SLR - May 2011 - Brant L. McCartan
Reference: Mann, J., Mann, R., Horton, E. STAR Ankle: Long-Term Results. Foot & Ankle International, (May 2011) Vol. 32, No. 5: 473-484
Scientific Literature Review
Reviewed by: Brant L. McCartan DPM, MBA, MS
Residency Program: Beth Israel Deaconess Medical Center/Harvard Medical School
Podiatric Relevance:
Total Ankle Replacements (TAR) is used frequently to treat painful ankle arthritis. Long-term results of ankle arthrodesis show incresased stress on adjacent joints as a result of eliminating ankle joint motion. Thanks to improved instrumentation, less bone resection, and newer generation implants, the viability of implants has improved. The STAR is the first U.S. approved three-component ankle implant, and this is the first long-term U.S. study on the STAR results. The primary purpose of this study was to determine if the patient retained his or her prosthesis.
Methods:
A prospective cohort of 84 ankles in 80 patients was performed - of which 78 ankles were analyzed (six lost to follow-up). AOFAS pain & function score, stability & alignment, as well as failure, subsequent procedures and complications were evaluated. The eighty-four procedures were between February 1998 to September 2000, and all were performed by the two senior authors. The average patient age was sixty-one; the average BMI was 28.8 Kg/M^2; the time between initial injury to joint replacement was 21.8 years. The surgical technique was similar to that described by Kofoed (designer of implant) and post-operatively the patients were immobilized for two weeks then weight-bearing in a cam-walker for 2-4 weeks. Follow-up appointments/radiographs were monthlyfor three months, then at six & twelve months post-op & annually after that. Position, alignment, subsidence, osteolytic, sclerotic & degenerative changes were also evaluated. Statistical analysis was computed on patient demographics, scores of outcomes, & survivorship. Complication was graded according to Glazebrooks classification (High Grade: aseptic loosening, deep infection, implant failure; Medium Grade:subsidence, post-op fracture; and Low Grade: intra-op fracture & superficial infection).
Results:
91% of prostheses remained implanted at an average of 9.1 years follow-up. Five-year implant survival was 96%, ten-year survival was 90%. There was a 39-point improvement in the AOFAS score with 92% of patients satisfied with their outcome. Range of motion averaged 4.5 degrees dorsiflexion + 34.7 degrees plantarflexion = 39.2 degrees (up from 32 degrees pre-op). 12% had high-grade complications, 7% had medium-grade complications and 7% had low-grade complications, resulting in 21 (or 25%) patients with a complication. 17% required an additional procedure (5.5 years following the initial implant), 9% required explantation with subsequent ankle arthrodesis.
Alignment of the implants was analyzed initially, and the average tibial & talar component alignment was three degrees of varus. The average tibial component sagittal plane alignment was four degrees dorsiflexion. Long-term tibial component alignent was two degrees varus & two degrees dorsiflexion. The talar component remained at three degrees varus. It is noted that there was not a correlation between the coronal plane deformity and recurrence or failure. Sclerosis and osteoloysis were divided into three categories: stress shielding (on top of the tibial tray), mechanical osteolysis (lateral malleolus & lateral tibial tray) and ballooning/epansile osteoloysis (>2mm lucency between the prosthesis and bone). Only the ballooning osteoloysis was associated with failure, which was found in 13% of the patients. Out of these 13% (10 patients), four required bone grafting surgery and two required explantation with fusion. 36% had sclerosis, six patients had symptomatic osteophytes that underwent osteophyte excision - 3.7 years following initial implantation. Finally, only 12% of the adjacent joints showed progression of arthritis at 10 years follow-up.
Conclusions:
This is the first medium-long term study on the results on the STAR. 90% of implants remained in 78 ankles after 10 years. These long-term results are similar or favorable to those found in European literature on the STAR as well as American studies on the Agility Total Ankle and the Hintegra prosthesis, as well as short-term results on the Salto TAR. In comparison to arthrodesis, TAR preserves ankle motion, and though a technically challenging procedure, with appropriate training, and the development of improved components and instrumentation, TAR is proven to be effective in treating ankle arthrosis.