Does Individualization of Cup Position Affect Prosthetic or Bone Impingement Following THA?

How Much Does a Computed Tomography-Based Mixed-Reality Navigation System Change Freehand Acetabular Component Position?

Background

This study evaluates how a computed tomography-based mixed-reality (MR) navigation system impacts acetabular component orientation compared to freehand positioning in total hip arthroplasty.

Methods

A series of 79 patients who underwent total hip arthroplasty utilizing a computed tomography-based MR navigation system were reviewed. The surgeon initially placed the acetabular cup freehand, attempting to achieve the preoperative plan, and this initial intraoperative orientation was recorded. The cup was then adjusted to the planned position. The difference between freehand and planned tilt-adjusted operative anteversion (OA) and inclination (OI) determined the navigation tool's impact.

Results

The mean preoperative planned OA was 30.1 ± 2.0 (range: 25, 35) degrees, and the mean freehand intraoperative OA was 30.2 ± 9.1 (range: 4, 57) degrees (P = .885), requiring a mean adjustment of 6.8 ± 5.1 (range: 0, 23) degrees. Freehand OA was corrected at least 5 degrees in 54.4% (43/79) of cases. The mean preoperative planned OI was 40.8 ± 0.6 (range: 39, 42) degrees, and the mean freehand intraoperative OI was 37.8 ± 6.6 (range: 18, 53) degrees (P < .001), requiring a mean adjustment of 5.7 ± 4.5 (range: 0, 22) degrees to achieve. Freehand OI was corrected at least 5 degrees in 43.0% (34/79) of cases.

Conclusions

Freehand acetabular component positioning in the lateral position is variable when attempting to execute patient-specific numerical cup orientation targets. Use of this navigation tool led the surgeon to correct more than 5 degrees in both OA and OI in roughly half of the hips.

Surgical procedure and retrospective comparative series of Microport's AnteriorPath® vs. AMIS® in total hip arthroplasty. Preliminary findings from a single institution

Objective

In recent years, the paradigm of surgical approaches for total hip arthroplasty (THA) has evolved, with portal-assisted techniques emerging as a promising avenue for increasing precision and minimizing invasiveness. The purpose of this study was to compare early experience with the Microport anterior percutaneously assisted total hip arthroplasty (MAP) system, with the established AMIS direct anterior approach (DAA).

Material and Methods

A retrospective chart analysis was performed on 200 consecutive patients who underwent DAA or MAP at our institution in 2022. The research was conducted in accordance with the Declaration of Helsinki (as revised in 2013), and was approved by the institutional review board of the University Duisburg-Essen (23-11274-BO).

Results

Two hundred patients were enrolled (100 DAA and 100 MAP; time to follow-up 1.7 years ±88 days). The mean operative time was 81 minutes (MAP) and 67 minutes (DAA, p>0.05). The mean cup tilt angle was 39° (MAP) and 40° (DAA; p>0.05). The mean cup anteversion angle was 13° (MAP) and 16° (DAA; p>0.05). The mean postoperative hemoglobin (Hb) decrease was 2.6 mg/dL ±0.9 mg/dL (MAP) and 2.5 mg/dL ±0.9 mg/dL (DAA; p>0.05). No major complications were documented in any of the 200 cases during the observation period. Additional screw fixation was performed in 7 cases and hybrid stem cementation was performed in 3 cases due to lack of rotational stability. All 10 cases were in patients with DAA. In only one of the 200 cases, two units of RBC were transfused postoperatively in a DAA case after a postoperative decrease of 5.7 mg/dL Hb.

Conclusion

Anterior Path® has been demonstrated to provide reliable results, despite the presence of a steep learning curve. The employment of a working cannula has been shown to enhance the surgeon's perspective during the preparation of the acetabulum. In relation to skin incision, the bikini line incision, which is regarded as advantageous due to its alignment with the cleavage lines, has been identified as a notable benefit that is acknowledged by the patient.

Impact of Flatback Deformity and Stiff Spinopelvic Mobility on 3-Dimensional Pelvic and Hip Kinematics After Total Hip Arthroplasty

Background

Spinopelvic abnormalities have been reported to be a risk factor for dislocation after total hip arthroplasty (THA). This study aimed to compare the kinematics of the pelvis and hip joints in patients with and without spinopelvic abnormalities after THA and to elucidate dynamic forward-leaning movement during chair-rising, which are not detectable through static radiographs.

