Over the past decade, the concept of femoroacetabular impingement (FAI) has been refined [26] and this constellation of disorders has been accepted as a common source of hip pain and dysfunction in young, active patients [11]. There is substantial evidence supporting the hypothesis that FAI is a major etiologic factor in the pathophysiology of secondary osteoarthritis of the hip [1, 5, 6, 13, 17, 18, 25, 27, 38–40]. Specifically, FAI is associated with a pathomechanical hip environment in which there is abnormal, repetitive abutment between the anterolateral femoral head-neck junction and the anterolateral rim of the acetabulum [17, 36]. These abnormal joint mechanics stem from a heterogeneous group of structural abnormalities in which there is a femoral-based (cam), acetabular-based (pincer), or combined impingement deformity [28, 34, 36, 37]. These deformities initiate a cascade of degenerative, intraarticular events including disruption of the labrochondral junction. Chondromalacia and delamination of the peripheral acetabular rim cartilage with adjacent acetabular labral disease are common characteristics in acetabular rim disease [17, 38]. As these focal lesions of the acetabular rim complex progress over time, more extensive, nonfocal degenerative disease ensues [5, 14].

In light of this contemporary understanding of FAI, a variety of surgical techniques have been utilized to treat prearthritic and early arthritic hip impingement disease [10]. These techniques include surgical dislocation of the hip [4, 6, 14, 16, 29, 30], periacetabular osteotomy [35], combined hip arthroscopy and a limited open exposure [12, 20, 24], and all other arthroscopic techniques [2, 8, 9, 19, 21–23, 31–33]. The goals of these surgical interventions are to relieve pain, enhance activity and function, and preserve the natural hip over time [3]. Although these surgical techniques stem from sound rationale regarding hip impingement disease, the published clinical results associated with these procedures are limited [7]. Therefore, there exists a major need to evaluate the current clinical evidence regarding hip impingement surgery.

We therefore performed a systematic review of the literature regarding the surgical treatment of FAI to (1) determine the level of clinical evidence regarding FAI surgery; (2) determine whether impingement surgery relieves pain and improves hip function; (3) identify complications associated with these procedures; and (4) identify modifiable causes of failure.

The current evidence regarding FAI surgery is primarily Level IV (Table 1). Nine of the 11 articles meeting our inclusion criteria were Level IV and two were Level III. No Level I or II studies were identified with our search. Espinosa et al. [14] published a Level III retrospective study comparing the clinical outcome of patients treated for FAI with labral refixation to patients treated with labral resection. Better outcomes were reported in the group of patients who underwent labral refixation. The report by Laude et al. [24] is also a Level III retrospective study, and when comparing labral refixation with partial resection, the investigators observed no difference in the nonarthritic hip score. No additional Level III studies were identified. Possible selection bias was identified in two studies [8, 14] due to excessive exclusion of patients. Additionally, the reports by Murphy et al. [29] and Peters and Erickson [30] had cases (five hips total) treated with additional procedures for structural instability in conjunction with the impingement surgery. These cases represent a distinct subgroup of patients whose clinical results may not be representative of FAI surgical cases.

Improvement in hip function was noted in all studies and in three studies clinical outcome scores corresponding to good or excellent results (as defined by a Merle d’Aubigné-Postel score of 15 to 18 points) were reported in 68% to 96% of patients at a minimum followup of 2 years (mean, 3.2 years; range, 2–5.2 years) (Table 2). The Merle d’Aubigné-Postel score was the most commonly used clinical outcome measure (four of 11 studies). The mean improvement in the Merle d’Aubigné-Postel score ranged from 2.4 to 5 points. Other commonly used outcome measures included the WOMAC osteoarthritis index (three studies) and the nonarthritic hip score (three studies), which had mean improvements ranging from 7 to 20.2 points and 14 to 31.3 points, respectively. Factors associated with a good outcome and increased satisfaction included no or mild secondary osteoarthritis (five studies), labral refixation for treatment of labral pathology (three studies), young age (two studies), and limited cartilage damage (one study).

Symptomatic hardware requiring removal was the only moderate complication reported. None of the studies reported minor complications. The reporting of complications was quite variable in these studies and there was no standard complication grading scheme for these procedures.

