Journal of Hand Therapy 28 (2015) 39e45

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Scientific/Clinical Article

The relationship between the Patient-rated Ulnar Nerve Evaluation and the common impairment measures of grip strength, pinch strength, and sensation Mike Szekeres PhD(c), OT Reg (Ont), CHT a, *, Joy C. MacDermid PT, PhD b, c, Graham J.W. King MD, MSc, FRCSC c, d, Ruby Grewal MD, MSc, FRCSC c, d a

Health and Rehabilitation Sciences, Western University, London, Ontario, Canada School of Rehabilitation Science, McMaster University, Hamilton, Ontario, Canada c The Roth McFarlane Hand and Upper Limb Centre, London, Ontario, Canada d Department of Surgery, Western University, London, Ontario, Canada b

a r t i c l e i n f o

a b s t r a c t

Article history: Received 3 July 2014 Accepted 9 October 2014 Available online 17 October 2014

Study design: Prospective cohort study. Introduction: Grip strength, pinch strength, and sensory threshold are common evaluations used on a daily basis. Identifying how these variables relate to function for patients allows these assessments to be used for screening to identify who may benefit from surgical intervention, and provides valuable information about what impairments patients think are important with respect to functional use of their upper extremity. Therapists can use this information to focus rehabilitation programs on the most important impairments. Purpose: To evaluate the relationship between the Patient-rated Ulnar Nerve Evaluation (PRUNE) and impairment measures of grip strength, pinch strength, and one-point sensory threshold. Methods: Data was prospectively collected from 77 patients before surgery and during regular time points for 2 years following surgery. Patients completed the PRUNE, grip and pinch strength measures, and a onepoint sensory threshold evaluation. Correlations between these variables were calculated at baseline, 2 years after surgery, and for change scores during the 2-year follow up. A multiple regression analysis was used to determine the contribution of the impairment variables for determining functional change. Results: Grip strength showed moderate, statistically significant correlation with PRUNE scores at both baseline (r ¼ 0.38) and at two years (r ¼ 0.29). There was also a statistically significant correlation between one point sensory threshold for the small finger at two years (r ¼ 0.36), but not at baseline. Change in grip strength (r ¼ 0.28) and pinch strength (r ¼ 0.30) both demonstrated significant correlations with PRUNE change scores. Overall, changes in grip strength, pinch strength, and sensation accounted for 20% of the variance in PRUNE changes. Conclusion: Since grip strength was most highly correlated with PRUNE scores at baseline and at two years, rehabilitation programs that target grip strengthening is supported. While neither grip nor pinch strength were significant contributors to the regression when used together, each showed significant contributions to PRUNE variability when used in the model independently. Therefore, a combination of grip and pinch strengthening may be important during rehabilitation for improving functional results in patients that undergo surgical intervention for cubital tunnel syndrome. Level of evidence: 2b Ó 2015 Hanley & Belfus, an imprint of Elsevier Inc. All rights reserved.

Keywords: PRUNE Nerve compression Ulnar nerve Outcome measures

Introduction

* Corresponding author. 1832 Stackhouse Crescent, London, Ontario N5X 4M6, Canada. Tel.: þ1 519 709 4263. E-mail address: [email protected] (M. Szekeres).

Entrapment of the ulnar nerve within the cubital tunnel of the elbow is the second most common peripheral nerve compression in the upper limb.1 Commonly referred to as cubital tunnel syndrome (CuTS), the mean annual incidence is higher in men than women,

0894-1130/$ e see front matter Ó 2015 Hanley & Belfus, an imprint of Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jht.2014.10.003

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M. Szekeres et al. / Journal of Hand Therapy 28 (2015) 39e45

