Bispherical metal augment improved biomechanical stability in severe acetabular deficiency reconstruction: a comparative finite element analysis.

BACKGROUND: This study used finite element analysis (FEA) to compare the biomechanical stability of bispherical metal augment (BA) and wedge-shaped trabecular-metal augment (TA) in different acetabular defect reconstruction models, thereby explaining the application value of this novel bispherical augment in complex hip revision. METHODS: Three different acetabular defect pelvis models originating from three representative patients with different types of severe acetabular defects (Paprosky IIC, IIIA, and IIIB) were constructed and reconstruction with BA and TA technique was simulated. Based on the FEA models, the displacement of reconstruction implants, relative displacement of bone implants, and hemi-pelvic von Mises stress were investigated under static loads. RESULTS: BA acquired smaller reconstruction system displacement, less relative displacement of bone implants, and lower pelvic von Mises stress than TA in all Paprosky IIC, IIIA, and IIIB defect reconstructions. CONCLUSION: The FEA results show that BA could acquire favourable biomechanical stability in severe acetabular defect reconstruction. This technique is a reliable method in complex hip revision.

Development of an aid to detect adults acetabular hip dysplasia (the ALPHA alert): A mixed methods study.

OBJECTIVES: To identify the signs and symptoms that people living with acetabular hip dysplasia (AHD) describe and to provide an aid for translating the findings into practice. METHODS: A three-phased mixed methods study. Phase 1 employed an open-question online survey that enabled people with AHD (aged ≥16 years) to describe features associated with their condition. Responses were thematically analysed. A Phase 2 survey used these themes to establish how common those features were. Phase 3 created a mnemonic that prompts clinicians to suspect AHD. RESULTS: Ninety-eight respondents completed Phase 1 and sixty-two completed Phase 2. From the responses, five themes were identified: Demographic and Diagnostic Profile; Characteristics of Posture and Gait; Pain; Childhood Hip and Family History; and Hip Joint Characteristics. Within these themes, 19 common signs and symptoms were reported, represented by the ALPHA mnemonic. ALPHA describes a young age at onset of problems (Age), a limp (Limp), progressing pain (Pain), a history of childhood and family hip anomalies (History) as well as hip joint hypermobility and instability (Articulation). CONCLUSION: The findings extend current understanding of AHD indicators. ALPHA alerts clinicians to suspect a diagnosis of AHD. ALPHA may facilitate timelier referral of patients for diagnostic X-Ray and appropriate treatment. Future studies should evaluate its clinical utility.

Biomechanical analysis of load distribution in porcine hip joints at different acetabular coverages.

BACKGROUND: Developmental dysplasia of the hip causes secondary osteoarthritis. Finite element analysis suggests high hip joint contact pressure in patients with hip dysplasia and a reduction in contact pressure after periacetabular osteotomy. However, few biomechanical studies have examined the load distribution in the hip joint. This study aimed to investigate the biomechanical properties of load distribution in porcine hip joints at different acetabular coverages. METHODS: Six porcine hip joints were analyzed using three models: 1) neutral coverage, 2) 15° under-coverage (defined as dysplasia model), and 3) 15° over-coverage created by varying the acetabular coverage. The load distribution was assessed using a pressure-mapping sensor system after applying a loading force of 100 N to the hip joint. RESULTS: In the dysplasia model, the load was concentrated at the acetabular rim; in the neutral and over-coverage models, it was dispersed. The average contact pressure was significantly higher in the dysplasia model than in the neutral coverage model ([0.42 vs. 0.3 MPa]; p = 0.004). The contact area was significantly smaller in the dysplasia model than in the neutral coverage model ([250.7 vs. 345.0 mm2]; p = 0.004). No significant differences were observed in contact pressure or area between the neutral and over-coverage models. CONCLUSIONS: Insufficient acetabular coverage in the dysplasia model demonstrated higher contact pressure and smaller contact area than the neutral model. Conversely, the contact pressure and area in the over-coverage model did not differ significantly from those in the normal model. Therefore, surgeons should note that acetabular coverage overcorrection has limited effect; normalization is crucial during periacetabular osteotomy.

An exercise and patient education intervention to reduce pain and physical limitations in adults with acetabular dysplasia: study protocol for a process evaluation integrated within a randomised controlled trial (the MovetheHip trial).

BACKGROUND: The Movethehip trial investigates the effectiveness of an exercise and patient education intervention for adults with acetabular dysplasia. The intervention involves eight tailored one-to-one sessions with trained providers who employ supportive feedback tools. The present protocol reports a planned process evaluation, which aims to determine how the intervention functions by examining the implementation of the intervention (process, dose and reach), its acceptability, mechanisms of change and the influence of contextual factors. METHODS: Two hundred trial participants aged 18-50 years will be recruited from a University Hospital in Denmark and randomised to the intervention or control group. Approximately ten providers will deliver the intervention. The process evaluation adopts a concurrent mixed-methods design. The implementation will be assessed using self-report questionnaires (at baseline and 6-month follow-up), training records and semi-structured focus group interviews with intervention providers (n = 10) and healthcare managers (n = 4-6). The mechanisms of change will be explored through semi-structured one-to-one interviews (at baseline and 6-month follow-up) with 15-20 purposefully sampled participants and by measuring changes in health outcomes (self-reported pain, physical functioning and quality of life completed at baseline and at 3- and 6-month follow-up). Additionally, change will be measured through an explorative examination of associations between dose and change in health outcomes, applying simple linear regression models. The acceptability of the intervention and the influence of contextual factors will be explored through one-to-one participant interviews and focus group interviews with 4-6 healthcare managers. The interviews will focus on expectations, experiences, events, personal understandings and interaction with interpersonal and organisational aspects. Interview data will be analysed using theoretical thematic analyses, and findings will be merged with quantitative data and reported jointly on a theme-by-theme basis. DISCUSSION: The process evaluation conducted as part of the MovetheHip trial will illuminate how the intervention functions, and if the intervention is proven effective, the findings of the evaluation will contribute to pinpoint how the intervention may be optimised to facilitate future up-scaling and implementation. TRIAL REGISTRATION: The MovetheHip protocol was approved by the Committee on Health Research Ethics in the Central Denmark Region. ClinicalTrials, NCT04795843. Registered on 20 March 2021.

