Immunohistochemical and histological study of human uncovertebral joints: a preliminary investigation

Acromioclavicular Disk as a Potential Source of Pain in AC Joint Injuries

BACKGROUND

Injuries of the acromioclavicular joint (ACJ) are common shoulder injuries that often lead to pain and dysfunction of the affected shoulder. Regardless of operative or nonoperative treatment, a relatively large number of patients remain symptomatic and experience pain. However, the specific source of persistent pain in the ACJ remains ambiguous.

PURPOSE

To investigate the presence of sensory nerve fibers or pain-generating neurotransmitters within the intra-articular disk of the ACJ to determine its potential role as an independent pain generator in ACJ disorders.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Twelve paired ACJs from 6 fresh human cadavers (mean age, 56 years; range, 41-82 years) were harvested and freed from surrounding soft tissues, leaving only the ACJ capsule intact. The specimens were placed in 4.5% formaldehyde fixative for a minimum of 48 hours. Coronal plane sections were obtained and demineralized in EDTA for a week, embedded in paraffin for 12 hours, and dehydrated overnight. With a rotation microtome, 2-μm sections were cut and stained with hematoxylin and eosin to investigate tissue architecture and confirm the presence of a fibrocartilaginous intra-articular disk. The sections were immunohistochemically stained with antisera against S100, neuropeptide Y (NPY), and substance P (SP) to detect for neural tissue. Additionally, a nerve fiber count per 10 high-power fields representing an area of 0.2 mm² was conducted for S100 stains. All sections were examined for the presence of positive immunoreactivity to S100, NPY, and SP.

RESULTS

The presence of a fibrocartilaginous intra-articular disk could be observed in all 12 examined ACJs. In all specimens, an immunoreactivity to S100, NPY, and SP could be observed within the superior peripheral region of the intra-articular disk. High-power field nerve counts of the S100 stains revealed a mean ± SD of 7.9 ± 2.28 nerves per 10 high-power fields (range, 4-12).

CONCLUSION

The documented immunoreactivity to S100, NPY, and SP indicates the presence of somatic and autonomic nerve fibers within the intra-articular disk of the ACJ.

CLINICAL RELEVANCE

Confirming the presence of nerve fibers within the intra-articular disk of the ACJ suggests that the disk itself could be an independent source of pain after injury and thus a possible explanation for recalcitrant pain after treatment.

Comparative Analysis of the Biomechanical Characteristics After Different Minimally Invasive Surgeries for Cervical Spondylopathy: A Finite Element Analysis

Minimally invasive surgeries, including posterior endoscopic cervical foraminotomy (PECF), microsurgical anterior cervical foraminotomy (MACF), anterior transdiscal approach of endoscopic cervical discectomy (ATd-ECD), and anterior transcorporeal approach of endoscopic cervical discectomy (ATc-ECD), have obtained positive results for cervical spondylotic radiculopathy. Nonetheless, there is a lack of comparison among them regarding their biomechanical performance. The purpose of this study is to investigate the biomechanical changes of operated and adjacent segments after minimally invasive surgeries compared to a normal cervical spine. A three-dimensional model of normal cervical vertebrae C3–C7 was established using finite element analysis. Afterwards, four surgical models (PECF, MACF, ATd-ECD, and ATc-ECD) were constructed on the basis of the normal model. Identical load conditions were applied to simulate flexion, extension, lateral bending, and axial rotation of the cervical spine. We calculated the range of motion (ROM), intradiscal pressure (IDP), annulus fibrosus pressure (AFP), uncovertebral joints contact pressure (CPRESS), and facet joints CPRESS under different motions. For all circumstances, ATc-ECD was close to the normal cervical spine model, whereas ATd-ECD significantly increased ROM and joints CPRESS and decreased IDP in the operated segment. PECF increased more the operated segment ROM than did the MACF, but the MACF obtained maximum IDP and AFP. Except for ATc-ECD, the other models increased joints CPRESS of the operated segment. For adjacent segments, ROM, IDP, and joints CPRESS showed a downward trend in all models. All models showed good biomechanical stability. With their combination biomechanics, safety, and conditions of application, PECF and ATc-ECD could be appropriate choices for cervical spondylotic radiculopathy.

