A Specific Capsular Repair Technique Lowered Early Dislocations in Primary Total Hip Arthroplasty Through a Posterior Approach

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.

Difference in Muscle Strength and Functional Outcome in Direct Lateral Approach versus Posterior Approach in Total Hip Arthroplasty: A Prospective Cohort Study

Background and Purpose

The choice between posterior approach (PA) and direct lateral approach (DLA) for total hip arthroplasty (THA) remains a contentious issue regarding clinical outcome optimization and restoring patient function. Previous studies have evaluated the postsurgical outcomes mostly in the form of Harris hip score (HHS), and the data to objectively measure the postoperative muscle power is scarce. We intend to objectively compare the hip abduction and extension strengths and other functional outcomes with a very simple tool in PA and DLA in the Indian population as most patients do not undergo as intensive rehabilitation in the postoperative period as in the western world.

Materials and Methods

A total of 158 patients underwent THA during the study period, of which 48 met inclusion criteria and only 42 completed 6 months follow-up. Patients were evaluated preoperatively, postoperatively at 2 weeks, 6 weeks, 3 months, and 6 months follow-up. At each visit, muscle strength was tested using a customized sling device mounted on a pulling apparatus fitted on the wall, as well as a pain score (VAS), Harris hip score (HHS), and Short Form Survey (SF-36).

Results

The study showed statistically significant better hip muscle strength at 2 weeks postoperative for leg press test and 2 weeks as well as 6 weeks postoperative for hip abduction strength in the PA. However, no differences were noted during the 3 or 6 months follow-up period among the DLA and PA. The surgical approach used has no effect on VAS, HHS, or SF-36 scorings.

Conclusion

The weak abductor mechanism at 2 and 6 weeks and extension mechanism at 2 weeks in a cohort of DLA in contrast to the PA are seen in the early postoperative period and hence are short-lived muscle weakness. However, there is no effect on VAS, HSS, and SF-36 scores. Therefore, the surgical approach is to be chosen according to the surgeon's expertise.

Redefining the 3D Topography of the Acetabular Safe Zone: A Multivariable Study Evaluating Prosthetic Hip Stability

BACKGROUND

Dislocation is the most common reason for early revision following total hip arthroplasty (THA). More than 40 years ago, Lewinnek et al. proposed an acetabular "safe zone" to avoid dislocation. While novel at the time, their study was substantially limited according to modern standards. The purpose of this study was to determine optimal acetabular cup positioning during THA as well as the effect of surgical approach on the topography of the acetabular safe zone and the hazard of dislocation.

METHODS

Primary THAs that had been performed at a single institution from 2000 to 2017 were reviewed. Acetabular inclination and anteversion were measured using an artificial intelligence neural network; they were validated with performance testing and comparison with blinded grading by 2 orthopaedic surgeons. Patient demographics and dislocation were noted during follow-up. Multivariable Cox proportional-hazards regression, including multidimensional analysis, was performed to define the 3D topography of the acetabular safe zone and its association with surgical approach.

RESULTS

We followed 9,907 THAs in 8,081 patients (4,166 women and 3,915 men; 64 ± 13 years of age) for a mean of 5 ± 3 years (range: 2 to 16); 316 hips (3%) sustained a dislocation during follow-up. The mean acetabular inclination was 44° ± 7° and the mean anteversion was 32° ± 9°. Patients who did not sustain a dislocation had a mean anteversion of 32° ± 9° (median, 32°), with the historic ideal anteversion of 15° observed to be only in the third percentile among non-dislocating THAs (p < 0.001). Multivariable modeling demonstrated the lowest dislocation hazards at an inclination of 37° and an anteversion of 27°, with an ideal modern safe zone of 27° to 47° of inclination and 18° to 38° of anteversion. Three-dimensional analysis demonstrated a similar safe-zone location but significantly different safe-zone topography among surgical approaches (p = 0.03) and sexes (p = 0.02).

CONCLUSIONS

Optimal acetabular positioning differs significantly from historic values, with increased anteversion providing decreased dislocation risk. Additionally, surgical approach and patient sex demonstrated clear effects on 3D safe-zone topography. Further study is needed to characterize the 3D interaction between acetabular positioning and spinopelvic as well as femoral-sided parameters.

LEVEL OF EVIDENCE

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

An Anatomic Study of the Relationship Between the Iliocapsularis Muscle and Iliofemoral Ligament in Total Hip Arthroplasty

Background

The preservation of soft tissues is an important factor for preventing dislocation after total hip arthroplasty. Anatomical studies have revealed that the inferior iliofemoral ligament (ILFL) contributes significantly to the native stability of the hip. This study aimed to investigate the anatomical structures of the iliocapsularis muscle (ICM) and ILFL from a surgical perspective.

Methods

In total, we assessed 50 hip specimens from 25 embalmed cadavers. The size and location of ICM and ILFL (at the upper, middle, and lower parts of the femoral head) were assessed in a neutral position. The ratio of ICM and ILFL widths to the femoral head was evaluated.

Results

The mean ICM and ILFL widths were 7.5 and 14.6, 12.0 and 14.2, and 12.8 and 15.2 mm at the upper, middle, and lower levels, respectively. The mean ICM thicknesses were 1.3, 9.0, and 9.1 mm at the upper, middle, and lower levels, respectively. The distributions of ICM and ILFL from the lateral edge of the femoral head were 21.1%–37.4% and 4.9%–36.5%, 9.5%–35.6% and 7.9%–38.7%, and 11.0%–38.7% and 9.5%–42.4% at the upper, middle, and lower levels, respectively.

Conclusion

ICM and ILFL were located at the anterolateral side of the femoral head, and the medial edge of the ILFL corresponded to that of the ICM. ICM can serve as a landmark for preserving ILFL in total hip arthroplasty using the anterior approach.