IntroductionLesions of the quadriceps or patellar tendon after total knee arthroplasty (TKA) are a rare but serious complication which, if left untreated, can lead to loss of function of the knee joint. While acute and subacute extensor mechanism disruptions may have several causes, chronic deficiencies are often related to multiple prior revision surgeries for joint infection or aseptic TKA failure. Up to date, biological allograft reconstruction showed unsatisfying results. The use of a monofilament polypropylene mesh is a promising approach for this pathological condition. The aim of the present study was to evaluate clinical, functional and patient reported outcomes of this procedure in patients with chronic extensor mechanism deficiency.Materials and MethodsTwenty-eight patients with chronic extensor mechanism deficiency (quadriceps tendon rupture n = 9, patellar tendon rupture n = 19) after TKA were included in this retrospective study. None of the patients were lost to follow-up. Surgical reconstruction was performed at one institution between 2014 and 2020 with a monofilament polypropylene mesh (Marlex Mesh, Bard, Murray Hill, USA). The mean age at the time of surgery was 69 years. Patients presented with a mean BMI of 33 kg/m2. The mean follow-up period was 23 months.ResultsThe 2-year survivorship free of mesh revision was 89% [95% confidence interval (CI): 75% to 100%]. Three patients (11%) had to undergo revision because of mechanical mesh failure and received another polypropylene mesh. No further revisions were performed thereafter. Flexion was 87° (range, 30–120°) on average. The majority of patients (75%, 21/28) had a full active extension. The mean active extension lag after surgery was 4 degrees (range, 0–30°).DiscussionWe observed a substantial improvement of extensor mechanism function. The majority of patients had full extension and showed good clinical results. A failure rate of over 50% has been published for alternative procedures. Thus, the use of the described augmentation technique represents a reasonable treatment option for chronic extensor mechanism disruptions of the patellar tendon as well as the quadriceps tendon after total knee arthroplasty. However, there might be a potentially higher risk for infection persistence in periprosthetic joint infection cases due to the presence of a foreign material.

ZusammenfassungBei der steigenden Zahl von revisionsendoprothetischen Eingriffen des Kniegelenkes stellt sich automatisch die Frage nach dem Umgang mit den explantierten Implantaten. Neben den praktischen Anforderungen an die Logistik und Lagerung stehen hier besonders rechtliche Fragen im Vordergrund. Grundsätzlich ist der Patient Eigentümer des Implantates und sollte stets in die Entscheidungen zur weiteren Vorgehensweise einbezogen werden. Dieses Kapitel beschäftigt sich mit den rechtlichen Rahmenbedingungen für die operierende Einrichtung und gibt praktische Hinweise zum Verbleib, der Aufbewahrung und Lagerung explantierter Knieendoprothesen. Besteht der Verdacht eines Schadensfalles sind weitere Punkte zu beachten, die im zweiten Teil des Kapitels dargestellt werden.

ZusammenfassungDie aseptische Revisionsendoprothetik macht einen Großteil der Knie-TEP-Revisionen aus. Bei Osteolysen und festsitzendem Implantat ist die Evidenzlage gering, sodass hier die Entscheidung zur Revision manchmal schwierig ist. In den häufigsten Fällen bestehen die Herausforderungen in der Behandlung von Instabilitäten (Rekonstruktion der Gelenkebene und Wahl eines korrekten Kopplungsgrades), der Rekonstruktion von Knochendefekten (Art der Defektfüllung und Verankerung) und Behandlung von Läsionen des Streckapparates (Quadrizepssehne, Patella und Patellarsehne). Mit einer systematischen Herangehensweise lassen sich mithilfe der beschriebenen Techniken und Implantatsysteme jedoch viele der Herausforderungen suffizient lösen.

