A qualitative literature review exploring the role of the inguinal ligament in the context of inguinal disruption management

Current management begins conservatively with physiotherapy to improve pelvic stability [25] that may be followed by non-steroidal anti-inflammatory agents or corticosteroid injection into the origin of adductor longus. The latter is considered an appropriate target as it has been pathologically implicated in groin injuries [9, 21, 26]. Interventional strategies, such as nerve blockade or surgery, may be considered after 2–3 months of unsuccessful conservative management. Novel treatments such as RFD may also be employed, although the exact mode of action is not yet fully understood [4].

Surgical interventions may be performed open or laparoscopically using a polypropylene mesh in either TAPP or totally extraperitoneal (TEP) repair. A non-randomised study has shown that minimally invasive techniques reduce return to play time when compared to open approaches [10]. The rationale for mesh placement is based on increased strain from several sources which converge on the PT. Theoretically, supporting this area should reduce strain and the long standing inflammatory process which had become pathological, thereby promoting recovery. Several operative adjuncts have been carried out by surgeons working in this area, such as adductor and inguinal ligament tenotomy. The rationale behind tenotomy of adductor–abdominal complex lies in a transmission of load to the pelvis, away from the lower limb. The subsequent reduction in muscle pull allows similar reduction of inflammation and subsequent healing of the enthesopathic tendon insertion [2], reducing pain and returning function. The above approaches highlight the variability in current practices when it comes to ID management.

In the study by Gilmore, all 65 football players were described as having ‘Gilmore’s Groin’, experiencing chronic inguinal region pain which was made worse by actions such as sprinting, kicking, coughing and sneezing [8]. In Lloyd et al. and Mann et al., to confirm inguinal ligament pathology, patients must have had tenderness near the insertion of the inguinal ligament onto the PT or superficial inguinal ring without any evidence of a hernia. Although these stringent criteria may have excluded potential participants from the study due to varying pain presentations, the outcome measures from the studies by Lloyd et al. and Mann et al. were comparable to high level outcomes in existing literature for surgical interventions managing ID [24]. Pain severity scores improved slightly in the study by Mann et al. [19], possibly explained by access to higher quality physiotherapy programmes in the all-athletic population (51% of whom were professional), or by slight improvement in intra-operative technique over time. Comin et al. studied participants who suffered chronic groin pain of no clearly identifiable cause, evaluating whether RFD of the inguinal ligament and ilioinguinal nerve was superior to conservative therapy comprised of local anaesthetic bupivacaine and corticosteroid triamcinolone [4]. Those who underwent RFD in Masala et al. experienced pain around the pubic symphysis and tenderness over the superficial inguinal ring [20]. None of the 264 patients were reported to have a demonstrable lump upon cough impulse, which is a cardinal feature of inguinal hernias [11]. The studies included in this review support existing literature in that presentation of ID is highly variable and hence diagnosis is difficult [7]. As such we believe that any intervention—particularly surgical—must be tailored to each individual patient’s clinical presentation and hence suggested underlying pathology.

Gilmore managed patients by surgically repairing the inguinal ligament with plication to the conjoint tendon, with a focus on restoration of normal anatomy involving a six-layered surgical technique [8]. The author concludes that for some patients, conservative management will never be effective until the underlying dehiscence between the inguinal ligament and conjoint tendon is addressed [8]. Lloyd et al. and Mann et al. postulated that the inguinal ligament may be the underlying cause of ID due to its attachment to musculature of the anterolateral abdominal wall and as such considered inguinal ligament tenotomy an effective treatment of ID [13, 19]. In both studies the same surgeon performed laparoscopic TAPP procedure with inguinal ligament tenotomy by hook diathermy. The inguinal ligament was completely separated at its medial end from the PT, whilst the lacunar and pectineal ligaments were also divided if found to be thickened [13, 19]. The possibility remains that mesh repair and subsequent alleviation of strain on the abdominal wall muscles may be the primary reason for the success of these studies. In the study by Mann et al., 11 participants (15%) underwent operations previously for groin injury (six Gilmore procedures, six inguinal hernia repairs and two adductor tenotomies) to no effect [19]. This suggests that inguinal ligament tenotomy has most likely been the determining factor in symptom alleviation, warranting further investigation of the inguinal ligament and its targeting in therapeutic procedures. One major issue with this surgical approach is the potential for post-operative herniation, however, Lloyd et al. and Mann et al. postulate that this can be addressed with the application of a polypropylene mesh. Additionally, whilst one would expect inguinal tenotomy with mesh repair to potentially destabilise the inguinal region, as division of a musculoskeletal ligament would lead to such a speculation, these studies have reported improved outcome measures for athletes including return to play time and rate. This suggests that a reinforced inguinal ligament withstands high forces while transmitting these from the muscles to the attaching bones which are forces experienced by professional athletes. These features are of a tendon rather than of a ligament [12], questioning the ligamentous classification of the inguinal ligament. We suggest an alternative possible way to circumvent the risk of herniation by performing a partial inguinal ligament tenotomy, whereby only aberrant attachments to bone are released. As yet, there is no published data evaluating this surgical intervention.

