Revision of Failed Osteochondral Lesions of the Talar Dome

Thomas S. Roukis, Jason Piraino

Osteochondral lesions of the talar dome (OCLTs) remain a common cause of ankle joint pain since first being recognized in 1887.¹ Despite much interest in the diagnosis and treatment of OCLT, the exact incidence and cause remain unknown since not all OCLTs are symptomatic, and, as a result, many go undetected.²^,³ Our best estimate of incidence comes from Orr et al⁴ who conducted a 10-year longitudinal study of military personnel and estimated the incidence of OCLT to be 27 per 100,000 (0.00027%). Similarly, the cause of OCLT remains an area of much debate. The most common etiology proposed is traumatic injury, either through an isolated significant event or repetitive more minor injuries.⁵ Symptomatic OCLTs have been identified in 6.5% of inversion ankle sprains, as well as, up to 50% of acute ankle fractures.⁵^,⁶ Although OCLTs can occur anywhere along the talar dome, the 2 most common locations, approximately 50% each, are anterior-lateral and posterior-medial. The anterior-lateral OCLT is most commonly correlated with a traumatic etiology following forced dorsiflexion-inversion of the ankle and results in a formal osteochondral fragment.⁷ Although the posterior-medial OCLT may be related to trauma following forced plantarflexion-inversion resulting in an impaction injury with subchondral cyst formation, it also has a higher potential of being idiopathic.⁸ The typical clinic presentation includes deep ankle joint pain made worse by weight-bearing, especially ballistic activities, or situations that increase axial load pressure in the ankle joint. The onset of the deep ankle joint pain is most consistently either during or after the activity and is associated with swelling, stiffness, clicking, and/or catching/locking, whereas range of motion tends to remain unaffected.

Following clinical history and physical examination, imaging modalities are performed and consist of plain film weight-bearing anterior-posterior, mortise, and lateral ankle radiographs. If after obtaining these radiographs an OCLT, especially posterior-medial, is suspected, then a weight-bearing mortise plantarflexion view with the heel elevated on a 4-cm lift has been demonstrated to accurately diagnose posterior-medial OCLTs and, in fact, has been proven to be superior to helical computed tomography (CT) for posterior lesions.⁹ Acute OCLTs, unless quite large and/or involving a significant segment of underlying subchondral bone, are often difficult to appreciate on plain film radiographs. In contrast, chronic OCLTs demonstrate radiolucency and on occasion cartilage depression. In the end, although useful for ruling out other pathology, plain film weight-bearing ankle radiographs are rarely sensitive enough to diagnose and fully evaluate an OCLT, thus advanced imaging modalities are necessary.

Magnetic resonance imaging (MRI) is often considered the advanced imaging modality of choice for a suspected OCLT. It has been shown that an MRI, including at a minimum T1 and T2 weighted images, can detect up to 50% of OCLTs that would otherwise be missed on plain film radiographs.¹⁰ On T1 fat enhancing imaging, sclerosis of the OCLT will show up as a low signal intensity. The T2 image will show any fluid collection around the OCLT, or in some cases, separation of the OCLT from the talar body.¹¹ Any bone marrow edema will show up as a hypertense signal within the talar dome on a T2 image and low signal intensity on a T1. Cystic changes within the talus may also be observed in a talar body susceptible to an OCLT, depending on the contents within the cysts, will determine the signal intensity on the MRI images.¹² Another advantage of obtaining an MRI when an OCLT is suspected is that it will allow for inspection of the surrounding ankle ligamentous structures and tendons. Due to the aforementioned reasons, an MRI is the modality of choice for the most efficacious diagnostic tool to diagnose an OCLT; however, once an OCLT is diagnosed and the surrounding structures assessed, a CT scan is considered the best imaging modality for surgical planning.

A CT scan is beneficial in determining the entire extent of the OCLT due to its ability to better differentiate viable from nonviable bone, thereby allowing for more accurate measurements of the size of the OCLT including any subchondral cysts present. However, a CT scan will not be able to determine if there is a loose body within the OCLT nor will it allow for assessment of the surrounding soft-tissue structures. Intra-articular contrast can be used in conjunction with a CT scan to better help visualize loose bodies by demonstrating the free space deep to the loose body and cystic lesions allowing for more accurate assessment of the extent of subchondral cysts. Single photon emission computed tomography (SPECT) is an advanced imaging modality that is not routinely available at many institutions but warrants mentioning. A SPECT combines imaging techniques from both a bone scan and CT to provide more accurate and specific images. Studies have demonstrated that a technetium-99m MDP bone scan can detect up to 99% of OCLTs ¹³ and has been shown to have a 94% sensitivity to OCLTs when missed on plain film radiographs. SPECT has been shown to provide more accurate images to the exact size of the lesion and to be more sensitive to changes in the OCLT when compared with an MRI or bone scan alone.¹⁴

