Does a prehospital applied pelvic binder improve patient survival?

INTRODUCTION: Pelvic fractures are serious and oftentimes require immediate medical attention. Pelvic binders have become a critical tool in the management of pelvic injuries, especially in the prehospital setting. Proper application of the pelvic binder is essential to achieve the desired result. This study evaluates the effectiveness of prehospitally applied pelvic binders in improving outcomes for patients with pelvic fractures. METHODS: This retrospective cohort study analyzed 66 patients with unstable pelvic ring fracture classified as AO61B or 61C, who were treated at a Level I hospital in the emergency room between January 2014 and December 2018. The ideal position for a pelvic binder was determined, and patients were divided into three sub-groups based on whether they received a pelvic binder in the ideal position, outside the optimal range, or not at all. The primary outcome measure was the survival rate of the patients. RESULTS: 66 trauma patients with unstable pelvic fractures were enrolled, with a mean age of 53.8 years, who presented to our ER between 2014 and 2018. The mean ISS score was 21.9, with 60.3 % of patients having a moderate to severe injury (ISS > 16 points). Pelvic binder usage did not differ significantly between patients with an ISS < or ≥ 16 points. A total of 9 patients (13.6 %) died during hospitalization, with a mean survival time of 8.1 days. The survival rate did not differ significantly between patients with or without a pelvic binder, or between those with an ideally placed pelvic binder versus those with a binder outside the ideal range. The ISS score, heart rate, blood pressure at admission, and hemoglobin level were significantly different between the group of patients who died and those who survived, indicating their importance in predicting outcomes. CONCLUSION: Our study found that prehospital pelvic binders did not significantly impact patient outcomes for unstable pelvic fractures, with injury severity score (ISS) being the strongest predictor of survival. Assessing injury severity and managing blood loss remain crucial for these patients. While pelvic binders may not impact survival significantly, they still play a role in stabilizing pelvic fractures and managing blood loss.

Visualization of the distal tibial plafond articular surface using four established approaches and the efficacy of instrumented distraction: a cadaveric study.

PURPOSE: Direct visualization is a very effective method in accomplishing adequate articular surface reconstruction in fracture repair. This study investigates distal tibial plafond articular surface visibility using the anteromedial, anterolateral, posteromedial, and posterolateral approaches, the effect of instrumented distraction on visibility, and which zones of the articular surface are visible for each approach. METHODS: The anteromedial, anterolateral, posteromedial, and posterolateral approaches to the distal tibial plafond were performed on 16 cadaveric ankle specimens. The articular surface visualization for each approach was marked using an electrocautery device with manual and instrumented distraction. Articular surface visualization was photographically documented. Digital axial segmentation and quantitative analysis of the visualized distal tibial plafond articular surface were performed. RESULTS: With manual distraction, distal tibial plafond articular surface visualization, expressed in percent of overall articular surface, was limited to 9% (SD ± 9) for the anteromedial, 24% (SD ± 18) for the anterolateral, 26% (SD ± 10) for the posteromedial, and 30% (SD ± 18) for the posterolateral approaches. Using instrumented distraction significantly improved articular surface visualization in all instances (p < 0.001). The anteromedial approach visible articular surface increased to 63% (SD ± 13), the anterolateral to 72% (SD ± 22), the posteromedial to 62% (SD ± 11), and the posterolateral to 50% (± 17). CONCLUSION: This study demonstrates the efficacy of instrumented distraction when attempting surgical visualization of the distal tibial plafond articular surface. Knowledge of approach specific articular surface visibility may assist the surgeon in choosing the appropriate approach(es) based on case-specific distal tibial plafond fracture patterns. LEVEL OF EVIDENCE: IV, cadaver study.

Accident Mechanisms and Injury Patterns in E-Scooter Users­A Retrospective Analysis and Comparison With Cyclists.

