Carrier-envelope offset frequency dynamics of a 10-GHz modelocked laser based on cascaded quadratic nonlinearities.

Cascaded quadratic nonlinearities from phase-mismatched second-harmonic generation build the foundation for robust soliton modelocking in straight-cavity laser configurations by providing a tunable and self-defocusing nonlinearity. The frequency dependence of the loss-related part of the corresponding nonlinear response function causes a power-dependent self-frequency shift (SFS). In this paper, we develop a simple analytical model for the SFS-induced changes on the carrier-envelope offset frequency (fCEO) and experimentally investigate the static and dynamic fCEO dependence on pump power. We find good agreement with the measured dependence of fCEO on laser output power, showing a broad fCEO tuning capability from zero up to the pulse repetition rate. Moreover, we stabilize the relative intensity noise to the -157 dBc/Hz level leading to a tenfold reduction in fCEO-linewidth.

High-speed interband cascade infrared photodetectors: photo-response saturation by a femtosecond oscillator.

Interband cascade infrared photodetectors (ICIPs) combine interband optical transitions with fast intraband transport to achieve high-frequency and broad-wavelength operation at room temperature. Here we study the bias-dependent electronic impulse response of ICIPs with a mid-infrared synchronously pumped optical parametric oscillator (OPO). Since the OPO produces ultrashort 104-fs pulses, it is possible to probe the impulse response of the ICIP. From this impulse response, we identify two characteristic decay times, indicating the contribution of electron as well as hole carriers. A reverse bias voltage applied to the ICIP reduces both time scales and leads to an increased electrical cut-off frequency. The OPO emits up to 500 mW average power, of which up to 10 mW is directed to the ICIP in order to test its saturation characteristics under short-pulse illumination. The peak of the impulse response profile as well as the average photocurrent experience a gradual saturation behavior, and we determine the corresponding saturation powers by measuring the photo-response as a function of average power directed to the ICIP. We demonstrate that an increasing reverse bias increases the saturation power as well as the responsivity of the ICIP.

Modified Ertl osteomyoplasty for terminal overgrowth in childhood limb deficiencies.

Terminal overgrowth continues to be a problem in children with amputations. Many operative treatment methods have been proposed, but no consensus has been reached regarding the procedure of choice. Six patients underwent a modified Ertl procedure for the treatment of terminal overgrowth in seven residual lower limbs (one bilateral). All these patients were skeletally immature. The average age at index procedure was 5 years 9 months (range, 1 year 3 months-6 years 11 months). Revision was necessary in four patients, with one patient requiring two revisions of the same limb. The modified Ertl osteomyoplasty can be performed safely in children, but appositional overgrowth may continue through the tibiofibular synostosis. The procedure is not recommended in skeletally immature patients.

Anatomy of a duplicated human foot from a limb with fibular dimelia.

At birth, a patient presented with a right lower limb featuring preaxial polydactyly and fibular dimelia with a complete absence of the tibia. Radiographic studies of the patient's foot revealed a duplicated tarsus with eight metatarsals and toes. The three preaxial toes were surgically removed at 1 year of age. A hallux and four normal-appearing postaxial toes remained. The foot was amputated when the patient was 3 years old. Dissection of the amputated foot revealed that the muscles of the dorsum were normal, except that the tendon of the extensor hallucis brevis muscle inserted into both the hallux and toe 2, rather than only into the hallux. The few abnormalities observed among the muscles on the plantar surface of the foot included absence of the insertions of the tibialis posterior and the abductor hallucis muscles. In addition, the two heads of the adductor hallucis muscle inserted abnormally into the medial (tibial) side of metatarsal 1, rather than into the lateral side. These various muscular anomalies, in addition to the mirror duplication of the foot with the presence of only a single metatarsal 1, leads us to propose that this metatarsal probably represents two lateral (fibular) halves that form a laterally duplicated bone. Although the dorsalis pedis artery was present on the dorsal surface of the foot, most of its derivatives were absent. This artery did give rise to a supernumerary medial branch that ended abruptly in the connective tissue (presumably postsurgical scar) at the medial border of the foot. This branch may have represented a duplicated dorsalis pedis artery associated with the duplicated preaxial portion of the foot. The arteries on the plantar surface of the foot were normal. Even though some anomalies in the pattern of the cutaneous innervation were observed, the nerves of the foot were largely normal. The gross and radiographic anatomy of this specimen and the radiographic anatomy of the leg suggest that some teratogenic event occurred when developmental specification reached the level of the future knee. The teratogenic event, which probably occurred early in the fifth week of development, may have caused damage that led to a lateral duplication of both the leg and the foot with the absence of some of the most medial structures. Teratology 60:272-282, 1999.

Fibular dimelia with deficiency of the tibia.

Longitudinal deficiency of the tibia associated with fibular dimelia is a very rare condition. We report our experience with six patients and outline management of this anomaly. Knee disarticulation is advised in cases with an associated normal femur, and femorofibular fusion is advised in cases of associated ipsilateral proximal focal femoral deficiency (PFFD) or congenital short femur. Fibulocalcaneal fusion and Boyd type amputation provide good end-bearing stumps.

Myoelectric and body-powered prostheses.

