Athletic groin pain (AGP) is a chronic condition common in multi-directional sports (Walden et al. 2007, Robinson et al. 2004, Murphy et al. 2012). It is a complex injury with a challenging diagnosis. Dramatic differences in the anatomical diagnoses of AGP cohorts exist in the literature (Renstrom et al. 1980, Lovell et al. 1995, Holmich et al. 2007, Bradshaw et al. 2008). This may be due to the complexity of the anatomy in the region and the absence of magnetic resonance imaging (MAGNETIC RESONANCE IMAGE) to confirm clinical examination.

Dynamic actions undertaken in field sports (including change of direction cutting) are particularly associated with the development of athletic groin pain (Holmich et al. 2014). Dynamic multi-plane, multi-joint actions can overload musculoskeletal and fascial structures in the hip and groin. Despite this, traditional groin pain assessments do not involve an examination of sport specific actions. An examination of jumping, hopping and cutting mechanics, which is possible with the use of three dimensional motion capture techniques, will provide additional information with which to diagnosis and rehabilitate athletes.

While the majority of published studies on AGP have focused on surgical management (Serner et al. 2015), exercise therapy has been found to be an effective treatment (Holmich et al. 1995). In exercise therapy studies the best results were shown by Holmich et al (1995) where subjects suffered for an average of 9.9 months with symptoms and a strength and stability program focused on adductor strength returned them to sport in 18.5 weeks. The latest paper on rehabilitation by Jardi et al. demonstrates little improvement with a mean time to return to training of 86 days +/-15. The focus remains on improving strength of isolated muscle groups and not attempting to address underlying biomechanical abnormalities that may be leading to overload. Accurate biomechanical assessment and individualized rehabilitation based on the high speed multiplanar movements that drive the athlete's symptoms may enhance the efficiency of rehabilitation. Moreover post-rehabilitation changes in biomechanical factors may provide a further insight into the biomechanical factors associated with AGP.

The purpose of this study was to:

1. Describe clinical presentation (physical examination and magnetic resonance imaging findings) for a group of athletes presenting with AGP
2. To describe the different biomechanical diagnoses that exist in AGP patients
3. To examine the effects of a biomechanics led exercise intervention to rehabilitate chronic groin pain

It is hypothesised that standardised magnetic resonance imaging will aid in the anatomical diagnosis of athletic groin pain patients. From a biomechanics perspective, distinct subgroups/clusters will exist that differ from each other in how they undertake dynamic sport specific actions. These distinct clusters will describe potential biomechanical diagnoses that exist in groin pain patients. A biomechanics led rehabilitation program will return groin pain patients back to sport more quickly than previous rehabilitation programs without biomechanical diagnostic information.

Brief protocol Participants will be recruited from patients with chronic athletic groin pain who present for investigation and rehabilitation at Sports Surgery Clinic, Ireland. A standardised clinical examination will be undertaken including range of motion assessment, pain provocation and load tolerance tests, and palpation.

A Magnetic Resonance Image of the hip and groin region will then be undertaken and read by a consultant sports physician.

Biomechanical assessment will include capturing of jumping, hopping and cutting mechanics through the use of three dimensional motion capture technology and force plates. Here reflective markers are placed on the skin at anatomical landmarks. These markers are picked up by the cameras and tracked at 200 frames per second. Participants will contact the force plate with their foot on undertaking the movements. Force and marker data will be combined to calculate joint angles and moments.

Physical therapy assessment will include an assessment of functional movement, range of motion testing, adductor squeeze tests, strength assessment of hip and trunk. Physiotherapists will utilise three dimensional biomechanical data during cutting and landing to inform individualised rehabilitation. Rehabilitation will consist of movement control, whole body strength and power, linear running mechanics, multi-directional mechanics and conditioning sessions. Participants will have follow up physical therapy appointments approximately every two weeks. A hip and groin outcome score (HAGOS) will be used to monitor the morbidity and severity of the injury throughout the rehabilitation process.

Once the physiotherapist determines that the patient is ready to return to play a biomechanical re-test will be undertaken.

Detailed Protocol

The following assessments will be undertaken by a consultant sports physician during the initial clinical examination:

• Hip joint range of motion (flexion, internal and external rotation)
• Flexion ADduction Internal Rotation (FADIR) and Flexion ABduction External Rotation (FABER) tests
• Squeeze tests (resisted adduction) at 90, 45 and 0 degrees were performed (SQ90°, SQ45° and SQ0° respectively)
• Resisted sit up
• Prone internal and external rotation
• Gaenslen's test
• Hip extension
• Femoral slump
• Thomas test
• Palpation of the adductor insertion to tubercle, pubic symphysis and superficial ring with resisted oblique sit up and deep ring scrotal invagination
• The crossover test Radiological examination will include magnetic resonance imaging of …..

