Mastering the Extended Distal Chevron Osteotomy for Hallux Valgus Correction

Introduction: Expanding the Distal Chevron Osteotomy

Alright, fellows, gather 'round. Today, we're tackling a procedure that has become a cornerstone of forefoot surgery: the distal chevron osteotomy. While traditionally reserved for mild to moderate hallux valgus, we're going to explore how we can extend its indications to more complex deformities, leveraging its inherent stability and reproducibility. This isn't just about moving bone; it's about restoring anatomical alignment and biomechanical function, ensuring a durable correction for our patients.

The fundamental principle here is to re-align the first metatarsal head, bringing it into a more anatomical relationship with the sesamoid complex and the second metatarsal. The ideal correction, as we've discussed in clinic, is achieved when a line drawn along the first metatarsal shaft becomes parallel to the second metatarsal shaft bisector and touches the medial base of the first metatarsal or cuneiform. This theoretical line is our guide, indicating the optimal location for our corrective osteotomy and estimating the necessary translational correction.

Figure 1: The "ideal correction" is found by drawing a line parallel to the second metatarsal bisector that touches the base of the first metatarsal. The position where this line crosses the first metatarsal bisector helps determine the location and degree of translation needed for the first metatarsal osteotomy.

What makes this "extended" technique so powerful? By modifying the apex of our chevron osteotomy to a more proximal location and slightly reducing its angle, we create a broader, more stable healing surface. This design facilitates maximal lateral translation of the distal metatarsal head fragment, which is crucial for larger corrections, while simultaneously reducing the risk of avascular necrosis (AVN) — a significant concern with more distal osteotomies. Furthermore, this proximalization allows us to safely perform a necessary lateral capsular release in cases of significant sesamoid subluxation, without compromising the vascularity of the distal fragment.

We'll also pay close attention to the Distal Metatarsal Articular Angle (DMAA). This angle, representing the orientation of the distal articular surface relative to the metatarsal shaft, can be altered by varus or valgus rotation during our osteotomy. Assessing and addressing the DMAA preoperatively and intraoperatively is vital for preventing iatrogenic hallux varus or persistent valgus.

Comprehensive Surgical Anatomy of the First Ray

Before we make our first incision, let's meticulously review the anatomy of the first ray. A thorough understanding is paramount to safe and effective surgery.

Osteology and Biomechanics

The first metatarsal is a robust bone, but its distal aspect, particularly the metatarsal head, is critical for weight-bearing and propulsion. The head articulates with the proximal phalanx of the great toe, forming the first metatarsophalangeal (MTP) joint. Plantar to this articulation lie the medial and lateral sesamoids, embedded within the flexor hallucis brevis tendons. These sesamoids act as fulcrums, enhancing the mechanical advantage of the flexor hallucis brevis and protecting the plantar aspect of the metatarsal head. In hallux valgus, the lateral sesamoid often subluxes laterally, disrupting normal joint mechanics.

The width of the distal metatarsal is a key anatomical factor influencing the amount of correction we can achieve with a translational osteotomy. In patients with a small, narrow, or "hourglass-shaped" metatarsal, the potential for lateral translation may be inherently limited. This needs to be templated and considered during our preoperative planning.

The Distal Metatarsal Articular Angle (DMAA) is the angle formed by a line perpendicular to the articular surface and the longitudinal axis of the metatarsal shaft. A normal DMAA is typically neutral or slightly valgus. An increased DMAA can contribute to the hallux valgus deformity by directing the great toe laterally, even with a well-aligned metatarsal. Correcting this rotational component during the osteotomy is essential.

Finally, we must assess for hypermobility of the first ray at the cuneiform-metatarsal joint. While the extended chevron addresses distal deformities, significant instability at the tarsometatarsal joint can compromise the long-term correction of a distal osteotomy, as it allows the first metatarsal to drift medially. If this hypermobility is severe, a concomitant proximal procedure like a Lapidus fusion might be indicated, though for today's procedure, we are assuming this instability is not the primary driver or is manageable.

Neurovascular Structures at Risk

The foot, particularly the medial aspect of the forefoot, is rich in crucial neurovascular structures. Meticulous dissection and constant vigilance are non-negotiable.

