Clinical Trial of the Diagonal Socket Prosthesis for Hip Disarticulation Amputation

D. G. Seaton, M.B., B.S., F.R.C.S. L. A. Wilson, M.B., B.S. W. Graeme Shepherd, L.R.C.P , M.R.C.S., F.A.C.M.A.


Reprinted from the Med. J. Australia, 1:730, April 3, 1971, by kind permission of the authors and publisher.

The surgical considerations in hip disarticulation and prosthetic management with the Canadian-type hip disarticulation prosthesis are discussed. A clinical trial of the diagonal type socket for this amputation has been undertaken, and the results are presented in this paper. It is believed that the use of this prosthesis represents a further step forward in the management of amputations at this severe level.

The Canadian type of prosthesis for hip disarticulation was introduced in about 1952. It has largely superseded the older tilting-table types of limb for amputations in the region of the hip. Primarily, the reasons for this are that the Canadian-type limb is more functional, better looking, more comfortable and more reliable.

Briefly, this type of prosthesis features an extensive laminated plastic socket, which not only contains the stump, but also encircles the pelvis. Reliefs have to be provided for bony prominences, principally the anterior and posterior superior iliac spines, the iliac crests on both sides and the spinous processes of the vertebrae. By gripping the pelvis firmly, it is said to minimize stump-socket motion.

The hip joint is located distal to the socket, so that the prosthetic knee is level with the normal knee when sitting. It is also placed anterior to and over a considerable width of the socket, to permit greater mechanical resistance to the very considerable shearing forces applied to the joint during walking. Mechanical failure of the hip joint was a constantly recurring problem with the laterally placed joint.

Anterior placement of the hip joint also allows the knee to be located posterior to the weight-bearing line, with greater alignment stability of the prosthesis. This permits elimination of hip-joint locks, and the free hip joint gives the patient a chance to achieve a much more natural gait.

Weight is borne principally by the ischium, with some contribution from neighbouring gluteal tissues and the ileum between the acetabulum and crest. The weight-bearing portion of the socket is made of rigid plastic, but has a flexible portion in the mid-posterior region so that flaps can be opened for applying the limb. The opening is anterior.

Suspension is achieved by careful moulding over the iliac crest. Unfortunately, this area and the overlying skin tolerate pressure and movement poorly. Additionally, inaccurate weight-bearing deformation of the stump during casting can lead to poor stabilization of the socket, with even less efficient suspension.

Fig. 1 , Fig. 2

At the Mount Wilga Rehabilitation Centre, where the Canadian-type prosthesis has been used for some time, patients with amputation in the region of the hip have frequently complained that their prostheses have numerous faults. Their complaints can be summarized as follows: (i) There has been pain over the ischial tuberosity and perineum on the side of the amputation, (ii) Suspension of the prosthesis has been inadequate, and the up-and-down pumping motion has led to abrasions of the skin, and to pain over the anterior superior spine and adjacent iliac crest on both sides of the pelvis, (iii) During use, the socket itself has been excessively hot, and with the resultant perspiration abrasions of the skin have occurred, (iv) The socket bulk has caused an unsightly appearance and has given a feeling of greatly restricted freedom of movement.

The problems associated with the Canadian-type limb are difficult to eliminate. Indeed, some patients have reverted to the use of crutches, because of inability to tolerate the level of discomfort which seems to be inherent in the design, casting and fabrication technique, for the following reasons:

  1. Undesirable pressures are transmitted to the soft tissues of the perineum and the inferior pubic ramus. This difficulty results from insufficient socket support of appropriate weight-bearing tissues and inadequate control of anteroposterior stump-socket movement causing pain over the bony prominences, particularly the ischial tuberosity.
  2. Mediolateral stump-socket movement often occurs. Throughout stance phase on the prosthesis, the body's centre of gravity exerts its downward force medial to the vertical support. Consequently, the stump tends to drop out of the socket toward the unsupported side. This downward sliding is inadequately opposed by lateral forces exerted on the socket wall on the sound side.
  3. Suspension over the iliac crests can seldom be made positive enough to prevent movement. This leads to friction and abrasion of the overlying skin. If the socket is too closely moulded over the crests, the level of discomfort is intolerable. If more relief is allowed, then suspension suffers.
  4. The socket bulk encloses a sufficiently large area of the remaining body surface to interfere significantly with heat-loss mechanisms.

We ourselves have been disappointed in the proficiency, tolerance and gait that our patients have achieved in the wearing of the Canadian prosthesis. We have thought that these disappointing results could be due to the level of discomfort inherent in the socket design and fabrication, and to the difficulty that our physiotherapy staff have experienced in grasping the biomechanical principles of operation of this type of prosthesis, particularly since teaching material is comparatively rare.

