Comparisons of Preoperative Three-Dimensional Planning and Surgical Reconstruction in Primary Cementless Total Hip Arthroplasty

Reconstruction of important parameters such as femoral offset and torsion is inaccurate, when templating is based on plain x-rays. We evaluate intraoperative reproducibility of pre-operative CT-based 3D-templating in a consecutive series of 50 patients undergoing primary cementless THA through an anterior approach. Pre-operative planning was compared to a postoperative CT scan by image fusion. The implant size was correctly predicted in 100% of the stems, 94% of the cups and 88% of the heads (length). The difference between the planned and the postoperative leg length was 0.3 + 2.3 mm. Values for overall offset, femoral anteversion, cup inclination and anteversion were 1.4 mm ± 3.1, 0.6° ± 3.3°, − 0.4° ± 5° and 6.9° ± 11.4°, respectively. This planning allows accurate implant size prediction. Stem position and cup inclination are accurately reproducible.     

Total Hip Arthroplasty Using Imageless Computer-Assisted Hip Navigation: A Prospective Randomized Study

In a prospective randomized study of two groups of 65 patients each, we compared the acetabular component position when using the imageless navigation system compared to the freehand conventional technique for cementless total hip arthroplasty. The position of the component was determined postoperatively on computed tomographic scans of the pelvis. There was no significant difference for postoperative mean inclination (P = 0.29), but a significant difference for mean postoperative acetabular component anteversion (P = 0.007), for mean deviation of the postoperative anteversion from the target position of 15° (P = 0.02) and for the outliers regarding inclination (P = 0.02) and anteversion (P < 0.05) between the computer-assisted and the freehand-placement group. Our results demonstrate the importance of imageless navigation for the accurate positioning of the acetabular component.     

A Validation Study for Estimation of Femoral Anteversion Using the Posterior Lesser Trochanter Line : An Analysis of Computed Tomography Measurement

The aim of this study was to introduce a simple and reliable intraoperative reference guide to reproduce the normal femoral anteversion during total hip arthroplasty (THA). We hypothesized that the posterior lesser trochanter line (PLTL) could be a useful guide for estimating femoral anteversion during THA. We conducted a study of 56 men (112 hips) to evaluate the relationship between the PLTL and the femoral anteversion using computed tomography scans. The mean femoral anteversion was 9.0° ± 8.1° (range, − 16.2° to 32.9°). The PLTL angle correlated (r² = 0.12, P < 0.05) with the femoral anteversion. We found a constant relationship between the PLTL and femoral anteversion, and the PLTL may be used as a guide for estimating the femoral stem anteversion during femoral stem fixation.     

Evaluation of the accuracy of acetabular cup orientation using the accelerometer-based portable navigation system

BackgroundAccurate orientation of acetabular and femoral components is important during total hip arthroplasty (THA). In recent years, several navigation systems have been developed. However, these navigation systems for THA are unpopular worldwide because of their high cost. We assessed the orientation accuracy of cups inserted using a disposable accelerometer-based portable navigation system for THAs.MethodsThis was a prospective cohort study. We analyzed 63 hips with navigation prospectively and 30 hips without navigation retrospectively as historical control. The patients underwent THA via the mini anterolateral approach in the supine position using an accelerometer-based portable navigation system. We compared the preoperative target angles, intraoperative cup angles using navigation records, postoperative angles using postoperative CT data, measurement errors of cup angles, and clinical parameters such as sex, treated side, age at surgery, and body mass index (BMI).ResultsThe average absolute error (postoperative CT-navigation record) was 2.7 ± 2.1° (inclination) and 2.7 ± 1.8° (anteversion), and the absolute error (postoperative CT-preoperative target angle) was 2.6 ± 1.9° (inclination) and 2.7 ± 2.2° (anteversion). The absolute error between postoperative CT and target angle with navigation was significantly lower than the error without navigation (inclination; p = 0.025, anteversion; p = 0.005). Cup malalignment (absolute difference of inclination or anteversion between postoperative CT and preoperative target angle of over 5°) was significantly associated with BMI value (OR: 1.3, 95% CI: 1.1–1.7). The absolute measurement error of cup inclination and anteversion was significantly correlated with patients’ BMI (inclination error: correlation coefficient = 0.53, p < 0.001, anteversion error: correlation coefficient = 0.58, p < 0.001).ConclusionsThe clinical accuracy of accelerometer-based portable navigation is precise for the orientation of cup placement, although accurate cup placement was affected by high BMI. This is the first study to report the accuracy of accelerometer-based portable navigation for THA in the supine position.     

