Key points

Introduction

Hip arthroscopy is a rapidly evolving procedure that has seen an exponential increase in the number of cases performed yearly. With hip arthroscopy still in its infancy in relation to knee and shoulder arthroscopy, there are still many questions yet to be answered. Axioms that were once thought to be true regarding the indications and treatment of hip arthroscopy are continually being revised. As with the knee and shoulder before it, the hip is now graduating into treatment that was otherwise thought to only be possible through an open surgical procedure.

Within this review, the authors set out to explore factors affecting the long-term survivorship of hip arthroscopy. As currently indicated, hip arthroscopy is generally reserved for relatively young patients; its goal should be to reduce pain, return function, and prevent or stave off the definite end point of hip arthroplasty. Advances in diagnostic imaging, arthroscopic devices and instruments, as well as the ability to now begin to retrospectively look back on our previous outcomes in hip arthroscopy all provide the window for viewing into the future of this evolving frontier.

Introduction

Hip arthroscopy is a rapidly evolving procedure that has seen an exponential increase in the number of cases performed yearly. With hip arthroscopy still in its infancy in relation to knee and shoulder arthroscopy, there are still many questions yet to be answered. Axioms that were once thought to be true regarding the indications and treatment of hip arthroscopy are continually being revised. As with the knee and shoulder before it, the hip is now graduating into treatment that was otherwise thought to only be possible through an open surgical procedure.

Within this review, the authors set out to explore factors affecting the long-term survivorship of hip arthroscopy. As currently indicated, hip arthroscopy is generally reserved for relatively young patients; its goal should be to reduce pain, return function, and prevent or stave off the definite end point of hip arthroplasty. Advances in diagnostic imaging, arthroscopic devices and instruments, as well as the ability to now begin to retrospectively look back on our previous outcomes in hip arthroscopy all provide the window for viewing into the future of this evolving frontier.

Indications of hip arthroscopy

When hip arthroscopy was initially begun, treatment indications were extremely limited. Reasons for these limitations, included a lack of understanding of underlying cause as well as shortcomings due to inadequate instrumentation. However, hip arthroscopy indications have expanded to include both intra-articular and extra-articular pathology; these include acetabular labral tears, femoroacetabular impingement, chondral lesions, osteochondritis dissecans, hip capsule laxity and instability, ligamentum teres injuries, infection, snapping hip syndrome, iliopsoas bursitis, and loose bodies ( Table 1 ). Looser indications include management of symptomatic osteoarthritis of the hip joint. Despite these expanding indications, it is still imperative that the correct diagnosis be made as to the root of the problem. As has been noted, hip pathology is a spectrum, often with numerous associations that must be identified, explored, and treated appropriately to best eradicate the patients’ pain.

Osteoarthritis

The presence of osteoarthritis in any joint has been associated with poor long-term survivorship. Long-term studies on the knee have demonstrated that previously performed lavage of osteoarthritic knees have had outcomes that were no better than placebo. Likewise, a review of the hip arthroscopy literature in the setting of osteoarthritis has generally has yielded poor Harris Hip Scores and a higher rate of conversion to total hip arthroplasty (THA).

In the authors’ prior retrospective study, they reviewed 324 patients (340 hips) who underwent arthroscopy for pain and/or catching. Of 111 hips (106 patients) that had a minimum follow-up of 10 years (mean, 13 years; range, 10–20 years), they found a survivorship of 63%. The survivorship end point was determined at the time of the THA. The average nonarthritic hip score for non-THA patients was 87.3 (±12.1). The survivorship was greater for acetabular and femoral Outerbridge grades normal through II. The age at arthroscopy and Outerbridge grades independently predicted eventual THA. Gender and the presence of a labral tear did not influence long-term survivorship. In conclusion, a 20 to 60 times higher incidence of need for THA was noted in patients with a higher-grade osteoarthritis.

Philippon and colleagues have written on several survivorship studies after hip arthroscopy with varying rates of THA conversion. In 2008, a prospective analysis of 112 hips that underwent arthroscopy for femoroacetabular impingement (FAI) treatment had a 9% conversion rate at a mean of 16 months (range 8–26 months). They found that preoperative modified harris hip score (mHHS), absence of joint space narrowing less than 2 mm and repair of labral pathology instead of debridement were associated with better outcomes. In 2012, Philippon and colleagues again examined survivorship of hip arthroscopy in a consecutive series of 153 patients aged 50 years or older who underwent treatment of FAI. Again, the length of time between arthroscopy and the need for conversion to THA was examined. Their findings revealed that conversion to THA was required in 20% of their patients. However, analysis of their 3-year follow-up data revealed survivorship of 90% in patients who had greater than 2 mm of joints space on plain radiographs. A 57% survivor rate was found in those patients with 2 mm or less. In patients who did not require THA, the mHHS and hip outcome score (HOS) scores significantly improved from 58 to 84 and 66 to 87 respectively.

Haviv and O’Donnell retrospectively reviewed 564 osteoarthritic patients that have had hip arthroscopy. Over a 7-year period, (mean follow-up of 3.2 years), they noted a 16% conversion to THA. Their findings noted that patients aged less than 55 years and with less arthritic changes had longer survivorship. Of note, the surgeon performed microfracture to any acetabular lesion that met the criteria. Importantly, patients who underwent femoral osteoplasty also had a lower conversion rate (16%) than those who did not (31%).

