A detachable actuator arm in combination with a distractor device comprising: a distractor device comprising a main body, bone plates and a distraction mechanism which upon actuation separates said bone plates, said distraction mechanism comprising an internal recess; a detachable actuator arm adapted to releasably connect with said distraction mechanism, said actuator arm comprising an elongated tubular main body having a distal end and a proximal end, and a distal head and a proximal head connected together by an internal member, wherein said distal head, said proximal head and said internal member are disposed within said main body and are axially movable within said main body, and wherein said distal end comprises a side opening; said distal head comprising a contact surface having a distal recess and a proximal recess, said distal recess being deeper than said proximal recess; a spring member biasing said distal head, said proximal head and said internal member in the distal direction within said main body; a detent ball disposed within said distal end between said opening and said proximal recess of said contact surface, wherein in a locked position a portion of said detent ball extends through said opening into said recess of said distraction mechanism, thereby locking said distal end of said actuator arm to said distraction mechanism; and wherein said distal head is movable in the proximal direction into a release position by pulling said proximal head in the proximal direction relative to said main body, thereby aligning said distal recess with said detent ball such that said detent ball does not extend through said opening into said internal recess of said distraction mechanism and said actuator arm is detachable from said distraction mechanism. a distractor device comprising a main body, bone plates and a distraction mechanism which upon actuation separates said bone plates, said distraction mechanism comprising an internal recess; a detachable actuator arm adapted to releasably connect with said distraction mechanism, said actuator arm comprising an elongated tubular main body having a distal end and a proximal end, and a distal head and a proximal head connected together by an internal member, wherein said distal head, said proximal head and said internal member are disposed within said main body and are axially movable within said main body, and wherein said distal end comprises a side opening; said distal head comprising a contact surface having a distal recess and a proximal recess, said distal recess being deeper than said proximal recess; a spring member biasing said distal head, said proximal head and said internal member in the distal direction within said main body; a detent ball disposed within said distal end between said opening and said proximal recess of said contact surface, wherein in a locked position a portion of said detent ball extends through said opening into said recess of said distraction mechanism, thereby locking said distal end of said actuator arm to said distraction mechanism; and wherein said distal head is movable in the proximal direction into a release position by pulling said proximal head in the proximal direction relative to said main body, thereby aligning said distal recess with said detent ball such that said detent ball does not extend through said opening into said internal recess of said distraction mechanism and said actuator arm is detachable from said distraction mechanism.