Optimal needle electromyography approach to the serratus anterior muscle.

INTRODUCTION/AIMS: There are two conventional needle electromyography (EMG) approaches to the serratus anterior (SA), both of which can result in erroneous insertion into adjacent structures such as the latissimus dorsi (LD), teres major, or external oblique abdominis muscles and pose a risk of long thoracic nerve (LTN) injury. Therefore, we identified a novel needle insertion point for the SA in cadavers that avoids other muscles and LTN injury. METHODS: This study included 17 cadavers: 12 to devise the new method and 5 to verify its accuracy. Novel landmarks were the inferior angle of the scapula (I), sternal notch (S), and xiphoid process (X). The relationships of the LD, pectoralis major (PM), SA, and LTN were determined relative to these landmarks. RESULTS: When inserting a needle into the proximal one third along the line connecting points I and X, there were adequate safety margins around the LD, PM, and LTN, and the new method had excellent accuracy. DISCUSSION: Compared to the conventional midaxillary method, our novel method improved the accuracy of needle EMG of the SA. Follow-up studies using clinical imaging techniques are needed to verify whether above findings are equally applicable in living subjects.

Proximal peroneal perforator flap, cadaveric study, and clinical applications for shallow defect reconstructions.

PURPOSE: Peroneal artery perforator offers a versatile range of microvascular tissue transfer methods from local flaps to vascularized osteocutaneous fibula flaps. It is one of the few flaps that can cover shallow defects that require thin and pliable skin paddles, such as in hands and feet (Han et al., 2018). The proximal region of the lower leg offers such flexible and thin flap compared to the middle and distal lower leg (Winters & de Jongh, 1999). However, the anatomy of the proximal peroneal artery perforator is relatively unknown in literature and its proximity to the common peroneal nerve (CPN) has not yet been studied. This study conducted a cadaveric study and put it in application into clinical settings. METHODS: Twenty lower leg specimens were dissected according to the methods of clinical proximal peroneal artery perforator flap harvest. Perforators arising in the proximal lower leg area of between 20 and 40 percentile of fibular length were inspected. Perforator length, location from fibular head, course, and location of CPN were recorded. Clinical reconstruction cases using the proximal lateral lower leg were analyzed. Six patients between the ages of thirty and seventy were included. Five cases were due to trauma, and one from mass excision, but all required thin and pliable flaps for reconstructions in hands or feet. Flaps were designed concentrical oval shapes, and harvest was done similarly to cadaveric perforator dissection, but perforator dissection was done only up to the required pedicle length. Perforator length, flap size, thickness, and long-term complications were recorded. RESULTS: Among 20 specimens, a total of 20 perforators were found in 18 cadavers (90%). Two specimens showed no perforators while two specimens showed multiple perforators. The perforators were located at an average of 101 mm from fibular head, with an average length of 55 mm ranging from 20 to 153 mm. The average size of perforator at origin was 2.0 mm, ranging from 1.0 to 3.6 mm. 45% showed septocutaneous course and 55% intramuscular course. Two out of 20 perforators were shown to arise from source vessels other than the peroneal artery. All clinical cases were successful without complications or debulking for contour shaping. Flap sizes ranged from 15 to 40 cm2 . Largest flap width was 5 cm, and all donor sites were primarily closed without complications. One year of follow-up showed no complications. CONCLUSION: Proximal peroneal artery perforator flap provides a reliable pedicle for a versatile tissue transfer. This study shows that the perforators of the proximal lateral lower leg often arise from vessels other than the peroneal artery, such as the anterior tibial artery or popliteal artery, as had been previously reported (Winters & de Jongh, 1999). Although the source vessel varies, perforator anatomy is at a safe distance from CPN. This variation of source vessels suggests a change in nomenclature to "proximal peroneal perforator flap." The clinical applications of this flap showed that it can be effectively used for reconstructions of shallow defects, such as in the hands and feet without secondary procedures for debulking.