Biomechanical testing involves the following progressive neuromuscular challenge tests which are undertaken after the clinical examination:

• Countermovement jump - Vertical jump as high as possible
• Single leg drop landing - Hop from a 30cm height onto one leg and hold the landing for 2sec
• Hurdle hop - Lateral hop over a 15cm hurdle followed by a hop back to the starting position and a hold for 2sec
• Change of direction cut - Sprint for 5 metres, make a 75 degree acute change of direction and sprint for a further five meters to the finish
• Indecision cut - Sprint for three meters then react to a light stimulus and make a 90 degree cut to the left or right for a further 1.5metres

Questionnaires

• Hip and groin outcome score (HAGOS)
• Marx activity rating scale

Physical therapy assessment:

• Single leg squat
• Straight leg raise
• Hip strength testing
• Hip range of motion
• Squeeze test
• Crossover test
• Linear running analysis

Rehabilitation Details

Movement Control Focusing on the deficits in large compound movement patterns evident during assessment as well as hip and trunk control deficits. High emphasis placed on the technical quality with which the sessions were carried out. Particular focus on pelvic control while improving sagittal and frontal plane hip and lumbopelvic control. Any symptoms during exercises indicates poor technique and the exercise will be reviewed and intensity reduced until appropriate technique achieved. The rep and set ranges reflected the emphasis on control while improving range at the thoracic spine, hip and ankle.

Strength-Power Double leg and single leg strength training carried out as necessary. Good form instructed throughout to ensure appropriate hip strategy especially under high load. Power work included single leg plyometric exercises to reduced ground contact and improve stiffness throughout the kinetic chain.

Linear Running Linear running drills focused on optimizing lumbo pelvic control in all three planes identified during assessment. Commence with wall drills and marching and skipping and progressing onto sled and harness drills which facilitate developing optimal posture with increased rate of force development and ground reaction forces to improve performance.

Multi Directional Multidirectional drills will be used to provide a neuromuscular challenge to the trunk on pelvis and hip control as well as optimizing foot position and the ability to control the centre of mass relative to the stance leg to reduce hip and pelvic overload and optimise cutting performance. Higher intensity cutting drills will be included as a progression once a painfree squeeze at 90 degrees has been achieved and symmetrical hip internal rotation bilaterally.

Conditioning With a view to ensuring all aspects of the athletes performance are addressed, conditioning will be carried out on a stationary bike to allow sufficient intensity without overloading the pubic/groin region. Sessions will be prescribed from Maximal Aerobic Power assessment on a wattbike and focused on alternate maximal and supramaximal sessions.

Hip and Groin Outcome Score (HAGOS) and MARX activity rating scale A HAGOS and MARX questionnaire will be completed by each groin patient on every visit -approximately every two weeks.

Patient Registry

Patient data will be inputted into iMedDoc medical data management software. Captured data will include:

Patient information - doubly de-identified patient code, electronic scan of consent form, anthropometric data, sport, playing position and playing level, time with pain, pain side or bilateral pain.

Sports medicine consultants findings - Diagnosis, magnetic resonance imaging findings, findings of clinical examination Physiotherapist's findings - clinical examination findings for initial test and post-rehabilitation HAGOS - hip and groin outcome score for initial test and throughout rehabilitation MARX activity rating scale - for initial test and throughout rehabilitation Magnetic resonance image files Quality assurance plan Weekly cross-checking will be undertaken by two members of staff to ensure data entered onto the registry is correct as per paper records and per acceptable ranges.

A six-monthly audit of the registry will be undertaken by external auditors (Dr Kieran Moran, Dublin City University and Dr Siobhan Strike, Roehampton University).

Registry standard operating procedures

Basic patient contact details are inputted by administration staff Patient consent form is uploaded to imeddoc software Doctors and physiotherapists input physical examination findings on imeddoc software HAGOS and Marx activity questionnaire are inputted by the patient using a tablet device. This data is uploaded to imeddoc automatically once questionnaire is completed.

Data is downloaded from imeddoc and placed into Microsoft excel. Patient name is de-identified.

Two researchers manage the registry updates and cross-check the data on a weekly basis. Where applicable paper records are checked to ensure the information submitted to the registry is complete and is within acceptable ranges.

A six-monthly audit of the registry will be undertaken by external auditors (Dr Kieran Moran, Dublin City University, Ireland and Dr Siobhan Strike, University of Roehampton, London).

