Electromyographic activity and strength during maximum isometric pronation and supination efforts in healthy adults

Upper arm muscle activity is influenced by both forearm posture and wrist exertion direction during isometric wrist flexion and extension

The purpose of this study was to determine how wrist exertion direction and forearm posture independently influence upper arm muscle activity during isometric wrist contractions. Surface electromyography was recorded from three muscles of the upper-limb: biceps brachii, triceps brachii, and brachioradialis. Participants were seated with their forearm supported in one of three postures (supinated/neutral/pronated) with an adjustable force transducer that could be placed either above, below, or to the right/left of the participant's hand. Participants performed randomized trials of isometric wrist flexion or extension at five relative intensities: 20, 40, 60, 80, or 100% of maximal force. Trials lasted 4.5 s and both wrist force and electromyography data were assessed. In general, the elbow flexors were more active during wrist flexion, while the triceps were more active in wrist extension, but this pattern reversed in certain forearm postures and wrist exertion directions. Both forearm posture and wrist exertion direction resulted in unique effects on upper arm muscle activity. These findings suggest that muscle activity of the upper arm muscles is influenced independently by both posture and force direction, which should be carefully considered by both motor control specialists and ergonomists.

Stability of the distal radioulnar joint with and without activation of forearm muscles

The purpose of this study was to quantify the effect of the flexor carpi ulnaris and the extensor carpi ulnaris muscles on distal radioulnar joint stability. The anteroposterior ulnar head translation in relation to the radius was measured sonographically when the forearm was in a neutral resting position and when the hand was actively pressed on to a surface, with and without intentional flexor carpi ulnaris and extensor carpi ulnaris activation, while also being monitored by an electromyogram. Data on 40 healthy participants indicated a mean anteroposterior translation in the distal radioulnar joint of 4.1 mm (SD 1.08) without and 1.2 mm (SD 0.54) with muscle activation. Our results indicate that intentional ulnar forearm muscle activation results in 70% less anteroposterior ulnar head translation and greater distal radioulnar joint stability. Therefore, the flexor carpi ulnaris and extensor carpi ulnaris muscles serve as dynamic stabilizers of the distal radioulnar joint. This finding may be clinically significant since ulnar forearm muscles strengthening may increase distal radioulnar joint stability.

Protocol for Forearm Pronosupination Strength Measuring in Different Postures: Reliability and Influence of Relevant Factors

IMPORTANCE

Despite the importance of pronosupination strength, which is key in daily activities, current evaluation protocols are disparate, and results differ regarding the influence of factors such as gender, age, limb dominance, or posture.

OBJECTIVE

To design a reliable device to measure pronation and supination torques in different forearm positions, considering the influence of gender, age, and limb dominance.

DESIGN

Reliability study with analysis of intrarater and interrater repeatability and examination of the influence of different factors on the strength of pronation and supination.

SETTING

Biomechanical analysis laboratory of the Instituto de Biomecánica de Valencia.

PARTICIPANTS

Convenience sample of 39 healthy male and female participants, ages 18 to 65 yr.

OUTCOMES AND MEASURES

Pronation strength and supination strength were studied in five forearm positions: 30° and 60° of supination, neutral rotation, and 30° and 60° of pronation. The influence of gender, age, and limb dominance was studied using repeated-measures analysis of variance. Intrarater and interrater reliabilities were studied in 17 participants, and the intraclass correlation coefficients (ICCs) were calculated from three measurement sessions.

RESULTS

Except for 60° of pronation, all ICCs ranged from .72 to .97. Gender, limb dominance, and posture significantly affected pronosupination strength (p < .05), with the highest supination strength at 60° of pronation and the highest pronation strength at 60° of supination.

CONCLUSIONS AND RELEVANCE

In using this reliable pronosupination torque assessment device and standardized protocol in the clinical setting, clinicians must consider the influence of gender, limb dominance, and forearm posture. What This Article Adds: The results of this study will allow occupational therapists to establish differences between patients' functionality in comparison with healthy individuals and to design recovery treatments and facilitate performance of manual tasks, considering which are the most advantageous positions to exert force. Furthermore, the developed device can be used to monitor the evolution of these torques in an objective and reliable manner.

Ultrasonographic appearance of the pronator quadratus muscle in high school baseball pitchers with and without elbow symptoms: a pilot study

PURPOSE

Earlier reports have described forearm flexor muscles as active stabilizers of the elbow to valgus stress during throwing motion. The pronator quadratus (PQ) muscle acts in coordination with the pronator teres muscle for forearm pronation. This study of high school pitchers was conducted to assess the association between sonographic appearance and a history of elbow symptoms.

METHODS

We examined 123 high school baseball pitchers, all of whom had completed a self-administered questionnaire, including items related to throwing-related elbow joint pain sustained during the prior year. Ultrasound examination was made of the pitchers with and without valgus stress of the medial aspect of the bilateral elbows. The sonographic appearance of the PQ was assessed on sagittal and axial images on the bilateral side. For participants with and without a history of elbow symptoms, we compared the maximum thickness of the PQ on sagittal and axial images of the throwing side.

RESULTS

Regarding maximum thickness of the PQ on the sagittal and axial images, a significant difference was found between the throwing and non-throwing sides (throwing side vs non-throwing side mean: sagittal 6.3 mm vs 5.7 mm, axial 8.2 mm vs 7.5 mm, 95% confidence interval: sagittal 0.41-0.70, p < 0.001, axial 0.53-0.82, p < 0.001). The maximum thickness of the PQ on axial images with elbow symptoms was significantly greater than the PQ thickness of those without elbow symptoms. Nevertheless, no association was found between elbow valgus instability and the maximum thickness of the PQ on sagittal and axial images of the throwing side.

CONCLUSION

Sonographic appearance of the PQ might be associated with elbow joint conditions in high school baseball players.

Pronator Quadratus Repair Does Not Affect Reoperation Rates Following Volar Locking Plate Fixation of Distal Radius Fractures

BACKGROUND

The purpose of this study was to evaluate the impact of pronator quadratus (PQ) repair on reoperation rates after distal radius open reduction internal fixation (ORIF) using a volar locking plate.

METHODS

A retrospective study of all patients undergoing distal radius ORIF with a volar locking plate between January 2012 and December 2016 at 2 urban, academic level I trauma centers was performed. Patient demographics, fracture and procedure characteristics, surgeon subspecialty, PQ repair, and reoperations were recorded. Descriptive statistics were used to determine whether patient-related or injury-related characteristics were associated with PQ repair. Bivariate and multivariable regression analyses were used to assess the effect of PQ repair on subsequent reoperations.

RESULTS

In total, 509 patients were included, including 31 patients with bilateral injuries. The average follow-up time was 3.7 ± 2.8 years. Patients undergoing PQ repair were younger (57 ± 17 years vs 61 ± 17 years) and were more likely to have a lower Soong grade (53% vs 44% with Soong grade 0) than patients without PQ repair. Pronator quadratus repair was not found to have a significant impact on hardware removal, reoperations for flexor tendon pathology, or overall reoperations.

