Arthroscopic marrow stimulation for contained OLT less than 1.0–1.5 cm squared
- Lesion size is the critical decision threshold: microfracture is favoured for lesions less than 1.0 to 1.5 cm squared with an intact, contained subchondral plate; lesions greater than 1.5 cm squared, cystic lesions, or those with extensive subchondral oedema favour osteochondral autograft transfer (OATS) or allograft.
- Anterior ankle arthroscopy through anteromedial and anterolateral portals reaches most talar dome lesions; posteromedial lesions may require a medial malleolar osteotomy for perpendicular access — the osteotomy is performed after preoperative planning and must be anatomically reduced and fixed with two screws.
- Complete removal of the calcified cartilage layer down to bleeding cancellous bone is mandatory before microfracture; a residual calcified layer prevents marrow element migration and fibrocartilage formation.
- Microfracture holes are created 3–4 mm apart, 2–4 mm deep, perpendicular to the surface; the awl or drill must not penetrate the subchondral plate excessively or create thermal necrosis — the goal is controlled marrow recruitment without collapse.
When & Why
Indication. Symptomatic osteochondral lesion of the talus (deep ankle pain, catching or locking, effusion) — typically after an inversion injury — that has failed non-operative treatment (activity modification, physiotherapy, NSAIDs and a period of immobilisation) for greater than 3–6 months, with an operable lesion on imaging: a contained defect less than 1.0–1.5 cm squared with an intact subchondral plate and stable cartilage shoulders. Absolute indications
- Symptomatic OLT less than 1.0–1.5 cm squared with failed non-operative treatment for greater than 3–6 months.
- Lesions with unstable cartilage flaps causing mechanical symptoms (locking, catching).
- Contained lesions with intact subchondral shoulders allowing clot containment. Relative indications
- Smaller lesions in low-demand patients where quick recovery is prioritised over hyaline cartilage restoration.
- Lesions in the anterior two-thirds of the talar dome accessible by standard anterior arthroscopy.
- Patients who understand the fibrocartilage nature of the repair and accept potential later revision. Contraindications
- Absolute: lesion size greater than 1.5 cm squared or cystic depth greater than 5–7 mm (these require OATS, allograft or scaffold); uncontained lesions with loss of the medial or lateral shoulder (the marrow clot will not be contained); active ankle infection or systemic inflammatory disease flare.
- Relative: high-demand athletes with lesions greater than 1 cm squared (consider OATS from the outset for better long-term durability); extensive subchondral oedema (greater than 50% of the talar dome on MRI — higher failure rate with microfracture alone); posterior lesions requiring osteotomy in patients with poor bone quality or significant comorbidities. The one decision that matters — size and containment drive everything. Every marrow-stimulation case stands or falls on whether the lesion is suitable for the technique:
First-line for small (less than 1.0–1.5 cm squared), contained lesions with an intact subchondral plate. Technically simple, low morbidity, good short-term results — but produces fibrocartilage that may deteriorate over time.
Preferred for lesions greater than 1.5 cm squared, cystic lesions, or high-demand patients. Restores hyaline cartilage with superior long-term durability, but requires an open arthrotomy or osteotomy and donor-site morbidity from the ipsilateral femoral condyle.
Emerging options for larger lesions without donor-site morbidity. Useful for uncontained defects or revision; long-term data are still maturing.
Consent specifically for the fibrocartilage nature of the repair, risk of incomplete fill or cyst formation (10–20%), persistent pain (15–25%), need for later revision (OATS or fusion in 5–15% at 5–10 years), and the rehabilitation timeline (non-weight-bearing 2–6 weeks, return to sport at 4–6 months). Setup. Supine on a radiolucent table, knee flexed 90 degrees over a bump or leg holder, ankle in neutral to slight plantarflexion. General or spinal anaesthesia with a regional block (popliteal plus saphenous). Thigh tourniquet (250–300 mmHg) or calf tourniquet (200–250 mmHg). A non-invasive ankle distractor is applied. Prophylactic antibiotics are given.
The Operation
The goal: reach the lesion through anterior ankle arthroscopy, debride it down to bleeding cancellous bone, perforate the subchondral plate to recruit marrow elements, and let a stable fibrocartilage-filled clot form — all while protecting the superficial peroneal nerve and avoiding over-penetration of the subchondral plate. The exposure (portal placement and the safe intervals) is laid out as the first steps below.
