Resection Angle Research Articles

The accuracy of Intramedullary Femoral alignment in Total Knee Replacement in the prescence of ipsilateral Hip Replacement

Objectives:During total knee replacement (TKR) surgery, the most commonly used method for aligning the distal femur appropriately is via an intramedullary (IM) distal femoral alignment rod. The alignment of the rod itself is reliant on the isthmus which is used to most accurately place the rod in the correct anatomical axis. In the instance of something preventing the rod from entering the isthmus correctly, such as a hip replacement, then the degree of accuracy could be assumed to be even less. Mechanical-anatomical malalignment has been shown to decrease the implant (TKR) survival and so methods of increasing accuracy of alignment relative to the mechanical axis have been developed. At present the most accurate method intraoperatively is computer navigation and several studies have demonstrated improved alignment. An increasing number of patients year on year are having both knee and hip replacements and as the population ages the likelihood of having both a knee and hip replacement will also increase. We propose that the presence of a hip replacement within the isthmus of the femur may further decrease the accuracy of the IM alignment of the femur leading to incorrect implant positioning.Methods:The study was conducted on 10 cadaveric specimens (20 femurs). Computational navigation instrumentation was attached in turn to each femur and the ideal alignment data recorded in a standard fashion by a single operator (principal investigator). A standard entry port was then be made in the femur for the introduction of the IM rod. An IM rod was then inserted with the distal femoral cutting block in the accepted position recorded blindly on the computer navigation (both in terms of varus/valgus alignment to the mechanical axis and the degree of flexion). The process was then repeated at 3 levels to represent primary and revision hip lengths from the greater trochanter (replicating the changes that would occur in the presence of a hip replacement) The process was recorded three times at each level.Results:The resection angles between the cutting surface and the mechanical axis were measured and collected by means of computer navigation system. The results show that the IM alignment had mean Valgus of 0 degrees +/- 0.8 but with a hip replacement in situ this increased to 0.46 degrees +/- 1.49 (range 2.5 varus to 4.5 valgus), with a revision stem 0.825 +/- 1.68 (range 2.5 varus to 4.5 valgus) and long stemmed revision 1.325 +/- 2.09 (range 5 varus to 6.5 valgus). In terms of Flexion IM alignment had a mean flexion of 0.92 +/- 1.7 (range 3 extension to 4 flexion) but with a hip replacement in situ this increased to 1.88 degrees +/- 2.03 (range 2.5 extension to 8.5 flexion), with a revision stem 2.35 +/- 2.2 (range 2.5 extension to 8 flexion) and long stemmed revision 2.75 +/- 2.16 (range 3.5 extension to 7 flexion).Conclusion:This Study concludes that the prescence of a hip replacement, in particular long stemmed prosthesis, further reduces the accuracy of IM alignment in the Femur for Total Knee Replacement. Consideration of an alternative method, such as navigation, should be considered in such situations.

Accuracy of virtually 3D planned resection templates in mandibular reconstruction.

Since reconstruction of composite defects in the head and neck region is a challenging and demanding problem for head and neck surgeons, surgical aids have been sought for decades. The purpose of this study was to evaluate the accuracy of prefabricated surgical resection templates used in mandibular segmental resections in comparison to the virtual surgical plan. A prospective study was performed in 11 consecutive patients, with a primary T4 oral squamous cell carcinoma or osteoradionecrosis of the mandible. Preoperatively, a CBCT scan was acquired to delineate the size and extension of tumor invasion; a virtual patient-specific resection template was designed based on this information. Intraoperatively, the resection template was positioned on the mandible and secured using four fixation screws. Postoperatively, a CBCT scan was acquired. This scan was superimposed on the preoperative scan. Positioning of the resection template and inclination of the resection planes were evaluated on the virtual head model. In order to test the interobserver reliability of these new measurement methods, two different observers executed all measurements. The mean shift of the proximal resection templates was 3.76mm (standard deviation [SD] 3.10mm). For the distal resection templates, the mean shift was 3.06mm (SD 1.57mm) with no significant interobserver difference (ICC=0.99). An absolute mean deviation of 8.5° (SD 5.3°) was found for the proximal resection angle and 10.4° (SD 5.0°) for the distal resection angle. Again, no significant interobserver differences were found (ICC=0.98). The resection templates used in this study proved reasonably accurate. Although the concept of virtual surgical planning aids significantly in mandibular reconstruction with microvascular free flaps, further improvement of resection accuracy is necessary for further improvement of reconstruction accuracy.