Methods

This case series included 108 hips that underwent dynamic anteroposterior radiographic imaging of the sit-to-stand motion after THA. The average age at surgery was 68 ± 10 years, with 95 hips (88%) in women (average body mass index, 23.5 ± 3.2 kg/m2). Kinematic analysis was performed to measure the anterior pelvic plane angle (APPa) and hip flexion/extension angles from seated to standing positions using model-image registration techniques. Pelvic incidence (PI) and lumbar lordosis (LL) were measured to calculate PI-LL.

Results

Flatback deformity was present in 45 hips (42%) and stiff spinopelvic mobility (SPM) in 35 hips (32%), with both deformities present in 21 hips (19%). The pelvis was consistently significantly posteriorly tilted in the flatback deformity group throughout the movement compared with the normal group, with the greatest difference observed in the standing position. The hip flexion angles in the flatback deformity group showed significant extension in the standing position (7° greater than that in the normal group). For stiff SPM, a significant posterior tilt in the standing position was observed. Accordingly, the range between the maximum hip flexion and extension was 13° greater. There was no significant difference between the maximal flexion and extension centers.

Conclusions

Patients with flatback deformities consistently exhibited posterior APPa, especially when standing. In stiff SPM, a large range of hip flexion and extension while chair-rising increased the risk of impingement, indicating the necessity for a wider range of motion without changing the target orientation. These findings highlight the importance of considering spinopelvic alignment when planning cup positioning in THA to minimize the risk of dislocation.

Level of Evidence

Level III. See Instructions for Authors for a complete description of levels of evidence.

In silico analysis of the patient-specific acetabular cup anteversion safe zone

INTRODUCTION

Various computer-assisted surgical systems claim to improve the accuracy of cup placement in total hip arthroplasties after assessing spinopelvic mobility to prevent prosthetic impingement. However, no study has yet analyzed the extent of the patient-specific cup anteversion safe zones.

HYPOTHESIS

We hypothesized that most patients have a safe zone >10 °, except those with abnormal spinopelvic mobility, who have a much narrower safe zone.

MATERIALS AND METHODS

We simulated the risks of prosthetic impingement using the planned cup anteversion. The consecutive cohort included 341 patients who underwent total hip arthroplasty. Our primary endpoint was the patient-specific impingement-free zone for cup anteversion, which was then divided into four subgroups: 0 °, 1 ° to 5 °, 6 ° to 10 °, and >10 °. This data was then secondarily analyzed for abnormal spinopelvic mobility (the difference in the spinopelvic tilt [ΔSPT] from a standing to a flexed seated position >20 °).

RESULTS

The mean anteversion safe zone was 22.8 ° with 82.4% (281/341) of patients with a zone strictly >10 °. The mean safe zone was 8.9 ° (+/- 9 °) in patients with an ΔSPT ≥20 ° (18.2%), with 37.1% of these patients having a zone of 0 °, 16.13% a zone between 1 ° and 5 °, 8.06% a zone between 6 ° and 10 ° and 38.71% a zone >10 °. The mean safe zone was 25.9 ° (+/- 9 °) in patients with an ΔSPT <20 ° (81.8%), and the proportion of cases in each zone was 2.51%, 1.08%, 4.3%, and 92.11%, respectively (p < 0.001).

CONCLUSION

The safe zone for anteversion appears to be fairly wide in most patients. However, identifying patients at risk of abnormal spinopelvic mobility seems necessary to identify the two-thirds of patients with a narrow safe zone.

LEVEL OF EVIDENCE

IV; retrospective study.

Intraoperative application of three-dimensional printed guides in total hip arthroplasty: A systematic review

BACKGROUND

Acetabular component positioning in total hip arthroplasty (THA) is of key importance to ensure satisfactory post-operative outcomes and to minimize the risk of complications. The majority of acetabular components are aligned freehand, without the use of navigation methods. Patient specific instruments (PSI) and three-dimensional (3D) printing of THA placement guides are increasingly used in primary THA to ensure optimal positioning.

AIM

To summarize the literature on 3D printing in THA and how they improve acetabular component alignment.

METHODS

PubMed was used to identify and access scientific studies reporting on different 3D printing methods used in THA. Eight studies with 236 hips in 228 patients were included. The studies could be divided into two main categories; 3D printed models and 3D printed guides.

RESULTS

3D printing in THA helped improve preoperative cup size planning and post-operative Harris hip scores between intervention and control groups (P = 0.019, P = 0.009). Otherwise, outcome measures were heterogeneous and thus difficult to compare. The overarching consensus between the studies is that the use of 3D guidance tools can assist in improving THA cup positioning and reduce the need for revision THA and the associated costs.

CONCLUSION

The implementation of 3D printing and PSI for primary THA can significantly improve the positioning accuracy of the acetabular cup component and reduce the number of complications caused by malpositioning.