Creating vascular models by postprocessing computed tomography angiography images: a guide for anatomical education

BACKGROUND

A new application of teaching anatomy includes the use of computed tomography angiography (CTA) images to create clinically relevant three-dimensional (3D) printed models. The purpose of this article is to review recent innovations on the process and the application of 3D printed models as a tool for using under and post-graduate medical education.

METHODS

Images of aortic arch pattern received by CTA were converted into 3D images using the Google SketchUp free software and were saved in stereolithography format. Using a 3D printer (Makerbot), a model mode polylactic acid material was printed.

RESULTS

A two-vessel left aortic arch was identified consisting of the brachiocephalic trunk and left subclavian artery. The life-like 3D models were rotated 360° in all axes in hand.

CONCLUSIONS

The early adopters in education and clinical practices have embraced the medical imaging-guided 3D printed anatomical models for their ability to provide tactile feedback and a superior appreciation of visuospatial relationship between the anatomical structures. Printed vascular models are used to assist in preoperative planning, develop intraoperative guidance tools, and to teach patients surgical trainees in surgical practice.

Cost-effective, personalized, 3D-printed liver model for preoperative planning before laparoscopic liver hemihepatectomy for colorectal cancer metastases

Purpose

Three-dimensional (3D) printing for preoperative planning has been intensively developed in the recent years. However, the implementation of these solutions in hospitals is still difficult due to high costs, extremely expensive industrial-grade printers, and software that is difficult to obtain and learn along with a lack of a defined process. This paper presents a cost-effective technique of preparing 3D-printed liver models that preserves the shape and all of the structures, including the vessels and the tumor, which in the present case is colorectal liver metastasis.

Methods

The patient’s computed tomography scans were used for the separation and visualization of virtual 3D anatomical structures. Those elements were transformed into stereolithographic files and subsequently printed on a desktop 3D printer. The multipart structure was assembled and filled with silicone. The patient underwent subsequent laparoscopic right hemihepatectomy. The entire process is described step-by-step, and only free-to-use and mostly open-source software was used.

Results

As a result, a transparent, full-sized liver model with visible vessels and colorectal metastasis was created for under $150, which—taking into account 3D printer prices—is much cheaper than models presented in previous research papers.

Conclusions

The increased accessibility of 3D models for physicians before complex laparoscopic surgical procedures such as hepatic resections could lead to beneficial breakthroughs in these sophisticated surgeries, as many reports show that these models reduce operative time and improve short term outcomes.

Digital templating in total hip arthroplasty: Additional anteroposterior hip view increases the accuracy

AIM

To analyze planning total hip arthroplasty (THA) with an additional anteroposterior hip view may increases the accuracy of preoperative planning in THA.

METHODS

We conducted prospective digital planning in 100 consecutive patients: 50 of these procedures were planned using pelvic overview only (first group), and the other 50 procedures were planned using pelvic overview plus antero-posterior (a.p.) hip view (second group). The planning and the procedure of each patient were performed exclusively by the senior surgeon. Fifty procedures with retrospective analogues planning were used as the control group (group zero). After the procedure, the planning was compared with the eventually implanted components (cup and stem). For statistic analysis the χ² test was used for nominal variables and the t test was used for a comparison of continuous variables.

RESULTS

Preoperative planning with an additional a.p. hip view (second group) significantly increased the exact component correlation when compared to pelvic overview only (first group) for both the acetabular cup and the femoral stem (76% cup and 66% stem vs 54% cup and 32% stem). When considering planning ± 1 size, the accuracy in the second group was 96% (48 of 50 patients) for the cup and 94% for the stem (47 of 50 patients). In the analogue control group (group zero), an exact correlation was observed in only 1/3 of the cases.

CONCLUSION

Digital THA planning performed by the operating surgeon and based on additional a.p. hip view significantly increases the correlation between preoperative planning and eventual implant sizes.

