Shape suitability and mechanical safety of customised hip implants: Three-dimensional printed acetabular cup for hip arthroplasty.

Background: Owing to an increase in the number of hip arthroplasty surgeries, the number of implant replacement surgeries is increasing rapidly as well. This necessitates the study of hip joint conditions. Therefore, Paprosky defined a classification system to indicate the degree of damage to the hip joint. In this study, a customised hip implant suitable for Paprosky classification Type ⅡC and over was designed. The shape, suitability, and mechanical safety of the worst-case model for the implant were evaluated. Materials and methods: To identify the implant size depending on states over Type ⅡC acetabulum bone loss, a size range was selected and a customised implant was designed according to the computed tomography data within the size range. The implant was designed for the flange, hook, and flattened model types. The worst-case selection test was conducted using finite element analysis. The von Mises stresses of the flange, hook, and flattened models were found as 76.223, 136.99, and 80.791 MPa, respectively. Therefore, the hook-type model was selected as the worst case for the mechanical performance test. Results: A bending test was conducted on the hook-type model without fracture and failure at 5344.56 N. The proposed customised implant was found suitable for Type ⅢA acetabulum bone loss, whereas the shape suitability and mechanical safety were verified for the worst case. Conclusion: The shape of a customised implant suitable for Paprosky ⅢA type was designed. The shape suitability and mechanical safety were evaluated using finite element method analysis and bending tests. Clinical validation is required through subsequent clinical evaluation.

Morphologic analysis of the proximal tibia after open wedge high tibial osteotomy for proper plate fitting.

BACKGROUND: After open wedge high tibial osteotomy (OWHTO), the proximal fragment resembles the anatomy of the proximal tibia that is aligned in the anterior-posterior direction and the distal fragment resembles the anatomy of the mid shaft that is aligned in the proximal-distal direction. In addition, the medial portion of the proximal fragment becomes aligned medially and the medial portion of the distal fragment, laterally, depending on the magnitude of the posterior opening gap. Therefore, there would be a mismatch between the post-correction bony surface and the previous pre-contoured plate geometry. The purpose of this study was to devise a new plate that best fit the post-contoured anatomy of the tibia by evaluating the surface geometry of the plate positioning site after OWHTO. METHODS: Thirty-one uni-planar and 38 bi-planar osteotomies were evaluated. Surgical indications were age of under 70 years, relatively active patient who performs recreational sports activities. Other indications were similar with general recommendation of HTO. Computed tomography (CT) of the operated knees was performed and it was used for the reconstruction of the 3D model. Bone model axis re-alignment was performed with coronal, sagittal, and axial plane. Morphologic analysis of the proximal tibia was performed using the following parameters: (1) radii in axial plane, 2) radii in coronal plane, and 3) angle and horizontal distance (Distance X) between the proximal and distal fragments. These were also analyzed according to the correction degree. The Analysis of Variance (ANOVA) test was conducted to verify the change depending on the correction amount of the posterior opening gap. The values obtained for the uni- and bi-planar osteotomy were compared by the independent t-test. RESULTS: There were 9 male and 60 female patients were recruited to this study; the mean age was 58.3 ± 8 and 56.9 ± 7.6 years, respectively. Preoperative weight bearing line (WBL) was 21.59 ± 11.36 and 22.32 ± 10.55 %, respectively. Mean correction degree was 10.9 ± 2.7 and 11.1 ± 2.6 mm, respectively. The radii of the tibial cross-sectional contour at the head portion tended to increase from the proximal to distal direction. The radii of the tibial cross-sectional contour at the neck portion tended to decrease from the proximal to distal direction. The radii of the coronal plane tended to increase from the proximal to distal direction. The angle between the proximal fragment and the distal one varied with the correction amount of the posterior opening gap. Shaft_Mid and Distance X of GroupI (110.08 mm and 6.11 mm, respectively) which had lower correction angle were lower than those of GroupII (130.05 mm and 6.41 mm, respectively) and those of GroupIII (136.35 mm, 8.01 mm, respectively) in coronal plane. There were significant differences (p = 0.023 < 0.05 and p = 0.009 < 0.01, respectively). CONCLUSION: Current plate design should be modified to the surface geometry of the post-correction for the proper fitting. As the correction degree increases, the plate should be bended at the both end of the opening gap in coronal plane. TRIAL REGISTRATION: 'retrospectively registered ( ISRCTN97792440 ).

