Successful Implant Retention in a Chronified Hematogenous Bilateral Periprosthetic Hip Joint Infection With Enterococcus faecalis.

We present a case with bilateral hematogenous hip periprosthetic joint infection with Enterococci which could be treated successfully with implant retention despite chronification and partial loosening. A debridement and replacement of the modular components was carried out with replacement of a loose acetabular cup on the right side. Considering poor local infection control, antibiotic treatment was enhanced by local application of vancomycin. In the present case, treatment of chronic enterococcal periprosthetic joint infection while preserving the implants was successful despite unfavorable odds. Considering the duration of infection, causative microorganism, and loosening of one of the implants, staged exchange of both hip replacements would have been the standard procedure. This case illustrates that some concepts have to be challenged from time to time.

Early failure of a highly cross-linked polyethylene inlay after total hip arthroplasty probably due to insufficient irradiation.

Highly cross-linked polyethylene (XLPE) is a major advance in total hip arthroplasty (THA), as it suffers from less wear and thus is associated with lower revision rates than standard ultra-high molecular weight polyethylene. Early failures are reported rarely, and associated with specific design or manufacturing issues. We report a case requiring early revision due to adverse reaction to polyethylene particles. Investigations identified insufficient irradiation as the most probable cause of failure. Here are reported the features of a clinical case with determination of the material properties of the retrieved XLPE liner and establishment of the appropriate calibration curves as reference. Periprosthetic joint infection could be ruled out with appropriate sampling as cause for the inflammatory periarticular tumour. Histology identified a massive macrophagic reaction to micrometric polyethylene particles. No component malposition was present, nor any third-body wear. The trans-vinylene index (TVI) indicated insufficient and potentially detrimental irradiation of the polyethylene, while gel content, crystallinity, melting temperature and oxidation index remained within expected ranges. Histologically proven failure of a XLPE THA liner was identifiable despite correct implantation of the components. The cause of failure most probably was an inadequate irradiation, as indicated by determination of the TVI. This case underscores the importance of histologic workup even in aseptic revisions, and of detailed analysis of retrievals. The calibration curves provided are essential for analysis of other retrievals.

Fluoroscopy-guided vs. navigated iliosacral screw placement with intraoperative 3D scan or postoperative CT control: Impact of the clinical workflow on patients' radiation exposure: Radiation exposure of different workflows for iliosacral screw placement.

INTRODUCTION: To guide iliosacral screws (ISS) and verify safe placement different techniques, e.g. Fluoroscopy-guided (FSG) or 3D navigation are known. However, higher radiation exposure for the conventional technique is a concern. It was the aim of this experimental study to evaluate radiation exposure for three clinical workflows. METHODS: An anthropomorphic, cross sectional dosimetry phantom was equipped with metal oxide semiconductor field effect transistors to measure organ specific radiation exposure. The effective dose was calculated. Radiation exposure was measured for FSG placement of 2 transverse ISS based on clinical experience regarding fluoroscopy time (240s). Additional measurements were conducted to calculate the effective dose for an intraoperative 3D scan as used for navigated ISS (high-quality 3D), for intraoperative verification of proper guide wire placement (standard-quality 3D) and for postoperative CT, using three different protocols. The following workflows were compared: FSG including postoperative CT (FSG-CT, including 3 different protocols) vs. FSG with intraoperative 3D scan in standard quality (FSG-3D) vs. navigation including two intraoperative 3D scan for navigated ISS (NAV-3D). RESULTS: The effective dose for FSG-CT ranged from 4.41 mSv to 5.27 mSv. FSG-3D resulted in a total of 4.93 mSv. For NAV-3D, the effective dose was the lowest (3.00 mSv). The effective dose of a high-quality 3D scan required for navigation was 1.94 mSv, compared to 1.06 mSv for a standard-quality 3D scan as used for control. CONCLUSIONS: Intraoperative 3D scanning may be recommended, either combined with prior FSG ISS placement or following 3D navigation without increasing radiation exposure compared with alternative workflows with postoperative CT control.

The surgical management of highly unstable fragility fractures of the sacrum with spinopelvic dissociation: A case series and proposal of a surgical treatment algorithm.

