Quantification of Skeletal Muscle Perfusion in Peripheral Artery Disease Using 18F-Sodium Fluoride Positron Emission Tomography Imaging

BACKGROUND

Perfusion deficits contribute to symptom severity, morbidity, and death in peripheral artery disease (PAD); however, no standard method for quantifying absolute measures of skeletal muscle perfusion exists. This study sought to preclinically test and clinically translate a positron emission tomography (PET) imaging approach using an atherosclerosis-targeted radionuclide, fluorine-18-sodium fluoride (18F-NaF), to quantify absolute perfusion in PAD.

METHODS AND RESULTS

Eight Yorkshire pigs underwent unilateral femoral artery ligation and dynamic 18F-NaF PET/computed tomography imaging on the day of and 2 weeks after occlusion. Following 2-week imaging, calf muscles were harvested to quantify microvascular density. PET methodology was validated with microspheres in 4 additional pig studies and translated to patients with PAD (n=39) to quantify differences in calf perfusion across clinical symptoms/stages and perfusion responses in a case of revascularization. Associations between PET perfusion, ankle-brachial index, toe-brachial index, and toe pressure were assessed in relation to symptoms. 18F-NaF PET/computed tomography quantified significant deficits in calf perfusion in pigs following arterial occlusion and perfusion recovery 2 weeks after occlusion that coincided with increased muscle microvascular density. Additional studies confirmed that PET-derived perfusion measures agreed with microsphere-derived perfusion measures. Translation of imaging methods demonstrated significant decreases in calf perfusion with increasing severity of PAD and quantified perfusion responses to revascularization. Perfusion measures were also significantly associated with symptom severity, whereas traditional hemodynamic measures were not.

CONCLUSIONS

18F-NaF PET imaging quantifies perfusion deficits that correspond to clinical stages of PAD and represents a novel perfusion imaging strategy that could be partnered with atherosclerosis-targeted 18F-NaF PET imaging using a single radioisotope injection.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT03622359.

Vessel-by-Vessel Computed Tomography Calcium Scoring of the Foot in Peripheral Artery Disease: Association with Patient-Level Factors

Objective: Peripheral artery disease (PAD) is associated with increased risk of nonhealing ulcers, amputation, and mortality due to occlusive atherosclerotic plaques. Computed tomography (CT) imaging detects vascular calcification in PAD; however, quantitative vessel-by-vessel analysis of calcium burden in the feet of PAD patients has not been assessed. This study sought to perform quantitative analysis of vessel-specific calcium burden and examine the patient-level determinants of foot calcium burden in PAD patients. Approach: PAD patients (n = 41) were prospectively enrolled and underwent CT imaging of the lower extremities. Manual segmentation of the medial plantar, lateral plantar, and dorsalis pedis arteries was performed. CT image Hounsfield units (HUs) were obtained for each artery to quantify vessel-by-vessel calcium mass using a cutoff value of ≥130 HU. Univariate analyses were performed to evaluate patient-level determinants of calcium burden for each foot artery. STROBE guidelines were used for reporting of data. Results: Univariate analyses revealed that body mass index, diabetes mellitus (DM), and chronic kidney disease (CKD) were significant determinants of foot calcium burden in PAD patients. Image analysis demonstrated that PAD patients with DM had significantly higher calcium mass for the medial plantar (p = 0.005), lateral plantar (p = 0.039), and dorsalis pedis (p = 0.001) arteries compared with PAD patients without DM. Innovation: This is the first study to use CT imaging to quantify vessel-specific calcium burden in the feet of patients with PAD and evaluate the patient-level determinants of foot calcium burden in the setting of PAD. Conclusion: CT imaging quantifies vessel-specific calcification in the feet of PAD patients, which is exacerbated with concomitant DM, CKD, and/or obesity.