Operative sequence
- Supine, radiolucent table, knee flexed over a bump, non-invasive ankle distractor applied.
- Mark the portals before incision: anteromedial (medial to the tibialis anterior tendon, lateral to the saphenous vein and nerve) and anterolateral (lateral to peroneus tertius, medial to the superficial peroneal nerve).
- Locate the superficial peroneal nerve by plantarflexing and inverting the ankle and marking it on the skin — it is the most commonly injured structure in anterior ankle arthroscopy.
- Establish the anteromedial portal first, under direct vision with 18-gauge needle localisation; introduce a 2.7 mm or 4.0 mm 30-degree arthroscope.
- Establish the anterolateral portal under direct vision, transilluminating the skin and staying medial to the superficial peroneal nerve.
- Use a 30-degree scope for the anterior two-thirds of the dome; switch to a 70-degree scope and plantarflex the ankle to reach posterior lesions.
- Distraction (non-invasive or invasive) opens the joint; plantarflexion brings anterior lesions into view and dorsiflexion improves posterior access.
- Inspect the entire talar dome, tibial plafond, medial and lateral gutters, and the syndesmosis.
- Document lesion location, size, cartilage status and any loose bodies; look for a second or "kissing" lesion on the tibial plafond.
- Probe the lesion to assess the stability of the cartilage rim and subchondral plate.
- Using curettes, a shaver and radiofrequency ablation, debride all unstable cartilage and fibrous tissue to create a stable, perpendicular cartilage rim around the entire defect — this contains the marrow clot.
- Remove the calcified cartilage layer completely down to the subchondral plate. The bed appears shiny white and avascular until the calcified layer is removed; once it is gone, punctate bleeding from cancellous bone is visible.
- This step is critical — residual calcified cartilage prevents clot adhesion and fibrocartilage formation. If bleeding is not seen, gently abrade with a burr on low speed until cancellous bone is exposed.
- Select an awl (2.5–3.5 mm) or a low-speed drill with a 2–3 mm Kirschner wire.
- Create holes perpendicular to the lesion surface, 3–4 mm apart, 2–4 mm deep, working from the periphery toward the centre.
- After each hole, confirm marrow elements extruding. Avoid over-penetration (greater than 4–5 mm) which weakens the plate, and avoid high-speed drilling without irrigation (thermal necrosis).
- If the plate feels soft or the lesion is borderline in size, consider adding a scaffold (BioCartilage, AMIC) to augment the repair.
- Release the tourniquet and confirm active bleeding from each microfracture hole; the bed should fill with a stable marrow clot within 5–10 minutes.
- Remove all instruments. Close the portals with absorbable suture or Steri-Strips.
- Apply a well-padded posterior splint or a controlled-ankle-motion (CAM) boot with the ankle in neutral.
- Indicated when the lesion lies in the posterior one-third of the medial talar dome and cannot be reached perpendicularly through anterior portals.
- An oblique osteotomy starts about 1 cm above the joint line and is directed toward the intercollicular groove of the medial malleolus; the posterior tibial tendon is retracted posteriorly and the deltoid ligament origin is protected.
- After treating the lesion, the osteotomy is reduced anatomically and fixed with two 4.0 mm partially threaded cancellous screws (or tension-band wiring in poor bone).
- Superficial peroneal nerve during anterolateral portal placement — transilluminate, plantarflex and invert the ankle to identify it, and stay medial; careful technique keeps injury risk below 1%.
- Iatrogenic chondral injury to the tibial plafond from aggressive distraction or instrument passage.
- Missing a second or "kissing" lesion on the tibial plafond — inspect the entire joint.
- Residual calcified cartilage layer — it sits between the tidemark and the subchondral plate and is invisible until debrided; if any is left, the marrow clot will not adhere and fibrocartilage will not form.
- Over-penetration of the subchondral plate (greater than 4–5 mm) — weakens the plate and increases cyst risk.
- Thermal necrosis from high-speed drilling without irrigation — use low RPM or a manual awl.
- Inadequate spacing (less than 3 mm) — creates confluent holes and subchondral collapse.
- Oblique holes from poor portal positioning — always achieve perpendicular access or convert to a medial malleolar osteotomy rather than accepting oblique microfracture.
