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Endoscopic Intermetatarsal Ligament Decompression
Endoscopic Intermetatarsal Ligament Decompression Tun Hing Lui, M.B.B.S.(HK), F.R.C.S.(Edin), F.H.K.A.M., F.H.K.C.O.S.
Abstract: Morton neuroma is an entrapment of the intermetatarsal nerve by the deep intermetatarsal ligament. It is usually treated conservatively. Surgery is considered if there is recalcitrant pain that is resistant to conservative treatment. The surgical options include resection of the neuroma or decompression of the involved nerve. Decompression of the nerve by release of the intermetatarsal ligament can be performed by either an open or minimally invasive approach. We describe 2-portal endoscopic decompression of the intermetatarsal nerve. The ligament is released by a retrograde knife through the toe-web portal under arthroscopic guidance through the plantar portal.
M
orton neuroma is one of the causes of forefoot pain. It is primarily a nerve entrapment disease in which the intermetatarsal nerve is irritated by the deep intermetatarsal ligament. Morton neuroma can typically be treated conservatively with shoe modifications, orthoses, physical therapy, anti-inflammatory medications, and corticosteroid injections.1 Surgery is reserved for those patients with recalcitrant pain that is not relieved by nonoperative management.1,2 Surgical options include resection of the neuroma and decompression of the nerve.1 The nerve is decompressed by release of the deep intermetatarsal ligament. This can be performed by either an open or endoscopic approach. We report a 2-portal endoscopic approach for decompression of the intermetatarsal nerve.
Technique The patient is supine with the legs spread. A thigh tourniquet is applied to obtain a bloodless surgical field. Fluid inflow is by gravity, and no arthroscopic pump is used. A 3- to 4-mm incision is made at the dorsal skin fold of the toe web, where the intermetatarsal ligament is planned to be released. This is followed by blunt dissection of the subcutaneous From the Department of Orthopaedics and Traumatology, North District Hospital, Sheung Shui, China. The author reports that he has no conflicts of interest in the authorship and publication of this article. Received April 20, 2015; accepted August 4, 2015. Address correspondence to Tun Hing Lui, M.B.B.S.(HK), F.R.C.S.(Edin), F.H.K.A.M., F.H.K.C.O.S., Department of Orthopaedics and Traumatology, North District Hospital, 9 Po Kin Road, Sheung Shui, NT, Hong Kong SAR, China. E-mail: [email protected] Ó 2016 by the Arthroscopy Association of North America 2212-6287/15364/$36.00 http://dx.doi.org/10.1016/j.eats.2015.08.003
tissue with a hemostat to develop a plane at the undersurface of the intermetatarsal ligament. This gives a washboard feeling when the tip of the mosquito hemostat scratches the undersurface of the ligament, which is similar to the commonly performed endoscopic carpal tunnel release.3 A 2.7-mm arthroscopic trocar (Henke Sass Wolf, Tuttlingen, Germany) is advanced gently along this plane and reaches the plantar aponeurosis at the level of the tarsometatarsal joint.4 The plantar aponeurosis is penetrated by the trocar, and a 3- to 4-mm plantar portal incision is made at this point. The trocar passes through the plantar portal, and an arthroscopic cannula (Henke Sass Wolf) is inserted along the trocar in a reciprocal manner through the plantar portal (Fig 1). The trocar is removed, and a 2.7-mm 30 arthroscope (Henke Sass Wolf) is inserted into the cannula. A retrograde knife (Smith & Nephew, Andover, MA) is inserted from the toe-web portal and advanced along the undersurface of the intermetatarsal ligament. The blunt tip of the retrograde knife acts as a probe, and the undersurface of the tough ligament is probed during the advancement of the retrograde knife. The edge is identified by a change in the feeling of probing from the tough ligament to the yieldable thin fascia covering the interosseous muscles. Moreover, the muscles can be seen through the fascia. The fascia is easily cut open by the knife, and the proximal edge of the ligament is hooked by the retrograde knife. The ligament is then released from the proximal edge distally under endoscopic visualization as the arthroscope is advanced in phase with the retrieval of the knife (Fig 2). The arthroscope is then inserted through the toe-web portal, and the condition of the intermetatarsal nerve can be assessed (Fig 3). The completeness of release of the distal edge of
Arthroscopy Techniques, Vol 4, No 6 (December), 2015: pp e807-e810
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T. H. LUI
Fig 1. Endoscopic decompression of second intermetatarsal ligament in left foot. The arthroscopic trocar is inserted through the toe-web portal to the plantar portal. The arthroscopic cannula is inserted along the trocar in a reciprocal manner through the plantar portal.
