Anthony M. DeLuise, Jr. and Randall W. Culp
DEFINITION
Scapholunate ligament tears are the most common form of carpal instability.
If left untreated, this injury will cause degenerative changes in the wrist.3,6,8,13
Complete tears of the scapholunate ligament exist, yet partial tears, or dynamic instability, occur as well. This diagnosis requires a high index of suspicion and specific imaging. Dynamic instability is defined as a wrist that maintains normal alignment at rest but will collapse with applied load. Consequently, stress radiographs or diagnostic arthroscopy is needed to make the diagnosis.3,13
Treatments of scapholunate ligament tears include primary repair, dorsal capsulodesis, tendon grafting, ligament reconstruction, proximal row carpectomy (PRC), and limited carpal arthrodesis.
Primary repair may not be possible if the remnant ligament is not amenable to repair.
Tendon weaves are technically challenging and do not recreate the unique motion between the scaphoid and lunate and thus may yield new problems. A PRC alters kinematics and may decrease grip strength.
Limited arthrodesis for the chronic scapholunate ligament tear with coincident radiocarpal arthrosis relieves pain but creates a decrease in range of motion and alters the mechanics of the wrist joint, potentially leading to degenerative changes in adjacent joints.3,6,13
ANATOMY
The scapholunate ligament is one of the many intrinsic ligaments of the wrist. It is intra-articular and is composed of collagen fascicles. It consists of three main parts: dorsal, membranous (or proximal), and volar (FIG 1).1,11
The dorsal portion is the strongest of the three. It is 2 to 3 mm thick and 3 to 5 mm long. Its collagen bundles are oriented transversely. It is most important in limiting dorsal–palmar translation. The most dorsal area always merges with the wrist articular capsule. More than 300 Newtons (N) of tensile stress is required for failure.
The proximal or membranous portion is weak and thin. It is composed of mostly fibrocartilage and there are no neurovascular bundles within it (avascular). Only 25 N of stress will cause this portion of the scapholunate ligament to fail.
The volar portion of the scapholunate ligament is only 1 mm thick and 4 to 5 mm long. Its collagen bundles are oriented obliquely. The volar and proximal portions are most important in limiting dorsal–palmar rotation. The volar and membranous portions of the scapholunate ligament are intersected by the loose radioscapholunate ligament (ligament of Testut). The amount of stress to failure here is 150 N.
The scaphocapitate, scaphotrapezium–trapezoid (intrinsic), radioscaphocapitate, long and short radiolunate (volar extrinsic), dorsal radiocarpal, and dorsal intercarpal (dorsal extrinsic) ligaments also provide support and stability in this area.
PATHOGENESIS
The mechanism of injury is often a fall on an outstretched hand. Mayfield et al9 described this injury occurring with an axial load in excessive dorsiflexion, ulnar deviation, and midcarpal supination. This position causes the capitate to separate the scaphoid (radial and dorsal) and lunate (ulnar and palmar).
An ipsilateral distal radius fracture or scaphoid fracture can occur up to 30% of the time.3,4
The lunate will naturally flex with the scaphoid and extend with the triquetrum. In a patient with a scapholunate ligament injury, the connection to the scaphoid is lacking, the scaphoid will flex and rotate away from the lunate because of its other attachments, and the lunate will fall into a dorsal intercalated segment instability (DISI) pattern. For this rotational instability to occur, the dorsal capsular ligaments must be injured as well.
An acute scapholunate injury may or may not coincide with an injury to the surrounding ligaments (ie, dorsal extrinsics). If it does, a DISI pattern may be noted soon after injury. If there is no injury to the surrounding structures, attenuation of these structures over time may occur and then subsequently cause a DISI pattern. When DISI does occur, this pattern of carpal instability must be corrected for any treatment of this injury to be successful.
