IMAGING ROLE FOR DIAGNOSIS AND TREATMENT

– Written by Rowena Johnson, UK

Groin injuries are prevalent in professional athletes, particularly in sports such as football, rugby and hockey which involve high intensity kicking, twisting, quick acceleration and rapid changes in direction. An epidemiological study of groin injuries reported an incidence of 4–19% of all injuries in male club football and 2–14% in women¹.

It remains a particularly challenging area to accurately diagnose and treat. Clinical practice is complicated by the varying terminology clinicians use for groin pain, where the same terms can have different interpretations². A systematic review has previously found 33 different diagnostic terms to characterise groin pain³. The history can often be ambiguous, with either a repetitive mechanism or an acute injury. Furthermore, the anatomy on this area is complex and can contribute to overlapping symptoms, referred pain and a multifactorial aetiology.

Understanding anatomy of the groin region is crucial for diagnosing these injuries. The inherent complexity of this anatomical region necessitates a clear understanding of the strengths and weakness of different diagnostic tools to accurately unmap the nature and extent of injuries. It is also important to be aware that there can be incidental radiological abnormalities that can be seen in this area which are common findings in athletes, and can be unrelated to the clinical presentation.  Imaging should be interpreted in the clinical context, with the aim to “treat the player not the picture”.

Imaging modalities play a pivotal role in the diagnosis and management of groin injuries in athletes. The terminology used to describe inguinal wall related groin pain in athletes is inconsistent and can be confusing, and includes sportsman’s hernia, incipient hernia, Gilmore’s groin, hockey player’s syndrome, athletic pubalgia and inguinal disruption^4,5. This article will include inguinal and adductor related imaging of groin pain, which can in particular pose a diagnostic significant challenge.

DOHA CONSENSUS ON GROIN PAIN

The consensus aimed to create a unified approach to diagnosing and managing groin pain in athletes, recognising that groin injuries are prevalent in sports but can be underdiagnosed or indeed misdiagnosed, with subsequent adverse effect on treatment².

The multidisciplinary group emphasised the need for a standardised framework to improve the accuracy of terminology in this area. It sought to characterise the aetiology of groin pain into three main subheadings namely

Defined clinical entities for groin pain:Adductor-related, iliopsoas-related, inguinal-related and pubic-related groin pain.

Hip-related groin pain.

Other causes of groin pain in athletes.

The group advocated a thorough history and physical examination, including careful palpation to identify painful structures.  It also discussed the use imaging modalities, such as ultrasound and MRI, to differentiate between various types of groin injuries effectively.

The Doha consensus is an important reference point for clinicians in managing groin related issues in athletes, fostering a standardised approach to terminology. It is important to remain aware that medical classifications are not always distinct, and there can be overlap between categories.

IMAGING MODALITIES

The primary imaging modalities in groin pain are ultrasound, magnetic resonance imaging (MRI), and radiographs, each offering unique advantages and facing certain limitations depending on the injury context. An accurate and clear diagnosis is essential at an early stage to plan treatment.

The effective diagnosis and treatment of groin injuries in athletes is influenced by the selection of the appropriate imaging modality to answer the clinical question. Each technique offers advantages and limitations, necessitating a comparative analysis to aid clinicians in making informed decisions based on the individual athlete’s presentation, injury specifics, and resource availability.

Radiographs

Radiographs are an easily accessible and inexpensive imaging modality, and a helpful first line imaging modality for bony pathology. They can demonstrate potential causes for groin pain in an athletes such as hip dysplasia, femeroacetabular  impingement , degenerative changes, stress fractures, bone spurs and features of pubic overload and apophyseal injuries.

Radiographs provide a good overview of hip morphology, and can identify small areas of apophyseal avulsions or heterotopic ossification more readily than MRI. The however provide limited assessment of the soft tissues. It is important to understand the strengths and weaknesses of each imaging modality in order to tailor it to the clinical presentation (Figures 1 and 2).

Ultrasound

Ultrasound is the gold standard in the assessment of inguinal related pain, as it allows dynamic assessment of inguinal canal including the posterior wall on Valsalva.⁶ It utilises high-frequency sound waves to create real-time images of soft tissues, making it particularly advantageous for assessing dynamic movements.  The athlete can be assessed in detail both supine and standing, which is superior to dynamic MRI. A high resolution linear probe should be used, ideally 12-24 MHz to assess the full length of the inguinal canal in both long and short axis, from the deep to the superficial ring. In an athlete, on both static and dynamic assessment there should be no bulging of the pre peritoneal fat through Hesselbach’s triangle or via the deep inguinal ring, nor widening of the posterior wall. 

