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69 (); 86-95
doi:
10.1016/j.jor.2025.03.037

Postoperative complications rates and outcomes following total hip arthroplasty in patients with ankylosing spondylitis: A systematic review

, , , , , ,
a Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
b College of Medicine, Northeast Ohio Medical University, Rootstown, OH, USA
c Department of Rehabilitation Services, University Hospitals, Cleveland, OH, USA
d Department Orthopedic Surgery, Medicover Hospitals, Madhapur, Hyderabad, India
e Department Orthopedic Surgery, University of Pennsylvania, Philadelphia, PA, USA

⁎Corresponding author: Omkar Anaspure. Omkar.Anaspure@pennmedicine.upenn.edu

Received: , Accepted: ,
The Author(s)
Disclaimer:
This article was originally published by Reed Elsevier India Pvt. Ltd. and was migrated to Scientific Scholar after the change of Publisher.

Abstract

Abstract

This study sought to identify key postoperative complications and clinical outcomes in patients with Ankylosing Spondylitis (AS) undergoing total hip arthroplasty (THA).

This systematic review evaluated postoperative complications and clinical outcomes in this population by querying PubMed, Embase, and CINAHL, up till June 19th, 2024.

Nineteen observational studies (n = 2003; 81.72 % male; mean age 38.95 ± 10.08 years; mean follow-up 76 ± 22.10 months) were included. Surgical approaches were posterolateral (n = 11 studies), Watson-Jones anterior (n = 1 study), and minimally invasive 2-incision (n = 1 study). Complications included infection (n = 65; 5.14 %), heterotopic ossification (n = 51; 4.03 %), prosthetic joint noise (n = 24; 1.90 %), perioperative fracture (n = 18; 1.42 %), improper implant placement (n = 14; 1.11 %), re-infection (n = 11; 0.87 %), and implant loosening (n = 8; 0.63 %). Hip dislocation occurred in 2.64 % (n = 22) of patients across 8 studies, and 4.06 % (n = 21) of patients required revision THA in six studies for various reasons, such as leg length discrepancy, joint loosening, or instability. HO was reported in 11 studies (n = 880), affecting 15.11 % (n = 133/880) of patients. All four studies assessing range of motion (ROM) found significant improvement after THA.

Observed trends suggest a noticeable occurrence of complications, such as joint dislocation and HO, following THA in patients with AS. While postoperative improvements in ROM and patient outcomes were reported, these qualitative findings warrant further investigation to confirm their significance. We recommend increased awareness and the exploration of strategies to minimize the risk of complications for high-risk patients with history of HO and other preexisting comorbidities to prevent progression of the complication profile seen in patients with AS.

Keywords

Ankylosing spondylitis
Total hip arthroplasty
Heterotopic ossification
Stiff spine
1

1 Introduction

Ankylosing spondylitis (AS) is a chronic inflammatory disease associated with human leukocyte antigen(HLA)-B27, primarily affecting the spine and sacroiliac joints, causing pain, stiffness, and spinal fusion, which severely impairs mobility and quality of life.1–4 Approximately 5–6 % of HLA-B27 positive patients are affected with AS, with mean age of onset typically between 15 and 30 years and demonstrating a global prevalence ranging from 0.1 % to 1.4 %.3,5–7 In addition to axial skeleton involvement, AS frequently affects peripheral joints, with the hip being particularly susceptible.3,8–11 Studies indicate that 30 %–50 % of patients with AS experience inflammation of the hip joint, which can progress to joint destruction.12–14 Consequently, a significant proportion of these patients—estimated between 12 % and 25 %—ultimately require total hip arthroplasty (THA) to alleviate pain and restore function, often at a younger age compared to those undergoing THA for osteoarthritis or other degenerative conditions.7,15,16

Patients with AS undergoing THA are at heightened risk of perioperative complications in orthopedic surgery due to the rigid yet brittle nature of the ankylosed spines, which may be associated with varying ranges of kyphotic spinal deformity.17–19 A major concern is the development of heterotopic ossification (HO), where abnormal bone forms in the soft tissues around the hip joint, typically triggered by surgical trauma and inflammation.20–22 This ectopic bone growth can further restrict range of motion (ROM), exacerbating the stiffness already present in AS and, in some cases, leading to re-ankylosis.3,22–25 This is particularly problematic for patients with AS, who already experience limited mobility. Thus, the risk of HO after THA and its impact on postoperative ROM must be carefully managed in patients with AS in the perioperative period to minimize the need for further interventions.

Though some prior studies on THA outcomes in patients with fused hips are present, key postoperative risk factors in AS remain poorly understood.7,26,27 Postoperative complications such as infection, heterotopic ossification, dislocation, and revision surgery continue to present challenges, potentially leading to further invasive procedures and increased morbidity, necessitating further study at this time given the significant attention in the literature. This systematic review seeks to address these gaps by providing comprehensive evidence on postoperative complications in patients with AS undergoing THA. Such findings could directly inform clinical decision-making by helping identify high-risk patients, optimize perioperative management, and aid clinicians in anticipating and managing complications.

2

2 Methods

2.1

2.1 Study creation and initial search

This study is a qualitative systematic review of the literature examining outcomes after THA in patients with AS using PubMed, EMBASE, and CINAHL from database inception until June 19th, 2024. Search terms used in each database were ("Ankylosing spondylitis" OR spondyloarthropathy OR spondylarthritis) AND (THA OR TKA OR "total hip" OR "hip arthroplasty" OR "hip replacement" OR arthroplasty). This study was performed under the guidelines of the most recent Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRIMSA) for proper data reporting and was registered in the Open Science Framework registry for systematic reviews and meta-analyses; this can be found at 10.17605/OSF.IO/HZ8KD.