Study of the variability of scapular inclination and the glenoid version - considerations for preoperative planning: clinical-radiological study

BACKGROUND

Preoperative planning with the aid of imaging methods is a principal factor in successful surgery on the shoulder. This work aims to evaluate the variability of glenoid version, spiralling twist and scapular inclination in relation to the frontal axis. Studies focusing on measuring the variability of scapular inclination in the standardised rest position are lacking in the literature.

METHODS

We evaluated 104 CT scans of the shoulder. We measured the glenoid version with respect to the scapular axis at three levels. We measured the scapular inclination angle in relation to the sagittal plane and we determined scapular inclination in relation to the frontal axis. Statistical evaluation was performed using the marginal linear model and parameters were estimated using the generalised least squares method, which enables the dependency of measurements performed on the same subject to be taken into consideration.

RESULTS

The highest values of retroversion are attained by the glenoid in the cranial section (average -9.96°, range -29.7 to +13.2°). Proof of the spiralling twist is the decline in retroversion at the centre of the glenoid (average -2.09°, range -16.7 to +11.6°). Retroversion decreases further in the inferior direction (average -0.5°, range -20.9 to +17.5°). The average thoracoscapular angle is 45.46°, ranging from 13.1 to 69.0°. The average scapular inclination in relation to the frontal plane is 44.54°, ranging from 21.0 to76.9°.

CONCLUSIONS

During preoperative planning, the surgeon should take into consideration not only the glenoid version in relation to the scapular axis, but also the value of the scapular inclination so as to eliminate possible surgical errors, optimise prosthesis implantation and thus decrease the risk of functional restrictions of the joint.

CLINICAL TRIAL REGISTRATION

Ethics Committee for Multi-Centric Clinical Trials (EK-554/14,29thApril 2014).

Predictability of anthropomorphic measurements in implant selection for breast reconstruction: a retrospective cohort study

Background

Preoperative implant planning for breast reconstruction is often at risk of being changed perioperatively. This study examined which factors are associated with a change of implant selection.

Methods

Women who had unilateral two-stage breast reconstruction between 2002 and 2007 were studied. Inclusion criteria were photographic evidence of preoperative skin markings indicating breast dimensions and a selected implant model. Multivariable logistic regression was used to identify variables associated with a changed selection.

Results

Among the 496 women studied, 308 preoperative implant choices (62.1%) were changed during surgery. A change in plan was significantly associated with symmetrization surgery involving contralateral reduction mammaplasty (OR = 1.92; 95% CI, 1.12 to 3.29) and contralateral mastopexy (OR = 2.26; 95% CI, 1.29 to 3.96), but not with BMI. The required implant width changed more than 0.5 cm in 70 cases (14.1%) while height changed more than 0.5 cm in 215 cases (43.2%). The likelihood of a change was high for large preoperative widths (OR = 9.66 for 15.5 cm) and small preoperative heights (OR = 2.97 for 10.5 cm). At a mean follow-up of 16.6 months, patient satisfaction was good or average in 92.1% of cases and 5.9% of implants had been replaced with another model, indicating that the perioperative implant selection was usually appropriate.

Conclusions

This study documents the frequency with which implant choices, despite accurate preoperative planning, are changed perioperatively as a result of relatively small differences in anthropomorphic measurements. Perioperative recalculation of breast dimensions may have an advantage in terms of patient reoperation rates. Changes in width were less frequent than changes in height and projection. Contralateral surgery, large width, and small height were the most influential factors.

Level of Evidence: Level IV, risk / prognostic study.

Does scripting operative plans in advance lead to better preparedness of trainees? A pilot study

BACKGROUND

We pondered if preoperative scripting might better prepare residents for the operating room (OR).

METHODS

Interns rotating on a general surgeon's service were instructed to script randomized cases prior to entering the OR. Scripts contained up to 20 points highlighting patient information perceived important for surgical management. The attending was blinded to the scripting process and completed a feedback sheet (Likert scale) following each procedure. Feedback questions were categorized into "preparedness" (aware of patient specific details, etc.) and "performance" (provided better assistance, etc.).

