Background
The extent of migration of the ankle joint arthroplasty components and associated joint space caused by ankle replacement is directly correlated to the efficacy and longevity of the implant. Recent advents have resulted in the increasing use of tibial implants with stems to achieve greater stability. The purpose of this study was to ascertain the differences in said migration between implants with tibial stems and those without to conclude which style of replacement leads to greater stability and therefore greater longevity and utility.
Methods
A series of cases, which consisted of patients receiving both tibial implants with and without stems, that met the inclusion criteria, was considered for this study to determine key differences in outcomes. Twenty patients received tibial implants with stems and twenty patients received tibial implants without stems matched in two groups. The average patient ages between the two groups were not significantly different- the mean age of patients with the stem was 65.4 compared to 68.7 for the non-stem group. The key variables considered included migration (AP and anterior/posterior), DTA, TTA, beta angles, gamma angles, coronal translation, and talar tilt. Two-tailed T-tests were utilized to determine statistically significant results.
Results
Differences in measurements from the first post-operative weight-bearing x-ray to the most recent weight-bearing x-ray were considered. The mean time between these two x-rays was 24.1 months for the patients who received tibial implants with stems and 29.8 months for patients who received tibial implants without stems. Across the population considered, it was found that patients receiving the implants without the stem had significantly less migration in the AP X-rays when compared to their tibial implant with stem patient counterparts at both follow-up periods (p<0.03). Additionally, patients without the tibial stem had significantly larger beta angles than those with the tibial stem in both x-rays (p<0.04).
Conclusion
Ankle replacements utilizing tibial stems lead to greater rates of migration when compared to those without said stems. Therefore, the supposed benefit of the stem should be further evaluated. Greater beta angles are seen with tibial implants without stems, however. Future research regarding the efficacy and long-term outcomes of each of these implants for total ankle replacement must be conducted to refine these findings.