Chronic Popliteus Tendon Avulsion Fracture with Chronic Knee Pain and Locking: A Case Report.

CASE: A 31-year-old man who had a chronic popliteus avulsion fracture 18 years earlier treated with physical therapy presented with new onset left knee locking after exercising at the gym. Magnetic resonance imaging demonstrated a chronic popliteus avulsion fracture of the lateral femoral condyle. Surgical excision of the nonunited bone fragment was performed. CONCLUSION: Isolated popliteus avulsion fractures are extremely rare injuries that occur primarily in a skeletally immature patient population and for which treatment options are not well understood. Treatment options include conservative management and early surgical intervention, both of which have inherent risks and benefits. We recommend prompt imaging with computed tomography (CT) to better characterize the degree of injury and follow-up CT imaging in patients who do not undergo early surgical intervention.

MOON's Strategy for Obtaining Over Eighty Percent Follow-up at 10 Years Following ACL Reconstruction.

ABSTRACT: The Multicenter Orthopaedic Outcomes Network (MOON) study of anterior cruciate ligament (ACL) reconstruction has achieved >80% follow-up for study subjects who were enrolled from 2002 to 2005; patient-reported outcome measures (PROMs) were reported at 2, 6, and 10 years through a carefully designed protocol that included surgeon involvement to encourage subjects to complete and return questionnaires. The process included emails and telephone calls from the central coordinating center, from research coordinators at each local institution, and lastly, from the subjects' surgeons for those who were less inclined to complete the follow-up. In order to quantify the effect of site and surgeon involvement, the enrollment year of 2005 was monitored for the 10-year follow-up (n = 516 subjects). In contact efforts made by the coordinating center, 73.8% (381) of study subjects were reached by the central site coordinator, contact information was verified, and questionnaires were subsequently sent, completed, and returned. An additional 54 subjects (10.5% of the overall study population) returned the questionnaire after local study site involvement, indicating the importance of individual surgeon and local site involvement to improve follow-up rates in multicenter studies in orthopaedic surgery. Follow-up rates were higher when a specific individual (the surgeon or the research coordinator) was given the task of final follow-up.

Complications Associated with Posterior Cruciate Ligament Reconstruction and Avoiding Them.

Posterior cruciate ligament (PCL) injuries often occur as part of a multiligament injury pattern and can present a significant challenge to the treating surgeon. When PCL reconstruction is indicated, complications can arise in the intraoperative and postoperative period that lead to poor outcomes. These complications include neurovascular injury, fracture, compartment syndrome, persistent posterior laxity, motion loss, residual knee pain, osteonecrosis, and heterotopic ossification. The purpose of this review is to highlight complications associated with PCL reconstruction and strategies to avoid them.

The DNA Sensor cGAS is Decorated by Acetylation and Phosphorylation Modifications in the Context of Immune Signaling.

The cyclic GMP-AMP synthase (cGAS) protein is a pattern-recognition receptor of the mammalian innate immune system that is recognized as a main cytosolic sensor of pathogenic or damaged DNA. cGAS DNA binding initiates catalytic production of the second messenger, cyclic GMP-AMP, which activates the STING-TBK1-IRF3 signaling axis to induce cytokine expression. Post-translational modification (PTM) has started to be recognized as a critical component of cGAS regulation, yet the extent of these modifications remains unclear. Here, we report the identification and functional analysis of cGAS phosphorylations and acetylations in several cell types under basal and immune-stimulated conditions. cGAS was enriched by immunoaffinity purification from human primary fibroblasts prior to and after infection with herpes simplex virus type 1 (HSV-1), as well as from immune-stimulated STING-HEK293T cells. Six phosphorylations and eight acetylations were detected, of which eight PTMs were not previously documented. PTMs were validated by parallel reaction monitoring (PRM) mass spectrometry in fibroblasts, HEK293T cells, and THP-1 macrophage-like cells. Primary sequence and structural analysis of cGAS highlighted a subset of PTM sites with elevated surface accessibility and high evolutionary sequence conservation. To assess the functional relevance of each PTM, we generated a series of single-point cGAS mutations. Stable cell lines were constructed to express cGAS with amino acid substitutions that prevented phosphorylation (Ser-to-Ala) and acetylation (Lys-to-Arg) or that mimicked the modification state (Ser-to-Asp and Lys-to-Gln). cGAS-dependent apoptotic and immune signaling activities were then assessed for each mutation. Our results show that acetyl-mimic mutations at Lys384 and Lys414 inhibit the ability of cGAS to induce apoptosis. In contrast, the Lys198 acetyl-mimic mutation increased cGAS-dependent interferon signaling when compared with the unmodified charge-mimic. Moreover, targeted PRM quantification showed that Lys198 acetylation is decreased upon infections with two herpesviruses-HSV-1 and human cytomegalovirus (HCMV), highlighting this residue as a regulatory point during virus infection.