V9-11 ROBOTIC PARTIAL NEPHRECTOMY FOR COMPLETELY ENDOPHYTIC RENAL MASSES: VARIATIONS IN SURGICAL TECHNIQUE

You have accessJournal of UrologyRobotics - Renal1 Apr 2016V9-11 ROBOTIC PARTIAL NEPHRECTOMY FOR COMPLETELY ENDOPHYTIC RENAL MASSES: VARIATIONS IN SURGICAL TECHNIQUE Daniel Ramirez, Matthew J. Maurice, Peter A. Caputo, Ryan J. Nelson, Ercan Malkoc, Onder Kara, and Jihad H. Kaouk Daniel RamirezDaniel Ramirez More articles by this author , Matthew J. MauriceMatthew J. Maurice More articles by this author , Peter A. CaputoPeter A. Caputo More articles by this author , Ryan J. NelsonRyan J. Nelson More articles by this author , Ercan MalkocErcan Malkoc More articles by this author , Onder KaraOnder Kara More articles by this author , and Jihad H. KaoukJihad H. Kaouk More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2016.02.1202AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Robotic partial nephrectomy (RPN) for completely endophytic renal masses is feasible with increased robotic surgical experience. In this video we demonstrate our surgical technique for robotic partial nephrectomy, focusing on the technical variations for RPN for completely endophytic tumors. METHODS Between June 2006 and August 2015, our institution performed 1,123 partial nephrectomies. 130 were performed for completely endophytic renal tumors. We present 2 patients with completely endophytic, central renal masses who underwent RPN, one in the left kidney and one in the right. Our approach to surgical removal of completely endophytic renal tumors includes the use of intraoperative ultrasound to delineate the margins of the mass, initial shallow angle of resection to improve visualization of the parenchymal margin and tumor base, and correction of excision trajectory at the renal sinus. This technique is described in detail in our video presentation. RESULTS Of the 1,123 RPN performed at our institution over the last 10 years, 11.6% were performed for completely endophytic renal masses. Mean operative time, warm ischemia and estimated blood loss in this cohort were 180 minutes, 24.5 minutes, and 197 cc, respectively. Minor complicate rate in this group was 13.9%, while major complication rate was 13.9%. 7 patients in this group had positive margins (5.4%). Successfully surgical extirpation of completely endophytic renal masses is optimized by an initially shallow incision in order to obtain a clear view of the parenchymal edge and base of tumor. Once the sinus fat and collecting system are exposed, the trajectory of the excision is corrected and the sides and back of the tumor are excised in a step-wise, circumferential fashion. CONCLUSIONS RPN for completely endophytic renal tumors is feasible and necessitates technical variations in excision in order to optimize outcomes. Excision of the tumor should be performed in a step-wise systematic fashion with a shallow initial incision to improve visualization into the renal defect and to avoid cutting into the tumor. © 2016FiguresReferencesRelatedDetails Volume 195Issue 4SApril 2016Page: e863 Advertisement Copyright & Permissions© 2016MetricsAuthor Information Daniel Ramirez More articles by this author Matthew J. Maurice More articles by this author Peter A. Caputo More articles by this author Ryan J. Nelson More articles by this author Ercan Malkoc More articles by this author Onder Kara More articles by this author Jihad H. Kaouk More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Does Use of a Variable Distal Femur Resection Angle Improve Radiographic Alignment in Primary Total Knee Arthroplasty?

BackgroundThe distal femur resection in total knee arthroplasty (TKA) is commonly made using a fixed angle relative to an intramedullary rod. This study’s purpose was to assess if a variable distal femur resection angle technique improves femoral component alignment in TKA. MethodsThis was a review of primary TKAs performed by 2 surgeons. One surgeon used a fixed resection angle of 5° for varus and 3° for valgus knees (“fixed” cohort). The second used hip-knee-ankle (HKA) radiographs to measure the angle between the femoral anatomic axis and a line perpendicular to the femoral mechanical axis, which was used as the resection angle for each patient (“variable” cohort).Femoral component and HKA alignment were measured from standing HKA radiographs by 2, independent, blinded observers. Two hundred ninety patients were needed for power to detect a 15% difference in femoral component “outliers” (target of 0° ± 2°; significance = P < .05). ResultsThree hundred twenty consecutive patients were included with no differences in age, body mass index, or preoperative deformity (P = .3-.8). A 5° resection angle was used in 46.3% of the variable and 80.0% of the fixed cohort patients.A total of 80.2% of femoral components in the variable and 63.1% in the fixed cohort were within 0° ± 2° (P = .002; 84.6% of variable and 56.3% of fixed for valgus knees, P < .001). The mean HKA alignment was improved in the variable cohort (−1.4° ± 3.3° vs −2.6° ± 3.3°, P = .001). ConclusionUse of a variable distal femur resection angle improves femoral component alignment after TKA.