It has been estimated that hip disarticulation amputees comprise less than 2% of the total amputee population in the North American continent. No doubt the figures are comparable in Australia.

In 1962, McLaurin and Hampton, of the Northwestern University Prosthetic Research Center, Chicago, published details of a new type of limb, which they called the "diagonal socket" type prosthesis. The following advantages were claimed for this socket: (i) The pelvic impression of the stump does not have to include the ilium of the side of amputation; hence, it is much simpler. For the same reason, the actual socket is easier to fabricate, (ii) Lateral support is more directly and firmly achieved, (iii) Some adjustment to lateral support can be achieved by providing an adjustable lateral opening, (iv) Suspension is completely adjustable, (v) The socket is cooler and less bulky. The lack of bulk allows more natural drape of clothing over the ilium on the side of amputation, (vi) Anteroposterior stability is improved by the elimination of the anterior opening.

Recently we have had several patients who illustrate well the problems of amputation in this region, and as the advantages claimed for the diagonal socket seemed to offer a sound approach, a clinical trial of this diagonal type socket was undertaken.

Reports of Cases

Case 1.-The patient was a young man, aged 19 years, who had had a recent hip disarticulation for osteogenic sarcoma and presented the classical stump. He was fitted with a diagonal socket prosthesis; the only difficulty encountered was pressure over the anterior-superior iliac spine on the sound side. This required some additional relief and padding, and a comfortable fitting was achieved with minimal trouble. He is able to wear his prosthesis all day at work, walks well and is fond of social dancing. He coaches a local junior Rugby football team. He was a manual worker, but since his amputation has undertaken a course of studies at technical college level, and is now working with a firm of accountants.

Fig. 3 , Fig. 4 , Fig. 5

Case 2.-The patient was a boy, aged 16 years, who, as the result of trauma at the age of eight years, had had a femoral amputation at the level of the lesser trochanter. Whilst the femoral remnant had an abduction contracture, flexion and extension were possible through a range of approximately 90°. Externally, the stump did not extend beyond the perineal level. This represented the type of stump recommended in many surgical texts as being ideal, in that it provided a bony protuberance to assist in suspension of the prosthesis. He was fitted with a diagonal socket prosthesis, but suspension was modified, and instead of the straps over the iliac crest, the socket was carefully moulded over the flexed femoral fragment for suspension. This required a number of adjustments, as he continually complained of a cramp-like pain after wearing the limb for a few hours. Eventually, a compromise was reached, but there remained a tolerable level of discomfort in this area. He had never been employed, and is now working in the leather industry with prospects of a traineeship in shoemaking.

Fig. 6 , Fig. 7

Case 3. - The patient was a man. aged 25 years, who, as the result of trauma and subsequent infection, had had a hip disarticulation at the age of 10 years, with gross scarring of the stump. He had not worn a prosthesis until the age of 19 years. There was a considerable degree of underdevelopment of the pelvis on the side of amputation- He was fitted with a diagonal socket prosthesis. Suspension had to be aided by the use of a single shoulder strap, owing to the under-development of the iliac crest on the side of amputation. Cosmesis was achieved by the addition of plastic fairing outside the socket. This man walks well, and is able to wear his prosthesis all day and for recreational purposes. He is attending university, where he is taking a course in mechanical engineering.

Fig. 8 , Fig. 9

Case 4. The patient was a boy, aged 17 years, who had a subtrochanteric femoral amputation at the age of 11 years after trauma. Residual skin defect was evident, and a large split-skin graft was present over the anterior surface of the stump. This graft was exquisitely sensitive to both light touch and deep pressure. The femoral remnant was involved in the scar tissue, and there was no useful movement of the hip joint. There had been a fracture involving the iliac crest at the time of injury, and a ridge of bony callus joined the iliac crest and the femoral fragment, so that it would not have been possible to mould a socket between the iliac crest and the femoral fragment to achieve suspension. This boy had ceased wearing a prosthesis some 12 months earlier, because of the high level of discomfort and the presence of severe pain arising in the skin graft. A revision of the amputation was carried out to remove the femoral fragment and the bar of callus, thus providing a classical hip disarticulation stump. With the additional clearance gained by the revision, the pendulous skin of the buttock was used, allowing the skin graft to be excised and replaced with normal skin. This boy was fitted with a diagonal socket prosthesis, with only minimal adjustment problems. He achieved a very satisfactory level of gait, and is able to wear the limb all day and for recreational purposes. He had only just left school, and was undertaking a course of studies at technical college level in fitting and turning: he is now employed in this field.

