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Orthopaedic Proceedings
Vol. 106-B, Issue SUPP_8 | Pages 2 - 2
10 May 2024
Chen W Tay ML Bolam S Rosser K Monk AP Young SW
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Introduction

A key outcome measured by national joint registries are revision events. This informs best practice and identifies poor-performing surgical devices. Although registry data often record reasons for revision arthroplasty, interpretation is limited by lack of standardised definitions of revision reasons and objective assessment of radiologic and laboratory parameters. Our study aim was to compare reasons for unicompartmental knee arthroplasty (UKA) revision reported to the New Zealand Joint Registry (NZJR) with reasons identified by independent clinical review.

Methods

A total of 2,272 patients undergoing primary medial and lateral UKA at four large tertiary hospitals between 2000 and 2017 were included. A total of 158 patients underwent subsequent revision with mean follow-up of 8 years. A systematic review of clinical findings, radiographs and operative data was performed to identify revision cases and to determine the reasons for revision using a standardised protocol. These were compared to reasons reported to the NZJR using Chi-squared and Fisher exact tests.


Bone & Joint Research
Vol. 12, Issue 12 | Pages 722 - 733
6 Dec 2023
Fu T Chen W Wang Y Chang C Lin T Wong C

Aims

Several artificial bone grafts have been developed but fail to achieve anticipated osteogenesis due to their insufficient neovascularization capacity and periosteum support. This study aimed to develop a vascularized bone-periosteum construct (VBPC) to provide better angiogenesis and osteogenesis for bone regeneration.

Methods

A total of 24 male New Zealand white rabbits were divided into four groups according to the experimental materials. Allogenic adipose-derived mesenchymal stem cells (AMSCs) were cultured and seeded evenly in the collagen/chitosan sheet to form cell sheet as periosteum. Simultaneously, allogenic AMSCs were seeded onto alginate beads and were cultured to differentiate to endothelial-like cells to form vascularized bone construct (VBC). The cell sheet was wrapped onto VBC to create a vascularized bone-periosteum construct (VBPC). Four different experimental materials – acellular construct, VBC, non-vascularized bone-periosteum construct, and VBPC – were then implanted in bilateral L4-L5 intertransverse space. At 12 weeks post-surgery, the bone-forming capacities were determined by CT, biomechanical testing, histology, and immunohistochemistry staining analyses.


Orthopaedic Proceedings
Vol. 105-B, Issue SUPP_3 | Pages 6 - 6
23 Feb 2023
Chen W Lightfoot N Boyle M
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Higher levels of socioeconomic deprivation have been associated with worse health outcomes. The influence of socioeconomic deprivation on patients undergoing periacetabular osteotomy (PAO) has not previously been investigated.

A total of 217 patients (171 female, 46 male; median age 23.4 years) who underwent PAO by a single surgeon were identified. Patients were categorised into three groups according to their New Zealand Deprivation (NZDep) Index: minimal deprivation (NZDep Index 1–3, n=89), moderate deprivation (NZDep Index 4–6, n=94), and maximal deprivation (NZDep Index 7–10, n=34). The three groups were compared with respect to baseline variables, surgical details, complications, and pre-operative and two-year post-operative functional scores (including International Hip Outcome Tool (iHOT-12), EQ-5D quality of life score, and University of California Los Angeles (UCLA) activity score). Multivariate regression was undertaken to assess for the effect of NZDep Index on patient outcomes.

Patients in the maximal deprivation group were more likely to be Māori (p<0.001) and have surgery in a public rather than a private hospital (p=0.004), while the minimal deprivation group demonstrated a lower BMI (p=0.005). There were otherwise no other significant differences in baseline variables, surgical details, complications, nor pre-operative or two-year post-operative functional scores between the three groups (all p>0.05). Multivariate analysis identified a higher NZDep Index to be independently predictive of a lower pre-operative UCLA activity score (p=0.014) and a higher two-year iHOT-12 score (p<0.001).

Our results demonstrate an inequality in access to PAO, with patients exposed to higher levels of socioeconomic deprivation under-represented in our study population. When provided access to PAO, these vulnerable patients achieve significant functional improvement at least as great as patients with less socioeconomic deprivation. Initiatives to improve access to hip preservation care in socioeconomically deprived populations appear warranted.


