Sven U. Scheffler

Graft choice and graft fixation in PCL reconstruction.

Several grafts and several fixation techniques have been introduced for PCL reconstruction over the past years. To date, autograft and allograft tissues are recommended for PCL reconstruction, whilst synthetic grafts should be avoided. Autograft tissues include the bone-patellar tendon-bone graft, the hamstrings and the quadriceps tendon. Allograft tissues are increasingly being used for primary PCL reconstruction. The use of allograft tissues requires a number of formal prerequisites to be fulfilled. Besides the previous mentioned graft types allograft tissues include Achilles and tibialis anterior/posterior tendons. To date no superior graft type has been identified. Several techniques and devices have been used for fixation of a PCL replacement graft. Most of these were originally developed for ACL reconstruction and then adapted to PCL reconstruction. However, biomechanical requirements of the PCL differ substantially from those of the ACL. To date, requirements for PCL graft fixations are not known. From a systematic approach femoral graft fixation can either be achieved within the bone tunnel (nearly anatomic) with an interference screw or outside the bone tunnel on the medial femoral condyle using a staple, an endobutton or a screw. Tibial graft fixation can be achieved either with an interference screw in the bone tunnel or with a staple, screw/washer or sutures tied over a bone bridge outside the bone tunnel (extra-anatomic). An alternative fixation on the tibial side is the inlay technique that reduces the acute angulation of the graft at the posterior aspect of the tibia. Further research is necessary to identify the differences between the various fixation techniques.

The extracellular remodeling of free-soft-tissue autografts and allografts for reconstruction of the anterior cruciate ligament: a comparison study in a sheep model.

Our study was aimed to advance the currently limited knowledge about differences in the biological remodeling of free soft-tissue tendon allografts and autografts for ACL reconstruction. Allogenic and autologous ACL reconstructions were performed in a sheep model using the flexor digitalis superficialis tendon. After 6, 12 and 52xa0weeks the animals were sacrificed. We analyzed the collagen crimp formation and its relationship to expression of contractile myofibroblasts in both graft types. Additionally, structural properties and ap-laxity were compared during biomechanical testing. At 6xa0weeks only descriptive differences were found between autografts and allografts with a more organized crimp pattern and myofibroblast distribution in autografts. Significant differences in myofibroblast density and crimp formation were found after 12xa0weeks. At these early stages, the progress of remodeling in autografts was more advanced toward the central areas than in allografts. At 1xa0year, grafts in both study groups returned to an ACL-similar structure. Structural properties and ap-laxity did not vary significantly between auto- and allografts at early healing stages. However, at 52xa0weeks, failure loads, stiffness and ap-drawer test showed superior values for autograft ACL reconstruction. Extracellular remodeling of allografts develops slower than in autografts. Therefore, rehabilitation procedures will have to be adapted according to graft and patient selection. Postoperative treatment regimens from autograft primary ACL reconstruction should not be directly transferred to allograft ACL reconstructions.

Stress radiography to measure posterior cruciate ligament insufficiency: a comparison of five different techniques

Stress radiography presents the golden standard to quantify posterior laxity in posterior cruciate ligament (PCL) insufficiency. Several different techniques are currently available, but comparative data are insufficient. Different stress radiographic techniques result in different values for posterior laxity. Comparative controlled clinical study was designed. Prior to PCL reconstruction 30 patients underwent a series of stress radiographs: Telos device, hamstring contraction, kneeling view, gravity view, and an axial view. Posterior displacement, side-to-side difference (SSD), condyle rotation, required time, and pain were measured. Posterior displacement was: Telos 12.7xa0±xa03xa0mm (SSD 10.6xa0±xa03.1xa0mm), hamstring contraction 11.2xa0±xa03.2xa0mm (SSD 8.5xa0±xa03.4xa0mm), kneeling 14.4xa0±xa03.8xa0mm (SSD 10.2xa0±xa03.5xa0mm), gravity view 10.5xa0±xa02.8xa0mm (SSD 9.1xa0±xa02.4xa0mm), and axial view 19.4xa0±xa06.9xa0mm (SSD 8.5xa0±xa04.1xa0mm). In comparison to Telos the hamstring contraction, gravity, and the axial view underestimated the SSD by approximately 2xa0mm. Telos and kneeling caused significantly more pain than all other techniques (Pxa0<xa00.001). The axial view was fastest (115xa0s, Pxa0<xa00.001) and Telos longest (305xa0s, Pxa0<xa00.001), respectively. Telos indicated the lowest rotational error with a significant difference between kneeling and gravity (Pxa0<xa00.003). In contrast to Telos as the golden standard, hamstring contraction, gravity, and axial view underestimated the SSD. Kneeling and Telos are comparable with respect to SSD and pain. Although kneeling indicates a greater rotational error than Telos, it seems to be a reliable alternative for quantifying posterior tibial displacement in a more simple and fast way.

