Assessing macroscopic and microscopic indicators of osteoarthritis in the distal interphalangeal joints: a cadaveric study

Osteoarthritis is manifested both by macroscopically visible lesions and by specific histological indicators. Although traditional views of the disease process invoke physical abrasion of joint surfaces, recent studies indicate that tissue-level changes may precede grossly visible lesions of articular cartilage. This study investigates the association between gross and histological indicators of osteoarthritis at the manual interphalangeal joints, and examines a sequence of events that may lead to the onset of cartilage degeneration. Interphalangeal joints from the hands of nine cadavers were dissected, of which 52 joints were collected and further evaluated. Gross degradation of the proximal articular surface was graded on a scale of 0-3 (with 0 representing normal cartilage with no visible lesions). Osteoarthritic lesions were found in 86% of specimens and showed no preferential occurrence between males and females or right and left hands. Histological analysis indicated that known microscopic indicators of osteoarthritis always occur in Grade 1-3 specimens, but can also be recognized in some macroscopically normal specimens. Many macroscopically normal specimens exhibited chondrocyte clustering (28.6%) and/or tide mark irregularities (57%), indicating that these features are most likely the earliest to develop in the progression of osteoarthritis. It is possible that the initiating etiology is thickening of the subchondral bone, but this was not directly observed. Results indicate significant thinning of the cartilage as macroscopic degradation progresses. Our study supports, with slight modification, a previously proposed cascade of histological changes that may ultimately lead to the physical destruction of articular cartilage.     

Mild degenerative changes of hip cartilage in elderly patients: an available sample representative of early osteoarthritis

This study investigated the cellular and molecular changes which occur in cartilage from adults with femoral neck fracture (FNF) and osteoarthritis (OA), and explored the similarities in hip cartilage obtained from elderly patients and patients with early OA. Femoral heads were retrieved from 23 female patients undergoing total hip arthroplasty (THA). This group included 7 healthy patients with FNF (hFNF), 8 elderly adults with FNF (eFNF), and 8 elderly patients with hip OA (OA). After high-field MRI T2 mapping, osteochondral plugs were harvested from the weight-bearing area of femoral heads for subsequent macroscopic, histologic, and immunochemical evaluation. Additionally, the contents of cartilage matrix were analyzed, and gene expression was detected. The surface of cartilage from hFNF and eFNF patients appeared smooth, regular, and elastic, whereas it showed irregularities, thinning, and defects in OA patients. Elevated T2 values and decreased accumulation of glycosaminoglycans (GAGs) were detected in cartilage from eFNF patients. Furthermore, type I collagen accumulation was slightly increased and type X collagen concentration was obviously elevated in eFNF patients; however, type II collagen distribution and the contents and anisotropy of collagen fibrils in eFNF patients showed no significant changes. Consistent with histology and immunohistochemical results, aggrecan was downregulated and type X collagen was upregulated, while collagens types I and II showed no significant changes in eFNF patients. The cellular and molecular characteristics of hip cartilage in eFNF patients who showed no symptoms of OA were similar to those in patients with mild OA. Thus, eFNF cartilage can serve as a comparative specimen for use in studies investigating early OA.     

A degeneration-based hypothesis for interpreting fibrillar changes in the osteoarthritic cartilage matrix

The collagen fibrillar architectures in the general matrix of cartilage slices removed from both normal and osteoarthritic femoral heads were examined by both differential interference light microscopy and scanning electron microscopy. Whereas the normal general matrix contained a finely differentiated pseudo-random weave of fibrils developed from an interconnected array of radial elements, the osteoarthritic general matrix was characterised by the presence of structurally distinct regions consisting of strongly aligned radial bundles of fibrils and associated intense tangles or 'knotted' features. Simple structural models were developed to explore possible transformation structures based on two different types of interconnectivity in the three-dimensional fibrillar network. These models support the hypothesis that the distinctive ultrastructural features of the osteoarthritic general matrix can develop as a consequence of largely passive degradative changes occurring in the fibrillar weave originally present in the normal matrix. This could, in principle, occur independently of any new structure that might develop as a consequence of any upregulation of collagen associated with the osteoarthritic process.     

