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Address correspondence to Dawid Szwedowski, M.D., Orthopaedic Arthroscopic Surgery International (OASI) Bioresearch Foundation Gobbi NPO, Milan, Italy.
“Bone marrow lesion” (BML) is a common term used to describe the presence of fluid in the bone marrow. Although various pathologies can cause BMLs seen on magnetic resonance imaging, in this Technical Note we focus on treating the lesions associated with osteoarthritis in the knee joint. The role of the subchondral bone in transferring loads within the knee joint, as well as in cartilage homeostasis, is well established. In addition, cartilage and subchondral bone are increasingly considered as an osteochondral unit, rather than as 2 separate structures. Knee osteoarthritis, along with insufficiency fracture, is one of the main indications for the treatment of painful BMLs. Nowadays, there is a growing interest in this field, and new approaches are being developed. Our technique can be defined as a surgical procedure aimed directly at pathology within the subchondral bone and is named “osteo-core plasty.” It consists of 2 parts: The first is decompression of bone marrow to decrease intraosseous pressure, and the second is administration of bone marrow aspirate concentrate for better healing potential and bone autograft to deliver supportive tissue. It should be noted that the cause of BMLs must be known before this kind of treatment is performed.
Technique Video
See video under supplementary data.
The subchondral bone is a structure present underneath cartilage consisting of 2 major parts: the bone plate and the spongiosa. It is responsible for cartilage nutrition and plays an important role in the healing of chondral lesions.
However, it is still an underappreciated component of joint health that should be viewed as a critical element of the osteochondral unit.
Focal changes in the subchondral bone, termed “bone marrow lesions” (BMLs), are features detected by magnetic resonance imaging (MRI). A BML describes an alteration of bone marrow signal intensity, with high signal on fluid-sensitive sequences (T2 and/or proton density with fat suppression and short tau inversion recovery [STIR]), with or without low T1-weighted imaging signal. These MRI alterations may correspond histologically to true edema but also to trabecular necrosis, cysts, fibrosis, and cartilage fragments. Therefore, instead of the commonly used term “bone marrow edema,” the expression “bone marrow edema–like signal” or “BMLs” is more appropriate. In patients with knee osteoarthritis (OA), BMLs can correlate with faster joint degeneration
Change in MRI-detected subchondral bone marrow lesions is associated with cartilage loss: The MOST Study—A longitudinal multicentre study of knee osteoarthritis.
Nonetheless, treatment options taking into account the subchondral bone are still limited.
Osteo-core plasty is a minimally invasive procedure for treating subchondral pathologies to prevent the progression of OA. The main indications are painful bone marrow edema and subchondral cysts associated with OA. During osteo-core plasty, the surgeon injects high-quality bone marrow (Marrow Cellution; Aspire Medical Innovation, Munich, Germany) and small dowels of autologous bone into the affected area under fluoroscopic imaging control to fill the intertrabecular space, thereby inducing improved bone remodeling.
Diagnosis
MRI is an essential diagnostic tool that allows for the recognition of BMLs. Additionally, it is widely used as the gold standard for evaluation of the morphologic status of cartilage. BMLs are easily visible on fat-saturated T2-weighted and short tau inversion recovery (STIR) sequences and appears as hyperintense regions within the trabecular subchondral bone, often at the site of increased mechanical stress
MRI-detected subchondral bone marrow signal alterations of the knee joint: Terminology, imaging appearance, relevance and radiological differential diagnosis.
(Fig 1). The clinician should expect to see BMLs after acute trauma. In this case, the lesions are poorly defined with heterogeneous patterns of subchondral signal changes.
The differential diagnosis includes stress fractures, complex regional pain syndrome (Sudeck syndrome), primary bone tumors, metastases to the femur, infection, rheumatoid arthritis, osteomyelitis, and avascular bone necrosis. In the setting of knee OA, the diagnosis of BMLs can only be recognized after more aggressive and irreversible diseases with similar clinical symptoms have been excluded. The patient’s history and symptoms can be helpful in evaluating the meaning of these BMLs.
Fig 1A magnetic resonance image (coronal view) of the left knee reveals a bone marrow lesion in the medial condyle (arrow). (I, inferior; L, left; R, right; S, superior.)
