Carbon Footprint of Minor Foot and Ankle Surgery: A Randomized Controlled Trial.

Background: Climate change poses a substantial threat to human health, and operating rooms (ORs) have an outsized environmental impact. The Program for Research in Sustainable Medicine (PRiSM) designed a protocol for minor foot and ankle surgery intended to reduce waste, streamline instrument trays, and minimize laundry. We conducted a randomized controlled trial to compare the carbon footprint of procedures performed using the PRiSM protocol vs a traditional protocol. Methods: Forty adult patients undergoing foreign body removal, hammertoe correction, toe amputation, hardware removal, mass excision, or gastrocnemius recession were randomized to the PRiSM or our "Traditional" protocol. The PRiSM protocol used a smaller instrument tray, fewer drapes and towels, and minimal positioning blankets. No changes were made to surgical site preparation or operative techniques. Environmental impact was estimated using the carbon footprint, measured in kilograms of carbon dioxide equivalents (CO2e). Emissions associated with OR waste, instrument processing, and laundry were calculated. Results: On average, PRiSM cases had a smaller carbon footprint than Traditional cases (17.3 kg CO2e [SD = 3.2] vs 20.6 kg CO2e [SD = 2.0], P < .001). Waste-associated emissions from PRiSM cases were reduced (16.0 kg CO2e [SD = 2.7] vs 18.4 kg CO2e [SD = 1.8], P = .002), as were modeled instrument processing-related emissions (0.34 vs 0.91 kg CO2e). One superficial surgical site infection occurred in each group. Conclusion: We found a small but statistically significant reduction in the environmental impact of minor foot and ankle surgery when using the PRiSM vs Traditional protocol. The environmental impact of these cases was dominated by plastic waste-related emissions. Orthopaedic surgeons should think critically about what components of their surgical setup are truly necessary for patient care, as minor changes in product utilization can have significant impacts on waste and greenhouse gas emissions. Level of Evidence: Level I, randomized controlled trial.

Differences in Baseline Physical Function and Mental Health PROM Scores in Patients With Foot and Ankle Conditions.

BACKGROUND: This study sought to establish normative values for baseline physical and mental health by foot and ankle diagnosis using validated PROMIS scores and to compare the correlation between these 2 outcomes across common diagnoses. Additionally, it investigated the effects associated with chronic vs acute conditions and specific diagnoses on mental health. METHODS: We reviewed baseline PROMIS Physical Function 10a (PF10a) and PROMIS Global-Mental (PGM) scores of 14,245 patients with one of the 10 most common foot and ankle diagnoses seen at our institution between 2016 and 2021. Pearson correlation coefficients were calculated to assess the relationship between PF10a and PGM by diagnosis. A multivariable regression model including age, sex, language, race, ethnicity, education level, income, and Charlson Comorbidity Index was used to determine the associated effect of diagnosis on PGM score. RESULTS: On unadjusted analysis, patients diagnosed with an ankle fracture had the lowest mean physical function, whereas patients with hallux valgus had the highest (PF10a = 33.9 vs 46.7, P < .001). Patients with foot/ankle osteoarthritis had the lowest mean self-reported mental health, whereas patients with hallux rigidus had the highest (PGM = 49.9 vs 53.4, P < .001). PF10a and PGM scores were significantly positively correlated for all diagnoses; the correlation was strongest in patients diagnosed with foot/ankle osteoarthritis or hammertoes (r = 0.511) and weakest in patients with ankle fractures (r = 0.232) or sprains (r = 0.280). Chronic conditions, including hammertoes (ß = -5.1, 95% CI [-5.8, -4.3], P < .001), foot/ankle osteoarthritis (ß = -5.0, 95% CI [-5.7, -4.3], P < .001), and hallux valgus (ß = -4.8, 95% CI [-5.5, -4.1], P < .001) were associated with the largest negative effects on patients' mental health. CONCLUSION: Self-reported physical function and mental health varied across common foot and ankle diagnoses and were more tightly correlated in chronic conditions. The associations between diagnosis and mental health scores appear larger for more chronic diagnoses, including those that are generally associated with relatively unimpaired physical function. LEVEL OF EVIDENCE: Level IV, retrospective, cross-sectional study.

Primary Care Physician Preferences Regarding Communication from Orthopaedic Surgeons.

