ORIGINAL ARTICLE

Three-Dimensional Fluoroscopy-Navigated Percutaneous Screw Fixation of Acetabular Fractures Philipp Schwabe, MD, Burak Altintas, MD, Klaus-Dieter Schaser, MD, Claudia Druschel, MD, Christian Kleber, MD, Norbert P. Haas, MD, and Sven Maerdian, MD

Objective: Anatomic reduction and articular restoration after acetabular fractures occur (Ac-Fxs) are accepted predictors for good function and slow progression of posttraumatic osteoarthritis of the hip. The aim of this study was to retrospectively analyze Ac-Fxs, which were treated with closed reduction and percutaneous (threedimensional) fluoroscopy-based navigated screw fixation.

Key Words: acetabulum fracture, percutaneous screw, computerassisted surgery, navigation, three-dimensional, fluoroscopy-based navigation, trauma

Level of Evidence: Therapeutic Level 4. See Instructions for Authors for a complete description of levels of evidence. (J Orthop Trauma 2014;28:700–706)

Design: Level 4, retrospective clinical and radiographic assessment. Setting: Level 1 trauma center.

INTRODUCTION

Accepted for publication March 11, 2014. From the Center for Musculoskeletal Surgery and Julius Wolff Institute, Charité— University Medicine Berlin, Berlin, Germany. The authors report no conflict of interest. Reprints: Philipp Schwabe, MD, Center for Musculoskeletal Surgery, Charité—University Medicine Berlin Campus, Virchow, Augustenburger Platz 1, D-13353 Berlin, Germany (e-mail: [email protected]). Copyright © 2014 by Lippincott Williams & Wilkins

The main goal of any operative treatment of acetabular fractures (Ac-Fxs) is the exact and congruent restoration of the articular surface followed by a stable osteosynthesis.1 Pioneering studies performed by Letournel and Judet and Matta et al have clearly demonstrated that an anatomic reduction and gap/step-free (,1- to 2-mm) reconstruction of the articular surface are decisive predictors for a good function and prevention of the delayed progression of posttraumatic hip arthritis.1–3 Due to the complex anatomy and the variety of fracture patterns, anterior, posterior, or combined surgical approaches are required to achieve the goal of anatomical reconstruction. To circumvent complicated exposure of the hip joint anatomy, minimally invasive percutaneous screw fixation has been described for specific Ac-Fx types.4,5 The pelvic anatomy and acetabular geometry make the percutaneous screw placement a challenging procedure. A knowledge of the correct location of the insertion point, screw direction, and angulation is essential to avoid injury to neurovascular structures. Chen et al6 demonstrated the risk of developing iatrogenic injuries during pelvic screw fixation. The standard technique with conventional fluoroscopy requires multiple images in all planes to determine the accurate insertion point and the direction of the screw. Multiple images are required during screw placement, which therefore increases the operation time and the amount of radiation the patient and the surgical team is exposed to. However, the implementation and adoption of the preoperatively planned reduction in surgical practice with realization of predetermined screw positions may be tremendously difficult due to the lateral, supine, or prone positioning of the patient in conjunction with complex periacetabular anatomy that may be additionally deranged in response to the fracture dislocation. In this context, new concepts of imageguided surgery with navigation of screw positioning have attracted major interest because they were expected to increase accuracy and precision during surgical procedures. During the past 2 decades, a scientific and technological effort

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Patients: Twelve patients (male/female: 9/3; mean age: 60 years; range: 16–80 years) with moderately displaced Ac-Fxs were included. Intervention: In enrolled patients, the treatment involved percutaneous three-dimensional fluoroscopy-based navigated lag screw positioning. Closed reduction was achieved by lag screws, or reduction was aided by the insertion of percutaneous Schanz pins. Main Outcome Measurements: The quality of the reduction and screw positions were assessed using intraoperative and postoperative computed tomography scans. Functional outcome was assessed using the Harris hip score, the visual analog scale for pain, and the Tegener activity scale. Results: A total of 22 periacetabular screws were placed (mean: 1.8 6 1.1 screws/patient, range: 1–5). The mean follow-up was done for 30 (16–72) months. The postoperative reduction was anatomical in all patients, and the mean fracture displacement was significantly reduced (gap: 4.1 6 1.8 mm to 0.4 6 0.7 mm/step: 1.4 6 0.6 mm to 0.2 6 0.4 mm). No secondary dislocations or malunions/nonunions were found. All screws correctly addressed the fracture morphology and corresponded to preoperative planning. The Harris hip score, the visual analog scale (motion), and Tegener activity scale showed excellent to very good results (92.4 6 6.8, 1.9 6 1.3, and 3.8 6 1.6, respectively).

