The innervation of the ankle joint. An anatomical and histological study in the cat

Structural and Distribution Analysis of Mechanoreceptors and Free Nerve Endings in the Annular Pulleys of the Flexor Tendons of the Hand

BACKGROUND

The hand is essential in enabling physical interaction with the environment, with the annular pulleys playing a key role in its functionality. These fibrocartilaginous structures, located along the flexor tendons, are vascularized and may contain nerve endings and mechanoreceptors, aligning tendons with the bones to optimize finger flexion. However, their innervation remains poorly understood, limiting therapeutic advancements for flexor tendon conditions, such as stenosing tenosynovitis (trigger finger). This study aims to analyze the presence and distribution of mechanoreceptors and free nerve endings in the A1 annular pulley to provide insights for improved surgical and therapeutic approaches.

METHODS

Twenty A1 pulleys from the ring fingers were obtained from fresh-frozen cadavers. The pulleys were submitted to cryostat sectioning. The sections were subjected to immunofluorescence with the PGP 9.5 (protein gene product 9.5) and confocal microscopy analysis.

RESULTS

The analysis revealed the presence of type I mechanoreceptors (Ruffini corpuscles) in a subset of samples, while type IV free nerve endings were consistently found in all specimens. Both types of neural structures were primarily located at the medial and lateral fibrocartilaginous insertions of the A1 pulley, highlighting specific areas of sensory innervation within the structure.

CONCLUSION

This study contributes to the anatomical characterization of the A1 pulley, highlighting the presence and distribution of mechanoreceptors and free nerve endings. While the clinical implications of these findings remain uncertain, they may serve as a basis for future research on proprioception, sensory feedback, and potential surgical considerations.

Using in vivo calcium imaging to examine joint neuron spontaneous activity and home cage analysis to monitor activity changes in mouse models of arthritis

BACKGROUND

Studying pain in rodent models of arthritis is challenging. For example, assessing functional changes in joint neurons is challenging due to their relative scarcity amongst all sensory neurons. Additionally, studying pain behaviors in rodent models of arthritis poses its own set of difficulties. Commonly used tests, such as static weight-bearing, often require restraint, which can induce stress and consequently alter nociception. The aim of this study was to evaluate two emerging techniques for investigating joint pain in mouse models of rheumatoid- and osteo-arthritis: In vivo calcium imaging to monitor joint afferent activity and group-housed home cage monitoring to assess pain-like behaviors. Specifically, we examined whether there was increased spontaneous activity in joint afferents and reduced locomotor activity following induction of arthritis.

METHODS

Antigen induced arthritis (AIA) was used to model rheumatoid arthritis and partial medial meniscectomy (PMX) was used to model osteoarthritis. Group-housed home cage monitoring was used to assess locomotor behavior in all mice, and weight bearing was assessed in PMX mice. In vivo calcium imaging with GCaMP6s was used to monitor spontaneous activity in L4 ganglion joint neurons retrogradely labelled with fast blue 2 days following AIA and 13-15 weeks following PMX model induction. Cartilage degradation was assessed in knee joint sections stained with Safranin O and fast green in PMX mice.

RESULTS

Antigen induced arthritis produced knee joint swelling and PMX caused degeneration of articular cartilage in the knee. In the first 46 h following AIA, mice travelled less distance and were less mobile compared to their control cage mates. In contrast, no such differences were found between PMX and sham mice when measured between 4-12 weeks post-surgery. A larger fraction of joint neurons showed spontaneous activity in AIA but not PMX mice. Spontaneous activity was mostly displayed by medium-sized neurons in AIA mice and was not correlated with any of the home cage behaviors.

CONCLUSION

Group-housed home cage monitoring revealed locomotor changes in AIA mice, but not PMX mice (with n = 10/group). In vivo calcium imaging can be used to assess activity in multiple retrogradely labelled joint afferents and revealed increased spontaneous activity in AIA but not PMX mice.

Proposed Classification of Syndesmotic Soft Tissue Impingement and Its Association With Lateral Talar Cartilage Lesions

BACKGROUND

Syndesmotic impingement syndrome has been described to explain persistent lateral or anterolateral ankle pain. This condition is thought to often result from a rotational ankle injury. This study aimed to identify the type of syndesmotic impingement tissue according to arthroscopic and histologic findings and to analyze its association with lateral talar cartilage lesions.

METHODS

This retrospective study included 107 ankles in 105 patients who underwent arthroscopic surgery for syndesmotic impingement syndrome from January 2017 to August 2019. Histologic findings of biopsied impingement tissue were obtained in 59 ankles (55.1%) and compared with gross findings on arthroscopy. Cartilage lesions were evaluated using the International Cartilage Repair Society grading system. Risk factors associated with lateral talar cartilage injury were evaluated using multivariate logistic regression analysis.

RESULTS

Based on the histologic results, the most common pathology was fibrosis (24 ankles [22.4%]), followed by fatty degeneration (23 ankles [21.5%]), synovial hyperplasia (8 ankles [7.5%]), and inflammatory synovium (4 ankles [3.7%]). Interclass correlation coefficient was 0.841 (P = .001) between histologic results and arthroscopic findings. Patients with fibrotic impingement tissue had on average a significantly longer duration of symptoms (12 vs 48 months, P = .021). A lateral talar dome cartilage lesion was detected in 25 ankles (23.4%). Fibrotic impingement tissue was the only factor significantly associated with lateral talar dome lesion on multivariate logistic regression analysis (odds ratio 10.04; 95% CI 1.84-54.9; P = .008).

CONCLUSION

Syndesmotic impingement with fibrotic tissue was often associated with cartilage lesions at the lateral talar dome. Patients with prolonged anterolateral or lateral ankle pain after a rotational ankle injury warrant careful assessment for possible syndesmotic impingement by fibrotic tissue and associated lateral talar cartilage injury.

Periarticular Proprioception: Analyzing the Three-Dimensional Structure of Corpuscular Mechanosensors in the Dorsal Part of the Scapholunate Ligament

INTRODUCTION

Sensory nerve endings transmit mechanical stimuli into afferent neural signals and form the basis of proprioception, giving rise to the self-perception of dynamic stability of joints. We aimed to analyze the three-dimensional structure of periarticular corpuscular sensory nerve endings in a carpal ligament to enhance our understanding of their microstructure.

METHODS

Two dorsal parts of the scapholunate ligament were excised from two human cadaveric wrist specimens. Consecutive cryosections were stained with immunofluorescence markers protein S100B, neurotrophin receptor p75, protein gene product 9.5 (PGP 9.5), and 4',6-diamidino-2-phenylindole. Three-dimensional images of sensory nerve endings were obtained using confocal laser scanning microscopy, and subsequent analysis was performed using Imaris software.

