Intra-articular Soft Tissue Pathology of the Postpartum Hip: A Systematic Review

Abstract

Purpose of Review

Pregnancy-related lumbopelvic and hip pain affects over half of postpartum females and has multiple aetiologies. The relative contribution of intra-articular soft tissue pathology to pregnancy-related hip pain is unknown. The current review investigates the available evidence regarding underlying intra-articular soft tissue aetiologies of hip pain in females during pregnancy and in the acute postpartum period.

Recent Findings

Three online databases (Embase, PubMed and Ovid [MEDLINE]) were searched from database inception until 11 April 2021. All titles, relevant abstracts and full-text articles were screened by two reviewers independently. The methodological quality of the included studies was assessed using the Methodological Index for Non-Randomized Studies (MINORS) instrument. Descriptive study characteristics are presented in a narrative summary. Five level IV evidence articles were eligible for inclusion. Twenty-two females were included. Twenty patients presented with labral pathology, 15 of which necessitated hip arthroscopy with labral debridement or repair with or without acetabuloplasty and/or femoroplasty. One patient presented with an incidental labral tear in the context of osteitis condensans illi. One patient presented with posttraumatic osteoarthritis necessitating a hip arthroplasty.

Summary

The contribution of intra-articular soft tissue injury is a documented, albeit sparse, aetiology contributing to pregnancy-related hip pain. Further research to better delineate the prevalence, natural history and optimal management options for females who sustained these injuries at a life-altering juncture is necessary to advance the care of these patients.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12178-022-09804-0.

Introduction

Over 50% of females experience pregnancy-related lumbopelvic or hip pain [1–3]. There are well-documented anatomic sources of pain and physiologic changes of pregnancy that contribute to the cause of these complaints. Low back, pelvic girdle and sacroiliac joint pain can be partially explained by physiologic weight gain and an anteriorly displaced centre of gravity, which lengthens the moment arm of the pelvic stabilizers [4–6]. Paraspinal, symphyseal and hip pain can be linked to increased soft tissue laxity, which may be associated with hormonal changes including an elevation in serum relaxin [7, 8]. Uncommon hip pathology such as transient osteoporosis of the hip (TOH) may be correlated to changes in bone mineral density in pregnancy [9–11]. Acetabular labral tears have also been associated with pregnancy-associated movement patterns such as forced hip flexion and internal rotation during vaginal delivery [12, 13].

Pregnancy-related hip pain can be divided into intra-articular and extra-articular aetiologies and should be separated from pelvic ring and lumbar pathologies [13]. Common extra-articular causes include round ligament of the uterus pain secondary to stretching during uterine growth, greater trochanteric pain syndrome, which comprises bursal inflammation, tendinopathy and tendon tears, and less commonly TOH [13–15]. Intra-articular pathologies consist of osteonecrosis of the femoral head and pre-arthritic hip disorders including femoroacetabular impingement (FAI) and hip dysplasia, which predispose individuals to labral tears and hip osteoarthritis [13, 16]. Although intra-articular pathologies are well described in the context of athletic injuries and joint preservation and reconstruction, there is a paucity of evidence with respect to their prevalence and management with relation to pregnancy.

The acetabular labrum is a triangular fibrocartilage rim that deepens the hip socket and provides a suction seal contributing to hip stability [17–19]. Labral tear aetiologies include trauma, underlying FAI, hip dysplasia, capsular laxity and degenerative wear [20]. Furthermore, it is relatively uncommon to sustain a labral tear in the absence of predisposing structural anatomy [21]. The management of labral tears includes non-operative and operative treatment options. There is sparce evidence about the differential diagnosis, appropriate work-up, natural history or optimal treatment of intraarticular hip pathology such as labral tears in the context of pregnancy. The objective of this systematic review is to document and assess the available evidence regarding the underlying intra-articular aetiologies of pregnancy-related hip pain.

