Shoulder Impingement Syndrome and Tears of the Rotator Cuff
Shoulder impingement is a very common problem in which the tendons of the rotator cuff (predominantly supraspinatus) rub on the underside of the acromion. This causes pain due to the repeated rubbing of those tendons and it is especially bad in certain positions of the arm. In particular it is difficult to put the arm behind the back and to use it in the elevated position. This makes it difficult to drive, change gears, hang clothes, comb one’s hair, and even to lie on the affected shoulder.
The cause of this problem can be:-
- A muscle imbalance problem due to poor functioning of the rotator cuff tendons themselves; thus allowing the arm to ride up and rub on the acromion squashing the rotator cuff tendons in the process.
- A mechanical problem where the space for the tendon is inadequate. One way this can occur is with an injury to the tendon itself which causes swelling of that tendon such that it becomes too large for the space at hand (primary tendonitis with secondary impingement). Alternatively the space itself can be narrowed, usually where the acromion itself is large and prominent (primary impingement with secondary tendonitis). A large acromion can occur as part of normal growth or later in life spurs can develop along the front of the bone and can stick into the tendon. If this is bad enough these spurs can actually dig into the tendon to such an extent that the tendon becomes eroded and ruptures.
How Does the Shoulder Work?
The shoulder, like the hip, is a ball and socket joint (like a tow bar). Unlike the hip however, the socket is very small and is not big enough to hold the head of the humerus in place. This gives the joint a large range of motion but as a consequence it also means that it is potentially unstable. To function normally, muscles on both sides of the joint must work together to hold the joint in place during movement. This means that when the deltoid (see diagram) lifts the arm out from the side of the body, the supraspinatus and other muscles of the rotator cuff must pull down on the top of the humerus. This causes a levering out of the humerus with the rotator cuff muscles working in conjunction with the deltoid. The rotator cuff thus prevents the deltoid from driving the humerus up into the overhanging acromion.
In the normal shoulder this mechanism is so finely tuned that it always keeps the reaction force of the humerus at right angles to the joint. The joint therefore is always stable unless taken unawares.
How Does the Problem Start?
The rotator cuff tendons can be injured by a single traumatic event such as a fall onto the point of the elbow (which drives the humerus up into the acromion and squashes the tendons), a fall onto the point of the shoulder or a traction injury. A single incident may not always be the cause however and the tendons can be injured by overuse activities such as swimming, or jobs involving raising of the arms for long periods of time (ceiling fixing or plastering). Where impingement (a narrow gap) is the primary problem the tendon recovers well and hence the chances that a normal shoulder will result is about 95%. Where tendonitis (a tendon injury or tendon inflammation) is the primary problem and the impingement develops because of the swelling of those tendons surgery seems less effective. A successful outcome here is only seen in about 85% of cases or less. Here the tendons seem to have more intrinsic damage and take longer to recover. That recovery may also be less complete leaving minor symptoms. As the rotator cuff muscles are small in comparison to the deltoid they fatigue easily and hence can no longer resist the upward thrust of that muscle. With the deltoid now overpowering the rotator cuff muscles the reaction force starts to be upward rather than across the joint (see diagram). This means that the cuff tendons start to become squashed when the arm is raised. Thus damage to the tendons begins, and the symptoms like the damage may come on slowly, gradually becoming worse.
MRI showing rotator cuff impingement and subacromial bursitis
MRI showing a rotator cuff tear
MRI showing a rotator cuff tear
Why Does it Progress?
Once the tendons have been damaged they become inflamed and swollen and thus narrow the gap between the head of the humerus and the acromion even further. As this occurs impingement occurs more easily and with less movement. The ache may thus become worse and may occur with smaller movements or even constantly. This is especially noticeable at night. With time the problem becomes worse and the damaged cuff continues to impinge and becomes increasingly inflamed and sore. With this increase in pain there is a concomitant decrease in function, thus causing more and more muscle imbalance, further impingement and a spiralling of problems.
Is Age a Factor?
