[Dynamic intraligamentary stabilization of the anterior cruciate ligament. Operative technique and short-term clinical results]. / Dynamische intraligamentäre Stabilisierung des vorderen Kreuzbandes. Operationstechnik und klinische Kurzzeitergebnisse.

BACKGROUND: Reconstruction of tears in the anterior cruciate ligament with a tendon graft is the current gold standard. OBJECTIVES: Dynamic intraligamentary stabilization is a new technique for preservation of the anterior cruciate ligament. METHODS: This article describes the indications, operative technique, rehabilitation and preliminary results after dynamic intraligamentary stabilization for acute anterior cruciate ligament ruptures. RESULTS: A total of 24 women and 31 men with an acute anterior cruciate ligament tear were included in a prospective clinical trial. Of the patients 26 had already been followed-up for 12 months and satisfying values for the Lysholm, Tegner and International Knee Documentation Committee (IKDC) outcome scores were achieved. High subjective patient satisfaction was also achieved. The Lachman test showed a mean anterior translation difference to the healthy side of 1.7 mm. CONCLUSION: Dynamic intraligamentary stabilization in combination with microfracturing of the notch can provide biomechanical and biological conditions for self-healing of the anterior cruciate ligament. Further clinical and biomechanical research is needed to identify appropriate patients and rupture types suitable for this new technique.

Comparison of outside-in and inside-out technique for tibial fixation of a soft-tissue graft in ACL reconstruction using the Shim technique.

INTRODUCTION: The aim of this study was to compare the biomechanical properties of tibial fixation of a free tendon graft in ACL reconstruction using the Shim, a new wedge-shaped implant, in an outside-in technique to fixation by the Shim used in an inside-out technique and fixation by interference screw in a porcine model. MATERIALS AND METHODS: Porcine tibia and flexor tendons were used. In Group 1, the Shim was applied outside-in. In Group 2, the Shim was inserted inside-out. In the Group 3, an 8-mm interference screw was used. Ten specimens were tested in each group. Load-to-failure, elongation, stiffness and failure mode were recorded. Cyclic loading was performed between 5 and 250 N for 1,000 cycles, followed by a load to failure testing. RESULTS: Mean maximum load-to-failure was 629.53 N in Group 1,648.54 N in Group 2 and 749.53 N in Group 3. There was no significant difference between the groups. Stiffness varied between 127.34 N/mm in Group 1, 151.27 N/mm in Group 2 and 182.25 N/mm in Group 3. No significant differences were found between outside-in Shim and interference screw fixation. No significant difference was found for elongation among the three groups. The main failure mode was a rupture of the tendon in the IFS group and a slippage of either the implant or the tendon in both groups using the Shim. CONCLUSIONS: As no statistically significant difference could be seen concerning load to failure, stiffness and elongation between the inside-out and the outside-in techniques, the Shim can be used for tibial fixation in an outside-in or inside-out technique depending on the preference of the surgeon. To prevent slippage of the graft a hybrid fixation should be considered.

Structural properties of a new device for graft fixation in cruciate ligament reconstruction: the shim technique.

INTRODUCTION: In ACL reconstruction using a soft tissue graft, aperture fixation with interference screws (IFS) can lacerate and rotate the graft and cause primary tunnel widening. To overcome these downsides, a new wedge-shaped implant (MegaShim, Karl Storz, Germany) was developed. We hypothesized that aperture fixation of hamstring ACL reconstruction using the MegaShim technique shows comparable structural properties when compared to interference screw fixation. METHODS: In a porcine knee model, ACL reconstructions with a tunnel diameter of 6, 7, 8 and 9 mm were performed and human hamstring grafts were fixed using the MegaShim technique (group I). In group 2, grafts were fixed in a hybrid fixation using a MegaShim and cortical flip button (FlippTack, Karl Storz, Germany). Interference screw graft fixation served as a control group (group III). Maximum load, yield load and stiffness were recorded using material testing machine. Grafts were cyclically preconditioned between 0 and 20 N for 10 cycles before the graft-bone complex was loaded to failure. Statistical evaluation was performed using SPSS Version 11.0. RESULTS: Mean maximum load to failure for the hybrid fixation was significantly higher than after interference screw or MegaShim fixation. The difference between MegaShim and interference screw fixation showed no significant difference for 6 and 7 mm sizes. An 8 and 9 mm MegaShim fixation resulted in significantly lower ultimate failure load compared to interference screw fixation. Stiffness of grafts fixed using 6 mm MegaShim was significantly lower than grafts fixed with hybrid or interference screw fixation, whereas no significant differences were found in the 7, 8, and 9 mm fixations. CONCLUSION: Aperture fixation using the MegaShim technique provides comparable structural properties compared to interference screw fixation. Hybrid fixation using MegaShim and cortical flip button results in significantly higher ultimate failure loads than both aperture fixation approaches. Smaller grafts (6 mm) showed significantly lower ultimate failure load and stiffness than interference screw fixation. The "MegaShim technique" is an alternative to interference screw fixation concerning initial fixation strength.

