Abstract
Repair of chronic Achilles tendon ruptures presents a significant surgical challenge due to tendon retraction, fibrosis, and degeneration. While isolated flexor hallucis longus (FHL) tendon transfer may provide adequate strength in low-demand patients, higher-demand individuals frequently require a more robust reconstruction that restores continuity of the gastrocnemius-soleus-Achilles complex. The purpose of this study is to describe clinical outcomes following reconstruction of chronic Achilles tendon ruptures with large defects using a central strap gastrocnemius aponeurosis turn-down flap augmented with FHL tendon transfer.
Three consecutive patients who underwent Achilles tendon reconstruction using this technique were included. Patients were followed for a minimum of 12 months with evaluation of functional outcomes, plantarflexion strength, and calf circumference measurements. The mean American Orthopaedic Foot and Ankle Society (AOFAS) hindfoot score at final follow-up was 93.3. All patients demonstrated 5/5 plantarflexion strength compared to the contralateral extremity. Calf circumference differences between limbs were minimal and did not exceed 1.0 cm in any patient. No re-ruptures or revision surgeries occurred.
The central strap gastrocnemius aponeurosis turn-down flap with FHL augmentation represents a reliable option for reconstruction of chronic Achilles tendon ruptures with large tendon defects in higher-demand patients. This technique allows restoration of the posterior muscle-tendon unit using autologous tissue while preserving plantarflexion strength and functional outcomes.
Introduction
The Achilles tendon is the most commonly ruptured tendon in the lower extremity, with a reported incidence between 6 and 12 ruptures per 100,000 individuals annually. ,, The incidence of this injury has continued to increase over recent decades, likely due to greater participation in recreational athletic activity among middle-aged individuals. ,
Acute Achilles tendon ruptures are often amenable to direct end-to-end repair because the tendon ends retain elasticity and can typically be approximated with gentle traction. However, delayed presentation presents a significantly greater reconstructive challenge. Chronic Achilles ruptures are generally defined as injuries presenting more than four to six weeks after the initial event. Over time, the tendon ends retract, fibrotic scar tissue forms within the rupture gap, and the gastrocnemius–soleus musculotendinous unit undergoes shortening and loss of elasticity. , These factors frequently prevent direct repair and result in substantial tendon defects after debridement of degenerative tissue.
Numerous reconstructive techniques have been described for the management of chronic Achilles tendon ruptures, including V-Y advancement flaps, tendon transfers, fascial turndown flaps, and free tendon graft reconstruction. ,, Selection of the optimal technique depends largely on the size of the tendon defect, the quality of the remaining tendon tissue, and the functional demands of the patient. Advancement procedures such as V-Y plasty can restore moderate tendon defects by advancing the proximal gastrocnemius–soleus complex, with reported advancement ranging from approximately 3–5 cm.
When larger tendon defects are encountered, however, advancement procedures alone may be insufficient to bridge the gap without excessive tension. In these situations, reconstruction with tendon transfers or fascial turndown flaps is frequently recommended to restore tendon continuity while preserving plantarflexion strength. , Gastrocnemius aponeurosis turndown flaps are particularly attractive because they utilize vascularized local tissue from the proximal tendon and maintain continuity of the gastrocnemius-soleus musculotendinous unit.
The senior author has previously described a gastrocnemius aponeurosis turndown flap utilizing medial and lateral fascial straps for reconstruction of chronic Achilles tendon ruptures. In certain patients, however, the width of the gastrocnemius aponeurosis may not permit harvesting two flaps of adequate size. In these situations, a central strap configuration may provide a more reliable reconstruction.
The purpose of this study is to describe the surgical technique and clinical outcomes of a central strap gastrocnemius aponeurosis turn-down flap augmented with flexor hallucis longus tendon transfer for reconstruction of chronic Achilles tendon ruptures with large tendon defects.
Case presentations
Case 1
A 36-year-old male presented to our service as a referral secondary to a known right Achilles injury. The initial injury had occurred 5 weeks previously, and he had been intermittently weight-bearing since that time. The patient was complaining of continued pain and inability to plantarflex his right ankle.
On exam, he had a palpable delve at the insertion of the Achilles tendon, a positive Thompson squeeze test, and 2/5 muscle strength for plantarflexion of the ankle. With the patient prone and knee flexed to vertical, the ankle sat in resting dorsiflexion without tension to the Achilles tendon.
Radiographs demonstrated calcification within the Achilles tendon, which had migrated 3–4 cm proximal to the insertion on the calcaneus. MRI imaging demonstrated an Achilles tendon rupture from the posterior calcaneus with a large enthesophyte within the distal tendon, and a tendon gap of 5 cm.
The patient elected to undergo surgical reconstruction and repair of the Achilles tendon. At the time of the surgery, the patient was 6 weeks post-initial injury. Intraoperatively, a large enthesophyte was found within the distal tendon stump, surrounded by significant fibrosis and mucoid degeneration consistent with chronic tendinosis. The Achilles and enthesophyte had completely detached from their insertion at the calcaneus. After debridement of the large enthesophyte and surrounding degenerative tendon, there was a 7-cm gap between the distal Achilles tendon stump and the proximal calcaneus.
This patient was reconstructed with a central strap gastrocnemius aponeurosis turn-down flap measuring 9 cm in length, which was attached to the calcaneus with a double anchor system. A decision was made to proceed with a central strap instead of a medial and lateral strap because of the narrow width of the gastrocnemius aponeurosis at the level of the flap. The repair was augmented with a flexor hallucis longus tendon transfer.
The patient had an uneventful postoperative course, began partial weightbearing at 6 weeks, full weightbearing at 8 weeks, and transitioned to regular shoe gear at 10 weeks. By 14 weeks, the patient was back to work.
