Novel 3D Custom-Made Silicone Tumor Model as a Support for Teaching Surgical Oncology Principles.

Alternative laboratory teaching methods are becoming increasingly desirable and effective in medical education environments. While ethical concerns associated with the use of live animals in terminal surgery laboratories have been reduced with cadaveric models, availability, and lack of pathology can limit their ability to adequately convey surgical principles and replicate clinical training. We have developed a three-dimensional (3D) custom-made silicone soft tissue tumor model using 3D-printed molds derived from canine soft tissue sarcoma computed tomography images. This novel teaching model allows users to apply surgical oncology principles and perform basic technical tasks such as incisional biopsy, margin demarcation, marginal and wide surgical excision, and inking of surgical margins. A large cohort of students in addition to a small number of professional veterinarians at different levels of specialty training followed the laboratory guidelines and evaluated the simulated tumor model based on a qualitative survey. All participants were able to successfully complete the practical training. The model also allowed the students to identify and correct technical errors associated with biopsy sampling and margin dissection, and to understand the clinical impacts related to those errors. Face and content validity of the model were assessed using Likert-style questionnaires with overall average instructors' scores of 3.8/5 and 4.6/5, respectively. Content validity assessment of the model by the students approximated instructors' evaluation with an overall average score of 4.4/5. This model development emphasizes the efficacy of alternative non-cadaveric laboratory teaching tools and could become a valuable aid in the veterinary curricula.

Multi-material 3D Models for Temporal Bone Surgical Simulation.

HYPOTHESIS: A simulated, multicolor, multi-material temporal bone model can be created using 3-dimensional (3D) printing that will prove both safe and beneficial in training for actual temporal bone surgical cases. BACKGROUND: As the process of additive manufacturing, or 3D printing, has become more practical and affordable, a number of applications for the technology in the field of Otolaryngology-Head and Neck Surgery have been considered. One area of promise is temporal bone surgical simulation. METHODS: Three-dimensional representations of human temporal bones were created from temporal bone computed tomography (CT) scans using biomedical image processing software. Multi-material models were then printed and dissected in a temporal bone laboratory by attending and resident otolaryngologists. A 5-point Likert scale was used to grade the models for their anatomical accuracy and suitability as a simulation of cadaveric and operative temporal bone drilling. RESULTS: The models produced for this study demonstrate significant anatomic detail and a likeness to human cadaver specimens for drilling and dissection. CONCLUSION: Simulated temporal bones created by this process have potential benefit in surgical training, preoperative simulation for challenging otologic cases, and the standardized testing of temporal bone surgical skills.

Correction of biapical radial deformities by use of bi-level hinged circular external fixation and distraction osteogenesis in 13 dogs.

OBJECTIVES: To describe clinical, radiographic, and computed tomographic (CT) assessment of biapical deformities of the radius in dogs and evaluate the effectiveness of their management by use of bilevel hinged circular external fixation frames. STUDY DESIGN: Prospective, non-randomized cohort study. ANIMALS: Dogs (N = 26: 13 with 14 limbs operated, 13 controls). METHODS: CT scans of the forelimbs were performed and CT-based polymer replicas prepared. Rotation within the elbow joint, varus of the proximal portion of the radius, radial torsion, valgus of the distal portion of the radius, procurvatum, and rotation within the carpal joint were measured on radiographs, on polymer replicas, and on CT scans. Bilevel hinged circular external fixation frames were assembled on polymer replicas and identical frames were placed on dogs. Torsion was corrected acutely and angulation was corrected progressively. Functional outcome was assessed subjectively. RESULTS: Buckling was present preoperatively in operated limbs. Mean (± SD) varus of the proximal portion of the radius was 36 ± 8°, valgus of the distal portion of the radius was 32 ± 5°, external radial torsion was 35 ± 6°, procurvatum was 41 ± 10°, and medial translation was 44 ± 11 mm. Treatment duration was 80 ± 24 days. Buckling was not observed after surgery. Lameness scores improved in all dogs (P < .001). CONCLUSIONS: The forelimbs of dogs with severe biapical radial deformities buckle and have increased radial head rotation and radial torsion. Biapical radial deformities can be managed with proximal and distal radial osteotomies and bilevel hinged circular external fixation.

