Bone loss in spinal cord-injured patients: from physiopathology to therapy.

STUDY DESIGN: Review article on bone metabolism and therapeutic approach on bone loss in patients with spinal cord injury (SCI). OBJECTIVE: The first part aims to describe the process of bone demineralization and its effects on bone mass in patients with SCI. The second part describes and discusses the therapeutic approaches to limiting the alteration in bone metabolism related to neurological lesions. SETTING: Propara Rehabilitation Center, Montpellier, France. RESULTS: During the first 24 months postinjury, demineralization occurs exclusively in the sublesional areas and predominantly in weight-bearing skeletal sites such as the distal femur and proximal tibia, both of which are trabecular-rich sites. Reduced bone mass, in association with a modified bone matrix property and composition, is very likely at the origin of pathological fractures after minor trauma to which these patients are frequently exposed. Since these fractures may be asymptomatic yet may lead to complications, preventing and managing 'neurological osteoporosis' remains a considerable challenge. Two main approaches are considered: the first consists in applying a mechanical stimulus to the bone tissue by standing, orthotically aided walking or functional electrical stimulation (FES). The second uses medications, particularly antiresorptive drugs such as calcitonin or diphosphonates. CONCLUSION: To develop well-adapted treatments, a more precise understanding of bone loss etiology is needed. The current rehabilitation programs are based on the idea that the bone physiological changes observed in patients with SCI are due to immobility, but results indicate that alterations inherent to neurological damage may play an even greater role in inducing osteoporosis.

Computer added locomotion by implanted electrical stimulation in paraplegic patients (SUAW).

Paraplegia means a live long sentence of sensory loss, paralysis and dependence with approximately 1000 new victims in every European country every year and 11.500 new traumatic SCI cases in the US. respectively. Sixty percent are injured before age 30. More than 90% of SCI victims may survive with nearly normal experience of live. Most patients will recover somewhat from SCI over time but no patient who remained plegic for one year regains voluntary motor function after that time period. Despite remarkable efforts and recent achievements in rehabilitation no treatment can be recommended so far to enhance functional recovery and restoring locomotion in paraplegic humans. FES as a technical compensation has become therefore a challenging treatment to restore muscle function and to prevent atrophy and to improve mobility and quality of life at the same time. In paraplegics FES could be the basis to restore locomotion. One of the advantages of an implanted FES version (neuroprosthesis) is that the FES system, electrodes, and cables remain permanently implanted within the body, so that the patient can stay without cables, the programmer attached to the crutches. The SUAW project, supported under BIOMED II Programme by the European Community was aimed to finalize and to put into practice the results of previous research and development. The novel implant with an ASCI-Chip has 16 channels, 8 on each side, 20 mA for monopolar and 2 mA for bipolar stimulation, only one electrode can be stimulated at a given time. Stimulation of 6 muscle groups of both legs are known to be sufficient for locomotion: M. ileopsoas (erector of the body, hip flexor), M. gluteus maximus (hip extensor), M. gluteus medius (lateral hip stabilisator, knee abductor), Mm. hamstrings (knee flexor) stimulated by epimysial electrodes, Mm. sartorius and rectus femoris (knee extensor) stimulated by neural, bipolar electrodes. Patient's selection criteria were: stable spinal cord lesion between T7 and T11, minimum 1 year after the accident without deformity of the spine, the muscle groups for locomotion responding to external FES with the EXOSTIM programmer with the same programme used later for the neuroprosthesis. Two paraplegic male patients, T8, 38 and 31 years old respectively, were operated on by an international group of surgeons according to the protocol in 09/1999, respectively 7/2000. The postop. course was uneventful. Because the threshold of the primary implant was too low regarding scare tissue around the electrodes, this implant was changed in 01/2000 and worked perfectly. Both patients are happy with the success of the novel treatment modalities.

[Modern techniques of restoration of locomotion in paralyzed persons]. / Les techniques modernes de restauration de la locomotion chez les personnes paralysées.

The destruction of neurons, in the nervous system, is an irreversible process, which makes difficult the therapy of lesions. The natural regeneration of nervous fibers has a different expression in peripheral and central nervous system. The biological research represents a long term hope. The only realistic approach at the moment is the Functional Electrostimulation of infralesional nerves and muscles by implanted neuroprosthesis.

[Dilator muscles of the pharynx and their implication in the sleep apnea syndrome of obstructive type. Review of the literature]. / Les muscles dilatateurs du pharynx et leur implication dans le syndrome d'apnée du sommeil de type obstructif. Revue de la littérature.

