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Biomedical subjects

C H Shih

Publications and source records attributed to C H Shih.

At least 37 records · Page 2Linked to original sources
PubMed1999

Characterization of acrylic bone cement using dynamic mechanical analysis.

Dynamic mechanical analysis (DMA) was used to characterize the properties of acrylic bone cement with the addition of tricalcium phosphate (TCP), hydroxyethyl methacrylate (HEMA), and ethylene glycol dimethacrylate (EGDMA). The glass transition temperature of acrylic bone cement is >100 degrees C; the cement has a flat modulus response near human body temperature. The height of the damping peak decreases and becomes broader with increasing TCP content. Thus, TCP is incompatibile with acrylic bone cement. When the frequency is changed from high to low, the damping peak shifts to low temperature. The shift in damping peak with frequency indicates that this relaxation is time-dependent. When acrylic bone cement contains TCP with HEMA and EGDMA, the incompatibility between acrylic bone cement and TCP can be ameliorated.

Biocompatible Materials↗
PubMed1999

In vitro elution of vancomycin from biodegradable beads.

The current antibiotics delivery system for orthopedic infection treatment uses polymethylmethacrylate (PMMA) beads as a drug release. However the nonbiodegradable nature of the PMMA necessitates a second operation to remove the beads. This article explores the alternative of using biodegradable polymers as antibiotic beads for a long-term drug release. The effect of different processing factors on the release rate of the beads was investigated. To manufacture an antibiotic bead, polylactide-polyglycolide copolymers were mixed with vancomycin. The mixture was compressed and sintered at 55 degrees C to form beads of different sizes. An elution method was employed to characterize the release rate of antibiotic over a 35-day period at 37 degrees C. Biodegradable beads released high concentrations of antibiotic (well above the breakpoint sensitivity concentration) in vitro for the period of time needed to treat bone infection; i.e., 4-6 weeks. A bacterial inhibition test was carried out to determine the relative activity of the released antibiotics. The diameter of the sample inhibition zone ranged from 6.5-10 mm, which is equivalent to 12.5-100% of relative activity. By changing the processing parameters, we were able to control the release rate of the beads. This provides advantages of meeting the specific antibiotics requirement for patients with various surgical infections.

Anti-Bacterial Agents↗
PubMed1999

Arthroscopic posterior cruciate ligament reconstruction with quadriceps tendon-patellar bone autograft.

Surgical reconstruction of the posterior cruciate ligament (PCL) is indicated in the PCL-deficient knee with symptomatic instability and multiple ligamentous injury. However, the choice of graft tissues continues to be controversial. We describe an arthroscopic PCL reconstruction technique using the quadriceps tendon-patellar bone autograft. From March through September 1996, this autograft was used in 12 patients with PCL injuries. After 1-1.5 years' follow-up, the clinical outcome has been encouraging. In addition, the quadriceps tendon-patellar autograft has the advantage of being self-available. Furthermore, the technique is easy to perform and has comparable anatomic and biomechanical qualities to other available techniques. Quadriceps tendon-patellar autograft is a reasonable alternative choice for PCL reconstruction.

Adult↗
PubMed1999

Effect of reaming bone grafting on treating femoral shaft aseptic nonunion after plating.

Rigid intramdullary nailing with cancellous bone grafting provided by intramedullary reaming was prospectively used to treat femoral shaft aseptic nonunions after plating. Indications for this technique were a femoral shaft nonunion with an inserted plate, no previous infection sign in the treatment course, less than 1.5 cm shortening, and no segmental bony defects. After the plate was removed, a flexible guidewire was inserted antegradely. The local wound was closed, and intramedullary reaming was done as widely as possible until some resistance to it occurred. Finally, a rigid intramedullary nail was inserted. Twenty-four consecutive patients were treated with this regimen, and 21 were followed-up for at least 1 year (range 1-5 years). All 21 nonunions healed with a union rate of 100% (21/21). The time to union was 4.5 +/- 1.0 months. There were no significant complications. We conclude that for indicated cases, reaming bone grafting is a very effective technique and avoided donor site morbidity. Therefore, whenever possible, this technique could be considered first.

Adult↗
PubMed1999

Early polyethylene wear and osteolysis in cementless total hip arthroplasty: the influence of femoral head size and polyethylene thickness.

