Reliability of a new method for lower-extremity measurements based on stereoradiographic three-dimensional reconstruction

Validity and reliability of ultrasonographic assessment of femoral and tibial torsion in children and adolescents: a systematic review

Torsional disorders of the lower limb are common in childhood, and they are one of the primary reasons parents seek consultation with healthcare providers. While clinical manoeuvres can assess femoral and tibial torsion, their reliability is medium to low. Various imaging-based techniques, including computed tomography, magnetic resonance imaging, fluoroscopy, biplanar radiology and ultrasonography, have been used to evaluate torsional alterations of the lower extremity. Among these, ultrasound assessment offers certain advantages: it is a low-cost, non-irradiating technique, which allows the follow-up of children's torsional development. However, to the best of the authors' knowledge, its validity and reliability have not been summarised in a systematic review. This study aims to analyse the validity and reliability of ultrasonography in determining femoral and tibial torsion in children and adolescents. A search from Medline (via PubMed), Web of Science, Scopus and CINAHL databases were performed from inception to 16 March 2023. No restrictions were placed on the publication year or language. The methodological quality of all eligible studies was independently reviewed by two authors using QUADAS and STARD checklists. Overall, 1546 articles were identified through the searches; 30 were considered eligible for full-text screening; and 8 studies were finally included in this review. The included studies were conducted in Germany, Norway and the UK. Among them, 7 studies analysed the validity of ultrasonography compared with other imaging techniques such as computed tomography, magnetic resonance imaging and biplanar X-ray, and 4 studies assessed intra- and inter-observer reliability. All the studies assessed femoral torsion, but only one of them also included tibial torsion.     Conclusion: Ultrasound is a good alternative for routine evaluation and follow-up of femoral torsional alterations in children and adolescents due to its safety, accessibility and immediate results in the clinical examination room. Although ultrasound has good accuracy and reliability for routine evaluations, there is controversy about whether it is sufficient for surgical planning. In cases where greater accuracy is required, magnetic resonance imaging and biplanar radiography are the preferred imaging techniques. What is Known: • Several imaging-based techniques have been described for the assessment of torsional alterations of the lower extremity. • Computed tomography, magnetic resonance imaging, biplanar radiology and ultrasonography are the most used and studied methods. What is New: • Ultrasonography represents a good alternative for the assessment of femoral and tibial torsional alterations in children and adolescents, given its safety, accessibility and immediacy of results in the consultation room. • Its accuracy and reliability are good but not sufficient for surgical planning, in which case MRI and biplanar X-ray will be the preferred choices.

Effect of Stem Design and Positioning on the Leg Axis after Total Hip Arthroplasty: A Secondary Analysis

Background/Objectives: Various parameters, like femoral offset and leg length, are associated with good patient outcomes after total hip arthroplasty. In this prospective study, the effects of stem design, its placement in the proximal femur and the resulting femoral offset on the total leg axis were investigated. Methods: The 27 patients included in this study received biplanar radiography (EOS®, EOS Imaging) with 3D reconstruction using sterEOS® both preoperatively and postoperatively. For all leg alignment parameters obtained from the 3D reconstruction and from measurements using mediCAD, the deltas between the postoperative and preoperative values were determined. Patients were divided into those who received a short-stem prosthesis and those who received a straight-stem prosthesis. Results: The change in femoral offset with the implantation of a short-stem prosthesis was significantly greater than that with the implantation of a straight-stem prosthesis (11.4 ± 5.9 vs. 4.6 ± 7.4 mm, p = 0.014). Compared with the straight-stem implantation, short-stem implantation caused a significantly greater increase in the varus orientation of the leg (-1.4 ± 0.9 vs. -0.4 ± 1.4°, p = 0.048). There was no significant difference in the positioning of the short-stem prosthesis compared to the straight-stem prosthesis in the proximal femur (3.6 ± 3.1 vs. 2.6 ± 1.9°, p = 0.317). Conclusions: These findings substantiate the impact of prosthesis design on offset and leg alignment. The implantation of short-stems is more variable and requires precise planning. Intraoperative non-physiological offset changes and varus deviation of the leg axis should be avoided. Trial registration: This study was retrospectively registered with the German Clinical Trials Register (DRKS) under the number DRKS00015053 on the 1 August 2018.

Induced-membrane technique for lower limb reconstruction after malignant bone tumour resection in paediatric patients: Complication and re-operation rates

BACKGROUND

The objective of this study was to assess the complication and re-operation rates, evaluate the risk of non-union, and describe the functional outcomes at last follow-up in children and adolescents after lower-limb malignant tumour resection and reconstruction using the induced-membrane technique.

HYPOTHESIS

Weight-bearing resumption 6 weeks after the second stage of the induced-membrane procedure promotes bone healing.

MATERIAL AND METHODS

The study included 13 patients (9 with osteosarcoma, 3 with Ewing's sarcomas, and 1 with alveolar sarcoma) managed between 2000 and 2020 by oncological femoral or tibial resection followed, at a distance from adjuvant chemotherapy, by reconstruction using the induced-membrane technique. Non-union was the primary outcome measure and the MusculoSkeletal Tumor Society (MSTS) lower-limb functional score was the secondary outcome measure. Mean follow-up was 6.1 years (range, 2.0-12.7). At last follow-up, mean age was 18.1 years (range, 11.0-26.0) and the mean MSTS score was 66.6% (37.0-93.0%).

RESULTS

After the second reconstruction stage, 8 complications developed in 6 patients (46%). Either a complication or limb-length inequality required 12 re-operations in 8 patients (61.5%). Non-union occurred after reconstruction in 5 (38.5%) patients. Early resumption of 50% weight-bearing 6 weeks after reconstruction was associated with bone healing (p=0.02).

CONCLUSION

The non-union rate was 38.5%. Partial, 50% weight-bearing with two elbow crutches and an orthosis, if allowed by construct stability, may promote bone healing.

LEVEL OF EVIDENCE

IV.

Significant difference in femoral torsion between coronal plane alignment of the knee type 1 and 4

PURPOSE

The purpose of this study was to find out whether the torsions of the femur and tibia are dependent on the coronal plane alignment of the knee (CPAK) type.

METHODS

Five hundred patients (1000 legs) were included, who received a whole leg standing three-dimensional (3D) radiograph using EOS imaging (EOS Imaging, Paris, France). SterEOS software was used for digital reconstruction. Femoral and tibial torsions were determined by analysing 3D reconstructions of each leg. Femoral torsion was defined as the angle between the femoral neck axis (FNA) and the posterior condylar axis (PCA). Tibial torsion was defined as the angle between the axis tangent to the posterior part of the tibia plateau and the transmalleolar axis. Arithmetic hip-knee-ankle angle (aHKA) and joint-line obliquity (JLO) were also determined, allowing each leg to be assigned one of nine possible phenotypes according to CPAK.

RESULTS

The mean femoral torsion in CPAK type 1 was significantly higher (+ 2.6° ± 0.8°) than in CPAK type 4 (p = 0.02). All other CPAK types did not differ in the degree of femoral torsions. No differences could be demonstrated for the tibial torsion.

CONCLUSION

There is a correlation between the coronal alignment of the lower limb and femoral torsion. This may provide the basis for extending the CPAK classification beyond the coronal plane.

LEVEL OF EVIDENCE

Level III.

Hybrid Closed Wedge High Tibial Osteotomy Maintains the Leg Length After Surgery Compared With Open Wedge High Tibial Osteotomy

BACKGROUND

This study aimed to assess the changes in leg length following open wedge high tibial osteotomy (OWHTO) and hybrid closed wedge high tibial osteotomy (h-CWHTO) and whether the change in leg length was associated with preoperative radiographic factors and the change in planned opening or closing width.

METHODS

We retrospectively evaluated the data of patients who underwent OWHTO (n=57) and h-CWHTO (n=31) between 2016 and 2019. Standing full-length anteroposterior radiographs were obtained preoperatively and one year postoperatively. Changes in the lower leg and tibial length were measured using radiography, and the planned opening or closing width was decided via operative planning. Flexion contracture was examined preoperatively and one year postoperatively using a goniometer, and the correlation factors and changes in leg length were analyzed using Spearman's rank correlation.

RESULTS

In the OWHTO group, the lower leg was significantly longer by a mean of 6.0±8.7 mm compared to that preoperatively (p<0.01); however, no significant difference was observed in the h-CWHTO group (mean, -0.56±11.6 mm) (p=0.788). In the OWHTO group, flexion contracture did not improve after surgery, however, in the h-CWHTO group, flexion contracture significantly improved from -7.1±7.0 degrees to -4.7±6.2 degrees postoperatively (p<0.01). No radiographic factors or bone opening or closing width were associated with changes in leg length in both groups.

CONCLUSION

OWHTO led to a significant elongation of the lower leg while leg length was maintained post-h-CWHTO. However, the changes in leg length following both OWHTO and h-CWHTO were not predictable from preoperative radiographic factors or changes in bone width.

Towards a better understanding of knee angular deformities: discrepancies between clinical examination and 2D/3D assessments

INTRODUCTION

Discrepancy between the clinical examination and the 2D/3D radiographs is a common concern in patients with angular or rotational deformities of the lower limbs, as it may alter clinical judgment and subsequent treatment. The aim was to identify such discrepancies and assess determinants that may contribute to their existence.

MATERIALS AND METHODS

A retrospective chart review was conducted on 329 consecutive patients (658 lower limbs) who underwent physical examination and long-leg biplanar radiographs in our institution between 2013 and 2018 for limb length discrepancy or angular deformity of the knees (varus/valgus). Eleven parameters were measured on 2D and 3D images. 3D measurements were based on standing biplanar X-rays and their 3D reconstructions and were considered the gold standard. Contingency tables and multiple linear regression were used to assess discrepancies between the three modalities and their determinants respectively.

