Histopathologic retrieval analysis of clinically failed porous tantalum osteonecrosis implants.
BACKGROUND
An Osteonecrosis Intervention Implant made of porous tantalum was recently developed to provide structural support and a compatible surface for tissue ingrowth in osteonecrotic femoral heads. From an investigational device exemption study that comprised 113 implants, we carried out a retrieval analysis of clinically failed implants.


METHODS
Seventeen porous tantalum implants that had been used for the treatment of Steinberg stage-II osteonecrosis of the hip were retrieved at the time of conversion to a total hip arthroplasty. Fifteen implants that had been transected near the base of the femoral neck with the proximal portion left in situ within the femoral head underwent histopathologic analysis at an average of 13.4 months (range, three to thirty-six months) after implantation.


RESULTS
Residual osteonecrosis was present in fourteen of the fifteen specimens. Fracture of the subchondral bone of the femoral head was present in all instances, and collapse of the femoral head was present in nine instances (60%). Backscattered scanning electron microscopy confirmed the presence of bone ingrowth in thirteen (87%) of the fifteen specimens. The mean extent of bone ingrowth was 1.9% (range, 0% to 4.4%).


CONCLUSIONS
The retrieved implants were associated with little bone ingrowth and insufficient mechanical support of subchondral bone. The implant design, the surgical technique, its application, and the clinical characteristics of candidates for this procedure should continue to be monitored closely.
Division of Orthopaedics, Department of Surgery, McGill University, 1650 Cedar Avenue #B5.159, Montreal, Quebec H3G 1A4, Canada.
M
M
Tanzer
J D
JD
Bobyn
J J
JJ
Krygier
D
D
Karabasz
D000328:Adult; D000368:Aged; D020878:Device Removal; D005260:Female; D005271:Femur Head Necrosis / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D006801:Humans; D008297:Male; D008855:Microscopy, Electron, Scanning; D008875:Middle Aged; D011474:Prosthesis Design; D011475:Prosthesis Failure; D019919:Prosthesis Implantation; D011859:Radiography; D013635:Tantalum
D013635:Tantalum