INTRODUCTION: U- and H-shaped fragility fractures of the sacrum (FFP IVb) are unstable fractures. Non-operative treatment may be associated with impaired walking abilities, chronic pain and the potential loss of independency. However, different treatment options are still controversially debated. The aim of surgical treatment includes sufficient fracture stability for immediate full weight bearing and good pain control postoperatively. A new surgical treatment algorithm was developed. This algorithm was evaluated in a cohort of geriatric patients with FFP type IVb regarding surgical complications and patient-related outcome. METHODS: Retrospective case series. Patients ≥65 years, admitted with FFP IVb between 01/2017 and 12/2020 were included. Pelvic CT was performed and the surgical technique was chosen according to the proposed surgical treatment algorithm. For this algorithm, the technique of fracture stabilisation was adapted to sacral anatomy and the specific fracture pattern to minimize the impact of surgery and postoperative complications without compromising a sufficient fracture stability. Pain levels, complications and surgical revisions were recorded. Level of independency, walking abilities and -aids were compared 3- and 12- months postoperatively to the pre-injury situation. RESULTS: Twenty-three patients were included. Outcome parameters could be obtained in 20 patients (85%) after three months and in 18 patients (78%) patients one year postoperatively. All patients were treated according to the algorithm. Sixteen patients received two transilio-transsacral screws (TI-TSS), whereas either lumbopelvic fixation (LPF) combined with a TI-TSS or bilateral ilio-sacral screws (ISS) was performed four times. Three patients underwent bilateral ISS into S1 with one TI-TSS into S2. Three days postoperatively, median pain VAS was 2 (0-8) compared to 7 (4-10) before surgery. One loosened TI-TSS was removed six weeks postoperatively. Three-month mortality was 14% (n=3). At one-year follow-up, all patients regained their pre-injury level of walking abilities. CONCLUSIONS: Restoration of walking abilities, preservation of independency and efficient pain control can be achieved with surgical fixation of FFP type IVb fractures. With the proposed surgical algorithm, the fixation techniques are adapted to the fracture pattern to minimize the surgical burden. LEVEL OF EVIDENCE: IV.

The impact of the fluoroscopic view on radiation exposure in pelvic surgery: organ involvement, effective dose and the misleading concept of only measuring fluoroscopy time or the dose area product.

INTRODUCTION: Minimally invasive fluoroscopy-guided screw fixation is an established technique to stabilize fractures of the posterior pelvic ring in orthopaedic surgery. However, safe placement of the screws may be associated with prolonged intervention time and extensive fluoroscopy is a concern. In the current literature, the dose area product (DAP) and fluoroscopy time are often used to describe radiation exposure of the patient. It was the aim of the study to compare DAP to organ doses and the effective dose for four standard views commonly used in pelvic surgery. METHODS: An anthropomorphic cross-sectional dosimetry phantom, representing the body of a male human (173 cm/73 kg), was equipped with metal-oxide-semiconductor field-effect transistors (MOSFET) in different organ locations to measure radiation exposure. Anteroposterior (APV), lateral (LV), outlet (OLV) and inlet (ILV) of the phantom were obtained with a mobile C-arm, and effective dose and organ doses were calculated. DAP was measured in the built-in ionisation chamber beyond the collimator of the C-arm. The measurements were repeated with a fat layer to simulate an obese patient. RESULTS: Overall, the highest organ dose was measured in the stomach for ILV (0.918 mSv/min). Effective dose for ILV showed the highest values by far (1.85 mSv/min) and the lowest for LV (0.46 mSv/min). The DAP pattern was completely different to the effective dose with similar values for LV and ILV (12.2 and 12.3 µGy·m2/s). Adding a fat layer had no major effect on the measurements. CONCLUSION: The exposure to radiation varies considerably between different orthopaedic standard views of the pelvis. About the fourfold amount of the effective dose was measured for ILV compared to LV. DAP and irradiation time do not respect either the body region in the field of radiation or the radiosensitivity of the affected organs. Thus, they do not allow a reliable interpretation of the radiation burden the patient is exposed to.

Protective effects of new femoral reaming techniques (Reamer irrigator aspirator, RIA I and II) on pulmonary function and posttraumatic contusion (CT morphology) - results from a standardized large animal model.

