Navigated Acetabular Cup Fixation for Acetabular Deformity or Revision Total Hip Arthroplasty

Improvement of surgical time and functional results after do-it-yourself 3D-printed model preoperative planning in acetabular defects Paprosky IIA-IIIB

INTRODUCTION

The correct positioning of the implant in revision total hip arthroplasty (rTHA) is critical to obtaining substantial functional outcomes, and to avoiding complications. Current literature supports three-dimensional (3D)-printed models as potentially useful tools for preplanning, as well as the "do it yourself (DIY)" methodology to reduce both the time and costs of this procedure. However, no study has determined the efficacy of both methods combined in a cohort of patients with severe acetabular defects. In the lack of bibliography, we performed rTHA after preoperative planning by DIY-3D-printed models to evaluate its influence in: 1) the surgical time, 2) the functional scores, 3) the intra and postoperative complications, and 4) the reconstruction of the center of rotation (COR) of the hip.

HYPOTHESIS

Preoperative planning through 3D-DIY printed models will both improve the accuracy of the implant positioning, and the surgical time, leading the latter to improved functional scores and reduced complications.

MATERIALS & METHODS

A comparative study of 21 patients with Paprosky IIB to IIIB acetabular defects who underwent rTHA after 3D-printed model preoperative planning by the DIY method between 2016 and 2019 was conducted. A historical cohort of 24 patients served as the comparator. Surgical time, reconstruction of the COR, functional scores, and complications were analyzed.

RESULTS

The mean follow-up was 32.4 (range, 12 to 60) months. All the patients showed significant improvement of the Harris hip score (HHS) after the operation (3D group: 26.58±10.73; control group 22.47±15.43 (p=0.00)). In the 3D-printed model preoperative planning group the mean operation time and the intraoperative complications were significantly lower (156.15±43.03min vs 187.5±54.38min (p=0.045); and 19% vs 62.5% (p=0.003), respectively), and the HHS and patient satisfaction score (PSS) were significantly greater (83.74±8.49 vs 75.59±11.46 (p=0.019); and 8.17±0.88 vs 7.36±1.17 (p=0.023), respectively). No differences were found in the postoperative complications, nor in the restoration of the COR as determined from the acetabular index, verticalization or horizontalization, although the acetabular index was closer to the intended one in the 3D-printed model planning group (46.67°±7.63 vs 49.22±8.1 (p=0.284)).

CONCLUSION

Preoperative planning of severe acetabular defects through 3D-printed models shortens the surgical time, leading to a decrease in complications and thus to better functional outcomes and greater patient satisfaction. Moreover, the DIY philosophy could decrease both the time and costs of traditional 3D planning.

LEVEL OF EVIDENCE

III, retrospective case matched study.

Lewinnek Safe Zone References are Frequently Misquoted

BACKGROUND

Optimal acetabular component orientation in total hip arthroplasty (THA) is a necessity in achieving a stable implant. Although there has been considerable debate in the literature concerning the safe zone, to date, there has not been any review to determine if these references are consistent with the definition applied by Lewinnek et al. in 1978. Therefore, this article aims to examine the available literature in the PubMed database to determine how often a correct reference to the safe zone as defined by Lewinnek was applied to discussions regarding THA.

METHODS

A search for literature in the PubMed database was performed for articles from 1978 to 2019. Search criteria included terms 'Lewinnek,' 'safe zone,' and 'total hip arthroplasty.' Exclusions included abstract-only articles, non-English articles, articles unrelated to THA, and those lacking full content.

RESULTS

A review of literature yielded 147 articles for inclusion. Overall, only 11% (17) cited the Lewinnek article correctly. Forty-five percent (66) of articles referenced measurements in the supine position, 18% (26) referenced other positions, and 37% (55) did not specify. Nineteen percent (28) reported measurements of the acetabular cup orthogonal to the anterior pelvic plane, while 73% (108) did not, and 7% (11) did not specify. Twenty-three percent (34) measured from computed tomography scans instead of other methods.

CONCLUSIONS

In the discussion of the safe zone regarding THA, only 11% of articles listed are consistent with the definition established by Lewinnek. This warrants further investigation into a consistent application of the term and its implications for THA implant stability and dislocation rates.

Comparison of cementless and cemented cups in revision total hip arthroplasty using a computed tomography-based navigation system

BACKGROUND

Studies comparing cementless and cemented cups are lacking, especially for revision total hip arthroplasty (THA). The aim of this study was to investigate and compare the differences in implant accuracy between two fixation methods in revision THA.

METHODS

We conducted a retrospective study of 85 hips in 70 patients who underwent revision THA using a computed tomography (CT)-based navigation system. Among these, 53 hips underwent cementless THA and 32 hips underwent cemented THA. We measured cup inclination and anteversion using the Kyocera two-dimensional-template with X-ray (Japan-Kyocera, Shiga, Japan) and stem anteversion with CT. We calculated the combined anteversion [cup anteversion+0.7×stem anteversion].

RESULTS

There were no significant differences between the two groups with respect to definitive cup inclination and anteversion. The mean deviations in the inclination and anteversion angle were 40.3 ± 4.3 and 19.6 ± 6.2° in the cementless group and 40.5 ± 3.3 and 17.1 ± 5.1° in the cemented group. There were 11 outliers with respect to the Lewinnek safe zone in the cementless group and two in the cemented group (P = 0.072). Although there was no statistically significant difference, the number of safe zone outliers in the cemented group was less than that in the cementless group.

