Biomedical subjects

Wen-Jer Chen

Publications and source records attributed to Wen-Jer Chen.

17 recordsLinked to original sources

PubMed2003

Intracorporal bone grafting for vertebral compression fractures with intraosseous vacuum phenomenon.

From April 1998 to January 2000 we treated 14 patients with vertebral osteoporotic compression fractures and intraosseous vacuum phenomenon with intracorporal bone grafting using a mixture of autogenous bone graft and calcium sulfate and posterior instrumentation. The mixture was packed into the fractured vertebral body through two tunnels created in the pedicles. Eleven patients were followed for a minimum of 24 months. All vertebral bodies healed. There were no perioperative complications. The average vertebral height restoration was 31%. On the visual analogue scale, there was an improvement of average 37 clinical scores.

Aged↗

PubMed2003

Finite element analysis of the cervico-trochanteric stemless femoral prosthesis.

OBJECTIVE: To investigate the biomechanical performance of a newly designed cervico-trochanteric stemless prosthesis by comparing the stress distribution with that of the traditional stem-type porous-coated anatomic prosthesis. DESIGN: Three-dimensional finite element models were created for the intact femur, cervico-trochanteric implanted femur and porous-coated anatomic implanted femur. The stress distributions on the femur and the implant were compared. The effects of using two or three screws fixation for the cervico-trochanteric implanted femur were also investigated. BACKGROUND: Local bone loss after implantation of traditional stem-type prostheses remains an unsolved problem during the long-term application of total hip replacement. The stress shielding effect and osteolysis were thought to be the two main factors that result in local bone loss after prosthesis implantation. In order to eliminate the mechanical and the biological causes of bone loss after total hip arthroplasty, a newly designed stemless femoral prosthesis was investigated. METHODS: Three-dimensional finite element models were created for the intact, cervico-trochanteric (with two or three fixation screws), and porous-coated anatomic implanted femora with the geometry of a standardized composite femur. Analysis was performed for a loading condition simulating the single-legged stance. The von Mises stress distributions of each model were analyzed and compared. RESULTS: The results can be summarized as follows: (1) Von Mises stress in the proximal, medial femur for the cervico-trochanteric implanted model was higher than that of the intact model and the porous-coated anatomic implanted model; (2) stress-shielding effect of the cervico-trochanteric models (with two or three fixation screws) were eliminated as compared with the porous-coated anatomic model; (3) no obvious difference in von Mises stress distribution for the cervico-trochanteric implanted model with two or three fixation screws. CONCLUSIONS: The cervico-trochanteric femoral prosthesis may reduce the stress-shielding effect of the proximal femur and achieve a more physiological stress distribution on the proximal femur than that of the porous-coated anatomic prosthesis. RELEVANCE: The new concept of cervico-trochanteric stemless prosthesis has proven to possess several advantages based on the current results, and may be an alternative for traditional stem-type prostheses in future clinical applications.

Biomechanical Phenomena↗

PubMed2003

Enveloping the tendon graft with periosteum to enhance tendon-bone healing in a bone tunnel: A biomechanical and histologic study in rabbits.

PURPOSE: Fixing and incorporating the tendon graft within the bone tunnel is a major concern when using grafts for ligament reconstruction. The periosteum contains multipotent stem cells and has the potential to form osteogenic and chondrogenic tissues. This study uses histologic and biomechanical analyses to examine the effect of periosteum on tendon-bone healing within a bone tunnel. TYPE OF STUDY: Experimental study in an animal model. METHODS: In this study, 36 adult New Zealand White rabbits were used. The long digitorum extensor tendon was transplanted into a bone tunnel of the proximal tibia. The periosteum from the proximal tibia was sutured on the surface of the tendon portion. The tendon was pulled through a drill-hole in the proximal tibia and attached to the medial aspect of the tibia. Histologic examination of the tendon-bone interface and biomechanical test for maximal pullout load were evaluated at 4, 8, and 12 weeks after operation. RESULTS: Histologic analysis of the tendon-bone interface showed a fibrous layer formed between the tendon and the bone by the periosteum. This layer became progressively integrated with the tendon and bone surface during the healing process. At 4 weeks, the cancellous bone lining in the bone tunnel was interdigitated with the fibrous interface tissue. At 8 weeks, progressive new bone grew into the interface fibrous layer. At 12 weeks, collagen fibers anchored to the bone and organization with fibrocartilage formation developed between the tendon and bone. Biomechanical testing revealed higher maximal pullout strength in the periosteum-enveloped group at all time points, with a statistically significant difference at 8 and 12 weeks. The periosteum-treated group had a higher interface strength-to-length ratio and significant increase at 8 weeks and 12 weeks. CONCLUSIONS: The histologic and biomechanical studies demonstrated that, if periosteum was sutured on the tendon that was transplanted within a bone tunnel, it resulted in a superior healing process and better healed strength. When doing ligament reconstruction with a tendon graft, the periosteum can be sutured to the graft to enhance tendon-bone healing.