and has been estimated in the range of 25e33 cases per 100,000 person-years for men and 17 to 19 cases per 100,000 person-years for women.1,2 The higher incidence in men may be due to job related factors and prolonged flexion postures of the elbow during work. This is suggested by the higher incidence in manual jobs, having been reported as high as 57 cases per 100,000 personyears.2 A recent study reported that smoking was associated with an elevated risk (OR ¼ 4.3) of ulnar neuropathy.3 Other potential risk factors for CuTS may include education level, work experience, and diabetes.4,5 The ulnar nerve is susceptible to entrapment on the medial side of the elbow in several areas. These areas include the arcade of struthers, the medial inter-muscular septum, the medial epicondyle, the cubital tunnel, and under an anomalous muscle called the anconeus epitrochlearis. Ulnar neuropathy at the elbow (UNE) is an umbrella term that includes compression of the nerve at any of these sites, however, compression is still most often referred to as CuTS, regardless of the precise site of compression. The actual cubital tunnel extends from the medial epicondyle for approximately 2 cm distally. The floor is the medial collateral ligament of the elbow. The roof of the tunnel lies between the two heads of the flexor carpi ulnaris muscle under a variably sized band of tissue called the cubital tunnel retinaculum.6 This retinaculum is drawn taut with flexion of the elbow and can compress the nerve beneath. The nerve can also be stretched or elongated with prolonged elbow flexion.7 Distal to the aforementioned sites of compression, the ulnar nerve supplies the ulnar heads of the flexor digitorum profundus muscles, the flexor carpi ulnaris, most of the hand intrinsic muscles, and sensation to the small finger, the ulnar half of the ring finger, and the ulnar border of the hand. Based on this anatomical course of the ulnar nerve, the potential physical impairments related to CuTS include decreased grip strength, pinch strength, finger dexterity, and sensibility in the ulnar nerve distribution. Treatment for CuTS often starts with conservative approaches and progresses to surgical management if nerve dysfunction and associated symptoms and disability do not resolve. A recent trial of extension splinting has shown that conservative management can be a successful management option, with 21 of 24 patients successfully avoiding surgical intervention with the use of a night-time thermoplastic extension orthosis.8 Operation rates for patients that report to general medical practices with CuTS have been reported at 30%, and this is likely higher for patients referred to specialty surgical centers.1 The surgical procedure for treatment of CuTS may include either simple decompression or anterior ulnar nerve transposition, with good evidence supporting both interventions.9e12 With both decompression and nerve transposition, sensory and motor recovery is expected if the nerve compression is not too severe or prolonged. The outcome measures used across clinical trials for measuring this recovery are variable, making it more difficult to compare outcomes across studies. Several patient-reported and clinician-based outcome measures have been used to evaluate the functional limitations for patients with elbow pathology. These include the Patient-rated Ulnar Nerve Evaluation (PRUNE)13 which is specific to CuTS, and measures that focus on the upper limb disability like the Disabilities of the Arm, Shoulder, and Hand Questionnaire (DASH) which has been validated for CuTS.14,15 There are also measures that focus on elbow-related pain and disability such as the Patient Rated Elbow Evaluation (PREE).16,17 A clinician-based ulnar nerve outcome measure, the Bishop Rating Scale has also been used as an outcome measure but has yet to be reported. The PRUNE is an open access, self-reported measure that consists of 20-items that focus on ulnar-nerve related sensory/motor deficits and associated functional disability. The PRUNE has recently been shown to have excellent reliability and responsiveness for

individuals with CuTS, with an intra-class coefficient for total score of 0.98 and a standardized response mean of 1.55.13 A minimal detectable change of 7.1 points discriminates between clinically important subgroups based on work status, residual symptoms, motor recovery, and sensory recovery. As mentioned, CuTS may lead to impairment of grip strength, pinch strength, dexterity, and sensibility. The relationship between these impairment-based changes and overall functional limitation remains unclear. Measures of grip strength, pinch strength, and sensation are often measured clinically and can be used to inform decisions about treatment, functional status, or ability to return to work. Therefore, the knowledge of how these measures are related to function is important. Understanding the relative contribution of grip strength, pinch strength, and sensation to function can guide the design of rehabilitation programs and outcome measurement strategies. A recent systematic review of potential factors that predict outcomes following ulnar nerve transposition reported that “we were unable to conclude which predictor(s) affect surgical outcomes after anterior transposition of the ulnar nerve.”18 The purpose of this study was to estimate, in patients evaluated preoperatively and two years following ulnar nerve transposition, the extent to which 1) baseline and follow-up grip strength, pinch strength, and sensory scores are associated with functional outcomes as measured by the PRUNE and 2) changes in these impairment measures explain changes in function (PRUNE scores) in the two years following nerve transposition. Methods Subjects The data for this prospective cohort study was collected as part of a two year study of patients undergoing ulnar nerve transposition at the Roth McFarlane Hand & Upper Limb Centre.19 Patients were included in the study if they were over 18 years of age, had a CuTS diagnosis confirmed electrically and clinically by a fellowship trained upper extremity surgeon, and underwent surgical intervention. Surgical intervention was either a submuscular or a subcutaneous anterior transposition of the ulnar nerve. Surgery was performed by one of seven experienced upper limb surgeons. Exclusion criteria included previous surgical intervention for CuTS, age less than 18 years, inability to complete self-report outcome measures, or inability to return for follow up that was identified a priori. Outcome measures All patients were evaluated at the Roth McFarlane Hand & Upper Limb Centre Clinical Research Laboratory by a researcher not involved in the clinical care of the patient. The study was approved by the Western University Research Ethics Board. All patients provided written consent for participation. Impairments were measured using standardized procedures. Outcome measures included grip strength, lateral pinch strength, one-point sensory threshold using the Pressure Specified Sensory Device (PSSD), and the PRUNE before surgery and then at regular time points for two years following surgery. Lateral pinch was chosen rather than tripod pinch since this would most likely be affected during CuTS. All grip and pinch strength measures were recorded using an NK Biotechnical Corporation Hand Assessment System DIGIT-grip Device (Model DGR 001) using standardized positioning. Three trials of each measurement were recorded and then averaged by the device to record a score for each time point. This method has been

