Small RNA (sRNA)-induced mRNA degradation occurs through binding of an sRNA to a target mRNA with the concomitant action of the RNA degradosome, which induces an endoribonuclease E (RNase E)-dependent cleavage and degradation of the targeted mRNA. Because many sRNAs bind at the ribosome-binding site (RBS), it is possible that the resulting translation block is sufficient to promote the rapid degradation of the targeted mRNA. Contrary to this mechanism, we report here that the pairing of the sRNA RyhB to the target mRNA sodB initiates mRNA degradation even in the absence of translation on the mRNA target. Remarkably, even though it pairs at the RBS, the sRNA RyhB induces mRNA cleavage in vivo at a distal site located >350 nucleotides (nt) downstream from the RBS, ruling out local cleavage near the pairing site. Both the RNA chaperone Hfq and the RNA degradosome are required for efficient cleavage at the distal site. Thus, beyond translation initiation block, sRNAinduced mRNA cleavage requires several unexpected steps, many of which are determined by structural features of the target mRNA.

Rotational stability of the knee has been traditionally difficult to quantify, limiting the ability of the orthopedic community to determine the potential role of rotational laxity in the etiology of anterior cruciate ligament (ACL) injuries. The purposes of this multicenter cohort study were to evaluate the reliability of a robotic axial rotation measurement system, determine whether the uninjured knees of patients that had previous contralateral ACL reconstruction demonstrated different rotational biomechanical characteristics than a group of healthy volunteers, and determine whether knee rotational biomechanical characteristics differ between male and female non-injured limbs in groups of both healthy volunteers and patients with a previous contralateral ACL injury. Fourteen healthy volunteers and 79 patients with previous unilateral ACL injury participated in this study. Patients were tested using a computerized tibial axial rotation system. Only the normal (non-operated) knee data were used for analysis. In order to assess the reliability of the robotic measurement system, 10 healthy volunteers were tested daily over four consecutive days by four different examiners. Rotational laxity and compliance measures demonstrated excellent reliability (ICC = 0.97). Patients with a contralateral ACL injury demonstrated significantly increased tibial internal rotation (20.6° vs. 11.4°, P < 0.001) and reduced external rotation (16.7° vs. 26.6°, P < 0.001) compared to healthy volunteers. Females demonstrated significantly increased internal and external rotation, as well as significantly increased rotational compliance compared with males (P < 0.05). Computer-assisted measurement techniques may offer clinicians an accurate, reliable, non-invasive method to select the most appropriate preventative or surgical interventions for patients with increased knee rotational laxity.

The purpose of this study was to describe an original technique of reconstruction of the anteromedial bundle preserving the posterolateral bundle and to report the results of a consecutive 36 patients series with mean 24 months follow-up. Our hypothesis is that this selective reconstruction of ACL partial tears could restore knee stability and function. In a consecutive series of 256, ACL reconstructions, 36 patients in which intact ACL fibers remained in the location corresponding to the posterolateral bundle were perioperatively diagnosed. These patients (21 women and 15 men) underwent isolated reconstruction of the anteromedial bundle while keeping the remaining fibers intact. AM bundle reconstructions were performed by the same surgeon using an outside-in technique. A quadrupled hamstring graft was used in 20 patients and a doubled semitendinosus graft in 16 patients. The mean age of the patients at the time of surgery was 32 years (min 15, max 53). The delay between injury and surgery was 6.6 months (min 2, max 35). Patients were assessed with the IKDC ligament evaluation form. Instrumented knee testing was performed with the Rolimeter arthrometer. Statistical analysis was performed to compare the preoperative and postoperative objective evaluation. Eleven concomitant meniscal lesions at the time of reconstruction were found. One patient who underwent a traumatic graft rupture at 4 months post surgery and two patients with previous contralateral ACL reconstruction were excluded, leaving 33 patients for final evaluation. Three reoperations were performed, including two arthrolysis for cyclops syndrome and one revision for a traumatic graft rupture. At last follow-up, 24 (73%) patients were graded A, 8 (24%) graded B and 1 C (3%) at IKDC objective evaluation. Mean side to side instrumented laxity was 4.8 mm (min 3, max 6) preoperatively and 0.8 mm (min 0, max 2) postoperatively. AM bundle reconstruction with an outside-in technique remains simple and reproducible. The preliminary results are encouraging with excellent side to side laxity. Graft size should probably be adapted to limit cyclops syndrome occurrence.

We report on the long-term results of 163 bicruciate-retaining Hermes 2C total knee replacements in 130 patients at a mean follow-up of 22.4 years (20.3 to 23.5). Even when the anterior cruciate ligament had a partially degenerative appearance it was preserved as long as the knee had a normal anterior drawer and Lachman's test pre-operatively. The description and surgical technique of this minimally constrained prosthesis were published in 1983 and the ten-year clinical results in 1999. A total of 12% of the knees (20 of 163) in this study were revised because of wear of the polyethylene tibial insert. Excellent stability was achieved and the incidence of aseptic component loosening was 4.3% (seven of 163). The survival rate using revision for any reason as the endpoint was 82% (95% confidence interval 76.2 to 88.0). Although this series included a relatively small number of replacements, it demonstrated that the anterior cruciate ligament, even when partially degenerated at the time of TKR, remained functional and provided adequate stability at a long-term follow-up.

