1032 S.A. MEDICAL JOURNAL 18 May 1974

6 months from the date of dislocation. If we reallybe:ieve that weight-bearing is ~n important factor, wecould even avoid weight-bearing for perhaps 2 yearsafter injury!

Physiotherapy has not been mentioned to any extent inany authoritative series. Watson-Joness felt that earlyvigorous physiotherapy tended to result in myositisossificans. On the other hand, Stewart and Mitford'recommend early vigorous exercises to prevent arthro­fibrosis and to produce favourable functional results.

All our patients received very active physiotherapy,except to the affected joint, while they were inpatients.Unfortunately, after discharge from hospital only a fewavailed themselves of outpatient physiotherapy. We cannotprove or' disprove the importance of physiotherapy. Thesubjective element is too large. However, our patients inhip spicas, on the whole, did less favourably than thosewho lay in traction and received active physiotherapy toall except the affected joint.

Age is interesting in that some state that age is un­important, whereas others" feel that younger patients havea better prognosis. Our impression is that patients under40 years of age did better than those above this age.Elderly patients may suffer from intercurrent disease andconcurrent osteo-arthritis. They seem to have a higherincidence of heterotopic calcification.

CONCLUSIONS

Reduction of dislocation should be effected as early aspossible. Delays probably carry a worse prognosis, butare not always as generally disappointing as some authorsindicate.

Avascular necrosis develops regardless of weight-bearing,and seems related more to the degree of force applied inthe first instance, being possibly worsened by delay beyond12 hours in treatment. .

Earlier general physiotherapy does not seem to increasethe incidence of heterotopic calcification, but does seemto improve the rate of rehabilitation quite noticeably.

It seems logical to carry out primary open reductionand acetabular fixation in grade III posterior dislocations.

I should like to thank Professor C. Lewer AlIen andDr R. D. H. Baigrie for assistance.

REFERENCES

1. Stewart, M. G. and Mitford, L. V. (1954): J. Bone Jt Surg., 36A.315.

2. Brav, E. A. (1962): Ibid., 44A, 1115.3. Epstein, H. C. (1961): Ibid., 43A, 1079.4. Idem (1973): Clin. Orthop., 92, 116.5. Banks, S. W. (1941): J. Bone Jt Surg., 23, 753.6. Armstrong, J. R. (1948): Ibid., 3GB, 430.7. Rosingh, G. E. and James, J. (1969): Ibid., SIB, 165.~L \Vatson-Jones, Sir R. (1955): Fraclures and Joint Injuries, 4th ed.

Edinburgh: Living~t,.(.:::

Bio-engineering - A Perspectivec. P. RODSETH

SUMMARY

Bio-engineering is a general term used to describe theapplication of engineering techniques to the study ofmedical problems. Some fields of bio-engineering re­search are described, and the suggestion is made that abio-engineer be included in the clinical team. Thequestion of regularising the position of bio-engineeringwithin the medical and supplementary professions israised.

S. Afr. Med. J., 48, 1032 (1974).

The rapid increase In technology has entered thepractice of medicine, as it has almost all other aspectsof modern life. The truism that medicine is both an art

Department of Physiotherapy, University of Cape TownC. P. RODSETH, M.SC., B.se. (PHYSIOTHERAPY), M.e.S.p.,

DIP.T.P.

Date received: 7 January 1974.

and a science tends to be distorted in the attempt torationalise all normal and pathological processes and toestablish more firmly their scientific foundation. Similarly,the care of the critically ill patient involves the use ofscientific monitoring and therapeutic apparatus of a highdegree of sophistication. Professor J. F. Brock, in hisaddress to the 1973 medical graduates of the University ofCape Town, pleaded strongly for the preservation of thebalance between clinical medicine and laboratoryinvestigation. Current attempts at medical curriculumreform are faced with the insoluble problem of anincreasing body of scientific knowledge seeming to over­whelm the more traditional 'arts', which can only beacquired slowly, and largely by example from giftedclinical teachers.

The realisation by medical practitioners that moreknowledge and skill are required to be of maximumbenefit to patients than one individual is capable of, hasled to the establishment of clinical teams. Some suchteams include a physical scientist, who may be designatedvariously as a bio-, biomedical, medical, rehabilitation ororthopaedic engineer.

18 Mei 1974 S.-A. MEDIESE TYDSKRIF 1033

WHAT IS BIO-ENGINEERING?

