Consistent Anatomic Landmarks Research Articles

Defining the limits of the anterior wall of the cavernous sinus through an endoscopic view: Cadaveric anatomical study.

The anterior wall of the cavernous sinus (CS) represents an important landmark for endoscopic surgery that although mentioned before, no precise anatomical boundaries have been described. We describe the anatomical landmarks that delimit the anterior wall of the CS, emphasizing its importance as a reference for accessing the CS through endoscopic approaches. Six adult cadaveric heads fixed with formaldehyde and injected with colored silicone were studied. In all the heads, an endonasal endoscopic approach to the sellar and parasellar regions was performed and the anatomy of the anterior wall of the CS was studied. Four consistent anatomical landmarks that mark the limits of the anterior wall of the CS were found in all the specimens: anterosuperiorly, the lateral opticocarotid recess; posterosuperiorly, the medial opticocarotid recess; anteroinferiorly, the inferior part of the maxillary strut; and posteroinferiorly, the superolateral angle of the clival recess. It is of paramount importance to recognize the anatomical landmarks that define the limits of the anterior wall of the CS to achieve a safe access to this so complex region.

Internal Acoustic Meatus Localization During Anterior Petrosectomy: A Novel Technique

Anterior petrosectomy demands localization of the internal auditory canal (IAC) for safe bone drilling and maximum exposure. Various techniques have been described in the literature, each with shortcomings. We propose a new technique to localize the internal acoustic meatus (IAM) using more consistent anatomical landmarks. The study was done in three phases. In phase-I (radiological), computed tomography scan heads of fifty patients (100 sides) were analyzed. Arcuate eminence-Greater Superficial Petrosal Nerve bifurcation angle(Garcia-Ibanez technique), Arcuate eminence-IAC angle(Fisch technique) and a new angle formed between foramen ovale (FO) and foramen spinosum (FS) line, and FS and IAM line (FO-FS-IAM angle) was measured. The mean, standard deviation, and variance were calculated. In phase-II (cadaveric), the FO-FS-IAM angle was measured on five (10 sides) dry skulls. In phase-III (clinical), the IAM was localized using the FO-FS-IAM angle in 13 patients. The mean angle between arcuate eminence and Greater Superficial Petrosal Nerve (Garcia-Ibanez technique) was 126.20±11.63°(range 106-156) with a variance of 135.20. The mean bifurcation angle was 63±5.81°(range 53-78). By the Fisch technique, the mean arcuate-IAM angle was 73.5±11.70°(range 51-105) with a variance of 137.18. By our technique, the mean FO-FS-IAM angle was 94.72±5.89°(range 84-108). The variance was 34.73. The mean FO-FS-IAM angle on dry skulls was identical (95±1.97°) to our radiological measurements. This angle was reproduced reliably in clinical cases for localizing the IAM during anterior petrosectomy. The FO-FS-IAM angle variance was much lower than the analogous angles measured by Garcia-Ibanez and Fisch techniques, making it a more reliable and effective tool for localizing the IAM.

Retrograde incision from orifice (RIO) technique for endoscopic incision of ureterocele: 15 years of outcomes

Management of obstructing ureterocele often includes endoscopic transurethral incision (TUI) that can be challenging secondary to uncertainty in anatomic landmarks with risk of serious complications. To this end, we innovated a technique using predictable landmarks that begins endoscopic incision at the ureterocele orifice and extends retrograde proximal to the bladder neck (Figure). With over 15 years of experience in performing this retrograde incision from orifice (RIO) technique, we aimed to examine post-operative outcomes and risk of surgical failure after RIO compared to traditional TUI techniques for ureteroceles. We hypothesized that clinical outcomes after RIO would be superior to traditional endoscopic approaches to decompression of obstructing ureterocele in infants. A retrospective study of patients ≤12 months old who underwent TUI ureterocele at our institution between 2007 and -2021 was conducted. Pre-, intra- and post-operative characteristics were compared between patients who underwent RIO vs non-RIO TUI. Primary outcome was post-incision febrile urinary tract infection (fUTI). Secondary outcome was a composite failure measure of fUTI, secondary surgery, de novo bladder outlet obstruction, or vesicoureteral reflux. Multivariable Cox proportional hazard models were fitted to compare the time-to-event risk of primary and secondary outcomes between groups. Ninety patients with 92 ureteroceles were included (49 RIO, 43 non-RIO). Median follow-up from TUI was 33 months. RIO had a shorter median operative duration (27 vs 35min, p=0.021). Primary and secondary outcomes were similar between groups (fUTI: 29% RIO vs 19% non-RIO, p=0.27; composite failure 54% RIO vs 69% non-RIO, p=0.15). In multivariable Cox proportional hazard models, there was no significant difference in risk of fUTI (RIO aHR 0.98, 95% CI 0.38-2.54, p=0.97) or composite failure (RIO aHR 0.80, 95% CI 0.45-1.44, p=0.46) between TUI techniques. RIO technique for TUI ureterocele is attractive in that it uses predictable anatomic landmarks making it simple to perform. In analyzing this 15-year institutional experience of TUI ureterocele, RIO showed similar success to non-RIO endoscopic incisions. This study is a retrospective, non-randomized, single-institutional study over 15 years and is therefore subject to change in surgeon practice over time and variable practices between providers. Given comparable success and durability over time to other TUI ureterocele techniques, and with the advantage of operator ease using consistent anatomic landmarks, RIO is a worthy option for endoscopic ureterocele decompression.