Structural properties of a new fixation strategy in double bundle ACL reconstruction: the MiniShim.

INTRODUCTION: Double-bundle reconstruction of the ACL has become the focus of scientific and clinical interest in the last years. However, there is still a discussion about the most appropriate technique for graft fixation. Both, extracortical fixation systems like the Endobutton and aperture fixation by interference screws have advantages as well as disadvantages. Aim of this study was to analyze the biomechanical properties of a new small wedge shaped implant (MiniShim, Karl Storz, Germany) for the fixation of a soft tissue graft in double bundle ACL reconstruction and to compare it to an aperture fixation by interference screw and an extracortical fixation. METHODS: Porcine knees and flexor tendons were used for this study. 5 and 6 mm tunnels were drilled. The following fixation strategies were tested: 4 and 5 mm MiniShim (Karl Storz Germany), 6 mm interference screw (MegaFix, Karl Storz, Germany), hybridfixation by FlippTack (FlippTack, Karl Storz, Germany) and MiniShim and hybridfixation by FlippTack and 6 mm interference screw. All fixation strategies were tested with a 5 and 6 mm tendon graft. Maximum load, yield load and stiffness were recorded using a material testing machine. Load was applied in line with the bone tunnel. Grafts were cyclically preconditioned between 0 and 20 N for 10 cycles before the graft-bone-complex was loaded to failure. Statistical evaluation was performed using SPSS Version 11.0. RESULTS: Load to failure for the 5 mm graft was 81.1 and 118.0 N for the 4 and 5 mm MiniShims. Fixation by interference screw reached 237.4 N. The extracortical fixation resulted in a load to failure of 471.7 N. Load to failure for the 6 mm tendon grafts was 52.0 and 92.8 N for the 4 and 5 mm MiniShims. Fixation by interference screw resulted in a load to failure of 214.0 N. Extracortical fixation failed at 451.7 N. The difference between MiniShim and interference screw was statistically significant. Load to failure was significantly higher for extracortical fixation compared to fixation by MiniShim or interference screw. Hybrid fixation showed higher fixation strength compared to fixation by interference screw or MiniShim alone. This difference was statistically significant. Stiffness was significantly higher for fixation by interference screw compared to extracortical fixation and fixation by MiniShim. Four different modes of failure could be seen. All 4 mm MiniShims failed by slippage of the tendon past the MiniShim. In the 5 mm group the fixation failed by pullout of the MiniShim or the tendon past the MiniShim. Hybrid fixation failed by rupture of the linkage material. When the graft was fixed by an interference screw failure occurred by rupture of the tendon at the fixation side. CONCLUSION: Hybrid fixation using the MiniShim provides biomechanical properties strong enough to withstand the forces occurring during rehabilitation and comparable to the fixation strength provided by interference screw. While fixation by MiniShim alone does not provide sufficient fixation strength in double bundle ACL reconstruction, hybridfixation using a cortical fixation by FlippTack is an alternative to aperture fixation by interference screw concerning primary stability.

[Medial patellofemoral ligament reconstruction using quadriceps tendon]. / Rekonstruktion eines medialen patellofemoralen Ligaments mit Quadrizepssehnenstreifen.

