Chronic Carpal Instability

Fig. 10.1

If the SL ligaments are normal, closing the fist should not cause separation of the scaphoid and lunate bones. As compared to the contralateral side, any asymmetrical SL gap (arrow) greater than 5 mm is diagnostic of SLD

Injecting dye in the joint and analyzing the wrist with tomography or MRI scans may be useful in further defining partial tears of the SL ligaments or osteochondral defects. Notwithstanding, the gold standard technique in the diagnosis of intracarpal derangements, particularly when the diagnosis is still unclear, is arthroscopy [9, 13]. Information for a correct arthroscopic diagnosis of SLD dissociation is provided elsewhere in this book.

Treatment of SLD

Treatment of chronic SLD is not always predictable and often unsatisfactory [10, 11]. On the one hand, because the SL ligaments sustain considerable tension, most ligament reconstructions will deteriorate with time. In addition by the time the injury is recognized and treated the secondary stabilizers of the scaphoid may have also degenerated, thus limiting the chances for a successful surgical stabilization. Needless to say, treating the injury in the acute phase is more rewarding than dealing with a chronic case [13–15]. What follows is the description of the staging system we recommend to use in such cases [16], followed by a review of surgical alternatives proposed for the chronic, non-arthritic SLD.

When deciding treatment for an SLD, aside from the patient’s age, health status, and professional and/or vocational demands, five factors are to be considered:

Integrity of the dorsal SL ligament: It is important to establish whether the dorsal SL ligament is intact. Arthro-CT scans or MRI’s may be of help, but most often arthroscopy is the one that verifies the best the status of the important dorsal SL ligament.

Healing potential of the disrupted ligaments: If there is a mid-substance ligament rupture, with irregular ends, a poor healing potential is likely. By contrast, if there is an avulsion type of rupture with the ligament intact, the injury may heal if properly reattached.

Status of the secondary scaphoid stabilizers: It is important to evaluate whether the secondary scaphoid distal stabilizers (STT and SC ligaments) are functional or not. A radioscaphoid angle beyond 60° is indicative of a distal ligament disconnection.

Reducibility of carpal malalignment: Chronic SL dissociations often develop fibrosis at the level of the disrupted ligaments and capsular contractures, making reduction of its malalignment difficult. Reducibility, therefore, is an important parameter to consider. If the SL joint can be reduced with minimal force, the case is considered reducible. By contrast, if reduction can only be obtained by applying substantial force using “joy-sticks” wires, the case is to be considered irreducible. In general, no irreducible malalignment is likely to obtain good results by soft-tissue reconstruction.

Status of cartilage. It is important to note that if there is a cartilage defect, reactive chondrolysis, or joint degeneration in association to SL dissociation

By investigating these five parameters, each case can be classified into six stages (Table 10.1). The fact that the number of “no” answers increases from left to right, indicates a progression of the severity and/or chronicity of the problem from mild (Stage 1) to severe (Stage 6). The following is a description of the six stages [16].

Table 10.1

Staging of scapholunate dissociations

According to Garcia-Elias et al. [16]

SLD Stage 1 (Partial SL ligament injury): The SL ligaments are only partially ruptured and wrist alignment is normal. If there is pain, this is usually due to abnormal shear stress by the increased SL motion. Usually diagnosed by arthroscopy, these patients do well by debriding any unstable fragment of the disrupted proximal SL membrane, and percutaneously pinning the SL joint under arthroscopy control. In some instances, K-wire fixation may be supplemented by a dorsal capsulodesis [17–22]. After surgery, all these patients should follow an adequate program of proprioception, re-education of the muscles that may dynamically stabilize the scaphoid, namely the flexor carpi ulnaris, extensor carpi radialis longus and brevis, and the flexor carpi radialis (FCR) [23].
SLD Stage 2 (Complete SL ligament injury, repairable): This stage is characterized by complete disruption of the three components of the SL ligamentous complex, with a ruptured dorsal SL ligament still repairable, with good healing potential. The carpal bones are normally aligned, without cartilage degeneration. The secondary scaphoid stabilizers are still functional, and therefore there is no rotator subluxation of the scaphoid. Acceptable recovery of function is likely if the dorsal SL ligament is properly reattached in the early stage [21, 22].