Results of revision surgery and causes of unstable total knee arthroplasty.

BACKGROUND: The aim of this study was to evaluate causes of unstable total knee arthroplasty and results of revision surgery. METHODS: We retrospectively reviewed 24 knees that underwent a revision arthroplasty for unstable total knee arthroplasty. The average follow-up period was 33.8 months. We classified the instability and analyzed the treatment results according to its cause. Stress radiographs, postoperative component position, and joint level were measured. Clinical outcomes were assessed using the Hospital for Special Surgery (HSS) score and range of motion. RESULTS: Causes of instability included coronal instability with posteromedial polyethylene wear and lateral laxity in 13 knees, coronal instability with posteromedial polyethylene wear in 6 knees and coronal and sagittal instability in 3 knees including post breakage in 1 knee, global instability in 1 knee and flexion instability in 1 knee. Mean preoperative/postoperative varus and valgus angles were 5.8°/3.2° (p = 0.713) and 22.5°/5.6° (p = 0.032). Mean postoperative α, ß, γ, δ angle were 5.34°, 89.65°, 2.74°, 6.77°. Mean changes of joint levels were from 14.1 mm to 13.6 mm from fibular head (p = 0.82). The mean HSS score improved from 53.4 to 89.2 (p = 0.04). The average range of motion was changed from 123° to 122° (p = 0.82). CONCLUSIONS: Revision total knee arthroplasty with or without a more constrained prosthesis will be a definite solution for an unstable total knee arthroplasty. The solution according to cause is very important and seems to be helpful to avoid unnecessary over-constrained implant selection in revision surgery for total knee instability.

The Otto Aufranc Award: enhanced biocompatibility of stainless steel implants by titanium coating and microarc oxidation.

BACKGROUND: Stainless steel is one of the most widely used biomaterials for internal fixation devices, but is not used in cementless arthroplasty implants because a stable oxide layer essential for biocompatibility cannot be formed on the surface. We applied a Ti electron beam coating, to form oxide layer on the stainless steel surface. To form a thicker oxide layer, we used a microarc oxidation process on the surface of Ti coated stainless steel. Modification of the surface using Ti electron beam coating and microarc oxidation could improve the ability of stainless steel implants to osseointegrate. QUESTIONS/PURPOSES: The ability of cells to adhere to grit-blasted, titanium-coated, microarc-oxidated stainless steel in vitro was compared with that of two different types of surface modifications, machined and titanium-coated, and microarc-oxidated. METHODS: We performed energy-dispersive x-ray spectroscopy and scanning electron microscopy investigations to assess the chemical composition and structure of the stainless steel surfaces and cell morphology. The biologic responses of an osteoblastlike cell line (SaOS-2) were examined by measuring proliferation (cell proliferation assay), differentiation (alkaline phosphatase activity), and attraction ability (cell migration assay). RESULTS: Cell proliferation, alkaline phosphatase activity, migration, and adhesion were increased in the grit-blasted, titanium-coated, microarc-oxidated group compared to the two other groups. Osteoblastlike cells on the grit-blasted, titanium-coated, microarc-oxidated surface were strongly adhered, and proliferated well compared to those on the other surfaces. CONCLUSIONS: The surface modifications we used (grit blasting, titanium coating, microarc oxidation) enhanced the biocompatibility (proliferation and migration of osteoblastlike cells) of stainless steel. CLINICAL RELEVANCE: This process is not unique to stainless steel; it can be applied to many metals to improve their biocompatibility, thus allowing a broad range of materials to be used for cementless implants.

Rotational alignment of femoral component for minimal medial collateral ligament release in total knee arthroplasty.

