Interleukin-6 as a critical inflammatory marker for early diagnosis of surgical site infection after spine surgery.

PURPOSE: Early diagnosis of surgical site infections (SSIs) could prevent surgical revision. Inflammatory markers (IMs), such as procalcitonin (PCT), interleukin-6 (IL-6), and tumor necrosis factor α (TNF-α), seem more accurate in diagnosing SSI than C-reactive protein (CRP) and white blood cell (WBC) count. The aim was to compare the predictive values of CRP, WBC count, PCT, IL-6, and TNF-α in SSI detection. METHODS: A total of 130 patients undergoing dorsal spondylodesis from 2019 to 2024 were enrolled in a prospective diagnostic study at a maximum care spine center. IMs were measured preoperatively and on the postoperative days (PODs) 1, 2, 3, 5, and 7. Patients with high suspicion of SSI underwent revision surgery. SSI was diagnosed when the microbiological evidence was positive. Patients were divided a posteriori into the non-infection and infection groups. RESULTS: IMs of 118 patients (66.9 ± 13.0 years, 61.0% females) were measured. Fifteen of the 118 patients (12.7%) developed an SSI. The groups differed with respect to existing hypertension, number of instrumented segments, region of surgery, CRPPOD1,7, PCTPOD7, and IL-6POD3,5,7. Binary logistic regression for SSI detection including these parameters showed an area under the curve (AUC) of 0.88 (95% CI 0.79-0.98; P < 0.001). The main effect for SSI detection was maintained by IL-6POD7 (odds ratio = 1.13; 95% CI 1.05-1.23; P = 0.001), which itself showed an AUC of 0.86 (95% CI 0.75-0.97). CONCLUSION: Compared to CRP, WBC count, PCT, and TNF-α, IL-6 seems to be the critical IM for the early detection of an SSI. TRIAL REGISTRATION: drks.de: DRKS00033773, date of registration: 29.02.2024, retrospectively registered; Postoperative Markers of Inflammation in Spine Surgery (POMIS) Trial.

Psychostimulants Modafinil, Atomoxetine and Guanfacine Impair Bone Cell Differentiation and MSC Migration.

Attention deficit hyperactivity disorder (ADHD) is one of the most common worldwide mental disorders in children, young and adults. If left untreated, the disorder can continue into adulthood. The abuse of ADHD-related drugs to improve mental performance for studying, working and everyday life is also rising. The potentially high number of subjects with controlled or uncontrolled use of such substances increases the impact of possible side effects. It has been shown before that the early ADHD drug methylphenidate influences bone metabolism negatively. This study focused on the influence of three more recent cognitive enhancers, modafinil, atomoxetine and guanfacine, on the differentiation of mesenchymal stem cells to osteoblasts and on their cell functions, including migration. Human mesenchymal stem cells (hMSCs) were incubated with a therapeutic plasma dosage of modafinil, atomoxetine and guanfacine. Gene expression analyses revealed a high beta-2 adrenoreceptor expression in hMSC, suggesting it as a possible pathway to stimulate action. In bone formation assays, all three cognitive enhancers caused a significant decrease in the mineralized matrix and an early slight reduction of cell viability without triggering apoptosis or necrosis. While there was no effect of the three substances on early differentiation, they showed differing effects on the expression of osterix (OSX), receptor activator of NF-κB ligand (RANKL) and osteoprotegerin (OPG) in the later stages of osteoblast development, suggesting alternative modes of action. All three substances significantly inhibited hMSC migration. This effect could be rescued by a selective beta-blocker (Imperial Chemical Industries ICI-118,551) in modafinil and atomoxetine, suggesting mediation via beta-2 receptor stimulation. In conclusion, modafinil, atomoxetine and guanfacine negatively influence hMSC differentiation to bone-forming osteoblasts and cell migration through different intracellular pathways.

Outcome after Posterior Vertebral Column Resection in Patients with Severe Osteoporotic Fractures-A Retrospective Analysis from Two Centers.

