Transacetabular Screw Research Articles

Obtaining optimum screw placement for revision acetabular prostheses using the sciatic notch as reference

BackgroundThe use of transacetabular screws aid greatly in attaining acetabular component stability during acetabular revision surgery. There are, however, definite risks involved when using this technique. Inserting screws in the posterior superior safe zone has been advocated as a way to do this safely, but recent studies have shown that this does not hold true in conditions where acetabular anatomy is distorted or where the hip centre of rotation has moved. A method to insert these screws more accurately and safely is proposed. Questions/Purposes(1) Can using the greater sciatic notch as reference point when inserting transacetabular screws for revision acetabular cups ensure accurate and safe placement of screws? (2) How does this proposed new method compare with the posterior superior safe zone method? MethodsWith the use of an observational anatomic study we have developed a new method for the insertion of long transacetabular screws. This method uses the greater sciatic notch as a reference point. Our method was tested on 16 cadaveric hips (reamed to simulate revision conditions) and compared to the safe zone method. ResultsOur method achieved placement of 1–3 screws in the target area in all hips without penetration into the pelvis or sciatic notch. With the use of the safe zone only as reference the pelvis was penetrated 7 times and the sciatic notch twice. ConclusionUsing the greater sciatic notch as a reference guide enables the surgeon to engage a supportive bar of bone for one or more long home run screws whilst minimizing penetration of the pelvis and sciatic notch. In this study our method was superior to using the safe zone in isolation.

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

BackgroundIntraoperative 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.MethodsA 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.ResultsIn 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.ConclusionsThis 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.

Anthropometric Measurement About the Safe Zone for Transacetabular Screw Placement in Total Hip Arthroplasty in Asian Middle-Aged Women: In Vivo Three-Dimensional Model Analysis

BackgroundAlthough the pelvic vascular injury caused by a transacetabular screw is rare, it is a major local complication of total hip arthroplasty. We aimed to obtain anthropometric data about the safe zone for the placement of transacetabular screws by analyzing the three-dimensional (3D) reconstruction model and determine the safe length of transacetabular screws by performing the 3D simulated surgery. MethodsWe reviewed 50 hips of 25 patients who underwent lower extremity angiographic computed tomography scans retrospectively. We reconstructed the 3D models of 50 hips with normal pelvic bone and vascular status using the customized computer software. We measured the central angle and safe depth of the safe zone of the transacetabular screws on the 3D models. We also performed the 3D simulated surgery to confirm the safe length of screws in each hole of the customized cup implant. ResultsThe measured central angle of the posterior-superior area was 79.5°. And we determined a mean safe depth of 49.8 mm in the safe zone, with a central angle of 47.7°. During the 3D simulated surgery, we determined a mean safe length of the transacetabular screw of 43.3 mm when applied to a lateral hole on a line bisecting the posterior-superior area. ConclusionAlthough our study was limited by the use of a virtual computer program, the quantitative measurements obtained can help reduce the incidence of pelvic vascular injury during transacetabular screw fixation in total hip arthroplasty.

Biomechanical research on contour cage with transacetabular screws fixation in revision total hip arthroplasty

BackgroundUse biomechanical technique to access the strain distribution and stability of Contour anti-protrusion cage with or without the whole circumference acetabular cup fixation by the transacetabular screws. MethodsPelvic specimens from 10 male cadavers were used for the biomechanical test. The models of type C bone defect were copied according to the AAOS classification. Group 1: the contour reconstruction ring was fixed only by flange screws; Group 2: the contour reconstruction ring was fixed both by flange screws and transacetabular screws in dome. Under load in Heel Strike, Midstance, and Toe off phase, the transverse and longitudinal strains were measured in both the superior measure site near the root of the iliac wing and the inferior measure site near the root of the ischium. The relative displacement between the anterior inferior spine and the root of ischium below acetabular component was also measured. FindingsCompared with Group 1, the transverse and longitudinal pressure strain of Group 2 on the superior measure site decreased, and measure sites also showed reductions on the inferior under load under three different gait phases. The result of mean relative displacement showed transacetabular screws fixation couldn't provide significant improvement of displacement prevention. InterpretationBiomechanical test showed that under the premise of a satisfied bone allograft and well-fixed flange screws in iliac and ischium, the satisfactory initial stability of the reconstruction cup can be achieved, but could not be improved by transacetabular screw technique. However, the max strain in root part of the flange will be reduced using transacetabular screws in ilium, pubis and ischium together, and the strain distribution will also be improved.