Methods

Study Registration

This study was registered in the International prospective register of systematic reviews. No ethics or institutional review board approval was required.

Search Strategy

Three online databases (Embase, PubMed and Ovid [MEDLINE]) were searched from database inception until 11 April 2021, for literature that investigated intra-articular hip and labral pathology during the peripartum period. The search included broad terms such as “pregnancy”, “hip joint” and “labrum” (Appendix 1).

Assessment of Study Eligibility

The research question and study eligibility criteria were established a priori. The inclusion criteria were English language studies, human studies, studies with a level of evidence one to four and those regarding symptomatic labral pathology in the peripartum period, either during pregnancy or in the acute postpartum period. Exclusion criteria were animal studies, commentaries, book chapters, review articles and technical studies.

Study Screening

All titles, relevant abstracts and full-text articles were screened by two reviewers independently. Any disagreements were deliberated between the two reviewers and the senior author was consulted if a consensus could not be obtained. The references of the studies included in the review were manually screened for any articles that were not included in the initial search strategy.

Data Abstraction

Data was collected and recorded in an Excel spreadsheet (Version 16.48 2021; Microsoft Corp). Abstracted data included the author(s), year of publication, study design, sample size, mean age, clinical and radiographic findings, pathology, subsequent management and outcomes.

Quality Assessment

The methodological quality of the included studies was assessed using the Methodological Index for Non-Randomized Studies (MINORS) instrument. This instrument was designed to assess the methodological quality of comparative and noncomparative, nonrandomized surgical studies [22]. Using the MINORS checklist, noncomparative studies were assigned a maximum score of 16, and comparative studies a maximum score of 24. Non-comparative studies were categorized a priori as follows: 0–4, very low quality; 5–7, low quality; 8–12, fair quality; and greater than or equal to 13, high quality [23]. For comparative studies, the categorization was as follows: 0–6, very low quality; 7–10, low quality; 11–15, fair quality; 16–20, good quality; and greater than or equal to 21, high quality [23].

Statistical Analysis

Due to the predominantly low quality, noncomparative nature of the studies included in this review, the results are presented in a descriptive summary fashion. Descriptive statistics including means, proportions, standard deviations and 95% confidence intervals were calculated using IBM SPSS Statistics version 23, Chicago, IL.

Results

Search Strategy

The initial search of online databases identified 2472 studies. A systemic screening and assessment of eligibility identified five articles that satisfied the inclusion criteria (Fig. 1).

Fig. 1.

PRISMA (Preferred Reporting items for Systematic Reviews and Meta-Analysis) flow diagram demonstrating the systematic review of the literature for studies investigating hip labral pathology during the peripartum period

Study Quality

Five studies were included (Table 1) consisting of three retrospective case series and two retrospective case reports. The mean MINORS score of these five non-comparative studies was 2.8 (range, 0–7) demonstrating a low quality of evidence. Only one study identified a purpose [12]. Two studies included details about participant inclusion, exclusion and outcome endpoints [12, 24]. No studies collected prospective data, conducted a prospective power analysis or sample size calculation. Only one study attempted an unbiased assessment of outcome endpoints [12]. Three studies detailed a follow-up period, and four studies had less than 5% loss to follow-up [12, 24–26].

Table 1.

Characteristics of included studies and patients

Author (year)	Study design (level of evidence)	Mean MINORS score	Number of patients/hips	Age (range)	Follow-up, months (range)
Baker, JF, McGuire GM and Mulhall KJ [24]	Retrospective case series (4)	4	3/3	39.3 (36–42)	5.7 (3–8)
Brooks AG and Domb BG [12]	Retrospective case series (4)	7	10/10	NR (23–36)	4 (4)
Jones DL et al. [25]	Retrospective case report (4)	2	1/1	28 (28)	15 (15)
Miller JE, Mittal V and Kohler M [26]	Retrospective case report (4)	1	1/1	NR	NR
Raghavan S and Gillespie G [27]	Retrospective case series (4)	0	7/7	NR	NR

MINORS, Methodological Index for Non-Randomized Studies; NR, not reported

Study Characteristics

The studies comprised of 22 patients (22 hips), all of which were females. The age ranged from 23 to 42 years, although two studies failed to report the age of the participants [26, 27]. The mean number of patients per study was four (range 1–10). The mean follow-up was 4.9 months (range 3–15), two studies failed to report any follow-up times [26, 27] (Table 1).