Overview of current additive manufacturing technologies and selected applications.

Three-dimensional printing or rapid prototyping are processes by which components are fabricated directly from computer models by selectively curing, depositing or consolidating materials in successive layers. These technologies have traditionally been limited to the fabrication of models suitable for product visualization but, over the past decade, have quickly developed into a new paradigm called additive manufacturing. We are now beginning to see additive manufacturing used for the fabrication of a range of functional end use components. In this review, we briefly discuss the evolution of additive manufacturing from its roots in accelerating product development to its proliferation into a variety of fields. Here, we focus on some of the key technologies that are advancing additive manufacturing and present some state of the art applications.

In vitro evaluation of free-form biodegradable bone plates for fixation of distal femoral physeal fractures in dogs.

OBJECTIVE: To design and manufacture free-form biodegradable polycaprolactone (PCL) bone plates and to compare mechanical properties of femoral constructs with a distal physeal fracture repaired by use of 5 stabilization methods. SAMPLE POPULATION: 40 canine femoral replicas created by use of additive manufacturing and rapid tooling. PROCEDURES: Surgery duration, mediolateral and craniocaudal bending stiffness, and torsional stiffness of femoral physeal fracture repair constructs made by use of 5 stabilization methods were assessed. The implants included 2 Kirschner wires inserted medially and 2 inserted laterally (4KW), a commercial stainless steel plate (CSP), a custom free-form titanium plate (CTP), thin (2-mm-thick) biodegradable PCL plates (TNP) placed medially and laterally, and thick (4-mm-thick) PCL plates (TKP) placed medially and laterally. RESULTS: Surgical placement of 4KW was more rapid than placement of other implants The mean caudal cantilever bending stiffness of CTP and CSP constructs was greater than that for TNP TKP and 4KW constructs, and the mean caudal cantilever bending stiffness of TNP and TKP constructs was greater than that for 4KW constructs. The mean lateral cantilever bending stiffness of TKP constructs was greater than that for 4KW constructs. Differences among construct types were not significant in yield strength, ultimate strength, yield torque, and ultimate torque. CONCLUSIONS AND CLINICAL RELEVANCE: The mechanical properties of fracture repair constructs made from free-form PCL biodegradable plates compared favorably with those of constructs made from Kirschner wires. The impact of PCL plates on musculoskeletal soft tissues, bone healing, and bone growth should be evaluated before clinical use.

In vitro evaluation of a low-modulus mesh canine prosthetic hip stem.

OBJECTIVE: To compare an electron beam melting-processed (EBMP) low-modulus titanium alloy mesh stem with a commercial cobalt-chromium (CC) stem in a canine cadaver model. SAMPLE POPULATION: 9 pairs of cadaver femora. PROCEDURES: EBMP stems of 3 sizes were placed in randomly chosen sides of femora (left or right) and CC stems in opposite sides. Stem impaction distances were recorded. Five strain gauges were attached to the femoral surface to record transverse tensile (hoop) strains in the femur during axial loading. Constructs were axially loaded 4 times to 800 N and 4 times to 1,600 N in a materials testing machine. Axial stiffness of constructs and bone surface strains were compared between EBMP and CC constructs. RESULTS: Stems were impacted without creating femoral fissures or fractures. Stem impaction distances were larger for EBMP stems than for CC stems. Mean axial stiffness of EBMP constructs was lower than mean axial stiffness of CC constructs. Subsidence did not differ between groups. Bone strains varied among strain gauge positions and were largest at the distal aspect of the stems. At a load of 1,600 N, bones strains were higher in CC constructs than in EBMP constructs for 2 of 4 medial strain gauges. CONCLUSIONS AND CLINICAL RELEVANCE: EBMP stems were successfully impacted and stable and led to a focal decrease in bone strain; this may represent an acceptable option for conventional or custom joint replacement.

Evaluation of the geometric accuracy of computed tomography and microcomputed tomography of the articular surface of the distal portion of the radius of cats.

