Treatment of a Bone Marrow Lesion with Subchondroplasty
A 49-year-old female patient presents with full-thickness cartilage loss of the tibia and focal subchondral edema that has failed years of non-operative management. Are there any other non-arthroplasty options available?
Peters T. Otlans, MD, and Steven B. Cohen, MD
The management of early knee osteoarthritis in a young patient continues to be a challenge for orthopaedic surgeons and patients alike. The presence of bone marrow lesions on magnetic resonance imaging (MRI) of the knee, often referred to as subchondral edema, have been associated with pain, progression of arthritis, and the need for knee arthroplasty. [1-3] Recovery after knee arthroplasty is difficult for many patients and is not without risk of complications.  In addition, younger patient age remains a risk factor for revision arthroplasty. 
Subchondroplasty has emerged as a treatment for symptomatic bone marrow lesions in the distal femur or proximal tibia.  Histopathologic examination of these lesions has shown that they have areas of microfracture, subchondral sclerosis, marrow fibrosis, and fat necrosis.  Injection of calcium phosphate into the lesion can be done in an attempt to reinforce the area, stimulate bone remodeling, and provide symptomatic relief. 
A thorough workup should be performed for all patients considered for subchondroplasty:
- The history should focus on determining the etiology of the pain and the degree of disability.
- Standard radiographs, including weight-bearing anteroposterior (AP) imaging at 0° and 30° of flexion, lateral radiographs, and an axial view, should be obtained.
- MRI must demonstrate subchondral edema in a weight-bearing portion of the knee in the compartment that is symptomatic by history and exam.
Patients are considered for surgery only after failing to improve after several months of a combination of weight loss, physical therapy, anti-inflammatory drugs, injections (corticosteroids or viscosupplementation), and bracing (unloader). Patients with advanced tricompartmental disease, severe instability, or malalignment are not expected to do well and should not be treated with subchondroplasty.
Results of subchondroplasty have been favorable. Cohen and Sharkey  retrospectively reviewed 66 patients who presented to an arthroplasty clinic but who underwent subchondroplasty instead. Nearly all (96%) had grade 3 or 4 changes in the treated compartment. At a mean of 27.2 months, 88% of patients had improvement in VAS pain score, while 5% had worse scores and 7% were unchanged. Mean improvement in VAS was greater than 4 points (0-10 scale) and clinically meaningful. In addition, patients showed clinically meaningful improvement in IKDC scores through 2 years of follow-up. At final follow-up, 70% had not converted to arthroplasty. 
In this article, we review the case of a patient with severe knee pain who underwent subchondroplasty after failing years of non-operative treatment.
A 49-year-old female patient with a history of diabetes and hypertension presented with a 5-year history of severe lateral left knee pain that had not responded to conservative therapy, including viscosupplementation injections, corticosteroid injections, bracing, and physical therapy.
- Height: 5 feet, 5 inches; weight: 206 pounds; BMI: 35.4
- Knees neutrally aligned
- Minimal effusion; some crepitus with active extension
- Range of motion 0° to 125° and symmetric bilaterally
- Knee stable to drawer, Lachman, and varus/valgus testing
- Tender to palpation over the lateral joint line, with a McMurray test positive for pain laterally
- Radiographs demonstrated mild joint space narrowing of the medial, lateral, and patellofemoral compartments, with moderate-sized femoral and tibial osteophytes laterally (Figure 1).
- MRI demonstrated a tear of the mid-body portion of the lateral meniscus, areas of focal chondral loss in the lateral and patellofemoral compartments, and a large area of subchondral marrow edema in the posterolateral tibia (Figure 2).
Figure 1. AP, lateral, and Merchant view radiographs of the left knee demonstrate mild joint space narrowing with lateral compartment femoral and tibial osteophytes.
Figure 2. Coronal and saggital T2-weight MRI cuts of the left knee show focal chondral loss of the lateral tibia and femoral condyle with adjacent bone marrow edema in the proximal posterolateral tibia.
- Lateral meniscal tear with symptomatic subchondral marrow edema that has failed non-operative management.
The patient underwent standard diagnostic arthroscopy which revealed:
- A complex tear of the lateral meniscal body and posterior horn
- Grade 4 cartilage defect of the trochlea
- A small but stable high-grade cartilage lesion in an otherwise well-preserved medial compartment
- A focal grade 4 cartilage defect of the lateral tibia and grade 3 chondral loss of the lateral femoral condyle (Figure 3).
After partial lateral meniscectomy and chondroplasty of the lateral compartment, the decision was made to proceed with subchondroplasty.
Figure 3. Images from arthroscopy taken after chondroplasty and partial lateral meniscectomy demonstrating chondral lesions of the trochlea, medial femoral condyle, and lateral tibial plateau.
Subchondroplasty Technique 
- Preoperatively, note the location of the lesion and measure its size on multiple cuts of the MRI. The precise location can be determined by measuring the distance of the lesion from the joint surface and the nearest cortices on multiple sequences of the MRI. In addition, determine the preferred trajectory to the lesion avoiding ligaments and neurovascular structures. These relationships are used to pinpoint the lesion during intraoperative fluoroscopy.
