Use of intraoperative X-rays to optimize component position and leg length during total hip arthroplasty

Minimal pre-operative leg length discrepancy as a risk factor of post-operative leg length discrepancy after total hip arthroplasty: a retrospective study of patients with non-traumatic osteonecrosis of the femoral head

BACKGROUND

Leg length discrepancy (LLD) is one of the troublesome complications of total hip arthroplasty (THA). Previously, several risk factors have been suggested, but they were subjected to their inherent limitations. By controlling confounding variables, we hypothesized that known risk factors be re-evaluated and novel ones be discovered. This study aimed to analyze the independent risk factors for LLD after primary THA in patients with non-traumatic osteonecrosis of the femoral head (ONFH).

METHODS

We retrospectively reviewed patients with non-traumatic ONFH who underwent unilateral THA between 2014 and 2021. All patients were operated by one senior surgeon using a single implant. Demographic data, surgical parameters, and radiological findings (pre-operative LLD, Dorr classification, and femoral neck resection) were analyzed to identify the risk factors of ≥ 5 mm post-operative LLD based on radiological measurement and to calculate odds ratios by logistic regression analysis. Post hoc power analysis demonstrated that the number of analyzed patients was sufficient with 80% power.

RESULTS

One hundred and eighty-six patients were analyzed, including 96 females, with a mean age of 58.8 years at the time of initial THA. The average post-operative LLD was 1.2 ± 2.9 mm in the control group and 9.7 ± 3.2 mm in the LLD group, respectively. The LLD group tended to have minimal pre-operative LLD than the control group (-3.2 ± 5.1 mm vs. -7.9 ± 5.8 mm p = 2.38 × 10- 8). No significant difference was found between the groups in age, gender, body mass index, femoral cortical index, and implant size.

CONCLUSION

Mild pre-operative LLD is associated with an increased risk of post-operative LLD after primary THA in patients with ONFH. Thus, surgeons should recognize pre-operative LLD to achieve an optimal outcome and must inform patients about the risk of developing LLD.

Augmented reality-assisted versus conventional total hip arthroplasty: a systematic review and meta-analysis

BACKGROUND

Extended reality (XR), including virtual reality, augmented reality (AR), and mixed reality, has been used to help achieve accurate acetabular cup placement in total hip arthroplasty (THA). This study aimed to compare the differences between XR-assisted and conventional THA.

METHODS

In this systematic review and meta-analysis, electronic databases including PubMed, Embase, Web of Science, Cochrane Central Register of Controlled Trials (CENTRAL), and clinicaltrials.gov were searched for studies from inception to September 10, 2023. The outcomes were accuracy of inclination and anteversion, duration of surgery, and intraoperative blood loss. Meta-analysis was performed using Review Manager 5.4 software.

RESULTS

A total of five studies with 396 patients were included in our study. The pooled results indicated AR-assisted THA had better accuracy of inclination and anteversion than conventional THA (SMD = - 0.51, 95% CI [- 0.96 to - 0.07], P = 0.02; SMD = - 0.96, 95% CI [- 1.19 to - 0.72], P < 0.00001), but duration of surgery and intraoperative blood loss were similar in the two groups.

CONCLUSION

This systematic review and meta-analysis found that AR-assisted THA had better accuracy of inclination and anteversion than conventional THA, but the duration of surgery and intraoperative blood loss were similar in the two groups. Based on the pooled results, we suggested that AR can provide more precise acetabular cup placement than conventional methods in THA.

Combining the advantages of 3-D and 2-D templating of total hip arthroplasty using a new tin-filtered ultra-low-dose CT of the hip with comparable radiation dose to conventional radiographs

BACKGROUND

Inaccurately scaled radiographs for total hip arthroplasty (THA) templating are a source of error not recognizable to the surgeon and may lead to inaccurate reconstruction and thus revision surgery or litigation. Planning based on computed tomography (CT) scans is more accurate but associated with higher radiation exposure. The aim of this study was (1) to retrospectively assess the scaling deviation of pelvic radiographs; (2) to prospectively assess the feasibility and the radiation dose of THA templating on radiograph-like images reconstructed from a tin-filtered ultra-low-dose CT dataset.

METHODS

120 consecutive patients were retrospectively analyzed to assess the magnification error of our current THA templates. 27 consecutive patients were prospectively enrolled and a radiographic work-up in the supine position including a new tin-filtered ultra-low-dose CT scan protocol was obtained. THA was templated on both images. Radiation dose was calculated.

RESULTS

Scaling deviations between preoperative radiographs and CT of ≥ 5% were seen in 25% of the 120 retrospectively analyzed patients. Between the two templates trochanter tip distance differed significantly (Δ2.4 mm, 0-7 mm, p = 0.035)), predicted femoral shaft size/cup size was the same in 45%/41%. The radiation dose of the CT (0.58 mSv, range 0.53-0.64) was remarkably low.

CONCLUSION

Scaling deviations of pelvic radiographs for templating THA may lead to planning errors of ≥ 3 mm in 25% and ≥ 6 mm in 2% of the patients. 2-D templating on radiograph-like images based on tin-filtered ultra-low-dose CT eliminates this source of error without increased radiation dose.

LEVEL OF EVIDENCE

Retrospective and prospective comparative study, Level III.

Does Intra-operative Fluoroscopy Significantly Improve Component Position in a Primary Total Hip Arthroplasty? Our Experience in a Tertiary Care Hospital

Background

Optimal component placement, equalization of leg lengths, and recreation of offset are important surgical objectives during total hip arthroplasty (THA). Historically, many surgeons have aimed for the Lewinnek's " safe zone," which is defined as 30°-50° of abduction and 5°-25° of anteversion. Methods for optimizing cup position include anatomic landmarks, room landmarks, acetabular cup coverage, and ischial or pubis palpation. Malposition of the acetabular component after total hip arthroplasty (THA) is related to dislocation of the prosthetic femoral head, increased polyethylene liner wear, and limited range of motion. The orientation of the acetabular component comprises inclination and anteversion. Although the inclination of the acetabular component can be easily measured on plain radiographs, the calculation of the anteversion is difficult. This study evaluates the effect of intra-operative fluoroscopy on component position, mainly anteversion and inclination of the acetabular cup, during a total hip arthroplasty.

Methods

106 hips undergoing total hip arthroplasty were assessed, and the decision to use fluoroscopy assistance was randomized based on a simple randomization technique. A total of 48 patients were operated on with fluoroscopy assistance and 58 patients without fluoroscopy assistance. All patients were evaluated postoperatively for version of component on anteroposterior radiographs of the hip using the method of Liaw et al. and for inclination of component on anteroposterior radiographs using the method of Woo and Morrey.