BACKGROUND: E-scooter sharing systems were initiated in Hamburg in June 2019. The number of persons injured in Hamburg in e-scooter accidents rose thereafter. The goal of this study was to determine the typical accident mechanisms and injury patterns after e-scooter accidents in Germany, and to compare these with bicycle accidents. METHODS: In a retrospective study, accidents with e-scooters and bicycles that occurred from June 2019 to June 2020 were registered and analyzed with respect to demography, accident mechanisms, diagnostics, patterns of injury, emergency medical care, operations, and inpatient hospitalizations. RESULTS: 89 persons sustained e-scooter accidents (mean age 33.9 years, standard deviation [SD] 14 years); 435 persons who sustained bicycle accidents (mean age 42.5 years, SD 17 years) served as a comparison group. E-scooter accidents more commonly occurred at night (37% versus 14%), and 28% of the persons who sustained them were under the influence of alcohol (cyclists: 6%). 54% of the injured e-scooter riders suffered trauma to the head or face; 14% had a severe head injury and 16% had a severe facial injury. Fractures of the upper limbs were more common than fractures of the lower limbs (18% versus 6%). On initial assessment in the emergency room, injured cyclists were more frequently classified as needing immediate treatment than injured e-scooter riders (7% versus 1%). CONCLUSION: The head, face, and upper limbs are the most commonly affected parts of the body in e-scooter accidents. Compared to bicycle accidents, e-scooter accidents more commonly occur on weekends and in association with alcohol. From a medical point of view, abstaining from alcohol consumption and wearing a helmet when using an e-scooter is strongly recommended.

Comparative Biomechanical In Vitro Study of Different Modular Total Knee Arthroplasty Revision Stems With Bone Defects.

BACKGROUND: The aim of this study is to investigate the effects of different stem lengths and types including cones on primary stability in revision total knee arthroplasty with different femoral bone defects and fixation methods in order to maximize bone preservation. It is hypothesized that longer stems provide little additional mechanical stability. METHODS: Thirty-five human femurs were investigated. A distal bone defect, Anderson Orthopedic Research Institute classification (s. 33) type-F2a, was created in group 1-3 and type-F3 in group 4-6. A cemented, rotating hinge femoral component was combined with different stems (100 and 160 mm total or hybrid cemented cones, or a 100-mm custom-made anatomical cone stem). The femora were loaded according to in vivo loading during gait. Relative movements were measured to investigate primary stability. Pull-out testing was used to obtain a parameter for the primary stability of the construct. RESULTS: Relative movements were small and similar in all groups (<40 µm). For small defect, the pull-out forces of cemented long (4583 N) and short stems (4650 N) were similar and about twice as high as those of uncemented stems (2221 N). For large defects, short cemented stems with cones showed the highest pull-out forces (5500 N). Long uncemented stems (3324 N) and anatomical cone stems (3990 N) showed similar pull-out forces. CONCLUSION: All tested stems showed small relative movements. Long cemented stems show no advantages to short cemented stems in small bone defects. The use of cones or an anatomical cone stem with hybrid cementation seems to offer good stability even for larger bone defects. The use of a short cemented stem (with or without cone) may be a suitable choice with a high potential for bone preservation in total knee arthroplasty revision with respective bone defects.

Damage to the eye and optic nerve in seriously traumatized patients with concomitant head injury: analysis of 84,627 cases from the TraumaRegister DGU® between 2002 and 2015.

BACKGROUND: To determine the prevalence and characteristics of prechiasmatic visual system injuries (VSI) among seriously injured patients with concomitant head trauma in Europe by means of a multinational trauma registry. METHODS: The TraumaRegister DGU® was searched for patients suffering from serious trauma with a Maximum Abbreviated Injury Scale (AIS) ≥ 3 between 2002 and 2015 in Europe. After excluding cases without significant head injury defined by an AIS ≥ 2, groups were built regarding the existence of a concomitant damage to the prechiasmatic optic system comprising globe and optic nerve. Group comparisons were performed with respect to demographic, etiological, clinical and outcome characteristics. RESULTS: 2.2% (1901/84,627) of seriously injured patients with concomitant head trauma presented with additional VSI. These subjects tended to be younger (mean age 44.7 versus 50.9 years) and were more likely of male gender (74.8% versus 70.0%) compared to their counterparts without VSI. The most frequent trauma etiologies were car accidents in VSI patients (28.5%) and falls in the control group (43.2%). VSI cases were prone to additional soft tissue trauma of the head, skull and orbit fractures as well as pneumocephalus. Primary treatment duration was significantly longer in the VSI cohort (mean 23.3 versus 20.5 days) along with higher treatment costs and a larger proportion of patients with moderate or severe impairment at hospital discharge despite there being a similar average injury severity at admission in both groups. CONCLUSIONS: A substantial proportion of patients with head injury suffers from additional VSI. The correlation between VSI and prolonged hospitalization, increased direct treatment expenditures, and having a higher probability of posttraumatic impairment demonstrates the substantial socioeconomic relevance of these types of injuries.

