[Surgical procedures in mouth, jaw and facial surgery in Thiel embalmed body donors]

Vertical root fracture detection with cone-beam computed tomography in Biodentine™ filled teeth

PURPOSE

This study aimed to evaluate the accuracy of detecting vertical root fractures in Biodentine™-filled teeth using the Promax 3Dmax cone-beam computed tomography (CBCT) unit compared to periapical radiographs. It tested hypotheses regarding CBCT's diagnostic superiority in non-root-filled and Biodentine™-root-filled maxillary central incisors and assessed the impact of smaller field of view and lower intensity settings on detection accuracy.

MATERIALS AND METHODS

Extracted maxillary incisors were divided into groups based on fracture status and root filling material, then placed in a Thiel-embalmed skull to simulate clinical conditions. The teeth were imaged using periapical radiographs and the CBCT unit under different settings. Fracture thickness was measured with microcomputed tomography for accuracy benchmarking. Multiple observers assessed the images, and statistical analyses were conducted to evaluate diagnostic performance.

RESULTS

Intra-rater reliabilities of consensus scores ranged from good to very good. Specificities were generally higher than sensitivities across all imaging modalities, but sensitivities remained constantly low. None of the Area Under the Curve scores exceeded 0.6, indicating poor overall accuracy for all imaging modalities. Paired comparisons of the area differences under Receiver Operator Characteristic curves revealed no significant differences between the CBCT and periapical radiograph techniques for detecting vertical root fractures in either Biodentine™-filled or non-root-filled teeth.

CONCLUSIONS

There was no significant accuracy improvement of the current CBCT device (Promax 3Dmax, Planmeca, Finland) over periapical radiographs in detecting small vertical root fractures in both non-root-filled and Biodentine™-root-filled maxillary central incisors. A smaller field of view with lower intensity did not enhance detection accuracy. These results highlight the challenges in accurately detecting small VRFs, emphasizing the need for further research and technological advancements in this domain.

Evaluation of bone contact area and intercondylar distance changes in orthognathic surgery - a comparison between BSSO and HSSO technique depending on mandibular displacement extent

OBJECTIVES

The present study aims to assess the impact of bilateral and high oblique sagittal split osteotomy (BSSO/HSSO), as well as displacement distances and directions on the expected and achievable bone contact area (BCA) and changes in the intercondylar distance (ICD). The primary question addressed is whether mandibular splitting through BSSO results in a greater BCA and/or ICD when compared to splitting through HSSO.

MATERIALS AND METHODS

Totally 80 mandibular displacements were performed on 20 fresh cadavers, for each subject, four splints were produces to facilitate mandibular advancement as well as setbacks of 4 and 8 mm. Pre- and postoperative CBCT scans were performed to plan the surgical procedures and to analyze the expected and achieved BCA and ICD.

RESULTS

Regarding the maximum mandibular displacement, the expected BCA for HSSO/BSSO were 352.58 ± 96.55mm2 and 1164.00 ± 295.50mm2, respectively, after advancement and 349.11 ± 98.42mm2 and 1344.70 ± 287.23mm2, respectively, after setback. The achieved BCA for HSSO/BSSO were 229.37 ± 75.90mm2 and 391.38 ± 189.01mm2, respectively, after advancement and 278.03 ± 97.65mm2 and 413.52 ± 169.52 mm2, respectively after setback. The expected ICD for HSSO/BSSO were 4.51 ± 0.73 mm and 3.25 ± 1.17 mm after advancement and - 5.76 ± 1.07 mm and - 4.28 ± 1.58 mm after setback. The achieved ICD for HSSO/BSSO were 2.07 ± 2.9 mm and 1.7 ± 0.60 mm after advancement and - 2.57 ± 2.78 mm and - 1.28 ± 0.84 mm after setback. Significant differences between the BCA after HSSO and BSSO were at each displacement (p < 0.001), except for the achieved BCA after 8-mm setback and advancement (p ≥ 0.266). No significant differences were observed regarding ICD, except for the expected ICD after 8-mm setback and advancement (p ≤ 0.037).