The main indication for the described technique are BMLs and subchondral cysts associated with knee OA. Additionally, this technique has been used to treat insufficiency fractures, subchondral cysts, and avascular necrosis with good early results.
Surgical Technique
The procedure is initiated by aspiration of the bone marrow from the ipsilateral iliac crest using a sharp trocar with a hollow aspiration sleeve. The introducer needle with a sharp stylet is placed in the cancellous bone between the cortices (Fig 2). When 1 mL of bone marrow is aspirated to ensure proper positioning of the needle tip, a sharp stylet is replaced with a blunt one. From a single stick, the Marrow Cellution system is capable of collecting up to 10 mL of high-quality bone marrow (Fig 3). Additionally, a sharp trocar is used to harvest some bone dowels (Figs 4 and 5).
Fig 2The patient is in the supine position, with the left iliac crest shown. The area is draped in the usual sterile fashion for bone marrow aspiration. The introducer needle with a sharp stylet is placed in the cancellous bone between the cortices.
The patient, under regional or spinal anesthesia, is placed in the supine position as for a standard knee arthroscopy. Before Marrow Cellution injection proceeds, any concomitant abnormalities such as chondral lesions, meniscal tears, and ligament lesions should be addressed and treated. Limb alignment plays a crucial role in cartilage lesion treatment; therefore, any abnormalities should be treated as well. A 30° 4.0-mm arthroscope (Smith & Nephew, Andover, MA) is used to perform a comprehensive arthroscopic examination of the knee. Anteroposterior and lateral fluoroscopic images cross-referenced with the MRI study are used to place the guide pin exactly in the bone marrow edema (Figs 6 and 7). A cannula is then placed over the guide pin, which is subsequently removed. It is left in the bone for a few minutes to perform core decompression. Furthermore, bone dowels are inserted into the cannula and pushed through into the subchondral lesion by a blunt trocar (Figs 8 and 9). Then, the Marrow Cellution bone marrow is inserted through the cannula into the treated area (Fig 10). A final arthroscopic look is taken to confirm lack of intra-articular leakage (Fig 11). Osteo-core plasty is shown in Video 1.
Fig 6Anteroposterior and lateral fluoroscopic images cross-referenced with the magnetic resonance imaging study are used to place the guide pin exactly in the subchondral bone (circle).
Fig 7Anteroposterior and lateral fluoroscopic images cross-referenced with the magnetic resonance imaging study are used to place the guide pin exactly in the subchondral bone (circle).
The postoperative protocol must be adjusted according to the concomitant procedures conducted during surgery. The most important aspects of early postoperative rehabilitation are achieving pain control, maintaining the range of motion, and preventing muscle atrophy.
Touch-down weight bearing is allowed at 3 to 4 weeks postoperatively; full weight bearing is achieved at approximately 6 weeks. Immediately after the procedure, continuous passive motion and a cryo-cuff are applied to lessen pain and swelling and to maintain the joint fluid motion. On the second day after the procedure, isometric and isotonic exercises are introduced. After wound healing, pool exercises can be initiated to regain a normal gait pattern.
Discussion
The subchondral bone plays an important role in natural cartilage healing. Certain diseases of the cartilage are actually diseases of the osteochondral unit rather than diseases of the cartilage alone. Imhof et al.
showed the presence of arteriovenous complexes penetrating the subchondral bone plate and reaching into the calcified cartilage, so consequently, it possesses a blood supply layer up to the tidemark. A study by Lane et al.
The vascularity and remodelling of subchondrial bone and calcified cartilage in adult human femoral and humeral heads. An age- and stress-related phenomenon.
showed higher vascular perforations at the areas of higher stress, indicating that the subchondral bone responds to high loads by increasing the blood supply. However, overloading of the degenerated joint will impede the flow of nutrients from the subchondral bone to the cartilage and thus disturb natural healing. Although the mechanisms are still debated, pain may be a result of impaired venous drainage as the response to repetitive microtrauma.
Intraosseous phlebography, intraosseous pressure measurements and 99m Tc-polyphosphate scintigraphy in patients with various painful conditions in the hip and knee.
