G Model
JINJ-5887; No. of Pages 5 Injury, Int. J. Care Injured xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
Injury journal homepage: www.elsevier.com/locate/injury
Biomechanical studies: Science (f)or common sense? Jos J. Mellema a, Job N. Doornberg b, Thierry G. Guitton b, David Ring a,* Science of Variation Group1 a b
Orthopaedic Hand and Upper Extremity Service, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA University of Amsterdam Orthopaedic Residency Program (PGY 4), Academic Medical Center, Amsterdam, The Netherlands
A R T I C L E I N F O
A B S T R A C T
Article history: Accepted 14 September 2014
Introduction: It is our impression that many biomechanical studies invest substantial resources studying the obvious: that more and larger metal is stronger. The purpose of this study is to evaluate if a subset of biomechanical studies comparing fixation constructs just document common sense. Methods: Using a web-based survey, 274 orthopaedic surgeons and 81 medical students predicted the results of 11 biomechanical studies comparing fracture fixation constructs (selected based on the authors’ sense that the answer was obvious prior to performing the study). Sensitivity, specificity, and accuracy were calculated according to standard formulas. The agreement among the observers was calculated by using a multirater kappa, described by Siegel and Castellan. Results: The accuracy of predicting outcomes was 80% or greater for 10 of 11 studies. Accuracy was not influenced by level of experience (i.e., time in practice and medical students vs. surgeons). There were substantial differences in accuracy between observers from different regions. The overall categorical rating of inter-observer reliability according to Landis and Koch was moderate (k = 0.55; standard error (SE) = 0.01). Conclusion: The results of a subset of biomechanical studies comparing fracture fixation constructs can be predicted prior to doing the study. As these studies are time and resource intensive, one criterion for proceeding with a biomechanical study should be that the answer is not simply a matter of common sense. ß 2014 Elsevier Ltd. All rights reserved.
Keywords: Biomechanical Orthopaedic Fracture Fixation
Introduction It is our impression that many biomechanical studies [1–22] invest substantial resources studying the obvious: that more and larger metal is stronger. Studies that evaluate ‘‘which construct is the strongest’’ distract from the more important question: ‘‘How strong is strong enough in physiological loading conditions?’’. The purpose of this study is to evaluate if some biomechanical studies comparing fixation constructs just document common sense. If so, there is a need for more careful use of resources in the lab and better collaboration with surgeons to enhance clinical relevance. This study tested our hypothesis that a subset of biomechanical studies comparing fracture fixation constructs can be predicted based on common sense and do not require formal testing. Specifically our primary hypothesis was that outcomes of
* Corresponding author. Tel.: +1 617 643 7527; fax: +1 617 726 0460. E-mail address: [email protected] (D. Ring). 1 The members of Science of Variation Group are listed in Appendix.
some biomechanical studies comparing fracture fixation constructs are predictable with high accuracy. Our secondary hypotheses addressed inter-observer reliability and accuracy according to experience and other factors. Methods Between 2000 and 2012, we found 105 peer-reviewed biomechanical studies in peer-reviewed orthopaedic journals comparing two or more constructs in order to determine: ‘‘Which construct is the strongest?’’. We excluded six studies of spine, skull, and facial fractures. From the remaining 99 studies, 12 had a good illustration of the constructs. Among those 12 studies, we selected 11 for which we thought the answer was obvious prior to performing the study [2,7–9,11,12,14,15,19,21,23]. Orthopaedic and trauma surgeons affiliated with the Science of Variation Group (SOVG) and medical students from the University of Amsterdam were invited to predict the outcome of biomechanical studies comparing different fixation constructs. As many as 275 surgeons who treat musculoskeletal trauma and 81 medical
http://dx.doi.org/10.1016/j.injury.2014.09.014 0020–1383/ß 2014 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Mellema JJ, et al. Biomechanical studies: Science (f)or common sense? Injury (2014), http://dx.doi.org/ 10.1016/j.injury.2014.09.014
G Model
JINJ-5887; No. of Pages 5 2
J.J. Mellema et al. / Injury, Int. J. Care Injured xxx (2014) xxx–xxx
Fig. 1. Percutaneous pins versus volar plates for unstable distal radius fractures: a biomechanic study using a cadaver model [11].
students were interested in participating logged on to the website; 274 of these 275 surgeons (99.6%) and 81 of 81 students (100%), completed the study. The Institutional Research Board at the principal investigator’s hospital provided a waiver for the study protocol. All studies were selected and blinded by independent research fellows (JJM and JND) for use in this study. The blinded experimental designs were uploaded to the website. Upon login to the website, observers received a short descriptive summary of the study purpose. Observers were asked to answer one question: ‘‘Which construct is stronger?’’ based on provided illustrations that were copy-pasted from the original articles without manipulation.
No figure legends or explanatory text accompanied the illustrations. The outcome had to be predicted based on visual information judging the experimental test set-up only (Figs. 1 and 2). Observers could comment on each study. Every question had to be completed in order to continue with the next case. The observers completed the study at their own pace. The result of the original study was considered the reference standard. Sensitivity, specificity, accuracy, positive predictive value, and the negative predictive value were calculated to standard formulas. The agreement among the observers was calculated by using a multirater kappa, described by Siegel and Castellan [24]. It is a
Fig. 2. Biomechanical evaluation of proximal humeral fracture fixation supplemented with calcium phosphate cement [12].
Please cite this article in press as: Mellema JJ, et al. Biomechanical studies: Science (f)or common sense? Injury (2014), http://dx.doi.org/ 10.1016/j.injury.2014.09.014
G Model
JINJ-5887; No. of Pages 5 J.J. Mellema et al. / Injury, Int. J. Care Injured xxx (2014) xxx–xxx
commonly used statistic to describe chance-corrected agreement in a variety of intra-observer and inter-observer studies [25– 27]. The kappa values were interpreted by using the categorical rating that was proposed by Landis and Koch [26]: values of 0.01– 0.20 indicated slight agreement; 0.21–0.40 indicated fair agreement; 0.41–0.60, moderate agreement; 0.61–0.80, substantial agreement; and a value that was >0.81 indicated almost perfect agreement. Zero indicated that there was no agreement beyond what was expected due to chance alone. The value of 1.00 meant total disagreement and +1.00 represented perfect agreement [26,27]. We used previously described methods for evaluating the significance of differences between kappa values [28]. Results Accuracy was 80% or greater for 10 of 11 studies that have been predicted by members of the SOVG (Table 1). The diagnostic performance characteristics for guessing the results of the study were as follows: sensitivity averaged 84%, ranging from 60% (for study 1) to 99% (for study 7); specificity 86%, ranging from 60% (for study 1) to 99% (for study 7), and accuracy averaged 86%, ranging from 60% (for study 1) to 99% (for study 7). Study 5 was predicted with the highest accuracy (accuracy 97% and 98% for members of the SOVG and medical students, respectively) (Fig. 1), and study 1 was predicted with least accuracy (accuracy 61% and 60% for members of the SOVG and medical students, respectively) (Fig. 2). The level of experience (i.e., time in practice and medical students vs. surgeons) had no influence on accuracy (Tables 1 and 2). There were substantial differences in accuracy between Canadians and observers from other regions (p < 0.05). Canadian observers predicted with the highest accuracy (accuracy 94%, range 58–100%). The average accuracy in the American observer group was 88% (range 57–97%) compared with 84% (range 69–99%) in the European observer group (p < 0.05). The overall categorical rating of inter-observer reliability according to Landis and Koch was moderate (k = 0.55; SE = 0.01), ranging from k = 0.33 (SE = 0.06) to k = 0.82 (SE = 0.03) (Table 2). Analyses of SOVG subgroups identified excellent agreement among Canadian surgeons. Moderate and substantial agreement were found in most of other subgroups: ranging from moderate (k = 0.48; SE = 0.01) among specialists 21 years or more in practice to moderate (k = 0.59; SE = 0.01) among specialists 11–20 years in practice; and moderate, ranging from k = 0.47 (SE = 0.06) to k = 0.60 (SE = 0.01), among specialists who practice in Australia, Europe, and United States. There was no significant difference in kappa value between SOVG members and Table 1 Accuracy and agreement for predicting outcome of biomechanical studies selected. Members SOVG (accuracy)
Members SOVG (% agreementa)
Study (Experimental test set-up) 1 0.61 61 2 0.80 60 3 0.93 93 4 0.89 89 5 0.97 97 6 0.90 90 7 0.84 84 8 0.93 93 9 0.80 80 10 0.90 90 11 0.89 89 Average a
100.
