Advanced quantitative 3D imaging improves the reliability of the classification of acetabular defects

INTRODUCTION

Classifying complex acetabular defects in revision total hip arthroplasty (THA) by means of conventional radiographs comes with significant limitations. Statistical shape modelling allows the virtual reconstruction of the native pelvic morphology, hereby enabling an analytic acetabular defect assessment. Our objective was to evaluate the effect of advanced imaging augmented with analytic representations of the defect on (1) intra- and inter-rater reliability, and (2) up- or downscaling of classification scores when evaluating acetabular defects in patients undergoing revision THA.

MATERIALS AND METHODS

The acetabular defects of 50 patients undergoing revision THA were evaluated by three independent, fellowship-trained orthopaedic surgeons. Defects were classified according to the acetabular defect classification (ADC) using four different imaging-based representations, namely, standard radiographs, CT imaging, a virtual three-dimensional (3D) model and a quantitative analytic representation of the defect based on a statistical shape model reconstruction. Intra- and inter-rater reliabilities were quantified using Fleiss' and Cohen's kappa scores, respectively. Up- and downscaling of classification scores were compared for each of the imaging-based representations and differences were tested.

RESULTS

Overall inter-rater agreement across all imaging-based representations for the classification was fair (κ 0.29 95% CI 0.28-0.30). Inter-rater agreement was lowest for radiographs (κ 0.21 95% CI 0.19-0.22) and increased for other representations with agreement being highest when using analytic defect models (κ 0.46 95% CI 0.43-0.48). Overall intra-rater agreement was moderate (κ 0.51 95% CI 0.42-0.60). Intra-rater agreement was lowest for radiographs (κ 0.40 95% CI 0.23-0.57), and highest for ratings including analytic defect models (κ 0.64:95% CI 0.46-0.82). Virtual 3D models with quantitative analytic defect representations upscaled acetabular defect scores in comparison to standard radiographs.

CONCLUSIONS

Using 3D CT imaging with statistical shape models doubles the intra- and inter-rater reliability and results in upscaling of acetabular defect classification when compared to standard radiographs. This method of evaluating defects will aid in planning surgical reconstruction and stimulate the development of new classification systems based on advanced imaging techniques.

Improvement of surgical time and functional results after do-it-yourself 3D-printed model preoperative planning in acetabular defects Paprosky IIA-IIIB

INTRODUCTION

The correct positioning of the implant in revision total hip arthroplasty (rTHA) is critical to obtaining substantial functional outcomes, and to avoiding complications. Current literature supports three-dimensional (3D)-printed models as potentially useful tools for preplanning, as well as the "do it yourself (DIY)" methodology to reduce both the time and costs of this procedure. However, no study has determined the efficacy of both methods combined in a cohort of patients with severe acetabular defects. In the lack of bibliography, we performed rTHA after preoperative planning by DIY-3D-printed models to evaluate its influence in: 1) the surgical time, 2) the functional scores, 3) the intra and postoperative complications, and 4) the reconstruction of the center of rotation (COR) of the hip.

HYPOTHESIS

Preoperative planning through 3D-DIY printed models will both improve the accuracy of the implant positioning, and the surgical time, leading the latter to improved functional scores and reduced complications.

MATERIALS & METHODS

A comparative study of 21 patients with Paprosky IIB to IIIB acetabular defects who underwent rTHA after 3D-printed model preoperative planning by the DIY method between 2016 and 2019 was conducted. A historical cohort of 24 patients served as the comparator. Surgical time, reconstruction of the COR, functional scores, and complications were analyzed.

RESULTS

The mean follow-up was 32.4 (range, 12 to 60) months. All the patients showed significant improvement of the Harris hip score (HHS) after the operation (3D group: 26.58±10.73; control group 22.47±15.43 (p=0.00)). In the 3D-printed model preoperative planning group the mean operation time and the intraoperative complications were significantly lower (156.15±43.03min vs 187.5±54.38min (p=0.045); and 19% vs 62.5% (p=0.003), respectively), and the HHS and patient satisfaction score (PSS) were significantly greater (83.74±8.49 vs 75.59±11.46 (p=0.019); and 8.17±0.88 vs 7.36±1.17 (p=0.023), respectively). No differences were found in the postoperative complications, nor in the restoration of the COR as determined from the acetabular index, verticalization or horizontalization, although the acetabular index was closer to the intended one in the 3D-printed model planning group (46.67°±7.63 vs 49.22±8.1 (p=0.284)).

