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Posttraumatic malalignments are a frequent sequlae of IM nailing of lower extremity fractures. Conventional US has proven to be inferior to CT determinations of tibial or femural length and torsion. A new 3-D US method is presented that allows for accurate single step determination of lower extremity length and torsion without ionizing radiation. A regular US machine with a 5 Mhz linear probe is combined with an US localizer. Reference markers affixed to the lower extremity eliminate errors associated with patient position or motion. The 3-D US method was compared against CT (Ulm's method) in the measurement of torsion and length of the tibia and femur in 50 adults and 50 children. In both methods, the maximum difference of the intraindividual torsional angles and length measurements was 7 degrees and 7 mm. The maximum standard deviation for reproducibility in length measurement was 1.6 mm and 1.5 degrees for angular torsion. The new 3-D US technique was superior to CT in terms of reliability and reproducibility. Clinical advantages of the 3-D US technique include rapidity, independence from patient motion or positioning and the avoidance of ionizing radiation. Indications for 3-D torsional and length determinations include follow-up evaluation of adult and pediatric tibial and femoral fractures, pediatric limb and gait evaluations, and osteotomy planning.

Ziel der prospektiven Studie war die Rolle der MRT zur Darstellung von BDI im Bereich der Extremitaten und deren Abbau zu untersuchen. Dazu wurden SR-polyglycolic acid (SR-PGA)-Schrauben zur Versorgung von 8 Sprunggelenks- und 1 Humerusfraktur bei 9 Patienten sowie Poly-DL-lactid-Stifte (PDLLA) bei 9 Patienten mit Radiuskopfchenfrakturen verwendet und mittels MRT (1,5 Tesla) nachuntersucht. In allen Fallen liesen sich Lage und Grose der BDI mittels MRT nachweisen. Wahrend SR-PGA-Schrauben zunehmende Heterogenitat aufwiesen, erschienen PDLLA-Stifte bis zu 18 Monaten postop. Unverandert. Die MRT erwies sich als geeignetes Verfahren zur nichtinvasiven Darstellung von Grose und Lokalisation von DBI, wobei erstmals Zeichen der Degradation von SR-PGA-Schrauben mittels MRT nachgewiesen werden konnten.

Defects of the dorsal and ventral ligament complexes of the lumbar spine results to an instability of the functional spinal unit. For the prognosis of secondary instability due to disko-ligamentous injuries the functional insufficiency of the lasting scars is a larger problem than the primary loss of osseous stability with fast healing tendency. The main goal of the present biomechanical study in vitro was to demonstrate the different grades of instability in the correlation to progressive disko-ligamentous defects as well as stabilisation through dynamic and static procedures. With a transpedicular screw-ringband-system the segmental function was preserved and instability was abolished. After rigid instrumentation with a fixateur intern remained a residual range of motion due to which can result refuse to bending moments without spondylodesis in an implant failure.

The purpose of this study was to quantify in vivo the three-dimensional motion patterns of the sacroiliac joint during passive manipulations as the opinions about the extent of motion of this joint are varied. 12 sacroiliac joints of 6 patients with clinically and radiologically normal joints were investigated. All patients were treated with an external fixator for diagnostic purposes of low back pain unrelated of this study. The motion of the sacroiliac joint was measured continuously with a three-dimensional goniometric system, which was mounted at the end of Schanz screws implanted in S1 and the ilium. All measurements showed relatively small rotation angles around the three main axis to the body between the ilium and the sacrum (2 degrees) and very small translations between the screw entry points into the bones (1 mm). The maximum rotation angle in the sagittal plane was 1.3 degrees on the right joint and 1.6 degrees on the left joint for flexion plus extension. It is questionable whether this motion can be quantified during manual manipulation. Extension of the hip always produced the largest motion in the sacroiliac joint.

A cell culture system has been developed that enables application of well characterized, homogeneously distributed cyclic strains to monolayer cell cultures. Optically clear silicone culture dishes atop Plexiglas base plates are deformed by four-point bending of flexible silicone culture wells driven in user specified strain cycle patterns using computer controlled electromagnetic linear actuators. Cyclic mechano-transduction can be induced in amplitudes of 0 to 3000 mustrain, in frequencies of 0 to 30 Hz and in any specified strain cycle pattern. The cell culture system, which contains six simultaneously driven culture wells, has been mechanically characterized by holographic interferometry, laser displacement sensor recordings of the dish surfaces, strain gauge monitoring of the base plates, and finite element modeling of the dishes on the base plates. The standard deviation of the strain amplitudes among the six simultaneously stimulated culture wells is less than 5%. The cell culture system allows accurate generation of small magnitudes of well characterized, homogeneous strain, easy handling of the culture wells, flexible setting of cyclic strain pattern parameters, simultaneous stimulation of 6 culture wells, and light microscopic observation of the cell cultures.

