Fig. 1 A, Supine arthroscopic view of a right hip with acetabuli protrusio under distraction demonstrates the view of the central compartment, perimetric rim trimming, and large cam deformity (*). B, Arthroscopic view without distraction shows the labral fluid seal restored with gracilis (Gr) labral reconstruction and the region of femoroplasty extending into the anteromedial critical corner (blue *). AR=acetabular rim, 3,10,12 = clockface positions, FN = femoral neck, L = labrum.
Courtesy of Dean K. Matsuda, MD

AAOS Now

Published 7/1/2016
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Dean K. Matsuda, MD

Trends and Recent Research in Hip Arthroscopy

It has been 4 years since the last AAOS Now update on advances in hip arthroscopy. Since then, arthroscopic techniques and the field of hip preservation have rapidly evolved. This updated overview explores some of the latest hot topics, technical advancements, and emerging evidence-based studies in hip arthroscopy. As in any evolving field, current information and analysis is subject to change.

FAI
Hip arthroscopy's growth is attributable in large part to its use in the treatment of femoroacetabular impingement (FAI). Between 1999 and 2009, the number of hip arthroscopy procedures performed in the United States by American Board of Orthopaedic Surgery candidates increased 18-fold. Several cross-sectional studies have estimated that the prevalence of FAI may range from 14 percent to 17 percent among asymptomatic young adults to almost 95 percent among competitive athletes. A recent study on provider perception and demographics of surgeons who perform FAI surgery suggests that FAI management is early in the innovation cycle—ie, the time period in which a procedure becomes more widespread, indications broaden, measurements become increasingly objective, and an increase in prospective studies is seen; however, we may be at a tipping point toward wider use.

One such study—a systematic review of research published in Arthroscopy and The American Journal of Sports Medicine from 2012 to 2015—identified some key findings. In the absence of significant degenerative changes, arthroscopic intervention resulted in improvements in functional outcomes at both the short-term and midterm for patients with symptomatic FAI. The researchers also found that labral repair may result in improvements over labral débridement. Complication rates were very low, but were found to be expertise-dependent. In addition, several studies report high rates of return-to-sport in elite athletes, and two recent studies suggest that arthroscopic surgery for FAI is cost effective. Overall, however, there is a need for improved methodologic quality and reporting of research on FAI as well as more reporting of long-term outcomes.

Advances in imaging techniques and modalities have made improved characterization of FAI morphology possible. Cam impingement has been classically described as an anterolateral bony deformity at the femoral head-neck junction. Virtual computed tomography studies have demonstrated extension of cam impingement to the anteromedial region, while a recent clinical study has demonstrated improved cam decompression with arthroscopic femoroplasty of the anteromedial "critical corner" in patients who have insufficient flexed-hip internal rotation after anterolateral femoroplasty.

Preoperative delayed gadolinium-enhanced magnetic resonance imaging (MRI) of cartilage (dGEMRIC) may be predictive of the magnitude of clinical improvement following hip arthroscopic surgery for FAI. Technical advances include the arthroscopic treatment of global pincer FAI (including severe coxa profunda and protrusio acetabuli) and posterior cam FAI (Fig. 1). Subspine impingement, which may cause pain with hip flexion, can be caused by a prominent distally protruding anterior inferior iliac spine. Early successful outcomes have been reported from arthroscopic subspine decompression and arthroscopic treatment of global pincer FAI.

Proximal femoral version appears to have little influence on outcomes of arthroscopic FAI surgery, although one study demonstrated less improvement in patients with relative retroversion (less than 5 degrees anteversion). In more extreme cases, less invasive derotational osteotomy with an intramedullary saw may be a feasible option.

Although most studies demonstrate greater improvement via labral repair, selective débridement (retaining the labral fluid seal) has been associated with significant improvement and may still be a viable option in some patients. Moreover, the labral suture configuration (circumferential versus midsubstance) has not been demonstrated to significantly influence outcomes. Because of a presumed labral hip preservative effect, an irreparable labrum may be treated with labral reconstruction using various autografts and allografts. Early and midterm outcomes of these procedures have been encouraging.

It should be noted that some centers perform concurrent bilateral arthroscopic surgery in patients with bilateral, symptomatic FAI. A recent study demonstrated that immediate weight bearing may have no deleterious effect on outcomes, enabling simultaneous surgery in select patients. Other recent studies have suggested that hip abduction and flexion strength deficits in patients with FAI and modifiable hip deficits of hip flexion range of motion—as well as deficits of flexor and adductor strength—may significantly affect clinical outcomes.

