Caixia Zhao

Assessment of Lower Limb Alignment: Supine Fluoroscopy Compared with a Standing Full-Length Radiograph

BACKGROUND While a full-length standing anteroposterior radiograph of the lower extremity provides the best radiographic method for assessing limb alignment, other methods must be used intraoperatively. We have employed intraoperative fluoroscopy with use of an electrocautery cord to assess limb alignment in the supine patient. METHODS We retrospectively compared the measurements of lower limb alignment that were obtained with use of supine intraoperative fluoroscopy with those that were obtained with use of a full-length standing anteroposterior radiograph of the lower extremity. A single examiner compared 102 sets of supine fluoroscopy images and full-length standing anteroposterior radiographs of the lower extremity to assess mechanical axis deviation and the joint line convergence angle. For the intraoperative fluoroscopic examination, an electrocautery cord was positioned overlying the center of the femoral head and the tibial plafond and an anteroposterior radiograph of the knee was made. The effect of age, gender, diagnosis, body mass index, pelvic height difference, joint line convergence angle, and the magnitude and direction of malalignment (varus or valgus) on the discrepancy in the observed mechanical axis deviation with use of the two methods was assessed. RESULTS The mean absolute difference between the two techniques was 13.4 mm for the measurement of mechanical axis deviation (p < 0.0001) and 2.8 degrees for the joint line convergence angle (p < 0.0001). The correlation coefficient (r) for the measurement of mechanical axis deviation with use of the two radiographic methods was 0.88. An increase in body mass index was associated with a greater magnitude of discrepancy in the measurement of mechanical axis deviation between the two techniques (p = 0.0014). Age, gender, pelvic height difference, and the direction of malalignment had no effect on the discrepancy in the measurement of mechanical axis deviation. Limbs with >2 cm of mechanical axis deviation and those with a joint line convergence angle of >3 degrees on the standing radiograph were significantly more likely to have >10 mm of discrepancy in the measurement of mechanical axis deviation with use of the two imaging techniques (p < 0.005). CONCLUSIONS Intraoperative fluoroscopy with use of the electrocautery cord method is a useful tool for assessing lower limb alignment in patients with a normal body mass index and </=2 cm of mechanical axis deviation and </=3 degrees of joint line convergence angle on the standing anteroposterior radiograph. However, the results obtained with fluoroscopy should be interpreted with caution in patients who are obese or who have substantial residual mechanical axis deviation or pathologic laxity of the knee joint.

Computed radiographic measurement of limb-length discrepancy. Full-length standing anteroposterior radiograph compared with scanogram.

BACKGROUND Although a scanogram is commonly used to measure limb-length discrepancy, there are several potential pitfalls associated with this imaging technique. The purpose of the present study was to evaluate the results obtained with use of a full-length standing anteroposterior radiograph of the lower extremities and to compare them with those obtained with use of a scanogram. Both imaging studies were performed using computed radiography. METHODS One hundred and eleven patients with limb-length discrepancy had a full-length standing anteroposterior radiograph and a scanogram made on the same day. The patients included seventy-nine children and thirty-two adults in whom the discrepancy was secondary to trauma (55%), congenital shortening (18%), Blount disease (14%), or another cause (13%). Limb length and limb-length discrepancy were measured utilizing both imaging studies. The agreement between the standing anteroposterior radiograph and the scanogram was assessed with use of the correlation coefficient r, and the limits of agreement between the two imaging studies were assessed. RESULTS An average magnification of 4.6% (3.3 cm) was observed in association with the measurement of lower extremity length with use of the full-length standing anteroposterior radiograph. The mean difference in limb-length-discrepancy measurements between the two techniques was 0.5 cm, and the limits of agreement (that is, the mean plus or minus two standard deviations) were 0.5 to 1.5 cm. When the limb-length discrepancy on the standing anteroposterior radiograph was compared with that on the scanogram, the correlation coefficient r was 0.96. A difference of >0.5 cm between the limb-length discrepancy measured on the standing radiograph and that measured on the scanogram was associated with a mechanical axis deviation of >2 cm. Remaining variables, including age, gender, etiology, and scanogram ruler inclination, did not correlate with a difference in the measurement of limb-length discrepancy with use of these two imaging studies. CONCLUSIONS The measurement of limb-length discrepancy on a standing anteroposterior radiograph was very similar to that on a scanogram, especially in the absence of substantial mechanical axis deviation. These findings support the use of a standing anteroposterior radiograph of the lower extremities as the initial imaging study for patients presenting with unequal limb lengths. This approach allows for a more comprehensive radiographic evaluation of the lower extremity, including deformity analysis, while reducing the expense and radiation exposure as compared with the use of additional imaging studies for the assessment of limb-length discrepancy.

