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Cross-Education for Improving Strength and Mobility After Distal Radius Fractures: A Randomized Controlled Trial

Published:March 25, 2013DOI:https://doi.org/10.1016/j.apmr.2013.03.005

      Abstract

      Objective

      To evaluate the effects of cross-education (contralateral effect of unilateral strength training) during recovery from unilateral distal radius fractures on muscle strength, range of motion (ROM), and function.

      Design

      Randomized controlled trial (26-wk follow-up).

      Setting

      Hospital, orthopedic fracture clinic.

      Participants

      Women older than 50 years with a unilateral distal radius fracture. Fifty-one participants were randomized and 39 participants were included in the final data analysis.

      Interventions

      Participants were randomized to standard rehabilitation (Control) or standard rehabilitation plus strength training (Train). Standard rehabilitation included forearm casting for 40.4±6.2 days and hand exercises for the fractured extremity. Nonfractured hand strength training for the training group began immediately postfracture and was conducted at home 3 times/week for 26 weeks.

      Main Outcome Measures

      The primary outcome measure was peak force (handgrip dynamometer). Secondary outcomes were ROM (flexion/extension; supination/pronation) via goniometer and the Patient Rated Wrist Evaluation questionnaire score for the fractured arm.

      Results

      For the fractured hand, the training group (17.3±7.4kg) was significantly stronger than the control group (11.8±5.8kg) at 12 weeks postfracture (P<.017). There were no significant strength differences between the training and control groups at 9 (12.5±8.2kg; 11.3±6.9kg) or 26 weeks (23.0±7.6kg; 19.6±5.5kg) postfracture, respectively. Fractured hand ROM showed that the training group had significantly improved wrist flexion/extension (100.5°±19.2°) than the control group (80.2°±18.7°) at 12 weeks postfracture (P<.017). There were no significant differences between the training and control groups for flexion/extension ROM at 9 (78.0°±20.7°; 81.7°±25.7°) or 26 weeks (104.4°±15.5°; 106.0°±26.5°) or supination/pronation ROM at 9 (153.9°±23.9°; 151.8°±33.0°), 12 (170.9°±9.3°; 156.7°±20.8°) or 26 weeks (169.4°±11.9°; 162.8°±18.1°), respectively. There were no significant differences in Patient Rated Wrist Evaluation questionnaire scores between the training and control groups at 9 (54.2±39.0; 65.2±28.9), 12 (36.4±37.2; 46.2±35.3), or 26 weeks (23.6±25.6; 19.4±16.5), respectively.

      Conclusions

      Strength training for the nonfractured limb after a distal radius fracture was associated with improved strength and ROM in the fractured limb at 12 weeks postfracture. These results have important implications for rehabilitation strategies after unilateral injuries.

      Keywords

      List of abbreviations:

