Challenging Resection Comes in Many Forms: Addressing Difficult Cam Morphology

Abstract

Femoroacetabular impingement with cam morphology that fails nonoperative management can be addressed with hip arthroscopy and cam resection. There exists a wide variation of cam morphology due to various etiologies that can make some cam lesions more challenging to address. A thorough preoperative evaluation and the utilization of a variety of intraoperative techniques can allow for adequate arthroscopic resection of these otherwise challenging cam lesions. In this technique video, we describe a systematic approach for the preoperative assessment of femoroacetabular impingement due to a cam lesion and consideration of different approaches for arthroscopic resection based on cam‐specific morphology.

Arthroscopic cam resection is a well‐established surgical treatment for femoroacetabular impingement (FAI). In patients with FAI who fail nonoperative management, arthroscopic resection has been reported to lead to improvement in postoperative outcomes. ¹ , ² , ³ FAI with cam impingement can be due to a variety of pathologies, including femoral retroversion, acetabular retroversion, postslipped capital femoral epiphysis deformity, and autoimmune disorders. ⁴ Different morphologies of cam impingement present their own challenges with arthroscopic access and resection. Inadequate resection of the cam is one of the most common reasons for revision hip arthroscopy. ⁵ Therefore, it is imperative that the surgeon has a thorough understanding of the presenting cam morphology with an array of techniques for addressing challenging cam lesions. The purpose of this technical note is to review various presentations of cam lesions and discuss strategies for addressing the lesion based on cam‐specific morphology. This technique is shown in Video 1. The pearls and pitfalls of the application of various techniques to address difficult cam morphology are listed in in Table 1, and advantages and disadvantages are provided in Table 2.

VIDEO 1.

Download video file ^{(94MB, mp4)}

Technique for evaluation and management of challenging cam morphology. Examples in this video show hip arthroscopy performed on a left hip in the supine position utilizing a traction table with a post. Video content can be viewed at https://doi.org/10.1002/atn2.70119.

TABLE 1.

Pearls and Pitfalls of Applying Various Techniques for Addressing Difficult Cam Morphology

Pearls	Pitfalls
T‐Capsulotomy, when indicated, can substantially improve distal cam access and visualization	Care should be taken not to disrupt zona orbicularis when performing T‐capsulotomy for distal cam access
The known width of the burr utilized for resection can be used as intraoperative resection guide	Positioning hip in extension can result in tension on iliofemoral ligament and subsequently decrease effective working space
Placement of hip in extension will allow for more proximal cam access, and adding traction to the operative extremity will provide even more proximal access	Increased use of traction time during central compartment work can limit amount of traction time available to access proximal cam in post‐SCFE deformity
When patient is safely positioned on the table, removal of the central post can improve lateral working space and improve access to posterolateral cams

SCFE, slipped capital femoral epiphysis.

TABLE 2.

Advantages and Disadvantages, Including Risks and Limitations of Applying Various Techniques for Addressing Difficult Cam Morphology

Advantages	Disadvantages, Risks, and Limitations
Understanding location of cam morphology on multiple radiographic views and use of 3‐dimensional reconstruction of CT scan can improve intraoperative spatial recognition of cam	Increased radiation and cost associated with preoperative CT scan
The use of the two‐tiered technique for planning your resection can allow for restoration of femoral head‐neck offset and femoral head sphericity	Cam lesions proximal to the physeal scan may require alterations in the standard two‐tier technique to obtain an adequate resection
Manipulation of the hip capsule, hip position, and traction can assist with access to otherwise challenging locations	Resection of a cam proximal to the physeal scar can result in damage to articular cartilage to the femoral head

CT, computed tomography.

SURGICAL TECHNIQUE

Preoperative Planning

A thorough preoperative plan should be established prior to proceeding with an arthroscopic cam resection. The history and physical exam can aid in the diagnosis of FAI and clue the surgeon into the location at which pathological impingement occurs. Imaging in the form of radiographs, a computed tomography scan, and an magnetic resonance imaging allows for a thorough assessment of the cam both around and along the femoral head‐neck junction. For radiographic assessment of a cam, multiple radiographic views should be obtained, as different views can highlight the cam in different locations. The radiographic view that best highlights the traditional anterolateral (AL) cam is the 45° Dunn lateral radiograph. ⁶ In addition to the Dunn lateral, a cross‐table lateral can be added to visualize the anterior extent of the cam, and a standard anteroposterior radiograph can highlight the posterolateral extent of the cam (Figure 1). A computed tomography scan and an magnetic resonance imaging can also provide vital information for understanding the extent of the cam on cross‐sectional imaging. Supplementing with a 3‐dimensional reconstruction of cross‐sectional images can provide further insight into the location of the cam and assist with spatial recognition, particularly in patients with atypical cam morphology. Additionally, computed tomography‐based software exists that can aid in identifying zones of impingement that not only offer a 3‐dimensional view of the cam lesion, but also the depth of the lesion in millimeters. Altogether, these imaging tools can aid the surgeon in determining which arthroscopic approaches can be employed for optimal access and resection of the cam.

