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Advanced, Imageless Navigation in Contemporary THA - Optimising Acetabular Component Placement
Abstract
Total hip arthroplasty (THA) stands as a reliable and effective way to manage end-stage hip disease secondary to a number of aetiologic conditions. While target 'safe zones' are widely quoted and endorsed, an increasingly robust body of evidence suggests that such idealised implantation goals have limited utility in patient-to-patient considerations and that even with a precise goal in mind, surgeons perform inconsistently in achieving these targets intra-operatively. Inter-patient variability, the concept of 'functional' safe zones and the largely under-appreciated impact of poor patient positioning (and progressive loss of position during the case) are all recognised and evidence-supported opponents of conventional ‘40 / 15’ approaches. In an environment whereby accountable cost utility, maximised surgical consistency (i.e., outlier minimisation), improved attainment of target position, and awareness of the radiation exposure burden of many pre-operative templating regimes are all paramount, there appears to be an increasing role for the application of imageless 'mini' intra-operative navigation systems for primary (and revision) THA procedures. This chapter reviews the evolution of THA navigation and discusses contemporary applications, defines the challenges associated with unanticipated pelvic movement, and explores potential future directions in the use of this exciting technology.
... starting) position [7,13]. Additionally, such devices are also associated with a not inconsequential morbidity profile, including medically important local skin pressure ulceration [6,16]. ...
Background
Unintended pelvic positional change is an acknowledged intra-operative problem for hip arthroplasty, seen commonly with procedures performed in the lateral position. If unrecognised, such changes can dramatically alter final acetabular component anteversion potentially resulting in suboptimal construct performance. It has previously been suggested that pelvic roll of just 13° may be enough to place an otherwise perfectly orientated cup outside of conventional ± 10° safe zones. Using the real-time tracking capacity of a commercially available optical navigation system, we aimed to accurately quantify pelvic roll occurring during total hip arthroplasties (THAs) performed in the decubitus position.
Methods
Prospectively collected data for 107 consecutive, unilateral, THAs were interrogated to determine the magnitude of pelvic movement around a central longitudinal axis (i.e. AP roll). Correlation statistics with patient age and body mass index (BMI) were also calculated.
Results
A mean pelvic roll of 9.5° was observed, being anterior in 96% of cases. Of these, 18.3% of hips had a magnitude of roll greater than 13°. There were no statistically significant independent correlations observed between age ( p = 0.87) or BMI ( p = 0.59) and mean roll.
Conclusions
Errors in achieving acetabular target version may result in numerous post-operative concerns including instability/dislocation, bearing wear, squeaking, range-of-movement limitation and increased revision rate. In a general cohort, our findings suggest a mean anterior pelvic roll during THA of nearly 10°. Without purposeful correction, this may cause substantial deviation from intended target positions. Future work is indicated to map changing pelvic roll during THA which is likely to follow a nonlinear trajectory.
Level of evidence : IV.
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... 'Imageless' systems entail that anatomic feature recognition is taking place intraoperatively and this information is used to create the surgical navigation plan. Despite the fact that CT-based navigation has been highly accurate, it is related to increased costs, the necessity for specific pre-operative imaging, and the unavoidable radiation exposure risk [24]. A large cohort study, based on a single-surgeon data series, compared an imageless navigation system with CT-based navigation systems [25]. ...
Total hip arthroplasty (THA) for end-stage osteoarthritis is one of the most effective surgical treatments in medicine. Impressive outcomes have been well documented in the literature with patients gaining ambulation and recovery of hip joint function. Nevertheless, there are still debatable issues and controversies that the orthopedic community has not been able to provide a definitive answer for. This review is focused on the current three most debatable issues surrounding the THA procedure: (1) new cutting-edge technology, (2) spinopelvic mobility, and (3) fast-track protocols. The scope of the herein narrative review is to analyze the debatable issues surrounding the three aforementioned topics and conclude the best contemporary clinical approaches regarding each issue.
Aims
Hip resurfacing remains a potentially valuable surgical procedure for appropriately-selected patients with optimised implant choices. However, concern regarding high early failure rates continues to undermine confidence in use. A large contributor to failure is adverse local tissue reactions around metal-on-metal (MoM) bearing surfaces. Such phenomena have been well-explored around MoM total hip arthroplasties, but comparable data in equivalent hip resurfacing procedures is lacking. In order to define genetic predisposition, we performed a case-control study investigating the role of human leucocyte antigen (HLA) genotype in the development of pseudotumours around MoM hip resurfacings.
