Kongkhet Riansuwan, MD,
Melvin P. Rosenwasser, MD
Scapholunate interosseous ligament (SLIL) injuries are common causes of mechanical wrist pain. Despite an increased knowledge of carpal injuries and improvements in radiological evaluation, the diagnosis of a SLIL tear can be difficult or missed unless the evaluating physician has a high index of suspicion and an appropriate level of understanding of wrist anatomy and injury patterns. Usually a detailed history and physical examination and a series of plain radiographs are sufficient to make a diagnosis of SLIL injury (Fig. 47-1). Occasionally, advanced imaging techniques, such as magnetic resonance imaging (MRI) with or without intra-articular contrast enhancement, can be helpful in establishing a diagnosis and evaluating the wrist for associated injuries.[1-3] MRI usually detects large, complete tears better than partial, smaller tears, however, particularly if the tear configuration is oblique to the imaging plane, or the tear is smaller than the distance between contiguous image slices.
After successful introduction in the knee and shoulder, arthroscopy gained popularity as a useful modality to diagnose and treat a wide spectrum of wrist pathology.[4,5] This procedure has become the gold standard for diagnosis of SLIL injuries.[6-8] Arthroscopy is a minimally invasive procedure allowing direct observation of intrinsic and extrinsic carpal ligaments and articular cartilage integrity under static and dynamic conditions. Comprehensive and accurate diagnosis and treatment of all carpal injuries can be done concurrently.
Because a delayed or missed diagnosis of an SLIL tear can lead to progressive carpal instability and predispose the patient to a predictable pattern of carpal arthritis called scapholunate advanced collapse (SLAC),[9-11] we believe that wrist arthroscopy should be considered early during the evaluation and management of a patient with a suspected SLIL injury. It should be used selectively, however, for patients with significant symptoms, for patients with a mechanism of injury consistent with SLIL injury, and for patients in whom conservative treatment has failed or in whom acute operative management is indicated.
Anatomy of the Scapholunate Complex
The wrist is a complex structure comprising multiple small joint articulations with stability resulting from a complex linkage of intrinsic, intercarpal ligaments and extrinsic capsular ligaments. The wrist can be thought of as two separate rows with hand motion being the composite effect of motion between the radius, ulna, proximal carpal row (scaphoid, lunate, and triquetrum) and distal carpal row (scaphoid, trapezium, trapezoid, capitate, and hamate). The scaphoid is uniquely situated in both rows on an oblique axis to stabilize the carpus, while still permitting coordinated relative motion between the two rows and the radius and ulna. The scaphoid is stabilized by many ligaments, including the SLIL, radioscaphocapitate, scaphotrapeziotrapezoid, scaphocapitate, and dorsal intercarpal.
The SLIL is a C-shaped structure connecting the dorsal, proximal, and palmar surface between the scaphoid and the lunate, leaving the distal aspect of the joint bare of soft tissue allowing the evaluation of scapholunate articular congruity, preservation, and instability. This midcarpal visualization is essential in assessing the degree of instability between the two bones and in grading the spectrum of partial to complete injury. The dorsal and palmar portions of the SLIL are true ligamentous structures. The proximal portion is a membranous structure composed mainly of fibrocartilaginous tissue. In the absence of a tear, the transition between the dorsal and the proximal portion is not readily visualized during arthroscopy. Palpation of the SLIL with a probe permits differentiation, however, between the thick, taut dorsal ligament and the softer, thin proximal portion.
A partial SLIL tear may appear as a patulous, convex outpouching, rather than a confluent, barely discernible structure (Fig. 47-2). The probe may uncover a complete disruption of the insertion of the SLIL often from the lunate, which could not be perceived with observation alone. Partial tears may require palpation in the radiocarpal joint with a probe to appreciate the laxity and a thorough evaluation of the distal scapholunate joint articular surface congruity in the midcarpal joint to observe subtle incongruity or diastasis. A significant complete intrasubstance SLIL tear is readily visualized in the radiocarpal and the midcarpal joints.
