Anatomy of the anterior cruciate ligament

The anterior cruciate ligament (ACL) is a band of dense connective tissue which courses from the femur to the tibia. The ACL is a key structure in the knee joint, as it resists anterior tibial translation and rotational loads. When the knee is extended, the ACL has a mean length of 32 mm and a width of 7-12 mm. There are two components of the ACL, the anteromedial bundle (AMB) and the posterolateral bundle (PLB). They are not isometric with the main change being lengthening of the AMB and shortening of the PLB during flexion. The ACL has a microstructure of collagen bundles of multiple types (mostly type I) and a matrix made of a network of proteins, glycoproteins, elastic systems, and glycosaminoglycans with multiple functional interactions. The complex ultrastructural organization and abundant elastic system of the ACL allow it to withstand multiaxial stresses and varying tensile strains. The ACL is innervated by posterior articular branches of the tibial nerve and is vascularized by branches of the middle genicular artery.

Human tibia bone marrow blood perfusion by non-invasive near infrared spectroscopy: a new tool for studies on microgravity

Human tibia bone marrow (BM) and tibialis anterior muscle (TA) perfusion index (PI) was assessed non-invasively by near infrared spectroscopy. A decrease in the postis-chaemic reperfusion capability of the human tibia BM and TA muscle was observed for increasing age i.e., PI increases linearly as a function of age, starting from 30 years, both for BM (0.062 %/year, from -4.185 to -0.967 %/s) and TA muscle (0.046 %/year, from -5.760 to -3.883 %/s). The results define a "normal" baseline and demonstrate the sensitivity of the method to PI changes. The present technique should allow one to investigate physio-pathological effects induced by microgravity on tibia BM blood perfusion.

Endoscopic neck dissection in human cadavers

OBJECTIVE

To evaluate the feasibility and efficacy of endoscopic neck dissection (END) in human cadavers.

STUDY DESIGN

Experimental self-controlled study.

METHODS

END on five human cadavers through three openings: one for the camera, one for the dissecting instrument, and one for a grasping one. The tissue specimens removed were divided into traditional neck groups (I to V). After the completion of END, open neck dissection was performed using standard surgical techniques and the remaining tissue within each neck group was retrieved. The important neck structures (carotid artery, internal jugular vein, cranial nerves X, XI, and XII, phrenic nerve) were evaluated for lesions. A pathologist evaluated each specimen, without knowing its exact origin in terms of neck group or side, and type of surgical technique used. For each specimen, the number of retrieved lymph nodes and their anatomic integrity was analyzed.

RESULTS

Ten neck dissections were performed on 5 cadavers, without any major difficulty. An injury of the internal jugular vein occurred twice and once the phrenic nerve was cut. Little tissue was usually left for open surgical dissection. The average number of retrieved lymph nodes by endoscopy was 4.9 +/- 2.7 (mean +/- standard deviation). Completion open neck dissection retrieved an additional 0.5 +/- 0.5 lymph nodes. Efficacy of END was 92 +/- 10%. The majority of retrieved lymph nodes were intact but exhibited important postmortem autolysis artifacts.

CONCLUSIONS

Endoscopic neck dissection is possible in human cadavers and is free of lesions to major structures. The majority of neck lymph nodes can be removed endoscopically.

Anatomic relationship between arachnoid granulations in the transverse sinus and the termination of the vein of Labbé: an angiographic study

We studied the anatomic relationship between arachnoid granulations in the transverse sinus and the termination of the vein of Labbé in 57 consecutive angiograms. Patients with pathology in intracranial venous structures or with inadequate image quality of the venous system were excluded. Arachnoid granulations were found in 12 of the 57 patients (21.1%), always at the junction of the vein of Labbé and the transverse sinus; the vein of Labbé was present in 55 patients (96.5%), most often without associated arachnoid granulations; the latter, however, were not observed in the absence of a vein of Labbé. This study confirms the close, constant anatomic relationship between arachnoid granulations in the transverse sinus and the termination of the vein of Labbé. This observation may help to differentiate arachnoid granulations from pathologic conditions involving the transverse sinus such as dural sinus thrombosis. The constant character of this relationship suggests a developmental role of afferent veins in the formation of arachnoid granulations.

Angiographic anatomy of the laterocavernous sinus

BACKGROUND AND PURPOSE

The laterocavernous sinus (LCS) has recently been recognized as one of the major drainage pathways of the superficial middle cerebral vein (SMCV). Our purpose was to investigate the drainage pattern of the SMCV, with special emphasis on the angiographic anatomy of the LCS.