Start with the 30-degree scope through the anteromedial portal to survey the anterior two-thirds of the dome; for posteromedial lesions switch to the 70-degree scope and plantarflex the ankle maximally. If perpendicular access to the lesion bed still cannot be achieved, proceed to a medial malleolar osteotomy rather than accepting oblique microfracture holes.
A posteromedial lesion in the posterior one-third of the medial dome lies behind the medial malleolus. Attempting angled microfracture through anterior portals creates poor-quality holes and risks chondral injury to the tibial plafond. Plan the osteotomy preoperatively on CT and perform it for direct perpendicular access.
Aftercare & Complications
Rehabilitation | Phase | Timing | Weight-bearing | Therapy focus | |-------|--------|----------------|----------------| | 1 — Protection | 0–2 wk (small contained) to 6 wk (larger or osteotomy) | Non-weight-bearing in CAM boot | Oedema control; ankle ROM (dorsiflexion/plantarflexion only) from 1–2 wk | | 2 — Progressive loading | 3–8 wk | Partial then full weight-bearing (advance 25% weekly) | Stationary cycling, pool therapy; proprioception once full weight-bearing | | 3 — Functional recovery | 2–6 months | Full | Strengthening, balance, sport-specific drills from 3–4 months | | 4 — Return to sport | 4–6 months | Full | Running from 4 months if pain-free; competitive sport at 5–6 months after functional testing | If a medial malleolar osteotomy was performed, keep the patient non-weight-bearing for 6 weeks, then progress weight-bearing with radiographic confirmation of osteotomy healing. Outcomes. Microfracture is the first-line marrow-stimulation technique for small contained OLT because of its technical simplicity, low morbidity and good short-term results — fibrocartilage fill in 60–80% at second-look arthroscopy and good-to-excellent AOFAS scores in 70–85% at 2 years, with lesions less than 1 cm squared doing better than 1–1.5 cm squared lesions. However, the fibrocartilage repair is mechanically inferior to native hyaline cartilage and deteriorates over time — 30–50% of patients show deterioration in pain and function by 10 years, higher for lesions greater than 1 cm squared and in athletes. For larger or cystic lesions, OATS offers superior long-term durability at the cost of donor-site morbidity and a more invasive approach. Complications
- Timing
- Early (less than 6 wk)
- Recognition
- Erythema, discharge at portal
- Prevention / management
- Sterile technique, absorbable closure; antibiotics if infected
- Timing
- Early
- Recognition
- Diffuse chondral damage seen at arthroscopy
- Prevention / management
- Careful distraction and instrument passage
- Timing
- Early
- Recognition
- Calf swelling and pain
- Prevention / management
- Consider prophylaxis in high-risk patients
- Timing
- Early to intermediate (2–5%)
- Recognition
- Pain; radiographic gap or malalignment
- Prevention / management
- Anatomic reduction and rigid fixation with two screws
- Timing
- 6 wk – 1 yr (10–20% on MRI)
- Recognition
- Cyst at the lesion on follow-up MRI
- Prevention / management
- Avoid over-depth; treat the right-size lesion
- Timing
- 6 wk – 1 yr (30–50%)
- Recognition
- Oedema on MRI with ongoing pain
- Prevention / management
- Adequate debridement; patience with recovery
- Timing
- 6 wk – 1 yr (20–40% at second-look)
- Recognition
- Persistent defect on MRI
- Prevention / management
- Complete calcified layer removal at index surgery
- Timing
- Intermediate
- Recognition
- Loss of dorsiflexion after immobilisation
- Prevention / management
- Early range of motion
- Timing
- Late (greater than 1 yr; 30–50%)
- Recognition
- Recurrent activity-related pain
- Prevention / management
- Counsel pre-op; stage lesion correctly first time
- Timing
- Late
- Recognition
- Joint-space narrowing
- Prevention / management
- Higher in lesions greater than 1 cm squared and athletes; address lesion early
- Timing
- Late (5–15% at 10 yr)
- Recognition
- Refractory symptoms
- Prevention / management
- Correct initial selection; OATS, allograft or fusion if it fails
Viva & Exam Focus
MICROMICRO — microfracture principles
OLT-SIZEOLT — SIZE: classification and decision-making
Clinical Decision Scenarios
Practise clinical reasoning and management decisions out loud
“A 28-year-old recreational footballer presents with 8 months of deep ankle pain after an inversion injury. MRI shows a 0.8 cm squared contained osteochondral lesion on the anterolateral talar dome with mild subchondral oedema and no cystic change. He has failed 6 months of activity modification and physiotherapy. How do you manage him?”