Die guten funktionellen Ergebnisse der Tumorendoprothetik des Kniegelenks in Kombination mit modernen onkochirurgischen Konzepten haben in der Vergangenheit zu einer Abnahme der primären Amputationshäufigkeit bei Patienten mit malignen Tumoren der kniegelenknahen Region geführt. Der Extremitätenerhalt durch die Tumorendoprothetik resultiert in einem hohen Maß an Lebensqualität für die betroffenen Patienten. Ziel der Arbeit war die Aufarbeitung von Komplikationen, die insgesamt durch die Komplexität der Eingriffe sowie die Größe der notwendigen endoprothetischen Rekonstruktionen und neo-/adjuvanten Therapien häufiger sind als in der Primärendoprothetik bei Arthrose oder nach Trauma. Mögliche intra- und postoperative Komplikationen werden dargestellt und realisierbare Therapieoptionen aufgezeigt. Als intraoperative Komplikationen sind die fehlerhafte Ausrichtung des Implantats in Länge, Achse und Rotation, ungeplante Weichteildefekte, Probleme bei der Implantatverankerung bzw. intraoperative Frakturen, Gefäß- und Nervenverletzungen sowie Läsionen des Streckapparats zu nennen. Zu den relevanten postoperativen Komplikationen gehören das Lokalrezidiv, die periprothetische Infektion, periprothetische Frakturen, thrombembolische Ereignisse und das mechanische Implantatversagen (Lockerung bzw. Versagen des Kopplungsmechanismus). In Abhängigkeit von den lokalen anatomischen Verhältnissen und dem systemischen onkologischen Zustand des Patienten können diese Komplikationen zu großen Herausforderungen im Management werden. Durch die Kenntnis der potenziellen Probleme lassen sie sich aber vermeiden. Dazu ist eine profunde onkochirurgische und revisionsendoprothetische Erfahrung erforderlich.

This prospective cohort study aimed to examine objective and subjective parameters in patients who underwent total knee replacement (TKR) to assess from when on driving a car can be deemed safe again. Thirty patients (16 women, 14 men, age 66 ± 11 years) who received TKR of the right knee and 45 healthy controls (26 women, 19 men, age 32 ± 9 years) were asked to perform an emergency braking manoeuvre using a driving simulator. Brake pedal force (BPF), neuronal reaction time (NRT), brake reaction time (BRT), and subjective parameters (pain, subjective driving ability) were measured preoperatively as well as 5 days, 3–4, and 6 weeks after TKR. Preoperative NRT was 506 ± 162 ms, BRT 985 ± 356 ms, and BPF 614 ± 292 N. NRT increased to 561 ± 218 ms, BRT to 1091 ± 404 ms and BPF decreased to 411 ± 191 N 5 days after TKR. Three weeks after surgery, NRT was 581 ± 164 ms and BRT 1013 ± 260 ms, while BPF increased to 555 ± 200 N. Only BPF showed significant differences (p < 0.01). In week 6, all parameters were restored to baseline levels; patients showed significant pain decrease and evaluated their driving ability as “good” again. BPF was the only parameter displaying a significant postoperative decrease. However, preoperative patients’ baseline levels and subjective confidence in driving ability were only reached 6 weeks after the operation. These results indicate that a minimum waiting period of 6 weeks should be considered before patients can safely participate in road traffic at their individual preoperative safety level again. II.

The aim of this prospective randomized controlled trial was to evaluate if an app-based, feedback-controlled active muscle training can be used to improve the early outcome after total knee arthroplasty. Sixty patients (mean age 67.3 years, range 45 to 84) awaiting primary total knee arthroplasty (TKA) were randomized into a control- and training group. Both Groups followed an identical postoperative protocol. Additionally, the training group performed an appbased, feedback-controlled active muscle training multiple times daily postoperatively. Outcome measures were active and passive range of motion, pain at rest and in motion, knee extension strength, the Timed “Up and Go”, 10 Meter Walk Test, 30 Second Chair Stand Test, Knee Injury and Osteoarthritis Outcome Score (KOOS), Knee Society Score (KSS) and inpatient data. Mean time to follow-up was 6.88 days in the control group and 6.59 days in the training group for a total of 47 patients (78.3 percent follow-up). The training group used the GenuSport Knietrainer a total of 18.4 times (range 6 to 42 times) on average. Active range of motion was 11.4 degrees higher in the training group (p=0.038), while passive range of motion was almost the same (p=0.906). Mean pain was significantly lower in the training group both at rest (p=0.01) and in motion (p=0.002). The training group reported significantly better outcomes in the KOOS Activities of Daily Living Score (p=0.037). No significant differences were observed in KOOS pain, symptoms, sports and quality of life (p=219, p=0.625, p=0.204, p=0.452, respectively). The KSS Knee Score and KSS Function Score were significantly better in the training group (p<0.001, p=0.011, respectively). An app-based and feedback-controlled active muscle training can significantly improve the early outcome after total knee arthroplasty, particularly reduce pain and improve the range of motion. More training had better effects on the outcome than less training. Treatment costs could possibly be reduced. These findings are highly relevant regarding rising expectations from patients and the need to reduce costs in the health care system. Further studies with a longer follow up are necessary.

