Although interventional procedures should be used cautiously in the setting of chronic pain, there is a role for a variety of injections to facilitate a patient’s overall rehabilitation program. There are many resources available, including a prior issue of Physical Medicine and Rehabilitation Clinics of North America , which discuss the more conventional spinal injections. The focus of this article is on lesser-known injection options for treating chronic pain. The authors separately discuss trigger point injections, regenerative injections (prolotherapy), and injections using botulin toxins.
Key points
- •
Even in the setting of chronic pain, various injections can still have a useful role in facilitating a rehabilitation program.
- •
Spinal injections, such as epidural steroid injections and facet joint injections, are among the most commonly used procedures in most pain practices; but a growing number of practices are considering less common injections, such as trigger point injections, regenerative injections/prolotherapy, and injections using botulinum toxins.
Introduction
Although interventional procedures should be used cautiously in the setting of chronic pain, there is a role for a variety of injections to facilitate patients’ overall rehabilitation program. There are many resources available, including a prior edition of Physical Medicine and Rehabilitation Clinics of North America , which discuss the more conventional spinal injections. The focus of this article is on lesser-known injection options for treating chronic pain. The authors separately discuss trigger point injections (TPIs), regenerative injections (prolotherapy), and injections using botulinum toxins (BTx).
Introduction
Although interventional procedures should be used cautiously in the setting of chronic pain, there is a role for a variety of injections to facilitate patients’ overall rehabilitation program. There are many resources available, including a prior edition of Physical Medicine and Rehabilitation Clinics of North America , which discuss the more conventional spinal injections. The focus of this article is on lesser-known injection options for treating chronic pain. The authors separately discuss trigger point injections (TPIs), regenerative injections (prolotherapy), and injections using botulinum toxins (BTx).
Trigger point injections
Myofascial pain syndrome (MPS) is a common musculoskeletal pain syndrome characterized by a myofascial trigger point (MTrP) at muscle, fascia, or tendinous insertions. A MTrP is a hyperirritable tender spot, frequently associated with taut band that, on palpation, is firmer in consistency than adjacent muscle fibers. When compressed, an MTrP may cause patient vocalization or a visible withdrawal (which is known as the jump sign).
Stretching and exercise are the foundation of treatment and management of MPS; however, for refractory cases, needle therapy may be offered. This therapy may include TPIs (using local anesthetics, corticosteroids, and/or BTx), dry needling (DN) (intramuscular stimulation [IMS]), and acupuncture.
Local Anesthetics
Despite the popularity of TPIs, there is no conclusive evidence that demonstrates superior effectiveness of TPIs over DN in the treatment of MPS. One systematic review of randomized controlled trials found that direct injection to MTrPs was indeed effective but that the nature of the injected substance did not influence the outcome; hence, the investigators concluded that the beneficial effects of TPIs were likely the result of needle insertion or placebo. However, another review showed short-term benefits of TPIs with lidocaine that were superior to DN or placebo. It is conceivable that local pain and soreness associated with needling can be ameliorated with local anesthetic injection.
Corticosteroids
Although inflammation may play a role in MPS, there is no evidence that the injection of corticosteroid provides any enhanced benefits. In addition, corticosteroids carry the risk of local muscle necrosis and adrenal suppression. Thus, the use of corticosteroids for TPIs is not recommended.
Botulinum Toxin
Botulinum toxin (BTx) is a potent neurotoxin produced by the bacterium Clostridium botulinum that blocks acetylcholine release into the neuromuscular junction, leading to prolonged muscle relaxation (typically lasting 3 to 4 months). BTx is used for a variety of pain procedures as discussed separately in this article later. Briefly, the authors discuss the use of BTx in TPIs.
In TPIs, BTx is thought to reduce muscular ischemia and free entrapped nerve endings. Central and peripheral antinociceptive properties of BTx have also been postulated. Despite these mechanisms that could theoretically offer a benefit for patients with MPS, the use of BTx injections for myofascial trigger points is controversial. Meta-analyses of randomized trials in patients with neck pain have found no benefit of BTx intramuscular injections in the short-term (4 weeks) or long-term (6 months) when compared with placebo. Although a recent review showed inconclusive evidence regarding the effectiveness of BTx in the treatment of MPS, an older Cochrane review found moderate evidence that BTx injections are not effective. In sum, given the high cost of the medication and questionable evidence for its efficacy, cost and clinical value should be carefully assessed before considering BTx injections for MPS.
Dry Needling
Dry needling (DN) (also known as intramuscular stimulation [IMS]) involves the practice of using a small-gauge needle (sometimes acupuncture needles) to irritate the MTrP without injecting any substance (as opposed to those discussed earlier). Systemic reviews and meta-analyses of randomized controlled trials suggest that DN is an effective therapy for MPS. If DN is used to specifically target MTrPs, it is most effective when a local twitch response (LTR) (brisk contraction of the taut band) is elicited. A fast-in-fast-out technique has been advocated to elicit a maximal number of LTRs. The needle penetrates the taut band of the muscle, is withdrawn to superficial subcutaneous tissue, then redirected to another area in proximity ( Fig. 1 ). Deep DN to the muscle (eg, 15 mm) has been shown to be more effective than superficial DN (eg, 2 mm).