OBJECTIVE: To evaluate accuracy of articular surfaces determined by use of 2 perpendicular CT orientations, micro-CT, and laser scanning. SAMPLE: 23 cat cadavers. PROCEDURES: Images of antebrachia were obtained by use of CT (voxel size, 0.6 mm) in longitudinal orientation (CTLO images) and transverse orientation (CTTO images) and by use of micro-CT (voxel size, 0.024 mm) in a longitudinal orientation. Images were reconstructed. Craniocaudal and mediolateral length, radius of curvature, and deviation of the articular surface of the distal portion of the radius of 3-D renderings for CTLO, CTTO, and micro-CT images were compared with results of 3-D renderings acquired with a laser scanner (resolution, 0.025 mm). RESULTS: Measurement of CTLO and CTTO images overestimated craniocaudal and mediolateral length of the articular surface by 4% to 10%. Measurement of micro-CT images underestimated craniocaudal and mediolateral length by 1%. Measurement of CTLO and CTTO images underestimated mediolateral radius of curvature by 15% and overestimated craniocaudal radius of curvature by > 100%; use of micro-CT images underestimated them by 3% and 5%, respectively. Mean ± SD surface deviation was 0.26 ± 0.09 mm for CTLO images, 0.30 ± 0.28 mm for CTTO images, and 0.04 ± 0.02 mm for micro-CT images. CONCLUSIONS AND CLINICAL RELEVANCE: Articular surface models derived from CT images had dimensional errors that approximately matched the voxel size. Thus, CT cannot be used to plan conforming arthroplasties in small joints and could lack precision when used to plan the correction of a limb deformity or repair of a fracture.

In vitro evaluation of a custom cutting jig and custom plate for canine tibial plateau leveling.

OBJECTIVE: To design and manufacture custom titanium bone plates and a custom cutting and drill guide by use of free-form fabrication methods and to compare variables and mechanical properties of 2 canine tibial plateau leveling methods with each other and with historical control values. SAMPLE POPULATION: 10 canine tibial replicas created by rapid prototyping methods. PROCEDURES: Application time, accuracy of correction of the tibial plateau slope (TPS), presence and magnitude of rotational and angular deformation, and replica axial stiffness for 2 chevron wedge osteotomy (CWO) methods were assessed. One involved use of freehand CWO (FHCWO) and screw hole drilling, whereas the other used jig-guided CWO (JGCWO) and screw hole drilling. RESULTS: Replicas used for FHCWO and JGCWO methods had similar stiffness. Although JGCWO and FHCWO did not weaken the replicas, mean axial stiffness of replicas after JGCWO was higher than after FHCWO. The JGCWO method was faster than the FHCWO method. Mean +/- SD TPS after osteotomy was lower for FHCWO (4.4 +/- 1.1 degrees ) than for JGCWO (9.5 +/- 0.4 degrees ), and JGCWO was more accurate (target TPS, 8.9 degrees ). Slight varus was evident after FHCWO but not after JGCWO. Mean postoperative rotation after JGCWO and FHCWO did not differ from the target value or between methods. CONCLUSIONS AND CLINICAL RELEVANCE: The JGCWO method was more accurate and more rapid and resulted in more stability than the FHCWO method. Use of custom drill guides could enhance the speed, accuracy, and stability of corrective osteotomies in dogs.

Improved osseointegration with as-built electron beam melted textured implants and improved peri­implant bone volume with whole body vibration.

Transcutaneous osseointegrated prostheses provide stable connections to the skeleton while eliminating skin lesions experienced with socket prosthetics. Additive manufacturing can create custom textured implants capable of interfacing with amputees' residual bones. Our objective was to compare osseointegration of textured surface implants made by electron beam melting (EBM), an additive manufacturing process, to machine threaded implants. Whole body vibration was investigated to accelerate osseointegration. Two cohorts of Sprague-Dawley rats received bilateral, titanium implants (EBM vs. threaded) in their tibiae. One cohort comprising five groups vibrated at 45 Hz: 0.0 (control), 0.15, 0.3, 0.6 or 1.2 g was followed for six weeks. Osseointegration was evaluated through torsional testing and bone volume fraction (BV/TV). A second cohort, divided into two groups (control and 0.6 g), was followed for 24 days and evaluated for resonant frequency, bone-implant contact (BIC) and fluorochrome labeling. The EBM textured implants exhibited significantly improved mechanical stability independent of vibration, highlighting the benefits of using EBM to produce custom textured surfaces. Bone formation on and around the EBM textured implants increased compared to machined implants, as seen by BIC and fluorescence. No difference in torque, BIC or fluorescence among vibration levels was detected. BV/TV significantly increased at 0.6 g compared to control for both implant types.