Results

The mean version for the non-fluoroscopy (NF) group was 15.62° and the mean inclination was 44.22°, with 15.5% (9 out of 58) of the patients who did not fit into Lewinnek's safe zone for version and 25.9% (15 out of 58) of the patients who were outliers for inclination of the acetabular cup position. The mean version for the fluoroscopy group (F) was 11.80° and the mean inclination was 47.05°, with 0% (0 out of 48) of the patients who did not fit into Lewinnek's safe zone for version and 12.5% (6 out of 48) of the patients who were outliers for inclination of the acetabular cup position.

Conclusion

While the mean version and inclination of the acetabular component were comparable for both groups, outliers for version and inclination were far more common in the group of patients who underwent surgery without intra-operative fluoroscopic assistance. Therefore, intra-operative fluoroscopy imaging confirms appropriate inclination (abduction) and version of acetabular cup position according to Lewinnek's safe zone and prevents undesirable component position during a total hip arthroplasty while adding a maximum of 5 min to the operative time.

Assessing Leg Length and Offset in Anterior Total Hip Arthroplasty: Overlay Versus AP Pelvis Intraoperative Radiographic Techniques: A Retrospective Cohort Study

INTRODUCTION

Two intraoperative radiographic techniques to determine leg length and offset during anterior total hip arthroplasty (THA) are the AP pelvis and overlay techniques. The AP pelvis method measures LLDs and offset using AP fluoroscopic images, whereas the overlay method uses printed images of the native and replaced hips. The purpose of this study was to compare these techniques regarding clinical and radiographic LLD and offset discrepancies.

METHODS

Patients of a single surgeon at two hospitals from September 2017 to January 2021 were retrospectively reviewed. Clinically detectable LLD was recorded. Radiographic measurements were obtained from preoperative and postoperative radiographs. LLD was determined based on the vertical distance between the lesser trochanters and the ischial tuberosities. Total offset was measured using a combination of femoral and medial offset. The Student t-test, Fisher exact test, and Wilcoxon rank sum tests were used for statistical analysis.

RESULTS

Seventy-one procedures were done using the overlay technique and 61 used for the AP pelvis technique. No significant differences were observed in mean postoperative LLD (2.66 versus 2.88 mm, P = 0.66) and mean postoperative offset discrepancy (5.37 versus 4.21 mm, P = 0.143) between the overlay versus AP pelvis groups. The mean preoperative to postoperative absolute difference in offset was less than 5 mm in both groups. Clinically detectable LLD was noted in six of 71 patients in the overlay group and one of 61 in the AP pelvis group (P = 0.123).

CONCLUSION

No notable differences were observed in intraoperative leg length and offset discrepancies during direct anterior THA between the AP pelvis and overlay techniques, suggesting they are equally effective in determining LLD and offset intraoperatively. The choice of technique to use anterior THA should be based primarily on the surgeon's preference, comfort, and available resources.

Perioperative management of leg-length discrepancy in total hip arthroplasty: a review

Leg-length discrepancy (LLD) presents a significant management challenge to orthopedic surgeons and remains a leading cause of patient dissatisfaction and litigation after total hip arthroplasty (THA). Over or under-lengthening of the operative extremity has been shown to have inferior outcomes, such as dislocation, exacerbation of back pain and sciatica, and general dissatisfaction postoperatively. The management of LLD in the setting of THA is multifactorial, and must be taken into consideration in the pre-operative, intra-operative, and post-operative settings. In our review, we aim to summarize the best available practices and techniques for minimizing LLD through each of these phases of care. Pre-operatively, we provide an overview of the appropriate radiographic studies to be obtained and their interpretation, as well as considerations to be made when templating. Intra-operatively, we discuss several techniques for the assessment of limb length in real time, and post-operatively, we discuss both operative and non-operative management of LLD. By providing a summary of the best available practices and strategies for mitigating the impact of a perceived LLD in the setting of THA, we hope to maximize the potential for an excellent surgical and clinical outcome.

Are immediate postoperative X-Rays valuable in evaluating complications of primary total hip arthroplasty?

PURPOSE

This study aimed to investigate the complications of primary total hip arthroplasty based on immediate postoperative X-rays. The overall quality and cost of X-rays were assessed.

METHODS

The institutional database was queried to identify all patients who underwent total hip arthroplasty in a single institution between January 1, 2018, and December 31, 2018. Immediate postoperative X-rays were reviewed to identify the complications such as periprosthetic fractures, dislocation, and fixation failure. The quality and cost of X-ray were assessed. The complications were categorized as "known" and "unknown" according to the intraoperative fluoroscopic results.

RESULTS

A total of 518 total hip arthroplasties were included in this study. Based on intraoperative fluoroscopy, periprosthetic fractures were found in 10 (2%) THAs. Compared to the X-rays taken immediately after surgery, 9 periprosthetic fractures (recorded as "known") were found and 1 was not (recorded as "unknown"). There was no significant difference between intraoperative fluoroscopy and X-rays (P > 0.05). Of the 518 X-rays, 225 (43%) were of suboptimal quality. The cost of a single portable pelvic X-ray was $647.

CONCLUSION

In total hip arthroplasty, X-rays taken immediately after surgery rarely reveal unknown complications. The X-rays are often of suboptimal quality, have minimal clinical utility, and are less cost-effective.

The effect of varus stem placement on joint offset during total hip arthroplasty: a virtual study

INTRODUCTION AND AIMS

With total hip replacement (THR), varus alignment of an uncemented stem will increase offset which can have significant detrimental effects on muscular balance, leg length and overall satisfaction. Thus, we used 3D planning software to determine the change in joint offset with increasing varus stem placement.

METHODS

Eight patients undergoing THR had routine computed tomography (CT) scans to allow for 3D hip planning. Each set of CTs was templated with a straight stem and an uncemented acetabular cup. Initial templating was performed to reproduce native leg length and offset. The templated stem was then rotated into varus at 1° intervals, up to 6° varus while offset changes for all varus positions were noted. This was repeated for each of 3 neck angles, 125°, 135° and 135° lateral and for each stem sizes 1, 3, 5 and 7.

RESULTS

Overall, there was a mean 1.5 mm increase in offset for every 1° of varus. The stems with a 125° neck angle had the greatest increase in mean offset at 1.6 mm for every 1° of varus. The stem neck angles of 135° lateral offset and 135° standard offset, had a mean increase in offset of 1.5 mm and 1.4 mm respectively for every 1° of varus. A greater mean increase in offset for every 1° of varus was observed with increasing stem size.

CONCLUSIONS

We have quantified the relationship between alignment and offset with every 1° of varus placement increasing hip offset for straight stems by 1.5 mm. This can be used as a guide for surgeons during THR so that they have a better quantitative understanding of how varus placement of the stem affects the hip offset.

