USE OF THE AUSTIN MOORE PROSTHESIS FOR ADVANCED

OSTEOARTHRITIS OF THE HIP

M. B. HEYWOOD-WADDINGTON, LONDON, ENGLAND

From the Royal National Orthopaedic Hospital, London

The management of advanced degenerative arthritis of the hip, especially when bilateral,
remains an unsolved problem. The Vitallium cup arthroplasty pioneered by Smith-Petersen
(1939) has been refined and its indications, scope and results well documented (Aufranc 1962,
Law 1962). We know now what it can offer in the most experienced hands, and there is
unlikely to be much further useful development of this procedure.
The value of the stem prosthesis and its place in the treatment of advanced osteoarthritis
are more controversial. The original design of the Judet brothers failed after initial success
because of structural faults inherent in the short stem and acrylic head. Medullary stem
prostheses of Vitallium have proved much more satisfactory, and of these the Austin Moore
and Thompson design are the ones most commonly used. Introduced in the correct way the
Austin Moore prosthesis maintains a stable articulation with the acetabulum. preserves length,
and by virtue of its fenestrations becomes firmly fixed into the femoral shaft.

FIG. 2
Figure 1-Advanced osteoarthritis of hip. Figure 2-Femoral head replacement with Austin Moore
prosthesis and acetabular reaming.

The Austin Moore prosthesis has become of established value in conditions in which
damage or disease is confined to the femoral head or neck, and the acetabulum remains
healthy: thus it has gained a secure place in the management of certain fresh fractures of the
femoral neck, for non-union of these fractures, and for avascular necrosis of the femoral
head. Its place in the surgery of osteoarthritis of the hip is less certain, and though it has
been widely used for this condition, little information has been recorded of the results. Most
authorities are agreed that when acetabular remodelling is carried out the results cannot
be expected to be more than fair, though they may be worth while.

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 USE OF THE AUSTIN MOORE PROSTHESIS IN OSTEOARTHRITIS OF THE HIP 237

This report concerns the results at short-term follow-up of a series of cases of advanced
osteoarthritis treated by one surgeon at the Royal National Orthopaedic Hospital,
Stanmore, using the Austin Moore Vitallium prosthesis in a standard way.

TECHNIQUE
In all cases a low posterior gluteal-splitting “ Southern “ approach was used as described
by Moore (1959). The acetabulum was remodelled with a Pridie reamer, being enlarged to
form a smooth hemisphere lined by healthy cancellous bone; into this an exactly matched
prosthesis, two millimetres less in diameter than the reamer used, was fitted, with the aim of
distributing the total pressure across the joint evenly over the prosthetic head (Figs. 1 and 2).
The new acetabulum was fashioned to take as large a head as could reasonably be accommodated
within the available bone. The diameter of prosthetic heads used varied between one and
seven-eighths inches and two and one-eighth inches.

DURATION OF STAY IN HOSPITAL

In unilateral cases the stay in hospital varied from seven to thirteen weeks, with an average
of ten weeks. In bilateral cases (operations on both hips during the same admission) the
length of stay varied from twelve to twenty-seven weeks. The patients were discharged when
confidently walking on crutches.
MATERIAL

All cases of Austin Moore prosthesis for degenerative arthritis in which the acetabulum
had been reamed as described and in which the operation had been done more than one
year before were selected for follow-up. As shown in Table I, thirty-three such operations
in twenty-eight patients appeared in the records, and thirty relevant hips in twenty-five patients
were examined. The two deaths were from unrelated causes (one from carcinoma of the
bronchus six months after operation, and one from carcinoma of the rectum and urinary
infection two and a half years after operation). One patient was not able to attend for follow-up.
Table 11 shows the indications for operation. “Primary” osteoarthritis implies the
absence of any previous overt hip disorder.

TABLE I TABLE II
CLINICAL MATERIAL INDICATIONS FOR OPERATION

Patients
Relevant Indication Hips
operations
Primary osteoarthritis . . 24
Total . . . 28 33
Osteoarthritis superimposed on
rheumatoid arthritis . . 3
Unavailable . .

