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Whiplash injuries of the cervical spine are of special medical and socio-economic importance. Biomechanical studies of the injury have proven, that a hypertranslation of the capito-cervical region takes place first, leading to ligamentous hyperdistension and ruptures, when exceeding elastic deformation, thus possibly resulting in mechanical disturbance and rotatory malpositioning. Diagnosis of so called "functional disorders" bears difficulties concerning objective tests for structural lesions. This demands the definition of diagnostic parameters and clinical signs, which also consider vegetative phenomena. This paper aims at a systematic clinical and radiological check. Adequate therapeutic means have to be concordant to prognosis. Therefore functional parameters should already determine differential diagnosis. This is based on technical feasibilities and needs future scientific efforts.

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The article reports a new hypothesis of whiplash injury based on a series of experimental studies using isolated human cadaveric specimens. Although the clinical symptoms of whiplash are widely known, the understanding of the underlying injury mechanism is poor. The prevailing view of neck-hyper-extension as the essential injury mechanisms was not supported by recent experiments. In a series of experiments using eight human cadaveric specimens which underwent experimental stepwise whiplash acceleration from 2.5 to 10.5 g functional radiographs and flexibility tests were performed at the end of each acceleration step. Ligament strains, vertebral alignment and elongation of the vertebral artery were monitored during the whiplash trauma by highspeed cinematography and specially designed transducers. After the trauma CT- and MRI-scans were taken and specimens were sectioned using Cryomicrotomy. We found a distinct biphasic kinematic response of the cervical spine to whiplash trauma. In the first phase the spine formed an S-shaped curve with flexion at the upper levels and hyper-extension at the lower levels. This phase was found to be the vulnerable phase of whiplash trauma. The largest dynamic elongation of the capsular ligaments was observed at the C6-C7 level during this initial S-shaped phase of whiplash. The maximum elongation of the vertebral artery could be observed synchronously in the first S-shaped curve of the cervical spine. In the second phase of whiplash all levels of the cervical spine were extended, so that the head reached is maximum extension. No injuries were observed in the second phase. We propose, based on our experimental findings, that with low accelerations the anterior structures of the lower cervical spine are injured during the first phase of whiplash, when the cervical spine forms an S-shaped curve and before the neck is fully extended. At higher trauma accelerations there is also a tendency for the injuries to occur at upper levels of the cervical spine. Based on our findings the traditional view of whiplash as hyper-extension injury can be modified by a differentiated, time dependent, biphasic biomechanical model of the injury, thus allowing better and more effective injury prevention, diagnosis and therapy.

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Motion analysis of the cervical spine is a sensitive tool in the fields of preventive and clinical biomechanics of whiplash. In the field of preventive biomechanics motion analysis contributes to validation and optimisation of dummy based crash test experiments and simulations. In the clinical field motion analysis up to now is of restricted value. Data exist about restrictions and pathologies of movement and motion of the cervical spine, coordinative disturbances, postural control, TMJ-function and oculomotor disturbances after whiplash. The standardisation of technical and clinical set-ups is necessary to establish a well proven biomechanical model of whiplash and whiplash related biomechanical dysfunction. Without this model the value of motion analysis for clinical use will be restricted due to lack of comparable data on sensitivity and specificity although motion analysis of the cervical spine is neither cost- nor time consuming and free of adverse effects. Within a prospective series of 28 patients (14 m/14 f) with a follow-up to six weeks we were lucky to describe numerically two different types of reaction to low energy (delta v < 20 km/h) rear end collision: Type I with disturbances in complex movements only, Type II with overall restriction of movement. Control of angular velocity during cyclic movements of the head was disturbed by oscillations of higher frequency in all patients. Recovery from whiplash within 6 weeks could be monitored.

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Cylindric titanium rods with different surfaces were axially implanted into the femora of sheep. The three surfaces were grit-blasted titanium, plasma-sprayed titanium and plasma-sprayed hydroxyapatite (HA). After 2 months, a 2-cm segment of the femoral shaft was completely resected to load the implant, and the animals were allowed full weight-bearing for 9 months. Biomechanical and histological evaluation of the implants was undertaken 2 months after implantation and 9 months after the segmental resection. The mechanical testings of well-fixed implants were performed 9 months after segmental resection. Loosening of 45% of the titanium-coated implants was observed in the first 3 weeks, but thereafter, no further loosening occurred. The HA-coated implants remained entirely fixed for 3 weeks, but thereafter, a progressively increasing incidence of loosening up to 55% after 9 months of loading was detected as subsidence on X-radiographs. The maximum push-out strength of the titanium-coated implants was 4.9 MPa compared with 2.3 MPa for HA-coated ones. No significant mechanical interlock between the grit-blasted surface and bone was observed. The HA coating was found to be delaminated in all unstable implants, whereas the titanium coating remained completely intact. Morphometric analyses of well-fixed rods showed complete bony ingrowth onto the HA surface, whereas the contact area between the bone and the two titanium surfaces was less than 40%. Concerning clinical significance bony ingrowth with long-term mechanical interlock between the implant surface and the bone cannot be achieved by grit-blasting or HA-coating.(ABSTRACT TRUNCATED AT 250 WORDS)

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