Bone & Joint Research
Vol. 10, Issue 4 | Pages 237 - 249
1 Apr 2021
Chen X Chen W Aung ZM Han W Zhang Y Chai G

Aims

LY3023414 is a novel oral phosphatidylinositol 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) dual inhibitor designed for advanced cancers, for which a phase II clinical study was completed in March 2020; however, little is known about its effect on bone modelling/remodelling. In this study, we aimed to explore the function of LY3023414 in bone modelling/remodelling.

Methods

The function of LY3023414 was explored in the context of osteogenesis (bone formation by osteoblasts) and osteoclastogenesis (osteoclast formation and bone resorption). Murine preosteoblast MC3T3-E1 cell line and murine bone marrow-derived macrophage cells (BMMs) were subjected to different treatments. An MTS cell proliferation assay was used to examine the cytotoxicity. Thereafter, different induction conditions were applied, such as MCSF and RANKL for osteoclastogenesis and osteogenic media for osteogenesis. Specific staining, a bone resorption assay, and quantitative real-time polymerase chain reaction (qRT-PCR) were subsequently used to evaluate the effect of LY3023414. Moreover, small interfering RNA (siRNA) was applied to knockdown Akt1 or Akt2 for further validation. Lastly, western blot was used to examine the exact mechanism of action.


Bone & Joint Research
Vol. 9, Issue 10 | Pages 653 - 666
7 Oct 2020
Li W Li G Chen W Cong L

Aims

The aim of this study was to systematically compare the safety and accuracy of robot-assisted (RA) technique with conventional freehand with/without fluoroscopy-assisted (CT) pedicle screw insertion for spine disease.

Methods

A systematic search was performed on PubMed, EMBASE, the Cochrane Library, MEDLINE, China National Knowledge Infrastructure (CNKI), and WANFANG for randomized controlled trials (RCTs) that investigated the safety and accuracy of RA compared with conventional freehand with/without fluoroscopy-assisted pedicle screw insertion for spine disease from 2012 to 2019. This meta-analysis used Mantel-Haenszel or inverse variance method with mixed-effects model for heterogeneity, calculating the odds ratio (OR), mean difference (MD), standardized mean difference (SMD), and 95% confidence intervals (CIs). The results of heterogeneity, subgroup analysis, and risk of bias were analyzed.


The Bone & Joint Journal
Vol. 102-B, Issue 8 | Pages 967 - 980
1 Aug 2020
Chou TA Ma H Wang J Tsai S Chen C Wu P Chen W

Aims

The aims of this study were to validate the outcome of total elbow arthroplasty (TEA) in patients with rheumatoid arthritis (RA), and to identify factors that affect the outcome.

Methods

We searched PubMed, MEDLINE, Cochrane Reviews, and Embase from between January 2003 and March 2019. The primary aim was to determine the implant failure rate, the mode of failure, and risk factors predisposing to failure. A secondary aim was to identify the overall complication rate, associated risk factors, and clinical performance. A meta-regression analysis was completed to identify the association between each parameter with the outcome.


The Bone & Joint Journal
Vol. 101-B, Issue 12 | Pages 1489 - 1497
1 Dec 2019
Wang J Ma H Chou TA Tsai S Chen C Wu P Chen W

Aims

The aim of this meta-analysis was to compare the outcome of total elbow arthroplasty (TEA) undertaken for rheumatoid arthritis (RA) with TEA performed for post-traumatic conditions with regard to implant failure, functional outcome, and perioperative complications.

Materials and Methods

We completed a comprehensive literature search on PubMed, Web of Science, Embase, and the Cochrane Library and conducted a systematic review and meta-analysis. Nine cohort studies investigated the outcome of TEA between RA and post-traumatic conditions. The preferred reporting items for systematic reviews and meta-analysis (Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)) guidelines and Newcastle-Ottawa scale were applied to assess the quality of the included studies. We assessed three major outcome domains: implant failures (including aseptic loosening, septic loosening, bushing wear, axle failure, component disassembly, or component fracture); functional outcomes (including arc of range of movement, Mayo Elbow Performance Score (MEPS), and the Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire), and perioperative complications (including deep infection, intraoperative fracture, postoperative fracture, and ulnar neuropathy).


Orthopaedic Proceedings
Vol. 100-B, Issue SUPP_11 | Pages 40 - 40
1 Aug 2018
Chen W
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The purpose of this study was to evaluate the functional and oncological outcome of recycled autograft reconstruction after a wide excision for primary malignant bone tumor around the hip.

