Control of wrist movement in deafferented man: evidence for a mixed strategy of position and amplitude control.

There is a continuing debate about control of voluntary movement, with conflicted evidence about the balance between control of movement vectors (amplitude control) that implies knowledge of the starting position for accuracy, and equilibrium point or final position control, that is independent of the starting conditions. We tested wrist flexion and extension movements in a man with a chronic peripheral neuronopathy that deprived him of proprioceptive knowledge of his wrist angles. In a series of experiments, we demonstrate that he could scale the amplitude of his wrist movements in flexion/extension, even without visual feedback, and appeared to adopt a strategy of moving via a central wrist position when asked to reach target angles from unknown start locations. When examining the relationship between positional error at the start and end of each movement in long sequences of movements, we report that he appears to have three canonical positions that he can reach relatively successfully, in flexion, in extension and in the centre. These are consistent with end-point or position control. Other positions were reached with errors that suggest amplitude control. Recording wrist flexor and extensor EMG confirmed that the flexion and extension canonical positions were reached by strong flexor and extensor activity, without antagonist activity, and other positions were reached with graded muscle activation levels. The central canonical position does not appear to be reached by either maximal co-contraction or by complete relaxation, but may have been reached by matched low-level co-contraction.

Preserved and impaired aspects of feed-forward grip force control after chronic somatosensory deafferentation.

BACKGROUND: Although feed-forward mechanisms of grip force control are a prerequisite for skilled object manipulation, somatosensory feedback is essential to acquire, maintain, and adapt these mechanisms. OBJECTIVE: Individuals with complete peripheral deafferentation provide the unique opportunity to study the function of the motor system deprived of somatosensory feedback. METHODS: Two individuals (GL and IW) with complete chronic deafferentation of the trunk and limbs were tested during cyclic vertical movements of a hand-held object. Such movements induce oscillating loads that are typically anticipated by parallel modulations of the grip force. Load magnitude was altered by varying either the movement frequency or object weight. RESULTS: GL and IW employed excessive grip forces probably reflecting a compensatory mechanism. Despite this overall force increase, both deafferented participants adjusted their grip force level according to the load magnitude, indicating preserved scaling of the background grip force to physical demands. The dynamic modulation of the grip force with the load force was largely absent in GL, whereas in IW only slower movements were clearly affected. CONCLUSIONS: The authors hypothesize that the deafferented patients may have utilized visual and vestibular cues and/or an efferent copy of the motor command of the arm movement to scale the grip force level. Severely impaired grip force-load coupling in GL suggests that sensory information is important for maintaining a precise internal model of dynamic grip force control. However, comparably better performance in IW argues for the possibility that alternative cues can be used to trigger a residual internal model.

Osteogenic protein-1 (bone morphogenetic protein-7) in the treatment of tibial nonunions.

BACKGROUND: The role of bone morphogenetic proteins (BMPs) in osseous repair has been demonstrated in numerous animal models. Recombinant human osteogenic protein-1 (rhOP-1 or BMP-7) has now been produced and was evaluated in a clinical trial conducted under a Food and Drug Administration approved Investigational Device Exemption to establish both the safety and efficacy of this BMP in the treatment of tibial nonunions. The study also compared the clinical and radiographic results with this osteogenic molecule and those achieved with fresh autogenous bone. MATERIALS AND METHODS: One hundred and twenty-two patients (with 124 tibial nonunions) were enrolled in a controlled, prospective, randomized, partially blinded, multi-center clinical trial between February, 1992, and August, 1996, and were followed at frequent intervals over 24 months. Each patient was treated by insertion of an intramedullary rod, accompanied by rhOP-1 in a type I collagen carrier or by fresh bone autograft. Assessment criteria included the severity of pain at the fracture site, the ability to walk with full weight-bearing, the need for surgical re-treatment of the nonunion during the course of this study, plain radiographic evaluation of healing, and physician satisfaction with the clinical course. In addition, adverse events were recorded, and sera were screened for antibodies to OP-1 and type-I collagen at each outpatient visit. RESULTS: At 9 months following the operative procedures (the primary end-point of this study), 81% of the OP-1-treated nonunions (n = 63) and 85% of those receiving autogenous bone (n = 61) were judged by clinical criteria to have been treated successfully (p = 0.524). By radiographic criteria, at this same time point, 75% of those in the OP-1-treated group and 84% of the autograft-treated patients had healed fractures (p = 0.218). These clinical results continued at similar levels of success throughout 2 years of observation, and there was no statistically significant difference in outcome between the two groups of patients at this point (p = 0.939). All patients experienced adverse events. Forty-four percent of patients in each treatment group had serious events, none of which were related to their bone grafts. More than 20% of patients treated with autografts had chronic donor site pain following the procedure. CONCLUSIONS: rhOP-1 (BMP-7), implanted with a type I collagen carrier, was a safe and effective treatment for tibial nonunions. This molecule provided clinical and radiographic results comparable with those achieved with bone autograft, without donor site morbidity.

