Role of toe flexor tendoscopy in management of an unusual cause of metatarsalgia

Endoscopically Assisted Percutaneous Harvesting of the Flexor Hallucis Tendon in Zone 2: An Anatomical Study

BACKGROUND

Flexor hallucis longus (FHL) transfer is a well-established method for treating chronic Achilles tendon ruptures and tendinopathy. Harvesting of the FHL tendon in zone 2 results in greater length but is also associated with an increased risk of injury to the medial plantar nerve and requires an additional plantar incision. Because of the anatomic proximity of the FHL tendon to the tibial neurovascular bundle in zone 2, the purpose of this study was to investigate the risk of vascular or nerve injury with arthroscopic assisted percutaneous tenotomy in zone 2 of the FHL tendon.

METHODS

Endoscopically assisted percutaneous FHL transfer was performed on 10 right lower extremities from 10 cadaveric human specimens. The FHL tendon lengths and the relationship between FHL tendon and the tibial neurovascular bundle at zone 2 was analyzed.

RESULTS

We observed a complete transection of the medial plantar nerve in 1 case (10%). The mean length of the FHL tendon was 54.7 ± 9.5 mm and the mean distance from the distal stump of the FHL tendon to local neurovascular structures was 1.3 ± 0.7 mm.

CONCLUSION

There is a risk of neurovascular injury after endoscopic FHL tenotomy in zone 2. The tenotomy site is within 2 mm of the local neurovascular structures in the majority of cases. The additional length gained from this technique is unlikely to be required for the majority of FHL tendon transfer procedures. If additional length is needed, we would recommend the use of intraoperative ultrasonography or a mini-open approach to minimize injury risk.

LEVEL OF EVIDENCE

Level V, expert opinion.

Flexor Hallucis Longus Tenosynovitis and First Metatarsophalangeal Synovitis After Penetrating Nail Prick Injury: Treated by Zone 3 Flexor Hallucis Longus Tendoscopy and Metatarsosesamoid Arthroscopy

Pedal penetrating nail prick injury around the first metatarsal head can result in persistent synovitis of the first metatarsophalangeal joint and tenosynovitis of the flexor hallucis longus tendon. Exploration and debridement is indicated if the condition does not improve with antibiotics. Open surgery requires extensive dorsal and plantar incisions. The purpose of this Technical Note is to report the combined arthroscopic and tendoscopic approaches to address the first metatarsophalangeal joint and flexor hallucis longus tendon pathologies. Because it is a result of a pedal injury, the layer-by-layer exploration and debridement is from plantar dorsally. It starts with zone 3 flexor hallucis longus tendoscopy, followed by arthroscopy of the metatarsosesamoid compartment, and finally arthroscopy of the metatarsophalangeal compartment.

Safe Zone for the Plantar Portal: A Cadaveric Study

BACKGROUND

Understanding the plantar nerve anatomy is crucial for safe endoscopic surgery of the sole. We aimed to anatomically dissect the lateral aspect and soles of cadaveric feet to investigate the safety of peroneus longus tendoscopy with a plantar lateral portal and the safe zones for plantar portals.

METHODS

We studied 36 feet of 24 cadavers (mean age, 86.5 years). A cannula for 2.7-mm scope was inserted from the plantar lateral portal to the peroneus longus tendon, and the positional relationship between the cannula and sural nerve was observed. Then, the soft tissue of the sole was dissected, and the relationships between the plantar nerve and flexor digitorum longus tendon and flexor hallucis longus tendon was observed. The plantar nerve course was digitally imaged and uploaded into Image J software to determine nerve position. We further observed the positional relationship between the cannula and plantar nerve.

RESULT

The mean minimum distance between the cannula and sural nerve was 13.8 mm, and the closest distance was 4.2 mm, allowing for the relatively safe creation of a plantar lateral portal. The use of the plantar lateral portal and evaluation of the peroneal tendon was safe with respect to the lateral plantar nerve as the nerve was in a different tissue layer of the foot. Dissection of the plantar foot demonstrated a relatively safe zone, 36.4% to 56% along a line between the medial aspect of the base of the first metatarsal bone to the proximal tip of the fifth metatarsal. This region may allow for a plantar endoscopic portal; however an anatomic variation may result in the plantar nerve being within this zone. The flexor digitorum longus tendon and peroneus longus tendon passed through the deep layer of the relatively safe zone.

