Pelvic position, lying on a traction table, during THA by direct anterior approach. Comparison with the standing position and influence on the acetabular cup anteversion

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.

Variations in pelvic tilt during day-to-day activities after total hip arthroplasty measured with an ultrasound system

INTRODUCTION

The pelvis plays a major role in the orientation of total hip arthroplasty (THA) implants and consequently, on the postoperative stability of the new hip joint. The relationship between the spine and pelvis affects the functional orientation of the acetabular cup, although this relationship differs between individuals and the positions encountered in everyday life. We believe this should be factored in when planning the THA procedure. This led us to conduct an in vivo ultrasound study to document the values of pelvic tilt in standing, sitting and lying positions in patients who have advanced hip osteoarthritis, before and after they undergo THA.

HYPOTHESIS

The pelvic tilt when standing, sitting and lying supine does not change significantly after THA.

MATERIALS AND METHODS

The pelvic tilt, defined as the angle between the anterior pelvic plane and a vertical line was measured using an ultrasound device in 30 patients before the THA procedure and again 6 months later in standing, sitting and lying positions. The measurements were done during an office visit with the patient on an examination table for the lying position, on a chair for the sitting position and with the heels and occiput against the wall for the standing position.

RESULTS

The preoperative and 6-month postoperative pelvic tilt were -5.6̊±10.4̊ [-30.6̊; 11.7̊] and -5.8̊±7.9̊ [-20.6̊; 10.4̊] (p=0.4129) when standing, -44.5̊±6.10 [-53.8̊; -23.9̊] and -43.5̊±6.9̊ [-54.4̊; -17.3̊] (p=0.5760) when sitting, -88.3̊±5.1̊ [-99.3̊; -78.7̊] and -87.9̊±5.9̊ [-97.6̊; -72.4̊] (p=0.6106) when lying supine, respectively. There was no significant difference in the pelvic tilt before and 6 months after THA procedure. Variations of±5̊; ±5-10̊; ±10-15̊ and 15-20̊ were found in 72% (18); 20% (5); 4% (1) and 4% (1) of patients when lying supine, 56% (14); 36% (9); 8% (2); 0% (0) of patients when standing and 76% (19); 24% (6); 0% (0); 0% (0) when sitting. The mean variation for each patient between the preoperative and 6 months postoperative measurement was 4.8±3.4̊ [0.8̊; 10.4̊] (p=0.4129), 3.5±2.3̊ [0.2̊; 9.1̊] (p=0.5760), and 4.6̊±3.2̊ [1.2̊; 15.4̊] (p=0.6106) for the standing, sitting and lying positions respectively.

CONCLUSION

The pelvic tilt does not significantly change 6 months after THA. Taking into account the various positions used in everyday life may help to optimize the implant position. We have described the use of an affordable, accurate and non-irradiating device that provides fast and easy measurements of pelvic tilt in various positions.

LEVEL OF EVIDENCE

IV.

How the hip-spine relationship influences total hip arthroplasty

INTRODUCTION

Motion in the spine, pelvis and hips which make up the spinopelvic femoral complex (SPFC) implies mechanical relationships that help maintain trunk balance and optimize hip functionThe aim of this study was to understand the physiology of the SPFC and evaluate the dysfunctions of the SPFC and their implications for total hip arthroplasty considering the hip-spine relationship.

METHODS

A review of relevant and comprehensive studies on this subject is reported in order to highlight a pathophysiology that integrates the description of the evaluations of the spine-pelvic and hip parameters and recommendations for the kinematic planning of the THA procedure. The primary objective was to determine which type of hip-spine relationship has the highest risk for THA complications and to become proficient in selecting the priority surgical intervention when both the hip and spine are affected. Finally, this review attempted to assist hip surgeons with surgical technique, tools, implant selection, and goals of planning a THA that requires personalized kinematic alignment. Determine the influence of THA on these kinematics and the effect of stiffness of the lumbopelvic complex on the risk of THA failure.

RESULTS

When a person sits, the pelvis goes into retroversion and the acetabulum opens forward. This frees the femoral head and neck to allow hip flexion. The opposite - pelvic anteversion - occurs when a person stands. When pelvic mobility is limited, the hip must increase its range of motion to accommodate these posture changes. Disturbances in spinal and pelvic kinematics lead to abnormal hip function, which may contribute to complications following total hip arthroplasty (THA).

CONCLUSION

A precise evaluation of the parameters governing the SPFC must be taken into account in order to best optimize the placement and choice of THA implants.