Intervertebral Foramen Width Is an Important Factor in Deciding Additional Uncinate Process Resection in ACDF-a Retrospective Study

Background: Anterior cervical discectomy and fusion (ACDF) has been established as a classic procedure for the management of cervical radiculopathy. However, it is unclear whether combined uncinate process resection (UPR) is necessary for treating cervical radiculopathy. Here, we investigated the clinical outcome of ACDF combined with UPR compared to ACDF alone to determine the necessity of UPR in treating cervical radiculopathy. Hypothesis: Uncinate process resection may be necessary in certain patients along with ACDF to achieve better clinical outcomes of cervical radiculopathy. Patients and Methods: Fifty-five patients underwent ACDF with UPR, and 126 patients without UPR were reviewed. The width and height of the intervertebral foramen were measured by 45° oblique X-rays. We also measured the Japanese Orthopedic Association (JOA) score and visual analog scale (VAS) score. C2-C7 Cobb angles were obtained from all patients pre- and post-operatively. Meanwhile, linear regression analysis was used to evaluate the relationship between the clinical outcomes and the intervertebral foramen width before surgery. Results: Linear regression analysis indicated that the improvement in the JOA and VAS scores was irrelevant to both the pre-operative width of the intervertebral foramen (wIVF) and the height of the intervertebral foramen (hIVF) in the ACDF+UPR group. However, pre-operative wIVF was associated with post-operative JOA and VAS scores in the ACDF alone group. Those with pre-operative wIVF <3 mm in the ACDF group had the least improvement in post-operative clinical symptoms due to the change in wIVF (P > 0.05). The ACDF group whose wIVF was over 3 mm showed similar clinical outcomes to the ACDF + UPR group, and wIVF significantly increased post-operatively (P < 0.05). The fusion rate and C2-C7 Cobb angles did not show significant differences between the two groups (P > 0.05). Discussion: Our current findings suggest that UPR should be considered when wIVF is <3 mm pre-operatively. However, there is no need to sacrifice the uncovertebral joint in ACDF when the pre-operative wIVF is over 3 mm. Level of Evidence: Level III.

Developing a grading scale for the evaluation of degenerative changes in uncovertebral (Luschka) joints

The study aimed to develop a grading scale for evaluating degenerative changes in uncovertebral joints (UVJs) found on computed tomography (CT) scans, and assess the intra- and inter-rater reliability of this scale. The study included 50 subjects (average age 55.12 ± 13.76 years) referred for CT examinations due to cervical complaints. Three researchers developed a reading protocol using a semiquantitative grading scale of UVJ degenerative changes. CTs were read and reread several times to refine the protocol. Subsequently, the reader read and reread 20 CTs (C3-C7 bilateral, altogether 200 UVJs) 2 weeks apart in order to assess the intra-rater reliability. The second reader, after the training, read the same 20 CTs (yet, C4-C6 bilateral, altogether 120 UVJs) in order to assess the inter-rater reliability. The additional 30 CTs were evaluated to analyze the prevalence and associations between the studied parameters. The final grading scale included joint space narrowing, osteophyte, subchondral sclerosis, subchondral cyst, hypertrophy, cortical erosion, and vacuum phenomenon. The intra-rater agreement ranged from very good in joint space narrowing (k = 0.757), osteophyte grade (k = 0.748), subchondral cyst (k = 0.716), hypertrophy (k = 0.728), vacuum phenomenon (k = 0.712) to good (k = 0.544) in subchondral sclerosis, and fair in cortical erosion (k = 0.36). For the overall UVJ degeneration grade, the intra-rater agreement was very good (k = 0.616) and the inter-rater reliability was good (k = 0.468). 77.6% of the evaluated UVJs exhibited some degenerative changes. Our grading scale is the first to evaluate UVJs presenting good-very good intra-rater and inter-rater reliability which can be utilized in further clinical studies and assess degenerative changes in UVJs.

Biomechanical effects of uncinate process excision in cervical disc arthroplasty

BACKGROUND

Studies on the role of uncinate process have been limited to responses of the intact spine and patient's outcomes, and procedures to perform the excision. The aim of this study was to determine the role of uncinate process on the biomechanical response at the index and adjacent levels in three artificial discs used in cervical disc arthroplasty.