CONCLUSION

We conclude that when using a navigation system for revision THA, high precision can be obtained for the cup placement angle with or without cement. However, it seems that a major error in the installation angle of the cup is less likely to occur when using a cemented cup than when using a cementless cup in revision THA with a navigation system.

Three-dimensional technology assisted trabecular metal cup and augments positioning in revision total hip arthroplasty with complex acetabular defects

BACKGROUND

Revision total hip arthroplasty (THA) with large acetabular defect remains a challenge. Though trabecular metal (TM) cup and augments have been introduced in defect reconstruction with good result, the accurate positioning of implant is important to avoid complications. Therefore, we aimed to evaluate the usefulness of three-dimensional (3D) simulation and 3D model in assisting implant positioning during complex revision THA.

METHODS

Sixteen patients (18 hips) who underwent revision THA with a Paprosky type III acetabular defect were analyzed retrospectively. Placement of acetabular cup and TM augments was simulated with 3D simulation software and 3D model preoperatively. Cup anteversion, abduction angle, and hip center were measured in each case preoperatively and postoperatively. Primary outcome was the percentage of outliers according to Lewinnek safe zone and Harris hip score (HHS). Secondary outcome was the correlation between the 3D planned and the postoperative value.

RESULTS

The percentage of outliers was significantly corrected from 77.78% (14/18) preoperatively to 38.88% (7/18) postoperatively (p = 0.04). There was a significant correlation between mean planned cup anteversion and postoperative value (13.39 vs 11.99, r = 0.894; p < 0.001). There was a significant correlation between mean planned abduction and postoperative value (42.67 vs 44.91, r = 0.921, p < 0.001). The number of planned and used augments was the same in all the cases. In 15 cases (83.33%), the size of planned and used TM augments was the same. The HHS was significantly improved at final follow-up (80.94 vs 27.50, p < 0.001). No cases presented dislocation or radiological signs of loosening.

CONCLUSION

Preoperative 3D simulation and model were considered the useful method to assist implant positioning in revision THA with complex acetabular defect, with moderate to high accuracy and satisfied clinical outcome.

Efficacy of Computed Tomography-Based Navigation for Cup Placement in Revision Total Hip Arthroplasty

Background

Navigation systems are an effective tool to improve the installation accuracy of the cup in primary total hip arthroplasty. This study aimed to evaluate the efficacy of a computed tomography-based navigation system in achieving optimal installation accuracy of implants in revision total hip arthroplasty and to clarify the usefulness of the navigation system.

Methods

We conducted a retrospective study of 23 hips in 23 patients who underwent revision total hip arthroplasty using a computed tomography-based navigation system; the control group comprised 33 hips in 33 patients who underwent revision total hip arthroplasty without a navigation system.

Results

The average cup position with the navigation system was 40.0° ± 3.7° in radiographic abduction angle, 18.8° ± 4.8° in radiographic anteversion, and 41.2° ± 8.9° in combined anteversion; without the navigation system, the average cup position was 38.7° ± 6.1°, 19.0° ± 9.1°, and 33.6° ± 20.5°, respectively. The achievement rate of cup positioning within the Lewinnek safe zone was not significantly different between the navigation group (82.6%) and control group (63.6%). In contrast, the achievement rate of cup positioning within the Widmer combined anteversion guidelines was significantly greater in the navigation group (78.3%) than in the control group (48.0%, p = 0.029). Furthermore, outlier cases in the navigation group had a smaller variance of deviation from the optimal cup position than those in the control group did.

Conclusions

The results show that the use of navigation for revision total hip arthroplasty improved cup positioning and reduced the range of outliers. Improvement of cup placement accuracy influenced the installation of the stem and also improved the achievement rate of combined anteversion. Thus, a computed tomography-based navigation system is very useful for surgeons when placing the cup within the target angle in revision total hip arthroplasty.

The Evolution of Computer-Assisted Total Hip Arthroplasty and Relevant Applications

In total hip arthroplasty (THA), the accurate positioning of implants is the key to achieve a good clinical outcome. Computer-assisted orthopaedic surgery (CAOS) has been developed for more accurate positioning of implants during the THA. There are passive, semi-active, and active systems in CAOS for THA. Navigation is a passive system that only provides information and guidance to the surgeon. There are 3 types of navigation: imageless navigation, computed tomography (CT)-based navigation, and fluoroscopy-based navigation. In imageless navigation system, a new method of registration without the need to register the anterior pelvic plane was introduced. CT-based navigation can be efficiently used for pelvic plane reference, the functional pelvic plane in supine which adjusts anterior pelvic plane sagittal tilt for targeting the cup orientation. Robot-assisted system can be either active or semi-active. The active robotic system performs the preparation for implant positioning as programmed preoperatively. It has been used for only femoral implant cavity preparation. Recently, program for cup positioning was additionally developed. Alternatively, for ease of surgeon acceptance, semi-active robot systems are developed. It was initially applied only for cup positioning. However, with the development of enhanced femoral workflows, this system can now be used to position both cup and stem. Though there have been substantial advancements in computer-assisted THA, its use can still be controversial at present due to the steep learning curve, intraoperative technical issues, high cost and etc. However, in the future, CAOS will certainly enable the surgeon to operate more accurately and lead to improved outcomes in THA as the technology continues to evolve rapidly.