Osteoporotic Ankle Fractures: An Approach to Operative Management

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1 Section Editors: David J. Hak, MD, MBA & Philip F. Stahel, MD Osteoporotic Ankle Fractures: An Approach to Operative Management Jason McKean, MD; Derly O. Cuellar, MD; David Hak, MD, MBA; Cyril Mauffrey, MD, FRCS Abstract: The incidence of osteoporosis is increasing as the elderly population grows. Because these patients remain active, fragility fractures of the ankle are becoming more common. The literature indicates a relatively high complication rate for nonoperative management of ankle fractures in this patient cohort, leading surgeons to face challenges unique to patients with poor bone and skin quality. This article discusses techniques to address osteoporotic ankle fractures and reviews the current literature relevant to this issue. [Orthopedics. 2013; 36(12): ] Osteoporosis is an asymptomatic systemic disease characterized by deterioration of the microarchitecture of bone and low bone mass, which ultimately predisposes patients to fractures secondary to low-energy mechanisms. The incidence of osteoporosis is increasing rapidly as the population ages. Ankle fractures are one of the most commonly occurring fractures, and fragility fractures of the ankle are becoming proportionally more common in the elderly population, especially among women. 1,2 The World Health Organization 3 established that osteoporosis is diagnosed with a T-score of less than -2.5 (ie, the bone mineral density is 2.5 SDs below the young adult average bone mineral density) obtained by dual-energy x-ray absorptiometry scan or by the presence of a fragility fracture. A patient The authors are from the Department of Orthopaedic Surgery, Denver Health Medical Center, University of Colorado, School of Medicine, Denver, Colorado. The authors have no relevant financial relationships to disclose. Correspondence should be addressed to: Cyril Mauffrey, MD, FRCS, Department of Orthopaedic Surgery, Denver Health Medical Center, University of Colorado, School of Medicine, 777 Bannock St, Denver, CO (cyril. mauffrey@dhha.org). doi: / with a T-score between -1.0 and -2.5 is considered to have osteopenia. The etiology behind decreasing bone density differs from patient to patient but primarily relates to the disruption of homeostasis between osteoclasts and osteoblasts. Receptor activator of nuclear factorkappa-b ligand (RANK-L) is a key cytokine involved in this homeostasis and is mainly produced by osteoblasts and bone marrow stromal cells. Coordination between RANK-L and its receptor, RANK, expressed on osteoclasts is a major mediator of osteoblast-osteoclast coordination and bone turnover. 4 Once bone homeostasis is disrupted, the architecture changes, and ultimately the structural properties of the bone are altered. 5 Trabecular bone structure is affected first, due to its high metabolic rate. 6 Cortical thinning then follows, having a drastic impact on overall bone strength. Osteoporotic fractures are difficult to treat in general due to poor hardware purchase, and fractures of the weight-bearing lower extremities create an even greater challenge. Previously, the trend was to treat all osteoporotic ankle fractures nonoperatively due to the high complication rate. 7,8 Rates of malunion or nonunion in patients older than 60 years treated by closed reduction and cast immobilization are as high as 48% to 73%. 7,9 More recent studies have shown significantly greater functional outcomes with operative treatment of ankle fractures in elderly patients. 10,11 A construct providing greater stability is particularly important in elderly patients because it is often difficult for them to adhere to a strict nonweightbearing protocol. This article reviews the different strategies used in treating osteoporotic ankle fractures. Strategies for Treating Osteoporotic Ankle Fractures Locking Plates Locked plating has been one of the most helpful techniques in addressing fractures in osteoporotic bone. Locking plates create a fixed-angle construct similar to a blade 936 ORTHOPEDICS Healio.com/Orthopedics

