Veterinary Surgery, 20, 4, 274-278, 1991
Trigger Points in 48 Dogs with Myofascial Pain Syndromes LUC A. A. JANSSENS, DMV, PhD
Seven foci of pain (trigger points) were identified in the triceps brachii, infraspinatus,adductorpectineus, peroneus longus, gluteus medius, ileocostorum lumborum, and quadriceps femoris muscles in 48 lame dogs. The dogs had been lame for 1 day to 150 weeks (mean, 24 weeks). Thirty-one dogs had been treated unsuccessfully with corticosteroids, nonsteroidal anti-inflammatory drugs, analgesics, or acupuncture. Palpating the trigger points induced severe pain. Treatment consisted of weekly stimulation of the trigger points by needling or injection of a local anesthetic. The mean treatment period was 2.8 weeks. Excellent results and complete recovery were observed in 34 dogs (60%).
been described in human medicine since the early 1950s but seem to be unknown to most veterinarians.'-' Trigger points are localized most frequently in a muscle or fascia, and only rarely are they localized on periosteum or subcutaneously. Upon palpation, trigger points appear as hyperimtable foci in which nonpainful stimuli are experienced as painful. In a muscle, trigger points are localized in a taut band of muscle fibers in which a hard nodular structure can be felt if the muscle is palpable and the trigger points are not too deep. Trigger points can be active or passive. Active trigger points are spontaneously painful and painful on palpation. Passive trigger points are painful only after being squeezed, palpated, or compressed. Trigger points are active when acute or after activation of a passive trigger point. Passive trigger points are chronic and nonactivated. Active and passive trigger points have the same clinical characteristics: They are tender on palpation, prevent full niuscle lengthening and thus shorten muscles, weaken the niuscle without atrophy, and refer pain on direct compression. They trigger pain. The referred pain is felt locally or at a distance. It is reproducible and does not coincide with a dermatome or peripheral nerve distribution pattern. The referred pain may last for hours or even days after a trigger point has been palpated. When a trigger point is compressed, the resulting referred pain is recognized by humans as the pain they complained about and for which they sought medical assistance. If
T
RIGGER POINTS H A V E
medical treatment is focused on the referred pain zone alone, no cure occurs. If its origin (the trigger point) is treated, however, the referred symptoms For example, in humans. chronic temporal headache and occipital pains are often caused by a trigger point in the splenius cervicis muscle (Fig. 1). Only treatment of the trigger point will cure the patient, while local temporooccipital treatments are of no use.7 Trigger point treatment consists of local trigger point stimulation. This may be achieved by dry needling, injection of saline or a local anesthetic, transcutaneous electrical stimulation, or laser therapy.8 Blocking the sympathetic innervation of a trigger point area abolishes the trigger point.' Some stimulation techniques, such as ultrasound and faradism, are ineffe~tive.'.~ When a trigger point is stimulated, a local muscle twitch response may be observed. The local twitch is a transient contraction of a group of muscle fibers that contain the trigger point. It is a sign of successful stimulation of the trigger point. One stimulation session may abolish all symptoms of referred pain for hours, days, or even permanently.'-'."' Needling or injecting the trigger point is painful and may cause local pain for as long as 2 days after treatment. Successful trigger point treatment abolishes or diminishes the trigger point. The purpose of this article is to describe the anatomy and treatment of seven trigger points in 48 lame dogs with myofascial pain syndromes.
~~~
The author thanks Janet Travel\, MD, for her work, which introduced him to the subject of trigger points; David Ashton, PhD. for his criticism arid linguistic help, Piet Van Bree, DMV, and Herman Hazewinkel, DMV, PhD, for the interpretation of the radiographs; and Suzy De Cauwer for her technical assistance. Reprint requests: L.A.A. Janssens, DVM, PhD, Oudestraat 37, 2610 Antwerp, Belgium.
