Proximal Crescentic Osteotomy: A Masterclass in Hallux Valgus Correction
Key Takeaway
Join us in the OR for an immersive masterclass on the Proximal Crescentic Osteotomy for hallux valgus. We'll meticulously dissect the anatomy, detail precise surgical steps from incision to fixation, and share critical pearls for avoiding complications. Learn expert techniques for lateral release, medial capsular management, medial eminence excision, and osteotomy correction, ensuring optimal patient outcomes.
Alright fellows, gather 'round. Today, we're tackling a foundational procedure in forefoot surgery: the Proximal Crescentic Osteotomy for hallux valgus correction. This is a workhorse procedure, reliable and reproducible, effectively addressing a broad spectrum of bunion deformities. It's crucial to master the nuances, as precision here directly translates to long-term patient satisfaction and functional outcomes.
Indications for the Proximal Crescentic Osteotomy
This procedure is ideally suited for patients presenting with:
* A symptomatic hallux valgus deformity.
* An incongruent first metatarsophalangeal (MTP) joint, meaning the joint surfaces are not properly aligned.
* An intermetatarsal (IM) angle exceeding 10 to 12 degrees, indicating significant splaying between the first and second metatarsals.
* A distal metatarsal articular angle (DMAA) of less than 10 degrees, suggesting the articular surface of the first metatarsal head is not significantly deviated laterally. This helps confirm that the primary deformity is proximal.
Preoperative Planning & Patient Positioning
Before we even make an incision, meticulous planning is paramount.
1. Radiographic Templating: We'll review the weight-bearing radiographs. I've already templated the IM angle and DMAA measurements. We'll also consider the potential amount of lateral translation needed for the osteotomy and estimate the required screw length.
2. Fluoroscopy Setup: The C-arm will be draped and positioned to allow for immediate AP, lateral, and oblique views of the foot without repositioning the patient. This is critical for real-time assessment of osteotomy placement and fixation.
3. Patient Positioning: The patient is supine on the operating table. We'll ensure proper padding of all pressure points. A tourniquet will be applied to the proximal thigh to provide a bloodless field, crucial for identifying delicate neurovascular structures. The foot will be prepped and draped in the usual sterile fashion, allowing full access to the medial and dorsal aspects of the first ray, as well as the first web space.
Comprehensive Surgical Anatomy Review
Let's quickly review the key anatomical landmarks and structures we'll encounter:
* First Web Space: Contains the common digital nerve to the first web space and accompanying vessels. The transverse metatarsal ligament spans between the metatarsal heads.
* Lateral MTP Joint: Here, the adductor hallucis tendon inserts into the lateral sesamoid and the base of the proximal phalanx. The fibular sesamoid is subluxated laterally in hallux valgus. The lateral joint capsule is often contracted.
* Medial MTP Joint: The dorsal medial cutaneous nerve and plantar medial cutaneous nerve are superficial but crucial to protect. The abductor hallucis muscle and tendon lie plantar-medially. The medial eminence of the first metatarsal head is hypertrophic. The tibial sesamoid is located plantar to the metatarsal head.
* First Metatarsal: We'll identify the metatarsocuneiform (MC) joint proximally, the diaphyseal-metaphyseal flare, and the sagittal sulcus on the medial aspect of the metatarsal head.
Now, let's scrub in.
Step-by-Step Intraoperative Execution: The Operating Surgeon's Viewpoint
1. Release of the Lateral Joint Structures
Our first objective is to address the contracted lateral structures responsible for pulling the hallux into valgus. This is performed through a separate dorsal web space incision.
- Initial Incision: I'm making a 2.5-cm longitudinal incision on the dorsal aspect of the first web space, precisely between the first and second metatarsal heads. This is a critical access point.
- Deep Dissection & Retraction: Carefully deepen this incision through the subcutaneous tissue. We want to avoid any damage to the superficial nerves here. Now, let's place a Weitlander retractor with its blades gently positioned between the first and second metatarsal heads. This maneuver puts the transverse metatarsal ligament under tension, making it easier to identify.
TECH FIG 2 • Diagram of Techniques Figure 1, illustrating the insertion of the adductor hallucis tendon into the base of the proximal phalanx and lateral sesamoid. Note the position of the transverse metatarsal ligament.
TECH FIG 2 • Diagram of Techniques Figure 1, illustrating the insertion of the adductor hallucis tendon into the base of the proximal phalanx and lateral sesamoid.
