Arthritis can be a debilitating sequela of chronic shoulder instability and surgical stabilization. These patients are often young, and conservative options are limited. Arthroplasty in these patients is often technically more difficult than in patients with primary osteoarthritis. There is often distortion of anatomy, contractures, and decentering of the joint. The limited reports of the results of shoulder arthroplasty in patients with arthritis of instability or instability surgery reveal relatively high failure and complication rates. Careful preoperative planning and surgical technique are critical to achieve a successful outcome.
Prevent arthritis by recognizing recurrent instability and treating the patient appropriately without over tightening the soft tissues.
Carefully evaluate patients with arthritis of instability, including prior surgical procedures.
Perform a thorough preoperative assessment of the static (ligaments, labrum) and dynamic soft tissue stabilizers (muscles, tendons), as well as the bone quality and orientation.
Anatomic reconstruction of the glenohumeral joint with meticulous soft tissue balancing is critical.
Optimize function and prevent injury during healing with customized rehabilitation.
Examine for concomitant instability.
Understand prior surgical intervention (anatomic versus nonanatomic reconstruction).
Preoperative radiographic evaluation should include three-dimensional studies such as computed tomography arthrogram and/or magnetic resonance imaging arthrogram.
Soft tissue releases should be performed as needed to allow adequate exposure.
Restoration of anatomic humeral position: height, offset, version, inclination and head size.
Placement of glenoid component in neutral version and inclination.
Soft tissue balancing.
Secure, strong repair of the subscapularis.
Placement of the humeral component in excess anteversion or retroversion may lead to postoperative instability or limitations in motion.
Excess humeral offset from varus stem position or a head that is too large may cause rotator cuff attenuation, pain, glenoid loosening and limited motion.
Placement of the glenoid component with abnormal version or inclination can lead to instability, edge loading, and early component failure.
Improper soft tissue balancing may lead to instability and limited motion.
Failure of the subscapularis may occur due to poor tissue quality, poor repair technique, or overly aggressive rehabilitation.
HISTORY AND SCOPE OF THE PROBLEM
Traumatic shoulder dislocation is a relatively uncommon disorder with a prevalence of less than 2%. Historically, patients were treated conservatively, with surgery reserved for chronic and recurrent cases of instability. Recently some surgeons have proposed early surgery in young, highly athletic patients to avoid a documented high incidence of recurrent instability.
The development of post-dislocation arthropathy is well documented. Marx et al. found that the rate of shoulder arthritis was 10 to 20 times greater in patients who dislocate. It is unclear whether the subsequent arthritis is secondary to the primary dislocation or the resultant instability surgery. Hovelius et al. studied 208 patients with primary anterior dislocation over 10 years. Twenty-three (11%) had mild arthropathy and 18 (9%) had moderate or severe arthropathy. Interestingly, patients with one recurrence had the same degree of arthropathy as those patients with multiple recurrences or those who had been surgically treated.
Treatment of patients who develop osteoarthritis secondary to shoulder instability presents several challenges. First, patients with prior open anterior shoulder stabilization or chronic dislocations may have distorted anatomy and soft tissue contractures. Second, significant bony deficiencies of the glenoid rim or proximal humerus may be present, especially in patients with chronic or locked dislocations. Moreover, postcapsulorrhaphy arthritis may present in relatively young patients, making treatment decisions difficult.
Several factors must be taken into account when considering total shoulder arthroplasty (TSA) in patients with prior shoulder stabilization procedures. These include patient expectations, the type of procedure that was previously performed, the cause of the arthritic changes, the current stability of the joint, the bony quality and orientation, and the integrity of the soft tissue envelope.
A thorough history must be obtained in order to determine the patient’s primary complaint: pain, weakness, instability, or loss of motion. This must be considered in the context of the patient’s current and future demands on the shoulder. The surgeon should determine the indication for the stabilization procedure, the type of procedure that has been performed, whether it was anatomic or nonanatomic, and whether it included repair only of the soft tissue or whether bony defect repair was included as well. The surgeon should also evaluate the outcome of the stability procedure, namely, whether recurrent instability is present. Obtaining prior operative reports may be very helpful because documentation of tissue quality, bony defects, and arthrosis may be present.
Physical examination should include a systemic evaluation of the shoulder, upper extremity, and cervical spine. It should begin with an inspection for previous surgical scars, abnormal posture, and muscular atrophy. A careful assessment of the active and passive range of motion of the shoulder is performed and is compared with the contralateral shoulder. Scapular tracking should be observed because unrecognized scapular winging or dyskinesia may contribute to glenohumeral instability. In cases of loss of motion, the reason for that limitation should be evaluated (whether by soft tissue contracture, bony impingement, or hardware impingement). The stability of the joint should be assessed, documenting the degree and direction of any instability. The load-and-shift and sulcus tests are performed in the upright position, evaluating for anteroposterior and inferior translation, respectively. A sulcus test in 30 degrees of external rotation provides information about the competency of the rotator interval capsule. While supine, the modified load-and-shift test is used to assess stability of the joint. However, patients with severe arthritis and pain may not tolerate stability testing. Muscle strength should also be examined, ideally with a dynamometer, with particular attention to rotator cuff and deltoid function. Prior open stabilization procedures may violate the subscapularis. The lift-off and belly-press tests should be performed to assess for subscapularis insufficiency.
