To determine if decreased vascular responsiveness in the medial collateral ligament (MCL) of anterior cruciate ligament transected (ACL-t) rabbit knees is due to pericyte deficiency associated with angiogenesis. Vascular responses to potassium chloride (KCl), phenylephrine, acetylcholine, and sodium nitroprusside (SNP) were evaluated in ACL-t rabbit knees (n ¼ 6) and control knees (n ¼ 5) using laser speckle perfusion imaging. Ligament degeneration was determined by ultrasound imaging. Vascular and pericyte volume were measured using quantitative immunohistochemical volumetric analysis using CD31 and a-smooth muscle actin antibodies with co-localization analysis. Perfusion was increased in the ACL-t rabbits 2.5-fold. Responsiveness to phenylephrine, SNP, and acetylcholine was significantly decreased in the ACL knee while no change in KCl responses was seen. MCL ultrasound imaging revealed decreased collagen organization, increased ligament thickness, and increased water content in the ACL-t MCL. Vascular Volume was increased fourfold in ACL deficient knees, while pericyte volume to endothelial volume was not changed. No difference in CD31 and a-SMA co-localization was found. Blood vessels in the MCL of ACL-t knees do not lack smooth muscle. [2]. Our focus has centered on the pathologic changes that occur in the MCL following rupture of the anterior cruciate ligament. Our hope is that understanding early secondary OA pathology future interventions may be developed to preserve joint function and improve outcomes.The rabbit ACL transected (ACL-t) model has been extensively tested and is well known model of secondary OA having a reliable and reproducible natural history [3]. Joint instability induces osteoarthritic degeneration of rabbit knees, whereas immediate ACL reconstruction prevents joint degeneration [7]. The MCL tensile strength decreases after ACL-t, exacerbating joint instability [7]. A strong angiogenic response occurs in the MCL following ACL-t [8].The MCL vasculature does not respond appropriately to vasoactive mediators such as phenylephrine (PHE) and acetylcholine (ACH) after ACL-t [9,10].These processes are known as endothelial dysfunctionloss of vasodilatory responses mediated through the endothelium; and vascular dysfunction-loss of vasocontractile responses mediated through smooth muscle. Typically endothelial and vascular dysfunction are associated with inflammation [11]. Alternatively, angiogenesis may lead to decreased vascular smooth muscle and therefore decreased dilatory and contractile responses as has been found in synovium of rheumatoid arthritis patients [12].Quantification of the a-smooth muscle actin (a-SMA) content can be utilized to determine the anatomic state of blood vessels and if these vessels are capable of vasoregulation. 1 A volume based ratiometric analysis of the endothelial volume (CD31 label) to a-SMA content has been previously utilized to determine the composition of angiogenic vessels, 2,3 and using similar methods will define the vascular anatomy of the MC...

Background: Single photon emission computed tomography combined with computed tomography (SPECT/CT) could potentially aid in diagnosing periarticular arthritis/activity and progression, facilitate effective treatment options, and evaluate the effect surgery has on the clinical outcome of patients with ankle arthritis. The goal of our study was to assess SPECT/CT activity in the ankle and periarticular joints before and after ankle fusion surgery and determine whether it was associated with clinical pain and function scores. Methods: Thirty-four patients recruited into this study underwent either arthroscopic or open ankle fusion. X-ray (XR) and SPECT/CT imaging was obtained as well as completion of patient Ankle Osteoarthritis Scale (AOS) and 36-item Short Form Survey (SF-36) questionnaires preoperatively and at 6 months postoperatively. Ankle, subtalar, and talonavicular joint arthritis grading on XR and CT, along with SPECT/CT activity, was evaluated by 2 nuclear medicine radiologists. Data were assessed for normality and analyzed with the appropriate comparative test. P value was set at <.05. Thirty patients (31 ankles) completed follow-up and were analyzed. Results: SPECT/CT activity showed no significant difference in the ankle joint at 6 months postoperatively while periarticular joint activity significantly increased ( P < .05). Six months postoperatively, patients had significant improvements in their AOS and SF-36 scores ( P < .05). SPECT/CT grading of all joints analyzed, however, was not associated with AOS or SF-36 scores preoperatively or at 6 months postoperatively. Conclusion: In this study, intensity of activity as evaluated by SPECT/CT in periarticular hindfoot joints in patients who had ankle arthrodesis was not associated with clinical/functional scores at 6 months postoperatively. Level of Evidence: Level IV, diagnostic study.

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