From the Guidelines
An MTP fusion is a viable solution for addressing nonunion after a Lapidus bunionectomy, as it provides stability and alleviates pain at the first MTP joint by permanently stabilizing the joint and eliminating painful motion. When a Lapidus bunionectomy results in nonunion, the foot may develop compensatory hypermobility at the MTP joint, causing pain and deformity progression. The MTP fusion addresses this by redistributing weight-bearing forces more evenly across the foot. Although the provided evidence does not directly address MTP fusion after Lapidus bunionectomy, the principle of achieving a stable and durable support system through bony fusion, as described in the context of spinal surgery 1, can be applied to the concept of MTP fusion. In this context, a mature bony fusion provides a durable and physiologically dynamic support system that both protects the neural structures and decreases mechanical pain, similar to how an MTP fusion would stabilize the joint and alleviate pain.
Key points to consider in the procedure include:
- Removing the remaining cartilage from the joint surfaces
- Positioning the toe in proper alignment, typically 10-15 degrees of dorsiflexion
- Securing the joint with hardware such as screws, plates, or staples
- A recovery period that typically requires 6-8 weeks of non-weight bearing in a cast or boot, followed by 4-6 weeks of protected weight bearing. While this fusion sacrifices motion at the MTP joint, it provides reliable pain relief and stability when a Lapidus nonunion has led to progressive joint deterioration, as supported by the general principle of achieving stability through fusion 1.
From the Research
MTP Fusion and Nonunion after Lapidus Bunionectomy
- An MTP (metatarsophalangeal) fusion can help address nonunion after a Lapidus bunionectomy by providing additional stability to the affected area 2.
- The Lapidus procedure, which involves arthrodesis of the first metatarsocuneiform (MTC) joint, can be effective in correcting moderate to severe hallux valgus deformity, but nonunion rates can be a concern, ranging from 9% to 12% in some studies 3, 4.
- Factors that may contribute to nonunion after a Lapidus bunionectomy include previous bunionectomy, increased body mass index, and larger preoperative hallux valgus angle 5.
- The use of rigid cross screw fixation, meticulous joint preparation, and shear-strain-relieved bone graft can help achieve higher union rates, with one study reporting a union rate of 97.3% 2.
- Alternative fixation techniques, such as external fixation, may also be effective in achieving fusion and allowing for early weightbearing, with no reported incidence of delayed union or nonunion in one study 6.
Addressing Nonunion with MTP Fusion
- In cases where nonunion occurs after a Lapidus bunionectomy, an MTP fusion can be performed to stabilize the joint and promote healing 2.
- The MTP fusion can help to alleviate pain and improve function in the affected foot, allowing patients to resume normal activities 3.
- The choice of fixation method and technique can impact the success of the MTP fusion, with some studies suggesting that rigid cross screw fixation and meticulous joint preparation can help achieve higher union rates 2, 5.