Shoulder Arthroplasty in Posttraumatic Arthropathy: Technique and Results

CHAPTER PREVIEW

CHAPTER SYNOPSIS

Shoulder arthroplasty for posttraumatic arthropathy is more technically challenging than arthroplasty for primary degenerative arthritis. This procedure is reserved for patients with painful malunions and glenohumeral joint incongruity, as some malunited injuries are relatively asymptomatic. Special consideration of surgical techniques, particularly related to the avoidance of greater tuberosity osteotomy, is presented. Patients should be counseled on a limited-goals rehabilitation program preoperatively, as functional outcomes are inferior to those of patients undergoing primary arthroplasty for degenerative joint disease.

IMPORTANT POINTS

1

Beware of occult infection in patients with prior surgery.
2

If extensive releases of contracted soft tissues is required:
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  Consider release of the axillary and musculocutaneous nerves encased in scar.
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  Mobilize the rotator cuff to enhance excursion.
3

Accommodate a greater tuberosity malunion whenever possible.

CLINICAL/SURGICAL PEARLS

1

Identify the biceps tendon.
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  Proximal humeral malunion alters usual bony landmarks.
2

Distinguish the greater and lesser tuberosities.
3

Modify the head resection to preserve proximal bone stock.
4

Accommodate greater tuberosity malunion.
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  Employ varus placement of prosthesis.
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  Use a short, narrow humeral stem.

CLINICAL/SURGICAL PITFALLS

1

Appreciate the axillary and musculocutaneous nerves during surgical dissection and releases to avoid injury.
2

If greater tuberosity osteotomy is required, ensure secure fixation of the tuberosity at time of closure, using tuberosity-to-shaft and tuberosity-to-prosthesis fixation.

Posttraumatic glenohumeral arthropathy is one of the most challenging procedures in shoulder surgery. Distorted bony anatomy, extensive soft tissue contractures, adhesions, rotator cuff defects, nerve injury, and occult infection render this procedure technically demanding and difficult. Such anatomic factors lead to higher complication rates and poorer clinical outcomes when compared with arthroplasty for primary degenerative arthritis. Nevertheless, prosthetic arthroplasty is a valuable option in symptomatic patients with posttraumatic proximal humeral malunion and glenohumeral incongruity.

INDICATIONS

Shoulder arthroplasty for arthritis following fracture is uncommon. It is generally reserved for three- and four-part proximal humeral malunions with painful glenohumeral arthritis. Posttraumatic glenohumeral arthropathy is ideally treated by prophylaxis. Malunion leading to arthropathy is best avoided with proper initial management of acutely displaced fractures. Nonconstrained prosthetic replacement in the setting of malunion is a technically demanding procedure associated with high complication rates. In addition, functional outcomes are inferior when compared with prosthetic replacements in acute fractures. Therefore, the orthopedic surgeon should not accept suboptimal acute treatment of displaced proximal humerus fractures with the expectation that delayed prosthetic salvage will offer equivalent results.

Shoulder arthrodesis may be considered an option in proximal humeral arthropathy. It provides adequate pain control at the expense of a fixed glenohumeral joint. This alternative should be considered in the patient with a malunited fracture, deficient rotator cuff, or deficient deltoid muscle function. Arthrodesis should also be considered a surgical option in proximal humeral malunions complicated by infection resistant to thorough debridement and antibiotic treatment. Although considered an acceptable treatment option, fusion is poorly tolerated by patients older than 70. Because this age-group comprises the predominant cohort of patients with traumatic glenohumeral arthropathy, the option of arthrodesis is rarely indicated.

Proximal humeral prosthetic replacement for traumatic glenohumeral arthritis is fraught with many challenges. The axillary and musculocutaneous nerves are often encased in scar tissue and frequently at risk during the time of surgical releases. The incidence of nerve injury has been reported to be as high as 30%. Additionally, extensive releases are often necessary to lengthen contracted and shortened soft tissues. Contractures of the rotator cuff and capsule are commonly observed. Lastly, greater tuberosity osteotomy, when required during prosthetic replacement in malunited fractures, is often associated with increased complication rates and suboptimal outcomes.

CONTRAINDICATIONS

Posttraumatic proximal humeral arthropathy can be asymptomatic even in the presence of significant glenohumeral involvement on radiographs. Surprisingly, some patients demonstrate minimal pain and good function, obviating the need for surgical intervention ( Fig. 15-1 ).

The presence of infection is an absolute contraindication to prosthetic replacement. Although infection is rare in patients with fractures initially managed nonoperatively, occult infection should be suspected in the posttraumatic patient with a stiff and painful shoulder following previous surgery. Staged procedures are indicated when intraoperative purulent fluid or suspicious inflammatory tissue is found. Intraoperative cultures, hardware removal, debridement of nonviable tissue, and a 6-week course of intravenous antibiotics are all considered vital components in comprehensive surgical infection control. Staged hemiarthroplasty may be considered when the infection has been definitively eliminated.

Noncompliance or inability to comply with postoperative rehabilitation is considered a relative contraindication. The ability to participate and comply with postoperative exercises is vital to achieving good outcomes. Patients unable or unwilling to do so should be maintained on a nonoperative treatment regimen.

A functioning deltoid muscle is essential for even a limited-goals postoperative rehabilitation program. If equivocal on physical examination, deltoid function should be confirmed with a preoperative electromyogram (EMG) to assess the integrity of the axillary nerve.

SURGICAL TECHNIQUE

Preoperative Evaluation

Prior to surgery, a complete history and physical evaluation of the patient should be performed with particular attention paid to preinjury function. It is often difficult to properly ascertain the integrity of the rotator cuff given the stiffness commonly experienced by patients with posttraumatic arthropathy. Discrepancy between passive and active ranges of motion suggests the presence of rotator cuff insufficiency. Crepitus with passive range of motion may indicate the presence of glenohumeral incongruity. In patients who have had previous attempts at open reduction internal fixation, it is especially important to review operative notes.

