Inversion of the acetabular labrum causes increased localized contact pressure on the femoral head: a biomechanical study

Postoperative femoral head cartilage injury after hip arthroscopic treatment for femoroacetabular impingement syndrome and labral tear

BACKGROUND

Postoperative femoral head cartilage injury (FHCI) is a rare condition that can be observed in a certain proportion of patients undergoing hip arthroscopy. However, the prevalence and associated factors of FHCI, and the effect of this condition on clinical outcomes still remain unknown.

PATIENTS AND METHODS

Consecutive patients who were diagnosed with femoroacetabular impingement syndrome (FAIS) and labral tear and underwent hip arthroscopic treatment in our institute between July 2020 and July 2021 were retrospectively evaluated. Supine anteroposterior hip radiographs, cross-table lateral radiographs, magnetic resonance imaging (MRI), and computed tomography (CT) were obtained preoperatively. Postoperative MRI, at least 6 months after arthroscopy, was performed. Postoperative FHCI was evaluated by two surgeons through MRI. Preoperative patient-reported outcomes (PROs) including visual analog scale (VAS) for pain, and modified Harris Hip Score (mHHS) before surgery and at final followup were obtained.

RESULTS

A total of 196 patients were included. Postoperative FHCI was identified in 21 (10.7%) patients. The intraobserver reliability of the observer A and B for detecting postoperative FHCI using 3.0-T MRI was high (k = 0.929, and k = 0.947, respectively). The interobserver reliability between the two observers for detecting FHCI using 3.0-T MRI was high (k = 0.919). There was no significant difference in preoperative and postoperative mHHS, VAS, and percentage of patients who surpassed minimal clinically important difference (MCID) and achieved patient acceptable symptom state (PASS) between patients with and without postoperative FHCI (P > 0.05).

CONCLUSION

Although postoperative FHCI was observed in 10.7% of patients, which was associated with larger labrum, this condition did not result in inferior clinical outcomes. Level of evidence IV, retrospective case series. Trial registration The Chinese Clinical Trial Registry approved the registration (ChiCTR2200061166). The date of registration is 2022-06-15.

Bibliometric analysis of the acetabular labrum

The acetabular labrum (AL) plays a crucial role in the normal physiological functioning of the hip joint. This study aims to present an overview of the current status and research hotspots concerning the AL and to explore the field from a bibliometric perspective. A total of 1918 AL-related records published between January 1, 2000 and November 8, 2023 were gathered from the Web of Science Core Collection database. By utilizing tools such as HisCite, CiteSpace, VOSviewer, and the R package "bibliometrix," the regions, institutions, journals, authors, and keywords were analyzed to predict the latest trends in AL research. Global research interest and publication output related to this topic continues to escalate. The United States leads in international collaborations, number of publications, and citation frequency, underscoring its preeminent position in this field. The American Hip Institute emerged as the most prolific institution, making the greatest contribution to publications. Notably, Arthroscopy and the American Journal of Sports Medicine are the 2 most popular journals in this domain, accounting for 13.29% and 10.1% of publications, respectively, and were also found to be the most co-cited journals. Amongst authors, Benjamin G. Domb leads with 160 articles (8.35%), while Marc J. Philippon is the most frequently cited author. The keyword co-occurrence network showed 3 hot clusters, including "AL," "femoral acetabular impingement (FAI)," and "osteoarthritis." In addition, "survivorship," "FAI," and "patient-reported outcomes" were identified as trending topics for future exploration. This study represents the first comprehensive bibliometric analysis, summarizing the present state and future trends in AL research. The findings serve as a valuable resource for scholars, offering practical insights into key information within the field and identifying potential research frontiers and emerging directions in the near future.

