Medial malleolar osteotomy for the treatment of talar osteochondral lesions: anatomical and morbidity considerations.

PURPOSE: Osteochondral lesions of the talus are often located posteromedially requiring open surgery to facilitate solid and complete osteochondral reconstruction. The aim of the study was to identify the optimal anatomical site for medial malleolar osteotomy based on the criteria of minimal cartilage damage (Study I) and to report on the morbidity in patients receiving osteotomy performed at the previously identified site (Study II). METHODS: For Study I, cartilage coverage of the tibiofibular ankle joint facet was measured in 40 cadaveric ankles (20 cadaver specimens). In Study II, we assessed clinical (VAS pain score, AOFAS score, range of motion) and radiological outcome measures (SPECT-CT) in 17 patients (mean age, 36.8 ± 10.8 years) undergoing medial malleolar osteotomy. RESULTS: The medial edge in the transition zone of the tibial plafond to the medial malleolus showed less than 75 % of cartilage coverage in 62.5 % of cadavers (Study I). Surgery resulted in lower pain levels (2.4 ± 2.6 compared with 6.3 ± 1.8 points; p < 0.001) and greater AOFAS scores (82.9 ± 14.1 compared with 43.5 ± 10.8 to points; p < 0.001) compared with baseline (Study II). No signs of intra-operative damage or mal- or non-union were found. Long-term morbidity was found in one patient. Implant removal was necessary in 12 of 17 patients (71 %). CONCLUSION: Anatomically, there is an optimal location for the medial malleolar osteotomy at the medial ankle edge involving minimal cartilage damage. Clinical results using this location showed no short- or mid-term morbidity and little long-term morbidity. However, many patients required re-intervention for implant removal. LEVEL OF EVIDENCE: IV.

Histomorphometric, CT arthrographic, and biomechanical mapping of the human ankle.

BACKGROUND: The specific morphological and biomechanical characteristics of the osteochondral unit of the ankle joint are not yet fully understood. This anatomical study aimed to map regional thickness of the articular hyaline uncalcified cartilage and its adjacent layers of mineralized cartilage and subchondral bone as well as to measure the regional indentation stiffness of human ankle joint cartilage. MATERIALS AND METHODS: A total of 20 pairs of human cadaver ankle joints (median age: 78 years) were evaluated by histomorphometry and multidetector row double-contrast CT arthrography for cartilage thickness in 17 distinct anatomical regions. In addition, regional distribution of the subchondral bone plate and of the mineralized cartilage was scrutinized histologically. Cartilage indentation stiffness was measured using an arthroscopic handheld device (Artscan200), especially validated for use in thin cartilage. The correlation between the thickness of different components of the osteochondral unit and the cartilage indentation stiffness was evaluated. RESULTS: The thinnest uncalcified cartilage was measured at the anterior talar dome and the distal fibula. The thickest uncalcified cartilage was found in the mid and posterior talar dome, as well as in the tibial plafond. Mineralized cartilage and subchondral bone showed highest values at the anteromedial talar dome. Cartilage indentation stiffness showed a bicentric distribution pattern in 14/20 ankle pairs and was highest in regions with thin cartilage. Positive correlation between the thickness of the mineralized cartilage and the subchondral bone plate was found. No correlation between the thickness of the uncalcified and the mineralized cartilage could be identified. CONCLUSION: This anatomical study provides a comprehensive mapping of the osteochondral unit of the human ankle joint in elderly people. Articular hyaline uncalcified cartilage and the subchondral bone plate showed clear regional differences and were reciprocally distributed. Cartilage indentation stiffness was inversely correlated to cartilage thickness in elderly people. CLINICAL RELEVANCE: Thorough understanding of the osteochondral unit of the ankle joint could be helpful for clinicians and researchers in the development of improved operative repair techniques for osteochondral defects in the ankle joint, for example, in constructing specific tissue-engineered osteochondral plugs.

Autologous matrix-induced chondrogenesis aided reconstruction of a large focal osteochondral lesion of the talus.

The aim of this case report is to describe a novel technique for treatment of large osteochondral lesions of the talus using autologous matrix-induced chondrogenesis with a collagen I/III membrane.

Differentiation of osteoblasts in three-dimensional culture in processed cancellous bone matrix: quantitative analysis of gene expression based on real-time reverse transcription-polymerase chain reaction.

Processed bovine cancellous bone (PBCB) is an attractive material for tissue engineering of bone. It is biocompatible, osteoconductive, nonimmunogenic, and porous and its biomechanical properties are close to those of native bone. In this study, differentiation of primary rat osteoblasts (rOBs) incubated on PBCB was investigated in vitro. rOBs were isolated and expanded in two-dimensional culture. Expanded rOBs were seeded into PBCB disks and cultured either in basal medium (BM) or differentiation medium (DM) containing ascorbic acid, beta-glycerol phosphate, and dexamethasone. Alkaline phosphatase (ALP) activity and RNA expression of ALP, bone sialoprotein (BSP), collagen type I (COL1), osteocalcin (OC), and osteopontin (OPN) were assessed by chemiluminescence assay and quantitative real-time RT-PCR over 14 days. Histologic analysis was performed on day 14. ALP increased over the observation period independent of stimulation. OPN and BSP expression was significantly higher in the DM group whereas COL1 and OC expression was significantly higher in the BM group. Matrix calcification was detectable only in the DM group by von Kossa stain. The observed expression patterns suggest a physiological response of rOBs to the differentiation stimulus. PBCB is a suitable matrix for in vitro differentiation of osteoblasts. Cell-seeded PBCB is a potential osteogenic construct for in vivo application.