Vascular persistence following precision micropuncture.

OBJECTIVE: The success of engineered tissues continues to be limited by time to vascularization and perfusion. Recently, we described a simple microsurgical approach, termed micropuncture (MP), which could be used to rapidly vascularize an adjacently placed scaffold from the recipient macrovasculature. Here we studied the long-term persistence of the MP-induced microvasculature. METHODS: Segmental 60 µm diameter MPs were created in the recipient rat femoral artery and vein followed by coverage with a simple Type 1 collagen scaffold. The recipient vasculature and scaffold were then wrapped en bloc with a silicone sheet to isolate intrinsic vascularization. Scaffolds were harvested at 28 days post-implantation for detailed analysis, including using a novel artificial intelligence (AI) approach. RESULTS: MP scaffolds demonstrated a sustained increase of vascular density compared to internal non-MP control scaffolds (p < 0.05) secondary to increases in both vessel diameters (p < 0.05) and branch counts (p < 0.05). MP scaffolds also demonstrated statistically significant increases in red blood cell (RBC) perfused lumens. CONCLUSIONS: This study further highlights that the intrinsic MP-induced vasculature continues to persist long-term. Its combination of rapid and stable angiogenesis represents a novel surgical platform for engineered scaffold and graft perfusion.

Reawakening Neuritis of the Median Nerve after Carpal Tunnel Release: Defining and Predicting Patients at Risk.

BACKGROUND: Patients with long-standing carpal tunnel symptoms may develop transient and, paradoxically, worsened neuropathic pain immediately following release. The authors have termed this "reawakening phenomenon." The purpose of this study was to compare the characteristics of patients with this phenomenon to those with a standard postoperative course. METHODS: A retrospective chart review was performed on all patients who underwent carpal tunnel release at a single institution between January of 2012 to December of 2017. Patients demonstrating increased neuropathic pain in the median nerve distribution postoperatively without evidence of complex regional pain syndrome were included. A comparison cohort was composed of the remaining patients identified. Demographic data, medical history, carpal tunnel history, and electromyogram and nerve conduction study findings were recorded. RESULTS: A total of 640 patients were identified; 440 met criteria. Seventeen patients were found to have symptoms consistent with median nerve reawakening phenomenon. The reawakening cohort was older (71.1 versus 56.8 years), more likely to have evidence of thenar muscle atrophy (58.8 percent versus 13.48 percent), and more likely to have fibrillations and sharp waves on electrodiagnostic studies. Although not statistically significant, they also had a longer duration of symptoms (4.9 versus 2.9 years). Of those patients with reawakening phenomenon, 14 had resolution of their symptoms at an average period of 4.4 months. Three remaining patients who were subjectively symptomatic had normal or improved postoperative electromyogram and nerve conduction studies. CONCLUSIONS: Reawakening of the median nerve has not been previously described but occurs in 3.9 percent of hands following routine carpal tunnel release. Preoperative counseling of patients at high risk for reawakening phenomenon is recommended. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, III.

Induction of scaffold angiogenesis by recipient vasculature precision micropuncture.

The success of engineered tissues continues to be limited by time to vascularization and perfusion. Here, we studied the effects of precision injury to a recipient macrovasculature in promoting neovessel formation in an adjacently placed scaffold. Segmental 60 µm diameter micropunctures (MP) were created in the recipient rat femoral artery and vein followed by coverage with a simple collagen scaffold. Scaffolds were harvested at 24, 48, 72, and 96 h post-implantation for detailed analysis. Those placed on top of an MP segment showed an earlier and more robust cellular infiltration, including both endothelial cells (CD31) and macrophages (F4/80), compared to internal non-micropunctured control limbs (p < 0.05). At the 96-hour timepoint, MP scaffolds demonstrated an increase in physiologic perfusion (p < 0.003) and a 2.5-fold increase in capillary network formation (p < 0.001). These were attributed to an overall upsurge in small vessel quantity. Furthermore, MP positioned scaffolds demonstrated significant increases in many modulators of angiogenesis, including VEGFR2 and Tie-2 despite a decrease in HIF-1α at all timepoints. This study highlights a novel microsurgical approach that can be used to rapidly vascularize or inosculate contiguously placed scaffolds and grafts. Thereby, offering an easily translatable route towards the creation of thicker and more clinically relevant engineered tissues.