The intramedullary skeletal kinetic distractor (ISKD): first clinical results of a new intramedullary nail for lengthening of the femur and tibia.

In 1986, a programme was initiated by the senior author to develop a reliable, mechanically activated, intramedullary lengthening device with a non-invasive means of measuring the progress of lengthening without X-ray. We report results of design, biomechanical testing, in vivo animal testing and clinical implantation of the first 20 intramedullary skeletal kinetic distractors (ISKDs) in adult patients with limb-length discrepancies. Twenty ISKD devices were implanted in 18 patients (14 males and four females). Lengthening was required due to infection (ten), trauma (six), polio (one) and burn (one). Six femurs and 14 tibias were lengthened. Mean patient age was 40 years (range, 18-65 years). No implant related infections, non-unions, malunions or joint contractures were observed. A design change was made following two initial hardware failures, after which there were no further breakages. Average lengthening was 49 mm (range, 29-110 mm). The average lengthening rate was 0.82 mm/day (range, 1.7-0.4 mm/day). Ability to work, walk and drive before, during and after treatment with the ISKD compared favourably with that of similar patients undergoing lengthening using the 'monorail' method in our practice. The ISKD appears to be a safe and cost-effective alternative to external fixators that reduces lifestyle disruption and complications during adult limb-lengthening procedures.

Weight estimation in a "deafferented" man and in control subjects: are judgements influenced by peripheral or central signals?

It is not yet certain which sources of information are most important in judging the weight of a held object. In order to study this question further, a "deafferented" man and five controls flexed their wrist to lift a container weighing 1,000 g. Direct vision of the arm and weight was denied; the container's vertical position was displayed to the subjects on an oscilloscope at the start of each trial and, then, in most experimental conditions, this display was removed. The weight was then either gradually increased or decreased over 20 s or left unchanged, on a pseudorandom basis. A verbal judgement of its change was required at the end of each trial, lasting 20 or 40 s. Under these conditions, the "deafferented" subject was unable to correctly judge the weight changes (38% accuracy, n.s. chi2, compared with 77% in control subjects), and even the control subjects, when exposed to muscle vibration, made many errors (54% accuracy). However, in many trials, including those in which the weight was unchanged, the vertical height of the container was not held constant by the subjects, but drifted up or down (mean absolute drift: approximately 2 cm). Hence, the change in muscular activation or stiffness could be estimated by the observers in the majority of trials. This allowed the verbal judgements of both the "deafferented" man and of control subjects undergoing muscle vibration to be correlated with the muscle activation produced, independent of the actual weight being tested. Post-hoc predictions of controls' responses during vibration, based on the direction of the change in muscle activity which these drifts in position implied, were 77% and 66% accurate for +/-750 g and +/-375 g tasks and 73% accurate for forearm-vibration trials (P<0.0001, chi2). Predictions of the "deafferented" subject's responses were 64% accurate (P=0.0002, chi2), even though his own responses were at a chance level with respect to the actual weight change. The judgements made by these subjects might have been based upon a peripheral sensory input, as small afferent fibres are still present in the "deafferented" man and vibration only partly blocked sensory function in the control subjects. Care was taken to minimise all other possible cues to the weight changes, e.g. vestibular, thermal, pressure or pain cues. However, peripheral inputs may not be the only signals used in the subjects' perceptual judgements. They might, instead, be based upon a centrally originating, but illusory changing sense of body position or, possibly, a changing sense of effort. In both cases, a perceived discordance between voluntary muscle activation and body image could underlie the subjects' responses. Our data do not yet allow us to distinguish between these alternative peripheral and central hypotheses, but do highlight the need to include perceptions of body position and motion into judgements of force control.

