Introduction. Mesenchymal stem cells (MSCs) are a potential source of cells for the repair of articular cartilage and osteochondral defects (OCD) in the ankle. Synovial tissue has been shown to be a rich source of MSCs with the ability to undergo chondrogenic differentiation. Although these cells represent a heterogenous population, clonal populations have not been previously studied. Methods. MSCs were isolated from synovial tissue of a patient undergoing joint arthroplasty and expanded in culture. Six clonal populations were also isolated and expanded. The cells from the mixed parent population and the derived clonal populations were characterised for stem cell surface epitopes, and then cultured in chondrogenic mediums. Various assays were determined to analyse for features of differentiation. Results. Cells from the mixed parent population and the derived clonal populations stained strongly for markers of adult mesenchymal stem cells including CD44, CD90 and CD105, and they were negative for the haematopoietic marker CD34 and for the neural and myogenic marker CD56. Interestingly, a variable number of cells were also positive for the pericyte marker 3G5 both in the mixed parent and clonal populations. The clonal populations exhibited a variable chondrogenic response. Conclusion. Pericytes are a candidate stem cell in many tissues and our results show that all six clonal populations derived from the heterogenous synovium population express the pericyte marker 3G5. The chondrogenic potential of synovial tissue could be optimised by the identification of clonal populations with a propensity to differentiate down particular differentiation pathways. Our study demonstrates a role for MSCs in of osteochondral defects (OCDs) and areas of focal cartilage damage in the ankle joint

We carried out 123 consecutive total ankle replacements in 111 patients with a mean follow-up of four years (2 to 8). Patients with a hindfoot deformity of up to 10° (group A, 91 ankles) were compared with those with a deformity of 11° to 30° (group B, 32 ankles). There were 18 failures (14.6%), with no significant difference in survival between groups A and B. The clinical outcome as measured by the post-operative American Orthopaedic Foot and Ankle Surgeons score was significantly better in group B (p = 0.036). There was no difference between the groups regarding the post-operative range of movement and complications. Correction of the hindfoot deformity was achieved to within 5° of neutral in 27 ankles (84%) of group B patients. However, gross instability was the most common mode of failure in group B. This was not adequately corrected by reconstruction of the lateral ligament.

Total ankle replacement can safely be performed in patients with a hindfoot deformity of up to 30°. The importance of adequate correction of alignment and instability is highlighted.