Extensor mechanism laxity at the metacarpophalangeal joint as identified by a new provocative test: predisposition to dislocation

[Extensor tendon injuries of fingers in the region of the metacarpophalangeal joint (zone V)]

Due to the exposed situation of the extension side of the metacarpophalangeal joint when the fingers are bent, injuries in this region are not uncommon. The extensor apparatus lies directly below the skin and the various parts can be easily injured. Due to the complex anatomical structure, the different clinical appearances and the various forms of treatment, injuries of the extensor tendons in the region of the metacarpophalangeal joint must be examined in a very differentiated manner. The not uncommonly occurring deviation phenomenon makes all injuries in zone V suspicious and special attention must be paid to them. The alarming multitude of revision surgeries with tenolysis, arthrolysis and restoration of the balance of extensor tendons or centering show that these operations are much more demanding than the way they are appreciated in the literature and by many surgeons (beginner's operation). The article presents the surgical treatment with suture techniques and reconstruction possibilities as well as the aftercare, in addition to the special anatomy and diagnostics.

A Reconstructive Extensor Tendon Centralization Technique for Sagittal Band Disruption

Sagittal band injuries may result in extensor digitorum communis (EDC) tendon instability and may require operative treatment for symptomatic loss of extension, pain, and snapping at the metacarpophalangeal joint (MCPJ). Operative methods vary according to the source of donor tissue, as well as the anchor point of attachment. We present a surgical technique that diminishes tension of the repair with MCPJ flexion. Twenty-two EDC tendon stabilization procedures were performed between 2006 and 2017 using a tendon flap method. The selection criteria for this group of patients included completely dislocating extensor tendons with persistent complaints of pain and decrease in finger extension despite at least a 6-week conservative treatment attempt. All subjects underwent surgical treatment for tendon centralization using a distally based tendinous flap from the EDC sutured to the adjacent finger volar plate. A mathematical model was developed to analyze repair tension at 30, 60, and 90 degrees of MCPJ flexion calculating the flap length difference of 2 attachment points: deep transverse metacarpal ligament versus adjacent volar plate. Centralization was maintained in all digits with no evidence of subluxation at final postoperative evaluation. Clinical symptoms of pain and weakness resolved in all patients. Mathematical modeling provided evidence that translation of the anchor point of reconstructed flap to the volar plate of the adjacent finger resulted in lower tensile forces when compared with attachment at the intermetacarpal ligament. This optimized forces on reconstructed tendon flap experienced during MCPJ flexion.Level of Evidence: Level IV-therapeutic, case series.

Boxer'S Knuckle of Non-Boxer Patients

Boxer's knuckle is the eponym describing injuries to the sagittal band at the metacarpophalangeal joint, resulting in subluxation or dislocation of the extensor tendon, classically in boxers. This condition is often devastating because it can cause severe morbidity not only in professional athletes but also in manual workers. The unique anatomical position of the extensor apparatus system predisposes fingers to this type of injury. With better understanding of the anatomy and pathology of this injury, good functional outcome can be anticipated with appropriate treatment. Two cases of extensor tendon subluxation in non-athletic patients are presented here. The anatomy, diagnosis and current management of this particular injury are discussed.