CONCLUSIONS

Pronator quadratus repair was more commonly performed in younger patients and in patients with a lower Soong grade. Hand-subspecialized surgeons are more likely to pursue PQ repair than trauma-subspecialized surgeons. This study did not detect statistically significant differences in hardware removal, flexor tendon pathology, or overall reoperations between groups.

Use of free radial forearm and pronator quadratus muscle flap: Anatomical study and clinical application

The authors present an anatomical study and clinical experience with radial forearm flap (RFF) and pronator quadratus muscle (PQM) application in the reconstruction of various body areas. The aim was to describe the anatomical placement and proportions of the PQM, the anatomical location of the major arterial branch of the radial artery supplying the PQM, and the application of this knowledge in clinical practice. The anatomical study was based upon an analysis of 13 fresh adult cadaver upper extremities, of which nine were female and four male; both arms from the same donors were used in four cases. The study of the PQM was performed using a dye-containing intraarterial injection, standard macro- and micro-preparation techniques, and chemical digestion. The data on the PQM size in males and females, thickness of the radial artery branch (the principal artery nourishing the muscle), and its position were analysed. The radial artery branch nourishing the PQM was identified in all cadaveric specimens of the anatomical study. In addition, 12 patients underwent reconstructions of soft and bony tissue defects using a RFF + PQM (pedicled or free flap). The radial artery branch perfusing the PQM was identified in all cases. The flap was used for the management of defects of the head (seven cases), arm (three cases) and lower leg (two cases). The harvest site healed well in all cases and, with the exception of one case in which a partial necrosis of the flap was observed, all flaps remained viable, which demonstrated the safety of the method.

Neurovascular anatomy of pronator quadratus for reanimation of blepharoptosis

PURPOSE

Pronator quadratus (PQ) is a quadrilateral muscle on a volar distal side of the forearm. The purpose of this study was to establish a novel surgical technique for reanimation of the upper eyelid for severe ptosis using PQ functional free muscle flap.

METHODS

The current study is a cadaveric study, designed to assess a PQ free flap transfer that lies between the frontalis muscle and the upper eyelid. Fourteen PQ from fourteen embalmed cadavers were dissected, and their neurovascular pedicles were isolated. Then they were transferred to the area on the contralateral side between the frontalis muscle and upper eyelid tarsal cartilage. Measurements of the PQ flap, antebrachial region, orbitofrontal region, recipient vessels, and motor nerve were performed using a caliper. The extendibility of neurovascular pedicles was evaluated by measurements of lengths. In addition, the diameter of PQ flap vascular pedicle vessels was compared with recipient vessels.

RESULTS

The mean width of the proximal border of PQ was 41.92 ± 2.05 mm and the distal border of the PQ was 42.84 ± 4.04 mm. The mean PQ artery (type II, Mathes-Nahai flap classification) length was found to be 117.72 ± 7.77 mm. The mean diameter of the anterior interosseous nerve was 1.89 ± 0.08 mm. The mean diameter of the uppermost branch of the frontal branch of the facial nerve was 1.18 ± 0.25 mm. The length and diameter of neurovascular pedicles of muscle flaps were adequate for microvascular anastomoses and neurorrhaphy.

CONCLUSIONS

The results of this anatomical study demonstrate that the PQ free flap transfer has anatomical features that are suitable and compatible with the surgical treatment of blepharoptosis.

A parallel classification strategy to simultaneous control elbow, wrist, and hand movements

Background

In the field of myoelectric control systems, pattern recognition (PR) algorithms have become always more interesting for predicting complex electromyography patterns involving movements with more than 2 Degrees of Freedom (DoFs). The majority of classification strategies, used for the prosthetic control, are based on single, hierarchical and parallel linear discriminant analysis (LDA) classifiers able to discriminate up to 19 wrist/hand gestures (in the 3-DoFs case), considering both combined and discrete motions. However, these strategies were introduced to simultaneously classify only 2 DoFs and their use is limited by the lack of online performance measures. This study introduces a novel classification strategy based on the Logistic Regression (LR) algorithm with regularization parameter to provide simultaneous classification of 3 DoFs motion classes.

Methods

The parallel PR-based strategy was tested on 15 healthy subjects, by using only six surface EMG sensors. Twenty-seven discrete and complex elbow, hand and wrist motions were classified by keeping the number of electromyographic (EMG) electrodes to a bare minimum and the classification error rate under 10 %. To this purpose, the parallel classification strategy was implemented by using three classifiers one for each DoF: the “Elbow classifier”, the “Wrist classifier”, and the “Hand classifier” provided the simultaneous control of the elbow, hand, and wrist joints, respectively.

Results

Both the offline and real-time performance metrics were evaluated and compared with the LDA parallel classification results. The real-time recognition results were statistically better with the LR classifier with respect to the LDA classifier, for all motion classes (elbow, hand and wrist).

Conclusions

In this paper, a novel parallel PR-based strategy was proposed for classifying up to 3 DoFs: three joint classifiers were employed simultaneously for classifying 27 motion classes related to the elbow, wrist, and hand and promising results were obtained.

IS VOLAR PLATING IN DISTAL RADIUS FRACTURES SAFE REGARDING PRONATOR QUADRATUS?

ABSTRACT Objective: This study aimed to investigate whether isokinetic strength decrease significantly after using volar plating for distal radius fractures and evaluate the pronator quadratus muscle regarding atrophy. Methods: This study took place between 2011 and 2015 and included 18 distal radius fracture patients (group 1) who were treated via volar plating at least one year prior and 14 healthy controls (group 2). All participants were tested isokinetically. Grip strength, radiological evaluation, wrist range of motion, disabilities of the arm, shoulder, and hand and visual analog scale scores were assessed for clinical and functional outcomes. Ultrasonography evaluated the pronator quadratus muscle thicknesses. Results: The peak supination torque (PT) and supination work per repetition (WPT) strength values significantly decreased (p:0.039, p:0.025, respectively). Although we determined an 11% pronation PT deficit and a 19% pronation WPT deficit, neither were significant. In group 1, the pronator quadratus muscle thickness decreased 5.9% ± 13.3 in the radial area and 9.7% ± 10.5 in the interosseous area according with ultrasonography; these results were not statistically significant compared to group 2. All clinical and functional outcomes were not statistically significant between the groups. Conclusion: The use of volar plating after distal radius fractures is a safe method regarding isokinetic strength and pronator quadratus muscle atrophy. Level of evidence III; Retrospective case-control study .

An Adaptive Multi-Modal Control Strategy to Attenuate the Limb Position Effect in Myoelectric Pattern Recognition

Over the last few decades, pattern recognition algorithms have shown promising results in the field of upper limb prostheses myoelectric control and are now gradually being incorporated in commercial devices. A widely used approach is based on a classifier which assigns a specific input value to a selected hand motion. While this method guarantees good performance and robustness within each class, it still shows limitations in adapting to different conditions encountered in real-world applications, such as changes in limb position or external loads. This paper proposes an adaptive method based on a pattern recognition classifier that takes advantage of an augmented dataset-i.e., representing variations in limb position or external loads-to selectively adapt to underrepresented variations. The proposed method was evaluated using a series of target achievement control tests with ten able-bodied volunteers. Results indicated a higher median completion rate >3.33% for the adapted algorithm compared to a classical pattern recognition classifier used as a baseline model. Subject-specific performance showed the potential for improved control after adaptation and a ≤13% completion rate; and in many instances, the adapted points were able to provide new information within classes. These preliminary results show the potential of the proposed method and encourage further development.