      ANOVA (analysis of variance), MCAR (missing completely at random), PRWE (Patient Rated Wrist Evaluation), ROM (range of motion)
      Cross-education is a neural adaptation defined as the increase in strength or functional performance of the untrained contralateral limb after unilateral training of the opposite homologous limb.
      • Farthing J.P.
      • Chilibeck P.D.
      • Binsted G.
      Cross-education of arm muscular strength is unidirectional in right-handed individuals.
      • Carroll T.J.
      • Herbert R.D.
      • Munn J.
      • Lee M.
      • Gandevia S.C.
      Contralateral effects of strength training: evidence and possible mechanisms.
      The increase in strength in the untrained limb is related to the gain in magnitude of the trained limb, and is on average 52% of the strength gain observed in the trained muscle.
      • Carroll T.J.
      • Herbert R.D.
      • Munn J.
      • Lee M.
      • Gandevia S.C.
      Contralateral effects of strength training: evidence and possible mechanisms.
      Cross-education is thought to be primarily controlled by neural mechanisms,
      • Carroll T.J.
      • Herbert R.D.
      • Munn J.
      • Lee M.
      • Gandevia S.C.
      Contralateral effects of strength training: evidence and possible mechanisms.
      • Lagerquist O.
      • Zehr E.P.
      • Docherty D.
      Increased spinal reflex excitability is not associated with neural plasticity underlying the cross-education effect.
      • Farthing J.P.
      • Borowsky R.
      • Chilibeck P.D.
      • Binsted G.
      • Sarty G.E.
      Neuro-physiological adaptions associated with cross-education of strength.
      • Fimland M.S.
      • Helegerud J.
      • Solstad G.M.
      • Iversen V.M.
      • Leivseth G.
      • Hoff J.
      Neural adaptations underlying cross-education after unilateral strength training.
      • Farthing J.P.
      • Krentz J.R.
      • Magnus C.R.A.
      • et al.
      Changes in functional magnetic resonance imaging cortical activation with cross education to an immobilized limb.
      but the exact mechanisms are unknown.
      A large gap in the literature remains in applying cross-education to clinical rehabilitation settings. The potential benefit of cross-education for rehabilitation from unilateral injuries (ie, a fractured limb) is an obvious, clinically relevant extension of the work; however, little research has been conducted in clinical application of cross-education.
      • Stromberg B.V.
      Contralateral therapy in upper extremity rehabilitation.
      Stromberg
      • Stromberg B.V.
      Contralateral therapy in upper extremity rehabilitation.
      applied cross-education after wrist/forearm surgeries, but several limitations such as not including raw data, not accounting for baseline differences, and not reporting details of the training program have made it difficult to draw any conclusions from the results. Three studies have applied cross-education to unilateral immobilization in healthy (ie, nonfractured) limbs.
      • Farthing J.P.
      • Krentz J.R.
      • Magnus C.R.A.
      • et al.
      Changes in functional magnetic resonance imaging cortical activation with cross education to an immobilized limb.
      • Farthing J.P.
      • Krentz J.R.
      • Magnus C.R.A.
      Strength training the free limb attenuates strength loss during unilateral limb immobilization.
      • Magnus C.R.A.
      • Barss T.S.
      • Lanovaz J.L.
      • Farthing J.P.
      The effects of cross-education on the muscle after a period of unilateral limb immobilization using a shoulder sling and swathe.
      Farthing et al
      • Farthing J.P.
      • Krentz J.R.
      • Magnus C.R.A.
      • et al.
      Changes in functional magnetic resonance imaging cortical activation with cross education to an immobilized limb.
      • Farthing J.P.
      • Krentz J.R.
      • Magnus C.R.A.
      Strength training the free limb attenuates strength loss during unilateral limb immobilization.
      found that cross-education strength training on the nonimmobilized limb provided a maintenance of strength in the immobilized healthy limb after wearing a forearm cast for 3 weeks. Similarly, Magnus et al
      • Magnus C.R.A.
      • Barss T.S.
      • Lanovaz J.L.
      • Farthing J.P.
      The effects of cross-education on the muscle after a period of unilateral limb immobilization using a shoulder sling and swathe.
      found that strength training of the nonimmobilized arm provided an increase in strength in the healthy immobilized arm after wearing an arm sling for 4 weeks. These studies suggest that cross-education can benefit a healthy immobilized limb. As yet, there are no randomized controlled clinical trials that have investigated these effects in real injuries that require limb immobilization. More research in this area may help improve the rehabilitation techniques clinicians use postinjury, and in turn may improve function for those with unilateral injuries such as distal radius fractures.
      Distal radius fractures are one of the most common types of fracture,
      • Larsen C.F.
      • Lauritsen J.
      Epidemiology of acute wrist trauma.
      especially in older women.
      • Handoll H.H.G.
      • Madhok R.
      • Howe T.E.
      Rehabilitation for distal radial fractures in adults.
      Rehabilitation after a distal radius fracture is quite slow, and it can often be difficult for individuals to return to their normal level of functioning. Brogren et al
      • Brogren E.
      • Hofer M.
      • Petranek M.
      • Dahlin L.B.
      • Atroshi I.
      Fractures of the distal radius in women aged 50 to 75 years: natural course of patient-reported outcome, wrist motion and grip strength between 1 year and 2-4 years after fracture.
      showed that 1 year postfracture, grip strength was 88% of the nonfractured limb. Similarly, Trumble et al
      • Trumble T.E.
      • Schmitt S.R.
      • Vedder N.B.
      Factors affecting functional outcome of displaced intra-articular distal radius fractures.
      found that 2.4 years postfracture, grip strength was 69% of the nonfractured limb and range of motion (ROM) was 75% of the nonfractured limb. A Cochrane Review by Handoll et al
      • Handoll H.H.G.
      • Madhok R.
      • Howe T.E.
      Rehabilitation for distal radial fractures in adults.
      examined the effects of rehabilitation beginning both during and after immobilization in adults with distal radius fractures. Fifteen randomized controlled trials were included, whereby treatment was conservative and involved plaster cast immobilization. The review found that there was insufficient evidence to determine the best form of rehabilitation after distal radius fractures. New ways of improving rehabilitation to enhance recovery and to provide better functional outcome are important to investigate.
      One way of improving strength and functional gains in the fractured hand may be to apply cross-education during recovery from unilateral distal radius fractures. Unilateral distal radius fractures represent an adequate clinical model to test the efficacy of cross-education due to the standard immobilization intervention of forearm casting for approximately 6 weeks. In our clinic, there is no rigorous therapeutic intervention prescribed for individuals beyond ROM exercises for the fractured limb, and potential referral to physical therapy for more severe fractures. To our knowledge, there are no rehabilitation protocols that incorporate a formal strength training program of the nonfractured side as part of the recovery for the fractured side after distal radius fractures.
      • Handoll H.H.G.
      • Madhok R.
      • Howe T.E.
      Rehabilitation for distal radial fractures in adults.
      The purpose of this study was to apply cross-education to unilateral distal radius fractures in women 50 years of age and older and to evaluate the effects on grip strength, ROM, and function. The hypothesis was that strength training of the nonfractured limb in addition to standard rehabilitation of the fractured limb would provide better strength and functional outcome than standard rehabilitation alone after a unilateral distal radius fracture.

