A comparison of embalming fluids for use in surgical workshops

History and future of human cadaver preservation for surgical training: from formalin to saturated salt solution method

Traditionally, surgical training meant on-the-job training with live patients in an operating room. However, due to advancing surgical techniques, such as minimally invasive surgery, and increasing safety demands during procedures, human cadavers have been used for surgical training. When considering the use of human cadavers for surgical training, one of the most important factors is their preservation. In this review, we summarize four preservation methods: fresh-frozen cadaver, formalin, Thiel's, and saturated salt solution methods. Fresh-frozen cadaver is currently the model that is closest to reality, but it also presents myriad problems, including the requirement of freezers for storage, limited work time because of rapid putrefaction, and risk of infection. Formalin is still used ubiquitously due to its low cost and wide availability, but it is not ideal because formaldehyde has an adverse health effect and formalin-embalmed cadavers do not exhibit many of the qualities of living organs. Thiel's method results in soft and flexible cadavers with almost natural colors, and Thiel-embalmed cadavers have been appraised widely in various medical disciplines. However, Thiel's method is relatively expensive and technically complicated. In addition, Thiel-embalmed cadavers have a limited dissection time. The saturated salt solution method is simple, carries a low risk of infection, and is relatively low cost. Although more research is needed, this method seems to be sufficiently useful for surgical training and has noteworthy features that expand the capability of clinical training. The saturated salt solution method will contribute to a wider use of cadavers for surgical training.

Postoperative ulnar neuropathy is not necessarily iatrogenic: a prospective study on dynamic ulnar nerve dislocation at the elbow

BACKGROUND

Patients who undergo surgery may develop ulnar neuropathy. Although the mechanism of ulnar neuropathy is still not clear, ulnar neuropathies are common causes of successful lawsuits against surgeons. Recently, the concept developed that endogenous patient factors can lead to postoperative peripheral neuropathies. We hypothesize that dynamic ulnar nerve dislocation at the elbow (DUNDE) may be a predisposing factor for ulnar irritation (i.e., neuropathy) in normal subjects.

METHODS

In a prospective investigation, patients aged 20 years and older presenting in our emergency department were asked to participate. Three physicians examined both elbows of subjects included in our study for evidence of DUNDE (through clinical and sonographic examination) and for clinical symptoms related to ulnar neuropathy.

RESULTS

Dynamic ulnar nerve dislocation was observed in 29.3% of examined subjects. No significant difference in its occurrence was observed in relation to gender or dominant side. Physical examination with provocation tests demonstrated significantly more positive Tinel tests and spontaneous signs of neuropathy in patients with dynamic dislocating ulnar nerves (14.7 vs. 1.1%).

CONCLUSION

Dynamic ulnar nerve dislocation may be linked to ulnar nerve irritability (i.e., ulnar neuropathy) in normal subjects without history of trauma, surgical procedure, or anesthesia. Considering the high incidence of this variant in the general population, our study supports previous investigations suggesting that many postoperative ulnar nerve deficits are traceable to chronic patient conditions. Our study suggests that dynamic ulnar nerve dislocation is a predisposing factor in the development of ulnar neuropathy in the postoperative period.

NOTES

(1) neuropathy should be viewed as a broad definition as signs of nerve irritation/inflammation, and independently of the pathophysiology and etiology; (2) because no specific term exists in the international anatomic nomenclature (Nomina Anatomica) to designate this variant, several synonyms have been used in the literature, leading to confusion and misleading conclusions concerning its traumatic etiologies and their consequences: (a) recurrent or habitual ulnar nerve luxation (or subluxation); (b) recurrent or habitual ulnar nerve dislocation; (c) ulnar nerve instability; (d) laxity of the ulnar nerve; and (e) ulnar nerve hypermobility.

