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Introduction: Function and kinematics following unicondylar knee arthroplasty (UKA) have been reported to be close to the native knee. Gait, stair climbing and activities of daily living expose the knee joint to a combination of varus and valgus moments. Replacement of the medial compartment via UKA is likely to change the physiologic knee stability and its ability to respond to varus and valgus moments. It was hypothesized that UKA implantation would stiffen the knee and decrease range of motion in the frontal plane., Materials and Methods: Six fresh frozen cadaver knees were prepared and mounted in a six-degrees-of-freedom robot. An axial load of 200 N was applied with the knee in 15°, 45° and 90° of flexion. Varus and valgus moments were added, respectively, before and after implantation of medial UKA. Tests were than redone with a thicker polyethylene inlay to simulate overstuffing of the medial compartment. Range of motion in the frontal plane and the tibial response to moments were recorded via the industrial robot., Results: The range of motion in the frontal plane was decreased with both, balanced and overstuffed UKA and shifted towards valgus. When exposed to valgus moments, knees following UKA were stiffer in comparison with the native knee. The effect was even more pronounced with medial overstuffing., Conclusion: In UKA, the compressive anatomy is replaced by much stiffer components. This lack of medial compression and relative overstuffing leads to a tighter medial collateral ligament. This drives the trend towards a stiffer joint as documented by a decrease in frontal plane range of motion. Overstuffing should strictly be avoided when performing UKA.

Introduction: Patient-specific instrumentation (PSI) was introduced in an attempt to reduce positional outliers of components in total knee arthroplasty (TKA). It was hypothesized that PSI could help with the positioning of tibial components in optimal rotational alignment., Methods: A magnetic resonance imaging (MRI) analysis of 58 patients following TKA was conducted. Of these, 30 operations were performed using PSI and 28 using conventional instrumentation. The rotation of the tibial components was determined in MRI using three different reference lines: a tangent to the dorsal tibial condyles, the tibial epicondylar line, and the tibial tubercle. Deviations >9° were considered outliers. Also internal rotation >1° was considered an outlier. Data were analyzed statistically for positional outliers using the Chi-squared test., Results: There was excellent inter- and intraobserver reliability with low standard deviations for the determination of tibial component rotation using the tangent to the dorsal condyles and the tibial epicondylar line as reference. Using the dorsal tangent as reference, there were eight components in excessive external rotation (28.6 %) and one component being in relative internal rotation (5.4°) in the conventional group, while there were two components in excessive external rotation in the PSI group (6.7 %). Using the tibial epicondyles as reference, there were seven components in excessive external rotation (21.4 %) and one component being in relative internal rotation (4.4°) in the conventional group; while there were two components in excessive external rotation in the PSI group (6.7 %). These differences were statistically significant (p < 0.05). Measurements based on the tibial tubercle showed poor reproducibility in terms of intra- and interobserver reliability and was of little use in the context of the research question., Discussion and Conclusion: In this setup, PSI was effective in significantly reducing outliers of optimal rotational tibial component alignment during TKA. Anatomy of the proximal tibia does not deliver clear landmarks that are prominent and consistent. This makes both, MRI analysis as well as cutting jig production and intraoperative placement a challenge.

Background: Loosening is one of the major long-term failure modes in unicondylar knee arthroplasty (UKA). The aim of the study is to describe and characterize implant-bone interface of femoral and tibial components after UKA by means of magnet resonance imaging (MRI)., Material and Methods: MRI tailored to reduce metallic artefact of the knee after medial UKA was performed in 10 patients as a pilot study. The component-bone interface at femoral and tibial components was evaluated by two independent investigators. They gave degree of confidence to their evaluation of each parameter on a five-point scale. Inter-observer reliability was determined., Results: Artefacts provoked by the implants were rare. Inter-observer reliability and confidence were excellent for the femoral interface. They were lower at the tibial interface but results were still satisfactory., Conclusions: Tailored MRI allows reproducible analysis of the component-bone interface after UKA. It is helpful in assessment of suspected loosening after UKA.