RESULTS

Ruffini endings were characterized by a PGP 9.5-positive central axon, with a median diameter of 4.63 μm and a median of 25 cells. The p75-positive capsule had a range in thickness of 0.94 μm and 15.5 μm, consisting of single to three layers of lamellar cells. Ruffini endings were significantly smaller in volume than Pacini corpuscles or Golgi-like endings. The latter contained a median of three intracorpuscular structures. Ruffini endings and Golgi-like endings presented a similar structural composition of their capsule and subscapular space. The central axon of Pacini corpuscles was surrounded by S100-positive cells forming the inner core which was significantly smaller than the outer core, which was immunoreactive for p75 and PGP 9.5.

CONCLUSION

This study reports new data regarding the intricate outer and intracorpuscular three-dimensional morphology of periarticular sensory nerve endings, including the volume, number of cells, and structural composition. These results may form a basis to differ between normal and pathological morphological changes in periarticular sensory nerve endings in future studies.

INTRODUCTION

Sensory nerve endings transmit mechanical stimuli into afferent neural signals and form the basis of proprioception, giving rise to the self-perception of dynamic stability of joints. We aimed to analyze the three-dimensional structure of periarticular corpuscular sensory nerve endings in a carpal ligament to enhance our understanding of their microstructure.

METHODS

Two dorsal parts of the scapholunate ligament were excised from two human cadaveric wrist specimens. Consecutive cryosections were stained with immunofluorescence markers protein S100B, neurotrophin receptor p75, protein gene product 9.5 (PGP 9.5), and 4',6-diamidino-2-phenylindole. Three-dimensional images of sensory nerve endings were obtained using confocal laser scanning microscopy, and subsequent analysis was performed using Imaris software.

RESULTS

Ruffini endings were characterized by a PGP 9.5-positive central axon, with a median diameter of 4.63 μm and a median of 25 cells. The p75-positive capsule had a range in thickness of 0.94 μm and 15.5 μm, consisting of single to three layers of lamellar cells. Ruffini endings were significantly smaller in volume than Pacini corpuscles or Golgi-like endings. The latter contained a median of three intracorpuscular structures. Ruffini endings and Golgi-like endings presented a similar structural composition of their capsule and subscapular space. The central axon of Pacini corpuscles was surrounded by S100-positive cells forming the inner core which was significantly smaller than the outer core, which was immunoreactive for p75 and PGP 9.5.

CONCLUSION

This study reports new data regarding the intricate outer and intracorpuscular three-dimensional morphology of periarticular sensory nerve endings, including the volume, number of cells, and structural composition. These results may form a basis to differ between normal and pathological morphological changes in periarticular sensory nerve endings in future studies.

Study of the nerve endings and mechanoreceptors of the medial meniscotibial ligament of the knee: A structural and distribution analysis

BACKGROUND

The aim of the present study is to describe the morphology and distribution of the nerve endings of the meniscotibial ligament (MTL) of the knee, in order to understand the interaction between the proprioceptive system and knee mechanics.

METHODS

Twenty medial MTLs were obtained from deceased organ donors. The ligaments were measured, weighed and cut. Sections (10 mm) were prepared on hematoxylin and eosin-stained slides for analysis of tissue integrity, and 50 mm sections were submitted to immunofluorescence with the protein gene product (PGP) 9.5 as primary antibody and Alexa Fluor 488 as secondary antibody, followed by microscopic analysis.

RESULTS

The medial MTL was identified in 100% of the dissections, with average length, width, thickness and weight of 7.07 ± 1.34 mm, 32.25 ± 3.09 mm, 3.53 ± 0.27 mm and 0.67 ± 0.13 g, respectively. The hematoxylin and eosin-stained histological sections exhibited typical ligament structure, with dense well-organized collagen fibers and vascular tissue. All the specimens analyzed contained type I (Ruffini) mechanoreceptors and free (type IV) nerve endings, varying from parallel to intertwined fibers. Nerve endings not classified with different irregular shapes were also found. Most type I mechanoreceptors were found close to the MTL insertions on the tibial plateau, while the free nerve endings were found adjacent to the capsule.

CONCLUSION

The medial MTL showed a peripheral nerve structure, primarily type I and IV mechanoreceptors. These findings suggest that the medial MTL is important for proprioception and medial knee stabilization.

Analysis of Mechanoreceptors and Free Nerve Endings of the Transverse Carpal Ligament

Background: The treatment of carpal tunnel syndrome (CTS) by sectioning the transverse carpal ligament (TCL) is not exempt from complications. Some nerve branches may be damaged by the incision. The aim of this study is to identify and map the TCL nerve endings, serving as a guide for sectioning this structure in a zone with less nerve ending density. Methods: Ten TCLs were obtained from fresh frozen cadavers. The TCLs were measured, divided into 3 equal bands (radial, central, and ulnar), and submitted to cryostat sectioning. The sections were subjected to immunofluorescence with the protein gene product (PGP) 9.5 and confocal microscopy analysis. Results: All the specimens contained type I and type IV mechanoreceptors. Neural elements occupied 0.695 ± 0.056% of the ligament area. The density of the neural elements was greater in the radial, followed by the ulnar and central bands, with 0.730 ± 0.083%, 0.686 ± 0.009%, and 0.669 ± 0.031%, respectively. Conclusion: The present findings suggest that the region with the least potential for neural element injury during TCL release is the central third near the transition with the ulnar third. When performed distally to proximally with a slight inclination from the radial to the ulnar, this release compromises the lowest nerve element density. Topographically, the proximal limit of the release is the distal wrist crease, while the distal limit is the intersection of Kaplan cardinal line and the axis of the third webspace.

Immunofluorescence analysis of sensory nerve endings in the periarticular tissue of the human elbow joint

INTRODUCTION

To investigate the dynamic aspects of elbow stability, we aimed to analyze sensory nerve endings in the ligaments and the capsule of elbow joints.

MATERIALS AND METHODS

The capsule with its anterior (AJC) and posterior (PJC) parts, the radial collateral ligament (RCL), the annular ligament (AL), and the ulnar collateral ligament with its posterior (PUCL), transverse (TUCL) and anterior parts (AUCL) were dissected from eleven human cadaver elbow joints. Sensory nerve endings were analyzed in two levels per specimen as total cell amount/ cm² after immunofluorescence staining with low-affinity neurotrophin receptor p75, protein gene product 9.5, S-100 protein and 4',6-Diamidin-2-phenylindol, Carbonic anhydrase II and choline acetyltransferase on an Apotome microscope according to Freeman and Wyke's classification.

RESULTS

Free nerve endings were the predominant mechanoreceptor in all seven structures followed by Ruffini, unclassifiable, Golgi-like, and Pacini corpuscles (p ≤ 0.00001, respectively). Free nerve endings were observed significant more often in the AJC than in the RCL (p < 0.00002). A higher density of Ruffini endings than Golgi-like endings was observed in the PJC (p = 0.004). The RCL contained significant more Ruffini endings than Pacini corpuscles (p = 0.004). Carbonic anhydrase II was significantly more frequently positively immunoreactive than choline acetyltransferase in all sensory nerve endings (p < 0.05). Sensory nerve endings were significant more often epifascicular distributed in all structures (p < 0.006, respectively) except for the AJC, which had a pronounced equal distribution (p < 0.00005).

