Flexor Digitorum Longus Tendon Research Articles

Presoaking Grafts in Vancomycin Does Not Impair Graft-Bone Healing in a Rat Anterior Cruciate Ligament Reconstruction Model.

The vancomycin presoaking technique (wherein grafts are treated with a vancomycin solution [VS] for anterior cruciate ligament reconstruction [ACLR]) reduces the infection rate after ACLR. However, the effects of this technique on graft-bone healing have not been fully elucidated. To investigate the effects of vancomycin presoaking on graft-bone healing in a rat ACLR model. Controlled laboratory study. Long flexor digitorum longus tendons were obtained from 9 Wistar rats, and each was randomly allocated to the normal saline (NS) or VS groups. The grafts were immersed in sterile saline for 30 minutes in the NS group and in a 5-mg/mL VS in the VS group. The presence of time-zero graft bacterial contamination was confirmed, and the grafts were incubated in Fluidised Thioglycollate Broth for 2 weeks. ACLR was performed on the right knees of 65 male Wistar rats using the flexor digitorum longus tendons. Each graft was similarly treated. Biomechanical testing, micro-computed tomography, and histological evaluations were performed 4 and 12 weeks postoperatively. The VS group showed significantly reduced graft contamination at time zero (P = .02). The mean maximum loads to failure were 13.7 ± 8.2 N and 11.6 ± 4.8 N in the NS and VS groups, respectively, at 4 weeks (P = .95); and 23.2 ± 13.2 N and 30.4 ± 18.0 N in the NS and VS groups, respectively, at 12 weeks (P = .35). Regarding micro-computed tomography, the mean bone tunnel volumes were 3.76 ± 0.48 mm3 and 4.40 ± 0.58 mm3 in the NS and VS groups, respectively, at 4 weeks (P = .41); and 3.51 ± 0.38 mm3 and 3.67 ± 0.35 mm3 in the NS and VS groups, respectively, at 12 weeks (P = .54). Histological semiquantitative examination revealed no clear between-group differences at any time point. Presoaking grafts in vancomycin in a rat ACLR model demonstrated no discernible adverse effects on short- and midterm biomechanical, radiological, and histological investigations. The findings provide guidance for surgeons when considering this technique.

Localization of advanced glycation end-products and their receptor in tendinopathic lesions.

This study was designed to investigate the accumulation of advanced glycation end-products (AGEs) and the expression of the receptor of AGEs (RAGE) in tendinopathic tissues. In this study, tendinopathic posterior tibial tendons (PTT) were collected from patients (n=6). Redundant autografts of flexor digitorum longus tendon (FDL; n=3) were used for controls. The control and tendinopathic tendon tissues were used for extraction of proteins for western blot and sectioned for histology and immunohistochemistry. Tendinopathy of the PTT was confirmed histologically by the presentation of disorderly organized collagen fibers, high cellularity and increased vascularity. By immunohistochemistry, heterogeneous accumulation of AGEs was detected on the PTT sections and concentrated in areas, where collagen fibers were disorderly and tangled. In the PTT, roundish tenocytes were also AGEs-positive. In contrast, AGEs were diffuse, lightly stained in the FDL. A greater number of tenocytes within the tendinopathic lesions in the PTT were RAGE positive, compared to the tenocytes in the FDL. Western blot confirmed the expression of AGEs and RAGE in both tendinopathic PTT and control FDL but their band densities were not significantly different. The spatial relation of the accumulated AGEs and RAGE- positive tenocytes within the tendinopathic lesions indicates their involvement in the molecular pathology of tendinopathy.

Treatment of Dynamic Claw Toe Deformity Through Lengthening of the Flexor Tendons of the Hallux and Toes at the Midfoot Level.

The claw toe deformity is characterized by the flexion of interphalangeal joints (IPJs) with hyperextension of the metatarsophalangeal (MTP) joint. It can be flexible and reducible or rigid and irreducible, or dynamic. The most common cause of dynamic claw toes is a neurological disorder, like sequelae of an ischemic contracture of the muscle belly after a compartment syndrome. Most of the surgical techniques require multiple procedures and may be associated with complications such as toe stiffness, persisting metatarsalgia, and toe malalignment. The aim of this study is to present an option for the surgical treatment of the dynamic claw toe deformity, by simultaneous tenodesis and lengthening of the flexor hallucis longus (FHL) and flexor digitorum longus (FDL) tendons at Henry's knot through a single midfoot incision.Levels of Evidence: V; Therapeutic Study; Expert Opinion.