Background: Component malposition is one of the major reasons for early failure of unicompartmental knee arthroplasty (UKA)., Questions/purposes: It was investigated how reproducibly patient-specific instrumentation (PSI) achieved preoperatively planned placement of the tibial component in UKA specifically assessing coronal alignment, slope and flexion of the components and axial rotation., Patients and Methods: Based on computer tomography models of ten cadaver legs, PSI jigs were generated to guide cuts perpendicular to the tibial axis in the coronal and sagittal planes and in neutral axial rotation. Deviation ≥3° from the designed orientation in a postoperative CT was defined as outside the range of acceptable alignment., Results: Mean coronal alignment was 0.4 ± 3.2° varus with two outliers. Mean slope was 2.8 ± 3.9° with six components in excessive flexion. It was noted that the implants were put in a mean of 1.7 ± 8.0° of external rotation with seven outliers., Conclusions: PSI helped achieve the planned coronal orientation of the component. The guides were less accurate in setting optimal tray rotation and slope.

Evidence for the efficacy of extracorporeal shock wave therapy (ESWT) in supraspinatus tendinopathy without calcification is sparse, and therefore this treatment option is often controversial. Patients of a randomized placebo-controlled study to analyze the effects of ESWT on function and pain were revisited 10 years after the initial consultation. The former verum group received 6000 impulses (energy flux density, 0.11 mJ/mm²) in three sessions after local anesthesia between 1999 and 2000. The placebo group had 6000 impulses of a sham ESWT after local anesthesia in the same period. Re-evaluation of the patients included a relative Constant score as well as pain measurements (visual analogue scale) during activity and at rest. No significant changes (p>0.05) in relative Constant scores, pain at rest, or pain during activity could be found after a 10-year follow-up between the placebo and verum groups after ESWT. The treatment of non-calcific supraspinatus tendinopathy with ESWT does not seem to have an effect on function or pain improvement in the long run. The results of the present study cannot advise the use of ESWT in cases of non-calcific supraspinatus tendinopathy.

Purpose: It is assumed that unicondylar knee arthroplasty (UKA) features kinematics close to the natural knee. Clinical studies have also shown functional benefits for UKA. There is to date only little biomechanical data to support or explain these findings. The purpose of this study was to investigate whether UKA is able to preserve natural knee kinematics or not., Methods: Six fresh frozen full leg cadaver specimens were prepared to be mounted in a kinematic rig with six degrees of freedom for the knee joint. Three motion patterns were applied before and after medial UKA: passive flexion-extension, open chain extension, and squatting. During the loaded motions, quadriceps and hamstrings muscle forces were applied. Infrared cameras continuously recorded the trajectories of marker frames rigidly attached to femur, tibia, and patella. Prior computer tomography allowed identification of coordinate frames of the bones and calculations of anatomical rotations and translations., Results: Native kinematics was reproduced after UKA in all the specimens. In the unloaded knee and during open chain extension, femoral rollback patterns after UKA were very close to those in the native knee. During squatting, the medial femoral condyle after UKA tended to be more posterior and superior with flexion and there was less tibial internal rotation. The tibia was found to be more in valgus after UKA during all motion patterns., Conclusion: As ligaments, lateral compartment and patellofemoral anatomy are preserved with UKA; the unloaded knee closely resembles native kinematics. The slight kinematic changes that were found under load are probably due to loss of the conforming medial meniscus and to the mismatch in geometry and stiffness introduced by UKA. These patterns resemble those found in knees with significant loss of function of the medial meniscus.