Accuracy and Reliability of Software Navigation for Acetabular Component Placement in THA: An In Vitro Validation Study

Background and Objectives: Intraoperative fluoroscopy can be used to increase the accuracy of the acetabular component positioning during total hip arthroplasty. However, given the three-dimensional nature of cup positioning, it can be difficult to accurately assess inclination and anteversion angles based on two-dimensional imaging. The purpose of this study is to validate a novel method for calculating the 3D orientation of the acetabular cup from 2D fluoroscopic imaging. Materials and Methods: An acetabular cup was implanted into a radio-opaque pelvis model in nine positions sequentially, and the inclination and anteversion angles were collected in each position using two methods: (1) a coordinate measurement machine (CMM) was used to establish a digitalized anatomical coordinate frame based on pelvic landmarks of the cadaveric specimen, and the 3D position of the cup was then expressed with respect to the anatomical planes; (2) AP radiographic images were collected, and a mathematical formula was utilized to calculate the 3D inclination and anteversion based on the 2D images. The results of each method were compared, and interrater and intrarater reliably of the 2D method were calculated. Results: Interrater reliability was excellent, with an interclass correlation coefficient (ICC) of 0.988 (95% CI 0.975–0.994) for anteversion and 0.997 (95% CI 0.991–0.999) for inclination, as was intrarater reliability, with an ICC of 0.995 (95% CI 0.985–0.998) for anteversion and 0.998 (95% CI 0.994–0.999) for inclination. Intermethod accuracy was excellent with an ICC of 0.986 (95% CI: 0.972–0.993) for anteversion and 0.993 (95% CI: 0.989–0.995) for inclination. The Bland–Altman limit of agreement, which represents the error between the 2D and 3D methods, was found to range between 2 to 5 degrees. Conclusions: This data validates the proposed methodology to calculate 3D anteversion and inclination angles based on 2D fluoroscopic images to within five degrees. This method can be utilized to improve acetabular component placing intraoperatively and to check component placement postoperatively.

Does Surgical Approach Influence the Natural History of the Unstable Total Hip Arthroplasty?

BACKGROUND

Dislocation following total hip arthroplasty (THA) is a significant complication that occurs in 0.3%-10% of cases with 13%-42% of patients requiring revision surgery. The literature has primarily focused on the dislocation risk associated with different surgical approaches. However, little is known about the natural history of the dislocated hip and whether surgical approach of the index THA is associated with further instability and revision surgery.

METHODS

This is a retrospective, single-center, multi-surgeon consecutive case series of all patients who experienced THA dislocation from 2002 to 2020. Patients were excluded if the initial dislocation was secondary to infection or fracture. The natural history of the cohort as per approach was determined. Outcome measurements of interest were the number of dislocations; the treatment surrounding each dislocation; the necessity and type of revision; and the complications encountered.

RESULTS

Of the 75 patients, 58 (77%) dislocated within 6 months following primary THA. The anterior group had greater odds of dislocation within 2 weeks post-THA compared to the lateral and posterior groups (P = .04). The mean number of dislocations per patient was significantly lower in the anterior (1.5 ± 0.7) compared to the lateral (2.4 ± 1.2) and posterior (2.1 ± 1.0) groups (P = .02). Revision surgery was needed in 30% (6/20) of patients in the anterior, 69% (25/36) of the posterior, and 68% (13/19) of the lateral groups (P = .01).

CONCLUSION

This study illustrates that while primary THA dislocations happen earlier with the anterior approach, they are typically less complicated and have a lower risk of recurrent instability and revision surgery.

Accuracy of the Horizontal Calibrator in Correcting Leg Length and Restoring Femoral Offset in Total Hip Arthroplasty

Background

Limb length discrepancy (LLD) is one of the most common postoperative complications and can cause serious consequences. Poor recovery of femoral offset (OD) will result in weakness of the patient's external rotator muscles and affect the patient's postoperative function. The study is aimed to present a simple approach that compensates for the shortcomings of previous measuring devices and combines the advantages of different measuring devices to provide more accurate limb length and femoral offset restoration in total hip arthroplasty (THA).

Methods

This study was a prospective controlled trial involving 89 patients with THA. Group I (n = 44) was used for intraoperative measurement of THA with our self-designed horizontal calibrator. Group II (n = 45) was measured by a traditional freehand technique. The main outcome indicators were measured on the Neusoft PACS, including LLD, femoral offset deviation, and operative time. IBM SPSS 23.0 was used for data analysis.

Results

The independent sample t-test was performed for all the data. The operative time, preoperative radiographic LLD, and OD of Group I and Group II had no statistical significance. Postoperative LLD of Group I and Group II were 2.5 ± 2.1 mm (range −5.7 to 8.3 mm) and 6.2 ± 4.3 mm (range −18.0 to 15.2 mm), and the independent sample t-test data of both (P < 0.001; 95% CI = −5.1, −2.2) showed statistical significance. In Group I, there were 38 THAs with LLD <5 mm, accounting for 86% and there were 44 THAs with LLD <10 mm, accounting for 100%. In Group II, there were 20 THAs with LLD <5 mm, accounting for 44%. There were 36 THAs with LLD <10 mm, covering for 80%. There was no significant difference in postoperative femoral offset and OD.

Conclusion

The horizontal calibrator can provide more accurate limb length and femoral offset recovery in THA. It is a simple surgical technique that does not add additionally surgical costs and does not significantly increase operative time, providing a new solution for surgeons to resolve postoperative LLD and restore femoral offset.

The Use of Intraoperative Digital Radiography Alignment Software to Assess Implant Placement in Total Hip Arthroplasty

PURPOSE OF REVIEW

Total hip arthroplasty (THA) is a highly successful surgery with growing rates of utilization in the USA, but surgical outliers leading to postoperative complications remain a concern. There is need for a standard system of accurate, predictable intraoperative evaluation to decrease component positioning outliers. Many current intraoperative imaging systems have shown promise, but there are drawbacks that have led to slow adoption. Digital radiography, in conjunction with Radlink™ technology, is a potential solution to this problem. This review summarizes the clinical application and scientific literature regarding the use of Radlink™ in THA.

RECENT FINDINGS

Traditional surgeon-directed component placement can result in surgical outliers. This is especially true not only among low-volume arthroplasty surgeons, but can also occur with experienced, high-volume surgeons. Digital radiography allows for more precise and accurate placement of the acetabular cup in a targeted range in an effort to improve THA outcomes. Intraoperative images are obtained quickly, and they are accurate when compared to postoperative images. Additionally, the use of Radlink™ results in a significant decrease in leg length and femoral offset outliers. The adoption of Radlink™ technology in THA can significantly decrease surgical outliers, especially errors in acetabular cup placement, leg length, and femoral offset. Digital radiography avoids many of the previous aversions to intraoperative imaging as it produces a fast, reliable image with little radiation exposure and minimal interruption to workflow. There is the potential for Radlink™ use to provide superior patient outcomes, as a decrease in surgical outliers can minimize implant malpositioning with resultant need for revision THAs. Radlink™ may also provide benefit in analyzing other parameters, such as component sizing.