Failed Judet prosthesis . . 1

Died . . . 2 2
Failed forage . . . I
Available for follow-up 25 30 Failed neurectomy. . . I

The sex incidence was approximately equal-thirteen men and twelve women.
The mean age at operation in women was 588 years and in men 581 years. The patient
was between fifty and sixty-nine years at the time of operation in twenty-three of the thirty
cases. The duration of follow-up was from one year two months to five and a quarter years,
with an average of two and a half years. Ten hips were seen less than two years after operation
and may not have reached their greatest recovery.
In twelve patients one hip alone was operated upon, and in thirteen patients both hips
were operated upon (bilateral Austin Moore arthoplasty six; Austin Moore arthoplasty
and osteotomy five; and Austin Moore arthoplasty and cup arthoplasty two.

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238 M. B. HEYWOOD-WADDINGTON

COMPLICATIONS
These are shown in Table lii. The contracture of the tensor fasciae latae caused pain
and tightness over the outer side of the thigh two and a half years after operation, and was
relieved by fasciotomy.
TABLE III
COMPLICATIONS

Early Late

Mortality . . . . . 0 Fracture . . . . .

Infection. . . . . . 0 Contracture of tensor fasciae Iatae I

Deep venous thrombosis (no embolism) 4 Ankylosis. . . . . 4

Dislocation . . . . .

Fracture . . . . . . 1

RESULTS
The results have been assessed diagrammatically according to a modified Gade system
as shown in Tables IV, V and VI.
It will be seen that the best effect was in relief of pain. Pain is the predominant symptom
which drives the patient to accept operation, and if pain alone is relieved the operation may
be considered to have been at least partly successful. Pain after operation was consistently
described as of an altogether different and more tolerable quality than before operation. It
was usually described as a discomfort at rest, and amounting to an ache on exercise of a
fatigue type. The deeper seated and more intolerable pain of osteoarthritis was always relieved
except in one case, to be referred to later.

TABLE IV
RESULTS ASSESSED BY MODIFIED GADE METHOD: RANGE OF MovEMENT

Movement Pre-operative Follow-up \Ioement

(per cent) (Number of hips) (Number of hips) (per cent)

I Normal Normal I

2 6080 2 1u1i1 60-802

3 40-60 13 40-60 3

42040 12 J6 2O4O4

5 5-20 8 1 - 5-25

6 None 5 1 None 6

I I I I
24 16 8 4 4 8 16 24
Number of hips

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 USE OF THE AUSTIN MOORE PROSTHESIS IN OSTEOARTHRITIS OF THE HIP 239

TABLE V
RESULTS ASSESSED BY MODIFIED GADE METHOD: PAIN

Pre-operative Follow-up B
B am (Number of cases)
am
(Number of cases)

1 None None 1

Slight on
2 12 Slight on
exercise exercise -

3 Moderate 5 12 Moderate 3

4 Severe 18 1 Severe 4

Very severe: :::::::::::::::::::: Very severe:

5 sleep 5 sleep 5
disturbed ::..::::: disturbed

6 Intolerable 116 2 2 Intolerable 6

Number of hips

TABLE VI
RESULTS ASSESSED BY MODIFIED GADE METHOD: WALKING RANGE

Pre-operative Follow-up
#{128}R ange
(Number of cases) (Number of cases) Range C

1 Normal 5 (4 unilateral) Normal I

2 1 mile I (unilateral) I mile 2

l 12 (6 unilateral)
with aid

Short :.#{149}:::: Short

4 distances 23 12 (1 unilateral) distances 4
only . only

Confined Contlnt.d
6
to house :): to house

Confined Confined
6 tobed tobed 6
or chair or chair

I I I I I
24 16 8 4 4 8 16 24
Number of hips

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240 M. B. HEYWOOD-WADDINGTON

