Multimodal nerve monitoring during periacetabular osteotomy identifies surgical steps associated with risk of injury.

PURPOSE: Sciatic nerve palsy after periacetabular osteotomy (PAO) is a serious complication. The purpose of this study was to determine whether a multimodal sciatic monitoring technique allows for identification of surgical steps that place the sciatic nerve at risk. METHODS: Transcranial electrical motor evoked potentials (TcMEPs), somatosensory evoked potentials (SSEPs), and spontaneous electromyography (EMG) were monitored in a consecutive series of 34 patients (40 hips) who underwent PAO for the treatment of symptomatic hip dysplasia between January 2012 and November 2014. There were 29 females (85%) and five males (15%) with an average age of 19 years (range, 12-36 years) at the time of surgery. RESULTS: We detected eight temporary sciatic nerve monitoring alerts in six patients (incidence of 15%). The events included decrease in amplitude of the TcMEPs related to the position of the hip during incomplete ischium osteotomy and placement of a retractor in the sciatic notch during the posterior column osteotomy (N = 3), generalized bilateral decrease in TcMEPs during fragment manipulation and fixation in association with acute blood loss (N = 2), and a change in SSEPs during a superior pubic osteotomy and supra-acetabular osteotomy (N = 1). At the end of the procedure, TcMEPs and SSEPs were at baseline and there was no abnormal pattern on EMG in all patients. Post-operatively, at two, six, 12 weeks, and six and 12 months, no motor weakness or sensory deficits were noted. CONCLUSION: Multimodal neuromonitoring allowed for identification of intra-operative steps and maneuvers that potentially place the sciatic nerve at higher risk of injury.

Effect of split posterior tibialis tendon transfer on foot progression angle in children with cerebral palsy.

OBJECTIVES: A common orthopedic issue for patients with spastic cerebral palsy (CP) is hindfoot varus deformity. One method of treatment is the split posterior tibialis tendon transfer (SPOTT). There is limited literature on the effect of SPOTT on foot progression angle (FPA) in children with CP who have equinovarus deformities. The objective of our study was to evaluate the change in FPA after SPOTT to determine if this procedure can improve FPA. RESEARCH QUESTION: This study aims to determine what axial changes are generated from a split posterior tibial tendon transfer in children with CP. METHODS: We performed a retrospective analysis of all ambulatory children with a diagnosis of CP who underwent SPOTT at our institution. Patients with bony rotational procedures were excluded. Descriptive statistics including mean and standard deviation (SD) were used to characterize continuous variables. Paired t-tests were used to evaluate outcomes, in which a target outcome was defined as a post-operative FPA between 0-10° of external rotation. RESULTS: 44 limbs were included. Demographics were as follows: 26/13 female/male; mean age[SD] (years): 9.8[3.5]; 30 hemiplegic, 9 diplegic, and 1 triplegic. Of the 44 limbs, 18 limbs had a target outcome, 4 had no change, and 22 had a non-target outcome. Of the 22 with an outcome outside of the target, 4 limbs trended away from a target outcome. The overall change in FPA measured was - 10.9 ± 14.7° (p < 0.0001) Age at time of surgery, CP involvement, pre-operative FPA, and GMFCS level were not predictors of outcome (p > 0.05). CONCLUSIONS: SPOTT produced a change of 10.9° external rotation in FPA post-operatively and its effects should be considered when planning a SEMLS.

Risk factors for screw breach and iatrogenic nerve injury in percutaneous posterior pelvic ring fixation.