For the patients with ID who did not undergo surgery, the results of the studies by Comin et al. and Masala et al. demonstrated that neuromodulation by RFD is effective in reducing pain. Masala et al. show that denervation around the groin area is effective in the short term [20], whilst Comin et al. provide evidence that the inguinal ligament is involved in the underlying pathology of ID [4]. Given that Comin et al. successfully treated what is described as a tendonitis of the inguinal ligament, we believe this provides additional evidence of the tendinous properties of the inguinal ligament.

As recommended in the 2014 multidisciplinary consensus, we believe that athletes with unexplained groin pain causing functional limitation should undergo an initial treatment period involving 2 months of tailored physiotherapy, prehabilitation, analgesia and rest, utilising a multidisciplinary approach [28]. Those whose symptoms extend beyond 2–3 months should be investigated by MRI with orthopaedic review to exclude relevant orthopaedic conditions. The scan may also demonstrate pathologies associated with ID such as tendinopathies of adductor longus and rectus abdominis as they insert upon the pubis [20]. Athletes who remain symptomatic should be seen by an experienced general surgeon for thorough clinical examination to elicit any tenderness over the inguinal ligament or its attachments in addition to the superficial and deep inguinal rings and exclude the possibility of herniation. Patients should then be considered for surgical intervention, with operative adjuncts taking into consideration each individual’s clinical signs and investigative findings.

The pubic bone is important in ID as the site of attachment of several structures which, if damaged, may precipitate a sport injury. From the PT, the inguinal ligament continues as the pre-pubic aponeurotic complex (P-PAC) which connects to the underlying fibrocartilaginous disk of the pubic symphysis. In addition, the pubic bone receives the tendons of adductor longus and rectus abdominis. It has also been suggested that ID is the result of a weakness or tear in the posterior wall of the inguinal canal [28]. Another possible mechanism is imbalance of force across the pubis due to the strong adductor muscles opposing the comparatively weak lower abdominal muscles, creating a shearing force across the hemipelvis [7]. This results in weakening of the posterior wall of the inguinal canal and enthesopathy—disorder of attachment—of the rectus tendon.

Gilmore describes a pathophysiological mechanism of ID comprising a torn external oblique aponeurosis causing a dilated superficial inguinal ring, in addition to dehiscence between the inguinal ligament and a torn conjoint tendon (sometimes called ‘Gilmore’s Groin’) [8]. It has also been suggested that an avulsion injury to the P-PAC could result in microavulsion of the inguinal ligament medially [17]. There is intra-operative photographic [13] and ultrasound data [4] that the inguinal ligament itself was torn medially in patients with ID.

One might argue that the taxonomy—tendon versus ligament—of the inguinal ligament is purely semantic as they are broadly similar types of connective tissue. Macroscopically, these are classified according to their connections; either bone to bone for ligaments or skeletal muscle to bone for tendons. However, this rudimentary logic cannot be applied to the inguinal ligament, which connects the ASIS to PT whilst arising from the aponeurosis of the external oblique. Another consideration is that the purpose of a musculoskeletal ligament is to stabilise a joint between two bones. Although separate in the pre-adolescent, the ileum and pubis are fused as the singular hip bone in the mature adult. Resultantly, the inguinal ligament has no joint to stabilise per se.

Although ligaments and tendons comprised of the same basic components, the exact proportion and arrangement of each of these varies histologically according to the mechanical and functional needs of structures [27]. Amiel et al. noted significant histological differences between tendons and ligaments of ovine tissues. The authors reported that tendinous structures such as the patellar and Achilles tendons were hypocellular compared with the ligaments of the knee [3]. Amiel et al. also discussed that tendons contained a significantly higher total collagen concentration. Although both tendons and ligaments contain type I collagen, ligaments contain a higher proportion of type III collagen (10%) that is found in embryonic tissues than tendons (5%) [3]. This disproportionate amount of collagen may account for the functions of tendons including shock absorption and tension transfer from muscle to bone [12]. Historically, the literature has dictated that ligaments are for stability and must always be preserved (i.e. never divided surgically). As surgeons have now started performing tenotomy on the inguinal ligament, this raises questions over this structure’s anatomical classification and the implications for clinical practice.

Although there is literature relating to the treatment of ID in elite sportspeople, particularly utilising mesh repair procedures and adductor longus tenotomy [9, 21, 26], direct targeting of the inguinal ligament for therapeutic purposes is a relatively new and unexplored innovation and this review provides novel insights into this topic.

Reported differences in the discussed studies could be due to the intervention allocation itself rather than the actual intervention. As such, outcome data for interventions performed by Lloyd et al. and Mann et al. are only applicable to patients with symptoms and characteristics similar to those within these studies. This review has also highlighted widespread heterogeneity of outcome reporting. Currently, there is no consensus on the most appropriate outcome measures for athletic groin pain. Outcomes most commonly reported are on pain severity by visual analogue scale, return to play time and return to play rate. There is, however, an alternative patient-reported outcome questionnaire based on assessment of pain, symptoms and function which has been validated in young to middle-aged patients [29]. Our view is that there must be more consistent reporting based on these criteria to minimise data heterogeneity.