METHODS

A validated finite element model of cervical spine was used. Flexion, extension, and lateral moments and follower load were applied to Bryan, Mobi-C, and Prestige LP artificial discs at C5-C6 level with and without uncinate process. Ranges of motion at index level and adjacent caudal and cranial segments, intradiscal pressures at adjacent segments, and facet loads at index level and adjacent segments were obtained. Data were normalized with respect to the preservation of uncinate process.

FINDINGS

Uncinate process removal increased motions up to 27% at index and decreased up to 10% at adjacent levels, decreased disc pressures up to 14% at adjacent segments, decreased facet loads at adjacent segments up to 14%, while at index level, change in loads depended on mode and arthroplasty, with Mobi-C responding with up to 51% increase and Bryan disc up to 11% decrease, while Prestige LP increased loads by 17% in extension and decreased by 9%% in lateral bending.

INTERPRETATION

As surgical selection is based on morphology and surgeon's experience, the present computational findings provide quantitative information for an optimal choice of the device and procedure, while further studies (in vitro/clinical) would be required.

The Diagnostic Value of an X-ray-based Scoring System for Degeneration of the Cervical Spine: A Reproducibility and Validation Study

Background

In interventional pain medicine, cervical facet joint (CFJ) pain is commonly treated with CFJ denervation techniques, almost automatically assuming degeneration of the CFJs as an important cause of CFJ pain. A standard cervical X‐ray is still commonly used in the clinical evaluation of patients suspected for CFJ degeneration. Although degenerative features can be visualized by different radiological imaging techniques, the relation between radiological degenerative features of the cervical spine and pain remains controversial. Paramount in order to estimate the clinical usefulness of a radiological imaging is to establish the reproducibility of the radiological scoring system. A reproducible and clinically feasible diagnostic scoring system was developed to estimate cervical degeneration on standard cervical X‐rays.

Materials and Methods

A reproducibility study for the interpretation of degenerative abnormalities on standard cervical X‐rays was performed, using a dichotomous outcome (degenerative abnormalities present Yes/No). The estimation of intervertebral disc height loss on standard cervical X‐rays was validated with computed tomography (CT) scan measurements.

Results

Five radiological degenerative features on standard cervical X‐rays (disc height loss, anterior vertebral osteophytes, posterior vertebral osteophytes, vertebral end plate sclerosis, and uncovertebral osteoarthritis) showed a substantial to excellent reproducibility (kappa value ≥ 0.60). The qualitative definition of disc height loss used in the reproducibility study showed a substantial agreement with the actual measurements of disc height loss on CT scan (kappa value = 0.69).

Conclusion

Subjective judgment of a cervical standard X‐ray is a reproducible method to demonstrate degenerative abnormalities of the cervical spine.

Neuropeptide Y prevents nucleus pulposus cells from cell apoptosis and IL‑1β‑induced extracellular matrix degradation

Intervertebral disc degeneration (IDD) is characterized by excessive inflammatory reaction, and neuropeptide Y (NPY) was reported to have anti-inflammatory effect. However, the effect of NPY on NP cells has not been investigated up to date. This study aimed to clarify the role of NPY on the process of IDD. Fourteen fresh human lumbar intervertebral discs were harvested, and degeneration-related proteins were examined. Pfirrmann grading system was used to evaluate IDD. Rat nucleus pulposus (NP) cells were used to investigate the effect of NPY on the proliferation, apoptosis, and extracellular matrix (ECM) in NP cell induced by IL-1βin vitro. The expression levels of NPY and its receptors (type 1 receptor, Y1R, and type 2 receptor, Y2R) were detected via immunohistochemical analysis, western blot, and quantitative real-time polymerase chain reaction (qRT-PCR). Cell viability and proliferation were explored using cell counting kit-8 assay, western blot, and immunofluorescence analysis. Cell apoptosis was investigated by Hoechst staining, JC-1 Staining, annexin V-FITC/PI double staining, and western blot. The secretion of NPY from NP cells was determined via enzyme-linked immunosorbent assay (ELISA). The expression of anabolic and catabolic gene was analyzed by qRT-PCR, western blot, immunofluorescence analysis, and ELISA. The expression of Y2R was significantly increased in both human degenerative intervertebral discs and IL-1β-induced NP cells. Although no positive results for NPY indicated by western blot both in vivo and in vitro, ELISA results demonstrated that the secretion of NPY from NP cells was increased by low-concentration IL-1β, but was decreased when the concentration of IL-1β was 30 ng/ml and above. In addition, NPY could promote NP cells proliferation and protect NP cells against IL‑1β‑induced apoptosis via suppressing mitochondrial-mediated apoptosis pathway. What's more, NPY can suppress the expression of catabolic gene and ameliorate IL-1β- induced matrix degeneration in NP cells. In conclusion, NPY could promote NP cell proliferation and alleviate IL‑1β‑induced cell apoptosis via mitochondrial pathway. In addition, NPY can suppress the expression of ECM‑catabolic proteinases and ameliorate IL-1β- induced ECM degeneration in vitro.