0.86
84
Medical students (accuracy)
Medical students (% agreementa)
0.60 0.87 0.93 0.84 0.98 0.90 0.99 0.93 0.79 0.74 0.91
60 74 93 84 98 90 99 93 79 74 91
0.86
85
% Agreement, number of agreements/(number of agreements + disagreements)
3
Table 2 Observer demographics, accuracy, and kappa values.
Members SOVG Observers’ gender Male Female Practice Asia Australia Canada Europe United Kingdom United States Other Years in practice 0–5 6–10 11–20 21–30 Specialization General orthopaedics Orthopaedic traumatology Shoulder and elbow Hand and wrist Other
N
%
Kappa (SE)a
% Accuracy (95% CI)
252 22
92.0 8.0
0.55 (0.01) 0.45 (0.02)
86 (85–87) 82 (79–85)
11 6 12 68 6 146 25
4.0 2.2 4.4 24.8 2.2 53.3 9.1
0.36 0.47 0.82 0.51 0.33 0.60 0.42
(0.03) (0.06) (0.03) (0.01) (0.06) (0.01) (0.02)
80 81 94 84 82 88 82
(75–85) (75–87) (91–97) (82–86) (76–88) (87–89) (79–85)
94 60 75 45
34.3 21.9 27.4 16.4
0.54 0.50 0.59 0.48
(0.01) (0.01) (0.01) (0.01)
86 85 86 84
(84–88) (83–87) (84–88) (82–86)
16 96 41 107 14
5.8 35.0 15.0 39.1 5.1
0.33 0.53 0.58 0.60 0.42
(0.02) (0.01) (0.01) (0.01) (0.02)
81 84 88 86 85
(77–85) (83–85) (86–90) (85–87) (81–89)
32 14 35
39.5 17.3 43.2
0.55 (0.01) 0.60 (0.03) 0.54 (0.01)
Medical students Years of study 1–2 3–4 5–6 a
86 (84–88) 86 (82–90) 86 (84–88)
Overall kappa = 0.55; SE, 0.01.
medical students (k = 0.54; SE = 0.01 and k = 0.56; SE = 0.01, respectively); the difference was judged not to be significant as 95% confidence interval did overlap.
Discussion This study confirms our hypothesis that outcomes of a subset of biomechanical studies – comparing fixation constructs – are quite predictable as accuracy was at least 80% for all but one study. In addition, the secondary null hypothesis that the experience of observers has no influence on the accuracy of predicting outcomes was not rejected because medical students and experienced surgeons performed equally well. In other words, it seems that some comparative biomechanical studies just confirm common sense. The important thing is not ‘‘which construct is strongest?’’ – because it seems obvious that more metal is stronger – but rather ‘‘how strong is strong enough?’’ given that larger and stronger constructs might be too prominent or bulky. In other words, what is the best treatment option when one considers all the advantages and disadvantages? For example, Hutchinson and colleagues evaluated four types of olecranon fixation techniques for simple transverse fractures [9]. The fixation type with the most metal (a 7.3-mm cancellous crew combined with a tension-band construct) provided the most stable fixation. Fixation techniques with less metal, that is, (a) intramedullary or (b) transcortical K-wires with an 18-gauge tension band, or (c) 7.3 mm cancellous screws without tension band wiring, were less strong. These results seem predictable and the clinical relevance unclear given that the smaller tension band wire fixation has a good track record [29,30]. A second example is the study by Markolf and colleagues. The authors analyzed the effect of radial head replacement on elbow joint stability after fracture–dislocation [31]. It is no surprise that the largest radial head tightens the ligaments more, but this does not account for the clinical problem of ‘‘overstuffing’’ the radiocapitellar
Please cite this article in press as: Mellema JJ, et al. Biomechanical studies: Science (f)or common sense? Injury (2014), http://dx.doi.org/ 10.1016/j.injury.2014.09.014
G Model
JINJ-5887; No. of Pages 5 J.J. Mellema et al. / Injury, Int. J. Care Injured xxx (2014) xxx–xxx
4
joint [32,33]. In other words, the best biomechanical construct is not as good for patients. We acknowledge inherent weaknesses of this study. First, there is the effect of deliberate selection bias for inclusion and exclusion of biomechanical studies presented. In a broad spectrum of biomechanical studies, only this subset of studies comparing fixation constructs, with proper illustration of the experimental test set-up in the original article, were selected based on our sense that the answer of the main study question was obvious prior to performing the study. Furthermore, we simplified the selected studies to a comparison of which construct was strongest, when these studies actually consisted of more sophisticated analyses of stiffness, strength to failure, and resistance to deformation. On the other hand, these variables amount to what orthopaedic surgeons would consider the ‘‘strength’’ of the implant. In our opinion, biomechanical studies should address adequate mechanics in relation to other important factors such as biology, risks, and costs rather than superior strength in a lab situation alone. Biomechanical aspects of fixation techniques are important, but should not be overemphasized. The rationale for using the ‘‘strongest’’ implant can be compelling to the human mind out of proportion to the overall safety, effectiveness, and resourcefulness of the implant. Conclusion According to our findings, a subset of biomechanical studies comparing fracture fixation constructs can be predicted prior to doing the study. As these studies are time and resource intensive, one criterion for proceeding with a biomechanical study should be that the answer is not simply a matter of common sense. Authors’ contributions All authors have participated in a material way to at least three of the five elements below: Study design: JJM, JND, TGG, DR. Gathered data: JJM, TGG. Analyzed data: JJM, JND, DR. Initial draft: JJM, JND, DR. Ensured accuracy of data: JJM, JND, TGG, DR. Estimated effort: JJM 50%, JND 20%, TGG 10%, DR 20%. Conflicts of interest The authors declare that there are no conflicts of interest.
