The aim of this study was to evaluate prospective patients with periarticular fractures where a metaphyseal

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1 Hernia Repair Calcium Sulfate Cement in Contained Traumatic Metaphyseal Bone Defects GEORGIOS I. DROSOS, MD, PHD ASSISTANT PROFESSOR OF ORTHOPAEDICS ELENI C. BABOURDA, MD ORTHOPAEDIC SURGEON ATHANASIOS VERVERIDIS, MD, PHD LECTURER OF ORTHOPAEDICS DESPOINA KAKAGIA, MD, PHD ASSISTANT PROFESSOR OF PLASTIC SURGERY DEPARTMENT OF PLASTIC AND RECONSTRUCTIVE SURGERY DIONISIOS-ALEXANDROS VERETTAS, MD, PHD, MSC(ORTH) PROFESSOR OF ORTHOPAEDICS UNIVERSITY GENERAL HOSPITAL OF ALEXANDROUPOLIS ALEXANDROUPOLIS, GREECE ABSTRACT The aim of this study was to evaluate prospective patients with periarticular fractures where a metaphyseal bone defect was grafted with high compressive calcium sulfate cement. The calcium sulfate cement MIIG X3, (Wright Medical Technology, Inc, Arlington, TN) was used in 45 patients with periarticular fractures distal radial, tibial plateau, humeral head, and calcaneal fractures to fill the metaphyseal defect. All fractures were treated either with open or closed reduction, fracture fixation, and the cement was applied openly or closed. Radiographs were evaluated for fracture reduction, joint line gap, and step, as well as for rate of graft replacement by bone. All fractures united without an additional procedure. There were no wound infections or other complications attributed to the graft. At three-month follow-up, a complete graft replacement by bone was observed in all fractures. Joint line step was not developed in any patient, but a joint line gap of 3 mm was observed postoperatively in one patient with a tibial plateau fracture. Loss of reduction occurred in one patient with an extra-articular distal radial fracture treated with closed reduction and k-wire fixation

2 Calcium Sulfate Cement in Contained Traumatic Metaphyseal Bone Defects DROSOS/BABOURDA/VERVERIDIS/KAKAGIA/VERETTAS Cement that escaped into the joint or the surrounding soft tissues was not visible at the six-week follow-up. In conclusion, the results of this study confirm the safety and the efficacy of this cement when it is used as graft with the appropriate fixation method in traumatic metaphyseal bone defects. INTRODUCTION Fractures involving the metaphyseal and epiphyseal bone often are associated with compression of the cancellous bone. The defect which results after fracture reduction is often significant and bone grafting is used in order to augment the internal fixation, providing additional support to the articular surface. Bone grafting of these defects has been utilized using autogenous bone, allogenic bone, and various bone graft substitutes (BGSs). 1-3 BGSs, known as ceramics, are biocompatible osteoconductive calciumbased products. They have several advantages compared with autogenous and allogenic bone grafting. Using these products, the second site operation and the additional morbidity associated with autogenous bone grafting is avoided. 4-6 Furthermore, there is no risk of disease transmission or immunological response as there is with allogenic bone grafting. 1,2 Fracture Distal radius (18) Tibial plateau (20) Humeral head (5) Calcaneous (2) Table I. Fractures and treatment Type AO/OTA type A3 (4) type B2 (4) type C2 (9) type C3 (1) Schatzker type II (12) type III (4) type V (2) type VI (2) Neer 3 part (4) 4 part (1) Sanders type II (2) Treatment Plate (4) Plate (9) Nail (3) Plate (2) MIIGX3 Application Open (9) Closed (9) Followup in Months mean 9.4 Open (20) 9.2 Open (5) 9.0 Plate (2) Open (2) 9.0 AO/OTA, Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association; MIIG, Minimally Invasive Injectable Graft. BGSs are produced as blocks, granules, pellets, powders, and cements. 