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At least 163 records · Page 9Linked to original sources
PubMed1999

[Proximal scaphoid pseudarthrosis--reconstruction by dorsal bone screw and spongiosa transplantation].

Stable fixation of small proximal pole nonunions of the scaphoid by conventional techniques of bone grafting remains difficult. Because of this, long-lasting immobilisation is necessary. Treatment by retrograde Herbert-screw fixation offers the possibility of stable osteosynthesis resulting in shorter immobilisation. Even in case of avascular proximal fragments, it allows healing of the nonunion. We report on the 29 months follow-up of 23 patients treated in this manner showing bony consolidation in 17 cases (74%). Four patients demonstrated fibrous nonunion with minor symptoms, and in two patients persistent nonunion with slight impairment was seen. Evaluation with the DASH-questionnaire revealed slight disability with an average score of ten points. The availability of the mini-Herbert-screw has improved this treatment concept.

Adult↗
PubMed1995

Increase of stability in external fracture fixation by hydroxyapatite-coated bone screws.

A major problem in fracture treatment by external fixation is screw loosening, which often results in reduced stability and can lead to prolonged treatment. A load-carrying experiment was conducted to determine whether coating implants with bioactive hydroxyapatite (HA) increases screw stability. Twelve HA-coated ASIF screws with 3 different macroporosities were inserted in 12 sheep that had already been fitted with a 6-pin external fixator for the treatment of a tibial osteotomy. The same number of uncoated polished steel screws served as controls. Although initial stability was not different for HA-coated screws, average removal torque after a 9-week implantation period increased with increasing macroporosity of the HA coating (p < .002). Instability of some screws was accompanied by histologic findings of cartilagenous tissue and proliferation of periosteal callus. Near the threads in the tibial cortex and in the shaft area of the screw were seen large numbers of HA particles that had been sheared off during implantation as well as during screw removal because of high contact forces between the HA coating and bone. Particulate debris of HA particles as well as the release of small bone fragments during explanation is likely to be unavoidable since HA adherence to bone is greater than adherence to steel after several weeks of implantation.

Animals↗
PubMed1990

Biomechanical measurements on scaphoid bone screws in an experimental model.

A number of screws commonly used for internal fixation in scaphoid bone fractures and nonunions are compared regarding biomechanical properties and clinical applicability. The experiments were carried out on models made of ash-wood, representing a reconstruction and fixation as is performed in a cortico-cancellous inlay bone graft for scaphoid non-union. For fixation use was made of 2.7 and 3.5 AO/ASIF cortical screws respectively, 4.0 AO/ASIF cancellous screws, Herbert screws, and a newly designed screw called the three components screw (D.K.S.). The models with implanted screws were tested for bending strength, tensile strength and torsion stability. No large differences between the various screws were found regarding the measured parameters, so that a small intra-osteal implant such as the Herbert screw and the D.K.S., which can be inserted easily and which gives a certain amount of interfragmentary compression, will be sufficient for osteosynthesis of the scaphoid bone. In case an intra-osteal implant is not available a single 3.5 AO/ASIF cortical screw, inserted following lag-screw principles, is recommended.

Alloys↗
PubMed1989

[Treatment of fractures of the carpal scaphoid with Herbert's bone screw. Review of 21 clinical cases].

Twenty-one patients with scaphoid fractures treated by internal fixation with the Herbert screw are reviewed. Nine patients presented acute fractures and twelve had fractures with delayed or non-union. The results of these two kinds of lesions are analyzed following the criteria established by Herbert and Fisher in 1984. This type of internal fixation gives excellent results in isolated lesions of the scaphoid provided it is correctly executed.

Adolescent↗