Appendix. Science of Variation Group A.L. van der Zwan, A.B. Spoor, A.B. van Vugt, A.D. Armstrong, A. Shrivastava, A.L. Wahegaonkar, A.B. Shafritz, J. Adams, A. Ilyas, A.J.H. Vochteloo, A.P. Castillo, A. Basak, P. Andreas, A. Barquet, A. Kristan, A. Berner, A.B. Ranade, S. Ashish, A.L. Terrono, A. Jubel, B. Frieman, H.B. Bamberger, M.P J. van den Bekerom, W.D. Belangero, B.F. Hearon, J.M. Boler, F.L. Walter, M. Boyer, B.P.D. Wills, H. Broekhuyse, R. Buckley, B. Watkins, B.W. Sears, R.P. Calfee, C. Ekholm, C.H. Fernandes, C. Swigart, C. Cassidy, C.J. Wilson, L.C. Bainbridge, C. Wilson, C. M. Jones, C. Cornell, B.D. Crist, D.F.P. van Deurzen, D. Beingessner, D.J. Rowland, G.J. Della Rocca, D. Eygendaal, D.M. McKee, D.O.F. Verbeek, D.M. Kalainov, D. Polatsch, C.J.R. Barreto, M. Merchant, D. Brilej, N. Bijlani, D.M. Silva, E. Maman, I.M. Ibrahim, R. Nyszkiewicz, P.D.G. Henry, D. Ruchelsman, I.M. Vishwanath, D.F. Scott, E. Harvey, E. Grosso, E. Stojkovska Pemovska, E.T. Tolo, E.D. Schumer, F. Suarez, F. Frihagen, F. LopezGonzalez, F.M. Rodrı´guez, G.C. Zambrano Caro, C. Garnavos, G.S. Athwal, G. DeSilva, G.S.M. Dyer, G.C. Babis, G. Gradl, G.K. Frykman, R.G. Gaston, G. Garrigues, G.J. Bayne, G. Merrell, G.R. Hernandez, G.
Gadbled, L.A.B. Campinhos, G.W. Balfour, H. van der Heide, M. Nancollas, C. Young, G.M. Pess, H. Goost, H. Alonso, Villamizar, H. Awan, H.D. Routman, H.L. Kimball, E. Hofmeister, I. McGraw, K. Erol, J. Biert, J.C. Goslings, J.F. di Giovanni, J. Bishop, J.M. Abzug, J.A. Greenberg, J. Ahn, J. McAuliffe, J.C. Fanuele, J.G. Boretto, J. Choueka, J. Murachovsky, J. E.G. Ribeiro Filho, J. Isaacs, J.A. Izzi Jr., J. Kellam, J.L. Giuffre, J.M. Conflitti, J.M. Wolf, J.H. Scheer, J.T. Capo, J. Rubio, J. Taras, J. Wint, J. Wolkenfelt, S. Kakar, K. Chivers, K. Zyto, J.D. Keener, K. Eng, K. Jeray, K. Lee, K.J. Malone, K. Kabir, G.A. Kraan, K. Radcliff, K. Dickson, L.M.S.J. Poelhekke, L. Mica, L. Weiss, L.E. Adolfsson, L.C. Borris, N.G. Lasanianos, L.M. Schulte, L. Paz, N.E.L. Felipe, Verhofstad, M.A.J. van de Sande, M. Mormino, M.J. Richard, M. Bonczar, E.M. Hammerberg, M. Menon, A.D. Mazzocca, M.W.G.A. Bronkhorst, M. Mckee, M. Soong, R.M. Costanzo, M.M. Wood, M.I. Abdel-Ghany, M. Baskies, M. Behrman, M. Quell, M.W. Kessler, M.J. Palmer, M. Prayson, M. Pirpiris, M.M. Ragsdell, M.R. Krijnen, M. Tyllianakis, M.W. Grafe, N. Schep, E. Nelson, N.M. Akabudike, N.L. Shortt, N.J. Horangic, N.L. Leung, N.W. Gummerson, N.K. Kanakaris, N. Wilson, J. Calandruccio, O.M. Semenkin, R. Omid, C.J.H. Veillette, M. Richardson, J.A. Ortiz Jr., J.E. Forigua, P.R.G. Brink, P. Kloen, P.V. van Eerten, I. Prashanth, P. Althausen, P. Lygdas, N. Parnes, P.A. Martineau, P. Benhaim, P. Blazar, Schandelmaier, B. Petrisor, P. Jebson, P. Levin, W.A. Batson, F. Garcı´a, P.W. Owens, L. Guenter, R. Haverlag, R.W. Peters, R. de Bedout, R. Shatford, S. Rowinski, R.A.W. Verhagen, R.H. Babst, R. Hauck, R Papandrea, R.S. Gilbert, M. Rizzo, R. Jenkinson, R.L. Hutchison, R. Liem, R.M. Smith, R. Tashijan, R.D. Zura, R.S. Page, R. Pesantez, R. Wagenmakers, J. Abrams, S. Spruijt, S.A. Kennedy, S. Mehta, S. Beldner, A. Schmidt, S. Mitchell, S.T. Fischer, S.L. Checchia, S. Dodds, B.M. Nolan, S. Kaplan, S.G. Kaar, S. Kronlage, S.A. Meylaerts, S. Steinmann, S.J. McCabe, P.N. Streubel, T. Omara, M. Swiontkowski, T. Gosens, T. DeCoster, L. Taitsman, T. Baxamusa, T. Dienstknecht, F.T.D. Kaplan, T. Siff, T. Begue, T. Higgins, T. Mittlmeier, T. Apard, T. Hughes, T. Havlicˇek, T. Wyrick, Rozental, T.G. Stackhouse, V. Giordano, T.F. Varecka, V.S. Nikolaou, V. Jokhi, V. Philippe, C.J. Wall, C.J. Walsh, W.C. Hammert, Y. Weil, W. Satora, T. Wright, C. Zalavras.