Bilateral symmetry of the subtalar joint facets and the relationship between the morphology and osteoarthritic changes

There is a paucity in the literature regarding bilateral symmetry between the facets of the subtalar joint. Often surgeons use the contralateral side as a reference when dealing with a fracture or other joint pathology. Moreover, the presence of osteoarthritic (OA) changes in the subtalar joint is suggested to have a relation with its morphology. In this study, we addressed both these issues. Forty pairs of cadaveric tali and calcanei were analyzed by dissection and measurement. Twenty pairs of asymptomatic calcanei were morphologically analyzed by computer tomography imaging. In the cadaveric feet, the length and width of the facets, the number and interfacet connections, the intersection angle, and the presence of OA changes were registered. In the healthy feet, the orientation and curvature of the posterior facet were analyzed based on cylinder fittings. Bilateral symmetry was tested with paired Student's t tests. Significant associations between morphometric parameters and the presence of OA changes were tested with generalized estimating equation logistic regression models. The morphometric data demonstrated a high degree of bilateral symmetry. The types of tali and calcanei between left and right differed in about one-fifth of the individuals. No significant interactions were found between morphological parameters and the presence of OA changes. Only age had a significant association. There was a high degree of symmetry in the subtalar joints facets. No significant associations were found between OA changes and morphological features, whereas other studies did. Further research is needed to explore this relationship in further detail. Clin. Anat., 33:997–1006, 2020. © 2019 Wiley Periodicals, Inc.     

Rapid volumetric gagCEST imaging of knee articular cartilage at 3 T: evaluation of improved dynamic range and an osteoarthritic population

Chemical exchange saturation transfer of glycosaminoglycans, gagCEST, is a quantitative MR technique that has potential for assessing cartilage proteoglycan content at field strengths of 7 T and higher. However, its utility at 3 T remains unclear. The objective of this work was to implement a rapid volumetric gagCEST sequence with higher gagCEST asymmetry at 3 T to evaluate its sensitivity to osteoarthritic changes in knee articular cartilage and in comparison with T₂ and T_1ρ measures. We hypothesize that gagCEST asymmetry at 3 T decreases with increasing severity of osteoarthritis (OA). Forty‐two human volunteers, including 10 healthy subjects and 32 subjects with medial OA, were included in the study. Knee Injury and Osteoarthritis Outcome Scores (KOOS) were assessed for all subjects, and Kellgren‐Lawrence grading was performed for OA volunteers. Healthy subjects were scanned consecutively at 3 T to assess the repeatability of the volumetric gagCEST sequence at 3 T. For healthy and OA subjects, gagCEST asymmetry and T₂ and T_1ρ relaxation times were calculated for the femoral articular cartilage to assess sensitivity to OA severity. Volumetric gagCEST imaging had higher gagCEST asymmetry than single‐slice acquisitions (p = 0.015). The average scan‐rescan coefficient of variation was 6.8%. There were no significant differences in average gagCEST asymmetry between younger and older healthy controls (p = 0.655) or between healthy controls and OA subjects (p = 0.310). T₂ and T_1ρ relaxation times were elevated in OA subjects (p < 0.001 for both) compared with healthy controls and both were moderately correlated with total KOOS scores (rho = ?0.181 and rho = ?0.332 respectively). The gagCEST technique developed here, with volumetric scan times under 10 min and high gagCEST asymmetry at 3 T, did not vary significantly between healthy subjects and those with mild‐moderate OA. This further supports a limited utility for gagCEST imaging at 3 T for assessment of early changes in cartilage composition in OA.     

On fragmenting,densely mineralised acellular protrusions into articular cartilage and their possible role in osteoarthritis

High density mineralised protrusions (HDMP) from the tidemark mineralising front into hyaline articular cartilage (HAC) were first described in Thoroughbred racehorse fetlock joints and later in Icelandic horse hock joints. We now report them in human material. Whole femoral heads removed at operation for joint replacement or from dissection room cadavers were imaged using magnetic resonance imaging (MRI) dual echo steady state at 0.23 mm resolution, then 26‐μm resolution high contrast X‐ray microtomography, sectioned and embedded in polymethylmethacrylate, blocks cut and polished and re‐imaged with 6‐μm resolution X‐ray microtomography. Tissue mineralisation density was imaged using backscattered electron SEM (BSE SEM) at 20 kV with uncoated samples. HAC histology was studied by BSE SEM after staining block faces with ammonium triiodide solution. HDMP arise via the extrusion of an unknown mineralisable matrix into clefts in HAC, a process of acellular dystrophic calcification. Their formation may be an extension of a crack self‐healing mechanism found in bone and articular calcified cartilage. Mineral concentration exceeds that of articular calcified cartilage and is not uniform. It is probable that they have not been reported previously because they are removed by decalcification with standard protocols. Mineral phase morphology frequently shows the agglomeration of many fine particles into larger concretions. HDMP are surrounded by HAC, are brittle, and show fault lines within them. Dense fragments found within damaged HAC could make a significant contribution to joint destruction. At least larger HDMP can be detected with the best MRI imaging ex vivo.     