Conclusions: The navigated, percutaneous screw fixation of selected Ac-Fxs is a promising method that allows for closed reduction and fixation while obtaining a very good radiographic and functional outcome.

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Navigated Screw Fixation of Acetabular Fractures

made worldwide has generated information concerning image-guided technologies and their application in musculoskeletal surgery.7 The introduction of high-resolution imaging methods with multiplanary reconstructions and their integration into powerful computer systems together with the development of substantially improved image processing methods and instrument-tracking techniques have provided the prerequisites for the application of image guidance of instruments and screws in pelvic and spinal surgery.8–10 Despite numerous publications in this field, several central issues remain controversial, such as whether the application of image-guided surgery can assist in achieving identical results for quality of reduction and fixation when compared with that in open techniques. In comparison with the results from many other studies that seem to demonstrate a clear clinical benefit from the use of image-guided/computed tomography (CT)-based navigation in critical areas, for example, sacroiliac-joint arthrodesis or pedicle screw insertion,11–13 there are only few reports about image-guided approaches for Ac-Fxs available, and they are limited to case reports or to very small series.14 The aim of this retrospective study was to analyze a consecutive series of specific types of Ac-Fxs, which underwent minimally invasive and navigated percutaneous screw fixation.

mildly displaced fractures with intraarticular fragments were excluded from the study due to the necessity of the standard treatment with an open reduction and internal fixation.

PATIENTS AND METHODS Patients Patients with Ac-Fxs who underwent three-dimensional (3D) fluoroscopy-navigated screw fixation were reviewed for this study. Patient demographics, surgical details, radiologic data, functional outcome, and complications were collected from each patient. The trauma mechanisms and collateral injuries were assessed, and their association with the functional outcome was analyzed. Patients who suffered from Ac-Fxs with fragment displacement .1-cm/comminution, isolated or combined wall fractures, associated both-column fractures, or

Fracture Classification Preoperatively, every patient underwent conventional radiographic imaging and a CT scan of the pelvis. On the basis of these images, fracture patterns were categorized according to the OTA classification,15 and indication for percutaneous reduction with subsequent percutaneous screw fixation was evaluated.

Surgical Procedure Depending on the fracture morphology, the patients were placed in either the supine or the lateral position on a radiolucent carbon table. Each patient received a single shot intravenous antibiotic (ampicillin/sulbactam), and operations were carried out under general anesthesia. If reduction could not be performed with lag screws or by manual traction/reduction maneuvers, a percutaneous Schanz pin was placed to aid fracture reduction. A 3D fluoroscopy–based scan with the Arcadis Orbic 3D (Siemens, Erlangen, Germany) was performed after mounting the reference base to the ipsilateral iliac crest. It was of crucial importance that reduction in the form of longitudinal traction or Schanz pin maneuvers had to precede the reference scan, because any movement in the fracture site afterward would have made the stored 3D scan inaccurate and therefore no longer valid for navigation. After initial reduction and an ensuing 3D scan, the acquired images were transferred to the VectorVision navigation system (BrainLab, Feldkirchen, Germany). Basic screw trajectories available to the surgeon are antegrade and retrograde anterior or posterior column screws and supraacetabular ilium screws.8,9,14,16 The screw trajectories preferred in our series were antegrade anterior and posterior column screws and supraacetabular ilium screws in a solitary or combined manner (Fig. 1). For screw positioning, a small

