The Kidner procedure is a surgical technique designed to address a painful anatomical variation in the foot involving an extra bone near the inner arch. This operation involves two primary actions: the removal of the accessory navicular bone and the stabilization of the nearby posterior tibial tendon. The goal of the procedure is to eliminate the source of chronic irritation and restore proper mechanical function to the foot. The process is typically performed after non-surgical treatments have failed to relieve persistent discomfort.
Understanding Accessory Navicular Syndrome
Accessory Navicular Syndrome (ANS) is a condition that develops when a congenital bone, called the accessory navicular, causes pain or inflammation in the midfoot. This small bone is located on the inner side of the foot, positioned near the arch where the posterior tibial tendon attaches to the main navicular bone. While many people have this extra bone without issue, symptoms can arise, especially during adolescence when bone maturation occurs.
The accessory navicular is categorized into three types based on its connection to the main navicular bone. Type I is a small, separate bone embedded within the tendon and is generally asymptomatic. Type III is a bony prominence or “hooked” navicular, representing a fully fused accessory bone.
The Type II accessory navicular is the most common cause of painful symptoms requiring the Kidner procedure, as it is connected to the main bone by a fibrous or cartilaginous bridge called a synchondrosis.
This synchondrosis in Type II can become irritated and painful due to trauma or overuse. When symptomatic, the area presents with localized pain, swelling, and a visible bony prominence on the inner side of the foot just above the arch. The pain often worsens with physical activity or prolonged standing and can make wearing standard shoes difficult. If conservative measures like rest, orthotics, or immobilization fail to provide relief, surgical intervention may be considered.
Steps of the Kidner Procedure
The Kidner procedure is typically performed on an outpatient basis under regional or general anesthesia. A small incision is made along the inner side of the foot, positioned over the prominent accessory bone. This allows the surgical team to access the accessory navicular bone and the surrounding soft tissues.
The first component of the operation is the excision of the accessory bone. The accessory navicular is often found embedded within the insertion point of the posterior tibial tendon. The surgeon must detach the portion of the posterior tibial tendon that connects to the accessory ossicle before the extra bone is removed.
The second component is the repositioning and reattachment of the posterior tibial tendon. Since the tendon’s natural insertion point was compromised by the accessory bone, it must be securely fixed to the main navicular bone. This reattachment restores the proper tension and function of the tendon, which maintains the foot’s medial arch.
The surgeon may utilize specific fixation techniques for reattachment. This involves drilling small tunnels into the navicular bone and passing strong sutures through the tendon and the drilled holes. Alternatively, specialized bone anchors may be used to secure the tendon directly to the navicular bone. The incision is then closed with sutures, and the foot is dressed and placed in a protective splint or cast.
Recovery and Rehabilitation Timeline
Recovery begins immediately after surgery with a period of non-weight-bearing (NWB) to protect the site of the tendon reattachment. Patients use crutches or a knee scooter during this initial phase, which typically lasts between four to six weeks. During this time, the foot is usually immobilized in a cast or a protective boot.
After the initial NWB period, the patient transitions into a controlled weight-bearing phase. This transition is usually gradual, with the patient slowly increasing the amount of weight placed on the foot over a period of days or weeks. The goal is to allow the tendon to fully heal and secure its new attachment to the navicular bone.
Physical therapy (PT) typically begins around six weeks post-operation and is crucial for restoring full function. PT focuses on regaining ankle and foot range of motion, improving strength, and eventually working on balance and coordination. Patients progress from basic exercises to more dynamic activities under the supervision of a therapist.
While return to daily walking often occurs between six and ten weeks, a full return to high-impact activities, such as running or sports, can take several months. Post-operative swelling and pain are expected, and managing these symptoms through elevation and icing is an important part of the early recovery process. Rehabilitation ensures the foot achieves maximum strength and stability.