Conversion to THA was reported in 0% to 26% of cases. Radiographic osteoarthritis progression was reported in five studies and noted in 0% to 33% of cases. Factors associated with surgical failures and conversion to THA included more advanced preoperative osteoarthritis (four studies), advanced articular cartilage disease (four studies), older age (two studies), and more severe preoperative pain (one study). In general, major complications were uncommonly reported yet occurred in 0% to 18% of the procedures (Table 4).

Surgical treatment of symptomatic FAI has become more commonplace over the past several years, yet the published data evaluating surgical treatment are limited. Most studies are relatively small, single-surgeon cohorts. Our purposes were to define the level of evidence regarding hip impingement surgery, determine the impact of surgery on hip pain and function, and to investigate treatment failures and complications.

The limitations in the literature are substantial and primarily result from the limited number of published studies, the heterogeneous study methods and surgical techniques used in the included studies. For example, these studies have substantial variability for documenting disease characteristics, describing details of surgical treatment, measuring clinical outcomes and reporting complications. Some studies do not used contemporary validated outcome measures. Additionally, the surgical techniques utilized in the different studies vary. Open [4, 6, 14, 16, 29, 30, 35], combined arthroscopic and limited open [12, 24], and arthroscopic surgical approaches [2, 8, 9, 15, 19, 21–23, 31–33] are summarized in this review. This introduces limitations in making general conclusions because each surgical technique may have unique issues related to clinical outcomes and complications. The description of disease characteristics (labral and articular cartilage lesions) relative to severity, location, and size is also nonuniform in these studies and introduces restrictions in making prognostic conclusions relative to intraarticular findings. Finally, the documentation and reporting of complications related to surgery is extremely variable. There is no consensus or standard system of documenting complications and, therefore, these data may not provide comprehensive information regarding the potential risks of hip impingement surgery.

Given these limitations we have performed a rigorous review of the literature and summarized the current information regarding the outcomes of hip impingement surgery. These data provide a reference for surgeons performing hip impingement surgery and can be utilized for patient counseling and discussions regarding the expectations of surgical treatment. Specifically, functional scores, risk of treatment failure, and potential complications can be derived from these data. Our review encompassed a variety of surgical techniques for treating hip impingement surgery. Despite these various techniques and heterogeneous patient populations the general findings are relatively consistent and therefore the data are more generalizable when compared to single-surgeon case series and represent an overview of surgical treatment results. The systematic review has enabled us to review a large group (496 cases) of FAI procedures and to identify common observations among the different studies.

All studies documented short-term improvement with decreased pain and improved function in the majority (65 to 96%) of patients (Table 2). Many of the studies also propose certain factors are associated with a subjectively-defined fair or poor functional score and/or surgical failure. These poor prognostic factors, although variably reported, include more advanced preoperative osteoarthritis, advanced articular cartilage disease, older age, and more severe preoperative pain. These observations highlight the negative impact of secondary osteoarthritis on the long-term results of surgical intervention. Therefore, joint preservation impingement surgery should be undertaken with caution in the presence of secondary osteoarthritis. The reporting of complications was variable but did suggest impingement procedures are relatively safe, with minimal risk for major perioperative complications (Table 4).

In conclusion, our review of the literature suggests hip impingement surgery is associated with early relief of pain and improved function. The impact of impingement procedures on long-term clinical results and natural history has not been established. The role of nonsurgical management has not been defined. These unresolved issues deserve intense investigation. Future research initiatives in this discipline must focus on an improved set of end points to study this patient population more precisely. Refined, standardized, and validated methods of documenting disease classification, measuring clinical outcomes, and reporting perioperative complications are needed to facilitate more sophisticated clinical investigation. Large patient populations must be evaluated to better answer clinically relevant questions. Given this major need for investigation regarding hip impingement disorders, serious consideration should be given to establishing multicenter clinical research initiatives to build consensus regarding optimal outcome endpoints and to analyze clinical outcomes of large patient cohorts. Most importantly, future clinical trials are needed to determine the relative efficacy of nonsurgical and surgical treatment. Predictors of treatment outcome and the efficacy of various surgical techniques need to be established in well-designed clinical trials.