Screw-hole clusters in acetabular cups: a morphological study of optimal positioning of screw-holes.

Rigid and safe transacetabular screw fixation in total hip arthroplasty (THA) is achieved by pursuing deeper bone stock and avoiding injuries to the neurovascular structures, but these efforts can be restricted by the distribution of screw-holes on cups by the manufacturer. We therefore tried to determine: (i) optimal screw-hole positions on cups to allow anatomical placement of screws; (ii) rationality of the basic 3-screw-hole cluster on commercial cups; and (iii) the optimum method for placing commercial cups in accordance with acetabular anatomy. Periacetabular osseous structure of 64 hips and arterial structures of 50 hips were three-dimensionally reconstructed. Simulated transacetabular screw fixation during THA was performed in these hips with 3 different screw lengths (15, 25, and 35 mm) to define deeper and safer screw trajectories. Screw-hole locations of 7 commercially available cups were measured and matched with the periacetabular anatomy. When the cup was placed into the acetabulum at 45° of abduction and 20° of anteversion, the optimal locations of 2 screw-holes on the cups were at 30° and 64° of latitude, with a 35° separation angle. The inversetriangle distribution pattern was safer than the triangle pattern in basic 3-screw-hole-cluster cups. When placing the commercial cups, 5°-10° of anterior rotation can be added to allow better screw trajectories. Our study determined optimal screw-hole positions and their distribution pattern on cups. We describe methods to place the commercial cups that are not designed according to acetabular anatomy.

La zone de sécurité pour les vis acétabulaires des croix de Kerboull : une étude scannographique prospective

BackgroundImplantation of Kerboull acetabular reinforcement cross-plates (Kerboull plate) carries a risk for injury to vascular structures and pelvic organs. To our knowledge, there is no study assessing anatomical assessment related to this risk with this specific design. Therefore, we performed a prospective study to answer the following four questions: (1) What is the minimum distance and angle between the plate and iliac vessels? (2) What is the distance between the plate and the inner cortex of the ilium? (3) What is the ratio of views with muscle tissue present on the inner surface of the ilium? (4) What are the boundaries of the safe zone for transacetabular screw fixation for a Kerboull plate? HypothesisA safe zone for fixation screws would be defined by a narrow range of insertion angles. Materials and methodsThis is a CT based 3D templating prospective study. Simulations were performed for 18 patients fitted with a Kerboull plate. An original Kerboull plate (Stryker, Mahwah, NJ, USA) was placed at a 45° abduction angle relative to the x-axis (alignment A) and the palette was placed vertically to the x-axis (alignment B). We measured the distance from the centre of the plate to the inner surface of the cortex of the ilium, the shortest distance to vessels and the angle of existing vessels, and the ratio of muscles on the inner surface of the ilium. ResultsThe shortest distance to the vascular structures increased with increasing angle of insertion of the fixation screws, 85.8±12.1mm for A and 111.4±12.0mm for B at 45°. The distance to the inner cortex was further increased for screws inserted in posterior direction. At insertion angles≥40°, the screws passed through muscle before invading the pelvis in most cases. However, at anterior-posterior angle (AP angles)≤−10°, the risk of direct insertion of screws into the sacroiliac joint increased. DiscussionThe safe zone for transacetabular screws would be insertion at an angle≥40°, with an AP angle between 0° and –10° (slight posterior direction). Level of evidenceLevel IV prospective diagnostic study.