Cadaveric Study for Safe Elevation of a Profunda Artery Perforator Flap: Anatomy of the Perforators and Obturator Nerves.

BACKGROUND: This cadaveric study aimed to describe the anatomy of the profunda artery perforators (PAPs). METHODS: In total, nine free cadavers with 18 upper thighs were dissected, 12 of which were from female cadavers, and 6 were from male cadavers. The average age of the cadavers was 84.7 ± 4.2 years. Dissection was performed to evaluate the anatomic position and characteristics of the femoral PAPs. The perforator distance from the gluteal sulcus, number of perforators, perforating muscles, diameter of the perforators, origin of the perforators, and number of nerves passing above and below the perforators were determined. RESULTS: The average number of perforators that penetrate the adductor magnus muscle was 2.5. The average distance from the origin of the perforators to the gluteal sulcus was 71.72 ± 28.23 mm. The average numbers of the obturator nerves passing above and below the perforator in the adductor magnus muscle were 1.3 (range, 0-4) and 0.7 (range, 0-2), respectively. CONCLUSION: The results provide a detailed anatomic basis for the PAP flap. The perforators of a PAP flap may be included in a flap with a transverse design. Sacrificing the small obturator nerves during dissection may not lead to significant donor site morbidity.

Anatomy of the nerves to the teres minor and the long head of the triceps brachii for electromyography.

BACKGROUND: We investigated the branching pattern and topographic anatomy of the nerves to the teres minor (Tm) and the long head of the triceps brachii (LHT) in relation to reference lines extending between surface landmarks, to identify the innervation patterns of, and the optimal needle placement points within, the Tm and the LHT. METHODS: The anatomical courses of the nerves to the Tm and the LHT were investigated in 37 upper limbs of fresh-frozen cadavers. Distances from the acromion to nerve penetration points, and crossing points of reference lines with the Tm and LHT were measured in 27 cadaveric upper limbs. RESULTS: The Tm was innervated by the axillary nerve in all specimens in three patterns, and the LHT was innervated exclusively by the radial nerve. Our dissection and measurements indicate that the midpoint of the reference line from the acromion to the inferior angle of the scapula is the optimal needle insertion point for the Tm. The target point for the LHT appears to be the one-third point of the reference line from the acromion to the medial epicondyle, or the two-thirds point of the reference line from the acromion to the axillary fold. CONCLUSIONS: We investigated the branching pattern of the nerves to the Tm and the LHT and propose optimal needle placement points for electromyography of the Tm and LHT.

Novel, user-friendly landmarks for localizing Baxter's nerve: A cadaveric study.

INTRODUCTION: Identification of Baxter's nerve (BN) has proven challenging for less experienced practitioners using ultrasonography due to a lack of adequate landmarks. This study aimed to establish novel, user-friendly anatomical landmarks and to describe useful structures to localize BN. MATERIALS AND METHODS: We examined 10 fresh cadaveric feet and identified the interobserver agreement of measuring three surface landmarks: the most medially protruded point on the medial malleolus (P), the navicular tuberosity (Q), and the center of the calcaneus (B). Next, 24 fresh cadaveric feet were used to identify the point of BN entry into the quadratus plantae (QP) muscle, which corresponds to the proximal BN impingement site. The rectangular coordinate system consisted of the origin (point P), X-axis, extension line P-Q, and Y-axis (the perpendicular line to the X-axis). To consider various foot sizes, the X and Y values were divided by the P-Q length and were designated as the ratios X and Y. RESULTS: Points P and Q showed smaller interobserver differences than that of point B. Ratios X and Y were 61.25 and 99.80%, respectively, for the QP. BN arose from the lateral plantar nerve in 20 of 24 specimens. The adjacent vessel was <3 mm from the entrapment site of BN in 20 of 24 specimens. CONCLUSION: New landmarks will improve the precision of localizing the entrapment site of BN and will provide advanced guidelines for podiatric patients.

