Anatomic landmarks of the glossopharyngeal nerve: a microsurgical anatomic study

OBJECTIVE: Compared with other lower cranial nerves, the glossopharyngeal nerve (GPhN) is well hidden within the jugular foramen, at the infratemporal fossa, and in the deep layers of the neck. This study aims to disclose the course of the GPhN and point out landmarks to aid in its exposure. METHODS: The GPhN was studied in 10 cadaveric heads (20 sides) injected with colored latex for microsurgical dissection. The specimens were dissected under the surgical microscope. RESULTS: The GPhN can be divided into three portions: cisternal, jugular foramen, and extracranial. The rootlets of the GPhN emerge from the postolivary sulcus and course ventral to the flocculus and choroid plexus of the lateral recess of the fourth ventricle. The nerve then enters the jugular foramen through the uppermost porus (pars nervosa) and is separated from the vagus and accessory nerves by a fibrous crest. The cochlear aqueduct opens to the roof of this porus. On four sides in the cadaver specimens (20%), the GPhN traversed a separate bony canal within the jugular foramen; no separate canal was found in the other cadavers. In all specimens, the Jacobson's (tympanic) nerve emerged from the inferior ganglion of the GPhN, and the Arnold's (auricular branch of the vagus) nerve also consisted of branches from the GPhN. The GPhN exits from the jugular foramen posteromedial to the styloid process and the styloid muscles. The last four cranial nerves and the internal jugular vein pass through a narrow space between the transverse process of the atlas (C1) and the styloid process. The styloid muscles are a pyramid shape, the tip of which is formed by the attachment of the styloid muscles to the styloid process. The GPhN crosses to the anterior side of the stylopharyngeus muscle at the junction of the stylopharyngeus, middle constrictor, and hyoglossal muscles, which are at the base of the pyramid. The middle constrictor muscle forms a wall between the GPhN and the hypoglossal nerve in this region. Then, the GPhN gives off a lingual branch and deepens to innervate the pharyngeal mucosa. CONCLUSION: Two landmarks help to identify the GPhN in the subarachnoid space: the choroid plexus of the lateral recess of the fourth ventricle and the dural entrance porus of the jugular foramen. The opening of the cochlear aqueduct, the mastoid canaliculus, and the inferior tympanic canaliculus are three landmarks of the GPhN within the jugular foramen. Finally, the base of the styloid process, the base of the styloid pyramid, and the transverse process of the atlas serve as three landmarks of the GPhN at the extracranial region in the infratemporal fossa.     

Comparison of isometric and anatomic reconstruction of the medial patellofemoral ligament: a cadaveric study

Recent surgical procedures designed to correct recurrent posttraumatic lateral patellar instability focus on reconstructing the medial patellofemoral ligament. This study evaluated and compared patellofemoral kinematics of isometric and anatomic medial patellofemoral ligament reconstructions. Using an infrared motion capture analysis system, patellar tracking was evaluated in the coronal plane in 6 cadaveric specimens. Reconstruction of the medial patellofemoral ligament using an isometric technique did not restore normal patellar tracking at any flexion angle; however, reconstruction using an anatomic technique restored statistically normal patellar tracking from maximal knee extension to 28 degrees of flexion. Neither technique was able to restore normal kinematics in deeper angles of knee flexion.     

Radiological determination of the anatomic hip centre from pelvic landmarks

There are various methods to locate the rotation centre of the hip joint on standard pelvic radiographs. When the geometry of both femoral heads is abnormal, a number of methods are available to locate the physiological hip centre from anatomical landmarks on pelvic radiographs. The accuracy and reliability of six methods were retrospectively investigated on 115 standard pelvic radiographs of both hips of healthy individuals. As a reference against the hip joint centre predicted by these methods, we used the true anatomical centre of the femoral head. Measurements were normalized in relation to pelvic height. The calculated hip rotation centre most closely approached the true anatomical centre of the femoral head when the acetabular teardrop was used as a landmark.     

