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Femoroacetabular impingement describes a pathologic interaction between the bony femoral head/neck junction and acetabulum. Cam-type femoroacetabular impingement results from an aspherical femoral head architecture, which increases early contact along the acetabular surface during hip range of motion. Errant arthroscopic femoroplasty recently has been discussed within the literature to describe a preventable etiology of failed hip arthroscopy, most notably cam over- and under-resection. We present an arthroscopic surgical technique for achieving the perfectly spherical femoroplasty, meant to minimize complications and improve postoperative outcomes.
See video under supplementary data.
Femoroacetabular impingement (FAI) is an increasingly understood cause of anterior groin pain. This condition describes a pathologic interaction between the femoral head/neck junction and acetabulum due to abnormal bony morphology. Cam morphology (defined as an alpha angle of >55°)
of the femoral head/neck junction, a type of FAI, results from an aspherical femoral head architecture, which increases early contact along the acetabular surface during hip flexion and rotation. Increased frictional contact between these structures can lead to injuries of the chondrolabral junction. Repetitive injury, left symptomatic and untreated, can in turn predispose patients to irreversible chondrolabral degeneration.
Cam-type FAI was first addressed with open surgical dislocation; however, more recently hip arthroscopy has been used as a minimally invasive method for achieving clinical improvement with decreased morbidity, equivalent or better patient-reported outcomes, and return to sport or function.
Arthroscopic femoroplasty aims to sculpt the femoral head in ideally a perfectly spherical contour, thereby providing relief of mechanical symptoms previously unresponsive to conservative, nonoperative measures. Errant femoroplasty has recently been discussed within the literature to describe a preventable etiology of failed hip arthroscopy, most notably cam over- and under-resection. In fact, the most common etiology of revision hip arthroscopy is residual cam lesions due to under-resection.
We present an arthroscopic surgical technique for achieving the perfectly spherical femoroplasty, meant to minimize complications using fluoroscopic guidance to confirm accuracy of resection, and ultimately improve postoperative patient outcomes.
This study was performed in accordance with the ethical standards in the 1964 Declaration of Helsinki. This study was carried out in accordance with relevant regulations of the US Health Insurance Portability and Accountability Act. Details that might disclose the identity of the subjects under study have been omitted. This study was approved by the institutional research board (ID: 5276).
Step-by-Step Surgical Technique (With Video Illustration)
Video 1 explains the spherical femoroplasty technique in detail. Clockface values for the identified head/neck junction are based on the study by Ross et al.
Part A. Patient Preparation, Positioning, and Portal Placement
General anesthesia and full muscle relaxation of the operative extremity are essential for manipulation and accurate cam resection; verify with the anesthesiologist that this is optimized before the start of the case. Place the patient in the modified supine position on a traction table (Supine Hip Positioning System, Smith & Nephew, Andover, MA) with a well-padded wide perineal post. Abut the medial thigh of the operative extremity to provide patient stability as well as a lateralizing force vector along the femoral head, which will aid in arthroscopic visualization of the central compartment.
Place the patient in the 10° to 15° Trendelenburg position. This position harnesses the gravitational force and helps decrease pressure along the perineum, therefore minimizing potential traction-related complications such as pudendal nerve neuropathy or tissue necrosis.
Once the patient is secured: (1) Apply manual bilateral traction simultaneously to achieve full contact between the perineum and the padded post; and (2) adduct, slightly flex, and apply slight 5° to 10° of internal rotation to the operative extremity. Using a 70° arthroscope, access the hip joint via anterolateral (AL), mid-anterior (MA), distal anterolateral accessory (DALA), as well as posterolateral portals if needed for labral reconstruction (Fig 1A).
Perform an interportal capsulotomy between the AL and MA portals.
Part C. Diagnostic Arthroscopy, Central Compartment Management
Although beyond the scope of this article, the presence of other abnormalities commonly seen with FAI should be systematically identified, classified, and treated with grading schemes and treatment algorithms previously described.
Other abnormalities you may encounter and address include ligamentum teres and labral tears, loose bodies, acetabular cartilage damage, and uncommon extra-articular lesions.
Part D. Spherical Femoroplasty Setup Within the Peripheral Compartment
Provided a spherical femoroplasty is indicated (Table 2), position the operative hip in 45° of flexion, neutral foot rotation, and remove the perineal post (Fig 1A). Place a draped, sterile C-arm fluoroscopy on the nonoperative side of the patient at 0° tilt, –30° cantilever. Then, position the 70° arthroscope within the AL portal through a 5.0-mm cannula (Fig 1A). This improves visualization and helps to increase pump inflow in the peripheral compartment, which in turn with constant outflow helps to decrease the occurrence of postoperative heterotopic ossification.