Correlation of body mass index and radiographic deformities in children with Blount disease.

BACKGROUND Children with Blount disease tend to be heavier than their peers; however, the relationship between the magnitude of obesity and the severity of limb deformities in Blount disease has not been well studied. METHODS A retrospective review of the preoperative medical records and radiographs of patients with previously untreated Blount disease was conducted. Demographic information including gender, ethnicity, the age when deformity was first noted, the age at the examination, and the body mass index was recorded. Frontal and sagittal plane deformities were analyzed by one examiner using full-length standing radiographs. The association of body mass index with various demographic and deformity parameters was then analyzed. RESULTS Over an eight-year period, forty-five patients with sixty-five limbs affected by Blount disease were identified. Seventeen children (twenty-seven limbs) had early-onset Blount disease, and twenty-eight children (thirty-eight limbs) had late-onset disease. Fifteen of the children with early-onset disease and twenty-six of those with late-onset disease were overweight. There was no significant relationship between body mass index and gender, ethnicity, or laterality. The children with early-onset disease tended to have a lower body mass index but a greater magnitude of radiographic deformities compared with the children with late-onset disease. Greater varus malalignment (r = 0.74, p < 0.0001) and tibial procurvatum (r = -0.79, p = 0.002) were noted with an increasing body mass index in the early-onset, but not the late-onset, group of patients. Irrespective of the age at onset, the correlation of body mass index with frontal and sagittal plane deformities was stronger in extremely obese children (body mass index of > or =40). CONCLUSIONS There is a significant relationship between the magnitude of obesity and biplanar radiographic deformities in children with the early-onset form of Blount disease and in those with a body mass index of > or =40. These clinical findings are consistent with the literature concerning the effect of compressive forces on growth at the proximal tibial physis. LEVEL OF EVIDENCE Prognostic Level II.

Reliability analysis for radiographic measurement of limb length discrepancy: full-length standing anteroposterior radiograph versus scanogram.

Patients with limb length discrepancy (LLD) often have associated angular deformities requiring a standing full-length radiograph of the lower limb in addition to a scanogram. The purpose of our study was to determine the intraobserver and interobserver reliability of measuring LLD with both techniques, using computed radiography. The LLD was measured on 70 supine scanograms and standing anteroposterior radiographs of the lower extremity by 5 blinded observers on 2 separate occasions. Intraclass correlation coefficient (ICC) and mean absolute difference (in millimeters) was calculated to assess intraobserver and interobserver reliability and found to be excellent for both radiographic techniques. Intraobserver ICC and mean absolute difference was 0.975 to 0.995 and 1.5 to 2.6 mm for scanogram and 0.939 to 0.996 and 1.5 to 4.6 mm for the standing radiograph, respectively. Repeated measurements for both radiographic studies were within 5 mm of the first measurement greater than 90% and within 10 mm greater than 95% of times. Interobserver ICC and mean absolute difference was 0.979 and 2.6 mm for scanogram and 0.968 and 3.0 mm for the standing radiograph. The reliability was excellent irrespective of age, sex, and underlying diagnosis other than Blount disease, which had good reliability. A standing anteroposterior radiograph of the lower extremity should be the imaging modality of choice when evaluating patients with limb length inequality who may have angular deformities because it allows a comprehensive evaluation of the extremity and is as reliable as a scanogram for measuring LLD. This approach may decrease the radiation exposure and financial burden involved in assessing patients with unequal limb lengths.