BACKGROUND: Musculoskeletal consultations constitute a growing portion of primary care physician (PCP) referrals. Optimizing communication between PCPs and orthopaedists can potentially reduce time spent in the electronic medical record (EMR) as well as physician burnout. Little is known about the preferences of PCPs regarding communication from orthopaedic surgeons. Hence, the present study investigated, across a large health network, the preferences of PCPs regarding communication from orthopaedists. METHODS: A total of 175 PCPs across 15 practices within our health network were surveyed. These providers universally utilized Epic as their EMR platform. Five-point, labeled Likert scales were utilized to assess the PCP-perceived importance of communication from orthopaedists in specific clinical scenarios. PCPs were further asked to report their preferred method of communication in each scenario and their overall interest in communication from orthopaedists. Logistic regression analyses were performed to determine whether any PCP characteristics were associated with the preferred method of communication and the overall PCP interest in communication from orthopaedists. RESULTS: A total of 107 PCPs (61.1%) responded to the survey. PCPs most commonly rated communication from orthopaedists as highly important in the scenario of an orthopaedist needing information from the PCP. In this scenario, PCPs preferred to receive an Epic Staff Message. Scenarios involving a recommendation for surgery, hospitalization, or a major clinical change were also rated as highly important. In these scenarios, an Epic CC'd Chart rather than a Staff Message was preferred. Increased after-hours EMR use was associated with diminished odds of having a high interest in communication from orthopaedists (odds ratio, 0.65; 95% confidence interval, 0.48 to 0.88; p = 0.005). Ninety-three PCPs (86.9%) reported spending 1 to 1.5 hours or more per day in Epic after normal clinical hours, and 27 (25.2%) spent >3 hours per day. Forty-six PCPs (43.0%) reported experiencing ≥1 symptom of burnout. CONCLUSIONS: There were distinct preferences among PCPs regarding clinical communication from orthopaedic surgeons. There was also evidence of substantial burnout and after-hours work effort by PCPs. These results may help to optimize communication between PCPs and orthopaedists while reducing the amount of time that PCPs spend in the EMR.

The Use of the Lateral Tibial Line to Assess Ankle Alignment: A Preliminary Investigation.

BACKGROUND: Although the medial clear space (MCS) is commonly used to assess talar alignment and ankle stability, its measurement is variable with multiple reported normal values. We have observed that the lateral tibial shaft is a reliable landmark to assess talar alignment. The objective of the current investigation was to determine the normal relationship of the lateral tibia to the superolateral talus using a tangent drawn inferiorly from the lateral tibial shaft, which we refer to as the "lateral tibial line" (LTL). METHODS: The relationship of the LTL to the superolateral talus was assessed by three reviewers on 99 standing ankle mortise radiographs in uninjured patients. This relationship was quantified by measuring the distance (in millimeters) between the LTL and the superolateral talus. In addition, the interobserver reliability of the LTL measurement was recorded and compared with that of the MCS. RESULTS: The median value for the distance between the superolateral talus and LTL was -0.50 mm with an interquartile range of -1.4 to 0.0 mm. The LTL was within 1 mm of the lateral talus in 176 of 297 reviewer measurements (59.3%). Moreover, it was either lateral to or at most 1 mm medial to the lateral talus in 90.9% of cases. The LTL measurement also demonstrated good interobserver reliability (0.764, 95% confidence interval, 0.670 to 0.834), similar to the measurement of MCS (0.742, 95% confidence interval, 0.539 to 0.846). CONCLUSIONS: The relationship between the LTL and superolateral talus is easily measured with good reliability for assessing the anatomic relationship of the tibia and talus. The LTL uncommonly fell more than 1 mm medial to the superolateral talus, as might be seen with displaced ankle fractures. These findings will hopefully serve as a basis for future studies evaluating its role in assessing lateral displacement and stability of isolated fibula fractures. LEVEL OF EVIDENCE: Level III, retrospective review.

Intraarticular Injections in the Foot and Ankle: Medication Selection Patterns and Perceived Risk Of Chondrotoxicity.

