Humerus

Intraoperative complications involving the humerus are common. The most frequent humeral complication is iatrogenic fracture, which usually occurs during an overly aggressive dislocation maneuver without previous adequate soft tissue release or during extraction of a well-fixed humeral stem. Patients with osteopenia and those with severe preoperative stiffness are most at risk for this complication. These fractures may occur at the humeral diaphysis or proximally and involve the tuberosities. Fractures involving the diaphysis should be reduced and a long-stem humeral implant placed. Allograft struts and cerclage cables may be added in patients with severe osteopenia (Fig. 42-1).

Figure 42-1 Radiograph of a patient with an intraoperative humeral shaft fracture incurred during revision arthroplasty that was treated with a long-stem humeral implant and allograft struts fixated with cerclage cables.

Intraoperative fractures involving the greater or lesser tuberosities (or both) usually occur during removal of the humeral stem. Many of these fractures can be successfully stabilized by suture fixation. If a tuberosity fracture is not satisfactorily stable despite suture fixation, use of a reverse prosthesis is considered as the revision implant.

Glenoid

Intraoperative glenoid fractures at the time of revision shoulder arthroplasty occur during extraction of the glenoid component or during preparation (reaming) of the glenoid. Patients with osteopenia are most at risk. Fractures may involve only the peripheral glenoid rim or may extend significantly into the articular surface. Adequate capsular release helps minimize the risk for glenoid fracture. Additionally, a motorized reamer (not a drill) should be used for preparation of the glenoid surface. The reamer should be started before the surgeon applies force to engage the reamer onto the glenoid face. This avoids having the reamer “catch” an edge of the glenoid, which may cause a fracture.

When implanting an unconstrained glenoid component, fractures that involve only a small portion of the peripheral rim generally require no treatment and the glenoid component can be inserted as planned. Glenoid fractures that extend into the central portion of the glenoid (keel slot or peg holes) should be bone-grafted with autogenous iliac crest bone graft and placement of a glenoid component avoided. Placement of a glenoid component in the face of a fracture involving the central portion of the glenoid can result in early glenoid failure.

When implanting a reverse glenoid component, fractures that involve only a small portion of the peripheral rim generally require no treatment, and the glenoid component can be inserted as planned. Glenoid fractures that extend into the central portion of the glenoid should be bone-grafted with autogenous iliac crest bone graft. The reverse glenoid component can be placed to help secure the bone graft and internally fix the fracture. If the central post of the reverse component (a long-posted revision base plate can be used) is firmly seated within native glenoid bone, consideration can be given to placing the humeral component during the same surgical setting. If the glenoid component does not seem to be secure or the central post of the glenoid base plate is not firmly seated in unfractured native glenoid bone, insertion of the humeral component should be delayed for 6 months to allow the fracture to heal. After 6 months, a humeral component can be placed as the second part of a two-stage procedure. Alternatively, if an intraoperative glenoid fracture occurs, the fracture can be bone-grafted, and the humeral stem with a hemiarthroplasty adapter can be placed. After the fracture has healed and remodeled (around 6 months after the index attempt at reverse shoulder arthroplasty), the second stage of the procedure consisting of implantation of the glenoid component may be performed.

Rotator Cuff

Damage to the rotator cuff during revision shoulder arthroplasty usually occurs during the surgical approach and glenohumeral exposure. The anatomy is commonly distorted by the primary arthroplasty. Dissection should be slow and meticulous to avoid inadvertent damage to the rotator cuff. In the event that the rotator cuff is substantially compromised during the surgical procedure, consideration is given to implantation of a reverse prosthesis as the revision implant.

Neurovascular Structures

Catastrophic injury to the neurovascular structures around the shoulder is rare during revision shoulder arthroplasty. The neural structures most at risk during revision shoulder arthroplasty are the axillary and musculocutaneous nerves. If a humeral osteotomy is performed or if revision surgery is performed for a periprosthetic fracture, the radial nerve is also at risk. Nerve injury during revision shoulder arthroplasty can occur as a neuropraxic stretch injury or as a transection injury. Neuropraxic injury caused by stretch most commonly involves the axillary nerve but can involve any nerves within the brachial plexus. Care should be taken when positioning the patient to maintain the cervical spine in neutral alignment to avoid a stretch injury to the brachial plexus. When treating a periprosthetic fracture with revision arthroplasty or when a humeral osteotomy is anticipated for extraction of the humeral stem, the radial nerve should be carefully exposed to ensure its protection. Careful exposure of the radial nerve often results in transient neuropraxia. Patient education preoperatively is of paramount importance in dealing with neuropraxia inasmuch as patients are much more accepting if they have heard about the possibility of this complication before surgery. Axillary and radial nerve neuropraxia is treated by observation, with most patients recovering by 3 to 4 months postoperatively.

