My primary complete accomplishment of the Fall 2017 semester in the Musculoskeletal Soft Tissue Laboratory is the addition of 3 3D printed parts to the grip strength device to improve the precision of the device. To reach the end result of these 3 parts, I 3D-modelled the parts, 3D printed the prototypes, and integrated the parts into the device for testing. Near the end of the semester I had seen this process through, and the grip strength device is now fully functional and the most accurate and precise it has been. Aside from my primary project of the grip strength device, Alex Reiter and I reconstructed AGATHA with thicker acrylic

Kivitz, Griffin

Lake, Spencer, Dr.

English

Washington University St. Louis: Open Scholarship

Washington University in St. Louis Washington University Open Scholarship Mechanical Engineering and Materials Science Independent Study Mechanical Engineering & Materials Science 12-21-2017 Redesigning a Bilateral Grip Strength Device for Assessing Forelimb Function in Rodents Griffin Kivitz Washington University in St. Louis Spencer Lake Dr. Washington University in St. Louis Follow this and additional works at: https://openscholarship.wustl.edu/mems500 Recommended Citation Kivitz, Griffin and Lake, Spencer Dr., "Redesigning a Bilateral Grip Strength Device for Assessing Forelimb Function in Rodents" (2017). Mechanical Engineering and Materials Science Independent Study. 55. https://openscholarship.wustl.edu/mems500/55 This Final Report is brought to you for free and open access by the Mechanical Engineering & Materials Science at Washington University Open Scholarship. It has been accepted for inclusion in Mechanical Engineering and Materials Science Independent Study by an authorized administrator of Washington University Open Scholarship. For more information, please contact digital@wumail.wustl.edu. 	  	   	  Griffin	  Kivitz	  Progress	  Report	  Fall	  2017	  Kivitz,	  Griffin	  Musculoskeletal	  Soft	  Tissue	  Laboratory	  Summary:	  	  My	  primary	  complete	  accomplishment	  of	  the	  Fall	  2017	  semester	  in	  the	  Musculoskeletal	  Soft	  Tissue	  Laboratory	  is	  the	  addition	  of	  3	  3D	  printed	  parts	  to	  the	  grip	  strength	  device	  to	  improve	  the	  precision	  of	  the	  device.	  	  To	  reach	  the	  end	  result	  of	  these	  3	  parts,	  I	  3D-­‐modelled	  the	  parts,	  3D	  printed	  the	  prototypes,	  and	  integrated	  the	  parts	  into	  the	  device	  for	  testing.	  	  Near	  the	  end	  of	  the	  semester	  I	  had	  seen	  this	  process	  through,	  and	  the	  grip	  strength	  device	  is	  now	  fully	  functional	  and	  the	  most	  accurate	  and	  precise	  it	  has	  been.	  	  Aside	  from	  my	  primary	  project	  of	  the	  grip	  strength	  device,	  Alex	  Reiter	  and	  I	  reconstructed	  AGATHA	  with	  thicker	  acrylic.	  	  	  	  	  Introduction:	  	  I	  have	  been	  working	  in	  this	  lab	  since	  May	  of	  2017.	  	  During	  the	  summer,	  Alex	  and	  I	  performed	  a	  preliminary	  study	  to	  determine	  any	  issues	  we	  would	  face	  and	  if	  any	  modifications	  need	  to	  be	  made	  to	  the	  methods	  we	  use.	  	  	  My	  primary	  project	  in	  the	  lab	  is	  analyzing	  and	  performing	  grip	  strength	  tests	  on	  our	  rat	  elbow	  model.	  	  We	  use	  the	  grip	  strength	  device	  to	  measure	  individual	  limb	  strength	  of	  the	  rats	  during	  the	  6	  weeks	  after	  free	  mobilization.	  	  An	  in	  depth	  description	  of	  the	  grip	  strength	  device	  can	  be	  found	  in	  Appendix	  A.	  	   Upon	  returning	  to	  the	  lab	  from	  my	  summer	  work,	  Alex	  informed	  me	  of	  a	  drop	  in	  force	  readings	  of	  the	  left	  load	  cell	  in	  our	  setup.	  	  	  