M. Szekeres et al. / Journal of Hand Therapy 28 (2015) 39e45

shown to have excellent test-retest reliability for grip and pinch strength measurement.20,21 The Pressure Specified Sensory Device (PSSD) is an electronic measurement tool used to evaluate sensory thresholds and two point discrimination. Psychometric properties of this device are well established, with excellent reliability (r ¼ 0.95) in patients with neuropathy.22,23 The PSSD has been shown to have equivalent sensitivity to nerve conduction studies for the diagnosis of carpal tunnel syndrome, and has been an effective diagnostic aid for other peripheral neuropathies.24,25 The PSSD was used in this study to evaluate static one point sensory threshold. The patient was in a seated position, with the hand on a cushion for support. With the patient’s vision occluded, the probe was placed on the area to be measured. The patient then recorded a positive response to the stimulus by pressing a button. Pressure threshold was then recorded by the device, with a range of 0.1e100 g/square mm. Measurements were taken at the small finger pulp as this corresponds with the sensory distribution of the ulnar nerve. Analysis

Table 1 Demographic data Mean (range)

Gender Male Female Dominance Right Left Affected side Right Left

Table 2 Pearson correlations with the PRUNE at baseline and at two year follow up

Grip strength Correlation Sig. (2-tailed) Lateral pinch Correlation Sig. (2-tailed) PSSD small finger Correlation Sig. (2-tailed) Age Correlation Sig. (2-tailed)

Baseline PRUNE

2 year follow up PRUNE

0.38a 0.001

0.29a 0.009

0.22 0.06

0.14 0.22 0.36a 0.001

0.09 0.45

0.11 0.32

0.09 0.45

a Significant after modified Bonferroni correction to control for multiple comparisons.

model. Finally, both grip and pinch strength were forced into the model along with sensation, age, and gender. Results

From a total of 89 eligible patients in the cohort, 77 patients (57 males and 20 females) were included in the analysis. Nine patients decided not to proceed with surgery and were ineligible for the study. Three of the 80 eligible patients had baseline measurements but did not return for at least two of the measurement sessions during the follow up period and were excluded. Recorded demographic data included age, gender, dominance, duration of symptoms, and affected side (Table 1). Pearson correlations between pinch strength, grip strength, PSSD, age, and PRUNE scores were calculated for baseline and at two years postoperatively. Correlations were also computed for change scores on these variables to determine if changes in the impairment-based variables were related to a change in the PRUNE. For all comparisons, a modified Bonferroni correction was used to control for multiple comparison error.26 Multiple regression analysis was then performed on the change scores to determine the extent to which changes in grip strength, pinch strength, and PSSD scores predicted changes in the PRUNE. Age and gender were also entered as variables into each model to evaluate their contribution to overall variance in the PRUNE. Due to the expectations of co-linearity between grip and pinch strength for predicting changes in PRUNE, the following steps were taken in the regression analysis. Firstly, change scores for grip and pinch strength were entered into separate models with the other independent variables to determine their unique effect for predicting PRUNE change. Next, a stepwise regression was performed for all variables, allowing the statistical program to determine the best

