Background: Ankle fusion is considered a treatment of choice for end-stage ankle arthritis when a total ankle replacement procedure is not indicated. However, the potential risk of secondary arthritis in the adjacent joint after ankle fusion raises arguments on whether preserving the adjacent joint during an isolated tibiotalar (TT) fusion brings about any future benefits with regard to pain and gait discomfort. In this study, we intended to present midterm results following TT or tibiotalocalcaneal (TTC) fusion using an Ilizarov external fixator and to investigate whether spontaneous fusion occurred in the subtalar or midtarsal joint. Methods: This is a retrospective observational study. Medical records of patients who underwent TT or TTC fusion using an Ilizarov external fixator for substantial bone defects around the ankle joint between 1994 and 2018 were manually searched. Fortyone patients were included and the status of the joints adjacent to the fusion site was evaluated in radiographic examinations. Results: Of the 34 patients who underwent TT fusion, 30 patients (88.3%) had a spontaneous fusion in the adjacent joints. Specifically, 11 patients (29.4%) had subtalar joint fusion and 19 patients (55.9%) had both midtarsal joint and subtalar joint fusion. In TTC fusion, the midtarsal joint was spontaneously fused in all 7 patients. Conclusions In this study, we observed spontaneous adjacent joint fusion following TT or TTC fusion using an Ilizarov external fixator for substantial bone defects around the ankle joint. Although a careful approach should be made since patients treated in this study may not represent typical candidates that need primary joint-sacrificing procedures, we believe that this study may draw attention from surgeons concerned about the fate of the adjacent joint status after TT or TTC fusion.

BACKGROUND: After surgical repair of chronic rotator cuff tears, healing of the repaired tendons often fails and is accompanied by high-level fatty degeneration. Our purpose was to explore the effects of polydeoxyribonucleotide (PDRN) and polynucleotide (PN) on tendon healing and the reversal of fatty degeneration in a chronic rotator cuff tear model using a rat infraspinatus. METHODS: Sixty rats were randomly assigned to the following three groups (20 rats per group: 12 for histological evaluation and 8 for mechanical testing): saline + repair (SR), PDRN + repair (PR), and PN + repair (PNR). The right shoulder was used for experimental intervention, and the left served as a control. Four weeks after detaching the infraspinatus, the torn tendon was repaired. Saline, PDRN, and PN were applied to the repair sites. Histological evaluation was performed 3 and 6 weeks after repair and biomechanical analysis was performed at 6 weeks. RESULTS: Three weeks after repair, the PR and PNR groups had more CD168-stained cells than the SR group. The PR group showed a larger cross-sectional area (CSA) of muscle fibers than the SR and PNR groups. Six weeks after repair, the PR and PNR groups showed more adipose cells, less CD68-stained cells, and more parallel tendon collagen fibers than the SR group. The PR group had more CD 68-stained cells than the PNR group. The PR group showed a larger CSA than the SR group. The mean load-to-failure values of the PR and PNR groups were higher than that of the SR group, although these differences were not significant. CONCLUSION PDRN and PN may improve tendon healing and decrease fatty degeneration after cuff repair.