髋关节软骨高、低负重区微纳结构的力学性质对比

文题释义：微纳层面：相对于宏观层面而言,是对宏观层面的一个补充,由肉眼可见的毫米级别到肉眼不可见的微米、纳米级别。分别使用微米级、纳米级原子力显微镜探针测量软骨微纳弹性模量,以揭示软骨在微纳层面力学性能的特点,以及与宏观层面力学性能的关系。 负重区：在日常活动运动中,由于机体力线等不同,势必造成软骨不同区域负重出现不同,不同的负重也会影响到胶原纤维等物质的重塑重构,引起软骨力学性能的改变。 背景：髋关节软骨具有高、低负重区域,既往研究表明2个区域的宏观弹性模量是不同的。然而在微米和纳米水平上的弹性模量尚不清楚,这些信息对于进一步理解软骨微米和纳米力学性质至关重要。此外,影响软骨2个区域机械性能的微纳结构至今仍有待阐明。 目的：探究微纳层面髋关节软骨高、低负重区力学性质与结构。 方法：取新鲜正常猪股骨头软骨,使用原子力显微镜直径为5 μm的球形尖端测量不同负重区微米级压缩弹性模量,使用曲率半径为5 nm的ScanAsyst-Air探针测量其纳米级压缩弹性模量、纳米结构和胶原纤维直径。扫描电子显微镜用于识别软骨不同负重区微米结构。 结果与结论：①股骨头软骨高负重区微米级弹性模量为(433.05±146.52) kPa,低负重区微米级弹性模量为(331.19±84.88) kPa,高负重区域在微米水平上的压缩弹性模量显著高于低负重区域(P=0.029 8);②股骨头软骨高负重区纳米级弹性模量为(1.24±0.42) GPa,低负重区纳米级弹性模量为(1.28±0.41) GPa,在纳米水平上2个区域的胶原纤维的压缩弹性模量差异无显著性意义(P=0.846 2);③在微米水平上,股骨头软骨高负重区域的胶原纤维排列更规则;在纳米水平上,2个负重区域的胶原纤维直径差异无显著性意义(P=0.926 4);④以上结果表明,股骨头软骨高负重区胶原纤维较低负重区交联更规则,使软骨高负重区微米级压缩弹性模量高于低负重区,与宏观上压缩弹性模量趋势一致,但高负重并没有影响到纳米层面单个胶原纤维。 ORCID: 0000-0001-7971-5372(郭江博) 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程     

Associations between the properties of the cartilage matrix and findings from quantitative MRI in human osteoarthritic cartilage of the knee

The aim of this study was to investigate the associations between the properties of the cartilage matrix and the results of T2 mapping and delayed gadolinium-enhanced magnetic resonance imaging (dGEMRIC) in human knee osteoarthritic cartilage. Osteochondral samples were harvested from the middle part of the femoral condyle and tibial plateaus of 20 patients with knee osteoarthritis (OA) during total knee arthroplasty. Sagittal T2 mapping, T1pre, and T1Gd were performed using 7.0T magnetic resonance imaging (MRI). Gycosaminoglycan (GAG) distribution was evaluated by OARSI, collagen anisotropy was assessed by polarized light microscopy (PLM), and biochemical analyses measured water, GAG, and collagen content. Associations between properties of the cartilage matrix and T2 and ΔR1 (1/T1Gd-1/T1pre) values were explored using correlation analysis. T2 and ΔR1 values were significantly correlated with the degree of cartilage degeneration (OARSI grade; Ρ = 0.53 and 0.77). T2 values were significantly correlated with water content (r = 0.69; P < 0.001), GAG content (r = -0.43; P < 0.001), and PLM grade (r = 0.47; P < 0.001), but not with collagen content (r = -0.02; P = 0.110). ΔR1 values were significantly correlated with GAG content (r = -0.84; P < 0.001) and PLM grade (r = 0.41; P < 0.001). Taken together, T2 mapping and dGEMRIC results were correlated with the properties of the cartilage matrix in human knee osteoarthritic cartilage. Combination T2 mapping and dGEMRIC represents a potential non-invasive monitoring technique to detect the progress of knee OA.     