This	  report	  with	  cover	  the	  methods	  we	  used	  to	  determine	  the	  issue	  and	  the	  process	  we	  went	  through	  to	  fix	  the	  issue.	  	  In	  addition,	  I	  will	  briefly	  discuss	  the	  smaller	  contribution	  of	  reconstructing	  AGATHA.	  	  	  Methods:	  	  The	  journey	  to	  the	  current	  product	  in	  the	  lab	  consisted	  of	  3	  distinct	  steps.	  	  First,	  we	  simply	  replaced	  the	  load	  cells	  with	  new	  load	  cells	  with	  a	  higher	  maximum	  load	  capacity	  of	  2kg.	  	  Next,	  we	  removed	  the	  linear	  slides	  from	  their	  housing	  and	  reconstructed	  the	  entire	  device	  with	  extremely	  small	  tolerances.	  	  Finally,	  we	  came	  to	  the	  realization	  that	  designing	  the	  device	  in	  a	  way	  that	  the	  load	  cells	  align	  themselves	  is	  the	  only	  way	  to	  get	  consistent	  and	  logical	  measurements.	  The	  parts	  for	  the	  final	  design	  were	  3D	  modelled	  and	  3D	  printed	  in	  PLA.	  	  	  	  Replacing	  the	  Load	  Cells:	  	  To	  determine	  the	  calibration	  error	  in	  our	  setup,	  I	  oriented	  the	  grip	  strength	  device	  so	  the	  ladders	  are	  pointed	  straight	  down,	  as	  shown	  in	  fig.	  1.	  	  When	  hanging	  500g	  and	  200g	  masses	  from	  the	  rungs,	  the	  load	  cell	  did	  not	  give	  a	  correct	  reading	  according	  to	  the	  weight	  of	  the	  calibration	  mass.	  	  	  	  After	  recalibrating	  each	  load	  cell	  several	  times,	  we	  were	  unable	  to	  obtain	  any	  sort	  of	  accurate	  and	  precise	  reading.	  	  It	  was	  known	  that	  the	  left	  load	  cell	  was	  slightly	  bent,	  so	  we	  blamed	  that	  for	  our	  difficulties.	  	  We	  upgraded	  load	  cell	  from	  the	  LoadStar	  REB7	  1kg	  mini-­‐load	  cell	  to	  the	  2kg	  version	  of	  the	  same	  model.	  	  When	  replacing	  the	  load	  cells	  didn’t	  solve	  our	  problems,	  we	  tried	  to	  reconstruct	  the	  set	  up	  to	  more	  properly	  align	  the	  load	  cells	  with	  the	  rungs	  through	  the	  linear	  slide.	  	  	  Reconstructing	  the	  Device:	  	  The	  most	  notable	  change	  we	  made	  was	  removing	  the	  linear	  slide	  from	  its	  housing	  to	  have	  it	  attached	  directly	  to	  the	  base	  plate,	  as	  opposed	  to	  attached	  to	  a	  housing	  which	  is	  attached	  to	  a	  base	  plate.	  	  In	  addition,	  the	  holes	  were	  drilled	  with	  very	  low	  tolerances	  to	  ensure	  proper	  alignment	  of	  the	  device.	  	  	  This	  did	  not	  fix	  the	  problem	  of	  getting	  repeatable	  and	  representative	  readings.	  	  The	  linear	  slide	  was	  not	  fully	  eliminating	  2	  and	  3	  dimensional	  motion,	  and	  the	  metal	  rungs	  slightly	  deflect	  as	  well	  when	  under	  load.	  	  We	  had	  the	  idea,	  instead	  of	  making	  the	  parts	  of	  the	  device	  tight	  to	  ensure	  alignment,	  we	  should	  give	  the	  load	  cell	  the	  freedom	  for	  its	  position	  to	  move	  depending	  on	  the	  direction	  of	  the	  force	  on	  the	  rungs.	  	  	  	  3D	  Modelling	  and	  Printing:	  	  After	  a	  few	  dimensioning	  and	  tolerance	  errors,	  we	  arrived	  at	  the	  final	  3-­‐part	  assembly.	  	  The	  SolidWorks	  drawings	  for	  each	  part	  can	  be	  found	  in	  Appendix	  B.	  	  Images	  of	  the	  final	  and	  tested	  device	  can	  be	  seen	  below	  in	  fig.	  2.	  	  Fig	  1.	  	  The	  old	  (summer)	  version	  of	  the	  grip	  strength	  device	  is	  shown,	  and	  the	  red	  arrow	  indicates	  the	  direction	  of	  gravity.	  	  This	  is	  the	  orientation	  of	  the	  device	  used	  for	  calibration.	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  This	  assembly	  works	  because	  the	  load	  cell	  is	  not	  tightened	  to	  a	  fixed	  part,	  but	  it	  is	  still	  restricted	  in	  movement	  by	  its	  surroundings.	  	  