Reliable angle of distal femoral resection in total knee arthroplasty using portable navigation

Reliable angle of distal femoral resection in total knee arthroplasty using portable navigation

Unconstrained total knee arthroplasty in significant valgus deformity: a modified surgical technique to balance the knee and avoid instability.

Correction of valgus deformity in total knee arthroplasty (TKA) is technically challenging and has produced variable results. A modified surgical technique involving adapting the distal femoral cut with minimal soft tissue release is proposed. The authors hypothesise that using this technique would result in satisfactory radiological and functional outcome. The technique involves balancing the knee in extension by changing the distal femoral resection angle and confining soft tissue release to only the posterolateral capsule if required. Retrospective analysis of 276 consecutive TKAs performed using this technique under the care of a single surgeon in patients with valgus knee deformity ≥10° was undertaken. An unconstrained mobilebearing implant was used in all knees with a medial para-patellar approach, and outcome scores were collected prospectively. Seventy-five percent of the knees were cementless. [corrected] Mean coronal alignment of the lower limb was corrected from 15.6° (±5.7°) to 3.8° (±2.5°). 97.8% knees had their coronal alignment restored to ≤7°. Seventy-eight knees (28%) were balanced by only changing the distal femoral resection angle. One hundred and ninety-eight knees (72%) had release of the posterolateral capsule. Sixteen knees (5.8%) also had release of iliotibial band. Lateral patellar release was performed in 39 knees (14%). 93.1% had central patello-femoral alignment. At between 5.8 and 10.5 year follow-up, there has been one spinout, managed by closed reduction, and one revision of tibial tray for subsidence. The mean American Knee Society clinical score improved from 19.1 to 86.5 (±12.2). Adequate correction of valgus knee deformity was successfully achieved using this modified technique with satisfactory medium-term outcome and avoidance of instability.

Influence of the Rotational Alignment of the Femoral and Patellar Components on Patellar Tilt in Total Knee Arthroplasty.

PurposeThe purpose of this study was to analyze the influence of rotational alignment of the femoral and patellar components on patellar tilt after total knee arthroplasty (TKA).Materials and MethodsA total of 56 patients (76 knees) who underwent TKA using Advance Medial Pivot Knee system between May 2009 and April 2011 and were available for minimum 1-year follow-up were enrolled in this study. Whiteside's line and the transepicondylar line were used to determine the rotational alignment of the femoral component. Patella cut was aimed to be parallel to the anterior patellar cortex during surgery. Radiographic evaluation was performed using plain axial radiographs. The rotational alignment of the femoral component was measured as the angle between the anterior condylar axis and the surgical transepicondylar axis. The patellar resection angle was measured between the patellar resection axis and the anterior cortical line of the patella. Patellar tilt was evaluated to investigate the correlation with the rotation of the femoral component and patellar resection angle.ResultsThe mean rotation of the femoral component was 0.42°±3.18° of internal rotation. The mean patellar resection angle was 1.82°±3.44°, indicating medial overresection. The mean patellar tilt was 6.12°±4.31° of lateral tilt. The rotational angle of the femoral component showed a negative correlation with patellar tilt in the linear regression analysis (p=0.749), but the patellar resection angle showed a positive correlation with patellar tilt (p<0.001).ConclusionsAccurate patellar resection is recommended for proper patellar tracking in TKA.

The effect of femoral neck osteotomy on femoral component position of a primary cementless total hip arthroplasty.