Detailed anatomy of the trochlear nerve in the superior oblique muscle.

PURPOSE: The purpose of this study was to elucidate the detailed anatomy of the trochlear nerve in the superior oblique muscle (SOM) and the intramuscular innervation pattern using Sihler staining. METHODS: SOMs were dissected from their origin to the insertion in 28 eyes of 14 cadavers. The following distances were determined: from the SOM insertion to the trochlear, from the trochlear to the entry site of the anterior branch or posterior branch, and the widths of the main trunk and anterior and posterior branches. Sihler staining was then performed. RESULTS: The trochlear nerve traveled straight ahead medially and divided. Eighteen of 28 (64.3%) orbits showed two anterior and posterior branches, six (21.4%) showed three branches, and four (14.3%) showed no branching. The most distally located intramuscular nerve ending was observed at 62.4 ± 2.4% of the length of each muscle (35.8 mm from insertion when considering that the length of the SOM was 57.4 mm) and at 29.9 ± 3.2% of the length of each muscle (17.2 mm from the trochlear). Additionally, the length of the intramuscular arborization part was 9.4 ± 1.1% of the length of the SOM (5.4 mm when considering that the length of the SOM was 57.4 mm). Nonoverlap between two intramuscular arborizations of the nerve was detected in 20 of 28 cases (71.4%). Eight cases (28.6%) showed a definite overlap of two zones. CONCLUSIONS: This study provided a good understanding of the anatomy of the trochlear nerve in the SOM.

Selective Osteotomies to Correct Deviated Bony Vaults of Asian Noses.

BACKGROUND: Standard osteotomies for the correction of deviated noses are bilateral and comprise a combination of medial and lateral osteotomy procedures. However, their uniform application to the small/delicate Asian bony vault is inappropriate and often results in suboptimal outcomes. OBJECTIVES: This study describes how asymmetric bony pyramids were defined through 3-component analysis, which was then used to inform selective/individualized osteotomies. METHODS: Bony vault deviations were categorized after 3-component analysis in 117 patients seeking correction of a deviated nose. Selective osteotomies were applied accordingly. Pre- and postoperative photographs were compared and rated by 2 independent evaluators. Patients' subjective evaluations were also included. RESULTS: Selective osteotomies were possible in 79 (68%) out of 117 patients. Among the 79 study subjects, outcome ratings were excellent in 37 (47%), acceptable in 25 (32%), unsatisfactory in 8 (10%), and unspecified in 9 (11%). Unspecified cases aside, satisfactory correction was achieved in 88% (62/70 patients). Of the 54 patients who responded to telephone interviews, patient satisfaction was excellent in 43 (80%), improved in 10 (18.2%), and unchanged in 1 (1.8%). Follow-up of the 88% of patients with satisfactory correction showed a stable long-term outcome. CONCLUSIONS: Each bony vault in deviated noses is different, and thus, its correction must be individualized for each patient and for each side. The protocol described herein achieves a controlled correction of deviated bony vault. Restoration of bony pyramid symmetry via current techniques is best suited to short Asian bony vaults, where additional structural needs from routine nasal augmentation/lengthening are required.

Detailed Anatomy of Osteoperiosteal Ligamentous Structures in the Forehead.