The	  Square	  Nut	  is	  a	  square	  piece	  with	  a	  hexagonal	  hole	  in	  the	  center.	  	  We	  superglued	  an	  M3	  nut	  into	  the	  hole,	  and	  essentially	  created	  a	  square	  nut.	  	  	  	  The	  Front	  Cover	  piece	  simply	  sits	  on	  the	  top	  of	  the	  linear	  slide.	  It	  is	  dimensioned	  to	  fit	  over	  it	  perfectly	  and	  not	  slide	  forward	  or	  backward.	  	  	  	  Two	  bolts	  run	  through	  the	  front	  cover	  toward	  the	  back	  of	  the	  device	  to	  secure	  the	  Back	  Wall	  in	  place.	  	  The	  Back	  Wall	  prevents	  the	  load	  cell	  from	  being	  pushed	  backward.	  	  Also,	  the	  Back	  Wall	  has	  a	  square	  hole	  in	  it	  that	  the	  Square	  Nut	  fits	  through.	  	  This	  Square	  Nut	  in	  the	  Square	  Hole	  restricts	  rotation	  of	  the	  load	  cell	  because	  the	  corners	  of	  the	  square	  nut	  will	  hit	  the	  walls	  of	  the	  square	  hole.	  	  	  	  After	  assembling	  the	  device,	  we	  performed	  a	  calibration	  test	  and	  found	  that	  the	  newly	  improved	  setup	  gave	  accurate	  and	  repeatable	  readings.	  	  We	  then	  conducted	  a	  test	  with	  rats	  to	  ensure	  that	  the	  device	  would	  work	  in	  practice,	  and	  everything	  proceeded	  as	  expected.	  	  	  	  The	  grip	  strength	  device	  is	  ready	  to	  be	  used.	  	  	  Square	  Nut	  Back	  Wall	  Front	  Cover	  Fig	  2:	  The	  Square	  Nut,	  Back	  Wall,	  and	  Front	  Cover	  3D-­‐printed	  pieces	  are	  labelled,	  and	  the	  device	  is	  shown	  at	  three	  different	  angles.	  	  Reconstructing	  AGATHA:	  	  A	  difficult	  problem	  we	  faced	  with	  the	  AGATHA	  arena	  was	  the	  lack	  of	  precision	  with	  which	  the	  acrylic	  was	  cut.	  	  The	  back	  wall	  of	  the	  arena	  did	  not	  sit	  flush	  with	  the	  bottom,	  so	  shadows	  formed	  and	  the	  lighting	  was	  not	  ideal.	  	  	  	  After	  testing	  potential	  solutions,	  including	  the	  use	  of	  a	  rubber	  gasket	  on	  the	  bottom	  of	  the	  back	  wall,	  and	  lining	  the	  bottom	  of	  the	  back	  wall	  with	  foam,	  we	  realized	  that	  we	  need	  to	  just	  buy	  new	  acrylic.	  	  We	  bought	  all	  new	  acrylic	  pieces	  for	  the	  arena	  and	  had	  them	  cut	  thicker	  to	  ensure	  a	  smooth	  edge.	  	  On	  my	  last	  day,	  we	  constructed	  the	  new	  arena	  from	  these	  pieces,	  and	  although	  they	  were	  not	  cut	  quite	  as	  precise	  as	  we	  would	  have	  liked,	  we	  will	  be	  able	  to	  trouble	  shoot	  the	  slight	  imprecisions.	  	  	  Conclusion	  and	  Future	  Work:	  	  The	  primary	  accomplishment	  of	  my	  time	  in	  the	  lab	  this	  semester	  was	  the	  redesigning	  and	  prototyping	  of	  the	  grip	  strength	  device.	  	  This	  entire	  semester	  was	  in	  a	  way	  a	  trouble	  shooting	  semester	  to	  fix	  the	  problems	  we	  encountered	  from	  the	  summer.	  Next	  semester	  and	  over	  winter	  break,	  Alex	  and	  I	  will	  be	  collecting	  data	  with	  the	  newly	  improved	  grip	  strength	  device	  to	  assess	  the	  effectiveness	  of	  treatment	  therapies	  for	  recovery	  of	  strength	  after	  injury.	