Computed tomography for preoperative planning in minimal-invasive total hip arthroplasty: radiation exposure and cost analysis

Robotic Assistance is Associated With No Intraoperative Fluoroscopy or Radiation Exposure During Direct Anterior Total Hip Arthroplasty

Background

As more total hip arthroplasty (THA) procedures continue to be performed and concomitant intraoperative fluoroscopic utilization continues to increase, it is important for surgeons to critically analyze this practice during their procedures. The direct anterior approach (DAA) is a popular technique, but often requires the use of fluoroscopy for evaluation of component positioning and implantation. Computed tomography (CT)-based robotic-assisted THA (RA-THA) may represent an alternative to conventional procedures, which may allow the avoidance of the use of intraoperative fluoroscopy to be avoided and instead rely on a preoperative CT scan of the patient and intraoperative mapping. The purpose of this study was to evaluate the difference in radiation exposure from CT-based RA-THA DAA vs fluoroscopy-guided conventional THA DAA based on values from a cadaver study.

Methods

There were 2 surgeons who had previous extensive experience with the DAA, as well as conventional and RA-THA. They completed bilateral direct anterior THAs on 6 cadaver specimens. For each cadaver, a conventional THA with fluoroscopy was performed on the first hip, and a robotically assisted THA without fluoroscopy was performed on the contralateral hip. For all robotic-assisted cases, a preoperative 3-dimensional CT was performed. The radiation dosage from the preoperative scan was acquired through the radiation dose structured reports. Radiation exposure dosage for intraoperative fluoroscopy required tabulation of the number of fluoroscopy shots performed for each case as well as the length of time of exposure. This time was then converted to an effective radiation dose based on accepted standards, and this was multiplied by the average number of fluoroscopy shots per case to determine the average dosage per case.

Results

No fluoroscopic images were taken during the RA-THA using the DAA. There was a mean of 21 ± 8.9 fluoroscopic shots taken during each fluoroscopy-guided conventional THA using the DAA. The minimum number of fluoroscopic shots was 9, with a maximum of 31. Total radiation exposure ranged from 300 to 1033 mrem, with an average of 700 mrem. The average radiation exposure for a hip CT scan was 289 mrem.

Conclusions

In this cadaver-based study, the use of a CT-based RA-THA DAA eliminated the need for intraoperative fluoroscopy, removing the concern of radiation exposure to the surgeon and surgical staff. The CT-based RA-THA DAA does require a preoperative CT scan of the patient; however, the radiation dosage to the patient was equivalent to 8.7 intraoperative fluoroscopy shots. As more surgeons, patients, and surgical staff are exposed to an increasing number of orthopaedic procedures that require ionizing radiation to generate images, such as fluoroscopy and CT, it is important to consider the radiation dosage for all individuals and understand the positives and negatives of each treatment. We must consider the overall long-term health impacts of continuous fluoroscopy vs a one-time CT scan. This is of particular importance to the surgeon and surgical staff who may be exposed to cumulative doses during multiple procedures.

The accuracy of a patient-specific femoral planning and delivery system for total hip arthroplasty

INTRODUCTION

A primary objective when performing a total hip arthroplasty (THA) is to restore hip biomechanics in accordance with a chosen surgical plan. The aim of this study was to assess the accuracy of a 3D-printed patient-specific guide for delivering a planned femoral osteotomy for both a posterior and an anterior approach.

METHODOLOGY

40 patients (20 anterior and 20 posterior) scheduled for THA received a preoperative work-up allowing for patient-specific implant sizing and positioning. Following surgeon confirmation, a patient-specific guide was designed and printed, enabling the desired osteotomy to be executed. Achieved osteotomies were assessed using commercially available software platforms. Planning accuracy was also assessed using both the planning platform as well as more traditional 2D-templating techniques.

RESULTS

The mean deviation between the planned and achieved osteotomy level was -0.6 mm (range -4.1-6.4 mm). 95% of the achieved osteotomy levels were within 3 mm of the plan for both the posterior and anterior approach groups. 70% of the Optimized Positioning System (OPS) planned femoral components were the exact size as planned versus 25% of the 2D-planned components. 98% of the OPS planned femoral components were within 1 size of plan versus 58% for the 2D-planned components. No sizing accuracy difference was observed between planning approaches (p = 0.70).

CONCLUSIONS

A patient-specific osteotomy guide can be a simple and accurate method to reproduce a planned femoral neck resection through an anterior or posterior approach. Further, 3D planning appears to more accurately predict femoral sizing in THA than more conventional 2D methods.

Lewinnek zone not "the be-all and end-all" functional planning for acetabular component positioning in total hip arthroplasty

BACKGROUND

Proper positioning of a total hip arthroplasty (THA) plays a crucial role in the success and long-term survivorship of the implant. Cup positioning within the Lewinnek Safe Zone (LSZ) does not, however, avoid implant dislocation. Thus, the concept of a functional cup position has been introduced. The purpose of this study was to assess the discrepancy between LSZ and the acetabular cup position suggested by the patient's specific functional planning. The hypothesis was that a mismatch does exist.

METHODS

One hundred consecutive patients with primary hip osteoarthritis undergoing primary THA with a personalized functional preoperative planning and patient-specific cup implantation system were enrolled. Anatomical and spino-pelvic functional parameters were recorded and, for each patient, a "safe cup orientation" was suggested. The suggested functional safe zone was compared to the LSZ.

RESULTS

The mean suggested inclination was 39° ± 3° (range 32°-45°). The mean suggested anteversion was 21° ± 3° (range 12°-28°). The patient's functional acetabular inclination (AI) corresponded to the LSZ in one of the 100 patients, whereas the acetabular anteversion (AV) was outside the LSZ in 8 of the 100 patients. The mean pelvic tilt while standing and sitting were 0.5° ± 7° (range 21°-45°) and -6° ± 16.7° (range -63°-33°), respectively. The mean pelvic incidence was 52° ± 9.7° (range 33°-83°).

CONCLUSION

When a functional patient's specific preoperative planning is performed, the LZS does not correspond to the patient's functional safe zone in about 8% of patients. The concept of a universal safe zone should be revisited, and a functional personalized safe zone may have to be more widely considered.

The advantages of artificial intelligence-assisted total hip arthroplasty: A randomized controlled trial followed by 12 months

OBJECTION

The rapid advancement of artificial intelligence has brought significant breakthroughs to various medical disciplines，This study aimed to compare perioperative factors and postoperative hip function recovery in primary total hip arthroplasty (THA)by evaluating the use of an artificial intelligence (AI) preoperative planning system versus traditional two-dimensional X-ray planning.

PATIENTS AND METHODS

A total of 45 eligible patients underwent primary THA at Beijing Shijitan Hospital, Capital Medical University, between July 2022 and August 2022. The patients were randomly assigned to either the experimental group (n = 19) or the control group (n = 26). The experimental group utilized AI planning, while the control group employed traditional two-dimensional X-ray planning. Statistical analysis was performed to compare the accuracy of prosthesis prediction, operation time, intraoperative blood loss, frequency of intraoperative model testing, length of hospital stay, postoperative imaging data, and postoperative hip function scores. These comparisons were made to assess the effects of different preoperative planning methods on perioperative and postoperative hip function recovery.

RESULTS

The accuracy of preoperative planning for the acetabular and femoral sides in AI-assisted total hip arthroplasty was 84.2 % and 89.5 %, respectively, which was significantly better than that of the traditional two-dimensional X-ray planning group (P < 0.05). The operation time for AI-assisted total hip arthroplasty was 104.32 ± 18.10 min, which was shorter than that of the traditional two-dimensional X-ray planning group (P < 0.05). At 3 months post-operation, the grade of Harris score for hip function in the AI planning group was significantly better than that in the traditional two-dimensional X-ray planning group (P < 0.05). The average postoperative Harris score of the artificial intelligence group was higher than that of the traditional two-dimensional X-ray planning (P < 0.05).

CONCLUSION

Artificial intelligence-assisted total hip arthroplasty demonstrated superior accuracy in prosthesis prediction, shorter operation time, higher average Harris score at postoperative follow-up, and better hip function recovery at 3 months compared to traditional two-dimensional X-ray planning.

LEVEL OF EVIDENCE

III, case-control study.

Planning Accuracy and Stem Offset Assessment in Digital Two-Dimensional Versus Three-Dimensional Planning in Cementless Hip Arthroplasty: A Systematic Review and Meta-Analysis

Background/Objectives: Total hip arthroplasty (THA) planning is crucial for restoring hip function and minimizing complications. The present systematic review and meta-analysis aimed to assess and compare the accuracy of 2D versus 3D preoperative planning in THA. Methods: The inclusion criteria were randomized controlled trials (RCTs) and observational studies (ROSs) published in English comparing the accuracy of 2D and 3D preoperative planning for total hip arthroplasty. We excluded review articles, registers, studies not written in English, studies that did not report the cup sizing accuracy or stem sizing accuracy or give a description of the preoperative planning method used, and non-comparative studies. In June 2024, following the PRISMA 2020 statement, a systematic review and a meta-analysis of the literature were conducted in PubMed, Scopus, and the Cochrane Library. The statistical analysis software Review Manager (RevMan) version 5.4 was used to perform the meta-analysis to compare the accuracy of 2D and 3D planning, and to assess the risk of bias, the ROBINS-I tool was used. Results: The analysis included 777 patients from six studies. The analysis showed that 3D planning offers superior precision compared to 2D planning, both for the cup (96.92% vs. 87.14%) and the stem (94.72% vs. 86.28%). The forest plots assessed a better trend for 3D planning in terms of exact size prediction and accuracy within ±1 size. Conclusions: The three-dimensional method was more precise and accurate than two-dimensional planning, both for the stem and the cup. It offered a detailed three-dimensional view of the patient's anatomy. The main limitation was the challenge in finding homogeneous data regarding biomechanical parameters, surgical approaches, and different planning systems for both three-dimensional and two-dimensional methods.