Neurologic evaluation in these patients can be a challenge given their limited motion, weakness, and pain. Nevertheless, a complete neurologic assessment is necessary prior to operative intervention, especially to evaluate for often unrecognized axillary nerve injuries. Electromyographic studies should be considered prior to surgery if any question exists regarding neurologic integrity.

Infection must always be suspected in the patient with a stiff and painful shoulder following initial open reduction internal fixation. Standard evaluation of such patients to rule out infection includes inspection of the wound, history of any drainage in the past, complete blood cell count (CBC), erythrocyte sediment rate (ESR), and, if suspicion for occult infection is high, an aspiration of the glenohumeral joint under fluoroscopic control for culture and sensitivity.

A thorough evaluation of the patient’s radiographic images can provide valuable information. Initial radiographs can present crucial insight into the patient’s index injury. Preoperative radiographs can provide information on the extent of arthropathy ( Fig. 15-2 ). Axillary views of the involved shoulder can reveal the extent of posterior displacement of the greater tuberosity and the necessity for an intraoperative greater tuberosity osteotomy ( Fig. 15-3 ).

Anesthesia and Positioning

At our institution, an interscalene block with intravenous sedation is used in the vast majority of our patients. Brachial blocks provide excellent perioperative pain control for up to 12 to 18 hours following surgery. At our hospital, interscelene blocks are performed by a dedicated group of anesthesiologists with extensive experience in regional anesthetic technique.

Once the brachial block has been performed, the patient is placed in the beach-chair position with a standard headrest. During draping and final positioning, mobility of the shoulder during surgery must be considered. The patient must be positioned on the edge of a standard operating table to permit sufficient arm extension to deliver the humeral head into the operating field. The sterile draping must allow for a wide surgical field, typically from the sternum, base of the neck, and body of the scapula posteriorly.

Surgical Approach and Releases

The deltopectoral approach typically allows for extensive exposure. Soft tissue contracture releases can be undertaken as the surgical dissection deepens. The often dense scar tissue between the humerus and deep surface of the deltoid is the first to be lysed. The dissection continues medially and cephalad into the subacromial space where adhesions between the acromion and rotator cuff are released to allow for adequate mobilization of the humerus and rotator cuff muscles. Adhesions between the strap muscles and the subscapularis need to be released with attention to the proximity of the musculocutaneous nerve, which may course as close as 3 cm from the tip of the coracoid. Location and mobility of the axillary nerve through palpation or direct visualization is important prior to subscapularis tenotomy.

The subscapularis tendon can be elevated directly from its insertion or with a small wafer of bone off the lesser tuberosity to facilitate bone-on-bone healing at the time of repair. Tenotomy should be performed as far laterally as possible to maximize subscapularis length. The anterior capsule is dissected free from the subscapularis muscle, leaving its lateral portion continuous with the subscapularis tendon to enhance subsequent subscapularis repair. Finally, all adhesions around the subscapularis should be freed. These three steps will maximize subscapularis excursion and length, allowing for greater external rotation of the shoulder. For additional exposure, the superior portion of the pectoralis major tendon may be released and tagged at this time, with subsequent repair upon closure.

In an effort to obtain greater exposure, the rotator interval at the superior border of the subscapularis tendon should be released to the base of the coracoid process. The posterior capsule is released to the teres minor insertion, and the humeral head is delivered through the wound with extension and external rotation of the arm.

The orientation of humeral head osteotomy is determined by the degree of humeral malunion estimated on preoperative radiographs and confirmed intraoperatively. A standard osteotomy at the humeral neck with preexisting malunion may not provide adequate access to the humeral shaft. Adjustments in the humeral neck cut should to be made to accommodate the existing malunion, and standard resection guides may not be applicable. The surface plane of the neck following osteotomy should face the glenoid with the arm in neutral rotation. The humeral head should be saved for subsequent bone graft if required. After head resection and adequate releases, the humerus should be retracted posteriorly using a Fukuda retractor to gain access to the glenoid.

Glenoid exposure and rotator cuff mobilization are further enhanced with a circumferential perilabral release accomplished with a scalpel or elevator. The axillary nerve should be identified at the inferior margin of the glenoid to adequately protect it during the release at the inferior glenoid rim. Mobilization of supraspinatus and infraspinatus from the glenoid neck can be performed with the use of an elevator. Injury of the suprascapular nerve can occur during the elevation and therefore should be limited to within 1 cm medial to the glenoid rim. Once the glenoid is fully exposed, the presence of glenoid arthropathy can be assessed. If there is a functioning rotator cuff and extensive wear of the glenoid articular surface, routine principles for glenoid resurfacing are followed.

Preparation for Trial Prosthesis

All measures should be considered prior to performing a greater tuberosity osteotomy. The available options are determined by the accessibility of the humerus for trial stem insertion. Preservation of an intact greater tuberosity is paramount given the poor clinical consequences associated with the osteotomy. Alterations in prosthesis placement and technique can accommodate a malunited greater tuberosity. These options include varus placement of the stem in the humeral canal, use of a small humeral head, use of a narrow and sometimes short humeral stem, and appropriate placement of an eccentric modular head. Care should be taken when placing the stem in a varus position so as to avoid perforation of the lateral humeral cortex ( Fig. 15-4 ). If these maneuvers do not restore the appropriate anatomic relation of the head and greater tuberosity with proper soft tissue tension, then a greater tuberosity osteotomy should be performed ( Fig. 15-5 ).