Accessing perinatal substance use disorder care in your local community: A case study of an innovative hub and spoke network in western North Carolina

INTRODUCTION

The incidence of substance use disorders (SUD) in the general population and in the pregnant person population has risen over the last 20 years. Concurrently, both perinatal and SUD care in rural areas is laden with access barriers including but not limited to geographical distance from potential treatment and stigma. An integrated outpatient perinatal substance use disorder (PSUD) clinic in an urban area in western North Carolina (WNC) found that patients who traveled further for prenatal care were less likely to continue seeking care in the postpartum period. Acknowledging that the risk of overdose increases in the postpartum period, the PSUD clinic utilized a hub and spoke model to promote healthcare accessibility.

METHODS

The clinic adapted the Vermont hub and spoke model and the CHARM (Children and Recovering Mothers) collaborative. The urban hub in WNC has now developed eight spokes in rural communities. The hub provides education and technical assistance to the rural spokes, and the two engage in bidirectional referral pathways. This manuscript details the model and analyzes the existing strengths and barriers at two spokes, a family medicine Federally Qualified Health Center and a hospital affiliated obstetrics and gynecology practice and analyzes their process of implementation of integrated outpatient perinatal substance use care.

RESULTS

Both spokes found coaching relationships and the sharing of resources such as clinical guidelines useful to begin prescribing buprenorphine for PSUD. Their context led one spoke to begin prescribing within one year while the other took two years.

CONCLUSION

Comparing and contrasting these spokes serves to demonstrate that across many contexts, a hub and spoke model is a replicable intervention for rural perinatal substance use access to care barriers. Comparing the two spokes emphasizes the need for adaptation as well as standardization of the model to improve evidence-based PSUD care most effectively.

Naloxone access in perinatal substance use disorder

BACKGROUND

Risk of fatal drug overdose is higher in pregnant and postpartum people with substance use disorder (SUD) than for nonpregnant women of reproductive age. It is recommended that naloxone is prescribed for pregnancies complicated by opioid or stimulant use disorder.

OBJECTIVE

The purpose of this study was to assess the rates of naloxone coprescribing with buprenorphine in a perinatal SUD (PSUD) specialty clinic and identify opportunities for pharmacist-led interventions to improve communication and documentation surrounding naloxone access to achieve a rate of 100% coprescribing of naloxone with buprenorphine.

PRACTICE DESCRIPTION

A clinical pharmacist practitioner is embedded on the Project CARA (Care that Advocates Respect/Resilience/Recovery for All) team, which provides outpatient SUD care integrated with perinatal care in Western North Carolina.

PRACTICE INNOVATION

The clinical pharmacist practitioner assessed baseline rates of naloxone coprescribing with medications for opioid use disorder. Interventions to improve rates of coprescribing include provider education, electronic health record (EHR) documentation templates, and direct patient outreach.

EVALUATION METHODS

Baseline rates of naloxone coprescribing were assessed and then re-evaluated after different interventions to measure pharmacist impact.

RESULTS

Each intervention improved rates of naloxone coprescribing in a PSUD clinic. EHR documentation templates had the largest impact on baseline efforts, although the long-term benefits derived from these efforts have not yet been demonstrated. Substantial time investment from the pharmacist was required to address patients' barriers to obtaining naloxone after their visits.

CONCLUSION

Further process improvement should address barriers to naloxone access for both patients and providers. This may include proactive identification of patients in need of naloxone and a "meds-to-beds" pilot to assist patients in navigating logistical challenges.

Information needs on nutrition in link to cancer prevention among cancer patients, high-risk individuals and general population - A national cross-sectional study

BACKGROUND & AIMS

Nutrition is one of the fundamentals of cancer prevention. Knowing what are the patients' needs and beliefs in terms of "nutrition and cancer" information helps tailor future nutritional interventions. The aim of this study was to evaluate specific information needs about "nutrition in relation to cancer prevention", including primary and tertiary prevention, among cancer patients, cancer-free individuals, and genetic high cancer risk individuals.

METHODS

This online survey was shared within two large National cancer social networks and proposed to all attendees and carers of a comprehensive cancer center.

