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Electrostimulative therapy has been used for more than 20 years to improve the healing of bone fractures. The objective is to adopt electrostimulative procedures to an acetabular cup revision system. One main issue is the optimization of the implants inherent electrical system using adjustable geometry and coil parameters to achieve an electric field distribution within the area of relevance with the appropriate strength and as homogeneous as possible. In the work described here the field distribution on the surface of the acetabular cup was determined by “finite-integration-theory” electromagnetic field simulations.

Electrostimulation is indicated for fracture healing and the treatment of avascular necrosis of the femoral head. In the present work a new concept was developed to implement the option of electrostimulation in the reconstruction of acetabular bone defects in case of revision of the total hip replacement providing improved implant fixation at the surrounding bone stock. In specific revision situations enhanced primary fixation stability of the acetabular cup is achieved by additional polyaxial and angular stable fixation pegs and a modular adaptable lateral flap. An external oscillating magnetic field, generated by a primary coil placed around the patient’s hip, is used to transfer inductively energy into the revision cup. Secondary coils, integrated into stimulation elements within the implant, are the source for the generation of the electric field in the surrounding bone stock. In the present study we conducted preclinical numerical simulations of the acetabular cup revision system with regard to the electric field distribution and field homogeneity. Considering optimal position of the stimulation elements improved periprosthetic bone regeneration should be realized to provide secondary fixation stability of the revision implant.

Implant infections remain feared and severe complications after total joint arthroplasty. The incidence of multi-resistant pathogens, causing such infections, is rising continuously, and orthopaedic surgeons are confronted with an ever-changing resistance pattern. Anti-infectious surface coatings aim for a high local effective concentration and a low systemic toxicity at the same time. Antibacterial efficacy and biomechanical stability of a novel broad-spectrum anti-infectious coating is assessed in the present study. Antibacterial efficacy of a sol-gel derived titanium dioxide (TiO(2)) coating for metal implants with and without integrated copper ions as antibiotic agent was assessed against methicillin resistant Staphylococcus aureus (MRSA 27065). Both bacterial surface adhesion and growth of planktonic bacteria were assessed with bare and various TiO(2)-coated Ti6Al4V metal discs. Furthermore, bonding strength of the TiO(2) surface coating, using standard testing procedures, as well as surface roughness were determined. We found a significant reduction of the bacterial growth rate for the coatings with integrated copper ions, with highest reduction rates observed for a fourfold copper TiO(2)-coating. Pure TiO(2) without integrated copper ions did not reduce bacterial growth compared to uncoated Ti6Al4V. The coating was not detached from the substrate by standard adhesive failure testing, which indicated an excellent durability of the implant coating. The TiO(2) coating with integrated copper ions could offer a new strategy for preventing implant-associated infections, with antibacterial properties not only against the most common bacteria causing implant infections but also against multiresistant strains such as MRSA.

Hyaluronidase is an enzyme additive used in local anaesthesia and interventional pain reducing procedures such as adhesiolysis of epidural scar tissue after spinal surgery. Only a limited number of studies describe the influence of drugs on hyaluronidase activity. Postulated effects and effectiveness of hyaluronidase are only based on clinical observations.The aim of this study is to investigate the influence of the combined drugs on the activity of hyaluronidase under standardized conditions and to verify the effectiveness of the enzyme.An ELISA-based microtiter-technique is used to evaluate the activity of hyaluronidase in combination with local anaesthetics, corticosteroids, NaCl 10%, and iodinated contrast media.Microtiter plates were coated with biotinylated hyaluronate and incubated with hyaluronidase in combination with the above-mentioned drugs. The activity of hyaluronidase was determined by an avidin-peroxidase-based procedure using an ELISA reader. Incubations were carried out at room temperature as well as at 37 degrees C.The data show that drugs affect the activity of hyaluronidase in different ways. Iodinated contrast media, NaCl (10%), and the absence of corticosteroids reduce hyaluronidase activity. In contrast, higher activities were detected at a lower NaCl concentration (0.9%). We cannot attribute a significant influence to local anaesthetics.Hyaluronidase is effective in all combinations with drugs. To get the maximum effect calculated use of accompanying drugs is necessary.

