[The clinical efficacy of treatment on the cases of severe hallux valgus by the first metatarsal basal osteotomy combined with Chevron-Gerbert operation].

OBJECTIVE: To evaluate the clinical efficacy of treatment on the cases of severe hallux valgus by the first metatarsal basal osteotomy combined with Chevron-Gerbert operation. METHODS: From June 2004 to August 2008, 37 cases of severe hallux valgus (66 feet) underwent first metatarsal basal osteotomy combined with Chevron-Gerbert operation. There were 5 males (10 feet) and 21 females (38 feet), aged 21 - 76 years (mean 58 years). For all patients with follow-up, radiographic measurements of frontal and lateral position of foot were taken to measure the hallux valgus angle (HVA), the IMA (intermetatarsal angle) and the proximal articular set angle (PASA) preoperatively, postoperatively and in follow-up respectively. The measuring results were compared among the preoperative, the 6-week postoperative and the final follow-up. At the same time the patients were evaluated with the AOFAS Maryland score. RESULTS: Of the original 37 patients, 26 patients (48 feet) were followed up. The mean durations of follow-up was 2.3 years (range from 1 to 4 years). At final follow-up, HVA corrected 25.6° ± 3.8°, IMA corrected 8.6° ± 2.4°, and PASA corrected 4.7° ± 4.2°. According to AOFAS rating system, 91.7% patients were rated as excellent or good with excellent in 15 patients (28 feet), good in 8 patients (16 feet), and fair in 3 patients (4 feet). CONCLUSIONS: First metatarsal basal osteotomy combined with Chevron-Gerbert operation has good efficacy to the patients with severe hallux valgus. However there are disadvantages such as complexity relatively for multi-stage osteotomy and internal fixation.

S-band optical amplification by an internally generated pump in thulium ytterbium codoped fiber.

We propose a novel scheme in which Yb3+ codoping and a laser cavity are introduced in Tm3+ doped fiber to achieve efficient S-band optical amplification with a 980 nm pump source. This scheme makes it possible for conventional 980 nm pump sources for Er3+ doped fiber amplifiers to be used for S-band Tm3+ doped fiber amplifiers (TDFAs). By introducing a laser cavity into an amplifier, an internally generated pump from Yb3+ at a desirable wavelength for pumping Tm3+ could be produced. We establish and analyze, for the first time to our knowledge, a new theoretical model that takes into consideration both the internal lasing operation inside the optical amplification process and the energy transfer between the Tm3+ and the Yb3+ ions in TDFAs. Various situations such as Tm3+ doping concentration and cavity reflectivity have been investigated. The results show that high optical gain and high pump efficiency can be achieved by use of 980 nm sources. With a laser cavity of 1050 nm in Tm3+ and Yb3+ codoped fiber, for example, it is possible to achieve high optical gain of greater than 20 dB, a noise figure of approximately 5 dB in the wavelength range from 1450 to 1480 nm with a 0.3 W power at 980 nm pump source.