Vertical acetabular positioning with an inclinometer in total hip arthroplasty

Inclinometer use in primary total hip arthroplasty does not improve acetabular component positioning: a non-randomized control trial

INTRODUCTION

Total hip arthroplasty (THA) is a common surgical procedure that aims to relieve pain, improve function, and increase mobility in patients with hip joint pathology. One of the most challenging aspects of THA is to determine the correct angle of the acetabular component's placement. Intraoperative inclinometers have emerged as a promising tool to obtain accurate measurements of the acetabular component's inclination. The primary objective of this study was to evaluate the accuracy and efficacy of using intraoperative inclinometers for THA.

METHODS

This non-randomized control trial evaluated patients undergoing primary THA. Patients in the inclinometer group had an inclinometer used intraoperatively to measure acetabular component inclination, and patients in the control group had no inclinometer. Inclination and anteversion of the acetabular component were measured on postoperative radiographs.

RESULTS

A total of 223 patients were included in the study. The mean inclination angle of the acetabular cup was significantly higher in the inclinometer group (43.9° vs. 41.5°, P < 0.001). This difference was not clinically significant. There was no significant difference in anteversion. There were no significant differences in the number of patients within the safe zones for inclination or anteversion, or in the number of patients experiencing a dislocation. No correlation was found between inclinometer measurement and measured acetabular component inclination. Inclinometer use and body mass index (BMI) were the sole statistically significant factors in determining acetabular component inclination.

CONCLUSIONS

This study indicated no current benefit to inclinometer use during primary THA, as measured by inclination, anteversion, and dislocation rate. However, this might be confounded by subtle variations in patient positioning, which may be a strong area of study in the future.

Smart Drill for a Streamlined Estimation of the Drilling Angle and Channel Length in Orthopedic Surgical Procedures

The estimation of distances and angles is a routine part of an orthopedic surgical procedure. However, despite their prevalence, these steps are most often performed manually, heavily relying on the surgeon's skill and experience. To address these issues, this study presents a sensor-equipped drill system which enables automatic estimation of the drilling angle and channel length. The angular accuracy and precision of the system were tested over a range of inclination angles and proved to be superior to the manual approach, with mean absolute errors ranging from 1.9 to 4.5 degrees for the manual approach, and from 0.6 to 1.3 degrees with the guided approach. When sensors were used for simultaneous estimation of both the inclination and anteversion angles, the obtained mean absolute errors were 0.35 ± 0.25 and 2 ± 1.33 degrees for the inclination and anteversion angles, respectively. Regarding channel length estimation, using measurements obtained with a Vernier caliper as a reference, the mean absolute error was 0.33 mm and the standard deviation of errors was 0.41 mm. The obtained results indicate a high potential of smart drill systems for improvement of accuracy and precision in orthopedic surgical procedures, enabling better patient clinical outcomes.

Intraoperative Angle Measurement of Anatomical Structures: A Systematic Review

Ensuring precise angle measurement during surgical correction of orientation-related deformities is crucial for optimal postoperative outcomes, yet there is a lack of an ideal commercial solution. Current measurement sensors and instrumentation have limitations that make their use context-specific, demanding a methodical evaluation of the field. A systematic review was carried out in March 2023. Studies reporting technologies and validation methods for intraoperative angular measurement of anatomical structures were analyzed. A total of 32 studies were included, 17 focused on image-based technologies (6 fluoroscopy, 4 camera-based tracking, and 7 CT-based), while 15 explored non-image-based technologies (6 manual instruments and 9 inertial sensor-based instruments). Image-based technologies offer better accuracy and 3D capabilities but pose challenges like additional equipment, increased radiation exposure, time, and cost. Non-image-based technologies are cost-effective but may be influenced by the surgeon's perception and require careful calibration. Nevertheless, the choice of the proper technology should take into consideration the influence of the expected error in the surgery, surgery type, and radiation dose limit. This comprehensive review serves as a valuable guide for surgeons seeking precise angle measurements intraoperatively. It not only explores the performance and application of existing technologies but also aids in the future development of innovative solutions.

