Radiographic evaluation of screw position in revision total hip arthroplasty

Simulated full weight bearing following posterior column acetabular fracture fixation: a biomechanical comparability study

PURPOSE

The incidence of acetabular fractures (AFs) is increasing in all industrial nations, with posterior column fractures (PCFs) accounting for 18.5-22% of these cases. Treating displaced AFs in elderly patients is a known challenge. The optimal surgical strategy implementing open reduction and internal fixation (ORIF), total hip arthroplasty (THA), or percutaneous screw fixation (SF), remains debated. Additionally, with either of these treatment methods, the post-surgical weight bearing protocols are also ambiguous. The aim of this biomechanical study was to evaluate construct stiffness and failure load following a PCF fixation with either standard plate osteosynthesis, SF, or using a screwable cup for THA under full weight bearing conditions.

METHODS

Twelve composite osteoporotic pelvises were used. A PCF according to the Letournel Classification was created in 24 hemi-pelvis constructs stratified into three groups (n = 8) as follows: (i) posterior column fracture with plate fixation (PCPF); (ii) posterior column fracture with SF (PCSF); (iii) posterior column fracture with screwable cup fixation (PCSC). All specimens were biomechanically tested under progressively increasing cyclic loading until failure, with monitoring of the interfragmentary movements via motion tracking.

RESULTS

Initial construct stiffness (N/mm) was 154.8 ± 68.3 for PCPF, 107.3 ± 41.0 for PCSF, and 133.3 ± 27.5 for PCSC, with no significant differences among the groups, p = 0.173. Cycles to failure and failure load were 7822 ± 2281 and 982.2 ± 428.1 N for PCPF, 3662 ± 1664 and 566.2 ± 366.4 N for PCSF, and 5989 ± 3440 and 798.9 ± 544.0 N for PCSC, being significantly higher for PCPF versus PCSF, p = 0.012.

CONCLUSION

Standard ORIF of PCF with either plate osteosynthesis or using a screwable cup for THA demonstrated encouraging results for application of a post-surgical treatment concept with a full weight bearing approach. Further biomechanical cadaveric studies with larger sample size should be initiated for a better understanding of AF treatment with full weight bearing and its potential as a concept for PCF fixation.

Strategy to avoid vascular injuries in revision total hip arthroplasty with intrapelvic implants

Aims

Our objective was describing an algorithm to identify and prevent vascular injury in patients with intrapelvic components.

Methods

Patients were defined as at risk to vascular injuries when components or cement migrated 5 mm or more beyond the ilioischial line in any of the pelvic incidences (anteroposterior and Judet view). In those patients, a serial investigation was initiated by a CT angiography, followed by a vascular surgeon evaluation. The investigation proceeded if necessary. The main goal was to assure a safe tissue plane between the hardware and the vessels.

Results

In ten at-risk patients undergoing revision hip arthroplasty and submitted to our algorithm, six were recognized as being high risk to vascular injury during surgery. In those six high-risk patients, a preventive preoperative stent was implanted before the orthopaedic procedure. Four patients needed a second reinforcing stent to protect and to maintain the vessel anatomy deformed by the intrapelvic implants.

Conclusion

The evaluation algorithm was useful to avoid blood vessels injury during revision total hip arthroplasty in high-risk patients. Cite this article: Bone Jt Open 2022;3(11):859–866.

Intraoperative Radiographic Detection of Intrapelvic Acetabular Screw Penetration: Lessons Learned From Our Trauma Colleagues

BACKGROUND

Intraoperative vascular injury during total hip arthroplasty represents a catastrophic complication. Acetabular screw placement represents one possible mode of injury. The purpose of this study was to evaluate the utility of various fluoroscopic views in the detection of intrapelvic screw penetration.

METHODS

A radiopaque pelvis Sawbones model was instrumented with a hemispherical acetabular component. Four intrapelvic quadrants were defined. Screws were placed, 3 in each quadrant, and imaged sequentially at 3 depths: 0 mm, 5 mm, and 10 mm penetrated. Eight fluoroscopic images were used: anteroposterior, inlet, outlet, iliac oblique, obturator oblique, "down the wing," obturator outlet, and a "quad" view. Three blinded, independent surgeons evaluated the images for intrapelvic screw penetration. Images were analyzed in isolation and as a "triple-shot series" consisting of the "quad," obturator outlet, and iliac oblique views. Sensitivity and specificity values were then calculated.