RESULTS

2887 individuals answered the survey (of whom 33% were cancer patients, 13% high-risk individuals and 55% participants of the general population). More than 80% of participants were women, had at least a high school degree. Median body mass index was 23.2 kg/m². Eleven percent (n = 321) were following a diet, mostly low carbohydrate and weight-loss diets. Around 70% of all categories felt they lacked information on nutrition and cancer interplays. Only 12% of cancer patients (n = 108) considered they had received enough information on nutrition during their care pathway. A majority of participants agreed that food can modify cancer risk (93%, n = 2526) and 66% (n = 1781) considered that nutrition should be personalized according to the risk of cancer. Only twenty-nine percent (n = 792) believed that eating 5 fruits and vegetables a day was enough to avoid cancer, but 64% (n = 1720) thought that dietary supplements could help obtain a better health. All proposed nutrition topics were considered important by the participants.

CONCLUSIONS

Although cancer patients and cancer-free respondents, whether at high risk of cancer or not, share a common broad interest on the interplay between nutrition and cancer and seek after more information on this topic, some false beliefs are observed. Healthcare providers could successfully propose more evidence-based information to these populations.

Clinical utility of circulating tumor DNA sequencing with a large panel: a National Center for Precision Medicine (PRISM) study

BACKGROUND

Circulating tumor DNA (ctDNA) sequencing is a promising approach for tailoring therapy in patients with cancer. We report hereby the results from a prospective study where we investigated the impact of comprehensive molecular profiling of ctDNA in patients with advanced solid tumors.

PATIENTS AND METHODS

Genomic analysis was performed using the FoundationOne Liquid CDx Assay [324 genes, tumor mutational burden (TMB), microsatellite instability status]. Each individual genomic report was reviewed and discussed weekly by a multidisciplinary tumor board (MTB). Actionable targets were classified by ESMO Scale for Clinical Actionability of Molecular Targets (ESCAT) tier leading to molecular-based treatment suggestions wherever it was possible.

RESULTS

Between December 2020 and November 2021, 1772 patients with metastatic solid tumors underwent molecular profiling. Median time to assay results was 12 days. Results were contributive for 1658 patients (94%). At least one actionable target was detected in 1059 patients (64%) with a total of 1825 actionable alterations including alteration of the DNA damage repair response pathway (n = 336, 18%), high TMB (>16 mutations/Mb; n = 243, 13%), PIK3CA mutations (n = 150, 8%), ERBB family pathway alterations (n = 127, 7%), PTEN alterations (n = 95, 5%), FGFR alterations (n = 67, 4%) and MET activations (n = 13, 0.7%). The MTB recommended a matched therapy for 597 patients (56%) with a total of 819 therapeutic orientations: clinical trials (n = 639, 78%), off-label/compassionate use (n = 81, 10%), approved drug (n = 51, 6%), and early access program (n = 48, 6%). In total, 122 patients (21%) were treated. Among the assessable patients (n = 107), 4 (4%) had complete response, 35 (33%) had partial response, 27 (25%) had stable disease, and 41 (38%) a progressive disease as best response. The median progression-free survival and median overall survival were 4.7 months (95% confidence interval 2.7-6.7 months) and 8.3 months (95% confidence interval 4.7-11.9 months) respectively.

CONCLUSIONS

ctDNA sequencing with a large panel is an efficient approach to match patients with advanced cancer with targeted therapies.

The Frequency of Germline BRCA and Non-BRCA HR-Gene-Variants in a Cohort of Pancreatic Cancer Patients

Germline DNA alterations affecting homologous recombination pathway genes have been associated with pancreatic cancer (PC) risk. BRCA2 is the most studied gene and affects the management of PC patients and their families. Even though recent reports have suggested a similar role of germline ATM pathogenic variants (PV) in familial PC, there is still a disagreement between experts on how it could affect patient management given the lack of proper PC risk estimates. We retrospectively analyzed the germline data of 257 PC patients among whom nearly 50% were sporadic cases. We showed similar frequencies of BRCA2 (4.9%) and ATM (4.4%) PV or likely pathogenic variants, which were not related to familial history. Based on our findings and that of the literature, we suggest including ATM gene among the panel of genes analyzed in PC patients pending the publication of prospective studies.