2.2

2.2 Inclusion and exclusion criteria

Inclusion criteria were retrospective or prospective studies that examined patients with AS who underwent THA that reported clinical outcomes of patients after surgery. Exclusion criteria were case reports, studies that not involving the hip, studies that reported AS clinical outcomes in combination with outcomes of other rheumatologic condition, or studies that failed to report any clinical outcomes.

2.3

2.3 Article screening process

After the search algorithm was executed in each of the four databases for the initial search, all articles were uploaded into Rayyan, a public website used for systematic reviews.28 Two screeners performed a manual de-duplication of articles, and subsequently performed article screening based on title and abstract. This was followed by full-text screening based on inclusion and exclusion criteria. Any conflicts during the article screening process were resolved by the first author.

2.4

2.4 Data extraction

Data extraction was completed by two authors. Data extracted included first author, year of publication, procedure type, number of patients, sex, average age, follow-up time, implant type, complications, and any other relevant qualitative data with associated p-values for narrative reporting.

2.5

2.5 Article quality grading

All observational studies included in this systematic review were classified as either “comparative” or “non-comparative” to appropriately grade their quality using the Methodological Index for Non-Randomized Studies (MINORS) scale.29 Comparative studies were graded out of 24 points and non-comparative studies were graded out of 16 points. For comparative studies, there are 8 items on the scale, and for non-comparative studies, there are 12 items on the scale with each item being rated from 0 to 2 points. All articles were considered to be “high-quality”, “moderate-quality”, or “low-quality” based on their scoring and comparative/non-comparative nature. For comparative studies, high-quality articles scored 24 points, moderate-quality articles scored 15–23 points, and low-quality articles scored less than 15 points.30 For non-comparative studies, high-quality articles scored 16 points, moderate-quality articles scored 10–15 points, and low-quality articles scored less than 10 points.30

2.6

2.6 Statistical analysis

This study utilized the Statistical Package for the Social Sciences (SPSS) version 29.0 (Armonk, NY: IBM Corp) for statistical analysis. Frequency weighted means and other descriptive statistics were used to describe the data where no statistical significance could be calculated.

3

3 Results

3.1

3.1 Initial search results

The database search resulted in 2070 articles; after manual de-duplication, 1551 articles remained. After title and abstract screening, 437 articles were included in full-text analysis. Citation search yielded no additional studies. After this process, 19 articles met inclusion criteria and were included in the data extraction process16,23,31–47 (Fig. 1).

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) diagram outlining the entire search progress, from initial search in four databases to final article inclusion.
Fig. 1 The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) diagram outlining the entire search progress, from initial search in four databases to final article inclusion.
3.2

3.2 Article quality results

Of the 19 included articles, all were observational studies (16 retrospective, 3 prospective) (Table 1). There were 3 non-comparative studies and 16 comparative studies. Mean MINORS score was 15.7 ± 2.9. Mean MINORS score for non-comparative studies (n = 3) was 10.0 ± 2.0 points (out of 16.0 points). Mean MINORS score for comparative studies (n = 16) was 16.8 ± 1.4 points (out of 24.0 points). Ultimately, 17 articles were "moderate quality," 2 articles were "low quality," and no articles were "high quality" (Table 1).

Table 1 The Methodological Index for Non-Randomized Studies (MINORS) grading for all included articles in this systematic review.
First Author (Year) Study Type Total MINORS Score Clearly stated aim Inclusion of consecutive patients Prospective collection of data End points appropriate to study aim Unbiased assessment of study end point What Follow-up period appropriate to study aim Less than 5 % lost to follow up Prospective calculation of the study size Adequate control group Contemporary groups Baseline equivalence of groups Adequate statistical analysis
Bangjian et al. (2012) Non-comparative 10 2 2 0 2 0 2 2 0 – – – –
Chai et al. (2020) Comparative 16 2 2 0 2 0 2 0 0 2 2 2 2
Dabir et al. (2015) Non-comparative 12 2 2 2 2 0 2 2 0 – – – –
Ding et al. (2018) Comparative 18 2 2 0 2 0 2 2 2 2 2 0 2
Hu et al. (2020) Comparative 18 2 2 0 2 0 2 2 0 2 2 2 2
Im et al. (2023) Comparative 16 2 2 0 2 0 2 0 0 2 2 2 2
Jacob et al. (2022) Non-comparative 8 2 2 0 2 0 2 0 0 – – – –
Katakam et al. (2020) Comparative 15 2 2 0 2 0 2 1 0 2 2 0 2
Lee et al. (2017) Comparative 18 2 2 0 2 0 2 2 0 2 2 2 2
Li et al. (2020) Comparative 16 2 2 0 2 0 2 2 0 2 2 0 2
Li et al. (2021) Comparative 16 2 2 0 2 0 2 2 0 2 2 0 2
Li et al. (2022) Comparative 18 2 2 0 2 0 2 0 2 2 2 2 2
Man et al. (2020) Comparative 18 2 2 0 2 1 2 1 0 2 2 2 2
Mou-Li et al. (2021) Comparative 16 2 2 0 2 0 2 2 0 2 2 0 2
Mou-Zeng et al. (2021) Comparative 19 2 2 2 2 0 2 1 0 2 2 2 2
Qian et al. (2023) Comparative 18 2 2 2 2 0 2 2 0 2 2 0 2
Saglam et al. (2016) Comparative 16 2 2 0 2 0 2 1 0 2 2 1 2
Thilak et al. (2015) Comparative 14 2 2 0 2 0 2 0 0 2 2 0 2
Wang et al. (2013) Comparative 17 2 2 0 2 0 2 2 0 2 1 2 2
3.3

3.3 Patient and study characteristics

In total, 2003 patients (n = 2055 hips; FWM age: 38.95 ± 10.08 years; 81.72 % male (n = 1565) were included in this review, and all patients underwent THA as the primary method of correcting the underlying pathology. The most frequent surgical approach was posterolateral (n = 11 studies), Watson-Jones anterior approach (n = 1 study), and minimally invasive 2-inscision approach (n = 1 study). Three studies used cemented implants, and 14 studies used uncemented implants. The mean postoperative follow-up time across the six studies that reported this metric was 76 ± 22.10 months. The studies were performed in the China (n = 12), USA (n = 2), India (n = 2), Korea (n = 2), and Turkey (n = 1). Further patient and study demographic information can be found in Table 2.