Although not strictly age related, it can generally be said that different age groups tend to have different types of pathology at presentation even though we believe that the course of the disease is similar in each case. Usually those under 25 years present at the stage of swelling and inflammation, those between 25 and 35 present with fibrosis and scarring, and those over 35 present with tendon degeneration and sometimes tendon rupture. The problem becomes increasingly common with age as spurs develop on the anterior acromion and by the age of 65 years this is an extremely common condition.
What About the Other Shoulder?
In cases where the primary problem is the shape or size of the acromion (primary impingement) it would seem reasonable to assume that the opposite shoulder might be similar. Studies in fact show that this is the case 60% of the time and hence the chances of the other shoulder becoming involved to some degree is of that order.If the primary problem is an injury to the tendon rather than a narrow gap for the tendon (primary tendonitis), then the other shoulder is likely also to have a normal gap. In this situation therefore the other shoulder is almost never involved. What is the Treatment? All those in stage 1 (swelling and inflammation – an acute injury) and about half of those in stage 2 (fibrosis and scarring – chronic problem) can be treated by conservative means. This means treatment for the local pain and swelling (which may include injection of an anti-inflammatory such as cortisone) and a therapy program to re-balance the shoulder by strengthening the supraspinatus and other rotator cuff muscles. Once these muscles are functioning again they will hold the shoulder down and prevent further impingement. The tendon injury will then gradually resolve, or settle.Those with more advanced disease generally will come to operative treatment. This includes long standing problems, rotator cuff tears and cases where the acromion is so large that impingement will clearly continue unless the bone is trimmed to widen the gap for the tendons.
The surgery for this condition is called sub-acromial decompression. The main part of this procedure is called an acromioplasty whereby the acromion is reshaped and the prominent areas underneath are removed to increase the size of the space beneath it. This is performed as an arthroscopy (through a telescope) which means that the shoulder itself is never actually opened. This means that less than 24 hours is needed in hospital. Despite a good early range of motion however it has been found that most shoulders do not show marked improvement in pain for 2 or 3 months and thereafter they gradually improve over 6 – 9 months. It is thought that the reason for the delay in recovery is that the tendons still have to recover even after any rubbing has ceased and like tendons elsewhere this takes several months and involves a fair degree of rest. The success rate of subacromial decompression is 90% at one year from surgery.
Rotator cuff tear
Removing the front of the acromion
The front of acromion removed
Reducing the rotator cuff to its insertion
Preparing hole for suture anchor
Enlarging hole for suture anchor
Suture anchor insertion
Suture attached to anchor emerging from bone
Suture through the rotator cuff
Rotator cuff reattached
Rotator Cuff Repair
If there is a major tear of the tendons, then an attempt should be made to repair this if possible. If the tear is very large then this sometimes cannot be performed, but in most cases it is possible. Once the stage is reached where the tendons require a large repair, the results tend not to be as good as they are when the tendons are intact or when only a small repair is needed. Although pain relief can often be achieved in the more severe cases by decompression and clean up of the tear, without those tendons functioning the shoulder will be weak and some of the shoulder active movement may be lost. Rotator cuff repair is always preceded by sub-acromial decompression, this being necessary to both remove any damaging spurs and also to increase the space to allow for the repair. Almost always the decompression can be done as an arthroscopic procedure which is then followed by an arthroscopic repair of the cuff tendons. Whilst this is more complicated than doing the whole procedure open it does have many advantages for the patient. An arthroscopic procedure allows for better strength post-operatively, much less pain and earlier motion.The tendon repair is generally done by suturing the tendon ends onto the bone using plastic bone anchors and permanent stitches or sutures. Healing is slow and it takes about 8-12 weeks for the repair to be strong enough to allow the arm to be raised up under its own power. Attempts to do this before that time may result in breakdown of the repair. Results of repair are good provided that the tendon heals into the bone satisfactorily. Pain relief is almost universal however arm function and power return is related to the quality of that repair. The tendon is repaired if this is technically possible and the tendon end is not too retracted. Scanning gives some idea about the degree of retraction but the tendon has to have some ‘elasticity’ to allow it to be pulled back to where it belongs. It is only possible to decide whether or not the tendon is repairable at the time of surgery.