274
275
JANSSENS
I'
X
Trigger point
@& Cenier of referred pain
,& Circumference area of referred
pain
, f
Fig 1 The human upper splenius cervicis trigger point with referred pain zone
Materials and Methods Forty-eight dogs aged 0.5 to I ? years (mean. 5 years) were presented for treatment of lameness in onc 01'inorc limbs. There were 30 males and 18 females. and 2 2 breeds were represented. Boxers and poodles were the most frequently affected. Thirty-one dogs werc lame in onc limb. 16 dogs were lame in two limbs, and one dog wiis lainc in three limbs (Table I ) . Most of the dogs had beeii lame for many months. and two-thirds oftheni (31 dogs) had been treated ineffectively with rest ( 13 dogs). adniinistration of nonsteroidal anti-inflammatory drugs (phcnylbutazone or aspirin. 26 dogs). an analgesic ( pentarocine. 6 dogs). or acupuncture (6 dogs). Radiographs were made in 32 dogs (67";). Kadiographic abnormalities were found in seven dogs ( 14%): hip dysplasia in three dogs. arthritis of the elbow i n two dogs. osteochondritis dissecans of the shouldcr in one dog, and rheumatoid arthritis in stifles and elbows of' one dog positive for blood rheumatoid factor. Two dogs had histories ofprevious trauma. In 39 dogs (8 l1Z ). there was no clinical diagnosis to explain the cause of' the lameness. All dogs were examined for joint pain o n palpation. flexion, and stretching, and the muscles were palpated. It' a trigger point was discovered. it was treated at \veckly intervals by dry needling with a 28-gauge stainless steel acupuncture needle or by injection of 1 % lidocainc (0.25 m L to 2.0 mL) with a disposable 23-gauge hypodermic needle. depending on the size of the trigger points. The depth of the needle was 0.5 cm to 5.0 cni. according to the weight of the dog and the depth of the trigger- point. For example, a trigger point in thc triceps brachii of-a 2 0 kg dog would be 0.5 cm to 2.5 cm deep. The dry needle
was lett in situ for about 5 minutes. As a rule, dry needling could be performed onl) in calm dogs. Dogs that moved during trigger point treatment could be treated only by injection because it \\as faster. N o other lorm o f thei-apq was administered, and no rest was adLocated. 'The follw-up was 2 months to 6 years. The effecti\cncss of' trigger point therapy was determined by the drsappeiirancc of trigger points from the muscle and by concurrent cessation of the lameness. The result was scored "complete recovery" if the trigger point vanished, no lameness could be detected. and no relapse occurred. 'The result was scored "good" if a trigger point almost vanished but still caused minimal lameness after many kilonieter-long malks or when relapse occurred within 8 weeks. 'Thc result was scored as "amelioration" when the trigger point became smaller but did not vanish and lameness mas diminished but still present. Results The pretreatment period was I day to approximately 150 weeks (median, 24 wecks). Eighty-two localized. extremely painful spots (trigger points) were identified by palpation of' muscles. Even \cry timid, nice dogs would bite immediately when these spots were squeezed. In most muscles. trigger points were palpable as hard nodular or oblong structures \vith ;I diameter of 0.5 cm to 4.0 cm. In the triceps brachii. the) could be palpated between fingers medially and the thumb laterally. In other muscles. they could be palpated trom the lateral or dorsal aspect by deep palpation 'The peroneus muscle had only a hyperirritable. painful spot M ith no nodule palpable. The stretch range of motion was abnormal in the hindlimbs only n;lien trigger points were present in the qiiadriceps or the adductor and pectineus niuscles. In the fir-SI case. the stifle could not be flexed fully and the tuber calcanei would not touch the tuber ischii. In the second case. abduction of the hindlimb was restricted. Stretching of the muscle containing a trigger point was experienced as painful (biting. screaming. restlessness). Trigger points were found in the triceps brachii, infraspinatus. peroneus longus, gluteus medius, iliocostalis lumborum, adductor-pectineus, and quadriceps temoris muscles (Fig. 2 and Table 1 ) . Dogs that were lame in only one limb and had one trigger point had this trigger point in the triceps (30 dogs) and the infiaspinatus ( I dog). Dogs that were lame in more than one limb ( I 7 dogs) had several trigger points. mostly in the hindlimbs (Table 1). The triceps trigger points tended to be unilateral and left sided. while hindlimb trigger points were bilateral. The mean number of treatments was 2.8 (minimum I . maximum I 1 ). When the quadiiceps femoris or triceps brachii trigger point was punctured or injected. a muscle twitch of the
276
TRIGGER POINTS TABLE 1. Description of Trigger Point Prevalence, Method of Stimulation, Mean Number of Treatments and Results of Trigger Point Treatment Number of Lame Limbs
Front leg
Hind leg
Left
Right
28
16
11
11
Prevalence
Method of Stimulation
Success Ratio
Trigger Point Localization
Number of Trigger Points
Triceps brachii lnfraspinatus
43 1
11
32 1
2.5 1
22 1
12 0
5 0
4
0
Adductor and pectineus
12
3
9
5.4
3
4
3
2
Peroneus longus
10
4
6
4.6
2
0
6
2
Gluteus medius
8
2
6
6.5
1
1
6
0
lliocostalis lumborum
5
3
2
5.0
0
0
5
0
Quadriceps femoris
3
0
3
8.0
0
2
1
0
19
26
a
Dry Needling
Injection
Mean Number of Treatments
Complete Recovery
Good
Amelioration
No Improvement
~
lotal
66
82
23
59
4.0
affected muscle was often observed. After a successful treatment, the trigger point disappeared, and during successful treatment, hyperimtability on palpation and the trigger point magnitude diminished progressively. Side effects were not encountered apart from an increase in lameness for 1 or 2 days in some dogs. Of the 82 trigger points, 29 disappeared completely (Table 1). Nineteen treatments had good results, 26 were ameliorated, and eight had no improvement. The best results were obtained in the triceps trigger points, in which 34 dogs (7 1%) recovered completely or scored "good." The results of treatment of the other points were less favorable. Relapses occurred within 4 weeks to 1 year in 16 dogs (33%). Fourteen dogs had multiple relapses. Most relapses were retreated successfully with the same method.
