Talar osteochondral defect is a combined lesion involving the talar articular cartilage and the underlying subchondral bone.1 In general, osteochondral defects are caused by either direct trauma or repetitive microtrauma leading to partial or complete detachment of the cartilage-bone fragment. A subchondral layer of bone responsible for absorbing mechanical forces and uniformly distributing joint stress supports the articular cartilage.
Subchondral bone abnormalities such as bone marrow lesions and edema are frequently identified in symptomatic talar osteochondral defects and may represent evidence of advancing cartilage destruction, subchondral bone attenuation, and accelerated joint deterioration.2–5 Changes to subchondral bone, including increased fat-suppressed T2-weighted signaling on magnetic resonance imaging (MRI), and histologic signs of abnormal bone remodeling, such as fibrosis and microfractures of the trabeculae, have been observed in bone marrow lesions.3,6,7
Subchondroplasty (Zimmer, Warsaw, Indiana) is a relatively novel technique used to treat multiple conditions associated with bone marrow edema under fluoroscopic guidance.8 The procedure involves percutaneous injection of flowable nanocrystalline calcium phosphate synthetic bone graft into the cancellous trabeculae of the subchondral bone. It is hypothesized that the calcium phosphate improves the structural integrity and biomechanical strength of pathologic subchondral bone without damaging the existing bone scaffold. In addition, the highly porous osteoconductive nature of this material allows for eventual ingrowth of healthy cancellous bone capable of weight bearing.9 Current applications in the literature have been limited to the knee, in which subchondroplasty has proven to be a safe and efficacious procedure for symptomatic bone marrow lesions.8 To the authors' knowledge, only 1 article has reported the use of subchondroplasty in the ankle in the capacity of 2 case studies.10
Bone marrow aspirate concentrate (BMAC) is a potent source of growth factors such as platelet-derived growth factor, vascular endothelial growth factor, and transforming growth factor-ß.11–16 Results of clinical studies support the use of BMAC to facilitate cartilage repair and reduce joint inflammation, whereas in vivo studies provide evidence for increased rates of bone healing, increased area, and torsional stiffness in bone defects.17–22
The aim of this retrospective case series was to assess the safety and effectiveness of an arthroscopic-percutaneous procedure that uses subchondral highly porous injectable calcium phosphate and BMAC to treat painful talar osteochondral defects. A secondary aim was to assess the potential of subchondroplasty combined with BMAC to provide pain relief and improve function in patients with symptomatic osteochondral lesions.
Materials and Methods
From September 2016 to April 2017, 11 consecutive patients with an isolated symptomatic osteochondral defect were included in the study. The cohort consisted of 4 men and 7 women, with a mean age at surgery of 34 years (range, 22–48 years). Three patients had previous surgeries (ie, microfractures) to address the osteochondral defect. The Foot and Ankle Outcome Score was administered preoperatively and at final follow-up, and the visual analog scale for pain was administered preoperatively and at 2 weeks, 6 weeks, and 1 year postoperatively. At 52 weeks, patients were asked if they would have the procedure again. Statistical analysis was not performed because of the underpowered sample number.
Bone marrow aspirate concentrate was obtained using the HARVEST system (Terumo BCT, Inc, Lakewood, Colorado). The bone marrow aspirate is harvested from the ipsilateral proximal medial tibial metaphysis. A sharp trochar with a hollow aspiration sleeve is advanced between the anteromedial and the posterolateral cortices into the cancellous bone. Approximately 60 mL of bone marrow can then be extracted using a standard syringe. The aspirate is then prepared and centrifuged using a standard commercially available BMAC centrifuge system, typically yielding approximately 8 mL of pluripotent cells.
The procedure was then performed arthroscopically with the patient in the supine position and standard anteromedial and anterolateral ankle portals used. A noninvasive ankle distraction was also used. The unstable cartilage and joint synovitic tissue were then debrided using a shaver. Under fluoroscopic guidance, a trochar with lateral fenestrations was inserted into the talus from anterior to posterior aiming at the area of maximal signal intensity on the preoperative MRI. Under arthroscopic visualization, to debride any calcium paste leakage, a mean of 1.7 cm3 (range, 1.5–2.5 cm3) of calcium paste was injected into the subchondral bone at the level of the osteochondral defect. To prevent spilling of calcium paste into the joint, microfracture was not performed. The calcium paste was allowed to set for 10 minutes prior to removing the trochar. At the end of the procedure, 8 cm3 of BMAC that had been previously aspirated from the proximal tibial metaphysis was injected into the joint. Patients were allowed to bear weight as tolerated in a sneaker or controlled ankle motion boot postoperatively. Return to sports was also indicated as tolerated.
Mean osteochondral defect size as measured on pre-operative MRI was 1.3×1.4 cm (range, 1×0.8 to 2×2.3 cm). All outcome measures showed marked improvement from baseline to final follow-up. The mean weight-bearing visual analog scale pain score improved from 7.8 (range, 6–9) to 5.4 (range, 3–7) at 2 weeks, 2.1 (range, 0–8) at 6 weeks, and 1.8 (range, 0–8) at 52 weeks. The mean total Foot and Ankle Outcome Score improved from 67.1 (range, 55–79) to 89.6 (range, 60–95). At the 1-year postoperative visit, all but 1 patient declared that they would have the procedure again.
