Innervation of the distal part of the vastus medialis muscle is endangered by splitting its muscle fibers during total knee replacement: an anatomical study using modified Sihler's technique.

Background and purpose - The distal part of the vastus medialis muscle is an important stabilizer for the patella. Thus, knowledge of the intramuscular nerve course and branching pattern is important to estimate whether the muscle's innervation is at risk if splitting the muscle. We determined the intramuscular course of the nerve branches supplying the distal part of the vastus medialis muscle to identify the surgical approach that best preserves its innervation.Material and methods - 8 vastus medialis muscles from embalmed anatomic specimens underwent Sihler's procedure to make soft tissue translucent while staining the nerves to study their intramuscular course. After dissection under transillumination using magnification glasses all nerve branches were evaluated.Results - The terminal nerve branches were located in different layers of the muscle and ran mostly parallel but also transverse to the muscle fibers. In half of the cases, the latter formed 1 to 3 anastomoses and coursed close to the myotendinous junction. Additionally, most of the branches extended into the ventromedial part of the knee joint capsule.Interpretation - To preserve the innervation of the distal part of the vastus medialis muscle, any split of the muscle during surgical approaches to the knee joint should be avoided.

There are no safe areas for avoiding the perforating arteries along the proximal part of the femur: A word of caution.

Knowledge about the variable course of the perforating arteries near the body of the femur is essential during surgical procedures (e.g., percutaneous cerclage wiring, plate osteosynthesis, Ilizarov technique). Our aims were to determine the number of perforating arteries, and to identify safe zones along the body of the femur within which perforating arteries are unlikely to pass toward the back of the thigh. The number of perforating arteries was determined in both legs of 100 formalin-fixed anatomic specimens of both sexes. The level of passage of perforating arteries near the body of the femur was measured in reference to a line from the anterior superior iliac spine to the medial femoral condyle. In each leg, two to seven perforating arteries were present. In 64% of legs, at least one artery divided into two to four branches before entering the back of the thigh. Thus, the total number of branches passing near the body of the femur varied between two to nine. Perforating arteries passed to the back of the thigh at every level between 14.0 and 36.5 cm from the anterior superior iliac spine (16-39% of the leg length). Within this distance, no safe zones along the body of the femur could be identified. The present study shows the high variability regarding number and course of the perforating arteries. Surgeons can be faced with an artery at every level on the posteromedial aspect of the body of the femur between 14.0 and 36.5 cm distally to the anterior superior iliac spine. Clin. Anat. 33:507-515, 2020. © 2019 Wiley Periodicals, Inc.

A Phylogenetic and Ontogenetic Perspective of the Unique Accumulation of Arterial Variations in One Human Anatomic Specimen.

Background and objectives: Anatomical dissection is an indispensable means of acquiring knowledge about the variability of the human body. We detected the co-existence of several arterial variations within one female anatomic specimen during routine anatomical dissection. The aim of this study was to evaluate if this status is a regular pattern in any of other vertebrates. Materials and Methods: Besides of a meticulous anatomic dissection, we performed a literature review concerning the frequency, the phylogenesis, and ontogenesis of all of these variations. Results: Exceptionally, the middle colic artery arose from an extraordinarily divided celiac trunk. The kidneys received three polar arteries. On the left side, a corona mortis replaced the obturator artery. The aortic arch gave rise to a bicarotid trunk, and the right subclavian artery originated and coursed as a typical lusorial artery leading to a non-recurrent laryngeal nerve on the right side. Furthermore, variations of the branches of the thyrocervical trunk were found to be present. Extraordinarily, in their cervical portion both internal carotid arteries gave rise to two arteries each. All of these variations developed within two to three weeks, around the sixth week of gestation. It was not possible to ascribe all or even one of the variations to a singular species of vertebrates. Conclusion: Apparently, arterial variations are frequently a result of random development. Medical professionals must always be aware of anatomical variations; the absence of such awareness would create major difficulties during surgery. The present case confirms the relevance of anatomical dissection, particularly for medical students.

Congenital Bilateral Absence of the Radial Artery: A Very Rare Variation in Humans - Phylogenetic and Ontogenetic Aspects.