Neural transection injury is rare in revision shoulder arthroplasty. Careful identification of nerves at risk (axillary nerve and, in certain situations as outlined earlier, the radial nerve) is the best way to prevent this complication. If a transection injury does occur, the ends of the nerve are identified and consultation with a microvascular surgeon obtained.

Although tearing of the cephalic vein is common and largely without consequence, significant arterial and venous injuries do occur, though rarely, during revision reverse shoulder arthroplasty. The brachial artery is most at risk during revision surgery requiring an extensile exposure (periprosthetic fracture, humeral osteotomy). Should one of these injuries occur, after cross-clamping of the injured structure, emergency intraoperative consultation with a vascular surgeon is required.

Wound Problems

Wound problems occur early after revision shoulder arthroplasty. Hematoma is most easily avoided by extensive use of electrocautery during shoulder arthroplasty. When a reverse shoulder prosthesis is used for revision shoulder arthroplasty, closed suction drainage is maintained for 24 hours after surgery. When a hematoma occurs, it is managed by symptomatic nonoperative treatment (warm compresses, pain medication). Operative drainage is reserved for situations in which drainage persists beyond 1 week or infection is suspected (see later) but is rarely necessary.

In most revision cases, the skin is closed with stainless steel skin staples. Problems with skin staples are extremely infrequent. Rarely, susceptible patients have a reaction to dissolving subcutaneous sutures. The presence of minimal serous drainage distinguishes this complication from the more serious deep infection. Superficial wound dehiscence is treated by local wound care, including removal of any residual dissolving suture material and chemical cauterization of any granulating tissue with silver nitrate applicators.

Glenoid Problems

Glenoid complications after revision arthroplasty are related to the type of revision arthroplasty performed–hemiarthroplasty, unconstrained total shoulder ar-throplasty, or reverse shoulder arthroplasty. As with primary hemiarthroplasty, erosion of the remaining glenoid articular cartilage and osseous glenoid can occur. Successful treatment of glenoid erosion usually requires further revision surgery during which the glenoid is resurfaced.

Glenoid component failure after revision to unconstrained total shoulder arthroplasty can occur as a result of loosening of the glenoid component from the host bone or mechanical breakage of the glenoid implant (Fig. 42-2). Glenoid component problems, when symptomatic, generally require further revision surgery.

Figure 42-2 Unconstrained glenoid component loosening occurring 3 years after revision shoulder arthroplasty.

Glenoid component failure after revision to reverse shoulder arthroplasty, as with primary reverse shoulder arthroplasty, has been associated in all cases of which we are aware with initial placement of the glenoid component in a superiorly oriented direction, implantation of the prosthesis in the presence of an intraoperative glenoid fracture, or insertion of the glenoid component with the central post anchored only in grafted bone. These complications are best avoided. As with primary reverse shoulder arthroplasty, we implant the reverse prosthesis for revision arthroplasty through a deltopectoral approach to avoid inadvertent placement of the glenoid component in a superiorly oriented position, which can occur with use of the superior lateral approach. If an intraoperative glenoid fracture occurs, we treat it as described previously in this chapter. When glenoid failure occurs, further revision surgery consisting of glenoid reconstruction and conversion to a hemiarthroplasty is required.

Humeral Problems

Humeral problems after revision shoulder arthroplasty are rare and can be divided into loosening of the humeral component and periprosthetic humeral fracture. Most unconstrained humeral stems that we use for revision arthroplasty are cemented. Aseptic loosening of these stems is rare. Whenever loosening of a humeral stem occurs, infection must be ruled out (see later). In the rare instance of symptomatic aseptic loosening of an unconstrained humeral component, treatment is further revision of the humeral stem.

Loosening of a reverse humeral stem after revision surgery is uncommon. The predominant risk factor for aseptic loosening of a revision reverse humeral stem is proximal humeral bone loss (Fig. 42-3). Whenever loosening of a revision reverse humeral stem occurs, infection must be ruled out, as with loosening of an unconstrained revision humeral stem (see later). In the rare instance of symptomatic aseptic loosening of a revision reverse humeral component, treatment is further revision of the humeral stem, usually combined with allograft reconstruction of the proximal humerus to provide osseous support of the proximal portion of the revision stem.

Figure 42-3 Aseptic loosening of a reverse humeral stem resulting from a fall.

Mechanical problems of a revision reverse humeral component are exceedingly rare and related to the polyethylene liner. Incomplete seating of the polyethylene component at the revision arthroplasty can be responsible for dissociation of the polyethylene liner from the humeral stem. In this scenario, further revision surgery with replacement of the polyethylene liner is indicated. Polyethylene wear occurs medially on the rim of the polyethylene liner in many patients, as seen at the time of retrieval during revision surgery. It occurs as a result of scapular notching, as discussed later.