References [1] Afshar R, Fong TS, Latifi MH, Kanthan SR, Kamarul T. A biomechanical study comparing plate fixation using unicortical and bicortical screws in transverse metacarpal fracture models subjected to cyclic loading. J Hand Surg 2012;37:396–401. [2] Bae JH, Oh JK, Chon CS, Oh CW, Hwang JH, Yoon YC. The biomechanical performance of locking plate fixation with intramedullary fibular strut graft augmentation in the treatment of unstable fractures of the proximal humerus. J Bone Joint Surg Br 2011;93:937–41. [3] Chacon Y, Fallat LM, Dau N, Bir C. Biomechanical comparison of internal fixation techniques for the Akin osteotomy of the proximal phalanx. J Foot Ankle Surg 2012;51:561–5. [4] Chiodo CP, Acevedo JI, Sammarco VJ, Parks BG, Boucher HR, Myerson MS, et al. Intramedullary rod fixation compared with blade-plate-and-screw fixation for tibiotalocalcaneal arthrodesis: a biomechanical investigation. J Bone Joint Surg Am 2003;85-A:2425–8. [5] Cullen AB, Curtiss S, Lee MA. Biomechanical comparison of polyaxial and uniaxial locking plate fixation in a proximal tibial gap model. J Orthop Trauma 2009;23:507–13. [6] Dennis MG, Simon JA, Kummer FJ, Koval KJ, Di Cesare PE. Fixation of periprosthetic femoral shaft fractures: a biomechanical comparison of two techniques. J Orthop Trauma 2001;15:177–80. [7] Dodds SD, Panjabi MM, Slade III JF. Screw fixation of scaphoid fractures: a biomechanical assessment of screw length and screw augmentation. J Hand Surg Am 2006;31:405–13. [8] Fowler TT, Pugh KJ, Litsky AS, Taylor BC, French BG. Medial malleolar fractures: a biomechanical study of fixation techniques. Orthopedics 2011;34:e349–55. [9] Hutchinson DT, Horwitz DS, Ha G, Thomas CW, Bachus KN. Cyclic loading of olecranon fracture fixation constructs. J Bone Joint Surg Am 2003;85-A:831–7. [10] Klos K, Rausch S, Loffler M, Frober R, Hofmeier K, Lenz M, et al. A biomechanical comparison of a biodegradable volar locked plate with two titanium volar locked plates in a distal radius fracture model. J Trauma 2010;68:984–91. [11] Knox J, Ambrose H, McCallister W, Trumble T. Percutaneous pins versus volar plates for unstable distal radius fractures: a biomechanic study using a cadaver model. J Hand Surg Am 2007;32:813–7.
Please cite this article in press as: Mellema JJ, et al. Biomechanical studies: Science (f)or common sense? Injury (2014), http://dx.doi.org/ 10.1016/j.injury.2014.09.014
G Model
JINJ-5887; No. of Pages 5 J.J. Mellema et al. / Injury, Int. J. Care Injured xxx (2014) xxx–xxx [12] Kwon BK, Goertzen DJ, O’Brien PJ, Broekhuyse HM, Oxland TR. Biomechanical evaluation of proximal humeral fracture fixation supplemented with calcium phosphate cement. J Bone Joint Surg Am 2002;84-A:951–61. [13] McCallister WV, Knight J, Kaliappan R, Trumble TE. Central placement of the screw in simulated fractures of the scaphoid waist: a biomechanical study. J Bone Joint Surg Am 2003;85-A:72–7. [14] Nowak TE, Burkhart KJ, Mueller LP, Mattyasovszky SG, Andres T, Sternstein W, et al. New intramedullary locking nail for olecranon fracture fixation – an in vitro biomechanical comparison with tension band wiring. J Trauma 2010;69:E56–61. [15] Patel R, Neu CP, Curtiss S, Fyhrie DP, Yoo B. Crutch weightbearing on comminuted humeral shaft fractures: a biomechanical comparison of large versus small fragment fixation for humeral shaft fractures. J Orthop Trauma 2011;25:300–5. [16] Peine R, Rikli DA, Hoffmann R, Duda G, Regazzoni P. Comparison of three different plating techniques for the dorsum of the distal radius: a biomechanical study. J Hand Surg Am 2000;25:29–33. [17] Renner SM, Lim TH, Kim WJ, Katolik L, An HS, Andersson GB. Augmentation of pedicle screw fixation strength using an injectable calcium phosphate cement as a function of injection timing and method. Spine (Phila Pa 1976) 2004;29:E212–6. [18] Ricci WM, Tornetta P, Borrelli Jr J. Lag screw fixation of medial malleolar fractures: a biomechanical, radiographic, and clinical comparison of unicortical partially threaded lag screws and bicortical fully threaded lag screws. J Orthop Trauma 2012;26:602–6. [19] Rubel IF, Kloen P, Campbell D, Schwartz M, Liew A, Myers E, et al. Open reduction and internal fixation of humeral nonunions: a biomechanical and clinical study. J Bone Joint Surg Am 2002;84-A:1315–22. [20] Siffri PC, Peindl RD, Coley ER, Norton J, Connor PM, Kellam JF. Biomechanical analysis of blade plate versus locking plate fixation for a proximal humerus fracture: comparison using cadaveric and synthetic humeri. J Orthop Trauma 2006;20:547–54. [21] Tabaie SA, Bledsoe JG, Moed BR. Biomechanical comparison of standard iliosacral screw fixation to transsacral locked screw fixation in a type C zone II pelvic fracture model. J Orthop Trauma 2013;27:521–6.
5
[22] Wilkens KJ, Curtiss S, Lee MA. Polyaxial locking plate fixation in distal femur fractures: a biomechanical comparison. J Orthop Trauma 2008;22:624–8. [23] Zheng ZM, Zhang KB, Zhang JF, Yu BS, Liu H, Zhuang XM. The effect of screw length and bone cement augmentation on the fixation strength of iliac screws: a biomechanical study. J Spinal Disord Tech 2009;22:545–50. [24] Siegel S, Castellan JN. Nonparametric statistics for the behavioral sciences. New York: McGraw-Hill; 1988. [25] Cohen J. A coefficient of agreement for nominal scales. Educ Psychol Meas 1960;20:37–46. [26] Landis JR, Koch GG. The measurement of observer agreement for categorical data. Biometrics 1977;33:159–74. [27] Posner KL, Sampson PD, Caplan RA, Ward RJ, Cheney FW. Measuring interrater reliability among multiple raters: an example of methods for nominal data. Stat Med 1990;9:1103–15. [28] Doornberg J, Lindenhovius A, Kloen P, van Dijk CN, Zurakowski D, Ring D. Two and three-dimensional computed tomography for the classification and management of distal humeral fractures. Evaluation of reliability and diagnostic accuracy. J Bone Joint Surg Am 2006;88:1795–801. [29] Flinterman HJ, Doornberg JN, Guitton TG, Ring D, Goslings JC, Kloen P. Longterm outcome of displaced, transverse. Noncomminuted olecranon fractures. Clin Orthop Relat Res 2014. [30] Karlsson MK, Hasserius R, Karlsson C, Besjakov J, Josefsson PO. Fractures of the olecranon: a 15- to 25-year follow up of 73 patients. Clin Orthop Relat Res 2002;205–12. [31] Markolf KL, Tejwani SG, O’Neil G, Benhaim P. Load-sharing at the wrist following radial head replacement with a metal implant. A cadaveric study. J Bone Joint Surg Am 2004;86-A:1023–30. [32] Doornberg JN, Linzel DS, Zurakowski D, Ring D. Reference points for radial head prosthesis size. J Hand Surg Am 2006;31:53–7. [33] Doornberg JN, Parisien R, van Duijn PJ, Ring D. Radial head arthroplasty with a modular metal spacer to treat acute traumatic elbow instability. J Bone Joint Surg Am 2007;89:1075–80.