This study aimed to present the anatomic characteristics of osteoperiosteal ligamentous attachments of the forehead and provide a better understanding of lateral eyebrow descent for safe and effective foreheadplasty. Anatomic dissections of the face were performed in 10 fresh Korean adult cadavers (20 hemifaces) using 2.5× magnification surgical loupes. Supraorbital, inferomedial orbital, and frontonasal osteoperiosteal ligamentous attachments were identified as fibrous tissues originating from a bone, and their tensile strengths were measured. The supraorbital osteoperiosteal ligamentous attachment had medial and lateral parts. It can be classified into 4 subtypes. It was located 11.0 ±â€Š6.6 mm lateral to the midline and 9.2 ±â€Š12.3 mm superior to the superior orbital margin. The inferomedial orbital osteoperiosteal ligamentous attachment was located 16.2 ±â€Š3.9 mm lateral to the midline and 2.2 ±â€Š2.7 mm inferior to the superior orbital margin, whereas the frontonasal osteoperiosteal ligamentous attachment was located 5.4 ±â€Š2.3 mm lateral to the midline and 1.4 ±â€Š8.5 mm superior to the superior orbital margin. Tensile strengths of all the osteoperiosteal ligamentous attachments in the forehead were above 10 N. These results indicate that osteoperiosteal ligamentous attachments develop in the rather medial region of the eyebrow and have a tensile strength adequate enough to maintain the medial eyebrow. Thus, the current study provides surgeons with detailed anatomic information that can be used as a valuable reference for forehead rejuvenation procedures.

Three Skin Zones in the Asian Upper Eyelid Pertaining to the Asian Blepharoplasty.

BACKGROUND: Natural looking double fold is an essential and aesthetically pleasing masterpiece in Asian blepharoplasty. This study aims to emphasize the 3 skin zone concept in the Asian upper blepharoplasty. METHODS: The authors examined the anterior lamella of each skin zone microscopically by performing 31 double-eyelid surgeries and 11 infrabrow lifts. Characteristics of dermal components, subcutaneous tissue, and outer fascia of OOM (OFOOM) at each skin zone were documented. The authors evaluated the vertical scales of each skin zone in young and aged Asian patients who visited the first author's clinic for the primary or secondary upper blepharoplasty with ×3.5 magnifying surgical loupe. RESULTS: The thickness of OOM had no difference among zones 1, 2, and 3. The skin and subdermal tissue had varying characteristics according to its skin zone. At zone 1, it seemed that only thin skin was on the OOM. The anterior lamella of zone 2 seemed to consist of skin, white fascia (OFOOM) including a venous network, and OOM in a gross field. At zone 3, thick skin, thick subcutaneous fatty layer, and OOM were magnified. The OFOOM of zone 3 was not significantly identified due to a sticky adherence with OOM. At the point of vertical scales of skin zone, good eyelids have lower zone 3 ratio and higher zones 1 and 2 ratio with qualified topographic condition. CONCLUSION: The authors classified the Asian upper eyelid as with 3 skin zones. Based on its anatomical investigation, the authors can afford anthropometric data and supplemental theory for the creation of aesthetic folds.

Detailed anatomy of the abducens nerve in the lateral rectus muscle.

The aims of this study were to elucidate the detailed anatomy of the abducens nerve in the lateral rectus muscle (LRM) and the intramuscular innervation pattern using Sihler staining. In this cohort study, 32 eyes of 16 cadavers were assessed. Dissection was performed from the LRM origin to its insertion. The following distances were measured: from LRM insertion to the bifurcation point of the abducens nerve, from LRM insertion to the entry site of the superior branch or inferior branch, from the upper border of the LRM to the entry site of the superior branch, from the lower border of LRM to the entry site of inferior branch, and the widths of the main trunk and superior and inferior branches. The single trunk of the abducens nerve divided into two branches 37 mm from insertion of the LRM, and 22 of 32 (68.8%) orbits showed only two superior and inferior branches with no subdivision. The superior branch entered the LRM more anteriorly (P = 0.037) and the superior branch was thinner than the inferior branch (P = 0.040). The most distally located intramuscular nerve ending was observed at 52.9 ± 3.5% of the length of each muscle. Non-overlap between the superior and inferior intramuscular arborization of the nerve was detected in 27 of 32 cases (84.4%). Five cases (15.6%) showed definite overlap of the superior and inferior zones. This study revealed the detailed anatomy of the abducens nerve in the LRM and provides helpful information to understand abducens nerve palsy. Clin. Anat. 30:873-877, 2017. © 2017 Wiley Periodicals, Inc.

