Elbow flexion and forearm supination strength in a healthy population

ARTICLE IN PRESS J Shoulder Elbow Surg (2017) ■■, ■■–■■

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ORIGINAL ARTICLE

Elbow flexion and forearm supination strength in a healthy population Maximilian Kerschbaum, MD, Nina Maziak, Elisabeth Böhm, Markus Scheibel, MD* Center for Musculoskeletal Surgery, Campus-Virchow/Campus-Mitte, Charité-Unversitätsmedizin Berlin, Berlin, Germany Background and Hypothesis: Despite the lack of representative data of a healthy population, many clinical trials concerning the measurement of postoperative elbow flexion or forearm supination strength use the contralateral side as a control. We hypothesized that there are no differences in elbow flexion and supination strength between the dominant and nondominant sides in healthy volunteers. Methods: The study was performed on a cross-sectional cohort of healthy subjects without any prior injuries or surgical interventions of the upper extremities. Isometric elbow flexion strength and supination strength were measured on both the dominant and nondominant sides. The results were analyzed for the entire group and subanalyzed for female vs. male, for different age groups, and according to handedness and regular practice of overhead sports. Results: A total of 150 subjects (75 female and 75 male subjects; mean age, 44 ± 15 years [range, 18-72 years]) were included in this study. Within the entire collective, no significant differences concerning the elbow flexion strength between the dominant and nondominant sides could be detected, whereas the supination strength was 7% higher on the dominant side (P = .010). Women, right-hand–dominant subjects, and subjects who do not regularly practice overhead sports have a significant 8% higher supination strength on the dominant side compared with the nondominant side (P < .05). Left-hand–dominant subjects have an 8% higher elbow flexion strength on the nondominant right side (P < .05). Conclusion: Elbow flexion strength and forearm supination strength differ between the dominant and nondominant sides. The contralateral upper extremity cannot be used as a matched control without some adjustments. Level of evidence: Descriptive Epidemiology Study © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved. Keywords: Biceps muscle; biceps tendon; elbow flexion strength; forearm supination strength; isometric muscle strength; biceps tenotomy; biceps tenodesis

Impairments of elbow flexion and forearm supination strength in patients with pathologic processes of the long or distal biceps tendon or after surgical interventions are an im-

The Ethics Committee of Charité-Universitätsmedizin Berlin approved this study: EA4/094/16. *Reprint requests: Markus Scheibel, MD, Center for Musculoskeletal Surgery, Campus-Virchow/Campus-Mitte, Charité-Unversitätsmedizin Berlin, Augustenburgerplatz 1, D-13353 Berlin, Germany. E-mail address: [email protected] (M. Scheibel).

portant clinical issue as well as interesting in clinical research. Most of the studies concerning these impairments after long or distal biceps tendon surgery compared their results with the nonsurgical contralateral side without any adjustments to the operated side, handedness, age, sex, or activity level of the patients.2-4,6-8,11,12 Previous investigations on this topic using healthy subjects are contradictory.1,9,10,13 These investigations did not analyze the influence of age, handedness, or activity level of the subjects between the dominant and nondominant sides.

1058-2746/$ - see front matter © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved. http://dx.doi.org/10.1016/j.jse.2017.05.031

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The purpose of this study was to determine differences in isometric muscle strength for both elbow flexion and supination between dominant and nondominant upper extremities in a representative cross-sectional cohort of healthy subjects. We hypothesized that there are no differences between dominant and nondominant upper extremities concerning elbow flexion and supination strength regardless of sex, age, handedness, or activity level.