2 plate or an external fixator (Figure 1). The advantages of locking plate constructs have been shown in various anatomic sites, both weightbearing and nonweight-bearing, throughout the body, including the cervical spine, mandible, distal radius, and femur Traditional plate constructs can fail over time, with consecutive loosening of individual screws. However, locking plates tend to fail in a more catastrophic way, with all the screws failing at once. To avoid penetration of the ankle joint, screws in the distal fibula are able to obtain purchase in only a single cortex. Kim et al 16 demonstrated the advantage of locking plates in cadaveric distal fibulas and determined that fewer unicortical screws are needed to achieve the same biomechanical stability found with an increased number of traditional unicortical nonlocking screws. Some currently available newer plates provide an increased number of options for locked screw placement in the distal fibula. These plates are precontoured and low profile for a more anatomic fit and are especially useful when there is significant comminution with small fragments distally. Zahn et al 17 showed that fixation strength with a precontoured locking plate was independent of bone mineral density (BMD), whereas fixation strength of nonlocking screws was dependent on BMD. The plates more elaborate design results in an increased cost compared with the standard one-third tubular plates. 1A Figure 1: Anteroposterior radiograph of an ankle fracture in a 69-year-old woman (A). Intraoperative lateral radiograph of the same patient treated with posterolateral plating for the distal fibula fracture. Note the spanning of 2 cortices and the limitation of the number of screws to avoid peroneal tendon irritation (B). Posterolateral Plating Placing the plate on the lateral aspect of the fibula allows only unicortical screw purchase distally to avoid joint penetration. Compared with bicortical screw purchase, this unicortical screw purchase leads to a weaker construct, especially in osteoporotic bone. Placing the plate more posteriorly on the fibula allows the screw trajectory to aim more anteriorly away from the joint and achieve bicortical purchase, thus increasing the stability of the construct (Figure 2). During the application of the plate, the plate can create an axilla with the cortex at the apex of the fracture. The plate in this position prevents displacement of the fracture and provides the opportunity to add a compression screw across the oblique fracture through the plate. This antiglide plating 1B 2 Figure 2: Radiograph of locked screws used in the distal fibula and syndesmotic screws placed through the plate. technique works best with an oblique fracture and has shown greater strength compared with lateral locked plating. 18 In short oblique cadaveric distal fibula fractures, Schaffer and Manoli 19 showed better biomechanical properties with a posterior antiglide plate compared with a lateral plate. Frequently, osteoporotic bone is found in the elderly population, who tend to have poorer skin quality. Placing the plate in an antiglide fashion prevents prominent screw heads laterally that could irritate the wound or the skin in the late postoperative phase after swelling has decreased. The peroneal tendons can cover the screw heads posteriorly, but this can lead to irritation of the tendons. Although the antiglide plate can outperform the lateral plate in a biomechanics laboratory, clinically the antiglide plate has been shown to be associated with an increased rate of hardware removal secondary to peroneal tendon lesions. 20 Injectable Cement By definition, osteoporotic bone has a decreased amount of dense bone for screw purchase. Multiple studies have investigated various injectable cements to increase the density, and therefore the pullout strength, of screws. Polymethylmethacrylate (PMMA) has been used in cases of severe osteoporosis. 21,22 Polymethylmethacrylate can be used for individual stripped screws; the stripped screws are removed from their holes, the cement is injected into the stripped screw holes, and the screws are reintroduced into the holes but not completely tightened. The ce- DECEMBER 2013 Volume 36 Number

3 Figure 3: Illustration of the tension band technique in the medial malleolus. Kirschner wires are inserted in a retrograde manner, capturing as many fragments as possible. A 3.5-mm screw inserted proximally helps tension the metal wire looped around the ends of the Kirschner wires. ment is allowed to set, and the screws are subsequently tightened. Alternatively, the cement can be introduced and allowed to set completely before inserting the screw. The hardened cement can then be drilled and tapped before inserting the screw. 22 Although PMMA provides a relatively inexpensive, ubiquitous, and strong augmenting lattice for screw purchase, it has poor biocompatibility, is nonresorbable, and is highly exothermic. A more biocompatible option is an osteoconductive material such as calcium-phosphate cement. Calcium-phosphate cement is progressively replacing PMMA as an option in traumatology. 23,24 Recent in vitro and in vivo (rabbit model) studies have shown that using calcium-phosphate cement has increased the pullout force of cancellous bone screws. 