Significant Chondrocyte Viability Is Present in Acetabular Chondral Flaps Associated With Femoroacetabular Impingement

Minced Cartilage Implantation in Acetabular Cartilage Defects: Case Series with 2-Year Results

OBJECTIVE

The objective was to evaluate clinical outcome and safety of arthroscopic, autologous minced cartilage implantation for acetabular cartilage lesions observed during hip arthroscopy to treat femoroacetabular impingement syndrome (FAIS).

DESIGN

Eleven male patients, average age: 29.4 ± 5.4 years, average body mass index (BMI): 24.2 ± 2.2 kg/m2, scheduled for hip arthroscopy due to FAIS accompanied by an acetabular cartilage lesion were included in the case series. Cartilage tissue was harvested and minced from the loose cartilage flap at the chondrolabral lesion by arthroscopic shaver, augmented with autologous conditioned plasma, implanted into the defect, and fixated by autologous thrombin. Concomitant interventions were performed as indicated. The patients were evaluated preoperatively and at 24-month follow-up, using the International Hip Outcome Tool-12 (iHOT-12) and Visual Analog Scale (VAS) pain score and by magnetic resonance imaging (MRI) using the Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART) grading scale at the 2-year follow-up.

RESULTS

The defect size was on average 3.5 cm2 (1.5-4.5 cm2). From preoperatively to 2 years postoperatively, the iHOT-12 significantly improved from 50.2 ± 18 to 86.5 ± 19 (P < 0.0001), and pain score decreased from 5.6 ± 1.8 to 1.0 ± 1.5 (P < 0.0001) on the Visual Analog Scale pain score. Regarding functional outcome and pain, 10 of the 11 patients and all patients reached the minimal clinically important difference (MCID), respectively. The postoperative average MOCART score was 87.2 (± 9.2). No adverse events or reoperations were observed.

CONCLUSIONS

Arthroscopic, autologous minced cartilage implantation for treating full-thickness acetabular cartilage lesions in FAIS shows statistically and clinically significant improvement at short-term follow-up.

[Minced cartilage procedure for the treatment of acetabular cartilage lesions of the hip joint]

OBJECTIVE

Treatment of acetabular cartilage defects using autologous cartilage fragments.

INDICATIONS

Acetabular cartilage damage (1-6 cm2) associated with femoroacetabular impingement syndrome (FAIS).

CONTRAINDICATIONS

Advanced osteoarthritis (≥ 2 according to Tönnis) and extensive acetabular cartilage damage > 6 cm2. Lack of labral containment due to irreparable labral damage.

SURGICAL TECHNIQUE

Arthroscopic preparation of the acetabular cartilage damage and removal of unstable cartilage fragments using a 4.0 mm shaver, which minces the cartilage fragments. If necessary, additional cartilage harvesting over the CAM morphology requiring resection. Collection of the cartilage fragments using GraftnetTM and augmentation with autologous conditioned plasma (ACP). Treatment of associated pathologies such as CAM morphology, pincer morphology, and labral refixation or reconstruction. Implantation of cartilage mass and remodeling into the defect zone. Final sealing with autologous fibrin.

POSTOPERATIVE MANAGEMENT

Postoperatively, weight bearing is restricted to 20 kg and range of motion to 90° of flexion for 6 weeks. This is supplemented by passive movement using a continuous passive motion (CPM) device.

RESULTS

Since 2021, 13 patients treated with the described method were followed up for at least 6 months. A significant increase in the International Hip Outcome Tool (iHot)-12 and a significant reduction of pain were observed. No severe complications occurred.

Acetabular cartilage delamination: performance of MRI using arthroscopy as the standard of reference

BACKGROUND

Femoroacetabular impingement (FAI) frequently leads to acetabular chondral delamination. Early identification and treatment of these cases is crucial to prevent further damage to the hip.

PURPOSE

To evaluate the accuracy of morphological signs of cartilage acetabular delamination in non-arthrographic magnetic resonance imaging (MRI) using intra-articular arthroscopic findings in patients undergoing FAI surgery.

MATERIAL AND METHODS

All hip MRI scans were assessed individually by three independent radiologists. Images were assessed for signs of delamination including the presence of a linear area of bright signal intensity along the acetabular subchondral bone and an area of darker tissue at the surface of the acetabular cartilage. All FAI patients underwent surgery; arthroscopy served as the standard of reference.

RESULTS

The mean age of participants was 36.1±10.9 years with 36 (48.6%) women. In the FAI group, arthroscopic surgery showed acetabular chondral delamination in 37 hips. In all hips (including the controls), MRI signs of acetabular cartilage delamination showed an average sensitivity across the three raters of 73.0% with a specificity of 71.0%. In a separate analysis of only the FAI patients, a slightly higher sensitivity (77.7%) but lower specificity (66.7%) was demonstrated. The interrater reliability showed a moderate agreement (average [k]) across the raters (0.450).

