Medical Education 1990, 24, 389-395

Learning human anatomy: by dissection or from prosections?

J. 0. NNODIM

Department ofAnatomy, College of Medical Sciences, University of Benin

Summary. Two matched groups of first-year preclinical medical students studied the gross anatomy of the lower limb by different methods. One group dissected in the traditional manner (as in the existing curriculum) while the other worked according to an experimental pro- gramme which excluded dissection by students. Preparatory study guides were supplied to the experimental group and each of their practical classes on soft tissues began with a priming session at which the structures to be encountered were introduced. The instructor then demon- strated these structures to the group on a prosec- ted wet specimen and bones. Thereafter, the students were allowed to handle and discuss the specimens without staff supervision. At the end of the programme, both groups submitted to a 300-item two-choice paper and a practical test. A debriefing questionnaire was also completed by the experimental group.

In both tests, the experimental group per- formed better than the traditional group and the difference was statistically significant ( P < 0.05) in the theory paper. Further, the experimental programme was completed in about 74% of the time taken by the traditional programme. All the participants commented positively on the experimental programme and expressed the opinion that it had helped them understand the lower limb better than dissection had done for the upper limb.

These results suggest that working from pro- sections is a very effective way oflearning human

Correspondence: Dr Joseph 0. Nnodim, Depart- ment of Anatomy, College of Medical Sciences, Univ- ersity of Benin, PMB 1154, Benin City, Nigeria.

gross anatomy. Such a programme is worthy of consideration by departments having to contend with unfavourable student:cadaver ratios and curtailed teaching time.

Key words: anatomy/*educ; *dissection; teaching/*methods; *education, medical, under- graduate; leg/anat; Nigeria

Introduction

Traditionally, a major part of practical workin gross anatomy consists of cadaver dissection by students. This method of learning human gross anatomy is time-honoured, dating back to the Renaissance period, and alternative approaches did not come under serious consideration until the middle of the present century. At that time, the number of students matriculating into medical school in Europe and North America began to rise very rapidly, a trend which was manifest in African and other nascent countries around the world about 2 decades later.

In many of the latter countries, cultural prac- tices severely limited the acquisition of cadavera and the ratio of students to bodies became increasingly unfavourable with time. The result was that only a few students would dissect, while the majority looked on passively (Sinclair 1965, 1972) and quite conceivably, a large number successfully completed their preclinical training without actually dissecting.

For many institutions, the decline in student: cadaver ratios may well be irreversible and thus compels a rethinking of the scheme for practical work in human gross anatomy. The present study evaluates an experimental programme which excludes dissection by students.

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Table 1. Features of the experimental programme

(1) Advance organizers (2) Primer (for classes on soft tissues) (3) Demonstration by lecturer (4) Directed reading 6) Grour, review

Subjects and methods

The participants, volunteer first-year preclinical students, were initially sorted into 10 levels on the basis of identical scores at the Joint Matricu- lation Examination UME). In Nigeria, perform- ance at the JME is the main objective criterion for admission into the first (premedical) year of university., It was used in the present study as an index of general academic ability.

At each of the 10 JME score levels, the volunteers were divided into two halves: one was assigned to the experimental group and the other to the control or traditional group. Both groups, each consisting of 21 students, were thus con- sidered to be evenly matched.

The choice of the lower limb, the second region ofthe body studied in the curriculum, was dictated by the necessity for the experimental group to have had some experience with dissec- tion in order to be able to make meaningful comparisons between it and the experimental programme.

Experimental programme

The main features of the experimental pro- gramme are summarized in Table 1. The study of the lower limb was divided into 14 headings, half ofthem on soft tissues and the other halfon bones

and joints (Table 2) . The headings were taken in proximodistal order, one per practical class. For each heading, an advance organizer was prepared and supplied to the participants at least one week ahead of its practical class. These advance organizers were hand-outs consisting of descrip- tions in outline form of structures, important spatial relationships and relevant applied information at the desired level of detail. The students were advised to use them as preparatory study guides.