Range of Motion Measurements of the Hip Joint Are Useful in Screening for Acetabular Dysplasia in Healthy Young Japanese Women.

The purpose of this study is to clarify whether a hip range of motion (ROM) measurement is useful in screening for early hip osteoarthritis with acetabular dysplasia (AD). Subjects were 58 healthy Japanese women volunteers (21.1 ± 0.7 (20 - 22)). We evaluated a total of 116 hip joints in these 58 cases. Sharp angle and centeredge angle were 44.1° ± 3.1° (37.0° - 51.5°) and 30.7°± 6.2° (19.5° - 47.0°), respectively. AD was present in 47.4%, but there were no severe cases. First, we compared the ROM of the hip joints with AD (AD group) and without AD (control group) according to the Mann-Whitney U test. Extension angles and external rotation angles in the AD group were significantly smaller than in the control group (18.9°± 6.1° VS. 22.1°± 4.2°, p= 0.01636, 26.3°± 8.9° VS. 34.1°± 8.8°, p= 0.001362, respectively). Next, we evaluated the following factors associated with AD by logistic regression analysis after adjustment for age: flexion, extension and internal and external rotation angles of the hip joint. As a result, internal rotation and external rotation were extracted as related factors. The area under the ROC curve was determined to have a moderate accuracy (0.72996). Cut off values of internal rotation and external rotation angles were 50 degrees and 35 degrees, respectively. Our findings suggest that ROM measurement of the internal and external rotation angles would be useful as a screening for AD in healthy young Japanese women without symptoms.

Does Periacetabular Osteotomy Change Sagittal Spinopelvic Alignment?

BACKGROUND: There are few data on the impact of periacetabular osteotomy (PAO) on sagittal spinopelvic alignment. Prior studies have attempted to delineate the relationship by performing measurements on AP radiographs and using mathematical models to determine changes in postoperative pelvic tilt. This information is clinically significant to a surgeon when evaluating acetabular/pelvic position intraoperatively and understanding spinopelvic alignment changes postoperatively; therefore, radiographic changes from PAO should be described in more detail. QUESTIONS/PURPOSES: In this study, we asked: (1) Does the performance of PAO result in consistent changes in spinopelvic alignment, as measured on EOS radiographs? (2) Does this differ for unilateral versus bilateral PAOs? (3) Does this differ in the setting of a mobile spine versus an immobile spine? (4) Does this differ based on preoperative pelvic tilt? METHODS: Mean preoperative and at least 1-year postoperative (15 ± 8 months from surgery, minimum 11 months, maximum 65 months) EOS hip-to-ankle standing and sitting radiographs for 55 patients in a prospectively collected registry who underwent PAO with a single surgeon from January 1, 2019, to January 11, 2022, were measured for pelvic incidence, pelvic tilt, sacral slope, lumbar lordosis, lateral center-edge angle, L1 pelvic angle, and pubic symphysis to the sacroiliac index. Normality was assessed and paired sample t-tests (normally distributed data) or Wilcoxon signed rank tests (not normally distributed data) were utilized to assess if any measurements changed from preoperative to postoperative. Patients were then divided based on whether they had unilateral or bilateral dysplasia and unilateral or bilateral surgery, and these subgroups were analyzed the same way as the entire cohort. Two more subgroups were then formed based on lumbar mobility, defined as a change in sitting-to-standing lumbar lordosis less or greater than 1 SD from the population mean preoperatively, and the subgroups were analyzed the same way as the entire cohort. Finally, two additional subgroups were formed, preoperative standing pelvic tilt less than 10° and more than 20°, and analyzed the same as the entire cohort. RESULTS: For the entire cohort, the median (IQR) standing lateral-center edge angle increased 17°, from a median of 21° (10°) to a median of 38° (8° [95% confidence interval (CI) 16° to 20°; p < 0.001). The median sitting lateral center-edge angle increased 17°, from a median of 18° (8°) to a median of 35° (8° [95% CI 14° to 19°]; p < 0.001). Standing pelvic incidence increased from 50° ± 11° to 52° ± 12° (mean difference 2° [95% CI 1° to 3°]; p = 0.004), but there were no changes for other measured parameters. There were no changes in any of the spinopelvic parameters for patients with unilateral dysplasia receiving a unilateral PAO, but patients with bilateral dysplasia who underwent bilateral PAOs demonstrated an increase in pelvic incidence from 57° (14°) to 60° (16°) (95% CI 1° to 5°; p = 0.02) and a decrease in pubic symphysis to sacroiliac index from 84 mm (24 mm) to 77 mm (23 mm) (95% CI -7° to -2°; p = 0.007). Patients with mobile lumbar spines preoperatively did not exhibit any changes in sagittal spinopelvic alignment, but patients with immobile lumbar spines preoperatively experienced several changes after surgery. Patients with less than 10° of standing pelvic tilt demonstrated a median (IQR) 2° increase in pelvic incidence from median 43° (9°) to 45° (12° [95% CI 0.3° to 4°]; p = 0.03), but they did not experience any other changes in sagittal spinopelvic alignment parameters postoperatively. Patients with preoperative pelvic tilt more than 20° did not experience any change in sagittal spinopelvic parameters. CONCLUSION: PAO increases pelvic incidence, potentially because of anterior translation of the hip center. There were no changes in other spinopelvic parameters postoperatively except after bilateral PAO. Additionally, patients lacking spine mobility preoperatively, indicated by a minimal change in lumbar lordosis between standing and sitting positions, may experience several changes in spinopelvic alignment, including increased mobility of their spine after PAO. This may be because of decreased compensatory spine splinting after increasing acetabular coverage, but further research including patient-reported outcomes is warranted. LEVEL OF EVIDENCE: Level III, therapeutic study.