FIGURE 1. Examples of screw trajectories used in our patient series: antegrade anterior column screw for OTA 63-A3 Fx (A), antegrade posterior column screw for OTA 62-B1 Fx (B), supraacetabular ilium screw for OTA 62-A3 Fx (C), possible combination of (A) and (B) for an OTA 62-B1 Fx (D). Ó 2014 Lippincott Williams & Wilkins

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stab incision of 5–8 mm was made, and soft tissues were bluntly set aside. The navigated drill guide was slid to the cortical surface and a threaded K-wire was set perpendicular to the fracture line after the orientation of the guide showed accurate virtual alignment. The direction, angulation, and drilling depth of the navigated K-wire were multidimensionally controlled in real-time modus, allowing immediate correction. After length measurement and overreaming, a lag screw was placed. The quality of the reduction and the screw positions were controlled with an intraoperative 3D fluoroscopy scan. Physiotherapeutic supervised mobilization with 30 kg of weight bearing on the ipsilateral extremity with crutches or a mobile walking device was begun during the first day after the operation. Full weight bearing was allowed postoperatively after 6 weeks.

At the follow-up visit, 1 independent observer, who was not involved in the patient treatment regime, examined all the patients. The hip function and postoperative complications were recorded. The Harris hip score (HHS) was used to evaluate the clinical outcome. The visual analog scale for pain at rest and in motion and the Tegener Activity Scale were used.

was treated with an open surgical procedure. This patient’s condition was classified as a monotrauma, because no additional ipsilateral injuries on the side of percutaneous fixation were present. Five patients were classified as having relevant associated injuries. These patients had additional injuries located around the ipsilateral acetabular region or the same lower extremity and therefore had a potential for a bias in the postoperative functional outcome. Two patients had an additional fracture of the ipsilateral inferior pubic bone as part of the pelvic trauma with no direct relation to the Ac-Fx, which was treated conservatively in both patients. Three patients suffered from a polytrauma with a mean injury severity score of 40 (range, 29–48). As for the relevant associated injuries of this study, 1 patient suffered from a pelvic C-type injury with bilateral transsacral fractures, which were treated using bilateral sacroiliac screws in the same session as that of using the percutaneous acetabular screw. Another patient suffered from a pelvic B-type injury and an additional multisegmental lower leg fracture, which was treated using a sacroiliac screw and a locked intramedullary tibial nail simultaneously to the percutaneous acetabular fixation. The third patient presented with an ipsilateral femoral fracture, which was already pretreated using a locked femoral nail in an external hospital. A total of 22 periacetabular screws were placed (mean: 1.8 6 1.1 screws/patient, range 1–5). The mean follow-up was conducted for 30 months (median 24.5 months; range, 16–72). Preoperative planning was successfully realized in all patients. No correction of initially placed guide wires and no intraoperative conversion to an open procedure or extension of the surgical approach were necessary. The mean postoperative hospital stay was for 8.6 (8 6 4.7, range 3–17) days. An exemplary case of a 53-year-old patient with an anterior column fracture (OTA 62-A3) is presented in Figures 2A–E.

Statistics

Radiographic Outcome

Radiographic Assessment A postoperative CT scan was performed at the time of the follow-up visit. The maximum gap and the step size of the fractures were measured in 3 standardized planes (anterior posterior, coronal, and sagittal) and recorded for identical planes of the preoperative and postoperative images using digital image analysis (Osirix). The values were compared between preoperative and postoperative CT scans. Also, screw position, alignment, and consolidation of the fracture were evaluated.

Functional Assessment, Pain, and Activity Level

Comparison of the data and testing for normality (Kolmogorov–Smirnov) showed a normal distribution. Therefore, the paired t test was used for the comparison of matched samples (IBM SPSS Statistics Release 19.0.0.1; IBM Corporation, Armonk, NY).