From 1998 to 2015, 67 patients with a primary malignant bone tumor involving proximal femur or periacetabular zone (P2) were included. There were 36 males and 31 females with a mean age of 34 years (13 to 58). Of these, 29 patients had grade I or II chondrosarcoma, 28 high-grade osteosarcoma, 6 Ewing's sarcoma and 4 undifferentiated pleomorphic sarcoma. Enneking stage of all 67 patients was stage II. Of the resection classification, proximal femur resection was performed in 29 patients, P1+P2 in 15, P2+P3 in 14, P1+P2+P3 in 4, P2 only in 4, and P2+proximal femur in 1. Extracorporeally irradiated recycled autograft and liquid nitrogen frozen autograft were performed in 44 and 23 patients, respectively.

At a mean follow-up of 98 months (10 to 239), 48 patients (72%) were continuously disease-free, 12 (18%) died of disease and 7 (10%) were alive with disease. The tumors of these patients who had died of disease were usually located in pelvic bones (10/12). Of these 37 patients with pelvic tumors, 7 patients (22%) had local recurrence, four of them received external hemipelvectomy. Other complications included hip dislocation in 2 patients, nerve injury in 2 and deep infection in 2. However, the above complications were rarely occurred in the patients with proximal femur reconstruction. The mean Musculoskeletal Tumor Society functional score were 77% (53 to 93).

Recycled autograft reconstruction for primary malignant bone tumor around the hip is a valid method with acceptable morbidity and a favorable functional outcome.


Two-stage reconstruction with total implant removal and re-implantation after infection control is considered the gold standard treatment forinfection after hip arthroplasty. However, removal of the well-fixed stem or cup may cause substantial bone loss and other complications, thereby making reconstruction difficult. We evaluated whether an infection posttotal hip arthroplasty can be treated without removal of the radiographically and clinically well-fixed femoral stem or acetabular cup. Patients with a chronic infection aftertotal hip arthroplasty, with a radiographically well-fixed, cementless stem or cup, were selected. During the first surgical stage, we retained the stem or cup if we were unable to removethese with a stem or cup extractor. An antibiotic-impregnated cement spacer was then implanted. After control of infection (C-reactive proteinlevel within normal value), we performed the secondstage of re-implantation surgery. Treatment failure was defined as uncontrolled infection requiringremoval of the retained implant.

From January 2004 to December 2013, 16 patients underwent partial component-retained 2-stage reconstruction. Thirteen patients (81.3%) were free of infection, with a mean follow-up time of 5 years. The remaining 3 patients, who had high-risk comorbidities and, of whom, 2 were infected by high-virulence organism, had uncontrolled infection and required furthersurgery to remove the retained implant.

We conclude that partial component-retained 2-stage reconstruction could be an alternative treatment option for chronic infection afteran uncemented total hip arthroplasty with a radiographically and clinically well-fixed component in selected patients, who are notimmunocompromised and are infected by a low-virulence organism.


Orthopaedic Proceedings
Vol. 99-B, Issue SUPP_3 | Pages 67 - 67
1 Feb 2017
Muratoglu O Chen W Suhardi V Bichara D
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Introduction

Periprosthetic joint infection (PJI) and particle-induced osteolysis are closely related to peri-implant local immunity and macrophage function. We previously demonstrated that titanium particles attenuate the immune response of macrophages caused by chronic inflammation [1]. In a separate study, we have determined that UHMWPE wear particles containing vitamin E (VE) induce less osteolysis compared to HXL UHMWPE wear particles in a murine calvarium model [2]. For this study we hypothesized that macrophages exposed to HXL UHMWPE particles containing VE would better maintain their ability to respond to S. aureus compared to HXL UHMWPE without VE.

Methods

A gamma-sterilized, HXL UHMWPE tibial bearing containing VE (E1, Biomet, “VE-PE”) and 100kGy irradiated and melted UHMWPE (“CISM 100”) were cryomilled to particles by Bioengineering Solutions (Oak Park, IL). In the first in vitro study, RAW 264.7 mouse macrophages were exposed (inverted co-culture) to either VE-PE particles or CISM100 particles and lipopolysaccharide (LPS) for 1–7 days. Macrophage viability was measured using a cell counting kit (CCK-8). Control group with no particles and a LPS group were also included. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining was performed to determine macrophage apoptosis rate in response to particle exposure over time. In the second study, macrophages were exposed to VE-PE or CISM100 particles for 48h, then exposed to LPS for 30 min. Subsequently, reactive oxygen species (ROS) generation and extracellular regulated protein kinase (ERK) phosphorylation were measured. In a third study, after exposure to particles for 48h, fatigued macrophages were co-cultured with bioluminescent S. aureus strain Xen29 for 3h and 6h. Bioluminescence signal was determined to measure the total amount of bacteria. Bacterial live/dead staining and optical density at 600 nm (OD 600) were also performed to determine S. aureus viability. Statistical analysis was performed using one-way or two-way ANOVA with a post hoc examination. *indicates p<0.05.


