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Predictors of outcomes of conservative management in chronic coccydynia - Results from a prospective clinicoradiological observational study
, R Dinesh Iyer, Praveen R. Iyer, Ajoy Prasad Shetty T, KS Sri Vijayanand, Rishi Mugesh Kanna, Rajasekaran Shanmuganathan
⁎Corresponding author: Ajoy Prasad Shetty T. ajoyshetty@gmail.com
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Received: ,
Accepted: ,
This article was originally published by Reed Elsevier India Pvt. Ltd. and was migrated to Scientific Scholar after the change of Publisher.
Abstract
Abstract
Chronic coccydynia is a difficult pathology to treat due to limited understanding of the etiology and risk factors. Aim of the study was to analyse the clinical and radiological factors associated with poor outcomes in coccydynia.
Prospective observational study.
Patients who visited the spine outpatient department between September 2019 to August 2021 with coccygeal pain of more than two months were included in the study. Lateral radiographs in seated and standing position were done to evaluate their Intercoccygeal angle (ICA), Sacrococcygeal angle (SCA), Basal Angle (BA) and Coccygeal Length. MRI was done for patients who were not relieved with 2 months of conservative treatment. Baseline VAS and ODI scores were documented at the first visit and at six months follow-up to evaluate the outcomes.
168 patients were included - 106 females and 62 males (M:F ratio 1.76) with a mean age of 41.71 years. 109 out of 168 (64.9 %) were obese and 31(18.5 %) were overweight. Type 2 and 4 coccyges were the most commonly seen morphology (67 patients each). Traumatic coccydynia had a better outcome with a mean VAS score of 3.54 compared to 4.36 in the idiopathic group(p < 0.05). Higher Intercoccygeal angle (ICA) was the only radiographic parameter that had coorelation with the outcomes. Mean ICA in good outcomes group was 34.8° (13.2) compared to 42.1° (14.6) in those with poor outcomes(p < 0.05). All 7 patients with pseudoarthrosis had VAS scores reduction of more than 50 %.
Type 2 and type 4 were the most common coccyx morphology encountered in patients with chronic coccydynia. Outcomes were better in traumatic group compared to idiopathic group and in those with pseudoarthrosis on MRI. Higher Intercoccygeal angle(ICA) was the only radiographic parameter associated with poor outcome of conservative management.
Keywords
Coccyx
Coccydynia
Chronic pain
Intercoccygeal angle
Basal angle
1 Introduction
The coccyx (greek word for cuckoo's beak) is the terminal segment of spine with many anatomical variations. It is considered a vestigial remnant of tail, with its only described function in humans is to serve as an attachment for the pelvic floor muscles. However, an affliction of this small bone has been one of the most difficult pathologies to treat in orthopaedics. Coccydynia is a common condition presenting to the spine outpatient department with a reported incidence of 2 % of the patients presenting with back pain1,2. Conservative treatment including - analgesics, doughnut pillow and pelvic floor exercises are the mainstay of management of coccydynia. Yet, nearly half of these patients do not respond to conservative measures or the pain relapses after initial relief. A prospective study on the outcomes of conservative management by Charrière S et al. reported that 59 out 115 patients (51 %) had unfavourable outcomes at 36 months follow up.3 A systematic review by Howard PD et al.4 reported that the current evidence on the various conservative options (pharmacological, manipulations, prolotherapy etc.) are limited and low quality and were unable to recommend the most effective conservative intervention.
Studies have tried to identify the radiological and clinical risk factors for poor outcomes but most of the existing studies are retrospective in nature with a relatively smaller sample size. Female gender, obesity and non-traumatic etiology have been hypothesized as causes of poor outcomes.5 Postacchini F et al.6 proposed a morphological classification of the coccyx based on its angulation into 4 types (Fig. 1). Based on their study, types 2,3 and 4 has been associated with higher incidence of coccydynia. Study by Maigne JY et al.7 reported that obesity was a risk factor for coccydynia as it affects the biomechanics of sitting compared to persons with normal BMI. Females owing to the inherent ligamentous laxity, susceptible coccygeal morphology and child birth, were found to be five times more prone to develop coccydynia than men.8
With this background we conducted a prospective study to analyse the clinical and radiological factors associated with poor outcomes in coccydynia and whether any particular morphological type or radiographic parameter is associated with higher chances of relapse and poor response.
