Posterior Malalignment Research Articles

MALALIGNMENT OF TOTAL ANKLE ARTHROPLASTY INCREASES PEAK CONTACT PRESSURE AND SHEAR STRESS ON THE BONE-IMPLANT INTERFACE

An increasingly used treatment for end-stage ankle osteoarthritis is total ankle replacement (TAR). However, implant loosening and subsidence are commonly reported complications, leading to relatively high TAR failure rates. Malalignment of the TAR has often been postulated as the main reason for the high incidence of these complications. It remains unclear to what extent malalignment of the TAR affects the stresses at the bone-implant interface. Therefore, this study aims to elucidate the effect of TAR malalignment on the contact stresses on the bone-implant interface, thereby gaining more understanding of the potential role of malalignment in TAR failure.FE models of the neutrally aligned as well as malaligned CCI Evolution TAR implant (Van Straten Medical) were developed. Separate models were developed for the tibial and talar segment, with the TAR components in neutral alignment and 5° and 10° varus, valgus, anterior and posterior malalignment, resulting in a total of 9 differently aligned TAR models. Loading conditions of the terminal stance phase of the gait cycle, when the force on the ankle joint is highest (5.2x body weight), were applied. Peak and mean contact pressure and shear stress at the bone-implant interface were analyzed. Also, stress distributions on the bone-implant interface were visualized.In the neutrally aligned tibial and talar TAR models, peak contact pressures of respectively 98.4 MPa and 68.2 MPa, and shear stresses of respectively 49.3 MPa and 39.0 MPa were found. TAR malalignment increases peak contact pressure and shear stress on the bone-implant interface. A maximum peak contact pressure of 177 MPa was found for the 10° valgus malaligned tibial component and the highest shear stress found was 98.5 MPa for the 10° posterior malaligned talar model.Upon TAR malalignment contact stresses increase substantially, suggesting that proper orientation of the TAR is needed to minimize peak stresses on the bone-implant interface. This is in line with previous studies, which state that malalignment considerably increases bone strains, micromotion, and internal TAR contact pressures, which might increase the risk of TAR failure. Further research is needed to investigate the relationship between increased contact stresses at the bone-implant interface and TAR failure.

Malalignment of the total ankle replacement increases peak contact stresses on the bone-implant interface: a finite element analysis

IntroductionMalalignment of the Total Ankle Replacement (TAR) has often been postulated as the main reason for the high incidence of TAR failure. As the ankle joint has a small contact area, stresses are typically high, and malalignment may lead to non-homogeneous stress distributions, including stress peaks that may initiate failure. This study aims to elucidate the effect of TAR malalignment on the contact stresses on the bone-implant interface, thereby gaining more understanding of the potential role of malalignment in TAR failure.MethodsFinite Element (FE) models of the neutrally aligned as well as malaligned CCI (Ceramic Coated Implant) Evolution TAR implant (Van Straten Medical) were developed. The CCI components were virtually inserted in a generic three-dimensional (3D) reconstruction of the tibia and talus. The tibial and talar TAR components were placed in neutral alignment and in 5° and 10° varus, valgus, anterior and posterior malalignment. Loading conditions of the terminal stance phase of the gait cycle were applied. Peak contact pressure and shear stress at the bone-implant interface were simulated and stress distributions on the bone-implant interface were visualized.ResultsIn the neutral position, a peak contact pressure and shear stress of respectively 98.4 MPa and 31.9 MPa were found on the tibial bone-implant interface. For the talar bone-implant interface, this was respectively 68.2 MPa and 39.0 MPa. TAR malalignment increases peak contact pressure and shear stress on the bone-implant interface. The highest peak contact pressure of 177 MPa was found for the 10° valgus malaligned tibial component, and the highest shear stress of 98.5 MPa was found for the 10° posterior malaligned talar model. High contact stresses were mainly located at the edges of the bone-implant interface and the fixation pegs of the talar component.ConclusionsThe current study demonstrates that TAR malalignment leads to increased peak stresses. High peak stresses could contribute to bone damage and subsequently reduced implant fixation, micromotion, and loosening. Further research is needed to investigate the relationship between increased contact stresses at the bone-implant interface and TAR failure.

Interrupted aortic arch: Is it always a neonatal emergency?

