Kristina M. Calder

Relationship of intermuscular fat volume in the thigh with knee extensor strength and physical performance in women at risk of or with knee osteoarthritis

To determine the extent to which thigh intermuscular fat (IMF) and quadriceps muscle (QM) volumes explained variance in knee extensor strength and physical performance in women with radiographic knee osteoarthritis (ROA) and without.

Motor unit potential morphology differences in individuals with non-specific arm pain and lateral epicondylitis

BackgroundThe pathophysiology of non-specific arm pain (NSAP) is unclear and the diagnosis is made by excluding other specific upper limb pathologies, such as lateral epicondylitis or cervical radiculopathy. The purpose of this study was to determine: (i) if the quantitative parameters related to motor unit potential morphology and/or motor unit firing patterns derived from electromyographic (EMG) signals detected from an affected muscle of patients with NSAP are different from those detected in the same muscle of individuals with lateral epicondylitis (LE) and/or control subjects and (ii) if the quantitative EMG parameters suggest that the underlying pathophysiology in NSAP is either myopathic or neuropathic in nature.MethodsSixteen subjects with NSAP, 11 subjects with LE, eight subjects deemed to be at-risk for developing a repetitive strain injury, and 37 control subjects participated. A quantitative electromyography evaluation was completed using decomposition-based quantitative electromyography (DQEMG). Needle- and surface-detected EMG signals were collected during low-level isometric contractions of the extensor carpi radialis brevis (ECRB) muscle. DQEMG was used to extract needle-detected motor unit potential trains (MUPTs), and needle-detected motor unit potential (MUP) and surface detected motor unit potential (SMUP) morphology and motor unit (MU) firing rates were compared among the four groups using one-way analysis of variance (ANOVA). Post hoc analyses were performed using Tukeys pairwise comparisons.ResultsSignificant group differences were found for all MUP variables and for MU firing rate (p < 0.006). The post-hoc analyses revealed that patients with NSAP had smaller MUP amplitude and SMUP amplitude and area compared to the control and LE groups (p < 0.006). MUP duration and AAR values were significantly larger in the NSAP, LE and at-risk groups compared to the control group (p < 0.006); while MUP amplitude, duration and AAR values were smaller in the NSAP compared to the LE group. SMUP duration was significantly shorter in the NSAP group compared to the control group (p < 0.006). NSAP, LE and at-risk subjects had lower mean MU firing rates than the control subjects (p < 0.006).ConclusionThe size-related parameters suggest that the NSAP group had significantly smaller MUPs and SMUPs than the control and LE subjects. Smaller MUPs and SMUPs may be indicative of muscle fiber atrophy and/or loss. A prospective study is needed to confirm any causal relationship between smaller MUPs and SMUPs and NSAP as found in this work.

Knee power is an important parameter in understanding medial knee joint load in knee osteoarthritis.

To determine the extent to which knee extensor strength and power explain variance in knee adduction moment (KAM) peak and impulse in clinical knee osteoarthritis (OA).

Muscle activation during hand dexterity tasks in women with hand osteoarthritis and control subjects.

STUDY DESIGNnDescriptive cross-sectional study.nnnINTRODUCTIONnHand osteoarthritis (OA) is a condition that results in hand pain and disability. It is important to understand how muscle function impairments contribute to impaired dexterity.nnnPURPOSE OF THE STUDYnTo compare muscle activation in women with and without hand OA and determine if the activation relates to measures of impairment and disability.nnnMETHODSnElectromyography (EMG) was recorded from four muscles of the hand/forearm while subjects threaded (assembly) and unthreaded (disassembly) a small bolt. The groups were compared on the integrated EMG (IEMG) of four muscles using two-way repeated-measures analyses of covariance for the assembly and disassembly tasks.nnnRESULTSnNo differences were found in muscle activation between groups when IEMG values were normalized by time (p>0.05).nnnCONCLUSIONSnPatients with OA have some indicators of altered muscle function. It is unclear whether these are adaptive or predisposing changes. When controlling for the time to perform a task, there were no significant IEMG differences between women with hand OA and control subjects.nnnLEVEL OF EVIDENCEn2b.