We examined initial polyethylene thickness, early polyethylene liner wear, and osteolysis in 350 primary, cementless total hip arthroplasties (THAs). All of the prostheses were of identical design and used Omnifit components. In the 32-mm head group, the mean liner wear correlated significantly with polyethylene thickness (P<.001) and increased rapidly with initial thinner polyethylene following a logarithmic model, although this increase was not statistically significant (r = -.633). Inadequate polyethylene thickness in the 32-mm head group was implicated as the major cause of higher liner wear. A minimal polyethylene thickness of 7 mm is recommended in cementless metal-backed THAs. The use of a large head combined with poor prosthetic design appeared to be responsible for the unacceptably high incidence of femoral osteolysis.

Acetabulum↗
PubMed1999

High success rate with exchange nailing to treat a tibial shaft aseptic nonunion.

OBJECTIVE: To investigate the effects of tibial exchange nailing in treating a tibial shaft aseptic nonunion and to establish optimal indications for using this technique. DESIGN: Prospective, consecutive. SETTING: University hospital. METHODS: Twenty-five consecutive tibial shaft aseptic nonunions were prospectively treated with the exchange nailing technique. Indications for this procedure were a tibial shaft aseptic nonunion that had previously been treated with an inserted nonreamed or reamed intramedullary nail, displayed less than one centimeter of shortening, was with or without rotational or angular deformity, exhibited no segmental bony defects, and was anatomically suited for conventional or locked reamed intramedullary nail stabilization. The marrow cavity was reamed as extensively as possible, and a rigid intramedullary nail with stable fixation was inserted. RESULTS: During a follow-up period of two to four years (median thirty-two months), twenty-four nonunions healed, on average, in four months (range three to six months). The one remaining nonunion healed four months after a cancellous bone grafting procedure. No wound infection or malunion was noted. CONCLUSION: Because of its high union rate, low complication rate, and simplicity of method, we believe that the exchange nailing technique should be considered preferentially for all indicated cases.

Adolescent↗
PubMed1999

Management of femoral diaphyseal infected nonunion with antibiotic beads local therapy, external skeletal fixation, and staged bone grafting.

BACKGROUND: Fifteen patients with femoral shaft fractures complicated by infected nonunions were treated with a two-stage protocol. METHODS: In the first stage, radical debridement was performed along with antibiotic bead chains local therapy and external skeletal fixation. In the second stage, the debrided nonunion site was repaired with bone grafting and the external skeletal fixator was used until bony union was achieved. The time between the first and second stages of treatment was 2 to 6 weeks. The debrided bone defects ranged from 0.5 to 15 cm. Autogenous iliac cancellous bone grafting was performed in 11 patients, and microvascularized osteoseptocutaneous fibular transfer was performed in 4 patients. RESULTS: Wound healing and bone union were achieved in all 15 cases. The duration of external fixation of these patients ranged from 7 to 15 months, with an average of 9 months. Minor pin-track infection was seen in seven patients. Postoperative infection after the second-stage bone grafting occurred in three patients. These three infections were arrested by limited debridement along with 2 to 4 weeks of parenteral antibiotic therapy. In one case, stress fracture occurred at 11 months after microvascularized fibular transfer; this was managed with another 5 months of external skeletal fixation. With an aggressive physical therapy program, 10 patients achieved nearly full range of knee motion and 5 patients had relevant knee flexion deficits. The follow-up averaged 58 months (range, 40-76 months); no recurrence of osteomyelitis was observed even at 76 months. CONCLUSION: We have found that our two-stage treatment with antibiotic beads local therapy, definitive external skeletal fixation, and staged bone grafting is an acceptable treatment protocol for the management of femoral diaphyseal infected nonunion. It results in rapid recovery from osteomyelitis and a predictable recovery from nonunion.

Adolescent↗
PubMed1999

Bone healing of tibial lengthening is delayed by cigarette smoking: study of bone mineral density and torsional strength on rabbits.