Two-staged delayed open reduction and internal fixation of severe pilon fractures.

OBJECTIVE: To evaluate the use of a two-staged technique for the treatment of C3 pilon fractures. DESIGN: Retrospective. SETTING: Level I trauma center. PATIENTS/PARTICIPANTS: Twenty-one consecutive patients with twenty-two C3 pilon fractures. Patients with C1 or C2 fractures and patients with open growth plates were excluded. INTERVENTION: All patients underwent immediate fibular fixation and placement of a medial spanning external fixator. After, on average, twenty-four days, patients underwent removal of the external fixator and formal open reduction and internal fixation of the pilon fractures. MAIN OUTCOME MEASUREMENTS: At average follow-up of twenty-two months, all patients were evaluated by using subjective, objective, and radiographic measurements as described by Burwell and Chamley (J Bone Joint Surg 1965;47B:634-659). Range of motion and postoperative complications were also recorded. RESULTS: Twenty-one of the twenty-two fractures healed within an average of 4.2 months. Average range of motion was 7 degrees of dorsiflexion, 33 degrees of plantar flexion, 17 degrees of eversion, and 11 degrees of inversion. Subjective and objective measurements showed 77 percent good results, 14 percent fair results, and 9 percent poor results. Radiographic reduction showed 73 percent anatomic and 27 percent fair reductions. There were no infections or soft tissue complications. The arthrodesis rate was 9 percent. CONCLUSIONS: A two-staged approach offers acceptable results for the treatment of severe pilon fractures. These results compare favorably with those of primary open reduction and of internal fixation and external fixation techniques. The major advantages include limited soft tissue complications and improved articular reconstruction.

Psychotherapy with the chronic pain patient using coping skills development: outcome study.

This study provided outcome data measuring variables of a psychoeducational group approach to self-management of 88 chronic pain patients and 25 controls. Most of the injuries were back injuries and work related. At the completion of the 16 group sessions, patients reported decreased depression, pain severity, interference, and affective distress and increased life control and general activity. At 1-year follow-up, there was continued increased return to work, lowered workers' compensation, fewer health care visits, and less prescribed pain medication than demographically similar controls. Results suggest that a group psychoeducational program involving learning of general coping skills primarily and pain coping skills secondarily produces an effective approach for the management of chronic pain.

Outcome after fixation of unstable posterior pelvic ring injuries.

Between June 1989 and May 1995, the authors surgically treated 64 patients with unstable posterior pelvic in juries. Fracture types included Tile Type C1 (75%), C2 (8%), and C3 (17%). There were 19 sacroiliac dislocations, 12 sacral fractures, 4 transiliac fractures, and 29 sacroiliac fracture dislocations. Average patient age was 32 years and Injury Severity Score was 27 points. Posterior fixation was accomplished by percutaneous iliosacral screw insertion in 53 patients (83%). Only pure transiliac fractures were treated without iliosacral screws. There were no iatrogenic nerve palsies. During the study, there was increased reliance on internal fixation of the anterior pelvic ring that aided in anatomic alignment of the pelvis for posterior fixation and resulted in decreased chronic pubic tenderness. The use of external fixation for definitive treatment was abandoned. Patients were observed for an average of 36 months (range, 5-74 months). Fifty-two patients were available for recent complete followup. Fifty-one patients (98%) healed their pelvic disruptions; there was 1 sacral nonunion. A 40-point pelvic outcome grading scale was developed based on physical examination, pain, radiographic analysis, and activity/work status. Scores obtained by this scale correlated closely with the Short Form-36 Health Survey scores. Patient functional outcome after posterior pelvic fracture was not associated with Injury Severity Score or fracture location.

Gait of a deafferented subject without large myelinated sensory fibers below the neck.