Purpose: During surgical procedures, some amount of irrigation fluid leaks from the surgical site and accumulates on the sterile drapes. Whether these fluid collections show bacterial contamination over time in primary total knee arthroplasty remains unclear. Methods: In this study, we included 100 patients. We collected the samples of irrigation fluid before skin incision and every 30 minutes after the start of surgery. In addition, at the end of surgery, we evaluated the suction tip for bacterial contamination. After 3 months, we clinically evaluated all patients for periprosthetic joint infection. Results: Although the drapes were found to be sterile after 30 minutes, fluid residues on the surgical drapes show a contamination rate of 22% after 60 minutes and thus a marked correlation between advanced duration of surgery and bacterial contamination. The suction tip was contaminated with bacteria in 22% of cases. The spectrum of pathogens typical of periprosthetic joint infection could be demonstrated. Conclusion: Fluid surgical drape reservoirs were abacterial during the first 30 minutes but showed marked bacterial contamination over time. For total knee arthroplasty, we recommend regular replacement of the suction tip every 30 minutes. In addition, irrigation fluid reservoirs should not be withdrawn by suction 30 minutes after skin incision.

BackgroundThe onset and progression of osteoarthritis, but also the wear and loosening of the components of an artificial joint, are commonly associated with mechanical overloading of the structures. Knowledge of the mechanical forces acting at the joints, together with an understanding of the key factors that can alter them, are critical to develop effective treatments for restoring joint function. While static anatomy is usually the clinical focus, less is known about the impact of dynamic factors, such as individual muscle recruitment, on joint contact forces.MethodsIn this study, instrumented knee implants provided accurate in vivo tibio-femoral contact forces in a unique cohort of 9 patients, which were used as input for subject specific musculoskeletal models, to quantify the individual muscle forces during walking and stair negotiation.ResultsEven between patients with a very similar self-selected gait speed, the total tibio-femoral peak forces varied 1.7-fold, but had only weak correlation with static alignment (varus/valgus). In some patients, muscle co-contraction of quadriceps and gastrocnemii during walking added up to 1 bodyweight (50%) to the peak tibio-femoral contact force during late stance. The greatest impact of co-contraction was observed in the late stance phase of stair ascent, with an increase of the peak tibio-femoral contact force by up to 1.7 bodyweight (66%).ConclusionsTreatment of diseased and failed joints should therefore not only be restricted to anatomical reconstruction of static limb axes alignment. The dynamic activation of muscles, as a key modifier of lower limb biomechanics, should also be taken into account and thus also represents a promising target for restoring function, patient mobility, and preventing future joint failure.Trial registrationGerman Clinical Trials Register: ID: DRKS00000606, date: 05.11.2010.

Patient-specific instrumentation (PSI) uses 3D preoperative imaging to produce individualized cutting blocks specific to patients’ anatomy and according to the preoperative plan with the aim to reduce the number of mechanical leg alignment (MLA) outliers, to improve implant positioning and to decrease surgery time. The primary purpose of this study was to investigate the efficacy of a specific PSI in comparison with standard instrumentation (SI) in reducing the number of MLA outliers. It was hypothesized that the number of MLA outliers would be significantly lower in the PSI group.

As the aims of changes in total knee arthroplasty (TKA) designs are to reinstate more natural kinematics, the current study evaluated the in vivo kinematics in patients who underwent a cruciate retaining gradually changing femoral radius (“G-CURVE”) against a cruciate retaining conventional changing femoral radius (“J-CURVE”) geometry TKA design. The hypothesis of the study is that the G-CURVE design would allow a substantial increase in the femoral rollback compared to the J-CURVE design.

