Arthroscopic Debridement and Fixation of Osteochondritis Dissecans Lesions of the Medial Femoral Condyle

Abstract

Unstable osteochondritis dissecans lesions of the medial femoral condyle have classically been treated with open reduction and fixation under direct visualization through an open arthrotomy. Given the value of avoiding open arthrotomies, we present an arthroscopic approach for lesion elevation, debridement, and fixation. The lesion is first elevated using an arthroscopic elevator, leaving a laterally based osseous hinge. Once elevated, fibrous debris is debrided from the base of the lesion. Subsequently, the fragment is reduced, and percutaneous transpatellar instrumentation is used for fixation. The use of this technique allows for excellent mobilization, debridement, and fixation of the osteochondritis dissecans lesion while minimizing violation of periarticular soft tissues.

Unstable osteochondritis dissecans (OCD) lesions of the medial femoral condyle (MFC) are a common cause of knee pain in the adolescent population, with an incidence of 11.2 per 100,000.¹ These lesions have classically been treated with reduction and fixation through an open arthrotomy. Given the increased morbidity associated with open arthrotomies, there has been growing interest in managing these lesions arthroscopically. We present an arthroscopic approach for debridement and fixation of MFC OCD lesions. The technique is demonstrated in a video (Video 1) along with a list of pearls and pitfalls (Table 1) in addition to advantages and disadvantages (Table 2) is provided. The described technique allows for excellent mobilization, debridement, and fixation of the OCD lesion while minimizing violation of the periarticular soft tissues.

Table 1.

Pearls and Pitfalls of Arthroscopic Debridement and Fixation of Osteochondritis Dissecans Lesions Using a Hinge-Based Construct

Pearls	Pitfalls
-When creating the anteromedial portal, use the spinal needle to localize the optimal position for accessing the entire rim of the defect for flap creation and elevation.	-Avoid aggressively retracting the hinged fragment with the arthroscope. Gentle, consistent traction yields improved visualization over time as plastic deformation of the hinge occurs.
-The number of transpatellar instrumentation portals may be minimized by flexing and extending the knee to bring the desired fixation points in line with the previously established portal.	-Ensure that the sharpened edge of the #11 blade is inserted deep to the skin while tracing the defect to avoid undue propagation of the skin incision.
-A distal/lateral to proximal/medial trajectory allows for increased screw length while reducing the risk for intra-articular or physeal screw penetration.
-Arthroscopic as well as clinical photographs of the K-wires in position are helpful for recreating the trajectory for cannulation of the screws during subsequent hardware removal.

Table 2.

Advantages and Limitations of Arthroscopic Debridement and Fixation of Osteochondritis Dissecans Lesions Using a Hinge-Based Construct

Advantages	Limitations
-An arthroscopic approach to fixation forgoes the morbidity associated with an open procedure.	-This approach would not be favorable in stable lesions, fragmented lesions, or lesions with exposed subchondral bone and chondral loss.
-Excellent visualization and access to subchondral bone to promote bleeding and subsequent healing with standard portal configuration.	-Possibility of persistent pain and symptoms secondary to malreduction or inadequate base preparation.
-Excellent fixation and outcomes in appropriately selected patients and lesion architecture.

Surgical Technique

Patient Positioning and Preparation

The patient is positioned supine on the operating table with the leg positioned such that it can be abducted away from the operating table to allow knee flexion (Fig 1). A tourniquet is applied to the proximal thigh, and the leg is prepared and draped in the standard fashion for arthroscopic intervention. The extremity is exsanguinated, and the tourniquet is inflated to 250 mm Hg.

Fig 1.

Patient is positioned supine with the left leg abducted to facilitate flexion intraoperatively.

Portal Placement and Diagnostic Arthroscopy

A standard anterolateral (AL) portal is created just lateral to the patellar tendon at the level of the distal pole of the patella. A 30° arthroscope is introduced into the joint, and the MFC OCD lesion is identified. Next, the anteromedial portal is created under arthroscopic visualization. A spinal needle is introduced to the medial compartment, aiming for the medial edge of the OCD lesion (Fig 2). This trajectory is selected because it optimizes the position for subsequent passage of a #11 blade into the medial aspect the lesion. Once needle positioning is satisfactory, a vertical anteromedial portal is established. With both portals established, diagnostic arthroscopy is carried out in the standard fashion to evaluate for loose bodies or other intra-articular pathology. A 4-mm arthroscopic shaver (Arthrex Torpedo) is then used to perform a limited infrapatellar fat pad resection to allow for visualization of the lesion.

Fig 2.

Arthroscopic image through the anterolateral portal of the left knee demonstrating spinal needle (arrow) introduction to the medial compartment for mapping trajectory before establishing the anteromedial portal.