We evaluated the gait pattern of a deafferented subject who suffered a permanent loss of large sensory myelinated fibers below the neck following an acute episode of purely sensory neuropathy 21 years ago. The subject has developed several strategies to achieve a secure gait, namely: (1) a reduction of the degrees of freedom by freezing the knee articulations during the stance phase, (2) a preservation of body balance by enlarging his base of support, and (3) visual monitoring of his step by stabilizing the head-trunk linkage together with a characteristic forward tilt. As a result, the gait of the deafferented subject lacks the fluidity of normal gait. Compared with normal subjects, the gait pattern of the deafferented subjects is characterized by a shorter cycle length, a longer cycle duration, a slower speed, and a lower cadence. Using a dual-task paradigm, the attentional demands for walking were particularly important (as indexed by longer probe reaction times) during the double-support phase, suggesting that the deafferented subject uses the double-support phase as a transitory stable phase to update cognitively the postural features necessary for generating his next step.

Mechanical failures of intramedullary tibial nails applied without reaming.

The clinical mechanical failures of small diameter intramedullary interlocking nails were evaluated to determine the relationship of failure modes to the type or location of tibial fractures. Methods were developed to duplicate failure modes in vitro in standardized tests to simulate the clinical situations. Where standard test methods were inadequate, new methods were developed to provide quantifiable, reliable methods of evaluating potential clinical performance. The modes and rates of mechanical failure in the clinical series were consistent among participating centers: (1) In diaphyseal fractures with secondary trauma, the intramedullary nail bent at the fracture site where the working length was unsupported; (2) failures that occurred several weeks after nailing were the result of fatigue fractures of the locking screws, usually at the distal end; and (3) nail and screw failures occurred most commonly in proximal and distal tibial fractures. The strength of the 8- and 9-mm sizes of Synthes and Russell-Taylor nails were comparable.

A sequential protocol for management of severe open tibial fractures.

Fifty consecutive open fractures of the tibia, including 22 Grade IIIB and 4 Grade IIIC, were treated using a protocol of debridement, immediate wound coverage, and intramedullary nailing. Fasciocutaneous flaps were used extensively to cover areas of exposed bone. The severity of the soft tissue injury dictated the timing of definitive fixation. Fracture location determined implant selection and nailing technique. Patients were observed for an average of 21 months. Ninety-eight percent of the fractures united < 6 months postoperatively. There was 1 infection (2%), 2 malunions (4%), and 1 case of partial flap necrosis. Locking screws broke in 1 patient (2%); the fracture united with < 5 mm of shortening. Immediate postdebridement wound coverage, and intramedullary nailing after reconstruction of the soft tissue envelope facilitate fracture healing in these complex open injuries. Intramedullary nailing can be performed safely to include all grades of open tibial fractures from the proximal to distal metaphysis.

Evoked potentials in a subject with a large-fibre sensory neuropathy below the neck.

The results from experiments in various modalities of evoked potentials are described in a subject with a complete large peripheral neuropathy below the neck. He has no tactile or position sensitivity below that level, but has retained fatigue, pain, and temperature sensation. Percutaneous electrical stimulation of peripheral nerves led to scalp recorded evoked potentials with thresholds and propagation velocities compatible with conduction along A-delta peripheral pathways. CO2 laser evoked potentials were similar to those seen in controls, further support for intact A-delta peripheral fibres. Movement-related cortical potentials (MRCPs) were recorded associated with active and passive movement of the middle finger. The former were normal, evidence that the termination of the MRCP is not dependent on peripheral feedback. By comparing passive MRCPs between controls and the subject it was possible to establish which parts of the potentials are visual and which are proprioceptive and to gain evidence of central reorganisation in the subject. Magnetic brain stimulation was used to show that the subject did not perceive induced movement, had a normal centrally originating silent period, and could focus his attention during real and imagined movement of the finger more successfully than could normal controls.

Evidence of a limited visuo-motor memory used in programming wrist movements.

