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Clinical Problem
Clinical Problem
There are about 400,000 total hip replacement procedures per year in US.
Dislocation happens in 0.2-10% of total hip replacements.
77% of those dislocations happen within the first year after the procedure.
Dislocations are painful, damaging to implants, and can require revisional procedures to fix the damage caused by dislocations.
- It is difficult to train patients to abide by motion restrictions after a total hip replacement.
This is a significant factor in dislocation of the hip.
The main restrictions are to keep the hip joint less than 90° of flexion and less than 15° external (lateral) rotation.
Examples of habitual movements violating motion restrictions:
bending down to grab something from the floor
bending to put on socks or shoes
getting up from a seat
Risk chart designed in collaboration with Dr. Andrew Schmidt, orthopedic surgeon at Hennepin County Medical Center
The chart outlines the risk of hip angles following a total hip replacement.
The device will reference this chart to warn the user when the approach high risk positions.
Current solutions
Current solutions
Restrictive Bracing
Restrictive Bracing
Mechanical locking braces (left) that physically restrict the hip from risky positions.
They have not shown to be significantly effective in preventing dislocation (Y. Ishii et. al. 2012).
Abduction cushions (right) are used when sleeping to physically restrict the hip from risky positions.
Additional Surgical Procedures
Additional Surgical Procedures
Retention ring system (left) mechanically locks the prosthetic into place.
Has a 42% failure rate after 10 years (Biomet Orthopedics, 2002)
Robotic assisted surgery (right) helps surgeons to optimally place the hip implant.
High cost but limited efficacy (Waddell et. al 2017)
Need Statement
Need Statement
There is a clinical need to reduce the occurrence of hip dislocations after total hip replacements without the use of bulky restrictive braces by better educating patients on their motion restrictions in real-time.
There is a clinical need to reduce the occurrence of hip dislocations after total hip replacements without the use of bulky restrictive braces by better educating patients on their motion restrictions in real-time.
Proposed Solution
Proposed Solution
Wearable hip angle monitor that measures
Flexion and extension
Internal and external rotation
Consists of 2 sensors connected via Bluetooth
Sensor 1: above the hip on the pelvis
Sensor 2: proximal end of the femur
Calculates flexion/extension and internal/external rotation angles to determine if patient is in risky position
Each encased sensor unit includes
Vibration motor
Speaker
LED
9V battery
MPU6050 Inertial Measurement Unit
Sensor units are held in compression fabric to be held tight to the body but comfortable to allow free movement
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