What is a Thermal Capsular Shift?
A thermal capsular shift is a fairly recent technique for tightening up the ligaments of the shoulder for patients whose shoulders are unstable (see Patient Guide to Shoulder Instability). The shoulder is a ball and socket joint, and when unstable, the ball can slide part of the way out of the socket (subluxate) or it can come all the way out of the socket (dislocate). In all joints in the body there are ligaments (tethers of tissue) between the bones that control how much the bones glide or bend on each other. When the joint begins to subluxate or dislocated, these tethers get stretched and heal too long. This allows the bones to move too much in relationship to each other. Other structures in the shoulder can also be torn when the shoulder subluxates or dislocates, such as the labrum or the rotator cuff (see Patient Guide to Rotator Cuff Tears and Patient Guide to Labrum Tears). In the most common form of instability of the shoulder, which is where the shoulder dislocates all the way out of the socket, often the ligaments are stretched and the labrum is torn off of part of the socket.
In surgery to correct instability of the shoulder, the surgeon attempts to repair the damaged structures. If just the labrum is torn off of the bone, then the labrum has to be repaired back to the rim of the bone. If the ligaments are stretched then they have to be shortened in some way to eliminate the looseness in them. The traditional way of doing this is to make an incision on the front of the shoulder and move the muscles out of the way, and down by the joint to fix the labrum and loose ligaments. When the ligaments are shortened, they are moved or "shifted" to eliminate the laxity or looseness in them (see "Patient Guide to Shoulder Instability".) In the past fifteen years attempts have been made to do these repairs through smaller incisions using the arthroscope and small instruments. While arthroscopic techniques can be successful, it is controversial whether they can be as effective as the traditional open techniques.
In the quest for finding easier ways to tighten the ligaments, some surgeons tried to use lasers to tighten the ligaments. The idea was that the lasers would heat the ligaments, causing them to shrink and tighten. It was hoped that the ligaments would tighten enough to stabilize the joint without having to cut them and sew them back together, like in the open or arthroscopic techniques. Unfortunately these techniques never proved to be beneficial nor were they used by many surgeons.
Recently a new technique of heating the ligaments to make them shorten and tighten was devised using a different type of energy than laser energy. These techniques are called "thermal capsular shifts" since they are a way to "shift" or "tighten" the ligaments by using heat.
How does this new type of procedure work?
This procedure is a surgical procedure done under anesthesia (either a general anesthetic or a regional block of the whole arm) using the small incisions typical of arthroscopy of the shoulder (usually less than a centimeter in size). Through the small incisions a probe smaller than a pencil is inserted into the joint and its location in the joint is viewed with the arthroscope. The surgeon then directs the end of the probe to the ligaments where it touches them and causes them to heat and then shrink. The procedure takes twenty to forty minutes depending upon how many ligaments have to be tightened and depending upon if other things have to be corrected at the same time.
The heat probe works by creating electromagnetic energy, which heats the tissue. The interesting thing about this is that the tip of the probe does not get hot like you would expect, but rather it heats the tissue by exciting the molecules themselves in the tissue. The molecules in the ligament (called "collagen molecules") essentially vibrate; giving off energy which is expressed as heat. This causes the tissue to heat and shrink. One surgeon has said that it is analogous to "making bacon" in that the tissue shrinks, but there is not heat made anywhere except where the probe is located.
Research upon the exact effects of this type of treatment upon ligaments has only recently been published in the past two years. Under the microscope the heat causes the cells to die and the collagen molecules become larger as the heat causes it to denature or unravel. This is accompanied by a shortening of the tissue as the collagen contracts. These changes appear to make the tissue weaker initially, an effect that may last several weeks according to experiments done upon animals. As a result, the initial recommendations were to start moving the arm immediately after the surgery, but now it is recommended that the arm be held immobile for about three weeks (some motion is allowed but it is carefully controlled to prevent stretching the ligaments).
After the tissue is heated the body mounts a healing response to the changes in the tissue caused by the heating. In this healing response the body replaces the dead cells with alive, new ones, and the collagen is partially replaced. This process takes several months, and biopsies of the ligaments of patients who have had this surgery seem to show that the process is complete by nine months. It is interesting that the exact mechanisms of how thermal capsular shrinkage works are not entirely known, but early clinical results suggest that it does stabilize the shoulder.
When is this procedure indicated?