Osteoporosis, Osteoarthritis, and Subchondral Insufficiency Fracture: Recent Insights

The increased incidence of osteoarthritis (OA), particularly knee and hip OA, and osteoporosis (OP), owing to population aging, have escalated the medical expense burden. Osteoarthritis is more prevalent in older women, and the involvement of subchondral bone fragility spotlights its association with OP. Notably, subchondral insufficiency fracture (SIF) may represent a more pronounced condition of OA pathophysiology. This review summarizes the relationship between OA and OP, incorporating recent insights into SIF. Progressive SIF leads to joint collapse and secondary OA and is associated with OP. Furthermore, the thinning and fragility of subchondral bone in early-stage OA suggest that SIF may be a subtype of OA (osteoporosis-related OA, OPOA) characterized by significant subchondral bone damage. The high bone mineral density observed in OA may be overestimated due to osteophytes and sclerosis and can potentially contribute to OPOA. The incidence of OPOA is expected to increase along with population aging. Therefore, prioritizing OP screening, early interventions for patients with early-stage OA, and fracture prevention measures such as rehabilitation, fracture liaison services, nutritional management, and medication guidance are essential.

The role of torsional stress in the development of subchondral insufficiency fracture of the femoral head: A finite element model analysis

BACKGROUND

Subchondral insufficiency fracture of the femoral head generally occurs without evidence of trauma or with a history of minor trauma. Insufficient bone quality is considered one cause; however, the detailed mechanism of fracture development at the subchondral area (SA) is not understood. The aim of this study was to clarify the directions of force that cause subchondral fracture using finite element model analysis.

METHODS

Two types of finite element models were generated from the CT data of femurs obtained from three individuals without osteoporosis (normal models) and another three with osteoporosis (osteoporosis models). Three directions of force, including compressive, shearing, and torsional, were applied to the femoral head. The distribution of von Mises stress (Mises stress) was evaluated at the SA, principal compressive trabeculae (PC), and principal tensile trabeculae.

RESULTS

Under compressive force, the mean Mises stress value was greatest at the PC in both the normal and osteoporosis models. Under shearing force, the mean Mises stress value tended to be greatest at the SA in the normal model and at the PC in the osteoporosis model. Under torsional force, the mean Mises stress value was greatest at the SA in both types of models.

CONCLUSIONS

The torsional force showed the greatest Mises stress at the SA in both the normal and osteoporosis models, suggesting the importance of torsion as a possible force responsible for subchondral insufficiency fracture development.

MRI assessment of femoral head docking following closed reduction of developmental dysplasia of the hip

AIMS

Eccentric reductions may become concentric through femoral head 'docking' (FHD) following closed reduction (CR) for developmental dysplasia of the hip (DDH). However, changes regarding position and morphology through FHD are not well understood. We aimed to assess these changes using serial MRI.

METHODS

We reviewed 103 patients with DDH successfully treated by CR and spica casting in a single institution between January 2016 and December 2020. MRI was routinely performed immediately after CR and at the end of each cast. Using MRI, we described the labrum-acetabular cartilage complex (LACC) morphology, and measured the femoral head to triradiate cartilage distance (FTD) on the midcoronal section. A total of 13 hips with initial complete reduction (i.e. FTD < 1 mm) and ten hips with incomplete MRI follow-up were excluded. A total of 86 patients (92 hips) with a FTD > 1 mm were included in the analysis.

RESULTS

At the end of the first cast period, 73 hips (79.3%) had a FTD < 1 mm. Multiple regression analysis showed that FTD (p = 0.011) and immobilization duration (p = 0.028) were associated with complete reduction. At the end of the second cast period, all 92 hips achieved complete reduction. The LACC on initial MRI was inverted in 69 hips (75.0%), partly inverted in 16 hips (17.4%), and everted in seven hips (7.6%). The LACC became everted-congruent in 45 hips (48.9%) and 92 hips (100%) at the end of the first and second cast period, respectively. However, a residual inverted labrum was present in 50/85 hips (58.8%) with an initial inverted or partly inverted LACC.

CONCLUSION

An eccentric reduction can become concentric after complete reduction and LACC remodelling following CR for DDH. Varying immobilization durations were required for achieving complete reduction. A residual inverted labrum was present in more than half of all hips after LACC remodelling.Cite this article: Bone Joint J 2023;105-B(2):140-147.