Interrupted aortic arch (IAA) is a rare congenital ductal-dependent heart disease. It commonly presents in infancy following spontaneous closure of the patent ductus arteriosus (PDA) [1] , [2] . Few cases have been reported in pediatric age [3] . We present the case of 13 years old boy with IAA and a large ventricular septal defect (VSD), a restrictive PDA and an Eisenmenger syndrome. A thirteen years old Tunisian boy presented to our consultation with malaise, headache and weakness of his legs. He reported reduced exercise tolerance since two years. There was no family history of congenital heart disease or sudden unexpected death ( Fig. 1 , Fig. 2 ). Physical examinations noted a generalized cyanosis. Radial pulses were normal but his femoral pulses were weak. The systolic pressure difference between the upper and lower limbs was 40 mmHg. Transthoracic echocardiography noted a conal VSD with a posterior malalignment of the conal septum with right to left shunt. The short axis examination showed a large pulmonary tract and a restrictive PDA with an increased velocity of 3.3 m/s and right to left shunt. The high left parasternal examination with a slightly rightward angulation of the transducer demonstrated a complete interruption of aortic arch. Computed tomography revealed an IAA between the left common carotid artery and the left subclavian artery (type B) and a PDA (3.3 mm) between the left pulmonary artery (LPA) and the descending aorta. Pulmonary arterial hypertension was confirmed in cathlab with mean pulmonary arterial pressure (mPAP) at 100 mmHg. Following multidisciplinary team discussion, on regard of patient health state, Eisenmenger syndrome, the restrictive PDA and the contraindication to performing surgery, we discuss the percutaneous stenting of the PDA. Interrupted aortic arch is a rare congenital abnormality that presents in infancy. We presented the case of 13 years old boy with IAA, Eisenmenger syndrome and a restrictive PDA. Following multidisciplinary team discussion, giving the restrictive pattern of the PDA and the Eisenmenger syndrome, we discuss a percutaneous of the PDA.

Damus-Kay-Stansel procedure with ventricular septal defect enlargement.

A full-term infant who had tricuspid atresia with transposed great arteries, a ventricular septal defect, subpulmonary stenosis with posterior malalignment of the conus septum, bicuspid pulmonary valve, and a high-takeoff left coronary artery was referred to our institution. The subpulmonary stenosis gradually progressed and cyanosis worsened. We successfully performed a Damus-Kay-Stansel procedure and a bidirectional Glenn shunt concomitant with ventricular septal defect enlargement. The conus septum was resected along with thick fibrous tissue through both semilunar valves (without ventriculotomy). Postoperative echocardiography demonstrated that both the ventricular septal defect and the subpulmonary space were enlarged effectively without semilunar valve regurgitation.

Altered Range of Motion and Plantar Pressure in Anterior and Posterior Malaligned Total Ankle Arthroplasty: A Cadaveric Gait Study.

Malaligned ankle arthroplasty components have been associated with increased postoperative pain and reduced ankle range of motion. With this study, we aimed to quantify how anterior and posterior malalignment of the talar component affects foot bone kinematics and plantar pressures in a dynamic, cadaveric gait simulation. Ten cadaveric foot specimens received a modified ankle prosthesis. Proper alignment was defined as the prosthesis being neutral to a plantigrade foot, where varus/valgus and internal/external rotation were determined using the tibial alignment guide from the prosthesis manufacturer. Axially loaded lateral radiographs were made to measure the tibiotalar ratio (TTR) preoperatively and postoperatively. Specimens were prepared for gait simulation and mounted into the robotic gait simulator. Foot bone kinematics and plantar pressures were measured for each alignment condition. Posterior malalignment of the talar component decreased mean sagittal-plane range of motion (p ≤ 0.0005) in the tibiotalar joint (by up to 3.9°) and in the first metatarsophalangeal joint (by up to 7.7°) and increased sagittal-plane range of motion (p ≤ 0.0005) in the calcaneocuboid joint (by up to 2.0°). Posterior malalignment increased mean transverse-plane range of motion (p ≤ 0.0005 and p = 0.012) in the tibiotalar joint (by up to 2.3°) and in the calcaneocuboid joint (by 2.3°). Posterior malalignment decreased mean peak plantar pressures (p = 0.001 and p = 0.013) under the hallux and the first metatarsal (by up to 82.1 and 110.1 kPa, respectively) and increased (p = 0.012 and p = 0.0006) peak plantar pressures under the third metatarsal and the hindfoot (by 23.0 and 47.8 kPa, respectively). Anterior malalignment decreased (p = 0.0006) mean hindfoot peak plantar pressure (by 127.7 kPa). Anterior and posterior malalignments shifted center of pressure laterally during early and late stance. The TTR weakly to moderately correlated with range-of-motion changes in the tibiotalar, calcaneocuboid, and first metatarsophalangeal joints (r ≤ 0.39) and weakly correlated with plantar pressure changes under the hindfoot, the first metatarsal, and the hallux (r ≤ 0.15). Anterior and posterior malalignments of the talar component altered foot bone kinematics and plantar pressures. Mild malalignments produced fewer significant differences than moderate and extreme malalignments. A greater number of significant differences were found for posterior malalignments than for anterior. The TTR weakly to moderately correlated with changes in range of motion and plantar pressures. The observed changes in range of motion and plantar pressures may explain why malaligned ankle arthroplasties are associated with unfavorable clinical outcomes and poor prosthesis longevity. Posterior malalignments may produce worse clinical outcomes than anterior malalignments.

