Undisplaced Femoral Neck Fractures 2 Hansson Pins or 3 Pins Interlocked in Plate (Pinloc) Using RSA

Femoral neck fractures represent about half of the hip fractures and are further divided into displaced and undisplaced fractures. Displaced femoral neck fractures are almost always treated surgically with arthroplasty. However there is an ongoing debate on which implant is superior for undisplaced fractures.

A novel implant design (Pinloc) has been developed by Swemac Innovation AB. While the original implant consisted of 2 isolated hook pins, the modified design consists of 3 titanium hook pins interlocked in an aluminum plate. Interlocking is a new principle of implant design and improves fixation and load transfer amongst the pins. The superiority of the modified design is so far only proven preclinically. The role of the Pinloc in clinical use remains unclear.

A series of studies is now planned at Oslo University Hospital in collaboration with Diakonhjemmet Hospital in hope to further clarify this debate. The use of the Pinloc has been introduced in some regions (e.g. Norway, Sweden and Japan). The role of the Pinloc remains unclear and very little has been published on it's use, even though it is believed to be an important contributor of stability to the fixation.

Femoral neck fractures are mainly caused by a fall from own height in the elderly. The fractures are most often classified as displaced or not, using the simplified Garden classification. Several other classification systems also exist, but these have not been shown to be of reliable clinical usefulness. The ideal classification system should be easily applicable, reliable, and aid in treatment decision making and prognosis.

The treatment of femoral neck fractures comprise perioperative and operative modalities. The perioperative modalities consist among others of medical optimalization preoperatively, early rehabilitation and prevention of new fractures by treating osteoporosis and preventing new falls. The main scope of the current study will, however, be the operative modalities.

Surgery for undsiplaced femoral neck fractures is performed mainly with internal fixation on a traction table, using either screws, pins or a sliding hip screw (SHS), available in various designs from different manufacturers. The latest Cochrane review did not conclude on which implant is the superior.

Radiostereometry (RSA) is the most precise and accurate method to measure motion in vivo between different segments in orthopaedic research. To do so, radioopaque tantalum markers are implanted into the bone defining different segments. Stereoradiographs are performed over time to detect movement and monitor the healing (or non healing) process. This movement can be calculated both as translations and rotations. They are ideal to describe and compare the stability of fracture systems. RSA has been used successfully in earlier studies on fracture healing. Due to the high accuracy and precision, RSA yield reliable results with relatively small study-groups. Investigators plan to use RSA to measure fracture dislocation and time to healing in our studies. The study will be on the function of the Pinloc and it´s ability to prevent secondary dislocation in undisplaced femoral neck fractures. Investigators will utilize RSA for measurements during follow-up.

Inclusion criteria

• undisplaced femoral neck fractures
• able to walk independently, aids such as crutches or walker allowed
• able to consent
• fit for surgery with pins with or without plate

Exclusion criteria

• not willing or able to attain follow up
• previous fracture or surgery with retained metal work in the same hip
• concomitant disease that will shorten life expectancy (i.e. cancer, COPD)