Extrinsic Flexor Research Articles

Longitudinal changes of grip strength and forearm muscle thickness in young children.

Grip strength is a marker of future health conditions and is mainly generated by the extrinsic flexor muscles of the fingers. Therefore, whether or not there is a relationship between grip strength and forearm muscle size is vital in considering strategies for grip strength development during growth. Thus, this study aimed to examine the association between changes in grip strength and forearm muscle thickness in young children. Two hundred eighteen young children (104 boys and 114 girls) performed maximum voluntary grip strength and ultrasound-measured muscle thickness measurements in the righthand. Two muscle thicknesses were measured as the perpendicular distance between the adipose tissue-muscle interface and muscle-bone interface of the radius (MT-radius) and ulna (MT-ulna). All participants completed the first measurement and underwent a second measurement one year after the first one. There were significant (P < 0.001) within-subject correlations between MT-ulna and grip strength [r = 0.50 (0.40, 0.60)] and MT-radius and grip strength [r = 0.59 (0.49, 0.67)]. There was no significant between-subject correlation between MT-ulna and grip strength [r = 0.07 (-0.05, 0.20)], but there was a statistically significant (P < 0.001) between-subject relationship between MT-radius and grip strength [r = 0.27 (0.14, 0.39)]. Although we cannot infer causation from the present study, our findings suggest that as muscle size increases within a child, so does muscle strength. Our between-subject analysis, however, suggests that those who observed the greatest change in muscle size did not necessarily get the strongest.

427.9: Total Bilateral Arm Transplantation: Functional Recovery and Psychosocial Outcomes at One Year

Introduction: Although arm loss causes severe disability and compromission of body image, functional recovery after allotransplantation still presents many challenges. Objective: A bilateral arm transplantation including reconstruction of the left shoulder was performed on January 13, 2021 in Lyon (France). Functional recovery and psychosocial outcomes are reported one year after the transplantation. Materials and Methods: The recipient was a 48-year old patient with bilateral amputation at proximal arm level after electric shock in January 1998, who underwent liver transplantation in 2002. The patient used mechanic prostheses with poor satisfaction. The surgical procedure consisted in a total arm transplantation on the left side with reconstruction of the gleno-humeral joint. The maintenance immunosuppressive therapy included tacrolimus, mycophenolate mofetil and prednisone. Rehabilitation therapy started on day one. It progressively included manual lymphatic drainage, passive motion of all joints in a total range except limitations for the shoulders during the first 6 weeks. Then, electrostimulation on denervated muscles was performed. After 6 weeks the protocol included hand therapy, psychomotricity, physical activities, occupational therapy and sensory-motor simulation training approaches (motor imagery, virtual mirror therapy, virtual reality). Results: Motor recovery was already appreciated 8 months after the transplantation. At one year, passive ranges of motion of upper limbs are subnormal. According to MRC scale, muscular strength at shoulder level is from 3 to 4/5 on the right side and from 1 to 2/5 on the left side; from 3 to 4/5 for elbow flexors and from 1 to 2 for elbow extensors on both sides; 3/5 for wrist flexors on the right side and 0/5 on the left side; 1 to 2/5 for wrist extensors on both sides; 3/5 for pronators and supinators on the right side and 1/5 on the left side. Slight contraction and movements of the extrinsic flexors and extensor muscles of the fingers have been evidenced on both sides, and the first prehension movements started on the right hand. The Semmes-Weinstein monofilament test for sensory threshold was 6.65 in the right palm and below the left elbow; deep pressure sensation is recovered in both hands. Functional Independence Measure is 96/126 and the DASH score 75.8. The patient is able to perform the same daily activities as with the prostheses before the transplantation.The patient was psychologically tested during the follow-up using a specific questionnaire for upper extremity allotransplantation and MADRS, Hamilton and Rosenberg tests. The results (Table 1) show the difficulties, the patient’s strong motivation and capacity to cope, and his satisfaction reached at the first year of follow-up. Conclusions: The patient is very satisfied of his grafts and of his restored body image, which was his main expectation.

