A controlled force surgical implant impaction instrument, comprising: a. a housing having a proximal end and a distal end and defining a longitudinal axis, b. a striking assembly which includes a hammer component which can slide within the housing along the housing longitudinal axis to apply an impaction force when it slides from the proximal end towards the distal end, the hammer component having a protrusion with a flat end face which faces distally, with an outermost point, and with an angled face which faces proximally and is inclined relative to the housing axis, c. a hammer biassing component which acts between the housing and the hammer component to urge the hammer component distally, d. an actuator component which is mounted on the housing so that it can rotate, the actuator component having a channel formed in it which is substantially L-shaped with a retaining portion and a reloading portion which are in open communication with one another, e. a retaining pin which can slide within the channel in the actuator component between the retaining portion and the reloading portion, and within the reloading portion, in which use of the instrument involves causing the actuator component to rotate in a use direction while the retaining pin is in the retaining portion of the channel so that the retaining pin acts on the flat end face of the protrusion on the hammer component to cause the hammer component to move proximally and to compress the hammer biassing component, continued rotation of the actuator component causing the retaining pin to slip over the outermost point of the protrusion and on to the proximal face of the protrusion, to allow the hammer component to slide in a distal direction as a result of force applied by the hammer biassing component, and in which the instrument is restored for reuse by rotating the actuator in a restore direction which is opposite to the use direction while the retaining pin is in the reloading portion of the channel in the actuator component, the retaining pin sliding in the reloading portion of the channel as the retaining pin travels distally along the angled face of the protrusion and over the outermost point of the protrusion. a. a housing having a proximal end and a distal end and defining a longitudinal axis, b. a striking assembly which includes a hammer component which can slide within the housing along the housing longitudinal axis to apply an impaction force when it slides from the proximal end towards the distal end, the hammer component having a protrusion with a flat end face which faces distally, with an outermost point, and with an angled face which faces proximally and is inclined relative to the housing axis, c. a hammer biassing component which acts between the housing and the hammer component to urge the hammer component distally, d. an actuator component which is mounted on the housing so that it can rotate, the actuator component having a channel formed in it which is substantially L-shaped with a retaining portion and a reloading portion which are in open communication with one another, e. a retaining pin which can slide within the channel in the actuator component between the retaining portion and the reloading portion, and within the reloading portion,