A novel method of image-based navigation in fracture surgery

Use of External Fixators as a 3-Dimensional Navigation Drill Guide for Arthroscopic Ankle Arthrodesis

In this article, we describe a novel technique using external fixators and cannulated screws to construct a 3-dimensional navigation drill guide to predict the screw trajectory before screw insertion that can prevent screw collision during arthroscopic ankle arthrodesis. Four orthopedic residents who had no prior experience of ankle arthrodesis were instructed on how to use the 3-dimensional navigation drill guide and where to insert the screws for ankle arthrodesis. Each resident inserted 6.5 cannulated screws on 8 sawbone ankle models using the device and the C-arm fluoroscopy. An experienced attending surgeon also inserted the same screws on 2 sawbone ankle models to find out if there is any difference between the experienced and inexperienced surgeons. All four residents and an attending surgeon did not experience any collision of screws for the three cannulated screws. Notably, one resident had collision of the 4th screw on his first sawbone model. On the second saw bone model, all surgeons could insert 5 screws without redrilling. A 3-dimensional navigation drill guide constructed with external fixators can assist surgeons in implementing percutaneous screws for arthroscopic ankle arthrodesis.

Three-Dimensional Evaluation of Similarity of Right and Left Knee Joints

Purpose

The purpose of this study was to evaluate the anatomical similarity of three-dimensional (3D) morphometric parameters between right and left knees.

Materials and Methods

Ten fresh-frozen paired cadaveric knees were tested. Following dissection, footprint areas of the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) were measured. Surface scanning was performed using a 3D scanner. Scanned data were reproduced and morphometric parameters were measured on specialized software. After making mirror models, we compared footprint center positions of the ACL and PCL of both sides and calculated the average deviation of 3D alignment between the right- and left-side models.

Results

No significant side-to-side differences were found in any morphometric parameters. Bony shapes displayed a side-to-side difference of <1 mm. Distal femoral and proximal tibial volumes did not present side-to-side differences, either; the average 3D deviations of alignment between the right and left sides were 0.8±0.4/1.1±0.6 mm (distal femur/proximal tibia). Center-to-center distances between the right and left ACL footprints were 2.6/2.7 mm (femur/tibia) for the anteromedial bundle and 2.4/2.8 mm for the posterolateral bundle. They were 1.9/1.5 mm for the anterolateral bundle and 2.2/1.8 mm for the posteromedial bundle of the PCL.

Conclusions

There was a remarkable 3D morphometric similarity between right and left knees. Our results might support the concept of obtaining morphologic reference data from the uninvolved contralateral knee.

A New Electromagnetic Navigation System for Pedicle Screws Placement: A Human Cadaver Study at the Lumbar Spine

Introduction

Technical developments for improving the safety and accuracy of pedicle screw placement play an increasingly important role in spine surgery. In addition to the standard techniques of free-hand placement and fluoroscopic navigation, the rate of complications is reduced by 3D fluoroscopy, cone-beam CT, intraoperative CT/MRI, and various other navigation techniques. Another important aspect that should be emphasized is the reduction of intraoperative radiation exposure for personnel and patient.

The aim of this study was to investigate the accuracy of a new navigation system for the spine based on an electromagnetic field.

Material and Method

Twenty pedicle screws were placed in the lumbar spine of human cadavers using EMF navigation. Navigation was based on data from a preoperative thin-slice CT scan. The cadavers were positioned on a special field generator and the system was matched using a patient tracker on the spinous process. Navigation was conducted using especially developed instruments that can be tracked in the electromagnetic field. Another thin-slice CT scan was made postoperatively to assess the result. The evaluation included the position of the screws in the direction of trajectory and any injury to the surrounding cortical bone. The results were classified in 5 groups: grade 1: ideal screw position in the center of the pedicle with no cortical bone injury; grade 2: acceptable screw position, cortical bone injury with cortical penetration ≤ 2 mm; grade 3: cortical bone injury with cortical penetration 2,1-4 mm, grad 4: cortical bone injury with cortical penetration 4,1-6 mm, grade 5: cortical bone injury with cortical penetration >6 mm.

Results

The initial evaluation of the system showed good accuracy for the lumbar spine (65% grade 1, 20% grade 2, 15% grade 3, 0% grade 4, 0% grade 5). A comparison of the initial results with other navigation techniques in literature (CT navigation, 2D fluoroscopic navigation) shows that the accuracy of this system is comparable.

Conclusion

EMF navigation offers a high accuracy in Pedicle screw placement with additional advantages compared to other techniques. The short set-up time and easy handling of EMF navigation should be emphasized. Additional advantages are the absence of intraoperative radiation exposure for the operator and surgical team in the current set-up and the operator’s free mobility without interfering with navigation. Further studies with navigation at higher levels of the spine, larger numbers of cases and studies with control group are planned.

Computer-assisted navigation in orthopedic surgery

Computer-assisted navigation has a role in some orthopedic procedures. It allows the surgeons to obtain real-time feedback and offers the potential to decrease intra-operative errors and optimize the surgical result. Computer-assisted navigation systems can be active or passive. Active navigation systems can either perform surgical tasks or prohibit the surgeon from moving past a predefined zone. Passive navigation systems provide intraoperative information, which is displayed on a monitor, but the surgeon is free to make any decisions he or she deems necessary. This article reviews the available types of computer-assisted navigation, summarizes the clinical applications and reviews the results of related series using navigation, and informs surgeons of the disadvantages and pitfalls of computer-assisted navigation in orthopedic surgery.

Subjective and objective results of arthroscopic debridement of ulnar-sided TFCC (Palmer type 1B) lesions with stable distal radio-ulnar joint

PURPOSE

The purpose of this study was to determine functional and subjective results of patients who received arthroscopic debridement for their TFCC Palmer 1B lesions and to compare their results with those of arthroscopic suture repair.

METHODS

Between March 2007 and August 2011, 36 patients were diagnosed with Palmer type 1B tears and underwent arthroscopic debridement. 31 patients (15 males and 16 females) were followed up for an average of 26.7 months (±17.4 months) postoperatively. Their average age was 36.7 years (±12.7 years). Follow-up included the determination of range of motion (ROM), grip strength, pain, and wrist scores (modified Mayo wrist score (MMWS), Disabilities of the Arm, Shoulder and Hand questionnaire (DASH score)).

RESULTS

Postoperative ROM averaged 99.2 % for the extension/flexion arc, 95.5 % for the radial/ulnar deviation arc, and 99.4 % for the pronation/supination arc of motion when compared with the contralateral wrist. The MMWS was rated excellent in 48 % of patients, good in 39 %, fair in 13 %, and poor in 0 %. The average DASH score was 17.02 (±14.92). There was a significant reduction in pain. The grip strength was 96.7 % (±15.8), pulp-to-pulp pinch 101.9 % (±17.4), and the ulnar variance -0.12 ± 1.69 mm.

CONCLUSIONS

Arthroscopic debridement of Palmer type 1B lesions in stable DRUJ yields satisfactory to excellent results. Our study showed similar results compared with the studies of arthroscopic suture repair with shorter postoperative care and fewer complications.