Periprosthetic humeral fractures after revision arthroplasty are more common than loosening of the humeral component and are almost always the result of a fall or similar low-energy trauma. The majority of these fractures occur just distal to the tip of the humeral stem, and most can be treated nonoperatively. Nonoperative treatment consists of fracture bracing, activity modification, pain medication, and frequent radiographic monitoring. If the fracture has not healed within 3 months, we will incorporate the use of an external bone stimulator (OL 1000 Bone Growth Stimulator, Donjoy Orthopedics, Vista, CA). Despite these measures, periprosthetic humeral fractures treated nonoperatively may take longer than 9 months to heal.3 Our criteria for recommending operative treatment of periprosthetic fractures include complete displacement, angulation greater than 30 degrees, loosening of the humeral component, or failure of nonoperative treatment.

Instability

Instability after Revision Surgery with a Reverse Shoulder Prosthesis

Instability after revision surgery with a reverse shoulder prosthesis is twice as common as that observed in the primary reverse arthroplasty scenario. Dislocations after revision arthroplasty with a reverse prosthesis occur early (within 6 weeks of revision surgery). Instability of a reverse prosthesis can be related to various factors. In revision cases, proximal humeral bone loss seems to be the greatest risk factor for dislocation of a reverse prosthesis. In this scenario, deltoid muscle tension is often solely responsible for the stability of the implant because no rotator cuff or joint capsule exists to provide stability. Even if the deltoid is properly tensioned initially, it can gradually lose its tension and result in dislocation. A second major risk factor for dislocation of a reverse prosthesis is subscapularis insufficiency, a common condition encountered when performing revision shoulder arthroplasty with a reverse prosthesis. A less common factor contributing to dislocation of a reverse prosthesis is mechanical impingement causing the prosthetic socket to be levered away from the glenoid component. This impingement usually occurs inferiorly as the arm is adducted and is often related to too superior positioning of the glenoid component on the glenoid face, as detailed schematically in Chapter 32. Finally, in the revision situation, the integrity and function of the axillary nerve should be ensured before performing revision arthroplasty with a reverse prosthesis because this neural deficit can result in prosthetic dislocation.

In most cases, as with dislocation of a primary reverse prosthesis, treatment initially consists of closed reduction and a period of bracing. Closed reduction is performed in the operating room with the patient either heavily sedated or under general anesthesia. An attempt is made to reduce the dislocation under fluoroscopic guidance. If the prosthesis is successfully reduced, fluoroscopic examination is performed to ensure that mechanical impingement is not responsible for the instability. If the problem is not related to mechanical impingement and the prosthesis is successfully reduced, a brace is applied to maintain the arm with the humeral component centered on the glenoid component, usually in about 90 degrees of abduction and 30 degrees of forward flexion (Fig. 42-4). The patient maintains this brace at all times for 6 weeks, and radiographs are taken in the brace every 7 to 10 days to confirm that the prosthesis has remained located (Fig. 42-5). After 6 weeks the brace is discontinued and a normal rehabilitation regimen ensues.

Figure 42-4 Placement of a brace used for the treatment of a dislocated revision reverse prosthesis after closed reduction.

Figure 42-5 A and B, Radiographs obtained in the brace confirming maintenance of prosthetic reduction.

If the prosthesis is not reducible by closed means, mechanical impingement causing dislocation exists, or closed reduction plus bracing has failed, open reduction with insertion of a thicker polyethylene spacer or metallic augment (or both) is performed (Fig. 42-6). Any mechanical impingement can simultaneously be addressed by careful removal of bone at the lateral aspect of the scapula just inferior to the glenoid component, if necessary. Postoperatively, the patient is treated with the same bracing protocol used after closed reduction of a dislocated reverse prosthesis.

Figure 42-6 Treatment of a dislocated revision reverse prosthesis (A) with the addition of an augment to increase deltoid tension (B).

Rotator Cuff Problems

Symptomatic problems of the rotator cuff after unconstrained revision shoulder arthroplasty often result in instability and were described earlier. Failure of the subscapularis repair is the most common postoperative rotator cuff problem that we observe. When subscapularis failure is minimally symptomatic or asymptomatic, no treatment is indicated. When symptomatic, treatment is indicated as described previously in the “Instability” section of this chapter.

Isolated internal rotation weakness is not diagnostic of subscapularis failure after unconstrained revision shoulder arthroplasty. It is common for individuals to lose internal rotation strength after tenotomy and repair of the subscapularis during primary shoulder arthroplasty, and this finding becomes more pronounced after revision surgery. Subscapularis failure should be documented by computed tomographic arthrography before considering operative treatment of this complication.

