Computer Modelling of Wrist Biomechanics: Translation into Specific Tasks and Injuries

Author(s): Michael J. Sandow*

Journal Name: Current Rheumatology Reviews

Volume 16 , Issue 3 , 2020

Become EABM
Become Reviewer

Graphical Abstract:


Background: The carpus is a complicated and functionally challenged mechanical system, advancements in the understanding of which have been compromised by the recognition that there is no standard carpal mechanical system and no typical wrist. This paper covers components of a larger project that seeks to develop a kinetic model of wrist mechanics to allow reverse analysis of the specific biomechanical controls or rules of a specific patient’s carpus. Those rules, unique to each patient, could be used to create a forward synthesis mathematical model to reproduce the individual’s anatomical motion in a virtual environment.

Objective and Methods: Based on the previous observations, the carpus essentially moves with only two degrees of freedom-pitch (flexion/extension) and yaw (radial deviation/ulnar deviation)-while largely preventing roll (pronation/supination). The objective of this paper is, therefore, to present the background and justification to support the rules-based motion (RBM) concept, which states that the motion of a mechanical system, such as the wrist, is the net interplay of four rules: morphology, constraint, interaction, and load. The stable central column theory (SCCT) of wrist mechanics applies the concept of RBM to the carpus, and by using a reverse engineering computational analysis model, a consistent pattern of isometric constraints was identified, creating a “two-gear four-bar” linkage. This study assessed the motion of the carpus using a 3D (three-dimensional) dynamic visualization model. The hypothesis was that the pattern and direction of motion of the proximal row and the distal row with respect to the immediately cephalad carpal bones or radius would be similar in all directions of wrist motion. To identify the unique motion segments, 3D models were created from five normal wrists that underwent CT scanning in multiple positions of radial and ulnar deviation as well as flexion and extension. Each carpal row (proximal and distal) was animated in a virtual environment with the cephalad carpal bones or radius held immobile. The rotational axis and position of each bone and each row were then compared in sagittal (flexion-extension) and coronal (radial and ulnar deviation) motion.

Results: The carpus appeared to have only two degrees of freedom, and yet was stable in those arcs with the loads applied proximally in the forearm. The proximal row moved in a singular arc, but with a varying extent during sagittal and coronal motion. The isometric constraints were consistent in both directions. The distal row moved on an axis formed by a pivot joint laterally (between the trapezium and scaphoid) and a saddle joint medially (between hamate and triquetrum). The sagittal and coronal alignment of this axis changed as the proximal row moved. This created a distinct pattern of row motion to achieve the various required positions of wrist function. On wrist radial deviation, the scaphoid (with the proximal row) was flexed and the distal row was extended, whereas, in wrist flexion, the scaphoid flexed (with the proximal row) and so did the distal row. The pattern was reversed in the opposite wrist movements. While the general direction of motion of each row was consistent, the extent was quite variable.

Conclusion: This review supports the SCCT of carpal mechanics and the carpus acting as a twogear four-bar linkage, as well as the concept of RBM as a means to understand the biomechanics of the wrist, and how this is translated into specific functional tasks. More sophisticated 3D modelling will be required to further understand the specifics of carpal motion; however, reverse engineering of the specific rules that define each individual wrist can also be applied to a mathematical model to provide a “what if” test of particular surgical interventions for a variety of wrist injuries. The use of quantitative 3D Computed Tomography Scan (CT) analysis, surgical planning and virtual surgical intervention allows potential surgical solutions to be applied to a computer model of an injured wrist to test the possible outcomes and prognosis of a proposed treatment.

Keywords: Computer modelling, injuries, computed tomography, SCCT, RBM, treatment.

Peh WC, Gilula LA. Normal disruption of carpal arcs. J Hand Surg Am 1996; 21(4): 561-6.
[] [PMID: 8842944]
Sandow MJ, Fisher TJ, Howard CQ, Papas S. Unifying model of carpal mechanics based on computationally derived isometric constraints and rules-based motion - the stable central column theory. J Hand Surg Eur Vol 2014; 39(4): 353-63.
[] [PMID: 24072199]
Moojen TM, Snel JG, Ritt MJ, Kauer JM, Venema HW, Bos KE. Three-dimensional carpal kinematics in vivo. Clin Biomech (Bristol, Avon) 2002; 17(7): 506-14.
[] [PMID: 12206941]
Crisco JJ, Coburn JC, Moore DC, Akelman E, Weiss APC, Wolfe SW. In vivo radiocarpal kinematics and the dart thrower’s motion. J Bone Joint Surg Am 2005; 87(12): 2729-40.
[] [PMID: 16322624]
Werner FW, Short WH, Green JK. Changes in patterns of scaphoid and lunate motion during functional arcs of wrist motion induced by ligament division. J Hand Surg Am 2005; 30(6): 1156-60.
[] [PMID: 16344171]
Short WH, Werner FW, Green JK, Sutton LG, Brutus JP. Biomechanical evaluation of the ligamentous stabilizers of the scaphoid and lunate: part III. J Hand Surg Am 2007; 32(3): 297-309.
[] [PMID: 17336835]
Hawking S. The illustrated brief history of time.Updated and expanded ed.. New York: Bantam Books. 1996; p. 15.
Papas S, Sandow MJ. (True Life Creations (SA) Pty Ltd, Australia): Animation technology. US Patent 7,236,817 2001 March; 5
Sandow M. The why, what, how and where of 3D imaging. J Hand Surg Eur Vol 2014; 39(4): 343-5.
[] [PMID: 24742741]
Sandow MJ III. Dynamic analysis of the wrist. Hand Surg 2015; 20(3): 366-8.
[] [PMID: 26387995]
Kuszyk BS, Heath DG, Bliss DF, Fishman EK. Skeletal 3-D CT: advantages of volume rendering over surface rendering. Skeletal Radiol 1996; 25(3): 207-14.
[] [PMID: 8741053]
Wikipedia. Occam’s Razor [Internet]. [Oct 18]; Available from:
Wikiquote. (Albert Einstein). [Oct 15]; Available from:
Salva-Coll G, Garcia-Elias M, Hagert E. Scapholunate instability: proprioception and neuromuscular control. J Wrist Surg 2013; 2(2): 136-40.
[] [PMID: 24436806]
Moritomo H, Apergis EP, Garcia-Elias M, Werner FW, Wolfe SW. International Federation of Societies for Surgery of the Hand 2013 Committee’s report on wrist dart-throwing motion. J Hand Surg Am 2014; 39(7): 1433-9.
[] [PMID: 24888529]
Taleisnik J. The ligaments of the wrist. J Hand Surg Am 1976; 1(2): 110-8.
[] [PMID: 1018078]
Craigen MA, Stanley JK. Wrist kinematics. Row, column or both? J Hand Surg [Br] 1995; 20(2): 165-70.
[] [PMID: 7797964]
Lichtman DM, Schneider JR, Swafford AR, Mack GR. Ulnar midcarpal instability-clinical and laboratory analysis. J Hand Surg Am 1981; 6(5): 515-23.
[] [PMID: 7276484]
Hargreaves DG. Midcarpal instability. J Hand Surg Eur Vol 2016; 41(1): 86-93.
[] [PMID: 26598109]

Rights & PermissionsPrintExport Cite as

Article Details

Year: 2020
Published on: 22 September, 2020
Page: [178 - 183]
Pages: 6
DOI: 10.2174/1573397115666190119095311
Price: $65

Article Metrics

PDF: 16