Current Evidence for Spinopelvic Characteristics Influencing Total Hip Arthroplasty Dislocation Risk

The Impact of Pelvic Incidence on Spinopelvic and Hip Alignment and Mobility in Asymptomatic Subjects

BACKGROUND

The influence of pelvic incidence (PI) on spinopelvic and hip alignment and mobility has not been well investigated. The aim of this study was to evaluate the influence of PI on spinopelvic and hip alignment and mobility, including the pelvic-femoral angle (PFA) and motion (ΔPFA), in functional positions in a cohort of asymptomatic volunteers.

METHODS

This was a single-center, prospective, cross-sectional study. We included 136 healthy volunteers (69% female; mean age, 38 ± 11 years; mean body mass index, 22 ± 3 kg/m2) divided into 3 subgroups on the basis of their PI: PI < 45° (low PI), 45° ≤ PI ≤ 60° (medium PI), and PI > 60° (high PI). We made full-body lateral radiographs in free-standing, standing with extension, relaxed-seated, and flexed-seated positions. We measured the sacral slope (SS), lumbar lordosis (LL), and PFA. We calculated lumbar (∆LL), pelvic (∆SS), and hip (∆PFA) mobilities as the change between the standing (i.e., standing with or without extension) and sitting (i.e., relaxed-seated or flexed-seated) positions.

RESULTS

There were significant differences between some of the 3 subgroups with respect to the LL, SS, and PFA in each of the 4 positions. There were no significant differences in ΔLL, ΔSS, or ΔPFA between the 3 groups when moving from a standing to a sitting position. PI had an inverse linear correlation with PFAextension (R = -0.48; p < 0.0001), PFAstanding (R = -0.53; p < 0.0001), PFArelaxed-seated (R = -0.37; p < 0.0001), and PFAflexed-seated (R = -0.47; p < 0.0001). However, PI was not correlated with ΔPFAstanding/relaxed-seated (R = -0.062; p = 0.48) or ΔPFAextension/flexed-seated (R = -0.12; p = 0.18). Similarly, PI was not significantly correlated with ΔLL or ΔSS in either pair of positions.

CONCLUSIONS

This study confirmed that spinopelvic and hip parameters in functional positions were affected by PI, whereas lumbar, pelvic, and hip mobilities did not depend on PI. These findings suggest that hip surgeons should consider the PI of the patient to determine the patient's specific functional safe zones before and after total hip arthroplasty.

LEVEL OF EVIDENCE

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

Clinical effects of combined anteversion and offset on postoperative dislocation in total hip arthroplasty

BACKGROUND

Implant impingement and soft tissue tension are factors involved in dislocation after total hip arthroplasty (THA). Combined anteversion (CA) has been used as an indicator for implant placement. However, optimal implant placement remains a challenge. Moreover, the effect of changes in offset on dislocation is still unclear. In this study, we aimed to clarify the effects of postoperative CA and pre- and postoperative changes in offset on dislocation.

METHODS

Included were patients who underwent primary cementless THA between 2013 and 2020. The mean values of CA and offset in the dislocation and non-dislocation groups were compared. The CA values within ± 10% of the recommended values were defined as good CA, and those outside the range were rated as poor CA. The dislocation rates were compared between the good and poor CA groups and between the groups with and without increased offset.

RESULTS

A total of 283 hips were included. The mean values of CA in the dislocation and non-dislocation groups were significantly different (P < 0.05). The dislocation rate was significantly lower in the good CA group (P < 0.05). The dislocation rates in the groups with and without increased total offset were 0.5% and 4.3%, respectively (P = 0.004). There were no dislocations in patients with good CA and increased offset.

CONCLUSIONS

The dislocation rate was significantly lower when implants were placed within ± 10% of the recommended CA value. Our results suggest that dislocation can be avoided by placing the implant in the good CA range and considering the increase in total offset on the operative side.

Evaluation of changes in radiographic spinopelvic parameters after primary total hip arthroplasty and its relationship with short-term patient function

PURPOSE

Total hip arthroplasty (THA) is commonly used worldwide in pelvic osteoarthritis treatment. This surgery can change the spinopelvic parameters, which in turn affects the performance of the patients after surgery. However, the relationship between functional disability following THA and spinopelvic alignment is not completely understood. The limited available studies have also been conducted on the population with spinopelvic malalignments. This study aimed to examine the changes in spinopelvic parameters after primary THA in patients with normal preoperative spinopelvic characteristics and the association of these parameters with the performance, gender, and age of the patients after THA.

METHODS

Fifty-eight eligible patients with unilateral primary hip osteoarthritis (HOA) scheduled for total hip arthroplasty between February and September 2021 were studied. Spinopelvic parameters including pelvic incidence (PI), sacral slope (SS), and pelvic tilt (PT) were measured before surgery and three months after surgery, and the relationship between these parameters and patients' performance (Harris hip score) was assessed. Also, the relationship between the age and gender of the patients with these parameters was evaluated.

