CT Analysis of INBONE Use in Total Ankle Arthroplasty
Authors: Materon Solangel Rodriguez , Morningstar Joshua L. , Guareshi Alexander S. , Scott Daniel J. , Gross Christopher E. 
Published: December 2024

Category: Ankle; Ankle Arthritis Introduction/Purpose: Osseointegration is an important determinant of clinical success following the insertion of a orthopaedic implants. The success of osseointegration is an important predictor of the long-term clinical success of many implants, especially total joint arthroplasties. Total ankle arthroplasty (TAA) is a common surgical treatment for patients with end-stage ankle osteoarthritis. Aseptic loosening is a common complication following TAA and may be related to poor osseointegration between the prosthesis and the host bone. Thus, the purpose of this study is to investigate the patterns of ingrowth and ongrowth bone formation that occur following implantation with in Inbone TAA, and the correlation of those with patient outcomes. Methods: We conducted a retrospective review of eleven patients that underwent primary (n=8) or revision (n=3) total ankle arthroplasty with a single fixed bearing stemmed total ankle implant for end stage ankle arthritis. All participants underwent surgery at a single academic medical center with one of two foot and ankle fellowship trained surgeons. Data was collected from medical charts and imaging software. Radiographic measurements were performed on both weightbearing preoperative and postoperative radiographs and non-weightbearing CT scans. The cohort was majority male (72.7%%), with mean age 62.42 (range 40.54-81.00) years, and mean radiographic follow-up of 1.95 (range 0.46-10.39) years. Of the eleven subjects, ten had preoperative cysts on the tibia and talus. Three of the subjects exhibited new cyst formation post-implantation, notably including the patient who had no preoperative cysts. Results: Following implantation, four patients underwent reoperation, but none required revision. Cyst size and location did not significantly affect reoperation rates or alignment measurements. At 2-years postoperatively, increased radiolucency at the 2nd or 4th quadrants of the tibial stem tip was correlated with more valgus tibiotalar angle (r=.960: p=.010), while increased radiolucency in the 1st quadrant of the tibial stem shaft was correlated with a more valgus tibiotalar angle (r=-.960; p=.010). Increased radiolucency at the 3rd quadrant of the tibial stem tip (r=.957: p=.011), and 1st (r=.926: p=.024) or 2nd (r=.915: p=.029) region of the tibial stem base were correlated with a more valgus coronal tibial angle. Increased radiolucency at the 2nd quadrant of the tibial stem shaft was associated with greater sagittal displacement (r=-.926, p=.024). Conclusion: Our results demonstrate that the TAA outcomes were not affected by preoperative cyst presence nor postoperative cyst presence, region, or size. There were, however, a number of radiographic alignment measurements affected by radiolucency around the implant at 1 and 2 years postoperatively. Given the rapidly expanding implementation of TAA and the relatively high revision rate following the procedure, extensive research should be conducted to determine if osseointegration affects desirable patient outcomes.