How Small Is Too Small? Decision-Making and Management of the Small Aortic Root in the Setting of Interrupted Aortic Arch.

Interrupted aortic arch is commonly associated with a posterior malalignment ventricular septal defect (VSD) and left ventricular outflow tract (LVOT) hypoplasia. Standard repair is carried out in the neonatal period and includes re-establishing arc continuity and VSD closure. Reintervention on the LVOT for obstruction is a common and an ongoing source of morbidity and mortality. A variety of preoperative echocardiographic measurements have been identified to identify patients at risk for developing LVOT obstruction but an aortic valve annulus dimension (mm) < patient's weight (kg) + 1 mm is a reasonable threshold to identify a patient at increased risk for future LVOT reintervention. Prophylactic direct approaches to prevent future LVOT obstruction include myectomy/myotomy and left-sided placement of the VSD patch but do not reliably prevent late LVOT obstruction. Patients amendable to a biventricular repair but with important LVOT hypoplasia are probably best served with a Yasui operation, either as a primary operation or staged with a Norwood procedure. In the case of complex redo operations, a Ross-Konno provides another valuable option for a durable repair. Though smaller preoperative LVOT structures predict the need for reoperation, careful preoperative planning may minimize the need for LVOT reintervention and improve long-term survival.

A new anatomic approach of the ventricular septal defect in the interruption of the aortic arch.

The aim of this study was to analyse the anatomy of the ventricular septal defect (VSD) in heart specimens with interruption of the aortic arch (IAA) in order to explore the hypothesis of different embryologic mechanisms for the different anatomic types of IAA. We examined 42 human heart specimens, 25 with IAA as the main disease with concordant atrioventricular and ventriculo-arterial connections and two distinct great arteries, and 17 hearts with IAA associated with other malformations [six common arterial trunk (CAT), five double-outlet right ventricle (DORV), three transposition of the great arteries (TGA), three atrioventricular septal defect (AVSD)]. The interruption was classified according to Celoria and Patton. We focused on the anatomy of the VSD viewed from the right ventricular side. There were 15 IAA type A, 27 type B, no type C. The VSD in IAA type B was always an outlet VSD, located between the two limbs of the septal band, with posterior malalignment of the outlet septum in hearts with concordant ventriculo-arterial connections, without any fibrous tricuspid-aortic continuity. In addition, the aortic arch was always completely absent. Conversely, the VSD in IAA type A could be of any type (outlet in six, muscular in four, central perimembranous in two, inlet in three) and the aortic arch was either atretic or absent. In addition, IAA type B, when found in the setting of another anomaly, was always associated with neural crest-related anomalies (CAT and DORV), whereas IAA type A was found in association with anomalies not related to the neural crest (TGA and AVSD). These results reinforce the hypothesis that different pathogenic mechanisms are responsible for the two types of IAA, and the inclusion of IAA type B in the group of neural crest defects. Conversely, IAA type A could be due to overlapping mechanisms: flow-related defect (coarctation-like) and neural crest contribution.

Utility of balloon assisted technique in trans catheter closure of very large (≥35 mm) atrial septal defects.

