Christian Stärke

The Effect of a Nonanatomic Repair of the Meniscal Horn Attachment on Meniscal Tension: A Biomechanical Study

PURPOSE The purpose of this biomechanical study was to investigate the potential effect of a nonanatomic repair of the meniscal horn attachment on the resultant circumferential tension in a large animal model and to show that the circumferential tension of the meniscus affects the local stress of the cartilage. METHODS All investigations were done in the medial compartment of porcine knees. First, the anterior horn attachment of the meniscus was mechanically separated from the surrounding tibial bone and fitted with a force transducer (n = 8). The femorotibial joint was loaded in compression at different flexion angles, and the resultant tension at the horn attachment was recorded. The measurements were done with the horn attachment at its anatomic position and repeated with the horn attachment being displaced medially or laterally by 3 mm. In the second part the local deformation of the cartilage under a femorotibial compressive load was measured at different levels of meniscal hoop tension (n = 5). RESULTS A nonanatomic position of the horn attachment had a significant effect on the resultant tension (P < .01). Placing the horn attachment 3 mm medially decreased the tension at the horn attachment by 49% to 73%, depending on flexion angle and femorotibial load. The opposite placement resulted in a relative increase in the tension by 28% to 68%. Lower levels of meniscal hoop tension caused increased deformation of the cartilage (P < .05), indicating increased local stress. CONCLUSIONS A nonanatomic position of the horn attachment strongly affects conversion of femorotibial loads into circumferential tension. There is a narrow window for a functionally sufficient repair of meniscal root tears. CLINICAL RELEVANCE Although clinical inferences are limited because the specimens used were from a different species, there seems to be only a narrow window for a mechanically sufficient repair of root tears.

Biomechanical properties under cyclic loading of seven meniscus repair techniques

The purpose of the current study was to obtain additional information about the biomechanical behavior of different fixation techniques for meniscus repair using recently developed biodegradable implants and suture repair techniques. The posterior horns of human menisci were used to investigate the meniscus repair construct of the Arrow™, Screw™, Stinger™, Fastener™, T-fix™, and horizontal and vertical mattress suture. A 20 mm-longitudinal incision was made in the meniscus, similar to a bucket handle lesion, 3 mm from the meniscosynovial rim and was repaired. One hundred cycles between 5 N and 15 N were done using a tension load machine with a loading rate of 10 N/second. The stiffness, displacement, and pullout strength were examined. The significantly highest stiffness was found for the vertical mattress suture (17.1 N/mm) and Stinger (15 N/mm) followed by the Arrow (13.7 N/mm), T-fix (10.5 N/mm), and horizontal mattress suture (10 N/mm). Superior load to failure was obtained for the suture repair in comparison with the biodegradable implants. Despite the lower pullout strength of biodegradable implants, similar stiffnesses were found for the Stinger and Arrow in comparison with the mattress suture technique. These techniques provide the most rigid fixation that is essential for tissue healing.

Local treatment of meniscal lesions with vascular endothelial growth factor.

BACKGROUND The healing potential in the avascular regions of the meniscus is very limited, and improving the vascularity might be a reasonable way to improve healing. Vascular endothelial growth factor (VEGF) is one of the most potent proangiogenetic factors. We hypothesized that the local application of VEGF(165) would (1) improve the healing of a lesion in the avascular region of the meniscus, (2) induce angiogenesis in both the avascular and vascular regions, and (3) increase the amounts of VEGF mRNA and VEGF. METHODS In eighteen sheep, the medial menisci were cut longitudinally in the avascular region and were sutured. Three groups were established depending on the suture material: (1) uncoated Ethibond, (2) Ethibond coated with VEGF(165) and its carrier Poly(D,L-Lactide) (PDLLA), and (3) Ethibond coated with PDLLA. The contralateral medial menisci served as a control group. Each of the three suture type groups included six animals. After eight weeks, the sheep were killed, and the menisci were examined macroscopically. Immunohistochemistry of Factor VIII and VEGF and real-time reverse-transcription polymerase chain reaction (RT-PCR) of VEGF mRNA were performed. Additionally, the VEGF release kinetics from the VEGF/PDLLA-coated suture were evaluated in vitro. RESULTS In this model, VEGF did not improve meniscal healing. It did not increase angiogenesis in the avascular or vascular region, the VEGF concentration, or the amount of VEGF mRNA. VEGF release from the coated suture peaked on Day 3 and was nearly zero on Day 9. CONCLUSIONS The local application of VEGF(165) as eluted from suture did not increase meniscal angiogenesis or improve meniscal healing. In addition, there was no effect on the amount of VEGF mRNA and VEGF. The VEGF carrier (PDLLA) may have been inadequate because of the short duration of VEGF supply.

