Biomechanische Evaluation von MPFL-Rekonstruktionen : Unterschiede der dynamischen retropatellaren Druckverteilung zwischen Gracilis- und Fascia lata-Transplantat

Ziel dieser Arbeit war die Evaluation des dynamischen patellofemoralen Anpressdruckes unter Verwendung der Gracilis-Sehne und der Fascia lata als alternatives Transplantat zur MPFL-Rekonstruktion bei intaktem, reseziertem und rekonstruiertem medialem patellofemoralem Ligament. Weiterhin wurden Auswirkungen des resezierten und rekonstruierten MPFL auf den patellaren Tilt und –Shift im Vergleich zum intakten Kniegelenk radiologisch festgestellt. Die Belastbarkeit der gesamten MPFL-Rekonstruktion mit dem jeweiligen Transplantat wurde abschließend mittels einer Materialprüfmaschine untersucht und die biomechanischen Eigenschaften der Transplantate hinsichtlich Stabilität und Reißfestigkeit unter zyklischer Belastung verglichen. Um die Versuche durchzuführen, wurden acht gepaarte menschliche Kniepräparate in einer Vorrichtung zur Evaluation der Kniekinematik fixiert. Der patellofemorale Anpressdruck wurde während einer dynamischen Flexionsbewegung bei 15°–30°–45°–60°–75° und 90° mittels einer Sensorfolie (Tek-Scan) aufgezeichnet. Das mediale patellofemorale Ligament wurde reseziert und die Messungen wurden wiederholt. Schließlich folgte die Rekonstruktion des MPFL unter Verwendung der Gracilis-Sehne (Gruppe I) oder des Fascia lata-Transplantates (Gruppe II). Die ossären femoralen und patellaren Fixierungspunkte der Grafts wurden unter fluoroskopischer Kontrolle aufgesucht. Die Transplantate wurden bei 30° Flexion des Kniegelenkes fixiert und die Messungen nach Rekonstruktion wiederholt. Darüber hinaus wurde mittels einer axialen Röntgenaufnahme der patellare Tilt und –Shift im nativen, MPFL-resezierten und MPFL-rekonstruierten Knie gemessen. Nach Abschluss der Versuchsdurchführung wurden die Transplantate in einer Materialprüfmaschine befestigt und sowohl die Elongation unter zyklischer Belastung als auch die maximale Versagenslast der Transplantate evaluiert. Als Ergebnis zeigte die Resektion des medialen patellofemoralen Ligamentes einen signifikant reduzierten patellofemoralen Anpressdruck medialseitig bei 15°, 30°, und 45° Flexion im Kniegelenk verglichen mit dem intakten Knie (p < 0,05), wohingegen die Rekonstruktion des MPFL sowohl unter Verwendung der Gracilis-Sehne als auch der Fascia lata zu einer Wiederherstellung der ursprünglichen Druckverteilung bei 15° und 30° Flexion führte. Jedoch fand man in der Gracilis-Gruppe nach Rekonstruktion des MPFL signifikant reduzierte Anpressdrücke an der gesamten Patellrückfläche während einer Flexion von 45° im Vergleich zum intakten Kniegelenk. In der Facia lata Gruppe wurde diese Reduzierung des patellaren Anpressdruckes nach MPFL-Rekonstruktion bei 45°, 60°, 75° und 90° festgestellt (p < 0,05). Radiologisch führte die Resektion des MPFL zu einer signifikanten Lateralisierung der Patella auf der axialen Röntgenaufnahme (p = 0,039), wohingegen die Rekonstruktion des MPFL mit beiden Transplantat-Varianten dazu führte, dass die ursprüngliche Position der Patella nahezu wiederhergestellt wurde. Bei Evaluation des patellaren Öffnungswinkels nach Laurin wurden keine signifikanten Unterschiede zwischen intaktem, reseziertem und rekonstruiertem MPFL gefunden (p > 0,05). Eine durchschnittliche Elongation von 2,92 mm und 11,02 mm wurde bei zyklischer Belastung für die Gracilis-Sehne bei 20 N und 50 N Zugkraft gefunden. Für die Fascia lata wurde bei gleicher Zugkraft eine Elongation von 3,2 mm und 12,9 mm detektiert. Eine ultimative Versagenslast wurde für die Gracilis-Sehne bei 78,5 N aufgezeichnet, wohingegen die Versagenslast der Fascia-lata Transplantate bei durchschnittlich 92,17 N lag. Der Vergleich dieser biomechanischen Eigenschaften der getesteten Transplantate zeigte keinen statistisch signifikanten Unterschied sowohl die bei zyklischer Belastung aufgetretene Elongation als auch die Versagenslast betreffend (p > 0,05). Zusammenfassend zeigte die anatomische Rekonstruktion des