Outside-In Capsulotomy for Intra-articular Hip Access

Abstract

Background:

Arthroscopic treatment of excessive acetabular coverage with pincer morphology or coxa profunda can be challenging. In patients with excessive acetabular coverage with nondistractible hips, an outside-in capsuolotomy can be considered to gain safe and efficient intra-articular access to the hip.

Indications:

The indications for an outside-in capsulotomy include patients with acetabular retroversion, a lateral center-edge angle >40°, coxa profunda or protrusio, or stiff, older male patients who remain hip preservation candidates.

Technique Description:

The outside-in capsulotomy is performed once it is recognized that traction on the operative extremity will not provide adequate working space for safe intra-articular access. Traction is taken off the operative extremity, and an anterolateral portal is localized to the 12:00 position on the hip joint with the use of fluoroscopy. The camera is then placed in a juxta-capsular location, and a modified anterior portal is created under direct arthroscopic visualization. We then proceed with extracapsular dissection to identify the indirect head of the rectus. An outside-in capsulotomy is then performed parallel to the indirect head of the rectus, approximately 5 mm distal to its insertion on the acetabular rim. Prior to deep completion of the capsulotomy, the hip joint is flexed to 30° to protect the articular cartilage of the femoral head. Once intra-articular access is obtained, traction can be reapplied, and one can proceed with hip arthroscopy in a standard fashion.

Results:

This technique decreases the traction time needed, given that the capsulotomy is performed without traction applied. Additionally, the amount of force required for hip distraction is decreased once the capsuolotomy has been completed, through usual sectioning of the iliofemoral ligament. The presented technique is both safe and efficacious, with no published difference in complications as compared to standard inside-out access. A published series of patients with severe pincer morphology and lateral overcoverage who undergo hip arthroscopy with outside-in access demonstrates satisfactory postoperative improvements in patient-reported outcome measures.

Discussion/Conclusion:

The outside-in capsulotomy provides a means for safe access to the hip joint in otherwise limited or nondistractible hips.

Graphical Abstract

This is a visual representation of the abstract.

Video Transcript

In this video, we will demonstrate our technique for an outside-in capsulotomy for intra-articular access to the hip.We report the following disclosures. An outline for our video can be seen here.

Background

Arthroscopic treatment of severe pincer morphology, or coxa profunda, is challenging. ³ An outside-in capsulotomy is performed, starting from an extra-articular location to gain access in otherwise difficult-to-access hips due to limited joint distraction. Releasing the iliofemoral ligament when performing a capsulotomy allows for increased hip joint distraction and improves the available working space. The relative indications for this technique are in patients who are nondistractible, which can include patients with acetabular retroversion, overcoverage with pincer morphology, a lateral center-edge angle greater than 40°, coxa profunda, or older men with decreased range of motion.^2,3,6 In these instances, pulling traction tends to lateralize the hip more than axial distraction. Ultimately, distraction does not effectively increase available working space.

Indications

This photo of a cadaveric dissection highlights the relevant periarticular anatomy for an outside-in capsulotomy. It is important to recognize that the indirect head of the rectus originates at the 12:30 position on the clock face, about 5.1 mm medial to the superior lateral acetabular rim. ⁴ In addition, this photo of a cadaveric dissection highlights the relationship of the indirect head of the rectus to the capsule and underlying labrum. As the indirect head of the rectus traverses medially toward the direct head, it runs parallel to the anterior acetabular rim and labrum.

In this video presentation, our patient is a 23-year-old woman with right hip pain that has been present for several years. The pain is localized to the groin and anterior hip.It is exacerbated with athletic activity and prolonged sitting. She has had unsuccessful conservative management but was able to achieve 100% relief of her pain for 2 to 3 hours with an intra-articular corticosteroid injection with lidocaine. On physical examination, her range of motion is decreased with limitations in hip flexion strength and range of motion due to pain. She has a positive subspine test and positive FADIR (flexion, adduction, internal rotation) test, consistent with intra-articular pathology.

We obtained our pelvic radiographic series, which includes an anterior-posterior pelvis, a Dunn lateral, and a cross-table lateral. The lateral center-edge angle measured 67°, and the Tönnis angle measured −13°, consistent with overcoverage pincer morphology. The Tönnis grade is zero, demonstrating a well-preserved femoroacetabular joint. The α angle measured 43.9° on a Dunn lateral but 56.9° on the cross-table lateral, likely due to difficulties with positioning due to her pathology. Given her excessive acetabular lateral overcoverage, a computed tomography (CT) scan was obtained to assist with preoperative planning. A 3-dimensional reconstruction was created of the CT scan, which assists with preoperative planning by providing a better understanding of the 3D spatial anatomy of her pincer morphology. A magnetic resonance arthrogram was also obtained for evaluation of the labrum. We included T1 axial oblique, axial, and coronal sequences, which demonstrate the presence of a labral tear.

