Biomedical subjects

J M Boon

Publications and source records attributed to J M Boon.

At least 19 recordsLinked to original sources

PubMed2007

Anatomical considerations on Sudeck's critical point and its relevance to colorectal surgery.

Sudeck's critical point at the rectosigmoid junction is described as the point of origin of the last sigmoid arterial branch, originating from the inferior mesenteric artery (IMA). There is controversy on the importance of Sudeck's point, and the frequency in which the anastomosis is found. Furthermore, the diameter of the anastomosis, if present, may also impact on the viability of the caudal stump. This study aimed to determine the frequency in which a macroscopic anastomosis occurs, between the superior rectal artery and the last sigmoidal branch, in a cadaver population; the diameter of this anastomosis and the distance from the origin of the IMA to Sudeck's point. Sixty-four cadavers were included in the study, excluding those with previous surgery to the rectosigmoid junction. Sudeck's point was carefully identified and dissected to establish the presence of an anastomosis. Subsequent measurements were performed using a digital caliper (accuracy = 0.01 mm). A macroscopic anatomosis was absent in three cases (4.7%). The mean diameter of the anastomosis when present was 1.9 mm (SD: 0.5 mm), and the distance from the origin of the IMA to Sudeck's point was 55.5 mm (SD: 14.6 mm). Although an anastomosis is present in the majority of cases, the vessel is very small in diameter, and may not be sufficient to meet the demands of the caudal stump. The distance from the origin of the IMA to Sudeck's point is sufficient enough to allow for ligation of the IMA proximal to Sudeck's point.

Arteriovenous Anastomosis↗

PubMed2006

Evaluation of Allen's test in both arms and arteries of left and right-handed people.

The Allen's test as described in 1929 by Edgar V. Allen has been modified, adapted and complemented by other newer modalities but remains a first line standard test to evaluate the arterial supply of the hand. In this study an attempt has been made to add more information regarding the arterial supply of the hand, in left- and right-handed individuals, left and right hands and the ulnar and radial arteries, when doing the Allen's test. A modified Allen's test using an oxygen saturation monitor was used. The sample group consisted of 80 (30 left-handed and 50 right-handed) students. No significant differences between the Allen's test of the left and right hands in the left and right-handed individuals were found. There was a marginal but not significant difference between the two arteries. The ulnar artery took slightly longer to reach baseline values as compared to the radial artery. The results suggest that a positive Allen's test can be found in both left and right-handed people, with regard to the left and right hands and both radial and ulnar arteries may be implicated. This information should be kept in mind when selecting either the radial or ulnar artery for grafting purposes (e.g. coronary angiosurgery) and forearm artery cannulation.

Adult↗

PubMed2006

Anatomical considerations of the anterior approach for central venous catheter placement.

Central venous catheterization (CVC) entails the catheterization of the superior vena cava via either the subclavian or the internal jugular vein (IJV). This study looked at the frequency in which a needle was inserted into the IJV using the anterior CVC approach, which entails inserting the needle into the apex of Sedillot's triangle, formed by the sternal and clavicular heads of sternocleidomastoid (SCM). The ipsilateral distances from the apex of Sedillot's triangle to the superior aspect of the sternoclavicular joint and the diameter of the IJV were also measured. A needle was inserted into the apex of Sedillot's triangle in 36 adult cadavers with mean age of 62 +/- 19 years (mean +/- SD), mean height of 1.6 +/- 0.18 m, and a mean weight of 55 +/- 16 kg. Subsequent dissections of this area revealed the relation of the needle to the IJV. Results indicate that on the right, the needle was inserted into the IJV in 97.14% of the cases. On the left, the needle entered the IJV in 78.79% of the cases. From the sternoclavicular joint, the apex of Sedillot's triangle was found to be 40.87 +/- 1.62 mm and 38.73 +/- 6.34 mm on the right and left, respectively. The IJV diameter was 17.29 +/- 1.07 mm on the right and 15.30 +/- 0.25 mm on the left. We conclude that the anterior CVC approach is an anatomically accurate technique. It is furthermore important to realize that when performing any invasive procedure, a sound anatomical knowledge of the region is extremely important, as complications are often due to lack of understanding or misunderstanding of the relevant anatomy.

Adult↗

PubMed2006

Superficial radial nerve injury during standard K-wire fixation of uncomplicated distal radial fractures.