MPFL sowohl unter Verwendung des Gracilis-Transplantates, als auch der Fascia lata vergleichbare patellofemorale Druckverteilungen, welche den ursprünglichen Zustand des nativen Knies annähernd wiederherstellte. Ebenfalls wurden ähnliche biomechanische Eigenschaften der Transplantate und eine radiologisch vergleichbare Patella-Position in der Trochlea femoris aufgezeichnet. Das Fascia lata Transplantat zeigte sich als eine wertvolle Alternative zur Gracilis-Sehne im Hinblick auf die anatomische Rekonstruktion des MPFL.The purpose of the present work was to evaluate the dynamic patellofemoral contact pressure using the gracilis tendon and the fascia lata as an alternative graft option for reconstruction of the MPFL with an intact, MPFL-ruptured and MPFL-reconstructed knee. Furthermore, influences of the ruptured and reconstructed MPFL on patellar tilt and –shift were radiologically detected. The toughness of the complete MPFL-reconstruction using each of the grafts was finally evaluated with a material testing machine and the stiffness and stability of the grafts were analyzed during cyclic testing. Eight paired human cadaveric knees were fixed in a custom-made fixation device. Patellofemoral contact pressure was assessed during a dynamic flexion movement at 15°–30°–45°–60°–75° and 90° using a pressure-sensitive film (Tekscan). The medial patellofemoral ligament was cut, and measurements were repeated. Finally, reconstruction of the MPFL was performed using the gracilis tendon (group I) or a fascia lata graft (group II). Tunnel localization was performed under fluoroscopic control. Grafts were fixed at 30° of knee flexion, and pressure measurements were repeated. Moreover, radiological measurements were performed on an axial view in the native, MPFL-resected and MPFL-reconstructed status. After completing the tests, the transplants were fixed in a material testing machine to evaluate the elongation during cylcic testing and the ultimate failure load of each of the grafts. As a result, the incision of the medial patellofemoral ligament significantly reduced patellofemoral contact pressure at 15°, 30° and 45° of knee flexion on the medial side compared to the intact knee (p < 0.05), whereas reconstruction of the MPFL using either gracilis tendon of the fascia lata was able to restore pressure distributions at 15° and 30° of knee flexion. However, in the gracilis group, reconstruction of the MPFL revealed a significantly reduced contact pressure on the total retropatellar surface at 45° of flexion (p = 0.038) compared to the intact knee. In the fascia lata group, a significant reduction in patellofemoral contact pressure was observed after MPFL reconstruction at 45°, 60°, 75° and 90° of knee flexion (p < 0.05). Resection of the MPFL led to a significant lateralization of the patella on axial view (p = 0.039), whereas MPFL reconstruction with using either the gracilis tendon or the fascia lata was able to restore patella position compared to the intact knee (p > 0.05). No significant differences in the Laurin angle were found between the intact, MPFL - resected and MPFL - reconstructed knee (p > 0.05). A mean cyclic displacement of 2,92 mm and 11,02 mm were found for the gracilis tendon at 20 N and 50 N. A mean cyclic displacement of 3,2 mm and 12,9 mm were calculated for the fascia lata. A mean ultimate failure load of 78,5 N was found for the gracilis and 92,17 N for the fascia lata graft. Comparison of the biomechanical properties of the tested grafts revealed no significant differences neither in cyclic displacement nor in ultimate failure load (p > 0.05). In conclusion, anatomic reconstruction of the MPFL with either a gracilis or a fascia lata graft showed comparable patellofemoral pressure distributions which were closely restored compared to the native knee. Also similar biomechanical properties and radiological evaluated patellar positioning were detected. Therefore, the fascia lata has shown to be a viable alternative to the gracilis tendon for reconstruction of the MPFL

