Reciprocating rotary arthroscopic surgical instrument

A driving assembly of a surgical instrument, comprising:

• a drive coupler configured to receive a rotational input;
• a helical member operably coupled to the drive coupler such that rotation of the drive coupler rotates the helical member, the helical member defining a helical groove having a first threaded helical channel and a second threaded helical channel, the first and second threaded helical channels coupled together at their ends to define transitions therebetween, wherein the first threaded helical channel defines a first pitch and wherein the second threaded helical channel defines a second pitch different from the first pitch;
• and
• a translation piece engaged within the helical groove such that the helical member provides both a rotational output and translational output in response to the rotational input, wherein, as a result of the different first and second pitches, the translation output defines a first speed in a first direction and a second, different speed in a second, opposite direction.