Human preservation techniques in anatomy: A 21st century medical education perspective

Anatomy is the cornerstone of education for healthcare professionals with the use of human material providing an excellent teaching tool in the modern curricula. The ability and quality of preservation of human remains has enabled such use. The introduction of formaldehyde as a preservative in 1893 was an important step in the history of preservation. With the European Union directive on the use of formaldehyde and its expected banning, anatomists are trying to find a more convenient and safe substitute. In this review, we compare the different techniques used based on the need for embalming, fixative used, period of preservation and the features of the embalmed specimen. The fact that embalming is used in different disciplines, multiple purposes and described in different languages has led to the development of ambiguous interchangeable terminology. Overall, there is a lack of information specifically classifying, listing and comparing different embalming techniques, and this may be due to the fact that no internationally recognized experimental standards are adhered to in this field. Anatomists strive to find an embalming technique that allows the preserved specimen to accurately resemble the living tissue, preserve the body for a long period of time and reduces health risk concerns related to working with cadavers. There is a need for embalming to shift to an independent modern day science with well-founded research at the heart of it. While this may take time and agreement across nations, we feel that this review adds to the literature to provide a variety of different methods that can be employed for human tissue preservation depending on the desired outcome.

Comparison of modified Thiel embalming and ethanol-glycerin fixation in an anatomy environment: Potentials and limitations of two complementary techniques

Thiel-fixed specimens have outstandingly lifelike visual and haptic properties. However, the original Thiel method is expensive and requires an elaborate setup. It is therefore of principal interest to modify the Thiel method in order to make it available to a broader user group. A modified Thiel embalming method will be described in detail and compared to ethanol-glycerin fixation with the help of illustrative examples. The visual properties, haptic properties, the usability for performing histological investigations, costs and potential health aspects will be considered. Tissues fixed with the modified Thiel technique gave results similar to the original method, providing more realistic visual and haptic properties than ethanol-glycerin embalming. However, Thiel fixation is significantly more expensive and requires more precautions to minimize potential health hazards than ethanol-glycerin-fixed tissues. In contrast to ethanol-glycerin-fixed specimens, the Thiel-fixed specimens are not suitable for histological investigations. Both modes of fixation are inappropriate for biomechanical testing. Modified Thiel embalming simplifies the availability of body donors with lifelike properties and has cost-saving advantages to the original technique. Thiel-embalmed body donors are ideally suited for clinical workshops but have restrictions for student dissection courses in facilities with limited storage space, air circulation or technical staff. Vice versa, ethanol-glycerin-fixed body donors are well suited for student dissection courses in such an environment but are limited in their use for clinical workshops. Modified Thiel embalming therefore ideally complements ethanol-glycerin fixation in order to provide customized solutions for clinical workshops and student dissection courses in a wide range of applications.

A pilot study comparing the use of Thiel- and formalin-embalmed cadavers in the teaching of human anatomy

Formalin had traditionally been used to preserve human material to teach gross anatomy. In 2008 the Centre for Anatomy and Human Identification (CAHID) at the University of Dundee embarked on the use of the Thiel method of embalming. The aim of this pilot study was to assess the difference between formalin-embalmed cadavers (FEC) and Thiel-embalmed cadavers (TEC) used for teaching and surgical training. Three different questionnaires were prepared for data collection from undergraduate and postgraduate students and clinical staff. All undergraduate and postgraduate students as well as clinical staff commented on the appearance of the TEC. There was no overall consensus concerning the use of TEC, some respondents preferred TEC for the entire dissection, some only for certain areas such as the musculoskeletal system. On a technical level TEC were considered less hazardous then FEC by one-third of participants with fewer than 10% regarding TEC as more irritating than FEC. Psychologically, 32.7% of undergraduate students expressed the view that TEC made them feel more uncomfortable compared with FEC because of their life-like appearance. However, 57.1% of undergraduate students encountered the same uncomfortable feelings when viewing both TEC and FEC. The use of Thiel-embalmed cadavers to teach anatomy has an added value, though further research is required over longer periods of time to identify its best usage.