Custom-designed orthopedic implants evaluated using finite element analysis of patient-specific computed tomography data: femoral-component case study.

BACKGROUND: Conventional knee and hip implant systems have been in use for many years with good success. However, the custom design of implant components based on patient-specific anatomy has been attempted to overcome existing shortcomings of current designs. The longevity of cementless implant components is highly dependent on the initial fit between the bone surface and the implant. The bone-implant interface design has historically been limited by the surgical tools and cutting guides available; and the cost of fabricating custom-designed implant components has been prohibitive. METHODS: This paper describes an approach where the custom design is based on a Computed Tomography scan of the patient's joint. The proposed design will customize both the articulating surface and the bone-implant interface to address the most common problems found with conventional knee-implant components. Finite Element Analysis is used to evaluate and compare the proposed design of a custom femoral component with a conventional design. RESULTS: The proposed design shows a more even stress distribution on the bone-implant interface surface, which will reduce the uneven bone remodeling that can lead to premature loosening. CONCLUSION: The proposed custom femoral component design has the following advantages compared with a conventional femoral component. (i) Since the articulating surface closely mimics the shape of the distal femur, there is no need for resurfacing of the patella or gait change. (ii) Owing to the resulting stress distribution, bone remodeling is even and the risk of premature loosening might be reduced. (iii) Because the bone-implant interface can accommodate anatomical abnormalities at the distal femur, the need for surgical interventions and fitting of filler components is reduced. (iv) Given that the bone-implant interface is customized, about 40% less bone must be removed. The primary disadvantages are the time and cost required for the design and the possible need for a surgical robot to perform the bone resection. Some of these disadvantages may be eliminated by the use of rapid prototyping technologies, especially the use of Electron Beam Melting technology for quick and economical fabrication of custom implant components.

Custom total knee replacement in a dog with femoral condylar bone loss.

OBJECTIVE: To report surgical planning, technique, and outcome of custom total knee replacement (TKR) performed to manage a medial femoral condylar nonunion in a dog. STUDY DESIGN: Clinical case report. ANIMAL: A 3-year-old, 20 kg Karelian Bear Hound. METHODS: Computed tomographic scan of the left pelvic limb was used to build a stereolithography model of the distal portion of the femur. The model was used to create a custom augment to replace the missing medial femoral condyle and a custom stem for intramedullary condylar cemented fixation. The augment and stem were adapted to femoral and tibial components already available. The model was used to rehearse the surgery and then the custom prosthesis was implanted. RESULTS: Weight bearing returned 8 hours after surgery and improved thereafter. Joint alignment was normal and prosthetic joint motion was 60-165 degrees postoperatively. The dog resumed moose hunting 3 months after surgery. Peak vertical force and impulse of the operated limb measured 17 months after surgery were 65% and 47% of the normal, contralateral limb. CONCLUSION: Based on short-term follow-up, cemented canine TKR was successfully achieved for management of a severely abnormal stifle joint. CLINICAL RELEVANCE: With further refinement and development of commercially available prostheses, TKR should be possible for canine patients.

Accuracy and repeatability of long-bone replicas of small animals fabricated by use of low-end and high-end commercial three-dimensional printers.