Materials and methods To receive a representative cross section through all age groups, 5 age groups were defined: 18-29 years, 30-39 years, 40-49 years, 50-59 years, and >60 years. In each age group, 15 women and 15 men were recruited and tested. Subjects were excluded if they had a history of injury or prior operations as well as any symptoms concerning the upper extremities. In addition to age, the Disabilities of the Arm, Shoulder, and Hand score was obtained to verify the state of health of the upper extremity.5 Furthermore, handedness and regular practice (>2 times a week) of overhead sports were documented. Both elbow flexion strength and forearm supination strength were tested on both sides of each subject. Before testing, each participant received detailed instructions. Elbow flexion strength was measured using an isometric dynamometer (IsoBex dynamometer; MDS AG, Burgdorf, Switzerland). The measurement was performed in 90° of elbow flexion and repeated 3 times (Fig. 1). Elbow flexion strength was measured in newtons.

Figure 2 Forearm supination strength measurement. The participant was seated with shoulder and elbow in approximately 45° of flexion, grasping the T-handle with the forearm in neutral position. Supination strength was tested using a Baseline hydraulic dynamometer (Fabrication Enterprises Inc., White Plains, NY, USA) and repeated 3 times. The participant was seated with shoulder and elbow in approximately 45° of flexion, grasping the T-handle with the forearm in neutral position. To control the elbow position, the elbow was immobilized through a motion control splint (Fig. 2). Free forearm rotation without any restrictions due to the splint was ensured. Previous investigations have shown that the Baseline hydraulic dynamometer is a valid and reliable tool for measuring forearm supination strength.14 The forearm supination strength was measured in kilograms. Participants had a minimum of 5 minutes of rest between flexion and forearm supination strength testing. Testing started alternately on the right or left side. Before the first measurement was performed, each subject started with 3 practice trials on the contralateral side. Furthermore, an alternating flexion and supination strength measurement test protocol was used to prevent a systematic bias due to fatigue of the biceps muscle. A paired Student t-test was used to compare dominant and nondominant upper extremities. A P value of < .05 was considered significant. The statistical analysis was carried out using SPSS software (IBM, Armonk, NY, USA).

Results

Figure 1 Isometric elbow flexion strength measurement in 90° of elbow flexion.

A total of 150 subjects (75 female and 75 male subjects) were included in this study. The mean age was 44 ± 15 years (range, 18-72 years). Female and male subjects showed no significant differences concerning the mean age (female subjects, 45 ± 15 years [range, 18-72 years]; male subjects, 44 ± 15 years [range, 22-72 years]; P = .828). The mean body mass index of all participants was 25.6 ± 4.4 (range, 18-41). All subjects showed the lowest point value (0 points) in the Disabilities of the Arm, Shoulder, and Hand score, which indicates no disability of the upper extremities; 133 subjects were righthanded (89%) and 17 were left-handed (11%). Of 150 participants, 16 reported regular practice of overhead sports (11%). Within the entire collective, no significant difference for elbow flexion strength between the dominant side and the nondominant side was detected (P = .160). The mean flexion strength was 135 ± 7 N on the dominant side vs. 132 ± 6 N

ARTICLE IN PRESS Normal elbow flexion and supination strength Table I

3

Dominant vs. nondominant elbow flexion and forearm supination strength in women and men Peak elbow flexion (N) (mean ± standard deviation)

Women (n = 75) Men (n = 75)

Peak forearm supination (kg) (mean ± standard deviation)

Dominant

Nondominant

Dominant/ nondominant

P value

Dominant

Nondominant

Dominant/ nondominant

P value

85 ± 30

85 ± 32

100%

.836

91 ± 29

84 ± 27

92%

.000

184 ± 58

179 ± 53

97%

.146

172 ± 55

163 ± 54

95%

.050

Bold values: MOON Shoulder Group.

Table II

Dominant vs. nondominant elbow flexion and forearm supination strength in right- and left-hand–dominant participants Peak elbow flexion (N) (mean ± standard deviation)

Right-hand dominant (n = 133) Left-hand dominant (n = 17)

Peak forearm supination (kg) (mean ± standard deviation)

Dominant

Nondominant

Dominant/ nondominant

P value

Dominant

Nondominant

Dominant/ nondominant

P value

133 ± 70

129 ± 64

97%

.029

130 ± 59

120 ± 57

92%

.000

146 ± 49

157 ± 59

108%

.033

144 ± 64

149 ± 62

103%

.409

Bold values: MOON Shoulder Group.

