Primary stability of a robodoc implanted anatomical stem versus manual implantation.

Abstract

To assess the initial stability of anatomical stems implanted in manually broached femoral cavities compared with that assessed in cavities milled with the robodoc system. The bone-prosthesis interface motion was measured in matched pairs of cadaveric femora to assess the initial stability of anatomical stems implanted with two different implantation techniques. The high costs of surgical robots and the increased perioperative efforts associated with their use can only be justified if measurable benefits for patients can be achieved. Increased initial stability of the stem as an early indicator for better bone ongrowth would be such a benefit. Seven pairs of fresh frozen human cadaveric femora were used. One femur of each pair was randomly assigned to receive the robotic milling method; the other femur underwent manual broaching by an experienced surgeon. Initial micromotions of the anatomical stems were measured during simulated gait cycles with loads of < or =1500 N, and both groups underwent matched-pair analysis. Results. High motion of the prostheses was found for both implantation techniques. The robodoc system did not enhance the primary stability of the anatomical prosthesis compared with the manual broaching method.