Healing of full-thickness articular cartilage defects treated with cultured autologous chondrogenic satellite cells isolated from chondral stem cell niche in rabbits.

BACKGROUND: Healing of articular cartilage has remained in question with the use of conventional treatment modalities such as subchondral drilling and microfracture. As demonstrated in the past, adult stem cells retain promising clonogenicity. Therefore, we conducted this study to elucidate the effects of cultured autologous chondrogenic satellite cells (CACSCs) compared with subchondral drilling (SCD) for the repair of full-thickness articular cartilage defects. MATERIALS AND METHODS: We examined CACSCs isolated from the knee of rabbits using flow cytometry for the expression of stemness and chondrocyte-specific factors. Subsequently, we created a full-thickness cartilage defect model with a diameter of 3 mm and depth of 2 mm on the articular surface of trochlear grooves in the left knee of 24 New Zealand white rabbits. Then we drilled subchondrally through the defect in all animals and stuffed the defects with 10-µg/cm(2) collagen scaffolds. In the treatment group, we instilled CACSCs at 5 × 10(6) cells/mL in the collagen scaffold and collected samples on days 15, 30, and 45. RESULTS: The CACSCs revealed significant expression of CD106, CD44, collagen type 2, and aggrecan. In conjunction with SCD, CACSCs improved healing of the articular cartilage defect, as evidenced by the formation of hyaline-like tissue grossly and histologically. The healed tissue also revealed a significant (P < 0.05) increase in the expression of collagen type 2 and aggrecan (by real-time polymerase chain reaction) during the experiment. CONCLUSIONS: In conjunction with SCD, CACSCs may be considered to improve articular cartilage damage.

Management of tibial fractures using a circular external fixator in two calves.

OBJECTIVES: To report the repair of tibial diaphyseal fractures in 2 calves using a circular external skeletal fixator (CEF). STUDY DESIGN: Clinical report. ANIMALS: Crossbred calves (n=2; age: 6 months; weight: 55 and 60 kg). METHODS: Mid-diaphyseal tibial fractures were repaired by the use of a 4-ring CEF (made of aluminum rings with 2 mm K-wires) alone in 1 calf and in combination with hemicerclage wiring in 1 calf. RESULTS: Both calves had good weight bearing with moderate lameness postoperatively. Fracture healing occurred by day 60 in 1 calf and by day 30 in calf 2. The CEF was well maintained and tolerated by both calves through fracture healing. Joint mobility and limb usage improved gradually after CEF removal. CONCLUSIONS: CEF provided a stable fixation of tibial fractures and healing within 60 days and functional recovery within 90 days. CLINICAL RELEVANCE: CEF can be safely and successfully used for the management of selected tibial fractures in calves.

In vitro biomechanical properties of linear, circular, and hybrid external skeletal fixation devices for use in large ruminants.

OBJECTIVE: To report the biomechanical properties of 3 external skeletal fixation (ESF) devices for use in large ruminants. STUDY DESIGN: In vitro biomechanical testing of ESF constructs. SAMPLE POPULATION: Adult buffalo (weighing, 250-350 kg) tibiae (n=27). METHODS: ESF constructs (bilateral linear fixator [BLF], 4-ring circular external fixator [CEF], and hybrid fixator [HF]) were made using mild (low carbon) steel implants plated with nickel and cadaveric buffalo tibiae. After ESF application, a 1 cm mid-diaphyseal gap was created. Constructs were loaded to failure, on a materials testing machine, in axial compression (n=5/ESF type) and craniocaudal bending (n=3/ESF type). In addition, 3 CEF constructs were tested in intact tibiae under craniocaudal bending. RESULT: In compression, HF was the strongest and most rigid construct; yield load was significantly higher for HF than for BLF or CEF. Under bending, both CEF and HF had similar strength and modulus of elasticity. Strength for BLF was higher than CEF and HF, whereas the reverse was true for modulus of elasticity. CONCLUSIONS: ESF made from mild steel for use in large ruminants could withstand

Evaluation of two dynamic axial fixators for large ruminants.

OBJECTIVES: To evaluate healing of a radial osteotomy repaired by application of dynamic axial fixation devices (DAF) in large ruminants. STUDY DESIGN: In vivo study of bone healing after application of 2 DAF types. Model I had 2 sidebars, each with a central cylindrical cuff (internally threaded) with 2 detachable connecting rods telescoping within the cuff. Model II had 2 side bars with 2 moveable clamps with multiple holes. SAMPLE POPULATION: Bull calves (n=8; aged, 1.5-2.0 years; weighing, 175-250 kg). METHODS: A mid-diaphyseal radial osteotomy was repaired by use of a model I (n=4) or model II (n=4) DAF. Calves were monitored for weight bearing, stability of fixation, and radiographically for fracture reduction, alignment and healing at intervals for 6 months. Fixators were removed when there was radiographic evidence of healing. RESULTS: Both the fixators were well tolerated with free movement of adjacent joints. Fragment fixation was maintained until healing in all but 1 model I calf where failure occurred within 7 days. Model II DAF provided more rigid fixation as indicated by early full weight bearing and fracture healing with less callus formation. Functional recovery of repaired limbs occurred within 60 days in surviving calves. CONCLUSIONS: Both bilateral DAFs were easy to apply; however, the model II DAF provided better fixation. CLINICAL RELEVANCE: The model II DAF made of low carbon steel was economical and may be useful for treating long bone fractures in large ruminants.