In an 80-year-old Caucasian woman, both radial arteries were found to be replaced by an enlarged anterior interosseous artery. Additionally, the right forearm revealed a persistent median artery which formed the superficial palmar arch together with the ulnar artery. In both hands, the replaced radial artery was connected only to the deep but not the superficial palmar arch. In clinical practice, lack of an arterial pulse on the radial aspect of the wrist joint may indicate the presence of this anatomic variation. In this case, arterial blood sample collections, application of contrast media, invasive measurements of blood pressure, and several angiographic interventions cannot be performed via the radial artery. As this is the fourth reported case since 1830, bilateral aplasia of the radial artery appears to be an exceptional variation in humans. Thus, the phylo- and ontogenetic aspects of this anomaly are discussed.

High-resolution ultrasound visualization of the subcutaneous nerves of the forearm: a feasibility study in anatomic specimens.

INTRODUCTION: The aim of this ultrasound-anatomical study was to evaluate the ability of high-resolution ultrasound (HRUS) to visualize and infiltrate small subcutaneous nerves of the forearm in anatomic specimens. METHODS: Seven nonembalmed human bodies (4 men, 3 women; mean age at death, 60 years) were included in the study. Two investigators scanned the anatomic specimens using 15-MHz and 18-MHz HRUS transducers. The lateral, medial, and posterior antebrachial cutaneous nerves were scanned and interventionally marked with ink using HRUS-guidance. Subsequently, dissections were performed to assess the anatomical correlation of HRUS findings. RESULTS: All 3 nerves were identified consistently using HRUS. The precision of the ink-markings was excellent, with good correlation with the small peripheral branches of all 3 nerves. CONCLUSIONS: HRUS can identify precisely the small subcutaneous nerves of the forearm and may aid in both diagnosis and therapy in cases of neuropathy.

Finite element based nonlinear normalization of human lumbar intervertebral disc stiffness to account for its morphology.

Disc degeneration, usually associated with low back pain and changes of intervertebral stiffness, represents a major health issue. As the intervertebral disc (IVD) morphology influences its stiffness, the link between mechanical properties and degenerative grade is partially lost without an efficient normalization of the stiffness with respect to the morphology. Moreover, although the behavior of soft tissues is highly nonlinear, only linear normalization protocols have been defined so far for the disc stiffness. Thus, the aim of this work is to propose a nonlinear normalization based on finite elements (FE) simulations and evaluate its impact on the stiffness of human anatomical specimens of lumbar IVD. First, a parameter study involving simulations of biomechanical tests (compression, flexion/extension, bilateral torsion and bending) on 20 FE models of IVDs with various dimensions was carried out to evaluate the effect of the disc's geometry on its compliance and establish stiffness/morphology relations necessary to the nonlinear normalization. The computed stiffness was then normalized by height (H), cross-sectional area (CSA), polar moment of inertia (J) or moments of inertia (Ixx, Iyy) to quantify the effect of both linear and nonlinear normalizations. In the second part of the study, T1-weighted MRI images were acquired to determine H, CSA, J, Ixx and Iyy of 14 human lumbar IVDs. Based on the measured morphology and pre-established relation with stiffness, linear and nonlinear normalization routines were then applied to the compliance of the specimens for each quasi-static biomechanical test. The variability of the stiffness prior to and after normalization was assessed via coefficient of variation (CV). The FE study confirmed that larger and thinner IVDs were stiffer while the normalization strongly attenuated the effect of the disc geometry on its stiffness. Yet, notwithstanding the results of the FE study, the experimental stiffness showed consistently higher CV after normalization. Assuming that geometry and material properties affect the mechanical response, they can also compensate for one another. Therefore, the larger CV after normalization can be interpreted as a strong variability of the material properties, previously hidden by the geometry's own influence. In conclusion, a new normalization protocol for the intervertebral disc stiffness in compression, flexion, extension, bilateral torsion and bending was proposed, with the possible use of MRI and FE to acquire the discs' anatomy and determine the nonlinear relations between stiffness and morphology. Such protocol may be useful to relate the disc's mechanical properties to its degree of degeneration.

Nomina anatomica-unde venient et quo vaditis?