Does two dimensional templating allow for the use of reduced-size ancillaries in total hip arthroplasty?

PURPOSE

Rising costs in healthcare for total hip arthroplasty (THA) mean that new solutions must be considered, such as the use of single-use ancillaries (SUA). The goal of this study was to assess the accuracy of 2D templating in primary THA for the use of reduced-size SUA. Our hypothesis was that the accuracy of 2D templating in primary THA would be higher than 95%, give or take two sizes.

METHOD

This single-centre prospective study included all primary THAs performed over two years. Templating was carried out using 2D templating on anteroposterior pelvic X-rays. The template sizes were compared to the implant sizes. The primary endpoint was the rate of coincidence between digitally templated estimates and the actual implant sizes. The secondary endpoint was the difference of accuracy based on patient parameters.

RESULTS

We analysed 512 cases of THA. Accuracy within two sizes was 96.9% for acetabular implants and 98.5% for femoral implants. Accuracy was below the 95% threshold only in patients under 55 and over 85 years old. A BMI above 30.0 kg/m2 significantly reduced accuracy but did not fall below the 95% threshold. The operated hip, the type of implant, and the operative indication did not significantly influence templating accuracy.

CONCLUSION

Using reduced-size SUA with five rasps and five reamers depending on template sizes means that THA can be performed in more than 95% of cases allowing the use of compact single use ancillaries.

Functional Acetabular Component Positioning During Direct Anterior Approach Hip Arthroplasty Using a Novel Three-Dimensional Virtual Mesh Imaging System With Fluoroscopy

BACKGROUND

Optimal position of total hip arthroplasty (THA) components is critical for joint mechanics and stability. Acetabular component positioning during supine surgery in direct anterior approach (DAA) THA may be different in the standing position postoperatively, which traditional fluoroscopy is unable to predict. A novel 3-dimensional (3D) image analysis technology (IAT) that uses artificial intelligence to measure the tilt and rotation of the pelvis has enabled prediction of component positioning from supine to standing. The purpose of this study was to compare intraoperative fluoroscopy, non-3D-IAT, and 3D-IAT with postoperative standing radiographs to assess the accuracy of component positioning.

METHODS

From 2022 to 2023, 30 consecutive patients (86.6% women, mean age 59 [range, 55 to 67]) undergoing primary DAA THA with the use of the 3D-IAT were identified. A separate cohort of 148 patients from 2020 to 2021 (85% women, mean age 65 [range, 55 to 69]) who underwent DAA THA with non-3D-IAT was used for comparison. Leg length discrepancy (LLD), cup anteversion, and inclination were manually measured on intraoperative fluoroscopic images and digitally measured using IAT. Follow-up evaluation occurred at 1 month with standing pelvis radiographs measured using Ein Bild Röntgen Analyze-Cup software. Measurements were compared via Wilcoxon signed rank tests where P ≤ .05 indicates significantly different measurements.

RESULTS

Median LLD, inclination, and anteversion measurements via non-3D-IAT and fluoroscopy were significantly different compared to postoperative standing radiographs (P < .001). The 3D-IAT more accurately predicted LLD, abduction, and anteversion, with values not significantly different from postoperative standing measurements (P = .23, P = .93, and P = .36, respectively).

CONCLUSIONS

The use of the 3D-IAT during DAA THA allowed for the more accurate prediction of acetabular component position in the standing position postoperatively.

The current role of CT in total knee arthroplasty

Advanced 3D imaging and CT-based navigation have emerged as valuable tools to use in total knee arthroplasty (TKA), for both preoperative planning and the intraoperative execution of different philosophies of alignment. Preoperative planning using CT-based 3D imaging enables more accurate prediction of the size of components, enhancing surgical workflow and optimizing the precision of the positioning of components. Surgeons can assess alignment, osteophytes, and arthritic changes better. These scans provide improved insights into the patellofemoral joint and facilitate tibial sizing and the evaluation of implant-bone contact area in cementless TKA. Preoperative CT imaging is also required for the development of patient-specific instrumentation cutting guides, aiming to reduce intraoperative blood loss and improve the surgical technique in complex cases. Intraoperative CT-based navigation and haptic guidance facilitates precise execution of the preoperative plan, aiming for optimal positioning of the components and accurate alignment, as determined by the surgeon's philosophy. It also helps reduce iatrogenic injury to the periarticular soft-tissue structures with subsequent reduction in the local and systemic inflammatory response, enhancing early outcomes. Despite the increased costs and radiation exposure associated with CT-based navigation, these many benefits have facilitated the adoption of imaged based robotic surgery into routine practice. Further research on ultra-low-dose CT scans and exploration of the possible translation of the use of 3D imaging into improved clinical outcomes are required to justify its broader implementation.

Two-Dimensional Versus Three-Dimensional Preoperative Planning in Total Hip Arthroplasty

BACKGROUND

Preoperative planning in total hip arthroplasty (THA) involves utilizing radiographs or advanced imaging modalities, including computerized tomography scans, for precise prediction of implant sizing and positioning. This study aimed to compare 3-dimensional (3D) versus 2-dimensional (2D) preoperative planning in primary THA with respect to key surgical metrics, including restoration of the horizontal and vertical center of rotation (COR), combined offset, and leg length.

METHODS

This study included 60 patients undergoing primary THA for symptomatic hip osteoarthritis (OA), randomly allocated to either robotic arm-assisted or conventional THA. Digital 2D templating and 3D planning using the robotic software were performed for all patients. All measurements to evaluate the accuracy of templating methods were conducted on the preoperative computerized tomography scanogram, using the contralateral hip as a reference. Sensitivity analyses explored differences between 2D and 3D planning in patients who had superolateral or medial OA patterns.

RESULTS

Compared to 2D templating, 3D templating was associated with less medialization of the horizontal COR (-1.2 versus -0.2 mm, P = .002) and more accurate restoration of the vertical COR (1.63 versus 0.3 mm, P < .001) with respect to the contralateral side. Furthermore, 3D templating was superior for planned restoration of leg length (+0.23 versus -0.74 mm, P = .019). Sensitivity analyses demonstrated that in patients who had medial OA, 3D planning resulted in less medialization of horizontal COR and less offset reduction. Conversely, in patients who had superolateral OA, there was less lateralization of horizontal COR and less offset increase using 3D planning. Additionally, 3D planning showed superior reproducibility for stem, acetabular cup sizes, and neck angle, while 2D planning often led to smaller stem and cup sizes.

CONCLUSIONS

Our findings indicated higher accuracy in the planned restoration of native joint mechanics using 3D planning. Additionally, this study highlights distinct variances between the 2 planning methods across different OA pattern subtypes, offering valuable insights for clinicians employing 2D planning.

Assessment of preoperative planning and intraoperative accuracy of the AIKNEE system for total knee arthroplasty

BACKGROUND

The aim of this retrospective study was to evaluate the effectiveness and accuracy of the AIKNEE system in preoperative planning and intraoperative alignment for total knee arthroplasty (TKA).

METHODS

A total of 64 patients were planned preoperatively by the AIKNEE system, including the measurement of mechanical femorotibial angle (mFTA), lateral distal femoral angle (LDFA), and medial proximal tibial angle (MPTA) using three-dimensional reconstructed images. Intraoperatively, the actual prosthesis size and alignment were compared to the planned parameters. Postoperative outcomes, including pain levels, range of motion (ROM), and Knee Scoring System (KSS) scores, were assessed after surgery. Statistical analyses were performed to evaluate the correlation between alignment deviations and postoperative function.

RESULTS

The AIKNEE system accurately predicted the prosthesis size in thirty-one of femoral cases (48%) and forty-seven of tibial cases (73%). Deviations of mFTA, LDFA, and MPTA from the target value were within 3° in 88%, 92%, and 95% of cases, respectively. A significant improvement was observed in postoperative pain, ROM, and KSS scores (p < 0.001). Correlation analysis revealed that greater deviations in mFTA and LDFA were associated with increased pain (p = 0.004, 0.047) and lower KSS scores (p = 0.027).

CONCLUSION

The AIKNEE system demonstrated promising results in predicting prosthesis size and achieved alignment within the desired range in a majority of cases. Postoperative outcomes, including pain levels and functional improvement, were favorable.

Quantifying radiation exposure in the radiological investigation of non-arthritic hip pain

Radiological investigations are essential for evaluating underlying structural abnormalities in patients presenting with non-arthritic hip pain. The aim of this study is to quantify the radiation exposure associated with common radiological investigations performed in assessing patients presenting with non-arthritic hip pain. A retrospective review of our institutional imaging database was performed. Data were obtained for antero-posterior, cross-table lateral, frog lateral radiographs and low-dose CT hip protocol. The radiation dose of each imaging technique was measured in terms of dose-area product with units of mGy cm2, and the effective doses (ED, mSv) calculated. The effective radiation dose for each individual hip radiograph performed was in the range of 0.03-0.83 mSv [mean dose-area product 126.7-156.2 mGy cm2]. The mean ED associated with the low-dose CT hip protocol (including assessment of femoral anteversion and tibial torsion) was 3.04 mSv (416.8 mGy cm2). The radiation dose associated with the use of CT imaging was significantly greater than plain radiographs (P < 0.005). Investigation of non-arthritic hip pain can lead to significant ionizing radiation exposure for patients. In our institution, the routine protocol is to obtain an antero-posterior pelvic radiograph and then a specific hip sequence Magnetic Resonance Imaging (MRI) scan which includes the assessment of femoral anteversion. This provides the necessary information in the majority of cases, with CT scanning reserved for more complex cases where we feel there is a specific indication. We would encourage the hip preservation community to carefully consider and review the use of ionizing radiation investigations.