NATURAL HISTORY
The natural history of the wrist with a scapholunate ligament injury has been described by several authors. Pain and instability can result from a static injury. A DISI pattern deformity as described earlier will develop, and a very specific sequential pattern of wrist arthrosis will progress (scapholunate advanced collapse [SLAC]):
Stage IA: radial styloid with or without scaphoid arthrosis
Stage IB: radioscaphoid arthrosis
FIG 1 • The scapholunate ligament viewed from the proximalradial side with the scaphoid removed.
Stage II: capitolunate arthrosis
Stage III: panarthritis
The radiolunate joint is typically spared.14,15
PATIENT HISTORY AND PHYSICAL FINDINGS
Commonly, the patient will describe radial-sided wrist pain, pain with loading activities, and weakness.
Physical examination methods include the following:
Observation and palpation of gross edema
Wrist range of motion in extension, flexion, ulnar, and radial directions. Decreased range of motion or pain with extremes of motion will be evident.
Palpation just distal to the tubercle of Lister to assess for scapholunate interval tenderness
Ballottement test: Pain or instability here is concerning for a scapholunate ligament tear
Watson test: Pressure on the scaphoid tuberosity during ulnar-to-radial deviation of the wrist prevents the scaphoid from normally flexing. In a wrist with a scapholunate ligament tear, the proximal pole of the scaphoid will dorsally subluxate out of the scaphoid fossa with this maneuver, causing a clunk. A palpable clunk is indicative of instability.
Grip strength weakness is sensitive but not specific for scapholunate ligament disruption.
A complete examination of the wrist should also include evaluation of associated injuries and ruling out differential diagnoses. This includes but is not limited to the following:
Lunatotriquetral tears: pain with “shuck” of the lunate and triquetrum
Masses: examine carefully for any cysts or masses that may be causing pain
Distal radius or scaphoid fracture: tenderness at the distal end of the radius or the snuffbox as well as a fracture noted on radiographs
Triangular fibrocartilage complex (TFCC) tears: pain with a TFCC stress test, which is an axially applied load via ulnar deviation while moving the wrist through a flexion–extension arc
IMAGING AND OTHER DIAGNOSTIC STUDIES
Plain radiographs include posteroanterior (PA), lateral, and scaphoid views, although some authors will advocate the “complete” series to include a clenched-fist PA, a radial deviation PA, and flexion and extension lateral radiographs. It is helpful to compare the radiographs with the contralateral extremity.3,13
A static scapholunate ligament injury will reveal an increased space between the scaphoid and lunate on a PA radiograph. The normal scapholunate distance is less than 3 mm. If this interval is greater than 3 mm, the patient has what is known as the Terry Thomas sign. Additionally, as mentioned earlier, the scaphoid will collapse into flexion and the tuberosity will project in the coronal plane, revealing a scaphoid ring sign. The astute observer may also note the volar lip of the extended lunate overlapping with the capitate (FIG 2A–C).
The lateral radiograph may reveal an increased scapholunate angle. This angle is found by drawing lines through the longitudinal axes of the scaphoid and lunate and measuring the angle. Normally, it falls between 30 and 60 degrees. A radiolunate angle greater than 15 degrees indicates a DISI deformity (FIG 2D).
Flexion and extension lateral radiographs will show motion occurring at the lunocapitate joint and an uncoupling of the normally synchronous scapholunate motion.
Radial and ulnar deviation radiographs and a clenchedfist radiograph may portray a dynamic instability picture in that a static radiograph reveals no deformity (ie, normal scapholunate gap), but one of these views will reveal an abnormal scapholunate diastasis.
The chronic scapholunate injury may have evidence of arthritis on any of these views and the physician must recognize these findings, which indicate an old injury (FIG 2E,F).
Magnetic resonance imaging has become valuable in assessing acute or chronic scapholunate ligament tears (FIG 2G).
Arthroscopy is the imaging method of choice. It allows the experienced surgeon to diagnose most wrist pathology as well as affording the ability to possibly treat it (FIG 2H).
Geissler et al4 published four stages of scapholunate ligament tears based on arthroscopic examination (see Chap. HA-41).