An investigation of the anatomy of the infrapatellar fat pad and its possible involvement in anterior pain syndrome: a cadaveric study

The infrapatellar fat pad (IFP) is an extrasynovial, intracapsular, adipose body occupying the space in the knee joint between the inferior border of the patella, the femoral condyles, tibial plateau and patellar tendon. Little is known about the anatomy and normal function of the IFP, but it has been suggested to play a role in the aetiology of Anterior knee pain syndrome, including that associated with osteoarthritis. Forty-three knees from 11 male and 15 female embalmed cadavers (mean age 84 years; range 55–97 years) were investigated. The cadavers were donated and the study performed in compliance with the provisions of the UK Human Tissue Act (2004). The quadriceps tendon and the medial and lateral patellar retinacula were dissected from the patella, which was then reflected antero-distally. The IFP was carefully excised and details of its morphology and attachments to components of the knee joint were recorded, together with the presence of articular surface pathology on the patella and femoral condyles. The principal novel findings of the current study were that 81% of IFPs were attached to the superior border of the patella by supero-medial extensions and 65% were attached by supero-lateral extensions; the supero-medial extensions were larger than the supero-lateral extensions. The superior extensions of the IFP were always attached anteriorly to the patellar retinacula and in four individuals the extensions formed a full loop around the superior border of the patella. The volume of IFPs with attachments to the superior border of the patella was significantly greater (p = .007) than those without, and the IFP was attached to the medial meniscus in significantly (p = .009) more knees with IFP attachment to the superior border of the patella than those without. All IFPs were attached to the medial anterior horn of the meniscus and the medial Kaplan’s ligament. Ninety-seven per cent were attached to the lateral anterior horn of the meniscus and 97% to the lateral Kaplan’s ligament. The length of IFP attachment to the lateral meniscus was significantly longer (p = .004) than that to the medial meniscus. Ninety-seven per cent of IFPs were attached to the superior portion of the patellar tendon with the mean tendon attachment being 60%. Ninety-one per cent of IFPs were attached to the inferior border of the patella. Significantly fewer knees with patellar (p = .001) and femoral (p = .002) articular surface osteophytes exhibited superior IFP extensions and these extensions were significantly shorter in knees with patellar (p = .000) and femoral (p = .006) osteophytes, compared with those without. The IFP was attached to the medial meniscus in significantly fewer knees with femoral (p = .050) and patellar (p = .023) osteophytes than those without. All IFPs not attached to the anterior horn of the lateral menisci, medial Kaplan’s ligament, superior patella or inferior border of the patella, were in knees with articular surface osteophytes. This relationship between IFP morphology and knee joint pathology suggests a functional role for the IFP that requires further investigation.     

发育性髋关节发育不良一个家系调查及其危险因素分析

目的了解发育性髋关节发育不良(developmental dysplasia of the hip,DDH)家系患者的临床表现及其危险因素。方法对1个DDH家系中的全部成员进行详细的流行病学调查、体格检查、运动功能评定、实验室检查及X线拍片检查。结果9代218人聚居的家系,现存145人中DDH的发生率为31.03%,患者主要表现为双侧膝关节和髋关节对称性疼痛,髋屈曲、内外旋、活动受限,部分患者出现关节运动功能障碍及畸形而跛行。影像学改变主要以髋臼浅平,倾斜度增加,对股骨头包容不足、股骨头形态失常、关节间隙狭窄呈退行性改变为主。DDH发生的主要危险因素为遗传因素、性别、出生的季节等,家系中双亲或一方为DDH者其子女发生DDH的危险性比非患者双亲高,有一级亲属患DDH者比二、三级亲属者患病的危险性高;女性患病高于男性,冬季出生者高于其它几个季节,但儿童青少年发病率与成人无差异,与家系无血缘关系的迁入者与有血缘关系的家族成员发病率也无差异。结论遗传因素对发育性髋关节发育不良的发生有一定作用,但后天的一些环境因素也起着重要作用。     

Recent advances in the understanding of molecular mechanisms of cartilage degeneration,synovitis and subchondral bone changes in osteoarthritis

Osteoarthritis (OA), the most common form of degenerative joint disease, is linked to high morbidity. It is predicted to be the single greatest cause of disability in the general population by 2030. The development of disease-modifying therapy for OA currently face great obstacle mainly because the onset and development of the disease involve complex molecular mechanisms. In this review, we will comprehensively summarize biological and pathological mechanisms of three key aspects: degeneration of articular cartilage, synovial immunopathogenesis, and changes in subchondral bone. For each tissue, we will focus on the molecular receptors, cytokines, peptidases, related cell, and signal pathways. Agents that specifically block mechanisms involved in synovial inflammation, degeneration of articular cartilage, and subchondral bone remodeling can potentially be exploited to produce targeted therapy for OA. Such new comprehensive agents will benefit affected patients and bring exciting new hope for the treatment of OA.     