Safe zone for transacetabular screw fixation using a Kerboull cross-plate: A CT-scan templating prospective study

BackgroundImplantation of Kerboull acetabular reinforcement cross-plates (Kerboull plate) carries a risk for injury to vascular structures and pelvic organs. To our knowledge, there is no study assessing anatomical assessment related to this risk with this specific design. Therefore, we performed a prospective study to answer the following four questions: 1) What is the minimum distance and angle between the plate and iliac vessels? 2) What is the distance between the plate and the inner cortex of the ilium? 3) What is the ratio of views with muscle tissue present on the inner surface of the ilium? 4) What are the boundaries of the safe zone for transacetabular screw fixation for a Kerboull plate? HypothesisA safe zone for fixation screws would be defined by a narrow range of insertion angles. Materials and methodsThis is a CT-based 3D templating prospective study. Simulations were performed for 18 patients fitted with a Kerboull plate. An original Kerboull plate (Stryker, Mahwah, NJ, USA) was placed at a 45° abduction angle relative to the X-axis (alignment A) and the palette was placed vertically to the X-axis (alignment B). We measured the distance from the centre of the plate to the inner surface of the cortex of the ilium, the shortest distance to vessels and the angle of existing vessels, and the ratio of muscles on the inner surface of the ilium. ResultsThe shortest distance to the vascular structures increased with increasing angle of insertion of the fixation screws, 85.8±12.1mm for A and 111.4±12.0mm for B at 45°. The distance to the inner cortex was further increased for screws inserted in posterior direction. At insertion angles ≥40°, the screws passed through muscle before invading the pelvis in most cases. However, at anterior-posterior angle (AP angles) ≤−10°, the risk of direct insertion of screws into the sacroiliac joint increased. DiscussionThe safe zone for transacetabular screws would be insertion at an angle≥40°, with an AP angle between 0° and −10° (slight posterior direction). Level of evidenceLevel IV prospective diagnostic study.

Periphery transacetabular screws fixation in Contour revision cup: a cadaveric biomechanical study in vitro

Brigham and Women's Hospital, Second Affiliated Hospital of Zhejiang University, Hangzhou, Zhejiang, China

Acetabular revision using an anti-protrusion cage in patients with periprosthetic acetabular bone loss

Objective To investigate the risk factors related to the survival time of anti-protrusion cage in acetabular revision.Methods Data of 40 patients who had received acetabular revision using antiprotrusion cages between January 2002 and June 2010 were retrospectively analyzed.There were 16 males and 24 females,aged from 22 to 77 years (average,60.3 years).All patients were followed up for 12 to 82 months (average,39.2 months).According to the AAOS classification,there were 29 cases of type C and 11 cases of type D； while according to the Paprosky classification,there were 29 cases of type ⅢA and 11 cases of type Ⅲ B.The multiple regression analysis was utilized to investigate the relationships between different factors and anti-protrusion cage failure.The corresponding factors included gender,age,bone loss classification,superior or lateral migration of acetabular center of rotation,abduction angle,fixation manners (simple flange fixation or flange fixation plus transacetabular screw fixation),bone grafting techniques and cup type.Results At final follow-up,the average Harris score was 74.5±15.4.Two patients received rerevision due to prosthetic loosening.Obvious radiological loosening of prosthesis combined with pain was found in 2 cases.The statistical analysis indicated that superior migration of acetabular center of rotation,abduction angle and fixation manners were correlated with cup failure,especially when the superior migration was more than 8.5 mm or the abduction angle was larger than 53.5°.Flange fixation plus transacetabular screw fixation could reduce risk of cup failure.Conclusion There is a higher cup failure risk in acetabular revision using an anti-protrusion cage for patients with serious bone defect.However,implanting cup at the level of the true acetabulum as far as possible,decreasing abduction angle properly and using flange fixation plus transacetabular screw fixation can reduce cup failure risk. Key words: Acetabulum; Arthroplasty, replacement, hip; Reoperation