CONCLUSION

The high density of free nerve endings in the joint capsule indicates that it has pronounced nociceptive functions. Joint position sense is mainly detected by the RCL, AUCL, PUCL, and the PJC. Proprioceptive control of the elbow joint is mainly monitored by the joint capsule and the UCL, respectively. However, the extreme range of motion is primarily controlled by the RCL mediated by Golgi-like endings.

Innervation of the Human Intervertebral Disc: A Scoping Review

OBJECTIVE

Back pain is an elusive symptom complicated by a variety of possible causes, precipitating and maintaining factors, and consequences. Notably, the underlying pathology remains unknown in a significant number of cases. Changes to the intervertebral disc (IVD) have been associated with back pain, leading many to postulate that the IVD may be a direct source of pain, typically referred to as discogenic back pain. Yet despite decades of research into the neuroanatomy of the IVD, there is a lack of consensus in the literature as to the distribution and function of neural elements within the tissue. The current scoping review provides a comprehensive systematic overview of studies that document the topography, morphology, and immunoreactivity of neural elements within the IVD in humans.

METHOD

Articles were retrieved from six separate databases in a three-step systematic search and were independently evaluated by two reviewers.

RESULTS

Three categories of neural elements were described within the IVD: perivascular nerves, sensory nerves independent of blood vessels, and mechanoreceptors. Nerves were consistently localized within the outer layers of the annulus fibrosus. Neural ingrowth into the inner annulus fibrosus and nucleus pulposus was found to occur only in degenerative and disease states.

CONCLUSION

While the pattern of innervation within the IVD is clear, the specific topographic arrangement and function of neural elements in the context of back pain remains unclear.

A Histological Comparison Between Anterior Cruciate Ligament Remnant Tissue, Anatomically Reconstructed Graft, and Non-Anatomically Reconstructed Graft

Introduction: To our knowledge, no studies have investigated the histological comparison between primary injured anterior cruciate ligament (ACL), initially anatomically reconstructed grafts and non-anatomically reconstructed grafts at the time of revision ACL reconstruction. The purpose of this study was to histologically clarify the differences between ACL remnant tissue, reconstructed graft after anatomic double-bundle ACL reconstruction, and reconstructed graft after non-anatomic single-bundle ACL reconstruction.

Methods: This histological study included five patients after anatomic double-bundle ACL reconstruction, three patients after non-anatomic single-bundle ACL reconstruction performed who injured their operated knees again, and five patients who injured their ACL for the first time and agreed to participate. All of the grafts and ACL remnant tissue were harvested, stained with hematoxylin and eosin, S-100, and alpha smooth muscle actin and evaluated using light microscopy.

Results: There was no area of necrosis in the reconstructed graft after an anatomic double-bundle ACL reconstruction. However, there were obvious areas of necrosis in the reconstructed graft after non-anatomic single-bundle ACL reconstruction. Additionally, the collagen fibers were more longitudinally oriented, and most cells were spindle shaped like those in ACL remnant tissue after an anatomic double-bundle ACL reconstruction in contrast with the finding of the grafts after non-anatomic single-bundle ACL reconstruction.

Conclusion: Initially reconstructed graft after an anatomic double-bundle ACL reconstruction may be beneficial if preserved at the time of the revision surgery.

Investigation of sensory nerve endings in pulvinar, ligamentum teres, and hip joint capsule: A prospective immunohistochemical study of 36 cases with developmental hip dysplasia

OBJECTIVE

The aim of this study was to immunohistochemically identify and characterize the presence of sensory nerve endings (SNEs) in pulvinar, ligamentum teres (LT), and hip joint capsule (HJC) of children with developmental dysplasia of the hip (DDH).

METHODS

Pulvinar, LT, and HJC specimens were obtained from 38 hips of 36 children (31 girls, five boys; mean age=49 months; age range=18-132 months) during open reduction surgery for DDH. All specimens underwent subsequent routine tissue processing (formalin fixation and paraffin embedding). To determine tissue morphology, haematoxylin and eosin staining was used. SNEs were analyzed immunohistochemically using a mouse monoclonal antibody against S-100 Beta Protein based on the classification of Freeman and Wyke including four types of SNEs including mechanoreceptors: type I Ruffini corpuscles, type II Pacini corpuscles, type III Golgi organs, and type IVa unmyelinated free nerve endings (FNEs). Additionally, children were sorted into three groups based on their age at the time of surgery: Group 1 (age <3 years; 19 hips of 18), Group 2 (age: 3-5 years; 10 hips of 10 children), and Group 3 (age >5 years; 9 hips of 8 children).

RESULTS

Although no Type I, II, or III SNEs were identified in any specimen, type IVa mechanoreceptor (FNEs) was immunohistochemically characterized in 13 (34%) pulvinar, 19 (50%) LT, and 16 (42%) HJC specimens. The total density of FNEs was 3.31±5.70)/50 mm2 (range 0-21) in pulvinar specimens, 3.18 ± 5.92)/50 mm2 (range 0-24) in HJC specimens, and 4.51±6.61/50 mm2 (range 0-22) in LT specimens. Furthermore, the operated side, gender, and the number of FNEs in specimens did not differ significantly among the age groups (p>0.05 for all), and the number of FNEs was not significantly correlated with age, gender, or the operated side (p>0.05 for all).

CONCLUSION

Evidence from this study revealed that pulvinar, LT, and HJC include only FNEs, which play a role in pain sensation, among mechanoreceptors. Surgical excision of these tissues may not cause a significant loss of sensory function in the hip joint of children with DDH.

LEVEL OF EVIDENCE

Level II, Therapeutic Study.

Immunofluorescence analysis of sensory nerve endings in the interosseous membrane of the forearm

The human interosseous membrane (IOM) is a fundamental stabilizer during forearm rotation. To investigate the dynamic aspects of forearm stability, we analyzed sensory nerve endings in the IOM. The distal oblique bundle (DOB), the distal accessory band (DAB), the central band (CB), the proximal accessory band (PAB), the dorsal oblique accessory cord (DOAC) and the proximal oblique cord (POC) were dissected from 11 human cadaver forearms. Sensory nerve endings were analyzed at two levels per specimen as total cell amount/mm² after immunofluorescence staining with low-affinity neurotrophin receptor p75, protein gene product 9.5, S-100 protein and 4',6-diamidino-2-phenylindole on an Apotome microscope, according to Freeman and Wyke's classification. Sensory nerve endings were significantly more commonly found to be equally distributed throughout the structures, rather than being epifascicular, interstitial, or close to the insertion into bone (P ≤ 0.001, respectively). Free nerve endings were the predominant mechanoreceptor in all six structures, with highest density in the DOB, followed by the POC (P ≤ 0.0001, respectively). The DOB had the highest density of Pacini corpuscles. The DOAC and CB had the lowest amounts of sensory innervation. The high density of sensory corpuscles in the DOB, PAB and POC indicate that proprioceptive control of the compressive and directional muscular forces acting on the distal and proximal radioulnar joints is monitored by the DOB, PAB and POC, respectively, due to their closed proximity to both joints, whereas the central parts of the IOM act as structures of passive restraint.