RESULTS

In isolation, the "quad" view had the highest sensitivity for screw penetration (62%). The triple-shot series was found to be 100% sensitive in all 4 quadrants for detecting 10 mm of screw penetration. The specificity of the series was found to be 100% in all quadrants except for the posterior superior quadrant where it was 67%. Interobserver agreement approached perfection (Kappa ≥0.947) between all surgeons (P < .001) when using the 3-view series.

CONCLUSIONS

This study is the first to assess the use of fluoroscopy in the detection of intrapelvic penetration of transacetabular screws. We found that a 3-radiograph series provided a sensitive and specific metric for the detection of intrapelvic screw penetration.

External iliac pseudoaneurysm secondary to medial wall penetration of an acetabular screw: a rare cause of total hip arthroplasty failure 15 years after implantation

Vascular injury as a result of total hip arthroplasty (THA) represents an uncommon complication. Although these injuries typically present acutely, delayed presentation has been reported. In this case, a 70-year-old female presented with groin pain and medial thigh numbness 15 years after a left THA. After initially being misdiagnosed, repeat imaging revealed a large external iliac pseudoaneurysm as a result of a transacetabular screw penetrating the medial acetabular wall. The patient underwent staged endovascular exclusion of the pseudoaneurysm, percutaneous drainage, and revision THA. She had resolution of her symptoms. To our knowledge, this is the only reported case of a late vascular injury related to an aseptic THA with well-fixed components. Staged treatment with endovascular exclusion and revision THA is a viable approach.

Effect of design on the initial stability of press-fit cups in the presence of acetabular rim defects: experimental evaluation of the effect of adding circumferential fins

PURPOSE

This experimental study was undertaken to examine the fixation characteristics of a six-finned acetabular cup in both primary and revision arthroplasty in comparison with two other commonly used cup designs without fins.

METHODS

All three cup designs (Ananova® [Intraplant], Plasmacup® NSC [Aesculap]; Exceed ABT™ [Biomet]) were implanted into validated models of normal and revision acetabula. The defect models were designed to simulate a dorso-cranial rim defect of 90° width and 10 mm in depth (moderate rim defect) and a dorso-cranial rim defect of 130° width and 15 mm in depth (severe rim defect). The fixation strength of the three cup designs was tested by cyclically edge-loading the implanted cups using a mechanical testing machine.

RESULTS

The six-finned Ananova implant exhibited greater resistance to foam-cup interface motion than both the Plasmacup and Exceed ABT implants. The largest average differences were observed in the resistance to ultimate spin-out, with Ananova outperforming Exceed ABT and Plasmacup by 26% and 17% in the moderate and by 36% and 38% in the severe defect models, respectively.

CONCLUSIONS

The six-finned Ananova cup was significantly more resistant to edge loading both in the normal acetabulum and in acetabula with moderate to severe dorso-cranial rim defects than cup designs without fins, indicating that it may cover a wider range of clinical indications than conventional press-fit cups and provide clinicians with the confidence that, in primary and simple revision arthroplasty, adequate fixation strength can be obtained.

Location of intrapelvic vessels around the acetabulum assessed by three-dimensional computed tomographic angiography: prevention of vascular-related complications in total hip arthroplasty

BACKGROUND

During total hip arthroplasty (THA), the external iliac, femoral, and obturator vessels are at risk of vascular injury when penetrating the inner cortex of the pelvis. The purpose of this study was to clarify the location of these vessels using three-dimensional computed tomographic angiography (3DCT-A).

METHODS

We enrolled 100 subjects (200 hips) without hip disease and performed examinations on the following. (1) External iliac-femoral vessels: we measured the shortest distance from these vessels to the pelvis on axial CT images and investigated the factors affecting distance. The anatomical course of the iliac artery was classified as straight, curved, or tortuous, and the correlation between course and age was established. (2) Obturator vessels: we measured the shortest distance from the obturator vessels to the quadrilateral surface on axial CT images. (3) Visualization of pelvic vessels was through the pelvis by dual-phase 3DCT-A.

