Application of deep learning algorithms in classification and localization of implant cutout for the postoperative hip

OBJECTIVE

This study aims to explore the feasibility of employing convolutional neural networks for detecting and localizing implant cutouts on anteroposterior pelvic radiographs.

MATERIALS AND METHODS

The research involves the development of two Deep Learning models. Initially, a model was created for image-level classification of implant cutouts using 40191 pelvic radiographs obtained from a single institution. The radiographs were partitioned into training, validation, and hold-out test datasets in a 6/2/2 ratio. Performance metrics including the area under the receiver operator characteristics curve (AUROC), sensitivity, and specificity were calculated using the test dataset. Additionally, a second object detection model was trained to localize implant cutouts within the same dataset. Bounding box visualizations were generated on images predicted as cutout-positive by the classification model in the test dataset, serving as an adjunct for assessing algorithm validity.

RESULTS

The classification model had an accuracy of 99.7%, sensitivity of 84.6%, specificity of 99.8%, AUROC of 0.998 (95% CI: 0.996, 0.999) and AUPRC of 0.774 (95% CI: 0.646, 0.880). From the pelvic radiographs predicted as cutout-positive, the object detection model could achieve 95.5% localization accuracy on true positive images, but falsely generated 14 results from the 15 false-positive predictions.

CONCLUSION

The classification model showed fair accuracy for detection of implant cutouts, while the object detection model effectively localized cutout. This serves as proof of concept of using a deep learning-based approach for classification and localization of implant cutouts from pelvic radiographs.

A Modified Transgluteal Approach Sparing Abductor Function in Total Hip Arthroplasty Results in a Low Postoperative Dislocation Rate: A Retrospective Study of Short- and Long-Term Outcomes

Background A modified transgluteal approach in total hip arthroplasty (THA) can be utilized to preserve abductor muscle function and reduce dislocation rate. We present a study evaluating outcomes for a modified transgluteal approach using a validated patient-reported outcome measure (PROM) tool, the Oxford Hip Score (OHS). Methods This was a retrospective single-centre study over a four-year period. Short-term data was collected including intraoperative and postoperative complications, length of stay (LOS) in the hospital, and time from operation to mobilising independently. One year of data was collected, including plain radiograph findings and the incidence of Trendelenburg gait. Patients were contacted at a mean time of 2.7 years post-operatively so that OHS could be conducted. Results A total of 100 patients were identified within the inclusion criteria. The mean LOS for all patients was 2.8 days. The mean time from operation to mobilising independently without walking aids was 4.9 weeks. At the one-year follow-up, there was satisfactory radiographic assessment in 100% of patients. The mean OHS was 45.5 at 2.7 years, indicating satisfactory joint function in all patients. Conclusion This study supports the use of the modified transgluteal approach in THA, showing favourable outcomes in the time from operation to cessation in the use of walking aids, LOS and OHS. We report zero cases of Trendelenburg gait at the one-year follow-up and no dislocations at the three-year follow-up. Further studies are required to compare the outcomes of TGA to other approaches in THA.

Radiological Comparison of Canal Fill between Collared and Non-Collared Femoral Stems: A Two-Year Follow-Up after Total Hip Arthroplasty

Collared femoral stems in total hip arthroplasty (THA) offer reduced subsidence and periprosthetic fractures but raise concerns about fit accuracy and stem sizing. This study compares collared and non-collared stems to assess the stem-canal fill ratio (CFR) and fixation indicators, aiming to guide implant selection and enhance THA outcomes. This retrospective single-center study examined primary THA patients who received Corail cementless stems between August 2015 and October 2020, with a minimum of two years of radiological follow-up. The study compared preoperative bone quality assessments, including the Dorr classification, the canal flare index (CFI), the morphological cortical index (MCI), and the canal bone ratio (CBR), as well as postoperative radiographic evaluations, such as the CFR and component fixation, between patients who received a collared or a non-collared femoral stem. The study analyzed 202 THAs, with 103 in the collared cohort and 99 in the non-collared cohort. Patients' demographics showed differences in age (p = 0.02) and ASA classification (p = 0.01) but similar preoperative bone quality between groups, as suggested by the Dorr classification (p = 0.15), CFI (p = 0.12), MCI (p = 0.26), and CBR (p = 0.50). At the two-year follow-up, femoral stem CFRs (p = 0.59 and p = 0.27) were comparable between collared and non-collared cohorts. Subsidence rates were almost doubled for non-collared patients (19.2 vs. 11.7%, p = 0.17), however, not to a level of clinical significance. The findings of this study show that both collared and non-collared Corail stems produce comparable outcomes in terms of the CFR and radiographic indicators for stem fixation. These findings reduce concerns about stem under-sizing and micro-motion in collared stems. While this study provides insights into the collar design debate in THA, further research remains necessary.