DIFFERENTIAL DIAGNOSIS
Distal radius fracture
Scaphoid fracture
Radioscaphoid arthritis
Scaphotrapezial arthritis
FIG 2 • A. PA radiograph demonstrating an increased scapholunate gap and a scaphoid ring sign. B. A fluoroscopic image of another example of an increased scapholunate gap. C. The contralateral wrist demonstrates a normal scapholunate interval. D. A lateral radiograph demonstrating an increased scapholunate angle. E,F. Scapholunate advanced collapse (SLAC) wrist. E. Early-stage arthrosis from a chronic scapholunate ligament injury affecting the radial styloid. F. This PA view on the right demonstrates a more advanced stage. Bone–ligament–bone reconstruction may not be the preferred choice of treatment here. G. MRI with a scapholunate ligament injury. H. Arthroscopic view. Arthroscopy can easily identify scapholunate ligament tears.
deQuervain tenosynovitis
Dorsal wrist impaction syndrome
Dorsal ganglion cyst
Lunatotriquetral instability
Midcarpal instability
NONOPERATIVE MANAGEMENT
Nonoperative management of a scapholunate injury is seldom indicated. Geissler grade 1 injuries are the only injuries treated with just immobilization. We prefer a removable volar splint worn full time for 4 weeks followed by 4 weeks of splinting and removal of the splint for active range-of-motion exercises of the wrist. At the conclusion of 8 weeks, passive range of motion is initiated if necessary, followed by strengthening.
SURGICAL MANAGEMENT
Less invasive surgical procedures are used for partial scapholunate ligament tears and the wrist with dynamic instability. This can consist of thermal shrinkage through the arthroscope, arthroscopic débridement, and percutaneous pinning of the scaphoid and lunate in a reduced position. A capsulodesis may be considered.
The surgical treatment of complete scapholunate ligament tears depends on the chronicity of the injury and the presence of joint arthrosis. Ligament injuries older than 3 weeks have a lower rate of healing because of the ligament's lack of vascularity. In these more subacute or chronic injuries, it may be difficult to obtain a good outcome when performing a primary direct repair of the ligament.3
In addition, repair or reconstruction of the scapholunate ligament is a futile exercise in those joints with SLAC arthrosis, demonstrated by imaging studies preoperatively or arthroscopic findings intraoperatively. These procedures will not address arthritic pain.
Our algorithm is given in Table 1.
The purpose of this chapter is to review the techniques for bone-ligament-bone reconstruction of the scapholunate ligament.
The advantages of this technique compared to other techniques are a more anatomic reconstruction, better approximating carpal kinematics; bone-to-bone healing as opposed to tendon-to-bone healing; and local availability.
Preoperative Planning
The surgeon should review radiographs for any evidence of arthrosis. MRI is reviewed for pathology.
Associated fractures or other soft tissue pathology should be addressed.
Any evidence of joint arthrosis should indicate to the surgeon that a salvage procedure should be performed rather than a ligament reconstruction.
A Watson shift test is performed while the patient is under anesthesia. The examiner may better appreciate a clunk while the patient is under anesthesia in contrast to the awake patient where pain may be present, making it difficult for the examiner to perform this maneuver well.
Positioning
Often, a diagnostic wrist arthroscopy is performed initially.
The patient is positioned supine. A hand table is appropriately positioned. A nonsterile tourniquet (set to 250 mm Hg) is placed on the upper arm.
After preparation and draping, the wrist is placed in the arthroscopic tower. About 10 to 15 pounds of traction is used to distract the joint for the arthroscopy.
Arthroscopy aids in evaluating the extent of the injury to the scapholunate ligament, assessing the quality of tissue remaining, and diagnosing concomitant injuries (FIG 3).
Once the diagnostic arthroscopy is completed and the decision to perform a reconstruction is made, the wrist is taken out of the tower and placed pronated on the hand table.