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_10 | Pages 27 - 27
1 May 2016
Sheng P Li Z Luo G Wang H Chen W Zhang Y Yang X
Full Access

Objective

To investigate the biomechanical mechanism and report preliminary clinical efficacy of eccentric rotational acetabular osteotomy (ERAO) when conduct treatment for developmental dysplasia of the hip (DDH).

Methods

Biomechanical model of the hip joint was established on six female cadaveric hips embalmed by formalin and stimulate ERAO was then performed on the model. Vertical force was loaded on the cadaveric spine from 0 N to 500 N and strain value on femoral head was measured preoperatively and postoperatively when loading force on spine reached the point of 100, 200, 300, 400 and 500 N. Stress value were then calculated base on the measurements. Besides, we reported postoperative follow up cases which were underwent ERAO to treat DDH in our hospital from July 2007 to October 2014. A total of 25 patients (26 hips) were reported, including 6 males and 19 females. Age varies from 11 to 57 years old, and the average age was 31 years old. Postoperative hip function was evaluated by Harris hip score and anteroposterior X⁃ray of pelvic was taken preoperatively and postoperatively to measure the Acetabular⁃head index (AHI), CE angle and Sharp angle.


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_4 | Pages 4 - 4
1 Jan 2016
Yang X Chen W Yu S Zhang Y Luo G Wang H Sheng P
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Objective

To investigate the biomechanical basis and report preliminary clinical efficacy of eccentric rotational acetabular osteotomy (ERAO) when treating developmental dysplasia of the hip (DDH).

Methods

Biomechanical model of the hip joint was established on cadaveric hips. After performed ERAO on the biomechanical model, we explored the impact of this surgery on biomechanics of the hip joint. Meanwhile, we reported postoperative follow-up cases who underwent ERAO in our hospital between November 2007 to July 2012. A total of 14 patients (15 hips) were reported, including 4 males and 10 females, mean age was 30 years old. Harris hip score was defined as clinical evaluation standard and radiographic assessment was based on the measurement and further comparison of pre- and post-operative AHI (Acetabular-head index), CE angle (Center-edge angle) and Sharp angle.


Orthopaedic Proceedings
Vol. 93-B, Issue SUPP_IV | Pages 414 - 414
1 Nov 2011
Nagamine R D’Lima D Patil S Chen W Kondo K Todo M Hara T Sugioka Y
Full Access

Routinely in TKA, at least one of the cruciate ligaments are sacrificed. The cruciate ligaments excision may have an impact in the stability of the reconstructed knee by virtue of the impact on the gap kinematics. In this study, a selective cutting protocol was designed to quantify the individual contribution of ACL and PCL about the knee by means of a loaded cadaveric model.

Five fresh frozen normal cadaver specimens were used. The femur was fixed to a specially designed machine, and 3D tibial movements relative to the femur and joint gap distances were measured by means of a navigation system from full extension to 140° flexion. The joint was distracted with 10 pounds. The measurement was performed before and after ACL and PCL excision.

Medial gap distance at 90° flexion before and after cruciate ligaments excision was 4.3 ± 2.7 mm (mean ± SD) and 5.1 ± 2.8 mm (p< 0.05) respectively. Cruciate ligaments excision significantly widened the medial and lateral gaps at many flexion angles, and the effect of excision on the gap distance was different between medial and lateral sides especially at 90° knee flexion. Cruciate ligaments excision also significantly influenced knee kinematics. If this varying gap is not accounted for either through implant shape and orientation or through soft tissue adjustments, instability could be the result.

Surgeons should be made aware of the influence of cruciate excision on varus/valgus laxity throughout the range of motion. Design modification of the femoral component may also be necessary in order to obtain optimal stability in deep flexion.


