Brian R. Kotajarvi

The Effect of Seat Position on Wheelchair Propulsion Biomechanics

This study examined the effect of seat position on handrim biomechanics. Thirteen experienced users propelled a wheelchair over a smooth level floor at a self-selected speed. Kinetic and temporal-distance data were collected with the use of an instrumented rim and a motion analysis system. A custom-designed axle was used to change the seat position. We used repeated measures analysis of variance to evaluate if differences existed in the temporal-distance and kinetic data with change in seat position. Results showed that a shorter distance between the axle and shoulder (low seat height) improved the push time and push angle temporal variables (p < 0.0001). Tangential force output did not change with seat position. Axial and radial forces were highest in the lowest seat position (p < 0.001). Propulsion efficiency as measured by the fraction of effective force did not significantly change with seat position.

Quantification of GDF11 and Myostatin in Human Aging and Cardiovascular Disease.

Growth and differentiation factor 11 (GDF11) is a transforming growth factor β superfamily member with a controversial role in aging processes. We have developed a highly specific LC-MS/MS assay to quantify GDF11, resolved from its homolog, myostatin (MSTN), based on unique amino acid sequence features. Here, we demonstrate that MSTN, but not GDF11, declines in healthy men throughout aging. Neither GDF11 nor MSTN levels differ as a function of age in healthy women. In an independent cohort of older adults with severe aortic stenosis, we show that individuals with higher GDF11 were more likely to be frail and have diabetes or prior cardiac conditions. Following valve replacement surgery, higher GDF11 at surgical baseline was associated with rehospitalization and multiple adverse events. Cumulatively, our results show that GDF11 levels do not decline throughout aging but are associated with comorbidity, frailty, and greater operative risk in older adults with cardiovascular disease.

Functional outcome of patients with rotationplasty about the knee.

Rotationplasty is a surgical procedure designed to achieve a durable reconstruction after the resection of tumors about the knee. However, because of the recent advances with expandable prostheses, rotationplasty has been less popular in the skeletally immature patient, particularly in the United States. We assessed the functional outcome of patients who had rotationplasty to allow better comparison with other operative techniques in this patient population. Seven patients, who were operated on at our institution at an average age of 9.4 years (range, 5–14 years), had a followup of at least 4 years and were evaluated in the Motion Analysis Laboratory. The gait analysis included kinetic, kinematic and temporal-distance parameters to evaluate the patient’s functional performance. The data also were compared with measurements of a population of 25 able-bodied subjects and with four subjects with distal above-knee amputation. All patients had the ability to weightbear fully. All patients ambulated without assistive devices. Gait analysis of patients with rotationplasty revealed only slight asymmetry regarding stride duration, stride length, cadence, velocity and stance-swing ratio compared with healthy subjects. Although the gait was similar to subjects with distal above-knee amputation, knee motion was superior in patients who had rotationplasty. Rotationplasty offers a durable reconstruction. Rotationplasty allows the patient to actively control the knee, which results in a coordinated gait pattern, which is similar to the gait of the able-bodied population, and better than in subjects with distal-knee amputation.

The Impact of Frailty on Patient-Centered Outcomes Following Aortic Valve Replacement

Background Frailty confers risk for surgical morbidity and mortality. Whether patient-reported measures of health, well-being, or quality of life respond differently to surgery in non-frail and frail individuals is unknown. Methods Older adults with severe aortic stenosis presenting for surgery were assessed for frailty using Cardiovascular Health Study Criteria. Patient-reported measures of functional capacity (Duke Activity Status Index [DASI]), physical and mental health (Medical Outcomes Study Short Form-Physical and Mental Component Scales [SF-12 PCS and SF-12 MCS, respectively]), well-being (linear analogue self-assessment [LASA]), and quality of life (LASA) were administered before and 3 months after surgery. Results Of 103 participants (mean age of 80.6 years), 54 were frail. Frail participants had lower baseline DASI, SF-12 PCS, SF-12 MCS, physical well-being, and quality of life scores than non-frail participants. At follow-up, frail participants showed significant improvement in physical function, with DASI and SF-12 PCS scores improving by 50% and 14%, respectively. Non-frail subjects did not significantly improve in these measures. SF-12 MCS scores also improved to a greater extent in frail compared to non-frail participants (3.6 vs < 1 point). Furthermore, the frail participants improved to a greater extent than non-frail participants in physical well-being (21.6 vs 7.1 points) and quality of life measures (25.1 vs 8.7 points). Conclusions Frailty is prevalent in older adults with severe aortic stenosis and is associated with poor physical and mental function, physical well-being, and quality of life. In response to surgery, frail participants exhibited greater improvement in these patient-centered outcomes than non-frail peers.