• Superficial Peroneal Nerve: Specifically, its dorsomedial cutaneous branch is highly vulnerable during the medial longitudinal incision and subsequent dissection. This nerve typically courses superficially over the dorsum of the foot, often crossing the first MTP joint area. It provides sensation to the dorsum of the great toe and the medial side of the second toe. We must identify and protect it throughout the approach. Injury can lead to painful neuromas or persistent numbness.
• Medial Plantar Digital Nerve: This nerve, a branch of the medial plantar nerve, runs along the medial aspect of the great toe, providing sensation to the medial plantar aspect of the great toe and the medial sesamoid region. As our dissection nears the medial sesamoid and the plantar aspect of the first MTP joint, this nerve is at risk. It's crucial to stay dorsal to its typical course during capsular incisions and medial eminence resection.
• Vascularity of the Metatarsal Head: The distal metatarsal head receives its primary blood supply from the dorsal metatarsal artery, which anastomoses with plantar vessels. However, the majority of the blood supply to the metatarsal head, particularly the dorsal aspect, comes from the periosteal plexus and small vessels entering the metaphysis. When performing a distal osteotomy, especially a chevron, preserving the soft tissue attachments (periosteum, capsule, and plantar plate) to the distal fragment is paramount to prevent avascular necrosis. Our proximalized chevron helps mitigate this risk by leaving a larger, more robust bony fragment with intact soft tissue attachments.

Soft Tissue Considerations

• Adductor Hallucis Tendon: This tendon inserts into the lateral aspect of the proximal phalanx and the lateral sesamoid. It is a significant deforming force in hallux valgus. During a lateral capsular release, it's important to understand its anatomy. While some surgeons advocate for its release or tenotomy, in our extended chevron, we aim to preserve the adductor tendon itself, focusing our lateral release on the capsule, thus maintaining some lateral stability. The intermetatarsal ligament, which connects the first and second metatarsal heads, should also be preserved to prevent destabilization of the first web space.
• Capsule and Plantar Plate: The joint capsule, a fibrous envelope surrounding the MTP joint, becomes attenuated medially and contracted laterally in hallux valgus. The plantar plate, a fibrocartilaginous structure on the plantar aspect of the joint, provides significant stability and houses the sesamoids. Our capsular releases and repairs are designed to rebalance these structures.

Preoperative Planning and Patient Positioning

Fellows, effective surgery begins long before the first incision. This is where we finalize our blueprint.

Radiographic Analysis and Templating

We rely heavily on weight-bearing AP and lateral radiographs of the foot. Weight-bearing views are absolutely critical as they reveal the true extent of the deformity under physiological load. On these films, we're meticulously assessing:

• Hallux Valgus Angle (HVA): The angle between the longitudinal axis of the first proximal phalanx and the longitudinal axis of the first metatarsal.
• Intermetatarsal Angle (IMA): The angle between the longitudinal axes of the first and second metatarsals.
• Distal Metatarsal Articular Angle (DMAA): As discussed, this guides our rotational correction.
• Sesamoid Position: We grade sesamoid subluxation using the Hardcastle classification (0-7, or simplified I-III). Grade III subluxation, where the lateral sesamoid is completely lateral to the lateral border of the metatarsal head, almost invariably requires a lateral capsular release.
• Presence of Medial Eminence: The size and shape of the "bunion bump."
• Metatarsal Morphology: Specifically, the width and shape of the distal metatarsal to gauge translational potential.
• First Ray Hypermobility: While not always evident on plain films, we look for signs of splaying at the TMT joint.

Using these measurements, we template our osteotomy. We draw our "ideal correction" line (refer back to Figure 1) on the preoperative radiographs. This helps us determine the optimal apex of the chevron osteotomy, typically 15 to 20 mm proximal to the articular surface, and the desired amount of lateral translation. We also plan for any necessary rotational correction based on the DMAA.

Operating Room Setup and Anesthesia

For this procedure, the patient will receive either a regional ankle block combined with local anesthetic infiltration for excellent pain control and muscle relaxation, or general or spinal anesthesia. If an ankle block is used, we'll apply an ankle tourniquet. Otherwise, a thigh tourniquet is preferred for general or spinal anesthesia, ensuring a bloodless field. The tourniquet time will be closely monitored.

Our C-arm fluoroscopy unit will be positioned to allow for immediate AP and lateral views without significant repositioning of the patient or the unit. We'll ensure the image intensifier is draped and ready for sterile use.

Patient Positioning and Tourniquet Application

The patient is positioned supine on the operating table. The affected foot is positioned at the end of the table, allowing the knee to be slightly flexed and the hip externally rotated for optimal access to the medial aspect of the foot. A small bump or roll can be placed under the ipsilateral hip to prevent excessive external rotation and maintain a neutral alignment of the lower extremity.