A Comprehensive Review of Total Hip Arthroplasty Outcomes in Post-traumatic Hip Arthritis: Insights and Perspectives

Post-traumatic hip arthritis presents a challenging condition characterized by degenerative changes in the hip joint following traumatic injury. Total hip arthroplasty (THA) is a cornerstone in managing this condition, offering significant pain relief, functional improvement, and enhanced quality of life. This comprehensive review aims to synthesize existing literature to elucidate the outcomes of THA in post-traumatic hip arthritis, exploring factors influencing surgical success and identifying areas for further research. Key findings reveal favourable clinical outcomes associated with THA, though considerations such as patient characteristics, surgical techniques, and implant selection impact outcomes. Implications for clinical practice underscore the importance of tailored preoperative assessment and ongoing advancements in surgical approaches and implant technology. Furthermore, opportunities for future research lie in long-term durability studies, patient-reported outcomes assessment, and exploration of innovative surgical techniques. Overall, THA emerges as a promising intervention for post-traumatic hip arthritis, yet continual refinement through research and innovation remains imperative to optimize patient care in this population.

Hip and Knee Arthroplasty: A Review of Complications and Advances in Imaging

Arthroplasty-related complications are challenging to diagnose as they often present with nonspecific signs and symptoms, and can lead to long-term morbidity if inadequately managed. The difficulty in imaging implants is compounded by its intrinsic propensity to artifacts. Strategies to reduce this include: Judicious use of the appropriate imaging modality for the relevant clinical indication; knowledge of optimizing imaging acquisition parameters; and use of metal artifact reduction (MAR) software. We review the literature on expected normal appearances of hip and knee arthroplasties, findings of arthroplasty-related complications on various imaging modalities, advances in imaging techniques, and subsequently, suggest an algorithm for painful arthroplasty assessment. Serial radiographs remain key in identifying subtle changes in component position, hardware failure, periprosthetic osteolysis, and potential for loosening, given their ready availability, high resolution, and minimal metal-related artifact. Computed tomography with MAR provides 3D assessment and information on bone stock for surgical planning and custom implants. Magnetic resonance imaging with MAR can identify complications at earlier stages, such as loosening, capsular dehiscence in instability, and periprosthetic edema in nondisplaced fractures. It has high diagnostic performance in infection (lamellated synovitis), particle disease, adverse reactions to metal debris, in addition to demonstrating impingement on neurovascular structures. Nuclear medicine imaging is used as a problem-solving tool and is valuable in its high negative predictive value. Novel imaging techniques can further reduce artifacts and improve visualization of the implant-bone interface, and machine learning can facilitate image interpretation although attaining sufficient data and clinical validation will be challenging.

Staged replacement of both hips and both knees in patients with rheumatoid arthritis

BACKGROUND

Patients with rheumatoid arthritis (RA) undergoing bilateral total hip arthroplasty (THA) and total knee arthroplasty (TKA) are an uncommon population, and their outcomes are also difficult to predict. The purpose of this study was to evaluate whether both bilateral cementless THA and cemented posterior-stabilized TKA (PS-TKA) can provide reliable outcomes for RA patients.

METHODS

We retrospectively reviewed 30 RA patients (60 hips and 60 knees) who underwent both elective bilateral cementless THA and cemented PS-TKA, with a minimum follow-up of 2 years. Clinical, patient-reported, and radiographic data were retrospectively analyzed.

RESULTS

The mean follow-up was 84 months (range, 24-156). By the last follow-up, the post-operative range of motion, Harris Hip Score, Knee Society Score (KSS) clinical, KSS functional, Western Ontario and McMaster Universities Index of Osteoarthritis (WOMAC) hip, and WOMAC knee scores were significantly improved compared to the preoperative values. All patients achieved the ability to walk. In addition, overall satisfaction scores on a 100-point scale were 92.5 after THA and 89.6 after TKA. Only one patient underwent revision surgery due to knee joint instability, and all replaced hips and knees were radiographically stable by the assessment of the radiolucent line. The proportion of implants that did not suffer loosening or require revision surgery was 99.2% during the 84-month follow-up, based on Kaplan-Meier analysis.