the intermetatarsal ligament can be confirmed if the arthroscope can be moved in a dorsal and plantar manner through the cut edges of the ligament (Video 1).
Discussion The deep intermetatarsal ligament is about 10 to 15 mm in length and 2 to 3 mm in thickness.2 The intermetatarsal nerve lies plantar to the ligament. The deep intermetatarsal ligament has increased tension and becomes more rigid during the late stage of mid
stance and early stage of toe off. Mechanical irritation of the intermetatarsal nerve against the anterior edge of the intermetatarsal ligament can occur during gait.5 This results in nerve entrapment and development of Morton neuroma. Resection of the affected nerve has been the treatment of choice. However, this results in loss of sensation and the formation of a stump neuroma, which is more difficult to treat than the original lesion.1,2 Gauthier5 reported an open approach for release of the intermetatarsal ligament without resection of the neuroma. Decompression of the intermetatarsal nerve is usually effective in reducing the neuroma symptoms.1,2,5 Failure to respond to decompression can be due to the nerve being severely degenerated and resistant to regeneration after decompression.1 Nerve resection is reserved for those patients with persistent symptoms after nerve decompression.2 Barrett and Pignetti6 reported the technique of endoscopic decompression of the intermetatarsal nerve. This technique is less traumatic, allowing an earlier return to normal activity, with less patient discomfort than with traditional surgical techniques.6,7 However, the technique requires 3 incisions and delicate instrumentation.2 Moreover, the intermetatarsal nerve cannot be visualized and the learning curve is steep.2 Shapiro2 developed a uniportal endoscopic technique. Zelent et al.1 developed another minimally invasive technique of nerve decompression without the need for endoscopy. Their technique has the advantage of being technically easier because an endoscopic technique is not required. However, both the nerve and the ligament cannot be visualized, and
Fig 2. Endoscopic decompression of second intermetatarsal ligament in left foot. (A) The plantar portal is the viewing portal. (B) The retrograde knife is inserted along the undersurface of the intermetatarsal ligament (a) through the toe-web portal until the proximal edge of the ligament is reached. (C) The interosseous muscles (b) can be seen through the thin fascia that is proximal to the ligament (a). (D) The ligament (a) is cut from the proximal edge distally.
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Table 1. Pearls of Endoscopic Intermetatarsal Ligament Decompression The trocar should be advanced gently toward the plantar aponeurosis. The plantar aponeurosis is penetrated at the level of the tarsometatarsal joint to achieve an adequate working length for the release. The advancement of the retrograde knife through the toe-web portal should be performed under arthroscopic guidance. Attention should be paid during the release of the distal end of the ligament. Sudden “giving way” of the knife should be controlled to avoid laceration of the toe-web portal incision. Normally, the nerve cannot be visualized by the 30 arthroscope through the plantar portal even if the arthroscope is turned toward the nerve. If the nerve is visualized, the positioning of the arthroscope is too plantar.