The aim of this study was to quantify the femoral canal diameter and version at different femoral neck osteotomy locations, and to investigate the effect of the osteotomy plane on femoral component position in total hip arthroplasty (THA). Preoperative and postoperative three-dimensional models were reconstructed in 15 patients (19 hips) who underwent primary cementless THA with tapered non-anatomical femoral stem. On the pre-operative models, the osteotomy plane was simulated at different levels (-5, 0, 5, and 10 mm from the femoral saddle [piriformis fossa]) and angles (30, 40, 50, and 60° from the femoral anatomical axis). Medullary canal version and mediolateral diameter were measured on the osteotomy surfaces. On the postoperative models, the femoral neck osteotomy plane, stem anteversion and alignment were measured. The average canal diameter ranged from 22.8 to 26.3 mm at different osteotomy levels and from 20.8 to 29.0 mm at different osteotomy angles. The average canal version ranged from 11.4 to 23.2° at different resection levels and from 12.8 to 21° at different resection angles. The femoral stem anteversion was correlated with neck osteotomy angle (R = 0.72), whereas stem alignment in frontal plane (varus/valgus) was correlated with neck osteotomy level (R = 0.87). The femoral neck osteotomy plane in THA affects the postoperative stem position due to the complex morphology of the proximal femoral medullary canal, suggesting that both femoral neck resection level and angle should be considered in optimizing femoral component alignment in THA patients.

Short Leg Film Is Sufficient for Postoperative Follow-Up in Total Knee Arthroplasty

The gold standard for evaluating postoperative alignment after total knee arthroplasty (TKA) has been standing AP hip to ankle radiograph. The objective of this study was to determine if the angle between the anatomic axis of the tibia and femur measured on short standard radiographs accurately reflected overall coronal and mechanical alignment from full length knee films. Both full length and short length knee films were retrospectively compared measurements made on from 188 knees in 129 consecutive patients after primary TKA between July 1990 and January 1991. The tibiofemoral angle, distal femur and proximal tibia resection angles, and mechanical alignment were evaluated on the long leg by a blinded observer. The difference in the tibiofemoral angle measured on short and long leg films, 4.4 (+/﹣2.9) vs 5.2 (+/﹣3.0) degrees of valgus, respectively, was statistically significant (p < 0.01). The correlation coefficient between the tibiofemoral angle and mechanical axis was 0.9 (p < 0.01). There was no difference in the distal femur or proximal tibia resection angle measured on short length knee vs long leg films. In conclusion, the tibiofemoral angle measured on short length knee radiographs accurately reflects postoperative alignment. The differences between tibiofemoral angle and the mechanical alignment are highly correlated and equivalent measures of overall alignment.

Variability of distal femoral valgus resection angle in patients with end-stage osteoarthritis and genu varum deformity: Radiographic study in an ethnic Asian population.

When performing a total knee arthroplasty, most surgeons use the intramedullary alignment guide with a fixed distal femoral valgus resection angle. In this study, we assessed the variability of the distal femoral valgus resection angle in ethnic Asian patients by reviewing our arthroplasty database. Between January 2004 and December 2012, the patients with end-stage osteoarthritis with genu varum deformity who underwent total knee arthroplasty were enrolled in this retrospective review. Clinical and radiographic data were collected and analyzed. Nine hundred and fifty-two knees met the inclusion criteria. Three hundred and four (31.9%) knees had a distal femoral valgus resection angle value outside the range of 5° ±2° (range, 4°-14°). There were significant differences in the mean distal femoral valgus resection angle between males and females (p < 0.001) and between non-bowed femur and bowed femur (p < 0.001) cohorts. With regard to the correlation coefficients between the distal femoral valgus resection angle and the usual radiographic measurements, only the coronal femoral bowing angle demonstrated a good correlation (r = 0.72). 32% of Asian patients present with a distal femoral valgus resection angle that is outside the range of 5° ±2°. Taking a long-leg weight-bearing split scanogram may provide information that allows the surgeon to determine the true distal femoral valgus resection angle and adjust the cut accordingly. Therapeutic level III.

Sagittal Alignment Following Lumbar Three-Column Osteotomy: Does the Level of Resection Matter?

3‐Column osteotomy (3CO) is an effective technique to correct sagittal malalignment, but is associated with high complication rates. Whether the angle of wedge resection and spinal level of the osteotomy are well correlated to the correction of spino‐pelvic parameters remains unclear. This study sought to investigate the impact of the osteotomy site on sagittal correction. Post‐operative apex of lumbar lordosis has a significant impact on pelvic tilt with more caudal 3CO levels associated with higher post‐operative motor deficits and revision.

The influence of the choice of closing wedge angle on leg length discrepancy after proximal femoral varus osteotomy.

