A Biomechanical Advantage of the Lengthening with an External Fixator Over an Intramedullary Nail: An Experimental Study in Saw Bones and Cadeveric Bones

PURPOSE: To know biomechanical differences in methods of limb lengthening between using monolateral external fixator and using external fixator over an intramedullary nail. MATERIALS AND METHODS: In acryl rods, saw-bone, and cadeveric bone, we created two lengthening models of using monolateral external fixator and using external fixator over an intramedullary nail. The axial compression test was done on the site of osteotomy for lengthening. To fix the models, half pins of 5 mm in diameter and nails of 9 mm in diameter were used. Using MTS (Material Test System) machine, we evaluated the differences of axial stiffness according to the presence of an intramedullary nail or the numbers of half-pins which were fixed at each side of osteotomy. RESULTS: Lengthening over an intramedullary nail, comparing to monolateral external fixator only, increased the axial stiffness by 1.1~1.2 times in acryl rods, 1.2~1.6 times in saw bones, and 15.6~15.9 times in cadeveric bones when the same numbers of half-pins were used. In saw bone and cadaveric bone, the group of two half pins in lengthening over an intramedullary nail was stiffer than the group of three pins in lengthening with monolateral external fixator. CONCLUSION: In the distraction of the limb, the addition of an intramedullary nail may increase the axial stiffness of the frame of monolateral external fixator. In lengthening over an intramedullary nail, it is enough to distract the bone with fixing two half pins at each sides of osteotomy.

The Carpal Tunnel Syndrome / 대한정형외과학회잡지

The carpal tunnel syndroms is the most common peripheral nerve entrapment syndrome. The typical symptom is pain, numbness and paresthesia in the median nerve territory of the hand and progressive thenar atrophy. When the symptom is mild and its duration is short, conservative treatment such as splinting or local steroid injection is considered, but when neurological deficit is promiment and conservative treatment is not effective, surgical decompression is indicated.Authors reviewed 15 patients (23 cases) of carpal tunnel syndrome treated with surgical decomression at the Department of Orthopedic Surgery, Kyung-pook National University Hospital from March 1983 to October 1988. The follow up results are as follows; 1. Preoperatively, Tinel sign was present in 17 cases. Phalen test was positive in 17 cases. Sensory disturbance was present in 8 cases. Thenar muscle atrophy was present in 19 cases. Motor weakness was present in 13 cases. 2. Preoperatively, delay of motor conduction velocity of median nerve was noted in 15 cases (65.2%) and sensory nerve conduction velocity in 20 cases (86.9%). Denervation findings such as fibrillation or sharp waves were seen in 15 cases (65.2%). 3. The operative findings were as follows; Synovial hypertrophy in 12 cases, hypertrophy of transcarpal ligament in 4 cases, pseudoneuroma in 3 cases, ganglion in 2 cases, neurilemmoma in 1 case, gout in 1 case. 4. As the operative findings, median nerve had evidence of compression beneath the transcarpal ligament, consisting of flattening. narrowing and decreased epineurial vascularity. 5. External neurolysis was performed in all cases. 6. In case of long duration and severe thenar atrophy, internal neurolysis would be recommendable. 7. Fllow up period was ranged from 7 months to 6 years. 8. 19 cases (82.6%) were excellent or good results.