Hip arthroscopy for femoroacetabular impingement: use escalating beyond the evidence

There is a concerning lack of data comparing surgical with non-surgical management of femoroacetabular impingement

Femoroacetabular impingement (FAI) is a common cause of groin pain in physically active young adults, accompanied by limited hip movements. It occurs when bony anatomical abnormalities of the femoral head-neck junction (cam deformity) and acetabular rim (pincer deformity) result in abnormal contact between the two joint surfaces during hip motion. Radiological evidence of FAI is present in about 25% of asymptomatic young adults in the general community.1 FAI increases the risk of end-stage hip osteoarthritis (OA) in later life and is a long term risk factor for joint replacement;2 it may be very disabling. The quality of life of young adults with FAI is comparable to that of older adults who had a total hip replacement for OA.3

No effective treatment for FAI currently exists. However, there has been a very rapid increase in the use of hip arthroscopy for this condition, a procedure that aims to correct hip bone shape and improve symptoms. Hip arthroscopy rates have increased almost four-fold from 2004 to 2009 in the United States4 and over seven-fold from 2002 to 2013 in England,5 with FAI being the most common indication.4 This has resulted in escalating health care costs, despite the uncertainty about its effectiveness.

Although surgical correction of hip bone shape provides a biologically plausible approach for reducing hip pain and slowing the incidence and progression of hip OA, the evidence supporting the use of hip arthroscopy in the management of FAI is limited.6

Evidence for symptom benefit of hip arthroscopy for pain in femoroacetabular impingement

While there is some evidence that hip arthroscopy results in short to medium term symptomatic improvement in FAI,6-8 these conclusions are based on examining patients only treated surgically, and no study has compared surgical with non-surgical therapy. Although one systematic review concluded that symptom outcomes with hip arthroscopy were superior to non-surgical management of FAI,7 this conclusion may be misleading since the systematic review was largely based on case series with no head-to-head comparisons between surgical and non-surgical groups. Such claims must be tempered by the lack of clinical trials with non-surgical control groups.

Evidence for structural benefit of hip arthroscopy for correcting hip bone shape

Evidence shows that bone shape abnormalities in FAI increase the risk of hip OA in later life.2 One rationale for correcting hip shape abnormalities in FAI is based on the premise that this will reduce future structural damage at the hip. Most hip arthroscopies that aim to correct bone shape have focused on reducing the alpha angle,6 a measure of cam deformity associated with the 20-year risk for developing radiographic hip OA.2

Although hip arthroscopy can improve alpha angles,6 there is no evidence that this modifies the risk of incident or progressive hip OA. Indeed, the only available data, albeit over a short follow-up period (1–2 years), showed radiographic progression of disease following arthroscopy.6 One recent systematic review showed excellent hip survival rates following hip arthroscopy: 90.5% of arthroscopic procedures did not require total hip replacement after an average follow-up of 4 years.8 However, it is important to note that of the 16 studies examined, the mean age of the participants was less than 40 years in 14 studies, and less than 20 years in two studies. It therefore stands to reason that the young age of participants is likely to have precluded progression to hip joint replacement, and that these results have limited generalisability. Since FAI is predominantly seen in younger participants, a relatively long follow-up is required when joint replacement is the outcome of interest.

Rationale for non-surgical therapy in femoroacetabular impingement

The data on non-surgical therapy for FAI is limited, although a recent systematic review suggested that physical therapy and activity modification were effective for symptom reduction.9 While the lack of high quality studies in the systematic review was acknowledged, observational data showed that surgery was avoided in at least 39% of patients and in up to 89% of young patients when non-surgical management comprised exercise avoidance, activity modification, non-steroidal anti-inflammatory drugs, intra-articular steroid injection and physiotherapy.6 Nevertheless, these observational studies provide low quality evidence, and head-to-head comparisons between surgical and non-surgical groups for the management of FAI are urgently required.

