Bone-Ligament–Bone Reconstruction for Scapholunate Disruption

HISTORICAL PERSPECTIVE Scapholunate dissociation is arguably the most common form of carpal instability and eventually will produce degenerative changes in the wrist. 1–7 At this time, one of the most common surgical options for the management of chronic dissociation is intercarpal fusion, although fusion does not restore normal wrist kinematics and eventually may lead to wrist arthrosis. 2–4,8,9 Publications that describe the use of dorsal periosteum from the radius near the tubercle or ligament replacement from the foot illustrate the concept of more anatomic repairs. 10–12 Retinacular replacement of the scapholunate ligament 11,13 has shown clinical success. This replacement was biomechanically tested and was found to be significantly weaker than the scapholunate ligament it replaced. 13 Ligament replacement from the foot necessitates two surgical approaches with added morbidity of a lower-extremity wound. 10 The Concept Carpometacarpal ligaments were identified as a possible replacement for the scapholunate ligament. Motion studies and clinical observation of the hand's small joints reveal that several of the joints that are available through the same incision might be used for scapholunate ligament repair. These ligament grafts can be taken with a bone block on either side, allowing repair reminiscent of the bone-ligament–bone repair of the knee's cruciate ligaments. Before the first clinical case was attempted, biomechanic studies of potential grafts were accomplished. The scapholunate ligament was compared with the second metacarpal-trapezoid ligament, the third metacarpal-capitate ligament, and the dorsal-periosteum ligament substitute popularized by Weiss. 11 The scapholunate ligament was compared with the second metacarpal-trapezoid ligament, the third metacarpal-capitate ligament, and the dorsal-periosteum ligament substitute. The scapholunate ligament was not significantly different from the third metacarpal-capitate ligament or second metacarpal-trapezoid ligament in strength (p = 0.825) or stiffness (p = 0.767), but was significantly stronger (p = 0.003) and stiffer (p = 0.045) than the dorsal-periosteum ligament substitute. 14 In clinical cases, progression towards using the third metacarpal-capitate ligament was met with good results in short-term follow-up analysis. 15 INDICATIONS Our technique was used for chronic scapholunate dissociation. TECHNIQUE Figures 1A and B illustrate anterior-posterior and lateral radiographs of a patient with typical, fixed, scapholunate dissociation. The procedure is performed through a dorsal wrist incision in the interval between the third and fourth extensor compartment including the base of the third metacarpal (Fig. 2). Fluoroscopy and a needle are often used to locate the third metacarpal capitate joint to ensure a full bone-ligament–bone specimen for harvest (Fig. 3). The entire width of the ligament with the appropriate bone blocks is taken at this interval as shown in Figures 4A and B. Large grafts are used to ensure adequate bone fixation for the screws.FIG. 1.: (A) Anterior-posterior radiograph of a typical fixed scapholunate gap dissociation. Note the foreshortened scaphoid and the wide separation between the proximal pole of the scaphoid and the lunate. (B) Lateral view of the same wrist with a large scapholunate angle and dorsal intercalated segment-instability deformity.FIG. 2.: The approach to the wrist is between the third and fourth interval-extensor compartment to include the base of the third metacarpal. The dark line represents the incision. The arrow points to an outline of the base of the third metacarpal, and the solid ellipse is Lister's tubercle.FIG. 3.: Intraoperative view of the left wrist. The arrow points to the separation between the scaphoid (S) and lunate (L). Fingers are at the left of the photograph. A needle is being used to locate the third metacarpal capitate joint.FIG. 4.: (A) Schematic anteroposterior and lateral diagrams of the third metacarpal (MC) and capitate (C) joint with covering ligament (arrow). Large grafts are taken to ensure adequate bone fixation for the screws. (B) The appearance of the bone-ligament–bone graft. The capitate portion (white arrow) is attached to the metacarpal portion (black arrow) by the intact third metacarpal capitate ligament.An osteotome is used to cut a trough in the scaphoid and lunate after the bones were pinned in a reduced fashion (Fig. 5). Often, the lunate is first reduced with a transarticular pin that is removed after the scaphocapitate and scapholunate pins are introduced. This technique allows full wrist flexion so that the trough to