One screw or two?

It's getting towards the end of the Australian rules football season. It always seems around now that I see more people with hand and wrist fractures than I did at the start of the year. maybe it's the cold, maybe it's fatigue, maybe it's that the games become more desperate with finals around the corner. Surely someone knows?

Better in brown & gold! Scaphoid 2016.

In any case, this week I have seen 4 footballers with scaphoid fractures. All were simple non-displaced waist fractures. Two were casted, two had surgery. One of these had one screw inserted to repair the bone, the other two. A physio I really respect asked whether the two screw thing was new, and why would the surgeon opt for what appears on the outside to be much more difficult surgery to a small bone that already has a poor reputation for healing. The surgery and the science weren't new to me, but a translation of their impact was obviously required so let's start at the start. 

Facts about the Scaphoid (1,2)

Scaphoid fracture through waist. One screw, result at 4mths. Not my patient.

• Most commonly injured carpal bone
• Frequently diagnosed late if at all, with high rates of bone non-union
• Best assessment indicator remains pain on palpation of scaphoid in radial snuffbox (below thumb)
• The part nearest your wrist (proximal) has poor blood supply, often lost with a fracture of the middle section (waist)
• Casting can be required for 2-6 months
• Surgery appears to have better outcomes in the short term
• It appears thumb immobilisation is unnecessary in a cast (3) (but I still include the thumb at least initially because I definitely don't trust young, male footballers!). 

Not an option in Aussie rules footy!!

If I am just talking about athletes, then they are looking at the quickest possible return to their sport. This makes a fracture during the season more likely to be addressed with surgery in spite of the real risk of complications. There remains a risk though. Surgery will ensure good bone compression and stability, but the bone still requires protection in a splint, and active movement outside of the splint is not always encouraged such is the reputation of this poor little bone (1,2). 

The reason surgeons started looking at two screw fixation was that they wanted earlier movement at the wrist to reduce concomitant weakness, and there have been significant improvements in available hardware since development of the Herbert screw in 1984(5). There was also a recognition of the potential benefit of permitting controlled stress across the joint to augment bone growth. 

Cupcake bouquets. Who knew they were a thing?

Keen students of previous blogs will be aware that the scaphoid is a tricky little beast, not always moving in a singular plane. The problem with a single screw, was that it still permitted rotation of the scaphoid. Proponents of the two screw method argued that torsional stability of the bone would be enhanced with two points of fixation (4,5). This makes sense to me. One toothpick in a cupcake bouquet and the cupcake will slide off. Two toothpicks and it can't. Simple! 

Obvious complications are that inserting two screws is technically very difficult, it effectively doubles the likelihood of malpositioning, and it is more expensive (4). It is a new technique; one that is not available to all patients, and one that is not yet supported definitively. Rehabilitation protocols specific to this surgery have not yet been established. 

Notwithstanding the risks, and relative newness of the research, the biomechanical theory comparing one vs two screws is promising. Both lab based and clinical results do indicate a better stability, stiffness and energy absorption compared to a single screw. Whilst these studies concentrated on scaphoid fractures involving non-union or displacement, the implications are that an earlier introduction of mobilisation, loading and strengthening may be tolerated (4,5); possibly even an earlier return to play... just in time for finals!

Look after those fingers,

Hamish

References

1. Rambau GM et al. Evaluation & management of nondisplaced scaphoid waist fractures in the athlete. Operative Tecniques in Sports Medicine 2016 24:87-93
2. Winston, M., Weiland AJ. Scaphoid fractures in the athlete. Curr Rev Musculoskelet Med 2017 10:38-44
3. Buijze, GA. et al. Cast immobilisation with and without immobilisation of the thumb for nondisplaced and minimally displaced scaphoid waist fractures: A multicentre, randomised, controlled trial. JHS Am 2014; 39(4):621-627
4. Mandaleson, A. et al. Scaphoid fracture fixation in a nonunion model: a biomechanical study comparing three types of fixation. JHS Am 2018;43(3):221-228
5. Garcia RM. et al. Scaphoid nonunions treated with two headless compression screws and bone grafting. JHS Am 2014;39(7):1301-1307