Review Article Ankle Distraction Arthroplasty: Indications, Technique, and Outcomes Abstract Mitchell Bernstein, MD, FRCSC Ankle distraction is an alternative to ankle arthrodesis or total ankle Jay Reidler, MD, MPH arthroplasty in younger patients with arthritis. Ankle distraction involves the use of external fixation to mechanically unload the ankle Austin Fragomen, MD joint, which allows for stable, congruent range of motion in the setting S. Robert Rozbruch, MD of decreased mechanical loading, potentially promoting cartilage repair. Adjunct surgical procedures are frequently done to address lower-extremity malalignment, ankle equinus contractures, and impinging tibiotalar osteophytes. Patients can bear full weight during the treatment course. The distraction frame frequently uses a hinge, and patients are encouraged to do daily range-of-motion exercises. Although the initial goal of the procedure is to delay arthrodesis, many patients achieve lasting clinical benefits, obviating the need for total ankle arthroplasty or fusion. Complications associated with external fixation are common, and patients should be counseled that clinical improvements occur slowly and often are not achieved until at least 1 year after frame removal. nkle osteoarthritis is generally ambulation do occur.5 Unlike fusion, Aa progressive condition, most TAA does not affect range of motion commonly the result of high-energy (ROM); however, its use in young tibial plafond fractures, bimalleolar active patients may be contra- ankle fractures, recurrent ankle insta- indicated because of wear, failure, bility, and neuropathy.1-3 Lower- and subsequent revisions.6 extremity posttraumatic arthritis has In contrast to the aims of TAA and an estimated cost of $12 billion ankle fusion, the aim of distraction annually in the United States.4 It is arthroplasty is to optimize the body’s From the Department of Orthopaedic often disabling, predominantly regenerative capacity and the func- Surgery, Loyola University Chicago 7,8 Stritch School of Medicine, Chicago, affects young, active persons, and has tion of the diseased joint. An IL (Dr. Bernstein), the Department of a negative effect on quality-of-life external fixator is used to mechan- Orthopaedics, Johns Hopkins measures that is comparable to that ically unload the ankle to relieve University, Baltimore, MD of hip and knee arthritis.1 The pain, preserve ROM, and potentially (Dr. Reidler), and the Department of Orthopaedic Surgery, Hospital for mainstay of surgical treatment of delay or even partially reverse the Special Surgery, Cornell University, advanced ankle arthritis has tradi- effects of arthritis (Figure 1). The New York, NY (Dr. Fragomen and tionally included ankle arthrodesis or surgeon should be aware of this Dr. Rozbruch). total ankle arthroplasty (TAA). treatment option, as well as its J Am Acad Orthop Surg 2016;0:1-11 Ankle arthrodesis reliably provides indications, outcomes, and potential DOI: 10.5435/JAAOS-D-14-00077 pain relief. However, loss of ankle adverse effects for ankle arthritis. motion, increased stress at adjacent Recent short- and intermediate-term Copyright 2016 by the American Academy of Orthopaedic Surgeons. joints that leads to degeneration, and evidence suggests that distraction increased energy expenditure with arthroplasty may be a viable surgical Month 2016, Vol 0, No 0 1 Copyright Ó the American Academy of Orthopaedic Surgeons. Unauthorized reproduction of this article is prohibited. Ankle Distraction Arthroplasty: Indications, Technique, and Outcomes 18,19 Figure 1 ability to withstand up to 5.5 times with a circular fixator. The body weight during ambulation concept of the hinge is based on the depends on a stable relationship theory that the talar dome is a frus- among the bony and ligamentous tum of a cone with its apex medially structures of the distal tibia, fibula, directed. and talus.11 The tibial plafond has a Articular cartilage, or hyaline car- central ridge oriented in the sagittal tilage, lacks blood supply, nerve plane that is complementary to a innervation, and lymphatic drainage. concavity on the talar dome. The It receives nutrition and expels waste relationship between the distal fib- via diffusion and imbibition. Its high ula, tibiotalar joint, and the medial tensile strength and elasticity func- malleolus is maintained by the stout tion to withstand high loads, protect ligaments that make up the ankle subchondral bone, and decrease syndesmosis. friction between the two opposing Ankle distraction frame mounted on One study demonstrated that even surfaces. Hyaline cartilage is primar- an extremity model demonstrating our a 1-mm displacement of the talus in ily composed of type