Scarf Fixation

A strong fixation is necessary, not only to make secure the location of the plantar distal fragment once displaced, but also to have a strong osteosynthesis allowing early and harmless functional recovery. Several authors emphasized the quality of fixation [2, 123].

First, I designed a special clamp to hold the fragments for fixation. The length of the fragments allows the use of two well separated screws, which achieve easy and reliable fixation: The evolution of the scarf screws I designed in collaboration with the engineers from DePuy Company, is later described.

We have designed and developed a specific scarf screw. It has a threaded head, provides sufficient compression but avoids elevation of the metatarsal head, is self tapping, has a long distal threaded part, and is cannulated. This last feature allows the use of two fine K-wires (1 mm) that are placed (and replaced if necessary) between both fragments with less potential damage than it could result from primary drilling. The setting of the K-wires is critical. The last improvement of scarf screw is now made in collaboration with L. S. Weil: It is the FRS screw, which has new features, such as a longer head allowing more compression and, above all, is self cutting in the distal and proximal threads. Therefore, the use of a countersink is not necessary except in very hard bone (young patients). Furthermore a low profile screw is now available (core 2.5 mm with a special low profile head).

L. S. Weil uses a 2 mm threaded pin instead of K-wire and cannulated drill, and then takes the screw measurement with a standard depth gauge.

Hallux Valgus Weil

Fig. 08a. M1 scarf fixation.

1, 2. The special clamp to hold the displaced fragments.

3. The head of a normal screw may provide problems.

4. Features of the special scarf screw (DePuy).

5. The distal screw is oblique in the head, the proximal is bicortical. This screw is cannulated, which allows to use first a thin K-wire. Furthemore, it may be set and set again until it is in the accurate and correct location.

6. Evolution of the scarf screw: a) 3 mm diameter, original scarf screw. b) 2.5 mm scarf screw with a low profile and longer head. c) the new self cutting screw: It is the FRS screw, designed by L. S. Weil, myself and the Foot + group.

7. Proximally the 2.5 mm screw (b, or the FRS screw) allows to fix very displaced fragments and avoid the risk of proximal secondary fracture.

Fig. 08a. M1 scarf fixation.

1, 2. The special clamp to hold the displaced fragments.

3. The head of a normal screw may provide problems.

4. Features of the special scarf screw (DePuy).

5. The distal screw is oblique in the head, the proximal is bicortical. This screw is cannulated, which allows to use first a thin K-wire. Furthemore, it may be set and set again until it is in the accurate and correct location.

6. Evolution of the scarf screw: a) 3 mm diameter, original scarf screw. b) 2.5 mm scarf screw with a low profile and longer head. c) the new self cutting screw: It is the FRS screw, designed by L. S. Weil, myself and the Foot + group.

7. Proximally the 2.5 mm screw (b, or the FRS screw) allows to fix very displaced fragments and avoid the risk of proximal secondary fracture.

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