Saturated salt solution method: a useful cadaver embalming for surgical skills training

This article evaluates the suitability of cadavers embalmed by the saturated salt solution (SSS) method for surgical skills training (SST). SST courses using cadavers have been performed to advance a surgeon's techniques without any risk to patients. One important factor for improving SST is the suitability of specimens, which depends on the embalming method. In addition, the infectious risk and cost involved in using cadavers are problems that need to be solved. Six cadavers were embalmed by 3 methods: formalin solution, Thiel solution (TS), and SSS methods. Bacterial and fungal culture tests and measurement of ranges of motion were conducted for each cadaver. Fourteen surgeons evaluated the 3 embalming methods and 9 SST instructors (7 trauma surgeons and 2 orthopedists) operated the cadavers by 21 procedures. In addition, ultrasonography, central venous catheterization, and incision with cauterization followed by autosuture stapling were performed in some cadavers. The SSS method had a sufficient antibiotic effect and produced cadavers with flexible joints and a high tissue quality suitable for SST. The surgeons evaluated the cadavers embalmed by the SSS method to be highly equal to those embalmed by the TS method. Ultrasound images were clear in the cadavers embalmed by both the methods. Central venous catheterization could be performed in a cadaver embalmed by the SSS method and then be affirmed by x-ray. Lungs and intestines could be incised with cauterization and autosuture stapling in the cadavers embalmed by TS and SSS methods. Cadavers embalmed by the SSS method are sufficiently useful for SST. This method is simple, carries a low infectious risk, and is relatively of low cost, enabling a wider use of cadavers for SST.

From "silent teachers" to models

In this essay Roos Eisma and Tracey Wilkinson describe how the Thiel technique has expanded the range of applications in which embalmed human cadavers can be used.

For decades, embalmed cadavers have played an important role in teaching anatomy to the scientists and doctors of the future. Most anatomy departments use a traditional formaldehyde-based embalming method, but formalin embalming makes the bodies very rigid, which limits their usefulness for procedures other than dissection. A more recent embalming method developed by W. Thiel has allowed these “silent teachers” to take on a further role in applied anatomy research and teaching: to act as models for surgical training and medical research.

Kinematics of primate midfoot flexibility

This study describes a unique assessment of primate intrinsic foot joint kinematics based upon bone pin rigid cluster tracking. It challenges the assumption that human evolution resulted in a reduction of midfoot flexibility, which has been identified in other primates as the "midtarsal break." Rigid cluster pins were inserted into the foot bones of human, chimpanzee, baboon, and macaque cadavers. The positions of these bone pins were monitored during a plantarflexion-dorsiflexion movement cycle. Analysis resolved flexion-extension movement patterns and the associated orientation of rotational axes for the talonavicular, calcaneocuboid, and lateral cubometatarsal joints. Results show that midfoot flexibility occurs primarily at the talonavicular and cubometatarsal joints. The rotational magnitudes are roughly similar between humans and chimps. There is also a similarity among evaluated primates in the observed rotations of the lateral cubometatarsal joint, but there was much greater rotation observed for the talonavicular joint, which may serve to differentiate monkeys from the hominines. It appears that the capability for a midtarsal break is present within the human foot. A consideration of the joint axes shows that the medial and lateral joints have opposing orientations, which has been associated with a rigid locking mechanism in the human foot. However, the potential for this same mechanism also appears in the chimpanzee foot. These findings demonstrate a functional similarity within the midfoot of the hominines. Therefore, the kinematic capabilities and restrictions for the skeletal linkages of the human foot may not be as unique as has been previously suggested.

The role of simulation in developing surgical skills

Surgical training has followed the master-apprentice model for centuries but is currently undergoing a paradigm shift. The traditional model is inefficient with no guarantee of case mix, quality, or quantity. There is a growing focus on competency-based medical education in response to restrictions on doctors' working hours and the traditional mantra of "see one, do one, teach one" is being increasingly questioned. The medical profession is subject to more scrutiny than ever before and is facing mounting financial, clinical, and political pressures. Simulation may be a means of addressing these challenges. It provides a way for trainees to practice technical tasks in a protected environment without putting patients at risk and helps to shorten the learning curve. The evidence for simulation-based training in orthopedic surgery using synthetic models, cadavers, and virtual reality simulators is constantly developing, though further work is needed to ensure the transfer of skills to the operating theatre.