Please cite this article in press as: Mellema JJ, et al. Biomechanical studies: Science (f)or common sense? Injury (2014), http://dx.doi.org/ 10.1016/j.injury.2014.09.014
JINJ-5887; No. of Pages 5 Injury, Int. J. Care Injured xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
Injury journal homepage: www.elsevier.com/locate/injury
Biomechanical studies: Science (f)or common sense? Jos J. Mellema a, Job N. Doornberg b, Thierry G. Guitton b, David Ring a,* Science of Variation Group1 a b
Orthopaedic Hand and Upper Extremity Service, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA University of Amsterdam Orthopaedic Residency Program (PGY 4), Academic Medical Center, Amsterdam, The Netherlands
A R T I C L E I N F O
A B S T R A C T
Article history: Accepted 14 September 2014
Introduction: It is our impression that many biomechanical studies invest substantial resources studying the obvious: that more and larger metal is stronger. The purpose of this study is to evaluate if a subset of biomechanical studies comparing fixation constructs just document common sense. Methods: Using a web-based survey, 274 orthopaedic surgeons and 81 medical students predicted the results of 11 biomechanical studies comparing fracture fixation constructs (selected based on the authors’ sense that the answer was obvious prior to performing the study). Sensitivity, specificity, and accuracy were calculated according to standard formulas. The agreement among the observers was calculated by using a multirater kappa, described by Siegel and Castellan. Results: The accuracy of predicting outcomes was 80% or greater for 10 of 11 studies. Accuracy was not influenced by level of experience (i.e., time in practice and medical students vs. surgeons). There were substantial differences in accuracy between observers from different regions. The overall categorical rating of inter-observer reliability according to Landis and Koch was moderate (k = 0.55; standard error (SE) = 0.01). Conclusion: The results of a subset of biomechanical studies comparing fracture fixation constructs can be predicted prior to doing the study. As these studies are time and resource intensive, one criterion for proceeding with a biomechanical study should be that the answer is not simply a matter of common sense. ß 2014 Elsevier Ltd. All rights reserved.
Keywords: Biomechanical Orthopaedic Fracture Fixation
Introduction It is our impression that many biomechanical studies [1–22] invest substantial resources studying the obvious: that more and larger metal is stronger. Studies that evaluate ‘‘which construct is the strongest’’ distract from the more important question: ‘‘How strong is strong enough in physiological loading conditions?’’. The purpose of this study is to evaluate if some biomechanical studies comparing fixation constructs just document common sense. If so, there is a need for more careful use of resources in the lab and better collaboration with surgeons to enhance clinical relevance. This study tested our hypothesis that a subset of biomechanical studies comparing fracture fixation constructs can be predicted based on common sense and do not require formal testing. Specifically our primary hypothesis was that outcomes of
* Corresponding author. Tel.: +1 617 643 7527; fax: +1 617 726 0460. E-mail address: [email protected] (D. Ring). 1 The members of Science of Variation Group are listed in Appendix.
some biomechanical studies comparing fracture fixation constructs are predictable with high accuracy. Our secondary hypotheses addressed inter-observer reliability and accuracy according to experience and other factors. Methods Between 2000 and 2012, we found 105 peer-reviewed biomechanical studies in peer-reviewed orthopaedic journals comparing two or more constructs in order to determine: ‘‘Which construct is the strongest?’’. We excluded six studies of spine, skull, and facial fractures. From the remaining 99 studies, 12 had a good illustration of the constructs. Among those 12 studies, we selected 11 for which we thought the answer was obvious prior to performing the study [2,7–9,11,12,14,15,19,21,23]. Orthopaedic and trauma surgeons affiliated with the Science of Variation Group (SOVG) and medical students from the University of Amsterdam were invited to predict the outcome of biomechanical studies comparing different fixation constructs. As many as 275 surgeons who treat musculoskeletal trauma and 81 medical
http://dx.doi.org/10.1016/j.injury.2014.09.014 0020–1383/ß 2014 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Mellema JJ, et al. Biomechanical studies: Science (f)or common sense? Injury (2014), http://dx.doi.org/ 10.1016/j.injury.2014.09.014
G Model
JINJ-5887; No. of Pages 5 2
J.J. Mellema et al. / Injury, Int. J. Care Injured xxx (2014) xxx–xxx
Fig. 1. Percutaneous pins versus volar plates for unstable distal radius fractures: a biomechanic study using a cadaver model [11].
students were interested in participating logged on to the website; 274 of these 275 surgeons (99.6%) and 81 of 81 students (100%), completed the study. The Institutional Research Board at the principal investigator’s hospital provided a waiver for the study protocol. All studies were selected and blinded by independent research fellows (JJM and JND) for use in this study. The blinded experimental designs were uploaded to the website. Upon login to the website, observers received a short descriptive summary of the study purpose. Observers were asked to answer one question: ‘‘Which construct is stronger?’’ based on provided illustrations that were copy-pasted from the original articles without manipulation.
No figure legends or explanatory text accompanied the illustrations. The outcome had to be predicted based on visual information judging the experimental test set-up only (Figs. 1 and 2). Observers could comment on each study. Every question had to be completed in order to continue with the next case. The observers completed the study at their own pace. The result of the original study was considered the reference standard. Sensitivity, specificity, accuracy, positive predictive value, and the negative predictive value were calculated to standard formulas. The agreement among the observers was calculated by using a multirater kappa, described by Siegel and Castellan [24]. It is a
Fig. 2. Biomechanical evaluation of proximal humeral fracture fixation supplemented with calcium phosphate cement [12].
Please cite this article in press as: Mellema JJ, et al. Biomechanical studies: Science (f)or common sense? Injury (2014), http://dx.doi.org/ 10.1016/j.injury.2014.09.014
G Model
JINJ-5887; No. of Pages 5 J.J. Mellema et al. / Injury, Int. J. Care Injured xxx (2014) xxx–xxx
commonly used statistic to describe chance-corrected agreement in a variety of intra-observer and inter-observer studies [25– 27]. The kappa values were interpreted by using the categorical rating that was proposed by Landis and Koch [26]: values of 0.01– 0.20 indicated slight agreement; 0.21–0.40 indicated fair agreement; 0.41–0.60, moderate agreement; 0.61–0.80, substantial agreement; and a value that was >0.81 indicated almost perfect agreement. Zero indicated that there was no agreement beyond what was expected due to chance alone. The value of 1.00 meant total disagreement and +1.00 represented perfect agreement [26,27]. We used previously described methods for evaluating the significance of differences between kappa values [28]. Results Accuracy was 80% or greater for 10 of 11 studies that have been predicted by members of the SOVG (Table 1). The diagnostic performance characteristics for guessing the results of the study were as follows: sensitivity averaged 84%, ranging from 60% (for study 1) to 99% (for study 7); specificity 86%, ranging from 60% (for study 1) to 99% (for study 7), and accuracy averaged 86%, ranging from 60% (for study 1) to 99% (for study 7). Study 5 was predicted with the highest accuracy (accuracy 97% and 98% for members of the SOVG and medical students, respectively) (Fig. 1), and study 1 was predicted with least accuracy (accuracy 61% and 60% for members of the SOVG and medical students, respectively) (Fig. 2). The level of experience (i.e., time in practice and medical students vs. surgeons) had no influence on accuracy (Tables 1 and 2). There were substantial differences in accuracy between Canadians and observers from other regions (p < 0.05). Canadian observers predicted with the highest accuracy (accuracy 94%, range 58–100%). The average accuracy in the American observer group was 88% (range 57–97%) compared with 84% (range 69–99%) in the European observer group (p < 0.05). The overall categorical rating of inter-observer reliability according to Landis and Koch was moderate (k = 0.55; SE = 0.01), ranging from k = 0.33 (SE = 0.06) to k = 0.82 (SE = 0.03) (Table 2). Analyses of SOVG subgroups identified excellent agreement among Canadian surgeons. Moderate and substantial agreement were found in most of other subgroups: ranging from moderate (k = 0.48; SE = 0.01) among specialists 21 years or more in practice to moderate (k = 0.59; SE = 0.01) among specialists 11–20 years in practice; and moderate, ranging from k = 0.47 (SE = 0.06) to k = 0.60 (SE = 0.01), among specialists who practice in Australia, Europe, and United States. There was no significant difference in kappa value between SOVG members and Table 1 Accuracy and agreement for predicting outcome of biomechanical studies selected. Members SOVG (accuracy)
Members SOVG (% agreementa)
Study (Experimental test set-up) 1 0.61 61 2 0.80 60 3 0.93 93 4 0.89 89 5 0.97 97 6 0.90 90 7 0.84 84 8 0.93 93 9 0.80 80 10 0.90 90 11 0.89 89 Average a
100.