One hundred twenty below-elbow child amputees compared cosmetically identical myoelectric (MYO) and body-powered (BP) hands after wearing each for 3 months; 78% chose the MYO and 22% chose the BP. However, at 2-year follow-up, only 44% wore the MYO, 33% used a BP hand or hook, and 23% became nonwearers (NW). Eighty percent of children aged > or = 8 years used active prosthetic prehension for both the MYO and BP prostheses. Comparatively, only 30% aged < 8 years and 0% aged < 5 years demonstrated any active prosthetic prehension. Active BP wearers were clearly most pleased with the features of their prostheses.

Failure of centralization of the fibula for congenital longitudinal deficiency of the tibia.

Between 1962 and 1983, fourteen patients (twenty knees) had centralization of the fibula for congenital longitudinal deficiency: tibial, complete. Eleven of the twenty index procedures were performed on patients who were one year old or less. A progressive flexion deformity of the knee developed after all twenty index procedures. Twenty-six secondary procedures were needed, including disarticulation at the knee, posterior release, extension osteotomy, femorofibular arthrodesis, and biceps-to-quadriceps transfer, and one patient had a second attempt at centralization of the fibula. The duration of follow-up after the initial centralization of the fibula ranged from four years to twenty-two years and seven months (average, twelve years and four months). Seven patients (eight limbs) in whom the index procedure resulted in failure had a satisfactory result after disarticulation at the knee. The patients who did not have secondary disarticulation at the knee are also considered to have had a failed index procedure because they had a flexion deformity at the latest follow-up. Attempts to reconstruct the knee joint by centralization of the fibula are not warranted for patients who have congenital longitudinal deficiency: tibial, complete. Early disarticulation at the knee and fitting with a prosthesis, with close follow-up, is the treatment of choice.

Fibula dimelia in association with ipsilateral proximal focal femoral deficiency, tibial deficiency, and polydactyly. A case report.

A 16-year-old girl with bilateral tibial deficiency, left fibula dimelia, left proximal focal femoral deficiency, polydactyly, and congenital heart disease is now ambulatory and able to attend public school. This combination of anomalies has been overcome by cardiac surgery followed by Boyd-type amputation, prosthetic restoration, and therapy. The shortened left distal femur was lengthened by implanting both amputation fibulae proximally. In the same surgery, the amputation os calcis was fused distally to these fibulae. The right fibula was disarticulated at the knee. The female patient was fitted with bilateral knee disarticulation prostheses. She became fully ambulatory with a walker, progressing to bilateral forearm crutches. Recurrent deformity at the fusion site of the left femoral segment to the fibulae required a subsequent wedge osteotomy and multiple surgeries during the years following. Today she remains ambulatory with the use of nonaxillary crutches, attends public school, and is without pain. She takes part in athletics within the range of her abilities and hopes to obtain a driver's license and use a modified car. She is independent and well adjusted. Her progress has been followed from the age of 11-and-one-half months to present.

Stubby prostheses in the rehabilitation of infants and small children with bilateral lower limb deficiencies.

Stubby prostheses have been used in the habilitation of very small children with bilateral lower limb deficiencies, particularly bilateral above knee limb deficiencies. While we reported on "The Use of Stubbies For the Child with Bilateral Lower Limb Deficiencies" in 1973, the literature has very little except in relation to the geriatric amputee. We have continued since 1973 to use stubbies in the bilateral above knee limb deficient child, as well as in the child with an above knee/below knee combination, with great success in establishing early balance, followed within several months by the application of articulated prostheses with equal success in establishing independent walking without the use of crutches or walkers.

Suction-assisted lipectomy--an adjunct to orthopaedic treatment.

Suction-assisted lipectomy was first performed in 1964 but did not become popular until 1981. Many thousands of patients are now so treated for cosmetic reasons each year, but no previous use of this technique as an adjunct to orthopaedic treatment has been reported. Two patients were successfully treated by suction-assisted lipectomy to reduce the circumferential measurement and shape of the residual limb so that prosthetic restoration could be more easily performed.

Ulnar deficiency.

Twenty-nine patients with 34 ulnar deficient limbs were studied; the average follow-up was 7.7 years. To permit early determination of prognosis and decisions regarding treatment, four subtypes of this condition have been identified. Progressive ulnar deviation of the wrist was not observed in any case, and the fibrocartilaginous ulnar anlage was resected only to correct fixed deformities of the wrist. The most useful operation was humeral or radial osteotomy to correct the hand on flank deformity. A group of patients who were optimally treated with prosthetic fitting is discussed.

Intraoperative autologous transfusion in children undergoing spinal surgery.

An intraoperative autologous transfusion program was used in conjunction with preoperative phlebotomy in 25 children undergoing elective spinal surgery. Operative red blood cells, 10,000 ml, with an average hematocrit of 55%, as well as 7,300 ml of preoperative phlebotomy blood were returned to the patients. No complications were noted. The complete blood count on discharge was satisfactory, and the clotting parameters were unchanged. The results of this study show that intraoperative autologous transfusion with preoperative phlebotomy is safe, easy to perform, and cost-effective in children undergoing elective spinal surgery. The risks of homologous blood transfusions were eliminated.

Recent advances in surgery of lower limb deficiencies.

A vast literature describing the treatment of lower limb deficiencies has accumulated in the past 20 years. Amputation and prosthetic replacement has come to be recognized as the major technique of limb-length restoration in these major lower-limb deficiencies. Experience has shown that early amputation can avoid major repetitive surgical procedures, and that disarticulation is the procedure of choice in the young child. A better understanding of the natural history of these major limb deficiencies has permitted the surgeon to develop a treatment program when the child is first seen, and to be able to recommended it to the parents with confidence.