Should We Repair the Pronator Quadratus in a Distal Radius Fracture with an Ulnar Styloid Base Fracture? A Biomechanical Study

Background  Merits of repairing the pronator quadratus (PQ) to restore distal radioulnar joint (DRUJ) stability after a volar approach remain controversial. Distal radius fractures are often associated with ulnar styloid fractures (USF). When involving the fovea, this USF can lead to a DRUJ instability. The PQ repair may be key in reducing this DRUJ instability. Methods  This study aims to assess the biomechanical role of PQ repair in a cadaveric model of USF. In 17 forearm specimens, a USF including the fovea was executed. Positional changes of the DRUJ in forearm rotation and dorso-palmar (DP) translation were measured with variable loads (0, 2.5, and 5N) applied to the PQ origin. Results  Forearm rotation and DP-translation decreased significantly with PQ loading of 5N, changing on average by 5 degrees and 0.6 mm, respectively. Conclusion  We found a significant decrease in forearm rotation and DP-translation comparing a fully loaded PQ to an unloaded PQ in our cadaveric model.

Volar plating: functional recovery of the pronator quadratus

Purpose

The pronator quadratus (PQ) is reflected in the surgical approach to the distal radius. This study explores the functional strength of PQ, 12 months after volar plating without repair of PQ.

Methods

A total of 135 patients were identified from our prospectively collected database. All volunteers had grip strength and pronation power tested in the treated and contralateral forearms at 45, 90 and 135 degrees of elbow flexion using a custom-built torque measuring device and hydraulic hand dynamometer to evaluate forearm pronation.

Results

Twenty-seven participants were included in the study. No significant difference was identified in mean peak pronation torque between the volar plated and non-treated forearms. Pronation strength was identified as being independent of angle of elbow flexion. Grip strength was correlated with forearm pronation showing no significant difference between groups.

Conclusions

Our results suggest adequate long-term (15–32 months) functional recovery of the pronator quadratus after volar plating.

Level of Evidence

III.

Effectiveness of Distal Nerve Transfers for Claw Correction With Proximal Ulnar Nerve Lesions

PURPOSE

To evaluate claw deformity correction following anterior interosseous nerve (AIN) end-to-end transfer to the deep motor branch of the ulnar nerve (DMBUN) in high ulnar nerve injuries.

METHODS

Eleven patients were retrospectively evaluated for metacarpophalangeal joint hyperextension and proximal interphalangeal joint extension lag in the fourth and fifth digits following ulnar nerve injury adjacent or proximal to the elbow, who underwent AIN end-to-end transfer to the DMBUN.

RESULTS

Patients underwent surgery an average of 5 months following injury (range, 2-9 months) and were followed for an average of 19 months after surgery (range, 12-30 months). At the last follow-up, clawing was observed in all patients, with proximal interphalangeal joint extension lag averaging 46.8° (SD, ±20°) in the fourth digit and 57.7° (SD, ±12°) in the little finger.

CONCLUSIONS

None of our patients experienced claw correction after AIN end-to-end transfer to the DMBUN.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

A Comparison of Pronator Quadratus Preservation and Dissection Approaches for Volar Plating of Comminuted Intra-articular Distal Radius Fracture

PURPOSE

Although the pronator quadratus (PQ) preservation approach for volar plating of distal radius fracture has been commonly used recently, its superiority to the conventional PQ dissection approach, especially for comminuted intra-articular distal radius fractures, has not been well established. The purpose of this study was to assess the efficacy of PQ preservation for comminuted intra-articular fractures and to evaluate the healed PQ during hardware removal surgery.

MATERIALS AND METHODS

From January 2014 to March 2019, 86 patients who underwent both volar plating for AO Foundation/Orthopedic Trauma Association classification type C2 or C3 distal radius fractures and subsequent hardware removal were assessed in this study. Radiographic measurements, clinical outcomes at each follow-up, and the integrity of healed PQ during hardware removal were compared between the PQ dissection (group D) and PQ preservation (group P) groups.

RESULTS

Complete union with acceptable reduction on radiographic measurements was achieved in both groups. Group P showed a statistically significant earlier recovery of clinical outcomes at 2 weeks and 1 month postoperatively and improved anatomical restoration of PQ muscle covering the plate, which was identified during hardware removal surgery. Flexor tendon rupture was identified in 2 patients (5%) and tenosynovitis in 6 patients (14%) in group D; no patient had flexor tendon rupture (0%), and 2 patients (5%) had tenosynovitis in group P.

CONCLUSIONS

Pronator quadratus preservation approach for volar plating is easily applicable and useful even for comminuted intra-articular distal radius fractures and is helpful for earlier restoration of wrist function and in preventing flexor tendon problems in the latter postoperative period.

Correlation of Flexor Pollicis Longus Tendon Status by Ultrasonography with Plate Position on Radiographs Following Volar Plate Fixation of Distal Radius Fractures with Pronator Quadratus Repair

BACKGROUND

Purpose was to correlate flexor pollicis longus tendon (FPL) attrition using Ultrasonography with plate position on radiographs following volar locked compression plate fixation (LCP) in patients who have undergone pronator quadratus (PQ) repair for distal radius fractures.

METHODS

Status of flexor pollicis longus tendon was analyzed by ultrasonography in patients who underwent volar locked compression plating with pronator quadratus repair at a minimum of one year follow up. Soong's criteria was used to assess the plate position and then correlated the ultrasonography findings of flexor pollicis longus.

RESULTS

There were 33 patients included in our study, of which 15 belonged to Soong's grade zero, 10 were grade one and eight were grade two. Flexor pollicis longus attrition was noted in all cases with grade two plating.

CONCLUSION

Pronator quadratus repair may not prevent attritional changes in higher grades of Soong's, hence follow up may be required in these patients to identify attritional changes and early implant removal to prevent complications.

Comparison of maximal isometric forearm supination torque in two elbow positions between subjects with and without limited forearm supination range of motion

Study Design: Cross-sectional comparison. Introduction: Forearm supination range of motion is often limited by short or stiff pronators. Many studies have examined maximal isometric forearm supination torque (MIFST). However, there is little research comparing MIFST in two elbow positions between subjects with and without limited forearm supination range of motion (LSR). Purpose of the Study: The purpose of this study was to compare MIFST in two elbow positions (90º flexed elbow, extended elbow) between subjects with and without LSR. Methods: Thirteen right-handed subjects (seven men, six women) with LSR and 13 age- and gender-matched healthy controls participated in this study. The forearm supination range of motion and MIFST were measured using a Smart KEMA system. Two-way repeated-measures analysis of variance was used to compare MIFST in two elbow positions between subjects with and without LSR. Results: No significant difference between groups (p > .05) was found. However, there was an interaction effect between elbow position and group on MIFST (p < .05). Independent t-tests were used to confirm the simple effects. In the LSR group, the value of MIFST was significantly lower in the elbow-extended position than in the group without LSR (p < .05). Conclusions: These findings indicate that elbow position should be considered when assessing the strength or increasing the strength of the supinator muscle, especially in patients with LSR.