METHODS

The drainage pathways of the SMCV were evaluated prospectively on 100 selective carotid angiograms obtained in 65 consecutive patients.

RESULTS

The SMCV was absent in 19% of cases. A classic termination into the cavernous sinus (CS) was found in 20%, a paracavernous sinus in 39%, and an LCS in 22%. The LCS drained toward the pterygoid plexus (27%), the superior petrosal sinus (18%), the posterior aspect of the CS (32%), or a combination of these pathways (23%). A complete absence of connection between the LCS and CS was observed in 63.5% of the patients.

CONCLUSION

The LCS is a laterosellar venous space that is anatomically and angiographically distinct from the CS. Secondary small anastomoses between the LCS and CS may make it difficult to differentiate the two structures. Appreciation of the course and connection pattern of the LCS is important, particularly when planning an endovascular approach to treatment of lesions in the region of the CS.

Liver of the "visible man"

Endoscopic surgery, also called minimally invasive surgery, is presumed drastically to reduce postoperative morbidity and thus to offer both human and economic benefits. For the surgeon, however, this approach leads to a number of gestural challenges that require extensive training to be mastered. In order to replace experimentation on animals and patients, we developed a simulator for endoscopic surgery. To achieve this goal, a first step was to develop a working prototype, a "standard patient," on which the informatic and microengineering tools could be validated. We used the visible man dataset for this purpose. The external shape of the visible man's liver, his biliary passages, and his extrahepatic portal system turned out to be fully within the standard pattern of normal anatomy. Anatomic variations were observed in the intrahepatic right portal vein, the hepatic veins, and the arterial blood supply to the liver. Thus, the visible man dataset reveals itself to be well suited for the simulation of minimally invasive surgical operation such as endoscopic cholecystectomy.

Termination of the inferior petrosal sinus: an anatomical variant

Unusual caudal terminations of the inferior petrosal sinus (IPS) characterized by an extracranial extension joining the internal jugular vein up to 40 mm below the external skull base are reported. This variation was observed bilaterally on an anatomical specimen and unilaterally on four patients during diagnostic cerebral angiography. It may be considered an accessory internal jugular vein and, if present, may allow for an alternate endovascular access to the IPS.

Anatomy teaching for medical undergraduates: general practice as a guideline? The brain

Basic science teaching, particularly the teaching of gross anatomy, is at present a highly controversial topic. How much and what kind of anatomy should be taught to medical undergraduates nowadays? In conducting the present study we based our proposals on the criterion of general medical relevance. Therefore, we sent an anatomical questionnaire to a sample of Swiss general practitioners. Here, we present the results derived from questions on the human brain, discussing them in connection with the other organs so far investigated. The results obtained suggest that a common body of anatomical knowledge appropriate for the field of general medical practice does in fact exist. We believe that this basic stock can serve as a guideline for decision makers involved in the development of curricula, which can be fitted into the time frame available for anatomy teaching today while still guaranteeing a sound level of competence required for general practice of medicine. We also hope that this approach may serve as a model for the teaching of other basic sciences.

Pathology findings with acrylic implants

We report the pathological findings in cases of acrylic implants obtained by direct intratumoral injection of polymethyl-methacrylate (PMMA) and N-butyl-cyano-acrylate (NBCA). Direct intratumoral injection of acrylic implants was performed for a variety of primary and secondary bone lesions. These types of treatments have been used at our institution in the last 4 years for 40 vertebroplasty (PMMA) procedures and for nine bone lesions of other locations (PMMA, NBCA). Postmortem histology became available for 1 case of PMMA and for 5 cases with NBCA intratumoral acrylic implants. The pathological findings associated with PMMA and NBCA were evaluated and compared. PMMA exhibited a macroscopic and microscopic rim of tumor necrosis, 6 months after implantation. NBCA exhibited compressive effects on the nearby tumor tissue, however, without signs of significant necrosis outside the acrylic tumor cast. Tumor captured inside the acrylic cast showed extensive to near complete necrosis. Acrylic implants may lead to necrosis when injected directly in tumors. The necrotizing effect may extend beyond the limits of an implant in the case of PMMA. Such an extended effect of PMMA, when compared with NBCA, may be due to the variable toxicity of acrylic implants, including the different degrees of the exothermic reaction during polymerization.

