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Editorial Commentary: Incremental Decompression of Cam Femoroacetabular Impingement Must Be Assessed in Real Time by Arthroscopic Dynamic Examination: Playbook for the Perfect Femoroplasty

      Abstract

      The perfect femoroplasty varies with the individual patient’s pathoanatomy and is a prime example of the art and science of surgery. Radiographs are two-dimensional representations of a three-dimensional reality and can miss detection of cam impingement. Cam impingement may occur without cam morphology as femoral retrotorsion and/or supraphysiological range of motion (e.g., dancers and martial artists) may cause cam impingement with normal α-angles and anterior offset. Acetabuloplasty or acetabular reorientation osteotomy may change the dynamic interaction between the proximal femur and acetabular rim and may alter the location and extent of cam decompression. Although much is discussed about the α-angle, restoration of anterior offset is also important. Incremental femoroplasty assessed in real time by arthroscopic dynamic examination is key, as the surgeon sculpts a nonimpinging proximal femur using a burr rather than a chisel in creating a customized surgical masterpiece.
      When invited to write a commentary on ”Intraoperative Automated Radiographic Visualization Tool Allows for Higher Accuracy of Cam Lesion Resection When Used by Novice Surgeons for Arthroscopic Femoroplasty: Lowering the Learning Curve” by Beck, Chahla, Krivicich, Rasio, Taylor, Godbey, and Nho,
      • Beck E.C.
      • Chahla J.
      • Krivicich L.
      • Rasio J.
      • Taylor H.
      • Godbey R.
      • Nho S.J.
      Intraoperative automated radiographic visualization tool allows for higher accuracy of cam lesion resection when used by novice surgeons for arthroscopic femoroplasty: lowering the learning curve.
      I saw this as an opportunity to share my playbook in search of the perfect femoroplasty. In this cadaveric study, arthroscopic femoroplasties were performed by two surgeons of different experience using fluoroscopic versus an automated radiographic visualization tool with real-time estimation of α-angles. The key finding was that post-femoroplasty, “better” α-angles were achieved by the novice surgeon when using this tool, whereas there was no significant improvement in this index measure of cam decompression by the experienced surgeon.

      Playbook

      Know your Opponent

      Cam Surveillance

      Just as one would study past films about an opposing team, surgeons need to know the presence, extent, and location of cam morphology. Radiographs are two dimensional representations of a three-dimensional reality, and as such, they can miss detection of cam femoroacetabular impingement.
      • Matsuda D.K.
      The case for cam surveillance: the arthroscopic detection of cam femoroacetabular impingement missed on preoperative imaging and its significance.
      Cam impingement without cam morphology: femoral retrotorsion
      • Matsuda D.K.
      • Gupta N.
      • Martin H.D.
      Closed intramedullary derotational osteotomy and hip arthroscopy for cam femoroacetabular impingement from femoral retroversion.
      and/or supraphysiological range of motion (e.g., dancers and martial artists) may cause cam impingement with normal α-angles and anterior offset.

      Audible at Line of Scrimmage

      Cam femoroacetabular impingement (FAI) occurs as a complex pathological abutment of the proximal femur and acetabular rim. Acetabuloplasty or acetabular reorientation will alter this relationship and merits intraoperative adjustments to femoroplasty location and volumetric reduction. Acetabuloplasty and reverse PAO can decrease cam impingement, whereas PAO for dysplasia can increase it, even causing subspine impingement, supporting the case of performing femoroplasty after acetabular side surgery.
      • Matsuda D.K.
      • Martin H.D.
      • Parvizi J.
      Endoscopy-assisted periacetabular osteotomy.

