Biomechanical Assessment of the Total Wrist

6.4 Finite Element Analysis

6.4.4 Biomechanical Assessment of the Total Wrist

As far as treatment is concerned, it is vital to solve two main problems caused by RA as shown in the previous chapter; which were the effect of high contact pressure and imbalance load transmission. The ReMotion^TM implant used in the TWA model anticipated two main design concepts—distal radius resurfacing and intercarpal fusion—to minimize motion that could cause metacarpal perforation and implant loosening. FEA results have confirmed the ability of this implant system to reduce high contact pressure in RA bones through intercarpal fusion approach. This implant system fused the affected bones using two screws, one central peg and bone grafts, thus has resulted in minimised stress concentration and therefore reduced the potential problem of wear at the articulation.

In terms of load transmission, the disproportionate pattern of stress distributions observed in the RA model changed to a more uniform pattern after TWA (Fig.6.5).

This finding complied with the implant design concept of intercarpal fusion to

6.4 Finite Element Analysis 67

attain solid bony mass and therefore uniform pattern of loading [23]. Better fusion could be achieved by using bone graft with a modulus close to the bone; our parametric analyses showed that bone graft with a modulus of 5 GPa produced more encouraging results in terms of uniform load transmission and lower contact pressure (Fig.6.7). This is in agreement with the concept of avoiding elasticity mismatch [24] to prevent unphysiological loading and unwarranted bone remod- elling. In clinical practice, there were various sources of bone grafts with different modulus ranging from 0.1 (iliac crest) to 5 GPa (fibula) [19].

This chapter has presented several findings that reaffirmed the good clinical outcome of a specific implant system for TWA as confirmed in a short term follow-up study reported by Herzberg [25]. We have provided further insights into the biomechanical aspects of rheumatic wrist and the corresponding changes after TWA. As long term follow-up study is still required, this study strongly recom- mends the use of TWA as a viable alternative to total wrist fusion in patients with rheumatoid arthritis especially in case of bilateral involvement [26].

References

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2. MacCullough MBA (2006) Clinical and biomechanical analysis of total wrist arthroplasty devices. Dissertation, University of Iowa, Iowa

3. Bajuri MN, Kadir MRA (2010) Biocomputational comparative study of Rheumatoid Arthritis of the wrist joint before and after arthroplasty; carpal stability analysis. In: Biomedical Engineering and Sciences (IECBES), 2010 IEEE EMBS conference on 30 Novemb 2010–2 Dec 2010, pp 270–275

4. Lorei MP, Figgie MP, Ranawat CS, Inglis AE (1997) Failed total wrist arthroplasty. Analysis of failures and results of operative management. Clin Orthop Relat Res 342:84–93 5. Huang KM, Naidu SH (2002) Total wrist arthroplasty: is there a role? Curr Opin Orthop

13(4):260–268

6. Adams BD (2010) Complications of wrist arthroplasty. Hand Clin 26(2):213–220 7. Anderson MC, Adams BD (2005) Total wrist arthroplasty. Hand Clin 21(4):621–630 8. Abdul-Kadir MR, Hansen U, Klabunde R, Lucas D, Amis A (2008) Finite element modelling

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durability and knee function after total knee arthroplasty in the morbidly obese patient.

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10. Menon J (1998) Universal total wrist implant: experience with a carpal component fixed with three screws. J Arthroplast 13(5):515–523

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13. Rahman WA, Garbuz DS, Masri BA (2010) Randomized controlled trial of radiographic and patient-assessed outcomes following fixed versus rotating platform total knee arthroplasty.