Aseptic loosening of total hip replacement is mainly caused by wear particles. Abrasive wear occurs at articulating surfaces or as a consequence of micro-motions at the interface between femoral stem and bone cement. Direct impact of wear particles on osteolysis, the remodeling of the bone stock and a directly affected function of osteoblasts was described. The present study examined the response of human osteoblasts exposed to different wear particles, which were generated in a test device providing oscillating micro-motions at the interface between femoral stem and standard bone cement. Characterization of released particles was performed by quantifying the size distribution and the metal content of the wear debris. Human osteoblasts were incubated with particles obtained from hip stems with different material compositions (Ti-6Al-7Nb and Co-28Cr-6Mo) and rough and smooth surface finishings combined with standard bone cement (Palacos(R) R) containing zirconium oxide particles. Commercially pure titanium particles (cp-Ti) and particulate zirconium oxide (ZrO(2)) were used for comparative analyses. The results revealed significant (p < 0.05) reduction of the cell viability after exposure to higher concentration of metallic particles, particularly from Co-based alloys. In contrast, ZrO(2) alone showed significantly less adverse effects on the cells. When increasing metallic particle concentrations massive inhibition was also observed in the release of cytokines including interleukine-6 (IL-6) and interleukine-8 (IL-8), but the expression of Procollagen I and the cell viability showed the highest reduction after exposure to Co-based alloy particles from rough stems.

With regard to the growing potential of finite-element-analysis (FEA) in the field of orthopaedic biomechanics, we present an approach helping in the development of appropriate models of the implant-bone compound. The algorithm is based on computed-tomography data of the bone and accordant computer-aided-design (CAD) data of the implant and aims at predicting the bone strains and interface mechanics of the included parts. The developed algorithm was validated exemplary using an acetabular cup in combination with a left and a right fresh-frozen human hemipelvis. The strains under maximum loads during the gait cycle as well as the micromotion in the bone-implant interface were measured and compared to results from equivalent finite-element-analyses. Thereby, we found strong correlation between the calculated and measured principal strains with correlation coefficients of r(2)=0.94 (left side) and r(2)=0.86 (right side). A validation of micromotion was not possible due to limited accuracy of the motion tracking system.

Gas-discharge plasma processes could be very valuable for the modification of titanium surfaces to improve implant performance. Surface properties determine cellular acceptance, a crucial factor of implant healing. There already exists fundamental knowledge about the influence of physicochemical surface properties like roughness, titanium dioxide modifications, cleanness, and (mainly ceramic) coatings on cell behavior in vitro and in vivo. In this process, the cell adhesion and spreading via integrins was recognised to be a prerequisite for the occupancy of an orthopaedic implant surface. But recent findings indicate an additional adhesion mechanism. Hyaluronan seems to play a key role in the very first encounter with the substrate. Based on this adhesion mechanism of osteoblasts with their negativeley charged hyaluronan coat, a new surface functionalization strategiy was developed utilizing a positively charged metal surface. For this purpose, titanium was coated with a microwave plasma polymer made from allylamine (PPAAm) to boost the initial adhesion processes. The process development was accompanied by physicochemical surface analysis like XPS, FTIR, contact angle, SEM, and AFM. A very thin, adherent, cross-linked, pinhole- and additive- free PPAAm layer could be deposited, which is resistant to hydrolysis and delamination and equipped with a high density of positively charged amino groups. This titanium surface functionalization was found to be advantageous concerning osteoblastic focal adhesion formation and, in consequence in differentiated cell functions in vitro. Intramuscular implantation of test samples in rats revealed a reduced inflammation reaction compared to uncoated titanium in vivo.

Die Anzahl an notwendigen Revisions-und Wechseloperationen nach Hufttotalendoprothesen steigt kontinuierlich (◘ Abb. 4.1) [1, 2]. Nicht verhindern lasst sich der damit verbundene Knochenverlust im Azetabulum und am Femur [3]. Die Wiederherstellung von anatomisch knochernen Verhaltnissen und biomechanisch korrekter Implantatlage ist eine grose Herausforderung, die auf unterschiedliche Weise angegangen werden kann. Fur die Revision des Azetabulums wurden z. B. grose zementfreie Pfannen (sog. Jumbo-Pfannen), Revisionsringe, Stutzschalen und schlussendlich auch Keramiktransplantate verwendet. Diese Methoden stellen zwar die Biomechanik wieder her, fuhren aber nicht zum Wiederherstellen des Knochenlagers. Andere Methoden, wie z. B. Medialisierung der Pfanne oder Implantation in einem hoheren Huftzentrum, konfigurieren eine Situation, die nicht der normalen Biomechanik entspricht. Alternativ konnen Knochendefekte durch modulare porose Metallaugmentationen uberbruckt werden. Als Hauptziel bei der Hufttotalendoprothesenrevisionsoperation sollte neben dem Wiederherstellen der biomechanischen Physiologie immer auch die Wiederherstellung des Knochenlagers im Vordergrund stehen, um im Falle einer weiteren Revision wieder anatomische knocherne Verhaltnisse vorzufinden, die eine neuerliche Implantation ermoglichen. Dieses Kapitel behandelt den Einsatz von Allografts aus der Knochenbank zum Erreichen dieses Ziels.