Ultrasound also allows sonopalaption of the affected region during the study, as well as careful interrogation of adjacent structures including the femoral canal and iliopsoas tendon.

It is an easily accessible tool that carries no radiation burden. It is however operator dependent, with the quality of the imaging relying on the skill and experience of operator. It warrants an experienced person undertaking the scan who understands the anatomy of the groin and range of pathologies. Additionally, it can be more challenging to assess deep structures compared to other modalities, such as MRI. They are potential weakness of imaging in that certain pathologies such as a tear of the external oblique fascia may not be evident on US or indeed MRI imaging. Other non-musculoskeletal causes of groin pain including gastrointestinal, gynaecological and urological should also be considered.

In the context of inguinal pathology, ultrasound allows for concurrent selective diagnostic blocks and if indicated a neurolysis of the ilioinguinal, iliohypogastric and genital branch of the genitofemoral nerve to unmap an athlete’s symptoms and identify their cause of pain. It is key to understand the potential anatomical variants in this area and identify accessory or aberrant nerves prior to a selective nerve block, and ensure a targeted approach.

Ultrasound also plays a role in rectus adbominus injuries particularly in overhead throwing athletes. This area can be challenging to assess on MRI due to adjacent peristalsing bowel, Furthermore the real time nature of ultrasound also allows for dynamic assessment of a torn adductor longus tendon, including to assess tendon tension and retraction.

MRI

MRI provides superior multiplanar soft tissue contrast enabling a comprehensive assessment of other regions such as the pubic symphysis, adductors, and hips. The technique is non-invasive and has no radiation exposure.

It is essential to have the clinical context when interpreting the imaging. There are certain findings that are commonly seen in athletes such as pubic symphysis hypertrophy, which can be incidental. Further common findings in athletes include a cam morphology of the hips and labral tears- a clear clinical history is needed to understand if these are clinically significant findings or not. It is well recognised that some abnormalities can be seen in an asymptomatic athletes⁷.

Osteitis pubis is an overuse injury causing inflammation of the pubic symphysis. This condition is typically seen in athletes subjected to repetitive shearing forces at the pelvis, who present with pain worsened by activity. Biomechanical stress from repetitive movements such as kicking and twisting can contribute to overload, which can also be exacerbated by changes in surface and footwear (Figure 3).

It is important to identify an apophyseal pathology and understand that the pubic apophyses are the last in the body to fuse. Traditional pubic overload versus an apophysitis may warrant different management. A T1 VIBE (volumetric interpolated breath-hold examination) sequence is helpful imaging tool for assessing osseous anatomy, including the apophyses⁸. It is a 3D gradient echo volumetric MR sequence with high intrinsic contrast between the bone and soft tissues. It improves through plane spatial resolution and allows for multiplanar reformatting. The images are then inverted to mimic a CT sequence. Similar to a standard T1 sequence, VIBE images have low contrast resolution for soft tissue and cartilage surfaces compared to other MRI sequences (Figure 4).

An awareness of different MRI techniques is important, for example different sequences have different sensitivities for marrow oedema, with a STIR sequence being more sensitive than a T2 fat saturated or PD fat saturated sequence. Certain radiological findings may not necessarily be the cause of the athlete’s pain, such as pubic overload, adductor secondary clefts, labral tears, labral cysts.

MRI is also the imaging modality of choice for adductor longus injuries. Proximal adductor longus avulsions can be difficult to accurately diagnose and manage effectively. Delayed or incorrect diagnosis can lead to functional impairment in high level athletes. Adductor injuries are prevalent in football, comprising up to 23% of all muscle injuries⁹.

A dedicated small field of view groin MRI is advised for assessing injuries of the pyramidalis- anterior pubic ligament- adductor longus complex (PLAC). ¹⁰ This includes small field of view axial oblique and sagittal images of the groin, centred on the pubic symphysis (Figure 5).