Distraction Forces on Repaired Bucket-Handle Lesions in the Medial Meniscus

Background Numerous studies have investigated the biomechanical properties of meniscal repair techniques. One of the most commonly discussed parameters is the failure load in the axis of insertion, although little is known about the distraction forces actually occurring at repaired bucket-handle lesions. Hypothesis There are clinically relevant distraction forces on repaired meniscus bucket-handle lesions. Study Design Controlled laboratory study. Methods Meniscus bucket-handle lesions were created and repaired in human cadaveric knees with a vertical suture made from a braided steel wire. A small-sized load sensor was connected to the wire at the periphery of the meniscus. The distraction forces acting on the lesion were measured at different knee joint angles (0°-120° of flexion) with internal and external rotation and with and without weight loading. Forces in excess of 10 N were considered to have clinical relevance. Results Mean forces on the meniscus repair ranged from 1.64 to 4.72 N. Irrespective of the modalities (ie, different flexion angles, weight load, direction of rotation), it was found that the forces were well below the cutoff value of 10 N (P <. 01). Increasing flexion angles generally did not cause an increase in distraction forces. Conclusion The data suggest that distraction forces are not the primary factor in the mechanical stability of meniscal repair. It must therefore be assumed that other factors such as shear forces are of greater significance. Clinical Relevance The results may help to validate the biomechanical properties of different meniscal repair techniques.

Structural Properties of Sutures Used in Anchoring Multistranded Hamstrings in Anterior Cruciate Ligament Reconstruction: A Biomechanical Study

Sutures are frequently used in anchoring hamstring or quadriceps tendon grafts in cruciate ligament reconstruction. Trumpet like widening of the femoral bone canal was found in patients having had anterior cruciate ligament reconstruction with hamstring autograft. We investigated 5-mm Polylene tape (Genzyme, Boston, MA) and Mersilene tape (Ethicon, Somerville, NJ) as well as No. 6 Ethibond sutures (Ethicon) for ultimate load, stiffness, and elongation under tension of 50 N, 150 N, 250 N, and ultimate load. The Mersilene and Polylene tapes were tested in single loops and Ethibond in double loops having a length of 30 mm. The length is similar to that used intraoperatively for the graft fixation. The suture materials were loaded using a material testing machine at a strain rate of 60 mm/min. The ultimate loads of the loops with knots were 474 N +/-24.7 N for Polylene, 437 N +/-38.2 N for Mersilene, and 338 N +/-16.8 N for Ethibond, and was statistically significant (analysis of variance [ANOVA], P<.05). The elongation under a tension load of 50 N was similar for Ethibond (1.2+/-0.216 mm) and Polylene (1.3+/-0.32 mm). Mersilene (1.7+/-0.34 mm) showed an increased elongation (ANOVA, P=.03). The stiffness for Ethibond was 37.1+/-2.7 N/mm, for Mersilene 38.4+/-3.8 N/mm, and for Polylene was 47+/-3.1 N/mm. The Polylene tape appears to be the most suitable material in terms of strength and stiffness. Nevertheless, the stiffness of all the tested materials is greatly inferior to the stiffness of the commonly used grafts. We believe that a stiffer graft construct might reduce motion during the early period of ingrowing.

Tensile Forces on Repaired Medial Meniscal Root Tears

PURPOSE The goals of this study were to measure the tensile forces acting on repaired medial meniscal root lesions and to investigate how they depend on femorotibial rotation, flexion, and compressive load. METHODS In 6 human cadaveric knees, the posterior medial meniscal root was completely detached and then repaired with a pullout suture. A force transducer was installed such that it measured tensile forces acting on the suture. The resultant tension at the posterior medial meniscal root was measured for flexion angles up to 120° at 2 levels of femorotibial compressive load (100 and 500 N) in neutral, internal, and external rotation of the knee. RESULTS Rotation had a highly significant effect on root tension (P < .001). Internal rotation of the femur increased the resultant tension, whereas external rotation decreased it. The tension at the meniscal root was related to the femorotibial load (P < .001). Although no significance was reached, a trend toward higher flexion angles causing more tension was observed. The highest mean tension of 60.1 ± 20.2 N was generated with internal rotation, a 500-N load, and 90° flexion. CONCLUSIONS Our study shows in a human in vitro model that motion and weight loading of the knee can generate considerable tensile forces in the posterior medial meniscal root. Internal rotation of the femur increases the resultant tension substantially, whereas external rotation has the opposite effect. CLINICAL RELEVANCE The data can potentially aid the surgeon in finding appropriate rehabilitation exercises after a medial meniscal root repair.

