Description

1. Background and Rationale Femoroacetabular impingement (FAI) is a common sports-related disorder of the hip caused by abnormal anatomical morphology of the proximal femur and the acetabulum. Diagnosis requires the combination of patient-reported symptoms, physical examination findings, and imaging abnormalities. Affected patients typically present with activity-related groin or peritrochanteric pain, mechanical symptoms such as clicking, and reduced range of motion. If left untreated, repetitive abnormal osseous impingement can damage the acetabular labrum and articular cartilage, accelerating the degenerative progression toward hip osteoarthritis.

Current management strategies for FAI center on conservative rehabilitation (primarily physiotherapy) and minimally invasive hip arthroscopic surgery. However, the optimal treatment pathway among rehabilitation alone, direct surgery, and the combination of surgery with preoperative rehabilitation remains controversial, and high-level comparative evidence is lacking.

Physical rehabilitation and hip arthroscopy have distinct and complementary mechanisms of action, yet their relative efficacy and appropriate indications are not fully defined. Rehabilitation focuses on correcting abnormal movement patterns and strengthening pelvic and core stability; it is non-invasive and associated with fewer complications, but it cannot eliminate the underlying Cam- or Pincer-type osseous deformity. Consequently, patients with significant structural impingement often experience recurrent pain and difficulty returning to high-level sport after conservative treatment alone. In contrast, hip arthroscopy allows precise resection of the impinging osseous deformity and repair or reconstruction of the damaged labrum, and it has become the mainstream treatment for patients with moderate-to-severe disease. Nevertheless, functional recovery and long-term satisfaction after direct surgery vary considerably among individuals; a substantial proportion of patients experience delayed functional recovery and slow pain relief in the early postoperative period due to pre-existing muscle atrophy, impaired neuromuscular proprioception, and the physiological stress of surgical trauma.

Introducing prehabilitation into the perioperative management of FAI offers a promising approach to address this limitation. Preoperative exercise-based prehabilitation aims to improve patients' physiological reserve and neuromuscular compensation through targeted functional exercise, strength conditioning, and patient education before surgery, thereby improving tolerance of the surgical insult and accelerating postoperative recovery. Although a few randomized trials have suggested that a short preoperative prehabilitation program may improve certain early postoperative functional outcomes, current evidence remains insufficient to demonstrate sustained medium- and long-term gains in clinically meaningful patient-reported outcomes. More importantly, no prospective three-arm trial has directly compared surgery combined with prehabilitation, direct surgery, and standardized rehabilitation alone within a single evaluation framework, leaving clinicians without high-level evidence to guide stepped care decision-making. 2. Objectives This study systematically compares the clinical efficacy of three treatment strategies - surgery combined with prehabilitation, direct hip arthroscopic surgery, and standardized rehabilitation alone - in patients with FAI. The primary focus is on patient-reported outcomes, including the iHOT-12 and HOS instruments, supplemented by dynamic pain scores, hip range of motion, periarticular muscle strength, and return-to-sport (RTS) indicators across the intervention and follow-up periods. The study further explores dynamic changes in periarticular muscle strength and neuromuscular control, aiming to clarify the physiological gains attributable to prehabilitation and their association with long-term postoperative outcomes. The ultimate goal is to define the differential clinical value of each intervention and to provide high-quality evidence for individualized hip-preserving treatment and accelerated perioperative rehabilitation strategies. 3. Study Design

This is a prospective, randomized, three-arm, parallel-group controlled trial. Eligible participants are allocated in a 1:1:1 ratio to one of three arms:

• Arm A (Surgery + Prehabilitation): A structured preoperative prehabilitation program followed by hip arthroscopic surgery.
• Arm B (Direct Surgery): Conventional hip arthroscopic surgery without preoperative prehabilitation.
• Arm C (Rehabilitation Alone): A standardized, predominantly home-based progressive rehabilitation program. 4. Participants

Inclusion Criteria:

Presence of hip pain with imaging evidence of Cam- or Pincer-type femoroacetabular impingement morphology; Age ≥ 16 years; Able to provide written informed consent; Physician judgment that the patient is likely to benefit from hip arthroscopic surgery or a rehabilitation program.

Exclusion Criteria:

Concomitant hip osteoarthritis (Tönnis grade \> 1, or joint space \< 2 mm on the anteroposterior pelvic radiograph); History of prior hip pathology, including Legg-Calvé-Perthes disease, slipped capital femoral epiphysis, or avascular necrosis of the femoral head; History of prior hip trauma, including acetabular fracture, hip dislocation, or femoral neck fracture; Previous hip surgery (open or arthroscopic); Completion of a rehabilitation program specifically for FAIS within the past 12 months; Hip dysplasia (lateral center-edge angle \< 20°).

Note on bilateral disease: Patients with bilateral FAIS may be enrolled; only the more symptomatic hip is randomized and followed for the purposes of this study. 5. Interventions Rehabilitation Protocol (Arms A and C): The rehabilitation program is predominantly home-based and progressive, built upon disease education and activity modification. It is designed with reference to prior studies and systematic reviews, and comprises: (1) resistance training of the periarticular hip musculature; (2) functional motor-control training; (3) hip range-of-motion and flexibility training; and (4) trunk and pelvic stability training. The program is performed four times per week, with each session lasting approximately 30-45 minutes. After the baseline assessment, a rehabilitation therapist instructs participants in the exercises and provides training materials. During the intervention, training load, repetitions, range of motion, and exercise difficulty are individually adjusted according to each participant's symptoms, movement quality, and completion status. If symptoms markedly worsen after a session and do not resolve within 24 hours, the load is reduced and the relevant exercises are suspended; if necessary, the participant is evaluated by the rehabilitation therapist or a clinician. Training completion is recorded by the research staff.