Table 2 Study demographics table with relevant study characteristics such as comparison group, number of patients, mean age, and mean follow-up time.
First Author (Year) Groups Patients (n) Average age at THA Number of Male/Female Follow-up time
Bangjian (2012)31 Pre-operative 12 36.5 (26–50) Male (n = 8), Female (n = 4) 4.2 years
Post-operative 12
Chai (2020)32 Robot 22 41.92 ± 6.81 (29–66) Male (n = 20), Female (n = 2) 97.53 ± 3.18 days
Control 23 34.87 ± 5.96 (24–49) Male (n-22), Female (n = 1) 96.08 ± 2.98 days
Dabir (2015)33 Uncemented THA 20 35.1 Male (n = 18), Female (n = 2) 22 months
Ding (2018)34 Hip non-fusion 20 42.2 ± 14.2 Male (n = 15), Female (n = 5) 27 months
Hip fusion 23 35 ± 6.71 Male (n = 19), Female (n = 4)
Hu (2020)35 Stable AS 17 31.65 ± 8.70 Male (n = 13), Female (n = 4) 1 year
Active AS 32 33.72 ± 11.92 Male (n = 30), Female (n = 2)
Im (2023)36 LLD < 5 mm 41 41.6 (22–59) Male (n = 40), Female (n = 1) 10.08 years
5 mm ≤ LLD <10 mm 21 46.9 (26–59) Male (n = 19), Female (n = 2) 8.2 years
Jacob (2022)37 AS with stiff hips 40 (69 hips) 36.6 (24–58) Male: 36 Female: 4 –
Katakam (2020)38 AS 142 58.07 ± 15.6 Male (n = 75), Female (n = 67) 74.15 ± 61.2 months
Spinal Fusion 135 66.32 ± 10.4 Male (n = 53), Female (n = 82) 50.13 ± 40.6 months
Lee (2017)39 Diagnosed with AS 30 39.6 (22–55) Male (n = 26), Female (n = 4) 69.0 months
Avascular necrosis of femoral head 30 42.6 (33–58) Male (n = 26), Female (n = 4) 71.5 months
Li (2020)40 <750 mL Blood Loss 49 32 (19–67) Male (n = 37), Female (n = 12) –
750–1500 mL Blood Loss 121 32 (19–59) Male (n = 110), Female (n = 11)
>1500 mL Blood Loss 73 34 (22–53) Male (n = 71), Female (n = 2)
Li (2021)41 Unilateral THA 122 31 (19–67) Male (106) Female (1) –
Bilateral THA 251 32 (19–67) Male (234) Female 17
Li (2022)42 Noise Hip 52 33 ± 7 Male (n = 51), Female (n = 1) –
No Noise Hip 128 32 ± 10 Male (n = 114), Female (n = 14)
Man (2020)43 Satisfaction 94 35.85 ± 11.28 Male (n = 80), Female (n = 14) –
Dissatisfaction 87 36.48 ± 12.13 Male (n = 66), Female (n = 21)
Mou-Li (2021)44 Group A: Non-ankylosed 69 42.20 ± 13.8 Male (n = 58), Female (n = 11) 79.4 ± 29.5 months
Group B: Fibrous Ankylosed 40 40.60 ± 13.3 Male (n = 38), Female (n = 2) 80.6 ± 28.9 months
Group C: Bony Ankylosed 28 38.8 ± 8.5 Male (n = 24), Female (n = 4) 79.1 ± 28.9 months
Mou-Zeng (2021)45 Synchronous Bilateral THA 11 (22 Hips) – Male (n = 10), Female (n = 1) 81.9 ± 36.3 months
Sequential Bilateral THA 12 (24 hips) Male (n = 10), Female (n = 2) 79.9 ± 29.1 months
Qian (2023)46 Group NA: Mobility 22 31.5 (26–33) Male (n = 16), Female (n = 6) –
Group A: 0 Degrees of Mobility 40 51 (41–58) Male (n = 35), Female (n = 5)
Saglam (2016)16 Cemented 22 hips 41.3 ± 10.2 Male (n = 50), Female (n = 11) –
Uncemented 83 hips
Thilak (2015)23 Non-Heterotopic Ossification 40 36.6 ± 8.6 Male (n = 33), Female (n = 7) –
Heterotopic Ossification 7 31.4 ± 8 Male (n = 2), Female (n = 5)
Wang (2013)47 Infliximab 11 – – –
Control 21
3.4

