The intra-muscular course and distribution of the anterior interosseous nerve within pronator quadratus: An anatomical study.

Background: The anterior interosseous nerve (AIN) is a terminal motor branch of the median nerve innervating the following three muscles from proximal to distal: Flexor pollicis longus (FPL), the radial half of flexor digitorum profundus (FDP), and the pronator quadratus (PQ). The aim of this study was to define the course of the AIN within the PQ to aid surgeons performing distal radial procedures. Methods: Ten embalmed cadaveric forearms were dissected to identify the path of the AIN within PQ. An en-bloc excision of the PQ with its supplying AIN and vasculature was performed to identify a safe zone where PQ can be elevated without damaging AIN. A scoping literature search was performed to identify other studies reporting the path of AIN through PQ. Results: The mean distance from the radial border of the radius perpendicular to the point at which the AIN enters the PQ was 22.3 mm (range 21-24 mm). The mean distance from the distal wrist crease to the AIN entering PQ was 74.3 mm (range 59-84 mm). The mean number of nerve branches to PQ was 5.2 (range 3-8). In all specimens, the AIN was found to lie on the radial side of the anterior interosseous artery (AIA). Conclusions: The AIN courses on the deep surface of the PQ in a longitudinal proximal to distal direction. A 'safe zone' was identified within 20 mm of the radial border of the distal radius, which may be utilised by surgeons in a muscle-splitting approach to the distal radius.

Impact of radiologic variables on item responses of ODI, SRS22 and SF-36. in adult spinal deformity patients: differential item functioning (DIF) analysis results from a multi-center database.

PURPOSE: To determine if responses given to each question of the Scoliosis Research Society-22 (SRS22), Oswestry disability index (ODI) and Short Form-36 (SF-36) questionnaires are influenced by the radiological parameters. METHODS: Patients enrolled in a multi-centre prospectively collected adult spinal deformity database who had complete SRS22, ODI and SF-36 data at baseline and at one-year follow-up were analysed. The presence of a differential item function of each question within each score in relation to radiological parameters was analysed using a mixed Rasch model with the radiological threshold value(s) determined. RESULTS: Of those patients analysed (n = 1745; 1406 female, average age 51.0 ± 19.8 years), 944 were surgically and 801 were non-surgically treated. For the SRS22, questions (Q) 3, 5 and 18 were sensitive to almost all radiological parameters and the overall score was found sensitive to the Cobb angle. For the ODI, Q3, 6, 9 and 10 were not sensitive to any radiologic parameters whereas Q4 and 5 were sensitive to most. In contrast, only 3 of the SF-36 items were sensitive to radiological parameters. CONCLUSIONS: 78% of the SRS-22, 60% of the ODI and 8% of the questions in the SF-36 are sensitive to radiological parameters. Sagittal imbalance is independently associated with a poor overall outcome, but affects mental status and function more than pain and self-image. The assembly of questions responsive to radiological parameters may be useful in establishing a connection between changes in radiologic parameters and HRQL.

Ballistic gelatin calibration standardisation.

INTRODUCTION: A review of ballistic gelatin calibration standards has highlighted that data used from studies with different calibrations methods may not be able to be compared. Calibration of ballistic gelatin did not occur until the mid-1980s when Fackler recognised the deficiencies of uncalibrated gelatin. He determined that the calibration standard should be 85±5 mm of ball bearing penetration for a 180 m/s impact velocity. This study looks to improve on and optimise current ballistic gelatin calibration standards METHODS: Nine 0.177 cal (4.5 mm) spheres were fired using a Daisy Powerline air rifle at velocities between 134 m/s and 224 m/s at 25 gelatin blocks (n=225). Velocities were measured using an Oehler Model 36 Chronograph with three Model 57 screens. Depth of penetration (DoP) was measured from the entry surface to the back end of the sphere via a Mitutoyo Absolute vernier calliper. RESULTS: The R-squared regression model showed that all batches had a close fit to the regression line. Using the R-squared regression model, the equation y=0.584x - 20.02 (where x is the velocity) returned a DoP of 84.918 mm for a 180 m/s impact and therefore needed minimal adjustment to align with Fackler's 85 mm DoP. The equation can be adjusted to y=0.584x - 20.12 to return a DoP of 85 mm for 180 m/s. CONCLUSIONS: We propose that the calibration standard of ballistic gelatin with 4.5 mm spheres is DoP=0.584x - 20.12 where DoP is the depth of penetration (mm) and x is the impact velocity (m/s), The measured DoP should be within 5% of the calculated DoP.

