University of Groningen
Grip on prognostic factors after forearm fractures
Ploegmakers, Joris Jan Willem
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Publication date: 2019
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Ploegmakers, J. J. W. (2019). Grip on prognostic factors after forearm fractures. Rijksuniversiteit Groningen.
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J.J.W. Ploegmakers M. Brutty
A.W. Wang T.R. Ackland
Chapter 5
Normative torque and grip strength profiles with variation in
forearm rotation
ABSTRACT
Objective: This study evaluates the pattern of pronation and supination strength as well as
grip strength, between individuals in varying positions of forearm orientation as a therapeutic instrument.
Method: Both forearms were assessed with a Baseline dynamometer (pronosupination strength)
and Jamar dynamometer (grip strength) to measure isometric peak strength in different forearm positions, varying from 60ºpronation to 60ºsupination.
Results: 71 healthy volunteers (22 years ± 3.6 (SD)) participated in this study. By observing the
standard error values at each angle, there is a significant effect of sex and forearm angle on forearm strength as well as grip strength at all measured angles.
Conclusion: An important relationship in this study is the consistent general linear effect
of pronosupination and grip strength on forearm orientation in the healthy population. Pronosupination strength measurements at 20° supination could provide clinicians an easily obtainable and sensitive, however, non-specific indicative measure of forearm pathology.
INTRODUCTION
An evaluation of grip strength has long been used as a measure of upper extremity function. Furthermore, some studies indicated that abnormal grip strength measurements were deemed an acceptable, non-specific, objective measure for wrist pathology.1,2,3,4
Given that pronosupination strength is also a major function of the forearm, relatively little attention has been paid to defining normative pronosupination strength.5,6
For data that exists, several assumptions have been made, including: (1) that maximal prono-supination strength is dependent on having a stable and painless upper extremity; (2) normal neuromuscular status; and (3) appropriate abilities for grasp and effort. It is also assumed that the presence of pain and instability will decrease the pronation and supination potential in the forearm.4 In light of these studies, it has become clear that in order to understand the function of
the forearm-wrist complex, comprehensive normative pronation and supination strength values should first be defined.
Forearm rotation has been identified as key function, affected by triangular fibrocartilage complex (TFCC) lesions, distal radial fractures and associated distal radioulnar joint (DRUJ) dislocation. Pronation and/or supination strength, might be distorted due to intracarpal or TFCC lesions, impairing the proper functioning of the upper extremity as a result.7 Therefore, monitoring the
functioning of the forearm post operatively and as the patient progresses through rehabilitation is strongly advised.8,9,10,11
However, there is a lack of standard norms in the literature. Given that forearm orientation has been shown to greatly affect forearm strength, it appears important clinically to assess pronosupination and grip strength at varying angles when evaluating injuries of the forearm.4,5,12,13,14 It is commonly accepted that the position of the forearm affects the contribution
of each of the stabilizers of the forearm and wrist. Therefore, it is reasonable to assume that injury of a specific ligament will contribute to a position dependent isokinetic strength reduction. Such data would be beneficial for the evaluation and understanding of patients with forearm injuries. This study focuses on the normative data related to forearm pronosupination strength and grip strength; in particular, the effect of varying orientations of the forearm on strength, to determine if there is a consistent pattern.
METHOD
Participants
This study examined 71 (42 male, 29 female) healthy volunteers (average age 22 ±3.6 years; (body mass index (BMI) 22.9 ±2.8) with no history of substantial forearm or wrist injury, 62 were staff and students recruited from the University of Western Australia (UWA) and nine were recruited externally (Table 1.). Of these participants, 63 were right-hand dominant (RHD) and eight were left-hand dominant (LHD), providing data from tests on a total of 142 forearms. Exclusion criteria included age outside the range of 18-35 years, a history of trauma to the wrist, forearm or elbow in the 5 years prior, or significant trauma affecting the function of the upper extremity. Participants were recruited through advertising announcements at UWA. The Sir Charles Gairdner Hospital Human Research Ethics Committee approved this study, and all participants signed an informed consent document.