Release of retromalleolar flexor retinaculum and combined flexor digitorum longus and flexor hallucis longus Z-plasty in checkrein deformity: a case report

BackgroundCheckrein deformity is a rare abnormality comprising flexor hallucis longus (FHL) tendon entrapment in the posterior foot due to post-traumatic or ischemic retraction of the FHLtendon following soft tissue trauma. The diagnosis is essentially clinical, but complemented by imaging to rule out unrecognized causes and evaluate the fracture healing process. This case report is the first Indonesian study to describe release of the flexor retinaculum and Z-plasty (lengthening) of flexor digitorum longus (FDL) and FHL tendons through a medial retromalleolar approach to repair the deformity. Case DescriptionWe present the case of a 51-year-old male who complained of clawing of his right first and second toes. The interest of this study lies in the fact that this patient had never experienced ankle or distal tibial fractures, only a trivial injury two years back when the patient kicked a stone at work and had a bruise on his right second toe with no fracture. Exploration of FHL tendons was performed at the level of the midfoot. The patient was planned for surgery with a medial retromalleolar ankle approach, which facilitates the release of the flexor retinaculum, in conjunction with a Z-tenotomy on the FHL and FDL tendons. ConclusionA correction was achieved, and two months post-surgery there were no recurrences of the deformity. However, this surgical procedure requires more cases to support an evaluation of its effectiveness. We suggest that exploration at the ankle and midfoot should be the primary surgical intervention in similar cases of checkrein deformity.

Aged tendons lack adaptive response to acute compressive injury.

Rotator cuff tendinopathy has a multifactorial etiology, with both aging and external compression found to influence disease progression. However, tendon's response to these factors is still poorly understood and in vivo animal models make it difficult to decouple these effects. Therefore, we developed an explant culture model that allows us to directly apply compression to tendons and then observe their biological responses. Using this model, we applied a single acute compressive injury to C57BL/6J flexor digitorum longus tendon explants and observed changes in viability, metabolic activity, matrix composition, matrix biosynthesis, matrix structure, gene expression, and mechanical properties. We hypothesized that a single acute compressive load would result in an injury response in tendon and that this effect would be amplified in aged tendons. We found that young tendons had increased matrix turnover with a decrease in small leucine-rich proteoglycans, increase in compression-resistant proteoglycan aggrecan, increase in collagen synthesis, and an upregulation of collagen-degrading MMP-9. Aged tendons lacked any of these adaptive responses and instead had decreased metabolic activity and collagen synthesis. This implies that aged tendons lack the adaptation mechanisms required to return to homeostasis, and therefore are at greater risk for compression-induced injury. Overall, we present a novel compressive injury model that demonstrates lasting age-dependent changes and has the potential to examine the long-term response of tendon to a variety of compressive loading conditions.

Experimental study on the mechanical properties and thermal damage of laser welding the ruptured flexor digitorum longus tendons.

To investigate the influence of laser parameters on the performance of tendon tissue, experiments were conducted and the process of laser-assisted tendon welding was studied. Several conclusions were drawn by analyzing the effects of laser parameters on the tensile strength, microstructure, and collagen content of tendon tissue incisions. The optimal parameters for laser welding tendon tissue were found to be a laser power of 5 W, a scanning speed of 150 mm/s, and a defocus amount of 0 mm, resulting in a laser energy density of 32.164 J/cm2 . At these parameters, the percentage of inactivated cells due to thermal damage was only 23.78%, and the tensile strength of the tendon tissue incisions reached 0.61 MPa. Additionally, the collagen content around the incision was measured to be 33.679%, composed of type I and type III collagens, with the latter accounting for 50.714% of the total collagen content.