Background: Percutaneous screw fixation of the posterior pelvic ring is technically demanding and can result in cortical breach. The purpose of this study was to examine risk factors for screw breach and iatrogenic nerve injury. Methods: A retrospective review at a single level-one trauma center identified 245 patients treated with 249 screws for pelvic ring injuries with postoperative computed tomography (CT) scans. Cortical screw breach, iatrogenic nerve injury, and associated risk factors were evaluated. Results: There were 86 (35%) breached screws. The breach rate was similar between screw types (33% S1-iliosacral (S1-IS), 44% S1-transsacral (S1-TS), 31% S2-IS, and 30% S2-TS) and was not associated with patient characteristics, Tile C injuries, or corridor size or angle. The overall rate of screw revision for screw malpositioning was 1.2% (3/249). Iatrogenic nerve injuries occurred in 8 (3.2%) of the 249 screws. Screws that caused iatrogenic nerve injuries had greater screw breach distances (5.4 vs. 0 mm, MD 5, CI 2.3 to 8.7, p < 0.0001), were more likely to be S1-IS screws (88% vs. 47%, PD 40%, CI 7 to 58%, p = 0.006), more likely to be placed in Tile C injuries (75% vs. 44%, PD 31%, CI -3 to 55%, p = 0.04), and there was a trend for having a screw corridor size <10 mm (75% vs. 47%, PD 28, CI -6 to 52%, p = 0.06). Of the 7 iatrogenic nerve injuries adjacent to screw breaches, two nerve injuries recovered after screw removal, three recovered with screw retention, and two did not recover with screw retention. Conclusion: Screw breaches were common and iatrogenic nerve injuries were more likely with S1-IS screws. Surgeons should maintain a high degree of caution when placing these screws and consider removal of any breached screw associated with nerve injury.

Defining Sacral Dysmorphism: What Size Corridor Precludes Transsacral Screw Placement.

OBJECTIVE: To determine what size S1-transsacral (TS) corridor is amenable to TS screw placement, as this is commonly used to identify sacral dysmorphism, and to determine if gender, ethnicity, or screw breach is associated with narrow corridors. DESIGN: Retrospective review. SETTING: Urban level-1 trauma center. PATIENTS: Two hundred ninety patients with pelvic ring injuries and preoperative computed tomography (CT) scans. INTERVENTION: Percutaneous posterior pelvic ring fixation. MAIN OUTCOME MEASUREMENTS: The width of the S1-TS corridor was measured on the axial (inlet) and coronal (outlet) reformatted CT images. Patients with S1-TS screw fixation and postoperative CT scans were identified. Corridor size, gender, ethnicity, and screw breach were documented. RESULTS: S1-TS screws were placed in 55 of the 290 patients. No S1-TS screws were placed in corridors less than 8 mm. Corridors of <8 mm were present in 114 (39%) of the 290 patients and were not associated with gender or ethnicity. S1-TS screws placed in small (<10 mm) versus large (≥10 mm) corridors did not have a detectable difference in screw breaches (5 of 8, 62% versus 19 of 47 40%; difference, 22%, 95% confidence interval -14% to 52%) or median (interquartile range) screw breach distance [3 mm (2.5-4.8) versus 3 mm (1.2-4.8); difference, 0.9 mm; confidence interval -1.6 to 2.2]. CONCLUSION: These data are useful for the standardization of sacral dysmorphism reporting based on corridor size. Screw breaches were common irrespective of TS corridor size, emphasizing the small degree of error allowed by this procedure. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Using Reformatted Axial Computed Tomography Images in Isolation Will Miss Narrow S1 Transsacral Screw Corridors.

