Jürgen Koebke

Femoral bone tunnel placement using the transtibial tunnel or the anteromedial portal in ACL reconstruction: a radiographic evaluation

Correct placement of the tibial and femoral bone tunnel is prerequisite to a successful anterior cruciate ligament (ACL) reconstruction. This study compares the resulting radiographic femoral bone tunnel position of two commonly used techniques for arthroscopically assisted drilling of the femoral bone tunnel: the transtibial approach or drilling through the anteromedial arthroscopy portal. The resulting bone tunnel position was assessed in postoperative knee radiographs of 70 patients after ACL reconstruction. Three independent observers identified the femoral bone tunnel and determined its position in the lateral and A–P view. Differences in femoral tunnel position between transtibial and anteromedial drilling were evaluated. In the sagittal plane, significantly more femoral bone tunnels were positioned close to the reference value using an anteromedial drilling technique (86%) when compared to transtibial drilling (57%). Drilling through the transtibial tunnel resulted in a significantly more anterior position of the femoral tunnel. In the frontal plane, femoral bone tunnels which were placed through the anteromedial arthroscopy portal displayed a significantly greater angulation towards the lateral condylar cortex (50.92°) when compared to transtibial drilling (58.82°). In conclusion, drilling the femoral tunnel through the anteromedial arthroscopy portal results in a radiographic femoral bone tunnel position which is suggested to allow stabilization of both anterior tibial translation and rotational instability when using a single bundle reconstruction technique. Further studies may evaluate if there are any clinical advantages using the anteromedial portal technique.

Biomechanics of the anterior cruciate ligament and implications for surgical reconstruction

Injury to the anterior cruciate ligament (ACL) is regarded as critical to the physiological kinematics of the femoral-tibial joint, its disruption eventually causing long-term functional impairment. Both the initial trauma and the pathologic motion pattern of the injured knee may result in primary degenerative lesions of the secondary stabilisers of the knee, each of which are associated with the early onset of osteoarthritis. Consequently, there is a wide consensus that young and active patients may profit from reconstructing the ACL. Several factors have been identified as significantly influencing the biomechanical characteristics and the functional outcome of an ACL reconstructed knee joint. These factors are: (1) individual choice of autologous graft material using either patellar tendon-bone grafts or quadrupled hamstring tendon grafts, (2) anatomical bone tunnel placement within the footprints of the native ACL, (3) adequate substitute tension after cyclic graft preconditioning, and (4) graft fixation close to the joint line using biodegradable graft fixation materials that provide an initial fixation strength exceeding those loads commonly expected during rehabilitation. Under observance of these factors, the literature encourages mid-to long-term clinical and functional outcomes after ACL reconstruction.

The arteries of the humeral head and their relevance in fracture treatment.

Bone vascularisation has gained increased interest in relation to the blood supply of bone fragments during treatment of fractures. In the current study the pattern of vascular supply of the proximal humerus was studied in six cadavers by the corrosion technique. Furthermore, the effect of fractures on the vascular supply was also investigated. In all preparations the intraosseous arteries of the humeral head arose from the circumflex arteries, which surrounded the humerus and dispatched branches towards the proximal end. The main vessel was the branch of the anterior circumflex artery, penetrating the major tubercle in six of six cases. Due to the intraosseous arch shape of this vessel it is referred to as the arcuate artery. Besides other smaller vessels, there was also a vascular network arising from the posterior circumflex artery. Their branches penetrated medially at the cartilage bone interface in five of six preparations. The medial bone arteries appear to gain distinctive importance in humeral head fractures by their impact on the vascularisation of the fracture fragments. After disruption of the arterial supply from the arcuate artery, the vascularisation of the head fragments is most likely ensured by this group of vessels. Therefore, necessary repositioning manoeuvres during open reduction of the fracture should be conducted with care in order to preserve these arteries.