CONCLUSIONS

Our study suggests that bilateral cementless THA and cemented PS-TKA provides reliable mid-long-term clinical, patient-reported, and radiographic outcomes in RA patients, with high survivorship and patient satisfaction.

Particularities on Anatomy and Normal Postsurgical Appearances of the Hip

Detailed knowledge of anatomy helps to understand pathologic processes. This article focuses on the anatomy and functionality of the hip, with emphasis on recently studied concepts and anatomic features that have an association with the development of symptoms. The most common anatomic variants posing a challenge for diagnosis and other common findings in asymptomatic patients are reviewed. Good understanding of the different surgical procedures helps in providing as much information as possible to guarantee a favorable outcome, improving prognosis. We review what are the commonly expected postsurgical appearances and the most common postsurgical complications.

The Utility of Routine Postoperative Radiographs in the Asymptomatic Total Hip Arthroplasty Patient

BACKGROUND

Total hip arthroplasty (THA) patients often receive routine radiographs in the year following their index surgery. This study sought to investigate the clinical and economic value of obtaining routine postoperative hip radiographs for asymptomatic patients following primary elective THA.

METHODS

A retrospective cohort study of consecutive patients who underwent primary elective THA from 2016 to 2019 was conducted. Patients undergoing nonelective or revision THA, radiographic follow-up <10 months, and patients aged <18 years were excluded. All radiographs were reviewed for abnormalities in the first postoperative year by an arthroplasty fellowship-trained orthopaedic surgeon, blinded to the symptoms of the patient.

RESULTS

Of the 327 patients (351 hips) included, 57.2% were women and 68.2% were White, with an average age of 65 years (range, 22-97 years) and average body mass index of 29.1 kg/m² (range, 16.2-49.8 kg/m²). Only four (0.4%) radiographic series revealed abnormalities with the potential to alter postoperative management. One patient experienced a change in management directly related to their abnormal finding (closed reduction for dislocation at 10.2 months postoperatively). The remaining three abnormal radiographic findings included femoral stem subsidence, progressive radiolucencies around an acetabular component, and cement mantle fracture. The average cost for each radiographic series was $155.27, resulting in total direct charges of $167,691.60.

CONCLUSION

Routine postoperative radiographs may be of limited utility in the asymptomatic patient in the first year following elective primary THA. Consideration should be given to limit postoperative radiographs following standard elective THA, while reserving postoperative radiographic evaluation for patients who are symptomatic.

LEVEL OF EVIDENCE

Level III.

Imaging in Hip Arthroplasty Management Part 2: Postoperative Diagnostic Imaging Strategy

Hip arthroplasty (HA) is a frequently used procedure with high success rates, but 7% to 27% of the patients complain of persistent postsurgical pain 1 to 4 years post-operation. HA complications depend on the post-operative delay, the type of material used, the patient’s characteristics, and the surgical approach. Radiographs are still the first imaging modality used for routine follow-up, in asymptomatic and painful cases. CT and MRI used to suffer from metallic artifacts but are nowadays central in HA complications diagnosis, both having their advantages and drawbacks. Additionally, there is no consensus on the optimal imaging workup for HA complication diagnosis, which may have an impact on patient management. After a brief reminder about the different types of prostheses, this article reviews their normal and pathologic appearance, according to each imaging modality, keeping in mind that few abnormalities might be present, not anyone requiring treatment, depending on the clinical scenario. A diagnostic imaging workup is also discussed, to aid the therapist in his imaging studies prescription and the radiologist in their practical aspects.

Retrospective Review of Arthroplasty Radiographs: How to Define an Adequate Radiograph

Introduction

Adequacy of postoperative hip and knee radiographs has a direct impact on its interpretation. We undertook a quality improvement project by creating local standards to meet the arthroplasty team expectations for a satisfactory radiograph. The purposes of the study are 1. Assessment of the adequacy of radiographs according to defined criteria, and 2. Correlation of system and patient factors with inadequate radiographs.

Methods

Stage I: We conducted a single centre, retrospective audit to check the adequacy of a postoperative radiography following a total hip or knee replacement. A total of 100 radiographs were assessed against the nine criteria laid out with the consensus of orthopaedic surgeons and radiologists.

