What are the association/possible etiologies of Keinbockï¿½s?
– trauma – repetitive or single; although, severe trauma (perilunate dislocations) often do not get this
– ulnar variance – the ulnar negative wrist
– vascular anomalies in supply – having only one feeding vessel rather than two
– it is bilateral in 15%
X-rays: remember that to assess ulnar variance (the ulnar variance view) the forearm must be in neutral rotation. The easiest way to do this x-ray is with the patient seated, shoulder abducted to 90, elbow flexed to 90, and the forearm in neutral rotation, and the x-ray aimed right at the wrist joint, not at the forearm or hand. Supination will make it look more ulnar minus (supination makes the ulnar look short), while pronation will make it look more ulnar positive (pronation prolongs the ulna).
What is ulnar minus? 3 millimeters is considered pathologic.
1 – pre-radiographic
2 – sclerosis
3A – fragmentation and early collapse without scaphoid rotation
3B – fragemetation and early collapse with scaphoid rotation
4 – collapse and arthritis – assess collapse with carpal height ratio – carpal height / 3rd metacarpal height
There are a number of scenarios. The first differentiation is the EARLY vesus ADVANCED Keinbockï¿½s – based on the scaphoid rotation. – ie. Stages 1 to 3A versus 3B and 4
In stages 1 to 3A (pre-scaphoid rotation) and the ulna is short (ulnar minus), then start with a radial shortening, which seems to be simpler than the ulnar lengthening. Favero favors a volar approach to the distal radius through FCR sheath. Cuts the radius near the metaphyseal/diaphyseal junction so that he can get a plate with a few good screws in the distal fragment. Often you only need a few millimeters of shortening. Apply the plate and compress across the osteotomy.
In stages 1 to 3A (pre-scaphoid rotation) and the ulna is NOT short (ulnar neutral), then you cannot do a radial shortening. In this case, probably best to start with an intercarpal fusion – ie. STT fusion, or try to change the joint biomechanics by doing an osteotomy to increase the radial inclination (ulnar closing wedge or radial opening wedge). Other possibility would be a revascularization procedure, but these sound pretty experimental.
In stages 3B (post-scaphoid rotation), basically, you have some collapse of the carpus. The scaphoid rotates (flexes) as the capitate collapses. Youï¿½re kinda screwed here. At this stage, you can excise the lunate and do a limited carpal fusion (either an STT or scapho-capitate), or do a proximal row carpectomy if the proximal pole of the capitate is not severely degenerative.
NOTE: the prerequisites for doing a PRC are 1. an intact lunate fossa, and 2. an intact proximal pole of the capitate (although some say that mild degenerative changes on the capitate are not a contraindications to PRC).
In stage 4, there are fairly advanced degenerative changes. The choices here are pretty limited, and basically come down to the patientï¿½s functional demands.
– If active and want some wrist motion – lunate excision and scapho-capitate fusion
– If just want pain relief and donï¿½t mind the idea of a stiff wrist – wrist arthrodesis