Very few published data is available on the outcomes of balloon assisted techniques (BATs) for trans catheter closure (TCC) of very large (Defined as ≥35 mm size) ostium secundum atrial septal defect (ASD). To study the utility of BAT as against conventional techniques (CT) in TCC of very large ostium secundum ASD (≥35 mm) over the past 5-year period and to find out the association of different morphological features of the defects in relation to TCC outcomes. Descriptive single center retrospective study of patients with very large ostium secundum ASD (≥35 mm size) who were subjected to TCC. Thirty-three out of 36 patients with ≥35 mm ASD and complex morphological features underwent successful TCC. The study patients had high prevalence of absent aortic and posterior rims with posterior mal-alignment of the septum. BAT was successful in 28/31 (90.3%) patients while CT had a success rate of 16%. The mean trans-esophageal echocardiography (TEE) ASD size with BAT success 37 (SD 1.3) mm and CT failure 36.2 (SD 1.1) mm was not different (P=0.06). On univariate analysis of different morphological features, posterior mal alignment of the septum was associated failure of CT (P=0.01). There was no urgent referral for surgery and patients did well on follow up. Balloon assisted device closure of (≥35 mm) ASD had 90% success rate. BAT helps in controlled delivery and device alignment in very large ASD with posterior malalignment of the septum and is often helpful when CT fails.

Posterior Global Malalignment After Osteotomy for Sagittal Plane Deformity

Multicenter, retrospective analysis of 183 consecutive patients undergoing lumbar osteotomy. To evaluate cause and impact of posterior postoperative alignment. Sagittal malalignment in the setting of adult spinal deformity (ASD) has shown significant correlation with pain and disability. Surgical treatment often entails correction of deformity by pedicle subtraction osteotomies (PSO). Key radiographical spinopelvic objectives to reach improvement in clinical outcomes have been previously reported. Although anterior alignment is a cause of poor outcomes, the impact and cause of posterior spinal alignment by PSO has not been reported. The patient inclusion criteria were age, more than 18 years, with a diagnosis of sagittal plane deformity (C7 plumbline offset >5 cm, a pelvic tilt >20°, or a lumbar lordosis to pelvic incidence mismatch of ≥10°) requiring a surgical procedure involving a lumbar posterior osteotomy and a long fusion. Patients were divided into 3 groups based on postoperative sagittal vertical axis (SVA): neutral alignment (0 < SVA < 50 mm), anterior alignment (SVA > 50 mm), and posterior alignment (SVA < 0 mm). All patients underwent pre- and postoperative full-length sagittal spine radiography. Differences between groups were evaluated using ANOVA and χ² analysis. Seventy-six patients were postoperatively classified in the anterior group: 59 in the neutral group and 48 in the posterior group. These groups were comparable preoperatively in terms of surgical status (revision vs. primary surgery) and regional alignment (lumbar lordosis and thoracic kyphosis). The patients with posterior alignment were younger and had a significantly lower pelvic incidence (53° vs. 62°), preoperative pelvic tilt (30 vs. 36°), SVA (94 vs. 185 mm) and cervical lordosis (16° vs. 25°) than patients in the anterior alignment group. No significant differences were found in terms surgical procedure. Patients in the posterior alignment group demonstrated a significantly greater change in SVA and pelvic tilt correction (P < 0.05) but with a lower gain in thoracic kyphosis (5 vs. 12°) and reduction of cervical lordosis (4° vs. 22°). A significantly lower pelvic incidence and lack of restoration of thoracic kyphosis may lead to sagittal overcorrection with a posterior alignment. Although the clinical significance of posterior malalignment is still unclear, this study showed a compensatory loss of cervical lordosis in these patients. Particular attention must be paid to preoperative planning before sagittal realignment procedures. Further study will be necessary to evaluate long-term clinical outcomes of these patients.

Arterial Switch and Modified Konno Procedure With Detachment of the Aortic Root for Transposition of the Great Arteries and Left Ventricular Outflow Tract Obstruction

The arterial switch operation for the transposition of the great arteries accompanied by a ventricular septal defect and posterior malalignment of the outlet septum is a surgical challenge. We describe a new surgical technique in 2 patients having this pathology. The surgical technique consists of the arterial switch operation and a modified Konno procedure through partial detachment of the semilunar valve of the right ventricle as in the Ross procedure.

