Emerging Concepts With Post-Lapidus Bunionectomy Weightbearing
The design allows for three locking screws on each side of the fusion. The screw angles are oriented to maximize bone purchase. The periarticular screws form a trapezoidal configuration, which resists significant loads. The medial cuneiform surface is maximized for screw options and creates a strong anchor in the proximal fixation block while the long metatarsal component aims to resist the cantilever forces. Compression can also occur with a dedicated tear-shaped compression hole.
This plate was specifically designed to be a load bearing plate. It was not intended to be a buttress plate. Therefore, there is no need to place an isolated screw (not incorporated into the plate) across the fusion. Since this “extra” screw is not necessary, there is more bone available centrally at the fusion surface. There is a clinical benefit to having the fusion interface devoid of fixation. The fusion site is clearly visible on a medial oblique X-ray view and surgeons can easily assess radiographic healing without obstructing traversing fixation.
Key Considerations For Early Weightbearing
Early Lapidus weightbearing is best defined as “allowing patients to place weight through the operative extremity prior to bony consolidation.” We all know that radiographic fusion typically takes six to eight weeks. What is not clearly defined is: 1) how much weight can one place, 2) the timeframe from surgery to initiating weightbearing or 3) what kind of extrinsic support is needed.
A proper patient selection and fixation method are probably the most critical factors when determining the viability of a postoperative weightbearing program after Lapidus bunionectomy.1,2 Having a stable fixation construct to resist the weightbearing forces is the first consideration because fixation failure can lead to malunion and/or nonunion.
Time to start early weightbearing protocol. Some may begin early weightbearing immediately after surgery while others may wait until the soft tissue is healed and sutures are out.1,6 I have tried both approaches. In my early experience with the protocol, I waited two weeks to be sure the soft tissue closed in order to avoid a swelling dehiscence. This is a fine and safe approach. Now, in my practice, most patients are allowed to ambulate immediately and this depends on a variety of patient factors such as skin turgor, general health status and the ability to communicate a possible problem. However, the most important consideration is having a stable construct that can resist the weightbearing loads.
Type of extrinsic protection. Some form of extrinsic support (i.e., cast, removable walking boot or post-op shoe) is still necessary during the postoperative healing process. A cast provides the most extrinsic support and is the most restrictive. The least support comes from the post-op shoe but allows for significant freedom for the patient. The removable walking boot provides a good balance of support and reassurance for the surgeon that the loads are lighter in comparison to a post-op shoe.
In all situations, surgeons should be confident that their fixation construct is stable to counteract any early weightbearing for a particular patient. With screw fixation, I tend to use a controlled ankle motion (CAM) walker. With specialty plate fixation, I transition patients to a post-op shoe in most cases.
Amount of weight allowance. When considering the amount of weightbearing, surgeons initially need to answer two key questions: How stable is the fixation? Will this construct support both the weight and activity demands of the patient?