Quantitative T2 mapping of the patella at 3.0T is sensitive to early cartilage degeneration, but also to loading of the knee

The aim of the study was to explore the sensitivity and robustness of T2 mapping in the detection and quantification of early degenerative cartilage changes at the patella.

Bioabsorbable pins for treatment of osteochondral fractures of the knee after acute patella dislocation in children and young adolescents

A retrospective study was performed on the use of bioabsorbable pins in the fixation of osteochondral fractures (OCFs) after traumatic patellar dislocation in children. Eighteen children (13 females, 5 males) aged 11 to 15 years (mean age 13.1 years) with osteochondral fracture (OCF) of the knee joint were treated at the authors' institution. Followup ranged from 22 months to 5 years. Diagnosis was verified by X-ray and magnetic resonance imaging (MRI) of the knee and patella. In seven patients the osteochondral fragment was detached from the patella and in 11 it was detached from the lateral femoral condyle. All patients were subjected to open reduction and fixation of the lesion with bioabsorbable pins. Postoperatively, the knee was immobilized in a cast and all patients were mobilized applying a standardized protocol. Bone consolidation was successful in 17 of the 18 patients. Bioabsorbable pins reliably fix OCF in children and adolescents, demonstrating a high incidence of consolidation of the detached osteochondral fragment in short- and middle-term followup without requiring further operative procedures.

Tripartite patella: late appearance of a third ossification center in childhood

Bilateral radiographic progression of the supero-lateral fragment of a bipartite- into a tripartite patella with unilateral symptoms. An 8 year old girl presented a bilateral bipartite patella Stage III as an incidental finding after fall on the flexed right knee. Serial radiographs two years later revealed a bilateral progression of the bipartite- into a tripartite patella with complaints only on the post-traumatic right side. Observation was opted as therapy. There was no correlation of symptoms and radiological findings of the fragmentation of the bipartite- into a tripartite patella. Therefore we conclude the etiology of a bilateral late appearance of a third ossification center.

Evaluation and comparison of cartilage repair tissue of the patella and medial femoral condyle by using morphological MRI and biochemical zonal T2 mapping

The objective of this study was to use advanced MR techniques to evaluate and compare cartilage repair tissue after matrix-associated autologous chondrocyte transplantation (MACT) in the patella and medial femoral condyle (MFC). Thirty-four patients treated with MACT underwent 3-T MRI of the knee. Patients were treated on either patella (n = 17) or MFC (n = 17) cartilage and were matched by age and postoperative interval. For morphological evaluation, the MR observation of cartilage repair tissue (MOCART) score was used, with a 3D-True-FISP sequence. For biochemical assessment, T2 mapping was prepared by using a multiecho spin-echo approach with particular attention to the cartilage zonal structure. Statistical evaluation was done by analyses of variance. The MOCART score showed no significant differences between the patella and MFC (p > or = 0.05). With regard to biochemical T2 relaxation, higher T2 values were found throughout the MFC (p < 0.05). The zonal increase in T2 values from deep to superficial was significant for control cartilage (p < 0.001) and cartilage repair tissue (p < 0.05), with an earlier onset in the repair tissue of the patella. The assessment of cartilage repair tissue of the patella and MFC afforded comparable morphological results, whereas biochemical T2 values showed differences, possibly due to dissimilar biomechanical loading conditions.

[Medium-term results after m. vastus medialis obliquus-plasty for lateral patellar dislocation]

Progressive retropatellar arthrosis is often seen in dated rigid distal realignment (i.e. osteotomy of tuberositas) at long-term follow-ups. Therefore, operations for lateral dislocation of the patella are still discussed controversially. Dynamic, proximal realignments seem to have lower rates of arthrosis but higher rates of redislocation. Recently, in anatomic and biomechanic studies, the m. vastus medialis obliquus (vmo) was found to be one of the most important proximal restraints to lateral dislocation of the patella.A total of 28 patients (mean age 21.5 years) were treated between 1994 and 2003 with a plasty of the vmo for lateral patellar dislocation. The technique was performed for most etiologies of femoropatellar instability.For this proximal soft tissue technique, the muscle tendon is detached from its patellar insertion. Subsequently, the tendon is reinserted at the patella 10-15 mm more distally and fixed with Mitek anchors. Full weight bearing in extension is possible immediately after surgery. An active vastus medialis training is started after 6 weeks.Of the patients, 27 were evaluated clinically and radiologically in 2004 (a mean of 5 years postoperatively). A total of 83% of the patients estimated the result to be good or excellent, 10% were satisfied and 7% were discontent. The mean Lysholm-Knee-Score was 83.1 points. Two patients suffered a patella redislocation (7%). A statistically significant improvement of the congruence angle was noted in the radiographs, even in medium-term controls. In 89% of the cases no or only little retropatellar arthrosis was observed. These 5 year results are comparable to those of other techniques for distal or proximal realignments. The rate of redislocation was below average. Compared to the rate of retropatellar arthrosis in long-term results of rigid distal realignment, our patients demonstrated a relative low rate after 5 years. We attribute this to the minimal interference in physiological joint mechanics and to the restored anatomy. In terms of future long-term results, our findings are promising. The idea of a proximal dynamic stabilization and the causal operative approach at the origin of pathology using vmo-plasty was confirmed in recent anatomic and biomechanic studies. Over or under correction of soft tissues could be adapted. More rigid techniques of distal realignment do not allow an adaptation to this extent and can lead to prearthrotic hyperpression in the medial femoropatellar and femorotibial joints.