FIGURE 1.

Radiographic assessment of a left hip cam lesion. The anteroposterior radiograph (A) provides assessment of more posterolateral cam location. The Dunn lateral (B) brings the peak of an anterolateral cam into plane for improved visualization. The cross‐table (C) lateral will show the anterior extent of the cam.

Patient Positioning and Joint Access

The patient is positioned supine on a hip distraction table (Hip Positioning System, Smith & Nephew, Andover, MA) (Figure 2). The feet are placed in well‐padded traction boots. For our technique, we prefer the use of a central padded perineal post; however, a postless distraction system may also be used for this technique. The hip is then prepped and draped in a usual sterile fashion, and traction is applied.

FIGURE 2.

The patient is position supine on a hip distraction table with a padded perineal post with the left hip draped.

Under fluoroscopic guidance, a standard AL portal is established, and a modified mid‐anterior portal is subsequently made under direct visualization. An interportal capsulotomy is then performed with a Samurai blade (Stryker Sports Medicine, Greenwood Village, CO) between the AL and mid‐anterior portal. The interportal capsulotomy is made to ensure that adequate proximal capsule remains for later capsular closure. Additionally, to preserve the integrity of the native capsule, the interportal capsulotomy is not extended posterior to the AL portal or medial to the mid‐anterior portal unless underlying pathology necessitates a larger capsulotomy. Another important technical pearl is to perform the interportal capsulotomy as distal as possible. This helps in reaching and resecting far distal cam lesions.

Central Compartment

With the capsulotomy complete, a combination of a radiofrequency ablation device and an arthroscopic shaver is utilized to dissect the capsulolabral junction to better define the labrum and underlying pathology. Once the capsulolabral junction is dissected, traction sutures can be placed in the proximal capsule to improve visualization of the labrum and central compartment. A diagnostic arthroscopy is then performed, evaluating the femoral head cartilage, acetabular cartilage, ligamentum teres, and labrum. Pathology in the central compartment is then addressed as indicated.

Peripheral Compartment

Once the central compartment pathology has been addressed, traction can be taken off the hip, and attention is then turned to the peripheral compartment. The hip is then placed in 15° to 20° of flexion, and two traction sutures are placed into the distal capsular leaflet with a self‐retrieving suture passing device (Slingshot, Stryker Sports Medicine, Greenwood Village, CO) to improve visualization of the peripheral compartment. Further capsular management is dependent on the cam morphology present and surgeon preference.

Large Focal Sclerotic Cam

Resection of a large focal sclerotic cam can be challenging due to the size and hardness of the lesion. For this pathology, we recommend proceeding with a methodical approach using the two‐tier resection technique. ⁷ The tier 1 resection is started 1 cm distal to the articular cartilage and physeal scar (as identified under fluoroscopic guidance) and continued to a depth that restores femoral head sphericity and offset. The start of the resection can be measured by using the known width of the arthroscopic burr (XL Round Diamond Burr, 5.5 mm, Stryker Sports Medicine, Greenwood Village, CO). The tier 2 resection is then performed to resect the remainder of the cam deformity to the same depth as the tier 1 resection (Figure 3). The proximal head‐neck junction is then contoured to recreate the femoral head sphericity. This process can be repeated as needed on additional intraoperative fluoroscopic views with various degrees of flexion/extension, internal/external rotation, and abduction/adduction of the hip until native femoral head sphericity and offset have been restored in all planes (Figure 4).

FIGURE 3.

Intraoperative Dunn lateral fluoroscopic images of a left hip representing the two‐tiered resection technique. (A) The tier 1 resection is started 1.5 burr widths distal to the physeal scar as identified on the fluoroscopy. Once the resection depth is set at tier 1, the tier 2 resection is begun (B) with the resection of the distal aspect of the to match the tier 1 resection depth. The proximal femoral head‐neck junction is then contoured to recreate the femoral head sphericity.

FIGURE 4.

Intraoperative fluoroscopic views of a left hip showing adequate cam resection with restoration of femoral head sphericity on the (A) anterioposterior, (B) Dunn lateral, (C) extension external rotation, and (D) extension internal rotation view.

Geographic Distal Cam

Geographic distal cam morphology has been suggested to be associated with autoimmune disorders, and we would recommend consideration of an autoimmune workup in the preoperative setting. The distal location of these cams makes access complicated through a standard interportal capsulotomy. To improve visualization and working space distally, a T‐capsulotomy is performed down to the level of the zona orbicularis, being careful not to violate the zona orbicularis. Traction sutures can then be placed into each leaflet of the T‐capsulotomy, and the distal cam can be well visualized. The cam is then resected in a manner similar to the previously described two‐tier resection technique (Figure 5). Once the cam has been adequately resected, the T‐capsulotomy can be closed with the use of a self‐retrieving suture passing device (Slingshot, Stryker, Greenwood Village, CO).

FIGURE 5.