Anatomical Study of the Fingertip Artery in Tamai Zone I: Clinical Significance in Fingertip Replantation.

Background There are a few previous studies of the vascular anatomy of the fingertips. The aim of this study was to evaluate this anatomy and the distribution of fingertip arteries. Patients and Methods A total of 31 cadaveric hands were used for evaluation of the vascular pattern of the fingertips on X-ray images obtained using a radiopaque material. We analyze the anatomy of the fingertip arteries, and classified it into three types in Tamai zone I. If only one dominant artery branched off from the distal transverse palmar arch, it was classified as type I. If the fingertip had branches of two dominant arteries, it was classified as type II, and if the fingertip had branches of three or more dominant arteries, it was classified as type III. Results The incidence of type I was 27%, that of type II was 28%, and the incidence of type III was 45%, the latter being the most frequent. In addition, we analyzed the pattern in each finger. The frequency of type III decreased from the index finger to the little finger, and the frequencies of types I and II increased from the index finger to the little finger. Conclusion Type III was the most common type in fingers, and its frequency decreased from the index finger to the little finger.

Bilayered Structure of the Superficial Facial Fascia.

Background: The superficial facial fascia comprises the superficial musculoaponeurotic system (SMAS) and the temporoparietal fascia (TPF) and is regarded as a continuous monolayer. However, some evidence indicates that the superficial facial fascia consists of 2 layers in specific areas. Objectives: The authors evaluated the superficial facial fascia for bilayered regions. Methods: Twenty fresh cadavers (40 hemifaces) were dissected to observe the superficial facial fascia. Twelve cadavers were dissected to assess tensile strengths of the superficial and deep layers of the SMAS. Specimens were obtained from 2 cadavers for histologic analysis. Results: The SMAS and TPF were separable into superficial and deep layers, with intervening areolar tissue. The deep TPF was continuous with the deep SMAS inferiorly and the subgalea anteriorly. The superficial orbicularis oculi was invested by the superficial SMAS, whereas the deep orbicularis and the platysma were invested by the deep SMAS. Thus, 2 key structures addressed in facial rejuvenation are positioned in different surgical planes. Conclusions: Study results support the belief that the superficial facial fascia comprises 2 layers, with the superficial orbicularis oculi and platysma invested by different layers. These findings have implications for facial rejuvenation techniques that involve management of the SMAS and TPF.

Detailed anatomy of the transverse superior fascial expansion of the upper eyelid.

PURPOSE: This study was designed to elucidate the detailed anatomy of the transverse superior fascial expansion (TSFE) and its relationship to the superior rectus muscle (SRM) and the levator palpebrae superioris (LPS). METHODS: In this cohort study, 46 eyes of 23 cadavers were observed macroscopically. Dissection from the SRM origin to its insertion was performed, and the width, length, and tensile strength of the TSFE were determined. RESULTS: The TSFE was located between the LPS and SRM. It originated at the surface of the SRM, 32.75 ± 4.40 mm from the origin of the SRM, and extended anteriorly. The TSFE firmly adhered to the SRM surface, 1.53 ± 0.47 mm medially and 1.19 ± 0.19 mm laterally, extended upwards and anteriorly, and inserted to the under surface of the LPS. The TSFE width was 6.70 ± 1.17 mm at the origin site on the SRM surface and 11.42 ± 6.70 mm at the insertion site on the LPS under the surface. Its total length was 11.67 ± 0.87 mm medially and 11.55 ± 0.94 mm laterally The TSFE was first encountered 11.49 ± 1.17 mm laterally and 11.57 ± 1.27 mm medially from the SRM insertion on the SRM's anterior surface. The tensile strength of the TSFE was significantly greater than that of the intermuscular fascia between the SRM and LPS (9.74 ± 4.53 N vs 3.02 ± 1.85 N, P =0.001). CONCLUSIONS: This study provides a good understanding of the TSFE structures conducive to performing SRM surgery.