OBJECTIVE: We investigated the effect of intermittent cigarette smoke inhalation on the bone healing of tibial lengthening in rabbits. METHODS: Twelve male rabbits were divided into two groups of six animals each. The first group underwent intermittent cigarette smoke inhalation, and the second group did not undergo intermittent cigarette smoke inhalation. Each animal's right tibia was lengthened 5 mm by using an uniplanar lengthening device. Bone mineral density (BMD) study was performed for all of the animals 1 day before operation and 3, 4, 5, and 6 weeks after operation. All of the animals were killed 6 weeks postoperatively for biomechanical testing. RESULTS: By using the preoperative BMD as an internal control, we found that the BMD of the smoke-inhalation group was decreased significantly compared with the non-smoke-inhalation group. The mean %BMD at 3, 4, 5, and 6 weeks were 49.9%, 61.2%, 65.9%, and 71.0%, respectively, in the smoke-inhalation group, whereas the mean %BMD were 54.9%, 71.8%, 76.4%, and 82.0%, respectively, in the non-smoke-inhalation group (two-tailed t test, p > 0.05, p < 0.01, p < 0.01 and p < 0.01 at 3, 4, 5, and 6 weeks, respectively). By using the contralateral nonoperated tibia as internal control, we found that torsional strength of the smoke-inhalation group was decreased significantly compared with the non-smoke-inhalation group. The mean percentage of maximal torque was 63.8% in the smoke-inhalation group, whereas the mean percentage of maximal torque was 77.1% in the non-smoke-inhalation group (two tailed t test, p < 0.01). CONCLUSION: This study suggests that cigarette smoking delays the mineralization during the bone healing process of distraction osteogenesis and, thus, decreases the mechanical strength of the regenerating bone.

Absorptiometry, Photon↗
PubMed1999

Treatment of femoral neck nonunions with a sliding compression screw: comparison with and without subtrochanteric valgus osteotomy.

BACKGROUND: The aim of this prospective study was to investigate and compare the results of treatment of femoral neck nonunions using a sliding compression screw (SCS) with and without subtrochanteric valgus osteotomy (SVO). METHODS: Thirty-two consecutive patients with femoral neck nonunions, which sustained no osteonecrosis of the femoral head based on bone scan study, were prospectively treated with SCS with (21 patients) or without (11 patients) SVO. The indication for SCS with SVO was a femoral neck nonunion with leg shortening of more than 1.5 cm. SCS without SVO was for leg shortening of less than 1.5 cm. RESULTS: Seventeen patients with osteotomy and nine patients without osteotomy were followed for at least 2 years (range, 2-8 years). All femoral neck fractures healed, with a union period of 4.6+/-1.0 months (95% confidence interval, 4.1-5.1 months) for osteotomy cases and 4.6+/-1.1 months (95% confidence interval, 3.8-5.4 months) for nonosteotomy cases (p = 0.83). However, in the osteotomy group, two patients sustained osteonecrosis of the femoral head, and nonunion remained in 1 patient at the osteotomy site (complication rate, 18%; 3 of 17 patients). There were no complications in the nonosteotomy group (p = 0.26). The average lengthening achieved from osteotomy was 1.0 to 1.5 cm (p < 0.001). CONCLUSION: Using SCS without SVO to treat femoral neck nonunions can result in a very satisfactory outcome. It is thus preferred for indicated patients. SCS without SVO, however, cannot concomitantly correct a femoral neck shortening; furthermore, shortening may deteriorate because of a telescoping effect. For patients with evident shortening, therefore, combined SVO with SCS is more suitable.

Adolescent↗
PubMed1999

Arthroscopic anterior cruciate ligament reconstruction with quadriceps tendon-patellar bone autograft.

BACKGROUND: Surgical reconstruction of the anterior cruciate ligament (ACL) is indicated in the ACL-deficient knee with symptomatic instability and multiple ligaments injuries. Bone patellar tendon-bone and the hamstring tendon generally have been used. In the present study, we describe an alternative graft, the quadriceps tendon-patellar bone autograft, by using arthroscopic ACL reconstruction. METHODS: From March of 1996 through March of 1997, a quadriceps tendon-patellar bone autograft was used in 12 patients with ACL injuries. RESULTS: After 15 to 24 months of follow-up, the clinical outcome for those patients with this graft have been encouraging. Ten patients could return to the same or a higher level of preinjury sports activity. According to the International Knee Documentation Committee rating system, 10 of the 12 patients had normal or nearly normal ratings. Recovery of quadriceps muscle strength to 80% of the normal knee was achieved in 11 patients in 1 year. CONCLUSION: The advantages of the quadriceps tendon graft include the following: the graft is larger and stronger than the patellar tendon; morbidity of harvest technique and donor site is less than that of patellar tendon graft; there is little quadriceps inhibition after quadriceps harvest; there is quicker return to sports activities with aggressive rehabilitation. A quadriceps tendon-patellar autograft is a reasonable alternative to ACL reconstruction in patients who are not suitable for either a bone-patellar tendon-bone autograft or a hamstring tendon autograft.