Following this type of surgery therapy should include proprioception to re-educate the scaphoid dynamic stabilizers [23].
SLD Stage 3 (Complete SL ligament injury, non-repairable, normally aligned scaphoid): In this stage there is complete, non repairable rupture of all three components of the SL ligamentous complex. Carpal alignment is still normal owing to the integrity of the secondary stabilizers [6]. In these cases, either a bone-ligament-bone graft or a tendon reconstruction would be indicated. This will be the main subject of this chapter
SLD Stage 4 (Complete SL ligament injury, non-repairable, with carpal collapse): This stage is defined by a complete loss of the SL linkage, plus insufficiency of the distal scaphoid stabilizers (STT and SC ligaments). The carpus has collapsed, the radioscaphoid angle is larger than 60°, and the lunate may be abnormally ulnarly translocated and in DISI. To be included in this stage however, the malalignment needs to be easily reducible [16]. Cases in this stage may be treated by a tendon reconstruction [24–26], or by a reduction-association of the SL joint (RASL procedure) [27, 28] as described below.
SLD Stage 5 (Complete SL ligament injury with irreducible malalignment, but normal cartilage): Chronic malalignment may become fixed, either by bone deformity, by capsular contracture or both, thus preventing an easy reduction. In such cases, even if there is no cartilage damage, no soft-tissue procedure can achieve long lasting stability. In most instances, these cases are better treated by a partial intracarpal fusion [29–34] than by a soft tissue procedure.
SLD Stage 6 (Chronic SL ligament injury with degenerative osteoarthritis) : Chronic SLD tends to develop cartilage degeneration following a specific pattern called “Scapho-Lunate Advanced Collapse” (SLAC) [7]. These cases are usually treated by motion preserving, salvage procedures, such as proximal row carpectomy or a scaphoidectomy plus midcarpal (“four corner” or lunocapitate) fusion.

Summary

Stage 1	Debridement and stabilization
Stage 2	Repair
Stage 3 & 4	Reconstruction
Stage 5	Intercarpal fusion
Stage 6	Salvage

Surgical Techniques Used for the Treatment of SLD

When deciding a treatment for a patient with SLD, it helps to take into account the staging system described above, as well as the individual requirements that each patient may have. The following is a description of the most commonly utilized surgical operations for the chronic SLD. Salvage procedures for the degenerative osteoarthritis caused by the unsolved SLD (stage 6) will not be discussed in this chapter.

Tendon Reconstruction of SL Stability. The 3LT Method

The first suggested treatment for SLD was described in 1975 by Dobyns and Linscheid [11], and consisted of passing a strip of tendon through anteroposterior tunnels in the proximal pole of the scaphoid and the lunate. Immediate stability was obtained by tightly suturing the tendon graft around the joint. Unfortunately, the drill holes across poorly vascularized areas of bone often fractured, inducing early joint osteoarthritis. In 1995, Brunelli and Brunelli recommended using a strip of the FCR tendon to reconstruct both the proximal and distal connections of the scaphoid, in cases with a SLD with carpal collapse [24]. The strip of tendon, which was left attached distally, was passed through a transverse drill hole, across the distal scaphoid and anchored to the dorsal-ulnar corner of the distal radius by transosseous sutures. The method was subsequently modified by Garcia-Elias, Lluch and Stanley [16], who suggested using a strip of FCR tendon to augment the palmar distal connections of the scaphoid, to reconstruct the dorsal SL ligament, and to prevent the lunate from sliding ulnarly (Fig. 10.2a, b). Because this tendon reconstruction replicates the action of three ligaments, it has been named “three-ligament tenodesis” or “3LT” procedure. It is principally indicated in cases of SLD Stage 4, that is cases with non-repairable SL ligament injury, very easily reducible and without cartilage degeneration.