CONCLUSION

Performance of non-arthrographic MRI in diagnosing acetabular chondral delamination showed good results, yet inter-observer reproducibility among different radiologists was only moderate. Our results suggest that an increased level of awareness, for signs of delamination using MRI, will be helpful for detecting chondral delamination in patients with a history of FAI.

Treatment of Full-Thickness Acetabular Chondral Flaps During Hip Arthroscopy: Bone Marrow Aspirate Concentrate Versus Microfracture

Background:

The optimal treatment strategy for patients with full-thickness chondral flaps undergoing hip arthroscopy is controversial.

Purpose:

To compare functional outcomes of patients who underwent bone marrow aspirate concentrate (BMAC) application with those of patients who underwent microfracture.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

This was a retrospective case series of prospectively collected data on patients who underwent arthroscopic acetabular labral repair by 1 surgeon between June 2014 and April 2020. The inclusion criteria for this study were age ≥18 years, preoperative radiographs of the pelvis, arthroscopic acetabular labral repair, exposed subchondral bone with overlying chondral flap seen at the time of hip arthroscopy, microfracture or BMAC to address this lesion, and completed patient-reported outcome measures (PROMs) (International Hip Outcome Tool–33 [iHOT-33], Hip Outcome Score–Activities of Daily Living [HOS-ADL], Hip Outcome Score–Sports Subscale [HOS-Sport], modified Harris Hip Score [mHHS], and visual analog scale [VAS] for pain) at enrollment and 12-month follow-up. Clinical outcomes were assessed using PROM scores.

Results:

A total of 81 hips with full-thickness chondral flaps were included in this study: 50 treated with BMAC and 31 treated with microfracture. There were no significant differences between groups in age, sex, body mass index, tear size, radiographic osteoarthritis, or radiographic femoroacetabular impingement. In the BMAC cohort, all PROM scores improved significantly from preoperatively to follow-up: 41.7 to 75.6 for iHOT-33, 67.6 to 91.0 for HOS-ADL, 41.5 to 72.3 for HOS-Sport, 59.4 to 87.2 for mHHS, and 6.2 to 2.2 for VAS pain (P < .001 for all). In the microfracture cohort, the score improvements were 48.0 to 65.1 for iHOT-33 (P = .001), 80.5 to 83.3 for HOS-ADL (P = .275), 59.2 to 62.4 for HOS-Sport (P = .568), 70.4 to 78.3 for mHHS (P = .028), and 4.9 to 3.6 for VAS pain (P = .036). Regarding clinically meaningful outcomes, 77.6% of the BMAC group and 50.0% of the microfracture group met the minimal clinically important difference for iHOT-33 at the 12-month follow-up (P = .013).

Conclusion:

Patients with full-thickness chondral flaps at the time of hip arthroscopy experienced greater improvements in functional outcome scores at the 12-month follow-up when treated with BMAC as opposed to microfracture.

Arthroscopic Bone and Cartilage Grafting of Acetabular Cysts With Autologous Tissue

Repair of acetabular cysts and cartilage defects presents a challenge for the hip-preservation surgeon. Currently, most techniques involve allograft sources or open surgery. We present an arthroscopic technique using autologous graft sources for both bone and cartilage to repair subchondral acetabular cysts and the overlying cartilage defect. This technique uses new technology in combination with familiar arthroscopic instruments to decrease morbidity, hasten rehabilitation, and possibly improve the prognosis of these difficult to treat lesions.

The 'wave sign' in hip arthroscopy: a systematic review of epidemiological factors, current diagnostic methods and treatment options