Ligament balancing in TKA: Evaluation of a force-sensing device and the influence of patellar eversion and ligament release

Ligament balancing in total knee arthroplasty may have an important influence on joint stability and prosthesis lifetime. In order to provide quantitative information and assistance during ligament balancing, a device that intraoperatively measures knee joint forces and moments was developed. Its performance and surgical advantages were evaluated on six cadaver specimens mounted on a knee joint loading apparatus allowing unconstrained knee motion as well as compression and varus-valgus loading. Four different experiments were performed on each specimen. (1) Knee joints were axially loaded. Comparison between applied and measured compressive forces demonstrated the accuracy and reliability of in situ measurements (1.8N). (2) Assessment of knee stability based on condyle contact forces or varus-valgus moments were compared to the current surgical method (difference of varus-valgus loads causing condyle lift-off). The force-based approach was equivalent to the surgical method while the moment-based, which is considered optimal, showed a tendency of lateral imbalance. (3) To estimate the importance of keeping the patella in its anatomical position during imbalance assessment, the effect of patellar eversion on the mediolateral distribution of tibiofemoral contact forces was measured. One fourth of the contact force induced by the patellar load was shifted to the lateral compartment. (4) The effect of minor and major medial collateral ligament releases was biomechanically quantified. On average, the medial contact force was reduced by 20% and 46%, respectively. Large variation among specimens reflected the difficulty of ligament release and the need for intraoperative force monitoring. This series of experiments thus demonstrated the device's potential to improve ligament balancing and survivorship of total knee arthroplasty.

The new Australasian goblin spider genus Prethopalpus (Araneae, Oonopidae)

The new goblin spider genus Prethopalpus is restricted to the Australasian tropics, from the lower Himalayan Mountains in Nepal and India to the Malaysian Peninsula, Indonesia, Papua New Guinea, and Australia. Prethopalpus contains those species with a swollen palpal patella, which is one to two times the size of the femur, together with a cymbium and bulb that is usually separated, although it is largely fused in four species. The type species Opopaea fosuma Burger et al. from Sumatra, and Camptoscaphiella infernalis Harvey and Edward from Western Australia are newly transferred to Prethopalpus. The genus consists of 41 species of which 39 are newly described: P. ilam Baehr (♂, ♀) from Nepal; P. khasi Baehr (♂), P. madurai Baehr (♂), P. mahanadi Baehr (♂, ♀), and P. meghalaya Baehr (♂, ♀) from India; P. bali Baehr (♂), P. bellicosus Baehr and Thoma (♂, ♀), P. brunei Baehr (♂, ♀), P. deelemanae Baehr and Thoma (♂), P. java Baehr (♂, ♀), P. kranzae Baehr (♂), P. kropfi Baehr (♂, ♀), P. leuser Baehr (♂, ♀), P. magnocularis Baehr and Thoma (♂), P. pahang Baehr (♂), P. perak Baehr (♂, ♀), P. sabah Baehr (♂, ♀), P. sarawak Baehr (♂), P. schwendingeri Baehr (♂, ♀), and P. utara Baehr (♂, ♀) from Indonesia and Malaysia; and P. alexanderi Baehr and Harvey (♂), P. attenboroughi Baehr and Harvey (♂), P. blosfeldsorum Baehr and Harvey (♂), P. boltoni Baehr and Harvey (♂, ♀), P. callani Baehr and Harvey (♂, ♀), P. cooperi Baehr and Harvey (♂), P. eberhardi Baehr and Harvey (♂, ♀), P. framenaui Baehr and Harvey (♂, ♀), P. humphreysi Baehr and Harvey (♂, ♀), P. kintyre Baehr and Harvey (♂), P. scanloni Baehr and Harvey (♂), P. pearsoni Baehr and Harvey (♂), P. julianneae Baehr and Harvey (♂), P. maini Baehr and Harvey (♂, ♀), P. marionae Baehr and Harvey (♂, ♀), P. platnicki Baehr and Harvey (♂, ♀), P. oneillae Baehr and Harvey (♂), P. rawlinsoni Baehr and Harvey (♂), and P. tropicus Baehr and Harvey (♂, ♀) from Australia and Papua New Guinea. Three separate keys to species from different geographical regions are provided. Most species are recorded from single locations and only three species are more widely distributed. A significant radiation of blind troglobites comprising 14 species living in subterranean ecosystems in Western Australia is discussed. These include several species that lack abdominal scuta, a feature previously used to define subfamilies of Oonopidae.