Background: Oxidized zirconium (OxZr) was introduced as an alternative bearing for femoral components in total knee arthroplasty (TKA) in an attempt to reduce wear compared with conventional cobalt-chromium (CoCr) alloys., Questions/purposes: The aim of this study was to compare matched pairs of retrieved OxZr and CoCr components using surface profilometry; specifically, we sought to compare the surface roughness of (1) retrieved OxZr TKA components with retrieved CoCr components; (2) the medial versus the lateral femoral condyles of retrieved components; and (3) unimplanted OxZr TKA components with unimplanted CoCr components., Methods: Ten retrieved posterior-stabilized Genesis II TKA with OxZr femoral components were identified and matched to retrieved CoCr femoral components by duration of implantation, patient age, and body mass index. A noncontact white light interferometer was used to evaluate surface roughness. One pristine, unimplanted component of each design was analyzed as a control., Results: The retrieved components showed significantly (p < 0.0001) lower roughness for the OxZr components than the CoCr components. CoCr retrievals showed a significantly greater average surface roughness on the medial condyle. No difference was found between the condyles of the OxZr components. The pristine CoCr implant had a significantly lower surface roughness than the pristine OxZr component., Conclusions: CoCr roughens significantly more in situ compared with OxZr components., Clinical Relevance: Bearing surfaces are typically damaged in vivo. The extent of damage is variable between patients and implants; however, rougher surfaces should be associated with more wear. Whether the differences observed in our study prove meaningful requires long-term clinical data.

Background: Total knee arthroplasty (TKA) for juvenile idiopathic arthritis is rare but is nonetheless indicated for many patients with this disease. Few reports exist on the results of TKA in patients with juvenile idiopathic arthritis., Questions/purposes: It was sought to determine (1) survivorship and (2) functional outcomes of TKAs in patients with juvenile idiopathic arthritis., Methods: Results were combined from patients treated by experienced surgeons at five hospitals between 1979 and 2011. Two hundred nineteen patients (349 TKAs) were identified and contacted to survey their outcomes at a minimum followup of 2 years (mean, 12 ± 8 years; range, 2-33 years). The average age at surgery was 28.9 ± 9.7 years (range, 11-58 years). Data on revision surgery and ability to perform daily activities were collected., Results: The 10-year survivorship was 95%, decreasing to 82% by 20 years. At latest followup, 31 of 349 TKAs (8.9%) had been revised for either polyethylene failure or loosening (18 TKAs), infection (four), stiffness (three), periprosthetic fractures (two), bilateral amputation for vascular reasons (two), patellar resurfacing (one), and instability (one). Walking tolerance was unlimited in 49%, five to 10 blocks in 23%, and less than five blocks in 28%. Eleven percent could not manage stairs, and another 59% depended on railings. A cane was used by 12% and crutches by 7%; 12% were wheelchair-dependent., Conclusions: TKA survivorship in patients with juvenile idiopathic arthritis was inferior to that typically seen in younger patients with osteoarthritis or even rheumatoid arthritis confirming results of earlier studies with smaller patient numbers. This is especially disconcerting because younger patients require better durability of their TKAs.

Background: Bleeding remains an ongoing concern after total knee arthroplasty (TKA). Intraarticular application of human fibrinogen with a topical thrombin has been described to stop diffuse bleeding in knee arthroplasty., Questions/purposes: It was hypothesized that the use of human fibrinogen as a topical agent would result in a reduction of bleeding and transfusions required after TKA; secondary end points included comparison of early clinical results including pain scores and range of motion (ROM) at 6 weeks and complications after surgery., Methods: Two hundred patients undergoing TKA were randomized into a double-blind clinical trial to receive either intraarticular fibrinogen 2 minutes before tourniquet release or no such treatment. Postoperative hemoglobin and hematocrit levels, drain output, and transfusion requirements were recorded and blood loss was calculated. Clinical outcomes and adverse events were tracked prospectively. Descriptive analysis was performed using a two-sample t-test., Results: There were no differences in calculated blood loss between the fibrinogen and the control groups; the mean postoperative drain output was 780 ± 378 mL in the fibrinogen group compared with 673 ± 301 mL in the control group (p = 0.029), but the hemoglobin drop at Day 2 was 3.47 ± 1.53 g/L in the fibrinogen group and 3.84 ± 1.24 g/Ll in the control group (p = 0.051). There were no differences in in transfusions, early ROM, visual analog pain scores, or complications between the groups., Conclusions: The use of fibrinogen in TKA did not lead to a significant reduction of blood loss or transfusions in primary TKA for osteoarthritis. Given the lack of benefits and the costs this procedure adds to TKA, its routine use cannot be justified during primary TKA for osteoarthritis.