2 Materials and methods
The study was conducted in a tertiary referral spine care center and was approved by the institutional review board of the institute (IRB no. 2019/08/17). Informed consent for participating in the study and use of their clinical and radiological data was taken from each participant.
We conducted a prospective study to assess the clinical outcomes of chronic coccydynia and identify the clinical and radiological features associated with poor treatment outcomes. Patients who presented to us in the outpatient clinic with coccydynia of more than 2 months duration between September 2019 to August 2021 were included in the study. We excluded patients less than 18 years of age, history of previous lumbar spine surgery, presence of local pathologies like hemorroids, anal fissures or fistula and those who underwent coccygeal manipulation or local steroid injections in the last 3 months.
Management protocol - All patients were evaluated using an anteroposterior (AP) radiograph of pelvis, standing lateral radiographs of lumbosacral spine and dynamic lateral radiographs of sacrum with coccyx in standing and seated position to look for any instability and their coccyx morphology. Initial treatment comprised of analgesics (NSAIDs), pelvic floor strengthening exercises and advised using U-pillow while sitting. Patients were called for follow up after 2 months. Those who did not report improvement after 2 months, underwent MRI to rule out bursitis, sacrococcygeal arthritis or neoplasms followed by final follow up at 6 months.
Clinical assessment - Pain scores were documented using Visual analogue scale (VAS)9 and functional outcomes using Oswestry Disability Index (ODI).10 Both these scores were documented at initial presentation and each follow ups and were compared to assess the outcomes. For this study we used the following criteria to define good clinical outcome - patients in whom VAS score decreased to more than 50 % of their baseline value.11
Radiological assessment - The radiological measurements were done using standard lateral dynamic radiographs in sitting and standing positions. The morphology of coccyx, intercoccygeal angle (ICA), sacrococcygeal angle (SCA), base angle (BA), coccygeal length (CA) and joint mobility were assessed.12–14
The parameters assessed and method of their measurements have been summarised in Table 1 and Fig. 2.
| Sr No. | Radiographic Parameters | Method of Assessment |
| 1 | Intercoccygeal angle (ICA) | The angle between the two intercoccygeal lines drawn that pass through the center of the coccyx |
| 2 | Sacrococcygeal angle (SCA) | The angle formed by the intersection of a line between the midpoint of the upper borders of S1 and Co1 and a line between the midpoint of Co1 and the tip of the coccyx |
| 3 | Base angle (BA) | The coccygeal angle of incidence, also known as base angle (BA), is defined as the angle at which the coccyx strikes the seat when the subject is sitting down |
| 4 | Joint subluxation | Abnormal translational movement between 2 adjacent vertebrae at the intervertebral disc (at sacrococcygeal and intercoccygeal joint) |
| 5 | Coccygeal Length | Measured in a straight line from the middle of the upper border of Co1 to the coccygeal tip |
Statistical analysis - Data were statistically analyzed using IBM SPSS version 22.0, 2013. Descriptive analysis was performed to understand the age and gender distributions in study sample. To study about the morphology of coccyx, to formulate various measured radiological parameters of chronic coccydynia,we used Chi-square test, ANCOVA, Post hoc test, cochran test for multivariate analysis statistically to correlate with functional and clinical outcomes. Significance level was set at p value less than 0.05.
3 Results
3.1 Demographic data
Out patient records of 180 patients with coccygeal pain during the study duration was screened. 12 patients were excluded as they had local pathologies mimicking coccygeal pain (5-anal fissures; 4-pilonidal sinus and 3-hemarroids). 168 patients were included in the study, consisting of 106 females and 62 males. Mean (SD) age of the cohort was 41.71(11.12) years with an age range of 18–83 years. There were higher number of females compared to males with coccydynia in the study population (63 % females; M:F ratio 1.76).Analysis of BMI in the study population showed that 109 out of 168 (64.9 %) were obese (BMI >30) and 31(18.5 %)were overweight (BMI 25–29.9).