RESULTS

Eight surgical interns completed 55 scripted and 61 non-scripted cases. Total scores were higher in scripted cases (p = 0.02). Performance scores were higher for scripted cases (3.31 versus 3.13, p = 0.007), while preparedness did not differ (3.65 and 3.62, p = 0.51).

CONCLUSIONS

This pilot study suggests scripting cases may be a useful preoperative planning tool to increase interns' operative and patient care performance but may not affect perceived preparedness.

New approach for predictive measurement of knee cartilage defects with three-dimensional printing based on CT-arthrography: A feasibility study

PURPOSE

The aim was to prove the possibility of creating an exact module of knee cartilage defects using 3D printing.

METHODS

Defects were created in cadaver knees. CT-arthrography and 3-Tesla MRI were performed. Based on CTA images a model of the cartilage was created using 3D printing. Defect-sizes in the imaging modalities were compared.

RESULTS

Estimated lesion area in 3D model differed approximately 5% comparing to the defect sizes in knees. MRI underestimated the defect on average of 12%, whereas the CTA overestimated the defect about 3%.

CONCLUSIONS

We proved the feasibility of creating an accurate module of knee cartilage.

3D surgical printing and pre contoured plates for acetabular fractures

We describe the methodical and possibilities of 3D surgical printing in preoperative planning of acetabular fractures showing a case of a 45-year-old with an associated transverse fracture of the left acetabulum with posterior wall fracture, with multiple fragments, and posterior ipsilateral hip dislocation, defending the do it your-self mode.

Building 3D anatomical model of coiling of the internal carotid artery derived from CT angiographic data

The purpose of this study is to recreate live patient arterial anomalies using new recent application of three-dimensional (3D) printed anatomical models. Another purpose of building such models is to evaluate the effectiveness of angiographic data. With the help of the DICOM files from computed tomographic angiography (CT-A), we were able to build a printed model of variant course of the internal carotid artery (ICA). Images of coiling of the ICA taken by CT-A, were then converted into 3D images using Google SketchUp free software, and the images were saved in stereolithography format. Imaging helped us conduct the examination in details with reference to geometrical features of ICA, degree of curve, its extension, location and presence of loop. Challenging vascular anatomy was exposed with models of adverse curve of carotid anatomy, including highly angulated necks, conical necks, short necks, tortuous carotid arteries, and narrowed carotid lumens. It assisted us to comprehend spatial anatomy configuration of life-like models. 3D model can be very effective in cases when anatomical difficulties are detected through the CT-A, and therefore, a tactile approach is demanded preoperatively. 3D life-like models serve as an essential office-based tool in vascular surgery as they assist surgeons in preoperative planning, develop intraoperative guidance, teach both the patients and the surgical trainees, and simulate to show patient-specific procedures in medical field.

Application of an innovative computerized virtual planning system in acetabular fracture surgery: A feasibility study

INTRODUCTION

Acetabular fracture surgery is amongst the most challenging tasks in the field of trauma surgery and careful preoperative planning is crucial for success. The aim of this paper is to describe the preliminary outcome of the utilization of an innovative computerized virtual planning system for acetabular fractures.

METHODS

3D models of acetabular fractures and surrounding soft tissues from six patients were constructed from preoperative CT scans. A novel highly-automatic segmentation technique was performed on the 3D model to separate each fracture fragment, then 3D virtual reduction was performed. Additionally, the models were used to assess potential surgical approaches with reference to both the fracture and the surrounding soft tissues. The time required for virtual planning was recorded. After surgery, the virtual plan was compared to the real surgery with respect to surgical approach and reduction sequence. A Likert scale questionnaire was completed by the surgeons to evaluate their satisfaction with the system.

RESULTS

Virtual planning was successfully completed in all cases. The planned surgical approach was followed in all cases with the planned reduction sequence followed completely in five cases and partially in one. The mean time required for virtual planning was 38.7min (range 21-57, SD=15.5). The mean time required for planning of B-type fractures was 25.0min (range 21-30, SD=4.6), of C-type fracture 52.3min (range 49-57, SD=4.2). The results of the questionnaire demonstrated a high level of satisfaction with the planning system.