Background: Patient-specific instrumentation (PSI) was introduced in an attempt to reduce positional outliers of components in total knee arthroplasty (TKA). It was hypothesized that PSI could help with the positioning of femoral components in optimal rotational alignment., Methods: A magnetic resonance imaging (MRI) analysis of 94 patients following TKA was conducted. Of these, 46 operations were performed using PSI and 48 using conventional instrumentation. The rotation of the femoral components was determined in the MRI and deviations>3° were considered outliers. Data were analyzed for positional outliers, observer reliability, and a variance comparison between implant groups., Results: There was excellent inter- and intraobserver reliability with low standard deviations for the determination of femoral component rotation. There were significantly more outliers in the conventional (22.9%) group than in the PSI group (2.2%, p=0.003)., Conclusion: In this setup, PSI was effective in significantly reducing outliers of optimal rotational femoral component alignment during TKA., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Purpose: The aim of this study was to assess the reproducibility of using magnetic resonance imaging (MRI) to analyze the preserved anatomic knee compartments following unicondylar knee arthroplasty (UKA) with zirconium femoral components. It was hypothesized that evaluation of the cartilage, ligaments, meniscus, and tendons would result in a high rate of inter-observer reliability., Scope: Ten patients underwent MRI of the knee tailored to reduce metallic artifact following medial UKA with zirconium femoral implants. Cartilage, external meniscus, collateral and cruciate ligaments, the quadriceps and patellar tendons, and the presence of joint effusion were evaluated by two independent investigators. The reviewers provided degrees of confidence with their evaluation of each parameter through the use of a five-point scale. Inter-observer agreement was calculated and inter-observer reliability was determined by use of Cohen's Kappa. Artifacts originating from the implants were rarely observed. There was excellent inter-observer reliability (i.e., high Cohen's Kappa) for all assessed structures, and a high level of observer confidence for the evaluation of the cartilage, meniscus, tendons, ligaments, and joint effusion., Conclusion: In this study tailored MRI allows for reproducible analysis of the preserved knee joint compartment after UKA for zirconium implants. This technique might prove helpful in the assessment of painful knee joints after UKA with other metallic materials as new MRI software programs, which suppress metal artifacts, are developed., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Background: Unicompartmental knee arthroplasty (UKA) is known to be a viable procedure allowing for preservation of the intact compartments and delivering excellent function at long-term follow-up. The primary purpose of this single-surgeon study was to analyse the survivorship of a fixed bearing UKA in patients younger than 60 years., Methods: From all UKAs implanted between 1993 and 2005 at the senior authors' centre, 223 patients <60 years at operation with a minimum follow-up of 5 years were identified including all-poly and metal-backed tibiae. They were evaluated applying the Knee Society Score (KSS) at latest follow-up. Survivorship was calculated using Kaplan-Meier analysis, which considered the following variables: gender, type of tibial implant, medial vs. lateral UKA, and age., Results: Average age at index operation was mean 53.7 (SD 5.8, range 30-60) years at a mean follow-up of 10.8 (SD 3.5, range 5-17) years. From the KSS, the knee score was 94.3 (SD 7.8) and the function score was 94.9 (SD 6.8). At latest follow-up, the implant survival rate was 94.3%. Survivorship for the entire cohort was 93.5% at 10 years (medial UKA 94.1% vs. lateral 91.8%), and 86.3% at 15 years (85.1% medial vs. 91.7% lateral), Conclusion: In conclusion, excellent survival and function outcomes were noted in this subgroup of patients younger than 60 years. Revision rates were comparable to those studies in which UKA was performed on an elderly patient population. UKA can successfully be performed in patients younger than 60 years with appropriate patient selection., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Purpose: The aim of this study was to analyze rotation of total knee (TKA) implant components using magnetic resonance imaging (MRI) and to assess the reproducibility of results. It was hypothesized that rotation of both femoral and tibial implants would be reliably reproduced., Methods: A retrospective analysis of 55 MRI studies in subjects with painful TKA implants was conducted. There were 27 zirconium and 28 cobalt/chrome/molybdenum alloy (CoCrMo) femoral components in the group. The rotation angle of femoral and tibial components was measured and determined. Statistical analysis included tests for reliability, variance between implant groups, standard deviations and confidence intervals., Results: There was a sufficient inter- and intra-observer reliability determined for rotation in all implants. The inter-observer reliability was notably higher in the zirconium femur group with significant less variance and lower standard deviations than the CoCrMo femoral component comparison group. Standard deviations for femoral rotational analysis were within a clinically acceptable range. The standard deviations were considerably higher in the tibial component rotational analysis., Conclusion: MRI analysis of the rotation of femoral implants after TKA allows good reproducibility, especially with review of zirconium implants. There is less reproducibility for tibial components related to the applied geometric method to quantify rotation and not to the MRI technique., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Introduction: The aim of this study was to assess the reproducibility of magnet resonance imaging (MRI) analysis of preserved anatomic structures of the knee after patellofemoral replacement (PFR). It was hypothesized that evaluation of cartilage, ligaments, meniscus and tendons would result in high inter-observer reliability after PFR., Material and Methods: MRI, tailored to reduce metallic artefacts of the knee, after PFR was performed in seven patients. Two independent investigators evaluated cartilage, menisci, collateral and cruciate ligaments, the quadriceps and patellar tendons and the presence of joint effusion. The reviewers used a five-point scale to give a degree of confidence to their evaluation of each parameter. Inter-observer reliability was determined by calculation of Cohen's Kappas., Results: Artefact provoked by the implants was not observed. For all assessed structures, there was excellent inter-observer reliability, with high Cohen's Kappas. There were also high levels of inter-observer agreement and observer confidence in the evaluation of cartilage, meniscus, tendons, ligaments and joint effusion., Conclusion: Tailored MRI allows reproducible analysis of the preserved knee joint structures after PFR. It might prove helpful in assessment of painful knee joints after PFR., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)

