Scaphoid pseudarthrosis is when a scaphoid fracture fails to heal, leading to the formation of a “false joint”.
It is primarily caused by undiscovered and consequently untreated scaphoid fractures. However, because of the generally poor blood circulation to this wrist bone, even scaphoid fractures that have been subject to treatment can develop pseudarthrosis if they have not healed. Studies have shown the annual incidence rate to be between 4 and 11%.
Scaphoid pseudarthrosis may initially remain undiscovered over a period of years and is often revealed incidentally during an x-ray examination (e.g. in the event of another fall). The radiological image of the absence of bone consolidation in a scaphoid fracture between the fifth and ninth month is known as delayed union and should be distinguished from scaphoid pseudoarthrosis because there is still the possibility of healing.
Over time, there is an increase in arthritic changes in the wrist with progressive deterioration of the symptoms in the wrist joint and carpus. In 33 to 86% of scaphoid pseudarthrosis cases, instability of the carpus with subsequent carpal collapse is observed.
Examination and Diagnosis
Most scaphoid pseudarthrosis patients report pain related to load bearing in the radiodorsal area of the wrist. Grip strength is severely reduced. There is notable tenderness on palpation in the region of the anatomical snuff box.
Diagnosis consists of multi-view x-rays of the wrist and carpus. The use of the Stecher method is also of importance in these cases. High-resolution thin-layer computed tomography (CT) is the best way to show the full extent of the disease. The CT provides excellent images to help identify malpositioning, compression zones, or scaphoid or carpus dislocation. MRI with contrast agent is used to determine blood circulation in the scaphoid bone. A diagnostic wrist arthroscopy can be helpful in detecting arthritic changes in the region of the wrist.
Scaphoid pseudarthrosis that has been dormant for many years can suddenly become symptomatic and painful as the result of minor trauma. Conservative measures such as immobilisation, electrostimulation or shock-wave therapy are rarely successful. Low-intensity pulsed ultrasound only occasionally shows satisfactory results for fractures with delayed union, but not in cases of scaphoid pseudarthrosis.
In the long term, if left untreated, scaphoid pseudarthrosis leads to progressive and painful wrist arthrosis. Therefore, pseudarthrosis should be operatively treated as early as possible.
The earlier the surgery takes place after the accident, the less severe the already developed secondary arthritic changes and the better the prognosis for the patient.
The following operative techniques are the most commonly used:
Insertion of a bone graft taken from the iliac crest or the radius bone coupled with stabilisation using double-threaded cannulated screws or a small stable-angle plate.
In this type of procedure, the altered bone tissue is removed, and a radial or iliac crest bone graft is inserted. The stabilisation takes place using screws, as in cases of fresh scaphoid fractures. Only in exceptional cases is a mini plate used for bone stabilisation.
Scaphoid reconstruction using a vascularised radius bone graft
This technique is used especially in the treatment of the proximal section of the scaphoid. During the procedure, a vascularised bone graft collected from the radius is implanted into the scaphoid and fixated using cannulated screws or drilling wires.
Scaphoid reconstruction using a microvascular bone graft taken from the femoral bone.
This method uses a bone transplant collected from the inner or outer areas of the femoral bone at the knee and removed with a section of artery and vein attached. These vascular connections are then microsurgically conjoined with an artery and vein in the wrist joint. The advantage of this procedure is the improved blood circulation on the inserted bone graft. The disadvantage is that the surgery is more complex. This technique is most often used in cases with very poor blood circulation in the scaphoid.
For exceptional cases, there are further operative methods available. In some instances, wrist arthroscopy is used. Due to the complexity associated with these cases, the operative technique should be selected only after a comprehensive analysis of each case.
Scaphoid pseudarthrosis reconstruction is a complex procedure that can last several hours and should only be performed by an experienced hand surgeon. General anaesthesia is often required in these cases. The procedure is normally carried out on an inpatient basis with an expected stay of between 2 to 5 days.
After the operation has been completed, a plaster cast will be fitted to the wrist while still in the operating theatre. A follow-up x-ray will be carried out on the day of discharge. The suture material will be removed after 12 to 14 days. After the swelling of the wrist has subsided, a circular thermoplastic splint will be fitted by a hand therapist. This splint should be worn for between 6 to 8 weeks. Then, a further follow-up x-ray assessment is necessary and if ossification is confirmed, then hand therapy can begin. Approx. 12 weeks after the operation, another follow-up, this time a thin-layer CT, is necessary. At this time, increasing load bearing of the wrist joint can begin.