Mid-Term Migration Behavior of an Uncemented Proximally Anchored Straight Stem-A Retrospective EBRA Migration Analysis.

BACKGROUND: Aseptic loosening is one of the most-common causes of the failure of cementless stems. Einzel Bild Röntgen Analyse-Femoral Component Analysis (EBRA-FCA) allows the diagnosis of stem migration, which can be considered a factor in predicting implant survival. The current study aimed to present the migration behavior of a tapered proximally anchored straight stem. METHODS: This retrospective study reviewed all consecutive patients who received a cementless CBC straight stem (Mathys AG, Bettlach, Switzerland) between 2005 and 2019. We analyzed the migration pattern using the EBRA-FCA software and reviewed their medical histories. In addition, periprosthetic radiolucency was rated according to the Gruen zones and femoral configuration according to Dorr. RESULTS: A total of 333 stems in 332 patients (female 191; male 141) met our inclusion criteria. The mean age at surgery was 63 (range 21-87) years. Migration analysis by EBRA-FCA showed a mean subsidence of 1.6 mm at final follow-up at 96 months with a maximum noted mean subsidence of 2.0 mm at 72 and 84 months. Dorr Type A showed a tendency of less subsidence than did Dorr Type B and was statistically significant at 6 (p = 0.0396) and 72 months (p = 0.0127). The body mass index (BMI) and increased subsidence were not found to correlate (p > 0.05). For this cohort, the overall femoral revision-free rate was 95.2% and the revision-free rate for aseptic loosening was 99.1%. CONCLUSIONS: The results showed migration behavior in cementless stems with initial increased migration and subsequent secondary stabilization, suggesting an excellent long-term outcome. Stem migration of this tapered proximally anchored stem might be lower in Dorr Type A than in Dorr Type B femurs without being statistically significant at all time points.

Injuries related to sauna bathing.

PURPOSE: Awareness of well-being and health issues have contributed to increased popularity of sauna bathing. However, little is known about potential risks and injuries. The aim of this study was to identify the causes for injuries, the affected body regions and to define recommendations for prevention. METHODS: A retrospective chart data analysis was conducted among patients treated for an injury related to sauna bathing at the local trauma centre of the Medical University of Innsbruck between January 1, 2005 and December 31, 2021. Patients' demographics, the cause for the injury, the diagnosis, the body region of the trauma and the treatment methods were collected. RESULTS: Two hundred and nine patients with injuries related to sauna bathing (83 female [39.7%] and 126 male [60.3%]) were identified. Fifty-one patients showed more than one injuries leading to a total of 274 diagnosis: contusions/distorsions (113; 41.2%), wounds (79; 28.8%), fractures (42; 15.3%), ligament injuries (17; 6.2%), concussions (15; 5.5%), burns (4; 1.5%) and brain bleeding (3; 1.1%). The most common cause for an injury was a slip/fall (157; 57.5%) followed by dizziness/syncope (82; 30.0%). Interestingly, head and face injuries were mostly caused by dizziness/syncope, whereas slip/fall was the leading cause for injuries of foot, hand, forearm and wrist. Nine patients(4.3%) needed surgical treatment mainly due to fractures. Eight patients got injured by wood splinters. One patient sustained grade IIB-III burns lying unconscious with an alcohol intoxication of 3.6‰ in the sauna. CONCLUSION: The main causes for injuries during sauna bathing were slip/falls and dizziness/syncopes. The latter one might be prevented by improved of the personal behaviour (e.g. drink enough water before and after each sauna bathing), whereas slip/falls might be prevented by the revision of safety regulations, particularly the obligation to wear slip resistant slippers. Thus, everyone himself as well as the operators can contribute to reduce injuries related sauna bathing.

Brachytherapy in the Treatment of Soft-Tissue Sarcomas of the Extremities-A Current Concept and Systematic Review of the Literature.