The femoral components of the total knee replacements are generally made of metal. In contrast, ceramic femoral components promise improved tribological and allergological properties. However, ceramic components present a risk of failure as a result of stress peaks. Stress peaks can be minimised through adequate implant design, proper material composition and optimum force transmission between bone and implant. Thus, the quality of the implant fixation is a crucial factor. The objective of the present study was to analyse the influence of the cement layer thickness on stress states in the ceramic femoral component and in the femur. Two- and three- dimensional finite element analyses of an artificial knee joint with cement layers of different thickness and with an unbalanced cement layer thickness between the ceramic femoral component and the femur were performed. Higher stress regions occurred in the area of force transmission and in the median plane. The maximum calculated stresses were below the accepted tensile strength. Stresses were found to be lower for cement layer thickness of2.0 mm.

After total hip replacement (THR) impingement of the implant components causes shear stresses at the acetabular implant-bone interface. In the current study the finite element method (FEM) was applied to analyse the shear stresses at a fully bonded implant-bone interface assuming total ingrowth of the cup. The FE model of a press-fit acetabular component and the proximal part of the femoral component incorporates non-linear material and large sliding contact. The model was loaded with a superior-medial joint load of 435 N simulating a two-legged stance. Starting at initial impingement, the femoral component was medially rotated by 20 degrees . The peak tilting shear stress of -2.6 MPa at the impingement site takes effect towards the pole of the cup. The torsional shear stress at the impingement site is zero. On each side of the impingement site, there are extrema of torsional shear stress reaching -1.8 and 1.8 MPa, respectively. The global peak shear stress during impingement may indicate a possible starting point for cup loosening. The pattern of the torsional shear stresses suggests that besides the symmetric lever-out, an additional asymmetrical tilting of the cup occurs that can be explained by the orientation of the applied joint load.

Improvements of ceramic components and design changes have reduced failure rates over the past 30 years in total hip arthroplasty. We present a series of n = 11 cases with ceramic failure out of n = 113 implantations, from which n = 66 were ceramic-on-ceramic (n = 50 with ceramic insert with sandwich in polyethylene and n = 16 with directly fixed ceramic inlay) and n = 47 ceramic on polyethylene bearings, between 1999 and 2001 after introduction of a new implantation system to the market. The overall fracture rate of ceramic for the whole series (n = 113) was 9.7%. For the combination ceramic head with UHMW-PE (n = 47) the fracture rate was 2.1%. For the combination ceramic with ceramic (n = 66) the fracture rate was 15.2%. For the combination ceramic with ceramic sandwich in PE (n = 50) the failure rate was 18%. Only three patients experienced a trauma. Demography of patients (age, gender, body weight and BMI) was not statistically different between patients with failed ceramics and the rest of the patients making patient-specific risk factors unlikely to be an explanation for the failures. Retrospective X-ray analysis of the cup positioning did not show significant difference between failed and non-failed implants in terms of mean cup inclination and version making also operation-specific factors unlikely to be the only reason of this high failure rate. Therefore, manufacturer-specific factors such as design features may have contributed to this high failure rate. Further analysis of the whole series with biomechanical testing of the retrieved material needs to be performed.

Die steigende Anzahl der Wechseloperation von Endoprothesen mit ebenfalls zunehmenden Mehrfachwechseln stellt hohe Anforderungen an Operateure, Implantate und die Moglichkeiten des Wiederaufbaus von Knochengewebe. Gerade der limitierende biologische Faktor Knochen erfordert eine prazise praoperative Planung und ein flexibles auf die jeweilige Defektsituation anzupassendes Therapiekonzept.

The acetabular cup position after total hip arthroplasty (THA) regarding its inclination and version angles are influential parameters concerning the postoperative range of motion and dislocation stability. Standard anterior-posterior X-rays remain an important diagnostic instrument to observe the postoperative outcome and to secure quality control after THA, where an optimal positioning of the patient is recommended when taking these X-rays. The purpose of this preliminary study was to determine the effect of pelvic tilting regarding the positioning calculation of the acetabular cup from standard radiographs using a modified method according to Pettersson et al. (Acta Radiol Diagn, 23:259-263, 1982). In our model experiment, we were able to show that pelvic tilting to either side causes a considerable difference between the radiographic and calculated version angles following approximately linear functions. However, pelvic tilting to either side, leads, regarding the calculation of the inclination, to an average deviation between radiographic and calculated inclination angles less than 2 degrees .