Two studies (seven hips) specified the onset of hip pain during pregnancy prior to the onset of labour [12, 25]. One study (four hips) identified a specific injury event during childbirth [12]. In three studies (11 hips), the pain was first noted after delivery [24, 26, 27]. All studies (22 hips) noted the persistence of pain after childbirth, which was not present before pregnancy. Three studies (11 hips) described the chief complaint as pain as in the groin [24, 25, 27]. Two studies (four hips) described mechanical symptoms such as popping or clicking in the hip and one study (10 hips) described a specific injury mechanism during childbirth consisting of forced hip flexion and internal rotation [12, 24, 25] (Table 2).

Table 2.

Preoperative clinical findings

Author (year)	History	Physical examination	Diagnostic tests
Baker, McGuire and Mulhall [24]	Pain onset following delivery. Groin pain, buttock pain, mechanical symptoms	Labral pathology signs, greater trochanter tenderness, pain with ROM	Radiography, MRA, Radioisotope bone scan
Brooks and Domb [12]	Pain onset during pregnancy or after delivery. Forced flexion and internal rotation at delivery	NR	Diagnostic arthroscopy
Jones et al. [25]	Pre-existing dysplasia. Hip arthroscopy with revision. Pain onset during pregnancy. Groin pain, mechanical symptoms	Anterior impingement and FABER tests positive. Pain and apprehension with axial distraction	Radiographs, CT, MRA
Miller, Mittal and Kohler [26]	Pain after pregnancy	Pain with ROM. Bilateral SI joint tenderness. Greater trochanter tenderness	Ultrasound CT, MRI
Raghavan and Gillespie [27]	Pain onset following delivery. Groin pain	NR	MRA

ROM, range of motion; MRA, magnetic resonance arthrography; NR, not reported; FABER, flexion, abduction, external rotation position of the hip; CT, computed tomography; SI, sacroiliac

Three of the five studies (five hips) supplemented the clinical history with physical examination findings [24–26]. Two studies (four hips) described tenderness over the greater trochanter and the presence of hip pain with range of motion [24, 26]. Two studies (four hips) reported positive examination findings for labral pathology including anterior impingement, flexion, abduction, external rotation position and pain and apprehension with axial distraction [24, 25] (Table 2).

All five studies (22 hips) included diagnostic assessments, the most common being magnetic resonance imaging (MRI) with or without arthrography (MRA). The only study (10 hips) that did not include MRI or MRA used hip arthroscopy to make the labral pathology diagnosis [12]. Two studies (four hips) made use of radiography, two studies (two hips) included computed tomography and ultrasound (one hip) and bone scan (three hips) were included in one study respectively [24–26] (Table 2).

Only two studies (11 hips) detailed initial non-operative management including oral pain medications, physical therapy, activity modification and intra-articular injections [12, 25]. These two studies (11 hips) also reported indications for surgery [12, 25]. One study detailed clinical symptoms, failure of non-operative management and being at least 6 months postpartum as indications for hip arthroscopy while another presented radiographic arthritic changes as an indication for total hip arthroplasty (THA) [12, 25]. Three studies (15 hips) described hip arthroscopy with labral debridement or repair with acetabuloplasty and/or femoroplasty when indicated for symptomatic intra-articular pathology [12, 24, 27]. In one study (one hip), definitive management consisted of a THA for osteoarthritis [25] (Table 3).

Table 3.