0
~
29
thermography. I ' - I 6 Trigger points were characterized by less depth of penetration and a decreased pressure threshold. Both measurements increased after trigger point treatment.' ' - I 4 Two classes of myofascial pain syndrome have been established in humans. Persons in good general health with one or more acute or chronic trigger points are classified as true trigger point patients. The second class contains patients with multiple, chronic trigger points and with other tender spots that do not refer pain on palpation. These patients, who also have depression. nonrapid eye movement sleep disorders, exercise intolerance, generalized pain, and fatigue are classified as fibromyalgia patients.' l 6 l 7 Fibromyalgia patients are not helped by trigger point treatment: they seem to react positively to tricyclic antidepressants and certain benzodiazepines. Discussion Body regions especially susceptible to trigger points are those in which large nerves and blood vessels lie close to Trigger points are induced by many factors: trauma. the body surface.' The triceps, pectineus-adductor, and internal disease, viral infections, and many still unknown peroneus longus trigger points are typical examples of this factors. Passive trigger points may become active under observation, as they lie close to the radial, femoral, and influences such as stress, trauma, fatigue, and f e ~ e r . ~ . ~ peroneus nerves. Methods used in humans to demonstrate and measure Histologic lesions in trigger point biopsies consist of trigger points objectively include measuring the depth of "fat-dusting" and nonspecific dystrophic changes such as penetration in soft tissue of a 1 cm2rubber disc in relation variations in size of muscle fibers, clusters of nuclei, exto the force with a tissue compliance meter, measuring the minimum pressure inducing pain or discomfort with cessive collagen fibers, contracture knots of myofibrils, a pressure threshold meter, magnetic resonance, and and loss of cross-striation.'6.'9.'0 There is a remarkably "3'
JANSSENS
high degree of correspondence ( 7 I %) between human trigger points and acupuncture points with respect to their localization and their clinical use.'.' Although acupuncture points have been described extensively in animals,?'-'3 trigger points have not been described i n animals. Acupuncture points are points in the skin with a diameter of about I mm and with a lower electrical resistance than surrounding skin. They are grouped on lines called meridians, which have different organ names. Twelve meridians are described. Meridian points are numbered from I to the last point on that meridian (9 to 67)? In this series of dogs, a correlation is seen between acupuncture points and four trigger points: the peroneus
277
longus point is gallbladder 34. the adductor-pectineus point is liver 10 or 1 1 . the gluteus medius point corresponds to gallbladder 29. and the infraspinatus point coincides with small intestine x The gluteus. adductor-pectineus. peroneus longus, infraspinatus. and iliocostalis lumborum trigger points compare anatomically with those described in hum a n ~ . ~ -The ' - ~ 'triceps point is not an acupuncture point and is not comparable with a human trigger point. The quadriceps trigger point location is not an acupuncture point. Although veterinary acupuncture is used frequently for various conditions."-'7 it should be differentiated from
278
TRIGGER POINTS
trigger point therapy. Acupuncture sometimes uses painful points, called A-shi points, as part of the total treatment. Trigger point therapy focuses on trigger points only. The weekly treatment interval was chosen according to human literature.’ In humans, only acute trigger points, as in acute lumbago, are treated twice a week. In the dogs, almost all lesions were chronic. Some trigger points were treated with injections and some by dry needle stimulation because trigger points were originally stimulated as acupuncture points. However, many dogs did not tolerate having the needle in situ for about 5 minutes. Whenever they moved, the needle caused discomfort. Therefore, the method was changed to injection of lidocaine, which is fast and affects a larger area so that less anatomic accuracy was needed. Two types of patients could be discerned. Most dogs with a triceps. infraspinatus, adductor-pectineus, or quadriceps trigger point had only one trigger point, and most of them reacted favorably to trigger point treatment. On the other hand, most dogs with multiple, symmetrical hindlimb trigger points reacted poorly to trigger point treatment. They should probably be classified as fibromyalgia patients. No separate control group was examined in this project because it was thought to be unethical toward owners and mimals to use a placebo trigger point treatment. However, the dogs served as their own controls. The mean period of 6 months of lameness before treatment, the prompt results with a minimum of treatments in 60% of the animals, and the ineffectiveness of all previous treatments were strong factors in favor of the effectiveness of the rreatment. It is also thought that confounding factors can be excluded because of the lack of improvement in the lameness after successive previous treatments, and because of the stability of the clinical lameness in trigger point patients. References I . Kennard M4. Haugen FP. The relation of subcutaneous focal sensivit) to referred pain of cardiac origin. Anesthesiology 1955; 16: 297-299. 2. Melzack R. Stillwell D, Fox E. Trigger points and acupuncture points for pain: Correlations and implications. Pain 1977: 3:3-23. 3. Melzack R. Acupuncture and musculoskeletal pain. J Rhcuniatol 1978: 5: I 19- 123. 4. Sinions DG. Muscular pain syndromes. In: Frictoii JR, Awad EA, eds. 4 ~ l w i r w/ t~i Puin Re.tcwrcti ( i t i d Tlrwapi, . 2 f j ~ c $ i . w c i / Puiri riiid / ~ i / ~ t - o n ~ y ~New ~ l ~ qYork: i u . Raven Press. 1989:1-42, 5. Sola A. Williams R. Myofascial pain syndromes. Neurology 1956; 6:91-96.