The anatomical structure of the proximal adductor longus (AL) tendon has long been a subject of debate. Historically it was believed that the rectus abdominis maintained continuity with the adductor longus tendon. Cadaveric research by Schilders et al. provided further light on this area demonstrating that no direct continuity exists between the rectus adbominus and the adductor longus tendon¹¹. The term PLAC is widely used and a helpful acronym for radiologists and clinicians when assessing adductor longus avulsions to look for associated injuries.  A study on 145 athletes found that proximal adductor avulsions are rarely isolated; they often involve injuries to adjacent structures. It identified six distinct injury patterns based on the involvement of these structures. They concluded that MRI should be used to evaluate all components of the PLAC following injury to accurately identify the specific injury pattern, which can inform appropriate management strategies (Figures 6 and 7).

MRI is also the imaging modality of choice for evaluating the hip, offering excellent contrast resolution for both osseous and soft tissue structures.  It characterises a range of hip injuries common in athletes, including labral tears, cartilage loss, osteonecrosis, and osseous abnormalities associated with femoroacetabular impingement (FAI). Hip MRI also allows for interrogation of extra-osseous structures, including the iliopsoas tendon¹².

Hip intra-articular pathology is best imaged on small field of view high resolution MRI. 3T MRI will typically show chondral and labral pathologies well, and MRI arthrography is not typically needed, particularly as a first line imaging modality. Where further information on cartilage is needed, more comprehensive assessment of the cartilage may be obtained with the use of quantitative MR techniques such as T2 mapping.

The hip, a ball-and-socket joint, endures repetitive stress during sporting activities. High congruency between the femoral head and the acetabulum allows predominantly rotational motion, but also predisposes athletes to injuries if osseous stability is compromised or if abnormal biomechanical forces are present. The labrum deepens the acetabular cup, and blends with the transverse ligament at the inferior joint margin.  The range of motion is constrained by bony and ligamentous structures, and inadequate osseous stability such as a dysplastic hip can disrupt force transmission and contribute to joint damage. Furthermore abnormal bone contact, as seen in femoroacetabular impingement (FAI), can result in damage to the chondral surfaces. In cases of cam-type FAI, shear forces from the aspherical femoral head-neck junction can lead to cartilage delamination at the acetabulum.  Femoral torsion, defined by the angle between the femoral condyles and the femoral neck axis, also plays a role in joint mechanics (Figure 8).

Femoral head and acetabular hyaline cartilage are essential for force transmission within the hip joint. MRI remains and invaluable for assessing chrondral surfaces and labral pathology, however it is to be emphasised that radiological abnormalities in this area can be seen as an incidental findings in athletes, and should be interpreted in the clinical context.

DEXA

DEXA is a helpful adjunct tool in chronic pubic pain which has not responded to standard rehabilitation treatment. Focal osteopenia can be a cause of chronic pubic pain even in the absence of marrow oedema on MRI, and in those patients where the standard treatment options have not helped, a small field of view DEXA can assess for localised osteopenia¹³.

OTHER IMAGING MODALITIES

SPECT-CT is rarely used in assessing groin pain in athletes, however warrants a mention as it can be used a troubleshooting imaging tool in selective patients. It fuses separately acquired single photon emission CT and CT studies, and allows fusion of anatomical and functional imaging. It can be used for example when MRI is contraindicated or equivocal, as well as in the setting of an infectious or inflammatory process¹⁴.

CONCLUSION

The recognition and accurate diagnosis of groin injuries necessitates optimal imaging strategies tailored to identify specific pathologies. The complex interplay of anatomical challenges, necessitates the need for precise imaging which will contribute towards improving clinical outcomes. Understanding the anatomy of the groin and common injury mechanisms is essential for selecting the most appropriate imaging modalities and interpreting results effectively, thereby facilitating effective clinical management and rehabilitation strategies.

Each imaging technique offers certain benefits and limitations, making it essential to understand their applications in the context of imaging groin pain in athletes. Ultrasound provides a dynamic assessment and real-time imaging, and is an excellent tool for inguinal related pathology. Furthermore it guides targeted, selective nerve blocks at the time of assessment where clinically appropriate. Its limitations include operator dependency. MRI provided superior soft tissue contrast and provides detailed assessment of bone marrow, cartilage, and soft tissues. In particular, it is the gold standard for assessing adductor injuries. Radiographs are helpful for assessing bony pathology including hip joint morphology, apophyseal injuries of fractures. They do not however provide soft tissue assessment.  Small field of view DEXA is helpful trouble shooting tool in select patients for chronic unresolved pubic pain. 

