Congenital posteromedial bowing of tibia (CPMBT) progresses with decreasing deformity and increasing shortening. Lengthening in CPMBT has not been studied extensively. Our series compares duration and complications of lengthening in younger vs older children. 28 tibial lengthenings (23 patients) by a single surgeon, divided into two equal groups of 14 segments: group-A ≤ 5 years, Group-B > 5 years. Lengthening was done in all with external fixators. We measured preoperative (bo) and postoperative (po) deformities, initial limb length discrepancy (LLD), LLD at maturity (LLDm), % LLD, amount of lengthening (AmtL) and %L, external fixator duration (EFD) and external fixator index (EFI). We graded complications by Lascombes' criteria, results by ASAMI Bone score. Mean age was 8.8 ± 7.1 years. Follow-up was 7.9 years. Group-A had significantly greater preoperative deformities. LLD was similar in both. Expected LLD at maturity (LLDM) using the multiplier method was greater than previously reported (group-A: 4.4 – 9.5 cm; group-B: 2.5 – 9.7 cm).%L was 24% in group-A and 15.7% in group-B (p=0.002). EFD and EFI were lesser in group-A than group-B. Lascombes' triple contract was fulfilled in 11/14 lengthenings in group-A vs. 3/14 in group-B. ASAMI bone score was good and excellent in both groups.Abstract
Methods
Results
We assessed the role of four different High Tibial osteotomies (HTOs) for medial compartment osteoarthritis of knee (MCOA): Medial Opening Wedge High Tibial Osteotomy (MOWHTO), Focal Dome Osteotomy with Ilizarov Fixator (FDO-I), intra-articular, Tibial Condylar Valgus Osteotomy with plating (TCVO-P) and intra-articular plus extra-articular osteotomy with Ilizarov(TCVO-I); in correcting three deformity categories: primary coronal plane varus measured by Mechanical Axis deviation (MAD), secondary intra-articular deformities measured by Condylar Plateau Angle (CPA) and Joint Line Convergence Angle (JLCA), and tertiary sagittal, rotational and axial plane deformities in choosing them. We retrospectively studied HTOs in 141 knees (126 patients). There were 58, 40, 26, and 17 knees respectively in MOWHTO, FDO-I, TCVO-P and TCVO-I. We measured preoperative (bo) And postoperative (po) deformity parameters.Introduction
Materials and Methods
Congenital posteromedial bowing of tibia (CPMBT) is characterized by a decreasing deformity and an increasing limb shortening. Our series compares the duration and complications of lengthening in younger vs older children. We studied 28 tibial lengthenings in 23 patients, divided into two equal groups of 14 segments: group-A ≤5 years (preschool) and Group-B >5 years. We measured preoperative (bo) and postoperative (po) sagittal, coronal, and oblique plane deformities, limb length discrepancy (LLD), amount of lengthening (AmtL), percentage lengthening (%L), external fixator duration (EFD) and external fixator index (EFI). Complications were graded by Lascombes’ criteria, results by ASAMI Bone score.Introduction
Materials and Methods
Ceramic heads are used in hip revision surgery to mitigate corrosion concerns. Manufacturers recommend using a pristine titanium sleeve in conjunction with a well-fixed metal stem to prevent early failure of the ceramic head. However, the influence of impact force, head size, and sleeve offset on pull-off strength and seating displacement of a revision head assembly is not fully understood. Therefore, the purpose of this study was to investigate the pull-off strength and displacement of commercially available revision ceramic heads and titanium taper sleeve offsets (BIOLOX OPTION, CeramTec GmbH, Plochingen, Germany) while covering a range of clinically relevant impaction forces. Two head sizes (28 mm, n = 12 and 36 mm, n = 12) and two taper adapter sleeve offsets (small, n = 12 and extra-large, n =12) were tested in this study. A dynamic impaction rig was constructed to seat the head, sleeve, and stem assembly. Consistent impaction forces were achieved by a dropping a hammer fixed to a lever arm from a pre-determined height onto a standard impactor instrumented with a piezoelectric force sensor (PCB Piezotronics Inc.). Axially applied forces of 2 kN and 6 kN were used to cover a range of typical impaction forces. Three non-contact differential variable reluctance transducers (LORD Sensing Systems) were used to track the displacement of the head relative to the stem. Subsequently, samples were transferred a servo hydraulic testing machine, and a pull-off test was carried out per ISO 7206- 10 to measure the disassembly force.INTRODUCTION
METHODS
Postoperative functional limitations after Total Knee Arthroplasty (TKA) are caused, in part, by a mismatch between a patient's natural anatomy and conventional “off-the-shelf” implants. To address this, we propose a new concept combining off-the-shelf femur and tibia implants with custom polyethylene tibial inserts designed to account for a patient's unique anatomy. Our goal in this study was to use knee specific computational modeling to determine the neutral path of motion and laxity of an intact knee under axial compression and shear forces through full flexion and compare intact motion against the same knee implanted with a conventional off-the-shelf vs. a custom tibial insert. 3D models of a healthy knee joint were acquired from an open development repository funded by the National Institute of Biomedical Imagining and Bioengineering (Harris et al., 2016). The knee model was virtually implanted with conventional (off-the-shelf) posterior cruciate retaining (CR) components including the femoral component, tibial tray, and a conventional insert. A custom CR tibial insert was designed taking into account native articular geometry and compatibility with placement of the off-the-shelf femoral/tibial tray. Bone, cartilage and implant models were imported into ANSYS Workbench. Ligaments were calibrated using data from in-vitro experimental tests (Harris et al., 2016). The following load conditions were applied to the femur: 20 N axial compression (neutral path), 20 N axial compression with 80 N anterior shear force, and 20 N axial compression with 80 N posterior shear force. Simultaneously for each loading condition, the knee was flexed from 0 – 120 degrees. A circular axis system was used to describe the motion of the femur relative to the tibia.INTRODUCTION