Stage II: We created a quality improvement proforma for use in the radiology department. We re-assessed 100 radiographs during the second cycle against the nine criteria to check the adequacy of hip and knee arthroplasty radiographs,

Results

Stage I: Of 100 radiographs, 51 were from the knee and 49 from the hip arthroplasty group. Sixty-nine radiographs were adequate considering overall criteria, and 31 radiographs were inadequate. The inadequacy in radiographs was related to the visibility of prosthesis, cement or relevant anatomy.

Stage II: We created a quality improvement performa for use in radiology department, highlighting the nine initial criteria. One hundred radiographs of hip and knee arthroplasty were re-assessed. Overall, 84 radiographs fulfilled the criteria of being adequate.

Conclusion

Adequacy of knee and hip arthroplasty radiographs is essential in picking up pathologies that can be missed otherwise. We present simple criteria to improve the adequacy of x-ray and prevent repetition of radiographs.

Identification of risk factors for treatment failure of closed reduction and abduction bracing after first-time total hip arthroplasty dislocation

INTRODUCTION

After a first-time total hip arthroplasty (THA) dislocation, a closed reduction followed by partial immobilization in an abduction brace is the recommended therapy. Despite modern abduction braces the success rate of conservative therapy is limited and evidence is scarce. The aim of this study was to identify risk factors for failure of conservative treatment after THA dislocation.

MATERIAL AND METHODS

Eighty-seven patients, with conservative treatment of a first-time dislocation of a primary or revision THA, were included in this retrospective cohort study. Success was defined as a stable THA for a minimum of 6 months. Re-dislocation, open reduction or revision was defined as failure. The following risk factors were analyzed: gender, age, body mass index (BMI), ASA (American Society of Anesthesiologists) score, time of dislocation, head size, cup orientation, leg length, center of rotation and offset.

RESULTS

Sixty-seven percent of all patients experienced a re-dislocation, despite standardized conservative therapy. A BMI ≥ 25 kg/m², early THA dislocation, and low cup anteversion were associated with a statistically significantly higher risk for re-dislocation. None of the other risk-factors achieved statistical significance. A multifactorial risk-factor analysis was performed to assess whether a cup position outside of Lewinnek's safe zone in combination with gender, BMI and time to dislocation showed statistical significance for re-dislocation. Both BMI ≥ 25 kg/m² and early dislocation showed a statistically higher failure rate. Cup position and gender were not significant.

CONCLUSIONS

BMI ≥ 25 kg/m², early THA dislocation and low cup anteversion were identified as significant risk factors for failure of conservative treatment with an abduction brace for first-time THA dislocation.

Mechanic ileus due to retroperitoneal migration of total hip prosthesis; A case report

Intrapelvic migration of total hip prosthesis is a rare but severe complication of total hip arthroplasty that can cause severe outcomes for elderly patients. A 78-year-old female patient was referred to our hospital with the complaint of no gas-stool excretion for 3-4 days, abdominal distension, nausea, vomiting, and a preliminary diagnosis of ileus. Computed tomography showed the migration of the left total hip prosthesis to the pelvis, causing a hematoma around the prosthesis and mechanical ileus due to the compression of the hematoma. To our knowledge, this case report is the only reported mechanic ileus due to migration of total hip prosthesis. Although postop paralytic ileus is one of the complications of total hip arthroplasty, mechanical ileus has not been described before. This case report shows that mechanical ileus might be an unreported complication of total hip arthroplasty. It should be kept in mind that mechanical ileus complications may also occur after hip arthroplasty.

Distribution and outliers of anteversion of short-length cementless stem

INTRODUCTION

Inadequate stem version might lead to impingement and instability after cementless total hip arthroplasty (THA). We evaluated (1) the distribution of short-stem anteversion, (2) the proportion of stems with an anteversion less than 5° or larger than 25°, (3) combined cup and stem anteversion, and (4) dislocation rate.

MATERIALS AND METHODS

We evaluated the native femoral anteversion and stem anteversion in 340 patients (340 THAs): 144 men and 196 women. Their mean age was 56.2 (22-87) years and mean body mass index was 25.1 (15.2-40.7) kg/m². The femoral neck anteversion was measured on pre-operative CT scan and the stem anteversion was obtained during the operation. The safe zone of the stem anteversion was defined as 5 to 25°.