0.86
84
Medical students (accuracy)
Medical students (% agreementa)
0.60 0.87 0.93 0.84 0.98 0.90 0.99 0.93 0.79 0.74 0.91
60 74 93 84 98 90 99 93 79 74 91
0.86
85
% Agreement, number of agreements/(number of agreements + disagreements)
3
Table 2 Observer demographics, accuracy, and kappa values.
Members SOVG Observers’ gender Male Female Practice Asia Australia Canada Europe United Kingdom United States Other Years in practice 0–5 6–10 11–20 21–30 Specialization General orthopaedics Orthopaedic traumatology Shoulder and elbow Hand and wrist Other
N
%
Kappa (SE)a
% Accuracy (95% CI)
252 22
92.0 8.0
0.55 (0.01) 0.45 (0.02)
86 (85–87) 82 (79–85)
11 6 12 68 6 146 25
4.0 2.2 4.4 24.8 2.2 53.3 9.1
0.36 0.47 0.82 0.51 0.33 0.60 0.42
(0.03) (0.06) (0.03) (0.01) (0.06) (0.01) (0.02)
80 81 94 84 82 88 82
(75–85) (75–87) (91–97) (82–86) (76–88) (87–89) (79–85)
94 60 75 45
34.3 21.9 27.4 16.4
0.54 0.50 0.59 0.48
(0.01) (0.01) (0.01) (0.01)
86 85 86 84
(84–88) (83–87) (84–88) (82–86)
16 96 41 107 14
5.8 35.0 15.0 39.1 5.1
0.33 0.53 0.58 0.60 0.42
(0.02) (0.01) (0.01) (0.01) (0.02)
81 84 88 86 85
(77–85) (83–85) (86–90) (85–87) (81–89)
32 14 35
39.5 17.3 43.2
0.55 (0.01) 0.60 (0.03) 0.54 (0.01)
Medical students Years of study 1–2 3–4 5–6 a
86 (84–88) 86 (82–90) 86 (84–88)
Overall kappa = 0.55; SE, 0.01.
medical students (k = 0.54; SE = 0.01 and k = 0.56; SE = 0.01, respectively); the difference was judged not to be significant as 95% confidence interval did overlap.
Discussion This study confirms our hypothesis that outcomes of a subset of biomechanical studies – comparing fixation constructs – are quite predictable as accuracy was at least 80% for all but one study. In addition, the secondary null hypothesis that the experience of observers has no influence on the accuracy of predicting outcomes was not rejected because medical students and experienced surgeons performed equally well. In other words, it seems that some comparative biomechanical studies just confirm common sense. The important thing is not ‘‘which construct is strongest?’’ – because it seems obvious that more metal is stronger – but rather ‘‘how strong is strong enough?’’ given that larger and stronger constructs might be too prominent or bulky. In other words, what is the best treatment option when one considers all the advantages and disadvantages? For example, Hutchinson and colleagues evaluated four types of olecranon fixation techniques for simple transverse fractures [9]. The fixation type with the most metal (a 7.3-mm cancellous crew combined with a tension-band construct) provided the most stable fixation. Fixation techniques with less metal, that is, (a) intramedullary or (b) transcortical K-wires with an 18-gauge tension band, or (c) 7.3 mm cancellous screws without tension band wiring, were less strong. These results seem predictable and the clinical relevance unclear given that the smaller tension band wire fixation has a good track record [29,30]. A second example is the study by Markolf and colleagues. The authors analyzed the effect of radial head replacement on elbow joint stability after fracture–dislocation [31]. It is no surprise that the largest radial head tightens the ligaments more, but this does not account for the clinical problem of ‘‘overstuffing’’ the radiocapitellar
Please cite this article in press as: Mellema JJ, et al. Biomechanical studies: Science (f)or common sense? Injury (2014), http://dx.doi.org/ 10.1016/j.injury.2014.09.014
G Model
JINJ-5887; No. of Pages 5 J.J. Mellema et al. / Injury, Int. J. Care Injured xxx (2014) xxx–xxx
4
joint [32,33]. In other words, the best biomechanical construct is not as good for patients. We acknowledge inherent weaknesses of this study. First, there is the effect of deliberate selection bias for inclusion and exclusion of biomechanical studies presented. In a broad spectrum of biomechanical studies, only this subset of studies comparing fixation constructs, with proper illustration of the experimental test set-up in the original article, were selected based on our sense that the answer of the main study question was obvious prior to performing the study. Furthermore, we simplified the selected studies to a comparison of which construct was strongest, when these studies actually consisted of more sophisticated analyses of stiffness, strength to failure, and resistance to deformation. On the other hand, these variables amount to what orthopaedic surgeons would consider the ‘‘strength’’ of the implant. In our opinion, biomechanical studies should address adequate mechanics in relation to other important factors such as biology, risks, and costs rather than superior strength in a lab situation alone. Biomechanical aspects of fixation techniques are important, but should not be overemphasized. The rationale for using the ‘‘strongest’’ implant can be compelling to the human mind out of proportion to the overall safety, effectiveness, and resourcefulness of the implant. Conclusion According to our findings, a subset of biomechanical studies comparing fracture fixation constructs can be predicted prior to doing the study. As these studies are time and resource intensive, one criterion for proceeding with a biomechanical study should be that the answer is not simply a matter of common sense. Authors’ contributions All authors have participated in a material way to at least three of the five elements below: Study design: JJM, JND, TGG, DR. Gathered data: JJM, TGG. Analyzed data: JJM, JND, DR. Initial draft: JJM, JND, DR. Ensured accuracy of data: JJM, JND, TGG, DR. Estimated effort: JJM 50%, JND 20%, TGG 10%, DR 20%. Conflicts of interest The authors declare that there are no conflicts of interest.
