Cadaver based education remains a powerful tool in the gross anatomy learning armamentarium. Visualizing, palpating and discovering the three dimensional relationships of human anatomy cannot be substituted by any other method. Therefore, it is paramount that the time spent around the cadaver is spent in the most effective and productive manner.
In this study we observed that a prosection based curriculum when compared to a dissection based curriculum was equally effective at establishing a core of gross anatomy knowledge that could be recalled after a considerable amount of time. Contrary to expectations the prosected group performed better in the diagram identification part of the assessment. Given the large amount of time spent on dissecting between tissue planes and discovering anatomical landmarks the dissections group was expected to succeed in this segment of the assessment.
Similar observations have also been shared by previous investigators who compared these two learning methods albeit under different circumstances. In a similar study Nonidum(1990) compared the long term retention power of these two methods by testing the student’s level of knowledge on the lower limb anatomy four years after it was thought. He concluded prosections were superior to dissections in achieving this objective. In a paper that reviewed the effect of cadaver based self dissection versus other teaching methods in anatomy (Winkelmann, 2007), of the 14 studies reviewed, 12 studies compared dissections to various prosection based teaching methods. Among these 12 studies, the dissected group performed better in 5 while in 4 the prosected group performed better, in 3 studies the performance between the two groups did not differ significantly. Although the results were indefinite and most studies were stunted with methodological weaknesses, the final advantage was tilted in favor of traditional dissection when taking into account the presumed bias towards the newly introduced prosection based courses. However, in our case the results were contrary to expectations as all authors expected the dissection group to fare better given the higher amount of time allocated in the dissection based curriculum. The above review also highlights common errors that have prevented definite conclusions being drawn from these studies. We feel it prudent to see how we fared against the common methodological deficiencies that have marred previous studies that have compared prosections and dissections.
A more comprehensive assessment would have included practical stations with “tag tests” that could give a better reflection of the student’s visual and spatial knowledge. The authors felt it unfair to subject the students to such an assessment at this point of their medical curriculum purely for research purposes. The questions on diagram identification were included in order to compensate for this deficit in the assessment tool used. The multiple choice questions were of the true/ false type where students were penalized for a wrong response with a negative mark. Although there is sufficient evidence to state that the, “best of five” type questions are a better assessment tool and while most of the assessments in the students curriculum had graduated to “best of five” type questions, we persisted with the true/false type questions as this was the question type that was used in their anatomy assessment during the first year in these student groups.
We used non randomized groups thus making this a quasi experimental study and therefore were unable to completely eliminate the effect of confounding variables between the two groups such as intelligence, visuospatial ability, time spent on self study, instruction time, the use of text books and other learning material. But we were able to control to a great extent variables such as, the number and quality of lectures, student: teacher ratios and pre knowledge which have been observed in other studies.
It is fair to presume that medical students represent a highly motivated and a selected group of high performers and they possess the ability to compensate to any intervention through their inherent abilities, thus we felt any comparison between learning methods in cadaver based learning should be done through a separate assessment preferably unannounced and more importantly away from any assessment which is part of the regular curriculum.
Finally, two very important observations need mentioning. An important advantage the new curriculum brought with it was a reduction in the amount of time spent in the dissection halls. It reduced the time spent in the dissection hall from a staggering 375 hours in the dissections group to 54 hours in the prosected group. (Table 1)
The reason for this difference in hours was due to the fact that the students were relieved of the laborious task of dissecting through fat and fascia to discover important anatomical structures and relations. This task was tackled by the anatomy demonstrators while specific times and targets were given to the students to cover each section using prosections. Thus, the time saved, could have very well been put to use in the self study of anatomy as well as of other basic sciences such as physiology and biochemistry. The additional time saved could also be used to include more curriculum content in fields such as molecular medicine and genetics which are basic sciences that are expanding daily. Thus, the results of this study could be attributed to the more structured nature of the prosections curriculum that let the students go about their learning in a more organized and time efficient manner. Kooloos et al (2010) demonstrated a similar advantage in long term recall when the anatomy education was strictly guided and station based.
The other important aspect to be considered in a dissection based curriculum is the proportion of students who actually engage in cadaver based self dissection. Increasing numbers in medical school admissions coupled with dwindling numbers in cadaveric donations equal to an unfavorable student to cadaver ratio. In this study the dissected group had 8–9 students allocated to one cadaver. This invariably meant that while two or three students took the task of dissecting the cadaver the remaining students engaged in learning from the prosected cadaver or self or group learning activities by the side of the dissection table. Thus, a majority of students actually completed their basic science training without engaging in self dissection. The fact that although the name implies such, a dissection based course may not be a uniform experience for all the students is an important factor that needs to be borne in mind by all investigators that try to compare dissections with other teaching methods (Winkelmann et al,2007). Similarly, the time devoted to dissections by each student has been shown to decline towards the end of each semester indicating that it is not a uniform experience for each individual either (Winkelmann et al,2007). It is thus we feel the structure of the dissection based curriculum and how it is applied in the given circumstance becomes the deciding factor on the student’s performance. A good balance can be achieved by combining student dissection with facilitated learning using prosections. As shown by Dinsmore et al (1999). This can be easily achieved by alternating the two learning methods between student groups on a roster basis, as have been successfully implemented in certain medical schools.
On the flip side of it one may argue that dissecting through tissue planes is a fundamental exercise in the deep learning process and a skill that will also be invaluable as surgeons. The other disadvantage in using prosections is the loss of superficial anatomical relations and surface landmarks. But this problem can be easily overcome by having prosections at different stages of dissections available for students. By allowing students to dissect it automatically allows students to use prosections as well thus allowing each student to cultivate their own study method.
Anatomy teaching is a far too important a subject to be decided by individual whims and fancies. Any change in how anatomy is taught has to be based on robust evidence and not mere personal reflection. And any change that is introduced should be followed up with continuous evaluation for its effectiveness and students performance. Learning from human cadavers is a complex experience that is difficult to measure objectively. As those who have come before us, we too suffer from confounding factors that make it difficult to arrive at concrete conclusions. Despite these shortcomings we feel that this study on its own adds to the thin body of evidence that exists to compare the two methods of cadaver based gross anatomy learning.