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Osteochondral Lesions of the Talus

Autologous osteochondral grafting of the Talus is normally reserved as a secondary procedure after a failed arthroscopic microfracture of the osteochondral defect.

Though there is some evidence that the high grade lesions  do less well with an arthroscopic debridement and microfracture, this is a much smaller operation than open grafting and is therefore a reasonable starting point for surgical intervention.

The grafts used in this technique are cylindrical plugs “cored” out of a peripheral part of the ipsilateral knee, which can lead to secondary knee pain in some patients.

Sizing of the cylindrical grafts required(noting diameter and depth) precedes removal of the defect in this fashion, into which one or more cylindrical grafts from the knee are carefully impacted.

It is key that the Osteochondral grafts are placed as precisely (and flush) with the existing articular surface as possible, which in most cases means a malleolar osteotomy will be required to allow exact placement.

Secondary interventions are also on occasion required post grafting, such as steroid injection and on occasion further arthroscopy, and a return to normal and full function is not likely for at least 6 months post surgery.

Broadly speaking success rates of 85% or so can be anticipated, and in the longer term, as with all osteochondral surgery more minor symptoms may persist and late deterioration can occur.

OrthOracle readers will also find on interest the following associated instructional operative techniques:

Ankle arthroscopy using the Smith and Nephew Guhl non-invasive ankle distractor

HAMIC and Medial malleolar osteotomy for Osteochondral defect of talus, using Chondrotissue by Biofuse.

Stem cell harvest and transplant for knee osteochondral defect (Synergy Medical technologies)

Knee arthroscopy and microfracture of osteochondral defect

Read more »

This overview is brought to you by Orthoracle - the online e-learning Orthopeadic Surgery Atlas

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View this procedure on OrthOracle.com

Discussion

  • although a traumatic etiology is believed to play a major role in production of these lesions, idiopathic osteonecrosis may be another factor;
  • anterolateral lesions:
    • may result from impaction of talus on fibula as the dorsiflexed ankle is forced into inversion (see ankle sprain);
    • the vast majority are caused by trauma;
    • these lesions tend to be shallow;
  • posteromedial lesions:
    • most of these lesions probably arised from trauma (but many will have an atraumatic etiology);
    • may result from impaction of posteromedial talus on tibia, as plantar flexion ankle is forced into inversion and exteranal rotation;
    • these lesions are deeper and cup shaped;
    • exam: palpate just posterior to the medial malleolus with the ankle dorsiflexed (may resemble pending rupture of posterior tib)

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Exam

  • joint line tenderness and effusion;

Radiographs

  • osteochondral frx may be anterior or posterior to dome, requiring plantar or dorsiflexion of ankle to be visible on mortise view;
  • if radiographs are negative consider repeat radiographs in 2-4 weeks;
  • radiographic classification: (Berndt and Harty)
    • note: that radiographic findings may or may not correlate w/ arthroscopic findings nor prognosis;
      • I: small area of compression;
      • II: partially detached osteochondral lesion;
      • III: completely detached, non-displaced fragment;
      • IV: detached and displaced fragment;

Bone Scan

  • usually not ordered until 8-12 weeks following diagnosis;
  • a negative bone scan will r/o the diagnosis;
  • if bone scan is positive then order either CT or MRI;

CT Scan

  • offers more accurate staging of the lesion;

Treatments

Non Operative Treatment

  • no evidence that non wt bearing cast offers improved results over wt bearing casts;
  • no evidence that patients need to be immobilized if they are kept non wt bearing;

Operative Treatment

The ankle is the third most common joint(after the knee and elbow) to be effected by osteochondritis dissecans , its incidence being approximately 0.09%, and most commonly presenting during the second decade of life.  Several studies have shown that the majority of such lesions are located in the centro-medial and centro-lateral zones. Medial lesions tended to be deeper and are associated with subchondral changes. The deeper, sometimes cystic nature of the medial talar lesions could be interpreted as lending support the theory that a pathophysiology other than trauma may contribute to the development of these lesions.

The limited capacity of talar osteochondral lesions to heal is multifactorial. 60% of the talus is covered by cartilage, which itself has poor intrinsic regenerative capacity due to its avascularity. Cartilage relies on nutrition from synovial fluid and from the subchondral bone. The talus also has a poor blood supply which leads to a further diminished ability for talar cartilage to heal after injury. The blood supply to the talus comes from a complex anastomotic network between the peroneal, posterior tibial, and anterior tibial arterial angiosomes. This complex network from multiple vessels results in certain “watershed areas”, with poor blood supply that sit on the margins of such areas, where this limited overlap in the vessels.

A cadeveric study by Lomax et al 2014, showed relatively poor perfusion in the posteromedial, posterolateral, and mid-medial sections of subchondral bone. Shepherd et al |(1999) found a thickness of 0.7 to 1.2 mm in the ankle compared to 1.5 to 2.6 mm in the knee, which may reduce the ability of the local cartilage to resist shear and impact loads.