Usefulness of intraoperative C-arm image intensifier in reducing errors of acetabular component during primary total hip arthroplasty: an application of Widmer's method

Background

Acetabular prosthesis positioning in total hip arthroplasty (THA) is crucial in reducing the risk of dislocation. There has been minimal research on the proper way to put the acetabular components into the safe zone intraoperatively. Assessment of version by intraoperative imaging intensifier is very valuable. The value of Widmer’s method, using the intraoperative C-arm available to determine cup anteversion was assessed.

Methods

One hundred one hips in 91 patients who underwent primary THA were eligible for inclusion. Utilizing intraoperative C-arm images, measurement was performed using the technique described by Widmer. The values obtained using 3D computed tomography postoperatively, which determined the anteversion of the acetabular component, were regarded as the reference standard.

Results

The method of Widmer obtained values similar to those obtained using 3D computed tomography and was considered accurate (n.s.). All 101 hips were positioned in the set target zone. Among the 101 hips, the cup position in nine hips (8.9%) was changed. The dislocation rate in our study was 1.0% with all dislocations occurring in hips placed in the target zone. The mean Harris hip score after THA in 1 year was 94.2 (82-98).

Conclusions

The method of Widmer was accurate using intraoperative imaging intensifier for the measurement of the anteversion of the acetabular component during THA, with reference to the anteversion obtained from the 3D computed tomography. Also, utilizing intraoperative C-arm imaging was very useful because it allowed for correction of the position of the acetabular cup.

The Effect of Intraoperative Radiographs on Component Position and Leg Length during Routine Posterior Approach Total Hip Arthroplasty

Purpose

Accurate component placement and restoration of patient anatomy are critical in total hip arthroplasty (THA) surgery. Although intraoperative radiographs are sometimes utilized, it is unclear whether this practice can improve accuracy.

Materials and Methods

This study evaluated acetabular cup abduction, anteversion, leg length, and offset among 100 posterior approach THAs performed without imaging (No X-ray group) and compared them to a subsequent series of 100 THAs where an intraoperative radiograph was taken with the trial components in place (X-ray group). THAs were performed using a posterior approach by a single, experienced surgeon whose goal was to place the cup at 45° of abduction and 30° of anteversion. Supine anteroposterior pelvic digital radiographs taken at the first (nominal 4-week) postoperative visit were used for measurements.

Results

Slight differences in cup abduction (47°±6° vs 44°±6°, respectively, P=0.003) and anteversion angle (35°±6° vs 31°±6°, respectively, P<0.001) were observed between the X-ray and No X-ray groups; however, a similar proportion of cups within 10° of the target angles was observed (76% vs 83%, respectively, P=0.22). No difference in offset measurements (1.1±6.6 mm vs 0.3±6.9 mm, respectively, P=0.42) or leg lengths (0.3±3.8 mm vs 0.3±4.8 mm, respectively, P=0.94) was observed between the X-ray and No X-ray groups; however, the X-ray group showed less leg length variation (P=0.05).

Conclusion

In this study, the routine use of intraoperative radiographs was not associated with improved implant positioning for uncomplicated primary THA.

Usefulness of a Simple Preoperative Planning Technique using Plain X-rays for Direct Anterior Approach for Total Hip Arthroplasty

Objective

To examine the accuracy, reliability, and reproducibility of a simple preoperative planning technique using plain X‐rays.

Methods

A retrospective analysis of 96 consecutive cases of primary direct anterior approach (DAA)‐total hip arthroplasty (THA) from July 2015 to December 2018 was performed. The 96 patients included 24 males and 72 females, with an average age of 70 years. The standard AP pelvis radiographs with the patients' hips extended and internally rotated were obtained pre‐ and postoperatively. The preoperative planning was also completed on the standardized AP pelvic radiographs. The prearranged cup positioning was radiologically measured intraoperatively using fluoroscopy. The correct leg length was assessed intraoperatively, which was compared with the preoperative planning. The component positioning was measured by three independent researchers. Two of the researchers completed the measurements three times, and intra‐observer and inter‐observer reliability were calculated. All patients received at least 6 months follow‐up (6 months–4 years).

Results

In all cases, the median leg length discrepancy (LLD) was 4.4 mm (range 1.6–15.9 mm), and 84 patients had an LLD smaller than 10 mm, of which 58 patients had an LLD of less than 5 mm. None of the patients had a critical LLD of 2 cm or larger. The multivariable logistic regression for LLD (safe range: yes/no) with the co‐variables including gender, ASA classification, type of cup, the surgeon's experience level, and the presence of a total hip arthroplasty (THA) on the contralateral side did not present statistical significance. The median angle of the inclination of the acetabular component (IA) was 42.3° (range: 28.7°–52.2°). Ninety‐one patients were within the defined safe range. The hit ratio for the cup to be within the safe zone was significantly higher for the Pinnacle cups than that for the Continuum cups (P < 0.05). However, there was no significant difference in gender, ASA classification, the surgeon's experience level, and the presence of a total hip arthroplasty (THA) on the contralateral side. The median of its anteversion (AA) was 20.6° (range: 10.6°–40.1°). Only 41 patients were within the defined safe range. None of the co‐variables presented a statistical significance affecting the AA of the cup positioning. Meanwhile, the average fluoroscopy time for the cup positioning (n = 86, missing data in 10 cases) was 4 seconds (range: 1–74), with most of the patients (97.9%) having a fluoroscopy time of fewer than 20 seconds.

Conclusions

The combination of correct preoperative planning and standardized intraoperative measurements can reestablish right leg length and assure the correct cup positioning.

Misshapen Pelvis Landmark Detection With Local-Global Feature Learning for Diagnosing Developmental Dysplasia of the Hip

Developmental dysplasia of the hip (DDH) is one of the most common orthopedic disorders in infants and young children. Accurately detecting and identifying the misshapen anatomical landmarks plays a crucial role in the diagnosis of DDH. However, the diversity during the calcification and the deformity due to the dislocation lead it a difficult task to detect the misshapen pelvis landmarks for both human expert and computer. Generally, the anatomical landmarks exhibit stable morphological features in part regions and rigid structural features in long ranges, which can be strong identification for the landmarks. In this paper, we investigate the local morphological features and global structural features for the misshapen landmark detection with a novel Pyramid Non-local UNet (PN-UNet). Firstly, we mine the local morphological features with a series of convolutional neural network (CNN) stacks, and convert the detection of a landmark to the segmentation of the landmark's local neighborhood by UNet. Secondly, a non-local module is employed to capture the global structural features with high-level structural knowledge. With the end-to-end and accurate detection of pelvis landmarks, we realize a fully automatic and highly reliable diagnosis of DDH. In addition, a dataset with 10,000 pelvis X-ray images is constructed in our work. It is the first public dataset for diagnosing DDH and has been already released for open research. To the best of our knowledge, this is the first attempt to apply deep learning method in the diagnosis of DDH. Experimental results show that our approach achieves an excellent precision in landmark detection (average point to point error of 0.9286mm) and illness diagnosis over human experts. Project is available at http://imcc.ustc.edu.cn/project/ddh/.