A Consistent Anatomic Landmark for Identifying the Lateral Femoral Circumflex Artery in a Direct Anterior Hip Approach.

A direct anterior approach (DAA) is a technique practiced by arthroplasty surgeons that can be technically challenging, most notably for inexperienced surgeons. The lateral femoral circumflex artery (LFCA) is a branch of the femoral artery that crosses the surgical field during DAA and is an important landmark for superficial surgical dissection. If the vessel is not identified, significant bleeding may occur, and visualization may be impaired. This study aimed to develop a reliable method to identify and ligate the LFCA with minimal bleeding. First, a retrospective review was performed on a series of patients who underwent primary DAA total hip arthroplasty. Epidemiologic and intraoperative radiologic information was collected to determine the 2-dimensional location of the LFCA as it coursed through the surgical interval. Second, a series of computed tomography (CT) angiograms were compared to validate the intraoperative anatomic findings. In this study, 108 patients were evaluated fluoroscopically and 100 CT angiograms were obtained, for 208 total patients. The distance of the LFCA from the lesser trochanter with standard fluoroscopy (LT/TD) was 0.600 vs 0.438 on CT angiogram. Mean offset from midline (offset/femur diameter) was 0.166 lateral to midline vs 0.36 medial to midline. Median value of offset was 0 vs 0.411-representing a position on the anatomic axis of the femur. This study confirmed that the LFCA is found approximately one-third to two-thirds of the way between the lesser and greater trochanters along the anatomic axis of the femur for most patients. Surgeons who are new to DAA can use the LFCA as a reliable landmark to confirm the correct interval. [Orthopedics. 2022;45(5):262-268.].

Defining the limits of caesarean scar niche repair: new anatomical landmarks

BackgroundCaesarean scar niche is increasingly being seen due to the rise in the number of caesarean sections worldwide. Indications and the ideal route for niche repair are still being researched. If the residual myometrium is less than 3 mm thick and potential fertility is needed, laparoscopy is the ideal surgical method for caesarean scar niche repair. The aim of this video presentation is to demonstrate techniques of identifying new anatomical landmarks during laparoscopic uterine niche repair.ResultsAs seen in the video, Caesarean scar niche repair can be done in a step-by-step manner, with lateral bands serving as anatomical landmarks.ConclusionsLateral bands are a consistent anatomical landmark which identify the level and width of the uterine niche and thus simplify the laparoscopic repair making this a reproducible technique.

Topographic and Neural Anatomy of the Depressor Anguli Oris Muscle and Implications for Treatment of Synkinetic Facial Paralysis.