INTRODUCTION: Evidence on the use of brachytherapy in soft-tissue sarcoma (STS) is sparse. Therapy regimens are determined more by local interdisciplinary tumor conferences than by standardized protocols. Patient-specific factors complicate the standardized application of therapy protocols. The individuality of the treatment makes it difficult to compare results. MATERIALS AND METHODS: A comprehensive literature search was conducted, whereby the literature from a period of almost 44 years (1977-2021) was graded and included in this systematic review. For this purpose, PubMed was used as the primary database. Search string included "soft-tissue sarcoma", "brachytherapy", and "extremity." Four independent researchers reviewed the literature. Only full-text articles written in English or German were included. RESULTS: Of the 175 identified studies, 70 were eligible for analysis based on the inclusion and exclusion criteria. The key points to compare were local complications, recurrence rate and correlation with margins of resection, and the use of brachytherapy regarding tumor grading. CONCLUSION: Brachytherapy represents an important subset of radiotherapy techniques used in STSs, whose indications and applications are constantly evolving, and for which a local control rate of 50% to 96% has been reported as monotherapy, depending on risk factors. However, the best benefit is seen in the combination of further resection and brachytherapy, and most authors at many other centers agree with this treatment strategy.

Radiographic and clinical outcome of tibial plateau fractures treated with bone allograft.

BACKGROUND: To determine the clinical outcome of patients who had been treated with bone allografts during open reduction and internal fixation (ORIF) of tibial head fractures. METHODS: Patients who suffered a medial, lateral, or bicondylar fracture of the tibial plateau and underwent surgical treatment by open reduction and internal fixation (ORIF) using human femoral head bone allografts were included. Patients were invited to provide information for the following: Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), EuroQol Five Dimension score (EQ-5D), Lower Extremity Functional Scale (LEFS) and Parker Mobility Score. Bone mineral density (BMD) of the allograft area and the healthy human bone tissue were measured by quantitative computed tomography. RESULTS: A total of 22 patients with a mean follow-up time of 2.88 ± 2.46 years were included in our study. The most common fractures observed in this study were classified as Schatzker II (11 patients, 50.0%) or AO/OTA 41.B3 (12 patients, 54.5%) fractures. Postoperative WOMAC total was 13.0 (IQR = 16.3, range 0-33). Median quality of life (EQ-5D) score was 0.887 ± 0.121 (range 0.361-1.000). Median Lower Extremity Functional Scale (LEFS) score was 57.5 ± 19.0 (range 33-79). Mean Parker Mobility Score was 9 (range 6-9). Median bone mineral density (BMD) for the whole group was 300.04 ± 226.02 mg/cm3 (range - 88.68 to 555.06 mg/cm3) for region of interest (ROI 5) (central), 214.80 ± 167.45 mg/cm3 (range - 7.16 to 597.21 mg/cm3) for ROI 1-4 (marginal zones: medial, lateral, ventral, dorsal) and 168.14 ± 65.54 mg/cm3 (range 17.47-208.97 mg/cm3) for healthy bone tissue (femur and tibia). CONCLUSION: Based on WOMAC scores, LEFS, ambulatory status, and quality of life findings, it can be concluded that following tibial head ORIF with allograft bone patients has promising results.

Operative versus conservative treatment of acute Achilles tendon ruptures: preliminary results of clinical outcome, kinematic MRI and contrast-enhanced ultrasound.

INTRODUCTION: There is no uniform consensus on the gold standard therapy for acute Achilles tendon rupture. The aim of this pilot study was to compare operative and conservative treatment regarding imaging findings and clinical outcome. MATERIALS AND METHODS: Surgically or conservatively treated patients with acute Achilles tendon rupture were retrospectively evaluated. Differences in tendon length and diameter with and without load were analysed using kinematic MRI, tendon perfusion, structural alterations, movement and scar tissue by means of grey-scale and contrast-enhanced ultrasound (CEUS). Intra- and interobserver agreement were recorded. RESULTS: No significant difference was detected regarding clinical outcome, B mode ultrasonography, contrast-enhanced sonography or MRI findings, although alterations in MRI-based measurements of tendon elasticity were found for both groups. Considerable elongation and thickening of the injured tendon were detected in both groups. CONCLUSION: Both, conservative and surgical treatment showed comparable outcomes in our preliminary results and may suggest non-inferiority of a conservative approach.

Common Pitfalls in the Management of Bone Metastasis of the Extremities - a Current Concept and Systematic Review of the Literature.