II collagen, current assembly method. The red the ankle mortise generates a 42% water, and chondrocytes. Chon- (circular) and blue (U-shaped) rings are secured with 6-mm decrease in available joint contact drocytes, which produce enzymes, hydroxyapatite-coated half pins and area.12 Consequently, the remaining proteins, and collagen, are responsi- 1.8-mm bayonet Kirschner wires to cartilage is exposed to compressive ble for the normal and pathologic the tibia and foot, respectively. The forces over a smaller surface area, state of the articular surface.20,21 hinge (red arrow) is aligned with the Inman axis. The acute and gradual potentially leading to degeneration Chondrocytes are metabolically distraction is achieved with clockwise and arthritis. controlled via the surrounding rotations of the square nuts (red The orientation of the ankle joint, mechanical environment and thus, arrowhead), which are attached to the as described by a line perpendicular can upregulate the synthesis of deg- tibial ring. Range-of-motion exercises occur with unlocking the connection to the diaphysis of the tibia, is in slight radative cytokines, increasing cata- between the two rings (yellow arrow). valgus. Named the lateral distal tibial bolic enzymes in the local milieu—a Gradual dorsiflexion of the ankle, in angle, it measures on average 89° concept referred to as mechanoelec- the setting of chronic ankle equinus, is (range, 86º to 92°). The axis of the trochemical events.22 achieved by gradually increasing the distance between the square nut ankle joint is created through the Arthritis in the ankle is most often (yellow arrow) and the proximal end of relationship between, and the geo- secondary, usually resulting from the rod. (Copyright Mitchell Bernstein, metric constraints of, the talar dome, trauma.2,3 The energy dissipated MD, FRCSC, Chicago, IL.) tibial plafond, and the lateral and through the articular surface and the medial malleoli.13 The traditionally ensuing inflammatory response is option with the use of appropriate accepted theory, proposed in the thought to be critical in post- 23,24 patient selection criteria.9,10 1950s, suggests that the ankle rotates traumatic arthritis. It has been with one-degree of freedom about an demonstrated that the inflammation axis (ie, the Inman axis) that lies resulting from the energy loss causes Anatomy and between the tips of the medial and the production of dysfunctional Biomechanics of the Ankle lateral malleoli.14-16 This axis is the cellular elements and chondrocyte Joint basis for total ankle prosthesis apoptosis.25 In the subacute phase, designs17 and forms the basis on articular cartilage changes its com- The ankle is a highly constrained and which the hinge is built when dis- position, increasing its water con- congruent weight-bearing joint. Its traction arthroplasty is performed tent and decreasing its proteoglycan Dr. Bernstein or an immediate family member serves as a paid consultant to NuVasive, Smith & Nephew, and DuPuy Synthes and serves as a board member, owner, officer, or committee member of the Limb Lengthening Reconstruction Society. Dr. Fragomen or an immediate family member has received royalties from Small Bone Innovations; is a member of a speakers’ bureau, or has made paid presentations on behalf of Smith & Nephew; and serves as a paid consultant to Smith & Nephew and DePuy Synthes. Dr. Rozbruch or an immediate family member has received royalties from Small Bone Innovations and Smith & Nephew; is a member of a speakers’ bureau, or has made paid presentations on behalf of Smith & Nephew; serves as a paid consultant to Small Bone Innovations and Smith & Nephew; and serves as a board member, owner, officer, or committee member of the Limb Lengthening Reconstruction Society. Neither Dr. Reidler nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this article. 2 Journal of the American Academy of Orthopaedic Surgeons Copyright Ó the American Academy of Orthopaedic Surgeons. Unauthorized reproduction of this article is prohibited. Mitchell Bernstein, MD, FRCSC, et al concentration. Furthermore, type II and has recalcitrant pain in the setting distraction, the etiology of ankle collagen is weakened by a combina- of a congruent joint with preserved arthritis is critical. A history of injury tion of decreased production by motion of .20°.33 Relative contra- or repetitive instability is therefore chondrocytes and increased concen- indications include complex regional carefully elucidated. tration of proinflammatory cytokines. pain syndrome, inflammatory ar- The physical examination begins To restore normal homeostasis, thritides, previous infection, neuro- with an assessment to identify any deeper