Axial pullout strength comparison of different screw designs: fenestrated screw, dual outer diameter screw and standard pedicle screw

Scoliosis

Konstantinos Kafchitsas²  Philipp Drees⁴  Thomas Apostolou¹  Saif Khalil³  Divya Reddy³  Suresh Chinthakunta³  Evangelos Christodoulou² 

[1] G. Papanikalaou Hospital Exohi, Thessaloniki, 570 10, Greece;Asklepios Klinik Lindenlohe, Schwandorf, Germany;Globus Medical Inc., Ave 2560 General Armistead Ave, Audubon 19403, PA, USA;Universitätsmedizin Mainz, Langenbeckstr 1 55131, Germany

关键词: Large diameter screws;    Pedicle screws;    Biomechanical study;    Fenestrated screws;    Pullout strength;   

Others  :  1194945
DOI  :  10.1186/s13013-015-0039-6

 received in 2014-11-03, accepted in 2015-04-19,  发布年份 2015

【 摘 要 】

Background

The pullout strength of pedicle screws is influenced by many factors, including diameter of the screws, implant design, and augmentation with bone cement such as PMMA. In the present study, the pullout strength of an innovative fenestrated screw augmented with PMMA was investigated and was compared to unaugmented fenestrated, standard and dual outer diameter screw.

Methods

Twenty four thoracolumbar vertebrae (T10-L5, age 60 to 70 years) from three cadavers were implanted with the four different pedicle screws. Twelve screws of each type were instrumented into either left or right pedicle with standard screw paired with unaugmented and dual outer diameter screw paired with augmented fenestrated screw in any given vertebra. Axial pullout testing was conducted at a rate of 5 mm/min. Force to failure (Newtons) for each pedicle screw was recorded.

Results

The augmented fenestrated screws had the highest pullout strength, which represented an average increase of 149%, 141%, and 78% in comparison to unaugmented, standard, and dual outer diameter screws, respectively. Pullout strength of unaugmented screws was comparable to that of standard screws, however it was significantly lower than dual outer diameter screws.

Conclusions

Fenestrated screws augmented with PMMA improve the fixation strength and result in significantly higher pullout strength compared to dual outer diameter, standard and unaugmented fenestrated screws. Screws with dual outer diameter provided enhanced bone-screw purchase and may be considered as an alternative technique to increase the bone-screw interface in cases where augmentation using bone cement is not feasible. Unaugmented screws can be left in the pedicle even without cement and provide similar pullout strength to standard screws.