Initial treatment and definitive management

Author (year)	Initial nonoperative management	Indications for surgery	Procedure
Baker, McGuire and Mulhall [24]	NR	NR	Hip arthroscopy, labral debridement
Brooks and Domb [12]	Oral pain medications, injections, physical therapy	Clinical history, no long-term relief from non-operative management. Minimum 6 months postpartum	Hip arthroscopy, labral fixation or debridement. Acetabuloplasty and femoroplasty when FAI present
Jones et al. [25]	NSAIDs, physical and pool therapy, activity modification, intra-articular steroid and hyaluronic acid injections	Radiographic advanced arthritic changes. Lateral subluxation of the femoral head	Total hip replacement
Miller, Mittal and Kohler [26]	NR	NR	NR
Raghavan and Gillespie [27]	Mentioned, not detailed	NR	Hip arthroscopy

NR, not reported; FAI, femoroacetabular impingement; NSAIDs, non-steroidal anti-inflammatory drugs

Clinical Outcomes

Three studies (14 hips) reported clinical outcomes [12, 24, 25]. While all three studies reported subjective clinical outcomes, only one study (10 hips) reported an outcome score, the Harris Hip Score (HSS) [12]. Subjective clinical outcomes were not standardized with respect to timing, scale or measure in any of the studies. In the study that recorded the HSS, the pre-operative mean of 53.1 improved to 84.3 postoperatively [12]. Two studies (four hips) noted complications including psoas snapping and conversion to THA [24, 25]. No studies commented on return to daily activities, return to work, recurrent symptoms, radiological outcomes or further surgery (Table 4).

Table 4.

Clinical outcomes

Author (year)	Clinical outcomes	Outcome scores (pre-operative to postoperative)	Complications
Baker, McGuire and Mulhall (2010)	After surgery: Steady improvement at 6 months. Great improvement at 8 months. Significant pain reduction and no mobility restrictions at 3 months	NR	Psoas snapping
Brooks and Domb (2012)	Relief of symptoms within 4 months after procedure. All patients satisfied with surgery	HHS: 53.1 to 84.3	NR
Jones et al. (2018)	4 months of moderate pain relief with non-operative management before worsening	NR	Advanced arthritic changes, lateral subluxation of femoral head, definitive THA
Miller, Mittal and Kohler (2015)	NR	NR	NR
Raghavan and Gillespie (2012)	NR	NR	NR

NR, not reported; HHS, Harris Hip Score; THA, total hip arthroplasty

One study reported intra-operative findings on three postpartum females [24]. A 42-year-old had an extensive anterosuperior labral tear with grade I–II chondral defects on both femoral and acetabular surfaces. A 36-year-old had a full thickness chondral lesion on the anterior femoral head and an extensive anterior labral tear both necessitating debridement. A 40-year-old had widespread degenerative changes and a degenerative labrum with an unstable tear necessitating debridement [24].

Discussion

The primary finding of this study was that although pregnancy-related labral pathology of the hip has been recognized, the true prevalence, natural history and optimal management are not well delineated in the current literature. The overall quality of evidence for available studies documenting pregnancy-related labral injury was low based on the MINORS quality of evidence categorization adapted from a previous study [23]. Second, in 32% (7/22) of cases, symptoms began during pregnancy before the onset of labour, while in the other 68% (15/22) of cases symptoms were associated with a specific event during childbirth or first noted in the postpartum period. Individuals who experienced an insidious onset of symptoms during pregnancy were predisposed to injury due to physiologic changes of pregnancy such as weight gain and increased ligamentous laxity [7, 8, 20]. In cases of insidious symptom onset, the mechanism of injury may be consistent with a low energy repetitive pivoting and twisting, which has been suggested as a traumatic cause of labral tears [28]. On the other hand, a forced hip flexion and internal rotation mechanism of labral tearing during vaginal delivery has also been theorized [12]. Additionally, a regional anaesthetic during childbirth may predispose females to injury due to it allowing abnormal hip positions that would normally cause pain [24]. Maternal childbirth positioning may be analogous to anterior impingement and FAI-related labral pathology in athletic hips [21, 29–32]. Third, pregnancy-related labral pathology presents similarly to labral pathology of other aetiologies. Groin pain, mechanical symptoms and physical exam findings (such a positive anterior impingement test) were documented in the included studies in this review and have been well documented for labral pathology of other causes [24, 25, 27, 30, 33–35]. Finally, although the general surgical indications for pregnancy-related labral pathology are likely equivalent to that of other aetiologies, in one study, patients were also a minimum of 6 months postpartum before hip arthroscopy was considered [12]. Obstetricians use the same duration before considering surgery for postpartum pelvic floor injury citing this is the time needed for connective tissue recovery [36]. Pregnancy-related labral pathology may not have as strong a correlation with childbirth as pelvic floor injury, but the shortest, safe duration postpartum to undergo hip arthroscopy is not known and could be an area of further research.