Analysis on synergistic cocontraction of extrinsic finger flexors and extensors during flexion movements: A finite element digital human hand model.

Fine hand movements require the synergistic contraction of intrinsic and extrinsic muscles to achieve them. In this paper, a Finite Element Digital Human Hand Model (FE-DHHM) containing solid tendons and ligaments and driven by the Muscle-Tendon Junction (MTJ) displacements of FDS, FDP and ED measured by ultrasound imaging was developed. The synergistic contraction of these muscles during the finger flexion movements was analyzed by simulating five sets of finger flexion movements. The results showed that the FDS and FDP contracted together to provide power during the flexion movements, while the ED acted as an antagonist. The peak stresses of the FDS, FDP and ED were all at the joints. In the flexion without resistance, the FDS provided the main driving force, and the FDS and FDP alternated in a "plateau" of muscle force. In the flexion with resistance, the muscle forces of FDS, FDP, and ED were all positively correlated with fingertip forces. The FDS still provided the main driving force, but the stress maxima occurred in the FDP at the DIP joint.

Associations between the size of individual plantar intrinsic and extrinsic foot muscles and toe flexor strength

BackgroundThe size of the plantar intrinsic and extrinsic foot muscles has been shown to be associated with toe flexor strength (TFS). Previous studies adopted the size of limited plantar intrinsic foot muscles or a compartment containing several muscles as an independent variable for TFS. Among the plantar intrinsic and extrinsic foot muscles, therefore, it is unclear which muscle(s) primarily contributes to TFS production. The present study aimed to clarify this subject.MethodsIn 17 young adult men, a series of anatomical cross-sectional area of individual plantar intrinsic and extrinsic foot muscles was obtained along the foot length and the lower leg length, respectively, using magnetic resonance imaging. Maximal anatomical cross-sectional area (ACSAmax) and muscle volume (MV) for each constituent muscle of the plantar intrinsic foot muscles (flexor hallucis brevis; flexor digitorum brevis, FDB; abductor hallucis; adductor hallucis oblique head, ADDH-OH; adductor hallucis transverse head, ADDH-TH; abductor digiti minimi; quadratus plantae) and extrinsic foot muscles (flexor hallucis longus; flexor digitorum longus) were measured. TFS was measured with a toe grip dynamometry.ResultsTFS was significantly associated with the ACSAmax for each of the ADDH-OH (r = 0.674, p = 0.003), ADDH-TH (r = 0.523, p = 0.031), and FDB (r = 0.492, p = 0.045), and the MV of the ADDH-OH (r = 0.582, p = 0.014). As for the ADDH-OH, the correlation coefficient with TFS was not statistically different between ACSAmax and MV (p = 0.189). Stepwise multiple linear regression analysis indicated that ACSAmax and MV of the ADDH-OH alone explained 42 and 29%, respectively, of the variance in TFS.ConclusionThe ADDH-OH is the primary contributor to TFS production among the plantar intrinsic and extrinsic foot muscles as the result of the stepwise multiple linear regression analysis.

Computational analysis of the clinical presentation of a ligamentous Lisfranc injury.

Lisfranc injuries in the midfoot disrupt key arches of the foot which, if left untreated, can progress to pain, dysfunction, and arthritis. A clinical challenge is that 30-40% of Lisfranc injuries are missed in initial evaluations. The objective of this study was to explore different conditions of limb loading that could influence the biomechanics of the Lisfranc joint in a validated computational model. A computational model was created using SolidWorks software to represent the bones and soft tissues of the lower leg and foot. The model was compared to a cadaveric study of healthy and injured Lisfranc joints. The model was then used to simulate weight-bearing radiographs and evaluate how muscle activity and foot position impacted the diastasis of the Lisfranc joint, a key indicator used to diagnose Lisfranc injuries. The computational model was within one standard deviation of the cadaveric study in all measurements for the healthy and injured foot. When simulating weight-bearing radiographs, the presence of muscle activity or inversion/eversion resulted in less joint separation for the model with ligamentous Lisfranc injuries. While previous research has noted that weight-bearing radiographs provide better conditions to assess Lisfranc injuries than nonweight-bearing, this study suggests that in weight-bearing radiographs both altering the position of the foot, possibly due to pain, and the active contraction of the extrinsic flexor muscles can obfuscate indications of a Lisfranc injury.