3.4 General postoperative complications after THA in patients with AS

Fourteen studies (n = 1265) detailed postoperative complications in patients with AS following THA.16,31–33,35–39,42–46 The most common complications included infection (n = 65; 5.14 %), heterotopic ossification (n = 51; 4.03 %), prosthetic joint noise (n = 24; 1.90 %), perioperative fracture (n = 18; 1.42 %), implants placed outside the safe zone (n = 14; 1.11 %), re-infection (n = 11; 0.87 %), and implant loosening (n = 8; 0.63 %). Specifically, hip dislocation occurred in 2.64 % (n = 22) of patients, as reported by eight studies, while 4.06 % (n = 21) required revision THA, as noted in six studies. A complete breakdown of all complication types can be found in Table 3. Li et al. (2021) reported that in their study of 373 patients with AS undergoing THA, those who received bilateral THA had a significantly longer median disease duration compared to those who underwent unilateral THA (12 years, range 0.5–34.0 years vs. 9 years, range 0.5–40.3 years; p < 0.05).41 Similarly, another study by Li et al. (2020) involving 243 patients with AS with severe hip involvement undergoing primary THA found that male patients (odds ratio [OR] = 3.287; 95 % confidence interval [CI]: 1.022, 10.567), patients with 0° hip range of motion (OR = 2.513; 95 % CI: 1.277, 4.946), and those undergoing bilateral THA (OR = 13.896; 95 % CI: 4.950, 39.011) were significantly more likely to experience increased blood loss during surgery.40 Katakam et al. (2020) studied 142 patients with AS alongside 135 patients with lumbosacral spinal fusion, revealing that each 1° increase in lumbar lordosis was associated with a 13 % higher risk of hip dislocation.38 Moreover, hips located outside the Lewinnek safe zone had a 5.18-fold increased likelihood of dislocation. In a separate study, Chai et al. (2020) examined 45 patients with AS with hip arthrodesis undergoing THA and found that robotic-assisted THA significantly enhanced the accuracy of cup positioning within the target zone (94.29 % vs. 67.56 %, p = 0.042), minimized radiation exposure (2.16 ± 1.61 vs. 0.47 ± 0.61, p = 0.000), and achieved these improvements without prolonging the surgery time.32

Table 3 Postoperative complications following index hip arthroplasty as reported by fourteen studies.
Bangjian (2012)
Osteolysis n = 2, 8.3 %
Stem loosening n = 0, 0 %
Intraoperative femur fracture n = 2, 8.3 %
Heterotopic ossification n = 3, 12.5 %
Transient femoral nerve palsy n = 1, 4.2 %
Chai (2020)
Robot Group Control Group
Intraoperative fracture n = 0, 0 % n = 3, 8.1 %
Intraoperative neurovascular injury n = 0, 0 % n = 0, 0 %
Outside safe zone n = 2, 5.7 % n = 12, 32.4 %
Cup malposition n = 0, 0 % n = 6, 16.2 %
Dislocation n = 0, 0 % n = 2, 5.4 %
Dabir (2015)
Breach in medial wall of acetabulum during reaming n = 4, 20 %
Posterior dislocation n = 1, 5 %
Infection n = 0, 0 %
Urinary symptoms n = 1, 5 %
Osteolysis n = 0, 0 %
Hu (2018)
Periprosthetic fracture n = 3, 6.1 %
Dislocation n = 2, 4.1 %
Implant loosening n = 0, 0 %
Infection n = 0, 0 %
Im (2023)
LLD <5 mm Group LLD 5–10 mm Group
Wound dehiscence n = 2, 4.9 % n = 0, 0 %
Discomfort due to LLD n = 1, 2.4 % n = 0, 0 %
Jacob (2022)
Dislocation n = 0, 0 %
Infection n = 1, 2.5 %
Katakam (2020)
Ankylosing Spondylitis Group Spinal Fusion Group
Dislocation n = 4, 2.8 % n = 16, 11.9 %
Lee (2017)
Ankylosing Spondylitis Group Femoral AVN Group
Wound dehiscence n = 1, 3.3 % n = 0, 0 %
Discomfort due to LLD n = 1, 3.3 % n = 0, 0 %
Li (2022)
Dislocation n = 1, 0.6 %
Periprosthetic Joint Infection n = 1, 0.6 %
Mild to moderate pain n = 5, 2.8 %
Heterotopic ossification n = 12, 6.7 %
Noise n = 52, 28.9 %
Man (2020)
Dislocation n = 2, 1.1 %
Periprosthetic femur fracture n = 1, 0.6 %
Iatrogenic sciatic nerve injury n = 2, 1.1 %
Heterotopic ossification n = 42, 23.2 %
Mou-Li (2021)
Non-ankylosed Group Fibrous Ankylosed Group Bony Ankylosed Group
Delayed wound union n = 1, 1.1 % n = 0, 0 % n = 1, 1.9 %
Dislocation n = 0, 0 % n = 0, 0 % n = 1, 1.9 %
Intraoperative femur fracture n = 0, 0 % n = 0, 0 % n = 1, 1.9 %
Heterotopic ossification n = 12, 12.8 % n = 6, 12.2 % n = 6, 11.5 %
Mou-Zeng (2021)
Synchronous THA Group Sequential THA Group
Intraoperative femur fracture n = 1, 4.5 % n = 0, 0 %
Dislocation n = 1, 4.5 % n = 0, 0 %
Heterotopic ossification n = 3, 13.6 % n = 3, 12.5 %
Qian (2023)
Sciatic nerve injury n = 2, 3.2 %
Infection n = 0, 0 %
Saglam (2016)
Cemented Group Cementless Group
Superficial Wound Infection n = 1, 4.5 % n = 2, 2.4 %
Deep infection n = 2, 9.0 % n = 4, 4.8 %
Girdlestone pseudoarthrosis n = 1, 4.5 % n = 1, 1.2 %
Periprosthetic fracture n = 0, 0 % n = 4, 4.8 %
Sciatic neuropraxy n = 0, 0 % n = 1, 1.2 %
Dislocation n = 1, 4.5 % n = 1, 1.2 %
Aseptic implant loosening n = 4, 18.2 % n = 4, 4.8 %
Heterotopic ossification n = 5, 22.7 % n = 9, 10.8 %
3.5

