The accuracy of estimating proximal tibial translation during natural cadence walking: bone vs. skin mounted targets.

OBJECTIVE: To assess the efficacy of estimating proximal tibial translation using video-based motion capture and an array of surface-mounted targets ideal for tracking motion of the tibia. DESIGN: Superficial and bone-anchored tracking targets were used to create two independent sets of data locating the proximal tibia in a global coordinate system. BACKGROUND: Knowledge of the effect that soft tissue movement has on estimates of proximal tibial translation has not been reported to date. This basic information is necessary to establish construct validity for any study proposing to document tibial translation using standard video-based motion capture methods. METHODS: A six camera motion capture system was used to collect surface-mounted and bone-anchored data for seven healthy adult subjects walking at a self-selected speed. The subjects walked along the positive Y-axis of the global reference system, with the positive Z-axis oriented vertically. RESULTS: Average peak differences in the location of the proximal tibia calculated from the bone and surface-mounted targets were 7.1, 3.7 and 2.1 mm along the X, Y and Z axes of the global coordinate system respectively. Individual subject peak differences were as large as 14.1, 11.8 and 8.3 mm along the X, Y and Z axes. CONCLUSIONS: Estimates of tibial translation with a measurement resolution better than 3 mm are not likely using standard motion capture methods and tracking targets attached superficially to the lower leg. RELEVANCE: The results of this study clearly depict the considerable effect that soft tissue motion of the lower leg has on estimates of proximal tibial translation. Without consideration for the difficulties in measuring femoral, or patellar motion, we believe it is not feasible to routinely obtain sufficiently accurate estimates of detailed knee joint translations using superficial tracking target attachment methods.

Knee moment profiles during walking: errors due to soft tissue movement of the shank and the influence of the reference coordinate system.

The effect soft tissue movement of the shank had on knee joint moments during natural cadence walking was investigated in this study. This was examined by comparing knee moments determined from bone-anchored and surface mounted tracking targets. Six healthy adult subjects participated in this study. The largest difference (3 N m) occurred about the AP axis, with smaller differences of approximately 2 and 1 N m about the flexion/extension (F/E) and longitudinal (Long) axes, respectively. The magnitude of these differences would not likely affect the clinical interpretation of the data. The effect of reporting knee moments in two different orthogonal reference systems was also examined. The peak extension moment was significantly greater when expressed about an anatomical axis following the line of the malleoli than when the moment was reported about an axis parallel to the frontal plane of the shank. In contrast, the first peak abduction moment was significantly greater when expressed about an axis perpendicular to the frontal plane of the shank. Care should therefore be exercised whenever comparisons between studies are made in which the reference axes are not aligned.

Objective evaluation of knee laxity in children.

This study was designed to measure objectively knee laxity in children. Physical examination and the KT 1000 arthrometer were used to test the knee laxity of 150 healthy, uninjured children between 6 and 18 years of age. Data from the knee examinations and the KT 1000 measurements were compared and statistically analyzed to determine the change in knee laxity with age, laxity differences between boys and girls, and the correlation between the KT1000 measurements and subjective tests for laxity described by Carter and Wilkinson. There was no statistical difference in knee laxity between boys and girls of similar ages. We found that knee laxity, determined by measuring the millimeters of tibial translation using the KT 1000 arthrometer, was significantly greater in younger children.

Comparison of surface mounted markers and attachment methods in estimating tibial rotations during walking: an in vivo study.

The overall goal of this work was to determine an optimal surface-tracking marker set for tracking motion of the tibia during natural cadence walking. Eleven different marker sets were evaluated. The marker sets differed in the location they were attached to the shank, the method used to attach the marker sets to the segment and the physical characteristics of the marker sets. Angular position during stance for each marker set was expressed relative to the orientation of the tibia as measured using bone anchored markers. A marker set consisting of four markers attached to a rigid shell positioned over the distal lateral shank and attached to the leg using an underwrap attachment yielded the best estimate of tibial rotation. Rotational deviations of+/-2 degrees about the medio-lateral and antero-posterior axes, and+/-4 degrees about the longitudinal axis did occur even when using the optimal set of markers.

The relationship of developmental narrowing of the cervical spinal canal to reversible and irreversible injury of the cervical spinal cord in football players.

