Explanation:
Correct Option: A. The optimal pore size for maximizing osteoconduction and biological fixation via bone ingrowth into cementless implants is strictly between 50 and 400 micrometers. Pores smaller than 50 micrometers limit vascularization and osteon formation, while pores larger than 400 micrometers decrease the structural integrity of the coating and interface. (Ref: Bobyn et al., Clin Orthop Relat Res, 1980)