OSTEOSYNTHESIS OF HUMERAL DIAPHYSEAL FRACTURE BY INTRAMEDULLARY NAIL WITH ELECTROMAGNETIC DISTAL LOCKING - INTRODUCTION OF THE METHOD AND FIRST EXPERIENCE

Summary

INTRODUCTION: Distal targeting of intramedullary nails has different solutions worldwide, but none of them is used as a standard. The most common method used in practice is targeting by means of the aforementioned peroperative skiascopy, which increases the dose of Xrays for both the patient and the staff. In 2018, an intramedullary nail for osteosynthesis of humeral diaphyseal fractures with the possibility of targeting the distal locking screws using an electromagnetic system for distal targeting was registered in the Czech Republic.

AIM OF THE STUDY: Description of a new method and first experience with distal targeting of the intramedullary humeral nail using an electromagnetic system for distal targeting.

MATERIAL AND METHOD: At the Department of Trauma Surgery, Ostrava University Hospital, we have so far performed 6 osteosyntheses of humeral diaphyseal fractures using an intramedullary nail with electromagnetic distal targeting in 6 patients - 5 men and one woman. The average age of patients was 38 years (24-52). Osteosynthesis was indicated for type 12A (n-4) and 12B (n-2) fractures according to the AO/OTA classification.

RESULTS: The average operative time was 56 min, the average electromagnetic targeting preparation time was 13.33 min, the average distal fixation time was 8.33 min, the average skiascopic time during the operation was 4,05 min.

CONCLUSION: The Austofix Ezy-aim distal targeting system for long humeral studs offers an innovative way of targeting and drilling holes for distal locking screws. Its advantage is the minimization of X-ray radiation during the operation and also the accuracy of drilling. The disadvantage is more complex preparation of the arm for distal targeting and its calibration, as well as connection to the control unit by cables.

Keywords:

Electromagnetic system – distal nail targeting

INTRODUCTION

Osteosyntheses of diaphyseal fractures of long bones with intramedullary nails are nowadays a standard method of treatment of these fractures. The pioneer of intramedullary nail osteosynthesis is considered to be G. Küntscher, who repeatedly published his findings and advantages of this osteosynthesis [3, 4]. This type of osteosynthesis is minimally invasive, the nail is usually introduced from the trepanation hole in the proximal or distal part of the bone by intramedullary way. Reduction of the fracture is performed using the closed method, if possible, without the need for open preparation of the fracture site. The nail must be secured with locking screws at both ends of the nail to maintain the stability of the osteosynthesis, especially its rotational component. The drilling of the canal for the securing bolts is carried out by means of a aiming device firmly connected with the nail. However, this aiming device allows precise targeting only in the proximal part of the nail, distal targeting must be performed under the control of the skiascopy, as the nail deforms during insertion into the bone and the rigid aiming device does not respect this deformation. Distal targeting of intramedullary nails has different solutions worldwide, but none of them is used as a standard. The most common method used in practice is targeting by means of the aforementioned peroperative skiascopy, which increases the dose of Xrays for both the patient and the staff. In 2018, an intramedullary nail for osteosynthesis of humeral diaphyseal fractures with the possibility of targeting the distal locking screws using an electromagnetic system for distal targeting was registered in the Czech Republic.

AIM OF THE STUDY

Description of a new method and first experience with distal targeting of the intramedullary humeral nail using an electromagnetic system for distal targeting.

MATERIAL AND METHOD

The Austofix Ezy-aim electromagnetic distal targeting system is based on the principle of electromagnetic pulse detection. The basic part of the system is an arm for targeting the distal part with the possibility of correcting the position of the distal part. The arm is fixed to the nail holder in a similar way to the proximal targeting arms. The advantage is that the arm can be fixed dorsally or ventrally and the canal can be drilled in safe areas outside the area of the n. radialis course and branching. In the distal part of the arm there are 2 holes for drill sleeves with a locking mechanism to prevent the sleeves from falling out during the operation. The detection of holes in the nail is provided by a transmitter and an electromagnetic signal sensor. The transmitter is placed at a defined location in the distal part of the distal-locking arm - the dynamic hole area. The sensor in a form of a probe is inserted into the canal of the Austofix cannulated nail, after first setting the appropriate length using the stop. Both devices are connected by sterile cables to a control unit that transmits and detects the electromagnetic signal. It is powered by a built-in rechargeable battery. On the display of the control unit it is possible to monitor the calibration of the arm and also the movement of the distal part of the arm with the distal targeting sleeves.

Surgical procedure: After preparing the surgical field and draping the patient, we reduce the fracture with traction and use a gauge to determine the optimal length of the nail. The assistant then assembles the selected nail with the distal targeting arm. After placing the transmitter on the distal part of the arm, the assistant inserts the transducer with the stop set to the length as the selected nail inside the cannulated nail. It then connects the cables to the control unit.

Calibration of the nail follows. The drill sleeves are inserted into the distal holes of the arm and the positioning screw of the arm is used to adjust its position so that when the drill bits are inserted into the sleeves, the drill bits pass through the centre of the distal locking holes. This position is stored in the control unit, the green light in on the monitor in the corresponding distal hole (Fig. 1, 2).

One or both distal holes are calibrated according to the selected type of distal protection. During this preparation, the surgeon can make a trepanation hole for intramedullary nailing from the proximal end of the humerus using a standard approach.