Biomechanical and Kinematic Considerations
The three different portions of the SLIL have different biomechanical properties. The dorsal portion of the SLIL has a highest load at ultimate failure, followed by the palmar portion and then the proximal portion. Serial, sequential ligament sectioning studies in cadavers have shown that the SLIL is the primary ligament scapholunate stabilizer.[16-21] No significant dissociation between the scaphoid and the lunate is shown, however, on static radiographs with an isolated, complete SLIL disruption.[16,22] This is explained by the presence of secondary stabilizers of the scapholunate joint, which must be injured either acutely or chronically to show radiographic instability. Injury to the volar extrinsic (radiolunate and radioscaphocapitate),[16,23] the distal intrinsic (scaphotrapezial),[16,24] or the dorsal intercarpal ligaments and the SLIL is needed to visualize pathological carpal bone rotation radiographically.
An isolated tear of the SLIL changes carpal loading and kinematics even without demonstrable radiographic abnormalities. Isolated loss of this major stabilizer of the carpus may lead to attenuation of the secondary supporting structures and progressive dissociation and rotation of the scaphoid and the lunate. With axial loading over time and without proximal restraint by the intact scapholunate joint, the capitate can descend proximally, further driving the scaphoid and lunate apart like a wedge. This results in midcarpal instability, loss of carpal height, and increased clinical symptoms as the bones increase their abnormal rotation. Changes in the radiocarpal, intercarpal, and midcarpal joint contact areas and loads in conjunction with the altered kinematics result in predictable SLAC arthritis. This process begins with radial styloid beaking and radial styloscaphoid joint narrowing (stage 1), then progresses proximally to alter the radioscaphoid facet proximal pole scaphoid articulation (stage 2), and finally progresses to the midcarpal capitolunate joint (stage 3).Treatment Options
Several factors need to be considered in clinical decision making about an arthroscopic procedure, not only to diagnose, but also to treat symptomatic scapholunate injuries (Fig. 47-3). Acute repairable lesions have heretofore been treated with open suture repair or reattachment with bone anchors. Previous reports have sought to separate acute injuries from chronic by using an arbitrary and unproven 6 weeks as a cutoff, with the implied understanding that only acute injuries could be repaired. Because the patient history is often unreliable regarding the first subtle injury versus the most recent and now symptomatic injury, however, dates alone should not indicate irreparable ligaments. We believe all such presumed SLIL injuries should be evaluated arthroscopically to stage properly and treat all injured structures. Repair, if possible, is preferred. Arthroscopy also has the added advantages that it is real time, can include direct palpation of structures, and can assess the dynamic nature of the instability and its reducibility (neither of which can be known from even the best MRI study).
Stable wrists with symptomatic tears (predynamic radiographic instability) are assumed after obtaining normal static and stress radiographs. Unstable wrists with tears demonstrable on grip films or cineradiography only (dynamic radiographic instability) have abnormal carpal alignment on stress radiographs (e.g., pronated posteroanterior grip), but normal alignment on unloaded routine radiographs. Unstable wrists with static instability on routine plain films (static radiographic instability) are obvious injuries and are not missed. These wrists may have advancing cartilage degeneration, however, which is often underappreciated, especially at the capitolunate joint. The presence of significant polyarticular arthritis changes treatment options and often precludes reconstruction and indicates salvage procedures, which usually fall outside of the purvey of arthroscopy except for a master arthroscopist.
Arthroscopic assessment guides and rationalizes the potential for repair by confirming the degree of injury and the severity of instability. Arthroscopic treatment options include the following either in isolation or in combination: ligament débridement, ligament thermal shrinkage, transarticular Kirschner wire (K-wire) fixation, and radial styloidectomy (see Fig. 47-3).