7,8 BGS cements fill the defects more uniformly. Due to their load-bearing capacity, they provide superior mechanical support compared with that of autogenous and allogenic cancellous bone grafting. This has been shown by cadaveric and experimental in vivo studies 9-14 as well as by clinical studies where calcium phosphate and hydroxyapatite cements have been compared with cancellous autologous bone grafting when used to fill metaphyseal traumatic bone defects During the last two decades. a variety of different BGS cement products, based on their chemical formulations, have been used in clinical practice to fill metaphyseal bone defects secondary to trauma. Although calcium phosphate cements are the most commonly used, 15,17,18 there are limited reports of clinical application of other BGS cements such as hydroxyapatite cement, 15 nanocrystalline hydroxyapatite paste, and surgical-grade calcium sulfate in cement form. 22,23 Watson in reported the use of calcium sulfate cement Minimally Invasive Injectable Graft (MIIG) (Wright Medical Technology, Inc, Arlington, TN)- in eight consecutive patients with severely comminuted proximal or distal tibial metaphyseal fractures. More recently, the use of new calcium sulfate cement in 31 patients with tibial plateau fractures was reported. 23 This new product, the MIIG X3, offers high compressive strength. The aim of this study was to evaluate prospective patients with periarticular fractures where a metaphyseal bone defect after fracture reduction was grafted with MIIG X3. Our hypothesis was that augmenting the fixation with this BGS cement will result in prevention of fracture collapse. PATIENTS AND METHODS This is a prospective study of 45 patients (table I) with periarticular fractures treated either with open or closed reduction, and fracture fixation where the metaphyseal defect was filled with high compressive-strength calcium sulfate cement (MIIG X3). All patients were followed up at six and 12 weeks and at six and 12 months. Patients with a follow-up of at least six months were included in this report. Immediate postoperative and follow-up radiographs were evaluated by one observer. Eighteen patients sustained fractures of the distal radius, 14 of them after a simple fall and four in road traffic accidents. The fractures were classified using the AO/OTA (Arbeitsgemeinschaft für Osteosynthesefragen /Orthopaedic Trauma Association) classification. 24,25 Displacement was measured using the method described by van der Linden and Ericson (1981). 26 Fracture reduction and final position were defined according to previously described criteria. 27 Distal radial fractures were treated with external fixation with or without supplementary k-wire fixation (Figs. 1-3), with a volar plate and one patient with K-wire fixation. An open reduction was necessary - 2 -

3 Orthopaedic Surgery Figure 1. (A1, A2) Type C distal radial fracture; (B1, B2) Closed reduction, external fixation, and closed application of the cement; (C1, C2) Radiographs at six weeks post-operatively; (D1, D2) Radiographs at six months post-operatively. in nine patients (Fig. 2); in those cases, the cement was applied openly while in the rest of the cases, the cement was applied percutaneously (Fig. 1). Twenty patients suffered from a tibial plateau fracture after a road traffic accident (n:15) or a fall (n:5). Eight patients sustained at least one more injury. The fractures were classified according to the Schatzker classification 28 and were evaluated using an anatomical grading score system. 29 All patients were treated with open reduction and open application of the cement. The fractures were fixed with a plate (Fig. 4), cannulated screws (Fig. 5A, B), or a limited internal fixation with cannulated screws and a hybrid external fixation. Four patients with three-part humeral head fractures 30 were treated with an intramedullary nail. One patient with a four-part humeral head fracture was treated with an open reduction and internal fixation with a locking plate. The shaft-head angle was measured post-operatively and at each follow-up. Two patients, each with a type II isolated calcaneal fracture 31 due to a fall from a height, were treated with an open reduction, plate fixation, and cement application through a lateral approach (Fig. 6). In those patients, the Bohler s angle was evaluated pos-operatively. In addition to these, all radiographs were also evaluated for joint line gap and step using a specific scale (table II). Furthermore, the rate of graft replacement by bone was assessed by using the scale described by Moed et al with some modification (table II). RESULTS All fractures united without an