Casting materials and their application in research and teaching

From a biological point of view, casting refers to filling of anatomical and/or pathological spaces with extraneous material that reproduces a three-dimensional replica of the space. Casting may be accompanied by additional procedures such as corrosion, in which the soft tissue is digested out, leaving a clean cast, or the material may be mixed with radiopaque substances to allow x-ray photography or micro computed topography (µCT) scanning. Alternatively, clearing of the surrounding soft tissue increases transparency and allows visualization of the casted cavities. Combination of casting with tissue fixation allows anatomical dissection and didactic surgical procedures on the tissue. Casting materials fall into three categories namely, aqueous substances (India ink, Prussian blue ink), pliable materials (gelatins, latex, and silicone rubber), or hard materials (methyl methacrylates, polyurethanes, polyesters, and epoxy resins). Casting has proved invaluable in both teaching and research and many phenomenal biological processes have been discovered through casting. The choice of a particular material depends inter alia on the targeted use and the intended subsequent investigative procedures, such as dissection, microscopy, or µCT. The casting material needs to be pliable where anatomical and surgical manipulations are intended, and capillary-passable for ultrastructural investigations.

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.

Composite bone models in orthopaedic surgery research and education

Composite bone models are increasingly used in orthopaedic biomechanics research and surgical education-applications that traditionally relied on cadavers. Cadaver bones are suboptimal for many reasons, including issues of cost, availability, preservation, and inconsistency between specimens. Further, cadaver samples disproportionately represent the elderly, whose bone quality may not be representative of the greater orthopaedic population. The current fourth-generation composite bone models provide an accurate reproduction of the biomechanical properties of human bone when placed under bending, axial, and torsional loads. The combination of glass fiber and epoxy resin components into a single phase has enabled manufacturing by injection molding. The high level of anatomic fidelity of the cadaver-based molds and negligible shrinkage properties of the epoxy resin results in a process that allows for excellent definition of anatomic detail in the cortical wall and optimized consistency of features between models. Recent biomechanical studies of composites have validated their use as a suitable substitute for cadaver specimens.

Function of the ligamentum teres during multi-planar movement of the hip joint

PURPOSE

The purpose of this study was to describe the orientation of the ligamentum teres and quantify the limb position when the ligamentum teres reached its endpoint during a simulated squat position in human cadavers.

METHODS

Dissection of eight (4 male; 4 female) cadavers resulted in the complete removal of all soft tissue attachment of the femur to the acetabulum, leaving only the ligamentum teres intact. The limb was then moved into combined flexion and abduction of the hip joint to simulate a deep squat position until a ligamentous endpoint of the ligamentum teres was achieved. The orientation of the ligamentum teres in relation to the femoral head was described and the position of the limb relative to the sagittal plane (flexion) and frontal plane (abduction) was quantified. The mean, standard deviation, 95 % confidence intervals, and standard error of the measurement were calculated for the observed angles.

RESULTS

Multi-planar movement of flexion and abduction moved the ligamentum teres into an anterior/inferior position relative to the femoral head and prevented the femoral head from anterior/inferior subluxation. The ligamentum teres endpoint was obtained at a combined average position of 100.6° (range 94°-112°; SD 5.5º; 95 % CI 96º-105º) and 20.0° (range 12°-32°; SD 7.0º; 95 % CI 14º-26º) flexion and abduction angle.

CONCLUSIONS

The ligamentum teres formed a "sling-like" structure to support the femoral head inferiorly as the hip joint was moved into a combined position of flexion and abduction that resembled a squat position. The results help to define a possible role of the ligamentum teres in hip joint stability and possible mechanisms of injury.

