Collateral artery pathways of the femoral and popliteal artery.

BACKGROUND: The role of collateral artery circulation in the lower limb is under debate but clinically relevant, particularly when using covered stents for occlusive disease. Covered stents seem to outperform nitinol stents in extensive disease, but collaterals could be essential in case of acute thrombosis. In the present study, we describe the collateral pathways of the deep and superficial femoral artery (DFA, SFA) and the popliteal artery (PA), observed in human cadavers. METHODS: Ten fresh frozen cadaver legs were selected. The SFA and DFA were separately cannulated and injected with a different colored latex mixture simultaneously. After curing of the latex, the circulation was dissected thus visualizing the main arteries and their collateral vessels. The process was photographed and recorded, and collateral pathways were analyzed using a standardized vessel segmentation. The upper leg was divided in three regions, that is, the femoral triangle (F), the adductor canal (H), and the popliteal fossa (P) that, in turn, were split in three segments (1, 2, and 3, from proximal to distal). RESULTS: Overall, 113 collateral vessels were found; 69 originated from the DFA, 34 from the SFA, and 10 from the PA. The majority of collaterals originating from the DFA terminated in the SFA (57%). Fifty-six of 113 collaterals (50%) ended in either the distal adductor channel (H3) or the proximal PA (P1). Another 28 collateral arteries (25%) had their origin in this segment (H3, P1) and mostly connected to the P2 and P3 segments. Forty-three collaterals of the DFA and H3 segment had a direct or indirect connection to below the knee muscles. CONCLUSIONS: The majority of collaterals originate from the DFA, and the greater part of all collaterals has a connection with the H3-P1 segment. This observation may have clinical implications in the planning of endovascular procedures.

Uncovering students' misconceptions by assessment of their written questions.

BACKGROUND: Misconceptions are ideas that are inconsistent with current scientific views. They are difficult to detect and refractory to change. Misconceptions can negatively influence how new concepts in science are learned, but are rarely measured in biomedical courses. Early identification of misconceptions is of critical relevance for effective teaching, but presents a difficult task for teachers as they tend to either over- or underestimate students' prior knowledge. A systematic appreciation of the existing misconceptions is desirable. This explorative study was performed to determine whether written questions generated by students can be used to uncover their misconceptions. METHODS: During a small-group work (SGW) session on Tumour Pathology in a (bio)medical bachelor course on General Pathology, students were asked to write down a question about the topic. This concerned a deepening question on disease mechanisms and not mere factual knowledge. Three independent expert pathologists determined whether the content of the questions was compatible with a misconception. Consensus was reached in all cases. Study outcomes were to determine whether misconceptions can be identified in students' written questions, and if so, to measure the frequency of misconceptions that can be encountered, and finally, to determine if the presence of such misconceptions is negatively associated with the students' course formal examination score. A subgroup analysis was performed according to gender and discipline. RESULTS: A total of 242 students participated in the SGW sessions, of whom 221 (91 %) formulated a question. Thirty-six questions did not meet the inclusion criteria. Of the 185 questions rated, 11 % (n = 20) was compatible with a misconception. Misconceptions were only found in medical students' questions, not in biomedical science students' questions. Formal examination score on Tumour Pathology was 5.0 (SD 2.0) in the group with misconceptions and 6.7 (SD 2.4) in the group without misconceptions (p = 0.003). CONCLUSIONS: This study demonstrates that misconceptions can be uncovered in students' written questions. The occurrence of these misconceptions was negatively associated with the formal examination score. Identification of misconceptions creates an opportunity to repair them during the remaining course sessions, in advance of the formal examination.

Challenging students to formulate written questions: a randomized controlled trial to assess learning effects.

