Proximal Mini-Invasive Plantaris Tendon Harvest: An Intraoperative Masterclass

Welcome, fellows, to the operating theater. Today, we're going to delve into a fundamental skill for any foot and ankle surgeon: the proximal mini-invasive harvest of the plantaris tendon. This is an invaluable autograft source, often overlooked, but possessing superior biomechanical properties and minimal donor site morbidity. We'll walk through every step, from meticulous anatomical review to the precise intraoperative execution, ensuring you master this technique.

The Plantaris Tendon: An Ideal Autograft

The plantaris tendon is an exceptional choice for soft tissue augmentation in ligament reconstructions or tendon repairs within the foot and ankle. Its primary advantages are its remarkable tensile strength and structured collagen, mirroring that of a physiological tendon. In fact, comparative studies have shown the plantaris tendon to possess the highest tensile strength per cubic millimeter (94 N/mm³) among commonly used autografts, significantly surpassing the peroneus longus (61 N/mm³), peroneus brevis (41 N/mm³), Achilles split (36 N/mm³), and fascia lata (27 N/mm³).

This robust graft is particularly indicated in cases of chronic joint instability or chronically degenerated tendon ruptures. When ligaments scar in an elongated state or tendons demonstrate irreversible degeneration due to repeated trauma, local tissue may be insufficient for reconstruction. The plantaris autograft offers a readily available, local solution, often within the sterile field of most foot and ankle procedures, without creating appreciable donor site morbidity.

Comprehensive Surgical Anatomy

Before we make any incision, a thorough understanding of the plantaris anatomy is paramount. This knowledge is your shield against complications.

Origin, Course, and Musculotendinous Junction

The plantaris muscle originates from the lateral femoral condyle, just superior to the lateral head of the gastrocnemius. It then courses obliquely distally and medially, along the superficial posterior compartment of the lower leg. Its musculotendinous junction typically lies just distal to the level of the knee joint.

Proximal and Distal Relationships

Proximally, the plantaris tendon is nestled in a distinct fascial plane between the medial head of the gastrocnemius and the soleus muscle. This intermuscular space is a critical anatomical landmark for our proximal approach. Distally, it runs immediately adjacent to the Achilles tendon in the distal third of the lower leg.

Insertion Variability

The plantaris tendon's length typically ranges from 30 to 45 cm, offering ample graft material. However, its distal insertion is highly variable. While it commonly inserts into the calcaneal tuberosity, it may also attach to the bursa calcanei, retinaculum flexorum, ankle capsule, plantar aponeurosis, or blend with the Achilles tendon or intermuscular septum. This variability is a key reason why distal harvesting procedures have a higher failure rate, reported to be unsuccessful in 12% to 20% of cases.

Fellows, observe this anatomical illustration (FIG 1A). Notice how the plantaris tendon is the only tubular structure located between the gastrocnemius and soleus muscles. This anatomical arrangement is our safety net for the proximal harvest.

Now, look at the variability of the distal insertions (FIG 1B). This is precisely why we prefer the proximal approach to avoid unnecessary dissection and potential frustration.

Neurovascular Considerations

Crucially, in the intermuscular plane between the gastrocnemius and soleus, no major nerves or vessels are at risk. The significant neurovascular structures, including the tibial nerve and the posterior tibial artery and veins, run deep to the soleus muscle. This makes the plane between the gastrocnemius and soleus a remarkably safe corridor for blunt dissection.

However, for the proximal approach, we must be mindful of superficial structures:
* Saphenous nerve: A sensory branch of the femoral nerve, it courses superficially along the medial aspect of the calf.
* Great saphenous vein: This major superficial vein also runs along the medial calf.
Both structures lie within the subcutaneous fat and must be carefully protected during the initial skin and subcutaneous dissection.

Functional Significance and Absence

In humans, the plantaris muscle and tendon serve little functional purpose, often described as a vestigial structure. It is absent in approximately 6% to 7% of individuals. Therefore, harvesting this tendon causes no appreciable donor site morbidity or functional deficit.

Preoperative Planning and Patient Positioning

Thorough planning ensures a smooth and efficient procedure.

Preoperative Imaging

While not strictly mandatory, if an MRI scan was obtained for the primary pathology, it can be invaluable to confirm the presence and location of the plantaris tendon. A preoperative ultrasound examination is also highly effective, boasting high specificity in identifying the tendon, especially helpful if the primary pathology imaging doesn't clearly show it. This helps avoid intraoperative surprises.