Fig 3. Endoscopic decompression of second intermetatarsal ligament in left foot. The toe-web portal is the viewing portal. The intermetatarsal nerve (n) can be seen through the cut edges of the intermetatarsal ligament (a).
the ligament is released from distally to proximally. The intermetatarsal ligament is visualized through a slotted cannula in both the Barrett-Pignetti technique and Shapiro technique. Although Shapiro has proposed that the nerve can be visualized through the slotted cannula, the arthroscopic view is limited and fragmented. The intermetatarsal ligament is released from distally to proximally in the Shapiro technique and from proximally to distally in the Barrett-Pignetti technique. Our technique is adapted from the endoscopic soft-tissue procedure for correction of hallux valgus deformity.3,4,8,9 The advantage of this approach is that the view is broader because no slotted cannula is used. The nerve can be seen, and the relation of the nerve to the adjacent structures, especially the cut intermetatarsal ligament, can be examined. The completeness of release of the ligament can be confirmed by moving the arthroscope across the cut edges of the ligament. The dynamic relation of the nerve to the ligament can be visualized endoscopically by dorsiflexion of the toes. Moreover, any bleeding spots can be detected and cauterized to reduce hematoma formation. The portals still serve as coaxial portals, and the portal tract between them is a straight line even though a slotted cannula is not used. The advancement of the retrograde knife through the toe-web portal should be performed under endoscopic guidance by withdrawal of the arthroscope from the toe-web portal. This is not a difficult procedure, but it requires some practice before the surgeon can
become familiar with performing the procedure without a slotted cannula. The release of the intermetatarsal ligament is similar to that in the BarrettPignetti technique and starts from the proximal edge of the ligament. The proximal edge of the ligament can be identified by probing with the retrograde knife, and the interosseous muscles can be seen through the thin fascia. The cutting edge of the retrograde knife faces away from the nerve. The technique may yield less risk of damage to the nerve than release of the ligament from distally to proximally in which the cutting edge of the knife faces the intermetatarsal nerve. The major potential risk with our technique is damage to the intermetatarsal nerve during insertion of the trocar for creation of the plantar portal. The trocar should be passed through the intermetatarsal space gently without excessive force. There should not be any significant resistance encountered by the trocar before the plantar aponeurosis is reached. The trocar should be moved slightly sideways if any resistance is encountered during its advancement through the intermetatarsal space. This can minimize the risk of damage to the intermetatarsal nerve (Table 1). In conclusion, 2-portal endoscopic decompression of the intermetatarsal nerve is a feasible minimally invasive surgical option for the treatment of Morton neuroma.
References 1. Zelent ME, Kane RM, Neese DJ, Lockner WB. Minimally invasive Morton’s intermetatarsal neuroma decompression. Foot Ankle Int 2007;28:263-265. 2. Shapiro SL. Endoscopic decompression of the intermetatarsal nerve for Morton’s neuroma. Foot Ankle Clin 2004;9:297-304. 3. Lui TH, Ng S, Chan KB. Endoscopic distal soft tissue procedure in hallux valgus surgery. Arthroscopy 2005;21:1403. e1-1403.e7. 4. Lui TH, Chan KB, Chan LK. Endoscopic distal soft-tissue release in the treatment of hallux valgus: A cadaveric study. Arthroscopy 2010;26:1111-1116.
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5. Gauthier G. Thomas Morton’s disease: A nerve entrapment syndrome. Clin Orthop Relat Res 1979;142: 90-92. 6. Barrett SL, Pignetti TT. Endoscopic decompression for intermetatarsal nerve entrapmentdThe EDIN technique: Preliminary study with cadaveric specimens; early clinical results. J Foot Ankle Surg 1994;33: 503-508.
7. Barrett SL, Walsh AS. Endoscopic decompression of intermetatarsal nerve entrapment: A retrospective study. J Am Podiatr Med Assoc 2006;96:19-23. 8. Lui TH. Arthroscopy and endoscopy of the foot and ankle: Indications for new techniques. Arthroscopy 2007;23:889-902. 9. Lui TH, Chan KB, Chow HT, Ma CM, Chan PK, Ngai WK. Arthroscopy-assisted correction of hallux valgus deformity. Arthroscopy 2008;24:875-880.