Histopathological analysis of the synovium in trapeziometacarpal osteoarthritis

Dorsoradial and anterior oblique ligaments were harvested during surgery in 13 patients with symptomatic trapeziometacarpal osteoarthritis, which had been graded preoperatively by a modified Eaton-Littler radiographic grading. Ligaments, including the periligamentous synovium, were stained with S100 protein, neurotrophic receptor p75, protein gene product 9.5, calcitonin gene related peptide, acetylcholine, substance P, neuropeptide Y, noradrenaline, N-methyl-D-aspartate-receptor and Met/Leu-enkephalin. The synovium was classified as showing no, low-grade or high-grade synovitis. Free nerve endings had higher immunoreactivity for substance P than for N-methyl-D-aspartate-receptor, enkephalin and noradrenaline. The synovial stroma had less immunoreactivity for N-methyl-D-aspartate-receptor than for noradrenaline, substance P and calcitonin gene related peptide. There was no relation between the grade of osteoarthritis and the visual pain analogue scale, synovitis score, immunoreactivity of all antibodies and quantity of free nerve endings or blood vessels. Synovium in trapeziometacarpal joint osteoarthritis produces several neuromediators causing a polymodal neurogenic inflammation and which may serve as biomarkers for osteoarthritis or therapeutic targets.

Study of the Nerve Endings and Mechanoreceptors of the Anterolateral Ligament of the Knee

PURPOSE

To describe the morphology and distribution of the anterolateral ligament of the knee (ALL) nerve endings, aiming to understand the interaction between the proprioceptive system and knee mechanics.

METHODS

Twenty ALLs were obtained from fresh frozen cadavers. The ligaments were measured, weighed, and cut. Sections (10 μm) were prepared in hematoxylin and eosin-stained slides to analyze tissue integrity, and 50-μm sections were subjected to immunofluorescence with the protein gene product 9.5 as primary antibody and Alexa Fluor 488 as secondary antibody, followed by microscopic analysis.

RESULTS

The ALL was identified in 100% of the dissections, exhibiting a mean (± standard deviation) length of 4.0 ± 0.4 cm, a mean width of 5.5 ± 0.8 mm, and a mean weight of 0.9 ± 0.2 g. The histological sections in hematoxylin and eosin showed dense, well-organized collagen and the presence of vascular tissue. All the specimens analyzed contained type I (Ruffini-like) mechanoreceptors and free nerve endings (type IV), varying from parallel to intertwined fibers. Unclassified nerve endings with different irregular shapes were also found. The neural elements occupied 0.6% ± 0.3% of the ligament area, and most were observed near the origin of ALL insertions.

CONCLUSION

The ALL exhibits a peripheral nerve structure, primarily type I and IV mechanoreceptors. These findings suggest that the ALL is important for the proprioception and anterolateral stabilization of the knee.

CLINICAL RELEVANCE

It is important to understand ALL innervation and infer how an injury could compromise the proprioceptive role of the lateral compartment, as the ligaments contribute dynamically to stability through proprioceptive control of muscle forces. The findings confirm that the ALL is highly innervated by mechanoreceptors and may have a proprioceptive role in conjunction with the lateral collateral ligament in the lateral region of the knee.

Effects of Stochastic Resonance Whole-Body Vibration in Individuals with Unilateral Brain Lesion: A Single-Blind Randomized Controlled Trial: Whole-Body Vibration and Neuromuscular Function

Introduction

Stochastic resonance whole-body vibration (SR-WBV) devices are promising sensorimotor interventions to address muscle weakness and to improve balance and mobility particularly in the elderly. However, it remains inconclusive whether individuals with stroke or traumatic brain injury (TBI) can profit from this method. The aim of this prospective single-blind randomized controlled trial was to investigate the effects of SR-WBV on muscle strength as well as gait and balance performance in this population.

Methods

Forty-eight individuals with stroke or TBI were randomly allocated to an experimental and a sham group. Participants were exposed daily to 5 consecutives 1-minute SR-WBV sessions, whereas the experimental group trained in a standing position with 5 Hz and the sham group in a seated position with 1 Hz. Isometric muscle strength properties of the paretic knee extensor muscles as well as balance and gait performance were measured at baseline, after the first session and after two weeks of SR-WBV.

Results

Both groups showed short- and long-term effects in gait performance. However, no between-group effects could be found at the three measurement points.

Discussion

Complementary SR-WBV showed no beneficial effects immediately after the intervention and after two weeks of conventional rehabilitation therapy. Future research is needed to identify the potential efficacy of SR-WBV in individuals with stroke and TBI using shorter and less exhausting test procedures and a generally prolonged intervention time.

Scapholunate interosseous ligament dysfunction as a source of elbow pain syndromes: Possible mechanisms and implications for hand surgeons and therapists

Elbow pain syndromes are common upper extremity musculoskeletal disorders, and they are usually associated with repetitive occupational exposure. Ligaments are often one of the sources of musculoskeletal disorders because of their mechanical and neurological properties. The wrist ligaments are some of the ligaments most vulnerable to occupational exposure. Since most occupational tasks require wrist extension for handling tools and loading, the scapholunate interosseous ligament (SLIL) bears greater strain during loading, which results in creep deformation and hysteresis. Ligamentous creep may result in diminished ability to detect signal changes during joint movements, which impairs neuromuscular control established by ligamentomuscular reflex arcs elicited from mechanoreceptors in the ligaments. Changes in muscle activation patterns of forearm muscles due to diminished ligamentomuscular reflexes may initiate a positive feedback loop, leading to musculoskeletal pain syndromes. The relationship between elbow pain syndromes and SLIL injury will be presented through two hypotheses and relevant pain mechanisms: 1. Repetitive tasks may cause creep deformation of the SLIL, which then impairs ligamentomuscular reflexes, leading to elbow pain disorders. 2. Lateral epicondylalgia may increase the risk of SLIL injury through the compensation of the lower extensor carpi radialis muscle activity by higher extensor carpi ulnaris muscle activity, which may alter carpal kinematics, leading to SLIL degeneration over time. The differential diagnosis is usually complicated in musculoskeletal pain disorders. The failure of treatment methods is one of the issues of concern for many researchers. A key element in developing treatment strategies is to understand the source of the disorder and the nature of the injury. We proposed that the differential diagnosis include SLIL injuries when describing elbow pain syndromes, particularly, lateral epicondylalgia.

