Radioscapholunate fusion using Medartis plate with distal Scaphoid excision

The radius, ulna, CMCJs, Lister’s tubercle and the incision line is draw.
With the patient supine and arm prepped and draped on the arm board the skin is tested to assure the Axillary Block is effective.
The skin incision is drawn central to the wrist over the 4th Extensor compartment (EC) extending from the CMCJs to 2cms proximal to the proximal border of the DRUJ.
Once this preparation is complete the arm is exsanguinated with a sterile Esmarch bandage and tourniquet inflated to 250mmHg
The arm is positioned in pronation. Due to the tendency of the arm to supinate the surgeon is best seated at the head end and the Image intensifier entering from the foot end of the patient when required

Soft tissues are dissected to expose the transverse fibres of the Extensor Retinaculum (ER).As the incision is in the midline there are rarely any large cutaneous nerve branches seen although a number of small vessels perforate the ER which are best coagulated. The fat, veins and superficial nerves are elevated as one.
Forceps are shown pointing at Lister’s tubercle beneath the ER.

The 3rd EC is opened.Cut directly onto the bony prominence of Lister’s tubercle to open the radial side of the 3rd EC.
Use tenotomy scissors with the blades very slightly open either side of the retinaculum. Open along the 3rd compartment by pushing distally and proximally as shown on the image (don’t close the scissors and cut, just push firmly).

Use the same technique to open the 4th EC.The 4th EC is accessed at its proximal radial border where the tendons of EDC are clearly visible through the thin film of synovium.

Excise the Posterior Interosseous Nerve (PIN) and Artery (PIA) from bed of 4th EC using diathermy to coagulate the vessel.Place a small self retainer at the level of radio-carpal joint on tendons of 2nd and 4th extensor compartments.
Image shows forceps pointing to PIN and PIA.

Using the scissors the capsular attachment to the distal radius is identified and opened.

The capsule is then sharply dissected off the distal radius to the tip of the radial styloid.The incision is extended beneath the 2nd EC and to the radial border of the 5th EC protecting the tendons and the integrity of the TFCC, DRUJ and Dorsal radio-ulnar ligament.

A Hohmann retractor can be used between the scaphoid and radial styloid to stabilise the scaphoid and protect the 2nd compartment extensor tendons while dissecting

The capsule and periosteum is sharply dissected from the 4th EC for a clearer view of the radio-carpal joint.

The dorsal distal lip of the radius is removed with a sharp osteotome and the plate sited.The bony cut is perpendicular to the long axis of the bone to give a clear view into the joint and the scaphoid and lunate proximal articular surfaces. Lister’s tubercle is also removed to accomodate the plate.
Proximally in the wound, muscle attachments are elevated with a periosteal elevator to allow good seating of the plate on the radius.
A Medartis TM RSL fusion plate (left or right) is then sited on the radius crossing over the radio-carpal joint with the two L-limbs aligning two holes over both the lunate and proximal scaphoid.
The location of the plate over the scaphoid is marked with a k-wire at its distal extent to assure adequate bone is preserved when the distal scaphoid excision is undertaken.

With the K-wire in situ the distal scaphoid excision is undertaken.The osteotome is placed a few millimeters distal to the wire to assure enough scaphoid will be left for the plate to hold and enough bone remains to avoid radial subluxation of the capitate once the patient begins to mobilise.
When performing the osteotomy the scaphoid should be in its normal 45 degree or less flexed position (which can be achieved using the wire as a joystick). The angle of the cut with the osteotome should aim slightly dorso-distal to volar radial otherwise the remaining volar tubercle lip which will impinge in the volar aspect of the STT joint on the trapezium in radial deviation. Small flakes of bone often remain on the volar capsule where the scaphoid tubercle was attached to the flexor retinaculum – every small flake does not need to be excised as this scarring with fill the area in the post operative period.
If good quality the excised scaphoid may be used for part of the bone graft.

The intra-operative radiograph checks the bony resection of the distal scaphoid from the lateral view.

The joints to be fused are then decorticated.With most patients this can be undertaken easily with a sharp curved osteotome with lift the cartilage and subchondral bone the the curve following the joint surfaces easily. In some cases where the surface is more sclerotic, a burr may be useful to decorticate the joints.
Decorticate the proximal lunate and scaphoid and then the distal radius lunate and scaphoid fossae.
It is important not to destabilise the TFCC attachments therefore before decorticating the lunate fossae an osteotome is used to create a cut just radial to the TFCC insertion which will then be the most ulna extent of the decortication and prevent accidental DRUJ injury.