Procedures
All participants enrolled for a single session of testing, during which pronation and supination strength were assessed with a Baseline® hydraulic dynamometer (BHD) (Fabrication Enterprises Inc., White Plains, NY) and grip strength was measured using the Jamar® hydraulic hand dynamometer (JHD). An inclinometer was used to measure passive flexion/extension as well as pronation/supination and active range of motion (ROM). The (BHD) was fitted with a “shovel handle” grip and was mounted on a frame with the ability to rotate and lock the device in varying degrees of pronation (60°, 40°, 20°), supination (60°, 40°, 20°) and in neutral (Picture 1.). Each participant was instructed by a single assessor to sit grasping the handle with the elbow positioned in approximately 45° of flexion and resting 5cm proximally from the patella for stability. The forearm was positioned horizontally in line with the axis of the shovel handle and BHD; the chair and table allowed seated height to be adjusted for correct positioning. Isometric twisting force on the BHD was measured in pounds then converted to kilograms (kg) for data presentation. Strength and ROM assessments were performed by an Accredited Exercise Physiologist.
Table 1. Participant Characteristics
NOTE: RHD = Right Hand Dominant; LHD = Left Hand Dominant
Characteristic Measurement
Participants -TOTAL 71 (63 RHD, 8 LHD)
- MALE 42 (39 RHD, 3 LHD)
- FEMALE 29 (24 RHD, 5 LHD)
Age (average) 22 ± 3.6 years
Height (average) 173.7 ± 10.6 cm
Weight (average) 69.6 ± 13.2 kg
Participants were instructed to perform two pre-test maximal isometric contractions, one of pronation, the other of supination, with the verbal prompt “contract as hard as you can without compromising your wrist, elbow and shoulder positioning”. The participant then repeated two trials for each pronation and supination assessment at each of the test angles using the same verbal prompts. If the wrist, elbow or shoulder position was compromised during testing, the trial was repeated. Both left and right hands were assessed at the same angle and the assessment sequence was such that at an angle of ‘-60°’, the left hand was measured 60° in a supine position and the right hand was measured 60° in a prone position. This allowed each hand approximately 1 minute rest in order to recover before testing commenced at the next angle. The same method of testing was utilized while assessing grip strength.
Statistical Analysis
All data were collected within a single session, then entered into an excel spreadsheet and processed to determine: (1) the maximum absolute strength values for each of two trials performed at each of the seven angles and (2) the percentage of individual maximal pronation, supination and grip strength values at all angles. A series of two factor, repeated measures ANOVA were performed to determine the effect of sex and forearm orientation on strength scores. All statistical analyses were performed using SPSS v 18.0.
RESULTS
Significant main effects for sex and forearm orientation (p<0.001) were found in left and right forearm pronation and supination strength as well for grip strength. By observing the standard error values at each angle, we can state that the significant main effects of sex and forearm angle on forearm strength as well as grip strength existed at all measurement angles (pronation 60°, 40°, 20°; neutral 0° and supination 20°, 40°, 60°).
Supination
A distinct difference between male and female “absolute” supination strength values at each measurement angle is evident, with female values being, on average 56% of that recorded for males (Figure 1). The difference between the left and right hands for males in supination was found to be 4% with the right hand marginally stronger. The difference between the left and right hands for females in supination was found to be 2%. When addressing the influence of forearm angle, a general linear relationship was identified, indicating that supination strength increases as positions of forearm rotation move from 60º supination to 60º pronation.
This means of presenting the data facilitates clinical comparisons of participants’ strength with healthy counterparts. This is evident for both male and female participants. For males, the weakest supination strength values were recorded at 60° in a supinated position for both the left and right hands, representing approximately 50% of the maximum recorded value. For females, the weakest supination strength values were also recorded at 60° in a supinated position for both the left and right hands. At this position the right hand supination strength was approximately 48% of the maxi-mum recorded value, while for the left hand this was approximately 57% of the maximaxi-mum score.