Nerve injury in severe trauma with upper extremity involvement: evaluation of 49,382 patients from the TraumaRegister DGU® between 2002 and 2015.

BACKGROUND: Peripheral nerve injury (PNI) as an adjunct lesion in patients with upper extremity trauma has not been investigated in a Central European setting so far, despite of its devastating long-term consequences. This study evaluates a large multinational trauma registry for prevalence, mechanisms, injury severity and outcome characteristics of upper limb nerve lesions. METHODS: After formal approval the TraumaRegister DGU® (TR-DGU) was searched for severely injured cases with upper extremity involvement between 2002 and 2015. Patients were separated into two cohorts with regard to presence of an accompanying nerve injury. For all cases demographic data, trauma mechanism, concomitant lesions, severity of injury and outcome characteristics were obtained and group comparisons performed. RESULTS: About 3,3% of all trauma patients with upper limb affection (n = 49,382) revealed additional nerve injuries. PNI cases were more likely of male gender (78,6% vs.73,2%) and tended to be significantly younger than their counterparts without nerve lesions (mean age 40,6 y vs. 47,2 y). Motorcycle accidents were the most frequently encountered single cause of injury in PNI patients (32,5%), whereas control cases primarily sustained their trauma from high or low falls (32,2%). Typical lesions recognized in PNI patients were fractures of the humerus (37,2%) or ulna (20,3%), vascular lacerations (arterial 10,9%; venous 2,4%) and extensive soft tissue damage (21,3%). Despite of similar average trauma severity in both groups patients with nerve affection had a longer primary hospital stay (30,6 d vs. 24,2 d) and required more subsequent inpatient rehabilitation (36,0% vs. 29,2%). CONCLUSION: PNI complicating upper extremity trauma might be more commonly encountered in Central Europe than suggested by previous foreign studies. PNI typically affect males of young age who show significantly increased length of hospitalization and subsequent need for inpatient rehabilitation. Hence these lesions induce extraordinary high financial expenses besides their impact on health related quality of life for the individual patient. Further research is necessary to develop specific prevention strategies for this kind of trauma.

Nerve trauma of the lower extremity: evaluation of 60,422 leg injured patients from the TraumaRegister DGU® between 2002 and 2015.

BACKGROUND: Nerve lesions are well known reasons for reduced functional capacity and diminished quality of life. By now only a few epidemiological studies focus on lower extremity trauma related nerve injuries. This study reveals frequency and characteristics of nerve damages in patients with leg trauma in the European context. METHODS: Sixty thousand four hundred twenty-two significant limb trauma cases were derived from the TraumaRegister DGU® between 2002 and 2015. The TR-DGU is a multi- centre database of severely injured patients. We compared patients with additional nerve injury to those with intact neural structures for demographic data, trauma mechanisms, concomitant injuries, treatment and outcome parameters. RESULTS: Approximately 1,8% of patients with injured lower extremities suffer from additional nerve trauma. These patients were younger (mean age 38,1 y) and more likely of male sex (80%) compared to the patients without nerve injury (mean age 46,7 y; 68,4% male). This study suggests the peroneal nerve to be the most frequently involved neural structure (50,9%). Patients with concomitant nerve lesions generally required a longer hospital stay and exhibited a higher rate for subsequent rehabilitation. Peripheral nerve damage was mainly a consequence of motorbike (31,2%) and car accidents (30,7%), whereas leg trauma without nerve lesion most frequently resulted from car collisions (29,6%) and falls (29,8%). CONCLUSION: Despite of its low frequency nerve injury remains a main cause for reduced functional capacity and induces high socioeconomic expenditures due to prolonged rehabilitation and absenteeism of the mostly young trauma victims. Further research is necessary to get insight into management and long term outcome of peripheral nerve injuries.

