To stimulate research proposals, the report stresses the need for a comprehensive research and development program regarding sensory aids for the visually handicapped and describes 17 representative projects viewed as warranting immediate attention. The 17 projects are categorized in two different ways. In a brief summary section, projects are classified according to whether they relate primarily to organization and planning or to R and D needs. Provided in the next section is a more detailed description of short-ter projects that .may be expected to yield successful early results (including new reading and mobility aids for the blind and studies of visual capabilitiei among the partially sighted) as well as long-ter projects (involving broader research in such areas as vocational opportunities, public information programs, sensory aids centers, technological applications, and research on the reading process among sighted individuals). Also listed are 19 source documents said to define problems, to describe the current state-of-the-art, or to indicate organizations and people currently active in the field of sensory aids for the visually impaired. (LH) *********************************************************************** Documents acquired by ERIC include many informal unpublished * materials not available from other sources. ERIC makes every effort * * to obtain the best copy available. Nevertheless, items of marginal * * reproducibility are often encountered and this affects the quality * * of the microfiche and hardcopy reproductions ERIC makes available * * via the ERIC Document Reproduction Service (EDRS). EDRS is not * responsible for the quality of the original document. Reproductions * * supplied by EDRS are the best that can be made from the original. * ***********************************************************************

My academic career of more than 50 years has been committed to involving undergraduate and graduate students in the engineering design process [1]. A variety of experiences—childhood model making, vocational high school education, draftsman jobs, and military assignments during World War II—have convinced me that design is best learned by the necessity of reaching wellestablished and defined design goals during a specific time period. At MIT, first as a research engineer and then as faculty, I mounted an unending search for appropriate topics to develop into engineering design goals as well as thesis topics for my students. As part of that search I became involved in rehabilitation engineering (RE) in the late 1950s and early 1960s through a combination of prior unrelated R&D work and the influence of two individuals. A chance meeting with John Kenneth Dupress led to blindness-related projects, and an accident befalling Norbert Wiener led indirectly to my limb prostheses research. For my students as well as for me, RE proved a winner! Students were challenged technically while working on projects that had real human significance—that indeed would ultimately improve the quality of life for thousands of people. The prospect of making such contributions attracted the best students to my research projects.

Pressures on normal human acetabular cartilage have been collected from two implanted instrumented femoral head hemiprostheses. Despite significant differences in subjects' gender, morphology, mobility, and coordination, in vivo pressure measurements from both subjects covered similar ranges, with maximums of 5-6 MPa in gait, and as high as 18 MPa in other movements. Normalized for subject weight and height (nMPa), for free-speed walking the maximum pressure values were 25.2 for the female subject and 24.5 for the male subject. The overall maximum nMPa values were 76.2 for the female subject during rising from a chair at 11 months postoperative and 82.3 for the male subject while descending steps at 9 months postoperative. These unique in vivo data are consistent with corresponding cadaver experiments and model analyses. The collective results, in vitro data, model studies, and now corroborating in vivo data support the self-pressurizing "weeping" theory of synovial joint lubrication and provide unique information to evaluate the influence of in vivo pressure regimes on osteoarthritis causation and the efficacy of augmentations to, and substitutions for, natural cartilage.

Whitaker Professor Emeritus of Biomedical Engineering Department of Mechanical Engineering Massachusetts Institute of Technology Cambridge, Massachusetts, U.S.A.

In vivo acetabular contact pressures were measured over 32 months in an elderly man with a pressure instrumented hemiarthroplasty. After death, left (hemiarthroplasty) and right (control) acetabula were explanted. Cartilage thickness and degeneration were quantified from magnetic resonance imaging and histological analysis. Highest repetitive in vivo contact pressures during gait (4.5 to 6.5 MPa) were measured in the superior dome of the acetabulum and decreased at a rate of approximately 1 MPa per year after implant (R2 = 0.48, P < .001). Contact pressure magnitudes measured during gait correlated positively with regional histology score (R2 = 0.34, P < .0001) and negatively with cartilage thickness (R2 = 0.35, P < .0001). Although histology scores were typical of early osteoarthritis (histological grade of 4–6), there were no significant differences in overall histology score for the left and right acetabula (P = .23). We conclude that acetabular cartilage degeneration was explained, in part, by repetitive stress, but the degeneration did not appear to be mediated solely by articulation with the metallic endoprosthesis.

The biomechanical literature over the past three decades reports direct measurements of human hip joint contact forces from instrumented implants which in general are quite different than estimates of contact forces based on external kinematic-ground reaction force data and inverse Newtonian analyses. Because direct physical measurement establishes veridical values in science, the higher analytical estimates may overestimate the balanced muscle force increments in agonist–antagonistic muscles about the joint (called co-contraction) which control joint impedance and contribute to joint stability. We studied the extent of muscle co-contraction by comparing in vivo endoprosthesis pressure measurements on hip articular cartilage and intersegmental force estimations from concurrent kinetic–kinematic data. Muscle co-contraction was evident from pressure magnitudes higher than those consistent with external data, from pressure rises before foot–floor contact, and substantial differences in the locations on the acetabulum of the highest pressures compared with the corresponding force vectors estimated from external data. Therefore, joint force and pressure inferences from external kinematic and kinetic data, without corroborating direct, internal measurements, should be made with more caution than is evident in the current literature.

The development of improved orthopedic implants, diagnostic tools and surgical procedures for clinicians requires a better understanding of the human musculoskeletal system and joint kinematics. Mathematical models continue to play an important role in advancing the understanding of musculoskeletal system performance. At the core of any useful mathematical model is a sound representation of the fundamental mechanics of the system and reliable, repeatable measurements of the necessary physical parameters. For joint models, essential data include the three dimensional geometry of the articulating surfaces and ligament insertion sites, the articulating cartilage thickness, and material properties of the different tissues.