Complete repairable tears in the senior author's (M.P.R.) experience are best managed with open techniques. If the dorsal ligament has been avulsed from its attachment, it can and should be primarily repaired either with transosseous suture or with suture anchor. Depending on the amount of associated soft tissue injuries, this can be augmented with any of the numerous variations on dorsal capsulodesis.[26-28]
SLAC wrist evolution beyond the radial styloid and scaphoid waist articulation often requires more extensive, open surgical procedures. Complete irreparable tears in a young, active patient with a wide scapholunate diastasis and significant carpal malrotation should be considered for any procedure that can realign the carpus and preserve carpal kinematics so that the natural history of end-stage SLAC wrist can be forestalled. One such procedure used by the senior author since 1989 is the reduction and association of the scaphoid and lunate (RASL) creating a SLIL neoligament and protecting the repair with a transosseous scapholunate headless bone screw.Standard Arthroscopic Technique
Similar patient positioning and technique are used in each of the arthroscopic surgical techniques. The patient is placed supine with the symptomatic arm abducted on a hand table. Regional anesthesia is preferred, and prophylactic intravenous antibiotics are administered. The arm is elevated, and prepared and draped in the usual manner, and a sterile tourniquet is applied to the upper arm. The index and middle fingers are placed in finger traps and suspended from a traction tower with the elbow flexed 90 degrees. The upper arm is strapped to the hand table and traction tower for countertraction. Care is taken to ensure all of the ulnar nerve and all bony prominences are well-padded and protected. Ten pounds of traction is applied.
All arthroscopic portals are outlined with a skin marker before exsanguination so that the superficial veins are noted and avoided during portal creation. The arm is exsanguinated, and the tourniquet is inflated to 250 mm Hg. An 18-gauge needle is used to confirm the location of each arthroscopic portal, ensuring that the entry angle corresponds to the volar tilt and radial inclination of the distal radius. The radiocarpal joint is distended with 3 to 5 mL of normal saline to increase the working space of the joint and reduce the risk of iatrogenic chondral injury.
A no. 11 blade is used to make a push incision through the skin only, which minimizes the chance for an injury to any adjacent cutaneous nerve branches. Then a fine curved hemostat is used to penetrate the capsule bluntly. The hemostat is spread to establish a viewing portal, and a blunt-tipped trocar within a cannula is inserted in a controlled manner with a gentle pressure. If there is any resistance to instrument advancement, the needle should be used to confirm portal location. Iatrogenic damage to the articular cartilage or intercarpal ligaments usually occurs during forced introduction of the trocar at the wrong angle or starting point.
After successful cannula placement, the trocar is removed, and a 30-degree angled, 2.7-mm arthroscope is inserted. Distention of the radiocarpal space is maintained by a pressurized irrigation system through the cannula with outflow through a separately placed 18-gauge needle into the radiocarpal joint in the 1,2 portal or the ulnocarpal joint through the 6R or 6U portals. The 3,4, 4,5, 6U, 6R, midcarpal radial, and midcarpal ulnar portals are necessary to complete a thorough diagnostic evaluation and allow therapeutic procedures.Arthroscopic DébridementIndications
Arthroscopic débridement alone is indicated for acute or chronic partial, but stable tears of the volar or membranous portion of the ligament in a patient with mechanical symptoms (Fig. 47-4). These patients usually have focal reproducible mechanical wrist pain over the dorsal scapholunate joint worsened by activity and normal x-rays. It is common to treat these patients conservatively for several months with splints and activity modification. Persistent symptoms often lead to MRI; imaging rarely provides a definitive diagnosis and does not illuminate the treatment options. Arthroscopy in these patients typically reveals a stable Geissler grade 1 or 2 injury pattern with slight midcarpal incongruity and joint widening. Patients’ symptoms are due to tears in the substance of the ligament, which, although not destabilizing, create mechanical impingement during wrist motion causing focal dorsal wrist pain and occasionally leading to a synovitis and dorsal capsular thickening. Débridement of these SLIL flap tears in either the dorsal or the membranous portions and partial synovectomy often ameliorate symptoms.
Contraindication to Débridement Alone
An absolute contraindication is a complete reparable tear or a more advanced Geissler instability pattern that was underappreciated in the preoperative evaluation. Static instability patterns with preexistent arthritis are not helped except in a few selected cases of elderly patients with low demand. A staged débridement and synovectomy can be offered with the full understanding that it may fail and necessitate a more comprehensive salvage procedure.Technique
Evaluation of the instability is central in indicating the appropriate procedure and requires radiocarpal and midcarpal arthroscopy to determine the Geissler grade. If the wrist is stable (Geissler grade 1 or 2 injuries), the tear can be débrided by alternating the arthroscope and working instruments between the 3,4 and 4,5 radiocarpal portals. The torn portion of the SLIL is débrided to stable margins, with care taken to preserve healthy, intact fibers. This is facilitated by using the least aggressive shaver, such as a full radius resector, which would not injure healthy intact tissue. After débridement, it is important to reprobe the midcarpal scapholunate articulation to ensure that stability has not been affected.Results
Isolated arthroscopic débridement has been reported in several small case series (Table 47-1).[5,7,29] Most patients have predynamic or dynamic radiographic instability and Geissler grade 1 or 2 tears. Good pain relief, grip strength improvement, and maintenance of range of motion have been reported. The need for postoperative immobilization is unclear because some studies treated patients in a soft dressing with immediate motion, and some studies reported wrist immobilization for 6 to 8 weeks.