Weltweit werden heutzutage mehr als eine Million kunstliche Gelenke pro Jahr implantiert. In Deutschland sind es etwa 250.000 Implantationen. Der Grosteil mit etwa 180.000 entfallt dabei auf kunstliche Huftgelenke [11]. Epidemiologische Untersuchungen vornehmlich aus dem skandinavischen Raum zeigen hierfur nach 10 Jahren ein relatives Revisionsrisiko von 7–13% in Abhangigkeit von Verankerungsart und Implantat [27]. Bei weiterhin steigenden Implantationszahlen in der Primarendoprothetik ergibt sich daraus zwangslaufig eine zunehmende Anzahl an notwendigen Revisionsoperationen [22]. Die mit Abstand haufigste Ursache fur Wechseloperationen ist die aseptische Implantatlockerung. Seltener sind Fruhoder Spatinfektionen, periprothetische Frakturen, Prothesenluxationen oder technisches Versagen Indikationen zu Austauschoperationen. Bei Wechseloperationen ist eine praoperative Diagnostik und Operationsplanung fur die Wahl geeigneter Revisionimplantate unerlasslich. Der Implantatauswahl auf der Grundlage funktioneller, biomechanischer, tribologischer aber auch juristischer und okonomischer Uberlegungen kommt hierbei eine grose Bedeutung zu [28].

Introduction: Aseptic loosening associated with osteolysis and release of wear particles is the main reason for revision of total hip arthroplasty (THA). Damage of femoral heads is well known to increase the wear rate at the articulating surface. Instability and dislocation are serious complications and are the second most frequent reason for revision surgery after THA. In the present work the possible damaging of the femoral head as a result of difficult reduction maneuvers of dislocated THA should be investigated. Patients and methods: In three cases of total hip dislocation an open reduction was performed after dislocation of primary THA. Thereby one metal and two ceramic femoral heads were retrieved. Each head was analyzed macroscopically and by scanning electron microscopy (SEM) subsequently. Results: In the first case the SEM analysis revealed severe titanium deposits on the retrieved ceramic head in the case of repeated unsuccessful closed reduction maneuvers. In the second case the retrieved ceramic head showed multiple scratches and a spalling of the surface structure. In the third case the retrieved metal head presented a roughened surface and severe scratches at the articulating area. Discussion: Difficult reduction maneuvers following total hip dislocation can lead to severe damaging of the femoral head associated with an increase of the surface roughness. While repeated reduction maneuvers can lead to metallic deposits and spalling of the surface of ceramic heads, severe scratches can occur at metal heads. The damaging of the femoral head at the articulating surface can lead to increased wear and subsequent aseptic implant loosening. Therefore, open joint reduction has to be considered in cases of difficult or unsuccessful closed reduction maneuvers to prevent severe femoral head damage which may cause an increased release of wear particles.

The authors report a case of total hip replacement in which, following several revision operations ending up in a Girdlestone arthroplasty, a patient presented recurrent episodes of posterior dislocation of his total hip prosthesis after revision using an antiprotrusio cage. The main causes for dislocation were anterior impingement of the neck against the anterior wall of the antiprotrusio cage and slackness of the periarticular musculature, due to shortening and reduced femoral offset. In order to avoid further major reconstruction and minimise the risk of infection recurrence, a limited revision operation was performed to address the factors responsible for the instability: the anterior wall of the antiprotrusio cage was removed and an extension module was added to the femoral component. Good stability of the arthroplasty was achieved with this limited procedure.

After total hip replacement an insufficient range of motion (ROM) can lead to contact between femoral neck and rim of the cup (= impingement) causing dislocation and consecutive material failure. The purpose of this study was to analyse the influence of different wear couples on the ROM and stability against dislocation. By means of a special testing device the ROM until impingement, the ROM until dislocation as well as the resisting moment against levering the head out of the cup were experimentally determined. Various total hip systems with cup inserts made of ceramic and polyethylene were comparatively examined in different implant positions. Maximum resisting moment as well as the ROM until impingement and dislocation were clearly influenced by the implant position. Furthermore, the stability against dislocation was affected by design parameters, whereas in the case of appropriate implant position differing wear couples (metal-on-polyethylene vs. ceramic-on-ceramic) had a minor impact. However, as shown by tests under lubricant conditions, ceramic-on-ceramic couples provided less dislocation stability in unfavourable implant position in comparison to metal-on-polyethylene. Therefore, ceramic-on-ceramic couples should only be applied in the case of optimised implant orientation preventing impingement and dislocation with subsequent material failure like chipping off or breakage.

