Interposition arthroplasty: Current indications, technique and expectations

Abstract

The ultimate means of functional restoration of joints with end stage arthritis is prosthetic replacement. Even though there is reluctance to replace the joint of a younger individual, the mean age of joint replacement continues to decrease. This is due to three factors: 1) social expectations, 2) uncertainty with many joint preservation procedures and 3) the ever-increasing reliability and longevity of prosthetic replacement. Unfortunately, the elbow does not share in these advantageous trends to the extent as is the case for the hip, knee and shoulder. Social pressure for restoration of normal or near normal function is certainly present, but the desired improvement of longevity and fewer restrictions of activity have not been documented. Hence, possibly somewhat disproportionately to other joints, there is great need for a reliable and functional non replacement joint reconstruction option. For most other joints, fusion is the ultimate non replacement option. Further, for most joints an optimum position has been defined to allow the greatest chance of normal function of the individual. Unfortunately, there is no truly 'optimum' functional position of elbow fusion, and the recommended 90° of flexion is considered the 'least worse' position. Further, unfortunately, elbow fusion dysfunction cannot be mitigated by compensated shoulder motion. Hence, while there is little experience in general with interposition arthroplasty of the elbow, in the authors' opinion it remains the treatment of choice in some individuals and in certain circumstances for the reasons explained above. In our judgment, the reason for avoiding this procedure is that it is technically difficult, the absolute frequency of need is not great, and outcomes do appear to be a function of experience and technique. Based on these considerations, in this chapter we review the current indications and assessment and selection considerations. Emphasis is placed on our current technique with technical tips to enhance the likelihood of success and longevity. We conclude with a review of expectations based on current literature.

Fig. 1

Cystic change on the CT scan can help the surgeon understand if interposition is a viable option. Patients with cystic changes of the distal humerus are not good candidates as the subchondral support for the graft is absent which can lead to collapse and subsequent instability.

Fig. 2

A triceps preserving approach is favored. An extensile modified Kocher that releases the lateral collateral ligament and about 20% of the lateral triceps attachment (A) permits the radius and ulna to be rotated medially providing adequate exposure of the distal humerus while preserving the medial collateral ligament (B).

Fig. 3

Four drill holes are made taking care to assure the medial and lateral most tunnels diverge from posterior to anterior to assure cover the entire width of the distal humerus.

Fig. 4

By placing the posterior suture slightly distal to the tunnel the graft will be drawn taught when the suture is tied.

Fig. 5

To assure collateral integrity, strips are fashioned from the excess graft (A) and attached to the anatomic flexion axis. The graft then reinforces the deficient collateral ligament. If both sides are deficient a “sling” or “loop” reconstruction is performed by creating a tunnel between the sublime tubercle medially and the tubercle christus supinatoris laterally and secured to reinforce each ligament (B).

Fig. 6

A guide is helpful to introduce the axis pin for the articulated external fixator laterally(A). The stylus is inserted with a mallet, avoiding potential suture cut out caused by a drill (B).

Fig. 7

The radial nerve is at risk if the proximal humeral pin is more proximal than 1 epicondylar width (A). Tissue protecting trocars are also used in the placement of the humeral pins (B).

Fig. 8

The radial nerve is at risk if the proximal humeral pin is more proximal than 1 epicondylar width (A). Tissue protecting trocars are also used in the placement of the humeral pins (B).