The shape of retractor handles

Surgery

Gillies' skin hook is a good example of the lightest of retractors. It is applied to a skin flap whose tension must he gentle and controlled. Therefore, its lightness and its small area of contact with the hand are two important factors in concentrating the feel of the tissues on the sensitivity of the hand.

This contrasts with retraction for a deep intra-abdominal dissection. Here a firm, steady pull is necessary, perhaps for an hour or two. If the handle is well shaped for the hand, tension can be maintained by the more powerful and therefore steadier muscles of the arm and shoulder. Apart from pull, the handle is subject to tilt, rotation and, to a lesser degree, vertical and lateral placement.

THE GRIP OF THE HAND

Napier (1956) has analysed the two types of hand grip in commonest use and applied to them the terms "power" and "precision grip". Here the former concerns us, and it consists of the powerful application of the fingers pressing an object into the hollow of the hand and on to the thenar and hypothenar eminences. A study of everyday handles by the same writer (1961) shows that they are often designed badly. Fortunately, another study by Tomrley (1952) shows that there can be a rational basis for the design of handles.

REQUIREMENTS OF A RETRACTOR HANDLE

Daily observation in the operating theatre suggests that a retractor should fit comfortably into hands of various sizes, both right and left. The shape should suggest the way ft is best held, and allow firm control of tilt. The grip should be secure without tension. and should also be capable of reversal to allow a pull directly upwards. Like many good surgical instruments, it should be robust, easily cleaned, and straightforward to manufacture.

Tomrley (1952) points out that milling and ribbing are of limited use. They provide a non-slip surface for light pressures, but for strong pull the effect is unpleasant, and no substitute for true shaping. The slip of wet surgical gloves adds further weight to this argument.

The actual shape of a good abdominal retractor handle should therefore include the following features:

1. A rounded, light-weight handle for the fingers to curl round, with a large area for contact with the hand. It should not reflect light out of the wound.

2. An area for the thumb to bear on for downward pressure. (Rarely is the thumb used directly as a pulling agent.) Slight hollowing of this area will give the wielder early information of any slipping of his grip, an important proprioceptive mechanism. Opposite this area, a gentle groove for the index finger allows stronger pull.

3. A pommel, like that on some swords and daggers, bent to the ulnar border of the hand. This prevents losing the handle with momentary relaxation of grip, and also reassures the hand of its place. The pommel also provides a good bearing surface if the grip is reversed for upward pull on the handle.

4. Some flattening of the handle from side to side to allow control of rotation.
Other possible features, such as grooves for the separate fingers do not appear worthwhile, in view of observations made on several wooden handle models. There are the disadvantages of more complicated manufacture, and the ill fit of very small or very large hands.

PRESENT-DAY RETRACTORS

A gently moulded handle with a correctly turned pommel is, found in Doyeu's abdominal retractor, Allison's lung retractor, and Young's perineal prostatectomy retractor. The use of the Deaver retractor, with its sharp-edged handle, is a tribute to the tenacity and loyalty of successive generations of surgeons, and to the excellent view afforded by its blade; its shape for gripping is not an endearing feature.

CONCLUSION

General rules will not design a retractor handle to suit all surgeons. However, a conscious analysis of instrument design will help greatly in selecting new equipment and in devising the surgical tools of the future.'

REFERENCES

NAPIER, .J. R. (1956), "The Prehensile Movements of the Human Hand", J. Bone Jt Surg.. 38B : 902.
NAPIER, J. R. (1961), "Hand and Handles", New Scientist, 9:797.
TOMRLEY. C. G. (1952), "The Problem of Handles", Design, 39 : 8.

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The shape of retractor handles

Michael Patkin
Dungog, New South Wales
Reprinted from The Medical Journal of Australia, 1966, 1: 599 (April 2)

AUSTRALASIAN MEDICAL PUBLISHING COMPANY Limited
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