- Place the patient supine on the operating table and induce anesthesia. A tourniquet can be placed to improve visualization at the time of arthroscopy. Examination under anesthesia is performed.
- As we did with our patient, perform standard diagnostic arthroscopy to assess and treat pathology within the knee, such as removal of loose bodies, partial meniscectomy, or chondroplasty.
- After arthroscopy, place the operative leg on a bump and use fluoroscopy to obtain either a perfect lateral of the proximal tibia or a perfect lateral of the distal femur, depending on the location of the lesion.
- Introduce the cannula into the lesion and confirm its position radiographically (Figure 4).
Figure 4. Placement of the cannula under fluoroscopic guidance after obtaining a perfect lateral of the tibia.
- The calcium phosphate bone substitute (AccuFill, Zimmer Knee Creations; Exton, Pennsylvania) is prepared on the back table.
- Using an AP view of the proximal tibia, introduce the cannula to the appropriate depth. The fenestrations in the cannula must be in the bone and directed toward the lesion. Once the location is satisfactory, remove the trocar from the cannula, secure the Luer lock syringe containing the bone graft substitute, and inject the bone graft substitute using steady digital pressure (Figure 5).
Figure 5. Placement of the cannula with all fenestrations within bone and injection of the calcium phoshate.
- Rotatate the cannula to fill the appropriate area with bone graft substitute. Perform serial imaging during injection to ensure that the lesion is filled and that none of the substance has extravasated into the joint.
- After the lesions have been filled, enter the joint arthroscopically to confirm the absence of extravasation of the bone graft substitute into the joint.
- Close and dress the wounds in standard fashion.
- Postoperatively, patients are allowed to weight-bear as tolerated, using crutches for the first 1 to 2 weeks.
- Any non-absorbable sutures are removed at 10 to 14 days after the procedure.
- Physical therapy focused on strength and range of motion is initiated at 2 weeks.
- Full, unrestricted activity is allowed at 4 to 8 weeks, depending on the patient’s symptoms.
At early follow-up (2 months), our patient was doing well, with minimal pain at baseline and a maximum of 4/10 pain with activity (down from 10/10 preoperatively). She reported occasional stiffness in the knee with prolonged sitting.
She continued physical therapy, focusing on strengthening and range of motion. She was advised that although she should continue to see improvements with further time from surgery, some symptoms may persist due to the degenerative changes in her knee.
Management of osteoarthritis in the young patient remains a unique challenge in orthopaedic surgery. When a symptomatic bone lesion is present in a patient without contraindications (such as advaned tricompartmental disease, malalignment, or instability), subchondroplasty is a viable option.
Several investigations have shown favorable results with minimal complications. [8-11] Cohen and Sharkey  demonstrated that 70% of patients who were otherwise arthroplasty candidates had successfully avoided arthroplasty 2 years after subchondroplasty. Even subchondroplasty patients who subsequently underwent joint replacement saw improvements in knee function and pain after subchondroplasty. 
Farr and Cohen  followed patients for a mean of 14.7 months and noted that pain scores quickly improved after subchondroplasty (within 1 week) followed by continued, steady improvement. Although functional scores lacked an immediate jump, they progressively increased at each visit postoperatively, attaining a clinically meaningful improvement. 
The calcium phosphate substitute used in this case report acts as an osteoconductive scaffold. Compared with other bone graft substitutes, its compressive strength is similar to that of cancellous bone.  This permits immediate weight-bearing and provides additional stability to unhealthy bone which, in turn, may explain some of the immediate response seen by patients. As the calcium phosphate slowly resorbs over time, it is replaced by native bone that fills the previous area of unhealthy tissue. This may help to explain the slow but steady improvement seen postoperatively.
Complications of subchondroplasty are typically limited to extravasation of the bone graft substitute into the joint, which can most often be managed prior to leaving the operating room. The knee is lavaged after injection and the hydrophilic calcium phosphate is removed with a shaver. Persistent drainage and osteomyelitis have been reported, however. [10-11, 14] In addition, other complications associated with knee arthroscopy, such as deep vein thrombosis and septic arthritis, can occur.
Subchondroplasty for bone marrow lesions is a relatively novel approach to treating focal lesions in the knee. Given the positive outcomes and few complications, it can serve as a helpful alternative to joint replacement, particularly in young patients or those with limited osteoarthritis. Future investigations will help to further identify prognostic factors associated with failure and success of the treatment and aid surgeons hoping to alleviate this difficult problem.
Peters T. Otlans, MD, is an orthopaedic sports medicine fellow at The Rothman Orthopaedic Institute at Thomas Jefferson University in Philadelphia, Pennsylvania. Steven B. Cohen, MD, is a surgeon at The Rothman Orthopaedic Institute and a Professor of Orthopaedic Surgery at Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, Pennsylvania.
Sports Medicine Editor, Rothman Institute Grand Rounds
Disclosures: Dr. Otlans has no disclosures relevant to this article. Dr. Cohen has disclosed that he is a consultant for Zimmer Biomet and that he receives research support from Major League Baseball.
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