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68 6 Finite Element Analysis

14. Adams BD (2006) Total wrist arthroplasty for rheumatoid arthritis. Int Congr Ser 1295:83–93 15. Tajdari M, Javadi M (2006) A new experimental procedure of evaluating the friction

coefficient in elastic and plastic regions. J Mater Process Technol 177(1–3):247–250 16. Cheng H-YK, Lin C-L, Lin Y-H, Chen AC-Y (2007) Biomechanical evaluation of the

modified double-plating fixation for the distal radius fracture. Clin Biomech 22(5):510–517 17. Sun D, Wharton JA, Wood RJK (2009) Micro-abrasion-corrosion of cast CoCrMo—effects

of micron and sub-micron sized abrasives. Wear 267(1–4):52–60

18. Dowson D, Fisher J, Jin ZM, Auger DD, Jobbins B (1991) Design considerations for cushion form bearings in artificial hip joints. ARCHIVE: Proc Inst Mech Eng Part H J Eng Med 1989–1996 203–210, 205(28):59–68

19. Zander T, Rohlmann A, Klöckner C, Bergmann G (2002) Effect of bone graft characteristics on the mechanical behavior of the lumbar spine. J Biomech 35(4):491–497

20. Gislason MK, Nash DH, Nicol A, Kanellopoulos A, Bransby-Zachary M, Hems T, Condon B, Stansfield B (2009) A three-dimensional finite element model of maximal grip loading in the human wrist. Proc Inst Mech Eng Part H J Eng Med 223(7):849–861

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23. Gupta A (2008) Total wrist athroplasty. J Orthop Res 37:12–16

24. Murali P, Bhandakkar TK, Cheah WL, Jhon MH, Gao H, Ahluwalia R (2011) Role of modulus mismatch on crack propagation and toughness enhancement in bioinspired composites. Phys Rev E 84(1):015102

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References 69

Summary

This monograph has sufficiently presented outcomes from finite element analyses of the simulated healthy, diseased and treated wrist joint, and they could be summarised as follows:

1. The absence of the cartilage, the abnormal dislocations of bones with sharp edges and the laxity of the ligaments in the rheumatic wrist have resulted in significant unphysiological alteration of the biomechanical behaviours of the wrist joint, as shown and elucidated in this monograph. TWA was then proving to provide improvement in reducing contact pressure and assuring balance load transmission. However, there were rooms for enhancements as the ultimate goal to restore the function of the healthy wrist still not absolutely achieved.

2. Efforts in simulating the complex wrist joint experienced various difficulties and it was even pronounced when dealing with the pathological conditions and its treatments. Therefore, the finite element model development and analyses mentioned here were performed under certain level of uncertainty and assumptions. Quantification was found to be very challenging as the available information is fairly limited. For the RA model construction, for instance, there was only one out of 10 characteristics has been quantified which was the carpometacarpal ratio. The remaining characteristics were simulated by making relevance assumptions according to clinical reports.

3. Technical aspects of the model development need to be further explored. Issues on linearity (linear or non-linear) of the simulated ligaments, material properties (isotropic, othotropic etc.) order of elements element type (tetrahedral–

hexahedrals), contact modeling and also effect of sharp gradient between two material properties, require further explorations.

M. Nazri Bajuri and M. R. Abdul Kadir,Computational Biomechanics of the Wrist Joint, SpringerBriefs in Computational Mechanics, DOI: 10.1007/978-3-642-31906-8, ÓSpringer-Verlag Berlin Heidelberg 2013

Index

Arthrodesis,30 Arthroplasty,59,60,67 Atrophy,52

Bone graft,60,63,67,68

Cancellous,33,35,42,49, 52,60,63

Capitate,1,2,5,8,9,14,37,45,60 Carpal,1–5,8–10,15,16,19,20,29,42–45,

47,60,63,66,67

Carpometacarpal,2,43,49,64,71 Carpus,1,2,5,29,43,53,60 Cartilage,4,14,21,28,38,42 Contact pressure,52–56,65,67 Cortical,33,35,42,49,50,60,63

Distal,1,2,5,6,8,9,19,33,43,45

Elastic modulus,49 Erosion,28,29,42,47,53

Fatigue,18

Force,4,14–16,20,49,62 Forearm,1,9,11,19,33,50

Hamate,1–3,5,11,37,38,49 Hip,8,19,59

Impaction,29,59

Kienbock’s,19

Knee,8,14,16,19,59,60

Ligament,2,3,5,7,8,11,15,20,29 Linear,15,20,36,39,49,60 Load transmission,13,20,66–68 Lunate,1,2,19,29,45,47,60

Metacarpal,1–3,5,9,17,25,30,31,33,43, 46,49,53,62,64,67

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