Table III Dominant vs. nondominant elbow flexion and forearm supination strength in participants with or without regular practice of overhead sports Peak elbow flexion (N) (mean ± standard deviation)

Overhead (n = 16) No overhead (n = 134)

Peak forearm supination (kg) (mean ± standard deviation)

Dominant

Nondominant

Dominant/ nondominant

P value

Dominant

Nondominant

Dominant/ nondominant

P value

169 ± 69

167 ± 69

99%

.760

157 ± 68

158 ± 72

101%

.898

131 ± 66

128 ± 63

98%

.168

129 ± 58

119 ± 56

92%

.000

Bold values indicate statistical significance.

on the nondominant side (98%). In contrast, the forearm supination strength showed significant differences between the dominant and the nondominant upper extremities (dominant vs. nondominant, 132 ± 6 kg vs. 123 ± 6 kg [93%]; P = .010). In the women’s group, forearm supination strength was significantly higher on the dominant side compared with the nondominant side, whereas no differences concerning the elbow flexion strength were found (Table I). None of the age groups displayed significant differences between the dominant and the nondominant upper extremities. In right-hand–dominant participants, elbow flexion strength and supination strength were significantly higher on the dominant side (Table II). In left-hand–dominant subjects, the nondominant right side showed a significantly higher elbow flexion strength, whereas no differences concerning the forearm supination strength were found (Table II). Although no differences could be detected in participants practicing overhead sports, the supination strength in

subjects who did not regularly practice overhead sports was significantly higher on the dominant side compared with the nondominant side (Table III).

Discussion This is the first study detailing elbow flexion and supination strength measurement in a representative cross-sectional cohort of healthy subjects. Through this study, we were able to identify significant differences between the dominant and nondominant sides. Previous investigations showed inconsistent results. Matsuoka et al and Wittstein et al could not identify any significant differences concerning elbow flexion and forearm supination strength between the dominant and nondominant upper extremities.9,13 Wittstein et al concluded that the contralateral side can be used as a matched control without

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any adjustments. In contrast to this, other studies showed significant differences in elbow flexion and supination strength.1,10 Askew et al described a 3% higher elbow flexion strength and 8% higher supination strength on the dominant side compared with the nondominant side.1 Similar results were published by Morrey et al (flexion strength +6% dominant side; supination strength +10% dominant side).10 The informative value of these studies is limited because the enrolled participants do not represent the entire collective of patients undergoing proximal or distal biceps procedures. Wittstein et al as well as Morrey et al examined only right-handed subjects with a mean age of 26 years and 28 years, respectively. The strength of this study is the representative crosssectional cohort of healthy participants. In addition, as well as right-hand–dominant participants, left-hand–dominant participants were also evaluated. Nevertheless, there are some weaknesses to this study. First of all, a possible learning bias on the side tested second, as described by Wittstein et al, cannot be excluded.13 We tried to prevent this learning bias by altering the test starting side and by 3 practice trials on the side tested second. Another weakness is that fatigue of the biceps muscle due to the first measurement could influence the second measurement. To prevent a systematic bias, we used a test protocol that alternates flexion and supination strength measurement. In addition, a 5-minute rest between flexion and supination strength measurement was implemented. Peak flexion strength and supination strength were measured, but not strength endurance. In contrast to previous studies on smaller, limitedly representative collectives, we found that elbow flexion and supination strength between the dominant and nondominant sides depends on sex, handedness, and regular practice of overhead sport. These adjustments are necessary to compare postoperative strength with the contralateral side. Especially women, right-hand–dominant subjects, and subjects without a history of overhead sport have an 8% higher supination strength on the dominant side compared with the nondominant side. Left-hand–dominant subjects have an 8% higher elbow flexion strength on the nondominant right side.