Careful attention should be paid to identifying the particular motions and shoulder positions that elicit pain or apprehension and a sense of instability. A click or clunk during the examination may indicate a loose body, a cartilage or labral injury, or an active subluxation-relocation process. Finally, a detailed neurologic examination of the upper extremity should be performed, and if a deficit is suspected, an investigation with electrodiagnostic tools should be done.
A standard radiographic series should be performed in all patients, including a 40-degree posterior oblique view in internal and external rotation, a lateral Y scapular view, and an axillary view. Plain radiographs are not reliable for calculating glenoid version due to variations based on technique and patient positioning. Several authors have therefore recommend a preoperative computed tomography (CT) scan. The preoperative CT scan is also valuable in the assessment of glenoid erosion, bone loss, and centering of the humeral head. The typical anterior soft tissue contracture can cause posterior subluxation and posterior glenoid erosion.
In young patients with instability, the rotator cuff is usually intact. However, in the setting of prior surgeries, rupture or insufficiency of the rotator cuff may occur. A magnetic resonance imaging (MRI) scan can help to assess the soft tissues in patients with rotator cuff weakness noted on physical examination. Concomitant cervical spine pathology or peripheral nerve injury may result in weakness and dysfunction. Cervical spine imaging may be indicated in patients with neck pain or radicular symptoms. Electromyography and nerve conduction studies may be helpful in assessing patients who are suspected to have neurologic abnormalities.
For patients with suspicion of low-grade infection, adjunctive tests should be considered, such as a white blood cell count with differential, C-reactive protein, and erythrocyte sedimentation rate. Additionally, one should consider paired bone and indium-labeled white cell radioisotope scans to further exclude the possibility of a low-grade infection. If more acute infection is suspected, a shoulder arthrogram and aspiration should be obtained.
With the information supplemented by adjunctive tests as necessary, the surgeon can better define the bone and soft tissue abnormalities and then proceed to plan the treatment.
The primary indication for surgical treatment is severe pain. Patients may report intractable pain that interferes with sleep, recreation, or work. Instability or stiffness may or may not also be secondary complaints.
Contraindications to shoulder arthroplasty include medical conditions that preclude elective surgery, such as severe cardiac or pulmonary disease, an inability to cooperate with the rehabilitation plan, inadequate bone stock, active infection, or prior injury to the deltoid or axillary artery. Some surgeons may also consider young age a relative contraindication to shoulder arthroplasty and may prefer more conservative options.
Shoulder arthroplasty in patients with a history of instability or surgery for instability has a higher complication rate than if performed for osteoarthritis alone. Therefore, care must be taken preoperatively to identify pathology to be treated and careful surgical technique must be employed to optimize results. A standard preoperative planning checklist includes the following:
CT scan and/or MRI arthrogram
Other tests (see discussion on preoperative evaluation earlier)
Need for bone graft (allograft vs. autograft)
Need for soft tissue graft (Achilles tendon)
Need for tendon transfers
Setup and Exposure
The patient is placed in the beach-chair position with the operative arm free. If an additional posterior approach is anticipated, care must be taken to include this area in the operative field to allow sufficient access. An articulated arm holder may be used to allow variable positioning of the extremity in space during different portions of the procedure ( Fig. 16-1 ). Before beginning the procedure, an examination under anesthesia is performed, documenting range of motion (forward flexion, external rotation with the arm at the side, and external and internal rotation in 90 degrees of abduction) and stability (load-and-shift examination and sulcus test). This information may be valuable in further identifying abnormalities in the static stabilizers.
A standard deltopectoral approach is used to give access to the glenohumeral joint. The cephalic vein is mobilized and retracted medially. The biceps tendon is tenodesed to the pectoralis major tendon. Following the biceps tendon proximally gives access to the rotator interval and allows identification of the superior border of the subscapularis. The remaining borders of the subscapularis are then identified. The anterior circumflex vessels lie at the inferior border of the tendon, and they are suture ligated and divided. The interval between the conjoined tendon and subscapularis is developed bluntly, taking care to protect the neurovascular structures that lie deep and distal to the coracoid. The axillary nerve is identified and protected with a vessel loop. This allows more aggressive soft tissue releases to be performed without risk to the nerve. The anatomy in this area may be distorted if prior anterior stabilization procedures were performed, especially if nonanatomic techniques were used. In these situations, such as after a prior Latarjet procedure, significant scar tissue may be present. It is advisable to leave the previous coracoid transfer in place because the distorted anatomy places the axillary and musculocutaneous nerves at risk. If the subscapularis is still tethered by the transfer through its substance despite extensive releases, the tissue passing through it may be simply divided or the coracoid can be taken down and reattached to its anatomic position.