Altered hand proprioception following regional anesthesia as a cause of traumatic jersey finger: Report of two cases

The sense of body ownership is being increasingly studied by manipulating incoming signals from the periphery with local anesthetics. We sought to understand how altered proprioception induced by anesthesia triggered a traumatic jersey finger, immediately postoperatively, in two patients who underwent surgical carpal tunnel release. Multiple mechanisms contributed to these postoperative injuries associated with a fall. Hand anesthesia deprives the brain of important afferent sensory information and modifies hand size perception in the brain. Moreover, it blocks efferent motor signals that contribute to the perception of hand position with sensory afferent signals. When the patients fell, their movement control was inadequate, generating a strong contraction of the hand extrinsic flexor muscles, against forceful distal phalanx extension. Lastly, both patients had removed their numb operated hand from their arm sling. Disrupted sensory and motor paths modify self-attribution of the hand, and thus halt adequate efferent commands. Protecting the operated hand until full sensory and motor control is regained could have prevented such rare accidents from happening. Level of evidence: V

Efficacy of Single-Dose Radiotherapy in Preventing Posttraumatic Tendon Adhesion.

Background and AimPosttraumatic peritendinous adhesion is the greatest obstacle to achieve normal tendon function following lacerations of extrinsic flexor tendons of the hand. In this study, we aimed to evaluate whether single-dose radiotherapy (RT) has the potential to modulate intrasynovial tendon adhesions.Materials and MethodsA total of 80 tendons from the third to fourth flexor profundus of both hind paws of 20 adult New Zealand rabbits were used in this study. Rabbits in the RT group received 3 Gy of X-irradiation in a single fraction. Histopathological evaluation of longitudinal sections of tendons was made using the Tang grading system for peritendinous adhesions. Intratendinous quality of the healing tissue in the laceration zone was assessed using a modified Movin scale.ResultsAdhesion and inflammatory response were greater in the RT group (p˂0.001). Tendon healing in the radiation group was found to be more uniform and organized compared with the control group. However, this difference was not statistically significant. The nuclei of the tenocytes in the radiation group showed a closer resemblance to normal tendon tissue when compared with the control group (p=0.007).ConclusionsDespite RT’s certain advantages such as extracorporeal use, anti-inflammatory effect, and homogenous tissue penetration, 3-Gy X-irradiation resulted in increased peritendinous posttraumatic adhesion, possibly due to dose imbalance. Increased roundness in the tenocyte nuclei was present in the RT group. Studies with different dosing regimens and a higher number of subjects are necessary to establish an ideal dose suppressing the synovial response without compromising tendon healing.

Complex couplings between joints, muscles and performance: the role of the wrist in grasping

The relationship between posture, muscle length properties and performance remains unclear, because of a lack of quantitative data. Studies on grasping tasks suggested that wrist position could favour the extrinsic finger flexor in regards to their length to maximise grip force performance. The present study aimed at providing quantitative evidence of the links between wrist posture, muscle capacities and grip capabilities. It combines experimental measurements and a musculoskeletal model including the force-length relationship of the four prime muscles used in grasping. Participants exerted their maximum grip force on a cylindrical dynamometer in four different wrist postures, including one freely chosen by participants (spontaneous). A musculoskeletal model computed the muscle force level and length from motion capture and muscle activation. Results revealed that participants exerted maximum grip force spontaneously, with a loss of force when using other postures. At muscle force and length level, grip force variation seems to be associated with all the muscles under study. This observation led to a first quantitative link between power grip, posture and muscle properties, which could provide more insight into neuromechanical interaction involved when grasping. The design of ergonomic devices could also benefit from this quantification of the relationship between wrist angle and muscle length properties.