Intraobserver errors in obtaining visually selected anatomic landmarks during registration process in nonimage-based navigation-assisted total knee arthroplasty: a cadaveric experiment

This study investigated the intraobserver errors in obtaining visually selected anatomic landmarks that were used in registration process in a nonimage-based computer-assisted total knee replacement (TKR) system. The landmarks studied were center of distal femur, medial and lateral femoral epicondyle, center of proximal tibia, medial malleolus, and lateral malleolus. Repeated registration in the above sequence was done for 100 times by a single surgeon. The maximum combined errors in the mechanical axis of the lower limb were only 1.32 degrees (varus/valgus) in the coronal plane and 4.17 degrees (flexion/extension) in the sagittal plane. The maximum error in transepicondylar axis was 8.2 degrees. The errors using the visual selection of anatomic landmarks for the registration technique of bony landmarks in nonimage-based navigated TKR did not introduce significant error in the mechanical axis of the lower limb in the coronal plane. However, the error in the transepicondylar axis was significant in the "worst-case scenario."     

Screw placement in percutaneous acetabular surgery: gender differences of anatomical landmarks in a cadaveric study

Purpose

Percutaneous reduction and periarticular screw implantation techniques have been successfully introduced in acetabular surgery. The advantages of this less invasive approach are attenuated by higher risks of screw misplacement. Anatomical landmarks are strongly needed to prevent malplacement. This cadaver study was designed to identify reliable anatomical osseous landmarks in the pelvic region for screw placement in acetabular surgery. Gender differences were specifically addressed.

Methods

Twenty-seven embalmed cadaveric hemipelvic specimens (13 male, 14 female) were used. After soft-tissue removal, anterior and posterior column acetabular screw placement was conducted by one orthopaedic trauma surgeon under direct vision. Each column was addressed by antegrade and retrograde screw insertion. Radiographic verification of ideal screw placement was followed by assessment of the distance from the different entry points to adjoining anatomical osseous structures.

Results

For anterior column screw positioning, the posterior superior iliac spine (PSIS), posterior inferior iliac spine (PIIS), iliopectineal eminence and centre of the symphysis were most reliable regarding gender differences. For posterior column screw positioning, the distance to the anterior superior iliac spine (ASIS) and the ischial tuberosity showed the lowest deviation between the different gender specimens. Highest gender differences were seen in relation to the cranial rim of the superior pubic ramus in retrograde anterior column screw positioning (p = 0.002). Most landmarks could be targeted within a 2.5-cm range in all specimens.

Conclusions

The findings emphasise the relevance of osseous landmarks in acetabular surgery. By adhering to easily identifiable structures, screw placement can be safely performed. Significant gender differences must be taken into consideration during preoperative planning.     

Pelvic emergency clamps: anatomic landmarks for a safe primary application

The application of the pelvic clamp as a tool for emergency stabilization of unstable pelvic ring fractures has proved to be a life-saving procedure. Using correct technique, the pelvic clamp can be applied within a few minutes after the patient's admission. To avoid severe complications (eg, pin perforation into the pelvis) during the application, anatomic landmarks for the correct pin placement have to be defined. The surface landmarks that are presently recommended for the correct pin placement are not always reliably found due to deformation of the body surface caused by swelling and hematoma. Our experience with 43 emergency applications of the pelvic C-clamp showed that reliable anatomic landmarks on the bony surface of the innominate bone could be identified to ensure correct pin placement. The ideal insertion point of the pins is an anatomic region on the lateral cortex of the ileum, where an easily palpable "groove" is formed by angulations of the lateral cortex of the iliac wing. Being increasingly used as an entry point for percutaneous transiliosacral screw fixations of sacroiliac joint injuries and sacral fractures, this region, which is close to the sacroiliac joint, represents an ideal point for maximum compression of the posterior pelvic ring. With the described technique, this "groove" can be identified easily even in emergency situations by blunt palpation with an instrument, avoiding the time-consuming use of a fluoroscope in most cases.     

Thecaloscopy through sacral bone approaches, cadaver study: further anatomic landmarks.

