Metacarpophalangeal Joint Arthrodesis of the Thumb

Metacarpophalangeal Joint Arthrodesis of the Thumb


In this video, we show how we carry out a
thumb metacarpophalangeal joint arthrodesis with the Shark Screw allograft. The patient is a 73-year-old female on whom
we are performing a resection and suspension arthroplasty due to Carpometacarpal joint
arthrosis of the left thumb. The patient also shows a hyperextension in
the metacarpophalangeal joint, which is why we will perform a metacarpophalangeal arthrodesis
in addition. We make a straight dorsal skin incision over
the metacarpophalangeal joint of the thumb. We separate the extensor system, cut through
the collateral ligaments and expose the head of the metacarpus. In this case, we decide on the cup and cone
technique. With a double-pointed 1.6 K-wire, we mark
the center for the conical head in a slightly palmar position. This wire already defines the direction for
the Shark Screw allograft which will be inserted later. We ream over the guidewire with a 16 mm cone
reamer. Next, we place a central K-wire into the base
of the proximal phalanx, where we remove the cartilage all the way to the subchondral bone
with the cup reamer. We use a thin 1 mm drill to freshen the partially
sclerotic bone. The shavings remain in place. Now we place both joint surfaces under maximum
compression at an angle of around 20 degrees. We introduce a 1.6 K-wire from proximal dorsal
towards distal palmar. To ensure stable positioning during later
drilling and threading, we additionally set two temporary 1 mm-thin K-wires. We now replace the thick 1.6 K-wire with a
1.2 wire which serves as a guidewire for drilling with the thinnest – the blue – drill. Based on the size of the bone we decide which
dimension of Shark Screw to use. We always try to use the allograft with the
largest diameter. This ensures that a maximum amount of bone
bridges the arthrodesis gap. Drilling is carried out step by step starting
with a small drill and enlarging up to the desired size. In this case, we use the 4.5 mm Shark Screw,
marked in red. To prevent heating of the bone, threading
is carried out slowly using the red 4.5 thread cutter. The depth of the drill and of the thread cutter
is shown on the laser markings. Finally, we thoroughly rinse the female thread
with saline solution, because even small shavings would prevent the screwing-in of the Shark
Screw. After insertion of the Shark Screw allograft,
we remove the temporary K-wires and cut off the protruding screw material with an oscillating
saw at bone level. The Shark Screw allograft ensures an absolutely
rotationally stable arthrodesis that is under compression. It resides within the bone and does not rise
above its surface. Shark Screw allografts are clearly visible
in post-operative X-rays. By the physiological bone metabolism the bone
screw becomes completely integrated and remodeled to own bone material. After the operation, we apply an open thumb
cast for 3 weeks. The arthrodesis should be kept load-free for
6 weeks in total.

Leave a Reply

Your email address will not be published. Required fields are marked *