additional procedure. There was no case with deep or superficial infection at the fracture site. In two patients with distal radial fractures, pin track infections of the external fixation were treated successfully with oral antibiotics. Wound exudations were also not observed in Figure 2. (A) Type C distal radial fracture; (B) Open reduction, external fixation, K-wire fixation, and open application of the cement; (C1, C2) Post-operative radiographs; (D1, D2) Radiographs at 12 months post-operatively. Figure 3. (A1, A2) Type A3 distal radial fracture; (B1, B2) Closed reduction, external fixation, and closed application of the cement; (C1, C2) Post-operative radiographs showing cement escaped to the soft tissues volarly; (D1, D2) Radiographs at six weeks post-operatively showing complete absorption of the cement

4 Calcium Sulfate Cement in Contained Traumatic Metaphyseal Bone Defects DROSOS/BABOURDA/VERVERIDIS/KAKAGIA/VERETTAS this series. In distal radial fractures, calcaneal fractures, and fractures of the humeral head, there was no joint line gap or step in either the post-operative or the final radiograph in any case. In one case with a tibial plateau fracture, a joint line gap category C (3 mm) became apparent at six weeks. In all fractures, the graft replacement by bone was in category B at six weeks and in category A (complete replacement) at the three-month follow-up. Cement escaped into the joint (in two cases with plateau fracture) (Fig. 4) or the surrounding soft tissues (in four cases in distal radial fractures) (Fig. 3). It was not visible at the six-week follow-up in any of the cases. An acceptable reduction was obtained in all patients with distal radial fractures and at final follow-up; all but one fracture united in an acceptable position. The mean loss of the radial length was of 0.8 mm (range 1-4 mm) and of radial inclination was of two Table II. Radiographic evaluation of joint line and graft replacement by bone Joint line Gap Category A: No visible gap Category B: Gap up to 2 mm Category C: Gap 2-5 mm Category D: Gap 5-10 mm Joint Line Step Category A: No visible step Category B: Step up to 2 mm Category C: Step 2-5 mm Category D: Step 5-10 mm Graft Replacement by Bone Category A: 100% Category B: >50% Category C: 0%-50% Category D: 0% Figure 4. (A1, A2) Type III lateral tibial plateau fracture; (B1, B2) CT scan images; (C) Post-operative radiographs after internal fixation with a plate and open application of the cement, showing cement escaped to the joint (arrow head); (D) Radiographs at six weeks post-operatively showing complete absorption of the intra-articularly escaped cement; (E) Radiographs at six months post-operatively. degrees (range 0-10 degrees). The 4- mm loss of radial length and ten degrees of radial inclination were observed in the case treated with k-wire fixation. In tibial plateau fractures at final follow-up, the anatomical grading score was not different from the post-operative score and humeral head fractures, as well as calcaneal fractures, were healed without any loss of the reduction. DISCUSSION The results of this study confirm the safety and efficacy of this cement when it is used with the appropriate fixation method as graft in traumatic metaphyseal bone defects. There were no complications related to the graft and any graft material that escaped into the joint or the soft tissues resorbed without any sequelae. These results are in agreement with those of a previously reported study. 23 Calcium sulfate in its hemihydrate form is known as plaster of Paris and has long been used in vivo to fill defects in bone In 1996 it became available in surgical grade calcium sulfate form (Osteoset, Wright Medical, Arlington, TN). This new form of calcium sulfate is crystallized in a highly controlled microenvironment producing regularly shaped medical grade crystals of similar size and shape. 36,37 This assures a predictable resorption, generally within 30 to 60 days of implantation, depending on the location and volume implanted. 36,37 Calcium sulfate does not incite an inflammatory or foreign body reaction 34, 32 by the host. No appreciable increased serum calcium levels have been detected with resorption of this material. 34 The absorption of the calcium sulfate is done by osteoclasts, in the same fashion that bone is absorbed. 38 It has been shown that osteoblasts bind to this material during this process and during remodeling of the surrounding bone. 38 It seems that the rate of calcium sulfate resorption coincides with the rate of new bone formation. 34,39 Today, several different commercial preparations in different forms such as pellets, cements, pastes, and antibioticimpregnated calcium sulfate preparations are available. 40 They have been used for a wide variety of clinical situa

