The role of iliopsoas fractional lengthening in hip arthroscopy: a systematic review

ABSTRACT Arthroscopic iliopsoas fractional lengthening (IFL) is a surgical option for the treatment of internal snapping hip syndrome (ISHS) after failing conservative management. Systematic review. A search of PubMed central, National Library of Medicine (MEDLINE) and Scopus databases were performed by two individuals from the date of inception to April 2023. Inclusion criteria were ISHS treated with arthroscopy. Sample size, patient-reported outcomes and complications were recorded for 24 selected papers. Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed and registered on PROSPERO database for systematic reviews (CRD42023427466). Thirteen retrospective case series, ten retrospective comparative studies, and one randomized control trial from 2005 to 2022 were reported on 1021 patients who received an iliopsoas fractional lengthening. The extracted data included patient satisfaction, visual analogue scale, the modified Harris hip score and additional outcome measures. All 24 papers reported statistically significant improvements in post-operative patient-reported outcome measures after primary hip arthroscopy and iliopsoas fractional lengthening. However, none of the comparative studies found a statistical benefit in performing IFL. Existing studies lack conclusive evidence on the benefits of Iliopsoas Fractional Lengthening (IFL), especially for competitive athletes, individuals with Femoroacetabular Impingement (FAI), and borderline hip dysplasia. Some research suggests IFL may be a safe addition to hip arthroscopy for Internal Snapping Hip Syndrome, but more comprehensive investigations are needed. Future studies should distinguish between concurrent procedures and develop methods to determine if the psoas muscle is the source of pain, instead of solely attributing it to the joint.


IN TRODUCTION
Hip pain is a common orthopedic condition that can significantly impact an individual's quality of life [1].Internal snapping hip syndrome (ISHS), which presents with a snapping sensation over the hip joint during certain activities, can be a cause of hip pain.The condition occurs when the iliopsoas tendon slides over the iliopectinal eminence or the anterior aspect of the femoral head.Oftentimes, this mechanism can lead to iliopsoas tendinitis.While conservative measures are often used for initial management, surgical intervention may be necessary if these methods fail [2].
Arthroscopic iliopsoas release is a minimally invasive surgical option that involves releasing the iliopsoas tendon to reduce friction and snapping in the hip joint [3].Despite the welldefined arthroscopic techniques, there still remain several controversial aspects of the procedure.The release of the iliopsoas carries inherent risks and has the potential to heighten instability or lead to intraabdominal fluid extravasation [3].Surgeons often run into the question of whether to combine iliopsoas releases with their arthroscopic labral repairs when a patient has a concomitant internal snapping hip pathology.In addition, iliopsoas impingement may be found during arthroscopy and there is no consensus of whether to treat the impingement in addition to the original labral pathology [4].
To inform clinical decision-making, this systematic review examines the efficacy and safety of performing an iliopsoas release during hip arthroscopy.The studies reviewed provide insights into the medium and long-term functional outcomes, return to sport rates, and reoccurrence of hip pain following surgical intervention.The results of this systematic review will help optimize patient outcomes in the management of internal snapping hip.

M ETHODS
This systematic review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines to identify a final selection of papers for analysis.The plan was registered on PROSPERO before starting the systematic review (CRD42023427466).The inclusion criteria for this study specified patients diagnosed with ISHS who underwent  arthroscopic iliopsoas fractional lengthening (IFL).Exclusion criteria encompassed open surgical procedures, previous total hip arthroplasty and studies lacking patient outcome reporting.
To compile the definitive list of papers for inclusion, a comprehensive search was conducted of the PUBMED Central, MED-LINE, and Scopus databases by two independent reviewers.The search strategy employed the following Boolean terms: 'iliopsoas OR snapping hip OR extra-articular hip' in the title, resulting in an initial pool of 1103 papers.Subsequently, the inclusion criteria were refined by incorporating 'arthroscopy OR surgical management' in any field, reducing the number to 176 papers.
Further application of exclusion criteria involved excluding papers with the keywords 'arthroplasty OR external snapping' in the title, which yielded a set of 75 papers.The abstracts of these papers were then scrutinized, leading to the exclusion of various study types such as cadaveric studies, surgical tutorials, commentary, case studies, imaging studies and systematic reviews.Additional exclusion criteria were employed based on the subject matter of the study, resulting in the elimination of papers related to abscesses, hematomas and studies with unreported patient outcome measures.Ultimately, a total of 17 papers met the inclusion and exclusion criteria and were reviewed and analyzed to address the research question of this study.
To augment the analysis, the references of these 17 papers were examined, leading to the identification of 7 additional relevant studies.Consequently, a final set of 24 papers was utilized for the comprehensive analysis of the research question Figure 1.