Multichannel Nerve Stimulation for Diverse Activation of Finger Flexors.

Neuromuscular electrical stimulation (NMES) is a common approach to restore muscle strength of individuals with a neurological injury but restoring hand dexterity is still a challenge. This study sought to quantify the diversity of finger movements elicited by a multichannel nerve stimulation technique. A 2 × 8 stimulation grid, placed on the upper arm along the ulnar and median nerves, was used to activate different finger flexors by automatically switching between randomized bipolar electrodes. The forces from each individual finger as well as the high-density electromyogram (HDEMG) of the intrinsic and extrinsic flexors were recorded. The elicited finger forces were categorized using hierarchical clustering, and the 2D correlation of the spatial patterns of muscle activation was also calculated. A wide range of movement patterns were identified, including multi-finger and single-digit movements. Additionally, a number of electrode pairs elicited similar finger movements. The muscle activation patterns showed similar and distinct spatial patterns, signifying activation redundancy. These results revealed the diversity of elicitable finger movements and muscle activations. The system redundancy can be explored to compensate for system instability due to fatigue or electrode shift. The outcomes can also enable the development of an automatic calibration of the stimulation.

SEEDS, simultaneous recordings of high-density EMG and finger joint angles during multiple hand movements

We present the SurfacE Electromyographic with hanD kinematicS (SEEDS) database. It contains electromyographic (EMG) signals and hand kinematics recorded from the forearm muscles of 25 non-disabled subjects while performing 13 different movements at normal and slow-paced speeds. EMG signals were recorded with a high-density 126-channel array centered on the extrinsic flexors of the fingers and 8 further electrodes placed on the extrinsic extensor muscles. A data-glove was used to record 18 angles from the joints of the wrist and fingers. The correct synchronisation of the data-glove and the EMG was ascertained and the resulting data were further validated by implementing a simple classification of the movements. These data can be used to test experimental hypotheses regarding EMG and hand kinematics. Our database allows for the extraction of the neural drive as well as performing electrode selection from the high-density EMG signals. Moreover, the hand kinematic signals allow the development of proportional methods of control of the hand in addition to the more traditional movement classification approaches.

Musculoskeletal models of a human and bonobo finger: parameter identification and comparison to in vitro experiments.

IntroductionKnowledge of internal finger loading during human and non-human primate activities such as tool use or knuckle-walking has become increasingly important to reconstruct the behaviour of fossil hominins based on bone morphology. Musculoskeletal models have proven useful for predicting these internal loads during human activities, but load predictions for non-human primate activities are missing due to a lack of suitable finger models. The main goal of this study was to implement both a human and a representative non-human primate finger model to facilitate comparative studies on metacarpal bone loading. To ensure that the model predictions are sufficiently accurate, the specific goals were: (1) to identify species-specific model parameters based on in vitro measured fingertip forces resulting from single tendon loading and (2) to evaluate the model accuracy of predicted fingertip forces and net metacarpal bone loading in a different loading scenario.Materials & MethodsThree human and one bonobo (Pan paniscus) fingers were tested in vitro using a previously developed experimental setup. The cadaveric fingers were positioned in four static postures and load was applied by attaching weights to the tendons of the finger muscles. For parameter identification, fingertip forces were measured by loading each tendon individually in each posture. For the evaluation of model accuracy, the extrinsic flexor muscles were loaded simultaneously and both the fingertip force and net metacarpal bone force were measured. The finger models were implemented using custom Python scripts. Initial parameters were taken from literature for the human model and own dissection data for the bonobo model. Optimized model parameters were identified by minimizing the error between predicted and experimentally measured fingertip forces. Fingertip forces and net metacarpal bone loading in the combined loading scenario were predicted using the optimized models and the remaining error with respect to the experimental data was evaluated.ResultsThe parameter identification procedure led to minor model adjustments but considerably reduced the error in the predicted fingertip forces (root mean square error reduced from 0.53/0.69 N to 0.11/0.20 N for the human/bonobo model). Both models remained physiologically plausible after the parameter identification. In the combined loading scenario, fingertip and net metacarpal forces were predicted with average directional errors below 6° and magnitude errors below 12%.ConclusionsThis study presents the first attempt to implement both a human and non-human primate finger model for comparative palaeoanthropological studies. The good agreement between predicted and experimental forces involving the action of extrinsic flexors—which are most relevant for forceful grasping—shows that the models are likely sufficiently accurate for comparisons of internal loads occurring during human and non-human primate manual activities.