Animals↗

PubMed2003

Tibial lengthening: technique for speedy lengthening by external fixation and secondary internal fixation.

BACKGROUND: The conventional Ilizarov technique for tibial lengthening is frequently time-consuming, causes suffering, and is associated with many complications. This study takes a retrospective approach to investigate the outcome of applying a slightly speedier procedure using an Ilizarov apparatus and secondary internal fixation. METHODS: Twelve adult patients displaying tibial shortening (median, 4.0 cm; mean, 4.6 cm; range, 3.0-12.0 cm) with various causes were treated with or without tibial osteotomy and stabilized using an Ilizarov lengthening apparatus. Postoperatively, lengthening of 1 to 1.5 mm/day was performed until the desired length was achieved. External fixation was then converted to internal fixation and either pure autogenous bone graft, or a mixture of autogenous and allogenous bone graft was supplemented. Postoperatively, protected weight bearing was advised until bony union was achieved. RESULTS: Eleven patients were followed up for a median of 3.4 years (mean, 4.0 years; range, 2.1-6.7 years) and solid union was achieved in all cases. Median external fixation occurred after 1.8 months (mean, 1.9 months; range, 1.2-4.5 months) and the median time until union after internal fixation was 4.5 months (mean, 4.8 months; range, 4-6 months). Two patients with rigid equinus feet required concomitant Achillis tendon lengthening. No other significant complications were noted. Classification of the results revealed that improvement from an unsatisfactory to a satisfactory outcome was achieved in all patients (p < 0.001). CONCLUSION: The described technique shortens the external fixation period and reduces patient suffering. Moreover, a high union rate and a low complication rate are achieved. Subjectively and objectively, patients can achieve satisfactory outcomes. Consequently, the described technique may be considered as an alternative to conventional techniques when indicated.

Adult↗

PubMed2002

Combined anterior and posterior surgeries in the treatment of spinal tuberculous spondylitis.

Methods for the treatment of tuberculous spondylitis still are controversial. The authors treated 32 consecutive patients with a two-stage surgical technique combined with antituberculous chemotherapy for 1 year. After anterior debridement, fusion with autogenous anterior iliac tricortical strut bone graft was done, and in a second stage, posterior instrumentation and fusion with autogenous posterior iliac corticocancellous bone graft was done 11 days (range, 4-22 days) later. Postoperatively, patients were encouraged to ambulate with brace protection as early as possible. Twenty-nine patients were followed up for a minimum of 2 years (median, 4.7 years; range, 2-10 years) of whom 28 patients achieved solid fusion (97%). All patients had improvement of back pain including the only patient with pseudarthrosis. Neurologic deficits completely recovered in 84% (16 of 19) of patients after 3 months. Kyphotic deformity improved in all 29 patients (34.6 degrees versus 17.3 degrees ) with the average correction angle of 17.3 degrees. Clinically, 27 patients had achieved a satisfactory outcome (93%). There were no evident surgical complications. The authors, therefore, recommend a two-stage surgical technique combined with antituberculous chemotherapy to treat patients with severe vertebral body destruction attributable to tuberculosis because of its high success rate and a low complication rate.

Adolescent↗

PubMed2002

Surgical treatment for distal clavicle fracture with coracoclavicular ligament disruption.