INTRODUCTION: The effects of reaming for preparation of intramedullary fixation in long bone fractures have been widely studied. We compared pulmonary and systemic effects between conventional reaming with reamer irrigator aspirator and unreamed nailing in an acute porcine trauma model with a standardized femur fracture. MATERIALS AND METHODS: In a standardized porcine model, (moderate blunt chest trauma, abdominal injury and femoral shaft fracture), the femur was submitted to intramedullary nailing after resuscitation and normalization of pulmonary function. The treatment groups included 3 reamer types (Group RFN: conventional reaming with Synream; group RIA1; reamer irrigator aspirator, version 2005; group RIA 2; reamer irrigator aspirator, version 2019) and were compared to unreamed femoral nailing (Group UFN). Pulmonary function measurements included arterial partial carbon-dioxide pressure (paCO2 [kPa]) (baseline, post reaming, 2,4,6 h) and volumetric measures of contusion in chest computer tomography (CT) (at 6 hrs.). Systemic inflammatory response was measured at baseline and every second hour until six hours after trauma. RESULTS: This study included 24 male animals, mean weight 50.76 ± 4.1 kg n = 6 per group). Group RFN developed a significantly higher partial CO2 (pCO2) at one hour after reaming when compared with all other groups (7.4 ± 0.4 kPa versus 5.4 ± 0.6 RIA 1, 5.6 ± 0.4 RIA 2, and 5.5 ± 0.5 UFN, p < 0.001), along with a had lower pO2 (12.3 ± 1.3 kPa versus 17.2 ± 1.9 RIA 1, 17.4 ± 1.6 RIA 2, and 16.4 ± 0.7 UFN, p < 0.001) and the degree of pulmonary hyperdense changes in the CT analysis was higher in RFN (485.2 ± 98.5 cm3 versus 344.4 ± 74.4 cm3 RIA 1 and 335.2 ± 58.1 cm3 RIA 2, p < 0.01). The inflammatory reaction was lowest in both RIA groups when compared with group RFN or UFN (p < 0.001). CONCLUSION: Both RIA 1 and RIA 2 protect the lung from reaming induced dysfunction and have no systemic inflammatory effects, while the negative effects were more sustained after reamed or unreamed nailing. Both RIA 1 and RIA II appear to be of value in terms of a Safe Definitive Surgery (SDS) strategy.

Use of cortical buttons for the fixation of the distal biceps tendon in combination with the double-incision technique-the relationship between the drill trajectory and the proximity to the posterior interosseous nerve: a cadaveric study.

BACKGROUND: The aim of this cadaveric study was to investigate different defined drill trajectories through the radial tuberosity for the placement of a cortical button and their proximity to the posterior interosseous nerve (PIN) by using the double-incision technique. METHODS: A total of 10 elbows from 5 fresh entire cadavers were used in this study. Detachment of the distal biceps tendon was performed to simulate its rupture. A standardized double-incision approach was performed, and the radial tuberosity was exposed in full pronation. A drill hole was applied perpendicular through the center of the tuberosity. Another 8 drill holes were applied with the same starting point at the tuberosity with defined trajectories. A cortical button was then placed through the center hole. The distances between the PIN and the exit holes of the different trajectories were measured. The cortical button was analyzed regarding muscle entrapment as well as its closest distance to the PIN. RESULTS: Contact of the PIN and the drill hole was observed for 6 of the 9 trajectories; only the proximal-ulnar, ulnar, and ulnar-distal trajectories had no contact with the PIN in any of the experiments. No contact of the cortical button and the PIN was observed for the ulnar and distal-ulnar drill trajectories only. The minimal distance to the PIN was 1.6 mm for both. CONCLUSION: Because of the potential risk of PIN injuries, the use of cortical button fixation in combination with the double-incision approach cannot be recommended.

Nonoperative Treatment of Midshaft Clavicle Fractures in Adults.

Clavicle fractures are among the most common skeletal injuries accounting for 2-5% of all adult fractures. Historically, nonoperative treatment of midshaft clavicular fractures was considered the gold standard of care. Furthermore, nonoperative treatment has been challenged by an increasing popularity and rate of surgical fixations in recent years despite a lack of clear evidence in the current literature. Most fractures are suitable for conservative treatment. There is solid evidence in favour of nonoperative treatment for fractures with a displacement of less than 2cm and remaining contact of the bone fragments. Clear indications for conservative treatment versus surgical fixation of displaced midshaft fractures have not finally been established yet, leaving some questions and problems unanswered. Furthermore, there are no evidence-based recommendations concerning the kind and duration of shoulder immobilisation with no clear advantage for any treatment modality.