3.2 Etiology
The study population was divided into two groups based on etiology-traumatic and non-traumatic (Idiopathic, post partum etc.). Non-traumatic etiology were seen in 96 patients and traumatic in 72 (42.85 %). There was no difference in gender distribution in traumatic and idiopathic pathologies (Chi square test; p-value 0.019). There was no difference in the number of obese and overweight patients in the traumatic and non-traumatic groups. Summary of the demographic data and results in Table 2.
| Parameter | Overall (n = 168) | Idiopathic (n = 96) | Traumatic (n = 72) | p-value |
| 1. Age | 41.71 (11.12) | 39.3(10.3) | 44.12(11.9) | 0.091 |
| 2. Gender | Males - 62 (36.9 %) | Males - 35 | Males - 27 | 0.019 |
| Females - 106 (63.1 %) | Females - 61 | Females - 45 | ||
| 3. BMI | ||||
| Normal (18.5–24.9) | Normal - 31 | Normal - 21 | Normal - 10 | 0.089 |
| Overweight (25–29.9) | Overweight - 28 | Overweight - 11 | Overweight - 17 | |
| Obese (>30) | Obese - 109 | Obese - 64 | Obese - 45 | |
| 4. VAS score (Pre-treatment) | 6.24 (1.09) | 6.42 (0.77) | 6.06 (0.65) | 0.92 |
| 5. ODI scores (Pre-treatment) | 17.15 (1.61) | 16.62 (1.67) | 17.68 (1.15) | 0.87 |
| Morphology type | Frequency | Percentage |
| I | 20 | 11.9 |
| II | 67 | 39.9 |
| III | 10 | 6.0 |
| IV | 67 | 39.9 |
| V | 4 | 2.4 |
| VI | 0 | 0 |
| Total | 168 | 100 |
3.3 Radiological parameters
1.Coccyx morphology - The most common morphology were type 2 (n = 67, 39.9 %) and type 4 (n = 67, 39.9 %). Type 5 was seen in only 4 patients and we did not encounter any type 6 morphology (Table 3).2.Radiographic measurements - In seated position, the overall mean Intercoccygeal angle was 38.45°(13.9), Sacrococcygeal angle was 135.97° (16.2) and Basal angle was 71.07° (15.8). The mean coccygeal length of the cohort was 2.92 cm.
Summary of radiographic data given in Table 4. Except for ICA (p-value 0.003), no statistically significant correlation between the measured parameters and outcomes was observed.3.Coccygeal mobility - The coccygeal mobility was assessed by intercoccygeal angle. The coccygeal instability was categorized into four types as described by Maigne et al., Rigid (<5°), Normal (5°–25°), Hypermobile (>35°) and Subluxation (Abnormal translation between the two coccyges). Subluxation was the most common type, found in 69 patients (41.07 %). Amoung the various coccyx morphologies, subluxation was most common in type 4 coccyx - 59/69 subluxed coccyges while type 2 had the highest proportions of normal and rigid coccyx.4.MRI parameters - 48 patients who did not have improvement with initial conservative measures underwent MRI scans. The qualitative parameters noted were transitional vertebrae in 14 (29.16 %), marrow edema in 29 (60.41 %), pseudoarthrosis in 7 (14.58 %), and bursitis in 19(39.58 %) patients. The presence of marrow edema was the most common finding on evaluation by MRI. These qualitative parameters were correlated with clinical outcomes and analyzed using the ANOVA test. The presence of pseudoarthrosis correlated with good outcomes with statistical significance. All 7 patients with pseudoarthrosis had VAS scores reduction of more than 50 %.