All patients reported moderate to severe pain within the first 2 weeks postoperatively. At their first postoperative visit, 2 patients presented with ankle erythema, which subsided with diclofenac gel applied to the area. There were no infections. One female patient, having a body mass index of 34 kg/m2, being 46 years old, and having no previous surgical treatments for the osteochondral defect, reported full resolution of symptoms between weeks 2 and 5. Between weeks 5 and 6, she reported substantial worsening of the pain, and MRI revealed a stress fracture of the talar neck at the bone–calcium paste interface. A review of the operative record revealed that the patient had been injected with 2.5 cm3 of calcium paste for an osteochondral defect measuring 16×11 mm and had associated unstable cartilage that was debrided at the time of surgery.
All but the above-mentioned patient returned to all activities between 3 and 9 weeks postoperatively. The youngest patient in the cohort returned to running 3 weeks postoperatively.
The gold standard for treatment of symptomatic osteochondral defect lesions in the talus remains controversial. Treatment is typically based on the size of the lesion as well as the quality of subchondral bone and overlying cartilage.22 To the best of the authors' knowledge, this is the first cohort study to examine the effect of subchondroplasty and BMAC in patients with symptomatic talar osteochondral defect lesions and associated bone edema in the subchondral bone on MRI. The magnitude and durability of pain relief and functional improvement observed in this retrospective study are promising. The mean pain improvement was 6.0 points on the visual analog scale pain score at 1-year follow-up, corresponding to “excellent” pain relief based on historical data.23 The mean total Foot and Ankle Outcome Score improvement was 22.5 at 1-year follow-up, which is also encouraging. Minimally important change values of foot- and ankle-specific patient-reported outcome measures are scarce, and minimally important change estimates of the Foot and Ankle Outcome Score have seldom been reported.24 Nevertheless, the mean changes in visual analog scale pain score and Foot and Ankle Outcome Score suggest that subchondroplasty may be a promising treatment for symptomatic talar osteochondral defects with concomitant bone marrow edema.
The improvements in mean Foot and Ankle Outcome Scores observed in this cohort corroborate those seen in previous studies in which BMAC was used to reduce joint inflammation and improve postoperative pain. Hernigou et al25 compared the use of bone marrow stimulation with concentrated bone marrow aspirate (n=10) with bone marrow stimulation alone (n=12) for the treatment of talar osteochondral defects. They found that, in addition to offering a statistically significant improvement in postoperative Foot and Ankle Outcome Scores, bone marrow stimulation with concentrated bone marrow aspirate conferred complete infill of the defect in 77.3% of patients, compared with 25% of patients treated with bone marrow stimulation alone (P=.007). Similarly, in a study of 72 patients who underwent autologous osteochondral transplantation with concentrated bone marrow aspirate, Kennedy and Murawski26 observed an improvement of mean Foot and Ankle Outcome Score from 52.67 preoperatively to 86.19 postoperatively at a mean of 28.02 months of follow-up (range, 12–64 months). Although a minimum Foot and Ankle Outcome Score that defines successful treatment of talar osteochondral defects has yet to be established, the results of these studies indicate that BMAC has strong potential to mitigate postoperative pain.
In this study, at the 1-year postoperative visit, 10 of 11 patients reported that they would have the procedure again, and they returned to activity 3 to 9 weeks postoperatively. One patient developed a stress fracture of the talar neck at the bone–calcium interface. The authors noted that this patient had a defect of 1.8×1.2 cm, larger than the mean of 1.4×1.3 cm. In addition, it was found that 2.5 cm3 of calcium phosphate had been injected in this patient, whereas the mean calcium phosphate application of the whole cohort was 1.7 cm3. Current literature on the use of subchondroplasty in the knee reports that over-pressurization or failure to fill the entire area of bone marrow lesion can lead to inferior results.27 It is possible that failure in this patient may have been due to overpressurization of calcium phosphate injection at the site of the osteochondral defect. The authors suggest that the injectable volume be dependent on defect volume and, to prevent failure of subchondroplasty in talar osteochondral defects, that no more than 1.5 cm3 of calcium phosphate be injected. Current literature does not discuss specific calcium phosphate injection volume based on defect size; therefore, future research should investigate standardizing the amount of injectable calcium phosphate according to lesion size.
One challenge with subchondroplasty is accurate localization of the lesion intraoperatively. Because intraoperative fluoroscopy cannot identify the lesion, surgeons must rely on preoperative MRI in the operating room as a reference to localize the lesion. However, with careful preoperative planning and arthroscopic assistance, localization issues can be minimized.
There were several limitations to this study. First, in the absence of a control cohort, the relative contributions of subchondroplasty, BMAC, and arthroscopic debridement cannot be clearly defined. Similarly, it is difficult to extrapolate the benefits of subchondroplasty when used in conjunction with BMAC and arthroscopic debridement, as these modalities in combination have previously shown benefit.28–33 Another limitation of this study was the lack of postoperative imaging. It is difficult to assess the morphologic effects of this material on the healing of bone marrow lesions without postoperative imaging.8 Other study limitations included the small number of patients (n=11) and the short follow-up. Future studies need to confirm these results and assess the longevity of subchondroplasty in talar osteochondral defects.
This is the first retrospective cohort study to examine the 1-year clinical outcomes of subchondroplasty with adjunct BMAC in symptomatic talar osteochondral defects. Patients had a clinically significant improvement in pain and function. The procedure is not technically challenging and does not appear to compromise future treatments in case of recurrence of symptoms. The authors believe that subchondroplasty with BMAC is a viable treatment option for patients with symptomatic talar osteochondral defects after refractory nonoperative management.
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