CONCLUSION

This study demonstrates that the virtual planning system is feasible in clinical settings with high satisfaction and acceptability from the surgeons. It provides a viable option for the planning of acetabular fracture surgery.

Preoperative planning for implant placement with consideration of pelvic tilt in total hip arthroplasty: postoperative efficacy evaluation

Background

In total hip arthroplasty (THA), tilting of the pelvis alters the cup placement angles. Thus, the cup angles need to be planned with consideration of the effects of pelvic tilt. In the present study, we evaluated the efficacy of preoperative planning for implant placement with consideration of pelvic tilt in THA, and the accuracy of a CT-based computer navigation for implant positioning.

Methods

We examined 75 hips of 75 patients who underwent THA and were followed-up for one year postoperatively. The patients were divided into three groups (anterior, intermediate, posterior tilt) according to their preoperative pelvic tilt. Preoperative planning for implant placement was made with consideration of pelvic tilt and a CT-based navigation was used to execute the preoperative planning. Cup inclination, cup anteversion, and combined anteversion (CA) in supine and standing positions were examined 1 year after THA. The accuracy of the computer navigation was also examined.

Results

Mean CA was 35.0 ± 5.8° in supine position and 39.3 ± 5.7° in standing position. CA did not differ among the three subgroups (anterior, intermediate, posterior tilt) in either supine or standing position, indicating implant placements to be equally effective. The desired CA (37.3°) was midway between those in supine and standing positions for each subgroup. Respective mean absolute errors between preoperative planning and postoperative CT measurement was 5.3 ± 5.2° for CA.

Conclusion

We obtained favorable THA results with preoperative planning with consideration of pelvic tilt by demonstrating supine and standing CA to be unaffected by preoperative pelvic tilt one year postoperatively. Mean absolute error of CA between preoperative planning and postoperative measurement was 5° with use of the CT-based navigation.

Software-assisted morphometry and volumetry of the lumbar spine

The aim of the study was to measure volumes of the lumbar vertebral bodies with use dedicated Computed Tomography (CT) workstation software to predict expected volume of PMMA for vertebroplasty and supplement calculations using computed tomography scanogram. Quantitative CT scans of 87 women's (mean age 69.4 years; SD 10.9) and 15 men's (mean age 64.3 years; SD 11.8) lumbar spines were analyzed; this made a total of 379 vertebrae. The population of patients was divided into three groups depending on measured BMD value, in accordance with American College of Radiology Practice Parameter for the Performance of Quantitative Computed Tomography (QCT) Bone Densitometry. With the use of the general linear model and least squares means groups were compared regarding vertebral volume, anterior, middle, and posterior vertebral heights. Morphometric parameters tended to be greater in males than in females, in a population of diversified bone mineral density. BMD result should be considered as the modifying factor for preoperative planning of the bone cement volume to be deposited inside the vertebra. Vertebral body volumetry might prove to be a useful tool in pre-operative planning as well as an alternative for treatment monitoring after minimally invasive spinal procedures.

Preoperative planning of left-sided valve surgery with 3D computed tomography reconstruction models: sternotomy or a minimally invasive approach?

OBJECTIVES

With the emergence of a new concept aimed at individualization of patient care, the focus will shift from whether a minimally invasive procedure is better than conventional treatment, to the question of which patients will benefit most from which technique? The superiority of minimally invasive valve surgery (MIVS) has not yet been proved. We believe that through better patient selection advantages of this technique can become more pronounced. In our current study, we evaluate the feasibility of 3D computed tomography (CT) imaging reconstruction in the preoperative planning of patients referred for MIVS.

METHODS

We retrospectively analysed all consecutive patients who were referred for minimally invasive mitral valve surgery (MIMVS) and minimally invasive aortic valve replacement (MIAVR) to a single surgeon in a tertiary referral centre for MIVS between March 2014 and 2015. Prospective preoperative planning was done for all patients and was based on evaluations by a multidisciplinary heart-team, an echocardiography, conventional CT images and 3D CT reconstruction models.

