Standard versus low-dose computed tomography for assessment of acetabular fracture reduction using novel step and gap measurement technique.

PURPOSE: Quality of reduction is of paramount importance after acetabular fracture and is best assessed on computed tomography (CT). A recently proposed measurement technique for assessment of step and gap displacement is reproducible but has not been validated. The purpose of this study is to validate a well-established measurement technique against known displacements and to determine if it can be used with low dose CT. METHODS: Posterior wall acetabular fractures were created in 8 cadaveric hips and fixed at known step and gap displacements. CT was performed at multiple radiation doses for each hip. Four surgeons measured step and gap displacement for each hip at all doses, and the measurements were compared to known values. RESULTS: There were no significant differences in measurements across surgeons, and all measurements were found to have positive agreement. Measurement error < 1.5 mm was present in 58% of gap measurements and 46% of step measurements. Only for step measurements at a dose of 120 kVp did we observe a statistically significant measurement error. There was a significant difference in step measurements made by those with greater and those with fewer years in practice. CONCLUSION: Our study suggests this technique is valid and accurate across all doses. This is important as it may reduce the amount of radiation exposure for patients with acetabular fractures.

Optimizing the Entry Point for Medullary Hip Screws.

INTRODUCTION: Medullary hip screws (MHSs) are the most common treatment of intertrochanteric hip fractures because they can be used for varied fracture patterns and resist shortening. Identifying the appropriate MHS entry point can be intellectually and technically challenging. We aimed to quantify the variability in the ideal entry point (IEP) for MHSs. METHODS: Standing alignment radiographs of 50 patients were evaluated using TraumaCad (Brainlab). The femoral neck shaft angle and the offset from the tip of the greater trochanter (GT) to the femur's longitudinal axis ('greater trochanter offset') were measured. Five MHS system templates were superimposed on the femur's longitudinal axis, and the distance from the GT tip to MHS's top center was measured. Five independent reviewers each templated 20 images such that all images were measured at least twice. A random sample of five images was selected for all five raters to measure and to calculate an intraclass coefficient Mean IEPs were compared with an independent sample Student t -test. RESULTS: The mean GT offset was 13.5 ± 5.6 mm (range 12.9 to 26.7 mm). The mean neck shaft angle was 129.5 ± 4.0 (range 120 to 139). The mean IEP for nail systems ranged from 5.7 to 7.1 mm medial to the GT tip; there was no notable difference in pairwise comparison of nail systems or in aggregate. Intraclass coefficient for all ratings, measurements, and nail types ranged from moderate to good. Both intra-rater and inter-rater reliability were excellent. DISCUSSION AND CONCLUSION: In a sample with broad variation in femoral anatomy, there is a specific, roughly 1.5 mm wide interval that is 6.4 mm medial to the GT tip that serves as the IEP for the most common MHS systems. No notable difference seems to exist in the IEP among these MHS systems.

A Central Collinear Start Point for Reconstruction Nailing of Femur Fractures: A Technical Trick and Case Series.

SUMMARY: Selecting the optimal entry point for reconstruction nailing is critical to avoid iatrogenic malalignment and optimize mechanical stability. In-line nailing is familiar to surgeons and desirable for its on-axis position. However, there are several potential drawbacks. We describe a modified entry point and present an accompanying clinical series emphasizing an entry point in line with the medullary canal and central on the femoral neck. This central collinear start point is anterior to the traditional piriformis start point and may obviate some of the potential drawbacks with traditional piriformis nailing.

Does Fibular Displacement Predict Tibial Malrotation in Simulated Tibia-Fibula Fractures.

INTRODUCTION: Tibial malrotation can occur with medullary nailing of diaphyseal tibial fractures. Fibular alignment has been proposed as a surrogate for axial plane reduction intraoperatively. The purpose of this study was to determine whether fibular alignment is a reliable marker of accurate tibial rotation. METHODS: Deidentified CT scans of 50 patients with normal tibial anatomy were selected. Using ImageJ software, we simulated osteotomies at three sites (proximal third, mid-diaphysis, and distal third). We overlaid adjacent CT slices and rotated them around the central axis of the tibia in 5° increments of external rotation (ER) and internal rotation (IR). At each increment, measurements of fibular overlap (%) were obtained from anteroposterior (AP) and lateral views. To simulate fixation of the fibula, we repeated rotation around the axis of the fibula with and without a simulated medullary implant in the tibia. RESULTS: A total of 50 patients were included. The mean age was 62 years, average BMI was 25.8, and 28 of 50 patients (56%) were male. Earliest loss of fibular contact occurred at 24° ER and 22° IR at the proximal site. Contact was lost at 26° ER and 28° IR on the AP view and 42° ER and 29° IR on the lateral view. The mean fibular contact at each 5° increment was similar for ER and IR. Fibular contact was reduced to 50% at 10 to 15° of rotation in ER and IR at all sites. Tibial canal contact was lost at 24° in both ER and IR around the fibula. With a virtual medullary implant, the mean maximal rotation was 6°. DISCUSSION: Surgeons should be aware that 20° or more of malrotation is likely present when fibular contact is lost during medullary nailing of the tibia. Greater than 50% loss of contact should raise suspicion for malrotation. A fixed fibula and medullary tibial implant theoretically preclude significant tibial malrotation.

Optimizing the Entry Point for Reconstruction Nailing of the Femur.

INTRODUCTION: Varus after antegrade medullary nailing of the proximal femur is associated with worse outcomes. Anecdotally, a more medialized "trochiformis" entry is beneficial to avoid varus with valgus-bend (greater trochanteric entry) femoral nails. However, the optimal entry point remains unknown. The purpose of this study was to define the optimal entry point for reconstruction nailing. METHODS: Using standing alignment radiographs from 51 patients, we templated the ideal entry point for straight and valgus-bend nails from three major manufacturers using TraumaCad software. We measured the distance from the tip of the trochanter to the ideal entry site for each nail. We compared piriformis (PF) with trochanteric (GT) entry for each company and across manufacturers. RESULTS: The mean greater trochanter offset from the femoral axis was 15.2 mm. The mean PF entry was 5.9 to 6.7 mm medial to the mean GT entry for each company's nail and was statistically distinct. No differences were observed in GT and PF entry points across manufacturers. Only 2 of 153 ideal GT entry points were lateral to the tip of the trochanter. An increased neck-shaft angle (NSA) and increased GT offset were correlated with a more medial ideal entry point. DISCUSSION: The ideal entry point for GT nails is similar across manufacturers and is medial to the tip of the greater trochanter; however, PF and GT entry sites remain distinct. During preoperative planning and when executing femoral nailing intraoperatively, it may also be important to consider the NSA and GT offset of a patient before committing to a certain entry point.

Phosphaturic Mesenchymal Tumor-induced Osteomalacia Masquerading as an Orthopedic Polytrauma Patient: A Case Report and Review of the Literature.

Introduction: Phosphaturic mesenchymal tumor (PMT) is a rare benign tumor (500 cases to date) that can present in combination with a paraneoplastic syndrome called tumor-induced osteomalacia (TIO). To the best of our knowledge, it is the first case to date that presented as an orthopedic trauma patient. Case Report: This is a case of a 61-year-old male who initially presented as a polytrauma patient, but further investigation revealed a PMT causing TIO. This report describes his initial diagnosis and management from 2015 to 2021. Conclusion: TIO resultant of PMT may lead to severe bone pain, impending fractures, and delayed or misdiagnosis. This case demonstrates the importance of careful diagnosis and a team-based approach to managing PMT and its sequelae.