Synkinetic patients often fail to produce a satisfactory smile because of antagonistic action of a hypertonic depressor anguli oris muscle and concomitantly weak depressor labii inferioris muscle. This study investigated their neurovascular anatomy to partially explain this paradoxical depressor anguli oris hypertonicity and depressor labii inferioris hypotonicity and delineated consistent anatomical landmarks to assist in depressor anguli oris muscle injection and myectomy. Ten hemifaces from five fresh human cadavers were dissected to delineate the neurovascular supply of the depressor anguli oris and depressor labii inferioris muscles in addition to the depressor anguli oris muscle relation to consistent anatomical landmarks. The depressor anguli oris muscle received innervation from both lower buccal and marginal mandibular facial nerve branches, whereas the depressor labii inferioris muscle was solely innervated by marginal mandibular branches. The mandibular depressor anguli oris origin was on average 39 mm wide, and its medial and lateral borders were located 17 mm from the symphysis and 41 mm from the mandibular angle, respectively. The depressor anguli oris fibers consistently passed anterior to the first mandibular molar toward their insertion into the modiolus, which was located 10 mm lateral and 10 mm caudal to the oral commissure. Depressor anguli oris muscle dual innervation versus depressor labii inferioris single innervation may explain why depressor anguli oris hypertonicity and depressor labii inferioris weakness are commonly observed concomitantly in synkinetic patients. Based on treatment goals, diagnostic percutaneous injection with lidocaine can be performed on the depressor anguli oris muscle along a cutaneous line from the modiolus to the mandibular first molar border, and an intraoral depressor anguli oris myectomy can be performed along that same transmucosal line.

Endoscopic anatomy of distal biceps tendon insertion and bicipitoradial bursa: a cadaveric study.

Distal biceps endoscopy has emerged as a minimally invasive alternative to open procedures for distal biceps tendon (DBT) pathology. The purpose of this study was to systematically describe the static and dynamic appearance and variations of the DBT insertional region using a standardized endoscopic technique and dissection in healthy cadaveric elbows. Endoscopic assessment of the DBT insertional region was performed using a standard proximal parabiceps portal in 20 fresh frozen cadaveric upper extremities. A 6-point endoscopic evaluation of the DBT and bicipitoradial bursa was performed in a static supination position and with dynamic rotation. Anatomic variations in the DBT insertional characteristics, as well as the extent and appearance of the intrabursal space, were documented. Each cadaver was then dissected to correlate endoscopic findings with gross anatomic structures. A bare oval tuberosity area (n = 20) bounded by the supinator and DBT was observed. The DBT inserted ulnar to the bare area (n = 16) and the presence of an intervening wide (n = 1) or narrow (n = 3) tuberosity sulcus were documented. The dorsoradial DBT surface was consistently intrabursal and was differentiated into 2-5 fiber bundles (n = 15). The volar-ulnar DBT surface was always extrabursal and was associated with endoscopically identifiable proximal and distal fat pads. The bicipitoradial bursa formed a bursal sac that was attached to the dorsoradial (n = 13) or volar (n = 7) aspect of the tuberosity and extended proximally along the DBT for 3-5 cm (parabiceps space). A distinct ligament-like band (transverse radioulnar ligament) extended transversely across the proximal radioulnar space and appeared to form a sling that provided ulnar support to the DBT during dynamic rotation. The intact DBT surface was robust and could not be breached, even with firm pressure using a probe. The bare tuberosity area, the bursal sac, and the parabiceps space are consistent anatomic landmarks that can be used during DBT endoscopy. An insertional tuberosity sulcus and DBT surface differentiation are normal anatomic variations. The transverse radioulnar ligament provides ulnar support for the DBT during pronation and forms a pulley mechanism for smooth tendon gliding motion.

Anatomy and physiology of the sentinel lymph nodes of the upper extremity: Implications for axillary reverse mapping in breast cancer.

This study characterizes the physiological drainage of the normal upper extremity using single-photon emission computed tomography/computed tomography (SPECT/CT) lymphoscintigraphy axillary reverse lymphatic mapping (ARM). A consecutive series of patients assessed with SPECT/CT lymphoscintigraphy ARM of the upper extremity were included. Anatomical localization of the axillary sentinel lymph nodes (SLN) was completed in normal axillae in relation to consistent anatomic landmarks. Retrospective case note analysis was performed to collect patient demographic data. A total of 169 patients underwent SPECT/CT lymphoscintigraphy, and imaging of 182 normal axillae was obtained. All patients (100%) had an axillary SLN identified: 19% had a single contrast-enhanced SLN in the axilla and the remainder had multiple. The SLN(s) of the upper extremity was located in the upper outer quadrant (UOQ) of the axilla in 97% of cases (177 axillae). When the SLN(s) was found in the UOQ of the axilla, second-tier lymph nodes were found predominantly in the upper inner quadrant (50% of cases). The upper extremity SLN(s) is located in a constant region of the axilla. This study provides the most complete investigation to date and results can be directly applied clinically to ARM techniques and adjuvant radiation planning.

Use of the medial canthal point (MCP) as a reliable anatomical landmark to the frontal sinus.