RESULTS

The femoral neck anteversion ranged from -15 to 61° (mean, 15.0°; SD, ±10.6°). The stem anteversion ranged -7 to 50° (mean, 15.7°; SD, ±9.5°). It was optimal (5-25°) in 71.2% (242/340), insufficient (<5°) in 13.3% (45/340), and excessive (>25°) in 15.6% (53/340). The stem anteversion had a medium correlation with the femoral neck anteversion (correlation coefficient = 0.449). The combined anteversion was 42.0° (range, 35.2-52.3°; SD, ±2.8°). During two to four year follow-up, no hip dislocated.

CONCLUSIONS

Short-length stem had a great variability in the anteversion and considerable portion (28.9%, 98/340) of stems had an anteversion outside the safe zone. Surgeons should be aware of this variability of stem anteversion to compensate for abnormal stem anteversion, which might lead to impingement and instability after THA.

No Difference in Dislocation Rates Comparing Large Diameter Jumbo Femoral Heads and Dual-Mobility Bearings in Revision Total Hip Arthroplasty

BACKGROUND

Dual-mobility (DM) bearings reduce instability in revision total hip arthroplasty (THA); however, DM bearings are costly and reports of corrosion have recently emerged. Furthermore, no study has compared DM to standard bearings with large diameter femoral heads ≥40-mm. This study's purpose was to compare postoperative dislocation rates of standard and DM bearings with large femoral heads after revision THA.

METHODS

A retrospective review of 301 consecutive revision THAs was performed. The mean follow-up was 37.1 months. To isolate the effect of the double articulation, standard and DM bearings with femoral heads ≥40-mm were compared. Outcomes were postoperative dislocation and reoperation within 90 days.

RESULTS

The cohort consisted of 182 standard bearings and 75 DM bearings. There were no differences in revision indication comparing standard and DM bearings (P = .258). Overall dislocation rate was 8.6% (22 of 257). The dislocation rate was 5.7% for standard bearings with ≥40-mm femoral heads compared with 6.9% in DM bearings with ≥40-mm femoral heads (P = 1.000). In multivariate analysis, lower body mass index (odds ratio 1.72), female sex (odds ratio 2.01), and decreased outer femoral head diameter-to-cup component size ratio (odds ratio 1.64) were predictors of postoperative dislocation regardless of bearing type.

CONCLUSION

This study showed no difference in dislocation rates between standard and DM bearings when comparing similar femoral head diameters of ≥40-mm used in revision THAs. Considering the cost and potential deleterious issues associated with additional interfaces, DM bearings should be used judiciously considering similar results may be achieved with single-articulation bearings using large femoral heads.

LEVEL OF EVIDENCE

Level III.

Prospective and longitudinal evolution of postoperative periprosthetic findings on metal artifact-reduced MR imaging in asymptomatic patients after uncemented total hip arthroplasty

OBJECTIVE

To prospectively assess the evolution of postoperative MRI findings in asymptomatic patients after total hip arthroplasty (THA) over 24 months (mo).

METHODS

This prospective cohort study included 9 asymptomatic patients (56.7 ± 15.0 years) after THA. Metal artifact-reduced 1.5-T MRI was performed at 3, 6, 12, and 24 mo after surgery. The femoral stem and acetabular cup were assessed by two readers for bone marrow edema (BME), periprosthetic bone resorption, and periosteal edema in addition to periarticular soft tissue edema and joint effusion.

RESULTS

BME was common around the femoral stem in all Gruen zones after 3 mo (range: 50-100%) and 6 mo (range: 33-100%) and in the acetabulum in DeLee and Charnley zone II after 3 mo (100%) and 6 mo (33%). BME decreased substantially after 12 mo (range: 0-78%) and 24 mo (range: 0-50%), may however persist in particular in Gruen zones 1 + 7. Periosteal edema along the stem was common 3 mo postoperatively (range: 63-75%) and rare after 24 mo: 13% only in Gruen zones 2 and 5. Twelve months and 24 mo postoperatively, periprosthetic bone resorption was occasionally present around the femoral stem (range: 11-33% and 13-38%, respectively). Soft tissue edema occurred exclusively along the surgical access route after 3 mo (100%) and 6 mo (89%) and never at 12 mo or 24 mo (0%).