25,26 An in vitro study comparing augmentation with tricalcium phosphate cement vs PMMA vs no 3 augmentation showed comparable pullout strengths between tricalcium phosphate cement and PMMA. 27 Both tricalcium phosphate cement and PMMA showed a 4-fold increase in pullout strength compared with no augmentation in the osteoporotic cancellous bone model. The techniques described above for PMMA can be used for osteoconductive bone cement. Tension Band Wiring The technique of tension band wiring is frequently used in olecranon and patellar fractures to turn tensile forces created by muscle contraction into compression along the fracture site. The technique can be used in a different context in relation to fragility fractures about the ankle. Fractures of the medial malleolus that have significant comminution or fragments that are too small to accept screw fixation can be reduced and fixated using K-wires. The tension band wire can then be passed under the K-wires (and under the deltoid ligament) and wrapped around a screw placed proximally in the tibia (Figure 3). The tension band wire can be placed in a figure-8 fashion and tightened by twisting the opposing ends. Tibio-Talar-Calcaneal Nail The use of Steinmann pins as a temporary indirect stabilization technique is well documented, and they are currently used for extremely unstable ankle fractures. 28,29 In patients with poor bone stock, poor soft tissue envelope, and a likely inability to follow nonweightbearing instructions, a tibio-talar-calcaneal device is a viable option as primary and definitive treatment. Patients who fall into this category often have multiple comorbidities that make them poor candidates for revision surgery if their initial traditional ankle fixation method fails. Postoperatively, these patients have relatively smaller wounds and are allowed to bear weight as tolerated. Two recent studies have shown good outcomes with no wound complications following fixation of osteoporotic ankle fractures treated definitively with nails that cross the tibio-talo-calcaneal joints. 30,31 Although this may not be an ideal first-line treatment for the active patient with osteoporosis, a tibio-talocalcaneal nail is a great option for the relatively inactive patient who may not tolerate a revision surgery. Syndesmotic Screws The syndesmosis maintains the stability of the ankle mortise and, in effect, the stability of the ankle in general. The syndesmosis is not frequently injured in osteoporotic fractures because the bone tends to fail before the ligamentous structures; however, even without a specific syndesmotic injury, the method of syndesmotic fixation can be used to add structural integrity to lateral fibula plating. 32 The notion of using tibia-pro-fibula screws makes sense conceptually because the screws are obtaining purchase in 4 cortices instead of 2. Panchbhavi et al 33 investigated the use of tibia-pro-fibula screws and found that, compared with the same construct without the additional screws, they added a 9% increase in torque, a 24% increase in the amount of external rotation, and a 34% increase in energy observed before failure of the construct. Tibia-profibula screws are a relatively quick, inexpensive, and technically straightforward method to increase the strength of a plate construct. The screws can be left in because complication rates can be as high as 22% with removal. 34 Fibular Nail When using a plate and screw construct to address a fracture, fixation strength is established by creating frictional force between a plate and the bone. 35,36 Osteoporotic bone is more prone to having screws strip and lose purchase in the relatively weak bone, creating an overall less stable construct. 37 Changing to a larger diameter of screw, a so-called rescue screw, to attempt to achieve better purchase does not 938 ORTHOPEDICS Healio.com/Orthopedics

4 necessarily solve the problem. Wall et al 38 showed that changing from the traditional 3.5-mm screw to a 4.0-mm screw does not increase the pullout strength of the screw in osteoporotic bone. To circumvent the issue of screw pullout, a fibular nail can be used. Advantages to using a fibular nail include a smaller incision, decreased soft tissue stripping, and minimal disruption of the biology at the fracture site. A retrospective review of 24 patients with fragility fractures of the distal fibula who received a fibular nail showed that this was a successful method of treatment with low risk of complication, good restoration of function, and good patient satisfaction. 