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Logo of nihpaAbout Author manuscriptsSubmit a manuscriptHHS Public Access; Author Manuscript; Accepted for publication in peer reviewed journal;
 
J Hand Surg Am. Author manuscript; available in PMC 2011 April 1.
Published in final edited form as:
PMCID: PMC2872177
NIHMSID: NIHMS186903

Wrist tendon forces during different dynamic wrist motions

Abstract

Purpose

A common treatment of arthritis of the first carpometacarpal joint requires all or a portion of the flexor carpi radialis tendon (FCR) to be used as an interpositional graft. The purpose of this study was to examine the in vitro tendon forces in six wrist flexor and extensors to determine if their force contribution changes during different dynamic wrist motions along with a specific application to the FCR.

Methods

Sixty two fresh frozen cadaver wrists were tested in a wrist joint motion simulator. During wrist flexion-extension, radioulnar deviation, dart throwing and circumduction motions, the peak and average tendon forces were determined for the extensor carpi ulnaris, extensor carpi radialis brevis and longus, abductor pollicis longus, flexor carpi radialis and flexor carpi ulnaris.

Results

During a dart throwing motion, the mean and peak FCR forces were statistically less than during the other 3 motions. Conversely, the mean and peak flexor carpi ulnaris forces were statistically greater during the dart throwing motion than during the other 3 motions.

Discussion

Patients who have undergone a surgical procedure in which all or a portion of the FCR has been harvested, may experience a decrease in wrist strength with wrist motion as the FCR tendon normally applies force during wrist motion. The motion least likely to be affected by such surgery is the dart throwing motion when the force on the remaining FCR is minimized.

Keywords: Tendon Force, Wrist tendons

Introduction

A common treatment of arthritis of the first carpometacarpal joint requires all or a portion of the flexor carpi radialis tendon (FCR) to be used as an interpositional graft. Despite excellent results as reported by Tomaino and Coleman 1, Naidu et al have shown clinically 2 that wrist kinetics are altered when the entire FCR is used in performing a ligament reconstruction tendon interposition (LRTI) and based on this, have advised caution in treating high demand patients. In Naidu et al’s study, the wrist flexion-extension torque ratio was decreased and wrist flexion fatigue resistance decreased when the entire FCR tendon was harvested.

The purpose of this study was to examine the in vitro tendon forces in six wrist flexor and extensors to determine if their force contribution changes during different dynamic wrist motions along with a specific application to the FCR.

Methods

Sixty-two fresh frozen cadaver wrists were tested in a wrist joint motion simulator 36. Each wrist was dynamically moved using a servohydraulic system under computer control. Wrist motion was achieved by applying physiological forces to the extensor carpi ulnaris (ECU), extensor carpi radialis brevis (ECRB), extensor carpi radialis longus (ECRL), abductor pollicis longus (APL), flexor carpi radialis (FCR) and flexor carpi ulnaris (FCU). The forces were applied by separate hydraulic actuators for each tendon. Agonist motion control was used to cause the desired wrist motion while antagonist force control was used to apply a nominal resistive force. The control signals were continuously send to each individual actuator associated with a wrist tendon for each motion. The resultant applied forces in each tendon were measured with load cells in series with each tendon.

Each wrist was moved in cyclic flexion-extension, radioulnar deviation, dart throwing and circumduction motions. The flexion-extension motion was from 30 degrees of extension to 30 degrees of flexion and back. This arc of motion was selected to match the range of flexion-extension motion during the dart and circumduction motions. The radioulnar deviation motion was from 20 degrees of ulnar deviation to 10 degrees of radial deviation and back. The dart throwing motion was from 30 degrees of extension and 10 degrees of radial deviation to 30 degrees of flexion and 10 degrees of ulnar deviation and back. The circumduction motion was an elliptical motion from 30 degrees of extension to 10 degrees of radial deviation to 30 degrees of flexion to 10 degrees of ulnar deviation to 30 degrees of extension. Prior to data collection, each wrist was pre-conditioned by cyclicly moving it through at least 24 cycles of motion under computer control. For the flexion-extension, radioulnar deviation, dart throwing and circumduction motions, data was collected continuously during 6 cycles of motion. The data during the 4th cycle of motion was used for analysis.

During each cycle of each motion, the peak and average force in each tendon was determined. Differences in the peak and average tendon forces among the different wrist motions were statistically compared using a repeated measures ANOVA at p<.05 with a Bonferroni adjustment for multiple comparisons.

Results

During a dart throwing motion, both the peak and mean FCR forces were statistically less (p < 0.026 or less for the peak force; p = 0.000 for the mean force) than during any other of the 3 wrist motions (Tables 1, ,2,2, figure 1). Conversely, during wrist circumduction, the mean and peak FCR forces were statistically greater (p = 0.000 for the peak and the mean forces) than during wrist flexion-extension, wrist radioulnar deviation or the dart throwing motion. During wrist flexion-extension, the mean FCR forces were statistically greater (p = 0.000) than during the radioulnar deviation motion.

Figure 1
FCR forces during one cycle of four wrist motions for an illustrative arm. The x-axis denotes the approximate wrist position during the cycle of motion for each dynamic wrist motion.
Table 1
Peak Tendon Force in N (standard deviation) during four wrist motions
Table 2
Mean Tendon Force in N (standard deviation) during four wrist motions

Of interest, the peak and mean FCU forces were statistically greatest (p = 0.000 for the peak and the mean forces) during a dart throw motion (figure 2). During a flexion-extension motion the peak FCU forces were statistically greater (p = 0.01 or less) than during circumduction or radioulnar deviation while the mean FCU forces during a flexion-extension motion were statistically greater (p = 0.000) than during radioulnar deviation. During radioulnar deviation, the peak and mean FCU forces were statistically less (p = 0.000 for the peak and the mean forces) than during the other 3 motions.