RESULTS

Significant mismatches were found between physical examination and 2D images (1% in varus and 1% in valgus), between physical examination and 3D assessment (1% in varus and 4.6% in valgus) as well as between 2 and 3D assessments (1.9% in varus and 7.6% in valgus). The significant determinants of the mismatch between 2 and 3D modalities were frontal pelvic obliquity, neck shaft angle, knee flexion, femoral torsion, and tibial mechanical angle.

CONCLUSION

In the presence of positional and/or morphological deformities, physical examination and 2D assessment of knee alignment could be biased due to axes projection errors. A better understanding of 3D alignment of the knee as part of the entire lower limb from pelvis to toes, may lead to a better diagnosis and subsequently a better treatment of knee angular deformities.

Calibration of magnification in two-dimensional low-dose full-body imaging for preoperative planning of total hip arthroplasty

INTRODUCTION

Preoperative planning of total hip arthroplasty (THA) using two-dimensional low-dose (2DLD) full-body imaging has gained popularity in recent years. The low-dose imaging system is said to produce a calibrated image with constant 1:1 magnification. However, the planning software used in conjunction with those images may introduce variations in the degree of magnification in 2DLD imaging, and this has not yet been investigated. The purpose of the present study was to quantify any variation in 2DLD image to assess the need for image calibration when using conventional planning software.

METHODS

Postoperative 2DLD images from 137 patients were retrospectively evaluated. Only patients who underwent THA for primary osteoarthritis were included in the study cohort. The femoral head diameter was measured by two independent observers using both Orthoview™ and TraumaCad™ planning software programs. Actual sizes of the femoral head implants were extracted from surgical reports to calculate image magnification. Magnification measurement reliability was calculated with the intra-class correlation coefficient (ICC) index.

RESULTS

Image magnification varied among cases (mean 133%, range 129-135%). There was no statistical difference in mean image magnification among the various implant sizes (p = 0.8). Mean observer and inter-observer reliability was rated excellent.

CONCLUSION

THA planning with 2DLD imaging is subject to variation in magnification as analyzed with conventional planning software in this series. This finding is of paramount importance for surgeons using 2DLD imaging in preparation for THA since errors in magnification could affect the accuracy of preoperative planning and ultimately the clinical outcome.

Safe range of femoral neck system insertion and the risk of perforation

BACKGROUND

Internal fixation of the femoral neck carries a risk of perforation due to the presence of the isthmus of the femoral neck. At present, there are few studies on the safe and risk zones of the femoral neck system (FNS) implantation. This study aimed to recommend the safe range of injection of FNS in the lateral wall of the proximal femur, parallel to the axis of the femoral neck, during FNS treatment of femoral neck fracture (FNF).

METHODS

Femoral computed tomography (CT) data of 80 patients (male: 40; female: 40) who met the inclusion criteria were collected. Mimics 21.0 software was used to complete the modeling. 3-Matic 13.0 software was used to establish the axis of the femoral neck and its vertical plane, perform the cutting of the femoral neck, and project it on the vertical plane of the femoral neck axis. After matching a rectangle for each projection map, all sample sizes (80 cases) were standardized and superimposed to obtain gradient maps of the safe zone (SZ) and dangerous zone (RZ), thereby securing edge key points and safe FNS insertion range.

RESULTS

In the 80 samples, the mean diameter of the smallest femoral neck section was 33.87 ± 2.32 mm for men and 29.36 ± 1.92 mm for women. All 80 femoral necks had safe and risky areas. The SZ/S × 100% was 77.59 (± 2.22%), and the RS/S × 100% was 22.39% (± 2.22%). The risk area was composed of four parts: (1), (2), (3), and (4), respectively, corresponding to 3.45 ± 1.74%, 5.51 ± 2.63%, 6.22 ± 1.41%, and 7.22 ± 1.39%. Four marginal key points, perforation risk, and safe ranges (SR) of FNS were analyzed on the lateral wall of the femoral neck.

CONCLUSIONS

The SR of FNS placement was recommended by digital simulation. In addition, Regions (3) and (4) posed a higher risk of penetrating the cortex. Using the gradient map of RZ for preoperative evaluation is recommended to avoid iatrogenic perforation.

Assessing Leg Length Discrepancy Is Necessary Before Arthroplasty in Patients With Unilateral Crowe Type IV Hip Dislocation

BACKGROUND

THA for high-riding developmental dysplasia of the hip (DDH) is challenging in terms of length equalization. Although previous studies suggested preoperative templating on AP pelvic radiographs is insufficient in patients with unilateral high-riding DDH because of hypoplasia of the hemipelvis on the affected side and unequal femoral and tibial length on scanograms, the results were controversial. The EOS™ (EOS™ Imaging) is a biplane X-ray imaging system using slot-scanning technology. Length and alignment measurements have been shown to be accurate. We used the EOS to compare the lower limb length and alignment in patients with unilateral high-riding DDH.

QUESTIONS/PURPOSES

(1) Is there an overall leg length difference in patients with unilateral Crowe Type IV hip dysplasia? (2) In patients with unilateral Crowe Type IV hip dysplasia with an overall leg length difference, is there a consistent pattern of abnormalities in the femur or tibia that account for observed differences? (3) What is the impact of unilateral high-riding Crowe Type IV dysplasia on femoral neck offset and knee coronal alignment?

METHODS

Between March 2018 and April 2021, we treated 61 patients with THA for Crowe Type IV DDH (high-riding dislocation). EOS imaging was performed preoperatively in all patients. Eighteen percent (11 of 61) of the patients were excluded because of involvement of the opposite hip, 3% (two of 61) were excluded for neuromuscular involvement, and 13% (eight of 61) had previous surgery or fracture, leaving 40 patients for analysis in this prospective, cross-sectional study. Each patient's demographic, clinical, and radiographic information was collected with a checklist using charts, Picture Archiving and Communication System, and an EOS database. EOS-related measurements that were related to the proximal femur, limb length, and knee-related angles were recorded for both sides by two examiners. The findings of the two sides were statistically compared.

RESULTS

The overall limb length was not different between the dislocated and nondislocated sides (mean 725 ± 40 mm versus 722 ± 45 mm, mean difference 3 mm [95% CI -3 to 9 mm); p = 0.08). Apparent leg length was shorter on the dislocated side (mean 742 ± 44 mm versus 767 ± 52 mm, mean difference -25 mm [95% CI -32 to 3 mm]; p < 0.001). We observed that a longer tibia on the dislocated side was the only consistent pattern (mean 338 ± 19 mm versus 335 ± 20 mm, mean difference 4 [95% CI 2 to 6 mm]; p = 0.002), but there was no difference between the femur length (mean 346 ± 21 mm versus 343 ± 19 mm, mean difference 3 mm [95% CI -1 to 7]; p = 0.10). The femur of the dislocated side was longer by greater than 5 mm in 40% (16 of 40) of patients and shorter in 20% (eight of 40). The mean femoral neck offset of the involved side was shorter than that of the normal side (mean 28 ± 8 mm versus 39 ± 8 mm, mean difference -11 mm [95% CI -14 to -8 mm]; p < 0.001). There was a higher valgus alignment of the knee on the dislocated side with a decreased lateral distal femoral angle (mean 84° ± 3° versus 89° ± 3°, mean difference - 5° [95% CI -6° to -4°]; p < 0.001) and increased medial proximal tibia angle (mean 89° ± 3° versus 87° ± 3°, mean difference 1° [95% CI 0° to 2°]; p = 0.04).

CONCLUSION

A consistent pattern of anatomic alteration on the contralateral side does not exist in Crowe Type IV hips except for the length of the tibia. All parameters of the limb length could be shorter, equal to, or longer on the dislocated side. Given this unpredictability, AP pelvis radiographs are not sufficient for preoperative planning, and individualized preoperative planning using full-length images of the lower limbs should be performed before arthroplasty in Crowe Type IV hips.

LEVEL OF EVIDENCE

Level I, prognostic study.

Osteotomies around the knee are not correlated to substantial post-operative ankle pain

PURPOSE

The relationship between osteotomies around the knee and ankle alignment has been well established. However, little is known about the incidence of new-onset ankle pain after knee osteotomies in the setting of both varus and valgus lower limb malalignments. The purpose of this study is to determine the incidence and characteristics of ankle pain after knee osteotomies; and to clarify the relationship between knee alignment correction, coronal changes suffered by the ankle joint and the development of new-onset ankle pain.

METHODS

Fifty-four lower limbs in 51 consecutive patients, who underwent realignment osteotomies around the knee between April 2013 and October 2020, were retrospectively reviewed. Ultimately, 39 patients (42 knees) were enrolled: 34 had varus deformities and eight had valgus deformities. Ankle pain was assessed according to the Numerical Pain Rating Scale by telephonic interview. The magnitude of alignment correction and the consequent change of both knee and ankle joint lines were analyzed. Correlation between the former and the onset of post-operative ankle pain was evaluated. Patient satisfaction and complications were also noted.

RESULTS

The incidence of new-onset ankle pain after knee realignment osteotomy was 14%, at a mean follow-up of 55 ± 26 months (range 12-93 months). The mean time between osteotomy and onset of ankle pain was 21 ± 25 months (range 2-60 months). The degree of coronal correction was significantly correlated with ankle joint obliquity changes. However, a significant correlation with post-operative ankle pain was not found (p > 0.05).

CONCLUSION

Fourteen percent of the patients who underwent osteotomies around the knee developed new-onset persistent low-intensity ankle pain. The knee and ankle joint biomechanics are closely related, however, only a small percentage of patients suffer from low-intensity ankle pain which is successfully managed with occasional analgesics. Most osteotomies around the knee seem to require no particular concern for the ipsilateral ankle function.

Clinical application of EOS imaging system: a scoping review protocol

OBJECTIVE

The objective of this scoping review is to examine and map the existing literature on the clinical application of the EOS imaging system and to identify related evidence gaps.