["General practice" educational goals: the role of anatomy, exemplified by the lymphatic system]

One of the most frequent criticisms of present-day medical studies is that they are unrelated to practical clinical needs. This criticism is levelled in particular at the preclinical stage. The present article is a contribution to finding a pragmatic solution to this problem. The design of the study is a survey of a representative sample of general practitioners who were asked to identify, from a complete list of structures included in the international anatomic nomenclature, those items that they regarded as indispensable in practice. Two main conclusions emerged from the survey: (1) there was a very high degree of concordance among the choices made by the physicians involved (including 92.3% of structures listed for the lymphatic system); (2) the quota of structures considered to be of practical clinical relevance was small (15.4%). These results suggest that it would be possible to teach a clinically relevant common trunk of knowledge to medical students. For this purpose, however, similar studies need to be undertaken for the other basic medical sciences. Furthermore, to ensure that medical education is really related to practical needs, clinicians will need to exert influence on the policy and content of teaching programmes in departments of basic medical science.

In vitro models of intracranial arteriovenous fistulas for the evaluation of new endovascular treatment materials

BACKGROUND AND PURPOSE

The purpose of this study was to create and test an in vitro model of intracranial arteriovenous fistulas (AVFs) that simulates the geometry of human vasculature and allows realistic testing of devices used in endovascular therapy.

METHODS

The models were derived from corrosion casts of the main cervicocranial arteries and veins obtained from two nonfixed human specimens. Wax copies of the casts were produced and combined to create complex models simulating various types of intracranial AVFs. Wax assemblies were embedded with liquid silicone solidified into transparent blocks containing, after wax evacuation, hollow reproductions of the original vascular trees. The models were connected to a pulsatile pump and their compatibility with various imaging techniques and endovascular treatment materials was evaluated.

RESULTS

The models were compatible with digital subtraction angiography, CT, MR imaging, and transcranial Doppler sonography. They provided a realistic endovascular environment for the simulation of interventional neuroradiologic procedures.

CONCLUSION

Anatomically accurate and reproducible in vitro models of intracranial AVFs provide a valuable method for evaluating new endovascular treatment materials and for teaching purposes.

Laterocavernous sinus

Here we describe an anatomic structure that takes the form of a venous channel (VC) within the two layers of the lateral wall of the cavernous sinus (CS). Colored gelatin was injected in both superficial middle cerebral veins (SMCV) of 29 human specimens. When a SMCV terminated into the CS, the latter was dissected giving particular attention to its lateral wall. The termination of the VC and its eventual communications with the CS and adjacent venous structures were studied. A VC in the lateral wall of the CS was found in 14 of 58 lateral walls (24.1%). It was in continuation with the SMCV in 13 cases, with the uncal vein in one case. The VC drained into the superior petrosal sinus (71.4%), the pterygoid plexus (21.4%), or the posterior part of the CS (7.2%). Two alternate drainage pathways for the SMCV were observed, toward the anterosuperior aspect of the CS (13.8%) or through a paracavernous sinus located along the floor of the middle cranial fossa (32.8%). These different pathways were not observed to occur concomitantly. SMCV were absent in 29.3%. Despite its close topographic relation with the CS, the VC in the lateral wall can be considered as an anatomic entity with potential clinical relevance. We propose to call it the laterocavernous sinus.

Second-generation three-dimensional reconstruction for rotational three-dimensional angiography

RATIONALE AND OBJECTIVES

The purpose of this study was to assess the feasibility and accuracy of three-dimensional (3D) reconstruction techniques for digital subtraction angiography (DSA) in planning and evaluation of minimally invasive image-controlled therapy.

MATERIALS AND METHODS

Using a standard, commercially available system, the authors acquired DSA images and corrected them for inherent distortions. They designed and implemented parallel and multiresolution versions of cone-beam reconstruction techniques to reconstruct high-resolution targeted volumes in a short period of time. Testing was performed on anatomically correct, calibrated in vitro models of a cerebral aneurysm. These models were used with a pulsatile circulation circuit to allow for blood flow simulation during DSA, computed tomographic (CT) angiography, and magnetic resonance (MR) angiography image acquisitions.

RESULTS

The multiresolution DSA-based reconstruction protocol and its implementation allowed the authors to achieve reconstruction times and levels of accuracy for the volume measurement of the aneurysmal cavities that were considered compatible with actual clinical practice. Comparison with data obtained from other imaging modalities shows that, besides vascular tree depiction, the DSA-based true 3D technique provides volume estimates at least as good as those obtained from CT and MR angiography.

CONCLUSION

The authors demonstrated the feasibility and potential of true 3D reconstruction for angiographic imaging with DSA. On the basis of the model testing, this work addresses both the timing and quantification required to support minimally invasive image-controlled therapy.