Artificial intelligence technology improves the accuracy of preoperative planning in primary total hip arthroplasty

OBJECTIVE

Successful total hip arthroplasty relies on accurate preoperative planning. However, the conventional preoperative planning, a two-dimensional method using X-ray template, has shown poor reliability of predicting component size. To our knowledge, artificial intelligence technology assisted three-dimensional preoperative planning is promising to improve the accuracy of preoperative planning but there is a dearth of clinical evidence. Therefore, in this study we compared the prediction accuracy of these two maneuvers.

METHODS

We conducted a prospective study consisting of 117 consecutive patients who underwent a primary cementless total hip arthroplasty to compare the prediction accuracy of these two methods. The two-dimensional and artificial intelligence assisted three-dimensional planning results of the same patient were compared with the definitive implant size respectively.

RESULTS

The prediction accuracy of artificial intelligence assisted three-dimensional planning for cup and the stem sizes were 66.67% (78/117) and 65.81% (77/117), two-dimensional planning was 30.77% (36/117) and 37.61% (44/117) (p < 0.05). There were poor prediction results of two-dimensional planning in patients with hip dysplasia (p = 0.004, OR = 7.143) and excessive femoral anteversion (p = 0.012, OR = 1.052), meanwhile the failure risk of stem side two-dimensional planning increased as patients got older (p = 0.003, OR = 1.118). The accuracy of artificial intelligence assisted three-dimensional planning cannot be affected by above factors.

CONCLUSIONS

We confirmed that artificial intelligence assisted three-dimensional preoperative planning showed higher accuracy and stability than two-dimensional preoperative planning in primary cementless total hip arthroplasty. We believe artificial intelligence assisted three-dimensional preoperative planning technology provides surgeons a new reliable choice and offers advantages whether in simple or complicated cases.

Comparative analysis of radiation exposure in robot-assisted total knee arthroplasty using popular robotic systems

Robotic-assisted TKA (RATKA) is a rapidly emerging technique that has been shown to improve precision and accuracy in implant alignment in TKA. Robotic-assisted TKA (RATKA) uses computer software to create a three-dimensional model of the patient's knee. Different types of preoperative imaging, including radiographs and CT scans, are used to create these models, each with varying levels of radiation exposure. This study aims to determine the radiation dose associated with each type of imaging used in RATKA, to inform patients of the potential risks. A retrospective search of our clinical radiology and arthroplasty database was conducted to identify 140 knees. The patients were divided into three groups based on the type of preoperative imaging they received: (1) CT image-based MAKO Protocol, (2) Antero-posterior long leg alignment films (LLAF), (3) standard AP, lateral, and skyline knee radiographs. The dose of CT imaging technique for each knee was measured using the dose-length product (DLP) with units of mGycm2, whereas the measurement for XRAY images was with the dose area product (DAP) with units of Gycm2. The mean radiation dose for patients in the CT (MAKO protocol) image-based group was 1135 mGy.cm2. The mean radiation dose for patients in the LLAF group was 3081 Gycm2. The mean radiation dose for patients undergoing knee AP/lateral and skyline radiographs was the lowest of the groups, averaging 4.43 Gycm2. Through an ANOVA and post hoc analysis, the results between groups was statistically significant. In this study, we found a significant difference in radiation exposure between standard knee radiographs, LLAF and CT imaging. Nonetheless, the radiation dose for all groups is still within acceptable safety limits.

The Value of Computed Tomography Scan in Three-dimensional Planning and Intraoperative Navigation in Primary Total Hip Arthroplasty

Total hip arthroplasty (THA) is a frequently performed procedure; the objective is restoration of native hip biomechanics and achieving functional range of motion (ROM) through precise positioning of the prosthetic components. Advanced three-dimensional (3D) imaging and computed tomography (CT)-based navigation are valuable tools in both the preoperative planning and intraoperative execution. The aim of this study is to provide a thorough overview on the applications of CT scans in both the preoperative and intraoperative settings of primary THA. Preoperative planning using CT-based 3D imaging enables greater accuracy in prediction of implant sizes, leading to enhancement of surgical workflow with optimization of implant inventory. Surgeons can perform a more thorough assessment of posterior and anterior acetabular wall coverage, acetabular osteophytes, anatomical landmarks, and thus achieve more functional implant positioning. Intraoperative CT-based navigation can facilitate precise execution of the preoperative plan, to attain optimal positioning of the prosthetic components to avoid impingement. Medial reaming can be minimized preserving native bone stock, which can enable restoration of femoral, acetabular, and combined offsets. In addition, it is associated with greater accuracy in leg length adjustment, a critical factor in patients' postoperative satisfaction. Despite the higher costs and radiation exposure, which currently limits its widespread adoption, it offers many benefits, and the increasing interest in robotic surgery has facilitated its integration into routine practice. Conducting additional research on ultra-low-dose CT scans and examining the potential for translation of 3D imaging into improved clinical outcomes will be necessary to warrant its expanded application.

Femoral Head Osteonecrosis: Computed Tomography Not Needed to Identify Collapse When Using the Association Research Circulation Osseous Staging System

Background

The 2019 Revised Association Research Circulation Osseous (ARCO) Staging Criteria for Osteonecrosis of the Femoral Head (ONFH) only requires plain radiographs and magnetic resonance imaging (MRI) to diagnose and stage ONFH; however, the effectiveness of the 2019 ARCO criteria in the absence of computed tomography (CT) scans has not been investigated. Therefore, the purpose of this study was to evaluate whether CT scanning is a necessary modality for diagnosing/staging ONFH using the ARCO staging system. More specifically, do CT scans help differentiate pre- and post-collapse lesions more than MRI scans?

Methods

A study was conducted on 228 ONFH patients diagnosed between January 1, 2008, and December 31, 2018, at a single academic medical center. CT and MRI scans were reviewed by the senior author and other contributors. The ONFH classification was compared between the 2 scans to determine if CT scans were able to further differentiate staging of collapsed lesions vs MRI scans.

Results

A diagnosis of ONFH was made by MRI first in 57% (129/228) while 21% (48/228) used MRI and CT simultaneously. Only 22% (51/228) of cases were diagnosed by CT scans first. There were no cases where collapse was found by a CT scan that were not diagnosed by standard x-rays and/or MRIs.

Conclusions

CT scans are not a useful adjunct for diagnosing or treating ONFH and are not necessary if MRI is ordered when using the Revised ARCO Staging System for ONFH diagnosis.

Accuracy of Personalized Computed Tomographic 3D Templating for Acetabular Cup Placement in Revision Arthroplasty

Background: Revision hip arthroplasty presents a surgical challenge, necessitating meticulous preoperative planning to avert complications like periprosthetic fractures and aseptic loosening. Historically, assessment of the accuracy of three-dimensional (3D) versus two-dimensional (2D) templating has focused exclusively on primary hip arthroplasty. Materials and Methods: In this retrospective study, we examined the accuracy of 3D templating for acetabular revision cups in 30 patients who underwent revision hip arthroplasty. Utilizing computed tomography scans of the patients' pelvis and 3D templates of the implants (Aesculap Plasmafit, B. Braun; Aesculap Plasmafit Revision, B. Braun; Avantage Acetabular System, Zimmerbiomet, EcoFit 2M, Implantcast; Tritanium Revision, Stryker), we performed 3D templating and positioned the acetabular cup implants accordingly. To evaluate accuracy, we compared the planned sizes of the acetabular cups in 2D and 3D with the sizes implanted during surgery. Results: An analysis was performed to examine potential influences on templating accuracy, specifically considering factors such as gender and body mass index (BMI). Significant statistical differences (p < 0.001) in the accuracy of size prediction were observed between 3D and 2D templating. Personalized 3D templating exhibited an accuracy rate of 66.7% for the correct prediction of the size of the acetabular cup, while 2D templating achieved an exact size prediction in only 26.7% of cases. There were no statistically significant differences between the 2D and 3D templating methods regarding gender or BMI. Conclusion: This study demonstrates that 3D templating improves the accuracy of predicting acetabular cup sizes in revision arthroplasty when compared to 2D templating. However, it should be noted that the predicted implant size generated through 3D templating tended to overestimate the implanted implant size by an average of 1.3 sizes.

Three-Dimensional Preoperative Planning Software for Hip Resurfacing Arthroplasty

Three-dimensional planning of hip arthroplasty is associated with better visualisation of anatomical landmarks and enhanced mapping for preoperative implant sizing, which can lead to a decrease in surgical time and complications. Despite the advantages of hip resurfacing arthroplasty (HRA), it is considered a technically challenging procedure and associated with inaccurate implant placement. This study aimed to examine the validity, reliability, and usability of preoperative 3D Hip Planner software for HRA. Fifty random cases of various hip osteoarthritis severity were planned twice by two junior trainees using the 3D Hip Planner within a one-month interval. Outcome measures included femoral/cup implant size, stem-shaft angle, and cup inclination angle, and were assessed by comparing outcomes from 2D and 3D planning. An adapted unified theory of acceptance and use of technology (UTAUT) survey was used for software usability. Bland-Altman plots between 3D and 2D planning for stem-shaft and inclination angles showed mean differences of 0.7 and -0.6, respectively (r = 0.93, p < 0.001). Stem-shaft and inclination angles showed inter-rater reliability biases of around -2° and 3°, respectively. Chi-square and Pearson's correlation for femoral implant size showed a significant association between the two assessors (r = 0.91, p < 0.001). The 3D test-retest coefficient of repeatability for stem-shaft and inclination angles were around ±2° and ±3°, respectively, with a strong significant association for femoral implant size (r = 0.98, p < 0.001). Survey analyses showed that 70-90% agreed that 3D planning improved expectancy in four domains. 3D hip planner appears to be valid and reliable in preoperative HRA and shows significant potential in optimising the quality and accuracy of surgical planning.