Immunohistochemical Mapping of Sensory Nerve Endings in the Human Triangular Fibrocartilage Complex

BACKGROUND

The triangular fibrocartilage complex is the main stabilizer of the distal radioulnar joint. While static joint stability is constituted by osseous and ligamentous integrity, the dynamic aspects of joint stability chiefly concern proprioceptive control of the compressive and directional muscular forces acting on the joint. Therefore, an investigation of the pattern and types of sensory nerve endings gives more insight in dynamic distal radioulnar joint stability.

QUESTIONS/PURPOSES

We aimed to (1) analyze the general distribution of sensory nerve endings and blood vessels; (2) examine interstructural distribution of sensory nerve endings and blood vessels; (3) compare the number and types of mechanoreceptors in each part; and (4) analyze intrastructural distribution of nerve endings at different tissue depth.

METHODS

The subsheath of the extensor carpi ulnaris tendon sheath, the ulnocarpal meniscoid, the articular disc, the dorsal and volar radioulnar ligaments, and the ulnolunate and ulnotriquetral ligaments were dissected from 11 human cadaver wrists. Sensory nerve endings were counted in five levels per specimen as total cell amount/cm(2) after staining with low-affinity neurotrophin receptor p75, protein gene product 9.5, and S-100 protein and thereafter classified according to Freeman and Wyke.

RESULTS

All types of sensory corpuscles were found in the various structures of the triangular fibrocartilage complex with the exception of the ulnolunate ligament, which contained only Golgi-like endings, free nerve endings, and unclassifiable corpuscles. The articular disc had only free nerve endings. Furthermore, free nerve endings were the predominant sensory nerve ending (median, 72.6/cm(2); range, 0-469.4/cm(2)) and more prevalent than all other types of mechanoreceptors: Ruffini (median, 0; range, 0-5.6/cm(2); difference of medians, 72.6; p < 0.001), Pacini (median, 0; range, 0-3.8/cm(2); difference of medians, 72.6; p < 0.001), Golgi-like (median, 0; range, 0-2.1/cm(2); difference of medians, 72.6; p < 0.001), and unclassifiable corpuscles (median, 0; range, 0-2.5/cm(2); difference of medians, 72.6; p < 0.001). The articular disc contained fewer free nerve endings (median, 1.8; range, 0-17.8/cm(2)) and fewer blood vessels (median, 29.8; range, 0-112.2/cm(2); difference of medians: 255.9) than all other structures of the triangular fibrocartilage complex (p ≤ 0.001, respectively) except the ulnolunate ligament. More blood vessels were seen in the volar radioulnar ligament (median, 363.62; range, 117.8-871.8/cm(2)) compared with the ulnolunate ligament (median, 107.7; range, 15.9-410.3/cm(2); difference of medians: 255.91; p = 0.002) and the dorsal radioulnar ligament (median, 116.2; range, 53.9-185.1/cm(2); difference of medians: 247.47; p = 0.001). Free nerve endings were obtained in each structure more often than all other types of sensory nerve endings (p < 0.001, respectively). The intrastructural analysis revealed no differences in mechanoreceptor distribution in all investigated specimens with the numbers available, showing a homogenous distribution of proprioceptive qualities in all seven parts of the triangular fibrocartilage complex.

CONCLUSIONS

Nociception has a primary proprioceptive role in the neuromuscular stability of the distal radioulnar joint. The articular disc and ulnolunate ligament rarely are innervated, which implies mainly mechanical functions, whereas all other structures have pronounced proprioceptive qualities, prerequisite for dynamic joint stability.

CLINICAL RELEVANCE

Lesions of the volar and dorsal radioulnar ligaments have immense consequences not only for mechanical but also for dynamic stability of the distal radioulnar joint, and surgical reconstruction in instances of radioulnar ligament injury is important.

Morphological study of mechanoreceptors in collateral ligaments of the ankle joint

BACKGROUND

The aim of this study was to analyze the pattern and types of sensory nerve endings in ankle collateral ligaments using histological techniques, in order to observe the morphology and distribution of mechanoreceptors in the collateral ligaments of cadaver ankle joint, and to provide the morphological evidence for the role of the ligament in joint sensory function.

METHODS

Twelve lateral collateral ligaments including anterior talofibular ligament (ATFL; n = 6), posterior talofibular ligament (PTFL; n = 6), and calcaneofibular ligament (CFL; n = 6) were harvested from six fresh frozen cadavers. The ligaments were embedded in paraffin, sectioned at 4 μm, and then stained using a modified gold-chloride staining methods. The collateral ligament was divided into three segments: proximal, middle, and distal segments. Fifty-four ATFL slides, 90 PTFL slides, and 108 CFL slides were analyzed. Mechanoreceptors were classified based on Freemen and Wyke's classification. Mechanoreceptor distribution was analyzed statistically. One-way ANOVA (postHoc LSD) was used for statistical analysis.

RESULTS

All the four typical types of nerve endings (the Ruffini corpuscles, Pacinian corpuscles, Golgi tendon organs, and free nerve endings) were identified in these ligaments. Pacinian corpuscles were the predominant in all four complexes. More mechanoreceptors were found in synovial membrane near both ends of the ligaments attached to the bone. No statistical differences were found in the amount of mechanoreceptors among distal, middle, and proximal parts of the ligaments.

CONCLUSIONS

The four typical types of mechanoreceptors were all identified in the collateral ligaments of the human ankle. Pacinian corpuscles were the predominant in all four complexes. This indicates that the main function of ankle collateral ligaments is to sense joint speeds in motions.

Balance training and center-of-pressure location in participants with chronic ankle instability

CONTEXT

Chronic ankle instability (CAI) occurs in some people after a lateral ankle sprain and often results in residual feelings of instability and episodes of the ankle's giving way. Compared with healthy people, patients with CAI demonstrated poor postural control and used a more anteriorly and laterally positioned center of pressure (COP) during a single-limb static-balance task on a force plate. Balance training is an effective means of altering traditional COP measures; however, whether the overall location of the COP distribution under the foot also changes is unknown.

OBJECTIVE

To determine if the spatial locations of COP data points in participants with CAI change after a 4-week balance-training program.

DESIGN

Randomized controlled trial.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

Thirty-one persons with self-reported CAI.

INTERVENTION(S)

Participants were randomly assigned to a 4-week balance-training program or no balance training.

MAIN OUTCOME MEASURE(S)

We collected a total of 500 COP data points while participants balanced using a single limb on a force plate during a 10-second trial. The location of each COP data point relative to the geometric center of the foot was determined, and the frequency count in 4 sections (anteromedial, anterolateral, posteromedial, posterolateral) was analyzed for differences between groups.