Sample size assessment to specify the number of participants or participant years necessary to demonstrate an effect Suggested sample size = 600 Biomechanical clustering techniques (which will be used to describe the different biomechanical diagnoses that exist in AGP patients) require relatively large numbers of participants. Previous studies have utilised an n = 588 for this purpose (Sutherland and Davids), therefore it is hypothesised that 600 will be sufficient for such an analysis in the current study.

A sample size of n = 600 will allow a comprehensive examination of the clinical presentation of groin pain. Previous studies have only utilised up to 218 participants (Bradshaw et al 2008).

Finally, a sample size of 600 will be sufficient to account for drop out from the rehabilitation intervention. Drop out may be relatively high due to the regular physical therapy contact required (approximately every 2 weeks) despite the wide geographical spread of participants (throughout Ireland).

Registry Data Dictionary

Term Definition Rt Right Lt Left Dx Ant Plate Diagnosis of anterior plate pathology as a source of the groin pain Dx Hip Diagnosis of hip pathology as a source of the groin pain Dx Inguinal Diagnosis of inguinal ligament pathology as a source of the groin pain Dx Hip Flex Diagnosis of hip flexor pathology as a source of the groin pain Dx Labral Tear Diagnosis of hip labral tear pathology as a source of the groin pain Dx Apon Tear Diagnosis of pubic aponeurosis pathology as a source of the groin pain MRI BMO UNI Presence of bony oedema on magnetic resonance image - one side only MRI BMO BL Presence of bony oedema on magnetic resonance image - both sides MRI Rec Abd Ins Magnetic resonance image signal in the rectus abdominals insertion MRI Add Ins Magnetic resonance image signal in the adductor insertion MRI CAM Magnetic resonance image finding of a CAM hip impingement MRI FAI Magnetic resonance image finding of a femeroacetabular impingement MRI Apon Tear Magnetic resonance image finding of a aponeurosis tear Reduced Hip Flex Reduced hip flexion range of motion Reduced Hip IR Reduced hip internal range of motion Reduced Hip ER Reduced hip external range of motion FADIR Flexion, adduction and internal rotation symptomatic FABER Flexion, abduction and internal rotation symptomatic Squeeze 90 Squeeze test at 90 degrees is symptomatic Squeeze 45 Squeeze test at 45 degrees is symptomatic Squeeze 0 Straight leg squeeze test is symptomatic Thomas Thomas test symptomatic Mod Thom Modified Thomas test is symptomatic Res Leg Lift Resisted leg lift is symptomatic Adduct Tub Adductor tubercle is symptomatic on palpation Res Rot Resisted hip rotation is symptomatic Superf Inguin Ring Superficial inguinal ring symptomatic on palpation Rec Abd Insert Rectus abdominals insertion is symptomatic on palpation Deep Ring Deep inguinal ring is symptomatic on palpation Pubic Symp Pubic symphysis is symptomatic on palpation Slump Slump test positive SIJ Shear Sacro iliac joint shear is symptomatic Prone In/Et Rot Pronated internal/external hip rotation range of motion Femoral Slump Femoral slump test is positive Obs Lx Spine Observation of lumbar spine SL Squat Movement control in a single squat SL Bridge Lt Movement control in a single leg bridge Funct ASLR RT Functional active straight leg raise right Funct ASLR Lt Functional active straight leg raise right Res Hip Fle Resisted hip flexion strength test Hip Flex Hip flexion range of motion Hip IR Hip internal rotation range of motion Hip ER Hip external range of motion Prone IR Pronated hip internal rotation Short Hip FLex Short hip flexor range of motion Long Hip Flex Long hip flexor range of motion ASLR Active straight leg raise Crossover +ve Crossover test symptomatic Crossover -ve Crossover test non-symptomatic HAGOS Pain Pain score from the HAGOS questionnaire HAGOS Symptom Symptoms score from the HAGOS questionnaire HAGOS ADL Activities of daily living score from the HAGOS questionnaire HAGOS SportRec Sport and Recreation score from the HAGOS questionnaire HAGOS PA Physical activity score from the HAGOS questionnaire HAGOS QOL Quality of life score from the HAGOS questionnaire

Plan for missing data

Physical therapist completes a checklist once per week to flag missing data. This data is then completed from paper records.

Statistical analysis plan

Primary outcome measure (HAGOS) - Chi square test to examine changes in repeat HAGOS Secondary outcome measures (Kinetics and kinematics) - Repeated measures ANOVA to examine post-training changes in biomechanical variables Other outcome measures (Physical therapy measures) - Repeated measures ANOVA to examine post-training changes in physiotherapist measures

Inclusion Criteria:

• Diagnosis of athletic groin pain
• Professional athlete in full time training with groin pain diagnosis

Exclusion Criteria:

• Post infective osteitis
• Bone tumour
• Acute injury