Remnant tissue enhances early postoperative biomechanical strength and infiltration of Scleraxis-positive cells within the grafted tendon in a rat anterior cruciate ligament reconstruction model

When ruptured, ligaments and tendons have limited self-repair capacity and rarely heal spontaneously. In the knee, the Anterior Cruciate Ligament (ACL) often ruptures during sports activities, causing functional impairment and requiring surgery using tendon grafts. Patients with insufficient time to recover before resuming sports risk re-injury. To develop more effective treatment, it is necessary to define mechanisms underlying ligament repair. For this, animal models can be useful, but mice are too small to create an ACL reconstruction model. Thus, we developed a transgenic rat model using control elements of Scleraxis (Scx), a transcription factor essential for ligament and tendon development, to drive GFP expression in order to localize Scx-expressing cells. As anticipated, Tg rats exhibited Scx-GFP in ACL during developmental but not adult stages. Interestingly, when we transplanted the flexor digitorum longus (FDP) tendon derived from adult Scx-GFP+ rats into WT adults, Scx-GFP was not expressed in transplanted tendons. However, tendons transplanted from adult WT rats into Scx-GFP rats showed upregulated Scx expression in tendon, suggesting that Scx-GFP+ cells are mobilized from tissues outside the tendon. Importantly, at 4 weeks post-surgery, Scx-GFP-expressing cells were more frequent within the grafted tendon when an ACL remnant was preserved (P group) relative to when it was not (R group) (P vs R groups (both n = 5), p<0.05), and by 6 weeks, biomechanical strength of the transplanted tendon was significantly increased if the remnant was preserved (P vsR groups (both n = 14), p<0.05). Scx-GFP+ cells increased in remnant tissue after surgery, suggesting remnant tissue is a source of Scx+ cells in grafted tendons. We conclude that the novel Scx-GFP Tg rat is useful to monitor emergence of Scx-positive cells, which likely contribute to increased graft strength after ACL reconstruction.

"Biological Fixation" of Flexor Digitorum Longus: A New Modification of Tendon Transfer for Treatment of Posterior Tibialis Tendon Dysfunction.

Numerous surgical procedures for the treatment of posterior tibialis tendon (PTT) dysfunction have been developed, including tendon transfers, osteotomies, and arthrodesis. Among these methods, foot and ankle surgeons most frequently use flexor digitorum longus (FDL) tendon transfer in conjunction with medial translational osteotomy of the calcaneus. Formerly, some less invasive techniques have been described to reduce surgical-related complications after FDL tendon transfer. Herein, we introduced a new modification of short-stump FDL tendon fixation to the navicular bone and reported the functional outcomes of the current technique in a patient with PTT dysfunction. In the current technique, the FDL tendon was fixed to the navicular bone via a trans-osseous tunnel using a split PTT stump. This method does not require any kind of fixation devices, such as an interference screw or anchor suture.Level of Evidence: V.

Exploring morphological variations and clinical significance of interconnections between flexor hallucis longus and flexor digitorum longus tendons

BackgroundThe tendons of the flexor hallucis longus (FHL) and flexor digitorum longus (FDL) are commonly utilized in reconstructive foot surgery to address deformities. These tendons intersect on the plantar surface and exhibit varying interconnections that can significantly impact graft length and complicate the tendon harvesting process. The objective of this study was to comprehensively categorize these interconnections using a modified classification system and precisely determine their positional relationships with surgically significant bony landmarks. MethodsSixty embalmed feet of 30 cadavers were studied to analyze the interconnections between FHL and FDL in the planta pedis, classify them in a modified classification system and measure distances to surgically relevant anatomic landmark. ResultsThe study revealed three primary types of interconnections. Type I, representing a proximal-to-distal connection from the FHL to the FDL, was observed in 85% of the feet. Type II, signifying a proximal-to-distal connection from the FDL to the FHL, was found in 11.66% of the feet. Type III, characterized by a crossed connection, was identified in 3.33% of the feet. The average point of branching for the FHL and FDL tendons was situated 4.5 cm and 3.5 cm distal to the navicular tuberosity, respectively. ConclusionThe presence of atypical proximal-to-distal interconnections from the FHL to the FDL may play a role in preserving residual function in the lesser toes following FDL transfer procedures. Awareness of anatomical variations in the location of these interconnections is crucial for preserving them during surgical interventions, ultimately mitigating the risk of functional impairment in the lateral toes post-tendon grafting.