An evaluation of the relationship between the degree of entheseal changes and the severity of osteodegenerative processes at fibrocartilaginous entheses

An enthesis refers to the interface at which a tendon or a ligament integrates into the periosteum. Its morphology can be influenced by intrinsic factors such as sex, age, and extrinsic factors such as levels of activity, which will in turn impact on bone remodeling and lead to morphological changes. In bioarcheology, entheseal changes have had a long tradition of being used for the reconstruction of past activities. The literature has shown that in some cases of osteoarthritis, entheseal changes are associated with osteoarthritic manifestations. This work aims to evaluate the relationship between the degree of entheseal changes and the severity of osteodegenerative processes. The studied materials consisted of 30 humeri and 30 femora from the osteological collection at St George's University of London. Intensities of both entheseal changes and osteodegenerative processes were macroscopically assessed and scored. The difference in scores of entheseal changes between osteoarthritic groups and nonosteoarthritic groups is statistically significant at a confidence level of 95% (α = .05) for both the humeri and femora. Results show a positive correlation between the degree of entheseal changes and the severity of osteodegenerative processes in the femora, suggesting that enthesis may play a role in osteoarthritis. Findings from this work supports the proposed hypothesis that the degree of entheseal changes and the severity of osteoarthritic manifestation are related. This work contributes to current knowledge that osteoarthritis is a disease involving the whole joint; the enthesis could potentially be a target for the diagnosis of osteoarthritis.     

Discrepancy between sonographic and radiographic values after ultrasound-monitored treatment of developmental dysplasia of the hip

Introduction

The purpose of the study was to examine the accordance between the actually used sonographic and radiographic standard values after ultrasound-monitored treatment of developmental dysplasia of the hip (DDH).

Material and methods

One hundred and fifty-three (119 children) ultrasound-monitored treated hips (initial staging according to Graf: type IIc–IV) which attained normal ultrasound findings (type I according to Graf) during treatment and underwent an anteroposterior radiograph of the pelvis at the time of starting walking (mean age 18.6 months) were evaluated retrospectively.

Results

While all hips showed normal sonographic values (Graf type I), 26 (17%) showed mild and 17 (11.1%) severe dysplasia (by measuring the acetabular index) according to the radiographic Toennis classification system, and 29 (19%) showed mild and 48 (31.4%) severe dysplasia according to the Wiberg centre-edge angle.

Conclusions

This data show that the actually used sonographic and radiographic standard values concerning DDH do not correlate appropriately. It must be put up for discussion whether the radiographic standard values might be too strict. Further criteria must be developed to better assess the prognosis of residual dysplasia.     

High heritability of bone size at the hip and spine in Chinese

Bone size, an independent determinant of bone strength, is an important risk factor for osteoporotic fracture. In the present study, we investigated the magnitude of the genetic determination of bone size at the spine and hip and their genetic covariation (if any) in a population of Chinese residing in Shanghai City of P.R. China. The subjects were 50 healthy full-sib pairs of females, 188 mother-daughter pairs, and 128 husband-wife pairs selected from 401 nuclear families. Bone size (centimeters squared) was measured at the spine and hip by dual-energy X-ray absorptiometry (DEXA). The narrow-sense heritabilities h ² (SE) of bone size at the spine and hip were 0.63 (0.14) and 0.45 (0.14) respectively when estimated by full-sib pairs, and 0.60 (0.07) and 0.69 (0.07) respectively when estimated by mother-daughter pairs. Marginally significant genetic correlation was observed between the spine and hip bone size. The significantly and moderately high h ² values for bone size demonstrated in this study warrant a subsequent genetic study to search for the genes or genomic regions underlying the phenotype in Chinese.     