Endoscopy of the spinal canal, for interventional studies, diagnosis and therapy, is a scientific topic that has attracted the interest of neurosurgeons, anesthesiologists and orthopedic surgeons for the past twenty years. Endoscopy of the thecal sac was assumed to be less important than endoscopy of the ventricular system by neurosurgeons. Nevertheless, during the last years it has attained increasing scientific interest, firstly because of the introduction of small diameter flexible endoscopes and secondly due to the growing interest for minimal invasive diagnostic and therapeutic procedures in modern neurosurgery. Until now thecaloscopy was performed by the ISGT (International Study Group for Thecaloscopy) using co-axial downward orientated approaches. We have examined transsacral approaches to facilitate the navigation of flexible scopes in the lumbosacral subarachnoid space, and thus we now introduce further recognizable endoscopic anatomic landmarks.     

Sonographically guided percutaneous carpal tunnel release: an anatomic and cadaveric study

Minimally invasive techniques have become the standard of care for multiple procedures. This paper demonstrates both the surgeons' capacity to perform an accurate anatomic evaluation of the hand and forearm (n=10) and the use of this anatomic information to accurately perform sonographically guided, percutaneous carpal tunnel release using a single-portal endoscope without direct or indirect visualization in a cadaver model (n=6). Open dissection was then performed to confirm complete ligament transection and to evaluate the surrounding structures for injury. In all 6 cadavers, the transverse carpal ligament was transected completely without injury to any surrounding structures. With further investigation, this novel technique may offer a less invasive, office-based method for the surgical treatment of carpal tunnel syndrome that may offer patients an expedited recovery.     

The anatomic basis of the fourth dorsal metacarpal flap: a cadaveric dissection

PURPOSE: To study the vascularization of the fourth dorsal intermetacarpal space and to determine the contribution of the dorsal metacarpal artery and the interosseous muscle fascia to flap viability. The fourth dorsal intermetacarpal space is considered to be less reliable as a donor site because of previously reported vascular variations. METHODS: We performed 15 cadaver dissections. The vascular tree was injected with black latex through the radial and ulnar arteries at the forearm. The skin paddle was designed within the fourth intermetacarpal space. The proximal border was placed at the wrist joint line. The distal border was located 1 cm proximal to the head of the fourth and fifth metacarpal. The width of the skin paddle was based on whether the donor site could be closed directly. A zigzag incision was performed from the distal end of the skin paddle to the volar edge of the interdigital web. The borders of the skin paddle were outlined down to the fascia of the dorsal interosseous muscle. Once the fourth dorsal metacarpal artery was identified each vascular connection was dissected and recorded. RESULTS: The fourth dorsal metacarpal artery was identified in all specimens under the dorsal interosseous muscle fascia. The distal recurrent branch consistently entered the base of the flap superficial to the extensor digitorum communis tendon of the small finger and the dorsal interosseous muscle fascia. Cutaneous perforators branching off the dorsal metacarpal artery were not found consistently. CONCLUSIONS: Reliable flaps can be raised from the fourth dorsal intermetacarpal space based solely on the distal recurrent branch, excluding the dorsal metacarpal artery and interosseous muscle fascia.     

Computed tomography analysis of the coracoid process and anatomic structures of the shoulder after arthroscopic coracoid decompression: a cadaveric study

The purpose of this anatomic study is to define the morphologic changes of the coracoid and surrounding soft tissue after arthroscopic coracoid decompression. We obtained 5 fresh-frozen forequarter cadaveric specimens, 3 female and 2 male, with a mean age of 86.2 years. Arthroscopic coracoid decompression was performed, and intraarticular pathology was documented. Preoperative and postoperative measures of coracoid overlap, coracoid index, and coracohumeral distance were made on limited-cut axial computed tomography scans. Dissection was performed to assess anatomic relationships after coracoid decompression. Arthroscopic findings revealed subscapularis pathology and glenohumeral arthritis in all specimens, long head of biceps pathology in 3, and supraspinatus pathology in 2. Gross dissection confirmed the pathologic findings. Arthroscopic coracoid decompression effectively improves coracoid overlap, coracoid index, and coracohumeral distance. The adjacent major neurovascular structures are at a safe distance from the decompression site.