6. Travell J. Rinrler S. The myofascial genesis of pain. Postgrad Med J 1952; 111425-434, 7. Travell JG. Simons DG. Myofascial Pain and Dysfunction. ?hc’ Trigiyr Poinr ,\funi/u/. Baltimore: Williams and Wilkins. 1983: 1-164. 8. Bengtsson A , Bengtsson M. Regional sympathetic blockade in primary fibroniyalgia. Pain 1988; 33:161-167. 9. Airaksinen 0. Rantanen P, Kolari PJ, Pontinen PJ. Effects of infrared laser irradiation at the trigger points. Scandinavian Journal of Acupuncture and Electrotherapeutics 1988: 3:56-6 I. 10. Dongo B, Bartoli V. Grisillo D. Beconi D. Fibrositic m?ohscial pain in intermittent claudication: Effect of anesthetic block o f trigger points on exercise tolerance. Pain 1979; 6: 183- 190. 1 1 . Fischer AA. Cliiazal use oftissue compliance meter for documentation of soft tissue pathology. The Clin J Pain 1987: 323-30. 12. Fischer AA. Pressure threshold measurement for diagnosis of inyofascia1 pain and evaluation of treatment results. ‘The Clin J Pain 1087; 2:207-214. 13. Fischer AA. Letter to the editor. Pain 1987: 28:4 I 1-4 14. 14. MikcIi S, Piintinen PJ. Reliability of pressure threshold meter in location of latent trigger points in healthy subjects. Scandinavian Journal of Acupuncture and Electrotherapeutics 1988: 3:45-50. I S . Bach-Andersen R. Jacobsen S. Danneskiold-Samsoe B. et 31. New diagnostic tools in priniae fibromyalgia: Findings from the Copenhagen research group on fibromyalgia. In: Fricton JR. Awad EA. eds. .Idvcitrc~~,s i n Puin RcwurcA uiid Thiwpl. I f j ~ o f u w u l I’uit7 u i ~ d F i h r ~ ~ i ) ~ ~ uNew / g i aYork: Raven Press. 1989:269-276. 16. Bennett RM. Myofascial pain syndromes and the 1ibrom)algia syndrome: A comparative analysis. In: Fricton JR, Awad EA. eds. : l d w i i c ~ c ~ .it7 t 1’0111 Rrtcarc~lrund Ttierqi!~.,LIyo/u wiul Puiii riiid b’r/~roiiij,ulg~. New Y a k : Raven Press. 1989:43-66. 17. Goldenberg DL.. Clinical features of fibromyalgia. In: Fricton JR. Awad EA. eds. .1dwiiie.s i t i t’uiii Revc.arc,li ond T/imqi),., \ f i ~ ) / u s ( , i dPuiii c i i d I,’ihroiii.i,ulgia. New York: Raven Press. 1989: 139146. 18. McCain GA. Management of the libromyalgia syndrome. In: Fricton JR, Awad EA. eds. : l t / r . c i t i c ~ ~ siii Pain Rtwur.di rind 7Iiwcipi, .\lsoh\c~id Priin rind I.’//~~omjnlgiff. New York: Raven Press. 1989: 289-304. 19. Awad EA. Histopathological changes in fibrositis. In: Fricton JR. Awad EA. eds. .-lr/vunc,e, / t i Puin R m ~ r r d rund TtlCrUpi‘ ,211.r~/o.sc~rcil Pain mtl Fihr.otnj.a/,yiu New York: Raven Press. 1989: 249-258. 20. Henriksson KG. Bengtsson A. Muscular changes in fibromyalgia and their significance in diagnosis. In: Fricton JR. Awad EA. eds. . Idvuric.i~\in l’uiti Rrcc~urchcrnd Tlrrrapj. .lfj,i>luwiu/I’u1ir uird F i / ~ r o i t r I d y i uNew York: Raven Press. I989:259-268. 2 1. Janssens LA. The treatment of thoracolumbar disc disease in dogs by means of acupuncture: A comparison of two techniques. J Am Anim Hosp Assoc. 1989: 25:169-174. 22. Jaiissens LA. General acupuncture with special reference to therapeutic and analgetic aspects in animals. Vlaams diergeneeskundig Ti-jdschrift 1977: Part 1:46:266-276. 1978: Part 2:47:339-35 1, 19x0: Part 3:49:31-42. 23. Klide A. Kung S. l’c,iwintrr.i, riciipfrt~ctfrri~. Philadelphia: UniLersity of Pennsylvania Press. 1977: 1-276 24. Jaiissens LA. . 4 c i i p ~ / r i ~ ~points i u r ~ and r n t w d i u i ? . \ iti ilie dog Beersel: Blondiau Print. Belgium. 1984:l-14.