Human subjects can pre-program movements on the basis of visual cues. Experience in a particular task leads to the storage of appropriate control parameters which are used in programming subsequent movements, via a short-term motor memory. The form, duration and usage of this memory are, however, uncertain. Repetitive wrist flexion and extension movements were measured in four subjects. Three were neurologically normal men; the fourth subject had a peripheral large-fibre sensory neuropathy, depriving him of proprioceptive information about wrist movement. Subjects made alternating 45 degrees wrist movements between two visual targets; visual feedback of wrist position was provided for the first part of each trial. After 10 s of tracking, the subjects paused for an interval of 0-24 s before resuming tracking without visual feedback of wrist position. The positional accuracy of subsequent movements was analysed with respect to pause interval. Movement accuracy was reduced by the removal of visual feedback in all four subjects: movements after the pause interval were less accurate than those before the pause. Errors also accumulated within each sequence of movements made without visual feedback. Analysis of the first movement in each trial after the pause indicated a clear relationship between movement accuracy and pause interval. In all four subjects, movement accuracy decayed with longer pause intervals. In the deafferented subject, manipulation of the visual inputs (requiring visual fixation, rather than normal pursuit of the target; or direct viewing of the hand instead of viewing a cursor on a computer screen) affected the relationship between pause interval and subsequent movement accuracy. We propose that the memory used when producing these movements is a short-lasting visuo-motor signal, lasting a few seconds, which is derived from visual knowledge of previous movements, rather than a memory of a particular motor output. This visuo-motor signal is used to scale the amplitude of subsequent wrist movements. The brevity of the visuo-motor memory and the resultant inaccuracy of this deafferented subject and of our neurologically normal subjects implies that human feedforward control of the amplitude and position of wrist movements is severely limited.

Acetabular fracture fixation via a modified Stoppa limited intrapelvic approach. Description of operative technique and preliminary treatment results.

Between March 1991 and December 1992 the authors surgically treated 55 acetabular fractures using a modified Stoppa anterior intrapelvic extensile approach. Indications for utilization of this approach included displaced anterior column or wall fractures, transverse fractures, T shaped fractures, both column fractures and anterior column or wall fractures associated with a posterior hemitransverse component. The approach involves a transverse skin incision 2 cm above the pubic symphysis followed by a midline split of the rectus abdominis. Access to the intrapelvic aspect of the pelvis and acetabulum is gained by retraction of the muscular, neurovascular and urological structures. This modified Stoppa approach affords excellent visualization of the pelvic ring, facilitating the development and utilization of improved reduction and plating options. Patients were followed for an average of 17.7 months. All fractures united 6-12 weeks postoperatively. Radiographic grades were excellent (64%), good (25%), fair (7%) and poor (4%). Fixation and subsequent reduction were lost in 1 patient. Two transient obturator nerve palsies were diagnosed. There was 1 infection and 1 inguinal hernia. Posttraumatic arthritic changes were noted in 6 patients within the first postoperative year. There was no significant heterotopic ossification, major vascular injury iatrogenic palsy or intraarticular hardware placement. Clinical results were excellent (47%), good (42%), fair (9%) and poor (2%). The modified Stoppa incision offers the experienced trauma surgeon a new approach for fixation of displaced acetabular fractures. The approach offers improved reduction and fixation possibilities and may decrease the rate of complications associated with extrapelvic or extensile approaches.

Intramedullary nail and lag-screw fixation of proximal femur fractures. Operative technique and preliminary results.

Fifty patients with intertrochanteric and subtrochanteric fractures of the femur were treated with closed reduction and internal fixation with Vector intramedullary nail (Biomet Inc, Warsaw, Indiana) and lag-screw fixation. Sixty-five percent of intertrochanteric fractures were unstable, with subtrochanteric extension in 12 cases. Lag-screw fixation preceded closed, unreamed nailing. Weight bearing, as tolerated, was initiated on the first post-operative day in all patients. Overall mortality and complications were lower than those reported in comparable series of intertrochanteric fractures treated with internal fixation. One nail breakage occurred. No cases of lag-screw cutout, nonunion, or femoral shaft fracture were documented. The Vector nail has recently been introduced as an alternative form of fixation for complex proximal femur fractures. In the present study, consistently good results were obtained, despite the stability or location of the fracture. We especially recommend using the Vector nail for managing complex, unstable intertrochanteric and subtrochanteric fractures.

Predictive validity of the Level of Expressed Emotion (LEE) Scale: readmission follow-up data for 1, 2, and 5-year periods.