【 授权许可】

   
2015 Christodoulou et al.; licensee BioMed Central.

【 图 表 】

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【 参考文献 】

• [1]Abshire BB, McLain RF, Valdevit A, Kambic HE. Characteristics of pullout failure in conical and cylindrical pedicle screws after full insertion and back-out. Spine J. 2001; 1:408-14.
• [2]Rohmiller MT, Schwalm D, Glattes RC, Elalayli TG, Spengler DM. Evaluation of calcium sulfate paste for augmentation of lumbar pedicle screw pullout strength. Spine J. 2002; 2:255-60.
• [3]Cook SD, Salkeld SL, Stanley T, Faciane A, Miller SD. Biomechanical study of pedicle screw fixation in severely osteoporotic bone. Spine J. 2004; 4:402-8.
• [4]Liu D, Wu ZX, Pan XM, Fu SC, Gao MX, Shi L et al.. Biomechanical comparison of different techniques in primary spinal surgery in osteoporotic cadaveric lumbar vertebrae: expansive pedicle screw versus polymethylmethacrylate-augmented pedicle screw. Arch Orthop Trauma Surg. 2011; 131:1227-32.
• [5]Yazu M, Kin A, Kosaka R, Kinoshita M, Abe M. Efficacy of novel-concept pedicle screw fixation augmented with calcium phosphate cement in the osteoporotic spine. J Orthop Sci. 2005; 10(1):56-61.
• [6]Santoni BG, Hynes RA, McGilvray KC, Rodriguez-Canessa G, Lyons AS, Henson MA et al.. Cortical bone trajectory for lumbar pedicle screws. Spine J. 2009; 9(5):366-73.
• [7]Frankel BM, D'Agostino S, Wang C. A biomechanical 350 cadaveric analysis of polymethylmethacrylate-augmented pedicle screw fixation. J Neurosurg Spine. 2007; 7:47-53.
• [8]Burval DJ, McLain RF, Milks R, Inceoglu S. Primary pedicle screw augmentation in osteoporotic lumbar vertebrae: biomechanical analysis of pedicle fixation strength. Spine. 2007; 32:1077-83.
• [9]Kiner DW, Wybo CD, Sterba W, Yeni YN, Bartol SW, Vaidya R. Biomechanical analysis of different techniques in revision spinal instrumentation: larger diameter screws versus cement augmentation. Spine. 2008; 33:2618-22.
• [10]Wittenberg RH, Lee KS, Shea M, White AA, Hayes WC. Effect of screw diameter, insertion technique, and bone cement augmentation of pedicular screw fixation strength. Clin Orthop Relat Res. 1993; 296:278-87.
• [11]Polly DW, Orchowski JR, Ellenbogen RG. Revision pedicle screws: bigger, longer shims–what is best? Spine. 1998; 23:1374-9.
• [12]Cho W, Wu C, Erkan S, Kang MM, Mehbod AA, Transfeldt EE. The effect on the pullout strength by the timing of pedicle screw insertion after calcium phosphate cement injection. J Spinal Disord Tech. 2011; 24:116-20.
• [13]Barber JW, Boden SD, Ganey T, Hutton WC. Biomechanical study of lumbar pedicle screws: does convergence affect axial pullout strength? J Spinal Disord. 1998; 11:215-20.
• [14]Felsenberg D, Gowin W. Bone densitometry by dual energy methods. Radiochemistry. 1999; 39(3):186-93.
• [15]Blattert T, Weckbach A. Kalziumphosphat vs. Polymethylmethacrylat. Erste Ergebnisse einer prospektiven, randomisierten, klinischen Vergleichsstudie zur perkutanen Ballonkyphoplastie. Trauma Berufskrankheit. 2004; 6:273-8.
• [16]Chang MC, Liu CL, Chen TH. Polymethylmethacrylate augmentation of pedicle screw for osteoporotic spinal surgery: a novel technique. Spine. 2008; 33(10):E317-24.
• [17]Bullmann V, Schmoelz W, Richter M, Grathwohl C, Schulte TL. Revision of cannulated and perforated cement-augmented pedicle screws: a biomechanical study in human cadavers. Spine. 2010; 35(19):E932-9.
• [18]Sterba W, Kim DG, Fyhrie DP, Yeni YN, Vaidya R. Biomechanical analysis of differing pedicle screw insertion angles. Clin Biomech (Bristol, Avon). 2007; 22:385-91.
• [19]Belkoff SM, Molloy S. Temperature measurement during polymerization of polymethylmethacrylate cement used for vertebroplasty. Spine. 2003; 28:1555-9.
• [20]Erkan S, Hsu B, Wu C, Mehbod AA, Perl J, Transfeldt EE. Alignment of pedicle screws with pilot holes: can tapping improve screw trajectory in thoracic spines? Eur Spine J. 2010; 19(1):71-7.
• [21]Chapman JR, Harrington RM, Lee KM, Anderson PA, Tencer AF, Kowalski DJ. Factors affecting the pullout strength of cancellous bone screws. Biomech Eng. 1996; 118(3):391-8.
• [22]Karataglis D, Kapetanos G, Lontos A, Christodoulou A, Christoforides J, Pournaras J. The role of the dorsal vertebral cortex in the stability of transpedicular screws: a biomechanical study in human cadaveric vertebrae. J Bone Joint Surg Br Vol. 2006; 88(5):692-5.
• [23]Hirano T, Hasegawa K, Washio T, Hara T, Takahashi H. Fracture risk during pedicle screw insertion in osteoporotic spine. J Spinal Disord. 1998; 11(6):493-7.
• [24]Kumano K, Hirabayashi S, Ogawa Y, Aota Y. Pedicle screws and bone mineral density. Spine. 1994; 19(10):1157-61.
• [25]Hirano T, Hasegawa K, Takahashi HE, Uchiyama S, Hara T, Washio T et al.. Structural characteristics of the pedicle and its role in screw stability. Spine. 1997; 22(21):2504-9.