Improving the Accuracy of Metatarsal Osteotomies in Minimally Invasive Foot Surgery Using a Digital Inclinometer: Preliminary Study

Minimally invasive foot surgery (MIS) has become a common procedure to treat various pathologies, and accuracy in the angle of metatarsal osteotomies is crucial to ensure optimal results. This randomized controlled trial with 37 patients investigates whether the implementation of a digital inclinometer can improve the accuracy of osteotomies compared to traditional freehand techniques. Patients were randomly allocated to group A (n = 15) receiving inclinometer-assisted surgery or group B (n = 22) receiving conventional surgery. Osteotomies were performed and outcomes were evaluated using an inclinometer. The inclinometer group showed a significant decrease in plantar pressure from 684.1 g/cm2 pretreatment to 449.5 g/cm2 post-treatment (p < 0.001, Cohen's d = 5.477). The control group decreased from 584.5 g/cm2 to 521.5 g/cm2 (p = 0.001, Cohen's d = 0.801). The effect size between groups was large (Cohen's d = -2.572, p < 0.001). The findings indicate a significant improvement in accuracy and reduction in outliers when using an inclinometer, suggesting that this technology has the potential to improve surgical practice and patient outcomes in minimally invasive metatarsal osteotomies.

Contemporary, non-navigation, cup orientation techniques improve accuracy and eliminate differences seen between the anterior and posterior approach in THA

BACKGROUND

This study aimed to: (1) Determine the ability to achieve the surgeons' desired cup orientation, without navigation, using contemporary measures with the anterior- (AA) and posterior- approaches (PA); and (2) assess whether surgical approach is associated with cup orientation accuracy, as previously reported, when contemporary measures are used.

METHODS

A prospective, 2-centre, multi-surgeon study of 400 THAs (200 AA; 200 PA) was performed. Intraoperative radiographs were obtained with the AA. A digital inclinometer and 3-point pelvic support were used with the PA. With the PA, intraoperative cup inclination at impaction was recorded. Radiographic inclination/anteversion (RI/RA) was measured from intraoperative radiographs (AA-only) and from postoperative radiographs for all cases. Optimum inclination/anteversion was defined as 40°/20° (±10°). The difference between intra- and postoperative orientations allowed for determination of the difference in pelvic position at impaction.

RESULTS

Optimum RI and RA were achieved in 91.3% (n = 365) and 92% (n = 368) of cases respectively. Optimum cup orientation was detected in 84% of cases (n = 336). There was equivalent ability to achieve cup orientation between approaches (AA: 82.5% vs. PA: 85.5%; p = 0.41). The use of an inclinometer in the PA was associated with a smaller variability of inclination at implantation (10° vs. 14°) and counteracted the greater difference in pelvic position (4.4° vs. 2.1°) seen with the PA.

CONCLUSIONS

Over 80% of cases can have optimum orientation without navigation, using simple, cheap contemporary measures. Such measures eliminate differences between approaches, related to patient position. Narrower implantation angles will further reduce variability in cup orientation achieved.

Cup placement in primary total hip arthroplasty: how to get it right without navigation or robotics

Acetabular component orientation and position are important factors in the short- and long-term outcomes of total hip arthroplasty.

Different definitions of inclination and anteversion are used in the orthopaedic literature and surgeons should be aware of these differences and understand their relationships.

There is no universal safe zone.

Preoperative planning should be used to determine the optimum position and orientation of the cup and assess spinopelvic characteristics to adjust cup orientation accordingly.

A peripheral reaming technique leads to a more accurate restoration of the centre of rotation with less variability compared with a standard reaming technique.

Several intraoperative landmarks can be used to control the version of the cup, the most commonly used and studied is the transverse acetabular ligament.

The use of an inclinometer reduces the variability associated with the use of freehand or mechanical alignment guides.