BACKGROUND: Underutilization of dialogue among students during small-group work is a threat to active meaningful learning. To encourage small-group learning, we challenged students to generate written questions during a small-group work session. As gender differences have been shown to affect learning, these were also inventoried. METHODS: Prospective randomized study during a bachelor General Pathology course including 459 (bio) medical students, 315 females and 144 males. The intervention was to individually generate an extra written question on disease mechanisms, followed by a selection, by each student group, of the two questions considered to be most relevant. These selected questions were open for discussion during the subsequent interactive lecture. Outcome measure was the score on tumour pathology (range 1-10) on the course examination; the effect of gender was assessed. RESULTS: The mean score per student was 7.2 (intervention) and 6.9 (control; p = 0.22). Male students in the intervention group scored 0.5 point higher than controls (p = 0.05). In female students, this was only 0.1 point higher (p = 0.75). CONCLUSIONS: Formulating and prioritizing an extra written question during small-group work seems to exert a positive learning effect on male students. This is an interesting approach to improve learning in male students, as they generally tend to perform less well than their female colleagues.

Effects of learning content in context on knowledge acquisition and recall: a pretest-posttest control group design.

BACKGROUND: It is generally assumed that learning in context increases performance. This study investigates the relationship between the characteristics of a paper-patient context (relevance and familiarity), the mechanisms through which the cognitive dimension of context could improve learning (activation of prior knowledge, elaboration and increasing retrieval cues), and test performance. METHODS: A total of 145 medical students completed a pretest of 40 questions, of which half were with a patient vignette. One week later, they studied musculoskeletal anatomy in the dissection room without a paper-patient context (control group) or with (ir)relevant-(un)familiar context (experimental groups), and completed a cognitive load scale. Following a short delay, the students completed a posttest. RESULTS: Surprisingly, our results show that students who studied in context did not perform better than students who studied without context. This finding may be explained by an interaction of the participants' expertise level, the nature of anatomical knowledge and students' approaches to learning. A relevant-familiar context only reduced the negative effect of learning the content in context. Our results suggest discouraging the introduction of an uncommon disease to illustrate a basic science concept. Higher self-perceived learning scores predict higher performance. Interestingly, students performed significantly better on the questions with context in both tests, possibly due to a 'framing effect'. CONCLUSIONS: Since studies focusing on the physical and affective dimensions of context have also failed to find a positive influence of learning in a clinically relevant context, further research seems necessary to refine our theories around the role of context in learning.

Lateral lower leg perforator flaps: an anatomical study to localize and classify lateral lower leg perforators.

Despite increasing use of lateral lower leg perforator flaps, comprehensive anatomical data are still lacking. The aim of this article was to comprehensively document the pattern of usable lateral lower leg perforators. Systematic mapping of 16 cadaver leg perforators in a well-defined area was performed to elucidate location, course, length, diameter, and origin. Overall, 197 perforators were found in 16 lateral lower legs. The mean number of perforators per leg with a diameter ≥ 0.3 mm was 13.4 ± 3.6. Most perforators were found in the distal third (39.0%), followed by the middle third (32.0%), and proximal third (29.0%). A musculocutaneous course was found in 26.9% of the perforators, whereas 73.1% revealed a septocutaneous course. Most septocutaneous perforators (50.0%) were found in the distal third and most musculocutaneous perforators (58.5%) in the proximal third (P < 0.001). The majority of perforators originated from the anterior tibial artery (53.0%), followed by the peroneal artery (41.6%), and the popliteal artery (5.1%). Popliteal artery perforators (1.64 mm) were significantly larger than anterior tibial artery (0.91 mm) and peroneal artery perforators (1.02 mm; P < 0.001). These results may facilitate tissue transfer around the lateral lower leg.

Posterior thigh perforator flaps: an anatomical study to localize and classify posterior thigh perforators.