RESULTS

A total of 39 patients were included in our study; 16 for mitral valve surgery (MVS) and 23 patients for aortic valve replacement (AVR). Eleven patients (69%) within the MVS group underwent MIMVS. Five patients (31%) underwent conventional MVS. Findings leading to exclusion for MIMVS were a tortuous or slender femoro-iliac tract, calcification of the aortic bifurcation, aortic elongation and pericardial calcifications. Furthermore, 2 patients had a change of operative strategy based on preoperative planning. Seventeen (74%) patients in the AVR group underwent MIAVR. Six patients (26%) underwent conventional AVR. Indications for conventional AVR instead of MIAVR were an elongated ascending aorta, ascending aortic calcification and ascending aortic dilatation. One patient (6%) in the MIAVR group was converted to a sternotomy due to excessive intraoperative bleeding. Two mortalities were reported during conventional MVS. There were no mortalities reported in the MIMVS, MIAVR or conventional AVR group.

CONCLUSIONS

Preoperative planning of minimally invasive left-sided valve surgery with 3D CT reconstruction models is a useful and feasible method to determine operative strategy and exclude patients ineligible for a minimally invasive approach, thus potentially preventing complications.

Two-dimensional planning can result in internal rotation of the femoral component in total knee arthroplasty

PURPOSE

The first purpose of this study was to compare the reproducibility of two-dimensional (2D) and three-dimensional (3D) measurements for preoperative planning of the femoral side in total knee arthroplasty (TKA). The second purpose was to evaluate the factors affecting the differences between the 2D and 3D measurements.

METHODS

Two-dimensional and 3D measurements for preoperative planning of the femoral side in TKA were evaluated in 75 varus knees with osteoarthritis. The femoral valgus angle, defined as the angle between the mechanical and anatomical axes of the femur, and the clinical rotation angle and surgical rotation angle, defined by the angles between the posterior condylar line and the clinical or surgical transepicondylar axes, respectively, were analysed using 2D (radiographs and axial CT slices) and 3D (3D bone models reconstructed from CT images) measurements.

RESULTS

For all variables, 3D measurements were more reliable and reproducible than 2D measurements. The medians and ranges of the clinical rotation angle and surgical rotation angle were 6.6° (-1.7° to 12.1°) and 2.3° (-2.5° to 8.6°) in 2D, and 7.1° (2.7° to 11.4°) and 3.0° (-2.0° to 7.5°) in 3D. Varus/valgus alteration of the CT scanning direction relative to the mechanical axis affected the difference in clinical rotation angles between 2D and 3D measurements.

CONCLUSION

Significantly, smaller values of the clinical rotation angle and surgical rotation angle were obtained by 2D compared to 3D measurements, which could result in internal rotation of the femoral component even if the surgeon performs the bone cutting precisely. Regarding clinical relevance, first, this study confirmed the reliability of 3D measurements. Second, it underscored the risk of internal rotation of the femoral component when using 2D measurement, even with precise bone cutting technique. These results will help surgeons avoid malpositioning of the femoral component if 2D measurements are used for preoperative planning in TKA.

LEVEL OF EVIDENCE

Prospective comparative study, Level Ш.

The change on vertebral axial rotation after posterior instrumentation of idiopathic scoliosis

PURPOSE

Agreement between the correction objectives and the instrumentation strategies remains controversial in idiopathic scoliosis. Most studies have focus on the frontal and sagittal plane. The goal of this study was to evaluate the change on vertebral axial rotation after posterior instrumentation in fused and unfused segments.

METHODS

Fourteen patients operated on for idiopathic scoliosis were prospectively included. Fusion and instrumentation were done by posterior approach. All patients had a pre-operative and a 10-day post-operative radiological evaluation with the EOS system. Axial orientation of the vertebrae with special interest to the apical, junctional, and unfused areas was obtained thanks to the reconstruction software.

RESULTS

Mean apical vertebra axial rotation statistically decreased from 21° pre-operatively to 13° post-operatively. But, there were no statistically significant differences between pre-operative and post-operative mean axial intervertebral rotations in the main curve and axial rotation of the non-instrumented lower counter curve.