Background In end-stage medial osteoarthritis, the surgeon can decide whether to use unicompartmental or total knee arthroplasty for operative treatment of the patient. Despite the available literature there is a lack of evidence to suggest if one procedure can be rated as being superior to the other. With increasing demand for knee arthroplasty, treatment with the highest expectation of success will be of particular interest. The purpose of this manuscript was to analyse and compare the available literature on unicompartmental vs. total knee arthroplasty for the treatment of medial osteoarthritis. Material and Methods In this review of literature, the two procedures were compared regarding their clinical outcome, implant survival, and complication rates. Results Regarding the clinical outcome the unicompartmental knee arthroplasty was shown to be superior over total knee arthroplasty. However, studies were mostly retrospective and groups were also different preoperatively. Patients treated with unicompartmental knee arthroplasty had better preoperative range of motion and function scores. Unicompartmental and total knee arthroplasty showed comparably increased functional scores. Taking the implant survival as parameter, institutional registries, multicenter studies and arthroplasty registries found total knee arthroplasties to have a significantly better long-term survival in comparison to unicompartmental knee arthroplasty. However, data might be biased by the lower threshold to revise unicompartmental knee arthroplasty due to expected simple revision and more subjective indications for revision. Looking at the complication rate, one has to differentiate between general and implant-specific complications. While the unicompartmental knee arthroplasty was shown to be advantageous in terms of general complications and mortality, it was also shown to be inferior in terms of implant-specific complications. ConclusionThe available literature does not show one procedure to be superior to the other. The trend to a better clinical outcome and a lower mortality rate is advantageous for unicompartmental knee arthroplasty, while the better long-term survival and a lower risk of implant-specific complications may make total knee arthroplasty preferable.

Despite the lack of validation, synovial aspiration remains a common practice during 2-stage septic revision total knee arthroplasty (TKA). The goal of this study was to investigate the diagnostic validity of synovial polymethylmethacrylate (PMMA) spacer aspiration of temporary knee arthrodesis to detect persistent periprosthetic joint infection before TKA reimplantation. This retrospective cohort study included 73 consecutive patients who underwent 2-stage septic revision TKA according to a standard protocol. After explantation surgery, including temporary arthrodesis with an intramedullary stabilized PMMA spacer, all patients had synovial aspiration 2 weeks before reimplantation to exclude persistent periprosthetic joint infection. Patients had a 2-week antibiotic holiday before aspiration. Sensitivity and specificity of the synovial PMMA spacer joint aspiration for the detection of periprosthetic joint infection were determined and referenced against intraoperative microbiologic and histologic samples obtained at second-stage surgery. Sensitivity of the synovial PMMA spacer aspiration was 21%. Because of poor diagnostic validity, synovial PMMA spacer aspiration cannot be recommended for routine exclusion of persistent periprosthetic joint infection before TKA reimplantation. Therefore, exclusion of persistent periprosthetic joint infection should be supplemented by other diagnostic methods, and it is not necessary to delay TKA reimplantation for PMMA spacer aspiration. [Orthopedics. 2017; 40(4):231-234.].

Quadriceps tendon injuries and insufficiencies in total knee arthroplasty are rare, but are followed by a devastating complication that left untreated leads to a complete loss of function of the knee. This review article summarizes the functional anatomy, risk factors, and the prevalence and diagnosis of quadriceps tendon injuries, in addition to the possible management options for partial and complete ruptures. The treatment options are adapted according to the extent of the loss of function (partial, complete) and the duration of the injury (acute vs chronic). Furthermore, the choice of treatment should take into account the quality and availability of primary tissue, the patient's general health, along with their likely functional requirements. Conservative treatment is often justified in partial ruptures with good results. Complete ruptures require surgical intervention and multiple operative techniques are described. Treatment options for acute ruptures include direct primary repair with autogenous or synthetic tissue augmentation. In the case of chronic insufficiency and a lack of soft-tissue surroundings, reconstruction with the aid of a muscle flap or allograft tissue can be considered. All surgical intervention techniques used so far have been fraught with complications and rarely lead to satisfactory results. A new surgical approach to the reconstruction and augmentation of the extensor mechanism consists of the use of a synthetic mesh. The technique is described here in detail.

Revision of total knee arthroplasty (TKA) is growing rapidly all over the world. The introduction of intramedullary stems for additional stability in revision is well accepted by most of the surgeons, while the philosophy of stem fixation is still under controversy. A meta-analysis was performed to compare the survivorship of revised implants with regard to a cemented or cementless stem fixation.

Nach knieendoprothetischer Versorgung sind ca. 20 % der Patienten mit dem postoperativen Ergebnis unzufrieden. Hauptursachen hierfür sind die periprothetische Infektion, die aseptische Lockerung, Instabilität, Malalignment und in selteneren Fällen die sekundäre Retropatellararthrose, periprothetische Frakturen, Streckapparatinsuffizienzen, Polyethylenabrieb und die Arthrofibrose. Die Identifikation der Schmerzursache ist dabei häufig schwierig, jedoch Voraussetzung für eine erfolgreiche Therapie.

