The Anterior Modified San Diego Acetabuloplasty Does Not Increase Superior-Anterior Coverage in Patient-Specific 3D-Printed Models.

BACKGROUND: Patients with developmental dysplasia of the hip may require pelvic osteotomies to improve acetabular coverage. The purpose of this study was to compare the changes in acetabular version, tilt, and regional coverage angles following the San Diego acetabuloplasty (SDA), the modified San Diego acetabuloplasty (mSDA), and the Pemberton acetabuloplasty (PA). METHODS: Fourteen patients with developmental dysplasia of the hip and computed tomography (CT) imaging were identified. From CT images, 2 identical pelvises were 3-dimensional-printed for each patient. Bone was printed with rigid material, and cartilage with flexible material. For each model pair, the SDA was performed on one and the PA was performed on the other. CT scans were obtained before and after acetabuloplasties. Next, the bone graft in the SDA model was moved anteriorly, representing the mSDA, and the model was rescanned. Acetabular version, tilt, and coverage angles (posterior, superior-posterior, superior, superior-anterior, and anterior) were calculated. Preoperative to postoperative differences were compared (repeated measures analysis of variance or Wilcoxon signed rank test). The significance was set to P <0.05. RESULTS: The mean age at CT was 5.8±1.2 years (range: 3.9 to 7.5 y). All 3 procedures (SDA, mSDA, and PA) significantly increased acetabular tilt; P <0.045), with a similar change observed for all 3 ( P =0.868). PA was the only procedure to significantly decrease relative acetabular version (6.5±6.5 degrees, preoperative: 12.9±5.3 degrees; P =0.004). Both the SDA and mSDA procedures significantly increased coverage in the superior-posterior octant (SDA: 92.6±9.3 degrees, mSDA: 92.3±9.8 degrees, preoperative: 81.9±9.5 degrees; P <0.02), with a similar percent change among the 2 ( P =1.0). All 3 procedures significantly increased superior coverage ( P <0.04); the increase was similar among the 3 ( P =0.205). The PA was the only procedure to produce a significant increase in coverage in the superior-anterior octant (91.0±16.7 degrees, preoperative: 74.0±12.1 degrees; P =0.005) or the anterior octant (50.7±11.7 degrees, preoperative: 45.8±8.9 degrees; P =0.012). CONCLUSIONS: The SDA and mSDA procedures produced similar postoperative changes, primarily in the superior and superior-posterior acetabular octants. Placing the graft more anteriorly did not increase anterior coverage in the mSDA, and only the PA increased coverage in the superior and superior-anterior acetabular octants.

Three-dimensional assessment of subchondral arc and hip joint coverage angles in the asymptomatic young adult hip.

The primary objective of this study was to develop a custom algorithm to assess three-dimensional (3D) acetabular coverage of the femoral head based on surface models generated from computed tomography (CT) imaging. The secondary objective was to apply this algorithm to asymptomatic young adult hip joints to assess the regional 3D acetabular coverage variability and understand how these novel 3D metrics relate to traditional two-dimensional (2D) radiographic measurements of coverage. The algorithm developed automatically identifies the lateral- and medial-most edges of the acetabular lunate at one-degree intervals around the acetabular rim based on local radius of curvature. The acetabular edges and the center of a best-fit sphere to the femoral head are then used to compute the mean 3D subchondral arc angles and hip joint coverage angles in five acetabular octants. This algorithm was applied to hip models generated from pelvis/hip CT imaging or abdomen/pelvis CT angiograms of 50 patients between 17 and 25 years of age who had no history of congenital or developmental hip pathology, neuromuscular conditions, or bilateral pelvic and/or femoral fractures. Corresponding 2D acetabular coverage measures of lateral center edge angle (LCEA) and acetabular arc angle (AAA) were assessed on the patients' clinical or digitally reconstructed radiographs. The 3D subchondral arc angle in the superior region (58.0 [54.6-64.8] degrees) was significantly higher (p < 0.001) than all other acetabular subregions. The 3D hip joint coverage angle in the superior region (26.2 [20.7-28.5] degrees) was also significantly higher (p < 0.001) than all other acetabular subregions. 3D superior hip joint coverage angle demonstrated the strongest correlation with 2D LCEA (r = 0.649, p < 0.001), while 3D superior-anterior subchondral arc angle demonstrated the strongest correlation with 2D AAA (r = 0.718, p < 0.001). The 3D coverage metrics in the remaining acetabular regions did not strongly correlate with typical 2D radiographic measures. The discrepancy between standard 2D measures of radiographic acetabular coverage and actual 3D coverage identified on advanced imaging indicates potential discord between anatomic coverage and the standard clinical measures of coverage on 2D imaging. As 2D measurement of acetabular coverage is increasingly used to guide surgical decision-making to address acetabular deformities, this work would suggest that 3D measures of acetabular coverage may be important to help discriminate local coverage deficiencies, avoid inconsistencies resulting from differences in radiographic measurement techniques, and provide a better understanding of acetabular coverage in the hip joint, potentially altering surgical planning and guiding surgical technique.