Segmental anatomy of the liver: poor correlation with CT

PURPOSE

To evaluate qualitatively and quantitatively the current procedures for radiologic delineation of the segmental and subsegmental anatomy of the liver.

MATERIALS AND METHODS

Vascular casts of 10 livers were examined with helical computed tomography (CT). Liver segmental and subsegmental anatomy were determined on the CT scans according to customary radiologic practice guidelines. CT anatomic findings were compared with authentic anatomic territories seen at anatomic examination. The differences were assessed quantitatively in five of the 10 livers.

RESULTS

For the marginal (cranial and caudal) portions of the liver, an average (+/- 1 standard deviation) of 17.3% +/- 6.5 of the hepatic area visualized on axial CT scans was attributed to an incorrect subsegment. For the central zones (those adjacent to the right and left branches of the portal vein), this error amounted to 51.6% +/- 19.9. Expressed in absolute numbers, the error amounted to 40 mm on axial CT scans.

CONCLUSION

The radiologic determination of portal venous territories within the liver must be revised. The indirect landmarks currently used are not reliable for proper delineation. Only procedures that account for the portal venous distribution pattern, including peripheral branches, will result in correct depiction of the complex and variable anatomic reality.

A case in favor of aneurysmographic studies: a perforating artery originating from the dome of a basilar tip aneurysm

A posterior perforating artery originating from the dome of a basilar tip aneurysm is reported. The exact origin of this perforator was identified by selective aneurysmography only. This observation provides an argument favoring the consideration of aneurysmographic studies before treatment of large aneurysms located in proximity to areas of normal perforating arteries.

An in vitro anatomic model of the human cerebral arteries with saccular arterial aneurysms

An in vitro model of the main human cerebral arteries with or without saccular arterial aneurysms is presented. A cast of the cerebral arteries was obtained in a human specimen. Three aneurysms were simulated and added to the cast. Wax copies of the cast were produced, and embedded with liquid resin solidifying into solid blocks. After evacuation of the wax, a model consisting of a hollow reproduction of the cast within the resin block was obtained. The model is reproducible and anatomically accurate. Since it is transparent to visible light, and compatible with x-ray, magnetic resonance and transcranial doppler techniques, it should prove useful for a wide range of haemodynamic and radiologic investigations. The reported technique may be adapted to any structure with a hollow configuration, allowing for the preparation of arterial and venous models from other vascular areas, as well as models from other anatomic systems, such as the biliary or urinary tracts.

Segmental anatomy of the liver: a review and a proposal for an international working nomenclature

The segmental anatomy of the human liver has become a field of increasing interest to radiologists during the past few years. The number of different terminologies which have been used since the topic has been systemically investigated is, however, a source of serious confusion. The present paper describes the reasons why the authors plead for an international working nomenclature which distinguishes a right hemiliver consisting of a right posterior and a right anterior segment, formed by subsegments 6 and 7, and 5 and 8, respectively, and a left hemiliver consisting of a left medial and a left lateral segment, the former corresponding to segment 4, and the latter to subsegments 2 and 3. This basic concept, however, must be carefully tailored to the highly variable individual anatomy of each patient. Furthermore, some aspects of hepatic segmentation are not yet understood and require additional anatomical investigation.

General medical practice as a guideline for preclinical anatomy teaching? The veins

The amount of time assigned for teaching anatomy to medical undergraduates has been drastically reduced in all countries of the world during the sixties. This restriction has intensified the debate about the contents to be taught. The present study is intended to be a contribution to defining, against this background, a "tronc commun", a basic stock of anatomical knowledge that should be required from every medical student, whatever clinical speciality he may eventually engage in. The criterion proposed is the need of anatomical knowledge in general medical practice. With regard to the veins, the following conclusions have emerged from a questionnaire directed to general practitioners: 1) 92.8% of the vessels were agreed upon by the physicians asked. 2) General medical relevance was granted to 9.6% of the vessels mentioned in the international anatomical nomenclature. These results, which are in accordance with those recorded for the other chapters investigated so far, suggest that an adaptation of the amount of information taught to the time disponible in our days is possible, without endangering the basic knowledge necessary for general clinical practice. But the results also show that any reduction beneath the time necessary for teaching these notions jeopardizes the fundamental education indispensable to every physician. Thus, they clearly contradict tendencies considering that anatomy has become a branch that can be neglected in modern medical curricula.