A Novel Method for Accurate Preoperative Templating for Total Hip Arthroplasty Using a Biplanar Digital Radiographic (EOS) System

Background:

Accurate preoperative planning for total hip arthroplasty (THA) relies on conventional anteroposterior radiographs. The difficulty of determining the magnification factor of radiographs is a major limitation. Despite the use of markers for calibration, identifying the plane of the hip joint is a major challenge. The aim of this study was to evaluate the accuracy of a novel method for image calibration and preoperative planning in THA involving the use of a biplanar radiographic (EOS imaging) system and a self-designed coin device.

Methods:

Biplanar radiographs (with the self-designed coin device) and a conventional anteroposterior radiograph (with a coin) were made for 26 patients after primary THA. The agreement between the actual and calculated diameters for each method was assessed using the concordance correlation coefficient (CCC) and Bland-Altman plots. In addition, 15 patients undergoing primary THA were prospectively enrolled to evaluate the EOS imaging-based method (EOS method), with biplanar radiographs made with use of the coin device. The accuracy of the preoperative predicted size of the implants was evaluated.

Results:

Both the EOS and conventional anteroposterior radiograph-based methods were reliable in repeated measurements of the diameter of the artificial femoral head in the reproducibility study, with the average CCCs for both methods >0.990. The agreement between the actual and EOS-based calculated diameters of the artificial femoral head was excellent, with a CCC of >0.990, while the agreement was poor between the actual and anteroposterior radiograph-based calculated diameters, with a CCC of <0.75. The EOS method exhibited a lower absolute difference (0.09 ± 0.07 mm) between the actual and calculated diameters compared with conventional anteroposterior radiography (1.26 ± 0.86 mm) (p < 0.001). EOS-based preoperative plans also exhibited excellent performance on the accuracy of the planning of the cups and stems; only 1 patient (6.7%) had a final implanted cup that differed by 1 size from the predicted size. Two patients (13.3%) had final implanted stems that differed by 1 size from the predicted size, and for 1 patient (6.7%), the stem size was off by ≥2 sizes.

Conclusions:

We describe a novel and easy-to-use method for the accurate calibration of radiographs and preoperative planning for THA. The EOS method evaluated in this study is an alternative method for preoperative planning in clinical practice.

Does An Augmented Reality-based Portable Navigation System Improve the Accuracy of Acetabular Component Orientation During THA? A Randomized Controlled Trial

BACKGROUND

We developed an augmented reality (AR)-based portable navigation system in which the surgeon can view the pelvic plane and placement angle of an acetabular cup on the display of a smartphone during THA.

QUESTIONS/PURPOSES

(1) Is acetabular component placement more accurate using the AR-based portable navigation system compared with the conventional freehand technique? (2) Is intraoperative measurement of placement angle more accurate when using the AR-based portable navigation system compared with a goniometer?

METHODS

Forty-six patients were randomly assigned to undergo acetabular cup placement during THA using the AR-based portable navigation system (AR navigation group) or placement of a mechanical alignment guide (conventional group). All surgeries were performed with the patient in the lateral decubitus position. We compared the absolute value of the difference between the targeted placement angle and postoperative measured placement angle between the groups using two types of imaging (radiography and CT).

RESULTS

In terms of radiographic inclination, the mean differences between the targeted placement angle and postoperative measured angle were smaller in the AR navigation group than in the conventional group for both radiographs and CT images (2.3° ± 1.4° versus 3.9° ± 2.4°, respectively; p = 0.009 and 1.9° ± 1.3° versus 3.4° ± 2.6°, respectively; p = 0.02). There were no differences in radiographic anteversion between the two groups. No complications were associated with the use of the AR-based portable navigation system.

CONCLUSIONS

This system yielded no differences in acetabular anteversion accuracy, and no clinically important differences in acetabular inclination. Therefore, at this time we cannot recommend this device as its costs and risks cannot be justified based on the absence of a clinically meaningful difference in cup placement accuracy. Although we detected no complications, this was a small series, and this approach adds both surgical time and pins in the ilium.

LEVEL OF EVIDENCE

Level I, therapeutic study.

Determining and Achieving Target Limb Length and Offset in Total Hip Arthroplasty Using Intraoperative Digital Radiography

BACKGROUND

Achieving appropriate limb length and offset in total hip arthroplasty (THA) is challenging. Target limb length and offset may not always mean equal radiographic measurements bilaterally. The goal of this study is to introduce a method for determining as well as achieving target limb length and offset using digital radiographic measurements.

METHODS

One hundred and two consecutive patients with unilateral hip osteoarthritis undergoing primary THA in the lateral decubitus position were included. Limb length and offset were measured on anterior-posterior pelvic radiographs preoperatively, intraoperatively, and postoperatively. Offset was defined as the length of a line parallel to the inter-teardrop line, extending from the edge of the ischium, at about the lower border of the ipsilateral obturator foramen, to the edge of the femoral cortex, usually at, or just below, the neck resection level. Target limb length was determined for each patient based on patient perception and severity of disease. Target offset equaled the contralateral limb. Using intraoperative digital radiography, adjustments were made until targets were achieved and the hip was stable. Patients were followed for an average of 4.2 years postoperatively.

RESULTS

Limb length was within 5 mm of target measurements in 100% of patients and offset was within 5 mm of targets in 97.1%. Target measurements differed by >5 mm from the contralateral side in 2.0% of limb length and 2.9% of offset measurements. There were no significant differences between intraoperative and postoperative limb length (P = .261) or offset (P = .747) measurements. At final follow-up, there were no dislocations or reoperations and average Hip disability and Osteoarthritis Outcome Score for Joint Replacement was 95.78.

CONCLUSION

Target limb length and offset goals can be determined for most patients undergoing THA. Targets are not always equal to the contralateral side. Intraoperative digital radiography can allow surgeons to accurately achieve target limb length and offset to within 5 mm in a homogenous cohort of patients with unilateral hip osteoarthritis with excellent clinical outcomes.