This is an extremely difficult question to answer. As anevolving discipline, it would be a disservice to it tolimit its scope by too narrow and rigid a definition.A fair, working description may be that 'bio-engineeringcomprises the application of engineering techniques to thestudy of medical problems'.' However, those already doingthis type of work accept its interdisciplinary nature, andthose institutions which undertake to train bio-engineers(at least in the UK) are prepared to accept candidateswith a medical or biological background and to modifytheir courses appropriately.

Possibly a better comprehension of the scope of bio­engineering may be gained from some examples of thetype of work undertaken. If groupings roughly equivalentto the divisions within engineering are used, the followingare some of the fields of interest.'

Mechanics

The first accurate, quantitative analysis of the forcestransmitted by the hip joint during normal walking wasundertaken by a mechanical eng:neer when asked by agroup of orthopaedic surgeons to design a better nail forfractured necks of femur. The study was made becausethe surgeons could not answer the elementary engineeringquestion of what forces the nail had to carry, and theengineer felt incapable of producing a good design with­out such fundamental information. This work has beencontinued, and now full engineering analyses of the forcesat knee and ankle are available, which have been checkedby different experimental methods. These findings formthe basis for design work on artificial joints and for thestudy of natural joint lubrication. Tribology, the study offriction and lubrication, is becoming important in thefundamental study of the arthropathies.

There is also an intimate working relationship betweenengineers and clinicians in the closely related fields ofprosthetics and orthotics. The design, manufacture andintroduction to clinical use of the modular systems oflower-limb prostheses have depended largely on the interestof engineers. Similarly, the development of effective upper­limb prostheses, spurred on by the aftermath of thalido­mide, has reached a high level as a result of co-operationbetween mechanical and control engineers and theclinicians responsible for the care of amelic patients.

Considerable work on the mechanics of the spine isalso being carried out.

Techniques of a more diagnostic nature are also beingdeveloped. This is being done, for example, in response tosurgeons who feel that a quantitative assessment of gaitis desirable in order to judge more accurately the degreeof disability before performing lower-limb joint surgeryand to gauge its effectiveness postoperatively. Such techni­ques could also be used to evaluate the effectiveness ofmedication in the conservative treatment of arthriticconditions. The balance which needs to be struck, however.as in all such refinements, is between a very complicated.time-consuming and expensive, yet highly accurate,laboratory investigation and subjective, quick, clin~cal

evaluation with poor correlation between independentobservers and no true record with which to comparelater observations.

Chemistry

Chemical engineers, chemists and fluid-mechanicsengineers are collaborating in the design of devices forthe exchange of substances between the body and theenvironment. The prime example is the artificial kidney,where there is great room for improvement in theefficiency of the conventional devices and a huge potentialfor the development of small, safe, disposable devices.Both the membrane itself and its support, together withits ancillary porting, pumps, etc., are amenable tobetter design. Extensions of this work include replacingthe filtering function of the liver (as in extracting para­cetamol in cases of overdosage) and perfecting mem­brane oxygenators for incorporation in heart-lung bypassmachines. All the work done on prosthetic heart valves,cardiac-assist devices and, in the long run, artificialhearts, may also be considered in this group.

Because of the necessity for biocompatibility of themembranes in these devices with blood, these workershave become interested in the whole problem of bio­compatibility of synthetic materials with the human body.This enables them to collaborate with those designingimplant devices on the aspect of materials to be used ora biocompatible coating to be applied prior to insertigninto the body.

Materials Science

The behaviour of the tissues of the body at gross andmicroscopic levels is of great interest.

A fairly early bio-engineering project arose from theposing, by an eminent plastic surgeon, to a struc.turalengineer specialising in materials, of the problem of whyskin could stretch more in one direction than in another.This, of course, especially affects the design of flap-grafts.An instrument was constructed to measure the strain(extension per unit original length) produced for a givenstress in skin all over the body. The results are usuallypresented as a diagram of the body covered with ellip:es,representing strain for given stress, with long axes gene­rally running craniocaudally, and the proportion of longto short axis is generally greatest on the dorsal surfaceof the body over the joints. These workers expandedtheir studies to include tendon and other collagenousstructures and articular cartilage. The mechanical propertiesof these tissues are tested on orthodox engineering te t­rigs, suitably modified for in \'itro conditions, to ascertaintheir gross behaviour. Their microstructure is also studied,using both light and electron microscopy, and an attemptis made to account for their properties on this basis.

This branch of work is fairly basic in nature. althoughit does have direct bearing on the design of safetyequipment such as crash helmet and safety harnesses.The cartilage studies are extremely relevant to jointlubrication investigations.