Patient Positioning

The beauty of the plantaris harvest is its adaptability to various primary foot and ankle procedures. For a proximal harvest, the patient can be positioned either supine with the hip externally rotated and knee slightly flexed, or prone, depending on the main procedure.

For most foot and ankle ligament or tendon reconstructions, a supine position is common. We'll place a gel pad or small bolster under the ipsilateral hip to internally rotate the limb slightly, presenting the medial aspect of the calf. The knee should be slightly flexed to relax the gastrocnemius-soleus complex, making the intermuscular plane easier to access. The entire lower extremity, from the mid-thigh down to the toes, will be prepped and draped in a sterile fashion, ensuring full access to the medial calf. A standard OR table with appropriate padding for pressure points is used; no special attachments like leg holders are typically required for the harvest itself.

No tourniquet is needed for the plantaris tendon harvest, as the dissection is relatively avascular and superficial. This avoids additional patient discomfort and potential risks associated with tourniquet use.

Step-by-Step Intraoperative Execution: The Proximal Approach

Now, fellows, let's get scrubbed in. We'll begin with the authors' preferred technique: the proximal mini-invasive harvest. This approach offers superior success rates due to the consistent anatomy proximally, and it minimizes the risk of cosmetically undesirable scarring at the ankle.

1. Initial Incision and Subcutaneous Dissection

"Alright team, let's begin. We've prepped and draped the limb meticulously. Our incision site for the proximal approach will be a 2-cm longitudinal incision, located approximately 30 cm proximal to the medial malleolus along the medial aspect of the calf. This places us just distal to the musculotendinous junction, where the tendon is well-formed."

• Action: Using a No. 15 scalpel blade, make a precise 2-cm longitudinal skin incision centered over the anticipated course of the plantaris tendon.
• Directive: "Now, with Metzenbaum scissors or a No. 10 scalpel with gentle blunt spreading, we'll perform subcutaneous blunt dissection down to the deep fascia. Be exceedingly careful here, fellows. We are superficial to the deep fascia, and this is where the saphenous nerve and great saphenous vein reside. Use gentle spreading motions parallel to the course of these structures to protect them."

• Observation: "As you can see in this illustration (TECH FIG 1A), we're gently spreading the subcutaneous fat, aiming to visualize the glistening deep fascia without damaging any neurovascular structures."

Surgical Warning: Always prioritize blunt dissection in the subcutaneous layer. Sharp dissection increases the risk of transecting the saphenous nerve, which can lead to a painful neuroma or persistent paresthesia.

2. Fascial Incision and Identification of the Intermuscular Plane

"Once we've reached the deep fascia, our next step is to open this fascial envelope to access the underlying muscle compartments."

• Action: Using the No. 15 scalpel, make a 2-cm longitudinal incision directly through the deep fascia. This incision should be centered within our skin incision.
• Directive: "Now, fellows, we're going to use our index finger – your most sensitive instrument – to gently enter the intermuscular space. Palpate carefully. You'll feel the distinct muscular bellies of the gastrocnemius superficially and the soleus muscle deep to it. Gently spread them apart."

• Observation: "Observe how a 2-cm fascial incision is made (TECH FIG 1B), and then, with blunt finger dissection, we enter the plane between the gastrocnemius and soleus. This is the crucial step. The plantaris tendon is the only tubular structure you will encounter in this plane. No nerves, no major vessels are at risk here."

3. Mobilization and Isolation of the Plantaris Tendon

"With our finger in the intermuscular plane, we can now specifically target the plantaris tendon."

• Action: Gently sweep your finger proximally and distally within this intermuscular interval. You should feel a taut, cord-like structure. This is our plantaris tendon.
• Directive: "Once identified, we'll use a nerve retractor or a small right-angle retractor to gently elevate and mobilize the tendon. This provides clear visualization and allows us to get a good purchase on it."

• Observation: "Here (TECH FIG 1C), you can see the plantaris tendon being developed and mobilized with a nerve retractor. It's often a surprisingly thin but incredibly strong structure."

4. Introduction of the Tendon Stripper

"Now for the harvest itself. We need a specialized instrument for this: a tendon stripper."

• Action: Securely grasp the proximal end of the isolated plantaris tendon with a heavy suture (e.g., 2-0 FiberWire) or a hemostat. Apply gentle tension.
• Directive: "Carefully introduce the tendon stripper over the tendon. We'll advance the stripper distally, maintaining constant gentle tension on the tendon. The stripper should glide smoothly along the tendon's length, separating it from any surrounding fascial attachments."