Reverse shoulder arthroplasty for complex fractures of the proximal humerus in elderly patients: impact on the level of independency, early function, and pain medication.

BACKGROUND: This study investigated early functional outcome, quality of life, and the level of independency in elderly patients after primary reverse shoulder arthroplasty (RSA) for complex fractures of the proximal humerus. METHODS: This was a prospective case series that included 33 patients, aged ≥70 years, with a high level of independency who received RSA for complex fractures of the humerus (Orthopaedic Trauma Association B2/C) from January 2012 to April 2014. RESULTS: Level of independency, quality of life (Short Form 36 Health Survey score), early functional outcome (Constant-Murley score, Disabilities of the Arm, Shoulder and Hand Outcome Measure), and pain medication (World Health Organization grading) were obtained at the 6-month follow-up and 1 year after surgery. The Constant-Murley score was 64 ± 14 after 6 months and 71 ± 12 at 1 year (P < .001), reaching 87% compared with the contralateral shoulder. The Disabilities of the Arm, Shoulder and Hand score reached 29 ± 20 at 6 months and 30 ± 21 at 1 year. The Short Form 36 score was comparable to normative data. After 6 months, 84% of our study group were back at their previous level of independency. Within 1 year, this rate increased to 91%. At the 1-year follow-up, analgesia intake was back at the level before the injury in 97% of the patients. CONCLUSIONS: Primary RSA provides good early functional results, reliable pain control, and excellent restoration of an independent life style in elderly patients. Thus, RSA may be considered for active patients with a high demand on shoulder function.

Effect of Mirrored Views on Endoscopic and Arthroscopic Skill Performance.

BACKGROUND: Arthroscopic procedures may be technically challenging because of impaired vision, limited space, and the 2-dimensional vision of a 3-dimensional structure. Spatial orientation may get more complicated when the camera is pointing toward the surgeon. HYPOTHESIS: Spatial orientation and arthroscopic performance may be improved by simply mirroring the image on the monitor in different configurations regarding the position and orientation of camera and instrument. STUDY DESIGN: Descriptive laboratory study. METHODS: Thirty volunteers from an orthopaedic department were divided into 3 equal groups according to their arthroscopic experience (beginners, intermediates, seniors). All subjects were asked to perform a standardized task in a closed box mimicking an endoscopic space. The same task had to be performed in 4 different configurations regarding camera and instrument position and orientation (pointing toward or away from the subject) with either the original or mirrored image on the monitor. Efficiency (time per stick; TPS), precision (successful completion of the task), and difficulty rating using a visual analog scale (VAS) were analyzed. RESULTS: Mirroring the image demonstrated no advantage over the original images in any configuration regarding TPS. Successful completion of the task was significantly better when the image was mirrored in the configuration with the camera pointing toward and the instrument away from the surgeon. There was a positive correlation between TPS and subjective VAS difficulty rating (r = 0.762, P = .000) and a negative correlation between the successful completion of the task and VAS (r = -0.515, P = .000). CONCLUSION: Mirroring the image may have a positive effect on arthroscopic performance of surgeons in certain configurations. A significantly improved performance was seen when the arthroscope was pointing toward and the grasping instrument pointing away from the subject. Mirroring the image may facilitate surgery in such clinical situations. CLINICAL RELEVANCE: Mirroring the image may facilitate arthroscopic procedures in certain clinical situations.

Minimally invasive lateral plate placement for metadiaphyseal fractures of the humerus and its implications for the distal deltoid insertion- it is not only about the radial nerve. A cadaveric study.