Conotruncal anomalies in fetal life: Accuracy of diagnosis, associated defects and outcome

Objectives To assess the accuracy of prenatal echocardiography, associated anomalies, and outcome of fetuses with conotruncal anomalies (CTA). Study design We searched our database for CTA prenatally diagnosed between 1990 and 2005. We included tetralogy of Fallot (TOF), transposition of the great arteries (TGA), double-outlet right ventricle (DORV), truncus arteriosus (TA), pulmonary atresia with ventricular septal defect (PA-VSD) and posterior malalignment type VSD with aortic arch obstruction (pmtVSD-AAO). Data of 144 fetuses with complete follow-up were retrieved and analyzed. Results The main reason for referral was suspected heart defect on a routine obstetric scan (72%). Most cases were detected ≤22 weeks (55%). The presence of a CTA was confirmed postnatally in 143 cases (99%), and the diagnosis of the first fetal echocardiography was correct in 126 (87.5%). Most diagnosis of TOF (33/36, 91.7%), TGA (34/38, 89.5%) and DORV (34/38, 89.5%) were proved correct. Inadequate assessment of the interventricular septum, the distal aortic arch and/or the severity of the right outflow tract obstruction accounted for most errors. The accuracy rate was lower in TA (11/14, 78.6%) and PA-VSD (4/7, 57.1%), with evaluation of the branch pulmonary arteries as the main source of discrepancies. In 7/18 incorrect cases subsequent scans allowed to obtain a correct diagnosis. Most fetuses (64%) had an isolated CTA. Thirty-seven had chromosomal anomalies (26%) but none were found in TGA. 22q11 deletion affected 8.7% of the tested patients. Nuchal translucency (NT) was above 95th centile in 19/104 cases (18%) in which NT were measured. Fifty cases were interrupted. The overall one-year survival rate was 71%, with differences between cases with and without associated defects (9/25, 36% vs. 57/68, 83.8%; p < 0.01). The uncomplicated forms of TGA and TOF had the best survival rates (100%). Conclusions Most CTA can be diagnosed by fetal echocardiography with a high degree of accuracy. Chromosomal defects should always be ruled out, except for simple TGA. Current survival figures in many isolated CTA, especially simple TGA and TOF, support a change in the “classical” concept that congenital heart defects detected prenatally often have the worst outlook. Condensation Most CTA can be diagnosed by fetal echocardiography with a high degree of accuracy. Isolated CTA are more common and most of these may have a favourable outcome.

Selective management of the left ventricular outflow tract for repair of interrupted aortic arch with ventricular septal defect: Management of left ventricular outflow tract obstruction

Left ventricular outflow tract obstruction remains an early and late complication after repair of interrupted aortic arch and ventricular septal defect. We reviewed our experience with the selective management of the infundibular septum during primary repair to address left ventricular outflow tract obstruction. From 1991 through 2001, all 27 patients presenting with interrupted aortic arch/ventricular septal defect and posterior deviation of the infundibular septum were analyzed. Fifteen patients with the smallest subaortic areas underwent myectomy or myotomy of the infundibular septum concomitant with interrupted aortic arch/ventricular septal defect repair. Patients undergoing myectomy-myotomy (Group I) had significantly smaller subaortic diameter indexes (0.83 +/- 0.16 cm/m2) when compared with those who had only interrupted aortic arch/ventricular septal defect repair (group 2: 0.99 +/- 0.13 cm/m2, P = .012). Two hospital deaths occurred in group 1, and 1 occurred in group 2. No late deaths occurred. No patient in group 2 required reoperation. Six group 1 patients required 9 reoperations for left ventricular outflow tract obstruction. Five patients underwent resection of a new subaortic membrane. Only 1 patient had recurrent muscular left ventricular outflow tract obstruction. Three patients required a second reoperation, primarily related to aortic valve stenosis. Interrupted aortic arch/ventricular septal defect with posterior malalignment of the infundibular septum can be repaired with low mortality in the neonatal period. Tailored to the degree of subaortic narrowing, resection or incision of the infundibular septum at the time of primary repair was very effective in preventing or prolonging the interval to recurrent left ventricular outflow tract obstruction compared with the published data. However, reoperation for left ventricular outflow tract obstruction, often related to the development of a new and discrete subaortic membrane or valvar stenosis, is still required in a subset of patients.

Chromosome 22q11 deletion in patients with ventricular septal defect: frequency and associated cardiovascular anomalies.