Evaluation of the Accuracy of Computed Tomography-Based Navigation for Femoral Stem Orientation and Leg Length Discrepancy

Although there is a great deal in the literature about the clinical accuracy of computed tomography (CT)-based navigation systems for acetabular cup orientation and leg length discrepancy in total hip arthroplasty, there is little analysis of femoral stem orientation. Thirty total hip arthroplasties in which CT-based navigation system had been used had their anteversion, valgus angle of stem, and leg length discrepancy measured on postoperative CT data. Differences in postoperative measurements from intraoperative records were −0.6° ± 4.8° (range, −11° to 10°) for stem anteversion, −0.2° ± 1.8° (range, −4° to 3°) for valgus angle of stem, and 1.3 ± 4.1 mm (range, −6 to 10 mm) for leg length. Although this system may need further improvement for stem orientation, it was helpful for intraoperative leg length adjustment.     

Comparison of Acetabular Shell Position Using Patient Specific Instruments vs. Standard Surgical Instruments: A Randomized Clinical Trial

Total hip arthroplasty (THA) survivorship relies largely upon appropriate acetabular cup placement. The purpose of this prospective randomized controlled trial was to determine whether the use of a preoperative 3D planning software in combination with patient specific instrumentation (PSI) results in improved cup placement compared with traditional techniques. Thirty-six THA patients were randomized into standard (STD) or PSI technique. Standard approach was completed using traditional techniques, while PSI cases were planned and customized surgical instruments were manufactured. Postoperative CT scans were used to compare planned to actual results. Differences found between planned and actual anteversion were − 0.2° ± 6.9° (PSI) and − 6.9° ± 8.9° (STD) (P = 0.018). Use of 3D preoperative planning along with PSIs resulted in significantly greater anteversion accuracy than traditional planning and instrumentation.     

Acetabular Component Positioning in Total Hip Arthroplasty With and Without a Computer-Assisted System: A Prospective,Randomized and Controlled Study

In a study of the acetabular component in total hip arthroplasty, 20 hips were operated on using imageless navigation and 20 hips were operated on using the conventional method. The correct position of the acetabular component was evaluated with computed tomography, measuring the operative anteversion and the operative inclination and determining the cases inside Lewinnek's safe zone. The results were similar in all the analyses: a mean anteversion of 17.4° in the navigated group and 14.5° in the control group (P = .215); a mean inclination of 41.7° and 42.2° (P = .633); a mean deviation from the desired anteversion (15°) of 5.5° and 6.6° (P = .429); a mean deviation from the desired inclination of 3° and 3.2° (P = .783); and location inside the safe zone of 90% and 80% (P = .661). The acetabular component position's tomography analyses were similar whether using the imageless navigation or performing it conventionally.     

Femoral Bow Predicts Postoperative Malalignment in Revision Total Knee Arthroplasty

Diaphyseal bowing may compromise axial alignment in revision total knee arthroplasty (TKA). 277 patients undergoing revision TKA were evaluated for coronal bowing and hip–knee–ankle (HKA) axis. The mean femoral bow was 1.52° ± 0.18° varus (− 10.1° to + 8.4°). The mean tibial bow was 1.25° ± 0.13° valgus (− 5.9° to + 10°). HKA axis averaged 3.08° ± 0.35° varus preoperatively compared to 0.86° ± 0.25° varus postoperatively. Inter-rater and intra-rater reliability was high. Femoral bow greater than 4° significantly correlated with postoperative HKA axis malalignment (r = 0.402, P = 0.008). 39.7% of patients deviated 3° or greater from a neutral mechanical axis with a significant difference in femoral bow (0.94° ± 0.31°, P = 0.003). Diaphyseal bowing clearly has an important effect on postoperative limb alignment in revision TKA.     