|No. patients||23 cases||28 cases||7 cases||10 cases||16 cases||8 cases||40 cases||11 cases|
|Average age||30 yr||32 yr||41 yr||37 yr||34 yr||38 yr||Not mentioned||40 yr|
|Average length of preoperative symptoms||6 mo||8 mo||>6 mo||2 (<6 mo); 6 (>6 mo); 2 unknown||5 mo||25 mo||Variable||Acute|
|Clinical instability||6 cases||30 cases||Not mentioned||10 cases||13 cases||4 cases||Not mentioned||7 cases|
|Radiographic instability||Not mentioned||Not mentioned|
|Predynamic||23 cases||Not mentioned||7 cases||8 cases||16 cases||5 cases|
|Dynamic||8 cases||2 cases||3 cases|
|Geissler grade (no.)||1 or 2 (21); 3 (2)||Complete (15)||Not mentioned||2 (10)||1 (2); 2 (14)||1 (1); 2 (7)||Not mentioned||3 or 4 (7)|
|Procedure (postoperative immobilization)||Débridement (6-8 wk)||Débridement (2 wk)||Débridement (none)||Monopolar thermal shrinkage (4-6 wk)||Débridement + bipolar thermal shrinkage (2 wk)||4 débridement + shrinkage (none); 4 débridement + shrinkage + pinning (6-8 wk)||Temporary pinning (unknown)||Temporary pinning (8 wk)|
|Average follow-up||15 mo||27 mo||34 mo||28 mo||19 mo||3-8 mo||24-96 mo||36 mo|
|Outcome||11 excellent; 9 good; 1 fair; 2 poor||67% completed; 85% partial resolved||Good pain relief; minimal loss of motion||9/10 pain resolved; average DASH = 20||8 pain-free; VAS 8-4 mm; grip 80%; flexion/extension 142 degrees||7 good pain relief; minimal loss of motion; 1 finally wrist fusion||85% pain relief if <3 mo and <3 mm of scapholunate diastasis||4 pain relief; 3 mild pain; residual pain may be related to distal radial fractures|
Radiofrequency Thermal Collagen ShrinkageIndications
The indications for radiofrequency thermal collagen shrinkage are similar to the indications described in the débridement section. In particular, it may be most useful in partial membranous tears or ligament redundancy. If the surgeon appreciates increased motion between the scaphoid and the lunate, particularly after débridement, without significant rotation, radiofrequency thermal collagen shrinkage can be performed in an attempt to tighten the intact portions of the SLIL and improve carpal kinematics. Additionally, if there is a redundancy or laxity in the SLIL, usually corresponding to Geissler grade 1, radiofrequency thermal collagen shrinkage can be performed with or without débridement based on surgeon judgment.Contraindications
Radiofrequency thermal collagen shrinkage alone is contraindicated in the presence of significant, unstable flaps of ligamentous tissue because débridement of this tissue is necessary to decrease mechanical symptoms. It also is contraindicated as an isolated procedure in patients with carpal bone rotation, in patients with repairable ligament tears, and in patients with significant arthritis.Technique
One study describes thermal stabilization using monopolar cautery (Oratec, Mountain View, CA) placed through the 4,5 portal. The probe is applied to the SLIL starting volarly and working dorsally until all the lax and redundant SLIL has been made taut. The authors recommend continuous irrigation with a safety limit on the probe set to 75°C to prevent chondral thermal injury. When midcarpal examination reveals the scapholunate joint congruency without gapping, the thermal shrinkage is complete. The authors believe postoperative immobilization for 4 to 6 weeks is crucial to allow ligament healing and to prevent recurrent laxity.
