X-ray-based machine vision system for distal locking of intramedullary nails

Intramedullary nail holes laser indicator, a non-invasive technique for interlocking of intramedullary nails

Interlocking of intramedullary nails is a challenging procedure in orthopedic trauma surgery. Numerous methods have been described to facilitate this process. But they are exposed patient and surgical team to X-rays or involves trial and error. An accurate and non-invasive method has been provided to easily interlocking intramedullary nails. By transferring a safe visible light inside the nail, a drilling position appears which use to drilling bone toward the nail hole. The wavelength of this light was obtained from ex-vivo spectroscopy on biological tissues which has optimal transmission, reflectance, and absorption properties. Moreover, animal and human experiments were performed to evaluate performance of the proposed system. Ex-vivo performance experiments were performed successfully on two groups of cow and sheep samples. Output parameters were procedure time and drilling quality which there were significant differences between the two groups in procedure time (P < 0.05). But no significant differences were observed in drilling quality (P > 0.05). Moreover, an In-vivo performance experiment was performed successfully on a middle-aged man. To compare the provided method, targeting-arm, and free-hand techniques, two human experiments were performed on a middle-aged and a young man. The results indicate the advantage of the proposed technique in the procedure time (P < 0.05), while the drilling quality is equal to the free-hand technique (P = 0.05). Intramedullary nail holes laser indicator is a safe and accurate method that reduced surgical time and simplifies the process. This new technology makes it easier to interlocking the intramedullary nail which can have good clinical applications.

Is a magnetic-manual targeting device an appealing alternative for distal locking of tibial intramedullary nails?

Background

In order to enable a radiation-free, accurate and simple positioning of distal locking screws, a combined magnetic and manual targeting system has been developed by Sanatmetal®. Where a low-frequency magnetic field is initially used to detect the position of the first drill hole and three more holes can be found with a mechanical template.

Objectives

Our cadaver study was performed to evaluate the accuracy and efficiency of this device.

Materials and Methods

In two runs, 30 probands (group 1: 10 students; group 2: 10 residents; group 3: 10 attendings), none of who being familiar with the device, tested the radiation-free system using 60 intact cadaver tibias. Each proband performed the surgical procedure twice in succession.

Results

Referring to the first attempts, 9.6, 7.2 and 7.1 minutes were the time periods required to insert the four distal screws and the relevant values for the second attempts were 8.6, 6.3 and 6.2 minutes; in both cases revealing a significant difference between group 1 and 2 and group 1 and 3. Furthermore, the mean values within each group indicated a significant decrease of the test duration. Out of the 240 drillings, only one failure (group 1) occurred, representing an accuracy of 99.58 %. Of the probands, 90 % rated the targeting device better than the free-hand technique and 77 % at least attested a high user-friendliness.

Conclusions

Due to our satisfactory test results, the brief training, the steep learning curve and the radiation-free technique the new device has to be considered an appealing alternative for distal locking.

Reinforcing the role of the conventional C-arm--a novel method for simplified distal interlocking

Background

The common practice for insertion of distal locking screws of intramedullary nails is a freehand technique under fluoroscopic control. The process is technically demanding, time-consuming and afflicted to considerable radiation exposure of the patient and the surgical personnel. A new concept is introduced utilizing information from within conventional radiographic images to help accurately guide the surgeon to place the interlocking bolt into the interlocking hole. The newly developed technique was compared to conventional freehand in an operating room (OR) like setting on human cadaveric lower legs in terms of operating time and radiation exposure.

Methods

The proposed concept (guided freehand), generally based on the freehand gold standard, additionally guides the surgeon by means of visible landmarks projected into the C-arm image. A computer program plans the correct drilling trajectory by processing the lens-shaped hole projections of the interlocking holes from a single image. Holes can be drilled by visually aligning the drill to the planned trajectory. Besides a conventional C-arm, no additional tracking or navigation equipment is required.

Ten fresh frozen human below-knee specimens were instrumented with an Expert Tibial Nail (Synthes GmbH, Switzerland). The implants were distally locked by performing the newly proposed technique as well as the conventional freehand technique on each specimen. An orthopedic resident surgeon inserted four distal screws per procedure. Operating time, number of images and radiation time were recorded and statistically compared between interlocking techniques using non-parametric tests.

Results

A 58% reduction in number of taken images per screw was found for the guided freehand technique (7.4 ± 3.4) (mean ± SD) compared to the freehand technique (17.6 ± 10.3) (p < 0.001). Total radiation time (all 4 screws) was 55% lower for the guided freehand technique compared to conventional freehand (p = 0.001). Operating time per screw (from first shot to screw tightened) was on average 22% reduced by guided freehand (p = 0.018).

Conclusions

In an experimental setting, the newly developed guided freehand technique for distal interlocking has proven to markedly reduce radiation exposure when compared to the conventional freehand technique. The method utilizes established clinical workflows and does not require cost intensive add-on devices or extensive training. The underlying principle carries potential to assist implant positioning in numerous other applications within orthopedics and trauma from screw insertions to placement of plates, nails or prostheses.

Surgical technique: static intramedullary nailing of the femur and tibia without intraoperative fluoroscopy

BACKGROUND

On a recent mission directed at definitive care for victims of the Haitian earthquake, the orthopaedic team developed a technique for freehand distal locking of femoral and tibial nails without intraoperative fluoroscopy or proximally mounted targeting jigs.

DESCRIPTION OF TECHNIQUE

After performing open antegrade or retrograde nailing by standard techniques, the freehand lock must be obtained before doing standard outrigger locking. This allows the surgeon to control the nail and deliver the locking hole in the nail to a unicortical drill hole in the femur. Before nail insertion, the distance of the desired locking hole is measured from the outrigger in a standard way such that it can be reproduced after the nail is inserted. Through a unicortical drill hole, the nail is palpated with the tip of a Kirschner wire and systematic maneuvers allow the Kirschner wire to palpate and fall into the locking hole. The Kirschner wire is tapped across the second cortex before drilling. The screw is inserted, and the ball-tipped insertion guidewire is placed back into the nail to palpate the crossing screw confirming position.

PATIENTS AND METHODS

We treated 16 patients with 18 long bone fractures using the described technique. We assessed patients clinically and radiographically immediately postoperatively.

RESULTS

A total of 19 blind freehand interlocks were attempted, and 17 were successful as assessed by direct intraoperative observations and by postoperative radiographs.

CONCLUSIONS

We describe a simple technique for performing static locked intramedullary nailing of the femur and tibia without fluoroscopy. This technique was successful in most cases and is intended for use with any nailing system only when fluoroscopy or specialized systems for nailing without fluoroscopy are not available.