Bone cements are used to treat compression fractures, fill bone defects and improve implant fixation in osteoporotic patients through reinforcement of weak bone. When the fracture repair is complete the bone cement ideally should degrade. In general, calcium-phosphate bone cements are biodegradable and can fulfill this temporary function. Several research groups have developed calcium-phosphate bone cements in the last years which have a chemical structure similar to that of the apatite of bone. However the conditions for processing the cement intraoperatively, as well as the mechanical properties and degradation characteristic of the various products show great variations. Clinical long-term studies have not yet been reported so far. Whether these new types of bone cements fulfill all the requirements for clinical application is still not certain and remains to be determined in future studies.

Chronic functional instability of the lateral ankle may be difficult to distinguish from mechanical instability when radiological stress test reveal only small ligamentous defects. When a decision for or against surgical reconstruction of the ligaments has to be made it can be helpful to use additional information on joint function. Therefore, a prospective study of 65 patients (mean age 24.1 +/- 4.6 years) with long-standing chronic ankle instability was conducted to demonstrate that the dynamic measurement of plantar pressure distribution can identify patients with functional ankle instability. Plantar pressure patterns were measured during gait by means of a capacitive platform, the EMED-SF system. The impulses at eight points of the foot were calculated intraindividually and compared with those in a group of 100 healthy subjects. On the basis of clinical criteria alone, the two groups of patients were distinguished, 35 with functional instability and 30 with mechanical instability. The patients with functional instability showed significantly increased lateral loading of the unstable foot (P = 0.01), whereas the group with mechanical instability tended to walk more on the medial side of the unstable foot. This finding is explained by a deficit or peroneal strength during the stance phase, based on a proprioceptive deficit after trauma. The new technique provides additional information, which is relevant and sufficiently important to help in making decisions about the individual patient with chronic instability.

Das wichtigste Ziel der biomechanischen Forschung in der Chirurgie war und ist die Wiederherstellung einer durch Verletzung oder Erkrankung verloren gegangenen biomechanischen Funktion eines Organteiles oder Organes.

Die klinische Versorgung von unfallverletzten Patienten findet in Deutschland auf einem im internationalen Vergleich hervorragenden Niveau statt. Mit ihrer angewandten klinischen Forschung hat die deutsche Unfallchirurgie hierzu in der Vergangenheit wichtige Beitrage geleistet. In den letzten Jahren hat es jedoch zwei Entwicklungen gegeben, die die unfallchirurgische Forschung im internationalen Vergleich zuruckfallen liesen.

In this multicentre retrospective study 30 patients with benign salivary gland tumours are reviewed. Initial operation consisted of total parotidectomy in 6 patients, superficial lobectomy in 13 and tumour enucleation in 11. There were 5 recurrences, treated by enucleation in 1, superficial lobectomy in 2 and extensive total resection in 2 patients. In 18 cases a typical facial nerve dissection was performed. The resected specimens showed a pleiomorph adenoma in 24 cases and monomorph adenoma's in 6 cases. Complications were haematoma formation, Frey syndrome and facial nerve paresis. Recurrences were related to incomplete resection or fragmentation during operation. In this study benign tumours of the salivary glands proved to have a good prognosis, provided a total tumour excision with nerve dissection is performed; the excision should consist of a superficial lobectomy or total parotidectomy depending on the location of the tumour in the lateral or medial part of the gland.

The present study investigated the clinical and functional outcome of calcaneal fractures. 14 patients were evaluated at a mean follow-up of 52 months. Two groups, group A with good and group B with poor calcaneal restoration were distinguished by Böhler's angle. Ten normal subjects were used for comparison. Clinical results were evaluated with a questionnaire, radiography and range of motion measurements. Plantar pressure patterns were recorded with a capacitive pressure distribution platform. A comparison of the injured and healthy foot of all patients revealed a load shift towards lateral foot regions. A comparison of the patient groups with the controls did not reveal more pronounced changes in the poorly restored group. The results demonstrate that a disturbance of foot function persists even after long healing.