RESULTS Patients Twelve patients (male/female: 9/3) were included in this study. Their median age was 65 (range, 16–80) years. According to the OTA classification, 5, 4, and 3 patients had an anterior column fracture (OTA 62-A3), a transverse fracture (OTA 62-B1), and an anterior column posterior hemitransverse fracture (OTA 62-B3), respectively. Trauma mechanisms were bicycle/motorcycle accidents in 7 cases. One patient fell from a height of 2 m, whereas another 4 patients fell due to gait disturbances. Seven patients did not have additional injuries and were considered as being affected by an acetabulum monotrauma. One patient had a bilateral acetabulum fracture, where the contralateral side

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The radiographic results showed a complete fracture consolidation in all cases. The postoperative alignment and reduction in the radiographic controls were “anatomic” according to Matta criteria.2 The mean preoperative fracture displacement was 4.1 6 1.8 mm (gap)/1.2 6 0.6 mm (step) and could be successfully and significantly reduced to a postoperative fracture displacement of 0.4 6 0.7 mm (gap) and 0.2 6 0.4 mm (step) (P , 0.005) (Table 1).

Functional Outcome, Pain, and Activity level At the latest follow-up (minimum 16 months after the surgery), all patients were satisfied with their surgical procedure. The HHS indicated good results in 4 patients and an excellent result in 8 patients. The mean value was excellent with 92 points (range, 81–100) (Fig. 3). Two patients with an HHS of 81 points were those affected by polytrauma with additional ipsilateral lower extremity fractures as mentioned above. One patient with an HHS of 88 points had a bilateral acetabulum fracture, which was treated using open reduction and internal plate-screw fixation on the contralateral side. Ó 2014 Lippincott Williams & Wilkins

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FIGURE 2. A, A 53-year-old, male patient suffered from a left anterior column fracture (OTA 62-A3) after he had a bicycle accident. The displaced fracture is illustrated in the radiographs in the anterior posterior view and axial view (inset). B, Anterior column fracture (OTA 62-A3) in 2D (anterior posterior in the first row, sagittal in the second row) and 3D CT scan reconstructions. C, After registration with the reference base on the iliac crest, threaded K-wires were inserted, followed by overreaming with a cannulated drill bit, and finally the screws were placed. The patient received 2 (due to the high extension of the fracture into the iliac wing) antegrade periacetabular screws. D, Intraoperative. 3D visualization for the surgeon in the axial (upper left), sagittal (upper right), and anterior posterior (lower left) planes with real-time imaging of the entry point and tracking (red) of the navigated drill guide. E, Two-year postoperative image. Radiographic outcome (upper row: sagittal CT scan reconstruction left, 3D reconstruction right, conventional X-ray on the lower left, and anterior posterior CT scan reconstruction on the lower right). The initial fracture gap of 6 mm was closed completely. The HHS is 100. Editor’s note: A color image accompanies the online version of this article. Ó 2014 Lippincott Williams & Wilkins

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TABLE 1. Display of the Mean Fracture Gap/Step in Millimeters (Preoperative and Postoperative) With SD and Display of Mean Values With a Significant Reduction of the Fracture Dislocation From Preoperative to Postoperative (Paired t test) Maximum Gap (SD) Preoperative Postoperative P*

Maximum Step (SD)

Axial

Coronal

Sagittal

Mean

Axial

Coronal

Sagittal

Mean

4.7 (1.9) 0.4 (0.7) ,0.001

4.2 (1.6) 0.4 (0.7) ,0.001

3.5 (1.9) 0.3 (0.6) ,0.001

4.1 (1.8) 0.4 (0.7) ,0.001

0.3 (0.2) 0.1 (0.3) 0.3 (n.s.)

1.9 (1.0) 0.2 (0.5) ,0.001

1.6 (1.0) 0.2 (0.3) ,0.001

1.2 (0.6) 0.2 (0.4) ,0.005

*Paired t test. n.s., not significant.

The patients’ pain level at the follow-up visit on the visual analog scale for pain at rest was 1.3 6 0.7 (range, 1–3), and in motion it was 1.9 6 1.3 (range, 1–4). The highest values were observed in the polytraumatized patients. The mean activity level on the Tegener activity scale was 3.8 6 1.6 (range, 2–6), which means that the patients were able to do heavy work comparable with that of a painter, a maid, or a housewife in a big household. In terms of sports activity, a value of 4 corresponds to activities such as bicycle riding, crosscountry skiing, or jogging 2 times a week on even ground.