Viability of Bos taurus scapulae as a flat bone proxy for ballistic testing.

BACKGROUND: Handguns and rifles are often involved in violent deaths such as homicide and suicide. Consequently, forensic investigations are important to clarify the nature of ballistic trauma. METHODS: This study investigated the differences in entrance and exit wound morphology with Bos taurus (bovine) scapulae that have two cortical layers surrounding a central cancellous bone section which are comparable with human flat bones, with a series of experiments using six different calibres (0.22 Long Rifle, 9×19 mm North Atlantic Treaty Organization, 0.40 Smith & Wesson, 0.45 Automatic Colt Pistol, 5.56×45 mm and 7.62×51 mm). B. taurus (bovine) scapulae were used for closed range 30 cm simulated executions. RESULTS: The ballistic experiments presented similarities in entrance wound morphology and exit wound bevelling with that of recognised forensic cases. As muzzle velocity increased, bevelling increased. Circumferential delamination is clearly visible with full metal jacket rounds, yielding similar bone damage morphology as human crania. CONCLUSION: Bovine scapulae seem appropriate for ballistic simulations of flat bone injuries on the macroscopic level, if the correct portion of the scapulae is deployed. More research is needed to further substantiate these interpretations.

Microscopic and macroscopic comparisons of 0.223 soft point and full metal jacket ammunition with bos taurus scapulae as a proxy to human flat bones.

BACKGROUND: The prevalence of civilian 0.223 ammunition is widespread. Due to low costs and the same dimensions as a 5.56×45 mm North Atlantic Treaty Organization, this round is exceptionally popular. However, recent mass shootings have employed soft point (SP) expanding ammunition to cause grievous wounds compared with military full metal jacket (FMJ) rounds that do not rapidly expand on impact. METHODS: The aim of this given study is to compare FMJ and SP rounds to determine if there are diagnostic differences between the bullet types in the wounds inflicted to flat bones. Bos taurus scapulae were used for 25 m simulated cranial gunshot injuries. Scanning electron microscopy was employed to assess the difference in wound morphology and elemental analysis between SP and FMJ rounds. RESULTS: Entrance and exit wound morphology change significantly between the two different types of ammunition as seen with circumferential delamination which is indicative of FMJ rounds and is not seen with the softer SP hunting rounds. Lead staining of the entrance wound is visible on only the SP rounds. CONCLUSION: Gunshot flat bone wound morphology is distinctively different between SP and FMJ rounds. Circumferential delamination is only seen with FMJ due to the hardness of the round. Lead staining is only seen with SP rounds due to bullet composition.

The Impact of Corrective Surgery on Health-Related Quality of Life Subclasses in Adult Scoliosis: Will Degree of Correction Prognosticate Degree of Improvement?

PURPOSE: Objectives in scoliosis corrective surgery include restoration of normal sagittal and coronal parameters to achieve patient satisfaction. HRQLs improvements remain limited after corrective surgery. The aim of this study was to evaluate the HRQL subclass variability specific to the sagittal and coronal correction in adult scoliosis surgery. METHODS: This multi-centre prospective analysis of consecutive adult spinal deformity (ASD) patients, from five European centres, only included multilevel instrumentation for scoliosis. d-(delta) values for each parameter represented pre to post-operative changes. Parameters included demographics, baseline, 1- and 2-year. HRQL outcomes (Oswestry disability index (ODI), Scoliosis Research Society (SRS)-22 and Short Form (SF36)), sagittal correction including relative spinopelvic alignment (dRSA) and coronal correction including major Cobb (dCobb) angles. RESULTS: A total of 353 patients reached 1-year and 2-year follow up. All HRQL total scores significantly improved postoperatively, including ODI, SRS-22 and SF36. HRQL subclasses which displayed persistent improvements correlated to dRSA included sex-life, self-image, fatigue, vitality, social functioning. The only HRQL subclass improvement that correlated with dCobb was self-image. CONCLUSION: Adult scoliosis surgery improves overall HRQL, having a minimal effect on each variable. Importantly, greater coronal deformity correction affects only greater self-image scores, whereas with greater sagittal correction there are many greater HRQL sub-class impacts. Correction and restoration of coronal balance is one of the surgical goals in adult scoliosis but the degree to which Cobb angle is corrected, apart from self-image, does not correlate with gains in sub-classes of HRQL. These results need to be taken into account when planning surgery.

