Case Report

Achilles Bone-Tendon Allograft Replacement for Chronic Insertional Tendon Rupture in the Setting of Chronic Tendinosis

10/15/2024

The Achilles tendon is one of the most frequently ruptured tendons despite its inherent strength. Chronic Achilles ruptures are those with a delay in diagnosis or treatment greater than 6 weeks, and can be difficult to surgically address.¹ Even more so, patients presenting with chronic insertional ruptures with or without calcaneal tendon insertion site bone loss and concomitant Haglund’s deformity or retrocalcaneal exostosis can exponentially complicate surgical treatment.

**Figure 1.** **Radiographs Before and After Avulsion of Calcific Achilles Tendon:** The patient saw an outsider provider 4 months prior to injury for a Haglund’s deformity with a prominent retrocalcaneal exostosis (a). At urgent care, an updated radiograph demonstrated the foci of tendon calcification located more proximally (green circle), raising concern for an Achilles tendon tear.

Currently there is a paucity of surgical treatment options in the literature for chronic insertional Achilles tendon ruptures. Even less reports exist on patient selection criteria and surgical technique pearls for Achilles bone-tendon allograft reconstruction for this challenging patient cohort.

**Figure 2.** **Preoperative Weightbearing MRI Demonstrating an 8 cm Defect:** Two sagittal views (a) and (b) demonstrate a full-thickness tear of the distal Achilles tendon with approximately 8 cm of proximal retraction of the distal Achilles tendon fibers.

Many surgeons agree chronic ruptures should be managed surgically, with the goal of restoring and maintaining the length and tension of the Achilles tendon, to enable propulsive gait through the gastroc-soleus muscle-tendon complex.² Surgeons have demonstrated numerous surgical techniques; however, there has not been a gold standard of treatment for neglected ruptures of the Achilles tendon. Song and Hua discussed that allografts are often the best substitute for Achilles tendon in active, athletic patients who have a strong wish to continue competitive sports, including sudden turning and jumping maneuvers.³ Jiménez-Carrasco and colleagues discussed the advantage of augmenting repairs with a flexor hallucis longus transfer, specifically for defects > 4 cm, as it not only improves the strength of the repair, but also improves allograft healing due to the proximity of the muscle with its increased blood flow.²

**Figure 3. Full-Thickness Achilles Tendon Tear:** Surgeons excised the deep fascia, as well as the residual paratenon revealing full-thickness tear of the Achilles tendon (a). Note the extensive thickening and degeneration of the Achilles tendon at the proximal stump site, which was debulked prior to repair (b).

What You Should Know About the Patient Presentation

A healthy 66-year-old female who presented at our office via urgent care referral for a chronic left Achilles tendon rupture. She had been diagnosed by an another provider with Achilles tendinitis with retrocalcaneal spurring (Figure 1a) several months prior and had been working with physical therapy. She presented to urgent care with concern for possible deep vein thrombosis (DVT) as she experienced worsening calf pain while trying to walk for the previous couple of weeks. She had no recollection of a provoking injury, so the exact timing of rupture is unknown, but it likely took place about 7 weeks prior. Urgent care obtained updated radiographs and a magnetic resonance imaging (MRI) study (Figures 1b & 2).

**Figure 4.** **Short Harvest Technique of Flexor Hallucis Longus:** The surgeon harvests the FHL tendon through an incision made in the posterior fascia. While maximally plantarflexing the ankle and hallux, one transects the FHL and transfers the tendon to the more anterior, superior portion the calcaneus to avoid interfering with planned bone-tendon allograft. Tensioning the tendon creates a resting plantarflexed position similar to the contralateral limb, utilizing an interference screw.

The patient presented to our office with a palpable dell of the Achilles tendon extending from the insertion site to the mid-calf region. There was no plantarflexion with calf squeeze and the patient had a positive Thompson’s test. The patient elected to move forward with surgical intervention consisting of a flexor hallucis longus tendon transfer and open repair of the Achilles tendon rupture with bone-tendon allograft and remodeling of the posterior calcaneus.

**Figure 5.** **Calcaneus Preparation for Achilles Bone-Tendon Allograft:** After the Achilles bone-tendon allograft thaws, one measures an appropriate size graft and marks this same size onto the posterior aspect of the calcaneus. Keep in mind that the size of the allograft bone needs to be big enough to accept a screw. Utilizing a sagittal saw, one cuts roughly 1.5 cm in depth along the inferior (a), medial (b), and lateral (c) aspects of the planned resection margins. Then using an osteotome chisels out the posterior superior portion of the calcaneus in preparation for allograft placement. A healthy cancellous bone trough is appreciable in the recipient site, about 1.5 cm in depth, and is now ready for placement of allograft (d).

Insights on the Surgical Technique

Following administration of general anesthesia, we placed a thigh tourniquet on the patient in prone position. A full-thickness longitudinal midline linear incision over the palpable dell extended distally over the posterior aspect of the calcaneus. We carried blunt dissection deeper to visualize the full-thickness tear (Figure 3). Next, we harvested the flexor hallucis longus (FHL) tendon using the short harvest technique (Figure 4). Subsequently, we remodeled the posterior aspect of the calcaneus to remove any underlying pathology.