CONCLUSION

Peroneus longus tendoscopy was relatively safe to perform from a plantar lateral portal. No neurovascular structure exists on the slightly medial aspect of the central region of the sole, potentially allowing for a relatively safe creation of plantar central portal. An approach from the plantar central portal to the flexor digitorum longus tendon, flexor hallucis longus tendon, and peroneus longus tendon allows for a greater range of vision and treatment options as compared with conventional approaches. The combination of the plantar central portal with portals such as the plantar lateral portal may further the development of endoscopic surgery of the sole.

CLINICAL RELEVANCE

We found the anatomic characteristics of a relatively safe zone for the plantar portal for plantar lateral portal.

Foot and ankle tendoscopy: evidence-based recommendations

PURPOSE

The purpose of this study was to provide a comprehensive review of the current literature on tendoscopy of the foot and ankle and assign an evidence-based grade of recommendation for or against intervention.

METHODS

A comprehensive review of the literature was performed on May 26, 2013, using the PubMed, Cochrane, and Scopus databases. Studies focusing on the use of foot and ankle tendoscopy were isolated, and these articles were then reviewed and assigned a Level of Evidence (I through V). The literature was then analyzed, and a grade of recommendation was assigned for tendoscopy of the tendons of the foot and ankle on which the procedure is generally performed.

RESULTS

There is weak evidence (grade Cf) to support the use of tendoscopy on the Achilles, flexor hallucis longus, and peroneal tendons. Insufficient evidence (grade I) exists to assign a grade of recommendation for tendoscopy of the tibialis posterior, tibialis anterior, flexor digitorum longus, extensor hallucis longus, and extensor digitorum longus.

CONCLUSIONS

A comprehensive review of the literature on foot and ankle tendoscopy has shown predominantly Level IV and V studies, with just 1 Level II study. On the basis of the current literature available, there is poor evidence (grade Cf) in support of Achilles, flexor hallucis longus, and peroneal tendoscopy for the common indications. There is insufficient evidence to make a recommendation (grade I) for or against tendoscopy of the tibialis posterior, tibialis anterior, flexor digitorum longus, extensor hallucis longus, and extensor digitorum longus. Although current literature suggests that tendoscopy is a safe and effective procedure, original scientific articles of higher levels of evidence are needed before a stronger recommendation can be assigned.

LEVEL OF EVIDENCE

Level IV, systematic review of Level II, IV, and V studies.

Flexor digitorum longus tendoscopy

The flexor digitorum longus tendon is susceptible to injury along its entire course, and lacerations, ruptures, longitudinal tears, and stenosing tenosynovitis have all been reported. Moreover, this tendon is commonly used for reconstruction of dysfunctional posterior tibial and Achilles tendons. Traditionally, surgery involving the flexor digitorum longus tendon was performed via open incision. We describe a technique of flexor digitorum longus tendoscopy that may encourage the future development of a minimally invasive approach to flexor digitorum longus tendon procedures.

Extensor tendoscopy of the ankle

The extensor digitorum longus muscle (EDL) arises from the upper three-quarters of the extensor surface of the fibula, the interosseous septum and from a small area of the tibia across the superior tibiofibular joint. It forms its four tendons which are restrained by the superior and inferior extensor retinacula. The two retinacula prevent the EDL and extensor hallucis longus (EHL) tendons from bow stringing. The inferior extensor retinaculum also contributes to the stability of the subtalar joint. Extensor tendoscopy has been performed in 3 patients and no neural injury was noted.

Lateral plantar nerve neuropraxia after FHL tendoscopy: case report and anatomic evaluation

BACKGROUND

FHL tendoscopy has been described as minimally invasive method used to create some pathologies or facilitate some surgeries. As we have encountered lateral plantar nerve neurapraxia, we investigate the cause of lateral nerve injury during Zone 2 flexor digitorum longus (FHL) tendoscopy with a cadaveric model.