A model of soft-tissue graft anterior cruciate ligament reconstruction in sheep

IntroductionSince there is to our knowledge no clinically valid and reproducible animal model of soft-tissue anterior cruciate ligament (ACL) reconstruction currently available, we developed one in sheep, in terms of graft suitability, postsurgical recovery, and knee stability.Materials and methodsTo find a suitable graft, anatomical dissections of the hind limbs of 7 sheep were performed. After a pilot study in 3 sheep, we reconstructed the ACL with an ipsilateral, longitudinally split, superficial digital flexor tendon autograft and anatomic graft fixation in 42 sheep (study 1) and with a full, superficial digital flexor tendon autograft and extracortical graft fixation in 48 sheep (study 2). Follow-up examinations ranged from 6 to 104xa0weeks (study 1) and 3 to 24xa0weeks (study 2).ResultsAll animals tolerated the graft harvest well and returned to physiological movement after about 4xa0weeks. Only 1 out of 93 ACL reconstructions failed. At final follow-up, the anteroposterior (AP) drawer displacement in both studies had almost regained the value of the intact contralateral knee. Maximum load-to-failure improved over time in both studies but was significantly lower at all time points compared with the intact ACL and the graft tissues. Tensile stress was significantly lower at final follow-up in both studies compared with the intact ACL and graft tissues. It attained 43.3% of the intact ACL and 58.3% of the graft tissue in study 1 and 28.9% and 22.8% in study 2, respectively.ConclusionThe flexor tendon is suitable, and sheep appear to be an appropriate animal model for soft-tissue graft ACL reconstruction. They tolerate the graft harvest well and quickly return to full weight-bearing and physiological movement. Their knees become stable without showing signs of macroscopically evident osteoarthritis.

Intra-articular remodelling of hamstring tendon grafts after anterior cruciate ligament reconstruction

AbstractPurposenA summary is provided on the existing knowledge about the specific healing phases of the intra-articular hamstring tendon graft used for ACL reconstruction. Differences between human and animal in vivo studies are explained, and implications for the postoperative time period are laid out.MethodsA systematic review of the existing literature was performed on the topic of tendon remodelling of hamstring grafts in ACL reconstruction using Medline database. Publications between 1982 and 2012 were included. Special focus was directed on in vivo human and animal studies analysing intra-articular free tendon graft remodelling.ResultsAnimal and human in vitro and vivo researches have demonstrated three characteristic stages of graft healing after ACL reconstruction: an early graft healing phase with central graft necrosis and hypocellularity and no detectable revascularization of the graft tissue, followed by a phase of proliferation, the time of most intensive remodelling and revascularization and finally, a ligamentization phase with characteristic restructuring of the graft towards the properties of the intact ACL. However, a full restoration of either the biological or biomechanical properties of the intact ACL is not achieved.ConclusionSignificant knowledge on human cruciate ligament remodelling has been added in the understanding of the processes during the course of graft healing. Most importantly, the remodelling process in humans is prolonged compared to animal studies. While today´s rehabilitation protocols are often extrapolated from findings of animal in vivo healing studies, current findings of human in vivo healing studies might require new post-operative regimens following hamstring ACL reconstruction.

Remodelling of human hamstring autografts after anterior cruciate ligament reconstruction

PurposeHistological analysis of the remodelling process of human hamstring tendon (HT) grafts after standardized anterior cruciate ligament reconstruction (ACLR) with an accelerated rehabilitation protocol.MethodsSixty-seven patients underwent retrieval of mid-substance biopsies after clinically successful hamstring autograft ACLR. Samples were allocated to one of three groups depending on the time point of retrieval: group 1 (6–12xa0months; nxa0=xa015), group 2 (13–24xa0months; nxa0=xa016) and group 3 (>24xa0months; nxa0=xa011).Biopsies from native HT (nxa0=xa017) and ACL (nxa0=xa08) served as controls. Cellular density, vascular density and myofibroblast density and collagen fibril alignment were analysed by haematoxylin–eosin, Masson-Goldner-Trichrom and immunohistochemical staining protocols.ResultsCompared with native HT (330.4/mm²), total cell number was increased in groups 1-3 (Group 1xa0=xa0482.0/mm² (Pxa0=xa00.036); group 2xa0=xa0850.9/mm² (Pxa0=xa00.005); and group 3xa0=xa0595.6/mm² (Pxa0=xa00.043). There were no significant differences between the groups for vessel density. Myofibroblast density was higher in group 2 (199.6/mm²) compared with native HT (1.9/mm², Pxa0=xa00.014). Collagen orientation was irregular up to 12xa0months. Thereafter, collagen orientation became more regular, adapting to, but not fully restoring, the appearance of the intact ACL. For the first 12xa0months, cells were predominantly ovoid. Ensuing cell morphology changed to spindle shaped in group 2 and predominantly narrow long cells over 24xa0months.ConclusionHuman hamstring grafts showed typical stages of graft remodelling, which was not complete up to 2xa0years after ACLR. The remodelling process in humans was prolonged compared with the results obtained in several animal studies.Level of evidenceCase–control study, Level III.

