Purpose of the study: Construction of a key grip is the final objective of programmed functional surgery of the upper limb in the tetraplegic. Three phases are necessary: activation of the grip, simplification of the poly-articular chain, and positioning the thumb column. For this operative phase, two techniques can be used, either fusion of the articulation with a trapezometacarpal arthrodesis (TMA) or a soft tissue procedure (tenodesis of the abductor pollicis longus). Our study compared analytically these two techniques, considering grip force and stability and the quality of the key grip opening.
Material and methods: This was a retrospective study of 38 key grips with a mean follow-up of 7.4 years in a population of tetraplegic patients (groups 1 – 5 in the International Classification of Giens. Seventeen active key grips including 11 with TMA and 21 passive key grips including 16 without TMA with regulation of the thumb position by soft tissue procedures. The active and passive grips according to the procedures were comparable statistically for their median ASIA motor scores.
Results: The force of the active key grips with TMA (mean 2.7± 1.3 kg) was significantly greater than that obtained after tenodesis (1.3±0.7 kg) (p=0.05). For passive key grips, the difference was not significant, 1.1±0.6 kg with TMA versus 1.0±0.9 kg without. Twenty-three percent of the grips were unstable after TMA versus 24% after tenodesis. Regarding grip opening, the mean distance between the pulp of the thumb and the index was 3.7 cm for active key grips after TMA by tenodesis effect and 5.4 cm for holding large objects while without TMA these values were 3.2 cm and 6.4 cm respectively. For passive grips, these same values were 2.2 and 3.4 cm after TMA versus 2.4 and 6.8 after tenodesis.
Discussion: For the active key grip, TMA enables a stronger grip but with loss of opening distance for large objects. Conversely, for the passive key grip, TMA does not enable a stronger grip but significantly limits passive opening. Globally TMA yields a more constant result. In patients with a limited motor potential, it is important to favour the creation of two different grips.