An evaluation of forty-five athletes who had had an episode of transient neurapraxia of the cervical spinal cord revealed a consistent finding of developmental narrowing of the cervical spinal canal. The purpose of the present epidemiological study was to determine the relationship, if any, between a developmentally narrowed cervical canal and reversible and irreversible injury of the cervical cord with use of various cohorts of football players as well as a large control group. Cohort I comprised college football players who were asymptomatic and had no known history of transient neurapraxia of the cervical cord. Cohort II consisted of professional football players who also were asymptomatic and had no known history of transient neurapraxia of the cervical cord. Cohort III was a group of high-school, college, and professional football players who had had at least one episode of transient neurapraxia of the cervical cord. Cohort IV comprised individuals who were permanently quadriplegic as a result of an injury while playing high-school or college football. Cohort V consisted of a control group of male subjects who were non-athletes and had no history of a major injury of the cervical spine, an episode of transient neurapraxia, or neurological symptoms. The mean and standard deviation of the diameter of the spinal canal, the diameter of the vertebral body, and the ratio of the diameter of the spinal canal to that of the vertebral body were determined for the third through sixth cervical levels on the radiographs for each cohort. In addition, the sensitivity, specificity, and positive predictive value of a ratio of the diameter of the spinal canal to that of the vertebral body of 0.80 or less was evaluated. The findings of the present study demonstrated that a ratio of 0.80 or less had a high sensitivity (93 per cent) for transient neurapraxia. The findings also support the concept that symptoms may result from a transient reversible deformation of the spinal cord in a developmentally narrowed osseous canal. The low positive predictive value of the ratio (0.2 per cent) however, precludes its use as a screening mechanism for determining the suitability of an athlete for participation in contact sports. Developmental narrowing of the cervical canal in a stable spine does not appear to predispose an individual to permanent catastrophic neurological injury and therefore should not preclude an athlete from participation in contact sports.

Nonoperative treatment of acute anterior cruciate ligament injuries in a selected group of patients.

Conservative treatment of acute anterior cruciate ligament injuries was recommended to selected patients, including those with sedentary occupations, low athletic demands, or ages greater than 30 years. Patients with generalized hyperligamentous laxity were excluded. Fifty-five of 61 patients were available at an average followup of 46 months from the time of initial injury. At followup, giving-way symptoms had not occurred in 23 patients (42%); in 22 (40%) giving way occurred occasionally. Of the 44 patients involved in high- or moderate-demand athletics, 33 (70%) were able to continue with moderate-demand sports. Presence of a medial collateral ligament sprain did not affect the longterm function. Forty-eight percent of the patients scored excellent or good (9 and 18 patients, respectively) on the Hospital for Special Surgery ligament scoring system; 8 (15%) later chose surgical reconstruction. The remaining 47 patients did not believe that their symptoms were severe enough to warrant any further intervention. In a group of individuals who are older and relatively inactive, nonoperative management of anterior cruciate ligament injuries can yield satisfactory results, provided the patients are willing to accept a modest amount of instability and a slight risk of meniscal injury.

Arthroscopically assisted reconstruction of the anterior cruciate ligament with use of autogenous patellar-ligament grafts. Results after twenty-four to forty-two months.

The results of the first sixty-nine consecutive patients who had had seventy arthroscopically assisted reconstructions of the anterior cruciate ligament with use of an autogenous patellar-ligament graft at our institution were reviewed retrospectively. Sixty-seven patients (sixty-eight knees) were available for evaluation after a minimum of two years. All patients had been managed with early, postoperative range-of-motion exercises and a standardized program of physical therapy. At the time of the most recent follow-up evaluation, the median ligament score, according to the rating system of The Hospital for Special Surgery, was 93 of a possible 100 points. Of the sixty-eight knees, forty-four were rated excellent; fifteen, good; six, fair; and three, poor. Eighteen knees had symptoms related to the patellofemoral joint and sixty-three had a full range of motion; two knees had had manipulation for loss of flexion. At the follow-up evaluation, KT-1000 arthrometric measurements were obtained for both knees of fifty-six patients. Eighty-four per cent of the patients had an increase of three millimeters or less in anterior-posterior displacement of the tibia on the reconstructed side compared with the normal side, while 93 per cent had an increase of four millimeters or less. Postoperatively, there was no apparent association between changes in the Insall-Salvati patellar ligament-to-patella ratios and pain in the patellofemoral joint. The results of the arthroscopically assisted reconstructions combined with use of early range-of-motion exercises were comparable with those reported after open reconstruction and immobilization of the limb in a plaster cast. The frequency of pain in the patellofemoral joint and the need for manipulation because of loss of motion were decreased after the arthroscopically assisted procedures.

The glenoid-labral socket. A constrained articular surface.

An anatomic study was designed to test the hypothesis that the articular surface of the glenoid fossa and labrum produces a composite socket of significant depth. Measurements were obtained from 25 anatomic specimen shoulders. The glenoid articular surface and labrum combine to create a socket that is approximately 9 mm deep in the superoinferior (SI) direction and 5 mm deep in the anteroposterior (AP) direction. The circular, pliable, fibrous labrum contributes approximately 50% of the total depth of the socket. Detachment of the labrum anteriorly, as in a Bankart lesion, may reduce the depth of the socket in the AP direction from approximately 5.0 to 2.4 mm. These anatomic observations provide some evidence that the socket may be an important factor in shoulder stability. Further in vivo kinematic studies of shoulders will be needed to better define the stabilizing role of the glenoid-labral socket.

Normal and abnormal mechanics of the glenohumeral joint in the horizontal plane.