The peridural membrane of the spine has characteristics of synovium

The peridural membrane (PDM) is a well-defined structure between dura mater and the wall of the spinal canal. The spine may be viewed as a multi-segmented joint, with the epidural cavity and neural foramina as joint spaces and PDM as synovial lining. The objective of this investigation was to determine if PDM has histological characteristics of synovium. Samples of the PDM of the thoraco-lumbar spine were taken from 23 human cadavers and analyzed with conventional light microscopy and confocal microscopy. Results were compared to reports on similar analyses of synovium in the literature. Histological distribution of areolar, fibrous, and adipose connective tissue in PDM was similar to synovium. The PDM has an intima and sub-intima. No basement membrane was identified. CD68, a marker for macrophage-like-synoviocytes, and CD55, a marker for fibroblast-like synoviocytes, were seen in the lining and sub-lining of the PDM. Multifunctional hyaluronan receptor CD44 and hyaluronic acid synthetase 2 marker HAS2 were abundantly present throughout the membrane. Marked presence of CD44, CD55, and HAS2 in the well-developed tunica muscularis of blood vessels and in the body of the PDM suggests a role in the maintenance and lubrication of the epidural cavity and neural foramina. Presence of CD68, CD55, and CD44 suggests a scavenging function and a role in the inflammatory response to noxious stimuli. Thus, the human PDM has histological and immunohistochemical characteristics of synovium. This suggests that the PDM may be important for the homeostasis of the flexible spine and the neural structures it contains.

Microanatomical considerations for safe uncinate removal during anterior cervical discectomy and fusion: 10-year experience

Cervical radiculopathy from uncovertebral joint (UVJ) hypertrophy and nerve root compression often occurs anterior and lateral within the cervical intervertebral foramen, presenting a challenge for complete decompression through anterior cervical approaches owing to the intimate association with the vertebral artery and associated venous plexus. Complete uncinatectomy during anterior cervical discectomy and fusion (ACDF) is a controversial topic, many surgeons relying on indirect nerve root decompression from restoration of disc space height. However, in cases of severe UVJ hypertrophy, indirect decompression does not adequately address the underlying pathophysiology of anterolateral foraminal stenosis. Previous reports in the literature have described techniques involving extensive dissection of the cervical transverse process and lateral uncinate process (UP) in order to identify the vertebral artery for safe removal of the UP. Recent anatomical investigations have detailed the microanatomical organization of the fibroligamentous complex surrounding the UP and neurovascular structures. The use of the natural planes formed from the encapsulation of these connective tissue layers provides a safe passage for lateral UP dissection during anterior cervical approaches. This can be performed from within the disc space during ACDF to avoid extensive lateral dissection. In this article, we present our 10-year experience using an anatomy-based microsurgical technique for safe and complete removal of the UP during ACDF for cervical radiculopathy caused by UVJ hypertrophy.

CGRP and Painful Pathologies Other than Headache

CGRP has long been suspected as a mediator of arthritis pain, although evidence that CGRP directly mediates human musculoskeletal pain remains circumstantial. This chapter describes in depth the evidence surrounding CGRP's association with pain in musculoskeletal disorders and also summarises evidence for CGRP being a direct cause of pain in other conditions. CGRP-immunoreactive nerves are present in musculoskeletal tissues, and CGRP expression is altered in musculoskeletal pain. CGRP modulates musculoskeletal pain through actions both in the periphery and central nervous system. Human observational studies, research on animal arthritis models and the few reported randomised controlled trials in humans of treatments that target CGRP provide the context of CGRP as a possible pain biomarker or mediator in conditions other than migraine.