The practical classes on soft tissues began with a priming session in a tutorial room, lasting an average of 25 minutes, at which the work ahead was defined. The students were then conducted in two shifts of 10 and 11 in succession to the dissecting room and the material was demon- strated to them on a prosected specimen by the investigator. Questions were entertained and thereafter the students retired to reading rooms to revise the text on what had just been seen, while their colleagues on the other shift had their demonstration. Finally, each shift reconvened in the dissecting room and re-enacted the demon- stration, members taking turns to handle the specimen and lead the discussion. The investiga- tor attended the first group review, in order to explain its essence and proper conduct. Subse- quently, the students worked without staff supervision in that part of the programme. Classes on bones and joints were held entirely in the tutorial room, using separate bones and articulated skeletons.

A time log was kept by one ofthe students and, at the end of the programme, a debriefing questionnaire (see Appendix) consisting of both forced-choice and open-ended items, was administered.

Table 2. Lower limb subject areas

Bones and joints Soft tissues

Innominate bone Femur, tibia, fibula, patella Hip joint Knee joint Skeleton of the foot Pedal arches Ankle and other joints of foot

Thigh 1: Extensor compartment Thigh 2: Adductor compartment Gluteal region Thigh 3: Posterior compartment Crural region Foot Joint ligaments

Learning human anatomy from prosections 39 1

Table 3. Duration of programmes (in hours)

Experimental Primer 3 Demonstration 11

Group review 14

Total 40

Directed reading 12

- -

Traditional Eighteen 3-hour sessions -

Total 54 -

Traditional programme

In the control group, one member read aloud from a dissecting manual (Zuckerman 1981) while another dissected and demonstrated to the rest of the group. Staff involvement took the form of visits during which questions were asked and the exposed structures discussed. The inves- tigator spent 15 - 20 minutes with the traditional group towards the end of each %hour dissecting session. Other teachers came at other times and students were at liberty to summon an instructor for help at all times.

Both groups (traditional and experimental) listened to the same formal lectures and watched the same films.

Assessment and analysis

O n completing the programme, the experi- mental and control groups submitted to two tests: a theory paper of 60 multiple true/falsr questions (Harden 1979) and a practical 30- station ‘steeplechase’. Forty-two of the questions

Table 4. Assessment results

in the two-choice paper were drawn from a bank of items shown by previous’analysis to possess satisfactory discrimination and facility as defined by Lipton & Huxham (1970). The rest were of recent construction. Scoring was according to the Glasgow scheme, with ‘fair’ countermarking of wrong responses (Harden et a l . 1969). However, in computing the knowledge level exhibited (Nnodim 1988a), uncorrected .scores were utilized. Differences were evaluated by Students’s t-test for statistical significance.

The experimental and control groups were also compared, JME score level by JME score level. At score levels with more than one member, a simple mean of their performance at assessment was taken.

Results

The times spent on both programmes are set out in Table 3. They show a 14-hour gain by the experimental programme on the traditional. Only just over half of the time taken by the experimental programme (25 hours) was actually spent in the dissecting room.

Table 4 depicts the test scores recorded in the theory and practical assessments. The experi- mental group outperformed the traditional group in both tests and, in the case of the theory paper, the difference was significant at the 5% level.

Comparing the scores gained by participants according to JME score level (see Subjects and methods), it was observed that the experimental group did better at more score levels in both tests than the traditional group (Table 5). However, neither test segregated the groups Getter than the other, as revealed by x2 analysis.

Test score

Group Theory” Practical***

Experimental Traditional

48.95 i 10.25 38.20 i 10.72

70.64 ? 7.91 65.61 k 11.59

1. . given as mean k standard deviation Experimental vs traditional: * * (0.05 > P > 0.02)

* * * (0.3 > P > 0.2)

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Table 5. Two-by-two contingency table of performance by Joint Matriculation Examination (JME) score level

Number ofJME score levels

Test Experimental group better

Traditional group better

Theory 6 4 Practical 7 3

xz = 0.218 (P > 0.05).

The knowledge levels (Pa) exhibited by both groups in the two-choice paper were superior to guesswork (Pa > 0) but that of the experimental group was higher, although the difference was non-significant (Table 6).

An analysis of the responses of the experimen- tal group to the debriefing questionnaire is presented in Table 7.

Discussion

Two schemes of practical work in gross anatomy, viz. dissection by students and the study of prosections, were compared in the present investigation. A similar experiment by Sinclair (1965) was spread over several years, using several cohorts. The benefit of a long time-frame was undermined, however, by the lack of control over such variables as intercurrent developments in the other preclinical subject areas. According to Sinclair (.1965), curricular changes in physiology and biochemistry took place during the period ofthe study and probably impinged on the anatomy programme in such a way as to render the overall result equivocal.