Byrd and Jones, in their prospective 10-year follow-up, reported a 27% (14 of 52 hips) conversion rate to THA. They identified arthritis (defined as radiographic features of subchondral sclerosis or erosions, joint space narrowing, and osteophyte formation) as an indicator of poor long-term outcomes. The investigators, however, appropriately pointed out that neither the bony treatment of FAI nor labral repairs were performed on any of the patients because these current treatment options were not routinely being practiced arthroscopically at the time of surgery.

Further preoperative radiologic predictors of survivorship were presented by Franco and colleagues. In their analysis of 263 hips, they found the presence of subcortical acetabular cysts on preoperative magnetic resonance imaging (MRI) were 4 times more likely to require conversion to THA at 2 years. Finally, Larson and colleagues noted no improvement in postoperative score measures in patients who had preoperative joint space narrowing greater than 50% or less than 2 mm of joint space remaining on plain radiographs. At a minimum 12-month follow-up on 210 patients (227 hips) treated for FAI, an overall failure rate of 52% was reported for the arthritic group, whereas the nonarthritic group was (12%). Based on their finding, the investigators noted decreased remaining joint space, advanced MRI chondral grade, and a longer duration of preoperative symptoms predicted lower scores and led to negative survivorship after hip arthroscopy.

A review of the literature for outcomes after hip arthroscopy for osteoarthritis yields scant long-term studies. Prior published studies fail to support arthroscopic intervention as beneficial for osteoarthritis, noting conversion to THA rates ranging from 9% to 37% ( Table 2 ). It should be pointed out that femoral osteoplasties and/or acetabuloplasties were not being routinely performed during many of the long-term studies because arthroscopic treatment of FAI had not grown in popularity until the midportion of the last decade. Likewise, labral repair was often not performed in these studies because many of the tears were managed with debridement. Future follow-up studies addressing both FAI treatment and survivorship after arthroscopy with higher levels of arthritis are warranted because THA conversion rates have been reported to be lower in those patients treated for FAI.

Osteochondral defects

Osteochondral damage within the hip is often a silent lesion. Conventional radiographs often cannot identify these lesions, leaving them to be discovered during arthroscopy. MRI arthrography has improved the identification of chondral injuries; however, lesions are still often underdiagnosed. Nevertheless, the severity of osteochondral defects can negatively impact long-term outcomes after hip arthroscopy.

In 2010, McCarthy and colleagues performed a 10-year retrospective analysis of patients who underwent hip arthroscopy. It was found that patients who had Outerbridge scores of III or IV demonstrated a 20 to 58 times higher incidence of requiring a THA. Those with Outerbridge scores of O to II had zero conversions to THA and demonstrated a Modified Harris Hip Score (mHHS) of 87.3 (±12.1). It should be noted, however, that the treatment rendered to these patients did not address the pathology associated with FAI.

Byrd and Jones likewise retrospectively reviewed 52 hips in 50 patients over 10 years. The spectrum of pathology treated included labral tears, osteoarthritis, chondral defects, and loose bodies. They noted a 25-point increase in the mHSS across all patients; however, they noted osteoarthritis to be a negative prognostic indicator for positive outcomes. Fourteen patients, all with noted osteoarthritis at the time of arthroscopy, were converted to THA. Underscoring the differentiation between chondral defects and arthritis was a 19-point improvement in the mHSS when patients with hallmark signs of arthritis were excluded. The investigators concluded that arthroscopic management of traumatic chondral lesions in the absence of arthritis can be quite favorable.

Philippon and colleagues have reported on the successful management of full-thickness chondral lesions of the hip via microfracture. In their report on athletes, they found high success rates and high rates of returning to competitive sports. Karthikeyan and colleagues were able to report the successful management of an isolate full-thickness chondral defect through microfracture. In their report, 20 hips met criteria for microfracture. At an average 17-month follow-up, they were able to evaluate the cartilage via second-look arthroscopy, noting a 95% fill rate. Pain scores and function were also noted to have improved in the patients with successful fibrocartilage growth.

Recently, Philippon and colleagues presented their findings on 5- to 7-year survivorship following hip arthroscopy for the treatment of labral pathology and FAI. They found that across 247 hips (average age of 41.7 years) the 5- and 7-year survivorship rate was 72% and 70%, respectively. However, most significant among their findings was that patients with diffuse changes in their cartilage at arthroscopy were 4.3 times more likely to undergo conversion to THA, with a survivorship at 5 years of 43%. Those patients without diffuse changes had a survivorship of 79%.

In 2004, McCarthy noted that the severity of the chondral lesion has a highly correlative effect with the outcome of hip arthroscopy. Patients with an Outerbridge score of grade III or IV were 20 to 58 times more likely to require eventual THA. Osteochondral lesions are often missed during preoperative evaluation. Nevertheless, their presence has a negative effect on survivorship. Higher THA conversion rates have been found in patients identified with Outerbridge lesions of III or higher, with some conversions occurring as early as 1.4 years. A lack of correlation between intraoperative Outerbridge scores and preoperative Tonnis scores has been cited repeatedly and may further necessitate the need to other preoperative predictors of long-term survivorship. Horsiberger and colleagues found that preoperative radiographs and Tonnis grading were poor indicators of the intra-articular lesions actually found at the time of arthroscopy. This finding again echoes the thought that early to midterm chondral damage that has yet to manifest itself into fulminant arthritis can be a setup for failed survivorship. In an effort to further preoperative identifying indicators, Franco and colleagues found that the presence of a subchondral acetabular cyst on presurgical MRI was noted to have higher sensitivity for predicting eventual THA conversion than other reported indicators, such as minimum joint space. Furthermore, they noted that these cysts led to similar conversion odds ratios as those reported by McCarthy and colleagues earlier.