| The piriformis muscle is a thinner deep muscle overlying underneath the gluteus maximus muscle.The muscle arises from the ventrolateral surface of the S2-S4 sacral vertebrae.It passes through the greater sciatic foramen,becomes tendinous,and ends in the greater trochanter of femur,It is mainly involved in the abduction and external rotation of the hip joint,especially during weight-bearing activities.It can reduce the excessive axial internal rotation of the hip to provide the best hip joint load and positioning,and maintain the stability of the pelvis-femur position.It could control pelvic-femoral position and stability and predict the incidence of knee and hip injury.Previous,Magnetic resonance imaging(MRI)examination has been the first choice in the clinical about study of muscle.It has high resolution for soft tissue and multi-parameter and multi-aspect imaging and clearly show myopathy and obvious advantages in the diagnosis and differential diagnosis of myopathy.However,MRI examination is expensive and takes a long time,so it cannot be widely used in clinical practice.Nevertheless,ultrasound examination could be applied to all kinds of people,more easily in clinical promotion and application.In addition,in recent years,with the continuous improvement of ultrasound instruments,muscles display more clearly.Therefore,musculoskeletal ultrasound has become a hot topic in recent years.At present,Musculoskeletal ultrasound mainly focus on the examination of superficial muscles of limbs.Little research has been done on the piriformis muscle,the most common lesion of the muscle of which is piriformis syndrome.Piriformis syndrome(PS)is a controversial neuromuscular disease,resulting in difficult and elusive diagnosis to make.Anatomically,the sciatic nerve has an intimate relationship to the piriformis muscle.The syndrome results from prolonged or excessive contraction of the piriformis muscle due to entrapment of the sciatic nerve at the level of the piriformis muscle.It causes pain in the buttocks and hips,with or without radiating pain in the lower limbs,and sometimes with paresthesias in the groin area,perineum,calves,feet,and rectum.In 1928,Yeoman firstly described the sciatica due to sacro-iliac joint periarthritis with fibrosis of the piriformis muscle.In 1947,Robinson coined the term"piriformis syndrome",describing it as a nerve entrapment syndrome.The disease is used in the literature,and also called "deep hip syndrome","pelvic outlet syndrome"or "inferior piriformis syndrome".Currently,the pathogenesis of PS is unclear.Potential etiologies include history of trauma to the hip or pelvis,muscle injury or chronic muscle stretching associated with ait disturbances and overtraining.The abnormal anatomical relationship between the sciatic nerve and the piriformis muscle is also considered to be the reason why the nerve is more susceptible to compression because of the variant anatomy.Beaton and Anson described the six anatomical relationships between the sciatic nerve and piriformis,and proposed that anatomical variation is also the cause of sciatic nerve pain.In the majority of cases,PS occurs in middle-aged patients.The ratio of female to male patients with PS has been reported as 6:1.Sciatica is a common clinical condition,with a lifetime incidence as high as 12.2%-27%.This disease could be aggravated with increased abdominal pressure,such as defecation and cough.In severe cases,the pain in the affected side of the hip is like as severe as cutting or burning,or even Walking broken.And hip abduction and external rotation that contracts the piriformis muscle(Pace test and Beatty test)could also exacerbated the syndrome.It is pointed out that its diagnosis is impeded by a lack of agreed upon clinical criteria and a paucity of established investigations,including imaging.This disease is similar to the pain caused by the compression of the sciatic nerve caused by other reasons(such as lumbar disc herniation,etc.).It is extremely easy to misdiagnose and missed diagnose the disease.Aside from those signs,notably,the Freiberg and Pace tests are positive in only 67%of the patients.Fishman et al designed a neuroelectrophysiological test,the FAIR test,emphasizes the position of muscles in flexion,adduction,and internal rotation.He found the H reflection time delay.However,this test is not specific enough to identify the cause of sciatic nerve injury,which is difficult to be widely applyed in clinical practice.At present,the researchers who use imaging examination to diagnose PS mainly use MRI to study and find the piriformis muscle hypertrophy in patients with PS.Recently,some articles reported that use of diffusion tensor imaging(DTI)and diffusion tensor fiber tracing(DTT)as an innovative tool preliminary evaluated function of the sciatic nerve.proposed a clinical scoring system consisting of clinical symptoms,signs,and several provocation maneuver tests for the diagnosis of PS.The sensitivity and specificity of these scores were 96.4%and 100%,respectively,with a positive predictive value of 100%and a negative predictive value of 86.9%.So far,he is the first to propose a clinical diagnosis of PS.Occasionally,some scholars put forward a score using the pressure pain threshold to diagnose PS.But these aboved methods have not been further clinically validated.At present,in the absence of a specific test,PS is primarily diagnosed by physician based on clinical symptoms,physical examination,and a positive response to local injection of anesthetic into the muscle when adequate inquiry suggested no spinal cause of significant sciatic pain,it is merely a clinical and exclusion diagnosis,compromising the credibility of this entity as a valid diagnosis.Many