As the title indicates, this article deals with the origins of anatomic terminology and its development up to the present day. The first attempt to name anatomical structures in animals and humans date back to Alkmaion, i.e. to the fifth century BC. Further work has been done at the same time by the Hippocratics and about 100 years later by Aristotle. As the Alexandrians Erasistratos and Herophilos first in history dissected human bodies, they expanded the anatomical terms. Until Celsus (around Christ's birth) and even later on, anatomical terminology was almost exclusively based on the Greek language. Thus, Celsus and not-as frequently done-Galenos has to be called the father of Latin-based anatomical terminology. Due to several translations including Arabic, first periods of proverbial Bable resulted. Return to systematic order was achieved finally by Andreas Vesal (1514/15-1564) and Caspar Bauhin (1560-1624). But again due to translations into several national languages, the uniformity of the anatomical nomenclature was undermined. Thus, by the end of the nineteenth century, in 1895 the newly founded Anatomische Gesellschaft created a uniform terminology, the Basle Nomina Anatomica (BNA). Although it has been revised several times, it is still the very basic of human anatomical terminology. Recently, an attempt was made to replace it by English translations of the original Latin (and also still Greek) terms to mainly get machine-readable denominations. As this will result again in non-uniformity of terminology, the Anatomische Gesellschaft proposes a version of the latest, generally accepted terminology, based on the Latin terms but incorporating recent developments.

Injury of the gluteal aponeurotic fascia and proximal iliotibial band: anatomy, pathologic conditions, and MR imaging.

The fascia lata, or deep fascia of the thigh, is a complex anatomic structure that has not been emphasized as a potential source of pelvic and hip pain. This structure represents a broad continuum of fibrous tissue about the buttock, hip, and thigh that receives contributions from the posteriorly located aponeurotic fascia covering the gluteus medius muscle and from the more laterally located iliotibial band (ITB). At the pelvis and hip, the ITB consists of three layers that merge at the lower portion of the tensor fasciae latae muscle. The gluteal aponeurotic fascia and ITB merge at the buttock and hip before extending inferiorly to the Gerdy tubercle at the anterolateral tibia. Injuries to these anatomic structures are an underdiagnosed cause of pain and disability and may clinically mimic more common processes affecting the hip and proximal thigh. Categories of disease include overuse injuries, traumatic injuries, degenerative lesions, and inflammatory lesions. Familiarity with the anatomy and pathologic conditions of the fascia lata and its components is important in their recognition as a potential source of symptoms. This article illustrates the anatomy of this complex fascia through anatomic-pathologic correlation and describes the magnetic resonance imaging appearances of the pathologic conditions involving it.

The Corona mortis is similar in size to the regular obturator artery, but is highly variable at the level of origin: an anatomical study.

An enlarged anastomosis connecting the vascular territory of the external iliac and the obturator artery may replace most or all of the latter. This relatively common vascular variation, known as Corona mortis, can lead to death in the worst-case scenario if injured. Despite being well-known, exact anthropometric data are lacking. The purpose of this study was to determine diameters of the regular obturator artery, the Corona mortis and the inferior epigastric artery. In addition, the level of origin of the Corona mortis was quantified. The obturator artery and its norm variants were dissected bilaterally in 75 specimens (37 females, 38 males) and measured using two different methods. The Corona mortis was present in 36 of the 150 hemipelves (24%), presenting in one third of all cases bilaterally. Its level of origin measured from the commencement of the inferior epigastric artery was subject to high variability (4.4-28.3 mm). The mean diameters of the Corona mortis (mean 2.5 and 2.1 mm, respectively) and the regular obturator artery (mean 2.4 and 2.0 mm, respectively) were similar for both methods. There were no significant sex nor side differences. The diameter of the inferior epigastric artery was significantly smaller distal to the origin of the Corona mortis. The high incidence, non-predictable level of origin of the Corona mortis and its size similar to the regular obturator artery support its clinical relevance even to date. Clinicians should always be aware of an additional arterial vessel close to the pelvic brim.

Topographical Anatomy of the Adductor Muscle Group in the Albino Rat (Rattus norvegicus).

