Low Rate of AVN and Complications in Unstable SCFE With Epiphyseal-metaphyseal Discontinuity After Treatment With a Modified Dunn Procedure.

BACKGROUND: The risk of developing avascular necrosis (AVN) in the setting of an unstable slipped capital femoral epiphysis (SCFE) that is undergoing treatment with the modified Dunn procedure is not well understood. In addition, since the Loder classification of unstable is reportedly different than actual intraoperatively observed instability (that is, discontinuity between the femoral head epiphysis and proximal femoral metaphysis), the overall risk of developing AVN, as well as the potential complications of treatment of these patients with the modified Dunn procedure, are unknown. QUESTIONS/PURPOSES: To evaluate the modified Dunn procedure for the treatment of patients with epiphyseal-metaphyseal discontinuity, we asked: (1) What was the survivorship free from AVN at 10 years? (2) What was the survivorship free from subsequent surgery and/or complications at 10 years? (3) What were the clinical and patient-reported outcome scores? METHODS: In a retrospective analysis, we identified 159 patients (159 hips) treated with a modified Dunn procedure for SCFE between 1998 and 2020, of whom 97% (155 of 159) had documentation about intraoperatively observed epiphyseal-metaphyseal stability. Of those, 37% (58 of 155) of patients were documented to have intraoperatively observed epiphyseal-metaphyseal discontinuity and were considered eligible for inclusion, whereas 63% (97 of 155) had documented epiphyseal-metaphyseal stability and were excluded. No patients were lost to follow-up before the 2-year minimum. All patients were assessed for survival, but 7% (4 of 58) did not fill out our outcomes score questionnaire. This resulted in 93% (54 of 58) of patients who were available for outcome score assessment. Additionally, 50% (29 of 58) of patients had not been seen within the last 5 years; they are included, but we note that there is uncertainty about their status. The median (range) age at surgery was 13 years (10 to 16), and the sex ratio was 60% (35 of 58) male and 40% (23 of 58) female patients. Sixty-four percent (37 of 58) of patients were classified as acute-on-chronic, and 17% (10 of 58) of patients were classified as acute. Forty-seven percent (27 of 58) of patients presented with severe slips and 43% (25 of 58) of patients with moderate slips based on radiographic classification. All patients underwent surgical hip dislocation with the modified Dunn procedure to correct the slip deformity and provide stabilization. Complications and reoperations were assessed from a review of electronic medical records, and a Kaplan-Meier estimator was used to estimate survivorship free from complications and reoperations at 10 years. Clinical examination results and questionnaire responses were evaluated at minimum 2-year follow-up. RESULTS: Kaplan-Meier survivorship free from AVN was 93% (95% CI 87% to 100%) at 10 years. Survivorship free from any reoperation was 75% (95% CI 64% to 88%) at 10 years. In addition, survivorship free from complications, defined as development of AVN, reoperation, or a Sink Grade II complication or higher, was 57% (95% CI 45% to 73%) at 10 years. The median (range) Merle D'Aubigne Postel score was 18 (14 to 18) for the patients who did not develop AVN, and 12 (6 to 16) for the four patients who developed AVN (p < 0.001). The median modified Harris hip score was 100 (74 to 100) in the non-AVN cohort and 65 (37 to 82) in the AVN cohort (p = 0.001). Median HOOS total score was 95 (50 to 100) in the non-AVN cohort and 53 (40 to 82) in the AVN cohort (p = 0.002). CONCLUSION: Although the modified Dunn procedure is technically challenging, this study shows that in experienced hands, patients with who have demonstrated epiphyseal-metaphyseal discontinuity can be treated with a low risk of AVN and subsequent surgery. Referral of these patients to specialists who have substantial expertise in this procedure is recommended to improve patient outcomes. Prospective, long-term observational studies will help us identify these high-risk patients preoperatively and determine the long-term success of this procedure. LEVEL OF EVIDENCE: Level IV, therapeutic study.

How Strong Is the Ligamentum Teres of the Hip? A Biomechanical Analysis.

BACKGROUND: Intraarticular hip pain represents a substantial clinical challenge, with recent studies implicating lesions in the ligamentum teres as potential contributors. Even more so, damage to the ligamentum teres is particularly prevalent among young patients undergoing joint-preserving interventions. Although several studies have investigated the biomechanical attributes of the ligamentum teres, inconsistencies in reported findings and reliance on cadaveric or animal models have raised concerns regarding the extrapolation of results to clinical practice. Furthermore, there is a lack of research examining ligamentum teres biomechanics specifically within the relevant patient cohort-individuals who benefit from joint-preserving surgical interventions. QUESTIONS/PURPOSES: We sought (1) to determine the biomechanical properties (ultimate load to failure, tensile strength, stiffness, and elastic modulus) of fresh-frozen ligaments from patients undergoing surgical hip dislocation, and (2) to identify patient-specific factors that are associated with them. METHODS: This was an institutional review board-approved study on intraoperatively harvested ligamentum teres from 74 consecutive patients undergoing surgical hip dislocation for joint preservation (August 2021 to September 2022). After the exclusion of patients with previous surgery, posttraumatic deformities, avascular necrosis, slipped capital femoral epiphysis, and Perthes disease, 31 ligaments from 31 patients were analyzed. The mean age of the study group was 27 ± 8 years, and 61% (19) of participants were male. The main indication for surgery was femoroacetabular impingement. Standardized AP pelvic and axial radiographs and CT scans were performed in all patients for better radiological description of the population and to identify associated radiological factors. The ligament was thoroughly transected at its origin on the fossa acetabuli and at the insertion area on the fovea capitis and stored at -20°C until utilization. Specimens were mounted to a materials testing machine via custom clamps that minimized slippage and the likelihood of failure at the clamp. Force-displacement and stress-strain curves were generated. Ultimate failure load (N), tensile strength (MPa), stiffness (N/mm), and elastic modulus (MPa) were determined. Using a multivariate regression analysis and a subgroup analysis, we tested demographic, degenerative, and radiographic factors as potential associated factors. RESULTS: The ligamentum teres demonstrated an ultimate load to failure of 126 ± 92 N, and the tensile strength was 1 ± 1 MPa. The ligaments exhibited a stiffness of 24 ± 15 N/mm and an elastic modulus of 7 ± 5 MPa. After controlling for potential confounding variables like age, fossa/fovea degeneration, and acetabular/femoral morphologies, we found that female sex was an independent factor for higher tensile strength, stiffness, and elastic modulus. Excessive femoral version was independently associated with lower load to failure (HR 122 [95% CI 47 to 197]) and stiffness (HR 15 [95% CI 2 to 27]). Damage to the acetabular fossa was associated with reduced load to failure (HR -93 [95% CI -159 to -27]). CONCLUSION: Overall, the ligamentum teres is a relatively weak ligament. Sex, degeneration, and excessive femoral version are influencing factors on strength of the ligamentum teres. The ligamentum teres exhibits lower strength compared with other joint-stabilizing ligaments, which calls into question its overall contribution to hip stability. CLINICAL RELEVANCE: Young patients undergoing hip-preserving surgery are the population at risk for ligamentum teres lesions. Baseline values for load to failure, tensile strength, elastic modulus, and stiffness are needed to better understand those lesions in this cohort of interest.