Background and Objectives: In osteoporotic fractures of the spine with resulting kyphosis and threatening compression of neural structures, therapeutic decisions are difficult. The posterior vertebral column resection (pVCR) has been described by different authors as a surgical treatment in a single-stage posterior procedure. The aim of this study is to evaluate midterm outcomes of patients treated by pVCR due to severe osteoporotic fractures. Materials and Methods: Retrospective data analysis of all the patients treated for osteoporotic fractures by pVCR from 2012-2020 at two centers was performed. Demographic data, visual analog scale (VAS), Frankel scale (FS), Karnofsky performance status (KPS), radiological result and spinal fusion rates were evaluated. Results: A total of 17 patients were included. The mean age was 70 ± 10.2 y. The mean VAS decreased significantly from 7.7 ± 2.8 preoperatively to 3.0 ± 1.6 at last follow-up (p < 0.001) and the segmental kyphosis decreased from 29.4 ± 14.1° to 7.9 ± 8.0° (p < 0.001). The neurologic function on the FS did not worsen in any and improved in four of the patients. The median KPS remained stable over the whole observation period (70% vs. 70%). Spinal fusion was observed in nine out of nine patients who received CT follow-up >120 days after index surgery. Conclusions: This study showed that pVCR is a safe surgical technique with few surgical complications and no neurological deterioration considering the cohort. The patients' segmental kyphosis and VAS improved significantly, while the KPS remained stable.

Cortical threaded pedicle screw improves fatigue strength in decreased bone quality.

PURPOSE: Inadequate anchoring of pedicle screws in vertebrae with poor bone quality is a major problem in spine surgery. The aim was to evaluate whether a modified thread in the area of the pedicle could significantly improve the pedicle screw fatigue strength. METHODS: Fourteen human cadaveric vertebral bodies (L2 and L3) were used for in vitro testing. Bone density (BMD) was determined by quantitative computed tomography. Vertebral bodies were instrumented by standard pedicle screws with a constant double thread on the right pedicle and a partial doubling of the threads-quad thread-(cortical thread) in the area of the pedicle on the left pedicle. Pulsating sinusoidal, cyclic load (0.5 Hz) with increasing peak force (100 N + 0.1 N/cycles) was applied orthogonal to the screw axis. The baseline force remained constant (50 N). Fatigue test was terminated after exceeding 5.4-mm head displacement (~ 20° screw tilting). RESULTS: The mean fatigue load at failure was 264.9 N (1682 cycles) for the standard screws and was increased significantly to 324.7 N (2285 cycles) by the use of cortical threaded screws (p = 0.014). This effect is particularly evident in reduced BMD (standard thread 241.2 N vs. cortical thread 328.4 N; p = 0.016), whereas in the group of vertebrae with normal BMD no significant difference could be detected (standard thread 296.5 N vs. cortical thread 319.8 N; p = 0.463). CONCLUSIONS: Compared to a conventional pedicle screw, the use of a cortical threaded pedicle screw promises superior fatigue load in vertebrae with reduced bone quality.

Cage or Pelvic Graft-Study on Bony Fusion of the Ventral Thoracic and Lumbar Spine in Traumatic Vertebral Fractures.

Background and Objectives: Stabilization of the spine by cage implantation or autologous pelvic bone graft are surgical methods for the treatment of traumatic spine fractures. These methods serve to stably re-adjust the spine and to prevent late detrimental effects such as pain or increasing kyphosis. They both involve ventral interventions using interbody fusion to replace the intervertebral disc space between the vertebral bodies either by cages or autologous pelvic bone grafts. We examined which of these methods serves the patients better in terms of bone fusion and the long-term clinical outcome. Materials and Methods: Forty-six patients with traumatic fractures (12 cages; mean age: 54.08/34 pelvic bone grafts; mean age: 42.18) who received an anterior fusion in the thoracic or lumbar spine were included in the study. Postoperative X-ray images were evaluated, and fusion of the stabilized segment was inspected by two experienced spine surgeons. The time to discharge from hospital and gender differences were evaluated. Results: There was a significant difference of the bone fusion rate of patients with autologous pelvic bone grafts in favor of cage implantation (p = 0.0216). Also, the stationary phase of patients who received cage implantations was clearly shorter (17.50 days vs. 23.85 days; p = 0.0089). In addition, we observed a significant gender difference with respect to the bony fusion rate in favor of females treated with cage implantations (p < 0.0001). Conclusions: Cage implantations after spinal fractures result in better bony fusion rates as compared to autologous pelvic bone grafts and a shorter stay of the patients in the hospital. Thus, we conclude that cage implantations rather than autologous pelvic bone grafts should be the preferred surgical treatment for stabilizing the spine after fracture.

