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PURPOSE: The primary objective of this study was to quantify the variations of the medial posterior tibial slope (MPTS) and the lateral posterior tibial slope (LPTS), as well as of the medial proximal tibial angle (MPTA), and to determine the fraction of patients for which standard techniques including different alignment techniques would result in alteration of the patient's individual posterior tibial slope (PTS) and MPTA. Furthermore, it was of interest if a positive correlation between PTS and MPTA or between medial and lateral slope exists. METHODS: A retrospective study was performed on CT-scans of 234 consecutively selected European patients undergoing individual total knee replacement. All measurements were done on three-dimensional CAD models, which were generated on the basis of individual CT-scans, including the hip, knee, and ankle center. Measurements included the medial and lateral PTS and the MPTA. PTS was measured as the angle between the patient's articular surface and a plane perpendicular to the mechanical axis of the tibia in the sagittal plane. MPTA was defined as the angle between the tibial mechanical axis and the proximal articular surface of the tibia in the coronal plane. RESULTS: Analysis revealed a wide variation of the MPTS, LPTS, and MPTA among the patients. MPTS and LPTS varied significantly both interindividually and intraindividually. The range of PTS was up to 20° for MPTS (from - 4.3° to 16.8°) and for LPTS (from - 2.9 to 17.2°). The mean intraindividual difference between MPTS and LPTS in the same knee was 2.6° (SD 2.0) with a maximum of 9.5°. MPTA ranged from 79.8 to 92.1° with a mean of 86.6° (SD ± 2.4). Statistical analysis revealed a weak positive correlation between MPTA and MPTS. CONCLUSION: The study demonstrates a huge interindividual variability in PTS and MPTA as well as significant intraindividual differences in MPTS and LPTS. Therefore, the question arises, whether the use of standard techniques, including fixed PTSs a

PURPOSE: Local infiltration analgesia (LIA) has attracted growing interest in recent years. To prolong the positive effects of LIA, a continuous intraarticular perfusion has been introduced in total knee arthroplasty with good clinical results. The purpose of the present study was to evaluate if similar results can be obtained with the use of a continuous periarticular perfusion in unicondylar knee arthroplasty (UKA). METHODS: 50 consecutively selected patients undergoing UKA received either a single-shot LIA (control group; n = 25) or single-shot LIA combined with a continuous postoperative periarticular perfusion for 2 postoperative days (intervention group, n = 25). VAS (visual analogue scale) for pain, pain medication consumption and range of flexion were recorded postoperatively for 6 days. The catheter was removed after 2 days. RESULTS: Only minor advantages of using a continuous periarticular catheter could be shown. Patients in the intervention group showed significant lower VAS scores on day 1 and required significant less pain medication on day 6. Further, there was a significant difference in the range of flexion on day 3, on which patients of the intervention group were able to bend the knee joint on average by 12° more than patients of the control group. On the other days, any significant differences between the two groups were not observed. CONCLUSION: In summary, the present study could not identify any superiority of a periarticular catheter over single-shot LIA in UKA. Because of additional costs and the potential risk of infection, the conclusion of this study is to not recommend adding a periarticular catheter to the single-shot LIA in UKA. LEVEL OF EVIDENCE: II.

In den letzten Jahren hat sich im Bereich der Endoprothetik immer mehr die Philosophie einer pathologiegerechten Behebung der Schäden bei gleichzeitigem Erhalt gesunder Strukturen durchgesetzt. Daher scheint auch der patellofemorale Gelenkersatz (PFG) eine logische Therapieoption bei fortgeschrittener isolierter patellofemoraler Arthrose zu sein. Allerdings werden die Ergebnisse des PFG in der Literatur kontrovers diskutiert, sodass manche Operateure die Implantation einer totalen Endoprothese vorziehen. Allerdings könnte man dies insbesondere bei jungen Patienten als Overkill betrachten, da wichtige Strukturen geopfert werden. Die Bevorzugung der totalen Endoprothese gegenüber dem PFG beruht v. a. auf den hohen Revisionsraten, die insbesondere bei Implantatdesigns älterer Generationen zu finden sind. Dabei müssen verschiedene Faktoren, die zu einer hohen Revisionsrate beitragen können, beachtet werden. So stellt der PFG, trotz häufiger Inzidenz von knapp 10 % der über 40-Jährigen, eine selten durchgeführte Operation dar. Die pro Operateur niedrige Fallzahl hat eine flache Lernkurve zur Folge und führt zu einer geringeren Erfahrung des Chirurgen. Außerdem ist die Revisionsschwelle bei einem PFG niedriger im Vergleich zur primären Totalendoprothese am Knie (TKA). Für ein erfolgreiches Outcome des PFG sind sowohl das Implantatdesign, das korrekte Alignment und insbesondere die richtige Indikationsstellung von entscheidender Bedeutung. Vor jeder Implantation eines PFG sollten potenzielle ursächliche Deformitäten erkannt und behandelt werden. Bei zusätzlich vorhandenen, fortgeschrittenen, degenerativen Veränderungen der tibiofemoralen Kompartimente, Instabilitäten oder stärkeren Beinachsabweichungen sollte die Endoprothetik auch auf tibiofemorale Gelenkanteile ausgedehnt werden., [Patellofemoral joint arthroplasty : What is the current situation?] In recent years the philosophy of pathology-based repair of damage while preserving healthy structures has become increasingly prevalent in the field of endoprosthetics. Therefore, patellofemoral joint arthroplasty (PFA) seems to be a logical treatment option for advanced isolated patellofemoral arthrosis; however, the results of PFA are controversially discussed in the literature, so that some orthopedic surgeons prefer total knee arthroplasty (TKA); however, especially in young patients, this can be considered as overkill, since important structures are sacrificed. The preference of a total endoprosthesis over PFA is mainly due to the high revision rates, which can be found especially in older generation implant designs. Various factors that can contribute to a high revision rate must be taken into account. Despite the frequent incidence of almost 10% in the population over 40 years old, PFA is a rarely performed operation. This low number of cases per surgeon results in a flat learning curve and leads to a reduced experience of the surgeon. Furthermore, the revision threshold for PFA is lower compared to primary TKA. For a successful outcome of PFA the implant design but particularly the correct alignment and the correct indications are crucial. Before each PFA implantation, potential causative deformities should be identified and treated if necessary. In the presence of additional advanced degenerative changes of the tibiofemoral compartments, instability or severe leg axis deviations, the endoprosthetics should be extended to also include parts of the tibiofemoral joint.