INTRODUCTION: Minimally invasive lateral placement of plates on the humerus may be associated with a risk of injury to the radial nerve. Whereas this potential complication has been investigated in several studies, there is no data regarding potential injuries to the distal insertion of the deltoid muscle when the plates are passed distally in a submuscular tunnel. METHODS: Minimally invasive plate placement was performed on eight arms in fresh cadavers. A lateral deltoid split approach was made and the plates were introduced in an antegrade submuscular manner from proximal to distal. A lateral distal incison was made to adjust the position of the plate at the lateral aspect of the humerus without formal exploration of the radial nerve. The arms were dissected to identify the seven intramuscular tendons of the deltoid and their insertions at the humerus. The position of the plate and its relation to the intramuscular tendons of the deltoid was explored. Furthermore, potential injuries to the axillary and radial nerve were investigated. Damage to the brachialis muscle its interference with plate positioning were explored. RESULTS: The distal deltoid insertion was affected in all eight examined arms. The two most anterior and two most posterior segments were intact in all. In two arms, the third intramuscular tendon was perforated. In three specimens, the insertion of the fourth segment was damaged. The fifth segment was partially disrupted in three arms. Overall, injuries to the intramuscular tendons were limited to one tendon in all arms. Partial brachial muscle entrapment underneath the plate was observed in four specimens. The axillary nerve was not damaged in any of the examined arms. The radial nerve was entrapped between plate and humeral shaft in one case. CONCLUSIONS: Lateral plate placement in MIPO technique damages central parts of the distal deltoid muscle insertion. However, the most anterior and posterior tendons are not involved and the clinical significance on muscle function remains unclear. Introduction of the plate without prior distal incision and elevation of the brachial muscle may be associated with partial entrapment of the brachial muscle and a higher risk of injuring the radial nerve. LEVEL OF EVIDENCE: Experimental study.

The extended medial elbow approach-a cadaveric study.

BACKGROUND: The two most commonly used approaches to expose medial elbow structures are the flexor carpi ulnaris split and the Hotchkiss over-the-top approach. The aim of this study was to define the extended medial approach to the elbow, featuring advantages of over-the-top (proximal exposure) and additional complete exposure of the coronoid and proximal medial ulna, while respecting the internervous plane between the flexor pronator mass and flexor carpi ulnaris muscle. METHODS: In this comparative anatomic study, 12 fresh frozen cadaveric elbows were dissected alternately to study the distal limitation and exposed area of the extended medial elbow approach compared with splitting the flexor carpi ulnaris. RESULTS: Proximal ulna exposure area was comparable between the extended medial elbow approach (average, 840 mm(2)) and the flexor carpi ulnaris split (average, 810 mm(2); P = .44). The extended medial approach was limited distally by the posterior recurrent ulnar artery (mean 68 mm from medial epicondyle), whereas the first motor branch for the flexor carpi ulnaris muscle limited the second approach in 75% of the specimens (mean 29 mm from medial epicondyle, P < .001). CONCLUSIONS: The extended medial elbow approach is a single approach allowing full exposure of the medial elbow and combining the advantages of the over-the-top approach with a safe distal extension to the medial ulna. In contrast to the flexor carpi ulnaris split, our approach respects the internervous plane.

Deltoid Tuberosity Index: A Simple Radiographic Tool to Assess Local Bone Quality in Proximal Humerus Fractures.

