; p = 0.0241) at the DDFT insertion in the distal phalanx. We concluded that the flexor tendons of the forelimb in equines with NS have different proportions of collagen than those that do not present the diagnosis, indicated by histologically visible increased proportions of non-aligned collagen and decreased of aligned collagen in the extracellular matrix.

Is there a relationship between muscle-tendon properties and a variety of functional tasks in children with spastic cerebral palsy?

BACKGROUND: Cerebral palsy (CP) is the most common motor and movement disability in childhood. The mechano-morphological alterations of the spastic muscle itself as well as the functional limitations in CP are well documented. However, the relationship between muscle tendon properties and functional tests in CP remains unknown. RESEARCH QUESTION: The aim of this study was to explore the relationship between spastic muscle mechano-morphological properties and functional performance in children with CP. METHODS: This study included retrospective data from 22 children with spastic cerebral palsy with a mean age of 12.8 years (19 GMFCS I/3 GMFC II, 15 male/7 female, 8 unilateral involved/14 bilateral). Mechano-morphological properties of gastrocnemius (GM) and Achilles tendon (AT) were correlated with a variety of functional measures, maximal isometric strength, the Muscle Power Sprint test (MPST), 6-minute walk test (6MWT) and 3D-gait analysis using the Pearson Coefficient. RESULTS: Muscle-tendon properties were normalized to remove anthropometric dimensions because of strong associations with anthropometric data. Higher isometric muscle strength was related to longer normalized GM fascicle lengths (r = 0.67, p < 0.01). The distance reached in the 6MWT positively correlated with normalized GM fascicle lengths (r = 0.61, p < 0.01). Higher AT stiffness was associated with faster performance in the MPST (r = 0.77, p < 0.01). Finally, there was an association between ankle power and both longer normalized AT length and shorter muscle belly (r = 0.60 and r = 0.54, p < 0.01). SIGNIFICANCE: The findings of this study give more insight into the function specific adaptations of a spastic muscle-tendon unit. While walking, assessed through the 6MWT, was related to normalized gastrocnemius fascicle length, sprint performance was associated with an increased AT stiffness. These results provide a better understanding of the relationship between functional tasks and spastic muscle-tendon properties, which offers potential for improved and targeted interventions in CP.

Dysregulated assembly of elastic fibers in fibulin-5 knockout mice results in a tendon-specific increase in elastic modulus.

Elastic fiber assembly is coordinated in part by fibulin-5, a matricellular protein. When fibulin-5 is not available to guide elastogenesis, elastin forms into disconnected globules instead of the dense elastic fiber core found in healthy tissues. Despite the growing evidence for a significant role of elastic fibers in tendon mechanics and the clinical relevance to cutis laxa, a human disease which can be caused by a mutation in the gene encoding fibulin-5, it is unknown how malformed elastic fibers affect tendon function. Therefore, this study investigated the effects of dysregulated elastic fiber assembly in tendons from fibulin-5 knockout mice in comparison to wild-type controls. Due to evidence for a more prominent role of elastic fibers in tendons with higher functional demands, both the energy-storing Achilles tendon and the more positional tibialis anterior tendon were evaluated. The linear modulus of knockout Achilles tendons was increased compared to controls, yet there was no discernible change in mechanical properties of the tibialis anterior tendon across genotypes. Transmission electron microscopy confirmed the presence of malformed elastic fibers in knockout tendons while no other changes to tendon composition or structure were found. The mechanism behind the increase in linear modulus in fibulin-5 knockout Achilles tendons may be greater collagen engagement due to decreased regulation of strain-induced structural reorganization. These findings support the theory of a significant, functionally distinct role of elastic fibers in tendon mechanics.

Short-term neuromuscular, morphological, and architectural responses to eccentric quasi-isometric muscle actions.