      Methods

      Participants

      Women aged 50 years and older with a unilateral distal radius fracture were recruited for 1 year from the fracture clinic at Royal University Hospital in Saskatoon, Saskatchewan, Canada, under the direction of 1 orthopedic surgeon. Patients referred to the clinic who met inclusion criteria were invited to participate in the study before their first visit to the clinic. Exclusion criteria included any prior upper body injury or joint problem interfering with daily life, or any history of upper-extremity neurologic problems (eg, stroke, multiple sclerosis, Parkinson's disease, vestibular disorders, reflex neuropathy). Participants were also excluded if the fracture was >2 weeks old at the time of the first visit to the clinic or if there were multiple fractures of the wrist and forearm. All participants completed the Mini-Cognitive Assessment Instrument for Dementia
      • Borson S.
      • Scanlan J.
      • Brush M.
      • Vitaliano P.
      • Dokmak A.
      The mini-cog: a cognitive “vital signs” measure for dementia screening in multi-lingual elderly.
      to screen for cognitive impairment. Those who were unable to remember any words in the word recall and those who scored an abnormal clock draw test and recalled only 1 or 2 words were not included in the study.
      A sample size calculation was completed using G Power 3.1
      • Faul F.
      • Erdfelder E.
      • Buchner A.
      • Lang A.G.
      Statistical power analyses using G*Power 3.1: tests for correlation and regression analyses.
      ,a for the primary outcome variable (ie, strength). On the basis of our previous immobilization cross-education studies involving forearm casting,
      • Farthing J.P.
      • Krentz J.R.
      • Magnus C.R.A.
      • et al.
      Changes in functional magnetic resonance imaging cortical activation with cross education to an immobilized limb.
      • Farthing J.P.
      • Krentz J.R.
      • Magnus C.R.A.
      Strength training the free limb attenuates strength loss during unilateral limb immobilization.
      we anticipated a 13% difference in affected limb strength between training and control. Because we have no previous data on cross-education effects on injured participants, we used a much smaller effect size estimate based on a 5% difference between groups to achieve a more conservative sample size estimate. Using alpha of .05 at 80% power, and an effect size of 0.2, the total required sample size was 36 (ie, 18 per group). Before the commencement of the study, all participants completed written informed consent approved by the Biomedical Ethics Review Board at the University of Saskatchewan with subsequent operational approval from the Saskatoon Health Region. Participants completed the Waterloo Handedness Questionnaire
      • Bryden M.P.
      Measuring handedness with questionnaires.
      at the first clinic visit to determine handedness. The 10-item questionnaire is scored from −20 to +20, whereby negative scores indicate left-handedness and positive scores indicate right-handedness. Participant characteristics per group are shown in table 1.
      Table 1Descriptive characteristics for all randomized participants
      GroupAge (y)Height (cm)Weight (kg)Waterloo Handedness ScoreCasting Period (d)Dominant/Nondominant FractureNumber of Fractures Repaired SurgicallyNumber Attended Physiotherapy
      Train (n=27)63.3±10.0161.8±6.270.3±17.514.6±9.442.2±6.0Dominant=12

      Nondominant=15
      97
      Control (n=24)62.7±10.2159.6±6.870.1±19.716.4±8.138.9±6.0Dominant=13

      Nondominant=11
      27
      NOTE. Values for age, height, weight, Waterloo Handedness Score, and casting period are mean ± SD. Dominant/nondominant fracture, number of surgeries, and number attended physiotherapy are frequencies per group. There are no significant differences between groups for any participant characteristics.

      Study design

      Participants were randomly assigned to 1 of 2 groups using a computer random number generator (see fig 1 for participant enrollment flow diagram). Randomization was completed at the first visit to the clinic by a researcher who did not conduct any of the testing procedures. The orthopedic surgeon and all other testing staff were blinded to the randomization of groups to limit any bias, altered treatment, or encouragement during testing procedures. Group 1 participants received the standard clinical rehabilitation protocol after a distal radius fracture and strength trained their nonfractured limb throughout the duration of the study (Train), and Group 2 received the standard clinical rehabilitation protocol after a distal radius fracture (Control). The standard clinical rehabilitation protocol included forearm casting; 6 visits to the fracture clinic at weeks 1, 3, 6, 9, 12, and 26 postfracture; and the adoption of 3 paper-based exercise protocols designed by a panel of physical therapists targeting the fractured side (in cast, 6wk postfracture, and 9wk postfracture). The orthopedic surgeon coached patients on each of the time-specific protocols at the appropriate time. Standard rehabilitation began with active ROM exercises for the neck, shoulder, elbow, fingers, and thumb while in the cast. Once the cast was removed, exercises focused on improving active and passive ROM of the fractured wrist and hand (ie, supination, pronation, flexion, extension). Stretching continued at 9 weeks postfracture, and strengthening exercises were integrated into the exercise regimen. Strengthening exercises such as wrist curls and gripping a soft ball/sponge/play dough were prescribed once per day. Participants were instructed to complete the exercises 10 to 12 times per day. At 12 weeks postfracture, the patients were encouraged to continue with their exercises, and no formal limitations on their activity levels were imposed. The standard rehabilitation protocol encouraged patients to continue these exercises throughout recovery; however, no training log or formalized regimen was implemented to track adherence. All exercises were to be completed at home, unsupervised on the patient's own time, with no prescribed exercises given to the nonfractured arm. Standard rehabilitation did not require patients to see a physiotherapist, but some were referred by the orthopedic surgeon or by their own family physician and attended physiotherapy on their own initiative (see table 1).
      Figure thumbnail gr1
      Fig 1Participant enrollment flow diagram. Final n for Train=18. Final n for Control=21. All dropouts left the study prior to the 9-week follow-up testing point; therefore, no data were collected on the fractured arm and dropouts were not included in the final analysis.