Another study uses a 2.3-mm bipolar probe (Vapr; Mitek, Westwood, MA), which is placed through the 4,5 portal. The probe was carefully applied to the torn rim of the volar portion of the ligament, the proximal membranous portion, and a small part of the dorsal ligament using multiple strokes similar to a paintbrush until visual color changes occurred. The probe was used intermittently, delivering energy for only a few seconds at a time to allow adequate outflow of warmed fluid. The tissue quality was palpated with a probe to confirm decreased laxity.
The senior author (M.P.R.) often applies the radiofrequency probe (Microblator 30 1.4 mm; Arthrocare, Sunnyvale, CA) to the proximal, membranous portion of the SLIL and the palmar midcarpal ligaments. In the midcarpal joint, the palmar ligamentous tissue at the junction of the scaphoid and lunate corresponds to the distal edge of the palmar SLIL and the radioscaphocapitate ligament (Fig. 47-5). Careful, limited, short bursts of thermal energy applied to this palmar midcarpal ligamentous and capsular tissue tightens the scapholunate and scapholunocapitate articulations. This midcarpal application of thermal collagen shrinkage can address proximal row intercarpal and midcarpal instability. Decreased gapping between the scaphoid and the lunate is readily observable. Manual reciprocal palmar-dorsal translation between the scaphoid and lunate before and after thermal shrinkage should be performed without traction to determine if there are any changes in stability after shrinkage. Without reduction of traction, a false increased sense of stability may be appreciated. Additionally, it should be more difficult to insert a probe in the midcarpal scapholunate interval.
There are two published series of 10 and 16 patients treated with monopolar and bipolar electrothermal collagen shrinkage and postoperative immobilization ranging from 2 to 6 weeks (see Table 47-1).[30,31] Complete pain relief ranged from 50% to 90% with preservation of wrist motion and no postoperative radiographic instability.Arthroscopic-Assisted Temporary Transarticular Wire PlacementIndications
Transarticular pinning has been hypothesized to result in ligament stiffening and the formation of fibrosis along the pin tract, which can lead to joint stability and alleviate symptoms in patients with mild scapholunate instability. This technique may be useful in patients with mild carpal bone malrotation and diastasis from partial SLIL injuries. When carpal bone anatomical position needs to be restored, transarticular pin placement is necessary to hold the bones in the reduced position until soft tissue healing occurs. In patients with partial tears without carpal malrotation in whom the surgeon would like to try to increase stability but does not want to perform radiofrequency thermal collagen shrinkage, or there is minimal remaining ligament to débride, the placement of temporary wires may result in increased scapholunate stability.Contraindications
There are no absolute contraindications to transarticular wire placement. Wire placement across the intercarpal joints may be unnecessary, however, in the absence of carpal malrotation.Technique
Using manual pressure applied on the distal scaphoid tubercle, palmar to dorsal, the scaphoid can be rotated out of palmar flexion. Radial to ulnar pressure between the scaphoid and triquetrum can close the scapholunate gap. Fluoroscopy and arthroscopy should be used to confirm anatomical reduction. If the lunate is dorsiflexed on the lateral view, it is impossible to be reduced by closed manipulation. Separate wires can be placed into individual bones and used as joysticks to derotate the scaphoid and lunate. The scaphoid joystick wire is placed obliquely into the scaphoid aiming from distal-dorsal to proximal-palmar so that pressure applied to the wire from distal to proximal causes scaphoid extension. The lunate joystick wire is placed obliquely from proximal-dorsal to distal-palmar so that proximal to distal pressure results in lunate flexion.