Safety of assisted reproductive techniques in young women harboring germline pathogenic variants in BRCA1/2 with a pregnancy after prior history of breast cancer

BACKGROUND

Knowledge is growing on the safety of assisted reproductive techniques (ART) in cancer survivors. No data exist, however, for the specific population of breast cancer patients harboring germline BRCA1/2 pathogenic variants.

PATIENTS AND METHODS

This is a multicenter retrospective cohort study across 30 centers worldwide including women diagnosed at ≤40 years with stage I-III breast cancer, between January 2000 and December 2012, harboring known germline BRCA1/2 pathogenic variants. Patients included in this analysis had a post-treatment pregnancy either achieved through use of ART (ART group) or naturally (non-ART group). ART procedures included ovulation induction, ovarian stimulation for in vitro fertilization or intracytoplasmic sperm injection, and embryo transfer under hormonal replacement therapy.

RESULTS

Among the 1424 patients registered in the study, 168 were eligible for inclusion in the present analysis, of whom 22 were in the ART group and 146 in the non-ART group. Survivors in the ART group conceived at an older age compared with those in the non-ART group (median age: 39.7 versus 35.4 years, respectively). Women in the ART group experienced more delivery complications compared with those in the non-ART group (22.1% versus 4.1%, respectively). No other apparent differences in obstetrical outcomes were observed between cohorts. The median follow-up from pregnancy was 3.4 years (range: 0.8-8.6 years) in the ART group and 5.0 years (range: 0.8-17.6 years) in the non-ART group. Two patients (9.1%) in the ART group experienced a disease-free survival event (specifically, a locoregional recurrence) compared with 40 patients (27.4%) in the non-ART group. In the ART group, no patients deceased compared with 10 patients (6.9%) in the non-ART group.

CONCLUSION

This study provides encouraging safety data on the use of ART in breast cancer survivors harboring germline pathogenic variants in BRCA1/2, when natural conception fails or when they opt for ART in order to carry out preimplantation genetic testing.

[Recommendations for genetic testing and management of individuals genetically at-risk of cutaneous melanoma]

Cutaneous melanoma is a multifactorial disease resulting from both environmental and genetic factors. Five susceptibility genes have been identified over the past years, comprising high-risk susceptibility genes (CDKN2A, CDK4, and BAP1 genes) and intermediate-risk susceptibility genes (MITF, and MC1R genes). The aim of this expert consensus was to define clinical contexts justifying genetic analyses, to describe the conduct of these analyses, and to propose surveillance recommendations. Given the regulatory constraints, it is recommended that dermatologists work in tandem with a geneticist. Genetic analysis may be prescribed when at least two episodes of histologically proven invasive cutaneous melanoma have been diagnosed before the age of 75 years in two 1st or 2nd degree relatives or in the same individual. The occurrence in the same individual or in a relative of invasive cutaneous melanoma with ocular melanoma, pancreatic cancer, renal cancer, mesothelioma or a central nervous system tumour are also indications for genetic testing. Management is based upon properly managed photoprotection and dermatological monitoring according to genetic status. Finally, depending on the mutated gene and the familial history, associated tumour risks require specific management (e.g. ocular melanoma, pancreatic cancer). Due to the rapid progress in genetics, these recommendations will need to be updated regularly.

Guidelines for surveillance of individuals with constitutional mismatch repair-deficiency proposed by the European Consortium "Care for CMMR-D" (C4CMMR-D)

Lynch syndrome (LS) is an autosomal dominant disorder caused by a defect in one of the DNA mismatch repair genes: MLH1, MSH2, MSH6 and PMS2. In the last 15 years, an increasing number of patients have been described with biallelic mismatch repair gene mutations causing a syndrome referred to as 'constitutional mismatch repair-deficiency' (CMMR-D). The spectrum of cancers observed in this syndrome differs from that found in LS, as about half develop brain tumours, around half develop digestive tract cancers and a third develop haematological malignancies. Brain tumours and haematological malignancies are mainly diagnosed in the first decade of life, and colorectal cancer (CRC) and small bowel cancer in the second and third decades of life. Surveillance for CRC in patients with LS is very effective. Therefore, an important question is whether surveillance for the most common CMMR-D-associated cancers will also be effective. Recently, a new European consortium was established with the aim of improving care for patients with CMMR-D. At a workshop of this group held in Paris in June 2013, one of the issues addressed was the development of surveillance guidelines. In 1968, criteria were proposed by WHO that should be met prior to the implementation of screening programmes. These criteria were used to assess surveillance in CMMR-D. The evaluation showed that surveillance for CRC is the only part of the programme that largely complies with the WHO criteria. The values of all other suggested screening protocols are unknown. In particular, it is questionable whether surveillance for haematological malignancies improves the already favourable outcome for patients with these tumours. Based on the available knowledge and the discussions at the workshop, the European consortium proposed a surveillance protocol. Prospective collection of all results of the surveillance is needed to evaluate the effectiveness of the programme.