BACKGROUND: Surgical reconstruction is usually indicated for distal clavicle fractures with coracoclavicular ligament disruption due to a high rate of nonunion and delayed union. We report the outcome of a surgical technique for this type of fracture. METHODS: The procedures consist of coracoclavicular reconstruction with a Mersilene tape, repair of torn coracoclavicular ligament, and wire fixation of the fracture fragments. From 1993 through 1998, this technique has been used on 13 patients with distal clavicle fracture and associated coracoclavicular ligament disruption. Eleven patients with at least 18 months of complete postoperative follow-up were included for functional and radiographic evaluation. RESULTS: After 18 to 48 months' follow-up, the clinical outcome has been encouraging. Solid union of the fracture could be achieved at 3 months after operation in 10 patients. The remaining one fracture achieved bony union at 6 months. Ten patients could return to the same or a higher level of preinjury activity. Good and excellent results were obtained in 10 patients. CONCLUSION: The advantages of this technique include that the disrupted coracoclavicular articulation is rigidly restored and then the fracture site can be easily reduced and fixed with a wire. This technique allows for stable fixation with early mobilization and early return to work and sports.

Adult↗

PubMed2002

The effect of hyperbaric oxygen therapy on spinal fusion: using the model of posterolateral intertransverse fusion in rabbits.

BACKGROUND: The purpose of this study is to evaluate the facilitating effect of hyperbaric oxygen (HBO) on posterolateral intertransverse fusion using a validated rabbit model. METHODS: Twenty-four male New Zealand rabbits underwent posterolateral intertransverse fusion at L5-L6 with autogenous iliac bone graft. They were evenly divided into two groups: the HBO group and the normal room air (RA) group. Each group had six rabbits killed at 4 weeks and 8 weeks, respectively. The rabbits in the HBO groups were treated with 100% oxygen at 2.5 atm for 2 hours a day. After being killed, all rabbits were subjected to radiographic examination, manual testing, and torsional loading to evaluate the results of spinal fusion. RESULT: Radiographic union of intertransverse fusion areas at 4-week RA, 4-week HBO, 8-week RA, and 8-week HBO were 2 of 12, 7 of 12, 7 of 12, and 10 of 12, respectively. Solid union proven by manual palpation was found to be zero of six, three of six, four of six, and five of six of the cases, respectively. The average peak torsional momentums were 2120.2, 2576.5, 2661.6, and 3079.8 N-mm, respectively. Spinal fusion was significantly improved in the HBO groups at both 4 weeks and 8 weeks. CONCLUSION: The results of this study suggest that intermittent hyperbaric oxygen therapy will hasten the bone healing process and improve the fusion rate as compared with the non-HBO group.

Animals↗

PubMed2002

Arthroscopic reconstruction of the posterior cruciate ligament with quadruple hamstring tendon graft: a double fixation method.

BACKGROUND: Surgical reconstruction is indicated for posterior cruciate ligament (PCL) reconstruction for a grade III or IV injury, combined ligament or meniscus injuries, and chronic symptomatic posterior instability. Considerable controversy continues over the choice of graft tissues. Hamstring tendon has been popular in recent years. The purpose of this study is to prospectively assess the outcomes of PCL reconstruction using quadruple hamstring tendon autograft with a double-fixation technique at minimal 2-year follow-up. METHODS: Only patients who received PCL reconstruction without combined associated posterolateral injury reconstruction were included in the series. A hamstring tendon graft is composed of a quadruple-stranded semitendinosus tendon and gracilis tendon 10 cm in length. An arthroscopic technique using a two-incision method and a double-fixation technique were used. Clinical assessments were performed for 30 patients, of which 27 were available for final outcome analysis. Clinical review of patients included the Lysholm knee scores, International Knee Documentation Committee (IKDC) scores, thigh muscle assessment, and radiographic evaluation. RESULTS: On the Lysholm knee rating, 89% of the patients demonstrated good or excellent results in the final assessment. In the IKDC rating analyses, 56% of the patients revealed 3- to 5-mm ligament laxity. Four patients (15%) had grade II laxity. For the IKDC final rating, 26% were normal and 55% were nearly normal. Seventy-eight percent of the patients had less than a 10-mm difference in thigh girth between their reconstructed and opposite limbs. CONCLUSION: Arthroscopic PCL reconstruction with quadruple hamstring tendon autograft appears to produce acceptable results at a minimal 2-year follow-up. The four-stranded hamstring tendon graft is adequate in graft size and associated with minimal harvesting morbidity. The double-fixation method for the graft could provide a rigid fixation. We believe that this technique could afford good ligament function after reconstruction and could be a reasonably acceptable choice for PCL injury.