This study determines the incidence of superficial radial nerve injury after Kirchner wire insertion. An experienced orthopedic surgeon inserted the K-wires into the radii of 92 adult cadavers. Subsequent dissection of the area exposed the superficial radial nerve and any observed nerve injury was documented. It is clear from the results that nerve injury may still occur as a result of K-wire insertion; however, the current method of K-wire insertion still proves to be a reliable and safe procedure for fixation of distal radial fractures.

Bone Wires↗

PubMed2005

Mandibular landmarks as an aid in minimizing injury to the marginal mandibular branch: A metric and geometric anatomical study.

Iatrogenic injury to the marginal mandibular branch is an important reason for medicolegal actions. The aim of this study was to determine the distance of the marginal mandibular branch to the inferior border of the mandible as well as variation of nerve position in relation to this border. The marginal mandibular branch was dissected carefully in a number of 36 facial halves. Three points were identified on the inferior border of the mandibular ramus: Point A at the angle of the mandible, Point B just anterior to the facial artery, and Point C, 2 cm anterior to Point B. A metric and geometric morphometric analysis, including thin-plate spline and relative warp analysis was done to determine the variation of nerve position in relation to these three bony landmarks. The metric study indicated a median distance from Point A to the nerve 2.3 mm inferior to Point A, 2.4 mm superior to Point B, and 10.7 mm superior to Point C. The shape analysis indicated that variation in the position of the nerve occurs most commonly at Points A and B. We conclude that these mandibular landmarks may assist surgeons in minimizing marginal mandibular branch injury and patient discomfort.

Aged↗

PubMed2005

Easily identifiable bony landmarks as an aid in targeted regional ankle blockade.

Regional anesthesia around the ankle joint is well suited to a large number of surgical procedures of the foot. Previous studies have alluded to the variable nerve distribution of the foot, which may result in incomplete blocks. The aim of the study was to determine the position of the nerves in relation to the ankle joint to easily identifiable bony and prominent soft tissue landmarks to aid more accurate targeting of these nerves. A number of 94 ankles (47 left; 47 right) were dissected to expose the tibial, sural, deep fibular (peroneal), superficial fibular (peroneal), and saphenous nerves. The distance of the nerves relative to easy to find bony landmarks was measured. A distance (alpha) was measured from the middle of the tibial nerve to the most medial aspect of the medial malleolus. Measurement beta was considered from the inferior tip of the lateral malleolus to the anterior border of the sural nerve on a horizontal plane. Measurement delta was taken from the medial border of the deep fibular (peroneal) nerve to the most anterior aspect of the medial malleolus. epsilon was measured from the middle of the superficial fibular (peroneal) nerve to the most anterior aspect of the medial malleolus on a horizontal plane. The saphenous nerve was measured (gamma) from its medial border to the most anterior aspect of the medial malleolus on a horizontal plane. Factors such as sex, length, and ankle side were also analyzed concerning their influence on the position of the nerves. This study suggests that a greater degree of certainty may possibly be attained when palpable and easy to find bony landmarks are used to determine the position of the nerves around the ankle and ensure a simple to perform, predictable, and selectively targeted block.

Anesthetics, Local↗

PubMed2005

The versatility of progress testing assessed in an international context: a start for benchmarking global standardization?

Sharing and collaboration relating to progress testing already takes place on a national level and allows for quality control and comparisons of the participating institutions. This study explores the possibilities of international sharing of the progress test after correction for cultural bias and translation problems. Three progress tests were reviewed and administered to 3043 Pretoria and 3001 Maastricht medical students. In total, 16% of the items were potentially biased and removed from the test items administered to the Pretoria students (9% due to translation problems; 7% due to cultural differences). Of the three clusters (basic, clinical and social sciences) the social sciences contained most bias (32%), basic sciences least (11%). The differences that were found, comparing the student results of both schools, seem a reflection of the deliberate accentuations that both curricula pursue. The results suggest that the progress test methodology provides a versatile instrument that can be used to assess medical schools across the world. Sharing of test material is a viable strategy and test outcomes are interesting and can be used in international quality control.

Benchmarking↗

PubMed2005

Anatomical considerations of the pediatric ilioinguinal/iliohypogastric nerve block.

