Comparison of surgical approaches of total hip arthroplasty in Crowe 3/4 dysplastic hips in adults: a systematic review and meta-analysis

INTRODUCTION

Developmental dysplasia of the hip (DDH) is one of the most common congenital conditions diagnosed in children.^1,2 If left untreated, DDH can persist into adulthood, leading to abnormal gait patterns, restricted movement, weakened muscles, and an increased risk of joint degeneration.³

In adults with DDH, several surgical treatment options are available. The University of Colorado Periacetabular Osteotomy (CU PAO) is a common procedure used to realign the acetabulum in cases of symptomatic acetabular dysplasia.⁴ This approach allows for early weight-bearing, cosmetic incisions, and favorable short-term outcomes. Another option, the Birmingham Interlocking Pelvic Osteotomy (BIPO), focuses on enhancing the reproducibility of pelvic osteotomies, leading to quicker recovery.⁵ Lastly, total hip arthroplasty (THA) is the most effective solution for reducing pain, improving joint function, and adjusting differences in leg length for individuals with severe arthritis resulting from DDH.⁶

Among all surgical treatment options for DDH, THA remains the main treatment for patients with end-stage osteoarthritis secondary to DDH.⁷ The primary surgical methods used in hip replacement surgery are the posterior and lateral approaches, only a small number of orthopaedic surgeons opt for the anterior approach.⁸ In the most extensive study to date, cementless THA combined with a subtrochanteric femoral shortening osteotomy in patients with a high-grade hip dislocation secondary to dysplasia showed high rates of successful implant fixation and stable clinical improvement.⁹

Complications may arise following THA, such as leg length discrepancy (LLD), early dislocation, and temporary and permanent nerve injuries.¹⁰ Moreover, other complications may involve wound healing issues, infection, and periprosthetic fractures.¹¹ Additionally, THA for severe DDH poses a challenge for surgeons due to anatomical abnormalities like a small femoral canal, increased anteversion, and a hypoplastic acetabulum.^12,13

A review of the literature reveals a significant gap in research comparing the various THA approaches for Crowe type 3/4 DDH in adults. The goal of this study is to address this gap by comparing the outcomes of different THA approaches in managing DDH in adult patients. Specifically, we aim to evaluate differences in Harris hip score (HHS), LLD, operative characteristics, and postoperative complications among the most commonly used approaches.

METHODS

This systematic review was conducted in line with the preferred reporting items for systematic reviews and meta-analyses (PRISMA).¹⁴ It was also registered with PROSPERO with the ID (CRD42024517038).

Eligibility criteria

Studies were considered eligible if they satisfied the following criteria: all retrospective cohorts reporting outcomes of interest post THA in Crowe 3/4 DDH in adults; direct anterior approach, posterolateral approach, anterolateral approach of THA whether they were with osteotomy or without osteotomy; and published in the English language.

Exclusion criteria included: studies including Crowe 1/2 DDH only; studies including other different approaches of THA; studies with incomplete or unextractable data for review; and review articles, preclinical, cadaveric and anatomical studies, and case reports.

Search strategy

We performed computer systematic literature searches of the PubMed and Cochrane databases for published papers from inception till March 2024 with the following keywords and their derivatives “(crowe) OR (iii/iv) OR (DDH) OR (hip dysplasia) AND (total hip arthroplasty in adults)” in all fields (title, keywords, and abstract). A second search was conducted with the terms “hip dysplasia” and “arthroplasty” in all fields. A third search was conducted with the terms “Crowe 3/4” and “arthroplasty”. Searches performed with very broad search terms were used to ensure we did not miss any articles presenting different surgical approaches of THA in adult DDH. Search results were screened against the eligibility criteria by two authors independently based on the title and/or abstract. Conflicts were resolved via a discrepancy meeting with a third senior author, if needed. The abstracts were compiled in a reference management software, Rayyan.ai.