It is possible to do a decompression to stop rubbing of the tendons and yet leave a tendon tear unrepaired. The results of this however are not as good as a decompression with tendon repair and this procedure is reserved for patients whose general health and low demands outweighs the need for the best possible result.
Rotator cuff inflammation
Rotator cuff split to allow calcium removal
Soft calcium deposit coming from the rotator cuff
Potential Complications of Surgery
Fortunately, complications with this type of surgery are uncommon. The most likely is that of bleeding and bruising and this is because the surgery is being performed in an area that is very vascular and does bleed easily. Mostly the problem is minor and self limiting, but very occasionally a bruise is large enough to require exploration and drainage. Clots in veins (deep vein thromboses or DVTs) and the spread of these to the lungs (pulmonary embolism or PE) are very uncommon in all upper limb surgery but we do use stockings and leg pumps after surgery to further reduce these risks.
Infection is very uncommon, with only a small percentage of people even developing a minor superficial wound infection. This rarely requires anything more than a few days of antibiotics to settle, and it does not interfere with the repair. Deep infection occurs in less than 1% of cases, and certainly, this has become very uncommon since all patients undergoing this procedure have prophylactic antibiotics given to them before the commencement of their surgery. If deep infection does occur it may require removal of the bone anchors and other hardware, but generally the repair still succeeds.
Following subacromial decompression 2 – 3% of individuals develop a frozen shoulder. This usually develops within 4-6 weeks of surgery and the shoulder becomes increasingly painful and stiff. This should be reported immediately as steroid injections rectify this problem rapidly. Some studies suggest that approximately 3% of individuals feel that their shoulder is more painful or weak following rotator cuff repair.
The Physiotherapy Program
Therapy consists of two factors. The first is to avoid further damage to the tendons and the second is to strengthen the rotator cuff tendons and make them functional. This means stopping all activities that cause pain and for swimmers and throwing athletes, this may also mean a style modification if that is possible. Rest of the injured shoulder may be accompanied by local heat or ultrasound and sometimes an anti-inflammatory agent. As pain settles a strengthening program is begun with emphasis on strengthening supraspinatus and infraspinatus which are the main two muscles involved in this process. Often it is not possible to work on these muscles straight away and supraspinatus exercises particularly may cause pain. If this is the case then scapula stabilizing exercises will need to be done first and this will require the supervision of a therapist skilled in this area. Supraspinatus can be strengthened by holding a light weight (1/2 kg – such as a full soft-drinks can) in the hand, straightening the arm by the side and turning the hand in until the thumb points to the floor. The arm is then taken out from the side and slightly forwards and raised up about 45 degrees (it must not be raised into the area where pain is felt). The weight is then held for a second and then lowered, resting before the next lift. Ten such lifts make up one set and the number of sets is increased with training to about 15. Between sets the weight should be put down to allow the muscle and tendon to fully recover. Infraspinatus can be strengthened by lying on the good side and holding the weight in the upper hand. With the elbow locked at the side and bent up to 90 degrees, the weight is then lifted until the forearm is parallel to the floor. As with the other exercise, sets of 10 can be performed without ever getting into the area where pain begins.
Supraspinatus Strengthening Exercise – This is performed as illustrated above, with the arm not being raised more than 45 degrees at any part of the program. If this exercise causes pain it should not be introduced until later on in the program. When the pain is under control and the shoulder has improved to a stage whereby a return to normal activities is possible, the range can be extended along with other exercises and stretches. This will require supervision by a physiotherapist and will be arranged for you when it is necessary.
What if the Rotator Cuff is not Repairable?
If the rotator cuff is not repairable it is possible to improve your symptoms of pain and to some extent improve your range of movement through the use of a subacromial spacer or a limited resurfacing of the greater tuberosity of the humerus. The operation involves an overnight stay and the use of a sling for the period of a week.
Hemicap on the greater tuberosity of the humerus for a non reconstructable rotator cuff tear.
General information about anaesthesia and arthroscopic shoulder surgery can be found HERE.
For more information on rehabilitation following rotator cuff repair, please click the button