Acetabular Revision with McMinn Cup: Development and Application of a Patient-Specific Targeting Device.

BACKGROUND: Surgeries of severe periacetabular bone defects (Paprosky ≥ 2B) are a major challenge in current practice. Although solutions are available for this serious clinical problem, they all have their disadvantages as well as their advantages. An alternative method of reconstructing such extensive defects was the use of a cup with a stem to solve these revision situations. As the instrumentation offered is typically designed for scenarios where a significant bone defect is not present, our unique technique has been developed for implantation in cases where reference points are missing. Our hypothesis was that a targeting device designed based on the CT scan of a patient's pelvis could facilitate the safe insertion of the guiding wire. METHODS: Briefly, our surgical solution consists of a two-step operation. If periacetabular bone loss was found to be more significant during revision surgery, all implants were removed, and two titanium marker screws in the anterior iliac crest were percutaneously inserted. Next, by applying the metal artifact removal (MAR) algorithm, a CT scan of the pelvis was performed. Based on that, the dimensions and positioning of the cup to be inserted were determined, and a patient-specific 3D printed targeting device made of biocompatible material was created to safely insert the guidewire, which is essential to the implantation process. RESULTS: In this study, medical, engineering, and technical tasks related to the design, the surgical technique, and experiences from 17 surgical cases between February 2018 and July 2021 are reported. There were no surgical complications in any cases. The implant had to be removed due to septic reasons (independently from the technique) in a single case, consistent with the septic statistics for this type of surgery. There was not any perforation of the linea terminalis of the pelvis due to the guiding method. The wound healing of patients was uneventful, and the implant was fixed securely. Following rehabilitation, the joints were able to bear weight again. After one to four years of follow-up, the patient satisfaction level was high, and the gait function of the patients improved a lot in all cases. CONCLUSIONS: Our results show that CT-based virtual surgical planning and, based on it, the use of a patient-specific 3D printed aiming device is a reliable method for major hip surgeries with significant bone loss. This technique has also made it possible to perform these operations with minimal X-ray exposure.

Custom-made 3D printing-based cranioplasty using a silicone mould and PMMA.

All types of cranioplasty techniques restore the morphology of the skull and affect patient aesthetics. Safe and easy techniques are required to enhance patients' recovery and the rehabilitation process. We propose a new method of cranioplasty. The 3-dimensional (3D) reconstruction of a thin-layer computed tomography (CT) scan of the skull was used to reflect the intact side onto the defect and subtract the overlapping points from one another. In this way, a 3D model of the planned implant can be built in the required shape and size. The precise fit of the implant can be checked by printing the defective part of the skull in case it can be modified. A sterilisable silicone mould based on the finalized model was created afterwards. Polymethyl methacrylate implants were prepared directly in an aseptic environment in the operating room during surgery. Between 2005 and 2020, we performed 54 cranioplasties on 52 patients whose craniotomies were performed previously for indications of traumatic brain injury, stroke or tumour surgeries. No technical problems were noted during the operations. In 2 cases, septic complications that occurred were not connected to the technique itself, and the implants were removed and later replaced. Our proposed technique based on 3D-printed individual silicone moulds is a reliable, safe, easily reproducible and low-cost method to repair different skull defects.

Comparative Analysis of Bone Ingrowth in 3D-Printed Titanium Lattice Structures with Different Patterns.

In this study, metal 3D printing technology was used to create lattice-shaped test specimens of orthopedic implants to determine the effect of different lattice shapes on bone ingrowth. Six different lattice shapes were used: gyroid, cube, cylinder, tetrahedron, double pyramid, and Voronoi. The lattice-structured implants were produced from Ti6Al4V alloy using direct metal laser sintering 3D printing technology with an EOS M290 printer. The implants were implanted into the femoral condyles of sheep, and the animals were euthanized 8 and 12 weeks after surgery. To determine the degree of bone ingrowth for different lattice-shaped implants, mechanical, histological, and image processing tests on ground samples and optical microscopic images were performed. In the mechanical test, the force required to compress the different lattice-shaped implants and the force required for a solid implant were compared, and significant differences were found in several instances. Statistically evaluating the results of our image processing algorithm, it was found that the digitally segmented areas clearly consisted of ingrown bone tissue; this finding is also supported by the results of classical histological processing. Our main goal was realized, so the bone ingrowth efficiencies of the six lattice shapes were ranked. It was found that the gyroid, double pyramid, and cube-shaped lattice implants had the highest degree of bone tissue growth per unit time. This ranking of the three lattice shapes remained the same at both 8 and 12 weeks after euthanasia. In accordance with the study, as a side project, a new image processing algorithm was developed that proved suitable for determining the degree of bone ingrowth in lattice implants from optical microscopic images. Along with the cube lattice shape, whose high bone ingrowth values have been previously reported in many studies, it was found that the gyroid and double pyramid lattice shapes produced similarly good results.