Abstract: Morton neuroma is an entrapment of the intermetatarsal nerve by the deep intermetatarsal ligament. It is usually treated conservatively. Surgery is considered if there is recalcitrant pain that is resistant to conservative treatment. The surgical options include resection of the neuroma or decompression of the involved nerve. Decompression of the nerve by release of the intermetatarsal ligament can be performed by either an open or minimally invasive approach. We describe 2-portal endoscopic decompression of the intermetatarsal nerve. The ligament is released by a retrograde knife through the toe-web portal under arthroscopic guidance through the plantar portal.
M
orton neuroma is one of the causes of forefoot pain. It is primarily a nerve entrapment disease in which the intermetatarsal nerve is irritated by the deep intermetatarsal ligament. Morton neuroma can typically be treated conservatively with shoe modifications, orthoses, physical therapy, anti-inflammatory medications, and corticosteroid injections.1 Surgery is reserved for those patients with recalcitrant pain that is not relieved by nonoperative management.1,2 Surgical options include resection of the neuroma and decompression of the nerve.1 The nerve is decompressed by release of the deep intermetatarsal ligament. This can be performed by either an open or endoscopic approach. We report a 2-portal endoscopic approach for decompression of the intermetatarsal nerve.
Technique The patient is supine with the legs spread. A thigh tourniquet is applied to obtain a bloodless surgical field. Fluid inflow is by gravity, and no arthroscopic pump is used. A 3- to 4-mm incision is made at the dorsal skin fold of the toe web, where the intermetatarsal ligament is planned to be released. This is followed by blunt dissection of the subcutaneous From the Department of Orthopaedics and Traumatology, North District Hospital, Sheung Shui, China. The author reports that he has no conflicts of interest in the authorship and publication of this article. Received April 20, 2015; accepted August 4, 2015. Address correspondence to Tun Hing Lui, M.B.B.S.(HK), F.R.C.S.(Edin), F.H.K.A.M., F.H.K.C.O.S., Department of Orthopaedics and Traumatology, North District Hospital, 9 Po Kin Road, Sheung Shui, NT, Hong Kong SAR, China. E-mail: [email protected] Ó 2016 by the Arthroscopy Association of North America 2212-6287/15364/$36.00 http://dx.doi.org/10.1016/j.eats.2015.08.003
tissue with a hemostat to develop a plane at the undersurface of the intermetatarsal ligament. This gives a washboard feeling when the tip of the mosquito hemostat scratches the undersurface of the ligament, which is similar to the commonly performed endoscopic carpal tunnel release.3 A 2.7-mm arthroscopic trocar (Henke Sass Wolf, Tuttlingen, Germany) is advanced gently along this plane and reaches the plantar aponeurosis at the level of the tarsometatarsal joint.4 The plantar aponeurosis is penetrated by the trocar, and a 3- to 4-mm plantar portal incision is made at this point. The trocar passes through the plantar portal, and an arthroscopic cannula (Henke Sass Wolf) is inserted along the trocar in a reciprocal manner through the plantar portal (Fig 1). The trocar is removed, and a 2.7-mm 30 arthroscope (Henke Sass Wolf) is inserted into the cannula. A retrograde knife (Smith & Nephew, Andover, MA) is inserted from the toe-web portal and advanced along the undersurface of the intermetatarsal ligament. The blunt tip of the retrograde knife acts as a probe, and the undersurface of the tough ligament is probed during the advancement of the retrograde knife. The edge is identified by a change in the feeling of probing from the tough ligament to the yieldable thin fascia covering the interosseous muscles. Moreover, the muscles can be seen through the fascia. The fascia is easily cut open by the knife, and the proximal edge of the ligament is hooked by the retrograde knife. The ligament is then released from the proximal edge distally under endoscopic visualization as the arthroscope is advanced in phase with the retrieval of the knife (Fig 2). The arthroscope is then inserted through the toe-web portal, and the condition of the intermetatarsal nerve can be assessed (Fig 3). The completeness of release of the distal edge of
Arthroscopy Techniques, Vol 4, No 6 (December), 2015: pp e807-e810
e807
e808
T. H. LUI
Fig 1. Endoscopic decompression of second intermetatarsal ligament in left foot. The arthroscopic trocar is inserted through the toe-web portal to the plantar portal. The arthroscopic cannula is inserted along the trocar in a reciprocal manner through the plantar portal.
