A Novel Retrograde Nail for Internal Fixation of Condylar and Supracondylar Fractures of the Distal Femur. Design Concept and Early Clinical Experience

Retrograde intra-medullary nailing for treatment of fractures of the femoral shaft is gaining in popularity, particularly in trauma centres in the United States of America.

Indications include obesity, patients with multiple injuries, and the “floating knee” with ipsilateral femoral and tibial fractures, where the easy surgical approach through the knee offers clear advantages. Retrograde nails may also be useful for distal shaft fractures in patients where a previous hip replacement (THR) precludes the use of an antegrade nail.

Another specific indication for retrograde nails is for internal fixation of supracondylar and condylar fractures of the distal femur.

In the case of such fractures, the first generation of retrograde nails with conventional transverse locking bolts or screws has provided only relatively tenuous fixation of the condyles with respect to the shaft.

The majority of the bone mass of the condyles lies posterior to the axis of the intra-medullary canal and transverse locking screws therefore miss their target.

A new generation of nails with specially adapted geometry of the distal locking bolts is now being developed.

One such novel implant for secure internal fixation for supracondylar and condylar fractures of the distal femur has been developed by Biomet Merck.

This involves a retrograde intra-medullary nail with a unique “cruciate” configuration of distal locking bolts which stabilise the femoral condyles in relation to the shaft. The distal locking bolts have large (10 mm o. d.) cancellous threads to provide a secure grip within the mass of each condyle (Figs. [1 a, b])

Fig. 1 a, b The new retrograde femur nail with “cruciate” configuration.
Fig. 1 a

Fig. 1 b

The optimal geometrical configuration of the distal locking bolts has been developed with the aid of cadaver studies.

For some time it has been the practice for new joint replacements to have to undergo rigorous biomechanical testing and clinical trials before being licensed for general use. Trauma products have until recently escaped such close scrutiny, however this is no longer acceptable.

After finalisation of the design, a protocol for testing and clinical evaluation was therefore agreed between Biomet Merck and the UK Medical Devices Agency.

Laboratory mechanical testing of fixations of both segmental defects and “T” fractures of the distal femur using the “cruciate” retrograde nail have shown that this compares favourably with fixation using a Dynamic Condylar Screw (DCS) implant.

The new nail has now also completed a clinical trial in a series of patients over a limited two year trial period. This has confirmed ease of use and the effectiveness of jigs for both distal and proximal locking (Figs. [2, 3]).

Fig. 2 a-c Implantation of the nail in the operation theatre.
Fig. 2 a

Fig. 2 b

Fig. 2 c

Fig. 3 a-c X-ray control after implatation.
Fig. 3 a

Fig. 3 b

Fig. 3 c

Following completion of testing and clinical trials, the Medical Devices Agency has now granted approval for general use of the new Biomet Merck retrograde femoral nail.

Sulzer Medica is also developing a new retrograde nailing system at the present time incorporating specially adapted geometry of the distal locking screws.

It is anticipated that this new generation of nails will greatly facilitate the management of distal femoral fractures.