CONCLUSIONS

Compared to the virtual planning, the predictability regarding BCA and ICD was limited. ICD showed smaller clinical changes, BCA decreased significantly in the BSSO group.

CLINICAL RELEVANCE

BCA and ICD might have been less important in choosing the suitable split technique. in orthognathic surgery.

Thiel embalming in neonates: methodology and benefits in medical training

Current teaching and training methods for surgical techniques in the pediatric population involve artificial models (manikins), animals or adult human cadavers embalmed using various techniques. We found no references in the literature concerning the use of the Thiel method in the pediatric population. The aim of this study, therefore, was to assess the viability of using pediatric human cadavers embalmed through Thiel’s technique and to compare them with standard pediatric manikins. After donation of a 24-week stillborn, the Thiel technique was carried out for fixation following the usual protocol. A video recording with eye-tracking glasses was used to perform an examination, and techniques. The same procedures were conducted on a pediatric manikin. Medical students, medical residents and physicians were asked to respond to questions in an online survey after being shown the video. A total of 92 responses were obtained. The Thiel-embalmed stillborn was assessed as superior to the manikin in all items. Our study confirmed that this technique is feasible even with extremely small donors. The value of this form of preservation for medical training is not widely known though it is receiving increasing interest. Our results show that Thiel fixation in pediatrics is clearly more highly valued than a manikin and offers great potential. This innovative application of the Thiel method in the pediatric population is technically possible. It poses no additional difficulties and is very positively assessed for undergraduate and postgraduate teaching.

Accuracy of fully guided orthodontic mini-implant placement evaluated by cone-beam computed tomography: a study involving human cadaver heads

OBJECTIVES

The aim of this study was to evaluate the accuracy of fully guided orthodontic mini-implant (OMI) placements supported by tooth- (TBGs) or gingiva-borne silicone guides (GBGs) based on virtually superimposed lateral cephalograms on virtual plaster models.

MATERIALS AND METHODS

Lateral cephalograms and corresponding plaster models were virtually superimposed for the planning of OMI positions; fully guided TBGs and GBGs were fabricated (each, n = 10). A total of 40 OMIs were inserted in a paramedian position into the palate of 20 human cadavers. Postoperative cone-beam computer tomographies (CBCTs) were carried out, and an accuracy evaluation was performed by comparing preoperative planning models and postoperative CBCTs. Deviations of the axis, tip, centre of the shoulder and vertical position of each of the implants were evaluated. Furthermore, the transfer accuracy measured by postoperative CBCT scans were compared with the accuracy determined using an intraoral scanner.

RESULTS

A significant deviation between TBGs (2.81° SD 2.69) and GBGs (6.22° SD 4.26) regarding implant angulation was evaluated (p = 0.005). Implant tip and implant shoulder deviations revealed no statistical differences between the guides. Accuracy values of oral scans regarding vertical deviations were significantly more inaccurate when compared with CBCTs (p < 0.001).

CONCLUSIONS

The accuracy of an OMI position can be significantly increased by using a guide extension over the teeth. Vertical implant positions presented the lowest deviations. Postoperative oral scans and CBCTs represent diverging accuracy measurements when compared with virtual planning.

CLINICAL RELEVANCE

Users must keep in mind that despite virtual planning deviations, inaccuracies of a few millimetres may occur.

Cadaveric Models for Renal Transplant Surgery Education: a Comprehensive Review

PURPOSE OF REVIEW

To evaluate the utility of cadaveric models for kidney transplant (KT) surgery training.