OBJECTIVE To assess the repeatability and accuracy of polymer replicas of small, medium, and large long bones of small animals fabricated by use of 2 low-end and 2 high-end 3-D printers. SAMPLE Polymer replicas of a cat femur, dog radius, and dog tibia were fabricated in triplicate by use of each of four 3-D printing methods. PROCEDURES 3-D renderings of the 3 bones reconstructed from CT images were prepared, and length, width of the proximal aspect, and width of the distal aspect of each CT image were measured in triplicate. Polymer replicas were fabricated by use of a high-end system that relied on jetting of curable liquid photopolymer, a high-end system that relied on polymer extrusion, a triple-nozzle polymer extrusion low-end system, and a dual-nozzle polymer extrusion low-end system. Polymer replicas were scanned by use of a laser-based coordinate measurement machine. Length, width of the proximal aspect, and width of the distal aspect of the scans of replicas were measured and compared with measurements for the 3-D renderings. RESULTS 129 measurements were collected for 34 replicas (fabrication of 1 large long-bone replica was unsuccessful on each of the 2 low-end printers). Replicas were highly repeatable for all 3-D printers. The 3-D printers overestimated dimensions of large replicas by approximately 1%. CONCLUSIONS AND CLINICAL RELEVANCE Low-end and high-end 3-D printers fabricated CT-derived replicas of bones of small animals with high repeatability. Replicas were slightly larger than the original bones.

Three-dimensional assessment of curvature, torsion, and canal flare index of the humerus of skeletally mature nonchondrodystrophic dogs.

OBJECTIVE To assess 3-D geometry of the humerus of dogs and determine whether the craniocaudal canal flare index (CFI) is associated with specific geometric features. SAMPLE CT images (n = 40) and radiographs (38) for 2 groups of skeletally mature nonchondrodystrophic dogs. PROCEDURES General dimensions (length, CFI, cortical thickness, and humeral head offset), curvature (shaft, humeral head, and glenoid cavity), version (humeral head and greater tubercle), and torsion were evaluated on CT images. Dogs were allocated into 3 groups on the basis of the craniocaudal CFI, and results were compared among these 3 groups. The CT measurements were compared with radiographic measurements obtained for another group of dogs. RESULTS Mean ± SD humeral head version was -75.9 ± 9.6° (range, -100.7° to -59.4°). Mean mechanical lateral distal humeral angle, mechanical caudal proximal humeral angle, and mechanical cranial distal humeral angle were 89.5 ± 3.5°, 50.2 ± 4.5°, and 72.9 ± 7.8°, respectively, and did not differ from corresponding radiographic measurements. Mean humeral curvature was 20.4 ± 4.4° (range, 9.6° to 30.5°). Mean craniocaudal CFI was 1.74 ± 0.18 (range, 1.37 to 2.10). Dogs with a high craniocaudal CFI had thicker cranial and medial cortices than dogs with a low craniocaudal CFI. Increased body weight was associated with a lower craniocaudal CFI. Radiographic and CT measurements of craniocaudal CFI and curvature differed significantly. CONCLUSIONS AND CLINICAL RELEVANCE CT-based 3-D reconstructions allowed the assessment of shaft angulation, torsion, and CFI. Radiographic and CT measurements of shaft curvature and CFI may differ.

Osseointegration of Coarse and Fine Textured Implants Manufactured by Electron Beam Melting and Direct Metal Laser Sintering.

Osseointegrated implants transfer loads from native bone to a synthetic joint and can also function transdermally to provide a stable connection between the skeleton and the prostheses, eliminating many problems associated with socket prostheses. Additive manufacturing provides a cost-effective means to create patient-specific implants and allows for customized textures for integration with bone and other tissues. Our objective was to compare the osseointegration strength of two primary additive manufacturing methods of producing textured implants: electron beam melting (EBM) (mean Ra = 23 µm) and direct metal laser sintering (DMLS) (mean Ra = 10 µm). Due to spatial resolution, DMLS can produce surfaces with a roughness comparable to EBM. Two cohorts of Sprague-Dawley rats received bilateral, titanium implants in their distal femurs and were followed for 4 weeks. The first-cohort animals received EBM implants transcortically in one femur and a DMLS implant in the contralateral femur. The second cohort received DMLS implants (either fine textured or coarse textured to mimic EBM) in the intramedullary canal of each femur. Osseointegration was evaluated through mechanical testing and micro-computed tomography (bone volume fraction [BV/TV] and bone-implant contact [BIC]). The fixation strength of coarse textured implants provided superior interlocking relative to fine textured implants without affecting BV/TV or BIC in both cohorts. Coarse EBM implants in a transcortical model demonstrated an 85% increase in removal torque relative to the fine DMLS textured implants. The thrust load in the intramedullary model saw a 35% increase from fine to coarse DMLS implants.