RESULTS

Overall, COP position in the balance-training group shifted from being more anterior to less anterior in both eyes-open trials (before trial = 319.1 ± 165.4, after trial = 160.5 ± 149.5; P = .006) and eyes-closed trials (before trial = 387.9 ± 123.8, after trial = 189.4 ± 102.9; P < .001). The COP for the group that did not perform balance training remained the same in the eyes-open trials (before trial = 214.1 ± 193.3, after trial = 230.0 ± 176.3; P = .54) and eyes-closed trials (before trial = 326.9 ± 134.3, after trial = 338.2 ± 126.1; P = .69).

CONCLUSIONS

In participants with CAI, the balance-training program shifted the COP location from anterolateral to posterolateral. The program may have repaired some of the damaged sensorimotor system pathways, resulting in a more optimally functioning and less constrained system.

Neuroanatomical distribution of mechanoreceptors in the human cadaveric shoulder capsule and labrum

The distribution, location, and spatial arrangement of mechanoreceptors are important for neural signal conciseness and accuracy in proprioceptive information required to maintain functional joint stability. The glenohumeral joint capsule and labrum are mechanoreceptor-containing tissues for which the distribution of mechanoreceptors has not been determined despite the importance of these tissues in stabilizing the shoulder. More recently, it has been shown that damage to articular mechanoreceptors can result in proprioceptive deficits that may lead to recurrent instability. Awareness of mechanoreceptor distribution in the glenohumeral joint capsule and labrum may allow preservation of the mechanoreceptors during surgical treatment for shoulder instability, and in turn retain the joint's proprioceptive integrity. For this reason, we sought to develop a neuroanatomical map of the mechanoreceptors within the capsule and labrum. We postulated that the mechanoreceptors in these tissues are distributed in a unique pattern, with mechanoreceptor-scarce regions that may be more appropriate for surgical dissection. We determined the neuroanatomical distribution of mechanoreceptors and their associated fascicles in the capsule and labrum from eight human cadaver shoulder pairs using our improved gold chloride staining technique and light microscopy. A distribution pattern was consistently observed in the capsule and labrum from which we derived a neuroanatomical map. Both tissues demonstrated mechanoreceptor-dense and -scarce regions that may be considered during surgical treatment for instability. Capsular fascicles were located in the subsynovial layer, whereas labral fascicles were concentrated in the peri-core zone. The capsular fascicles presented as a lattice network and with a plexiform appearance. Fascicles within the labrum resembled a cable structure with the fascicles running in parallel. Our findings contribute to the neuroanatomical knowledge of the two glenohumeral joint stabilizers, namely, capsule and labrum, primarily involved in the onset of shoulder instability and recurrent instability. Neuroanatomical knowledge of articular mechanoreceptors is important for (i) developing a topographical map that reflects correspondence between the joint and surrounding musculature, (ii) understanding proprioceptive deficits that are only partially restored post surgical and post rehabilitative treatment, and (iii) gaining further knowledge about articular mechanoreceptors.

The architecture of the connective tissue in the musculoskeletal system-an often overlooked functional parameter as to proprioception in the locomotor apparatus

The architecture of the connective tissue, including structures such as fasciae, sheaths, and membranes, is more important for understanding functional meaning than is more traditional anatomy, whose anatomical dissection method neglects and denies the continuity of the connective tissue as integrating matrix of the body.

The connective tissue anatomy and architecture exhibits two functional tendencies that are present in all areas of the body in different ways and relationships. In body cavities, the “disconnecting” quality of shaping space enables mobility; between organs and body parts, the “connecting” dimension enables functional mechanical interactions. In the musculoskeletal system, those two features of the connective tissue are also present. They cannot be found by the usual analytic dissection procedures. An architectural description is necessary.

This article uses such a methodologic approach and gives such a description for the lateral elbow region. The result is an alternative architectural view of the anatomic substrate involved in the transmission and conveyance of forces over synovial joints. An architectural description of the muscular and connective tissue organized in series with each other to enable the transmission of forces over these dynamic entities is more appropriate than is the classical concept of “passive” force-guiding structures such as ligaments organized in parallel to actively force-transmitting structures such as muscles with tendons.

The discrimination between so-called joint receptors and muscle receptors is an artificial distinction when function is considered. Mechanoreceptors, also the so-called muscle receptors, are arranged in the context of force circumstances—that is, of the architecture of muscle and connective tissue rather than of the classical anatomic structures such as muscle, capsules, and ligaments. In the lateral cubital region of the rat, a spectrum of mechanosensitive substrate occurs at the transitional areas between regular dense connective tissue layers and the muscle fascicles organized in series with them. This substrate exhibits features of type and location of the mechanosensitive nerve terminals that usually are considered characteristic for “joint receptors” as well as for “muscle receptors.”

The receptors for proprioception are concentrated in those areas where tensile stresses are conveyed over the elbow joint. Structures cannot be divided into either joint receptors or muscle receptors when muscular and collagenous connective tissue structures function in series to maintain joint integrity and stability. In vivo, those connective tissue structures are strained during movements of the skeletal parts, those movements in turn being induced and led by tension in muscular tissue. In principle, because of the architecture, receptors can also be stimulated by changes in muscle tension without skeletal movement, or by skeletal movement without change in muscle tension. A mutual relationship exists between structure (and function) of the mechanoreceptors and the architecture of the muscular and regular dense connective tissue. Both are instrumental in the coding of proprioceptive information to the central nervous system.

Sensorimotor deficits with ankle sprains and chronic ankle instability

The presence of sensorimotor deficits in patients who have suffered ankle sprains or who have chronic ankle instability has been recognized for several decades; however, a body of research literature has developed that elucidates potential physiologic explanations for these deficits. Alterations in a spectrum of sensorimotor measures make it apparent that conscious perception of afferent somatosensory information, reflex responses, and efferent motor control deficits are present with ankle instability. The specific origin of these deficits local to the ankle ligaments or at the spinal or supraspinal levels of motor control have yet to be fully elucidated. It is clear, however, that both feedback and feedforward mechanisms of motor control are altered with ankle instability.

Unloading reaction to electrical stimulation at neutral and supinated ankle positions

An unloading reaction has been characterized as a modified flexor reflex (FR), in which the standing subjects decrease the load on the stimulated foot and increase the load on the contralateral side, but, without withdrawal of the stimulated foot. Different behavioral circumstances have been shown to modulate this reflex. It is not known whether unloading reactions can be modulated with a loaded supinated ankle position, which, in excess, may result in an ankle sprain injury. Since ankle sprain depends on the load applied to a supinated foot, our premise is that unloading reactions may protect the ankle from a sprain injury. Therefore, this study investigated how the unloading reactions were modulated during a loaded supinated ankle condition. We delivered non-nociceptive and nociceptive electrical stimulations on the lateral aspect of the ankle in standing subjects with the foot in neutral and in a supinated position. The magnitude and latencies of reflex responses were registered using kinetic and kinematic analyses and subsequently compared among the conditions. The analysis demonstrated greater reactions for the supinated ankle condition. The individuals also moved their whole body downwards and shifted the body weight to the non-stimulated foot. Therefore, this study suggested that a modified type of the classic flexion reflex, i.e., unloading reaction, may be used as a strategy to unload a supinated ankle and potentially minimize the risk of ankle sprain injuries.

