Complications in surgical treatment of thoracolumbar injuries.

The range of surgical methods for operative treatment of thoracolumbar injuries, with their different ways of approach, grafts and techniques, remains wide. The authors present sources of error and specific complications based on their own experience and on the results of a multicenter study of the Spine Study Group of the German Trauma Association (DGU). A systematic overview of possible mistakes and complications is first presented in anatomical order. A detailed analysis is then presented of the complications reported in a multicenter study, carried out prospectively between 1994 and 1996, on 682 patients operated for acute traumatic injuries of the thoracolumbar spine. In 101 cases (15%) at least one complication occurred intra- or postoperatively. In 41 patients (6%) a revision was performed, and in 60 patients (9%) complications without operative revision were observed. These complications were analysed according to the chosen method of initial treatment.

[Development and validation of the Visual Analogue Scale (VAS) Spine Score]. / Entwicklung und Validierung des VAS-Wirbelsäulenscores.

The aim of the study was the development and validation of a new subjective rating scale for assessment of outcome in patients with thoracolumbar fractures and fracture dislocations. The VAS spine score consists of 19 score items, using 100-mm visual analogue scales. The items are answered by the patients independently of rater assessment. To measure the analogue scales and calculate the score, a computer-aided system was evolved consisting of self-developed software and digitizer board. The overall score is the mean of all items answered with values between 0 and 100. The individual score loss is calculated as the difference between the preinjury score and at follow-up with values between 0 and 100. The VAS spine score was tested for reliability with a group of 136 healthy volunteers. We performed a test-retest study with an interval of 24 h. For statistical analysis of the validity, we prospectively followed a group of 53 patients with the new outcome score. We chose patients with injuries of the thoracolumbar spine, all having been operatively treated by combined posterior-anterior stabilization and fusion between 1994 and 1996. In the reference group, the average test score was 91.95 (58-100) and 92.10 (58-100) at retest. The mean individual difference between test and retest scored 1.037 (0-8). A high reliability was proved by a strong correlation with a coefficient of 0.976 (p < 0.001). A high internal consistency of the VAS spine score was shown by a Cronbach-alpha of 0.9117. The mean score for the preinjury status of the patients was comparable to the reference group, amounting to 89.60 (21-100). The mean score at the time of implant removal was significantly (p < 0.001) decreased to 58.25 (13-97). Until the time of follow-up a significant (p < 0.001) increase was noted, and the group scored 66.08 (15-100) at follow-up. This was a significant (p < 0.001) difference compared with the preinjury status. The individual score loss averaged 24.1 (0-80). In the patient group we also noted a Cronbach-alpha > 0.95, indicating a high internal consistency. With the VAS spine score the authors have inaugurated a new tool for outcome measurement in the treatment of patients with thoracolumbar injuries. The study has proved the score to be both reliable and valid. The application of the score is helpful in analyzing the subjective outcome, and the results can be correlated with objective measures. The score is a useful tool for comparative clinical studies, addressing the outcome after different methods of treatment.

[Comparative biomechanical compression trials with a new vertebral prosthetic implant]. / Vergleichende biomechanische Kompressionsversuche mit einem neuen Wirbelkörperersatzimplantat.

UNLABELLED: The authors present a new titanium implant for replacement of the vertebral body (Synex). Possible indications would be fractures or dislocations with destruction of the anterior column, posttraumatic kyphosis as well as tumors in the throracolumbar spine. The construction has to be completed by a stabilizing implant. For best fit and contact to adjacent end-plates Synex is distractable in situ. The possibility of secondary dislocation or loss of correction should thereby be minimised. OBJECTIVES: We performed comparative compression tests with Synex and MOSS ("Harms mesh cage") on human cadaveric specimens of intact vertebrae (L1). The aim of the study was to measure the compressive strength of the vertebral body end-plate in uniaxial loading via both implants to exclude a caving of Synex in vivo. METHODS: 12 human cadaveric specimens of intact vertebrae (L1) were divided in 2 similar groups (matched pairs) according to bone mineral density (BMD), determined using DE-QCT. The specimens were loaded with axial compression force at a constant speed of 5 mm/min to failure and the displacement was recorded with a continuous load-displacement curve. RESULTS: The mean ultimate compression force (Fmax) showed a tendency towards a higher result testing Synex with 3396 N versus 2719 N (non significant). The displacement until Fmax was 2.9 mm in group S (Synex), which was half as long as in group M (5.8 mm). The difference was significant (p < 0.001). The compression force was twice as high and significantly (p < 0.05) higher with Synex at a displacement of 1 mm, 1.5 mm and 2 mm. A significant (p < 0.001) correlation (R = 0.89) between Fmax and BMD was found. CONCLUSIONS: Synex was found to be at least comparable to MOSS for suspensory replacement of the vertebral body at the thoracolumbar spine. A possible consequence of the significantly higher mean compression forces between 1 and 2 mm displacement might be a decreased segmental deformation or loss of correction.

Biomechanical compression tests with a new implant for thoracolumbar vertebral body replacement.

The authors present an investigation into the biomechanical functioning of a new titanium implant for vertebral body replacement (Synex). Possible indications are fractures and/or dislocations with damage of the anterior column, posttraumatic kyphosis and tumors of the thoracolumbar spine. The construction must be supplemented by a stabilizing posterior or anterior implant. For best fit and contact with adjacent end-plates, Synex is distractable in situ. We performed comparative compression tests with Synex and MOSS ("Harms mesh cage") on human cadaveric specimens of intact vertebrae (L1). The aim of the study was to measure the compressive strength of the vertebral body end-plate in uniaxial loading via both implants to exclude collapse of Synex in vivo. Twelve human cadaveric specimens of intact vertebrae (L1) were divided into two identical groups (matched pairs) according to bone mineral density (BMD), determined using dual-energy quantitative computed tomography (DE-QCT). The specimens were loaded with an axial compression force at a constant speed of 5 mm/min to failure, and the displacement was recorded with a continuous load-displacement curve. The mean ultimate compression force (Fmax) showed a tendency towards a higher reading for Synex: 3396 N versus 2719 N (non-significant). The displacement until Fmax was 2.9 mm in the Synex group, which was half as far as in the MOSS group (5.8 mm). The difference was significant (P < 0.001). The compression force was twice as high, and significantly (P < 0.05) higher with Synex at displacements of 1 mm, 1.5 mm and 2 mm. A significant (P < 0.001) correlation (R = 0.89) between Fmax and BMD was found. Synex was found to be at least comparable to MOSS concerning the compressive performance at the vertebral end-plate. A possible consequence of the significantly higher mean compression forces between 1 and 2 mm displacement might be decreased collapse of the implant into the vertebral body in vivo.

[The image of the temporomandibular joint in the panoramic radiographs]. / Die Darstellung der Kiefergelenke auf Panoramaübersichtsaufnahman.

Of the general panoramic radiographs those with an intraoral focus (magnifying panoramic radiography) are not suitable to represent the temporo-mandibular joint. In contrast, panoramic tomograms represent the temporo-mandibular joint better, but they cannot be recommended unreservedly for the exact evaluation of this region. Presently there is no substitute for conventional radiographs.