Current Research on Subchondral Insufficiency Fracture of the Femoral Head

Subchondral insufficiency fracture (SIF) of the femoral head is one of the predominant etiologies of rapidly progressive osteoarthritis of the hip (RPOH). SIF is a rare disease that causes acute pain in the hip joint. It is most frequently found in elderly women with osteoporosis. It is often underdiagnosed or misdiagnosed as osteonecrosis of the femoral head. SIF is currently a well-established cause of RPOH; however, the deeper etiology of SIF is not clear. Good clinical outcomes have been reported for hip preservation therapy and hip replacement. SIF is not obvious radiologically in the early stage, and a T1-weighted magnetic resonance imaging shows a discontinuous low-intensity band under the articular cartilage convex to the articular surface as its characteristic manifestation. Some patients will lose the opportunity to preserve the hip joint due to symptoms such as progressive joint space narrowing and subchondral collapse within a very short period. Patients with progressive hip space narrowing and subchondral collapse on X-ray should be converted to total hip arthroplasty. Based on the characteristics of the disease, surgeons need to master the clinical and radiological characteristics of SIF and strive for early diagnosis and treatment.

Management and effects of residual limbus inversion following closed reduction in developmental hip dysplasia: Protocol for a multicenter randomized controlled trial

Closed reduction is a common treatment method for developmental dysplasia of the hip (DDH) in children aged 6-18 months. Residual acetabular dysplasia (RAD) is the most common complication associated with closed reduction. Residual limbus inversion (RLI) is a common condition following DDH closed reduction. Previously, we confirmed that when limbus inversion exceeds 32.2% of the acetabular depth after closed reduction, RLI persists and leads to RAD; however, this was based on a small cohort with a short-term follow-up period. The long-term fate of RLI and the correlation between RLI and RAD have yet to be verified. Therefore, this multicenter clinical study protocol was designed in three parts to investigate the effect of RLI on acetabular development after closed reduction of DDH (a multicenter retrospective cohort study), effect of RLI clearance on acetabular development (a multicenter retrospective and prospective randomized controlled study), and influence of inverted limbus clearance on acetabular development during DDH reduction (a multicenter prospective cohort study). Statistical analysis was performed by assessing the basic measures of acetabular development including the acetabular index and central-edge angle using frontal pelvic radiographs; the magnitude of limbus inversion, cartilaginous acetabular index, and T1ρ mapping values were measured using magnetic resonance imaging. The multicenter retrospective cohort studies required 5 years of follow-up period at minimum, and the prospective randomized controlled studies required reviews of frontal pelvic radiographs every 6 months as well as data pooling every 2 years to compare the short- and mid-term outcomes of hip joint morphological development between the two groups of pediatric patients. This research program is expected to verify that RLI following closed reduction of DDH can affect acetabular development and that limbus excision during DDH reduction can improve postoperative RAD. Therefore, the indication and timing of surgical intervention for RLI after closed reduction of DDH provide a basis for revising the acceptable criteria for utilizing closed reduction of DDH to reduce the incidence of osteoarthritis caused by RAD following DDH treatment. Clinical Trial: http://www.chictr.org.cn/showproj.aspx?proj=35045 (ChiCTR1900020996).

Acetabular development and fate of inverted limbus in rabbits: Experimental observation from an animal model

Using an animal model, we aimed to investigate the effects of an inverted limbus on acetabular development following closed reduction of developmental dysplasia of the hip (DDH). We interpositioned the menisci of 5-week-old rabbits (n = 40) into the hip joints to simulate limbus inversion following closed reduction for DDH. The acetabular index (AI) on anteroposterior pelvic radiographs and magnetic resonance imaging were used to evaluate acetabular development. Animals were euthanized at 4 and 8 weeks after surgery. Histological sections of the acetabular cartilage were stained and scored in accordance with the modified Mankin system. Scanning electron microscopy and transmission electron microscopy were used to examine the ultrastructure of the acetabular cartilage. Terminal deoxynucleotidyl transferase dUTP nick end-labeling staining was used to evaluate chondrocyte apoptosis. Immunohistochemistry and Western blot analyses were used to examine the expression of type X collagen (Col-X) and matrix metalloproteinase 13 (MMP-13) in the acetabular cartilage. AI values increased over a period and were higher in the experimental group than in the sham group. In the experimental group, the acetabular surface had become rough and had split in some cases. Chondrocytes within the acetabular cartilage had become hypertrophic, gradually forming clusters, and taking on an apoptotic appearance. Col-X and MMP-13 expression also increased with time. Our findings suggest that residual limbus inversion following closed reduction for DDH can cause progressive dysplasia of the acetabulum, apoptosis of acetabular chondrocytes, accelerated cartilage degeneration, and even early-stage osteoarthritis.