Appendix. Science of Variation Group A.L. van der Zwan, A.B. Spoor, A.B. van Vugt, A.D. Armstrong, A. Shrivastava, A.L. Wahegaonkar, A.B. Shafritz, J. Adams, A. Ilyas, A.J.H. Vochteloo, A.P. Castillo, A. Basak, P. Andreas, A. Barquet, A. Kristan, A. Berner, A.B. Ranade, S. Ashish, A.L. Terrono, A. Jubel, B. Frieman, H.B. Bamberger, M.P J. van den Bekerom, W.D. Belangero, B.F. Hearon, J.M. Boler, F.L. Walter, M. Boyer, B.P.D. Wills, H. Broekhuyse, R. Buckley, B. Watkins, B.W. Sears, R.P. Calfee, C. Ekholm, C.H. Fernandes, C. Swigart, C. Cassidy, C.J. Wilson, L.C. Bainbridge, C. Wilson, C. M. Jones, C. Cornell, B.D. Crist, D.F.P. van Deurzen, D. Beingessner, D.J. Rowland, G.J. Della Rocca, D. Eygendaal, D.M. McKee, D.O.F. Verbeek, D.M. Kalainov, D. Polatsch, C.J.R. Barreto, M. Merchant, D. Brilej, N. Bijlani, D.M. Silva, E. Maman, I.M. Ibrahim, R. Nyszkiewicz, P.D.G. Henry, D. Ruchelsman, I.M. Vishwanath, D.F. Scott, E. Harvey, E. Grosso, E. Stojkovska Pemovska, E.T. Tolo, E.D. Schumer, F. Suarez, F. Frihagen, F. LopezGonzalez, F.M. Rodrı´guez, G.C. Zambrano Caro, C. Garnavos, G.S. Athwal, G. DeSilva, G.S.M. Dyer, G.C. Babis, G. Gradl, G.K. Frykman, R.G. Gaston, G. Garrigues, G.J. Bayne, G. Merrell, G.R. Hernandez, G.
Gadbled, L.A.B. Campinhos, G.W. Balfour, H. van der Heide, M. Nancollas, C. Young, G.M. Pess, H. Goost, H. Alonso, Villamizar, H. Awan, H.D. Routman, H.L. Kimball, E. Hofmeister, I. McGraw, K. Erol, J. Biert, J.C. Goslings, J.F. di Giovanni, J. Bishop, J.M. Abzug, J.A. Greenberg, J. Ahn, J. McAuliffe, J.C. Fanuele, J.G. Boretto, J. Choueka, J. Murachovsky, J. E.G. Ribeiro Filho, J. Isaacs, J.A. Izzi Jr., J. Kellam, J.L. Giuffre, J.M. Conflitti, J.M. Wolf, J.H. Scheer, J.T. Capo, J. Rubio, J. Taras, J. Wint, J. Wolkenfelt, S. Kakar, K. Chivers, K. Zyto, J.D. Keener, K. Eng, K. Jeray, K. Lee, K.J. Malone, K. Kabir, G.A. Kraan, K. Radcliff, K. Dickson, L.M.S.J. Poelhekke, L. Mica, L. Weiss, L.E. Adolfsson, L.C. Borris, N.G. Lasanianos, L.M. Schulte, L. Paz, N.E.L. Felipe, Verhofstad, M.A.J. van de Sande, M. Mormino, M.J. Richard, M. Bonczar, E.M. Hammerberg, M. Menon, A.D. Mazzocca, M.W.G.A. Bronkhorst, M. Mckee, M. Soong, R.M. Costanzo, M.M. Wood, M.I. Abdel-Ghany, M. Baskies, M. Behrman, M. Quell, M.W. Kessler, M.J. Palmer, M. Prayson, M. Pirpiris, M.M. Ragsdell, M.R. Krijnen, M. Tyllianakis, M.W. Grafe, N. Schep, E. Nelson, N.M. Akabudike, N.L. Shortt, N.J. Horangic, N.L. Leung, N.W. Gummerson, N.K. Kanakaris, N. Wilson, J. Calandruccio, O.M. Semenkin, R. Omid, C.J.H. Veillette, M. Richardson, J.A. Ortiz Jr., J.E. Forigua, P.R.G. Brink, P. Kloen, P.V. van Eerten, I. Prashanth, P. Althausen, P. Lygdas, N. Parnes, P.A. Martineau, P. Benhaim, P. Blazar, Schandelmaier, B. Petrisor, P. Jebson, P. Levin, W.A. Batson, F. Garcı´a, P.W. Owens, L. Guenter, R. Haverlag, R.W. Peters, R. de Bedout, R. Shatford, S. Rowinski, R.A.W. Verhagen, R.H. Babst, R. Hauck, R Papandrea, R.S. Gilbert, M. Rizzo, R. Jenkinson, R.L. Hutchison, R. Liem, R.M. Smith, R. Tashijan, R.D. Zura, R.S. Page, R. Pesantez, R. Wagenmakers, J. Abrams, S. Spruijt, S.A. Kennedy, S. Mehta, S. Beldner, A. Schmidt, S. Mitchell, S.T. Fischer, S.L. Checchia, S. Dodds, B.M. Nolan, S. Kaplan, S.G. Kaar, S. Kronlage, S.A. Meylaerts, S. Steinmann, S.J. McCabe, P.N. Streubel, T. Omara, M. Swiontkowski, T. Gosens, T. DeCoster, L. Taitsman, T. Baxamusa, T. Dienstknecht, F.T.D. Kaplan, T. Siff, T. Begue, T. Higgins, T. Mittlmeier, T. Apard, T. Hughes, T. Havlicˇek, T. Wyrick, Rozental, T.G. Stackhouse, V. Giordano, T.F. Varecka, V.S. Nikolaou, V. Jokhi, V. Philippe, C.J. Wall, C.J. Walsh, W.C. Hammert, Y. Weil, W. Satora, T. Wright, C. Zalavras.
