1. Osteochondral lesions of the talus (OLTs) are isolated cartilage and/or bone lesions that occur commonly on the central-medial or central-lateral aspect of the talar dome. They can occur as the result of a single acute ankle injury or from repetitive loading of the talus. 2. Medial talar lesions are more common than lateral lesions. Medial OLTs are thought to result from compression of the medial aspect of the talar dome against the tibia either acutely in the case of an ankle sprain with subluxation of the talus or from repetitive loading to the medial aspect of the ankle joint such as might occur in a varus hindfoot. Lateral lesions are less common. They are usually a result of an acute trauma, often from a shear injury as the talus subluxates out of the ankle joint. 3. Some OLTs will be seen on plain ankle x-rays. However, many will require MRI or CT scans to confirm the diagnosis. 4. Characteristics which are important in assessing an OLT include: the type of lesion (chondral, subchondral, cystic), the stability of the lesion, whether the lesion is displaced, the location, whether the lesion is contained or on the shoulder of the talar dome, and the size of the OLT. 5. Many OLTs are asymptomatic and many symptomatic OLTs can be effectively treated non-operatively provided that they are non-displaced. Displaced OLTs or lesions that have failed non-operative treatment may benefit from surgery. 6. Marrow stimulation of the OLT, usually via arthroscopic debridement and microfracture, has proven to be an effective treatment option for the majority of symptomatic talar OLTs. However, the reparative tissue that forms in response to the marrow stimulation is fibrocartilage rather than hyaline cartilage. 7. Osteochondral autografting has a rate of clinical success that appears equivalent to marrow stimulation. It is typically performed with cylindrical plugs of bone and cartilage most commonly harvested from the ipsilateral knee or talus. This technique offers the advantage of replacing the lost cartilage with real hyaline cartilage. However, disadvantages include a prolonged recovery time compared to marrow stimulation, the potential for donor site morbidity, and difficulty matching the graft to the contour of the talus. 8. Autologous Chondrocyte Implantation (ACI) offers the theoretical advantage of replacing the cartilage defect with the patient's own cartilage cells. However, to date there is insufficient evidence to fully assess the effectiveness of this technique.
"In cases of osteochondral lesions of the talus, there are several ways to reconstruct the hyaline cartilage after osteochondral debridement, that is, autologous chondrocyte implantation (ACI), mesenchymal stem cell implantation and osteochondral graft [4, 23, 29]. For ACI, chondrocytes are first collected and then cultured for cell proliferation. "
[Show abstract][Hide abstract] ABSTRACT: Purpose:
This study assessed the clinical results and second-look arthroscopy after fibrin matrix-mixed gel-type autologous chondrocyte implantation to treat osteochondral lesions of the talus.
Chondrocytes were harvested from the cuboid surface of the calcaneus in 38 patients and cultured, and gel-type autologous chondrocyte implantation was performed with or without medial malleolar osteotomy. Preoperative American orthopedic foot and ankle society ankle-hind foot scores, visual analogue score, Hannover scoring system and subjective satisfaction were investigated, and the comparison of arthroscopic results (36/38, 94.7 %) and MRI investigation of chondral recovery was performed. Direct tenderness and relationship to the active daily life of the donor site was evaluated.
The preoperative mean ankle-hind foot scores (71 ± 14) and Hannover scoring system (65 ± 10) had increased to 91 ± 12 and 93 ± 14, respectively, at 24-month follow-up (p < 0.0001), and the preoperative visual analogue score of 58 mm had decreased to 21 mm (p < 0.0001). Regarding subjective satisfaction, 34 cases (89.5 %) reported excellent, good or fair. Chondral regeneration was analysed by second-look arthroscopy and MRI. Complications included one non-union and two delayed-unions of the osteotomy sites, and 9 ankles (9/31, 29.0 %) sustained damaged medial malleolar cartilage due to osteotomy. Marked symptoms at the biopsy site did not adversely affect the patient's active daily life.
Fibrin matrix-mixed gel-type autologous chondrocyte implantation using the cuboid surface of the calcaneus as a donor can be used for treating osteochondral lesions of the talus.
"The osteochondral autograft transfer (OATS) procedure is commonly used for resurfacing articular cartilage defects [22, 25, 38, 39]. In OATS, the lateral and medial trochlea [15, 16], femoral condyles [12, 13], as well as the intercondylar notch  are common harvesting sites. "
[Show abstract][Hide abstract] ABSTRACT: It is unknown what causes donor site morbidity following the osteochondral autograft transfer procedure or how donor sites heal. Contact pressure and edge loading at donor sites may play a role in the healing process. It was hypothesized that an artificially created osteochondral defect in a weightbearing area of an ovine femoral condyle will cause osseous bridging of the defect from the upper edges, resulting in incomplete and irregular repair of the subchondral bone plate.
To simulate edge loading, large osteochondral defects were created in the most unfavourable weightbearing area of 24 ovine femoral condyles. After killing at 3 and 6 months, osteochondral defects were histologically and histomorphometrically evaluated with specific attention to subchondral bone healing and subchondral bone plate restoration.
Osteochondral defect healing showed progressive osseous defect bridging by sclerotic circumferential bone apposition. Unfilled area decreased significantly from 3 to 6 months (P = 0.004), whereas bone content increased (n.s.). Complete but irregular subchondral bone plate restoration occurred in ten animals. In fourteen animals, an incomplete subchondral bone plate was found. Further common findings included cavitary lesion formation, degenerative cartilage changes and cartilage and subchondral bone collapse.
Osteochondral defect healing starts with subchondral bone plate restoration. However, after 6 months, incomplete or irregular subchondral bone plate restoration and subsequent failure of osteochondral defect closure is common. Graft harvesting in the osteochondral autograft transfer procedure must be viewed critically, as similar changes are also present in humans.
Prognostic study, Level III.
[Show abstract][Hide abstract] ABSTRACT: Conventional time-frequency analysis methods are generally too computationally intensive for real-time implementation. A relatively new method based on a dynamic state-space model is inherently a real-time method and can be implemented in parallel processing. It has O(n) computational complexity per signal sample, where n is the number of frequencies in the analysis. Its offered concurrency allows only sublinear speedup with parallel digital implementations, but linear speedup with a partially analog implementation
Acoustics, Speech, and Signal Processing, 1988. ICASSP-88., 1988 International Conference on 01/1989; DOI:10.1109/ICASSP.1989.266909 · 4.63 Impact Factor
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