Trigger Points in 48 Dogs with Myofascial Pain Syndromes LUC A. A. JANSSENS, DMV, PhD
Seven foci of pain (trigger points) were identified in the triceps brachii, infraspinatus,adductorpectineus, peroneus longus, gluteus medius, ileocostorum lumborum, and quadriceps femoris muscles in 48 lame dogs. The dogs had been lame for 1 day to 150 weeks (mean, 24 weeks). Thirty-one dogs had been treated unsuccessfully with corticosteroids, nonsteroidal anti-inflammatory drugs, analgesics, or acupuncture. Palpating the trigger points induced severe pain. Treatment consisted of weekly stimulation of the trigger points by needling or injection of a local anesthetic. The mean treatment period was 2.8 weeks. Excellent results and complete recovery were observed in 34 dogs (60%).
been described in human medicine since the early 1950s but seem to be unknown to most veterinarians.'-' Trigger points are localized most frequently in a muscle or fascia, and only rarely are they localized on periosteum or subcutaneously. Upon palpation, trigger points appear as hyperimtable foci in which nonpainful stimuli are experienced as painful. In a muscle, trigger points are localized in a taut band of muscle fibers in which a hard nodular structure can be felt if the muscle is palpable and the trigger points are not too deep. Trigger points can be active or passive. Active trigger points are spontaneously painful and painful on palpation. Passive trigger points are painful only after being squeezed, palpated, or compressed. Trigger points are active when acute or after activation of a passive trigger point. Passive trigger points are chronic and nonactivated. Active and passive trigger points have the same clinical characteristics: They are tender on palpation, prevent full niuscle lengthening and thus shorten muscles, weaken the niuscle without atrophy, and refer pain on direct compression. They trigger pain. The referred pain is felt locally or at a distance. It is reproducible and does not coincide with a dermatome or peripheral nerve distribution pattern. The referred pain may last for hours or even days after a trigger point has been palpated. When a trigger point is compressed, the resulting referred pain is recognized by humans as the pain they complained about and for which they sought medical assistance. If
T
RIGGER POINTS H A V E
medical treatment is focused on the referred pain zone alone, no cure occurs. If its origin (the trigger point) is treated, however, the referred symptoms For example, in humans. chronic temporal headache and occipital pains are often caused by a trigger point in the splenius cervicis muscle (Fig. 1). Only treatment of the trigger point will cure the patient, while local temporooccipital treatments are of no use.7 Trigger point treatment consists of local trigger point stimulation. This may be achieved by dry needling, injection of saline or a local anesthetic, transcutaneous electrical stimulation, or laser therapy.8 Blocking the sympathetic innervation of a trigger point area abolishes the trigger point.' Some stimulation techniques, such as ultrasound and faradism, are ineffe~tive.'.~ When a trigger point is stimulated, a local muscle twitch response may be observed. The local twitch is a transient contraction of a group of muscle fibers that contain the trigger point. It is a sign of successful stimulation of the trigger point. One stimulation session may abolish all symptoms of referred pain for hours, days, or even permanently.'-'."' Needling or injecting the trigger point is painful and may cause local pain for as long as 2 days after treatment. Successful trigger point treatment abolishes or diminishes the trigger point. The purpose of this article is to describe the anatomy and treatment of seven trigger points in 48 lame dogs with myofascial pain syndromes.
~~~
The author thanks Janet Travel\, MD, for her work, which introduced him to the subject of trigger points; David Ashton, PhD. for his criticism arid linguistic help, Piet Van Bree, DMV, and Herman Hazewinkel, DMV, PhD, for the interpretation of the radiographs; and Suzy De Cauwer for her technical assistance. Reprint requests: L.A.A. Janssens, DVM, PhD, Oudestraat 37, 2610 Antwerp, Belgium.