Data extraction

Two independent reviewers used a predesigned data collection sheet in Microsoft excel to extract data. The extracted demographic data included the first authors’ surnames, study year, design and country, number of participants and hips, the mean age of patients, approach used, osteotomy type, follow-up duration, the mean of preoperative and postoperative HHS, LLD, operative data including operative time and estimated blood loss, postoperative complications including nerve palsy, non-union, osteolysis, loosening, dislocation rate, infection rate, and fracture rate.

Risk of bias and quality assessment

The methodological quality of the included studies was assessed using the quality assessment tool for before-after (pre-post) studies with no control group developed by the National Heart Lung and Blood Institute website (NHLBI).¹⁵ The publication bias of the primary outcomes was assessed by checking for asymmetry in the funnel plots either visually, or statistically using Egger’s test for continuous outcomes or the method suggested by Peters et al.^16,17

Outcomes of interest

Our main outcomes of interest were preoperative and postoperative HHS, LLD, operative data including operative time and estimated blood loss, postoperative complications including nerve palsy, non-union, osteolysis, loosening, dislocation rate, infection rate, and fracture rate.

Statistical analysis

The continuous outcomes were presented as mean difference (MD) with its respective 95% confidence interval (95% CI) while binary outcomes were presented as proportions (%) with their corresponding 95% (95% CI). The data analysis was conducted using the package "meta" in R statistical software (v4.1.2; R Core Team 2021).¹⁸ Random effects model was adopted when significant heterogeneity was detected (I² >60%), while a fixed effects model was used when the data was more homogenous. Results were presented using a forest plot for each outcome.

Subgroup analysis was conducted for each of the primary outcomes to check for differences between different surgical approaches and between doing osteotomies or not.

RESULTS

Study selection

Searching the databases yielded 4459 articles, and after removing 4331, 159 records were screened by title and abstracts, of which 59 were excluded. A total of 46 papers were eligible for a full-text review. As a result, 35 studies met the eligibility criteria and were included in the qualitative and quantitative synthesis. The PRISMA flowchart is displayed in Figure 1.

Pooled study characteristics

The search yielded 4459 records, of which 35 records were included in the review and analysis, that encompassed 1501 DDH hips of 1246 patients that underwent surgeries, with an average age of 46.9 years. The posterior approach was the most used approach (24 records, 69%), with 30 records reporting doing an osteotomy (86%). The oldest record was published in 2001, and about a third of the records were conducted solely in China (13 records, 37%), followed by Italy (5, 14%), and Turkey (4, 11%). More details regarding the characteristics of the included studies can be found in Table 1.

Harris hip score

The mean change of Harris score between before and after the operation of the 35 included reports were pooled using a random effects model and yielded a mean improvement of 47.08 points on the Harris score (95% CI = [44.37; 49.80]), with significant heterogeneity (I²=97%). The forest plot of the change in Harris score is seen in Figure 2.

Subgroup analysis showed no significant difference in the Harris score between different approaches nor between doing an osteotomy or not (p=0.81 and p=0.96, respectively). Studies that reported using multiple approaches or doing an osteotomy for some patients without reporting the result of each group separately were not included in the subgroup analysis.

Limb length discrepancy

The change in LLD between the two limbs was reported in 27 studies including 936 hips, and the mean change between pre-op and post-op was pooled under random effects model and showed a reduction in the LLD of 3.50 cm [-3.80; -3.19], with significant heterogeneity (I²=95%). The forest plot of the change in LLD is seen in Figure 3.

Subgroup analysis showed no significant association between the change in LLD and doing an osteotomy (p=0.750). However, a significant difference between the approaches used was noted (p=0.050), where the posterior approach was found to provide the highest reduction in LLD (-3.67, [-4.06; -3.28]) compared to direct anterior approach (-2.84, [-3.39; -2.29]) and anterolateral approach (-3.44, [-4.23; -2.65]).

Operative variables

The operation time and blood loss outcomes were only reported by 9 and 6 studies, respectively with all of them doing an osteotomy. Figures 4 and 5 represent the forest plots of the operation time and blood loss outcomes along with their subgroup analyses.

