The Ultimate Guide To Lock Screw And Plate Fixation

Lock screw and plate fixation is a common method used in orthopedic surgery to stabilize and fixate fractures. This technique involves the use of plates and screws to hold bone fragments in place, allowing for anatomical restoration, fracture stability, preservation of blood supply for healing, and early postoperative mobility. The locking mechanism provides increased resistance to disassembly and can be particularly useful in cases of mediocre or osteoporotic bone quality. Plate and screw fixation can be applied to various bone shapes and sizes, with different types of plates available, such as neutralization, buttress, and bridge plates, each serving a specific purpose. The success of this technique relies on proper pre-operative planning, including determining the appropriate type of plate, screws, and their positioning to achieve the desired mechanical properties and promote healing.

Locking plates are used for periprosthetic fractures where conventional osteosynthesis is often unsuccessful

Locking plates are a valuable tool in the treatment of periprosthetic fractures, which have seen an increase in incidence alongside the rise in knee and hip arthroplasty procedures. Conventional osteosynthesis often encounters limited success in treating periprosthetic fractures due to the presence of an intramedullary implant in the femur, resulting in high complication rates and poor functional outcomes.

Locking plates, on the other hand, have demonstrated advantages over conventional plates, making them the most common treatment for periprosthetic fractures. They provide better bone purchase, especially in osteoporotic bone, and their screws thread into the plate, creating fixed-angle anchorage. This design allows the screws to act in concert, gaining purchase in multiple regions of bone rather than individual sites, as seen with traditional screws.

The use of locking plates can lead to successful union and restoration of function in elderly patients with periprosthetic fractures. For instance, in the treatment of periprosthetic femur fractures, locking plates have achieved union rates of up to 95%, with lower complication and revision rates compared to conventional methods.

However, it is important to note that locking plates are not without their challenges. Failure of locking plate fixation can occur due to inadequate planning, incorrect fracture reduction, improper implant length, or inappropriate screw type, number, location, and sequence. Additionally, locking plates can be difficult to remove and may require specialised instrumentation.

Locking plates are more resistant to disassembly than conventional bone plates

The advantages of locking plates become more apparent when dealing with mediocre-quality or osteoporotic bone. In such cases, conventional bone plates with non-locking screws may not achieve adequate purchase, leading to poor bone fixation. On the other hand, locking plates provide better bone purchase and stability, even in osteoporotic bone. This is because locking plates do not rely solely on bone-plate compression for stability; instead, they utilize a fixed-angle implant where the plate and screws function together as a unit. As a result, locking plates can maintain fracture reduction without the need for perfect contouring to the bone surface, which is often required for conventional bone plates.

Additionally, locking plates offer the advantage of minimally invasive surgical techniques. The stability provided by the locking screw system reduces the need for extensive soft tissue exposure during implantation, minimizing surgical trauma and promoting faster healing. This is particularly beneficial for periprosthetic fractures, where conventional osteosynthesis often encounters limited success.

While locking plates offer superior resistance to disassembly, it is important to note that improper planning, such as incorrect implant length or inappropriate screw type, can lead to complications. These include an overly rigid or flexible construct, which can compromise healing and potentially result in implant failure. Therefore, preoperative planning and proper technique are crucial to maximizing the benefits of locking plates.

Locking plates are better for fixation of fractures in low-quality bone

Locking plates are a metal plate with screws that can be tightened to stabilise a fracture and hold it in place to allow for healing. They are particularly useful for patients with osteoporosis, a disease that weakens bones and increases the risk of fractures.

Locking plates are an effective treatment option for fractures in low-quality bone, especially in older adults who are at a higher risk of osteoporosis. The stability and pullout strength of locking plates are determined by the sum of all locked screws. When screws are locked into fixed angles, the broken bones stay closer together, increasing the likelihood of quality healing.

In comparison to traditional plates, locking plates have greater resistance to failure, especially in low-quality bone. This is because locking plates achieve stability without the need for direct contact with the bone surface. The screws in locking plates act in concert, gaining purchase in multiple regions of bone rather than individual sites as with traditional screws.

Additionally, locking plates are less invasive than other types of surgery and can be performed on an outpatient basis, making them an attractive option for older patients who may be at risk for complications from more traditional surgeries. They also allow for less invasive approaches, which may benefit soft tissue healing.

While locking plates have become a preferred choice for treating fractures, particularly in osteoporotic patients, it is important to note that they are not a cure-all. Failure of fixation and intra-articular penetration of implants can still occur, especially if stable fracture reduction is not achieved.

Locking plates are more resistant to en bloc pulling out of the implant

The fundamental difference between conventional bone plates and locking plates lies in the way the screw head is locked into the plate. In locking plates, the screw head is locked in the plate with a locknut, either by screwing in a threaded chamber on the plate or by screwing through an adapted ring. This mechanism provides greater resistance to disassembly compared to conventional plates.

The advantages of locking plates are particularly evident in epiphyseal fixation and the fixation of periprosthetic fractures. Locking plates also offer better bone purchase, especially in osteoporotic bones. The threads on the screw heads lock directly into the plate, providing stability and creating a fixed-angle construct. This design makes the entire segment attached to a bone fragment pull out as a unit, rather than individual screws failing in sequence as seen in non-locked plate constructs.

While "en bloc" pulling out of the implant is still possible with locking plates, the correct biomechanical choices during fixation can prevent this. The type of plate, the type of screws, and their position are critical factors that determine the mechanical properties of the construct and influence the resistance to implant failure.

Locking plates can be difficult to remove

A study comparing the complication rates of Locking Compression Plate (LCP) removal and conventional non-locking plate removal found that the median operation time of LCP removal was significantly longer than that of non-locking plate removal (72 vs. 54 minutes, p < 0.001). The complication rate of LCP removal was also significantly higher (17.7% vs. 2.5%, p = 0.001).

The difficulty in removing locking plates is due to the locking mechanism between the screw head and the plate, which provides increased stability to the construct. This mechanism creates a fixed-angle construct that fails as a unit, with the entire segment attached to a bone fragment pulling out rather than individual screws failing in sequence.

In some cases, technical difficulties may arise during the removal of locking screws from locking plates. For example, the hexagonal recess of the screw may strip during attempts at screw removal using a conical extraction device. However, there are techniques to overcome such challenges, such as drilling another hole immediately adjacent to the screw and applying leverage force to the plate with an elevator.

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