BACKGROUND: Osteoporosis may complicate surgical fixation and healing of proximal humerus fractures and should be assessed preoperatively. Peripheral quantitative CT (pQCT) and the Tingart measurement are helpful methods, but both have limitations in clinical use because of limited availability (pQCT) or fracture lines crossing the area of interest (Tingart measurement). The aim of our study was to introduce and validate a simple cortical index to assess the quality of bone in proximal humerus fractures using AP radiographs. QUESTIONS/PURPOSES: We asked: (1) How do the deltoid tuberosity index and Tingart measurement correlate with each other, with patient age, and local bone mineral density (BMD) of the humeral head, measured by pQCT? (2) Which threshold values for the deltoid tuberosity index and Tingart measurement optimally discriminate poor local bone quality of the proximal humerus? (3) Are the deltoid tuberosity index and Tingart measurement clinically applicable and reproducible in patients with proximal humerus fractures? METHODS: The deltoid tuberosity index was measured immediately above the upper end of the deltoid tuberosity. At this position, where the outer cortical borders become parallel, the deltoid tuberosity index equals the ratio between the outer cortical and inner endosteal diameter. In the first part of our study, we retrospectively measured the deltoid tuberosity index on 31 patients (16 women, 15 men; mean age, 65 years; range, 22-83 years) who were scheduled for elective surgery other than fracture repair. Inclusion criteria were available native pQCT scans, AP shoulder radiographs taken in internal rotation, and no previous shoulder surgery. The deltoid tuberosity index and the Tingart measurement were measured on the preoperative internal rotation AP radiograph. The second part of our study was performed by reviewing 40 radiographs of patients with proximal humerus fractures (31 women, nine men; median age, 65 years; range, 22-88 years). Interrater (two surgeons) and intrarater (two readings) reliabilities, applicability, and diagnostic accuracy were assessed. RESULTS: The correlations between radiograph measurements and local BMD (pQCT) were strong for the deltoid tuberosity index (r = 0.80; 95% CI, 0.63-0.90; p < 0.001) and moderate for the Tingart measurement (r = 0.67; 95% CI, 0.42-0.83; p < 0.001). There was moderate correlation between patient age and the deltoid tuberosity index (r = 0.65; p < 0.001), patient age and the Tingart measurement (r = 0.69; p < 0.001), and patient age and pQCT (r = 0.73; p < 0.001). The correlation between the deltoid tuberosity index and the Tingart measurement was strong (r = 0.84; p < 0.001). We determined the cutoff value for the deltoid tuberosity index to be 1.44, with the area under the curve = 0.87 (95% CI, 0.74-0.99). This provided a sensitivity of 0.88 and specificity of 0.80. For the Tingart measurement, we determined the cutoff value to be 5.3 mm, with the area under the curve = 0.83 (95% CI, 0.67-0.98), which resulted in a sensitivity of 0.81 and specificity of 0.85. The intraobserver reliability was high and not different between the Tingart measurement (intraclass correlation coefficients [ICC] = 0.75 and 0.88) and deltoid tuberosity index (ICC = 0.88 and 0.82). However, interobserver reliability was higher for the deltoid tuberosity index (ICC = 0.96; 95% CI, 0.93-0.98) than for the Tingart measurement (ICC = 0.85; 95% CI, 0.69-0.93).The clinical applicability on AP radiographs of fractures was better for the deltoid tuberosity index (p = 0.025) because it was measureable on more of the radiographs (77/80; 96%) than the Tingart measurement (69/80; 86%). CONCLUSIONS: The deltoid tuberosity index correlated strongly with local BMD measured on pQCT and our study evidence shows that it is a reliable, simple, and applicable tool to assess local bone quality in the proximal humerus. We found that deltoid tuberosity index values consistently lower than 1.4 indicated low local BMD of the proximal humerus. Furthermore, the use of the deltoid tuberosity index has important advantages over the Tingart measurement regarding clinical applicability in patients with proximal humerus fractures, when fracture lines obscure the Tingart measurement landmarks. However, further studies are needed to assess the effect of the deltoid tuberosity index measurement and osteoporosis on treatment and outcome in patients with proximal humerus fractures. LEVEL OF EVIDENCE: Level IV, diagnostic study.

Inferior results of salvage arthrodesis after failed ankle replacement compared to primary arthrodesis.

BACKGROUND: Up to now, there has been no evidence that salvage arthrodesis would perform inferior when compared with primary ankle arthrodesis. The purpose of this study was to compare their clinical and radiographic results. METHODS: A retrospective analysis was performed using 2 validated scores and assessment of radiographic union by comparing 23 patients who underwent salvage ankle arthrodesis (group SA = salvage arthrodesis) after failed total ankle replacement with 23 matched patients who received primary ankle arthrodesis (group PA = primary arthrodesis). The mean follow-up period was 38 (range 16-92) months in group SA and 56 (23-94) months in group PA. RESULTS: Complete union was achieved in 17 patients (74%) after a mean time of 50 (13- 114) weeks in group SA and in 16 patients (70%) after a mean time of 23 (10-115) weeks in group PA. The SF-36 score averaged 48 points (7-80) in SA and 66 points (14-94; P = .006) in group PA. In group SA the mean FFI was 57% (22-82) for pain and 71% (44-98) for function. In group PA significantly better results for pain with 34% (0-88; P = .002) and function with 48% (1-92; P = .002) were found. CONCLUSION: Salvage arthrodesis led to impaired life quality and reduced function combined with significantly higher pain when compared with primary ankle arthrodesis. These findings can be used to counsel our patients preoperatively. LEVEL OF EVIDENCE: Level III, retrospective case series.

How many radiographs are needed to detect angular stable head screw cut outs of the proximal humerus - a cadaver study.