Surgical Intervention (Arms A and B): Hip arthroscopic surgery is performed to resect the impinging osseous deformity and to repair or reconstruct the damaged labrum as appropriate. Detailed intraoperative findings, including labral damage, cartilage injury, round ligament and other intra-articular pathology, as well as the specific surgical procedures performed (labral repair/reconstruction, cartilage treatment, tendon repair, capsular management, osteotomy type and fixation where applicable), are documented. 6. Outcome Measures

Primary outcome measures:

• International Hip Outcome Tool (iHOT-12) score at 6 and 12 months after intervention.

Secondary outcome measures:

• Visual Analogue Scale (VAS) pain score;
• Hip range of motion (active and passive);
• Periarticular hip muscle strength (manual muscle testing);
• UCLA Activity-Level Rating Scale;
• Modified Harris Hip Score (mHHS);
• Hip Outcome Score (HOS-ADL and HOS-SSS);
• Psychosocial measures: SF-12 Health Survey, Pittsburgh Sleep Quality Index (PSQI), Pain Catastrophizing Scale (PCS), Patient Health Questionnaire (PHQ), Generalized Anxiety Disorder Scale (GAD), EuroQol 5-Dimension Questionnaire (EQ5D);
• Imaging assessments (X-ray, CT, MRI) of structural change and recovery. 7. Assessments and Follow-up Baseline data collection includes demographic characteristics, disease-related data, and preoperative imaging. Outcome assessments are performed at baseline and at 6 and 12 months after the intervention. Subjective functional questionnaires are completed by participants at each follow-up point. Rehabilitation-specific functional assessments (range of motion, manual muscle testing, single-leg stance with eyes closed) are performed by trained rehabilitation professionals. Imaging studies are collected preoperatively and during postoperative follow-up to evaluate structural changes and recovery. Surgical data, including operative approach, intra-articular pathology, and management of the labrum, cartilage, soft tissues, capsule, and osteotomy, are recorded to support analysis of surgical factors on long-term outcomes. 8. Safety and Adverse Events All examination and rehabilitation activities are performed within the normal range of motion and only to a tolerable extent. Participants are instructed to contact the medical team regarding any discomfort occurring during the study, whether or not it is related to the intervention. Adverse events (AEs) are defined as any untoward medical occurrence after treatment, without necessarily implying a causal relationship. AEs are classified into five categories of causality (definitely related, probably related, possibly related, possibly unrelated, definitely unrelated); the first three categories are counted in the incidence of adverse reactions. Serious adverse events (SAEs) include events requiring hospitalization, prolongation of hospitalization, disability, impairment of working capacity, permanent organ damage, life-threatening events, death, carcinogenicity, teratogenicity, or birth defects. Any SAE or significant adverse event, whether or not related to the intervention, must be reported to the sponsor by telephone or fax within 24 hours of its occurrence or of the investigator becoming aware of it. 9. Data Management and Statistical Analysis Data are collected via structured questionnaires and entered into a dedicated database using double-entry by two independent operators, followed by two rounds of cross-checking. Queries are exchanged using query forms, which are retained for audit. After verification, the database is locked following review by the principal investigator, sponsor representatives, monitors, data manager, and statistician. Original records are archived according to applicable retention requirements, with multiple electronic backups stored on separate media.

Statistical analysis is performed using SPSS 26.0 software. Categorical data are expressed as percentages and compared between groups using the chi-square test. Continuous data are expressed as mean ± standard deviation and compared using t-tests or non-parametric tests as appropriate. Spearman correlation analysis and multiple linear regression are used to evaluate associations between psychosocial factors and surgical outcomes. Unless otherwise specified, a two-sided p-value \< 0.05 is considered statistically significant. 10. Human Subjects Protection and Ethics The trial will not begin until the protocol and informed consent form have been submitted to and approved by the responsible ethics committee. Any protocol amendment will be implemented only after the relevant revised sections and the revised informed consent form (if applicable) have been reviewed and approved by the ethics committee; a copy of the approval letter will be provided to the clinical monitor. Amendments intended to reduce clear risk to participants may be implemented immediately but must be filed with the ethics committee as soon as possible. In accordance with applicable regulations, investigators will provide written and oral explanations of the study background, nature, purpose, procedures, benefits, risks, compensation, injury compensation, and withdrawal rights before enrollment, and written informed consent must be obtained from every participant (or their legal representative). The informed consent form is dated, and both the investigator and the participant retain a copy. Measures to protect confidentiality include: limiting access to participant data to designated personnel; de-identifying data in case report forms (using participant codes rather than names, telephone numbers, or home addresses) with a separate linkage table; and protecting personal privacy in any publication. 11. Quality Control and Study Management Clinical monitors designated by the sponsor conduct periodic on-site supervision visits to ensure strict adherence to the protocol and accuracy of recorded data. Participating research staff receive uniform training to ensure consistent recording methods and evaluation standards. Monitoring activities include verification of protocol submission and ethics approval, compliance with standard operating procedures, review of the correctness and completeness of case report form data, and verification of all observed findings against source data. 12. Study Duration and Termination The study is expected to be completed within three years. The trial may be terminated early if: (1) a serious safety issue is identified; (2) the treatment effect is judged too poor to have clinical value; (3) a major protocol error or serious deviation makes the effect unassessable; or (4) the applicant or a regulatory authority requires termination.