In the last decade perforator flaps have been used increasingly for different indications. Many regions may serve as donor site. In this respect the posterior thigh region (PTR) has been neglected as a potential donor site for many years. The purpose of this study was to provide complete mapping of perforators supplying the posterior thigh region. Twelve fresh cadaver thighs were prepared injecting diluted acrylic paint into the iliac artery. Thereafter the posterior thighs were dissected from medial to lateral, distinguishing the perforators at the level of the superficial fascia. The perforators were localized and origin, source, length and diameter of the perforators were documented. Analysis occurred using ANOVA and the two proportion Z test. The distribution of musculocutaneous and septocutaneous perforators was respectively 69.1% and 30.9% (P = 0.002). The PTR was divided in thirds. Most perforators (53.2%) were found in de middle third of the PTR. The deep femoral artery (DFA) was the main origin of perforators (61.7%), followed by the superficial femoral artery (SFA) (27.7%) and the popliteal artery (PA) (10.6%). The DFA perforators were the longest with a mean length of 13.7 ± 4,69 cm, the SFA perforators were 9.79 ± 3.76 cm and the PA perforators were 8.6 ± 3.37 cm. The PTR offers a sufficient number of suitable perforators to serve as an adequate donorsite for pedicled and free flaps.

Collaborative group work: effects of group size and assignment structure on learning gain, student satisfaction and perceived participation.

BACKGROUND: Collaborative group sessions in Nijmegen include 15 students who work all together on a group assignment. Sometimes, the group is split-up in three and every subgroup elaborates a part of the assignment. At the end, they peer-teach each other. It is believed that the split-up enhances participation and therefore learning gain. AIMS: To establish the effect of group size and structure of the assignment on the perceived participation, the satisfaction and learning gain of collaborative group sessions. METHODS: In this study, 27 groups of 15 students were equally divided into: A-group: all 15 students working on the complete assignment. B-group: subgroups of 5 students working on the complete assignment. C-group: subgroups of 5 students working on a smaller part, and peer-teaching each other at the end of the group session. All students took a pre-test, a post-test and a follow-up test and completed a questionnaire. Questionnaires were analyzed with a one-way analysis of variance (ANOVA) and post hoc by multiple comparisons. Learning gain was analyzed using a repeated measures ANOVA. RESULTS: A group size effect is observed in favor of working in subgroups. Perceived participation of the students differs between A and B (p ≤ 0.001) and between A and C (p ≤ 0.001), but not between B and C. Also, an assignment effect is found in favor of the smaller assignment combined with peer-teaching. The students' satisfaction differs between A and C (p ≤ 0.003) and between B and C (p ≤ 0.001), but not between A and B. The C-group also shows higher test results (p ≤ 0.043). CONCLUSIONS: The students prefer smaller groups as well as smaller assignments including peer-teaching. A possible larger learning gain of this format needs to be re-investigated.

Anteromedial thigh flaps: an anatomical study to localize and classify anteromedial thigh perforators.

Until now, research on flaps in the anteromedial thigh region has focused on flaps in specific regions. To elucidate the complete pattern of suitable anteromedial thigh perforators, an anatomical study was performed by dissecting nine thighs from different cadavers. The ideal perforator has maximum length and diameter and runs through a septum. According to the data found in our study, these perforators can predominantly be found in the middle third of the anteromedial thigh region. All of the three main thigh vessels supply perforators which can be used for flaps. Pertaining to length and diameter the most suitable perforators originate from the deep femoral artery, which can be found in the proximal and middle third of the anteromedial thigh. Musculocutaneous perforators are found to be longer than septocutaneous perforators. Because of their position, the proximal and distal third perforators should preferentially be used for local pedicled flaps. Defects in the pelvic area and around the knee can be closed with perforator flaps from the proximal and distal anteromedial thigh, respectively. Because of their diameter, length, and number, the middle third perforators should be the first choice for harvesting free flaps. Skin closure is easily achieved in the anteromedial thigh region even when larger flaps are used.

The Effect of Passive and Active Education Methods Applied in Repetition Activities on the Retention of Anatomical Knowledge.

