It is debated whether a combined approach to the carpus is always necessary for perilunate injuries, but it will be described here. In most cases, the dorsal approach is made first. Start with a palmar approach in cases of palmar dislocation of the lunate (shown in the radiograph), or in the rarer palmar luxation of other carpal bones.
2. Surgical anatomy
The extensor compartments on the dorsum of the radiocarpal region are five in number. The first compartment contains the tendons of abductor pollicis longus (APL) and extensor pollicis brevis (EPB). The second compartment contains the extensors carpi radialis longus (ECRL) and brevis(ECRB). The third compartment contains the tendon of extensor pollicis longus (EPL).
3. Dorsal skin incision
Make a straight skin incision beginning proximal and ulnar to Lister’s tubercle, and ending distally at the level of the third carpo-metacarpal joint. The incision should be about 8 cm long. The incision can be extended proximally, or distally, if necessary.
4. Elevate the skin flap
Preserve the large longitudinal veins and ligate and divide the crossing branches to achieve exposure.
Elevate the skin flaps, complete with subcutaneous tissue, from the extensor retinaculum. The dorsal superficial branch of the radial nerve should be identified and elevated with the skin flap.
5. Open the third compartment
Incise the extensor retinaculum over the EPL tendon, opening the third extensor compartment.
The EPL tendon is released and retracted radially, together with the extensor tendons of the second compartment.
6. Elevate the fourth compartment
Continue the dissection in an ulnar direction by subperiosteal elevation from the distal radius of the fourth extensor compartment and its contents, and expose the wrist capsule distally.
Retract the fourth extensor compartment in an ulnar direction, further exposing the capsule.
7. Capsular incision
Depending on the exact type of the carpal injury, and any existing tears in the capsule, a longitudinal or inverted T-shaped capsulotomy can be used. It is important that the radiolunotriquetral ligament insertion onto the radius be preserved.
8. Radially based capsule incision
In order to gain a complete view of the carpus, a radially-based capsular ligamentous flap is elevated. The capsulotomy incision starts radially deep to the floor of the second extensor compartment. Leave a fringe of 2-3 mm of the capsular attachment at the dorsal rim of the radius, for subsequent suture repair.
The incision continues in an ulnar direction along the dorsal rim of the radius.
It then turns distally in line with the fibers of the radioluno-triquetral ligament.
At the triquetrum it turns radially in line with the fibers of the dorsal intercarpal ligament.
9. Note: Protect the DRUJ
Be careful not to cut the dorsal radioulnar ligament or the triangular fibrocartilage (TFC) of the distal radioulnar joint (DRUJ), which must be protected.
10. Elevate the capsular flap
The capsular flap is elevated by sharp dissection in an ulnar-to-radial direction.
The proximal carpal row, with its intrinsic ligaments, and the midcarpal joint are exposed.
11. Extended carpal tunnel incision
After the dorsal approach, with temporary fixation on the dorsal side, the palmar approach is performed.
The incision begins at the level of the distal edge of the flexor retinaculum, in the palm, in line with the third metacarpal. It continues proximally in the intereminence crease to the level of the transverse flexor crease of the wrist.
At this point, the incision angles 90 degrees in an ulnar direction for 2 cm in the line of the wrist flexor crease, and then turns proximally as a slightly curved, longitudinal extension, as far as necessary.
12. Elevate the skin flaps
Elevate the skin flaps by sharp dissection, firstly from the surface of the palmar aponeurosis distally, then from the antebrachial fascia proximally - on the ulnar side of the palmaris longus tendon.
This protects the palmar cutaneous branch of the median nerve, which passes to the radial side of the palmaris longus tendon.
13. Open the carpal tunnel
Identify the median nerve, which lies radial and deep to the palmaris longus tendon.
Insert a blunt instrument into the carpal tunnel, between the median nerve and the flexor retinaculum. Now divide the flexor retinaculum longitudinally over the blunt instrument, which protects the median nerve.
The retinaculum should be divided to the ulnar side of the the median nerve in order to protect its motor branch to the thenar muscles.
14. Retract the flexor tendons
In order to expose the palmar carpal ligaments, retract all the flexor tendons radially.
Only the ulnar nerve and artery remain on the ulnar side.
15. Option: approach to the radial palmar capsule
Sometimes the median nerve must be retracted radially, together with the tendon of flexor pollicis longus (FPL), and the flexor tendons of the fingers are retracted in an ulnar direction, thereby exposing the radial side of the palmar capsule.
16. Closure (dorsal)
Closing the capsular incision Repair the radially-based flap with interrupted sutures.
Closing the extensor compartments Close the third compartment, avoiding any tension over the EPL tendon. The EPL tendon must glide smoothly. If not, the tendon is left superficial to the extensor retinaculum, in the subcutaneous tissue.