Trabecular Metal Cup without Augments for Acetabular Revision in Case of Extensive Bone Loss and Low Bone-Prosthesis Contact

Current evidences in revision hip arthroplasty suggest to treat severe acetabular bone loss with dedicated implants, such as anti-protrusio cages, stemmed cups, modular systems supplied with iliac flanges and obturatory hook. However recent literature is reporting satisfactory outcomes with simple elliptical Trabecular Metal cups. Purpose of the study was to evaluate mid-term results of such a surgical procedure. All hip revisions performed from 2008 to 2009 with implantation of a TMT multi-hole acetabular cup without augmentations were retrospectively reviewed. The cases with low-degree acetabular bone loss (stage I and II according to GIR classification), with surgical report poorly describing the bone defect, with inadequate pre- and post-operative x-rays were ruled out. Twenty-five cases were identified, but four were lost to follow-up. The twenty-one patients were 71 year-old on average (from 60 to 82), with stage IV bone loss in 6 cases and stage III bone loss in 15 cases. Mean interval from surgery to evaluation was 20.9 months (from 13 to 30). The evaluation included bone-prosthesis contact estimation, component position, survivorship, complications, final Harris Hip Score, presence of periprosthetic radiolucencies. Host bone-prosthesis contact was estimated to be about 35%. Only three implant were subsequently reoperated (for infection, early migration, recurrent dislocation). The HHS among non-reoperated 18 patients was 81.96 on average (from 63.44 to 95.82). Six cases showed thin radiolucencies in one of the three Charnley zones, while three cases showed radiolucencies in two. None of these images was evolutive, thus they were not considered signs of loosening. The mid-term results of this series confirm the hypothesis that a porous tantalum acetabular cup is an effective option to deal with difficult acetabular revisions. Although no extra-acetabular fixation device is available, the very high surface friction guaranteed by the material and the supplemental stability provided by trans-acetabular screws seem to be sufficient to allow satisfactory reimplantation even in severely damaged pelves.

A computer-aided system for longer transacetabular screw trajectory research.

Objective To overcome the inherent limitations of traditional technique, we promoted that long transacetabular screws could be safely implanted into ilium, pubis and ischium. Methods Twenty 3D hemi-pelvis models were constructed using CT data, and each was divided into four parts: posterior ilium, anterior ilium, pubis and ischium. Each part was undertaken parallel osteotomy and the contour coordinates of each section were recorded. The acetabular cup in each model was defined as a hemisphere with 52 mm diameter. An uniform lattice at equal intervals of 2° in longitude-latitude on the acetabular cup were regard-ed as entry points. A computer aided program was developed to simulate screw trajectories in all directions through every entry point, then select out all the useful entry points and corresponding trajectories. Then the optimum direction of screw trajectory of each entry point was also calculated. Topographic maps of entry zone were delineated in the acetabular quadrant system to present the results. Results According the bone anatomy, the posterior ilium was the most favorable area for the implantation of long screws, secondly the an-terior ilium, thirdly the pubis and minimally the ischium. The entry zone in posterior ilium has the longitude from -148.0° to 29.2°, latitude from 7.5° to 87.3°, and α angle for trajectory direction was from -85.3° to -53.8°,β angle from 46.3° to 60.2°. In anterior ilium has the longitude from -29.0° to 31.4°, latitude from 7.6° to 54.2°, and α angle was from -36.2° to -49.8° ,β angle from 19.7° to 33.8°. In pubis has the longi-tude from 56.4° to 100.6°, latitude from 6.8° to 23.2°, and α angle was from 91.3° to 117.2°, β angle from 10.5° to 17.9°. And the anatomy of ischium was not permitted transacetabular screws to reach the distant 1/3 part of the isehium ramus. Conclusion The long transacetabular screws were permitted to deeper insertion when the trajectories were not perpendicular to the cup wall. The computer-aided system developed in the study was useful for screw trajectory simulation and selection. Key words: Acetabulum; Tomography,X-ray computed; Bone screws

Safe Zone for Transacetabular Screw Fixation in Prosthetic Acetabular Reconstruction of High Developmental Dysplasia of the Hip

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. 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. 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. 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.