| Parameter | Overall(n = 168) | Good outcomesn = 104(VAS score reduction to less than 50 % of baseline) | Poor outcomesn = 64(VAS score reduction to less than 50 % of baseline) | p-value |
| BMI | Normal - 31 (18.5 %) | Normal - 17 | Normal - 14 | 0.548 |
| Overweight - 28 (16.67 %) | Overweight - 22 | Overweight - 6 | ||
| Obese - 109 (64.8 %) | Obese - 79 | Obese - 30 | ||
| Coccygeal morphology | Type 1 - 20 | Type 1 - 7 | Type 1 - 13 | NA |
| Type 2 - 67 | Type 2 - 22 | Type 2 - 45 | ||
| Type 3 - 10 | Type 3 - 4 | Type 3 - 6 | ||
| Type 4 - 67 | Type 4 - 38 | Type 4 - 29 | ||
| Type 5 - 4 | Type 5 - 2 | Type 5 - 2 | ||
| Type 6 - 0 | Type 6 - 0 | Type 6 - 0 | ||
| Coccygeal mobility | Normal - 53 | Normal - 39 | Normal - 14 | 0.019 |
| Rigid - 33 | Rigid - 16 | Rigid - 17 | ||
| Hypermobile - 12 | Hypermobile - 9 | Hypermobile - 3 | ||
| Subluxed - 69 | Subluxed - 56 | Subluxed - 13 | ||
| MRI findings | Transitional vertebra - 14 | Transitional vertebra - 9 | Transitional vertebra - 0 | NA |
| Signal intensity changes/marrow edema - 29 | Signal intensity changes/marrow edema - 21 | Signal intensity changes/marrow edema - 8 | ||
| Bursitis - 19 | Bursitis - 13 | Bursitis - 6 | ||
| Pseudoarthrosis - 7 | Pseudoarthrosis - 7 | Pseudoarthrosis - 0 | ||
| Intercoccygeal angle/ICA (Sitting) | 38.45° (13.9) | 34.8° (13.2) | 42.1° (14.6) | 0.003 |
| Intercoccygeal angle/ICA (Standing) | 35.57° (13.2) | 33.95° (13.3) | 37.2°(13.1) | 0.152 |
| Sacrococcygeal angle/SCA (Sitting) | 135.97° (16.2) | 137.2° (16.52) | 134.75° (15.93) | 0.17 |
| Sacrococcygeal angle/SCA (Standing) | 129.35° (15.2) | 131.1° (16.5) | 127.6° (13.9) | 0.391 |
| Base angle | 71.07° (15.8) | 73.4° (18.2) | 68.75° (13.4) | 0.777 |
| Coccygeal Length (cm) | 2.92 (0.56) | 3.04 (0.65) | 2.8 (0.47) | 0.82 |
3.4 Clinical outcomes -
The mean VAS score of the study group at presentation was 6.91. The VAS scores improved to a mean of 3.95 following six months of conservative management with an average improvement by 43 %. VAS scores reduced to less than 2 in 24 patients and reduced by more than 50 % of their baseline in 92 patients while 32 patients had worsening of symptoms.
The mean ODI score of the study group at presentation was 17.15. The scores improved to a mean of 11.68 following six months of conservative management. At six months, follow-up the ODI scores were not statistically significant between patients with different etiologies. The outcomes are summarised in Table 4.
3.5 Correlation between variables and outcomes -
1.BMI and outcomes - The correlation of BMI with clinical outcomes of conservative management in chronic coccydynia showed no statistically significant correlation between BMI and clinical outcome.2.Etiology and outcomes - Analysis of outcomes in patients with different etiology showed that patients with a traumatic etiology had better pain relief compared to the idiopathic group. In patients with traumatic etiology, the mean VAS score at follow up was 3.54 compared to 4.36 in the non-trauma group and this difference was statistically significant (ANOVA test; p-value<0.05).3.Coccyx morphology and outcomes - The morphological parameters described by Postachini and Massobrio were correlated with clinical outcomes. Type 4, followed by type 2 morphology, had better results following conservative management, and the correlation was statistically significant (p-value 0.025). Out of the 92 patients with VAS scores reduction >50 %, 38 were Type 4 and 22 were type 2 coccyx.
Radiographic measurements and outcomes - Intercoccygeal angle (both sitting and standing), Sacrococcygeal angle and Base angles were similar in both the traumatic and idiopathic groups (Table 5). ICA(sitting) was the only radiographic parameter that was associated with poor outcomes of conservative management (p-value <0.05).
| Parameters | Traumatic | Idiopathic | p-value |
| ICA SIT | 49.1° (17.56) | 37.5°(12.74) | 0.27 |
| ICA STAND | 34.56° (10.9) | 33.09°(20.01) | 0.383 |
| SCA SIT | 119.7° (16.8) | 136.7° (19) | 0.25 |
| SCA STAND | 120.4° (11.34) | 129.4° (9.16) | 0.36 |
| BASE ANGLE | 52.1° (27.4) | 76° (11.17) | 0.174 |
| COCCYGEAL LENGTH (cm) | 3.01 (0.50) | 2.83 (0.63) | 0.732 |
Pearsons coefficient was used to correlate the coccyx mobility with clinical outcomes. Hypermobile and subluxation had good outcomes. 56 of the 69 patients (81.1 %) with subluxed coccyx had good outcomes compared to 16/33 (48.5 %) with rigid coccyges.
4 Discussion
Direct trauma to the coccyx is a frequent cause for coccydynia. Maigne et al. reported a 38 % incidence of direct trauma in their series of occydynia and Pennekamp et al. reported a 50 % incidence of trauma.15,16 In our study 72/168 (43 %) patients had history of direct trauma to the coccygeal region.
