Total Ankle Replacement (TAR) is increasingly being offered to patients as an alternative to arthrodesis for the operative management of debilitating end-stage ankle arthritis. The Mobility Total Ankle System is a third-generation design consisting of a three component, cementless, unconstrained, mobile-bearing prosthesis. This study reports the early results of a multi-centre prospective study of the Mobility prosthesis. This is the first such report by independent researchers. The senior authors implanted 86 consecutive Mobility prostheses. The underlying diagnosis was primary OA in 24 ankles, secondary OA in 47 ankles and inflammatory arthritis in 15 ankles. There were 41 males (Mean age 67 / Range 51–87) and 44 females (Mean age 60 / Range 29–72). The mean BMI was 28 (Range 22–36) for males, and 28 (Range 20–39) for females. Previous ankle operations were performed in 24 patients, 22 of which were for fracture fixation. Ankles were classified according to the COFAS end-stage ankle arthritis classification system. Coronal plane deformity was quantified pre-operatively. Clinical outcome was assessed using the AOFAS hindfoot score. Radiological assessment was performed from weight-bearing radiographs, documenting post-operative alignment, osseous integration, edge-loading and heterotopic bone formation. The mean follow-up time was 40 months (Range 30–60). Survival analysis was calculated according to the Kaplan-Meier method. Failure was defined as exchange of any component of the TAR, arthrodesis or amputation.Purpose
Method
Magnetic resonance imaging has emerged as an important modality in the non-invasive evaluation of osseous and soft-tissue structures in the post-traumatic knee. However, it is sometimes radiologically impossible to determine with confidence if a focus of high signal intensity in the meniscus is confined to the substance of the meniscus or if it extends to involve the joint surface. This is a critical differentiation because the latter represents menisci tears that can be found and treated arthroscopically, whereas the former represents degradation, intrasubstance tears or perhaps normal variants that are not amenable to arthroscopic intervention. The aim of this study was to investigate the occurrence of altered signal intensity in the posterior horn of the medial meniscus in correlation with arthroscopic findings. Sixty-four patients with suspected post-traumatic internal derangement of the knee who underwent magnetic resonance imaging prior to arthroscopy were evaluated retrospectively. There were 48 males and 16 females. Mean age was 28.2 years. Tears of the posterior horn of the medial meniscus were diagnosed unequivocally (Grade 3 signal) in 18 patients and equivocally (Grade 2/3 signal) in 10 patients. Arthroscopic correlation revealed 16 tears (89%) in the unequivocal group and only one tear (10%) in the equivocal group). A meniscal tear is unlikely when magnetic resonance imaging shows a focus of high signal intensity in the posterior horn of the medial meniscus that does not unequivocally extend to involve the inferior or superior joint surface. An appropriate trial of non-operative treatment is recommended in such questionable cases. Magnetic resonance imaging is a useful diagnostic tool, however, it should be used selectively, and in conjunction with history and clinical examination in evaluating internal derangement of the knee.