Surgical comfort and clinical outcomes of MIPO with an extra-short plate designed for distal radius fractures

OBJECTIVES

Volar locking plates (VLPs) are increasingly used for distal radius fractures (DRFs) with minimally invasive plate osteosynthesis (MIPO), but surgery learning curves could be long. The purpose of this study was to assess a new extra-short plate with two locking diaphyseal divergent screws, specifically designed for MIPO, preserving the pronator quadratus muscle.

MATERIALS AND METHODS

This retrospective study consisted of three phases: (i) the evaluation of surgical comfort with the incision size and the duration of 59 consecutive surgeries using the extra-short plate in DRFs; (ii) the verification of the implant ability to maintain radiographic indices compared immediately postoperatively and at consolidation. They included radial inclination (RI), volar tilt (VT) and ulnar variance (UV); (iii) the assessment of clinical outcomes at last follow-up through: pain measured on the visual analogue scale (VAS), QuickDASH score, patient-rated wrist evaluation (PRWE) score, grip strength, range of motion and complications.

RESULTS

In the first phase: mean incision size was 32 mm, and mean operative time was 28.5 min. In the second phase, there was no statistical difference between the two measures of the indices studied. In the third phase, mean follow-up time was 14.2 months, VAS score was 1.1, QuickDASH score was 11.4/100, and PRWE score was 9.5/100. Flexion was 91%, extension was 94%, and grip strength was 86% compared to the contralateral side.

CONCLUSION

The surgical comfort may be related to short operative time and incision. The implant allowed maintaining the radiographic indices without secondary displacement. Functional clinical outcomes were satisfactory. This extra-short plate design belongs to a novel generation of VLPs.

Residual rotation of forearm amputation: cadaveric study

Background

The purpose of this study was to investigate residual rotation of patients with forearm amputation and the contribution of involved muscle to residual rotation.

Methods

Testing was performed using five fresh-frozen cadaveric specimens prepared by isolating muscles involved in forearm rotation. Amputation was implemented at 25 cm (wrist disarticulation), 18 cm, or 10 cm from the tip of olecranon. Supination and pronation in the amputation stump were simulated with traction of involved muscle (supinator, biceps brachii, pronator teres, pronator quadratus) using an electric actuator. The degree of rotation was examined at 30°, 60°, 90°, and 120° in flexion of elbow.

Results

Average rotation of 25 cm forearm stump was 148° (SD: 23.1). The rotation was decreased to 117.5° (SD: 26.6) at 18 cm forearm stump. It was further decreased to 63° (SD 31.5) at 10 cm forearm stump. Tendency of disorganized rotation was observed in close proximity of the amputation site to the elbow. Full residual pronation was achieved with traction of each pronator teres and pronator quadratus. Although traction of supinator could implement residual supination, the contribution of biceps brachii ranged from 4 to 88% according to the degree of flexion.

Conclusions

Close proximity of the amputation site to the elbow decreased the residual rotation significantly compared to residual rotation of wrist disarticulation. The preservation of pronosupination was 80% at 18 cm forearm stump. Although the pronator teres and the pronator quadratus could make a full residual pronation separately, the supinator was essential to a residual supination.

A Novel Technique to Assess Distal Radioulnar Joint Stability Using Increasing Torque

Background  Previous studies on computed tomography (CT) in patients with a suspected triangular fibrocartilage complex (TFCC) injury have not been successful in assessing distal radioulnar joint (DRUJ) laxity. The aim of this study was to develop a novel servomotor-driven device for the assessment of DRUJ by applying increasing torque to the DRUJ in pronation and supination. Methods  A custom-built device was designed to function during four-dimensional (4D) CT of the wrist. A torque meter, positioned between the incoming hand holder, and a direct current (DC) servomotor were used for angular positioning and for applying rotational force to the patient's arm. A total of 110 healthy participants were recruited to gather reference values for the range of motion (ROM), maximum torque in neutral and supinated/pronated position, and the ability to withstand an increasing, device-generated torque in these positions. The device was also used during 4D DRUJ CT in five patients with suspected TFCC injuries. Results  A gender- and age-relevant reference chart for ROM and torque was created. Men showed a tendency (ns) toward having a larger ROM and increasing strength with increasing age, whereas women showed the opposite. Also, the dominant hand showed a tendency toward having a larger ROM and being stronger than the nondominant hand (ns). A smaller cohort of patients ( n  = 5) with suspected TFCC injuries showed a significantly decreased ability to withstand increasing torque in both supination (2.1 ± 0.3 vs. 3.1 ± 0.2 s; p  < 0.005) and pronation (2.3 ± 0.5 vs. 3.1 ± 0.4 s; p  < 0.0005) and also showed a clear laxity on real-time 4D CT image sequences. Decreased strength at all positions was also found (average 74% decrease compared to noninjured side). Conclusion  Reference values for torque strength and ability to withstand increasing torque can be used clinically in the assessment of patients with symptoms that could represent ligamentous injuries to the TFCC. The ability to use the device during CT enables radiographic evaluation of instability during increasing torque. Level of Evidence This is a Level II study.

A suite of automated tools to quantify hand and wrist motor function after cervical spinal cord injury

BACKGROUND

Cervical spinal cord injury (cSCI) often causes chronic upper extremity disability. Reliable measurement of arm function is critical for development of therapies to improve recovery after cSCI. In this study, we report a suite of automated rehabilitative tools to allow simple, quantitative assessment of hand and wrist motor function.

METHODS

We measured range of motion and force production using these devices in cSCI participants with a range of upper limb disability and in neurologically intact participants at two time points separated by approximately 4 months. Additionally, we determined whether measures collected with the rehabilitative tools correlated with standard upper limb assessments, including the Graded Redefined Assessment of Strength, Sensibility, and Prehension (GRASSP) and the Jebsen Hand Function Test (JHFT).

RESULTS

We find that the rehabilitative devices are useful to provide assessment of upper limb function in physical units over time in SCI participants and are well-correlated with standard assessments.

CONCLUSIONS

These results indicate that these tools represent a reliable system for longitudinal evaluation of upper extremity function after cSCI and may provide a framework to assess the efficacy of strategies aimed at improving recovery of upper limb function.

Neuromechanical Simulation of Hand Pronation and Supination Task in Parkinson's disease

Parkinson's disease is a prevalent and debilitating neurological disorder, where the severity of motor symptoms are frequently monitored using clinical tests that include a hand pronation and supination task. Objective quantification of motor symptoms in persons with Parkinson's disease and detection of dopamine-induced dyskinesias during treatment is important for the management of the most common symptoms in persons with Parkinson's disease. Thus, the development of a neuromechanical model of rhythmic hand pronation and supination may further our understanding of the mechanisms underlying motor symptoms during rhythmic upper extremity tasks in persons with Parkinson's disease. The aim of this study was to create a model for a rhythmic hand pronation and supination task. This was done to create a simulation of a popular diagnostic task used in determining the severity of motor impairments in persons with Parkinson's disease. It is imperative to understand the neural dynamics as well as the physiological constraints placed on a system such as this in both the creation of a usable model as well as understanding the neuromechanical interactions occurring during this diagnostic task. This model of either normal or slowed, clinical behavior, can then serve as a springboard for the creation of models that characterize disordered motor movement and perhaps even the creation of models that could be incorporated into the diagnostic process.