INTRODUCTION

The EOS imaging system was originally developed to conduct imaging for medical conditions, such as scoliosis and anisomelia. However, recent research suggests that the modality has other clinical uses that may benefit patients via reduced radiation dose and, thus, improve patient safety.

INCLUSION CRITERIA

This scoping review will consider all quantitative study designs, including systematic reviews and meta-analyses. Imaging phantom studies and conference abstracts will be excluded.

METHODS

Databases that will be searched include Embase, MEDLINE, CINAHL Complete, Scopus, Cochrane Library, Academic Search Premier, and OpenGrey. Relevant secondary material will be identified using citation searching (backwards and forwards) of included studies through Google Scholar. In addition, we will search by author name where more than 3 included studies from the same first author are identified. Articles published from 2003 in English, Danish, Norwegian, Swedish, French, and German will be included. Two independent reviewers will perform title/abstract screening, followed by full-text screening. Data extraction will include study type and design, age of participants, anatomical/physiological region, pathology, clinical endpoint, outcome measures, sample size, and clinical application. Data will be presented in tabular format and as a narrative summary.

REVIEW REGISTRATION NUMBER

Open Science Framework https://osf.io/yc85j/.

Definition and reliability of 3D acetabular and global offset measurements from bi-plane X-rays

The importance of the global offset, the sum of femoral and acetabular offset, has been underlined in the literature as a key factor for the functional outcome of total hip arthroplasty (THA). However, the acetabular offset is not defined for bi-plane X-rays, a technology providing 3D measurements of the lower limb and commonly used for patients undergoing THA. The aim of this paper is to introduce a measurement method of the 3D acetabular offset with bi-plane X-rays. Our method combines the use of technical and anatomical coordinate systems. The most appropriate definition will be selected based on the best reliability and measurement error. The consequent reliability of the global offset was also assessed. Twenty-eight patients undergoing primary THA were selected retrospectively. Two operators performed three reconstructions for each patients before and after THA. Intraclass correlation (ICC) and smallest detectable change (SDC) were computed for intra-operator, inter-operator and test-retest conditions for all combinations of technical and anatomical coordinate systems. ICCs were good to excellent. One combination was more reliable than others with a moderate mean SDC of 6.3 mm (4.3-8.7 mm) for the acetabular offset and a moderate mean SDC of 6.2 mm (5.6-6.7 mm) for the global offset. This is similar to the reliability and mean SDC of the femoral offset (4.8 mm) approved for clinical use which indicates that this method of acetabular offset measurement is appropriate. This opens a research avenue to better understand the role of the acetabular offset on THA outcomes, which seems overlooked in the literature.

Reliability of the pelvis and femur anatomical landmarks and geometry with the EOS system before and after total hip arthroplasty

Bi-plane X-ray provides 3D measurements of the lower limb based on the identification of anatomical landmarks in sagittal and frontal X-rays. In clinical practice, such measurements involve multiple operators and sessions. This study aimed at evaluating the reliability of anatomical landmarks identification and geometric parameters of the pelvis and femur measured with bi-plane X-rays before and after total hip arthroplasty (THA). Twenty-eight patients undergoing primary THA were selected retrospectively. Two operators performed three reconstructions for each patient before and after THA. Intraclass correlation (ICC) and smallest detectable change (SDC) were computed for intra-operator, inter-operator, and test-retest conditions. Most anatomical landmark positions had good to excellent SDC (< 5 mm) apart from the centre of the sacral slope, greater trochanter, and anterior superior iliac spines (up to 7.1, 16.9, and 21.5 mm respectively). Geometric parameters had moderate to excellent SDC, apart from femoral and stem torsion, pelvic incidence, and APP inclination with poor SDC (9-12°). The sagittal view had significantly higher measurement errors than the frontal view. Test-retest and inter-operator conditions had no significant differences suggesting a low influence of patient posture. Osteoarthritis and the presence of implants did not seem to influence reliability and measurement error. This study could be used as a reference when assessing lower limb structure with bi-plane X-rays.

Is Valgus Cut Angle Based on Radiographic Measurements in Total Knee Arthroplasty Really Inaccurate? A Comparison of Two- and Three-Dimensional Measurements

Radiographs are widely used to measure distal femoral valgus cut angle (VCA) in total knee arthroplasty (TKA), but its accuracy is controversial. This study used three-dimensional (3D) reconstruction models to verify the accuracy of VCA measurements on radiographs, and explore the correlation of VCA with hip-knee-ankle (HKA) angle and lateral femoral bowing angle (FBA). A total of 444 osteoarthritis knees of 444 patients from August 2016 to June 2018 was included retrospectively. On radiographs, two-dimensional VCA (VCA-2D) was measured between the femoral mechanical axis and the distal femoral anatomical axis, and HKA was measured between the femoral mechanical axis and the tibial mechanical axis. On the coronal projection of computed tomography 3D models, the anatomical landmarks used for VCA-3D measurements were the same as those on the radiographs, FBA was measured between the proximal and distal femoral anatomical axis. The distributions of VCA-2D and VCA-3D were evaluated by means and variances. The correlation between HKA and VCA and between FBA and VCA was explored. There was a statistical difference between VCA-2D and VCA-3D (p < 0.001), but the deviation was very small (0.15 ± 0.69 degrees), 83.3% of the deviations were less than 1 degree. VCA would increase both in 2D and 3D with increasing of FBA and HKA varus. There was no statistically significant difference between VCA-2D and VCA-3D in patients with moderate varus knees (0-8 degrees of varus) and mild bowing femurs (FBA <5 degrees). Overall, the deviation caused by using radiography to measure VCA was negligible. VCA measurements using radiographs were accurate in patients with moderate varus knees and mildly bowed femurs. This study reflects level of evidence III.

Measurement Techniques for Leg Length Discrepancy in Total Hip Arthroplasty: A Systematic Review of Reliability and Validity

BACKGROUND

Total hip arthroplasty (THA) carries a substantial litigative burden. THA may introduce leg length discrepancy (LLD), necessitating a valid and reliable technique for LLD measurement. This study investigates the reliability and validity of techniques quantitively measuring LLD in both pre- and post-THA.

METHODS

Embase and MEDLINE databases were searched following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines for articles assessing either the validity or reliability of LLD measurement techniques. Data was pooled using random effects meta-analysis to derive reliability estimates. Study quality was assessed using the Brink and Louw checklist.

RESULTS

Forty-two articles with 2059 participants were included. Thirty-three investigated reliability and 25 validity. Reliability displayed high heterogeneity. Poor to excellent intra-rater reliability was reported for antero-posterior pelvis radiographs, moderate to excellent for computed tomography scanograms, and good to excellent for clinical methods and teleradiography, and excellent for bi-planar radiography (BPR). Poor to excellent inter-rater reliability was reported for antero-posterior pelvis radiographs and clinical methods, moderate to excellent for teleradiography, good to excellent for computed tomography scanogram and excellent for BPR. The tape measure method is a valid clinical measure of LLD whilst markerless motion analysis and the block method are not. Imaging techniques are appropriately cross-validated with the exception of BPR.

CONCLUSION

The reported intra- and inter-rater reliability for most measurement techniques vary widely. The tape measure method is a valid clinical measurement of LLD. Imaging techniques have been appropriately cross-validated, with the exception of BPR, although they lack validation against a common reference technique.

Influence of implantation of a total hip endoprosthesis on the ipsilateral leg alignment: the effect of sex and dysplasia of the hip

INTRODUCTION

Differences in leg and hip morphology exist between sexes and developmental hip dysplasia is known to alter proximal femoral morphology. The purpose of this study was to determine whether existing differences in leg alignment due to sex or developmental hip dysplasia have an effect on changes in leg alignment after total hip arthroplasty.

MATERIALS AND METHODS

30 hip osteoarthritis patients underwent biplanar full-length radiography in the standing position preoperatively and 3 months after total hip arthroplasty. Differences in leg alignment between men and women and between patients with primary hip osteoarthritis and patients with developmental dysplasia before and after surgery were tested using a general linear model for repeated measures.

RESULTS

Implantation of a hip prosthesis had no differential effect on ipsilateral leg alignment in patients with hip osteoarthritis due to dysplasia and in patients with primary hip osteoarthritis. However, patients with hip osteoarthritis due to dysplasia had a 2.1° higher valgus both before and after surgery. After total hip arthroplasty, women had a significantly greater increase in varus angle (1.6° vs. 0°) and femoral offset (10.5 vs. 4.6 mm) compared with men. Because the change in acetabular offset was smaller (2.2 vs. 6.2 mm), the global femoral offset was only increased in women. Femoral torsion was constant for men (15.0° and 16.5°), whereas femoral torsion was significantly reduced in women (19.9° and 13.2°).

CONCLUSIONS

Hip arthroplasty has a greater effect on leg axis in women than in men. The axial leg alignment of women could change from a natural valgus to a varus alignment. Therefore, surgeons should consider the effects of total hip arthroplasty on leg alignment in patients with hip osteoarthritis. Whether these changes in leg alignment are also clinically relevant and lead to premature medial or lateral knee osteoarthritis should be investigated in future work.

TRIAL REGISTRATION

This study was registered with DRKS (German Clinical Trials Register) under the number DRKS00015053. Registered 1st of August 2018.

O papel da estereorradiografia na avaliação das deformidades dos membros inferiores

Deformities of the lower limbs are a common condition and can lead to changes in gait, as well as affecting the function and longevity of the hips, knees, and spine. A systematic approach is essential to achieve the desired therapeutic result with the lowest rate of complications. Panoramic radiography is a widely available, low-cost method that is commonly used in order to assess the length and angular deformities of the lower limbs, by measuring the length and angular deviations of the axes. However, because the combination of lower limb deformities in two or three orthogonal planes is common, conventional radiography lacks accuracy because it is a two-dimensional imaging method. Therefore, the measurements of valgus/varus deformities on X-rays restricted to the coronal plane will present increasing variations in measurements depending on the degree of flexion/recurvatum alignment, anomalous bone torsions, or, last but not least, inappropriate patient positioning. Low-dose biplanar stereoradiography using three-dimensional models increases the accuracy of the measurement of several parameters used in the evaluation of lower limb alignment, including lengths, axes, and tibial/femoral torsions, parameters that could previously be evaluated only by computed tomography. Stereoradiography also makes it possible to perform a head-to-toe evaluation, as well as to evaluate the interactions among the lower limbs, pelvis, and spine.

