Merete PlantarMAX Lapidus Plate Surgical Technique. Description of Plate

Transcription

1 Merete PlantarMAX Lapidus Plate Surgical Technique Description of Plate Merete Medical has designed the PlantarMax; a special Plantar/Medial Locking Lapidus plate which places the plate in the most biomechanically advantageous location for fixation as cited in the literature. The PlantarMax design takes advantage of the tension (plantar) side of the MTC (Metatarsal/Cuneiform) joint during a Lapidus Hallux Valgus correction procedure, maximizing the strength of this construct. This is the first FDA-approved Lapidus Plate designed specifically for plantar fixation. The Merete PlantarMAX Lapidus Plate is designed with 2 plantar locking screws, an interfragmentary screw hole and 2 medial locking (or non locking) screws for additional fixation. There are specially designed bending locations in the plate to allow the plate to be contoured by the surgeon to accommodate varying patient anatomy. With the PlantarMax plate you achieve compression and rigid, stable fixation, facilitating early weight bearing.

2 A single plate length is available for left and right. The low profile bone plates and screws are manufactured from Titanium alloy Ti-6Al-4V ELI.

3 The patented Merete PlantarMax Lapidus plate has been developed in conjunction with Matthew M. Buchanan, MD, Orthopedic Foot and Ankle Center of Washington. Joint Exposure and Preparation 1. A longitudinal medial approach is performed and required, centered slightly plantar to midline over the medial aspect of the 1st Metatarsal Cuneiform (MTC) joint.

4 2. This medial incision may be extended distally to the 1st MTP joint to allow for resection of the medial eminence. A second incision over the 1st web space may be indicated to complete the Modified McBride Procedure (release of the adductor tendon, transverse metatarsal ligament and metatarsal sesamoid ligament). 3. Soft tissue dissection protects branches of the superficial peroneal nerve. Next, identify the insertion of the anterior tibial tendon and retract this tendon plantarly. Expose the 1st MTC joint through a longitudinal capsular incision dorsal to the anterior tibial tendon. A small bone distractor is used to facilitate joint exposure. Care is taken to avoid injury to the insertion of the anterior tibial and peroneus longus tendons.

5 4. Preparation of the joint surface can proceed either with flat saw cuts or by hand with curettes. We prefer hand preparation as the use of curettes minimizes bone loss, thus preventing shortening of the 1st ray. Curettes remove the articular cartilage; small drills penetrate the subchondral bone and osteotomes feather the first MTC joint, thus minimizing bone removal/resection. The goal is to expose healthy, bleeding cancellous bone on both sides of the fusion. If saw cuts are used, care must be taken to avoid shortening the first ray. It is important to ensure complete preparation of the plantar and lateral aspects of the joint. Preparation of the 1-2 interspace is typically not necessary but if chosen, this area can be exposed either through the joint (by the use of a distractor) or by extending the capsular dissection dorsally and laterally. 5. The 1st metatarsal is then manually adducted and plantarflexed as needed to obtain an acceptable position. Optimal positioning includes the sesamoids reduced under the 1 st Metatarsal head, Intermetatarsal Angle of 0-9 degrees, and a congruent 1 st MTP joint. Sagittal plane alignment should reveal that the 1st Metatarsal is parallel to the lesser metatarsals. 6. A number of intra-operative techniques may be used to maintain optimal positioning during plate implantation. The surgeon can use manual pressure applied to the 1 st metatarsal head to reduce the deformity. Alternatively, grasp the Hallux and gently manipulate it in a varus and dorsiflexed posture. This pushes the 1st MT head laterally and plantarly, correcting a large IM angle and plantarflexing the 1 st ray, if indicated. Finally, the use of a bone reduction tenaculum applied between the 1st and 2nd metatarsal heads may be useful in difficult cases.