A ventricular septal defect (VSD) is the most common form of congenital heart disease and is one of the most common cardiovascular anomalies in individuals with chromosome 22q11 deletion syndrome. However, the frequency of a chromosome 22q11 deletion in patients with a VSD is not known. In addition, among patients with a VSD, it is not clear whether particular types of VSD or associated cardiovascular phenotypic features are associated with a chromosome 22q11 deletion. We prospectively enrolled 125 patients with a conoventricular (n = 100), posterior malalignment (n = 14), or conoseptal hypoplasia (n = 11) VSD who were admitted to Children's Hospital of Philadelphia between November 1991 and December 2001. Patients were studied for a chromosome 22q11 deletion by using fluorescence in situ hybridization. A chromosome 22q11 deletion was detected in 12 (10%) of the 125 patients. Anatomic features that were significantly associated with a chromosome 22q11 deletion included abnormal aortic arch sidedness, an abnormal aortic arch branching pattern, a cervical aortic arch, and discontinuous pulmonary arteries. There was no correlation between the type of VSD and chromosome 22q11 deletion. Of 20 patients with an abnormal aortic arch and/or discontinuous pulmonary arteries, 45% had a chromosome 22q11 deletion compared with only 3% of those with a left aortic arch, normal aortic arch branching pattern, and continuous branch pulmonary arteries A chromosome 22q11 deletion is common in individuals with a conoventricular, posterior malalignment, or conoseptal hypoplasia VSD and anomalies of the aortic arch or branch pulmonary arteries. On the basis of these findings, at a minimum, we recommend testing for a chromosome 22q11 deletion in patients with these types of VSD who have abnormalities of aortic arch sidedness or branching, a cervical aortic arch, and/or discontinuous pulmonary arteries. Testing of patients with these types of VSD but a normal aortic arch and pulmonary arteries may be performed routinely or guided by the presence of associated noncardiovascular features of chromosome 22q11 deletion syndrome.

Comparison of left ventricular outflow tract obstruction in interruption of the aortic arch and in coarctation of the aorta, with diagnostic, developmental, and surgical implications

A morphometric comparison of the anatomic causes of left ventricular (LV) outflow obstruction in interruption of the aortic arch and in coarctation of the aorta with ventricular septal defect (VSD), based on 30 postmortem cases of each, revealed that posterior malalignment of the conal septum with a conoventricular VSD was significantly more prevalent with interruption (93%) than with coarctation (47%) (p <0.001). The ratio of the aortic valve diameter-to-the pulmonary valve diameter, which provided a quantitative index of the degree of posterior conal septal malalignment and of the consequent LV outflow tract obstruction at and immediately below the level of the aortic valve, was significantly smaller with interruption (≤0.50 in 67%) than with coarctation (≤0.50 in 17%) (p <0.001). A bicuspid or unicuspid aortic valve, both with interruption and with coarctation, was more prevalent with posterior conal septal malalignment (74%) than with normal conal septal alignment (42%) (p <0.05). Posterior conal septal malalignment was associated with LV outflow tract obstruction at 3 different sites: subvalvar, annular, and leaflet. The anatomic findings explain the incidence of postoperative LV outflow tract obstruction in patients with interrupted aortic arch after simple VSD closure, and may support a surgical strategy of elevating or otherwise removing the posteriorly malaligned conal septum from the LV outflow tract at the time of VSD closure.

The influence of contact alignment of the tibiofemoral joint of the prostheses in in vitro biomechanical testing

Objective. To investigate the influence of contact alignment of the tibiofemoral joint of the prostheses in in vitro biomechanical testing. Design. An experimental set-up was used to measure the total contact areas of the tibiofemoral joint of the prostheses subjected to a compressive load, and the malalignment situations were simulated. Background. The contact alignment of the femoral component related to the tibial component in the literature was not described clearly and the effect of malalignment on the testing method has not been reported well. Methods. Three commercial knee prostheses (Omnifit, Genesis, and AMK) were used for testing under a compression load (3000 N) at flexion 0° and 10°. After aligning the normal contact alignment, the simulated malalignment was done to evaluate the influence on the total contact areas in these conditions relative to the normal contact alignment. The simulated malalignment includes the medial–lateral translation (0.5 and 1 mm), anterior–posterior translation (2 and 4 mm) and internal–external rotation (1°, 3° and 5°) of the femoral component relative to the tibial component. Results. The ratios of total contact areas of malalignment relative to normal contact alignment ranged from 1.06 to 0.93 in medial–lateral malalignment in these three prostheses. In anterior–posterior malalignment, the ratios ranged from 0.69 to 0.79 in Omnifit, 0.93–0.96 in Genesis and 0.96–1.04 in AMK. In internal–external malrotation, the ratios ranged from 0.90 to 1.03 in these prostheses. Conclusions. This study proposes that contact alignment would affect the contact characteristics, especially in anterior–posterior alignment when high conformity knee prosthesis is tested. The contact alignment must be standardized in the procedure in in vitro biomechanical testing, which will be more objective to evaluate the contact characteristics of different knee prostheses. Relevance This study revealed the importance of contact alignment of the tibiofemoral joint of the prosthesis in in vitro biomechanical testing. Many published reports of the biomechanical evaluations on different designs of knee prostheses would show different results due to contact alignment. Furthermore, this study indicates that the ideal contact characteristics of the tibiofemoral joint in original design will be changed when the prosthesis under the malalignment condition which was caused by surgery technique or soft tissues imbalance.