39 Bugler et al 40 also examined the results for 105 patients treated with a fibular nail for unstable ankle fractures and found good radiological outcomes and patient satisfaction with minimal complications. There are various manufacturers of nails with different locking options, including the option to cross the syndesmosis. Multiple or Longer Plates When extensive comminution is present, some have advocated shortening through the zone of comminution until there is cortical contact. 41 This is not a viable option in fractures of the fibula because even slight shortening of the fibula can cause a disruption in ankle mechanics and lead to ankle pain. To strengthen a construct across the comminuted section of a fracture, 2 plates can be used one posterolaterally and the other laterally. Longer plates with fewer screws can also be used to spread the stress load over a longer distance. Conclusion Because osteoporosis is an asymptomatic disease, the orthopedic surgeon treating fragility fractures may be the first to recognize the condition and should refer the patient to the primary care practitioner for medical evaluation and management. Significant morbidity exists with casting in elderly patients, so operative treatment should be considered for questionably unstable ankle fractures. Locked plating and/or posterolateral plating are relatively universally available options for addressing ankle fractures. Tibio-talar-calcaneal nails should be considered primary definitive treatment for patients who have a low activity level or multiple comorbidities. References 1. Court-Brown CM, McBirnie J, Wilson G. Adult ankle fractures: an increasing problem? Acta Orthop Scand. 1998; 69(1): Kannus P, Palvanen M, Niemi S, Parkkari J, Jarvinen M. Increasing number and incidence of low-trauma ankle fractures in elderly people: Finnish statistics during and projections for the future. Bone. 2002; 31(3): Assessment of fracture risk and its application to screening for postmenopausal osteoporosis: report of a WHO Study Group. World Health Organ Tech Rep Ser. 1994; 843: Rauner M, Sipos W, Pietschmann P. Osteoimmunology. 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5 27. Collinge C, Merk B, Lautenschlager EP. Mechanical evaluation of fracture fixation augmented with tricalcium phosphate bone cement in a porous osteoporotic cancellous bone model. J Orthop Trauma. 2007; 21(2): Childress HM. Vertical transarticular pin fixation for unstable ankle fractures: impressions after 16 years of experience. Clin Orthop Relat Res. 1976; 120: Duke RF. Severe fracture-dislocation of ankle treated by transarticular Steinmann pin. Lancet. 1963; 2(7320): Jonas SC, Young AF, Curwen CH, McCann PA. Functional outcome following tibio-talarcalcaneal nailing for unstable osteoporotic ankle fractures. Injury. 2012; 44(7): Lemon M, Somayaji HS, Khaleel A, Elliott DS. Fragility fractures of the ankle: stabilisation with an expandable calcaneotalotibial nail. J Bone Joint Surg Br. 2005; 87(6): Dunn WR, Easley ME, Parks BG, Trnka HJ, Schon LC. An augmented fixation method for distal fibular fractures in elderly patients: a biomechanical evaluation. Foot Ankle Int. 2004; 25(3): Panchbhavi VK, Vallurupalli S, Morris R. Comparison of augmentation methods for internal fixation of osteoporotic ankle fractures. Foot Ankle Int. 2009; 30(7): Schepers T, Van Lieshout EM, de Vries MR, Van der Elst M. Complications of syndesmotic screw removal. Foot Ankle Int. 2011; 32(11): Borgeaud M, Cordey J, Leyvraz PE, Perren SM. Mechanical analysis of the bone to plate interface of the LC-DCP and of the PC- FIX on human femora. Injury. 2000; 31(suppl 3):C29-C Cordey J, Borgeaud M, Perren SM. Force transfer between the plate and the bone: relative importance of the bending stiffness of the screws friction between plate and bone. Injury. 2000; 31(suppl 3):C21-C Thiele OC, Eckhardt C, Linke B, Schneider E, Lill CA. Factors affecting the stability of screws in human cortical osteoporotic bone: a cadaver study. J Bone Joint Surg Br. 2007; 89(5): Wall SJ, Soin SP, Knight TA, Mears SC, Belkoff SM. Mechanical evaluation of a 4-mm cancellous rescue screw in osteoporotic cortical bone: a cadaveric study. J Orthop Trauma. 2010; 24(6): Rajeev A, Senevirathna S, Radha S, Kashayap NS. Functional outcomes after fibula locking nail for fragility fractures of the ankle. J Foot Ankle Surg. 2011; 50(5): Bugler KE, Watson CD, Hardie AR, et al. The treatment of unstable fractures of the ankle using the Acumed fibular nail: development of a technique. J Bone Joint Surg Br. 2012; 94(8): Blatter G, Konig H, Janssen M, Magerl F. Primary femoral shortening osteosynthesis in the management of comminuted supracondylar femoral fractures. Arch Orthop Trauma Surg. 1994; 113(3): ORTHOPEDICS Healio.com/Orthopedics