ACL reconstruction with physiological graft tension by intraoperative adjustment of the anteroposterior translation to the uninjured contralateral knee.

PURPOSE Fixation of anterior cruciate ligament (ACL) substitutes with non-physiological anteroposterior translation (APT) worsens outcome. The aim was to present a technique for physiological APT adjustment of the transplant in ACL reconstruction and its outcome at midterm. METHODS In a consecutive series of 28 patients (age 32 ± 11 years, 24 male), chronic ACL deficiency was treated by bone-patella-tendon-bone reconstruction. Transplant APT was adjusted to that of the contralateral uninjured ACL, measured 3, 6, and 12 months postoperatively using the Rolimeter. At a median follow-up of 5.3 years (3-8 years), 82% of the patients were re-evaluated with APT measurement and using IKDC-, Tegner-, Lysholm-Scores, conventional radiographs and MRI. RESULTS No differences in APT (mean ± SD) between uninjured and reconstructed knees were observed after adjustment (6 ± 1 versus 6 ± 1 mm, n.s.). Three months postoperatively, a statistically significant increase in APT (7 ± 1 mm) and a further increase at midterm (9 ± 2 mm) were observed. Patients scored "normal" or "nearly normal", respectively, in 79% (IKDC) and 4 (3-9) points (Tegner; median, range) or 89 ± 9 points (Lysholm; mean ± SD). Radiological evaluation showed no, minimal or moderate joint degeneration in 5, 20 and 75% of patients, respectively. MRI confirmed intact ACL transplants in all patients. CONCLUSION ACL reconstruction using the presented technique was considered successful, as patients did not suffer from subjective instability, radiographic analysis did not provide evidence for graft rupture at midterm. However, APT increase and occurrence of degenerative changes in reconstructed knees at the midterm might not be prevented even by restoration of a physiological APT in ACL reconstruction. The Rolimeter can be used for quick and easy intraoperative indirect control of the applied tension to the ACL transplant by measuring the APT to obtain physiological tensioning resulting in a satisfying outcome at midterm. LEVEL OF EVIDENCE IV.

Can 3D ultrasound identify trochlea dysplasia in newborns? Evaluation and applicability of a technique.

Femoro-patellar dysplasia is considered as a significant risk factor of patellar instability. Different studies suggest that the shape of the trochlea is already developed in early childhood. Therefore early identification of a dysplastic configuration might be relevant information for the treating physician. An easy applicable routine screening of the trochlea is yet not available. The purpose of this study was to establish and evaluate a screening method for femoro-patellar dysplasia using 3D ultrasound. From 2012 to 2013 we prospectively imaged 160 consecutive femoro-patellar joints in 80 newborns from the 36th to 61st gestational week that underwent a routine hip sonography (Graf). All ultrasounds were performed by a pediatric radiologist with only minimal additional time to the routine hip ultrasound. In 30° flexion of the knee, axial, coronal, and sagittal reformats were used to standardize a reconstructed axial plane through the femoral condyle and the mid-patella. The sulcus angle, the lateral-to-medial facet ratio of the trochlea and the shape of the patella (Wiberg Classification) were evaluated. In all examinations reconstruction of the standardized axial plane was achieved, the mean trochlea angle was 149.1° (SD 4.9°), the lateral-to-medial facet ratio of the trochlea ratio was 1.3 (SD 0.22), and a Wiberg type I patella was found in 95% of the newborn. No statistical difference was detected between boys and girls. Using standardized reconstructions of the axial plane allows measurements to be made with lower operator dependency and higher accuracy in a short time. Therefore 3D ultrasound is an easy applicable and powerful tool to identify trochlea dysplasia in newborns and might be used for screening for trochlea dysplasia.

Is a Revision a Revision? An Analysis of National Arthroplasty Registries' Definitions of Revision.