Muscle activity during maximal isometric forearm rotation using a power grip

This study aimed to provide quantitative activation data for muscles of the forearm during pronation and supination while using a power grip. Electromyographic data was collected from 15 forearm muscles in 11 subjects while they performed maximal isometric pronating and supinating efforts in nine positions of forearm rotation. Biceps brachii was the only muscle with substantial activation in only one effort direction. It was significantly more active when supinating (µ = 52.1%, SD = 17.5%) than pronating (µ = 5.1%, SD = 4.8%, p < .001). All other muscles showed considerable muscle activity during both pronation and supination. Brachioradialis, flexor carpi radialis, palmaris longus, pronator quadratus and pronator teres were significantly more active when pronating the forearm. Abductor pollicis longus and biceps brachii were significantly more active when supinating. This data highlights the importance of including muscles additional to the primary forearm rotators in a biomechanical analysis of forearm rotation. Doing so will further our understanding of forearm function and lead to the improved treatment of forearm fractures, trauma-induced muscle dysfunction and joint replacements.

Reference Values of Flexion and Supination in the Elbow Joint of a Cohort without Shoulder Pathologies

Background

After surgery of the long head of the biceps tendon, the examination of the biceps brachii muscle function and strength is common clinical practice. The muscle strength is usually compared with the uninjured contralateral side or with a matched pair group assuming that the uninjured side can be used as an appropriate reference.

Hypothesis/Purpose

The purpose of this study was to define reference values of the supination and flexion strength in the elbow joint and to investigate the influence of the arm positions and various anthropometric factors.

Methods

105 participants without any shoulder pathologies were enrolled. A full medical history was obtained and a physical examination was performed. The bilateral isometric testing included the supination torque in various forearm positions and elbow flexion strength with a custom engineered dynamometer. Multiple linear regression analysis was used to investigate the correlation of the strength and anthropometric factors.

Results

Only age and gender were significant supination and flexion strength predictors of the elbow. Hence, it was possible to calculate a gender-specific regression line for each forearm position to predict the age-dependent supination torque. The supination strength was greatest with the arm in 90° elbow flexion and the upper arm in full pronation.

Rehabilitation of distal radioulnar joint instability

Distal radioulnar joint (DRUJ) instabilities are common and often combined with other injuries of the interosseous membrane and/or the proximal radioulnar joint. Once they are diagnosed and the treatment is chosen, physiotherapists have limited choices due to the lack of validated protocols. The benefits of proprioception and neuromuscular rehabilitation have been brought to light for the shoulder, knee and ankle joints, among others. However, no program has been described for the DRUJ. The purpose of this article is to study the muscular elements responsible for active DRUJ stability, and to propose a proprioceptive rehabilitation program suited to this condition.

Repair of the pronator quadratus after volar plate fixation in distal radius fractures: a systematic review

To position the volar plate on the distal radius fracture site, the pronator quadratus muscle needs to be detached from its distal and radial side and lifted for optimal exposure to the fracture site. Although the conventional approach involves repair of the pronator quadratus, controversy surrounds the merits of this repair. The purpose of this study was to compare the functional outcomes of patients with distal radius fractures treated with pronator quadratus repair after volar plate fixation versus no pronator quadratus repair. A systematic search was conducted in Medline, EMBASE and the Cochrane Central Register of Controlled Trials, on 23 July 2015. All studies comparing pronator quadratus repair with no pronator quadratus repair in adult patients undergoing volar plate fixation for distal radius fractures were included. The primary outcome was the Disability of the Arm, Shoulder and Hand (DASH) score at 12 months. Secondary outcomes included range of motion, grip strength, post-operative pain and complications. A total of 169 patients were included, of which 95 underwent pronator quadratus repair, while 74 patients underwent no pronator quadratus repair. At 12 months follow-up no statistically significant differences in DASH-scores and range of motion were observed between pronator quadratus repair and no repair. Moreover, post-operative pain and complication rates were similar between both groups. At 12 months of follow-up, we do not see any advantages of pronator quadratus repair after volar plate fixation in the distal radius. However, a definitive conclusion cannot be drawn from this systematic review due to a lack of available evidence.

Distal radioulnar joint: functional anatomy, including pathomechanics

The distal radioulnar joint allows the human to rotate the forearm to place the hand in a desired position to perform different tasks, without interfering with the grasping function of the hand. The ulna is the stable part of the forearm around which the radius rotates; the stability of the distal radioulnar joint is provided by the interaction between ligaments, muscles and bones. The stabilizing structures are the triangular fibrocartilage complex, the ulnocarpal ligament complex, the extensor carpi ulnaris tendon and tendon sheath, the pronator quadratus, the interosseous membrane and ligament, the bone itself and the joint capsule. The purpose of this review article is to present and illustrate the current understanding of the functional anatomy and pathomechanics of this joint.

Sonographic Quantification of Pronator Quadratus Activity During Gripping Effort

OBJECTIVES

The aim of this study was to obtain quantitative data related to the activity of each head of the pronator quadratus based on dynamic sonographic parameters during gripping effort and to assess their relationships with grip and pronation strengths.

METHODS

The forearms of 33 healthy volunteers were evaluated at 5 positions of axial rotation (full supination, 45° supination, neutral, 45° pronation, and full pronation). Echogenic intensity ratios and muscle thicknesses of each head of the pronator quadratus were measured from transverse cross-sectional sonograms obtained during maximal grip and release. Grip strengths and maximal isokinetic pronation torques at 90°/s and 360°/s were evaluated as strength parameters and correlated with sonographic measures.

RESULTS

Echogenic intensity ratios of both heads significantly decreased during power grip (P ≤ .002). Changes in echogenic intensity ratios of the superficial head were greater when the forearm was pronated compared to supination (P < .001), whereas changes in echogenic intensity ratios of the deep head were constant at all forearm positions. Muscle thicknesses of the superficial head maximally increased at the neutral position during power grip (P < .001), whereas muscle thicknesses of the deep head did not change. There were significant negative correlations between grip strength and echogenic intensity ratios of both heads at all respective forearm positions (P ≤ .048). Pronation torque was significantly correlated with echogenic intensity ratios of the superficial head at all forearm positions and the deep head at 45° and full pronation positions (P ≤ .034).

CONCLUSIONS

The data revealed that the superficial head of the pronator quadratus more actively contracts when the forearm is in pronation, whereas the deep head constantly contracts at all positions. This study suggests that both heads of the pronator quadratus also play a role in grip strength, but the superficial head contributes more to pronation strength.

Sonographic swelling of pronator quadratus muscle in patients with occult bone injury

Background

The disarranged fat stripe of the pronator quadratus muscle (PQ) on radiographs (the PQ sign) is reported to be predictive of subtle bone fractures. This study aimed to report the results of magnetic resonance imaging (MRI) study in the patients in whom bone injury was not radiographically detected around the wrist joint, and the PQ was sonographically swollen following acute trauma.