Effect of osteoporosis-related reduction in the mechanical properties of bone on the acetabular fracture during a sideways fall: A parametric finite element approach.

PURPOSE: The incidence of acetabular fractures due to low-energy falls is increasing among the geriatric population. Studies have shown that several biomechanical factors such as body configuration, impact velocity, and trochanteric soft-tissue thickness contribute to the severity and type of acetabular fracture. The effect of reduction in apparent density and elastic modulus of bone as well as other bone mechanical properties due to osteoporosis on low-energy acetabular fractures has not been investigated. METHODS: The current comprehensive finite element study aimed to study the effect of reduction in bone mechanical properties (trabecular, cortical, and trabecular + cortical) on the risk and type of acetabular fracture. Also, the effect of reduction in the mechanical properties of bone on the load-transferring mechanism within the pelvic girdle was examined. RESULTS: We observed that while the reduction in the mechanical properties of trabecular bone considerably affects the severity and area of trabecular bone failure, reduction in mechanical properties of cortical bone moderately influences both cortical and trabecular bone failure. The results also indicated that by reducing bone mechanical properties, the type of acetabular fracture turns from elementary to associated, which requires a more extensive intervention and rehabilitation period. Finally, we observed that the cortical bone plays a substantial role in load transfer, and by increasing reduction in the mechanical properties of cortical bone, a greater share of load is transmitted toward the pubic symphysis. CONCLUSION: This study increases our understanding of the effect of osteoporosis progression on the incidence of low-energy acetabular fractures. The osteoporosis-related reduction in the mechanical properties of cortical bone appears to affect both the cortical and trabecular bones. Also, during the extreme reduction in the mechanical properties of bone, the acetabular fracture type will be more complicated. Finally, during the final stages of osteoporosis (high reduction in mechanical properties of bone) a smaller share of impact load is transferred by impact-side hemipelvis to the sacrum, therefore, an osteoporotic pelvis might mitigate the risk of sacral fracture.

The Hip-Spine Challenge.

➤: The proper diagnosis and treatment of patients with concurrent hip and spine pathological processes can be challenging because of the substantial overlap in symptomatology. ➤: There is no consensus on which pathological condition should be addressed first. ➤: Factors such as advanced spinal degeneration, deformity, and prior fusion alter the biomechanics of the spinopelvic unit. Attention should be paid to recognizing these issues during the work-up for a total hip arthroplasty as they can result in an increased risk of dislocation. ➤: In patients with concurrent spine and hip degeneration, the surgeon must pay close attention to appropriate implant positioning and have consideration for implants with enhanced stability to minimize the risk of dislocation. ➤: A proper understanding of sagittal balance and restoration of this balance is integral to improving patient outcomes following spinal surgery. ➤: The advent of new imaging modalities, increased awareness of spinopelvic mobility, as well as a better understanding of sagittal alignment will hopefully improve our treatment of patients with hip-spine syndrome.

Correlation of Acetabular Anteversion and Thoracic Kyphosis Postoperatively with Proximal Junctional Failure in Adult Spinal Deformity Fused to Pelvis.

OBJECTIVES: To investigate whether the immediate thoracic kyphosis (TK) and acetabular anteversion (AA) postoperatively are correlated with proximal junctional failure (PJF) in adult spinal deformity (ASD) patients underwent surgical treatment. METHODS: This is a retrospective study. Following institutional ethics approval, a total of 57 patients (49 Female, eight Male) with ASD underwent surgery fused to sacroiliac bone (S1, S2, or ilium) from March 2014 to January 2019 were included. All of those patients were followed up for at least 2 years. Demographic, radiographic and surgical data were recorded. The maximum range of flexion motion (F-ROM) and extension motion (E-ROM) actively of hip joints was measured and recorded at pre- and postoperation. The sum of F-ROM and E-ROM was defined as the range of hip motion (H-ROM). Receiver operating characteristic (ROC) curve analysis was used to obtain the cut off value of parameters for PJF. A Kaplan-Meier curve and log-rank test were used to analyze the differences in PJF-free survival. RESULTS: In all, 14 patients developed PJF during follow-up. Comparisons between patients with and without PJF showed significant differences in immediate TK (P < 0.001) and AA (P = 0.027) postoperatively. ROC curve analysis determined an optimal threshold of 13° for immediate AA postoperatively (sensitivity = 74.3%, specificity = 85.7%, area under the ROC curve [AUC] = 0.806, 95% CI [0.686-0.926]). Nineteen patients with post-AA ≤13° were assigned into the observational group, and 38 patients with post-AA >13° were being as the control group. Patients in the observational group had smaller H-ROM (P = 0.016) and F-ROM (P < 0.001), but much larger E-ROM (P < 0.001). There were 10 patients showing PJF in the observational group and four in the control group (10/9 vs 4/34, P < 0.001). PJF-free survival time significantly decreased in the observational group (P = 0.001, log-rank test). Furthermore, patients in the observational group had much larger TK (post-TK, P = 0.015). The optimal threshold for post-TK (sensitivity = 85.7%, specificity = 76.7%; AUC = 0.823, 95% CI [0.672-0.974]) was 28.1° after the ROC curve was analyzed. In the observational group, those patients with post-TK ≥28.1° had significantly higher incidence of PJF (9/2 vs 1/7, P < 0.001) than those with post-TK < 28.1°. Moreover, PJF-free survival time in those patients significantly decreased (P = 0.001, log-rank test). CONCLUSIONS: ASD patients with acetabular anteversion of ≤13° at early postoperation may suffer significantly restricted hip motion and much higher incidence of PJF during follow-up, moreover, in those patients, postoperative TK ≥28.1° would be a significant risk factor for PJF developing.