RECENT FINDINGS

Medline® and PubMed® databases were searched for English and Spanish language articles published describing different learning models used in KT formation. We evaluated the use of cadavers preserved by Thiel's embalming method (TEM) as KT simulation models. Students were divided in groups of 4 people: four trainees mentored by an expert in KT surgery. Among the trainees were surgical residents and low-experience surgeons. A total of 39 TEM preserved bodies were used, of which 75 viable renal grafts were obtained. In each cadaver, two complete transplantation processes were performed, each consisting of en bloc nephrectomy with the trunk of aorta and inferior vena cava, bench surgery and perfusion with saline of the organ, and KT surgery. As with any surgical procedure, learning KT surgery is a stepwise process that requires years of dedication. The models available for the surgical simulation of KT surgery allow to practice and achieve dexterity in performing the procedure in a safe and reproducible way. Training on TEM-preserved corpses offers a highly realistic model for the surgical simulation of KT surgery.

The intercarotid or alar fascia, other cervical fascias, and their adjacent spaces - a plea for clarification of cervical fascia and spaces terminology

Due to varying descriptions and terminology of fascias of the neck, medical advice relying on this basic knowledge is insufficient. Our goal was to provide a precise anatomical description of cervical fascias and spaces with special focus on the intercarotid fascia, or the alar fascia. One hundred bodies donated to science embalmed with Thiel's method were investigated, cervical fascias were dissected layer by layer, and the results were documented by photography, with a focus on the intercarotid fascia. In addition, we performed a review of recent literature concerning cervical surgical interventions, radiological diagnostic pathways, and basic anatomical works focusing on core information on anatomical relations of cervical fascias and spaces. In another 10 bodies donated to science, the spaces of the neck were injected with coloured latex under ultrasound guidance, dissected, and documented by photography. The intercarotid fascia was a constantly developed connective tissue interconnecting the carotid sheath of both sides. In 52 of 100 specimens (52%) it crossed to the opposite side without any fusion to the ventrally situated visceral fascia. Fusion with the visceral fascia was found in 48%, either at the lateral border of the pharynx or on its dorsal side. The results of our dissections strengthen the precise description of the cervical fascias provided by Grodinsky and Holyoke in 1938. Spaces can be confirmed as described by Hafferl in 1969. The international anatomical and ENT societies should codify a unified anatomical terminology of the cervical spaces and fascias to prevent varying interpretations in the future.

The utility and benefit of a newly established postgraduate training course in surgical exposures for orthopedic and trauma surgery

INTRODUCTION

Limited data exist on specialty surgical cadaver courses for graduates, their skill gain, and whether the course contents are transferable to other surgical disciplines.

AIM

We present the details on the establishment of a specialist trauma and orthopedics approach course, and explore educational and career outcomes from this program.

METHODS

A 3-day surgical approach course was developed, including a dissection program utilizing Thiel embalmed cadavers. The course was accredited with the local orthopedics association. Participants were assessed by survey on acquired surgical knowledge, skill, decision-making, confidence, and on self-development and effect on career.

RESULTS

Thirty-one participants successfully completed the courses over 3 years. Increases in surgical skill, knowledge, surgical decision-making and confidence were reported. Skills and confidence also positively impacted on other surgical disciplines. Courses rated highly for learning outcomes; comments highlighted usefulness, applicability, and practicing opportunities, while also impacting positively on career opportunities.

CONCLUSION

Surgical courses have shown being useful for the acquisition of skills, knowledge, confidence and decision-making, with a positive impact on confidence and decision-making. This information is relevant to future participants, benefactors, surgical programs, and tertiary institutions who want to establish specialist surgical courses.

Kinematic and Kinetic Comparison of Fresh Frozen and Thiel-Embalmed Human Feet for Suitability for Biomechanical Educational and Research Settings

BACKGROUND

In vitro biomechanical testing of the human foot often involves the use of fresh frozen cadaveric specimens to investigate interventions that would be detrimental to human subjects. The Thiel method is an alternative embalming technique that maintains soft-tissue consistency similar to that of living tissue. However, its suitability for biomechanical testing is unknown. Thus, the aim of this study was to determine whether Thiel-embalmed foot specimens exhibit kinematic and kinetic biomechanical properties similar to those of fresh frozen specimens.

