Volar Dislocation Of The Metacarpophalangeal Joint Of The Thumb Report Of Four Cases And A Review Of The Literature

Objective：Palmar dislocation of the thumb metacarpophalangeal (MP) joint is a veryrare injury,and the mechanisms,treatments, and prognosis have not beendefined. Our four cases of Palmar dislocation of the thumbmetacarpophalangeal joint are reported in this paper.We have reviewedthe previously literature,and26cases are found.Our cases and the casesform literature are put together to find the general rules of injurymechanisms,diagnosis, treatments and prognosis.these findings may bebeneficial to our clinical practice,improve the recovery of patient,andreduce complications.Materials and methods：We report our four cases of Palmar dislocation of the thumbmetacarpophalangeal joint,one case was treated with closed reduction,3cases were treated surgically.19of26cases from literature were treatedwith open reduction, others were treated with closed reduction.weclassify these cases with the histories,physical examinations,treatments,and prognosis. General rules of these case are analysed.Anatomical study:To define the functions of the stable structures in MP joint such as thecollateral ligaments,volar plate by autopsy examination. Together withclinical cases, we want to clear the injury mechanism and its effects on the prognosis.Results and conclusions:The mechanisms of the Palmar dislocation of the thumb MP joint: thedirectly pressure to the dorsum of the proximal phalanx is responsible forhyperflexion of the MP joint,plus rotational forces or not, leading to theinjury of volar plate,capsular of MP joint and collateral ligaments, are themostly possible causes of the palmar dislocation of the thumb MP joint.The injury of collateral ligaments is the most factors of dislocation.Patients are more satisfied who were treated in early stage,includingearly closed reduction or open reduction,and took correctly functionalexercises. In open reduction cases,repairing the stable structures andinsuring the stability of the MP joint, adjusting the tension of the softtissues around the joint, using extracting suture to reduce the foreignbody reactions around the MP joint,will improve the prognosis.