Purpose: The aim of the study is to describe and characterize the implant-bone interface of femoral, tibial and patellar components after TKA using magnet resonance imaging (MRI)., Scope: Fifty-five patients who underwent MRI modified to reduce artifacts after TKA were identified retrospectively from medical records. This included 27 TKA with a zirconium femoral component and 28 TKA with conventional cobalt/chrome/molybdenum alloy component (CoCrMo). The MRIs were evaluated by two blinded, independent investigators and Cohen's Kappa was applied to determine the interobserver reliability. Excellent visibility, interobserver agreement and reliability was found for the interface of the tibial components, patellar buttons, and for femoral components made of zirconium. Conventional CoCrMo components caused significant artifact that interfered with the evaluation of the interface of femoral components., Conclusion: MRI performed with a special protocol allows good reproducibility of analysis of implant-bone interface at tibia and patella after TKA. The femoral interface was visualized for components made of zirconium. Conventional CoCrMo femoral components caused considerable artifact and interfered with the evaluation of the femoral interface. MRI tailored to reduce metallic susceptibility artifact can be a helpful tool for evaluation of prosthesis bone interface and may be helpful for the diagnosis of component loosening., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Oxidized zirconium (OxZr) was introduced to serve as a ceramic surface for femoral components in TKA. The aim of this study was to compare retrieved OxZr components and corresponding PE inserts in matched comparison with conventional cobalt/chrome/molybdenum alloy (CoCrMo). Eleven retrieved posterior stabilized TKA with an OxZr femoral component were included. This included 6 implants from an earlier preliminary study. From a cohort of 56 retrieved TKA with conventional CoCrMo femoral components, pairs were matched according to duration of implantation, patient age, reason for revision, and BMI. Polyethylene inlays and femoral components were optically scored for in vivo damage. The average damage score of the tibial PE inserts was significantly lower with OxZr components (p=0.01). Mainly burnishing and scratches were found. The average wear score in the visual analysis of the femoral components was significantly lower for the OxZr as well (p=0.005). Femoral components made of OxZr were less sensitive to in vivo damage and corresponding PE inlays also showed less damage than CoCrMo components., (Copyright © 2010 Elsevier B.V. All rights reserved.)

