Piriformis syndrome is a symptom complex that occurs when the sciatic nerve is compressed in the sub-piriformis orifice. Clinically characterized by pain of the gluteal-sacral localization and along the affected nerve, sensitivity disorder, peripheral paresis of the foot. In the diagnosis, the main role belongs to specific clinical symptoms, a novocaine test, X-ray, ultrasound, and tomographic studies are additionally carried out. Treatment includes pharmacotherapy, physiotherapy, osteopathic and manual techniques, kinesiotherapy. With low efficiency of conservative methods, surgical treatment is indicated.
ICD 10
G57.0 Sciatic nerve lesion
General information
The assumption about the participation of the piriformis muscle in the occurrence of sciatic nerve neuropathy has been put forward for a long time. In 1937, the German doctor Freyberg studied this syndrome in detail and proposed its surgical treatment — the intersection of muscle fibers. According to the mechanism of its development, piriformis syndrome (PS) refers to tunnel compression-ischemic neuropathies. Exact data on the prevalence of the disease are not given in the literature. The syndrome occurs in 50% of patients with discogenic lumbar radiculitis. 80% of cases of PS is secondary, is not associated with a direct lesion of the piriformis muscle, but is caused by its reflex tonic contraction due to other pathological processes.
Causes
The disease is based on pathological changes in the piriformis muscle: spasm, damage, inflammation, fibrosis, volume increase. Sometimes there is an iatrogenic etiology associated with intramuscular injections into the gluteal region, in some cases leading to the formation of an infiltrate, extremely rarely an intramuscular abscess. The main etiofactors of PS are:
- Vertebrogenic pathology. Lumbar osteochondrosis, spondyloarthrosis, intervertebral hernia of the lumbar spine, spinal tumors, extramedullary spinal tumors occur with irritation of the spinal roots and sacral plexus fibers innervating the piriformis muscle. The result is her reflex spasm.
- Traumatic injuries. It is possible to directly injure (tear) muscle fibers, their overextension due to displacement of the pelvic bones with bruises and fractures of the pelvis. Subsequently, fibrosis develops, the muscle shortens and thickens. PS may be caused by the formation of a post-traumatic hematoma of this area.
- Muscle overload. It is observed with prolonged forced position of the pelvic-iliac segment due to work activity, incorrect fixation in the treatment of fractures. An increased load on the piriformis muscle occurs if the patient tries to take an antalgic pose with radicular syndrome. Overload is possible with excessive training in cross-country sports, weightlifting.
- Inflammatory processes. Myositis affecting the piriformis muscle is a fairly rare phenomenon. More often, the syndrome is caused by reflex spasm that occurs against the background of sacroiliitis, inflammatory diseases of the pelvic organs (cystitis, prostatitis, prostate adenoma, adnexitis, endometriosis, uterine fibroids).
- Asymmetry of the pelvis. It is formed with scoliosis, shortening of the lower limb, improperly fused fracture of the pelvic bones, pathology of the hip joint. As a result, the piriformis muscle is subjected to increased stress and overextension.
- Oncopathology. Tumor processes of the proximal femur, sacral region cause changes in the relative position of anatomical structures, as a result of which the piriformis muscle suffers. Pelvic neoplasia is the cause of reflex muscle spasm.
- Hip amputation. PS in a patient with an amputated hip was described in 1944. The afferent impulse coming from the stump reflexively introduces the piriformis muscle into a permanent spastic state, causing the presence of phantom pains.
Pathogenesis
The piriformis muscle is attached with a wide end to the sacrum, with a narrow end to the large trochanter of the femur. It provides the abduction and external rotation of the thigh. Passing through the large sciatic foramen, the piriformis muscle forms a slit-like subgrushoid foramen, bounded from below by the sacro-tuberous ligament. Through it, the sciatic, lower gluteal, genital and posterior cutaneous nerves exit from the pelvis, as well as the lower gluteal arteries and veins pass through. In 10% of cases, the sciatic nerve goes through the thickness of muscle fibers.
Due to various etiofactors, persistent tonic contraction is accompanied by a thickening of the pear-shaped muscle, which leads to a significant reduction in the size of the sub-pear-shaped hole. The result is compression of nerves and blood vessels passing through the hole. First of all, the largest sciatic nerve suffers. Vascular compression causes deterioration of blood supply to the nerve trunk, which acts as an additional pathogenetic component of sciatica.
Classification
Piriformis syndrome does not differ in clinical diversity or the presence of different variants of the course. The classification used in practical neurology is based on the etiological principle, the understanding of which plays a leading role in treatment planning. Accordingly , the etiology of the syndrome is divided into 2 main forms:
- Primary. It is caused by a direct lesion of the muscle itself. The primary forms include PS on the background of myositis, physical overstrain, injuries.
- Secondary. It occurs as a result of prolonged pathological impulses from the lumbar or sacral spine, pelvis, sacroiliac joint. It is formed in diseases, tumors of the spine, pelvic organs, hip joint.
