A novel device to measure acetabular inclination with patients in lateral decubitus

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.

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.

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.

Variability of Pelvic Orientation in the Lateral Decubitus Position: Are External Alignment Guides Trustworthy?

BACKGROUND

The position of the acetabular component in total hip arthroplasty (THA) is critical for success. However, this remains the most variable aspect of the surgery. We hypothesized that there is wide variation in pelvic orientation in the lateral decubitus position. We sought to determine the variability in pelvic positioning and the frequency of pelvic malposition during THA in lateral decubitus with regard to pelvic tilt and pelvic rotation.

METHODS

We analyzed preoperative standing and intraoperative anteroposterior pelvis X-rays in 248 consecutive THAs performed in lateral decubitus by one surgeon. Pelvic tilt and rotation were determined for preoperative and intraoperative X-rays. Proper intraoperative positioning was defined as less than 10° change in tilt or rotation between preoperative and intraoperative X-rays.

RESULTS

With regard to pelvic tilt, the intraoperative position was proper in 188 (76%) cases. There was a pelvic tilt discrepancy of 10°-20° in 43 (17.5%) cases and greater than 20° in 16 (6.5%) patients. With regard to pelvic rotation, the intraoperative position was proper in 202 (81%) cases. There was a pelvic rotation discrepancy of 10°-20° in 38 (15.4%) cases and greater than 20° in 7 (2.8%) cases. In 248 cases, only 154 (62.1%) had intraoperative positioning within 10° of preoperative tilt and axial rotation. Pelvic malposition occurred in 38% of cases overall.

CONCLUSION

There is wide variation in pelvic orientation in lateral decubitus and frequent discrepancy in pelvic tilt and rotation between preoperative and intraoperative anteroposterior X-rays. Anatomic landmarks should be used to guide acetabular component positioning.

LEVEL OF EVIDENCE III

Diagnostic.

Can the use of an inclinometer improve the positioning of the acetabular component in total hip arthroplasty?

Aims

Accurate placement of the acetabular component is essential in total hip arthroplasty (THA). The purpose of this study was to determine if the ability to achieve inclination of the acetabular component within the 'safe-zone' of 30° to 50° could be improved with the use of an inclinometer.

Patients and Methods

We reviewed 167 primary THAs performed by a single surgeon over a period of 14 months. Procedures were performed at two institutions: an inpatient hospital, where an inclinometer was used (inclinometer group); and an ambulatory centre, where an inclinometer was not used as it could not be adequately sterilized (control group). We excluded 47 patients with a body mass index (BMI) of > 40 kg/m², age of > 68 years, or a surgical indication other than osteoarthritis whose treatment could not be undertaken in the ambulatory centre. There were thus 120 patients in the study, 68 in the inclinometer group and 52 in the control group. The inclination angles of the acetabular component were measured from de-identified plain radiographs by two blinded investigators who were not involved in the surgery. The effect of the use of the inclinometer on the inclination angle was determined using multivariate regression analysis.

Results

The mean inclination angle for the THAs in the inclinometer group was 42.9° (95% confidence interval (CI) 41.7° to 44.0°; range 29.0° to 63.8°) and 46.5° (95% CI 45.2° to 47.7°; range 32.8° to 63.2°) in the control group (p < 0.001). Regression analysis identified a 9.1% difference in inclination due to the use of an inclinometer (p < 0.001), and THAs performed without the inclinometer were three times more likely to result in inclination angles of > 50° (odds ratio (OR) 2.8, p = 0.036). The correlation coefficient for the interobserver reliability of the measurement of the two investigators was 0.95 (95% CI 0.93 to 0.97).

Conclusion

The use of a simple inclinometer resulted in a significant reduction in the number of outliers compared with a freehand technique. Cite this article: Bone Joint J 2018;100-B:862-6.

Impact of a learning curve on the survivorship of 4802 cementless total hip arthroplasties

AIMS

Our aim was to report survivorship data and lessons learned with the Corail/Pinnacle cementless total hip arthroplasty (THA) system.

PATIENTS AND METHODS

Between August 2005 and March 2015, a total of 4802 primary cementless Corail/Pinnacle THAs were performed in 4309 patients. In March 2016, we reviewed these hips from a prospectively maintained database.

RESULTS

A total of 80 hips (1.67%) have been revised which is equivalent to a cumulative risk of revision of 2.5% at ten years. The rate of revision was not significantly higher in patients aged ≥ 70 years (p = 0.93). The leading indications for revision were instability (n = 22, 0.46%), infection (n = 20, 0.42%), aseptic femoral loosening (n = 15, 0.31%) and femoral fracture (n = 6, 0.12%). There were changes in the surgical technique with respect to the Corail femoral component during the ten-year period involving a change to collared components and a trend towards larger size. These resulted in a decrease in the rate of iatrogenic femoral fracture and a decrease in the rate of aseptic loosening.

CONCLUSION

The rate of revision in this series is comparable with the best performing THAs in registry data. Most revisions were not directly related to the implants. Despite extensive previous experience with cemented femoral components, the senior author noted a learning curve requiring increased focus on primary stability. The number of revisions related to the femoral component is reducing. Any new technology has a learning curve that may be independent of surgical experience. Cite this article: Bone Joint J 2016;98-B:1589-96.

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.