Short-term psychological impact of the BRCA1/2 test result in women with breast cancer according to their perceived probability of genetic predisposition to cancer

Background:

The effect of BRCA1/2 gene test result on anxiety, depression, cancer-related thought intrusion or avoidance and perceived control over cancer risk was assessed in breast cancer (BC) patients, according to their perceived probability of genetic predisposition to cancer.

Methods:

Two hundred and forty-three (89% response rate) women with BC completed questionnaires after an initial genetic counselling visit (T1), of which 180 (66%) completed questionnaires again after receiving the BRCA1/2 results (T2). The discrepancy between women's perceived probability of cancer genetic predisposition at T1 and the geneticist's computed estimates was assessed.

Results:

In all, 74% of women received a negative uninformative (NU), 11% a positive BRCA1/2 and 15% an unclassified variant (UV) result. On hierarchical regression analysis, in women with a positive BRCA1/2 result (vs NU or UV), a lower perceived probability of cancer genetic predisposition than objective estimates at T1 predicted lower levels of anxiety at T2 (β=−0.28; P<0.01), whereas in women receiving a UV result (vs NU or positive BRCA1/2), a lower perceived probability of cancer genetic predisposition than objective estimates at T1 predicted higher levels of anxiety (β=0.20; P<0.01), depression (β=0.19; P<0.05) and intrusion (β=0.18; P<0.05) at T2.

Conclusion:

The type of BRCA1/2 test result differently affects distress according to women's perceived probability of genetic predisposition before testing.

P2-13-06: Feasibility of Fast-Track Germline Genetic Analyses for Localized Breast Cancer Patients and Its Impact on Local Management

Background

Patients with BRCA1-BRCA2 germline mutation who developed a first breast cancer (BC) have a high risk to develop a second BC, especially if aged less than 40 at first diagnosis. Thus, a positive BRCA test may influence the therapeutic management and orients towards non conservative surgery to reduce new BC occurrence. We set up a fast-track process to get BRCA1/2 and sometimes p53 mutation results within the shortest possible interval, in recently diagnosed BC patients whose probability to be mutation carriers was high (&gt; 20%).

Methods: Between 05/02/2009 and 03/01/2011, 61 patients diagnosed with localized BC requesting neo-adjuvant or adjuvant chemotherapy and whose personal or familial history fulfilled BRCA1/2 or P53 genetic testing criteria, were proposed genetic counselling. After a first multisciplinary team meeting (MT), genetic testing was proposed and performed according to usual genetic counselling rules. Psychological support was offered at every step of the process. Patients were informed that their test would be analysed as part of a fast-track process and were aware of the potential consequences of a positive test. Results were communicated and discussed during a second MT, when initial therapeutic plan was eventually changed.

Results: All women who were referred to the genetic clinic for fasttrack testing accepted the analysis. The mean age at diagnosis was 38 (range 26–55). The whole process (from 1st genetic consultation till disclosure consultation) was completed in a median interval of 99 days (range 19–245). All pts received appointment within 5 days, when results were available. 50% pts postponed for more than 15 days their disclosure appointment (range 0–113 days). One patient (pt) declined result disclosure. 18 pts (30%) were found to be carrier of a deleterious mutation (13 BRCA1, 4 BRCA2, 1 p53). Variants of unknown significance (UV) in BRCA1 or BRCA2 genes were identified in another 4 patients. In 18 cases, surgery type initially proposed was changed because of the presence of the germline mutation: all pts were proposed ipsilateral mastectomy eventually associated to immediate reconstruction as often possible, as well as controlateral mastectomy. Final surgery turned to bilateral mastectomy in 3 patients with deleterious BRCA mutation and in one suspect UV 14 patients with mutation accepted the change, but four BRCA2 and one BRCA1 mutation carriers refused mastectomy or bilateral mastectomy. Radiotherapy was cancelled in a p53 mutation carrier.

