Young patients who have hip disease early on requiring fixation with hardware such as pins, wires, plates, and/or screws provide surgeons with some interesting challenges. Conversion to a total hip replacement does require removal of some (if not all) previously placed hardware.
Holes placed in the bone for the screws do create stress points that can result in fracture during removal. The surgeon may need to surgically dislocate the hip in order to reduce the amount of force placed on the bone during hardware removal. Although it may sound extreme, surgical hip dislocation actually results in fewer complications.
If there is extensive hardware that would require destroying much of the bone to remove, then the surgeon may choose to leave the hardware alone. Each patient is evaluated individually. All factors are considered including your age, general health, underlying diagnosis (reason hip has been a problem), presence of structural deformity, biomechanics, and so on.
Your surgeon is the best one to advise you properly on what to expect and any plans for hardware removal. Every effort will be made to preserve bone integrity, joint motion, and muscle function. Now that more younger patients are having this type of surgery, surgical techniques, tools, and approaches have improved quite a bit. The result has been better outcomes, even in the long-term.