Instability of the Hip Joint After Posterior Acetabular Wall Fracture: Independent Risk Factors Remain Elusive

Radiological predictors of outcomes in hip arthroscopy for femoroacetabular impingement

Aims

Hip arthroscopy has gained prominence as a primary surgical intervention for symptomatic femoroacetabular impingement (FAI). This study aimed to identify radiological features, and their combinations, that predict the outcome of hip arthroscopy for FAI.

Methods

A prognostic cross-sectional cohort study was conducted involving patients from a single centre who underwent hip arthroscopy between January 2013 and April 2021. Radiological metrics measured on conventional radiographs and magnetic resonance arthrography were systematically assessed. The study analyzed the relationship between these metrics and complication rates, revision rates, and patient-reported outcomes.

Results

Out of 810 identified hip arthroscopies, 359 hips were included in the study. Radiological risk factors associated with unsatisfactory outcomes after cam resection included a dysplastic posterior wall, Tönnis grade 2 or higher, and over-correction of the α angle. The presence of acetabular retroversion and dysplasia were also significant predictors for worse surgical outcomes. Notably, over-correction of both cam and pincer deformities resulted in poorer outcomes than under-correction.

Conclusion

We recommend caution in performing hip arthroscopy in patients who have three positive acetabular retroversion signs. Acetabular dysplasia with a lateral centre-edge angle of less than 20° should not be treated with isolated hip arthroscopy. Acetabular rim-trimming should be avoided in patients with borderline dysplasia, and care should be taken to avoid over-correction of a cam deformity and/or pincer deformity.

Assessment of Force Applied During Examination Under Anesthesia Used to Determine Stability in Posterior Wall Acetabular Fractures

OBJECTIVES

Determination of hip instability associated with posterior wall acetabular fractures may be difficult. Thus, dynamic stress examination under anesthesia (EUA) was developed as a tool for guiding treatment. EUA uses positioning of the hip and application of force across the hip to detect instability. While aspects of the EUA technique seems consistently described in the literature and practiced by surgeons, some components are ill-defined. The goal of this study was to assess standardization of applied force during EUA among experienced acetabular surgeons.

METHODS

Fellowship-trained orthopaedic trauma surgeons with experience in acetabular fracture treatment performed EUA for posterior wall instability on an intact, fresh human cadaver. All surgeons used a similar method, and each expert performed EUA multiple times separated by a brief hiatus. The maximum force applied along the femur's vector in Newtons (N) was measured using a hand-held digital dynamometer.

RESULTS

The EUAs of 19 surgeons were evaluated. Five surgeons had been practicing for <5 years, six for 6 to 10 years, five for 11 to 20 years, and three for >20 years. The mean force applied during EUA was 173N, with a notable variability between surgeons (range, 77-368N). Notable variability was also observed between sequential measures of individual surgeons with six surgeons (31.6%) having a >50N range on repeat trials.

CONCLUSION

This is the first study to report force applied during an EUA to assess for posterior wall acetabular fracture stability. Notable variability was observed among surgeons performing the examination and in repeated examinations by the same surgeon, suggesting that results of EUA may be surgeon-dependent. Further study is needed to determine what optimal applied force should be used to assess hip stability after a posterior wall acetabular fracture.

LEVEL OF EVIDENCE

Level V. An assessment of a diagnostic tool.

Acetabular dysplasia and posterior wall fractures: The missing link?

BACKGROUND

Traumatologists are unable to predict hip instability based on CT scans and standard radiographs in posterior wall (PW) fractures comprising <50-60 % of the wall, necessitating an examination under anesthesia (EUA). Risk factors for instability have not been clarified, but acetabular dysplasia has been theorized as a potential etiology. Unfortunately, dysplasia is difficult to evaluate in the traumatic setting. The purpose of this study was to compare acetabular morphology between unstable and stable fractures with a novel method to detect dysplasia.

METHODS

Patients ≥ 18 years old with a PW fracture that underwent an EUA from 2013 to 2023 were retrospectively identified. For our experimental measurements, the axial distances on CT between the acetabular dome, lateral acetabular opening, and femoral head vertex were recorded. Acetabular geometry was quantified at these levels. Conventional dysplasia metrics (e.g., Tonnis angle) were obtained. Variables were compared between stable and unstable fractures.