We tested the hypothesis that the application of strain during callus distraction induces systemic osteoblast stimulating factors that enhance osteoblast activity both locally and systemically. To study the systemic occurence of strain-induced osteoblast stimulating factor during callus distraction, we investigated the mitogenic capacity of sera from 12 patients who had undergone callus distraction on the osteoblastic cell line SaOS-2 (part I). Serum samples from six patients who had undergone rigidly fixed high tibial osteotomy (i.e., without distraction) served as controls. The sera were assayed for platelet-derived growth factor and transforming growth factor-beta. In part II of the study, the in vitro effects of mechanical strain were investigated in a simplified model by cyclic stimulation of osteoblast cultures isolated from cortical bone explants from the same patients; a specially developed apparatus was used for cell-stretching. Sera taken during the third to fourth week of callus distraction demonstrated a significant increase in proliferation of SaOS-2 cells (p < 0.005). In contrast, sera from patients who had had an osteotomy failed to induce or decreased the mitogenic capacity of SaOS-2 cells. The concentration of platelet-derived growth factor increased significantly (p < 0.01) in sera from both the patients who had undergone callus distraction and the controls who had had osteotomy. However, the level of transforming growth factor-beta was increased (p < 0.05) in the sera from the patients who had distraction (sera that stimulated proliferation of SaOS-2 cells), but the level was not increased in the sera from patients who had osteotomy.(ABSTRACT TRUNCATED AT 250 WORDS)

Internal fixation of unstable intertrochanteric fractures of osteoporotic femurs often leads to complications, which are primarily caused by the mechanically weak bone. The aim of this study was to test whether a new glass-ionomeric cement could reinforce the weak trabecular bone of the femoral head and thus improve the preliminary stability of dynamic hip screws (DHS) used for internal fixation. As a standardized model, a intertrochanteric osteotomy was performed on eight pairs of human, female, cadaver femora; a bony defect was also created medially to diminish support of the femoral neck. To stabilize the osteotomy a 135 degrees DHS was inserted. In one femur of each pair the glass-ionomer cement was applied to see whether this would enhance stability. The elastic and irreversible deformation of the internal fixation was measured at the osteotomy level under a cyclic load of 1400 N applied to the femoral head. In both the cemented and the uncemented cases, the femoral head shifted irreversibly in the caudal direction and tilted into a varus position. Movements of the femoral head in other directions were mainly reversible and small. The irreversible movement of the femoral head was significantly larger, approximately twice as great, following uncemented DHS fixation than after cemented fixation. Most movement occurred during the first ten load cycles; higher load cycles did not increase the irreversible deformation in the cemented group, but in the uncemented group a further increase in deformation was detected. These results indicate that internal fixation of unstable intertrochanteric femoral fractures can be significantly improved by the use of cement.(ABSTRACT TRUNCATED AT 250 WORDS)

Forty patients (mean age, 22.8 years) admitted for displaced ankle fracture were observed retrospectively to determine by clinical examination and measurement of plantar pressure distribution whether successful surgical treatment of ankle fractures led to gait symmetry, and whether intraindividual differences were related to fracture type and clinical outcome. The mean followup was 18.5 months (range, 12-36 months). The deviation of gait was quantified using a symmetry index of the total impulse. Using a clinical score, 6 patients had unsatisfactory results, and the remaining 34 had satisfactory results. The symmetry index of the good (-1.1%) and the poor results (-2.3%) decreased in the range of a healthy control group (-0.31%, n = 90), indicating that overall gait symmetry was achieved after trauma. The plantar pressure distribution showed significant load asymmetries. There was increased loading in the lateral forefoot of the injured leg in patients with good results and decreased pressure under the metatarsal heads of patients with bad results. Although those asymmetries were related neither to fracture type nor clinical outcome, the findings may illustrate compensation mechanisms that are used to regain gait symmetry after ankle alteration by trauma.

Durch mechanischen Dehnungsreiz induziert tangentialer Hautzug eine Flachenvermehrung, gleichzeitig werden jedoch auch proliferative Effekte in Gang gesetzt. Im Bereich der Epidermis zeigt sich eine erhohte Mitoserate der Keratinozyten. Im Bereich der Dermis uberwiegen die Vorgange des Matrixumbaues. Die Moglichkeiten der klinischen Anwendung von tangentialen Hautzugverfahren werden an einem Beispiel erlautert.

We know it is important to avoid excessive strain on reconstructed ligaments, but we do not know how individual muscles affect cruciate ligament strain. To answer this, we studied the effect of muscle forces and external loads on cruciate ligament strain. Nine cadaveric knee joints were tested in an apparatus that allowed unconstrained knee joint motion. Quadriceps, hamstring, and gastrocnemius muscle forces were simulated. Additionally, external loads were applied such as varus-internal or valgus-external rotation forces. Cruciate ligament strain was recorded at different knee flexion angles. Activation of the gastrocnemius muscle significantly (P < 0.05) strained the posterior cruciate ligament at flexion angles larger than 40 degrees. Quadriceps muscle activation significantly strained the anterior cruciate ligament when the knee was flexed 20 degrees to 60 degrees (P < 0.01) and reduced the strain on the posterior cruciate ligament in the same flexion range (P < 0.05). Activation of the hamstring muscles strained the posterior cruciate ligament when the knee was flexed 70 degrees to 110 degrees (P < 0.05). Combined varus and internal rotation forces significantly increased anterior cruciate ligament strain throughout the flexion range (P < 0.05). The results suggest that to minimize strain on the ligament after posterior cruciate ligament surgery, strong gastrocnemius muscle contractions should be avoided beyond 30 degrees of knee flexion. The study also calls into question the use of vigorous quadriceps exercises in the range of 20 degrees to 60 degrees of knee flexion after anterior cruciate ligament reconstruction.