Once the patient is positioned, we apply the chosen tourniquet. For an ankle tourniquet, ensure proper padding to prevent skin irritation or nerve compression. Inflate the tourniquet to a pressure typically 100 mmHg above systolic blood pressure (for ankle) or 250-300 mmHg (for thigh). Confirm loss of distal pulses. We'll then prep and drape the foot and ankle in the usual sterile fashion, ensuring access to the entire first ray and the first web space.

Intraoperative Masterclass: The Extended Distal Chevron Osteotomy

Alright, fellows, we're scrubbed in, patient is prepped and draped. Let's begin.

Step 1: Surgical Incisions and Initial Exposure

Our first step is to gain access to the joint. We'll typically use two incisions for this extended technique, especially if a lateral release is anticipated.

First, let's address the potential need for a lateral capsular release. This is indicated for significant sesamoid subluxation, typically Grade II or III.

• Dorsal First Web Incision: For the lateral release, we'll make a small, approximately 1.5 to 2 cm, dorsal longitudinal incision in the first web space, just distal to the intermetatarsal ligament. Carefully deepen this incision through the skin and subcutaneous tissue.

  Surgical Warning: Be extremely mindful of the dorsal digital nerves that supply the adjacent sides of the great and second toes. These nerves course superficially in the subcutaneous tissue. Use fine scissors and careful blunt dissection to identify and protect them. Retract them dorsally or plantarly as needed.

  Through this incision, we'll expose the lateral capsule of the first MTP joint. A Freer elevator is invaluable here. Use it to gently probe and identify the dorsal margin of the subluxed lateral sesamoid. Once identified, we'll incise the capsule longitudinally. This incision should extend from the base of the proximal phalanx well proximal to the lateral sesamoid. The goal of this longitudinal cut is to allow medialization of the plantar sesamoid complex at the time of capsule repair from the medial side. Crucially, we will preserve the adductor hallucis tendon, which lies plantar to this incision, and leave the intermetatarsal ligament intact to maintain stability between the metatarsals.

Now, let's turn our attention to the medial side for the main approach.

• Medial Longitudinal Incision: We'll make a medial longitudinal incision, approximately 4-5 cm in length, centered over the first MTP joint. This incision should be slightly curvilinear, following the natural skin creases, extending from just proximal to the joint to the mid-shaft of the proximal phalanx.

  Surgical Warning: As we deepen this incision through the subcutaneous tissue, we must identify and protect the dorsomedial branch of the superficial peroneal nerve. It often runs superficially in this area. Use careful blunt dissection with small Metzenbaum scissors or a fine hemostat to isolate and retract it. Similarly, as we approach the medial sesamoid inferiorly, the medial plantar digital nerve is at risk. Keep your dissection slightly dorsal to avoid it.

  Once the subcutaneous tissues are divided, we'll mobilize the tissues to expose the joint capsule from the medial sesamoid inferiorly to the extensor hallucis longus (EHL) tendon superiorly. The EHL tendon is our dorsal landmark.

Step 2: Lateral Capsular Release (if indicated)

(This step is performed through the dorsal first web incision described above, if indicated by significant sesamoid subluxation.)

With the lateral capsule exposed, we'll use a small scalpel (e.g., #15 blade) or fine scissors to perform our longitudinal capsulotomy. Ensure the incision is truly longitudinal and extends adequately proximal to the sesamoid. Use a Freer elevator to gently tease apart any remaining adhesions, ensuring the lateral sesamoid is now free to move medially. Confirm with palpation that the lateral sesamoid complex is no longer tightly tethered laterally. This completes the lateral release. We will leave this incision open for now and return to close it later.

Step 3: Medial Joint Exposure and Medial Eminence Resection

Back on the medial side, we'll now expose the joint thoroughly.

• Medial Capsulotomy: We'll incise the medial capsule longitudinally. This incision should be made slightly plantar to the center of the metatarsal, extending from the proximal phalanx to well proximal to the medial eminence. Use a small scalpel or electrocautery on a low setting. Once incised, use a small periosteal elevator, such as a Freer, to carefully reflect the capsule dorsally and plantarly. This exposes the medial metatarsal eminence and the articular surface of the joint.

  Surgical Warning: When reflecting the capsule, be gentle. We want to preserve the capsular and periosteal attachments to the distal metatarsal head as much as possible, especially on the dorsal and plantar aspects, to minimize the risk of vascular compromise to the distal fragment.