5 Orthopaedic Surgery tions requiring grafting procedures. 40 Data concerning the clinical use of calcium sulfate cements is limited. The clinical use of calcium sulfate cement MIIG in fractures and bone cysts treatment was reported in ,41 More recently, the MIIG X3, a new injectable bone graft substitute based on calcium sulfate which can cure with high compressive strength, was developed. The results of using this cement as graft in 31 patients with tibial plateau fractures were published by Yu et al. in Calcium phosphate bone cement and hydroxyapatite cement have been tested in randomized clinical trials compared with cancellous autologous bone grafting when used to fill metaphyseal traumatic bone defects Their mechanical support was proven to be superior to that of cancellous autologous bone grafting concerning the maintenance of fracture reduction Nevertheless, calcium phosphate cement is not replaced by bone for several years 9 and it is actually unknown when, if ever, this happens. Although it has been reported that the presence of this material intra-articularly had no adverse sequelae at 12-month followup, 42 it is difficult to accept that a foreign material will cause no damage to the articular cartilage in the long term. As far as the other BGS cements are concerned, hydroxyapatite cement and nanocrystalline hydroxyapatite paste, information about the time of their 15, replacement by bone is limited but it seemingly also takes a very long time. The main advantage of the calcium sulfate cement as an alternative graft is that of rapid absorption when it escapes into the joint or the soft tissues. Furthermore, it seems that the calcium sulfate follows the natural phases of bone remodelling and after the first three months in the fracture site, there is no other material visible but bone. This may be important in case of a new injury or if another operation becomes necessary. The main concern about the calcium sulfate is the mechanical support when it is used as filler for structurally important metaphyseal defects because of its rapid replacement by bone. 8 Currently, there is no evidence from any in vivo experimental or clinical study to support this hypothesis. In a recently repor ted in vitro study, 43 the authors studied the compressive and flexural characteristics of various commercially available BGS cements, in their initial as-mixed condition, strictly following specified manufacturers instructions. It was found that all the tested BGSs exhibited lower compression and bending strength than the selected polymethyl methacrylate, but the calcium sulfate extra-strength cement (MIIG X3) showed a strength value higher than the calcium phosphate and the nanocrystalline hydroxyapatite paste. Nevertheless, the authors concluded that these findings cannot be directly extrapolated to surgical or clinical implications, since the adopted in vitro context does not necessarily reflect the actual in vivo conditions met by such biomaterials. Our study has some limitations as it is not a comparative study and it includes patients with fractures in different sites. However, it seems to be the second report of using this new BGS cement and the first report of using cal- Figure 5A. (A1-3) Type III lateral tibial plateau fracture; (B1-3) Intra-operative images: fracture reduction, fixation with two cannulated screws and application of the cement. Figure 5B. (C1-2) Post-operative radiographs; (D1-2) Radiographs at six weeks post-operatively; (E1-2) Radiographs at 12 weeks post-operatively