R E SULTS Paper characteristics
Thirteen papers from 2005 to 2018 reported on case series with cohort sizes ranging from 6 to 67, totaling 374 patients.An additional nine papers from 2016 to 2022 reported retrospective comparative studies with a total of 641 patients in the study groups and 704 patients in the control groups.Additionally, one randomized controlled trial in 2009 and a similar comparative study in 2014 reported on smaller patient groups of two different techniques, with 10 and 9 patients in one and 6 and 14 patients in the other, respectively.Various surgical techniques were examined and listed in Table I.Eighteen papers reported a modified Harris Hip Score (mHHS), ten papers reported a visual analogue scale (VAS), eight papers reported a non-arthritic hip score (NAHS), five papers reported a hip outcome score (HOS), five papers reported a hip outcome score sport scale (HOS-SSS), four papers reported a hip outcome score activities daily living (HOS-ADL), five papers reported patient satisfaction, four papers reported an international hip outcome tool (iHOT) and 3 papers reported a Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC).
All papers reported primarily on the outcomes following IFL or iliopsoas tenotomy but included various concomitant arthroscopic repairs as well.While the primary focus of the papers was the IFL, additional procedures listed included debridement, acetabuloplasty, femoroplasty, labral repair and capsule repair.

Clinical outcomes
This systematic review provides evidence for the effectiveness of surgical treatments for ISHS, particularly IFL, in alleviating associated symptoms.Patients who underwent IFL in conjugation with other surgical interventions reported improved patient-reported outcome (PRO) scores, pain and snapping resolution and restoration of function.The results of this systematic review provide important clinical considerations for patients [2014] [24] Prospective case series [4] 55 patients mHHS: Pre-operatively 63.  [5,6].In the Jimenez et al. study, athletes with FAI and painful ISHS were identified as a specific patient population that could benefit from intrabursal IFL [5].The study found that this treatment approach was effective for managing hip pain in these athletes, allowing them to return to their pre-injury level of sport and achieve favorable functional outcomes.The Perets et al. study, on the other hand, focused on athletes with hip flexor pain and found that arthroscopic IFL can be an effective treatment option for this population [6].These studies suggest that IFL can be used in conjunction with arthroscopic labral repair surgery to manage hip pain in competitive athletes.
Another large population undergoing hip arthroscopy are patients with labral tears and FAI.The Perets and Maldonado study both added IFL to this population.Both of these studies found IFL does not adversely affect clinical outcomes [7,8].However, there was no statistical significant improvement in patient outcomes.[18] All patients returned to original or better level of function shortly after operation.All had maximum strength of hip flexion, extension, abduction, and adduction Two patients had no improvement in pain despite resolution of the snapping.No patient had any post-operative complications.

Fabricant et al. [2012] [20]
The purpose of this study was to identify the functional outcomes of high version compared to low/normal version.
Patients with increased femoral anteversion may be at greater risk for inferior clinical outcomes after arthroscopic lengthening.No intraoperative or perioperative complications.

Hain et al. [2013] [21]
The majority of post-operative symptomatic patients have atrophy of the iliacus and psoas muscles and distortion and disruption of the iliopsoas tendon.

Garala et al. [2014] [22]
Ten patients reported pain relief after their tenotomy and 5 patients reported no change in pain.
For those patients with only temporary relief from injection, psoas tenotomy can provide good long-term pain relief.

Ilizaliturri et al. [2014] [23]
Every patient in both groups had an improvement in WOMAC score.
One patient in group 2 presented with recurrence of snapping that required surgical intervention.El Bitar et al. [2014] [24] Statistically significant improvement in all PROs 81.8% good/excellent satisfaction and 81.8% resolution of painful snapping.[5] 89.5% of athletes who attempted to return to sport in IFL were successful.76.0% of athletes who attempted to return in the non-IFL were successful.e main finding of the present study was that at minimum 5-year follow-up, competitive athletes who underwent primary hip arthroscopy for FAIS and IFL for painful internal snapping hip demonstrated significant improvement in all recorded PROs.
The IFL group underwent 2 revision arthro-scopiesThe control group underwent 3 revision arthroscopiesControl group had higher rates of undergoing femorplasties when compared to the IFL group.
Similar to FAI, hip dysplasia is a condition that can affect individuals with ISHS, especially women.It is a condition where the socket of the hip joint is slightly shallow, which can lead to early degeneration of the hip joint and other hip pathologies.Importantly, the degree of hip dysplasia should be carefully considered prior to surgery.In patients with moderate to severe hip dysplasia, arthroscopic treatment may not be sufficient and they may require a periacetabular osteotomy.A recent study by Maldonado et al. focused on the addition of IFL with hip arthroscopy in female patients with borderline dysplasia and The role of iliopsoas fractional lengthening in hip arthroscopy • 77 painful ISHS.In this population, iatrogenic hip instability is of increased concern because the iliopsoas is an important dynamic anterior stabilizer.In their study, Maldonado performed the IFL with capsular plication to address this instability risk.The Jimenez et al. study reiterated the importance of capsular management in individuals at risk of instability.In their study, Maldonado et al. study found that IFL followed by capsular plication was beneficial to patients in addition to a primary arthroscopic hip procedure.Specifically, the paper found significantly improved patient outcome measures and there were no instances of post-operative complications or reoperations related to IFL.Even with this paper showing positive results, this procedure is highly controversial due to the inherent risk of instability.
While there is positive evidence for IFL, it is important not to overlook the potential complications associated with this procedure.IFL and tenotomy have been linked to damaging surrounding soft tissues, such as the iliopsoas and gluteal tendons, or the lateral femoral cutaneous nerve, according to Walczak et al. [9].Iliopsoas tendon tears are a common complication of IFL arthroscopy, with some studies reporting rates as high as 20%.Revision surgery and conversion to total hip arthroplasty (THA) may also be necessary in some cases.Additionally, two recent studies by Matsuda et al. (2021) and Meghpara et al. (2020) have highlighted the importance of careful patient selection and judicious use of IFL [4,10].Matsuda et al. found that only 1% of their patients undergoing arthroscopic hip surgery had iliopsoas pathology, and only 17% of those with pathology were surgically managed [10].Meghpara et al. found that IFL did not significantly improve PRO for patients without painful internal snapping, further emphasizing the need for careful patient selection and consideration of alternative treatment options [4].Thus, iliopsoas tenotomy and IFL should not be routinely used without clear internal snapping hip pathology present pre-operatively.