      Training intervention

      The training group participants (Train) strength trained their nonfractured arm during the casting period and continued to strength train their nonfractured arm throughout the follow-up period (ie, 26wk total). The strength training intervention was completed in addition to the standard clinical rehabilitation protocol described above (Control). Strength training during the casting period was progressive in nature, beginning with 2 sets of 8 repetitions and increasing up to a maximum of 5 sets of 8 repetitions of maximal voluntary effort handgrip contractions as tolerated.
      Strength training of the nonfractured side began immediately after the first clinic visit. Handgrip training was performed using standard handgrip trainersb to train finger, hand, and forearm strength. The resistance levels in the handgrip trainers ranged from extra light (0.7-2.3kg) to extra heavy (4.1-14.1kg). In the event that the extra heavy handgrip trainersb were not strong enough, participants used coil resistance handgrip trainersc to progress their training. Each maximal handgrip contraction was held for 3 seconds, and therefore was essentially isometric in nature. Participants were instructed to increase resistance with the coil resistance trainersc by beginning with the hand at the bottom of the handles, and to move the hand up (closer to the coil) as the exercises became less difficult. Strength was assessed for each participant to determine which handgrip trainer would begin the training program. Progression in resistance was individually determined and monitored throughout the study by telephone calls and at subsequent visits. Participants completed the exercises 3 times per week, and recorded adherence in a training log monitored by the researchers. Participants had to complete at least 1 training session/week (on average) to be considered trained and included in the final data analysis. The strength training intervention was unsupervised and conducted individually at home. Training participants were contacted via telephone biweekly to encourage adherence and to monitor training. To ensure there was no effect of the phone calls on rehabilitation, the control group participants were also called via telephone biweekly and were asked how their wrist was feeling, and whether there had been any changes in their wrist since the last time they were contacted.
      All participants were tested at regular visits to the clinic (weeks 1, 3, 6, 9, 12, and 26); however, the present study displays results only from 4 time points: weeks 1 (1–2wk postfracture), 9, 12, and 26. Weeks 3 and 6 were not included in the analysis because only the nonfractured side could be measured at these time points for practical reasons.

      Strength

      Isometric grip strength was assessed using a calibrated hand dynamometer.d Testing was conducted with participants seated, the shoulder completely adducted, elbow flexed at 90°, and the wrist in neutral position (palm facing medially). The peak value obtained from 3 maximal voluntary efforts was used for comparison. The contractions were 3 seconds in duration with each contraction separated by a 1-minute rest. The nonfractured extremity was always tested first. At week 1, grip strength was assessed on the nonfractured side only. Week 9 (ie, 3wk after cast removal) was the first time point that participants were able to complete a maximal contraction on the fractured side. Both sides were tested for strength at weeks 9, 12, and 26. Participants were instructed to squeeze the dynamometer as hard as they could for the duration of the contraction and were given verbal encouragement at each trial. To minimize the learning effect, all participants were familiarized with the dynamometer before the contractions.

      Range of motion

      Active ROM was assessed manually using a goniometer for wrist flexion, extension, supination, and pronation. Wrist flexion and extension scores were added together to give a combined flexion/extension range. Supination and pronation were also added together for a combined supination/pronation range. All measures were conducted with the participant seated, shoulder fully adducted, and the elbow bent 90°. ROM was measured on the fractured limb only at weeks 9, 12, and 26.

      Patient Rated Wrist Evaluation

      The Patient Rated Wrist Evaluation (PRWE)
      • MacDermid J.C.
      • Turgeon T.
      • Richards R.S.
      • Beadle M.
      • Roth J.H.
      Patient rating of wrist pain and disability: a reliable and valid measurement tool.
      is a 15-item questionnaire designed to assess wrist pain and function with activities of daily living. Respondents self-reported levels of wrist pain and function using a scale ranging from 0 to 10 (0=no pain/no difficulty; 10=worst pain/unable to do activity). A total score was calculated by adding the responses for each question (best score=0; worst score=150). Results for the PRWE questionnaire are shown for weeks 1, 9, 12, and 26. Week 1 was answered as a retrospective prefracture score. Weeks 9, 12, and 26 were completed for the corresponding time point postfracture.

      Data analysis

      All data were analyzed using SPSS 20.0e and were checked for normality using skewness and kurtosis tests. The primary outcome for the study was strength for the fractured arm, and secondary outcomes were ROM and the PRWE questionnaire score for the fractured arm. As described in the Consolidated Standards of Reporting Trials statement, a modified intention-to-treat analysis
      • Abraha I.
      • Montedori A.
      • Romagnoli C.
      Modified intention to treat: frequency, definition and implication for clinical trials.
      • Abraha I.
      • Montedori A.
      Modified intention to treat reporting in randomized controlled trials: systematic review.
      was used to determine whether the trial would work in a group of adhering participants. This was the first clinical trial that attempted to apply cross-education in a wrist fracture setting, and future trials should use intention-to-treat analysis to determine the outcome in both adhering and nonadhering participants once the preliminary trial has been conducted. Group series mean was used to replace missing data if they were determined to be missing completely at random (MCAR).
      • Tabachnick B.G.
      • Fidell L.S.
      Using multivariate statistics.
      Strength was analyzed using a Group (Train, Control)×Time (Week 1, 9, 12, and 26)×Arm (Fractured, Nonfractured) repeated-measures analysis of variance (ANOVA). Week 1 strength values for the nonfractured arm were used as week 1 strength values for the fractured arm. The nonfractured arm baseline measurement was also assumed as the fractured arm baseline measurement because it was impossible to get a strength measure on the fractured arm at week 1. ROM (fractured arm only) was analyzed using a Group (Train, Control)×Time (Week 9, 12, and 26) repeated-measures ANOVA. The PRWE questionnaire was analyzed using a Group (Train, Control)×Time (Week 1, 9, 12, and 26) repeated-measures ANOVA. Week 1 for the PRWE questionnaire was a retrospective prefracture score. If significant main effects or interactions were detected, simple main effects analysis continued using 1-way ANOVA and Bonferroni adjustments. Bonferroni adjustments were made using SPSS programming where possible (identified by stating Bonferroni adjustments were made for multiple comparisons) or were adjusted for manually by dividing by the number of tests (ie, P<.05/3=.017). Significance was accepted at P<.05.