Conclusion: This data show that genetic testing might be considered as a part of therapeutic decision. Moreover, 22% (4/18) opted for a simultaneous controlateral prophylactic mastectomy. On the other hand, some women did not change their mind with mutation knowledge (4/18, 22%). Psychological impact of this procedure is currently retrospectively assessed by a self-questionnaire, fulfilled by mail. Analyses will be available for the meeting.

Dynamic Breast Magnetic Resonance Imaging in the Assessment of Breast Glandular Tissue in High Risk Patients after Prophylactic Ovariectomy

Purpose: To evaluate the enhancement of breast glandular tissue by dynamic magnetic resonance imaging (MRI) in high risk patients, before and after prophylactic ovariectomy.Materials and Methods: A retrospective study was performed on 28 patients with high risk for breast and ovarian cancer who underwent preventive bilateral ovariectomy. Seven patients who were at hormone replacement therapy and chemotherapy were excluded. From the 21 patients included, 12 were BRCA 1; 6 were BRCA 2; 1 was BRCA 1 – 2; and 2 patients had strong familiar history. All patients underwent contrast breast MRI before and after surgery, for breast cancer screening. MRI was performed at GE Healthcare 1.5 Tesla equipement before (mask) and after 5 phases of contrast injection. All pre contrast images were subtracted from the post contrast images. The second subtracted sequences of MRI images were analyzed qualitatively according to the type of glandular enhancement (1. no enhancement, 2. mild homogeneous, 3. strong heterogeneous, 4. strong homogeneous, 5. mild heterogeneous), and quantitatively by measuring signal intensity of glandular tissue in the upper outer quadrant of the breast in the second sequence of post-contrast images. Patients were divided into 2 groups: with and without the appearance of a lesion between the first and second MRI, for comparative analysis with the fibroglandular tissue.Results: Mean age was 44 years (39-51). In qualitative analysis at MRI before ovariectomy (MRI 1), 33% of the patients showed type 3 enhancement; 33% type 5; 29% type 4 and 5% type 1. At MRI post-ovariectomy (MRI 2), 67% of the patients presented enhancement type 1; 19% type 4 and 14% type 3. Twenty patients showed a higher enhancement at MRI 1 and for 1 patient the enhancement was the same at MRI 1 and 2. In quantitative analysis, the average of enhancement of the glandular tissue at MRI 1 was 356.1 and for MRI 2 was 65.2. Three patients presented an enhanced nodule on the first and second MRI. The average of enhancement of the lesions at MRI 1 was 890.9 and at MRI 2 was 452.9.Conclusion: Ovariectomy substantially reduces the physiological fibroglandular breast enhancement. The significant decrease of the glandular breast enhancement in MRI can help to detect organic focal breast lesion, such as atypical ductal hyperplasia and to differentiate it from functional foci. The comprehension of this changes can lead to decrease the number of false positives in breast MRI interpretation.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 4024.

Influence of loco-regional radiation therapy on subsequent cancer risk among BC pts with p53 germline mutations

11043

Background: The management of breast cancer (BC) patients (pts) with germline p53 mutations, a rare genetic condition, is not the object of specific recommendations. Preclinical data and preliminary clinical observations suggest a theoretically major radio-sensitivity and high risk of secondary radio-induced malignancies. It remains discussed whether the knowledge of a germline p53 mutation may influence treatment (trt) choices and have prognostic importance. We reviewed our cohort of BC diagnosed as first tumor in pts with germline p53 mutations within the past 11 years, with an attempt to describe secondary malignancies occurring after trt of primary tumor. Patients and Methods: 9 pts have been diagnosed and treated in our institution within the past 11 years for BC as first tumor in the context of a documented germline p53 mutation. Their tumor characteristics, treatment and follow-up data were extracted from prospectively-registered medical records. Results: Median age at diagnosis of primary BC was 32 (22–48). 7/9 pts had a family history compatible with Li Fraumeni syndrome, while 2 had no family history. No pt had previous knowledge of her p53 mutation. Primary tumors were ductal carcinoma in situ (4), infiltrating ductal carcinoma (4), phyllode tumor (1). 3 pts had conservative surgery and 6/9 underwent mastectomy (M). 6 received loco-regional radiation therapy (RT). None had prophylactic contra lateral mastectomy. Loco-regional (LRR) and contra-lateral relapses are listed in the Table , as well as incidence of second primaries within or outside radiation field. Second primaries were sarcoma in 3/4 cases and 1 was papillary thyroid carcinoma. Conclusions: Because of high risk of second breast primary and probably very high risk of radio-induced breast cancer, BC pts with germline p53 mutations should be advised bilateral prophylactic mastectomy and avoidance of radiation therapy. In this context, the knowledge of the mutation might be of great importance. [Table: see text]