INTRODUCTION: Cut out of locking head screws is the most common complication of locking plates in fracture fixation of the proximal humerus with potentially disastrous consequences. Aim of the study was to find the single best and combination of radiographic projections to reliably detect screw cut outs. MATERIALS AND METHODS: The locking plate was fixed to six cadaveric proximal humeri. Six different radiographs were performed: anteriorposterior in internal (apIR), in neutral (ap0) and in 30° external rotation (apER); axial in 30° (ax30) and 60° (ax60) abduction and an outlet view. Each head screw (n=9) was sequentially exchanged to perforate the humeral head with the tip and all radiographs were repeated for each cut out. Randomized image reading by two blinded examiners for cut out was done for single projection and combinations. RESULTS: Interrater agreement was 0.72-0.93. Best single projection was ax30 (sensitivity 76%) and the worst was the outlet view (sens. 17%). Standard combination of apIR/outlet reached a sens. of 54%. The best combination of two was: apER/ax30 (90% sens.), of three: apIR/apER/ax30 (96% sens.) and of four: apIR/ap0/apER/ax30 (100% sens.). CONCLUSION: Standard radiographs (ap/outlet), especially in internal rotation, may miss nearly half of screw cut outs. Single best radiographic projection was an axial view with 30° abduction. To account for all cut outs and correct screw position a combination of four projections was needed. These simple and feasible intraoperative and postoperative radiographs help to detect screw perforations of the locking plate reliably. LEVEL OF EVIDENCE: I (Study of Diagnostic Test).

Primary stability and stiffness in ankle arthrodes-crossed screws versus anterior plating.

BACKGROUND: Ankle arthrodesis is commonly used for the treatment of osteoarthritis or failed arthroplasty. Screw fixation is the predominant technique to perform ankle arthrodesis. Due to a considerable frequency of failures research suggests the use of an anatomically shaped anterior double plate system as a reliable method for isolated tibiotalar arthrodesis. The purpose of the present biomechanical study was to compare two groups of ankle fusion constructs - three screw fixation and an anterior double plate system - in terms of primary stability and stiffness. METHODS: Six matched-pairs human cadaveric lower legs (Thiel fixated) were used in this study. One specimen from each pair was randomly assigned to be stabilized with the anterior double plate system and the other with the three-screw technique. The different arthrodesis methods were tested by dorsiflexing the foot until failure of the system, defined as rotation of the talus relative to the tibia in the sagittal plane. Experiments were performed on a universal materials testing machine. The force required to make arthrodesis fail was documented. For calculation of the stiffness, a linear regression was fitted to the force-displacement curve in the linear portion of the curve and its slope taken as the stiffness. RESULTS: For the anatomically shaped double-plate system a mean load of 967N was needed (range from 570N to 1400N) to make arthrodesis fail. The three-screw fixation method resisted a mean load of 190N (range from 100N to 280N) (p=0.005). In terms of stiffness a mean of 56N/mm (range from 35N/mm to 79N/mm) was achieved for the anatomically shaped double-plate system whereas a mean of 10N/mm (range from 6N/mm to 18N/mm) was achieved for the three-screw fixation method (p=0.004). CONCLUSIONS: Our biomechanical data demonstrates that the anterior double-plate system is significantly superior to the three-screw fixation technique for ankle arthrodesis in terms of primary stability and stiffness.

Endostatin inhibits Callus remodeling during fracture healing in mice.

Information on the impact of endogenous anti-angiogenic factors on bone repair is limited. The hypothesis of the present study was endostatin, an endogenous inhibitor of angiogenesis, disturbs fracture healing. We evaluated this hypothesis in a closed femoral fracture model studying two groups of mice, one that was treated by a daily injection of 10 µg recombinant endostatin subcutaneously (n = 38) and a second one that received the vehicle for control (n = 37). Histomorphometric analysis showed a significantly increased callus formation in endostatin-treated animals at 2 and 5 weeks post-fracture. This was associated with a significantly higher callus tissue fraction of cartilage and fibrous tissue at 2 weeks and a significantly higher fraction of bone at 5 weeks post-fracture. Biomechanical testing revealed a significantly higher torsional stiffness in the endostatin group at 2 weeks. For both groups, we could demonstrate the expression of the endostatin receptor unit integrin alpha5 in endothelial cells, osteoblasts, osteoclasts, and chondrocytes at 2 weeks. Immunohistochemical fluorescence staining of CD31 showed a lower number of blood vessels in endostatin-treated animals compared to controls. The results of the present study indicate endostatin promotes soft callus formation but inhibits callus remodeling during fracture healing most probably by an inhibition of angiogenesis.