This study examines the long-term retention of anatomical knowledge from 180 students after various repetition activities. The retention of anatomical knowledge was assessed by multiple-choice tests at five different points in time: before and after a course in Functional Anatomy, before and after repetition activities that occurred 14 weeks after this course, and 28 weeks after this course to establish long-term retention. Students were divided into five groups: one without any repetition activity, one with a restricted repetition activity (the multiple-choice test), and three groups that were offered repetition activities (traditional lecture, e-learning module, and small group work in the dissection room). During all three repetition activities the same information was conveyed, and this content was not revisited in other courses for the duration of the study. The results showed that students who did not engage in a repetition activity scored significantly lower on the long-term retention test compared to all other groups (ANCOVA: P = 0.0001). Pair-wise comparison with estimated means showed that the other four groups, regardless of the type of repeating activity, did not differ in the amount of knowledge they retained during any of the five assessments (P = 0.008, P = 0.0001, P = 0.001, and P = 0.0001, respectively). This study suggests that the type of repetition activity has no effect on knowledge retention both immediately following the activity and in the long term. It is concluded that the repetition of anatomical knowledge in any form is beneficial for students and will likely improve student outcomes in a curriculum that builds on prior knowledge.

Neuroanatomy Learning: Augmented Reality vs. Cross-Sections.

Neuroanatomy education is a challenging field which could benefit from modern innovations, such as augmented reality (AR) applications. This study investigates the differences on test scores, cognitive load, and motivation after neuroanatomy learning using AR applications or using cross-sections of the brain. Prior to two practical assignments, a pretest (extended matching questions, double-choice questions and a test on cross-sectional anatomy) and a mental rotation test (MRT) were completed. Sex and MRT scores were used to stratify students over the two groups. The two practical assignments were designed to study (1) general brain anatomy and (2) subcortical structures. Subsequently, participants completed a posttest similar to the pretest and a motivational questionnaire. Finally, a focus group interview was conducted to appraise participants' perceptions. Medical and biomedical students (n = 31); 19 males (61.3%) and 12 females (38.7%), mean age 19.2 ± 1.7 years participated in this experiment. Students who worked with cross-sections (n = 16) showed significantly more improvement on test scores than students who worked with GreyMapp-AR (P = 0.035) (n = 15). Further analysis showed that this difference was primarily caused by significant improvement on the cross-sectional questions. Students in the cross-section group, moreover, experienced a significantly higher germane (P = 0.009) and extraneous cognitive load (P = 0.016) than students in the GreyMapp-AR group. No significant differences were found in motivational scores. To conclude, this study suggests that AR applications can play a role in future anatomy education as an add-on educational tool, especially in learning three-dimensional relations of anatomical structures.

The nasolabial fold as potential vascular receptor site: an anatomic study.

Free and pedicled flaps are frequently used in reconstruction of the lower two-thirds of the face. For these reconstructions, the submandibular facial vessels are extensively used as a receptor site. In this anatomic study, we investigate if the facial vessels in the nasolabial fold can be used as a receptor site as well. In 13 human cadavers, the facial artery and vein were dissected in the nasolabial fold in the same way as would be done during surgery. The ease of dissection and length, diameter, and location of the vessels were analyzed. The average length of the dissected artery was 28 mm (+/-11 standard deviations [SD]) and of the dissected vein, 19 mm (+/-6 SD). The mean diameter of the artery was 1.5 mm (+/-0.4 SD) and 2.5 mm (+/-0.8 SD) for the vein. In 85% of the sides, both vessels were suitable to use as a microsurgical receptor site. The easy access and the measured diameter of the facial vessels in the nasolabial fold make it a potential site for microsurgical anastomosis.

Inducing targeted failure in cadaveric testing of 3-segment spinal units with and without simulated metastases.

We propose an experimental setup and protocol able to induce targeted failure of the middle vertebra in 3-segment spinal units and to capture the specimens' deformation in their post-failure state. Sixteen 3-segment spinal units with and without artificial metastases were destructively tested in axial compression using one of two failure criteria; either: (A) A clear drop in force (>10-15% of peak force) (n = 4); or (B) A minimum displacement of 5 mm (n = 12). Subsequently, the specimens were fully fixated in polymethylmethacrylate (PMMA), thereby preserving their post-failure state. Pre- and post-experiment computed tomography (CT) scans were acquired to determine the occurrence of failure in one of the vertebral bodies. All specimens were successfully fixated in their post-failure state. When applying failure criterion A, two specimens showed signs of failure. When applying failure criterion B, all specimens showed signs of failure; in 9 out of 12 specimens this occurred in the middle vertebrae only. In conclusion, this research provides an experimental setup and protocol able to induce targeted failure of 3-segment spinal units and to capture the specimens' deformation in their post-failure state. Furthermore, this study illustrates the importance of an adequate failure criterion for successful simulation of vertebral fractures in an experimental setup.