Verletzungen und Insuffizienzen der Quadrizepssehne bei liegender Knietotalendoprothese stellen eine seltene, aber schwerwiegende Verletzung dar, die unbehandelt zum weitgehenden Funktionsverlust des Kniegelenks führt. Der Übersichtsbeitrag erläutert die funktionelle Anatomie, die Risikofaktoren, die Diagnostik von Verletzungen der Quadrizepssehne sowie die möglichen Versorgungsverfahren bei Partial- und Komplettrupturen. Die Behandlungsoptionen richten sich nach dem Grad des funktionellen Verlusts (partiell, komplett) sowie dem Verletzungszeitpunkt (akut vs. chronisch). Weitergehend muss in die Wahl des Behandlungsverfahrens die Qualität und Verfügbarkeit des Primärgewebes, der allgemeine Gesundheitszustand sowie das funktionelle Anforderungspotenzial des Patienten in die Entscheidung einbezogen werden. Ein konservatives Vorgehen ist häufig bei Partialrupturen gerechtfertigt und mit guten klinischen Ergebnissen assoziiert. Die vollständige Ruptur der Quadrizepssehne erfordert die operative Intervention. Für die Versorgung von Komplettrupturen sind vielfältige operative Versorgungstechniken beschrieben. In der Erstversorgung kompletter Quadrizepssehnenrupturen nach Implantation einer Knieendoprothese ist die primäre Naht mit autologer oder synthetischer Augmentation zu präferieren. Bei chronischen Insuffizienzen sowie desolater Weichteilsituation stellen die Versorgungen mithilfe gestielter Muskellappen oder tendoossärer Allografts Behandlungsalternativen dar. Alle bisher zur Verfügung stehenden operativen Interventionsmöglichkeiten sind komplikationsbehaftet und führen nicht selten zu einem unbefriedigenden Ergebnis. Ein neuer operativer Ansatz zur Rekonstruktion und Augmentation des Streckapparats ist die Verwendung eines synthetischen Netzes, deren Technik im Detail beschrieben wird.

Individual implant alignment in total knee arthroplasty (TKA) has seen growing interest over the past years. This study therefore aimed to develop a surgical technique for implant alignment based on native ligament tension, and to present the results obtained using this technique.

Indikation: Beim zweizeitigen septischen Knieendoprothesenwechsel kommen nach dem Prothesenausbau im Intervall regelhaft Platzhalter aus Knochenzement (PMMA) zum Einsatz. Grundsätzlich wird hierbei zwischen fixen und artikulierenden Platzhaltern unterschieden. Ungeachtet ihrer spezifischen Vor- und Nachteile, sind Spacer ohne zusätzliche Stabilisierung (intern oder extern) bei höhergradigen Knochendefekten und Instabilitäten ungeeignet. Zielsetzung: Voraussetzung für die Verwendung eines Spacers beim zweizeitigen Knieendoprothesenwechsel mit ausgedehnten Knochendefekten ist die Möglichkeit der stabilen Verankerung im verbleibenden Knochen und gleichzeitig Stabilisierung des ligamentär insuffizienten Gelenks. Methode: Nach dem Prothesenausbau und dem radikalen Débridement des Kniegelenks werden zur internen Stabilisierung konventionelle Stahlstangen des AO-Fixateur-externe an beide Markräume angepasst. Die Länge wird so gewählt, dass ein „diaphysäres Pressfit“ entsteht. Die gelenkfernen Öffnungen der Fixateurstangen werden mit Zement verschlossen. Nach Platzierung der beiden Stangen, werden diese folgend mit einem „Tube-to-Tube“-Konnektor (ebenfalls vom AO-Fixateur-externe) im Gelenk gekoppelt und in ca. 5 °Flexion bei gerader Beinachse fixiert. Nachfolgend wird der Gelenkraum inklusive Knochendefekt mit antibiotikabeladenem Zement ausgefüllt. Dabei ist durch Distraktion des Gelenks ebenso auf den Erhalt des Gelenkraums für eine neue Endoprothese wie auf eine achsgerechte Einstellung zu achten. Eine Außenrotationsstellung des Unterschenkels ist unbedingt zu vermeiden. Die postoperative Mobilisation erfolgt ohne externe Stabilisierung unter schmerzadaptierter Vollbelastung. Schlussfolgerung: Die vorliegende Technik ist hervorragend zur Versorgung von Patienten mit ausgeprägten Knochendefekten beim zweizeitigen septischen Knieendoprothesenwechsel geeignet. Hierbei ist im Vergleich zu konventionellen statischen Spacern eine stabile diaphysäre Verankerung und damit Reduktion der Komplikationsrate bei identischer Infektsanierungsrate möglich.