Equivalent radiation exposure with robotic total hip replacement using a novel, fluoroscopic-guided (CT-free) system: case-control study versus manual technique

Accurate and precise positioning of the acetabular cup remains a prevalent challenge in total hip arthroplasty (THA). Robotic assistance for THA has increased over the past decade due to the potential to improve the accuracy of implant placement. However, a common criticism of existing robotic systems is the requirement for preoperative computerized tomography (CT) scans. This additional imaging increases patient radiation exposure, as well as cost, and requires pin placement during surgery. The goal of this study was to analyze the radiation burden associated with a novel, CT-free robotic THA system compared to an unassisted manual THA approach (n = 100/arm). On average, the study cohort had a higher number of fluoroscopic images captured (7.5 vs. 4.3 images; p < 0.001), radiation dose (3.0 vs. 1.0 mGy; p < 0.001), and a longer duration of radiation exposure (18.8 vs. 6.3 s; p < 0.001), per procedure, than the control group. Additionally, no learning curve was detected by CUSUM analysis with respect to the number of fluoroscopic images taken during the adoption of the robotic THA system. While statistically significant, in comparison to published literature, the radiation exposure of the CT-free robotic THA system was comparable to that of unassisted manual THA approach and less than that of CT-based robotic approaches. Thus, the novel CT-free robotic system likely poses no clinically significant increase in radiation exposure to the patient compared to manual approaches.

The role of 3-dimensional preoperative planning for primary total hip arthroplasty based on artificial intelligence technology to different surgeons: A retrospective cohort study

Preoperative planning with computed tomography (CT)-based 3-dimensiona (3D) templating has been achieved precise placement of hip components. This study investigated the role of the software (3-dimensional preoperative planning for primary total hip arthroplasty [THA] based on artificial intelligence technology, artificial intelligence hip [AIHIP]) for surgeons with different experience levels in primary THA. In this retrospective cohort study, we included patients, who had undergone THA with the help of the AIHIP, and matched to patients, who had undergone THA without the help of the AIHIP, by age and the doctor who operated on them. The subjects were divided into 4 groups, senior surgeon (Chief of Surgery) with AIHIP group, senior surgeon without AIHIP group, junior surgeon (Associate Chief of Surgery) with AIHIP group and junior surgeon without AIHIP group. The general data, imaging index, clinical outcomes and accuracy of stem size prediction and cup size prediction were retrospectively documented for all patients. There was a significant difference in discrepancy in leg length (P = .010), neck-shaft angle (P = .025) and femoral offset (P = .031) between the healthy side and the affected side, operation duration (P < .001), decrease in hemoglobin (Hb) per 24 hours (P = .046), intraoperative radiation exposure frequency (P < .050) and postoperative complications (overall P = .035) among the patients in junior surgeon group. No significant differences were found between senior surgeon groups with respect to discrepancy in leg length (P = .793), neck-shaft angle (P = .088)and femoral offset (P = .946) between the healthy side and the affected side, operation duration (P = .085), decrease in Hb per 24 hours (P = .952), intraoperative radiation exposure frequency (P = .094) and postoperative complications (overall P = .378). The stem sizes of 95% were accurately estimated to be within 1 stem size, and 97% of the cup size estimates were accurate to within 1 cup size in senior surgeon group with AIHIP. A total of 87% stem sizes were accurately estimated to be within 1 stem size, and 85% cup sizes were accurate to within 1 cup size in junior surgeon group with AIHIP. In conclusion, our study suggests that an AI-based preoperative 3D planning system for THA is a valuable adjunctive tool for junior doctor and should routinely be performed preoperatively.

Comparison of the Accuracy of 2D and 3D Templating for Revision Total Hip Replacement

Introduction: Revision hip arthroplasty is a challenging surgical procedure, especially in cases of advanced acetabular bone loss. Accurate preoperative planning can prevent complications such as periprosthetic fractures or aseptic loosening. To date, the accuracy of three-dimensional (3D) versus two-dimensional (2D) templating has been evaluated only in primary hip and knee arthroplasty. Methods: We retrospectively investigated the accuracy of 3D personalized planning of reinforcement cages (Burch Schneider) in 27 patients who underwent revision hip arthroplasty. Personalized 3D modeling and positioning of the reinforcement cages were performed using computed tomography (CT) of the pelvis of each patient and 3D templates of the implant. To evaluate accuracy, the sizes of the reinforcement cages planned in 2D and 3D were compared with the sizes of the finally implanted cages. Factors that may potentially influence planning accuracy such as gender and body mass index (BMI) were analyzed. Results: There was a significant difference (p = 0.003) in the accuracy of correct size prediction between personalized 3D templating and 2D templating. Personalized 3D templating predicted the exact size of the reinforcement cage in 96.3% of the patients, while the exact size was predicted in only 55.6% by 2D templating. Regarding gender and BMI, no statistically significant differences in planning accuracy either for 2D or 3D templating were observed. Conclusion: Personalized 3D planning of revision hip arthroplasty using Burch Schneider reinforcement cages leads to greater accuracy in the prediction of the required size of implants than conventional 2D templating.

Accuracy of Total Hip Arthroplasty Templating Using Set Calibration Magnifications

Background Templating for total hip arthroplasty has been adopted over recent decades as a reliable and accurate method for pre-operative planning. The use of calibration markers for this process provides a recognised benefit at the expense of cost, availability and error. Many surgeons use a set magnification of 118% to account for calibration errors when templating total hip arthroplasty. This study aims to assess the accuracy of templating with standardised magnifications and assess the effect of BMI on templating accuracy. Materials and methods A retrospective analysis was performed using a single-surgeon series of 119 consecutive total hip arthroplasties. Anteroposterior radiographs were taken pre- or post-operatively without calibration hardware. Pre-operatively, the total hip arthroplasty was templated on TraumaCad (BrainLab Inc, Westchester, IL) using either 118% or 119% calibration magnification. Post-operative magnification was calibrated using the known femoral head diameter. Templated and implanted prostheses were compared for size. Results At 118%, 61.1% of cups matched those templated with 96.3% of cups within two sizes. At 119%, 52.5% of cups used matched their templates with 100% within two sizes. There was no significant difference between 118% and 119% cup size prediction (p=0.49). A trend was noticed in increasing magnification error with increasing BMI. However, BMI had no significant effect on the accuracy of templating cup size within two cup sizes (p=0.58). Conclusion. Templating acetabular cups using a set magnification of 118% or 119% yields accurate results and provides a reliable method to template without calibration equipment. Whilst BMI can affect magnification error, this has no significant effect on the accuracy of implanted cups and stems within two sizes.

A novel method of manual positioning based on anatomical mark (shoulder-to-shoulder) to prevent postoperative leg-length discrepancy for femoral neck fractures in hip arthroplasty

OBJECTIVE

To determine whether the two lower extremities are of equal length after hip arthroplasty for femoral neck fractures, we developed a novel method of manual positioning based on anatomical mark (shoulder-to-shoulder) in hip arthroplasty.

METHODS

Patients with femoral neck fractures requiring hip arthroplasty from July 2020 to March 2022 in the orthopedic department of Jinjiang Municipal Hospital, Fujian Province, China were recruited. Hip arthroplasty was performed using the proposed "shoulder-to-shoulder" method of manual positioning based on anatomical mark in 52 patients with femoral neck fractures who met the inclusion criteria. "Shoulder-to-shoulder" was achieved by alignment of the marked femoral "shoulder" and the "shoulder" of prosthesis stem. There were 16 male and 36 female patients, with 27 undergoing total hip arthroplasty (THA) and 25 undergoing hip hemiarthroplasty (HA). The fractures were categorized according to the Garden classification: type II, type III, and type IV in 5, 11, and 36 patients, respectively. The vertical distance from the apex of the medial margin of the femoral trochanter to the tear drop line on both sides which was regarded as the length of both limbs were compared via postoperative imaging, and the apex-shoulder distance on the ipsilateral side measured via postoperative imaging was compared with those measured intraoperatively.

RESULTS

All patients completed the surgery successfully. The measurement results for the lower extremities after THA were as follows: contralateral group, 43.87 ± 5.59 mm; ipsilateral group, 44.64 ± 5.43 mm. The measurement results for the lower extremities after HA were as follows: contralateral group, 45.18 ± 7.82 mm; ipsilateral group, 45.16 ± 6.43 mm. The measurement results for the lower extremities after all arthroplasties were as follows: contralateral group, 44.50 ± 6.72 mm; ipsilateral group, 44.89 ± 5.90 mm. The results for the apex-shoulder distance were as follows: postoperative imaging, 19.44 ± 3.54 mm; intraoperative apex-shoulder distance, 27.28 ± 2.84 mm. Statistical analysis results indicated no statistically significant difference in the postoperative bilateral lower extremity length after hip arthroplasty (P = 0.75), while a statistically significant difference was found between the intraoperative and postoperative imaging measurements of the apex-shoulder distance (P < 0.01).

CONCLUSION

The novel method of manual positioning based on anatomical mark (shoulder-to-shoulder) for femoral neck fractures in hip arthroplasty is simple and accurate, making it effective for preventing postoperative bilateral leg length discrepancy.