Methods

We evaluated sonographically the PQ of 55 patients who showed normal radiographs following acute trauma. The sonographic appearance of the PQ was checked on both longitudinal and transverse images. On the longitudinal image, the probe was positioned along the flexor carpi radialis tendon. For the transverse image, we adopted the image of the same level in which the PQ of the unaffected hand showed maximal thickness. The PQ was considered to be swollen with disproportionate hyperechogenicity and/or thickening compared with the unaffected side at least in one of the two images. Of the 55 patients, 25 patients whose PQ was considered to be swollen underwent MRI study. PQ thickness in millimeters was retrospectively measured on longitudinal and transverse sonographic images.

Results

Twenty-three patients (92.0%) had occult bone injury, and two adult patients (8.0%) showed only wrist joint effusion on MRI. Among these 23, the distal radius was the most frequent location of the occult bone injury (20 patients; 9 [36.0%] with an occult fracture line and 11 [44.0%] with bone bruising). In longitudinal image, the mean value of the PQ thickness of affected hands was 6.2 (3.7–9.6 mm; standard deviation [SD], 1.5) and that of unaffected hands was 4.5 (2.3–6.7 mm; SD, 1.2), respectively. In transverse image, that of dominant and nondominant hands was 7.6 (4.6–13.2 mm; SD, 2.0) and 5.5 (3.6–7.5 mm; SD, 1.1), respectively. The mean difference in PQ thickness between affected and unaffected hands was 1.7 (0.1–5.0 mm; SD, 1.1) in longitudinal image and 2.0 (0.3–6.8 mm; SD, 1.7) in transverse image.

Conclusions

Sonographic swelling of the PQ might be indicative of occult bone injury in patients with normal radiographs following acute trauma.

Pronator-sparing technique for volar plating of distal radius fractures

Acute distal radius fractures are commonly treated by volar locking plate fixation and typically involve reflection of the pronator quadratus for adequate exposure of the fracture. Recently, attention has been centered on the role and repair of the pronator quadratus. This article presents an alternative approach to fixation of distal radius fractures with a pronator-sparing technique that offers similar short-term radiographic outcomes to the conventional volar plating approach.

An anatomic study of the structure and innervation of the pronator quadratus muscle

The pronator quadratus muscle is composed of the superficial and deep heads. However, to date there is no consensus on the variations of each head. To add to this enigma, the innervation patterns of each head have not been thoroughly studied. The present study was conducted to clarify the structure and innervation of the pronator quadratus muscle by minute dissection of 46 forearms from 26 cadavers. The origin, insertion, shape, and direction of the muscle fascicles in each head were observed. The intramuscular distribution and the innervation patterns to each head were investigated. The attachment of the deep head was examined using Masson's trichrome staining technique. Each head consisted of various muscle fascicles which differed in shape and direction. The most distal muscle fascicle extended toward the head of the ulna. On microscopic study, this most distal fascicle was observed to reach the base of the ulnar styloid process. The nerves innervating the superficial head penetrated through the deep head and ran on the anterior surface of the radius from medial to lateral. This tendency was common to all of the forearms studied. We confirmed that each head of the pronator quadratus muscle consisted of various muscle fascicles. The attachment to the base of the ulnar styloid process is considered to be an important structure that prevents the head of the ulna from impacting against the carpal bones. Knowledge of the innervation pattern to each head is critical for preserving the function of the pronator quadratus muscle during surgery for distal radial fracture.

Biomechanics of forearm rotation: force and efficiency of pronator teres

Biomechanical models are useful to assess the effect of muscular forces on bone structure. Using skeletal remains, we analyze pronator teres rotational efficiency and its force components throughout the entire flexion-extension and pronation-supination ranges by means of a new biomechanical model and 3D imaging techniques, and we explore the relationship between these parameters and skeletal structure. The results show that maximal efficiency is the highest in full elbow flexion and is close to forearm neutral position for each elbow angle. The vertical component of pronator teres force is the highest among all components and is greater in pronation and elbow extension. The radial component becomes negative in pronation and reaches lower values as the elbow flexes. Both components could enhance radial curvature, especially in pronation. The model also enables to calculate efficiency and force components simulating changes in osteometric parameters. An increase of radial curvature improves efficiency and displaces the position where the radial component becomes negative towards the end of pronation. A more proximal location of pronator teres radial enthesis and a larger humeral medial epicondyle increase efficiency and displace the position where this component becomes negative towards forearm neutral position, which enhances radial curvature. Efficiency is also affected by medial epicondylar orientation and carrying angle. Moreover, reaching an object and bringing it close to the face in a close-to-neutral position improve efficiency and entail an equilibrium between the forces affecting the elbow joint stability. When the upper-limb skeleton is used in positions of low efficiency, implying unbalanced force components, it undergoes plastic changes, which improve these parameters. These findings are useful for studies on ergonomics and orthopaedics, and the model could also be applied to fossil primates in order to infer their locomotor form. Moreover, activity patterns in human ancient populations could be deduced from parameters reported here.

The lacertus fibrosus of the biceps brachii muscle: an anatomical study

PURPOSE

The lacertus fibrosus (LF) is involved in various surgical procedures. However, the anatomy, morphometry, topography and biomechanical involvements of LF are not clear. The purpose of this study was to determine the anatomical and morphometric variations of LF, and to correlate this with anthropometric and morphometric measurements of the upper limb. Furthermore, the presence or absence of a deep layer of LF was verified using forearm cross-sections and dissections.

METHODS

This anatomical study was performed by observation of dissections and transverse sections obtained from 50 cadavers. Morphometric analyses [length and width of LF and biceps tendon, stature, length of upper limb, forearm, bi-epicondylar width, forearm perimeter, biceps brachii muscle perimeter (BBm)] were also performed.

RESULTS

The results demonstrated that there was no significant correlation between LF morphology and morphometric upper limb measurements. The deep layer of LF was observed in all specimens.

CONCLUSION

Results of this paper indicate that the LF presents individual characteristics such as length and width. The deeper layer of LF was observed on all specimens. The possible role of LF in force transmission during flexion, BBm moment arm adjustment and supination reduction is discussed in view of these results.

Sonographic appearance of the pronator quadratus muscle in healthy volunteers

OBJECTIVES

The purpose of this study was to investigate the sonographic appearance of the pronator quadratus muscle in healthy volunteers.

METHODS

We sonographically evaluated 30 healthy volunteers (15 men and 15 women). The maximum thickness of the pronator quadratus in millimeters on the volar side at the cortical level was measured on sagittal and axial sonographic images with the volunteers' hands supinated. On the axial image, we classified each hand according to the sonographic contour of the pronator quadratus.

RESULTS

A significant difference in the maximum pronator quadratus thickness between dominant and nondominant hands was shown on each image (P < .01). A comparison between men and women also showed a significant difference irrespective of image or hand dominance. Approximately 1.5 mm on the sagittal image and 1.4 mm on the axial image seemed to be adequate practical values for detecting pronator quadratus thickening. In terms of the pronator quadratus contour, the convex type appeared in most men in both the dominant and nondominant hands. In women, the convex and concave types appeared often in both the dominant and nondominant hands.