Can the use of an inclinometer improve acetabular cup inclination in total hip arthroplasty? A review of the literature

INTRODUCTION

The angle of acetabular (cup) radiographic inclination is an important measurement in total hip arthroplasty (THA) procedures. Abnormal radiographic inclination is associated with dislocation, edge loading and higher failure rates. Consistently achieving a satisfactory radiographic inclination remains a challenge. Inclinometers have been increasingly used over the last decade. This paper reviews the literature to determine whether using an inclinometer improves the accuracy of acetabular cup inclination in THA.

METHODS

A systematic literature search was performed. The following search terms were used: ('hip' OR 'hip replacement' OR 'hip arthroplasty' OR 'primary hip replacement' OR 'THR' OR 'THA' OR 'Acetabular cup Inclination') AND ('Inclinometer'). Titles and abstracts were screened for relevance. Both radiographic and operative inclination comparisons were included.

RESULTS

7 studies met the inclusion criteria. 2 were randomised control trials with level I evidence, and the remaining studies were cohort studies with level III/IV evidence. 5 were clinical and 2 experimental. In total there were 16 cohorts: 7 using an inclinometer, 6 freehand, and 3 using MAG techniques. All studies comparing radiographic inclination and 1 of 2 studies comparing operative inclination showed an improvement in the attainment of the optimal inclination. Similarly, the use of an inclinometer showed a reduction in the number of outliers when compared to MAG and freehand techniques.

DISCUSSION

This review demonstrates that using an inclinometer improved the surgeon's ability to achieve their intended inclination (both operative and radiographic) and reduced the incidence of positioning outside the safe-zone. However, only 2 of the studies were randomised control trials and these resulted in opposing conclusions. Therefore, further studies looking at the use of inclinometers would prove useful in understanding their true benefit.

A novel mechanical inclinometer device to measure acetabular cup inclination in total hip arthroplasty

It is well recognised that acetabular cup orientation influences patient function and implant survival post-THR. Reliable intra-operative determination of cup orientation remains a challenge. We describe the design and testing of a novel mechanical inclinometer to measure intra-operative acetabular cup inclination. The aim was to design a generic inclinometer to measure acetabular inclination to within + 5° without requiring modification to existing instrumentation while remaining easy to handle, robust/reusable, and sterilizable. The device was drafted using CAD software, prototyped using a 3D printer and constructed using stainless steel. Two experiments were undertaken to test accuracy: (1) the absolute accuracy was tested; (2) placement of an acetabular component using the device was compared to a freehand technique using a sawbone pelvis. 18 surgeons were asked to place an uncemented acetabular cup in a saw bone pelvis to a target of 40°. The average root-mean-square error was 1.1° (SD: 0.9°). Comparison showed that with the freehand component placement 50% of the surgeons were outside the specified range (35°-45°) where all participants achieved placement within range when using the inclinometer. This work demonstrates that the design and initial testing of a mechanical inclinometer which is suitable for use in determining the acetabular cup inclination in THR.

The difference between the radiographic and the operative angle of inclination of the acetabular component in total hip arthroplasty: use of a digital protractor and the circumference of the hip to improve orientation

A high radiographic inclination angle (RI) contributes to accelerated wear and has been associated with dislocation after total hip arthroplasty (THA). With freehand positioning of the acetabular component there is a lack of accuracy, with a trend towards a high radiographic inclination angle. The aim of this study was to investigate whether the use of a digital protractor to measure the operative inclination angle (OI) could improve the positioning of the acetabular component in relation to a 'safe zone'. We measured the radiographic inclination angles of 200 consecutive uncemented primary THAs. In the first 100 the component was introduced freehand and in the second 100 a digital protractor was used to measure the operative inclination angle. The mean difference between the operative and the radiographic inclination angles (∆RI-OI) in the second cohort was 12.3° (3.8° to 19.8°). There was a strong correlation between the circumference of the hip and ∆RI-OI. The number of RI outliers was significantly reduced in the protractor group (p = 0.002). Adjusting the OI, using a digital protractor and taking into account the circumference of the patient's hip, improves the RI significantly (p < 0.001) and does not require additional operating time.

A new method for the measurement of anteversion of the acetabular cup after total hip arthroplasty

OBJECTIVE

Many methods of determining the anteversion of the acetabular cup have been described in the literature. The advantages and disadvantages of each of these methods are discussed in this paper. We present a new method of measuring the acetabular anteversion at the anteroposterior hip.