Analysis of ankle−hindfoot stability in patients with ankle instability and normals

PurposeWe devised a testing apparatus for in vivo analysis of ankle stability. The purpose of the study was to test the reliability of this apparatus and to determine the stability pattern of the ankle−hindfoot complex in healthy, asymptomatic volunteers and in patients with ankle instability.MethodsTen healthy individuals were studied, and testing was repeated on the same day and different days. Three patients with symptomatic, unstable ankles were also tested on both involved and uninvolved sides. Constant inversion torque was applied, then internal rotation torque, while moving the ankle throughout the range of sagittal motion. Three-dimensional kinematics of the ankle−hindfoot complex were measured by an electromagnetic tracking system.ResultsMeasurements were repeatable, with intraclass correlation coefficients 0.9 or better. Variability was observed among controls, but motion curve patterns were consistent. Motion curve slopes were sensitive in differentiating between unstable and stable ankles.ConclusionsMost previous reports are in vitro studies conducted with the ankle in one position, manual stress applied, or joint positions estimated with planar radiographs. Our study indicated that more accurate diagnosis of severity of ankle ligament injuries may be possible.

Relationship between pre‐transplant physical function and outcomes after kidney transplant Elizabeth

Performance‐based measures of physical function predict morbidity following non‐transplant surgery. Study objectives were to determine whether physical function predicts outcomes after kidney transplant and assess how physical function changes post‐transplant.

Functional outcome measures of patients following hemipelvectomy

Background: Major amputations are indicated for curative treatment of some tumors of the pelvis. Previous literature suggests that patients with a hemipelvectomy amputation are more efficient walking with crutches than using a prosthesis. Objectives: The purpose of this study was to evaluate whether modern prosthetic use after hemipelvectomy may be a viable option for patients than in the past. Study Design: Case control trial. Methods: We identified five patients who underwent hemipelvectomy amputation and fit with high-level prosthetic components. Patients were evaluated using a timed up and go, 5-m walk, 400-m walk, and stair climb tests to evaluate functional performance with a prosthesis and without. Short Form–36 scores were collected as well. These results were compared to matched controls. Results: There was a trend for faster locomotion using crutches over wearing a prosthesis in the timed up and go, and 5-m and 400-m walk; no difference was seen in stair climbing. Short Form–36 scores showed decreased physical component score, but equal mental component score compared to the general population. Conclusion: Our results show that in addition to advances in surgical techniques, prosthetic rehabilitation and management are beginning to optimize functional mobility with the prosthesis. Clinical relevance Patients who use a modern prosthesis following hemipelvectomy demonstrated good clinical function with and without their prosthesis. Although health status scores were decreased in the physical component, mental component scores were equal to healthy controls.

Poster 147: The effect of wheelchair seat position on peak shoulder joint moments during propulsion up an incline.1

Abstract Objective: To assess the effect of changes in wheelchair seat position on peak shoulder joint internal moments during propulsion up an incline. Design: Randomized interventional study. Setting: Motion analysis laboratory. Participants: 11 subjects (9 men, 2 women) with paraplegia who used a wheelchair for mobility. Interventions: Subjects propelled up an 8% incline in a wheelchair with an instrumented pushrim and an adjustable axle that produced 4 different elbow angles by raising or lowering the seat. Main Outcome Measures: Kinetic information from the instrumented pushrim and kinematic information from a 10-camera motion analysis system were used to calculate seated elbow angle and mean peak sagittal, frontal, and transverse plane internal shoulder joint moments during the propulsive phase. Results: The elbow angle with the participant’s hand at the top dead center position of the pushrim ranged from an average of 55.1°±6.4° of flexion in the highest seat position to 76.9°±4.5° in the lowest. The shoulder flexors, adductors, and external rotators generated the largest moments in the sagittal, frontal, and transverse planes, respectively, during the propulsive phase of the cycle. Repeated-measures analysis of variance revealed that changes in seat position did not significantly affect the peak moment values in the sagittal and transverse planes. In contrast, the frontal plane moment values were significantly higher in the low seat position conditions ( P =.004). Conclusions: It has been suggested in the literature that low seat positions result in greater propulsion efficiency. This study showed that, during a challenging activity such as ramp ascension, lower seat positions resulted in a significantly higher shoulder adductor moment. This may be because greater shoulder abduction is present during the stroke cycle with the seat low. Therefore, this position may lead to increased fatigue of the shoulder adductors.