RESULTS

58 patients met inclusion criteria with 42 stable versus 16 unstable fractures. Unstable fractures had higher distances between the acetabular dome and femoral head vertex (p > 0.05). They had more cranial fracture exit points (p = 0.0015), lower femoral head coverage (p = 0.0102), and lower posterior acetabular sector angles (p = 0.0281). No other differences in acetabular geometry, demographics, injury characteristics, or other markers of dysplasia were identified.

CONCLUSIONS

Unstable hips demonstrated a more recessed acetabular dome when compared to stable hips. Posterior acetabular femoral head coverage and cranial fracture exit point may be related to hip instability. A larger sample size is needed to validate these findings.

A New Computed Tomography-Based Measure that Provides Insight Into Hip Stability in Patients With Posterior Wall Acetabular Fractures

OBJECTIVES

To describe the technique and results of a new sagittal plane computed tomography (CT)-based angular measure for predicting stability after posterior wall acetabular fractures (PWF).

METHODS

DESIGN

Retrospective review.

SETTING

Academic Level II trauma center.

PATIENT SELECTION CRITERIA

Fifty-eight consecutive patients with PWF (AO/OTA class 62A.1), 98% were high-energy injuries.

INTERVENTION

A new sagittal CT measure of PWF based on the angle subtending the joint center, cranial and caudal fracture exits.

OUTCOME MEASURES AND COMPARISONS

Hip incongruity or dislocation demonstrated using gold standard test, examination under anesthesia (EUA), or instability on static images. Prediction of hip instability using a sagittal CT angular measure based on cranial and caudal fracture exits was compared with previous axial CT measures suggestive of increased risk for instability including posterior wall size >50%, and those with cranial exit within 5.0 mm of the acetabular dome.

RESULTS

There were 32 operative and 26 nonoperatively treated fractures. Thirty fractures were determined to be unstable, and 28 were stable after EUA. Measurements of >70 degrees using the sagittal CT angular measure predicted instability in 28 of 28 patients, and ≤70 degrees predicted stability in 30 of 30 patients (sensitivity 100% and specificity 100%). Prevalence of EUA confirmed instability for subgroups with PWF based on prior axial CT measures were as follows: ≥50% wall involvement (11/16; sensitivity 67% and specificity 60%; 95% CI, 45%-89%/45%-75%), fracture within 5.0 mm of dome (5/18; sensitivity 86% and specificity 73%; 95% CI, 71%-100%/59%-87%), fracture within 5.0 mm of dome and ≥50% involvement (1/9; sensitivity 89% and specificity 56%; 95% CI, 69%-100%/24%-88%).

CONCLUSIONS

In a sample of 58 mostly high energy posterior wall fractures all having had an EUA, a new sagittal angular CT measurement of ≤70 degrees predicted hip stability and >70 degrees predicted instability with 100% sensitivity and specificity.

LEVEL OF EVIDENCE

Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Predictors for post-traumatic hip osteoarthritis in patients with transverse acetabular fractures following open reduction internal fixation: a minimum of 2 years' follow-up multicenter study

BACKGROUND

The predictors of post-traumatic osteoarthritis (PTOA) in patients with transverse acetabular fractures (TAFs) following open reduction internal fixation (ORIF) remain unclear. This study aimed to investigate the risk factors for PTOA in TAFs after ORIF.

METHODS

Data of TAF patients receiving ORIF were collected from January 2012 and February 2021. Patients suffered PTOA were classified as the osteoarthritis group (OG), while those without PTOA were classified as the non- osteoarthritis group (NG) with a minimum follow-up of 2 years. PTOA was diagnosed according to Tönnis OA classification during the period of follow-up. Univariate analysis, logistic regression analysis, and receiver operating characteristic (ROC) curve analyses were used to evaluate demographics, injury-related characteristics, perioperative and post-discharge information.