There is evidence for an effect of physical activity on the development of FAI. Bone is a dynamic tissue with the capacity to remodel across the various life stages. The prevalence of cam abnormalities in skeletally mature, non-athletic men is 9%, but 89% in basketball players who have practiced their sport from childhood.10 The mechanism is thought to be due to either new bone formation or changes in the growth plate shape due to high shear forces at the growing hip. This highlights the importance of activity modification, particularly in early childhood and adolescence, in order to reduce the prevalence and severity of FAI in early adulthood. We have recently shown that obesity in adulthood is associated with pincer deformity in community-based middle-aged adults,11 suggesting that adult hip bone shape may be modifiable. Such data provide a rationale for exploring non-surgical management for FAI across the lifespan.

Hip arthroscopy for femoroacetabular impingement: lessons from arthroscopic partial meniscectomy

The evolution of hip arthroscopy for FAI shares a number of similarities with the evolution of knee arthroscopy. Arthroscopic management of knee pain in OA was commonplace until a randomised controlled trial (RCT) showed a lack of efficacy for arthroscopic intervention.12 This has resulted in a transient reduction in the rate of knee arthroscopy for knee OA in Australia (although it was not sustained), a pattern mirrored by practice in the United Kingdom and the US.13-15

There is now significant debate about the role of arthroscopic partial meniscectomy (APM) in those patients with symptomatic knee OA and meniscal tears.16 The rationale for this procedure is that meniscal pathology may have a significant role in knee pain. However, recent RCTs have shown no superior symptom benefit of APM when compared with non-surgical management,16 although there may be a subgroup of patients who benefit. These results are not surprising because it is now clear that knee OA is a disease of the whole joint, and thus targeting one structural abnormality does not address the whole joint nature of the disease and may not address the genesis of knee pain. It is important to note that about 30% of patients crossed over from non-surgical to surgical management with improved symptom outcomes.16 It may be that certain subgroups of patients with knee pain and meniscal pathology benefit from APM. However, further efforts are required to characterise the individuals who may benefit. Moreover, there is no evidence that APM reduces structural progression of knee OA. Indeed, available evidence suggests an adverse effect of APM on knee structure.17

Meniscal repair has been postulated as a viable alternative to APM for pain reduction. This is technically and theoretically analogous to labral preservation at hip arthroscopy. However, when comparing meniscal repair and APM, meniscal repair was exclusive to young patients (eg, ≤ 35 years), while APM was the mainstay of management among older patients.18 This is likely because the two groups represented different pathologies: one group had an isolated tear easily repaired in the young, and the other group had part of a wider degenerative process observed in older people. Likewise, although labral preservation may be important for improving hip symptoms,7 it is unclear whether this is because preservation surgery was biased to a population with isolated, rather than whole joint disease. There is some evidence to support this possibility, as factors such as degeneration, complex tears, calcification and ossification reduce the potential for labral repair and debridement is necessary.19 Labral debridement may, therefore, be a marker of more widespread hip degeneration, which is a worse prognosis.

It is concerning that the increasing trend toward hip arthroscopy for FAI is following a similar pattern to the history of APM. Lessons learned from the knee strongly support the need for an evidence-based approach to examining the role of hip arthroscopy for FAI. It is well accepted that there is a direct correlation between the invasiveness of an intervention and the placebo effect it can exert. While studies have shown that hip arthroscopy for FAI improves hip pain in the short to medium term,6-8 it is unclear how much of this symptomatic improvement may be driven by a placebo effect. Moreover, the percentage of pain improvement achieved by hip arthroscopy for FAI6 is similar to that achieved by sham surgery for degenerative meniscal tears.20 There is a pressing need for head-to-head RCTs with adequate control arms before definitively advocating hip arthroscopy for FAI. Such studies are also important to ensure that arthroscopic surgery is not associated with harm, such as accelerated disease.

Conclusions

Despite the increasing use of hip arthroscopy for FAI, there have been no RCTs comparing the efficacy of hip arthroscopy with either non-surgical management or sham surgery. There are no data available to help the clinician determine which, if any, patients may benefit from surgery for either improving symptoms or preventing development of hip OA. Lessons learned from knee arthroscopy should be heeded. High quality evidence is required to optimise the management of FAI.