      Results

      Fifty-one women with an average age of 63.0±10.0 years, height of 160.7±6.5cm, and weight of 70.2±18.4kg were randomized in the study (see fig 1 for participant enrollment flow diagram and table 1 for participant characteristics). Of the 40 women who initiated the intervention or control period and completed the study, there was one nonadherent participant in the training group who did not complete the minimum requirement of strength training sessions (at least 1 training session/week) and therefore was not included in the data analysis following a modified intention-to-treat
      • Abraha I.
      • Montedori A.
      • Romagnoli C.
      Modified intention to treat: frequency, definition and implication for clinical trials.
      • Abraha I.
      • Montedori A.
      Modified intention to treat reporting in randomized controlled trials: systematic review.
      approach. Dropouts were not included in the final data analysis because all left the study before the 9-week follow-up testing point; therefore, no data were collected on the fractured arm (ie, no group comparisons could be made for the primary outcome). The final number of participants included in the analysis was 18 in the training group and 21 in the control group.

      Strength

      Little's MCAR test was used to determine that missing data for strength (χ232=39.89, P=.159) were MCAR. There were a total of 21 of 312 missing data points for strength (see table 2 for a description of missing data). Therefore, group series means were used to replace all missing data.
      • Tabachnick B.G.
      • Fidell L.S.
      Using multivariate statistics.
      There were no significant differences between groups for strength at week 1. There was a significant Group×Time interaction (F3,37=4.01, P=.009, partial η2=.098), and a significant Time×Arm interaction (F3,37=108.38, P<.001, partial η2=.745). Post hoc analysis for the fractured arm showed that there was a significant difference between the training and control groups at 12 weeks postfracture (17.3±7.4kg and 11.8±5.8kg, respectively) (Bonferroni adjusted, P<.05/3=.017) (fig 2). There were no significant strength differences in the fractured arm between the training and control groups at 9 (12.5±8.2kg; 11.3±6.9kg) or 26 weeks (23.0±7.6kg; 19.6±5.5kg) postfracture, respectively. Week 1 was significantly different than all other time points for both the training group and the control group in the fractured arm (Bonferroni adjusted for multiple comparisons, P<.05). For the fractured arm of the training group, week 9 (12.5±8.2kg) was significantly different than week 12 (17.3±7.4kg) and weeks 9 and 12 were significantly different than week 26 (23.0±7.6kg) (Bonferroni adjusted for multiple comparisons, P<.05). For the fractured arm of the control group, weeks 9 (11.3±6.9kg) and 12 (11.8±5.8kg) were significantly different than week 26 (19.6±5.5kg) (Bonferroni adjusted for multiple comparisons, P<.05).
      Table 2Number of missing data points per group
      VariableGroupWeek 1Week 9Week 12Week 26Total Missing
      StrengthTrain011021
      Control0586
      Flexion/extension ROMTrainNT21024
      ControlNT243
      Supination/pronation ROMTrainNT210
      ControlNT243
      PRWE questionnaireTrain710228
      Control8325
      NOTE. ROM was not tested at week 1. Train n=18, Control n=21. Table includes all participants in the final analysis. The total number of data points for strength was 312, ROM 234, and PRWE questionnaire 156.
      Abbreviation: NT, not tested.
      Figure thumbnail gr2
      Fig 2Fractured limb handgrip strength (mean ± SE). There was a significant Group×Time interaction, and a significant Time×Arm interaction for strength (P<.05). NOTE. Dotted line is week 1 nonfractured limb strength. *Significantly different than all other time points. **Significantly different than week 9. ***Significantly different than weeks 9 and 12 (adjusted for multiple comparisons, P<.05). #Significant difference between groups (Bonferroni-adjusted, P<.05/3=.017).
      The nonfractured arm of the training group significantly increased strength from week 1 (28.1±6.0kg) to weeks 9 (30.8±6.9kg), 12 (30.7±6.5kg), and 26 (31.0±6.9kg) (Bonferroni adjusted for multiple comparisons, P<.05) (fig 3). The nonfractured arm of the control group significantly decreased strength from week 9 (26.9±4.4kg) to week 12 (24.9±4.4kg) (Bonferroni adjusted for multiple comparisons, P<.05). There was a significant difference between groups at 9, 12, and 26 weeks for nonfractured arm strength (P<.05), and when Bonferroni adjusted, week 12 remained significantly different (P<.05/3=P<.017). Raw strength data can be viewed in table 3.
      Figure thumbnail gr3
      Fig 3Nonfractured limb handgrip strength (mean ± SE). There was a significant Group×Time interaction, and a significant Time×Arm interaction for strength (P<.05). *Significantly different than week 1. **Significantly different than week 9 (adjusted for multiple comparisons, P<.05). #Significant difference between groups (unadjusted). ##Significant difference between groups (Bonferroni-adjusted, P<.05/3=.017).
      Table 3Raw handgrip strength data (kg)
      GroupNonfractured ArmFractured Arm
      Week 1Week 9Week 12Week 26Week 1Week 9Week 12Week 26
      Train (n=18)28.1±6.030.8±6.9
      Significant difference between groups (unadjusted, P<.05).
      30.7±6.5
      Significant difference between groups (Bonferroni-adjusted, P<.05/3=.017).
      31.0±6.9
      Significant difference between groups (unadjusted, P<.05).
      28.1±6.012.5±8.217.3±7.4
      Significant difference between groups (Bonferroni-adjusted, P<.05/3=.017).
      23.0±7.6
      Control (n=21)26.4±5.026.9±4.424.9±4.427.0±5.026.4±5.011.3±6.911.8±5.819.6±5.5
      NOTE. Values are mean ± SD. Only significant differences between groups are displayed in the table. Week 1 strength for the fractured arm was not measured; therefore, values are borrowed from the nonfractured arm at week 1.
      Significant difference between groups (unadjusted, P<.05).
      Significant difference between groups (Bonferroni-adjusted, P<.05/3=.017).