Conclusion Elbow flexion strength and forearm supination strength differ between the dominant and nondominant sides. The contralateral upper extremity cannot be used as a matched control during isometric testing of the biceps muscle without some adjustments.

Disclaimer The authors, their immediate families, and any research foundations with which they are affiliated have not received any financial payments or other benefits from any commercial entity related to the subject of this article.

References 1. Askew LJ, An KN, Morrey BF, Chao EY. Isometric elbow strength in normal individuals. Clin Orthop Relat Res 1987;222:261-6. 2. Banerjee M, Bouillon B, Balke M. [Change of drilling direction for placement of EndoButton for distal biceps refixation can protect the posterior interosseous nerve—report of 37 cases.] Obere Extremität 2014;9:289-94. http://dx.doi.org/10.1007/s11678-014-0253-5 3. D’Alessandro DF, Shields CL, Tibone JE, Chandler RW. Repair of distal biceps tendon ruptures in athletes. Am J Sports Med 1993;21:114-9. 4. Duff SJ, Campbell PT. Patient acceptance of long head of biceps brachii tenotomy. J Shoulder Elbow Surg 2012;21:61-5. http://dx.doi.org/ 10.1016/j.jse.2011.01.014 5. Germann G, Wind G, Harth A. [The DASH (Disability of ArmShoulder-Hand) Questionnaire—a new instrument for evaluating upper extremity treatment outcome]. Handchir Mikrochir Plast Chir 1999;31:149-52. 6. Kerschbaum M, Maziak N, Scheuermann M, Scheibel M. [Arthroscopic tenodesis or tenotomy of the long head of the biceps tendon in preselected patients: does it make a difference?] Orthopade 2017;46:215-21. http://dx.doi.org/10.1007/s00132-016-3358-2 7. Kerschbaum M, Scheuermann M, Gerhardt C, Scheibel M. Arthroscopic knotless suprapectoral tenodesis of the long head of biceps: clinical and structural results. Arch Orthop Trauma Surg 2016;136:1135-42. http:// dx.doi.org/10.1007/s00402-016-2466-0 8. Lim TK, Moon ES, Koh KH, Yoo JC. Patient-related factors and complications after arthroscopic tenotomy of the long head of the biceps tendon. Am J Sports Med 2011;39:783-9. http://dx.doi.org/10.1177/ 0363546510388158 9. Matsuoka J, Berger RA, Berglund LJ, An K-N. An analysis of symmetry of torque strength of the forearm under resisted forearm rotation in normal subjects. J Hand Surg Am 2006;31:801-5. http://dx.doi.org/ 10.1016/j.jhsa.2006.02.019 10. Morrey BF, Chao EY, Hui FC. Biomechanical study of the elbow following excision of the radial head. J Bone Joint Surg Am 1979;61:638. 11. Shank JR, Singleton SB, Braun S, Kissenberth MJ, Ramappa A, Ellis H, et al. A comparison of forearm supination and elbow flexion strength in patients with long head of the biceps tenotomy or tenodesis. Arthroscopy 2011;27:9-16. http://dx.doi.org/10.1016/j.arthro.2010.06.022 12. The B, Brutty M, Wang A, Campbell PT, Halliday MJC, Ackland TR. Long-term functional results and isokinetic strength evaluation after arthroscopic tenotomy of the long head of biceps tendon. Int J Shoulder Surg 2014;8:76-80. http://dx.doi.org/10.4103/0973-6042.140114 13. Wittstein J, Queen R, Abbey A, Moorman CT. Isokinetic testing of biceps strength and endurance in dominant versus nondominant upper extremities. J Shoulder Elbow Surg 2010;19:874-7. http://dx.doi.org/ 10.1016/j.jse.2010.01.018 14. Wong CK, Moskovitz N. New assessment of forearm strength: reliability and validity. Am J Occup Ther 2010;64:809-13. http://dx.doi.org/ 10.5014/ajot.2010.09140