Approach
There are several dorsal approaches to the wrist. Some prefer a trans-fourth compartment approach. We prefer an approach between the second and fourth compartments while transposing the extensor pollicis longus.
Another decision to be made is where to obtain the bone–ligament–bone graft. We prefer local tissue, such as the capitohamate ligament, while some would advocate autograft from the foot. Autograft from the foot creates two operative sites and thus a second potential site of morbidity. In addition, there have been no clinical studies at this point verifying its merit; however, biomechanical studies are encouraging.2,12
FIG 3 • Arthroscopic setup. The arthroscopic tower uses plastic hookand-eye straps and finger traps. About 10 to 15 lb of traction is used to distract the joint for the diagnostic arthroscopy.
TECHNIQUES
APPROACH TO THE DORSAL WRIST
An incision of about 6 to 8 cm is made just ulnar to the tubercle of Lister, extending distally to include the third metacarpal (TECH FIG 1A).
The extensor pollicis longus sheath is incised and the tendon is transposed in a radial direction (TECH FIG 1B).
The interval continues between the second and fourth compartment.
The posterior interosseous nerve is excised to decrease residual pain.
A ligament-splitting dorsal wrist capsulotomy described is made through the dorsal intercarpal and dorsal radiocarpal ligaments (TECH FIG 1C).1,3,13
Direct visual inspection and probing allows the surgeon to further assess the scapholunate ligament for direct primary repair versus reconstruction.
TECH FIG 1 • Approach. A. A 6- to 8-cm incision is made ulnar to the tubercle of Lister, extending distally. B. The third extensor compartment is incised and the tendon is radialized. C. A ligament-splitting incision is made in the capsule.
GRAFT HARVESTING
Fluoroscopy and an 18-gauge needle can help identify the capitohamate ligament.
Using a quarter-inch osteotome, a portion of the ligament with bone blocks (10 × 5 × 5 mm) is taken. This concept is quite similar to a bone–patellar tendon–bone autograft for anterior cruciate ligament reconstructions (TECH FIG 2A,B).
Other ligaments from the upper extremity that can be used include the third metacarpal–capitate ligament, the capito–trapezoid ligament, the second metacarpal– trapezoid ligament, and the dorsal extensor retinaculum bone block.10,16 This last choice was the weakest of all in a biomechanical study.7
The dorsal tarsometatarsal ligaments between the lateral cuneiform and the third metatarsal or the ligament between the navicular and the first cuneiform of the foot have also been shown to be both geometrically and biomechanically similar to the scapholunate ligament, and they remain an option for grafting.2,12
If the surgeon prefers this dorsal foot graft, a longitudinal incision is made over the base of the third metatarsal. Sharp dissection is used for exposure to the joint. An osteotome is used to harvest the ligament with large bone blocks as close to the size of the scapholunate recipient site as possible—typically no greater than a 5to 8-mmwide section. The remainder of the dorsal ligament as well as the plantar ligament remains in place, ensuring maintained stability for the foot (TECH FIG 2C).
TECH FIG 2 • Graft harvesting. A. The capitohamate ligament is outlined with a marking pen after identification with the aid of fluoroscopy. B. A quarter-inch osteotome is used to carefully remove the autograft, which measures about 10 mm long, 5 to 8 mm wide, and 5 to 8 mm deep. C. If a ligament from the foot is used, exposure is performed and an osteotome is used to obtain the graft from the third metatarsal-lateral cuneiform ligament or the navicular-medial cuneiform ligament.
PREPARATION OF THE RECIPIENT SITE AND FIXATION
Using fluoroscopic guidance, 0.062 Kirschner wires are used to reduce the DISI (ie, joysticks) and hold the scaphoid and lunate in position (TECH FIG 3A).
Two Kirschner wires from scaphoid to lunate and, if required, one from scaphoid to capitate to stabilize the reduced scapholunate interval (TECH FIG 3B). More recently, we have been using a cannulated scapholunate screw for fixation.