Impact of COVID-19 on the pain and disability of patients with adult spinal deformity.

PURPOSE: To evaluate the pain and functional effect of the COVID-19 pandemic on patients with ASD reflected by their response to SRS-22, ODI, and SF-36 questionnaires. METHODS: Patients who had stable pain and functional outcome scores over the preceding 2 years were enrolled in a local prospectively collected adult spinal deformity (ASD) database. A reanalysis of their SRS22, ODI and SF-36 data 14 days into confinement were compared to their last pre-confinement scores. RESULTS: 89 patients were included in this study (average age 60.7 years, 91% female) with an average time from last FU until confinement of 9.6 months. The ODI total score worsened by 5 points post-confinement with no difference seen in personal care, walking and social life. In contrast, the SRS-22 score showed small improvements in function/activity and satisfaction, but no significant differences for the other domains. Similarly, the SF-36 showed small improvements in physical function, physical and emotional role, vitality and PCS. CONCLUSION: The global COVID-19 pandemic and ensuing confinement had variable overall effects on ASD patients, without the expected marked worsening. In addition, this study illustrates that the SRS-22 questionnaire is less influenced by environmental and psychological factors than the ODI supporting its objectivity and accuracy in the evaluation of the QoL of ASD patients.

Relative position of the supra-acetabular bone to the crestal plane: a radiological analysis.

INTRODUCTION: Displaced unstable pelvic injuries are life threatening and require rapid reduction and stabilisation, typically achieved with an external fixator. Recently, the benefits of supra-acetabular pins have been proven; however, these are usually inserted under fluoroscopic guidance. In austere environments and in extremis, this facility is limited and fixation using anatomical landmarks is required. Thus, the aim of this study is to determine the relative position of the supra-acetabular bone to the crestal plane and examine its consistency in military-aged European personnel. METHODS: A radiological review of 50 randomised pelvic CT scans in European patients aged 18-30 years from a Level 1 trauma centre was performed. The CT scans were analysed using 3D rendering software. The relative position of the supra-acetabular bone to the crestal plane was determined. RESULTS: The supra-acetabular bone relative to the crestal plane was approximately 28° caudal and 24° medial to the crestal plane. The mean minimum distance from the pin's entry point to the sciatic notch was approximately 73 mm. There were no differences noted between genders or hemipelvic side. CONCLUSIONS: The supra-acetabular bone maintains a consistent relative position to the crestal plane. Thus, with the surgeon's thumb on the anterior superior iliac spine (ASIS) and index finger on the iliac tubercle, defining the crestal plane, a supra-acetabular pin can be inserted into the anterior inferior iliac spine, which lies 3 cm inferior and 2 cm medial to the ASIS, and advanced along the supra-acetabular bone by angling the pin 30° caudal and 25° medial to the crestal plane.

Assessment of plantaris and peroneus tertius tendons as graft materials for ankle ligament reconstructions - A cadaveric biomechanical study.

