Since the inception of the chiropractic profession its practitioners have struggled with models of spinal dysfunction. While early notions of structural misalignment have largely given way to ‘functional’ concepts, the average field doctor still questions the exact nature of such lesions. So the question still remains, “What exactly is going on inside the spines and nervous systems of our patients?”
Clearly there are many differing clinical diagnoses that can be made when we attempt to pick a source of pain or a ‘tissue in lesion’. These might include a meniscoid extrapment, a zygapophysial synovitis or one of the various grades of annular tear/disc herniation. However, in such instances we could view any tissue damage as the result of a functional derangement that was already in existence at the time of injury. In other words, many spinal pain syndromes are a symptom of a greater deficit underneath - not simply the unlucky result of an inappropriate movement or accident.
But what ‘deficit’ might precede a spinal injury? And how would we know it was present if our patients are asymptomatic?
In short, these patients may well suffer a loss of proprioception...
The literature is increasingly documenting the poor proprioceptive sensibilities of the average spinal pain patient. The ability to accurately place a joint in the required position for load bearing, and then chaperone that joint through an appropriate trajectory of movement is no mean feat. And to do so without injuring any of the delicate soft-tissues encasing the articulation (not to mention the discs) requires a precision that is truly impressive. Interestingly, it is just such a failure of this system that might be the most important ingredient in the conundrum of recurrent or persistent spinal pain.
According to O’Sullivan et al (1), “Proprioceptive deficit may lead to delayed neuromuscular protective reflexes and coordination such that muscle contraction occurs too late to protect the joint from excessive joint movement. It has been hypothesized that this may lead to abnormal loading transmitted repetitively across joint surfaces, resulting in pain and articular damage.”
But it gets worse. Just think for a moment about all of the consequences of reduced proprioceptive input from a spinal segment...
We know that proprioception is an important component in pain control - effectively acting as a mechanical analgesic at the dorsal horn level.
We know that proprioception drives segmental muscle recruitment and helps to maintain local muscle tone. In patients with unilateral back pain we will typically see a specific pattern of multifidus atrophy that is limited to the level and side of lesion (2) i.e. it is a specific reaction to injury and not simply due to disuse. But think about this - the multifidus muscle itself is probably one of the largest contributors to spinal proprioception! So as this tissue wastes away the poor patient can also kiss goodbye to much of their functional proprioception at the damaged segment. So the problem just gets worse.
We know that proprioception is ultimately integrated at higher control centres and is used to facilitate posture. Patients with recurrent lower back pain show reorganisation of the motor cortex and postural control deficits (3).
In fact I could go on and on... and we would see an increasing body of evidence to suggest that the longer a patient’s history of spinal pain the greater the neurological consequences upstream in the brain itself (to be the subject of another blog entry).
All of the above could be summarised in one phrase and concept... 'poor proprioception’.
Our patients are often walking around with all manner of functional inadequacies and joint positioning deficits, oblivious to it all until something is injured. Even worse, many of our patients are really ‘proprioceptively starved’ in a global sense, as they pursue sedentary occupations and rarely exercise. Think of mechanical stimulation as a ‘nutrient’ to the nervous system, and your goal is to deliver this as appropriately as possible.
As chiropractors, our job is to give back to our patients the proprioceptive stimulation that they need, where they need it, in a highly leveraged and refined dosage. And that is just what your adjustment does.
So have a think about your clinical protocols and how you might investigate proprioceptive control. Then ask yourself how you might try to do this better, for your patients’ sake. Matthew D. Long BSc (Syd) M.Chiro (Macq)
References: 1. O’Sullivan PB, Burnett A, Floyd AN, Gadsdon K, Logiudice J, Miller D, Quirke H. Lumbar repositioning deficit in a specific low back pain population. SPINE 2003; 28 (1): 1074-1079 2. Hides J, Gilmore W, Stanton E, Bohlscheid E. Multifidus size and symmetry among chronic LBP and healthy asymptomatic subject. Manual Ther 2008;13(1):43-49 3. Tsao H, Galea MP, Hodges PW. Reorganization of the motor cortex is associated with postural control deficits in recurrent low back pain. Brain 2008; 131: 2161-2171