This study aims to present a systematic review and synthesized evidence on the epidemiological factors, diagnostic methods and treatment options available for this phenomenon. A multi-database search (OVID Medline, EMBASE and PubMed) was performed according to PRISMA guidelines on 18 June 2019. All studies of any study design discussing on the epidemiological factors, diagnostic methods, classification systems and treatment options of the wave sign were included. The Newcastle–Ottawa quality assessment tool was used to appraise articles. No quantitative analysis could be performed due to heterogeneous data reported; 11 studies with a total of 501 patients with the wave sign were included. Three studies examined risk factors for wave sign and concluded that cam lesions were most common. Other risk factors include alpha angle >65^° (OR=4.00, 95% CI: 1.26–12.71, P=0.02), male gender (OR 2.24, 95% CI: 1.09–4.62, P=0.03) and older age (OR=1.04, 95% CI: 1.01–1.07, P=0.03). Increased acetabular coverage in setting of concurrent cam lesions may be a protective factor. Wave signs most commonly occur at the anterior, superior and anterosuperior acetabulum. In terms of staging accuracy, the Haddad classification had the highest coefficients in intraclass correlation (k=0.81, 95% CI: 0.23–0.95, P=0.011), inter-observer reliability (k=0.88, 95% CI: 0.72–0.97, P<0.001) and internal validity (k=0.89). One study investigated the utility of quantitative magnetic imaging for wave sign, concluding that significant heterogeneity in T1_ρ and T2 values (P<0.05) of acetabular cartilage is indicative of acetabular debonding. Four studies reported treatment techniques, including bridging suture repair, reverse microfracture with bubble decompression and microfracture with fibrin adhesive glue, with the latter reporting statistically significant improvements in modified Harris hip scores at 6-months (MD=19.2, P<0.05), 12-months (MD=22.0, P<0.05) and 28-months (MD=17.5, P<0.001). No clinical studies were available for other treatment options. There is a scarcity of literature on the wave sign. Identifying at risk symptomatic patients is important to provide prompt diagnosis and treatment. Diagnostic techniques and operative options are still in early developmental stages. More research is needed to understand the natural history of wave sign lesions after arthroscopic surgery and whether intervention can improve long-term outcomes. Level IV, Systematic review of non-homogeneous studies.

Femoral Head Chondrocyte Viability at the Cam Deformity in Patients With Femoroacetabular Impingement Syndrome

BACKGROUND

Patients with hip pathology, such as femoroacetabular impingement (FAI) or hip dysplasia, are known to sustain chondral delamination injuries identifiable during hip arthroscopy, with an incidence of 44% to 75%. There are studies focused on understanding acetabular chondral flap viability, but there is a dearth of research regarding the viability of femoral head cartilage overlying the cam deformity in FAI.

PURPOSE

To describe the viability and immunohistochemistry staining patterns of femoral head cartilage in the setting of FAI.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Between September 2018 and August 2019, a single surgeon prospectively collected full-thickness femoral cartilage from cam deformities in 14 patients with FAI undergoing osteoplasty. Samples were assessed for viability and underwent immunohistochemistry staining for collagen type I, collagen type II, and aggrecan.

RESULTS

The data set included 14 patients. Twelve samples were assessed for viability and 14 for immunohistochemistry straining. The mean patient age was 34.1 years, and the mean body mass index was 24.69. Mean ± SD chondrocyte viability per patient was 52% ± 11%. At the time of cell isolation, 8 of the 12 patients had viability >50%, with a maximum of 68.2%. This viability increased after a primary culture period, varying from 9 to 13 days, with 10 of 12 samples having viability >90%. The viability mean after the culture period was 94.54% ± 4.89%. Harvested cartilage showed expressions of type I cartilage, type II collagen, and aggrecan in a pattern that is predictable for native cartilage.

CONCLUSION

These data reveal that the cartilage in femoral head cartilage overlying cam deformity-much like that from acetabular chondral flaps-not only has baseline viability >50% (51.99% ± 10.83%) but the ability to increase in viability >90% after a culture period. There may be a role for use of femoral head cartilage as autograft to repair full-thickness cartilage defects of the acetabulum and femoral head, either at the time of osteochondroplasty or after a period of cell culture to improve cell viability.

CLINICAL RELEVANCE

A dearth of information is available regarding the viability of femoral head cartilage. This study provides insight into the cartilage viability and response to culture.

Distinct Pattern of Inflammation of Articular Cartilage and the Synovium in Early and Late Hip Femoroacetabular Impingement

BACKGROUND

The molecular mechanism of how femoroacetabular impingement (FAI) morphology leads to hip osteoarthritis (OA) is yet to be determined. The expression and location of inflammation-related molecules during early- and late-stage FAI have not been previously described. Moreover, the characterization of intra-articular inflammation away from the cam deformity as well as the nature of adjacent synovial tissue have also not been extensively reported.

HYPOTHESIS

Early-stage FAI has a similar expression of inflammation-related markers in the head-neck and acetabular cartilage but less synovitis than late-stage FAI.

STUDY DESIGN

Controlled laboratory study.

