Basic Science and Anatomy

Indications

Patients presenting with a symptomatic triangular fibrocartilage complex (TFCC) tear, either acute or chronic, in combination with an ulnar zero or ulnar plus variance are unlikely to respond to a simple debridement of the TFCC. These patients are suffering from an ulnar abutment syndrome in which the TFCC is “pinched” between the ulnar head and the proximal surface of the lunate. Such patients are candidates for arthroscopic debridement of the TFCC combined with an arthroscopic ulnar shortening.

Contraindications

Arthroscopic ulnar shortening is unlikely to help those patients who present with an ulnar abutment syndrome combined with additional ulnocarpal and/or lunatotriquetral pathology. A lunatotriquetral ligament instability or ulnocarpal ligament laxity in the presence of an ulnar abutment syndrome will not respond to an arthroscopic ulnar shortening because the arthroscopic ulnar shortening does not address the LT or ulnocarpal instability. An ulnar shortening osteotomy combined with an arthroscopic TFCC debridement would be a reasonable approach in this case. The LT and ulnocarpal instability cannot be treated with ulnocarpal capsular shrinkage because the capsular shrinkage demands immobilization for six to eight weeks. The postoperative regimen for an arthroscopically assisted ulnar shortening consists of early range of motion of the wrist and distal radioulnar joint.

Technique

The initial approach to the TFCC and distal ulna is through the 3-4 and 4-5 portals or through the 6-R portal. The arthroscope is placed in the 3-4 portal, whereas the 4-5 or 6-R portals are used as instrument portals. The arthroscopic treatment of the ulnar abutment syndrome is facilitated by using the Holmium:YAG laser.⁵ Hyaline cartilage is very efficiently removed with the laser at higher energy settings (2.0 joules at 20 pulses per second). Not only is the ulnar head hyalin cartilage and subchondral bone rapidly removed but in contrast to burring is removed without producing much debris.

Once the cancellous bone of the ulnar head is exposed, however, the bur becomes the most effective tool for completing the ulnar shortening. This is because it becomes very time consuming to focus the laser beam on each trabecula. During the ulnar head resection, care must be taken to not injure the sigmoid notch with either the laser or the bur. Care must also be taken to not detach the insertion of the triangular fibrocartilage from the fovea at the base of the ulnar styloid. The successful arthroscopic ulnar shortening relies on teamwork. The assistant brings the surfaces of the ulnar head to be resected to the laser being held by the operating surgeon. By progressively supinating and pronating the forearm, an appropriate amount of ulnar head is excised.

The resection should be carried out in a systematic fashion. For example, start the cartilage ablation with the wrist fully pronated and gradually rotate the radius around the ulna, bringing the forearm into full supination. Next, ablate the subchondral plate rotating from pronation to supination. Finally, the ablation of the cancellous bone is accomplished while rotating the radius from supination into pronation. The depth of the first pass with the bur is easily kept uniform by burying the bur head in the bone to the level of its guard and using that depth as a guide for the rest of the burring.

The goal is to resect sufficient ulna to produce a 2-mm negative ulnar variance. The amount of ulna resected must be verified with intraoperative fluoroscopy. Occasionally, complete visualization of the ulnar head requires the scope to be placed in the 4-5 portal (with the laser and bur entering the distal radioulnar joint through the distal radioulnar joint portal). This portal is established just proximal to the 4-5 portal and TFCC.

An effort is made to leave a smooth surface on the remaining distal ulna. The trabeculae of the distal ulna always produce a somewhat rough distal ulnar surface at the completion of the procedure. However, these irregularities disappear during the months following the surgery (Figures 3.1 and 3.2). Large irregularities must be avoided because they can catch on the proximal surface of the residual TFCC during supination and pronation. Once the ulnar shortening is complete, the traction should be removed from the wrist and the wrist should be ulnarly deviated, axially loaded, and taken through a full range of supination and pronation. If this maneuver produces no popping and clicking or catching, the ulnar head surface is probably smooth.

FIGURE 3.1 Anatomy of the triangular fibrocartilage.

(Redrawn from Ishii S, Palmer AK, Werner FW, Short WH, Fortino MD. An anatomic study of the ligamentous structure of the triangular fibrocartilage complex. J Hand Surg [Am] 1998; 23:977–85.)

FIGURE 3.2 Early and late post laser-assisted arthroscopic ulnar shortening demonstrating smoothing of resection site with time: (A) ulnar abutment, (B) six weeks postoperatively, and (C) six months postoperatively.

The postoperative regimen after ulnar shortening includes providing the patient with a wrist splint to be worn as needed, as well as a home therapy program consisting of active and passive range-of-motion exercises. Early range-of-motion exercises are essential. Immobilization of the wrist leads to a loss of motion due to postoperative scar contracture. The sutures (wounds are closed using subcuticular sutures of 4–0 Prolene) are removed at two weeks. Strengthening exercises can be started at six weeks if needed. Premature resumption of heavy lifting or repetitive activities will lead to radiocarpal synovitis. The recovery after an ulnar shortening can be as long as six months (as suggested by Feldon).⁶ However, the majority of patients will be improved long before six months.

Results

Arthroscopically assisted ulnar shortening has proven to be an effective method of treating patients with an ulnar abutment syndrome.^7,8 Eighty-one percent of our patients had an excellent or good outcome. Eight of Tomaino’s 12 patients were pain free, and 4 had minimal symptoms.

This technique has been shown to be as effective as formal ulnar shortening osteotomy for the treatment of ulnar abutment syndrome.⁹ Arthroscopically assisted ulnar shortening has the advantage of being less invasive and is not associated with complications associated with plate fixation of an osteotomy, such as nonunion and the need for subsequent plate removal (56%).