The roof step cut: A novel technique for bony reconstruction of acetabular roof deficiency during total hip replacement.

OBJECTIVES: This study aims to present a new technique, the roof step cut (RSC), for acetabular augmentation of hip dysplasia. PATIENTS AND METHODS: Between December 2008 and March 2020, we applied the RSC technique in a total of 48 hips of 41 patients (2 males, 39 females; mean age: 50.1±9.5 years; range, 30 to 75 years) with Hartofilakidis type A, B, C hip dysplasia. The RSC technique uses a L-shaped graft cut from the femoral head. The graft is partially inside the acetabulum and partially on the lateral aspect of the ilium. It is fixed with two screws at a 45° angle allowing simultaneous distalization and lateral covering of the cementless cup. Follow-up was done at six weeks, three months, and annually thereafter using standard pelvis anteroposterior X-ray and function scores. The 99mTc bone scintigraphy examination was also performed at around two weeks, six months, and 12 months postoperatively to evaluate the healing process of the graft. RESULTS: The mean follow-up time was 59.6±25.6 (range, 12 to 109) months. No significant center-edge angle changes and no contiguous radiolucent zones at the bone prosthesis interface were observed at the final follow-up. The single-photon emission tomography (SPECT) showed the activity of the bone graft gradually increased after surgery and became almost the same as the reference area after 12 months. Functional evaluation showed a significant improvement after the operation. No complication directly related to the technique was observed. CONCLUSION: In the short-term follow-up, the RSC technique is a reliable procedure for acetabular augmentation of hip dysplasia, providing enough coverage for the cementless cup and assuring proper stability.

Critical analysis of in vitro stability testing of spinal implants and proposal for standardization.

BACKGROUND: The American Society for Testing and Materials (ASTM), considered the gold standard worldwide, requires only testing in physiological saline solution to simulate in vivo conditions in standard testing of spinal implants. RESEARCH DESIGN AND METHODS: We conducted an in vitro study to identify an industrial lubricant with characteristics that are most similar to those of biologically lubricating fat, blood, and tissue fluids. The use of such a material could standardize the results of in vitro mechanical tests for better clinical applications. RESULTS: Our study has shown that the lubricity of physiological saline was well below that of human soft tissues and tissue fluids, and among the motor oils, Castrol GTX3 provided a testing environment similar to that of a living organism. CONCLUSIONS: With the intention of standardizing and preventing a biological hazard, we have developed a reproducible mechanical testing proposal based on our experiments, which, in addition, would allow us to avoid many misunderstandings and contingencies.

[Preparation and characteristics of aerogel-based bioactive materials used in dentistry]. / Fogászatban alkalmazható aerogél alapú bioaktív anyagok eloállítása és sajátosságai.

A variety of bioactive materials have been investigated as substitute materials for diseased or damaged bone tissues in dentistry. The aim of this study was to prepare mesoporous silica containing biomaterials by sol-gel technology. These materials may be combinated with hydroxyapatite and ß-tricalcium phosphate, as bioactive agents. The synthesis and testing of important physical parameters were performed. Based on these measurements, the silica aerogel can be an applicable material in the dental field in the future.

Application of a vibrating device for the prevention of flexion contracture after total knee arthroplasty.

Our research team developed a new, heel support-based static and vibrating complementary treatment method for the prevention of flexion contractures often arising after total knee arthroplasty. We examined the efficiency of the method performing a randomized clinical trial with 144 patients undergoing total knee replacement. Seventy-nine patients were treated for 1 week with a generally used continuous passive motion (CPM) device complemented with our new method, which was based on the application of a static and an alternating heel support. The 65 patients in the control group were treated with only a CPM device as in usual clinical practice. The femoro-tibial angle was measured immediately following surgery, and after 1 week of treatment. At the end of the 1 week treatment, the target extension angle (0° ± 5°) was achieved by significantly more patients with the new combined method. This way the elevated heel rest and the vibrating device proved to be a good adjunct treatment along with the CPM used in routine clinical practice in the first place for the prevention of flexion contractures.