Adult↗

PubMed2002

Clinical outcomes of revision lumbar spinal surgery: 124 patients with a minimum of two years of follow-up.

BACKGROUND: Pertinent literature on revision lumbar spinal surgery has revealed a wide variation in success rates, ranging from 12% to 82%. In addition, a solid consensus has not yet been reached on its positive factors. We retrospectively reviewed 124 consecutive patients who underwent revision lumbar spinal surgery and investigated the factors that affected the outcomes of their surgery. METHODS: Revision lumbar spinal surgery was performed in 124 patients from January 1992 to December 1996, with an average follow-up of 37.6 months (range, 24-89 months). The various factors analyzed included age, gender, previous diagnosis, number of previous operations, period of pain-free interval, neurologic deficit, operative procedure, and fusion status. This analysis revealed the effect of each factor on the overall results. Radiographs were obtained, and patients were assessed during the final follow-up or by questionnaire. RESULTS: The success rate of revision lumbar spine surgery in this study was 83.9%. Successful outcomes were significantly associated with the spinal procedure with fusion and with union of the spinal fusion. Patients with defined mechanical instability had better results than did those with stenosis only. In addition, the complication rate for repeated lumbar spinal surgery was 9.6% and major complications attributed to poor results. CONCLUSION: This study reveals a high success rate of revision spinal surgery. We recommend performing spinal fusion, and achievement of solid fusion in repeated low back surgery is invaluable for patients with spinal instability. Targeting the specific pathology of failed back surgery syndrome is crucial in attaining satisfactory results with revision lumbar spinal surgery.

Adult↗

PubMed2002

Surgical outcomes of short-segment fixation for thoracolumbar fracture dislocation.

BACKGROUND: Currently long-segment pedicle instrumentation for a thoracolumbar (T-L) fracture-dislocation is gaining in popularity. Otherwise, short-segment fixation may be chosen as an another treatment method. This article evaluates the efficacy and complications of short-segment fixation for the treatment of thoracic or lumbar spine fracture-dislocation. METHODS: Twenty patients with thoracic or lumbar spine fracture-dislocation were included in the study. The mean follow-up period was 3 years. Clinical, neurologic, radiologic (angle of deformity, displacement percentage, fusion rate), and complication outcomes were analyzed retrospectively. RESULTS: The rate of failure, defined as an increase of 10" or more in local kyphosis, an increase of 10% or more in displacement percentage, the development of pseudarthrosis, and/or implant failure, was analyzed. Short-segment instrumentation had a higher failure rate in the lower lumbar region (L3-L5) and a lower rate at the thoracolumbar junction (T11-L2). CONCLUSION: Thoracolumbar fracture-dislocation required firmer fixation especially in the low lumbar region, and short-segment fixation resulted in a high failure rate. Circumferential anterior and posterior fusion often played a role in certain severely injured cases. Good postoperative spinal alignment is crucial to a good outcome.

Female↗

PubMed2002

Aseptic nonunion of a femoral shaft treated using exchange nailing.

BACKGROUND: There are many methods for treating femoral shaft aseptic nonunions of which exchange nailing is the simplest technique. However, the reported success rate varies. Therefore, a prospective study was conducted to further clarify the role of exchange nailing. METHODS: From October 1994 through December 1999, 40 femoral shaft aseptic nonunions in 39 patients were treated using exchange nailing. The indications for this technique included a femoral shaft aseptic nonunion with a previously inserted intramedullary nail, less than 1 cm shortening, a radiolucent line of the nonunion, and no segmental bony defects. The surgical technique consisted of close removal of the previously inserted intramedullary nail, reaming the intramedullary canal as widely as possible (1 or 2 mm oversized), and re-insertion of a stable unlocked or locked intramedullary nail. RESULTS: Thirty-six femoral shaft aseptic nonunions in 35 patients were followed-up for at least 1 year (median, 2.9 years; range, 1.1-6.0 years) and 33 nonunions healed. The union rate was 91.7% (33/36) and the union period was median 4 months (range, 3-8 months). No major surgical complications were noted. The other three patients with persistent nonunions were continuously followed-up due to their reluctance for further operations. CONCLUSION: Although exchange nailing is a relatively simple surgical technique, it can still achieve a high union rate with a low complication rate. Despite that factors to induce a persistent nonunion are still unclear, clinically, exchange nailing should be used as the first choice in the treatment of an indicated femoral shaft aseptic nonunion.

