Results and complications

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 ).

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 to minimize the risk for glenoid fracture. In addition, 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 or screw of the reverse component (a long-post/screw 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 or screw 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 ( Fig. 42.2 ). 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 (approximately 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, although 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.