• Medial Eminence Resection: Now, we address the "bunion bump." We'll use a small oscillating power saw to remove the medial eminence. The amount of bone removed is guided by our preoperative radiographic assessment. Typically, the cut is made 1 to 2 mm medial to the articular margin or the sagittal groove. The goal is to create a flush medial border without over-resecting.

  Surgical Warning: Avoid excessive removal of the medial eminence, as this can lead to an iatrogenic hallux varus deformity postoperatively. The cut should be straight or with a slight distal angulation, avoiding dorsal or plantar angulation that could affect the joint line.

Step 4: The Proximalized Chevron Osteotomy

This is the core of our procedure, fellows. We're performing an extended, proximalized chevron.

• Periosteal Stripping: With a Freer elevator, gently but thoroughly strip the periosteum and soft tissues from the dorsal and plantar aspects of the first metatarsal shaft in the area where we anticipate our osteotomy. This creates a clear bony window for our saw cuts. Again, ensure that the tissues distal to where your bone cut will be are left in place to preserve the vascularity to the distal head fragment.

• Osteotomy Marking: Now, let's mark our osteotomy. The apex of this chevron osteotomy will be more proximal than a traditional distal chevron, typically 15 to 20 mm from the articular surface of the metatarsal head. Use a surgical pen to clearly mark this apex. From this apex, outline the proximal limbs of the chevron at an angle of about 35 to 45 degrees.

  
  
  

> **Surgical Warning:** The angle and length of these limbs are critical. If the limbs are too short, the osteotomy may be unstable after translation. If they are too long, you'll encounter difficulty translating or rotating the distal head portion. A good balance provides stability and allows for adequate correction.

• Performing the Osteotomy: Using a small oscillating saw, meticulously make the cuts along your marked lines. Ensure your saw blade is perpendicular to the metatarsal shaft in the sagittal plane, aiming for a neutral cut. Avoid dorsal, plantar, proximal, or distal angulation of the saw blade, which can alter the biomechanics of the joint. The saw cuts should meet precisely at your marked apex.

Step 5: Distal Head Translation and Rotational Correction

Once the osteotomy is complete, the distal head fragment should be readily mobilized.

• Mobilization: To facilitate translation, apply gentle traction to the great toe with one hand. With your other hand, use a small towel clip or a bone clamp placed on the apex of the proximal metatarsal fragment to provide counter-pressure. Then, use your thumb to apply gentle but firm pressure against the medial aspect of the distal head, pushing it laterally. This combination of traction and counter-pressure allows for smooth repositioning of the metatarsal head with minimum force.

  
  
  

> **Surgical Warning:** If the head fragment is not readily mobilizing, **do not force it**. This indicates an incomplete osteotomy. Recheck your cuts, ensuring they are complete and meet at the apex. Sometimes, a small bony bridge remains.

• Translation and Perching: Due to the proximal location of our osteotomy, the lateral cortex of the proximal metatarsal often appears as a distinct spike. The distal head fragment is then translated laterally and "perched" stably on this lateral process. This provides excellent inherent stability, allowing for significant lateral translation—up to 90% translation is possible and well-tolerated with this technique.

  
  
  

Tech Figure 2B: The lateral cortex of the proximal metatarsal provides a stable spike to perch the distal head fragment.

• Rotational Correction: At this stage, we can also apply slight varus or valgus tilt to the distal head fragment as indicated by our preoperative DMAA assessment. If the DMAA was excessively valgus, we can rotate the distal fragment slightly into varus to neutralize the articular angle. Use fluoroscopy to confirm your correction.

Step 6: Provisional and Definitive Fixation

Once the desired translation and rotation are achieved, we need to stabilize the osteotomy.

• Kirschner Wire Placement: We'll use 0.054 smooth Kirschner wires for fixation. My preference is for two wires to maximize stability and prevent head migration, especially with large corrections.
  1. First Pin: Direct the first K-wire from the proximal third of the first metatarsal, aiming slightly medially. The pin should exit the lateral cortex of the proximal fragment and then enter the distal head fragment. This creates a stable three-point fixation (proximal medial cortex, lateral cortex of proximal fragment, and distal head fragment). Advance the pin carefully, ensuring it engages both fragments securely.
  2. Second Pin: Place a second similar pin, parallel to the first, to enhance rotational stability and prevent sag or dorsal malunion.
• Radiographic Confirmation: Immediately after placing the pins, obtain fluoroscopic images (AP and lateral) to confirm the position of the distal head fragment, the adequacy of translation, the correction of the DMAA, and the secure placement of the Kirschner wires. Ensure no pin is intra-articular.
  