MATERIALS AND METHODS

The formula designed by the authors was anteversion angle (α) = arc sin |PK|/√ |AK| × |BK|. The formula was tested using the AutoCAD software, and an experimental study was conducted to evaluate the accuracy. Three groups were created, and 16 X-ray images were taken and coded. Ten orthopaedic surgeons measured the acetabular anteversion from these X-rays using our formula.

RESULTS

The results in Group 1 were closer to the actual value; in contrast, the results in Group 2 differed from the actual values. The results in Group 3 were as close to the actual anteversion values as were those in Group 1.

CONCLUSION

Developments in technology often bring an increase in complications. Despite newly developed surgical methods and technology, the position of the acetabular cup is still used to determine the results of a total hip arthroplasty. Our method is simple, cost-effective and achieves almost 100 % accuracy.

Accuracy and potential pitfalls of fluoroscopy-guided acetabular cup placement

Using a total of 30 cadaveric hips, the accuracy of a fluoroscopy-based computer navigation system for cup placement in total hip arthroplasty (THA) was investigated and an error analysis was carried out. The accuracy of placing the acetabular component within a predefined safe zone using computer guidance was compared to the precision that could be achieved with a freehand approach. Accurate control measurements of the implanted cup were obtained using fiducial-based matching to a pre-operative CT scan with respect to the anterior pelvic plane. A significantly higher number of cups were placed in the safe zone with the help of the navigation system. The variability of cup placement could be reduced for cup abduction but not substantially for cup version. An error analysis of inaccurate landmark reconstruction revealed that the registration of the mid-pubic point with fluoroscopy was a potential source of error. Keeping this pitfall in mind, fluoroscopy-based navigation in THA is a useful tool for registration of the pelvic coordinate system, particularly those points that cannot be reached by direct pointer digitization with the patient in the lateral decubitus position.

Randomised controlled trial comparing two methods of acetabular cup positioning during total hip arthroplasty

BACKGROUND

Acetabular cup positioning is an important technical aspect in total hip arthroplasty. Most surgeons estimate cup abduction angle during surgery with the insertion rod position according to the patient's body anatomical landmarks or other reference points in the operating room. High acetabular component abduction angle is associated with an increased risk of dislocation, premature polyethylene wear and osteolysis.

METHOD

To evaluate the potential benefits of a new technique for vertical acetabular cup positioning, 100 acetabular cups were randomised to be inserted with or without an inclinometer. Abduction angles were measured on postoperative radiographs by 2 evaluators blind to the treatment group.

RESULTS

Of the cups, 57% (27/47) were positioned within the desirable abduction angle range of 40-49 with the inclinometer, compared with 50% (27/53) by visuospatial perception (p=0.454). The proportion of cups positioned outside a safe angle range of 30-55 was low in both groups: 6% (3/47) for the inclinometer group versus 4% (2/53) for the visuospatial perception group (p=0.536).

CONCLUSION

The use of an inclinometer did not significantly improve the acetabular cup abduction angle obtained by our group of surgeons when compared with visuospatial perception. Newer techniques such as navigation may be useful in further optimising cup positioning and reducing the outliers.

A novel acetabular alignment guide for THR using selective anatomic landmarks on the pelvis

This paper presents a novel approach for acetabular alignment during the implant of a prosthetic hip joint in a natural pelvis. The alignment instrument uses selective anatomic bony landmarks on the pelvis, which are accessible in surgery, to guide the placement of the acetabular component in the appropriate orientation. A closed form solution, involving both a forward and reverse analysis, is presented to relate the parameters of the device with the abduction and anteversion angles. Using mathematical models, this device should allow the surgeon to place the acetabular component with an orientation between 10.9 degrees and 19.1 degrees anteversion and 35.7 degrees and 44.3 degrees abduction with 95% confidence in a male/left specimen for the commonly accepted target of 15 degrees anteversion and 40 degrees abduction. This device is currently being used successfully by one of the authors in THR surgery.