Adult↗
PubMed1999

Fixation of small tibial avulsion fracture of the posterior cruciate ligament using the double bundles pull-through suture method.

BACKGROUND: Avulsion of the tibial insertion of the posterior cruciate ligament is commonly repaired via open reduction and internal fixation with a screw, Kirschner's wire, and suture. In the case of a major bony fragment, this technique is adequate to achieve rigid fixation. In the case of an avulsion fracture with a small bony fragment, however, it is not uncommon to break the bone fragment during screw fixation. We describe a new technique for fixation of an avulsion fracture with a small bony fragment. The technique uses a double bundles pull-through suture technique that repairs the anterolateral and posteromedial components of the posterior cruciate ligament simultaneously. METHODS: From March 1994 through May 1997, 12 patients with small tibial avulsion fractures of the posterior cruciate ligament were treated using this technique. RESULTS: At an average of 18 months after surgery (range, 12-24 months), the preliminary clinical and radiographic results were satisfactory. Eleven patients could return to the same or a higher level of preinjury sports activity. According to the International Knee Documentation Committee rating system, 10 of the 12 patients had normal or nearly normal ratings. CONCLUSION: The double bundles pull-through suture technique can avoid the risk of breakage of the small bony fragment, does not require the removal of hardware, and can achieve adequate repair in the anatomic situation. Our clinical experience suggests that it is a good choice for fixation in cases of avulsion fracture with a small bony fragment.

Adult↗
PubMed1999

Hyperbaric oxygen therapy mitigates the adverse effect of cigarette smoking on the bone healing of tibial lengthening: an experimental study on rabbits.

OBJECT: We investigated whether -intermittent hyperbaric oxygen (HBO) therapy can mitigate the adverse effects of cigarette smoking on the bone healing of tibial lengthening by using a previously validated rabbit model. METHODS: Eighteen male rabbits were randomly divided into three groups of six animals each. Group 1 (smoking plus HBO) went through intermittent cigarette smoke inhalation and hyperbaric oxygen therapy, group 2 (control) did not go through intermittent cigarette smoke inhalation or hyperbaric oxygen therapy and group 3 (smoking) went through intermittent cigarette smoke inhalation. Each animal's right tibia was lengthened 5 mm by using an uniplanar lengthening device. Bone mineral density (BMD) study was performed for all the animals at 1 day before operation and 3, 4, 5, and 6 weeks after operation. All of the animals were killed at 6 weeks postoperatively for biomechanical testing. RESULTS: By using the preoperative BMD as an internal control, we found that the BMD of group 1 (smoking plus HBO)and group 2 (control) was superior to that of group 3 (smoking). The mean %BMD at 3, 4, 5, and 6 weeks were 58.6%, 66.6%, 73.7%, and 83.8%, respectively, in group 1, whereas the mean %BMD were 52.0%, 64.3%, 70.1%, and 76.2%, respectively, in group 2, and the mean %BMD were 46.2%, 54.0%, 64.9%, and 69.4%, respectively, in group 3 (two-tailed t test, p > 0.05, p > 0.05, p > 0.05, and p < 0.05 at 3, 4, 5, and 6 week respectively between group 1 and group 2, p < 0.01,p < 0.01,p < 0.01, and p < 0.01 at 3, 4, 5, and 6 week, respectively, between group 1 and group 3 and p < 0.05, p < 0.05, p < 0.05, and p < 0.05 at 3, 4, 5, and 6 week respectively between group 2 and group 3). By using the contralateral nonoperated tibia as an internal control, we found that the torsional strength of group 1 (smoking plus HBO) and group 2 (control) was superior to that of group 3 (smoking). The mean percentage of maximum torque was 80.9% in group 1 (smoking plus HBO) and was 78.0% in group 2 (control), whereas the mean percentage of maximum torque was 59.6 % in group 3 (smoking) (two-tailed t test, p < 0.05 between groups land 3 and between groups 2 and 3, whereas p > 0.05 between groups 1 and 2). CONCLUSION: This study suggests that smoke inhalation delays the bone healing in tibial lengthening; however, HBO mitigates the delayed healing effect of smoke inhalation and, thus, helps the smoking animal in achieving an expeditious bone healing in tibial lengthening.