Figure 1. Average (n=71) peak supination strength for left and right hands at each forearm angle for male
and females participants. Note: (s) = supinated position, (p) = pronated position. Error bars represent standard deviation values.
Supina
tion str
ength (k
g)
Angles of supination (s) and pronation (p)
250 200 150 100 50 0 (s) 60 (s) 40 (s) 20 0 (p) 20 (p) 40 (p) 60 Male left Male right Female left Female right
Pronation
A distinct difference between male and female absolute pronation strength values at each measurement angle is evident, with female values being, on average, 56% of that recorded by males (Figure 2). The difference between left and right hands for males in pronation was found to be 10%, with the right hand side marginally stronger. The difference between left and right for females in pronation is greater (17%). When addressing the influences of forearm angle, a general linear relationship was identified, indicating that pronation strength increases as positions of forearm rotation move from pronation to supination.
The greatest strength values for pronation are found, on average, to be recorded at 60° in a supinated position for both hands which is evident for male and female participants. For males, the weakest pronation strength values were recorded at 60° in a pronated position for both the left and right hands, representing approximately 12% of the maximum recorded value. For females, the weakest strength values for pronation were also recorded at 60° in a pronated position for left and right hands, representing approximately 10% of the maximum recorded value.
Combined Pronation and Supination Data
When combining pronation and supination strengths, a general inverse relationship is evident, whereby supination strength increases as pronation strength decreases when moving from a supinated to pronated forearm positions. This relationship is evident between males and females as well for left and right hands as seen in Figure 3. At the neutral position of 0°, pronation strength in males is approximately 69% of supination strength, while female pronation strength is approximately 75% of supination strength. Left and right hand pronation and supination strength for both males and females intersect at approximately 20° in a supinated position (Figure 3a and b).
Figure 2. Average (n=71) peak pronation strength for left and right hands at each forearm angle for male and
females participants. Note: (s) = supinated position, (p) = pronated position. Error bars represent standard deviation values. Pr ona tion str ength (k g) 250 200 150 100 50 0
Angles of supination (s) and pronation (p)
(s) 60 (s) 40 (s) 20 0 (p) 20 (p) 40 (p) 60
Male left Male right Female left Female right
(s) 60 (s) 40 (s) 20 0 (p) 20 (p) 40 (p) 60
Rota
tional str
ength (k
g)
Angles of supination (s) and pronation (p)
Male left hand Supination Male left hand Pronation Female left hand Supination Female left hand Pronation 200 180 160 140 120 100 80 60 40 20 0 Rota tional str ength (k
g) Male right hand
supination Male right hand pronation Female right hand supination Female right hand pronation 200 180 160 140 120 100 80 60 40 20 0 (s) 60 (s) 40 (s) 20 0 (p) 20 (p) 40 (p) 60
Angles of supination (s) and pronation (p)
Figure 3b. Average (n=71) peak pronation and supination strength values at each forearm angle for the
right hand of male and female participants. Note: (s) = supinated position, (p) = pronated position.
Figure 3a. Average (n=71) peak pronation and supination strength values at each forearm angle for the left
Grip Strength
A distinct difference between male and female absolute grip strength values at each measurement angle is evident with female values being, on average, 52% of that recorded by males. A difference between left and right hand strength is also evident with the left hand being, on average, 8.6% weaker in males and 14.3% weaker in females. When addressing the influences of forearm angle, a general linear relationship was identified, indicating that grip strength decreases as positions of forearm rotation move from supination to pronation (Figure 4).
The greatest grip strength values are found, on average, to be recorded at 60° in a supinated position for both the right and left hands. This is evident for both males and females. The remaining scores recorded for the other forearm orientation angles are expressed as a percentage of the maximum score recorded in the strongest supinated position.
For males, the weakest grip strength values were recorded, on average, at 60° in a pronated position for both the left and right hands, representing approximately 68% of the maximum scores recorded. For females, the weakest grip strength values were also recorded, on average, at 60° in a pronated position for both hands, representing approximately 65% of the maximum scores recorded.