What Is the Influence of Femoral Version on Size, Tear Location, and Tear Pattern of the Acetabular Labrum in Patients With FAI?

BACKGROUND: Femoral version deformities have recently been identified as a major contributor to femoroacetabular impingement (FAI). An in-depth understanding of the specific labral damage patterns caused by femoral version deformities may help to understand the underlying pathomorphologies in symptomatic patients and select the appropriate surgical treatment. QUESTIONS/PURPOSES: We asked: (1) Is there a correlation between femoral version and the mean cross-sectional area of the acetabular labrum? (2) Is there a difference in the location of lesions of the acetabular labrum between hips with increased femoral version and hips with decreased femoral version? (3) Is there a difference in the pattern of lesions of the acetabular labrum between hips with increased femoral version and hips with decreased femoral version? METHODS: This was a retrospective, comparative study. Between November 2009 and September 2016, we evaluated 640 hips with FAI. We considered patients with complete diagnostic imaging including magnetic resonance arthrography (MRA) of the affected hip with radial slices of the proximal femur and axial imaging of the distal femoral condyles (allowing for calculation of femoral version) as eligible. Based on that, 97% (620 of 640 hips) were eligible; a further 77% (491 of 640 hips) were excluded because they had either normal femoral version (384 hips), incomplete imaging (20 hips), a lateral center-edge angle < 22° (43 hips) or > 39° (16 hips), age > 50 years (8 hips), or a history of pediatric hip disease (20 hips), leaving 20% (129 of 640 hips) of patients with a mean age of 27 ± 9 years for analysis, and 61% (79 of 129 hips) were female. Patients were assigned to either the increased (> 30°) or decreased (< 5°) femoral version group. The labral cross-sectional area was measured on radial MR images in all patients. The location-dependent labral cross-sectional area, presence of labral tears, and labral tear patterns were assessed using the acetabular clockface system and compared among groups. RESULTS: In hips with increased femoral version, the labrum was normal in size (21 ± 6 mm 2 [95% confidence interval 20 to 23 mm 2 ]), whereas hips with decreased femoral version showed labral hypotrophy (14 ± 4 mm 2 [95% CI 13 to 15 mm 2 ]; p < 0.01). In hips with increased femoral version, labral tears were located more anteriorly (median 1:30 versus 12:00; p < 0.01). Hips with increased femoral version exhibited damage of the anterior labrum with more intrasubstance tears anterosuperiorly (17% [222 of 1322] versus 9% [93 of 1084]; p < 0.01) and partial tears anteroinferiorly (22% [36 of 165] versus 6% [8 of 126]; p < 0.01). Hips with decreased femoral version showed superior labral damage consisting primarily of partial labral tears. CONCLUSION: In the evaluation of patients with FAI, the term "labral tear" is not accurate enough to describe labral pathology. Based on high-quality radial MR images, surgeons should always evaluate the combination of labral tear location and labral tear pattern, because these may provide insight into associated femoral version abnormalities, which can inform appropriate surgical treatment. Future studies should examine symptomatic patients with normal femoral version, as well as an asymptomatic control group, to describe the effect of femoral version on labral morphology across the entire spectrum of pathomorphologies. LEVEL OF EVIDENCE: Level III, prognostic study.

Drop in survivorship 13 years after AMIC procedures in aligned knees: A long-term follow-up.

PURPOSE: Autologous matrix-induced chondrogenesis (AMIC) showed promising short-term results comparable to microfracture. This study aims to assess the 19-year outcomes of AMIC, addressing the lack of long-term data. METHODS: Retrospective cohort of 34 knees treated with AMIC underwent a 19-year follow-up. The primary outcome was AMIC survival, considering total knee arthroplasty as a failure event. Survival analysis for factors that were associated with longer survival of the AMIC was also performed. Clinical and radiological outcome scores were analysed for the AMIC group. RESULTS: Twenty-three knees were available for follow-up analysis. Of these, 14 (61%) underwent revision surgery for total knee arthroplasty (TKA). The mean time was 13.3 ± 2.5 years (range: 9-17 years). Secondary outcomes showed that increased age at surgery (hazard ratio [HR]: 1.05; p = 0.021) and larger defect size (HR: 1.95; p = 0.018) were risk factors for failure. Concomitant proximal tibial osteotomy (HR: 0.22; p = 0.019) was associated with longer survival. The remaining nine knees (39%) were analysed as a single group. The mean clinical score at follow-up of 18.6 ± 0.9 SD years was 79.5 ± 19.7 SD for the Lysholm score, 1.8 ± 1.5 SD for the visual analog scale score, 74.2 ± 22.4 SD for the KOOS score and a median of 3 (range: 3-4) for the Tegner activity scale. CONCLUSIONS: The mean survival time of 13.3 years indicates the durability of AMIC in properly aligned knees. Nonetheless, despite a 61% conversion to TKA, the knees that persisted until the 19-year follow-up remained stable, underscoring the procedure's longevity and consistent clinical outcomes. LEVEL OF EVIDENCE: Level IV.

Validation of a computerized model for a new biomechanical concept- the fossa-foveolar mismatch- the answer to lesions of the ligamentous fossa-foveolar complex in the hip?