CONCLUSION

Preoperative planning of severe acetabular defects through 3D-printed models shortens the surgical time, leading to a decrease in complications and thus to better functional outcomes and greater patient satisfaction. Moreover, the DIY philosophy could decrease both the time and costs of traditional 3D planning.

LEVEL OF EVIDENCE

III, retrospective case matched study.

A novel and secure technique of stemmed acetabular cup implantation in complex hip reconstructions: a comparative study and technical note

PURPOSE

The stemmed acetabular cup (SAC) can be considered in several complicated situations. This type of prosthesis uses the iliac isthmus, which is most often preserved, thus allowing solid anchorage. Its implantation is prone to mechanical complications intraoperatively, such as extra-isthmic effraction, fracture, and early aseptic loosening. The aim of our study was to compare a new technique using a flexible motorized reamer combined with isthmus catheterization (Group A) versus the standard technique deploying a rigid reamer alone (Group B).

MATERIALS AND METHODS

A retrospective analysis was carried out of the SACs implanted at our hospital. The main evaluation criterion was visualization of extra-isthmic effraction (EIE) of the stem.

RESULTS

Fifty-six SACs (Integra Lepine®, Genay, France) were implanted, 31 in group A and 25 in group B. The mean follow-up was 21.6 months ± 22.3. This study found fewer EIEs using a flexible motorized reamer (0 versus 5, p = 0.014), less perioperative bleeding (p = 0.054), and less aseptic loosening in group A (p = 0.034). There was no difference in terms of infection or other mechanical complications post-operatively between the two groups.

CONCLUSION

Using iliac catheterization combined with a flexible motorized reamer when implanting a SAC helps to avoid EIE and it also appears to reduce complications such as peri-operative bleeding and early aseptic loosening. We recommend use of this surgical technique rather than a rigid reamer alone, and this new technique should allow widespread and more accessible use of this specific type of implant.

Modular revision strategy with bispherical augments in severe acetabular deficiency reconstruction

PURPOSE

Reconstruction of severe acetabular deficiency is extremely challenging in total hip arthroplasty (THA) revisions. Novel bispherical augments were designed to fill acetabular bone loss and facilitate restoration of hip center of rotation (HCOR). Current study aims to compare the outcomes of bispherical augments and tantalum augments.

METHODS

Between July 2017 and December 2018, bispherical augments (BA group) were implanted in 25 patients (25 hips) and 22 patients (22 hips) underwent porous tantalum augments (TA group) reconstruction in revision THA. Clinical and radiographic results were evaluated for 25 hips in BA group and 20 hips in TA group at the final follow-up. The mean duration of follow-up was 2.9 years (range, 2.2 ~ 3.7) in BA group and 2.9 years (range, 2.3 ~ 3.8) in TA group.

RESULTS

Harris hip scores, HCOR, and leg length discrepancy (LLD) correction did not differ between the treatment groups. The bispherical augments were located more closer to the medial-superior part (zone II) of acetabular shell while the majority of tantalum augments were located at the lateral-superior part (zone I) (P = 0.010). More screws were used in the BA group for augment fixation (mean 2.1 vs. 1.3) (P = 0.000). There was no evidence of loosening or migration in all hips. Only one dislocation occurred in BA group and treated with closed reduction, no recurrence of instability up to the final follow-up.

CONCLUSION

The clinical and radiological outcomes of bispherical augments were comparable with tantalum augments; this technique was a reliable alternative method in severe acetabular deficiency reconstruction.

Multicup reconstruction technique for the management of severe protrusio acetabular defects

Background

In revision hip arthroplasty, managing the large protrusio acetabular defects remains a challenge. The report described a novel technique which employs a trabecular metal revision shell as a super-augment to buttress the superior medial structure.

Methods

Between January 2015 and December 2018, the multicup reconstruction was performed in 21 patients with severe protrusio acetabular defects. The revision shell, plus two similar porous acetabular components was implanted into the initial shell to create a “multicup” construct. The functional outcomes were evaluated in terms of the Harris Hip Score. Acetabular loosening, restoration of hip center of rotation, and bone ingrowth etc., were radiographically assessed. The survival rate of the implants was also evaluated.

