Osteochondral Lesion of the Talus

Introduction

Osteochondral lesion of the talus is a common condition associated with ankle injury. Symptoms may be nonspecific including pain, swelling, stiffness and mechanical symptoms of locking and catching. Acute osteochondral injuries mostly result  from ankle sprains. Clinical examination may only reveal a diffuse swelling and painful range of motion.

All lateral lesions are considered to have a history of trauma, while only 64% of medial lesions are reported to be traumatic. Medial lesions are usually deeper and more likely to change into cystic lesions, while lateral lesions are shallower and more likely to have an associated wafer or flake fracture. 

Historically lesion position was considered to be anterolateral or posteromedial; however a recent analysis of 428 ankle MRIs with known OCDs showed 53% of lesions medial and middle, and 26% lateral and middle. The vast majority of lesions were in the middle (80%), with relatively fewer anterior or posterior (6% and 14%, respectively).

 

Imaging

Imaging includes plain ankle radiographs (AP, lateral and mortise views) on which the most common finding is the presence of poorly defined radiolucent area in the affected talar dome. The low sensitivity of plain radiographs (41%) often warrants further imaging.

Verhagen et al. reported that CT was 81% sensitive and 99% specific for the diagnosis of OCDs; however CT is limited in providing information on the quality of the articular cartilage; but it is helpful in assessment of bone changes associated with injury, size, location and displacement of the lesion. SPECT adds to the diagnostic value of CT by identifying co-existing pathology as well as showing the activity around the lesion of interest. 

MRI is considered the gold-standard imaging for OCDs of the ankle as it provides assessment of articular cartilage, presence of subchondral inflammatory changes and the depth of the chondral lesion. Studies have shown that MRI is 96% sensitive and 96% specific for the diagnosis of OCDs and is able to accurately predict stability of the lesion.

 

Classification

Brendt and Harty classification is considered to be the most widespread classification for osteochondral lesions of the talus and has four stages (Radiographic classification):

Stage I – small focal subchondral compression

Stage II – partially detached fragment

Stage III – completely detached but undisplaced fragment

Stage IV – completely detached and displaced fragment

Stage V – (added by Scranton and McDermott, 2001) – osteochondral cysts just below the damaged articular surface

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Hepple et al. described an MRI-based classification system:

Stage 1 - Articular cartilage damage only

Stage 2a - Cartilage injury with underlying fracture and surrounding bony oedema

Stage 2b - Stage 2a without surrounding bony oedema

Stage 3 - Detached but nondisplaced fragment

Stage 4 - Detached and displaced fragment

Stage 5 - Subchondral cyst formation

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Mintz et al. combined arthroscopic findings with MRI findings:

Stage 0 – normal cartilage

Stage 1 – hypersignal cartilage on MRI, but normal arthroscopic appearance

Stage 2 – fibrillation and cracks that do not reach the bone

Stage 3 – presence of cartilage flap, with exposure of the subchondral bone

Stage 4 – loose fragment, non-diverted

Stage 5 – diverted fragment​

 

Treatment

​Only symptomatic lesions require treatment. Incidental findings may require follow up depending on patient’s age and level of physical activities.

The natural history of the OCDs remains unclear due to paucity of longitudinal follow-up studies.

 

Conservative Treatment

The purpose of conservative treatment is to offload the injured cartilage, resolve the bone oedema, prevent necrosis and to allow the detached fragment to heal to the underlying and surrounding bone. Options include activity modification, immobilisation in acute phase with or without the use of NSAIDs for 3-4 weeks, progressive weight bearing in a walker boot with physical therapy for 6-10 weeks, orthotics and intra-articular injections of steroids. PRP injections are also used in clinical practice but require further evaluation for long-term effects.​

The results of these modalities are unpredictable and may benefit only less than half of the patients. Based on current literature, there is no specific conclusion regarding duration of non-operative treatment, method of immobilisation, weight bearing status, the use of NSAIDs, and physical therapy protocol. Recently, meta-analysis by Tol et al. demonstrated that the overall good/excellent results were 45% (91/201 patients) patients with OCDs and were treated by conservative management; however, the truly successful rate of conservative treatment remains debatable. Few studies report that arthritis of the ankle joint has been observed in approximately 50%  patients who were treated with conservative treatment. McCullough et al. studied a small case series (n = 10) with an average follow-up of 15 years  and found that OCD lesions may not heal over many years, but ankle joint were relatively asymptomatic and arthrosis was minimal. 

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Surgical Treatment

There are numerous surgical treatment strategies available, with a substantial increase in the number of procedures over the past decades. Options include excision, excision with curettage, excision with curette and drilling/microfracture, excision with curette and autogenous grafting, excision with curetted and particulated juvenile cartilage, retrograde drilling, autogenous chondrocyte implantation, osteochondral autograft transplantation and osteochondral allograft transplantation.​

In acute cases, after establishing appropriate diagnosis, patient should be treated with urgent arthroscopy and, when feasible, the fragments should be reduced and fixed (absorbable headless screws) to their anatomical location. Smaller or devitalized fragments are resected, and the base of the lesion is treated by stimulating the bone marrow.

For primary talar OCDs, bone marrow stimulation is the most frequently performed treatment. This technique has shown good clinical results at short-term and mid-term follow-up. The most recent available evidence suggests that the outcome of a combined excision of osteochondral fragments, curettage of the affected area, and microfracture treatment resulted in successful outcome in 85% cases, combined excision of fragments and curettage resulted in good outcome in 77% cases and excision of fragments alone in good results in 32% cases.

