New biomechanics study of hoffmann® external fixation.

While remaining faithful to the Hoffmann Vidal external fixator, the authors have been trying for the past 15 years to improve both the stiffness and versatility of the double frame device. Taking into account the different btomechanical studies about the double frame made by different research laboratories, the authors have improved the double frame device by certain modifications in the pins and rods configuration. They have thus obtained the quadrangular triple frame mounting and the triangulate triple frame. The latter device is comparable to a "chalet," being very rigid under any demands but also very versatile due to its smaller dimensions.

[Scapulohumeral arthrodesis by combined external and internal fixation. A biomechanical, technical and clinical study]. / Arthrodése scapulo-humérale par fixation combinée externe et interne. Etude biomécanique, technique et clinique.

The indications for arthrodesis of the shoulder are controversial and limited and fusion is difficult to achieve, as is shown by the number of methods described in the literature. Since 1970, the authors have used combined internal and external fixation for arthrodesis of the shoulder. From a biomechanical study of arthrodesed shoulders, an attempt has been made to define the best combination of fixation. Three progressively more complex methods combining intra-articular fixation with a Hoffmann external fixator in compression have been tested. The ideal method combines transverse double scapulo-humeral screws with a vertical acromio-humeral screw. The addition of a bony subacromial strut controls the shearing effects arising from the application of the fixator in compression and also provides an upper site of fusion. In 14 arthrodeses using combined internal and external fixation analysed with a two to sixteen year follow-up, acromio-humeral fixation has been used in 11 cases with 10 primary successes and in 3 cases triple screw fixation has given very rapid fusion without the need for spica immobilisation.

[Combination of external fixator and internal synthesis in fractures and pseudoarthrosis of the leg. Principle indications and results]. / Association fixateur externe et synthèse interne dans les fractures et pseudarthroses de jambe. Principales indications et résultats.

A combination of internal and external fixation has been used on 58 occasions in fractures and pseudarthroses in the leg. In almost two-thirds of the cases, the fractures were compound. Several situations favour this combination of fixation: internal fixation complements an initial external fixation by stabilising the fracture site in the shaft or by allowing reconstruction of joint surfaces, external fixation complements any inadequate internal fixation due to comminution of the fracture or poor skin cover that only allows a minimum of internal fixation, external fixation secondarily comes to the help of internal fixation in cases of skin necrosis or secondary bone infection. The authors believe that a combination of internal and external fixation has real advantages and that, when used with good sense, it should not lead to any specific complications.

[Aseptic loosening of a total hip prosthesis]. / Descellement aseptique d'une prothèse totale de hanche.

Detachment of a total hip prosthesis, whether or not it is cemented, presents as an abnormal mobility between the implant and the bone. Mechanical pain, which may be continuous from the time of the operation or which may appear after a variable pain free period, is the usual presenting symptom. Clinical examination may induce the pain by forced rotation, by a shaking maneuver or by traction-impaction of the lower limb. The most suggestive signs of detachment of the prosthesis are the inability to extend the limb and the instability of weight-bearing on one foot. At this stage, the findings of radiological and laboratory investigations are able to characterise the type of detachment and its septic or aseptic nature. Two clinical situations can be defined on the basis of this survey: the diagnosis of detachment is obvious due to rupture or fracture of the prosthesis, of the cement or of the bone, by displacement of the prosthetic elements or by the destruction of the bone in contact with the prosthetic elements; the diagnosis may be suspected and can be confirmed by careful comparative analysis with the initial films or by further investigations: dynamic tests, scintigraphy, arthrography under traction and possibly coxonar. There are a number of causes of detachment: poor positioning, incorrect conception or design of the prosthesis, poor bony support and host reaction to the implant.(ABSTRACT TRUNCATED AT 250 WORDS)