be formed in the scaphoid and lunate is of adequate size to accept the bone-ligament–bone construct. This also allows the distal radius to cover the graft in an anatomic position. The graft is introduced into the trough cut by the osteotome and held in place with two 1.5-mm screws, one each in the scaphoid and the lunate. The scaphoid and lunate will be partially obscured by the ligament and fascia over the graft itself (Fig. 6). This area is under the radius and in an anatomic position.FIG. 5.: Donor graft has been removed from the metacarpal capitate area (MC) indicated by a long arrow. The proximal arm and radiocapitate (R) is on the right. An osteotome is being used to cut a trough in the scaphoid and lunate after the bones were pinned in a reduced position.FIG. 6.: The radius (R) and proximal arm are on the right. The graft has been introduced into the trough cut by the osteotome and held in place with two 1.5-mm screws (long white arrows). The scaphoid (S) and lunate (L) are now partially obscured by the bone-ligament–bone graft.Figure 7 shows a lateral radiograph taken immediately after surgery, with reduction of the scapholunate angle and normal relation between the radius and the lunate (no dorsal intercalated segment-instability deformity) (See also Figure 8).FIG. 7.: Lateral radiograph taken immediately after surgery to show reduction of the scapholunate angle and normal relation of the radius and the lunate (no dorsal intercalated segment-instability deformity).FIG. 8.: Anterior-posterior radiograph taken 6 months after surgery shows internal fixation in good position with maintenance of the scapholunate gap (white arrow). The scaphoid (Sc) and lunate (L) remain reduced.RESULTS The results of this study are not worse than the results found in others in the literature; however, the best short-term results have been those with a shorter period between injury and treatment, those that had a more dynamic component than static, and those that did not have a fixed radio-lunate angle greater than 30°. The few patients treated for acute injuries have done well. At last evaluation, patients had returned to all work activities but continued to have difficulty with some sports activities. 15 The two patients observed for 3 years had significantly better results than the patients evaluated at 1 year. The average follow-up period was 2 years, and the average age of the patients was 39 years. The following results were obtained. Average functional MFA score, 12.7 Average bother MFA score, 11.88 Average disability (DASH) score, 28.1 Average sports DASH score, 53.7 The musculoskeletal functional assessment score (MFA) 16 and the disabilities of the arm, shoulder, and hands (DASH) 17 are both standardized functional assessment tools for evaluation of surgical procedures. In particular, the Bother index and the sports DASH score are subgroups of the overall relative-assessment scores. These particular scores illustrate patient-particular outcomes (Bother index refers to the patient's perception of the extremity as being limiting in daily activity. The sports score refers to the ability in the DASH outcome of the patient being able to return to recreational activities). These results are comparable with the results for other treatment options currently in the literature. When asked, all patients would have the surgery again and felt that it helped with their day-to-day activities. COMPLICATIONS The major complication with this procedure has been bone failure (fragmentation) at the screw site either acutely at the time of the surgery or with trauma. One patient playing basketball 3 months after surgery jammed his wrist on the rim and had recurrence of his scapholunate space but no dorsal intercalated segment-instability deformity. This resulted in a painless decrease in range of motion. Three patients had fragmentation of the bone during graft insertion and were left without fixation on one side. They all went on to heal in place, but one of the three patients had slight movement of his graft and recurrence of some of his scapholunate gap. At surgery, particularly in the patients with a large, fixed, radiolunate angle, the lunate was often devoid of punctate bleeding unless a deep trough was designed. This avascularity may influence graft incorporation. REHABILITATION Cast and pins are removed at 8 weeks, and a removable splint is fitted. Gentle, active, assisted range of motion is begun, followed by passive range of motion at 12 weeks, as can be tolerated by the patient. After surgery, finger and elbow range and strengthening are encouraged, even while the patient is in the cast.

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