Discussion
This is the first study evaluating the interexaminer reliability of commonly performed abdominal palpation and resistance tests for classifying inguinal-related groin pain in athletes. The interexaminer reliability of palpation pain provocation tests varied from fair to moderate (κ=0.35–0.49). The reliability of posterior wall structure palpation was slight (κ=0.01), posterior wall bulging fair (κ=0.29) and external ring size moderate (κ=0.56). The interexaminer reliability for abdominal resistance tests varied from fair to substantial (κ=0.35–0.72). Abdominal resistance tests were positive in 21%–49% of athletes classified with defined inguinal-related groin pain.
No previous studies have been published on the interexaminer reliability of clinical examination tests to classify inguinal-related groin pain, or the presence of an inguinal hernia. Only one study15 investigated the reliability of rectus abdominis palpation and resistance tests. This study included nine athletes with and nine athletes without groin pain who were assessed by four blinded examiners. The interexaminer reliability values for abdominal resistance tests found in that study (κ=0.41–0.57) are in line with our findings (κ=0.35–0.72). Contrarily, rectus abdominis palpation as pain provocation test was found less reliable in our study: κ=0.17–0.66 compared with κ=0.83 reported by Holmich.15 The wide confidence intervals around the kappa values for rectus abdominis palpations tests in our study indicate a higher uncertainty around our estimated reliability. Additionally, the prevalence index in our study was relatively high (−0.54 and 0.72), which increases chance agreement and reduces the kappa accordingly.12 Pain provocation tests reproducing recognisable injury pain in the rectus abdominis area are categorised as ‘other causes for groin pain’ and not as inguinal-related groin pain according to the Doha agreement meeting classification system.4
An additional potential explanation for the slight reliability of the rectus abdominis insertion (κ=0.17) is the close proximity of the pubic symphysis. Pubic-related groin pain is classified when athletes report recognisable injury pain during palpation of the pubic symphysis and the directly adjacent bone.4 It can be challenging for clinicians (and patients) to determine if recognisable injury pain originates from pubic symphysis, the distal rectus abdominis, or both. It should also be noted that the distal rectus abdominis insertion comprises an external tendon (attaching cranially on the pubic bone) and an internal tendon (interlaced with the contralateral tendon, anterior of the pubic symphysis), and that the palpation in our study was focused on the external tendon insertion only.16 The proximity of these structures may cause confusion in the classification/diagnosis.
There is no consensus on what level of reliability is needed before recommending a test in clinical practice. Interexaminer reliability values of widely used musculoskeletal clinical examination tests vary a lot. For example: kappa values for classifying subacromial pain syndrome (κ=0.10–1.00),17 medial tibial stress syndrome or concurrent lower leg injury (κ=0.73–0.89),18 or sacroiliac joint, disc and facet joint pain (κ<0.20) vary from poor to perfect reliability. Using a combination of clinical examination tests is recommended by the Dutch guideline for the diagnosis and treatment of subacromial pain syndrome to improve the diagnostic accuracy based on level 2 evidence.19 In our study, the interexaminer reliability of the individual inguinal palpation pain provocation tests was fair to moderate (κ=0.35–0.49), while for the clustered palpation tests (ie, ‘any’ inguinal palpation pain) moderate to substantial (κ=0.54–0.65). The interexaminer reliability of the majority of abdominal resistance tests was higher than those of the palpation tests.
In athletes classified with defined inguinal-related groin pain, palpation pain was almost always present during scrotal invagination (94%). Four out of every five of these athletes also reported pain during at least one of the transabdominal palpation tests. Scrotal invagination is not part of standard training for some musculoskeletal health professionals (such as physiotherapists). The combination of transabdominal palpation tests and abdominal resistance tests will be sufficient to classify ~90% of the cases with inguinal-related groin pain. Not performing scrotal invagination may lead to missing the classification in 1 in 10 cases (figure 2).
Abdominal resistance tests were positive in approximately half of the athletes classified with inguinal-related groin pain. The most prevalent positive abdominal resistance test (49%) was the cross-test with shoulder resistance on the contralateral side and resisted hip flexion on the ipsilateral side. A recent study20 investigated the diagnostic accuracy of four different clinical examination tests for the diagnosis of ‘core muscle injury’, which is a different term used for groin pain in the inguinal canal region.6 This study found a sensitivity of 100% and specificity of 3% for both a ‘resisted cross-body sit up’ test (which has similarities with the cross test in our study) and an adductor contracture test. These sensitivity values may be overestimated due to incorporation bias, since the index tests were part of the reference standard.
