Dysfunctional Instability

History and Presentation

Younger patients often present after high-energy trauma, while more elderly patients typically present with a long-standing issue such as rheumatoid arthritis or nonunion ( Fig. 97.1 ). In patients with rheumatoid arthritis, the process occurs gradually, with progressive osseous resorption and a sudden marked increase of instability caused by a fracture occurring from minor trauma.

It is critical to obtain a detailed surgical history, searching for evidence of infection or prior nerve injury from the injury or from subsequent treatment. As much detail as possible regarding prior treatment and the postoperative course is very helpful. If there is any evidence of prior sepsis, the joint is aspirated as part of the assessment.

Physical Examination

The physical examination ascertains findings that may affect surgical decision making or influence outcome. Soft tissues should be carefully evaluated for contracture and compliance, and the locations of previous incisions are noted.

The neurologic examination pays attention to the motor and sensory function of all three nerves crossing the joint. The effect of tourniquet application and nerve function after prior procedures is noted during the examination. Motor function of the triceps, brachialis, and biceps is of particular concern as the insertions are often violated by the disorder.

Both active and passive motion are assessed, and the extent of instability and any effective dynamic stabilizing function of the musculature is noted. Minor degrees of elbow instability maintain enough of a fulcrum in the adducted position to allow active range of motion. However, abduction of the arm creates a varus moment at the elbow, compromising the fulcrum and resulting in instability ( Fig. 97.2 ). Major degrees of instability, such as a flail elbow, have dissociation of the forearm referable to the brachium and over time shorten and displace because of the unopposed pull of the extensors and flexors of the arm ( Fig. 97.3 ).

Imaging Studies

Standard anteroposterior and lateral radiographs are typically sufficient to provide an appreciation of the cause and extent of the injury. Long-standing fixed deformities such as with a nonunion can make interpretation of standard radiographs difficult. For instance, lack of full elbow extension results in a foreshortened projection of the humeral shaft in the anteroposterior plane, making this fragment appear smaller than it actually is. In this scenario one may erroneously conclude that the joint is not salvageable. Advanced imaging, including computed tomography with three-dimensional reconstruction, can be helpful when different treatment options are being considered, such as revision fixation and grafting of a nonunion. However, when the decision to proceed with total elbow arthroplasty has already been made, advanced imaging is rarely indicated and provides little additional information.

Additional Studies

If there is a history or findings of nerve damage, an electromyographic study is performed. This allows thorough documentation of nerve status and aids in the preoperative discussion of expectations with the patient as well as in helping develop the surgical plan of exposure and execution.

In addition to the usual preoperative laboratory studies, in all instances inflammatory markers must be measured before surgery: complete blood count with differential, erythrocyte sedimentation rate, and C-reactive protein level. If these suggest a possibility of an infection or if the history reveals or is suggestive of a prior infection, the joint area is aspirated under ultrasound guidance. If the entire workup for infection is negative but concern for infection remains high, a débridement and staged implantation should be considered as a real-time option, and the patient is so informed (see Chapters 100 and 101 ).