Influence of Hyponatremia on Spinal Bone Quality and Fractures Due to Low-Energy Trauma.

Background and Objectives: Hyponatremia is the most common electrolyte disorder in elderly and associated with increased risk of falls. Clinical studies as well as small animal experiments suggested an association between chronic hyponatremia and osteoporosis. Furthermore, it has been assumed that subtle hyponatremia may be an independent fracture risk in the elderly. Therefore, this study was designed to evaluate the possible influence of chronic hyponatremia on osteoporosis and low-energy fractures of the spine. Materials and Methods: 144 patients with a vertebral body fracture (mean age: 69.15 ± 16.08; 73 females and 71 males) due to low-energy trauma were treated in a level one trauma center within one year and were included in the study. Chronic hyponatremia was defined as serum sodium < 135 mmol/L at admission. Bone mineral density (BMD) of the spine was measured using quantitative computed tomography in each patient. Results: Overall, 19.44% (n = 28) of patients in the low-energy trauma group had hyponatremia. In the group with fractures caused by low-energy trauma, the proportion of hyponatremia of patients older than 65 years was significantly increased as compared to younger patients (p** = 0.0016). Furthermore, there was no significant gender difference in the hyponatremia group. Of 28 patients with chronic hyponatremia, all patients had decreased bone quality. Four patients showed osteopenia and the other 24 patients even showed osteoporosis. In the low-energy trauma group, the BMD correlated significantly with serum sodium (r = 0.396; p*** < 0.001). Conclusions: The results suggest that chronic hyponatremia affects bone quality. Patients with chronic hyponatremia have an increased prevalence of fractures after low-energy trauma due to a decreased bone quality. Therefore, physicians from different specialties should focus on the treatment of chronic hyponatremia to reduce the fracture rate after low-energy trauma, particularly with elderly patients.

Reduced cement volume does not affect screw stability in augmented pedicle screws.

PURPOSE: Cement augmentation of pedicle screws is able to improve screw anchorage in osteoporotic vertebrae but is associated with a high complication rate. The goal of this study was to evaluate the impact of different cement volumes on pedicle screw fatigue strength. METHODS: Twenty-five human vertebral bodies (T12-L4) were collected from donors between 73 and 97 years of age. Bone density (BMD) was determined by quantitative computed tomography. Vertebral bodies were instrumented by conventional pedicle screws, and unilateral cement augmentation was performed. Thirteen vertebrae were augmented with a volume of 1 ml and twelve with a volume of 3 ml bone cement. A fatigue test was performed using a cranial-caudal sinusoidal, cyclic load (0.5 Hz) with increasing compression force (100 N + 0.1 N/cycles). RESULTS: The load to failure was 183.8 N for the non-augmented screws and was increased significantly to 268.1 N (p < 0.001) by cement augmentation. Augmentation with 1 ml bone cement increased the fatigue load by 41% while augmentation with 3 ml increased the failure load by 51% compared to the non-augmented screws, but there was no significant difference in fatigue loads between the specimens with screws augmented with 1 ml and screws augmented with 3 ml of bone cement (p = 0.504). CONCLUSION: Cement augmentation significantly increases pedicle screw stability. The benefit of augmentation on screw anchorage was not significantly affected by reducing the applied volume of cement from 3 ml to 1 ml. Considering the high risk of cement leakage during augmentation, we recommend the usage of a reduced volume of 1 ml bone cement for each pedicle screw. These slides can be retrieved under Electronic Supplementary Material .