Proximal femoral varus osteotomy improves the biomechanics of the hip and can stimulate normal acetabular development in a dysplastic hip. Medial closing wedge osteotomy remains the most popular technique, but is associated with shortening of the ipsilateral femur. We produced a trigonometric formula which may be used pre-operatively to predict the resultant leg length discrepancy (LLD). We retrospectively examined the influence of the choice of angle in a closing wedge femoral osteotomy on LLD in 120 patients (135 osteotomies, 53% male, mean age six years, (3 to 21), 96% caucasian) over a 15-year period (1998 to 2013). A total of 16 of these patients were excluded due to under or over varus correction. The patients were divided into three age groups: paediatric (< 10 years), adolescent (10 to 16 years) and adult (> 16 years). When using the same saw blades as in this series, the results indicated that for each 10° of angle of resection the resultant LLD equates approximately to multiples of 4 mm, 8 mm and 12 mm in the three age groups, respectively. Statistical testing of the 59 patients who had a complete set of pre- and post-operative standing long leg radiographs, revealed a Pearson's correlation coefficient for predicted versus radiologically observed shortening when using a wedge of either 10° or 20° of 0.93 (p < 0.001). The 95% limits of agreement from the Bland-Altman analysis for this subgroup were -3.5 mm to +3.3 mm. It has been accepted that a 10 mm discrepancy is clinically acceptable. This study identified a geometric model that provided satisfactory accuracy when using specific saw blades of known thicknesses for this formula to be used in clinical practice.

Errors in knee alignment using fixed femoral resection angles.

This study describes the variance within a representative population of total knee arthroplasty (TKA) patients to provide guidance in improving coronal alignment. The authors retrospectively reviewed 250 preoperative full-length standing radiographs in a consecutive series of TKAs performed by one surgeon. The distal femoral resection was templated on each radiograph to establish a femoral mechanical anatomical (FMA) angle to guide resection. Mean FMA angle was 5.35°, with a wide variation in FMA angle ranging from 1° to 10°. Slightly more than half (56%) of patients had either a 5° or 6° FMA angle, which is concerning for surgeons using a fixed resection angle. Ninety percent of patients measured within the 5°±2° window. Similarly, 90.7% of patients measured within the 6°±2° window. However, nearly 10% of patients (9.75%) had measurements greater than 7° or less than 3°. This study reports a wide variance in the angle of resection required to establish proper femoral mechanical alignment in TKA. Surgeons should be cognizant of the numerous variables that play a role in TKA and influence overall coronal alignment. Many of these variables can be fully assessed by evaluating full-length standing leg radiographs preoperatively. With experience, templating long-leg films can be reproducible and informative in preparing for each surgical procedure. Routine reliance on a single fixed resection angle could result in malalignment in 10% of patients.

A Comparison of Variable Angle Versus Fixed Angle Distal Femoral Resection in Primary Total Knee Arthroplasty

This study assessed whether using a variable distal valgus resection angle improved post-operative coronal lower limb alignment in total knee arthroplasty (TKA). Two groups were compared: Fixed (n=124), where a fixed distal valgus resection angle of 7° was used; Variable (n=87), where the resection angle was adjusted to the measured femoral mechanical anatomical (FMA) angle of the patient. FMA and mechanical femoro-tibial (MFT) angles were measured on pre-operative and post-operative hip-knee-ankle radiographs. 85% of patients in the Variable group had a post-operative MFT angle within 0°±3°compared to 69% in the Fixed group (P=0.006). The use of a fixed distal femoral resection angle for all patients is not appropriate. Setting the resection to an individual patient’s FMA angle can significantly improve the post-operative MFT angle.

Is it safe the empirical distal femoral resection angle of 5° to 6° of valgus in the Brazilian geriatric population?