Outcomes and Tendon Integrity After Arthroscopic Treatment for Articular-Sided Partial-Thickness Tears of the Supraspinatus Tendon: Results at Minimum 2-Year Follow-Up

Background: The best surgical treatment option for symptomatic moderate- to high-grade articular-sided partial-thickness rotator cuff tears (PTRCTs) is still controversial. Purpose/Hypothesis: The purpose of this study was to evaluate patient-reported and clinical outcomes and tendon integrity after arthroscopic debridement or repair for PTRCTs at a minimum of 2 years postoperatively. We hypothesized that the overall outcomes would be positive, showing pain relief, good shoulder function, and high tendon integrity. Study Design: Cohort study; Level of evidence, 3. Methods: We evaluated 30 patients (16 men, 14 women; mean age, 51 years) who underwent arthroscopic treatment for symptomatic PTRCTs (Ellman grades 2 and 3). Debridement was performed in 15 patients, and arthroscopic tendon repair was performed in the remaining 15 patients. Patients completed the Constant score; American Shoulder and Elbow Surgeons (ASES) shoulder score; Western Ontario Rotator Cuff Index; Simple Shoulder Test; and visual analog scale (VAS) for pain, function, and satisfaction. In addition, patients were examined clinically (range of motion, impingement tests, rotator cuff tests, and tests for the long head of the biceps tendon), and morphologic assessment of rotator cuff integrity was performed using direct magnetic resonance arthrography and was classified according to Sugaya. Results: The mean follow-up period was 55 months. The patient-reported outcome measures showed high patient satisfaction, reduction in persistent pain, and good shoulder function. Linear regression analysis showed that the debridement group had significantly better results on the Constant (bias-corrected and accelerated [BCa] 95% CI, 4.20-26.30), ASES (BCa 95% CI, 5.24-39.26), and VAS (pain: BCa 95% CI, 0.13-3.62; function: BCa 95% CI, 1.04-4.84; satisfaction: BCa 95% CI, 0.14-6.28) scores than did the repair group. At follow-up, there was no significant difference between the groups in clinical testing results. Good supraspinatus tendon integrity was seen in most patients: Sugaya classification grade 1 in 13 patients, grade 2 in 11 patients, and grade 3 in 6 patients. Conclusion: Midterm results after arthroscopic debridement and repair for PTRCTs showed high patient satisfaction, good shoulder function, and high tendon integrity for both procedures. Patients who underwent arthroscopic debridement had higher Constant, ASES, and VAS scores compared with patients who underwent tendon repair

Numerical comparative study of five currently used implants for high tibial osteotomy: realistic loading including muscle forces versus simplified experimental loading