Postoperative Complications There were no secondary fragment dislocation or malunion/nonunion, and no implant failure was observed in our patients. All screws were placed extraarticularly and correctly addressed the fracture morphology. There were no delayed wound healings and no infections in any of the treated patients. No neurovascular damage and no heterotopic ossifications were found.

DISCUSSION The understanding of factors that dictate the outcome after Ac-Fxs occur has grown enormously over the past decades because of improved multidimensional radiographic imaging and intensively increased reconstructive surgical effort. However, the accepted goals and standards of treatment for displaced Ac-Fxs, that is, open anatomical reduction of the articular surface with rigid internal fixation, have remained unchanged. Among the factors known to predict long-term prognostic treatment results, the degree to which the anatomical reduction of the articular surface is reached (,1–2 mm gap/step) has turned out to be the most important. Most of the classic anterior and posterior approaches are traumatic and challenging. They may cause scar formation, infectious complications, and heterotopic bone formation. Consequently, treatment concepts for minimally displaced Ac-Fxs that allow closed reduction and percutaneous, biomechanically sufficient stabilization thereby avoiding soft tissue damage could have a profound impact on future surgical strategies by possibly

FIGURE 3. Postoperative HHS.

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improving functional results and decreasing the abovementioned complications of open surgery. Pursuing this idea, navigated implant positioning and fixation are attracting major clinical interest. In the current literature, the knowledge about minimally invasive treatment of mildly displaced Ac-Fxs is rather limited. This weak knowledge base is underscored by the few and only recent reports that could show satisfactory results after conventional4,5,16 or navigated percutaneous screw fixation.8,14,17 Moushine et al16 reviewed 18 patients with a mildly displaced acetabulum fracture at a mean follow-up of 3.5 years after fluoroscopically controlled, percutaneous screw fixation. In the 17 patients who showed satisfactory clinical results, fractures healed at a mean time of 12 weeks, and no secondary dislocation or screw failure was seen. Similarly, Hong et al presented a case series of 12 patients with nondisplaced AcFxs and 8 patients with displaced Ac-Fxs who underwent a 2D-navigated percutaneous screw fixation. The clinical outcome according to the Merle d’Aubigne score was good to excellent in 17 patients after a mean follow-up of 21 months. Except for 1 patient with a transient femoral nerve palsy, no complications were reported.8 The results of these studies and our results suggest the good feasibility and safety of this procedure. In parallel, none of our patients suffered from any complications, and the functional and radiologic outcome was excellent. In our opinion, closed reduction and fixation of mildly displaced Ac-Fxs can prevent secondary fracture displacement and allow a more aggressive mobilization and earlier return to full weight bearing. This is of particular benefit for patients who are not able to perform partial weight bearing due to their reduced general condition or due to patients suffering from additional lower extremity injuries. Especially patients of the geriatric population suffering from Ac-Fxs mainly involving the anterior column might represent a potential subgroup for the application of this technique and could take advantage of early mobilization, to prevent secondary complications such as pulmonary infections/thromboembolism or decubital ulcers. In the case of ipsilateral injuries, a free motion and earlier weight bearing of the hip joint may also be advantageous in terms of early physical therapy of the extremity injury. For patients with additional contralateral extremity injuries that do not allow weight bearing, stabilization of the acetabulum after sustaining a fracture is crucial for gaining acceptable mobilization.5 Three-dimensional fluoroscopy–based navigation offers the advantage of an accurate screw placement with an excellent intraoperative orientation. The image quality is relatively reduced compared with that of a conventional CT scan but is still sufficient to clearly visualize the fracture morphology and navigate the screw direction in the small bony periacetabular corridors. Despite this, we recommend that one recheck the guidance and placement of the K-wire navigation (virtuality) using conventional fluoroscopy or a new 3D CT scan (reality).10 Minimal changes in the position of the reference base due to an accidental and unnoticed collision by the surgeon or instruments can derange the field of navigation inevitably resulting in a matching error. In our series, the intermittently