RESULTS

Three hundred and eleven TAF patients were analyzed in this study, including 261 males and 50 females, with a mean age of 40.4 years (range 18 to 64 years). The incidence of PTOA was 29.6% (92 of 311) during the mean follow-up of 36.8 months (range 24 to 70 months). Several factors of PTOA were found using univariate analysis, including transverse fracture associated with posterior wall acetabular fracture (TPW-AF, p = 0.002), acetabular roof fracture (ARF, p = 0.001), femoral head lesion (FHL, p = 0.016), longer time from injury to surgery (TIS, p＜0.001) and physical work after surgery (PWAS, p＜0.001). Logistic regression analysis showed that TPW-AF (p = 0.007, OR = 2.610, 95%CI: 1.302-5.232), ARF (p = 0.001, OR = 2.887, 95%CI: 1.512-5.512), FHL (p = 0.005, OR = 2.302, 95%CI: 1.283-4.131), TIS (p<0.0001, OR = 1.294, 95%CI: 1.192-1.405) and PWAS (p<0.0001, 3.198, 95%CI: 1.765-5.797) were independent risk factors of PTOA. Furthermore, ROC curve analysis indicated 11.5 days as the cut-off values to predict PTOA.

CONCLUSIONS

Our findings identified that TPW-AF, ARF, FHL, TIS and PWAS were independent risk factors for PTOA in patients with TAFs following ORIF. It can help orthopedic surgeons to take early individualized interventions to reduce its incidence.

Three-Dimensional Printed Plate Template Versus Hemipelvis Model in Patient-Specific Plate Preparation for Posterior Wall Acetabular Fractures

OBJECTIVE

The application of three-dimensional (3D) printing technology in the management of posterior wall acetabular fractures can greatly reduce surgical invasiveness and operative time and simplify the procedure of reconstruction plate contouring, but the cost and time of patient-specific plate preparation on the basis of traditional 3D-printed pelvis model should not be neglected. We described a new method for patient-specific plate preparation by using 3D-printed plate template. The study aimed to assess the effectiveness and feasibility of the 3D-printed plate template in patient-specific plate preparation for posterior wall acetabular fractures.

METHODS

A total of 65 cases of posterior wall acetabular fractures with surgical treatment from December 2012 to December 2020 were chosen. According to the different plate contouring methods, the 65 cases were divided into three groups, which were group A (21 cases), group B (20 cases), and group C (24 cases). In group A, the 3D-printed plate template was used to contour the patient-specific reconstruction plate before surgery, whereas the 3D-printed hemipelvis model was adopted for group B. In group C, the reconstruction plate was contoured intraoperatively. Among the three groups, the instrumentation time, surgical time, blood loss, patient-specific plate preparation time, complications, reduction quality, and hip function were compared. The Kruskal-Wallis test was used to analyze the reduction quality and hip function among three groups.

RESULTS

In comparison with group C, patients in groups A and B were featured by obviously shorter instrumentation time (-22, -23 min), shorter surgical time (-46, -44 min), and less intraoperative blood loss (-110, -122 mL). Compared to the hemipelvis model in group B (2.29 ± 0.56 vs. 12.70 ± 3.79 days), the 3D printing time for plate templates in group A was significantly shorter. The reduction quality and hip function had no obvious statistical difference among the three groups. The complication rate within group A (3/21) and group B (3/20) were both slightly lower than group C (5/24), with no obvious difference.

CONCLUSIONS

Both the patient-specific pre-contoured plate fixation methods based on the 3D-printed hemipelvis model and plate template can achieve satisfactory clinical efficacy, with the advantage of shorter instrumentation and surgical time, and less intraoperative blood loss. However, 3D printing of plate template is easier and less time-consuming, considering the shorter time and less cost for 3D printing of physical model.

Both-column Acetabular Fractures with Posterior Wall Involved can be Managed through Single Anterior Approach by Evaluation of Computer-assisted Virtual Surgery Technique

OBJECTIVE

Posterior wall (PW) fractures were sometimes associated in both-column acetabular fractures. How to evaluate pre-operatively the necessity for the performance of the posterior approach was an issue to be solved. In order to solve this issue, the computer-assisted virtual surgery technique was used to evaluate if the involved PW in both-column acetabular fractures (BACF) should be managed through posterior approach and verify the feasibility of this method.

