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Surgical repair of an abductor Hallucis muscle herniation with tarsal tunnel syndrome: A rare case report with a long term follow-up

Open AccessPublished:January 21, 2022DOI:https://doi.org/10.1016/j.fastrc.2022.100162

      Abstract

      Atramatic, painful herniation of the abductor hallucis muscle is rare. During the period of writing this case study, we found less than ten published articles on abductor hallucis muscle anatomy and only three case reports on the abnormalities within the abductor hallucis muscle. Familiarity with the condition is needed for early diagnosis, surgical intervention, and prevention of recurrence. It is also important to have an experienced musculoskeletal radiologist to identify this unique pathology.
      This is a unique case study of a young active female who presented with an abductor hallucis muscle herniation, tarsal tunnel syndrome, and ligamentous laxity. She suffered from foot pain and was misdiagnosed for multiple years. She began living with normal foot pain during her exercise activities. Her symptoms began to worsen with numbness and tingling. After failing modification of shoe gear, physical therapy, resting, and offloading, she was further worked up with imaging. This MRI was evaluated by a musculoskeletal radiologist. It was discovered that she has a large muscle belly, with a retinaculum injury, and impingement along the tarsal tunnel.
      She was successfully treated with a surgical repair of the herniation, application of synthetic dynamic matrix graft, and decompression of the tarsal tunnel at the porta pedis. She had a complete resolution of symptoms in 6 weeks and she was followed up for 3 years with no recurrence. The purpose of this case report is to add to the body of literature on treatment options for muscle herniation in foot and ankle surgery.