Dysplasia
The jury is still out on the indications for repair of the hip capsulotomy, with one large series showing no demonstrable difference in arthroscopic outcomes. Capsular repair or plication, however, tends to be commonly used in the treatment of dysplasia. Two recent studies demonstrate successful outcomes in patients with borderline dysplasia when arthroscopic capsular repair is performed.

A recent study on arthroscopic outcomes of dysplasia identified a broken Shenton's line (suggesting instability), lateral center-edge angle less than 19 degrees, and high femoral neck shaft angle as significant predictors of poor outcomes. Another study found arthroscopic visualization of chondral damage on the posterior femoral head and anterior acetabulum as strong predictors of ultimate conversion to total hip arthroplasty in dysplastic patients.

Endoscopic shelf acetabuloplasty was developed in Japan, where there is a relatively high prevalence of dysplasia. In addition to intra-articular arthroscopy, this procedure has been reported to yield encouraging early outcomes and may provide a less invasive option for patients with mild to moderate dysplasia.

Periacetabular osteotomy (PAO), which reorients the acetabulum into a biomechanically favorable position, is considered by many as the gold standard treatment for significant dysplasia. However, it is an open surgery with prolonged rehabilitation and the potential for significant complications. Endoscopy-assisted PAO has recently been performed as a less invasive alternative and may decrease the incidence of complications. Perhaps one of the most important benefits of arthroscopic/endoscopic approaches to classic open hip preservation procedures is the collaboration among specialists who perform these procedures, which has been encouraged by societies such as the International Society for Hip Arthroscopy.

Peritrochanteric procedures
Gluteus medius and/or minimus tears may be responsible for some of the recalcitrant cases of what were previously considered trochanteric bursitis, typically found in older patients. Promising outcomes from endoscopic repair of these "rotator cuff tears of the hip" are emerging. Fatty infiltration and/or severe atrophy of the abductor muscles on MRI may be a relative contraindication to repair.

Ischiofemoral impingement is a less common cause of posterior hip pain that may be exemplified by pain on long-stride gait. The quadratus muscle may be pinched between the ischium and lesser trochanter and become inflamed. Endoscopic decompression of the ischium or lesser trochanter (via anterior or posterior approach) appears to be a feasible surgical option in recalcitrant cases.

Symptomatic sciatic nerve entrapment from piriformis syndrome, fibrovascular scar, or other etiologies may be effectively treated with endoscopic sciatic nerve release and neurolysis. It has not been clearly established which cases are better treated by formal open surgery.

Athletic pubalgia
Constrained range of motion from FAI may cause transfer stress to the lumbar spine, sacroiliac joints, and pubic symphysis. Many athletes with FAI also have athletic pubalgia. Endoscopic pubic symphysectomy—when performed concurrently with arthroscopic or mini-open FAI surgery—has been reported to yield successful outcomes in the midterm for athletes with recalcitrant osteitis pubis.

Osteonecrosis
In the setting of classic superoanterior osteonecrosis of the femoral head without subchondral collapse, arthroscopic-assisted core decompression permits treatment of intra-articular pathology as well as assessment of the overlying articular cartilage. Beyond core decompression, arthroscopic backfill procedures using self-hardening calcium phosphate synthetic bone graft material have been introduced into the orthopaedic literature. Bone marrow aspirate injection has been used as an isolated and adjunctive procedure in the less invasive treatment of femoral head osteonecrosis.

Trauma
The role of hip arthroscopy in trauma is still undefined and evolving. However, several case series support arthroscopic loose body removal and treatment of intra-articular pathology, even in hips with traumatic dislocations, despite congruent reductions and acetabular fractures (anterior and posterior wall). Emerging evidence suggests FAI morphology is associated with hip instability and may contribute via a leverage mechanism causing posterior dislocation. Recent articles have noted successful arthroscopic osteosynthesis of femoral head fractures and femoral head malunion.

Proximal hamstring tears and more
Endoscopic repair of proximal hamstring tears has been performed with reported success, but significant retraction demonstrated on preoperative MRI may be a relative contraindication. Researchers have found positive outcomes of cartilage restoration performed via microfracture chondroplasty. Other research has demonstrated that short-term clinical outcomes improve in patients with acetabular chondral damage following both microfracture and autologous matrix-induced chondrogenesis (AMIC). However, the AMIC group had better and more durable improvement, particularly in patients with large (≥ 4 cm) lesions at 5-year follow-up. Finally, intense investigation of orthobiologics, including stem cells harvested through various sites (bone marrow, adipose tissue, amniotic membrane) is ongoing.

Dean K. Matsuda, MD, is director of Hip Arthroscopy at DISC Sports and Spine in Marina del Rey, Calif., and chair of the AAOS Sports Medicine/Arthroscopy Program Committee.

Editor's note: This is a review of current and potential applications of hip arthroscopy; it is not an endorsement of any evolving techniques.