Methods
A matched case-control study was performed using the prospectively-collected
database at the host institution. In all, 16 MoM hip resurfacing 'cases' were identified as having symptomatic periprosthetic pseudotumours on preoperative metal artefact reduction sequence (MARS) MRI, and were subsequently histologically confirmed as high-grade aseptic lymphocyte-dominated vasculitis-associated lesions (ALVALs) at revision surgery. ‘Controls’ were matched by implant type in the absence of evidence of pseudotumour. Blood samples from all cases and controls were collected prospectively for high resolution genetic analysis targeting 11 separate HLA loci. Statistical significance was set at 0.10 a priori to determine the association between HLA genotype and pseudotumour formation, given the small sample size.
Results
Using a previously-reported ALVAL classification, the majority of pseudotumour-positive cases were found to have intermediate-grade group 2 (n = 10; 63%) or group 3 (n = 4; 25%) histological findings. Two further patients (13%) had high-grade group 4 lesions. HLA-DQB1*05:03:01 (p = 0.0676) and HLA-DRB1*14:54:01 (p = 0.0676) alleles were significantly associated with a higher risk of pseudotumour formation, while HLA-DQA1*03:01:01 (p = 0.0240), HLA-DRB1*04:04:01 (p = 0.0453), HLA-C*01:02:01 (p = 0.0453), and HLA-B* 27:05:02 (p = 0.0855) were noted to confer risk reduction.
Conclusion
These findings confirm the association between specific HLA genotypes and the risk of pseudotumour development around MoM hip resurfacings. Specifically, the two ‘at risk’ alleles (DQB1*05:03:01 and DRB1*14:54:01) may hold clinical value in preoperative screening and prospective surgical decision-making.
Background
Total hip arthroplasty (THA) is an effective treatment for symptomatic hip osteoarthritis. The aim of this study was to determine the revision outcome of commercially available navigation technologies.
Methods
Data from the Australian Orthopaedic Association National Joint Replacement Registry from January 2016 to December 2020 included all primary THA procedures performed for osteoarthritis. Procedures using the Intellijoint HIP navigation system were identified and compared to procedures using “other” computer navigation systems and to nonnavigated procedures. The cumulative percent revision (CPR) was compared between the 3 groups using Kaplan-Meier estimates of survivorship and hazard ratios from Cox proportional hazards models, adjusted for age and gender.
Results
There were 1911 procedures that used the Intellijoint system, 4081 used “other” computer navigation systems, and 160,661 were nonnavigated procedures. The all-cause 2-year CPR rate for the Intellijoint system was 1.8% (95% confidence interval [CI], 1.2-2.6), compared to 2.2% (95% CI, 1.8-2.8) for other navigated cases and 2.2% (95% CI, 2.1-2.3) for nonnavigated cases. A prosthesis analysis identified the Paragon/Acetabular Shell THAs combined with the Intellijoint system to have a higher (3.4%) rate of revision than nonnavigated THAs (hazard ratio = 2.00 [95% CI, 1.01-4.00], P = .048). When this combination was excluded, the Intellijoint group demonstrated a 2-year CPR of 1.3%. There was no statistical difference in the CPR between the 3 groups before or after excluding the Paragon/Acetabular Shell system.
Conclusions
The preliminary data presented demonstrate no statistical difference in all-cause revision rates when comparing the Intellijoint system with “other” navigation systems and “nonnavigated” approaches for primary THAs.
Level of evidence
III (National registry analysis).
Background: Conventional lateral decubitus positioning for Total Hip Arthroplasties (THAs) is highly imprecise and further loss-of-position occurs during the procedure itself. This unintended movement is poorly recognised and can introduce substantial error in definitive acetabular component orientation. Failure to achieve desired target cup position is strongly-associated with a number of adverse outcome measures, including bearing wear, increased revision rate and dislocation.