RESULTS

(1) The external iliac vein was located significantly closer to the pelvis than the artery, especially on the left side and in aged and female subjects. The single-curved and tortuous double-curved vessel types were found in aged subjects, and external iliac vessels of these types were closer to the pelvis than vessels of the straight type. In 36 subjects, the external iliac veins lay directly on the osseous surface of the pelvis (right 16, left 36). Of these 36 subjects, only one had straight-type vessels. (2) Obturator vessels were located just behind the acetabulum near the obturator foramen. (3) Reconstructed 3DCT images enabled us to visualize the pelvic vessels and demonstrated the danger area for penetrating the inner cortex of the pelvis.

CONCLUSION

Understanding the anatomical orientation of the pelvic vessels around the acetabulum using 3DCT-A could be helpful for preventing vascular injury during THA.

Iliopsoas tendonitis due to the protrusion of an acetabular component fixation screw after total hip arthroplasty

Postoperative pain after total hip arthroplasty can have a wide range of underlying causes. Iliopsoas tendonitis secondary to the impingement of this tendon is a relatively rare cause of pain after arthroplasty. This condition is characterized by pain on active flexion and an absence of signs or symptoms of loosening or infection. In this report, we describe the case of a patient who had signs and symptoms of iliopsoas tendonitis secondary to the protrusion of an acetabular fixation screw through the ilium after primary total hip arthroplasty. Nonoperative treatment was ineffective, and the patient ultimately underwent surgical removal of the screw. The severity of the patient's symptoms decreased significantly after the operation.

Safe zone for transacetabular screw fixation in prosthetic acetabular reconstruction of high developmental dysplasia of the hip

BACKGROUND

Prosthetic reconstruction of hips with Crowe type-IV developmental dysplasia (a high complete dislocation) is technically demanding. Insufficient osseous coverage and osteopenic bone stock frequently necessitate transacetabular screw fixation to augment primary stability of the metal acetabular shell. We sought to determine whether a previously reported quadrant system for screw fixation of the acetabular cup can be applied in patients with high dislocation of the hip and to define a specialized safe zone for screw fixation in these hips, if needed.

METHODS

Using volumetric computed tomographic data and image-processing software, we made three-dimensional reconstructions of the osseous and vascular structures in eighteen hips in twelve patients. We virtually reconstructed a cup in the true acetabulum and dynamically simulated transacetabular screw fixation. We mapped the hemispheric cup into several areas and, for each, measured the distance between the virtual screw and the external iliac (femoral) and obturator blood vessels. In the six patients with unilateral high dislocation of the hip and a relatively normal, contralateral hip, the six relatively normal hips served as controls.

RESULTS

Reconstruction of the cup at the level of the true acetabulum shifted the center of rotation anteroinferiorly in the hips with a high, complete dislocation. Screws guided by the quadrant system frequently injured the obturator blood vessels in the hips with a high dislocation. In these patients, the safe zone shifted as a result of moving the prosthetic cup.

CONCLUSIONS

The quadrant system, although helpful in determining screw placement in hips with a normal center of rotation, can be misleading and of less value in guiding screw insertion to augment acetabular shells for hips with a high dislocation. We believe that a safe zone specific to hips with a high dislocation should be used to guide transacetabular screw fixation.

Acetabular anatomy and transacetabular screw fixation at the high hip center

A quadrant system that defines the safe acetabular locations for screw placement exists for the anatomic hip center. We wanted to develop a similar system for the high hip center. The purposes of our study were to identify the anatomic structures at risk during placement of transacetabular screws in the high hip center, to identify maximum bone depth for screw purchase, and to determine if a high hip center quadrant system could be validated to guide placement of screws during acetabular arthroplasty. For this cadaver study of nine pelves, an acetabulum was reamed superiorly into the high hip center a distance equal to (1/2) of the native acetabular diameter. Screws exiting the acetabular bone by 15 mm were inserted before a computed tomography scan and a precise anatomic dissection were done. Structures at risk of penetration by screws include the external iliac vessels, the obturator nerve and vessels, the superior gluteal nerve and vessels, and the sciatic nerve. We found that a quadrant system at the high hip center can demarcate safe zones for screw placement. At the high hip center, only the peripheral (1/2) of the posterior quadrants are safe for screw placement.