CONCLUSIONS

3D analysis of the spine in standing position is a great advancement for post-operative analysis of adolescent idiopathic scoliosis (AIS) corrections. This study confirmed that actual instrumentations are able to achieve "en bloc" 3D correction of the spine but not intervertebral axial rotation correction.

A novel approach for monitoring writing interferences during navigated transcranial magnetic stimulation mappings of writing related cortical areas

BACKGROUND

It has recently been shown that navigated repetitive transcranial magnetic stimulation (nTMS) is useful in preoperative neurosurgical mapping of motor and language brain areas. In TMS mapping of motor cortices the evoked responses can be quantitatively monitored by electromyographic (EMG) recordings. No such setup exists for monitoring of writing during nTMS mappings of writing related cortical areas.

NEW METHOD

We present a novel approach for monitoring writing during nTMS mappings of motor writing related cortical areas.

COMPARISON WITH EXISTING METHOD(S)

To our best knowledge, this is the first demonstration of quantitative monitoring of motor evoked responses from hand by EMG, and of pen related activity during writing with our custom made pen, together with the application of chronometric TMS design and patterned protocol of rTMS.

RESULTS

The method was applied in four healthy subjects participating in writing during nTMS mapping of the premotor cortical area corresponding to BA 6 and close to the superior frontal sulcus. The results showed that stimulation impaired writing in all subjects. The corresponding spectra of measured signal related to writing movements was observed in the frequency band 0-20 Hz. Magnetic stimulation affected writing by suppressing normal writing frequency band.

CONCLUSION

The proposed setup for monitoring of writing provides additional quantitative data for monitoring and the analysis of rTMS induced writing response modifications. The setup can be useful for investigation of neurophysiologic mechanisms of writing, for therapeutic effects of nTMS, and in preoperative mapping of language cortical areas in patients undergoing brain surgery.

Percutaneous Sacroiliac Screw Fixation of the Posterior Pelvic Ring

Percutaneous sacroiliac (SI) screw fixation is indicated for unstable posterior pelvic ring injuries, sacral fractures, and SI joint dislocations. This article provides a review of indications and contraindications, preoperative planning, imaging techniques and relevant anatomy, surgical technique, complications and their management, and outcomes after SI screw insertion.

Correlating preoperative imaging with intraoperative fluoroscopy in iliosacral screw placement

Background

Percutaneous iliosacral screw placement can successfully stabilize unstable posterior pelvic ring injuries. Intraoperative fluoroscopic imaging is a vital component needed in safely placing iliosacral screws. Obtaining and appropriately interpreting fluoroscopic views can be challenging in certain clinical scenarios. We report on a series of patients to demonstrate how preoperative computed tomography (CT) imaging can be used to anticipate the appropriate intraoperative inlet and outlet fluoroscopic views.

Materials and methods

24 patients were retrospectively identified with unstable pelvic ring injuries requiring operative fixation using percutaneous iliosacral screws. Utilizing the sagittal reconstructions of the preoperative CT scans, anticipated inlet and outlet angle measurements were calculated. The operative reports were reviewed to determine the angles used intraoperatively. Postoperative CT scans were reviewed for repeat measurements and to determine the location and safety of each screw.

Results

Preoperative CT scans showed an average inlet of 20.5° (7°–37°) and an average outlet of 42.8° (30°–59°). Intraoperative views showed an average inlet of 24.9° (12°–38°) and an average outlet of 42.4° (29°–52°). Postoperative CT scans showed an average inlet of 19.4° (8°–31°) and an average outlet of 43.2° (31°–56°). The average difference from preoperative to intraoperative was 4.4° (−21° to 5°) for the inlet and 0.45° (−9° to 7°) for the outlet. The average difference between the preoperative and postoperative CT was 2.04° (0°–6°) for the inlet and 2.54° (0°–7°) for the outlet.