      Range of motion

      Little's MCAR test was used to determine that missing data for ROM (χ212=11.75, P=.466) were MCAR. There were a total of 24 of 234 missing data points for ROM (see table 2 for a description of missing data). Therefore, group series means were used to replace all missing data.
      • Tabachnick B.G.
      • Fidell L.S.
      Using multivariate statistics.
      For ROM, there was a significant Group×Time interaction for flexion/extension (F2,37=8.20, P=.001, partial η2=0.181) and a significant time main effect for flexion/extension (F2,37=30.09, P<.001, partial η2=0.449) and supination/pronation (F2,37=8.13, P=.001, partial η2=.180). Post hoc analyses revealed that for flexion/extension ROM, there was a significant difference between the training group (100.5°±19.2°) and the control group (80.2°±28.7°) at 12 weeks postfracture (Bonferroni adjusted, P<.05/3=.017) (fig 4). There were no significant differences between the training and control groups for flexion/extension ROM at 9 (78.0°±20.7°; 81.7°±25.7°) or 26 weeks (104.4°±15.5°; 106.0°±26.5°) (see fig 4) or for supination/pronation ROM at 9 (153.9°±23.9°; 151.8°±33.0°), 12 (170.9°±9.3°; 156.7°±20.8°), or 26 weeks (169.4°±11.9°; 162.8±18.1°), respectively (fig 5). For flexion/extension in the training group, week 9 (78.1°±20.7°) was significantly different than weeks 12 (100.5°±19.2°) and 26 (104.4°±15.5°) (see fig 4) (Bonferroni adjusted for multiple comparisons, P<.05). For the control group, weeks 9 (81.7°±25.7°) and 12 (80.2°±28.7°) were significantly different than week 26 (106.0°±26.5°) (Bonferroni adjusted for multiple comparisons, P<.05). There were no other significant differences for supination/pronation ROM (see fig 5). Raw ROM data can be viewed in table 4.
      Figure thumbnail gr4
      Fig 4Flexion/extension ROM for fractured hand only (mean ± SE). *Significantly different than week 9. **Significantly different than weeks 9 and 12 (adjusted for multiple comparisons, P<.05). #Significant difference between groups (Bonferroni-adjusted, P<.05/3=.017).
      Figure thumbnail gr5
      Fig 5Supination/pronation ROM for fractured hand only (mean ± SE). No significant differences.
      Table 4Raw ROM data (degrees)
      GroupFlexion/ExtensionSupination/Pronation
      Week 9Week 12Week 26Week 9Week 12Week 26
      Train (n=18)78.0±20.7100.5±19.2
      Significant difference between groups (Bonferroni-adjusted, P<.05/3=.017).
      104.4±15.5153.9±23.9170.9±9.3169.4±11.9
      Control (n=21)81.7±25.780.2±28.7106.0±26.5151.8±33.0156.7±20.8162.8±18.1
      NOTE. Values are mean ± SD. Only significant differences between groups are displayed in the table.
      Significant difference between groups (Bonferroni-adjusted, P<.05/3=.017).

      Patient Rated Wrist Evaluation

      Little's MCAR test was used to determine that missing data for the PRWE questionnaire (χ220=22.87, P=.295) were MCAR. There were a total of 28 of 156 missing data points for the PRWE questionnaire (see table 2 for a description of missing data). Therefore, group series means were used to replace all missing data.
      • Tabachnick B.G.
      • Fidell L.S.
      Using multivariate statistics.
      There were no significant differences between groups at week 1 for the PRWE questionnaire. There was a time main effect pooled across group (F3,37=48.93, P<.001, partial η2=.569); however, there were no significant differences between the training and control groups at 9 (54.2±39.0; 65.2±28.9), 12 (36.4±37.2; 46.2±35.3), or 26 weeks (23.6±25.6; 19.4±16.5), respectively (table 5). No other significant differences were found.
      Table 5PRWE questionnaire scores
      GroupWeek 1Week 9Week 12Week 26
      Train (n=18)3.1±4.254.2±39.036.4±37.223.6±25.6
      Control (n=21)6.4±6.065.2±28.946.2±35.319.4±16.5
      NOTE. Values are mean ± SD. There are no significant differences. A high score is more symptomatic. Week 1 is retrospective prefracture score. Weeks 9, 12, and 26 are postfracture scores for corresponding time point.