Average ROM data indicates that pronation ROM (83º ± 14.0º) is less than supination ROM (101º ± 9.9º) for both males and females, on both the right and left hands. Pronation ROM values for males (80º ± 11.8º) are less than measurements recorded for females (89º ± 14.9º) on both hands. Likewise, supination ROM values for males (99º ± 10.4º) are less than measurements recorded for females (104º ± 8.2º) on both hands.
Figure 4. Average (n=71) peak grip strength values for left and right hands at each forearm angle for male
and female participants. Note: (s) = supinated position, (p) = pronated position. Error bars represent standard deviation values. G rip str ength (k g) 50 45 40 35 30 25 20 15 10 5 0
Angles of supination (s) and pronation (p)
(s) 60 (s) 40 (s) 20 0 (p) 20 (p) 40 (p) 60
Male left Male right Female left Female right
DISCUSSION
Sex Differences in Forearm and Hand Strength
The significant main effect for sex on forearm pronosupination strength demonstrated that for females, both pronation and supination strength across the left and right hands is 56% of that recorded for males. Likewise, Kramer et al indicated that the forearm pronation and supination strength of women was 53-58% of that recorded by men.16 Similar results showed men to be
63% stronger in pronation (p < .001) and 69% stronger in supination (p < .05) when compared to women.17
Lack of consensus between studies investigating forearm strength has been attributed to a variety of factors including upper limb posture and positioning, handle types and the interpretation of the effect of physiological cross sectional area (PCSA), moment arm (MA) and electromyography (EMG) data. When looking at the differences between pronation and supination, published research highlighted that pronation was stronger than supination.4,16,17,18 Some studies however,
have indicated that supination strength was greater than pronation strength,5,6,14,15,19 while
others reported no significant difference between supination and pronation strength.13,20 This
study observed that, on average, male and female pronation strength was 72% of supination. Comparisons made at the anatomically neutral position of 0°, found pronation strength to be 69% of supination in males and 75% of that of supination in females. These findings support previous published research indicating that, over varying forearm orientations, average pronation strength values were weaker than supination, and when measured specifically at the neutral orientation (0°), supination was 17% stronger than pronation.5,14,15
Wong, and Moskovitz, (2010) on the other hand found pronation strength to be 5%-8% greater than supination, measured in a neutral position.17
The variation in findings from previous published research may be affected by the elbow position since the 45° elbow angle has been found to produce the strongest pronation strength,17 whereas
the 90° elbow angle was found to produce the strongest supination strength due to the optimal moment arm of the biceps brachii muscle.15,21 Gordon et al., (2004) however, set the elbow at 90°
yet found no significant difference between pronation and supination strength.13
An important relationship highlighted in this study, is the consistent, general linear effect that forearm position has on supination and pronation strength. The trends could be explained in reference to the length-tension relationship and analysis of moment arms of relevant musculature. Published research has reported supination strength to be greater in pronated positions and pronation strength to be greater in supinated positions, thereby demonstrating that lengthened muscle positions provide for optimum actin-myosin interaction and mechanical advantage to the agonist muscles.4,13,14,15 The mechanical advantage of the biceps brachii is supposed to be
greater in a pronated position, slightly lower in neutral and considerably weaker from neutral through to a supinated position.22 This model of mechanical advantage in biceps brachii was
supported by
O’Sullivan, and Gallwey, (2005), who recorded the highest supination strengths at the prone and neutral angles, with supination strengths decreasing considerably from neutral to supine.5 Given
that O’Sullivan, and Gallwey, (2005) had their participant’s elbows set at 90° of flexion compared to 45° in this study, the variation in findings between studies may be partly contributed by the position of the elbow during testing.5
The 45° elbow position was utilized in this study since the biceps brachii muscle is a strong supinator, more involved in fast or resisted supination, therefore it would account for a larger percentage of strength compared to the other musculature involved in supination. Reducing some of the relative contribution of biceps brachii by using a 45° elbow angle would, therefore, induce more contribution from the other supinating muscles in the forearm. When comparing these normative data to populations with forearm and wrist pathology, the differences in forearm function may be more visible with a reduced contribution of the biceps brachii muscle.