A musculoskeletal model of the hand and wrist: model definition and evaluation

To improve our understanding on the neuromechanics of finger movements, a comprehensive musculoskeletal model is needed. The aim of this study was to build a musculoskeletal model of the hand and wrist, based on one consistent data set of the relevant anatomical parameters. We built and tested a model including the hand and wrist segments, as well as the muscles of the forearm and hand in OpenSim. In total, the model comprises 19 segments (with the carpal bones modeled as one segment) with 23 degrees of freedom and 43 muscles. All required anatomical input data, including bone masses and inertias, joint axis positions and orientations as well as muscle morphological parameters (i.e. PCSA, mass, optimal fiber length and tendon length) were obtained from one cadaver of which the data set was recently published. Model validity was investigated by first comparing computed muscle moment arms at the index finger metacarpophalangeal (MCP) joint and wrist joint to published reference values. Secondly, the muscle forces during pinching were computed using static optimization and compared to previously measured intraoperative reference values. Computed and measured moment arms of muscles at both index MCP and wrist showed high correlation coefficients (r = 0.88 averaged across all muscles) and modest root mean square deviation (RMSD = 23% averaged across all muscles). Computed extrinsic flexor forces of the index finger during index pinch task were within one standard deviation of previously measured in-vivo tendon forces. These results provide an indication of model validity for use in estimating muscle forces during static tasks.

P144 Motor cortical stimulation versus voluntary relaxation to study muscle relaxation properties in different muscle conditions

Question Transcranial magnetic stimulation (TMS) over the motor cortex can induce abrupt muscle relaxation by inhibition of corticospinal drive to the activated muscles. Voluntary relaxation (VR) is more commonly used to study muscle relaxation properties. These two methods have never directly been compared. The aim of our study is to investigate if variability of TMS-induced relaxation is lower compared to VR. To further validate the use of TMS in assessing muscle relaxation we studied the effects of cooling and fatigue to see if we could reproduce the well-known slowing effects of these conditions on muscle relaxation. Methods Twenty-five subjects (14 men, 11 women) participated in this study. Handgrip dynamometry was used to assess relaxation properties of extrinsic finger flexors. Subjects performed repeated maximal voluntary contractions with VR and TMS-induced relaxation in fresh, cooled, and fatigued muscle conditions (Fig. 1). Peak relaxation rate (pRR), pRR normalized to maximal force (NpRR), and relaxation times were calculated. Within- and between-subject variability was assessed by calculating within- and between-subject coefficient of variability (CV), intraclass correlation coefficient (ICC), and repeatability coefficient (RC). Results All outcome measures showed lower variability in TMS-induced relaxation compared to VR. This is demonstrated by lower within- and between-subject CV, ICC, and RC; e.g. for NpRR in men, TMS-induced relaxation has a within-subject CV of 3.3% vs 22.2% in VR, RC of 1.3 vs 6.1 s−1, ICC of 0.95 vs 0.60, and between-subject CV of 15.2% vs 27.4%.The slowing effects of cooling and fatigue could reliably be demonstrated using TMS (Fig. 2). Conclusions Variability of TMS-induced muscle relaxation was lower compared to VR. A clinical implication is that for future studies on muscle relaxation, measurements are more reliable and less subjects would be needed using TMS to demonstrate differences in relaxation properties. Download : Download high-res image (379KB) Download : Download full-size image Download : Download high-res image (214KB) Download : Download full-size image