MATERIAL AND METHOD

Eight feet of 4 embalmed cadavers were used for this study. Posterior ankle endoscopy (Zone 1 FHL tendoscopy) was performed with posteromedial and posterolateral portals. A 4.0-mm metal rod was inserted into the Zone 2 tendon health through the posteromedial portal. The distance between the posteromedial portal and the posterior tibial nerve was measured with the ankle in neutral position. Then, the shortest distance between the posterior tibial nerve and the rod was measured with the ankle in three positions: 20 degrees plan-tarflexion, neutral, and the 20 degrees dorsiflexion.

RESULT

The average distance between the posterior tibial nerve and the posteromedial portal was 9.3 mm. The average shortest distance between the posterior tibial nerve and the metal rod was 5 mm with the ankle in 20 degrees dorsiflexion.

CONCLUSION

Ankle dorsiflexion brings the posterior tibial nerve in contact with the arthroscope during Zone 2 tendoscopy.

CLINICAL RELEVANCE

In order to avoid potential nerve injury during Zone 2 FHL tendoscopy, ankle dorsiflexion should be avoided.

Cadaveric study of zone 2 flexor hallucis longus tendon sheath

PURPOSE

The purpose of this study was to investigate the anatomy of the zone 2 flexor hallucis longus (FHL) tendon sheath.

METHODS

Dissection of the zone 2 FHL tendon sheath was performed in 12 feet of 6 cadavers. The tendon sheath was subdivided into proximal fibrous (zone 2A) and distal fascial (zone 2B) parts. The lengths of the zone 2A and 2B FHL tendon were measured and represented the length of the corresponding tendon sheaths, and the relation of the medial plantar nerve to each part of the zone 2 FHL tendon sheath was studied.

RESULTS

In all specimens there were fibrous and fascial components of the zone 2 FHL tendon sheath. The medial plantar nerve crossed the zone 2B tendon sheaths and then became plantar lateral to the sheath in 7 specimens. The distance between the medial plantar nerve and the orifice of the zone 2A tendon sheath averaged 7.6 mm. The distance between the medial plantar nerve and the junction between zones 2A and 2B averaged 3.2 mm. The distance between the medial plantar nerve and the distal end of the zone 2B tendon sheath averaged 4.2 mm. The mean length of the zone 2A tendon sheath was 35.9 mm, and the mean length of the zone 2B tendon sheath was 30.5 mm.

CONCLUSIONS

The zone 2 FHL tendon sheath can be subdivided into a proximal fibrous zone (2A) and a distal fascial zone (2B). Because of the close proximity of the medial plantar nerve to the tendon sheath, there is a significant risk of iatrogenic nerve injury when surgical procedures are performed in zone 2B.

CLINICAL RELEVANCE

An understanding of the anatomy of the zone 2 FHL tendon sheath is useful for the safe practice of zone 2 FHL tendoscopy.

Zone 2 flexor hallucis longus tendoscopy: a cadaveric study

BACKGROUND

The purpose of this study was to verify the safety and efficacy of zone 2 flexor hallucis longus tendoscopy with the patient in the prone position.

MATERIALS AND METHODS

The technique was performed in 12 cadaver feet (6 pairs). The endoscopic findings were compared to an anatomic dissection. The locations of the posteromedial and plantar portals were studied. The relationship between the medial plantar nerve and the tract of FHL tendoscopy was also studied.

RESULT

The average distance of the posteromedial portal above the medial malleolar tip was 10.3 mm. The average distance between the posteromedial portal and the posterior tibial nerve was 9.9 mm. The average distance between the plantar portal and the intermalleolar line was 41.5 mm. The average distance between the rod simulating the tenoscope and the nerve was 4.8 mm. The nerve was medial to the rod in 4 specimens and lateral to the rod in 8 specimens.

CONCLUSION

Zone 2 flexor hallucis longus tendoscopy was a feasible approach to the deep portion of the flexor hallucis longus tendon in this cadaveric study. There is potential risk of damage to the medial plantar nerve.

CLINICAL RELEVANCE

These findings can help guide a surgeon who is considering trying this clinically.