In comparative anatomy, the adductor muscles are said to be quite variable and to often cause difficulty in separation. The arrangement of these muscles and the possible occurrence of the adductor minimus and obturator intermedius muscles in the albino rat has not been investigated. The aim of this study was to accurately describe the adductor muscles in the albino rat (Rattus norvegicus). We hypothesized that all adductor muscles are constantly present and can be separated in a constant manner, and that the adductor minimus and obturator intermedius muscles are constant structures. Both pelvic limbs of 30 formalin-embalmed male albino rats were carefully dissected. The identification of the individual muscles was made based on their position in relation to the two branches of the obturator nerve and by comparing our results with previous findings in other species including humans. All examined rats had two gracilis muscles. The adductor longus muscle was the most superficial and smallest individual. The adductor brevis split into two parts of insertion-the femoral and genicular parts. The adductor magnus and minimus muscles could be separated constantly. The obturator intermedius muscle was a constant structure next to the obturator externus muscle. The adductor muscles of the albino rat were constantly separable and could be clearly assigned to their names. Further research is needed to investigate these muscles, especially the obturator intermedius muscle, in other species including humans.

Phrenic Nerve Transfer to Musculocutaneous Nerve: An Anatomical and Histological Study.

BACKGROUND: To restore elbow flexor muscle function in case of traumatic brachial plexus avulsion, the phrenic nerve transfer to the musculocutaneous nerve has become part of clinical practice. The nerve transfer can be done by means of video-assisted thoracic surgery without nerve graft or via supraclavicular approach in combination with an autograft. This study focuses on a detailed microscopic and macroscopic examination of the phrenic nerve. It will allow a better interpretation of existing clinical results and, thus, serve as a basis for future clinical studies. MATERIAL AND METHODS: An anatomical study was conducted on 28 body donors of Caucasian origin (female n = 14, male n = 14). A sliding caliper and measuring tape were used to measure the diameter and length of the nerves. Sudan black staining was performed on 15 µm thick cryostat sections mounted on glass slides and the number of axons was determined by the ImageJ counting tool. In 23 individuals, the phrenic nerve could be examined on both sides. In 5 individuals, however, only one side was examined. Thus, a total of 51 nerves were examined. RESULTS: The mean length of the left phrenic nerves (33 cm (29-38 cm)) was significantly longer compared to the mean length of the right phrenic nerves (30 cm (24-33 cm)) (p < 0.001). Accessory phrenic nerves were present in 9 of 51 (18%) phrenic nerves. The mean number of phrenic nerves axons at the level of the first intercostal space in body donors with a right accessory phrenic nerve was significantly greater compared to the mean number of phrenic nerves axons at the same level in body donors without a right accessory phrenic nerve (3145 (range, 2688-3877) vs. 2278 (range, 1558-3276)), p = 0.034. A negative correlation was registered between age and the nerve number of axons in left (0.742, p < 0.001) and right (-0.273, p = 0.197) phrenic nerves. The mean distance from the upper edge of the ventral ramus of the fourth cervical spinal nerve to the point of entrance of the musculocutaneous nerve between the two parts of the coracobrachialis muscle was 19 cm (range, 15-24 cm) for the right and 20 cm (range, 15-25 cm) for the left arm. CONCLUSIONS: If an accessory phrenic nerve is available, it presumably should be spared. Thus, in that case, a supraclavicular approach in combination with a nerve graft would probably be of advantage.

Undergraduate medical student perceptions and learning outcomes related to anatomy training using Thiel- and ethanol-glycerin-embalmed tissues.

Anatomical dissection is known to serve as an integral tool in teaching gross anatomy, including postgraduate training. A variety of embalming techniques exist, resulting in different haptic and optical tissue properties. This study aimed to objectify learning outcomes and medical student perceptions related to the use of two widely used embalming techniques, namely Thiel and ethanol-glycerin embalming. Between 2020 and 2022, first- and second-year medical students enrolled in the course on topographic anatomy participated in this study. Objective structured practical examinations were carried out for the head, neck, thorax, abdomen, pelvis, and extremity regions following regional dissection just before the oral examinations began. Six to ten numbered tags were marked in prosections of each region in Thiel- and ethanol-glycerin-embalmed specimens. Following the examinations, the students were surveyed regarding the suitability of the two embalming techniques with respect to preservation, colorfastness, tissue pliability, and the suitability in preparing for their anatomy examinations. Consistently higher scores were achieved for the thoracic and abdominal regions in ethanol-glycerin-embalmed specimens when compared to Thiel. No benefit was found for Thiel-embalmed upper or lower extremities. Tissues embalmed with ethanol-glycerin were rated higher for preservation and suitability to achieve the learning objectives, tissue pliability was rated higher for Thiel-embalmed tissues. Ethanol-glycerin embalming appears to offer certain advantages for undergraduate students in recognizing visceral structures, which may align with students' ideas on tissue suitability for their learning. Consequently, the benefits reported for Thiel embalming for postgraduate study unlikely reflect its suitability for novices.