Navigating the Reaming of the Acetabular Cavity in Total Hip Arthroplasty: Does it Improve Implantation Accuracy?

Computer navigation in total hip arthroplasty is used to improve accuracy of component implantation. Reaming of the acetabular cavity during total hip arthroplasty (THA) can be navigated although this is not done routinely. We hypothesised that navigating the reaming of the acetabular cavity will improve implantation accuracy. A single surgeon series of 100 navigated THAs were analysed retrospectively. In 49 the reaming of the acetabular cavity was done using navigation and in 51 this was done freehand. The verified cup position and the error from the planned position were recorded. The mean error from planned to verified inclination was 2.20 degrees (SD 1.59°) in the navigated group versus 2.33 degrees (SD 1.96°) in the freehand group. The mean anteversion error was 1.92 degrees (SD 1.51°) for the navigated group and 1.45 degrees (SD 1.38°) for the freehand group. This was not statistically significant. This rejects our hypothesis. Navigating the reaming of the acetabular cavity did not improve the accuracy of the implantation against the set inclination and anteversion target during computer navigated THA.     

Accuracy of Computer Navigation for Acetabular Component Placement in THA

The accuracy and precision of any computer-aided surgical device is critical to its utility. We asked the following question: how accurate and precise are the values measured by an imageless computer navigation system as compared with those measured using postoperative CT scans? Twenty-five patients (26 hips) underwent primary THA using an imageless computer navigation system for placement of the acetabular component. Inclination and anteversion were measured in the operative coordinate system as defined by Murray. Accuracy, precision, and bias were computed, and Bland-Altman analysis was used to assess levels of agreement. The accuracy (mean ± standard deviation of the absolute difference between computer-assisted navigation and CT) was 1.8° ± 1.2° for inclination and 2.0° ± 2.0° for anteversion. Precision was 3.4° for inclination and 5.5° for anteversion. Bias was 0.52° for inclination and 0.35° for anteversion. Limits of agreement were 4.26° for inclination and 5.58° for anteversion. An imageless computer navigation system can precisely determine acetabular cup position.     

Navigation in femoral-shaft fractures--from lab tests to clinical routine

Introduction

This study evaluates the use of a navigation system (BrainLAB, Feldkirchen, Germany) to intra-operatively check for correct length, axis and rotation in intramedullary nailing of femoral-shaft fractures in an experimental setting and in clinical routine.

Materials and methods

We tested the navigation system in two experimental settings before introducing it into clinical routine. In the first experiment, 10 osteotomised model femora were fixed with intramedullary nails by using a navigation system. The goal was a locking fixation in predefined values for length and rotation.In the second experiment, eight examiners assessed values for rotation and length of one femur 10 times to examine the accuracy and reproducibility of that determination.Following this, we navigated 40 femoral nailing procedures in our department. Preoperatively, we assessed values of femur geometry on the contralateral side in a computed tomography (CT) scan and reproduced these values intra-operatively on the fractured side, guided by the navigation system. During the intervention, we recorded the length of the procedure steps and the fluoroscopy time.We verified the intra-operative values achieved with the navigation system in a postoperative CT scan and documented differences in rotation and length.After the assessment, we analysed the data for different findings on femur geometry, fluoroscopy time and procedure duration.

Results

The experimental evaluation showed a range of ±5° for anteversion differences and ±2.3 mm for length differences. We estimated this accuracy as sufficient to use the system in clinical routine. The navigation system was used for 40 fracture fixations. All our criteria for restoring femoral geometry could be achieved by navigation guidance in these procedures.Setting up the system took on average 33 ± 11.5 min. An additional fluoroscopy time of 36 ± 22 s was needed to acquire the reference X-rays and to verify pin placement.The differences between anteversion values assessed in intra-operative planning steps on the navigation system and values assessed with a postoperative CT were on average 5.4 ± 3.5°, whilst femur length differed on average by 4 ± 4 mm.

Discussion

Many authors judge intra-operative control of anteversion in femoral-shaft fracture fixation as problematic.Neither our experimental navigation assessment nor our clinical navigated evaluation showed relevant anteversion differences to a postoperative CT assessment of femur geometry. After initial training, guidance by a navigation system achieves consistent results in a clinical situation.