CONCLUSIONS

The difference in pronator quadratus thickness between dominant and nondominant hands might need to be taken into account during sonographic studies. However, in many cases, the difference seems to be slight and considerably less than the calculated cutoff value in this study. These results might be useful for sonographic comparison of bilateral pronator quadratus muscles in the clinical setting.

Elbow joint biomechanics for preclinical evaluation of total elbow prostheses

Total elbow arthroplasty is a clinically successful procedure, yet long-term implant survival rates have historically lagged behind those reported for total hips and knees. Clinical complications associated with implant wear, osteolysis, stem loosening and device fracture have been implicated as reasons for limited long-term survivorship. Unfortunately, there is little published information on the biomechanics and method(s) for preclinical evaluation of total elbow prostheses that could provide insight into the mechanisms of failure. Additionally, there are no consensus testing standards or summaries of loading profiles of the humero-ulnar joint associated with a range of activities of daily living. Such data would facilitate the standardized preclinical assessment of total elbow devices such is commonplace for other large joints. The objective of the work here is therefore to provide a comprehensive review of elbow joint biomechanics as it relates to preclinical evaluation of total elbow implants. This summary includes a review of elbow joint forces, kinematics, the types and frequency of humero-ulnar joint motions associated with activities of daily living and clinical outcomes, as well as proposing a methodology for deriving humero-ulnar joint reaction force magnitudes and vector orientations as a function of a known mass/force at the hand. From these data, a scalable, bi-axial loading profile is proposed as a foundation for the development of clinically relevant, laboratory simulations for assessment of total elbow prostheses performance.

Selective use of hand and forearm muscles during mini-implant insertion: a natural torquimeter

OBJECTIVE

To compare maximum torque produced by different muscular groups and its influence on mini-implant insertion torque and fracture prevention.

DESIGN

A prospective study involving in vivo and in vitro laboratory experiments.

MATERIALS AND METHODS

Eighty-seven professionals were evaluated for maximum torque produced using a screwdriver with combined action between thumb and index fingers [maximum digital torque (MDT)] and by forearm supination movement [maximum brachial torque (MBT)]. Ninety mini-implants distributed over nine different diameters and twenty commercially available mini-implants of two different diameters and trademarks were fractured to determine the fracture torque (FT). The fracture resistance index (FRI) was obtained from: FRI_MDT = FT/MDT and FRI_MBT = FT/MBT. The analysis of variance (ANOVA) and t tests were used to compare the groups.

RESULTS

MDT was smaller than MBT and both were smaller in females. FT increased for each 0·1 mm of diameter increment. FRI_MDT was greater than FRI_MBT for all diameters. FRI_MDT>1 was found when the diameter was greater than or equal to 1·5 mm. FRI_MBT>1 occurred with diameters equal or greater than 1·7 mm for females and 1·8 mm for males. The 1.5 mm and 1.6 mm diameter of commercially available and mini-implants presented FRI_MBT<1 and FRI_MDT>1.

CONCLUSIONS

Digital torque was 42% smaller than brachial torque, and it was mechanically safer and biologically more compatible, allowing fracture prevention of 1·5 mm or thicker mini-implant diameter due to insertion torque limitation at 15 N/cm.

Biomechanical study of the extensor carpi ulnaris as a dynamic wrist stabilizer

PURPOSE

To investigate the dynamic stabilizing effect of the extensor carpi ulnaris (ECU) on the distal radioulnar joint (DRUJ) and the ulnocarpal joint in a simulated model of triangular fibrocartilage complex (TFCC) injury.

METHODS

Using 8 fresh-frozen cadavers, we fixed the humerus and ulna at 90° of elbow flexion, and the radius and hand were allowed to rotate freely around the ulna. Passive mobility was tested by translating the radiocarpal unit relative to the ulna along dorsal-palmar directions. Unit displacement was measured by an electromagnetic tracking device in different forearm rotations and under varied loading to the wrist motor tendons. Magnitudes of displacement were compared between different loading patterns of the prime wrist movers in the TFCC-sectioned wrists. The effect of sectioning the ECU subsheath was analyzed.

RESULTS

When physiological loads were applied to all of the prime wrist movers, the magnitude of displacement during passive mobility testing decreased in supination and neutral rotation. After ECU tendon loading was released, mobility increased again in supination and neutral rotation. When the load was applied only to the ECU tendon, mobility decreased in supination and neutral rotation as compared with unloaded. Little change in the mobility was found in pronation regardless of the tendon loading pattern. After sectioning of the ECU subsheath, the stabilizing effect of the ECU decreased in neutral rotation.

CONCLUSIONS

In a neutral wrist position with complete sectioning of the TFCC, the ECU dynamically stabilized the DRUJ and the ulnocarpal joint in supination and neutral forearm rotation. The ECU subsheath assisted ECU tendon stabilization on the ulnar side of the wrist, especially in the neutral rotation.

CLINICAL RELEVANCE

Maintaining the ECU and its subsheath may reduce DRUJ instability in patients with TFCC injuries.

Assessment of pronator quadratus repair integrity following volar plate fixation for distal radius fractures: a prospective clinical cohort study

PURPOSE

To assess prospectively the integrity of pronator quadratus (PQ) muscle repair following volar plate fixation of distal radius fractures and to compare the clinical and radiographic outcomes of durable versus failed repairs in 24 subjects. In addition, by grading the degree of PQ injury, an attempt was made to correlate failure of repair with the PQ injury severity.

METHODS

The extent of PQ injury was graded for each fracture. After fracture fixation, the PQ muscle was repaired along its radial and distal borders. Radiopaque hemoclips were attached to each side of the PQ repair, 2 radially and 2 distally. The distance between these markers at time 0 versus x-rays taken at approximately 2 weeks, 6 weeks, and 3 months was recorded. Clip displacement of 1 cm or more compared to time 0 indicated repair failure.

RESULTS

One of 24 repairs (4%) failed at 3 months. No statistical difference was noted between the type of PQ injury and wrist flexion/extension, pronation/supination, and grip strength.

CONCLUSIONS

Pronator quadratus repairs after volar plate fracture fixation are generally durable. They withstand forces that occur at the distal radius during the healing process with a 4% failure rate. No correlation was shown between type of PQ injury and radiographic failure of the repair.

Club position relative to the golfer's swing plane meaningfully affects swing dynamics

Previous research indicates that the motion of the golf club is not planar and that the plane traced out by the club is different than that of the golfer's hands. The aim of the present study was to investigate how the position of the club, relative to the golfer's swing plane, influences the motion of the club by using a four-segment (torso, upper arm, forearm, and club), three-dimensional forward dynamics model. A genetic algorithm optimized the coordination of the model's four muscular torque generators to produce the best golf swings possible under six different conditions. The series of simulations were designed to demonstrate the effect of positioning the club above, and below, the golfer's swing plane as well as the effect of changing the steepness of the golfer's swing plane. The simulation results suggest that positioning the club below the golfer's swing plane, early in the downswing, will facilitate the squaring of the clubface for impact, while positioning the club above the plane will have the opposite effect. It was also demonstrated that changing the steepness of the golfer's swing plane by 10 degrees can have little effect on the delivery of the clubhead to the ball.