Vertical Expandable Rib-based Distraction Device for Correction of Congenital Scoliosis in Children of 3 Years of Age or Younger: A Preliminary Report.

BACKGROUND: This study was designed to evaluate the treatment outcome of very young children with congenital scoliosis aged 3 years or under after surgery with a vertical expandable prosthetic titanium rib (VEPTR)-based distraction device. METHODS: A retrospective study of 13 children undergoing implantation of a vertical expandable rib-based distraction device. From September 2007 to June 2018, 13 children (7 male and 6 female patients) with congenital scoliosis were followed after treatment with a VEPTR. The outcome parameters were complications, thoracic height, kyphosis, lordosis, and coronal major scoliosis curve. In addition, the American Society of Anaesthesiologists (ASA) score, assisted ventilation rating, and hemoglobin and body mass index were analyzed. Data were examined separately by 2 investigators. RESULTS: The mean age at initial surgical treatment was 24.4±10.6 months, follow-up was 91.5±23.1 months. The mean number of surgical procedures per patient was 14±3.9 (total 182 operations). Apart from planned operations every 6 months, 5 unplanned operations (2.7%) were performed. The major scoliosis curve improved significantly from 55.2±21.9 degrees to 40.5±18.7 degrees, thoracic spine height T1-T12 significantly from 111±12 mm to 137±23 mm, T1-S1 height significantly from 211±13 mm to 252±36 mm and space available for the lung from 80.9%±11.3% to 84.4%±8.8% (preoperatively and at 5-y follow-up, respectively). Kyphosis increased significantly from 30±21.4 degrees to 42.6±23.5 degrees and lordosis from 32.4±20.9 degrees to 37.6±10.4 degrees. Hemoglobin levels were virtually unchanged. Weight increased from 10.6±2.8 kg to 20.2±5.0 kg at final follow-up, but body mass index decreased from 16.6±3.7 kg/m² to 15.7±2.9 kg/m². CONCLUSIONS: The expandable rib-based distraction device is an effective method to treat severe congenital scoliosis in very young children. It can control the deformity and promotes spinal and thoracic growth. LEVEL OF EVIDENCE: Level IV.

Posterior vertebral column resection with 360-degree osteosynthesis in osteoporotic kyphotic deformity and spinal cord compression.

Osteoporotic fractures with severe kyphosis and neurologic deficits often require decompression and stabilisation. To reduce the risk of procedure-related complications, single-stage posterolateral vertebrectomy and a 360-degree fusion can be performed. An adequate reduction of kyphotic deformity through this approach has not been reported. The aim of this study is to investigate the efficacy of kyphotic deformity reduction by this approach in osteoporotic situation. A retrospective analysis and chart review was performed for 10 consecutive patients who underwent posterolateral decompression and posterior vertebrectomy with dorsal mesh stabilisation and reduction of kyphotic deformity. Preoperative back pain was 8.6 on a visual analogue scale; it was reduced to 5.5 at discharge and 3.7 at the latest follow-up (18 months). The Frankel score improved from D to E (three patients) or was equal (E). Radiological segmental kyphosis was corrected from a mean of 25° to 5° (p < 0.008) postoperatively with a loss of 3° at follow-up (p < 0.005). Single-stage posterolateral vertebrectomy allow for a fast and safe reconstitution/preservation of neurological function in patients with osteoporotic fracture and kyphotic deformity. A significant correction of often-accompanied hyperkyphosis is possible without neurological deterioration and with an improved sagittal profile and good pain reduction.

Time to augment?! Impact of cement augmentation on pedicle screw fixation strength depending on bone mineral density.