BACKGROUND: Hip-preserving surgery in young patients frequently reveals lesions of the ligamentum teres (LT). Histological and clinical evidence supports that those lesions could be source of intraarticular hip pain. It has been hypothesized that LT degeneration could be linked to the abnormal positioning of the fovea outside the lunate surface during various daily motions. We introduce the "fossa-foveolar mismatch" (FFM) by determining the trajectory of the fovea in the fossa during hip motions, enabling a comparison across diverse hip-pathomorphologies. AIMS: to determine (1) intraobserver reliability and (2) interobserver reproducibility of our computer-assisted 3-dimensional (3D) model of the FFM. MATERIALS AND METHODS: All patients with joint preserving surgery for femoroacetabular impingement syndrome (FAIS) or developmental dysplasia of the hip (DDH) at our institution (11. 2015-08.2019)were initially eligible. We employed a simple random sampling technique to select 15 patients for analysis. Three-dimensional surface models based on preoperative computed tomography (CT) scans were built, the fossa virtually excised, the fovea capitis marked. Models were subjected to physiological range of motion with validated 3D collision detection software. Using a standardized medial view on the resected fossa and the transparent lunate surface, the FFM-index was calculated for 17 motions. It was obtained by dividing the surface occupied by the fovea outside of the fossa by the total foveolar tracking surface. Three observers independently performed all analyses twice. (1) Intraobserver reliability and (2) interobserver reproducibility were calculated using intraclass correlation coefficients (ICCs). RESULTS: (1) We obtained excellent intraobserver ICCs for the FFM-index averaging 0.92 with 95% CI 0.77-0.9 among the three raters for all motions. (2) Interobserver reproducibility between raters was good to excellent, ranging from 0.76 to 0.98. CONCLUSIONS: The FFM-index showed excellent intraobserver reliability and interobserver reproducibility for all motions. This innovative approach deepens our understanding of biomechanical implications, providing valuable insights for identifying patient populations at risk.

Open reduction and internal fixation of modified Mason type III/IV radial head fractures with more than three fragments: an analysis of the clinical outcome and reoperation rate.

PURPOSE: It is generally accepted that a radial head fracture (RHF) with more than three parts is not suitable for repair; therefore, most authors suggest straightforward radial head arthroplasty (RHA). With up to 20% risk for reoperation after RHA, improvement in reduction and fixation techniques may represent a valuable alternative before further extending the indications for arthroplasty. To determine the functional results and radiological failure rate after osteosynthesis of multi-fragmentary RHF with more than three articular fragments. We specifically determined (1) the one-year Broberg and Morrey functional elbow score, (2) duration of fracture healing, (3) complication rate, and (4) number of patients converted to RHA. METHODS: This study is a retrospective single-center case series. All patients who underwent primary osteosynthesis for RHF between 2012 and 2019 were included. Nine patients with an average age of 52 years had an average clinical and/or radiological follow-up of 49 months. RESULTS: The preoperative imaging identified nine fractures with four fragments. Three patients underwent osteosynthesis with plates and screws, whereas six patients underwent osteosynthesis with only screws. The mean Broberg and Morrey score was 95 points. Overall, eight of the nine patients had satisfactory results. All patients retained their radial heads and showed radiological fracture healing. Only two patients presented with low-grade complications requiring no further surgery. CONCLUSION: Our study showed that osteosynthesis of RHF with up to four fragments can achieve good functional results with a low complication rate and seems to be a valid alternative to RHA.

Modified Kapandji technique in pediatric displaced distal radius fractures: results in 195 patients.

PURPOSE: The modified Kapandji technique has been proposed for fracture reduction in pediatric displaced distal radius fractures (DDRFs), but evidence is sparse. The purpose of this study was to evaluate our outcomes and complications, critically and systematically, when performing the modified Kapandji technique in pediatric DDRFs. Using this technique since 2011, we asked: (1) What is the quality of fracture reduction using this technique? (2) How stable is fracture alignment with this technique? (3) What are the postoperative complications and complication rates? METHODS: Retrospective observational study of 195 pediatric patients treated with the modified Kapandji technique. Quality of fracture reduction, fixation type (intrafocal, combined, or extrafocal), and coronal/sagittal angulation were recorded at surgery and healing. Perioperative complications were graded. Patients were stratified by fracture (metaphyseal or Salter-Harris) and fixation type, as well as age (≤ 6 years; 6 to 10 years; > 10 years). RESULTS: Fracture reduction was 'good' to 'anatomical' in 85% of patients. 'Anatomical' fracture reduction was less frequent in metaphyseal fractures (21% vs. 51%; p < .001). Mean angulation change was higher in metaphyseal fractures in both the sagittal (p = .011) and coronal (p = .021) planes. Metaphyseal fractures showed a higher mean change in sagittal angulation during fracture healing for the 'intrafocal' group. We observed a 15% overall complication rate with 1% being modified Sink Grade 3. CONCLUSION: The modified Kapandji technique for pediatric DDRFs is a safe and effective treatment option. Metaphyseal fractures that do not involve the physis should be treated with extrafocal or combined wire fixation. Complications that require additional surgical treatment are rare. LEVEL OF EVIDENCE: Level of evidence IV.

[Femoroacetabular impingement in 2024 : concept and diagnosis]. / Conflit fémoro-acétabulaire : concept et diagnostic.

Femoroacetabular impingement (FAI) is a condition that predominantly affects young people between the ages of 20 and 40. It is characterized by hip pain associated with reduced range of movement of the hip joint. If left untreated, FAI leads to osteoarthritis. When first described in the scientific literature in 2003, the concept of FAI was based on two different anatomic features: cam-type deformity and pincer-type deformity. Since that initial description clinical experience and scientific investigation have identified a third pillar of FAI: abnormal femoral torsion. This first article reviews the concept and diagnosis of FAI.

Le conflit fémoro-acétabulaire (CFA) est une pathologie qui touche les sujets jeunes de 20 à 40 ans, entraînant des douleurs associées à une diminution de l'amplitude de mouvement de l'articulation de la hanche. Non traité, le CFA est responsable d'une coxarthrose précoce. Lors de sa première description dans la littérature scientifique en 2003, le concept du CFA était basé sur deux piliers : came et pince. Ces 20 dernières années, de nouvelles connaissances ont émergé, avec notamment la mise en évidence du rôle important de la torsion fémorale, considérée à présent comme le troisième pilier du CFA. Ce premier article fait le point sur le concept et le diagnostic du CFA.

Are degenerative findings detected on traction MR arthrography of the hip associated with failure of arthroscopic femoroacetabular impingement surgery?