Three-dimensional Analysis of Acetabular Morphology and Orientation in Patients With Slipped Capital Femoral Epiphysis.

BACKGROUND: Previous studies analyzing the acetabuli in patients with slipped capital femoral epiphysis (SCFE) have not definitively addressed the relationship between SCFE and acetabular shape. Femoral head overcoverage and acetabular version are thought to contribute to SCFE. The purpose of this study was to determine the acetabular morphology and orientation in hips with SCFE and compare them with normally developing children. METHODS: Pelvic computed tomography (CT) images of patients with SCFE were compared with pelvic CTs of patients without orthopedic abnormalities (normal controls). Three-dimensional (3-D) reconstructions were created from each CT examination. Custom software uniformly aligned the pelvis then determined acetabular measures from the reconstructions including acetabular version, acetabular tilt, articular surface area, and acetabular coverage angle measured in a radial manner dividing the acetabulum into octants. RESULTS: Two-hundred forty-four hips were included (53 SCFE, 31 unaffected contralateral hips in patients with SCFE, and 160 controls). The acetabular version was similar among SCFE hips, unaffected contralateral hips, and normal controls (P=0.48). Control hips had higher acetabular tilt than SCFE-affected hips (P=0.01) and unaffected contralateral hips (P=0.04). The acetabular surface area was higher in SCFE-affected hips compared with controls (P<0.05). SCFE-affected hips and the unaffected contralateral hips in patients with SCFE had increased acetabular coverage compared with controls in all 5 acetabular octants. CONCLUSIONS: Contrary to some previous studies, the authors did not find the acetabulum to be retroverted in patients with SCFE compared with controls. Both affected and unaffected hips of patients with SCFE have decreased acetabular tilt. Acetabular surface area is higher in hips with SCFE compared with normal controls, and both the SCFE-affected hips and unaffected hips had increased acetabular coverage compared with controls in all 5 octants of the acetabulum. The shared morphology of affected and unaffected hips in patients with SCFE suggests that their acetabular anatomy may predispose them to slip. LEVEL OF EVIDENCE: Level III.

Reliability of Low-dose Biplanar Radiography in Assessing Pediatric Torsional Pathology.

BACKGROUND: Low-dose biplanar radiographs (LDBRs) significantly reduce ionizing radiation exposure and may be of use in evaluating lower extremity torsion in children. In this study, we evaluated how well femoral and tibial torsional profiles obtained by LDBR correspond with 3-dimensional (3D) computed tomography (CT) and magnetic resonance axial imaging (MRI) in pediatric patients with suspected rotational abnormalities. METHODS: Patients who had both LDBR and CT/MRI studies performed for suspected lower extremity rotational deformities were included. Unlike previous publications, this study focused on patients with lower extremity torsional pathology, and bilateral lower extremities of 17 patients were included. CT/MRI torsion was measured using the Reikerås method, after conversion to 3D reconstructions. The LDBRs were deidentified and sent to the software division of EOS imaging, who created 3D reconstructions and evaluated each reconstruction for the torsional quantification of the femurs and tibiae. These imaging modalities were compared using correlation statistics and Bland-Altman analyses. RESULTS: The mean age of the cohort was 12.1±1.7 years old. Torsional values of the femur were significantly lower in LDBRs versus 3D CT/MRIs at 17.7±15.1 and 23.3±17.3, respectively (P=0.001). Torsional values of the tibia were similar in LDBRs versus 3D CT/MRIs at 23.6±10.6 and 25.3±11.2, respectively (P=0.503). There was a good intermodality agreement between LDBR and 3D CT/MRI torsional values in the femur (intraclass correlation coefficient=0.807) and tibia (intraclass correlation coefficient=0.768). Bland-Altman analyses showed a fixed bias with a mean difference of -5.6±8.8 degrees between femoral torsion measurements in LDBRs versus 3D CT/MRIs (P=0.001); 15% (5/34) of femurs had a clinically significant measurement discrepancy. Fixed bias for LDBR measurements compared with 3D CT/MRIs for the tibia was not observed (P=0.193), however, 12% (4/34) of tibias had a clinically significant measurement discrepancy. CONCLUSION: Although we found strong correlations between torsional values of the femur and tibia measured from LDBRs and 3D CT/MRIs, torsional values of the femur produced from LDBRs were significantly lower than values obtained from 3D CT/MRIs with some notable outliers. LEVEL OF EVIDENCE: Level III.