patients delays in diagnosis,severely haved affected the basic life function of patients.Therefore,it is urgent to find a rapid and effective diagnostic method to diagnose the disease in timely and accurately and to formulate a correct treatment plan to improve the quality of life of patients.As a means of image examination,ultrasound has been widely used in clinical practice.Especially in recent years,the application of ultrasound in many musculoskeletal examination has been favored by the majority of clinicians.To date,ultrasound has exhibited promise as a visual guidance tool for piriformis muscle injections,and is more convenient than other approaches,and introduces no radiation hazard.Therefore,it is possible to use ultrasound to diagnose PS.However,only a few case reports using ultrasound for PS diagnosis have been published.So far,there is no systematic research on ultrasound in patients with PS.Part 1 Assessment of Piriformis Muscle Anatomical Morphology with Ultrasound in Healthy PeopleObjectiveTo investigate piriformis muscle thickness and cross-sectional area(CSA)in healthy people of different labor types(mental workers and physical workers)and correlation between body mass index(BMI)and piriformis thickness and CSA by ultrasoundMaterial and MethodsFrom March 1,2015 to May 28,2018,we enrolled 60 healthy subjects who were referred physical examination at the physical examination center from Shan Dong Province Qianfoshan Hospital and age over 20 years old.All the volunteers had no history of pain in the lumbosacral,pelvic,hip and sacroiliac joint regions,no positive findings in neurosurgical physical examination,and no systemic diseases.According to the types of labor,the research objects are divided into two types:mental workers and physical workers.Bilateral piriformis muscle was performed on all healthy volunteers by ultrasound examination:in order to ensure the repeatability,two indicators in all cases were completed by 10 years experienced ultrasonogists under the conditions of not knowing the other ultrasonogists's,measurement data.The thickness,CSA,boundary,morphology and internal echoes of their bilateral piriformises was observed and Compared in mental workers and physical workers.The correlation between BMI and piriformis thickness and CSA was also compared in statistical analysis.Results1.A total of 60 healthy volunteers were included and divided into two groups:mental workers and physical workers.There were no significant differences in the patients' age,gender,BMI and the thickness and CSA of their bilateral of piriformises between the two groups(P>0.05).However,it was found that the gluteus maximus muscle of physical workers was thicker than mental workers.2.Work of different types of occupation,there were no significant statistically difference in piriformis muscle thickness and cross-sectional area in mental workers(P>0.05);there were no significant statistically difference in piriformis muscle thickness and cross-sectional area in physical workers(P>0.05).3.There was no statistically significant difference in piriformis thickness and CSA between the right side and the left side,and the data on both sides were highly correlated(P<0.001).Thus,this paper used the right piriformis thickness and CSA to explore the correlation between BMI and them in different types of occupation,respectively.There was no linear correlation between BMI and the thickness and CSA of the right piriformis muscle.4.A normal ultrasonographic findings of the longitudinal planes of the piriformis muscle:The piriformis muscle looks like "pear" shape.It has clear contour,smooth outer muscular membrane,linear high echo,oblique internal muscle texture,uniform echo and clear demarcation.Anormal ultrasonographic findings of the transverse planes of the piriformis muscle:It is "semicircle" or "triangle" with clear boundary,smooth and fine outer membrane of muscle,low echo between internal muscle bundles and Interspersed spotty hyperechoic.5.Two cases of piriformis variant were excluded:In one case,the ultrasound revealed unclear decomposition of piriformis and gluteus medius,which was later confirmed as fusion of piriformis and gluteus medius by MRI.In another case,the border between the piriformis and the superior gemellus was not clearly demarcated by ultrasonography,and the partial fusion of the piriformis and the superior gemellus was confirmed by MRI.Conclusion1.There was no significant correlation between workers of different types of occupation and piriformis muscle thickness and CSA.2.Work of different types of occupation,there was no significant correlation between BMI and piriformis muscle thickness and CSA.The conclusions obtained above establishesd a foundation for the further study of piriformis syndrome and the selection of healthy volunteers as the control group.Part 2 Application value of ultrasound in the diagnosis of piriformis syndromeObjective1.Ultrasound and MRI were used to measure patients with clinical suspicious piriformis syndrome:The thickness and cross-sectional area(CSA)of the piriformis on both sides and the echogenic changes of internal the muscle were analyzed.2.Based on the existing method(Michel method),a new clinical diagnosis score grading method for piriformis syndrome was established.3.To evaluate the specificity and sensitivity of ultrasound measurement parameters:increased thickness(iTh)and increased cross-sectional area(iCSA)for the diagnosis of PS.Material and MethodsThis is a cross-section study.Ethical approval was granted by Shan Dong Province Qianfoshan Hospital Institutional Clinical Research Ethical Committee.We collected written consent forms from all subjects before the examinations.From March 1,2015 to May 