Both the plantaris tendon and the peroneus tertius tendon are used as auto- and allogenous graft materials to reconstruct the ankle ligament complex. However, it is unclear to what extent these graft materials resemble the load-deformation behavior of the ankle ligaments. A total of 34 human ankle ligaments and 35 tendons were assessed mechanically deploying a quasi-static tensile testing setup. Tendons were significantly stiffer (median elastic moduli: plantaris tendon = 465.7 MPa, peroneus tertius tendon = 338.5 MPa, medial ligament = 61.4 MPa, lateral ligament = 49.3 MPa; p ≤ 0.035), but more distensible (median strain at maximum force: plantaris tendon = 15.1%, peroneus tertius tendon = 15.3%, medial ligament = 9.3%, lateral ligament = 9.6%; p ≤ 0.008) and mechanically tougher (median ultimate tensile strength: plantaris tendon = 51.0 MPa, peroneus tertius tendon = 40.5 MPa, medial ligament = 4.1 MPa, lateral ligament = 3.5 MPa; p ≤ 0.033) when compared to medial and lateral ankle ligaments. The lateral ligaments of the right ankle were significantly tougher compared to the left side (p = 0.015). The elastic modulus of the medial ligament (r = 0.489, p = 0.045) and the peroneus tertius tendon (r = 0.517, p = 0.014) yielded an age-dependent increase. Both tendons seem biomechanically suitable graft materials to replace the medial and lateral ankle ligaments during physiological loading. The age-dependent increase in tissue elastic properties of the medial vs. lateral ankle ligaments, and differences in ultimate tensile strength between the lateral ligaments left vs. right, may reflect the complex asymmetric loading behavior of both ankle ligaments.

The Value of Routine Intravenous Tranexamic Acid in Total Hip Arthroplasty: A Preliminary Study.

OBJECTIVE: To determine the effect on the need for transfusion when intravenous tranexamic acid (TXA) is administered intraoperatively in patients undergoing total hip arthroplasty (THA). METHOD: A prospective, double blinded, randomised control trial of 88 patients undergoing THA was randomly allocated to receive 1 g of intravenous TXA or normal saline on induction of anaesthesia. All patients received spinal anaesthesia. The primary outcome measure was transfusion rate, and the secondary outcomes were intraoperative blood loss, haemoglobin levels, length of hospital stay, functional scores, and thromboembolic complications. RESULTS: 19.0% of patients given TXA required a blood transfusion, compared with 20.5% given placebo (p=0.87). Secondary outcomes included mean intraoperative blood loss, which was 536.5 ml in the TXA group and 469.8 ml in the placebo group (p=0.87). Secondary outcomes included mean intraoperative blood loss, which was 536.5 ml in the TXA group and 469.8 ml in the placebo group (p=0.87). Secondary outcomes included mean intraoperative blood loss, which was 536.5 ml in the TXA group and 469.8 ml in the placebo group (p=0.87). Secondary outcomes included mean intraoperative blood loss, which was 536.5 ml in the TXA group and 469.8 ml in the placebo group (p=0.87). Secondary outcomes included mean intraoperative blood loss, which was 536.5 ml in the TXA group and 469.8 ml in the placebo group (p=0.87). Secondary outcomes included mean intraoperative blood loss, which was 536.5 ml in the TXA group and 469.8 ml in the placebo group (. CONCLUSIONS: 1 g IV TXA administered on induction did not significantly reduce the need for blood transfusion, postoperative blood loss, functional scores, or the length of stay in patients undergoing THA. This trial is registered with ACTRN12610001065088.

Validation of a Simplified SRS-Schwab Classification Using a Sagittal Modifier.

STUDY DESIGN: Multicenter, prospective study of consecutive adult spinal deformity (ASD) patients. OBJECTIVE: To Validate Schwab's classification accuracy for surgical indication, and to evaluate a simplified sagittal modifier. SUMMARY OF BACKGROUND DATA: The SRS-Schwab Radiologic Classification based on clinical impact parameters, offers 27 different sagittal classification possibilities regarding sagittal vertical alignment (SVA), pelvic tilt (PT), and pelvic incidence-lumbar lordosis (PI-LL). The high number of classification possibilities makes it complex to use. METHODS: Inclusion criteria were ASD patients, presenting at least 1 criteria: Cobb ≥ 20°, SVA ≥ 5 cm, thoracic kyphosis ≥ 60°, or PT ≥ 25°. A total of 1,004 patients (410 nonoperative and 594 operative) were classified regarding SVA, PT, and PI-LL (0, +, ++), and 27 possibilities were identified. Categories were formed by adding the number of + signs, considering PT, SVA, and PI-LL. Three specific categories were identified: Aligned: 0 +; Moderate deformity: 1 to 3+; and Severe deformity: 4 to 6+. A χ-square test was performed for surgical indication (operated or not) and an analysis of variance was performed to evaluate the relationship between categories and Oswestry Disability Index (ODI). Probability <.05 was considered significant. RESULTS: Significant differences for HRQoL scores and surgical indication were found in the 27 sagittal parameter possibilities. For nonoperative patients, 230 (56.1%) were classified as aligned, 145 (35.4%) as moderate, and 35 (8.5%) as severe. For operative patients, there were 200 (33.7%), 215 (36.2%), and 179 (30.1%) in each respective subgroup. For HRQoL scores and surgical indication, no significant differences were found within each category, but significant differences were found when comparing the subgroups. CONCLUSIONS: Despite the correlation between SRS-Schwab classification and surgical indication, it is complex to use, with a total of 27 possibilities regarding sagittal modifiers. This simplification into three categories offers more readability, without losing any significant information, and could replace Schwab sagittal modifiers. In association with other parameters, they could be used for decision-making. LEVEL OF EVIDENCE: Level II.