After the bones have been derotated, a percutaneous wire is placed across the scapholunate joint from radial to ulnar. Either 0.045-inch or 0.062-inch wires can be used. Pin insertion technique is crucial because the anatomical snuffbox contains the dorsal branch of the radial artery, the cephalic vein, and multiple sensory nerve branches with a narrow safe zone. Wires should be pushed through the skin and down to the scaphoid freehand. Then the wire driver is placed over the wire and turned on. By having the wire tip fixed to the bone before wire rotation by the driver, soft tissue injury is minimized. Several divergent pins can be placed across the scapholunate and scaphocapitate joint in this manner. This is the best way to maintain the reduction of the scapholunate diastasis achieved through derotation.Results
Two case series have been reported on patients who underwent arthroscopic reduction of the scapholunate joint and temporary transarticular scapholunate joint fixation for isolated SLIL injury or associated with a distal radius fracture (see Table 47-1).[33,34] These types of injuries are very different and do not act the same way clinically over long-term follow-up. Acute injuries recognized and treated after trauma have more predictable outcomes, in contradistinction to chronic injuries with a vague history of significant antecedent trauma; this correlates with the quality of the tissue at the ligamentocapsular injury site and its capacity to heal.Arthroscopic Débridement, with or without Thermal Shrinkage, with or without Temporary Transarticular PinningIndications
SLIL débridement combined with thermal capsular shrinkage is indicated in the context of clinical localizing signs and symptoms, radiographic instability, and arthroscopic grading of injury. Any carpal bone malrotation (dynamic instability) or incongruence requiring reduction should be supported further with temporary transarticular pinning.Contraindications
This procedure is contraindicated and inadequate for patients with static carpal malalignment. Static carpal malalignment corresponds to chronicity, and that translates to a lack of adequate residual ligament as scaffolding that could foster repair and provide stability and improved carpal kinematics. These patients require supplemental tissue grafting using open or closed techniques, such as various capsulodeses and ligament reconstruction with tendon grafts or bone-ligament-bone constructs or salvage procedures that restrict carpal motion and maintain reduction through limited intercarpal fusions, such as scaphotrapeziotrapezoid. Simple débridement and Kirschner pinning for these static instabilities routinely fail to maintain the correction of carpal alignment achieved at surgery.[26,35,36]Technique
Ligament débridement, thermal shrinkage, and temporary transarticular pinning are performed together in a similar fashion as described in the previous sections.Results
To date, there are no published reports detailing the outcomes of patients treated with this protocol. This communication is the opinion of the senior author (M.P.R.), who has performed thermal ligament shrinkage in eight patients with follow-up to an early clinical result. The average age of patients was 38.3 years (range 21 to 54 years) (personal communication) (see Table 47-1), and all met the clinical and radiographic inclusion criteria discussed previously. Procedures included ligament débridement (eight), scaphocapitate (four) and scapholunate (four) transarticular pinning (0.045-inch K-wire), dorsal ganglionectomy (one), débridement of the triangular fibrocartilage complex (two), and posterior interosseous neurectomy (one). Predynamic and dynamic radiographic instability was observed in five (predynamic) and three (dynamic) patients. The proximal scapholunate ligament was thermally shrunk in all patients, and the midcarpal palmar ligaments were shrunk in four patients.
Postoperative immobilization was used in the four patients with reducible instability who underwent pinning. Seven of eight patients had pain and symptom resolution. One patient with a workers’ compensation claim and a prior wrist arthroscopy complained of persistent pain after thermal capsulorrhaphy done by the senior author (M.P.R.). He was revised to a total wrist arthrodesis, which allowed him to return to work. During intraoperative assessment 12 months after thermal shrinkage, there was no visible evidence of cartilage or ligament injury from the thermal shrinkage.Arthroscopic StyloidectomyIndications
Arthroscopic radial styloidectomy eliminates the painful impingement between the distal scaphoid and the radial styloid in stage I SLAC. It is typically done in combination with arthroscopic SLIL débridement. The presence of arthritis indicates long-standing carpal instability with secondary ligament attenuation. Arthroscopic styloidectomy and SLIL débridement alone are usually recommended in older patients with low demand who present with localizing radial wrist pain during activities of daily living. They must be counseled that styloidectomy and débridement may provide only temporary relief of symptoms.Contraindications