28,2018,we enrolled 33 clinically diagnosed PS patients who were referred from Shan Dong Province Qianfoshan Hospital and complained of acute pain in their buttocks thighs,and lower limbs(Pain duration?6 months),and collected 26 healthy volunteers for physical examination in our hospital as the control group.In our study,we modified the Michel scoring system as follows:scores less than 6 were defined as stage 0,scores between 6 and 8 were defined as stage 2,and scores between 8 and 11 were defined as stage 2,scores greater than or equal to 11 were defined as stage 3.Bilateral piriformis muscle was performed on all PS patients and healthy volunteers by ultrasound and/or MRI examination.Ultrasound Parameters(iTh and iCSA):in order to ensure the repeatability,two indicators in all cases were completed by 10 years experienced ultrasonogists under the conditions of not knowing the other ultrasonogists's,measurement data.the thickness and CSA of their both sides of piriformises were measured in the longitudinal planes and transverse planes.These parameters of the patients and voluteers were recorded.The thickness,CSA and iTh,iCSA of piriformises of the two groups were respectively compared in statistical analysis.Meanwhile,the iTh and iCSA of piriformises of the two groups were also respectively compared in statistical analysis.MRI:A Siemens Magnetom Skyra 3T MR scanner(Siemens,Erlangen,Germany)was used.The protocol was as follows:pelvic MRI with a spin echo T1-weighted acquisition of axial cross-sections.ImageJ software(Version 1.50q)was used for the piriformis muscle measurement on echo intensity in US images and muscle CSA and thickness measurement in MRI images.For US images,echo intensity of piriformis muscle was also measured in all patients by ImageJ.The echo intensity of piriformis muscle of the two groups was respectively compared in statistical analysis.For MRI images,the muscle CSA and thickness were also measured.The thickness and CSA of piriformises of the two groups were respectively compared in statistical analysis.The areas under the receiver operating characteristic curve(AUROCs)of the ultrasound parameters(iTh and iCSA)in the clinical PS scoring stages were evaluated.The intra-rater reliability of the piriformis muscle measurements was high.left intra-class correlation coefficient(ICC1,1)=0.90;right intra-class correlation coefficient(ICC1,)=0.99.Results1.On both ultrasound and MRI,the piriformis muscle thickness and CSA were significantly increased on the abnormal side compared with those on the asymptomatic side of the PS patients(P<0.05).There was no significant difference were found the thickness and CSA of healthy voluteers.2.The gray scale value was significantly increased in abnormal piriformis muscle compared with the asymptomatic sides in PS patients(P<0.05),while no significant difference were found in healthy volunteers(P>0.05).3.Although there were no significant differences between the normal(stage 0)group and stage 1 group in iTh,the normal group had a significantly lower iTh than the stages 2 and 3 groups,and the stage 2 group had a significantly lower iTh than the stage 3 group.The stage 0 group had a lower iCS A than patient groups,and asignificantly lower iCSA was found in stage 1 group than in stage 2 group and in stage 2 group than in stage 3 group.4.ROC analyses were performed on the iTh and iCSA values to discriminate between the between the stage 0 and over all PS groups(stages 1-3)and stage 2 and stage 3 groups.The areas under the ROC curve(AUROCs)for iTh and iCSA for discriminating between the stage 2 and stage 3 groups were 0.82(95%CI,0.64-1.00)and 0.89(95%CI,0.78-1.00),respectively.AUROCs for iTh and iCSA for the discrimination of stage 0 from stages 1-3 were 0.88(95%CI,0.80-0.97)and 0.95(95%CI,0.89-1.00),respectively.The AUROCs for iCSA were higher than those for iTh for discriminating between the different stage groups.In addition,increased PM thickness for the diagnosis of clinical score stage0(healthy group)and piriformis syndrome disease(stagel-3)specificity and sensitivity were 0.769,0.878,respectively.Increased PM CSA for diagnosis of stage0(healthy group)and piriformis syndrome disease group(stage1-3)of the specificity and sensitivity were 0.923,0.909,respectively.5.Ultrasound observation of sciatic nerve changes:There were 5 patients with rough sciatic nerve trunk and blurred edge margins,which the internal honeycomb structure was blurred.The asymptomatic lateral sciatic nerve trunk was clear and straight,and the internal honeycomb structure showed Clear.Conclusions1.ultrasound and MRI found that the thickness and cross-sectional area of the piriformis were increased in patients with piriformis syndrome.there was a good consistency in the measurement of the piriformis between Ultrasound and MRI.2.We adopted a new diagnostic grading method for piriformis syndrome compared with Michel's diagnosis of the disease by clinical score solely,which has had more imaging basis support and has better reflected the severity of different degrees of piriformis syndrome.ITH and iCSA of ultrasound measurement has a high sensitivity and specificity for the diagnosis of piriformis syndrome.Additionally,ultrasound also showed echogenic changes in the peripiriform soft tissue and muscle itself.3.Fishman et al,a senior specialist in PS patients at Columbia University Medical School,New York,USA,also affirmed our research methods many times and pointed out that ultrasound could be used to evaluate PS patients in the future.In conclusion,ultrasound has a good diagnostic value for piriformis syndrome and is easier to be popularized and applied in in clinical practice. |
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