Distal locking of femoral nails: evaluation of a new radiation-independent targeting system

Free-hand distal locking of intramedullary nails: How to quickly achieve perfect circles without specific instrumentation

INTRODUCTION

Intramedullary locked nails are mainly used for the fixation of mid-shaft fractures in the long bones. But inserting the distal locking screws by the free-hand technique may require high exposure to radiation. Our method achieves perfect circles on radiographs on the first attempt for lower limb fractures without any specific instrumentation.

SURGICAL TECHNIQUE

We applied a geometric principle in which two lines perpendicular to another line are parallel to each other. Proximal locking, whether it is done or not, serves as a guide for the first perpendicular line to the nail. The fluoroscopy unit is aligned along the drill sleeve or the screwdriver left in place to achieve perfect circles on the first attempt.

DISCUSSION

This technique is simple, reliable, and reproducible. It does not require any specific instrumentation, allows the surgeon to choose any manufacturer's nail and reduces the operating room staff's exposure to radiation.

Preliminary Results with the Shape Memory Nail: A Self-contained Distal Locking Mechanism for Diaphyseal Femur Fractures

Distal interlocking of intramedullary nails can be challenging if not done regularly and can be associated with a prolonged operating time and excessive radiation exposure. Multiple techniques have been developed to overcome these problems but all still rely on conventional distal locking methods. Between December 2011 and March 2013, 18 patients with diaphyseal femur fractures were treated with the shape memory nail (Orthofix, Verona, Italy). These nails use self-contained nitinol memory metal ‘wings’ at the distal aspect of the nail to provide rotational and longitudinal stability. We observed fracture union in all 18 cases with no non-unions, rotational malalignments or peri-prosthetic infections. Median theatre time was 35 (18–71) minutes and median total radiation time was 50 (20–209) seconds. The shape memory nail (Orthofix, Verona, Italy) is an attractive alternative to conventional interlocking femoral nails. It provides sufficient stability to allow fracture union while decreasing theater time and limiting radiation exposure.

Pre-planning of intramedullary nailing procedures: A methodology for predicting the position of the distal hole

Inserting the distal locking screws is a challenging step of the intramedullary nailing procedures due to the nail deformation that makes the proximally mounted targeting systems ineffective. A pre-planning methodology is proposed, based on an analytical model of the nail-bone construct, to predict the nail deformation during surgery using orthogonal preoperative radiographs. Each of the femoral shaft and the nail was modeled as a curved tubular Euler-Bernoulli beam. The unknown positions and forces of the nail-bone interaction were found using a systematic trial and error approach, which minimized the total strain energy of the system while satisfying the force and geometrical constraints. The predictions of the model for the nail deformation were compared with the experimental results of five cadaver specimens in 15 test conditions. Relatively large displacements (up to 13 mm) were found for the distal hole in sagittal plane only. The model predictions were in close agreement with the experimental results, with a root mean square error of 1.2 mm. It was concluded that the proposed pre-planning methodology is promising for practical clinical use in intramedullary nailing operations, in order to provide the compensatory information that is required for tuning of proximally mounted targeting systems.

Radiation-free methods for navigated screw placement in slipped capital femoral epiphysis surgery

PURPOSE

For orthopedic procedures, surgeons utilize intra-operative medical images such as fluoroscopy to plan screw placement and accurately position the guide wire with the intended trajectory. The number of fluoroscopic images needed depends on the complexity of the case and skill of the surgeon. Since more fluoroscopic images lead to more exposure and higher radiation dose for both surgeon and patient, a solution that decreases the number of fluoroscopic images would be an improvement in clinical care.

METHODS

This article describes and compares three different novel navigation methods and techniques for screw placement using an attachable Inertial Measurement Unit device or a robotic arm. These methods provide projection and visualization of the surgical tool trajectory during the slipped capital femoral epiphysis procedure.

RESULTS

These techniques resulted in faster and more efficient preoperative calibration and set up times compared to other intra-operative navigation systems in our phantom study. We conducted an experiment using 120 model bones to measure the accuracy of the methods.

CONCLUSION

As conclusion, these approaches have the potential to improve accuracy of surgical tool navigation and decrease the number of required X-ray images without any change in the clinical workflow. The results also show 65% decrease in total error compared to the conventional manual approach.

Distal targeting device for long Gamma nail(®). Monocentric observational study

INTRODUCTION

Intramedullary nail distal locking screws make it possible to control length and rotation but include an increased risk of radiation exposure. A distal targeting device was recently developed for long Gamma(®) nails (Stryker(®)). The aim of this practical observational study was to evaluate the reliability of this system. Our hypothesis was that the targeting device would be systematically used without conversion or complications.

MATERIALS AND METHODS

All of the long Gamma(®) nails implanted between November 2011 and October 2012 were recorded: 91 nails (59W/32M, mean age 73.5years old) for 68 traumatic fractures, 14 preventive nailings and nine pathological fractures. A junior surgeon performed the procedure in 45 cases and a senior in 46 cases. The number of times the device was used, the difficulties and complications encountered, the duration of fluoroscopy and the dose of radiation were noted. Risk factors were looked for.

RESULTS

The targeting device was used 79 times (the surgeon chose not to use it 11 times, and it was not available in one case). There was a measurement error in one case, therefore 78 nails could be evaluated. Three wrong positions of the distal locking screw occurred. No statistically significant risk factors were identified. Distal locking screw corresponded to 18% of the entire procedure at a radiation dose of 7.44% (this was higher with titanium nails and pathological fractures). Total fluoroscopy time was longer with junior than with senior surgeons but the dose and duration for distal locking were not different.

DISCUSSION

The hypothesis was not confirmed. The device was not systematically used and the risk of complications was not null. No risk factors were identified. The distal locking screw is a difficult step but the use of the targeting device can limit the dose of radiation. This device is effective and allows young surgeons to perform distal locking without increasing the dose of radiation compared to senior surgeons.

LEVEL OF EVIDENCE

Level IV, cohort study, observational prospective follow-up.