Extensor Tendon Dislocation at the Metacarpophalangeal Joint of Both Ring Fingers Caused by a Specific Hand Posture in a Shiatsu Therapist

A 43-year-old female shiatsu therapist complained of sudden snapping of the metacarpophalangeal joints (MCPjs) of both ring fingers during a specific hand posture. The extensor tendon of the ring finger was dislocated ulnarly when the MCPj of the ring finger was flexed and deviated ulnarly and the MCPj of the middle finger was extended. Surgical exploration revealed an attenuated radial sagittal band. We plicated the juncturae tendinum of the extensor digitorum communis between the middle and ring fingers and released the ulnar sagittal band partially to centralise the extensor tendon excursion. Twenty-six months postoperatively, the patient regained full active and passive range of motion of all fingers without extensor tendon dislocation or snapping in either hand during work.

A Cadaveric Study of the Juncturae Tendinum

Introduction The superficial extensor tendons of the fingers are connected by juncturae tendinum (JT). JTs are of three types namely JT-1, JT-2, and JT-3. JT-3 are very thick with maximum occurrence in fourth intermetacarpal space (IMCS), where it is associated with agenesis of extensor digitorum communis to small finger (EDCs). Awareness of frequency and morphology of JT is essential in surgical repair of tendon injury. Methods JTs were dissected in 80 free adult cadaveric upper limbs and 32 fetal upper limbs of 16 stillborn and embalmed fetuses present in the department. The pattern and frequency of JT was studied. Frequency of JT-3 in association with agenesis of EDCs was looked into. The length and width of JT were measured and analyzed using ANOVA and post hoc analysis. Results JT-1 and JT-2 were commonly observed in the second and third IMCS, respectively. JT-3 had a maximum frequency in the fourth space and was observed in 78.37% of cases of agenesis of EDCs. A gradual increase in length and a decrease in the width of JT were observed from JT-1 to JT-2, JT-3r, and JT-3y. Conclusion JTs are absent in the first IMCS and in 6.25% of second IMCS. The commonest pattern of distribution of JT in the second, third and fourth IMCS is JT-1, JT-2, and JT-3, respectively. JT-3 is the longest and thickest JT, and partially compensates for agenesis of EDCs. The structural resemblance to tendons enables JT-3 utilization for a tendon graft.

Role of the Juncturae Tendinum in Preventing Radial Subluxation of the Extensor Communis Tendons after Ulnar Sagittal Band Rupture: A Cadaveric Study

Background. Radial subluxation of the extensor communis tendons at the metacarpophalangeal (MCP) joints is a rarely reportedvinjury. These injuries have proved difficult to reproduce in cadaveric studies and have a low biomechanical likelihood of occurrence due to the ulnar direction of pull of the extensor communis tendons. It has been suggested that the juncturae tendinum may have a stabilising role, preventing radial subluxation after ulnar sagittal band rupture; however this has not been established. Methods. 40 cadaveric digits were dissected to reveal the extensor mechanism around the MCP joints. The ulnar sagittal bands were released and then the juncturae tendinum divided, in stages, before observing for radial subluxation or dislocation during finger flexion. Results. Radial subluxation of the extensor tendon was observed in only one digit after complete ulnar sagisttal band release. When all the fingers were flexed, after the juncturae tendinorum were divided, four additional tendons subluxed radially and a fifth tendon dislocated in this direction. When the digits were then flexed individually, there were eight unstable tendons in total. Conclusions. The juncturae tendinum appear to have a role in stabilising the extensor communis tendons at the MCP joints and preventing radial subluxation after ulnar sagittal band rupture.