• Observation: "As depicted here (TECH FIG 1D), the tendon stripper is being introduced and advanced. The key is to keep the tendon under tension; this helps guide the stripper and ensures a clean harvest."

Surgical Warning: If the stripper encounters significant resistance, do not force it. This could indicate a fascial attachment, a bifurcated tendon, or even an incorrect plane. Withdraw slightly, re-evaluate with palpation or a small retractor, and then re-advance. Forcing the stripper can damage the graft or surrounding tissues.

5. Tendon Transection and Graft Retrieval

"We'll continue advancing the stripper until we reach the desired length, typically aiming for the level of the calcaneus, which should provide us with a graft of 30-45 cm."

• Action: Once the stripper has been advanced to its maximal extent or the desired length, and you feel the distal resistance, rotate the inner cylinder of the tendon stripper. This action severs the tendon cleanly at its distal attachment point.
• Directive: "With the tendon transected, gently withdraw the stripper, bringing the harvested plantaris tendon with it. Inspect the graft for its integrity and length."

• Observation: "And there it is (TECH FIG 1E), our harvested autograft, typically around 30 cm long, ready for use. It's a beautiful, strong, and viable tissue."
• Action: Immediately place the harvested tendon in a wet sponge moistened with normal saline or a specialized tissue preservation solution to prevent desiccation.

6. Wound Closure

"With our graft secured, we'll now close our donor site meticulously."

• Action: Reapproximate the incised deep fascia using absorbable suture (e.g., 2-0 Vicryl) in an interrupted or simple running fashion. This helps restore the anatomical plane and minimizes dead space.
• Action: Close the subcutaneous layer with absorbable sutures (e.g., 3-0 Vicryl) to obliterate dead space and provide a solid foundation for skin closure.
• Action: Close the skin with a subcuticular running stitch (e.g., 4-0 Monocryl) for optimal cosmetic appearance.
• Action: Apply adhesive strips (Steri-Strips) over the incision to promote optimal wound healing and further support the closure.
• Action: Dress the wound with a sterile non-adherent dressing and a light compressive bandage.

• Observation: "This image (TECH FIG 1F) illustrates a well-closed wound, ready for dressing. A clean, cosmetically pleasing closure is always our goal."

Step-by-Step Intraoperative Execution: The Distal Approach (Alternative)

While the proximal approach is preferred, it's important to understand the distal technique, especially if anatomical variations or a specific primary procedure makes a distal harvest more convenient. However, remember the higher risk of failure due to insertion variability and potential for hypertrophic scarring.

1. Initial Incision

"For a distal harvest, our incision will be different."

• Action: Make a 2-cm skin incision at the medial border of the Achilles tendon insertion on the medial calcaneal tuberosity.

2. Dissection and Tendon Identification

"This approach requires careful dissection due to the variable distal insertions."

• Action: Perform blunt dissection down to the Achilles tendon. Carefully sweep your finger or a small retractor along the medial aspect of the Achilles.
• Directive: "Here, fellows, you might need to be a bit more involved with your dissection to identify the distal extent of the plantaris tendon, given its variable insertions. It may be blending with the Achilles, the flexor retinaculum, or even the plantar fascia. Take your time to positively identify it."

3. Mobilization and Tendon Stripper Introduction

"Once identified, we'll mobilize it similarly to the proximal approach."

• Action: Grasp the distal end of the plantaris tendon securely.
• Directive: "Now, introduce the blunt tendon stripper from distal to proximal. Maintain constant tension on the tendon as you advance the stripper towards the popliteal fossa."

• Observation: "As shown here (TECH FIG 2A), the plantaris tendon is located by blunt dissection, and the stripper is being advanced."

4. Tendon Transection and Graft Retrieval

"We'll advance the stripper proximally until we reach the level of the popliteal fossa, ensuring maximal length."

• Action: Once the stripper reaches the popliteal fossa, rotate the inner cylinder to transect the tendon proximally.
• Directive: "Gently withdraw the stripper, retrieving the harvested tendon. Again, inspect the graft and place it in a wet sponge."

• Observation: "This illustration (TECH FIG 2B) shows the stripper advanced from distal to proximal, reaching the popliteal fossa, ready for transection."

5. Wound Closure

"For the distal approach, skin closure is typically performed with interrupted sutures, followed by adhesive strips."

• Action: Close the subcutaneous layer with absorbable sutures.
• Action: Close the skin with interrupted non-absorbable sutures (e.g., 3-0 Nylon), followed by adhesive strips. A light compressive dressing is applied.

