In contrast to a frozen shoulder, where the cause of stiffness is only related to tightness of the soft tissues, the arthritic shoulder is stiff because of the loss of the normal concave shape of the socket (the glenoid) and the normal convex shape of the ball (the humeral head). Compare the x-rays of an arthritic shoulder shown below to those of the normal shoulder shown in our March 22 post.
Here is the AP view showing the flattened humeral head and glenoid.
Here is the axillary view showing the socket wear and flattening of the joint surfaces.
Here is a CT (Cat Scan) showing even better the irregular joint surfaces and the bone spurs on the back of the humeral head that block normal joint rotation.
When shoulder arthritis gets to this point, physical therapy and injections are unlikely to improve the function of the joint. Surgical treatment may be indicated to restore the roundness, stability and load transfer characteristics of the joint surfaces as well as balancing the soft tissues around the joint.
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If we look back at the March 23 post, we see the joint space was lost and bone responded to osteoarthritis by building up new bone (osteophytes), this is can be called a hypertrophic response. By contrast in conditions such as chondrolysis the joint space is lost but the bone does not respond, this can be called an atrophic response.
The image above is the AP X-ray of a recent patient who developed post arthroscopic glenohumeral chondrolysis. In contrast to the X-rays of a patient with degenerative joint disease shown in the March 23 post, there are minimal bone spurs and the density of the bone is reduced. The two white arrows are suture anchors used in the arthroscopic procedure.
The image above is the Axillary X-ray of the same patient showing again the atrophic response of the bone to chondrolysis. Additional examples can be see here.
A recent post on the causation of chondrolysis can be found here
The lack of a hypertrophic response in chondrolysis may be one of the reasons that total shoulder arthroplasty may be the preferred joint replacement in this condition as opposed to procedures that do not replace both the ball and socket aspects of the joint.
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The image above is the AP X-ray of a patient from our surgical schedule this week with osteoarthritis (degenerative joint disease) of the shoulder. Note the loss of the normal joint space, the flattened joint surface and the bone spurs above and below the joint.
The image above is the Axillary X-ray of our patient with osteoarthritis (degenerative joint disease) of the shoulder. Note the loss of the normal joint space and the displacement of the ball towards the back of the socket (downward on this image) so that the 'golf ball' is not sitting centered in the 'tee'.
The image above is the AP view of this shoulder in the recovery room after a ream and run procedure. Note the ball of the humeral prosthesis sits centered in the contoured glenoid bone. The staples for wound closure and the drain are seen at upper left.
The image above is the Axillary view of this shoulder in the recovery room after a ream and run procedure. Note the ball of the humeral prosthesis sits centered in the contoured glenoid bone. The 'golf ball' is back in the 'tee'.
In the normal shoulder, the ball of the humeral head and the glenoid socket of the scapula are covered with smooth articular cartilage. This cartilage gives the joint a coefficient of friction less than that of an ice skate on ice. It is this cartilage that is destroyed in shoulder arthritis.
Cartilage cannot be seen on X-rays, but the thickness of cartilage can be detected by observing the separation of the bones, the 'radiographic joint space'.
Let's take a look at how the shoulder should be x-rayed to diagnose shoulder arthritis and to plan a joint replacement.
In the shoulder, two X-ray views are essential for determining the 'joint space', the AP (anteroposterior) and the axillary views.
An AP view of a normal shoulder looks like this:
and an axillary view of a normal shoulder looks like this:
In each view one can see the separation of the ball from the socket due to the presence of cartilage in this normal right shoulder.
These views must be taken carefully to make sure that poor technique does not hide the true condition of the joint.
In the normal shoulder, the ball of the humeral head and the glenoid socket of the scapula are covered with smooth articular cartilage. This cartilage gives the joint a coefficient of friction less than that of an ice skate on ice. It is this cartilage that is destroyed in shoulder arthritis.
Cartilage cannot be seen on X-rays, but the thickness of cartilage can be detected by observing the separation of the bones, the 'radiographic joint space'.
Let's take a look at how the shoulder should be x-rayed to diagnose shoulder arthritis and to plan a joint replacement.
In the shoulder, two X-ray views are essential for determining the 'joint space', the AP (anteroposterior) and the axillary views.
An AP view of a normal shoulder looks like this:
and an axillary view of a normal shoulder looks like this:
In each view one can see the separation of the ball from the socket due to the presence of cartilage in this normal right shoulder.
These views must be taken carefully to make sure that poor technique does not hide the true condition of the joint.
This is a cross-section of a normal left shoulder provided by my friend Chris Jobe. Front is up and the side of the body is to the right. The ball shaped object in the middle is the head of the humerus. The triangular object at the lower left is the glenoid socket. The reddish tissue on either side of the glenoid represent the rotator cuff muscles that hold the ball in the glenoid socket. The reddish tissue above and to the right of the humeral head is the deltoid muscle.
One can see how shallow the glenoid socket is - this allows of a great range of motion of the shoulder, but also puts the joint at risk for dislocation. Even though it is shallow, the glenoid concavity is critical to the stability of the joint. Note the thin layers of cartilage covering the joint surfaces of the humeral head and glenoid. It is this cartilage that enables smooth motion of the normal shoulder. It is this cartilage that is destroyed in shoulder arthritis.
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