Trigger point injections should be performed using sterile technique. When injecting myofascial trigger points present in the levator ani, the patient should be placed in the dorsal lithotomy position, prepped, and draped. A vaginal exam is performed to confirm the location of the trigger points and the planned site(s) of injection. We tend to first perform a bilateral pudendal nerve block just medial to the ischial spines to achieve analgesia before administering trigger point injections throughout the levator ani. Injections can be performed transvaginally, transperineally, or subgluteally. In the latter approach, the needle is inserted inferior and medial to the ischial tuberosities and is guided towards a finger placed transvaginally or transrectally [5]. Transperineal injections can be performed for trigger points located in the perineal muscles or puborectalis, while the transvaginal approach offers access to trigger points located in the obturator internus muscles. The authors prefer either a transperineal or transvaginal approach (Fig. 14.2) given the proximity of the injection site to the trigger point and the relative ease of injection.

After identifying the location of the trigger points, the needle is inserted which may elicit a local twitch response [4, 5]. The syringe should be aspirated to avoid intravascular injection. Local anesthetic is then injected into the trigger point. We use 1 % lidocaine initially, and if a therapeutic effect is achieved, we then inject 9 cc of 0.5 % bupivacaine mixed with 1 cc of 40 mg of triamcinolone for longer lasting pain relief at a subsequent visit. Injections may be accomplished while slowly withdrawing the needle [4]. The needle may also need to be redirected to adequately infiltrate the entire trigger point. The number of injections performed depends on how many trigger points are identified on exam. Although we administer a steroid agent in addition to a local anesthetic, some authors [5] caution against use of steroid agents for myofascial trigger point injections because of the theoretical concern of muscle wasting with repeated use.

Botulinum neurotoxin has also been used for the treatment of trigger points. It is administered using the same technique of injection employed for injection of local anesthetic and steroid agents. The typical dose of botulinum toxin varies in the literature and most of the evidence supporting its efficacy is derived from treatment of conditions involving generalized levator ani spasm [6, 10–15]. Doses between 20 and 400 units diluted in sterile normal saline have been used [15]. The clinical effects of toxin injection may not become apparent until 24 to 72 h post-procedure [11] and have been reported to last between 2 and 6 months [10, 11]. Because botulinum toxin is a heat-labile protein, it may be prudent to instruct patients to avoid hot baths, Jacuzzis, steam rooms, and saunas for the first 2 weeks following injection [5].