A computed tomography assessment of femoral and acetabular bone changes after total hip arthroplasty.

Using computed tomography-assisted (CT) osteodensitometry, we studied the bone changes that occurred in 12 patients at 2 weeks and again at 1 year after total hip arthroplasty with insertion of a press-fit acetabular cup and an uncemented femoral tapered stem. There was a greater decrease in full bone density (BD) lateral to the femoral stem when compared to the medial side, at the proximal end of the femur this difference was significant (-22.1% versus -16.2%) ( P<0.001). At the tip of the stem cortical BD had decreased between 2.3% and 1.9% only. Proximal to the cup, the cortical BD increased by about 3.4% ( P< or =0.05), while the full BD decreased markedly by 8% ( P< or =0.001). These changes represent a response to a decrease in regional bone stress induced by the presence of the press-fit implant, and this might be considered as retro-acetabular stress shielding. No focal bone resorption was found.

[The MACS-HMA hollow screw. An alternative possibility for stable implant anchoring in the vertebral body also for long fusions]. / Die MACS-HMA-Hohltonne. Eine alternative Möglichkeit der stabilen Implantatverankerung im Wirbelkörper auch für langstreckige Fusionen.

Our biomechanical in vitro tests compared the stability of the MACS HMA (Aesculap, Tuttlingen) implants to three established systems. The MACS HMA is a modular system consisting of porous hollow titanium screws with an outer diameter of 12 mm for monocortical use. We report the preliminary results of MACS HMA used for correction of scoliosis. All other implant systems used are designed with bicortical screws; one is for application with two screws/two rods and one uses a pullout-resistant nut behind the opposite cortex to increase stability. Significantly increased motion in the craniocaudal direction was recognized for bicortical standard screws (20 +/- 17 microns) compared to MACS HMA (10 +/- 11 microns) or the dual screw system (12 +/- 6 microns). Two-tailed t-test showed significantly higher stability for the dual screw system (4.2 kN) and the system with pullout-resistant nut (4.0 kN) compared to all other systems (p < 0.025 or higher). Bicortical implants (2.1-3.2 kN) and MACS HMA (2.6 kN) did not reveal significant differences in pullout strength. All biomechanical tests and in vivo use demonstrated favorable performance of MACS HMA implants.

Osteodensitometry in uncemented total hip arthroplasty using computertomography.

The aim of this investigation was to evaluate a new method developed for the measurement of bone mineral density and bone remodelling phenomena after total hip arthroplasty using computer tomography. Computertomography is a radiological technique to examine bone structures in high resolution. Using an extended scale it is possible to investigate bone scans and implants with fewer metal artifacts. For osteodensitometry measurement a special software (IMPact HIP) for the analysis of the data was used. The measured parameters were the overall bone mineral density (mg Calcium-Hydroxyapatite/ml) and the cortical bone structure. A standard scan mode enable to compare the computertomography scans at follow-up. Nineteen total hip arthroplasty patients (20 hips) with a mean age of 58 years (31-70) were operated on using an uncemented titanium alloy stem with a tapered design. The periprosthetic bone was assessed using computertomography-assisted osteodensitometry two weeks and one year after surgery. We observed a decrease of the overall bone mineral density (15%) and of the cortical bone structure (20%) one year after insertion of the stem in the proximal part of the femur. The area corresponds to the Gruen zones 1 and 7. On the other hand, a decrease of mineral density of 5% for the overall bone and of 3% for the cortical bone was found at the level of the tip of the stem, which corresponds to the Gruen zones 3, 4 and 5. Computertomography-assisted osteodensitometry allows to investigate the bone remodelling after total hip arthroplasty by separating the analysis of the overall bone mineral density and of the cortical structure. The present method is a reliable tool for quality-control in total hip arthroplasty.

In vivo and in vitro CT analysis of the occiput.

Arguments concerning the best procedure for occipito-cervical fusion have rarely been based upon occipital bone thickness or only based on in vitro studies. To close this gap and to offer an outlook on preoperative evaluation of the patient, 28 patients were analysed in vivo by means of spiral CT. Ten macerated human skulls were measured by means of CT and directly. Measurements were taken according to a matrix of 66 points following a grid with 1 cm spacing based upon McRae's line. Maximum thickness in the patient group was met 4 cm above the reference plane in the median slice (11.87 mm; SD 3.41 mm) and 5 cm above it in the skull group (15.85 mm; SD 1.81 mm). Correlation between CT and direct measurements was good (91.79%). Intra-individual discrepancies from one side to the respective point on the other side are common (difference > 1 mm in 60%). Judging areas suitable for operative fixation using the 10% percentile value (6.68 mm for the maximum value of 11.87 mm) led to the conclusion that screws should only be inserted along the occipital crest in an area extending from 1.5 cm above the posterior margin of the foramen magnum to the external occipital protuberance (EOP). At the level of the EOP screws may also be inserted up to 1 cm lateral of the midline. A reduction of screw length to 7 mm (9 mm for the EOP) is proposed. Preoperative evaluation of the patient should be carried out by spiral CT with 1 mm slicing and sagittal reconstructions.

Specific acromesomelia with facial and renal anomalies: a new syndrome.