This procedure has become popular because of its simplicity and it is easy to shorten multiple ligaments at one time. Advocates of this procedure think that it has effectiveness for a variety of kinds of instability. For example, there is a theory that in athletes who throw a ball or use their arms overhead a lot in their sport (e.g. tennis or swimming) can develop tendinitis pain as a result of their sport. The theory is that they have pain in the rotator cuff tendons because their shoulders have over time become loose, and that the ligaments of the shoulder have gradually stretched out because of the demands of their sport. This kind of instability is "occult instability" because they do not feel subluxations or dislocations, but their main symptom is pain. When these patients have surgery the main findings are that their ligaments are stretched but there are no other abnormalities that might require a larger, open operation. Some surgeons feel that a thermal operation might be a good choice of operative procedure in this case since the only suspected abnormality is in the ligaments.
Advocates of the thermal capsular shift also think it may have particular usefulness in patients who have instability of the shoulder in more than one direction. This instability may be overt in that the patient may have subluxations or dislocations in several different directions, or they may be just loose in more than one direction as judged by the physician. This type of instability is called "multi-directional instability." Most patients with this type of instability can be effectively treated with physical therapy, but some patients require surgery. If they do need surgery, and if they have few findings at the time of surgery, except loose ligaments, then some surgeons feel a thermal capsular shift allows tightening of ligaments in more than one place (i.e. for the ligaments involved in instability in the front, back or inferior (downward) parts of the shoulder.) Some surgeons believe that the thermal capsular shift can be combined with repair of other structures if they are torn.
The last group where thermal capsular shifts may have effectiveness is in patients who have ligamentous laxity as part of other conditions, such as Ehlers-Danlos Syndrome or Marfan’s Syndrome. In these conditions the collagen of the ligaments is believed to be altered, so that the ligaments stretch more easily than when the collagen is normal. The effect of thermal shrinkage upon the collagen or tissues in these conditions has not been studied.
What is the postoperative recovery from surgery like?
Most patients go home the same day the surgery is done with an arm sling or immobilizer. Pain pills are needed for a few days to a few weeks, and cold therapy with ice packs or cryocuffs is usually recommended. Range of motion of the hand, wrist and elbow can begin immediately, and some restricted shoulder motion is allowed to prevent a frozen shoulder. However, motion of the shoulder without limits begins at three to four weeks. Full return of motion and strength varies but usually is within three months after surgery. Return to sports activities after depends upon many factors.
What are the results of surgery?
The exact results of surgical treatment of shoulder instability are difficult to ascertain since there have been no published papers of the results in medical publications which undergo close, peer-reviewed scrutiny. Results that have been anecdotal (in the sense that they have been presented in meetings or perhaps published as part of an article discussing the technique) suggest that the recurrence of instability is around ten to fifteen percent. The recurrence rate may be higher for forms of multi-directional instability according to one presentation at a scientific meeting, but the exact definition of multi-directional instability was not perfectly clear in that study. One study presented at a national orthopaedic meeting found that baseball pitchers who had a thermal capsular shift returned to throwing at about the same rate as if they had the capsule tightened using an open procedure. But that study did not scientifically compare the two groups and the patients were studied for only one year (minimum two years of follow-up after surgery is the standard).
Are there any problems with this technique?
The problems with this technique are similar to those seen with more conventional operations for shoulder instability. The most common concern with any operation for instability is recurrence of the instability, which happens in about 3-5% of patients who have an open procedure for instability. The exact recurrence rate after thermal capsulorraphy is not exactly known since there are no published reports using this procedure. A recent study at the Orthopaedic Surgery Convention in March 2000 reported a failure rate of around 20 percent for all types of instability (mostly multidirectional).
The second most common problem after conventional procedures is loss of range of motion, which usually is only around five degrees or less in most cases. However, in some cases the motion loss can be severe for reasons not entirely understood. There have been reports of patients getting stiff after thermal capsulorraphy in the literature but like after an open procedure, the incidence seems to be very small.
Nerve injury can be seen after any operation to stabilize the shoulder due to the proximity of the nerves to the joint capsule. When there is a nerve injury it usually is due to retractors that are placed near the nerve, so the nerve is only stretched a little. This type of stretch injury usually recovers with no problems. There have been reports of partial injury to nerves after the thermal capsular shift, presumably due to the heat penetrating all the way through the capsule. To our knowledge these injuries have been minor and all have recovered over time.
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