BACKGROUND/AIM: The surgical treatment of patients with bone metastasis of the extremities poses a set of unique challenges. We aimed to highlight common hazards when treating pathological fractures as well as hazards surrounding assumptions on metastatic status and life expectancy. MATERIALS AND METHODS: This systematic literature review includes studies published from January 1, 1985 to May 7, 2021. Published articles were surveyed using PubMed. Of 99 studies, 32 original articles were found to meet the inclusion criteria. The PRISMA guidelines were used to select articles. RESULTS: Current literature reports a variety of common pitfalls. In order to avoid pitfalls, it is essential to secure the diagnosis. Furthermore, life expectancy must be given consideration when planning surgical therapy. In addition, a well-functioning multidisciplinary team is needed to coordinate further options such as radiation or embolization. CONCLUSION: Despite the fact that the surgical principles for treating bone metastases of the extremities are often to the point, incorporating all the nuances of treatment is a meticulous procedure.

Pathological Fracture of the Tibia as a First Sign of Hyperparathyroidism - A Case Report and Systematic Review of the Current Literature.

BACKGROUND/AIM: Pathological fractures are rare, suspicious and in some cases mentioned as the first sign of a malignant tumor. We present an uncommon case with a pathological fracture of the tibia diaphysis as the first sign of severe hyperparathyroidism. CASE REPORT: We report the case of a female patient who was referred to the emergency department with a history of progressively worsening pain in the lower left leg and an inability to fully bear weight. No history of trauma or any other injury was reported. An x-ray revealed an extensive osteolytic lesion in the tibial shaft with cortical bone destruction. CONCLUSION: Our case, together with very few cases described in the current literature, emphasizes that in the presence of hypercalcemia and lytic lesions primary hyperparathyroidism should always be considered as a differential diagnosis. Lytic bone lesions can lead to pathological fractures and severe impairment of quality of life.

Three-dimensional computed tomography reconstruction improves the reliability of tibial pilon fracture classification and preoperative surgical planning.

PURPOSE: In the present study, we aimed to evaluate the impact of two-dimensional multi-planar computed tomography (2D-MP-CT) scans and three-dimensional surface rendering computed tomography reconstruction (3D-SR-CT) on the inter- and intra-observer reliability of four commonly used classification systems for tibial pilon fractures, and on the reliability and validity of surgical treatment planning for fracture fixation. METHODS: Four observers evaluated computed tomography images of 35 cases with pilon fractures according to the classifications of Rüedi and Allgöwer, AO/OTA, Topliss, and Tang, and recommended a surgical treatment plan, including the surgical approach, implant position, and need for bone graft augmentation. Fractures were first evaluated using 2D-MP-CT, followed by 3D-SR-CT. We calculated the Kappa values for the correlation between the fracture classifications, types of surgical approaches, implant positions, and bone graft recommendations by the observers. Furthermore, we assessed the correlation between the treatment plans recommended by the observers and the actual surgical procedure performed. RESULTS: All classifications showed poor inter-observer reliability and moderate intra-observer reliability with 2D-MP-CT scans. The inter-observer reliability of the Rüedi and Allgöwer, AO/OTA, and Tang classifications improved to moderate, whereas the intra-observer reliability of the AO/OTA classification improved to good with additional 3D-SR-CT. The correlation between the suggested and the actually performed surgical approaches was poor with 2D-MP-CT, but improved to moderate with 3D-SR-CT. The suggested plate positions showed a moderate correlation with the actually performed plating; although the correlation improved significantly, it remained moderate with 3D-SR-CT. CONCLUSION: The use of 3D-SR-CT reconstruction can improve the reliability of the Rüedi and Allgöwer, AO/OTA, and Tang classifications. Furthermore, three-dimensional imaging enables a more valid planning of the surgical approach and implant position.

Effect of pedicle screw augmentation with a self-curing elastomeric material under cranio-caudal cyclic loading-a cadaveric biomechanical study.