Arthroscopic styloidectomy is contraindicated when arthritis extends beyond the radial styloscaphoid waist articulation, as in stage II or III SLAC wrist. It is not recommended as the definitive intervention in a younger, more active patient with higher demands because it does not treat the underlying chronic instability.Technique
After diagnostic arthroscopy confirms advanced midcarpal or proximal radioscaphoid arthritis, the working instrumentation portal is the 1,2 portal, which is established between the extensor pollicis brevis and extensor carpi radialis longus tendons. A shielded bur is inserted in the 1,2 portal. Alternatively, the arthroscope may be placed in the 4,5 portal with the bur placed through the 3,4 portal. Radiocarpal synovectomy improves visualization of the radial styloid and volar extrinsic ligaments. Less than 4 mm of styloid should be removed to avoid detachment of the radioscaphocapitate ligament. The radioscaphocapitate ligament prevents ulnar translation of the carpus. The diameter of the bur helps guide the resection depth, but the degree of resection and decompression also should be assessed with the mini-fluoroscope and in the provocative positions of wrist flexion and radial deviation.Results
There are no published reports on the outcome of arthroscopic radial styloidectomy in the treatment of SLIL injury and its sequelae. Arthroscopic and open radial styloidectomy were discussed in relation to SLAC wrist in a study by Yao and Osterman, without clinical results.Reduction and Association of the Scaphoid and Lunate
The RASL procedure was developed as an open reconstructive procedure to reassociate the scapholunate joint and foster a fibrous neoligament by dechondrification of the interface and maintaining the reduction through healing with a headless bone screw, which is placed transarticularly by the senior author (M.P.R.). The procedure can be and is being done arthroscopically, and although the follow-up time is shorter, the results are similar.[38-40]Indications
The RASL procedure is a technique developed for treatment of a chronic static scapholunate instability in which the ligament is irreparable and the resultant arthritis is focal. It is also indicated in salvage after a failed primary surgical reconstruction such as scapholunate ligament repair, scapholunate pinning, or a dorsal capsulodesis.
The premise of RASL technique is that it is important to maintain the obligatory intercarpal scapholunate rotation, while still controlling the aberrant scaphoid flexion and lunate extension by relinking the joints without fusing them. The crucial elements of a successful RASL procedure are the dechondrification of the opposing surfaces of the scaphoid and lunate; the anatomical reduction of the scaphoid, lunate, and capitate; and the maintenance of this normal carpal alignment during the reparative phase in which the formation of a fibrous neoligament between the scaphoid and the lunate occurs. The planned retention of a headless bone screw (Fig. 47-6) augments and protects the fibrous neoligament, while undergoing an expected lucency around the lunate screw threads as it permits near-physiological motion between the scaphoid and the lunate. This concept has been confirmed by a cadaver biomechanical study in which scapholunate motion after the RASL procedure was found to be preserved within 5 degrees of the preinjury state for all positions of wrist motion.
The RASL procedure is contraindicated in patients with partial tears without instability or with repairable, unstable SLIL tears. Additionally, this procedure would not relieve pain in the presence of advanced radiocarpal or midcarpal arthritis. Limited radial styloscaphoid arthritis is not a contraindication because a radial styloidectomy is an integral part of the procedure to gain access for the placement of the screw in the central axis of rotation of the lunate.Technique
A longitudinal dorsal skin incision is made just ulnar to Lister's tubercle. The third compartment is opened longitudinally, and the extensor pollicis longus is retracted radially. The fourth compartment is elevated subperiosteally in an ulnar direction. Wrist arthrotomy is performed in a ligament-sparing fashion through a transverse incision parallel and proximal to the dorsal intercarpal ligament. The dorsal radiotriquetral ligament also is preserved.
The radial styloid is approached through a separate, short, longitudinal, radially based incision. Identification and protection of the superficial radial sensory nerve branches and the radial artery are mandatory. Next, the first dorsal compartment retinaculum is incised and reflected, and later is used to imbricate the radial collateral ligament and capsule at closure. The thumb tendons are retracted, and the capsule is opened longitudinally. A limited styloidectomy is performed, preserving the scaphoid fossa and most of the radioscaphocapitate ligament origin; this provides access to the radial proximal scaphoid for later screw placement and treats the concomitant radial styloscaphoid arthritis. The dorsal capsulotomy is performed through two transverse windows, which respect the dorsal intercarpal ligament, an important secondary stabilizer of the wrist.
