Comparison of sagittal subluxation in two different three-component total ankle replacement systems

Syndesmotic Overload in 3-Component Total Ankle Replacement

BACKGROUND

Mobile-bearing total ankle replacement (TAR) potentially enables motion at the tibial implant-polyethylene insert (PI) interface. Such additional freedom of movement may overload periarticular ligaments and subsequently result in coronal translation of the talus. The aim of this study was to assess whether syndesmotic overload affects clinical and radiographic outcomes following mobile-bearing TAR and whether tibiofibular fusion is an effective treatment option.

METHODS

Thirty-one patients who underwent revision surgery for syndesmotic overload after mobile-bearing TAR were retrospectively analyzed. Clinical and radiographic outcomes were assessed before and after index TAR, preoperatively to revision surgery, and at the last follow-up after revision surgery. Computed tomography scans were also analyzed.

RESULTS

Ankles with lateral talar translation prior to revision surgery were about 10 times more likely to have valgus tibial implant position (P = .003). A wide tibiofibular distance at the level of the syndesmosis after index TAR was associated with an increased hindfoot moment arm at revision surgery (P = .025). Decrease of PI height at revision surgery and a PI fracture were evident in 10 (32%) and 4 (13%) cases, respectively. Talar cyst formation at revision surgery was evident in 12 (39%) cases. Tibiofibular fusion was effective in restoring function of the replaced ankle and providing pain relief.

CONCLUSION

Syndesmotic overload impaired clinical and radiographic outcomes after mobile-bearing TAR. Proper implant positioning and additional realignment procedures may prevent overload of periarticular soft tissue structures after mobile-bearing TAR.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Lower limb joint repair and replacement: an overview

In the last few years, much has been published concerning total joint arthroplasty, and debates and discussions to new questions and points of view started many years ago. In this commentary, we report the latest evidence of best practice in the field of lower limb arthroplasty; this evidence is based on a literature search conducted by using PubMed and Scopus databases with a time limit of five years. We found novel evidence regarding cemented and not cemented implant, implant design, anticoagulant use, tourniquets, and other aspects of joints replacement surgery that we consider a common part of modern orthopedic practice. We specifically focus on lower limb joint replacement.

Sagittal tibiotalar translation and clinical outcomes in mobile and fixed-bearing total ankle replacement

BACKGROUND

Sagittal implant malalignment after total ankle replacement (TAR) has been considered to be a possible cause for premature implant failure. In a prior study, the change over time of the tibiotalar ratio (T-T ratio), which is the ratio between the posterior longitudinal talar length and the full longitudinal talar length, was assessed in 66 TARs where an unconstrained, mobile-bearing implant was implanted. The analysis documented an increase in the T-T ratio between 2 and 6 months post-surgery (on average from 34.6% to 37.2%). We hypothesized that this change might have been related to the presence of a mobile-bearing insert. In order to test our hypothesis, we designed a study to compare the translation of the talus in TARs performed with an unconstrained, mobile-bearing implant (designated the "Mobile ankle") and those performed with a semi-constrained, fixed-bearing implant (designated the "Fixed ankle").

METHODS

The study included 71 consecutive patients (71 ankles) who underwent TAR with the Mobile ankle and 24 consecutive patients (24 ankles) who received the Fixed ankle from May 2011 to December 2014. Patients were assessed clinically and radiologically preoperatively (T₀), at 6 months (T₂) and 12 months (T₃) post-surgery. There was also a radiological assessment at 2 months post-surgery (T₁).

RESULTS

The comparison of the T-T ratio between the two implant groups and over time indicated an interaction between time and group, therefore the changes of the T-T ratio over time were affected by the implant type factor (P<0.001). The changes of the postoperative T-T ratio over time were not significant in the Fixed ankle group (35.7±6.7% at T₁, T₂, and T₃; P=1.0 for each pairwise comparison). In the Mobile ankle group, the T-T ratio at 2 months (34.4±5.5%) was significantly different to the T-T ratio at 6 months (37.0±5.8%; P<0.001; i.e. there was a significant posterior translation of the talus). The AOFAS score increased from preop to 12 months post-surgery in both the Mobile ankle (72.7±12.8 at 12 months; P<0.001) and the Fixed ankle (85.0±9.7 at 12 months; P<0.001).

CONCLUSION

The significant posterior translation of the talus from 2 to 6 months documented only in the Mobile ankle group may have been associated with the presence of the mobile bearing interface.

Comparison of the outcomes between two 3-component total ankle implants

BACKGROUND

Total ankle arthroplasty (TAA) with the use of third generation implants has demonstrated favorable clinical results and improved survival. However, few studies have compared the different types of implants. The purpose of this study was to perform a retrospective evaluation of patient outcomes and complications by comparing TAA procedures performed with HINTEGRA versus MOBILITY systems.

METHODS

Fifty-two consecutively enrolled patients (28 men and 24 women; mean age 64.8 years) underwent TAA using HINTEGRA (21 ankles) or MOBILITY (33 ankles) between September 2004 and July 2012. Visual analog scale (VAS) pain scores and the American Orthopaedic Foot & Ankle Society (AOFAS) ankle-hindfoot scores were determined at each follow-up visit. The radiographs were reviewed to assess component positioning, radiolucency, heterotopic ossification, and other factors. The mean follow-up period was 28.3 months in the HINTEGRA group and 32.5 months in the MOBILITY group.

RESULTS

VAS decreased from 8.3 to 2.0 for the HINTEGRA group and from 7.9 to 2.7 for the MOBILITY group. The AOFAS score increased from 43.8 to 87.3 for the HINTEGRA group and from 46.6 to 83.7 for the MOBILITY group. Intra- and postoperative malleolar fractures were not noted in the HINTEGRA group, whereas 5 ankles (15.2%) in the MOBILITY group sustained this injury (P = .144). Ankle impingement syndrome was noted in 8 ankles (38.1%) in the HINTEGRA group and 3 (9.1%) in the MOBILITY group (P = .015). However, no significant differences in postoperative osteolysis and neuralgia were noted between the groups.

CONCLUSIONS

Both implants exhibited favorable clinical outcome without significant differences. However, in terms of complications, ankle impingement syndrome was significantly more common in the HINTEGRA group, while intraoperative malleolar fracture was observed only in the MOBILITY group.

LEVEL OF EVIDENCE

Level III, comparative series.