OBJECTIVE: To evaluate S1 transsacral (TS) corridors on reformatted and nonreformatted computed tomography (CT) images to determine which most reliably identifies narrow corridors. DESIGN: Retrospective cohort. SETTING: Level 1 trauma center. PATIENTS: Two hundred forty-five patients with operative pelvic ring injuries. INTERVENTION: CT scan review. MAIN OUTCOME MEASUREMENTS: Preoperative CT scans were evaluated to determine the width of the S1 TS corridor on standard axial nonreformatted (ANR), axial reformatted (AR), and coronal reformatted images. Sensitivity and specificity of each format to detect a narrow corridor (<10 mm on AR or coronal reformatted) were calculated. Patients with S1 TS screws were evaluated to determine the rate of screw breach with narrow corridors. RESULTS: The axial width of the S1 TS corridor was consistently smaller on ANR versus AR images (mean difference 1.4mm, 95% confidence interval 1.1-1.5). The corridor width on ANR images was on average 86% of the AR measurement. ANR images had the highest sensitivity and specificity (100% and 98%) for detecting S1 TS corridors <10 mm. Fifty-three S1 TS screws were placed in corridors ranging 10-23 mm on AR images and 7-19 mm on ANR images. Four (57%) of the 7 screws placed in corridors less than 10 mm in width on ANR images breached the sacral cortex. CONCLUSION: Using ANR images to measure the S1 TS corridor consistently measured smaller widths than AR images and identified all narrow corridors. A high rate of screw breach was noted with screw placement in narrow corridors. LEVEL OF EVIDENCE: Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Size and location of posterior wall fragment on CT can predict hip instability in a cadaveric model.

PURPOSE: Previous research has been unable to elucidate the exact factors that contribute to hip instability in the setting of posterior wall acetabular fractures. The purpose of this study was to determine the influence of posterior wall fracture fragment size and fracture angle on the stability of the hip joint in a cadaveric model. METHODS: Six fresh human cadavers (12 hips) were used. Specimens underwent pre-procedure CT evaluation and were then randomized to one of three groups: posterior wall fragment size (FS) of 15%, 20% and 25%. Osteotomies were performed starting at a fracture angle (FA) of 40°. The specimens underwent an exam under anesthesia (EUA). If the hip remained stable, the fracture angle was increased in 20° increments and re-tested until it became unstable. RESULTS: In the group with a FS of 15%, all hips were stable with a FA of 40°. Increasing the FA to 60° caused all hips to be unstable (subluxation or dislocation). In the group with a FS of 20% and 25%, all hips were unstable with a FA of 40°. CONCLUSION: In all specimens, a FS of 15% and FA of 40° were stable on EUA. Varying combinations of increasing FS size and increasing FA were all unstable. This study provides data for a CT-based measurement to predict hip instability in the setting of posterior wall acetabular fractures based on FS and FA. More research is required to validate this data in a clinical setting.

Factors That Predict Blood Loss After Bernese Periacetabular Osteotomy.

Although strategies to reduce bleeding and avoid allogeneic transfusion have been described, there is controversy about the factors associated with blood loss after Bernese periacetabular osteotomy. This study was conducted to determine risk factors for postoperative blood loss. After institutional review board approval was obtained, a retrospective review was conducted of 41 young patients who underwent periacetabular osteotomy for symptomatic acetabular dysplasia over a 3-year period. Of these patients, two-thirds donated blood before surgery. A Cell Saver Elite autotransfusion system (Haemonetics, Braintree, Massachusetts) was used intraoperatively in all cases. Hemoglobin and hematocrit were obtained before surgery and during the hospital stay. The primary outcome variable was the percentage of total blood volume lost during surgery. Univariate analysis was performed to test the association between potential predictors of blood volume loss. Candidate variables that were significant at alpha=0.15 were tested with multivariate analysis. The average percentage of blood volume lost during surgery was 30.3% (95% confidence interval, 25.1%-35.5%). Univariate analysis showed that operative time, arthrotomy, femoral head-neck osteochondroplasty, labral procedure, male sex, and age were prognostic factors associated with increased blood volume loss. However, operative time (average, 294.6 minutes; range, 204-444 minutes) was the only independent predictor of increased blood loss in the final model. Additional procedures, such as femoral head-neck osteochondroplasty and labral repair or debridement performed through an anterior hip arthrotomy at the time of periacetabular osteotomy, were associated with increased operative time. The findings suggest that all patients undergoing periacetabular osteotomy, including those having concomitant procedures, may benefit from pre- and intraoperative strategies to conserve blood and avoid allogeneic transfusion. [Orthopedics. 2016; 39(6):e1147-e1153.].