Antegrade femoral nailing: an anatomical determination of the correct entry point

Operative problems in the application of femoral locking nails are frequently related to an unfavourable entry point at the greater trochanter. Especially in more distally located fractures the nail is forced to follow the cortex abutted medullary canal. A wrong defined entry point either in the medio-lateral or dorso-ventral direction inevitably leads to tension between nail and femur. Forceful insertion in this situation may cause disastrous iatrogenic comminution at the fracture side or additional fractures at the proximal femur. To avoid tension between nail and femur the best suited entry point must be defined according to the natural medullary cavity. In 16 human cadaver femora, the natural medullary cavity was opened and after cleaning filled with a radio-opaque substance (barium sulphate). Twelve radiographs where taken from each bone starting with the anterior-posterior view and then turning the bone axially in steps of 15 degrees. From these radiographs, the ideal entry point at the greater trochanter was calculated. In 88% of the specimen the ideal entry point for a straight nail was found constantly at the medial border of the greater trochanter overlaying the tendinous insertion of the piriformis muscle. The axis of the medullary cavity was in average 2.1cm anterior to the dorsal border of the greater trochanter. In a second step the ideal entry point for bend nails was calculated. According to this calculation a bend nail with a radius of 100 cm needs an entry point 0.7 mm anterior to the dorsal edge of the greater trochanter. Overlaying the hook like shape of the posterior part of the trochanter.

Asymmetrical loading of the human triceps surae: I. Mediolateral force differences in the Achilles tendon.

An in vitro experiment was designed to identify whether tensile force on different triceps surae components would result in nonhomogenous force distribution across the human Achilles tendon. Medial tendon forces were significantly higher than lateral (23.2 ± 6.6%; P ≤ 0.05) when only the gastrocnemius medialis was subjected to force. Lateral forces were significantly higher when both gastrocnemii (30.6 ± 16.5%) or all three muscles (20.7 ± 10.9%) were loaded. Experimental identification of force concentrations in the human Achilles tendon contributes to the understanding of the origin of its injury.

Fine thread versus coarse thread. A comparison of the maximum holding power.

For osteosynthesis in the epiphyseal region of long bones, specialized screw types are available to achieve a better purchase in cancellous bone. Typically, the cancellous bone screw has a large outer thread diameter with a relatively small core diameter and a great pitch. Due to its dimensions, this screw type is not suited for the cancellous bone areas in hand and foot surgery, respectively. Fine machine screws are better adapted to the bone dimensions in this part of the skeleton. To compare the holding power of fine machine screws with the holding power of other screw types available in the market, a biomechanical study was undertaken. Different screw types were compared: 4 mm cancellous screw, 3.5 and 2.7 mm cortical screws and three different diameters of a fine machine screw (2.2, 1.6 and 1.2 mm). Both cortical screws were tested in pretapped and self-tapping version. Polyurethane foam and bovine cancellous bone were tested. The screws were applied according to the manufacturers instructions and an axial extraction force was applied. The 4 mm cancellous bone screws were superior to all the other screws in both test materials (P<0.05). The 3.5 mm cortical screw showed a significant difference compared to the 2.7 mm cortical screw in both materials. A significant difference between the self-tapping and pretapped screws of the same diameter was only found in the 3.5 mm cortical screws in polyurethane foam (P<0.05). Interestingly, the maximum holding power of the 2.2 mm fine machine screws in homogeneous test material (polyurethane foam) was as high as the holding power of the 2.7 mm cortical screws (P<0.05). In natural bovine cancellous bone, the result was even more striking. There was no significant difference between the 2.2 mm fine machine screws and the 3.5 mm cortical screws (P<0.05). Relative to their thread diameter, the fine machine screws were superior to conventional cancellous and cortical screws in cancellous bone. The high holding power of this screw type is at least partly due to the impaction effect of the drilling debris between the thread and the abutting spongy bone structure.

Characterization of a new rat model of experimental combined neurotrauma.