Pronation data from O’Sullivan, and Gallwey, (2001; 2002) highlighted that pronation strength values were not affected by forearm position (as indicated by the almost identical mean strength values recorded in the neutral and supinated position).14,15 This observation shows
inconsistencies to the research of Gordon et al., (2004) and Matsuoka et al., (2006).4,13 Our study
demonstrates a similarly consistent, general linear relationship for pronation as that noted for supination strength.
The greatest strength values for supination were found, on average, to be recorded at 60° in a pronated position while the greatest strength values for pronation are found, on average, to be recorded at 60° in a supinated position. This was evident in both males and females for both the left and right hands. For male and female participants, the weakest strength values for supination were recorded at 60° in a supinated position for both the left and right hand, averaging 52% of the maximum score recorded. The weakest strength values for pronation on the other hand were recorded at 60° in a pronated position for the left and right hand in male and female participants, averaging 11% of the maximum score recorded.
When compared to supination, pronation strength (as a function of the maximum recorded value) decreased at a greater rate when moving from the strongest to the weakest forearm position, with the weaker end of values in pronation (pronated position) demonstrating far less capacity to generate strength. The results from this study found the minimum average pronation strengths of males to be only 24% of minimum average supination strength values. Likewise, the minimum average pronation strengths of females were found to be 20% of minimum average supination strength values.
Understanding the pattern and magnitude of forearm strength in a normal and healthy population would be beneficial for the evaluation of patients with forearm problems. Regardless of the rate of decline, the values situated between the 60° prone and 60° supine positions follow a consistent, general linear pattern. These results are of clinical relevance as, irrespective of a patient’s absolute strength compared to the participants in this study, pronation and supination strength follow a linear trend with respective forearm rotation, regardless of sex or left and right hand.
Prior research often lacked recognition that pronation and supination strength varies with the angle of forearm rotation.
O’Sullivan, and Gallwey, (2005) stated that over the range of 75% prone to 75% supine, the mean decrease in “torque strengths” was 30% for supination and 8% for pronation.5 Furthermore,
O’Sullivan, and Gallwey, (2001; 2002; 2005) reported that, although supination strength was greater than pronation strength overall, pronation strength was greater than supination strength when the forearm is in a supinated position.5,14,15 Our data revealed a similar pattern; with the
average peak pronation strength values exceeding supination strength values in the 60° and 40° supinated forearm position for both the left and right hands of male and female participants. This study also indicates that pronation and supination strength values intersect at approximately
20° in a supinated position. This may hold significant clinical relevance for patients with forearm injuries or DRUJ instability. It is proposed that clinical testing following the same methodology might only need to be conducted at 20° in a supinated position to provide a sensitive and specific measure of forearm/wrist pathology. Similarly, comparison of the injured to the non-injured hand at 20° of supination may provide a clear and time-efficient measure of functional deficit. The slight decrease in non-dominant hand strength may be accounted for by assuming no more than 20% variance for this parameter, though this difference was not found to be significant (p>0.05).4,17
Evaluation of grip strength has long been used as a measure of upper extremity function and abnormal grip strength measurements were deemed an acceptable, yet non-specific, objective measure of forearm and/or wrist pathology.1,2,3,4 Clearly, it is also important and relevant to
measure grip strength either at some standard, or at multiple angles of forearm rotation. This study demonstrates a distinct difference between male and female absolute grip strength values at each angle, with female values being on average 52% of that recorded by males. The results from this study support previous findings indicating that male grip strength values were shown to exceed those of females (p<0.0001) (Richards et al., 1996; Innes, 1999).