PURPOSE: Cement augmentation of pedicle screws is known to increase their mechanical strength. Aim was to evaluate the impact of cement augmentation on pedicle screw fatigue strength in dependence of the bone mineral density (BMD). METHODS: Twenty-one human L2 vertebral bodies from donors between 19 and 96 years of age were used for in vitro experiments. BMD was measured using quantitative computed tomography (QCT). Two pedicle screws were inserted in each specimen and unilaterally augmented with bone cement. Fatigue testing was performed using a cranio-caudal sinusoidal, cyclic load (0.5 Hz) with increasing compression force (100 N + 0.1 N/cycles). Results were evaluated for the BMD groups: normal: BMD > 120 mg/cm3, osteopenic: BMD 80-120 mg/cm3, and osteoporotic: BMD < 80 mg/cm3 bone mass. RESULTS: There was a significant correlation between fatigue force and BMD for the non-augmented and augmented screws (non-augmented R2 = 0.839, p < 0.001; augmented R2 = 0.551, p < 0.001). There was a significantly increased fatigue strength of the augmented screws over the non-augmented screws in the osteoporotic group (p = 0.001), while the differences in the other groups were not significant (normal p = 0.818/osteopenic p = 0.132). CONCLUSIONS: The benefit of pedicle screw cement augmentation significantly depends on the bone mineral density and has the greatest extent of increased fatigue strength in osteoporotic vertebrae. Preoperative measurement of the BMD is strongly recommended to predict the benefit of augmentation and reinforce the decision for cement augmentation. These slides can be retrieved under Electronic Supplementary Material.

Cartilage calcification of the ankle joint is associated with osteoarthritis in the general population.

BACKGROUND: Cartilage calcification (CC) is associated with osteoarthritis (OA) in weight-bearing joints, such as the hip and the knee. However, little is known about the impact of CC and degeneration on other weight-bearing joints, especially as it relates to the occurrence of OA in the ankles. The goal of this study is to analyse the prevalence of ankle joint cartilage calcification (AJ CC) and to determine its correlation with factors such as histological OA grade, age and BMI in the general population. METHODS: CC of the distal tibia and talus in 160 ankle joints obtained from 80 donors (mean age 62.4 years, 34 females, 46 males) was qualitatively and quantitatively analysed using high-resolution digital contact radiography (DCR). Correlations with factors, such as the joint's histological OA grade (OARSI score), donor's age and BMI, were investigated. RESULTS: The prevalence of AJ CC was 51.3% (95% CI [0.40, 0.63]), independent of gender (p = 0.18) and/or the joint's side (p = 0.82). CC of the distal tibia was detected in 35.0% (28/80) (95% CI [0.25, 0.47]) and talar CC in 47.5% (38/80) (95% CI [0.36, 0.59]) of all cases. Significant correlations were noted between the mean amount of tibial and talar CC (r = 0.59, p = 0.002), as well as between the mean amount of CC observed in one ankle joint with that of the contralateral side (r = 0.52, p = 0.02). Furthermore, although the amount of AJ CC observed in the distal tibia and talus correlated with the histological OA-grade of the joint (r = 0.70, p < 0.001 and r = 0.72, p < 0.001, respectively), no such correlation was seen in the general population with relation to age (p = 0.32 and p = 0.49) or BMI (p = 0.51 and p = 0.87). CONCLUSION: The prevalence of AJ CC in the general population is much higher than expected. The relationship between the amount of AJ CC and OA, independent of the donors' age and BMI, indicates that CC may play a causative role in the development of OA in ankles.

Reducing kyphotic deformity by posterior vertebral column resection with 360° osteosynthesis in metastatic epidural spinal cord compression (MESCC).

PURPOSE: Metastatic epidural spinal cord compression (MESCC) often requires anterior-posterior decompression and stabilization. To reduce approach-related complications, single-stage posterolateral vertebrectomy and 360° fusion is often performed. However, a sufficient reduction of kyphotic deformity through this approach has not been reported. The purpose of this study is to investigate the efficacy of kyphotic deformity reduction by this approach in MESCC. METHODS: A retrospective analysis and chart review was performed for 14 consecutive patients who underwent a vertebrectomy and decompression from a posterolateral approach. Anterior mesh stabilization of the ventral column is used as hypomochlion for the posterior compression manoeuvre, which leads to reduction of the kyphotic deformity. RESULTS: Pre-operative back pain was 7.2 on a visual analogue scale. Back pain was reduced to 4.4 at discharge and 2.0 at the latest follow-up with a mean follow-up of 12 months (p < 0.001). The Frankel score remains constant or improved from D to E. Radiological segmental kyphosis was corrected from a mean of 16° to 4° (p < 0.001) post-operatively with a loss of 3° at the final follow-up, but still with significant corrections compared with the pre-operative measurements (p < 0.003). CONCLUSION: Single-stage posterolateral vertebrectomy and reconstruction is a safe and less invasive approach that allows a sufficient reduction of hyperkyphosis and preservation of neurological function in patients with MESCC. This approach is an efficient alternative to anterior-posterior fusion with good pain reduction and improved sagittal profile.