      Discussion

      The main finding of this study was that strength training the nonfractured arm after a distal radius fracture improved strength and ROM at 12 weeks postfracture in the fractured arm. These results demonstrate that cross-education strength training may be beneficial to older women in recovery after a distal radial fracture. To our knowledge, this is the first randomized controlled trial to demonstrate the efficacy of cross-education of strength in a clinical setting involving limb fractures. These results have potential for changing current rehabilitation protocols in the early recovery stages after distal radius fracture, following further investigation.
      The study showed that the training group had a quicker recovery in both strength and ROM on the fractured limb than the control group. The control group had a 4.4% increase in strength from week 9 to week 12, whereas the training group had a 38.4% increase in strength from week 9 to week 12 (see fig 2). The difference between the training and control groups is approximately 34%; therefore, the effect of the training could be perceived as a 34% difference in recovery of strength between 9 and 12 weeks. The average transfer of strength in healthy, nonimmobilization cross-education studies is 52% of the strength in the trained limb.
      • Carroll T.J.
      • Herbert R.D.
      • Munn J.
      • Lee M.
      • Gandevia S.C.
      Contralateral effects of strength training: evidence and possible mechanisms.
      Carroll et al
      • Carroll T.J.
      • Herbert R.D.
      • Munn J.
      • Lee M.
      • Gandevia S.C.
      Contralateral effects of strength training: evidence and possible mechanisms.
      suggested that if cross-education were applied in a rehabilitation setting, the effect may be small and not show significant improvements in activities of daily living. Although a strength training effect was found, this did not transfer to significant differences between the groups for the PRWE questionnaire score. Results for flexion/extension ROM showed that the control group had a slight decline in range of −1.8% from 9 to 12 weeks postfracture and the training group showed an increase in range of 28.7% (see fig 4). This indicates that the control group had no improvement in flexion/extension ROM from 9 to 12 weeks whereas the training group was almost fully recovered by 12 weeks postfracture.
      The decline in strength after wrist fracture is comparable with other literature investigating grip strength after wrist fractures.
      • Földhazy Z.
      • Törnkvist H.
      • Elmstedt E.
      • Andersson G.
      • Hagsten B.
      • Ahrengart L.
      Long-term outcome of nonsurgically treated distal radius fractures.
      Földhazy et al
      • Földhazy Z.
      • Törnkvist H.
      • Elmstedt E.
      • Andersson G.
      • Hagsten B.
      • Ahrengart L.
      Long-term outcome of nonsurgically treated distal radius fractures.
      found that grip strength after 12 weeks of distal radius fracture was approximately 65% of the nonfractured limb, whereas our results showed that grip strength was 62% of the nonfractured limb for the training group and 45% for the control group. At 26 weeks postfracture, Földhazy
      • Földhazy Z.
      • Törnkvist H.
      • Elmstedt E.
      • Andersson G.
      • Hagsten B.
      • Ahrengart L.
      Long-term outcome of nonsurgically treated distal radius fractures.
      showed that strength was 76% of the nonfractured limb, and the training and control groups values were 82% and 74%, respectively. Although the studies have similar changes in strength, it is difficult to directly compare the 2 studies considering Földhazy et al's
      • Földhazy Z.
      • Törnkvist H.
      • Elmstedt E.
      • Andersson G.
      • Hagsten B.
      • Ahrengart L.
      Long-term outcome of nonsurgically treated distal radius fractures.
      study included participants with only nonsurgical fractures and the present study included participants with both surgical and nonsurgical fractures.
      Significant differences in strength between the training and control groups were evident at 12 weeks postfracture, roughly 6 weeks after the immobilization period ended. Why significant differences were shown at 12 weeks and not 9 weeks is unknown. It is possible that at 9 weeks postfracture, participants were still very sore, and potentially so sore that the pain during a handgrip contraction prevented comfortable and maximal strength testing. At 12 weeks postfracture, the participants may have been much more comfortable completing a maximal handgrip test, which may have accounted for the significant difference at 12 weeks.
      Cross-education literature from noninjury settings has shown the effect occurs in training programs varying from 3 to 8 weeks in duration
      • Farthing J.P.
      • Chilibeck P.D.
      • Binsted G.
      Cross-education of arm muscular strength is unidirectional in right-handed individuals.
      • Kannus P.
      • Alosa D.
      • Cook L.
      • et al.
      Effect of one-legged exercise on the strength, power and endurance of the contralateral leg: a randomized, controlled study using isometric and concentric isokinetic training.
      • Farthing J.P.
      • Chilibeck P.D.
      The effects of eccentric training at different velocities on cross-education.
      • Munn J.
      • Herbert R.D.
      • Hancock M.J.
      • Gandevia S.C.
      Training with unilateral resistance exercise increases contralateral strength.
      ; therefore, it may be expected that significant effects would be shown before 12 weeks postfracture (ie, at 9 weeks). Perhaps if participants were tested weekly for strength between weeks 9 and 12, significant differences may have been shown before 12 weeks postfracture. The significant effect at 12 weeks may be due to the time course of the injury itself, which could have altered the neurologic transfer in strength that would normally be shown in cross-education training without an injury. More research is needed to further investigate the time course and mechanisms behind these effects in a clinical setting.
      Importantly, the cross-education home-based strength training program effectively increased strength in the nonfractured hand of the training group from week 1 to weeks 9, 12, and 26. The training group showed an average increase of 9.6% in strength (average from weeks 9, 12, and 26). This increase in strength is comparable to that in Farthing et al's
      • Farthing J.P.
      • Krentz J.R.
      • Magnus C.R.A.
      • et al.
      Changes in functional magnetic resonance imaging cortical activation with cross education to an immobilized limb.
      study, which showed a 10.7% increase in handgrip strength in the trained limb using a supervised laboratory-based training program. The present study is also novel because of the unsupervised, at-home strength training program. Cross-education strength training studies have typically been completed in supervised controlled laboratory environments. Therefore, a 9.6% increase in strength from an at-home grip strength program demonstrates that this type of training is quite feasible in a clinical environment where supervised training is more difficult or impossible.
      Cross-education is known to produce contralateral limb strength adaptations following unilateral training; however, there is no apparent evidence to suggest that cross-education strength training can produce increases in ROM of an opposite limb. The present study showed that the training group had significantly improved wrist flexion/extension ROM at 12 weeks postfracture compared with the control group. Evidence is limited in examining the effects of cross-education on ROM. Although Nelson et al
      • Nelson A.G.
      • Kokkonen J.
      • Winchester J.B.
      • et al.
      A 10-week stretching program increases strength in the contralateral muscle.
      investigated the effect of unilateral stretching on strength in the opposite limb, to our knowledge there are no studies that have investigated the effect of unilateral strength training on ROM in the opposite limb. More research is needed to determine whether cross-education strength training can produce increased ROM in the opposite limb.
      There were no significant differences between groups for supination/pronation ROM. This is likely due to the quick recovery of supination/pronation for both groups, and a ceiling effect for the total ROM. The training group already had a range of 153.9° at 9 weeks postfracture and improved to 169.4° at 26 weeks postfracture. Similarly, the control group had a range of 151.8° at 9 weeks and 162.8° at 26 weeks postfracture.
      There were no significant differences between the training and control groups for the PRWE questionnaire scores (see table 5). Significant differences were likely not detected because of the high variability of the measure. Based on current data, there is no evidence to suggest that the cross-education intervention had a significant impact on self-reported pain and function during activities of daily living of the fractured limb, despite evidence for improved strength and ROM. The PRWE questionnaire is the most commonly used instrument for evaluating outcome in patients with distal radius fractures
      • Changulani M.
      • Okonkwo U.
      • Keswani T.
      • Kalairajah Y.
      Outcome evaluation measures for wrist and hand – which one to choose?.
      ; however, it may not be sensitive enough to detect small changes between groups. A more direct measure of function may be necessary to accurately assess the effects on recovery. The minimal clinically important difference, defined as the minimum change in a score that indicates a meaningful difference for the patient,
      • Smith M.V.
      • Calfee R.P.
      • Baumgarten K.M.
      • Brophy R.H.
      • Wright R.W.
      Upper extremity-specific measures of disability and outcomes in orthopaedic surgery.
      may be more relevant for evaluating changes in function. The minimal clinically important difference for the PRWE questionnaire is a change of 24 points (16%).
      • Schmitt J.S.
      • Di Fabio R.P.
      Reliable change and minimum important difference (MID) proportions facilitated group responsiveness comparisons using individual threshold criteria.
      The training group had a change of 30.6 points from 9 to 26 weeks, and the control group had a change of 45.8 points from 9 to 26 weeks, indicating that both groups had a clinical improvement in self-reported function by 26 weeks.

