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Abstract Background Fracture-healing depends on interfragmentary motion. For improved osteosynthesis and fracture-healing, the micromotion between fracture fragments is undergoing intensive research. The detection of 3D micromotions at the fracture gap still presents a challenge for conventional tactile measurement systems. Optical measurement systems may be easier to use than conventional systems, but, as yet, cannot guarantee accuracy. The purpose of this study was to validate the optical measurement system PONTOS 5M for use in biomechanical research, including measurement of micromotion. Methods A standardized transverse fracture model was created to detect interfragmentary motions under axial loadings of up to 200 N. Measurements were performed using the optical measurement system and compared with a conventional high-accuracy tactile system consisting of 3 standard digital dial indicators (1 μm resolution; 5 μm error limit). Results We found that the deviation in the mean average motion detection between the systems was at most 5.3 μm, indicating that detection of micromotion was possible with the optical measurement system. Furthermore, we could show two considerable advantages while using the optical measurement system. Only with the optical system interfragmentary motion could be analyzed directly at the fracture gap. Furthermore, the calibration of the optical system could be performed faster, safer and easier than that of the tactile system. Conclusion The PONTOS 5 M optical measurement system appears to be a favorable alternative to previously used tactile measurement systems for biomechanical applications. Easy handling, combined with a high accuracy for 3D detection of micromotions (≤ 5 μm), suggests the likelihood of high user acceptance. This study was performed in the context of the deployment of a new implant (dynamic locking screw; Synthes, Oberdorf, Switzerland).

Background: Although self-assessment questionnaires for the wrist joint are numerous, most validation studies focus on a specific pathology and patient collectives. In addition the available questionnaires focus on subjective parameters such as pain, usual and specific activities but the range of motion (ROM) as an essential objective parameter in wrist disorders is rarely considered. Therefore the purpose of the presented study was to develop and validate a new universally applicable self-assessment score, the Munich Wrist Questionnaire (MWQ), which allows for the assessment of subjective as well as objective parameters of the wrist joint., Methods: The MWQ consists of 16 items addressing three domains: pain, work and activities of daily living and wrist function including range of motion and grip strength. In a prospective clinical study validity, reliability and responsiveness of the MWQ of physical active patients were evaluated., Results: Validation study included 100 patients (mean age 41 years, SD 16.3 years; range, 18-77 years). Test-retest reliability was substantial, with intraclass correlation coefficients ranging from 0.75 to 0.83 for the three domains. Construct validity and responsiveness were confirmed by correlation coefficients of at least 0.86 for construct validity and for responsiveness ranging from 0.61 to 0.65., Conclusions: The MWQ presents a valid and reliable instrument for a qualitative self-assessment of subjective and objective parameters (e.g. range of motion) of the wrist joint. Quantitative measurement of wrist function may not longer be limited to specific wrist disorders or patient groups. The MWQ seems to allow for a broad application in clinical research and may facilitate the comparison of treatment results in wrist disorders.