Spontaneous spinal epidural haematomas in children.

PURPOSE: To understand the typical presentation, risk factors, location and size, treatment, neurological recovery and survival of spontaneous spinal epidural haematomas (SSEH) in children. METHODS: A systematic review of the English literature from 1 January 1960 to 1 March 2018 was performed on children aged 18 years and younger. Individual patient data were extracted and collated. Outcome measures were mode of presentation, risk factors, initial neurological findings, initial presumed diagnosis, diagnostic investigations, site and size of the SSEH, treatment, neurological recovery and survival. RESULTS: Thirty-one publications and 36 patients were reviewed. All age groups were affected. 83% of patients did not have a known risk factor. Back pain was reported in 61% and neurological dysfunction in 97% of patients, although not all articles defined these parameters. Initially 28% of patients were suspected of having an alternative diagnosis. All patients had an MRI and/or CT scan confirming the diagnosis. The cervical-thoracic region was most commonly affected, and the average haematoma size extended across 6.3 vertebral levels. Surgical decompression was performed in 72% of patients. Neurological function improved in 83% of patients. Two patients died as a consequence of their SSEH. CONCLUSIONS: SSEHs affect all paediatric age groups and typically present with neurological dysfunction and/or back pain. The initial diagnosis is incorrect in up to 28% of cases, but cross-sectional spinal imaging is diagnostic. Most SSEHs are located in the cervico-thoracic region and affect multiple spinal levels. The treatment depends on whether the patient has a bleeding disorder and their neurological status. These slides can be retrieved under Electronic Supplementary Material.

A Positive Quadriceps Active Test, without the Quadriceps Being Active.

CASE: A 55-year-old male with a chronic isolated grade 3 PCL injury who demonstrates a positive quadriceps active test without activating his quadriceps musculature. CONCLUSION: Gravity and hamstring contraction posteriorly translate the tibia into a subluxed position. Subsequent gastrocnemius contraction with the knee flexed causes an anterior tibial translation by virtue of the mass enlargement of the gastrocnemius muscular bulk, the string of a bow effect, and the anterior origin of the gastrocnemius in relation to the posterior border of the subluxed tibia aided by the normal posterior tibial slope.

A six-year observational study of 31 children with early-onset scoliosis treated using magnetically controlled growing rods with a minimum follow-up of two years.

