[A short history of the concept of bias in epidemiology]. / Une brève histoire du concept de biais en épidémiologie.

BACKGROUND: Bias is a major methodological issue for epidemiology. However, only a few studies have been dedicated to the past and present formulations of the concept of bias. Moreover, the classical definition of bias as systematic deviation from the truth of results or inferences, definition which can be found in dictionaries of epidemiology, does not seem to either match the way epidemiologists use it in practice, or correspond to the different definitions given throughout its history. It is consequently important to elucidate this paradox. METHODS: In this historical and conceptual article, we study the different uses of the word "bias" in epidemiological literature, from classic articles in the 1950's about the link between smoking and lung cancer to the most recent epidemiology textbooks, the objective being to analyze the ways in which epidemiologists have defined, applied and modified this concept over time. RESULTS: We show that D.L. Sackett's article on bias in analytic research, published in 1979, put an end, at least temporarily, to reflection in populational epidemiology that started thirty years before. More precisely, we show that Sackett's definition of bias corresponds more to the needs and goals of clinical epidemiology than to those of populational epidemiology. Concomitantly, populational epidemiologists such as K.J. Rothman redefined bias as a threat to the internal validity of a study, and epidemiological study as an "exercise in measurement of an effect rather than as a criterion-guided process for deciding whether an effect is present or not". CONCLUSION: It is thereby important to draw a distinction between two notions pertaining to bias: an epidemiological concept of bias, viewed as the lack of internal validity of an observational study; and a medical concept of bias, defined as deviation from the truth. The former concerns the design and methodology of epidemiological studies; the latter is more general and impels epidemiologists and physicians to be skeptical, and even critical, towards their own inferences.

[Superficial circumflex iliac artery perforator free flap in pediatric reconstruction: A case report]. / Lambeau libre SCIP en reconstruction pédiatrique : à propos d'un cas.

The dorsalis pedis reconstruction requires to bring a thin tissue to recover every noble structure of the foot including tendons, nerves and vessels while resisting the stress induced on these structures when walking or wearing shoes. We report the case of a thirteen year-old child who presented a third-degree burn sequelae on the dorsalis pedis with scar retraction and chronic ulceration on the fifth metatarsal despite multiple skin grafts. He couldn't put on his shoes because of the pain and walking was difficult. We performed a SCIP flap (Superficial Circumflex Iliac Artery Perforator) to reconstruct this defect. The flap measuring 12×7cm has been harvested on the right groin and anastomosed with the pedicle of the first intermetatarsal space. At 3 months postoperatively, the child can put on his shoes again and walk without pain. The donor site is discrete in the inguinal crease, hidden in the underwear. The SCIP flap is a thin and pliable flap with a discrete donor site. It is suitable for reconstructions of distal extremities of limbs, both in adults and children.

[Tongue reconstruction by thoracodorsal perforator flap: A new harvesting technique to reduce morbidity]. / Reconstruction d'hémilangue par lambeau perforant thoracodorsal : nouveau prélèvement à morbidité réduite.

The thoracodorsal artery perforator flap is increasingly used in head and neck reconstructions. One of its multiple advantages is the low donor site morbidity compared to the other free flaps usually used for this type of surgery, such as the radial forearm free flap and the anterolateral flap of the thigh. However, the current harvesting technique of the thoracodorsal artery free perforator flap needs a vertical incision rising high in the axillary hollow for the dissection of the pedicle, thus impeding optimal discretion of the donor site, especially for women. We describe an original technique to harvest a pure transversal skin paddle on its own perforator, leaving a horizontal scar thoroughly hidden in the bra and preserving the thoracodorsal pedicle. We detail the requirements for this new type of harvesting.

[A giant sacral chordoma resection and reconstruction with a gluteal perforator flap, a case report and literature review]. / Chordome géant du sacrum et reconstruction par lambeau perforant glutéal supérieur, à propos d'un cas clinique et revue de la littérature.

BACKGROUND: Sacral chordomas are rare primary bone tumors and represent more than half of all primary malignant sacral tumors. Surgical resection is the only treatment with close to 50% of remission at 10 years, with or without radiotherapy. This tissue removal can be very extensive and morbid, particularly for evolved tumors. The reconstruction mostly uses myocutaneous flaps, notably the gluteus maximus flap and the latissimus dorsi flap, increasing morbidity of the surgical procedure. To avoid a muscular sacrifice and reduce the post-surgical morbidity, we describe the case of a patient who underwent a giant sacral chordoma resection and a reconstruction with a superior gluteal artery perforator flap. CASE REPORT: A 57-y.o. patient with a voluminous sacral chordoma had undergone a partial sacrectomy and abdomino-perineal resection. Firstly, a laparoscopy was realized to create a colostomy, to dissect an omental flap and to prepare the monobloc resection. In a prone position, the resection of the tumor was achieved and a de-epithelialized superior gluteal artery perforator flap was performed to fill the space and to support pelvic organs. CONCLUSION: For resections of sacral chordomas, coelioscopy has considerably reduced the surgical morbidity. However, the majority of reconstructions use myocutaneous flaps, specifically gluteus maximus and latissimus dorsi, which their postural function is considerable. Muscular sacrifice can lead to functional impotence with difficulty walking and standing up and run contrary to the diminution morbidity initiated by oncologic surgeons.