Technique Description

We will now proceed with a demonstration of our surgical technique for an outside-in capsulotomy. The patient is positioned supine on a traction table with a perineal post. Her feet are placed in well-padded boots. The operative extremity is prepped and draped in the usual sterile fashion. Axial traction is applied to the operative extremity, and an anterolateral portal is localized with an 18-gauge needle under fluoroscopic guidance. Despite application of traction and venting of the capsule, there remains inadequate space for intra-articular access. With traction applied, it can be observed under fluoroscopy that the hip tends to subluxate laterally in addition to axial displacement, as opposed to inline axial displacement alone, which prevents intra-articular access to the hip along the lateral acetabulum. At this point, the leg can be released from traction, which allows us to preserve traction time for later in the case once intra-articular access has been achieved.

We then proceed with marking our portals. The anterolateral portal is marked approximately 2 cm medial to the anterior border of the greater trochanter. The modified anterior portal (MAP) is marked 2 cm distal and 4 cm medial to the anterolateral portal, and the distal anterolateral portal is marked 6 to 7 cm distal from the anterolateral portal. We also identify our arthroscopic safe zone with a line connecting the anterior superior iliac spine to the lateral border of the patella, making sure to remain lateral to this line. Under fluoroscopic guidance, an 18-gauge needle is inserted into the anterolateral portal and penetrates the capsule at the 12-o’clock position. The needle is then exchanged for a guidewire, and a cannula is inserted over the guidewire and placed in an extracapsular position. A 70° arthroscope is then inserted through the cannula. The MAP is then established by triangulating an 18-gauge needle toward the arthroscope with fluoroscopic assistance as needed. Once the needle is visualized with the arthroscope, it is exchanged for a guidewire, and a 5-mm cannula is used to dilate over the guidewire to create a path for the arthroscopic instrumentation.

With the camera in the anterolateral portal and the MAP functioning as the working portal, the extracapsular space is debrided with the combination of an arthroscopic shaver and radiofrequency ablation device. The radiofrequency ablation device can be used to define the indirect head of the rectus and the direct head of the rectus medially. It can also be used to create a plane between the capsule and the gluteus medius laterally to assist with capsular mobilization once the capsulotomy has been performed. The outside-in capsulotomy is then defined using the radiofrequency ablation device to mark a line 5 mm distal to the indirect head of the rectus, which runs parallel to the indirect head as it runs from lateral to medial, prior to merging with the direct head of the rectus.

The capsulotomy is then begun superficially, making sure to create a capsulotomy at least 10 to 15 mm in length to mimic a standard inside-out interportal capsulotomy. As the capsulotomy continues deep, the hip is repositioned into 30° of flexion to avoid iatrogenic damage to the articular cartilage of the femoral head deep to the capsule. Once the capsulotomy is complete, traction can be reapplied to the hip.The deep capsule, as well as synovial tissue, can be debrided with the arthroscopic shaver and radiofrequency ablation device from the MAP, being careful to avoid iatrogenic damage to the labrum. A cannula is then inserted into the MAP over a switching stick, and the camera is placed into the MAP. The arthroscopic shaver and radiofrequency ablation device are then introduced into the anterolateral portal to define the lateral capsulolabral junction. A traction stitch is then placed in the lateral aspect of the proximal capsular leaflet to improve exposure of the lateral acetabulum and labrum. The camera is then placed back into the anterolateral portal, and the distal anterolateral portal is created with an 18-gauge needle under direct visualization and dilated with a cannula. The anterior capsulolabral junction is then dissected, and a traction stitch is placed into the anterior aspect of the proximal capsular leaflet, deep to the indirect head of the rectus, to improve exposure of the anterior acetabulum and labrum. The radiofrequency ablation device is used to elevate the labrum and expose the lateral acetabular rim. The far lateral and anterior labrum are left intact to facilitate later repair.

