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Characterisation of the patellar tendon reflex in cerebral palsy children using motion analysis
Rory O'Sullivan1, Damien Kiernan2, Michael Walsh2
1The Gait Laboratory, Central Remedial Clinic, Vernon Avenue, Clontarf, Dublin 3, Ireland. rosullivan@crc.ie.
Insights
Children with cerebral palsy (CP) exhibit a brisk patellar tendon reflex (PTR), indicated by reduced EMG reflex latency. Motion analysis confirms differences in knee movement, but not movement latency or velocity, in CP patients.
Area of Science:
- Neurology
- Biomedical Engineering
- Pediatrics
Background:
- The patellar tendon reflex (PTR) is a key diagnostic tool for neurological assessment.
- Quantifying reflex responses can be subjective; motion analysis offers objective measurement.
- Motion analysis can objectively assess the PTR without specialized equipment.
Purpose of the Study:
- To compare the patellar tendon reflex (PTR) in children with cerebral palsy (CP) against age and height-matched controls.
Main Methods:
- Electromyography (EMG) assessed reflex latency in the rectus femoris muscle.
- Knee movement latency, angular displacement, and peak angular velocity were captured using motion analysis systems.
Main Results:
- EMG reflex latency was significantly reduced in CP children (13.11 ms) compared to controls (18.11 ms), indicating a brisk reflex.
- Knee angular displacement was significantly lower in CP (12.82°) versus controls (20.06°).
- No significant differences were found in knee movement latency or peak angular velocity between CP and control groups.
Conclusions:
- Motion analysis confirms reduced knee angular displacement in CP children during PTR.
- Reduced reflex latency in CP suggests a brisk reflex, differing from subjective assessments.
- Knee movement latency and peak angular velocity do not differentiate CP from typical development, warranting further investigation into the knee angular response.
Background:
The patellar tendon reflex (PTR) is an important spinal reflex and an important diagnostic tool assessing neurological disturbances. Reflexes are conveniently assessed but quantifying the response can be subjective. Motion analysis is commonly used to assess gait kinematics in a variety of populations. It can be used to objectively assess the PTR with the advantage that standard technique and hammer can be used without the need for bulky apparatus or fixing the subject position.
Aim:
To compare the PTR in 15 cerebral palsy (CP) children with age and height matched controls.
Methods:
EMG reflex latency in the rectus femoris was assessed using a Noraxon 2400T unit. Knee movement latency, knee angular displacement and peak angular velocity were captured using the CODA mpx 30 system.
Results:
EMG reflex latency was significantly reduced in CP compared to control limbs (13.11 versus 18.11 ms; p < 0.01) confirming a 'brisk' response in this population. The kinematic data found that while knee angular displacement was significantly reduced in CP (12.82° versus 20.06°; p < 0.01) there was no significant difference in movement latency or peak angular velocity compared to controls.
Conclusions:
Subjective evaluation of the PTR relies mostly on change in knee angle. Using motion analysis we have confirmed a difference in this variable in CP compared to controls. We have also shown reduced reflex latency associated with a brisk reflex. Knee movement latency and peak angular velocity did not differentiate CP from normal. Further examination of the knee angular response of the PTR is warranted in CP.
