History
Surface Replacement Arthroplasty of the Shoulder
S Copeland, L Funk, O Levy; 2002
1. Development of Shoulder Replacement
Modern shoulder replacement has developed in two different
sources. In Europe it has mainly evolved from massive replacement of
the proximal humerus for tumour [1]. Much of this work was done at
the Royal National Orthopaedic Hospital
in Stanmore in the 1950s and also in Germany [2]. However when the
diseased proximal humerus was removed the rotator cuff was often
also excised and hence the proximal humeral prosthesis was really
acting as a spacer. When attempting to use the arm actively these
prostheses would sublux upwards and forwards due to the unopposed
action of deltoid. Although functionally limited the long term
outlook for these prostheses was remarkably good. When this group at
Stanmore wished to develop a shoulder replacement for arthritis it
is with this background experience of tumour work that they decided
to developed a constrained joint. The Stanmore shoulder was widely
used for both osteoarthritis and rheumatoid arthritis. It’s design
looked remarkably like the design of hip replacements that were
available at that time (The McKee metal on metal prosthesis). Both the humeral and the glenoid side were cemented and the
joint was snap fit constrained. To prevent superior subluxation of
the humeral component, the glenoid component was built out from the
natural glenoid face and the centre of rotation lateralised. Under
modern biomechanical principals it would be predicted that this
would fail with the forces that would pass through the joint and
unfortunately this was true. The glenoid component did loosen and
the snap fit constrained design was prone to dislocation. Eventually
this constrained type of joint was abandoned. However, at this time
other joints were being developed that also pursued the constrained
ideal, both the Castle shoulder and the Liverpool shoulder had
reverse type of geometry as this was thought to improve range of
motion and power by lateralising the centre of rotation.
Unfortunately all these constrained designs had the problem of long
term loosening.
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In the USA, Dr Charles Neer was developing a shoulder replacement
for fractures of the proximal humerus [3]. He had initially been
working on the fracture service at Columbia Presbyter and was
impressed with the results of femoral hemi-arthroplasty for
subcapital fracture. He reviewed the results of severe fractures of
the proximal humerus and developed a classification of these, noting
that the four-part fracture did particularly badly as the head
fragment often underwent avascular necrosis way a the hip the
femoral head lost its blood supply because the retinacular vessels
were disrupted, the humeral head lost its blood supply. Because the
retinacular vessels were disrupted, the humeral head lost its blood
supply through fractures of the tuberosities and the muscle
attachments. This joint was an unconstrained hemi-arthroplasty on
the humeral side and represented a great advance in the treatment of
this type of fracture. He always stressed from the beginning that
this was a soft tissue operation and the prosthesis was there as a
scaffold to rebuild the shoulder around. Having gained good results
for the humeral hemi-arthroplasty he then developed a plastic
glenoid component for use in degenerative arthritis. The results of
this unconstrained prosthesis remained to this day the gold standard
by which other shoulder replacements are judged. The development of
a non-constrained joint really mirrored development of the hip
replacement.
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It was not long before modular prostheses were developed and then
cementless bony ingrowth prostheses (Copeland, Bi-Modular, McNabb),
but essentially these were all the same geometry as the Neer type
design. Following the work done by Roberts & Wallace in 1991 [4] and
Boileau and Walch in 1997 [5] the wide variation of anatomical
morphology at the proximal end of the humerus was noted and
prostheses have tried to mimic this. It was noted that the humeral
head was offset on the long axis of the humerus and if prosthetic
replacement was to mimic anatomy then the prosthetic humeral head
must be offset. Therefore any prosthesis that was not made
specifically for left or right shoulder could not directly mimic
anatomy. The so-called third generation prostheses (eg Tornier) were
developed in a modular way to allow for offset version and
angulation. But version can vary from -5 to +55 and the equipment to
do this and the stock of prostheses required makes this an extremely
expensive option.
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Hence the stemmed cemented prostheses have really developed in
Europe from tumour replacement and in the USA from fracture work.
Neither was specifically designed for the treatment of arthritis.
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