Multiplanar deformity analysis of untreated Blount disease.

Although varus malalignment of the proximal tibia is the primary pathology in Blount disease, other deformities may exist. To assess multiplanar lower limb deformities, children with previously untreated early- and late-onset Blount disease who subsequently needed surgical correction were identified. Preoperative frontal and sagittal plane deformity analysis using Paleys methodology and rotational profile assessment using prone clinical examination were performed by a single examiner. Results were compared between the 2 groups and with uninvolved limbs within each group. Additionally, rotational profile of the lower limb was compared with age-matched values. Over an 8-year period, 60 limbs (40 patients) including 26 with early-onset and 34 with late-onset Blount met the inclusion criteria. Although both groups exhibited proximal tibial varus, procurvatum, and internal torsion, patients with early-onset Blount disease had greater severity. Unlike the younger patients, approximately one third of the varus malalignment of the affected extremity was attributed to the distal femur in the late-onset patients. Neither group showed any significant deformity of the proximal femur and distal tibia or sagittal plane deformity of the distal femur. There was a correlation between the severity of varus malalignment of the limb with magnitude of proximal tibial deformities in both groups and with distal femoral varus in the late-onset group of patients. Multiplanar deformity analysis is a valuable tool in the comprehensive evaluation of children with Blount disease.

The hip-knee-ankle angle in children: reference values based on a full-length standing radiograph.

BACKGROUND It is well recognized that the alignment of the lower limb changes during early childhood. The hip-knee-ankle angle is often referred to as the mechanical femoral-tibial angle and is measured on a full-length radiograph of the lower extremity. While several authors have independently reported consistent reference values for the hip-knee-ankle angle in adults, such values have not been well documented for children. The purpose of our study was to establish reference values for the hip-knee-ankle angle and assess the relationship between it and the anatomic femoral-tibial angle in children. METHODS A database at a single institution was searched for patients who were between one and less than eighteen years old at the time that a standing full-length radiograph of the lower extremities was made. Radiographs of the uninvolved extremity (the limb without any radiographic abnormalities or documented clinical concerns) were analyzed. The angle between a line connecting the center of the ossified femoral head and the center of the distal femoral epiphysis and another line connecting the center of the distal femoral epiphysis and the center of the talar dome was measured. Simple regression analyses were performed to determine the relationship between this angle and the anatomic femoral-tibial angle. RESULTS A total of 354 unaffected lower extremities of 253 children were analyzed. The mean hip-knee-ankle angle was +3.6 degrees (varus) in children between one and two years old and -2.5 degrees (valgus) in those between two and three years old. After the age of seven years, the mean value was +0.3 degrees (varus), which was within 1 degrees of the reference values available for the adult population (mean, +1.2 degrees [varus]). There was a linear relationship between the hip-knee-ankle and anatomic femoral-tibial angles in the children (r = 0.87, p < 0.0001). Despite varying hip-knee-ankle angles at different ages, the mean absolute difference between that angle and the anatomic femoral-tibial angle remained relatively constant (mean, 6.7 degrees ) and was not associated with changing age (r = -0.09). CONCLUSIONS In our study sample, reference values for the hip-knee-ankle angle in children older than seven years of age approached those reported for adults in North America. Although this angle and the anatomic femoral-tibial angle in children younger than seven were distinct from those reported for the adult population, the difference between the two angular measurements remained essentially unaffected. The use of age-specific reference values for both the hip-knee-ankle and the anatomic femoral-tibial angle is recommended for children younger than seven years old.

Blood loss during posterior spinal fusion for adolescent idiopathic scoliosis.