Intraoperative (A) preresection and (B) postresection Dunn lateral fluoroscopic views of a left hip geographic distal cam lesion. The addition of a T‐capsulotomy facilitates visualization and access for more distal‐based cam lesions.

Proximal Cam

Cam lesions that continue proximal to the physeal scar pose a challenge for resection as they can extend into the articular cartilage of the femoral head. Typically, osteoplasty of the cam lesion is performed in a position of slight hip flexion to protect the articular cartilage of the femoral head. However, in cases with proximal cam morphology, the hip should be positioned in extension to deliver the proximal cam outside of the hip joint (Figure 6). Unfortunately, placing the hip in extension also increases the tension on the iliofemoral ligament, which will impede the effective working space. If access remains difficult with the hip in extension, the central traction post can be removed, as this post tends to lateralize the femur and subsequently decrease the available lateral working space. Of note, one should be cautious to make sure the patient is safely secured on the operative table before removing the traction post. Alternatively, gentle traction with hip extension and adduction can allow the surgeon to reach the proximal cam lesion, but as noted above, this tends to tighten the capsule and decrease working space. To counter this effect, adding some external rotation can decrease capsular tension and improve the working space needed to resect the cam lesion.

FIGURE 6.

Intraoperative fluoroscopic views of a left hip in (A) extension and (B) extension with internal rotation showing how changes in hip position can deliver a more proximal cam from inside the joint to improve access and allow for a more proximal and posterior resection.

Rotational and Version Abnormalities

Rotational and version deformities of the proximal femur, such as slipped capital femoral epiphysis, can be difficult to address due to increased difficulty obtaining intra‐articular access and disorienting anatomy with a retroverted femoral head‐neck junction and proximal cam morphology. Cam morphology in postslipped capital femoral epiphysis patients tends to be proximal and posterior due to the deformity of the physis at the time of injury (Figure 7). Despite optimization of hip positioning (including extension of the hip) access to the proximal cam may be limited. In this setting, slight traction can be applied to the operative extremity to further deliver the intra‐articular proximal cam for improved arthroscopic access (Figure 8).

FIGURE 7.

Fluoroscopic images of a left hip that highlight the proximal and posterior nature of the cam in post‐SCFE deformity on (A) anteroposterior, (B) extension with internal rotation, and (C) flexion with external rotation views. (SCFE, slipped capital femoral epiphysis.)

FIGURE 8.

Fluoroscopic images of a left hip that show (A) the inherent limitation of a proximal resection despite adequate hip positioning in extension. (B) With traction applied to the operative extremity, a more proximal, intra‐articular cam can be delivered outside of the joint to allow for adequate resection.

DISCUSSION

Hip arthroscopy with cam resection has been shown to be an effective treatment approach for FAI, resulting in improved patient‐reported outcomes. ¹ , ² , ³ However, hip arthroscopy is also recognized to be a difficult procedure with a steep learning curve. ⁸ In addition, the variety of cam morphologies that exist can make arthroscopic resection even more challenging in difficult‐to‐access cam lesions. Therefore, it is vital that the surgeon has a thorough understanding of both the cam lesion and patient‐specific anatomy to develop an effective strategy for resection of challenging cam morphologies.

There are many different approaches and resection techniques to consider when addressing challenging cam morphology. Capsular management is a highly debated topic. The periportal technique, interportal capsulotomy, and T‐capsulotomy each have their own advantages and disadvantages. ⁹ , ¹⁰ Ultimately, the use of each technique is based on surgeon preference. We have found a patient‐centered and cam‐specific approach for capsular management to be useful in guiding our approach, where a T‐capsulotomy may be employed when addressing geographic distal cam morphology in less flexible male patients, whereas an interportal capsulotomy may be adequate for patients with large focal cam lesions. Additionally, the use of a systematic cam resection strategy, such as the two‐tier resection technique, can be a helpful approach to address challenging cam morphology. ⁷

The presented technique provides considerations for the evaluation and treatment of a variety of cam morphologies. A thorough understanding of the cam lesion and techniques available to aid in arthroscopic cam resection provides the surgeon with tools to achieve an adequate resection of challenging cam lesions.

DISCLOSURES

The authors (M.J.S., B.A.L., A.J.K., M.H.) declare the following financial interests/personal relationships which may be considered as potential competing interests: M.J.S. participates in professional activities and has intellectual property with Strkyer. B.A.L. is on the editorial or governing board for Orthopedics Today and Journal of Knee Surgery, recieves IP royalties and is a paid consultant for Arthrex, and receives equity or Stocks in COVR Medical. A.J.K is a paid consultant for Arthrex, is a member of the editorial or governing board for the American Journal of Sports Medicine and Springer, receives research support from Aesculap/B.Braun, receives IP royalties from Arthrex and is a board member of the Arthroscopy Association of North America and the International Cartilage Repair Society. M.H. is a paid consultant for DJO ‐ Enovis, Moximed, Stryker, and Vericel, is on the editorial or governing board for the Journal of Cartilage and Joint Preservation, and receives publishing royalties, financial or material support from Elsevier. The other authors (J.G.I., S.Y.) declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this article.