TECH FIG 4 • The transverse metatarsal ligament is placed under tension using a Weitlander retractor.
> **Surgical Warning:** As you deepen this incision, remember that directly beneath the transverse metatarsal ligament lies the **common digital nerve to the first web space and its accompanying vessels**. Exercise extreme caution; we only cut ligamentous tissue, never blindly dissecting.
- Transection of the Transverse Metatarsal Ligament: With the ligament clearly identified and under tension from the retractor, I'm using a small scalpel blade to carefully transect it. This releases the tethering between the metatarsal heads.
- Exposure of Adductor Hallucis: Once the transverse metatarsal ligament is cut, the floor of the web space reveals the adductor hallucis muscle and tendon. It passes obliquely, inserting into the lateral sesamoid and the base of the proximal phalanx.
- Lateral Capsular Release & Adductor Tendon Detachment:
- Identify the contracted capsule between the subluxated fibular sesamoid and the lateral base of the first metatarsal head.
- Using a scalpel, I'll meticulously release this capsule. By extending the incision distally within this interval, we can detach the adductor hallucis tendon from its insertion into the base of the proximal phalanx.
- Next, detach the adductor tendon from the lateral aspect of the fibular sesamoid. We'll dissect proximally along the tendon until we note the more muscular tissue of the flexor hallucis brevis.
TECH FIG 3 • The adductor tendon has been detached from the lateral aspect of the fibular sesamoid and is being held in the forceps.
* Complete Lateral Capsular Release: With the blade well seated against the bone, I'm passing the scalpel proximally, stripping the origin of the lateral joint capsule off the metatarsal head over a distance of approximately 1.5 cm. This ensures a thorough release.
* Creating a Capsular Flap: I'm making an incision through the dorsal aspect of the lateral joint capsule at the level of the MTP joint line. I'll pass the knife blade to the plantar aspect of the metatarsal, creating a flap of lateral joint capsule. This flap will be invaluable later for repair and stabilization.
TECH FIG 5 • The scalpel has been placed through the dorsal aspect of the lateral joint capsule of the first metatarsophalangeal joint.
* Assessing Release: Now, I'll bring the hallux into about 25 degrees of varus. This maneuver allows us to confirm that no lateral contracture remains. If there's still resistance, further release is necessary.
2. Preparation of the Medial Joint Capsule
Now we shift our focus to the medial side, where we'll prepare the medial joint capsule for plication and expose the medial eminence.
- Medial Incision: I'm making a longitudinal incision in the midline, starting at the middle of the proximal phalanx and extending proximally, just past the medial eminence. This provides excellent exposure.
- Subcutaneous Dissection: Carefully identify the plane between the subcutaneous tissue and the joint capsule. We must meticulously work along this plane to protect superficial structures.
- Dorsal Flap Elevation & Nerve Protection: Dissecting dorsally first, I'll gently pull the skin flap away from the capsule. This exposes the dorsal medial cutaneous nerve, which we will carefully identify and retract to prevent injury.
- Plantar Flap Elevation & Abductor Hallucis Identification: Next, dissect the skin flap off the plantar half of the capsule until the abductor hallucis muscle and tendon are identified.
> Surgical Warning: As we make the cut through the abductor hallucis tendon, keep the tip of the knife blade inside the joint. The plantar medial cutaneous nerve lies just plantar to the abductor tendon, and accidental injury can lead to painful neuromas. - Capsulotomy Design (Modified H-Incision):
- I'll make an incision through the joint capsule on the dorsal aspect of the medial eminence.
- Our preferred capsulotomy starts with a vertical cut in the medial joint capsule, positioned 2 to 3 mm proximal to the base of the proximal phalanx.
- Then, I'll peel this capsular flap proximally and plantarward until the medial eminence is completely exposed.
TECH FIG 12 • The medial eminence has been completely exposed. The sagittal sulcus is demonstrated by the Freer elevator.
TECH FIG 12 • The medial eminence has been completely exposed. The sagittal sulcus is demonstrated by the Freer elevator.
* A second, parallel cut is then made 3 to 8 mm proximal to the first cut. The precise distance depends on the severity of the hallux valgus deformity; a more severe deformity requires a wider resection of redundant medial capsular tissue.
TECH FIG 8 • Exposure of the medial joint capsule, showing the parallel cuts that represent the vertical limbs of the capsulotomy.