After total hip replacement, some cemented titanium stems show above-average early loosening rates. Increased release of wear particles and resulting reaction of the peri-prosthetic tissue were considered responsible. The objective was to develop a test method for analysing the abrasive wear behaviour of cemented stems and for generating wear particles at the interface with the bone cement. By means of the novel test device, cemented hip stems with different designs, surface topographies and material compositions using various bone cements could be investigated. Before testing, the cemented stems were disconnected from the cement mantle to simulate the situation of stem loosening (debonding). Subsequently, constant radial contact pressures were applied on to the stem surface by a force-controlled hydraulic cylinder. Oscillating micromotions of the stem (± 250 μm; 3 × 106cycles; 5 Hz) were carried out at the cement interface initiating the wear process. The usability of the method was demonstrated by testing geometrically identical Ti-6A1-7Nb and Co-28Cr-6Mo hip stems ( n = 12) with definite rough and smooth surfaces, combined with commercially available bone cement containing zirconium oxide particles. Under identical frictional conditions with the rough shot-blasted stems, clearly more wear particles were generated than with the smooth stems, whereas the material composition of the hip stems had less impact on the wear behaviour.

Modular total hip replacement (THR) systems have been clinically proven and usually consist of a stem onto which a metal or ceramic temoral head is fixed. The acetabular cup is composed of a metal-back and an insert. Due to increased life expectancy of the population and a broadening of indications for hip arthroplasty a lengthening of performance life times of THR has become necessary. The most frequent reason for total hip prosthesis failure is the particle induced aseptic loosening [5], therefore lowwear bearing couples like ceramic-on-ceramic are increasingly used.

Juliane Pasold,1 Kathleen Zander,1 Benjamin Heskamp,1 Cordula Grüttner,2 Frank Lüthen,3 Thomas Tischer,1 Anika Jonitz-Heincke,1 Rainer Bader1 1Department of Orthopaedics, Biomechanics and Implant Technology Laboratory, University Medicine Rostock, Rostock, Germany; 2Micromod Particletechnology GmbH, Rostock, Germany; 3Institute of Cell Biology, University Medicine Rostock, Rostock, Germany Purpose: In the present study, silica nanoparticles (sNP) coupled with insulin-like growth factor 1 (IGF-1) were loaded on a collagen-based scaffold intended for cartilage repair, and the influence on the viability, proliferation, and differentiation potential of human primary articular chondrocytes was examined. Methods: Human chondrocytes were isolated from the hyaline cartilage of patients (n=4, female, mean age: 73±5.1 years) undergoing primary total knee joint replacement. Cells were dedifferentiated and then cultivated on a bioresorbable collagen matrix supplemented with fluorescent sNP coupled with IGF-1 (sNP–IGF-1). After 3, 7, and 14 days of cultivation, cell viability and integrity into the collagen scaffold as well as metabolic cell activity and synthesis rate of matrix proteins (collagen type I and II) were analyzed. Results: The number of vital cells increased over 14 days of cultivation, and the cells were able to infiltrate the collagen matrix (up to 120 µm by day 7). Chondrocytes cultured on the collagen scaffold supplemented with sNP–IGF-1 showed an increase in metabolic activity (5.98-fold), and reduced collagen type I (1.58-fold), but significantly increased collagen type II expression levels (1.53-fold; P=0.02) after 7 days of cultivation compared to 3 days. In contrast, chondrocytes grown in a monolayer on plastic supplemented with sNP-IGF-1 had significantly lower metabolic activity (1.32-fold; P=0.007), a consistent amount of collagen type I, and significantly reduced collagen type II protein expression (1.86-fold; P=0.001) after 7 days compared to 3 days. Conclusion: Collagen-based scaffolds enriched with growth factors, such as IGF-1 coupled to nanoparticles, represent an improved therapeutic intervention for the targeted and controlled treatment of articular cartilage lesions. Keywords: chondrogenic differentiation, silica nanoparticles, growth factor, 3D-matrix, cartilage repair

Die Indikationsstellung zum kunstlichen Huftgelenkersatz hat sich auf ein jungeres und insbesondere aktiveres Patientenklientel erweitert. Maximale bzw. freie postoperative Beweglichkeit im kunstlichen Huftgelenk ist deshalb ein wichtiger Einflussfaktor fur dessen ungestorte Langzeitfunktion.