The biological and biomechanical comparison of two bulk bone graft techniques used in case of dysplastic acetabulum.

BACKGROUND: The incorporation of bulk bone grafts in the replacement of dysplastic acetabulum is determined by the biological environment of the recipient site, the size of the contact surface, and the stability of the osteosynthesis used. Based on these, the present study compares the Harris acetabular plasty used routinely by us with the Radojevic L-shaped graft technique. METHODS: For our measurements, we used 20 hemi-pelvises removed from 10 cadavers. In 10 cases, acetabular plasty according to Harris, in 10 cases Radojevic L-plasty, was performed. The biological environment was analyzed; with geometric calculations, the contact surface was determined, and with a material testing apparatus, the primary stability of the osetosynthesis was measured. For the measurements, a new method was developed. RESULTS: The Radojevic technique provides a better biological environment for graft ingrowth. The contact surface is nearly twice as much as in Harris plasty. No significant difference was found in the primary stability of the osteosynthesis used. The deviation on the value of the stability measurements is explained by the differences in the bone quality of the cadavers used. CONCLUSIONS: Based on the 3 aspects examined, the Radojevic L-shaped graft technique has similar stability when compared to the Harris acetabular plasty, but provides better biological circumstances and larger graft host bone contact. Based on this, we started using the L-shaped technique in our department.

Our experience and early results with a complementary implant for the correction of major thoracic curves.

PURPOSE: In our article, we would like to introduce a new auxiliary implant called the CAB hook, for use in posterior approach scoliosis surgery. METHODS: Since 2007, we operated 42 patients with the CAB hook with an average preoperative Cobb angle of 59.3° (28°-92°). In three cases, the posterior approach was preceded by ventral release and Halo traction. In four cases, besides the CAB hooks, SCS hooks and pedicular screws, in three cases both CAB and SCS hooks, in nine cases CAB hooks with SCS pedicular screws, and in 23 cases, only CAB were used. The average follow-up time was 21.6 month (2-51). RESULTS: All the patients are satisfied with the results. No reoperation was needed due to the loss of correction, pain, implant failure, or infection. The average postoperative Cobb angle decreased to 24.7° (4°-60°). Based on this we calculated the Cincinnati Correction Index (CCI), which was 1.53 (0.7-4.8), which means that our correction exceeded the flexibility of the spine based on the lateral bending X-ray by 53 %. CONCLUSION: As with all new surgical techniques and implants after the short learning curve, we were able to improve the degree of correction and decrease the time of surgery. One of the advantages of the CAB hook is that besides a few implant-specific instruments, no special instrumentation is required for insertion, and image intensifier need not be used.

Biomechanical comparison of two stabilization techniques for unstable sacral fractures.

AIM: The purpose of the study was to assess the stability provided by an ilio-iliac dorsal plate fixation technique using an AO narrow DCP on the pelvic brim in vertically and rotationally unstable type-C pelvic ring injuries. MATERIALS AND METHODS: We examined 12 fresh cadaver pelvises in a single limb stance load. A type-C pelvic ring injury (a type I lateral sacral fracture in the classification of Denis with symphysis pubis rupture) was performed on the cadaver specimen and fixed with a four-hole narrow dynamic compression plate to stabilize the symphysis pubis rupture; the sacrum fracture was stabilized either anteriorly with two 3-hole reconstruction plates ("anterior plate osteosynthesis") or with a posterior fixation using a 12-hole narrow DCP. A cyclic load of between 100 and 250 N was applied to the fifth lumbar vertebra of the specimen. An extensometer was attached to both sides of the sacrum fracture to detect movements at the fracture site. RESULTS: We were able to achieve usable measurements in nine specimens. Three measurements were performed on each specimen, and the movements recorded at the fracture gap in trans-sacral plate fixation were higher than or similar to those observed for anterior plate synthesis in 23 out of 27 cases. CONCLUSION: Dorsal ilio-iliac bridge plate fixation provides somewhat reduced stability compared to anterior plate fixation, but the difference is not significant.

