TomoFix Medial High Tibia

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TomoFix Medial High Tibia

Left: Old design. Right: New design.

High-tibial osteotomy is a widely accepted technique in the treatment of varus malalignment and medial osteoarthritis of the knee. Middleand long-term results are good if the indications are respected and an adequate correction is achieved. Corrective osteotomy of the proximal tibia may be performed by a subtractive technique (closed-wedge), by a barrel-vault (dome) osteotomy, or by an additive technique (openwedge). The closed-wedge technique with removal of a bone wedge through a lateral approach and fixation with staples, a plate, or a tension-band system has disadvantages such as risk of peroneal nerve injuries, the need of osteotomy of the fibula, or separation of the proximal tibiofibular joint and of detachment of the extensor muscles. Large corrections cause significant shortening of the leg and an offset of the proximal tibia, which may compromise placement of the tibial component in a total-knee replacement. Open-wedge osteotomy from the medial side can be performed without any muscle detachment, the correction can be fine-tuned during the procedure and no leg shortening occurs. Open-wedge osteotomy has regained interest with the development of stable implants which enable the surgeon to fix the correction and to avoid bone grafts in most cases.

The existing TomoFix medial high tibia (TomoFix MHT) for openwedge osteotomies has been redesigned for better soft-tissue protection and to minimize rotation during compression.

The precontoured plate now has a chamfer at the proximal part and rounded edges at the lateral rims of the plate. A MIPO tapered end at the distal end was added to have a smoother pass to the bone. The two upper LCP holes in the distal part were slightly repositioned in line with the axis of the plate to eliminate the rotation of the plate during compression with cortex screws because of the former asymmetrical alignment of the holes. The two most distal LCP holes were changed to isolated LCP holes to hinder the use of cortex screws.

In a biomechanical comparison, the plates were tested after a right osteotomy. The results show a higher number of cycles with the new TomoFix MHT due to improvements in the manufacturing process. The quality of bone healing with the new TomoFix MHT is similar to the former one but the healing time is expected to be faster and insertion easier. The less prominent design reduces the pain and the higher stiffness activates the use of the compression screw. Handling, use, hospitalizations time, and all other biomechanical characteristics are comparable with the former plate.

The former TomoFix MHT will be replaced with the new version, the article numbers in the catalogue will remain the same.

Details
Instruments
Clinical Cases
Disclaimer

The success of lower-limb osteotomies depends on accurate correction of the mechanical axis and stable fixation during consolidation. Exact realignment of the leg requires precise resection of a bone wedge. The high precision reduces the risk of under- or overcorrection which is what improves the quality of an osteotomy and their durability (knee arthroplasty can be delayed or avoided completely).

The TomoFix Gap Measuring Device enables simple measuring of the depth of the osteotomy gap and determination of the suitable chronOS block (if used).

Guiding Blocks
The Guiding Blocks for TOMOFIX are indicated for medial and lateral high tibia osteotomy and lateral distal femur osteotomy. The Guiding Blocks facilitate the placement of the LCP drill sleeves in the head portion of the plates. The Guiding Blocks for the lateral high tibial osteotomy and for the lateral distal femur osteotomy come in a left and right version. The benefits of osteotomy fixation with TOMOFIX plates are early pain-free mobilization of the patient and a minimal risk of secondary loss-of-correction of the osteotomy. Open or closed wedge osteotomy technique is possible with TOMOFIX plates.

Osteotomy Chisel
Open wedge osteotomy ot the tibia seems to have several advantages over closed wedge osteotomy, including reduced risk of neurologic damage (e.g. peroneal nerve), no shortening of the medial tibial and easier insertion of a future knee arthroplaty if necessary. In addition, the elevation of the proximal tibia can be adjusted more posteriorly or anteriorly according to needs. On the other hand, it is difficult to maintain the open wedge situation with conventional implants.

For the osteotomy, one can use newly developed chisels with rounded edges and measuring scales to determine the depth of penetration. They also come in different widths.

A 68-year-old female.

Case provided by Alex Staubli, Luzern, CH

Preoperative x-rays.

Preoperative measuring.

Immediate postoperatively after osteosynthesis with the newly designed TomoFix for openwedge high-tibial ostotomies.

X-rays 6 weeks postoperatively.

X-rays 3 months postoperatively.

X-rays 12 months postoperatively.

X-rays 20 months postoperatively.

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