PURPOSE: We attempted to determine the degree of rotation of the femoral component to achieve an ideal rectangular flexion gap with minimal medial collateral ligament (MCL) release using a modified measured technique. MATERIALS AND METHODS: Group I consisted of 60 osteoarthritis patients (72 cases) who underwent total knee arthroplasty (TKA) with minimal MCL release and Group II consisted of 48 patients without osteoarthritis (61 cases). We performed computed tomography (CT) scanning of the knee with 90 degree flexion in all of the patients and analyzed the angles between the distal femur landmarks and the tibial mechanical axis using a Picture Archiving Communication system. External rotation of the femoral component from the Whiteside line and posterior condylar line was measured in group I who underwent TKA with minimum MCL release. The variance in the mediolateral flexion gap according to the degree of rotation was also measured using an Auto-Computer Aided Design program. RESULTS: The CT scans showed that the Whiteside line, posterior condylar line, and transepicondylar line was more internally rotated on average from the longitudinal axis of tibia by 4.12°, 5.54°, and 4.64°, respectively, in group I compared to group II. In group I, the femoral component was inserted with an average external rotation of 5.6° from the posterior condylar line and with an average external rotation of 2.0° from the Whiteside line with minimal MCL release. From the measurements of the femoral component size and the variance in the degree of rotation using an Auto-CAD program, it was found that the change in the mediolateral flexion gap was greater when the rotation angle was greater and it was greater when the size of femoral component was larger at the same rotation angle. CONCLUSIONS: The average rotation angle of the femoral component to achieve an ideal rectangular flexion gap with minimal MCL release in TKA was an external rotation of 5.6° from the posterior condylar line and an external rotation of 2.0° from the Whiteside line. We concluded that when a femoral component is small in size, greater than average external rotation needs to be applied and when a femoral component is large in size, less than average external rotation needs to be applied.

Postoperative mortality and factors related to mortality after bipolar hemiarthroplasty in patients with femoral neck fractures.

The purpose of this study was to determine the mortality rate and factors related to mortality in elderly patients with acute and monotraumatic femoral neck fractures. This study included 241 patients with femoral neck fractures after bipolar hemiarthroplasty. We analyzed the mortality rate and the relationship between postoperative mortality and risk factors, such as age, sex, body mass index, the time to surgery, and the Society of Anesthesiologists' score. The postoperative mortality rate 1 and 3 years after surgery was 11.2% and 19.5%, respectively. There proved to be a relationship between postoperative mortality and age, the time to surgery, and the Society of Anesthesiologists score. We recommend that surgery should not be delayed, and caution should be exercised for the high-risk group patients.

Enhanced cell integration to titanium alloy by surface treatment with microarc oxidation: a pilot study.

Microarc oxidation (MAO) is a surface treatment that provides nanoporous pits, and thick oxide layers, and incorporates calcium and phosphorus into the coating layer of titanium alloy. We presumed such modification on the surface of titanium alloy by MAO would improve the ability of cementless stems to osseointegrate. We therefore compared the in vitro ability of cells to adhere to MAOed titanium alloy to that of two different types of surface modifications: machined and grit-blasted. We performed energy-dispersive x-ray spectroscopy and scanned electron microscopy investigations to assess the structure and morphology of the surfaces. Biologic and morphologic responses to osteoblast cell lines (SaOS-2) were then examined by measuring cell proliferation, cell differentiation (alkaline phosphatase activity), and alpha v beta 3 integrin. The cell proliferation rate, alkaline phosphatase activity, and cell adhesion in the MAO group increased in comparison to those in the machined and grit-blasted groups. The osteoblast cell lines of the MAO group were also homogeneously spread on the surface, strongly adhered, and well differentiated when compared to the other groups. This method could be a reasonable option for treating the surfaces of titanium alloy for better osseointegration.

Modified posterior approach to total hip arthroplasty to enhance joint stability.

UNLABELLED: We modified the posterior approach by preserving the external rotator muscles to enhance joint stability after primary THA. We asked whether this modified posterior approach would have a lower dislocation rate than the conventional posterior approach, with and without a repair of external rotator muscles. We retrospectively divided 557 patients (670 hips) who had undergone primary THA into three groups based on how the external rotator muscles had been treated during surgery: (1) not repaired after sectioning, (2) repaired after sectioning, or (3) not sectioned and preserved. The minimum followup was 1 year. In the group with preserved external rotator muscles, we observed no dislocations; in comparison, the dislocation rates for the repaired rotator group and the no-repair group were 3.9% and 5.3%, respectively. This modified posterior approach, which preserves the short external rotator muscles, seemed effective in preventing early dislocation after primary THA. LEVEL OF EVIDENCE: Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Instrumented ligamentotaxis and stabilization of compression and burst fractures of dorsolumbar and mid-lumbar spines.