Pathophysiology of the obstructive sleep apnea syndrome shows three components: intra and peripharyngeal obstacles, excessive pharyngeal wall compliance and upper airway dilator muscle dysfunction. The intent of this paper is to provide an overview of the anatomy, histology, physiology and pathophysiology of the upper airway dilator muscles based on previously published articles. The upper airway dilator muscles can be separated in three different systems, main and accessory dilators, local and regional. They act in synergy. Their contraction occurs at the beginning of inspiration, thus maintaining opened the pharyngeal lumen through inspiration. Their action is modulated by several chemo or physical stimuli. In some apneic patients, these muscles demonstrate a dysfunction: hyperactivity during wakefulness, electromyogram wave amplitude reduced, delayed contraction during sleep and abnormal response to stimuli. This dysfunction might be due to neuromuscular histological abnormalities, a "fatigue" phenomenon or a central nervous command abnormality. Current explorations underlining an upper airway dilator muscle dysfunction will enable practitioners to decide which treatment is best and understand therapeutical failures; it will also help develop new therapeutical techniques such as functional electrical stimulation of the hypoglossal nerve/upper airway dilator muscles.

High-resolution computed tomographic study of the retrotympanum. Anatomic correlations.

The aim of this study was to define the imaging of the retrotympanum precisely by means of high-resolution CT. Based on 66 scans of petrous bones performed in 49 patients observed in an otologic department, several retrotympanic structures were studied: the pyramidal eminence, ponticulus, subiculum, chordal ridge, tympanic sinus of Proctor, sinus tympani and recess of the facial n. The variations in morphology and depth were noted as well as the relationship between the pyramid and the facial canal. In a second phase the same anatomic structures were studied in 24 temporal bones removed from embalmed cadavers and investigated with the same radiologic technique. Anatomic correlations were made for six temporal bones to confirm the general applicability of our radiologic hypotheses. In CT the pyramidal eminence was visualised in 100% of cases, the chordal ridge in 52%, the ponticulus in 63% and the subiculum in 57%. As regards the different recesses, the sinus tympani was visualised in 95% of cases, the posterior tympanic sinus of Proctor in 38%, the fossula of Grivot in 47% and the facial recess in 80%. The mean depth of the sinus tympani was 2.7 mm and that of the tympanic sinus of Proctor was 1.65 mm; the fossula of Grivot was assessed as 2.1 mm and the facial recess as 2.2 mm. A better knowledge of these sinuses and their variations will aid the surgeon, particularly in a posterior tympanotomy or a retro-facial approach.

Kinetic magnetic resonance imaging analysis of swallowing: a new approach to pharyngeal function.

The emergence of turbo-FLASH MR sequences allows us to acquire five 10-mm sections each second and thus to catch images of the soft tissues during function. One can trace the pathway of a liquid between the tongue, the soft palate, the epiglottis and the pharyngeal apparatus and analysis the role of the anatomic structures during swallowing. Restricted to the sagittal plane for the purpose of this preliminary study, this technique can be extended to the other planes to provide a three-dimensional analysis of oropharyngeal function or dysfunction.

High-resolution computed tomography of the canals of the temporal bone: anatomic correlations.

The aim of this study was to define precisely the imaging of the canals of the temporal bone by means of high-resolution computed tomography (HR CT). Based on 24 temporal bones removed from embalmed cadavers and investigated with HR CT, several canals were studied: the canal of the chorda tympani (CdT), the canal of the auricular branch of the vagus nerve (ABV), the canal of the tympanic nerve, the canal of the carotico-tympanic nerve and that of the lesser petrosal nerve. Anatomic correlations for six temporal bones were made to confirm the validity of our radiologic hypotheses. In CT, in axial sections OM 0 degree, the posterior canal of the CdT was visualized in 71% of cases, the ABV canal in 4%, the inferior tympanic canal in 12.5%, the carotico-tympanic canal in no cases and the canal of the lesser petrosal nerve in 50% (and in 75% with an incidence of OM + 10 degrees). In coronal incidence, the posterior canal of the CdT was seen in 20% of cases, the ABV canal in 25%, the inferior tympanic canal in 85%, the caroticotympanic canal in 65% and that of the lesser petrosal nerve in 15%. The six anatomic comparisons confirmed the radiologic hypotheses in every case. These different structures are easy to identify in HR CT and are important to define so that any lesion (tumoral or vascular) developing in their vicinity may not be overlooked.

[Transmission of pronation-supination movements in the wrist]. / Etude de la transmission des mouvements de pronosupination au niveau du poignet.