Distribution of nerve endings in the human dorsal radiocarpal ligament

PURPOSE

The purpose of this investigation was to evaluate the nerve-ending apparatus populations within a large number of adult human dorsal radiocarpal (DRC) ligaments to test the hypothesis that the majority of nerve endings could be grouped into established classifications and that the nerve endings could be found in predictable locations within the substance of the ligament.

METHODS

The DRC ligaments were harvested from 20 wrists of 10 fresh cadavers with an average age of 75.6 years within 12 to 18 hours of death. Before the tissues were harvested, radiographs were taken to exclude any arthritic conditions of the wrists. Tissues were fixed, sectioned with a cryostat, and serial sections were collected on glass slides. Slides were processed for fluorescence immunohistochemistry using antibody to protein gene product 9.5 and a secondary antibody conjugated to a fluorescent tag (Alexa Fluor 488). The sections were evaluated with an LSM-510 confocal laser microscope and a Kontron KS 400 image analyzer. Labeled nerve endings were counted, mapped, and reconstructed.

RESULTS

The average number of nerve endings in each DRC ligament was 10.1+/-4.7. More than 76% of the nerve endings were found in the 2 ends of the ligament with 23.3% in the central third and approximately 80% distributed in the superficial layer. More than 80% of the nerve endings were discovered in the epiligamentous sheath rather than in the perifascicular spaces.

CONCLUSIONS

The distribution of the nerve endings follows a consistent pattern. These results will provide a foundation of morphologic information useful in understanding normal and abnormal neural control of wrist joint mechanics.

Nerve endings of the wrist joint: a preliminary report of the dorsal radiocarpal ligament

As part of an investigation of the articular nerve ending populations in the wrist joint capsule associated with the anterior and posterior interosseous nerves, this study addresses the nerve ending population in the dorsal radiocarpal ligament. The ligaments were harvested from four wrists of two fresh cadavers within 12 h of death. Tissues were fixed, cryostat sectioned, and processed for fluorescence immunohistochemistry using antibody to protein gene product 9.5 (PGP 9.5), a general or pan neuronal marker, and a secondary antibody conjugated to a fluorescent tag (Alexa Fluor 488). The sections were evaluated with a confocal laser microscope and an image analyzer. Labeled nerve endings were mapped, measured, and categorized. Type I (Ruffini-like ending), Type III (Golgi-like tendon organ) and Type IV (noncorpuscular) nerve endings could be identified in all four DRC ligaments, with Types I and IV dominating. These receptors were distributed primarily over the superficial two thirds of the ligament (>80%), and near the bony attachments (>70%). The dorsal radiocarpal ligament has a rich sensory innervation from the posterior interosseous nerve terminating in nerve endings located in the superficial two-thirds of the ligaments, primarily near bony attachment sites.

Effects of circumferential ankle pressure on ankle proprioception, stiffness, and postural stability: a preliminary investigation

STUDY DESIGN

Cross-sectional repeated-measures design.

OBJECTIVE

Determine the effects of circumferential ankle pressure (CAP) intervention on proprioceptive acuity, ankle stiffness, and postural stability.

BACKGROUND

The application of CAP using braces, taping, and adaptive shoes or military boots is widely used to address chronic ankle instability (CAI). An underlying assumption is that the CAP intervention might improve ankle stability through increased proprioceptive acuity and stiffness in the ankle. METHOD AND MEASURES: A convenience sample of 10 subjects was recruited from the local university community and categorized according to proprioceptive acuity (high, low) and ankle stability (normal, CAI). Proprioceptive acuity was measured when blindfolded subjects were asked to accurately reproduce a self-selected target ankle position before and after the application of CAP. Proprioceptive acuity was determined in 5 different ankle joint position sense tests: neutral, inversion, eversion, plantar flexion, and dorsiflexion. Joint position angles were recorded electromechanically using a potentiometer. Passive ankle stiffness was computed from the ratio of applied static moment versus angular displacement. Active ankle stiffness was determined from biomechanical analyses of ankle motion following a mediolateral perturbation. Postural stability was quantified from the center of pressure displacement in the mediolateral and the anteroposterior directions in unipedal stance. All measurements were recorded with and without CAP applied by a pediatric blood pressure cuff. Data were analyzed using a separate mixed-model analysis of variance (ANOVA) for each dependent variable. Post hoc comparison using Tukey's honestly significant difference (HSD) test was performed if significant interactions were obtained. Significance level was set at P<.05 for all analyses.

RESULTS

Significant group (high versus low proprioceptive acuity) x CAP interactions were identified for postural stability. Passive ankle stiffness was not increased by an application of CAP. Active ankle stiffness was significantly different between the high and low proprioceptive acuity groups and was not affected by an application of CAP. Significant group (normal versus CAI) x CAP interactions were observed for mediolateral center-of-pressure displacement with a main effect of group on neutral joint position sense.

CONCLUSIONS

Application of CAP increased proprioceptive acuity and demonstrated trends toward increased active stiffness in the ankle, hence improved postural stability. The effects tend to be limited to individuals with low proprioceptive acuity.

Reflex from the ankle ligaments of the feline

It was found that two to three articular branches of the tibial nerve innervate the medial ligament of the feline ankle. No innervation was found to the laterial ligament. Supramaximal electrical stimulation of the articular nerves was found to elicit electromyographic (EMG) activity in the intrinsic muscles of the foot. EMG activity was not found in any of the calf muscles which cross the ankle. The average time delay from stimulus to EMG activity was 3.8 ms, indicating that a fast, bisynaptic reflex is active, probably for purposes of preventing or correcting foot eversion to maintain joint stability.

Proprioceptive training and prevention of anterior cruciate ligament injuries in soccer

This commentary describes a program developed to help reduce the incidence of anterior cruciate ligament injuries in soccer players. The basic principles underlying the injury prevention protocol are described with respect to the proprioceptive control mechanisms at the knee joint. This is followed by a detailed description of the program.

Treatment of ruptures of the lateral ankle ligaments: a meta-analysis

BACKGROUND

Ruptures of the lateral ankle ligaments are very common; however, treatment remains controversial. The aim of the current study was to perform a meta-analysis of randomized, controlled clinical trials of existing treatment strategies for acute ruptures of the lateral ankle ligaments.

METHODS

Randomized, controlled trials reported between 1966 and 1998 were included if they involved acute ruptures of the lateral ankle ligaments. Randomized, controlled trials are defined as comparative studies with an intervention group and a control group in which the assignment of participants to a group is determined by the formal procedure of randomization. Summary measures of effectiveness were expressed as relative risks with use of random effects modeling.