Results

A followup lasting a mean time of 31 months (range, 18–57 months) revealed that the average Harris Hip Score improved from preoperative 37.0 ± 7.1 to postoperative 76.4 ± 9.0. There were no revisions due to acetabular loosening. The horizontal offset increased by an average of 14 mm, and the vertical offset decreased by an average of 18 mm. Eighteen of the 21 patients (86 %) met at least 3 of 5 criteria associated with bone ingrowth. The survivorship free from re-revision for acetabular loosening after 2 years was 100 %.

Conclusions

The multicup reconstruction technique was a simplified re-revision procedure for managing the severe protrusio acetabular defects and could achieve a high survival rate.

Level of evidence

Therapeutic study, Level IVa.

Do Acetabular Buttress Augment Pose Risk to the Superior Gluteal Nerve? A Cadaveric Study

Background

Management of acetabular defects in total joint reconstruction can be challenging. Various algorithmic approaches have been developed, with some recommending using posterosuperior acetabular buttress augments for severe defects. The superior gluteal nerve lies in close proximity to their application, and damage to it results in deterioration of hip stability and gait mechanics. There has been investigation into the relationship of the superior gluteal nerve to various anatomic points. To our knowledge, no study exists examining the relationship between the acetabular rim and the superior gluteal nerve for the application of these particular devices.

Methods

Ten adult cadaver specimens were examined. A reproducible technique in relation to the typical placement of a buttress augment was used. From a distance of 20 millimeters (mm) lateral to the greater sciatic notch, the distance from the superior gluteal nerve to the posterosuperior acetabular rim was measured.

Results

The average distance between the posterosuperior acetabular rim and the superior gluteal nerve was found to be 52 mm, ranging from 48 mm to 60 mm.

Conclusion

With proprietary acetabular augments measuring up to 68 mm in length, the superior gluteal nerve could be at substantial risk with placement of these devices. Surgeons should take great care with dissection for and intraoperative placement of these devices, and particularly strive for optimized prosthetic hip stability to mitigate the risk of dislocation from nerve injury. To our knowledge, this study is the first of its kind and provides valuable anatomic and operative knowledge during these highly complex cases.

Reverse augmentation technique in hip revision arthroplasty: a new strategy for the management of acetabular reconstruction

BACKGROUND

The principle of acetabular total hip revision (THR) is based on acetabular reconstruction and restoration of the center of rotation. The use of augmentation in high cranial acetabular defects combined with a cementless revision shell was studied sufficiently. This study aimed to report a case with the use of an augment inside a cementless revision shell as a reverse augmentation technique.

METHODS

We describe the case of an 86-year-old female patient with a massive acetabular defect during second revision for total hip arthroplasty (THA). Two problems occurred: (1) a fixed cemented stem with a nonmodular head size of 33 mm and (2) a high acetabular defect with an elevated rotation center.

RESULTS

With the distraction technique, allograft filling was used to reconstruct the acetabular defect. A cementless revision shell (REDAPT, Smith and Nephew) with a size of 78 mm was used to stabilize the defect. Locking screws placed cranially and distally were used to stabilize the cup for secondary osseointegration. An augment was placed inside the cup to reconstruct the rotation center. A customized polyethylene liner (outer diameter, 54 mm/inner diameter, 33 mm) was positioned below the augment in the revision cup to reconstruct the center of rotation. An 18-month postoperative X-ray analysis showed a stable construct with full secondary osseointegration.

CONCLUSION

This is the first report of an augment used for a reverse technique inside a cementless shell to restore the center of rotation with the use of a customized polyethylene liner. This might be a reliable option for reconstruction of the center of rotation in large cementless revision cups in acetabular Paprosky type III defects. This technical note shows the possibility of using an augment as a reverse technique in a cementless revision cup.

Mid-term results of revision surgery using double-trabecular metal cups alone or combined with impaction bone grafting for complex acetabular defects

BACKGROUND

Revision surgery for complex acetabular defects is still technically challenging. In this study, we discussed and compared the clinical and radiological outcomes of revision surgery between two methods using double-trabecular metal (TM) cups alone or combined with impacting bone grafting (IBG).

