1 Introduction

Foot drop (FD) is characterized by the inability to dorsiflex the forefoot, as a result of muscular, skeletal or neurological disorders with common peroneal nerve (CPN) palsy being a frequent etiology.¹ Trauma, compression, iatrogenic injuries, systemic inflammatory and metabolic pathologies can cause CPN palsy. Diagnosis is based on history, physical examination, extremity imaging, electromyography and nerve conduction studies (NCS).² For refractory FD cases tendon transfer surgery, commonly using Tibialis Posterior tendon (TPT) is a standard approach, with various surgical techniques available for tendon transfer and fixation.³

This report details a technique involving TPT transfer through circumtibial (CT) route with tendon-to-tendon and tendon-to-bone fixation. The patient received treatment at a government-funded tertiary care hospital in Sri Lanka and the case report was prepared according to SCARE 2023 guidelines.⁴

2 Case Presentation

54-year-old Sri Lankan female was referred to the orthopedic clinic with a two-year history of progressive right foot dorsiflexion weakness, resulting in FD. Her medical history included diabetes, hypertension, and myocardial infarction, with no trauma. Examination revealed right ankle dorsiflexion power of 1/5, eversion of 2/5, and normal flexion and inversion. Passive dorsiflexion was able up to 30-degree. Limb deformities or masses were absent and radiography was unremarkable. NCS revealed complete palsy of CPN with a normal tibial nerve. Initial management with orthoses and physiotherapy was unsuccessful. Given her significant disability, decision was taken to go for TPT transfer with tri-tendon anastomosis without lengthening of Achilles tendon. Surgery was performed by an experienced orthopedic surgeon.

A 1-inch incision was made antero-inferior to right medial malleolus to locate TPT insertion at the navicular tuberosity. Tendon was detached and grasping sutures were applied (Fig. 1 - A). A second vertical incision was made 4 inches superior to first to access the musculotendinous junction of TPT. The detached TPT was then pulled through this incision. A third incision over the anterior compartment aligned with the second incision enabled subcutaneous routing of TPT anterior to the tibia, positioning it in the anterior compartment. A small vertical slit was made in the tibialis anterior tendon (TAT), through which TPT was passed. Absorbable horizontal mattress sutures were applied, securing the attachment. A fourth incision over the lateral compartment allowed the Peroneus Longus (PL) to be mobilized and attached to TPT-TAT anastomosis with the same suture technique (Fig. 1 - B). When the length of TPT was found to be insufficient in the 90-degree neutral ankle position, it was lengthened using the tendon-with-Z-lengthening (TWZL) technique and reinforced with Krackow sutures (Fig. 1 - C). A fifth incision was then made over the dorsal surface of intermediate cuneiform (IC) bone which was drilled to its full thickness. To access the opposite side, an incision was made on the sole. TPT was passed through the bone tunnel and pulled through the plantar incision. With the ankle in a neutral position, traction was applied, and the tendon was secured to the bone with a 7 × 30 mm interference screw (Fig. 1 - D). Closure was performed with non-absorbable sutures and a below-knee Plaster of Paris back slab was applied to secure the anastomosis and fixation.

Close

Fig. 1 A - Detachment of tibialis posterior tendon from its insertion, B - Tri-tendon anastomosis between tibialis posterior, tibialis anterior and peroneus longus, C - Lengthening of tibialis posterior tendon using TWZL technique and reinforcing with Krackow sutures, D - Tendon-to-bone fixation with interference screw.

Export to PPT

The patient was discharged two days post-operatively, with sutures removed on day 14 and gradual mobilization of the ankle initiated at four weeks. Over next three months, mobility was progressively improved with physiotherapy.