Extramuscular and Intramuscular Course of the Nerve Innervating the Abdominal Part of the Pectoralis Major Muscle: An Anatomical Study with Regard to Transaxillary Endoscopic Subpectoral Breast Augmentation.

BACKGROUND: During transaxillary endoscopic subpectoral breast augmentation, the innervation of the abdominal part of the pectoralis major muscle can be injured. The question has been raised whether this could even be of value, as for a better result, the caudal fibers of the pectoralis major muscle have to be detached from their origin. The authors' aim was to identify the exact position and the intramuscular course and target of these nerve branches. METHODS: Fifty pectoralis major muscles and their supplying nerve branches from 27 formalin-fixed anatomical specimens were studied using macroscopic dissection and anthropometry. Furthermore, eight muscles underwent the modified Sihler procedure to determine the intramuscular course and target of the supplying nerve branches. RESULTS: The branches for the abdominal part of the pectoralis major muscle pierced the pectoralis minor muscle or coursed around its lower border 3.2 to 8.4 cm from the tip of the coracoid process. Within the muscle, at least one small nerve branch, innervating the abdominal part, ascended into the lowermost portion of the sternocostal head, and anastomosed with the lowest small branch of its supplying nerve branches. CONCLUSIONS: Because of the variable position of the nerve branches, they may often cross the operative field during transaxillary endoscopic breast augmentation. However, their interruption can be of value, because weakening of the lower part of the pectoralis major muscle is desired to keep the implant in place, and to avoid animation deformity.

Topographical anatomy of the albino rat's ischiotrochanteric muscle group.

The obturator internus, gemelli, and quadratus femoris muscles are thought to be postural muscles. Thus, they are in the focus of research. Although these muscles are described in other species, detailed descriptions are still lacking for the albino rat. We hypothesized that the rat's ischiotrochanteric muscle group is comparable to that of humans. We aimed to provide a detailed description, and to compare the rat's condition with other species including humans. Both hind limbs of 30 adult male formalin-fixed albino rats were carefully dissected and photo documented. Our results were then compared with data for other species and descriptions of human anatomy. The gemellus muscle was one single muscle mass, originating from the lesser sciatic notch and an unnamed groove on the dorsal aspect of the ischium. The obturator internus muscle arose from the inner aspect of the tabula of ischium. Both muscles formed a continuum and inserted as one complex on the medial aspect of the greater trochanter. The quadratus femoris muscle originated from the outer aspect of the tabula of ischium and inserted on the distal portion of the intertrochanteric crest, and the dorsal aspect of the lesser trochanter. Despite minor differences, the topographical conditions of these muscles are comparable between rats and other mammals including humans.

Microbeam bending of hydrated human cortical bone lamellae from the central region of the body of femur shows viscoelastic behaviour.

Bone is a biological tissue with unique mechanical properties, owing to a complex hierarchical structure ranging from the nanoscale up to the macroscale. To better understand bone mechanics, investigation of mechanical properties of all structural elements at every hierarchical level and how they interact is necessary. Testing of bone structures at the lower microscale, e.g. bone lamellae, has been least performed and remains a challenge. Focused ion beam (FIB) milling is an attractive technique for machining microscopic samples from bone material and performing mechanical testing at the microscale using atomic force microscopy (AFM) and nanoindentation setups. So far, reported studies at this length scale have been performed on bone samples of animal origin, mostly in a dehydrated state, except for one study. Here we present an AFM-based microbeam bending method for performing bending measurements in both dehydrated and rehydrated conditions at the microscale. Single lamella bone microbeams of four human donors, aged 65-94 yrs, were machined via FIB and tested both in air and fully submerged in Hank's Balanced Salt Solution (HBSS) to investigate the effect of (de)hydration and to a certain extent, of age, on bone mechanics. Bending moduli were found to reduce up to 5 times after 2 h of rehydration and no trend of change in bending moduli with respect to age could be observed. Mechanical behavior changed from almost purely elastic to viscoelastic upon rehydration and a trend of lower dissipated energy in samples from older donors could be observed in the rehydrated state. These results confirm directly the importance of water for the mechanical properties of bone tissue at the microscale. Moreover, the trend of lowered capability of energy dissipation in older donors may contribute to a decrease of fracture toughness and thus an increase in bone fragility with age.