ObjectivesFrontal sinus surgery is considered one of the more challenging aspects of Functional Endoscopic Sinus Surgery, due to the complex variations in normal sinus anatomy but also increased morbidity due to the close proximity of critical structures such as the anterior cranial fossa and orbits. We aim to investigate the medial canthal point (MCP) as an anatomical landmark for safe frontal sinus access.MethodsThe MCP intranasally is identified during surgery with non‐tooth forceps, with one limb just anterior to the medial canthus and the other intranasally in the same coronal plane along the skull base. This point was identified on 100 paranasal sinus computed tomography (CT) scan reconstructions. The distance between the anterior cranial fossa and MCP was measured on imaging—medial canthal point distance (MCPD). The maximal anterior‐posterior (AP) distance was measured on all scans.ResultsThe average MCPD for males was 13.0 mm (8.7‐20.4 mm) and for females 12.0 mm (6.8‐22.8 mm). Mean AP distance for males was 12.0 mm (4.5‐20.2 mm) and for females 10.4 mm (3.8‐15.9 mm). Mean distance for all 100 patients was 12.6 mm (range 7.5‐22.8 mm). In all cases, the MCP was anterior to the cranial fossa. Mixed effects modelling analysis showed a significant correlation between the MCPD and AP distance (P = .006).ConclusionThe MCP is a consistent anatomical landmark that can serve as an adjunct to safe frontal sinus access alongside the first olfactory fiber and CT navigation systems. However, patient selection continues to be very important, with larger well pneumatized frontal sinuses being ideal to tackle earlier in a surgeon's career.Level of evidenceNA

The Ponticulus Ethmoidalis: A Newly Appreciated Anatomic Landmark in Endoscopic Sinus Surgery.

Ethmoid sinus anatomy is so variable it has been referred to as a "labyrinth." Accordingly, this provides a challenge for surgeons performing ethmoidectomy. Identifying consistent anatomic features or landmarks within the ethmoid sinus can aid surgeons performing sinus surgery. The goal of this investigation was to determine if subtle anatomic features are consistently present within the retrobullar recess and could potentially serve as a reliable landmark for surgeons performing ethmoid surgery. Ethmoid sinus anatomy was studied in 60 sinonasal complexes through several methods including gross anatomic dissection, endoscopic dissection and 3-D CT stereoscopic imaging. Review of gross sagittal sinonasal specimens revealed that the retrobullar recess was present in all specimens and a tissue bridge was noted emanating from the basal lamella deep within the retrobullar recess in 23/24 gross sagittal specimens; in 1/24 specimens it was quite small or difficult to appreciate. In the radiographic analysis, the tissue bridge was noted in 17/18, in 1/18 it was not appreciated. In the endoscopic dissections it was noted in 17/18, in 1/18 it was small or not appreciated. The small tissue bridge, or ponticulus within the retrobulbar recess was seen in nearly all ethmoid sinuses studied leading us to venture that could be used in surgery to orient surgical dissection through the basal lamella into the posterior ethmoid region.

Accuracy and Safety of Lateral Vertebral Notch-Referred Technique Used in Subaxial Cervical Pedicle Screw Placement.

Biomechanical studies revealed that pedicle screw instrumentation has a superior stabilizing effect compared with other internal fixations in reconstructing the subaxial cervical spine. However, severe neurovascular risks preclude surgeons from routinely conducting pedicle screw manipulation in cervical spine. To evaluate the accuracy and safety of the lateral vertebral notch (LVN)-referred technique used in subaxial cervical pedicle screw (CPS) placement. One hundred thirty-five consecutive retrospective patients with cervical disorders underwent the LVN-referred technique for CPS placements in 3 spine centers. Postoperative pedicle perforations were confirmed by CT scans to assess the technical accuracy. Neurovascular complications derived from CPS misplacements were recorded to evaluate the technical safety. A total of 718 CPSs were inserted into subaxial cervical spine. Postoperative CT scans revealed that the accuracy of CPS placement was superior. Neither vertebral artery injury nor spinal cord injury occurred. One radiculopathy was from a unilateral C6 nerve root compression. A screw-related neurovascular injury rate of 0.7% occurred in this cohort. Additionally, there was no significant difference in the accuracy of CPS placement among 3 surgeons (H=1.460, P=.482). The relative standard deviation values revealed that technical reproducibility was acceptable. Furthermore, there was no significant difference between the patients' pedicle transverse angles and inserted CPS transverse angles from C3 to C7 (all P>.05). The LVN is a reliable and consistent anatomic landmark for CPS placement. The accuracy and safety of subaxial CPS placement by using LVN-referred technique are highly acceptable, which may endow this technique to be practicably performed in selected patients.