Comparison of Lower-Limb Alignment in Patients with Advanced Knee Osteoarthritis: EOS Biplanar Stereoradiography versus Conventional Scanography

Background

Accurate measurement of the lower limb alignment is one of the most crucial factors in advanced knee osteoarthritis patients scheduled for surgery. Recently, EOS biplanar stereoradiography with three-dimensional reconstruction was developed. The purpose of this study was to compare radiographic parameters between conventional scanography and EOS in patients with advanced knee osteoarthritis who need surgical treatment.

Methods

A total of 52 consecutive patients (104 knees) with bilateral knee osteoarthritis of advanced stage (Kellgren-Lawrence [KL] grade 3 or 4) were retrospectively reviewed. We measured the hip-knee-ankle angle (HKA) on conventional scanograms. In EOS, we measured HKA, hip-knee-shaft angle, mechanical lateral distal femoral angle, and mechanical medial proximal tibial angle. To evaluate sagittal and axial plane alignment, knee flexion angle (KFA), and knee joint rotation (KJR) were also measured.

Results

Ninety knees were KL grade 4, and 14 knees were grade 3. The average HKA was 10.14° ± 6.16° on conventional scanograms and 11.26° ± 6.21° in EOS. HKA was greater in EOS than on conventional scanograms, and the difference (1.12°; range, −1.07° to 3.22°) was statistically significant (p < 0.001). Significant correlations were observed on the difference in HKA and mechanical medial proximal tibial angle (r = –0.198, p = 0.044), KFA (r = 0.193, p = 0.049), and KJR (r = 0.290, p = 0.003). In multivariable linear regression analysis, the difference in HKA had significant relationship with KFA (β = 0.286, p = 0.003) and KJR (β = 0.363, p < 0.001).

Conclusions

HKA measured on conventional scanograms and in EOS differed significantly and the difference had a significant correlations with KFA, KJR, and medial proximal tibial angle. Surgeons can consider these results before orthopedic surgery in patients who have advanced knee osteoarthritis.

Evaluation of the reliability of lower extremity alignment measurements using EOS imaging system while standing in an even weight-bearing posture

This study aimed to analyze the reproducibility and reliability of the alignment parameters measured using the EOS image system in both limbs while standing with an even weight-bearing posture. Overall, 104 lower extremities in 52 patients were analyzed retrospectively. The patients stood with an even load over both lower extremities then rotated 15° in both directions. Two EOS images were acquired and 104 pairs of lower extremities were compared according to the position of the indexed lower extremities. Then, the inter-observer reliability of the EOS system and the inter-modality reliability between EOS and computed tomography (CT) were evaluated. Femoro-tibial rotation (FTR) and tibial torsion demonstrated a significant difference between the anterior and posterior positions of the indexed lower extremity. In the inter-observer reliability analysis, all values except for FTR and tibial torsion demonstrated good or very good reliability. In the anterior position, FTR demonstrated moderate, and tibial torsion demonstrated poor reliability. In the posterior position, both FTR and tibial torsion demonstrated poor reliability. In the reliability analysis between the three-dimensional (3D) EOS model and 3D CT images, all measurements of the femur demonstrated very good reliability, but measurements of the tibia did not. For the coronal and sagittal alignment parameters measured by the EOS 3D system with rotated standing posture, except for the measurement including tibial torsion., there were no significant difference for either position of the indexed extremities with high agreement between the observers as well as with the CT 3D model.

Reconstruction of Orthographic Mosaics From Perspective X-Ray Images

Image stitching is a prominent challenge in medical imaging, where the limited field-of-view captured by single images prohibits holistic analysis of patient anatomy. The barrier that prevents straight-forward mosaicing of 2D images is depth mismatch due to parallax. In this work, we leverage the Fourier slice theorem to aggregate information from multiple transmission images in parallax-free domains using fundamental principles of X-ray image formation. The details of the stitched image are subsequently restored using a novel deep learning strategy that exploits similarity measures designed around frequency, as well as dense and sparse spatial image content. Our work provides evidence that reconstruction of orthographic mosaics is possible with realistic motions of the C-arm involving both translation and rotation. We also show that these orthographic mosaics enable metric measurements of clinically relevant quantities directly on the 2D image plane.

A novel technique to assess rotational deformities in lower extremities using CT-based motion analysis

Rotational deformities following intramedullary (IM) nailing of tibia has a reported incidence of as high as 20%. Common techniques to measure deformities following IM nailing of tibia are either based on clinical assessment, plain X-rays or Computed Tomography (CT) comparing the treated leg with the uninjured contralateral side. All these techniques are based on examiners manual calculation inherently subject to bias. Following our previous rigorous motion analysis and symmetry studies on hemi pelvises, femurs and orthopaedic implants, we aimed to introduce a novel fully digital technique to measure rotational deformities in the lower legs. Following formal institutional approval from the Imperial College, CT images of 10 pairs of human lower legs were retrieved. Images were anonymized and uploaded to a research server. Three dimensional CT images of the lower legs were bilaterally reconstructed. CT-based motion analysis (CTMA) was used and the mirrored images of the left side were merged with the right side proximally as stationary and distally as moving objects. Discrepancies in translation and rotation were automatically calculated. Our study population had a mean age of 54 ± 20 years. There were six males and four females. We observed a greater variation in translation (mm) of Centre of Mass (COM) in sagittal plane (95% CI − 2.959–.292) which was also presented as rotational difference alongside the antero-posterior direction or Y axis (95% CI .370–1.035). In other word the right lower legs in our study were more likely to be in varus compared to the left side. However, there were no statistically significant differences in coronal or axial planes. Using our proposed fully digital technique we found that lower legs of the human adults were symmetrical in axial and coronal plane. We found sagittal plane differences which need further addressing in future using bigger sample size. Our novel recommended technique is fully digital and commercially available. This new technique can be useful in clinical practice addressing rotational deformities following orthopaedic surgical intervention. This new technique can substitute the previously introduced techniques.

Robotic-assisted total knee arthroplasty improves the outlier of rotational alignment of the tibial prosthesis using 3DCT measurements

BACKGROUND

The aim of the present study was to compare the accuracy of prosthetic alignment with three-dimensional computed tomography (3DCT) measurements following total knee arthroplasty (TKA) performed using a robotic-assisted surgical technique versus a conventional TKA.

METHODS

41 TKAs were performed with a handheld robotic-assisted surgical procedure (Robot group) between 2019 and 2020. Another 41 patients underwent TKA with a conventional manual surgical procedure (Manual group) using the same prosthesis. The operation durations between both groups were investigated. 3DCT scans of the entire lower extremities were taken before and after the surgery and femoral and tibial alignments in the coronal, sagittal, and axial planes were measured using computer software. The differences in prosthetic alignment and translation between the preoperative 3DCT plan and postoperative 3DCT image were also measured.

RESULTS

There were no statistically significant differences in the post-operative outliers of the femorotibial angle between the groups. In the tibial-axial plane, the mean of prosthetic alignment in the anteroposterior plane was 4.0° in the Robot group and 6.7° in the Manual group (p < 0.01). The rate of outliers for tibial-axial alignment in the Robot group was significantly less than in the Manual group (p < 0.01). There were no statistically significant differences in prosthetic translation in the proximal-distal, anterior-posterior and medial-lateral orientations between the groups.

CONCLUSIONS

In a radiologic study using 3DCT, robotic-assisted TKA reduced the outliers for rotational alignment of the tibial prosthesis in comparison to conventional TKA, which can lead to improved tracking of the femoral-tibial bearing surfaces.

Knee joint loadings are related to tibial torsional alignments in people with radiographic medial knee osteoarthritis

Torsional malalignment was detected in subjects with medial knee osteoarthritis (KOA) but few studies have reported the effect of torsional deformity on knee joint loads during walking. Therefore, this study examined the relationships between lower limb torsional alignments and knee joint loads during gait in people with symptomatic medial KOA using cross-sectional study design. Lower limb alignments including tibial torsion, tibiofemoral rotation and varus/valgus alignments in standing were measured by EOS low-dose bi-planar x-ray system in 47 subjects with mild or moderate KOA. The external knee adduction moment (KAM), flexion moment (KFM) and the KAM index which was defined as (KAM/ (KAM+KFM)*100) during walking were analyzed using a motion analysis system so as to estimate the knee loads. Results revealed externaltibial torsion was positively associated with KAM in subjects with moderate KOA (r = 0.59, p = 0.02) but not in subjects with mild KOA. On the contrary, significant association was found between knee varus/valgus alignment and KAM in the mild KOA group (r = 0.58, p<0.001) and a sign of association in the moderate KOA group (r = 0.47, p = 0.08). We concluded tibial torsion and knee varus/valgus mal-alignments would be associated with joint loading in subjects with moderate medial KOA during walking. Radiographic severity might need to be considered when using gait modification as a rehabilitation strategy for this condition.

[Radiographic analysis of limb malalignment in the frontal plane]

Radiographic measurement of the lower limb alignment in the frontal plane is used to assess limb deformity, to plan corrective surgery and for follow-up. It is essential that age-related normal lower limb alignment and joint orientation angles are known before planning surgical treatment. EOS (EOS™ Imaging, Paris, France) can lead to supplemental information, especially in cases of severe multidimensional joint malalignment. It allows 3D reconstruction of a bone model of the limb to assess multi-dimensional deformity.