METHODS

Data of a consecutive cohort of 72 patients with both-acetabular fractures from January 2012 to January 2020 was collected for retrospective study, of which 44 patients had concomitant acetabular PW fractures, and patients without PW fractures were labeled as the BCAF group. Computer-assisted virtual surgery technique was performed pre-operatively to evaluate the necessity for performance of posterior approach in 44 patients, and posterior approach was required if more than 3 mm of displacement was still present in the reduced 3D model. The 23 patients without treatment through posterior approach were labeled as the BCAF-PW- group, and the 21 patients with treatment through posterior approach were labeled as the BCAF-PW+ group. Operation-related and post-operative parameters were recorded. The quality of reduction and functional outcomes were assessed by the Matta scoring system and modified Merle d'Aubigné and Postel scoring system. The measurement data were analyzed using the t-test of independent samples and rank-sum test of ranked data between every two groups. Also, the one-way analysis of variance (ANOVA) was used to analyze data between the three groups.

RESULTS

Comparing operation-related and post-operative parameters in the three groups, some PW fractures in both-column acetabular fractures could be ignored, and which could be evaluated pre-operatively for necessity of an additional posterior approach. Operative time (271.2 ± 32.8 mins) and intra-operative blood loss (1176.7 ± 211.1 mL) were significantly higher in the BCAF-PW+ group. The excellent/good of reduction (25/28 of the BCAF group, 21/23 of the BCAF-PW- group, 19/21 of the BCAF-PW+ group) and functional outcomes (24/28 of the BCAF group, 18/23 of the BCAF-PW- group, 18/21 of the BCAF-PW+ group) of three groups were similar. The incidence of complications, such as deep vein thrombosis (4/28 of the BCAF group >3/23 of the BCAF-PW- group >1/21 of the BCAF-PW+ group) and injury of lateral femoral cutaneous nerve (3/23 of the BCAF-PW- group >2/28 of the BCAF group >0/21 of the BCAF-PW+ group), was no significant difference.

CONCLUSION

The partial both-column acetabular fractures with PW involvement could be managed through a single anterior approach without another posterior approach by evaluation of computer-assisted virtual surgery technique.

One-stop computerized virtual planning system for the surgical management of posterior wall acetabular fractures

Background

Posterior wall acetabular fractures remain one of the most difficult fracture injuries to treat. Accurate assessment of fracture characteristics and appropriate preoperative surgical strategies are essential for excellent reduction. This paper evaluates the feasibility and effectiveness of a one-stop computerized virtual planning system for the surgical management of posterior wall acetabular fractures.

Methods

52 cases of posterior wall acetabular fractures treated surgically were selected in our department between January 2015 and December 2020 for retrospective analysis. 52 cases were classified into group A (25 patients) and group B (27 patients) according to whether computerized virtual planning procedures were performed preoperatively. In group A, virtual surgical simulation was conducted using a one-stop computerized planning system preoperatively. In group B, traditional surgery was employed. Reduction quality, surgical time, blood loss, hip function, complications, and instrumentation time were compared between the two groups.

Results

The actual surgery for all patients in group A was essentially the same as the virtual surgery before the operation. Compared to group B, patients in group A had markedly shorter surgical time (−43 min), shorter instrumentation time (−20 min), and less intraoperative blood loss (−130 ml). However, no significant statistical difference was observed in reduction quality and hip function. The complication rate was slightly lower in group A (4/25) than in group B (7/27), without a significant difference.

Conclusion

The one-stop computerized virtual planning system is a highly effective, user-friendly and educational tool for allowing the cost-efficient surgical simulation of posterior wall acetabular fractures and providing a more individualized therapeutic schedule. The one-stop computerized planning system is feasible to treat posterior wall acetabular fractures, which is an effective method than the conventional treatment of posterior wall acetabular fractures.

Trial registration: retrospective registration.

