Jennifer L. Cullmann

A cost-effective surgical navigation solution for periacetabular osteotomy (PAO) surgery

PurposeTo evaluate a low-cost, inertial sensor-based surgical navigation solution for periacetabular osteotomy (PAO) surgery without the line-of-sight impediment.MethodsTwo commercial inertial measurement units (IMU, Xsens Technologies, The Netherlands), are attached to a patient’s pelvis and to the acetabular fragment, respectively. Registration of the patient with a pre-operatively acquired computer model is done by recording the orientation of the patient’s anterior pelvic plane (APP) using one IMU. A custom-designed device is used to record the orientation of the APP in the reference coordinate system of the IMU. After registration, the two sensors are mounted to the patient’s pelvis and acetabular fragment, respectively. Once the initial position is recorded, the orientation is measured and displayed on a computer screen. A patient-specific computer model generated from a pre-operatively acquired computed tomography scan is used to visualize the updated orientation of the acetabular fragment.ResultsExperiments with plastic bones (eight hip joints) performed in an operating room comparing a previously developed optical navigation system with our inertial-based navigation system showed no statistically significant difference on the measurement of acetabular component reorientation. In all eight hip joints the mean absolute difference was below four degrees.ConclusionUsing two commercially available inertial measurement units we show that it is possible to accurately measure the orientation (inclination and anteversion) of the acetabular fragment during PAO surgery and therefore to successfully eliminate the line-of-sight impediment that optical navigation systems have.

Surgical exposures and options for instrumentation in acetabular fracture fixation: Pararectus approach versus the modified Stoppa

BACKGROUND As an alternative to the modified Stoppa approach, the Pararectus approach is used clinically for treatment of acetabular fractures involving the anterior column. The current study assessed the surgical exposure and the options for instrumentation using both of these approaches. METHODS Surgical dissections were conducted on five human cadavers (all male, mean age 88 years (82-97)) using the modified Stoppa and the Pararectus approach, with the same skin incision length (10cm). Distal boundaries of the exposed bony surfaces were marked using a chisel. After removal of all soft-tissues, distances from the boundaries in the false and true pelvis were measured with reference to the pelvic brim. The exposed bone was coloured and calibrated digital images of each inner hemipelvis were taken. The amount of exposed surface using both approaches was assessed and represented as a percentage of the total bony surface of each hemipelvis. For instrumentation, a suprapectineal quadrilateral buttress plate was used. Screw lengths were documented, and three-dimensional CT reconstructions were performed to assess screw trajectories qualitatively. Wilcoxons signed rank test for paired groups was used (level of significance: p<0.05). RESULTS After utilization of the Pararectus approach, the distances from the farthest boundaries of exposed bone towards the pelvic brim were significantly higher in the false but not the true pelvis, compared to the modified Stoppa approach. The percentage (mean±SD) of exposed bone accessible after utilizing the Pararectus approach was 42±8%, compared to 29±6% using the modified Stoppa (p=0.011). In cadavers exposed by the Pararectus approach, screws placed for posterior fixation and as a posterior column screw were longer by factor 1.8 and 2.1, respectively (p<0.05), and screws could be placed more posteromedial towards the posterior inferior iliac spine or in line with the posterior column directed towards the ischial tuberosity. CONCLUSION Compared to the modified Stoppa, the Pararectus approach facilitates a greater surgical access in the false pelvis, provides versatility for fracture fixation in the posterior pelvic ring and allows for the option to extend the approach without a new incision.

The Acute Scrotum in Adults and Children: Evidence-Based Emergency Imaging

Of the different etiologies of acute scrotal pain, testicular torsion is the only real emergency. It occurs when the testicle is abnormally mobile and twists on its vascular pedicle potentially resulting in testicular infarction. If testicular torsion is suspected, patients should be examined using color Doppler ultrasound with grayscale imaging, which is highly sensitive and specific. Successful manual detorsion of testicular torsion leads to reperfusion, which is immediately visible with Doppler ultrasound. But in cases of successful manual detorsion, surgical exploration with orchiopexy is still necessary.