A trough is cut in the dorsal aspect of the scaphoid and lunate using an osteotome (TECH FIG 3C). The trough must be large enough to accept the bone blocks of the bone–ligament–bone autograft. We aim to make the trough as equal to the bone blocks as possible.
The bone blocks are placed into the trough with digital pressure and they are held with a 1.5-mm screw in each bone. It is important to ensure that full flexion and extension of the wrist is still possible after fixation (TECH FIG 3D–F).
Another option would be to acquire a “press fit” with the bone blocks, thereby bypassing the need for screws. This will decrease the possibility of fragmenting the bone block with the screws. However, we prefer obtaining a larger bone block autograft and using screws for added stability.
A dorsal capsulodesis (see Chap. HA-43) can be performed for added stability. We prefer using a portion of the dorsal intercarpal ligament. This technique is described elsewhere in this part.
TECH FIG 3 • Preparation of the recipient site and fixation. A. Using fluoroscopic guidance, 0.062-inch Kirschner wires are placed into the scaphoid and lunate and used as joysticks to reduce and hold position. B. Two 0.045-inch Kirschner wires are placed from scaphoid to lunate and one is placed from scaphoid to capitate for additional fixation. The joysticks are removed. C. A trough is cut in the dorsal aspect of the scaphoid and lunate using a quarterinch osteotome; the surgeon should try to make the trough as equal to the bone blocks as possible. D. Bone– ligament–bone autograft. E. The bone blocks are placed into the trough with digital pressure. F. A 1.5-mm screw is placed in each bone. It is important to still have the ability of full flexion and extension.
CLOSURE
We prefer to deflate the tourniquet and obtain hemostasis before closure. Once hemostasis is achieved, the capsule and extensor retinaculum are closed.
The extensor pollicis longus tendon is left out of its sheath so swelling will not cause any attenuation and possible attritional rupture in its watershed area.
The skin is closed. Kirschner wires are cut under the skin to prevent pin tract infection.
Final radiographs should demonstrate screws to be adequately placed and the scaphoid and lunate to be in good position by noting a decreased scapholunate interval, a reduced scapholunate angle, and no evidence of DISI.
The wrist is splinted in neutral or 30 degrees of extension; theoretically, the dorsal rim of the radius buttresses the graft for additional support in this slightly extended position.
POSTOPERATIVE CARE
The wrist is strictly immobilized for 8 weeks. Finger and elbow range of motion is encouraged.
Pins are removed at 8 weeks and gentle active range-ofmotion exercises are started. A removable splint is still worn when not exercising for an additional 4 weeks.
Passive range of motion begins at 12 weeks, followed by strengthening.
OUTCOMES
Patients with a partial tear or dynamic component and patients with a shorter time from injury to treatment have a better outcome.
Weiss16 reported excellent results at a minimum of 2 years of follow-up in 13 of 14 patients with scapholunate gaps of less than 8 mm using a bone–retinaculum–bone autograft, even though it has been shown to be biomechanically weaker than the native scapholunate ligament. This may be due to graft remodeling or hypertrophy in vivo.
Lutz al18 used a periosteal flap of iliac crest as the autograft. With an average follow-up of 29 months, they reported 6 of 11 patients to be clinically excellent or good and 5 as fair. Average radiographic parameters improved.
Hanel5 reported that all 39 of his patients treated with the bone-ligament-bone reconstruction outlined in this chapter returned to work, but some had difficulty with return to some sports. All patients would have the surgery again as it had helped their day-to-day activities.
Although there are no long-term clinical outcome studies in the literature on bone–ligament–bone reconstruction, shortterm results are promising. A larger number of patients with a longer follow-up is required to fully recommend this technique for most scapholunate injuries.
COMPLICATIONS
Fragmentation of the bone block intraoperatively or postoperatively
Failure of graft to incorporate if the trough made in the scaphoid or lunate is not deep enough to cause punctate bleeding for the incorporation of the graft
Pin tract infections (which are treated with oral antibiotics)
Failure to achieve normal carpal alignment
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