Comparison of pQCT-Based Measures of Radial Bone Geometry and Apparent Trabecular Bone Structure Using Manufacturer and In-House-Developed Algorithms

Peripheral quantitative computed tomography (pQCT) provides noninvasive densitometric and morphometric measures of total, trabecular, and cortical bone compartments. Skeletal changes over time can be determined by repeated measurements. Image thickness of 2.5mm is thought to be advantageous with respect to test-retest reliability through interrogation of a significant tissue volume. However, the error associated with slight shifts in image location is unknown. The primary purpose of this study was to determine the effects of positional variability around the 4% site on radial bone measures. The secondary objective was to compare different software algorithms for estimating the same bone characteristics. Eight left cadaveric forearms (aged 65-88 yr) were imaged at 0.5-mm intervals around the 4% site of the radial bone using pQCT (10 slices; in-plane resolution: 0.2 × 0.2mm; thickness: 2.5mm; Stratec XCT2000L. We used the manufacturers software (Stratec v6.0B) to determine the total bone mineral density (BD_tot), total bone mineral content (BMC_tot), total bone area (Area_tot), trabecular bone mineral density (BD_trab), trabecular bone mineral content (BMC_trab), and trabecular bone area (Area_trab) from each image. For comparison, in-house-developed software was also used to analyze Area_tot and Area_trab at the 4% site. The in-house software also produced measures of apparent trabecular structure, including number (App.Tb.N), thickness (App.Tb.Th), and spacing (App.Tb.Sp), quantified using 2 different stereological approaches: the parallel-plate method using trabecular perimeter lengths and mean intercept length analysis. The effect of slice position was assessed using a 1-way repeated-measures analysis of variance (ANOVA). Reliability of nonsignificant slice distances around the 4% site was determined using intraclass correlation coefficients (ICCs). One-way repeated-measures ANOVA was used to compare measures of similar bone characteristics at the 4% site. Bland-Altman plots were created to assess the level of agreement between pairs of algorithms quantifying comparable apparent trabecular structure. Area_tot and Area_trab differed significantly at greater than or equal to 1.0mm proximal and greater than or equal to 0.5mm distal to the 4% site. BMC_tot and BMC_trab differ significantly greater than or equal to 1.5mm proximally (for both) and greater than or equal to 2.0 and 1.0mm distally, respectively. BD_tot differed significantly at greater than or equal to 1mm proximal and distal to the 4% site. BD_trab did not differ among the 10 slices. For images acquired at the 4% site, and 0.5mm more proximally, reliability was excellent (ICC=0.98 to 0.99). Although the in-house software yielded a higher value for Area_tot and Area_trab at the 4% site (p<0.05), no systematic bias was observed. The parallel-plate method yielded higher values for App.Tb.N and lower values for App.Tb.Th (p<0.05), with no systematic bias. App.Tb.Sp values were smaller using the parallel-plate method, and the difference in methods increased as App.Tb.Sp values increased. Statistically, tolerance for repositioning around the 4% site of the radial bone is least for measures of bone area and greatest for BD_trab. On repeated measures, a proximal shift of 0.5mm will not influence the results.

Sensory nerve action potentials and sensory perception in women with arthritis of the hand

BackgroundArthritis of the hand can limit a person’s ability to perform daily activities. Whether or not sensory deficits contribute to the disability in this population remains unknown. The primary purpose of this study was to determine if women with osteoarthritis (OA) or rheumatoid arthritis (RA) of the hand have sensory impairments.MethodsSensory function in the dominant hand of women with hand OA or RA and healthy women was evaluated by measuring sensory nerve action potentials (SNAPs) from the median, ulnar and radial nerves, sensory mapping (SM), and vibratory and current perception thresholds (VPT and CPT, respectively) of the second and fifth digits.ResultsAll SNAP amplitudes were significantly lower for the hand OA and hand RA groups compared with the healthy group (pu2009<u20090.05). No group differences were found for SNAP conduction velocities, SM, VPT, and CPT.DiscussionWe propose, based on these findings, that women with hand OA or RA may have axonal loss of sensory fibers in the median, ulnar and radial nerves. Less apparent were losses in conduction speed or sensory perception.