The dorsal scapho-lunate ligament is excised last if still intact as its initial preservation creates more stable bones to decorticate.The scapholunate joint is then decorticated with a bone nibbler taking great care not to damage the capitate head. The volar scapholunate ligament is preserved to maintain the normal gap between the scaphoid and lunate and allow a volar buttress to the bone graft when inserted.

Lister’s tubercle is then excised with an osteotome to allow better seating of the plate.It is also a convenient access into the dorsal radius to harvest the bone graft.

Bone graft is harvested from the dorsal distal radius.Bone graft is harvested with an narrow osteotome to slice into the cancellous bone and sweep sheets of it into the hole from each direction. This is then retrieved carefully with non-toothed forceps.
This technique gives much better graft maintaining its cancellous structure than using a curette which often crushes the cancellous matrix.
Bone wax can be used over the graft donor site to reduce bleeding.
The graft is then packed into the radiocarpal and scapholunate joints making sure there is no overspill of the graft into the midcarpal or ulnar carpal joints.

The fusion plate consists of two L-shaped plates attached at the waist with two k-wire holes and an oval non-locking hole on the scaphoid side and locking holes elsewhere with two on each angled limb to catch the scaphoid and the lunate. The locking screws have an ability to be angled with an arc of 30 degrees (15 degrees in any direction) to allow better placement in good quality bone.
The angulation is set by the drill guide which can lean 15 degree off central and still remain in the plate. It is however very easy to lean the guide too far and exceed the 15 degrees in a single direction as the guide clicks out of the low profile plate. If this happens the screw will not lock.
For this reason it can be useful to place locking screws 1 mm too short in the carpal bones and if they do not lock and the tract in the bone is threaded then a longer non locking screw can be used instead.
The radius screw a drilled bicortically.

The plate is placed on the bone and the oval hole on the radial limb of the plate is drilled and held with a non-locking gold screw.This then can be loosened if required to allow minor adjustment to provide optimal siting of the screws in the scaphoid and lunate.

A Hohmann retractor is used to stabilise the scaphoid.The scapholunate joint often gaps dorsally and therefore a Hohmann retractor is used to hold the scaphoid and lunate together when plate placement is undertaken.
Once happy with position, a locking screw is placed in the radius through a hole on the ulna limb of the plate. This then sets the plate position and the carpal screws can be inserted. It is imperative that the radiocarpal joint and therefore graft is compressed when setting the plate position and inserting the carpal screws.

Two locking screws are placed in both the lunate and the scaphoid.The surgeon needs to be aware of the depth of the midcarpal joint as if slightly distal it is easy to penetrate the midcarpal joint with screws. This can be avoided using the 15 degree variable angle to aim more proximally and is there are any concerns when taking final intra-operative images then the midcarpal joint can be viewed under direct vision to confirm the protection of the joint.
The rest of the radius screws can now be inserted and even the screw hole directly over the graft harvest site can be used achieving purchase on the volar cortex of the radius.

The dorsal capsule is closed with 3/0 vicryl covering as much of the plate as possible to aid tendon glide.

The extensor retinaculum is closed with 3/0 vicryl.
Due to the addition of a plate despite being low profile and the excision of Lister’s tubercle, the retinaculum will not closed to its normal position. The 4th compartment is then recreated as best as possible and the retinaculum can often the can be sutured to the plate on its radial aspect.
The 3rd compartment is closed if possible replacing the EPL in its normal position to avoid subluxation.

The skin is sutured.A 4/0 vicryl interrupted suture is used to close the deep dermal layer and a 4/0 monocryl absorbable sub-cuticular continuous suture is used for skin. The sub-cuticular suture starts and ends outside the skin with bulky knots which can be trimmed or will fall off in 2-3 weeks.
An adherent dressing is used over the wound.
The tourniquet is then released and the hand rested on the table for 5 MINUTES. This allows the initial reperfusion and swelling to occur before the wool and plaster cast is applied.

The wool is applied for a below elbow plaster cast.The wool placed circumferentially around the wrist is split (see image) then covered with a layer of non circumferential wool to allow for swelling and reduce painful constriction of the dressings.

A dorsal slab of plaster is then applied and held with a bandage and tape.

Pre-operative PA radiograph of patient.
The patient had sustained a very comminuted open distal radius and ulna fracture 8 months before which due to the comminution and severity of head injuries a bridging plate was used across the wrist as initial treatment. The plate was then removed and a ulna osteotomy performed.
Finally due to continue pain the ulna plate was removed and RSL fusion performed.

Lateral pre-operative radiograph.

Pre-operative CT showing step in radiocarpal joint.

Pre-operative CT showing step in radioulnar joint.

Post-operative PA radiograph at 6 weeks – On this particular patient the ulna proximal limb of the plate is not completely on the radius due to the pre-operative injury and radial deformity

Post-operative lateral radiograph at 6 weeks