Complex metacarpophalangeal joint dislocation of the litter finger: A sesamoid bone seen within joint. What does it mean?

The Application of Sesamoid Position in Diagnosing Thumb Metacarpophalangeal Joint Dorsal Dislocation: A Retrospective Study

OBJECTIVES

The position of sesamoid of thumb metacarpophalangeal (MCP) joint changed clearly when the joint was dislocated dorsally. However, the significance of sesamoid location in diagnosing joint dislocation was unclear. The present study aimed to explore the positional relationship between sesamoid bone and thumb metacarpophalangeal joint in normal and dorsal dislocation joints.

METHODS

Between January 2018 and August 2023, we collected 60 isometric plain films from sixty outpatients and reviewed 56 anisometric plain films from twenty-eight emergency patients with dorsal dislocation of thumb MCP joint at Tianjin Hospital, then took measurements on the hand X-ray images. The sesamoid length on its longitudinal axis was defined as DP, the distance between the distal edge of sesamoid and thumb MCP joint was defined as DJ, and the ratio of DJ and DP was R. An independent-samples t-test and paired-samples t-test was utilized to analyze difference among data groups.

RESULTS

The 60 isometric images were from 30 male and 30 female outpatients with normal bone structure in their hands, and the 56 anisometric images of the 28 emergency patients included both preoperative and postoperative materials. Among the outpatients, the actual distance between the distal edge of sesamoid and thumb MCP joint space (DJ) was 2.09 mm and 1.40 mm in males and females, respectively. The authentic average length of sesamoid (DP) was 4.46 mm in males and 4.22 mm in females. The average value of R (the ratio of DJ and DP) in males and females was 0.49 and 0.34, respectively. There were gender-related statistical differences in DJ (p < 0.01) and R (p=0.01), but no statistical difference in DP (p > 0.05). For the 28 emergency patients, the mean value of R was -0.47 before joint reduction and 0.58 after joint reduction, with statistical difference between them (p < 0.01).

CONCLUSIONS

There was significant difference in the relative position between sesamoid and thumb MCP joint when joint dislocation and joint reduction. The distal edge of sesamoid beyond thumb MCP joint could be an evidence in diagnosing joint dorsal dislocation. The distal edge of sesamoid below thumb MCP joint could be an evidence of joint reduction.

Volar Dislocation of Second Metacarpophalangeal Joint-open Reduction with Volar Approach - A rare Case Report

Introduction

In most cases, the volar plate interposition renders the complex metacarpophalangeal joint dislocation, commonly known as Kaplan's lesion, intractable, necessitating open reduction. The capsuloligamentous attachments around the joint and the head of the metacarpal are buttonholed in this dislocation, limiting closed reduction.

Case Report

It is presented here a case of 42-year-old male with the left Kaplan's lesion with open wound. The dorsal technique would have decreased neurovascular compromise and prevented the reduction otherwise by exposing the fibrocartilagenous volar plate directly; however, in this case, the volar route was adopted since an open wound exposed the metacarpal head volarly rather than dorsally. After repositioning the volar plate, a metacarpal head splint was applied and physiotherapy was started a few weeks later.

Conclusion

Volar technique has been confidently employed because the wound was not related to a fracture and the open wound through which the incision was extended was already existing, allowing for easy access to the lesion and leading to positive outcomes, such as better range of motion postoperatively.