Minimally Invasive Shoulder Joint Replacement

Shoulder joint replacement is a surgical procedure to replace damaged bone surfaces with artificial components to relieve pain and improve functional ability in the shoulder joint. Shoulder joint replacement can be done by a traditional "open" approach or through a minimally invasive approach. The incision in minimally invasive shoulder joint replacement is about 5 cm compared to 17 cm with the traditional approach. Other 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.

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 goal of surgery is to relieve pain and improve mobility by replacing the damaged bone surfaces of the shoulder joint with artificial humeral and glenoid components.

Shoulder anatomy

The shoulder is a highly movable ball and socket joint allowing for various arm movements. The head of the arm bone or humerus, articulates with the glenoid socket of the shoulder bone or scapula. The two articulating surfaces of the bones are covered with cartilage which prevents friction between the moving bones. The rotator cuff is a group of four tendons that joins the head of the humerus to the deeper muscles and provides stability and mobility to the shoulder joint.

Indications

The decision to perform shoulder replacement via the traditional approach or the minimally invasive approach depends on the pathology of the individual and the experience of the surgeon. Exposure of the glenoid is often difficult even when the incision is long as in the traditional approach. Therefore, if the pathology of the patient is such that more exposure of 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 check the pathology of the patient the 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, the 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.

Surgical procedure

The surgery is performed under sterile conditions in the operating room under regional or general anesthesia.

• The patient lies in the 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 is 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 surgeon's preference.
• If the glenoid also needs to be replaced the 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 the 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.
• Before sending the patient from the operating room, an X-ray is taken to verify the correct fit (size and position) of the implant.

Post-operative Care

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 given 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.

Risks and Complications

Some of the possible risks and complications of minimally invasive shoulder 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.