An Inverted Acetabular Labrum Is Predictive of Pavlik Harness Treatment Failure in Children With Developmental Hip Dysplasia

INTRODUCTION

The failure rate of Pavlik harness treatment for developmental dysplasia of the hip (DDH) has been reported as high as 55%. The purpose of this study is to investigate the effect of an inverted acetabular labrum on outcomes of Pavlik harness treatment for DDH.

METHODS

A retrospective review was conducted on DDH patients at a tertiary care pediatric hospital from 2004 to 2016. DDH patients that underwent index treatment with Pavlik harness and had minimum 12 months follow-up were included. Medical charts were reviewed for demographics, treatment, and outcomes. Outcomes were compared between patients with an inverted labrum versus those without an inverted labrum.

RESULTS

A total of 156 patients with 229 dysplastic hips were included. The mean age at initiation of Pavlik harness treatment was 1.9±1.4 months and mean follow-up was 37.7±23.0 months. Bilateral DDH was diagnosed in 46% (73/156) of patients. In all, 37% (75/229) of hips failed Pavlik harness index treatment. Second-line treatment was rigid hip abduction bracing in 91% (68/75) of hips, closed reduction in 5% (4/75) of hips, and open reduction in 4% (3/75) of hips. An inverted labrum was present in 10% (22/229) of all hips. The incidence of Pavlik harness treatment failure was 91% (20/22) in the inverted labrum group compared with 27% (55/207) in the control group (P<0.001). Closed or open reduction was required in 86% (15/22) of the inverted labrum group compared with 3% (7/207) of hips in the control group (P<0.001). The incidence of avascular necrosis was 18% (4/22) in hips with an inverted labrum compared with 0.4% (1/207) in the control group (P<0.001).

CONCLUSIONS

In children with DDH undergoing index treatment in a Pavlik harness, the presence of an inverted acetabular labrum is strongly predictive of treatment failure. Dysplastic hips with an inverted labrum also have a significantly higher risk of requiring closed or open reduction and developing avascular necrosis compared with those without an inverted labrum.

LEVEL OF EVIDENCE

Level III.

The fate of inverted limbus in children with developmental dysplasia of the hip: Clinical observation

In this study, we observed the fate of the inverted limbus after closed reduction for the treatment of developmental dysplasia of the hip (DDH) and its impact on acetabular development. Clinical data were reviewed for 26 DDH patients with an inverted or overriding limbus after closed reduction for hip dysplasia. Patients were divided into a residual inversion group (19 cases, 22 hips) and a spontaneous resolution group (7 cases, 7 hips) according to the limbus status at the last follow-up. Differences in the osseous acetabular index (AI) and cartilaginous AI (CAI), the magnitude of limbus inversion, center-edge angle (CEA), height-to-width index (HWI) of the femoral head epiphysis, and avascular necrosis (AVN) at last follow-up were compared. There were no statistically significant differences in the preoperative AI and CAI between groups. The magnitude of limbus inversion after reduction and the AI at the final follow-up in the residual inversion group were both larger than those in the spontaneous resolution group. The CAI, CEA, and HWI were not significantly different between groups. The magnitude of limbus inversion in the residual inversion group did not significantly decrease over time. AVN occurred in five hips in the residual inversion group. No cases of AVN occurred in the spontaneous resolution group. After closed reduction, the inverted limbus was not absorbed in the majority of cases; instead, it evolved into a thin layer of fibrous tissue embedded between the femoral head and acetabulum. This may delay the endochondral ossification of the acetabulum.

Differences in the microarchitectural features of the lateral collapsed lesion between osteonecrosis and subchondral insufficiency fracture of the femoral head

BACKGROUND

Like osteonecrosis of the femoral head (ONFH), subchondral insufficiency fracture of the femoral head (SIF) causes femoral head collapse. However, little is known about the differences between the two diseases regarding the morphological features of the collapsed lesion. We tested the hypothesis that the morphological features of the lateral collapsed lesion would differ between ONFH and SIF.