      Level of Clinical Evidence

      Introduction

      The abductor hallucis muscle (ABHM) is the most medial muscle in the first layer at the sole of the foot
      • Wong YS.
      Influence of the abductor hallucis muscle on the medial arch of the foot: a kinematic and anatomical cadaver study.
      . Anatomically, the action includes abduction and flexion of the metatarsophalangeal joint of the hallux and sustains the structure of the medial arch of the foot
      • Wong YS.
      Influence of the abductor hallucis muscle on the medial arch of the foot: a kinematic and anatomical cadaver study.
      ,
      • Wada JT
      • Akamatsu F
      • Hojaij F
      • Itezerote A
      • Scarpa JC
      • Andrade M
      • Jacomo A.
      An Anatomical Basis for the Myofascial Trigger Points of the Abductor Hallucis Muscle.
      . Sometimes it is overlooked that ABHM plays a significant role in the gait cycle
      • Wong YS.
      Influence of the abductor hallucis muscle on the medial arch of the foot: a kinematic and anatomical cadaver study.
      . Reeser et al found that ABHM demonstrated significant activity during late stance phase and toe-off in the gait cycle
      • Reeser LA
      • Susman RL
      • Stern JT Jr
      Electromyographic studies of the human foot: experimental approaches to hominid evolution.
      . Wada et al described that the ABHM is superficial, triangular, flat, and bipenniform muscle that fills the medial arch distally and attached at the calcaneus
      • Wong YS.
      Influence of the abductor hallucis muscle on the medial arch of the foot: a kinematic and anatomical cadaver study.
      . Proximally at the medial process of the calcaneus there is a flexor retinaculum that is part of the origin of the ABHM. The area is highly vascular with supply from medial calcaneal branch of the lateral plantar artery, medial plantar artery, first plantar metatarsal artery, and plantar arch arteries
      • Lui T.H.
      Endoscopic decompression of the first branch of the lateral plantar nerve and release of the plantar aponeurosis for chronic heel pain.
      ,
      • Stranding S.
      Gray's Anatomy: the Anatomical Basis of Clinical Practice.
      . During ABHM strain that retinaculum sustains a higher load of stress and leads to microtears to the area. Overtime, many skeletal muscle activities can worsen the injury and cause significant pain to the area. The innervation to the area is by the medial plantar nerve, a branch of the tibial nerve, so many times people have similar symptoms as tarsal tunnel syndrome. It is significant to note that the ABHM relates to painful plantar arch in about 17% of hindfoot pain
      • Wada JT
      • Akamatsu F
      • Hojaij F
      • Itezerote A
      • Scarpa JC
      • Andrade M
      • Jacomo A.
      An Anatomical Basis for the Myofascial Trigger Points of the Abductor Hallucis Muscle.
      . There is high correlation to myofascial pain with the ABHM at the plantar calcaneus due to the highest concentration of entry points of the medial plantar nerve branches.
      Herniation of muscles was first discovered in 1929 by Ihde who recognized it in military personnel. Since then there has not been any case series, only isolated single case studies. Most hernia occurrences are in the lower extremity. The predisposing factors include congenital issues, nerve impingement, vascular compromise, and over load of myofascial activity
      • Lee HS
      • James M.
      Painful bilateral herniation of the anterior tibial muscle: a case report.
      . ABHM herniation is very rare and there is limited literature on it.
      Another effect on muscle herniation can be pre-existing joint disease. Joint hypermobility is a genetic connective tissue disorder
      • Colombi M
      • Dordoni C
      • Chiarelli N
      • Ritelli M.
      Differential diagnosis and diagnostic flow chart of joint hypermobility syndrome/ehlers-danlos syndrome hypermobility type compared to other heritable connective tissue disorders.
      . The recurring joint dislocations, chronic joint/limb pain, and positive family history are diagnostic criteria
      • Colombi M
      • Dordoni C
      • Chiarelli N
      • Ritelli M.
      Differential diagnosis and diagnostic flow chart of joint hypermobility syndrome/ehlers-danlos syndrome hypermobility type compared to other heritable connective tissue disorders.
      . Golightly et al found that joint hypermobility was not associated with foot and ankle disorders, but more so knee disorders
      • Golightly YM
      • Hannan MT
      • Nelson AE
      • Hillstrom HJ
      • Cleveland RJ
      • Kraus VB
      • Schwartz TA
      • Goode AP
      • Flowers P
      • Renner JB
      • Jordan JM.
      Relationship of Joint Hypermobility with Ankle and Foot Radiographic Osteoarthritis and Symptoms in a Community-Based Cohort.
      . This is important, because the gait cycle can be affected in many ways and cause abnormal stress to muscle, tendons, and joints in the lower extremity including the hip, knee, ankle, and foot. There is adequate research showing that joint hypermobility affects lateral ankle ligaments, but little research has been collected on hypermobility's effects on medial ankle ligaments. This case study will show that hypermobility can affect the medial ankle anatomy, relate to tarsal tunnel syndrome, and possibly cause muscle herniation. This case study will also help add to the body of literature on ligamentous laxity, tarsal tunnel syndrome, and adjacent tissue herniations.