In a recent RCT, the result of microfractures were found to be better by adding hyaluronate intra-articular injection immediately after surgery, with improved function and pain results when compared to patients who did not receive this injection; however these results highlight a limited number of patients in this trial and require further and stronger evidence.

A recently published level IV evidence with an average follow up of 121 months showed an improvement in mean pre-operative AOFAS score of 58.7 to the mean post-operative AOFAS score of 85.5 with excellent symptomatic improvement in 65% patients. Although the technique is widely used with reasonably predictable short-term results but gives concerns since this fibrocartilage shows decrease in quality over time with a possible increase in osteoarthritic changes (in up to 1/3rd patients).​

Beacher et al. studied in 45 patients with arthroscopic debridement and microfracture with improvement of functional outcomes and pain scores at an average follow-up of 5.8 years. 

Chuckpaiwong et al. studied 105 patients with anterior ankle arthroscopic debridement and microfracture and reported that microfracture technique demonstrated significant improvement of functional outcomes (VAS and AOFAS) at 12 months follow-up.

Recently, a prospective study reported on a promising novel technique of minimally invasive arthroscopic internal fixation, the lift, drill, fill and fix (LDFF) procedure. This is recommended for arthroscopic fixation of primary lesions larger than 1cm2. Although the technique showed highly promising clinical and radiological short-term results with high fusion rates, but the study was limited by smaller number of patients (27 ankles, median age 17 years; range 11 to 63 years, and median follow-up of 27 months; range 18 to 43 months).

With regards to fixation of the fragment, one of the largest series has been reported by Kumai et al. with 27 patients and mean follow-up of 7 years, reporting 89% with good outcomes. Chandran et al. reported excellent results after fixation of inverted lesions using three absorbable pins. Schepers et al. also reported successful treatment of inverted lesions with the internal fixation with bioabsorbable pins.

Retrograde drilling with radiographic control is considered to be an effective treatment option for osteochondral lesions of the intact joint cartilage. Under fluoroscopic guidance and during arthroscopy, a guidewire is passed to the affected area restricting it under the articular surface, and then a cannulated drill is used. Through this tunnel, it is also possible to place the bone graft to fill the lesion. Alexander et al. reported 89% patients (16/18) with good/excellent long-term outcomes with an average follow-up of 58 months. Kono et al. also demonstrated that this technique yielded significant improvement in AOFAS scores. Ander et al. reported significant pain relief at 29-months post-operatively along with  subjective functional improvement.

A recently published level III evidence comparing microfractures with arthroscopic retrograde drilling did not show any significant differences between the two groups in terms of the AOFAS scores, VAS, and AAS.

The osteochondral autologous grafting (OAT) or mosaicplasty involves obtaining cylindrical cartilage and bone grafts, most commonly harvested from the non-weight-bearing surface of lateral femoral condyle, and transferring them to areas of osteochondral lesion in the loading surface of the talar dome. This is technically challenging and requires expertise and accuracy in order to achieve optimum results. The indications comprise of lesions larger than 1.5 cm2, recurrent or refractory to more conservative treatment methods, and lesions associated with subchondral cysts. The early results are superior to the combination of debridement and microfractures.

For lesions greater than 3 cm2, and especially affect the shoulder of the talus, fresh cadaver allograft, with viable chondrocytes and normal subchondral bone, appears as an interesting option. However, the implantation should be carried out within 2 weeks of obtaining the graft as the number of viable chondrocytes deteriorates with time. Scranton et al. reported 90% patients (45 of 50 patients) having good/excellent results and satisfied with the surgery with mean average of follow-up of 36 months.

​Autologous chondrocyte implantation (ACI) is indicated in recurrent osteochondral lesions of any size and primary treatment of larger lesions than 2.5 cm2 with or without subchondral cysts in patients aged between 15 and 55 years, without degenerative arthritis or mirror-image osteochondral lesions, and without instability or changes in joint alignment. Whittaker et al. studied 9 patients with an average of 23 months follow-up with mean improvement of the Mazur ankle score of 23 points with minor morbidity at the donor site. Baums et al. studied 12 patients with mean follow-up of 63 months reporting noticeable improvement of AOFAS score. Giannini et al. performed ACI on 46 patients and reported improvement in AOFAS score with an average follow-up of 18 months.

The second generation of ACI treatment involves the use of collagen membranes for carrying the cells, matrix-induced autologous chondrocyte implantation (MACI), which eliminates the need for obtaining the periosteum and all the difficulties and complications inherent to this period of the operation, and the results obtained are encouraging. Ander et al. reported their result with MACI in 22 patients and reported a significant improvement in AOFAS scores at a mean follow-up of 63.5 months.

An International Consensus Meeting on Cartilage Repair of the Ankle (Pittsburgh, Nov 2017) showed that there was a strong consensus that if possible the fragment should be fixed with two devices with at least one being used for compression and the other to prevent rotation. However it was also acknowledged that fragments may be small and fragile, and double fixation will not always be possible without compromising the stability of the fragment.

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Prognostic Factors

There have been multiple studies addressing different patient factors and lesion characteristics that may yield the likely outcomes. Lesions smaller than 1.5cm, contained lesions and anterolateral lesions are considered to be the positive prognostic indicators. Negative indicators include older age (> 33-40 years), lesions deeper than 7 mm, lesions larger than 1.5cm, cystic lesions, medial talar lesions, higher BMI, history of trauma, longer duration of symptom and presence of osteophytes.

 

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