Many techniques have been described regarding takedown and repair of the subscapularis for shoulder arthroplasty. Based on studies showing a high failure of the repair using techniques that involve takedown of the tendon off bone or division of the tendon, we prefer to perform a lesser tuberosity osteotomy. A small curved osteotome is used to lift off a thin wafer of the lesser tuberosity, measuring approximately 2 to 2.5 cm long by 1 cm wide. Traction sutures are then placed through the tendon to facilitate mobilization. Adhesions on the undersurface of the tendon are released back to the glenoid.
The arm is positioned in adduction, extension, and external rotation to dislocate the joint and expose the humerus for preparation. Preoperative templating from plain radiographs will guide component sizing. The capsule is released off the inferior humeral neck using electrocautery. Any osteophytes along the anatomic neck are removed. The interface between the osteophytes and normal bone is fibrous, and identifying this can help guide resection. The anatomic neck is identified and marked with electrocautery. The humeral resection is performed along the anatomic neck using an oscillating saw, taking care to protect the posterior and superior rotator cuff tendons. This cut restores the native version to the proximal humerus and will guide component positioning.
The normal height of the superior-most aspect of the humeral head is 5 to 8 mm above the greater tuberosity. A humeral component placed too low may lead to impingement of the greater tuberosity on the acromion, inferior subluxation, and inadequate tensioning of the deltoid with resultant dysfunction. If the humeral component is placed too high, superior subluxation, limited motion, and edge loading of the glenoid component with early loosening may occur. Nyffeler et al. showed in their cadaveric study that implanting the humeral component 5 to 10 mm too high causes premature tightening the inferior ligaments in abduction and decreases the maximum shoulder abduction angle that can be achieved. In addition, this study showed that a proud humeral component raises the center of rotation of the joint above the force vectors of the infraspinatus and subscapularis muscles, reducing their moment arms 20% to 50% and 50% to 100%, respectively.
In patients with significant humeral bone loss due to prior fracture or locked dislocation, the landmarks may be obscured or absent. Murachovsky et al. described a method to reference humeral head height off the pectoralis major tendon. Their study noted that the superior-most aspect of the humeral head is 56 +/− 5 mm from the proximal border of the pectoralis major tendon.
The offset of the humeral head center is about 11 mm medial to the center of the shaft. Placing the humeral component in varus position or using a head that is too large may result in excess offset. This can cause rotator cuff attenuation and dysfunction, limited motion, and abnormal stresses across the glenoid component. It is therefore important to use proper surgical technique combined with a component system that recreates the patient’s anatomy to ensure a well-functioning arthroplasty.
After the humeral canal has been reamed by hand and the metaphysis broached to the appropriate size, the final broach is left in place to protect the bone during retraction for glenoid exposure. In patients with dense or sclerotic metaphyseal bone, a burr may be used to remove this bone thus allowing safe broaching with less risk for iatrogenic fracture.
Controversy remains regarding whether or not to place a glenoid component in young patients. Studies have shown superior pain relief and functional scores when total shoulder arthroplasty is compared with hemiarthroplasty (HA). We therefore prefer to place a glenoid component when possible, even in young patients. In young active laborers, we will perform a hemiarthroplasty according to the rationale of Matsen. Some surgeons have reported favorable outcomes using meniscal allograft or Achilles tendon allograft resurfacing of the glenoid in young patients with glenohumeral arthritis. However, we have noted poor results in our patients treated with allograft soft tissue resurfacing of the glenoid. Patients generally have poor pain relief, and function and serial radiographs show rapid narrowing of the joint. When revision surgery is performed, the allograft tissue tends to be obliterated or absent ( Fig. 16-2 ). These results have led us to abandon these techniques.
Extensive capsular releases about the glenoid are usually required to allow complete exposure. After releasing the posterior capsule with electrocautery, the arm is abducted in neutral rotation to allow placement of a Fukuda retractor. The anterior and inferior capsule is released off the glenoid, and any remaining labrum is excised. An elevator may be used to release soft tissue off the anterior glenoid neck into the subscapularis fossa. The remaining biceps tendon and posterior labrum is then excised. The subscapularis muscle and lesser tuberosity are packed into the subscapularis fossa for protection and to provide added visualization during glenoid preparation.
The version of the patient’s glenoid is determined with a preoperative CT scan. Normal glenoid version is −10 to 10 degrees, and our goal is to place the glenoid component in this range.
Posterior glenoid erosion is commonly seen in capsulorraphy arthritis ( Fig. 16-3 ). Inadequate correction of the deformity can lead to premature loosening of the glenoid. The cadaveric study by Nyffeler et al. suggests that this increased rate of loosening is due to edge loading of the glenoid. Habermeyer has shown that each degree of glenoid retroversion results in 0.5 mm of posterior humeral displacement. In addition, with greater than 20 degrees of glenoid retroversion, the subluxation rate is 85%. Finite element analysis has revealed significant increases in stress on the cement mantle with retroversion greater than 10 degrees, increasing the risk of early loosening. These shoulders are at increased risk for posterior instability and component loosening after arthroplasty, and it is critical to correct the glenoid version and carefully balance the soft tissues.