Prevalence of cartilage lesions and early osteoarthritis in patients with patellar dislocation

AbstractObjectivesAssessment of cartilage lesions and osteoarthritis (OA) of the patellofemoral joint in patients following lateral patellar dislocation using magnetic resonance imaging (MRI).MethodsMR images of 129 knees (mean age 26xa0years, range 11–56) grouped as acute (A), recurrent (B), and chronic (C) dislocators were analysed regarding the prevalence and severity of patellofemoral cartilage lesions. Grades of OA were assessed using modified WORMS.ResultsIn groups A, B, and C the prevalence of cartilage lesions was 71%, 82%, and 97%, respectively. Most lesions were located on the central patella in groups A and B (central 69% and 78%; medial 56% and 47%; lateral 31% and 42%), whereas group C revealed all regions affected (73%, 61%, and 67%). Of group A, 14% had mild OA and 64% of group B. Group C showed mild OA in 62% and moderate OA in 18%. Cartilage defect size and prevalence of OA was correlated with number of dislocations (ru2009=u20090.41 and ru2009=u20090.59; Pu2009<u20090.001).ConclusionsCartilage lesions and early OA are common after patellar dislocation and appear to increase with the frequency of dislocation. Both conditions should be considered when interpreting MRI in such patients, because of implications for treatment.Key Points• Cartilage lesions are very common after patellar dislocation.n • The severity of cartilage lesions increases with number of dislocations.n • Osteoarthritis is common after recurrent patellar dislocation, even in young patients.n • Detecting cartilage lesions is important after patellar dislocation.

Fractionation of high-dose electron beam irradiation of BPTB grafts provides significantly improved viscoelastic and structural properties compared to standard gamma irradiation

PurposeIrradiation >30xa0kGy is required to achieve sterility against bacterial and viral pathogens in ACL allograft sterilization. However, doses >20xa0kGy substantially reduce the structural properties of soft-tissue grafts. Fractionation of irradiation doses is a standard procedure in oncology to reduce tissue damage but has not been applied in tissue graft sterilization.MethodsForty-four human 10-mm wide bone-patellar-tendon-bone grafts were randomized into four groups of sterilization with (1) 34xa0kGy of ebeam (2) 34xa0kGy gamma (3) 34xa0kGy fractionated ebeam, and (4) non sterilized controls. Graft´s biomechanical properties were evaluated at time zero. Biomechanical properties were analyzed during cyclic and load-to-failure testing.ResultsFractionation of ebeam irradiation resulted in significantly higher failure loads (1,327xa0±xa0305) than with one-time ebeam irradiation (1,024xa0±xa0204; Pxa0=xa00.008). Compared to gamma irradiation, significantly lower strain (2.9xa0±xa01.5 vs. 4.6xa0±xa02.0; Pxa0=xa00.008) and smaller cyclic elongation response (0.3xa0±xa00.2 vs. 0.6xa0±xa00.4; Pxa0=xa00.05), as well as higher failure loads (1,327xa0±xa0305 vs. 827xa0±xa0209; Pxa0=xa00.001), were found. Compared to non-irradiated BPTB grafts, no significant differences were found for any of the biomechanical parameters. Non-irradiated controls had significantly lower cyclic elongation response and higher failure loads than ebeam and gamma irradiation.ConclusionsIn this study, it was found that fractionation of high-dose electron beam irradiation facilitated a significant improvement of viscoelastic and structural properties of BPTB grafts compared to ebeam and gamma irradiation alone, while maintaining levels of non-irradiated controls. Therefore, this technique might pose an important alternative to common methods for sterilization of soft-tissue allografts.

