Does using autograft bone chips achieve consistent bone ingrowth in primary TKA?

BACKGROUND: Cementless fixation remains controversial in TKA due to the challenge of achieving consistent skeletal attachment. Factors predicting durable fixation are not clearly understood, but we presumed bone ingrowth could be enhanced by the quantity of host bone and application of autograft bone chips. QUESTIONS/PURPOSES: We asked: (1) Did the amount of bone ingrowth exceed the amount of periprosthetic and host bone with the addition of autograft bone chips? (2) Did the amount of bone ingrowth increase with implantation time? And (3) did osteolysis along the porous-coated interface and screw tracts progress with implantation time?
METHODS: We measured the amount of bone in the porous-coated, periprosthetic, and host bone regions in 19 postmortem retrieved cementless primary total knee implants. The amount of bone in apposition to the implant surface, and alternatively lysed bone, was analyzed radiographically to assess the progression of osteolysis.
RESULTS: While bone ingrowth tended to be less than periprosthetic and host bone in all three components, it was only significantly less in the patellar component. Bone ingrowth increased in all three components over time, but progression of osteolysis did not.
CONCLUSIONS: Even after long-term followup, the amount of bone ingrowth did not surpass host bone levels, suggesting the amount of a patient's host bone is a limiting factor in the amount of bone ingrowth achievable for this cementless design. It remains unknown whether compromised osteopenic bone could achieve the amount of bone attachment necessary to provide durable fixation over time.