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Sphincter Ani


The Sphincter Ani is a muscle of the perineum.

Anatomical Attachments: The Superficial fibers attach posteriorly to the anococcygeal raphe and encircle the anus and join at the point of the perineum. The Deep fibers surround the anal canal where they merge with the transverse perinea at the central point of the perineum.

Action: This muscle is in a state of constant tonic contraction, it closes the anal canal and orifice.

Nerve Supply: S4 nerve and the branches from the inferior rectal branch of the pudendal nerve.

Vascular supply: Inferior rectal and the transverse perineal artery.

Vascular entrapment: As this region has significant blood supply and soft tissue dysfunction is prevalent, the potential for vascular entrapment is great. Most tissues, due to this abundant blood supply, function normally. One can only extrapolate as to how many cases of urogenital or anal/rectal dysfunctions is simply the result of vascular impingement. We do know that compressive force attributes to habitual dysfunction, as well as altering the shape and function of the prostate. We also know that trauma and persistent stress can illicit ischemic muscles within the pelvic floor. What we do not know, as of now, is the correlation between the two.

Travell and Simons Trigger Point Pain Referral:  

Click on a small image to view an enlarged image


Trigger Point Signs and Symptoms: Anal pain during bowel movements, remote tenderness or pain in the anal region.

Authors' note: Dysesthesia associated with the pelvic floor are usually the direct result of trauma. While heavily innovated by nerve, the primary area of study has been devoted to coccygeal pain, referenced as Coccydynia. However, some authors choose to differentiate between Coccydynia (which is a compressive force caused by an anterior and laterally deviated coccyx exerting pressure on the nerve), and Coccyalgia (which is nerve pain experienced without osseous encroachment). Due to the numerous muscles that attach to the coccyx and the course that the nerve travels, it is possible that what some describe as coccyalgia, is the result of entrapments.

Trigger Point Activating and Perpetuating Factors: Physical or psychic trauma associated with the pelvic region, blunt trauma to the buttock, post surgical adhesions and/or trigger point formation within those adhesions.

Differential Diagnosis: Sexual abuse or Physical abuse, (Segmental, Subluxation, Somatic dysfunction) S1 S2 S3 S4 or S5 radiculopathy, Coccygodynia (Coccygeal nerve compression), Coccygeal spasm, Coccygeal fracture, Levator ani syndrome, Trauma to the pelvic region, Pregnancy, Spontaneous Abortion (Miscarriage), Tension myalgia of pelvic floor, Proctalgia fugax, Hemorrhoids, Polyps, Anal fissure, Lymphogranuloma venereum, Colorectal cancer, Crohn’s Disease, Diverticular disease, Fecal impaction or Constipation, Proctitis, Prostatitis, Prostatic hypertrophy (Enlarged prostate), Prostate cancer, Tetanus, Systemic infections or inflammation, Nutritional inadequacy, Metabolic imbalance, Toxicity, Side effects of medication.


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