Short- or long-stem prosthesis for intramedullary bypass of proximal humeral fractures with severe metaphyseal bone loss: evaluation of primary stability in a biomechanical model.

BACKGROUND: Proximal humeral fractures with substantial metaphyseal comminution are challenging to treat. In the elderly with osteoporotic bone, arthroplasty sometimes remains the only valuable option; however, the minimally required length of stem fixation is not known. The aim of this study was to investigate the primary stability of cemented short- and long-stem prostheses with different intramedullary fracture bypass lengths. MATERIALS AND METHODS: Osteoporotic composite bone models of the humerus (Synbone, Malans, Switzerland) with 3 different fracture levels (group A, 6 cm distal to surgical neck; group B, 7 cm distal to surgical neck; and group C, 8 cm distal to surgical neck) were prepared with a cemented standard short (S)- or long (L)-stem prosthesis and were tested for torque to failure. As a reference, we used models with intact bone (group R-O) and a short-stem prosthesis implanted at the surgical neck (group R-P). The radiographic bypass index (BI) was calculated before testing (fracture level to stem tip [in millimeters]/outer cortical diameter at fracture level [in millimeters]). RESULTS: The resulting BIs of each group were as follows: 1.7 in group A-S, 3.4 in group A-L, 1.4 in group B-S, 3.2 in group B-L, 1.0 in group C-S, and 2.9 in group C-L. Compared with group R-O, the torques to failure of groups B-S and C-S were significantly lower, whereas only group C-S was significantly weaker than group R-P (P < .01). Comparing short- and long-stem bypasses of different fracture heights, we found that only group C-L showed a significantly higher resistance to torque (P < .01). CONCLUSIONS: A short-stem bypass with a BI of 1.7 was sufficient for primary stability tested by torque to failure in this biomechanical setting. For smaller BIs, a long-stem prosthesis should be considered. LEVEL OF EVIDENCE: Basic science study, biomechanics.

Early detection of subclinical organ dysfunction by microdialysis of the rectus abdominis muscle in a porcine model of critical intra-abdominal hypertension.

The aim of this study was to evaluate microdialysis of the rectus abdominis muscle (RAM) for early detection of subclinical organ dysfunction in a porcine model of critical intra-abdominal hypertension (IAH). Microdialysis catheters for analyses of lactate, pyruvate, and glycerol levels were placed in cervical muscles (control), gastric and jejunal wall, liver, kidney, and RAM of 30 anesthetized mechanically ventilated pigs. Catheters for venous lactate and interleukin 6 samples were placed in the jugular, portal, and femoral vein. Intra-abdominal pressure (IAP) was increased to 20 mmHg (IAH20 group, n = 10) and 30 mmHg (IAH30, n = 10) for 6 h by controlled CO2 insufflation, whereas sham animals (n = 10) exhibited a physiological IAP. In contrast to 20 mmHg, an IAH of 30 mmHg induced pathophysiological alterations consistent with an abdominal compartment syndrome. Microdialysis showed significant increase in the lactate/pyruvate ratio in the RAM of the IAH20 group after 6 h. In the IAH30 group, the strongest increase in lactate/pyruvate ratio was detected in the RAM and less pronounced in the liver and gastric wall. Glycerol increased in the RAM only. After 6 h, there was a significant increase in venous interleukin 6 of the IAH30 group compared with baseline. Venous lactate was increased compared with baseline and shams in the femoral vein of the IAH30 group only. Intra-abdominal pressure-induced ischemic metabolic changes are detected more rapidly and pronounced by microdialysis of the RAM when compared with intra-abdominal organs. Thus, the RAM represents an important and easily accessible site for the early detection of subclinical organ dysfunction during critical IAH.

The varus ankle and instability.

Varus ankle associated with instability can be simple or complex. Multiple underlying diseases may contribute to this complex pathologic entity. These conditions should be recognized when attempting proper decision-making. Treatment options range from conservative measures to surgical reconstruction. Whereas conservative treatment might be a possible approach for patients with simple varus ankle instability, more complex instabilities require extensive surgical reconstructions. However, adequate diagnostic workup and accurate analysis of varus ankle instability provide a base for the successful treatment outcome.