Management of the distal radioulnar joint and ulnar styloid fracture

Fractures of the distal radius and ulnar styloid have the potential to disturb the normal function of the distal radioulnar joint (DRUJ), resulting in loss of motion, pain, arthritis, or instability. The DRUJ can be adversely affected by several mechanisms, including intra-articular injury with step-off, shortening, and angulation of an extra-articular fracture; injury to the radioulnar ligaments; ulnar styloid avulsion fracture; and injury of secondary soft tissue stabilizers. This article discusses the management of the DRUJ and ulnar styloid fracture in the presence of a distal radius fracture.

Anatomy and biomechanics of the distal radioulnar joint

The distal radioulnar joint (DRUJ) is a complex articulation allowing significant rotational and translational motion. Stability of the DRUJ depends on bony contact, intrinsic stabilizers of the triangular fibrocartilage complex, and extrinsic stabilizers of the distal forearm. Understanding the anatomy of this articulation is paramount in clinical decision making for the treatment of disorders involving the DRUJ.

Isokinetic evaluation of pronation after volar plating of a distal radius fracture

INTRODUCTION

Pronator quadratus (PQ) is an important contributor to forearm pronation, and there is concern that volar plating of a distal radius fracture (DRF) may damage the PQ function. The purpose of this study was to determine whether isokinetic pronation strength would decrease considerably after volar locking plating of a DRF, and whether clinical outcomes would be affected by any pronation strength decrease.

MATERIALS AND METHODS

Thirty-four patients of mean age of 55 years (range, 21-74 years) underwent bilateral isokinetic testing at 6 months and 1 year after open reduction and internal fixation using volar plating. Isokinetic pronation and supination strengths were compared between the operated and normal sides. Clinical outcomes such as grip strengths, range of motions and disabilities of the arm, shoulder and hand (DASH) scores were evaluated and analysed for any associations with isokinetic results.

RESULTS

At 6 months, peak torque and total work values for both pronation and supination were lower in the operated sides than in the normal sides (all p < 0.001). However, at 1 year postoperatively, the differences in pronation strength were not statistically significant (p = 0.188 for peak torque and p = 0.190 for total work), whilst supination torque and total work were still significantly lower in the operated sides (p = 0.015 and p = 0.029, respectively). Decreases in pronation strength were found to correlate significantly with decreases in supination strength and grip power. Wrist motion and DASH scores were not found to be correlated with decrease in pronation or supination strengths.

CONCLUSIONS

In patients with a DRF treated by volar plating, pronation strength was not significantly different between the operated and normal sides at 1 year postoperatively, and decreases in pronation or supination strengths were not found to affect clinical outcomes as assessed by DASH scores. This study suggests that dissection of the PQ may have minimal clinical impact on forearm pronation function.

Dorsally displaced distal radius fractures treated by fixed-angle volar plating: Grip and pronosupination strength recovery. A prospective study

INTRODUCTION

Malunion following open reduction and internal fixation of distal radius fracture threatens wrist function. Fixed-angle palmar plates provide rigid fixation that is stable over time; however, the pronator quadratus sectioning required by the anterior approach entails a risk of pronation strength loss and of distal radioulnar joint destabilization. The present study assessed recovery of grip, pronation and supination strength following such internal fixation.

PATIENTS AND METHOD

A prospective study included 26 distal radial fractures with dorsal displacement, osteosynthesized using a fixed-angle palmar plate, in 25 patients (mean age: 47.5 years; range: 17-72 years). Assessment concerned the classical parameters, plus grip and pronosupination strength recovery.

RESULTS

At a mean 14 months follow-up (range: 6-30 months), patients had recovered 91% grip strength, 88% pronation strength and 85% supination strength with respect to the healthy side. Complications comprised three cases of malunion, two of reflex sympathetic dystrophy syndrome, and four of post-traumatic carpal tunnel syndrome.

DISCUSSION

A study of the literature found 75-95% grip strength recovery following osteosynthesis using fixed-angle plates. Few studies, however, have focused on pronosupination strength, and none reported its evolution following osteosynthesis.

CONCLUSION

The present study found no drawbacks associated with a technique which usually involves sectioning the pronator quadratus. Except in case of malunion or joint stiffness, fixed-angle palmar plate osteosynthesis was followed by recovery of grip and pronosupination strength.

LEVEL OF EVIDENCE

Level IV: prospective non-randomized, non-comparative observational study.

Radioulnar laxity and clinical outcome do not correlate after a distal radius fracture

Injury to the triangular fibrocartilage complex associated with distal radius fracture may cause symptoms of ulnar instability. Assessed by a radioulnar stress test, increased laxity of the distal radioulnar joint has in two previous studies been depicted to be associated with poorer outcome. This prospective study of 40 adults investigates the correlation of this test with functional outcome as measured by DASH. No clinically significant difference was found in relation to this test at two and five years after injury. Therefore using this test alone to decide whether or not to perform an acute repair of the TFCC cannot be recommended.

Surgical approaches to the distal radioulnar joint

For the distal radioulnar joint (DRUJ) to be stable, not only do the articulating surfaces need to be congruent and well aligned but also the capsule and ligaments need to be mechanically and sensorially competent. According to recent investigations, ligaments should not be regarded as simple static structures maintaining articular alignment but as complex arrangements of collagen fibers containing mechanoreceptors, which are able to generate neural reflexes aiming at a more efficient and a more definitive muscular stabilization. By careful planning and meticulous execution of surgical incisions to approach the DRUJ, the nerve endings innervating the capsule and DRUJ ligaments may be safeguarded, thus preserving the proprioceptive function of the joint.

Understanding stability of the distal radioulnar joint through an understanding of its anatomy

The authors describe the anatomy of the distal radioulnar joint (DRUJ) and delineate the importance of viewing this joint as part of the whole forearm. The osseous congruity and ligamentous integrity is of essence for the stability of the DRUJ, according to the principles of tensegrity. The neuromuscular control and possible proprioceptive function of the DRUJ are also outlined.

New Assessment of Forearm Strength: Reliability and Validity

OBJECTIVE. The objective was to determine the reliability of a portable forearm strength hydraulic dynamometer with a doorknob handle and assess its validity compared with a Cybex 6000 (Cybex International, Inc., Medway, MA) isometric torque assessment.

METHOD. Eighteen volunteers (with a total of 30 forearms) participated in this one-session methodological study to determine the intra- and interrater reliability and criterion validity of a forearm dynamometer.

RESULTS. Intrarater reliability for both assessors for pronation was (intraclass correlation coefficient [ICC]3,1 = .937–.961) and for supination was (ICC3,1 = .923–.968). Interrater reliability for pronation was ICC3,2 = .927 and for supination was ICC3,2 = .847. Criterion validity of the Baseline hydraulic dynamometer (Fabrication Enterprises Inc., White Plains, NY) compared with the Cybex 6000 was .574–.664 for pronation and .749–.750 for supination.

CONCLUSION. The Baseline hydraulic dynamometer with a more functional doorknob handle had good intra- and interrater reliability and demonstrated moderate validity compared with Cybex 6000 strength testing.