Objective
This chapter is about a new distal targeting sys- tem that addresses the problems and concerns as- sociated with the amount of radiation exposure and difficulties experienced during the distal in- terlocking procedure of closed intramedullary nailing.
Introduction
Over the past 30 years, closed interlocking nailing has been the method of choice for the manage- ment of diaphyseal long bone fractures. Although evolutions and improvements have occurred in the nail design and material in an effort to (a) simplify the technique and (b) accommodate complicated fractures, distal locking remains the most difficult part of the procedure, requiring the greatest learning curve. Undoubtedly, there is de- mand for a radiation-free, reliable and easy to handle method for distal screw insertion, as tech- niques currently used for distal interlocking have not managed to reduce operation time and radia- tion exposure for patients, surgeons and operating room staff [14, 15, 20].
The objective is to describe a technique that would identify the location of the distal holes in intramedullary nails at a long distance. This tech- nique must reproducibly allow the surgeon to drill a hole axially through the bone and nail with a high level of accuracy.
Description of the Targeting System
The main concept for the development of the new targeting system is that if a specific location (a groove) nearby the distal holes could be identi- fied, the exact location of the distal holes could then be easily found.
There are three major elements in the design of the described radiation-independent system. These are:· A nail with a groove between the two distal holes. The groove is the orientating landmark for the surgeon, as it pinpoints the exact loca- tion of the distal holes.
· A bevelled-tip probe. With this probe the groove can be easily felt. In this way the detec- tion of the holes in the nail by the surgeon is facilitated (Fig. 6.4.1).
· A targeting device that matches the nail's ge- ometry (Fig. 6.4.2). It contributes towards accu- rate drilling of the distal holes and offers guid- ance for the insertion of the screws through these holes.
The distal targeting device consists of three main components:
· An articulation device, which is connected to the nail adapter and the targeting arm.
CHAPTER 6.4
Distal Locking with Mechanical Jig (Author's Own Technique)
G. Anastopoulos
Fig. 6.4.1. The bevelled-tip probe into the longitudinal groove between the distal locking holes of the nail
Fig. 6.4.2.The targeting device tightened on the nail adapter
· An arm.
· A targeting clip, which permits additional ad- justments for targeting the distal holes. The proximal and the distal holes in the targeting clip are in-line with the distal locking holes in the nail, while the middle hole in the targeting clip is in alignment with the centre of the nail's groove.
Surgical Technique
· Patient positioning, insertion of the guide wire, reaming of the femoral canal and nail selection are performed as usual.
· The selected nail must be calibrated with the distal targeting device prior to its insertion (Fig. 6.4.3).
· The nail is then introduced into the femoral ca- nal with the standard operative technique; how- ever, it must be inserted 10 mm deeper than its final position.
· The distal targeting device is attached to the nail adapter (note: the distal holes must always be locked first).
· A pilot hole is drilled on the lateral cortex only through the central hole of the targeting clip.
· The targeting device is removed from the nail adapter.
· An appropriately sized curette is used to clean the debris from the hole.
· The probe is then introduced through the opened hole until it touches the nail's groove.
· With constant pressure against the probe, the nail is pulled proximally until the probe falls into the distal locking hole (Fig. 6.4.4).
· A fixation sleeve is passed over the probe. The handle of the fixation sleeve is removed (Fig.
6.4.5).
· The distal targeting device is reattached to the nail adapter and to the fixation sleeve (Fig.
6.4.6).
· The more proximal hole is drilled and the ap- propriately sized screw is inserted.
272 G. Anastopoulos
Fig. 6.4.3. Calibration of the distal targeting device to the nail
Fig. 6.4.4.By back hammering of the nail the probe is slid- ing inside the groove of the nail and guided into the most distal locking hole
Fig. 6.4.5.The fixation sleeve has passed through the lock- ing hole over the probe (so the system is stable). The han- dle is then removed
Fig. 6.4.6.The distal targeting device is sliding over the nail adapter and over the fixation sleeve
· The probe and fixation sleeve are removed and the hole is completed by drilling through the medial cortex.
· The appropriately sized screw is inserted (Fig.
6.4.7).
· Proximal locking is performed as usual.
Results from Cadaveric Testing
The distal targeting system was used on 20 femo- ral and 20 tibial osteotomies in fresh human ca- davers over a period of 12 months.
· Distal locking was successful in all cases.
· No C-arm verification was required in any of the cases.
· Average time for distal locking with both screws was 5.3 min.
Discussion
Lafforgue and Grosse in Strasbourg invented the first system for distal locking in 1978 [9]. The system did not achieve widespread use because it was unstable, expensive and it could not be adapted on any image intensifier.
Since then, a variety of methods have been de- scribed for facilitating distal locking and reducing radiation exposure [1, 4±8, 11, 16±19, 21]. These methods had inconsistent success mainly because of the final deformation of the nail (axis-pivot phenomenon), which occurs as a result of bend- ing forces in the anteroposterior curvature and also torsion forces that distort the nail, especially in the femur [11]. There has not been a targeting device to address this issue so far. Inevitably, the ªfree-handº technique has become the method of choice for distal locking, where the amount of ra-
diation exposure is determined by the surgeon's skill and experience with the technique [2, 3, 10, 12, 13, 22]. Nevertheless, it has been reported that radiation exposure during distal locking of the fe- mur is on average 2.6 times the amount of radia- tion needed for the actual insertion of the nail [20].