**Figure 6. Remodeling of Achilles Bone-Tendon Allograft:** Remodel the allograft bone block piece to fit the recipient site anatomically (a), with no prominence utilizing previous measurements taken of the trough (green box). The allograft bone block should fit nice and snug into recipient site with no overlying bone (b).

The next step involves calcaneus preparation for the Achilles bone-tendon allograft (Figure 5). There is no consensus in the literature on exact parameters to size the allograft, but it should be large enough to accept a screw. We took the same steps in preparation of remodeling the allograft to anatomically fit the trough created in the calcaneus (Figure 6). After attaining adequate fit of allograft into calcaneus, we permanently fixated the allograft with a headless screw (Figure 7). Holding the foot slightly plantarflexed, we then measured the defect (Figure 8a) and remodeled the Achilles tendon portion of the allograft to the appropriate length (Figure 8c). While performing an anastomosis of the allograft to the native proximal Achilles tendon, the foot should be in a slightly plantarflexed position, knowing that tension will decrease over time.

**Figure 7. Fixation of Achilles Bone-Tendon Allograft:** Once happy with the snug fit of the bone-tendon allograft into the calaneal defect, one can permanently fixate the allograft utilizing a 5.0 mm headless screw (a). The authors note use of a headless screw to prevent future irritation of posterior heel with shoe gear. Intraoperative fluoroscopy confirms allograft placement into the posterior superior portion of the calcaneus (b).

We then performed layered closure in all areas and placed the patient in a posterior splint in a slightly plantarflexed position. Postoperatively, patients are non-weight-bearing for 6 weeks followed by 4 weeks of protected weight-bearing in an offloading boot. Physical therapy begins at 6 weeks postop to begin strengthening of the reconstructed Achilles tendon.

**Figure 8. Preparation of Allograft Placement and Anastomosis with Native Achilles Tendon:** With the foot in slight plantarflexion the surgeon measures the defect (green arrow) from the proximal Achilles tendon to the superior portion of the calcaneus, measuring about an 8 cm gap (a). The Achilles tendon portion of the allograft then fans out to span the large defect and is subsequently cut to appropriate length (b, c). The distal tendon allograft portion and the proximal native Achilles tendon undergo anastomosis via a Krackow stitch technique utilizing nonabsorbable suture (d). Then one can suture the allograft to the deep Achilles tendon flap along the medial and lateral margins.

Final Thoughts

This case report details the surgical procedure performed for a patient suffering from chronic underlying retrocalcaneal exostosis pathology. This patient subsequently developed an Achilles tendon rupture with initial misdiagnosis. The technique described allows the surgeon to restore the Achilles tendon while augmenting the strength of repair with subsequent FHL transfer, avoids donor site morbidity, and addresses the weakness of the posterior musculature group. We find this technique especially advantageous for chronic Achilles ruptures involving a substantial portion of the distal tendon segment, and we add internal fixation to help stabilize the allograft bone for incorporation into recipient bone.

**Figure 9. Final Postoperative Encounter:** Final postoperative radiograph demonstrates significant incorporation of the bone graft into the posterior, superior aspect of the calcaneus (a). Surgical site is well epithelialized and healed (b). Plantarflexion muscle strength was 5/5. At this time, the patient has been able to return to activities pain-free without the need for any bracing. No noted complications to date.

At final follow-up, the patient treated with this surgical technique was ambulatory in regular shoe gear without the need for any bracing. There was no loss in muscle strength and no noted complications to date with the procedure. One may consider this surgical technique in other patients suffering from retrocalcaneal exostosis pathology and subsequent development of a chronic Achilles tendon rupture, or in patients with extensive distal tendon calcification that leaves no viable tendon after debridement.

Dr. Abben is a fellowship-trained foot and ankle surgeon and attending of the Regions Hospital/HealthPartners Institute Foot & Ankle Surgical Residency program. He practices in the Minneapolis/St. Paul area with Park Nicollet Clinic and TRIA Orthopaedics.

Dr. Nack is a second-year resident of the Regions Hospital/HealthPartners Institute Foot & Ankle Surgical Residency program.

Dr. Brett is a foot and ankle surgeon and attending of the Hennepin Healthcare Institute Foot & Ankle Surgical Residency program in Minneapolis.

References
1. Maffulli N, Ziello S, Maisto G, Migliorini F, Oliva F. Local tendon transfers for chronic ruptures of the Achilles tendon: a systematic review. J Clin Med. 2023;12(2):707. Published 2023 Jan 16. doi:10.3390/jcm12020707
2. Jiménez-Carrasco C, Ammari-Sánchez-Villanueva F, Prada-Chamorro E, García-Guirao AJ, Tejero S. Allograft and autologous reconstruction techniques for neglected Achilles Tendon rupture: a mid-long-term follow-up analysis. J Clin Med. 2023;12(3):1135. Published 2023 Feb 1. doi:10.3390/jcm12031135
3. Song YJ, Hua YH. Tendon allograft for treatment of chronic Achilles tendon rupture: A systematic review. Foot Ankle Surg. 2019 Jun;25(3):252-257. doi: 10.1016/j.fas.2018.02.002. Epub 2018