Using Gait Analysis to Evaluate Hip Replacement Outcomes—Its Current Use, and Proposed Future Importance: A Narrative Review

Total hip replacement (THR) is one of the most common elective orthopaedic operations. However, evidence suggests that despite postoperative pain improvements, aspects of longer-term physical performance, such as walking ability, do not reach the levels expected when compared to the general population. Walking is best assessed by using gait analysis. This review aims to explain the concept of gait analysis, its use to evaluate THR outcomes, and its proposed future importance when evaluating new technologies proposed to improve functional recovery in individuals undergoing THR surgery. Furthermore, this review discusses the advantages and challenges of gait analysis in THR patients and provides recommendations for future work.

Imaging in Hip Arthroplasty Management-Part 1: Templating: Past, Present and Future

Hip arthroplasty is a frequently used procedure with high success rates. Its main indications are primary or secondary advanced osteoarthritis, due to acute fracture, osteonecrosis of the femoral head, and hip dysplasia. The goals of HA are to reduce pain and restore normal hip biomechanics, allowing a return to the patient’s normal activities. To reach those goals, the size of implants must suit, and their positioning must meet, quality criteria, which can be determined by preoperative imaging. Moreover, mechanical complications can be influenced by implant size and position, and could be avoided by precise preoperative templating. Templating used to rely on standard radiographs, but recently the use of EOS^® imaging and CT has been growing, given the 3D approach provided by these methods. However, there is no consensus on the optimal imaging work-up, which may have an impact on the outcomes of the procedure. This article reviews the current principles of templating, the various imaging techniques used for it, as well as their advantages and drawbacks, and their expected results.

The Use of Computerized Tomography Scans in Elective Knee and Hip Arthroplasty—What Do They Tell Us and at What Risk?

The average background radiation exposure in the United States has nearly doubled over the previous quarter century, with almost all the increase derived from medical imaging. Nearly 2% of all cancers in the United States may be attributable to radiation from computerized tomography (CT) scans. Given the nondiagnostic nature of CT scans that are used in elective knee and hip arthroplasty today, special consideration should be given to the inherent risk of radiation exposure with routine use of this technology. Methods to decrease radiation exposure including modulating the settings of the CT machine and using alternative non-CT-based systems can decrease patient exposure to radiation from CT scans. The rapid evolution of CT technology in arthroplasty has allowed for expanded clinical applications, the benefits of which remain controversial.

THA with Use of Patient-Specific Resurfacing Jigs and a Novel Customized Implant Design

»

Conventional total hip arthroplasty (THA) largely remains an unguided procedure dependent on the ability and experience of the surgeon. New technologies, such as patient-specific instrumentation and robotics, have shown promising results in improving implant positioning, which has the potential to improve patient outcomes.

»

The use of off-the-shelf (OTS) implant designs, however, limits the success of the technological advances since they are unable to recreate the native anatomy of the joint. The inability to restore femoral offset and version or the presence of implant-related leg-length discrepancies often lead to suboptimal surgical results that increase the risk of dislocation, fractures, and component wear, compromising postoperative functional outcomes and implant longevity.

»

A customized THA system, whereby the femoral stem is designed to restore patient anatomy, has recently been introduced. The THA system uses computed tomography (CT)-derived 3D imaging to create a custom stem, patient-specific component placement, and patient-specific instrumentation that matches the patient's native anatomy.

»

The purpose of this article is to provide information on the design and manufacturing process of this new THA implant, to illustrate the associated preoperative planning, and to describe the surgical technique; 3 surgical cases are presented.

Pre-operative templating in THA using a short stem system: precision and accuracy of 2D versus 3D planning method

Background

Total hip arthroplasty (THA) is the most successful orthopaedic surgery of the past century. The current study aimed to compare the accuracy of digital planning using 2D versus 3D templating.

Materials and methods

Ninety-five THAs in 90 patients were included in the current study. Pre- and post-operative X-rays (in two planes) and low-dose rotation computed tomography scans from hip to foot were performed. Paired t-test and regression analyses were conducted to compare 2D and 3D templating accuracy of the definitive implant.

Results

Cup size planned both with 2D (p < 0.0001) and 3D (p = 0.012) templating was significantly different from the definitively used cup size. The difference between the 2D-planned and implanted stem size (p < 0.0001) was statistically significant. In contrast, there were no significant differences in the 3D-planned and implanted stem size (p = 0.181). Three-dimensional templating showed significantly higher accuracy than 2D templating in terms of cup size (1.1 ± 1.4 versus 1.7 ± 1.8; p = 0.007) and stem size (0.3 ± 0.6 versus 0.7 ± 0.7; p < 0.0001).

With increasing body mass index (BMI), 2D templating of the stem became more inaccurate (p = 0.041). Remarkably, 3D templating remained accurate for all components (stem, p = 0.533; cup, p = 0.479) despite increasing BMI.

Conclusion

Despite extended planning time and increased exposure to radiation, 3D-based planning showed higher accuracy than 2D templating, especially in obese patients. On the basis of our results, we believe that 3D-based pre-operative planning in THA is justifiable and beneficial in patients with increased BMI.

Level of Evidence

III.

New Evaluation Method for Bone Formation around a Fully Hydroxyapatite-Coated Stem Using Digital Tomosynthesis: A Retrospective Cross-Sectional Study

Digital tomosynthesis (DTS) is a new imaging technique derived from radiography, and its usefulness has been gradually reported in the field of orthopedic diagnosis in recent years. A fully hydroxyapatite (HA)-coated stem, which is used for total hip arthroplasty (THA), is a type of cementless stem that has been widely used recently and reported to have good results. However, stem loosening on plain radiographs is difficult to determine in some cases due to cancellous condensation around the stem. In this retrospective cross-sectional study, we compared the results of plain radiography versus DTS to evaluate the imaging findings after THA using a fully HA-coated stem. Twenty joints each in the 3 y and 1 y postoperative groups underwent plain radiography and DTS. On DTS, bone formation around the stem was confirmed in all cases; however, this formation was not reproducible on plain radiography, and there were cases in which the reaction could not be confirmed or cases with cancellous condensation resembling reactive lines. This reaction was not reproducible on plain radiographs, and in some cases, the reaction could not be confirmed, or there were cases with cancellous condensation that resembled reactive lines. Therefore, DTS was useful in the diagnosis of bone formation around the implant.

The Patient-Specific Combined Target Zone for Morpho-Functional Planning of Total Hip Arthroplasty

Background Relevant criteria for total hip arthroplasty (THA) planning have been introduced in the literature which include the hip range of motion, bony coverage, anterior cup overhang, leg length discrepancy, edge loading risk, and wear. The optimal implant design and alignment depends on the patient’s anatomy and patient-specific functional parameters such as the pelvic tilt. The approaches proposed in literature often consider one or more criteria for THA planning. but to the best of our knowledge none of them follow an integrated approach including all criteria for the definition of a patient-specific combined target zone (PSCTZ). Questions/purposes (1) How can we calculate suitable THA implant and implantation parameters for a specific patient considering all relevant criteria? (2) Are the resulting target zones in the range of conventional safe zones? (3) Do patients who fulfil these combined criteria have a better outcome score? Methods A method is presented that calculates individual target zones based on the morphology, range of motion and load acting on the hip joint and merges them into the PSCTZ. In a retrospective analysis of 198 THA patients, it was calculated whether the patients were inside or outside the Lewinnek safe zone, Dorr combined anteversion range and PSCTZ. The postoperative Harris Hip Scores (HHS) between insiders and outsiders were compared. Results 11 patients were inside the PSCTZ. Patients inside and outside the PSCTZ showed no significant difference in the HHS. However, a significant higher HHS was observed for the insiders of two of the three sub-target zones incorporated in the PSCTZ. By combining the sub-target zones in the PSCTZ, all PSCTZ insiders except one had an HHS higher than 90. Conclusions The results might suggest that, for a prosthesis implanted in the PSCTZ a low outcome score of the patient is less likely than using the conventional safe zones by Lewinnek and Dorr. For future studies, a larger cohort of patients inside the PSCTZ is needed which can only be achieved if the cases are planned prospectively with the method introduced in this paper. Clinical Relevance The method presented in this paper could help the surgeon combining multiple different criteria during THA planning and find the suitable implant design and alignment for a specific patient.

Accuracy of Preoperative Templating in Total Hip Arthroplasty With Special Focus on Stem Morphology: A Randomized Comparison Between Common Digital and Three-Dimensional Planning Using Biplanar Radiographs

BACKGROUND

Accurate preoperative planning is a key component of successful total hip arthroplasty (THA). The purpose of the present study was to compare the accuracy and reliability of three-dimensional (hipEOS) and common digital two-dimensional (TraumaCad) templating with special focus on stem morphology.

METHODS

51 patients undergoing THA were randomized to two groups. Preoperative planning was performed on 23 patients with hipEOS (3D) and on 28 patients with TraumaCad (2D) planning software. Planning results were compared with the implanted component size. Inter- and intraobserver reliability as well as planning accuracy of both planning methods with special focus on straight and short stem design were recorded.

RESULTS

Intraobserver reliability of both planning methods was good for component planning (ICC_2,1: 0.835-0.967). Interobserver ICC_2,1 for stem and cup planning were higher for 3D templating (3D ICC_2,1: 0.906-0.918 vs. 2D ICC_2,1: 0.835-0.843). Total stem and cup size predictions were within 2 sizes for 3D and within 3 sizes for 2D planning. Comparing short stem planning accuracy of both planning methods, absolute difference between implanted and planned component size was significantly lower in 3D planning (P = .029). There was no significant difference in straight stem (P = .935) and cup (P = .954) planning accuracy.