Proximity of percutaneous tibial nerve stimulation needle insertion to surrounding anatomic structures: a cadaveric study

Percutaneous tibial nerve stimulation is a third-line treatment for overactive bladder and urgency urinary incontinence. During the procedure, a needle is inserted cephalad to the medial malleolus and posterior to the tibia. In recent years, permanent implants and leads have been developed for insertion into the medial ankle via a small incision. There are many important structures present in the medial compartment of the ankle, including the great saphenous vein, saphenous nerve, tibial nerve, posterior tibial vessels, and tendons of the posterior compartment leg muscles. The primary objective of this study was to identify the proximity of the percutaneous tibial nerve stimulation needle placed per Food and Drug Administration-approved device instructions to nearby important anatomic structures. The secondary objectives were to identify the proximity of the tibial nerve to the needle site, identify clinically relevant ankle anatomic structures, and confirm the tibial nerve and posterior tibial vasculature by histologic analysis. Detailed medial ankle dissections were performed bilaterally on 10 female lightly embalmed anatomic donors (cadavers) obtained from the Willed Body Program at the University of Louisville. A pin was inserted at the percutaneous tibial nerve stimulation needle site, and the medial ankle was minimally dissected so the surrounding anatomic structures were visible but not disrupted. The shortest distance from the pin to the selected structures of the medial ankle region was measured. On completion of each dissection and set of measurements, tissue was harvested for histologic examination. The distances between the pin and each structure were assessed using means and standard deviations. A paired t test was used to assess the difference in the locations between the left and right ankles. Statistical analysis was performed on left-sided, right-sided, and combined measurements. An 80% prediction interval was found to represent the expected range of values for the measurement of a new cadaver or patient, and the 95% confidence interval of the mean was computed to characterize the average distance across all cadavers or patients. The medial ankle of 10 adult female lightly embalmed cadavers were examined bilaterally. Dissections were completed from October 2021 to July 2022. Of note, 80% prediction intervals for the tibial nerve, the posterior tibial artery or vein, and the flexor digitorum longus tendon had a lower range of 0.0 mm from the pin and extending to 12.1, 9.5, and 13.9 mm, respectively. Moreover, 2 of the structures were found to be asymmetrical between the right and left ankles. The great saphenous vein was further from the pin on the left (20.5 mm [standard deviation of 6.4 mm] on the left vs 18.1 mm [standard deviation of 5.3 mm] on the right; P=.04). The calcaneal (Achilles) tendon was further from the pin on the right side (13.2 mm [standard deviation of 6.8 mm] vs 7.9 mm [standard deviation of 6.7 mm]; P=.04). Tibial neurovascular structures were confirmed with microscopic analysis. The anatomic structures within the medial ankle lie unexpectedly close to the percutaneous tibial nerve stimulation needle site as noted per Food and Drug Administration-approved device instructions. There is a possibility that some medial ankle structures are not symmetrical. It is crucial that practitioners understand medial ankle anatomy when performing percutaneous tibial nerve stimulation or permanent device insertion.

MRI evaluation of interconnections between flexor hallucis longus and flexor digitorum longus around the Master knot of Henry.