METHODS

An observational study design was conducted at a university biomechanics laboratory. Three cadavers had both limbs amputated, with one being fresh frozen and the other preserved by Thiel's embalming. Each foot was tested while undergoing plantarflexion and dorsiflexion in three states: unloaded and under loads of 10 and 20 kg. Their segment kinematics and foot pressure mapping were assessed simultaneously.

RESULTS

No statistically significant differences were detected between fresh frozen and Thiel-embalmed sample pairs regarding kinematics and kinetics.

CONCLUSIONS

These findings highlight similar kinematic and kinetic properties between fresh frozen and Thiel-embalmed foot specimens, thus possibly enabling these specimens to be interchanged due to the latter specimens' advantage of delayed decomposition. This can open innovative opportunities for the use of these specimens in applications related to the investigation of dynamic foot function in research and education.

A Multispecialty Evaluation of Thiel Cadavers for Surgical Training

Background

Changes in UK legislation allow for surgical procedures to be performed on cadavers. The aim of this study was to assess Thiel cadavers as high-fidelity simulators and to examine their suitability for surgical training.

Methods

Surgeons from various specialties were invited to attend a 1 day dissection workshop using Thiel cadavers. The surgeons completed a baseline questionnaire on cadaveric simulation. At the end of the workshop, they completed a similar questionnaire based on their experience with Thiel cadavers. Comparing the answers in the pre- and post-workshop questionnaires assessed whether using Thiel cadavers had changed the surgeons’ opinions of cadaveric simulation.

Results

According to the 27 participants, simulation is important for surgical training and a full-procedure model is beneficial for all levels of training. Currently, there is dissatisfaction with existing models and a need for high-fidelity alternatives. After the workshop, surgeons concluded that Thiel cadavers are suitable for surgical simulation (p = 0.015). Thiel were found to be realistic (p < 0.001) to have reduced odour (p = 0.002) and be more cost-effective (p = 0.003). Ethical constraints were considered to be small.

Conclusion

Thiel cadavers are suitable for training in most surgical specialties.

Assessment of Thiel-Embalmed Cadavers as a Teaching Tool for Oral Anatomy and Local Anesthesia

The aim of this study was to determine whether Thiel-embalmed cadavers would provide a useful anatomy teaching tool for topics that cannot be approached using formalin-fixed cadavers such as oral cavity examination and maxillary anesthesia. The suitability of Thiel-embalmed bodies for performing oral examinations was assessed by asking first-year dental and dental hygiene students at a dental school in Ireland to identify oral structures on a classmate and on a Thiel-embalmed body. The study was conducted in 2016. The ease of location was compared in the two settings, and their quality was assessed on the cadavers. The suitability of Thiel-embalmed cadavers to teach maxillary anesthesia was assessed by students' performing mock injections at five adjacent sites daily for five consecutive days, followed by inspection of the gingival surface by experienced anatomists and dentists. Data were obtained from 57 students, but only the 54 forms that were fully completed were analyzed, for an overall response rate of 85.7%. The results showed that most oral structures were more difficult to locate on cadavers. The texture and appearance of features in the cadavers were rated at a midpoint between realistic and unrealistic. The relative inexperience of the participants, the accumulation of fixative in the oral cavity, and discoloration were mentioned as potential confounding factors. Visual analysis of images obtained following repeated injections revealed no deterioration of the tissue. Importantly, the puncture marks appeared to reduce over time, suggesting that the gingival tissue maintains some elasticity following Thiel fixation. These findings suggest that Thiel-embalmed cadavers may be a useful tool to provide students more time to localize and study aspects of the oral cavity. Likewise, the recoiling capacity of gingival tissue suggests that Thiel-embalmed cadavers may provide an ideal tool for teaching injection technique of local anesthetics.

Osteosynthesis using cannulated headless Herbert screws in mandibular angle fracture treatment: A new approach?

INTRODUCTION

Fractures of the mandibular angle are a common type of facial skull fracture. Although operative treatment includes a wide range of fixation techniques, a definite gold standard method has yet to be established. Headless, cannulated Herbert screws, often used in many forms of minimally invasive trauma surgery, provide functional and stable fracture fixation.