Study Design. Retrospective uncontrolled case series. Objective. The purpose of this study was to determine the association, if any, between intraoperative blood loss and need for transfusion with the use of periapical (Ponte) osteotomies, as well as other patient and surgical variables among patients with adolescent idiopathic scoliosis (AIS) undergoing posterior spinal instrumentation and fusion. Summary of Background Data. Blood loss during posterior spinal fusion for AIS can be substantial. Numerous techniques are used to minimize intraoperative blood loss and the need for allogeneic transfusion. However, it is unclear which patient and surgeon variables affect blood loss most significantly. Methods. A review was conducted on consecutive patients with AIS who had undergone posterior spinal fusion from July 1997 to February 2013 by a single primary surgeon at 1 institution. The relationship of estimated blood loss, normalized blood loss (normalized blood loss = estimated blood loss/number of levels fused/patients weight in kilograms), autologous blood retrieved, and allogeneic transfusion received with various patient- and procedure-related variables were analyzed. Results. Estimated blood loss, normalized blood loss, and autologous blood retrieved were higher in patients who underwent periapical Ponte osteotomies (n = 38) (P < 0.0001, P < 0.001, P < 0.01, respectively). The mean major curve correction was 64% in patients without osteotomies, and 65% in patients with osteotomies (P = 0.81). All patients who underwent osteotomies (38/38) received allogeneic transfusion versus 26% (19/73) of those without osteotomies (P < 0.001). The likelihood of transfusion correlated with increasing number of osteotomies and a lower preoperative hemoglobin level (odds ratio, 3.34; P = 0.003; and odds ratio, 0.51; P = 0.02, respectively). Conclusion. In patients with AIS undergoing posterior spinal fusion with instrumentation, performing periapical osteotomies increased all measures of intraoperative blood loss and need for transfusion without substantially improving major curve correction. As expected, a lower preoperative hemoglobin level was observed in patients who received a blood transfusion after posterior instrumentation and fusion. Level of Evidence: 4

Intra-articular morphology of the knee joint in children with Blount disease: a case-control study using MRI.

BACKGROUND The clinical and radiographic abnormalities of the lower limb in children with Blount disease are well known. However, there is controversy regarding the intra-articular morphologic changes in the involved knee joint. The purpose of our study was to evaluate the meniscal and articular surface morphology in children with Blount disease with use of magnetic resonance imaging and to compare these findings with similar measurements in a control group. METHODS Preoperative magnetic resonance imaging scans of the knee of children with Blount disease were compared with those of a control group. Coronal and sagittal morphometric parameters including the height and width of the menisci, thickness of the unossified proximal tibial epiphysis, tibial condylar and meniscal inclination, and presence of signal changes and/or tears of the menisci were documented. RESULTS Twenty-six children (thirty-three) knees with Blount disease (mean age, 10.5 years) and twenty children without Blount disease (mean age, 9.6 years) were identified. The midcoronal medial meniscal height and width were greater in the Blount disease group (p < 0.0001). Abnormal signal changes were noted in the medial meniscus in twelve limbs (39%) in the Blount group and one limb (5%) in the control group (p = 0.008). The mean thickness of the unossified cartilage of the proximal medial tibial epiphysis was also greater in the Blount disease group (p = 0.0005). The morphology of the menisci and unossified cartilage in the lateral compartment did not differ between the two groups. The mean tibial condylar and bimeniscal inclinations in the coronal and sagittal planes were also similar in both groups. In a multivariate regression analysis, only body mass index correlated with the height of the medial meniscus in the coronal plane (p = 0.0035) and of the posterior horn of the medial meniscus in the sagittal plane (p = 0.0037) in children with Blount disease. CONCLUSIONS Children with Blount disease have increased thickness of the chondroepiphysis of the proximal medial aspect of the tibia, increased height and width of the medial meniscus, and greater frequency of abnormal signals in the posterior horn of the medial meniscus. These morphologic changes may compensate for the diminished height of the ossified portion of the medial proximal aspect of the tibia in patients with Blount disease.

