Rheumatoid Arthritis
Of The Glenohumeral Joint
Rheumatoid arthritis (RA) is an inflammatory
disease based within the joint lining (synovium). This inflam- matory disease
can be very destructive to the articular cartilage and bone but also affects
the surrounding soft tissues. Shoulder RA specifically can cause severe
thinning and then tearing of the rotator cuff and biceps tendon as well as
progressive destruction of the articular cartilage on both sides of the joint.
Unlike osteoarthritis, RA is a
nonproliferative arthritic condition and there is minimal new bone formation,
resulting in minimal osteophyte formation. This feature is important in
distinguishing between the two most common causes of shoulder arthritis. There
can be progressive bone loss with osteopenia and demineralization of the
humeral head. This is similar to patients with rotator cuff arthritis. Patients
with osteoarthritis have hard bone that becomes whiter on radiography related
to new bone formation. Glenoid bone loss is often centered within the glenoid
fossa, resulting in medial migration of the humeral head. Osteoarthritis shows
more eccentric glenoid wear primarily on the posterior glenoid. In many cases
of rheumatoid arthritis, there is superior migration of the humeral head seen
on radiographic views that is associated with destructive changes of the
rotator cuff. Rheumatoid arthritis, rotator cuff tear arthritis, and
crystal-induced arthritis (hydroxyapatite deposition disease, “Milwaukee
shoulder”) produce large rotator cuff tears and superior migration of the
humeral head, which, in turn, can result in asymmetric superior glenoid bone
loss. All of these findings are best seen on routine radiographs. CT is also
helpful in demonstrating these bone changes. The synovitis and joint effusion
and the rotator cuff damage are best seen with MRI.
The humeral head can show lack of
proliferative osteophyte formation but severe erosive changes of the articular
surface. A treatment option for younger patients is a conservative humeral
replacement maintaining most of the humeral bone stock using a surfaceonly
arthroplasty (no stem). Avoidance of a glenoid prosthetic plastic component may
be achieved by use of a meniscal allograft on the glenoid surface. This remains
a controversial method of treatment because the results are not as consistent
or predictable as those for traditional complete prosthetic joint replacement
(total shoulder arthroplasty). These patients can be very young, and a
traditional complete joint replacement can have its own difficulties with
long-term survivorship, and a more conservative joint replacement avoiding the
humeral stem and plastic glenoid prosthetic component can result in good
clinical outcome and therefore remains a surgical treatment option for the
young active patient.
More traditional treatment of rheumatoid
arthritis when the rotator cuff is intact is anatomic total shoulder
arthroplasty. The rotator cuff is intact, and this is treated with a cemented
stemmed total shoulder arthroplasty. When the rotator cuff is damaged and there
is associated superior migration of the humeral head, hemiarthroplasty is
preferred over total shoulder replacement. With superior migration of the
humeral head and anatomic total shoulder replacement, the prosthetic humeral
head will remain superiorly displaced and will therefore contact only the
superior part of the glenoid component, resulting in a continuous eccentric
loading of the glenoid component. This will result in early loosening of the
glenoid component. In some cases with severe rotator cuff deficiency a reverse
total shoulder replacement is the best option to relieve pain and improve
function related to rotator cuff deficiency, while avoiding the eccentric
loading conditions of an anatomic-type shoulder replacement.
Many of the newer disease-modifying
biologic drugs block the factors that result in the inflammatory mechanism that
lead to joint destruction. For this reason the need for shoulder replacement in
patients with rheumatoid arthritis has markedly decreased in the past 10 to 15
years.