METHODS

The records of 18 patients (18 hips) who underwent revision surgery using double-trabecular metal (double-TM) cups between 2008 and 2016 were retrospectively reviewed. All the patients were diagnosed with Paprosky III acetabular defects. The acetabular defects were reconstructed by double-TM cups alone or in combination with IBG. We used the modified Harris Hip Score (mHHS), University of California, Los Angeles (UCLA), and Short Form 36 (SF-36) to evaluate the clinical outcomes. Pelvis plain X-ray was used to assess hip center of rotation (COR), abduction angle and anteversion angle of acetabular cup, and incorporation of the bone graft to host bone.

RESULTS

The median follow-up time was 61.0 (IQR 56.0 to 65.8) months. No patients underwent re-revision for loosening or any other reasons. Complications included 3 patients (16.7%) with early dislocation and 3 patients (16.7%) with delayed wound healing. The average mHHS and UCLA preoperatively were 44.1 ± 4.0 (range 35 to 50) and 2.6 ± 0.7 (range 2 to 4), respectively and at the last follow-up were 73.7 ± 4.2 (range 68 to 85) and 7.3 ± 0.5 (range 7 to 8), respectively. The mean SF-36 scores at the last follow-up were improved significantly than preoperative scores, especially in bodily pain category (P < 0.05). The average limb-length discrepancy (LLD) decreased significantly from 24.2 ± 2.6 (range 20 to 32) mm preoperatively to 5.8 ± 1.8 (range 3 to 9) mm at the last follow-up, respectively. However, there was no significant difference between two methods at the last follow-up in terms of mHHS, UCLA, SF-36, LLD, and hip COR (P > 0.05). Radiographic evaluation demonstrated bone graft incorporation in all hips in the follow-up.

CONCLUSIONS

Defect reconstruction using double-TM cups alone or combined with IBG are practical and reliable treatment options for Paprosky III acetabular defects without pelvic discontinuity. Nevertheless, high postoperative complication rate, especially in terms of dislocation, remains a challenge.

Mid-term follow-up after all-size acetabular revision and proposal for a stability classification system

BACKGROUND

There is a trend for using jumbo cups/oblong devices for acetabular reconstruction as alternative to biological solutions. We report about a spectrum of reconstruction methods and their mid-term results.

METHODS

Inclusion of 214 consecutive patients undergoing total hip arthroplasty revision surgery. Patients were examined using the Harris Hip Score (HHS). Based on the intraoperative acetabular defect situation, cases were classified into 1 of 5 possible categories of a stability classification for acetabular replacement (SCAR).

RESULTS

Mean HHS improved from 42 preoperatively (range 12-62) to 77 (range 54-90; p < 0.05) 6 months after operation. There were significant differences of the pre-and postoperative HHS between SCAR subgroups (p < 0.05). Inter-observer reliability of the SCAR was high (kappa 0.94 (95% CI, 0.90-0.98)). Re-revision was performed in 15 cases (7%).

CONCLUSION

The SCAR classification is a practicable tool for intraoperative decision-making as it provides standardised treatment recommendations.

Cup-Cage Solution for Massive Acetabular Defects: A Systematic Review and Meta-Analysis

Our systematic review compiled multiple studies and evaluated survivorship and clinical outcomes of cup‐cage construct usage in the management of massive acetabular bone defects. This systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA) guidelines. Various combinations of “acetabular”, “pelvis”, “cup cage” and their corresponding synonyms were used to search relevant articles in the Cochrane, EMBASE, and PubMed databases. Basic information of the functional scores, implant revision rate, and complication rate were selected as outcomes for analysis. Finally, a total of 11 articles published between 1999 and 2019 were selected, which include 232 patients with an average age of 68.5 years (range, 30–90). The mean follow‐up period was 48.85 months (range, 1–140). Our study shows that the cup‐cage construct has a good clinical outcome with a low revision rate and a low complication rate. Improved clinical outcomes of cup‐cage constructs were seen with a revision rate of 8% and an all‐cause complication rate of 20%. The most commonly reported complication was dislocation, followed by aseptic loosening, infection, and nerve injuries. In summary, it is a promising method for managing large acetabular bone defects in total hip revision.

Total hip arthroplasty following acetabular fracture: a clinical and radiographic outcome analysis of 67 patients

BACKGROUND

Total hip arthroplasty (THA) is a challenging option for the treatment of posttraumatic arthritis due to acetabular fractures.

METHODS

The study aimed to determine the short- and mid-term clinical and radiographic results of THA following acetabular fracture. The fracture pattern, the extent of injury and the initial fracture treatment were considered to evaluate the influence of these factors on the clinical-radiographic outcome.