Semi-automated quantification of cartilage volume in knee osteoarthritis: responsiveness and concurrent validity

Purpose: Cartilage change on Magnetic Resonance Imaging (MRI) is a potential surrogate endpoint in osteoarthritis (OA) research. Semi-quantitative scoring systems are based on qualitative and subjective assessments that require expensive and time-intensive radiology expertise; ordinal scores also have limited sensitivity to change. Quantitative measurement of cartilage that involves manual segmentation of cartilage is also time-intensive and costly. To overcome these limitations, semi-automated software systems have been developed to measure cartilage - providing a rapid, inexpensive, quantitative and objective method of evaluating disease status and progression. A novel and semi-automated Local-Area Cartilage Segmentation (LACS) software for knee OA has previously been demonstrated to be fast, responsive, and associated with radiographic and pain progression. However, LACS was initially developed to segment medial femur cartilage only. We aimed to update and extend LACS to the lateral femur, medial tibia, and lateral tibia - and evaluate responsiveness to change, as well as correlation with existing cartilage measurements using an established independent manual segmentation method from publicly available Osteoarthritis Initiative (OAI) data. Methods: 115 participants with symptomatic knee OA were selected from the OAI progression sub-cohort, defined by definite osteophytes and frequent knee symptoms. Cartilage volume in fixed weight-bearing areas was measured with LACS on unilateral knee MRIs at the baseline and 24 month visit, paired and blinded to image date, using the sagittal 3D double-echo steady-state (DESS) sequence (3 Tesla, 0.365mm x 0.365mm, 0.7mm slice thickness, repetition time 16.5 msec, echo time 4.7 msec). Briefly, a non-expert reader identified a set of consistent anatomical landmarks for each compartment on the femur and tibia, which were used to generate consistent cartilage measurement areas. Automated edge detection algorithms then outlined cartilage in regions defined by the landmarks (Figure). The expert reader corrected the cartilage margins in areas of misidentified cartilage margins when necessary. Change in cartilage volume was calculated between the baseline and the 24-month visit. Responsiveness was quantified by standardized response mean (SRM = mean (ΔVol)/SD (ΔVol)). Concurrent validity was evaluated by estimating the correlation between LACS volume measurements and Chondrometrics measurements of cartilage thickness based on manual segmentation in the four corresponding sub-regions. Results: Baseline Kellgren-Lawrence grade distribution was KL1 4.3%, KL2 32.2%, KL3 61.7%, and KL4 1.7% in knees of the 115 participants (53% females, mean (SD) age 62.6 (±8.8) years, mean (SD) and BMI 30.1 (±5.3) kg/m2). The Figure shows a rendered 3D-model of segmented cartilage, with red areas indicating selected regions of measurement. The SRM was -0.54 for the medial femoral region and lower in the other sub-regions (Table 1). Correlation with Chondrometrics measures of cartilage thickness ranged between 0.67 and 0.88 (Table 2). The expert reader time was under 5 minutes and total reader time less than 10 minutes total per compartment. Conclusions: We updated the semi-automated LACS software method for knee cartilage segmentation to not only include the medial femur, but also medial tibia, lateral tibia, and lateral femur. The automated steps increase efficiency compared to manual segmentation, and limit the need and cost of an expert reader. We found favorable SRMs for cartilage volume change over two years with default regions of interest. The flexible nature of this software enables further adjustment of sub-regions to potentially improve responsiveness. The software correlated well against established measurements of cartilage thickness based on manual segmentation. Although a comparison between thickness and volume is not ideal, the current results are encouraging. In summary, the updated LACS software represents a powerful tool for fast segmentation of knee cartilage in larger cohorts and could facilitate clinical evaluation of potential structure modifying OA interventions.

The Anterior Ethmoidal "Genu": A Newly Appreciated Anatomic Landmark for Endoscopic Sinus Surgery.