Tensile forces at the porcine anterior meniscal horn attachment

Tibiofemoral compression causes circumferential tension in the knee meniscus, which is transferred to the tibial bone at the anterior and posterior attachments. The objective of the study was to measure the resulting tensile forces at the horn attachment in a porcine model. The anterior horn attachment of the porcine medial meniscus (n = 10) was separated from the surrounding bone with a core reamer. A force transducer was installed such that tensile forces acting upon the now mobile horn attachment could be measured. The tibiofemoral joint was loaded in compression, starting at a preload of 30 N, with three 150‐N increments, giving 180, 330, and 480 N load. Flexion angles of 0, 30, and 60° were investigated. The average resultant tension at the horn attachment was 26.3, 40.6, and 55.4 N with full extension, 29.2, 47.8, and 62.2 N at 30° flexion and 30.1, 49.6, and 68.1 N at 60° flexion. The tibiofemoral compression had a significant effect on the tension (p < 0.001), whereas no influence of the flexion angle was found (p = 0.291). The study demonstrates that tibiofemoral compressive loads cause considerable tensile forces at the anterior meniscal horn attachment. The data are of interest for models of the repair or replacement of the knee menisci.

Mechanische Eigenschaften von Fadenmaterialien zur Verankerung von Kreuzbandtransplantaten

ZusammenfassungBei der Verwendung von Semitendinosussehnen für die vordere Kreuzbandplastik kommen textile Materialen als Konnektoren für die Verankerung zum Einsatz. Vor Abschluss der ossären Integration besitzt die Verankerung hinsichtlich der biomechanischen Stabilität große Bedeutung. Die folgende Studie untersuchte die maximale Zuglast sowie die irreversible und elastische Elongation von Nr. 6 Ethibond, 5-mm Mersilene- und 5-mm-Polylenetape in Form von Schlaufen in einer Länge von 30 mm im konditionierten und nichtkonditionierten Zustand unter zyklischen Belastungen bis 50 und 100 N. Für die Untersuchungen wurde eine axiale Universalprüfmaschine verwendet. Die Ergebnisse ergaben nur für Mersilene eine signifikante Verbesserung der Bruchlast von 416 auf 462 N nach Konditionierung. Polylene besaß mit 479 N die signifikant höchste maximale Bruchlast. Bei oszillierenden Belastungen bis 100 N zeigten die unkonditionierten Schlaufen eine Elongation von 4,1 mm für Ethibond, 2,9 mm für Polylene und von 5,4 mm für Mersilene. Nach Konditionierung verringerte sich die Elongation auf maximal 1,4 mm. Auch auf die rein elastische Verlängerung bei Zyklen bis 50 und 100 N bewirkte die Konditionierung eine signifikante Verringerung. Basierend auf diesen Ergebnissen zeigte Polylene die besten mechanischen Eigenschaften. Unabhängig vom Material empfiehlt sich, vor intraoperativer Anwendung die Schlaufen vor zu dehnen, um eine irreversible Verlängerung sowie das elastische Verhalten zu reduzieren.AbstractThe fixation of hamstring grafts in ACL reconstruction requires a connector device. During the process of ingrowing the graft stability depends entirely on the fixation. The following study focused on the mechanical conditions of no 6 Ethibond, 5 mm Mersilene tape and 5 mm Polylene tape. The material were tested as loops with a length of 30 mm including the knot similar to intraoperative conditions. The ultimate tension load and elongation of the conditioned and unconditioned loops were investigated under cyclic load of 50 N and 100 N using a tension load machine. The ultimate tension load increased significantly only for Mersilene from 416 N to 462 N. However, the highest ultimate tension load showed Polylene with 479 N. The oscillating load up to 100 N revealed for unconditioned loops and elongation of 4.1 mm for Ethibond, 2.9 mm for Polylene and 5.4 mm for Mersilene. The elongation decreased significantly for the conditioned loops to a maximum of 1.4 mm. Concerning the amplitude during the period of oscillating load there was found a significant reduction as well. Based on our results Polylene showed the best mechanical properties. Regardless the intraoperatively used material we advocate the conditioning of the loops before anchoring the hamstring graft in ACL reconstruction.

Autologous proliferative therapies in recalcitrant lateral epicondylitis.