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.

Medial Epicondyle Fractures: Biomechanical Evaluation and Clinical Comparison of 3 Fixation Methods Used in Pediatric Patients.

BACKGROUND: Screw fixation is the most commonly employed fixation strategy for displaced medial epicondyle fractures, but in younger patients with minimal ossification, the fracture fragment may not accommodate a screw. In these situations, Kirschner-wires (K-wire) or suture anchors may be utilized as alternatives. The purposes of this study were to examine the biomechanical properties of medial epicondyle fractures fixed with a screw, K-wires, or suture anchors, to evaluate clinical outcomes and complications of patients 10 years of age or younger treated with these approaches, and to perform a cost-analysis. METHODS: Biomechanical assessment: Immature pig forelimbs underwent an osteotomy through the medial epicondyle apophysis, simulating a fracture. These were then fixed with a screw, K-wires or suture anchors. Cyclic elongation (mm), displacement (mm), load to failure (N), and stiffness (N/mm) were assessed. Clinical assessment: a retrospective review was performed of patients 10 years of age or younger with a medial epicondyle fracture fixed with these strategies. Radiographic outcomes, postoperative data and complications were compared. These data were used to perform a cost-analysis of each treatment approach. RESULTS: Biomechanically, screws were stronger (P=0.047) and stiffer (P=0.01) than the other constructs. Clinically, 51 patients met inclusion criteria (screw=27, wires=11, anchor=13). Patients treated with K-wires were younger (P<0.05) and patients treated with screw fixation had a shorter casting duration (P=0.008). Irrespective of treatment strategy, all fractures healed (100%) and only 1 patient in the screw group lost reduction. Clinical outcomes and complications were similar between groups, but the suture anchor group was less likely to require a second surgery for implant removal (P<0.05). This lower reoperation rate led to a cost-saving of 10%. CONCLUSIONS: Biomechanically, all 3 approaches provided initial fixation exceeding the forces observed across the elbow joint with routine motion. The screw construct was the strongest and stiffest. Clinically, all 3 strategies were acceptable, with screw fixation offering a shorter casting duration, but greater implant removal need with higher associated costs.

Comparison of 3 Pediatric Pelvic Osteotomies for Acetabular Dysplasia Using Patient-specific 3D-printed Models.

BACKGROUND: Children with developmental dysplasia of the hip may require a pelvic osteotomy to treat acetabular dysplasia. Three osteotomies are commonly performed in these patients (Pemberton, Dega, and San Diego), though comparative studies of each are limited. The purpose of this study was to compare changes in acetabular morphology (acetabular version, volume, and octant coverage angles) created by these 3 osteotomies using matched patient-specific 3D-printed pelvic models. METHODS: Fourteen patients with developmental dysplasia of the hip and preoperative computed tomography (CT) imaging were retrospectively included. For each patient CT, bone and cartilage tissues were independently segmented, and 3 identical pelvises were 3D-printed using a dual material printer. Bone was printed with rigid material and cartilage with flexible material to simulate the flexibility of the triradiate cartilage and pubic symphysis. Pemberton, Dega, and San Diego acetabular osteotomies were performed on the triplicate set of 3D prints. Acetabular version, volume, and octant coverage angles (posterior, superior-posterior, superior, superior-anterior, and anterior) were determined before and after each mock surgery by morphologic assessment using preoperative and postoperative CT images. RESULTS: San Diego osteotomy yielded a small increase (+3.34±1.71 degrees) in version, compared with decreases with Pemberton (-5.47±1.54 degrees) and Dega (-8.57±1.21 degrees, P<0.05). Acetabular volume decreased similarly for Pemberton (-13.36%±2.88%), Dega (-19.21%±2.73%), and San Diego (-19.29%±2.44%; P=0.215) osteotomies. San Diego osteotomy tended to have a larger postoperative increase in the posterior regions, and the Dega and Pemberton osteotomies tended to have larger postoperative increases in the anterior coverage regions. CONCLUSIONS: Quantifiable differences were identified in acetabular octant coverage angles and version between the 3 pelvic osteotomies. San Diego osteotomy increased acetabular coverage posteriorly resulting in acetabular anteversion, whereas Pemberton and Dega had greater superior-anterior coverage resulting in relative acetabular retroversion. This study is the first known to utilize 3D-printed models for comparison of surgical approaches in pediatric pelvic osteotomies.