PURPOSE: Eccentric quasi-isometric (EQI) contractions have been proposed as a novel training method for safely exposing the musculotendinous system to a large mechanical load/impulse, with few repetitions. However, understanding of this contraction type is rudimentary. We aimed to compare the acute effects of a single session of isotonic EQIs with isokinetic eccentric (ECC) contractions. METHODS: Fifteen well-trained men performed a session of impulse-equated EQI and ECC knee extensions, with each limb randomly allocated to one contraction type. Immediately PRE, POST, 24/48/72 h, and 7 days post-exercise, regional soreness, quadriceps swelling, architecture, and echo intensity were evaluated. Peak concentric and isometric torque, rate of torque development (RTD), and angle-specific impulse were evaluated at each time point. RESULTS: There were substantial differences in the number of contractions (ECC: 100.8 ± 54; EQI: 3.85 ± 1.1) and peak torque (mean: ECC: 215 ± 54 Nm; EQI: 179 ± 28.5 Nm). Both conditions elicited similar responses in 21/53 evaluated variables. EQIs resulted in greater vastus intermedius swelling (7.1-8.8%, ES = 0.20-0.29), whereas ECC resulted in greater soreness at the distal and middle vastus lateralis and distal rectus femoris (16.5-30.4%, ES = 0.32-0.54) and larger echogenicity increases at the distal rectus femoris and lateral vastus intermedius (11.9-15.1%, ES = 0.26--0.54). Furthermore, ECC led to larger reductions in concentric (8.3-19.7%, ES = 0.45-0.62) and isometric (6.3-32.3%, ES = 0.18-0.70) torque and RTD at medium-long muscle lengths. CONCLUSION: A single session of EQIs resulted in less soreness and smaller reductions in peak torque and RTD versus impulse-equated ECC contractions, yet morphological shifts were largely similar. Long-term morphological, architectural, and neuromuscular adaptations to EQI training requires investigation.

The quadriceps insertion of the medial patellofemoral complex demonstrates the greatest anisometry through flexion.

PURPOSE: A comprehensive understanding of the biomechanical properties of the medial patellofemoral complex (MPFC) is necessary when performing an MPFC reconstruction. How components of the MPFC change over the course of flexion can influence the surgeon's choice of location for graft fixation along the extensor mechanism. The purpose of this study was to (1) determine native MPFC length changes throughout a 90° arc using an anatomically based attachment and using Schöttle's point, and (2) compare native MPFC length changes with different MPFC attachment sites along the extensor mechanism. METHODS: Eight fresh-frozen (n = 8), cadaveric knees were dissected of all soft tissue structures except the MPFC. The distance between the femoral footprint (identified through anatomical landmarks and Schottle's point) and the MPFC was calculated at four attachment sites along the extensor mechanism [midpoint of the patella [MP], the center of the osseous footprint of the MPFC (FC), the superomedial corner of the patella at the quadriceps insertion (SM), and the proximal extent of the MPFC along the quadriceps tendon (QT)] at 0°, 20°, 40°, 60°, and 90° of flexion. RESULTS: Length changes were investigated between the MPFL femoral attachment site and the radiographic surrogate of the MPFL attachment site, Schottle's Point (SP). Paired t tests at each of the four components showed no differences in length change from 0° to 90° when comparing SP to the anatomic MPFC insertion. MPFL length changes from 0° to 90° were greatest at the QT point (13.9 ± 3.0 mm) and smallest at the MP point (2.7 ± 4.4 mm). The FC and SM points had a length change of 6.6 ± 4.2 and 9.0 ± 3.8, respectively. Finally, when examining how the length of the MPFC components changed through flexion, the greatest differences were seen at QT where all comparisons were significant (p < 0.01) except when comparing 0° vs 20° (n.s.). CONCLUSION: The MPFC demonstrates the most significant length changes between 0° and 20° of flexion, while more isometric behavior was seen during 20°-90°. The attachment points along the extensor mechanism demonstrate different length behaviors, where the more proximal components of the MPFC display greater anisometry through the arc of motion. When performing a proximal MPFC reconstruction, surgeons should expect increased length changes compared to reconstructions utilizing distal attachment sites.