In vitro evaluation of five canine tibial plateau leveling methods.

OBJECTIVE: To compare application time, accuracy of tibial plateau slope (TPS) correction, presence and magnitude of rotational and angular deformities, and mechanical properties of 5 canine tibial plateau leveling methods. SAMPLE POPULATION: 27 canine tibial replicas created by rapid prototyping methods. PROCEDURE: The application time, accuracy of TPS correction, presence and magnitude of rotational and angular deformation, and construct axial stiffness of 3 internal fixation methods (tibial plateau leveling osteotomy, tibial wedge osteotomy, and chevron wedge osteotomy [CWO]) and 2 external skeletal fixation (ESF) methods (hinged hybrid circular external fixation and wedge osteotomy linear fixation [WOLF]) were assessed. RESULTS: Mean bone model axial stiffness did not differ among methods. Mean application time was more rapid for WOLF than for other methods. Mean TPSs did not differ from our 5 degrees target and were lower for ESF methods, compared with internal fixation methods. Mean postoperative rotational malalignment did not differ from our target or among groups. Mean postoperative medio-lateral angulation did not differ from our target, except for CWO. Internal fixation methods lead to axially stiffer constructs than ESF methods. Reuse of ESF frames did not lead to a decrease in axial stiffness. CONCLUSIONS AND CLINICAL RELEVANCE: The 5 tibial plateau leveling methods had acceptable geometric and mechanical properties. External skeletal fixation methods were more accurate as a result of precise data available for determining the exact magnitude of correction required to achieve a 5 degrees TPS.

Influence of chondrodystrophy and brachycephaly on geometry of the humerus in dogs.

OBJECTIVE: To assess the geometry of canine humeri as seen on radiographs in chondrodystrophic dogs (CD) and brachycephalic dogs (BD) compared to non-chondrodystrophic dogs (NCD). METHODS: Mediolateral (ML) and craniocaudal (CC) radiographs of skeletally mature humeri were used (CD [n = 5], BD [n = 9], NCD [n = 48]) to evaluate general dimensions (length, width, canal flare, cortical thickness), curvature (shaft, humeral head, and glenoid), and angulation (humeral head and condyle). Measurements from CD, BD, and NCD were compared. RESULTS: Mean humeral length was shorter in CD (108 mm) compared to BD (184 mm, p = 0.001) and NCD (183 mm, p <0.001). Craniocaudal cortical thickness at 70% of humeral length and ML cortical thickness at 30%, 50%, and 70% of humeral length were less in CD compared to BD and NCD. Humeral shaft curvature was greater in CD (9.9°) compared to BD (6.7°, p = 0.023). The ratio of glenoid radius of curvature / humeral length was greater for CD (11.1%) compared to NCD (9.7%, p = 0.013). The ratio of humeral width / humeral length was greater for BD (29.4%) compared to NCD (26.2%, p = 0.043). The ratio of glenoid length / humeral length was greater in CD (18.0%) than BD (16.4%, p = 0.048) and NCD (15.6%, p <0.001). CLINICAL SIGNIFICANCE: Bone proportions and curvature in CD differ from BD and NCD. Differences are minor and unlikely to have clinical significance.

Pre-operative simulation of pediatric mastoid surgery with 3D-printed temporal bone models.