Under Pressure: The Utility of Spacers in Univalved Fiberglass Casts.

BACKGROUND: Univalving fiberglass casts after fracture manipulation or extremity surgery reduces the risk of developing compartment syndrome (CS). Previous experiments have demonstrated that univalving decreases intracompartmental pressures (ICPs), but increases the risk for loss of fracture reduction due to altering the mechanical properties of the cast. The purpose of this study was to correlate cast valve width within a univalved cast model to decreasing ICP. METHODS: Saline bags (1 L) were covered with stockinette, Webril, and fiberglass tape then connected to an arterial pressure line monitor. Resting pressure was recorded. A water column was added to simulate 2 groups (n=5 each) of clinical CS: low pressure CS (LPCS range, 28 to 31 mm Hg) and high pressure CS (HPCS, range, 64 to 68 mm Hg). After the designated pressure was reached, the fiberglass was cut (stockinette and Webril remained intact). Cast spacers were inserted into each univalve and secured with varying widths: position #1 (3 mm wide), #2 (6 mm), #3 (9 mm), and #4 (12 mm). Pressure was recorded after cutting the fiberglass and following each spacer placement. RESULTS: In LPCS and HPCS groups, after univalve and placement of spacer position #1, pressure dropped by a mean of 52% and 58%, respectively. Spacer #2, decreased the pressure by a mean of 78% and 80%, respectively. Both spacer sizes significantly decreased the underlying pressure in both groups. Spacer #3 and #4 progressively reduced pressure within the cast, but not statistically significantly more than the previous spacer widths. CONCLUSIONS: This experimental model replicates the iatrogenic elevation in interstitial compartment pressure due to rigid cast application, not necessarily a self-sustained true CS. Increasing the univalved cast spread by ≥9 mm of the initial cast diameter will reduce pressure to a pre-CS level; however, a spread of only 6 mm can effectively reduce the pressure to <30 mm Hg depending on the initial elevated ICP. Cutting the Webril and stockinette in our model yielded a pressure decrease of 91% and 94% from the starting experimental pressure in the LPCS and the HPCS groups, respectively. CLINICAL RELEVANCE: Although the utility of splitting fiberglass casts has been previously demonstrated, we present evidence highlighting the benefit of spacing the split by at least 6 to 9 mm.

A Medial Portal for Hip Arthroscopy in Children With Septic Arthritis: A Safety Study.

BACKGROUND: Prompt open arthrotomy is historically utilized to treat pediatric septic arthritis of the hip, but arthroscopy has been described as a valid alternative to prevent long-term sequelae. Standard hip arthroscopy in adolescents and adults utilizes lateral-based portals, but successful irrigation in infants may necessitate a medial portal due to the smaller joint size. The purpose of this study was to determine the safety of a medial hip portal in children based on its anatomic relation to neurovascular structures. METHODS: A retrospective review of children 6 years of age or below with septic hip arthritis who obtained a preoperative magnetic resonance imaging (MRI) between 2009 and 2015 was performed. Multiple measures were recorded from the MRI to create a 3D cone with the vertex just posterior to the adductor longus at the convergence of the gluteal and inguinal creases-a previously described posteromedial portal-with the cone base being a circle defined as the central joint diameter. The distance to the femoral vessels and nerve were then recorded. An adult cadaver was then utilized to replicate the proposed portal starting point and trajectory to confirm that it could be reproducible in a clinical setting. RESULTS: After applying criteria, 47 MRI were evaluated (21 boys, 26 girls) demonstrating a mean distance to femoral vessels and nerve: at insertion, 18.9 mm (minimum 10.5 mm) and at the hip joint, 11.1 mm (minimum 5.2 mm). Girls and boys did not differ significantly, but there was a significant correlation of both age (r=0.75) and body weight (r=0.84) to the measured distance (P<0.001). Imaging of the cadaver confirmed that the starting point could be replicated. CONCLUSIONS: There is a direct relation to size of the child and the distance from the neurovascular structures to the cannula trajectory, but even the smallest of children have at least 5.5 mm of adductor longus to protect the femoral structures. A medial-based portal that utilizes a medial needle for initial aspiration features a wide margin of safety for children requiring treatment for septic hip arthritis. LEVEL OF EVIDENCE: Level IV.

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.

The Distal Humerus Axial View: Assessment of Displacement in Medial Epicondyle Fractures.