Stiffness

Glenohumeral stiffness after revision shoulder arthroplasty is related to capsular contracture or the prosthesis, or both. It is much more commonly observed when using an unconstrained revision implant than when using a reverse revision implant. Prosthetic problems resulting in stiffness are generally the result of implantation of too large an unconstrained humeral component or malpositioning of the revision component (Fig. 42-7). Rehabilitation with capsular stretching can be attempted in an effort to improve mobility. If this fails (no improvement over a 6-month period), revision surgery is indicated and consists of downsizing of the humeral head with open release of any capsular contractures that are present.

Figure 42-7 Malpositioned revision humeral stem contributing to glenohumeral stiffness.

Stiffness related to capsular contracture almost always responds to nonoperative management involving aquatic-based rehabilitation (see Chapter 43). If the patient shows no improvement in mobility over a 6-month course of rehabilitation and has no obvious prosthetic problem, we will consider the patient a candidate for arthroscopic capsular contracture release if an unconstrained revision implant was used. We have no experience dealing with capsular contracture in a patient who has undergone revision shoulder arthroplasty with a reverse prosthesis.

Infection

Infection after revision shoulder arthroplasty is expectedly more common than infection after primary shoulder arthroplasty. Patients most at risk for infection are those with systemic illness (diabetes mellitus), those with compromised soft tissues (radiation-induced osteonecrosis, post-traumatic arthritis), and those with inflammatory arthropathy (rheumatoid arthritis). These infections are most commonly caused by Staphylococcus aureus or Propionibacterium acnes. Infections after revision shoulder arthroplasty can be divided into perioperative (within 6 weeks of surgery) and late (hematogenous) infections.

Early perioperative infections are initially treated with two or three irrigation and débridement procedures and retention of the components. At the last planned irrigation and débridement procedure, absorbable antibiotic-impregnated beads are placed in the soft tissues around the shoulder (Stimulan, Biocomposites, Inc., Staffordshire, England). Consultation with an infectious disease specialist is obtained, and a minimum of 6 weeks of intravenous antibiotics tailored to the specific organism causing the infection (or covering the most likely offending organisms, if cultures remain negative despite obvious infection) is usually recommended. If this regimen fails, the prosthesis is removed.

Late-appearing infections are treated by removal of the prosthesis and intravenous antibiotics. The decision whether to perform a repeat revision shoulder arthroplasty or continue with a resection arthroplasty is patient specific, with resection arthroplasty selected in most cases.

Acromial Problems

Occasionally, acromial stress fractures are seen after revision reverse shoulder arthroplasty, just as with primary reverse shoulder arthroplasty. These fractures result from deltoid tension applied to osteopenic bone. Frequently, these fractures exist preoperatively as a result of chronic superior migration of the humeral head with persistent acromiohumeral articulation (Fig. 42-8). Postoperatively, deltoid tension may cause the fracture fragment to tilt inferiorly. Despite these radiographic findings, no specific treatment is necessary for this complication. Additionally, patients obtain satisfactory results even with this radiographic finding.

Figure 42-8 A, Acromial stress fracture (arrow) occurring after hemiarthroplasty for rotator cuff tear arthropathy. B, This patient underwent revision to a reverse prosthesis, with the stress fracture requiring no additional treatment.

Scapular Notching

Though debatable whether it should be considered a complication, notching of the scapula occurs within 2 years of surgery in half the patients who have undergone reverse shoulder arthroplasty, both in the primary and in the revision situation (Fig. 42-9). This radiographic finding most likely occurs as a result of mechanical impingement of the medial aspect of the humeral component and the lateral aspect of the scapula just inferior to the glenoid. As the patient internally rotates the shoulder, the impingement is exacerbated. This mechanical impingement theory is further supported by the observation that patients’ internal rotation seems to improve as the scapular notch progresses, thus suggesting that the prosthesis must “carve out” a portion of the scapula to maximize postoperative internal rotation. Another theory of the cause of scapular notching is polyethylene wear causing osteolysis, although this theory currently has less support than the mechanical impingement theory.

Figure 42-9 Scapular notching occurring after revision arthroplasty with a reverse prosthesis.

Scapular notching is commonly accompanied by a scapular osteophyte just medial to the notch. The degree of scapular notching has also been graded by severity.4 The best way to avoid scapular notching seems to be by initially placing the glenoid component inferiorly on the glenoid face and by introducing slight inferior tilt during glenoid reaming, as discussed in Chapter 29. Despite the concerning appearance of this scapular notch, its clinical implications are unclear, with most of the evidence suggesting no adverse consequence. As long as the glenoid component remains stable, no treatment of an asymptomatic scapular notch is indicated.