OBJECTIVES: To identify preoperative degenerative features on traction MR arthrography associated with failure after arthroscopic femoroacetabular impingement (FAI) surgery. METHODS: Retrospective study including 102 patients (107 hips) undergoing traction magnetic resonance arthrography (MRA) of the hip at 1.5 T and subsequent hip arthroscopic FAI surgery performed (01/2016 to 02/2020) with complete follow-up. Clinical outcomes were assessed using the International Hip Outcome Tool (iHOT-12) score. Clinical endpoint for failure was defined as an iHOT-12 of < 60 points or conversion to total hip arthroplasty. MR images were assessed by two radiologists for presence of 9 degenerative lesions including osseous, chondrolabral/ligamentum teres lesions. Uni- and multivariate Cox regression analysis was performed to assess the association between MRI findings and failure of FAI surgery. RESULTS: Of the 107 hips, 27 hips (25%) met at least one endpoint at a mean 3.7 ± 0.9 years follow-up. Osteophytic changes of femur or acetabulum (hazard ratio [HR] 2.5-5.0), acetabular cysts (HR 3.4) and extensive cartilage (HR 5.1) and labral damage (HR 5.5) > 2 h on the clockface were univariate risk factors (all p < 0.05) for failure. Three risk factors for failure were identified in multivariate analysis: Acetabular cartilage damage > 2 h on the clockface (HR 3.2, p = 0.01), central femoral osteophyte (HR 3.1, p = 0.02), and femoral cartilage damage with ligamentum teres damage (HR 3.0, p = 0.04). CONCLUSION: Joint damage detected by preoperative traction MRA is associated with failure 4 years following arthroscopic FAI surgery and yields promise in preoperative risk stratification. CLINICAL RELEVANCE STATEMENT: Evaluation of negative predictors on preoperative traction MR arthrography holds the potential to improve risk stratification based on the already present joint degeneration ahead of FAI surgery. KEY POINTS: • Osteophytes, acetabular cysts, and extensive chondrolabral damage are risk factors for failure of FAI surgery. • Extensive acetabular cartilage damage, central femoral osteophytes, and combined femoral cartilage and ligamentum teres damage represent independent negative predictors. • Survival rates following hip arthroscopy progressively decrease with increasing prevalence of these three degenerative findings.

Do Osteochondroplasty Alone, Intertrochanteric Derotation Osteotomy, and Flexion-Derotation Osteotomy Improve Hip Flexion and Internal Rotation to Normal Range in Hips With Severe SCFE? - A 3D-CT Simulation Study.

BACKGROUND: Severe slipped capital femoral epiphysis (SCFE) leads to femoroacetabular impingement and restricted hip motion. We investigated the improvement of impingement-free flexion and internal rotation (IR) in 90 degrees of flexion following a simulated osteochondroplasty, a derotation osteotomy, and a combined flexion-derotation osteotomy in severe SCFE patients using 3D-CT-based collision detection software. METHODS: Preoperative pelvic CT of 18 untreated patients (21 hips) with severe SCFE (slip-angle>60 degrees) was used to generate patient-specific 3D models. The contralateral hips of the 15 patients with unilateral SCFE served as the control group. There were 14 male hips (mean age 13±2 y). No treatment was performed before CT. Specific collision detection software was used for the calculation of impingement-free flexion and IR in 90 degrees of flexion and simulation of osteochondroplasty, derotation osteotomy, and combined flexion-derotation osteotomy. RESULTS: Osteochondroplasty alone improved impingement-free motion but compared with the uninvolved contralateral control group, severe SCFE hips had persistently significantly decreased motion (mean flexion 59±32 degrees vs. 122±9 degrees, P <0.001; mean IR in 90 degrees of flexion -5±14 degrees vs. 36±11 degrees, P <0.001). Similarly, the impingement-free motion was improved after derotation osteotomy, and impingement-free flexion after a 30 degrees derotation was equivalent to the control group (113± 42 degrees vs. 122±9 degrees, P =0.052). However, even after the 30 degrees derotation, the impingement-free IR in 90 degrees of flexion persisted lower (13±15 degrees vs. 36±11 degrees, P <0.001). Following the simulation of flexion-derotation osteotomy, mean impingement-free flexion and IR in 90 degrees of flexion increased for combined correction of 20 degrees (20 degrees flexion and 20 degrees derotation) and 30 degrees (30 degrees flexion and 30 degrees derotation). Although mean flexion was equivalent to the control group for both (20 degrees and 30 degrees) combined correction, the mean IR in 90 degrees of flexion persisted decreased, even after the 30 degrees combined flexion-derotation (22±22 degrees vs. 36 degrees±11, P =0.009). CONCLUSIONS: Simulation of derotation-osteotomy (30 degrees correction) and flexion-derotation-osteotomy (20 degrees correction) normalized hip flexion for severe SCFE patients, but IR in 90 degrees of flexion persisted slightly lower despite significant improvement. Not all SCFE patients had improved hip motion with the performed simulations; therefore, some patients may need a higher degree of correction or combined treatment with osteotomy and cam-resection, although not directly investigated in this study. Patient-specific 3D-models could help individual preoperative planning for severe SCFE patients to normalize the hip motion. LEVEL OF EVIDENCE: III, case-control study.

Development of acetabular retroversion in LCPD hips-an observational radiographic study from early stage to healing.

BACKGROUND: Acetabular retroversion is observed frequently in healed Legg-Calvé-Perthes disease (LCPD). Currently, it is unknown at which stage and with what prevalence retroversion occurs because in non-ossified hips, retroversion cannot be measured with standard radiographic parameters. METHODS: In a retrospective, observational study; we examined pelvic radiographs in children with LCPD the time point of occurrence of acetabular retroversion and calculated predictive factors for retroversion. Between 2004 and 2017, we included 55 children with a mean age of 5.7 ± 2.4 years at diagnosis. The mean radiographic follow-up was 7.0 ± 4.4 years. We used two new radiographic parameters which allow assessment of acetabular version in non-ossified hips: the pelvic width index and the ilioischial angle. They are based on the fact that the pelvic morphology differs depending on the acetabular version. These parameters were compared among the four Waldenström stages and to the contralateral side. Logistic regression analysis was performed to determine predictive factors for acetabular retroversion. RESULTS: Both parameters differed significantly among the stages of Waldenström (p < 0.003 und 0.038, respectively). A more retroverted acetabulum was found in stage II and III (prevalence ranging from 54 to 56%) compared to stage I and IV (prevalence ranging from 23 to 39%). In hips of the contralateral side without LCPD, the prevalence of acetabular retroversion was 0% in all stages for both parameters. Predictive factors for retroversion were younger age at stage II and IV, collapse of the lateral pillar in stage II or a non-dysplastic hip. CONCLUSIONS: This is the first study evaluating acetabular version in children with LCPD from early stage to healing. In the developing hip, LCPD may result in acetabular retroversion and is most prevalent in the fragmentation (stage II) and early healing stage (stage III). Partial correction of acetabular retroversion can occur after healing. This has a potential clinical impact on the timing and type of surgical correction, especially in pelvic osteotomies for correction of acetabular version. LEVEL OF EVIDENCE: Level III, retrospective observational study.