This study was performed to evaluate the relationship of the humeral head to the scapula in the horizontal plane of motion and to describe in detail a method of obtaining and interpreting modified axillary roentgenograms. Twenty normal subjects and twelve patients who had anterior instability of the shoulder were evaluated with this technique. In the control group, the humeral head was centered in the glenoid cavity throughout the horizontal plane of motion except when the arm was in maximum extension and external rotation. In this position, the cocked stage of the throwing motion, the center of the humeral head rested approximately four millimeters posterior to the center of the glenoid cavity. When the arm was flexed or rotated from this cocked position, the humeral head glided anteriorly, producing a shearing stress on the articular surface of the glenoid and labrum. In seven of the twelve patients who had anterior instability, abnormal mechanics were observed: anterior translation of the humeral head occurred. This indicates a significant disruption of the structures responsible for containing the humeral head within the glenoid fossa.

Dislocation of the posterior stabilized total knee arthroplasty. A report of two cases.

This brief report details the previously unreported complication of dislocation of the posterior stabilized total knee arthroplasty. Both patients had valgus deformities requiring extensive release of the contracted lateral soft tissues. The mechanism of dislocation was one of slight flexion and external rotation. The prosthetic tibial spine became locked posterior to the femoral cam. Reduction was accomplished by applying traction and anterior translation on the tibia with the knee slightly flexed. No redislocations have occurred. A literature review is presented and the authors discuss technique modifications that may prevent this complication.

A new model of concussive brain injury in the cat produced by extradural fluid volume loading: I. Biomechanical properties.

This study presents a new device for producing experimental, concussive head injury together with a detailed description of biomechanical features of fluid percussion brain injury in the cat. Anaesthetized cats were subjected to multiple (N = 3) or single injuries (N = 87). The variables studied in repeated injury experiments included the volume of fluid injected intracranially, rate of fluid flow, and the associated pressure transients recorded extracranially in the injury device and intracranially at supratentorial and infratentorial sites. Peak fluid flow increased with increasing volumes of fluid loaded intracranially. Extracranial pressure peaks and durations increased when volume loading was increased. Extracranial and intracranial pressure transients were similar at all recording sites. The form of pressure transients recorded in single injury experiments was similar to that recorded in multiple injury experiments. In single injury experiments, the extracranial pressure peaks and durations also increased with increased intracranial fluid volume loading. The slopes describing the relationships between intracranial volume loading and extracranial pressure transients were significantly different in single and multiple injury experiments. Details of the design and use of the head injury device are also discussed.

A new model of concussive brain injury in the cat produced by extradural fluid volume loading: II. Physiological and neuropathological observations.

This study examined physiological and histopathological changes in the cat produced by a new experimental fluid injury device. Spontaneously breathing (N = 14) and artificially ventilated (N = 45) cats were subjected to systemically varied magnitudes of fluid percussion brain injury. Within certain injury ranges, increasing magnitudes of fluid percussion injury produced increasing durations of apnea, as well as greater transient increases in mean arterial blood pressure, intracranial pressure and cerebral perfusion pressure. Acute increases in intracranial pressure may have been related to cerebral vasodilatation produced by the systemic hypertension following brain injury. Injuries associated with pressure transients greater than 10 atm ms produced concussive responses, including irreversible apnea in spontaneously breathing cats and temporary pupillary dilatation, increases in heart rate and mean arterial blood pressure in artificially ventilated cats. Injuries greater than 39 atm ms frequently produced histopathological and physiological indices of significant irreversible brain damage, including fixed and dilated pupils, systemic cardiovascular hypotension and deteriorating blood gases. Injury magnitudes less than 20 atm ms did not produce macroscopic evidence of histopathology, intermediate injury ranges produced increasing evidence of subarachnoid and petechial hemorrhage while injury levels greater than 40 atm ms frequently produced significant histopathology including massive hematomas. Injury greater than 10 atm ms resulted in opening of the blood-brain barrier, as assessed by extravasation of horseradish peroxidase. Injury greater than 19 atm ms produced suppression of EEG amplitudes which did not recover for up to 40 minutes after injury. These data provide detailed information on the physiological and histopathological consequences of fluid percussion injury in the cat and indicate that this modified fluid percussion apparatus can produce graded levels of brain injury similar to those previously reported for fluid percussion injury.

Effects of naloxone on systemic and cerebral responses to experimental concussive brain injury in cats.

This study examined the effects of bolus injections of naloxone hydrochloride, a specific narcotic antagonist, on systemic cardiovascular function, intracranial and cerebral perfusion pressures, blood gas status, and cortical encephalograms (EEG's) in 38 cats after two different grades of experimental brain injury. Naloxone had no prolonged effects on uninjured control animals. However, as compared to a saline-injected control group, naloxone significantly reversed the hypotension and reduction in pulse pressure seen after higher grades of injury. These changes persisted for at least 60 minutes after injection and were accompanied by increased intracranial and perfusion pressures. More severely injured hypotensive cats injected with naloxone also had higher values of arterial pO2 and pH, lower pCO2, as well as higher EEG amplitudes. In less severely injured normotensive cats, naloxone produced greater effects on cardiovascular variables and intracranial pressure when injected 15 minutes rather than 45 minutes after injury. These data suggest that endogenous opiates may contribute to some instances of hypotension seen after concussive brain injury. Levels of endogenous opiates may also increase transiently even with lesser degrees of injury not associated with hypotension. The possible clinical application of narcotic antagonists to the treatment of head injury is discussed.