Fig. 1 Preoperative (A) and postoperative (B) radiographs of a 17-year-old female athlete with Perthes deformity of the proximal femur and acetabular dysplasia. The patient underwent combined surgical dislocation and periacetabular osteotomy, along with head reshaping, relative neck lengthening, trochanteric advancement, and acetabular reorientation.
Courtesy of John C. Clohisy, MD


Published 7/1/2014
Jennie McKee

Open vs. Arthroscopic: Which Is Better for Treating Extra-articular Hip Impingement?

Jennie McKee

Bryan T. Kelly, MD, of the Hospital for Special Surgery (HSS) in New York, and John C. Clohisy, MD, of Washington University in St. Louis, engaged in a point/counterpoint debate during the 2014 Specialty Day of the American Orthopaedic Society for Sports Medicine (AOSSM). They explored factors to consider before choosing an arthroscopic or open approach to treating patients with various forms of extra-articular hip impingement.

A role for arthroscopy
According to Dr. Kelly, clinical evidence suggests that extra-articular femoropelvic impingement exists in the following three forms: subspine, trochanteric pelvic, and ischiofemoral. Arthroscopic treatment may be most appropriate for subspine impingement; arthroscopy may not be possible in trochanteric pelvic impingement.

Subspine impingement is marked by abnormal morphologic changes in the anterior inferior iliac spine (AIIS). This form of impingement results from abnormal contact between the inferior femoral neck with straight flexion, and it causes compressive injury of the labrum, capsule, and indirectly, the head of the rectus.

“In subspine impingement—which I believe is a variation of rim impingement—there is an elongation of the AIIS, with impingement against the inferior medial neck of the femoral head,” noted Dr. Kelly. He went on to say that subspine impingement causes anterior hip pain with straight flexion and can sometimes be accompanied by cam morphology.

Resection of a prominent AIIS can reportedly improve function in patients with symptomatic subspine impingement; however, variability of AIIS morphology has raised questions regarding which variants should be treated with this procedure. To better understand how variability in AIIS morphology may affect outcomes, researchers at HSS performed a study in which they characterized AIIS morphology in patients with hip impingement and tested the link between hip range of motion and specific AIIS variants (type 1 has a smooth ilium wall between the AIIS and the acetabular rim; in type 2, the AIIS extends to the level of the rim; in type 3, the AIIS extends distally to the acetabular rim). The researchers found that type 2 and type 3 variants are linked to a decrease in hip flexion and internal rotation, thus supporting the rationale for considering decompression for AIIS variants that extend to and below the rim.

“Patients with downsloping or hooked AIIS morphology, where the AIIS extends beyond the pelvic rim, are those with the greatest risk for symptomatic impingement,” said Dr. Kelly. “Subpsine decompression can be performed arthroscopically on these patients, with good visualization of the interiliac spine.”

Arthroscopic treatment may not always be possible, however, for trochanteric pelvic impingement.

“Increasing evidence indicates the presence of extra-articular impingement of the greater trochanter against the pelvis in certain morphologic variants,” noted Dr. Kelly. “This can lead to pain and disability in the hip joint region that is not relieved by intra-articular injection.”

The most clinically obvious example of trochanteric pelvic impingement, said Dr. Kelly, is the varus deformity of the hip associated with Perthes disease, which often requires neck lengthening. More subtle forms of trochanteric pelvic impingement can be seen in hips that appear relatively normal.

“Most frequently, those more subtle forms need to be treated through surgical hip dislocation, because the areas with impingement can be difficult to address arthroscopically,” said Dr. Kelly.

He concluded by noting the increasing evidence for the presence of ischiofemoral impingement, a previously unrecognized condition.

“Ischiofemoral impingement is caused by abnormal contact between the lesser trochanter and the ischium,” he said, and pointed out that this form of impingement can be identified radiographically. Patients have edema in the quadratus femoris.

“We know that the close proximity of the sciatic nerve interposed between these two bony prominences leads to posterior hip pain,” he added.

Several factors must be considered in diagnosing ischiofemoral impingement, said Dr. Kelly.