A ratio to approximate the proximodistal extent of the flexor retinaculum in relation to the hand length.

The flexor retinaculum of the hand is a fibrous structure forming the carpal tunnel in conjunction with the carpal bones. To prevent incomplete release of the carpal tunnel it is of benefit to know about the expected longitudinal expansion of the flexor retinaculum. The objective of the present study was to identify a possible correlation between the proximodistal expansion of the flexor retinaculum and the length of the hand. We conducted an anatomical study on 124 hands of 62 body donors. The hand length and the length of the flexor retinaculum were measured in millimeters. By dividing the length of the flexor retinaculum by the hand length an individual ratio was calculated. The mean length of the observed hands was 187.8 mm. The mean proximodistal length of the flexor retinaculum was 27.2 mm (range, 14-39 mm). A positive correlation was noted between the proximodistal length of the flexor retinaculum and length of the hand (p = 0.01). On average, the length of the flexor retinaculum corresponded to 14% (range, 8-20%) of the hand length in right hands versus 15% (range, 11-20%) in left hands. A greater proximodistal length of the flexor retinaculum in longer hands compared to shorter hands can be expected. The length of the flexor retinaculum corresponds to 14-15% of the length of the hand. However, one should be aware that the length of the flexor retinaculum extends as far as 20 % of the length of the hand.

When and why was the phrenicoabdominal branch of the left phrenic nerve placed into the esophageal hiatus in German textbooks of anatomy? An anatomical study on 400 specimens reevaluating its course through the diaphragm.

BACKGROUND: The phrenicoabdominal branch of the left phrenic nerve passes between muscle fiber bundles within the costal part of the diaphragm near the pericardium. In most German textbooks of anatomy, however, its passage is described to be found in the esophageal hiatus. The aim of this study was to reevaluate its topography relative to the diaphragm in a multicentric study and to identify the initiation of this description. METHODS: In this multicentric study, the most dorsomedial branch of the left phrenic nerve was identified as the phrenicoabdominal branch in 400 embalmed anatomic specimens of Caucasian origin. The distance between its passage and the apex of the pericardium, the left border of the esophageal hiatus, and the inner aspect of the left sixth rib was measured on the cranial aspect of the diaphragm. Textbooks on human anatomy published in German language between 1700 and 2018 were reviewed for their description of the passage of the left phrenicoabdominal branch through the diaphragm. RESULTS: The first statement on the passage of the left phrenicoabdominal branch through the esophageal hiatus was given in 1791 by Sömmering. Since then, in German textbooks of anatomy, a duality in the description of the passage of the left phrenicoabdominal branch persists. In none of the individuals examined in this study, the left phrenicoabdominal branch passed through the esophageal hiatus. In 99.5% of all cases, it pierced the costal part of the diaphragm dorsal to or at the same level as the apex of the pericardium. The mean distances (standard deviations) were 3.4 (±1.5) cm to the apex of the pericardium, 5.8 (±2.2) cm to the esophageal hiatus, and 5.5 (±1.6) cm to the inner aspect of the left sixth rib. CONCLUSION: The findings on the position of the left phrenicoabdominal branch relative to the diaphragm help to improve topographical knowledge and prevent inadvertent nerve injury during surgical interventions on or near the diaphragm. Further to this, these results may form a substantial basis to adopt the correct description of the passage of the left phrenicoabdominal branch to anatomical textbook knowledge.

The anterolateral ligament of the knee and the lateral meniscotibial ligament - Anatomical phantom versus constant structure within the anterolateral complex.