A new method for intraoperative assessment of leg length, sizing and placement of the components in total hip replacement

BACKGROUND

Intraoperative radiograph of the pelvis is a well-established way to avoid misplacement/undersizing of the components and leg length discrepancy (LLD) in total hip replacement (THR). We describe a method for the obtainment and the evaluation of intraoperative radiographs with a sophisticated wireless radiographic system and a computerized digital tool originally used for preoperative templating.

METHODS

In this retrospective case-control study, 60 patients with unilateral hip osteoarthritis who underwent THR with intraoperative radiographic check with the conventional method (n = 30, control group) or the new method (AGFA flat panel DR14eG™/Orthosize™, n = 30, case group) were evaluated and compared for operation time, intraoperative changes in size/placement of the components and final radiological outcome (LLD, acetabular inclination and femoral offset) based on postoperative radiographs of the pelvis.

RESULTS

Mean operation time was lower in case group (85.3 min vs. 103.3 min, p value < 0.005), as well as mean absolute LLD (1.93 mm vs. 2.94 mm, p value = 0.242). There was a higher percentage of intraoperative changes in the offset of the prostheses' head (70% vs. 40%, p value = 0.018) and a significantly lower percentage of patients with LLD > 5 mm in the case group (0% vs. 27%, p value = 0.002).

CONCLUSIONS

This new method for the obtainment and assessment of intraoperative radiographs proved to be fast and assuring for keeping LLD below 5 mm in all patients.

Changes in acetabular orientation during total hip arthroplasty

AIMS

The aims of this study were to determine the change in pelvic sagittal alignment before, during, and after total hip arthroplasty (THA) undertaken with the patient in the lateral decubitus position, and to determine the impact of these changes on acetabular component position.

PATIENTS AND METHODS

We retrospectively compared the radiological pelvic ratio among 91 patients undergoing THA. In total, 41 patients (46%) were female. The mean age was 61.6 years (sd 10.7) and the mean body mass index (BMI) was 20.0 kg/m² (sd 5.5). Anteroposterior radiographs were obtained: in the standing position preoperatively and at six weeks postoperatively; in the lateral decubitus position after trial reduction intraoperatively; and in the supine position in the post-anaesthesia care unit. Pelvic ratio was defined as the ratio between the vertical distance from the inferior aspect of the sacroiliac (SI) joints to the superior pubic symphysis and the horizontal distance between the inferior aspect of the SI joints. Changes in the apparent component position based on changes in pelvic ratio were determined, with a change of > 5° considered clinically significant. Analyses were performed using Wilcoxon's signed-rank test, with p < 0.05 considered significant.

RESULTS

Intraoperatively, in the lateral decubitus position, the pelvic ratio increased (anterior tilt) in 69.4% of cases, did not change significantly in 20.4%, and decreased (posterior tilt) in 10.2% of cases. When six-week postoperative radiographs were compared with preoperative radiographs, the pelvic ratio decreased in 44.9% of cases, did not change significantly in 42.3%, and increased in 12.8% of cases. This change in alignment correlated with a change in acetabular component version of > 5° in 79.6% of cases intraoperatively and 57.7% of cases at six weeks postoperatively.

CONCLUSION

Changes in pelvic sagittal pelvic position occur throughout THA that, if unaccounted for, introduce errors in acetabular component placement. The use of intraoperative imaging may help the appropriate placement of the acetabular component. Cite this article: Bone Joint J 2019;101-B(6 Supple B):45-50.

Intra-operative digital imaging: assuring the alignment of components when undertaking total hip arthroplasty

Aims

The aims of this study were to examine the rate at which the positioning of the acetabular component, leg length discrepancy and femoral offset are outside an acceptable range in total hip arthroplasties (THAs) which either do or do not involve the use of intra-operative digital imaging.

Patients and Methods

A retrospective case-control study was undertaken with 50 patients before and 50 patients after the integration of an intra-operative digital imaging system in THA. The demographics of the two groups were comparable for body mass index, age, laterality and the indication for surgery. The digital imaging group had more men than the group without. Surgical data and radiographic parameters, including the inclination and anteversion of the acetabular component, leg length discrepancy, and the difference in femoral offset compared with the contralateral hip were collected and compared, as well as the incidence of altering the position of a component based on the intra-operative image.

Results

Digital imaging took a mean of five minutes (2.3 to 14.6) to perform. Intra-operative changes with the use of digital imaging were made for 43 patients (86%), most commonly to adjust leg length and femoral offset. There was a decrease in the incidence of outliers when using intra-operative imaging compared with not using it in regard to leg length discrepancy (20% versus 52%, p = 0.001) and femoral offset inequality (18% versus 44%, p = 0.004). There was also a difference in the incidence of outliers in acetabular inclination (0% versus 7%, p = 0.023) and version (0% versus 4%, p = 0.114) compared with historical results of a high-volume surgeon at the same centre.

Conclusion

The use of intra-operative digital imaging in THA improves the accuracy of the positioning of the components at THA without adding a substantial amount of time to the operation.

Cite this article: Bone Joint J 2018;100B(1 Supple A):36–43.

The learning curve in short-stem THA: influence of the surgeon's experience on intraoperative adjustments due to intraoperative radiography

Introduction

Short-stem THA has become increasingly popular over the last decade. However, implantation technique differs from conventional THA and thus possibly involves a distinct learning curve. The purpose of this study was to evaluate the value of intraoperative radiography and the influence of the surgeon’s experience on intraoperative adjustments in short-stem THA.

Methods

A total of 287 consecutive short-stem THAs, operated by a total of 24 senior consultants, consultants and residents in training, were prospectively included. Intraoperative radiography was performed after trial reduction. Preoperative planning and intraoperative outcome with regard to positioning, sizing of components as well as resulting offset and leg length were compared. Frequency, reason and type of intraoperative adjustments were documented in relation to the surgeon’s experience. Operation time was assessed.

Results

One hundred and fifty-six (54.4%) procedures were carried out by one of three senior consultants, and a total of nine consultants and 12 residents in training performed 105 (36.6%) and 26 (9.0%) operations, respectively. In 121 cases (42.2%), intraoperative adjustments were made following intraoperative radiography. Intraoperative adjustments of one or more components were made by senior consultants in 51 cases (32.7%), by consultants in 53 cases (50.5%) and by residents in 17 cases (65.4%), respectively. The most common cause was undersizing of the stem. Operation time varied markedly between groups of surgeons.

Discussion

Short-stem THA involves a learning curve. Intraoperative radiography is decisive for prevention of malpositioning and undersizing of components, as well as loss of offset and leg length discrepancies. Hence, it should be considered mandatory, especially for less experienced surgeons.