METHODS

Twenty femoral heads histopathologically diagnosed as ONFH (n = 10) or SIF (n = 10) were used in this study. In the lateral collapsed lesion of each femoral head, cubic regions of interest (ROIs) were selected within the collapsed subchondral area and the nearby non-collapsed subchondral area. Micro-CT-based microarchitectural parameters were compared between the ROIs in each disease. Additionally, correlations between histopathological and microarchitectural features were evaluated.

RESULTS

In ONFH, bone volume fraction, trabecular thickness, and bone mineral density in the collapsed area were all significantly lower than those in the nearby non-collapsed area where thickened bone trabeculae accompanied by appositional bone formation were invariably seen. On the other hand, in SIF there were no significant differences between the ROIs in any of these microarchitectural parameters. Histopathologically, varying degrees of callus formation overlying the fracture of the subchondral plate were seen around the lateral collapsed lesion.

CONCLUSION

The morphological features of the lateral collapsed lesion were inconsistent between ONFH and SIF, suggesting different pathomechanisms of femoral head collapse.

Does labral repair have a clinical benefit during arthroscopic treatment of femoro-acetabular impingement? Prospective multicentre study with 2-year follow-up

INTRODUCTION

Hip arthroscopy has emerged as an effective tool for treating labral tears associated with femoro-acetabular impingement (FAI).

OBJECTIVE

Compare the effectiveness of debridement versus labral repair on functional outcomes at 2 years after hip arthroscopy and evaluate the influence of the repair technique.

HYPOTHESIS

There is no statistical difference in short-term functional outcomes between debridement and repair. The type of repair technique has no influence on functional outcomes.

METHODS

From July 2017 to June 2018, a prospective study was done at 10 participating hospitals specialised in hip preservation surgery. Patients over 18 years of age, who underwent hip arthroscopy for a labral tear due to femoro-acetabular impingement, were enrolled. Patients underwent either labral repair or debridement. The labral repairs were performed with either the loop or mattress technique and functional outcomes were evaluated using the Non-Arthritic Hip Score (NAHS).

RESULTS

One hundred and eighty-seven patients who underwent arthroscopic treatment for FAI were enrolled; 42 (22.5%) underwent labral debridement and 145 (77.5%) underwent labral repair. In the repair group, 66 (46%) were mattress sutures and 79 (54%) were loop sutures. Mean patient age was 33.3±10.3 (18-63) and 38% of patients were women (n=71). Mean follow-up was 16.2 months (10-26.4). The mean NAHS improved from 47.3 to 72.8 (p<0.05) at final follow-up. There was no significant difference between the repair and debridement groups (p>0.05). There was no significant difference between the mattress and loop repair subgroups (p>0.05).

CONCLUSIONS

There is no statistical difference in short-term functional outcomes between debridement and repair. The type of repair technique has no influence on functional outcomes.

LEVEL OF EVIDENCE

II, prospective cohort study.

Distribution of Femoral Head Subchondral Fracture Site Relates to Contact Pressures, Age, and Acetabular Structure

OBJECTIVE. Nontraumatic subchondral fracture of the femoral head (FH) is often seen in elderly patients with osteoporosis and acetabular dysplasia. Although this injury can also occur in young people, even those without osteoporosis, it remains unclear who is at risk. We examined the acetabular structure and sites of subchondral fracture of the FH in young patients compared with those in middle-aged and older patients. MATERIALS AND METHODS. Forty-eight hips with nontraumatic subchondral fracture of the FH were divided into two groups according to patient age: young (< 40 years) and middle-aged and older (≥ 40 years). Dysplasia and retroversion were defined as a lateral center-edge angle of < 20° and crossover sign on anterosuperior radiographs, respectively. Locations and extents of fracture were evaluated by measuring the edge location of low-signal-intensity bands on coronal T1-weighted MR images. Stress distribution on subchondral bone in young patients was evaluated in contralateral unaffected hips with the same acetabular structure using finite element modeling based on CT. RESULTS. Twelve hips were in young patients and 36 were in middle-aged and older patients. Hips in young patients showed retroversion in 41.7%, whereas those in middle-aged and older patients had dysplasia in 38.9%. Young patients had larger mediolateral fractures; fractures in middle-aged and older patients were laterally located. Anterosuperior fractures were seen in both groups. Contact stress in patients with retroversion was mainly distributed on the mediolateral and superior sides but was concentrated laterally and superiorly in one patient with dysplasia. CONCLUSION. Mediolateral and anterosuperior fractures and stress distribution by retroversion were commonly observed in young patients, suggesting partial involvement of retroversion in the mechanism of injury of nontraumatic subchondral fractures of the FH in young patients.