Background: Intraarticular corticosteroid injections (ICIs) are widely used to treat foot and ankle conditions. Although laboratory studies indicate certain corticosteroids and local anesthetics used in ICIs are associated with chondrotoxic effects, and selected agents such as ropivacaine and triamcinolone may have less of these features, clinical evidence is lacking. We aimed to identify the patterns of drug selection, perceptions of injectate chondrotoxicity, and rationale for medication choice among surgeons in the American Orthopaedic Foot & Ankle Society (AOFAS). Methods: An e-survey including demographics, practice patterns, and rationale was disseminated to 2011 AOFAS members. Frequencies and percentages were calculated for demographic data, anesthetic and steroid choice, rationale for injectate choice, and perception of chondrotoxicity. Bivariate analysis was used to identify practice patterns significantly associated with perceptions of injectate risk and rationale. Results: In total, 387 surveys were completed. Lidocaine and triamcinolone were the most common anesthetic and corticosteroid used (51.2% and 39.3%, respectively). Less than half of respondents felt corticosteroids or local anesthetics bear risk of chondrotoxicity. Respondents agreeing that corticosteroids are chondrotoxic were more likely to use triamcinolone (P = .037). Respondents agreeing local anesthetics risk chondrotoxicity were less likely to use lidocaine (P = .023). Respondents choosing a local anesthetic based on literature were more likely to use ropivacaine (P < .001). Conclusion: Corticosteroid and local anesthetic use in ICIs varied greatly. Rationale for ICI formulation was also variable, as the clinical implications are largely unknown. Those who recognized potential chondrotoxicity and who chose based on literature were more likely to choose ropivacaine and triamcinolone, as reflected in the basic science literature. Further clinical studies are needed to establish guidelines that shape foot and ankle ICI practices based on scientific evidence and reduce the variation identified by this study. Level of Evidence: Level IV, cross-sectional survey study.

Efficiency and perceived safety of foot and ankle procedures performed on the preoperative stretcher versus operating room table.

BACKGROUND: Foot and ankle surgeons often perform minor surgeries on the preoperative stretcher instead of the operating room table. We examined whether stretcher-based and operating room table-based procedures differed with respect to operating room efficiency and staff perceptions. METHODS: We retrospectively reviewed medical records of patients undergoing minor foot and ankle surgery at an ambulatory surgery centre. We collected 'time to start', the duration between patient arrival in the operating room and incision time, and 'time to exit', the duration between procedure end time and patient exit from the operating room. Staff were surveyed regarding their perceptions of stretcher-based and operating room table-based procedures. RESULTS: 'Time to start' was significantly shorter for stretcher-based procedures, but 'time to exit' was not. Seventeen (81%) staff members thought stretcher-based procedures increased operating room efficiency. Thirteen (62%) thought stretcher-based procedures bettered staff safety. Nineteen (91%) thought stretcher-based procedures were equivalent to or better than operating room table-based procedures for patient safety. Most (67%) would recommend stretcher-based procedures. CONCLUSION: We found small but significant time savings associated with stretcher-based procedures. Without adapting surgical scheduling practices, the impact of stretcher-based procedures on overall operating room efficiency is questionable. Nevertheless, the majority of OR staff think stretcher-based procedures increase OR efficiency and are safer for staff. LEVEL OF EVIDENCE: Level IV, Retrospective case series.

Republication of "Treatment of Hallux Valgus Deformity Using a Suture Button Device: A Preliminary Report".