Dave et al. in a case control study of 92 patients (46 non traumatic coccydynia and 46 controls) reported that higher intercoccygeal angle (ICA),posterior subluxation and higher Basal angle (BA) are frequently seen in patients of nontraumatic coccygodynia.17 In this study, we did not find any significant difference among the radiological parameters in traumatic and non-traumatic etiology. However, the clinical outcomes and VAS score improvements were better in traumatic group (VAS score 3.54) compared to others (VAS score 4.56).
Apart from idiopathic and traumatic etiology, other causes for pain around the region of the coccyx include local patholgies like rectal abnormalities, pilonidal sinus, hemorroids, anal fissures and infections which should always be ruled out by thorough local examination.18,19 In this study, out of the initial 180 out patient records screened 12 had local pathologies mimicking coccydynia (5 - anal fissures; 4 pilonidal sinus and 3 - hemarroids) and hence excluded.
The incidence of coccydynia has been reported to be nearly 5 times higher in females than males.5 Although not as high, in our study population as well majority of them were females (106/168; 63.1 %).Females have higher incidence of coccydynia which has been attributed to the difference in pelvic morphology - greater inter-ischial tuberosity distance, wider greater sciatic notch with inclination of sacrum backward.20 Difficult labor and use of forceps during delivery is also a significant risk factor for post partum coccydynia.8
Maigne et al.7 also reported a body mass index of more than 27.4 in women and 29.4 in men as a risk factor for coccydynia. They postulated that when obese patients try to sit down, the coccyx juts out posteriorly due to inadequate sagittal rotation of the pelvis, predisposing them to coccygeal trauma. Our results showed that 64.9 % of the study population were obese with a BMI >30 and, 18 % were overweight with a BMI>25. However, both traumatic and idiopathic groups had a similar distribution of obese and overweight patients.
Coccyx morphology has been theorised to have an important role in the etiology of coccydynia. Postacchini et al.6 in their study on coccyx morphology reported that type 2, type 3, and type 4 coccyges were at a higher risk for chronic coccydynia. Woon et al.21 studied the relationship of the different coccyx morphologies on coccydynia and reported that the majority of patients with coccydynia had either a type 1 or a type 2 coccyx. An MRI study by Shams A et al.12 also reported higher incidence of coccydynia in Type 2 coccyx and in the presence of bony spicules. In our study, type 2 and type 4 were the most common morphologies, 67 (40 %) patients each. Type 4, followed by type 2 morphology, had excellent results following conservative management, and the correlation was statistically significant (p-value 0.025). Type 1 coccyx had the worse results of all with 30 % patients have persistent pain.
Mobility of the coccyx has also been theorized as a generator of coccydynia. Initially described by Maigne et al.,22 their study compared the mobility of the coccyx in patients with idiopathic coccydynia and those without coccydynia (51 patients in each group) using seated lateral radiographs. Findings of the group with coccydynia showed 13 (25.5 %) patients with luxation and 12 (23.5 %) patients with hypermobility as compared to only 1 (1.96 %) patient in the control group with luxation and no patients with hypermobility. Out of the 168 patients in our study, only 81 had instability (69- subluxations and 12 - hypermobility). Of all the qualitative parameters assessed by MRI, only pseudoarthrosis showed a statistically significant correlation with good outcomes. Woon et al.23 also analyzed the morphometry of coccyx and concluded that lower prevalence of sacrococcygeal fusion, increased intercoccygeal subluxation may predispose to coccydynia. Shams A et al.12 reported that lower sacral slope angle and intercoccygeal subluxation were more common in patients with idiopathic coccydynia. However, we did not observe such statistically significant incidences of instability. Higher Intercoccygeal angle (ICA) was the only radiographic parameter that was more common in patients with poor outcomes.
4.1 Limitations -
This was a study with a relatively small sample size and short term follow up. Our study did not have a control group to compare the results as it would not have been appropriate to get radiographs for normal volunteers. This study focuses only on the outcomes of conservative measures and did not compare with other modalities like ganglion impar block or coccygectomy. Also MRI evaluation was done only in 48 patients who did not respond to conservative measures and not for all the patients.