Validity of the EOS-determined pelvic parameters and orientation with pelvic positional variation: a phantom study

The EOS is a medical imaging system that incorporates simultaneous orthogonal images, producing three-dimensional (3D) reconstructions of the whole skeletal system in various functional positions. Despite growing interest in the pelvic 3D position, the validity of the EOS has not yet been well studied. We investigated the trueness and precision of EOS imaging for pelvic parameters and orientation and assessed whether the measurement using the EOS was affected by the pelvic orientation itself. The orientation of the anterior pelvic plane and pelvic parameters of a custom-made pelvic phantom were measured by three raters using the EOS, and the measurements obtained were compared with the true values. The standard deviations of the measurement errors were 3.23°, 0.26°, 0.23°, 2.98°, 0.88°, and 3.22° for flexion, obliquity, rotation, pelvic incidence, spinopelvic tilt, and sacral slope, respectively. The root-mean square averages of the standard deviation of each measurement were 4.05°, 0.41°, 0.28°, 4.80°, 0.99°, and 5.13°, respectively. The measurement errors for sacral slope correlated significantly with geometric means of flexion, obliquity, and rotation (r = 0.364, p = 2.67 × 10^-11). The EOS rendered accurate and reliable measurements regarding pelvic 3D position, even with positional variation, but positional variation could affect measurements of sacral slope.

Incidental extraspinal imaging findings on adult EOS full body radiographs: prevalence and clinical importance

Purpose

The purpose of this study was to review our institutional experience with the EOS machine in order to identify the incidence and clinical significance of incidental extraspinal findings (IESF) in an adult spinal deformity population.

Methods

Our institutional database was queried for all full-length standing radiographs generated by the EOS machine. Dictations were reviewed and the number of incidental extraspinal findings were classified using a previously described system. All findings related to the spine were excluded. A subset of electronic medical records were reviewed to determine further workup for individual findings of suspected clinical significance.

Results

Original database query based on radiology reports returned a total of 1857 EOS studies. Duplicate studies, studies without the entire body, and patients with more than 1 study during the search period were excluded. 503 patient studies (55.5% female, mean age 59-years-old, range 18 to 91-years-old) met inclusion criteria. The overall rate of incidental extraspinal findings in our study was 60.4% (304 findings in 503 patients). Most findings were classified as Minor. The rate of Major and Moderate findings was 4.8%. The final rate of clinically significant incidental extraspinal findings was 0.8% and included 3 presumed metastatic lesions in long bones and 1 pulmonary nodule.

Conclusion

To our knowledge this is the first study that reports the rate of incidental extraspinal findings on full body EOS studies. We report a low rate (0.8%) of clinically significant incidental extraspinal findings which is lower than that of CT or MRI. Further research is warranted in comparing EOS and standard radiography.

EOS Imaging is Accurate and Reproducible for Preoperative Total Hip Arthroplasty Templating

BACKGROUND

Templating is a critical part of preoperative planning for total hip arthroplasty (THA). The accuracy of templating on images acquired with EOS is unknown. This study sought to compare the accuracy and reproducibility of templating for THA using EOS imaging to conventional digital radiographs.

METHODS

Forty-three consecutive primary unilateral THAs were retrospectively templated, six months postoperatively, using preoperative 2D EOS imaging and conventional radiographs. Two blinded observers templated each case for acetabular and femoral component size and femoral offset. The retrospectively templated sizes were compared to the sizes selected during surgery. Interobserver agreement was calculated, and the influence of demographic variables was explored.

RESULTS

EOS templating predicted the exact acetabular and femoral size in 71% and 66% of cases, respectively, and to within one size in 98% of cases. The acetabular and femoral component size was more likely to be templated to the exact size using EOS compared to conventional imaging (P < .05). The femoral component offset choice was accurately predicted in 83% of EOS cases compared to 80% of conventional templates (P = .341). Component size and offset were not influenced by patient age, gender, laterality, or BMI. Interobserver agreement was excellent for acetabular (Cronbach's alpha = 0.94) and femoral (Cronbach's alpha = 0.96) component size.

CONCLUSIONS

Preoperative templating for THA using EOS imaging is accurate, with an excellent interobserver agreement. EOS exposes patients to less radiation than traditional radiographs, and its three-dimensional applications should be explored as they may further enhance preoperative plans.

Validity of clinical methods in the detection of leg-length discrepancies

INTRODUCTION

Lower limb-length discrepancy is highly prevalent in the general population. Numerous methods and measurement instruments for its diagnosis appear in the literature, but there has not been an agreement about their validity. The aim of this work is to determine the validity of the Weber-Barstow manoeuvre (WB) of the pelvic measuring device (PMD) and the block method (BM), in comparison with standing anteroposterior telemetry of the lower limbs in subjects with leg-length discrepancy (LLD).

METHODS

71 subjects took part in the study. First, the WB was carried out in the supine position. the LLD was then quantified standing with the PMD and with the BM. Lastly, standing anteroposterior telemetry of the lower limbs was obtained. This was measured with Autocad 2013, using the highest part of the head of the femur and the most distal edge of the bisection of the femur as points of reference.

RESULTS

The Kappa index was calculated to check the agreement between the WB manoeuvre and the telemetry. This was 0.52. The relation of the PMD, BM and telemetry difference variables was calculated. A direct relation between the BM and telemetry was shown, with p > 0.05 (0.48 cm and 0.51 cm, respectively).

CONCLUSIONS

The WB manoeuvre got acceptable validity results. The PMD was not valid according to the results obtained in this work. The BM achieved a good validity result for the diagnosis of LLD.

Accuracy of Preoperative Templating in Total Hip Arthroplasty With Special Focus on Stem Morphology: A Randomized Comparison Between Common Digital and Three-Dimensional Planning Using Biplanar Radiographs

BACKGROUND

Accurate preoperative planning is a key component of successful total hip arthroplasty (THA). The purpose of the present study was to compare the accuracy and reliability of three-dimensional (hipEOS) and common digital two-dimensional (TraumaCad) templating with special focus on stem morphology.

METHODS

51 patients undergoing THA were randomized to two groups. Preoperative planning was performed on 23 patients with hipEOS (3D) and on 28 patients with TraumaCad (2D) planning software. Planning results were compared with the implanted component size. Inter- and intraobserver reliability as well as planning accuracy of both planning methods with special focus on straight and short stem design were recorded.

RESULTS

Intraobserver reliability of both planning methods was good for component planning (ICC_2,1: 0.835-0.967). Interobserver ICC_2,1 for stem and cup planning were higher for 3D templating (3D ICC_2,1: 0.906-0.918 vs. 2D ICC_2,1: 0.835-0.843). Total stem and cup size predictions were within 2 sizes for 3D and within 3 sizes for 2D planning. Comparing short stem planning accuracy of both planning methods, absolute difference between implanted and planned component size was significantly lower in 3D planning (P = .029). There was no significant difference in straight stem (P = .935) and cup (P = .954) planning accuracy.

CONCLUSION

Our findings suggest that 3D templating with hipEOS software has a good overall reliability and may have a better planning accuracy of short stem prostheses than digital templating with TraumaCad software. Assuming that the number of implanted short stem prostheses will further increase in coming years, a more precise planning with 3D technique can contribute to improve surgery outcome.

Symptomatic leg length discrepancy after total hip arthroplasty is associated with new onset of lower back pain

BACKGROUND

Leg length discrepancy (LLD) is common after total hip arthroplasty (THA) with a plethora of clinical consequences. The associations between symptomatic (sLLD; disturbing perception of anatomical leg length discrepancy), anatomical (aLLD; side difference in leg length between the center of rotation of the hip and the center of the ankle joint) and intraarticular (iLLD; side difference between the tear drop figure and the most prominent point of the trochanter minor) LLD and lower back have not yet been reported in the literature. We performed a retrospective study to answer if postoperative (1) symptomatic LLD, (2) anatomic LLD, and (3) a change in intraarticular leg length are associated with lower back pain in patients undergoing THA. Further, we aimed to answer (4) whether symptomatic LLD is associated with the magnitude of anatomical LLD and the change in intraarticular leg length.

HYPOTHESIS

LLD after THA is associated with lower back pain.

MATERIALS AND METHODS

Seventy-nine consecutive patients were retrospectively analyzed for the presence of aLLD and iLLD using EOS™ and X-rays, and were interviewed for the presence of sLLD and lower back pain using a questionnaire 5 years after primary THA.

RESULTS

Postoperative new onset of lower back pain was reported by 9 (11%) patients. Twenty (25%) patients reported sLLD. Anatomical LLD>5mm was present in 44 (56%) (median 8.0 (IQR -3.0 to 12.0; range -22 to 22) mm) and>10mm in 17 (22%) (median 12.0 (IQR 11.0 to 16.5; range -22 to 22) mm) patients. iLLD changed>5mm in 44 (56%) (median 8.5 (IQR 7.0 to 10.0; range -8 to 18) mm) and>10mm in 10 (13%) (median 14.0 (IQR 12.5 to 14.5; range 11 to 18) mm). New onset lower back pain was associated with sLLD (p=0.002) but not with aLLD or iLLD. Patients without preoperative lower back pain had a statistically significant association between presence of sLLD and an aLLD of >10mm (p=0.01).

CONCLUSIONS

Symptomatic LLD after primary THA is associated with postoperative new onset of lower back pain irrespective of the magnitude of LLD. In patients without lower back pain prior to THA, symptomatic LLD is associated with anatomical LLD of more than 10mm.

LEVEL OF EVIDENCE

IV.