Magnetic resonance imaging (MRI) using measurement of the transverse relaxation time (R2*) is to be considered as a promising approach for cell tracking experiments to evaluate the fate of transplanted progenitor cells and develop successful cell therapies for tissue engineering. While the relationship between core composition of nanoparticles and their MRI properties is well studied, little is known about possible effects on progenitor cells. This in vitro study aims at comparing two magnetic iron oxide nanoparticle types, single vs. multi-core nanoparticles, regarding their physico-chemical characteristics, effects on cellular behavior of adipose tissue-derived stem cells (ASC) like differentiation and proliferation as well as their detection and quantification by means of MRI. Quantification of both nanoparticle types revealed a linear correlation between labeling concentration and R2* values. However, according to core composition, different levels of labeling concentrations were needed to achieve comparable R2* values. Cell viability was not altered for all labeling concentrations, whereas the proliferation rate increased with increasing labeling concentrations. Likewise, deposition of lipid droplets as well as matrix calcification revealed to be highly dose-dependent particularly regarding multi-core nanoparticle-labeled cells. Synthesis of cartilage matrix proteins and mRNA expression of collagen type II was also highly dependent on nanoparticle labeling. In general, the differentiation potential was decreased with increasing labeling concentrations. This in vitro study provides the proof of principle for further in vivo tracking experiments of progenitor cells using nanoparticles with different core compositions but also provides striking evidence that combined testing of biological and MRI properties is advisable as improved MRI properties of multi-core nanoparticles may result in altered cell functions.

The femoral components of total knee replacement are generally made of metal and are mainly implanted with bone cement. Common complications in total knee arthroplasty (TKA) include abrasive wear, malpositioning and material fatigue [2]. In comparison to metal, ceramic components provide a better biocompatibility as well as higher scratch and wear resistance. Laboratory tests showed a decrease in the wear debris rate with the bearing couple ceramic-on-polyethylene to more than one third compared to the couple metal-on-polyethylene [1,9]. Another benefit of ceramic implants also exists in the avoidance of allergic reactions in comparison to metal. A disadvantage of ceramic implants is the low fracture toughness respectively the brittle characteristics [19]. Hence the risk of implant damage resulting from stress peaks has to be minimised by an optimal load transmission in the adjacent bone stock. The load transmission also influences the long-time behaviour of the bone cement. Local cement breakage and cement wear debris induce inflammatory reactions, which can finally lead to aseptic loosening [11,4].

Background The parallel-group randomized active-controlled clinical study was conducted to compare the effectiveness of two in-hospital range of motion (ROM) exercise programs following total knee arthroplasty (TKA). Continuous passive motion (CPM) is frequently used to increase ROM and improve postoperative recovery despite little conclusive scientific evidence. In contrast, a new active sling-based ROM therapy requires the activation of the knee joint muscles and dynamic joint stabilization. It was hypothesized that higher demands on muscle strength and muscle coordination during sling exercise training (ST) might be advantageous for early recovery following TKA. Methods A total of 125 patients undergoing primary TKA were assessed for eligibility. Thirty-eight patients were randomly assigned to receive ST or CPM (control intervention) during hospital stay. Patients were assessed before TKA for baseline measurement (pretest), 1 day before discharge (posttest) and 3 months after TKA (follow-up). The passive knee flexion range of motion (pFL) was the primary outcome measure. Secondary outcome measures included active knee flexion range of motion, active and passive knee extension ROM, static postural control, physical activity, pain, length of hospital stay as well as clinical, functional and quality-of-life outcomes (SF-36, HSS and WOMAC scores). Data were analyzed according to the intention-to-treat principle. Differences between the groups were tested for significance by the unpaired Student’s t test or an analysis of covariance (ANCOVA) adjusted for baseline, weight, sex, age, pain and physical activity. Results A between-group difference could be determined at posttest. The pFL was significantly higher by 6.0° (95% CI 0.9 to 11.2°; P = 0.022) in the ST group. No difference between groups in pFL was documented at follow-up. Furthermore, no significant differences could be observed for any secondary outcome measure at posttest and follow-up. Conclusions ST seems to have a clinically relevant beneficial short-term effect on pFL compared to CPM. The results support the implementation of ST in rehabilitation programs following TKA. Level of evidence Therapy, level 2b