The purpose of the present study was to evaluate the precision of digital templating in total hip arthroplasty (THA) and the influence of the surgeons' level of experience on the accuracy of preoperative planning. A retrospective review of digital computer planned THA's was performed on 169 hips. The preoperatively planned component sizes were compared to the sizes used in the operation. An exact agreement between planned and actually used size was achieved in 33.7% of the hips for the acetabular cups and 36% for the femoral stems. A prediction of +/- 1 size was reached in 77.5% for acetabular components and 82.3% for the femoral stem. On average, the acetabular components were planned approximately 0.9 sizes too large, the femoral stems 0.3 sizes too small. The accuracy of preoperative planning showed no differences according to the level of training of the planning surgeon. We state that the digital templating is useful to predict the implant size. However, 15 of the 169 planned components showed a difference of more than 2 sizes. Therefore, digital templating cannot fully replace intraoperative X-ray use.

Grice-Green extra-articular subtalar arthrodesis is a treatment option for advanced valgus rearfoot deformity of neuromuscular origin in young patients. The purpose of this study was to evaluate long-term results of the procedure in ambulatory cerebral palsy patients. From January 1975 to December 1993, 57 operations were performed in 39 patients (22 males, 17 females) with a mean age of 7.8 ± 2.7 (range 3.9-14.4) years for excessive symptomatic hindfoot valgus. Thirty-five patients (51 feet) were followed for a mean 22.6 ± 4.6 (range 16.0-32.3) years. Preoperative GMFCS score, ambulation, hindfoot position, podoscopic view of the weight-bearing feet, and radiological examinations, along with complications and orthotic use, were compared. Based on a clinical rating scale, 39 results were excellent or good, 8 were fair, and 4 were poor. The poor results were attributed to hindfoot valgus recurrence or varus overcorrection. One case needed revisional surgery owing to slippage of the graft. Overall, the GMFCS score, level of ambulatory distance, and use of foot orthoses improved. Grice-Green subtalar arthrodesis did not result in early degenerative changes at the midterm follow-up. The procedure offers safe and long-lasting correction for severe and symptomatic hindfoot disorders in patients with cerebral palsy. Together with physiotherapy and orthotic use, it can improve ambulation. Whereas a slight hindfoot valgus in patients with cerebral palsy is tolerable without lack of function, overcorrection should be avoided., (Copyright © 2011 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.)

Thrombocytopenia has been reported to occur after total hip arthroplasty (THA). Several in vitro studies have investigated whether polymethylmethacrylate (PMMA) bone cement could be a possible origin for toxic agents that interfere with platelet function and survival. The aim of this study was to screen patient data for postoperative thrombocytopenia and the level of platelet concentrations in relation with the fixation method of THA. A consecutive series of 499 THAs was studied (24.6% fully cemented, 45.5% hybrid and 29.9% uncemented). Pre- and postoperative thrombocyte levels were recorded. Patient data were reviewed for age, indication, BMI, blood cell count, and thromboembolic events. Patients in the noncemented group were significantly younger and their thrombocyte levels were higher. There were no statistically significant differences in platelet loss between groups at any point in time following THA. Platelet concentrations had fully recovered at the time of discharge from hospital. Power analysis revealed that the cohort was large enough to show even small effect sizes. The use of PMMA cement in THA does not appear to affect postoperative platelet concentrations to any significant extent.

There are various methods to locate the rotation centre of the hip joint on standard pelvic radiographs. When the geometry of both femoral heads is abnormal, a number of methods are available to locate the physiological hip centre from anatomical landmarks on pelvic radiographs. The accuracy and reliability of six methods were retrospectively investigated on 115 standard pelvic radiographs of both hips of healthy individuals. As a reference against the hip joint centre predicted by these methods, we used the true anatomical centre of the femoral head. Measurements were normalized in relation to pelvic height. The calculated hip rotation centre most closely approached the true anatomical centre of the femoral head when the acetabular teardrop was used as a landmark.