Frequency of 22q11 deletions in patients with conotruncal defects

Objectives. This study was designed to determine the frequency of 22q11 deletions in a large, prospectively ascertained sample of patients with conotruncal defects and to evaluate the deletion frequency when additional cardiac findings are also considered.Background. Chromosome 22q11 deletions are present in the majority of patients with DiGeorge, velocardiofacial and conotruncal anomaly face syndromes in which conotruncal defects are a cardinal feature. Previous studies suggest that a substantial number of patients with congenital heart disease have a 22q11 deletion.Methods. Two hundred fifty-one patients with conotruncal defects were prospectively enrolled into the study and screened for the presence of a 22q11 deletion.Results. Deletions were found in 50.0% with interrupted aortic arch (IAA), 34.5% of patients with truncus arteriosus (TA), and 15.9% with tetralogy of Fallot (TOF). Two of 6 patients with a posterior malalignment type ventricular septal defect (PMVSD) and only 1 of 20 patients with double outlet right ventricle were found to have a 22q11 deletion. None of the 45 patients with transposition of the great arteries had a deletion. The frequency of 22q11 deletions was higher in patients with anomalies of the pulmonary arteries, aortic arch or its major branches as compared to patients with a normal left aortic arch regardless of intracardiac anatomy.Conclusions. A substantial proportion of patients with IAA, TA, TOF and PMVSD have a deletion of chromosome 22q11. Deletions are more common in patients with aortic arch or vessel anomalies. These results begin to define guidelines for deletion screening of patients with conotruncal defects.

The operative stabilization of pediatric diaphyseal femur fractures with flexible intramedullary nails: a prospective analysis.

Seventy-eight diaphyseal femur fractures in 77 children were stabilized with flexible intramedullary nails. The patients ranged in age from 2 + 9 to 18 years. All patients had open femoral growth plates at the time of fixation. Eleven percent of the fractures had an average varus or valgus malalignment of 6 degrees. Eight percent of the fractures had an average anterior or posterior malalignment of 8 degrees. Eight percent of the patients had a rotational malalignment that averaged 8 degrees. Sixty-eight percent of the children had equal leg lengths at follow-up. There were four unscheduled reoperations, but no major complications; all fractures united. The results obtained using flexible intramedullary nails for the stabilization of select pediatric diaphyseal femur fractures are comparable to nonoperative methods of treatment, but with less disruption to family life and a shorter hospitalization.

Morphology of ventricular septal defects in complete transposition: Surgical implications

Postmortem examination of 62 hearts with complete transposition (concordant atrioventricular and discordant ventriculoarterial connections) and an accompanying ventricular septal defect was performed to determine the morphologic variability of ventricular septal defects and to explore the surgical implications of these defects. Particular attention was directed toward assessing alignment of the outlet septum relative to the muscular septum. Coronary arterial distributions were also evaluated, but specific patterns of distribution did not correlate with morphology of the defect. Of 49 hearts with a normally aligned outlet septum, there were 24 perimembranous, 21 muscular, and 2 doubly committed and juxtaarterial defects. Two hearts had both perimembranous and muscular defects. Twelve of the 21 muscular defects were "central," being surrounded entirely by muscle and located just below the leaflets of the pulmonary valve, and 9 were located in the inlet or apical trabecular septum. There were 13 hearts with malalignment of the outlet septum, anteriorly in 11 and posteriorly in 2. All with anterior malalignment had a subpulmonary defect that was perimembranous in 7 and muscular in 4. Both defects with posterior malalignment had a subaortic perimembranous defect. Because variations in morphology of a ventricular septal defect have a direct impact on selection of the most suitable surgical repair, specific operative approaches are discussed.