A surgical instrument includes an outer housing shell defining a cavity. The outer housing shell defines an upper outer housing half and a lower outer housing half. The upper outer housing half defines a longitudinal axis. An instrument module is selectively insertable into the cavity of the outer housing shell. The instrument module includes an inner housing shell, at least one motor disposed within the inner housing shell, a control board being in electrical communication with the at least one motor, and an energy source being in electrical communication with the at least one motor and the control board. The instrument module is inserted into the cavity of the outer housing shell in such a manner that the operative axis of the at least one motor is substantially parallel to the longitudinal axis of the upper outer housing half.