Aims: Magnetically controlled growing rod (MCGR) systems use non-invasive spinal lengthening for the surgical treatment of early-onset scoliosis (EOS). The primary aim of this study was to evaluate the performance of these devices in the prevention of progression of the deformity. A secondary aim was to record the rate of complications. Patients and Methods: An observational study of 31 consecutive children with EOS, of whom 15 were male, who were treated between December 2011 and October 2017 was undertaken. Their mean age was 7.7 years (2 to 14). The mean follow-up was 47 months (24 to 69). Distractions were completed using the tailgating technique. The primary outcome measure was correction of the radiographic deformity. Secondary outcomes were growth, functional outcomes and complication rates. Results: The mean Cobb angle was 54° (14° to 91°) preoperatively and 37° (11° to 69°) at the latest follow-up (p < 0.001). The mean thoracic kyphosis (TK) was 45° (10° to 89°) preoperatively and 42° (9° to 84°) at the latest follow-up. The mean T1-S1 height increased from 287 mm (209 to 378) to 338 mm (240 to 427) (p < 0.001) and the mean sagittal balance reduced from 68 mm (-76 to 1470) preoperatively to 18 mm (-32 to 166) at the latest follow-up. The mean coronal balance was 3 mm (-336 to 64) preoperatively and 8 mm (-144 to 64) at the latest follow-up. The mean increase in weight and sitting and standing height at the latest follow-up was 45%, 10% and 15%, respectively. The mean Activity Scale for Kids (ASKp) scores increased in all domains, with only personal care and standing skills being significant at the latest follow-up (p = 0.02, p = 0.03). The improvements in Cobb angle, TK and T1-S1 heights were not related to gender, the aetiology of the EOS, or whether the procedure was primary or conversion from a conventional growing rod system. A total of 21 children developed 23 complications at a rate of 0.23 per patient per year. Seven developed MCGR-specific complications. Complications developed at a mean of 38 months (3 to 67) after the initial surgery and required 22 further procedures. Children who developed a complication were more likely to be younger, have syndromic EOS, and have a single-rod construct (6.9 versus 9.3 years, p = 0.034). Conclusion: The progression of EOS can be controlled using MCGRs allowing growth and improved function. Younger and syndromic children are more likely to develop complications following surgery. Cite this article: Bone Joint J 2018;100-B:1187-1200.

Influence of rib impact on thoracic gunshot trauma.

INTRODUCTION: The influence of rib impact on thoracic gunshot trauma remains unclear, despite its high occurrence. This study therefore investigates the effect of rib impact on a bullet's terminal properties and injury severity. METHODS: Two bullets were used: 5.56×45 mm (full charge and reduced charge) and 7.62×51 mm (full charge). For each bullet, three impact groups were tested: (1) plain 10% ballistic gelatin (control) conditioned at 4°C, (2) intercostal impact, and (3) rib impact, the latter two tested with samples of porcine thoracic walls embedded in gelatin. Analysis included penetration depth, trajectory change, yaw, fragmentation, velocity reduction, energy deposition and temporary and permanent cavity characteristics. RESULTS: No significant differences were observed for most variables. Differences were found between rib (and intercostal) impact and the control groups, suggesting that the inclusion of thoracic walls produces an effect more significant than the anatomical impact site. Effects were ammunition specific. For the 7.62×51 mm round, rib impact caused an earlier onset of yaw and more superficial permanent gelatin damage compared with plain gelatin. This round also formed a larger temporary cavity on rib impact than intercostal impact. Rib (and intercostal impact) created a smaller temporary cavity than the control for the 5.56×45 mm round. For the reduced-charge 5.56×45 mm round, rib and intercostal impact produced greater velocity reduction compared with plain gelatin. CONCLUSIONS: This study provides new insights into the role of rib impact in thoracic gunshot injuries, and indicates that the effects are ammunition dependent. Unlike the 5.56×45 mm rounds, rib impact with the 7.62×51 mm rounds increases the risk of severe wounding.

Effect of ageing on the calibration of ballistic gelatin.

PURPOSE: Ballistic gelatin is commonly used as a validated surrogate for soft tissue during terminal ballistic testing. However, the effect of a delay between production and testing of a gelatin mould remains unknown. The aim of this study was to determine any potential effects of ageing on ballistic gelatin. METHODS: Depth of penetration (DoP) of 4.5 mm spherical fragment simulating projectiles was ascertained using mixtures of 10%, 11.25% and 20% Type A 250 Bloom ballistic gelatin. Testing was performed daily for 5 days using velocities between 75 and 210 m/s. DoP at day 5 was statistically compared with day 1, and net mass change was recorded daily. RESULTS: No significant difference was found for DoP observed with time in any of the samples (P>0.05). Spearman correlation was excellent in all moulds. The moulds with known standard calibrations remained in calibration throughout the study period. Mass loss of less than 1% was noted in all samples. CONCLUSION: Mass loss was the only quantifiable measure of changes in the blocks with time, but did not correlate with any changes in DoP. This may provide reassurance when undertaking such testing that an inadvertent delay will not significantly alter the penetration properties of the mould. Future research is recommended to determine any potential effect on the mechanical properties of gelatin at higher velocity impacts and whether the calibration corresponds to an adequate simulation under such conditions.