Arthroscopic cartilage repair strategies include bone marrow stimulation by intra-articular drilling, known as microfracture, and also retrograde drilling. Bone marrow stimulation is often used as the first line of treatment after failure of nonoperative measures. The cells and growth factors arising from the bone marrow  stimulate repair, leading to the formation of fibrocartilage within the defect. Fibrocartilage is composed primarily of type I collagen rather than the type II collagen which is predominant in the hyaline cartilage that lines synovial joints. Though Type I collagen is biomechanically and structurally inferior to natural hyaline cartilage the technique produces reliable clinical improvement with reduction of pain and increase in function in 65% to 90% of cases.

There are a variety of relevant prognostic indicators associated with bone marrow stimulation, including patient age, lesion chronicity, size, location and containment, and presence of subchondral cysts or associated joint degeneration. OLT size shows an inverse relationship with outcome after microfracture. Chuckpaiwong et al reviewed 105 arthroscopically treated osteochondral lesions of the ankle and lesion size was strongly correlated with successful outcome. No treatment failures were reported when lesions had an average diameter less than 15 mm, whilst only 3% of patients had a successful outcome with a lesion 15 mm or larger. A further study by Choi et al reported similar findings, with lesions under 15 mm2 based on MRI imaging achieving successful clinical outcomes, and poor results in the over 15mm.

Microfracture therefore remains the gold standard for lesions measuring less than 15mm2.  though even when of this size talar shoulder lesions, cystic lesions and those with associated degenerative changes on tibial and talar surfaces are associated with poorer outcomes.

The limitations of arthroscopic bone marrow stimulation techniques in treating larger lesions, and as revision for failed treatment has lead to the adoption of other surgical techniques.

Cartilage regeneration strategies include autologous chondrocyte implantation (ACI), matrix-induced autologous chondrocyte implantation (MACI). These techniques are usually considered after unsuccessful arthroscopic bone marrow stimulation treatment or may be used to treat larger lesions that are thought unlikely to respond to arthroscopic treatment.

ACI and MACI are 2-stage procedures in which hyaline cartilage is harvested from the anterior talus or the non loading portion of the knee as a the first stage. The cartilage is cultured to expand the chondrocytes population, before the chondrocytes are re-implanted into the osteochondral lesion and kept in  place either by sewing a periosteal patch over the defect or using a collagen matrix. The aim being to regenerate new hyaline cartilage that can incorporate and fill the chondral lesion.

Unlike the ACI(autologous chondrocyte implantation) and MACI(matrix-induced autologous chondrocyte implantation) procedures, which require cartilage harvest during the first procedure and then a second procedure to implant the cells, the HAMIC procedure is a one stage technique. Giannini et al compared 56 patients receiving ACI to 25 patients treated with 1-step AMIC. Their group found no difference in the improvement in outcome scores and reported similar findings on MRI and second-look arthroscopy. Autologous Matrix Induced Chondrogenesis (AMIC) is a technique that utilises a porcine collagen membrane in association with bone marrow stimulation techniques to treat osteochondral lesions.

The HAMIC is a technique that uses polyglycolic acid (PGA) and hyaluronin scaffold(Chondrotissue®️) to treat osteochondral lesions. This scaffold is actually a membrane which is impregnated with freeze dried high concentration hyaluronic acid. The membrane provides immediate coverage of the osteochondral defect as well as mechanical stability over the surface of the lesion. It is porous and acts as a substrate for stem cells and growth factors produced from bone marrow stimulation to grow into and onto. The addition of  hyaluronic acid stimulates chondrogenesis from stem cells and results in type II collagen. The membrane is fully absorbed within 4 months.

Readers will also find of interest the following OrthOracle techniques:

Stem cell harvest and transplant for knee osteochondral defect (Synergy Medical technologies)

Osteochondral grafting of the talus (OATS procedure)

Read more »

This overview is brought to you by Orthoracle - the online e-learning Orthopeadic Surgery Atlas

Take the Tour

View this procedure on OrthOracle.com

For a comprehensive review of Osteochondral grafting on Wheeless readers should also visit:

Osteochondral Lesions of the Talus – Allograft Repair

 

  • Arthroscopy of the Ankle:
    • osteochondral lesions of the talus can be debrided, and loose bodies and small osteochondral fragments can be removed;
    • use of non-invasive or invasive distraction improves access to joint and allows adequate debridement and curettage of bed;
    • anterolateral lesions can be addressed from the anterolateral portal;
    • in the study by Kumai, et al (1999), the authors noted good clinical results w/ arthroscopy and K wire drilling of the OCD lesions in patients who were younger than 50 years;
    • posteromedial lesions can be difficult to access;
      • w/ large fragments ORIF may be required, w/ osteotomy of the medial malleolus being required for exposure;
      • ORIF allows direct observation of the lesion and accurate repair;
      • w/ ORIF immobilization in a non wt bearing cast is required for 6-10 weeks

References