Total Hip Arthroplasty After Transtrochanteric Rotational Osteotomy for Osteonecrosis of the Femoral Head: A Mean 10-Year Follow-Up

BACKGROUND

The objective of the present study was to investigate clinical, quality of life, and radiographic outcomes of patients who underwent total hip arthroplasty (THA) after transtrochanteric rotational osteotomy (TRO) for osteonecrosis of the femoral head (ONFH).

METHODS

We performed a case-control study. The participants were 29 patients (34 hips) who underwent THA after TRO (TRO group). These patients had a mean age at surgery of 51.6 years (range, 30-72 years) and underwent postoperative follow-up for a mean period of 10.5 years (range, 3-19 years). For the control group (primary group), we included 58 patients (68 hips) who underwent primary THA for ONFH, matching for age and gender.

RESULTS

The Harris Hip Scores at the last follow-up were significantly poorer in the TRO group than in the primary group. Similarly, preoperative and postoperative hip range of motion was significantly poorer in the TRO group than in the primary group. Quality of life (Short Form-36, Oxford Hip Score, and Japanese Orthopaedic Association Hip Disease Evaluation Questionnaire) and complication rates were not significantly different between the groups. The survival rates at 10 years, with revision for any reason as the endpoint, were 81% in the TRO group and 91% in the primary group, showing no significant difference between the groups. The TRO group had a larger average postoperative leg length discrepancy and a higher rate of stem malalignment than the primary group.

CONCLUSION

The clinical outcomes of THA after TRO for ONFH were poorer than those of primary THA.

Correcting pelvic obliquity in the lateral position to improve acetabular component orientation during total hip arthroplasty

BACKGROUND

The acetabular component orientation during total hip arthroplasty (THA) impacts future hip function and early revision. Correcting pelvic obliquity may improve outcomes.

OBJECTIVE

To correct pelvic obliquity in the lateral position by applying a gradienter and plumb during THA using fluoroscopy.

METHODS

Fifty patients undergoing THA were randomized and divided into 2 groups. In controls, acetabular components were placed using traditional methods. In experimental patients, acetabular components were placed after correcting pelvic obliquity. We measured pelvic obliquity and recorded intra-operative and post-operative abduction angles, comparing abduction angle bias between post-operative measurements and intra-operation estimations.

RESULTS

Before correction, the average pelvic obliquity was -1.647∘± 4.512∘ in experimental patients. The average abduction angle in experimental patients was 42.685∘± 3.355∘ postoperatively, differing by 1.962∘± 1.515∘ from intra-operative estimates, while in control patients, it was 44.534∘± 4.844∘ postoperatively, differing by 4.244∘± 3.042∘ from intra-operative estimates. The bias of the abduction angle was much greater in control than in experimental patients (P< 0.05).

CONCLUSION

The pelvic obliquity in the lateral position affects surgeon judgment during THA. By correcting pelvic obliquity with a gradienter and plumb, the abduction angle bias can be reduced.

Total Hip Arthroplasty After Periacetabular and Intertrochanteric Valgus Osteotomy

BACKGROUND

We performed periacetabular osteotomy (PAO) combined with intertrochanteric valgus osteotomy (TVO) to obtain better congruity for patients with acetabular dysplasia and nonspherical femoral head. These patients with PAO-combined TVO demonstrate long-term progression of osteoarthritis, thereby, needing conversion to total hip arthroplasty (THA) and is difficult due to morphological changes. The objective of the present study was to investigate outcomes of patients who underwent THA after PAO-combined TVO.

METHODS

We performed 3 groups' case-control study. The participants were 20 patients (20 hips) who underwent THA after PAO-combined TVO (PAO-TVO group); these patients had a mean age at surgery of 56.3 years and underwent postoperative follow-up for a mean period of 6.8 years. For the control group, we included 53 patients (57 joints) who underwent THA after PAO and 76 patients (80 joints) who underwent primary THA for hip dysplasia matching age, sex, and time of surgery.

RESULTS

Harris hip score at the last follow-up was significantly poorer in PAO-TVO group compare with PAO group and primary group. Short Form-36 of Physical Component Summary was significantly poorer in PAO-TVO group compared with primary group. The socket position in the PAO-TVO group was significantly superior and lateral compared with that in the primary THA group. Considering socket placement in Lewinnek's safe zone and stem malalignment, there were no significant differences in the 3 groups.

CONCLUSION

Harris hip score and Short Form-36-Physical Component Summary for THA after PAO-combined TVO were significantly poorer compared to those of primary THA.

An Alternative Intraoperative Radiographic Method for Optimizing Cup Inclination during Total Hip Arthroplasty

OBJECTIVE

During total hip arthroplasty (THA), the location of the acetabular prosthesis is very important for guaranteeing successful surgery. However, this remains a challenge for many surgeons. This study aimed to investigate the feasibility of using the intraoperative fluoroscopic iliopubic tangential angle (IPTA) to determine the valgus angles of acetabular prostheses.

METHODS

In the first stage, the IPTA and valgus angles of native acetabula were defined and measured in 102 THAs obtained from the picture archiving and communication systems of our hospital. Obturator foramen morphology was also measured and divided into groups according to the axial length ratio. Correlations between obturator foramen morphology and IPTA and valgus angles of native acetabula were then determined. In the second stage, angular differences (angle θ) between the IPTA and valgus angles of native acetabula were measured during unilateral THA in 136 patients to determine whether this is a stable value that could be used as a reference for placement of acetabular prostheses. Postoperative data such as Harris Hip Score (HHS) scores and complications were collected and evaluated.

RESULTS

The average IPTA at the apex of the true acetabulum was 58.8° ± 4.1°. The average valgus angle of native acetabula was 43.1° ± 3.9° and angle θ was 15.7° ± 1.3°. Obturator foramen morphology was divided into five groups according to the axial length ratio. IPTA was closely related to obturator foramen morphology (Pearson r = 0.489, P ≈ 0.000). Angle θ was stable and independent of obturator foramen morphology. When the IPTA and angle θ were used as references for placing acetabular prostheses in 136 THAs, the average postoperative valgus angles of acetabular prostheses was 45.13° ± 4.07° and the good-to-excellent rate was 97.05%. There were no short-term complications such as fracture, dislocation or infection. The average HHS score 6 months after surgery was 37.2 higher than the preoperative score, this difference being significant (P < 0.01). Neither infection nor dislocation was found 6 months after surgery.

CONCLUSIONS

The IPTA (at the apex of the true acetabulum) and angle θ (obtained by intraoperative fluoroscopy) are consistent in determining the postoperative valgus angle of acetabular prosthesis during THA. Thus, IPTA and angle θ are of value in guiding placement of acetabular prostheses; in particular, this method can facilitate the learning of young surgeons.