Accessory first lumbrical muscle within the carpal tunnel: a case report.

Carpal tunnel syndrome is the most common entrapment neuropathy in the upper extremity. Palmaris longus, flexor digitorum superficialis, and lumbricals have infrequently been reported as causes of nerve compression. During routine Korean cadaver dissection, we incidentally identified an anatomic variant of first lumbrical muscle within the carpal tunnel in both wrists. The aberrant musculature originated from the radial side of the second FDS muscle at distal forearm level, running separately across the wrist beneath the flexor retinaculum. The dissected anomalous muscle was identified as an additional muscle belly of the first lumbrical muscle. Compression of the median nerve at the wrist might rarely be caused by the presence of such a tendon or muscle anomaly found in this study. Surgeons should be aware of possible anatomic variations in the carpal tunnel, and be prepared to modify their surgical plan accordingly.

Surface anatomy and levator scapulae muscle injection: A cadaveric investigation.

Accurate detection of the levator scapulae muscle is critical for effective diagnostic and therapeutic interventions. The commonly used surface anatomy approach has not been validated and is less accurate than ultrasound-guided techniques. Therefore, we determined the needle insertion point for the levator scapulae using a new technique based on the anatomy of the scapula. This investigation used 15 fresh-frozen cadavers to explore the relationship between the acromial angle and medial tip of the scapular spine (O) of the scapular spine. Based on the x-axis (the distance [L] from Point O to point acromial angle) and the y-axis perpendicular to the x-axis passing through Point O, the barycentric coordinates were determined through the intersections of each axis and the superior angle of the scapula with the levator scapulae. Various ratios involving the established distance L) were ascertained, we compared the measurements and ratios between the male and female groups, and the accuracy of the new technique was compared with the conventional technique. The optimal site of the new technique was within 6 to 7% of distance L on the x-axis and 42 to 44% of distance L on the y-axis. This technique was significantly more accurate than the conventional technique (P = .006). Although ultrasound allows for accurate injections via real-time visualization, its unavailability in some cases highlights the importance of understanding surface anatomy landmarks. Our new technique, based on the anatomy of the scapula and relative measurements, is more accurate than the conventional technique. This should enable more precise detection of the levator scapulae for accurate and efficient diagnostic and therapeutic procedures.

Topographical anatomy of the anterior cervical approach for c2-3 level.

PURPOSE: To develop a clinically relevant anterior cervical approach (ACA) to the C2-3 level. METHODS: Frequently encountered nerves [hypoglossal (HyN), internal (ISLN) and external superior laryngeal nerves (ESLN)] and vessels [lingual (LiA), superior laryngeal (SLA) and superior thyroid arteries (STA)] in the field of high ACA and the anatomic spatial markers [submandibular gland (SMG); sling for digastrics muscle (SDG); hyoid bone (HyB), and thyroid cartilage (ThC)] were evaluated using 18 fresh cadavers. The vertical distance of each structure at the carotid sheath and larynx and each disc for cervical level were measured from the suprasternal notch. RESULTS: The cervical levels of SDG, SMG and HyB were mostly C3 and that of ThC was C5. The vertical locations of HyN and LiA were not significantly different and the levels corresponded to C2. The levels for ISLN and ESLN were C3 at carotid and C4 and C5 at larynx sides, respectively. The vertical locations of ISLN and HyN were significantly different at carotid (p = 0.001) and larynx (p < 0.001) sides. The vertical locations and cervical levels of SLA and STA at carotid and larynx sides were not significantly different with those of ISLN and ESLN, respectively. The HyN traversed C2 with accompanying LiA. The ISLN passed C3 and C4 from carotid to larynx sides and accompanied SLA. CONCLUSIONS: The C2-3 level can be exposed through the space between the HyN and the ISLN by retracting the LiA superiorly, the SLA inferiorly, the HyB medially, and the carotid sheath laterally.