RESULTS

67 patients who received THA for the treatment of posttraumatic osteoarthritis after acetabular fracture between January 2007 and December 2012 were analyzed consecutively. The group consisted of 13 female (19%) and 54 male (81%) patients with a mean age of 59 (25-87) years at the time of THA. The time between acetabular injury and arthroplasty was 107 (1-504) months on average. The all-cause 8-year survival rate was 0.87% (0.76-0.93) and there were 8 revisions, half of them were due to aseptic loosening of the cup. The Harris Hip Score achieved was 75.7 ± 21.3 (26.9-100) points. Prior to THA, heterotopic ossifications were detected in 28% and after THA implantation in 42%.

CONCLUSION

The decrease of the interval between injury and arthroplasty was associated with increasing patient age (p = 0.001) and surgical treatment of the acetabular fracture (p = 0.04). Complex fracture patterns were accompanied by acetabular bone defects more often than simple patterns (p = 0.03). Overall, arthroplasty due to posttraumatic osteoarthritis after acetabular fracture resulted in decreased overall survival rates and poorer clinical outcome as compared to primary arthroplasty.

An alternative treatment option for Paprosky Type IIIb acetabular defect using multiple tantalum wedges - A case report

The treatment of severe acetabular defects in revision total hip arthroplasty (Paprosky type IIIa and IIIb) is demanding and choosing the appropriate surgical technique remains controversial. The introduction of trabecular metal augments has led to a variety of new treatment options. The authors present a case of a Paprosky Type IIIb acetabular defect due to eight subsequent revisions of the left hip. The patient was treated with an alternative treatment option using multiple tantalum wedges. Anatomical reconstruction was achieved and at 12 months follow-up, the patient was pain free and was able to walk without walking aids.

Three-dimensional technology assisted trabecular metal cup and augments positioning in revision total hip arthroplasty with complex acetabular defects

BACKGROUND

Revision total hip arthroplasty (THA) with large acetabular defect remains a challenge. Though trabecular metal (TM) cup and augments have been introduced in defect reconstruction with good result, the accurate positioning of implant is important to avoid complications. Therefore, we aimed to evaluate the usefulness of three-dimensional (3D) simulation and 3D model in assisting implant positioning during complex revision THA.

METHODS

Sixteen patients (18 hips) who underwent revision THA with a Paprosky type III acetabular defect were analyzed retrospectively. Placement of acetabular cup and TM augments was simulated with 3D simulation software and 3D model preoperatively. Cup anteversion, abduction angle, and hip center were measured in each case preoperatively and postoperatively. Primary outcome was the percentage of outliers according to Lewinnek safe zone and Harris hip score (HHS). Secondary outcome was the correlation between the 3D planned and the postoperative value.

RESULTS

The percentage of outliers was significantly corrected from 77.78% (14/18) preoperatively to 38.88% (7/18) postoperatively (p = 0.04). There was a significant correlation between mean planned cup anteversion and postoperative value (13.39 vs 11.99, r = 0.894; p < 0.001). There was a significant correlation between mean planned abduction and postoperative value (42.67 vs 44.91, r = 0.921, p < 0.001). The number of planned and used augments was the same in all the cases. In 15 cases (83.33%), the size of planned and used TM augments was the same. The HHS was significantly improved at final follow-up (80.94 vs 27.50, p < 0.001). No cases presented dislocation or radiological signs of loosening.

CONCLUSION

Preoperative 3D simulation and model were considered the useful method to assist implant positioning in revision THA with complex acetabular defect, with moderate to high accuracy and satisfied clinical outcome.

Triflange acetabular reconstruction for pelvic discontinuity through a direct anterior approach

A 74-year-old female patient presented to our clinic with pelvic discontinuity after multiple revision total hip surgeries requiring custom triflange acetabular reconstruction, which we accomplished through a direct anterior approach to the hip. The direct anterior approach to the hip has grown in popularity but still has the reputation of being a minimally invasive approach without the capacity for extensile exposure in the revision setting. We describe the extensile technique and demonstrate through our case the ability to perform the most challenging cases through this approach and discuss the potential benefits of its utilization.