Duration of symptoms Age

41

22.1 months (1e180) 52.7 years (20e81) Frequency

Percent

57 20

74.0 26.0

70 6

92.1 7.9

31 46

40.3 59.7

Pearson correlations for all variables with the PRUNE, taken at baseline and again at two years postoperatively, are shown in Table 2. Grip strength showed moderate, statistically significant correlation with PRUNE scores at both baseline (r ¼ 0.38) and at two years (r ¼ 0.29). There was also a statistically significant correlation between one point sensory threshold for the small finger at two years (r ¼ 0.36), but not at baseline. The absolute PRUNE scores were not correlated significantly with any other variable at baseline or at two years. Overall changes in each of the variables are presented in Table 3. The mean differences between the pre-operative and two year time points, with 95% confidence intervals, were 18.87 (14.27, 23.48) for PRUNE, 4.59 kg (2.79, 6.39) for grip strength, 1.43 kg (0.99, 1.86) for pinch strength, and 2.01 g/square mm (0.39, 3.63) for PSSD to the small finger. All differences were significant (p < 0.05). The relative effect sizes for these change scores were e 0.93 for PRUNE, 0.58 for grip strength, 0.75 for pinch strength, and e 0.28 for the PSSD to the small finger. Pearson correlations for change scores on impairment variables and PRUNE change scores are shown in Table 4. Change in grip strength (r ¼ 0.28) and pinch strength (r ¼ 0.30) both demonstrated significant correlations with PRUNE change scores using a modified Bonferroni correction. One-point sensory threshold change scores and participant age did not demonstrate significant correlations with changes in the PRUNE. Results from the multiple regression analysis, showing overall fit of the regression lines and beta weights for each variable, are shown in Tables 5e8. Four models were created from the analysis. The first two models illustrate the contribution of grip and pinch strength change scores independent from each other. The third model highlights the results of a stepwise regression. The final model includes all variables forced into the analysis.

Table 3 Summary of change scores

PRUNE score Grip strength (kg) Lateral pinch (kg) PSSD small finger (g/square mm)

Mean change over two years (95% confidence interval)

Effect size

18.87 4.59 1.43 2.01

0.93 0.58 0.75 0.28

(14.27, 23.48) (2.79, 6.39) (0.99, 1.86) (0.39, 3.63)

All variables demonstrated significant change in the two years following surgery.

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M. Szekeres et al. / Journal of Hand Therapy 28 (2015) 39e45

Table 4 Correlations of change scores with changes in the PRUNE PRUNE change

Model summary

Grip strength change Correlation Sig. (2-tailed) Lateral pinch change Correlation Sig. (2-tailed) PSSD small finger change Correlation Sig. (2-tailed) Age Correlation Sig. (2-tailed)

0.28 0.015 0.30a 0.008 0.19 0.09 0.005 0.97

When including grip or pinch strength change scores independently from each other into separate models, both variables are significant predictors of changes in the PRUNE when the other is omitted (Tables 5 and 6). The overall fit of the regression lines for these first two models (R2 ¼ 0.15 and R2 ¼ 0.17) are similar whether grip strength or pinch strength change scores are included in the model, respectively. With a stepwise regression, all non-significant contributors to the model are excluded. The correlation between changes in pinch and PRUNE (r ¼ 0.3) were slightly higher than grip strength changes and PRUNE (r ¼ 0.28). Due to the co-linearity between grip and pinch strength, only pinch strength remains in the stepwise model and grip strength change and all other variables are removed (Table 7). With grip strength removed, the overall fit of the regression line for predicting PRUNE change reduces significantly (R2 ¼ 0.09). The best model for predicting changes in the PRUNE is the fourth model that includes all variables. Overall, changes in grip strength, pinch strength, and sensation accounted for 20% of the variance in PRUNE changes (R2 ¼ 0.20), with age and gender included in the model (Table 8). Due to the co-linearity between grip and pinch strength, no individual variable had a significant beta weight within the model, but the overall fit of the regression line was higher than any other model.

Discussion This study illustrates that impairments in grip, pinch and sensation can contribute to functional disability, while strength measures are more strongly and consistently associated with functional improvements following surgery. The effect sizes of functional improvements following surgery were largest in selfreported symptoms and disability and were observed to a lesser

Table 5 Model 1: Grip strength change scores, PSSD change, age, and gender (pinch strength change omitted) R2

Adjusted R2 0.15

0.10

Adjusted R2 0.17

0.12

Standard error 19.01

Coefficients

Beta

Significance

95% confidence interval

Constant Pinch strength change PSSD change Age Gender

12.84 3.23 0.69 0.04 8.38

0.17 0.006a 0.03 0.80 0.10

31.08, 5.51, 0.07, 0.29, 18.47,

5.39 0.94 1.31 0.37 1.70

a Significant after modified Bonferroni correction to control for multiple comparisons.