Figure 2
FCU forces during one cycle of four wrist motions for an illustrative arm. The x-axis denotes the approximate wrist position during the cycle of motion for each dynamic wrist motion.

Discussion

The purpose of this study was to examine the in vitro tendon forces in six wrist flexor and extensors to determine if their force contribution changes during different dynamic wrist motions along with a specific application to the FCR. The results demonstrate that the FCR has an important force contribution role during the 4 wrist motions studied, but especially during wrist flexion-extension, radioulnar deviation and circumduction. During a dart throwing motion, the FCU has an important role.

Limitations to this study include it being an in vitro study during which the force contributions of the finger flexor and extensors are not included. This may limit the extent to which these findings can be applied to the clinical situation, as the finger flexor and extensor tendons may compensate for the loss of the FCR. Also, this study doesn’t answer the clinical question of the consequences of using only 50% of the FCR for an interpositional graft. Another limitation is that only 4 wrist motions were studied. Other oblique motions that are similar to a dart throw motion could have been studied.

We previously reported 7 on the average maximum dynamic muscle tensions in four wrist flexors and extensors, for five intact wrists, using an early version of this wrist simulator for wrist flexion-extension and radioulnar deviation. In this earlier study, we used only the ECU, the ECR (where the ECRB and ECRL were clamped together as a single tendon), the FCU and the FCR to cause wrist motion. Although not statistically analyzed, the average maximum FCR force was reported to be greater in flexion-extension (32.9 N) than during radioulnar deviation (22.2 N) and the average maximum FCU force was greater in flexion-extension (44.0 N) than during radioulnar deviation (23.6 N). These peak magnitude values are similar to those found in the current study, when we included the APL and pulled separately on the ECRB and ECRL.

In a pilot study of 3 arms, we examined the wrist tendon forces before and after the FCR hydraulic actuator had been disconnected, so that the FCR could not apply any force during a wrist motion. In these 3 arms, the APL was not included as a wrist tendon, and therefore these arms could not be part of current study. However, we found during the flexion-extension motion, the average peak FCU force increased from 33.5 N to 111.9 N and the average peak ECRL force increased from 56.6 N to 94.2 N after the FCR was deactivated. These force increases occurred as the wrist was moving into wrist flexion. During the radioulnar deviation motion, the average peak FCU force increased from 31.5 N to 118.1 N and peak ECRL forces increase from 45.6 N to 137.6 N after the FCR was deactivated. These force increases occurred as the wrist was moving into radial deviation. As this is a sample size of only 3 arms, no statistical analysis was performed, however these results suggest a trend that much greater compensatory wrist tendon forces are needed to achieve the same wrist motions in the absence of the FCR.

In this study, during all wrist motions, all wrist motors participated in each motion. Removal of the entire FCR should, despite excellent clinical results, lead to wrist weakness. As the FCR is least effected during the dart throwing motion, this is the wrist motion during which the fewest symptoms should be seen. One possible reason for the good clinical results for this highly accepted procedure, has been posed by Beall et al 8. Based on an MRI study, they reported that in 14 patients in which the entire FCR was used for LRTI, 79% had partial regeneration of the FCR and 14% had complete regeneration.

The results of this study suggest that patients who have undergone a surgical procedure in which all or a portion of the FCR has been harvested, may experience difficulty with wrist motion as the FCR tendon is responsible for significant force during wrist motion. The motion least likely to be affected by such surgery is the dart throwing motion when the force on the remaining FCR is minimized.

Acknowledgment

Funded in part by NIH AR50099

Footnotes

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References

1. Tomaino MM, Coleman K. Use of the Entire Width of the Flexor Carpi Radialis Tendon for the Ligament Reconstruction Tendon Interposition Arthroplasty Does Not Impair Wrist Function. American Journal of Orthopedics. 2000;29:283–284. [PubMed]
2. Naidu SH, Poole J, Horne A. Entire Flexor Carpi Radialis Tendon Harvest for Thumb Carpometacarpal Arthroplasty Alters Wrist Kinetics. Journal of Hand Surgery - American Volume. 2006;31:1171–1175. [PubMed]
3. Short WH, Werner FW, Green JK, Sutton LG, Brutus JP. Biomechanical Evaluation of the Ligamentous Stabilizers of the Scaphoid and Lunate: Part 3. Journal of Hand Surgery. 2007;32A:297–309. [PMC free article] [PubMed]
4. Short WH, Werner FW, Green JK, Masaoka S. Biomechanical Evaluation of Ligamentous Stabilizers of the Scaphoid and Lunate. J Hand Surgery. 2002;27A:991–1002. [PMC free article] [PubMed]
5. Short WH, Werner FW, Green JK, Masaoka S. Biomechanical Evaluation of the Ligamentous Stabilizers of the Scaphoid and Lunate: Part 2. Journal of Hand Surgery. 2005;30A:24–34. [PubMed]
6. Werner FW, Palmer AK, Somerset JH, Tong JJ, Gillison DB, Fortino MD, et al. Wrist Joint Motion Simulator. Journal of Orthopaedic Research. 1996;14:639–646. [PubMed]
7. Werner FW, An KN, Palmer AK, Chao EYS. Force Analysis. In: An KN, Berger RA, Cooney WP, editors. Biomechanics of the Wrist Joint. New York: Springer-Verlag, Inc.; 1991. pp. 77–97.
8. Beall DP, Ritchie ER, Campbell SE, Tran HN, Ingari JV, Sanders TG, et al. Magnetic Resonance Imaging Appearance of the Flexor Carpi Radialis Tendon after Harvest in Ligamentous Reconstruction Tendon Interposition Arthroplasty. Skeletal Radiol. 2006;35:144–148. [PubMed]