Mid-thigh pain felt usually on the lateral side opposite the lower end of the prosthesis
was quite often described; in some it cleared up spontaneously-it could not be related to
any specific radiological appearance and it is thought to be soft-tissue (muscular) in origin.
Rest pain was much more reliably relieved than exercise pain, and whereas most patients
had no discomfort after operation while sitting, walking often caused some fatigue and aching.
Low back pain, sometimes severe, is often associated with the pain of an osteoarthritic
hip. It was gratifying to find that there was a definite improvement in the degree of back pain
after operation, especially when there was improvement in hip mobility (Table VII).
Movement-There was not generally a very marked improvement in the range of movement,
and with time there was a tendency for the arthroplasties gradually to stiffen up. Nevertheless
it was usually possible to overcome severe fixed deformity. After operation thirteen hips had
residual fixed flexion deformity of more than 10 degrees; three had some degree of residual
fixed adduction; and seven had some degree of residual fixed lateral rotation.
Though fixed deformity is obviously undesirable there was not necessarily any correlation
between this and the result from the patient’s point of view. One man of sixty-nine with
involvement of both hips has, because of extensive new bone formation around the joint, ended
up with one hip virtually ankylosed in a position very little better than that before operation-
20 degrees of fixed flexion, 20 degrees of adduction, 30 degrees of lateral rotation-yet he
only gets slight discomfort on exercise and plays nine holes of golf a day.
Walking range-From Table VI it will be seen that improvement in activity as judged by the
capacity for walking was confined virtually to patients with only one hip involved. Of twelve
hips remaining in category 4 after operation, eleven were in bilateral cases and one unilateral.

TABLE VII
INCIDENCE OF LOW BACK PAIN

TABLE VIII
IMPROVEMENT INDEX

Unilateral Bilateral Total

12 patIents, 12 hips 13 patIents, 18 hips 25 patients, 30 hips
(per cent) (per cent) (per cent)

A Movement. 44 24 33

BPain . . 67 55 59

C Walking range 57 22 36

Improvement index-An “improvement index” has been worked out on the basis of the
percentage of the theoretically possible improvement actually obtained (towards a target of
full movement, no pain, and a normal walking range) (Table VIII). This illustrates again the
greater effect of the operation in reducing pain than in improving mobility or walking ability,
and shows that function as a whole is not greatly improved in bilateral cases.
Function-A general idea of the functional result can be assessed only by estimating the
patients’ performance over a range of normal activities. From this I estimated that sixteen

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 USE OF THE AUSTIN MOORE PROSTHESIS IN OSTEOARTHRITIS OF THE HIP 241

patients had definite improvement of function, eight had none or only marginal improvement,
and one patient (with both hips involved) was worse. Seven patients remained partly dependent
on others for some aspect of their life, but the remaining eighteen felt that they could manage
completely by themselves if they had to.
The time taken to regain function is long, and improvement may continue slowly for
two years. Some patients felt that they continued to make ground beyond this period.
Stability-Unfortunately stability was the one factor in which any significant number of
patients considered they were worse off. Though ten patients thought that they had improved
stability and nine remained the same, eleven hips were considered to have deteriorated in this
respect. This may be due to the shortening that occurs-and with it shortening of the
abductors. In unilateral cases this varied from half an inch to one and a half inches and
averaged three-quarters of an inch (excluding the case in which dislocation occurred and was
left). Loss of proprioception from excision of a large part of the capsule might also be a factor.

FIG. 3 FIG. 4
Case 26-Recurrence of symptoms of osteoarthritis ten months after Austin Moore arthroplasty and
acetabular reaming. Figure 3-Initial post-operative radiograph. Figure 4-Six months after
progressive recurrence of osteoarthritic symptoms.

Deterioration-Deterioration after a period of greatest improvement was reported by four

patients in the series. In one the set-back was due to a spiral fracture of the shaft of the femur
at the level of the lower end of the prosthesis which had occurred fourteen months after
operation and four months before the review. In another a slight increase in pain was reported
in the months preceding the review two years after operation. In the third patient, a woman
of fifty-one, both hips became ankylosed in consequence of new bone formation around the
joint. She has moderate pain, walks steadily if stiffly with one stick, but remains virtually
independent. The fourth patient noticed a return of her original “osteoarthritic pain” about
ten months after operation in June 1963. This has become a little worse though it is not
so bad as before the operation (Figs. 3 and 4). The reason for her renewed pain
is not known.