Efficacy Evaluation of 3D Navigational Template for Salter Osteotomy of DDH in Children.

BACKGROUND: The aim of this study is to retrospectively evaluate the efficacy of 3D navigational template for Salter osteotomy of DDH in children. METHODS: Thirty-two consecutive patients with DDH who underwent Salter osteotomy were evaluated between July 2014 and August 2017, and they were divided into the conventional group (n = 16) and navigation template group (n = 16) according to different surgical methods. The corrective acetabular degrees, radiation exposure, and operation time were compared between the two groups. RESULTS: No nerve palsy or redislocation was reported in the navigation template group. Compared with the conventional group, the navigation template group had the advantages of more accurate acetabular degrees, less radiation exposure, and shorter operation time (P < 0.05). Meanwhile, the navigation template group achieved a better surgical outcome than the conventional group (McKay, P = 0.0293; Severin, P = 0.0949). CONCLUSIONS: The 3D navigational template for Salter osteotomy of DDH is simple and effective, which could be an alternative approach to improve the Salter osteotomy accuracy and optimize the efficacy.

Prominent Anterior Inferior Iliac Spine Morphologies Are Common in Patients with Acetabular Dysplasia Undergoing Periacetabular Osteotomy.

BACKGROUND: The anterior inferior iliac spine (AIIS) prominence is increasingly recognized in the setting of femoroacetabular impingement (FAI). The AIIS prominence may contribute to decreased hip flexion after acetabular reorientation in patients with acetabular dysplasia. AIIS morphologies have been characterized in numerous populations including asymptomatic, FAI, and athletic populations, but the morphology of the AIIS in patients with symptomatic acetabular dysplasia undergoing periacetabular osteotomy (PAO) has not been studied. In acetabular dysplasia, deficiency of the anterosuperior acetabular rim is commonly present and may result in the AIIS being positioned closer to the acetabular rim. Understanding morphological variation of the AIIS in patients with symptomatic dysplasia, and its relationship to dysplasia subtype and severity may aid preoperative planning, surgical technique, and evaluation of postoperative issues after PAO. QUESTIONS/PURPOSES: In this study, we sought to determine: (1) the variability of AIIS morphology types in hips with symptomatic acetabular dysplasia and (2) whether the differences in the proportion of AIIS morphologies are present between dysplasia pattern and severity subtypes. METHODS: Using our hip preservation database, we identified 153 hips (148 patients) who underwent PAO from October 2013 to July 2015. Inclusion criteria for the current study were (lateral center-edge angle [LCEA] < 20°), Tönnis Grade of 0 or 1 on plain AP radiographs of the pelvis, preoperative low-dose CT scan, and no prior surgery, trauma, neuromuscular, ischemic necrosis, or Perthes-like deformity. A total of 50 patients (50 hips) with symptomatic acetabular dysplasia undergoing evaluation for surgical planning of PAO remained for retrospective evaluation; we used these patients' low-dose CT scans for analysis. The median (range) age of patients in the study was 24 years (13 to 49). Ninety percent (45 of 50) of the hips were in female patients, whereas 10% (5 of 50) were in male patients. The morphology of the AIIS was classified on three-dimensional CT reconstructions according to a previously published classification to define the relationship between the AIIS and the acetabular rim. The morphology of the AIIS was classified as Type I (AIIS well proximal to acetabular rim), Type II (AIIS extending to level of acetabular rim), or Type III (AIIS extending distal to acetabular rim). Acetabular dysplasia subtype was characterized according to a prior protocol as either predominantly an anterosuperior acetabular deficiency, a posterosuperior acetabular deficiency, or a global acetabular deficiency. Acetabular dysplasia severity was distinguished as mild (LCEA 15° to 20°) or moderate/severe (LCEA < 15°). To answer our first question, regarding the proportions of each AIIS morphology in the dysplasia population, we calculated proportions and 95% CI estimates. To answer our second question, regarding the proposition of AIIS type between subtypes of dysplasia type and severity, we used a chi-square test or Fisher's exact test to compare categorical variables. A p value of < 0.05 was considered significant. RESULTS: Seventy-two percent (36 of 50; 95% CI 58% to 83%) of patients had a Type II or III AIIS morphology. Type I AIIS morphology was found in 28% of patients (14 of 50; 95% CI 18% to 42%), Type II AIIS morphology in 62% (31 of 50; 95% CI 48% to 74%), and Type III AIIS/morphology in 10% (5 of 50; 95% CI 4% to 21%). A Type I AIIS was seen in seven of 15 of patients with anterosuperior acetabular deficiency, three of 18 of patients with global deficiency, and four of 17 patients with posterosuperior deficiency (p = 0.08). There was no difference in the variability of AIIS morphologies between the different subtypes of acetabular dysplasia pattern and no difference in AIIS morphology variability between patients with mild versus moderate/severe dysplasia. CONCLUSIONS: The morphology of the AIIS in patients with acetabular dysplasia is commonly prominent, with 72% of hips having Type II or Type III morphologies. CLINICAL RELEVANCE: The AIIS is often prominent in patients with acetabular dysplasia undergoing PAO, regardless of dysplasia pattern or severity. Prominent AIIS morphologies may affect hip flexion ROM after acetabular reorientation. AIIS morphology is a variable that should be considered during preoperative planning for PAO. Future studies are needed to assess the clinical significance of a prominent AIIS on intraoperative findings and postoperative status after PAO.

Medialization of the Hip's Center with Periacetabular Osteotomy: Validation of Assessment with Plain Radiographs.