Three-dimensional pre-operative planning of primary hip arthroplasty: a systematic literature review

Three-dimensional (3D) pre-operative planning in total hip arthroplasty (THA) is being recognized as a useful tool in planning elective surgery, and as crucial to define the optimal component size, position and orientation. The aim of this study was to systematically review the existing literature for the use of 3D pre-operative planning in primary THA.A systematic literature search was performed using keywords, through PubMed, Scopus and Google Scholar, to retrieve all publications documenting the use of 3D planning in primary THA. We focussed on (1) the accuracy of implant sizing, restoration of hip biomechanics and component orientation; (2) the benefits and barriers of this tool; and (3) current gaps in literature and clinical practice.Clinical studies have highlighted the accuracy of 3D pre-operative planning in predicting the optimal component size and orientation in primary THAs. Component size planning accuracy ranged between 34-100% and 41-100% for the stem and cup respectively. The absolute, average difference between planned and achieved values of leg length, offset, centre of rotation, stem version, cup version, inclination and abduction were 1 mm, 1 mm, 2 mm, 4°, 7°, 0.5° and 4° respectively.Benefits include 3D representation of the human anatomy for precise sizing and surgical execution. Barriers include increased radiation dose, learning curve and cost. Long-term evidence investigating this technology is limited.Emphasis should be placed on understanding the health economics of an optimized implant inventory as well as long-term clinical outcomes. Cite this article: EFORT Open Rev 2020;5:845-855. DOI: 10.1302/2058-5241.5.200046.

Three-Dimensional Biometrics to Correlate Hindfoot and Knee Coronal Alignments Using Modern Weightbearing Imaging

BACKGROUND

Previous studies focusing on the effects of knee surgery on hindfoot alignment have suggested some degree of compensation between the knee and the hindfoot. However, these studies did not investigate a preoperative relationship in patients without end-stage knee osteoarthritis using 3-dimensional (3D) biometrics. The purpose of this study was to investigate the relationship between knee and hindfoot alignment using 3D weightbearing imaging.

METHODS

This retrospective comparative study included 95 lower limbs with weightbearing computed tomography and low-dose biplanar radiograph investigations. Cases with a history that may have caused a change in lower limb alignment were excluded. Hindfoot and knee alignments were measured using foot ankle offset (FAO) and hip-knee-ankle (HKA) angle, respectively. Patients were separated into 3 groups according to the knee deformity to investigate the distribution of FAO in each group.

RESULTS

The mean (SD) FAO was 2% (7%) for the knee varus group, 1% (6%) for the neutral knee group, and 4% (5%) for the valgus knee group (P = .12). Fifty-three percent of patients with knee valgus showed a pathological hindfoot valgus (P = .04). We found a positive but moderate correlation between hindfoot valgus and HKA (ρ = 0.53; P = .01). Female sex was associated with higher FAO (3% ± 4% vs 0.6% ± 6%; P = .009).

CONCLUSION

This feasibility study suggests a new opportunity using 3D biometrics to understand the relationship between knee and hindfoot alignment and to highlight different patterns of combined deformities in further investigations.

LEVEL OF EVIDENCE

Level III, comparative study.

Reliability of EOS compared to conventional radiographs for evaluation of lower extremity deformity in adult patients

OBJECTIVE

The purpose of this study was to compare reliability of lower extremity imaging measurements using EOS and conventional X-ray (CR) of adult patients with mechanical axis malalignment.

MATERIALS AND METHODS

Ten patients (20 lower limbs) of mean age of 31.6 years (range 21-39) with post-traumatic deformities who presented for evaluation of osteotomies and/or ligament and cartilage reconstructions were prospectively enrolled. Two independent observers performed full-length anterior-posterior (AP) measurements 2 weeks apart on both CXR and two-dimensional (2D) EOS images. Measurements included weight-bearing axis (WBA), varus/valgus angle (V/V), femoral length (FL), tibial length (TL), femoral mechanical axis (FMA), tibial mechanical axis (TMA), and total limb length (TLL). Reliability was determined with random effects modeling of intraclass correlation coefficients (ICC) set to consistency. Three statistical operations were performed to compare interrater validity in CXR and EOS: students' two-sample t test, paired two-sample t test, and Pearson's correlative r-statistical agreement.

RESULTS

There was a statistically significant difference for V/V, FL, and TLL (all p < 0.01) between CXR and EOS. A relatively large proportion of the population consistently had larger V/V measures for EOS compared to CXR. In contrast, the FL and TLL measures were consistently larger for CXR compared to EOS. The differences between CXR and EOS measurements were statistically significant, though the small differences in values were not clinically meaningful. Agreement of all measures remained high (r = 0.84-0.99).

CONCLUSION

Using 2D EOS for lower extremity measurements is reproducible, reliable, and comparable to the gold standard, standing long leg radiographs.

Two-dimensional/three-dimensional EOS™ imaging is reliable and comparable to traditional X-ray imaging assessment of knee osteoarthritis aiding surgical management

BACKGROUND

X-ray imaging is the gold standard for assessing lower limb conditions and preoperative planning. A novel low-radiation-dose EOS™ imaging system enables full-length weight-bearing imaging in one session and three-dimensional (3D) reconstruction. Thus, it can improve assessment of limb deformities, preoperative planning and follow-up with lower radiation exposure. The objective of this study was to measure lower limbs from EOS™ images to determine its accuracy and reproducibility in comparison with long-leg X-ray images.

METHODS

Over a one-year period, twenty patients (forty lower limbs) with knee osteoarthritis were recruited from clinic. Thirty-five (five excluded due to knee prosthesis) two-dimensional- (2D) EOS™, 3D EOS™ and X-ray images were measured independently by four observers, measuring lower limb angles and lengths. On average, twelve weeks later, observers repeated measurements on 2D EOS™ and X-ray images.

RESULTS

A t-test comparing 2D EOS™ with X-ray images showed no significant difference in all angle and length measurements (P > 0.05). When analysing observers separately, all measurements showed no significant difference, apart from the femoral anatomic-mechanical angle (fAMA) from observer 2 (2D EOS™ fAMA 6.21° vs. X-ray fAMA 7.10°, P = 0.02). Intra-observer intraclass correlation coefficient (ICC) for 2D EOS™ and X-ray was 1.00 and 1.00, respectively, and inter-observer ICC was 1.00 and 0.99, respectively. A t-test comparing 2D- with 3D EOS™ images showed no significant difference in all measurements. A t-test comparing 3D EOS™ with X-ray images showed no significant difference in all measurements.

CONCLUSION

This study showed the EOS™ imaging system to be a valid alternative method of imaging lower limbs for alignment, measurements and preoperative arthroplasty planning.

Biplanar Low-Dose Radiography Is Accurate for Measuring Combined Anteversion After Total Hip Arthroplasty

BACKGROUND

Acetabular component position alone has not been predictive of stability after total hip arthroplasty (THA). Combined anteversion of the acetabulum and femur has the potential of being more predictive of stability. Unfortunately, femoral component position is difficult to measure on plain radiographs. Computed tomography (CT) is the gold standard for measuring implant position post-operatively, but CT exposes patients to a substantial amount of radiation.

QUESTIONS/PURPOSES

We sought to determine whether biplanar low-dose radiography can be used to accurately measure both acetabular and femoral implant position after THA.

METHODS

Twenty patients underwent standing low-dose biplanar spine-to-ankle radiographs and supine CT scans 6 weeks after THA. Measurements of acetabular inclination, acetabular anteversion, and femoral anteversion were performed by two blinded observers and compared.

RESULTS

The average absolute differences between biplanar radiographs and CT scans were 2° ± 2° for acetabular inclination, 3° ± 2° for acetabular anteversion, and 4° ± 4° for femoral anteversion between EOS measurements and CT measurements. Interobserver agreement was good for acetabular inclination, acetabular anteversion, and femoral anteversion (Cronbach's α = 0.90) using biplanar low-dose imaging.

CONCLUSION

Biplanar radiography is a reliable low-radiation alternative for measuring acetabular inclination, acetabular anteversion, femoral version, and thus combined anteversion compared to CT. Femoral anteversion had the most variability but is still clinically relevant.

3D Modeling of Lower Extremities With Biplanar Radiographs: Reliability of Measures on Subsequent Examinations

BACKGROUND

Biplanar radiography with 3-dimensional (3D) modeling (EOS) provides a comprehensive assessment of lower limb alignment in an upright weight-bearing position with less radiation than conventional radiography. A study was performed to assess the consistency and reliability of 2 lower extremity 3D biplanar radiograph models created at least 1 year apart in a pediatric population.

METHODS

All patients who had 2 lower extremity radiographic evaluations with EOS performed at visits a minimum of 1 year apart were reviewed. Digital radiographs, of lower extremities in both frontal and sagittal planes, were acquired simultaneously, using the EOS system. The 3D reconstruction of the images was achieved utilizing the SterEOS software. Pelvic position, femoral and tibial anatomy, and the torsional profile were evaluated and compared using t tests.

RESULTS

In total, 53 patients with a mean age of 11.7 years (range, 6.1 to 18.9 y) met inclusion criteria. When comparing 3D models between visits, minimal differences were noted in proximal femoral anatomy and pelvic alignment (pelvic incidence, sacral slope, sagittal tilt, neck shaft angle). Expected differences in femoral and tibial length corresponded with normal longitudinal growth between visits. Sagittal plane knee position varied widely between examinations. Femoral and/or tibial rotational osteotomies were performed in 37% of extremities between examinations. After femoral derotational osteotomy, a significant difference in femoral anteversion was appreciated when comparing preoperative and postoperative 3D models. However, this difference was less than the expected difference based on the anatomic correction achieved intraoperatively. No differences were noted in tibial torsion measures after tibial derotational osteotomy.

CONCLUSIONS

The 3D modeling based on biplanar radiographs provides consistent and reliable measures of pelvic and hip joint anatomy of the lower extremity. Patient positioning may influence the reproducibility of knee alignment. The torsional profile assessment did not accurately reflect changes obtained by derotational osteotomy.

LEVEL OF EVIDENCE

Level III.

A precise method for determining acetabular component anteversion after total hip arthroplasty

AIMS

Several radiological methods of measuring anteversion of the acetabular component after total hip arthroplasty (THA) have been described. These are limited by low reproducibility, are less accurate than CT 3D reconstruction, and are cumbersome to use. These methods also partly rely on the identification of obscured radiological borders of the component. We propose two novel methods, the Area and Orthogonal methods, which have been designed to maximize use of readily identifiable points while maintaining the same trigonometric principles.