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Many authors presented the epicondylar axis as the fixed axis of rotation of the femoral condyles during flexion of the knee. Positioning of the femoral component of a total knee arthroplasty (TKA) based on the epicondyles has been proposed. This work is a critical analysis of this concept. Metallic bodies were inserted at the level of collateral ligament insertions on 16 dried femurs, allowing us to locate the surgical epicondylar axis. The dried femurs were studied using standard radiographs and CT-scan. CT cuts were made perpendicular to the epicondylar axis. The medial mechanical femoral angle and the epicondylar angle were measured on the radiographs. The posterior and distal epiphyseal rotations relative to the epicondylar axis (Posterior Condylar Angle, PCA, and Distal Condylar Angle, DCA, respectively) were measured on the CT-scans. PCA and DCA values were compared. The centre of the posterior femoral condyles was located on sagittal reconstructions using the tangent method and was confirmed with circular templates, and then compared to the location of the epicondyles. Circle-fitting of the entire femoral condylar contours centred on the epicondyles was also tried. The mechanical femoral axis was nearly perpendicular to the epicondylar axis but with important variations. The average PCA and DCA were 1.9 degrees +/- 1.8 degrees and 3.1 degrees +/- 2.1 degrees , respectively. No relationship could be established between the mechanical femoral angle and the PCA. The individual differences between the PCA and the DCA averaged 2.2 degrees . A significant distance was found between the centre of the condylar contours and the epicondyles: 6.5 mm in average on the lateral side (range 2.3-11.3 mm) and 8.4 mm on the medial side (range 4.0-11.6 mm). Circle-fitting of the entire medial or lateral femoral condylar contours centred on the epicondyles was not possible. The centre of the posterior femoral condyles is significantly different from the epicondylar axis, thus refuting the conclusions of previous authors. Furthermore, considering the differences between the distal and posterior condylar angles shown here, as well as the difficulty of repeatably locating the epicondyles during surgery, using the epicondylar axis as the only landmark to position the femoral component during a first intention TKA is not recommended. The surgical epicondylar axis does not appear to be an adequate basis for the understanding of the shape of the distal femur.

PurposeThe purpose of this study was to compare the biomechanical characteristics and patient outcomes after either isolated intraarticular ACL reconstruction or intraarticular reconstruction with lateral extra-articular tenodesis. In addition, we aimed to evaluate biomechanical parameters of the entire uninjured, contralateral knee as a baseline during the analysis.MethodsEighteen patients were evaluated at an average of 9.3 years after ACL reconstruction. Twelve patients had an intraarticular reconstruction (BTB), and six had an additional lateral extraarticular procedure (BTB/EAR). Patients were selected for the additional procedure by the operating surgeon based on clinical and radiological criteria. At the time of review, each patient was assessed using subjective patient questionnaires, manual laxity testing, and instrumented laxity testing. Each knee was also evaluated using a robotic lower leg axial rotation testing system. This system measured maximum internal and external rotations at 5.65 Nm of applied torque and generated load deformation curves and compliance data. Pointwise statistical comparisons within each group and between groups were performed using the appropriate paired or unpaired t test. Features were extracted from each load deformation curve for comparative analysis.ResultsThere were no significant differences between the two groups with respect to the patient satisfaction scores or to laxity testing (manual or instrumented). Robotic testing results for within-group comparisons demonstrated a significant reduction in maximum external rotation (8.77°) in the reconstructed leg when compared to the healthy leg (p < 0.05) in the BTB/EAR group, with a non-significant change in internal rotation. The slope of the curve at maximum internal rotation was also significantly greater in the reconstructed legs for the BTB/EAR group (p < 0.05), indicating reduced endpoint compliance or a harder endpoint. Finally, the leg that received the extra-articular tenodesis had a trend towards a reduced total leg axial rotation. Conversely, patients in the BTB group demonstrated no significant differences between their legs. For between-group comparisons, there was a significant increase in maximum internal rotation in the healthy legs in the BTB/EAR group compared with the healthy legs in the BTB group (p < 0.05). If the injured/reconstructed legs were compared, the significant difference at maximum internal rotation disappeared (p < 0.10). Similarly, the healthy legs in patients in the BTB/EAR group had a significantly more compliant or softer endpoint in internal rotation, greater maximum internal rotation, and more internal rotation at torque 0 in their healthy legs compared with the healthy legs in the BTB group (p < 0.05). These same differences were not noted in the reconstructed knees. The only identifiable significant difference between the injured/reconstructed legs was rotation at 0 torque (p < 0.05).ConclusionsIn this group of patients who were at an average of 9 years from surgery, the addition of a...

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