274
275
JANSSENS
I'
X
Trigger point
@& Cenier of referred pain
,& Circumference area of referred
pain
, f
Fig 1 The human upper splenius cervicis trigger point with referred pain zone
Materials and Methods Forty-eight dogs aged 0.5 to I ? years (mean. 5 years) were presented for treatment of lameness in onc 01'inorc limbs. There were 30 males and 18 females. and 2 2 breeds were represented. Boxers and poodles were the most frequently affected. Thirty-one dogs werc lame in onc limb. 16 dogs were lame in two limbs, and one dog wiis lainc in three limbs (Table I ) . Most of the dogs had beeii lame for many months. and two-thirds oftheni (31 dogs) had been treated ineffectively with rest ( 13 dogs). adniinistration of nonsteroidal anti-inflammatory drugs (phcnylbutazone or aspirin. 26 dogs). an analgesic ( pentarocine. 6 dogs). or acupuncture (6 dogs). Radiographs were made in 32 dogs (67";). Kadiographic abnormalities were found in seven dogs ( 14%): hip dysplasia in three dogs. arthritis of the elbow i n two dogs. osteochondritis dissecans of the shouldcr in one dog, and rheumatoid arthritis in stifles and elbows of' one dog positive for blood rheumatoid factor. Two dogs had histories ofprevious trauma. In 39 dogs (8 l1Z ). there was no clinical diagnosis to explain the cause of' the lameness. All dogs were examined for joint pain o n palpation. flexion, and stretching, and the muscles were palpated. It' a trigger point was discovered. it was treated at \veckly intervals by dry needling with a 28-gauge stainless steel acupuncture needle or by injection of 1 % lidocainc (0.25 m L to 2.0 mL) with a disposable 23-gauge hypodermic needle. depending on the size of the trigger points. The depth of the needle was 0.5 cm to 5.0 cni. according to the weight of the dog and the depth of the trigger- point. For example, a trigger point in thc triceps brachii of-a 2 0 kg dog would be 0.5 cm to 2.5 cm deep. The dry needle
was lett in situ for about 5 minutes. As a rule, dry needling could be performed onl) in calm dogs. Dogs that moved during trigger point treatment could be treated only by injection because it \\as faster. N o other lorm o f thei-apq was administered, and no rest was adLocated. 'The follw-up was 2 months to 6 years. The effecti\cncss of' trigger point therapy was determined by the drsappeiirancc of trigger points from the muscle and by concurrent cessation of the lameness. The result was scored "complete recovery" if the trigger point vanished, no lameness could be detected. and no relapse occurred. 'The result was scored "good" if a trigger point almost vanished but still caused minimal lameness after many kilonieter-long malks or when relapse occurred within 8 weeks. 'Thc result was scored as "amelioration" when the trigger point became smaller but did not vanish and lameness mas diminished but still present. Results The pretreatment period was I day to approximately 150 weeks (median, 24 wecks). Eighty-two localized. extremely painful spots (trigger points) were identified by palpation of' muscles. Even \cry timid, nice dogs would bite immediately when these spots were squeezed. In most muscles. trigger points were palpable as hard nodular or oblong structures \vith ;I diameter of 0.5 cm to 4.0 cm. In the triceps brachii. the) could be palpated between fingers medially and the thumb laterally. In other muscles. they could be palpated trom the lateral or dorsal aspect by deep palpation 'The peroneus muscle had only a hyperirritable. painful spot M ith no nodule palpable. The stretch range of motion was abnormal in the hindlimbs only n;lien trigger points were present in the qiiadriceps or the adductor and pectineus niuscles. In the fir-SI case. the stifle could not be flexed fully and the tuber calcanei would not touch the tuber ischii. In the second case. abduction of the hindlimb was restricted. Stretching of the muscle containing a trigger point was experienced as painful (biting. screaming. restlessness). Trigger points were found in the triceps brachii, infraspinatus. peroneus longus, gluteus medius, iliocostalis lumborum, adductor-pectineus, and quadriceps temoris muscles (Fig. 2 and Table 1 ) . Dogs that were lame in only one limb and had one trigger point had this trigger point in the triceps (30 dogs) and the infiaspinatus ( I dog). Dogs that were lame in more than one limb ( I 7 dogs) had several trigger points. mostly in the hindlimbs (Table 1). The triceps trigger points tended to be unilateral and left sided. while hindlimb trigger points were bilateral. The mean number of treatments was 2.8 (minimum I . maximum I 1 ). When the quadiiceps femoris or triceps brachii trigger point was punctured or injected. a muscle twitch of the
276
TRIGGER POINTS TABLE 1. Description of Trigger Point Prevalence, Method of Stimulation, Mean Number of Treatments and Results of Trigger Point Treatment Number of Lame Limbs
Front leg
Hind leg
Left
Right
28
16
11
11
Prevalence
Method of Stimulation
Success Ratio
Trigger Point Localization
Number of Trigger Points
Triceps brachii lnfraspinatus
43 1
11
32 1
2.5 1
22 1
12 0
5 0
4
0
Adductor and pectineus
12
3
9
5.4
3
4
3
2
Peroneus longus
10
4
6
4.6
2
0
6
2
Gluteus medius
8
2
6
6.5
1
1
6
0
lliocostalis lumborum
5
3
2
5.0
0
0
5
0
Quadriceps femoris
3
0
3
8.0
0
2
1
0
19
26
a
Dry Needling
Injection
Mean Number of Treatments
Complete Recovery
Good
Amelioration
No Improvement
~
lotal
66
82
23
59
4.0
affected muscle was often observed. After a successful treatment, the trigger point disappeared, and during successful treatment, hyperimtability on palpation and the trigger point magnitude diminished progressively. Side effects were not encountered apart from an increase in lameness for 1 or 2 days in some dogs. Of the 82 trigger points, 29 disappeared completely (Table 1). Nineteen treatments had good results, 26 were ameliorated, and eight had no improvement. The best results were obtained in the triceps trigger points, in which 34 dogs (7 1%) recovered completely or scored "good." The results of treatment of the other points were less favorable. Relapses occurred within 4 weeks to 1 year in 16 dogs (33%). Fourteen dogs had multiple relapses. Most relapses were retreated successfully with the same method.