BACKGROUND: Controversy continues regarding the best treatment for compression and burst fractures. The axial distraction reduction utilizing the technique employing the long straight rod or curved short rod without derotation to reduce fracture are practised together with short segment posterolateral fusion (PLF). Effects of the early postoperative mobilization without posterolateral fusion on reduction maintenance and fracture consolidation were not evaluated so far. The present prospective study is designed to assess the effectiveness of i) reduction and restoration of sagittal alignment, ii) no posterolateral fusion on the reduced, fractured vertebral body and injured disc, iii) fracture consolidation and iv) the fate of the unfused cephalad and caudal injured motion segments of the fractured vertebra. MATERIALS AND METHODS: The study includes 15 Denis burst and two Denis type D compression fractures between T(12) and L(3). The lordotic distraction technique was used for ligamentotaxis utilizing the contoured short rods and pedicle screw fixator. Three vertebrae including the fractured one were fixed. The patients after surgery were braced for ten weeks with activity restriction for 2-4 weeks. The patients were evaluated for change in vertebral body height, sagittal curve, reduction of retropulsion, improvement in neural deficit. The unfused motion segments, residual postoperative pain and bone and metal failure were also evaluated. RESULTS: The preoperative and postreduction percentile vertebral heights at, zero (immediate postoperative), at three, six and 12 months followup were 62.4, 94.8, 94.6, 94.5 and 94.5%, respectively. The percentages of the intracanal fragment retropulsion at preoperative, and postoperative at zero, 3, 6 and 12 months followup were 59.0, 36.2,, 36.0, 32.3, and 13.6% respectively. The preoperative and postreduction percentile loss of the canal dimension and at zero, three, six and 12 months were 52.1, 45.0, 44.0, 41.0 and 29% respectively suggesting that the under-reduced fragment was being resorbed gradually by a remodeling process. The mean initial kyphosis of 33° became mean 2° immediately after reduction and mean 3° at the final followup. The fractured vertebral bodies consolidated in an average period of ten weeks (range 8-14 weeks). The restored disc heights were relatively well maintained throughout the observation period. All paraparetic patients recovered neurologically. There were no postoperative complications. CONCLUSION: Instrument-aided ligamentotaxis for compression and burst fractures utilizing the short contoured rod derotation technique and the instrumented stabilization of the fractured spine are found to be effective procedures which contribute to the fractured vertebral body consolidation without recollapse and maintain the motion segment function.

Treatment of dens fracture in adults: A report of thirty-two cases.

Thirty-two adult patients with dens fractures (30 type II and 2 type III) were treated from 1983 to 2002 at the authors' institutions. The age of the patients ranged from 23 to 58 years. The postoperative follow-up period ranged from 1 to 10 years. The objective of this retrospective study was to evaluate the effectiveness of the osteosynthesis after screw fixation and postoperative bracing. In the 32 cases, 19 patients underwent single screw and 13 underwent double screw fixation. Postoperatively, light head halter traction was applied with the patients in bed for 1 to 4 weeks followed by a halo-vest for 8 to 14 weeks. Fractures healed in 9 weeks on average. There were no cases of delayed union. The overall results were excellent in 26 cases (81.3%), good in 5 (15.6%), and fair in 1 (3.1%) patient (who had a type Il fracture). There were no difference in dens union patterns between those receiving one-screw and two-screw fixation, and there were no complications during or after the operative procedure. Postoperatively there were no restriction of motion in the neck and no residual neck pain. Direct osteosynthesis of the fractured dens with screws is an effective procedure for unstable type II and III fracture of the dens. Postoperative external immobilization with a cervical brace seems to be an important contributing factor to the equal fusion rates in both groups of patients.

Human serum opsonization of orthopedic biomaterial particles: protein-binding and monocyte/macrophage activation in vitro.

Wear particles generated after total joint arthroplasty activate monocyte/macrophages and incite formation of a granulomatous periprosthetic tissue associated with bone loss and implant loosening. This study tested the hypothesis that selective opsonization of orthopedic implant biomaterial wear particles by human serum proteins influences monocyte/macrophage activation. Serum protein binding to metallic, polymeric, and ceramic particles was determined by one-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Individual proteins bound to particles were subsequently identified using two-dimensional SDS-PAGE, microsequencing techniques, and SWISS-PROT analysis. Effects of selective protein opsonization on particle-induced monocyte/macrophage activation were assessed by quantification of interleukin-1beta, interleukin-6, and tumor necrosis factor-alpha release. Results from one-dimensional gel analyses revealed distinct serum protein-binding patterns specific for each material tested. Two-dimensional gel analysis together with amino acid sequencing of the prominent protein species confirmed the presence of albumin and alpha-1-antitrypsin bound to all particles tested. In contrast to the metallic particles, apolipoprotein was a major species associated with polymeric particles. Opsonization of PMMA particles with purified preparations of each of the identified proteins showed that albumin significantly enhanced particle-induced monocyte/macrophage activation. These data confirm orthopedic biomaterial specific binding of human serum proteins and demonstrate that albumin exacerbates particle-induced monocyte/macrophage activation. Alterations in the chemical and surface properties of orthopedic biomaterials to modulate protein interactions may improve implant longevity.