To demonstrate the magnetic resonance imaging (MRI) findings of interconnections between flexor hallucis longus (FHL) and flexor digitorum longus (FDL) around the Master knot of Henry (MKH). Fifty-two MRI scans of adult patients were retrospectively analyzed. The types and subtypes of interconnections between the FHL and FDL were evaluated using the classification suggested by Beger et al based on the direction and number of the tendon slips and contributions to the lesser toes. The layering organization formed by the FDL, quadratus plantae, and tendon slip from the FHL was evaluated. The distance between bony landmarks and the branching site of tendon slips and the cross-sectional area (CSA) of the tendon slips were measured. Descriptive statistics were reported. MRI scans revealed that type 1 interconnection was the most common (81%), followed by type 5 (10%) and types 2 and 4 (4% each). All tendon slips from the FHL contributed to the second toe, and 51% of the tendon slips contributed to the second and third toes. For the layering organization, the two-layered type was the most common (59%), followed by the three-layered (35%) and single-layered (6%) types. The mean distance between the branching site and bony landmarks was longer in the FDL to FHL cases than that in the FHL to FDL cases. The mean CSA of the tendon slips from the FHL to FDL was larger than that of the FDL to FHL. MRI could provide detailed information about the anatomical variations around the MKH. In lower extremity reconstruction surgery, the flexor hallucis longus and flexor digitorum longus tendons serve as donor tendons. A preoperative MRI scan could provide information on anatomical variations around the Master knot of Henry, which can help predict postoperative functional outcomes. • Normal anatomical variations around the Master knot of Henry were not extensively studied in the radiology literature before. • MRI identified the various types, sizes, and locations of interconnections between the flexor digitorum longus tendon and the flexor hallucis longus tendon. • MRI is a useful noninvasive tool for evaluating the interconnections between the flexor digitorum longus tendon and the flexor hallucis longus tendon.

M2 Macrophage Membrane-Mediated Biomimetic-Nanoparticle Carrying COX-siRNA Targeted Delivery for Prevention of Tendon Adhesions by Inhibiting Inflammation.

Tendon adhesion is the most common outcome of tendon or tendon-to-bone healing after injury.Ourgroup developed a hydrogel-nanoparticle sustained-release system previously to inhibit cyclooxygenases (COXs) expression and consequently prevent tendon adhesion and achieved satisfactory results. However, effective treatment of multiple tendon adhesions is always a challenge in research on the prevention of tendon adhesion. In the present study, an M2M@PLGA/COX-siRNA delivery systemissuccessfully constructed using the cell membranes of M2 macrophages and poly (lactic-co-glycolic acid) (PLGA) nanoparticles. Targeting properties and therapeutic effectsareobserved in mice or rat models of flexor digitorum longus (FDL) tendon injury combined with rotator cuff injury. The results showed that the M2M@PLGA/COX-siRNA delivery system has low toxicity and remarkable targeting properties to the injured areas. Treatment with the M2M@PLGA/COX-siRNA delivery system reduced the inflammatory reaction and significantly improved tendon adhesion in both the FDL tendon and rotator cuff tissues. These findings indicatethat the M2M@PLGA delivery system can provide an effective biological strategy for preventing multiple tendon adhesions.

Earlier proteoglycan turnover promotes higher efficiency matrix remodeling in MRL/MpJ tendons.

While most mammalian tissue regeneration is limited, the Murphy Roths Large (MRL/MpJ) mouse has been identified to regenerate several tissues, including tendon. Recent studies have indicated that this regenerative response is innate to the tendon tissue and not reliant on a systemic inflammatory response. Therefore, we hypothesized that MRL/MpJ mice may also exhibit a more robust homeostatic regulation of tendon structure in response to mechanical loading. To assess this, MRL/MpJ and C57BL/6J flexor digitorum longus tendon explants were subjected to stress-deprived conditions in vitro for up to 14 days. Explant tendon health (metabolism, biosynthesis, and composition), matrix metalloproteinase (MMP) activity, gene expression, and tendon biomechanics were assessed periodically. We found a more robust response to the loss of mechanical stimulus in the MRL/MpJ tendon explants, exhibiting an increase in collagen production and MMP activity consistent with previous in vivo studies. This greater collagen turnover was preceded by an early expression of small leucine-rich proteoglycans and proteoglycan-degrading MMP-3, promoting efficient regulation and organization of newly synthesized collagen and allowing for more efficient overall turnover in MRL/MpJ tendons. Therefore, mechanisms of MRL/MpJ matrix homeostasis may be fundamentally different from that of B6 tendons and may indicate better recovery from mechanical microdamage in MRL/MpJ tendons. We demonstrate here the utility of the MRL/MpJ model in elucidating mechanisms of efficient matrix turnover and its potential to shed light on new targets for more effective treatments for degenerative matrix changes brought about by injury, disease, or aging.

