The Salto Total Ankle Prosthesis was developed between 1994 and 1996 by Michel Bonnin. This total ankle replacement (TAR) is the third generation of cementless meniscal-bearing designs. The tibial component has a flat surface that faces the mobile bearing, allowing free translation and rotation. The 3 mm medial rim is designed to avoid insert impingement against the medial malleolus. For osseous integration, the component has a keel and a fixation peg. The specific shape of the talar component mimics the natural talar geometry – the anterior width is wider than the posterior width and the lateral flange has a larger curvature radius than the medial. The mobile bearing is manufactured from UHMWPE and has full congruency with the talar component in flexion and extension. All components are available in three different sizes.

In 2008, Leszko et al performed an in vivo kinematics study of the Salto TAR in 20 patients using fluoroscopy and a 3D-to-2D registration technique. The motion of the prosthesis was described in terms of clinical rotations and as rotation about the helical axis. Among the clinical rotations, the dorsi-/plantarflexion was the most dominant with a mean ROM of 9.2 degrees. The anterior-posterior translation of the mobile bearing was measured at 1.5 mm and 2.3 mm for gait and step-up, respectively.

The first clinical study on the Salto prosthesis was published in 2004 by the prosthesis designer. Bonnin et al implanted 98 consecutive Salto prostheses between 1997 and 2000. Ninety-three implants in 91 patients were reviewed clinically and radiographically at a mean follow-up of 35 months. Most patients were pain free and showed a significant functional improvement as assessed by AOFAS score (from 32.2 to 83.1 points). Two prostheses had to be converted to ankle fusion, resulting in survivorship of over 95% at 68 months. In the following 2 years, 22 additional Salto implants were performed, as published by Weber et al, who included a total of 115 implants in their study. At a mean follow up of 22 months, four ankles had to undergo revision surgery.

Recently, Bonnin et al presented survivorship at 7 to 11 years in a retrospective review of 98 TARs performed between 1997 and 2000. Six replaced ankles had to be converted to ankle fusion and an additional 18 ankles underwent reoperation without ankle fusion (10-year survivorship 65% with 95% CI of 50% to 80%). The most common complications requiring additional surgery were bone cysts (11 ankles), fracture of polyethylene (5 ankles), and unexplained pain (3 ankles).

Furthermore, Bonnin et al addressed the sports activity level of 145 patients who underwent Salto TAR between 1997 and 2005. Ankle function was assessed using the Foot Function Index and Foot and Ankle Ability Measurement. In most cases, replaced ankles were reported to have normal (15.2%) or nearly normal (60.7%) function. Participation in sports and recreational activities was analyzed only in the osteoarthritis (OA) group (100 patients), but not in patients with rheumatoid arthritis. While most patients participated in some sport activities, a return to impact sports was rarely possible.

In conclusion, the mid-term results of the Salto TAR are promising. However, the only clinical reports come from the prosthesis designer. In the United States, a modified design of the Salto TAR is approved for use in patients with ankle OA. This fixed-bearing design includes a titanium tibial component with a highly conforming polyethylene articulating insert. However, to date no clinical studies reporting results of this prosthesis are available.

References

  1. Bonnin,M., Judet,T., Colombier,J.A., Buscayret,F., Graveleau,N., and Piriou,P.: Midterm results of the Salto Total Ankle Prosthesis. Clin Orthop Relat Res, 424:6-18, 2004.
  2. Leszko,F., Komistek,R.D., Mahfouz,M.R., Ratron,Y.A., Judet,T., Bonnin,M., Colombier,J.A., and Lin,S.S.: In vivo kinematics of the salto total ankle prosthesis. Foot Ankle Int, 29:1117-1125, 2008.
  3. Weber,M., Bonnin,M., Columbier,J.A., and Judet,T.: Erste Ergebnisse der SALTO-Sprunggelenkendoprothese: Eine französische Multizenterstudie mit 155 Implantaten. Fuss Sprungg, 2:29-37, 2004.
  4. Bonnin,M., Gaudot,F., Laurent,J.R., Ellis,S., Colombier,J.A., and Judet,T.: The Salto Total Ankle Arthroplasty: Survivorship and Analysis of Failures at 7 to 11 years. Clin Orthop Relat Res, 7-1-2010.
  5. Bonnin,M.P., Laurent,J.R., and Casillas,M.: Ankle function and sports activity after total ankle arthroplasty. Foot Ankle Int, 30:933-944, 2009.
  6. Yalamanchili,P., Donely,B., Casillas,M., Ables,A., and Lin,S.S.: Salto Talaris total ankle replacement. Oper Tech Orthop, 18:277-281, 2008.