Association of subchondral bone texture on magnetic resonance imaging with radiographic knee osteoarthritis progression: Data from the Osteoarthritis Initiative Bone Ancillary Study.
showed that subchondral bone texture is associated with radiographic knee OA progression. In addition, several studies have correlated outcomes with known subchondral BMLs prior to cartilage restoration procedures. Severe subchondral bone marrow edema was associated with poor knee function in patients with chondral lesions and was a reliable prognostic factor in the first year after autologous chondrocyte implantation.
Presence of subchondral bone marrow edema at the time of treatment represents a negative prognostic factor for early outcome after autologous chondrocyte implantation.
Correlation between magnetic resonance imaging and clinical outcomes after cartilage repair surgery in the knee: A systematic review and meta-analysis.
Biological adjuncts to cartilage injuries are becoming increasingly researched and may prove to be beneficial in addressing common concerns. High-quality bone marrow is an easily available source of mesenchymal stem cells and growth factors including platelet-derived growth factor, transforming growth factor β, and bone morphogenetic proteins 2 and 7, which have anabolic and anti-inflammatory effects.
Although high-quality bone marrow is one of the most attractive sources of mesenchymal stem cells, several aspects, such as the amount of aspirate, need further exploration. Bone autograft augmentation can deliver additional supportive and biologically active tissue to the subchondral lesion.
Osteo-core plasty is a minimally invasive procedure with reported efficacy in the treatment of painful bone marrow edema associated with knee OA. It may be particularly important for younger, active patients who wish to reduce pain and avoid or delay total knee arthroplasty. Although different treatment modalities have been tested in the hope that they might reduce pain and stop the progression of the disease, there is still a need for high-quality randomized controlled studies in the future to further improve treatment strategies in preventing or treating BMLs associated with OA.
Our technique has some limitations (Table 1). It is important to note the osteo-core plasty is a recently developed technique and long-term follow-up is needed. The major pitfall of this technique is the risk of cortex perforation during trocar insertion into the subchondral bone (Table 2).
Table 1Advantages and Limitations
Advantages
Minimally invasive technique with early postoperative mobilization
The patient is placed supine on a standard operating table. A diagnostic arthroscopy is performed, and any concurrent intra-articular pathology is addressed. The operated leg, as well as the skin over the iliac crest, undergoes preoperative skin preparation and is then draped in the usual sterile fashion for bone marrow aspiration. A dedicated aspiration kit is used to harvest approximately 7 to 10 mL of bone marrow and bone dowels from the ipsilateral iliac crest. A commercially available system is used to obtain high-quality bone marrow aspirate. Anteroposterior and lateral fluoroscopic images cross-referenced with the magnetic resonance imaging study are used to place the guide pin exactly in the subchondral bone. A cannula is then placed over the guide pin, which is subsequently removed. It is left in the bone for a few minutes to perform core decompression. Furthermore, bone dowels are inserted into the cannula and pushed through into the subchondral lesion by a blunt trocar. Then, the Marrow Cellution bone marrow is inserted through the cannula into the treated area.
Change in MRI-detected subchondral bone marrow lesions is associated with cartilage loss: The MOST Study—A longitudinal multicentre study of knee osteoarthritis.
MRI-detected subchondral bone marrow signal alterations of the knee joint: Terminology, imaging appearance, relevance and radiological differential diagnosis.
The vascularity and remodelling of subchondrial bone and calcified cartilage in adult human femoral and humeral heads. An age- and stress-related phenomenon.
Intraosseous phlebography, intraosseous pressure measurements and 99m Tc-polyphosphate scintigraphy in patients with various painful conditions in the hip and knee.
Association of subchondral bone texture on magnetic resonance imaging with radiographic knee osteoarthritis progression: Data from the Osteoarthritis Initiative Bone Ancillary Study.
Presence of subchondral bone marrow edema at the time of treatment represents a negative prognostic factor for early outcome after autologous chondrocyte implantation.
Correlation between magnetic resonance imaging and clinical outcomes after cartilage repair surgery in the knee: A systematic review and meta-analysis.
The authors report no conflicts of interest in the authorship and publication of this article. Full ICMJE author disclosure forms are available for this article online, as supplementary material.
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