Traumatic brain injury (TBI) is present in two-thirds of patients with multiple injuries and in one-third combined with injuries of the extremities. Studies on interactive effects between central and peripheral injuries are scarce due to the absence of clinically relevant models. To meet the demand for “more-hit” models, an experimental model of combined neurotrauma (CNT) incorporating a standardized TBI via lateral fluid percussion (LFP) together with a peripheral bone fracture, i.e., tibia fracture, is introduced. Sprague-Dawley rats were randomized to four experimental groups: controls (n = 10), animals with TBI (n = 30), animals with tibia fracture (n = 30), and animals with CNT (n = 30). Morphological aspects of brain and bone injury were analyzed via standard histopathological procedures and x-ray. Trauma-induced neuromotor dysfunction was assessed using a standardized neuroscore. For interactive effects between injuries, we studied the extent and temporal pattern of circulating interleukin 6 (IL-6) levels via immunoassay and callus formation at fracture sites by means of microradiography. LFP produced an ipsilateral lesion with cortical contusion, hemorrhage, mass shift, and neuronal cell loss (adjacent cortex and hippocampus CA-2/-3), along with contralateral neuromotor dysfunction. X-rays confirmed complete fractures in the middle of the bone shaft. The type of injury (P < 0.001) and time (P = 0.022) were significantly associated with increased IL-6 levels. CNT produced the highest IL-6 plasma levels with a maximum peak at 6 h after trauma (P < 0.001). Similarly, callus formation at fracture sites in CNT was significantly increased versus fracture only (P < 0,01). The CNT model mimics a variety of clinically relevant features known from human multiple injury, including TBI, and offers novel approaches for investigation of interactive mechanisms and therapeutic approaches.

The injury of the calcaneocuboid ligaments.

The selective rupture of the calcaneocuboid ligament is extremely rare and frequently misdiagnosed. This study tries to clarify the mechanism, classification and treatment of this entity. The necessity of radiographs with varus stress and in certain cases of computer tomography (CT) and magnetic resonance imaging (MRI), beside the routine antero-posterior and lateral views, is emphasized. Thirteen cases out of five-hundred-twenty-one sprain injuries of the ankle are described, classified and the therapy discussed: If on varus stress radiographs, there is a calcaneocuboid angle <10 degrees without a bony flake (type 1) strapping for six weeks is indicated. A calcaneocuboid angle >10 degrees with or without a small bony flake of the ligament insertion (type 2) should primarily be treated with a shoe cast for 6 weeks; if there are persistent symptoms a secondary peroneus brevis tendon graft is recommended. A calcaneocuboid angle >10 degrees with a big flake (type 3) should be treated by open reduction and refixation of the ligament. Complex injuries (type 4) are characterised by cuboid compression fracture and ligament rupture.

Biomechanical properties of orthodontic miniscrews. An in-vitro study.