The effect of wrist, elbow and shoulder position on grip strength has been studied by several authors, however, given that grip strength has long been used as a measure of upper extremity function, the effect of forearm rotation has received only minimal attention (De Smet et al., 1998). When addressing the influences in forearm angle on grip strength, the present study demonstrated that for both men and women and for both left and right hands, grip strength values were strongest at the fully supinated position. Grip strength then gradually decreased across the assessment angles, with the weakest grip strength being recorded at the fully pronated position. Previously published research has indicated the similar findings (Agresti, & Finlay, 1986; De Smet et al., 1998; Richards et al., 1996). Although the decreasing trend for grip strength appears linear, when considered as a function of an individual’s maximum value, the right and left hand results for females showed a plateau between 20° supination and 20° pronation. This pattern suggested similar grip strength scores in this neutral zone with larger variation observed at the more extremes of ROM. For both males and females and left and right hands, the greatest variation in grip strength values was noted between 40° and 60° in the pronated position. The reasoning behind this decrease in grip strength at full pronation was suggested to be as a result of the relative shortening of the flexor muscles that occurs during pronation. This has been attributed to the length-tension relationship whereby muscles require an ideal length to develop maximal contraction force, depending on the actin-myosin interaction.23,24 It would appear that
the position of full pronation shortens the forearm flexors and extrinsic hand muscles to such an extent that the actin-myosin cross bridge binding is compromised, thus resulting in lowered grip strength scores.
Grip Strength in Relation to Pronosupination Strength
When considering the information on normative grip strength values, we observe some relationship between grip strength normative values and normative values recorded for pronosupination strength. Given that forearm position has been shown to influence grip strength, grip strength capacity may, in turn, influence pronosupination strength when measured at varying angles of forearm rotation. As reported in this study, 60° pronation is close to the end
of ROM with average maximum pronation ROM measurements found to be 80° for males and 89° for females. This forearm position is associated with shortening of the muscles involved in grip strength and pronation (flexor compartment) thus, decreasing their capacity to contract. Therefore, it may be reasonable to suggest that grip strength and pronation strength may influence each other such that the weaker grip strength values may limit pronation strength at the 40° to 60° angles of pronation. Likewise, grip strength and supination strength may influence each other, such that the weaker positions of supination (40° and 60° supination) may be aided by the stronger grip strength values. Although supination is greatest in the position of 60° pronation when grip strength is weakest, this position has been shown to have the greatest mechanical advantage for the muscles that act to supinate the forearm, therefore stronger supination readings at this angle would be expected.4,13,14,15 In other words, the greater variance
in pronation strength (relative to maximum values) over the range of assessment angles when compare to supination, may be attributed to variations in grip strength capacity. Both grip strength and pronosupination strength have significant relevance although they may not be directly compared to each other since they address different forearm functions. Simultaneous testing of grip strength and pronosupination strength may provide useful insight in to the link between these measures of forearm and wrist functionality.
Conclusions: Both gip strength and pronosupination strength have significant relevance although may not be directly compared to each other since they address different forearm functions. While function of grip strength and pronation and supination are different, the sex difference on forearm strength, demonstrated to be for females across the left and right hands 52-56% of that recorded for males.
The patterns demonstrated in these normative data could prove useful for clinical comparisons among patients with forearm fractures or DRUJ instability providing a reproducible, sensitive and non-specific indication of abnormal forearm function. The results of this study also demonstrate that pronation and supination strength for both males and females are equal at approximately 20° in a supinated position. It is therefore proposed that clinical testing following the same methodology could be conducted at 20° in supination, providing a more easily obtainable and reproducible measure of forearm/wrist pathology.
REFERENCES
1. Nitschke JE, McMeeken JM, Burry HC, Matyas TA.When is a change a genuine change? A clinically meaningful interpretation of grip strength measurements in healthy and disabled women. Journal of Hand Therapy. 1999 Jan-March;12:25-30.
2. Shechtman O, Taylor C. The use of the rapid exchange grip test in detecting sincerity of effort, Part II: validity of the test. J Hand Ther. 2000 Jul-Sep;13(3):203-10.
3. Shechtman O. The coefficient of variation as a measure of sincerity of effort of grip strength, Part II: sensitivity and specificity. Journal Hand Ther.2001 Jul-Sep;14(3): 188-94.