the intermetatarsal ligament can be confirmed if the arthroscope can be moved in a dorsal and plantar manner through the cut edges of the ligament (Video 1).
Discussion The deep intermetatarsal ligament is about 10 to 15 mm in length and 2 to 3 mm in thickness.2 The intermetatarsal nerve lies plantar to the ligament. The deep intermetatarsal ligament has increased tension and becomes more rigid during the late stage of mid
stance and early stage of toe off. Mechanical irritation of the intermetatarsal nerve against the anterior edge of the intermetatarsal ligament can occur during gait.5 This results in nerve entrapment and development of Morton neuroma. Resection of the affected nerve has been the treatment of choice. However, this results in loss of sensation and the formation of a stump neuroma, which is more difficult to treat than the original lesion.1,2 Gauthier5 reported an open approach for release of the intermetatarsal ligament without resection of the neuroma. Decompression of the intermetatarsal nerve is usually effective in reducing the neuroma symptoms.1,2,5 Failure to respond to decompression can be due to the nerve being severely degenerated and resistant to regeneration after decompression.1 Nerve resection is reserved for those patients with persistent symptoms after nerve decompression.2 Barrett and Pignetti6 reported the technique of endoscopic decompression of the intermetatarsal nerve. This technique is less traumatic, allowing an earlier return to normal activity, with less patient discomfort than with traditional surgical techniques.6,7 However, the technique requires 3 incisions and delicate instrumentation.2 Moreover, the intermetatarsal nerve cannot be visualized and the learning curve is steep.2 Shapiro2 developed a uniportal endoscopic technique. Zelent et al.1 developed another minimally invasive technique of nerve decompression without the need for endoscopy. Their technique has the advantage of being technically easier because an endoscopic technique is not required. However, both the nerve and the ligament cannot be visualized, and
Fig 2. Endoscopic decompression of second intermetatarsal ligament in left foot. (A) The plantar portal is the viewing portal. (B) The retrograde knife is inserted along the undersurface of the intermetatarsal ligament (a) through the toe-web portal until the proximal edge of the ligament is reached. (C) The interosseous muscles (b) can be seen through the thin fascia that is proximal to the ligament (a). (D) The ligament (a) is cut from the proximal edge distally.
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Table 1. Pearls of Endoscopic Intermetatarsal Ligament Decompression The trocar should be advanced gently toward the plantar aponeurosis. The plantar aponeurosis is penetrated at the level of the tarsometatarsal joint to achieve an adequate working length for the release. The advancement of the retrograde knife through the toe-web portal should be performed under arthroscopic guidance. Attention should be paid during the release of the distal end of the ligament. Sudden “giving way” of the knife should be controlled to avoid laceration of the toe-web portal incision. Normally, the nerve cannot be visualized by the 30 arthroscope through the plantar portal even if the arthroscope is turned toward the nerve. If the nerve is visualized, the positioning of the arthroscope is too plantar.