Conclusions

The use of a navigation system to align axis, length and rotation led to a secure way of avoiding any relevant malalignment in complex femur-shaft fractures whilst exposing patients to an acceptable amount of additional procedure sequences.Malalignment can be avoided by using a navigation system in the operative treatment of femoral-shaft fractures and may be integrated into clinical routine in specialised centres.     

An In Vivo Comparison of the Orientation of the Transverse Acetabular Ligament and the Acetabulum

Aligning the acetabular component with the Transverse Acetabular Ligament (TAL) to ensure optimal anteversion has been reported to reduce dislocation rates. However, to our knowledge in vivo measurement of the TAL angle has not yet been reported in a large cohort of normal hips. CT scans of 218 normal hips were analyzed. The TAL and four acetabular rim anteversion angles were measured (superiorly to inferiorly) relative to the anterior pelvic plane. The mean TAL anteversion angle was 20.5° ± 7.0°, and the acetabular rim angles from superior to inferior were 11.0° ± 12.9°, 19.9° ± 8.8°, 20.9° ± 6.2° and 25.1° ± 6.2° respectively. Both the TAL and the acetabular rim were significantly more anteverted in females than in males. The TAL anteversion angle was comparable to the predominant orientation (central rim section) of the native acetabulum while the superior acetabulum was comparatively retroverted and the inferior was relatively more anteverted.     

Accuracy and Precision of Version Angle Measurements of the Acetabular Component After Total Hip Arthroplasty

The orientation of the acetabular component after total hip arthroplasty is expressed with inclination angle and anteversion angle (VA). We studied the differences in accuracy and precision between VA measured on AP radiographs of the pelvis and those measured on cross-table lateral radiographs when compared to the gold standard measurements on CT using a supine functional pelvic plane as reference. VA was measured for 66 hips at one week after surgery on an AP radiograph of the pelvis (VAP), a cross-table lateral radiograph of the hip (VCL), and CT of the pelvis. Mean (± SD) of error was 2.8° ± 4.1° for VCL, and − 0.57° ± 3.1° for VAP. VAP showed a higher accuracy and precision than VCL. For measurements of VA, we recommend that they be made on an AP radiograph of the pelvis rather than a cross-table lateral radiograph of the hip.     

The value of computed tomography based navigation in revision total hip arthroplasty

Purpose

This study investigates the accuracy of a computed tomography (CT)-based navigation system for accurate acetabular component placement during revision total hip arthroplasty (THA).

Methods

We performed a retrospective review of 30 hips in 26 patients who underwent cementless revision THA using a CT-based navigation system; the control group consisted of 25 hips in 25 patients who underwent cementless primary THA using the same system. We analysed the deviation of anteversion and inclination angles among the pre-operative plan, intra-operative records from the navigation system and data from postoperative CT scans.

Results

There were no significant differences between groups (P < 0.05) in terms of mean deviation between pre-operative planning and postoperative measurements or between intraoperative records and postoperative measurements.

Conclusion

CT-based navigation in revision THA is a useful tool that enables the surgeon to implant the acetabular component at the precise angle determined in pre-operative planning.     

Femoral Pinless Length and Offset Measurements During Computer-Assisted,Minimally Invasive Total Hip Arthroplasty

We asked whether the intraoperative assessment of leg length (LL) and offset (OS) change would be accurate using a novel pinless femoral reference system during unilateral minimally invasive THA in 50 patients with a mean age of 60 years (48–79). LL and OS change measured at surgery was compared with LL/OS change as measured on magnification-corrected preoperative and postoperative radiographs by two blinded examiners. The radiographic evaluation showed a high inter-rater reliability (r > 0.80 for all assessments). The mean differences (± 95% limits of agreement) between navigation and radiographic measurements on the treated side were + 0.4 mm (± 3.6) for LL and − 1.0 mm (± 3.9) for OS. Femoral pinless navigation technology represents a feasible assistance in THA.     