DISCUSSION
This literature review builds on the findings of two previous studies by Gouveia et al. and Longstaffe et al. in 2021 regarding the effectiveness of arthroscopic release of the iliopsoas tendon (IFL) for the treatment of ISHS [3,11].Since the cutoff for these systematic reviews in 2018, six additional level 3 comparative cohort studies have provided significant clinical insights into the use of IFL.Both review papers found that the procedure is an effective treatment for internal snapping hip.However, prior to 2020, no paper focused on IFL concluded that the procedure should be used with caution.Before the Meghpara et al. paper in 2020, all the papers reviewed in this paper emphasized the benefits of IFL and the positive PRO results [4].However, since the pioneering paper in 2005, many complications have been reported.Table II [4,10].An important complication that must be considered is the high rate of muscular atrophy of the iliopsoas which can highly impact athlete's performance [9].
While these studies are essential to consider the possible negative outcomes of IFL, the methodology should be closely analyzed to fully interpret their findings.When analyzing the Meghpara study methodology, the results should only be used to answer the question of how to manage benign iliopsoas impingement, as described by Domb et al. in 2011 [12].In their methodology, the control group that did not undergo an IFL did not have any pain.Therefore, this study should not be used to compare the overall effectiveness of IFL.Instead, this study should be used to conclude that patients without pain should not be considered good candidates for IFL.
The Matsuda study made even bolder claims against IFL.The tenotomy group (n = 16) was significantly smaller than the iliopsoas group without tenotomy (n = 76) [10].There could have been selection bias for the tenotomy group, and their pathology could have been worse pre-operatively.The only PRO outcome was iHOT, while many of the studies in this review also included additional PRO such as mHHS, VAS and HOS.While there may be weaknesses in their methodology, both studies clearly show the importance of the patient selection process for success.To achieve optimal patient outcomes, surgeons should carefully assess patients' suitability for the procedure based on individual needs and circumstances.
Regarding the most agreed-upon technique to treat ISHS, the literature does not state a superior technique.Several studies have used the central compartment technique and lesser trochanter technique, but none of the studies found a statistical difference in PRO.Further randomized clinical trials would be beneficial in this area.
As hip arthroscopy becomes increasingly popular and commonly used, additional techniques may be added to the procedures.Specifically, IFL has been shown to have positive PRO outcomes.Recently, these positive outcomes have been called into question which is exemplified by none of the comparative studies showing a significant improvement compared to the control non-IFL group.These new studies align with the trends reported in the paper by Chen et al.In their study, they reported that 75% of surgeons indicated a decrease in frequency of IFL.This is understandable because the IFL does have risks such as hip flexion weakness [9,13].
Future research endeavors should prioritize investigating the complications linked to Iliopsoas Impingement (IFL).Additionally, forthcoming studies should aim to establish diagnostic methods that can distinguish between hip pain stemming from the iliopsoas muscle and that originating from the hip joint itself.To date, no studies have reported cases of persistent painful snapping hip after successfully addressing hip joint issues and resolving Femoroacetabular Impingement (FAI).Hence, it is advisable to address painful snapping hip through a two-stage approach.Initially, surgical correction of the hip joint should be pursued.If persistent pain remains, a subsequent surgery involving Iliopsoas Lengthening (IFL) may be considered.

LI M ITATIONS
Limitations of this study include the lack of high-quality evidence, primarily relying on retrospective studies with only one randomized controlled trial.Potential publication bias arises from excluding unpublished data, which may affect the comprehensiveness of the review.The varying follow-up durations hinder the assessment of long-term outcomes and complications.Heterogeneous outcome measures make comparisons challenging.Confounding factors and the absence of 68 • A. Baur et al.

Table II . Results and complications Study Authors (year) Results and conclusions Recurrence/complications
The role of iliopsoas fractional lengthening in hip arthroscopy • 75 in this review discusses the complications each paper reported, including the Meghpara et al. paper and a paper by Matsuda et al., which directly reported negative outcomes for the IFL group in their study