Vessel-by-vessel analysis of lower extremity 18F-NaF PET/CT imaging quantifies diabetes- and chronic kidney disease-induced active microcalcification in patients with peripheral arterial disease

BACKGROUND

Positron emission tomography (PET)/computed tomography (CT) imaging with fluorine-18 (¹⁸F)-sodium fluoride (NaF) provides assessment of active vascular microcalcification, but its utility for evaluating diabetes mellitus (DM)- and chronic kidney disease (CKD)-induced atherosclerosis in peripheral arterial disease (PAD) has not been comprehensively evaluated. This study sought to use ¹⁸F-NaF PET/CT to quantify and compare active microcalcification on an artery-by-artery basis in healthy subjects, PAD patients with or without DM, and PAD patients with or without CKD. Additionally, we evaluated the contributions of DM, CKD, statin use and established CT-detectable calcium to ¹⁸F-NaF uptake for each lower extremity artery.

METHODS

PAD patients (n = 48) and healthy controls (n = 8) underwent lower extremity ¹⁸F-NaF PET/CT imaging. Fused PET/CT images guided segmentation of arteries of interest (i.e., femoral-popliteal, anterior tibial, tibioperoneal trunk, posterior tibial, and peroneal) and quantification of ¹⁸F-NaF uptake. ¹⁸F-NaF uptake was assessed for each artery and compared between subject groups. Additionally, established calcium burden was quantified for each artery using CT calcium mass score. Univariate and multivariate analyses were performed to evaluate DM, CKD, statin use, and CT calcium mass as predictors of ¹⁸F-NaF uptake in PAD.

RESULTS

PAD patients with DM or CKD demonstrated significantly higher active microcalcification (i.e., ¹⁸F-NaF uptake) for all arteries when compared to PAD patients without DM or CKD. Univariate and multivariate analyses revealed that concomitant DM or CKD was associated with increased microcalcification for all arteries of interest and this increased disease risk remained significant after adjusting for patient age, sex, and body mass index. Statin use was only associated with decreased microcalcification for the femoral-popliteal artery in multivariate analyses. Established CT-detectable calcium was not significantly associated with ¹⁸F-NaF uptake for 4 out of 5 arteries of interest.

CONCLUSIONS

¹⁸F-NaF PET/CT imaging quantifies vessel-specific active microcalcification in PAD that is increased in multiple lower extremity arteries by DM and CKD and decreased in the femoral-popliteal artery by statin use. ¹⁸F-NaF PET imaging is complementary to and largely independent of established CT-detectable arterial calcification. ¹⁸F-NaF PET/CT imaging may provide an approach for non-invasively quantifying vessel-specific responses to emerging anti-atherogenic therapies or CKD treatment in patients with PAD.

Novel Application of 18F-NaF PET/CT Imaging for Evaluation of Active Bone Remodeling in Diabetic Patients With Charcot Neuropathy: A Proof-of-Concept Report

Charcot neuropathic osteoarthropathy (CN) is a serious and potentially limb-threatening complication for patients with diabetes mellitus and peripheral arterial disease. In recent decades, nuclear medicine-based approaches have been used for non-invasive detection of CN; however, to date, a positron emission tomography (PET) radionuclide specifically focused on targeted imaging of active bone remodeling has not been explored or validated for patients with CN. The radionuclide 18F-sodium fluoride (NaF) has historically been used as a bone imaging probe due to its high sensitivity for targeting hydroxyapatite and bone turnover, but has not been applied in the context of CN. Therefore, the present study focused on novel application of 18F-NaF PET/computed tomography (CT) imaging to three clinical cases of CN to evaluate active bone remodeling at various time courses of CN. PET/CT imaging in all 3 cases demonstrated focal uptake of 18F-NaF in the bones of the feet afflicted with CN, with bone retention of 18F-NaF persisting for up to 5 years following surgical reconstruction of the foot in two cases. On a group level, 18F-NaF bone uptake in the CN foot was significantly higher compared to the healthy, non-CN foot (p = 0.039). 18F-NaF PET/CT imaging may provide a non-invasive tool for monitoring active bone remodeling in the setting of CN, thereby offering novel opportunities for tracking disease progression and improving treatment and surgical intervention.