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242 M. B. HEYWOOD-WADDINGTON

RADIOLOGICAL CHANGES

Coventry (1964) listed the common complications responsible for failure of prosthetic
operations on the hip. A study has been made of serial radiographs taken after operation
in these cases and the following points seem worth noting.
Loosening of the stem of the prosthesis-A faint halo was often seen around the stem
but no evidence of gross loosening. Presence or absence of such a halo did not appear to be
associated with pain. Probably the fenestrations in the Austin Moore prosthesis are very
effective in securing the stem firmly in the femur.
Migration-Early migration along the line of the axis of the neck was seen in nearly
all cases (Figs. 5 to 7). If continuous, it would lead to severe protrusio, and this is known
to be a potent cause of eventual failure for which salvage by removal of the prosthesis is a
difficult undertaking. In most of these cases, however, migration appeared to cease after

Fio. 5 FIG. 6 . 7
Case 20-Illustrating the usual proximal migration of the prosthesis along the line of the axis of the neck.
Figure 5-Before operation. Figure 6-Immediately after operation. Figure 7-One year after operation.
Note the proximal migration, sclerosis, and bulging of inner pelvic wall. No significant further migration has
occurred.

about a year and become limited by a zone of sclerosis developing uniformly around the head
of the prosthesis. The prosthesis has often bulged the inner wall of the pelvis, which was indeed
sometimes broached at operation, but so far there has been no progressive intrusion of the
head into the pelvis. Nevertheless it is possible that in some of these patients this may occur
in years to come.
New bone formation-Significant new bone formation in the capsule appeared to be present
in seven cases and was associated with a decreasing range of movement (Fig. 8). In four
cases there was virtual ankylosis but it was not necessarily painful.

DISCUSSION
The assessment of results following hip surgery is notoriously difficult to express if one is to
combine clarity and accuracy. The following are some of the factors which have to be taken
into account. I) The stage of the disease at the time of operation. Osteoarthritis tends to be
a progressive condition, but its rate of progress varies greatly from individual to individual.
It is always a matter of judgement-sometimes very difficult judgement-when to intervene
surgically. 2) The degree of muscle atrophy present, and the ability to re-educate deficient
muscles after operation. This is especially important in very stiff hips. 3) the patient’s
motivation-what the patient wants and expects to achieve after operation and to what

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 USE OF THE AUSTIN MOORE PROSTHESIS IN OSTEOARTHRITIS OF THE HIP 243

extent he is really prepared to take an active part in his own rehabilitation. 4) The presence
of concomitant disability. Degenerative disease of other joints, especially the other hip, spine
and knees, is important. Limitations ofgeneral health such as senility, obesity and cardiovascular
or respiratory deficiency must also be considered. 5) Technical considerations. 6) Complications
after operation. 7) Length of follow-up.
With so many variable factors it is impossible
to provide a truly “ homogeneous “ series of
patients. The shortcomings ofmany reports and
discussions on the results of arthroplasty were
well summarised by McKeever (1959) in his com-
ments on the final report of the Committee for
the Study of Femoral Prostheses of the American
Academy of Orthopaedic Surgeons.
ln this small series the following points
should be emphasised. Firstly, all cases were of
advanced and severely disabling or crippling
severity. as judged both radiologically and
clinically. Ofthe thirty hips assessed, twenty-four
had less than 50 degrees of flexion before
operation. The average duration of symptoms
was seven years, and most patients gave a story
of rapid final deterioration which had signalled
the necessity for radical surgical intervention.
As a series they were very different from
those. for instance, in Harris and Kirwan’s
(1964) report, which recorded the results of
osteotomy in early osteoarthritis. Secondly, in
- .. 8
the five cases in which an osteotomy was per- Case 8-Painless ankylosis of left hip fifteen
formed on one side and an Austin Moore months after Austin Moore arthroplasty. Note
the prosthesis deeply buried in the acetabulum,
prosthesis inserted on the other, the osteotomy and surrounding new bone formation.
was carried out on the less severely affected
side. Thirdly, the technique and post-operative management were standardised as already
outlined.
The results must be assessed against other methods of treatment appropriate to advanced
osteoarthritis. in general the success of any recognised radical operation will be greater in
strictly unilateral disease in relatively young patients vigorous both mentally and physically,
and in earlier stages ofthe disease, especially before marked stiffness and pain have developed.
In the short term it seems doubtful whether there is a great deal to choose between cup
arthroplasty and an Austin Moore prosthesis in such advanced cases, and only a few patients
may show more than marginal improvement over simple Girdlestone pseudarthrosis.
Moreover, there is a greater risk of complications after arthroplasty. Taking the longer view
there is the risk that many of the Austin Moore arthroplasties may in time begin to deteriorate
-particularly by progressive protrusion through the acetabulum. Salvage of such failures is
by no means a trivial matter, because extraction of an Austin Moore prosthesis well locked
home in the femur and protruding into the pelvis can be a formidable procedure.
For osteoarthritis it seems probable that the use of the Austin Moore prosthesis should
be limited to a relatively small proportion of cases, especially when the acetabulum requires
reaming. It should be reserved for otherwise active people preferably over sixty with unilateral
advanced disease, or at any rate where one hip is predominantly affected, as an alternative
to cup arthroplasty, or in preference to it, when the femoral head is grossly distorted or collapsed.

