Stable Lateral Meniscal Posterior Root Tears Left In Situ at Time of Anterior Cruciate Ligament Reconstruction Are of Minimal Long-Term Clinical Detriment.

PURPOSE: The purpose of this study was to compare long-term patient-reported outcomes in patients undergoing anterior cruciate ligament (ACL) reconstruction with untreated stable lateral meniscal posterior root (LMPR) tears to those with an intact meniscus. METHODS: Four hundred ninety-two subjects were followed for a minimum of 15-years post-ACL reconstruction and evaluated by an International Knee Documentation Committee questionnaire. The integrity of the meniscus was classified at surgery. Patients were grouped as either untreated injury to LMPR "with stable tear" (WST) group (n = 52) or intact lateral meniscus "no tear" (NT) group (n = 440). WST group included tears where those with a root avulsion within 9 mm of insertion and parrot beak tears with the integrity of the root attachment maintained. Outcomes were compared between groups. RESULTS: ACL graft rupture occurred in 10% in the WST group and in 11% in the NT group (P = .78). For participants with an intact graft (n = 440), the mean International Knee Documentation Committee scores were 82, in the WST group, and 87, in the NT group (P = .03), with a small effect size of .32. The WST group had a worse mean pain severity score (P = .04) and higher frequency of pain (P = .03) than the NT group, but the effect size was small (P < 0.3). There was no difference in the overall knee function (P = .209) or International Knee Documentation Committee activity level (P = .882). CONCLUSION: There was no adverse clinical outcome to leaving a stable LMPR tear in situ at the time of ACL reconstruction. LMPR tears left in situ were of minimal clinically significant long-term detriment, with outcomes similar to having an intact meniscus. There is an innate desire to fix the broken, but posterior meniscal root avulsions and stable parrot beak tears within 9 mm of insertion may not require intervention. At 15 years postinjury, most patients with a stable tear left in situ continue to enjoy an active lifestyle with a pain-free knee. LEVEL OF EVIDENCE: Level III, retrospective comparative study.

Fine structure of the Arabidopsis stem cuticle: effects of fixation and changes over development.

MAIN CONCLUSION: The Arabidopsis cuticle, as observed by electron microscopy, consists primarily of the cutin/cutan matrix. The cuticle possesses a complex substructure, which is correlated with the presence of intracuticular waxes. The plant cuticle is composed of an insoluble polyester, cutin, and organic solvent soluble cuticular waxes, which are embedded within and coat the surface of the cutin matrix. How these components are arranged in the cuticle is not well understood. The Arabidopsis cuticle is commonly understood as 'amorphous,' lacking in ultrastructural features, and is often observed as a thin (~80-100 nm) electron-dense layer on the surface of the cell wall. To examine this cuticle in more detail, we examined cuticles from both rapidly elongating and mature sections of the stem and compared the preservation of the cuticles using conventional chemical fixation methods and high-pressure freezing/freeze-substitution (HPF/FS). We found that HPF/FS preparation revealed a complex cuticle substructure, which was more evident in older stems. We also found that the cuticle increases in thickness with development, indicating an accretion of polymeric material, likely in the form of the non-hydrolyzable polymer, cutan. When wax was extracted by chloroform immersion prior to sample preparation, the contribution of waxes to cuticle morphology was revealed. Overall, the electron-dense cuticle layer was still visible but there was loss of the cuticle substructure. Furthermore, the cuticle of cer6, a wax-deficient mutant, also lacked this substructure, suggesting that these fine striations were dependent on the presence of cuticular waxes. Our findings show that HPF/FS preparation can better preserve plant cuticles, but also provide new insights into the fine structure of the Arabidopsis cuticle.