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  Design and Use of a Bilateral Grip Strength Device for Assessing Forelimb Function in Rodents Griffin Kivitz, Alex Reiter, Ryan Castile, Peter Andres, Chelsey Dunham, Aaron Chamberlain, and Spencer Lake  Washington University in St. Louis, St. Louis, MO   Introduction: Post traumatic joint contracture (PTJC) is a debilitating condition that effects up to 50% of patients after suffering an elbow dislocation or fracture [1]. PTJC can result in permanent joint stiffness and a loss of range of motion long after the injury [1]. Our lab has recently established the first animal model of PTJC in the elbow replicating this debilitating condition in Long-Evans rats [2-4]. We sought to make limb-specific longitudinal strength measurements to assess how PTJC affects elbow joint function, however commercially available devices compute an average value across both limbs [5]. A custom grip strength device was developed to track individual limb function during rehabilitation in our unilateral elbow injury model. In this study, we describe the novel grip strength device and demonstrate its use by showing functional differences between injured limbs and control/contralateral limbs in our rat model of PTJC. Materials and Methods: Long-term PTJC was induced in Long-Evans rats as done previously [2-4]. Briefly, animals received a lateral collateral ligament transection and capsulotomy of the left elbow, followed by unilateral immobilization of the injured limb. After 6 weeks, bandages were removed and grip strength measurements were obtained one day later using a custom grip strength test device. The device consists of two sets of metal rungs, or ladders, each held in place by a linear slide and connected to separate load cells (Fig. 1). This setup allows for the measurement of individual limb strength, important for tracking progression/recovery of a unilateral injury, and for variability in the pronation-supination positioning of the rungs. Specifically, each ladder can be rotated inward or outward to measure strength in a pronated, supinated, or neutral position. The paws of the rat were placed on the same rung of each ladder and the rat was pulled by the base of its tail along the direction of the linear slides. Six trials were collected on injured (n=8) and age-matched control rats (n=8). For each trial, the right, left, and total forces exerted on the load cells were recorded. For each animal, force values were averaged across the six trials; these average values were then used to compare groups (i.e., injured vs. control).  Side-to-side limb differences were compared within each group using paired t-tests, and unpaired t-tests were used to compare groups. Results and Discussion: The grip strength device is similar in concept to the setup of a grid or T-bar connected to a load cell, which is a common apparatus in grip strength studies [6]. However, this device presents a novel advance because it allows for the data collection of individual limbs as well as the ability to test grip strength in the pronated or supinated position. The grip strength of injured/immobilized limbs was significantly less than contralateral uninjured limbs and the grip strength of control animals (Fig 2a). Furthermore, contralateral limb grip strength was not significantly different from control (Fig 2a). Likewise, the ratio of the left to right grip strength of the injured rats (L/R ratio) was significantly less than the ratio for control rats (Fig 2b). As expected, L/R ratio for controls was ~1. During testing, three injured rats would not grip the ladder with their left paw; these rats were excluded from the data (thus, n=5 for injured data) but further demonstrate limb weakness in this animal model. Results show that the PTJC protocol induces significant functional consequences (i.e., decreased strength) in the injured limbs of animals, similar to deficits common to clinical patients with PTJC.  Conclusions: This study described a custom bilateral grip strength device/method and demonstrated its ability to measure functional changes in our rat elbow model of PTJC. Moving forward, these tests will be performed to track recovery of limb strength post-immobilization. We will also make longitudinal measurements to evaluate the effectiveness of therapy strategies looking to reduce or prevent PTJC in our rat elbow model of PTJC.  