BACKGROUND: Periacetabular osteotomy (PAO) increases acetabular coverage of the femoral head and medializes the hip's center, restoring normal joint biomechanics. Past studies have reported data regarding the degree of medialization achieved by PAO, but measurement of medialization has never been validated through a comparison of imaging modalities or measurement techniques. The ilioischial line appears to be altered by PAO and may be better visualized at the level of the inferior one-third of the femoral head, thus, an alternative method of measuring medialization that begins at the inferior one-third of the femoral head may be beneficial. QUESTIONS/PURPOSES: (1) What is the true amount and variability of medialization of the hip's center that is achieved with PAO? (2) Which radiographic factors (such as lateral center-edge angle [LCEA] and acetabular inclination [AI]) correlate with the degree of medialization achieved? (3) Does measurement of medialization on plain radiographs at the center of the femoral head (traditional method) or inferior one-third of the femoral head (alternative method) better correlate with true medialization? (4) Are intraoperative fluoroscopy images different than postoperative radiographs for measuring hip medialization? METHODS: We performed a retrospective study using a previously established cohort of patients who underwent low-dose CT after PAO. Inclusion criteria for this study included PAO as indicated for symptomatic acetabular dysplasia, preoperative CT scan, and follow-up between 9 months and 5 years. A total of 333 patients who underwent PAO from February 2009 to July 2018 met these criteria. Additionally, only patients who were between 16 and 50 years old at the time of surgery were included. Exclusion criteria included prior ipsilateral surgery, femoroacetabular impingement (FAI), pregnancy, neuromuscular disorder, Perthes-like deformity, inadequate preoperative CT, and inability to participate. Thirty-nine hips in 39 patients were included in the final study group; 87% (34 of 39) were in female patients and 13% (5 of 39 hips) were in male patients. The median (range) age at the time of surgery was 27 years (16 to 49). Low-dose CT images were obtained preoperatively and at the time of enrollment postoperatively; we also obtained preoperative and postoperative radiographs and intraoperative fluoroscopic images. The LCEA and AI were assessed on plain radiographs. Hip medialization was assessed on all imaging modalities by an independent, blinded assessor. On plain radiographs, the traditional and alternative methods of measuring hip medialization were used. Subgroups of good and fair radiographs, which were determined by the amount of pelvic rotation that was visible, were used for subgroup analyses. To answer our first question, medialization of all hips was assessed via measurements made on three-dimensional (3-D) CT hip reconstruction models. For our second question, Pearson correlation coefficients, one-way ANOVA, and the Student t-test were calculated to assess the correlation between radiographic parameters (such as LCEA and AI) and the amount of medialization achieved. For our third question, statistical analyses were performed that included a linear regression analysis to determine the correlation between the two radiographic methods of measuring medialization and the true medialization on CT using Pearson correlation coefficients, as well as 95% confidence intervals and standard error of the estimate. For our fourth question, Pearson correlation coefficients were calculated to determine whether using intraoperative fluoroscopy to make medialization measurements differs from measurements made on radiographs. RESULTS: The true amount of medialization of the hip center achieved by PAO in our study as assessed by reference-standard CT measurements was 4 ± 3 mm; 46% (18 of 39 hips) were medialized 0 to 5 mm, 36% (14 hips) were medialized 5 to 10 mm, and 5% (2 hips) were medialized greater than 10 mm. Thirteen percent (5 hips) were lateralized (medialized < 0 mm). There were small differences in medialization between LCEA subgroups (6 ± 3 mm for an LCEA of ≤ 15°, 4 ± 4 mm for an LCEA between 15° and 20°, and 2 ± 3 mm for an LCEA of 20° to 25° [p = 0.04]). Hips with AI ≥ 15° (6 ± 3 mm) achieved greater amounts of medialization than did hips with AI of < 15° (2 ± 3 mm; p < 0.001). Measurement of medialization on plain radiographs at the center of the femoral head (traditional method) had a weaker correlation than using the inferior one-third of the femoral head (alternative method) when compared with CT scan measurements, which were used as the reference standard. The traditional method was not correlated across all radiographs or only good radiographs (r = 0.16 [95% CI -0.17 to 0.45]; p = 0.34 and r = 0.26 [95% CI -0.06 to 0.53]; p = 0.30), whereas the alternative method had strong and very strong correlations when assessed across all radiographs and only good radiographs, respectively (r = 0.71 [95% CI 0.51 to 0.84]; p < 0.001 and r = 0.80 [95% CI 0.64 to 0.89]; p < 0.001). Measurements of hip medialization made on intraoperative fluoroscopic images were not found to be different than measurements made on postoperative radiographs (r = 0.85; p < 0.001 across all hips and r = 0.90; p < 0.001 across only good radiographs). CONCLUSION: Using measurements made on preoperative and postoperative CT, the current study demonstrates a mean true medialization achieved by PAO of 4 mm but with substantial variability. The traditional method of measuring medialization at the center of the femoral head may not be accurate; the alternate method of measuring medialization at the lower one-third of the femoral head is a superior way of assessing the hip center's location. We suggest transitioning to using this alternative method to obtain the best clinical and research data, with the realization that both methods using plain radiography appear to underestimate the true amount of medialization achieved with PAO. Lastly, this study provides evidence that the hip center's location and medialization can be accurately assessed intraoperatively using fluoroscopy. LEVEL OF EVIDENCE: Level III, diagnostic study.

Does Patient-specific Functional Pelvic Tilt Affect Joint Contact Pressure in Hip Dysplasia? A Finite-element Analysis Study.