ObjectiveThis study investigates the clinical effects of autologous conditioned plasma (ACP) injections and low-level laser application as therapy options for chronic lateral epicondylitis. DesignA total of 52 patients with chronic lateral epicondylitis were evaluated in this study; 26 of these patients received three ACP injections and the control group, with 26 patients, received 12 laser applications, with standardized physical therapy for all patients afterward. Control examinations took place before treatment, after 2 and 6 mos, and in the 1 yr final follow-up. The control examination included the visual analog scale for pain and Disabilities of the Arm, Shoulder and Hand outcome measure scores. ResultsThe analysis at final follow-up after 1 yr showed that both treatment options resulted in successful therapy outcome for the patients. In total, 63.5 % were successfully treated. Successful treatment was defined as more than 30% improvement in the visual analog score and more than 10.2 points in the Disabilities of the Arm, Shoulder and Hand score. Both groups showed a significant improvement in time response. ConclusionsThis study demonstrates the beneficial effects of autologous proliferative therapies in the treatment of lateral epicondylitis. The data show that laser application and ACP therapy lead to a clinical improvement in epicondylopathia. Especially the new treatment with ACP can be highlighted as an alternative and as an easy-to-apply therapy option for clinical practice.

Biomechanische Eigenschaften tibialer Fixationsverfahren von Hamstring-Transplantaten zur Kreuzbandrekonstruktion

Das Ziel der vorliegenden Arbeit bestand darin, unter Verwendung eines Tiermodells weitere Informationen zu unterschiedlichen Verankerungstechniken von Hamstring-Sehnen bei der vorderen Kreuzbandplastik hinsichtlich der maximalen Zuglast, Elongation und Steifigkeit zu gewinnen. Methode: Fünf verschiedene Fixationstechniken wurden untersucht. Die BTB-Gruppe beinhaltete die Verankerung des Lig. patellae mittels Titan-Interferenzschraube, die BIO-Gruppe die Verankerung der freien Sehen mittels Polylactatschraube, die SAN-Gruppe die Verwendung einer Sandwichtechnik mit Titan-Interferenzschraube, die STA-Gruppe die Verwendung von 2 Ligamentklammern und die FAD-Gruppe die Fadenverankerung mittels No.-6-Ethibond. Die Messungen erfolgten mit einer Universalprüfmaschine Typ Tiratest 2425®, die mit einer Zuggeschwindigkeit von 50 mm/min arbeitete. Ergebnisse: Die signifikant höchste Zuglast zeigte die BTB-Gruppe mit 718 ± 219 N (p < 0,01), gefolgt von der BIO-Gruppe (460 ± 116 N) und der STA-Gruppe (436 ± 52 N). Hinsichtlich der Steifigkeit bestanden keine Unterschiede zwischen der BTB- und BIO-Gruppe. Die signifikant geringste Steifigkeit boten die SAD-Gruppe und FAD-Gruppe (p < 0,05). Die Sandwichtechnik entsprach nicht der Stabilität, die für die Fixation von Kreuzbandtransplantaten erforderlich ist. Schlussfolgerungen: Für die Verankerung der Hamstring-Sehnen empfehlen wir neben der Verwendung der Biolactatschraube eine zusätzlich Sicherung mittels Ligamentklammer oder Pollerschraube über Ethibondfäden.The aim of our study was to gain more information about ultimate tension load, stiffness and elongation of different fixation techniques for Hamstring tendons in ACL-reconstruction in comparison to patellar ligainent fixation using a bovine model. Methods: Five different fixation techniques were investigated. The patella ligament (BTB-group) was fixed using a titanium interference screw. The four stranded tendons were anchored using either a biodegradable interference screw (BIO-group), two staples (STA-group), No. 6 ethibond sutures (FAD-group) or a new developed sandwich techniques with a titanium interference screw (SAD-group). The study was carried out using a material testing machine (Tiratest 2425®) under a loading rate of 50 mm/min. Results: The significantly highest pullout strength showed the BTB-group (718 ± 219 N) (p < 0,01) followed by the BIO-group (460 ± 116 N) and the STA-group (436 ± 52 N). Between the BTB- and STA-group there was no difference concerning the stiffness. The significantly lowest stiffness presented the SAD- and FAD-group (p < 0,05). The new sandwich-technique did not provided sufficient fixation strength for the fixation of four stranded tendons in ACL-reconstruction. Conclusion: We recommend for anchoring the Hamstring tendons the biodegradable interference screw and an additional fixation either using a staple or a screw via suture in order to provide sufficient fixation.