Joint Congruence and Capacity

The elbow is one of the most congruous joints in the body; hence, the ability to manipulate the joint to separate the articular surfaces and allow better visualization is extremely limited, and multiple portals may be needed.^2,9,18 Furthermore, the capacity of the joint is limited in the normal situ-ation and is even further curtailed by most pathology. O’Driscoll and colleagues²⁴ demonstrated an average normal capacity of approximately 30 mL. Post-traumatic and degenerative processes result in contracture of the joint, often allowing less than 10 mL of intra-articular distension. The soft tissue envelope of the elbow is extremely thin, the capsule being separated from the skin by a thin layer of subcutaneous tissue in some locations. Thus, the tendency for the portals to “seal” is limited. This feature predisposes to chronic drainage and the possibility of infection.¹⁵

Neurovascular Structures

Without question, the greatest concern regarding elbow anatomy is the proximity of the radial and ulnar nerves that cross the joint in proximity to the capsule. The relationship of the radial, median, and ulnar nerves to the capsule in both the distended and the nondistended positions has been studied extensively.^{1,3,6,19–22,30,31,33} Furthermore, the vulnerability of cutaneous nerves had also been studied in relationship to the arthroscopic portal sites. These data are summarized in Table 42-1. It is particularly important to note that distension of the joint does alter the relative location of cutaneous nerves as well as the radial and median nerves referable to the portal site. However, a distended joint in no way protects either of these nerves from an intra-articular procedure.²⁰ As a matter of fact, the distended capsule may theoretically render these nerves more, rather than less, vulnerable. The most vulnerable nerve anatomically is the posterior interosseous nerve.¹⁰ This nerve may typically be 5 to 10 mm from an anterolateral portal. However, there is significant variation, and in some instances. the nerve can be as close as 2 to 3 mm to the capsule because it lies over the radial neck. Similarly, the median nerve demonstrates a variation of approximately 5 mm between the distended and the nondistended capsule referable to the anteromedial portal. However, once again, the distended capsule approximates the nerve—it does not separate the nerve. Although it is clearly the most protected, median nerve injury has been reported.¹¹ Of great concern is that of a concurrent injury to the brachial artery or vein. Finally, the ulnar nerve actually rests on the medial capsule.³⁰ The greatest risk consists of procedures performed in the posteromedial corner of the elbow.¹² However, injury from portal placement has also been reported.⁷

In general, these nerves are not vulnerable to portal insertion if the portal sites are accurately defined and the joint is distended. The risk of nerve injury is as follows: least risk, the median nerve; moderate risk, the ulnar nerve; greatest risk, the radial nerve.

Rheumatoid Arthritis

The most common reason for arthroscopy of an elbow involved with rheumatoid arthritis is synovectomy. The capsule is extremely thin in these patients, and therefore, the nerves are at significant risk of injury with this procedure. One patient developed a temporary ulnar nerve paresthesia owing to the instability associated with rheumatoid synovitis and the vulnerability of the nerve referable to a thin capsule covered by proliferative synovium.

Loose Body

The removal of loose bodies is still probably the best and most common indication for elbow arthroscopy in both the degenerative and the post-traumatic elbow.^4,23,25,27 The complications are uncommon unless the portal site strays from the recommended positions or débridement is required. Both generally place the radial nerve at risk.

Degenerative Arthritis

Primary degenerative arthritis is a good indication for elbow arthroscopy.^4,14 The se-lection of a procedure may include removal of loose bodies, débridement of the coronoid and olecranon osteophytes, and anterior and posterior capsular release. The anterior capsular release places the median and, particularly, the radial nerve at risk. The posterior release may place the ulnar nerve at risk. In addition, the multiple portal sites necessary for effectively carrying out this procedure may further add an element of vulnerability to these nerves. In addition to the degenerative as well as the post-traumatic elbow, the capsular capacity is very limited,²⁴ making even a diagnostic procedure something of a risk particularly for articular scuffing. As confidence increases and a greater amount of bone is removed, the potential for ectopic bone has also been reported⁸ (Fig. 42-1).

FIGURE 42-1 Proximal anteromedial portal. A, Anterosuperior medial portal (proximal anteromedial portal). B, Illustration of gross anatomy.

Post-traumatic Elbow

The potential risks of this complication are similar to those with primary degenerative arthritis. Contracture and altered anatomy make the procedure technically difficult. The articular structures as well as the neural and even the vascular ones may be at risk, depending on the aggressiveness of the procedure, which is typically débridement of bone and soft tissue.

Loose Body

The procedure that has the lowest risk is that of loose body removal. However, attention must be paid to the location of the portal with the distended joint.

Osteophyte Removal

Removal of an osteophyte can predispose to articular scuffing, but removal of the medial corner of an olecranon space places the ulnar nerve at particular risk, because this osteophyte frequently extends to the medial joint line. This osteophyte may approximate the ulnar nerve. Certainly, any medial osteophytic removal from the humerus should be performed with extreme care, because the ulnar nerve frequently rests on or very near this medial osteophytic process.

Capsular Release

A capsular release may be the most dangerous arthroscopic procedure.^14,22 The capsule is usually thick, and the joint capacity limited. Some débridement may be required to obtain adequate visualization. The radial nerve is at particular risk because it is often closely applied to the anterior capsule at the radial head. As noted earlier, the ulnar nerve is valuable to posterior capsular release. Injury to the median nerve may also occur but at a lower risk.

Synovectomy

Complication from synovectomy is a function of the aggressiveness of the procedure.⁹ Multiple portals do place the nerves at some risk, even for the diagnostic component. In addition, the thin capsule generally present in the rheumatoid patient may unknowingly be violated, thus immediately placing the anterior nerves at risk. Furthermore, use of low suction may draw the nerve into the débriding instrument. Finally, the pathology itself frequently makes visualization difficult, and débridement to attain better visua-lization may violate the capsule, thus increasing the vulnerability to nerve injury. With care, these problems can be avoided. We have recently documented no permanent nerve problems after 83 elbow synovectomies. Of note, however, was that 6 did have some transient paresthesias of the radial (three) and ulnar (three) nerves.⁵

Mayo Clinic Experience

Because the potential risk is high and owing to a lack of information in the literature regarding the true incidence of elbow arthroscopy complications, we have reviewed our experience with elbow arthroscopy.¹⁵ After 449 procedures, 1% of individuals have a significant complication requiring treatment or altering outcome. There were no permanent neural vascular injuries in this series. Furthermore, 10% have a nonpermanent “problem” associated with the procedure. The data in Tables 42-3 and 42-4 reflect this experience.