BACKGROUND: Pedicle screws can be augmented with polymethylmethacrylate (PMMA) cement through cannulated and fenestrated pedicle screws to improve screw anchorage. To overcome the drawbacks of PMMA, a modified augmentation technique applying a self-curing elastomeric material into a balloon-created cavity prior to screw insertion was developed and evaluated. The aim of the study was to compare the effect of the established and novel augmentation technique on pedicle screw anchorage in a biomechanical in vitro experiment. METHODS: In ten lumbar vertebral bodies, the right pedicles were instrumented with monoaxial cannulated and fenestrated pedicle screws and augmented in situ with 2 ml PMMA. The left pedicles were instrumented with monoaxial cannulated pedicle screws. Prior to left screw insertion, a balloon cavity was created and filled with 3 ml of self-curing elastomer (silicone). Each screw was subjected to a cranio-caudal cyclic load starting from - 50 to 50 N while the upper load was increased by 5 N every 100 load cycles until loosening or 11,000 cycles (600 N). After cyclic loading, a pullout test of the screws was conducted. RESULTS: The mean cycles to screw loosening were 9824 ± 1982 and 7401 ± 1644 for the elastomer and PMMA group, respectively (P = 0.012). The post-cycling pullout test of the loosened screws showed differences in the failure mode and failure load, with predominantly pedicle/vertebrae fractures in the PMMA group (1188.6 N ± 288.1) and screw pullout through the pedicle (671.3 N ± 332.1) in the elastomer group. CONCLUSION: The modified pedicle screw augmentation technique involving a balloon cavity creation and a self-curing elastomeric silicone resulted in a significantly improved pedicle screw anchorage under cyclic cranio-caudal loading when compared to conventional in situ PMMA augmentation.

Biomechanical investigation of lumbar hybrid stabilization in two-level posterior instrumentation.

PURPOSE: Hybrid stabilization with a dynamic implant has been suggested to avoid adjacent segment disease by creating a smoother transition zone from the instrumented segments to the untreated levels above. This study aims to characterize the transition zones of two-level posterior instrumentation strategies for elucidating biomechanical differences between rigid fixation and the hybrid stabilization approach with a pedicle screw-based dynamic implant. METHODS: Eight human lumbar spines (L1-5) were loaded in a spine tester with pure moments of 7.5 Nm and with a hybrid loading protocol. The range of motion (ROM) of all segments for both loading protocols was evaluated and normalized to the native ROM. RESULTS: For pure moment loading, ROM of the segments cranial to both instrumentations were not affected by the type of instrumentation (p > 0.5). The dynamic instrumentation in L3-4 reduced the ROM compared to intact (p < 0.05) but allowed more motion than the rigid fixation of the same segment (p < 0.05). Under hybrid loading testing, the cranial segments (L1-2, L2-3) had a significant higher ROM for both instrumentations compared to the intact (p < 0.05). Comparing the two instrumentations with each other, the rigid fixation resulted in a higher increased ROM of L1-2 and L2-3 than hybrid stabilization. CONCLUSIONS: Regardless of the implant, two-level posterior instrumentation was accompanied by a considerable amount of compensatory movement in the cranial untreated segments under the hybrid protocol. Hybrid stabilization, however, showed a significant reduction of this compensatory movement in comparison to rigid fixation. These results could support the surgical strategy of hybrid stabilization, whereas the concept of topping-off, including a healthy segment, is discouraged.

Fracture reduction by postoperative mobilisation for the treatment of hyperextension injuries of the thoracolumbar spine in patients with ankylosing spinal disorders.

