|Year : 2021 | Volume
| Issue : 2 | Page : 141-145
Association of low-lying pubic tubercle with inguinal hernia
Manu Jose Chirayath, Meer M Chisthi
Department of General Surgery, Government Medical College, Thiruvananthapuram, Kerala, India
|Date of Submission||31-Jul-2021|
|Date of Decision||05-Sep-2021|
|Date of Acceptance||06-Sep-2021|
|Date of Web Publication||15-Nov-2021|
Dr. Meer M Chisthi
Department of General Surgery, Government Medical College, Thiruvananthapuram - 695 011, Kerala
Source of Support: None, Conflict of Interest: None
Background: Low-lying pubic tubercle can lead to narrow origin of internal oblique muscle and alteration in structural anatomy making the shutter mechanism of internal oblique ineffective and predispose to inguinal hernia. Methods: A case–control study was done to find the prevalence of inguinal hernia in patients with low pubic tubercle. Twenty-two cases and 22 control male patients with symptomatic uncomplicated inguinal hernia were studied. Distance between two anterior superior iliac spines and vertical distance from pubic tubercle to the inter-spinous spine were measured. The relation of these lines to patients' height and weight and to each other was calculated. Results: The mean value of spine to spine distance was 26.32 cm in cases and 25.86 cm in controls. The mean distance of this line from pubic tubercle was 7.82 cm in cases and 6.77 cm in controls. Vertical distance from the pubic tubercle to inter-spinous line and its ratio with height and weight were found to be significantly associated with inguinal hernia by multivariate analysis. Conclusions: People with low-lying pubic tubercle have a less efficient protective mechanism of inguinal canal and thus greater predisposition for inguinal hernia. Pelvimetric assessment can be used to pick up susceptible adults to plan early surgery and to decide about prophylactic repair of uninvolved contra-lateral side.
Keywords: Case–control studies, hernia, ilium, inguinal canal, inguinal, pubic bone
|How to cite this article:|
Chirayath MJ, Chisthi MM. Association of low-lying pubic tubercle with inguinal hernia. Kerala Surg J 2021;27:141-5
| Introduction|| |
The inguinal canal is a site of potential weakness in males and females. It measures 3.75 cm in length and stretches from deep to superficial inguinal rings. Indirect hernia emerges lateral to inferior epigastric artery. The congenital type occurs usually due to an abnormally persistent processus vaginalis. Direct inguinal and supravesical hernias occur just medial to the inferior epigastric vessels. The fascia transversalis forms the posterior layer of this arrangement along the inguinal canal.
There exist many protective mechanisms along the inguinal region to prevent the development of hernia, most of which are anatomical factors. The oblique nature of the canal does not allow the internal ring and superficial ring to lie opposite to each other. The deep ring is covered by a conjoint tendon and protects it when intra-abdominal pressure increases. The posterior wall of the canal with its counterpart, that is, the conjoint muscle, protects the superficial ring. During intra-abdominal pressure rise, the roof of the canal, that is, the conjoint muscle, collapses and becomes a flat structure that compresses the inguinal canal. The compressed inguinal canal, in turn, prevents the intra-abdominal contents from entering the canal. When the squatting position is adopted with excessive straining, the hip joints lie in a flexed position with thighs lying against the anterior wall of abdomen and thus protect the weakened lower abdomen.
To reiterate the facts, anatomic variations in pelvis including a low-lying nature of pubic tubercle can supposedly predispose to the occurrence of inguinal hernia. If the risk of development of hernia can be predicted, it can help the physicians to advice on early surgical repair to prevent complications. With this idea, we proceeded to study whether there is any association between low-lying pubic tubercle and development of inguinal hernia.
| Methods|| |
A case–control study was carried out at the inpatient wards of a tertiary level teaching institution. The primary objective was to assess the association between low-lying nature of pubic tubercle and inguinal hernia. The secondary objective was to check for the presence of any correlation between low-lying nature of pubic tubercle and height and weight of the patients. Institutional review committee and human ethics committee clearance was obtained before starting the study.
Male patients of Indian origin admitted in the hospital wards with unilateral inguinal hernia without any complications were included in the study. Patients of age <18 years, secondary hernias and complicated hernias and patients with pelvic anomalies were excluded. Purposive non-random sampling technique was employed. Based on the results from a previous study, which analysed the role of low-lying pubic tubercle in inguinal hernias, we calculated sample as 21.48.
Twenty-two patients with unilateral inguinal hernias and 22 healthy volunteers were included. After obtaining informed consent, the variables including low-lying pubic tubercle, age, gender, height, weight, build and, occupation and outcome variable as inguinal hernia were noted. The subjects were made to lie relaxed in supine position on a hard bed, lower limbs straight in such a way that the two anterior superior iliac spines are at the same level. A line was drawn on the anterior abdominal wall, connecting the two anterior superior iliac spines. This inter-spinous line (SS line) length was noted. Then, the ipsilateral pubic tubercle of the hernia was marked after palpation. The vertical distance between the tubercle and the previous SS line (ST line) was measured. The contralateral ST line was also measured. Similar positioning and measurement was also done on controls. SS and ST measurements were recorded in centimetres. Height was measured in feet and weight in kilogram. Analysis was done to check for any relationship between the ST line and SS line measurements and anthropometric values including height, weight and age of the patient. The ST lines of two sides were compared for mismatch. The SS and ST line measurements of the cases were compared with the values of controls to check for any association between low-lying pubic tubercle and inguinal hernia. It was attempted to check if there exists any correlation between ST line length and weight and height of the patients. Data were entered into Microsoft Excel sheets.