Measurement of three-dimensional, skeletal kinematics is important for clinicians and engineers alike. Most in vivo motion data are acquired using skin-mounted markers or marker arrays. Experiments were carried out to quantitatively evaluate the validity of using skin-mounted markers to measure the three-dimensional kinematics of the underlying bone. Kinematic data for marker arrays mounted on skeletal pins screwed directly into the bone were compared with data for markers, and arrays of markers, mounted on the skin. Findings included: (1) Task-dependent soft tissue motion relative to the underlying bone of up to twenty millimeters was measured; (2) The accuracy of segmental rigid body velocity estimates was inadequate for determining instantaneous helical axis (IHA) parameters; (3) Power spectra for skin- and pin-mounted arrays cover similar frequency bands and there was no evidence of a distinct, frequency domain soft tissue artifact; (4) Joint angles calculated from the relative rotation of skin-mounted arrays had significant differences compared to the expected values due to soft tissue effects; and (5) Skin-mounted marker data exhibited a transient response to heel strike in gait, but for low-mass markers the transient was well-damped and could be removed with optimal smoothing.

The American Academy of Pediatrics created evidence-based guidelines that encourage early identification and referral for children with developmental delays. Although pediatric primary care providers are poised to link 3-to-5-year-old children to school-based services, there are gaps in making referrals.Educational dissemination of streamlined referral packets was introduced. Knowledge and perceived confidence were measured following an educational presentation. Retrospective chart reviews compared referral rates to preschool special education services when developmental delays were identified.Mean pretest to posttest knowledge and perceived confidence to refer children to preschool special education increased following education. Referral rates for 3–5 years-old by pediatric primary care providers doubled during the initial 8-week implementation period and remained constant 9 months later.Educational dissemination of a streamlined referral process in pediatric primary care is a sustainable approach that ensures preschool-aged children with developmental delays receive timely referrals for further school-based evaluations and interventions.

Summary This study uses acetabular contact pressure data from the immediate post-operative period to examine some of the commonly held beliefs about early phase hemiarthroplasty rehabilitation. Data were obtained from an instrumented femoral head prosthesis implanted in an 82-year-old man (height 1.6 m; weight 54.5 kg) with a displaced left hip fracture. Data were collected daily during the two weeks of immediate post-operative hospitalisation. The shibboleths being examined are related to the functional activities: sit-to-stand, ambulation, and stair-climbing. Results support beliefs about rising from a chair: lower pressures were created when rising from a 62 cm hip chair (1.4 MPa) than from a 48 cm standard chair (7.09 MPa): and less pressure was created when rising from a 62 cm hip chair with operated leg out in front (1.21 MPa) than when rising from the same chair with feet together (2.96 MPa). Gait training beliefs are challenged by the study findings: there was no significant difference between touch weight bearing, partial weight bearing, and weight bearing as tolerated; and use of a very commonly used post-operative gait sequence (walker, then operated leg, then non-operated leg) generated a greater peak pressure than an ‘incorrect’ sequence (walker, then non-operated leg, then operated leg). Limited early post-operative stairs data prevented definitive conclusions from being reached about stair-climbing in the early post-operative period. However, examination of data from one year post-operatively demonstrates that unassisted reciprocal gait on stairs creates large (15.52 MPa) acetabular contact pressures.

Muscle mechanical work is likely affected by gait abnormalities in hemiparetic walking during the paretic pre-swing phase (i.e., double support phase preceding paretic toe-off). Previous experimental studies suggest that muscle work may be decreased in the paretic leg, but paretic work may have been underestimated since experimental approaches based on net joint moments do not account for co-contraction of antagonist muscles. Also, whether the non-paretic leg does more work compared to control subjects at matched speeds and how work generation may differ between hemiparetic subjects walking with different self-selected speeds remains unknown.Three-dimensional forward dynamics simulations of two representative hemiparetic subjects walking with different self-selected speeds (i.e., limited community = 0.45 m/s and community walkers = 0.9 m/s) and a speed and age-matched control subject were generated to quantify musculotendon (fiber and in-series tendon) work during paretic pre-swing.Total paretic and non-paretic fiber work were increased in both the limited community and community hemiparetic walkers compared to the control. Increased fiber work in the limited community walker was primarily related to decreased fiber and tendon work by the paretic plantar flexors requiring compensatory work by other muscles. Increased fiber work in the community walker was primarily related to increased work by the hip abductors and adductors.The hemiparetic walkers would expend more metabolic energy during pre-swing if the hemiparetic and control subjects were to perform work with the same mechanical efficiency. These results may partly explain the increased metabolic cost of hemiparetic walkers compared to nondisabled walkers at matched speeds.

The total surface stress measured in vitro on acetabular cartilage when step-loaded by an instrumented hemiprosthesis are partitioned into fluid and cartilage network stresses using a finite element model of the cartilage layer and measurements of the layer consolidation. The finite element model is based on in situ measurements of cartilage geometry and constitutive properties. Unique instrumentation was employed to collect the geometry and constitutive properties and pressure and consolidation data. When loaded, cartilage consolidates and exudes its interstitial fluid through and from its solid network into the interarticular gap. The finite element solutions include the spatial distributions of fluid and network stresses, the normal flow velocities into the gap, and the contact network stresses at the cartilage surface, all versus time. Even after long-duration application of physiological-level force, fluid pressure supports 90 percent of the load with the cartilage network stresses remaining well below the drained modulus of cartilage. The results support the “weeping” mechanism of joint lubrication proposed by McCutchen.