INTRODUCTION: The aim of this study was to evaluate results of surgical stabilisation of hyperextension injuries of the thoracolumbar spine in patients with ankylosing spinal disorders using two different treatment strategies: the conventional open rigid posterior instrumentation and percutaneous less rigid posterior instrumentation. Surgical and non-surgical complications, the postoperative radiological course, and clinical outcome at final follow-up were comparatively assessed. Moreover, we sought to discuss important biomechanical and surgical aspects specific to posterior instrumentation of the ankylosed thoracolumbar spine as well as to elaborate on the advantages and limitations of the proposed new treatment strategy involving percutaneous less rigid stabilisation and fracture reduction by postoperative mobilisation. MATERIALS AND METHODS: Between January 2006 and June 2012, a consecutive series of 20 patients were included in the study. Posterior instrumentation was performed either using an open approach with rigid 6.0 mm bars (open rigid (OR) group) or via a percutaneous approach using softer 5.5 mm bars (percutaneous less rigid (PLR) group). Complications as well as the radiological course were retrospectively assessed, and patient outcome was evaluated at final follow-up using validated outcome scores (VAS Spine Score, ODI, RMDQ, Parker Mobility Score, Barthel Score and WHOQOL-BREF). RESULTS: Surgical complications occurred more frequently in the OR group requiring revision surgery in two patients, while there was no revision surgery in the PLR group. The rate of postoperative complications was lower in the PLR group as well (0.7 vs. 1.3 complications per patient, respectively). Fracture reduction and restoration of pre-injury sagittal alignment by postoperative mobilisation occurred within the first 3 weeks in the PLR group, and within 6 months in the OR group. The clinical outcome at final follow-up was very good in both groups with no relevant loss in VAS Spine Score (pain and function), Parker Mobility Score (mobility), and Barthel Index (social independency) compared to pre-operative values. CONCLUSIONS: This study indicates that the proposed treatment concept involving percutaneous less rigid posterior instrumentation and fracture reduction by postoperative mobilisation is feasible, seems to facilitate adequate reduction and restoration of pre-injury sagittal alignment, and might have the potential to reduce the rate of complications in the management of hyperextension injuries of the ankylosed thoracolumbar spine.

Effect of augmentation techniques on the failure of pedicle screws under cranio-caudal cyclic loading.

PURPOSE: Augmentation of pedicle screws is recommended in selected indications (for instance: osteoporosis). Generally, there are two techniques for pedicle screw augmentation: inserting the screw in the non cured cement and in situ-augmentation with cannulated fenestrated screws, which can be applied percutaneously. Most of the published studies used an axial pull out test for evaluation of the pedicle screw anchorage. However, the loading and the failure mode of pullout tests do not simulate the cranio-caudal in vivo loading and failure mechanism of pedicle screws. The purpose of the present study was to assess the fixation effects of different augmentation techniques (including percutaneous cement application) and to investigate pedicle screw loosening under physiological cyclic cranio-caudal loading. METHODS: Each of the two test groups consisted of 15 vertebral bodies (L1-L5, three of each level per group). Mean age was 84.3 years (SD 7.8) for group 1 and 77.0 years (SD 7.00) for group 2. Mean bone mineral density was 53.3 mg/cm3 (SD 14.1) for group 1 and 53.2 mg/cm3 (SD 4.3) for group 2. 1.5 ml high viscosity PMMA bone cement was used for all augmentation techniques. For test group 1, pedicles on the right side of the vertebrae were instrumented with solid pedicle screws in standard fashion without augmentation and served as control group. Left pedicles were instrumented with cannulated screws (Viper cannulated, DePuy Spine) and augmented. For test group 2 pedicles on the left side of the vertebrae were instrumented with cannulated fenestrated screws and in situ augmented. On the right side solid pedicle screws were augmented with cement first technique. Each screw was subjected to a cranio-caudal cyclic load starting at 20-50 N with increasing upper load magnitude of 0.1 N per cycle (1 Hz) for a maximum of 5000 cycles or until total failure. Stress X-rays were taken after cyclic loading to evaluate screw loosening. RESULTS: Test group 1 showed a significant higher number of load cycles until failure for augmented screws compared to the control (4030 cycles, SD 827.8 vs. 1893.3 cycles, SD 1032.1; p < 0.001). Stress X-rays revealed significant less screw toggling for the augmented screws (5.2°, SD 5.4 vs. 16.1°, SD 5.9; p < 0.001). Test group 2 showed 3653.3 (SD 934) and 3723.3 (SD 560.6) load cycles until failure for in situ and cement first augmentation. Stress X-rays revealed a screw toggling of 5.1 (SD 1.9) and 6.6 (SD 4.6) degrees for in situ and cement first augmentation techniques (p > 0.05). CONCLUSION: Augmentation of pedicle screws in general significantly increased the number of load cycles and failure load comparing to the nonaugmented control group. For the augmentation technique (cement first, in situ augmented, percutaneously application) no effect could be exhibited on the failure of the pedicle screws. By the cranio-caudal cyclic loading failure of the pedicle screws occurred by screw cut through the superior endplate and the characteristic "windshield-wiper effect", typically observed in clinical practice, could be reproduced.

