Transcript Elbow reaction loads in a sit-to-stand activity are quite

6th ISOC Meeting
Elbow reaction loads
in a sit-to-stand activity
are quite high and
are unaffected by TEA
Tim Wright, PhD
Disclosures
Disclosure: I DO have a financial relationship with
commercial interests
Company
Type of Relationship
Lima, Inc.
Royalty
The Challenge


Total elbow arthroplasties predominantly fail
through aseptic loosening and bushing wear
These failure modes are associated with joint
loading during activities of daily living (ADL)
Wright, JSES 2005
3
The Approach
What can we learn from interrogating the
failures?
What are the mechanical demands of the
patient?
Can we apply the lessons that we learn to
improve performance?
Mechanical Demands


Low demand ADL’s studied in healthy patients
Less data available on higher demand ADL’s
TEA patients may have altered elbow mobility
that influences kinematics and joint loading
Mechanical Demands


Low demand ADL’s studied in healthy patients
Less data available on higher demand ADL’s
TEA patients may have altered elbow mobility
that influences kinematics and joint loading
Objective
To compare kinematics and reaction loads
across the elbow for normal and TEA patients
during a sit-to-stand and stand-to-sit activity
6
Kinematics – Feeding & Reach
Motion Analysis of TEA patients
Determining Elbow Forces
SIMM model of upper extremity
• Bone geometry
• Joint motion
• Muscle paths including wrap
• Muscle characteristics (PCSA)
Segmental inertial properties
•Mass
•Center of mass
Determining Elbow Forces
Optimization
• Objective
Minimize: Σ (Muscle stresses)3
• Constraints
 Stability – JRF must lie in the joint
 Muscle forces  0
 Muscle forces  Fmax  PCSA
Loads Across the Elbow
42%
Percent motion: 42%
Sit to Stand to Sit
Sit to Stand , Stand to Sit
9 Normal volunteers
8 Total elbow arthroplasty patients
Motion Capture with Instrumented Chair
Data: Kinematics & External Loads
Inverse Dynamic Computational Model
Sit
Stand
Sit
Reaction Loads in Elbow Coordinate System
Groups for Comparison
• Normals
• TEA patients: Operated Limb
• TEA patients: Non-Operated
Limb
11
12
13
Kinematics (Sit to Stand)
0%
20%
40%
60%
80%
100%
Reaction Loads (Sit to Stand)
0%
20%
40%
60%
80%
100%
Kinematics (Stand to Sit)
0%
20%
40%
60%
80%
100%
Reaction Loads (Stand to Sit)
0%
20%
40%
60%
80%
100%
Loads on the Implant
18
Summary

Joint loads in the elbow are large in both normal
volunteers and total elbow arthroplasty patients



Kinematics not different between normal volunteers
and total elbow arthroplasty patients


Lower loads on operated limbs vs. normals might reflect weakness
Lower loads on non-operated limbs vs. normals hint at lower
extremity compensation
Lumbar Pitch, Elbow Flexion, and Pronation were comparable to
previous studies
Given the importance of sit-to-stand ADL to patient
function, higher joint load cases should be considered
in total elbow arthroplasty and rehabilitation
Collaborators and Funding Source
Mark Figgie
Bob Hotchkiss
Joe Lipman
Dan Choi
Kirk Gunsallus Garry Hayeck Sherry Backus