3 Discussion

Peroneal neuropathies are a common cause of FD and may result from compression, fibular fractures, mass lesions, excessive traction, or inflammatory and metabolic disorders.² Management of FD depends on the underlying etiology, baseline functional level, and patient expectations for mobility. Tendon transfer surgery is indicated for patients with persistent, significant morbidity when other treatment options have failed.³

TPT has been used to transfer to the anterior and lateral compartments of the leg to restore dorsiflexion and eversion in FD for nearly 90 years. First described by Ober in 1933, this technique involved routing TPT subcutaneously around the tibia to the dorsum of the foot, known as the circumtibial (CT) route.⁵ Mayer later described routing TPT through a slit in the interosseus (IO) membrane.⁶ The Bridle procedure (BP), described by McCall et al., involves TPT transfer through IO membrane with tri-tendon anastomosis between TPT, TAT and PL.⁷ Rodriguez later modified this technique by incorporating tendon fixation to IC bone.⁸ Since then, various modifications of the BP have emerged.

Both CT and IO routes are established techniques for TPT transfer in treating FD. A systemic review by Stevoska et al. analyzing 37 studies, indicated that IO route is most commonly used TPT transfer method.⁹ IO route is favored for its strong dorsiflexion and lower risk of varus recurrence. However, it carries a higher risk of vascular injury and adhesion formation, and scarring within the IO tunnel may limit power and overall effectiveness. Conversely, CT route is often used due to its ease of use, lower risk, and ability to provide a longer tendon arm for improved mechanical advantage and also, in patients with calcified IO membranes. Nonetheless, it is associated with reduced range of motion and a risk of varus recurrence.¹⁰

Aydin et al.¹¹ and Ozkan et al.¹² reported favorable outcomes using CT route for TPT transfer. The former fixed TPT to IC bone, while the latter fixed TPT to TAT, Extensor Hallucis Longus (EHL), Extensor Digitorum Longus (EDL) and Peroneus Tertius (PT) tendons.

Few studies have compared IO and CT routes. Das et al. evaluated 381 patients with FD due to leprosy, selecting those with strong (Grade 4 or more) peronei muscles for CT route and those with lower grades for IO route. Fixation was performed to EHL, EDL, PT tendons, but not to the bones. Both techniques yielded comparable results in term of rest position, active dorsiflexion and effective range of motion. The risk of inversion deformity was not assessed as the study pre-selected patients with strong evertors for CT route.¹³

Eser and Hasturk reported a case demonstrating a successful outcome using CT route for TPT transfer, with fixation to both extensor tendons and the bones at the dorsum of the ankle. However, specific anatomical details regarding the fixation were not provided.¹⁴

The Rodriguez modification of BP via IO route uses both tri-tendon anastomosis and TPT fixation to IC bone. In comparison, TPT transfer via CT route usually uses either tendon-to-tendon or tendon-to-bone fixation. No studies or case reports in the literature have documented the combination of TPT transfer via CT route with both tri-tendon anastomosis and TPT fixation to IC bone, the key fixation techniques used in Rodriguez modification. In this case study, we demonstrated that successful outcomes can be achieved through TPT transfer through CT route with fixation to TAT and PL tendons at the distal tibial level along with fixation to IC bone. This approach was performed through small incisions, minimizing the need for deeper exploration, including dissection of IO membrane, thereby reducing the risk of vascular injury. This technique represents a modification of the Bridle procedure, utilizing CT route for TPT transfer. A limitation encountered was the insufficient length of TPT. Though it was addressed using TWZL technique, further studies are warranted to evaluate the effectiveness and applicability of this combined approach.

4 Conclusion

This case report highlights the successful application of a modified Bridle procedure utilizing CT route for TPT transfer in a patient with FD due to CPN palsy. By combining tendon-to-tendon and tendon-to-bone fixation techniques, we achieved effective restoration of function without the need for extensive dissection, thereby minimizing the risk of vascular complications.

CRediT authorship contribution statement

Dushan Piyarathne: gathered and analysed data as well as authored the manuscript, Writing – review & editing, coordinated the publishing process. Ralinda Pallawala: performed the procedures, oversaw the project, edited the report, and supervise the case report, All authors read and approved the final manuscript.

Informed consent

Informed written consent was obtained from the patient for publication of the data and clinical images. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.

Ethics approval

All procedures followed were in accordance with the ethical standards of the institution (Teaching Hospital, Peradeniya, Sri Lanka). Institution exempts ethics approval for reported cases.

Funding statement

This case study did not receive any specific grants from funding agencies in the public, commercial or not-for-profit sectors.