Conclusion

There is significant anatomic variation of the posterior pelvic ring. The preoperative CT sagittal reconstruction images allow for appropriate preoperative planning for anticipated intraoperative fluoroscopic inlet and outlet views within 5°. Having knowledge of the desired intraoperative views preoperatively prepares the surgeon, aids in efficiently obtaining correct intraoperative views, and ultimately assists in safe iliosacral screw placement.

Level of evidence

IV, Retrospective case series.

Management of severe femoral bone loss in revision total hip arthroplasty

Femoral bone loss is a complex problem in revision total hip arthroplasty. The Paprosky classification is used when determining the degree and location of bone loss. Meticulous operative planning is essential where severe bone loss is a concern. One must correctly identify the bone loss pattern, safely remove the existing components, and proceed with the proper reconstruction technique based on the pattern of bone loss. This article discusses the etiology and classification of bone loss, clinical and radiographic evaluation, components of effective preoperative planning, and clinical results of various treatment options with a focus on more severe bone loss patterns.

Correlation between nipple elevation and breast resection weight: How to preoperatively plan breast reduction

Breast hypertrophy is often associated with functional limitations. Beyond the aesthetic concerns, breast reduction can improve symptoms and self-esteem. In different countries, health-care system regulations have fixed the threshold for reimbursement in 500 g of predicted tissue resection for each breast. Different preoperative measurements have been proposed to predict breast-tissue weight to be removed, showing a variable correlation with post-operative evaluation. We describe a reliable, simple measurement to predict the quantity of breast reduction in grams, which can be applicable to any surgical technique. A total of 128 patients undergoing bilateral breast reduction were evaluated. The correlation between the preoperative nipple-areola complex (NAC) lift distance and the weight of removed breast tissue was tested with linear regression and Pearson's test. Other anthropometric measurements were tested as a control. The ratio between resected grams and lift distance was explored to find a multiplication coefficient to be used at preoperative planning. The mean resection weight was 686.65 g. The mean NAC-lift distance was 7.6 cm. Positive correlation between the NAC-lift distance and the weight of breast tissue removed was found (r: 0.87; p < 0.001). The mean weight of the removed breast tissue (g) per centimetre of NAC lift was 81 g/cm in the group between 6 and 12 cm and 70 g/cm in the group with >12 cm of lift distance. The NAC-lift distance is a single, objective, repeatable measure that can provide a reliable prediction of breast-tissue grams to be removed; it helps in classifying breast-reduction indications.

Preoperative Planning for Pedicle Subtraction Osteotomy: Does Pelvic Tilt Matter?

STUDY DESIGN

Multicenter, retrospective radiographic analysis.

OBJECTIVES

To evaluate the impact that preoperative spinopelvic parameters have on postoperative sagittal vertical axis (SVA). The researchers hypothesized that patients with a large preoperative pelvic tilt (PT) would require more extensive lumbar pedicle subtraction osteotomy (LPSO) procedures to reestablish anatomic postoperative SVA than patients with normal preoperative PT.

SUMMARY OF BACKGROUND DATA

Restoration of anatomic sagittal spinal alignment has been demonstrated to improve clinical outcomes. However, the degree to which spinopelvic parameters contribute to sagittal spinal malalignment is poorly understood.

METHODS

Multicenter, retrospective analysis of 183 consecutively enrolled adult spinal deformity patients treated with LPSO procedures for correction of sagittal malalignment. Preoperative and postoperative freestanding full-length sagittal X-rays were analyzed for regional curves, pelvic parameters, and global alignment. Only patients with a preoperative SVA greater than 10 cm and a postoperative SVA less than 5 cm were retained for analysis. Patients were divided into 2 groups according to preoperative PT (low PT, less than 30°; and high PT, ≥30°). Independent t test analysis was used to determine differences in correction required to achieve postoperative SVA less than 5 cm.

RESULTS

A total of 55 patients were identified for analysis. Low PT (n = 30) had lower preoperative PT than high PT (n = 25; 25° vs. 42°, respectively; p < .001). Analysis of the osteotomy performed demonstrated that the high PT group required a larger osteotomy resection (30° vs. 23°; p = .039) and a larger correction of lumbar lordosis (-43° vs. -31°; p = .006) to achieve an acceptable postoperative SVA (less than 5 cm).