Aktuelle Aspekte in der Verankerung von Hamstringsehnen-Transplantaten in der Kreuzbandchirurgie

Zusammenfassung. Die Verwendung von Hamstringsehnen-Transplantaten in der Kreuzbandchirurgie hat in den letzten Jahren wieder zunehmend an Bedeutung gewonnen. Der wesentliche Vorteil der Hamstringsehnen gegenüber dem mittleren Patellarsehnendrittel liegt in einer erheblich reduzierten Transplantatentnahmemorbidität, kombiniert mit einer sehr hohen Zugfestigkeit. Die ossäre Transplantatintegration unterliegt jedoch spezifischen biomechanischen und biologischen Rahmenbedingungen. Neue Entwicklungen auf dem Gebiet der Transplantatverankerung haben sich darauf konzentriert die initiale Verankerungsfestigkeit zu erhöhen und das Verankerungslevel weiter in Richtung Gelenkspalt zu verschieben. Es wird also eine anatomische Verankerung, möglichst nahe dem original Kreuzbandansatz angestrebt. Ziel der vorliegenden Übersichtsarbeit ist es neue Entwicklungen unter besonderer Berücksichtigung von biomechanischen und biologischen Faktoren vorzustellen und zu diskutieren. Spezielles Augenmerk liegt hier auf der Interferenzschrauben-Verankerung von Weichgewebe-Transplantaten, femoralen Transfixationsystemen und dem sog. Konzept der Hybridfixation.Abstract. The use of hamstring tendon grafts in cruciate ligament surgery has recently raised strong interest. Hamstring tendons are superior to the mid third patellar tendon graft by virtue of lower harvest site morbidity combined with high tensile strength. Osseous graft incorporation relies on a proper tendon-to-bone healing, which relies on specific biomechanical and biological boundary conditions. Several different fixation devices have recently been introduced, with special emphasis on high initial fixation strength and moving the level of fixation closer to the joint line, the so-called aperture fixation. The goal of the present review is to focus on the advantages and disadvantages of different fixation principles for hamstring tendon grafts in order to give a comprehensive insight into current developments, such as interference fit fixation, cross-pin fixation, and the concept of hybrid fixation.

Transplantatauswahl für den primären Ersatz des vorderen Kreuzbandes

ZusammenfassungFür den primären Ersatz des vorderen Kreuzbandes (VKB) wurde in den letzten Jahrzehnten eine Vielzahl verschiedener Transplantate und Rekonstruktionstechniken eingesetzt. Drei verschiedene Sehnentransplantate haben sich in den letzten Jahren als primäre Transplantatwahl herauskristallisiert: Patellarsehne, Hamstringsehnen und Quadrizepssehne.Klinische Studien konnten keine signifikanten Unterschiede im klinischen Ergebnis zwischen diesen Transplantatalternativen zeigen, unabhängig von den verschiedenen Verankerungsmöglichkeiten, die für das jeweilige Transplantat existieren. Daher erfährt die Morbidität der Transplantatentnahme zunehmend Bedeutung, da sie sich erheblich in Abhängigkeit vom Aktivitätsniveau, Morphotypen und Begleitverletzungen zwischen den Transplantaten unterscheiden kann. Ein Verständnis dieser Faktoren und der Parameter, die einen Einfluss auf das mechanische wie auch biologische Verhalten des rekonstruierten Kreuzbandes haben, ist daher Grundvoraussetzung, um eine differenzierte Indikation zur geeigneten Transplantatauswahl stellen zu können.Faktoren wie Entnahmemorbidität, Verankerungstechniken, ossäre Integration und Bohrkanalaufweitung werden anhand klinischer und grundlagenwissenschaftlicher Studien eingehend diskutiert. Zudem wird ein Ausblick in die Zukunft im Hinblick auf alternative Transplantatmöglichkeiten, wie die Verwendung von artgleichem (Allografts) und artfremdem (Xenografts) Spendergewebe und der Entwicklung von, die Gewebeeinheilung unterstützenden Methoden im Sinne des “tissue engineering”, gegeben.AbstractVarious graft choices have evolved over the past few decades for the primary reconstruction of the anterior cruciate ligament (ACL). Three predominant autologous graft choices exist today: patellar, hamstring, and quadriceps tendons.Clinical studies have as yet failed to demonstrate significant differences in clinical outcome among these grafts, irrespective of their varying fixation techniques. Therefore, other factors such as graft harvest morbidity have become more important when comparing different grafts. These factors can differ substantially between the grafts, depending on the type of patients activities, the injury pattern, and the associated injuries of the knee joint. A basic knowledge of these factors and the parameters that affect the mechanical and biological behavior of the reconstructed ACL can help to find the appropriate graft choice for each individual patient.Factors such as harvest site morbidity, fixation techniques, osseous integration, and tunnel widening are discussed based on current clinical and basic science studies. Finally, an outlook is given for future alternatives with evolving techniques for tissue-engineered grafts, allografts, or the transplantation of xenogeneic donor tissue.