Absorptiometry, Photon↗
PubMed1999

Nonunion and shortening after femoral fracture treated with one-stage lengthening using locked nailing technique. Good results in 48/51 patients.

We report on 56 consecutive aseptic femoral shaft nonunions with shortening, which were treated with local debridement, skeletal traction, a spine-spreader aiding lengthening, static locked nail stabilization and corticocancellous bone grafting. 51 patients were followed for 2 (1-4) years and 48 achieved a solid union. The median period to bony union was 4 (3-8) months and lengthening achieved was 2.8 (1.5-4.5) cm. 3 patients had nonunion, 2 without implant failure and 1 with implant failure. However, all 3 healed after reoperation. There was no neurovascular injury or deep infection.

Adolescent↗
PubMed1999

Development of a biodegradable antibiotic delivery system.

Antibiotic beads have been used as a drug delivery system for the treatment of various surgical infections. In this study, the copolymer 50:50 poly(DL-lactide):co-glycolide was mixed with vancomycin powder and hot compressing molded at 55 degrees C to form five types of biodegradable antibiotic beads. The beads were placed in 1 mL of phosphate buffered saline and incubated at 37 degrees C. The phosphate buffered saline was changed daily, and the removed buffer solutions were stored at -70 degrees C until the antibiotic concentration in each sample was determined by high performance liquid chromatography system assay. The concentration of vancomycin in each sample was well above the breakpoint sensitivity concentration (the antibiotic concentration at the transition point between bacterial killing and resistance to the antibiotic) for more than 32 days. The release was most marked during the first 48 hours. All copolymer 50:50 poly(DI lactide):co-glycolide biodegradable beads released high concentrations of the antibiotics in vitro for the time needed to treat bone infections (4 to 6 weeks). The diameter of the sample inhibition zone ranged from 6.5 mm to 10 mm, and the relative activity of vancomycin ranged from 12.5% to 100%. Copolymers with low heat of formation temperatures are required for making a controlled release system to prevent antibiotic decomposition, which occurs when using the hot compressing molded method. The rate and duration of release from the antibiotic beads can be adjusted by varying the diameter of the beads. This offers a convenient method to adjust the release rate to meet the specific antibiotic requirements for different patients.

Absorbable Implants↗
PubMed1999

Acute postoperative aggravation of radiculopathy as a complication of free fat transplantation in lumbar disc surgery: case report.

This case report illustrates a rare case of motor weakness caused by a free fat graft herniation. A 40-year-old woman who had undergone surgery for a herniated lumbar intervertebral disc experienced right lower leg weakness. On magnetic resonance image (MRI) a herniated free fat graft was noted. An emergent operation was performed and the herniated fat graft was removed. Postoperatively, the patient recovered well with improvement of the motor weakness. MRI is a good method for diagnosis of fat graft herniation. The mechanisms of this complication have been documented, and the size of the fat graft plays an important role. The methods for prevention of this herniation are also discussed. Although the transplantation of adipose tissue has many advantages, including the prevention of postoperative epidural fibrosis, great care is needed when applying a fat graft intra-operatively. When a postoperative neurologic deficit develops, herniation of the fat graft must be considered. An emergent operation is the treatment of choice for this particular complication.

Acute Disease↗
PubMed1998

Simultaneous anterior dislocation of the shoulder and fracture of the ipsilateral humeral shaft. Two case reports.

Two patients with anterior dislocation of the shoulder and ipsilateral fracture of the shaft of the humerus have been studied and the mechanism of their injuries has been documented. Closed reduction of the dislocations was performed under anaesthesia during surgery for humeral fixation with a dynamic compression plate. The fractures and dislocations healed without any problems at 6 to 9 months postoperatively. At recent follow-up, one patient had returned to work and regained normal mobility. The other patient had the sequelae of a brachial plexus injury. The literature on this subject is reviewed.

Adult↗