CONCLUSION

Our findings suggest that 3D templating with hipEOS software has a good overall reliability and may have a better planning accuracy of short stem prostheses than digital templating with TraumaCad software. Assuming that the number of implanted short stem prostheses will further increase in coming years, a more precise planning with 3D technique can contribute to improve surgery outcome.

Three-dimensional pre-operative planning of primary hip arthroplasty: a systematic literature review

Three-dimensional (3D) pre-operative planning in total hip arthroplasty (THA) is being recognized as a useful tool in planning elective surgery, and as crucial to define the optimal component size, position and orientation. The aim of this study was to systematically review the existing literature for the use of 3D pre-operative planning in primary THA.A systematic literature search was performed using keywords, through PubMed, Scopus and Google Scholar, to retrieve all publications documenting the use of 3D planning in primary THA. We focussed on (1) the accuracy of implant sizing, restoration of hip biomechanics and component orientation; (2) the benefits and barriers of this tool; and (3) current gaps in literature and clinical practice.Clinical studies have highlighted the accuracy of 3D pre-operative planning in predicting the optimal component size and orientation in primary THAs. Component size planning accuracy ranged between 34-100% and 41-100% for the stem and cup respectively. The absolute, average difference between planned and achieved values of leg length, offset, centre of rotation, stem version, cup version, inclination and abduction were 1 mm, 1 mm, 2 mm, 4°, 7°, 0.5° and 4° respectively.Benefits include 3D representation of the human anatomy for precise sizing and surgical execution. Barriers include increased radiation dose, learning curve and cost. Long-term evidence investigating this technology is limited.Emphasis should be placed on understanding the health economics of an optimized implant inventory as well as long-term clinical outcomes. Cite this article: EFORT Open Rev 2020;5:845-855. DOI: 10.1302/2058-5241.5.200046.

Preoperative imaging of spinopelvic pathologies : State of the art

The field of musculoskeletal diagnostics and personalized medicine has undergone a revolutionary transformation due to a deeper understanding of skeletal biomechanics and due to technological advancements. Analogous to this transformation, our understanding of spinopelvic conditions has experienced a paradigm shift in terms of both static and dynamic changes in spinopelvic pathologies and enabled a more accurate delineation of the drivers of disability. The purpose of this review is to describe the standard and state of the art of preoperative diagnostic and planning methods for common spinopelvic pathologies and to discuss both the added clinical value and limitations. The rationale is to accelerate the accurate and timely diagnosis and as well as the efficient and safe preoperative workflow.

Can 3D surgical planning and patient specific instrumentation reduce hip implant inventory? A prospective study

BACKGROUND

Modern designs of joint replacements require a large inventory of components to be available during surgery. Pre-operative CT imaging aids 3D surgical planning and implant sizing, which should reduce the inventory size and enhance clinical outcome. We aimed to better understand the impact of the use of 3D surgical planning and Patient Specific Instrumentation (PSI) on hip implant inventory.

METHODS

An initial feasibility study of 25 consecutive cases was undertaken to assess the discrepancy between the planned component sizes and those implanted to determine whether it was possible to reduce the inventory for future cases. Following this, we performed a pilot study to investigate the effect of an optimized inventory stock on the surgical outcome: we compared a group of 20 consecutive cases (experimental) with the 25 cases in the feasibility study (control). We assessed: (1) accuracy of the 3D planning system in predicting size (%); (2) inventory size changes (%); (3) intra and post-operative complications.

RESULTS

The feasibility study showed variability within 1 size range, enabling us to safely optimize inventory stock for the pilot study. (1) 3D surgical planning correctly predicted sizes in 93% of the femoral and 89% of the acetabular cup components; (2) there was a 61% reduction in the implant inventory size; (3) we recorded good surgical outcomes with no difference between the 2 groups, and all patients had appropriately sized implants.

CONCLUSIONS

3D planning is accurate in up to 95% of the cases. CT-based planning can reduce inventory size in the hospital setting potentially leading to a reduction in costs.

[Research and application of artificial intelligence based three-dimensional preoperative planning system for total hip arthroplasty]

OBJECTIVE

To develop an artificial intelligence based three-dimensional (3D) preoperative planning system (AIHIP) for total hip arthroplasty (THA) and verify its accuracy by preliminary clinical application.

METHODS

The CT image database consisting of manually segmented CT image series was built up to train the independently developed deep learning neural network. The deep learning neural network and preoperative planning module were assembled within a visual interactive interface-AIHIP. After that, 60 patients (60 hips) with unilateral primary THA between March 2017 and May 2020 were enrolled and divided into two groups. The AIHIP system was applied in the trial group ( n=30) and the traditional acetate templating was applied in the control group ( n=30). There was no significant difference in age, gender, operative side, and Association Research Circulation Osseous (ARCO) grading between the two groups ( P>0.05). The coincidence rate, preoperative and postoperative leg length discrepancy, the difference of bilateral femoral offsets, the difference of bilateral combined offsets of two groups were compared to evaluate the accuracy and efficiency of the AIHIP system.

RESULTS

The preoperative plan by the AIHIP system was completely realized in 27 patients (90.0%) of the trial group and the acetate templating was completely realized in 17 patients (56.7%) of the control group for the cup, showing significant difference ( P<0.05). The preoperative plan by the AIHIP system was completely realized in 25 patients (83.3%) of the trial group and the acetate templating was completely realized in 16 patients (53.3%) of the control group for the stem, showing significant difference ( P<0.05). There was no significant difference in the difference of bilateral femoral offsets, the difference of bilateral combined offsets, and the leg length discrepancy between the two groups before operation ( P>0.05). The difference of bilateral combined offsets at immediate after operation was significantly less in the trial group than in the control group ( t=-2.070, P=0.044); but there was no significant difference in the difference of bilateral femoral offsets and the leg length discrepancy between the two groups ( P>0.05).

CONCLUSION

Compared with the traditional 2D preoperative plan, the 3D preoperative plan by the AIHIP system is more accurate and detailed, especially in demonstrating the actual anatomical structures. In this study, the working flow of this artificial intelligent preoperative system was illustrated for the first time and preliminarily applied in THA. However, its potential clinical value needs to be discovered by advanced research.

Conventional computed tomography software can be used for accurate pre-operative templating in bipolar hip arthroplasty: A preliminary report

BACKGROUND

The aim of this study was to investigate the use of pre-operative templating for bipolar hip arthroplasty (BHA) for displaced femoral neck fracture using multiplanar reconstruction (MPR) of computed tomography (CT) images.

METHODS

Nineteen patients who underwent BHA were enrolled in this study. For pre- and post-operative evaluation, a CT scan was performed from the pelvis to the knee joints. MPR of the CT image was done using software to measure the femoral head cup diameter, offset, stem size, length of the modular neck, distance from the neck osteotomy, and femoral anteversion. We compared these parameters pre- and post-operatively.

RESULTS

Both the femoral head cup diameter and length of the modular neck were found to be significantly different between pre- and post-operative measurements, although the differences were minor. Other parameters, including the femoral offset, were not significantly different between the pre- and post-operative measurements. The size of the femoral stem, cup diameter, and length of the modular neck were consistent with the planned size and accurate (within ±1 size) in more than 84% cases.

CONCLUSION

Our pre-operative templating approach for BHA using MPR of CT has potential clinical utility as a complementary tool for pre-operative planning using three-dimensional templating software. Moreover, this technique could be feasible in most hospitals without additional expenditure.

Digitalized analyses of intraoperative acetabular component position using image-matching technique in total hip arthroplasty

Aims

Appropriate acetabular component placement has been proposed for prevention of postoperative dislocation in total hip arthroplasty (THA). Manual placements often cause outliers in spite of attempts to insert the component within the intended safe zone; therefore, some surgeons routinely evaluate intraoperative pelvic radiographs to exclude excessive acetabular component malposition. However, their evaluation is often ambiguous in case of the tilted or rotated pelvic position. The purpose of this study was to develop the computational analysis to digitalize the acetabular component orientation regardless of the pelvic tilt or rotation.

Methods

Intraoperative pelvic radiographs of 50 patients who underwent THA were collected retrospectively. The 3D pelvic bone model and the acetabular component were image-matched to the intraoperative pelvic radiograph. The radiological anteversion (RA) and radiological inclination (RI) of the acetabular component were calculated and those measurement errors from the postoperative CT data were compared relative to those of the 2D measurements. In addition, the intra- and interobserver differences of the image-matching analysis were evaluated.

Results

Mean measurement errors of the image-matching analyses were significantly small (2.5° (SD 1.4°) and 0.1° (SD 0.9°) in the RA and RI, respectively) relative to those of the 2D measurements. Intra- and interobserver differences were similarly small from the clinical perspective.

Conclusion

We have developed a computational analysis of acetabular component orientation using an image-matching technique with small measurement errors compared to visual evaluations regardless of the pelvic tilt or rotation.Cite this article: Bone Joint Res 2020;9(7):360-367.

Pre-operative templating in THA. Part I: a classification of architectural hip deformities

INTRODUCTION

While numerous classifications of hip arthritis have been proposed, none considered the magnitude and direction of femoral head translation relative to the native acetabulum. A more precise classification of architectural hip deformities is necessary to improve preoperative templating and anticipate surgical challenges of total hip arthroplasty (THA). The purpose of the present study was to introduce a classification system to distinguish different types of architectural hip deformities, based on femoral head translation patterns, and to evaluate its repeatability using plain radiographs (qualitative) and Computed Tomography (CT) measurements (quantitative).

MATERIALS AND METHODS

We studied pre-operative frontal and lateral hip radiographs and CT scans of 191 hips (184 patients) that received primary THA. The distance between the femoral head center (FC) and the acetabular center (AC) was measured, as well as femoral offset, acetabular offset, head center height, acetabular floor distance and femoral neck angle. The hips were classified qualitatively using frontal plain radiographs, and then quantitatively using CT scans (with an arbitrary threshold of 3 mm as Centered, Medialized, Lateralized, Proximalized or Proximo-lateralized. The agreement between qualitative and quantitative classification methods was compared for applying the same classification.