Technological advances continue to evolve at a breath-taking pace. Computer-navigation, robot-assistance and three-dimensional digital planning have become commonplace in many parts of the world. With near exponential advances in computer processing capacity, and the advent, progressive understanding and refinement of software algorithms, medicine and orthopaedic surgery have begun to delve into artificial intelligence (AI) systems. While for some, such applications still seem in the realm of science fiction, these technologies are already in selective clinical use and are likely to soon see wider uptake. The purpose of this structured review was to provide an understandable summary to non-academic orthopaedic surgeons, exploring key definitions and basic development principles of AI technology as it currently stands. To ensure content validity and representativeness, a structured, systematic review was performed following the accepted PRISMA principles. The paper concludes with a forward-look into heralded and potential applications of AI technology in orthopedic surgery.
While not intended to be a detailed technical description of the complex processing that underpins AI applications, this work will take a small step forward in demystifying some of the commonly-held misconceptions regarding AI and its potential benefits to patients and surgeons. With evidence-supported broader awareness, we aim to foster an open-mindedness among clinicians toward such technologies in the future.
Background and aim of the work
Implant dislocation in total hip arthroplasties (THA) is a common concern amongst the orthopedic surgeons and represents the most frequent complication after primary implant. Several causes could be responsible for the dislocation, including the malpositioning of the components. Conventional imaging techniques frequently fail to detect the mechanical source of dislocation mainly because they could not reproduce a dynamic evaluation of the components. The purpose of this study was to elaborate a diagnostic tool capable to virtually assess if the range of movement (ROM) of a THA is free from anterior and/or superior mechanical impingement. The ultimate aim is to give the surgeon the possibility to weigh the mechanical contribution in a THA dislocation.
Methods
A group of patients who underwent THA revision for acute dislocation was compared to a group of non-dislocating THA. CT scans and a virtual model of each patient was obtained. A software called “Prosthesis Impingement Simulator (PIS)” was developed for simulating the (ROM) of the prosthetic hip. The ROM free of mechanical impingement was compared between the two groups.
Results
The PIS test could detect the dislocations with a sensitivity of 71,4%, and a specificity of 85,7%. The Fisher’s exact test showed a p-value of 0,02.
Conclusion
The PIS seems to be an effective tool for the determination of hip prosthetic impingement, as the main aid of the software is the exclusion of mechanical causes in the event of a dislocation.
Background
As primary total hip arthroplasty volume continues to increase, so will the number of revision total hip arthroplasty (rTHA) procedures. These complex cases represent a significant clinical and financial burden to the health-care system.
Methods
This was a retrospective review using the National Inpatient Sample. International Classification of Diseases, 9th and 10th revision codes were used to identify patients who underwent rTHA and create cohorts based on rTHA indications from 2012 to 2018. National and regional trends for length of stay (LOS), cost, and discharge location were evaluated.
Results
A total of 292,250 rTHA procedures were identified. The annual number of rTHA procedures increased by 28.1% from 2012 to 2018 (37,325 to 47,810). The top 3 indications for rTHA were instability (20.4%), aseptic loosening (17.8%), and infection (11.1%). Over the study period, the proportion of patients discharged to skilled nursing facility decreased from 44.2% to 38% (P < .001). Hospital LOS decreased on average from 4.8 to 4.4 days (P < .001). Infections had the highest average LOS (7.3 days) followed by periprosthetic fractures (6.5 days). Hospital costs decreased over the study period, from $25,794 to $24,555 (P < .001). The proportion of rTHA cases performed at urban academic centers increased (58.0% to 75.3%, P < .001) while the proportion performed at urban nonacademic centers decreased (35.5% to 19.4%, P < .001).
Conclusion
Instability was the most common indication for rTHA between 2012 and 2018. The proportion of rTHA performed in urban academic centers has increased substantially, away from urban nonacademic centers. While cost and LOS have decreased, significant geographic variability exists.
Background:
Acetabular component malposition is a major cause of dislocation following total hip arthroplasty (THA). Intellijoint HIP is an imageless navigation tool that has been shown to provide accurate intraoperative measurement of cup position during primary THA without substantially increasing operative time. However, its accuracy in revision THA has not been evaluated. This study therefore aims to assess the accuracy of Intellijoint HIP in measuring cup inclination and anteversion in comparison with computed tomography (CT) during revision THA.
Methods:
Intellijoint HIP was used to measure the position of the preexisting cup in 53 consecutive patients undergoing revision THA between December 2018 and February 2020. Two authors blinded to the intraoperative navigation measurements also independently measured cup position using preoperative CT according to Murray's radiographic definitions. Pearson correlation coefficients with 95% confidence intervals (CIs), paired t tests and Bland-Altman plots were used to assess agreement between navigation- and CT-measured cup position. Statistical analysis was performed using GraphPad Prism, with p values less than 0.05 indicating statistical significance.