Neck function in early hominins and suspensory primates: Insights from the uncinate process

OBJECTIVES

Uncinate processes are protuberances on the cranial surface of subaxial cervical vertebrae that assist in stabilizing and guiding spinal motion. Shallow uncinate processes reduce cervical stability but confer an increased range of motion in clinical studies. Here we assess uncinate processes among extant primates and model cervical kinematics in early fossil hominins.

MATERIALS AND METHODS

We compare six fossil hominin vertebrae with 48 Homo sapiens and 99 nonhuman primates across 20 genera. We quantify uncinate morphology via geometric morphometric methods to understand how uncinate process shape relates to allometry, taxonomy, and mode of locomotion.

RESULTS

Across primates, allometry explains roughly 50% of shape variation, as small, narrow vertebrae feature the relatively tallest, most pronounced uncinate processes, whereas larger, wider vertebrae typically feature reduced uncinates. Taxonomy only weakly explains the residual variation, however, the association between Uncinate Shape and mode of locomotion is robust, as bipeds and suspensory primates occupy opposite extremes of the morphological continuum and are distinguished from arboreal generalists. Like humans, Australopithecus afarensis and Homo erectus exhibit shallow uncinate processes, whereas A. sediba resembles more arboreal taxa, but not fully suspensory primates.

DISCUSSION

Suspensory primates exhibit the most pronounced uncinates, likely to maintain visual field stabilization. East African hominins exhibit reduced uncinate processes compared with African apes and A. sediba, likely signaling different degrees of neck motility and modes of locomotion. Although soft tissues constrain neck flexibility beyond limits suggested by osteology alone, this study may assist in modeling cervical kinematics and positional behaviors in extinct taxa.

Musculoskeletal Ultrasound: A Novel Approach for Luschka's Joint and Vertebral Artery

Background

Cervical vertigo has been a controversial diagnosis for several years, and the lack of a diagnostic test is a critical problem. Musculoskeletal ultrasound (MSUS) is a real-time dynamic approach that is used to investigate the musculoskeletal and vascular systems.

Material/Methods

In this study, MSUS was used to examine whether there is a relationship among vertigo, the vertebral artery (VA), and Luschka’s joint proliferation in patients with cervical vertigo.

Results

MSUS clearly revealed the size, shape, and characteristics of the Luschka’s joint, the VA, and the surrounding structures. The Luschka’s joint proliferation was not distributed uniformly, but the predilection sites were C4/5 (50.5%) and C5/6 (32.3%). The proliferation from C4/5 and C5/6 Luschka’s joints was the major cause of the grade 2/3 VA tortuosity. Moreover, there was a significant correlation between VA compression from Luschka’s joint proliferation and the symptoms of cervical vertigo.

Conclusions

MSUS is a real-time and noninvasive technique that can be used to locate and observe Luschka’s joint and the VA during research and clinical applications. In future practice MSUS could be used as a diagnostic approach for patients with suspected cervical vertigo.

Anatomy and clinical significance of the uncinate process and uncovertebral joint: A comprehensive review

INTRODUCTION

The uncinate process and its associated uncovertebral articulation are features unique to the cervical spine. This review examines the morphology of these unique structures with particular emphasis on the regional anatomy, development and clinical significance.

MATERIALS AND METHODS

Five electronic databases were utilized in the literature search and additional relevant citations were retrieved from the references. A total of 74 citations were included for review.

RESULTS

This literature review found that the uncinate processes and uncovertebral articulations are rudimentary at birth and develop and evolve with age. With degeneration they become clinically apparent with compression of related structures; most importantly affecting the spinal nerve root and vertebral artery. The articulations have also been found to precipitate torticollis when edematous and be acutely damaged in severe head and neck injuries. The uncinate processes are also important in providing stability and guiding the motion of the cervical spine.

CONCLUSION

This review is intended to re-examine an often overlooked region of the cervical spine as not only an interesting anatomical feature but also a clinically relevant one.