Surgical Treatment

Primary surgical treatment of symptomatic OCLT involves a spectrum of care depending on the patient age, location of the OCLT, morphology of the OCLT, and integrity of the surrounding articular cartilage of the ankle joint.¹^,⁵^,⁷ Young patients, especially athletes, with contained lesions that are <1.5 cm² are predominantly treated with orthobiologic injections, bracing, physical therapy, and if surgery is indicated, with an excision of the loose, fragment, devitalized articular cartilage, and bone marrow stimulation through microfracture of the subchondral plate with or without application of platelet rich plasma or concentrated bone marrow aspirate to the osseous defect. In 2012, Donnenwerth and Roukis¹⁵ undertook a systematic review evaluating 29 total articles, of which 7 met inclusion criteria, on patient outcomes after arthroscopic debridement with microfracturing. This study encompassed 295 total patients and 299 ankles. All patients had undergone arthroscopic debridement with microfracture, and at a mean follow-up of 54 months, the authors determined an average increase in the American Orthopedic Foot and Ankle Score (AOFAS) of 25.1 points. The authors stated this correlated to a good or excellent outcome in 80% of the ankles after surgery.¹⁵ Since this systematic review was published, multiple “current concepts reviews” support arthroscopic debridement with microfracturing as the primary treatment of small, contained OCLT.¹⁶ ^–¹⁹ Additional mid- and long-term follow-up publications are available that provide further insight into outcomes following arthroscopic debridement with microfracture for OCLT. Choi et al²⁰ conducted a mid-term follow-up of 165 ankle with small to midsized OCLT treated with arthroscopic bone marrow stimulation through microfracture. They concluded that this approach resulted in good functional outcomes and improved quality of life with maintenance of satisfactory outcomes at a mean follow-up of 6.7 years. Park et al²¹ conducted a minimum 10-year (mean: 13.9 years) follow-up of OCLTs with a mean OCLT size of 1.05 cm² that were managed with arthroscopic bone marrow stimulation through microfracture in 202 ankles. Significant prognostic factors associated with revision surgery were the size of the lesion based on preoperative noncontrast MRI measurement of >1.5 cm² and obesity which was considered a body mass index of >25.

A recent systematic review determined that bone marrow stimulation with microfracture of OCLTs is best reserved for lesions <1.074 cm² or 10.2 mm in diameter.²² It is important to recognize that even if OCLT are small, those that are uncontained, as well as those with subchondral cysts have been demonstrated to have poorer clinical outcomes.²³ Further, young age, specifically pediatric and adolescent aged, patients undergoing surgical intervention for OCLT have a higher potential for failure requiring reoperation.²⁴ Unfortunately, there is a strong correlation of cystic changes within the subchondral bone associated with OCLT, with some studies suggesting cysts occur up to 25% of the time.²⁵ This is an important consideration because subchondral cysts tend to worsen over time following microfracture.²⁶ The addition of particulated juvenile cartilage allograft transplantation (DeNovo NT Natural Tissue Graft, Zimmer, Inc, Warsaw, IN) to the OCLT base has not been demonstrated to improve OCLT survivorship likely related to complicated biological and mechanical factors that have not been fully determined.²⁷ Additionally, better patient outcomes occur when concomitant lateral ankle instability is corrected at the time of surgical intervention for the symptomatic OCLT.²⁸ Unfortunately, the overall success rate for failed OCLT with bone marrow stimulation through microfracture is poor with a recent systematic review of 5 studies including 70 ankles determining a success rate of only 61% with 27% requiring additional revision surgery.²⁹

