A method of inserting a reusable surgical instrument module (110) into an outer housing shell (280) having a hinged instrument cover shell (290), wherein the outer housing shell defines a cavity (282) therein, and the outer housing shell (280) defines an upper outer housing half (280A), and a lower outer housing half (280B), the method comprising: inserting the instrument module (110) into the outer housing shell (280)； and connecting or attaching at least a portion of the lower outer housing half (280B) of the outer housing shell (280) to the instrument shell cover (290) via a hinged mechanism, characterised in that at least one motor (140) is disposed within a cavity defined in an inner housing shell (111) of the instrument module (110).