Fig 3. Endoscopic decompression of second intermetatarsal ligament in left foot. The toe-web portal is the viewing portal. The intermetatarsal nerve (n) can be seen through the cut edges of the intermetatarsal ligament (a).
the ligament is released from distally to proximally. The intermetatarsal ligament is visualized through a slotted cannula in both the Barrett-Pignetti technique and Shapiro technique. Although Shapiro has proposed that the nerve can be visualized through the slotted cannula, the arthroscopic view is limited and fragmented. The intermetatarsal ligament is released from distally to proximally in the Shapiro technique and from proximally to distally in the Barrett-Pignetti technique. Our technique is adapted from the endoscopic soft-tissue procedure for correction of hallux valgus deformity.3,4,8,9 The advantage of this approach is that the view is broader because no slotted cannula is used. The nerve can be seen, and the relation of the nerve to the adjacent structures, especially the cut intermetatarsal ligament, can be examined. The completeness of release of the ligament can be confirmed by moving the arthroscope across the cut edges of the ligament. The dynamic relation of the nerve to the ligament can be visualized endoscopically by dorsiflexion of the toes. Moreover, any bleeding spots can be detected and cauterized to reduce hematoma formation. The portals still serve as coaxial portals, and the portal tract between them is a straight line even though a slotted cannula is not used. The advancement of the retrograde knife through the toe-web portal should be performed under endoscopic guidance by withdrawal of the arthroscope from the toe-web portal. This is not a difficult procedure, but it requires some practice before the surgeon can
become familiar with performing the procedure without a slotted cannula. The release of the intermetatarsal ligament is similar to that in the BarrettPignetti technique and starts from the proximal edge of the ligament. The proximal edge of the ligament can be identified by probing with the retrograde knife, and the interosseous muscles can be seen through the thin fascia. The cutting edge of the retrograde knife faces away from the nerve. The technique may yield less risk of damage to the nerve than release of the ligament from distally to proximally in which the cutting edge of the knife faces the intermetatarsal nerve. The major potential risk with our technique is damage to the intermetatarsal nerve during insertion of the trocar for creation of the plantar portal. The trocar should be passed through the intermetatarsal space gently without excessive force. There should not be any significant resistance encountered by the trocar before the plantar aponeurosis is reached. The trocar should be moved slightly sideways if any resistance is encountered during its advancement through the intermetatarsal space. This can minimize the risk of damage to the intermetatarsal nerve (Table 1). In conclusion, 2-portal endoscopic decompression of the intermetatarsal nerve is a feasible minimally invasive surgical option for the treatment of Morton neuroma.
References 1. Zelent ME, Kane RM, Neese DJ, Lockner WB. Minimally invasive Morton’s intermetatarsal neuroma decompression. Foot Ankle Int 2007;28:263-265. 2. Shapiro SL. Endoscopic decompression of the intermetatarsal nerve for Morton’s neuroma. Foot Ankle Clin 2004;9:297-304. 3. Lui TH, Ng S, Chan KB. Endoscopic distal soft tissue procedure in hallux valgus surgery. Arthroscopy 2005;21:1403. e1-1403.e7. 4. Lui TH, Chan KB, Chan LK. Endoscopic distal soft-tissue release in the treatment of hallux valgus: A cadaveric study. Arthroscopy 2010;26:1111-1116.
e810
T. H. LUI
5. Gauthier G. Thomas Morton’s disease: A nerve entrapment syndrome. Clin Orthop Relat Res 1979;142: 90-92. 6. Barrett SL, Pignetti TT. Endoscopic decompression for intermetatarsal nerve entrapmentdThe EDIN technique: Preliminary study with cadaveric specimens; early clinical results. J Foot Ankle Surg 1994;33: 503-508.
7. Barrett SL, Walsh AS. Endoscopic decompression of intermetatarsal nerve entrapment: A retrospective study. J Am Podiatr Med Assoc 2006;96:19-23. 8. Lui TH. Arthroscopy and endoscopy of the foot and ankle: Indications for new techniques. Arthroscopy 2007;23:889-902. 9. Lui TH, Chan KB, Chow HT, Ma CM, Chan PK, Ngai WK. Arthroscopy-assisted correction of hallux valgus deformity. Arthroscopy 2008;24:875-880.