Acupuncture
Acupuncture is an increasingly popular treatment of a broad spectrum of chronic conditions, including chronic pain. However, the number of needles used, the frequency of sessions, stimulation frequency, and current amplitude to obtain optimal efficacy remains a matter of debate. A Cochrane review found that, in the short-term, acupuncture is more effective for chronic low back pain and neck pain compared to no treatment or sham acupuncture. Other meta-analyses have also demonstrated the effectiveness of acupuncture for chronic pain when compared with no acupuncture or sham (needles placed in non-acupucture sites).
The data suggest that the benefits of acupuncture are clinically relevant and greater than placebo; however, the observed differences in effectiveness between acupuncture and sham acupuncture are smaller than those between acupuncture and no acupuncture. This pattern of findings indicates that the nonspecific physiologic and psychological effects of needling may be more important than the actual acupuncture technique itself.
Needing Therapy: Mechanism of Action
The exact mechanism by which DN relieves MTrP and MPS has yet to be fully elucidated. DN has been shown to diminish spontaneous electrical activity when LTR is elicited. Hong and Simons suggested that LTR or referred pain seems to be mediated through a spinal reflex in response to stimulation of a sensitive locus (nociceptor) that is in the vicinity of an active locus (motor end plate). Because DN is most effective when LTR is elicited, it is theorized that DN may relieve MTrP via inhibition of dysfunctional activity in the motor end plate of the skeletal muscle motor neuron.
Acupuncture has been used for various pain conditions in addition to MPS. There is increasing evidence of correlations and similarities between MTrPs and acupuncture points in terms of their distribution and referred pain patterns. An electrophysiologic study showed that some acupuncture points are indeed MTrPs. Acupuncture analgesia seems to be a manifestation of integrative processes at different levels of the central nervous system (CNS). The gate control theory (Melzack and Wall ) may in part explain these processes; namely, the theory postulates that non-noxious sensory input (eg, touch, pressure, vibration) into the CNS can modulate pain perception by activating inhibitory interneurons. Furthermore, the possible role of endogenous opioids has been implicated in both TPIs and acupuncture as their analgesic effects can be in part reversed by naloxone.
Key Points
- •
There is no firm evidence that TPIs are superior to DN or acupuncture for MPS; however, TPIs with local anesthetic may offer additional benefits via relieving pain associated with soreness from the needling procedure itself.
- •
There is no strong evidence to support the use of corticosteroid or BTx in TPIs.
- •
DN seems to be effective for MPS, especially when LTR is elicited.
- •
Acupuncture seems to be effective for chronic pain, but nonspecific physiologic and psychological effects may play a significant role in its benefits.
- •
The mechanism of action in needling therapy seems to be multifactorial, including integrative CNS processes and endogenous opioid peptides.
Regenerative injections
Regenerative injection therapy (RIT) encompasses a spectrum of injection treatments designed to stimulate repair of damaged tissue. These injections range from prolotherapy (which provides a mild neurolytic effect followed by a complex restorative process with biochemically induced collagen regeneration), to platelet-rich plasma ([PRP], which uses autologous blood that has been spun down to separate out the platelets), to even stem cells (which can be autologous or banked).
In 1956, George Hackett introduced the term fibroproliferative therapy or prolotherapy , defined as “the rehabilitation of an incompetent structure by generation of new cellular tissue.” He proposed this new name because the term sclerotherapy that had been used previously implied scar formation rather than regeneration. In the same text, he published composite pain maps generated from ligaments and tendons, which have unfortunately remained largely unknown to the medical community ( Fig. 2 ). Contemporary understanding of the basic science of regenerative medicine is that the regenerative/reparative healing process consists of 3 overlapping phases: inflammatory , proliferative with granulation, and remodeling with contraction ( Fig. 3 ). The regenerative and reparative stages extend beyond the proliferative stage. The term RIT was originally coined by Felix Linetskey, MD to replace the name prolotherapy; but authors have used both terms to describe any of the treatments described next.
The first of these techniques, RIT/prolotherapy stimulates chemo-modulation of collagen by repetitive induction of inflammatory and proliferative stages, which leads to tissue regeneration and repair. As a result, the tensile strength, elasticity, mass, and load-bearing capacity of collagenous connective tissues increases. The proliferant, which can be any of a number solutions (including dextrose/lidocaine, dextrose/phenol/glycerin, sodium morrhuate, and pumice), creates an inflammatory reaction, thereby generating new tissue at the fibro-osseous junction. Hormones and multiple growth factors mediate this complex process. Fig. 4 shows rabbit tendon hypertrophy after prolotherapy.
The next technique, RIT/PRP relies on the injection of concentrated platelets that release growth factors to stimulate recovery in nonhealing soft tissues. Autologous blood is collected and centrifuged; the portion that contains a high proportion of platelets is syphoned off and injected into the tendon and ligament attachments at the enthesopathy site.
RIT/stem cell injection involves utilization of autologous adult pluripotent mesenchymal stem cells from an individual’s bone marrow or adipose tissue as the proliferating solution. Alternatively, banked placental stem cells are beginning to come onto the market, facilitating stem cell procurement.
Indications for RIT are listed in Box 1 . Appropriate presenting complaints are diverse. These include occipital and suboccipital headaches; pain in the posterior midline and paramedial cervical spine, the cervicothoracic spine, the thoracic spine, the thoracolumbar spine, the lumbar spine, the lumbosacral spine, the scapula, and the shoulder regions; pain between the shoulder blades, in the low back, buttocks, sacroiliac, trochanteric areas, and any combination of the aforementioned complaints.
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
