Melissa M. Morrow

Elevated Postoperative Blood Glucose and Preoperative Hemoglobin A1C Are Associated with Increased Wound Complications Following Total Joint Arthroplasty

BACKGROUND Diabetes is an established risk factor for complications following total joint arthroplasty. However, the correlation between postoperative blood glucose and preoperative hemoglobin A1C levels with complications following total joint arthroplasty is not well described. METHODS All patients undergoing elective primary total joint arthroplasty at our institution from 2004 through 2011 with both postoperative blood glucose and preoperative hemoglobin A1C levels were identified in a retrospective review. From among 1702 patients, those with wound complications within thirty days after the index arthroplasty were identified. A control group matched for exact age, sex, procedure, tourniquet use, surgical approach, and use of antibiotic cement was also created. Thirty patients met the study group inclusion criteria. The mean patient age was seventy-two years (range, fifty-three to eighty-nine years); the majority (53%) of patients were female. RESULTS The odds ratio for developing a wound complication was 3.75 (95% confidence interval, 1.25 to 11.22; p = 0.02) in patients with a mean postoperative glucose of >200 mg/dL, 3.0 (95% confidence interval, 0.97 to 9.30; p = 0.08) in patients with a maximum postoperative blood glucose of >260 mg/dL, and 9.0 (95% confidence interval, 1.14 to 71.20; p = 0.03) in patients with a preoperative hemoglobin A1C value of >6.7%. CONCLUSIONS Patients with a mean postoperative blood glucose of >200 mg/dL or a preoperative hemoglobin A1C level of >6.7% are at increased risk for wound complications following elective primary total joint arthroplasty. These results show that poor preoperative and postoperative glucose control is independently associated with wound complications.

Validity of using tri-axial accelerometers to measure human movement – Part II: Step counts at a wide range of gait velocities

A subject-specific step counting method with a high accuracy level at all walking speeds is needed to assess the functional level of impaired patients. The study aim was to validate step counts and cadence calculations from acceleration data by comparison to video data during dynamic activity. Custom-built activity monitors, each containing one tri-axial accelerometer, were placed on the ankles, thigh, and waist of 11 healthy adults. ICC values were greater than 0.98 for video inter-rater reliability of all step counts. The activity monitoring system (AMS) algorithm demonstrated a median (interquartile range; IQR) agreement of 92% (8%) with visual observations during walking/jogging trials at gait velocities ranging from 0.1 to 4.8m/s, while FitBits (ankle and waist), and a Nike Fuelband (wrist) demonstrated agreements of 92% (36%), 93% (22%), and 33% (35%), respectively. The algorithm results demonstrated high median (IQR) step detection sensitivity (95% (2%)), positive predictive value (PPV) (99% (1%)), and agreement (97% (3%)) during a laboratory-based simulated free-living protocol. The algorithm also showed high median (IQR) sensitivity, PPV, and agreement identifying walking steps (91% (5%), 98% (4%), and 96% (5%)), jogging steps (97% (6%), 100% (1%), and 95% (6%)), and less than 3% mean error in cadence calculations.

Validity of using tri-axial accelerometers to measure human movement - Part I: Posture and movement detection.

A robust method for identifying movement in the free-living environment is needed to objectively measure physical activity. The purpose of this study was to validate the identification of postural orientation and movement from acceleration data against visual inspection from video recordings. Using tri-axial accelerometers placed on the waist and thigh, static orientations of standing, sitting, and lying down, as well as dynamic movements of walking, jogging and transitions between postures were identified. Additionally, subjects walked and jogged at self-selected slow, comfortable, and fast speeds. Identification of tasks was performed using a combination of the signal magnitude area, continuous wavelet transforms and accelerometer orientations. Twelve healthy adults were studied in the laboratory, with two investigators identifying tasks during each second of video observation. The intraclass correlation coefficients for inter-rater reliability were greater than 0.95 for all activities except for transitions. Results demonstrated high validity, with sensitivity and positive predictive values of greater than 85% for sitting and lying, with walking and jogging identified at greater than 90%. The greatest disagreement in identification accuracy between the algorithm and video occurred when subjects were asked to fidget while standing or sitting. During variable speed tasks, gait was correctly identified for speeds between 0.1m/s and 4.8m/s. This study included a range of walking speeds and natural movements such as fidgeting during static postures, demonstrating that accelerometer data can be used to identify orientation and movement among the general population.

Shoulder demands in manual wheelchair users across a spectrum of activities.