Strengths

This review highlights an important emerging topic in women’s health, which has been considerably understudied. Second, this review utilized rigorous methods establishing aims, strict inclusion and exclusion criteria and a standardized method of assessment a priori to provide a reproducible search and applicable results. Last, the broad search of multiple databases ensured we did not omit any available evidence, which proved to be important considering the lack of current literature on the topic.

Limitations

The main limitation of this systematic review is the lack of available high-quality evidence concerning pregnancy-related labral tears. The retrospective, observational nature of the included studies precludes the formation of tangible conclusions about the prevalence, natural history, risk factors, diagnostic assessment or optimal management for these patients. The number of patients included in this review was also low, secondary to the small number of existing studies and their small sample sizes individually. The studies in this review lacked methodological rigour regarding participant selection, the collection of data, outcome reporting and assessment and therefore were susceptible to bias. Nevertheless, this review provides a baseline of knowledge about pregnancy-related labral tears and will provide a platform from which further high-quality research can be generated.

Future Directions

With the awareness generated by this review, the institution of surveillance protocols at hospitals providing high-volume obstetric care would not only benefit current patients, but also facilitate future research to further our understanding of pregnancy-related labral pathology. A screening pelvis radiograph for females with postpartum hip pain would identify those with underlying structural abnormalities that may benefit from further investigation and consideration of hip arthroscopy when appropriate. Furthermore, while postpartum lumbopelvic and pelvic-girdle pain are well-established entities, the increased recognition of pregnancy-related labral pathology provides clinicians with a wider differential for postpartum patients who present with hip pain and may aid in minimizing misdiagnoses. This also provides an opportunity for multi-disciplinary collaboration between physical therapists, primary care physicians, obstetricians and orthopaedic surgeons. Finally, from 2004 to 2009, there was a 365% increase in hip arthroscopy rates in the USA and by 2023, there is a projected 1388% increase in the rate of hip arthroscopy in England [37, 38]. As the rate of hip arthroscopy increases, females with pregnancy-related labral pathology necessitating surgery will hopefully be identified more easily to provide them with the care that they need.

Conclusion

There is little current evidence regarding pregnancy-related labral pathology. While multiple mechanisms of injury have been theorized, the true prevalence, natural history and optimal management are still unknown. Further research to advance our understanding of pregnancy-related labral pathology will help optimize care for these patients with hip pain at a critical juncture of their lives.

Authors Contribution

Conceptualization: Parth Lodhia. Literature search: Alex Hoffer and Doug Kingwell. Manuscript production: Alex Hoffer. Manuscript critical revision: Parth Lodhia, Olufemi Ayeni, Jordan Leith, Mark McConkey.

Data Availability

No new data were generated or analysed in support of this research.

Declarations

Conflict of Interest

The authors have no relevant conflicts of interest to disclose.

Human and Animal Rights and Informed Consent

This article does not contain any studies with human or animal subjects performed by any of the authors.