Longitudinal retention of anatomical knowledge in second-year medical students.

The Radboud University Medical Center has a problem-based, learner-oriented, horizontally, and vertically integrated medical curriculum. Anatomists and clinicians have noticed students' decreasing anatomical knowledge and the disability to apply knowledge in diagnostic reasoning and problem solving. In a longitudinal cohort, the retention of anatomical knowledge gained during the first year of medical school among second-year medical students was assessed. In May 2011, 346 medical students applied for the second-year gastro-intestinal (GI) tract course. The students were asked to participate in a reexamination of a selection of anatomical questions of an examination from October 2009. The examination consisted of a clinical anatomy case scenario and two computed tomography (CT) images of thorax and abdomen in an extended matching format. A total of 165 students were included for analysis. In 2011, students scored significantly lower for the anatomy examination compared to 2009 with a decline in overall examination score of 14.7% (±11.7%). Decrease in knowledge was higher in the radiological questions, compared to the clinical anatomy cases 17.5% (±13.6%) vs. 7.9% (±10.0%), respectively, d = 5.17. In both years, male students scored slightly better compared to female students, and decline of knowledge seems somewhat lower in male students (13.1% (±11.1%) vs. 15.5% (±12.0%), respectively), d = -0.21. Anatomical knowledge in the problem-oriented horizontal and vertical integrated medical curriculum, declined by approximately 15% 1.5 year after the initial anatomy course. The loss of knowledge in the present study is relative small compared to previous studies. Anat Sci Educ 10: 242-248. © 2016 American Association of Anatomists.

A dynamic extensor brace reduces electromyographic activity of wrist extensor muscles in patients with lateral epicondylalgia.

STUDY DESIGN: Semiexperimental study. OBJECTIVE: To investigate the effect of an external wrist extension force on extensor muscle activity during hand gripping in patients with lateral epicondylalgia. BACKGROUND: Lateral epicondylalgia or "tennis elbow" is a common, often disabling ailment affecting millions of people. An optimal treatment strategy remains to be identified. The use of an external wrist extension force may reduce the extensor muscle activity during gripping in these patients. METHODS: Muscle activity of the extensor carpi radialis brevis (ECRB), extensor digitorum communis (EDC), and extensor carpi radialis longus (ECRL) was measured using surface EMG. Subjects gripped at an intensity of 10%, 20%, and 30% of the maximum voluntary contraction (MVC) force with and without the dynamic extensor brace and with and without an applied external wrist extension force of 1%, 2%, and 3% of MVC. RESULTS: At all levels of MVC gripping, the EMG signal of the ECRB and EDC were significantly lower for gripping with than without brace. An extension force of 3% of the MVC force significantly reduced the EMG signal of all muscles in almost all measurement conditions. CONCLUSIONS: The results of this study indicate that the dynamic extensor brace as well as the external extension force significantly reduced the EMG signal of the wrist extensor muscles during gripping in patients with lateral epicondylalgia. Based on these results, the dynamic extensor brace could be a promising new intervention for lateral epicondylalgia.

An investigation of anatomical competence in junior medical doctors.