extent in impairments with an order of decreasing effects in grip, pinch and sensation. Absolute grip strength scores showed the highest bivariate correlation with PRUNE scores at baseline and at our two year follow up time. The correlation between grip strength and PRUNE scores is consistent with other studies indicating that grip contributes to hand function in hand conditions.27,28 Grip strength has been shown to be a reasonable surrogate measure for several other aspects of physical impairment and function, and has also been shown to decrease significantly as CuTS progresses.15,29 Decreased grip strength also correlates with increased pain for both elbow injuries and other general orthopedic conditions.30,31 Even in earlier stages of CuTS, the forceful contraction of the flexor pronator origin that is required during grip strength assessment may compress the ulnar nerve and cause an inhibitory effect due to a pain response. The PRUNE consists of a 20-item scale that measures sensory/ motor deficits and associated functional disability, but six of these items ask specifically about pain. Thus, some of the association between grip and PRUNE scores may reflect pain-related muscle inhibition. Several items on the PRUNE may have reflected more direct relationships with grip strength, such as holding an object for one hour, lifting a heavy object, household cleaning and maintenance, work, and a specific question about hand weakness. Pinch strength has been shown to progressively decrease with advanced stages of CuTS,15 reflecting the contributions of the ulnar nerve innervated muscles. Despite this, absolute values of pinch strength did not hold significant correlations with PRUNE scores in our study. Pinch strength assessment does not require the same level of contraction of the entire flexor-pronator group as required for grip and may not lead to the same inhibitory pain response during maximal strength assessment. For this reason, the correlation between the pain items on the PRUNE and pinch strength are likely less relevant. Another potential reason for absolute pinch strength scores to be less related to PRUNE scores at baseline and at two year follow up is the small number of items on the PRUNE where pinch strength may be integral to the task. The one item that asks specifically about hand weakness refers to both grip and pinch strength. Of the 10 items that evaluate functional limitation, only 3 items are likely affected by decreased pinch strength. These items

Standard error 19.21

Coefficients

Beta

Significance

95% confidence interval

Constant Grip strength change PSSD change Age Gender

10.50 0.71 0.65 0.03 8.38

0.27 0.01a 0.04 0.85 0.10

29.34, 1.27, 0.03, 0.37, 18.47,

a

R2

a

a Significant after modified Bonferroni correction to control for multiple comparisons.

Model summary

Table 6 Model 2: Pinch strength change scores, PSSD change, age, and gender (grip strength change omitted)

8.33 0.15 1.28 0.34 1.70

Significant after modified Bonferroni correction to control for multiple comparisons.

Table 7 Model 3: Stepwise regression Model summary

R2

Adjusted R2 0.09

0.08

Standard error 19.50

Coefficients

Beta

Significance

95% confidence interval

Constant Pinch strength change

14.35 3.17

0.001 0.008

19.89, 8.81 5.50, 0.84

M. Szekeres et al. / Journal of Hand Therapy 28 (2015) 39e45 Table 8 Model 4: All variables entered into the model Model summary

R2

Adjusted R2 0.20

0.13

Standard error 18.88

Coefficients

Beta

Significance

95% confidence interval

Constant Grip strength change Lateral pinch change PSSD change Age Gender

10.80 4.30 2.30 0.31 0.01 7.58

0.25 0.17 0.08 0.53 0.94 0.14

29.39, 1.05, 4.85, 0.67, 0.32, 17.58,

7.79 0.19 0.26 1.29 0.35 2.42

are eating, tasks with repetitive finger use, and personal care activities. Given that patients in our study had an average of 22 months of symptoms prior to surgery, many would likely have developed compensatory strategies for accomplishing these tasks over time. Since pinch represents a smaller group of muscles and a smaller range of force, the precision of the tool and scale issues may also have affected correlations. This is not to say pinch was unimportant as it did correlate with hand function e although to a lesser extent than grip strength measures. One point sensory threshold at the small finger demonstrated a significant correlation with PRUNE scores at our two year follow up, but not at baseline. With CuTS, there is potential to have both sensory and motor impairment. Typically, sensation is affected earlier with CuTS and motor changes occur in the later stages.32 The mean amount of time between onset of symptoms and surgery was 22 months in this study, and most patients had a combination of sensory and motor involvement. Since there was nearly two years from the onset of symptoms to study enrollment, nearly all patients had sensory involvement. This led to limited variability in one point sensory threshold measures at baseline and could have restricted correlation with the PRUNE at this time point. Recovery of sensation usually happens more quickly and predictably after surgery for nerve compression or trauma than motor recovery.32,33 If at two years following surgery, a patient still has sensory impairment in the ulnar nerve distribution, this indicates that their overall function remains limited despite surgical intervention. This may partially explain why sensory impairment was correlated at follow up only. In addition to looking at simple correlations between impairment measures and the PRUNE at individual time points, we also wanted to evaluate changes over time. This information is important for rehabilitation, as it can inform therapists of the important physical components to target during therapy programs. Overall, changes in pinch strength and grip strength were significantly correlated with changes in the PRUNE, while changes in sensation were not. The best correlation (r ¼ 0.3) was between improvement in pinch strength and PRUNE change scores. As mentioned, motor recovery is not as complete as sensory recovery following surgical intervention for nerve compression or trauma. A postoperative improvement in pinch strength in the hand (a long distance from the site of compression) is likely due to improved function of the intrinsic muscles. Patients fortunate enough to see positive changes in intrinsic muscle function following ulnar nerve transposition are likely experiencing a significant improvement in overall nerve recovery, and thus changes on the PRUNE. Changes in grip strength also showed a statistically significant correlation (r ¼ 0.28) with PRUNE change scores, indicating that as patient’s grip strength improved, so did their PRUNE score. Just as with the absolute measures, this is not surprising since improved grip strength could be an indicator of decreased pain and improved nerve function. Many of the items on the PRUNE also seem to directly rely on grip strength. Sensation measures may exhibit