PATIENTS AND METHODS

A retrospective study of plain radiographs was conducted on 160 hips of 141 patients who had undergone primary THA. We compared the reliability and accuracy of the Area and Orthogonal methods with two of the current leading methods: those of Widmer and Lewinnek, respectively.

RESULTS

The 160 anteroposterior pelvis films revealed that the proposed Area method was statistically different from those described by Widmer and Lewinnek (p < 0.001 and p = 0.004, respectively). They gave the highest inter- and intraobserver reliability (0.992 and 0.998, respectively), and took less time (27.50 seconds (sd 3.19); p < 0.001) to complete. In addition, 21 available CT 3D reconstructions revealed the Area method achieved the highest Pearson's correlation coefficient (r = 0.956; p < 0.001) and least statistical difference (p = 0.704) from CT with a mean within 1° of CT-3D reconstruction between ranges of 1° to 30° of measured radiological anteversion.

CONCLUSION

Our results support the proposed Area method to be the most reliable, accurate, and speedy. They did not support any statistical superiority of the proposed Orthogonal method to that of the Widmer or Lewinnek method. Cite this article: Bone Joint J 2019;101-B:1042-1049.

Femoral neck shortening after internal fixation of Garden I fractures increases the risk of femoral head collapse

BACKGROUND

Arthroplasty has not been proven superior over internal fixation for the treatment of non-displaced femoral neck fractures. However, internal fixation has been followed by high rates of revision for mechanical complications and of femoral neck impaction within the first postoperative year. The objective of this study was to determine whether femoral neck impaction was associated with avascular necrosis (AVN).

HYPOTHESIS

Fracture healing with femoral neck shortening by impaction after internal fixation of a femoral neck fracture is associated with AVN.

MATERIAL AND METHODS

A single-centre retrospective study in patients with Garden I fractures managed by screw fixation was performed to compare outcomes in the groups with and without femoral neck impaction. Follow-up radiographs were assessed for evidence of the femoral neck impaction during fracture healing. The occurrence of AVN was the primary evaluation criterion. The secondary evaluation criteria were risk factors for impaction and complications.

RESULTS

Of the 75 included patients, 9 (12%) experienced AVN. Impaction was significantly associated with AVN (p=0.02; relative risk, 4.38). Significant risk factors for impaction were a higher body mass index (p=0.0003) and valgus-impacted fracture reduction between the radiographs at baseline and immediately after surgery (p=0.0001).

DISCUSSION

Femoral neck impaction was a significant risk factor for AVN after screw fixation of Garden I fractures. Valgus-impacted fracture reduction must receive careful attention during fixation. We suggest static internal fixation if the impaction is reduced on a traction table and advise caution when using parallel screws. The diagnostic and therapeutic strategy proposed here deserves to be evaluated in a prospective study.

LEVEL OF EVIDENCE

III, retrospective comparative study.

An accelerometer-based portable navigation system improved prosthetic alignment after total knee arthroplasty in 3D measurements

PURPOSE

This study aimed to compare prosthetic alignment using three-dimensional (3D) measurements following total knee arthroplasty (TKA) performed using an accelerometer-based portable navigation system (KneeAlign2) versus the conventional technique.

METHODS

A total of 159 patients who had primary osteoarthritis of the knee with varus deformity underwent TKA. The KneeAlign2 system was used for distal femoral resection and tibial resection in 78 knees, and the conventional instrumentation (intramedullary for the femur and extramedullary for the tibia) was used in 81 knees. 3D computed tomography (CT) scans of the whole leg were taken after TKA. Femoral and tibial prosthetic alignments in the coronal, sagittal, and axial planes were measured using computer software. The operation time and estimated blood loss were calculated. Deep venous thrombosis (DVT) and pulmonary embolism (PE) were evaluated using the contrast-enhanced multi-detector row CT at 1 week after TKA.

RESULTS

In the femoral coronal plane, the mean and standard deviation of prosthetic alignment from neutral alignment were 1.2° [95% confidence interval (CI) 1.0°-1.4°) in the navigation group and 1.6° (95% CI 1.3°-2.0°) in the conventional group (p = 0.03). The femoral component outliers (> 3° away from the goal alignment) using the navigation system and the conventional technique were 3 and 15%, respectively, in the coronal plane (p < 0.01), and 15 and 43%, respectively, in the sagittal plane (p < 0.01). The outliers in tibial coronal and tibial sagittal planes were not statistically different between the two groups. There were no statistically significant differences between the two groups in operation time, blood loss, DVT, and PE.

CONCLUSION

Using an accelerometer-based portable navigation system decreased the outliers of prosthetic alignment in femoral coronal and sagittal planes, and did not increase the complications such as operation time, blood loss, DVT, and PE. To our knowledge, this study is the first to investigate the usefulness of an accelerometer-based portable navigation system using the validated 3D measurement.

LEVEL OF EVIDENCE

III.

New Technologies in Pediatric Deformity Correction

The ability to correct limb deformities is one of the core elements of pediatric orthopedics. The term, orthopedics, is derived from the Greek language and means straightening (ortho) children (paidos). New advances in the evaluation and management of children with limb alignment or limb length issues are constantly appearing. This review highlights some of the recent technologies that have been developed to improve the care of these children.

Leg length discrepancy after total hip arthroplasty: Can leg length be satisfactorily controlled via anterior approach without a traction table? Evaluation in 56 patients with EOS 3D

BACKGROUND

Leg length discrepancy (LLD) occurs in about 25% of cases after total hip arthroplasty (THA) and adversely affects function if greater than 10mm. When using the direct anterior approach (DAA), limb length control is considered easier with a standard operating table than with a traction table. However, this assumption has not been confirmed. More specifically, no studies have used EOS imaging, which is currently the reference for assessing limb length. The objectives of this retrospective study were: (1) to use EOS imaging to determine whether THA via the DAA on a standard table allowed satisfactory limb length control; (2) whether LLD was associated with other parameters such as age, gender, body mass index (BMI), or side; and (3) to compare clinical score values between patients with and without LLD.

HYPOTHESIS

The DAA without a traction table allows satisfactory limb length control as assessed using 3D EOS imaging.

MATERIAL AND METHODS

This retrospective descriptive study included 56 patients who underwent primary THA via the DAA between March 2013 and June 2014. LLD was measured on pre- and post-operative EOS images, using sterEOS™ 3D software. Age, gender, BMI, and side of THA were collected. The 12-item Short Form score, Harris Hip Score, and Postel-Merle d'Aubigné score were determined to look for radio-clinical correlations.

RESULTS

Of the 56 patients, 15 (26.8%) had an LLD >10mm before THA and 12 (21.4%) after THA. Limb length equality was restored in 7 patients with 1 with a shorter and 1 with a longer limb before THA. In 5 patients with equal limb length before THA, the operated limb was lengthened after THA, by a mean of 8.92mm (range, 5.8-10.8mm). Thus, in all, 5/56 (8.9%) patients experienced a detrimental change in limb length due to the surgery. No statistically significant differences were found between patients with and without LLD regarding age, gender, BMI, side, or clinical scores.

DISCUSSION

Although the frequency of LLD after THA in our study was consistent with earlier reports, our results show that good limb length control can be obtained via the DAA with a standard operating table. Thus, 7 of the 11 patients with a shorter limb and 1 of 4 with a longer limb before THA had equal limb lengths after THA, and only 8.9% of patients experienced a detrimental increase in limb length after THA. The DAA without a traction table allows satisfactory intra-operative limb length control based on visualisation of anatomical landmarks (antero-superior iliac spines and medial malleoli). This technique is therefore valuable for limiting the risk of LLD. When combined with 3D EOS planning, it may increase the accuracy of limb length adjustment.

LEVEL OF EVIDENCE

IV, retrospective study with no control group.

[Kinematic examination of the musculoskeletal system : Use of methods of image and image sequence analyses as well as shape and motion models]

Image-based preoperative planning has become a routine component in surgery on the musculoskeletal system. In joint arthroplasty it is obligatory. Surgeons are increasingly considering new approaches with additional computer-based kinematic examinations that also generate dynamic image analyses. This article describes several of these new examination techniques and discusses their clinical relevance.

Validity and reliability of different techniques of neck-shaft angle measurement

AIM

To determine a valid and reliable neck-shaft angle (NSA) measurement method while rotating the pelvises in increments of 5° in order to simulate patient malpositioning.

MATERIALS AND METHODS

CT images of 17 patients were used to produce digitally reconstructed radiographs in frontal and lateral views and three-dimensional (3D)-reconstructions of the femurs, considered to be the reference standard. Malpositioning was simulated by axially rotating the frontal radiographs from 0° to 20°. Three operators measured in two-dimensions the NSA using four different methods, three times each, at each axial rotation (AR) position. Method 1 (femoral neck axis drawn by joining the centre of the femoral head (CFH) to the median of the femoral neck base; femoral diaphysis axis drawn by joining the median of two lines passing through the medial and lateral edges of the femoral axis below the lesser trochanter) and method 2 (femoral axis taken as the median of a triangle passing through base of femoral neck and medial and lateral head-neck junction; femoral diaphysis as previous) were described for the first time; method 3 was based on a previous study; method 4 was a free-hand technique. Reliability, validity, and global uncertainty were assessed.

RESULTS

Method 1 showed the best reliability and validity. The global uncertainty also showed minimal values for method 1, ranging from 7.4° to 14.3° across AR positions.

CONCLUSION

Method 1, based on locating the CFH, was the most reliable and valid method and should be considered as a standardised two-dimensional NSA measurement method for clinical application.