3.5 Heterotopic ossification after THA in patients with AS

Eleven studies (n = 880) reported HO as a complication after the index procedure.16,23,31,33,37,39,42–45 In total, 15.11 % of the patients in these studies experienced HO as a postoperative complication (n = 133/880). Refer to Table 4 for a complete breakdown of HO prevalence for each study. Saglam et al. (2016) studied 61 patients with AS who underwent THA using a cementless or cemented approach. They found that acetabular component loosening was significantly higher in patients with any degree of HO (p = 0.04).16 Regardless of the type of femoral implant (cemented or cementless), femoral component loosening was higher in Dorr's type C patients (p = 0.005).16 Thilak et al. (2015) studied 47 hips to identify the risk factors of HO after THA.23 They showed that female gender (P = 0.008), preoperative ankylosed hip (P < 0.001), occurrence of HO in previous surgery (P = 0.036) were nonmodifiable risk factors which increased the prevalence of HO.23 Of the various modifiable risk factors, elevated preoperative ESR (P = 0.007), elevated preoperative CRP (P = 0.004) and prolonged duration of surgery (P = 0.014) were associated with increased occurrence of HO.23

Table 4 Prevalence of heterotopic ossification and Brooker Classification categorization.
Study Heterotopic Ossification
Bangjian (2012) Total n = 3 (12.5 %)
Class 1 |n = 1
Class 2 |n = 2
Dabir (2015) n = 0 (0 %)
Jacob (2022) Total n = 21 (30.4 %)
Class 1 |n = 14
Class 2 |n = 5
Class 3 |n = 2
Lee (2017) AS Group
Total n = 3 (10 %)
Class 1 |n = 1
Class 3 |n = 2
Femoral Head AVN Group
Total n = 1 (3.3 %)
Class 3 |n = 1
Li (2022) n = 12 (6.7 %)
Man (2023) n = 42 (23.2 %)
Mou-Li (2021) Non-Ankylosed Group
n = 12 (12.8 %)
Fibrous Ankylosed Group
n = 6 (12.2 %)
Bony Ankylosed Group
n = 6 (11.5 %)
Mou-Zeng (2021) Synchronous Bilateral THA Group
n = 3 (13.6 %)
Sequential Bilateral THA Group
n = 3 (12.5 %)
Saglam (2016) Cemented THA Group
n = 5 (22.7 %)
Non-cemented THA Group
n = 9 (10.8 %)
Total |n = 14 (13.3 %)
Class 1 |n = 9
Class 2 |n = 2
Class 3 |n = 2
Class 4 |n = 1
Thilak (2015) n = 7 (14.9 %)
3.6

3.6 Hip range of motion after THA in patients with AS

Four studies provided data regarding hip ROM after the index procedure.39,42–44 Li et al. (2022) reported a significant improvement in flexion-extension ROM in 110 patients with AS after THA, with the median range ROM increasing from 10° to 100° after surgery (p < 0.001).42 Mou-Li et al. (2021) retrospectively analyzed 195 hips, categorizing them into non-ankylosed (group A, 94 hips), fibrous ankylosed (group B, 49 hips), and bony ankylosed (group C, 52 hips).44 Postoperative hip ROM was highest in group A (p < 0.001), and significant differences in preoperative flexion contracture and flexion were noted among the groups (p < 0.001). At the latest follow-up, the average flexion-extension ROM was 106.2° ± 9.9° for group A, 102.3° ± 9.1° for group B, and 84.1° ± 4.9° for group C, with all groups showing significant differences in postoperative ROM (p < 0.001). Man et al. (2020) studied 181 hips post-THA and found that postoperative ROM improvement was significantly influenced by preoperative ROM, degree of joint space narrowing, and the use of ceramic-ceramic material for the weight-bearing surface (p < 0.001), with preoperative ROM being the most significant factor.43 Lee et al. (2017) compared THA outcomes in 30 patients with AS with those in 30 patients with avascular necrosis (AVN) of the femoral head, showing that the arc of ROM improved from 146.5° ± 13.2° preoperatively to 254.7° ± 17.2° postoperatively in the AS group, and from 182.6° ± 15.5°–260.4° ± 13.7° in the AVN group.39

3.7

3.7 Patient reported outcomes after THA in patients with AS

Eleven studies assessed patient-reported outcomes (PROs) following surgery, with the most commonly used metrics being the Harris Hip Score (HHS), Visual Analog Scale (VAS) for pain, and the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), among others.16,31,33–37,39,44,46,47Table 5 provides a summary of significant changes in PROs reported by each study. Notably, Li et al. (2022) found that a BASRI-hip score of 4 was significantly more common in patients necessitating a bilateral THA compared to those with unilateral THA (p < 0.05).41 Mou-Li et al. (2021) found that amongst 195 hips, the postoperative HHS in non-ankylosed and fibrous ankylosed groups were significantly higher than in the bony ankylosed group (p < 0.001), though no significant difference was found between the first two groups (p = 0.078).44 Mou-Zeng et al. observed significant improvements in HHS and ROM for both synchronous and sequential bilateral THA groups, but sequential THA allowed for a shorter time to first postoperative ambulation (3.6 ± 1.2 days, p = 0.02).45 Lee et al. (2017) compared patients with AS undergoing THA with those who had AVN of the femoral head, finding that preoperative HHS was lower in the AS group (55.6 ± 13.8 vs. 59.2 ± 2.8), and this difference remained significant postoperatively (92.8 ± 2.7 vs. 97.4 ± 2.6).39

