Abstract Background Porous metaphyseal cones are widely used in revision knee arthroplasty. A new system of porous titanium metaphyseal cones has been designed based on the femoral and tibial ...morphology derived from a computed tomography–based anatomical database. The purpose of this study is to evaluate the initial mechanical stability of the new porous titanium revision cone system by measuring the micromotion under physiologic loading compared with a widely-used existing porous tantalum metaphyseal cone system. Methods The new cones were designed to precisely fit the femoral and tibial anatomy, and 3D printing technology was used to manufacture these porous titanium cones. The stability of the new titanium cones and the widely-used tantalum cones were compared under physiologic loading conditions in bench top test model. Results The stability of the new titanium cones was either equivalent or better than the tantalum cones. The new titanium femoral cone construct had significantly less micromotion compared with the traditional femoral cone construct in 5 of the 12 directions measured ( P < .05), whereas no statistical difference was found in 7 directions. The new porous titanium metaphyseal tibial cones demonstrated less micromotion in medial varus/valgus ( P = .004) and posterior compressive micromotion ( P = .002) compared with the traditional porous tantalum system. Conclusion The findings of this biomechanical study demonstrate satisfactory mechanical stability of an anatomical-based porous titanium metaphyseal cone system for femoral and tibial bone loss as measured by micromotion under physiologic loading. The new cone design, in combination with instrumentation that facilitates surgical efficiency, is encouraging. Long-term clinical follow-up is warranted.
Abstract Most current tapered wedge hip stems were designed based upon the original Mueller straight stem design introduced in 1977. These stems were designed to have a single medial curvature and ...grew laterally to accommodate different sizes. In this preclinical study, the design and verification of a tapered wedge stem using computed tomography scans of 556 patients are presented. The computer simulation demonstrated that the novel stem, designed for proximal engagement, allowed for reduced distal fixation, particularly in the 40–60 year male population. Moreover, the physical micromotion testing and finite element analysis demonstrated that the novel stem allowed for reduced micromotion. In summary, preclinical data suggest that the computed tomography based stem design described here may offer enhanced implant fit and reduced micromotion.
Abstract Background Component positioning in total hip arthroplasty (THA) is among the primary indicators for longevity and success. Acetabular component positioning has been discussed in literature ...at length; however, femoral component positioning is also important as it contributes to combined anteversion. Methods In this study, we examined the changes in femoral anteversion after the implantation of anatomic stem ABG II. A cadaveric study, a computed tomography–based computer modeling study, and a clinical study using a navigation system were conducted to document these changes. Results These studies demonstrated that the anatomic stem ABG II increased the postimplantation femoral version by approximately 7°. The postimplantation versions followed a bimodal distribution. The computed tomography and navigation data also highlighted that the patient population may roughly be divided into 2 groups: the first group that needs anteverted stem and the second group that needs little or no anteversion in the stem to recreate the desired version and offset. Conclusion Based upon our data, we propose a new anatomic stem design that is offered in 2 version angles of 0° and 7° to help create the desired version and offset.
Abstract Jumbo acetabular cups are commonly used in revision total hip arthroplasty (THA). A straightforward reaming technique is used which is similar to primary THA. However, jumbo cups may also be ...associated with hip center elevation, limited screw fixation options, and anterior soft tissue impingement. A partially truncated hemispherical shell was designed with an offset center of rotation, thick superior rim, and beveled anterior and superior rims as an alternative to a conventional jumbo cup. A three dimensional computer simulation was used to assess head center position and safe screw trajectories. Results of this in vitro study indicate that a modified hemispherical implant geometry can reduce head center elevation while permitting favorable screw fixation trajectories into the pelvis in comparison to a conventional jumbo cup.
Cementless metaphyseal filling stems rely on fixation in the medial-to-lateral and anterior-to-posterior (AP) planes. The purpose of this preclinical study was to develop Insignia, a new metaphyseal ...filling system to match the anatomy of the proximal femur, and then compare it to clinically successful stems in multiple simulations.
