April highlighted article: Total Ankle Arthroplasty Radiographic Alignment Comparison Between Patient- Specific Instrumentation and Standard Instrumentation

Total Ankle Arthroplasty Radiographic Alignment Comparison Between Patient-Specific Instrumentation and Standard Instrumentation

Mario I Escudero, Vu Le, Thomas Bradford Bemenderfer, Maximiliano Barahona, Robert B Anderson, Hodges Davis, Kevin J Wing, Murray J Penner.

Abstract

Background: Several benefits are published supporting patient-specific instrumentation (PSI) in total ankle arthroplasty (TAA). This study seeks to determine if TAA with PSI yields different radiographic outcomes vs standard instrumentation (SI).

Methods: Sixty-seven primary TAA patients having surgery using PSI or SI between 2013 and 2015 were retrospectively reviewed using weightbearing radiographs at 6-12 weeks postsurgery. Radiographic parameters analyzed were the medial distal tibia angle (MDTA), talar-tilt angle (TTA), anatomic sagittal distal tibia angle (aSDTA), lateral talar station (LTS), and talar component inclination angle (TCI). A comparison of the 2 groups for each radiologic parameter’s distribution was performed using a nonparametric median test and Fisher exact test. Furthermore, TAAs with all radiographic measurements within acceptable limits were classified as “perfectly aligned.” The rate of “perfectly aligned” TAAs between groups was compared using a Fisher exact test with a significance of .05.

Results: Of the 67 TAAs, 51 were done with PSI and 16 with SI. There were no differences between groups in MDTA (P = .174), TTA (P = .145), aSDTA (P = .98), LTS (P = .922), or TCI angle (P = .98). When the rate of “perfectly aligned TAA” between the 2 groups were compared, there was no significant difference (P = .35).

Conclusion: No significant radiographic alignment differences were found between PSI and SI implants. This study showed that both techniques achieve reproducible TAA radiographic coronal and sagittal alignment for the tibial component when performed by experienced surgeons. The talar component’s sagittal alignment is similar whether or not PSI was used but is noticeably different from normal anatomic alignment by design.

Level of evidence: Level III, retrospective cohort study using prospectively collected data.

Keywords: ankle arthroplasty; ankle arthroplasty alignment; infinity total ankle system; patient-specific instrumentation; prophecy.

Author´s Comment

The advances in Total Ankle Arthroplasty (TAA) have been substantial in implant design and operative technique. One recent innovation is patient-specific instrumentation (PSI). PSI uses a preoperative computed tomographic (CT) scan and generates cutting blocks specific to each patient’s anatomy as well as a modifiable operative plan. TAA with PSI has several published advantages compared with standard instrumentation (SI) including cost-effectiveness, decreased operative time, and reduced radiation exposure without increasing osteolysis risk from more soft-tissue dissection.

Mario Escudero, MD
Department of Orthopaedics 
Universidad de Chile, Chile

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