Abstract Background Many different fixation devices are used to maintain the correction angle after medial open wedge high tibial osteotomy (MOWHTO). Each device must provide at least sufficient mechanical stability to avoid loss of correction and unwanted fracture of the contralateral cortex until the bone heals. In the present study, the mechanical stability of following different implants was compared: the TomoFix small stature (sm), the TomoFix standard (std), the Contour Lock, the iBalance and the second generation PEEKPower. Simplified loading, usually consisting of a vertical load applied to the tibia plateau, is used for experimental testing of fixation devices and also in numerical studies. Therefore, this study additionally compared this simplified experimental loading with a more realistic loading that includes the muscle forces. Method Two types of finite element models, according to the considered loading, were created. The first type numerically simulated the static tests of MOWHTO implants performed in a previous experimental biomechanical study, by applying a vertical compressive load perpendicularly to the plateau of the osteotomized tibia. The second type included muscle forces in finite element models of the lower limb with osteotomized tibiae and simulated the stance phase of normal gait. Section forces in the models were determined and compared. Stresses in the implants and contralateral cortex, and micromovements of the osteotomy wedge, were calculated. Results For both loading types, the stresses in the implants were lower than the threshold values defined by the material strength. The stresses in the lateral cortex were smaller than the ultimate tensile strength of the cortical bone. The implants iBalance and Contour Lock allowed the smallest micromovements of the wedge, while the PEEKPower allowed the highest. There was a correlation between the micromovements of the wedge, obtained for the simplified loading of the tibia, and the more realistic loading of the lower limb at 15% of the gait cycle (Pearson’s value r = 0.982). Conclusions An axial compressive load applied perpendicularly to the tibia plateau, with a magnitude equal to the first peak value of the knee joint contact forces, corresponds quite well to a realistic loading of the tibia during the stance phase of normal gait (at 15% of the gait cycle and a knee flexion of about 22 degrees). However, this magnitude of the knee joint contact forces overloads the tibia compared to more realistic calculations, where the muscle forces are considered. The iBalance and Contour Lock implants provide higher rigidity to the bone-implant constructs compared to the TomoFix and the PEEKPower plates

Numerical comparative study of five currently used implants for high tibial osteotomy: realistic loading including muscle forces versus simplified experimental loading

Background Many different fixation devices are used to maintain the correction angle after medial open wedge high tibial osteotomy (MOWHTO). Each device must provide at least sufficient mechanical stability to avoid loss of correction and unwanted fracture of the contralateral cortex until the bone heals. In the present study, the mechanical stability of following different implants was compared: the TomoFix small stature (sm), the TomoFix standard (std), the Contour Lock, the iBalance and the second generation PEEKPower. Simplified loading, usually consisting of a vertical load applied to the tibia plateau, is used for experimental testing of fixation devices and also in numerical studies. Therefore, this study additionally compared this simplified experimental loading with a more realistic loading that includes the muscle forces. Method Two types of finite element models, according to the considered loading, were created. The first type numerically simulated the static tests of MOWHTO implants performed in a previous experimental biomechanical study, by applying a vertical compressive load perpendicularly to the plateau of the osteotomized tibia. The second type included muscle forces in finite element models of the lower limb with osteotomized tibiae and simulated the stance phase of normal gait. Section forces in the models were determined and compared. Stresses in the implants and contralateral cortex, and micromovements of the osteotomy wedge, were calculated. Results For both loading types, the stresses in the implants were lower than the threshold values defined by the material strength. The stresses in the lateral cortex were smaller than the ultimate tensile strength of the cortical bone. The implants iBalance and Contour Lock allowed the smallest micromovements of the wedge, while the PEEKPower allowed the highest. There was a correlation between the micromovements of the wedge, obtained for the simplified loading of the tibia, and the more realistic loading of the lower limb at 15% of the gait cycle (Pearson’s value r = 0.982). Conclusions An axial compressive load applied perpendicularly to the tibia plateau, with a magnitude equal to the first peak value of the knee joint contact forces, corresponds quite well to a realistic loading of the tibia during the stance phase of normal gait (at 15% of the gait cycle and a knee flexion of about 22 degrees). However, this magnitude of the knee joint contact forces overloads the tibia compared to more realistic calculations, where the muscle forces are considered. The iBalance and Contour Lock implants provide higher rigidity to the bone-implant constructs compared to the TomoFix and the PEEKPower plates