Instruments and methods for minimally invasive carpal tunnel release

An instrument for use in minimally invasive carpal tunnel release wherein a transverse carpal ligament is severed with the assistance of endoscopic visualization, said instrument comprising

• a cannula for insertion in a distal direction along the subligamentous plane beneath the transverse carpal ligament, said cannula including an open proximal end, a closed distal tip, an elongate tubular member between said proximal end and said distal tip, said tubular member having a central longitudinal axis, a proximal length portion, a distal length portion joined to said distal tip, and a longitudinal interior passage in communication with said proximal end of said cannula, a slot in said tubular member in communication with said passage and extending longitudinally along said proximal length portion and said distal length portion in parallel with said central longitudinal axis, said slot along said distal length portion being positionable beneath the entire width of the transverse carpal ligament from a proximal edge of the ligament to a distal edge of the ligament, and a blade housing extending exteriorly outwardly from said tubular member along said proximal length portion and enclosing an interior channel extending entirely through said blade housing in communication with said slot, said blade housing having an open proximal end in communication with said channel and an open forward end in communication with said channel, said slot having a closed forward end on said distal length portion of said tubular member a sufficient distance distally of said forward end of said blade housing for the entire width of the transverse carpal ligament to be accommodated between said forward end of said blade housing and said forward end of said slot when said slot along said distal length portion is positioned beneath the transverse carpal ligament, said tubular member being of sufficient length for said slot along said distal length portion to be positioned beneath the entire width of the transverse carpal ligament with said proximal length portion extending through an incision in a distal volar aspect of a forearm;
• and
• a cutting member slidably receivable in said cannula, said cutting member including an elongate tube having a central longitudinal axis, a lumen extending longitudinally through said tube for slidably and rotatably receiving an endoscope, a cutting blade extending exteriorly outwardly from an outer surface of said tube, and at least one fenestration in said tube in communication with said lumen and extending longitudinally in parallel with said central longitudinal axis of said tube proximally of said cutting blade, said tube being siidable longitudinally in said passage of said cannula with said cutting blade extending through said slot to extend exteriorly outwardly from said tubular member and into said interior channel of said blade housing when disposed longitudinally along said proximal length portion of said tubular member, said blade being movable longitudinally distally from said forward end of said blade housing along said slot to expose said blade extending outwardly from said tubular member to sever the transverse carpal ligament disposed over said slot along said distal length portion of said tubular member, said blade being slidable within said slot from said forward end of said blade housing toward said forward end of said slot to sever the entire width of the transverse carpal ligament in the distal direction from the proximal edge to the distal edge of the ligament, said fenestration being aligned in parallel with said slot as said blade is moved distally from said forward end of said blade housing to permit an endoscope within said tube to visualize the ligament being severed through said fenestration and said slot aligned therewith.