Mouse Achilles tendons exhibit collagen disorganization but minimal collagen denaturation during cyclic loading to failure

While overuse is a prominent risk factor for tendinopathy, the fatigue-induced structural damage responsible for initiating tendon degeneration remains unclear. Denaturation of collagen molecules and collagen fiber disorganization have been observed within certain tendons in response to fatigue loading. However, no studies have investigated whether these forms of tissue damage occur in Achilles tendons, which commonly exhibit tendinopathy. Therefore, the objective of this study was to determine whether mouse Achilles tendons undergo collagen denaturation and collagen fiber disorganization when cyclically loaded to failure. Consistent with previous testing of other energy-storing tendons, we found that cyclic loading of mouse Achilles tendons produced collagen disorganization but minimal collagen denaturation. To determine whether the lack of collagen denaturation is unique to mouse Achilles tendons, we monotonically loaded the Achilles and other mouse tendons to failure. We found that the patellar tendon was also resistant to collagen denaturation, but the flexor digitorum longus (FDL) tendon and tail tendon fascicles were not. Furthermore, the Achilles and patellar tendons had a lower tensile strength and modulus. While this may be due to differences in tissue structure, it is likely that the lack of collagen denaturation during monotonic loading in both the Achilles and patellar tendons was due to failure near their bony insertions, which were absent in the FDL and tail tendons. These findings suggest that mouse Achilles tendons are resistant to collagen denaturation in situ and that Achilles tendon degeneration may not be initiated by mechanically-induced damage to collagen molecules.

The efficacy of flexor tenotomy to prevent recurrent diabetic foot ulcers (DIAFLEX trial): Study protocol for a randomized controlled trial

Foot ulcers are a frequent and costly problem in people with diabetes mellitus and can lead to amputations. Prevention of these ulcers is therefore of paramount importance. Claw/hammer toe deformities are commonly seen in people with diabetes. These deformities increase the risk of ulcer development specifically at the (tip of) the toe. Percutaneous needle tenotomy of the tendon of the m. flexor digitorum longus (tendon tenotomy) can be used to reduce the severity of claw/hammer toe deformity with the goal to prevent ulcer recurrence. The main objective of this randomized controlled trial is to assess the efficacy of flexor tenotomy to prevent recurrence of toe ulcers in people with diabetes and a history of toe (pre-)ulcers. Additionally, we aim to assess interphalangeal joints (IPJ) and metatarsophalangeal joint (MTPJ) angles in a weight-bearing and non-weight-bearing position, barefoot plantar pressure during walking, cost-effectiveness and quality of life before and after the intervention and compare intervention and control study groups. Sixty-six subjects with diabetes and claw/hammer toe deformity and a recent history of (pre-)ulceration on the tip of the toe will be included and randomized between flexor tenotomy of claw/hammer toes (intervention) versus standard of care including orthosis and shoe offloading (controls) in a mono-center randomized controlled trial. Clinicaltrials.gov registrationNCT05228340.

Tendon properties in a mouse model of severe osteogenesis imperfecta

ABSTRACT Purpose/Aim of the study Osteogenesis imperfecta is a heritable bone disorder that is usually caused by mutations in collagen type I encoding genes. The impact of such mutations on tendons, a structure with high collagen type I content, remains largely unexplored. We hypothesized that tendon properties are abnormal in the context of a mutation affecting collagen type I. The main purpose of the study was to assess the anatomical, mechanical, and material tendon properties of Col1a1 Jrt/+ mice, a model of severe dominant OI. Materials and Methods The Flexor Digitorum Longus (FDL) tendon of Col1a1 Jrt/+ mice and wild-type littermates (WT) was assessed with in vitro mechanical testing. Results The results showed that width and thickness of FDL tendons were about 40% larger in WT (p < 0.01) than in Col1a1 Jrt/+ mice, whereas the cross-sectional area was 138% larger (p < 0.001). The stiffness, peak- and yield-force were between 160% and 194% higher in WT vs. Col1a1 Jrt/+ mice. The material properties did not show significant differences between mouse strains with differences <15% between WT and Col1a1 Jrt/+ (p > 0.05). Analysis of the Achilles tendon collagen showed no difference between mice strains for the content but collagen solubility in acetic acid was 66% higher in WT than in Col1a1 Jrt/+ (p < 0.001). Conclusions This study shows that the FDL tendon of Col1a1 Jrt/+ mice has reduced mechanical properties but apparently normal material properties. It remains unclear whether the tendon phenotype of Col1a1 Jrt/+ mice is secondary to muscle weakness or a direct effect of the Col1a1 mutation or a combination of both.