Adolescent↗

PubMed2001

One-incision endoscopic technique for posterior cruciate ligament reconstruction with quadriceps tendon-patellar bone autograft.

Quadriceps tendon-patellar bone autograft is an alternative graft choice for posterior cruciate ligament (PCL) reconstruction. A 2-incision technique with outside-in fixation at the femoral condyle is generally used. In this article, we describe a 1-incision endoscopic technique for PCL reconstruction with quadriceps tendon-patellar bone autograft. The graft consists of a proximal patellar bone plug and central quadriceps tendon. The bone plug is trapezoidal, 20 mm long, 10 mm wide, and 8 mm thick. The tendon portion is 80 mm long, 10 mm wide, and 6 mm thick, including the full-thickness of the rectus femoris and partial thickness of the vastus intermedius. Three arthroscopic portals, including anteromedial, anterolateral, and posteromedial, are used. All procedures are performed in an endoscopic manner with only 1 incision at the proximal tibia. At the femoral side, the bone plug is fixed by an interference screw. At the tibial side, the tendon portion is fixed by a suture to a screw on the anterior cortex and an interference bioscrew in the posterior tibial tunnel opening. Quadriceps tendon autograft has the advantages of being self-available, allowing for easier arthroscopic technique, and providing comparable graft size. The 1-incision technique provides a simple reconstruction method for PCL insufficiency without a second incision at the medial femoral condyle.

Journal Article↗

PubMed2000

A revised protocol for more clearly classifying a nonunion.

Classifying a nonunion solely on the extent of callus formation on a radiograph is insufficient. We have conducted a study with a revised protocol to classify a nonunion more clearly, which uses both radiographic observation and fixation stability. 47 consecutive femoral shaft nonunions were studied using this protocol and 42 nonunions were followed up for at least one year after discovery (range, 1-3 years). 40 nonunions healed after treatment with a union rate of 95.2% (40/42) and a union period of 4.7 plus or minus 0.9 months. The 2 cases of failure were due to implant failure and both healed after reoperation. We recommend this revised protocol as a pretreatment assessment for all nonunions because of its integrity and effectiveness.

Journal Article↗

PubMed1998

A three-dimensional mathematical model for predicting spinal joint force distribution during manual liftings.

OBJECTIVE: A three-dimensional dynamic mathematical model was developed to discover what loads are imposed on the lumbar structures by performance of asymmetric manual liftings. DESIGN: An external model was used to estimate the intersegmental resultant forces and moments at the L(5)/S(1) joint in this dynamic biomechanical model. Using an optimization algorithm, an internal model then distributed the intersegmental resultants to forces of muscle, disc, facet joints, and ligaments. BACKGROUND: To study the relation between large loads and low-back disorders, many biomechanical models have been developed. Most of the models were two-dimensional models discussed with symmetric activities. Some three-dimensional biomechanical models were static models or only included limited elements of the disc and muscles in the model. METHODS: A healthy young male subject was asked to perform asymmetric lift with bent knees. Dynamic data of body motion and ground reaction forces were monitored, and the EMG of six muscles were recorded simultaneously. A Newtonian equation was used to calculate the joint intersegmental resultant forces and moments. In the internal model, three components of the disc force, eight muscle forces, two ligament forces and two facet joint forces were computed. RESULTS: The correlation between the reaction moments from the upper and lower models of the external part were generally above 0.94, and the root mean square differences were below 19 Nm. In this internal model, the maximal disc compression was close to the data showed on the literature, and the estimation of muscle forces corresponded to the EMG activities. CONCLUSIONS: A three-dimensional biomechanical model has been developed and evaluated to estimate the spinal joint force distribution during asymmetric manual lifting activities.

Journal Article↗

PubMed1998

Myo-electric behavior of the trunk muscles during static load holding in healthy subjects and low back pain patients.

