Advances and instrumentation in diagnosis and treatment of trigger points in human myofascial pain: veterinary implications

A.2. TRIGGER POINTS (TPs) AND MYOFASCIAL SYNDROMES IN ANIMALS

Veterinary acupuncturists have known for many years of the diagnostic and therapeutic relationships between functional disorder of internal organs and the presence of tender points in the paravertebral area (the Shu points, Kothbauer's Pain Points etc).

They also knew that stimulation of tender points (TPs, AhShi points) in muscle or scar tissue by dry needling, procaine/Impletol (Bayer, Germany) injection, laser or electrical methods etc could resolve many disorders (see references in Rogers 1974-1988). The classical AP reflex points (paravertebral Shu and thoracoabdominal Mupoints) and some diagnostic points have been described for cattle (Kothbauer and Meng 1983) and horses (Cain and Rogers 1987). However, documentation of the precise locations and related symptomatology of animal TPs is poor in comparison with that of human TPs.

Janssens (1984) was the first to document in detail the presence of muscular TPs as a cause of chronic pain in animals. Pain had been present in 21 dogs for a mean time of 6 months. TP therapy (dry needling for 5 minutes/week or injection of the TPs (0.25-2 ml 1.0% xylocaine or 0.5% procaine via 25-28 gauge needle)) gave 70% success in a mean time of 17 days (2.5 sessions). Relapse occurred in 33% and treatment of relapses gave the same result as initial treatment.

In a second paper (Janssens 1987), he reported the occurrence of TPs in 47 lame or claudicating dogs. Clinical signs had been present for a mean time of 6 months. TPs were found in the following muscles:

triceps (AP point LU 1 in animals) (52%);

 

adductor and pectineus (AP point LV 9 or 10) (15%);

 

peroneus longus (AP point GB34) (12%);

 

gluteus medius (AP point GB29) (10%),

 

iliocostalis lumborum (AP point BL26) (6%);

 

quadriceps (4%).

 

TP therapy gave successful outcome in 60% of cases in a mean time of 19 days. Results with Triceps TPs were better (79% success). Relapse occurred in 33%, usually with the original TPs recurring again. Repeat treatment gave similar results to the initial treatment.

As in humans, TPs in animals can be due to trauma, muscle overload and by reflex effects, associated with foci of irritation in internal organs or other body parts.

Fever or viral infection may initiate TPs: 'Flu is often associated with muscle pain and tenderness. The sequel to 'flu may be multiple TPs. This may explain why large racing stables may have many horses with recurrent myofascial pain and poor racing performance. There is often a history of equine viral epidemics (especially equine 'flu) preceding a period of 1-2 years of poor racing performance.

While TPs in animals have diagnostic and therapeutic implications in all species, they are of special importance in sports medicine. Animals used for competitive sports (racing, jumping, polo etc) or for active work (draught animals, hunting dogs etc) need to be at peak physical fitness. For top performance, they rely heavily on the musculoskeletal system. In particular, they need full flexion and extension of the paravertebral muscles for maximum stride and speed and to enable them to gallop around corners. TPs in the paraspinal muscles (neck to sacrum) are commonly associated with lameness or stiffness in horses and dogs. TPs are also common in the heavy muscles of the neck, shoulder and thigh. Unless TPs are "released", muscle power and flexibility is impaired and athletic performance is reduced. TPs are self- sustaining and may remain indefinitely unless detected and eliminated (Verhaert 1985).

TPs can induce abnormal muscular and autonomic nervous function. This may manifest as acute or chronic pain, spasm, tremor, incoordination, stiffness, muscle weakness (including buckling of a limb (knee in humans; shoulder, elbow, hip or stifle in horses)), paraesthesia, numbness and poor circulation. By firing spontaneously into the nervous system, TPs maintain a state of reflex muscle guarding (spasm), with consequent pain, restriction of movement and poor blood supply in affected muscles. Atrophy of disuse can arise but is rare unless nerve entrapment occurs. Weeks to years after the pain stimulus which initiated them, TPs can remain in an active or passive state. Effective TP therapy can have rapid, dramatic effects on the wellbeing of the patient. Chronic pain due to unreleased active TPs has lasted from months to several decades in human patients and TP therapy has eliminated it immediately or in a matter of days (Travell and Simons; Verhaert 1985).