Because of a decrease of the time available for anatomy education, decisions need to be made to reduce the relevant content of the anatomy curriculum. Several expert consensus initiatives resulted in lists of structures, lacking analysis of anatomical competence. This study aims to explore the use of anatomical knowledge by medical doctors in an attempt to delineate the nature of anatomical competence. The research question is: what kind of anatomical knowledge do junior medical doctors use during a consultation with a patient presenting with a shoulder complaint? Ten junior medical doctors participated in this stimulated recall study. Each of them was videotaped while performing a consultation with a standardized patient with a complex shoulder complaint. The recording was viewed immediately after. Participants were videotaped again while verbalizing the thoughts they remembered having during the consultation. Verbatim transcriptions were coded by two coders using the qualitative data analysis ATLAS.ti software. Results were that these junior medical doctors used anatomical knowledge in all phases of the consultation, especially during physical examination. The use of anatomical terms was strongly associated with clinical reasoning and it was apparent that every subject visualized relevant anatomical information. Conclusion is that young medical doctors actively use their anatomical knowledge and it seems that the relevant anatomy consists largely of adequate visual representations in memory. Anatomy teachers should focus the students' learning activity on building an adequate visual representation of anatomical structures. This should be supported by assessments that test the quality of the students' visual representations.

Actual drawing of histological images improves knowledge retention.

Medical students have to process a large amount of information during the first years of their study, which has to be retained over long periods of nonuse. Therefore, it would be beneficial when knowledge is gained in a way that promotes long-term retention. Paper-and-pencil drawings for the uptake of form-function relationships of basic tissues has been a teaching tool for a long time, but now seems to be redundant with virtual microscopy on computer-screens and printers everywhere. Several studies claimed that, apart from learning from pictures, actual drawing of images significantly improved knowledge retention. However, these studies applied only immediate post-tests. We investigated the effects of actual drawing of histological images, using randomized cross-over design and different retention periods. The first part of the study concerned esophageal and tracheal epithelium, with 384 medical and biomedical sciences students randomly assigned to either the drawing or the nondrawing group. For the second part of the study, concerning heart muscle cells, students from the previous drawing group were now assigned to the nondrawing group and vice versa. One, four, and six weeks after the experimental intervention, the students were given a free recall test and a questionnaire or drawing exercise, to determine the amount of knowledge retention. The data from this study showed that knowledge retention was significantly improved in the drawing groups compared with the nondrawing groups, even after four or six weeks. This suggests that actual drawing of histological images can be used as a tool to improve long-term knowledge retention.

Reliability of videotaped observational gait analysis in patients with orthopedic impairments.

BACKGROUND: In clinical practice, visual gait observation is often used to determine gait disorders and to evaluate treatment. Several reliability studies on observational gait analysis have been described in the literature and generally showed moderate reliability. However, patients with orthopedic disorders have received little attention. The objective of this study is to determine the reliability levels of visual observation of gait in patients with orthopedic disorders. METHODS: The gait of thirty patients referred to a physical therapist for gait treatment was videotaped. Ten raters, 4 experienced, 4 inexperienced and 2 experts, individually evaluated these videotaped gait patterns of the patients twice, by using a structured gait analysis form. Reliability levels were established by calculating the Intraclass Correlation Coefficient (ICC), using a two-way random design and based on absolute agreement. RESULTS: The inter-rater reliability among experienced raters (ICC = 0.42; 95%CI: 0.38-0.46) was comparable to that of the inexperienced raters (ICC = 0.40; 95%CI: 0.36-0.44). The expert raters reached a higher inter-rater reliability level (ICC = 0.54; 95%CI: 0.48-0.60). The average intra-rater reliability of the experienced raters was 0.63 (ICCs ranging from 0.57 to 0.70). The inexperienced raters reached an average intra-rater reliability of 0.57 (ICCs ranging from 0.52 to 0.62). The two expert raters attained ICC values of 0.70 and 0.74 respectively. CONCLUSION: Structured visual gait observation by use of a gait analysis form as described in this study was found to be moderately reliable. Clinical experience appears to increase the reliability of visual gait analysis.

What is more effective: a daily or a weekly formative test?