A facio-renal-acromesomelic syndrome is reported in a 15-year-old boy with normal intelligence. The main dysmorphic features are a large head and congenital ptosis with telecanthus. There is unilateral ureteral stenosis with hydronephrosis. Bone abnormalities consist of ulnar dysplasia and tibial hypoplasia, multiple synostoses of carpal and tarsal bones, proximal synostoses of metatarsals, and of brachydactyly. A similar case has not been published.

Atlantoaxial instability in a 7-year-old boy associated with traumatic disrupture of the ossiculum terminale (apical odontoid epiphysis).

A case of atlantoaxial instability with a rare etiology in a boy of 7 years and 3 months is presented. Computerized tomography with three-dimensional reconstruction revealed avulsion of the ossiculum terminale (apical odontoid epiphysis). Developmental peculiarities and relevant disorders of the infantile upper cervical spine are discussed. Temporary posterior C1/C2 fusion and transdental screw fixation of the ossiculum terminale were attempted in order to stabilize C1/C2 and avoid permanent fusion. After removal of the dorsal implants, the transdental screw broke, the instability recurred and a permanent atlantoaxial fusion had to be performed.

[The styloid syndrome. Differential diagnosis of degenerative diseases of the cervical vertebrae--case report with literature review]. / Das Styloid-Syndrom. Eine Differentialdiagnose degenerativer Erkrankungen der Halswirbelsäule--Kasuistik mit Literaturübersicht.

Elongated Styloid Process Syndrome requires its consideration in differential diagnosis of degenerative disease of the cervical spine. Radiating pain on certain movements of the cervical spine is a symptom of an elongated styloid process as well. First basic anatomy and pathology, symptoms and differential diagnosis of the elongated styloid syndrome are discussed. A case history is presented together with X-rays of the cervical spine and images of three dimensional CT-reconstruction to show the full length of an elongated styloid process.

[Biometric analysis of the unstable shoulder]. / Biometrische Analyse des instabilen Schultergelenkes.

An osteometry of instable glenohumeral-joints was done by computerized tomography. In comparison of type and direction of the instability, a marked retroversion of the glenoid was found in posterior luxation, not only in the instable, but also in the contralateral side. There seems no statistical prove of an influence by a changed radius or width of the humerus-head nor by a reduced retrotorsion of the humerus. Posttraumatic disorders like HILL-SACHS-lesions or BANKART-lesions are more easily detected by computerized tomography than by conventional radiography.

[Head posture in lateral roentgen image]. / Untersuchung zur Kopfhaltung im Fernröntgenseitbild.

A cervico-cephalometric examination of 61 yet untreated orthodontic patients was performed in order to analyze differences in head posture between standardized cephalograms and lateral cephalograms taken in natural head position. Additional x-rays were taken in extreme flexion and extention of the head in 48 patients examining the mobility of the upper cervical spine. Finding partly large differences in cranio-vertical and cranio-cervical parameters between the two methods of registration it could be shown, that head posture on the average was more proclined in natural than in fixed standardized position. Subjects with class III malocclusion tended to a more extended head posture relatively to those with class I or class II malocclusion. Judging the atlas position with regard to the functional mobility of the upper cervical spine, a superior and inferior atlas position was not thought to be a pathologic fixed malposition.

[Craniocarpotarsal dystrophy (Freeman-Sheldon Syndrome)]. / Die kranio-karpo-tarsale Dystrophie (Freeman-Sheldon-Syndrom).

In the case of a woman with Freeman-Sheldon syndrome clinical, radiographic and CT data were used to demonstrate specific craniofacial and dental characteristics. Three-dimensional surface reconstruction of the cranial morphology obtained from axial CT scans was found to provide the most useful means for analyzing the characteristic craniofacial deformities in this syndrome. Apart from the dentofacial structures also orthopedic disorders were evaluated clinically and radiographically with particular consideration of the cervical spine morphology.

[Roentgen morphologic study of arthrosis of the sternoclavicular joint]. / Röntgenmorphologische Studie zur Arthrose des Sternoclaviculargelenkes.

X-rays of 102 sternoclavicular joints from post-mortem examination were interpreted systematically. In 89 cases we found an osteoarthrosis. We investigated the correlation between stage of osteoarthrosis and size and form of articular surface, age, sex and right or left preference. We also made a review about anatomy, embryology and pathology of the sternoclavicular joint. The differential diagnosis of sternoclavicular pain is discussed.

[3-D reconstruction for assessing the morphology of craniofacial structures]. / 3-D-Rekonstruktion zur Beurteilung der Morphologie kraniofazialer Strukturen.

The diagnostic value of 3-D reconstructions from axial CT scans in evaluating craniofacial structures was analyzed on the basis of a selected orthodontic patient group. The results showed that, for the first time, a three-dimensional analysis of the craniofacial relationships could be obtained which was not a mere spatial evaluation of the morphological structures. The specific application of this imaging procedure in detailed evaluations of complex dysmorphias and asymmetries seems to be justified.

[The 3-dimensional surface reconstruction from computerized tomography sections]. / Dreidimensionale (3D) Oberflächenrekonstruktion aus computertomographischen Schnittbildern.

Three-dimensional (3D) images can easily be reconstructed from computed tomography (CT) data. Three-dimensional reconstruction of osseous surfaces facilitates the analysis and detection of post-traumatic dislocations, tumorous changes or disturbances in the mechanics of joints.