D'Ambrosia R

The RGO Generation II: Muscle Stimulation Powered Orthosis as a Practical Walking System for Thoracic Paraplegics

The RGO Generation II reciprocating gait orthosis was jointly developed by Louisiana State University Medical Center and Durr-Fillauer Medical, Inc, to overcome four problems encountered with the existing model: 1) The high energy cost of locomotion; 2) the great arm strength required for patients to stand up from the seated position without assistance; 3) difficulty (especially for patients with hamstring contracture) in remaining standing owing to failure of the knee latch to lock except in full extension; and 4) problems in balancing when ambulating on an incline. The RGO Generation II employs concurrent electrostimulation of the rectus femoris and hamstrings to assist in rising and balancing and a ratchet-type latching device to improve safety and stability in standing. Alternating stimulation of the rectus femoris and contralateral hamstrings are used for locomotion. Testing in six patients with thoracic paraplegia demonstrated an average 30+% reduction in energy expenditure at a walking speed of .05 m/s and a 15+% reduction at .37 m/s; improved mobility and better balance on inclines; and unassisted rising in all patients. Walking range was increased from an average of 100 m to an average of 800 m. More research is needed to provide stair-climbing ability and to further reduce energy expenditure.

Secondarily infected total joint replacements by hematogenous spread

Three fatal cases of infections that followed total joint replacement are repoarted, in each of which a hematogenous source of infection was identified. There also were five non-fatal cases presumable arising hematogenously which were reported in the literature. It is emphasized that concomitant disease, including active rheumatoid arthritis, may predispose to this complication.

Supracondylar Fractures of Humerus—prevention of Cubitus Varus

1. A comparative study of six methods of treatment in sixty-seven supracondylar fractures in children is presented. They were handled as orthopaedic emergencies, and, perhaps because of the prompt treatment, vascular complications were avoided. 2. Normal elbow motion resulted following each method of closed treatment but open reduction caused some loss in extension. 3. The seven nerve palsies recorded were transitory. 4. Myositis ossificans complicated one case following open reduction but was not otherwise observed in this series. 5. Overhead threaded pin traction was safe and the swelling of the elbow rapidly decreased as gravity hastened venous and lymphatic drainage. 6. Overhead pin traction prevented residual varus deformity possibly because it provided a position of mild pronation of the forearm. 7. Closed reduction followed by a collar and cuff also prevented residual varus deformity, possibly because of the neutral or pronated position of the forearm. 8. In our opinion the supinated position of the forearm should be avoided in the treatment of supracondylar fractures of the elbow in children.

The EMG-Force Model of Electrically Stimulated Muscle: Dependence on Control Strategy and Predominant Fiber Composition

The EMG-force relationships of electrically stimulated muscle under a wide range of firing rate and recruitment control strategies were studied in a predominantly slow (soleus) and fast (m. gas-trocnemius) twitch muscles with the objective of applying the results in rehabilitative systems where the EMG serves as a force feedback parameter.

SEIDEL INTRAMEDULLARY NAILING OF HUMERAL DIAPHYSEAL FRACTURES: A PRELIMINARY REPORT

Forty-two humeral diaphyseal fractures in 41 patients were treated at three centers between April 1988 and November 1989. There were 28 acute fractures; four were open. Average time to union was 8 weeks. There were no infections. Six patients with seven pathologic fractures due to metastatic disease died during the course of this study, but the nail had allowed them to be functional with minimal surgical dissection. Five of six nonunions united with one procedure. There was one residual nonunion in a patient with a wide canal and an arthrodesed shoulder above the nonunion. There were three preoperative radial and two preoperative axillary nerve palsies, and no iatrogenic nerve palsies. In all patients with anterior deltoid incisions, shoulder motion returned reliably, but took as long as 6 months. Four rods were left prominent in the rotator cuff and the patients had symptoms of impingement until rod removal. Six patients had restricted shoulder function, one due to a fracture of the humeral head and five from a lateral deltoid incision. This incision was used in 12 cases. There were no stiff shoulders when using an anterior deltoid incision.

The Myoelectric Signal of Electrically Stimulated Muscle During Recruitment: An Inherent Feedback Pareter for a Closed-Loop Control Scheme

The myoelectric profile of an electrically stimulated muscle with separate and simultaneous control of firing rate and recruitment was determined. The signal consists of low amplitude, desynchronous discharge at low recruitment levels and exhibits monotonic, distinct compound action potentials at moderate to full recruitment. The myoelectric signal-force model is described by sigmoidal function when the signal is represented by its median frequency (MF), rms, or mean absolute value (MAV) at firing rates inducing just above fused force response (~28 pps). At firing rates corresponding to the maximal tetanic force of the muscle (~51 pps) the MES-force model is represented by a second-order polynomial for MF, rms, and MAV. Dynamic tracking of force induced by a sinusoidal recruitment/derecruitment of the muscles motor unit pool at frequencies in the range of 0-1 Hz show that the MAV is independent, whereas the rms and MF are dependent on tracking frequency. The linearized MAV-force model was found superior for use as a sensorless force feedback measurement in a closed-loop control scheme aimed at restoration of regulated movement to a paralyzed limb joint.

Fractures of the femoral shaft treated by external fixation with the Wagner device.

The Wagner external skeletal-fixation system was used to treat twenty complex fractures involving the femur, and nineteen of the fractures healed. Chronic osteomyelitis did not develop in any of the patients.

The small pin circular fixator for proximal tibial fractures with soft tissue compromise.

We used a Monticelli-Spinelli small pin circular external fixator in five cases, in combination with closed reduction or limited open reduction internal fixation, to salvage a satisfactory result in juxtaarticular, intraarticular fractures of the proximal tibia, when associated soft tissue compromise prevented standard fixation with plates and screws. The small pin circular fixator allows juxtaarticular placement of the small pins, enhancing stabilization of the comminuted fractures, allowing early range of motion of the joint and early patient mobilization. The small diameter pins support the soft cancellous bone fragments. This technique attempts to combine the benefits of traction, external fixation, and limited internal fixation. We recommend this method as a salvage procedure when plates and screws are contraindicated because of poor bone and soft tissue conditions.

Mechanoreceptors in the human elbow ligaments.

The medial, annular, and lateral elbow ligaments from 6 fresh human cadavers were dissected from origin to insertion, stained, and examined with a light microscope to determine the existence of mechanoreceptors. It was shown that the anterior, posterior, and transverse medial ligaments as well as the annular and radial collateral ligaments were endowed with mechanoreceptors. The mechanoreceptors consisted of Golgi organs, Ruffini terminals, Pacinian corpuscles, and free nerve endings. The mechanoreceptors were distributed evenly throughout the annular and transverse medial ligament, but with increased density toward the origin and distal insertions in the radial, posterior, and anterior medial ligaments. It was concluded that the elbow ligaments may provide significant sensory function to the elbow joint, in addition to being its major mechanical restraints.

Scintigraphy in the diagnosis of osteonecrosis.

Scintigraphy, using 99mTc diphosphonate, has the potential for diagnosing osteonecrosis before irreversible changes are visible in routine roentgenograms. If obtained within weeks of an avascular insult, a cold area will appear on scintiscan. However, months later, the revascularization and reparative processes of the dead bone produce a hot area on scintiscan.