[Allogeneic bone transplantation in hip revision surgery : Indications and potential for reconstruction]

The increasing number of people having joint replacements will lead to increasing numbers of revision operations. The transplantation of allogeneic bones might reconstruct bone defects and improve long-term anchorage of the implant. A sufficient primary stability of the implanted construct is necessary to achieve osseous incorporation as well as tight contact between the implanted allogeneic and host bones. Transplantation of bone can contribute to downgrading acetabular defects and so avoid bigger reinforcement implants. An improvement of bone stock due to reconstruction of femoral bony defects might also reduce the size of the stem necessary since the indication might be limited in case of extensive bone defects. According to good longterm results of modular revision stems the Impaction-Bone-Grafting has not yet generally been established.

Double-trabecular metal cup technique for the management of Paprosky type III defects without pelvic discontinuity

INTRODUCTION:

Modular reconstruction systems based on trabecular metal (TM) prosthetic components have been increasingly used in the last decade for the management of severe acetabular bone defects. The aim of this study was to assess the clinical and radiographic outcomes of double-cup technique for the management of Paprosky type III defects without pelvic discontinuity.

METHODS:

A retrospective review was performed for all patients undergoing acetabular reconstruction with 2 TM cups at a tertiary referral centre between 2010 and 2015. Harris Hip Scores (HHS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores were evaluated preoperatively and at the latest follow-up. Radiographic assessment of the hip centre of rotation (COR) position and leg length discrepancy (LLD) was performed preoperatively and postoperatively. Osteolysis and radiolucencies, loosening of the implants, and heterotopic ossifications were evaluated with the latest follow-up radiographs.

RESULTS:

Patients included 5 men and 11 women (16 hips) with an average age of 68 (45-81) years. Acetabular bone defects included 9 Paprosky type IIIB and 7 type IIIA defects. No pelvic discontinuities were registered. The mean follow-up was 34 (24-72) months. HHS and WOMAC scores, LLD and COR position significantly improved after surgery. In only 1 (6.3%) hip a not progressive radiolucent line adjacent the acetabular construct was noted. Heterotopic ossifications were found in 2 (12.5%) hips. No patients underwent acetabular components revision surgery for any reason.

CONCLUSION:

The double-cup technique could be considered an effective management of selected Paprosky type III defects without pelvic discontinuity providing excellent clinical and radiographic outcomes in the short term.

Acetabular reconstruction using a cage in complex primary total hip replacement in a developing country: An assessment of early functional outcome

Background

Acetabular reconstruction following bone loss is a major challenge facing the arthroplasty surgeon. Traditionally, the armamentarium for the treatment of large bone defects (Paprosky Type 2C or 3) included antiprotrusio cages (APC). The aim of this study is to determine the pattern of presentation and assess the early functional outcome of patients who had undergone acetabular reconstruction using APC in complex primary total hip replacement (THR).

Patients and Method

Between November 2008 and November 2015, 38 THR were carried out in 35 patients who required acetabular reconstruction, at Davidson and Judith Consultants Clinics Enugu, Nigeria.

Results

There were 25 males and 10 females, with a ratio of 2.5:1. The average age of the patients was 61.33 ± 6.92 with a range of 56 to 72. The mean pre-op Harris score was 49.02 ± 2.3.The mean post-op Harris hip score (HSS) was 88.75 ± 10 (P < 0.001) at one year and 92.25 ± 13 (P < 0.001) at 5 years. The etiology showed that most (52.63%) of our patients had primary osteoarthritis with Type 3 acetabular defect. Two (5.26%) patients had the following complications: dislocation (2.63%) and screw breakage (2.63%). The minimum follow-up period was 5 years.

Discussion

After follow-up at 1 year and 5 years, the hips showed significant improvement concerning pain, gait, and mobility based on HHS and were able to return to their various professions.

Conclusion

APC provides a satisfactory solution for patients who present with acetabular deficiency in complex primary THR.

Cup-on-cup technique to manage severe protrusio acetabular defects

Previous studies have demonstrated that revision of total hip arthroplasty consumes considerably more resources than the primary procedure. Worse, patients who need revision procedures are more likely to have radiographic evidence of acetabular and femoral bone loss than those undergone primary total hip arthroplasty. Many techniques have been introduced to manage different conditions of acetabular deficiencies. We describe a rare case of a 67-year-old man with severe acetabular bone loss, which was caused by a long-term loose acetabular component and was successfully managed by cup-on-cup technique. We also discuss the similarities and differences between cup-on-cup and cup-in-cup techniques in the management of protrusio acetabular defects, with a case-based approach.