BACKGROUND: The ilioinguinal/iliohypogastric nerve block is safe, effective and easy to perform in order to provide analgesia for a variety of inguinal surgical procedures in pediatric patients. A relatively high failure rate of 10-25% has been reported, even in experienced hands. The aim of this study was to determine the exact anatomical position of the ilioinguinal and iliohypogastric nerves in relation to an easily identifiable constant bony landmark, the anterior superior iliac spine (ASIS) in neonates and infants. The current ilioinguinal/iliohypogastric nerve block techniques were also evaluated from an anatomical perspective. METHOD: Dissections were performed on a sample of 25 infant and neonatal cadavers (mean weight = 2.2 kg; mean height = 45.6 cm). The distance from the ASIS to both the ilioinguinal and iliohypogastric nerves, on a line connecting the ASIS to the umbilicus was carefully measured using a digital caliper. Three techniques, commonly used in clinical practice, were simulated on the anatomical specimens. RESULT: The left and right ilioinguinal nerves were closer to the ASIS than previously described, i.e. 1.9 +/- 0.9 mm (mean +/- sd) and 2.0 +/- 0.7 mm, respectively. The mean distance from the left and right iliohypogastric nerves to the ASIS are 3.3 +/- 0.8 mm and 3.9 +/- 1.0 mm, respectively. CONCLUSIONS: We suggest that the high failure rate of the ilioinguinal/iliohypogastric nerve block in this age group could be due to lack of specific spatial knowledge of the anatomy of these nerves in infants and neonates. This cadaver-based study suggests an insertion point closer to the ASIS, approximately 2.5 mm (range: 1.0-4.9) from the ASIS on a line drawn between the ipsilateral ASIS and the umbilicus.

Cadaver↗

PubMed2005

Dimensions of the neonatal cricothyroid membrane - how feasible is a surgical cricothyroidotomy?

BACKGROUND: Airway management of the neonate remains a cornerstone in neonatal resuscitation which in most cases involves tracheal intubation. However, difficult intubations do occur. Cricothyroidotomy is recognized as an entry point below the vocal cords. This procedure becomes increasingly difficult in young children and is not recommended in children under the age of 5 years. Little is known about the anatomy of the neonatal airway, especially the size of the cricothyroid membrane. The aim of the study was to determine the dimensions of the cricothyroid membrane in neonates. METHODS: Twenty-seven neonatal cadavers (mean height of 44.89 cm and a mean weight of 2.05 kg) were carefully dissected and the dimensions of the cricothyroid membrane recorded with a digital caliper (accuracy 0.01 mm) by two independent observers. RESULTS: The cricothyroid membrane has a mean height of 2.61 mm (sd: 0.71) and width of 3.03 mm (sd: 0.63). CONCLUSIONS: Results of this study indicate that the dimensions of the cricothyroid membrane are too small for passing a tracheal tube as the dimensions of the tube exceeds that of the cricothyroid membrane. This could fracture the cartilages of the larynx. The performance of a surgical cricothyroidotomy with passing of a tracheal tube is therefore strongly discouraged in neonatal patients.

Cadaver↗

PubMed2004

Cricothyroidotomy: a clinical anatomy review.

The safe and successful performance of a cricothyroidotomy demands a working and yet specific knowledge of anatomy. An ignorance or misunderstanding of anatomy may result in failure or complications. The Educational Affairs Committee of the American Association of Clinical Anatomists has highlighted the importance of clinical anatomy for several invasive procedures. This review is building on their work and contribute further to the understanding of the anatomical framework, particularly the pitfalls and complications related to performing a cricothyroidotomy.

Cricoid Cartilage↗

PubMed2004

Alternative approaches for regional ulnar nerve blockade: a cadaveric study.