儿童发育性髋关节发育不良解剖学改变与影像学表现

背景:发育性髋关节发育不良是常见的儿童髋关节发育畸形,该病不同时期的治疗效果不同,早期治疗疗效较好,并发症较少,远期的预后更好,可以减少复发率,减轻经济压力,提高生活质量,所以,临床上对发育性髋关节发育不良的早期诊断越来越重要。目的:对发育性髋关节发育不良的解剖学改变及影像学表现的研究进展进行综述。方法:以"DDH,Anatomy,X-ray Radiography,CT,MRI,Ultrasound"为英文检索词,"发育性髋关节发育不良,解剖,X线摄影,CT,MRI,超声"为中文检索词,对PubMed、Springerlink等英文数据库及万方、CNKI等中文数据库进行检索,检索时限为1990年1月至2019年12月,排除与文章研究目的无关及重复性研究,纳入符合标准的55篇文献进行综述。结果与结论:影像学诊断作为一种无创性的检查手段,已经成为诊断发育性髋关节发育不良首选的检查方法,而明确其解剖学改变更有助于临床影像学诊断,常规X射线片能够进行发育性髋关节发育不良的快速筛查;MRI有助于分辨软组织结构以及骨性结构早期信号改变;三维CT能够多角度评价髋臼骨性结构改变,排除了体位因素造成的遮挡;超声同样能够进行发育性髋关节发育不良筛查,并对关节积液更加敏感。所以,不同的影像学检查各有优势,相辅相成,提高发育性髋关节发育不良的早期诊断率。     

Mechanical complications and reconstruction strategies at the site of hip spacer implantation

Over the past two decades antibiotic-impregnated hip spacers have become a popular procedure in the treatment of hip joint infections. Besides infection persistence and/or reinfection, major complications after hip spacer implantation include spacer fracture, -dislocation, and bone fracture. Moreover, in cases with extensive loss of femoral and/or acetabular bone alternative reconstructive techniques should be used for a stable spacer fixation and prevention of fractures or dislocations. The present article reviews the different types of spacer fractures and dislocations and offers some suggestions about reconstructive techniques for management of extensive loss of femoral and/or acetabular bone at the site of hip spacer implantation.     

A correlative study of MR images and cryo-sections of the neonatal hip

Summary The complex anatomy of the neonatal hip is often difficult to image. Recently, magnetic resonance imaging (MRI) has been used to evaluate the normal and abnormal neonatal hip. We correlated the MRI scans of the hip of a newborn cadaver with multiplanar cryo-sections stained according to Mallory-Cason, to detail the anatomic structures of the normal hip joint space. In our experience, MRI was shown to provide excellent depiction of hip anatomy.

---

Corrélations anatomoradiologiques par cryosection et IRM de la hanche du nouveau-né

Résumé L'anatomie complexe de la hanche du nouveau-né est souvent difficile à illustrer. Récemment, l'IRM a été utilisée pour étudier la hanche normale et pathologique du nouveau-né. Nous avons corrélé des explorations IRM de la hanche d'un enfant mort-né avec des cryosections faites dans divers plans. La technique de coloration de Mallory-Cason a été utilisée pour montrer le détail des structures anatomiques de la hanche normale. Dans ce travail l'IRM s'est avérée un excellent moyen d'exploration de l'anatomie de la hanche.

     

Comparison of microscopic and endoscopic view of the internal acoustic meatus: A cadaveric study

The endoscope is thought to provide an improved exposure of the internal acoustic meatus after retrosigmoid craniotomy for microsurgical resection of intrameatal tumors. The aim of this study is to quantify the differences in internal acoustic meatus (IAM) exposure comparing microscopic and endoscopic visualization. A retrosigmoid approach was performed on 5 cadaver heads. A millimeter gauge was introduced into the internal acoustic meatus, and examinations with a surgical microscope and 0°, 30° and 70° rigid endoscopes were performed. The extent of IAM depth visualized with the microscope and the different angled endoscopes were analyzed. The microscopic view allowed an average IAM depth visualization of 2.8 mm. The endoscope allowed an improved exposure of IAM in all cases. The 0°, 30° and 70° endoscopes permitted an exposure that was respectively 96% (5.5 mm), 139% (6.7 mm) and 200% (8.4 mm) more lateral than the microscopic view. Angled optics, however, provided an image distortion, specifically the 70° endoscope. The endoscope provides a superior visualization of the IAM compared to the microscope when using a retrosigmoid approach. The 30° endoscope represented an ideal compromise of superior visualization with marginal image distortion. Additional implementation of the endoscope into microsurgery of intrameatal tumors likely facilitates complete tumor removal and might spare facial and vestibulocochlear function. Clin. Anat. 31:398–403, 2018. © 2017 Wiley Periodicals, Inc.