Human sinonasal anatomy varies widely between patients, challenging surgeons operating in the sinuses. Ethmoid sinus anatomy is so variable it has been referred to as a labyrinth. Accordingly, reliable, consistent anatomic landmarks aid surgeons operating in this region. The goal of this investigation was to explore our observations and hypothesis that the ethmoidal bulla and the uncinate process are not entirely separate structures but rather attach, and the attachment could potentially provide a landmark for surgeons performing ethmoid and frontal recess surgery. Ethmoid sinus anatomy was studied in 57 sinonasal complexes through a variety of methods including gross anatomic dissection, endoscopic dissection and 3D CT stereoscopic imaging. The uncinate process and ethmoidal bulla were noted to fuse at the superior aspect of the hiatus semilunaris in 57/57 cases, forming a genu-like feature in the anterior ethmoid. This consistent anatomic feature related closely to the frontal sinus drainage pathway, which drained medial to it in 44/57 (77%) cases. The anterior ethmoidal "genu" appears to be an excellent anatomic feature that surgeons can use during ethmoid and frontal recess surgery. High resolution 3D stereoscopic CT scan is capable of demonstrating sinonasal anatomy in a detailed fashion previously only achieved by cadaveric dissection. This technology can potentially allow for a virtual dissection of a patient's anatomy prior to surgery and could improve minimally invasive procedures and reduce complications. Clin. Anat. 32:534-540, 2019. © 2019 Wiley Periodicals, Inc.

Radiation therapy planning using MRI-CT fusion in dogs and cats with brain tumors.

Volume definition is a delicate step within the radiation treatment planning process and the precision of defining the volumes to irradiate is important for the success of the radiation treatment. Traditionally, radiation plans are created using computed tomography (CT) studies. Due to its different mechanism of action, magnetic resonance imaging (MRI) is more sensitive for detection of brain lesions. Therefore, using fused images of both imaging modalities should result in a more precise definition of the volumes to irradiate. The feasibility to fuse CT and MRI studies performed at different institutions was tested to subsequently analyse the influence of the fused images on target volume definition. Fourteen dogs and four cats with brain lesions having MR- and CT-imaging were included. Contrast-enhanced radiotherapy planning CT scans were fused to T1-weighted post-contrast and T2-weighted MRI scans. The gross tumor volume (GTV), the clinical tumor volume (CTV) and the planning target volume (PTV) were delineated on CT- and MRI studies. CT and MRI volumes were compared with regard to volumetric and spatial differences. The mean GTV was larger on MRI than on CT (2.15 vs.1.54 cm3). Also the mean CTV was larger on MRI than on CT (5.34 vs. 4.38 cm3). Consequently, the mean PTV was larger on MRI than on CT (14.20 vs. 10.82 cm3) as well. None of the differences in defined volumes were significant. Fusion images were accepted showing mean errors of 1.32 mm (mean error) and 1.73 mm (maximal error). CT-MRI fusion was feasible especially when defined, reliable, and consistent anatomic landmarks were used as registration points. Volumetric differences between CT and MRI were insignificant. In general, GTV and CTV were easier identified on MRI.

Nasal branch of the anterior ethmoid artery: a consistent landmark for a midline approach to the frontal sinus.

Frontal sinusotomy can be challenging when significant scarring or distorted anatomy is present. Identifying a reliable anatomic structure, when traditional landmarks or navigation are absent, may assist the surgeon in revision and complicated frontal sinusotomies via a midline approach. We aimed to characterize the anatomic relationship of the nasal branch of the anterior ethmoid artery (NBAEA) to the frontal infundibulum, specifically the first olfactory fili, posterior frontal infundibulum, and anterior cribriform plate. Dissection of the NBAEA was carried out in 11 cadaveric heads, resulting in a total of 21 dissections (1 aplastic frontal). Mean with standard deviation and a range were established for 7 relative measurements. The total length of NBAEA cleft when present (mean 2.43 mm), the anterior edge of NBAEA cleft to anterior infundibulum coronal plane (mean 1.71 mm), the posterior edge of NBAEA cleft to posterior infundibulum coronal plane (mean 3.33 mm), the posterior edge of NBAEA cleft to 1st olfactory fili (mean 2.86 mm), and the first olfactory fili to posterior infundibulum coronal plane (mean 0.48 mm) were consistent measurements supporting the use of the NBAEA as a consistent anatomical landmark for the correct surgical coronal trajectory into the midline frontal sinus. The NBAEA is a consistent anatomic landmark with minimal intercadaveric and intracadaveric variation. It can be used reliably as a "sentinel artery" notifying the surgeon when one is approaching the first olfactory fili, to determine the correct trajectory into the midline frontal sinus.