References [1] Afshar R, Fong TS, Latifi MH, Kanthan SR, Kamarul T. A biomechanical study comparing plate fixation using unicortical and bicortical screws in transverse metacarpal fracture models subjected to cyclic loading. J Hand Surg 2012;37:396–401. [2] Bae JH, Oh JK, Chon CS, Oh CW, Hwang JH, Yoon YC. The biomechanical performance of locking plate fixation with intramedullary fibular strut graft augmentation in the treatment of unstable fractures of the proximal humerus. J Bone Joint Surg Br 2011;93:937–41. [3] Chacon Y, Fallat LM, Dau N, Bir C. Biomechanical comparison of internal fixation techniques for the Akin osteotomy of the proximal phalanx. J Foot Ankle Surg 2012;51:561–5. [4] Chiodo CP, Acevedo JI, Sammarco VJ, Parks BG, Boucher HR, Myerson MS, et al. Intramedullary rod fixation compared with blade-plate-and-screw fixation for tibiotalocalcaneal arthrodesis: a biomechanical investigation. J Bone Joint Surg Am 2003;85-A:2425–8. [5] Cullen AB, Curtiss S, Lee MA. Biomechanical comparison of polyaxial and uniaxial locking plate fixation in a proximal tibial gap model. J Orthop Trauma 2009;23:507–13. [6] Dennis MG, Simon JA, Kummer FJ, Koval KJ, Di Cesare PE. Fixation of periprosthetic femoral shaft fractures: a biomechanical comparison of two techniques. J Orthop Trauma 2001;15:177–80. [7] Dodds SD, Panjabi MM, Slade III JF. Screw fixation of scaphoid fractures: a biomechanical assessment of screw length and screw augmentation. J Hand Surg Am 2006;31:405–13. [8] Fowler TT, Pugh KJ, Litsky AS, Taylor BC, French BG. Medial malleolar fractures: a biomechanical study of fixation techniques. Orthopedics 2011;34:e349–55. [9] Hutchinson DT, Horwitz DS, Ha G, Thomas CW, Bachus KN. Cyclic loading of olecranon fracture fixation constructs. J Bone Joint Surg Am 2003;85-A:831–7. [10] Klos K, Rausch S, Loffler M, Frober R, Hofmeier K, Lenz M, et al. A biomechanical comparison of a biodegradable volar locked plate with two titanium volar locked plates in a distal radius fracture model. J Trauma 2010;68:984–91. [11] Knox J, Ambrose H, McCallister W, Trumble T. Percutaneous pins versus volar plates for unstable distal radius fractures: a biomechanic study using a cadaver model. J Hand Surg Am 2007;32:813–7.
Please cite this article in press as: Mellema JJ, et al. Biomechanical studies: Science (f)or common sense? Injury (2014), http://dx.doi.org/ 10.1016/j.injury.2014.09.014
G Model
JINJ-5887; No. of Pages 5 J.J. Mellema et al. / Injury, Int. J. Care Injured xxx (2014) xxx–xxx [12] Kwon BK, Goertzen DJ, O’Brien PJ, Broekhuyse HM, Oxland TR. Biomechanical evaluation of proximal humeral fracture fixation supplemented with calcium phosphate cement. J Bone Joint Surg Am 2002;84-A:951–61. [13] McCallister WV, Knight J, Kaliappan R, Trumble TE. Central placement of the screw in simulated fractures of the scaphoid waist: a biomechanical study. J Bone Joint Surg Am 2003;85-A:72–7. [14] Nowak TE, Burkhart KJ, Mueller LP, Mattyasovszky SG, Andres T, Sternstein W, et al. New intramedullary locking nail for olecranon fracture fixation – an in vitro biomechanical comparison with tension band wiring. J Trauma 2010;69:E56–61. [15] Patel R, Neu CP, Curtiss S, Fyhrie DP, Yoo B. Crutch weightbearing on comminuted humeral shaft fractures: a biomechanical comparison of large versus small fragment fixation for humeral shaft fractures. J Orthop Trauma 2011;25:300–5. [16] Peine R, Rikli DA, Hoffmann R, Duda G, Regazzoni P. Comparison of three different plating techniques for the dorsum of the distal radius: a biomechanical study. J Hand Surg Am 2000;25:29–33. [17] Renner SM, Lim TH, Kim WJ, Katolik L, An HS, Andersson GB. Augmentation of pedicle screw fixation strength using an injectable calcium phosphate cement as a function of injection timing and method. Spine (Phila Pa 1976) 2004;29:E212–6. [18] Ricci WM, Tornetta P, Borrelli Jr J. Lag screw fixation of medial malleolar fractures: a biomechanical, radiographic, and clinical comparison of unicortical partially threaded lag screws and bicortical fully threaded lag screws. J Orthop Trauma 2012;26:602–6. [19] Rubel IF, Kloen P, Campbell D, Schwartz M, Liew A, Myers E, et al. Open reduction and internal fixation of humeral nonunions: a biomechanical and clinical study. J Bone Joint Surg Am 2002;84-A:1315–22. [20] Siffri PC, Peindl RD, Coley ER, Norton J, Connor PM, Kellam JF. Biomechanical analysis of blade plate versus locking plate fixation for a proximal humerus fracture: comparison using cadaveric and synthetic humeri. J Orthop Trauma 2006;20:547–54. [21] Tabaie SA, Bledsoe JG, Moed BR. Biomechanical comparison of standard iliosacral screw fixation to transsacral locked screw fixation in a type C zone II pelvic fracture model. J Orthop Trauma 2013;27:521–6.
5
[22] Wilkens KJ, Curtiss S, Lee MA. Polyaxial locking plate fixation in distal femur fractures: a biomechanical comparison. J Orthop Trauma 2008;22:624–8. [23] Zheng ZM, Zhang KB, Zhang JF, Yu BS, Liu H, Zhuang XM. The effect of screw length and bone cement augmentation on the fixation strength of iliac screws: a biomechanical study. J Spinal Disord Tech 2009;22:545–50. [24] Siegel S, Castellan JN. Nonparametric statistics for the behavioral sciences. New York: McGraw-Hill; 1988. [25] Cohen J. A coefficient of agreement for nominal scales. Educ Psychol Meas 1960;20:37–46. [26] Landis JR, Koch GG. The measurement of observer agreement for categorical data. Biometrics 1977;33:159–74. [27] Posner KL, Sampson PD, Caplan RA, Ward RJ, Cheney FW. Measuring interrater reliability among multiple raters: an example of methods for nominal data. Stat Med 1990;9:1103–15. [28] Doornberg J, Lindenhovius A, Kloen P, van Dijk CN, Zurakowski D, Ring D. Two and three-dimensional computed tomography for the classification and management of distal humeral fractures. Evaluation of reliability and diagnostic accuracy. J Bone Joint Surg Am 2006;88:1795–801. [29] Flinterman HJ, Doornberg JN, Guitton TG, Ring D, Goslings JC, Kloen P. Longterm outcome of displaced, transverse. Noncomminuted olecranon fractures. Clin Orthop Relat Res 2014. [30] Karlsson MK, Hasserius R, Karlsson C, Besjakov J, Josefsson PO. Fractures of the olecranon: a 15- to 25-year follow up of 73 patients. Clin Orthop Relat Res 2002;205–12. [31] Markolf KL, Tejwani SG, O’Neil G, Benhaim P. Load-sharing at the wrist following radial head replacement with a metal implant. A cadaveric study. J Bone Joint Surg Am 2004;86-A:1023–30. [32] Doornberg JN, Linzel DS, Zurakowski D, Ring D. Reference points for radial head prosthesis size. J Hand Surg Am 2006;31:53–7. [33] Doornberg JN, Parisien R, van Duijn PJ, Ring D. Radial head arthroplasty with a modular metal spacer to treat acute traumatic elbow instability. J Bone Joint Surg Am 2007;89:1075–80.
Please cite this article in press as: Mellema JJ, et al. Biomechanical studies: Science (f)or common sense? Injury (2014), http://dx.doi.org/ 10.1016/j.injury.2014.09.014