The wrist plays an essential in role the transmission of pronosupination movements. The four main muscles responsible for these movements are situated above the radiocarpal joint. This anatomic configuration allows a passive movement: Radio Metacarpal Rotation or RMR which is analysed here. Radio Metacarpal Rotation varies according to grip and the couple which is applied distally. An apparatus has been designed to simultaneously measure the angle, the force of grip and the couple. Radio Metacarpal Rotation is firstly measured with the wrist relaxed (grip strength < 5 N) and a distally applied rotation couple of 0.2 N.m in the supination direction and 0.5 N.m in the pronation direction. Secondly, the patient is asked to maintain a grip strength between 80 N and 100 N, and a couple of 1 N.m is applied distally in each direction. One hundred wrists were evaluated. We have looked for the rotation centers of active pronosupination and Radio Metacarpal Rotation. A three dimensional motion analysis device was used (ELITE system). Thirty normal wrists were evaluated. An anatomic study of the radiocarpal ligaments stretched by Radio Metacarpal Rotation was carried out on ten cadaver wrists. When the wrist is relaxed: there is an average Radio Metacarpal Rotation of 42 degrees. This Radio Metacarpal Rotation is reduced when grip is tightened. We have defined a locking test based on these two parameters. This clinical test is represented by two curves on a graph. The active pronosupination center and the radio metacarpal center do not coincide. The center of active pronosupination is situated near the center of the ulnar head and the center of radio-metacarpal rotation is always more lateral. On the anatomical preparations, we found a helicoidal configuration of the radiocarpal ligaments: a ligamentous double helix pronosupination. Radio Metacarpal Rotation interferes with transmission of pronosupination movements. When the wrist is not well locked there is a large lateral sweeping between radius and scaphoid. This sliding at the level of the cartilage can head to development of osteoarthritis of the wrist with a horizontal scaphoid and the good cartilage results after proximal row carpectomy. Radio Metacarpal Rotation must be taken into account when a prothesis designing. We propose a wrist locking test. The results of this test are directly related to the capacity of the joint surfaces to transmit pronosupination movements. Radio Metacarpal Rotation shows the importance of the horizontal plane in the wrist and its essential role in the transmission of pronosupination movements.

[Anatomy and pathophysiology of deglutition disorders]. / Anatomie und Pathophysiologie von Schluckstörungen.

In the nervous system there are many automatized functions that require multilevel control. Some of them are more important because of their link with some vital functions. Only two are crucial to survival: respiration and the pumping of the heart. Swallowing is integrated within the respiratory system, explaining the need for great reliability and justifying the complexity of the organization described. The progress of medical imaging techniques has created new conditions for practicing radiologists, who need to know much more anatomy than in the past. Therefore, it is easier to learn anatomical details if there details are understood as part of an intelligent construction. We hope to have been able to demonstrate that swallowing is one good example of the real competency of the constructor of this system.

Balance and stabilization capability of paraplegic wheelchair athletes.

The orientation of paraplegic athletes toward adapted sport activities required good knowledge of their functional characteristics. Wheelchair locomotion, especially for highly dynamic situations, poses the problem of trunk equilibrium management and head stabilization. The study aimed at designing a quantitative method to assess the ability of paraplegics to obtain trunk balance under dynamic stresses, and to analyze the various balance strategies, according to the spinal lesion level of the subjects. High (HPA) and low (LPA) paraplegic athletes were subjected to four series of antero-posterior stresses of increasing intensity, generated by an oscillating platform. By means of a computerized video-based movement analyzer, acceleration in the saggittal plane was measured at four different spinal level and, for each one, a damping factor was determined. This factor, computed at the head level, appeared to be representative of the subjects' ability to maintain balance. We attempted to differentiate balance strategies in the LPA and HPA groups through analysis of the relative contributions to damping of the thoracic and cervical spinal segments. The first results show an increasing tendency of neck reflex stiffening according to the neurological level.

[Determination of the instantaneous center of rotation of the shoulder using the ELITE system. Application to the study of normal and pathological abduction]. / Détermination du centre instantané de rotation de l'épaule par le système ELITE. Application à l'étude de l'abduction normale et pathologique.

The authors determined the in vivo displacement of the instantaneous center of rotation (ICR) of the shoulder from data supplied by an optoelectronic system (ELITE System) which uses a specifically designed software program to achieve 3-dimensional analysis of abduction. The study involved 10 control subjects and 20 patients suffering from a periarticular disorder of the shoulder capsule retraction in 10 cases and rotator cuff tears before and after rehabilitation in 10 cases. This method provides an objective assessment of humeral head misalignment in relation to the glenoid cavity induced by the periarticular shoulder disorder and of the realignment achieved through rehabilitation. The proposed ICR calculation technique is entirely harmless for the patient in (particular because it requires no radiation analysis).