Background: Hallux valgus (HV) is commonly treated with proximal or distal first metatarsal osteotomy. Despite good correction, these procedures have inherent risks such as malunion, nonunion, metatarsal shortening, loss of fixation, and avascular necrosis. Suture button fixation has been used for HV treatment. It avoids the risks of corrective osteotomies while maintaining reduction of the intermetatarsal angle (IMA). The goal of this study was to assess the radiographic and functional outcomes of patients undergoing HV correction with a distal soft tissue procedure and proximal suture button fixation. Methods: The authors retrospectively reviewed the charts and radiographs of 22 patients who had undergone HV correction using a distal soft tissue correction and proximal fixation with a miniature suture button device (Mini TightRope; Arthrex, Inc, Naples, FL). Mean follow-up was 27.7 months. The IMA, hallux valgus angle (HVA), and sesamoid station were measured on radiographs obtained preoperatively as well as in the immediate postoperative period and at final follow-up. Preoperative and postoperative Short Form-36 (SF-36) and Foot and Ankle Ability Measure (FAAM) scores were collected. Postoperative complications, and any additional operative procedures performed were also recorded. Results: The mean preoperative IMA and HVA were 16.9 and 32.6 degrees, respectively. The mean immediate postoperative IMA was 5.2 degrees (P < .0001) and the mean HVA was 9.8 degrees (P < .0001). At final follow-up, the mean IMA was 8.2 degrees (P < .0001) and the mean HVA was 16.7 degrees (P < .0001). The average change in HVA from preoperative to final follow-up was 16.0 degrees and the average change in IMA from preoperative to final follow-up was 8.6 degrees (P < .0001). Sesamoid station assessment at the 2-week follow-up showed that 22 patients (100%) were in the normal position group; at final follow-up, 17 patients (77%) had normal position and 5 patients (23%) had displaced position. Although there were no clinically symptomatic recurrences, asymptomatic radiographic recurrence was noted in 5 patients (23%) who had a final HVA >20 degrees. All components of the FAAM and the SF-36 showed improvement from preoperative to final follow-up, although these changes were not statistically significant. Three patients experienced complications, including an intraoperative second metatarsal fracture, a postoperative second metatarsal stress fracture, and a postoperative deep vein thrombosis. Conclusion: The use of a distal soft tissue procedure in conjunction with proximal suture button fixation is a safe and effective procedure for treating symptomatic HV deformity. Our results show that this technique can correct the IMA, HVA, and sesamoid station without the need for osteotomy. Level of evidence: Level IV.

The Fate of Delayed Unions After Isolated Ankle Fusion.

BACKGROUND: Nonunion remains the most common major complication of ankle arthrodesis. Although previous studies have reported delayed union or nonunion rates, few have elaborated on the clinical course of patients experiencing delayed union. In this retrospective cohort study, we sought to understand the trajectory of patients with delayed union by determining the rate of clinical success and failure and whether the extent of fusion on computed tomography scan (CT) was associated with outcomes. METHODS: Delayed union was defined as incomplete (<75%) fusion on CT between 2 and 6 months postoperatively. Thirty-six patients met the inclusion criterion: isolated tibiotalar arthrodesis with delayed union. Patient-reported outcomes were obtained including patient satisfaction with their fusion. Success was defined as patients who were not revised and reported satisfaction. Failure was defined as patients who required revision or reported being not satisfied. Fusion was assessed by measuring the percentage of osseous bridging across the joint on CT. The extent of fusion was categorized as absent (0%-24%), minimal (25%-49%), or moderate (50%-74%). RESULTS: We determined the clinical outcome of 28 (78%) patients with mean follow-up of 5.6 years (range, 1.3-10.2). The majority (71%) of patients failed. On average, CT scans were obtained 4 months after attempted ankle fusion. Patients with minimal or moderate fusion were more likely to succeed clinically than those with "absent" fusion (P = .040). Of those with absent fusion, 11 of 12 (92%) failed. In patients with minimal or moderate fusion, 9 of 16 (56%) failed. CONCLUSION: We found that 71% of patients with a delayed union at roughly 4 months after ankle fusion required revision or were not satisfied. Patients with less than 25% fusion on CT had an even lower rate of clinical success. These findings may help surgeons in counseling and managing patients experiencing a delayed union after ankle fusion. LEVEL OF EVIDENCE: Level IV, retrospective cohort study.

The Effects of Sociodemographic Factors on Baseline Patient-Reported Outcome Measures in Patients with Foot and Ankle Conditions.

BACKGROUND: Racial and ethnic care disparities persist within orthopaedics in the United States. This study aimed to deepen our understanding of which sociodemographic factors most impact patient-reported outcome measure (PROM) score variation and may explain racial and ethnic disparities in PROM scores. METHODS: We retrospectively reviewed baseline PROMIS (Patient-Reported Outcomes Measurement Information System) Global-Physical (PGP) and PROMIS Global-Mental (PGM) scores of 23,171 foot and ankle patients who completed the instrument from 2016 to 2021. A series of regression models was used to evaluate scores by race and ethnicity after adjusting in a stepwise fashion for household income, education level, primary language, Charlson Comorbidity Index (CCI), sex, and age. Full models were utilized to compare independent effects of predictors. RESULTS: For the PGP and PGM, adjusting for income, education level, and CCI reduced racial disparity by 61% and 54%, respectively, and adjusting for education level, language, and income reduced ethnic disparity by 67% and 65%, respectively. Full models revealed that an education level of high school or less and a severe CCI had the largest negative effects on scores. CONCLUSIONS: Education level, primary language, income, and CCI explained the majority (but not all) of the racial and ethnic disparities in our cohort. Among the explored factors, education level and CCI were predominant drivers of PROM score variation. LEVEL OF EVIDENCE: Prognostic Level IV . See Instructions for Authors for a complete description of levels of evidence.