Quantitative variables were expressed as means along with standard deviation, while qualitative variables were expressed as frequency and percentage. Comparison of quantitative variables between two groups was done by independent sample t-test. Between groups, comparison of qualitative variables was carried out by Chi-square test. Receiver operating characteristics (ROC) curves of various parameters were plotted to assess the optimum cut-off value to classify cases and controls and area under the curve (AUC) with 95% confidence interval was calculated. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value were calculated accordingly. Variables which were found significantly associated with hernia were subjected to multivariate analysis through binary logistic regression to evaluate the independent predictors. P value < 0.05 was set as statistically significant. All statistical analyses were performed using Microsoft Excel and Epi Info (CDC) and easyROC software ver 1.3.1. The findings are reported in line with the strengthening the reporting of cohort studies in surgery guidelines.
| Results|| |
The study sample consisted of 22 cases and 22 controls. The mean age group in years in cases was 55.82 ± 12.11 years and 46.64 ± 13.15 years in controls. The age-wise distribution of cases showed a peak in age group of 56–65 years. The youngest patient was 26 years old and the oldest was 75, while the youngest control was 23 years old and the oldest 69.
The mean duration of symptoms was found to be 4.6 years ± 4.21. About 72.7% of cases had right-sided inguinal hernia, majority of which were direct hernias. Mean height in cases was 5.44 feet ± 0.17 and that in controls was 5.58 ± 0.24. The mean weight in cases was 63.27 kg ± 8.67 and that in controls was 72.68 ± 9.20.
The mean SS value was 26.32 cm ± 2.8 in cases and 25.86 ± 3.5 in controls. There was no difference in ST line values between affected and normal side in the cases. The mean ST value was 7.82 cm ± 1.05 in cases and 6.77 cm ± 0.69 in controls. The mean SS/ST ratio was 3.44 ± 0.75 in cases and 3.83 ± 0.49 in controls. The mean height/ST ratio was found to be 0.71 ± 0.11 in cases and 0.83 ± 0.09 in controls. The mean weight/ST ratio was found to be 8.28 ± 1.82 in cases and 10.83 ± 1.69 in controls.
Chi-square test was applied to various parameters. Thirteen cases and 9 controls had inter-spinal distance ≥26 and odds ratio was 2. A cut-off value of 7 cm was established for ST, and it was found that among the 22 cases, 14 of them had an ST length of more than 7 cm and only 3 of the controls had a ST length >7 cm. Odds ratio was calculated and showed that there was 11 times risk for development of inguinal hernia if ST was >7 cm.
Weight/ST ratio as a parameter was selected to minimise any bearing that the weight of the patients might have on their ST length. A cut-off value of 8.57 was established for the weight/ratio and it was found that 54.5% of those with a weight/ST value ≤8.57 belonged to the case group. It was also found that majority of the cases, that is, 12 out of the total 22, had a lower weight/ST value. Weight/ST ratio estimation also predicts that there is 25.2 times risk for development of inguinal hernia if it is ≤8.57.
Height/ST as a parameter was selected for analysis to minimise any bearing that the height of the patients might have on their ST length. A cut-off value of ≤0.688 was established for the height/ST ratio and it was found that 63.6% of those with a height/ST value <0.688 belonged to the case group. Odds ratio was calculated and there was 36.5 times risk of developing inguinal hernia in those patients with height/ST ≤0.688.
The ratio of SS/ST had a cut-off point of 3.375 as per the ROC curve analysis. About 54.5% of patients who had a value ≤3.375 had an inguinal hernia. The ratio of SS/ST was calculated in order to see whether the inter-spinal length (SS) would cause any significant deviation in our calculations of ST length between the cases and controls. There was also a relative risk of 12 times of developing inguinal hernia in such groups [Figure 1] and [Table 1].
|Figure 1: Receiver operating characteristics curve analysis of various parameters|
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By using Chi-square test, it was found that age, height, weight, ST, SS/ST, height/ST and weight/ST all had a statistical significance with P < 0.05 when comparing cases with controls with maximum significance seen for ST, SS/ST, height/ST and weight/ST. T-value was found to be highest for ST, SS/ST, height/ST and weight/ST which showed a statistical significant difference between the cases and controls.