Biomechanical evaluation of a novel dynamic posterior cruciate ligament brace.

BACKGROUND: Use of a rigid brace or cast immobilization is recommended in conservative treatment or postoperative rehabilitation after a posterior cruciate ligament injury. To prevent the loss of knee joint function and muscle activity often associated with this, a flexible knee brace has been developed that allows an adjustable anteriorly directed force to be applied to the calf in order to prevent posterior tibial translation. The purpose of this biomechanical study was to evaluate the impact of this novel dynamic brace on posterior tibial translation after posterior cruciate ligament injury and reconstruction. METHODS: A Telos stress device was used to provoke posterior tibial translation in seven human lower limb specimens, and stress radiographs were taken at 90° of knee flexion. Posterior tibial translation was measured in the native knees with an intact posterior cruciate ligament; after arthroscopic posterior cruciate ligament dissection with and without a brace; and after posterior cruciate ligament reconstruction with and without a brace. The force applied with the brace was measured using a pressure sensor. FINDINGS: Posterior tibial translation was significantly reduced (P=0.032) after application of the brace with an anteriorly directed force of 50N to the knees with the dissected posterior cruciate ligament. The brace also significantly reduced posterior tibial translation after posterior cruciate ligament reconstruction in comparison with reconstructed knees without a brace (P=0.005). INTERPRETATION: Posterior tibial translation was reduced to physiological values using this dynamic brace system that allows an anteriorly directed force to be applied to the calf.

Biomechanical testing of circumferential instrumentation after cervical multilevel corpectomy.

STUDY DESIGN: Biomechanical investigation. PURPOSE: This study describes ex vivo evaluation of the range of motion (ROM) to characterize the stability and need for additional dorsal fixation after cervical single-level, two-level or multilevel corpectomy (CE) to elucidate biomechanical differences between anterior-only and supplemental dorsal instrumentation. METHODS: Twelve human cervical cadaveric spines were loaded in a spine tester with pure moments of 1.5 Nm in lateral bending (LB), flexion/extension (FE), and axial rotation (AR), followed by two cyclic loading periods for three-level corpectomies. After each cyclic loading session, flexibility tests were performed for anterior-only instrumentation (group_1, six specimens) and circumferential instrumentation (group_2, six specimens). RESULTS: The flexibility tests for all circumferential instrumentations showed a significant decrease in ROM in comparison with the intact state and anterior-only instrumentations. In comparison with the intact state, supplemental dorsal instrumentation after three-level CE reduced the ROM to 12% (±10%), 9% (±12%), and 22% (±18%) in LB, FE, and AR, respectively. The anterior-only construct outperformed the intact state only in FE, with a significant ROM reduction to 57% (±35 %), 60% (±27%), and 62% (±35%) for one-, two- and three-level CE, respectively. CONCLUSIONS: The supplemental dorsal instrumentation provided significantly more stability than the anterior-only instrumentation regardless of the number of levels resected and the direction of motion. After cyclic loading, the absolute differences in stability between the two instrumentations remained significant while both instrumentations showed a comparable increase of ROM after cyclic loading. The large difference in the absolute ROM of anterior-only compared to circumferential instrumentations supports a dorsal support in case of three-level approaches.

Primary stiffness of a modified transforaminal lumbar interbody fusion cage with integrated screw fixation: cadaveric biomechanical study.