Radiographic templating of total hip arthroplasty for femoral neck fractures

PURPOSE

The purpose of this study was to evaluate the use of pre-operative digital templating to minimize complications including limb length discrepancy (LLD), intraoperative fractures and early dislocations in patients with intracapsular femoral neck fractures.

METHODS

We retrospectively compared 23 patients undergoing total hip arthroplasty (THA) for intracapsular femoral fractures with pre-operative digital templating and 48 patients without templating.

RESULTS

The mean post-operative LLD was significantly lower in patients who had pre-operative templating than in the control group (6.7 vs. 11.5 mm, p = 0.023). Only three patients (13 %) with templating had LLD greater than 1.5 cm, compared to the 15 patients (31 %) without templating (p = 0.17). In eight cases the final femoral stem size matched the templated size, while 19 patients were within two size increments. Complications included one dislocation and one intra-operative fracture in the control group.

CONCLUSION

The present study demonstrated that careful pre-operative planning may reduce LLD in patients undergoing THA due to intracapsular hip fractures.

Algorithm for automatic angles measurement and screening for Developmental Dysplasia of the Hip (DDH)

Developmental Dysplasia of the Hip (DDH) is a medical term represent the hip joint instability that appear mainly in infants. The examination for this condition can be done by ultrasound for children under 6 months old and by X-ray for children over 6 months old. Physician's assessment is based on certain angles derived from those images, namely the Acetabular Angle, and the Center Edge Angle. In this paper, we are presenting a novel, fully automatic algorithm for measuring the diagnostic angles of DDH from the X-ray images. Our algorithm consists of Automatic segmentation and extraction of anatomical landmarks from X-ray images. Both of Acetabular angle and Center edge angle are automatically calculated. The analysis included X-ray images for 16 children recruited for the purposed of this study. The automatically acquired angles accuracy for Acetabular Angle was around 85%, and an absolute deviation of 3.4°±3.3° compared to the physician's manually calculated angle. The results of this method are very promising for the future development of an automatic method for screening X-ray images DDH that complement and aid the physicians' manual methods.

The Impact of Lumbar Spine Disease and Deformity on Total Hip Arthroplasty Outcomes

Concurrent spine and hip disease is common. Spinal deformities can restrict lumbar range of motion and lumbar lordosis, leading to pelvic obliquity and increased pelvic tilt. A comprehensive preoperative workup and component templating ensure appropriate compensation for altered pelvic parameters for implantation of components according to functional positioning. Pelvic obliquity from scoliosis must be measured to calculate appropriate leg length. Cup positioning should be templated on standing radiograph to limit impingement from cup malposition. In spinal deformity, the optimal position of the cup that accommodates pelvic parameters and limits impingement may lie outside the classic parameters of the safe zone.

Fluoroscopy and imageless navigation enable an equivalent reconstruction of leg length and global and femoral offset in THA

BACKGROUND

Restoration of biomechanics is a major goal in THA. Imageless navigation enables intraoperative control of leg length equalization and offset reconstruction. However, the effect of navigation compared with intraoperative fluoroscopy is unclear.

QUESTIONS/PURPOSES

We asked whether intraoperative use of imageless navigation (1) improves the relative accuracy of leg length and global and femoral offset restoration; (2) increases the absolute precision of leg length and global and femoral offset equalization; and (3) reduces outliers in a reconstruction zone of ± 5 mm for leg length and global and femoral offset restoration compared with intraoperative fluoroscopy during minimally invasive (MIS) THA with the patient in a lateral decubitus position.

METHODS

In this prospective study a consecutive series of 125 patients were randomized to either navigation-guided or fluoroscopy-controlled THA using sealed, opaque envelopes. All patients received the same cementless prosthetic components through an anterolateral MIS approach while they were in a lateral decubitus position. Leg length, global or total offset (representing the combination of femoral and acetabular offset), and femoral offset differences were restored using either navigation or fluoroscopy. Postoperatively, residual leg length and global and femoral offset discrepancies were analyzed on magnification-corrected radiographs of the pelvis by an independent and blinded examiner using digital planning software. Accuracy was defined as the relative postoperative difference between the surgically treated and the unaffected contralateral side for leg length and offset, respectively; precision was defined as the absolute postoperative deviation of leg length and global and femoral offset regardless of lengthening or shortening of leg length and offset throughout the THA. All analyses were performed per intention-to-treat.

RESULTS

Analyzing the relative accuracy of leg length restoration we found a mean difference of 0.2 mm (95% CI, -1.0 to +1.4 mm; p = 0.729) between fluoroscopy and navigation, 0.2 mm (95 % CI, -0.9 to +1.3 mm; p = 0.740) for global offset and 1.7 mm (95 % CI, +0.4 to +2.9 mm; p = 0.008) for femoral offset. For the absolute precision of leg length and global and femoral offset equalization, there was a mean difference of 1.7 ± 0.3 mm (p < 0.001) between fluoroscopy and navigation. The biomechanical reconstruction with a residual leg length and global and femoral offset discrepancy less than 5 mm and less than 8 mm, respectively, succeeded in 93% and 98%, respectively, in the navigation group and in 54% and 95%, respectively, in the fluoroscopy group.

CONCLUSIONS

Intraoperative fluoroscopy and imageless navigation seem equivalent in accuracy and precision to reconstruct leg length and global and femoral offset during MIS THA with the patient in the lateral decubitus position.

Early complications of primary total hip arthroplasty in the supine position with a modified Watson-Jones anterolateral approach

BACKGROUND

For total hip arthroplasty (THA), minimally invasive surgery (MIS) has been developed to reduce incision length, muscle damage, and a shorter hospital stay. However, reduced exposure of anatomical landmarks may result in technical errors and inferior implant survivorships. The aim of this study was to report the short-term results and clinical complications of primary MIS THA in the supine position.

METHODS

A consecutive series of 103 patients who underwent MIS cementless THA with a modified Watson-Jones anterolateral approach (AL) were enrolled. Outcomes data were reviewed at a minimum of 12 months following the procedure. Clinical evaluations were made using the Merle d'Aubigne and Postel hip score. The results of these procedures were retrospectively compared with those of a historical series of 98 total hip arthroplasties that had been performed by the same surgeon with use of a posterolateral approach (PL).

RESULTS

In the MIS AL THA group, intraoperative fracture was observed in 6 hips; 3 in greater trochanter and 3 in calcar femoral. One hip was subjected to irrigation because of postoperative infection was suspected. In the PL group, intraoperative fracture was demonstrated in 4 hips in calcar femoral. No postoperative dislocation and no pulmonary embolism or nerve paralysis was observed in both groups.

CONCLUSIONS

The MIS AL THA did not show a clinically relevant superior outcome compared with the PL THA. When performing MIS AL THA, special attention should pay for prevention of greater trochanter fracture.