“A 35-year-old professional dancer has a 1.8 cm squared posteromedial talar dome OLT with a 6 mm deep cyst and extensive subchondral oedema. She has failed 9 months of conservative treatment and wants to return to full dance. Discuss your surgical plan.”
“A 42-year-old office worker is 18 months after arthroscopic microfracture of a 1.2 cm squared anterolateral OLT. He reports good initial improvement but now has activity-related pain and swelling. MRI shows subchondral cyst formation and incomplete fibrocartilage fill. What are your options?”
Key decision points
- Size threshold: less than 1.0–1.5 cm squared contained favours microfracture; greater than 1.5 cm squared or cystic favours OATS or allograft
- Hepple MRI stage I–II with intact shoulders is the ideal candidate; stage V cystic needs grafting
- Anterolateral lesions: standard anterior arthroscopy; posteromedial lesions often need a medial malleolar osteotomy
- The calcified cartilage layer must be completely removed to expose bleeding cancellous bone before microfracture
- Holes: 3–4 mm apart, 2–4 mm deep, perpendicular to surface — avoid thermal necrosis and over-penetration
Classification & imaging
- Berndt-Harty (radiograph I–V): I compression, II partial detachment, III complete non-displaced, IV displaced, V cystic
- Hepple (MRI I–V): I cartilage only, II subchondral fracture/oedema, III detached non-displaced, IV displaced, V cystic
- CT is essential for size, containment, cystic depth and osteotomy planning
- MRI quantifies subchondral oedema — extensive oedema predicts a poorer microfracture outcome
- Measure in three planes: area equals length times width on the largest coronal and sagittal slices
Approach selection
- Anteromedial portal: medial to tibialis anterior, lateral to the saphenous vein and nerve
- Anterolateral portal: lateral to peroneus tertius, medial to the superficial peroneal nerve (transilluminate)
- Medial malleolar osteotomy: oblique, starting 1 cm above the joint line, toward the intercollicular groove; protect the posterior tibial tendon and deltoid
- Osteotomy fixation: two 4.0 mm partially threaded cancellous screws after anatomic reduction
- Posteromedial portal alternative: 70-degree scope between FHL and the neurovascular bundle — higher technical demand
Operative technique — key steps
- 1. Diagnostic arthroscopy: confirm lesion size, stability, containment and any kissing lesions
- 2. Debride to a stable perpendicular cartilage rim — it contains the marrow clot
- 3. Remove the calcified cartilage layer completely to expose bleeding cancellous bone
- 4. Microfracture: 3 mm awl, holes 3–4 mm apart, 2–4 mm deep, perpendicular, confirm bleeding
- 5. Release the tourniquet: confirm active bleeding and stable clot before closure
- 6. If posteromedial and inaccessible: convert to a medial malleolar osteotomy rather than accept oblique holes
Rehabilitation timeline
- Non-weight-bearing 2 weeks (small contained) to 6 weeks (larger lesion or osteotomy) in a CAM boot
- Progressive weight-bearing at 25% weekly from week 3–6
- Stationary bike and pool therapy once incisions heal (week 2–3)
- Proprioception and strengthening from full weight-bearing (week 6–8)
- Return to sport at 4–6 months after functional testing
Complications & outcomes
- Subchondral cyst formation: 10–20% at 1 year — higher with larger lesions and excessive hole depth
- Incomplete fibrocartilage fill: 20–40% at second-look arthroscopy
- Clinical deterioration after 5 years: 30–50% of patients, especially lesions greater than 1 cm squared and athletes
- Revision rate: 5–15% at 10 years (OATS, allograft or fusion)
- OATS gives superior long-term durability for lesions greater than 1.5 cm squared but needs donor-site morbidity
Danger zones
- Superficial peroneal nerve: at risk during anterolateral portal placement — transilluminate and stay medial
- Calcified layer left in place: prevents clot adhesion and fibrocartilage formation — debride aggressively
- Overly deep or dense holes: weaken the subchondral plate and promote cyst formation or collapse
- Oblique microfracture from poor portal position: a poor-quality repair — perform an osteotomy if needed
- Posteromedial lesion attempted anterior-only: incomplete debridement and poor clot containment
Background & Evidence
Pathoanatomy and the biology of the repair. The talar dome articular surface is hyaline cartilage (2–3 mm thick) resting on a calcified cartilage layer (the tidemark), with a thin subchondral plate (0.5–1 mm) separating cartilage from cancellous bone. Microfracture deliberately penetrates the subchondral plate to allow marrow elements — mesenchymal stem cells and growth factors — to fill the defect and form fibrocartilage (type I collagen dominant). Fibrocartilage is mechanically inferior to native hyaline cartilage, which is why results deteriorate over time. Vascular supply. The talar dome is supplied by the posterior tibial, peroneal and anterior tibial arteries via intraosseous anastomoses. Subchondral plate disruption during microfracture recruits these vessels — but excessive disruption risks osteonecrosis or cyst formation, which is why hole depth and spacing are tightly controlled. Classification systems. Two complementary systems stage OLT and guide treatment. Berndt-Harty (1959) is the original radiographic classification; Hepple (1999) is the MRI classification that defines the depth of subchondral oedema and cystic change and is the more useful planning tool.