Table 5 Comprehensive postoperative PRO scores and improvement from baseline for eleven studies. Abbreviations: Harris Hip Score (HHS); Visual Analog Scale (VAS); Simplified Acute Physiology Score (SAPS); Ankylosing Spondylitis Disease Activity Score (ASDAS); Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC); 36-Item Short Form Survey (SF-26); Bath Ankylosing Spondylitis Disease Activity Index (BASDAI); Bath Ankylosing Spondylitis Functional Index (BASFI).
Bangjian (2022)
Preoperative p
HHS 15.21 ± 1.52 <0.01
Postoperative
HHS 82.65 ± 4.77
Dabir (2015)
Preoperative p
HHS 26.0 (23.0, 43.0) <0.001
Postoperative
HHS 88.0 (86.0, 91.0)
Ding (2018)
Preoperative Hip Non-Fusion Group Hip Fusion Group p
HHS 40.25 (20.47) 54.13 (14.15) 0.016
HHS pain 15.4 (12.42) 38.09 (9.39) <0.001
HHS function 24.85 (13.97) 16.04 (7.93) 0.019
Barthel score 68.75 (14.68) 53.48 (7.14) <0.001
Other Hip Non-Fusion Group Hip Fusion Group p
SAPS 90.94 (8.48) 97.28 (3.17) 0.004
Index of function improvement 1.81 (1.31) 0.86 (0.62) 0.006
Index of self-care improvement 0.46 (0.31) 0.79 (0.22) <0.001
Hu (2020)
Other Stable AS Group Active AS Group p
ASDAS 0.97 ± 0.20 2.55 ± 0.90 <0.001
Im (2023)
Postoperative LLD < 5 mm Group 5 mm ≤ LLD <10 mm Group p
HHS 97.8 (88–100) 89.3 (42–100) 0.002
Other LLD < 5 mm Group 5 mm ≤ LLD <10 mm Group p
WOMAC: Pain 2.2 (0–15) 0.3 (0–4) 0.003
WOMAC: Physical Function 9.9 (0–51) 1.8 (0–17) 0.009
WOMAC: Stiffness 1 (0–4) 0.1 (0–2) 0.007
Jacob (2022)
Preoperative p
HHS 17.03 ± 6.02 <0.0001
Postoperative
HHS 90.66 ± 7.23
Lee (2017)
Preoperative AS Group AVN of Femoral Head Group p
HHS 55.6 ± 13.8 59.2 ± 2.8 0.001
Postoperative AS Group AVN of Femoral Head Group p
HHS 92.8 ± 2.8 97.4 ± 2.6 0.012
Mou-Li (2021)
HHS Postoperative p
Non-Ankylosed Group 89.1 ± 3.2 <0.001
Fibrous Ankylosed Group 88.2 ± 3.2
Bony Ankylosed Group 83.7 ± 2.3
Qian (2023)
Preoperative Mobility Group No Mobility Group p
HHS 39.27 ± 5.58 20.52 ± 3.64 <0.001
VAS 7.28 ± 0.31 3.85 ± 0.36 <0.001
Postoperative Mobility Group No Mobility Group p
HHS 81.95 ± 4.30 71.53 ± 2.21 <0.001
VAS 2.86 ± 0.37 2.36 ± 0.30 <0.001
Other Mobility Group No Mobility Group p
SF-36: Mental Health @ 1-week post-op 44.41 ± 0.57 31.58 ± 0.42 <0.001
SF-36: Mental Health @ 3 months post-op 54.40 ± 0.62 41.10 ± 0.58 <0.001
SF-36: Mental Health @ 6 months post-op 64.18 ± 0.60 51.30 ± 0.44 <0.001
SF-36: Mental Health @ 1-year post-op 74.04 ± 1.83 61.10 ± 0.47 <0.001
SF-36: General Health @ 1-week post-op 49.54 ± 4.32 35.13 ± 5.31 <0.001
SF-36: General Health @ 3 months post-op 55.05 ± 2.64 41.90 ± 2.37 <0.001
SF-36: General Health @ 6 months post-op 61.04 ± 2.12 51.48 ± 1.70 <0.001
SF-36: General Health @ 1-year post-op 69.18 ± 4.91 65.55 ± 4.38 <0.001
SF-36: Physical Function @ 1-week post-op 44.81 ± 3.03 38.28 ± 4.91 <0.001
SF-36: Physical Function @ 3 months post-op 54.77 ± 2.41 49.32 ± 2.51 <0.001
SF-36: Physical Function @ 6 months post-op 65.13 ± 1.67 55.95 ± 2.59 <0.001
SF-36: Physical Function @ 1-year post-op 71.18 ± 1.62 66.00 ± 2.22 <0.05
BASDAI 4.3 (3.8–4.6) 4.1 (3.6–4.6) 0.340
BASFI 43.5 (40–50) 70 (68–74) <0.001
Saglam (2016)
Preoperative Postoperative p
HHS 46.6 ± 16.b3 80.7 ± 18.7 <0.01
BASDAI 7.3 ± 1.6 4.1 ± 1.1 <0.01
Wang (2013)
Other Infliximab Group Control Group p
Change in VAS @ 12 mo. (−)4.00 (−6.00 to −1.00) (−)1.00 (−3.00- 1.00) 0.000
Change in HHS @ 6 mo. 16.00 (−6.00–31.00) 7.00 (4.00–13.00) 0.010
Change in HHS @ 12 mo. 23.00 (13.00–46.00) 17.00 (11.00–23.00) 0.014
Change in BASDAI @ 6 mo. (−)3.47 ± 0.92 (−)2.59 ± 0.88 0.012
Change in BASDAI @ 12 mo. (−)4.67 ± 0.75 (−)3.97 ± 0.95 0.041
3.8