BACKGROUND: The assessment and treatment of childhood medial epicondyle humerus fractures continues to be associated with significant debate. Several studies demonstrate that standard radiographic views are unable to accurately portray the true displacement. Without reliable ways to assess the amount of displacement, how can we debate treatment and outcomes? This study introduces a novel imaging technique for the evaluation of medial epicondyle fractures. METHODS: An osteotomy of a cadaveric humerus was performed to simulate a medial epicondyle fracture. Plain radiographs were obtained with the fracture fragment displaced anteriorly in 2-mm increments between 0 and 18 mm. Anteroposterior (AP), internal oblique (IR), lateral (LAT), and distal humerus axial (AXIAL) views were performed. Axial images were obtained by positioning the central ray above the shoulder at 15 to 20 degrees from the long axis of the humerus, centered on the distal humerus. Displacement (mm) was measured by 7 orthopaedic surgeons on digital radiographs. RESULTS: At 10 mm displacement, AP views underestimated displacement by 5.5±0.6 mm and IR views underestimated by 3.8±2.1 mm. On LAT views, readers were not able to visualize fragments with <10 mm displacement. Displacement ≥10 mm from LAT views was overestimated by 1 reader by up to 4.6 mm and underestimated by others by up to 18.0 mm. AXIAL images more closely estimated the true amount of displacement, with a mean 1.5±1.1 mm error in measurement for <10 mm displacement and a mean 0.8±0.7 mm error for displacements of ≥10 mm. AXIAL measurements correlated strongly with the actual displacement (r=0.998, P<0.05); AP measurements did not (r=0.655, P=0.55). Intraclass correlation coefficient (ICC) was 0.257 for AP and IR measurements; ICC was 0.974 for AXIAL measurements. CONCLUSIONS: Standard imaging, consisting of AP, IR, and LAT radiographs, consistently underestimates the actual displacement of medial epicondyle humerus fractures. The newly described AXIAL projection more accurately and reliably demonstrated the true displacement while reducing the need for advanced imaging such as computed tomography. CLINICAL RELEVANCE: This simple view can be easily obtained at a clinic visit, enhancing the surgeon's ability to determine the true displacement.

Biomechanical Testing of Unstable Slipped Capital Femoral Epiphysis Screw Fixation: Worth the Risk of a Second Screw?

BACKGROUND: In a prior biomechanical study, 2-screw fixation of anatomically reduced slipped capital femoral epiphysis (SCFE) demonstrated marginally greater stability than single-screw fixation. However, the authors judged the benefits of a second screw to be minimal compared with the additional complication risk. A similar evaluation of fixation stability in unstable moderately displaced SCFE is performed. METHODS: SCFE model: Transverse periosteal incision and epiphyseal separation from the metaphysis by leveraging in 25-month-old porcine femurs. Four groups were evaluated: pinned (3.5 mm cortex screws; Synthes, Monument, CO) with no displacement (1 screw=group N1; 2 screws=group N2) or with moderate posterior-inferior displacement of 50% of the epiphyseal diameter (1 screw=group D1; 2 screws=group D2). Biomechanical testing: Cyclical shear forces (40 to 200 N, 1 Hz) were applied along the physeal plane. Maximum load increased by 100 N every 500 cycles until failure (epiphyseal translation greater than one third the epiphyseal diameter). Force cycles (the sum of the maximum cycle loads) and number of cycles to failure were reported. RESULTS: A sample from each D1 and D2 had fixation problems (D1, D2: n=4; N1, N2: n=5). One D1 failed through the femoral neck; all others failed through the epiphysis. The data showed nonsignificant trends of greater force cycles for nondisplaced over displaced (P=0.13) and for 2 screws over 1 (P=0.19). Number of cycles to failure showed similar trends, with no significant differences between nondisplaced and displaced (P=0.10) and screw number (P=0.13). Force cycles were significantly greater in the N2 group than in the D1 group. CONCLUSIONS: A trend toward higher force cycles to failure in nondisplaced and 2-screw groups was observed. Higher force cycles correspond to greater physeal stability and thus decreased risk for subsequent displacement. Within displacement groups, adding a second screw did not significantly increase stability. Reduction of displaced SCFE also did not significantly increase stability. Only the D1 and N2 groups were significantly different. CLINICAL RELEVANCE: Nondisplaced SCFE does not require 2 screws. In situ fixation of displaced SCFE might be optimized with 2 screws.

Defining the segmental tension generated in a vertebral body tethering system for scoliosis.