References: [1] Anakwe RE JBJS, 2011;93(13): 1220-6. [2] Lake SP JOR, 2016;34(2):354-64. [3] Dunham CL JSES, 2017;26(4):611-618. [4] Dunham CL JBME, 2017;139(7). [5] Bonetto A BoneKey Rep, 2015;4(732)  [6] Maurissen JPJ Neuro Tera, 2003;25(5):543-553.  Acknowledgements: Funding from ASES, NIH (R03 ARR067504 and T32 EB018266), and NSF (DGE-1745038). Fig. 2: (A) Significant decrease in injured left arm strength compared to contralateral limb and control limbs. (B) Significant decrease in the injured rats’ left to right grip strength ratio compared with control ratio validating the method for grip strength testing.  (* p<.05) 01 5 03 0 04 5 06 0 07 5 09 0 0Max,Force,(g)C o n tro l In ju redL e ft L e ft R ig h tR ig h t* *A!0 .00 .20 .40 .60 .81 .01 .2L/R+Ratio *In ju redC o n tro lB!Fig. 1: Grip strength testing device has two ladders, each connected to separate load cells through a linear slide. !Appendix	  A	  –	  Abstract	  submitted	  to	  BMES	  discussing	  the	  grip	  strength	  device	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	   1.48  3.24  6.76  8.52  10  1.95  5  8.05  10  4 Griffin Kivitz2 1ABAB12DO NOT SCALE DRAWINGfit_nut_2  drawingSHEET 1 OF 1UNLESS OTHERWISE SPECIFIED:SCALE: 5:1 WEIGHT: REVDWG.  NO.ASIZETITLE:NAME DATECOMMENTS:Q.A.MFG APPR.ENG APPR.CHECKEDDRAWNFINISHMATERIALINTERPRET GEOMETRICTOLERANCING PER:DIMENSIONS ARE IN INCHESTOLERANCES:FRACTIONALANGULAR: MACH      BEND TWO PLACE DECIMAL    THREE PLACE DECIMAL  APPLICATIONUSED ONNEXT ASSYPROPRIETARY AND CONFIDENTIALTHE INFORMATION CONTAINED IN THISDRAWING IS THE SOLE PROPERTY OF<INSERT COMPANY NAME HERE>.  ANY REPRODUCTION IN PART OR AS A WHOLEWITHOUT THE WRITTEN PERMISSION OF<INSERT COMPANY NAME HERE> IS PROHIBITED. 3.03  5  6.97  10  11.60  22.40  24  27.03  29  30.97  34  2.60  13.40  16  16.54  36.47  40.47  8 X R1.97  3 Griffin Kivitz2 1ABAB12DO NOT SCALE DRAWINGback_part for nut_revised_2 drawingSHEET 1 OF 1UNLESS OTHERWISE SPECIFIED:SCALE: 2:1 WEIGHT: REVDWG.  NO.ASIZETITLE:NAME DATECOMMENTS:Q.A.MFG APPR.ENG APPR.CHECKEDDRAWNFINISHMATERIALINTERPRET GEOMETRICTOLERANCING PER:DIMENSIONS ARE IN INCHESTOLERANCES:FRACTIONALANGULAR: MACH      BEND TWO PLACE DECIMAL    THREE PLACE DECIMAL  APPLICATIONUSED ONNEXT ASSYPROPRIETARY AND CONFIDENTIALTHE INFORMATION CONTAINED IN THISDRAWING IS THE SOLE PROPERTY OF<INSERT COMPANY NAME HERE>.  ANY REPRODUCTION IN PART OR AS A WHOLEWITHOUT THE WRITTEN PERMISSION OF<INSERT COMPANY NAME HERE> IS PROHIBITED.Appendix	  B	  –	  SolidWorks	  drawings	  of	  the	  3	  3D-­‐printed	  parts	  –	  All	  dimensions	  are	  in	  mm.	  	  	  	  	   	  	  	  Square	  Nut	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  Back	  Wall	   1.50  6  9  27  30  34.50  36  6  18 20.50 23  27.50  32.92  4 X 2.90  1.50  24  32.50  34  39 Griffin Kivitz2 1ABAB12DO NOT SCALE DRAWINGFront part drawingSHEET 1 OF 1UNLESS OTHERWISE SPECIFIED:SCALE: 1:1 WEIGHT: REVDWG.  NO.ASIZETITLE:NAME DATECOMMENTS:Q.A.MFG APPR.ENG APPR.CHECKEDDRAWNFINISHMATERIALINTERPRET GEOMETRICTOLERANCING PER:DIMENSIONS ARE IN INCHESTOLERANCES:FRACTIONALANGULAR: MACH      BEND TWO PLACE DECIMAL    THREE PLACE DECIMAL  APPLICATIONUSED ONNEXT ASSYPROPRIETARY AND CONFIDENTIALTHE INFORMATION CONTAINED IN THISDRAWING IS THE SOLE PROPERTY OF<INSERT COMPANY NAME HERE>.  ANY REPRODUCTION IN PART OR AS A WHOLEWITHOUT THE WRITTEN PERMISSION OF<INSERT COMPANY NAME HERE> IS PROHIBITED.	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  Front	  Cover

Redesigning a Bilateral Grip Strength Device for Assessing Forelimb Function in Rodents

https://openscholarship.wustl.edu/cgi/viewcontent.cgi?article=1059&context=mems500

Redesigning a Bilateral Grip Strength Device for Assessing Forelimb Function in Rodents

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Washington University St. Louis: Open Scholarship