3.8 Radiographic outcomes after THA in patients with AS

Three studies examined various radiographic outcomes after surgery such as leg length discrepancy (LLD) and changes in femoral offset (FO) and inclination of the cup (IC) angles.36,43,45 Im et al. found in a study of 89 patients that those with a LLD of 5–10 mm experienced significantly worse WOMAC pain and stiffness compared to those with an LLD of less than 5 mm (p = 0.003).36 Mou-Zeng et al. (2021) compared 22 patients with synchronous bilateral THA (group A) and 24 with sequential bilateral THA (group B).45 They observed no significant difference in FO between right and left hips in group A (p = 0.07), whereas group B showed a significant difference (p = 0.04). The bilateral IC differed by 3.0 ± 2.1° in group A and 5.5 ± 2.4° in group B (p = 0.02), though no differences were found between the groups for bilateral FO (p = 0.78) or LLD (p = 0.83). Man et al. (2020) studied 181 hips to assess the impact of AS-related hip damage on THA outcomes.43 They found that the severity of femoral head erosion influenced recovery time for independent walking without crutches postoperatively (OR = 1.467, 95 % CI: 1.050–2.409, p = 0.025). The severe erosion group required an average of 7.3 ± 0.9 weeks to regain independent walking, which was 4.6 ± 0.4 weeks longer than the non-severe erosion group (p = 0.001). They concluded that severe femoral head erosion significantly prolongs recovery time after THA.

4

4 Discussion

This study explored postoperative complications, including HO, infection, hip dislocation, and revision surgery following THA in patients with AS, a critical yet underexamined area given the unique challenges of this patient population. Patients with AS often present with complex biomechanical and inflammatory profiles, making them particularly vulnerable to complications such as joint dislocation, infection, reoperation, and HO. Our systematic review revealed increasing trends of HO and a need for revision surgery in this cohort, indicating that surgeons need to be aware of the presence and magnitude of these associations. Plausible hypotheses are that these associations might be influenced by the rigid, ankylosed spine and altered biomechanics typical of AS.

Patients with AS undergoing THA were observed to have relatively high rates of complications such as perioperative infection (5.14 %). This remains a severely understudied complication at the single-center level in THA patients with AS given that rates tend to vary widely for postoperative infections after spine stabilization surgery in patients with AS (∼19 %).48,49 Joint dislocation is particularly common in patients with AS due to fixed and abnormal spino-pelvic alignment. The current study observed relatively high rates of joint dislocation (5.22 %) compared to lower rates seen in the literature (0.68 %–3.4 %), though this may be partially confounded by the summative nature of the study.50,51 This finding, however, cannot be disregarded given that this was still found to be significant amongst individual studies. Mechanical loosening, in particular, remains a significant concern in patients with AS due to the altered biomechanics and increased stress on implants caused by the rigid spino-pelvic alignment typical of AS.7,52,53 The rigidity of the spine and pelvic fusion alters biomechanics, complicating acetabular cup positioning.52,54,55 This requires meticulous preoperative planning and intraoperative adjustments. Specifically, fixed pelvic tilt necessitates precise adjustments in acetabular component anteversion and inclination to minimize dislocation risks.52,56,57 Robotic-assisted THA can offer substantial advantages in the treatment of these rigid spine patients, providing real-time feedback and precise implant positioning to aid in proper alignment and reduction in observed dislocation rates.58–60 Revision surgery, oftentimes necessitated due to mechanical loosening, was seen to be comparable to THA in general in this study's cohort (4.06 % vs 4 %–6 %).61,62 The altered load distribution caused by the fused spine and pelvis can place excessive stress on the implant, leading to gradual loosening. Additionally, the technical difficulties of the initial surgery, such as achieving proper alignment in a rigid and deformed hip, can further contribute to the risk of mechanical failure. Robotic-assisted THA mitigates these risks by enhancing implant placement precision, reducing misalignment, and ensuring stable positioning. This technology's ability to adapt to the unique anatomical challenges of AS, such as pelvic tilt and abnormal load distribution, has been shown to lower reoperation rates significantly.58–60 Furthermore, the long-term outcomes following THA in patients with AS are generally positive, even though they are tempered by specific challenges inherent to the condition. Studies have demonstrated that THA provides substantial and sustained improvements in pain relief, range of motion, and overall quality of life (QOL), with implant survival rates ranging from 85 % to 92 % at 10 years.16,63,64 THA seems to offer a robust improvement in QOL for patients with AS, with the observed long-term functional improvements potentially outweighing the operative challenges associated with the index procedure.

AS has traditionally been thought to predominantly affect males, though this is seemingly becoming a more homogenous difference between both sexes.65,66 Our study's cohort, primarily 81.72 % male with a much younger average age of 38.95 ± 10.08 years, aligns with existing literature indicating the increased severity of AS in males, which may necessitate THA due to greater hip involvement and spinal deformity.3,65 Older patients who have been untreated for prolonged periods of time also tend to face higher risk of prosthesis dislocation, a risk particularly exacerbated by a rather rigid, kyphotic spine and fixed pelvic tilt, which complicate optimal acetabular component positioning. This is especially pronounced in those aged 70 and above.50 Compared to other spondyloarthropathies like psoriatic arthritis, gender differences in THA outcomes are less pronounced, likely due to the milder axial skeletal involvement. In osteoarthritis (OA) patients, THA outcomes are generally consistent across genders, although females in general are at a higher risk for complications such as periprosthetic fractures and dislocations, largely due to differences in bone quality which may further complicate the operative approach.67,68 In systemic lupus erythematosus (SLE), which predominantly affects females, the complication profile following THA differs markedly, with higher risks of infection and poor wound healing due to chronic immunosuppression, though without the biomechanical challenges seen in AS. Postoperative care for male patients with AS may involve a more aggressive physical therapy regimen aimed at maintaining joint mobility and preventing complications such as heterotopic ossification, which is more prevalent in males.20,69–71 For female patients with AS, perioperative care should emphasize early diagnosis and management to mitigate the functional impairments often seen preoperatively.65 Female patients may benefit from tailored analgesic protocols to manage pain more effectively, considering that they often experience higher pain scores immediately after surgery and may be more sensitive to certain medications.72,73 Moreover, given that females with AS often have less severe spinal deformity but still face a high risk of systemic complications, perioperative care should also include close monitoring for signs of infection and proactive measures to support wound healing.65 These gender-specific strategies, grounded in a deep understanding of disease pathology and patient outcomes, are crucial for optimizing surgical results and minimizing complications in both male and female patients with AS undergoing THA.