No significant financial relationships to disclose.

Intensive breast cancer screening programs including MRI influence prognosis and treatment of breast cancer among BRCA 1/2 gene mutation carriers

Abstract #5004

Background: Several studies have highlighted the potential benefit of early breast cancer (BC) diagnosis through breast MRI for high risk patients (pts). However, MRI is an expensive test with a low positive predictive value and has not been proven to reduce mortality rates in women carrying BRCA1/2 deleterious gene mutations (mut).&#x2028; At Institut Gustave Roussy, we started intensive BC screening programs for BRCA1/2 carriers (annual MRI + mammogram + bi-annual US) in 2001. The aim of this study was to compare the characteristics and prognostic features of BC in BRCA1/2 pts diagnosed inside or outside screening programs.&#x2028; Patients and Methods: All female BRCA1/2 mut carriers who have been treated for a new BC in our institution between 2001 and 2008, were entered into this study. All BRCA1/2 mut testing have been performed under the French guidelines and recommendations.&#x2028; We compared the clinico-pathological data, treatments and prognostic features between group 1 (pts diagnosed while on an intensive dedicated screening program) and group 2 (pts diagnosed outside these programs). Pts characteristics were compared using student T-test, and survival curves using Log-Rank tests.&#x2028; Results: 122 pts met the inclusion criteria: 20 in group 1, 102 in group 2. &gt; 95% of pts in group 2 were not aware of their BRCA1/2 mut at time of diagnosis. In group 1, 17 cancers were diagnosed primarily through MRI (85%), while 3 were self-detected interval BC. Pts in group 1 had tumors with significantly better prognostic factors and received less CT.&#x2028; 3-year DFS significantly differed between groups 1 (100%) and 2 (74% (IC: 64-81 (p=0.04). 3-years MFS was 100 and 80% (p= 0.08), 3-years OS was 100 and 94% (p=0.26) in groups 1 and 2.&#x2028; &#x2028; Conclusion: These early data strongly suggest an important benefit in terms of disease-free survival and treatment sparing for i. the knowledge of a BRCA1/2 mut; ii. inclusion into intensive BC screening programs including MRI.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 5004.

Effects of the Removal of Vision on Body Sway During Different Postures in Elite Gymnasts

The aim of this study was to analyse the effects of the removal of vision on postural performance and postural control in function of the difficulty and specificity of the posture. Twelve elite gymnasts were instructed to be as stable as possible with eyes open and eyes closed in three postures: bipedal, unipedal, and handstand ranked from the less difficult and less specific to the more difficult and more specific. The ratios eyes closed on eyes open, computed on CP surface and CP mean velocity, which respectively represents postural performance and postural control, were similar in the bipedal and handstand postures. They were highly increased in the unipedal one. The effect of the removal of vision and so the role of vision on body sway was not directly linked to the difficulty or specificity of the posture; other tasks' characteristics like the segments configuration also played a role.

Is there a transfer of postural ability from specific to unspecific postures in elite gymnasts?

The purpose of this study was to investigate the transfer of postural ability by comparing the level of performance and postural control of elite gymnasts in postures specifically trained or not. Fifteen elite gymnasts were asked to stand as still as possible with eyes opened in three conditions: bipedal, unipedal and handstand. Surface and mean velocity of the centre of pressure motions were used to quantify respectively performance and postural control. A ranking was made for each parameter to determine the level of each subject. As a whole, the subject's level of postural performance and control in one condition was not correlated to the corresponded level in another condition. Therefore, postural ability of elite gymnasts in the handstand is not transferable to upright standing postures.