Further, studies on a very large scale may not be possible under most circumstances because the experimental programme often has to be intercalated into a pre-existing scheme of work. Not infrequently, such interventions tend to be regarded officially as disruptive, an attitude to which their design has to be reconciled.

The superior performance of the experimental group (Tables 4 - 6) can be regarded as evidence that their learning method was very highly effective. Subjectively, the experimental group gave a similar verdict (Table 7), in their com- parison of work on the upper limb by dissection

and on the prosected lower limb. According to the participants, it was the structure of the experimental programme that made the difference: it compelled them to use their time much better than they did under the traditional method. In planning the experimental pro- gramme, cognizance was taken of the revelation by an earlier survey (Nnodim 1988b) that students gained their anatomical information mainly through reading and other forms of private study. The view was thus taken that practical work ought to be closely integrated with reading in a mutually facilitatory way.

The advance organizers were very highly approved of as devices fon enhancing uptake during practical classes. One participant remarked that his eyes saw better that which his mind had already been well prepared for. With 14 hours of contact (priming and demonstration sessions), the experimental group had ample opportunity to ask the investigator questions and receive instant feedback. The group review segment offered all the valuable learning oppor- tunities of practical work in anatomy (Sinclair 1972): the students handled the specimens and discussed them among themselves. However, directed reading was not a critically important part of the experimental programme and could

Table 6. Knowledge levels in the two-choice paper

Group Knowledge level*

Experimental 0.224 f 0.271 Traditional 0.119 5 0,231

*: Values given as mean f standard deviation Difference non-significant (0.8 > P > 0.7).

Learning human anatomy from prosections 393

Table 7. Responses to debriefing questionnaire

Response n

Estimates ofthe contribution to the understanding ofstructure andfunction

Learning by dissection (upper limb): Minimal to average (1.81 f 0.46)’

Learning frcm prosections (lower limb): Substantial to very considerable (3.81 k 0.33)’

Merits of dissection Structures imprint better on dissector’s mind One learns to dissect- a skill useful later in surgery The tedium and ‘unpleasant’ smells are good training None

Demerits of dissection Wastes time Important structures often not seen, are damaged or misidentified Groups too large Very few students actually dissect Encourages idleness and other forms oflaziness

Remedies to improve learning by dissection More cadavera More demonstrators None feasible Better organization of work than afforded by manual Time-consuming chores (flaying, fasciectomy) should be performed by staff Access to specimens after hours

Merits of learning from prosections Programme highly and effectively structured Very time-economical All important structures seen

Demerits of learningfrom prosections Superficial structures (e.g. cutaneous nerves) not demonstrated Nil ofnote No training in how to dissect Speed ofwork rather too fast Compelled much reading Unfair to rest ofclass

Remedies to improve learningfrom prosections Superficial structures should be demonstrated Pace ofwork should be slowed down Some dissection by students should be allowed

Learningfrom prosections should replace learning by dissection Completely To a great extent To a small extent

10 7 5 5

19 17 9 5 5

20 17 12 5 5 4

21 18 18

12 9 7 6 6 5

8 5 3

6 14 1

*: Rating scale = 0 - 4. Values given as mean f standard deviation Difference significant ( P < 0.001).

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actually be dispensed with if working with groups of smaller size. It was introduced mainly to enable the investigator to conduct the demon- strations on the wet specimen in two shifts of more manageable student numbers.

The experimental programme, in contrast with the traditional, was clearly more econ- omical of time (Table 3). Even with directed reading included, a saving of 14 hours (25.7%) was made. This reckoning does not include the time spent in preparing the prosection which, in the long term, is negligible since the same material will remain available for use over several years.

Although the saphenous veins, saphenous and sural nerves were preserved, the excision of the superficial fascia and other cutaneous nerves and vessels was pointed out as a drawback of the experimental programme (Table 7). In the event, such a sacrifice was inevitable: only one limb was available for prosection (that which the experi- mental group would have dissected). If learning from prosections were adopted and incorporated into the curriculum, a second limb at least would have to be assigned to the programme, making it possible to prepare a flayed specimen in addition to a deep dissection.