* Dorsally, we'll connect these two parallel capsular cuts through an inverted V-shaped incision.
* On the plantar side, an upright V-shaped incision is made through the abductor hallucis tendon, ending at the tibial sesamoid.
* Capsular Tissue Excision: Now, carefully remove this redundant capsular tissue. This creates space for correction and allows for proper plication later.
TECH FIG 10 • Removing the medial joint capsular tissue.
3. Excision of the Medial Eminence
With the medial capsule prepared, our next step is to remove the hypertrophic medial eminence, which is often a source of pain and shoe wear issues.
- Osteotomy Planning: The osteotomy to remove the medial eminence is critical. It must start 1 to 2 mm medial to the sagittal sulcus and be performed precisely in line with the medial aspect of the metatarsal shaft. This ensures adequate bone removal without compromising the articular cartilage or creating a sharp corner.
TECH FIG 14 • The osteotomy to remove the medial eminence is started 1 to 2 mm medial to the sagittal sulcus and is performed in line with the medial aspect of the metatarsal shaft.
* Performing the Osteotomy: You have a choice here, fellows: a 16-mm osteotome or a small saw blade. For precise control, I often prefer a small oscillating saw blade. Make a clean cut, maintaining the planned alignment.
* Bone Contouring: After the osteotomy, carefully inspect the metatarsal head. Use a rongeur to smooth off any rough edges or bony prominences. We want a perfectly contoured medial aspect of the metatarsal head.
4. Approach to the Proximal Crescentic Osteotomy
Now, we'll shift our attention proximally to the first metatarsal shaft for the crescentic osteotomy.
- Dorsal Incision: I'm making a longitudinal incision directly over the extensor hallucis longus tendon, extending from just proximal to the metatarsocuneiform (MC) joint distally for about 2.5 to 3 cm.
- Vessel Management: As we deepen this incision, a large vessel often crosses this plane. Identify it, and either meticulously cauterize it or ligate it to maintain a clear field.
- Tendon Mobilization: Carefully mobilize the extensor hallucis longus tendon. Retract it either medially or laterally to expose the metatarsal shaft.
- Subperiosteal vs. Supra-periosteal Dissection: When exposing the metatarsal shaft, it's not strictly necessary to be subperiosteal. Working just above the periosteal plane often allows the surrounding tissues to move more easily, minimizing trauma.
- Identifying Key Landmarks:
- First, clearly identify the metatarsocuneiform joint.
- Make a mark on the metatarsal 1 cm distal to the MC joint. This is our precise site for the crescentic osteotomy.
- Make a second mark on the metatarsal 1 cm distal to the osteotomy site. This is where our fixation screw will be placed.
TECH FIG 15 • The first metatarsal shaft is exposed. The Freer elevator points to the metatarsocuneiform joint. One centimeter distal to the joint marks the site of the osteotomy, and 1 cm more distally marks the screw insertion site.
* Confirming Osteotomy Site: To confirm our osteotomy site, note the subtle flare on the lateral aspect of the metatarsal. This marks the junction of the diaphyseal and metaphyseal bone and is typically located about 1 cm distal to the metatarsocuneiform joint, precisely where we want our osteotomy.
* Guide Pin Placement: Now, advance a guide pin for a 4.0-mm cannulated screw a short distance into the metatarsal, beginning at our marked screw insertion site.
* The pin should be angled at approximately 50 degrees to the long axis of the metatarsal in the sagittal plane. This specific angle ensures the pin, and subsequently the screw, will pass into the plantar aspect of the proximal metatarsal fragment without violating the MC joint.
* The angle of the pin should be neither perpendicular to the bottom of the foot nor perpendicular to the metatarsal, but rather an intermediate position to achieve the desired sagittal plane trajectory.
5. Performing the Crescentic Osteotomy
This is the core of the procedure. Precision and control are paramount.
- Saw Blade Selection: We'll use a crescent-shaped saw blade. These often come in two lengths. It's often easier to start with a shorter blade for initial purchase and then switch to a longer blade if necessary to complete the osteotomy, especially in larger metatarsals.
TECH FIG 17 • The osteotomy is performed with a crescentshaped saw blade.
* Foot Positioning for Osteotomy: This is a critical part of the procedure. I'll sit at the side of the table, holding the patient's foot firmly in one hand. The foot must be held in a neutral position regarding dorsiflexion-plantarflexion and inversion-eversion throughout the cut.