HO is a common and significant complication following THA in patients with AS. The incidence of HO in patients with AS undergoing THA is notably higher than in the general population, with rates ranging from as low as 15 % to as high as 65 %–81 % in high-risk patients depending on the study and the presence of additional risk factors such as male gender, bilateral THA, and a previous history of HO.23,74 It is important to note that recent studies such as Thilak et al. (2015), have showed that the female gender was a significant risk factor of increased HO prevalence after surgery.23 In general, we hypothesize that the increased predisposition to HO is likely due to the chronic inflammatory state inherent in AS, which promotes abnormal bone formation in soft tissues. In contrast, other spondyloarthropathies, such as psoriatic arthritis, tend to have a lower incidence of HO following THA, likely due to less severe axial involvement and differing inflammatory pathways.20 SLE patients, while also at risk for postoperative complications, do not commonly develop HO to the same extent as, as the pathophysiology of SLE does not typically involve the same degree of chronic inflammation and axial skeletal rigidity seen in AS. However, these individuals will often require THA at some point due to the onset of AVN seen as a byproduct of chronic steroid use or secondary to pathologies such as vasculitis.

The development of HO can be particularly detrimental to postoperative outcomes, especially concerning ROM improvement, which is a critical goal of THA in patients with AS. Many studies, including those within our cohort, have demonstrated significant improvements in ROM following THA, with patients often experiencing a substantial increase in mobility and quality of life.42–44 However, the formation of HO can severely limit these gains by causing stiffness and restricting joint movement, which counters the intended benefits of the surgery. The presence of HO may not only reduce ROM but also necessitate further surgical intervention, thereby increasing the morbidity associated with THA in this already vulnerable population. Given the high risk of HO in patients with AS, effective perioperative management is essential. Prophylactic measures like NSAIDs, bisphosphonates, and selective use of postoperative radiation can reduce HO incidence.22 However, radiation therapy should be considered cautiously, as its benefits may not be universal.74,75 Moreover, minimizing soft tissue trauma and ensuring meticulous hemostasis during surgery are critical to preventing HO. Despite the risk of HO and other complications, the improvement in mobility post-THA often outweighs the potential drawbacks of HO, especially when appropriate preventive measures are employed. Even in cases where HO develops, the initial gains in ROM can noticeably enhance the patient's quality of life, reducing pain and increasing independence. THA should be considered a feasible and often necessary option for patients with AS suffering from severe hip involvement, especially those who present with a low comorbidity burden or lack the typical markers of developing HO postoperatively.

The limitations of this study must be considered in the context of several factors. First, the observational nature of the studies included may limit the generalizability of the findings. The variability in surgical techniques, implant types, and perioperative care protocols across the studies introduces heterogeneity, making it challenging to draw definitive conclusions. Additionally, the lack of consistent long-term follow-up data in many studies restricts our ability to assess the durability of the outcomes observed, particularly concerning complications such as HO and joint dislocation. Another limitation is the potential for publication bias, as studies reporting negative or non-significant findings may be underrepresented in the literature. Future research should focus on large, multicenter prospective studies to better understand the long-term outcomes of THA in patients with AS. Additionally, more research is needed to explore the effectiveness of different perioperative management strategies in reducing the incidence and severity of complications such as HO. Further investigation into the role of gender in influencing outcomes and the potential benefits of advanced surgical techniques, such as robotic-assisted THA, is also warranted. Such studies could provide valuable insights into optimizing surgical planning and improving patient outcomes in this challenging patient population.

5

5 Conclusion

AS may be associated with an increased incidence of postoperative complications after THA, such as joint dislocation, HO, and infection, necessitating surgeon awareness for optimal patient care. HO and joint dislocation in particular were seen to contribute to the postoperative complication profile of AS, likely attributed to the inflammatory and rigid nature of the nearby spinal region. While qualitative trends indicate significant improvements in range of motion and overall patient outcomes, the absence of statistical analysis limits the strength of these observations, requiring further research. The findings underscore the importance of vigilant perioperative management in patients with AS undergoing THA, particularly in high-risk patients with history of HO and other preexisting comorbid burden. To reduce both risk of readmission and reoperation or revision in this cohort, greater emphasis on the appropriate selection and prophylactic medication management of these patients may be needed. Future research should focus on larger, prospective studies that explore the long-term impact of advanced surgical techniques, such as robotic-assisted THA, and further investigate the gender-specific differences in outcomes to refine and enhance perioperative care strategies for this complex patient population.

CRediT authorship contribution statement

Omkar Anaspure: Idea inception, Writing – original draft, Formal analysis. Andrew Newsom: Data curation. Shiv Patel: Data curation. Anthony N. Baumann: statistics, Writing – review & editing. Krishna K. Eachempati: Writing – review & editing. Weston Smith: Writing – review & editing. Neil P. Sheth: Writing – review & editing.

Ethical statement

This systematic review used publicly available data and did not require IRB approval.

Funding information

No funding was received for this study.

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