Context: Focal sympathetic nerve blocks of the ganglion impar are often effective treatments for coccydynia (coccyx pain) and other pelvic pain syndromes. These injections are generally performed under contrast-enhanced fluoroscopic guidance. Vascular uptake may potentially occur during the injection and vascular uptake rates have been reported for other spinal injections, but never for ganglion impar blocks. Aims: The purpose of the study was to determine vascular uptake rates during fluoroscopy-guided ganglion impar blocks. Settings and Design: An academic/University-based Coccyx Pain Center. Methods and Materials: A total of 78 consecutive trans-coccygeal ganglion impar blocks were analyzed for vascular uptake of contrast as determined by intermittent fluoroscopy. Statistical Analysis Used: Direct calculation of incidence. Results: Only one patient (1.3%) demonstrated a vascular uptake pattern, which was readily recognized and corrected by slightly adjusting the position of the needle tip and thereby subsequently obtaining the desired contrast pattern at the ganglion impar. Conclusions: Vascular uptake incidence is low during ganglion impar blocks. This information can be one of the multiple factors considered when a physician is deciding whether or not to use contrast in an individual patient.

Objective The purpose of this case series is to report on the effectiveness of a single percutaneous injection of doxycycline as a primary treatment for aneurysmal bone cyst (ABC). Materials and methods A retrospective cohort study was conducted on seven patients diagnosed with ABC at various anatomical sites, with the intention to treat by a single percutaneous injection of doxycycline. Mean patient age was 14years. Results Signs of treatment response were seen in six of seven patients after one injection. Three of the seven received a second treatment, despite signs of response. Another had expansion of the lesion after treatment, requiring excision. In total, three patients had a single injection of doxycycline as their sole treatment and another three showed signs of response after a single injection. Conclusions A single percutaneous injection of doxycycline should be considered a viable primary treatment option for ABC.

The purpose of this study was to evaluate the magnetic resonance imaging (MRI) appearance of the hip capsule in patients with femoroacetabular impingement (FAI) undergoing hip arthroscopy with capsular repair versus non-repair. A multicenter clinical trial was performed with 31 patients (49 hips) undergoing hip arthroscopy for treatment of FAI. A small- to moderate-sized interportal capsulotomy was performed. Each hip was randomized to capsular repair versus non-repair of the interportal capsulotomy. MRI was performed at 6 and 24 weeks postoperatively and was analyzed by two musculoskeletal radiologists. Patients and the radiologists were blinded to the treatment applied. Capsular defect size and capsule thickness were recorded on each scan. Mean patient age was 31.4 years. Capsular repair was performed in 23 (46.9%) hips. Mean capsulotomy length was 35 mm at Center X and 23 mm at Center Y. At 6 weeks postoperatively, a healed hip capsule (with no apparent capsulotomy defect) was observed in 10 (43.4%) hips that underwent capsular repair and 4 (15.4%) hips that did not undergo capsular repair (P = 0.13). At 24 weeks postoperatively, 25/30 hips (83.3%) achieved complete closure of the capsulotomy defect, with no significant difference between treatment groups. Repair of an interportal capsulotomy following hip arthroscopy for FAI results in a non-significantly higher percentage of healed hip capsules at 6 weeks postoperatively compared with leaving the capsule unrepaired, though the difference normalizes by 24-week follow-up. Repair of a small- to moderate-sized interportal capsulotomy does not provide a radiographic advantage following hip arthroscopy for FAI.