Pott's paraplegia in patients with severely deformed dorsal or dorsolumbar spines: treatment and prognosis.

STUDY DESIGN: Pott's paraplegic patients with severe spinal deformity were reviewed retrospectively after being treated with chemotherapy and/or decompressive surgery. OBJECTIVES: To determine the most appropriate treatment protocol and to predict the prognosis for Pott's paraplegics with severe spinal deformity. SETTING: Catholic University of Korea Medical Center and Moon-Kim's Institute of Orthopedic Research, Seoul, Korea from 1971 to 1996. METHOD: In this study, there were 33 patients (eight children and 25 adults), ranging from 13 to 56 years of age. They developed spinal tuberculosis at the age of 9 years (range, 2-29 years), and remained neurologically symptom free from an average of 16 years (range, 4-27 years). Four adults who responded well to treatment initially suffered relapses of paraplegia. Only six patients had previously received a full course of triple chemotherapy. Seven (two children, five adults) had healed disease, and 26 (six children, 20 adults) had active disease. Eleven cases had frequent drainage from the sinuses. Kyphoscoliosis was found in 11 patients: four children and seven adults. The remaining patients had kyphosis only. Among the 26 patients with active tuberculosis, 10 had triple chemotherapy itself and the rest had additional decompression surgery (10 anterior and six posterior). All seven patients with healed tuberculosis were subjected only to surgery (two anterior and five posterior). RESULTS: In seven patients with healed tuberculosis, surgery did not improve neurologically except in one child patient. In four patients, the severity of paralysis remained unchanged and two patients, deteriorated neurologically after surgery. In six children with active tuberculosis, there were remarkable neurological recoveries by either conservative treatment or surgical decompression. Seven adults with active tuberculosis recovered slowly, improving by one or two Frankel grades (three Frankel C, three D, one E). In 11 out of 13 surgically treated adults with active disease, paralysis that had persisted for less than 3 months gradually improved by one or two Frankel grades. One Frankel A and one Frankel B paraplegic patients who had paralysis that had lasted through 6 months did not recover after surgery. CONCLUSION: The neurological recovery of Pott's paraplegics with severe spinal deformity resulted in three different outcomes: (1) severe deformity is different from moderate and mild deformities; (2) patients with healed tuberculosis had poorer prognosis than patients with active tuberculosis; (3) children had better prognosis than adults. Furthermore, patients with paralysis persisting over 6 months did not recover neurologically after surgery.

Conservative treatment of tuberculosis of the lumbar and lumbosacral spine.

Fifty-six adults (average age, 38 years) with active tuberculosis of the lumbar and lumbosacral spine were treated conservatively with triple chemotherapy for 12 to 18 months. The minimum followup was 3 years. Three methods of assessments of the chronologic changes of sagittal spinal deformity were used on lateral radiographs of the lumbar spine obtained with the patient standing: deformity, kyphos angles, and total lumbar lordosis. The lumbosacral joint angle was measured for tuberculosis of the lumbosacral joint. The disease healed in all patients with a minimum increase of kyphosis, although in 23 patients there was minimal new involvement of the adjacent vertebral bodies within 6 months of treatment. The pattern of the involved vertebral body collapse in tuberculosis of the lumbar and lumbosacral joints was vertical (telescoping), along a longitudinal axis that minimized the progression of kyphosis. The outcome was judged on the basis of residual kyphosis (British Medical Research Council criteria) and found to be favorable in 96.4% (54 patients). Triple chemotherapy for lumbar and lumbosacral tuberculosis is effective in curing the disease and in minimizing the residual kyphosis through early diagnosis and immediate initiation of chemotherapy. The pattern of vertebral body collapse is the telescoping type, which is the determining factor in minimizing residual spinal deformity.