obtained fluoroscopy images matched the navigation in all cases, and no additional scan had to be performed to correct a matching error. The use of navigation for closed reduction and percutaneous screw fixation, however, should not mislead surgeons to compromise with the main goal of the anatomic reduction of the acetabular joint, known to be the principal prognostic factor. For decision making, it should be kept in mind that the overwhelming majority of fracture types are not suitable for percutaneous screw fixation. These include all Ac-Fxs with fragment dislocation .1-cm/comminution, isolated or combined wall fractures, associated both-column fractures, and also mildly displaced fractures with intraarticular fragments. Thus, an exact preoperative concept with a precise analysis of patient characteristics, the type, morphology, and degree of dislocation of the fracture is crucial for achieving success and should precede any decision for performing a percutaneous procedure. Generally suitable fracture types for percutaneous screw fixation are anterior column and posterior columns fractures, transverse fractures, T-type fractures, and anterior column posterior hemitransverse fractures. Fractures that allow a fracture gap reduction and stable fixation using lag screws should be considered for this procedure and probably ,5% of fractures are amenable to this technique. If percutaneous fracture gap closure is not possible, an open procedure must be performed and mastered. Despite the novelty of this study, it has some limitations, and the results have to be interpreted accordingly. Radiation time and dose per screw were not documented. The radiation time of 1 operation in which the patients received multiple interventions, for example, intramedullary nail or sacroiliac screw in combination with the periacetabular screw was not cut down to each operative step. The Arcadis Orbic 3D image intensifier was used not only for the navigation procedure but also for intraoperative crosscheck fluoroscopy and for postoperative documentation. The radiation time was not documented separately for each step, thereby preventing a retrospective discrimination of the actual radiation time and dose for each individual screw placement. In comparison with previous studies of conventional percutaneous screw placement, the average radiation time was 62–73 seconds for each screw.5,16 Studies with navigated periacetabular procedures reported less radiation time ranging from 28 to 45 seconds per screw.8,14,17 For these fluoroscopy navigation studies, neither radiation dose nor image acquisition time and dose were displayed, which made a direct comparison difficult. In contrast to what was done in those studies, Ochs et al compared 2D fluoroscopy and 3D fluoroscopy navigation with the conventional technique for periacetabular screw placement using pelvis models and cadaver specimens. They could show that the length of the procedure and the radiation time and dose were higher for 3D fluoroscopy compared with those for the 2D fluoroscopy and with the conventional method. However, the accuracy of screw placement was significantly higher for the 3D fluoroscopy compared with that of the other groups.9 The accuracy reached in these studies was comparable with our accuracy. The 3D fluoroscopy–based navigated, percutaneous screw fixation of acetabulum fractures is a promising method

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with an excellent radiographic and functional outcome. In mildly to moderately dislocated and percutaneously reducible acetabulum fractures, this procedure enables an anatomic reduction combined with the efficient minimization of surgical exposure-related complications. The navigation and the intraoperative CT scan with multiplanary reconstructions allow an accurate placement of screws due to the real-time control of reduction and implant position.