      Study limitations

      One limitation of the present study is we cannot be absolutely certain that the training group completed the exercises as prescribed. The training program was taught to the intervention group at the initial visit to the clinic and was completed unsupervised at the participants' homes. Training logs were given out to track adherence and monitor progression. This self-monitored at-home program was chosen because it could be implemented in such a manner that would decrease participant travel burden and decrease clinical visits. Despite the unsupervised nature of the program and some uncertainty regarding adherence (ie, self-report training logs), it was effective for increasing strength. Arguably the strength increase for the training group participants was partly due to using their nonfractured arm more than normal for daily activities. However, the control group participants would have also used their nonfractured arm the same amount as the training group participants, and the control group participants showed a significant decrease in strength from week 9 to week 12. This is important because it points toward the possibility of a global strength decline in both arms after a unilateral distal radius fracture when attempting to implement the current clinical practice. This may suggest that patients may not be adhering to the standard rehabilitation program. Compliance to the standard rehabilitation program was not recorded and is not part of the standard clinical practice; therefore, there was no indication of adherence to the standard rehabilitation program for either group, which is an additional limitation to the study.
      Another potential limitation is that we did not account for the effect of physical therapy or surgery in the analysis. Conveniently, of the participants included in the final data analysis, the number who attended physical therapy was very similar between groups (Train 6; Control 7); therefore, this even distribution should not have affected the results if the physical therapy treatments received in each group were similar. The number of surgeries for participants included in the final data analysis was 6 in the training group and 2 in the control group. The small sample size limited the ability to separate out the number of participants who received surgery in the data analysis, which is a limitation of the study. We were unable to do any subgroup analyses because of the small sample size. Further analysis could have consisted of dividing by age, and surgical/nonsurgical fractures. Future studies may investigate these factors and may also look at a longer term of follow-up to determine the effects on overall function.

      Conclusions

      This intervention study found that strength training the nonfractured limb was associated with significantly improved strength and ROM in the fractured limb via cross-education in the early stages of rehabilitation. This study marks a crucial advancement in the field because, to the best of our knowledge, it is the first randomized controlled trial to demonstrate that training of a homologous noninjured limb may benefit an immobilized, injured limb. These findings may have potential implications for altering the current clinical rehabilitation protocols after wrist fractures. More investigations are warranted before changes to clinical practice can be recommended. Future research may investigate cross-education effects in other types of injuries, the effects over longer follow-up, and the mechanisms behind the effect. This work adds to the recent translational study by Dragert and Zehr
      • Dragert K
      • Zehr EP
      High-intensity unilateral dorsiflexor resistance training results in bilateral neuromuscular plasticity after stroke.
      where strength training of the less-affected limb was effective for inducing bilateral neuromuscular plasticity in chronic stroke patients.

      Suppliers

      • a.
        G Power 3.1, Department of Experimental Psychology, Heinrich-Heine-University, 40225 Düsseldorf, Germany. Software available as a free download.
      • b.
        DIGI-FLEX handgrip trainers; CANDO, PO Box 1174, White Plains, NY 10602.
      • c.
        ZoN Fitness Resistance Hand Grips, 1950 Stanley St, Northbrook, IL 60065.
      • d.
        Baseline Hydraulic Hand Dynamometer, PO Box 1500, White Plains, NY 10602.
      • e.
        SPSS Inc, 233 S Wacker Dr, 11th Fl, Chicago, IL 60606.

      Acknowledgments

      We thank the Royal University Hospital staff at the Outpatients Orthopaedic clinic for their contributions, and Karla Koehn, administrative assistant to Dr Johnston. We also thank the Saskatoon Health Region for the operational approval to conduct the study. We thank our research assistants, Nolan Carrier, BSc, Shane Schwanbeck, MSc, Mike Smith, MSc, Dominika Pindus, MSc, Kellie Boychuk, BSc, and Samantha Mitchell, MSc, for their work.

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