Results:
There was excellent agreement between navigation and CT measurements for both cup inclination (r = 0.89, 95% CI 0.81-0.93) and anteversion (r = 0.93, 95% CI 0.88-0.96), with the mean absolute difference being 5.2º (standard deviation [SD] 4.0º) for inclination and 4.8º (SD 5.4º) for anteversion. The navigation measurement was within 10º of the radiographic measurement in 47 of 53 (88.7%) cases for inclination and 46 of 53 (86.8%) cases for anteversion.
Conclusion:
Imageless navigation demonstrated excellent correlation and agreement with CT measurements for both inclination and anteversion over a wide range of acetabular component positions.
Introduction:
Pelvic rotation (PR) on preoperative radiograph templating can affect various critical measured acetabular angles and potentially outcomes of successful total hip arthroplasty (THA). Optimising anatomical reconstruction of the joint is essential to achieve function, longevity and prevention of complications following surgery. There is limited literature that standardises the degree of acceptable PR on radiograph or its effects on the fitting of acetabular prostheses.
Objective:
This study aimed to develop a proof-of-concept that quantifies how PR can affect various acetabular angles used in pre-operative THA templating and to formulate a practicable method of determining if the preoperative PR is acceptable.
Materials and methods:
Computerised tomography (CT) models from three control and two THA patients were generated and manipulated in various degrees of PR. CT slices were thickened to simulate radiographs and acetabular angles measured.
Results:
The acetabular anteversion distance (AAD) and lateral opening angle (LOA) demonstrated a linear and quadratic relationship with good correlation (R 2 = 0.923, R 2 = 0.710 respectively, p < 0.0001) in relation to PR. Change in area of prosthesis (AOP) demonstrated a good linear correlation (r 2 = 0.774 and r 2 = 0.875, p < 0.0001) with PR. Two novel measurements were used to estimate the degree of PR from a pelvic radiograph; the horizontal distance between pubic symphysis and middle of sacrococcygeal joint (PSSC) and the simplified pelvic rotation ratio (SPRR). A strong correlation between PSSC and SPRR with change in PR was observed (R 2 = 0.970, R 2 = 0.953, p < 0.001).
Conclusion:
Preliminary result suggests that an SPRR > 2.0 correlates to PR > 20° with potential to have a clinical impact on preoperative measurements.
Introduction
The purpose of this study was to compare patient-specific acetabular cup target orientation using functional simulation to the Lewinnek Safe Zone (LSZ) and determine associated rates of postoperative dislocation.
Methods
A retrospective review of 1500 consecutive primary THAs was performed. Inclination, anteversion, pelvic tilt, pelvic incidence, lumbar flexion, and dislocation rates were recorded.
Results
56% of dynamically planned cups were within LSZ (p < 0.05). 6/1500 (0.4%) of these cups dislocated at two year follow-up, and all were within LSZ.
Conclusion
Optimal acetabular cup positioning using dynamic imaging differs significantly from historical target parameters but results in low rates of dislocation.
Level of evidence
Level III: Retrospective;
Objectives
To examine whether trauma and orthopaedic surgeons could visually assess the anteversion and inclination of a total hip replacement acetabular component from standard anteroposterior radiograph and anteversion on a standard lateral radiograph with accuracy or reproducibility. Main outcome measurement: The main outcome was accuracy of visual estimations of angles. The secondary outcome was whether these estimations were reproducible though intra-observer variability.
Results
Mean angles of anteversion on the anteroposterior, inclination on the anteroposterior and anteversion on the lateral on formal measurements were 15.2°, 45.4° and 19.9°; and the visual estimates were 17.5°, 45.9° and 18.2°, respectively. When comparing the visual estimates of surgeons and formal measurements, the results ranged from very poor to very good. Intra-observer reproducibility was moderate for all angles. The difference between the consultants and speciality registrars was not significant.
Conclusion
This study illustrated that not all orthopaedic surgeons were able to visually estimate angles well. Although some of our participants were very accurate, there were some who statistically were very poor. This level of inaccuracy can lead to inconsistency and we strongly suggested specialist software is used to assess acetabular cup position on postoperative plane radiographs rather than relying on ‘visual estimations’.