Intermetatarsal Angle and Hallux Abductus Angle Reduction After First Metatarsophalangeal Joint Arthrodesis in Mild, Moderate, and Severe Hallux Valgus

BACKGROUND

First metatarsophalangeal joint fusion is a commonly used procedure for treating many pathologic disorders of the first ray. Historically, hallux valgus deformity with severely increased intermetatarsal angle or metatarsus primus adductus indicated need for a proximal metatarsal procedure. However, the effectiveness and reliability of first metatarsophalangeal joint arthrodesis in reducing the intermetatarsal angle has been increasingly described in the literature. We compared findings at our institution with current literature for further validation of this well-accepted procedure in correcting hallux valgus deformity with high intermetatarsal angle.

METHODS

Weightbearing preoperative and postoperative radiographs of 43 patients, 31 women and 12 men, meeting the inclusion and exclusion criteria were identified. Two independent investigators measured the hallux abductus and intermetatarsal angles. Preoperative and postoperative measurements for each angle were compared and average reduction calculated. The data were further analyzed by grouping deformities as mild, moderate, and severe. Mean follow-up was 10 months.

RESULTS

The overall mean preoperative intermetatarsal and hallux abductus angles decreased significantly (from 13.09° to 9.33° and from 23.72° to 12.19°, respectively; both P < .01). When grouping deformities as mild, moderate, and severe, all of the categories maintained reduction of intermetatarsal and hallux abductus angles (P < .01). Furthermore, the mean reduction of the intermetatarsal and hallux abductus angles seemed to correlate with preoperative deformity severity.

CONCLUSIONS

In patients undergoing correction of hallux valgus deformity, first metatarsophalangeal joint arthrodesis produced consistent reductions in the intermetatarsal and hallux abductus angles. Furthermore, these findings are consistent with those reported by other institutions.

SPECT/CT Imaging: A Noninvasive Approach for Evaluating Serial Changes in Angiosome Foot Perfusion in Critical Limb Ischemia

Objective: To investigate the feasibility of serial radiotracer-based imaging as a noninvasive approach for quantifying volumetric changes in microvascular perfusion within angiosomes of the foot following lower extremity revascularization in the setting of critical limb ischemia (CLI).

Approach: A CLI patient with a nonhealing foot ulcer underwent single-photon emission computed tomography (SPECT)/computed tomography (CT) imaging of the feet before and after balloon angioplasty of the superficial femoral artery (SFA) and popliteal artery. SPECT/CT imaging was used to evaluate serial changes in angiosome perfusion, which was compared to quantitative changes in peripheral vascular anatomy and hemodynamics, as assessed by standard clinical tools that included digital subtraction angiography (DSA), ankle-brachial index (ABI), and toe-brachial index (TBI).

Results: Following revascularization, upstream quantitative improvements in stenosis of the SFA (pre: 35.4% to post: 11.9%) and popliteal artery (pre: 59.1% to post: 21.7%) shown by DSA were associated with downstream angiosome-dependent improvements in SPECT microvascular foot perfusion that ranged from 2% to 16%. ABI measurement was not possible due to extensive arterial calcification, while TBI values decreased from 0.26 to 0.16 following revascularization.

Innovation: This is the first study to demonstrate the feasibility of assessing noninvasive volumetric changes in angiosome foot perfusion in response to lower extremity revascularization in a patient with CLI by utilizing radiotracer-based imaging.

Conclusion: SPECT/CT imaging allows for quantification of serial perfusion changes within angiosomes containing nonhealing ulcers and provides physiological assessment that is complementary to conventional anatomical (DSA) and hemodynamic (ABI/TBI) measures in the evaluation of lower extremity revascularization.

