Definition of scaphoid nonunion:
Nonunion refers to a defect or lack of consolidation. By definition, a fracture that does not heal beyond the sixth month after the initial injury is nonunion.
Nonunion of the scaphoid is thus a scaphoid fracture that has not healed after the sixth post-traumatic month.
There are two main clinical situations:
a scaphoid fracture that has been detected and treated and doesn’t heal despite treatment. This situation is unfortunately frequent, even with appropriate care, as the scaphoid is a poorly vascularised bone (few vessels for blood supply)
a neglected old scaphoid fracture (untreated) that becomes painful over time. In this case, the old unhealed scaphoid fracture is detected when pain occurs.
The spontaneous evolution of scaphoid nonunion that is untreated results in wrist pain and stiffness related to progressive wrist osteoarthritis; referred to as “Scaphoid Nonunion Advanced Collapse”, or “SNAC wrist”.
Before osteoarthritis of the wrist occurs, scaphoid nonunion can often be complicated by osteonecrosis of the scaphoid’s proximal pole.
Video of scaphoid nonunion treatment:
Scaphoid nonunion diagnosis:
Taking a CT arthrogram or an MRI of the wrist is essential to diagnose scaphoid nonunion accurately. These examinations will look for signs of osteonecrosis of the proximal pole: abnormal MRI signal, increased bone density on CT arthrography, pressure geodes (bone cysts); these tests will also look for signs of radiocarpal and mediocarpal wrist osteoarthritis.
The example below shows recent, one-year old scaphoid nonunion with no osteonecrosis or bending, it is the simplest form of nonunion to treat, and as a result, the most commonly treated by arthroscopic surgery currently.
Surgical treatment of scaphoid nonunion:
In the treatment of scaphoid nonunion, the aim of arthroscopy as opposed to the conventional treatment is to reduce risk and operative duration, shorten recovery and immobilization time and improve bone healing. Arthroscopic surgery indeed preserves vascularity as much as possible and makes the procedure safer and more accurate. The use of synthetic bone grafts (osteoinductive proteins) favour bone healing.
This difficult wrist surgery, under development, is specialized surgery, it is performed on an outpatient basis, under regional anaesthesia, the patient in supine.
The procedure begins with an arthroscopic radiocarpal assessment verifying the integrity of the various ligament structures, the absence of osteoarthritis and confirming nonunion.
The first stage consists in debriding and cleaning the nonunion site with a shaver under radio- and mediacarpal monitoring. Once the whole scaphoid nonunion surface is debrided, the nonunion site moves naturally.
The second stage consists in reduction of the nonunion site: a needle maintains the scaphoid proximally and then a transverse K-wire reduces the distal fragment over the proximal fragment.
Once the scaphoid nonunion site is fixed, 2 guide K-wires are inserted under x-ray monitoring from distal to proximal, positioning is verified arthroscopically.
A synthetic bone graft (osteoinducive protein) with an osteoinduction agent can be introduced in the fracture site through a needle; bone graft placement is verified using radiocarpal and mediocarpal arthroscopy.
The nonunion site can then be reduced and compressed with 2 buried screws positioned at the location offering the most depth to provide the best hold whilst avoiding articular conflict.
Reduction and compression are then verified arthroscopically through the radiocarpal and mediocarpal portals, and the provisional K-wires are removed.
The incisions are closed with Steri-strips, this hand surgery does not require sutures.
The post-operative x-ray shows perfect compression on the ulnar side of the scaphoid without interference of the screws; these can be left in place permanently and will not need removal.
Recovery after surgery for scaphoid nonunion
Bandages on the hand are necessary for 15 days, immobilization with a removable splint is essential for 1 month, but activities involving forceful wrist movements such as rugby can resume once the scaphoid has healed.