Utility of Radiographs, Computed Tomography, and Three Dimensional Computed Tomography Pelvis Reconstruction for Identification of Acetabular Defects in Residency Training

Purpose

The Paprosky classification system of acetabular defects is complex and its reliability has been questioned. The purpose of this study was to evaluate the effectiveness of different radiologic imaging modalities in classifying acetabular defects in revision total hip arthroplasty (THA) and their value of at different levels of training.

Materials and Methods

Bone defects in 8 revision THAs were classified by 2 fellowship-trained adult reconstruction surgeons. A timed presentation with representative images for each case (X-ray, two-dimensional computed tomography [CT] and three-dimensional [3D] reconstructions) was shown to 35 residents from the first postgraduate year of training year of training (PGY-1 to PGY-5), 2 adult reconstruction fellows and 2 attending orthopaedic surgeons. The Paprosky classification of bone defects was recorded. The influence of image modality and level of training on classification were analyzed using chi-square analysis (alpha=0.05).

Results

Overall correct classification was 30%. The level of training had no influence on correct classification (P=0.531). Using X-ray led to 37% correctly identified defects, CT scans to 33% and 3D reconstructions to 20% of correct answers (P<0.001). There was no difference in correct classification based defect type (P<0.001). Regardless of level of training or imaging, 64% of observers recognized type 1 defects, compared to only 16% correct recognition of type 3B defects.

Conclusion

Using plain X-rays led to an increased number of correct classification, while regular CT scan and 3D CT reconstructions did not improve accuracy. The classification system of acetabular defects can be used for treatment decisions; however, advanced imaging may not improve its utilization.

Reconstruction of AAOS type III and IV acetabular defects with the Ganz reinforcement ring: high failure in pelvic discontinuity

BACKGROUND

Large acetabular defects and pelvic discontinuity represent complex problems in revision total hip arthroplasty. This study aimed to investigate whether reconstruction with the Ganz reinforcement ring would provide durable function in large acetabular defects.

PATIENTS AND METHODS

46 hips (45 patients, 19 male, 26 female, mean age 68 years) with AAOS type III and IV defects undergoing acetabular revision with the Ganz reinforcement ring were evaluated at a mean follow-up of 74 months (24-161 months). Fourteen patients died during follow-up. All surviving patients were available for clinical assessment and radiographic studies. Radiographs were evaluated for bone healing and component loosening. A Cox-regression model was performed to identify factors influencing survival of the Ganz-ring.

RESULTS

In the group of AAOS III defects, 3 of 26 acetabular reconstructions failed, all due to aseptic loosening. In pelvic discontinuity (AAOS IV), 9 of 20 hips failed due to aseptic loosening (n = 4), deep infection (n = 3), and non-union of the pelvic ring (n = 2). With acetabular revision for any reason as an endpoint, the estimated Kaplan-Meier 5-year survival was 86% in type III defects and 57% in type IV defects, respectively. The presence of pelvic discontinuity was identified as the only independent predictive factor for failure of the Ganz ring acetabular reconstruction (AAOS III vs. IV, Hazard ratio: 0.217, 95%, Confidence interval: 0.054-0.880, p = 0.032).

CONCLUSION

The Ganz reinforcement ring remains a favorable implant for combined segmental and cavitary defects. However, defects with pelvic discontinuity demonstrate high failure rates. The indications should therefore be narrowed to acetabular defects not associated with pelvic discontinuity.

The direct anterior approach for acetabular augmentation in primary total hip arthroplasty

Addressing acetabular bone defects can be difficult and depends on the amount of bone loss. Augments, either with bone or highly porous metals, are options that still allow the use of a hemispherical cup. Almost all previous research and publication on acetabular augments have focused on revision hip arthroplasty utilizing either a modified lateral or a posterolateral surgical approach. We describe 3 cases of augmenting acetabular bone defects through a direct anterior approach for primary total hip arthroplasty. We achieved proper cup placement, alignment, and augment incorporation while reconstructing complex acetabular deficiencies. All patients had complete pain relief and a satisfactory clinical outcome with stable radiographs at follow-up. With appropriate training, acetabular augmentation can be performed safely and efficiently with excellent clinical results through this approach.