* Saw Blade Orientation: Position the saw with the concavity facing proximally, toward the heel.
* Initiating the Cut: Start the osteotomy cut by applying firm, controlled pressure to the blade.
* Evaluating Blade Position: After making the initial cut into the bone, immediately and carefully evaluate the position of the saw blade. It is essential to ensure that it will cut through both the medial and lateral cortices of the metatarsal shaft.
> Surgical Pitfall: In a wide metatarsal, the blade may not completely penetrate both cortices. If the medial cortex is not completely cut, it is relatively safe and simple to complete the osteotomy in this area with a small osteotome. However, it is difficult and potentially dangerous to complete an osteotomy laterally, as the major artery (dorsalis pedis branch) in the space between the first and second metatarsals could be harmed.
* Completing the Cut: Make the cut by moving the saw in a medial-lateral direction along the arc of the saw blade. While cutting, apply a slight, consistent pressure to the blade toward the heel. This helps to stabilize the blade in the plane of its cut. Once the cut is established, moving the saw blade back and forth with steady, gentle pressure will produce a nice, smooth cut.
* Ensuring Complete Transection: It is absolutely imperative that the cut passes all the way through the metatarsal, ensuring the distal portion of the bone is totally free and has no bony attachments to the proximal fragment. If a medial piece of bone is still present, use a 4- to 6-mm osteotome to complete the cut. Pass a knife blade along the medial side of the cut to confirm that it is completely free of any bony or periosteal attachment.
6. Correction and Fixation of the Osteotomy
This is arguably the most technically demanding part of the bunion procedure, requiring precise manipulation and stable fixation.
- Adductor Tendon Suture: Before we reduce the osteotomy, let's return our attention to the first web space. I'm placing a figure-of-eight suture of 2-0 chromic into the cut end of the adductor hallucis tendon. It's much easier to place this stitch now, before the osteotomy is reduced and the anatomy is shifted.
- Osteotomy Correction – Medial Translation:
- The first step is to push the proximal portion of the cut metatarsal in a medial direction. The objective is to stabilize the base of the metatarsal while rotating the distal portion.
- I'll use a Freer elevator to achieve this, pushing the proximal fragment medially to its medial excursion at the metatarsocuneiform joint.
TECH FIG 19 • Diagram of the osteotomy site. The surgeon’s hand is pushing the metatarsal shaft in a lateral direction. The Freer elevator is pushing the metatarsal base in a medial direction. Note the 2to 3-mm overhang on the lateral aspect of the osteotomy site.
* Osteotomy Correction – Lateral Rotation: While stabilizing the proximal fragment, I'll grasp the metatarsal head firmly with my other hand and rotate the distal aspect of the metatarsal in a lateral direction around the osteotomy site.
* Observe the osteotomy site: the distal fragment typically rotates no more than 2 to 3 mm around the "crescent" of the osteotomy. This creates a lateral overhang, which is normal and desired.
* Intraoperative Radiograph (Optional but Recommended for Learners): When learning this procedure, or if there's any question about the alignment, now is the time to obtain a radiograph. We'll get an AP view to assess the intermetatarsal angle.
* Salvage Maneuver: If the radiograph shows the intermetatarsal angle is not sufficiently corrected, remove the guide pin, remanipulate the osteotomy site, and re-insert the pin until adequate correction is achieved. If the guide pin isn't providing enough stability during this evaluation, a second Kirschner wire can be temporarily used for supplemental fixation.
* Drilling for Screw Fixation: While holding the osteotomy site firmly in its corrected alignment, we'll overdrill the guide pin with the appropriate-sized drill for our cannulated screw set.
TECH FIG 20 • The osteotomy site is being held while the cannulated drill is advanced over the guide pin.
* Advance the drill across the osteotomy site until the plantar cortex is engaged. Usually, it's adequate to advance the drill just past the osteotomy site, ensuring the guide pin doesn't back out when the drill is removed. Once this occurs, the osteotomy site is reasonably stable.
* Countersinking: Use a countersink, primarily on the distal side of the screw hole, to make the screw head less prominent.
> Surgical Pitfall: Be cautious with countersinking. Excessive countersinking can cause the screw head to pull through the screw hole, leading to instability of the osteotomy site.
* Screw Measurement and Insertion: Measure the guide pin to determine the correct screw length. Typically, a 28 to 30 mm partially threaded 4.0-mm cannulated screw is used. Insert the screw across the osteotomy site and carefully tighten it.