The most oft-cited advantage of dissection by students was that it conveyed a better three- dimensional perception of the body’s internal structure (Table 7). This was not borne out, however, by the scores recorded in the assess- ment tests (Table 4). It would seem to be a subjective impression based on a vision of dissec- tion under optimal conditions (e.g. two to a cadaver), rather than under existing local cir- cumstances. Besides, too few students actually dissect and even for these, the validity of the above claim has been challenged (Sinclair 1972).

Equally questionable is the view that knowing how to dissect, in itself, was a skill worth acquiring for later use in surgery. Understand- ably, the differences between dissection in gross anatomy and in operative surgery are yet to be appreciated by the students concerned, but even for the purposes of gross anatomy, it is doubtful that they possess the ability to produce good- quality dissections by themselves, especially during the early stages of the course.

The perception that the less pleasant aspects of learning by dissection (e.g. long hours in a

pungent atmosphere) are ‘good training’, reflects an acceptance of the mistaken image of gross anatomy as the ‘boot camp’ (Starr 1982) of the medical school. In reality, potentially grave health risks to both staff and students are involved and some ofthe literature on the subject has been cited by Bachop (1986), who strongly recommends the development of schemes for effective practical classes in gross anatomy entail- ing as little time over formalinized wet specimens as is possible.

As measures to improve learning by dissec- tion, the provision of more cadavera and demon- strators might indeed have been valid, were they not so difficult to implement. Cultural burial practices remain an impediment to the acqui- sition of bodies in sufficient numbers for use by medical students, while solutions to the problem of staff recruitment and training in anatomy (Nnodim 1988b) are yet to be found. In contrast, the main defect of learning from prosections, namely the loss of superficial structures, can be readily overcome by carrying out a superficial prosection on a second limb. In the study by Sinclair (1965), prosected materials remained in satisfactory condition for 6 years, over which period, six cadavera would be required in a traditional programme, compared to two in a non-dissecting programme.

The generalizability of the results of the present study is, of course, a somewhat moot point. Obviously, the effectiveness of a learning method might have more to do with the way that method is applied in the given circumstances than with the method itself (Harden 1986). However, it is worth mentioning that in a similar experiment (Sinclair 1965) in which students dissected under optimal conditions (two to a cadaver), the non-dissecting groups excelled in the essay-type and practical tests.

The experimental approach described in the present article is therefore deserving of con- sideration, especially by institutions faced with increasingly unfavourable student:body ratios or curtailed teaching time. Dissection by students has been completely dispensed with a t the Univ- ersity of Southampton Medical School with no deterioration in student performance (Bulmer et a l . 1982). Although such a radical reconstruction of the curriculum might not find ready accept- ance in many institutions, a combined pro-

Learning human anatomy f r o m prosections 395

gramme of some dissection by students and learning f rom prosections, as advocated by many of the participants in the present study (Table 7 ) and others (Besag et al. 1976; Hol t 1976), might be better received.

Acknowledgements I wish to express my sincere grati tude t o the students w h o volunteered to take part in this investigation, especially the members of the experimental group, for their willingness and courage to j o i n m e in trying ou t someth ing different.

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Appendix: Learning human anatomy: by dissection or from prosections? Debriefing questionnaire

(1) Using the following algorithm: 0 = nil 1 = minimal 2 = average 3 = substantial 4 = very considerable

estimate the contribution of (a) dissection to your understanding ofthe structure and function ofthe upper limb (b) learning from prosections to your understanding ofthe structure and function ofthe lower limb

......

...... RESPOND FREELY TO QUESTIONS 2 & 3. USE EXTRA SHEET/S IF NECESSARY

(2) (a) What are the MERITS of dissection? (b) What are the DEMERITS of dissection? (c) How can these demerits (if any) be remedied?

(b) What are the DEMERITS of learning from prosections? (c) How can these demerits (if any) be remedied?

(tick as appropriate) Y E S O N O 0

IfYES, to what extent? COMPLETELY 0 TO A GREAT EXTENT 0 T O A SMALL EXTENT 0

(3) (a) What are the MERITS of learning from prosections?

(4) Do you think learning from prosections should replace learning by dissection?

Received 13 July 1989; editorial comments to author 26 September 1989; accepted forpublication 9 January 1990