Montclair IPL doctors

Most likely the settings that treat acne, which are in the lower range of visible light, have also treated your freckles.  The first thing that happens when freckles are treated with IPL is they get darker, then they break up usually into what is called "coffee grounds" and then fade.  And some will disappear.

The question is whether the hyperpigmentation is darker than your skin was previously or just the dark areas that were not appropriately covered by the IPL treatment that remained dark after your skin was lightened by the treatment.

If they are just remaining dark areas, the handpiece was probably not placed close enough when the next pulse was delivered.  The handpiece has to be placed immediately adjacent to the previous pulse, but not overlapping as overlap can result in a burn.

If it is the remaining pigmentation, I would suggest a test spot before the following treatment.  If the hyperpigmentation is darker than the skin was previously, I would be very cautious about the next treatment as more hyperpigmentation may result.

Make sure that you have not had sun exposure to the areas that were or are about to be treated for at least 6 weeks prior to treatment.

IPL reaches to the deep dermis and the superficial subcutaneous fat layer.  Appliances such as metal screws are usually deeper than that, at the bony structures under the muscle.  It is safe to have IPL done in those areas.

For external fixating devices (ones on the outside of the skin), they would need to be covered and avoided so that the light does not reflect from them.