6 Calcium Sulfate Cement in Contained Traumatic Metaphyseal Bone Defects DROSOS/BABOURDA/VERVERIDIS/KAKAGIA/VERETTAS Figure 6. (A1) Type II calcaneal fracture; (A2, A3) CT scan images; (B1, B2) Intra-operative images of the reduction, internal fixation with a plate and open application of the cement; (B3) Post-operative radiographs; (C) Radiographs at six weeks post-operatively; (D) Radiographs at 12 weeks post-operatively. cium sulfate cement in distal radial, calcaneal, and humeral head fractures. CONCLUSION The results of this study confirm the safety and the efficacy of this cement when it is used as graft with the appropriate fixation method in traumatic metaphyseal bone defects. STI AUTHORS DISCLOSURES Conflict of Interest Statement: None REFERENCES 1. Finkemeier CG. Bone-grafting and bonegraft substitutes. J Bone Joint Surg [Am] 2002;84(3): Giannoudis PV, Dinopoulos H, Tsiridis E. Bone substitutes: an update. Injury 2005;36 Suppl 3:S Moroni A, Larsson S, Hoang Kim A, et al. Can we improve fixation and outcomes? Use of bone substitutes. J Orthop Trauma 2009; 23(6): Younger EM, Chapman MW. Morbidity at bone graft donor sites. J Orthop Trauma 1989;3(3): Goulet JA, Senunas LE, DeSilva GL, et al. Autogenous iliac crest bone graft: complications and functional assessment. Clin Orthop Relat Res 1997;339: Hierholzer C, Sama D, Toro JB, et al. Plate fixation of ununited humeral shaft fractures: effect of type of bone graft on healing. J Bone Joint Surg [Am] 2006;88(7): De Long WG Jr, Einhorn TA, Koval K, et al. Bone grafts and bone graft substitutes in orthopaedic trauma surgery: a critical analysis. J Bone Joint Surg [Am] 2007;89(3): Hak DJ. The use of osteoconductive bone graft substitutes in orthopaedic trauma. J Am Acad Orthop Surg 2007;15(9): Frankenburg EP, Goldstein SA, Bauer TW, et al. Biomechanical and histological evaluation of a calcium phosphate cement. J Bone Joint Surg [Am] 1998;80(8): Thordarson DB, Hedman TP, Yetkinler DN, et al. Superior compressive strength of a calcaneal fracture construct augmented with remodelable cancellous bone cement. J Bone Joint Surg [Am] 1999;81(2): Yetkinler DN, McClellan RT, Reindel ES, et al. Biomechanical comparison of conventional open reduction and internal fixation versus calcium phosphate cement fixation of a central depressed tibial plateau fracture. J Orthop Trauma 2001;15(3): Welch RD, Berry BH, Crawford K, et al. Subchondral defects in caprine femora augmented with in situ setting hydroxyapatite cement, polymethylmethacrylate, or autogenous bone graft: biomechanical and histomorphological analysis after two-years. J Orthop Res 2002;20(3): Welch RD, Zhang H, Bronson DG. Experimental tibial plateau fractures augmented with calcium phosphate cement or autologous bone graft. J Bone Joint Surg [Am] 2003;85(2): Trenholm A, Landry S, McLaughlin K, et al. Comparative fixation of tibial plateau fractures using alpha-bsm, a calcium phosphate cement, versus cancellous bone graft. J Orthop Trauma 2005;19(10): Dickson KF, Friedman J, Buchholz JG, et al. The use of BoneSource hydroxyapatite cement for traumatic metaphyseal bone void filling. J Trauma 2002;53(6): Simpson D, Keating JF. Outcome of tibial plateau fractures managed with calcium phosphate cement. Injury 2004;35(9): Russell TA, Leighton RK; Alpha-BSM Tibial Plateau Fracture Study Group. Comparison of autogenous bone graft and endothermic calcium phosphate cement for defect augmentation in tibial plateau fractures: a multicenter, prospective, randomized study. J Bone Joint Surg [Am] 2008; 90(10): Bajammal SS, Zlowodzki M, Lelwica A, et al. The use of calcium phosphate bone cement in fracture treatment: a meta-analysis of randomized trials. J Bone Joint Surg [Am] 2008;90(6): Huber FX, Hillmeier J, Herzog L, et al. Open reduction and palmar plate-osteosynthesis in combination with a nanocrystalline hydroxyapatite spacer in the treatment of comminuted fractures of the distal radius. J Hand Surg [Br] 2006;31(3): Huber FX, Hillmeier J, McArthur N, et al. The use of nanocrystalline hydroxyapatite for the reconstruction of calcaneal fractures: preliminary results. J Foot Ankle Surg 2006;45(5): Huber FX, McArthur N, Hillmeier J, et al. Void filling of tibia compression fracture zones using a novel resorbable nanocrystalline hydroxyapatite paste in combination with a - 6 -

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