      Case report

      A 29-year-old female presented with right foot pain. She suffered from chronic foot pain mostly during exercise and was possibly misdiagnosed for about 2 years. She was previously seen by multiple physicians who stated it was all related to the plantar fasciitis.
      About 1 month before presenting to our team, the patient began living with 5/10 dull pain during most of her daily activities like: walking, running, jogging, cycling. She states there was relief with complete bed rest, which was not possible with her lifestyle.
      About 1 week prior to the clinical visit, the patient stated she overdid it on activities (like cycling and running) and noticed numbness and tingling to the medial aspect of her foot. She reported pain, throbbing, with cramping located specifically to the medial arch. This pain was persistent even after normal activities of daily living. She tried over the counter pain medication without improvement. She stated she failed previous treatment options like modification of shoe gear, physical therapy, resting, and offloading. She tried over the counter orthotics with no relief. She tried those treatments for about 1 month before seeing our surgical team.
      The patient is a medical assistant who is on her feet at all times of the working day. She had a history of resolving plantar fasciitis. She had a past medical history of ligamentous laxity, plantar fasciitis, and no previous surgical history. She is not a smoker. She is not taking any prescription medications except over the counter pain relievers. She has no known drug allergies.
      The physical exam revealed palpable pulses to the right foot with unremarkable vascular status.
      The neurologic exam revealed there was an impingement of the tarsal tunnel with a positive tinel's sign upon the percussion of the posterior tibial nerve. The dermatologic exam revealed a prominent muscle belly of the abductor hallucis muscle belly with a bulging appearance at the medial arch. The musculoskeletal exam revealed that there was tenderness to palpation from the origin to the insertion of the muscle. Pre-operatively the digits had normal active and passive range of motion with no crepitus upon dorsiflexion or plantarflexion. The ankle joint, subtalar joint, and midtarsal joints were also normal. The function of the posterior tibial tendon was intact with the feeling of soreness and tightness during inversion and plantarflexion of the foot and ankle with no loss in muscle strength. The prominence appeared to be like a mass, non-mobile, non-pulsatile, and non-transilluminate. This was visible while the patient was resting, but the herniation became twice as prominent upon weight bearing (Fig. 1). Review of systems included ligamentous laxity in other joints of her body such as pulling her fingers backward and she was able to bend over and place her hands flat on the ground.
      Fig 1
      Fig. 1Clinical photograph of medial aspect of the foot displaying the abductor hallucis muscle prominence. The borders are marked out with a dotted circle.
      The radiographs were negative for pathology. The MRI showed compressed medial plantar neurovascular bundle with hypertrophied abductor hallucis muscle. In the coronal image one can appreciate the enlarged ABHM compared to the surrounding muscles. In the sagittal view, there is a tear of myotendinous junction of enlarged bulging abductor hallucis muscle. In the axial view you can appreciate the tear along intrasubstance myotendinous junction of abductor hallucis muscle (Fig. 2).
      Fig 2
      Fig. 2MRI Read from Musculoskeletal Radiologist-Axial, Sagittal, Coronal Views
      Conservative treatments were attempted for a 6-month period, and included the use of muscle relaxant, physical therapy, resting, non-weight bearing boot, over the counter orthotics with an additional offloading aperture to the medial arch, non-steroidal anti-inflammatories, and icing. The patient exhausted all conservative treatment and elected to have surgical intervention consisting of release and repair of the flexor retinaculum, partial excision of the muscle belly, decompression of the tarsal tunnel, and graft application.
      The detailed surgical plan included traditional curvilinear incision along the flexor retinaculum, dissection carried down in a layered fashion. There was a frank partial tear of the flexor retinaculum about 70% with only 30% attachment remaining to the area. At this time the foot was loaded and bulging of the muscle was noted within the tear. The flexor retinaculum was released. Upon further dissection the abductor hallucis muscle belly tear of about 20% was noted and debulked. The location was straight medial and central of the incision and central of the flexor retinaculum. It was debulked or excised along the same longitudinal plane using pick up and tenotomy scissors. The measurement exercise was 3cm long, 0.5 cm wide, and 0.5cm thick. The bleeding tissue was cauterized with bovie. Tarsal tunnel was released at the porta pedis by delicately decompressing the area around the nerve distally and proximally with pick up and metzenbaum scissors. The area was flushed with copious amounts of saline. A synthetic mesh graft (Artelon) was applied. The size of the graft was 4 cm x 6 cm. It laid directly on top of the muscle belly that was excised. The graft extended to the healthy muscle belly dorsally and plantarly. It was not wrapped around, but rather directly on top of the muscle. It was attached with absorbable stitches. The foot was re-loaded and the herniation was less prominent and adequately repaired (Refer to each step in Fig. 3). The patient was dressed with non-adherent, dry sterile dressing, and posterior splint with strict non-weight-bearing (NWB) for 2 weeks. The stitches were removed at 2 weeks and the patient was placed into a walking boot to continue NWB for an additional 2 weeks. The patient stayed NWB for a total of 4 weeks. At which time physical therapy was initiated. Patient was also in normal sneakers at this time frame. She was re-molded for a new pair of custom orthotics. The patient healed in 6 weeks without pain, normal range of motion, and a negative tinel's sign. The patient was followed up after 3 years and had a pristine incision site, no recurrence of herniation, negative Tinel's sign to the tarsal tunnel area, and pain free to the area during exercise and normal activities of daily living (Fig. 4).
      Fig 3
      Fig. 31) Clinical 2) Torn Retinaculum 70% 3) Abductor muscle belly herniation with tear 20% 4) Vein, Artery, Nerve at Porta Pedia 5) Graft application 6) Layered closure
      Fig 4
      Fig. 4Clinical photograph (before surgery Left, after 3 years right).