      Fundamentals, Fundamentals, Fundamentals

      A major function of the labrum is the fluid seal effect, as the proximal femur interacts with the acetabular rim and labrum. With the goal of restoring more normal nonimpinging anatomy, the femoroplasty should optimally have a gradual transition slope along the affected femoral head-neck junction. Moreover, it should be a 3-dimensional curvilinear rather than uniplanar resection. Although much is discussed about the α-angle, restoration of anterior offset is important (and was not studied in the aforementioned study). Intraoperative post-femoroplasty fluoroscopic 45° Dunn lateral views are helpful in this regard.
      Although the anterolateral femoral head-neck junction is most often involved, cam FAI is often detected only on a preoperative false-profile radiograph, which has been demonstrated to correlate with the anteromedial critical corner
      • Matsuda D.K.
      • Schnieder C.P.
      • Sehgal B.
      The critical corner of cam femoroacetabular impingement: Clinical support of an emerging concept.
      or 3:44 o’clock femoral head-neck location
      • Uemura K.
      • Atkins P.R.
      • Anderson A.E.
      • Aoki S.K.
      Do your routine radiographs to diagnose cam femoroacetabular impingement visualize the region of the femoral head-neck junction you intended?.
      and may be a source of ongoing FAI if not addressed.

      Run Pass Option

      As the surgical QB, instead of keying on the safety or outside linebacker, one should make decisions in real time based on the arthroscopic dynamic examination combined with incremental individualized cam decompression. One can always remove more bone, so starting with a conservative femoroplasty and then fine-tuning the cam resection based on the dynamic examination is very important. That being expressed, although one aims for the perfect femoroplasty, I tend to err slightly on over-resection rather than under-resection to minimize risk of leaving residual FAI, a major cause of revision arthroscopy.

      Back of the Playbook

      There are some trick plays that really can work. I typically begin with the hip in neutral extension/internal rotation (supine arthroscopy) for anterolateral femoroplasty, sequentially performing anterior femoroplasty in progressive hip flexion in neutral rotation. In terminal flexion, one may detect areas requiring relative distal femoroplasty. If arthroscopic dynamic examination reveals a need for further flexed-hip internal rotation on FADIR examination, I perform femoroplasty of the anteromedial critical corner, resecting the “resident’s ridge of the hip.”
      • Matsuda D.K.
      • Schnieder C.P.
      • Sehgal B.
      The critical corner of cam femoroacetabular impingement: Clinical support of an emerging concept.
      This study performed the femoroplasties using complete T capsulotomies, which arguably provide optimal visualization. I prefer a small oblique interportal capsulotomy
      • Matsuda D.K.
      • Villamor A.
      The modified mid-anterior portal for hip arthroscopy.
      or even periportal capsulotomies
      • Chambers C.C.
      • Monroe E.J.
      • Flores S.E.
      • Borak K.R.
      • Zhang A.L.
      Periportal capsulotomy: Technique and outcomes for a limited capsulotomy during hip arthroscopy.
      to retain more integrity to the capsule and iliofemoral ligament. This is technically demanding, and is recommended only after one is very facile with femoroplasty using a larger capsulotomy to minimize insufficient cam decompression. The concept is to bring the specific target area of incremental femoroplasty into view through the small capsular window. If one thinks of the peripheral compartment as a room with the floor being the proximal femur and the roof being the overlying capsule, here are some trick plays to expand the room, enabling smaller capsulotomies. In addition to progressive hip flexion, which raises the roof relative to the floor, femoroplasty of the floor actually increases the relative height of the room, enhancing arthroscopic visualization and instrument navigation. On occasion, I will raise the roof even higher by performing a partial thickness undersurface capsular reduction with a radiofrequency probe limited to a specific region of the femur to render sufficient cam decompression. And for patients with posterior cam FAI, staying proximal to the retinacular feeder vessels is key (with open or arthroscopic approach), and transient use of hip distraction with the hip in extension/internal rotation may facilitate posterior cam decompression.
      • Matsuda D.K.
      • Hanami D.
      Hip arthroscopy for challenging deformities: Posterior cam decompression.

      Supplementary Data

      References

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        Intraoperative automated radiographic visualization tool allows for higher accuracy of cam lesion resection when used by novice surgeons for arthroscopic femoroplasty: lowering the learning curve.
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