OBJECTIVE Investigate shoulder joint kinetics over a range of daily activity and mobility tasks associated with manual wheelchair propulsion to characterize demands placed on the shoulder during the daily activity of manual wheelchair users. DESIGN Case series. SUBJECTS Twelve individuals who were experienced manual wheelchair users. METHODS Upper extremity kinematics and handrim wheelchair kinetics were measured over level propulsion, ramp propulsion, start and stop over level terrain, and a weight relief maneuver. Shoulder intersegmental forces and moments were calculated from inverse dynamics for all conditions. RESULTS Weight relief resulted in significantly higher forces and ramp propulsion resulted in significantly higher moments than the other conditions. Surprisingly, the start condition resulted in large intersegmental moments about the shoulder equivalent with that of the ramp propulsion, while the demand imparted by the stop condition was shown to be equivalent to level propulsion across all forces and moments. CONCLUSIONS This study provides characterization of daily living and mobility activities associated with manual wheelchair propulsion not previously reported and identifies activities that result in higher shoulder kinetics when compared to standard level propulsion.

Biomechanic Evaluation of Upper-Extremity Symmetry During Manual Wheelchair Propulsion Over Varied Terrain

OBJECTIVE To evaluate upper-extremity symmetry during wheelchair propulsion across multiple terrain surfaces. DESIGN Case series. SETTING A biomechanics laboratory and the general community. PARTICIPANTS Manual wheelchair users (N=12). INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Symmetry indexes for the propulsion moment, total force, tangential force, fractional effective force, time-to-peak propulsion moment, work, length of push cycle, and power during wheelchair propulsion over outdoor and indoor community conditions, and in laboratory conditions. RESULTS Upper-extremity asymmetry was present within each condition. There were no differences in the magnitude of asymmetry when comparing laboratory with indoor community conditions. Outdoor community wheelchair propulsion asymmetry was significantly greater than asymmetry measured during laboratory conditions. CONCLUSIONS Investigators should be aware that manual wheelchair propulsion is an asymmetrical act, which may influence interpretation when data is collected from a single limb or averaged for both limbs. The greater asymmetry identified during outdoor versus laboratory conditions emphasizes the need to evaluate wheelchair biomechanics in the users natural environment.

Effectiveness of home exercise on pain, function, and strength of manual wheelchair users with spinal cord injury: A high-dose shoulder program with telerehabilitation

OBJECTIVE To test the effectiveness of a high-dose home exercise/telerehabilitation program for manual wheelchair users who have a spinal cord injury (SCI) by determining whether the intervention would reduce pain and increase function, as we hypothesized. DESIGN A pre-post trial with outcomes measured at 3 time points: baseline, postintervention (12wk), and follow-up (>24 wk). SETTING Subjects performed an exercise program at their homes using telerehabilitation for therapist monitoring of technique and exercise advancement. Baseline and postintervention data were collected at a motion analysis laboratory in a tertiary medical center. PARTICIPANTS A convenience sample of manual wheelchair users (N=16, 3 women; average age, 41y; average time in a wheelchair, 16y) with shoulder pain (average pain duration, 9y) and mechanical impingement signs on physical examination. INTERVENTIONS A 12-week home exercise program of rotator cuff and scapular stabilization exercises was given to each participant. The program included a high dose of 3 sets of 30 repetitions, 3 times weekly, and regular physical therapist supervision via videoconferencing. MAIN OUTCOME MEASURES Primary outcomes of pain and function were measured with the Wheelchair Users Shoulder Pain Index (WUSPI), Disabilities of Arm, Shoulder, and Hand (DASH) Index, and Shoulder Rating Questionnaire (SRQ). Secondary outcomes of strength were measured with isometric strength tests of scapulothoracic and glenohumeral muscles, and a static fatigue test of the lower trapezius. RESULTS Pain was reduced and function improved after the intervention. There was a significant main effect for pain and function between the 3 time points based on the Friedman signed-ranked test, WUSPI (χ(2)2=5.10, P=.014), DASH Index (χ(2)2=5.41, P=.012), and SRQ (χ(2)2=23.71, P≤.001). Wilcoxon signed-rank tests demonstrated that isometric strength measurements of the serratus anterior and scapular retractors increased after the exercise intervention ([t=2.42, P=.04] and [t=4.67, P=.003], respectively). Muscle impulse produced by the lower trapezius during a fatigue task also improved (t=2.2, P=.02). No differences were measured in isometric strength for the lower trapezius, glenohumeral rotators, and abductors between the baseline and 12-week time points. CONCLUSIONS A high-dose scapular stabilizer and rotator cuff strengthening program using telerehabilitation for supervision holds promise for shoulder pain treatment in manual wheelchair users with SCI. Additional work is needed to determine the effectiveness compared with other interventions, as well as the potential for earlier intervention to prevent development of shoulder pain.