METHODS

Head-neck cartilage, acetabular cartilage, and synovial samples were obtained from patients undergoing hip preservation surgery for the treatment of symptomatic cam FAI (early FAI group; n = 15) and advanced OA secondary to cam FAI (late FAI group; n = 15). Samples procured from healthy young adult donors served as the control group (n = 7). Cartilage degeneration was assessed by histology, and the expression of inflammation-related proteins (interleukin-1 beta [IL-1β], matrix metalloproteinase-13 [MMP-13], a disintegrin and metalloproteinase with thrombospondin motifs-4 [ADAMTS-4], type II collagen [COL2], and aggrecan neoepitope [NITEGE]) was measured by immunostaining. Synovial samples in the early and late FAI groups were examined for synovitis and the expression of IL-1β.

RESULTS

Head-neck cartilage in the early FAI group showed significantly more degeneration than the control group and an increased expression of inflammation-related proteins (IL-1β: 69.7% ± 18.1% vs 20.2% ± 4.9%, respectively; MMP-13: 79.6% ± 12.6% vs 25.3% ± 9.5%; ADAMTS-4: 83.9% ± 12.2% vs 24.3% ± 11.1%; NITEGE: 89.7% ± 7.7% vs 39.8% ± 20.5%) (P < .001). Head-neck and acetabular cartilage in the early and late FAI groups showed a similar degree of degeneration. Moreover, a similar expression of inflammation-related proteins was observed between the early and late FAI groups for head-neck cartilage (IL-1β: 69.7% ± 18.1% vs 72.5% ± 13.2%; MMP-13: 79.6% ± 12.6% vs 71.4% ± 18.8%; ADAMTS-4: 83.9% ± 12.2% vs 82.6% ± 12.5%; COL2: 93.6% ± 3.9% vs 92.5% ± 5.8%; NITEGE: 89.7% ± 7.7% vs 95.7% ± 4.7%) and acetabular cartilage (IL-1β: 83.3% ± 24.8% vs 80.7% ± 15.6%; MMP-13: 94.3% ± 9.7% vs 85.2% ± 12.3%; ADAMTS-4: 98.5% ± 2.3% vs 98.4% ± 3.4%; COL2: 99.8% ± 0.7% vs 99.7% ± 1.1%; NITEGE: 96.7% ± 6.7% vs 99.2% ± 2.2%). In contrast, synovitis was minimal with a low expression of IL-1β in the early FAI group compared with the late FAI group.

CONCLUSION

Hip cartilage exhibited an OA phenotype in patients with early-stage FAI, similar to what was observed in hip OA secondary to FAI. Severe synovitis was only evident with late-stage FAI.

CLINICAL RELEVANCE

This study supports the concept that early hip impingement is associated with cartilage degeneration and catabolism.

Is There a Scientific Rationale for the Refixation of Delaminated Chondral Flaps in Femoroacetabular Impingement? A Laboratory Study

BACKGROUND

Debonding of the acetabular cartilage is a characteristic type of hip damage found in cam-type femoroacetabular impingement (FAI), which remains a treatment challenge. In addition to resection, refixation of these flaps using fibrin sealants has been recently suggested. However, there is only limited evidence available that the proposed refixation method results in sufficient viable cartilage formation to ensure long-term flap grafting and restored tissue function.

QUESTIONS/PURPOSES

To determine the flap tissue characteristics that would justify refixation of delaminated chondral flaps with a fibrin sealant, we characterized (1) the extracellular matrix (ECM) of chondral flaps in terms of chondrocyte viability and distribution of ECM components and (2) the chondrogenic potential of resident cells to migrate into fibrin and produce a cartilaginous matrix.

METHODS

Ten acetabular chondral flaps and three non-delaminated control cartilage samples were resected during surgery. Chondrocyte viability was quantified using a live-dead assay. To assess the ECM, histological staining of glycosaminoglycans, collagen II, and collagen I allowed the qualitative study of their distribution. The ability of chondrocytes to migrate out of the ECM was tested by encapsulating minced flap cartilage in fibrin gels and semi-quantitatively assessing the projected area of the gel covered with migrating cells. The potential of chondrocytes to produce a cartilaginous matrix was studied with a pellet assay, a standard three-dimensional culture system to test chondrogenesis. Positive controls were pellets of knee chondrocytes of age-matched donors, which we found in a previous study to have a good capacity to produce cartilage matrix. Statistical significance of controlled quantitative assays was determined by the Student's t-test with Welch's correction.

RESULTS

The proportion of viable chondrocytes in flaps was lower than in nondelaminated cartilage (50% ± 19% versus 76 ± 6%; p = 0.02). Histology showed a disrupted ECM in flaps compared with nondelaminated controls, with the presence of fibrillation, a loss of glycosaminoglycan at the delaminated edge, collagen II throughout the whole thickness of the flap, and some collagen I-positive area in two samples. The resident chondrocytes migrated out of this disrupted ECM in all tested samples. However in pellet culture, cells isolated from the flaps showed a qualitatively lower chondrogenic potential compared with positive controls, with a clearly inhomogeneous cell and matrix distribution and an overall smaller projected area (0.4 versus 0.7 mm; p = 0.038).

