English to Swedish Medical Medical: Instruments medical term anatomy

Medical device user manual for XX retractor system (looks like a bent fork with blades and is used in surgical procedures to keep the incision open). You have to construct a frame to hold it fixed above the patient on the operating table.

Context: Position the upper abdominal angled arm in the rail clamp’s upper cam joint and secure it 8 to 10cm (3 - 4"), depending on desired elevation of the costal margin, above the patient’s chest.

Target audience: Surgeons and medical professionals

Costala marginalen/regionen?