The predictive validity of the Level of Expressed Emotion (LEE) Scale in a group of schizophrenic patients was examined. Forty-six patients with DSM-III diagnoses of schizophrenic disorders were administered the perceived expressed emotion measure (LEE) and followed up for a 5-year period. Patients' ratings of their social environments were related to rehospitalization 1 year, 2 years (p < .02) and 5 years (p < .01) after initial assessment. These results supported the utility of the LEE in identifying schizophrenic patients at high risk for rehospitalization.

The perceptions of force and of movement in a man without large myelinated sensory afferents below the neck.

1. Motor memory and the sense of effort have been investigated in a man with a complete large fibre sensory neuropathy for over 16 years. The perceptions of pain, heat, cold and muscular fatigue remained but he was without perceptions of light touch and proprioception below the neck. 2. The subject was able to discriminate weights held in the hand with an accuracy only slightly worse than control subjects (20 g in 200 g) when forearm movement and visual inspection were allowed. With eyes shut however he could only distinguish a weight of 200 g from 400 g. It is concluded that a crude sense of effort remains which may have a peripheral origin. 3. A limited motor memory was also present, which allowed him to maintain a posture or continue a simple repetitive movement. No novel movement was possible without visual feedback. 4. Differences in movement ability between this subject and others with similar if less pure sensory neuropathies are ascribed to rehabilitation.

Corticofugal actions on lemniscal neurons of the cuneate, gracile and lateral cervical nuclei of the cat.

Extracellular records were made from single identified lemniscal neurons of the cell-cluster regions of the cuneate and gracile nuclei, and of the lateral cervical nucleus, in pentobarbitone-anaesthetized cats. Forepaw, hind paw or face regions of the contralateral Sm I cortex were identified by recording through an inserted microelectrode which was then used for stimulation. The effect of a double cortical shock or train of shocks was usually inhibition: occasionally facilitation was observed, or mixed effects with facilitation preceding inhibition. Effects were seen in about half the cells studied in all three nuclei. Some cells of the lateral cervical nucleus were strongly excited, an effect not seen in the other nuclei. No component of these responses depended on suprathreshold stimulus intensities. Some lateral cervical cells were studied after deafferentiation by section of the dorsolateral spinal white matter; the same pattern of effects was seen. With an upper stimulus limit of 200 microA, cuneate but not gracile cells were affected from the cortical forepaw region, and gracile but not cuneate cells from the hind paw region. With threshold stimuli in an identified part of the forepaw cortical representation it was clear that cuneate cells with cutaneous receptive fields in corresponding parts of the forepaw had the lowest thresholds (minimum 6 microA). Threshold rose steeply with distance across the paw, suggesting quite sharp focusing of corticofugal effects in this system. When using similar procedures with the lateral cervical nucleus, with an upper limit of 200 microA, stimulation of forelimb cortex, or of facial cortex, affected both neurons with forelimb and those with hind limb fields.(ABSTRACT TRUNCATED AT 250 WORDS)

On the late failure of spinal cord stimulation for deafferentation pain.

Two cases are described in which spinal cord stimulation was effective in abolishing previously intractable deafferentation pain for a number of years, but in which late failure occurred for non-technical reasons. A possible explanation for this is advanced; namely that the dorsal column fibres have altered electrical properties due to a form of transganglionic degeneration.

Initial experience with a second generation locking femoral nail: the Russell-Taylor reconstruction nail.

A series of 36 patients with 20 subtrochanteric fractures, 12 ipsilateral neck/shaft fractures, and five intertrochanteric fractures with shaft extension underwent closed intramedullary nailing with the Russell-Taylor reconstruction (RECON) nail. The average Injury Severity Score was 16, and seven of the fractures were open. All fractures were acute injuries, and all but one were treated within 24 hours of admission. Follow-up was obtained at three, six, nine, 12, and 24 months or until the fracture healed. The range of follow-up was one to three years. Complete follow-up was obtained in 33 of 36 patients. Union was achieved in all acute fractures. Shortening occurred in two cases and chondrolysis and avascular necrosis occurred in another patient. Excellent hip and knee range of motion were obtained except in a few cases of ipsilateral limb injuries. While many complex femoral shaft fractures can be treated successfully with first generation locking nails, this study demonstrates that second generation locking nails, such as the RECON nail, offer the added strength and design features necessary for more effective treatment of complex proximal and ipsilateral femoral neck/shaft fractures.