A comprehensive approach to evaluating groin injuries often requires integrating different imaging modalities. The different techniques are complimentary and can provide vital information that contributes to a holistic understanding of the injury, thus guiding treatment decisions.

This paper reinforces the necessity of tailored imaging strategies in the management of groin injuries in athletes. By understanding the strengths and limitations of each modality, clinicians can implement a logical approach to imaging that not only enhances diagnosis but also plays a role in the rehabilitation follow up of patients.

Rowena Johnson

Professor

Department of Radiology

Fortius Clinic

London, UK

Carnegie School of Sport

Leeds Beckett University

Leeds, UK

Contact: rowpjohnson@gmail.com

Further reading

1. Waldén M, Hägglund M, Ekstrand J The epidemiology of groin injury in senior football: a systematic review of           prospective studies.  British Journal of Sports Medicine 2015;49:792-797.
2. Weir A, Brukner P, Delahunt E, et al. Doha agreement meeting on terminology and definitions in groin pain in athletes. British Journal of Sports Medicine 2015;49:768-774.
3. Serner A, van Eijck CH, Beumer BR, Hölmich P, Weir A, de Vos RJ. Study quality on groin injury management remains low: a systematic review on treatment of groin pain in athletes. Br J Sports Med. 2015;49:813.
4. Dimitrakopoulou A, Schilders E. Sportsman's hernia? An ambiguous term. J Hip Preserv Surg. 2016 Feb 24;3(1):16-22. doi: 10.1093/jhps/hnv083. PMID: 27026822; PMCID: PMC4808262.
5. Harmon KG. Evaluation of groin pain in athletes. Curr Sports Med Rep. 2007 Dec;6(6):354-61. PMID: 18001606.
6. Pesquer L, Rennie WJ, Lintingre PF, Reboul G, Silvestre A, Dallaudiere B, Meyer P. Ultrasound of Groin Pain in the Athlete. Semin Musculoskelet Radiol. 2024 Dec;28(6):672-682.
7. Blankenstein T, Grainger A, Dube B, Evans R, Robinson P. MRI hip findings in asymptomatic professional rugby players, ballet dancers, and age-matched controls. Clin Radiol. 2020 Feb;75(2):116-122. doi: 10.1016/j.crad.2019.08.024. Epub 2019 Sep 30. PMID: 31582172.
8. Koh E, Boyle J. Pubic apophysitis in elite Australian Rules football players: MRI findings and the utility of VIBE sequences in evaluating athletes with groin pain. Clin Radiol. 2020 Apr;75(4):293-301. doi: 10.1016/j.crad.2019.12.022. Epub 2020 Feb 1. PMID: 32019672.
9. Ekstrand J, Hagglund M, Walden M. Epidemiology of muscle injuries in professional football (soccer) Am J Sports Med. 2011;39:1226–1232.
10. Schilders E, Mitchell AWM, Johnson R, Dimitrakopoulou A, Kartsonaki C, Lee JC. Proximal adductor avulsions are rarely isolated but usually involve injury to the PLAC and pectineus: descriptive MRI findings in 145 athletes. Knee Surg Sports Traumatol Arthrosc. 2021 Aug;29(8):2424-2436.
11. The pyramidalis-anterior pubic ligament-adductor longus complex (PLAC) and its role with adductor injuries: a new anatomical concept. Schilders E, Bharam S, Golan E, et al. Knee Surg Sports Traumatol Arthrosc. 2017;25:3969–3977.
12. Christopher ZK, Hassebrock JD, Anastasi MB, Economopoulos KJ. Hip Flexor Injuries in the Athlete. Clin Sports Med. 2021 Apr;40(2):301-310. doi: 10.1016/j.csm.2020.11.006. Epub 2021 Jan 19. PMID: 33673888.
13. Dimitrakopoulou A, Schilders E. Focal osteopenia of pubic parasymphyseal bone as an underlying cause of groin pain in sports: a new perspective. BMJ Case Rep. 2018 May 4;2018:bcr2017223698. doi: 10.1136/bcr-2017-223698. PMID: 29728433; PMCID: PMC5935169.
14. Saha S, Burke C, Desai A, Vijayanathan S, Gnanasegaran G. SPECT-CT: applications in musculoskeletal radiology. Br J Radiol. 2013 Nov;86(1031):20120519. doi: 10.1259/bjr.20120519. Epub 2013 Oct 4. PMID: 24096590; PMCID: PMC3830427.

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