Ergonomics in microsurgery 1969

Surgery

" ... bein' only eyes, you see my wision's limited."
Sam Weller, in Pickwick Papers

" ... tremor, shake, ripple, jog, jolt, jar, jerk, ... hubbub, fuss, vibration ..."
Roget's Thesaurus

" Give me but a fulcrum close enough to the work, and sufficient visual acuity, and I will move a single atom."
cf. Archimedes, 200 B.C.

Ergonomics is the study of man in relation to -is working environment, and deals with such questions as the design of tools, work-place layout, the physical environment, and detailed analysis of working technique, both for efficiency and instruction. It has many possible applications to general ,macro) surgery. These provide a scientific basis for shortening operating times, not through haste, but through work simplification.

MINIATURE WORK using magnifying aids is found in non-surgical fields, such as watchmaking, micro-electronics, embryology, and physiology. The skill of ophthalmic surgeons owes more to tradition than to formal analysis, so far.

ERGONOMIC ASPECTS OF MICROSURGERY comprise tremor, visual acuity, hand-grips instrument design, efficiency, and study of forces applied by the operator. PHYSIOLOGICAL TREMOR has an amplitude of 0o5 to 3 mm. and a rate of 5 - 20 vibrations per second. It is determined by long-standing factors such as constitution and age; less permanent factors such as training, social poison (alcohol and cigarettes), and confidence; short-term factors comprising point of limb support, muscular strain, anxiety, visual feedback, and equipment design. These short-term factors are the ones most readily controlled, and to best effect, in a surgical situation.

VISUAL ACUITY is a function of many factors not often consciously appreciated but mostly capable of controlled alteration. Visual health, binocularity, magnification, luminous flux, colour rendering, luminance, contrast, and glare influence acuity, and should be studied with a lighting engineer.

For micro work, visual feedback far supercedes the kinaesthetic feedback of macro surgery, where fingertip sensation often guides dissection away from structures capable of irretrievable damage.

MOTOR HAND FUNCTIONS NEEDED FOR SURGICAL INSTRUMENTS are grip, displacement, rotation, and trigger function.

HAND GRIPS have been classified as the power and the precision grips, the latter comprising ulnar edge support and proprioception from the thumb cleft, as well as the finger tip pincer. Apart from the "pen" type of precision grip, there is an "ulnar storage grip" and an "internal precision grip." Study of these grips gives parameters for instrument dimensions and shapes.

ROTATION can be carried out either with the forearm or by fingertip rolling of a basically cylindrical shape. Awareness of this principle gives better assessment of instrument design adequacy.

TRIGGER FUNCTION may be defined as movement of one part of a tool while its main part is kept steady. This requires four contact pinpoints or adequate contact area for the fixing grip. Common trigger functions are index (gun), thumb (torch, end-button), little finger (Halsted needleholder), compression-rotation (artery forceps), simple pincer squeeze (tweezers, sugar tongs, pliers, scissors).

To minimise tremor, various remote control devices are possible. These may be hydraulic, pneumatic, mechanical, or electrical.

APPLIED FORCES: Breaking strain of umbilical cord, oesophagus, and bowel anastomosis are xnown, as is the pull on obstetric forceps. Little or no information exists on tissue resistance to needle penetration, which may be 5 to 10 pounds in scarred linea alba, or 50 grams in a two millimetre artery. The latter figure contrasts with 1000 grams to unlock a Castroviejo needleholder ratchet, and 4000 grams for a Matthews needleholder.

FURTHER APPLICATIONS OF ERGONOMICS.

Time standards for set procedures. Instrument design
Video-tape motion analysis
Doctor-engineer liason, not in the lecture-theatre, but in the grease of the engineering setup, ie. the animal laboratory, and at the side of the patient undergoing treatment.

SOME REFERENCES.

Napier, J.R. (1956) Prehensile Movements of the Human Hand. J.Bone Jt.Surg. 38, B 4, 902-913.
Patkin, M. (1965) The Hand Has Two Grips: An Aspect of Surgical Dexterity. Lancet, 1. 1384-1385
Patkin, M. (1967) Operative Surgery, the Human Hand, and Handle Design. 4th. Annual Conference, Ergonomics Society Aust. N.Z.
Patkin, M. (1969) Ergonomic Design of a Needleholder. Med.J.Aust. In press.
Barnes,R (1969) Motion and Time Study. 6th ed. Wiley
Dudley,H.A.F. Jones P.F. (1964) Access and Exposure in Abdominal Surgery.London Morgan et al. Human Engineering Guide to Equipment Design. McGraw Hill 1963 Tichauer, E.R. (1967) Ergonomics: The State of the Art. Amer.Indust.Hyg.J.
28, 105-116
Wilson, Edward (1961) The Time Factor in Surgery. Med.J. Aust. 699-702
Murre11, K.F.H. Ergonomics. {1965) Chapman & Hall

" the most significant and dangerous and the most easily avoided form of trauma is time." Sir Heneage Ogilvie, 1950
"Of all cases (of total gastrectomy) lasting more than six hours, 77.4 per cent developed anastomotic dehiscence." McNeer & Pack, 1954

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This is the text of a one-page handout for a talk I gave at the Microsurgery Research Foundation of Australia in 1969.

It was a few weeks after the pioneer microsurgeon, Earl Owen, heard me speak about ergonomics in surgery at St.George's Hospital, Sydney.

Thus began a 10 year association leading to concepts and publications in this area, and presentations around the world.

ERGONOMICS IN MICROSURGERY
Michael Patkin FRCS
Dungog and District Hospital, NSW
Microsurgery Workshop Sydney Post-Graduate Medical Committee
19 July 1969

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