BACKGROUND The reported survival of implants depends on the definition used for the endpoint, usually revision. When screening through registry reports from different countries, it appears that revision is defined quite differently. QUESTIONS/PURPOSES The purposes of this study were to compare the definitions of revision among registry reports and to apply common clinical scenarios to these definitions. METHODS We downloaded or requested reports of all available national joint registries. Of the 23 registries we identified, 13 had published reports that were available in English and were beyond the pilot phase. We searched these registries' reports for the definitions of the endpoint, mostly revision. We then applied the following scenarios to the definition of revision and analyzed if those scenarios were regarded as a revision: (A) wound revision without any addition or removal of implant components (such as hematoma evacuation); (B) exchange of head and/or liner (like for infection); (C) isolated secondary patella resurfacing; and (D) secondary patella resurfacing with a routine liner exchange. RESULTS All registries looked separately at the characteristic of primary implantation without a revision and 11 of 13 registers reported on the characteristics of revisions. Regarding the definition of revision, there were considerable differences across the reports. In 11 of 13 reports, the primary outcome was revision of the implant. In one registry the primary endpoint was "reintervention/revision" while another registry reported separately on "failure" and "reoperations". In three registries, the definition of the outcome was not provided, however in one report a results list gave an indication for the definition of the outcome. Wound revision without any addition or removal of implant components (scenario A) was considered a revision in three of nine reports that provided a clear definition on this question, whereas two others did not provide enough information to allow this determination. Exchange of the head and/or liner (like for infection; scenario B) was considered a revision in 11 of 11; isolated secondary patella resurfacing (scenario C) in six of eight; and secondary patella resurfacing with routine liner exchange (scenario D) was considered a revision in nine of nine reports. CONCLUSIONS Revision, which is the most common main endpoint used by arthroplasty registries, is not universally defined. This implies that some reoperations that are considered a revision in one registry are not considered a revision in another registry. Therefore, comparisons of implant performance using data from different registries have to be performed with caution. We suggest that registries work to harmonize their definitions of revision to help facilitate comparisons of results across the world's arthroplasty registries.

Biomechanical Role of Bone Anisotropy Estimated on Clinical CT Scans by Image Registration

Image-based modeling is a popular approach to perform patient-specific biomechanical simulations. Accurate modeling is critical for orthopedic application to evaluate implant design and surgical planning. It has been shown that bone strength can be estimated from the bone mineral density (BMD) and trabecular bone architecture. However, these findings cannot be directly and fully transferred to patient-specific modeling since only BMD can be derived from clinical CT. Therefore, the objective of this study was to propose a method to predict the trabecular bone structure using a µCT atlas and an image registration technique. The approach has been evaluated on femurs and patellae under physiological loading. The displacement and ultimate force for femurs loaded in stance position were predicted with an error of 2.5% and 3.7%, respectively, while predictions obtained with an isotropic material resulted in errors of 7.3% and 6.9%. Similar results were obtained for the patella, where the strain predicted using the registration approach resulted in an improved mean squared error compared to the isotropic model. We conclude that the registration of anisotropic information from of a single template bone enables more accurate patient-specific simulations from clinical image datasets than isotropic model.

Accuracy of cartilage-specific 3-Tesla 3D-DESS magnetic resonance imaging in the diagnosis of chondral lesions: comparison with knee arthroscopy

BACKGROUND Arthroscopy is considered as "the gold standard" for the diagnosis of traumatic intraarticular knee lesions. However, recent developments in magnetic resonance imaging (MRI) now offer good opportunities for the indirect assessment of the integrity and structural changes of the knee articular cartilage. The study was to investigate whether cartilage-specific sequences on a 3-Tesla MRI provide accurate assessment for the detection of cartilage defects. METHODS A 3-Tesla (3-T) MRI combined with three-dimensional double-echo steady-state (3D-DESS) cartilage specific sequences was performed on 210 patients with knee pain prior to knee arthroscopy. Sensitivity, specificity, and positive and negative predictive values of magnetic resonance imaging were calculated and correlated to the arthroscopic findings of cartilaginous lesions. Lesions were classified using the modified Outerbridge classification. RESULTS For the 210 patients (1260 cartilage surfaces: patella, trochlea, medial femoral condyle, medial tibia, lateral femoral condyle, lateral tibia) evaluated, the sensitivities, specificities, positive predictive values, and negative predictive values of 3-T MRI were 83.3, 99.8, 84.4, and 99.8 %, respectively, for the detection of grade IV lesions; 74.1, 99.6, 85.2, and 99.3 %, respectively, for grade III lesions; 67.9, 99.2, 76.6, and 98.2 %, respectively, for grade II lesions; and 8.8, 99.5, 80, and 92 %, respectively, for grade I lesions. CONCLUSIONS For grade III and IV lesions, 3-T MRI combined with 3D-DESS cartilage-specific sequences represents an accurate diagnostic tool. For grade II lesions, the technique demonstrates moderate sensitivity, while for grade I lesions, the sensitivity is limited to provide reliable diagnosis compared to knee arthroscopy.