The effect of the extensor mechanism on maximum isometric fingertip forces: A numerical study on the index finger

The extensor mechanism is a tendinous network connecting intrinsic and extrinsic muscles of the finger and its function has not yet been fully understood. The goal of this study was to assess the effect of the extensor mechanism on the maximum isometric fingertip forces – a parameter which is essential for grasping. For this purpose, maximum fingertip forces in all directions (i.e. feasible force sets) of two musculoskeletal models of the index finger were compared: the wEM model included a full representation of the extensor mechanism, whereas in the noEM model the extensor mechanism was replaced by a single extensor tendon without connectivity to intrinsic muscles. The feasible force sets were computed in the flexion-extension plane for nine postures. Forces in four predefined directions (palmar, proximal, dorsal, and distal), and the peak resultant forces were evaluated. Averaged forces in all four predefined directions were considerably larger in the wEM model (+187.6%). However, peak resultant forces were slightly lower in the wEM model (−4.3% on average). The general advantage of the wEM model could be explained by co-contraction of intrinsic and extrinsic extensor muscles which allowed reaching larger activation levels of the extrinsic flexors. Only within a narrow range of force directions the co-contraction of intrinsic muscles limited the fingertip forces and lead to lower peak resultant forces in the wEM model. Rather than maximizing peak resultant forces, it appears that the extensor mechanism is a sophisticated tool for increasing maximum fingertip forces over a broad range of postures and force directions – making the finger more versatile during grasping.

Keyboard Playing as a Hand Exercise for Patients with Subacute Stroke

Recent reports show that MIDI keyboard playing can improve upper-limb functions in neurorehabilitation, but little attention has been paid to this type of intervention with stroke patients in the subacute stage. The purpose of this study was to investigate the effects of keyboard-playing intervention that targeted hand dexterity of subacute stroke patients. A total of 17 subacute stroke patients participated in twelve 30-minute sessions over six weeks. The intervention included repetitive individuated, sequential, and simultaneous key-pressing to increase independent finger movements and strength. Of the four hand-function tests administered in this study, tip pinch in hand grip and pinch strength test and Box and Block Test (BBT) results showed the most significant improvement, indicating the largest effect sizes (0.785 for hand grip and pinch strength test and 0.840 for BBT). Better hand dexterity for subacute stroke patients may be achieved through repetitive key-pressing motions during keyboard playing by exercising the intrinsic and extrinsic flexor muscles primarily involved in the key-pressing motion. Overall, this study supports keyboard playing as a promising therapeutic intervention in subacute stroke rehabilitation.

Surgical Treatment of Pediatric Upper Limb Spasticity: The Wrist and Hand.

The wrist and hand are essential in the placement of the upper extremity in a functional position for grasp, pinch, and release activities. This depends on the delicate balance between the extrinsic and intrinsic muscles of the wrist and hand. Spasticity alters this equilibrium, limiting the interaction of the upper limb with the environment. Classically, pediatric patients with upper limb spasticity present with a flexed wrist, thumb-in-palm, and flexed finger posture. These contractures are typically secondary to spasticity of the extrinsic flexor muscles of the wrist and hand and intrinsic muscles of the thumb and digits. Tendon release, lengthening, or transfer procedures may help correct the resultant abnormal postures. A total wrist arthrodesis with or without proximal row carpectomy may help address the severely flexed wrist deformity. With proper diagnosis, a well-executed surgical plan, and a consistent hand rehabilitation regimen, successful surgical outcomes can be achieved.