RESULTS

Qualitative classification identified 120 centered (63%), 8 medialized (4%), 49 lateralized (26%), 3 proximalized (2%), and 11 proximo-lateralized (6%) hips, while quantitative classification identified 116 centered (61%), 8 medialized (4%), 51 lateralized (27%), 5 proximalized (3%), and 11 proximo-lateralized (6%) hips. The agreement between the two methods was excellent (0.94; CI 0.90-0.98). Medialization reached 9.7 mm, while lateralization reached 10.9 mm, and proximalization reached 8.5 mm. Proximalized and proximo-lateralized hips had more valgus necks, while medialized hips had more varus necks (p = 0.003).

CONCLUSIONS

The classification system enabled repeatable distinction of 5 types of architectural hip deformities. The excellent agreement between quantitative and qualitative methods suggests that plain radiographs are sufficient to classify architectural hip deformities.

Is computerised 3D templating more accurate than 2D templating to predict size of components in primary total hip arthroplasty?

INTRODUCTION

The aim of this study was to compare the accuracy of preoperative templating in total hip arthroplasty (THA) using conventional 2-dimensional (2D) and computed tomography (CT)-based 3-dimensional (3D) measures.

METHODS

One hundred and sixteen consecutive primary THAs were analysed. The preoperative diagnosis was primary osteoarthritis in all cases. The 2D templating and the 3D templating were performed by two different residents. All templating results were available for the orthopaedic surgeon performing the procedure. Accuracies with regard to the predicted and actual implant sizes were determined for each procedure. Implantation of the size as planned was defined as "exact", whereas the use of components within one size larger or smaller (±1) as planned were defined as "accurate."

RESULTS

The 3D templating was significantly more accurate in predicting implant sizing compared to 2D templating for primary total hip arthroplasty (THA). The difference was statistically significant for the cup templating (''exact'' p = 0.02; ''accurate'' p = 0.01) and for the stem templating (''exact'' p = 0.04; ''accurate'' p = 0.01).

CONCLUSION

Our results support the superiority of 3D templating over 2D templating in predicting implant size.

Low-Dose Computed Tomography Reduces Radiation Exposure by 90% Compared With Traditional Computed Tomography Among Patients Undergoing Hip-Preservation Surgery

PURPOSE

To compare the delivered radiation dose between a low-dose hip computed tomography (CT) scan protocol and traditional hip CT scan protocols (i.e., "traditional CT").

METHODS

This was a retrospective comparative cohort study. Patients who underwent hip-preservation surgery (including arthroscopy, surgical hip dislocation, or periacetabular osteotomy procedures) at our institution between 2016 and 2017 were identified. Patients were excluded if they had a body mass index (BMI) greater than 35, they underwent previous surgery, or a radiation dose report was absent. The low-dose group included patients who underwent hip CT at our institution using a standardized protocol of 100 kV (peak), 100 milliampere-seconds (mAs), and a limited scanning field. The traditional CT group included patients who had hip CT scans performed at outside institutions. The total effective dose (E_hip), effective dose per millimeter of body length scanned, patients' age, and patients' BMI were compared by univariate analysis. The correlation of E_hip to BMI was assessed.

RESULTS

The study included 41 consecutive patients in the low-dose group and 18 consecutive patients in the traditional CT group. Low-dose CT resulted in a 90% reduction in radiation exposure compared with traditional CT (E_hip, 0.97 ± 0.28 mSv vs 9.68 ± 6.67 mSv; P < .0001). Age (28 ± 11 years vs 26 ± 10 years, P = .42), sex (83% female patients vs 76% female patients, P = .74), and BMI (24 ± 3 vs 24 ± 3, P = .75) were not different between the 2 groups. E_hip had a poor but significant correlation to BMI in the low-dose CT group (R² = 0.14, slope = 0.03, P = .02) and did not correlate to BMI in the traditional CT group (R² = 0.13, P = .14).

CONCLUSIONS

A low-dose hip CT protocol for the purpose of hip-preservation surgical planning resulted in a 90% reduction in radiation exposure compared with traditional CT.

LEVEL OF EVIDENCE

Level II, diagnostic study.

Clinical accuracy of a patient-specific femoral osteotomy guide in minimally-invasive posterior hip arthroplasty

INTRODUCTION

Patient specific guides can be a valuable tool in improving the precision of planned femoral neck osteotomies, especially in minimally invasive hip surgery, where bony landmarks are often inaccessible. The aim of our study was to validate the accuracy of a novel patient specific femoral osteotomy guide for THR through a minimally invasive posterior approach, the direct superior approach (DSA).

METHODS

As part of our routine preoperative planning 30 patients underwent low dose CT scans of their arthritic hip. 3D printed patient specific femoral neck osteotomy guides were then produced. Intraoperatively, having cleared all soft tissue from the postero-lateral neck of the enlocated hip, the guide was placed and pinned onto the posterolateral femoral neck. The osteotomy was performed using an oscillating saw and the uncemented hip components were implanted as per routine. Postoperatively, the achieved level of the osteotomy at the medial calcar was compared with the planned level of resection using a 3D/2D matching analysis (Mimics X-ray module, Materialise, Belgium).

RESULTS

A total of 30 patients undergoing uncemented Trinity acetabular and TriFit TS femoral component arthroplasty (Corin, UK) were included in our analysis. All but one of our analysed osteotomies were found to be within 3 mm from the planned height of osteotomy. In one patient the level of osteotomy deviated 5 mm below the planned level of resection.

CONCLUSION

Preoperative planning and the use of patient specific osteotomy guides provides an accurate method of performing femoral neck osteotomies in minimally invasive hip arthroplasty using the direct superior approach.

LEVEL OF EVIDENCE

IV (Case series).

3D-printed Patient-specific Guides for Hip Arthroplasty

Surgeons and engineers constantly search for methods to improve the surgical positioning of implants used for joint arthroplasty. Rapid prototyping is being used to develop patient-specific instrumentation (PSI) and has already been successfully translated into large-scale clinical use for knee arthroplasty. PSI has been used in shoulder arthroplasty; however, it is not yet known whether PSI provides improved accuracy and outcomes compared with conventional methods in either shoulder arthroplasty or knee arthroplasty. In the hip, PSI has been limited to the positioning of custom-manufactured implants and a small number of surgeons testing the emerging solutions from different manufacturers. Early results indicate consistent accurate positioning of implants with the use of PSI in hip arthroplasty but with added costs and uncertain effect on clinical outcomes.

A Pilot Study of Augmented Reality Technology Applied to the Acetabular Cup Placement During Total Hip Arthroplasty

BACKGROUND

We developed an acetabular cup placement device, the AR-HIP system, using augmented reality (AR). The AR-HIP system allows the surgeon to view an acetabular cup image superimposed in the surgical field through a smartphone. The smartphone also shows the placement angle of the acetabular cup. This preliminary study was performed to assess the accuracy of the AR-HIP system for acetabular cup placement during total hip arthroplasty (THA).

METHODS

We prospectively measured the placement angles using both a goniometer and AR-HIP system in 56 hips of 54 patients undergoing primary THA. We randomly determined the order of intraoperative measurement using the 2 devices. At 3 months after THA, the placement angle of the acetabular cup was measured on computed tomography images. The primary outcome was the absolute value of the difference between intraoperative and postoperative computed tomography measurements.

RESULTS

The measurement angle using AR-HIP was significantly more accurate in terms of radiographic anteversion than that using a goniometer (2.7° vs 6.8°, respectively; mean difference 4.1°; 95% confidence interval, 3.0-5.2; P < .0001). There was no statistically significant difference in terms of radiographic inclination (2.1° vs 2.6°; mean difference 0.5°; 95% confidence interval, -1.1 to 0.1; P = .13).

CONCLUSION

In this pilot study, the AR-HIP system provided more accurate information regarding acetabular cup placement angle than the conventional method. Further studies are required to confirm the utility of the AR-HIP system as a navigation tool.

The Safe Zone Range for Cup Anteversion Is Narrower Than for Inclination in THA

BACKGROUND

Cup malposition is a common cause of impingement, limitation of ROM, acceleration of bearing wear, liner fracture, and instability in THA. Previous studies of the safe zone based on plain radiographs have limitations inherent to measuring angles from two-dimensional projections. The current study uses CT to measure component position in stable and unstable hips to assess the presence of a safe zone for cup position in THA.

QUESTIONS/PURPOSES

(1) Does acetabular component orientation, when measured on CT, differ in stable components and those revised for recurrent instability? (2) Do CT data support historic safe zone definitions for component orientation in THA?

METHODS

We identified 34 hips that had undergone revision of the acetabulum for recurrent instability that also had a CT scan of the pelvis between August 2003 and February 2017. We also identified 175 patients with stable hip replacements who also had a CT study for preoperative planning and intraoperative navigation of the contralateral side. For each CT study, one observer analyzed major factors including acetabular orientation, femoral anteversion, combined anteversion (the sum of femoral and anatomic anteversion), pelvic tilt, total offset difference, head diameter, age, sex, and body mass index. These measures were then compared among stable hips, hips with cup revision for anterior instability, and hips with cup revision for posterior instability. We used a clinically relevant measurement of operative anteversion and inclination as opposed to the historic use of radiographic anteversion and inclination. The percentage of unstable hips in the historic Lewinnek safe zone was calculated, and a new safe zone was proposed based on an area with no unstable hips.