43

moderate34e36 to high37,38 reliability and this can vary by modality, instrument, and clinical population. The PSSD has been shown to be less related to self-reported function and dexterity than vibrometry in patients with CTS, suggesting that lower correlations in CuTS are consistent with these findings.39 The multiple regression analyses evaluated the ability of the changes in our impairment-based measures, along with demographic factors of age and gender, to predict functional change on the PRUNE. Our best regression model (Model 4) was able to predict 20% of the variance on the PRUNE, and none of the individual variables carried significant Beta weights when they were all forced into the model at once. Prediction of disability is a very complex phenomenon and many factors could potentially impact a PRUNE score. These may include pain, dexterity, proprioception, general health, literacy, and other external factors like worker’s compensation. The overall fit of our regression (R2) is similar to other studies using a collection of individual variables to predict disability.40 Of interest, changes in pinch strength and grip strength were both significantly correlated with PRUNE changes. Yet, when forced into a multiple regression analysis together, neither carried a significant beta weight. This is likely due to the co-linearity between grip strength and pinch strength. To test this, we removed each from the regression model in turn. When this is done, the overall fit of the regression is decreased by 3e5% (R2 ¼ 0.15e0.17) in each case. When pinch strength is removed from the model, change in grip strength becomes a significant contributor to predicting PRUNE change. When grip strength is removed, change in pinch strength becomes significant. While both variables have significant correlations with PRUNE changes, the co-linearity between these two variables effectively cancels out their individual contributions to the regression model when entered into the model at once. The regression model that best predicts changes in PRUNE includes both grip and pinch strength, suggesting that rehabilitation programs should focus on both grip and pinch to achieve the best functional outcomes. This study was subject to limitations that affect internal validity and generalization. A larger sample size would have increased precision in our estimates, and variability resulting from having different surgeons and types of ulnar nerve transposition may have weakened associations. Grip strength might be affected by reflecting the flexor pronator group during surgery for some patients and not for others. Since we did not control for the type of surgery/surgeon, we cannot estimate the impact of these factors. The associations found in our study apply to moderate to severe CuTS in a tertiary care population. Clinical implications Grip strength, pinch strength, and sensory threshold are common evaluations used by hand therapists on a daily basis. Identifying how these variables relate to function for patients with CuTS is important for three reasons. First, it allows these assessments to be used for screening purposes to identify what patients might benefit from surgical intervention. Second, it provides valuable information about what impairments patients think are important with respect to functional use of their upper extremity. Finally, therapists can use this information to focus rehabilitation programs on the most important impairments. Since grip strength was most highly correlated with PRUNE scores at baseline and at two years, rehabilitation programs that target grip strengthening is supported. A residual limitation in one point sensory threshold at two years post-operatively correlated with poorer PRUNE scores suggesting that sensory measures may be relative measures, but the lower associations with function and