OBJECTIVE: The purposes of this study were to examine coactivational activities of four trunk muscles in various static holding tasks, and to examine the differences of muscle activation patterns between normal subjects and low back pain (LBP) patients. DESIGN: We used an one-way analysis of variance (anova) with repeated measures to analyze the effect of the knee angles, trunk flexion angles, and loading conditions on the amount of EMG activity. BACKGROUND: Epidemiologic studies attribute a considerable proportion of the incidence of LBP to lifting-related injuries. The relationship between LBP and trunk muscles integrated electromyography (IEMG) is controversial. METHODS: Forty volunteer subjects with no experience of LBP and 47 LBP patients recruited from Chung-Gung Memory Hospital participated in this experiment. Surface IEMG signals of four right and left trunk muscles (rectus abdominis, external oblique, erector spinae, and latissimus dorsi) were obtained in static holding tasks. RESULTS: In knee flexion, LBP patients had significant IEMG pattern change than normal subjects. In trunk flexion and loading conditions, normal subjects had significant IEMG pattern change than LBP patients. CONCLUSIONS: Trunk muscle groups have different muscle coactivation patterns in functional posture of load holding. Using surface EMG can discriminate LBP patients from normal subjects.

Journal Article↗

PubMedDate not supplied

Enveloping of periosteum on the hamstring tendon graft in anterior cruciate ligament reconstruction.

Tendon-bone incorporation of a tendon graft within the bone tunnel is a major concern when using tendon graft for ligament reconstruction. Periosteum consists of multipotent mesodermal cells to form all varieties of connective tissue, including osteogenic and chondrogenic tissues. From our histologic and biomechanical studies in animals, a superior healing process and stronger healing strength can be achieved when periosteum is sutured onto the tendon inserted within a bone tunnel. We applied this idea to anterior cruciate ligament reconstruction to enhance tendon-bone healing. A quadruple-stranded hamstring tendon graft is used. A piece of periosteum, 3 x 3 cm, harvested from the anterior cortex of proximal tibia, is split into 2 rectangle flaps (1.5 x 3 cm each). The periosteum flaps are wrapped and sutured around the tendon graft at the portions near the femoral and tibial tunnel openings. The cambium layer is faced outside to the bone tunnel. Periosteum is easy to harvest from proximal tibia, where is a routine incision for harvesting hamstring tendons. Besides the potential for enhancement of tendon-bone healing, periosteum may be able to seal off the intra-articular opening in a very early period to avoid synovial fluid reflux into the tunnel.

Animals↗

PubMedDate not supplied

Arthroscopic reconstruction of the posterior cruciate ligament: a comparison of quadriceps tendon autograft and quadruple hamstring tendon graft.

PURPOSE: Considerable controversies remain on the graft choice and fixation methods in the posterior cruciate ligament (PCL) reconstruction. The purpose of this study was to compare, at minimal 2-year follow-up, the outcomes of PCL reconstruction between using quadriceps tendon autograft and using quadruple hamstring tendon autograft. TYPE OF STUDY: Case series. METHODS: All patients received only PCL reconstruction without combined severe associated posterolateral instability. From 1996 to 1998, there were 24 patients who had a quadriceps tendon autograft, and 30 patients with hamstring tendon autograft. Twenty-two of the quadriceps tendon group and 27 of the hamstring tendon autograft group with 2 more years of complete follow-up were included for final analyses. Clinical assessments consisted of Lysholm knee scores, International Knee Documentation Committee (IKDC) scores, thigh muscle girth and strength, and radiographic evaluation. RESULTS: On the Lysholm knee rating, 86% of patients showed good or excellent results in the quadriceps tendon group and so did 89% of patients in the hamstring tendon group. Fifty-nine percent of the quadriceps tendon group and 56% of the hamstring tendon group revealed a 3- to 5-mm ligament laxity. Two patients with quadriceps tendon grafts and 4 patients with hamstring tendon grafts revealed grade II laxity. The IKDC rating showed no significant difference between the 2 groups in terms of activity level, ligament laxity, and final rating. In the thigh girth side-to-side difference, 82% of the quadriceps tendon group and 78% of the hamstring tendon group had less than a 10-mm difference. CONCLUSIONS: Comparable satisfactory results between the 2 surgical groups were shown at a minimal 2 years follow-up. We suggested that both grafts could afford good ligament reconstruction likelihood and that they are reasonably acceptable graft choices for PCL reconstruction.

Adult↗