Wheelchair propulsion demands during outdoor community ambulation

OBJECTIVE Quantify manual wheelchair propulsion effort during outdoor community ambulation. DESIGN Case series. SUBJECTS Thirteen individuals (12 with SCI, 1 with spina bifida) who were experienced manual wheelchair users and had no current upper extremity injury or pain complaints. METHODS Measurements were obtained from instrumented wheelchair rims during steady-state propulsion as subjects traversed outdoor concrete sidewalk terrain that included smooth level, aggregate level, and a ramp with a smooth surface. Propulsion effort was assessed using the average propulsion moment, average instantaneous power, and work for both upper extremities. RESULTS Propulsion effort, captured by the propulsion moment, work and power, varied across ground conditions (p<0.001). Propulsion effort was greater as the rolling resistance increased (i.e., smooth versus aggregate surfaces) and as the inclination angle progressed from level to inclined surfaces. There were no side-to-side differences across ground conditions for the propulsion moment or work. Power generation was significantly greater on the dominant compared to the non-dominant extremity during the more challenging aggregate surface and ramp conditions. CONCLUSIONS Propulsion effort varies with demands imposed by different ground conditions. Quantification of wheelchair propulsion demands provides rehabilitations specialists with objective information to guide treatment of patients adapting to manual wheelchair use.

Scapula kinematics and associated impingement risk in manual wheelchair users during propulsion and a weight relief lift

BACKGROUND Shoulder impingement syndrome is a common upper extremity pathology in manual wheelchair users. Central to impingement is the orientation of the scapula and humerus as they determine the available subacromial space. The purpose of this study was to examine the scapulothoracic and glenohumeral internal/external rotation kinematics during the time of peak shoulder loading of propulsion and weight relief lift conditions to assess possible risk of impingement. METHODS Scapula, humerus and trunk kinematics were measured for twelve manual wheelchair users over three conditions: level propulsion, ramp propulsion, and a weight relief lift. Scapulothoracic and glenohumeral kinematic variables were characterized for the full cycle of each condition as well as at the period of peak loading. FINDINGS Common to all activities was an externally rotated glenohumeral joint and an anteriorly tilted and internally rotated scapula. At peak loading, glenohumeral internal/external rotation showed a significant difference between conditions, and post hoc analysis revealed that the weight relief lift displayed significantly less external rotation at peak loading when compared to level and ramp propulsion. INTERPRETATION All activities placed the scapula in a potentially dangerous orientation for development of shoulder impingement. The weight relief lift, with a decrease in glenohumeral external rotation and large superior forces at the shoulder, potentially places the shoulder of the manual wheelchair user at the greatest risk for impingement soft tissue injury. Preventative strength training and activity modification may provide measures to slow progression of impingement development and associated pain in the manual wheelchair user.

Shoulder model validation and joint contact forces during wheelchair activities

Chronic shoulder impingement is a common problem for manual wheelchair users. The loading associated with performing manual wheelchair activities of daily living is substantial and often at a high frequency. Musculoskeletal modeling and optimization techniques can be used to estimate the joint contact forces occurring at the shoulder to assess the soft tissue loading during an activity and to possibly identify activities and strategies that place manual wheelchair users at risk for shoulder injuries. The purpose of this study was to validate an upper extremity musculoskeletal model and apply the model to wheelchair activities for analysis of the estimated joint contact forces. Upper extremity kinematics and handrim wheelchair kinetics were measured over three conditions: level propulsion, ramp propulsion, and a weight relief lift. The experimental data were used as input to a subject-specific musculoskeletal model utilizing optimization to predict joint contact forces of the shoulder during all conditions. The model was validated using a mean absolute error calculation. Model results confirmed that ramp propulsion and weight relief lifts place the shoulder under significantly higher joint contact loading than level propulsion. In addition, they exhibit large superior contact forces that could contribute to impingement. This study highlights the potential impingement risk associated with both the ramp and weight relief lift activities. Level propulsion was shown to have a low relative risk of causing injury, but with consideration of the frequency with which propulsion is performed, this observation is not conclusive.

Upper-limb joint kinetics expression during wheelchair propulsion

In the wheelchair propulsion literature, it is common to report upper-limb (UL) joint kinetics to express shoulder, elbow, and wrist loads. Choosing the appropriate kinetic resolution coordinate system (CS) for UL joint forces and moments has become a laboratory-specific process. The differences that arise during interpretation may hinder a clear and broad understanding of UL joint kinetics during wheelchair propulsion. This article addresses the inconsistency of kinetic reporting in the wheelchair literature that examines the pain and injury experienced by manual wheelchair users. To highlight the variety of reporting methods in wheelchair propulsion, this article surveys peer-reviewed, published articles reporting wrist-, elbow-, or shoulder-joint intersegmental forces and moments calculated from inverse dynamics during wheelchair propulsion. To correct this inconsistency, researchers may need to standardize kinetic reporting methods to achieve a cohesive comprehension of wheelchair biomechanics. This article is provided to open discussion on the anatomical and clinical relevance of currently employed CSs and other available options, with the additional goal of providing an initial recommendation for kinetic representation during wheelchair propulsion.