  
  
  

Figure 2A: Intraoperative radiographic appearance of the osteotomy. The “medial bump” still needs removal from the metatarsal.
* Pin Management: The K-wires are typically bent at a right angle and left protruding percutaneously for easy removal in the clinic. Alternatively, they can be cut adjacent to the bone and buried, requiring elective removal in a minor procedure later. For this specific technique, with its focus on aggressive medial contouring, leaving them percutaneous is often safer.

Step 7: Medial Metatarsal Contouring

This is a critical step often overlooked, leading to postoperative patient complaints.

• Aggressive Medial Bump Removal: After fixation, you'll notice a remaining prominence of bone from the proximal, medial metatarsal shaft. This is the "medial bump" created by the lateral translation of the distal head. It is absolutely essential to aggressively contour this back. Use your power saw to remove this bone, creating a smooth, continuous medial margin in line with the new, translated distal head. This often requires cutting into the medullary canal of the proximal metatarsal to achieve a truly flush contour.

  
  
  

> **Surgical Warning:** Be extremely careful during this step to **avoid cutting your Kirschner wires**. Ensure the pins are placed proximal enough to be clear of this aggressive contouring. If your pins are too distal, you risk destabilizing your osteotomy.

The goal is to prevent a residual bony bump at the mid-metatarsal area, which can be a source of significant irritation and pain for the patient postoperatively.

Step 8: Soft Tissue Closure and Capsul

Additional Intraoperative Imaging & Surgical Steps

REFERENCES

1. Antonio J, Sanhudo V. Correction of moderate to severe hallux valgus deformity by a modified chevron shaft osteotomy. Foot Ankle Int 2006;27:581–585.

2. Austin DW, Leventen EO. A new osteotomy for hallux valgus. Clin Orthop Relat Res 1981;157:25–30.

3. Harper MC. Correction of metarsus primus varus with the chevron metatarsal osteotomy. Clin Orthop Relat Res 1989;243:180–183.

4. Johnson KA, Cofield RH, Morrey BF. Chevron osteotomy for hallux valgus. Clin Orthop Relat Res 1979;142:44–47.

5. Murawski D, Beskin JL. Increased displacement maximizes the utility of the distal chevron osteotomy for hallux vagus deformity correction. Foor Ankle Int 2008;29:155–163.

6. Oh I, Kim MK, Lee SH. New modified technique of osteotomy for hallux valgus. J Orthop Surg 2004;12:235–238.

7. Sanhudo JA. Extending the indications for distal chevron osteotomy. Foot Ankle Int 2000;21:522–523.

8. Sarrafian SK. A method of predicting the degree of functional correction of the metatarsus primus varus with a distal lateral displacement osteotomy in hallux valgus. Foot Ankle Int 1985;5:322–326.

9. Schneider W, Aigner N, Pinggera O, et al. Chevron osteotomy in hallux valgus: ten-year result of 112 cases. J Bone Joint Surg Br 2004; 86B:1016–1020.

10. Stienstra JJ, Lee JA, Nakadate DT. Large displacement distal chevron osteotomy for the correction of hallux valgus deformity. J Foot Ankle Surg 2002;41:213–220.

11. Thordarson D, Ebramzadeh E, Moorthy M, et al. Correlation of hallux valgus surgical outcome with AOFAS forefoot score and radiological parameters. Foot Ankle Int 2005;26:122–127.

12. Patients are followed on a 3to 4-week basis to monitor healing and alignment ( FIG 2 ).

13. With larger osteotomy translation and correction, radiographic healing can take 3 months or more. However, the osteotomy is usually stable for activities of daily living within 2 months. Sports and strenuous activities may require 3 to 5 months of healing.

OUTCOMES
- We assessed 72 procedures in 62 patients operated on between Jan. 1, 2002, and Dec. 30, 2003. AOFAS scores and radiographic assessments were obtained from 39 at an average of 27.6 months after surgery. 5

• AOFAS scores averaged 93.3, with complete radiographic healing in all patients.

• Hallux valgus angle correction averaged 22.3 degrees and intermetatarsal angle correction averaged 7.7 degrees.

COMPLICATIONS
- Complications included three symptomatic hallux varus deformities that were felt to be due to routine adductor release. This has been revised to a limited lateral capsule release as described here with preservation of the adductor tendon in most cases.