The operation time had a significant heterogeneity (I²=99%) with reports ranging from 72 minutes up to 276 minutes. The pooled estimate of the operation time was 148.47 minutes [114.48; 182.46], with no difference between the direct anterior and the posterior approaches (p=0.59). Similarly, the reported intraoperative blood loss was highly heterogeneous among the studies (I²=96%). The pooled estimate was a mean blood loss of 832.74 ml [578.68; 1086.80], with no significant difference between the direct anterior and the posterior approaches (p=0.08).

Postoperative complications

The incidence rates of nerve palsy (0.01, [0.00; 0.02]), non-union (0.01, [0.00; 0.01]), osteolysis (0.00, [0.00; 0.01]), and loosening (0.00, [0.00; 0.01]) were very minimal with no significant heterogeneity. As can be seen in Figure 6, the pooled rate of occurrence of dislocations after the operation was 2% [1%; 3%] with minimal heterogeneity (I²=22%, fixed effect). Subgroup analysis comparing those with osteotomies and this without showed no significant difference (p=0.55), while comparing the different approaches showed that the posterior approach had a significantly higher rate of dislocations (p=0.04).

Similarly, presented in Figure 7, the pooled rate of fractures after the operation was 2% [1%; 2%] with some heterogeneity (I²=54%, fixed effect), with no significant differences noted between different approached or with osteotomies (p=0.14 and p=0.82, respectively).

On the other hand, the rate of postoperative infections was minimal (0%, [0%; 1%]), with only four studies reporting the occurrence of any infections, as can be found in Figure 8. There was no heterogeneity between the studies (I²=0%, fixed effect). Subgroup analyses showed no differences between approaches nor between surgeries with osteotomies and those without (p=0.94 and p=0.95, respectively).

Quality assessment [risk of bias and level of evidence (LoE)]

The methodological quality of the included studies was assessed using the quality assessment tool for before-after studies with no control group developed by the NHLBI.¹⁵ Results of the assessment can be found in Table 2.

Publication bias

Funnel plots for the major outcomes. The asymmetricity of the funnel plots for the Harris score and LLD indicate potential risk of publication bias, however an insignificant Egger’s test (p=0.472 and p=0.561) refute such possibility. On the other hand, funnel plots of dislocation, fracture, and infection rates do not suggest publication bias, however, only fractures rate was not statistically significant (p=0.223), while dislocation and infection rates were both significant for publication bias (p<0.001 and p=0.042, respectively).

DISCUSSION

In this study, both Harris scores and LLD showed significant improvements postoperatively in adult patients with DDH undergoing THA. The Harris score is a widely used tool for assessing hip conditions and outcomes of hip surgeries.^19-21 Despite its limitations—such as a high ceiling effect and inter-observer variability in some components—it remains a reliable method for evaluating postoperative outcomes.^22-24 Our analysis found a significant average improvement of 47.08 points in the HHS following THA across all surgical approaches. This is consistent with findings from a systematic review of 3,356 hips in Crowe type IV DDH patients, which also reported significant postoperative improvements in both the Harris score and LLD.²⁵ Additionally, a study of 104 patients with a minimum 13-year follow-up found a significant decline in Harris scores in the Crowe II-IV DDH group.²⁶

In our analysis, we compared outcomes between patients who underwent THA with and without osteotomy. Our findings revealed no significant difference in either the Harris score or LLD between these two groups. Although osteotomy is often considered the “gold standard” for THA in DDH patients, it has some limitations, particularly the potential for residual LLD.²⁷ However, this complication was not observed in our study, as complete limb symmetry was achieved in both groups, regardless of whether osteotomy was performed.