BACKGROUND: Exams in anatomy courses are traditionally summative. Formative testing induces retrieval practice, provides feedback and enhances learning results. We investigated the optimal frequency for retrieval practice during an anatomy course. METHOD: During a first-year course, students were offered four online daily quizzes a week that assessed thoracic anatomy. Once a week they received a quiz about abdominal anatomy. Students immediately received feedback afterwards. In the fourth course week, a survey about participation and satisfaction was taken. 424 students participated in the final summative exam. Trunk wall questions were used as a control. Relationship between participation and test results was investigated with a one-way ANOVA. RESULTS: More frequent participation in formative tests was correlated to higher scores in the summative exam with no difference between daily and weekly quizzes. This effect was found for thorax-abdomen and 'control' trunk wall questions. Participation in weekly quizzes was higher (p < 0.001). All survey responses showed a significant difference in favour of the weekly quiz (p < 0.001). DISCUSSION AND CONCLUSION: Participation in formative quizzes was correlated to summative exam scores. This correlation was not specific for the material tested, probably because of diligence. Student participation and preference were much higher in weekly quizzes.

Emphysema and pneumothorax after percutaneous tracheostomy: case reports and an anatomic study.

STUDY OBJECTIVE: Part 1: To describe cases of emphysema (subcutaneous and/or mediastinal) and pneumothorax after percutaneous dilational tracheostomy (PDT) in a series of 326 patients, and to review the existing literature describing the incidence and possible mechanisms. Part 2: To analyze the potential mechanisms for the development of emphysema and pneumothorax in human cadaver models. DESIGN: A retrospective analysis of PDTs, in combination with an anatomic study in human cadavers. MATERIALS AND METHODS: Part 1: All ICU patients who underwent PDT between 1997 and 2002 were enrolled in the study. We analyzed the cases of emphysema and pneumothorax. Similar cases were retrieved from the literature and underwent a systematic review. Part 2: The relevant anatomic structures were studied. We simulated the clinical situation after PDT in a human pathologic study in order to induce subcutaneous emphysema and pneumothorax. MEASUREMENTS AND RESULTS: Part 1: Five cases of subcutaneous emphysema (1.5%) and two cases of pneumothorax (0.6%) are described. In the literature search, we found 41 cases of emphysema (1.4%) and 25 cases of pneumothorax (0.8%) in a total of 3,012 patients. Part 2: Subcutaneous emphysema could easily be induced in a human cadaver model by inflating air in the pretracheal tissues and after posterior tracheal wall laceration. Air leakage was also possible through a fenestrated cannula via the space between the inner nonfenestrated cannula and outer cannula and then through the fenestration. CONCLUSIONS: We conclude that one mechanism for the development of emphysema is an imperfect positioning of the fenestrated cannula, whereby the fenestration is extraluminal. For this reason, fenestrated cannulas should not be used immediately after placement of a PDT. Posterior tracheal wall laceration is another mechanism responsible for emphysema after PDT. After perforation of the posterior tracheal wall, the pleural space can be reached easily. This may result in a pneumothorax.

The application of an external wrist extension force reduces electromyographic activity of wrist extensor muscles during gripping.

STUDY DESIGN: Experimental repeated-measures study. OBJECTIVE: To investigate the effect of different extension forces applied to the palm of the hand on electromyographic (EMG) activity of the wrist extensor muscles during hand gripping. BACKGROUND: Lateral epicondylitis is usually caused by repetitive wrist extension that leads to an overuse injury. The current theory is that the process of lateral epicondylitis begins with an overuse injury that leads to microtearing of the extensor carpi radialis brevis muscle and occasionally the extensor digitorum communis muscle. Use of an external wrist extension force might reduce muscle activity during gripping. METHODS: Muscle activity was measured using surface EMG while subjects gripped at an intensity of 10%, 20%, and 30% of the maximum voluntary contraction force without, and with, an applied external wrist extension force of 1%, 2%, and 3% of maximum voluntary contraction. RESULTS: Applying an extension force to the palm of the hand reduced EMG activity of the extensor muscles at the same strength generation during hand gripping. The muscles with the most significant reduction in EMG level, the extensor carpi radialis brevis and extensor digitorum communis, are those muscles that are most often involved with lateral epicondylitis. CONCLUSIONS: This study shows that an external extension force reduces EMG activity of the wrist extensor muscles during gripping in healthy volunteers. As the extension force increased, a greater reduction in muscle activity was noted.