THE ROYAL BERKSHIRE HOSPITAL 'HALO'

D. L. MACKENZIE, L.D.S.R.C.S., L.R.C.P., L.R.C.S.(Edin.) and K. R. RAY, B.D.S., F.D.S.R.C.S.(Eng.)

The Royal Berkshire HosPital , Reading, Berks

THE cranium is commonly used as a stable base to which fractured facial bases may be fixed, usually by means of a plaster headcap. One disadvantage of this method is a lack of stability owing to movement of both headcap and scalp. A stable, rigid fixation can be achieved if the plaster headcap is replaced by a halo frame pinned to the cranium.

In I943, Lieutenant M. J. Crawford of the United States Navy described an apparatus which he had devised to provide cranial fixation in the management of facial fractures. This alurninium skull frame, or 'tiara' as it came to be termed, was fixed by three pins which were 'attached against but not into the cortical plate of the skull', one each side in the parietal region and the third vertically in the midline.

Subsequently two American orthopaedic surgeons, Perry and Nickel (I959), modified the 'tiara' to a full ring or 'halo' of stainless steel completely encircling the skull. Four threaded pins were placed at the 2, 4, 6 and 8 o'clock positions. At each of these points on the halo frame there were three threaded holes, allowing some choice of pin position, to suit various skull contours, but the angle of incidence of the pin to the cranium could not otherwise be altered. To maintain a stable position of head and cervical spine in poliomyelitis patients undergoing cervical fusion operations these surgeons connected the skull halo above via a framework of rigid rods to a plaster jacket below.

Thompson (1962) later reported the use of this halo in the treatment of frac- ture dislocations of the cervical spine.

Panuska and Dedolph (I965) recommended its use in the treatment of facial fractures and listed the advantages over a piaster headcap.

Crewe (I966) described his modification of the orthopaedic halo and stated 'that within the limits of any external appliance there is nothing a plaster headcap can do which cannot be done more comfortably, quickly and efficiently with the halo'.

Development of the 'Royal Berkshire Hospital Halo'. The concept was to produce an apparatus, specifically designed for the treatment of maxillo-facial injuries.

Ideally it should fit any shape and size of skull and permit the attachment of the various fixation and traction devices used in the treatment of facial bone fractures.

The design problems were more of an engineering than a surgical exercise. Fortunately, the co-operation of a skilled engineer was readily available.

The physical properties sought for the halo frame were rigidity and lightness, plus the desirability that the metal from which the halo frame was constructed should have low electrolytic activity when used in conjunction with other metallic components employed in the fixation, such as skull pins, connecting rods and cap

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28 BRITISH JOURNAL OF ORAL SURGERY

splints. These properties were best achieved in a halo frame in the form of a horse- shoe section cut from a sheet of aluminium alloy with multiple perforations serving as points of application for both skull pins and fracture fixation attachments (Fig. i). The surface was anodised to provide interface protection in use with dissimilar metals. The dimensions were determined following a study of cranial morphology. The halo frame and components arrived in their present form through a series of transitional patterns modified as a result of experiments on cadavers, and assessment on patients by the authors and several colleagues who co-operated in clinical trials.

The Royal Berkshire Hospital halo frame encircles three-quarters of the skull leaving the occiput free (Fig. I). Positioning of the frame at a tilt, both laterally and antero-posteriorly, is possible, allowing surgical access to any part of the scalp and cranium if necessary (Figs. 4A and B). The skull pin component (Fig. 2) may be fixed in a wide range of positions either above or below the frame. The pin is constructed from a stainless steel screw turned to a shoulderless tapered point. The skull pin stud is made of a solid aluminium alloy cylinder tapped and threaded to receive the pin. The stud may be bolted to the halo frame to give any desired angle of incidence of pin to skull surface.

The rod attachment component (Fig. 3) consists of a stainless steel screw, with 1 , t diameter rod. This is locked in a convenient hole the head tapped to receive a

in the frame by a stainless steel nut and washer. Any number of fixation or traction devices may be attached to the halo frame with this component plus universal joints (Figs. 4 A and B).