When examining the impact of different surgical approaches, our analysis showed no significant differences in Harris scores between patients undergoing the anterior, posterior, or anterolateral approaches. This supports the findings of Liu et al., who compared the direct anterior approach (DAA) with the conventional posterolateral approach (PLA) in DDH patients and found no difference in Harris scores between the two.²⁸ However, we did observe significant differences in LLD reductions between the approaches, with the posterior approach achieving the greatest reduction in LLD. While many studies comparing the direct anterior and posterior approaches reported no significant differences in LLD, other studies favored the anterior approach for reducing LLD.^29-33

Regarding operative characteristics, our study found an average operative time of 148.47 minutes (approximately 2.5 hours), with no significant differences between the different THA approaches. Literature reports on THA operative times vary widely, ranging from 72 to 276.5 minutes.^34,35 Some studies have suggested that the posterior approach may be associated with shorter operative times compared to the anterior approach.^36-38 For intraoperative blood loss, we found that the mean estimated blood loss across the 6 studies reporting it was 832.74 ml, with no significant differences between the anterior and posterior approaches. Reported blood loss in the literature ranged from 434.6 ml to 1,557 m.^28,39 Consistent with our findings on operative time, a prospective randomized clinical trial has shown that the posterior approach tends to result in less blood loss compared to the anterior approach.³⁶

THA is generally considered a safe procedure with a low complication rate, though complications can still occur.⁴⁰ In this study, postoperative complications such as nerve injuries, non-union, osteolysis, and loosening were reported at low rates across different surgical approaches. However, literature suggests that sciatic nerve injury is more commonly reported with the posterior approach, while femoral nerve injury is more frequently associated with the anterior approach.^41,42 Non-union has been reported more often in patients undergoing posterior THA combined with osteotomy.^43-45 To mitigate this, some surgeons recommend using a stem with an appropriate length to bridge the osteotomy site and reinforcing the fixation with locking plates or wiring.⁴⁶ Regarding osteolysis, the highest incidence was reported in 17 out of 30 hips (56.7%) in a posterior THA cohort without osteotomy, attributed to polyethylene wear.⁴⁷ Other studies have also linked osteolysis to the posterior approach.^46,48 For patients undergoing femoral shortening osteotomy, a long-term complication of THA is femoral stem loosening, particularly in cases of severe hip dysplasia.⁴⁸ In our analysis, the highest rate of prosthesis loosening was observed in 5 cases (two cups and three stems) among 23 hips that underwent posterior THA with subtrochanteric osteotomy, where small, deeply seated components were used to achieve cup coverage and avoid loosening.⁴⁹ However, prosthesis loosening is a rare complication, with an incidence of less than 0.4% in most studies, while other studies reported a rate of 1%.^9,50,51

Other postoperative complications after THA include dislocations, fractures, and infections.⁴⁰ In our study, complications did not differ significantly between approaches, except for dislocation rates, which were higher in patients undergoing posterior THA. This aligns with findings from several studies that attribute the higher dislocation rate in the posterior approach to lower soft tissue tension, as tendons and muscles are left more intact in the anterior approach.^52-56 However, other studies have found no difference in dislocation rates between different approaches, and most studies included in our analysis did not show significant differences in overall complications between THA approaches.^36,57-61

This meta-analysis has several limitations. First, the studies included did not encompass patients from some important regions, such as the Middle East, Eastern Europe, Africa, and Southeast Asia, where healthcare services may differ and could influence outcomes. Second, many of the included studies focused on THA with osteotomy and the posterolateral approach (PLA), resulting in limited representation of other approaches. Finally, some studies did not report full operative data or clarify whether the surgeries were the initial procedures for DDH or subsequent revisions.

CONCLUSION

It can be concluded that there are no significant outcome differences between osteotomy vs no-osteotomy THA for Crowe types 3 and 4 DDH or between the different surgical approaches (DAA, PLA, ALA) in terms of Harris Score and post-op major complications (fracture, infection, dislocation). No difference was noted between the DAA and Posterior approaches among operative variables (blood loss and operative time). However, there has been an increased dislocation rate in the posterior approach in comparison to the other approaches. The incidence of nerve palsy, non-union, osteolysis and loosening were minimal across different approaches.

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: Not required

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