Scope of the Problem: Ankle Arthroscopy.

Ankle arthroscopy has seen increased utilization and application in recent years. Through the advent of improved instrumentation and techniques, indications have been expanded to include the management of traumatic, degenerative, inflammatory, and neoplastic conditions. It is important to review anterior and posterior ankle arthroscopies along with the history, pertinent anatomy, techniques, indications, and complications as well as gain insight into the future of ankle arthroscopy.

Scope of the Problem: Tendoscopy and Small Joint Arthroscopy of the Foot and Ankle.

It is important to identify and describe practical applications of arthroscopy in the management of foot and ankle pathology. Utilization of the arthroscope provides a minimally invasive means of evaluating and addressing pathology. It obviates the need for a large open approach, which has additional value in the setting of a multiprocedure surgery. In addition to reducing surgical time, arthroscopy provides a potentially enhanced field of view and an adequate working space to address injury. As interest in minimally invasive options grows, the need for safe, effective tendoscopic and arthroscopic options in the foot and ankle increases. A clear and high-yield reference is needed with which to approach these procedures.

Isolated Gastrocnemius Recession for Progressive Collapsing Foot Deformity.

INTRODUCTION: Progressive collapsing foot deformity (PCFD) is frequently associated with a gastrocnemius contracture. Surgical treatment of PCFD often includes a gastrocnemius recession in addition to other corrective procedures, which typically requires a period of restricted weight bearing postoperatively. Isolated gastrocnemius recession may allow passive correction of the deformity, improve orthotic fit, and obviate the need for full reconstruction and restricted weight bearing. The goal of this study was to evaluate patient-reported outcomes after an isolated gastrocnemius recession for flexible PCFD in patients anticipated to have difficulty with postoperative restricted weight bearing. METHODS: A total of 47 patients met the inclusion criteria: isolated gastrocnemius recession for flexible PCFD, no previous ipsilateral surgery, and more than 6 months of follow-up. Of 47 eligible patients, 29 (31 feet) participated. Available preoperative and postoperative patient-reported outcomes were gathered, including the Foot and Ankle Ability Measure Activities of Daily Living, visual analog scale, and the Patient-Reported Outcome Measurement Information System Physical Function Short Form 10a. In addition, patients were asked about satisfaction, willingness to undergo the procedure again, and whether orthotics provided better relief. RESULTS: At a mean of 5.1 (range, 0.6 to 9.0) years postoperatively, median Foot and Ankle Ability Measure Activities of Daily Living was 82.1, mean Patient-Reported Outcome Measurement Information System Physical Function Short Form 10a was 44.2, and median visual analog scale was 10 (of 100). Sixty-nine percent of patients were either satisfied or very satisfied, 69% would undergo the procedure again, and 62% reported improved relief with use of orthotics postoperatively. Among the 47 eligible patients, there were 5 (11%) subsequent flatfoot reconstructions. CONCLUSIONS: Isolated gastrocnemius recession for the management of flexible PCFD can be effective as this procedure demonstrated good outcomes scores with high procedural satisfaction and 11% of patients proceeding to subsequent flatfoot reconstruction. This alternative approach may be of particular value for patients anticipated to have difficulty with postoperative weight-bearing restrictions. LEVEL OF EVIDENCE: :IV.

A Prospective Randomized Controlled Trial Comparing Physical Therapy With Independent Home Stretching for Plantar Fasciitis.