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244 M. B. HEYWOOD-WADDINGTON

Even in such cases a total hip replacement may well come to prove preferable and very
little more demanding technically.
There is no doubt that as a method of treatment for osteoarthritis the Austin Moore
prosthesis with reaming falls far short of the ideal. It seems that in the future we shall be
looking more and more to the development of total hip replacement and the use of acrylic
cement. This is giving promise of providing the conditions in which a stable painless artificial
hip joint can function satisfactorily for as long as is necessary.

SUMMARY

1. The early results of thirty Austin Moore arthroplasty operations with acetabular reaming
in twenty-five patients with advanced osteoarthritis of the hip have been investigated.
2. The radiological changes after insertion of a prosthesis have been studied.
3. There was a variable degree of improvement in all patients. There was a worth-
while improvement in function and relief of pain. Stability, however, was disappointing in
more than half (and in all the bilateral cases). An average of three-quarters of an inch of
shortening was found in the unilateral cases.
4. In such advanced cases the results of Austin Moore arthroplasty are probably of the same
order as for cup arthroplasty, and in many cases they show no more than marginal improvement
over pseudarthrosis.
5. It is concluded that at the present stage of progress in the development of arthroplasty
the use of the Austin Moore prosthesis with acetabular reaming has very limited indications.

I wish to express my thanks to Mr P. H. Newman for permission to examine his patients and for his
encouragement and advice throughout. My grateful thanks are also due to Mrs M. A. Glen Haig and the staff
of the Records Department, the radiographers and staff of the Radiography Department, and Mr R. J. Whitley
of the Photographic Department of the Institute of Orthopaedics, all at the Royal National Orthopaedic
Hospital, whose collective help has been unstinted.

REFERENCES

AUFRANC, 0. E. (1962): Constructive Surgery of the Hip. St Louis: The C. V. Mosby Company.
COVENTRY, M. B. (1964): Salvage of the Painful Hip Prosthesis. Journal of Bone and Joint Surgerl, 46-A, 200.
HARRIS, N. H., and KIRWAN, E. (1964): The Results of Osteotomy for Early Primary Osteoarthritis of the Hip.
Journal of Bone and Joint Surgery, 46-B, 477.
LAW, W. A. (1962): Late Results in Vitallium-Mold Arthroplasty of the Hip. Journal of Bone and Joint Surgery,
44-A, 1497.
MCKEEVER, D. C. (1959): Discussion on Final Report of the Committee for the Study of Femoral-Head
Prostheses of The American Academy of Orthopaedic Surgeons. Journal of Bone and Joint Surgery,
41-A, 883.
MOORE, A. T. (1959): The Moore Self-locking Vitallium Prosthesis in Fresh Femoral Neck Fractures.
Instructional Course Lectures. American Academy of Ort/iopaedic Surgeons, 16, 311.
SMITH-PETERSEN, M. N. (1939): Arthroplasty of the Hip. A New Method. Journal of Bone and Joi,zt Surgery,
21, 269.

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