Vertebral body tethering (VBT) uses a flexible tether affixed across the curve convexity with tension applied at each segment to treat scoliosis. Intraoperative tether tension may be achieved directly with a counter-tensioner or with an extension spring tube. The purpose of this study was to quantify the force generated with and without the extension spring tube using current FDA-approved VBT instrumentation, to understand the variation between surgeons using the same instrumentation, and to define the force range that is generated intra-operatively. Using a benchtop mechanical testing setup to simulate a spinal segment, we affixed the tether and applied tension using a tensioner and counter-tensioner alone (method T1) or by adding an extension spring tube (method T2). Eight orthopedic surgeons used T1 and T2 at six tensioner settings, and one surgeon completed three trials. A two-way ANOVA with a Tukey's HSD post hoc test (p < 0.05) compared the tensioner methods and testing levels. Inter- and intra-rater reliabilities were calculated using intraclass correlation coefficients (ICCs). Methods T1 and T2 exhibited linear tension-setting relationships, with high determination coefficients (R2 > 0.93). T2 consistently produced higher forces (increase of 62.1 N/setting), compared to T1 (increase of 50.6 N/setting, p < 0.05). Inter-rater reliability exhibited excellent agreement (ICC = 0.951 and 0.943 for T1 and T2, respectively), as did intra-rater reliability (ICC = 0.971).

Growth modulation response in vertebral body tethering depends primarily on magnitude of concave vertebral body growth.

PURPOSE: There is variability in clinical outcomes with vertebral body tethering (VBT) partly due to a limited understanding of the growth modulation (GM) response. We used the largest sample of patients with 3D spine reconstructions to characterize the vertebra and disc morphologic changes that accompany growth modulation during the first two years following VBT. METHODS: A multicenter registry was used to identify idiopathic scoliosis patients who underwent VBT with 2 years of follow-up. Calibrated biplanar X-rays obtained at longitudinal timepoints underwent 3D reconstruction to obtain precision morphological measurements. GM was defined as change in instrumented coronal angulation from post-op to 2-years. RESULTS: Fifty patients (mean age: 12.5 ± 1.3yrs) were analyzed over a mean of 27.7 months. GM was positively correlated with concave vertebra height growth (r = 0.57, p < 0.001), 3D spine length growth (r = 0.36, p = 0.008), and decreased convex disc height (r = - 0.42, p = 0.002). High modulators (patients experiencing GM > 10°) experienced an additional 1.6 mm (229% increase) of mean concave vertebra growth during study period compared to the Poor Modulators (GM < - 10°) group, (2.3 vs. 0.7 mm, p = 0.039), while convex vertebra height growth was similar (1.3 vs. 1.4 mm, p = 0.91). CONCLUSION: When successful, VBT enables asymmetric vertebra body growth, leading to continued postoperative coronal angulation correction (GM). A strong GM response is correlated with concave vertebral body height growth and overall instrumented spine growth. A poor GM response is associated with an increase in convex disc height (suspected tether rupture). Future studies will investigate the patient and technique-specific factors that influence increased growth remodeling.

Negative pressure therapy for closed spine incisions: a pilot study.

UNLABELLED: Negative pressure therapy (NPT), used on open wounds or postoperative infections, has not been evaluated on closed spinal incisions. This was analyzed after 3 days and 5 days of NPT application using biomechanics and histology in a porcine model. METHODS: In 8 mature miniature pigs, 2 end-to-end midline spine incisions were closed in a standard fashion. Negative pressure (Prevena™ Incision Management System, KCI, San Antonio,TX) was applied to one incision (NPT group) while standard dry dressings were used on the other (control group). After 3 days or 5 days, all incisions underwent biomechanical (eg, failure load, failure energy, and stress), histological, and scar scale evaluation. ANALYSIS: ANOVAs compared the groups (3-day vs 5-day, NPT vs control, P < 0.05). Negative pressure therapy demonstrated a significantly improved scar scale height grade than the control (P = 0.026). Failure load (4.9 ± 4.0 vs 16.5 ± 14.6 N), energy absorbed (8.0 ± 9.0 vs. 26.9 ± 23.0 mJ), and ultimate stress (62 ± 53 vs. 204 ± 118 N/mm2) were lower in the control group. Histological analysis revealed no differences in incision scar width. CONCLUSION: Negative pressure therapy application on closed incisions presented a trend toward improved early healing strength, and in significantly improved incision appearance. Clinically, NPT may improve incision integrity, minimizing the risk of dehiscence or subsequent infection. Patients at high risk of postoperative incision site complications may benefit from primary application of NPT.

3-D acetabular morphology of the neuromuscular hip: implications for preoperative planning.

