Fusing Together the Bones at the Shoulder Joint: A Reasonable Alternative for Selective Desperate Situations

The whole purpose of joints is to provide motion between segments of the skeleton. Why would we ever consider surgically eliminating motion at the shoulder joint? At first, it sounds a little crazy, doesn’t it? But believe it or not, in certain desperate situations, shoulder fusion is a very good alternative…

What do we mean by fusing the shoulder?

Most of you probably think of the physics of atomic particles when you hear the word fusion, like in “nuclear fusion”. Well,… the word “fusion” is used in the field of Orthopedic Surgery to describe the physical union of two or more bones. A more technical word to describe fusion of joints is “arthrodesis” (from the combination of two greek words: “Arthros” – joint, and “desis” – to bind together). The three bones that meet at the shoulder joint include the bone in the arm (humerus), the shoulder blade (scapula), and the collarbone (clavicle). The term shoulder fusion or shoulder arthrodesis refers to eliminating the joint between the humerus and scapula by having these two bones heal into a single one. The clavicle is typically left alone when shoulder fusion is performed (although some surgeons remove a small portion at the very end of the collarbone to aid with motion, as discussed below).

Radiograophs of a normal shoulder and after fusion.jpg
Normal shoulder (A) and fused shoulder (B)

The first thought that comes to mind when discussing shoulder fusion is “… but then, there is no motion!” Which is paradoxically true and not true at the same time. Let me explain myself. Did you know that in the normal shoulder, the ability to reach up with our hands as high as possible requires the humerus to rotate relative to the scapula, but also the scapula to glide on the chest wall? Classic teaching is that one third of the ability to get the hand up in the air is provided by motion of the scapula relative to the chest wall, whereas the remaining two-thirds of motion are provided by the joint between humerus and scapula (glenohumeral joint). The same is true (with different relative rates of contribution) when the arm is turned out (external rotation) or turned in (internal rotation). This explains the surprising fact that when the shoulder is fused, individuals can still move their hand in space to some degree. The more flexible the scapula is on the chest wall, the better the motion.

When is shoulder arthrodesis considered?

At the present time, shoulder arthrodesis is rarely performed. However, there was a time when this was the most common procedure performed by shoulder surgeons. Shoulder arthrodesis was initially developed for patients with tuberculosis involving the shoulder joint: it became the only way to handle bone tuberculosis prior to the development of modern antituberculosis drugs. Today, fusion continues to be the best solution for a few selected individuals with really bad shoulder problems.

Why would a patient choose to sacrifice shoulder motion? And by the same token, why would a surgeon recommend such a drastic solution to patients? The reality is that some individuals are in so much pain, or their shoulder is so damaged, that arthrodesis leads to a major improvement in their quality of life. Shoulder fusion may be considered for really bad infections, paralysis, or severe instability. It can also be considered after catastrophic failure of shoulder replacement, and in situations where replacement would be an option, but patients are way too young (but this is rare).

Many of the situations where fusion was considered in the past are better off with joint replacement surgery, especially after the development of reverse shoulder arthroplasty However, replacement may fail in the presence of persistent infection that cannot be cured, or when there is absolutely no muscle to power the replacement (due to nerve or muscle damage).

How exactly is shoulder fusion done?

Fusion is achieved by creating the same conditions that lead to healing of a broken bone: the goal is to have the humerus heal to the scapula. The surgeon needs to remove any cartilage that may still remain covering the humeral head or the glenoid socket. The humeral head is contoured to fit against the socket and under the so-called acromion (the bony roof of the shoulder). Once the raw bone surfaces are positioned against each other, the bones are compressed and stabilized using plates and screws. It is key that the surgeon fixes the two bones together in a position that maximizes the patient’s ability to use their hand. Most of the time, the shoulder is fused with some internal rotation, forward flexion, and some separation from the trunk.

Shoulder arthrodesis.jpg
Glenohumeral arthrodesis

In patients missing a fair amount of bone prior to fusion (as a consequence of prior injuries or surgery), addition of bone graft may be needed; small amounts of bone may be replaced with cadaver bone, but larger amounts of bone typically require transplanting the patient’s own bone graft from the waist-line (iliac crest bone graft) to the shoulder. After surgery, the whole arm needs to be supported using a brace or a cast until healing is confirmed. Healing typically takes two to four months.

Shoulder spica cast
After surgery, the shoulder is immobilized in a cast or brace until healing

What to expect as a patient

Shoulder arthrodesis is a substantial surgical procedure. Before embarking into it, candidate individuals need to discuss at length the nature of the procedure, any possible alternatives, and the expected outcome with their shoulder specialist. Wearing a cast or brace for a number of weeks is not fun, but most of the time it is critical for a successful union, so patients need to be mentally prepared and compliant.

If things go well, most patients are satisfied because pain relief after shoulder arthrodesis is very reliable. When someone has suffered from severe, chronic shoulder pain despite several previous failed surgeries, the experience of not having pain any more can make the loss of motion really worth it.  Most patients are able to raise their hand to the horizontal, and easily reach their face, the front of the trunk, and the opposite shoulder. However, the ability to reach out and particularly reaching behind the back, is very limited.

Range of motion after fusion
Arm motion after shoulder fusion is limited but not completely eliminated

Any complications possible?

In addition to the well-understood complications of any shoulder surgical procedure (infection, nerve damage, etc), the most common complications of shoulder fusion are lack of union, and fracture of the bone in the arm. Getting the two bones to heal is the whole purpose of the procedure, but it does not always happen. To maximize the chances of union, patients should be compliant with their restrictions and cast or brace use. In addition, any modifiable factors that may impair bone healing must be addressed: smoking, poor nutrition, and uncontrolled diabetes are most common. Most surgeons will not perform the procedure on patients that are actively smoking.

The other potential worrisome complication is a fracture of the humerus. Since motion at the true shoulder joint is gone, it is extremely difficult to protect the arm from injury in an accidental fall. A bad accident can cause a fracture of the humerus, typically just below the lower end of the plate. Some of these fractures will heal in a cast, but some require surgical fixation.

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