“One of the most important considerations is the distance between the lesser trochanter and the ischium,” he said. “One study reported that control patients had 23 mm between the lesser trochanter and the ischium, while patients with symptomatic hip impingement had less than 12 mm.”

Although open surgical procedures may be optimal in these patients, said Dr. Kelly, “there may be a role for arthroscopy to decompress at the level of the lesser trochanter, although this is in an experimental phase.

“In conclusion,” said Dr. Kelly, “I believe we must be aware of various potential forms of extra-articular impingement before proceeding with more traditional surgical treatments.”

Using open procedures
“We all know that hip arthroscopy has had a revolutionary impact on the treatment of femoroacetabular impingement (FAI); nevertheless, it does have limitations, especially in complex situations such as extra-articular FAI,” said Dr. Clohisy.

Although he performs arthro-scopic procedures on approximately 80 percent of patients with FAI, noted Dr. Clohisy, he finds that approximately 20 percent of his FAI patients require open procedures.

“When we talk about the open procedure, we’re basically talking about safe surgical dislocation of the hip,” said Dr. Clohisy. “This is a lateral, transtrochanteric approach to the hip wherein we do an anterior dislocation of the hip. We preserve the blood supply to the femoral head and obtain circumferential exposure of the acetabulum and the proximal femur.

“I treat complex extra-articular FAI cases with open surgery for several reasons,” said Dr. Clohisy. “The first reason is to obtain an accurate diagnosis.”

Although orthopaedists can obtain the patient’s medical history, perform a physical examination, and use tools such as computed tomography scans, said Dr. Clohisy, “surgical visualization of the dynamics of the hip relative to impingement and instability in these patients is absolutely critical. I often prefer the open approach for complex deformities, because an intraoperative exam enables a very comprehensive understanding of hip pathomechanics.”

Secondly, he said, the surgeon must have surgical access to correct the deformity.

“The deformity can be widespread and nonfocal in these cases—on the proximal femur, the trochanters, the intertrochanteric line, and the distal neck,” he said. “We need to examine and access all those areas.”

The third reason for opting for open surgery, noted Dr. Clohisy, is what he called “surgical flexibility.” He gave the example of a patient with substantial head-neck and trochanteric-pelvic impingement.

“After we relieve the initial femoral head-neck junction impingement, the greater trochanteric impingement becomes evident, requiring a large trochanteric osteoplasty and a trochanteric advancement. Thus, in this patient, open surgery greatly increases treatment flexibility during the surgical procedure.

“Open treatment makes it possible to perform adjunctive procedures during surgery, such as trochanteric advancement, relative neck lengthening, and proximal femoral osteotomy for derotation,” he added.

One of the many complex cases Dr. Clohisy has treated with open surgery was that of a female patient with Perthes deformity of the proximal femur and acetabular dysplasia (Fig. 1).

“This very complex femoral deformity required head reshaping, neck thinning and lengthening, trochanteric advancement, and a periacetabular osteotomy,” said Dr. Clohisy. The patient was able to return to sport, without limitations.

According to the available literature—primarily level 4 and level 5 evidence—open treatment is “safe and has a low complication rate,” said Dr. Clohisy.

“So, for all of the reasons I have outlined, open surgery is my treatment of choice for patients with complex extra-articular FAI,” he concluded.

Disclosure information: Dr. Kelly—A-3 Surgical. Dr. Clohisy—Biomet, Pivot Medical, Wright Medical Technology, Inc., Zimmer, Journal of Bone and Joint Surgery.

Jennie McKee is a senior science writer for AAOS Now. She can be reached at


  1. Ganz R, Gill TJ, Gautier E, et al: Surgical dislocation of the adult hip: a technique with full access to the femoral head and acetabulum without the risk of avascular necrosis. J Bone Joint Surg Br 2001 Nov;83(8):1119-24.
  2. Gautier E, Ganz K, Krugel N, et al: Anatomy of the medial femoral circumflex artery and its surgical implications. J Bone Joint Surg Br 2000 Jul;82(5):679-83.
  3. Hetsroni I, Poultsides L, Bedia A, et al: Anterior inferior iliac spine morphology correlates with hip range of motion: a classification system and dynamic model. Clin Orthop Relat Res 2013 Aug;471(8): 2497-503.