SLR - October 2013 - Adam M. Lang
Reference: Trajkovski, T; Pinsker, E; Cadden, A; Daniels, T. J Bone Joint Surg Am. 2013;95:1382-8; August 2013.
Scientific Literature Review
Reviewed by: Adam M. Lang, DPM
Residency Program: University Hospital, Newark, NJ
Podiatric Relevance: Coronal plane mal-alignment is an important consideration for patient selection and perioperative planning in Total Ankle Replacement for foot and ankle surgeons. Varus deformity of less than 10˚ is usually acceptable for most current mobile bearing implants. Deformity of greater than 20˚ has been noted as an absolute contraindication to the procedure. Edge loading, polyethylene insert subluxation and wear, and ultimately implant failure are major consequences of large coronal plane deformity. Comparing the outcomes of total ankle replacement in patients with a pre-operative tibiotalar varus of ≥10˚ with those <10˚ is evaluated in this current study with noted attention to necessary adjuvant procedures, etiology of the varus deformity, and complications.
Methods: A cohort of 36 ankles (33 patients) was consecutively enrolled with tibiotalar coronal plane varus of ≥10˚ and underwent total ankle replacement. A matched “Neutral” cohort of 36 ankles (35 patients) with coronal plane varus of <10˚ were simultaneously enrolled. One of three current cementless mobile-bearing, three-component ankle replacements were selected and implanted: HINTEGRA, S.T.A.R., and MOBILITY. Ancillary procedures to correct a varus deformity were recorded. Pre-op weight bearing tibiotalar varum was measured on AP and Lateral radiographs by the methods of Pyevich et al, using the distal lateral tibial cortex and talar-tilt as guides. Patients completed the AOFAS ankle-hindfoot, AOS, and SF-36 functional evaluations.
Results: The primary diagnosis in the varus group was recurrent ankle sprains (67 percent), and posttraumatic arthritis (58 percent) in the neutral group. The HINTEGRA implant was implanted 31 times, MOBILITY 4 times, and S.T.A.R 1 time respectively for both groups. A total of 81 percent of the varus ankles and 47 percent of the “neutral” ankles had ancillary procedures. The two most common ancillary procedures in the varus group were osteotomies of the calcaneus and first metatarsal. Complication rates were 19 percent in the varus group (i.e. edge loading, lateral gutter impingement) and 14 percentin the “neutral” group (subsidence, edge loading). Complications were not reported as significant between groups. There was improvement seen across the board for the AOFAS, AOS, and SF-36 scoring systems, however, no significant difference was detected between the groups. The most interesting finding was that 50 percent of the ankles in the varus group had a pre-op deformity of ≥20˚.
Conclusions: The biomechanical and diagnostic indications for a Total Ankle Replacement can continually be extended. The HINTEGRA implant was used 31 times in both study groups compared to the MOBILITY(4) AND S.T.A.R (1). This study also had a majority of the varus deformities as a result of recurrent ankle sprains and lateral ankle instability, and 50 percent of them had a pre-op varus of ≥20˚. Although not the intention of the authors, one could gather from this study that the HINTEGRA may be used for large tibiotalar varus deformities. Overall, this study suggest that a tibiotalar varus of greater than 20˚, when performed with appropriate adjuvant procedures, makes mobile bearing ankle implants possible. The authors suggest that in addition, medial soft tissue releases and tendon transfers as well as extensive lateral gutter osteophyte debridements are usually always necessary. This study was limited by a rather short mean follow-up of 34.7 months, a non-randomized design, and a limited evaluation of the varus deformity.