- Radiographic feature
- Subchondral compression fracture, no displacement
- Radiographic feature
- Partial osteochondral fragment detachment
- Radiographic feature
- Complete detachment, non-displaced
- Radiographic feature
- Displaced osteochondral fragment
- Radiographic feature
- Subchondral cyst formation (added later)
- MRI feature
- Cartilage injury only, intact subchondral plate
- Typical management
- Microfracture if symptomatic
- MRI feature
- Cartilage injury with subchondral fracture and oedema
- Typical management
- Microfracture if small and contained
- MRI feature
- Detached osteochondral fragment, non-displaced
- Typical management
- Fixation, or microfracture if small
- MRI feature
- Displaced osteochondral fragment
- Typical management
- Fixation or removal, plus grafting
- MRI feature
- Subchondral cyst formation
- Typical management
- Grafting — OATS or allograft
Imaging workup. Weight-bearing AP, lateral and mortise radiographs assess alignment, loose bodies and gross architecture but miss small or posterior lesions (sensitivity approximately 50–60%). CT is essential for surgical planning — lesion size in three planes, subchondral plate integrity, cystic extent and shoulder containment — and decides anterior arthroscopy versus medial malleolar osteotomy. MRI is the gold standard for cartilage status, subchondral oedema volume and associated soft-tissue pathology: a stable cartilage rim greater than 2–3 mm around the defect is required for clot containment, and extensive oedema (greater than 50% of the talar body) predicts a poorer microfracture outcome. Key evidence. Microfracture produces fibrocartilage fill in 60–80% at second-look arthroscopy with good-to-excellent clinical scores in 70–85% at 2 years, but outcomes decline after 5 years — 30–50% of patients deteriorate by 10 years, especially those with lesions greater than 1 cm squared or athletes. Systematic review evidence (Zengerink 2010; Hannon 2013) shows microfracture and OATS are comparable on short-term clinical scores, but OATS demonstrates superior outcomes at longer-term follow-up for larger lesions — which underpins the size-based selection algorithm above.
References
Arthroscopic treatment of chronic osteochondral lesions of the talus: long-term results
- Long-term follow-up of patients after arthroscopic microfracture for OLT
- Good to excellent results in the majority at mean follow-up, but deterioration over time in a subset
- Lesion size greater than 1 cm squared and cystic lesions predicted poorer outcomes
Treatment of osteochondral lesions of the talus: a systematic review
- Systematic review of treatment strategies for osteochondral lesions of the talus
- Microfracture and bone marrow stimulation are effective for small contained lesions
- OATS and other grafting techniques showed better durability for larger lesions at mid-term follow-up
Microfracture for osteochondral lesions of the talus: a systematic review of reporting of outcome data
- Systematic review highlighting variability in outcome reporting for microfracture studies
- Clinical success rates vary but generally show good short-term results for small lesions
- A need for standardised outcome measures and longer follow-up was noted
Debridement, curettage and bone marrow stimulation: International Consensus Meeting on Cartilage Repair of the Ankle
- International consensus on bone marrow stimulation techniques for osteochondral talar defects
- Microfracture recommended as first-line for lesions less than 1.5 cm squared with an intact subchondral plate
- Subchondral bone quality and lesion containment are critical for success; adjuncts are considered for larger defects