Lesions >1.5 cm² are not indicated for treatment through arthroscopic means and require bone grafting with or without articular cartilage to restore the subchondral bone. In 2004, Hangody et al³⁰ described an autologous osteochondral mosaicplasty technique (OATS) where cylindrical subchondral grafts were removed from the non–weight-bearing part of the femoral condyle and transferred to the talar defect. A conical recipient defect was made overlying the OCLT and the graft was then transferred and impacted without fixation. The aim of this would be to fill the osseous defect and replace the damaged hyaline cartilage with new hyaline cartilage. In their initial study, Hangody et al³⁰ demonstrated a 94% good to excellent result in the patients undergoing a mosaicplasty for large, complex, cystic OCLTs. A subsequent large cohort study determined that female gender and medial cystic OCLT lesions were most commonly associated with an age >60 and responded well to OATS.³¹ A systematic review of 12 studies including 191 fresh OATS for large OCLTs determined the aggregate graft survival was 86.6% with 21.6% requiring minor subsequent revision surgery, predominantly arthroscopic debridement and hardware removal after a weighted mean follow-up of 56.8 months.³² Additionally, the presence of subchondral cysts was associated with OATS failure. To combat this, one study demonstrated that the addition of concentrated bone marrow aspirate reduced the occurrence of postoperative subchondral cyst formation at the OATS graft-host interface by approximately 60%.³³ Finally, at present, the decision between fresh autogenous and frozen allograft OATS remains a matter for conjecture. Bai et al³⁴ evaluated 19 ankles with planned second-look arthroscopic examination at 2 years following autogenous OATS for OCLT with large subchondral cysts and determined good clinical outcomes, as well as, healthy cartilage healing. Additionally, one study determined that the use of fresh rather than frozen OATS is associated with improved patient outcomes, less chondral wear measured on MRI, reduced cyst formation, and fewer secondary procedures.³⁵ However, another study evaluated 25 patients treated with frozen OATS for OCLT (mean size: 1.82 cm²) between 2009 and 2014 who were followed for a mean of 5.5 years. At final follow-up, graft incorporation occurred in 92%, and there was no evidence of graft collapse or need for revision.³⁶ Unfortunately, the biomechanical properties of the articular cartilage and subchondral bone differs substantially between the donor sites from the knee femoral trochlea and talar dome recipient sites within the ankle joint.³⁷ As a result, even after successful osseous and articular OATS incorporation with the host tissues, the contact mechanics of the ankle are not fully restored.³⁸

Uncontained OCLTs >1.5 cm² that involve the shoulder of the talar dome are often difficult to manage with the treatments listed above. Most of the prior studies that aim to look at the treatments of these larger lesions have a structural bulk talar allograft treatment algorithm.¹^,⁵^,⁷^,¹⁶ ^–¹⁹ The bulk talar allograft not only allows the surgeon to replace large osseous voids within the talar dome but also provides a structural integrity to the allograft that allows for repair of OCLTs that involve the shoulder of the talus.³⁹ Orr et al⁴⁰ performed a retrospective study evaluating fresh bulk talar allograft in highly active individuals. The study consisted of 8 procedures performed between 2010 and 2013. The mean size of the defect after excision was 2.25 cm³. All 8 patients went on to fully incorporate their bulk talar allografts at final follow-up of 28.5 months. A subsequent systematic review evaluated 5 studies involving 91 bulk talar allografts for OCLTs.⁴¹ At a weighted mean follow-up of 45 months, 25% required revision surgery to manage moderate to severe ankle osteoarthritis, painful hardware, extensive graft collapse, and delayed union of the osteotomy site. Ultimately, 13.2% of cases were considered failures with 8.8% culminating in ankle arthrodesis (AA) or total ankle replacement (TAR).⁴¹ At a minimum, the use of bulk talar allograft’s, fresh or frozen, allow for replacement of bone stock that will make future AA or TAR less complicated. These procedures are reserved for severe nonsalvageable OCLTs or as revision treatments after failed prior procedures. Patient factors and goals play a large role in determining which treatment to pursue. Ankle joints with moderate to severe arthrosis should be considered for an AA or TAR, as the procedures presented thus far will not address the concomitant ankle joint arthrosis present.

The goals to be achieved following any revision procedure for failed surgical management of OCLT include, in the short-term, pain relief and genesis of a functional limb with the need for protective bracing reserved for those patients with persistent pain. Longer-term goals are preservation of the ankle joint thereby avoiding, or delaying, the need for further revision surgery including AA and TAR.

Indications and Contraindications

Revision of failed surgically treated OCLTs primarily involves the following: (1) nonoperative management through continuation of conservative treatments focused on pain reduction and motion preservation⁴²; (2) arthroscopic management of secondary problems including subchondral cyst formation and symptomatic hardware removal; (3) secondary OATS⁴³ ^–⁴⁵; (4) bulk talar allograft transplantation⁴⁶; (5) vascularized osteochondral grafts⁴⁷; (6) AA; and (7) TAR.