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improvement suggest that these measures should not be used in isolation to make clinical judgments. Further research on different sensory evaluations for CuTS are needed. Since our chosen impairment-based variables were able to explain 20% of the variability in PRUNE change scores, other impairments and patient factors should be considered in future models. These may include intrinsic muscle strength, type of job, worker’s compensation status, and other patient health factors such as smoking status, diabetes, and general fitness level. While neither grip nor pinch strength were significant contributors to the regression when used together, each showed significant contributions to PRUNE variability when used in the model independently. Therefore, a combination of grip and pinch strengthening may be important during rehabilitation for improving functional results in patients that undergo surgical intervention for cubital tunnel syndrome. References 1. Latinovic R, Gulliford MC, Hughes RA. Incidence of common compressive neuropathies in primary care. J Neurol Neurosurg Psychiatry. 2006 Feb;77(2): 263e265. 2. Mondelli M, Giannini F, Ballerini M, Ginanneschi F, Martorelli E. Incidence of ulnar neuropathy at the elbow in the province of Siena (Italy). J Neurol Sci. 2005 Jul 15;234(1e2):5e10. 3. Frost P, Johnsen B, Fuglsang-Frederiksen A, Svendsen SW. Lifestyle risk factors for ulnar neuropathy and ulnar neuropathy-like symptoms. Muscle Nerve. 2013 Oct;48(4):507e515. 4. Pellieux S, Fouquet B, Lasfargues G. Ulnar nerve tunnel syndrome of the elbow and an occupational disorder. Analysis of socio-professional and physical parameters. Ann Readapt Med Phys. 2001 May;44(4):213e220. 5. Rota E, Zavaroni D, Parietti L, et al. Ulnar entrapment neuropathy in patients with type 2 diabetes mellitus: an electrodiagnostic study. Diabetes Res Clin Pract. 2014 Apr;104(1):73e78. 6. O’Driscoll SW, Horii E, Carmichael SW, Morrey BF. The cubital tunnel and ulnar neuropathy. J Bone Joint Surg Br. 1991 Jul;73(4):613e617. 7. Gelberman RH, Yamaguchi K, Hollstien SB, et al. Changes in interstitial pressure and cross-sectional area of the cubital tunnel and of the ulnar nerve with flexion of the elbow. An experimental study in human cadavera. J Bone Joint Surg Am. 1998 Apr;80(4):492e501. 8. Shah CM, Calfee RP, Gelberman RH, Goldfarb CA. Outcomes of rigid night splinting and activity modification in the treatment of cubital tunnel syndrome. J Hand Surg Am. 2013 Jun;38(6):1125e1130 e1. 9. Giladi AM, Gaston RG, Haase SC, et al. Trend of recovery after simple decompression for treatment of ulnar neuropathy at the elbow. Plast Reconstr Surg. 2013 Apr;131(4):563ee573e. 10. Charles YP, Coulet B, Rouzaud JC, Daures JP, Chammas M. Comparative clinical outcomes of submuscular and subcutaneous transposition of the ulnar nerve for cubital tunnel syndrome. J Hand Surg Am. 2009 May-Jun;34(5):866e874. 11. Chung KC. Treatment of ulnar nerve compression at the elbow. J Hand Surg Am. 2008 Nov;33(9):1625e1627. 12. Macadam SA, Gandhi R, Bezuhly M, Lefaivre KA. Simple decompression versus anterior subcutaneous and submuscular transposition of the ulnar nerve for cubital tunnel syndrome: a meta-analysis. J Hand Surg Am. 2008 Oct;33(8): 1314 e1e1341 e12. 13. MacDermid JC, Grewal R. Development and validation of the patient-rated ulnar nerve evaluation. BMC Musculoskelet Disord. 2013;14:146. 14. Ebersole GC, Davidge K, Damiano M, Mackinnon SE. Validity and responsiveness of the DASH questionnaire as an outcome measure following ulnar nerve transposition for cubital tunnel syndrome. Plast Reconstr Surg. 2013 Jul;132(1): 81ee90e. 15. Zimmerman NB, Kaye MB, Wilgis EF, Zimmerman RM, Dubin NH. Are standardized patient self-reporting instruments applicable to the evaluation of