Using ROC curve analysis and AUC, a value for each parameter was selected which would best distinguish the cases from the controls. A cut-off value of >7 cm was established for ST which showed a high specificity of 86.36% with a PPV of 82.40 and was statistically significant. The same was calculated for SS which was >25 cm but had low sensitivity and specificity and predictive value and was statistically insignificant. Specificity for weight/ST, height/ST and SS/ST was 95.45%, 95.45% and 90.91%, respectively, and cut-off was ≤ 8.5714, ≤0.6875 and ≤3.375, respectively [Table 2].
|Table 2: Sensitivity, specificity and predictive values of each parameter|
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Using the cut-off values obtained for the various parameters, odds ratio was used to calculate the risk for development of hernia. In the unadjusted analysis, all four parameters, i.e. ST, SS/ST, height/ST and weight/ST, had an odds ratio > 1 which shows that exposure is associated with higher odds of outcome and all four parameters were statistically significant with P < 0.05. The variables which were found significantly associated with hernia were subjected to multivariate analysis through binary logistic regression to evaluate the independent predictors of hernia. It was found that ST length, height/ST and weight/ST had an odds ratio >1 but only ST length, weight/ST and height/ST had a P < 0.05 which was statistically significant [Table 3]. SS/ST and SS length were statistically insignificant and were not independent predictors of hernia.
| Discussion|| |
The mean SS distances in cases and controls were 26.32 and 25.86, respectively, in our study. The mean SS value was 26 for cases in a study conducted by Babu et al. The average SS measurement for cases was 23.12 in the study by Juniorsundresh and Narendran, in which they found a significant difference from their control group. Farhan conducted a study of 50 inguinal hernia cases and 60 adult healthy males and revealed that inter-spinous SS line distance and the pubic tubercle height as measured by ST line were significantly greater in the cases than in the controls. Furthermore, the distance from the mid-inguinal point to the external inguinal ring was found to be shorter in inguinal hernia cases. The cut-off selected by them was 7.5 cm.
Navarro et al. also studied 156 cases of inguinal hernia and found that the distance from pubic tubercle to bi-crestal horizontal line was more than 7.0 cm in patients with inguinal hernia as compared to healthy volunteers. Sehgal et al. in their study observed that 73.6% of their cases had ST line > 7.5 cm and deduced that low-lying nature of pubic tubercle was a definite risk factor for inguinal hernia. In a study conducted by Thomas et al., the ST value was found out to be 7.607 cm. In their study, the specificity for ST was calculated as 86.36% and sensitivity as 63.64%. ST length was found to be statistically significant with P < 0.05. Odds ratio was calculated and it was found that cases with ST more than 7 cm had 11 times risk of developing inguinal hernia on the same side.
Fortuny et al., in their 1992 study of 156 cases of inguinal hernia, observed that the distance from the pubic tubercle to inter-spinal horizontal line was more than 7.0 cm in patients having inguinal hernia as compared to the volunteers. In the study by Ajmani et al., the mean measurement of ST line was 7.37 ± cm which was significantly greater than the controls, the mean value being 7.01 cm. In their study, 98% of the cases were found to have ST line of more than 7.01 cm, while 66% of the controls had ST line lower than 7.01 cm. In the study by Juniorsundresh and Narendran also, the mean ST value was 7.34 in the study group, while it was only 6.93 in the control group. In their study, the mid-inguinal point to pubic tubercle distance was 5.63 cm in the control group which was significantly higher than the study group who had a mean distance of 5.327 cm.
In the study by Thomas et al. also, the majority of the subjects with low-lying pubic tubercle were inguinal hernia cases. In their study, among all the patients who had ST length > 7.75 cm, 94.3% had indirect inguinal hernia. Furthermore, a statistically significant correlation could be made out between cases and the ratio of weight to ST length as well as ratio of height to ST length. In case of the study by Fortuny et al., the authors mentioned that the patients with low-lying pubic arch showed a significantly longer inguinal ligament as well as a higher angle between the inguinal ligament at its medial insertion and the upper border of the supra-inguinal space.
Ajmani and Ajmani noted that the origin of internal oblique from the inguinal ligament was farther away from the pubic tubercle in inguinal hernia patients, and its lower fibres did not cover the deep inguinal ring properly. Thus, the deep ring was rendered unprotected, allowing the hernia sac to bulge out when there is any rise in intra-abdominal pressure. Many other studies have found positive correlation between the pubic height and the development of inguinal hernia., Ami independently studied the pubic height and arrived at the conclusion that greater the pubic height, more likely are the chances of developing hernia due to a larger Fruchaud's area. However, the inter-spinal line did not differ significantly between hernia patients and non-hernia controls and also did not have any relation with subject's gender.
Our study has some drawbacks to be pointed out. Foremost is the sample size which being relatively small could potentially mitigate the significance of the study results. The single centre setting could reduce the external validity of the findings. Furthermore, the physical measurements were done manually and were not confirmed by radiology, which could have caused some subjective bias and lessened the study accuracy.
| Conclusions|| |
The study reveals significant association between a low-lying pubic tubercle and occurrence of inguinal hernias. Identification of the anthropometric risk factors in early adulthood could help in the prediction of occurrence of hernia. Additional simple non-invasive methods such as pelvimetry with radiograph correlation could accurately help in identification of the adults at risk. Furthermore, we suggest elective repair of the uninvolved contralateral side in those patients with a low pubic tubercle.
All staff and Residents of the Department of General Surgery, Government Medical College, Trivandrum.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]