Insufficient stability of pedicle screws in osteoporotic vertebrae: biomechanical correlation of bone mineral density and pedicle screw fixation strength.

PURPOSE: Loosening of pedicle screws is one major complication of posterior spinal stabilisation, especially in the patients with osteoporosis. Augmentation of pedicle screws with cement or lengthening of the instrumentation is widely used to improve implant stability in these patients. However, it is still unclear from which value of bone mineral density (BMD) the stability of pedicle screws is insufficient and an additional stabilisation should be performed. The aim of this study was to investigate the correlation of bone mineral density and pedicle screw fatigue strength as well as to define a threshold value for BMD below which an additional stabilisation is recommended. METHODS: Twenty-one human T12 vertebral bodies were collected from donors between 19 and 96 years of age and the BMD was measured using quantitative computed tomography. Each vertebral body was instrumented with one pedicle screw and mounted in a servo-hydraulic testing machine. Fatigue testing was performed by implementing a cranio-caudal sinusoidal, cyclic (0.5 Hz) load with stepwise increasing peak force. RESULTS: A significant correlation between BMD and cycles to failure (r = 0.862, r 2 = 0.743, p < 0.001) as well as for the linearly related fatigue load was found. Specimens with BMD below 80 mg/cm3 only reached 45% of the cycles to failure and only 60% of the fatigue load compared to the specimens with adequate bone quality (BMD > 120 mg/cm3). CONCLUSIONS: There is a close correlation between BMD and pedicle screw stability. If the BMD of the thoracolumbar spine is less than 80 mg/cm3, stability of pedicle screws might be insufficient and an additional stabilisation should be considered.

Acromioclavicular joint dislocations: coracoclavicular reconstruction with and without additional direct acromioclavicular repair.

PURPOSE: To evaluate different stabilisation techniques for acromioclavicular (AC) joint separations, including direct AC repair, and to compare the properties of the stabilised and native joints. METHODS: An established in vitro testing model for the AC joint was used to analyse joint stability after surgical reconstruction [double TightRope (DTR), DTR with AC repair (DTR + AC), single TR with AC repair (TR + AC), and PDS sling with AC repair (PDS + AC)]. Twenty-four human cadaveric shoulders were randomised by age into four testing groups. Joint stiffness was measured by applying an axial load during defined physiological ranges of motion. Similar tests were performed for the native joints, after dissecting the coracoclavicular and AC ligaments, and after surgical reconstruction. Cyclic loading was performed for 1000 cycles with 20-70 N and vertical load to failure determined after cyclic testing. RESULTS: Axial stiffness for all TR groups was significantly higher than for the native joint (DTR 38.94 N/mm, p = 0.005; DTR + AC 37.79 N/mm, p = 0.015; TR + AC 45.61 N/mm, p < 0.001 vs. native 26.05 N/mm). The axial stiffness of the PDS + AC group was similar to that of the native joint group (21.4 N/mm, n.s.). AC repair did not significantly influence rotational stiffness. Load to failure was similar and >600 N in all groups (n.s.). CONCLUSION: Reconstruction of AC dislocations with one or two TRs leads to stable results with a higher stiffness than the native joints. For the PDS + AC group, axial stiffness was similar to the native situation, although there might be a risk of elongation. Direct AC repair showed no significantly increased stability in comparison with reconstructions without direct AC repair. Thus, a direct AC repair seems to be dispensable in clinical practice, while TRs or PDS cerclages appear to provide sufficiently stable results.