MATERIALS AND METHODS

In a prospective, double-randomised, controlled, parallel-group - designed, in vitro trial, the biomechanical behaviour of the Herbert bone screw system was compared to that of a conventional locking plate system in 40 mandibular angle fractures of human mandible cadaver phantoms.

RESULTS

The mean stress values were 250 (±68.0) N in the plate subgroup and 200 (±61.0) N in the screw subgroup. The respective mean strain values were 7.90 (±2.7) mm and 6.90 (±2.2) mm, and the respective mean stiffness were values 1.10 (±0.61) N/m and 0.78 (±0.40) N/m. The differences in the results obtained using the two treatments were not significant (p = 0.55).

CONCLUSIONS

The biomechanical behaviour of the two fixation systems within the tested loads did not significantly differ with respect to postoperative parameters clinically relevant in osteosynthesis. Both systems met the mandibular angle assessment criterion, which is considered to be sufficient for clinical use. The results indicate the potential clinical utility of these two systems, and recommend further testing.

Evaluation of ultrasonic and conventional surgical techniques for genioplasty combined with two different osteosynthesis plates: a cadaveric study

OBJECTIVES

The aim of this study was to compare genioplasties performed using traditional saw or piezosurgery combined with different osteosynthesis plates.

MATERIALS AND METHODS

Thirty-two genioplasties were first performed on fresh human cadavers using a saw or piezosurgery, followed by chin osteosynthesis with bending or pre-shaped plates. The time required for osteotomy and plate fixation was measured, and the suprahyoid pedicle was inspected.

RESULTS

The mean time required was 204 s (SD 43) with the saw and 52 s (SD 67) with piezosurgery. Osteosynthesis fixation time was 100 s (SD 31) for pre-shaped plates and 124 s (SD 24) for individual plates. Statistical differences were found between both osteotomy techniques (p < 0.001) and osteosynthesis plates (p = 0.025). Injuries of the suprahyoid muscle pedicle were found in 10/16 saw cases and 3/16 piezosurgery cases (p = 0.012).

CONCLUSIONS

Although piezosurgery is more time consuming compared with saw osteotomy, it is still adequate in time and allows a reduction of the suprahyoid pedicle injuries. Therefore, piezosurgery seems to be a viable alternative technique for genioplasty. From a clinical point of view, the time difference for osteosynthesis fixation has no significance.

CLINICAL RELEVANCE

The time taken for ultrasonic surgery is suitable for clinical use and leads additional to less damage to the suprahyoid pedicle.

An experimental model for training in renal transplantation surgery with human cadavers preserved using W. Thiel's embalming technique

OBJECTIVE

To describe a novel cadaver-based model for practicing renal transplant (RT) surgery.

DESIGN

A simulating model using cadavers preserved by Thiel's method is developed to teach surgical anatomy and operative skills in RT surgery. Participants were asked to complete a voluntary, anonymous survey evaluating perceptions of the model and comparing cadaver sessions to other types of learning (rating questions from 0-10).

SETTING

Large university teaching hospital.

PARTICIPANTS

A total of 28 residents, junior transplant surgeons, and faculty members were participants in the cadaver simulation.

RESULTS

Overall, 9 cadavers were used with 17 grafts transplanted. Kidney procurement in human cadavers preserved using Thiel's embalming technique was performed following the conventional protocol; en bloc nephrectomy with the trunk of aorta and inferior vena cava. Bench surgery was performed, perfusing artery with saline and checking vascular permeability. Once suitability is established, RT was performed as is done in clinical practice. This embalming method enables tissue dissection that is comparable to the living body and provides suitable conditions for realistic RT simulation; handling human tissues and vessels in the same surgical field as the clinical scenario. This experimental model approximates to in vivo RT, providing a realistic and interesting learning to inexperienced surgeons. Overall, participants held a positive view of the cadaver sessions, believed them to be useful in their daily practice, and felt that the proposed model was similar to the clinical setting. Trainees believed that these practices improved skills and confidence in performing an RT.