0
~
29
thermography. I ' - I 6 Trigger points were characterized by less depth of penetration and a decreased pressure threshold. Both measurements increased after trigger point treatment.' ' - I 4 Two classes of myofascial pain syndrome have been established in humans. Persons in good general health with one or more acute or chronic trigger points are classified as true trigger point patients. The second class contains patients with multiple, chronic trigger points and with other tender spots that do not refer pain on palpation. These patients, who also have depression. nonrapid eye movement sleep disorders, exercise intolerance, generalized pain, and fatigue are classified as fibromyalgia patients.' l 6 l 7 Fibromyalgia patients are not helped by trigger point treatment: they seem to react positively to tricyclic antidepressants and certain benzodiazepines. Discussion Body regions especially susceptible to trigger points are those in which large nerves and blood vessels lie close to Trigger points are induced by many factors: trauma. the body surface.' The triceps, pectineus-adductor, and internal disease, viral infections, and many still unknown peroneus longus trigger points are typical examples of this factors. Passive trigger points may become active under observation, as they lie close to the radial, femoral, and influences such as stress, trauma, fatigue, and f e ~ e r . ~ . ~ peroneus nerves. Methods used in humans to demonstrate and measure Histologic lesions in trigger point biopsies consist of trigger points objectively include measuring the depth of "fat-dusting" and nonspecific dystrophic changes such as penetration in soft tissue of a 1 cm2rubber disc in relation variations in size of muscle fibers, clusters of nuclei, exto the force with a tissue compliance meter, measuring the minimum pressure inducing pain or discomfort with cessive collagen fibers, contracture knots of myofibrils, a pressure threshold meter, magnetic resonance, and and loss of cross-striation.'6.'9.'0 There is a remarkably "3'
JANSSENS
high degree of correspondence ( 7 I %) between human trigger points and acupuncture points with respect to their localization and their clinical use.'.' Although acupuncture points have been described extensively in animals,?'-'3 trigger points have not been described i n animals. Acupuncture points are points in the skin with a diameter of about I mm and with a lower electrical resistance than surrounding skin. They are grouped on lines called meridians, which have different organ names. Twelve meridians are described. Meridian points are numbered from I to the last point on that meridian (9 to 67)? In this series of dogs, a correlation is seen between acupuncture points and four trigger points: the peroneus
277
longus point is gallbladder 34. the adductor-pectineus point is liver 10 or 1 1 . the gluteus medius point corresponds to gallbladder 29. and the infraspinatus point coincides with small intestine x The gluteus. adductor-pectineus. peroneus longus, infraspinatus. and iliocostalis lumborum trigger points compare anatomically with those described in hum a n ~ . ~ -The ' - ~ 'triceps point is not an acupuncture point and is not comparable with a human trigger point. The quadriceps trigger point location is not an acupuncture point. Although veterinary acupuncture is used frequently for various conditions."-'7 it should be differentiated from
278
TRIGGER POINTS
trigger point therapy. Acupuncture sometimes uses painful points, called A-shi points, as part of the total treatment. Trigger point therapy focuses on trigger points only. The weekly treatment interval was chosen according to human literature.’ In humans, only acute trigger points, as in acute lumbago, are treated twice a week. In the dogs, almost all lesions were chronic. Some trigger points were treated with injections and some by dry needle stimulation because trigger points were originally stimulated as acupuncture points. However, many dogs did not tolerate having the needle in situ for about 5 minutes. Whenever they moved, the needle caused discomfort. Therefore, the method was changed to injection of lidocaine, which is fast and affects a larger area so that less anatomic accuracy was needed. Two types of patients could be discerned. Most dogs with a triceps. infraspinatus, adductor-pectineus, or quadriceps trigger point had only one trigger point, and most of them reacted favorably to trigger point treatment. On the other hand, most dogs with multiple, symmetrical hindlimb trigger points reacted poorly to trigger point treatment. They should probably be classified as fibromyalgia patients. No separate control group was examined in this project because it was thought to be unethical toward owners and mimals to use a placebo trigger point treatment. However, the dogs served as their own controls. The mean period of 6 months of lameness before treatment, the prompt results with a minimum of treatments in 60% of the animals, and the ineffectiveness of all previous treatments were strong factors in favor of the effectiveness of the rreatment. It is also thought that confounding factors can be excluded because of the lack of improvement in the lameness after successive previous treatments, and because of the stability of the clinical lameness in trigger point patients. References I . Kennard M4. Haugen FP. The relation of subcutaneous focal sensivit) to referred pain of cardiac origin. Anesthesiology 1955; 16: 297-299. 2. Melzack R. Stillwell D, Fox E. Trigger points and acupuncture points for pain: Correlations and implications. Pain 1977: 3:3-23. 3. Melzack R. Acupuncture and musculoskeletal pain. J Rhcuniatol 1978: 5: I 19- 123. 4. Sinions DG. Muscular pain syndromes. In: Frictoii JR, Awad EA, eds. 4 ~ l w i r w/ t~i Puin Re.tcwrcti ( i t i d Tlrwapi, . 2 f j ~ c $ i . w c i / Puiri riiid / ~ i / ~ t - o n ~ y ~New ~ l ~ qYork: i u . Raven Press. 1989:1-42, 5. Sola A. Williams R. Myofascial pain syndromes. Neurology 1956; 6:91-96.