Fig. 10 , Fig. 11

Discussion

All these patients were provided with a diagonal socket prosthesis, which does not enclose the iliac crest on the sides of amputation. The anterior superior iliac spine on the side of amputation remains free of any contact with the prosthesis or suspension.

Suspension in this prosthesis is achieved by the use of soft, adjustable straps which overlie the iliac crest. This strap suspension was used by two of the patients, but in Case 2 the socket was moulded over the fully flexed residual femur to give suspension, and no strapping was provided.

All patients reported that the prosthesis was comfortable, and that they felt secure. It was noted that suspension and lateral stability were uniformly satisfactory. There was no demonstrable difference of stability between the limb which used strap suspension and the one which used moulded socket suspension.

The three patients who had previously worn Canadian-type sockets reported the new limb as being much less bulky, more comfortable, more stable and much cooler to wear.

The comfort and efficiency afforded by the diagonal socket can alter the surgical concept of amputation about the hip joint, just as the development of the suction socket for the long femoral stump has lessened the popularity of knee disarticulation, as discussed in a previous communication.

The development of the diagonal socket could increase the popularity of hip disarticulation as a surgical procedure. The surgeon now has more freedom of choice, in that he is no longer forced to prefer subtrochanteric amputation on the grounds that this will provide a more useful and comfortable stump.

Textbooks which have favoured the femoral fragment so that it can sit at 90° of flexion on a "tilting table" type of prosthesis are now outmoded. As an example of this fact, the remnants left in Cases 2 and 4 caused far more trouble prosthetically than they were worth.

Hip disarticulation is a relatively simple surgical procedure, and it allows a good exposure for radical removal of iliac and inguinal glands. These can be removed without detriment to comfort or cosmesis.

Curved skin flaps are made anteriorly and posteriorly from a point beginning a little laterally to the anterior superior iliac spine and ending medially at the pubic tubercle. The posterior flap is wider and about three times longer than the anterior one. Human variations in this part of the anatomy in height, sex, age and race make precise measurements for flap length an impossibility, but in all cases the posterior flap should extend well below the gluteal fold.

Deeper dissection follows the long saphenous vein down to the femoral vein, and when neoplasm is the indication for this operation, such as a recurrence of melanoma, the inguinal glands are removed as a block and the gland of Cloquet is taken.

The inguinal ligament is divided at the femoral canal, and both sides are reflected back to allow the femoral vessels to be ligated above the profunda and circumflex branches. It is then an easy matter to strip down the iliac glands along the external iliac artery, commencing at the bifurcation of the common iliac vessel.

Muscles are cut down from the skin incision directly towards the hip joint, which is then disarticulated in the usual manner by circumcising the capsule. The muscles in the posterior flap are trimmed so that they may be sutured to the muscles anteriorly at the level of the inguinal ligament. In this way, the pendulous appearance which can be caused by excessive tissues in the posterior flap is avoided. A "Redi Vac" is used to drain the dead space in the acetabulum.

The indications for hip disarticulation are fortunately rare, but the most common site for osteogenic sarcoma is in the distal femur. Recurrences after high thigh amputation are not infrequent here. Neoplasm, injury, deformity and chronic uncontrollable infection in the hip joint can all be indications for hip disarticulation.

The introduction of the diagonal type socket stimulated renewed interest within our physiotherapy department; the patients achieved a very satisfactory gait, and all are able to wear their prosthesis for a full working day and for recreation at night and weekends.

Acknowledgements

We should like to acknowledge the help and advice given by Mr. G. Bullard and Mr. B. Irwin, Senior Prosthetists, Repatriation Artificial Limb and Appliance Centre, and Mr. T. Jones, Prosthetist, Limco, for assistance in fabricating the diagonal socket prosthesis. We would also like to thank the Director-General of the Department of Social Services for permission to publish this paper.

Mount Wilga Rehabilitation Centre Commonwealth Rehabilitation Service Sydney, Australia;D. G. Seaton is Consultant Orthopaedic Surgeon.

L. A. Wilson is Rehabilitation Medical Officer.

W. Graeme Shepherd is Medical Director.

References:
American Academy of Orthopaedic Surgeons, Orthopaedic appliances atlas- Vol 2. J. W. Edwards, Ann Arbor, Mich., 1960, pp. 230, 302, 422.
Foort, J., Construction and fitting of the Canadian-type hip-disarticulation prosthesis. Artif. Limbs, 4:2:39-70, Autumn 1957.
Loon, H. E., The past and present medical significance of hip disarticulation. Artif. Limbs, 4:2:4-21, Autumn 1957.
McLaurin, C. A., and F. Hampton, Diagonal type socket for hip-disarticulation amputees. Northwestern University Prosthetic Research Center, Chicago, 1962.