CONCLUSIONS

The proposed method of kidney procurement and RT in human cadavers preserved by Thiel's embalming technique is a promising, realistic, and reproducible method of practicing RT surgery.

Human body preservation - old and new techniques

This review deals with the art of (anatomical) embalming. The first part contains a brief historical review of the history of embalming, starting with ancient cultures such as the Egyptians and the lesser known Chinchorro culture, then going down the centuries and describing the anatomical techniques developed over the last two centuries. The second part deals in detail with the chemicals used for embalming purposes. The third part deals with several approaches to evaluating embalming methods, their suitability for biomechanical testing, antimicrobial properties, histological appearance, and usability. The fourth and final part analyze the European Biocidal Products Directive (98/8/EC) in the light of embalming.

Thiel embalming technique: a valuable method for teaching oral surgery and implantology

BACKGROUND

Because of its high requirements on surgical experience and the need of complete understanding of the anatomy, oral surgery and especially implantology belong to the most demanding procedures in dentistry. Therefore, hands-on courses for oral surgery and implantology are considered a prerequisite to prepare for clinical practice. To achieve teaching conditions as realistic as possible, we used a novel human cadaver embalming method enabling tissue dissection comparable with the living body.

METHODS

Thirty cadavers which were offered by the Institute of Anatomy for the purpose of running oral surgery and implantology courses were embalmed in the technique described by Thiel. On each cadaver, dissection of soft and hard tissue and implantological procedures were performed according to a structured protocol by each course participant. The conservation of fine anatomical structures and the suitability of the embalmed tissue for dissecting, drilling, and suturing were observed and photographically documented.

RESULTS

By means of the Thiel embalming technique, oral surgery and implantological procedures could be performed under realistic conditions similar to the living body. Due to the conservation procedure, preparations could be carried out without any time limit, always maintaining the same high quality of the tissue. The maxillary sinus membrane, mucosa, bone, and nerves could be exposed and allowed dissecting, drilling, and suturing even after weeks like fresh specimens.

CONCLUSION

The Thiel embalming method is a unique technique which is ideally suited to practice and teach oral surgery and implantology on human material.

Trainingsmethode für Regionalanästhesisten

INTRODUCTION

Optimized training facilities are the key to efficient teaching of regional anesthesia.

MATERIAL AND METHODS

A combination of Thiel's embalming method, flap dissection and pulse simulation was offered to participants in several workshops on regional anesthesia. Tutors, experienced anesthetists and anatomists, evaluated the workshop and compared Thiel's method to classic formaldehyde conservation. Additionally both embalming methods were assessed with regard to the mechanical properties according to the requirements of regional anesthesia.

RESULTS

The evaluation showed high acceptance of the method offered in the workshop. In a comparison of fixation methods Thiel's method was generally preferred as it presented more similar conditions to living patients and almost ideal conditions for regional anesthesia.

CONCLUSION

The presented method is an optimized, strongly accepted teaching and training tool for teaching regional anesthesia.

Perivascular axillary brachial plexus block and patient positioning: the influence of a lateral, head-down position

The aim of this study was to examine the effect of a 20 degrees Trendelenburg position on the blockade of nerves that exit the brachial plexus proximally in patients undergoing single-injection axillary brachial plexus block. After a pilot study of eight cadavers suggested that a head-down and lateral position would encourage the proximal spread of local anaesthetic, 72 patients undergoing elective surgery were divided into two equal groups: a Supine group and a Modified Position group (lateral position, 20 degrees head-down tilt). Patients were left in the allocated position for 30 min after an axillary block had been performed with alkalinised mepivacaine 1% 49.5 ml. Sensory and motor blockade evaluation showed that there was a significantly higher proportion of axillary nerve (76% vs. 0%, p < 0.001), thoracodorsal nerve (86% vs. 0%, p < 0.001) and subscapular nerve (89% vs. 0%, p < 0.001) blockade in the Modified Position group. Sensory block of the radial nerve was also improved by the modified position (100% vs. 86%, p < 0.05).