The diagnostic and therapeutic challenges of medial plantar neuropathy in jogger's foot: a case report

Jogger's foot is characterised by a neuropathic pain along the medial arch of the foot caused by compression of the medial plantar nerve. It is more common in runners, especially when there is an anatomical predisposition or some extrinsic factor that may exert compression on the nerve. This article presents the case of a 59-year-old man, who had pain and paraesthesia along the medial plantar arch of the left foot, lasting for several months. Despite having undergone some conservative treatments (plantar orthosis and physiotherapy) and minimal invasive procedures (cortico-anaesthetic injection and shockwave therapy) the symptoms persisted and amyotrophy of the abductor hallucis muscle became clinically evident. At this point, a magnetic resonance image was taken, showing compression of the medial plantar nerve at the intersection of the flexor hallucis longus and the flexor digitorum longus tendons. Ultrasound-guided treatment with pulsed radiofrequency of the medial plantar nerve was then proposed to try and modulate his chronic neuropathic pain. After the procedure, the patient reported immediate relief of the symptoms, which were maintained over 6 months of follow up after the procedure. This case report illustrates a rare and frequently misdiagnosed cause of midfoot pain and its management using electromagnetic modulation of peripheral nerves by pulsed radiofrequency. This seems to be an effective technique, with long-lasting results.

Targeted conditional collagen XII deletion alters tendon function

Collagen XII is a fibril-associated collagen with interrupted triple helices (FACIT). This non-fibrillar collagen is a homotrimer composed of three α1(XII) chains assembled into a collagenous molecule with a C terminal collagenous domain and a large N terminal non-collagenous domain. During tendon development and growth, collagen XII is broadly expressed throughout the extracellular matrix and enriched pericellularly around tenocytes. Tendons in a global Col12a1-/- knockout model demonstrated disrupted fibril and fiber structure and disordered tenocyte organization, highlighting the critical regulatory roles of collagen XII in determining tendon structure and function. However, muscle and bone also are affected in the collagen XII knockout model. Therefore, secondary effects on tendon due to involvement of bone and muscle may occur in the global knockout. The global knockout does not allow the definition of intrinsic mechanisms involving collagen XII in tendon versus extrinsic roles involving muscle and bone. To address this limitation, we created and characterized a conditional Col12a1-null mouse model to permit the spatial and temporal manipulation of Col12a1 expression. Collagen XII knockout was targeted to tendons by breeding conditional Col12a1flox/flox mice with Scleraxis-Cre (Scx-Cre) mice to yield a tendon-specific Col12a1-null mouse line, Col12a1Δten/Δten. Both mRNA and protein expression in Col12a1Δten/Δten mice decreased to near baseline levels in flexor digitorum longus tendons (FDL). Collagen XII immuno-localization revealed an absence of reactivity in the tendon proper, but there was reactivity in the cells of the surrounding peritenon. This supports a targeted knockout in tenocytes while peritenon cells from a non-tendon lineage were not targeted and retained collagen XII expression. The tendon-targeted, Col12a1Δten/Δtenmice had significantly reduced forelimb grip strength, altered gait and a significant decrease in biomechanical properties. While the observed decrease in tendon modulus suggests that differences in tendon material properties in the absence of Col12a1 expression underlie the functional deficiencies. Together, these findings suggest an intrinsic role for collagen XII critical for development of a functional tendon.