Method o f application of the halo to the cranium. The frame should form a rigid platform securely fixed to the cranium and not permit movement when forces are applied to it on reducing and fixing the fractured facial bones.

Fixation of the halo frame to the skull is by the four stainless steel pins which perforate the scalp to contact the outer cortical plate. All forces acting on the frame do so through the pins. Ideally such forces should be in balance if couples tending to distort or dislodge the halo are to be avoided. The irregular contour of the skull presents difficulties but it has been determined that with opposing pairs of pins placed coaxially, and equally tightened, a very stable system will be obtained. (Fig. 5). Therefore, the method of application is important and the sequence of fixation adjustments described below should be followed. In this manner the halo can be fitted in a few minutes using either local or general anaesthesia.

I. The occiput should be placed on a narrow support so that the open ends of the frame are well clear of the operating table.

2. The diagonally opposing skull pin components should be placed in simi- larly numbered holes in the frame (Fig. I). The two shorter pins are used pos- teriorly to avoid undue projection beyond the frame.

3- With the halo frame held in the selected position, preferably so that the pins come within the hairline, the coaxially arranged pins (Fig. 5) must be firmly clamped to the frame by tightening the stud nuts prior to driving the pins into the scalp. The actual angle of incidence of pin to skull is not critical provided the pins are coaxially placed in pairs.

4- One pair of opposing pins are now simultaneously tightened into the scalp with firm finger action only. Prior incision of the scalp is unnecessary.

THE ROYAL BERKSHIRE HOSPITAL ~HALO' 2 9

FIG. I

FIG. 2

FIG. 3

Fig. I . - - T h e halo frame encircles three-quarters of the skull leaving the occiput free. The tapered point of the skull pins engage against the outer cortical plate.

Fig. 2 . - -The skull pin component consisting of a stainless steel pin and anodised aluminium alloy stud via which the pin is clamped to the halo frame, by a stainless steel nu t and washer.

Fig. 3 . - -The rod attachment component consisting of a stainless steel screw with head tapped to take a ~" diameter rod.

FIGS. 4A AND B

The frame may be positioned with both lateral and anteroposterior tilt.

30 BRITISH JOURNAL OF ORAL SURGERY

5' The second pair of pins is then inserted, tightening first one then the other to minimise the production of side loads on the first pair.

The pillS should be tested for tightness every few days. Lock nuts for the pins are provided but are not necessary except in cases where a patient may be likely to tamper with the fixation.

FIG. 5

Opposing pairs of pins must be placed coaxially.

FIGS. 6A AND B

The halo frame used in the treatment of a Le Fort II pyramidal fracture with split maxillae.

The patient in Figures 6A and B was treated for a Le Fort pyramidal fracture. Figure 6B demonstrates that this halo does not interfere with lying down on pillows.

THE ROYAL BERKSHIRE HOSPITAL ~HALO' 3I

SUMMARY

A brief history of the use of cranial halo frames is given. The development of a simple but versatile halo is described and detailed instructions given of the method of application to the cranium.

A C K N O W L E D G E M E N T S

The unstinting efforts of Mr. J. Pearson and his colleagues at the Atomic Weapons Research Establishment, Atdermaston, in the design and construction of this apparatus are gratefully acknowledged.

Our thanks are also due to the Photographic Department of the Royal Berkshire Hospital and the Departments of Photography and Medical Art at the Royal Dental Hospital of London.

A halo frame of this design is now marketed by Messrs. Down Bros. Ltd., of London.

REFERENCES

CRAWFORD, M. J. (1943). United States Naval MedicaIBulletin. XLI, 1151. CP~WE, T. C. (1966). British Journal of Oral Surgery, 4, 147. PANUSKA, H. J. • DEDOLPH, T. H. (1965). Journal of Oral Surgery, 23, 212. PERRY, J. & NICKEL, V. L. (1959). Journal of Bone and Joint Surgery, 41A, 37. THOMPSON, H. (1962). Journal of Bone and Joint Surgery, 44B, 655.