Orthopaedic Proceedings
Vol. 92-B, Issue SUPP_I | Pages 153 - 153
1 Mar 2010
Chen W Nagamine R Todo M Kondo K Hara T Sugioka Y
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Posterior stabilized (PS) type knee prosthesis characterized by Post-Cam structure as stabilizer has successfully been used in TKA worldwide, while failure and fracture problems of tibial insert made from polymeric material (UHMNWPE) are still important issues from clinical and mechanical points of view. It is therefore needed to understand the mechanical conditions of the tibial insert under different kinds of TKA motions. The aim of this study is to characterize the mechanical condition of tibial insert under contact between femoral component and tibia insert during flexional motion using dynamic 3-D finite element (FE) method. 3-D FE models of two different kinds of PS type prostheses clinically used were developed and stress analyses were performed from full extension to 135 degree knee flexion. Effects of the different Post-Cam structures on the stress states were investigated, and a guideline towards risk assessment of PS type prosthesis was discussed.

Three-D FE models of Stryker’s PS type knee prostheses, Scorpio Superflex and NRG, were developed base on their CAD data. The tibial post of Scorpio Superflex type knee prosthesis shapes angular, while NRG shapes round. Four nodes tetrahedral elements were used to construct the FE models. Nonlinear spring models were attached to the front and back of the tibial component to express the effect of soft tissues on the movement of real TKA knees. Vertical load and horizontal load were applied to the femoral and tibial components, respectively, to express a deep knee bending (squatting) motion. Flexion motion was introduced by rotation the femoral component from full extension to 135 degree. Internal rotation of 5, 10, 15 degrees were also introduced by rotating the tibial component simultaneously with the flexional motion.

Maximum Mises equivalent stress during knee flexion with 5, 10 and 15 degrees internal rotation of the tibial component of Superflex were much higher than that of NRG, especially at the flexion angle of 120 degree. NRG exhibited stress concentrations on both the Post and condylar surfaces and stress levels were much lower that that of Superflex. The maximum stress in NRG was found to be reduced to about half of Superflex. Mises equivalent stress distribution also showed that flexion with internal rotation generated higher stress concentrations on the condylar surfaces of both prostheses.

The analytical results well demonstrated that the design modification of the tibial insert of NRG effectively reduced the stress concentration with rotated tibial component. The lower stress level in NRG corresponds to the lower reaction force and hence lower resistance to flexional motion than Superflex. This implies that the round post is more suitable for deep flexion than the angular post.


Orthopaedic Proceedings
Vol. 87-B, Issue SUPP_I | Pages 4 - 4
1 Mar 2005
Wu F Wang Z Chen W Zhu H
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Purpose of study: To investigate the safety, efficacy, and feasibility of using high intensity focused ultrasound (HIFU) for the treatment of malignant bone tumors.

Methods: Forty-four patients with biopsy-proven malignant bone tumors were treated with HIFU (osteosarcoma: 32; chondrosarcoma: 3; periosteal osteosarcoma: 2; Ewing sarcoma: 1; other malignant bone tumor: 3, and unclassified tumor: 2). These tumors were situated as follows: distal femur – 20; proximal tibia – 7; mid-shaft of femur – 6; ilium – 2; shaft of fibula – 2; other – 4. HIFU was given as a noninvasive limb-salvage treatment in combination with neoadjuvant chemotherapy (methotrexate, adriamycin, cisplatin and ifosfamide) in thirty-four patients (Enneking’s Stage_b). Ten patients with stage IIIb (9 patients with lung metastasis) were treated with HIFU alone with palliative intent. The largest dimension of the tumors ranged from 5 to 46 cm. Postoperative biopsy, follow-up imaging (DSA, CT or MRI, and ECT), and functional evaluation were performed, and median survival time was calculated using the Kaplan-Meier method.

Results: Histopathological examination demonstrated clear evidence of tumor destruction and regrowth of normal bone in the treated region. When compared with baseline, follow-up imaging indicated complete coagulative necrosis of the treated tumors. Enneking’s functional scores were > 20, 15–20, and < 15 in 20, 14 and 5 cases respectively. Median follow-up was 23 months (range 10 to 40 months). Total survival rate was 85% (38/44). One patient with stage_b disease, and 5 patients with stage IIIb disease died as a result of distant metastases after HIFU treatment. 5 patients underwent amputation after local recurrence. Few complications were observed during follow-up. These were limited to 3 pathological fractures, 2 cases of peripheral nerve damage, restricted joint movement in 1 case, and epiphyseal separation in 1 case.

Conclusions: HIFU is safe, effective, and feasible in the treatment of patients with malignant bone tumors.