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ulnar neuropathy at the elbow? J Shoulder Elbow Surg. 2009 May-Jun;18(3): 463e468. Vincent JI, MacDermid JC, King GJ, Grewal R. Validity and sensitivity to change of patient-reported pain and disability measures for elbow pathologies. J Orthop Sports Phys Ther. 2013 Apr;43(4):263e274. MacDermid JC. Outcome evaluation in patients with elbow pathology: issues in instrument development and evaluation. J Hand Ther. 2001 Apr-Jun;14(2): 105e114. Shi Q, MacDermid JC, Santaguida PL, Kyu HH. Predictors of surgical outcomes following anterior transposition of ulnar nerve for cubital tunnel syndrome: a systematic review. J Hand Surg Am. 2011 Dec;36(12):1996e2001 e1e6. Shi Q, MacDermid J, Grewal R, King GJ, Faber K, Miller TA. Predictors of functional outcome change 18 months after anterior ulnar nerve transposition. Arch Phys Med Rehabil. 2012 Feb;93(2):307e312. MacDermid JC, Evenhuis W, Louzon M. Inter-instrument reliability of pinch strength scores. J Hand Ther. 2001 Jan-Mar;14(1):36e42. American Society of Hand Therapists. Clinical Assessment Recommendations. Chicago: The Society; 1992. Tassler PL, Dellon AL. Correlation of measurements of pressure perception using the pressure-specified sensory device with electrodiagnostic testing. J Occup Environ Med. 1995 Jul;37(7):862e866. Dellon AL, Keller KM. Computer-assisted quantitative sensorimotor testing in patients with carpal and cubital tunnel syndromes. Ann Plast Surg. 1997 May;38(5):493e502. Nath RK, Bowen ME, Eichhorn MG. Pressure-specified sensory device versus electrodiagnostic testing in brachial plexus upper trunk injury. J Reconstr Microsurg. 2010 May;26(4):235e242. Weber RA, Schuchmann JA, Albers JH, Ortiz J. A prospective blinded evaluation of nerve conduction velocity versus Pressure-Specified Sensory Testing in carpal tunnel syndrome. Ann Plast Surg. 2000 Sep;45(3):252e257. Holm S. A simple sequentially rejective multiple test procedure. Scand J Stat. 1979;6:65e70. Chung KC, Kotsis SV, Kim HM. Predictors of functional outcomes after surgical treatment of distal radius fractures. J Hand Surg Am. 2007 Jan;32(1):76e83. Dellhag B, Burckhardt CS. Predictors of hand function in patients with rheumatoid arthritis. Arthritis Care Res. 1995 Mar;8(1):16e20. Rosen B. Recovery of sensory and motor function after nerve repair. A rationale for evaluation. J Hand Ther. 1996 Oct-Dec;9(4):315e327. Ekstrom H, Elmstahl S. Pain and fractures are independently related to lower walking speed and grip strength: results from the population study “Good Ageing in Skane”. Acta Orthop. 2006 Dec;77(6):902e911. Rosenberg N, Soudry M, Stahl S. Comparison of two methods for the evaluation of treatment in medial epicondylitis: pain estimation vs grip strength measurements. Arch Orthop Trauma Surg. 2004 Jul;124(6):363e365. Palmer BA, Hughes TB. Cubital tunnel syndrome. J Hand Surg Am. 2010 Jan;35(1):153e163. Huang JH, Samadani U, Zager EL. Ulnar nerve entrapment neuropathy at the elbow: simple decompression. Neurosurgery. 2004 Nov;55(5):1150e1153. Bell-Krotoski J, Weinstein S, Weinstein C. Testing sensibility, including touchpressure, two-point discrimination, point localization, and vibration. J Hand Ther. 1993 Apr-Jun;6(2):114e123. MacDermid JC, Kramer JF, Roth JH. Decision making in detecting abnormal Semmes-Weinstein monofilament thresholds in carpal tunnel syndrome. J Hand Ther. 1994 Jul-Sep;7(3):158e162. Macdermid JC, Kramer JF, McFarlane RM, Roth JH. Inter-rater agreement and accuracy of clinical tests used in diagnosis of Carpal Tunnel Syndrome. Work. 1997;8(1):37e44. Hubbard MC, MacDermid JC, Kramer JF, Birmingham TB. Quantitative vibration threshold testing in carpal tunnel syndrome: analysis strategies for optimizing reliability. J Hand Ther. 2004 Jan-Mar;17(1):24e30. Novak CB, Mackinnon SE, Williams JI, Kelly L. Establishment of reliability in the evaluation of hand sensibility. Plast Reconstr Surg. 1993 Aug;92(2):311e322. Cheung DK, MacDermid J, Walton D, Grewal R. The construct validity and responsiveness of sensory tests in patients with carpal tunnel syndrome. Open Orthop J. 2014;8:100e107. MacDermid JC, Donner A, Richards RS, Roth JH. Patient versus injury factors as predictors of pain and disability six months after a distal radius fracture. J Clin Epidemiol. 2002 Sep;55(9):849e854.

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JHT Read for Credit Quiz: #338

Record your answers on the Return Answer Form found on the tear-out coupon at the back of this issue or to complete online and use a credit card, go to JHTReadforCredit.com. There is only one best answer for each question. #1. In 2013 the PRUNE was described by a. Szekeres and King b. Bell and Fess c. MacDermid and Grewal d. Osterman and Skirven #2. Sensory testing was performed utilizing a. one-point sensory threshold b. moving 2 point discrimination (M2PD) c. Semmes Weinstein monofilament testing d. Seddon 2 point discrimination #3. Which measure showed the highest correlation with the PRUNE a. 9 hole peg test b. pinch strength

c. sensory testing d. grip strength #4. Study subjects included patients who had undergone a. cubital tunnel decompression b. ulnar nerve transposition c. either cubital tunnel decompression or ulnar nerve transposition d. no surgery #5. The correlation between the PRUNE and the common tests of ulnar nerve function suggests good validity of the PRUNE a. false b. true When submitting to the HTCC for re-certification, please batch your JHT RFC certificates in groups of 3 or more to get full credit.