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.

Determination of Femoral Neck Angle and Torsion Angle Utilizing a Novel Three-Dimensional Modeling and Analytical Technology Based on CT Datasets.

INTRODUCTION: Exact knowledge of femoral neck inclination and torsion angles is important in recognizing, understanding and treating pathologic conditions in the hip joint. However, published results vary widely between different studies, which indicates that there are persistent difficulties in carrying out exact measurements. METHODS: A three dimensional modeling and analytical technology was used for the analysis of 1070 CT datasets of skeletally mature femurs. Individual femoral neck angles and torsion angles were precisely computed, in order to establish whether gender, age, body mass index and ethnicity influence femoral neck angles and torsion angles. RESULTS: The median femoral neck angle was 122.2° (range 100.1-146.2°, IQR 117.9-125.6°). There are significant gender (female 123.0° vs. male 121.5°; p = 0.007) and ethnic (Asian 123.2° vs. Caucasian 121.9°; p = 0.0009) differences. The median femoral torsion angle was 14.2° (-23.6-48.7°, IQR 7.4-20.4°). There are significant gender differences (female 16.4° vs. male 12.1°; p = 0.0001). Femoral retroversion was found in 7.8% of the subjects. CONCLUSION: Precise femoral neck and torsion angles were obtained in over one thousand cases. Systematic deviations in measurement due to human error were eliminated by using automated high accuracy morphometric analysis. Small but significant gender and ethnic differences were found in femoral neck and torsion angles.

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.

What is the frequency of nerve injuries associated with acetabular fractures?

BACKGROUND: Acetabular fractures and surgical interventions used to treat them can result in nerve injuries. To date, only small case studies have tried to explore the frequency of nerve injuries and their association with patient and treatment characteristics. High-quality data on the risk of traumatic and iatrogenic nerve lesions and their epidemiology in relation to different fracture types and surgical approaches are lacking. QUESTIONS/PURPOSES: The purpose of this study was to determine (1) the proportion of patients who develop nerve injuries after acetabular fracture; (2) which fracture type(s) are associated with increased nerve injury risk; and (3) which surgical approach was associated with the highest proportion of patients developing nerve injuries using data from the German Pelvic Trauma Registry. Two secondary aims were (4) to assess hospital volume-nerve-injury relationship; and (5) internal data validity. METHODS: Between March 2001 and June 2012, 2236 patients with acetabular fractures were entered into a prospectively maintained registry from 29 hospitals; of those, 2073 (92.7%) had complete records on the endpoints of interest in this retrospective study and were analyzed. The neurological status in these patients was captured at their admission and at the discharge. A total of 1395 of 2073 (67%) patients underwent surgery, and the proportions of intervention-related and other hospital-acquired nerve injuries were obtained. Overall proportions of patients developing nerve injuries, risk based on fracture type, and risk of surgical approach type were analyzed. RESULTS: The proportion of patients being diagnosed with nerve injuries at hospital admission was 4% (76 of 2073) and at discharge 7% (134 or 2073). Patients with fractures of the "posterior wall" (relative risk [RR], 2.0; 95% confidence interval [CI], 1.4-2.8; p=0.001), "posterior column and posterior wall" (RR, 2.9; CI, 1.6-5.0; p=0.002), and "transverse+posterior wall" fracture (RR, 2.1; CI, 1.3-3.5; p=0.010) were more likely to have nerve injuries at hospital discharge. The proportion of patients with intervention-related nerve injuries and that of patients with other hospital-acquired nerve injuries was 2% (24 of 1395 and 46 of 2073, respectively). They both were associated with the Kocher-Langenbeck approach (RR, 3.0; CI, 1.4-6.2; p=0.006; and RR, 2.4; CI, 1.4-4.3; p=0.004, respectively). CONCLUSIONS: Acetabular fractures with the involvement of posterior wall were most commonly accompanied with nerve injuries. The data suggest also that Kocher-Langenbeck approach to the pelvic ring is associated with a higher risk of perioperative nerve injuries. Trauma surgeons should be aware of common nerve injuries, particularly in posterior wall fractures. The results of the study should help provide patients with more exact information on the risk of perioperative nerve injuries in acetabular fractures. LEVEL OF EVIDENCE: Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Malpositioning of the lag screws by 1- or 2-screw nailing systems for pertrochanteric femoral fractures: a biomechanical comparison of gamma 3 and intertan.