4. Matsuoka J, Berger RA, Berglund LJ, An KN. An analysis of symmetry of torque strength of the forearm under resisted forearm rotation in normal subjects. J Hand Surg Am. 2006 May-Jun;31(5):809-13. 5. O’Sullivan LW, Gallwey TJ. Forearm torque strengths and discomfort profiles in pronation and supination.
Ergonomics. 2005 May;48(6):703-21.
6. Timm WN, O’Driscoll SW, Johnson ME, An KN. Functional comparison of pronation and supination strengths. J Hand Ther. 1993 Jul-Sept;6(3):190-3.
7. Chirpaz-Cerbat JM, Ruatti S, Houillon C, Ionescu S. Dorsally displaced distal radius fractures treated by fixed-angle volar plating: grip and pronosupination strength recovery. A prospective study. Orthop Traumatol Surg Res. 2011 Sep;97(5):465-70.
8. Carlsen BT, Rizzo M, Moran SL, An KN. Soft-tissue injuries associated with distal radius fractures. Operative Techniques in Orthopaedics. 2009;19(2):107-18.
9. Carlsen BT, Dennison DG, Moran SL. Acute dislocations of the distal radioulnar joint and distal ulnar fractures. Hand Clin. 2010 Nov;26(4):503-16.
10. Giannoulis FS, Sotereanos DG. Galeazzi fractures and dislocations. Hand Clin. 2007 May; 23(2):153-63. 11. Hughston JC. Fracture of the distal radial shaft; mistakes in management. J Bone Joint Surg Am.1957
Apr;39(2):249-64.
12. Perron AD, Hersh RE, Brady WJ, Keats TE. Orthopaedic pitfalls in the ED: galeazzi and monteggia fracture-dislocation. Am J Emerg Med. 2001 May;19(3):225-8.
13. Gordon KD, Pardo R, Johnson JA, King GJ, Miller TA. Electromyographic activity and strength during maxi-mum isometric pronation and supination efforts in healthy adults. J Orthop Res. 2004 Jan;22(1):208–13. 14. O’Sullivan LW, Gallwey TJ. Forearm discomfort for repeated isometric torque exertions in pronation and
supination. Hanson, M.A., (Eds.), Contemporary Ergonomics, Taylor and Francis., London, 2001; :79–83. 15. O’Sullivan LW, Gallwey TJ. Upper-limb surface electro-myography at maximum supination and pronation
torques: the effect of elbow and forearm angle. J Electromyogr Kinesiol. 2002 Aug;12(4):275-85. 16. Kramer JF, Nusca D, Bisbee L, MacDermid J, Kemp D, Boley S. Forearm pronation and supination:
reliability of absolute torques and nondominant/dominant ratios. J Hand Ther. 1994 Jan-Mar;7(1):15–20. 17. Wong CK, Moskovitz N. New assessment of forearm strength: reliability and validity. Am J Occup Ther.
2010 Sep-Oct;64(5):809-13.
18. Wang B, Strasser H. Left and right handed screwdriver torque strength and physiological cost of muscles. in: Marras, W.S., Karwowski, W., Smith, J.L., Pacholski, L., (Eds.), The Ergonomics of Manual Work. Taylor and Francis, London, 1993; pp. 223–6.
19. Chaffin DB, Andersson GB, Martin BJ. Occupational biomechanics, 3rd ed. Wiley Inter-science, New York. 1999. 20. Winters JL, Kleweno DG. Effect of initial upper-limb alignment on muscle contributions to isometric
strength curves. J Biomech. 1993 Feb;26(2):143-53.
21. Bechtel R, Caldwell GE.The influence of task and angle on torque production and muscle activity at the elbow. J Electromyogr Kinesiol. 1994;4(4):195–204.
22. Murray WM, Delp SL, Buchanan TS. Variation of muscle moment arms with elbow and forearm postures. J Biomech. 1995 May; 28(5):513 – 25.
23. Innes, E. Handgrip strength testing: a review of the literature. Aust J Occup Ther. 1999;46(3):120-40. 24. Richards LG, Olson B, Palmiter-Thomas P. How forearm position affects grip strength. Am Occup Ther.