1034 S.A. MEDICAL JOURNAL 18 May 1974

Electronics and Data Analysis

Many of tbe body's functions can be monitored bydisplaying the very low voltage signals which theygenerate (ECG, EEG, EMG), or by transducing amechanical action into an electrical signal to be moreconveniently displayed and recorded. Any direct recordingfrom the body involves an interface between it and theapparatus. Such a junction is always a source of inter­ference. especially electrical 'noise' with direct electricalrecordings. Such a connexion is also a source of potentialdanger to the patient if there is any malfunctioning ofthe earthing circuits. Equally, from the medical point ofview. it is preferable to avoid invasive diagnostic techniquesif sufficiently accurate information can be obtained byother methods.

Thus electronic and mechanical engineers are developingnon-invasive and, if possible, even non-contact techniquesof monitoring various body functions. The ballistocardio­graph and displacement cardiograph are two examples ofsuch devices where highly sophisticated engineeringtechniques have been used to perfect devices whose prin­ciple has been long known.

Much work on diagnostic and therapeutic ultrasoundis also being carried out in various centres.

In many instances the analogue signal detected in thebody contains a great deal of superfluous information oreven just noise. In order for the observer to appreciatethe significance of the analogue signal, it needs to beprocessed in some way. It may also be necessary for theanalogue signal to be converted into numerical values(digitised) so that calculations may be performed. Suchsignal processing is most easily carried out by computers.Computer scientists understanding the biological signi­ficance of the signals are needed to advise on the analysesrequired, its reliability and statistical validity, and toprogramme and operate the computer. It is advisable toconsult data analysts who also have statistical trainingin the planning stage of investigations, to ensure thegreatest economy of effort and a maximum of reliableinformation.

The foregoing fields of interest relate almost entirelyto pure research carried out in the laboratories of anexpensive research institute. The question arises whetherthere is a place for the bio-engineer in the ordinaryhospital environment.

Hospital Practice

Hospital engineers' departments exist to deal with themaintenance of hospital buildings. structural alterationsto these and the supply of main services. power, heatingand ventilation. Some institutions also have workshopsstaffed by highly competent technicians where themore sophisticated equipment used, such as ventilators.monitors, ECG machines and electrotherapeutic physio­therapy apparatus. can be 'erviced. It would seem. how­ever, that there is a place in the larger hosp~tal for anengineer with knowledge of medical problems. He shouldbe immediately available to the clinician to help and

advise him on technical matters, be it in the purchase ofnew or the modification of existing equipment. or in thedesign of an experiment. Such an individual cannot bean expert in all technical matters but would. at least. bein an excellent position to know where .to turn' foradvice and to explain a medical problem to the technicalexpen in the language he understands-thus helping tobridge the communications gap.

INTEGRATION WITH MEDICINE

If the premise is accepted that there is a need, andtherefore a place, for bio-engineers in present and futuremedical practice and research, then the problem ofestablishing their position in the field of medicine andsupplementary health services must be solved. As such,personnel would deal directly with patients, and the esta­blishment of a register for bio-engineers by the relevantauthority (e.g. the South African Medical and DentalCouncil) would seem essential to protect both patientsand medical practioners who refer them to bio-engineersfor some procedure. -

The establishment of such a register would necessitatesome definition of a 'bio-engineer' in order to classifythose registrable and those not. There are very feworthodox training courses for bio-engineers and they there­fore come from a diverse field of basic trainings, so thattheir competence in any particular field is difficult toassess. It may be necessarf to incorporate in such regis­tration ethical rules requiring safety checking in mattersaffecting patients by someone professionally registered inthe field concerned, if it is not that of the bio-engineerhimself. Thus the design of, say, a mechanical device bya medical bio-engineer should be checke.d by a suitablyqualified mechanical engineer.

CONCLUSION

In the past, fruitful co-operation between medicalpractitioners and engineers occurred on a ratherhaphazard, personal basis. The maximisation of benefitto medicine from advanced technology can be,t be achievedby formalisation of the links between them. There areengineers interested in medical problems and anxiousto apply their knowledge and skills directly in thealleviation of human suffering. There are also medicalmen who realise that a better knowledge of whattechnology can offer their patients is an asset, and whothen acquire a technical training. Members of both thesegroups may be called bio-engineers and their contributionsto the future development of the technical aspects ofmedical practice can be very great.

A greater awareness by the medical profession of whatbio·engineering has to offer will be to the mutual benefitof all concerned.

REFERENCES

1. University of Strathclyde Postgraduate Study Booklet (1973): Bio­engineering.

2. Kenedi, R. M. ed. (1973): Perspectives in Biomedical Engineering.London: Macmillan.