High prevalence of hip lesions secondary to arthroscopic over- or undercorrection of femoroacetabular impingement in patients with postoperative pain.

OBJECTIVES: To compare the prevalence of pre- and postoperative osseous deformities and intra-articular lesions in patients with persistent pain following arthroscopic femoroacetabular impingement (FAI) correction and to identify imaging findings associated with progressive cartilage damage. METHODS: Retrospective study evaluating patients with hip pain following arthroscopic FAI correction between 2010 and 2018. Pre- and postoperative imaging studies were analyzed independently by two blinded readers for osseous deformities (cam-deformity, hip dysplasia, acetabular overcoverage, femoral torsion) and intra-articular lesions (chondro-labral damage, capsular lesions). Prevalence of osseous deformities and intra-articular lesions was compared with paired t-tests/McNemar tests for continuous/dichotomous data. Association between imaging findings and progressive cartilage damage was assessed with logistic regression. RESULTS: Forty-six patients (mean age 29 ± 10 years; 30 female) were included. Postoperatively, 74% (34/46) of patients had any osseous deformity including 48% (22/46) acetabular and femoral deformities. Ninety-six percent (44/46) had an intra-articular lesion ranging from 20% (9/46) for femoral to 65% (30/46) for acetabular cartilage lesions. Prevalence of hip dysplasia increased (2 to 20%, p = 0.01) from pre- to postoperatively while prevalence of cam-deformity decreased (83 to 28%, p < 0.001). Progressive cartilage damage was detected in 37% (17/46) of patients and was associated with extensive preoperative cartilage damage > 2 h, i.e., > 60° (OR 7.72; p = 0.02) and an incremental increase in postoperative alpha angles (OR 1.18; p = 0.04). CONCLUSION: Prevalence of osseous deformities secondary to over- or undercorrrection was high. Extensive preoperative cartilage damage and higher postoperative alpha angles increase the risk for progressive degeneration. KEY POINTS: • The majority of patients presented with osseous deformities of the acetabulum or femur (74%) and with intra-articular lesions (96%) on postoperative imaging. • Prevalence of hip dysplasia increased (2 to 20%, p = 0.01) from pre- to postoperatively while prevalence of a cam deformity decreased (83 to 28%, p < 0.001). • Progressive cartilage damage was present in 37% of patients and was associated with extensive preoperative cartilage damage > 2 h (OR 7.72; p = 0.02) and with an incremental increase in postoperative alpha angles (OR 1.18; p = 0.04).

Limited Hip Flexion and Internal Rotation Resulting From Early Hip Impingement Conflict on Anterior Metaphysis of Patients With Untreated Severe SCFE Using 3D Modelling.

INTRODUCTION: Slipped capital femoral epiphysis (SCFE) is the most common hip disorder in adolescent patients that can result in complex 3 dimensional (3D)-deformity and hip preservation surgery (eg, in situ pinning or proximal femoral osteotomy) is often performed. But there is little information about location of impingement.Purpose/Questions: The purpose of this study was to evaluate (1) impingement-free hip flexion and internal rotation (IR), (2) frequency of impingement in early flexion (30 to 60 degrees), and (3) location of acetabular and femoral impingement in IR in 90 degrees of flexion (IRF-90 degrees) and in maximal flexion for patients with untreated severe SCFE using preoperative 3D-computed tomography (CT) for impingement simulation. METHODS: A retrospective study involving 3D-CT scans of 18 patients (21 hips) with untreated severe SCFE (slip angle>60 degrees) was performed. Preoperative CT scans were used for bone segmentation of preoperative patient-specific 3D models. Three patients (15%) had bilateral SCFE. Mean age was 13±2 (10 to 16) years and 67% were male patients (86% unstable slip, 81% chronic slip). The contralateral hips of 15 patients with unilateral SCFE were evaluated (control group). Validated software was used for 3D impingement simulation (equidistant method). RESULTS: (1) Impingement-free flexion (46±32 degrees) and IRF-90 degrees (-17±18 degrees) were significantly ( P <0.001) decreased in untreated severe SCFE patients compared with contralateral side (122±9 and 36±11 degrees).(2) Frequency of impingement was significantly ( P <0.001) higher in 30 and 60 degrees flexion (48% and 71%) of patients with severe SCFE compared with control group (0%).(3) Acetabular impingement conflict was located anterior-superior (SCFE patients), mostly 12 o'clock (50%) in IRF-90 degrees (70% on 2 o'clock for maximal flexion). Femoral impingement was located on anterior-superior to anterior-inferior femoral metaphysis (between 2 and 6 o'clock, 40% on 3 o'clock and 40% on 5 o'clock) in IRF-90 degrees and on anterior metaphysis (40% on 3 o'clock) in maximal flexion and frequency was significantly ( P <0.001) different compared with control group. CONCLUSION: Severe SCFE patients have limited hip flexion and IR due to early hip impingement using patient-specific preoperative 3D models. Because of the large variety of hip motion, individual evaluation is recommended to plan the osseous correction for severe SCFE patients. LEVEL OF EVIDENCE: Level III.

Minimal Out-Toeing and Good Hip Scores of Severe SCFE Patients Treated With Modified Dunn Procedure and Contralateral Prophylactic Pinning at Minimal 5-year Follow up.

