Increased Hip Intracapsular Pressure Decreases Perfusion of the Capital Femoral Epiphysis in a Skeletally Immature Porcine Model.

BACKGROUND: Increased intracapsular hip pressure is thought to be one of the possible etiologies of femoral head avascular necrosis after intra-articular proximal femoral fractures or acute slipped capital femoral epiphysis. The purpose of this study was to evaluate the relationship between intra-articular hip pressure (IAP) and epiphyseal perfusion pressure (EPP), and its dependency on skeletal maturity using a porcine model. METHODS: Seven female Yorkshire-hybrid pigs were used to study the direct relationship between IAP and EPP. A needle inserted into the capsule provided both IAP monitoring and saline infiltration until IAP was above mean arterial pressure (MAP). Video simultaneously documented IAP, EPP, MAP. Parameters for all trials in each hip were averaged and compared between the 2 age groups. Significance was P<0.05. RESULTS: Four young hips (in pigs 10.3±1.0 wk, 27.4±2.0 kg) and 5 older hips (21.1±0.1 wk, 89.4±7.1 kg) were studied. There was no significant difference in the MAP (50.0±11.8 and 55.5±7.0 mm Hg respectively, P=0.411) between the 2 age groups. In the older hips, biphasic EPP persisted despite increasing IAP to an average of 177 mm Hg over MAP. In the young pigs, the biphasic EPP waveform ceased with increased IAP to an average of 28 mm Hg over MAP. Biphasic waveforms returned once IAP fell to an average of 5 mm Hg over MAP. CONCLUSIONS: Increased IAP resulted in tamponade of epiphyseal perfusion in the young, but not in the older hips. An intact physis may preclude intraosseous metaphyseal vessels from penetrating the epiphysis, leaving it vulnerable to retinacular artery tamponade. CLINICAL RELEVANCE: The IAP and EPP relationship has direct clinical practice implications. Hip capsulotomy and decompression in young patients with intra-articular proximal femoral fractures and increased intracapsular pressure may decrease avascular necrosis risk.

Torsional Growth Modulation of Long Bones by Oblique Plating in a Rabbit Model.

BACKGROUND: There is evidence that oblique tension band plating can affect torsional growth in long bones. This study sought to determine if the torsional growth could be modulated based on the angles of the tension band plating and whether or not oblique plating affected overall longitudinal growth. METHODS: New Zealand White rabbits (10.5 wk old) had one screw placed on the metaphyseal side and one on the epiphyseal side of both medial and lateral sides of the right knee distal femoral physis. The sham group (n=5) included screw placement only. For the plate group (n=13), unlocked plates, angled from 0 to 76 degrees, connected the screws and spanned the physis. Radiographs were taken at biweekly intervals. After 6 weeks of growth, hindlimbs were harvested and microCT scans performed. Femoral length, distances between screw heads and angle between the plates were measured on radiographs. Femoral length differences were compared between groups. Femoral version was measured from 3D microCT. Plate angle changes were correlated to the difference in femoral version between limbs using Pearson correlation (significance was set to P<0.05 for all comparisons). RESULTS: Femur length difference between the contralateral and the operative side was significantly greater in the plate group compared with the sham group over time (P=0.049). Medial and lateral screw distances changed significantly more in the sham group than the plate group on both sides (P<0.001). A greater initial angle between plates resulted in a greater change in the angle between plates (P<0.001). Significant correlations were found between right-left side femoral version differences and initial plate angle (P=0.003) and plate angle change (P=0.014). CONCLUSIONS: The torsional effect of oblique plating seems to correlate with the amount of initial plate angle, with an additional, not negligible, longitudinal growth effect. CLINICAL SIGNIFICANCE: Placing plates at given angles across open physes may result in predictable changes in bone torsion allowing for a safer and less invasive option when treating childhood torsional deformities, but the resulting shortening of the ipsilateral femur must be considered.

CT scans better assess lateral wall morphology of "stable appearing" intertrochanteric (IT) femur fractures and predict early failure of sliding hip screw (SHS) fixation.

To compare the efficacy of plain x-ray images and computed tomography (CT) to assess the morphology of the lateral wall (LW) component of intertrochanteric (IT) femur fractures and determine predictors of early fixation failure. DESIGN: Retrospective cohort study. SETTING: Level-one trauma center. PATIENTS/PARTICIPANTS: One hundred forty-two adult patients with IT fractures treated with either a sliding hip screw (SHS) or a cephalomedullary nail (CMN) who had both pre-op plain x-ray images and CT scans with at least 6 weeks of follow-up were reviewed. INTERVENTION: Preoperative CT scan and plain radiographs of the affected hip. MAIN OUTCOME MEASUREMENTS: Lateral wall assessment based on plain x-rays versus CT imaging in relation to implant failure. RESULTS: One hundred forty-two patients met inclusion criteria, 105 patients treated with a CMN, and 37 with a SHS. There was a poor correlation between the assessment of the LW on plain x-ray images and CT scans. Failures in the SHS group were significantly associated with all CT measurements (P < .05) but not with plain film LW assessment (P = .66). Fifteen patients had an early implant failure (6 CMN, 9 SHS). There were no statistically significant associations between any radiographic measurement (plain images and CT) and CMN failures. CONCLUSIONS: Plain film images are not accurate for assessing lateral wall morphology/integrity and are not predictive of SHS implant failures. Our novel CT measurements were effective at detecting lateral wall patterns at risk for treatment failure with SHS implants.Level of Evidence: Level III.

Predicting Trainee Clinical Success From Performance at Simulated Endotracheal Intubation.

INTRODUCTION: Multiple attempts and failure at endotracheal intubation (ETI) are common for inexperienced practitioners and can cause patient morbidity. A test to predict a provider's likelihood of success at patient ETI could assist decisions about training. This project investigated whether trainees' performance at laryngoscopy on airway mannequins predicted their laryngoscopy outcomes in patients. METHODS: Twenty-one consenting first-year anesthesiology residents, emergency medicine residents, and medical students enrolled in this prospective, observational study. They performed laryngoscopy and ETI with a curved laryngoscope on 4 airway mannequins. Metrics included peak dental force, procedure duration, esophageal intubation, laryngeal view, and first-pass ETI success on the mannequins. Trainee data from 203 patient ETIs were collected over a roughly 2-month period centered around the simulation test. Multivariable logistic regression analyzed the relationship of mannequin metrics, participant experience, and a patient difficult airway score with trainee ETI outcomes in patients. RESULTS: Median trainee first-pass success rate at patient ETI was 63%, the rate of ETI problems was 16%, and the esophageal intubation rate was 6%. Laryngoscopy peak dental force, first-pass ETI success, and duration on individual mannequins were significant predictors of patient ETI first-pass success. Metrics from 2 of the 4 mannequins predicted ETI problems. DISCUSSION: Performance metrics from simulated laryngoscopy predicted trainee outcomes during patient ETI. First-pass success and ETI problems affect patient safety and are related to trainee skill. Mannequin laryngoscopy tests could identify trainees who would benefit from additional practice. The metrics could be surrogate end points in research to optimize simulated laryngoscopy training.