Flexor hallucis longus tendoscopy: a technical note

The course of the flexor hallucis tendon (FHL) is divided into three zones. Zone 1 is located behind the ankle joint, from the musculotendinous junction to the orifice of the tunnel underneath the sustentaculum tali. Zone 2 is located from the tunnel underneath the sustentaculum tali to the knot of Henry. Zone 3 is located from the knot of Henry to the tendon insertion to the base of the distal phalanx of the big toe. The zone 1 FHL tendon is examined with posterior ankle endoscopy with the posterolateral and posteromedial portals. The zone 2 FHL tendon can be examined through the posteromedial and the plantar portals. The zone 3 FHL tendon is examined with the toe flexor tendoscopy. By means of different endoscopic approach to the each zone of the FHL tendon, the complete course of the tendon can be examined from the musclotendinous junction to its insertion.

Flexor hallucis longus tendoscopy: a technical note

The course of the flexor hallucis tendon (FHL) is divided into three zones. Zone 1 is located behind the ankle joint, from the musculotendinous junction to the orifice of the tunnel underneath the sustentaculum tali. Zone 2 is located from the tunnel underneath the sustentaculum tali to the knot of Henry. Zone 3 is located from the knot of Henry to the tendon insertion to the base of the distal phalanx of the big toe. The zone 1 FHL tendon is examined with posterior ankle endoscopy with the posterolateral and posteromedial portals. The zone 2 FHL tendon can be examined through the posteromedial and the plantar portals. The zone 3 FHL tendon is examined with the toe flexor tendoscopy. By means of different endoscopic approach to the each zone of the FHL tendon, the complete course of the tendon can be examined from the musclotendinous junction to its insertion.

Arthroscopically assisted Z-lengthening of extensor hallucis longus tendon

Extensor hallucis longus tendon contracture can lead to hyperextension deformity of the big toe. We describe an endoscopic approach of Z-lengthening of the tendon. Extensor hallucis longus tendoscopy is performed with a distal portal at the level of the metatarsal neck and a proximal portal at the level of the navicular. At the distal portal, the medial half of the extensor hallucis longus tendon is cut and a stay stitch of No. 2 ethibond is applied. It is then stripped proximally with a tendon stripper to the proximal portal. A stay stitch of No. 2 ethibond is applied to the lateral half of the tendon at the proximal portal and it is cut proximal to the stitch. With the ankle plantarflexed and the big toe kept in the similar position as the lesser toes, the tendon segments are kept in tension through the stay stitches via the proximal and distal portals. The stay stitches of distal tendon segment are sutured to the proximal segment at the same level of the cut end of the distal fragment with the aid of an eyed needle under arthroscopic visualization through the distal portal. The needle is passed through the tendon and then the skin. The suture is also passed through the skin and then retrieved to the proximal portal by a hemostat. It is then sutured to the proximal tendon segment at the proximal portal. Similarly, the proximal tendon end is sutured to the distal tendon segment at the corresponding level and the endoscopic Z-lengthening of the extensor hallucis longus tendon is then completed.

Arthroscopy and endoscopy of the foot and ankle: indications for new techniques

The scope of arthroscopy and endoscopy of the foot and ankle is expanding. New techniques are emerging to deal with diverse ankle pathology. Some of the conditions that can be dealt with arthroscopically are as follows: hallux valgus deformity, lesser toe deformity, first metatarsophalangeal instability, cock-up deformity of the big toe, peroneal tendon instability, lateral ankle and subtalar instability, hindfoot deformity or arthrosis, first metatarsocuneiform hypermobility, Lisfranc joint arthrosis, various stages of posterior tibial tendon insufficiency, foot and ankle arthrofibrosis, late complications after calcaneal fracture, acute and chronic Achilles tendon rupture, insertional Achilles tendinopathy, entrapment of the first branch of the lateral plantar nerve, Freiberg's infarction, flexor digitorum longus tenosynovitis, flexor hallucis longus pathology, calcaneonavicular coalition or "too-long" anterior process of the calcaneus, and ganglions. With sound knowledge regarding the indications, merits, and potential risks of new techniques, they will be powerful tools in foot and ankle surgery.