Interposition sleeve as treatment option for interprosthetic fractures of the femur: a biomechanical in vitro assessment.

PURPOSE: The number of patients having hip and knee arthroplasties on the ipsilateral leg is going to rise. In this regard, the prevalence of interprosthetic femoral fractures is going to increase further. The treatment of these fractures is difficult and sometimes it is impossible to perform an osteosynthesis because of worse bone quality. The goal of this study was to investigate the use of an interposition sleeve as an alternative treatment option for interprosthetic fractures with major bone loss. METHODS: Six human cadaveric femurs were instrumented using cemented hip- and knee prosthesis. Interprosthetic fractures were induced during a four-point-bending test and then treated using the interposition sleeve. Afterwards the constructs were tested using the four-point-bending test again. RESULTS: Load-to-failure of the construct before fracturing was significantly higher than after treatment with the interposition sleeve (10681 N vs. 5083 N; p = 0.002). The failure mechanism of the femurs with the interposition sleeve was plastic deformation of the hip or knee prosthesis. The interposition sleeve did not fail in any specimen. CONCLUSION: The interposition sleeve is a valuable treatment option for interprosthetic fractures in situations in which osteosynthesis is impossible or insecure due to major bone defects. However, fracture healing should be preferred whenever possible.

Extra- vs. intramedullary treatment of pertrochanteric fractures: a biomechanical in vitro study comparing dynamic hip screw and intramedullary nail.

INTRODUCTION: Due to the demographic trend, pertrochanteric fractures of the femur will gain increasing importance in the future. Both extra- and intramedullary implants are used with good results in the treatment of these fractures. New, angular stable extramedullary implants promise increased postoperative stability even with unstable fractures. Additional trochanteric plates are intended to prevent secondary impaction, varisation and shortening of the fracture, as well as medialisation of the femoral shaft. The aim of this study was to perform a biomechanical comparison of both procedures regarding their postoperative stability and failure mechanisms. MATERIALS AND METHODS: Twelve fresh-frozen human femurs were randomized into two groups based on the volumetric bone mineral density (vBMD). Standardized pertrochanteric fractures (AO31-A2.3) were generated and treated either with an angular stable dynamic hip screw (DHS) or an intramedullary nail (nail). Correct implant position and the tip-apex distance (TAD) were controlled postoperatively using X-ray. Specimens were mounted in a servohydraulic testing machine and an axial loading was applied according to a single-leg stance model. Both groups were biomechanically compared with regard to native and postoperative stiffness, survival during cyclic testing, load to failure, and failure mechanisms. RESULTS: TAD, vBMD, and native stiffness were similar for both groups. The stiffness decreased significantly from native to postoperative state in all specimens (p < 0.001). The postoperative stiffness of both groups varied non-significantly (p = 0.275). The failure loads for specimens treated with the nail were significantly higher than for those treated with the DHS (8480.8 ± 1238.9 N vs. 2778.2 ± 196.8 N; p = 0.008). CONCLUSIONS: Extra- and intramedullary osteosynthesis showed comparable results as regards postoperative stiffness and survival during cyclic testing. Since the failure load of the nail was significantly higher in the tested AO31-A2.3 fracture model, we conclude that intramedullary implants should be preferred in these, unstable, fractures.

The influence of pelvic tilt on sacral insufficiency fracture occurrence: Insights into the prevalence of high pelvic tilt among patients affected.