CONCLUSIONS

This study demonstrates that patients with high PT in conjunction with sagittal spinal malalignment require larger lumbar osteotomy procedures, including a greater osteotomy resection and larger lumbar lordosis correction, to obtain a satisfactory postoperative SVA. Surgeons performing LPSO procedures must evaluate preoperative spinopelvic parameters, including PT, to avoid undercorrection and residual deformity after complex sagittal realignment procedures.

Increasing shape modelling accuracy by adjusting for subject positioning: an application to the analysis of radiographic proximal femur symmetry using data from the Osteoarthritis Initiative

In total hip arthroplasty, the shape of the contra-lateral femur frequently serves as a template for preoperative planning. Previous research on contra-lateral femoral symmetry has been based on conventional hip geometric measurements (which reduce shape to a series of linear measurements) and did not take the effect of subject positioning on radiographic femur shape into account. The aim of this study was to analyse proximal femur symmetry based on statistical shape models (SSMs) which quantify global femoral shape while also adjusting for differences in subject positioning during image acquisition. We applied our recently developed fully automatic shape model matching (FASMM) system to automatically segment the proximal femur from AP pelvic radiographs to generate SSMs of the proximal femurs of 1258 Caucasian females (mean age: 61.3 SD=9.0). We used a combined SSM (capturing the left and right femurs) to identify and adjust for shape variation attributable to subject positioning as well as a single SSM (including all femurs as left femurs) to analyse proximal femur symmetry. We also calculated conventional hip geometric measurements (head diameter, neck width, shaft width and neck-shaft angle) using the output of the FASMM system. The combined SSM revealed two modes that were clearly attributable to subject positioning. The average difference (mean point-to-curve distance) between left and right femur shape was 1.0mm before and 0.8mm after adjusting for these two modes. The automatic calculation of conventional hip geometric measurements after adjustment gave an average absolute percent asymmetry of within 3.1% and an average absolute difference of within 1.1mm or 2.9° for all measurements. We conclude that (i) for Caucasian females the global shape of the right and left proximal femurs is symmetric without isolated locations of asymmetry; (ii) a combined left-right SSM can be used to adjust for radiographic shape variation due to subject positioning; and (iii) adjusting for subject positioning increases the accuracy of predicting the shape of the contra-lateral hip.

Disparity between reported and measured patient weight: can it affect planning in breast reduction surgery?

BACKGROUND

Patient weights are frequently used in surgery for essential calculations including preoperative surgical planning, dosing of medications, and qualification for insurance reimbursement. Often, there is a disparity between patient-reported and actual measured weights. This study examines differences between self-reported and measured weights and implications in breast reduction surgery.

METHODS

A review was performed of 197 consecutive women who presented for breast surgery at an academic institution. Self-reported weights were recorded during the initial encounter, and the patients were subsequently weighed on the same day. A paired t-test was used to compare the self-reported and actual measured weights and stratified analysis performed based on body mass index (BMI). The Schnur sliding scale was used to estimate resection weights for reduction mammaplasty.

RESULTS

The overall mean difference in reported and measured weight was 3.0 lbs standard deviation (SD) 8.9 (P < 0.0001) with a maximum overestimation of 25 lb and underestimation of 80 lb. Statistically significant differences were found when stratified analysis was performed based on BMI as mean differences in the overweight (BMI 25-30) and obese (BMI > 30) groups were 1.7 lb SD 5.5 (P < 0.026) and 4.9 lbs SD 11.8 (P < 0.0002), respectively. Significant differences in calculated breast reduction resection weights, based on the Schnur sliding scale, were also found when comparing self-reported and measured weights in all groups.

CONCLUSIONS

Significant disparities between self-reported and measured weights were identified in patients presenting for breast surgery. These differences can influence important calculations of resection weights for breast reduction surgery. These differences may also affect dosing of medications and preoperative planning.