RADIOLOGIC REVIEW OF OSTEOLYSIS IN THE HINTEGRA TOTAL ANKLE PROSTHESIS

Ankle arthritis is estimated to affect 1% of the world's adult population, with total ankle replacement (TAR) being a surgical option for patients with ankle arthritis who have failed conservative management. Newer implants have markedly improved TAR survivorship, however periprosthetic osteolysis causing aseptic loosening continues to be a main cause of TAR failure. Furthermore, the presence of periprosthetic osteolysis varies immensely in the literature. The HINTEGRA prosthesis is a mobile-bearing, three component TAR with survivorship being comparable to other third-generation TARs, but with fewer implant failures and reduced additional surgery for implant loosening. The objective of this study was to review the HINTEGRA TAR experience at a single institution specifically evaluating the radiographic formation, location and progression of cysts and the relation between cysts and prosthesis alignment, reoperations and implant survivorship. Retrospective study including all HINTEGRA TARs completed by one experienced foot and ankle surgeon from 2006 to 2014 using a direct anterior approach. Weight bearing anteroposterior (AP) and lateral preoperative, postoperative, 1-year postoperative and long-term weight bearing radiographs were reviewed, assessing for implant alignment as well as presence, location and progression of cysts. Implant survivorship and reoperations were reported to analysis any relationship with the alignment and presence of osteolysis. There were 51 TARs identified with radiographic and clinical follow up of 5.8 ± 3.5 years and 8.6 ± 3.0 years, respectively. The most common indication for surgery was posttraumatic arthritis found in 38 (75.0%) of patients. Eighty-four cysts were detected in 37 patients, with increasing number and size of cysts being correlated to length of time from surgery. The most common location for cysts to develop was the posterior tibia. Thirteen patients had enlarging cysts identified over time with the lateral malleolus being the most common location. Six patients met criteria for malaligned prosthesis, five of which were in the sagittal plane and did not appear to have any effect on development of osteolysis or implant survival. The one patient with coronal malalignment had a progressive talar cyst develop requiring reoperation. Seven patients met definition for a loosening prosthesis, two of which required reoperation because of osteolysis, and two others due to infection and impingement respectively. A total of 12 (23.5%) patients required a reoperation, two (3.9%) related to presence of osteolysis, four (7.8%) for deep infections and two (3.9%) required revision due to implant failure. Osteolysis is a very common finding after TAR using the HINTEGRA prosthesis, specifically on long-term radiographic follow up although most cysts do not appear clinically significant with no effect on outcomes. Progressive cysts termed “ballooning/expansile” and prosthesis coronal malalignment appear to be risk factors for developing osteolysis, prosthesis loosening and reoperation. This study also shows excellent and reliable outcomes of the HINTEGRA TAR compared to designer surgeons with acceptable complication and revision rates.