BACKGROUND: Although individual and postural variations in the physiologic pelvic tilt affect the acetabular orientation and coverage in patients with hip dysplasia, their effect on the mechanical environment in the hip has not been fully understood. Individual-specific, finite-element analyses that account for physiologic pelvic tilt may provide valuable insight into the contact mechanics of dysplastic hips, which can lead to further understanding of the pathogenesis and improved treatment of this patient population. QUESTION/PURPOSE: We used finite-element analysis to ask whether there are differences between patients with hip dysplasia and patients without dysplasia in terms of (1) physiologic pelvic tilt, (2) the pelvic position and joint contact pressure, and (3) the morphologic factors associated with joint contact pressure. METHODS: Between 2016 and 2019, 82 patients underwent pelvic osteotomy to treat hip dysplasia. Seventy patients with hip dysplasia (lateral center-edge angle ≥ 0° and < 20° on supine AP pelvic radiographs) were included. Patients with advanced osteoarthritis, femoral head deformity, prior hip or supine surgery, or poor-quality imaging were excluded. Thirty-two patients (32 hips) were eligible to this finite-element analysis study. For control groups, we reviewed 33 female volunteers without a history of hip disease. Individuals with frank or borderline hip dysplasia (lateral center-edge angle < 25°) or poor-quality imaging were excluded. Sixteen individuals (16 hips) were eligible as controls. Two board-certified orthopaedic surgeons measured sagittal pelvic tilt (the angle between the anterior pelvic plane and vertical axis: anterior pelvic plane [APP] angle) and acetabular version and coverage using pelvic radiographs and CT images. Intra- and interobserver reliabilities, evaluated using the kappa value and intraclass correlation coefficient, were good or excellent. We developed individual-specific, finite-element models using pelvic CT images, and performed nonlinear contact analysis to calculate the joint contact pressure on the acetabular cartilage during the single-leg stance with respect to three pelvic positions: standardized (anterior pelvic plane), supine, and standing. We compared physiologic pelvic tilt between patients with and without dysplasia using a t-test or the Wilcoxon rank sum test. A paired t-test or the Wilcoxon signed rank test with a Bonferroni correction was used to compare joint contact pressure between the three pelvic positions. We correlated joint contact pressure with morphologic parameters and pelvic tilt using the Pearson or the Spearman correlation coefficients. RESULTS: The APP angle in the supine and standing positions varied widely among individuals. It was greater in patients with hip dysplasia than in patients in the control group when in the standing position (3° ± 6° versus -2° ± 8°; mean difference 5° [95% CI 1° to 9°]; p = 0.02) but did not differ between the two groups when supine (8° ± 5° versus 5° ± 7°; mean difference 3° [95% CI 0° to 7°]; p = 0.06). The mean pelvic tilt was 6° ± 5° posteriorly when shifting from the supine to the standing position in patients with hip dysplasia. The median (range) maximum contact pressure was higher in dysplastic hips than in control individuals (in standing position; 7.3 megapascals [MPa] [4.1 to 14] versus 3.5 MPa [2.2 to 4.4]; difference of medians 3.8 MPa; p < 0.001). The median maximum contact pressure in the standing pelvic position was greater than that in the supine position in patients with hip dysplasia (7.3 MPa [4.1to 14] versus 5.8 MPa [3.5 to 12]; difference of medians 1.5 MPa; p < 0.001). Although the median maximum joint contact pressure in the standardized pelvic position did not differ from that in the standing position (7.4 MPa [4.3 to 15] versus 7.3 MPa [4.1 to 14]; difference of medians -0.1 MPa; p > 0.99), the difference in the maximum contact pressure varied from -3.3 MPa to 2.9 MPa, reflecting the wide range of APP angles (mean 3° ± 6° [-11° to 14°]) when standing. The maximum joint contact pressure in the standing position was negatively correlated with the standing APP angle (r = -0.46; p = 0.008) in patients with hip dysplasia. CONCLUSION: Based on our findings that individual and postural variations in the physiologic pelvic tilt affect joint contact pressure in the hip, future studies on the pathogenesis of hip dysplasia and joint preservation surgery should not only include the supine or standard pelvic position, but also they need to incorporate the effect of the patient-specific pelvic tilt in the standing position on the biomechanical environment of the hip. CLINICAL RELEVANCE: We recommend assessing postural change in sagittal pelvic tilt when diagnosing hip dysplasia and planning preservation hip surgery because assessment in a supine or standard pelvic position may overlook alterations in the hip's contact mechanics in the weightbearing positions. Further studies are needed to elucidate the effect of patient-specific functional pelvic tilt on the degeneration process of dysplastic hips, the acetabular reorientation maneuver, and the clinical result of joint preservation surgery.

Zürich cementless total hip arthroplasty as a treatment option for capital physeal fractures in dogs: Outcome in 53 cases.

OBJECTIVE: To review the outcome of dogs that underwent Zürich cementless total hip arthroplasty (Z-THA) for the repair of acute and chronic capital physeal fractures (CPF) and document the CPF-related hip remodeling. STUDY DESIGN: Retrospective study. SAMPLE POPULATION: Fifty-three Z-THA in 53 dogs. METHODS: Medical records of dogs (2006-2019) that underwent Z-THA for CPF management were reviewed. Dogs were divided into two groups on the basis of the days elapsed between CPF diagnosis and Z-THA, acute (≤30 days) and chronic (>30 days). Hip remodeling variables were determined from preoperative radiographs or intraoperatively. Descriptive statistics were performed, and the complication rates, outcome, and coxofemoral remodeling were recorded. Comparisons of remodeling variables and rates between groups were performed by using Fisher's exact test. RESULTS: In total, 23 of 53 (43.4%) cases were acute, and 30 of 53 (56.6%) cases were chronic. There was no difference in the femoral remodeling rates between the acute and chronic groups (P = .184), whereas acetabular remodeling was more prevalent in the chronic group (P < .001). Intraoperative complications occurred in four of 53 (7.5% [1/23 acute, 3/30 chronic]) cases, and postoperative complications occurred in six of 53 (11.3% [2/23 acute, 4/30 chronic]) cases. Good clinical outcomes were achieved in 51 of 53 (96.2% [21 acute, 30 chronic]) cases. CONCLUSION: Complication rates of Z-THA for CPF repair were similar to the complication rates reported for Z-THA of dysplastic hips. Hip remodeling was common regardless of CPF chronicity. CLINICAL SIGNIFICANCE: Zürich cementless total hip arthroplasty is viable for surgical management of CPF. There is a high likelihood that hip remodeling will be encountered, even in fractures treated within 30 days of presenting for hind limb lameness.