Venous thromboembolism in children: details of 46 cases based on a follow-up survey of POSNA members.

Introduction: On the basis of a recent survey of Pediatric Orthopedic Society of North America members, 59% of the respondents acknowledged having encountered at least 1 child with the diagnosis of venous thromboembolism (VTE). The current survey sought further information including patient demographics, underlying diagnosis, presence of certain risk factors for VTE, and the clinical outcome. Methods: A follow-up web-based questionnaire was sent to 121 active members of Pediatric Orthopedic Society of North America who had provided their contact information in the prior survey. Thirty-eight respondents provided clinical details on 46 children. Results: The mean age of the affected patients was 14.3 (95% confidence interval, 13.3-15.3) years and 61% were males. The average body mass index was 28 (95% confidence interval, 25-31). Forty-four percent of the patients were diagnosed with deep venous thrombosis (DVT) only, 26% with pulmonary embolism (PE) only, and 30% with both DVT and PE. Majority of the children had DVT involving the popliteal area or thigh (16 cases each). Lower extremity surgery (29 cases, including proximal femoral/tibial osteotomies, internal fixation of long bone fractures, anterior cruciate ligament reconstruction, and resection of osteochondroma around the knee) and adolescence (28 cases) were the 2 most commonly cited associations. Other cases were noted with spinal surgery (8 children) and musculoskeletal infections (7 children). Three patients developed a postphlebitic syndrome, 1 had recurrent DVT and 2 children died. Both deceased children were diagnosed with DVT and PE including a 9-year-old child with a positive family history of antithrombin-3 deficiency that was not noted preoperatively. Conclusions: Although uncommon, potentially fatal VTE can occur among children with a variety of musculoskeletal ailments. Obtaining a family history suggestive of thrombophilia preoperatively should be encouraged. Further investigation is warranted to ascertain the role of prophylaxis against VTE among children in an orthopaedic practice. Level of Evidence: Level IV—case series.

Advanced bone age in children with Blount disease: a case-control study.

Purpose: Children with Blount disease are often obese and have muliplanar limb deformities including leg length discrepancy. Surgical options for these skeletally immature patients include guided growth and realignment osteotomy. Suboptimal outcomes such as persistent valgus overcorrection after proximal tibial osteotomy in children with early-onset Blount disease and undercorrection after guided growth treatment among adolescents with late-onset Blount disease can occur. Although obesity has been associated with precocious puberty, whether children with Blount disease have advanced skeletal maturity has not been previously investigated. We hypothesized that compared to their peers, children with Blount disease will have advanced skeletal (bone) age. Methods: The relationship between skeletal and chronologic age was compared between 33 patients with Blount disease (12 early-onset, 21 late-onset) and 33 age-matched and sex-matched controls. The influence of variables such as the age of onset of Blount disease and patient’s chronologic age on the discrepancy between skeletal and chronologic age was also evaluated. Results: The mean body mass index was 39 kg/m2 in the Blount disease group and 23 kg/m2 in the control subjects (P<0.0001). Compared to their chronologic age, the bone age was advanced 16 months in Blount disease group (95% confidence interval, 10-22 mo) and 5 months in the control group (95% confidence interval, −1-10; P=0.003). On the basis of subgroup analysis, the bone age was advanced 26 months in early-onset and 10 months in late-onset Blount disease (P=0.01). The discrepancy between bone age and chronologic age decreased as chronologic age increased in both the control (r=−0.36, P=0.04) and Blount disease groups (r=−0.58, P=0.0004). Conclusion: Compared to their peers, children with Blount disease have advanced skeletal maturity. The difference between bone age and chronologic age decreases with growth. Since advanced skeletal maturity can impact the strategy for surgical realignment and magnitude of planned (over)correction of lower limb deformity, preoperative assessment of bone age should be considered when managing children with Blount disease. Level of Evidence: Level III.