BACKGROUND: Slipped capital femoral epiphyses (SCFE) is associated with out-toeing of the foot and external rotation gait. But it is unknown if SCFE patients treated with the modified Dunn procedure have out-toeing at follow up.Therefore, we used instrumented gait analysis and questioned (1) do severe SCFE patients treated with a modified Dunn procedure have symmetrical foot progression angle (FPA) compared with contralateral side and compared with asymptomatic volunteers (2) what is the prevalence of out-toeing gait and what are the outcome socres at follow up. METHODS: Gait analysis of 22 patients (22 hips) treated with an unilateral modified Dunn procedure for severe SCFE (slip angle >60 degrees, 2002 to 2011) was retrospectively evaluated. Of 38 patients with minimal 5-year follow up, 2 hips (4%) had avascular necrosis of the femoral head and were excluded for gait analysis. Twenty-two patients were available for gait analysis at follow up (mean follow up of 9±2 y). Mean age at follow up was 22±3 years. Mean preoperative slip angle was 64±8 degrees (33% unstable slips) and decreased postoperatively (slip angle of 8±4 degrees). Gait analysis was performed with computer-based instrumented walkway system (GAITRite) to measure FPA with embedded pressure sensors. Patients were compared with control group of 18 healthy asymptomatic volunteers (36 feet, mean age 29±6 y). RESULTS: (1) Mean FPA of SCFE patients (3.6±6.4 degrees) at follow up was not significantly different compared with their contralateral side (5.6±5.5 degrees) and compared with FPA of controls (4.0±4.5 degrees). (2) Of the 22 SCFE patients, most of them (19 hips, 86%) had normal FPA (-5 to 15 degrees), 2 patients had in-toeing (FPA<-5 degrees) and 1 had out-toeing (FPA >15 degrees) and was not significantly different compared with control group. (3) Mean modified Harris hip score (mHHS) was 93±11 points, mean Hip Disability and Osteoarthritis Outcome Score (HOOS) score was 91±10 points. Three patients (14%) had mHHS <80 points and walked with normal FPA. The 2 patients with in-toeing and one patient with out-toeing had mHHS >95 points. CONCLUSIONS: Patients with severe SCFE treated with modified Dunn procedure had mostly symmetrical FPA and good hip scores at long term follow up. This is in contrast to previous studies. Although 1 patient had out-toeing and 2 patients had in-toeing at follow up, they had good hip scores. LEVEL OF EVIDENCE: Level III-retrospective comparative study.

Image-Less THA Cup Navigation in Clinical Routine Setup: Individual Adjustments, Accuracy, Precision, and Robustness.

Background and Objectives: Even after the 'death' of Lewinnek's safe zone, the orientation of the prosthetic cup in total hip arthroplasty is crucial for success. Accurate cup placement can be achieved with surgical navigation systems. The literature lacks study cohorts with large numbers of hips because postoperative computer tomography is required for the reproducible evaluation of the acetabular component position. To overcome this limitation, we used a validated software program, HipMatch, to accurately assess the cup orientation based on an anterior-posterior pelvic X-ray. The aim of this study were to (1) determine the intraoperative 'individual adjustment' of the cup positioning compared to the widely suggested target values of 40° of inclination and 15° of anteversion, and evaluate the (2) 'accuracy', (3) 'precision', and (4) robustness, regarding systematic errors, of an image-free navigation system in routine clinical use. Material and Methods: We performed a retrospective, accuracy study in a single surgeon case series of 367 navigated primary total hip arthroplasties (PiGalileoTM, Smith+Nephew) through an anterolateral approach performed between January 2011 and August 2018. The individual adjustments were defined as the differences between the target cup orientation (40° of inclination, 15° of anteversion) and the intraoperative registration with the navigation software. The accuracy was the difference between the intraoperative captured cup orientation and the actual postoperative cup orientation determined by HipMatch. The precision was analyzed by the standard deviation of the difference between the intraoperative registered and the actual cup orientation. The outliers were detected using the Tukey method. Results: Compared to the target value (40° inclination, 15° anteversion), the individual adjustments showed that the cups are impacted in higher inclination (mean 3.2° ± 1.6°, range, (−2)−18°) and higher anteversion (mean 5.0° ± 7.0°, range, (−15)−23°) (p < 0.001). The accuracy of the navigated cup placement was −1.7° ± 3.0°, ((−15)−11°) for inclination, and −4.9° ± 6.2° ((−28)−18°) for anteversion (p < 0.001). Precision of the system was higher for inclination (standard deviation SD 3.0°) compared to anteversion (SD 6.2°) (p < 0.001). We found no difference in the prevalence of outliers for inclination (1.9% (7 out of 367)) compared to anteversion (1.63% (6 out of 367), p = 0.78). The Bland-Altman analysis showed that the differences between the intraoperatively captured final position and the postoperatively determined actual position were spread evenly and randomly for inclination and anteversion. Conclusion: The evaluation of an image-less navigation system in this large study cohort provides accurate and reliable intraoperative feedback. The accuracy and the precision were inferior compared to CT-based navigation systems particularly regarding the anteversion. However the assessed values are certainly within a clinically acceptable range. This use of image-less navigation offers an additional tool to address challenging hip prothesis in the context of the hip−spine relationship to achieve adequate placement of the acetabular components with a minimum of outliers.

Occurrence of inadequate ACL healing after Dynamic Intraligamentary Stabilization and functional outcome-a multicentre case series.

INTRODUCTION: Dynamic Intraligamentary Stabilization (DIS) is a technique for preservation, anatomical repair and stabilization of a freshly injured anterior cruciate ligament (ACL). The main purpose of this study was to evaluate the short-term re-operation rate when compared to traditional autograft reconstruction. METHODS: Four, from the developer independent, centres enrolled patients that underwent ACL repair by DIS, according to the specific indications given by MRI imaging at a minimum follow-up of 12 months. The re-operation rate was recorded as primary outcome. Secondary outcome measures were the postoperative antero-posterior knee laxity (using a portable Rolimeter®), as well as the Tegner, Lysholm and IKDC Scores. RESULTS: A total of 105 patients were investigated with a median follow-up of 21 months. Thirteen patients were lost to follow-up. Of the remaining 92 patients 15 (16.3%) had insufficient functional stability and required subsequent ACL reconstruction. These patients were excluded from further analysis, leaving 77 consecutive patients for a 12 months follow-up. The median age at time of surgery was 30 years for that group. At time of follow-up a median antero-posterior translation difference of 2 mm was measured. None of these patients reported subjective insufficiency (giving way), but in 14 patients (18.2%), the difference of antero-posterior translation was more than 3 mm. We found a median Tegner Score of 5.5, a median Lysholm Score of 95.0 and a median IKDC Score of 89.4. CONCLUSION: The main finding of this multicentre study is a relevant re-operation rate of 16.3%. Another 18.2% showed objective antero-posterior laxity (≥ 3 mm) during testing raising the suspicion of postoperative non-healing. The failure rate of DIS in this study is higher than for reconstruction with an autologous tendon graft. However, our successfully treated patients had a good clinical and functional outcome based on antero-posterior knee laxity and clinical scores, comparable to patients treated by autograft reconstruction.

Magnetization-prepared 2 Rapid Gradient-Echo MRI for B1 Insensitive 3D T1 Mapping of Hip Cartilage: An Experimental and Clinical Validation.