Development of Charcot Neuroarthropathy in Diabetic Patients who Received Kidney or Kidney-Pancreas Transplants

Only a small percentage of the general diabetic population develops Charcot neuroarthropathy. Charcot arthropathy greatly increases the risk of foot complications. At our academic institution, there appeared to be an increased incidence of Charcot arthropathy in transplant patients. We hypothesized that Charcot neuroarthropathy incidence is higher in the diabetic patients who had received kidney or kidney-pancreas transplants. The charts of 1000 patients were reviewed from January 2000 to January 2011. Four hundred and eighty-seven patients were included in the study. Of these diabetic patients, 249 had received a kidney transplant and 238 a kidney-pancreas transplant. The data were analyzed for the incidence of Charcot in each group. Other risk factors and sequelae were also evaluated and analyzed. The incidence of Charcot development in the diabetic patients who had a kidney-pancreas transplant was 18.4%, 44 of 238 patients. This was significantly higher than the incidence in kidney transplant patients, which was 11.2%, 28 of 249 patients (p < .05). Peripheral arterial disease was a statistically significant independent risk factor for developing ulceration, osteomyelitis, and subsequent amputation. Type 1 diabetic patients developed Charcot at a higher rate that was also statistically significant compared with type 2 diabetic patients. In our study, diabetic patients who had undergone kidney-pancreas transplants were associated with higher risk for development of Charcot neuroarthropathy than kidney transplants alone. The incidence of Charcot development in both these transplant groups was also much higher than in the general diabetic population. This is of particular interest to clinicians and surgeons as both transplant groups were found to be high risk for subsequent foot ulceration, infection, and amputation.

Gabapentin as an Adjunct to Standard Postoperative Pain Management Protocol in Lower Extremity Surgery

Postoperative pain is a problem that plagues physicians and has since the dawn of the surgical arts. Many interventions are available and used as the standard such as preoperative local anesthetic blocks, opiates, both oral and intravenous, and nonsteroidal antiinflammatory drugs. Although the temptation often exists to increase the postoperative opiate dose, opiate abuse is an increasing problem. This abuse has fueled the search for nonopiate pain adjuncts. Gabapentinoids have been shown to both decrease postoperative pain and, secondarily, decrease opiate dependence. This is a growing field in medical research, although it is relatively lacking in the specialty of lower extremity orthopedic surgery. A PubMed query was performed for related articles, which found only 8 related to lower extremity orthopedic surgery, and of these, none addressed the foot or ankle. Studies involving chronic pain, nonorthopedic surgery, orthopedic procedures proximal to and including the hip, studies involving only pregabalin, and studies regarding cancer pain were excluded. The results from our literature review are encouraging regarding the addition of gabapentin as a regular, perioperative adjunctive pain medication because all studied reported data evaluating preoperative administration have shown a statistically significant reduction in postoperative pain and opiate consumption.

Diabetic foot burns: a case series

Burn injury in diabetic patients has been a recent topic of interest in published studies. Previous studies have shown increased complications in diabetic patients compared with nondiabetic controls who have sustained these injuries. A paucity of research has been devoted to foot-specific diabetic burn injury. We present a case series evaluating the mechanisms and complications of diabetic foot burns.

Reamputation after minor foot amputation in diabetic patients: risk factors leading to limb loss

The prevalence of lower extremity reamputation in diabetic patients has been well-documented. We sought to determine the risk factors for major lower extremity amputation (LEA) after minor foot amputation in diabetic patients. We studied 163 diabetic patients who had undergone an initial minor foot amputation and then had undergone at least 1 subsequent major or minor LEA. The patients were separated into a minor LEA group (initial minor LEA followed by at least 1 subsequent minor LEA) and a major LEA group (initial minor LEA followed by at least 1 subsequent major LEA). We then studied the possible risk factors for both groups. The possible risk factors analyzed were age, glycemic control, kidney function, previous kidney or kidney-pancreas transplantation, smoking history, and presence and severity of peripheral arterial disease (PAD). No statistical significance was found between the 2 groups for hemoglobin A1c, smoking status, chronic kidney disease, end-stage renal disease requiring dialysis, kidney or kidney-pancreas transplantation, or vascular intervention (peripheral arterial bypass). In the minor group, 22.23% had severe PAD. In the major group, 71.15% had severe PAD. This was statistically significant (p < .001). The average interval to major amputation in those without PAD, mild to moderate PAD, and severe PAD was 1,180.9, 591.0, and 559.6 days, respectively. This demonstrates the importance of assessing the peripheral vascular status in all diabetic patients with minor LEA. Early referral to a vascular surgeon might delay (or prevent) major LEA.