CONCLUSION

Around the femoral stem, BME (33-100%) and periosteal edema (0-75%) are common until 6 mo after THA, decreasing substantially in the following period, may however persist up to 24 mo (BME: 0-50%; periosteal edema: 0-13%) in few non-adjoining Gruen zones. Soft tissue edema along the surgical access route should have disappeared 12 mo after surgery.

MRI with state-of-the-art metal artifact reduction after total hip arthroplasty: periprosthetic findings in asymptomatic and symptomatic patients

OBJECTIVES

To assess the spectrum of periprosthetic MRI findings after primary total hip arthroplasty (THA).

METHODS

This multi-center cohort study analyzed 31 asymptomatic patients (65.7 ± 12.7 years) and 27 symptomatic patients (62.3 ± 11.9 years) between 6 months and 2 years after THA. 1.5-T MRI was performed using Compressed Sensing SEMAC and high-bandwidth sequences. Femoral stem and acetabular cup were assessed for bone marrow edema, osteolysis, and periosteal reaction in Gruen zones and DeLee and Charnley zones. Student t test and Fisher's exact test were performed.

RESULTS

The asymptomatic and symptomatic groups showed different patterns of imaging findings. Bone marrow edema was seen in 19/31 (61.3%) asymptomatic and 22/27 (81.5%) symptomatic patients, most commonly in Gruen zones 1, 7, and 8 (p ≥ 0.18). Osteolysis occurred in 14/31 (45.2%) asymptomatic and 14/27 (51.9%) symptomatic patients and was significantly more common in Gruen zone 7 in the symptomatic group (8/27 (29.6%)) compared to the asymptomatic group (2/31 (6.5%)) (p = 0.03). Periosteal reaction was present in 4/31 asymptomatic (12.9%) and 9/27 symptomatic patients (33.3%) and more common in Gruen zones 5 and 6 in the symptomatic group (p = 0.04 and 0.02, respectively). In the acetabulum, bone marrow edema pattern was encountered in 3/27 (11.1%) symptomatic patients but not in asymptomatic patients (p ≥ 0.21). Patient management was altered in 8/27 (29.6%) patients based on MRI findings.

CONCLUSIONS

Periprosthetic bone marrow edema is common after THA both in asymptomatic and symptomatic patients. Osteolysis and periosteal reaction are more frequent in symptomatic patients. MRI findings led to altered patient management in 29.6% of patients.

KEY POINTS

• Bone marrow edema pattern was frequent in both asymptomatic and symptomatic patients after THA, particularly around the proximal femoral stem in Gruen zones 1, 7, and 8. • Osteolysis was significantly more frequent in symptomatic patients in Gruen zone 7. • Periosteal reaction occurred more frequently in symptomatic patients in Gruen zones 5 and 6.

Primary Total Hip Arthroplasty for Charcot Arthropathy is Associated With High Complications but Improved Clinical Outcomes

BACKGROUND

Neuropathic (Charcot) arthropathy of the hip is rare but can lead to joint destruction, bone loss, and dysfunction. While total hip arthroplasty (THA) may be considered a treatment option, only very limited data in the form of case reports are available on the results of THA. The goal of this study was to analyze the outcomes of primary THA for Charcot arthropathy with emphasis on implant survivorship, complications, and clinical outcomes.

METHODS

Eleven patients undergoing 12 primary THAs for Charcot arthropathy from 2007 to 2014 were retrospectively reviewed. All patients had a severe underlying neuropathy and clear radiographic evidence of Charcot arthropathy. Mean age was 54 years with 4 patients being female. Mean follow-up was 5 years.

RESULTS

Survivorship free of any revision was 75% at both 2 and 5 years. Three THAs (3/12) were revised: 2 for recurrent instability and 1 for femoral component loosening. Survivorship free of any reoperation was 67% at both 2 and 5 years. One additional THA underwent open reduction and internal fixation of a Vancouver B₁ periprosthetic fracture. The overall complication rate (including revisions and reoperations) was high at 58% with 3 recurrent dislocations, 2 periprosthetic fractures, 1 femoral component loosening, and 1 delayed wound healing. Harris Hip Scores improved from a mean of 43 preoperatively to 81 postoperatively (P < .001).

CONCLUSION

In this study, the largest to date, we found that patients undergoing primary THA for Charcot arthropathy have a significant improvement in clinical outcomes but that there was a high risk of early complications and revisions, mostly related to recurrent instability. Specific precautions to avoid early complications, namely utilization of components that provide robust fixation and strategies that provide enhanced hip stability, should be considered.