The importance of precisely understanding the pathoanatomy of acetabular dysplasia prior to surgical treatment has long been recognized. Acetabuloplasties for neuromuscular hip dysplasia have typically aimed to improve the acetabulum by increasing posterior-superior coverage, as previous three-dimensional (3-D) computed tomography (CT) studies have shown that acetabular dysplasia in neuromuscular hips is primarily in the direction of posterior-superior subluxation or dislocation. The purpose of this study was to identify differences in 3-D morphology between normal hips and dysplastic neuromuscular hips, specifically to identify areas of acetabular deficiency to guide preoperative decision-making. Patients treated for neuromuscular hip dysplasia at a single institution between 2009 and 2017 with a preoperative high-resolution pelvic CT scan (28 hips) were evaluated with custom software to measure acetabular morphology. Acetabuli were divided into equal octants; coverage angles were measured for each octant of interest. Variables were compared with age- and sex-matched normal controls (56 hips). We found a wide range of hip pathology in our study cohort. Five hips had no sectors with abnormal coverage. One hip (4%) was overcovered anteriorly. The remaining pathology was undercoverage located anteriorly [n = 7 (25%)], superiorly [n = 6 (21%)], posteriorly [n = 4 (14%)] or globally [n = 5 (18%)]. Our findings indicate that individual patients with neuromuscular acetabular dysplasia have unique deformities that do not uniformly conform to a specific area of acetabular deficiency. It is imperative to define the specific 3-D acetabular deficiency location and magnitude for accurate preoperative planning. Level of evidence: Level III.

A comparison of cone beam computed tomography, standard computed tomography and plain radiographs in the evaluation of medial epicondyle humerus fractures.

The ideal technique to measure medial epicondyle humerus fracture displacement minimizes radiation exposure while maximizing measurement accuracy and reliability. This study compares the radiation exposure and accuracy of displacement measurements of the four-view X-ray examination (XR), computed tomography (CT) and in-clinic cone-beam CT (CBCT). A cadaveric humerus underwent medial epicondyle osteotomy. The fragment was fixed to the humerus at clinically relevant displacements (6 to 18 mm). Dosimeters were placed around the distal humerus and simulating thyroid location. XR, CT and CBCT were performed at each displacement. Four pediatric orthopedists measured the maximum linear displacement on each XR and 3D reconstruction of the CT and CBCT images. Focal (elbow location) and thyroid radiation exposure was compared between modalities. Intra- and interclass correlation coefficients (ICC) for displacement measurements were determined. Mean focal radiation exposures for XR, CT and CBCT were 0.008, 2.061 and 0.478 rad, respectively (P = 0.001). Exposures 10 inches from the elbow for XR, CT and CBCT were 0.001, 0.066 and 0.010 rad, respectively (P = 0.006). At 12 inches, there was no significant difference in exposure between XR and CBCT ( P = 0.114). Intra- and interobserver reliabilities were excellent for all measures, except lateral x-ray. CBCT and CT had significantly less deviation from the actual displacement compared to XR ( P < 0.05). In-office CBCT of the elbow exposes patients to significantly less radiation than conventional CT. All X-ray images (except lateral), CT and CBCT had equal reliability in evaluating medial epicondyle fractures, which contrasts with previous evidence.

Distal tibial osteotomy to address internal tibial torsion: Should the fibula be cut?

Background Rotational tibial osteotomy seeks to address pathologic tibial torsion. Inclusion of fibular osteotomy during this procedure remains controversial. This study aimed to determine how external rotation through a tibial osteotomy, with or without a fibular osteotomy, would influence tibiofibular joint congruity. Methods Eight cadaveric legs underwent distal tibial osteotomies. Pins were placed to designate neutral, 10°, 20°, 30° of external rotation. Computed tomography (CT) imaging was performed at each rotation without, then with a fibular osteotomy. Magnetic Resonance Imaging was performed prior to fibular osteotomy to confirm that ligaments remained intact. Custom software calculated tibial torsion using CT scan 3D reconstructions. Proximal tibiofibular joint rotation, distal tibiofibular gapping and ankle mortise were measured on each CT exam. Groups without and with fibular osteotomy were compared. Findings There was no difference between tibial osteotomy rotation magnitude with or without the fibular osteotomy (P = 0.2). The group without the fibular osteotomy had greater proximal fibular rotation at the tibiofibular joint at 20°, 30° (P < 0.05), greater posterior distal tibiofibular gap at 10°, 20°, 30° (P < 0.05) and less anterior distal tibiofibular gap at 20°, 30° (P < 0.05). The medial tibiotalar space was narrowed without the fibular osteotomy at 20°, 30° (P < 0.05) compared to pre-rotation. Interpretation Deformity at the proximal tibiofibular and ankle joints become most pronounced at >20° of tibial rotation without a fibular osteotomy. The first joint to be affected is the distal tibiofibular joint. To limit ankle and proximal tibiofibular articular deformation during tibia rotational osteotomy, a fibular osteotomy is recommended when correcting over 20° of rotation.

