Testicular torsion (twisting of the testicle around its blood vessels) cuts off the blood supply to the testicle, which essentially kills it (atrophy + loss of function).
Surgery aims to prevent this. Orchiopexy fixes the testicle to the scrotum, decreasing its mobility, and preventing torsion. However, its possible testicular damage has already occurred by the time orchiopexy is carried out, which is why its an emergent procedure, and early intervention is critical. However, surgery CAUSING testicular damage is essentially a surgical complication, which obviously CAN happen, but is related to the skill of the surgeon, your specific anatomy etc. Consent forms generally list all possible complications.
Torsion at your age (I'm guessing you're at least a teenager) is usually due to a congenital defect that results in poor fixation of the testicle to the scrotum. This allows it to be more mobile than normal, creating the possibility of torsion. The congenital defect (usually something called a bell clapper deformity) is bilateral in upto 25% of cases, which is why orchiopexy should be bilateral. I'm not sure why he's suggesting unilateral orchiopexy, you should ask him for the specific reason, and get a second opinion if you want. I'm also not sure why your surgery hasn't been done already (its usually done on an emergent basis once you reach the ER). Was your torsion incomplete and not so severe?
This is from uptodate (it has paid access so I'm posting this here for your benefit):
Management — Treatment for suspected testicular torsion is urgent surgical exploration with intraoperative detorsion and fixation of the testes. Delay in detorsion of a few hours may lead to progressively higher rates of testicular nonviability. Manual detorsion should be performed if surgical intervention is not immediately available.
Surgery — Detorsion and fixation of both the involved testis and the contralateral uninvolved testis should be performed since inadequate gubernacular fixation is usually a bilateral defect. Extended periods of ischemia (>6 hours) may cause infarction of the testis with liquefaction requiring orchiectomy.
The outcome of surgery may be worse in adults than in children. In one retrospective study, the testicular salvage rates of patients age <21 years and age ≥21 years were 70 and 41 percent, respectively [10]. While the time to presentation was the most important factor affecting the salvage rate, adult men also had a greater degree of cord twisting than the younger group, which may partly explain the difference in outcomes.