Location and tension of the medial palpebral ligament.

The aim of this study was to elucidate the precise anatomic location and tension of the medial palpebral ligament (MPL). Eleven hemifaces of 10 fresh Korean adult cadavers were used in this study. Nine specimens were used for measurement of dissection and tension, and 2 were used for histologic study. Measurements of tensile strength of each part of the MPL and Horner muscle were performed using a force gauge.The MPL consisted of 2 layers in all specimens dissected. The superficial layer of the palpebral ligament (SMPL) was observed from the anterior lacrimal crest to the upper and lower tarsal plates. The deep layer of the palpebral ligament (DMPL) lay from the anterior lacrimal crest to the posterior lacrimal crest, covering the lacrimal sac. The Horner muscle was observed at the posterior lacrimal crest just lateral to the attachment of the DMPL and ran laterally to the tarsal plate deep to the SMPL. The SMPL began at 4.5 ± 2.3 mm lateral to the nasomaxillary suture line to the upper and lower tarsal plates. Its transverse length was 9.6 ± 1.5 mm, and vertical width was 2.4 ± 0.7 mm, and its thickness was 4.5 ± 2.3 mm. The transverse length of the DMPL was 3.7 ± 0.4 mm, and its vertical width was 2.9 ± 1.3 mm, with a thickness of 0.3 ± 0.1 mm. The transverse length of the Horner muscle was 7.6 ± 1.9 mm, and its vertical width was 4.06 ± 1.5 mm, with a thickness of 0.4 ± 0.1 mm. The tensile strength of the SMPL was 13.4 ± 3.2 N, that of the DMPL was 4.1 ± 1.7 N, and that for Horner muscle was 9.0 ± 3.1 N. The tensile strength of the SMPL was significantly higher than that of the DMPL (P = 0.003).We reconfirmed that the MPL consisted of 2 layers: superficial layer and deep layer. Our results might be of use in surgeries of the medial canthi.

Cadaveric analysis of transcranial versus endoscopic transorbital petrosectomy: comparison of surgical maneuverability and brainstem exposure.

Introduction: While accessing the posterior fossa, the anterior transpetrosal approach (ATPA) and endoscopic transorbital approach (ETOA) use the same bony landmarks during petrous apex drilling. However, owing to their contrasting surgical axes, they are expected to show differences in surgical view, maneuverability, and clinical implications. This study aimed to investigate the feasibility of ETOA in accessing the brainstem and to compare the surgical view and maneuverability of each approach. Methods: ATPA and ETOA were performed in four human cadaveric heads (eight sides and four sides in each procedure). The angle of attack (AOA) and surgical depth were measured at the target of interest (root exit zone [REZ] of cranial nerve [CN] V, VI, and VII). When measuring the area of exposure, the brainstem was divided into two areas (anterior and lateral brainstem) based on the longitudinal line crossing the entry zone of the trigeminal root, and the area of each was measured. Results: ATPA showed significantly greater value at the trigeminal REZ in both vertical (31.8 ± 6.7° vs. 14.3 ± 5.3°, p=0.006) and horizontal AOA (48.5 ± 2.9° vs. 15.0 ± 5.2°, p<0.001) than ETOA. The AOA at facial REZ was also greater in ATPA than ETOA (vertical, 27.5 ± 3.9° vs. 8.3 ± 3.3°, p<0.001; horizontal, 33.8 ± 2.2° vs. 11.8 ± 2.9°, p<0.001). ATPA presented significantly shorter surgical depth (CN V, 5.8 ± 0.5 cm vs. 9.0 ± 0.8, p<0.001; CN VII, 6.3 ± 0.5 cm vs. 9.5 ± 1.0, p=0.001) than ETOA. The mean area of brainstem exposure did not differ between the two approaches. However, ATPA showed significantly better exposure of anterior brainstem than ETOA (240.7 ± 9.6 mm2 vs. 171.7 ± 15.0 mm2, p<0.001), while ETOA demonstrated better lateral brainstem exposure (174.2 ± 29.1 mm2 vs. 231.1 ± 13.6 mm2, p=0.022). Conclusions: ETOA could be a valid surgical option, in selected cases, that provides a direct ventral route to the brainstem. Compared with ATPA, ETOA showed less surgical maneuverability, AOA and longer surgical depth; however, it presented comparable brainstem exposure and better exposure of the lateral brainstem.

