Shoulder Anatomy

The shoulder is a ball and socket joint that allows various arm movements. The head of the upper arm bone (humerus) articulates with the glenoid cavity of the shoulder bone (scapula). The two articulating surfaces of the bones are covered with cartilage which prevents friction between the moving bones. A rotator cuff is a group of four tendons that join the head of the humerus to the deeper muscles and provides stability and mobility to the shoulder joint.

What is Minimally Invasive Shoulder Joint Replacement?

Shoulder joint replacement is a surgical procedure that replaces damaged bone surfaces with artificial humeral and glenoid components to relieve pain and improve functional ability in the shoulder joint.

It can be performed by a traditional open approach or through a minimally invasive approach. The incision of a minimally invasive shoulder joint replacement is about 5 cm compared to 17 cm with the traditional approach.

Indications for Minimally Invasive Shoulder Joint Replacement

When conservative measures such as medications, injections, physical therapy, and activity changes do not help relieve pain from conditions such as arthritis, avascular necrosis, and humeral head fractures, then shoulder joint replacement is considered as a treatment option.

The decision to perform shoulder replacement via the traditional approach or the minimally invasive approach depends on the pathology. Exposure of the glenoid is often difficult even when the incision is long as in the traditional approach. Therefore, if the pathology is such that more exposure to the joint is required for the surgical treatment then a traditional approach is preferred.

The minimally invasive approach is generally preferred when the problem can be rectified by replacement of only the humeral head such as with the following conditions:

• Shoulder arthritis with not much damage to the glenoid and with only small bone spurs
• Four-part humerus fractures with intact rotator cuff
• Avascular necrosis of the humerus, resulting in tiny multiple fractures

Diagnosis

To determine the pathology, your surgeon orders an X-ray of the shoulder in the anteroposterior and axillary view. The axillary X-ray is especially important to check the condition of the glenoid. In case the condition is not very clear, your surgeon orders a CT scan of the shoulder to provide more detailed cross-sectional images of the bone and soft tissue of the shoulder including the glenoid.

Minimally Invasive Shoulder Joint Replacement Procedure

• The surgery is performed under sterile conditions in the operating room under regional or general anesthesia.
• You will lie in a beach chair position with the operated arm held by an arm positioner.
• A 5-cm incision is made over the shoulder joint.
• The muscle overlying the shoulder bones are cut just enough to expose the head of the humerus.
• The humeral head is dislocated and released from the capsule.
• The arthritic or damaged humeral head is cut at the neck and removed.
• The humeral component is matched in diameter and thickness to the natural humeral head.
• A bone tunnel is made in the humerus to take the humeral stem.
• The humeral stem is then inserted into the humerus. This may be press-fit, relying on the bone to grow into it or cemented, depending on several factors such as bone quality and your surgeon’s preference.
• If the glenoid also needs to be replaced, your surgeon then proceeds to the preparation of the glenoid component.
• The glenoid is sized for the appropriate implant.
• Next, the glenoid is prepared to take the artificial component by drilling holes in the glenoid to fix the plastic glenoid component.
• Bone cement is placed in the holes and the glenoid implant is inserted.
• Once the glenoid is replaced with the plastic component, your surgeon works on the humeral component.
• The correct sized metallic humeral component is then fixed to the humeral stem.
• The soft tissue covering the joint is sutured back together and the incision closed with absorbable sutures.
• An X-ray is taken to verify the correct fit (size and position) of the implant.

Postoperative Care for Minimally Invasive Shoulder Joint Replacement

After the surgery, your arm will be placed in a sling, which you will wear for 2-4 weeks while your shoulder heals. Pain medications and antibiotics are administered to keep you comfortable and prevent infection.
The rehabilitation program includes physical therapy, which is started soon after the surgery and is very important to strengthen and provide mobility to the shoulder. Follow your therapist’s instructions for home exercises to achieve the best outcome.

It is critical to follow the postoperative instructions given to you by your surgical team. The postoperative instructions include the following:

• Rest your shoulder. No lifting, pushing or pulling for the first few weeks.
• Perform home exercises as advised by your therapist.
• Do not overuse your shoulder while healing as it may result in severe limitations in motion later.
• Do not drive a car for the first few weeks after the surgery.
• Avoid getting the incision wet until fully healed.

Advantages of Minimally Invasive Shoulder Joint Replacement

The benefits of minimally invasive surgery include less damage to the soft tissues and underlying muscles, enabling a faster recovery with less pain and a smaller scar. Blood loss during the surgery is also less and complications after the surgery are fewer when compared to the open technique.

Risks and Complications of Minimally Invasive Shoulder Joint Replacement

Some of the possible risks and complications of minimally invasive shoulder joint replacement include infection, nerve injury and prosthesis problems. Most of these can be treated successfully; however, prosthesis problems such as excessive wear, loosening of components or dislocation may require additional revision surgery.