On August 1989, a 19-year-old male patient fell from a horse (high-energy incident) with minimal pain initially. He did not seek medical attention and therefore no X-rays were taken. Four months later, he presented to us complaining of minimal loss of motion, but intense pain and severe loss of strength, particularly when the wrist had what he described as “something that was suddenly out of its correct position.”
X-rays at that time, December 1989, demonstrated carpal misalignment with an increased scapholunate (SL) gap (Terry Thomas sign) and flexion of the scaphoid with a “ring sign” present. These signs were said to disappear under slight traction of the wrist; hence, the case was interpreted as a dynamic SL ligament injury.
The patient was taken to the operating theater and a closed reduction was performed obtaining what was thought to be a good anatomical reduction. A single 1.2-mm K-wire was used to hold the scaphoid and lunate in position. This fixation was deemed adequate at the time of surgery.
Follow-up X-rays at 6 days demonstrated an ongoing adequate reduction (▶Fig. 74.1). The arrow points at the expected area of contact between the remnants of the SL ligament. The SL gap is minimal and there is no pathological flexion of the scaphoid.
K-wires were removed at the 3-month mark. Unfortunately, a follow-up X-ray at 4 months was rather disappointing as it demonstrated recurrence of the misalignment.
When last seen, on February 1994, the patient was troubled by established SL dissociation. Clinical symptoms included pain, weakness, and inability to weight bear, making this an unstable wrist.
X-rays (see ▶Fig. 74.1) demonstrated a disruption of the linkage system between the scaphoid and the lunate, which means that the lunate no longer followed the scaphoid when it went into flexion. Given that the lunotriquetral (LTq) ligaments were competent, the lunate had a tendency to follow the triquetrum into extension instead (▶Fig. 74.2), the so-called dorsal intercalated segment instability (DISI) deformity.
With disruption of this linkage system, the carpal bones no longer followed their usual anatomical displacements when submitted to an axial force, and a painful dysfunction ensued.
It became evident that to establish the correct subsequent treatment we should have been aware of the difference between misalignment (improper positioning of the carpal bones in the three-dimensional space) and instability (the inability to resist a physiological load without yielding). Unfortunately, he could not be followed up any longer; the final long-term outcome remains unknown. Yet, the evolution of many such cases towards the so-called SL advanced collapse is so well described in the literature that we have little doubt that this was probably the fate of that wrist. This, however, does not mean that the wrist had to be necessarily painful or greatly dysfunctional.
When the SL ligament is not repairable, the surgeon needs to choose between reconstructing the ligament (ligamentoplasties) and performing a salvage procedure (proximal row carpectomy vs. partial wrist fusion, depending on the status of the capitate head cartilage).
• The reducibility of the carpal malalignment.
• The stability of the lunate relative to the radius.
• The status of the scaphoid, capitate, and distal radius cartilages (▶Table 74.1).
Reducibility can be determined via a dynamic assessment with image intensifier. Lunate instability can be evaluated forcing the bone in an ulnoradial direction, and finally the status of the surrounding cartilages is to be documented with an arthro-CT scan, MRI, or ideally by arthroscopy prior to committing to a definitive procedure in the operating theater.
If the joint surfaces are intact and the carpus is easily reducible, the surgeon should proceed with an SL ligament reconstruction (extensor carpi radialis longus [ECRL] tenodesis).
The procedure was developed following on the concept of helical antipronation ligaments (HAPL). This group of ligaments—namely, the radioscaphocapitate (RSC), the volar radiolunotriquetral, the dorsal intercarpal, and the palmar scaphocapitate (SC) ligamentous complexes—are set forming a helical system of passive restraints against the tendency of the distal row of rotating into pronation when the wrist is axially loaded. Indeed, the HAPL prevents excessive pronation of the distal carpal row. When the SL ligament and HAPL secondary stabilizers are injured, the scaphoid flexes and pronates out of its fossa. The ECRL tenodesis realigns the scaphoid back to its anatomical position by restoring this group of ligaments instead of solely addressing the dorsal SL ligament.
Two versions of the procedure exist: three-ligament tenodesis ECRL (3LT–ECRL) and ECRL spiral tenodesis. The first is indicated only if the lunate is stable enough as to resist all forces coming from the distal row under physiologic loads. If the lunate were found to be either excessively lax or fully unstable, the second procedure would be indicated.
The wrist is approached via a dorsal incision. Sensory branches of the ulnar and radial nerves are protected. The third extensor compartment is opened and extensor retinacular flaps are raised from the second to the fifth compartment. If the posterior interosseous nerve is identified with normal features, a nerve sparing proximally based capsulotomy is performed and the diagnosis of SL instability confirmed (▶Fig. 74.3).
It is essential to determine if the scaphoid and lunate are easily reducible. Any tenodesis will fail if they are not. Traction to the index and middle fingers should reduce the proximal carpal row without excessive force. In addition, the wrist should be visually explored. The presence of damaged cartilage is also a contraindication to perform a tenodesis.
A 2-cm transverse incision is made on the dorsoradial surface of the forearm, just proximal to the oblique contour of the abductor pollicis longus (APL) muscle belly and a distally based strip of ECRL tendon (3-mm diameter) is harvested. The ECRL tendon has a better control over the tendency of the scaphoid to flex and pronate than a volar wrist tendon (flexor carpi radialis [FCR]). This is because of its anatomical location and vector of pull.
A blunt mosquito is used to tent the volar wrist skin from dorsal to volar. A small skin incision is made onto the tented skin and a tendon passer is used to transfer the ECRL graft from dorsal to volar. The harvested tendon is passed through the so-called inside passage, the triangular space formed by the inner aspect of the scaphotrapeziotrapezoidal ligament, the radial surface of the distal scaphoid, and the proximolateral corner of the trapezium.
A tunnel is made through the scaphoid with a K-wire and a 2.7-mm cannulated drill, connecting the distal/radial corner of the scaphoid tuberosity and a point on the dorsal/ulnar surface of the scaphoid where the dorsal SL ligament had originally inserted. The ECRL tendon graft is then passed through this tunnel from volar to dorsal.