Sesamoid bone transfer for metacarpophalangeal hyperextension instability of the thumb: A CT-osteoabsorptiometry study

Background and aimHyperextension instability of the metacarpophalangeal (MCP) joint of the thumb may result in pain, malfunction, and accelerated osteoarthritis in the carpometacarpal (CMC) joint. One method of treatment is sesamoid arthrodesis. The aim of this study is to investigate if a sesamoid transfer as a treatment of hyperextension instability of the thumb MCP joint leads to an altered distribution of the subchondral mineralisation and a negative clinical outcome.MethodsSesamoid transfer was performed on 12 patients with hyperextension instability of the MCP joint of the thumb. The range of motion (ROM) and radiologic outcome were assessed. Pinch and power grip strength were measured and compared to the nonoperated side.To determine the areas of maximum subchondral mineralisation in the joint, computed tomography (CT)-osteoabsorptiometry was performed to determine the long-term stress distribution within the joint.ResultsThe distributions of the stress zones in the operated and nonoperated thumbs were not statistically different a median of 5 years following the sesamoid transfer procedure. There was no difference in the functional and radiological results between the operated and nonoperated thumbs.ConclusionIf it is assumed that the nonoperated thumb represents the normal condition for each individual, then it may be deduced that the operation achieves good clinical results, and the distribution of the subchondral mineralisation does not change.