Background Often used for T1 mapping of hip cartilage, three-dimensional (3D) dual-flip-angle (DFA) techniques are highly sensitive to flip angle variations related to B1 inhomogeneities. The authors hypothesized that 3D magnetization-prepared 2 rapid gradient-echo (MP2RAGE) MRI would help provide more accurate T1 mapping of hip cartilage at 3.0 T than would 3D DFA techniques. Purpose To compare 3D MP2RAGE MRI with 3D DFA techniques using two-dimensional (2D) inversion recovery T1 mapping as a standard of reference for hip cartilage T1 mapping in phantoms, healthy volunteers, and participants with hip pain. Materials and Methods T1 mapping at 3.0 T was performed in phantoms and in healthy volunteers using 3D MP2RAGE MRI and 3D DFA techniques with B1 field mapping for flip angle correction. Participants with hip pain prospectively (July 2019-January 2020) underwent indirect MR arthrography (with intravenous administration of 0.2 mmol/kg of gadoterate meglumine), including 3D MP2RAGE MRI. A 2D inversion recovery-based sequence served as a T1 reference in phantoms and in participants with hip pain. In healthy volunteers, cartilage T1 was compared between 3D MP2RAGE MRI and 3D DFA techniques. Paired t tests and Bland-Altman analysis were performed. Results Eleven phantoms, 10 healthy volunteers (median age, 27 years; range, 26-30 years; five men), and 20 participants with hip pain (mean age, 34 years ± 10 [standard deviation]; 17 women) were evaluated. In phantoms, T1 bias from 2D inversion recovery was lower for 3D MP2RAGE MRI than for 3D DFA techniques (mean, 3 msec ± 11 vs 253 msec ± 85; P < .001), and, unlike 3D DFA techniques, the deviation found with MP2RAGE MRI did not correlate with increasing B1 deviation. In healthy volunteers, regional cartilage T1 difference (109 msec ± 163; P = .008) was observed only for the 3D DFA technique. In participants with hip pain, the mean T1 bias of 3D MP2RAGE MRI from 2D inversion recovery was -23 msec ± 31 (P < .001). Conclusion Compared with three-dimensional (3D) dual-flip-angle techniques, 3D magnetization-prepared 2 rapid gradient-echo MRI enabled more accurate T1 mapping of hip cartilage, was less affected by B1 inhomogeneities, and showed high accuracy against a T1 reference in participants with hip pain. © RSNA, 2021.

The New Bern Chondrolabral Classification Is Reliable and Reproducible.

BACKGROUND: Several classification systems have been used to describe early lesions of hip cartilage and the acetabular labrum in young adults with hip pain. Some of them were introduced before the concept of femoroacetabular impingement was proposed. Others were developed for other joints (such as the patellofemoral joint). However, these often demonstrate inadequate reliability, and they do not characterize all possible lesions. Therefore, we developed a novel classification system. QUESTION/PURPOSE: We asked: What is the (1) intraobserver reliability, (2) interobserver reproducibility, and (3) percentage of nonclassifiable lesions of the new classification system for damage to the hip cartilage and labrum compared with six established classification systems for chondral lesions (Beck et al. [4], Konan et al. [10], Outerbridge et al. [14]) and labral lesions (Beck et al. [3], Lage et al. [12], Peters and Erickson [15])? METHODS: We performed a validation study of a new classification system of early chondrolabral degeneration lesions based on intraoperative video documentation taken during surgical hip dislocations for joint-preserving surgery in 57 hips (56 patients) performed by one surgeon with standard video documentation of intraarticular lesions. The exclusion criteria were low-quality videos, inadequate exposure angles, traumatic lesions, and incomplete radiographic documentation. This left 42 hips (41 patients) for the blinded and randomized analysis of six raters, including those with cam-pincer-type femoroacetabular impingement (FAI) (19 hips in 18 patients), isolated cam-type FAI (10 hips), extraarticular FAI due to femoral anteversion (seven hips), isolated pincer-type FAI (two hips), focal avascular necrosis (two hips), localized pigmented villonodular synovitis (one hip), and acetabular dysplasia as a sequelae of Perthes disease (one hip). The raters had various degrees of experience in hip surgery: Three were board-certified orthopaedic fellows and three were orthopaedic residents, in whom we chose to prove the general usability of the classification systems in less experienced readers. Every rater was given the original publication of all existing classification systems and a visual guide of the new Bern classification system. Every rater classified the lesions according the existing classifications (cartilage: Beck et al. [4], Konan et al. [10], and Outerbridge et al. [14]; labrum: Beck et al. [3], Peters and Erickson [15], and Lage et al. [12]) and our new Bern chondrolabral classification system. The intraclass correlation coefficient with 95% confidence interval was used to assess the intraobserver reliability and interobserver reproducibility. The percentage of nonclassifiable lesions was calculated as an absolute number and percentage. RESULTS: The intraobserver intercorrelation coefficients (ICCs) for cartilage lesions were as follows: the Bern classification system (0.68 [95% CI 0.61 to 0.70]), Beck (0.44 [95% CI 0.34 to 0.54]), Konan (0.39 [95% CI 0.29 to 0.49]), and the Outerbridge classification (0.57 [95% CI 0.48 to 0.65]). For labral lesions, the ICCs were as follows: the Bern classification (0.70 [95% CI 0.63 to 0.76]), Peters (0.42 [95% CI 0.31 to 0.51]), Lage (0.26 [95% CI 0.15 to 0.38]), and Beck (0.59 [95% CI 0.51 to 0.67]). The interobserver ICCs for cartilage were as follows: the Bern classification system (0.63 [95% CI 0.51 to 0.75), the Outerbridge (0.14 [95% CI 0.04 to 0.28]), Konan (0.58 [95% CI 0.40 to 0.76]), and Beck (0.52 [95% CI 0.39 to 0.66]). For labral lesions, the ICCs were as follows: the Bern classification (0.61 [95% CI 0.49 to 0.74]), Beck (0.31 [95% CI 0.19 to 0.46]), Peters (0.28 [95% CI 0.16 to 0.44]), and Lage (0.20 [95% CI 0.09 to 0.35]). The percentage of nonclassifiable cartilage lesions was 0% for the Bern, 0.04% for Beck, 17% for Konan, and 25% for the Outerbridge classification. The percentage of nonclassifiable labral lesions was 0% for Bern and Beck, 4% for Peters, and 25% for Lage. CONCLUSION: We have observed some shortcomings with currently used classification systems for hip pathology, and the new classification system we developed seems to have improved the intraobserver reliability compared with the Beck and Konan classifications in cartilage lesions and with the Peters and Lage classifications in labral lesions. The interrater reproducibility of the Bern classification seems to have improved in cartilage lesions compared with the Outerbridge classification and in labral lesions compared with the Beck, Peters, and Lage classifications. The Bern classification identified all present cartilage and labral lesions. It provides a solid clinical basis for accurate descriptions of early degenerative hip lesions independent of etiology, and it is reproducible enough to use in the reporting of clinical research. Further studies need to replicate our findings in the hands of nondevelopers and should focus on the prognostic value of this classification and its utility in guiding surgical indications. LEVEL OF EVIDENCE: Level II, diagnostic study.