BACKGROUND:Techniques used in hip arthroscopy continue to evolve, and controversy surrounds the need for capsular repair following this surgical intervention. The purpose of this study was to evaluate the magnetic resonance imaging (MRI) appearance of the hip capsule in patients with femoroacetabular impingement (FAI) who underwent simultaneous bilateral hip arthroscopy through an interportal capsulotomy with each hip randomized to undergo capsular repair or not undergo such a repair. METHODS:This double-blind, randomized controlled trial included 15 patients (30 hips), with a mean age of 29.2 years, who underwent simultaneous bilateral hip arthroscopy utilizing a small (<3-cm) interportal capsulotomy for the treatment of FAI. The first hip treated in each patient was intraoperatively randomized to undergo capsular repair or no capsular repair. The contralateral hip then received the opposite treatment. MRI was performed at 6 and 24 weeks postoperatively, and the scans were analyzed by 2 musculoskeletal radiologists. The patients and the radiologists were blinded to the treatment performed on each hip. Capsular dimensions were measured at the level of the healing capsulotomy site and, for hips with a persistent defect, at locations both proximal and distal to the defect. These values were then analyzed at both time points to assess the rate and extent of capsular healing. RESULTS:At 6 weeks postoperatively, a continuous hip capsule (with no apparent capsulotomy defect) was observed in 8 hips treated with capsular repair and 3 hips without such a repair. Of the 19 hips with a discontinuous capsule at 6 weeks, 17 were available for follow-up at 24 weeks postoperatively; all 17 demonstrated progression to healing, with a contiguous appearance without defects and no difference in capsular dimensions between treatment cohorts. CONCLUSIONS:Arthroscopic repair of a small interportal hip capsulotomy site yields an insignificant increase in the percentage of continuous hip capsules seen on MRI at 6 weeks postoperatively compared with no repair. Repaired and unrepaired capsulotomy sites progressed to healing with a contiguous appearance on MRI by 24 weeks postoperatively. LEVEL OF EVIDENCE:Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

We thank the correspondents for their kind comments about our recently published study [1]. We agree with their statement that certain bony features present in normal adults could nevertheless be a potential source of pain in some patients with coccydynia. Indeed, this prompted us to complete a further study comparing the bony morphology of the coccyx in normal adults with that in patients with coccydynia, which we have recently published [2]. In this study, women with coccydynia were found to have a significantly higher frequency of bony spicule formation than normal women (44 vs. 19 %; P

There has been no systematic study of the anatomy of the region between the sacral and coccygeal cornua. Reference texts describe an intercornual ligament connecting these structures. The aim of this study was to investigate the anatomy of this region, which may be relevant to unexplained cases of coccygeal pain (coccydynia) and local nerve blocks. The bony anatomy of the sacrococcygeal (SC) cornual region was analyzed in 33 CT scans obtained from supine adults of mostly European origin with no known SC pathology, 7 μCT scans of cadaver SC specimens, and 105 Asian Indian adult skeletons. A further five cadaver SC specimens were examined histologically. SC cornual fusion was seen in 45 % of CT/μCT scans (mean age 67 years, 20 males) and in 20 % of adult skeletons (78 males); there was no association with age or sex. In the absence of SC fusion, the mean intersacrococcygeal cornual gap was 7.1 ± 2.4 mm; this was bridged by an intercornual ligament composed of parallel vertical collagen fibers reinforced by elastin fibers on its anterior surface. Small nerve branches were observed adjacent to the ventral aspect of the intercornual ligament and, in one case, traversing the ligament. Ipsilateral sacral and coccygeal cornua are therefore normally bridged by an intercornual ligament that is probably innervated. The cornua are fused on one or both sides in 20–45 % of adults. These findings may have implications for some cases of coccydynia and for anesthetists performing local nerve blocks.

The coccygeal plexus is variably described in anatomy texts and has rarely been studied despite the idiopathic nature of coccydynia in up to one-third of affected patients. The plexus was therefore investigated using a combination of microdissection and histology. The distal sacrum and coccyx in continuity with ischiococcygeus were removed en bloc from 16 embalmed cadavers (mean age 78 ± 10 years, 7 females) with no local disease. Ten specimens underwent microdissection of the coccygeal plexus and the remaining six were examined histologically after staining with hematoxylin and eosin and S100 immunohistochemistry to demonstrate nerve fibers. The coccygeal plexus is formed within ischiococcygeus from the ventral rami of S4, S5, and Co1 with a contribution (gray rami communicantes) from the sacral sympathetic trunk. It gives rise to anococcygeal nerves which pierce ischiococcygeus and the sacrospinous ligament to supply the subcutaneous tissue on the dorsal aspect of the coccyx. Some branches from the plexus pass medially anterior to the coccyx. The coccycgeal plexus is formed within ischiococcygeus rather than on its pelvic surface and appears to supply skin in the anococcygeal region. It probably also contributes to the innervation of ischiococcygeus, the sacrospinous ligament, coccygeal ligaments, and periosteum. It deserves to be considered as a potential pain generator that may be implicated in some patients with coccydynia.