Relationship between intrahepatic vessels and computer-generated hepatic scissurae: an in vitro assay

Liver segmentation is a matter of increasing importance for radiologists, in particular with respect to accurate preoperative localisation of focal hepatic lesions. Procedures for delineating the segmental anatomy from CT or MR images are therefore much in demand. In this context, a convenient technique for generating the intersegmental scissurae by computer has recently been proposed [9]. The procedure, however, seemed questionable from an anatomical point of view. We therefore checked its relevance using anatomical vascular casts of post mortem livers and comparing the computer-generated scissurae with the actual course of the intrahepatic vessels. The results presented in this paper confirm that a rigid application of flat scissural planes is not able to render the real intrahepatic compartmentation. Only techniques considering the effective individual vascular anatomy can provide a correct determination of the hepatic segments.

Duplicated hepatic artery: radiologic and surgical implications

Preoperative angiography of the coeliac trunk and superior mesenteric artery is routinely performed before liver resections and transplantations. For this purpose, it is usual to inject each branch of the coeliac trunk separately. Selective angiographic studies, however, may lead to overlooking surgically essential anatomic variations of the hepatic blood supply, as demonstrated by the present report. A case of a duplicated hepatic artery is presented, its radiologic and surgical implications discussed, and the relevant literature reviewed. This uncommon and particularly evocative feature illustrates the clinical importance of a sound knowledge of anatomical variants.

[Anatomy for the future general physician: a guiding thread in undergraduate education]

In all countries of the world the amount of time allotted to teaching anatomy has been drastically reduced during the 'sixties. This restriction has intensified the discussion about the contents to be taught. Between the contradictory opinions concerning the problem, this study is intended to indicate a middle way, insofar as it advocates a basic anatomical knowledge orientated towards general medical practice. More detailed anatomy would then be studied during the postgraduate curriculum, according to the specific needs of the clinical specialty chosen. This paper presents the results concerning the respiratory system.

[Basic anatomy of the future for the general physician]

In all countries of the world the amount of time allotted to teaching anatomy has been drastically reduced during the 'sixties'. This restriction has intensified the discussion about the contents to be taught. Between the contradictory opinions concerning the problem, this study is intended to indicate a middle way, insofar as it advocates a basic anatomical knowledge orientated towards general medical practice. More detailed anatomy would then be studied during the postgraduate curriculum, according to the specific needs of the clinical specialty chosen. This paper presents the results concerning the reproductive organs of the female.

[The differential diagnosis of prescalene soft tissue shadows. A clinical-anatomical contribution]

In CT examination of a female patient of 72 years of age, a prescalenic soft tissue shadow situated unilaterally on the left side was seen. 3D reconstruction revealed a course of the relevant structure that would correspond to a variation of the muscle of the neck. This is presented briefly in the following article and discussed within the framework of soft tissue shadows due to muscular variations.

Elementary anatomy for the future general practitioner: the arteries

In all countries of the world the amount of time allotted to teaching anatomy has been drastically reduced. This study is intended to be a contribution to defining, against such a background, a basic stock of macroscopic anatomy that should be required from every medical student, whatever branch of the profession he may eventually engage in. More advanced knowledge, specific to a particular specialty, will be integrated into the resident's curriculum. In this way free time will be made available so that the gifted student can be given an effective introduction into contemporary morphological research. In the chapter on the arteries, general medical relevance is granted to only 13.2% of the vessels mentioned in the International Nomenclature. Marked reduction in the amount of teaching of macroscopic anatomy seems therefore to be possible, without surrendering a full, clinically-orientated education.

[Cricothyreotomy using the Quicktrach coniotomy instrument set]

Percutaneous cricothyroidotomy may be a lifesaving procedure for airway obstruction, which cannot be relieved by endotracheal intubation and can be performed with specially designed instruments. A new device, the "Quicktrach", was evaluated by an anatomical preparation, flow and resistance measurements, and puncture of the cricothyroid membrane in 55 corpses. The size of the parts of the instrument (needle, plastic cannula, depth gauge) in relation to the size of the larynx is adequate, thus there is little likelihood of perforation of the posterior wall of the larynx. Resistance of the plastic cannula is sufficiently low to allow for adequate ventilation. The duration of time until the cannula is positioned properly in the trachea is significantly shorter, when an incision prior to the puncture is done (83 +/- 88 seconds without incision versus 35 +/- 41 seconds with incision; mean +/- SD). The "Quicktrach" is easy to apply even by inexperienced persons. The incidence of damage to the larynx (lesions including fractures of the thyroid, cricoid and 1. tracheal cartilage in 18%; soft tissue injury in 9%) is relatively high, however considering the live saving character of the procedure these numbers appear to be acceptable. Technical problems which occur with the use of the device are discussed and suggestions for improvement are made.