Evaluation of functional and structural leg length discrepancy in patients with adolescent idiopathic scoliosis using the EOS imaging system: a prospective comparative study

Background

To our knowledge, no studies have reported the exact structural leg length discrepancies (LLDs) in patients with adolescent idiopathic scoliosis (AIS). Therefore, this study aimed to evaluate the differences between functional and structural LLDs and to examine the correlations between LLDs and spinopelvic parameters in patients with AIS using an EOS imaging system, which permits the three-dimensional reconstruction of spinal and lower-limb bony structures.

Methods

Eighty-two consecutive patients with AIS underwent whole-body EOS radiography in a standing position between August 2014 and March 2016. Functional LLD, lumbar Cobb angle, thoracic curve Cobb angle, coronal balance, and pelvic obliquity were measured using two-dimensional EOS radiography. Structural LLDs were measured using three-dimensional EOS-reconstructed images. The comparison between LLDs was assessed using paired t test. Pearson's correlation coefficient (r) was used to determine potential correlations between the LLDs and spinopelvic alignment parameters.

Results

Functional LLDs were significantly larger than structural LLDs (5.6 ± 5.0 vs. 0.2 ± 3.6 mm, respectively; p < 0.001). Both functional and structural LLDs were significantly correlated with pelvic obliquity (r = 0.69 and r = 0.51, respectively; p < 0.001 for both). Functional LLD, but not structural LLD, was correlated with lumbar Cobb angle (r = 0.44, p < 0.001; r = 0.17, p = 0.12, respectively). In addition, functional and structural LLDs were not correlated with thoracic Cobb angle (r = 0.09 and r = - 0.05, respectively; p ≥ 0.68 for both).

Conclusions

Although patients with AIS often have functional LLDs, structural LLDs tend to be smaller. The correlation between functional LLDs and the lumbar Cobb angle indicates that functional LLDs compensate for the lumbar curve. Thus, the difference between functional and structural LLDs indicates a compensatory mechanism involving extension and flexion of the lower limbs.

Radiation dose and magnification in pelvic X-ray: EOS™ imaging system versus plain radiographs

BACKGROUND

In plain pelvic X-ray, magnification makes measurement unreliable. The EOS™ (EOS Imaging, Paris France) imaging system is reputed to reproduce patient anatomy exactly, with a lower radiation dose. This, however, has not been assessed according to patient weight, although both magnification and irradiation are known to vary with weight. We therefore conducted a prospective comparative study, to compare: (1) image magnification and (2) radiation dose between the EOS imaging system and plain X-ray.

HYPOTHESIS

The EOS imaging system reproduces patient anatomy exactly, regardless of weight, unlike plain X-ray.

MATERIAL AND METHOD

A single-center comparative study of plain pelvic X-ray and 2D EOS radiography was performed in 183 patients: 186 arthroplasties; 104 male, 81 female; mean age 61.3±13.7years (range, 24-87years). Magnification and radiation dose (dose-area product [DAP]) were compared between the two systems in 186 hips in patients with a mean body-mass index (BMI) of 27.1±5.3kg/m² (range, 17.6-42.3kg/m²), including 7 with morbid obesity.

RESULTS

Mean magnification was zero using the EOS system, regardless of patient weight, compared to 1.15±0.05 (range, 1-1.32) on plain X-ray (P<10^-5). In patients with BMI<25, mean magnification on plain X-ray was 1.15±0.05 (range, 1-1.25) and, in patients with morbid obesity, 1.22±0.06 (range, 1.18-1.32). The mean radiation dose was 8.19±2.63dGy/cm² (range, 1.77-14.24) with the EOS system, versus 19.38±12.37dGy/cm² (range, 4.77-81.75) with plain X-ray (P<10^-4). For BMI >40, mean radiation dose was 9.36±2.57dGy/cm² (range, 7.4-14.2) with the EOS system, versus 44.76±22.21 (range, 25.2-81.7) with plain X-ray. Radiation dose increased by 0.20dGy with each extra BMI point for the EOS system, versus 0.74dGy for plain X-ray.

CONCLUSION

Magnification did not vary with patient weight using the EOS system, unlike plain X-ray, and radiation dose was 2.5-fold lower.

LEVEL OF EVIDENCE

3, prospective case-control study.

Reproducibility of length measurements of the lower limb by using EOS™

BACKGROUND

Lower-limb discrepancy following total hip arthroplasty is the third-most common reason for patient dissatisfaction in orthopaedic surgery. Therefore, accurate planning and evaluation methods are mandatory. The main aim of this study was to evaluate the reliability of the EOS™ system by establishing and comparing the reproducibility of lower-limb automatic and manual 3D measurements. We hypothesized that the reproducibility of the lower-limb measurements is similar regardless of the method used and with an agreement higher than 0.95 for the length parameters.

MATERIALS AND METHODS

This study utilized an EOS radiological database of 112 patients. Two independent observers performed two rounds of lower-limb measurements twice, either in manual 3D or automatic 3D mode. The intra- and inter-observer reproducibility was evaluated by the calculation of the intra-class coefficient for each measurement method. The methods were then compared.

RESULTS

The intra- and inter-observer reproducibility for length measurements found with the manual and automatic 3D methods was always > 0.98. There was no significant difference in the reproducibility between the two measurement modes, with the exception of the offset, hip-knee-shaft, and neck-shaft angles.

CONCLUSION

Our results indicate a very good reproducibility of EOS™ length measurement, regardless of the method used. Automated 3D mode is preferred for the collection of angular and offset measurements. Furthermore, manual mode measurements are not affected by surgical history. Level of evidence IV.

What is the Impact of a Spinal Fusion on Acetabular Implant Orientation in Functional Standing and Sitting Positions?

BACKGROUND

This study used EOS imaging of primary total hip arthroplasty (THA) patients, with and without predating spinal fusion, to investigate (1) the impact of spinal fusion on acetabular implant anteversion and inclination, and (2) whether more extensive spinal fusion (fusion starting above the thoracolumbar junction or extension of fusion to the sacrum) affects acetabular implant orientation differently than lumbar only spinal fusion.

METHODS

Ninety-three patients had spinal fusion (case group), and 150 patients were without spinal fusion (controls). None of the patients experienced dislocation. The change in sacral slope (SS) and cup orientation from standing to sitting was measured.

RESULTS

Mean SS change from the standing to sitting positions was -7.9°in the fusion group vs -18.4°in controls (P = .0001). Mean change in cup inclination from the standing to sitting positions was 4.9°in the fusion group vs 10.2°in controls (P = .0001). Mean change in cup anteversion from standing to sitting positions was 7.1°in the fusion group vs 12.1°in controls (P = .0001). For each additional level of spinal fusion, the change in SS from standing to sitting positions decreased by 1.6(95% confidence interval [CI], 2.2073-1.0741), the change in cup inclination decreased by 0.8(95% CI, 0.380-1.203), and the change in cup anteversion decreased by 0.9(95% CI, 0.518-1.352; P < .001 in all cases).

CONCLUSION

Patients with spinal fusion demonstrated less adaptability of the lumbosacral junction. Longer spinal fusion or inclusion of the pelvis in the fusion critically impacts hip-spine biomechanics and significantly affects the ability to compensate in the standing-to-sitting transition.

Microdose acquisition in adolescent leg length discrepancy using a low-dose biplane imaging system

Background Children with leg length discrepancy often undergo repeat imaging. Therefore, every effort to reduce radiation dose is important. Using low dose preview images and noise reduction software rather than diagnostic images for length measurements might contribute to reducing dose. Purpose To compare leg length measurements performed on diagnostic images and low dose preview images both acquired using a low-dose bi-planar imaging system. Material and Methods Preview and diagnostic images from 22 patients were retrospectively collected (14 girls, 8 boys; mean age, 12.8 years; age range, 10-15 years). All images were anonymized and measured independently by two musculoskeletal radiologists. Three sets of measurements were performed on all images; the mechanical axis lines of the femur and the tibia as well as the anatomical line of the entire extremity. Statistical significance was tested with a paired t-test. Results No statistically significant difference was found between measurements performed on the preview and on the diagnostic image. The mean tibial length difference between the observers was -0.06 cm (95% confidence interval [CI], -0.12 to 0.01) and -0.08 cm (95% CI, -0.21 to 0.05), respectively; 0.10 cm (95% CI, 0.02-0.17) and 0.06 cm (95% CI, -0.02 to 0.14) for the femoral measurements and 0.12 cm (95% CI, -0.05 to 0.26) and 0.08 cm (95% CI, -0.02 to 0.19) for total leg length discrepancy. ICCs were >0.99 indicating excellent inter- and intra-rater reliability. Conclusion The data strongly imply that leg length measurements performed on preview images from a low-dose bi-planar imaging system are comparable to measurements performed on diagnostic images.

Radiographic Assessment of Lower-Limb Discrepancy

BACKGROUND

This study compares different lower-limb length measurements using tests of lower-limb upright full-length radiography and anteroposterior radiography of load-bearing hips.

METHODS

Forty-seven consecutive individuals aged 17 to 61 years (mean ± SD, 31.47 ± 11.42 years) voluntarily took part in the study; 23 (48.9%) were women and 24 (51.1%) were men. All individuals presenting a difference of 5 mm or greater between both lower limbs quantified with a tape measure were included. All of the participants signed an informed consent form to take part in the study. Two anteroposterior load-bearing radiographs were taken: one of the hip and an upright full-length radiograph of the lower limbs. Lower-limb-length discrepancy was quantified by taking different reference points. Interobserver and intraobserver reliability was assessed for each radiographic measurement. Any correlation between the different measurements were also verified.

RESULTS

Interobserver and intraobserver reliability was high for all of the measurements because the intraclass correlation was greater than 0.75 in all of the cases. There was a strong and positive correlation between the different measurements because when performing bivariate correlations with the Pearson correlation coefficient, positive values close to 1 were found.

CONCLUSIONS

In this study, the different reference points reported in the upright full-length radiograph in addition to the hip radiographs are useful for assessing lower-limb-length discrepancy. The results showed that there is a correct correlation between the different measurements.