From formalin to Thiel embalming: What changes? One anatomy department's experiences

In 2009, the Centre for Anatomy and Human Identification started Thiel embalming on a small scale to assess (i) the suitability for our current teaching in which long-lasting dissection courses are key, (ii) the potential for new collaborations and activities, and (iii) the practical implications of changing our embalming method from formalin to Thiel. Twenty six Thiel-embalmed cadavers have been used for dissection by staff and students on a taught MSc course, as a model for clinical and surgical training, and increasingly as a model for evaluation of new medical devices and procedures. Our experiences with dissection were mostly positive especially for teaching the musculoskeletal system. Internal organs handle differently from formalin-fixed organs and dissection manuals need to be adjusted to reflect this. Durability of the cadavers was not an issue, though changes are seen over time due to gradual fluid loss. We have started new collaborations related to postgraduate anatomy teaching and advanced training in surgical and clinical skills. In general, feedback is very positive and demand for cadavers outstrips our current limited supply. Thiel-embalmed cadavers were found to provide a unique opportunity for evaluation of medical products especially in areas where no suitable alternative model is available, and without the complications associated with clinical testing. This has resulted in new collaborations and research projects. As a result Thiel-embalmed cadavers are used for longer and for more activities than formalin cadavers: this requires changes in our procedures and staff roles.

[Thiel's method of embalming and its usefulness in surgical assessments]

When we assess anatomical problems and the safety and effectiveness for performing a difficult surgical procedure or planning novel surgical approaches, preoperative human dissections are very helpful. However, embalming with the conventional formaldehyde method makes the soft tissue of the cadaver harder than that of a living body. Therefore, the cadaver embalmed with conventional formaldehyde is not appropriate for dissections when assess surgical approaches. Thiel's method is a novel embalming technique, first reported by W. Theil in 1992. This method can preserve color and softness of the cadaver without risk of infections. We have used cadavers embalmed with Thiel's method for preoperative assessments and have confirmed the usefulness of this method especially for the prevention of complications or in assessing surgical approaches. The cadaver embalmed with this method has several advantages over other embalming methods and it might be also useful for the developments of new surgical devices or evaluation of a surgeon's skill.

Modernization of an anatomy class: From conceptualization to implementation. A case for integrated multimodal-multidisciplinary teaching

It has become increasingly apparent that no single method for teaching anatomy is able to provide supremacy over another. In an effort to consolidate and enhance learning, a modernized anatomy curriculum was devised by attempting to take advantage of and maximize the benefits from different teaching methods. Both the more traditional approaches to anatomy teaching, as well as modern, innovative educational programs were embraced in a multimodal system implemented over a decade. In this effort, traditional teaching with lectures and dissection was supplemented with models, imaging, computer-assisted learning, problem-based learning through clinical cases, surface anatomy, clinical correlation lectures, peer teaching and team-based learning. Here, we review current thinking in medical education and present our transition from a passive, didactic, highly detailed anatomy course of the past, to a more interactive, as well as functionally and clinically relevant anatomy curriculum over the course of a decade.

A qualitative assessment of human cadavers embalmed by Thiel's method used in laparoscopic training for renal resection

Human cadaveric tissue is the fundamental substrate for basic anatomic and surgical skills training. A qualitative assessment of the use of human cadavers preserved by Thiel's method for a British Association of Urological Surgeons-approved, advanced laparoscopic renal resection skills training course is described in the present study. Four trainees and four experienced laparoscopic surgeons participated in the course. All participants completed a five-point Likert scale satisfaction questionnaire after their training sessions. The quality of cadaveric tissue and the training session were assessed with particular emphasis placed on the ease of patient positioning, the ease of trocar placement, the preservation of tissue planes, the ease of renal pedicle dissection, and the quality of tissue preservation. All of the participants highly rated the quality of the cadaveric tissue embalmed by Thiel's method (mean scores for quality on the five-point Likert scale were 4.5 and 4.3 by the trainees and experienced laparoscopic surgeons, respectively). All of the steps of laparoscopic renal resection were rated 4.0 or more on the Likert scale by both trainees and faculty members. The initial response rates for using a human cadaver embalmed by Thiel's method as a training tool for laparoscopic nephrectomy showed encouraging results. The performance of a laparoscopic nephrectomy on a human cadaver embalmed by Thiel's method bears close resemblance to real laparoscopic nephrectomy procedures, and thus demonstrates added advantages to the previously reported models.