BACKGROUND: Concerning the ongoing controversy about the existence and nature of the anterolateral ligament (ALL) of the knee joint, we reinvestigated the formation of the anterolateral part of its fibrous capsule in anatomic specimens. Furthermore, we wanted to clarify if the lateral meniscus has established a constant anchoring to the lateral tibial condyle via a lateral meniscotibial ligament (lmtl). METHODS: Forty paired embalmed lower extremities taken from 20 human body donors (15 men and five women) underwent exact macroscopic dissection. For the detailed evaluation of the lmtl, additionally 12 specially dissected joint specimens were used. In two of these specimens, the lmtl underwent further histological examination. RESULTS: In all specimens, the anterolateral part of the knee joint fibrous capsule was established by the iliotibial tract and the anterior arm of the aponeurosis of the biceps femoris muscle. According to their close connection and the fact that the anterolateral part of the fibrous capsule is exclusively assembled by these two aponeuroses, they do not leave any space for a distinct ALL connecting the lateral femoral epicondyle and the lateral tibial condyle. The constantly present lmtl was identified as a flat, rectangular bundle of collagen and also elastic fibers reinforcing the inner aspect of the fibrous capsule. Following an oblique direction, it connected the lateral face of the lateral meniscus with the superolateral margin of the lateral tibial condyle. The lmtl measured, on average, 17.1mm in longitudinal and 13mm in anteroposterior direction. CONCLUSION: Our results show that there is no evidence for the existence of an ALL in human knee joints. It is represented either by the iliotibial tract or - most likely - by the anterior arm of the short head of the biceps femoris muscle. On the other hand, the lmtl was found to be a constantly present structure.

Terminal bifurcation of the biceps brachii muscle and tendon: anatomic considerations and clinical implications.

OBJECTIVE: The objective of our study was to describe the anatomic variation of a bifurcated distal biceps tendon with MRI, histology, and dissection in cadavers and to report the MR appearance of superimposed lesions in a patient population with this anatomic variant. MATERIALS AND METHODS: Visual and histologic examinations of the distal biceps brachii tendon in eight sectioned fresh-frozen elbow specimens were performed. Dissection of 17 elbow specimens was performed to describe the distal biceps brachii tendon. In addition, all elbow MRI reports over a 3-year period (n = 411) were retrospectively reviewed to determine the presence of bifurcation of the distal biceps brachii tendon. RESULTS: The distal biceps brachii tendon appeared bifurcated in 25% of the sectioned specimens, and these findings were confirmed histologically. The distal biceps brachii tendon was completely separable into two components-that is, a short head and long head- throughout their proximal to distal extent in 41.2% of the dissected specimens. The distal biceps brachii tendon appeared bifurcated in 11.8% of 68 clinical cases that showed distal biceps brachii tendon abnormalities or injuries. The following patterns of injury were noted: complete rupture of both tendons (n = 1), complete rupture of the short head and normal insertion of the long head (n = 2), complete rupture of the short head and partial tear of the long head (n = 2), partial tear of both tendons (n = 2), and complete rupture of the short head and tendinosis in the long head (n = 1). CONCLUSION: A bifurcated distal biceps brachii tendon is an anatomic variant that arises from persistent division between the short head and long head of the distal biceps brachii tendon and can be characterized with MRI. Knowledge of a bifurcated distal biceps brachii tendon is important to characterize injury to the components and to avoid pitfalls in imaging diagnosis.

Comparison of laser surface scanning and fiducial marker-based registration in frameless stereotaxy. Technical note.

The authors compared the accuracy of laser surface scanning patient registration using the commercially available Fazer (Medtronic, Inc.) with the conventional registration procedure based on fiducial markers (FMs) in computer-assisted surgery. Four anatomical head specimens were prepared with 10 titanium microscrews placed at defined locations and scanned with a 16-slice spiral computed tomography unit. To compare the two registration methods, each method was applied five times for each cadaveric specimen; thus data were obtained from 40 registrations. Five microscrews (selected following a randomization protocol) were used for each FM-based registration; the other five FMs were selected for coordinate measurements by touching with a point measurement stylus. Coordinates of these points were also measured manually on the screen of the navigation computer. Coordinates were measured in the same manner after laser surface registration. The root mean square error as calculated by the navigation system ranged from 1.3 to 3.2 mm (mean 1.8 mm) with the Fazer and from 0.3 to 1.8 mm (mean 1.0 mm) with FM-based registration. The overall mean deviations (the arithmetic mean of the mean deviations of measurements on the four specimens) were 3.0 mm (standard deviation [SD] range 1.4-2.6 mm) with the Fazer and 1.4 mm (SD range 0.4-0.9 mm) with the FMs. The Fazer registration scans 300 surface points. Statistical tests showed the difference in the accuracy of these methods to be highly significant. In accordance with the findings of other groups, the authors concluded that the inclusion of a larger number of registration points might improve the accuracy of Fazer registration.