OBJECTIVES: The aim of this investigation was to perform a biomechanical comparison between 1- and 2-screw systems used for the treatment of intertrochanteric fractures for centralized and decentralized placement of femoral neck screws of failure loads, stiffness, survival rates, tip apex distance (TAD), and failure mode. METHODS: As fracture model, an AO 31A2.3 fracture was used. Twelve pairs of human cadaver femora were tested. Femoral neck screws were implanted in the femoral head in center/center, posterior/central, and anterior/superior position in axial/frontal plane. A single-screw system (Gamma 3 Locking Nail; Stryker GmbH & Co. KG) and a 2-screw system (Trigen-Intertan; Smith & Nephew GmbH) were used. To simulate the load in situ, a cyclic load was carried for 10,000 cycles in a material testing machine. If no cyclic failure occurred, femora were loaded until the failure. The systems were compared according to the stiffness, survivability through 10 k cycles, TAD, and load to failure. RESULTS: None of the tested bones failed at center/center location in the decentralized positions 3 Gamma Nail and 2 Intertan specimens failed during cyclic testing. The 2-screw system resisted higher forces in all positions (Gamma: 5370N ± 1924, Intertan: 7650N ± 2043; P = 0.014). CONCLUSIONS: Based on these data, it is clear that both the nail systems showed a higher biomechanical stability with a lower TAD. The 2 specimens that failed with the Intertan in the cyclic tests had a TAD ≥49 mm. The cutout failures that we detected during cyclic testing in the Gamma system had a TAD ≥30 mm. Thus, it is clear that the TAD affects failure independent of the implant used. With a less than ideal lag screw placement, however, the Intertan system with 2 integrated screws was able to withstand higher loads in this study.

Biomechanical evaluation of 3 stabilization methods on acromioclavicular joint dislocations.

BACKGROUND: Traumatic acromioclavicular (AC) joint dislocations can be addressed with several surgical stabilization techniques. The aim of this in vitro study was to evaluate biomechanical features of the native joint compared with 3 different stabilization methods: locking hook plate (HP), TightRope (TR), and bone anchor system (AS). HYPOTHESIS: The HP provides higher stiffness than the anatomic reconstruction techniques. STUDY DESIGN: Controlled laboratory study. METHODS: A new biomechanical in vitro model of the AC joint was used to analyze joint stability after surgical repair (HP, TR, and AS). Eighteen cadaveric specimens were randomized for bone density and diameter in the midclavicle section. Joint stiffness was measured by applying an axial load and a defined physiological range of motion for internal and external rotations and upward and downward rotations. Data were recorded at 3 stages: for the native joint after dissecting the AC ligaments, directly after repair, and after axial cyclic loading (1000 cycles with 20 and 70 N at 1 Hz). To evaluate which implant mimics physiological joint properties best, axial stiffness of vertical stability was assessed in combination with rotation. Finally, static loading in the superior direction was applied until failure of the joints occurred. RESULTS: Axial stiffness of the TR and AS groups was 2-fold higher than for the HP group and the native joint (67.1, 66.1, and 22.5 N/mm, respectively; P < .004). Decreased load-to-failure rates were recorded in the HP group compared with the TR and AS groups (248.9 ± 72.7, 832.0 ± 401.4, and 538.0 ± 166.1 N, respectively). The stiffness of the rotations was not significantly different between the treatment methods but was lower in horizontal and downward rotations compared with the native state. Thus, native AC ligaments contributed a significant share to joint stiffness. CONCLUSION: The TR and AS groups demonstrated higher vertical load capacity. Compared with the TR and AS, the HP demonstrated an axial stiffness closest to the native joint. For restoring physiological properties, reconstruction of the AC ligaments may be necessary. CLINICAL RELEVANCE: The results show different biomechanical properties of the HP and anatomic reconstructions.

Comparison of 2D and 3D navigation techniques for percutaneous screw insertion into the scaphoid: results of an experimental cadaver study.