For enhanced visualization, place a nonabsorbable FiberWire traction suture (Arthrex, Naples, FL) within the inferior leaflet of the capsule exiting the DALA portal (Fig 1). A T-capsulotomy is not routinely performed, which is why the use of a traction stitch is employed (Fig 1B). Avoiding T-capsulotomy can help prevent iatrogenic instability.
A modified Dunn lateral view (Fig 2A) of the hip is achieved with bringing the hip to 45° of flexion (Fig 3A). The C-arm remains at a 0° tilt, –30° cantilever (Fig 3B), allowing for excellent visualization of the anterolateral aspect of the femoral head/neck junction.
The most proximal extent of the osteoplasty is marked via electrocautery (Fig 4). Then, remove the periosteum from the marked region using a radiofrequency ablation device (Smith & Nephew) within the MA portal (Fig 5). The placement of the radiofrequency ablation device is based on the measured resection level needed to optimize alpha angle. The AL viewing portal provides excellent visualization of the femoral head/neck junction, both medially and laterally.
Use a 5.5-mm arthroscopic round burr to begin the femoral resection level, starting distally and working proximally (Fig 6). Care should be taken to remove more bone distally than proximally (Fig 7). This technique helps maintain convexity of the head/neck junction, improves the offset ratio, and prevents errant over-resection.
The same process is followed for the next 5 positions.
Position 2. Anteromedial Zone A: 1:30-2:30
Place the operative extremity into 60° of flexion, 30° of external rotation, and 25° of adduction (Fig 8A ). Keep the C-arm at a 0° tilt, –30° cantilever (Fig 8B). This allows for excellent visualization of the anteromedial aspect of the femoral head/neck junction (Fig 2B).
Position 3. Anteromedial Zone B: 2:30-3:30
Place the operative extremity into 60° of flexion, 60° of external rotation, and 25° of adduction (Fig 9). Keep the C-arm at a 0° tilt, –30° cantilever. This allows for extended visualization of the anteromedial aspect of the femoral head/neck junction (Fig 2C).
Position 4. Lateral Zone: 11:30-12:30
Place the operative extremity into 0° of flexion and 0° of rotation (neutral position, Fig 10A). Place the C-arm at a 0° tilt, –10° cantilever (Fig 10B). This allows for excellent visualization of the lateral aspect of the femoral head/neck junction (Fig 2D).
Position 5. Posterolateral Zone: 10:30-11:30
Keep the operative extremity into 0° of flexion and 0° of rotation (neutral position, Fig 11). Place the C-arm at a 0° tilt, 0° cantilever. This allows for visualization of the posterolateral aspect of the femoral head/neck junction (Fig 2E).
Position 6. Posterolateral Zone and Beyond: 9:30-10:30
Place the operative extremity into 0° of flexion and 30° of internal rotation (Fig 12). Keep the C-arm at a 0° tilt, 0° cantilever. Added internal rotation allows for greater posterolateral exposure. If needed, limb traction is required to address the most posterosuperior area of cam morphology (Fig 2F).
Inspection and Closure
To ensure full resection of the cam lesion, complete a dynamic examination of the joint and capture final fluoroscopic images of the operative extremity to show accurate resection of cam deformity, restoration of the femoral head/neck junction, and avoidance of over/under-resection. (Fig 8).
If there is joint instability present as indicated by preoperative and intraoperative criteria
The patient is placed in a brace (X-Act ROM Hip Brace; Donjoy, Vista, CA) for 2 weeks. Use of crutches is encouraged for 2 weeks with weight-bearing restriction of up to 20 pounds foot-flat weight bearing. Under physiotherapist supervision, active range-of-motion exercise is initiated during the first 48 hours with continuous passive motion and/or static bicycle. Formal physical therapy protocol is begun immediately postoperatively.
The goal of arthroscopic hip femoroplasty is to correct the anatomy of the femoral head/neck junction to restore and maintain the physiologic contact between the femoral head and native acetabular labrum, which confers inherent stability of the joint. When this contact is interrupted, the joint may become more susceptible to hip instability, labral tears, and chondrolabral delamination, thus predisposing it to developing arthritis.
Therefore, it becomes essential to correct the aberrant femoral head/neck offset to prevent these future complications. To date, there is a paucity of literature describing patient outcomes solely attributed to management of cam-type FAI. This is likely because cam lesions are usually present with additional central compartment pathology, such as chondrolabral damage, and thus the effects of femoroplasty are difficult to isolate. Instead, many studies have focused on results of hip arthroscopy overall, including patient indications and complications.
published a case series that included 37 revision hip arthroscopy procedures, performed 20.5 months after index procedure. The main cause of persistent hip pain in 95% of procedures was under-resected cam lesions and unresolved FAI. It has been proposed that the increasing prevalence of under-resection is a result of surgeons erring on the side of caution in fear of over-resection, and its irreversible complications. However, it is important to note that clinical outcomes for correction of residual cam with revision arthroscopy may not be equivalent to primary treatment. Larson et al.
published a study on a cohort of 237 cases in which 85 had residual FAI, and the authors showed that although revision hip arthroscopy improved patient outcomes, they were inferior to patients with primary FAI correction. Nonetheless, the consensus in hip arthroscopy is to be cautious rather than overzealous regarding cam resection.