To manipulate the scaphoid and the lunate during reduction, a 0.062-inch K-wire is placed into each bone and used as a joystick. Each K-wire should be placed in an orientation that does not block the guidewire placement in the center axis of rotation of the lunate and the subsequent headless screw fixation. If this is noted in subsequent passes of the guidewire, the joystick K-wire can be repositioned after reduction is obtained. One K-wire is placed distally near the scaphotrapezial joint and directed proximally into the palmar-flexed scaphoid, and another is placed proximally and directed distally in the dorsiflexed lunate. The cartilage of the scaphoid and the lunate at the articulation is burred to induce punctate subchondral bleeding. This bleeding facilitates the ingrowth of vascularity leading to the development of fibrous tissue and a neoligament.
The scapholunate joint is anatomically reduced by derotation reciprocally by performing flexion of the lunate and extension of the scaphoid using the wire joysticks. This also results in reduction of the capitolunate joint, which is anatomical when the cartilage of the capitate proximal pole is no longer visualized. A Kocher clamp is placed on the reduced K-wires to maintain the reduction, which is confirmed fluoroscopically and visually. Then the wire for the cannulated Headless Bone Screw (Hand Innovations, Miami, FL) is inserted through the radial incision just proximal to the scaphoid waist toward the lunate vertex. The wire should pass through the center of the scaphoid and lunate in the coronal and the sagittal planes to establish an isometric rotation point, which nearly restores carpal kinematics. The depth should be measured so that the screw can be countersunk slightly within the scaphoid. The screw is advanced, and fluoroscopy is used to confirm appropriate screw position and length. The K-wires all are removed. Interrupted absorbable sutures are used to close the radial capsule. The first dorsal retinaculum is closed over the relocated tendons. The dorsal wrist capsule is carefully repaired without imbrication, and no capsulodesis is performed to limit motion. The extensor pollicis longus remains transposed from its sheath.
A volar splint is used for comfort for 2 to 3 weeks. Then early, active motion in a supervised occupational therapy program is initiated. Gradual resistance exercises are begun several weeks later with unrestricted activity at 4 o 6 months.
The arthroscopic RASL procedure follows the same principles, but the wires and screw are placed percutaneously often aided by stab wound incisions with a no. 11 blade. The radial styloidectomy and decortication of the opposing scaphoid and lunate articular surfaces are performed arthroscopically with mechanical burs. Rather than direct observation, scapholunate and lunocapitate reductions are observed fluoroscopically. Time should be taken at the beginning of the procedure to ensure adequate fluoroscopic visualization. We teach that several open RASL procedures should be done before arthroscopic RASL is attempted.Results
A good outcome was achieved in 20 of 24 (83%) patients who underwent an open RASL procedure for chronic scapholunate injury (22 static and 2 dynamic tears an average of 16 months postinjury) with mean follow-up time of 62 months. The postoperative average visual analog score for pain was 1, and the average Disabilities of the Arm, Shoulder, and Hand (DASH) score was 23. Mean grip strength of the affected hand was 79% compared with the unaffected hand. Mean range of motion in flexion and extension was 103 degrees. Postoperative radiographs showed significant improvement of scapholunate diastasis (5.1 to 1.6 mm) and the scapholunate angle (81 to 53 degrees), and no significant change in carpal height ratio. Three patients needed reoperation because of chronic instability and pain and required intercarpal fusion or proximal row carpectomy. Two patients required screw removal at an average of 49 months after surgery because of screw head prominence. One patient is asymptomatic after screw removal, and the second patient has persistent instability and progressive arthritis.Conclusion
Scapholunate ligament injuries are common, but they are often difficult to diagnose with many overlapping and confounding conditions. Inadequate treatment can lead to progressive instability because of changes in associated intrinsic and extrinsic ligaments. Arthroscopy plays a major role in staging the degree of chondral and ligamentous injuries and indicating treatment. Various arthroscopic procedures can be performed alone or in combination based on radiographic instability, location, and extent of the ligament injuries. These arthroscopic techniques include débridement, thermal capsuloligamentous shrinkage, transarticular wire placement, styloidectomy, and the RASL procedure. Increasingly severe static deformity resistant to reduction via the arthroscope should be repaired with an open procedure. 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