Does Cup Position at the High Hip Center or Anatomic Hip Center in THA for Developmental Dysplasia of the Hip Result in Better Harris Hip Scores and Revision Incidence? A Systematic Review.

BACKGROUND: One goal of THA is to restore the anatomic hip center, which can be achieved in hips with developmental dysplasia by placing cups at the level of the native acetabulum. However, this might require adjuvant procedures such as femoral shortening osteotomy. Another option is to place the cup at the high hip center, potentially reducing surgical complexity. Currently, no clear consensus exists regarding which of these cup positions might offer better functional outcomes or long-term survival. QUESTION/PURPOSE: We performed a systematic review to determine whether (1) functional outcomes as measured by the Harris hip score, (2) revision incidence, and (3) complications that do not result in revision differ based on the position of the acetabular cup (high hip center versus anatomic hip center) in patients undergoing THA for developmental dysplasia of the hip (DDH). METHODS: We performed a systematic review using Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines, including studies comparing the functional outcomes, revision incidence, and complications of primary THA in dysplastic hips with acetabular cups placed at the high hip center versus those placed at the anatomic hip center, over any time frame. The review protocol was registered with PROSPERO (registration number CRD42020168183) before commencement. Of 238 records, eight comparative, retrospective nonrandomized studies of interventions were eligible for our systematic review, reporting on 207 hips with cups placed at the high hip center and 268 hips with cups at the anatomic hip center. Risk of bias within eligible studies was assessed using the Risk Of Bias In Non-randomized Studies of Interventions tool. Due to low comparability between studies, data could not be pooled, so these studies were assessed without summary effects. RESULTS: Six studies compared Harris hip scores, two of which favored high hip center cup placement and three of which favored anatomic hip center cup placement, although none of the differences between cohorts met the minimum clinically important difference. Five studies reliably compared revision incidence, which ranged from 2% to 9% for high hip center at 7 to 15 years and 0% to 5.9% for anatomic hip center at 6 to 16 years. Five studies reported intra- and postoperative complications, with the high hip center being associated with higher incidence of dislocation and lower incidence of neurological complications. No clear difference was observed in intraoperative complications between the high hip center and anatomic hip center. CONCLUSION: No obvious differences could be observed in Harris hip score or revision incidence after THA for osteoarthritis secondary to DDH between cups placed at the anatomic hip center and those placed at the high hip center. Placement of the acetabular cup in the high hip center may lead to higher risk of dislocation but lower risk of neurologic complications, although no difference in intraoperative complications was observed. Surgeons should be able to achieve satisfactory functional scores and revision incidence using either technique, although they should be aware of how their choice influences hip biomechanics and the need for adjunct procedures and associated risks and operative time. These recommendations should be considered with respect to the several limitations in the studies reviewed, including the presence of serious confounding factors and selection biases, inconsistent definitions of the high hip center, variations in dysplasia severity, small sample sizes, and follow-up periods. These weaknesses should be addressed in well-designed future studies. LEVEL OF EVIDENCE: Level III, therapeutic 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.

Can the Femoro-Epiphyseal Acetabular Roof (FEAR) Index Be Used to Distinguish Dysplasia from Impingement?

BACKGROUND: Classifying hips with structural deformity on the spectrum from impingement to dysplasia is often subjective and frequently inexact. Currently used radiographic measures may inaccurately predict a hip's morphological stability in borderline hips. A recently described radiographic measure, the Femoro-Epiphyseal Acetabular Roof (FEAR) index, has demonstrated an ability to predict stability in the borderline hip. This measure is attractive to clinicians because procedures can be used on the basis of a hip's pathomechanics. This study was designed to further validate and characterize the FEAR index in a skeletally immature population, in hips with dysplasia/femoroacetabular impingement (FAI), and in asymptomatic hips. QUESTIONS/PURPOSES: (1) What are the characteristics of the FEAR index in children and how does the index change with skeletal maturation? (2) How does the FEAR index correlate with clinical diagnosis and surgical treatment in a large cohort of symptomatic hips and asymptomatic controls? (3) How does the FEAR index correlate with clinical diagnosis in the borderline hip (lateral center-edge angle [LCEA] 20°-25°) group? METHODS: A total of 220 participants with symptomatic investigational hips with a clinical diagnosis of dysplasia or FAI between January 2008 and January 2018 were retrospectively collected from the senior author's practice. Investigational hips were excluded if they had any femoral head abnormalities preventing LCEA measurement (for example, Perthes disease), Tönnis osteoarthritis grade greater than 1, prior hip surgery, or prior femoral osteotomy. In the 220 participants, 395 hips met inclusion criteria. Once exclusion criteria were applied, 15 hips were excluded due to prior hip surgery or prior femoral osteotomy, and 12 hips were excluded due to femoral head deformity. A single hip was then randomly selected from each participant, resulting in 206 investigational hips with a mean age of 13 ± 3 years. Between January 2017 and December 2017, 70 asymptomatic control participants were retrospectively collected from the senior author's institutional trauma database. Control hips were included if the AP pelvis film had the coccyx centered over the pubic symphysis and within 1 to 3 cm of the superior aspect of the symphysis. Control hips were excluded if there was any fracture to the pelvis or ipsilateral femur or the participant had prior hip/pelvis surgery. After exclusion criteria were applied, 16 hips were excluded due to fracture. One hip was then randomly selected from each participant, resulting in 65 control hips with a mean age of 16 ± 8 years. Standardized standing AP pelvis radiographs were used to measure the FEAR index, LCEA, and Tönnis angle in the investigational cohort. Standardized false-profile radiographs were used to measure the anterior center-edge angle (ACEA) in the investigational cohort. Two blinded investigators measured the FEAR index with an intraclass correlation coefficient of 0.92 [95% CI 0.84 to 0.96]. Question 1 was answered by comparing the above radiographic measures in age subgroups (childhood: younger than 10 years; adolescence: 10 to 14 years old; maturity: older than 14 years) of dysplastic, FAI, and control hips. Question 2 was answered by comparing the radiographic measures in all dysplastic, FAI, control hips, and a subgroup of operatively or nonoperatively managed dysplasia and FAI hips. Question 3 was answered by comparing the radiographic measures in borderline (LCEA 20°-25°) dysplastic, FAI, and control hips. RESULTS: The FEAR index was lower in older dysplastic of hips (younger than 10 years, 6° ± 9°; 10 to 14 years, 4° ± 10°; older than 14 years, 5° ± 9°; p < 0.001) and control hips (younger than 10 years, -6° ± 5°; 10 to 14 years, -15° ± 4°; older than 14 years, -16° ± 7°; p < 0.001). The diagnosis and age groups were independently correlated with the FEAR index (p < 0.001). The relationship between the FEAR index and diagnosis remained consistent in each age group (p = 0.11). The FEAR index was higher in all dysplastic hips (mean 5° ± 10°) than in asymptomatic controls (mean -13° ± 7°; p < 0.001) and FAI hips (mean -10° ± 11°; p < 0.001). Using -1.3° as a cutoff for FAI/control hips and dysplastic hips, 81% (112 of 139) of hips with values below this threshold were FAI/control, and 89% (117 of 132) of hips with values above -1.3° were dysplastic. The receiver operator characteristics area under the curve (ROC-AUC) was 0.91. Similarly, the FEAR index was higher in borderline dysplastic hips than in both asymptomatic borderline controls (p < 0.001) and borderline FAI hips (p < 0.001). Eighty-nine percent (33 of 37) of hips with values below this threshold were FAI/control, and 90% (37 of 41) of hips with values above -1.3° were dysplastic. The ROC-AUC for borderline hips was 0.86. CONCLUSION: The FEAR index was associated with the diagnosis of hip dysplasia and FAI in a patient cohort with a wide age range and with varying degrees of acetabular deformity. Specifically, a FEAR index greater than -1.3° is associated with a dysplastic hip and a FEAR index less than -1.3° is associated with a hip displaying FAI. Using this reliable, developmentally based radiographic measure may help hip preservation surgeons establish a correct diagnosis and more appropriately guide treatment. LEVEL OF EVIDENCE LEVEL: III, diagnostic study.