BACKGROUND: Although formal physical therapy (PT) is effective in treating plantar fasciitis (PF), it is unclear how this compares with home-based plantar fascia stretching (HS). METHODS: Fifty-seven patients with PF were enrolled in a prospective randomized trial comparing PT with HS. Visual analog scale (VAS), Foot and Ankle Ability Measure (FAAM), and Short Form (36) Health Survey (SF-36) scores were analyzed at 6 weeks, 3 months, 6 months, and 1 year. RESULTS: At 6 months, VAS improved in both HS (35% decrease; P < 0.001) and PT (26% decrease; P = 0.002) relative to baseline. FAAM Activities of Daily Living scores improved 13.0% (P = 0.005) in HS and 21.3% (P < 0.001) in PT at 6 months relative to baseline. The SF-36 Physical Component Summary Scores demonstrated improvement at all time points in both groups. There were no notable intergroup differences in VAS, FAAM, or SF-36 at any time point. DICUSSION: The clinical outcomes of a home stretching protocol and PT did not markedly differ for the treatment of PF. LEVEL OF EVIDENCE: Therapeutic Level I.

Reliability of Fifth Metatarsal Base Fracture Classifications and Current Management.

BACKGROUND: Classification of fifth metatarsal base fractures has been a source of confusion since originally described by Jones in 1902. Zone classifications have been described but never evaluated for reliability. The most recent classification, metaphyseal vs meta-diaphyseal, may be unknown to many surgeons. The purpose of this study was to evaluate reliability of American Orthopaedic Foot & Ankle Society (AOFAS) members classifying fifth metatarsal base fractures and current management of these fractures. METHODS: A survey was emailed to AOFAS members including radiographs of 18 fifth metatarsal base fractures. Demographic information was collected in addition to evaluation of the radiographs. Interrater reliability was assessed for each measurement: presence of Jones fracture, zone classification, and metaphyseal vs metaphyseal-diaphyseal, using Fleiss kappa. After 3 weeks, a second email was sent to the members asking to retake the survey to evaluate intrarater reliability. Respondents were asked which region is a Jones fracture, which classification is used, if symptomatic zone 2 and 3 fractures are treated similarly, and what fractures are operative in healthy symptomatic acute fractures. RESULTS: A total of 223 AOFAS members, with a median time in practice of 12 years (range 0-50), completed the initial survey. Eighty members (36%) repeated the survey for intrarater comparison. Interrater reliability was moderate for Jones and zone classification but substantial for the 2-zone metaphyseal/meta-diaphyseal classification. The median intrarater kappa was 0.78, 0.75, and 0.78 for Jones, zone, and metaphyseal/meta-diaphyseal respectively. Seventy percent of respondents treat zones 2 and 3 similarly, and approximately 60% consider an acute symptomatic fracture identified as Jones, zone 2 or zone 3 operative. CONCLUSION: A 2-zone system may be the best available classification for fifth metatarsal base fractures given high interrater reliability and 70% of AOFAS members treat zones 2 and 3 in similar fashion. LEVEL OF EVIDENCE: Level III, diagnostic study.

Peroneal Sheath Volumes Are Greater in Patients With Peroneal Pathology Compared With Controls.

BACKGROUND: Peroneal tendon pathology is common. Several factors have been implicated, including low-lying muscles and accessory tendons. Studies have reported on the presence and length measurements of these structures. This study evaluates volume measurements within the sheath using magnetic resonance images for patients with operatively treated peroneal tendon pathology and control patients without peroneal disease. METHODS: Fifty-one patients with peroneal tendon pathology and 15 controls were included. The volumes of the peroneal sheath, peroneal tendons, peroneal muscle, and accessory peroneus tendons were measured. The distal extent of the peroneus brevis (PB) muscle was measured. Volume and length measurements were then compared. RESULTS: The mean PB muscle length from the tip of the fibula was 5.55 ± 2.5 mm (peroneal group) and 11.79 ± 4.07 mm (control) (P = .017). The mean peroneal sheath volume was 7.06 versus 5.12 mL, respectively (P = .001). The major contributors to this increased volume was the tenosynovitis (3.58 vs 2.56 mL, respectively; P = .019), the peroneal tendons (2.17 vs 1.7 mL, P = .004), and the accessory peroneus tendon + PB muscle (1.31 vs 0.86 mL, P = .023). CONCLUSION: The current study supports that the PB muscle belly is more distal in patients with peroneal tendon pathology. The study also demonstrates increased total volume within the peroneal sheath among the same patients. We propose that increased volume within the sheath, regardless of what structure is enlarged, is associated with peroneal tendon pathology. Further studies are needed to determine if debridement and decompression of the sheath will result in improved functional outcomes for these patients. LEVELS OF EVIDENCE: Level III: Case control imaging study.