5 Conclusion
The results from this study show that majority of the patients of idiopathic coccydynia respond well to conservative measures. Type 2 and type 4 were the most common coccyx morphology encountered in patients with chronic coccydynia. Outcomes were in traumatic group compared to idiopathic group and in those with pseudoarthrosis on MRI. Higher Intercoccygeal angle(ICA) was the only radiographic parameter associated with poor outcome of conservative management.
CRediT authorship contribution statement
R Manikandan: Data curation, Investigation, Writing – original draft. R Dinesh Iyer: Formal analysis, Writing – original draft. Praveen R. Iyer: Data curation, Investigation. Ajoy Prasad Shetty T: Conceptualization, Writing – review & editing. KS Sri Vijayanand: Writing – review & editing. Rishi Mugesh Kanna: Resources, Data curation. Rajasekaran Shanmuganathan: Supervision, Writing – review & editing.
Ethical approval and patient consent
The study was conducted in a tertiary referral spine care center and was approved by the institutional review board of the institute (IRB no. 2019/08/17). Informed consent for participating in the study and use of their clinical and radiological data was taken from each participant.
Funding STATEMENT
The authors received no funding/grant from any external agencies.
References
- Coccydynia: a review of pathoanatomy, aetiology, treatment and outcome. J Bone Joint Surg Br. 2010;92(12):1622-1627.
- [Google Scholar]
- Conservative treatment for chronic coccydynia: a 36-month prospective observational study of 115 patients. Eur Spine J. 2021;30(10):3009-3018.
- [Google Scholar]
- A comparison of conservative interventions and their effectiveness for coccydynia: a systematic review. J Man Manip Ther. 2013;21(4):213-219.
- [Google Scholar]
- Coccydynia: a review of anatomy, causes, diagnosis, and treatment. JBJS Rev. 2024;12(5)
- [Google Scholar]
- Idiopathic coccygodynia. Analysis of fifty-one operative cases and a radiographic study of the normal coccyx. J Bone Joint Surg. 1983;65:1116-1124.
- [Google Scholar]
- Causes and mechanisms of common coccydynia: role of body mass index and coccygeal trauma. Spine. 2000;25(23):3072-3079.
- [Google Scholar]
- Postpartum coccydynia: a case series study of 57 women. Eur J Phys Rehabil Med. 2012;48(3):387-392.
- [Google Scholar]
- A systematic review of the pain scales in adults: which to use? Am J Emerg Med. 2018;36(4):707-714.
- [Google Scholar]
- Oswestry Disability Index scoring made easy. Ann R Coll Surg Engl. 2008 Sep;90(6):497-499.
- [Google Scholar]
- Interpretation of visual analog scale ratings and change scores: a reanalysis of two clinical trials of postoperative pain. J Pain. 2003;4(7):407-414.
- [Google Scholar]
- Sacrococcygeal morphologic and morphometric risk factors for idiopathic coccydynia: a magnetic resonance imaging study. Global Spine J. 2023;13(1):140-148.
- [Google Scholar]
- Coccydynia: a comprehensive review on etiology, radiological features and management options. J Clin Orthop Trauma. 2021;12(1):123-129.
- [Google Scholar]
- Morphological features of the coccyx in the Turkish population and interrelationships among the parameters: a computerized tomography-based analysis. Cureus. November 18, 2021;13(11)
- [Google Scholar]
- Chronic coccydynia in adolescents. A series of 53 patients. Eur J Phys Rehabil Med. 2011;47(2):245-251.
- [Google Scholar]
- Coccygectomy for coccygodynia: does pathogenesis matter? J Trauma. 2005;59(6):1414-1419.
- [Google Scholar]
- A clinical and radiological study of nontraumatic coccygodynia in Indian population. Indian Spine Journal. Jul–Dec 2019;2(2):128-133.
- [Google Scholar]
- A retrospective study on the pathologies in patients with coccydynia-lumbosacralgia and their treatment. Asian J Surg. 2023;46(2):688-691.
- [Google Scholar]
- Magnetic resonance imaging morphology and morphometry of the coccyx in coccydynia. Spine. 2013;38(23):E1437-E1445.
- [Google Scholar]
- Idiopathic coccygodynia. Lateral roentgenograms in the sitting position and coccygeal discography. Spine. 1994;19(8):930-934.
- [Google Scholar]
- CT morphology and morphometry of the normal adult coccyx. Eur Spine J. 2013;22(4):863-870.
- [Google Scholar]