A Novel Method for Accurate and Reproducible Functional Cup Positioning in Total Hip Arthroplasty

Cup positioning is an important variable for short and long term function, stability, and durability of total hip arthroplasty (THA). This novel method utilizes internal and external bony landmarks, and the transverse acetabular ligament for positioning the acetabular component. The cup is placed parallel and superior to the transverse ligament and inside the anterior wall notch of the true acetabulum, then adjusted for femoral version and pelvic tilt and obliquity based on weight bearing radiographs. In 78 consecutive THAs, the mean functional anteversion and abduction angles were 17.9 ° ± 4.7 ° and 41.7 ° ± 3.8 °, respectively. 96% of the functional anteversion measurements and 100% of the functional abduction angles were within the safe zone. This technique is an easy, reproducible, and accurate method for functional cup placement.     

Measurement of the Knee Flexion Angle With a Smartphone-Application is Precise and Accurate

We hypothesized that the measurement of the knee flexion angle measured with a specific Smartphone application was different from the reference measurement with a navigation system designed for total knee arthroplasty (TKA). Ten consecutive patients operated on for navigation assisted TKA were selected. Six navigated and 6 Smartphone measurements of knee flexion angle were obtained for each patient. The paired difference between measurements and their correlation were analyzed. The mean paired difference between navigated and Smartphone measurements was − 1.1° ± 6.8° (n.s.). There was a significant correlation between both measurements. The coherence between both measurements was good. The intra-observer and inter-observer reproducibility were good. The Smartphone application used may be considered as precise and accurate. The accuracy may be higher than other conventional measurement techniques.     

Navigated total hip arthroplasty using a 3-D freehand ultrasound system: technical note and preliminary results

Ultrasound-navigated cementless total hip arthroplasty (THA) was performed in 10 consecutive patients with primary osteoarthritis of the hip between August 2008 and October 2009 (M:F, 6:4; median age, 61 years; age range, 30-86 years). The pelvic orientation was defined by preoperative digitization and registration of bony landmarks. Cup inclination and anteversion were documented for each patient intraoperatively (epidigitized vs ultrasound-assessed landmarks). The median difference between the palpated and ultrasound anterior pelvic plane was 8° (range, 4°-18°) for pelvic tilt (rotation around the transversal axis), 1° (range, -3° to 2°) for rotation around the longitudinal axis, and 0.25° (range, -2.0° to 5.0°) for rotation around the sagittal axis. The median difference in cup orientation resulting from pelvic tilt error was 6° (range, 3°-13°) for anteversion and 3° (range, -1° to 5°) for inclination. There were no intra- or postoperative complications. The measured width of soft tissue layer anterior to the pelvic symphysis correlated significantly with the measured difference in cup inclination and anteversion. One centimeter of soft tissue anterior to the symphysis resulted in a median 2° (range, 1.75°-2.3°) difference in pelvic tilt. Ultrasound-assisted navigation in THA is a promising technology able to eliminate systematic errors in anterior pelvic plane orientation, in contrast to conventionally navigated THA using percutaneous palpation of landmarks or THA without navigational support.     

Revision Total Hip Arthroplasty Using Imageless Navigation With the Concept of Combined Anteversion

Background

The purpose of the study was to evaluate the implant positions and clinical results of revision total hip arthroplasty (THA) using an imageless navigation with the concept of combined anteversion.

Is Cup Positioning Challenged in Hips Previously Treated With Periacetabular Osteotomy?

After periacetabular osteotomy (PAO), some patients develop osteoarthritis with need of a total hip arthroplasty (THA). We evaluated the outcome of THA following PAO and explored factors associated with inferior cup position and increased polyethylene wear. Follow-up were performed 4 to 10 years after THA in 34 patients (38 hips) with previous PAO. Computer analysis evaluated cup position and wear rates. No patient had dislocations or revision surgery. Median scores were: Harris hip 96, Oxford hip 38 and WOMAC 78. Mean cup anteversion and abduction angles were 22^o (range 7°–43°) and 45° (range 28°–65°). Outliers of cup abduction were associated with persisting dysplasia (CE < 25°). THA after PAO can produce excellent clinical results. Persisting acetabular dysplasia following PAO may lead surgeons to place the acetabular component in excessive cup abduction, and this tendency should be recognized at the time of the PAO.