Acute Pelvic Pain in Premenapausal Women, Children and Infants: Evidence-Based Emergency Imaging

Acute lower abdominal and pelvic pain in premenopausal women has a wide range of etiologies including gastrointestinal, urological, obstetrical, and gynecological causes. Specifically, in younger patients, it is difficult to localize the pain during both history and physical examination, making it a diagnostic challenge. Life- and/or fertility-threatening conditions are the first to be considered until they can be confidentially excluded. History, physical examination, and laboratory testing narrow the differential diagnosis and guide the physician to choose the proper imaging test. Ultrasound is the recommended initial imaging tool for pregnant and nonpregnant women and girls presenting with acute pelvic pain and in which a gynecological etiology is suspected.

The Pararectus approach provides secure access to the deep circumflex iliac vessel for harvest of a large sized and vascularized segment of the iliac crest

BACKGROUND The feasibility of harvesting a vascularized iliac crest utilizing the Pararectus approach was assessed in cadavers and then this new technique was implemented in a clinical case. METHODS Bilaterally in five cadavers the branches of both external iliac arteries were injected with colored silicone to assess their position to each other and to harvest a bone graft vascularized by the deep circumflex iliac artery (DCIA) through the Pararectus approach. This technique was implemented in a 68-years-old female patient, initially admitted to a level-I-trauma center after sustaining multiple injuries by falling from great height. For definitive treatment of a severely contaminated medially open (Gustilo-Anderson Type 3A) calcaneal luxation fracture (Sanders type IIIBC) in this patient a vascularized iliac crest autograft harvest by the Pararectus approach was used for reconstructive surgery. RESULTS The DCIA and the deep inferior epigastric vessels (DIEV: vascularizing the rectus abdominis muscle and main pedicle of the inferiorly based rectus abdominis myocutaneous flap) are very close on the lateral and medial border of the external iliac artery, respectively. As a consequence, the retrograde dissection of the DIEV towards the DCIA through the Pararectus approach made the dissection of the vascularized iliac crest more amenable, preserving both the lateral femoral cutaneous and the genitofemoral nerves. Four months after the surgery the patient was able to fully weight-bear in orthopedic shoes. Radiographs and CT scans showed correct hind foot alignment and bony integration of the vascularized iliac crest graft into the residual calcaneal body. CONCLUSION The Pararectus approach allowed for secure collection of large vascularized iliac grafts. The presented technique was successful as a salvage procedure in a clinical case with substantial bone loss after an open calcaneal fracture.

Secure Screw Placement in Management of Acetabular Fractures Using the Suprapectineal Quadrilateral Buttress Plate.

Acetabular fractures involving predominantly the anterior column associated with a disruption of the quadrilateral surface can be treated with instrumentation implementing the stabilization of the quadrilateral surface. The recently introduced suprapectineal quadrilateral buttress plate is specifically designed to prevent secondary medial subluxation of the femoral head, especially in elderly patients with reduced ability for partial weight bearing. Whereas there are guidelines available for safe screw fixation for the anterior and posterior columns, there might be a concern for intra-articular placement of screws placed through the infrapectineal part of the quadrilateral buttress plate. Within this report we analyzed retrospectively screw placement in 30 plates in postoperative CT scans using algorithms for metal artifact reduction. None of the screws of the buttress plate penetrated the hip joint. We describe the placement, length, and spatial orientation of the screws used for fracture fixation and suggest that the use of intraoperative image intensifiers with a combined inlet-obturator view of 30–45° best projects the screws and the hip joint. Preoperative knowledge of approximate screw placement and information for accurate intraoperative imaging may contribute to safe acetabular fracture fixation and may reduce operating time and limit radiation exposure to the patient and the personnel. This trial is registered with KEK-BE: 266/2014.