Objective:Comparing five commercially-available miniscrew types for skeletal anchorage with regard to the biomechanical properties influencing their primary stability.Material and Methods:Included in this study was a total of 196 self-tapping and self-drilling miniscrews having a diameter of 2 mm (or the largest possible diameter of the manufacturer in question), a thread shaft length of 10 mm, or the longest miniscrew supplied by the manufacturers. The screw types tested were the FAMI 2, Orlus mini-implant, T.I.T.A.N. Pin, tomas®-pin and Vector TAS™. Insertion and loosening torque measurements, and pullout tests in axial (0°), 20° and 40° directions, as well as test series with and without pilot hole drilling were performed. Bovine femoral heads having the same bone mineral density (BMD) were used as bone-testing material.Results:Higher insertion torques were found for the cylindrical FAMI 2 screw, the conical Orlus mini-implant and the Vector TAS™ screw (with mean values of 39.2 Ncm, 32.1 Ncm and 49.5 Ncm) than for the cylindrical T.I.T.A.N. pin and tomas®-pin. Insertion without predrilling led the insertion torques of all five screws to rise significantly. We noted statistically significant differences among the five screws in the pullout tests. Those highly significant differences at axial (0°) and 20°angles were not apparent at the 40° pullout angle. Compared with the pullout forces (load) in the axial direction, the cylindrical screws’ load values decreased markedly according to the angle (by up to –46.6%). The reduction in pullout force in conjunction with an increasing angle was much less pronounced in the conical screws (–0.8% to –29.0%). The tomas®-pin demonstrated the highest pullout force and stiffness values throughout the tests. A total of five tomas®-pins, two Orlus mini-implants and one FAMI 2 screw fractured during the pullout tests.Conclusions:Results from our insertion torque measurements suggest that a conical screw design will provide greater primary stability than cylindrical screw types. The cylindrical screw design’s superiority was evident in the pullout tests. All the miniscrews’ primary stability rose after drill-free insertion. The tomas ®-pin screws, although biomechanically superior to the other screws, were most prone to fracture.ZusammenfassungZiel:Ziel dieser Studie war der Vergleich fünf handelsüblicher Minischraubentypen zur skelettalen Verankerung hinsichtlich ihrer die Primärstabilität beeinflussenden biomechanischen Eigenschaften.Material und Methodik:Insgesamt wurden 196 zugleich selbstschneidende und selbstbohrende Minischrauben mit einem Durchmesser von 2 mm oder mit dem größtmöglichen Durchmesser des jeweiligen Fabrikats und einer Gewindeschaftlänge von 10 mm oder die längste von den Herstellern angebotene Minischraube, darunter die Schraubentypen FAMI 2, Orlus Mini- Implant, T.I.T.A.N. Pin, tomas®-pin und Vector TAS™, untersucht. Es wurden Eindrehmoment-, Lösemomentmessungen und Ausreißversuche in axialer (0°) sowie in 20°- und 40°-Zugrichtung durchgeführt sowie Testreihen mit und ohne Pilotbohrung vorgenommen. Als Knochentestmaterial wurden bovine Femurköpfe mit der gleichen Knochendichte (BMD) verwendet.Ergebnisse:Im Vergleich zu dem zylindrischen T.I.T.A.N. Pin und tomas®-pin waren die Eindrehmomente für die zylindrische FAMI-2-Schraube, das konische Orlus Mini-Implant und die Vector- TAS™-Schraube (mit Durchschnittswerten von 39,2 Ncm, 32,1 Ncm und 49,5 Ncm) höher. Bei der Insertion ohne Vorbohrung konnten die Eindrehmomente aller fünf Schraubentypen statistisch signifikant erhöht werden. In den Ausreißversuchen ergaben sich statistisch signifikante Unterschiede zwischen den fünf Schraubentypen. Die hochsignifikanten Unterschiede, die zwischen den fünf Schrauben für die Ausreißkräfte in axialer (0°) und 20°-Zugrichtung festgestellt wurden, waren für die Werte in 40°-Zugrichtung nicht ersichtlich. Verglichen mit den Ausreißkräften in axialer Zugrichtung, verringerten sich die Ausreißkräfte bei den zylindrischen Schrauben mit dem Winkel deutlich (um bis zu –46,6%). Bei den konischen Schrauben war die Abnahme der Ausreißkräfte mit steigendem Winkel deutlich geringer (–0,8% bis –29,0%). Der tomas®-pin erreichte in allen Testungen die höchsten Werte für Ausreißkraft und Steifigkeit. Insgesamt fünf tomas®-pins, zwei Orlus Mini-Implants und eine FAMI-2- Schraube frakturierten in den Ausreißversuchen.Schlussfolgerung:Der konische Schraubentyp weist bei den Eindrehmomentmessungen im Gegensatz zu den zylindrischen Schraubentypen eine höhere Primärstabilität auf. In den Ausreißversuchen war eine Überlegenheit der zylindrischen Schraubentypen zu erkennen. Durch die Insertion ohne Vorbohrung konnte die Primärstabilität bei allen Minipins gesteigert werden. Der tomas®-pin war trotz biomechanischer Überlegenheit gegenüber den anderen Schraubentypen am frakturanfälligsten.

Side differences in the anatomy of human knee joints

Side-to-side comparison of anatomical or functional parameters in the evaluation of unilateral pathologies of the human knee joint is common practice, although the amount of symmetry is unknown. The aim of this study was to test the hypothesis that there are no significant differences in the morphometric knee joint dimensions between the right and the left knee of a human subject and that side differences within subjects are smaller than intersubject variability. In 20 pairs of human cadaver knees, the morphometry of the articulating osseous structures of the femorotibial joint, the cruciate ligaments, and the menisci were measured using established measurement methods. Data were analyzed for overall side differences and the ratio between within-subject side differences and intersubject variability was calculated. In three out of 71 morphometric dimensions there was a significant side difference, including the posterior tibial slope, the anatomical valgus alignment of the distal femur, and the position of the femoral insertion area of the ACL. In two additional parameters, including the cross-sectional area of the ACL and PCL, within-subject side differences were larger than intersubject variability. In general, there was a positive correlation in morphometric dimensions between right and left knees in one subject. It is concluded that a good correlation in the morphometric dimensions of a human knee joint exists between the right and the left side. This study supports the concepts of obtaining morphometric reference data from the contralateral uninjured side in the evaluation of unilateral pathologies of the knee joint.