Over-resection is a much more devastating complication of aggressive cam deformity decompression. One major concern is femoral neck fractures due to weakening of the tension side of bone, however, weight-bearing protocols have made this a rarity. More commonly, excessive femoral resection has led to disruption of the native labral seal, adversely affecting hip joint biomechanics.
reviewed a cohort of 120 patients (130 hips) and divided them into 3 groups (over-resected, under-resected, and neutral resected) who had a mean follow-up from index procedure of 39.6 months. The authors found that over-resection greater than 5% of the femoral head diameter correlated with inferior clinical outcomes (modified Harris Hip Score) compared with the under-resected population. Furthermore, over-resection predicted inferior outcomes after revision hip arthroscopy and led to greater rates of conversion to total hip arthroplasty (30% vs 0% in the under-resected population), the final endpoint of a failed arthroscopic hip procedure. Clearly, over-resection is a complication that is irreversible with severe consequences. Yet, this complication is avoidable using proper caution and excellent surgical technique.
The technique for achieving a perfectly spherical femoroplasty requires a steep learning curve, but, when mastered, is a powerful tool that aims to achieve precise and accurate resection at the femoral head/neck junction. The method described here is a reproducible sculpting technique of treating cam-type FAI, which minimizes complications of over- or under-resection in an effort to improve hip biomechanics. This technique will likely lead to improved clinical results in patients undergoing arthroscopic femoral osteoplasty.
Technique for achieving a perfectly spherical femoroplasty during hip arthroscopy in a patient’s right hip. The patient is placed in a supine position with Trendelenburg. Position 1 is with the hip flexed at 45° with neutral rotation applied. The modified Dunn view is achieved with a 0° tilt and –30° cantilever to the C-arm. Under fluoroscopic guidance, work is done at the inferior most head/neck junction proximally, with an effort to maintain convexity to the femoral head. Care is taken to avoid concavity, which would disrupt the labral seal. For position 2, the operative extremity is brought into 60° of flexion with 30° external rotation and 25° adduction applied. The C-arm maintains its position, providing more medial exposure to the head/neck junction. Once work is completed in position 2, 30° further external rotation is applied to the extremity, totaling 60°, again, providing even more medial exposure to the head/neck junction. Next, position 4 is achieved with the operative extremity brought into full extension and neutral rotation. The C-arm is brought to –10° cantilever. This provides posterolateral exposure to the femoral head/neck junction. Work is done in this region, again, with direct visualization fluoroscopic guidance with a goal to maintain convexity at all times. For position 5, the C-arm is brought into neutral (0°) cantilever. At certain points, traction can be applied to work on the most proximal aspect of the noted cam lesion. Lastly, in position 6, the operative extremity is brought into 30o internal rotation, which provides further posterolateral exposure. Once the perfectly spherical femoroplasty is completed, traction is removed, the hip is flexed, and a dynamic impingement test is performed by alternating the operative extremity from positions 1 and 2. Before progressing to capsular management, it is ensured that the labral seal is maintained.
The authors report the following potential conflict of interest or source of funding: B.G.D., or a member of his immediate family, has or may receive payments or benefits, during the study period, an amount of USD 10,000-USD 100,000 from Arthrex; an amount of USD 10,000-USD 100,000 from DJO Global; an amount of USD 10,000-USD 100,000 from Medacta International; an amount of less than USD 10,000 from Orthomerica Products; an amount of less than USD 10,000 from Pacira Pharmaceuticals; an amount of less than USD 10,000 from Medwest Associates; an amount of less than USD 10,000 from Prime Surgical; an amount of less than USD 10,000 from Trice Medical; an amount of less than USD 10,000 from Smith & Nephew; and an amount of USD 100,001–USD 1,000,000 from Stryker. A.C.L., or a member of his immediate family, has or may receive payments or benefits, during the study period, an amount of USD 10,000-USD 100,000 from Arthrex; an amount of less than USD 10,000 from Medwest Associates; an amount of USD 10,000-USD 100,000 from Smith & Nephew; an amount of less than USD 10,000 from Stryker; and an amount of less than USD 10,000 from Zimmer Biomet Holdings. Full ICMJE author disclosure forms are available for this article online, as supplementary material.
This study was performed at the American Hip Institute, Des Plaines, Illinois, U.S.A.