Wrist blockade is a safe and effective alternative to general anesthesia in surgery of hand injuries. With regard to the ulnar nerve, the volar approach is used, where the needle passes through or medial to the flexor carpi ulnaris tendon; however, the ulnar artery is at risk because the needle may accidentally penetrate it, causing profuse bleeding. Alternatively, the wrist may be approached medially, the ulnar approach, and the needle tip placed posterior to the flexor carpi ulnaris tendon. To determine which of these methods may be preferable for avoiding ulnar artery injury, needles were inserted into the wrist area of cadaver hands (n = 57) using the volar and ulnar approaches; detailed dissection of the region around the inserted needles was subsequently carried out. The position of the ulnar nerve relative to the ulnar artery and injury to the artery was documented. Damage to the ulnar artery using the volar approach was 36.8% (21/57 cases) compared to no (0%) injury observed using the ulnar approach. At the level of the wrist crease just proximal to the pisiform bone, the ulnar nerve was medial to the artery in 92.9% (53/57) of cases, medial and posterior in 5.3% (3/57), and anterior to the artery in 1.8% (1/57) of cases. This study suggests that in cases where ulnar artery pulsation is not reliable, the ulnar approach may be preferable for ulnar nerve blockade due to an increased incidence of ulnar artery penetration with the volar approach.

Anesthesia, Conduction↗

PubMed2004

Lumbar puncture: anatomical review of a clinical skill.

The safe and successful performance of a lumbar puncture demands a working and specific knowledge of anatomy. Misunderstanding of anatomy may result in failure or complications. This review attempts to aid understanding of the anatomical framework, pitfalls, and complications of lumbar puncture. It includes special reference to 3D relationships, functional and imaging anatomy, and normal variation. Lumbar puncture is carried out for diagnostic and therapeutic purposes. Epidural and spinal anesthesia, for example, are common in obstetric practice and involve the same technique as diagnostic lumbar puncture except that the needle tip is placed in the epidural space in the former. The procedure is by no means innocuous and anatomical pitfalls include inability to find the correct entry site and lack of awareness of structures in relation to the advancing needle. Headache is the most common complication and it is important to avoid traumatic and dry taps, herniation syndromes, and injury to the conus medullaris. With a thorough knowledge of the contraindications, regional anatomy and rationale of the technique, and adequate prior skills practice, a lumbar puncture can be carried out safely and successfully.

Adult↗

PubMed2004

Evaluation of clinical relevance of a problem-orientated head and neck module.

Current trends in medical education focus on outcomes-based learning as a means to facilitate student learning. The aim of this study was to evaluate a clinically applied module in head and neck anatomy for third-year dental students. The module linked clinical examination, regional dental blocks simulated on cadaver specimens, radiographic images and clinical case scenarios. A Likert-type questionnaire, completed by all students (n = 49), was used to evaluate student perceptions of this module objectively. The results indicate that an average number of students found that clinical examination received sufficient time (mean: 2.98) during the module, while a substantial number of students agreed that the integration of dental procedures stimulated them to study specific regional anatomy (mean: 3.82) and increased their interest in their future careers as dentists (mean: 4.04). The radiographs improved their understanding of anatomy (mean: 3.41) while the clinical case studies were a positive learning experience (mean: 3.10). The majority of students (mean: 4.12) felt that they were continuously made aware that they were studying appropriate matter for their future work as dentists. It seems evident that the integration of clinically relevant content facilitates and encourages the understanding of anatomy.

Anatomy↗

PubMed2003

A safe area and angle for harvesting autogenous tendons for anterior cruciate ligament reconstruction.

Anterior cruciate ligament (ACL) reconstruction with autogenous semitendinosus and gracilis tendons has become a common surgical procedure. Lower leg paresthesia following injury to the infrapatellar nerve during harvesting of the tendons has been well documented. Few authors have described the position of the infrapatellar nerve on a flexed knee, which is the position used during ACL reconstruction. The purpose of this study was to determine a safe area and angle where an incision could be made for harvesting of the semitendinosus and gracilis tendons, with the knee in flexion. Twenty right cadaver knees and 20 left knees were dissected. Landmarks on the knee were identified, from where the distances to the nerves (infrapatellar and saphenous) were measured with a vernier caliper. A safe area on the right knee was determined to be on the tibial tuberosity plane between 3.7 and 5.5 cm with a safe angle of incision of 51.6 degrees. A safe area on the left knee was determined to be on the tibial tuberosity plane between 3.6 and 4.9 cm with a safe angle of incision of 52.5 degrees. The results may assist orthopedic surgeons performing ACL reconstruction with semitendinosus and gracilis tendons to avoid cutaneous nerve damage and, therefore, patient discomfort.

Anterior Cruciate Ligament↗

PubMed2003

Segmental nerve damage during a McBurney's incision: a cadaveric study.