RESULTS

When analyzing the trials, we searched for comparable outcome measures in both short and long-term follow-up studies (studies with six months to 3.8 years of follow-up). This resulted in the analyses of three outcome measures: time lost from work, residual pain, and giving-way. This report summarizes the results of twenty-seven trials. With respect to giving-way, a significant difference was noted between operative treatment and functional treatment (relative risk, 0.23; 95 percent confidence interval, 0.17 to 0.31) in favor of operative treatment and a significant difference was also noted between functional treatment and treatment with a cast for six weeks (relative risk, 0.69; 95 percent confidence interval, 0.50 to 0.94) in favor of functional treatment. With respect to residual pain, no significant difference was found between operative and functional treatment and a significant difference was found between functional treatment and treatment with a cast for six weeks (relative risk, 0.67; 95 percent confidence interval, 0.50 to 0.90). We found minimal or no treatment to result in more residual pain (relative risk, 0.53; 95 percent confidence interval, 0.27 to 1.02) and giving-way (relative risk, 0.34; 95 percent confidence interval, 0.17 to 0.71) than did functional treatment.

CONCLUSIONS

We concluded that a no-treatment strategy for ruptures of the lateral ankle ligaments leads to more residual symptoms. Operative treatment leads to better results than functional treatment, and functional treatment leads to better results than cast immobilization for six weeks.

The consistent presence of the human accessory deep peroneal nerve

Twenty-four human legs were dissected macroscopically to study the morphological details of the accessory deep peroneal nerve. This nerve arose from the superficial peroneal nerve and descended in the lateral compartment of the leg, deep to peroneus longus along the posterior border of peroneus brevis. Approaching the ankle joint, this nerve passed through the peroneal tunnels to wind around the lateral malleolus; it then crossed beneath the peroneus brevis tendon anteriorly to reach the dorsum of the foot. The accessory deep peroneal nerve was found in every case examined and constantly gave off muscular branches to peroneus brevis and sensory branches to the ankle region. In addition, this nerve occasionally had muscular branches to peroneus longus and extensor digitorum brevis, and sensory branches to the fibula and the foot. The anomalous muscles around the lateral malleolus were also innervated by this nerve. Neither cutaneous branches nor communicating branches with other nerves were found. The present study reveals that the accessory deep peroneal nerve is consistently present and possesses a proper motor and sensory distribution in the lateral region of the leg and ankle. It is not an anomalous nerve as has previously been suggested.

Ligamento-muscular protective reflex in the lumbar spine of the feline

A ligamento-muscular protective reflex in the lumbar spine was demonstrated in a feline model. Stimulating electrodes were applied to the supraspinous ligament between several lumbar vertebra (L1 to L6) while recording myoelectric discharge from the paraspinal muscles at the L3, L4 and L5, bilaterally. Electromyographic (EMG) activity was present in the paraspinal muscles bilaterally, upon stimulation of the supraspinous ligament, in six preparations. The EMG discharge was strongest in the muscles one level below that of the stimulated ligament, whereas weaker EMG signals were recorded from as far as two levels above and below. The mean time delay between the application of the stimulus to the ligament to the resulting EMG ranged from 2.52 to 2.77 ms at all levels. Stimulation of the supraspinous ligament in the L6 segment resulted in a weak reflex response, and stimulation in the L7 segment did not produce any EMG activity. It was concluded that mechanoreceptors in the supraspinous ligament at the L1/6 levels may initiate sensory signals upon strain of the ligament, during flexion. This, in turn, causes contraction of the paraspinal muscles, bilaterally, to extend the spine and prevent possible damage to the ligament while maintaining stability. The results may add to the understanding of low back pain, and to the formulation of surgical procedures which could spare the neural supply of the ligament, allowing advanced physiotherapeutic modalities to be implemented for post-surgical rehabilitation.

Mechanoreceptors in the human elbow ligaments

The medial, annular, and lateral elbow ligaments from 6 fresh human cadavers were dissected from origin to insertion, stained, and examined with a light microscope to determine the existence of mechanoreceptors. It was shown that the anterior, posterior, and transverse medial ligaments as well as the annular and radial collateral ligaments were endowed with mechanoreceptors. The mechanoreceptors consisted of Golgi organs, Ruffini terminals, Pacinian corpuscles, and free nerve endings. The mechanoreceptors were distributed evenly throughout the annular and transverse medial ligament, but with increased density toward the origin and distal insertions in the radial, posterior, and anterior medial ligaments. It was concluded that the elbow ligaments may provide significant sensory function to the elbow joint, in addition to being its major mechanical restraints.

Ligamentomuscular protective reflex in the elbow

A reflex are from the medial elbow ligaments to the forearm pronator muscles was shown to exist in the feline model. A single articular branch emerging from the median nerve and converging on the medial collateral ligament was identified and stimulated with supramaximal pulses of 100 microseconds duration at a rate of 10 pulses/s. Stimulation of the articular nerve elicited myoelectric activity in the flexor digitorum superficialis, flexor digitorum profundus, flexor carpi radialis, flexor carpi ulnaris, and pronator teres. Transection of the articular nerve between the electrodes and the median nerve resulted in the disappearance of any myoelectric activity in the muscles, thus confirming the afferent nature of the articular nerve. The mean time delay from the application of the stimulus to the corresponding myoelectric discharge ranged from 3.2 to 5.8 ms for the 5 muscles. The existence of a fast-acting reflex arc from the medial elbow ligaments to the forearm muscles both confirms the concept of ligamentomuscular protective synergy (shown to exist in the knee, shoulder, and ankle joints) and extends it to the elbow. This reflex arc has significant implications for both the planning of elbow surgery while preserving the neural supply of the ligaments and for the planning of postsurgical or conservative therapeutic rehabilitation modalities.

Clinical Rationale for Closed Kinetic Chain Activities in Functional Testing and Rehabilitation of Ankle Pathologies

Ankle injuries are the most common type of injury in sport worldwide, with ankle sprains accounting for 15% of all injuries. In this paper, the most recent, significant clinical research findings related to closed chain functional testing and rehabilitation of the ankle will be summarized. Biomechanical, physiological, and neurological rationales for integrated utilization of open and closed chain rehabilitation for the ankle will be discussed.

Measurement of joint capsule tissue loading in the cat knee using calibrated mechanoreceptors

The vertical loading in the posterior capsule of the cat knee has been measured while the knee is rotated into hyperextension. Tissue loading was determined using a previously verified model of the capsule that represents its upper edge as a catenary suspension cable. Tensile loads in the cable were measured using the discharge of mechanoreceptive sensory neurons that had been calibrated as load sensors. The results revealed that the capsule is very lightly loaded in extension rotations. Less than 4% of the applied moment is sustained by the capsule.

Neurohistology of lumbar spine ligaments

A study was conducted to identify neural elements in the posterior ligaments of the lumbar spine by using a modified gold-chloride method. Three morphologic types of mechanoreceptors were identified: Ruffini corpuscles, Ruffini end organs, and pacinian corpuscles. Free nerve endings, which are thought to be responsible for pain production, were also demonstrated within the ligaments.