METHODS
Ceramic heads are used in hip revision surgery to mitigate corrosion concerns. Manufacturers recommend using a pristine titanium sleeve in conjunction with a well-fixed metal stem to prevent early failure of the ceramic head. However, the influence of impact force, head size, and sleeve offset on pull-off strength and seating displacement of a revision head assembly is not fully understood. Therefore, the purpose of this study was to investigate the pull-off strength and displacement of commercially available revision ceramic heads and titanium taper sleeve offsets (BIOLOX OPTION, CeramTec GmbH, Plochingen, Germany) while covering a range of clinically relevant impaction forces. Two head sizes (28 mm, n = 12 and 36 mm, n = 12) and two taper adapter sleeve offsets (small, n = 12 and extra-large, n = 12) were tested in this study. A dynamic impaction rig was constructed to seat the head, sleeve, and stem assembly (Fig. 1). Consistent impaction forces were achieved by dropping a hammer fixed to a lever arm from a pre-determined height onto a standard impactor instrumented with a piezoelectric force sensor (PCB Piezotronics Inc.). Axially applied forces of 2 kN and 6 kN were used to cover a range of typical impaction forces. Three non-contact differential variable reluctance transducers (LORD Sensing Systems) were used to track the displacement of the head relative to the stem. Subsequently, samples were transferred to a servo hydraulic testing machine, and a pull-off test was carried out per ISO 7206–10 to measure the disassembly force.Introduction
Methods
The major loss of articular cartilage in medial osteoarthritis occurs in a central band on the distal femur, and in the center of the tibial plateau (Figure). This is consistent with varus deformity due to cartilage loss and meniscal degeneration, together with the sliding regions in walking. Treatment at an early stage such as KL grade 2 or 3, has the advantages of little bone deformity and cruciate preservation, and could be accomplished by resurfacing only the arthritic areas with Early Intervention (EI) components. Such components would need to be geometrically compatible with the surrounding bearing surfaces, to preserve continuity and stability. However because of the relatively small surface area covered, compared with total knees and even unicompartmentals, it is hypothesized that EI components will be an accurate fit on a population of knees with only a small number of sizes, and that accuracy can be maintained without requiring right-left components. We examined this hypothesis using unique design and methodology. Average femur and tibia models, including cartilage, were generated from MRI scans of 20 normal males. The images were imported into Geomagic software. Surface point clouds based on least squares algorithms produced the average models. Averages were also produced from different numbers to determine method validity. Average arthritic models were also generated from 12 KL 1–2 cases, and 13 KL 2–3 cases. The 3 averages were compared by deviation mapping. Using the average from the 20 knees, femoral and tibial implant surfaces were designed using contour matching to fit the arthritic regions, maintaining right-left symmetry. A 5 size system was designed corresponding to large male, average male, small male/large female, average female, small female. For the 20 knees, the components were fitted based on the best possible matching of the contours to the surrounding bearing surfaces. For the femoral component the target was 1 mm projection at the center, matching at the ends. The accuracy of reproducing the cartilage surfaces was then determined by mapping the deviations between the implant surfaces and the cartilage surfaces.INTRODUCTION
METHODS
Tibial component loosening is an important failure mode in unicompartmental knee arthroplasty (UKA) which may be due to the 6–8 mm of bone resection required or the limited surface area. To address component loosening and fixation, a new Early Intervention (EI) design is proposed which reverses the traditional material scheme between femoral and tibial components. That is, the EI design consists of a plastic inlay component for the distal femur and a thin metal plate for the proximal tibia. With this reversed materials scheme, the EI design requires minimal tibial bone resection compared to traditional UKA to preserve the dense and stiff bone in the proximal tibia. This study investigated, by means of finite element (FE) simulations, the potential advantages of a thin metal tibial component compared with traditional UKA tibial components, such as an all-plastic inlay or a metal-backed onlay. We hypothesized that an EI component would produce comparable stress, strain, and strain energy density characteristics to an intact knee and more favorable values than UKA components. Indeed, the finite element results showed that an EI design reduced stresses, strains and strain energy density in the underlying support bone compared to an all-plastic UKA component. Analyzed parameters were similar for an EI and a metal-backed onlay, but the EI component had the advantage of minimal resection of the stiffest bone.