6. Travell J. Rinrler S. The myofascial genesis of pain. Postgrad Med J 1952; 111425-434, 7. Travell JG. Simons DG. Myofascial Pain and Dysfunction. ?hc’ Trigiyr Poinr ,\funi/u/. Baltimore: Williams and Wilkins. 1983: 1-164. 8. Bengtsson A , Bengtsson M. Regional sympathetic blockade in primary fibroniyalgia. Pain 1988; 33:161-167. 9. Airaksinen 0. Rantanen P, Kolari PJ, Pontinen PJ. Effects of infrared laser irradiation at the trigger points. Scandinavian Journal of Acupuncture and Electrotherapeutics 1988: 3:56-6 I. 10. Dongo B, Bartoli V. Grisillo D. Beconi D. Fibrositic m?ohscial pain in intermittent claudication: Effect of anesthetic block o f trigger points on exercise tolerance. Pain 1979; 6: 183- 190. 1 1 . Fischer AA. Cliiazal use oftissue compliance meter for documentation of soft tissue pathology. The Clin J Pain 1987: 323-30. 12. Fischer AA. Pressure threshold measurement for diagnosis of inyofascia1 pain and evaluation of treatment results. ‘The Clin J Pain 1087; 2:207-214. 13. Fischer AA. Letter to the editor. Pain 1987: 28:4 I 1-4 14. 14. MikcIi S, Piintinen PJ. Reliability of pressure threshold meter in location of latent trigger points in healthy subjects. Scandinavian Journal of Acupuncture and Electrotherapeutics 1988: 3:45-50. I S . Bach-Andersen R. Jacobsen S. Danneskiold-Samsoe B. et 31. New diagnostic tools in priniae fibromyalgia: Findings from the Copenhagen research group on fibromyalgia. In: Fricton JR. Awad EA. eds. .Idvcitrc~~,s i n Puin RcwurcA uiid Thiwpl. I f j ~ o f u w u l I’uit7 u i ~ d F i h r ~ ~ i ) ~ ~ uNew / g i aYork: Raven Press. 1989:269-276. 16. Bennett RM. Myofascial pain syndromes and the 1ibrom)algia syndrome: A comparative analysis. In: Fricton JR, Awad EA. eds. : l d w i i c ~ c ~ .it7 t 1’0111 Rrtcarc~lrund Ttierqi!~.,LIyo/u wiul Puiii riiid b’r/~roiiij,ulg~. New Y a k : Raven Press. 1989:43-66. 17. Goldenberg DL.. Clinical features of fibromyalgia. In: Fricton JR. Awad EA. eds. .1dwiiie.s i t i t’uiii Revc.arc,li ond T/imqi),., \ f i ~ ) / u s ( , i dPuiii c i i d I,’ihroiii.i,ulgia. New York: Raven Press. 1989: 139146. 18. McCain GA. Management of the libromyalgia syndrome. In: Fricton JR, Awad EA. eds. : l t / r . c i t i c ~ ~ siii Pain Rtwur.di rind 7Iiwcipi, .\lsoh\c~id Priin rind I.’//~~omjnlgiff. New York: Raven Press. 1989: 289-304. 19. Awad EA. Histopathological changes in fibrositis. In: Fricton JR. Awad EA. eds. .-lr/vunc,e, / t i Puin R m ~ r r d rund TtlCrUpi‘ ,211.r~/o.sc~rcil Pain mtl Fihr.otnj.a/,yiu New York: Raven Press. 1989: 249-258. 20. Henriksson KG. Bengtsson A. Muscular changes in fibromyalgia and their significance in diagnosis. In: Fricton JR. Awad EA. eds. . Idvuric.i~\in l’uiti Rrcc~urchcrnd Tlrrrapj. .lfj,i>luwiu/I’u1ir uird F i / ~ r o i t r I d y i uNew York: Raven Press. I989:259-268. 2 1. Janssens LA. The treatment of thoracolumbar disc disease in dogs by means of acupuncture: A comparison of two techniques. J Am Anim Hosp Assoc. 1989: 25:169-174. 22. Jaiissens LA. General acupuncture with special reference to therapeutic and analgetic aspects in animals. Vlaams diergeneeskundig Ti-jdschrift 1977: Part 1:46:266-276. 1978: Part 2:47:339-35 1, 19x0: Part 3:49:31-42. 23. Klide A. Kung S. l’c,iwintrr.i, riciipfrt~ctfrri~. Philadelphia: UniLersity of Pennsylvania Press. 1977: 1-276 24. Jaiissens LA. . 4 c i i p ~ / r i ~ ~points i u r ~ and r n t w d i u i ? . \ iti ilie dog Beersel: Blondiau Print. Belgium. 1984:l-14.