OBJECTIVE: Stabilization of the patella by medial patellofemoral ligament (MPFL) reconstruction. INDICATIONS: Recurrent lateral patella instability with chronic weakening of the MPFL. CONTRAINDICATIONS: Femoropatellar cartilage defects ICRS grade 3° or higher. Tuberositas Tibiae Trochlear Groove Index (TTTG) >20 mm. Lateral hypercompression of the patella without instability. SURGICAL TECHNIQUE: A 3 cm transverse skin incision at the superomedial edge of the patella in 90° of flexion. Longitudinal incision of the prepatellar bursa and exposure of the quadriceps tendon. Preparation of a flat tendon strip with a length of 8 cm, a width of 10 mm, and a thickness of 3 mm, leaving the attachment at the patella intact. Flipping of the tendon strip and passing of the graft through a tunnel underneath the prepatellar tissue at the medial edge of the patella. Passing of the graft in layer two of the medial joint capsule just below the fascia (layer 1) and the vastus medialis. Fixation of the graft in a bone tunnel, drilled in the femoral insertion site of the native MPFL using a biodegradable interference screw. POSTOPERATIVE MANAGEMENT: Patella centralizing brace for 4 weeks with range of motion (ROM) 0/0/90°, 20 kg of partial weight bearing for 3 weeks. Full weight-bearing according to pain starting from week 4 postoperatively. ROM up to 90° of flexion directly postoperatively. Free ROM starting from week 6 postoperatively. Stationary cycling 6 weeks postoperatively. Swimming and running after 10 months. Return to pivoting sports after 4-5 months. RESULTS: A total of 17 patients (7 men and 10 women; average age 21.5 years ±3.9 years, average BMI 22.6 ±3.9) were treated using this technique between March 2011 and November 2012. Only patients with at least one recurrent patella dislocation following conservative treatment were included. Patient satisfaction 12 months postoperatively was very high. Overall, 94.1 % would undergo the procedure again and 94.1 % were very satisfied with the cosmetic result. Significant improvement in Lysholm score 6, 12, and 24 months postoperatively (p < 0.05). Free ROM in 94.1 % of cases 12 months postoperatively. The Kujala score was reported to be 89 (±7.1) 12 months following surgery. No redislocation occurred during the 24 months following surgery.

The potential of implant augmentation in the treatment of osteoporotic distal femur fractures: a biomechanical study.

PURPOSE: Osteoporotic fractures of the distal femur are an underestimated and increasing problem in trauma and orthopaedic surgery. Therefore, this study investigates the biomechanical potential of implant augmentation in the treatment of these fractures. METHODS: Twelve osteoporotic surrogate distal femora were randomly assigned to the augmented or non-augmented group. All specimens were fixed using the LCP DF. In the augmented group additionally 1ml Vertecem V+ was injected in each screw hole before screw positioning. The construct represents an AO 33 A3 fracture. Biomechanical testing was performed as sinusoidal axial loading between 50 and 500N with 2Hz for 45,000 cycles, followed by loading between 50 and 750N until failure. RESULTS: The augmented group showed significant higher axial stiffness (36%). Additionally the displacement after 45,000 cycles was 3.4 times lower for the augmented group (0.68±0.2mm vs. 2.28±0.2mm). Failure occurred after 45,130 cycles (SD 99) in all of the non-augmented specimens and in two specimens of the augmented group after 69,675 cycles (SD 1729). Four of the augmented specimens showed no failure. The failure mode of all specimens in both groups was a medial cut-out. CONCLUSIONS: This study shows a promising potential of implant augmentation in the treatment of osteoporotic distal femur fractures.

[Proliferation kinetics of Ehrlich ascites tumors during cisplatin administration]. / Proliferationskinetik des Ehrlich-Aszites-Tumors unter cis-Platin.

In order to study the relationship between numerical growth and DNA-frequency distribution of tumor cells model experiments were made on the Ehrlich ascites tumor of mice after a single doses of the cytostatic cis-Platin. In 84 mice the tumor growth was measured by cell counting and the DNA-histogram by flow-cytometry. With exception of the controls 4, 8, 16 mg cis-Pt/kg were applied i.p. at the 5th day of tumor growth. An inhibition or a retardation of tumor growth is always observed. The 4 mg doses leads to a G2-blockade resulting in an increase of the G2-peak in the DNA-histogram after 2 days (7th day of growth). After 7 days of tumor growth) the effect has been mainly subsided. The effect of 16 mg/kg is a blockade of G2- and S-phase as well, connected with a complete inhibition of tumor growth. Therefore after two days (7th day of growth) this DNA-histogram is very similar to that of the control. Later on a recovery of DNA-synthesis occurs while the G2-blockade is still existing. Therefore the G2-peak is very marked 7 days after application (12th day of growth). All doses result in a disturbance of higher ploid cycles with an increase of hyper-8c-nuclei.