Testing of the new targeting system on cadaveric bones confirmed that the following objectives were met:· Radiation-independent system.
· Accurate and reproducible.
· Easy to use.
· Safe for the patient.
· Sensitive to deformation of the nail.
These parameters will be validated during the clinical trial that has already begun.
Conclusion
The distal targeting device and the corresponding technique appear to be a significant addition to the current intramedullary nailing procedure, as distal locking is getting simpler and radiation in- dependent. Initial experience with cadaveric bones is encouraging and the usefulness of the device in clinical practice remains to be con- firmed in the near future.
References
1. Anastopoulos G, Asimakopoulos A, Exarchou E, Panta- zopoulos Th. Closed interlocked nailing in comminuted and segmental femoral shaft fractures. J Trauma 35 (5):
772±775, 1993
2. Brumback RJ. The rationale of interlocking nailing of the femur, tibia, and humerus. Clin Orth Rel Res 324:
292±320, 1996
3. Bucholtz RW, Rathjen K. Concomitant ipsilateral frac- tures of the hip and femur treated with interlocking nails. Orthopaedics 8: 1402±1406, 1985
4. Conlan DP. Grosse and Kempf locked intramedullary nailing: an improved distal locking screw drill guide. J R Coll Surg Edinb 35: 60±61, 1990
5. Gugala Z, Nana A, Lindsey RW. Tibial intramedullary nail distal interlocking screw placement: comparison of the free-hand versus distally based targeting device techniques. Injury 32: 21±25, 2001
6. Hashemi-Nejad A, Garlich N, Goddard NJ. A simple jig to ease the insertion of distal screws in intramedullary locking nails. Injury 25: 407±408, 1994
7. Hudson I. Locking nailing: an aid to distal targeting.
Injury 20: 129±130, 1989
8. Kelley SS, Bonar S, Hussamy OD, Morrison JA. A sim- ple technique for insertion of distal screws into inter- locking nails. J Orthop Trauma 9: 227±230, 1995 9. Kempf I, Grosse A, Lafforgue D. L' apport du verrouil-
lage dans l'enclouage centro-medullaire des os longs.
Rev Chir Orthop 74: 635±651, 1978
Chapter 6.4 Distal Locking with Mechanical Jig (Author's Own Technique) 273
Fig. 6.4.7.Distal locking through the distal targeting device
10. Klemm KW, Borner M. Interlocking nailing of complex fractures of the femur and tibia. Clin Orthop 212: 89±
100, 1986
11. Krettek C, Mann J, Miclau T, et al. The deformation of slotted and solid femoral nails with insertion: reasons for the failure of distal interlocking screw aiming arms.
J Orthop Res 16: 572±575, 1998
12. Krettek C, Miclau T, Konemann B, et al. A new me- chanical aiming device for the placement of distal inter- locking screws in femoral nails. Arch Orthop Trauma Surg 117: 147±152, 1998
13. Krettek C, Konemann B, Miclau T, et al. A mechanical distal aiming device for distal locking in femoral nails.
Clin Orthop Rel Res 364: 267±275, 1999
14. Kwong LM, Johanson PH, Zinar DM, et al. Shielding of the patient's gonads during intramedullary interlocking femoral nailing. J Bone Joint Surg 72-A (10): 1523±
1526, 1990
15. Levin PE, Schoen RW, Browner BD. Radiation exposure to the surgeon during closed interlocking intramedul- lary nailing. J Bone Joint Surg 69A (5): 761±766, 1987
16. MacMillan M, Gross RH. A simplified technique of dis- tal femoral screw insertion for the Grosse-Kempf inter- locking nail. Clin Orthop 226: 252±259, 1988
17. Pardiwala D, Prabhu V, Dudhniwala G, Katre R. The AO distal locking aiming device. An evaluation of efficacy and learning curve. Injury 32: 713±718, 2001
18. Penning D, Oppenheim W, Faccioli G, Rossi S. Intra- medullary locked nailing of femur and tibia: insertion of distal locking screws without image intensifier. In- jury 28 (4): 323±326, 1997
19. Rao JP, Allegra MP, Benavenia J, Dauhajre TA. Distal screw targeting of interlocking nails. Clin Orthop 238:
245±248, 1989
20. Sanders R, Koval KJ, DiPasquale T, Schmelling G, et al.
Exposure of the orthopaedic surgeon to radiation. J Bone Joint Surg 75A (3): 326±330, 1993
21. Tyropoulos S, Garnavos C. A new distal targeting de- vice for closed interlocking nailing. Injury 32: 732±735, 22. Wiss DA, Fleming CH, Matta JM, Clark D. Comminuted2001 and rotationally unstable fractures of the femur treated with an interlocking nail. Clin Orthop 212: 35±47, 1986 274 G. Anastopoulos: Chapter 6.4 Distal Locking with Mechanical Jig (Author's Own Technique)