Injury to the ilioinguinal and iliohypogastric nerves after a McBurney's incision have been reported to cause paralysis of the conjoint tendon that may lead to the development of an indirect inguinal hernia. This study reports on the incidence of ilioinguinal and iliohypogastric nerve sectioning after the performance of a classic McBurney's incision as well as the distance and relationship of the ilioinguinal and iliohypogastric nerves to the anterior superior iliac spine and a classic McBurney's incision. The right iliac fossa and lumbar region of 33 cadavers were dissected for the uncovering of the ilioinguinal and iliohypogastric nerves after a correct McBurney's incision was made. Injury to the ilioinguinal and iliohypogastric nerves was recorded. The mean distance between the ilioinguinal nerve and the incision line was 41.89 mm and 34.63 mm between the iliohypogastric nerve and the incision line. The ilioinguinal and iliohypogastric nerves were found to be 6.69 mm and 12.08 mm from the anterior superior iliac spine, respectively. No ilioinguinal or iliohypogastric nerve was injured during all 33 McBurney's incisions.

Cadaver↗

PubMed2003

Finding an ideal site for intraosseous infusion of the tibia: an anatomical study.

Intraosseous infusion is a technique used for the administration of fluids to a hemodynamically shocked child in whom attempts to access the vascular system have been unsuccessful. Although few complications are seen, injury to the epiphyseal growth plate during the performance of this technique remains a serious problem. This study investigates the relationship between the site of insertion of the intraosseous needle and the epiphyseal growth plate, and the ease of needle insertion into various locations of the tibia in newborn infants. Fourteen newborn infant cadavers (28 tibias in total) were dissected after placement of four needles: 1). through the tibial tuberosity (Site A); 2). 10 mm distal to the tibial tuberosity (Site B); 3). 20 mm distal to the tibial tuberosity (Site C) and; 4). 10 mm proximal to the tibial tuberosity (Site D). Distances from the distal end of the epiphyseal growth plate were measured. A high number of needle placements at Site A were inserted into the epiphyseal growth plate. Most placements at Site B were between 10 and 16 mm from the epiphyseal growth plate on the right side and between 10 and 15 mm on the left side, and all were inserted without difficulty. Although far from the epiphyseal growth plate, most placements at Site C were very difficult to insert because of the thick cortical bone. All placements at Site D entered the epiphysis or the epiphysis and joint space of the knee. An insertion site of at least 10 mm distal to the tibial tuberosity is therefore recommended to avoid epiphyseal growth plate injury and ensure ease of insertion.

Cadaver↗

PubMed2002

Clinical anatomy as the basis for clinical examination: development and evaluation of an Introduction to Clinical Examination in a problem-oriented medical curriculum.

Clinical anatomy is usually defined as anatomy applied to patient care. The question is asked whether students of a new horizontally and vertically integrated medical curriculum recognize the subject as the basis for clinical examination. A clinical anatomy practicum was developed in the special activity, "Introduction to Clinical Medicine," held in the second year of the Pretoria medical curriculum. The practicum was conducted on a station basis to anatomically prepare the student for the inspection, palpation, percussion, and auscultation of the cardiovascular, respiratory, abdominal, and urogenital systems. A total of 23 stations consisting of eight cardiovascular, seven respiratory, and eight abdominal/urogenital stations were designed. Standardized patients, cadavers, skeletons, prosected specimens, x-rays, computed tomography (CT) scans, magnetic resonance imaging (MRI), multimedia programs, and clinical case studies were used as resources. A Likert-type questionnaire was used for student evaluation of the practicum. Most students realized the importance of surface anatomy for a family physician. More than two-thirds thought the practicum improved their understanding of the anatomical basis for clinical examination. The minority of students were stimulated to do further reading on clinical examination. The students' response to their ability to integrate the clinical examination with the radiological anatomy was average. Most students were continuously aware of the appropriateness of the practicum for their future career. We conclude that medical students recognize the importance of anatomy as the basis for clinical examination when exposed to an appropriate integrated presentation format.

Anatomy↗

PubMed2002

Congenital undescended scapula (Sprengel deformity): a case study.

This study describes a congenital deformity of the shoulder joint in a 5-year-old female, associated with an undescended scapula and the presence of an omovertebral bone. Dissections on 16 cadavers were done to identify structures in danger of injure before operating on the patient. Surgeons need to take specific note of the dorsal scapular nerve.

Child, Preschool↗