Osteoarthritus refers to a process where cartilage is lost, exposing the subchondral bone and causing pain. This process is incompletely understood. The base of the thumb (carpo-metacarpal joint) is very commonly affected by osteoarthritis. The thumb has the ability to move in multiple planes and to pinch and oppose (touch the little finger). This is made possible by the carpo-metacarpal joint (CMC joint) and more specifically the metacarpal of the thumb articulating on the trapezium. This joint is a saddle joint and the metacarpal can circumduct (move 360 degrees) on the trapezium. Unfortunately when osteoarthritis is present in this joint, all thumb function becomes painful and especially pinching becomes very uncomfortable. It is thought that the thumb contributes 50-60% to hand function: therefore all hand function like key pinch, power pinch, grip strength and fine motoric movements become difficult when this joint is affected.
Once cartilage is lost it cannot be recreated and we need to do a salvage procedure. If a hip becomes arthritic, the diseased joint is excised and an artificial joint (arthroplasty) is fitted. In the thumb carpo-metacarpal joint there are a multitude of procedures described, but essentially the best procedure is performed once the joint has completely burnt out and all cartilage is lost. There are two main problems: we need to take away the source of pain (bone on bone phenomenon) and secondly we need to reconstruct the stability of the first metacarpal to continue its ability to move in all planes of movement (circumduct) and be a stable pillar in the position of pinching.
We perform a trapeziectomy (excision of the bone
that is causing the pain) and reconstruct the
ligaments that stabilise the thumb ray. This is an
excellent operation with great, predictable results.
The reconstruction of the ligaments suspending
the first metacarpal of the thumb to the second
metacarpal (after creating a void) was traditionally
done using or sacrificing a tendon. We have a new
technique using a clever simplistic implant
(Tightrope) that replaces the use of a tendon. It
has the advantage of earlier mobilisation after the
Once cartilage is lost it cannot be recreated.
The thumb becomes stronger without pain after 3 months.