After calibration, the assistant disconnects the arm from the nail holder and the operator inserts the nail into the prepared entry hole in the proximal part of the humerus. After reduction of the fracture by the assistant, the surgeon introduces the nail by intramedullary way gradually across the fracture line distally. Skiascopic control is necessary in this part of the operation. After insertion of the nail, the surgeon fixes the distal targeting arm with the transducer attached to the nail holder - both ventral and dorsal access for distal targeting is possible. The assistant connects the transmitter and sensor cables to the control unit, which is located in a sterile sheath or outside the operating field. The operator inserts the prepared transducer inside the cannulated nail. The arm screw corrects the position of the distal arm holes so that the correct position is confirmed by a green colour in the hole on the control unit‘s monitor (if the position is wrong, it is red). The surgeon then inserts the targeting sleeve into the distal opening of the shoulder. Through mini-incision and soft tissue preparation, the sheath is introduced to the bone. It is advisable to check the correct position of the distal holes of the arm, with potential correction, if appropriate. Then the surgeon uses the appropriate drill bit to drill through the targeting sleeve for distal targeting nail (Fig. 3).

Throughout the drilling process, especially at the start of the drill, it is crucial to make sure that the indicator light is green on the display. It is possible to check the correct drilling by pulling back on the nail holder with the drill bit inserted in the hole - the nail cannot be pulled out. The surgeon then inserts a static distal locking screw. After insertion of the screw, compression of the fracture can be performed by pulling the nail back. A second hole for distal targeting can be drilled in a similar way, which is dynamic for the Austofix nail. The operator then removes the distal targeting arm and transducer, fixes the proximal locking arm to the nail holder and secures the proximal part of the nail with securing screws.

At the Department of Trauma Surgery of the Ostrava University Hospital we have had the Austofix system since 2020. So far we have performed 6 osteosyntheses of humeral diaphyseal fractures in 6 patients - 5 men and one woman. The average age of patients was 38 years (24–52). Osteosynthesis was indicated for type 12A (n- 4) and 12B (n-2) fractures according to the AO/OTA classification; we did not indicate multifracture fractures where a different type of nail or plate osteosynthesis was necessary. Osteosynthesis was performed with a long intramedullary nail, 2 screws were used for distal fixation and 3 screws for proximal fixation (Fig. 4, 5, 6).

During the operations, we monitored the total operative time, nail preparation time and distal fixation time. We also monitored the total skiascopic time during the operation. Postoperative complications were monitored in this cohort of patients; other clinical outcomes, given the size of the cohort and the interval since osteosynthesis, will be the subject of further research.

RESULTS

The total operative time gradually decreased due to shorter preparation of the nail for surgery. In one case, we observed a technical problem where the arm had to be recalibrated to release the stop on the transducer, which resulted in a longer operating time - patient No. 2. In the postoperative period, we did not observe any infectious complications or loosening of osteosynthetic material or osteosynthesis failure. Detailed results are presented in the table (Table 1).

DISCUSSION

Intramedullary osteosynthesis of humeral diaphyseal fractures and its results have been described in many studies [7, 10]. Better results of surgical treatment with an intramedullary nail compared to a locking plate have been demonstrated in several studies [2, 11]. Various systems for distal targeting of humeral locking screws have been described in the literature. A meta-analytic study in the collected studies demonstrates a large margin of error for distal nail locking without fluoroscopy - 0– 27 % [7]. A higher risk of injury to the n. radialis has been described for lateral targeting [8, 9]. Experience with the use of an electromagnetic targeting device for distal targeting of tibial and femoral nails has been described in a study of 19 patients, where the mean distal targeting time for tibial nails (two screws) was 219 s (range of 200–250 s), which is similar to our study. The mean time of distal femoral nailing (two screws) was 249 seconds (range of 220–330 seconds) [8]. A similar positive experience was published in a comparative study of 59 patients with the humeral diaphyseal fractures, where the fluoroscopic distal nail locking technique and the Sureshot ™ Distal Targeting System were compared. The Sureshot ™ Distal Targeting System has proven to be equally effective compared to the fluoroscopic technique, with the added benefit of significantly reducing operating time and risk factors associated with exposure to ionizing radiation for all operating room staff and the patient. [6, 8, 9]. However, this system works with a hand-free locking technique and is not rigidly connected to the nail, which can lead to inaccurate drilling of the canal for distal securing holes - oblique channels. Similar results are described in a meta-analysis of studies comparing electromagnetic aiming systems with the fluoroscopic technique for all nailing methods, but the numbers of patients in each study are small (9 studies, 579 patients, heterogeneity of fractures) [12]. The experience with the Austofix Ezy-aim system has not yet been described in the available world literature. From our point of view, it was quire time-consuming to assemble and calibrate the arm for distal targeting; these times were gradually reduced. If the distal targeting arm is well calibrated, the system is accurate and we have not observed the need to re-drill the distal targeting holes.

CONCLUSION

The Austofix Ezy-aim distal targeting system for long humeral studs offers an innovative way of targeting and drilling holes for distal locking screws. Its advantage is the minimization of X-ray radiation during the operation and also the accuracy of drilling. The disadvantage is more complex preparation of the arm for distal targeting and its calibration, as well as connection to the control unit by cables. Given the relative novelty on the market, further investigation of this method will be necessary.

This paper was supported by project No. CZ.02.1.01/0.0/0.0/17_049/0008441 „Innovative Therapeutic Methods of Musculoskeletal System in Accident Surgery“ within the Operational Programme Research, Development and Education financed by the European Union and by the state budget of the Czech Republic.