Defect Elevation and Debridement

Attention is now turned to the OCD lesion, first using a probe to assess the stability and structural integrity of the lesion. Additionally, the probe is used to trace the border of the lesion, feeling for the subchondral cleft present between the healthy medial bone and the laterally based OCD lesion. In areas where the overlying cartilage is intact, this creates temporary indentation in the cartilage that aids in visualization of the lesion’s border (Fig 3). A #11 scalpel is then introduced to the joint, passing into the medial border of the defect, feeling for the cleft in the subchondral bone to help guide the blade in the appropriate trajectory (Fig 4). Care is taken to ensure that the scalpel is passed deep and does not further incise the skin. The lesion is traced along the anterior, medial, and posterior borders, leaving a medial hinge of bone, periosteum, and PCL fibers intact.

Fig 3.

Arthroscopic image through the anterolateral portal of the left knee demonstrating an arthroscopic probe assessing for lesion instability (arrow) and indenting area of unstable cartilage.

Fig 4.

Arthroscopic image through the anterolateral portal of the left knee demonstrating #11 scalpel passing into the medial border (arrow) of the osteochondritis dissecans lesion.

The 11-blade is removed, and an angled arthroscopic elevator is inserted along the medial border of the lesion (Fig 5). This is used to elevate the defect carefully, working anteriorly and posteriorly until the base of the defect can be sufficiently visualized. We are careful to avoid stressing the laterally based hinge by elevating too quickly or with excessive force, which could displace the fragment. With sufficient elevation of the lesion, the tip of the arthroscope is advanced and used to retract the lesion laterally while simultaneously visualizing the osseous base of the defect. This allows for excellent visualization of the defect bed for, while also allowing for slow, controlled opening of the osteochondral flap.

Fig 5.

Arthroscopic image through the anterolateral portal of the left knee demonstrating an angled arthroscopic elevator (arrow) inserted along the medial border of the osteochondritis dissecans lesion.

A combination of arthroscopic shavers and curettes are then used to debride fibrous tissue from the bed of lesion as well the undersurface of the osteochondral flap (Fig 6). We are careful to leave healthy subchondral bone intact. Once satisfactory debridement has been achieved, a 0.045-inch Kirchner wire is used to create several evenly spaced perforations into the subchondral bone to promote egress of marrow elements and increase the biologic healing potential of the lesion (Fig 7).

Fig 6.

Arthroscopic image through the anterolateral portal of the left knee demonstrating debridement of fibrous tissue from osteochondritis dissecans lesion bed using an arthroscopic shaver (arrow).

Fig 7.

Arthroscopic image through the anterolateral portal of the left knee demonstrating perforation (arrows) of subchondral bone using Kirchner wires.

Defect Reduction and Transpatellar Fixation

The arthroscope is partially withdrawn to allow the osteochondral flap to fall back into its native position. A probe is placed into the anteromedial portal and used to aid in reduction of the fragment. The probe is used to maintain the reduction of the lesion. On the basis of the lesion size, generally 2 to 3 fixation points are planned. With the knee in approximately 70° of flexion, a 0.045-inch guidewire is advanced through the skin and the patellar tendon in the desired trajectory for fixation. Once the position of the wire is satisfactory, it is advanced approximately 25 mm into the condyle, perpendicular to the chondral surface of the defect. Additional guidewires are placed in similar fashion to attain provisional fixation of the lesion. For each wire, an approximately 4-mm vertical incision is made through the skin only. A blunt-tipped depth gauge is then passed over the wire and advanced into the joint. This allows for splitting of the patellar tendon in line with its fibers and dilates the tract for subsequent drill and screw passage. Next, a 2.7-mm cannulated drill bit is inserted over the guidewire and drilled to the appropriate depth as templated on the preoperative magnetic resonance imaging scan, typically between 20 and 26 mm (Fig 8). Care is taken to avoid penetrating the medial cortex or violating the physis. A 3.5-mm cannulated headless compression screw (Arthrex Compression FT Screw, Mini) of appropriate length is then inserted, burying the screw 2 to 3 mm deep to the chondral surface (Fig 9). This process is repeated for the remaining screws. Varying degrees of knee flexion may be required to allow the necessary trajectory for instrumentation. Additionally, variations in knee flexion may allow for satisfactory screw trajectory through the same skin incision, avoiding the need for additional incisions.

Fig 8.

Arthroscopic image through the anterolateral portal of the left knee demonstrating insertion of 2.7-mm cannulated drill bit (arrow) over guidewire.

Fig 9.

Arthroscopic image through the anterolateral portal of the left knee demonstrating fixation of osteochondritis dissecans lesion using a 3.5-mm cannulated headless compression screw buried 2 to 3 mm deep to the chondral surface (arrow).

Following satisfactory fixation, the borders of the lesion are evaluated, and any unstable areas of cartilage are debrided. The Kirschner wires are then removed, and final fluoroscopic anterior–posterior and lateral images are obtained to ensure satisfactory screw trajectory and fragment reduction (Fig 10).