Navigation in hand surgery is still in the process of development. Initial studies have demonstrated the feasibility of 2D and 3D navigation for the palmar approach in scaphoid fractures, but a comparison of the possibilities of 2D and 3D navigation for the dorsal approach is still lacking. The aim of the present work was to test navigation for the dorsal approach in the scaphoid using cadaver bones. After development of a special radiolucent resting splint for the dorsal approach, we performed 2D- and 3D-navigated scaphoid osteosynthesis in 12 fresh-frozen cadaver forearms using a headless compression screw (Synthes). The operation time, radiation time, number of trials for screw insertion, and screw positions were analyzed. In six 2D-navigated screw osteosyntheses, we found two false positions with an average radiation time of 5 ± 2 seconds. Using 3D navigation, we detected one false position. A false position indicates divergence from the ideal line of the axis of the scaphoid but without penetration of the cortex. The initial scan clearly increased overall radiation time in the 3D-navigated group, and for both navigation procedures operating time was longer than in our clinical experience without navigation. Nonetheless, 2D and 3D navigation for non-dislocated scaphoid fractures is feasible, and navigation might reduce the risk of choosing an incorrect screw length, thereby possibly avoiding injury to the subtending cortex. The 3D navigation is more difficult to interpret than 2D fluoroscopic navigation but shows greater precision. Overall, navigation is costly, and the moderate advantages it offers for osteosynthesis of scaphoid fractures must be considered critically in comparisons with conventional operating techniques.

A comparative biomechanical analysis of fixation devices for unstable femoral neck fractures: the Intertan versus cannulated screws or a dynamic hip screw.

BACKGROUND: First introduced in 2005, the "Intertan" (IT), an intramedullary nail with two cephalocervical screws, has become an increasingly popular option for treating intertrochanteric fractures. The purpose of this study was to identify the utility of this device for stabilization of unstable femoral neck fractures compared with cannulated screws (CS) and a dynamic hip screw (DHS). METHODS: Twenty-four human cadaveric femurs were harvested and assigned to three groups that were matched with regard to bone mineral density (BMD). Standardized Pauwels-Type-III fractures were osteomized with a custom-made saw guide and fixated by an "IT," three CS, or a DHS. All constructs were biomechanically tested in a servohydraulic testing machine with a physiologic mechanical axis loading of the femoral head (700 N), cyclical compression to 1,400 N (10,000 cycles; 2 Hz), and loading to failure. All specimens were compared with respect to the number of survived cycles, mechanical strength, head displacement, load to failure, and failure mechanism. RESULTS: Regardless of the fixation, the mechanical strength of the stabilized femurs was significantly decreased to 71% compared with the intact femurs (100%). During cyclical testing 46% of the constructs (6 CS, 4 DHS, and 1 IT) failed. There was no difference between the mechanical strength of all survived constructs regarding the BMD, but the BMD of the failed specimens was significantly reduced compared with the surviving femurs (0.71 g/cm² ± 0.18 g/cm² vs. 1.07 g/cm² ± 0.33 g/cm²; p < 0.05). IT femurs survived significantly longer than CS specimens (IT, 9,063 cycles ± 2,480 cycles vs. CS, 3,325 cycles ± 3,885 cycles vs. DHS, 5,716 cycles ± 4,448 cycles; p < 0.01), endured higher failure loads (IT, 4,929 N ± 1,105 N vs. CS, 3,421 N ± 20 N vs. DHS, 3,505 N ± 905 N; p < 0.05), and presented a less inferior head displacement (IT, 8.5 mm ± 1.6 mm vs. CS, 16.4 mm ± 6.7 mm vs. DHS, 14.5 mm ± 6.4 mm; p < 0.05). CONCLUSION: Our results suggest that (1) none of the tested devices restore a comparable mechanical strength in the fractured specimens compared with the intact femurs, and (2) the "IT" possesses some biomechanical benefits for internal fixation of unstable femoral neck fractures compared with DHS and CS. Because the IT constructs failed with an inferior femoral neck fracture, complicating the mandatory anchorage of a prosthetic stem in a revision operation, more biomechanical experiments using the IT in the presence of a posterior comminution defect are required, along with clinical outcome studies.