> Surgical Warning: As the screw is tightened, be extremely cautious. The island of bone on the proximal fragment is only about 5 or 6 mm thick and can be easily cracked if the screw is tightened too firmly. Aim for firm compression, not overtightening.
* Assessing Osteotomy Stability: After screw insertion, check the stability of the osteotomy site by gently moving the distal fragment in the sagittal plane, looking for any motion.
* Salvage Maneuver: Mild instability can often be addressed by carefully tightening the screw a tiny bit more or by adding a small-diameter Kirschner wire for supplemental fixation. In rare cases of gross instability, a small plate may need to be added to the first metatarsal to secure the osteotomy.
7. Reconstruction of the Medial Joint Capsule
With the osteotomy corrected and fixed, our final step is to reconstruct the medial joint capsule to help maintain the correction and stabilize the joint.
- Capsular Plication: We will now plicate the medial joint capsule. The goal is to imbricate the capsule, tightening it to maintain the corrected alignment of the hallux. I'll bring the toe into a slightly overcorrected position (mild varus) and then use strong, non-absorbable sutures (e.g., 2-0 braided polyester) to bring the capsular flaps together. The goal is to create a tight, stable medial joint.
TECH FIG 22 • With the toe held in slight overcorrection, the medial capsule is plicated.
* Adductor Tendon Reattachment (Optional): The figure-of-eight suture previously placed in the adductor hallucis tendon can now be used to reattach the tendon to the lateral aspect of the metatarsal head periosteum or the lateral capsule. This step helps to further balance the forces across the MTP joint.
* Wound Closure: After confirming hemostasis, we'll close the subcutaneous layers with absorbable sutures and the skin incisions with non-absorbable sutures or staples. A sterile dressing and a compressive bunion dressing will be applied to maintain the correction and minimize swelling.
Pearls and Pitfalls for the Proximal Crescentic Osteotomy
- Nerve Protection: Always identify and protect the dorsal medial cutaneous nerve, plantar medial cutaneous nerve, and the common digital nerve to the first web space. Blind dissection is unacceptable.
- Complete Lateral Release: Inadequate lateral release is a common cause of recurrence. Ensure the adductor hallucis, transverse metatarsal ligament, and lateral capsule are fully released. Confirm with passive varus stress.
- Medial Eminence Resection: Resect the medial eminence flush with the medial metatarsal shaft, 1-2mm lateral to the sagittal sulcus. Over-resection can lead to hallux varus; under-resection can lead to persistent medial prominence.
- Osteotomy Cut: Ensure the crescentic saw blade passes through both cortices. Incomplete cuts can lead to unstable fixation and difficulty in reduction. If the lateral cortex is difficult to access, use a small osteotome medially to complete the cut, but never risk neurovascular injury laterally.
- Fluoroscopic Guidance: Use fluoroscopy liberally for guide pin placement and to confirm osteotomy correction before final screw insertion. Don't hesitate to remove and re-pin if the alignment is not perfect.
- Screw Fixation: A single, well-placed cannulated screw provides excellent compression and stability. Avoid overtightening, especially in osteoporotic bone, as this can lead to fracture of the bone island. If instability persists, supplementary K-wire or a small plate should be considered.
- Soft Tissue Balancing: The medial capsular plication and, if performed, adductor reattachment are crucial for maintaining the correction achieved by the osteotomy. Don't underestimate their importance.
REFERENCES
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At 3 to 5 weeks after surgery another radiograph is obtained to confirm the alignment of the toe.
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Dreeban S, Mann RA. Advanced hallux valgus deformity: long-term results utilizing the distal soft tissue procedure and proximal metatarsal osteotomy. Foot Ankle Int 1996;17:142–144.
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Mann RA, Coughlin MJ. Adult hallux valgus. In: Coughlin MJ, Mann RA, eds. Surgery of the Foot and Ankle, 7th ed. St. Louis: Mosby, 1999.
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Thordarson DB, Rudicel SA, Ebramzadeh E, et al. Outcome study of hallux valgus surgery—an AOFAS multi-center study. Foot Ankle Int 2001;22:956–959.
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If the alignment is not correct, it can still be corrected by pulling the toe into more varus or valgus, depending on what the radiograph dictates.
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After 8 weeks the dressings are removed and the patient is started on range-of-motion exercises.
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