Radiographic Evaluation of Screw Position in Revision Total Hip Arthroplasty

Injury to intrapelvic structures during removal of screws in revision acetabular arthroplasty is an uncommon, yet potentially serious complication. Bicortical screws are at greatest risk for causing injury during removal, especially if directed toward intrapelvic vessels and nerves. Complications can be minimized with thorough evaluation of screw position before revision surgery. A study of seven cadaveric pelves was done to determine if plain radiographic views provide useful information regarding screw position. In each pelvis, bicortical transacetabular screws were fixed in all acetabular quadrants 15 mm longer than the measured depth. Afterward, anteroposterior, inlet, Judet, and cross-table lateral radiographic views were obtained and intrapelvic dissections were done. Radiographs and intrapelvic dissections were compared to determine screw position. We found that the obturator and iliac oblique (Judet) views were most useful in defining screw position. The iliac oblique view clearly revealed screws that violated the quadrilateral surface and therefore were directed toward the obturator vessels and nerve. The obturator oblique view revealed screws that violated the anterior column and therefore were directed toward the external iliac vessels. The lateral view additionally clarified such screws by determining general anterior or posterior direction.

Anatomic Assessment of the Acetabular Fossa for Screw Fixation in Acetabular Fracture

Purpose: To obtain spatial information on the acetabular fossa concerning ‘transacetabular screw’ insertion through the acetabular fossa parallel to the quadrilateral surface for fixing an acetabular fracture. Materials and Methods: Each hemipelvis harvested from 25 adult fresh frozen cadavers was sectioned into eight segments. This resulted in seven measuring points located along the outer margin of the acetabular fossa. At these points, we measured and compared the vertical thicknesses of cartilage and bone from the quadrilateral surface. Results: The average thickness of the thinnest portion of the acetabular fossa floor was 3.9±1.9 ㎜. The entire thickness of the bone and cartilage measured vertically from the quadrilateral surface at the 7 points ranged from 12.7±2.1 ㎜ to 17.8±3.8 ㎜. The thinnest safe space of exposed threads of the ‘transacetabular screw’ inserted through the acetabular fossa was consistently just below the posterior conus of the lunate surface, measuring 4.8±1.6 mm (p Conclusion: We suggest that ‘transacetabular screws’ can be inserted safely if due consideration is paid to the spatial characteristics of on the acetabular fossa. Screw insertion into the postero-inferior portion of the acetbular fossa should be done carefully.

Placement of screws in the uncemented acetabulum: anatomic analysis of the danger zone.

Six cadavers were used to define the projection of the external iliac artery on the inner table of the acetabulum, and to quantitatively determine bony dimensions of the danger zone with regard to screw placement. The results showed that the majority of projections of the external iliac arteries were located on the superior portion of the posterosuperior quadrant and extended to the mid-superior portion of the anterosuperior quadrant (danger zone). The inferior portion of the danger zone was relatively far from the external iliac artery. The greatest depths of bone were found in the inferior portion of the danger zone, and the depths of bone in the middle and superior portion of the danger zone were relatively thinner. This anatomic study showed that the real danger zone was found in the middle and superior portions of the anterosuperior quadrant of the acetabulum. The inferior portion of the anterosuperior quadrant was relatively safer. This area may be considered if transacetabular screw replacement in the anterosuperior quadrant is required.

Obturator Nerve Palsy due to Fixation of an Acetabular Reinforcement Ring with Transacetabular Screws. A Case Report*

FRICKER, RENATO M. M.D.†; TROEGER, HANS M.D.†; PFEIFFER, KARL M. M.D.†, BASEL, SWITZERLAND Author Information