Three-dimensional mapping study of pure transverse acetabular fractures

BACKGROUND

To describe and analyze the morphological characteristics, location and frequency of pure transverse acetabular fracture lines through fracture mapping and quantitative measurements.

METHODS

Transverse fractures were retrospectively reviewed and analyzed. All computed tomography (CT) data were used for reconstruction and manual reduction. The reductive fracture fragments were graphically overlaid onto a three-dimensional (3D) right hemipelvis template. Then, the fracture lines were accurately depicted onto the surface of the 3D template. The fracture lines were overlapped onto the model to create the 3D fracture map and heatmap. All cases were subdivided into infratectal (62-B1.1), juxtatectal (62-B1.2), and transtectal (62-B1.3) types based on the AO Foundation/Orthopedic Trauma Association (AO/OTA) classification. Some anatomic parameters of the transverse fractures were also analyzed in these 3 groups.

RESULTS

Our study included forty-nine transverse fractures from 32 male and 17 female patients (mean age, 42 years; range 21-74 years) and included 19 type 62-B1.1, 17 type 62-B1.2, and 13 type 62-B1.3 fractures. The average anterior rim fracture angle was 70.0° (± 11.6°), and the posterior rim fracture angle was 92.4° (± 28.5°). The anterior rim fracture angles in 40 cases (40/49, 81.6%) fell within a wide range between 63° and 80°. On the heatmap, the hot zones were located on the highest position of the cotyloid fossa and the narrowed region, and the cold zone was on the inferior third of the articular surface. For type 62-B1.3 fractures, the hot zone was located on the posterior of the acetabular dome. There were no significant differences in anterior rim fracture angle and anterior height among the three patterns (P = 0.071, P = 0.072). Post hoc tests of the posterior rim fracture angle and the posterior height revealed significant differences among fracture subtypes (P < 0.01). The posterior intra-articular fracture line was significantly longer than the anterior intra-articular fracture line in type 62-B1.1 and type 62-B1.2 fractures (P < 0.01).

CONCLUSION

The fracture lines of transverse fractures through the anterior rim were concentrated on the narrowed zone, and the posterior fracture lines were diffusely distributed. The intra-articular fracture line distribution was focused on the superior and middle thirds of the joint surface. The recurrent fracture lines involving the weight-bearing dome mainly converged on the posterior region of the roof.

Is Plating Fixation Through the Kocher–Langenbeck Approach for Associated Posterior Wall Fragment Indispensable in Both‐Column Acetabular Fractures?

Objective

Methods

Results

Conclusions

Evaluation and Management of Posterior Wall Acetabulum Fractures

Posterior wall acetabulum fractures typically result from high-energy mechanisms and can be associated with various orthopaedic and nonorthopaedic injuries. They range from isolated simple patterns to multifragmentary with or without marginal impaction. Determination of hip stability, which can depend on fragment location, size, and displacement, directs management. Although important in the assessment of posterior wall fractures, CT is unreliable when used to determine stability. The dynamic fluoroscopic examination under anesthesia (EUA) is the benchmark in assessment of hip stability, and fractures deemed stable by EUA have good radiographic and functional outcomes. In fractures that meet surgical criteria, accurate joint reduction guides outcomes. Joint débridement, identification and elevation of impaction, and adjunctive fixation of posterosuperior and peripheral rim fragments along with standard buttress plate fixation are critical. Complications of the fracture and surgical fixation include sciatic nerve injury, posttraumatic osteoarthritis, osteonecrosis of the femoral head, and heterotopic ossification. Although accuracy of joint reduction is paramount for successful results, other factors out of the surgeon's control such as comminution, femoral head lesions, and dislocation contribute to poor outcomes. Even with anatomic restoration of the joint surface, good clinical outcomes are not guaranteed and residual functional deficits can be expected.

Modified lateralized head sign: An accurate marker in diagnosing adult hip dysplasia

BACKGROUND

Although lateralized head sign (LHS) is considered indicative of structural instability, it lacks reproducibility, and its usefulness in diagnosing adult hip dysplasia is unknown. In this study, we proposed a modified LHS and aimed to determine its reliability and accuracy in diagnosing adult hip dysplasia.