Biomechanical examination of the thoracic spine--the axial rotation moment and vertical loading capacity of the transverse process.

Our objective was to examine the load-bearing capacity of the transverse processes of human cadaveric thoracic vertebrae to vertical loads and axial rotation moments (i.e., moment applied in the transverse plane). A secondary objective was to examine the effect of the attached rib stumps. We wanted to demonstrate that the transverse process is durable enough to support the CAB hook--a complementary hook to the CD system--and can handle the vertical load or axial rotation moment during correction of scoliosis. We used 107 thoracic vertebrae removed from 10 cadavers. They were prepared in vertebral pairs, and were fixed into a material testing apparatus. Superoinferior vertical loads and axial rotation moments were applied to the transverse process using the CAB hooks at a rate of 30 mm/min and 8.5°/s respectively until it fractured. We recorded 142 measurements, 99 were for vertical load and 43 for axial rotation moment. The average ultimate vertical load was 338 (SD = 128) N and the average ultimate axial rotation moment was 14.4 (SD = 4.52) Nm. The ultimate axial rotation moment for specimens with rib stumps attached was significantly greater than for specimens without rib stumps 15.9 (SD = 4.1) Nm versus 12.5 (SD = 4.4) Nm. Our results showed that both the vertical and axial rotation loading capability of the transverse process are large enough to withstand significant correctional forces, without fracture, through the CAB hooks.

Biomechanical comparison of three cemented stem removal techniques in revision hip surgery.

BACKGROUND: There are various techniques available to remove a cemented femoral component and distal cement in the case of septic or aseptic loosening, periprosthetic or component fracture. The present study describes the mechanical effects of three techniques: the transfemoral approach (TFA), the distal fenestration technique (DF) and the retrograde stem removal technique (RSR). An experiment on cadaveric femora was performed to establish if there are any differences in the resistance to fracture in and between the various groups. METHODS: Twenty-two paired femora were recovered from human cadavers and were frozen. These were later subdivided into three groups to provide similar specimens in each group (TFA, DF, RSR). The femora were tested using an Instron 8874 biaxial testing system. The torque required to fracture was measured. Intra- and intergroup statistical analysis was performed. RESULTS: In the TFA group, the force required till fracture was significantly less than in controls. (p = 0.018). Similar results were found in the DF group (p = 0.048). There was no difference in the RSR group (p = 1). Intergroup analysis showed the following: Femora in the TFA group required significantly less force to fracture than specimens in the DF group (p = 0.018) or the RSR group (p = 0.0055). Femora in the DF group required significantly less force to fracture than specimens in the RSR (p = 0.037). CONCLUSIONS: The TFA technique decreases the mechanical resistance of human cadaveric femora very significantly against rotational forces. The DF technique in the same setup also significantly decreases the resistance of bone, whilst no significant change is seen with the RSR technique.

Ex vivo and in vitro determination of the axial rotational axis of the human thoracic spine.

STUDY DESIGN: Different geometrical and biomechanical evaluations were performed to determine the axial rotational axis of the thoracic spine. OBJECTIVE: Our research group has been dealing with the determination of the axial rotational axis of the thoracic spine. Here, we would like to present the geometrical and experimental results of our trials. With our experiments, we are trying to evaluate the contradictions of the related literature. SUMMARY OF BACKGROUND DATA: In the present state, we know quite a lot about the biomechanics of healthy and pathologic spines. Nevertheless, for a seemingly simple question like the position of the axial rotation of the thoracic spine, the literature gives contradicting results. During correction of a scoliotic deformity, when trying to correct the pathologic rotation, not knowing the physiologic rotation can be hazardous. METHODS: We wanted to clarify this question, so we examined the thoracic spine in many different ways. First, we examined the problem from a geometrical point of view then we modeled the different rotational axes by studying the change in volume of the spinal canal. Finally, we used cadaver spines that we rotated and examined with radiographs and digital pictures. RESULTS: Based on the results, we made the following establishments: most of the center points fell on the anterior half of the vertebral body or into the spinal canal, basically on the midsagittal axis of the vertebra. The rib cage has a significant effect on the place of the axis. After removing the ribs, the axis of axial rotation moved forward. CONCLUSIONS: After evaluating the results, we determined that the most likely place for the rotational axis is on the median-sagittal plane, in the anterior portion of the spinal canal.