Acetabular Rim Disorders/Pincer-type Femoroacetabular Impingement and Hip Arthroscopy.

Femoroacetabular impingement (FAI) can lead to acetabular impaction, chondral injury, and labral pathology secondary to deformities of the proximal femur (CAM-type FAI), acetabulum (pincer-type FAI), or with combined FAI. While the majority of cases are of the combined type, this paper focuses on acetabular overcoverage/pincer-type deformities. Various pincer subtypes include focal anterior overcoverage, global retroversion, global overcoverage/profunda, protrusio, subspine impingement, and os acetabuli/rim fracture variants. A thorough history and physical examination, plain radiographs, magnetic resonance imaging, 3-dimensional computerized tomography, and diagnostic injections can lead to an accurate assessment of pincer-type variants. Appropriately indicated arthroscopic management techniques and pearls for the various pincer subtypes can lead to improved patient-related outcome measures and a high rate of return to athletic activity for the majority of these patients.

What Are the Long-term Results of Cemented Revision THA with Use of Both Acetabular and Femoral Impaction Bone Grafting in Patients Younger Than 55 Years?

BACKGROUND: The increasing number of THAs in younger patients will inevitably result in an increase of revision procedures. However, there is little evidence about the outcome of revision procedures in this patient group. Therefore, we updated a previous study conducted 5 years ago about the outcome of revision procedures in patients younger than 55 years. QUESTIONS/PURPOSES: We sought to provide a concise update on the previously reported (1) long-term failure rate as defined by repeat revision, (2) clinical outcome as defined by the Oxford Hip score and the Harris Hip score, and (3) radiographic outcome of cemented revision THA performed with impaction bone grafting on both the acetabular and femoral sides in one surgery in patients younger than 55 years old. METHODS: Between 1991 and 2007, we performed 86 complete THA revisions in patients younger than 55 years. In 38% (33 of 86) of revisions, bone impaction grafting was used on both the acetabular and femoral side because of acetabular and femoral bone stock loss. Mean age at time of revision was 46 ± 8 years. No patient was lost to follow-up, but six patients died during follow-up, including three since 2015. Still, the hips of all 33 patients were included in analysis at a mean of 17 ± 5 years. Failure was calculated using competing risk analysis. For clinical outcome, we assessed the Harris Hip score and the Oxford Hip score from our longitudinally maintained institutional database. Radiographic analysis was performed to evaluate radiographic loosening, defined as radiolucencies ≥ 2 mm in all zones or ≥ 5 mm migration for both components. The acetabular component was also considered loose with tilting ≥ 5°. RESULTS: The 15-year failure rate of revision THA was 27% (95% CI 13 to 44) for re-revision of any component for any reason and 10% (95% CI 3 to 25) for re-revision of any component for aseptic loosening. The mean Harris Hip score increased from 55 ± 18 preoperatively to 74 ± 22 at latest follow-up. Eight cups were considered radiographically loose, seven of which were re-revised. No stems were considered radiographically loose. Failure rate with endpoint radiographic loosening at 15 years was 23% (95% CI 10 to 39). CONCLUSION: We found that impaction bone grafting with a cemented cup and a cemented stem is a valuable biological revision technique that results in a stable and durable solution, after one or even multiple previous revision THAs. Although current implants may prove sufficient in most cases, they do not promote bone stock preservation. We believe that in young patients with bone stock loss, impaction bone grafting can be used as long as the defect can be contained adequately with a metal mesh and viable bone bed is available for revascularization. LEVEL OF EVIDENCE: Level IV, therapeutic study.