6 7. While manipulating the 1st metatarsal, avoid translating the 1st MTC joint plantarly or medially as this reduces the surface area available for fusion and will prevent proper plate positioning. Shortening of the 1st ray will occur with any fusion procedure and this shortening can be accommodated by slight plantarflexion of the 1 st metatarsal. Ultimately, this amount will be based on surgeon judgment but the goal is to create a weight bearing presence of the 1st metatarsal head with plantigrade stance. When alignment has been achieved, a guide pin (1.4mm x 70mm) placed across the joint will provide temporary fixation. Plate Placement and Compression Screw Fixation 8. Place the PlantarMax plate along the plantar surface of the MTC joint, overlying the insertion of the anterior tibial and peroneus longus tendons. Care is taken to avoid excessive dissection of either tendon. The plate was anatomically designed to match the contour of the plantar surface of the 1st MTC joint and does not routinely require bending. If indicated, the PlantarMax plate may be molded and bent with the available bending irons to ensure a contoured fit. The placement of the plate on the plantar (tension) side of the joint provides a biomechanically superior construct for fusion. 9. Once proper placement of the plate is achieved, a temporary k-wire (1.4mm x 70mm) is placed through the plate in the slotted k-wire hole located on the cuneiform side of the joint. The temporary 1.4mm x 70mm k-wire is placed in the most proximal portion of

7 the slotted k-wire hole, to allow for compression of the joint when placing the interfragmentary screw. 10. Next, the guide wire for the interfragmentary compression screw (1.0mm x 150mm) is placed from distal to proximal, through the interfragmentary screw hole, going from the metatarsal to the cuneiform. This guide wire may be inserted with the available Merete Tissue Protector/K-wire Guide positioned in the interfragmentary screw hole prior to insertion to assist in guiding the K-wire into the appropriate position. 11. Fluoroscopy confirms proper positioning and length of the guide wire as well as the overall reduction of the pre-operative deformity. The sesamoids should be reduced under the 1st Metatarsal head, the Intermetatarsal Angle reduced to 0-9 degrees, and the 1st MTP joint should be congruent. The white Merete cannulated depth gauge is passed over the guide wire to measure the appropriate length. To ensure bicortical fixation of the screw, add 2mm to account for plate thickness. 12. Pre-drill over the guide wire with the Merete 2.0mm cannulated drill bit, drilling all 4 cortices. 13. Place the Merete 3.0mm gold cannulated compression screw over the guide wire to fixate and compress the TMT joint. Fluoroscan imaging confirms acceptable plate placement and anatomic osseous alignment. Proper screw length is critical as to avoid injury to the dorsal soft tissues. Plantar Locking Screw Placement

8 14. Next, the plantar screws are inserted. Place a short or long threaded drill guide into the plantar holes of the plate. It is recommended to thread one 2.5mm Drill Guide into the metatarsal/distal screw hole plantarly and one 2.5mm Drill Guide into the cuneiform/proximal screw hole. 15. Pre-drill the Metatarsal plantar side first with the 2.5 solid drill bit. Measure the appropriate length of the 3.5mm (green) locking screw with the sliding depth gauge. For measurements indicated with odd numbers, round up to ensure bi-cortical placement of the locking screw. 16. Pre-drill the Cuneiform plantar side next with the 2.5mm solid drill bit. Measure and place a 3.5mm (green) locking screw. Medial Locking or Non Locking Screw Placement 17. Finally, the medial screws are placed. The medial holes on the PlantarMax plate allow for either locking or non-locking screws. For most applications, locking screws are recommended. If the surgeon chooses to fuse the 1-2 interspace or the inter-cuneiform joint, compression screws may be utilized. 18. Pre-drill the medial Metatarsal side first with the 2.0mm solid drill bit, using the threaded drill guide if locking screws are chosen. Measure with the sliding depth gauge to determine length of the screw. Insert either a 3.0mm locking screw (Blue) or a non-

9 locking compression screw (Gold) for medial/distal fixation. 19. Pre-drill the medial Cuneiform side next with the 2.0mm Solid drill bit placed through the threaded guide. Measure with the sliding depth gauge to determine length of the screw. Insert a 3.0mm locking screw (Blue) or a 3.0mm non-locking compression screw

10 (Gold) into the medial/proximal screw location for final fixation. Closure 1. Final fluoroscan imaging confirms proper bone alignment and hardware placement. Proper screw length is critical as to avoid injury to the dorsal soft tissues. 2. Wounds are closed in layers in standard fashion. Bulky sterile dressing is applied. 3. If stable fixation is achieved and good bone stock is present, the patient may be heel weight bearing in a forefoot relief shoe after surgery. At the first post-operative visit, the patient is allowed full weight bearing in a bunion bootwalker. Ultimately, post-operative protocol will vary based on a number of factors including the overall health of the patient and quality of the soft tissues and final protocol will be based on surgeon judgment. The surgical techniques described in this technique manual serve only as guidelines only. The actual surgical procedure chosen by the surgeon will ultimately depend upon the medical judgment of the attending physician during pre-operative and intra-operative portions of the procedure.

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