💡 Pearls and Pitfalls

Pearls for Success

• Proximal is Preferred: Always favor the proximal approach. It significantly increases the success rate of finding and harvesting the tendon due to its consistent anatomy between the gastrocnemius and soleus.
• Reduced Complications: The proximal incision site is less prone to hypertrophic scarring and subsequent shoe wear irritation compared to an incision at the calcaneal tuberosity.
• Functional Sparing: Remember, harvesting the plantaris tendon does not further decrease dynamic control of lateral ankle instability or any other significant function. It's an expendable tendon.
• Pre-op Imaging: When available, use MRI or ultrasound to confirm the tendon's presence preoperatively, saving valuable OR time and avoiding unnecessary dissection.

Pitfalls and How to Salvage

• Tendon Not Found (Proximal Approach):
  • Re-evaluate Anatomy: Double-check your incision placement. Is it truly 30 cm proximal to the medial malleolus? Is your finger definitively in the plane between gastrocnemius and soleus? Sometimes the musculotendinous junction is slightly more proximal.
  • Gentle Exploration: Use a small blunt instrument (e.g., a blunt probe or small curved clamp) to gently explore the intermuscular plane more thoroughly.
  • Consider Absence: If, after thorough exploration, the tendon cannot be located, remember it's absent in 6-7% of individuals. At this point, you must consider alternative graft sources.
    • Contralateral Plantaris: If the primary procedure allows, consider harvesting from the contralateral limb.
    • Medial Split Achilles Tendon: This is a good local alternative. If you've committed to a distal incision and can't find the plantaris, a small, medial split Achilles tendon graft can be harvested with a tendon stripper advanced from distal to proximal.
    • Peroneus Brevis/Longus: These are excellent autograft options, though they require a separate incision and may have slightly higher donor site morbidity.
    • Allograft: In some cases, a well-matched allograft may be the best alternative, though it introduces different considerations.
• Saphenous Nerve Injury (Proximal Approach):
  • Prevention is Key: Meticulous, blunt subcutaneous dissection is the best prevention. Always visualize or palpate for the saphenous nerve and vein.
  • Intraoperative Recognition: If the nerve is inadvertently transected, a primary repair can be attempted with fine microsurgical technique (e.g., 8-0 or 9-0 nylon) if the defect is small and tension-free.
  • Postoperative Management: If a nerve injury leads to a painful neuroma postoperatively, conservative measures (neuropathic pain medication, nerve blocks) are tried first. If these fail, surgical excision of the neuroma with transposition or implantation into muscle may be necessary. Paresthesia or numbness is often tolerated.
• Incomplete Tendon Harvest:
  • Stripper Resistance: If the tendon stripper jams or doesn't advance smoothly, do not force it. It usually indicates a strong fascial attachment or a bifurcation of the tendon. Gently withdraw the stripper, use a small retractor to visualize the obstruction, and carefully release it with fine scissors or a scalpel before re-advancing the stripper.
  • Short Graft: If the harvested graft is shorter than anticipated, assess if it's still adequate

Additional Intraoperative Imaging & Surgical Steps

REFERENCES

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14. Adhesive wound strips can reduce skin tension and broadening of the scar.

15. After wound healing the patient may use scar massage to reduce subcutaneous adhesions.

OUTCOMES
- The proximal harvesting procedure of the plantaris tendon was reported in a clinical study of plantaris tendon autograft for lateral ligament reconstruction of chronic ankle instability. 7 In 52 cases (93%), a strong 25to 35-cm tendon graft was harvested. In one case (2%) the plantaris tendon was deemed too weak to serve as appropriate donor material. In three (5%) of 56 ankle reconstructions the plantaris tendon could not be located during surgery without preoperative imaging or ultrasound. This observation was consistent with incidence studies of the plantaris tendon in cadavers (absence ranged between 6% and 7%). 8,10,13

• Use of the distal approach to harvest the plantaris tendon also has been reported. Investigators failed to locate the plantaris tendon distally in 12% to 20% of cases in these studies. 4,9,12,13

COMPLICATIONS
- We have performed proximal plantaris harvesting in 102 cases with only one case of mild dysesthesia at a broadened scar. This did not create any functional deficits for the patient.

• Despite the close proximity of the saphenous nerve and vein, we have not observed any saphenous nerve or vein injuries.

• In 36 patients we have performed a distal approach plantaris harvest. Four of these patients (11% of cases) developed a hypertrophic or hypersensitive scar that created shoe irritation.