Biomechanics of the lumbar spinal nerve roots and the first sacral root within the intervertebral foramina.

This study consists of 3 sections: a descriptive study of the intervertebral foramen by dissection, supplemented by millimetric sections made with the cine-microabrasive apparatus (patented) on 12 specimens frozen with liquid nitrogen; a study of the attachments of the roots made during manipulations testing the resistance to avulsion of the rootlets, the roots, the dural sheath and the fibrous expansions at the periphery of the intervertebral foramen; and a study of the mobility of the roots in the foramina during movements effected within and outside the spine. We concluded that the classical description of an intervertebral foramen as occluded by a taut membrane like a drum-head is false as only perforated expansions attach the root to the foramen. Further, the points for attachment of the roots are the dura mater and the fibrous expansion passing from the foramen to the sheath of the spinal n. Finally, from the aspect of mobility, there are 2 distinct compartments and movements in one are not perceived in the other compartment if the attachments are unbroken. These attachments are a barrier interposed between the two compartments.

Contrast examination of the soft palate with cross sectional correlation.

In this exceptionally well illustrated article, the author demonstrates both the normal anatomy and the radiologic appearance of inflammatory, neurologic and neoplastic lesions of the soft palate.

[Scapulohumeral arthrodesis by combined external and internal fixation. A biomechanical, technical and clinical study]. / Arthrodése scapulo-humérale par fixation combinée externe et interne. Etude biomécanique, technique et clinique.

The indications for arthrodesis of the shoulder are controversial and limited and fusion is difficult to achieve, as is shown by the number of methods described in the literature. Since 1970, the authors have used combined internal and external fixation for arthrodesis of the shoulder. From a biomechanical study of arthrodesed shoulders, an attempt has been made to define the best combination of fixation. Three progressively more complex methods combining intra-articular fixation with a Hoffmann external fixator in compression have been tested. The ideal method combines transverse double scapulo-humeral screws with a vertical acromio-humeral screw. The addition of a bony subacromial strut controls the shearing effects arising from the application of the fixator in compression and also provides an upper site of fusion. In 14 arthrodeses using combined internal and external fixation analysed with a two to sixteen year follow-up, acromio-humeral fixation has been used in 11 cases with 10 primary successes and in 3 cases triple screw fixation has given very rapid fusion without the need for spica immobilisation.

Soft cervical disc herniations.

The authors report their findings in a series of 51 patients suffering from typical cervical radiculopathy. With the aid of the CT scanner and intravenous injection of a contrast medium, the quality and resolution of the resulting images allowed neurosurgical intervention in 42 patients in whom the symptomatology alone was not sufficiently informative to allow successful treatment. In most cases the CT images allowed an accurate diagnosis and revealed a free fragment that had torn the common posterior vertebra ligament.

An experimental study of traction on the cervical spinal nerves.

The authors present a study of experimental traction on 48 cervical spinal nerves obtained from fresh cadavers. 16 avulsions of the roots were produced, always after rupture of the dura mater. The different stages of traction and rupture are described, as well as the different specimens after rupture. Ways of protecting the spinal nerves against avulsion are discussed.

In vivo corrosion of sodium silicate glasses.

Square-shaped implants of various sodium silicate glasses were weighed and implanted intraperitoneally in rat for periods ranging from 8 to about 60 days. The implants were then removed and their aspect was compared to their aspect before exposure to physiological environment. The corrosion products were studied by x-ray diffraction and electron microprobe analysis. Weight changes were also measured to calculate a biodegradation rate. The glass 66 SO (66.6 SiO2-33.3 Na2O) was strongly corroded, as early as after the first week. The nonsoluble degradation products formed a cocoon encapsulating the now smaller specimen. The analysis of the cocoon showed that it was made of a silica-rich layer containing also calcium and phosphorus. In this layer the ratio Ca/P could correspond to that of an apatite. The biodegradation rate reached 71 x 10(-4) g . cm-2 . day-1. The glass 75 SO (75 SiO2-25 Na2O) was not so quickly corroded: Cracks appeared at the surface and progressively reached the center of the implants. There was no removable shell but a white deposit, adherent to the surface. This deposit contained silica and also calcium and phosphorus at the periphery. The biodegradation rate was only 2.6 x 10(-4) g . cm-2 . day-1.