Orthopaedic Proceedings
Vol. 84-B, Issue SUPP_III | Pages 231 - 231
1 Nov 2002
Chen W
Full Access

There have been many reports on fracture-dislocation of the lumbar spine in recent years. Hyperextension as a mechanism for fracture-dislocation in the thoracolumbar spine was first described by Holdsworth accounting for only less than 3 percent of all fractures of the spine. De Oliverira reported an unusual pattern of sagittal shear fracture-dislocation secondary to posterior impact injuries. Hyperextension injuries result in the disruption of all ligaments & supporting elements of the spine starting with the anterior column. Sagittal translation and comminution of the posterior elements are the most common radiographic findings. Computed Tomography can accurately demonstrate the destruction of the posterior elements, and MRI is able to demonstrate the anterior ligamentous disruption. Nearly all cases suffered from paraplegia known as lumberjack paraplegia or severe neurological deficit.

A case of complete fracture-dislocation of the L4-5 resulting from hyperextensive injury without lumberjack paraplegia or neurological deficit is presented.

The diagnosis & treatment will be discussed.


Orthopaedic Proceedings
Vol. 84-B, Issue SUPP_III | Pages 206 - 206
1 Nov 2002
Chen L Chen W Niu C Lai P Huang G
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Injection of PMMA bone cement into fractured vertebral bodies has been used clinically and proved to be effective. However, there are concerns about thermal injury to the cord and interferece of bone remodling .The purpose of this study is to use the biodegradable bone substitute as an alternative for augumentation of fractured vertebral bodies .

Material and Methods: From April 1998 to January 2000, 10 patients(Nine females and one male, age from 55 to 74 years) with osteoporotic compression fractures were retrospectively reviewed. The level of compression fracture mostly occurred at T12-L1 (Nine of ten cases). Eight of the ten cases were osteonecrosis of vertebral body with vaccum phenomenon. While other two cases had gross kyphotic deformity. Surgical indications for these ten patients include back pain, progressive kyphosis and failure of conservative medical treatment. (No neurological deficits were noted in all ten cases.) All ten cases underwent posterior instrumentation with vertebroplasty (Bipedicle impaction of osteoset and iliac bone autograft). The anterior body height and the kyphotic angle were measured preoperatively and postoperatively. The fusion mass was observed and followed up with T-L spine AP and Lateral X-ray regularly.

Result: The anterior body height increased over 50% in all cases in this series. The average correction of kyphosis angle is 10 degree. Stable arthrodesis with obvious fusion mass occurred in all patients under X-ray image. Postoperative pain relief were noted in all ten patients. No major complications were related to this procedure.

Conclusion: This preliminary study shows that vertebroplasty using osteoconductive biodegradable bone substitute and osteoinductive iliac bone autograft in osteoporotic compression fracture with osteonecrosis is feasable and effective. The technique might also provide an alternative for treatment of osteoporotic compression fractures instead of PMMA bone cement.


Orthopaedic Proceedings
Vol. 84-B, Issue SUPP_III | Pages 216 - 216
1 Nov 2002
Chen W Cheng C Chen L Niu C Lai P Tsai
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Background Data: Postoperative spondylothesis had been noted for many years, first reported by White in 1977. Biomechanic effect of the facetectomy was reported by Abumi in 1992. There were few reports about the results of surgical treatment for postoperative spondylolisthesis.

Purpose: To assess the outcome of surgical treatment for postoperastive spondylolisthesis and examine the factors that might correlate with postoperative spondylolisthesis.

Materials and Methods: This study retrospectively reviewed twenty seven patients (eleven male and sixteen female), from 1979 to 1996, who received pedicle screws instrumentation and posterolateral fusion for postoperative spondylolisthesis. Average age was 57.3 years old (from 36.6 to 79.5 years old). Average follow-up time was 40.0 months (from 24 months to 72 months). The grade of fcetectomy, percentage of vertebral slipping, and disc narrowing was checked by plain X-ray. End results were assessed using the modified Stauffer-Coventry’s evaluation criteria.

Results: The mean period of postoperative instability was 49.3 months (from 6 months to 141 months) in whole group, 43.7 months (from 6 months to 129 months) in laminectomy group, 43.4 months (from 17months to 82 months) in laminectomy and disectomy groups, and 74.6 months (13 months to 141 months) in disectomy group. After an average follow-up period of 40 months, 29.6 % of patients had excellent results, 44.5% had good results, and 25.9 % had fair result. No complication was found in this study.

Conclusions: Pedicle screw instrumentation with posterolateral fusion can get satisfactory result for postoperative spondylolisthesis.