Medial meniscal extrusion: a validation study comparing different methods of assessment

PurposeLongitudinal cohort studies of knee OA aetiology use MRI to assess meniscal extrusion within the same knee at sequential time points. A validated method of assessment is required to ensure that extrusion is measured at the same location within the knee at each time point. Absolute perpendicular extrusion from the tibial edge can be assessed using the reference standard of segmentation of the tibia and medial meniscus. This is labour intensive and unsuitable for large cohorts. Two methods are commonly used as proxy measurements. Firstly, the apex of the medial tibial spine is used to identify a reproducible MRI coronal slice, from which extrusion is measured. Secondly, the coronal MRI slice of the knee demonstrating the greatest extrusion is used. The purpose of this study was to validate these two methods against the reference standard and to determine the most appropriate method to use in longitudinal cohort studies. We hypothesised that there is no difference in absolute meniscal extrusion measurements between methods.MethodsTwenty high-resolution knee MRI scans were obtained in asymptomatic subjects. The tibia and medial meniscus were manually segmented. A custom MATLAB program was used to determine the difference in medial meniscal extrusion of the knee using the reference standard compared to the two other methods.ResultsAssessing extrusion using the single coronal MRI slice demonstrating the greatest extrusion overestimates the true extrusion of the medial meniscus. It incorrectly places the greatest meniscal extrusion at the anterior part of the tibia. Assessing extrusion using a consistent anatomical landmark, such as the medial tibial spine, most reliably corresponds to the reference of segmentation and measurement of true perpendicular extrusion from the tibial edge. Clinicians and researchers should consider this when assessing meniscal extrusion in the knee, and how it changes over time.ConclusionThis study suggests measuring meniscal extrusion on the coronal MRI slice corresponding to the apex of the medial tibial spine as this correlates most closely with the true perpendicular extrusion measurements obtained from manually segmented models.Level of evidenceDiagnostic, Level I.

The Reliability of the Tracheoesophageal Groove and the Ligament of Berry as Landmarks for Identifying the Recurrent Laryngeal Nerve: A Cadaveric Study and Meta-Analysis.

Purpose. The aim of this meta-analysis was to provide a comprehensive evidence-based assessment, supplemented by cadaveric dissections, of the value of using the Ligament of Berry and Tracheoesophageal Groove as anatomical landmarks for identifying the Recurrent Laryngeal Nerve. Methods. Seven major databases were searched to identify studies for inclusion. Eligibility was judged by two reviewers. Suitable studies were identified and extracted. MetaXL was used for analysis. All pooled prevalence rates were calculated using a random effects model. Heterogeneity among included studies was assessed using the Chi2 test and the I2 statistic. Results. Sixteen studies (n = 2,470 nerves), including original cadaveric data, were analyzed for the BL/RLN relationship. The RLN was most often located superficial to the BL with a pooled prevalence estimate of 78.2% of nerves, followed by deep to the BL in 14.8%. Twenty-three studies (n = 5,970 nerves) examined the RLN/TEG relationship. The RLN was located inside the TEG in 63.7% (95% CI: 55.3–77.7) of sides. Conclusions. Both the BL and TEG are landmarks that can help surgeons provide patients with complication-free procedures. Our analysis showed that the BL is a more consistent anatomical landmark than the TEG, but it is necessary to use both to prevent iatrogenic RLN injuries during thyroidectomies.

Cadaveric Analysis of the Distal Tibiofibular Syndesmosis.

Unstable ankle fractures with syndesmotic injuries commonly occur and can result in significant morbidity. Although the need for an anatomic reduction is clear, there is still debate surrounding the optimal operative treatment. Recent literature shows an increasing interest in anatomic ligament repair or reconstruction in the acute and chronic syndesmosis injury. Despite this trend, there is insufficient literature detailing anatomy of the distal tibiofibular syndesmosis. In the literature that does exist, there is controversy regarding the ligamentous anatomy of the syndesmosis. None of the current literature describes an anatomic constant that may be used as an intraoperative reference for anatomic ligament reconstructions. Ten sets of tibia and fibula free of all soft tissue were used to analyze osseous structures. Another 10 nonpaired, fresh-frozen specimens were used to study the distal tibiofibular syndesmosis. These were measured using a 3-dimensional tracking system. Measurement of each ligament width at origin and insertion, length, and distance from the tibial articular cartilage was performed. The superior and inferior insertions of the anterior inferior tibiofibular ligament measured 22.7 mm and 3.4 mm proximal to the distal articular cartilage of the tibia, respectively. The superior insertion of the posterior inferior tibiofibular ligament measured 15.2 mm proximal to the articular cartilage. The superior and inferior insertions of the interosseous ligament measured 31.8 mm and 9.2 mm proximal to the distal articular cartilage, respectively. The inferior transverse ligament was a prominent identifiable structure in 70% of specimens. The superior margin of the distal articular cartilage could serve as a consistent anatomic landmark for reconstruction. The inferior transverse ligament is an identifiable structure in 70% of the specimens studied. This article clarifies the anatomy and provides measurements from an anatomic constant that can guide reconstruction and intraoperative evaluation of the syndesmosis.