8. Hong G, Cong-Feng L, Cheng-Fang H, et al. Percutaneous screw fixation of acetabular fractures with 2D fluoroscopy-based computerized navigation. Arch Orthop Trauma Surg. 2010;130:1177–1183. 9. Ochs BG, Gonser C, Shiozawa T, et al. Computer-assisted periacetabular screw placement: comparison of different fluoroscopy-based navigation procedures with conventional technique. Injury. 2010;41:1297–1305. 10. Stockle U, Konig B, Dahne M, et al. Computer assisted pelvic and acetabular surgery. Clinical experiences and indications. Unfallchirurg. 2002;105:886–892. 11. Schnake KJ, Konig B, Berth U, et al. Accuracy of CT-based navigation of pedicle screws in the thoracic spine compared with conventional technique. Unfallchirurg. 2004;107:104–112. 12. Briem D, Windolf J, Rueger JM. Percutaneous, 2D-fluoroscopic navigated iliosacral screw placement in the supine position: technique, possibilities, and limits. Unfallchirurg. 2007;110:393–401. 13. Laine T, Lund T, Ylikoski M, et al. Accuracy of pedicle screw insertion with and without computer assistance: a randomised controlled clinical study in 100 consecutive patients. Eur Spine J. 2000;9:235–240. 14. Lin YC, Chen CH, Huang HT, et al. Percutaneous antegrade screwing for anterior column fracture of acetabulum with fluoroscopic-based computerized navigation. Arch Orthop Trauma Surg. 2008;128:223–226. 15. Marsh JL, Slongo TF, Agel J, et al. Fracture and Dislocation Classification Compendium - 2007: Orthopaedic Trauma Association Classification, Database and Outcomes Committee. J Orthop Trauma. 2007; 21(suppl 10):S1–S163. 16. Mouhsine E, Garofalo R, Borens O, et al. Percutaneous retrograde screwing for stabilization of acetabular fractures. Injury. 2005;36:1330–1336. 17. Crowl AC, Kahler DM. Closed reduction and percutaneous fixation of anterior column acetabular fractures. Comput Aided Surg. 2002;7:169–178.

REFERENCES 1. Letournel E, Judet J. Fractures of the Acetabulum. New York, NY: Springer-Verlag; 1993. 2. Matta JM. Fractures of the acetabulum: accuracy of reduction and clinical results in patients managed operatively within three weeks after the injury. J Bone Joint Surg Am. 1996;78:1632–1645. 3. Matta JM, Anderson LM, Epstein HC, et al. Fractures of the acetabulum. A retrospective analysis. Clin Orthop Relat Res. 1986;205:230–240. 4. Starr AJ, Reinert CM, Jones AL. Percutaneous fixation of the columns of the acetabulum: a new technique. J Orthop Trauma. 1998;12:51–58. 5. Starr AJ, Jones AL, Reinert CM, et al. Preliminary results and complications following limited open reduction and percutaneous screw fixation of displaced fractures of the acetabulum. Injury. 2001;32(suppl 1):SA45–SA50. 6. Chen KN, Wang G, Cao LG, et al. Differences of percutaneous retrograde screw fixation of anterior column acetabular fractures between male and female: a study of 164 virtual three-dimensional models. Injury. 2009;40:1067–1072. 7. Schep NW, Broeders IA, van der Werken C. Computer assisted orthopaedic and trauma surgery. State of the art and future perspectives. Injury. 2003;34:299–306.

Invited Commentary

T

his is an interesting study, and the authors are to be commended for doing a good job gathering and presenting their data. I think the article contains 2 major messages for readers of the journal. First, this technique worked. The authors were able to close down fracture gaps of approximately 4 mm using partially threaded screws with trajectories planned to compress the fracture. The preoperative and postoperative images nicely reveal the closure of the fracture gaps. This is an attractive method, with obvious benefits for the patient. Second, the authors describe very well the instances in which this technique cannot be used. Any surgeon wishing to replicate the authors’ procedure should study the exclusion criteria closely, and also needs to pay close attention to the authors’ comments regarding the validity of the stored

computed tomography (CT) data used to guide navigation. Once the CT is obtained, any motion of the fracture fragments makes the stored CT data worthless. The landscape will be changed—the computer can no longer help target the screws. This fact has obvious implications for the timing of the steps in the process. Most previous work describing computer-assisted navigation in acetabular fractures contains data on minimally displaced or nondisplaced fractures. In this series, the authors have tackled displaced fractures, and their technique shows promise. Adam Starr, MD Section Editor, Acetabulum Dallas, Texas

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Three-dimensional fluoroscopy-navigated percutaneous screw fixation of acetabular fractures.

Anatomic reduction and articular restoration after acetabular fractures occur (Ac-Fxs) are accepted predictors for good function and slow progression ...
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