Overclassification, or overdiagnosis, may be a pitfall after performing clinical examination in the inguinal canal area. We found that several palpation tests caused pain that was not recognisable injury pain, according to the athletes (6%–24%). To prevent overdiagnosis and potentially unnecessary treatment, it is important to always ask the athlete if pain during palpation tests replicates the injury pain and to elicit the pain location during abdominal resistance tests. On the contrary, some athletes report recognisable injury pain in the inguinal canal region during sports and/or during abdominal resistance testing, but are pain free on inguinal palpation. According to the Doha agreement definitions, these cases would not be classified as inguinal-related groin pain. In our study, examiners could classify these cases as ‘likely inguinal-related groin pain’, to provide a full overview of potentially involved clinical examination findings in inguinal-related groin pain. Future research should investigate if the specific presence of palpation pain is required to guide prognosis and/or treatment.
There is no gold standard for the classification of inguinal-related groin pain, nor an accepted reference standard. We believe it would be inappropriate to analyse and report our data for diagnostic accuracy purposes (sensitivity, specificity etc). For clinical implications, however, we reported the mean prevalence of positive test findings in athletes classified with inguinal-related groin pain. When a test is highly prevalent (such as recognisable injury pain during scrotal invagination), it should be included as part of the diagnostic work-up for the target condition (inguinal-related groin pain). In these instances, a negative test can potentially assist in ruling out the target condition.
Imaging is regularly used as part of the diagnostic process in athletes with groin pain in the inguinal region. Ultrasound is often the imaging modality of choice in these instances.21 There is, however, no sound evidence that specific ultrasound findings can differentiate between athletes with and without inguinal-related groin pain.22 For example, posterior wall bulging on ultrasound is suggested to be related to the pathoaetiology of ‘posterior wall weakness’,23 but is also found commonly (~65%) in asymptomatic athletes.22 The interobserver reliability of assessing the posterior wall for bulging on ultrasound is unknown. Clinically, we found that bulging was present in 26% of sides without inguinal-related groin, and a soft posterior wall in 54% of these sides. The interexaminer reliability adds uncertainty to this with κ=0.29 and κ=0.01, respectively. The unknown interexaminer or intraexaminer reliability of ultrasound findings and the presence of bulging and soft posterior walls without pain make interpretation complex. We recommend interpreting ultrasound findings with caution, and only using them as an adjunct to injury history and clinical examination findings, and not as a standalone diagnostic modality.
Our study showed that there is no single perfect test for classifying athletes with inguinal-related groin pain. Knowing the benefits and limitations of specific clinical examination tests can assist clinicians in their diagnostic work and ultimately in providing an optimal treatment plan. After history taking, we recommend performing abdominal palpation including scrotal invagination, and abdominal resistance as pain provocation tests to obtain a complete overview of all potentially relevant clinical examination findings. Further research is needed to evaluate if specific clinical examination findings influence management (conservative and/or surgical) or prognosis.
Limitations
This is the first study evaluating the interexaminer reliability of standardised clinical examination tests that clinicians use to classify athletes with inguinal-related groin pain. Our study has some limitations. First, the examiners were experienced clinicians that both worked in a specialised groin clinic and our results may therefore not be generalisable to less experienced clinicians. We tried to compensate for this by standardising and describing each test in detail (online supplemental appendix A), prior to commencement of our study. Second, there is no gold (reference) standard available for inguinal-related groin pain. For the overview of the prevalence of positive tests, examiners used the Doha agreement terminology, but were also allowed to classify likely inguinal-related groin pain when not all criteria were present. This approach potentially decreases the reproducibility due to a higher level of subjectivity. On the other hand, it might reflect clinical practice and increase external generalisability as not all diagnostic findings are always present during physical examination. Thirdly, the percentage of inguinal-related groin pain was higher than reported in the literature and probably reflects selection bias in a tertiary clinic with predominantly male athletes. Lastly, our study only included male athletes, which limits generalisability to female or transgender athletes. Inguinal-related groin pain is less prevalent in female athletes, potentially due to the different anatomy of the inguinal canal (the spermatic cord runs through the inguinal canal in men, while in women this is the round ligament of the uterus).