Decompression of the superficial peroneal nerve: clinical outcomes and anatomical study.

OBJECTIVE The authors of this study sought to determine the outcomes of patients undergoing superficial peroneal nerve (SPN) release to treat lower-extremity pain and describe consistent anatomical landmarks to direct surgical planning. METHODS This retrospective cohort study examined 54 patients with pain in the SPN distribution who were treated with decompression between 2011 and 2014. Patients rated pain and the effect of pain on quality of life (QOL) on the visual analog scale (VAS) from 0 to 10. Scores were then converted to percentages. Linear regression analysis was performed to assess the impact of the preoperative effect of pain on QOL, age, body mass index (BMI), and preoperative duration of pain on the postoperative effect of pain on QOL. Measurements were made intraoperatively in 13 patients to determine the landmarks for identifying the SPN. RESULTS A higher BMI was a negative predictor for improvement in the effect of pain on QOL. A decrease in pain compared with the initial level of pain suggested a nonlinear relationship between these variables. A minority of patients (7 of 16) with a preoperative pain VAS score ≤ 60 reported less pain after surgery. A large majority (30 of 36 patients) of those with a preoperative pain VAS score > 60 reported improvement. Intraoperative measurements demonstrated that the SPN was consistently found to be 5 ± 1.1, 5 ± 1.1, and 6 ± 1.2 cm lateral to the tibia at 10, 15, and 20 cm proximal to the lateral malleolus, respectively. CONCLUSIONS A majority of patients with a preoperative pain VAS score > 60 showed a decrease in postoperative pain. A higher BMI was associated with less improvement in the effect of pain on QOL. This information can be useful when counseling patients on treatment options. Based on the intraoperative data, the authors found that the SPN can be located at reliable points in reference to the tibia and lateral malleolus.

An anatomical study of the acetabulum with clinical applications to hip arthroscopy.

The clock face has been employed to define the position of labral pathology in relation to identifiable arthroscopically relevant acetabular landmarks. The purpose of this study was to qualitatively and quantitatively describe arthroscopically relevant anatomy of the acetabulum. We aimed to present a surgical landmark that is located in close proximity to the usual location of labral pathology as an alternative to the midpoint of the transverse acetabular ligament as a reference point. Fourteen fresh-frozen cadaveric hemipelves were dissected to evaluate osseous landmarks and relevant surrounding soft-tissue structures of the acetabulum. With use of a coordinate-measuring device, we determined the location, orientation, and relationship of key arthroscopic landmarks and the footprint areas formed by the insertions of the rectus femoris, capsule, and labrum. An analysis of variability of reference points around the acetabulum in relation to the anterior inferior iliac spine (AIIS) revealed that the superior margin of the anterior labral sulcus (psoas-u) was the most consistent anatomic landmark. The AIIS comprised superior and inferior facets, demarcated by the origins of the direct head of the rectus femoris and the iliocapsularis. The inferolateral corner of the footprint of the direct head of the rectus femoris was located 19.2 mm (95% confidence interval [CI], 18.0 to 20.4 mm) from the acetabular rim and the inferolateral aspect of the iliocapsularis footprint, 12.5 mm (95% CI, 10.1 to 15.0 mm) from the rim. The superior margin of the anterior labral sulcus (psoas-u) was a reliable landmark for reference of the clock face on the acetabulum. We propose that this point, denoting 3:00, be adopted as the new standard clock-face reference for intra-articular hip structures because of its universal presence and reliable arthroscopic visualization. This marker is also beneficial because of its proximity to the typical location of labral pathology. The data presented provide a comprehensive analysis of pertinent arthroscopically relevant acetabular anatomy. The establishment of a new standard reference point within the acetabulum will enhance the consistency of interpretation of the location of labral pathology and improve arthroscopic orientation and navigation.