Center of gravity motions and ankle joint stiffness control in upright undisturbed stance modeled through a fractional Brownian motion framework

The authors modeled the center of gravity vertical projection (CG(v)) and the difference, CP - CG(v), which, combined, constitute the center of pressure (CP) trajectory, as fractional Brownian motion in order to investigate their relative contributions and their spatiotemporal articulation. The results demonstrated that CG(v) and CP - CG(v) motions are both endowed in complementary fashion with strong stochastic and part-deterministic behaviors. In addition, if the temporal coordinates remain similar for all 3 trajectories by definition, the switch between the successive control mechanisms appears for shorter displacements for CP - CG(v) and CG(v) than for CP trajectories. Results deduced from both input (CG(v)) and muscular stiffness (CP - CG(v)) thus provide insight into the way the central nervous system regulates stance control and in particular how CG and CP - CG are controlled.

A comparative analysis of the center of gravity and center of pressure trajectory path lengths in standing posture: an estimation of active stiffness

The center of foot pressure (CP) motions, representing the net neuromuscular control, was compared to the center of gravity (CG) motions, representing the net performance. The comparison focused on the trajectory path length parameter along the medio-lateral and antero-posterior axes because these two variables depend on amplitude versus frequency relationship. This relationship was used to evaluate the CG motions based on the CP motions. Seven subjects stood still on a force plate with eyes open and eyes closed. The results showed that the ratio of (CP-CG)/CP trajectory path length was personal for each subject. These results suggest different levels of passive (ligaments, elastic properties) and active (reflex activity) stiffness. For some subjects, this ratio was significantly lower for the eyes open condition than for the eyes closed condition, indicating a decrease of the active stiffness for the eyes open condition. Therefore, a CG-CP comparative analysis appeared helpful in understanding the control of balance and necessary to quantify the subjects' net performance.

Estimating the centre of gravity of the body on the basis of the centre of pressure in standing posture

This study proposes to estimate the horizontal positions of the body's centre of gravity (CoG) in a standing posture, on the basis of the horizontal positions of the centre of pressure (CoP). The latter were measured with a force plate, and using a low-pass filter defined by a mathematical relationship of the relative magnitude of the CoG with respect to the magnitude of the CoP, as a function of the frequency oscillations (Brenière, 1996, Journal of Motor Behaviour 28, 291-298). This relationship was computed from the angular momentum equation applied to the whole body with respect to the CoG using the inverse dynamics approach and force plate recordings, and considering the CoP and CoG oscillations as simple periodic functions. Five subjects were asked to perform voluntary oscillations along medio-lateral and antero-posterior axes, keeping their bodies straight, and without moving their feet. The CoG accelerations measured by the force plate were compared with the CoG accelerations derived from the estimated CoG positions. The average root-mean-square difference between these accelerations was very small, confirming the accuracy of this method. This simplified way to calculate the CoG positions, rarely measured in standing, allows a comparative assessment of motion performance. This method could also be applied to other kinds of movement such as walking.

Influence of the initial projection of the centre of gravity on posturo-kinetic coordination in humans. Application from a horizontal quadrupedal stance during voluntary limb raising

The purpose of the study is to investigate the influence of initial projection of the centre of gravity (CG) on the spatial and temporal organization of the dynamic phenomena accompanying a voluntary movement in humans. From a horizontal quadrupedal stance, ten normal subjects were instructed to raise the right forelimb towards a support target in self paced velocity conditions. Three experimental conditions were tested for which the initial CG projection was either within (C1), at the limits of (C2) or outside the supporting triangle (C3). The results showed that vertical force variations on the four supports always preceded the first vertical displacement of the right wrist (onset of the movement). From C1 to C3, the duration of these anticipatory dynamic phenomena increased enabling an adjustment of the CG position such that equilibrium constraints were fulfilled. For all conditions, the acceleration peak of the CG occurred prior to the onset of movement and from C1 to C3, its magnitude increased in a single direction of the horizontal plane. For each condition, the load transfer was directed to the left forelimb and the right hindlimb (diagonal strategy) and reached a maximal value at the time of lift-off. With respect to this moment, the onset of the movement occurred increasingly early from C1 to C3. These results suggest that contribution of peripheral cues to postural control is more important, when the requirements of horizontal CG displacement increase.