In this preclinical study, the geometry of the proximal femur in the AP plane among 1321 healthy subjects was evaluated using computed tomography. This data was then used to design insignia. Preclinical studies were performed to compare the broaching effort required to prepare a canal using this system, assess the reliability of seating heights for the stem, and compare in vitro micromotion testing of the stem under simulated stair climb activity.
The proximal femur decreased approximately 50% in the AP plane spanning 20 mm above the lesser trochanter to 30 mm below the lesser trochanter. Additional bench top testing was performed, and the new stem system was found to demonstrate significantly reduced broaching effort (average 6 vs 29 hits, P-value = .000), reliable seating heights on stem placement, and 70% less proximal micromotion on 10,000-cyclic testing (P < .05) compared to another clinically successful metaphyseal filling stem.
The AP dimension of the proximal femur decreases nearly 50% throughout its length. Metaphyseal filling stems that match the AP anatomy of the proximal femur may require fewer hits during broaching, yield reproducible seating heights, and reduce micromotion on cyclic testing.
Numerous cementless stems are available to maximize implant stability, fit, and survivorship in total hip arthroplasty. Recently, a new metaphyseal-filling triple-taper collared stem was designed ...using femoral morphology data obtained from over 1300 computed tomography scans. The purpose of this study was to evaluate the radiographic fit and fill of this new stem in the coronal and sagittal dimensions.
In this retrospective review, postoperative radiographs of patients receiving this new stem were analyzed in accordance with previously published fit and fill analyses. All radiographs were taken 6 weeks postoperatively. Means and standard deviations were reported for all fit and fill parameters.
Fifty-nine hips were analyzed from 55 patients undergoing total hip arthroplasty. The coronal proximal fill was 85.02 ± 8.06%, and coronal distal fill was 75.21 ± 9.71%. The sagittal proximal fill was 86.51 ± 8.77%, and sagittal distal fill was 59.17 ± 8.66%. Mean calcar collar coverage was 80.64 ± 19.6% and all patients had full seating of the collar. Six cases (10.2%) had a collar length greater than the calcar length, with a mean collar overhang of 0.7 ± 0.4 mm.
This new stem demonstrated significant proximal fill in both the coronal and sagittal planes and validates the design intent of this implant. This is the first study to evaluate sagittal fit and fill of a femoral stem. Long-term follow-up is required to understand the clinical impact these fit and fill characteristics may have on patients’ long-term outcomes.
Several 2-dimensional and 3-dimensional surfaces are available for cementless acetabular fixation. Plain radiographs are used to assess osseointegration; however, the radiographs are limited by their ...inability to capture the bone fixation process occurring over the 3-dimensional cup surface. In this cadaveric study, we compared the bone apposition between 2-dimensional and 3-dimensional cups.
Both types of cups were implanted in 6 cadavers and pelvic radiographs obtained. Each cup was resected from the pelvis with adequate bone around it, and subsequently embedded in a polymer. Six sections of each cup were obtained to examine the metal and bone interface. Photographs and contact radiograph images were obtained for each section, and these were graded to arrive at percent metal-bone contact values for the cups.
On average, <30% of the cups' areas displayed radiolucencies on the pelvic radiographs for both cup types. For the section images and radiographs, there was about 80% aggregate contact between the cups and surrounding bone in both cup types. In the 3-dimensional cups group, some inconsistencies were found between the section photographs and the corresponding radiograph images. The radiolucencies observed on the section radiograph could not always be correlated with metal to bone gap on the section photograph.
Good metal-bone contact (75% + contact area) was observed on both cup types. The inconsistencies found in the 3-dimensional cup group may be because of the interaction of radiographs with the unique porous cup surface resulting in artifactual radiolucencies.
Letter to the EditorResponse by the author1 Faizan Z. Kashoo, MPTh; Mehrunnisha Ahmad, Msc; Harpreet Singh, MPT ...
Journal of Taibah University Medical Sciences,
04/2020, Volume:
15, Issue:
2
Journal Article
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