RESULTS

Anteriorly unstable hips compared with stable hips had higher operative anteversion of the cup (44° ± 12° versus 31° ± 11°, respectively; mean difference, 13°; 95% confidence interval [CI], 5°-21°; p = 0.003), tilt-adjusted operative anteversion of the cup (40° ± 6° versus 26° ± 10°, respectively; mean difference, 14°; 95% CI, 10°-18°; p < 0.001), and combined tilt-adjusted anteversion of the cup (64° ± 10° versus 54° ± 19°, respectively; mean difference, 10°; 95% CI, 1°-19°; p = 0.028). Posteriorly unstable hips compared with stable hips had lower operative anteversion of the cup (19° ± 15° versus 31° ± 11°, respectively; mean difference, -12°; 95% CI, -5° to -18°; p = 0.001), tilt-adjusted operative anteversion of the cup (19° ± 13° versus 26° ± 10°, respectively; mean difference, -8°; 95% CI, -14° to -2°; p = 0.014), pelvic tilt (0° ± 6° versus 4° ± 6°, respectively; mean difference, -4°; 95% CI, -7° to -1°; p = 0.007), and anatomic cup anteversion (25° ± 18° versus 34° ± 12°, respectively; mean difference, -9°; 95% CI, -1° to -17°; p = 0.033). Thirty-two percent of the unstable hips were located in the Lewinnek safe zone (11 of 34; 10 posterior dislocations, one anterior dislocation). In addition, a safe zone with no unstable hips was identified within 43° ± 12° of operative inclination and 31° ± 8° of tilt-adjusted operative anteversion.

CONCLUSIONS

The current study supports the notion of a safe zone for acetabular component orientation based on CT. However, the results demonstrate that the historic Lewinnek safe zone is not a reliable predictor of future stability. Analysis of tilt-adjusted operative anteversion and operative inclination demonstrates a new safe zone where no hips were revised for recurrent instability that is narrower for tilt-adjusted operative anteversion than for operative inclination. Tilt-adjusted operative anteversion is significantly different between stable and unstable hips, and surgeons should therefore prioritize assessment of preoperative pelvic tilt and accurate placement in operative anteversion. With improvements in patient-specific cup orientation goals and acetabular component placement, further refinement of a safe zone with CT data may reduce the incidence of cup malposition and its associated complications.

LEVEL OF EVIDENCE

Level III, diagnostic study.

Computed Tomography Scans in Patients With Young Adult Hip Pain Carry a Lifetime Risk of Malignancy

PURPOSE

To calculate the lifetime risk of malignancy in young adult patients with hip pain using 5 different imaging and radiation dose protocols with or without pre- and postoperative computed tomography (CT).

METHODS

Radiographic and CT patient radiation doses were retrospectively reviewed. Imaging protocols for hip pain composed of radiographs with or without pre- and postoperative CT scans were modeled and radiation doses were estimated using the PCXMC computer code. Based on these radiation doses, lifetime attributable risks of cancer and mortality for a 10- through 60-year-old male and female were calculated as published by the committee on the Biological Effects of Ionizing Radiation (BEIR) in the BEIR VII report. Relative risks and number needed to harm (NNH) were calculated for each protocol.

RESULTS

Based on a review of our institutional database, 2 CT scan doses were used for this study: a high 5.06 mSv and a low 2.86 mSv. Effective doses of radiation ranged from 0.59 to 0.66 mSv for radiographs alone to 10.71 to 10.78 mSv for radiographs and CT both pre- and postoperatively at the higher dose. Lifetime attributable risk of cancer for radiographs alone was 0.006% and 0.011% for a 20-year-old male and female, respectively. Lifetime attributable risk of cancer for radiographs along with pre- and postoperative CT scans at higher dose was 0.105% and 0.177% for a 20-year-old male and female, respectively. Radiographs alone lead to an NNH of 16,667 for males and 9,090 for females, whereas the protocol with pre- and postoperative CT scans at the higher dose led to an NNH of 952 for males and 564 for females. The relative risk of this protocol compared to radiographs alone was 17.5 for males and 16.1 for females.

CONCLUSION

Protocols with CT scans of the hip/pelvis pose a small lifetime attributable risk (0.034%-0.177% for a 20-year-old) but a large relative risk (5-17 times) of cancer compared with radiographs alone in the imaging evaluation for hip pain that decreases with increasing age.

CLINICAL RELEVANCE

This study illustrates the need for clinicians to understand the imaging protocols used at their institution to understand the risks and benefits of using those protocols in their practice.

Effective dose in low-dose CT compared with radiography for templating of total hip arthroplasty

Background Recently, total hip arthroplasty (THA) has come to focus on restoration of individual anatomy including femoral neck anteversion and global offset (femoral and acetabular offset). Three-dimensional (3D) computed tomography (CT) data could provide a better basis for preoperative templating. The use of CT has been hampered by high radiation dose. Purpose To evaluate the effective dose used in pelvis and hip CT for THA templating. Material and Methods CT data from two clinical trials of THA were evaluated for CT scan length and volume CT dose index (CTDI_vol). The effective doses from hip-knee-ankle CT and pelvis and hip radiography were compared. Conversion factors for effective dose for radiography were calculated using the PCXMC software. Results A reduced dose CT protocol for pelvis imaging gave a substantial dose reduction compared with standard CT, while maintaining sufficient image quality. Between the two clinical trials there was a significant reduction in effective CT dose corresponding to changes in the CT protocol ( P < 0.01). The CT dose for the latter group was similar to, but nevertheless significantly higher than for, radiography ( P < 0.01). However, in the latter group the theoretical minimum dose for CT, using the minimum scan length required by the templating software, was equal to the dose from radiography. Conclusion Although the CT dose remained higher than for radiography, potential reductions in scan length could reduce the dose further so that CT would have a comparable level of risk to radiography with the added benefit of 3D templating.

Variance in predicted cup size by 2-dimensional vs 3-dimensional computerized tomography-based templating in primary total hip arthroplasty

Background

Preoperative total hip arthroplasty templating can be performed with radiographs using acetate prints, digital viewing software, or with computed tomography (CT) images. Our hypothesis is that 3D templating is more precise and accurate with cup size prediction as compared to 2D templating with acetate prints and digital templating software.

Methods

Data collected from 45 patients undergoing robotic-assisted total hip arthroplasty compared cup sizes templated on acetate prints and OrthoView software to MAKOplasty software that uses CT scan. Kappa analysis determined strength of agreement between each templating modality and the final size used. t tests compared mean cup-size variance from the final size for each templating technique. Interclass correlation coefficient (ICC) determined reliability of digital and acetate planning by comparing predictions of the operating surgeon and a blinded adult reconstructive fellow.

Results

The Kappa values for CT-guided, digital, and acetate templating with the final size was 0.974, 0.233, and 0.262, respectively. Both digital and acetate templating significantly overpredicted cup size, compared to CT-guided methods (P < .001). There was no significant difference between digital and acetate templating (P = .117). Interclass correlation coefficient value for digital and acetate templating was 0.928 and 0.931, respectively.

Conclusions

CT-guided planning more accurately predicts hip implant cup size when compared to the significant overpredictions of digital and acetate templating. CT-guided templating may also lead to better outcomes due to bone stock preservation from a smaller and more accurate cup size predicted than that of digital and acetate predictions.

Simulated radiographic bone and joint modeling from 3D ankle MRI: feasibility and comparison with radiographs and 2D MRI

PURPOSE

The purpose of this work is to simulate radiographs from isotropic 3D MRI data, compare relationship of angle and joint space measurements on simulated radiographs with corresponding 2D MRIs and real radiographs (XR), and compare measurement times among the three modalities.

MATERIALS AND METHODS

Twenty-four consecutive ankles were included, eight males and 16 females, with a mean age of 46 years. Segmented joint models simulating radiographs were created from 3D MRI data sets. Three readers independently performed blinded angle and joint space measurements on the models, corresponding 2D MRIs, and XRs at two time points. Linear mixed models and the intraclass correlation coefficient (ICC) was ascertained, with p values less than 0.05 considered significant.

RESULTS

Simulated radiograph models were successfully created in all cases. Good agreement (ICC > 0.65) was noted among all readers across all modalities and among most measurements. Absolute measurement values differed between modalities. Measurement time was significantly greater (p < 0.05) on 2D versus simulated radiographs for most measurements and on XR versus simulated radiographs (p < 0.05) for nearly half the measurements.

CONCLUSIONS

Simulated radiographs can be successfully generated from 3D MRI data; however, measurements differ. Good inter-reader and moderate-to-good intra-reader reliability was observed and measurements obtained on simulated radiograph models took significantly less time compared to measurements with 2D and generally less time than XR.

Patient-specific instrumentation improves the accuracy of acetabular component placement in total hip arthroplasty

Aims

Accurate placement of the acetabular component during total hip arthroplasty (THA) is an important factor in the success of the procedure. However, the reported accuracy varies greatly and is dependent upon whether free hand or navigated techniques are used. The aim of this study was to assess the accuracy of an instrument system that incorporates 3D printed, patient-specific guides designed to optimise the placement of the acetabular component.

Patients and Methods

A total of 100 consecutive patients were prospectively enrolled and the accuracy of placement of the acetabular component was measured using post-operative CT scans.

Results

The mean absolute deviation from the planned inclination and anteversion was 3.9° (0.0° to 13.6°) and 3.6° (0.0° to 12.9°), respectively. In 91% of cases the planned target of +/-10° was achieved for both inclination and anteversion.

Conclusion

Accurate placement of the acetabular component can be achieved using patient-specific guides and is superior to free hand techniques and comparable to navigated and robotic techniques. Cite this article: Bone Joint J 2016;98-B:1342–6.