METHODS

We reviewed anteroposterior pelvic radiographs of 94 patients (134 hips) with hip dysplasia. As controls, 133 normal hips were evaluated. We defined the modified lateralization distance (LD) as the horizontal distance between the medial aspect of the femoral head to the acetabular fossa. The sensitivity, specificity, and cutoff value of modified LD in diagnosing hip dysplasia were calculated using receiver operating characteristic curve analysis.

RESULTS

The sensitivity and specificity of the modified LD (79% and 87%, respectively) were higher than those of the conventional LD (63% and 80%, respectively). Diagnostic accuracy was further improved when patients were divided on the basis of sex. The sensitivity and specificity of the modified LD in men were 89% and 97%, respectively, with a cutoff value of 12 mm, while in women, they were 80% and 96%, respectively, with a cutoff value of 9.7 mm. Therefore, we defined the modified LHS as presentation with a modified LD ≥ 12 mm in men and ≥10 mm in women. Between three observers, the kappa value for intraobserver reliability was ≥0.9, while that for interobserver reliability was >0.8. The mean sensitivity and specificity of the modified LHS in diagnosing hip dysplasia were 85% and 99%, respectively.

CONCLUSIONS

Modified LHS-a horizontal distance between the medial aspect of the femoral head and the acetabular fossa ≥12 mm in men and ≥10 mm in women-is a clinically useful marker in detecting lateral femoral head subluxation indicative of hip dysplasia or structural hip instability.

Novel Treatment for Recurrent Posttraumatic Hip Instability: A Case Report

CASE

A 26-year-old woman sustained a traumatic right hip dislocation with posterior wall component in a motor vehicle collision. Initial treatment consisted of open reduction internal fixation of her posterior wall fracture. Six years later, she developed low-energy recurrent hip instability. Imaging demonstrated posterior capsular insufficiency and femoral retrotorsion. The patient underwent intertrochanteric femoral rotational osteotomy. Nine years postoperatively, the patient has returned to activity without restriction or subsequent dislocations.

CONCLUSIONS

Recurrent posttraumatic hip instability requires careful identification of the etiology of instability. This case provides long-term follow-up after successful treatment with intertrochanteric femoral rotational osteotomy.

Different subchondral trabecular bone microstructure and biomechanical properties between developmental dysplasia of the hip and primary osteoarthritis

Objective

Developmental dysplasia of the hip (DDH) is recognized as a frequent cause of secondary osteoarthritis (OA). The purpose in this study was to compare structural and biomechanical properties of subchondral trabecular bone ​and its relationship with cartilage damage between patients with DDH and patients with primary hip OA.

Methods

Forty-three femoral head specimens obtained from patients who underwent total hip arthroplasty [DDH, n ​= ​17; primary OA, n ​= ​16; and normal control (NC), n ​= ​10] were scanned by microcomputed tomography and analyzed by individual trabecula segmentation to obtain the microstructural types of subchondral trabecular bone. The biomechanical properties were analyzed by micro-finite element analysis, and cartilage damage was evaluated by histology. The linear regression analysis was used to indicate the association between microstructures, biomechanical property, and articular cartilage.

Results

The DDH group showed the lowest total bone volume fractions (BV/TV) and plate BV/TV in the three groups (p ​< ​0.05). There were also different discrepancies between the three groups in plate/rod trabecular number, plate/rod trabecular thickness, trabecular plate surface area/trabecular rod length, and junction density with different modes (plate-plate, rod-rod, and plate-rod junction density). The micro-finite element analysis, histology, and linear regression revealed that the subchondral trabecular bone in the DDH group had inferior biomechanical properties ​and cartilage damage of patients with DDH was more serious with different subchondral trabecular bone microstructures.

Conclusion

Our findings detected deteriorating subchondral trabecular bone microstructures in patients with DDH. The mass and type of subchondral trabecular bone play a key role in mechanical properties in DDH, which might be related to cartilage damage.

The translational potential of this article

Our findings suggested that changes of subchondral trabecular bone play a critical role ​in DDH progression and that the improvement on subchondral trabecular bone may be a sensitive and promising way in treatment of DDH.