CLINICAL RESEARCH

Physio-Anatomical Feature of the Acupoints in Treating the Piriformis Syndrome

Jing Liu

The pain from Piriformis syndrome (PFS) may spread over multiple areas, including the buttocks, the back of thigh, the sacroiliac joint, the groin region, the low back and the coccyx. PFS could be easily confused with sciatic pain witch is caused by the lumber disk compression or the chemical inflammation at the nerve itself. A few authors have discussed in detail the issue of the treatment of PFS before. I observed a group of 29 PFS patients by using the acupuncture based on the physio-anatomical consideration. The results seem promising. The study suggests that the foremost issue of PFS and relative sciatic pain should consider releasing the muscular tension in a certain circumstances. The following is my brief summary of my clinical experiences on treating PFS.

Physical Examination and diagnosis

Trigger pain:

The most pain could be detected by pressing on Pf 2 and up to 1 to 2 cun downward from Pf 2 along the lateral sacrum border; Pf 1 was a trigger point found in almost every patient. One or more trigger points could be found on the line between Pf1 and the greater trochanter.

Straight leg rising:

A 45o to 50o limited leg rising was commonly seen, but the pain could be reduced by continue to rise over 70o ⁽¹⁾.

Medial rotation:

Tests were taken with patient supine. The thigh tested was flexed to 60o at the hip. A pain response was tested by further rotating and stretching ⁽³⁾.

The acupoints selected for treating PFS

Major Points: Pf 1, Pf 2, Ciliao (BL 32)

Assistant Points: Zhongliao (BL 33), Dachangshu (BL 25), Baohuang (BL53), Xi Yang Guan (GB 33)

Measurement of Pf 1 & Pf 2

A piriformis line was drawn from the proximal end of the greater trochanter to about 2 cm below the superior articula surface, leveled with Ciliao (BL 32) of the sacrum where it joins the illium. The line corresponds to the superficial projection of Piriformis. The Pf 1 is located one third of the line from greater trochanter. Pf2 is located immediately outside of the sacrum border on the Piriformis line.

Method of the treatment: The acupuncture needles, diameter 20, 2.5 to 3 cm, were used for Pf 1, Pf 2 and GB 30. The 1 to 1.5 cm needles were selected for the rest of the points. While patients are side lying, the needles are inserted and an even technique is applied for all of the points. Once a week of treatment is at least necessary. Two treatments in the first week are recommended.

The result seems promising by this method of the treatment. Most patients had immediate release from the pain right after the treatment and the effectiveness remained in most of them for one week after the first treatment. The effectiveness was accumulative following the treatments. It showed that tendon acu-stimulation on Pf 1, Pf 2 could release the spasm and tension of the muscle. The leg rising, rotation or adduction was improved. I feel that relief of muscle spasms could be the crucial factor in the release of entrapments in the sciatic nerve. The tendon stimulation with acupuncture not only give better results in reducing the pain, but also improve the function of the leg rotation and adduction which was comp ratable better than only selecting the traditional methods. Furthermore, the restoring of the muscular function brought a longer period of pain reduction or healing.

Discussion

PFS is often diagnosed as general sciatic pain or sacrum-illiac joint disorder. This clinical confusion can be understood by the physio-anatomy of the piriformis muscle. The review of piriformis muscle could give us a clearer guidance in selecting proper acupoints. The piriformis is anchored to the interior surface of the sacrum and supplied by the first and second sacral nerve the muscular fibers are located between the first and fourth anterior sacral foramina, which are in the location of BL 31,32, 33, and 34. The over tension or perpetuation of the muscle could cause the pain on the low back and coccyx in the case. Some muscular fibers may extend to the capsule of the sacroiliac joint and sacrospinous ligament and cause the pain in the area. BL 25, 24 are the usual selection for pain on the Sacroiliac joint. Since the other end of the piriformis muscle attach laterally to the superior surface of the greater trochanter, the pain is often located on the hip region with PFS as the result. There are no traditional acupoints, which are close enough to touch the PF near the greater trochanter. Pf 1 seems an optimal choice.

PF has innervation with three nerves. The sciatic nerve could be often affected by the PF; it is easy to be neglected in acupuncture practice. While PF passes through the greater sciatic foramen, it so closely attached to the nerve as to any increase in diameter of the muscle could compress on the nerve and cause clinical sciatic pain syndrome. It does not make much sense to use acupuncture to stimulate the sciatic nerve by inserting the needle on the sciatic foramen region without considering the muscular condition. Muscle spasms can certainly increase the diameter of the muscle. The compression of the superior and inferior gluteal nerves could cause buttock pain. The PF muscle could also entrap the pudendal nerve and cause groin and perineal pain and even sexual pain and dysfunction ⁽²⁾. The point selected on the meridian passing the region is not as effective as the issue on reducing the pressure directly on the PF according to my experiences.

Most authors selected GB 30 and BL 54, 32 as the main point in treating PFS. In my experiences, Pf 1, Pf 2 and BL 32 or 33 are considered as the major weapon for PFS. Both points are located on or near the either side of tendons of PF. Pf 1 is located above GB 30. The trigger pain is on Pf 1 but not on GB 30 in most circumstances. The location of Pf 2 should be similar to BL 53. The points of the BL 33 and 34 were usually inaccurately described as "3 cun lateral to the lower border of the spinous process of the sacral vertibra". The exact location of the Pf 2 should be the as mentioned above. However, the PF muscle on the lateral margin of sacrum is quite spread over the several sacral foraminas. Many times more than one trigger point could be detected along the borderline of the sacrum, approximately equal to BL 33, 34, 53 and 54. It would be better to consider using more than one point in this condition.

A new question arises in what could be the response of acupuncture on stimulating tendon instead of the muscle? The selection of Pf 1, Pf 2, BL 32 was to stimulate the tendon of PF mainly. I believe that tendon acu-stimulation could release the spasm or tension of the muscle. The leg rising, rotation or adduction may be improved better than traditional methods. Relief of muscle spasms could be the crucial factor in the release of entrapments in the sciatic nerve. Furthermore, the restoring of the muscular function may bring a longer period of pain reduction or healing.

How useful is acupuncture in reducing the over strained tendons of the muscle? Certainly, the traditional meridian theory or the neuro-endophin system theory of acupuncture could not given satisfactory answers. Few publications have touched specifically on the challenge. It is clearly stated in neuro-physiology however that tendons possess the function of controlling the tension of the skeletal muscle by the Golgi tendon receptors. The Golgi tendon receptor senses the tension of the muscle and prevents the muscle in excessive contraction. This process is called inhibitory disynaptic reflex. One question remains to be answered that is: if acupuncture can promote the process of releasing the muscular over-tension status by stimulating Golgi receptor. More studies need to be done to support the theory.

1. Shang Tianyu, Dong Fuhuei, Integrated Practical Orthopediology, Beijing University of Medicine Press.1998

2. Evjenth O, Hamberg J, Muscle Stretching in Manual Therapy, A Clinical Manual, P.97, 122,172, 1984, Alfta Rehab Forlag, Alfta, Sweden

3. Janet G. Travell, David G. Simons, Myofascial Pain and Dysfunction, P.186, Williams&Wilkins, Media, PA, 1984