ObjectiveThe purpose of this study is to determine if there is a safe distal femoral resection angle to restore the normal axial alignment of the limb in total knee arthroplasty (TKA) in the Brazilian geriatric population with knee arthrosis. MethodThis study analyzed 99 pre-operative hip-knee-ankle radiographs of osteoarthritic knees of 66 patients (54 women, 12 men) with knee osteoarthritis. The distal femoral cut angle was determined based on the femoral mechanical-anatomical angle (FMA). Mean, median and standard deviation measurements of the distal femoral cut angle were calculated, differentiated by gender and side. The mean result of the distal femoral resection angle was compared to 5.7°, the mean average angle of previous and similar study based on European population of patients with knee arthrosis. ResultsThe mean average of the distal femoral resection angle of the study was 6.05 (range 3–9°). The distribution of this angle between genders showed a slight superior average of the male population (6.17°) compared to the female (6.02°), but with no statistically significant difference (p=0.726). There was no statistically significant difference (p=0.052) between the mean average of this study (6.05°) compared to the mean average of the literature (5.7°). However, considering 3° as the limit of acceptable error in the coronal plane, this empirical femoral resection angle would not be appropriated for 19.7% of the population. ConclusionThe distal femoral resection angle of 5–6° is not completely safe for the Brazilian geriatric population.

Digital Measurements of 120 Mandibular Angles to Determine the Ideal Fibula Wedge Osteotomy to Re-Create the Mandibular Angle for Microvascular Reconstruction

Mandibular reconstruction continues to be a challenge, even for the seasoned reconstructive surgeon. The present study sought to determine the normal anatomic mandibular angle and to establish a predictable angle of resection for the fibula bone cut to re-create the neomandibular body-ascending ramus angle. A total of 30 random male and female panoramic radiographs were selected from our database. The selection criteria included age older than 21 years and a full or near total complement of teeth. The exclusion criteria were an edentulous mandible or maxilla, a history of trauma or maxillary or mandibular pathologic features, and age younger than 21 years. A total of 120 total measurements were performed. The angle measured was determined from a line coinciding with the posterior border of the ramus and the lower mandibular border. The measurements were taken from each side and from each gender group. The institutional review board of our institution approved the present study. The mean female mandibular right angle was 122.62°, and the left was 124.59° (average, 123.61°). The mean male mandibular right angle was 122.66°, and the left was 124.2° (average, 123.43°). The mean and median values were very similar. A statistically significant difference was identified between the left and right sides but not between the genders. Given this information, one can calculate a wedge cut in the fibula of about 56° to re-create the mean mandibular angle. This information can be used to make predictable fibula wedge closing osteotomies to re-create the normal mandibular ascending ramus body angle in a low-cost manner with the aid of an autoclavable metal wedge of 56°. This method would obviate the need for costly prefabricated guides.

É seguro o corte femoral distal em artroplastia total do joelho com 5° a 6° de valgo empiricamente na população geriátrica brasileira?

ObjectiveThe purpose of this study is to determine if there is a safe distal femoral resection angle to restore the normal axial alignment of the limb in Total Knee Arthroplasty (TKA) in the Brazilian geriatric population with knee arthrosis. MethodThis study analysed 99 pre-operative hip-knee-ankle radiographs of osteoarthritic knees of 66 pacientes (54 women, 12 men) with knee osteoarthritis. The distal femoral cut angle was determined based on the femoral mechanical-anatomical angle (FMA). Mean, median and stardard deviation measurements of the distal femoral cut angle were calculated, differentiated by gender and side. The mean result of the distal femoral resection angle was compared to 5.7°, the mean average angle of previous and similar study based on European population of pacients with knee arthrosis. ResultsThe mean average of the distal femoral resection angle of the study was 6.05 (range 3° to 9°). The distribution of this angle between genders howed a slight superior average of the male population (6.17°) compared to the female (6.02°), butwith no statistically significant difference (p=0,726). There was no statistically significant difference (p=0.052) between the mean average of this study (6.05°) compared to the mean average of the literature (5.7°). However, considering 3° as the limit of acceptable error in the coronal plane, this empirical femoral resection angle would not be apropriated for 19.7% of the population. ConclusionThe distal femoral resection angle of 5° to 6° is not completely safe for the Brazilian geriatric population.

Current strategy for successful periradicular surgery

Periradicular surgery is often used as a last resort to save an endodontically treated tooth with a persistent periapical lesion. The introduction of surgical microscopes, ultrasonics, and compatible root-end filling materials has made periradicular surgery a much more predictable treatment. The advantages of modern periradicular surgery include easier identification of root apices, smaller osteotomines, shallower resection angles, and tight sealing within the prepared root-end cavity. Modern periradicular surgical thus has a much higher success rate than traditional periradicular surgery.