The Usefulness of Extradural Anterior Clinoidectomy for Lower-Lying Posterior Communicating Artery Aneurysms : A Cadaveric Study.

Objective: To confirm the usefulness of the extradural anterior clinoidectomy during the clipping of a lower riding posterior communicating artery (PCoA) aneurysm through cadaver dissection. Methods: Anatomic measurements of 12 adult cadaveric heads (24 sides total) were performed to compare the microsurgical exposure of the PCoA and internal carotid artery (ICA) before and after clinoidectomy. A standard pterional craniotomy and transsylvian approach were performed in all cadavers. The distance from the ICA bifurcation to the origin of PCoA (D1), pre-anterior clinoidectomy distance from the ICA bifurcation to tentorium (D2), post-anterior clinoidectomy distance from the ICA bifurcation to tentorium (D3), pre-anterior clinoidectomy distance from the tentorium to the origin of PCoA (D4) and post-anterior clinoidectomy distance from the tentorium to the origin of PCoA (D5) and the distance of the ICA obtained after anterior clinoidectomy (D6) were measured. We measured the precise thickness of the blade for the Yasargil clip with a digital precision ruler to confirm the usefulness of the extradural anterior clinoidectomy. Results: Twenty-four sites were dissected from 12 cadavers. The age of the cadavers was 79.83±6.25 years. The number of males was the same as the females. The space from the proximal origin of the PCoA to the preclinoid-tentorium (D4) was 1.45±1.08 mm (max: 4.01, min: 0.56). After the clinoidectomy, the space from the proximal origin of the PCoA to the postclinoid-tentorium (D5) was 3.612±1.15 mm (max: 6.14, min: 1.83). The length (D6) of the exposed proximal ICA after the extradural clinoididectomy was 2.17±1.04 mm on the lateral side and 2.16±0.89 mm on the medial side. The thickness of the Yasargil clip blade used during the clipping surgery was 1.35 mm measured with a digital precision ruler. Conclusion: The proximal length obtained by performing an external anterior clinoidectomy is about 2 mm, sufficient for proximal control during PCoA aneurysm surgery, considering the thickness of the aneurysm clips. In a subarachnoid hemorrhage, performing an extradural anterior clinoidectomy could prevent a devastating situation during PCoA aneurysm clipping.

Cadaveric Study of Thread Carpal Tunnel Release Using Newly Developed Thread, With a Histologic Perspective.

OBJECTIVE: To examine the usefulness and feasibility of modified thread carpal tunnel release (TCTR) by comparing the results of using pre-existing commercial thread with those of a newly developed thread (Smartwire-01). METHODS: A total of 17 cadaveric wrists were used in the study. The modified TCTR method was practiced by two different experts. Pre-existing commercial surgical dissecting thread (Loop&ShearTM) was used for five wrists and the newly developed Smartwire-01 was used for twelve wrists. The gross and microanatomy of the specimens were evaluated by a blinded anatomist. RESULTS: Both types of thread were able to cut the TCL similarly. Gross anatomy and histologic findings showed that there was no significant difference between the two types of threads. However, the practitioners felt that it was easier to cut the TCL using the newly-developed thread. CONCLUSION: TCTR using Smartwire-01 was as effective as pre-existing Loop&ShearTM, with better user experiences.