Is tranexamic acid toxic to articular cartilage when administered topically? What is the safe dose?

Aims: The intra-articular administration of tranexamic acid (TXA) has been shown to be effective in reducing blood loss in unicompartmental knee arthroplasty and anterior cruciate reconstruction. The effects on human articular cartilage, however, remains unknown. Our aim, in this study, was to investigate any detrimental effect of TXA on chondrocytes, and to establish if there was a safe dose for its use in clinical practice. The hypothesis was that TXA would cause a dose-dependent damage to human articular cartilage. Materials and Methods: The cellular morphology, adhesion, metabolic activity, and viability of human chondrocytes when increasing the concentration (0 mg/ml to 40 mg/ml) and length of exposure to TXA (0 to 12 hours) were analyzed in a 2D model. This was then repeated, excluding cellular adhesion, in a 3D model and confirmed in viable samples of articular cartilage. Results: Increasing concentrations above 20 mg/ml resulted in atypical morphology, reduced cellular adhesion and metabolic activity associated with increased chondrocyte death. However, the cell matrix was not affected by the concentration of TXA or the length of exposure, and offered cellular protection for concentrations below 20 mg/ml. Conclusion: These results show that when in vitro chondrocytes are exposed to higher concentrations of TXA, such as that expected following recommended intra-articular administration, cytotoxicity is observed. This effect is dose-dependent, such that a tissue concentration of 10 mg/ml to 20 mg/ml could be expected to be safe. Cite this article: Bone Joint J 2018;100-B:404-12.

Delayed post-operative tension pneumocephalus and pneumorrhachis.

INTRODUCTION: The incidence of pneumocephalus and pneumorrhachis after spinal surgery is unknown, with a paucity of literature on this complication. MATERIALS AND METHODS: We present the first published case of delayed onset tension pneumocephalus and pneumorrhachis associated with spinal surgery. RESULTS: This complication occurred from a cerebro-spinal fluid (CSF) leak after posterior instrumentation removal and was successfully treated with emergent wound debridement and the formation of a CSF fistula. CONCLUSIONS: This case illustrates that delayed post-operative tension pneumocephalus and pneumorrhachis can occur after spinal surgery in a patient with a CSF leak. It also illustrates that pneumocephalus and pneumorrhachis can be easily diagnosed with cross-sectional CT imaging. Furthermore, in a patient with rapid deterioration emergent surgical debridement may be necessary. Lastly, if the dural tear cannot be identified intra-operatively, the formalization of a CSF fistula should be considered.

Erratum to: Delayed post-operative tension pneumocephalus and pneumorrhachis.

Unfortunately, two author names were missed out in author group of the original publication.

Projectile penetration into ballistic gelatin.

Ballistic gelatin is frequently used as a model for soft biological tissues that experience projectile impact. In this paper we investigate the response of a number of gelatin materials to the penetration of spherical steel projectiles (7 to 11mm diameter) with a range of lower impacting velocities (<120m/s). The results of sphere penetration depth versus projectile velocity are found to be linear for all systems above a certain threshold velocity required for initiating penetration. The data for a specific material impacted with different diameter spheres were able to be condensed to a single curve when the penetration depth was normalised by the projectile diameter. When the results are compared with a number of predictive relationships available in the literature, it is found that over the range of projectiles and compositions used, the results fit a simple relationship that takes into account the projectile diameter, the threshold velocity for penetration into the gelatin and a value of the shear modulus of the gelatin estimated from the threshold velocity for penetration. The normalised depth is found to fit the elastic Froude number when this is modified to allow for a threshold impact velocity. The normalised penetration data are found to best fit this modified elastic Froude number with a slope of 1/2 instead of 1/3 as suggested by Akers and Belmonte (2006). Possible explanations for this difference are discussed.