Paper 105: Changes in Patellar Alignment After Total Knee Arthroplasty

Although the results of total knee arthroplasty continue to improve, problems related to the patellofemoral joint remain significant. This study examined the factors affecting patellar alignment after total knee arthroplasty and subsequent changes during a postoperative period of 5.3 years. Fifty-five knees in 39 patients were retrospectively evaluated by radiography for postoperative patellar alignment. This study included four men and 35 women with a mean follow-up time of 5.3 years (range: 2.5 to 8.4). All procedures utilized identical surgical technique; through a midline skin incision and medial parapatellar arthrotomy, the patella was fully everted. We adjusted the rotation of the femoral component until it was parallel to the surgical epicondylar axis. Using the posterior femoral condyles as references, we inserted the femoral components with 3° to 5° of external rotation to the posterior condylar axis according to preoperative CT scans. Tibial components were set using the medial third of the tibial tuberosity as a reference. All patellae were resurfaced with three-peg offset-dome all-polyethylene patellar component. Patellar alignment was assessed by measuring the lateral tilt and lateral displacement in skyline views taken with the knees at approximately 60° of flexion. Patellar alignment was evaluated one month after surgery, and at final follow-up. Changes in patellar lateral tilt angle and lateral displacement in the postoperative period were calculated using data obtained one month after surgery and at final follow-up. We did not observe severe malalignment of the femorotibial joint, patellar bone fracture, prosthesis failure, or any other clinical complications after TKA in any cases. The mean patellar lateral tilt angle was -0.7° (range: −13.7 to 7.0°) one month after surgery and −0.4° (range: −11.4 to 11.6°) at final follow-up. The mean patellar lateral displacement was 1.1mm (−2.7 to 6.6mm) one month after surgery and 0.9mm (−3.7 to 5.8mm) at final follow-up. We observed a negative correlation between the patellar resection angle and lateral tilt one month after surgery (p<0.0001) and between the patellar resection angle and patellar lateral displacement one month after surgery (p=0.0003). Lateral retinacular release was required for thirteen knees. In these cases, the resection angle was significantly smaller than that seen in knees without lateral retinacular release (p=0.0012). These results demonstrate that a smaller resection angle correlated with an increased frequency of lateral retinacular release. The change in patellar lateral tilt angle after 5.3 years was 0.3° (range: −7.2 to 7.0°), while the change in patellar lateral displacement was −0.3 mm (range: −5.2 to 3.7 mm). These changes did not significantly correlate with patellar alignment at any time point, resection angle, resection thickness, lateral retinacular release, or clinical results. The postoperative femorotibial alignment, however, exhibited a statistically significant correlation with the changes in lateral tilt angle (p=0.020). A more varus postoperative alignment correlated with increased lateral tilt of the patella in the postoperative period. We observed a satisfactory patellar alignment after a postoperative period of 5.3 years. The patellar resection angle had a significant effect on postoperative patellar alignment. Our findings suggest that leaving a thicker patellar remnant on the medial side can decrease postoperative lateral tilt and the resulting need for lateral retinacular release. Postoperative changes in patellar alignment were very small; none of the knees demonstrated complications of the patellofemoral joints. In this study, we observed the tendency that a postoperative varus alignment leads to patellar lateral tilt. Surgeons should pay scrupulous attention to femorotibial alignment during total knee arthroplasty to decrease patellofemoral complications and femorotibial problems.

Influence of the distal femoral resection angle on the principal stresses in ceramic total knee components

PurposeA certain failure mode using a newly developed cemented ceramic femoral component in total knee replacement was observed in clinical application, i.e. fracture of the femoral component during intraoperative impaction. This may be caused by unintentional deflection of the saw blades during cutting with consecutive higher resection angle of the distal femur than desired, leading to bending of the femoral component during implantation. A finite-element-analysis was carried out to simulate implantation of the femoral component and to evaluate the influence of distal femur preparation on implant stress. ScopeWe developed and validated a numerical model of the ceramic femoral component including a contact formulation which allowed calculating the principal stresses of the implant during implantation onto the resected femur. The analysis considered different anterior and posterior resection angles with a total of 17 variations. By increasing the femoral resection angle in the finite-element-model it could be shown that a deviation of three degrees from the intended resection angle can cause critical stress amounts during implantation. ConclusionsWhen implanting the ceramic component in total knee arthroplasty, the femoral resection angles should be prepared very precisely, in particular anterior saw blade deflection has to be avoided. The implant manufacturer increased implant safety through an additional resection template. Moreover, the impaction of the ceramic femoral component during cementing was not further recommended by using a hammer.