INTRODUCTION: Fragility fractures without significant trauma of the pelvic ring in older patients have an increasing incidence due to demographic change. Influencing factors other than osteoporotic bone quality that lead to an insufficiency fracture are not yet known. However, it is suspected that the pelvic tilt (PT) has an effect on the development of such an insufficiency fracture. This study explores the influence of the PTs in patients with insufficiency fractures of the posterior pelvic ring. MATERIALS AND METHODS: A total of 49 geriatric patients with fragility fractures of the pelvic ring were treated at a university hospital level-1 trauma center during a period between February and December 2023, and their fractures were classified according to the FFP classification of Rommens and Hofmann. Complete sets of computer tomography (CT) and radiological images were available to determine the PT angle of the patients. RESULTS: 34 FFP type 2 and 15 FFP type 3 classified patients were included in the study. Significant difference was seen in the pelvic tilt (PT) angle between the patient group with insufficiency fractures (n= 49; mean age: 78.02 ± 11.80) and the control group with lumbago patients (n= 53; mean age: 69.23 ± 11.23). The PT was significantly higher in the patients with insufficiency fractures (25.74° ± 4.76; p⁎⁎⁎⁎ ≤ 0.0001). CONCLUSIONS: The study demonstrates a significant extension of the PT angle of individuals with insufficiency fractures when compared to those with lumbago. The result suggests a potential association between pelvic tilt and fracture susceptibility. TRIAL REGISTRATION: A retrospective study about the influence of sagittal balance of the spine on insufficiency fractures of the posterior pelvic ring measured by the "pelvic tilt angle", DRKS00032120. Registered 20th June 2023 - Prospectively registered. Trial registration number DRKS00032120.

Two-screw osteosynthesis is biomechanically superior to single-screw osteosynthesis for type II odontoid fractures.

The data on the use of a one- or two-screw technique (1S, 2S) for ventral osteosynthesis of type II dens fractures are contradictory. The aim was to design an apparatus to mimic the physiological conditions and test stability with 1S, 2S, and a headless compression screw (HCS) for osteosynthesis of artificially created type II odontoid fractures. The apparatus was mounted on a Zwick materials testing machine. A total of 18 C1-2 specimens were stratified into three groups (1S, 2S, HCS). Odontoid fractures were artificially created, and osteosynthesis was performed. Each specimen was tested at loads increasing from 1 to 40 N. Screw loosening was observed visually, by fatigue data, and by a camera tracking system. Analysis of the Zwick data and the camera data revealed a significant higher stability after 2S compared to 1S and HCS treatment (Zwick data: p = 0.021, camera data: p < 0.001), while visible screw loosening showed a superiority of the 2S only over HCS (p = 0.038). The developed apparatus allowed the dynamic study of the atlantoaxial joint with a high approximation to physiological conditions. The results demonstrated superiority of the 2S over the 1S and HCS in biomechanical stability in the treatment of type II odontoid fractures.

Cervical Disc Arthroplasties Fail to Maintain Physiological Kinematics Under Lateral Eccentric Loads.

STUDY DESIGN: In vitro human cadaveric biomechanical analysis. OBJECTIVES: Optimization of prostheses for cervical disc arthroplasties (CDA) reduces the risk of complications. The instantaneous helical axis (IHA) is a superior parameter for examining the kinematics of functional spinal units. There is no comprehensive study about the IHA after CDA considering all 3 motion dimensions. METHODS: Ten human functional spinal units C4-5 (83.2 ± 7.9 yrs.) were examined with an established measuring apparatus in intact conditions (IC), and after CDA, with 2 different types of prostheses during axial rotation, lateral bending, and flexion/extension. Eccentric preloads simulated strains. The IHA orientation and its position at the point of rest (IHA0-position) were analyzed. RESULTS: The results confirmed the existing data for IHA in IC. Lateral preloads showed structural alterations of kinematics after CDA: During axial rotation and lateral bending, the shift of the IHA0-position was corresponding with the lateral preloads' applied site in IC, while after CDAs, it was vice versa. During lateral bending, the lateral IHA orientation was inclined, corresponding with the lateral preloads' applied site in the IC and oppositely after the CDAs. During flexion/extension, the lateral IHA orientation was nearly vertical in the IC, while after CDA, it inclined, corresponding with the lateral preloads' applied site. The axial IHA orientation rotated to the lateral preloads' corresponding site in the IC; after CDA, it was vice versa. CONCLUSION: Both CDAs failed to maintain physiological IHA characteristics under lateral preloads, revealing a new aspect for improving prostheses' design and optimizing their kinematics.