At one-year follow-up, the patient reported AOFAS hindfoot and ankle score was 98/100, with points being deducted for functional limitation with some difficulty walking on uneven terrain. Plantarflexion muscle strength was 5/5 in both the operative and contralateral limb. At the level of the ankle, there was no difference in leg diameter (23.5 cm vs. 23.5 cm). At 5 cm proximal to the ankle joint operative leg was 1.0 cm larger than the non-operative leg (24.0 cm vs. 23.0 cm), and at 10 cm proximal to the ankle joint, the operative leg was 0.8 cm larger than the non-operative leg (28.8 cm vs. 28.0 cm).
Case 2
A 46-year-old female patient presented with right posterior calf and Achilles pain after a running injury 4 weeks previous. She had been ambulating daily with an ankle brace and working on the hospital floors as a nurse, however, this was painful and difficult.
On exam, the patient did have a suspicious Thompson test; however, not blatantly positive. Muscle strength was 2/5 and painful. There was a small delve at the posterior Achilles.
Radiographs demonstrated edema to the posterior leg and mild blunting of the Cager’s triangle, which was suspicious for a partial or complete tear of the Achilles. MRI demonstrated a full-thickness tear of the Achilles tendon just proximal to its insertion with 5.7-cm tendon retraction Fig. 1 .
T1 (Left) and T2 (Right) Sagittal Images demonstrating a significant Achilles tendon tear with a sizable defect and retraction.
The patient elected to undergo surgical reconstruction and repair of the Achilles tendon. Due to delays with obtaining advanced imaging, the patient was 8 weeks post-initial injury at the time of surgery. Intraoperatively, there was a deficit of just over 6 cm once the diseased and fibrotic ruptured portion of the Achilles tendon was removed. Because of the size of the deficit, we proceeded with an 8-cm central strap gastrocnemius aponeurosis turn-down flap. The repair was augmented with an FHL tendon transfer.
The patient had minor wound dehiscence in the postoperative course, which was easily resolved without the need for debridement or operative intervention. She also reported some intermittent tingling and numbness along the course of the L5 dermatome at the anterolateral lower leg, remote to the surgical site, which resolved within 2 months of the operation. She began partial weight-bearing in a surgical boot at 6 weeks, full weight-bearing at 8 weeks, and transitioned into shoes at 9 weeks. She returned to work at 10 weeks.
At one-year follow-up, the patient reported AOFAS hindfoot and ankle score was 87/100, with points being deducted for occasional mild pain and functional limitation with some difficulty walking on uneven terrain. Plantarflexion muscle strength was 5/5 in both the operative and contralateral limb. At the level of the ankle, the operative leg was 0.1 cm larger (23.0 cm vs. 22.9 cm). At 5 cm proximal to the ankle joint, the operative leg was 0.3 cm smaller than the non-operative leg (23.7 cm vs. 24.0 cm), and at 10 cm proximal to the ankle joint, the operative leg was 1.0 cm larger than the non-operative leg (28.0 cm vs. 27.0 cm).
Case 3
A 47-year-old female patient presented with posterior calf and Achilles pain with difficulty ambulating. She had undergone percutaneous tenotomy under ultrasound guidance for chronic insertional achilles tendonitis 4 weeks previously and had subsequently stepped down on the left foot and felt a pop in the posterior calf. Sadly, she had an identical injury to her right side years ago.
On exam, she had pain in the posterior calf and Achilles with a positive Thompson test.
On radiographs, blunting of the kager’s triangle was noted, and enthesophytes from the posterior calcaneus had retracted 3 cm. MRI confirmed the 3-cm gap as well as an additional 3 cm of distal Achilles tendon with significant tendinosis consistent with the patient’s history of insertional Achilles tendonitis.
The patient elected to undergo surgical reconstruction and repair of the Achilles tendon. Following debridement of significant tendinosis within the Achilles tendon, there was a deficit of 8 cm. Because of the size of the deficit, we proceeded with a central strap gastrocnemius aponeurosis turn-down flap. The repair was augmented with an FHL tendon transfer.
At one-year follow-up, the patient reported AOFAS hindfoot and ankle score was 95/100, with points being deducted for no limitations with daily activities but some limitations with recreational activities not requiring supportive devices, and functional limitation with some difficulty walking on uneven terrain. Plantarflexion muscle strength was 5/5 in both the operative and contralateral limb. At the level of the ankle, there was no difference in leg diameter (25.5 cm vs. 25.5 cm). At 5 cm proximal to the ankle joint, there was no difference in leg diameter in the operative leg (25.0 cm vs. 25.0 cm), and at 10 cm proximal to the ankle joint, the operative leg was 0.4 cm smaller than the non-operative leg (27.2 cm vs. 27.6 cm) ( Table 1 ).
Table 1
Table depicting the intraoperative gap length, the length of the central strap flap created, AOFAS score, and the circumference of the operative extremity at various levels, with the size difference compared to the non-operative extremity in parentheses. Of note, the plantarflexion strength was 5/5 for the operative and nonoperative lower extremities.
| Gap Length (cm) | Flap Length (cm) | AOFAS Score | Circumference at Insertion (cm) | Circumference 5 cm Proximal to insertion (cm) | Circumference 10 cm Proximal to Insertion (cm) | |
|---|---|---|---|---|---|---|
| Case 1 | 7 | 9 | 98/100 | 23.5 (+0) | 24.0 (+1.0) | 28.8 (+0.8) |
| Case 2 | 6 | 8 | 87/100 | 23.0 (+0.1) | 23.7 (−0.3) | 28 (+1.0) |
| Case 3 | 8 | 10 | 95/100 | 25.5 (+0) | 25.0 (+0) | 27.2 (−0.4) |
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