Piriformis syndrome symptoms
In 70% of patients, the disease manifests pain in the gluteal-sacral zone. Pain sensations have a constant, dragging, aching nature, painful cerebral pains are possible. The pain syndrome increases when walking, bringing the hip, squatting, trying to put one leg on top of the other. A slight dilution of the legs in a horizontal position or sitting reduces pain. Subsequently, sciatica joins — pain along the sciatic nerve. Against the background of constant cerebral pain, lumbago occurs along the back of the thigh — intense pain impulses going from the buttock to the foot. In the area of pain localization, hypesthesia (decreased pain sensitivity) and paresthesia (burning, tingling, crawling sensation) are observed.
A decrease in the strength of the muscles of the lower leg and foot is characteristic. In severe cases, with total compression of the sciatic nerve fibers, pronounced paresis leads to the appearance of a “dangling” foot. Vascular compression causes intermittent lameness syndrome — the appearance of pain in the calf muscle when walking, forcing the patient to stop. Symptoms of vascular disorders are also pale coloration of the skin of the foot, a decrease in local temperature and numbness of the fingers.
Complications
Constant exhausting pain syndrome limits the patient’s ability to work, provokes sleep disturbance, increased fatigue, emotional lability. Peripheral paresis of the foot and lower leg occurs with muscular atrophy. The long course of the disease leads to irreversible atrophic changes in the muscles with the formation of persistent paresis, leading to disability of the patient. In some cases, there is a secondary spasm of the pelvic floor muscles, accompanied by difficulty, discomfort during urination and defecation, in women — dyspareunia.
Diagnostics
The difficulties of clinical diagnosis are due to the similarity of symptoms with sciatic neuropathy, deep occurrence of the piriformis muscle. In everyday medical practice, the main diagnostic role belongs to clinical tests. The basic components in the diagnosis are:
- Neurologist’s examination. Determines the soreness of palpation of the upper medial surface of the large trochanter and sacroiliac joint. Pain is provoked by a number of tests: active internal rotation of the bent hip (Freiberg’s symptom), an attempt to raise the knee in a lying position on a healthy side (Beatty’s symptom), passive hip rotation inward (Bonnet-Bobrovnikova syndrome), bending the trunk forward with straight legs (Mirkin’s symptom).
- A sample with novocaine. Novocaine is injected into the thickness of the piriformis muscle. A marked reduction in pain within 2-3 minutes after injection confirms the diagnosis.
- Instrumental examinations. The assessment of the condition of the muscles of the lower limb and the conduction of the sciatic nerve is carried out using electroneurography. According to indications for the detection of pelvic asymmetry, oncopathology, traumatic injuries, radiography of the pelvic bones, CT and MRI of the spine, ultrasound of the pelvic organs is performed.
During the diagnosis, you may need to consult a vertebrologist, oncologist, urologist, gynecologist. Differential diagnosis of PS is carried out with radicular syndrome with intervertebral hernia of the lumbar region, lumbosacral plexitis, dysmetabolic, toxic lesion of the sciatic nerve. Intermittent lameness requires differential diagnosis of vascular diseases: obliterating atherosclerosis, obliterating endarteritis of the lower extremities.
Piriformis syndrome treatment
In most patients, conservative therapy is effective, which is a combination of pharmacotherapy and non-drug methods of treatment. In the presence of causal factors (tumors, pelvic asymmetry, inflammatory diseases), their elimination is necessary. Surgical operation for dissection of the piriformis muscle and neurolysis of the sciatic nerve is performed with the ineffectiveness of conservative techniques in cases where the syndrome proceeds with a rough paresis of the foot. The main components of conservative therapy are:
- Relief of pain syndrome. From medications, analgesics, nonsteroidal anti-inflammatory drugs are used. The most effective is the introduction of local analgesics and glucocorticosteroids in the form of therapeutic blockades. Some physiotherapy procedures have an anti-inflammatory effect: UHF therapy, hydrocortisone ultraphonophoresis, magnetotherapy. Analgesic effect is provided by acupuncture sessions, compresses with dimexide.
- Relieving muscle spasm. Medically achieved by prescribing muscle relaxants. A good result is the use of relaxing massage of the gluteal-sacral region, post-isometric relaxation, myofascial releasing.
- Kinesiotherapy. It is aimed at restoring the normal motor pattern. The correct sequential inclusion of various muscle groups in the movement ensures an adequate load on the affected area, promotes its speedy recovery and prevents the occurrence of relapses.
Prognosis and prevention
In most cases, under the condition of complex therapy, the syndrome has a favorable prognosis. The effectiveness of surgical treatment reaches 85%, but relapses are possible after it. Without proper treatment, persistent paresis of the foot develops throughout the year. Primary prevention of PS is to prevent muscle overload, traumatic injuries, osteochondrosis of the spine. Timely detection and treatment of vertebrogenic diseases, pathology of the pelvic cavity is important. Secondary prevention is aimed at preventing relapses, is carried out by kinesiotherapy, regular exercise therapy, exclusion of excessive physical exertion.