We followed 38 patients with chronic ankle instability treated by a modified Evans procedure. Evaluation at an average of 68 months follow-up included a standard clinical questionnaire and examination, radiological procedures, and gait analysis. Plantar pressure distribution measurements were recorded during walking and were compared with data from a group of normal subjects (N = 100). The subjective patient questionnaire revealed 87% good or excellent results, but residual pain was reported by 40% of the patients. The gait analysis indicated a significant increase in midfoot loading (22%) consistent with an observed restriction of inversion after surgery. However, the plantar pressure changes were not associated with poor clinical outcome. We cannot say whether these increased pressures will be associated with long-term outcome.

A measuring system for the determination of the six degrees of freedom of three-dimensional movements is described. The main advantages of this goniometer linkage system are ease of handling and good cost-quality relationship. For small movements it has an accuracy of about 0.1 mm and 0.1 degree. Six potentiometers are rod-linked in such a way that the system can follow any movement, unconstrained. From the rotation of the potentiometers, the spatial movement of two solid bodies can be calculated by a computer. The reliability of the system has been demonstrated in several in vitro and in vivo applications.

The present study investigated the long-term effects of calcaneal fractures on the plantar pressure distribution during human gait. Fourteen patients participated in a follow-up study and were assigned to a group with good or poor calceneus restoration as indicated by normal or reduced Bohler's angle. Ten normal subjects with similar anthropometric characteristics were used for comparison. Gait analysis was performed by means of a capacitive pressure distribution platform. A comparison of the injured with the healthy foot of all patients revealed a statistically significant peak pressure decrease under medial areas of the foot (first metatarsal -24%) and an increase in lateral areas (midfoot +135%, fifth metatarsal +122%). This load shift towards a lateral loading indicates a persisting deviation of the gait pattern long after healing. Furthermore we investigated whether the success of the restoration of hindfoot geometry as reflected in Bohler's angle had an effect on the foot loading characteristics. Therefore we compared the gait patterns of the two patient groups with the normal subjects. However, the results did not reveal more abnormal pressure patterns in the poorly reduced group. RELEVANCE:--The restoration of the shape of the calcaneus with joint surface congruity and reconstruction of Bohler's angle appears generally accepted as a major aim in the treatment of calcaneal fractures. While this goal can usually be achieved by contemporary surgical techniques, the restoration of foot function under dynamic loading conditions is not guaranteed and should be assessed objectively. The investigation of the foot loading characteristics by means of plantar pressure measurements can be used to support the evaluation of the patient's recovery after trauma.

There is a group for the development and testing of biodegradable implants within the German Section of AO/ASIF-International. After in-vitro screening of various polylactide materials and copolymers a L/DL-polylactide 70/30 was selected. In animal experiments it showed long durability over a period of 9 months and expected degradation afterwards. In clinical experience over more than three years the biodegradable pins with x-ray opaque markers (Polypin) applied for fixation of osteochondral lesions yielded good results and no infections. A multicenter clinical study now includes 57 patients. Polypin is the first biodegradable implant of the AO/ASIF-group.

We asked whether dynamization of externally fixed diaphyseal fractures could improve bone healing in comparison to rigid fixation of fractures having similar remaining gap sizes. To answer this question we evaluated metatarsal osteotomies in 12 sheep. The osteotomy with a 0.6-mm gap was stabilized with a specially designed high bending and torsional stiffness external ring fixator. Osteotomies in six sheep were stabilized rigidly (axial movement0.06 mm) or dynamically (axial movement 0.15-0.34 mm). The cyclical axial interfragmentary movement was caused by the load-bearing of the operated limb. With increasing healing time, the initially allowed movement was decreased by callus formation around the osteotomy. The reduction in interfragmentary movement was measured and monitored by a linear variable displacement transducer at the external fixator and a telemetry system. After 9 weeks the sheep were sacrificed and the healed bones were investigated biomechanically and histomorphologically. Compared to the rigidly fixed osteotomies, the dynamized osteotomies showed significantly (P0.05) greater (+41%) callus formation and 45% greater tensile strength of the newly formed bone in the cortical osteotomy gap. Histological analysis indicated that the effect of dynamization occurred mainly after the 5th week. RELEVANCE: From these results we conclude that dynamic fixation of diaphyseal gaps is advantageous in comparison to stable external fixation.