LEVEL OF EVIDENCE

Level IV.

Acetabular Component Position and the Risk of Dislocation Following Primary and Revision Total Hip Arthroplasty: A Matched Cohort Analysis

BACKGROUND

Recently, the importance of acetabular component positioning in the Lewinnek "safe zone" in preventing prosthetic dislocation following total hip arthroplasty (THA) has been questioned. The purpose of this study was to determine the proportion of acetabular components within the Lewinnek safe zone between primary and revision THAs that have sustained a dislocation vs matched controls without a dislocation event.

METHODS

This was a retrospective, institutional review board-approved investigation of THAs performed at our institution or referred to our institution between 1997 and 2013. Ninety-six primary THAs and 60 revision THAs that sustained a dislocation were included and matched 1:1 based on age, gender, and body mass index with nondislocated controls. Acetabular component inclination and anteversion were performed using Martell Hip Analysis Suite and compared between the 2 cohorts for both primary and revision THAs.

RESULTS

The proportion of acetabular components within the safe zone for both inclination and anteversion was 23 of 96 (24%) in primary THA dislocators vs 48 of 96 (50%, P < .001) in controls. The proportion of acetabular components within the safe zone for both inclination and anteversion was 28 of 60 (47%) in revision THA dislocators vs 40 of 60 (66%, P = .03) in controls.

CONCLUSION

Patients sustaining a dislocation following a primary or revision THA had acetabular components less frequently positioned within the safe zone compared to control patients. This study suggests acetabular component positioning remains an important variable in decreasing the risk of dislocation following primary and revision THA.

Imaging of the Painful Hip Arthroplasty

The incidence of complications following total hip arthroplasty is low, but due to the frequency of the procedure, they are quite commonly encountered and require appropriate investigation. Complications include aseptic loosening, infection, foreign body granulomatosis (osteolysis), adverse reactions to metal debris, periprosthetic fracture, heterotopic ossification, hardware failure, and a range of soft tissue complications, all of which may result in pain. Relevant imaging findings are illustrated and the role of various imaging modalities is reviewed. A suggested approach for the radiological investigation of each potential complication is outlined, based on our experience at a specialist referral unit.

Hip Arthroplasty Pseudotumors: Pathogenesis, Imaging, and Clinical Decision Making

Pseudotumors are a complication of hip arthroplasty. The goal of this article is to review the clinical presentation, pathogenesis, histology, and the role of diagnostic imaging in clinical decision making for treatment, and surveillance of pseudotumors. We will discuss the multimodal imaging appearances, differential diagnosis, associated complications, treatment, and prognosis of pseudotumors, as an aid to the assessment of orthopedic prostheses at the hip.

What Safe Zone? The Vast Majority of Dislocated THAs Are Within the Lewinnek Safe Zone for Acetabular Component Position

BACKGROUND

Numerous factors influence total hip arthroplasty (THA) stability including surgical approach and soft tissue tension, patient compliance, and component position. One long-held tenet regarding component position is that cup inclination and anteversion of 40° ± 10° and 15° ± 10°, respectively, represent a "safe zone" as defined by Lewinnek that minimizes dislocation after primary THA; however, it is clear that components positioned in this zone can and do dislocate.

QUESTIONS/PURPOSES

We sought to determine if these classic radiographic targets for cup inclination and anteversion accurately predicted a safe zone limiting dislocation in a contemporary THA practice.

METHODS

From a cohort of 9784 primary THAs performed between 2003 and 2012 at one institution, we retrospectively identified 206 THAs (2%) that subsequently dislocated. Radiographic parameters including inclination, anteversion, center of rotation, and limb length discrepancy were analyzed. Mean followup was 27 months (range, 0-133 months).

RESULTS

The majority (58% [120 of 206]) of dislocated THAs had a socket within the Lewinnek safe zone. Mean cup inclination was 44° ± 8° with 84% within the safe zone for inclination. Mean anteversion was 15° ± 9° with 69% within the safe zone for anteversion. Sixty-five percent of dislocated THAs that were performed through a posterior approach had an acetabular component within the combined acetabular safe zones, whereas this was true for only 33% performed through an anterolateral approach. An acetabular component performed through a posterior approach was three times as likely to be within the combined acetabular safe zones (odds ratio [OR], 1.3; 95% confidence interval [CI], 1.1-1.6) than after an anterolateral approach (OR, 0.4; 95% CI, 0.2-0.7; p < 0.0001). In contrast, acetabular components performed through a posterior approach (OR, 1.6; 95% CI, 1.2-1.9) had an increased risk of dislocation compared with those performed through an anterolateral approach (OR, 0.8; 95% CI, 0.7-0.9; p < 0.0001).