RESULTS

The mean age of study participants was 46.03 ± 14.25. Three months after THA, sacral slope decreased with the mean difference of 4.31 ± 10.26 degrees (p = 0.002) and Harris hip score (HHS) increased by 19.41 ± 26.55 points (p < 0.001). With increasing age in patients, the mean SS and PT decreased. Among the spinopelvic parameters, SS (β = 0.11) had a greater effect than PT on postoperative HHS changes and among the demographic parameters, age (β = -0.18) had a greater effect on HHS changes than gender.

CONCLUSION

Spinopelvic parameters are associated with age, gender, and patient's function after THA as sacral slope decreased and HHS increased after THA, and aging is accompanied by lowering of PT and SS.

Did the dislocation risk after primary total hip arthroplasty decrease over time? A meta-analysis across six decades

BACKGROUND

While continuous optimization is attempted to decrease the incidence of dislocation after total hip arthroplasty (THA), dislocation remains a major complication. This meta-analysis aims to analyze the evolution of the dislocation risk after primary THA over the decades and to evaluate its potential publication bias.

PATIENTS AND METHODS

A systematic search was performed according to the PRISMA guidelines for this meta-analysis in the literature published between 1962 and 2020. MEDLINE, Cochrane and Embase databases were searched for studies reporting the dislocation risk and length of follow-up. Studies that reported on revision rates only and did not mention separate dislocations were excluded. All study designs were eligible. Study quality was assessed by existing quality assessment tools adjusted for arthroplasty research. Overall risk and yearly dislocation rates were calculated and related to historical time frame, study design, sample size and length of follow-up.

RESULTS

In total, 174 studies were included with an overall moderate quality. In total there were 85.209 dislocations reported in 5.030.293 THAs, showing an overall dislocation risk of 1.7%, with a median follow-up of 24 months. The overall dislocation risk classified per decade decreased from 3.7% in 1960-1970 to 0.7% in 2010-2020. The yearly dislocation rate decreased from 1.8 to 0.7% within these same decades. There was no significant correlation between the reported dislocation risk and the duration of follow-up (p = 0.903) or sample size (p = 0.755). The reported dislocation risk was higher in articles with registry data compared to other study designs (p = 0.021).

CONCLUSION

The dislocation risk in THA has been decreasing over the past decades to 0.7%. Non-selective registry studies reported a higher dislocation risk compared to studies with selective cohorts and RCTs. This indicates that the actual dislocation risk is higher than often reported and 'real-world data' are reflected better in large-scale cohorts and registries.

Projected Savings Associated with Lowering the Risk of Total Hip Arthroplasty Revision Due to Dislocation in Patients with Spinopelvic Pathology

Purpose

In the United States (US), total hip arthroplasty (THA) is the most common hospital inpatient operation among Medicare beneficiaries and is ranked fourth when considering all payers. Spinopelvic pathology (SPP) is associated with an increased risk of THA revision (rTHA) due to dislocation. Several strategies have been proposed to mitigate the risk of instability in this population, including use of dual-mobility implants, anterior-based surgical approaches, and technology-assistance (digital 2D/3D pre-surgical planning, computer navigation, and robotic assistance). For primary THA (pTHA) patients with SPP who subsequently undergo rTHA due to dislocation, we aimed to estimate (1) target population size; (2) economic burden; and (3) 10-year projected savings to the US payer of lowering the risk of rTHA due to dislocation among pTHA patients with SPP.

Methods

A budget impact analysis from the US payer perspective was undertaken using published literature; American Academy of Orthopaedic Surgeons American Joint Replacement Registry 2021 Annual Report; Centers for Medicare & Medicaid Services MEDPAR 2019; and National (Nationwide) Inpatient Sample (NIS) 2019. Expenditures were inflation-adjusted to 2021 US dollars using the Medical Care component of the Consumer Price Index. Sensitivity analyses were performed.

Results

The target population size in 2021 was estimated at 5040 (range, 4830-6309) for Medicare (fee-for-service plus Medicare Advantage) and 8003 (range, 7669-10,018) for all-payer. Annual rTHA episode-of-care (through 90 days) expenditures for Medicare and all-payer were $185 million and $314 million, respectively. Using a 4.14% compound annual growth rate from NIS, the estimated number of applicable rTHA procedures that will be performed from 2022-2031 was 63,419 Medicare and 100,697 all-payer. With each 10% reduction in relative risk of rTHA due to dislocation, Medicare and all-payer could save $233 million and $395 million, respectively, over a 10-year period.

Conclusion

Among pTHA patients with spinopelvic pathology, a modest reduction in the risk of rTHA due to dislocation could achieve substantial cumulative savings to payers while improving healthcare quality.