Fig 10.

Postoperative fluoroscopic anterior-posterior (A) and lateral (B) images of the left knee following osteochondritis dissecans lesion fixation.

Closure and Postoperative Rehabilitation

Incisions are closed with 3-0 absorbable monofilament suture in in a horizontal mattress fashion and dry sterile dressings are applied. The patient is made toe-touch weightbearing for the first 6 weeks with passive range of motion restriction starting from 0° to 30°, gradually progressing to 120° as tolerated. At 6-week follow-up, postoperative radiographs are obtained, and patients are progressed to weightbearing as tolerated with the goal of full weightbearing by 12 weeks.

Hardware Removal

The patient is brought back to the operating room at 3 to 4 months postoperatively for removal of the headless compression screws. The technique for positioning and draping is repeated with standard access of the joint attained via the anterolateral and anteromedial portals. The prior portal incisions are generally well positioned for use. Once visualized, the lesion is probed to ensure stability before screw removal. The heads of the screws are identified deep to the surface of the articular cartilage and gentle debridement of soft tissues overlying the screw heads is carried out to allow for insertion of the screwdriver (Fig 11). The screw head is cannulated with an 0.045-inch guidewire, and the blunt-tipped depth gauge is used to establish and dilate the transpatellar portal.

Fig 11.

Arthroscopic image through the anterolateral portal of the left knee demonstrating screw removal (arrow) in a healed osteochondritis dissecans lesion.

It may be possible to remove all screws through a single transpatellar portal (Fig 12). To do this, the position of knee flexion may be varied to sequentially bring each screw into alignment with the portal.

Fig 12.

Arthroscopic image through the anterolateral portal of the left knee demonstrating complete hardware removal and healed osteochondritis dissecans lesion. Arrows demonstrate the previous location of explanted screws.

Discussion

This Technical Note describes a technique for arthroscopic debridement and fixation of OCD lesions of the femoral condyles. It has been well established that young patients, particularly with open physes, may heal with initial nonoperative management and offloading.² However, cases refractory to weightbearing and physical activity restrictions may warrant surgical intervention, particularly in the setting of unstable lesions.^3,4 When appropriate, preservation of the patient’s native cartilage and bone through fixation is most favorable. Fixation with screws can be done either with bioabsorbable or metal screws, as shown in this technique. Both biodegradable and metal hardware options have shown satisfactory outcomes.^5,6 In lesions unfavorable for fixation, small defects may be treated with osteochondral autograft transfer, and medium to large defects may be treated with osteochondral allograft transplantation.⁷

Although numerous classification systems exist, OCD lesions have been recently described through the Research in OsteoChondritis of the Knee classification system based on lesion architecture confirmed during arthroscopic evaluation.⁸ Lesions are designated to stable versus unstable categories, which are then further subcategorized based on structure, appearance, and behavior. This Technical Note is particularly suitable for unstable trap door cartilage lesions capable of hinging open as described in the Research in OsteoChondritis of the Knee classification. However, this may not be the best approach in the setting of stable lesions and fragmented lesions or those with exposed subchondral bone and chondral loss not amenable to fixation.

An arthroscopic approach to fixation forgoes the morbidity associated with an open procedure while still providing excellent visualization and access to subchondral bone to promote bleeding and subsequent healing. Although not every lesion may be amenable to arthroscopic fixation, our technique demonstrates excellent fixation and healing in the appropriate circumstances.

Disclosures

The authors declare the following financial interests/personal relationships that may be considered as potential competing interests: Support from the Foderaro-Quattrone Musculoskeletal-Orthopaedic Surgery Research Innovation Fund. D.B.F.S. is a board member of Cartilage; has received funding from JRF Ortho; and has been a consultant or advisor for NewClip. T.A.M. is a board member of the American Academy of Orthopaedic Surgeons, the Pediatric Orthopaedic Society of North America, and the Scoliosis Research Society; has received funding from Broadwater; is a paid consultant with Medtronic, OrthoPediatrics, and Zimmer; and owns equity or stock ownership in Viking Scientific. A.J.K. is a paid consultant to and has received royalties from Arthrex; has received research funding from Aesculap/B. Braun Medical; and is a board member of the American Journal of Sports Medicine, the International Cartilage Repair Society, and the International Society of Arthroscopy Knee Surgery and Orthopaedic Sports Medicine. M.H. is a paid consultant to Enovis; has received funding from Elsevier; is a board member of the Journal of Cartilage and Joint Preservation; and is a paid consultant to Moximed and Vericel. All other authors (C.L.H., X.P., A.J.T.) declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Supplementary Data

Video 1

Demonstration of an arthroscopic debridement and fixation of an osteochondritis dissecans lesion on the medial femoral condyle of the left knee using a lateral based osteochondral hinge.