Isocentric reattachment of ligamentum teres: a porcine study.

BACKGROUND: Recent reports reveal interest in the mechanical importance of ligamentum teres (LT) in hip dislocation. In the previously established procedure of anteroinferior acetabular LT reattachment in developmental dysplasia of the hip, the LT functions as a check-rein, showing promising results. However, this position of reattachment could potentially limit motion. The purpose of this study was to evaluate the feasibility of an isocentric point for reattachment of the LT and to study its impact on hip function using a young porcine model. METHODS: Pelvic specimens with intact anatomy were obtained from 6 skeletally immature pigs (12 hips). Through a careful anteromedial capsulotomy, the LT was detached from its acetabular insertion then reattached to 1 of 2 positions: (1) anteroinferior lip of the acetabulum; (2) proposed isocentric position. Intra-articular stress distribution was measured through a complete range of motion with a prescale Fuji pressure film. Tension was then applied to the LT and the stresses were recorded again. In addition, radioopaque solution was injected into the substance of the LT, then floroscopy tracked the LT location initially and after the 2 reattachment positions through a full hip range of motion. RESULTS: Reattachment of the LT at an isocentric point is feasible in a pig model. With careful physiologic tensioning of this reattachment, hip can maintain full motion with no excessive pressure areas created within the joint. On the contrary, the initial technique of anteroinferior extra-articular attachment limits external rotation and extremes of abduction. We found this LT tracking technique (with radioopaque dye injection) to be reliable and reproducible. CONCLUSIONS: The isocentric reattachment of the LT is feasible in this pig model and serves as a natural check-rein to dislocation without limiting joint motion or causing abnormal cartilage pressures. CLINICAL RELEVANCE: Isocentric LT reattachment may provide a method for improving stability of open reductions when treating children with such conditions.

3D cone-beam tomosynthesis provides axial imaging of the spine with lower radiation compared to computed tomography.

STUDY DESIGN: Three imaging techniques were compared using porcine spines. OBJECTIVES: To compare image acquisition time, radiation exposure, pedicle width measurement, assessment of screw breach, and image artifact between cone-beam tomosynthesis (CBT) single mode, CBT dual mode (stereotactic CBT), and computed tomography (CT) imaging with and without spinal implants. CT is the standard for axial imaging of orthopedic procedures. CBT technology is being developed, allowing real-time intraoperative imaging and 3D surgical guidance. CBT may deliver useful axial imaging quicker with less radiation than current technologies. METHODS: Six porcine spines were instrumented with bilateral pedicle screws at six levels connected with 5.5 mm rods. Dosimeters were attached to four surfaces of spines. CT, CBT single and CBT dual images were acquired pre-implant and post-implant. Image acquisition and 3D reconstruction times were recorded. Pedicle widths were measured before and after instrumentation. Screw medial breaches were graded (0: no breach, 1: < 2 mm, 2: 2-4 mm, 3: > 4 mm). Artifact and/or distortion of each image was ranked (0 = none, 1 = mild, 2 = moderate, 3 = large). Image acquisition and reconstruction times, radiation dose, pedicle width, screw breach and artifact were compared between techniques. RESULTS: Total image acquisition and reconstruction times of CBT was significantly less (single: 9.9 ± 0.2 s, p < 0.001; dual: 60.0 ± 8.7 s, p < 0.001) than CT (250.3 ± 36.7 s). CBT had significantly less radiation exposure than CT (CT: 0.7 ± 0.1 rad, single: 0.03 ± 0.02 rad, dual: 0.07 ± 0.03 rad; p < 0.001). No difference in pedicle width change pre-implant to post-implant was found (CT: p = 0.449, single: p = 0.430, dual: p = 0.528). Pedicle width (pre-implant: p > 0.5, post-implant: p > 0.9) and pedicle width change (p > 0.4) was similar amongst all techniques. Breach assessment was not different between groups (p = 0.257). CBT images had consistently lower artifact grades than CT. CONCLUSIONS: Although CBT axial image quality appeared subjectively inferior to CT, it enabled consistent assessment of pedicle width and screw breach, at half time and 10× lower radiation exposure. With continued refinements, CBT technology may allow for adequate intra-operative axial imaging using low radiation exposure.