Hwang et al⁴⁰ evaluated 40 patients who underwent primary arthroscopic bone marrow stimulation through microfracture that had persistent pain at a mean follow-up of 13 months. Each patient received an intra-articular injection of hyaluronic acid once per week for 3 weeks. At a mean follow-up of 29.1 months post injection therapy, the patients demonstrated significantly improved clinical and functional scores. The authors concluded that this represented a better clinical option than other conservative measures such as physical therapy, bracing, and oral/topical analgesics for management of failed OCLTs. The role autologous platelet rich plasma⁴⁸ and concentrated bone marrow aspirate⁴⁹ have following failed arthroscopic bone marrow stimulation through microfracture remains unanswered.

Due to the unpredictable outcomes following revision of failed arthroscopic bone marrow stimulation through microfracture with or without orthobiologic supplementation, secondary OATS has been proposed. Yoon et al⁴⁴ conducted a matched cohort study of 44 ankles who failed arthroscopic bone marrow stimulation through microfracture that underwent revision with either repeated bone marrow stimulation (N = 22) or OATS (N = 22). At a mean follow-up of 4 years, the OATS group had higher good to excellent subjective scores (81.8% vs 31.8%) and fewer revisions (0% vs 63.6%). The authors recommended judicious use of repeat arthroscopic bone marrow stimulation when this failed as the primary treatment. Park et al-2018 evaluated 46 patients between 2005 and 2014 who underwent primary OATS (N = 18 ankles) and secondary OATS (N = 28) for failed arthroscopic bone marrow stimulation through microfracture. The mean OCLT size for both treatment groups at surgery was 1.95 cm². At a mean follow-up of 6 years, there was no difference between groups for patient-related outcomes, pain, or the need for further revision surgery. Prior bone marrow stimulation through microfracture was not associated with increased risk of failure for the treatment group undergoing secondary OATS. Kaplan-Meier survival plots were not significantly different between the primary and secondary OATS groups. The only prognostic finding for clinical failure for both treatment groups was a lesion size >2.25 cm² on preoperative noncontrast MRI. The authors concluded that clinical outcomes of patients with large OCLT treated with secondary OATS after failed primary bone marrow stimulation through microfracture were found to be comparable with those treated with primary OATS.

Juels et al ⁵⁰ conducted a systematic review of failed bulk talar allograft procedures that included 11 studies and 522 ankles. The incidence of bulk talar allograft failure was 11.5% in the included studies with a reoperation rate of 18.9%. Although the reports of subsequent surgery were limited, patient satisfaction was 50% for revision bulk talar allograft, 50% for TAR, and 77.3% for AA. Extensive patient counseling is essential prior to performing revision of failed bulk talar allografts considering the consistently poor patient outcomes following the salvage surgery options available.

Surgical angiogenesis employing a free tissue transfer with vascularized medial femoral condyle autograft and microvascular anastomosis remains an option but represents a highly complicated and specialized technique that should only be performed in select instances by experienced microvascular surgeons.⁴⁷

Although they represent rationale end-stage operations following failed OCLT management, especially for large defects with concomitant arthritic changes within the ankle joint, AA and TAR outcomes following failed OCLT treatments has not been formally studied. A reasonable alternative prior to AA and TAR is the metal resurfacing inlay implant (Talus HemiCAP system, Arthrosurface/Anika Therapeutics, Inc, Franklin, MA) implanted through a medial malleolar osteotomy approach.⁵¹ This hemiprosthesis is indicated only for treatment of failed OCLT but is not available for use in the United States. The available literature reveals mixed results over medium-term follow-up likely due to the complexity of the unforgiving implantation technique.⁵⁰ ^–⁵⁴ More recently, a porous, biocompatible, bioresorbable scaffold consisting of inorganic calcium carbonate (Aligi-AC, CartiHeal, Inc, Kfar Saba, Israel) has been developed; however, this is an investigational device and only available in the United States at select medical centers as part of a Food and Drug Administration Breakthrough Device program for the treatment of mild/moderate osteoarthritis and focal defects, including complex OCLT.⁵⁵

All of these procedures are indicated in situations where the soft tissues are nonhostile; infection, if present, has been completely eradicated; and the patient is medically healthy enough to survive the revision surgery and accepting of the protracted recovery process, as well as, when below-knee amputation is not desired. The presence of these situations in addition to inadequate vascular supply are considered contraindications.

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