OBJECTIVES: As the process of additive manufacturing, or three-dimensional (3D) printing, has become more practical and affordable, a number of applications for the technology in the field of pediatric otolaryngology have been considered. One area of promise is temporal bone surgical simulation. Having previously developed a model for temporal bone surgical training using 3D printing, we sought to produce a patient-specific model for pre-operative simulation in pediatric otologic surgery. Our hypothesis was that the creation and pre-operative dissection of such a model was possible, and would demonstrate potential benefits in cases of abnormal temporal bone anatomy. METHODS: In the case presented, an 11-year-old boy underwent a planned canal-wall-down (CWD) tympano-mastoidectomy for recurrent cholesteatoma preceded by a pre-operative surgical simulation using 3D-printed models of the temporal bone. The models were based on the child's pre-operative clinical CT scan and printed using multiple materials to simulate both bone and soft tissue structures. To help confirm the models as accurate representations of the child's anatomy, distances between various anatomic landmarks were measured and compared to the temporal bone CT scan and the 3D model. RESULTS: The simulation allowed the surgical team to appreciate the child's unusual temporal bone anatomy as well as any challenges that might arise in the safety of the temporal bone laboratory, prior to actual surgery in the operating room (OR). There was minimal variability, in terms of absolute distance (mm) and relative distance (%), in measurements between anatomic landmarks obtained from the patient intra-operatively, the pre-operative CT scan and the 3D-printed models. CONCLUSIONS: Accurate 3D temporal bone models can be rapidly produced based on clinical CT scans for pre-operative simulation of specific challenging otologic cases in children, potentially reducing medical errors and improving patient safety.

In vitro dermal and epidermal cellular response to titanium alloy implants fabricated with electron beam melting.

Transdermal osseointegrated prostheses (TOPs) are emerging as an alternative to socket prostheses. Electron beam melting (EBM) is a promising additive manufacturing technology for manufacture of custom, freeform titanium alloy (Ti6Al4V) implants. Skin ongrowth for infection resistance and mechanical stability are critically important to the success of TOP, which can be influenced by material composition and surface characteristics. We assessed viability and proliferation of normal human epidermal keratinocytes (NHEK) and normal human dermal fibroblasts (NHDF) on several Ti6Al4V surfaces: solid polished commercial, solid polished EBM, solid unpolished EBM and porous unpolished EBM. Cell proliferation was evaluated at days 2 and 7 using alamarBlue(®) and cell viability was analyzed with a fluorescence-based live-dead assay after 1 week. NHDF and NHEK were viable and proliferated on all Ti6Al4V surfaces. NHDF proliferation was highest on commercial and EBM polished surfaces. NHEK was highest on commercial polished surfaces. All EBM Ti6Al4V discs exhibited an acceptable biocompatibility profile compared to solid Ti6Al4V discs from a commercial source for dermal and epidermal cells. EBM may be considered as an option for fabrication of custom transdermal implants.

Comparison of two stretching methods and optimization of stretching protocol for the piriformis muscle.

Piriformis syndrome is an uncommon diagnosis for a non-discogenic form of sciatica whose treatment has traditionally focused on stretching the piriformis muscle (PiM). Conventional stretches include hip flexion, adduction, and external rotation. Using three-dimensional modeling, we quantified the amount of (PiM) elongation resulting from two conventional stretches and we investigated by use of a computational model alternate stretching protocols that would optimize PiM stretching. Seven subjects underwent three CT scans: one supine, one with hip flexion, adduction, then external rotation (ADD stretch), and one with hip flexion, external rotation, then adduction (ExR stretch). Three-dimensional bone models were constructed from the CT scans. PiM elongation during these stretches, femoral neck inclination, femoral head anteversion, and trochanteric anteversion were measured. A computer program was developed to map PiM length over a range of hip joint positions and was validated against the measured scans. ExR and ADD stretches elongated the PiM similarly by approximately 12%. Femoral head and greater trochanter anteversion influenced PiM elongation. Placing the hip joints in 115° of hip flexion, 40° of external rotation and 25° of adduction or 120° of hip flexion, 50° of external rotation and 30° of adduction increased PiM elongation by 30-40% compared to conventional stretches (15.1 and 15.3% increases in PiM muscle length, respectively). ExR and ADD stretches elongate the PiM similarly and therefore may have similar clinical effectiveness. The optimized stretches led to larger increases in PiM length and may be more easily performed by some patients due to increased hip flexion.