LEVEL OF EVIDENCE

IV.

A Comparison of Radiographic Outcomes after Total Hip Arthroplasty between the Direct Lateral Approach and Posterior Lateral Approach with EOS 2D/3D X-Ray Imaging System

OBJECTIVE

The classical approaches for total hip arthroplasty (THA) are the direct lateral approach (DLA) and posterior lateral approach (PLA). There are few studies comparing implant orientation with these two approaches, and the impact of surgical approaches on implant orientation remains controversial. With the rise of the EOS imaging system, we aimed to use it to identify the differences between and factors associated with implant orientation after THA using DLA and PLA.

METHODS

In our department from January 2019 to December 2021, 321 primary unilateral THAs that used PLA and DLA were enrolled. A total of 201 patients who received PLA and 120 patients who received DLA were included in this study. Two blinded observers measured each case using EOS imaging data. Postoperative imaging metrics and other relevant influencing factors of the two surgical approaches were compared. Postoperative imaging metrics, including the anteversion and inclination of the cup, anteversion of the stem, and combined anteversion were measured based on EOS. Other relevant influencing factors included age, approach, gender, laterality, BMI, anterior pelvic plane inclination, femoral head diameter, femoral offset, lateral pelvic tilt, pelvic incidence, pelvis axial rotation, sacral slope, sagittal pelvic tilt, and surgery time. Multiple linear regression analyses were performed to identify the predictors of acceptability for each imaging data point.

RESULTS

No dislocation was found in the 321 patients who underwent primary THA during this period. The mean anteversion and combined anteversion of the cups using the DLA were 21.33° ± 17.31° (-51.7°-60.8°) and 33.71° ± 20.85° (-38.8°-77.6°) and PLA were 25.34° ± 12.76° (-5.5°-57.0°) and 42.37° ± 18.85° (-8.7°-84.7°), respectively. The DLA group had smaller anteversion (p = 0.038) and combined anteversion (p < 0.001). We found that surgical approach (p < 0.05), anterior pelvic plane inclination (p < 0.001), gender (p < 0.001), and femoral head diameter (p < 0.001) were important factors affecting acetabular cup anteversion (R2  = 0.375) and combined anteversion (R2  = 0.525).

CONCLUSIONS

In total hip arthroplasty, different prosthesis installation directions should be made according to different surgical approaches. Compared with the direct lateral approach, the acetabular anteversion can be intentionally enlarged when using the posterolateral approach. Surgical approach, anterior pelvic plane inclination (APPI), gender, and femoral head diameter were significant predictors of prosthesis orientation. The anterior pelvic plane inclination may be a useful standard for assessing the position of the prosthesis using EOS.

Determining the orientation of acetabular prosthesis in total hip arthroplasty by refering to the anatomical landmarker of acetabular notches

The aim of this study was to explore a novel method to determine the orientation of acetabular prosthesis in total hip arthroplasty (THA) by refering to the anatomical landmarker of acetabular notches. Forty-one normal developmental hips were included in the present study. The acetabulums were reamed according to standard surgical procedures of THA on life-size 3D printing pelvis models. The inferior edge of acetabular cup were placed (1-5) mm proximal and distal to the proximal line of the anterior and posterior acetabular notches (PLAPAN) respectively to determine cup inclination. The inferior edge of acetabular cup were placed (1-5) mm pronating and supinating around the proximal point of acetabular posterior notch (PPAPN) respectively to determine cup anteversion. The pelvis plain radiographs were took and the inclination and anteversion of the acetabular cup at 22 positions were calculated. In the normal developmental hip, the mean inclination of acetabular prothesis were (35.10 ± 3.22)° and (45.90 ± 2.68)° when the inferior edge of the acetabular cup was 3 mm proximal and 1 mm distal to the PLAPAN. The optimal cup inclination could be obtained when the inferior edge of the acetabular cup was 1 mm proximal to the PLAPAN (the mean inclination was (40.71 ± 2.80)°). The mean anteversion of acetabular prothesis were (10.67 ± 4.55)° and (20.86 ± 4.44)° when the inferior edge of the acetabular cup was 1 mm pronating and 1 mm supinating around the PPAPN. The optimal cup anteversion could be obtained when the inferior edge of the acetabular cup was parallel to the PLAPAN (the mean anteversion was (18.00 ± 1.64)°). The inclination and anteversion of acetabular prosthesis could be determined by refering the anatomical landmarks of acetabular notches, which could help orthopedists to install the acetabular prosthesis quickly and safely in THA.