STUDY DESIGN: In vitro biomechanical study using human fresh-frozen vertebrae. OBJECTIVE: To investigate the influence of the additional screw fixation on the stability of a noncommercially available prototype transforaminal lumbar interbody fusion (TLIF) cage, when used as a stand-alone fusion device and in combination with pedicle screws (PSs). SUMMARY OF BACKGROUND DATA: Generally interbody fusion cages are supplemented by additional fixation devices such as PS. However, such posterior instrumented techniques are associated with additional soft-tissue trauma and potentially increased complication rate. To limit such drawbacks, a conventional posterior TLIF cage was modified to allow supplemental screw fixation to the adjacent vertebral bodies, to increase initial stiffness and possibly allow as a stand-alone posterior interbody cage. METHODS: Six monosegmental lumbar spine segments were loaded in a spine simulator with pure bending moments of 7.5 Nm in lateral bending, flexion/extension, and axial rotation. The following paradigms were tested: intact spines; a destabilized spine (i.e., after discectomy and unilateral facetectomy); and the modified TLIF cage with (i.e., fixed TLIF cage) and without (i.e., TLIF cage) integrated screw fixation as a stand-alone model and with and without additional posterior fixation with bilateral PS. The range of motion (RoM) was recorded by a 3-dimensional motion analysis system. RESULTS: The TLIF cage with integrated screw fixation had minimal additional stabilizing effect in all motion planes with or without supplemental PS fixation. Moreover, compared with the intact spines, the stand-alone TLIF cage with and without integrated screw fixation did not reduce the RoM in any of the 3 motion planes. Comparison of the TLIF cage with integrated screw fixation to the TLIF cage supplemented with PS showed a significantly greater RoM in all testing conditions (P < 0.05). CONCLUSION: In several testing paradigms, the prototype TLIF cage with the integrated screw fixation had limited effect in reducing RoM and providing stability. The PS was the main contributor in reducing RoM in the destabilized spine and remains the current "gold standard" in posterolateral spinal fixation. LEVEL OF EVIDENCE: N/A.

Biomechanical comparison of vertebral augmentation with silicone and PMMA cement and two filling grades.

PURPOSE: Vertebral augmentation with PMMA is a widely applied treatment of vertebral osteoporotic compression fractures. Subsequent fractures are a common complication, possibly due to the relatively high stiffness of PMMA in comparison with bone. Silicone as an augmentation material has biomechanical properties closer to those of bone and might, therefore, be an alternative. The study aimed to investigate the biomechanical differences, especially stiffness, of vertebral bodies with two augmentation materials and two filling grades. METHODS: Forty intact human osteoporotic vertebrae (T10-L5) were studied. Wedge fractures were produced in a standardized manner. For treatment, PMMA and silicone at two filling grades (16 and 35 % vertebral body fill) were assigned to four groups. Each specimen received 5,000 load cycles with a high load range of 20-65 % of fracture force, and stiffness was measured. Additional low-load stiffness measurements (100-500 N) were performed for intact and augmented vertebrae and after cyclic loading. RESULTS: Low-load stiffness testing after cyclic loading normalized to intact vertebrae showed increased stiffness with 35 and 16 % PMMA (115 and 110 %) and reduced stiffness with 35 and 16 % silicone (87 and 82 %). After cyclic loading (high load range), the stiffness normalized to the untreated vertebrae was 361 and 304 % with 35 and 16 % PMMA, and 243 and 222 % with 35 and 16 % silicone augmentation. For both high and low load ranges, the augmentation material had a significant effect on the stiffness of the augmented vertebra, while the filling grade did not significantly affect stiffness. CONCLUSIONS: This study for the first time directly compared the stiffness of silicone-augmented and PMMA-augmented vertebral bodies. Silicone may be a viable option in the treatment of osteoporotic fractures and it has the biomechanical potential to reduce the risk of secondary fractures.

Accuracy of navigation in hip resurfacing with different surgeons and varying anatomy.

The accuracy of a commercial imageless navigation system for hip resurfacing and its reproducibility among different surgeons and for varying femoral anatomy was tested by comparing conventional and navigated implantation of the femoral component on different sawbones in a hip simulator. The position of the component was measured on postoperative radiographs. Variance for varus/valgus alignment and anteversion was higher for conventional implantation. Among the three surgeons, operation time, chosen implant size and anteversion were significantly different for conventional implantation but not for the navigated method. Using navigation, no difference was found for normal and abnormal anatomy. Values obtained with the navigation system were consistent with those measured on radiographs. Navigation appeared to be accurate and helped to reduce outliers. This was true for the three different surgeons and in varying anatomical situations.