Anatomic Landmarks for Minimally Invasive Exposure for Flexor Digitorum Longus (FDL) Tendon Transfers and Spring Ligament Reconstruction

Category: Other; Basic Sciences/Biologics; Hindfoot; Midfoot/Forefoot Introduction/Purpose: The approach for identification of the FDL tendon is classically described through an incision proximal to the medial malleolus extending past the navicular following the inferior border of the first metatarsal.1This incision is lengthy, and we believe that the navicular tuberosity, medial malleolus, and/or sustentaculum tali can be used as reliable landmarks for identification of the FDL more precisely and reliably. The purpose of this study is to detail spatial anatomy of the medial arch to allow for a more reliable and less invasive exposure of the FDL. Methods: Ten cadaver specimens were used for a total of 20 extremities. Anatomic locations were identified and pinned with the foot positioned in neutral dorsiflexion. Anatomic locations pinned included tip of the anterior colliculus, navicular tuberosity, proximal portion of the sustentaculum tali, and the distal portion of the sustentaculum tali. Photographs were taken of each cadaveric specimen with pins in place. Image J calibrated software was then used to calculate the distance between anatomic points. Averages were calculated for all measurements. Results: On average the superior margin of the sustentaculum tali was located 8 mm from the FDL with a range of 5-15 mm. Average distance from inferior sustentaculum tali to the FDL was 9 mm with a range of 5-12 mm. Average distance from medial malleolus to superior FDL was 18 mm with a range of 11-27 mm. Average distance from medial malleolus to inferior FDL was 27 mm with a range of 20-36mm. Average distance from navicular tuberosity to anterior FDL was 22 mm with a range of 11-27 mm. Average distance from navicular tuberosity to posterior FDL was 30 mm with a range of 19-42 mm. Conclusion: The 'lighthouse' for the harvest of the FDL tendon is the sustentaculum tali. Intraoperatively, the FDL tendon is found 22-31 mm directly posterior to the navicular and 18-27 mm inferior to the medial malleolus. This provides a reliable anatomic region where a 40 mm oblique approach can be made to access the FDL and spring ligament complex for a more minimally invasive approach in all of the studied specimen.

‘Haleem's Hen’: A Mnemonic for the Anatomy of Hindfoot Structures at the Level of Sustentaculum Tali on Coronal T1-Weighted Magnetic Resonance Images

Category: Hindfoot; Ankle Introduction/Purpose: Magnetic resonance anatomy of the hindfoot as seen at the level of the sustentaculum tali is intricate due to surrounding muscles, tendons, aponeurosis and ligaments. The objective of this work is to provide a mnemonic with illustrative figures to simplify this complex anatomical region on coronal T1-weighted magnetic resonance images (T1-MRIs). Methods: One hundred and twenty-four patients referred for foot and ankle complaints were scanned utilizing standard MRI imaging protocols for evaluation of the hindfoot. Only coronal T1-MRIs of the calcaneus at the level of sustentaculum tali of unremarkably reported patients were selected for the development of this mnemonic. T1- and T2-MRIs of an additional set of patients with hindfoot pathologies were selected to demonstrate how this mnemonic is adapted to identify specific pathologies. Results: Upon viewing the calcaneus with the adjacent anatomical structures on coronal T1-MRIs, the overall appearance resembles a ''Hen in the Nest with Four Eggs.'' The calcaneus represents the body of the hen, while the sustentaculum tali forms the head and neck. The posterior tibial tendon represents the crest of the hen, and the flexor digitorum longus and flexor hallucis longus tendons represent its beak and wattle, respectively. The peroneus brevis and peroneus longus tendons represent the tail, and the long plantar ligament represents the flexed legs of Haleem's hen. The plantar aponeurosis represents the hen's nest. Whereas the abductor hallucis, flexor digitorum brevis, abductor digiti minimi and quadratus plantae muscles are the four eggs. Pes planus, flexor digitorum brevis hemangioma, Baxter's neuropathy associated with chronic denervation abductor digiti minimi atrophy and peroneal tendonitis are some of the hindfoot pathologies that can be identified utilizing the mnemonic. Conclusion: The mnemonic, 'Haleem's Hen in the Nest with Four Eggs,' serves as a simplified phrase for orthopedic surgeons, radiologists and other physicians to easily recall the anatomy of the hindfoot when viewing it at the level of the sustentaculum tali on coronal T1-MRIs. In addition, this mnemonic could be particularly useful when utilized in medical education curriculum for residents, fellows, and medical students. Further research is required to validate this mnemonic as an educational tool in medical training and detail additional hindfoot pathologies that can be identified with it.