Fig. 10.2

(a, b) Schematic representation of the “Three-ligament tenodesis” technique to reconstruct unrepairable dorsal SL ligament, seen from a palmar (a) and dorsal (b) perspectives [16]. The FCR tendon is passed through a tunnel across the distal scaphoid aiming at the point where the dorsal SL ligament inserts. The tendon is then tensioned using the dorsal RTq ligament as an anchored point. Once around the ligament, the tendon is sutured onto itself. Unlike the original Brunelli method, this method does not attempt to cross the radiocarpal joint with the graft

The surgical technique for the 3LT procedure is as follows. The dorsum of the scaphoid and lunate are exposed using a standard dorsal approach, as described by Berger and Bishop [35]. Alternatively, a nerve sparing capsulotomy, as recommended by Hagert et al. [36] may be used. Using a cannulated drill, a 2.7 mm diameter tunnel is made across the scaphoid entering at the point of insertion of the dorsal SL ligament. The drill hole is made along the longitudinal axis of scaphoid, aiming at the palmar convexity of the scaphoid tuberosity. Through small transverse incisions a distally based, 8 cm long, strip of FCR tendon is obtained and passed through the scaphoid tunnel using a wire loop. A transverse trough or channel over the dorsum of the lunate is then made with a rongeur. This trough needs to be deep enough to uncover cancellous bone. To ensure intimate contact between the tendon strip and the decorticated dorsal aspect of the lunate, an anchor suture is placed into the floor of the trough. The dorsal radiotriquetral ligament is then identified and a slit is created in its distal end, just proximal to its triquetral attachment. The tendon strip is passed through that slit, and the ligament is used as a pulley to tension the ligament strip (Fig. 10.3a, b). Before tightening the tendon, the scaphoid, lunate and capitate are reduced and stabilized with K-wires. The tendon graft is finally sutured onto itself, and the anchor suture in the lunate is used to ensure close contact of the tendon graft to lunate cancellous bone.

Fig. 10.3

(a, b) Chronic, reducible SLD, without osteoarthritis (Stage 3). (a) Surgical picture of the SL joint, with a forceps demonstrating complete rupture of the SL ligaments. Only an elongated distal portion of the dorsal SL ligament is present, probably one of the reasons why the carpus had not collapsed yet. (b) Dorsal aspect of the “three-ligament tenodesis” before closing the capsulotomy. Note the tendon graft sutured onto itself, connecting the scaphoid to the dorsal radiotriquetral ligament

Complete wrist immobilization is maintained for 6 weeks, first in a short arm thumb spica cast for 4 weeks and a dorsal splint for another 2 weeks, when wires are removed. After this, a protective removable splint, allowing supervised rehabilitation, is retained for an additional 4 weeks. Contact sports are to be avoided for 6 months after surgery.

In a recent review of 38 patients with symptomatic SL dissociation who had undergone the 3LT procedure with an average follow-up of 46 months (range 7–98), pain relief at rest was obtained in 28 patients, with 8 complaining of mild discomfort during strenuous activity, and 2 having pain in most activities of daily life [16]. Twenty-nine resumed their normal occupational-vocational activities. Average ranges of motion at follow-up were for flexion 51 (74 % of contralateral), extension 52 (77 %), radial inclination 15 (78 %) and ulnar inclination 28 (92 %). Average grip strength relative to the contralateral normal side was 65 %. There were no signs of scaphoid necrosis. Seven patients showed mild signs of degenerative osteoarthritis at the tip of the radial styloid, while two developed subsequent global arthrosis (SLAC), although none were substantially symptomatic.

According to the more recent publications, the 3LT tenodesis appears to be a quite reliable solution for the unstable SLD, with less morbidity than partial fusions, and acceptable functional results [25, 26]. Whether or not the stabilizing efficacy of this technique deteriorates with time, however, is not known.

Bone-Ligament-Bone Grafts

In an attempt to replicate the positive results of replacing knee ligaments with bone-ligament-bone grafts, Weiss suggested transferring a bone-retinaculum-bone autograft harvested from the region of Lister’s tubercle to the dorsal SL ligament [37]. Harvey et al. [38] recommended the use of the third metacarpal-capitate ligament. The surgical technique is straightforward. Once the SL joint is reduced and transfixed by wires, a deep trough is carved at both sides of the joint and the bone-ligament-bone graft is buried and fixed with mini screws. In theory, the implanted ligament has similar elasticity and strength to the original structure. Unfortunately, the proximal scaphoid is poorly vascularized, making difficult the consolidation of the graft. Furthermore, the technique requires prolonged immobilization, which will result in the mechanical properties of the ligament deteriorating and ultimately potentially failing under the torques that will be exerted on it. However, the early clinical results are encouraging in the dynamic instabilities with normal secondary stabilizers [38]. By contrast, the rate of complications when used in static instabilities is still very high [37].

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