Distinct functional roles of primate grasping hands and feet during arboreal quadrupedal locomotion

It has long been thought that quadrupedal primates successfully occupy arboreal environments, in part, by relying on their grasping feet to control balance and propulsion, which frees their hands to test unstable branches and forage. If this interlimb decoupling of function is real, there should be discernible differences in forelimb versus hind limb musculoskeletal control, specifically in how manual and pedal digital flexor muscles are recruited to grasp during arboreal locomotion. New electromyography data from extrinsic flexor muscles in red ruffed lemurs (Varecia rubra) walking on a simulated arboreal substrate reveal that toe flexors are activated at relatively higher levels and for longer durations than finger flexors during stance phase. This demonstrates that the extremities of primates indeed have different functional roles during arboreal locomotion, with the feet emphasizing maintenance of secure grips. When this dichotomous muscle activity pattern between the forelimbs and hind limbs is coupled with other features of primate quadrupedal locomotion, including greater hind limb weight support and the use of diagonal-sequence footfall patterns, a complex suite of biomechanical characters emerges in primates that allow for the co-option of hands toward non-locomotor roles. Early selection for limb functional differentiation in primates probably aided the evolution of fine manipulation capabilities in the hands of bipedal humans.

Anatomía aplicada a la cirugía de los tendones flexores

Anatomy of the flexor tendons is important for the treatment and prognosis of flexor tendon injuries. It is imperative to have a good knowledge of the structure of the tendons in relation to the pathogenesis of injuries and repair, and in particular their blood supply. The extrinsic flexor tendons of the fingers and the thumb have fibrous sheaths and a system of pulleys to apply and conduct the tendons to the polyarticular chain on which they work. Slipping of the tendons and their vascularisation is facilitated by the synovial sheaths, mesotendons and vincula tendinums.

Biomechanical analyses of the human flexor tendon adhesion models in the hand: A cadaveric study.

Patients with longstanding trigger finger may develop flexion contracture at the proximal interphalangeal (PIP) joint that persists even after division of the A1 pulley. The purpose of this study was to explore the hypothesis that flexion deformity of the PIP joint in advanced trigger finger is caused by severe adhesion between the flexor digitorum superficialis (FDS) and the flexor digitorum profundus (FDP) tendons. Ten freshly frozen cadaveric hands were used in the experiments. After preparation of the extrinsic flexor, extrinsic extensor, and intrinsic muscle tendons, we applied weights to the flexor tendons and minimal tension to the extrinsic extensor and intrinsic muscle tendons. We then measured the initial flexion angles of the metacarpophalangeal (MCP) and PIP joints. Next, we measured the flexion angles of the MCP and PIP joints as increasing tension was applied to the extrinsic extensor and intrinsic muscle tendons, respectively. We repeated these experiments after constructing flexor tendon adhesion model. The initial flexion angles of the MCP and PIP joints were greater in the adhesion model, as were the average tensions required for full extension of these joints. Our results suggest that adhesion between two flexor tendons contributes to progression of flexion deformity in the PIP joint.

Wrist arthrodesis with intercalated iliac crest graft in mutilans rheumatoid arthritis

In mutilans rheumatoid arthritis (RA) patients with major wrist destruction, wrist arthrodesis is recommended. This type of arthrodesis needs carpal reconstruction and stable fixation. The goal of this study was to assess the functional and anatomical outcomes of an iliac crest graft and internal fixation with two medullary pins. Six wrists in three patients suffering from RA were reviewed clinically and radiologically at an average follow-up of 25months. We assessed the fusion of the iliac graft with the radius and the metacarpus, the preoperative and postoperative carpal height, and the bone stock in front of the thumb. All the patients had improved functionally. The iliac graft fused with the radius in all cases and fused with the metacarpus in 5 out of 6 cases; the non-union occurred in the wrist where only one pin was used. Restoration of carpal height was associated with improvements in hand function. The bone stock was sufficient to allow implantation of a trapezial cup during a total arthroplasty of the thumb trapeziometacarpal (TMC) joint. No major complications occurred. An iliac graft and two pins through the 2nd and 3rd metacarpals were used to reconstruct the carpal height and to obtain wrist fusion. Internal fixation with only one pin is not recommended. Functional improvement can be attributed to the normal tension within the extrinsic flexors and extensors of fingers and thumb being restored because the carpal height was restored. A secondary TMC arthroplasty is theoretically possible.