Subchondral fracture caused by unevenly stiffened meniscus after radiofrequency-assisted arthroscopic knee meniscectomy: A case report and review of the literature

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Although the worsening of symptoms following knee arthroscopy in older patients is often labeled as progression of arthritic symptoms, subchondral insufficiency fracture following arthroscopy may be underdiagnosed.

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There is a possibility that uneven stiffening of the meniscus causes concentration of stress that resulted in postarthroscopic subchondral fracture.

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Surgeons should consider avoiding subsequent subchondral fracture when to use radiofrequency in the debridement of a torn meniscus.

Introduction

Causality for postarthroscopic osteonecrosis of the knee is unknown, and related mechanisms have been poorly characterized.

Presentation of case

This report describes a case of a 69-year-old man with subchondral fracture occurring after arthroscopic meniscectomy using a radiofrequency assisted shaver. The patient experienced increasingly intense knee pain 10 months after the meniscectomy. MR imaging revealed postarthroscopic osteonecrosis of the knee in the femoral medial condyle, requiring unicompartmental knee arthroplasty. A mid-coronal cut section of the resected medial femoral condyle showed a linear fracture line parallel to the subchondral bone endplate. Histopathological examination showed prominent callus formation on both sides of the fracture, comprised of reactive woven bone and granulation tissue. The middle portion of the resected medial meniscus was of uneven height, with significant stiffening of the higher side. The stiffened region of the medial meniscus corresponded to the subchondral fracture in the medial femoral condyle.

Discussion

The etiology of post-arthroscopic osteonecrosis of the knee is controversial, but it seems possible that altered knee biomechanics after meniscectomy may predispose patients to osteonecrosis. The findings of the current case suggested that uneven stiffening of the meniscus caused concentration of stress that resulted in postarthroscopic subchondral fracture.

Conclusion

Subchondral insufficiency fracture following arthroscopy may be underdiagnosed. Surgeons need to carefully consider the risk of subchondral fracture following uneven stiffening of the meniscus when to use radiofrequency in the debridement of a torn meniscus.

Bilateral spontaneous simultaneous femoral neck occult fracture in a middle-aged man due to osteoporosis and vitamin D deficiency osteomalacia: A case report and literature review

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Physicians should take spontaneous femoral neck occult fracture into consideration if they report groin pain or difficulty in walking, even when findings from plain X-ray are normal.

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In a patient with spontaneous femoral neck occult fracture, diagnosing and treating the underlying etiology of osteoporosis and osteomalacia are essential for improving prognosis.

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This is the first report of a case of bilateral spontaneous simultaneous occult fracture of the femoral neck caused by osteoporosis and osteomalacia in a middle aged man.

Introduction

Bilateral stress fracture of the femoral neck is very rarely seen in healthy young patients who are neither athletes nor military recruits.

Presentation of case

The present report describes a 51-year-old male patient, not an athlete and with no previous history of disease, who developed bilateral stress fracture of the femoral neck without displacement.

Discussion

Simultaneous bilateral femoral neck fracture is a rare injury. In the present case, two factors predisposed to bilateral occult fracture of the femoral neck. The first was osteoporosis due to the patient’s smoking and alcohol abuse. The second was vitamin D deficiency osteomalacia associated with inadequate sun exposure.

Conclusion

All patients who present with spontaneous hip pain should be evaluated for osteoporosis and osteomalacia and assessed for underlying occult fracture if they report groin pain or difficulty in walking, even when findings from plain X-ray are normal, to improve prognosis in this rare and serious condition.