Once the labrum is adequately elevated, we can perform the rim resection with an arthroscopic burr. The goal of our resection is to restore the lateral center-edge angle to 40° in the setting of significant overcoverage. The fluoroscopic image on the left demonstrates the pincer morphology before resection. The fluoroscopic image on the right is postrim resection with the camera in the MAP and the arthroscopic burr in the anterolateral portal. Here, one can appreciate the restoration of the lateral center-edge angle and increased working space in the lateral hip.This photo, used with permission from Simon et al, ⁶ demonstrates the importance of elevating the labrum over the location of lateral overcoverage. Elevating the labrum allows for access to the distal-most aspect of the pincer lesion and prevents the creation of an incomplete concave resection. With improved access, a convex rim resection can be performed that better restores the anatomy of the acetabular rim. Adequate pincer resection allows for improved access to facilitate labral repair and other indicated procedures. In this case, we proceeded with a labral repair with knot-tied anchors. Once traction is released, we can visualize recreation of the suction seal. We then proceeded with femoral osteochondroplasty and capsular closure deep to the indirect head of the rectus, restoring the native anatomy.

The advantages to the outside-in capsulotomy technique include decreased traction time as the operative extremity is taken off traction while performing the capsulotomy. Additionally, once the capsulotomy is complete, the amount of force required for adequate distraction is relatively decreased. This technique also decreases the risk of iatrogenic cartilage injury and provides the surgeon with a means to safely increase the available working space in an otherwise nondistractible hip.Lastly, this technique allows for maintained ability to close the capsule by preserving adequate proximal and distal capsular leaflets and limiting the amount of capsular resection needed for intra-articular access.

Results

There are a few potential complications of this technique. Failure to elevate the labrum and obtain adequate exposure prior to acetabular pincer resection can result in inadequate resection of the rim. Overresection of the pincer lesion in patients who have substantial overcoverage can result in symptomatic instability, and failure to flex the hip when completing the capsulotomy can lead to damage to the femoral head articular cartilage. Some notable tips and tricks for a successful outside-in capsulotomy include releasing traction while gaining access to the hip to preserve traction time, initial utilization of fluoroscopy to localize needle placement from the anterolateral portal to the capsule at the 12-o’clock position and subsequent fluoroscopic assistance with creation of the MAP, identification of the distal border of the indirect head of the rectus to guide the outside-in capsulotomy location, flexing the hip to 30° when completing the capsulotomy to protect the articular cartilage of the femoral head, and debridement of the deep surface of the capsule and synovium and placement of capsule traction sutures to improve the exposure of the central compartment.

Our postoperative rehabilitation includes partial weightbearing for the first 2 weeks, with progression of weightbearing and range of motion over the subsequent 3 months. At 3 months postoperatively, patients can begin returning to physical activity, with return to sport at 4 months. We place our patients on meloxicam 15 mg daily for heterotopic ossification prophylaxis, as well as aspirin 81 mg twice per day for deep vein thrombosis prophylaxis.

Discussion/Conclusuion

To our knowledge, there are a limited number of studies evaluating the outside-in capsulotomy as well as outcomes in patients with acetabular overcoverage. Chandrasekaran et al ¹ performed a retrospective review of 36 patients with a lateral center-edge angle >40° and coxa profunda, matched these patients to those without overcoverage, and reported 2-year outcomes after hip arthroscopy. While both groups had improvement in outcomes, the overcoverage group had lower patient satisfaction scores and a higher rate of conversion to total hip arthroplasty. White et al ⁷ retrospectively reviewed 47 patients with a lateral center-edge angle greater than 45° who underwent arthroscopic acetabuloplasty and allograft labral reconstruction. They assessed patient-reported outcome measures and degrees of radiographic correction at a minimum 2-year follow-up.They reported improvement of lateral center-edge angle, Tönnis angle, and Modified Harris Hip Score, as well as lower extremity function scale. They had 1 patient who converted to a total hip arthroplasty. With regard to capsulotomy type, Sandoval et al ⁵ compared functional outcomes for an inside-out versus outside-in capsulotomy and 101 patients with 1-year follow-up.They reported no difference in operative time outcome scores or complications. However, they did find an increased rate of heterotopic ossification (HO) in the outside-in access group.Additional studies have evaluated outcomes associated with the outside-in capsulotomy and have reported improvement in outcome scores with no complications.^2,8

In summary, outside-in access may be helpful for patients with less distractible hips, including older, stiff men, patients with excessive lateral overcoverage, or patients with acetabular retroversion. Understanding the extracapsular anatomy is the key to safe intra-articular access, and hip flexion prior to completion of the outside-in capsulotomy can protect the articular cartilage of the femoral head.

These are our references. We thank you for your time and attention.