CONCLUSION

Despite the presence of viable chondrocytes with migration potential, the cells resided in a structurally altered ECM and had limited capacity to deposit ECM, leading us to question their capacity to produce sufficient ECM within the fibrin sealant for stable long-term attachment of such flaps.

CLINICAL RELEVANCE

The characterization of delaminated cartilage in cam FAI patients suggests that the refixation strategy might be adversely influenced by the low level of ECM produced by the residing cells.

Nonlabeling and quantitative assessment of chondrocyte viability in articular cartilage with intrinsic nonlinear optical signatures

Chondrocyte viability is a crucial factor for evaluating cartilage health. Most prevalent cell viability assays rely on dyes and are not applicable for in vivo or longitudinal studies. Here we demonstrated that the two-photon excited autofluorescence and second harmonic generation microscopy provided high-resolution imaging of cartilage tissue and distinguished live/dead chondrocytes by visual assessment. Furthermore, the normalized autofluorescence ratio was proposed as a quantitative indicator to determine chondrocyte viability. Based on the indicator, a curve fitting and simulated receiver operating characteristic method was proposed to identify the live/dead cell populations as well as the indicator threshold without dye labeling. Thus, it established the label-free imaging method for chondrocyte viability assay in cartilage tissue.

Impact statement

Chondrocytes are the only cellular component found in the cartilage, playing a critical role in maintaining the homeostasis of articular cartilage. The viability of chondrocytes is a crucial factor for evaluating cartilage health. However, the current prevalent cell viability assays rely on dye staining and thereby are not applicable in vivo or in longitudinal assessments. In this study, we demonstrate that the intrinsic signals such as two-photon excited autofluorescence and second harmonic generation can be used to classify live and dead chondrocytes in cartilage tissue. A quantitative measure is also proposed allowing development of automated assessment algorithms. The nonlabeling nature of this method suggests the potential applicability to nondestructive and in vivo assessment of cartilage health.

The "Outside-In" Lesion of Hip Impingement and the "Inside-Out" Lesion of Hip Dysplasia: Two Distinct Patterns of Acetabular Chondral Injury

BACKGROUND

Femoroacetabular impingement (FAI) and acetabular dysplasia lead to acetabular cartilage damage that commonly results in the chondral flaps seen during hip arthroscopy.

PURPOSE

To compare the acetabular chondral flap morphology seen during hip arthroscopy ("outside-in" vs "inside-out") with clinical and radiographic parameters underlying FAI and hip dysplasia.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Patients who underwent hip arthroscopy by the senior author between 2013 and 2017 with a finding of Outerbridge grade IV acetabular chondral flap were included. Each procedure was retrospectively reviewed on video and chondral flaps were categorized as inside-out or outside-in. An inside-out designation was made for flaps exhibiting an intact chondrolabral junction with a detached sleeve of chondrolabral tissue from the central acetabulum, and an outside-in designation was made for centrally anchored flaps exhibiting a break in the chondrolabral junction. Radiographic markers of hip impingement/dysplasia were noted for each patient during assignment into 1 of 2 radiographic groups: group 1, lateral center edge angle (LCEA) >20 with FAI, and group 2, LCEA ≤20 with or without cam FAI. Associations between chondral flap morphology and clinical diagnosis were tested using a chi-square test.

RESULTS

Overall, 95 patients (103 hips) were included (group 1, 78 hips; group 2, 25 hips). Among hips in group 2, 24 had concurrent cam FAI. There was a significant relationship between chondral flap type and radiographic diagnosis (P < .001). Among group 1 hips, 78% exhibited outside-in type chondral flaps, 12% exhibited combined outside-in and inside-out flaps, and 10% exhibited inside-out flaps. Group 2 hips showed 72% inside-out type chondral flaps, 16% combined, and 12% outside-in. Hips exhibiting outside-in type flaps were significantly more likely to be in group 1 (positive predictive value [PPV], 91%; negative predictive value [NPV], 69%). Similarly, hips exhibiting inside-out type flaps were significantly more likely to be in group 2 (PPV, 56%; NPV, 95%). Altogether, 90% of group 1 hips exhibited an outside-in lesion and 88% of group 2 hips exhibited an inside-out lesion.

CONCLUSION

Acetabular chondral flap type visualized during hip arthroscopy correlates with radiographic markers of hip impingement and hip instability. Outside-in flaps are highly predictive of FAI, whereas inside-out flaps are highly predictive of acetabular dysplasia.