Study Design. Retrospective case-control study.Objective. To determine if differences exists between the bony anatomy of the coccyx in patients with coccydynia and that in subjects with no known coccygeal pathology.Summary of Background Data. Numerous bony characteristics of the coccyx have been described in patients with coccydynia but their significance is uncertain. This study aimed to evaluate these in patients with coccydynia and compare them with normal coccyges.Methods. Magnetic resonance scans of the coccyx from 107 adults (mean age, 43 +/- 12 yr; 84 females) with clinically diagnosed coccydynia were retrospectively analyzed and compared with 112 computed tomographic scans from sex-matched adults with normal coccyges. The following were assessed: coccygeal segmentation; sacrococcygeal and intercoccygeal joint fusion, angles, and curvature; bony spicule formation; and subluxation.Results. Compared with normal, females with coccydynia had a more ventrally curved coccyx (curvature index, 85 +/- 7 vs. 90 +/- 5; P < 0.01), a lower prevalence of sacrococcygeal joint fusion (27% vs. 58%, P < 0.01), and a higher frequency of bony spicule formation (44% vs. 19%, P < 0.01). Males with coccydynia showed a trend toward a more ventrally curved coccyx (curvature index: 86 +/- 6 vs. 89 +/- 5, P < 0.08), and a lower prevalence of sacrococcygeal (27% vs. 60%, P < 0.02) and intercoccygeal (0% vs. 22%, P < 0.02) joint fusion. Combining statistically significant coccygeal parameters in a logistic regression model yielded sensitivity, specificity, and positive predictive values of 72%, 71%, and 73%, respectively in females and 52%, 92%, and 73%, respectively in males.Conclusion. This is the most detailed comparison of coccygeal morphology and morphometry in adults with and without coccydynia investigated using cross-sectional imaging. Anatomical differences in joint fusion and coccygeal curvature may either predispose to the development of coccydynia or arise as a result of this condition.

PURPOSE:Lack of data on the in vivo morphology and morphometry of the normal adult coccyx hampers understanding of radiological abnormalities in idiopathic coccydynia. The aim of this study was to investigate normal adult sacrococcygeal morphometry.METHODS:Retrospective analysis of 112 adult CT scans (mean age 63 ± 14.6 years, 50 males) evaluated the following: number of coccygeal segments; joint fusion; coccygeal spicules, subluxation, sacralization, and scoliosis; sacrococcygeal straight and curved lengths and curvature indices; sacrococcygeal and intercoccygeal angles; and lateral deviation of the coccyx tip.RESULTS:Four coccygeal segments were present in 76 % of scans. Sacrococcygeal fusion was present in 57 % and intercoccygeal fusion was increasingly common more caudally; there was no significant association with age or gender. A bony spicule was present in 23 %. Subluxation was rare. Nine of 12 coccyges with a retroverted tip were female. Mean coccygeal curved length was 4.4 ± 0.8 cm in men and 4.0 ± 0.8 cm in women (P < 0.01). Mean angle between first and last coccygeal segments was 138° ± 25° in men and 147° ± 25° in women (P = 0.08). There was no significant correlation between coccygeal length or curvature and stature, age or BMI.CONCLUSIONS:In this first detailed study of the CT morphology and morphometry of the adult coccyx, sacrococcygeal and intercoccygeal joint fusion was common. Female coccyges were shorter, straighter, and may be more prone to retroversion, factors that may be relevant to the markedly higher prevalence of idiopathic coccydynia in women.

The coccyx has been relatively neglected in anatomical research which is surprising given the population prevalence of coccydynia and our inadequate understanding of its etiology. This systematic review analyzes available information on the clinical anatomy of the coccyx. A literature search using five electronic databases and standard anatomy reference texts was conducted yielding 61 primary and 7 secondary English‐language sources. This was supplemented by a manual search of selected historical foreign language articles. The coccygeal vertebrae, associated joints, ligaments and muscles, coccygeal movements, nerves, and blood supply were analyzed in detail. Although the musculoskeletal aspects of the coccyx are reasonably well described, the precise anatomy of the coccygeal plexus and its distribution, the function of the coccygeal body, and the anatomy of the sacrococcygeal zygapophyseal joints are poorly documented. Further research into the anatomy of the coccyx may clarify the etiopathogenesis of coccydynia which remains uncertain in one‐third of affected patients. Clin. Anat. 25:158–167, 2012. © 2011 Wiley‐Liss, Inc.