Does the Rule of Thirds Adequately Detect Deficient and Excessive Acetabular Coverage?

BACKGROUND: Assessment of AP acetabular coverage is crucial for choosing the right surgery indication and for obtaining a good outcome after hip-preserving surgery. The quantification of anterior and posterior coverage is challenging and requires either other conventional projections, CT, MRI, or special measurement software, which is cumbersome, not widely available and implies additional radiation. We introduce the "rule of thirds" as a promising alternative to provide a more applicable and easy method to detect an excessive or deficient AP coverage. This method attributes the intersection point of the anterior (posterior) wall to thirds of the femoral head radius (diameter), the medial third suggesting deficient and the lateral third excessive coverage. QUESTION/PURPOSE: What is the validity (area under the curve [AUC], sensitivity, specificity, positive/negative likelihood ratios [LR(+)/LR(-)], positive/negative predictive values [PPV, NPV]) for the rule of thirds to detect (1) excessive and (2) deficient anterior and posterior coverages compared with previously established radiographic values of under-/overcoverage using Hip2Norm as the gold standard? METHODS: We retrospectively evaluated all consecutive patients between 2003 and 2015 from our institutional database who were referred to our hospital for hip pain and were potentially eligible for joint-preserving hip surgery. We divided the study group into six specific subgroups based on the respective acetabular pathomorphology to cover the entire range of anterior and posterior femoral coverage (dysplasia, overcoverage, severe overcoverage, excessive acetabular anteversion, acetabular retroversion, total acetabular retroversion). From this patient cohort, 161 hips were randomly selected for analysis. Anterior and posterior coverage was determined with Hip2Norm, a validated computer software program for evaluating acetabular morphology. The anterior and posterior wall indices were measured on standardized AP pelvis radiographs, and the rule of thirds was applied by one observer. RESULTS: The detection of excessive anterior and posterior acetabular wall using the rule of thirds revealed an AUC of 0.945 and 0.933, respectively. Also the detection of a deficient anterior and posterior acetabular wall by applying the rule of thirds revealed an AUC of 0.962 and 0.876, respectively. For both excessive and deficient anterior and posterior acetabular coverage, we found high specificities and PPVs but low sensitivities and NPVs. CONCLUSION: We found a high probability for an excessive (deficient) acetabular wall when this intersection point lies in the lateral (medial) third, which would qualify for surgical correction. On the other hand, if this point is not in the lateral (medial) third, an excessive (deficient) acetabular wall cannot be categorically excluded. Thus, the rule of thirds is very specific but not as sensitive as we had expected. LEVEL OF EVIDENCE: Level II, diagnostic study.

The Acetabular Wall Index Is Associated with Long-term Conversion to THA after PAO.

BACKGROUND: Periacetabular osteotomy (PAO) has been shown to be a valuable option for delaying the onset of osteoarthritis in patients with hip dysplasia. Published studies at 30 years of follow-up found that postoperative anterior overcoverage and posterior undercoverage were associated with early conversion to THA. The anterior and posterior wall indices are practical tools for assessing AP coverage on standard AP radiographs of the pelvis pre-, intra-, and postoperatively. However, no study that we know of has evaluated the relationship between the postoperative anterior and posterior wall indices and survivorship free from arthroplasty. QUESTIONS/PURPOSES: In a study including patients after PAO for developmental dysplasia of the hip (DDH), we evaluated whether the acetabular wall index is associated with conversion to THA in the long-term after PAO. We asked: (1) Is an abnormal postoperative anterior wall index associated with conversion to THA after PAO? (2) Is an abnormal postoperative posterior wall index associated with conversion to THA after PAO? (3) Are there other factors associated with joint replacement after PAO? METHODS: This retrospective study involved pooling data of PAO for DDH from two previously published sources. The first series (1984-1987) comprised the very first 75 PAOs for symptomatic DDH performed at the inventor's institution. The second (1997-2000) comprised a series of PAOs for symptomatic DDH completed at the same institution 10 years later. No patient was lost to follow-up. Fifty hips (44 patients) were excluded for predefined reasons (previous surgery, substantial femoral pathomorphologies, poor-quality radiographs), leaving 115 hips (102 patients, mean age 29 ± 11 years, 28% male) for analysis with a mean follow-up of 22 ± 6 years. One observer not involved in patient treatment digitally measured the anterior and posterior wall indices on postoperative AP pelvic radiographs of all patients. All patients were contacted by mail or telephone to confirm any conversion to THA and the timing of that procedure relative to the index procedure. We performed univariate and multivariate Cox regression analyses using conversion to THA as our endpoint to determine whether the anterior and posterior wall indices are associated with prosthetic replacement in the long-term after PAO. Thirty-one percent (36 of 115) of hips were converted to THA within a mean of 15 ± 7 years until failure. The mean follow-up duration of the remaining patients was 22 ± 6 years. RESULTS: A deficient anterior wall index was associated with conversion THA in the long-term after PAO (adjusted hazard ratio 10 [95% CI 3.6 to 27.9]; p < 0.001). Although observed in the univariate analysis, we could not find a multivariate association between the posterior wall index and a higher conversion rate to THA. Grade 0 Tönnis osteoarthritis was associated with joint preservation (adjusted HR 0.2 [95% CI 0.07 to 0.47]; p = 0.005). Tönnis osteoarthritis Grades 2 and 3 were associated with conversion to THA (adjusted HR 2.3 [95% CI 0.9 to 5.7]; p = 0.08). CONCLUSION: A deficient anterior wall index is associated with a decreased survivorship of the native hip in the long-term after PAO. Intraoperatively, in addition to following established radiographical guidelines, the acetabular wall indices should be measured systematically to ascertain optimal acetabular fragment version to increase the likelihood of reconstructive survival after PAO for DDH. LEVEL OF EVIDENCE: Level III, therapeutic study.