      Discussion

      Muscle herniation in the lower extremity can be a rare case scenario. ABHM herniation is a rare occurrence, but proper clinical management can identify and treat the problem in early stages. There are only a few documented cases. We found an MRI evaluated by a skilled musculoskeletal radiologist is the key for proper diagnosis and identification of the herniation early.
      Foot and ankle physicians should be aware of the literature on muscle width when examining the MRI results. Chittoria reported a mean total muscle length of 14.29±1.47 and a mean muscle width of 2.20±0.43 cm
      • Chittoria RK
      • Pratap H
      • Yekappa SH.
      Abductor Hallucis: Anatomical Variation and Its Clinical Implications in the Reconstruction of Chronic Nonhealing Ulcers and Defects of Foot.
      . This measurement can help identify early symptomatic herniations.
      The anatomy medially is important as well. The medial plantar nerve passes deep to the ABHM

      Kiel J, Kaiser K. Tarsal Tunnel Syndrome. 2020 Aug 12. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan–. PMID: 30020645.

      . The medial plantar nerve innervation is an important innervation of the ABHM. The medial calcaneal nerve typically branches off of the posterior tibial nerve proximal to the tarsal tunnel and provides sensory innervation to the posteromedial heel

      Kiel J, Kaiser K. Tarsal Tunnel Syndrome. 2020 Aug 12. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan–. PMID: 30020645.

      . This can end up over stimulating the ABHM during impingement syndrome

      Kiel J, Kaiser K. Tarsal Tunnel Syndrome. 2020 Aug 12. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan–. PMID: 30020645.

      . While surface electromyography was not used in our case study, studies have shown that it helps effectively assess physiotherapeutic, surgical, and pharmacological treatment options for overload muscle evaluation
      • Mortka K
      • Wiertel-Krawczuk A
      • Lisiński P.
      Muscle Activity Detectors-Surface Electromyography in the Evaluation of Abductor Hallucis Muscle.
      .
      Ligamentous laxity is studied in many lateral ankle impingements, but not medially at deltoid and tarsal tunnel. It may be worthwhile to study this area closer.
      Misdiagnosis and undertreatment of ABHM is common. Any damage to the area can complicate the area with haemangioma, herniation, and or nerve impingement with myofascial triggers (
      • Nicklas BJ
      • McEneaney PA
      • Lichniak JE
      • Baron RL
      • Brownell BA.
      Surgical repair of abductor hallucis muscle herniation: a case report.
      ,
      • Boedijono DR
      • Luthfi APWY
      Erlina. Intramuscular haemangioma of abductor hallucis muscle - A rare case report.
      ,
      • Mueller T.J.
      • Bowlus T.H.
      Abductor hallucis myocele: a discussion and case presentation.
      ). In this case study we did not consider a nerve graft wrap which may be helpful in long term tarsal tunnel impingement relief. Proper clinical work up, MRI evaluated by a musculoskeletal radiologist, early surgical intervention, and proper postoperative protocol can help treat the area. Another key is long term follow up for mass recurrence, foot function, neuralgia, and pain resolution.

      Conclusion

      Surgical intervention to treat foot and ankle muscle herniation, decompression of the neurovascular bundle at the porta pedis, and adding biologics to heal the area may be great treatment options if conservative measures have previously failed. Long term follow up will be key to prevent reoccurence.

      Ethics Statement

      IRB approval was submitted per institutional guidelines and was waived given the nature of this study. Written consent for publishing this study was obtained from the patient.

      Patient Informed Consent Statement

      Complete informed consent was obtained from the patient for the publication of this study and accompanying images.

      Declaration of Competing interest

      The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

      Acknowledgments

      None

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