CONCLUSIONS

The historical target values for cup inclination and anteversion may be useful but should not be considered a safe zone given that the majority of these contemporary THAs that dislocated were within those target values. Stability is likely multifactorial; the ideal cup position for some patients may lie outside the Lewinnek safe zone and more advanced analysis is required to identify the right target in that subgroup.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Subtrochanteric femur fractures: review of the complete pathologic spectrum with emphasis on distinguishing imaging features

Subtrochanteric femur fractures result from a variety of mechanisms of injury and underlying pathologies. Radiologists can play a pivotal role by differentiating the etiology of a subtrochanteric femur fracture, which assists the orthopedic surgeon in choosing the correct method of treatment. To provide this valuable service, one must be familiar with the characteristic radiologic features of the numerous causative etiologies, ranging from Paget disease to underlying bone lesions to iatrogenic fractures.

Current concepts in knee replacement: complications

OBJECTIVE

The purposes of this article are to review current concepts of knee replacement, including features of traditional and newer prosthetic designs, materials, and surgical techniques; illustrate normal and abnormal postoperative imaging findings; and to relate the complications to current understanding of how and why these failures occur.

CONCLUSION

Complications after knee replacement may be asymptomatic. For this reason, assessment with postoperative imaging is important. The foundation of radiologic interpretation of knee replacement is knowledge of the physiologic purpose, orthopedic trends, imaging findings, and complications.

Current concepts in knee replacement: features and imaging assessment

OBJECTIVE

This article reviews current concepts of knee replacement. Features of traditional and new prosthetic designs, materials, and surgical techniques are discussed. Normal and abnormal postoperative imaging findings are illustrated. Complications are reviewed and related to the current understanding about how and why these failures occur.

CONCLUSION

It is well known that after knee replacement, patients with complications may be asymptomatic, and, for this reason, assessment of postoperative imaging is important. The foundation of radiologic interpretation of knee replacement is knowledge of the physiologic purpose, orthopedic trends, imaging findings, and complications.

The utility of digital linear tomosynthesis imaging of total hip joint arthroplasty with suspicion of loosening: a prospective study in 40 patients

Aim. The clinical utility of digital linear tomosynthesis in musculoskeletal applications has been validated in only a few reports. Technical performance and utility in hip prosthesis imaging have been discussed in technical reports, but no clinical evaluation has been reported. The purpose of the current study was to assess the added clinical utility of digital linear tomosynthesis compared to radiography in loosening of total hip joint arthroplasty. Materials and Methods. In a prospective study, radiography and digital tomosynthesis were performed in 40 consecutive patients with total hip arthroplasty referred for suspect prosthesis loosening. Tomosynthesis images were compared to anterior-posterior (AP) and cross-table lateral radiographs regarding demarcation and extent of demineralization and osteolysis. Further noted were skeletal fractures, cement fractures, fragmentation, and artifacts interfering with the diagnosis. Results. Tomosynthesis was superior to radiography with sharper delineation of demineralization and osteolysis in the AP projection. A limitation was the inability to generate lateral tomosynthesis images, with inferior assessment of the area anterior and posterior to the acetabular cup compared to cross-table radiographs. Artifacts interfering with diagnosis were found in one hip. Conclusion. Tomosynthesis improved evaluation of total hip arthroplasty in the AP projection but was limited by the lack of lateral projections.

Current concepts of hip arthroplasty for radiologists: part 2, revisions and complications

OBJECTIVE

This article reviews the imaging features of revisions and complications of hip replacement arthroplasty and relates these features to the current understanding about how and why these failures occur.

CONCLUSION

Short-term failures of hip replacements are most commonly the result of instability and dislocation. Complications ranging from osteolysis caused by granulomatous reaction to particulate wear debris lead to many long-term failures. Attempts to reduce wear debris through changes in design and materials have reduced the rate of some complications but have resulted in new ones. Infection remains a devastating complication that is difficult to resolve.