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Treating metatarsalgia: current concepts
FOOT AND ANKLE
Treating metatarsalgia: current concepts
Anatomical considerations The normal distal parabola created by the metatarsal heads plays an important role on the loaded foot mechanics. During weightbearing, the five metatarsal heads are at the same distance from the ground. The angle between the bone and the ground decreases from the M1 (20 ) to M5 (5 ). The metatarsals are connected by the transverse inter-metatarsal ligament and, therefore, act together as a single functional unit.4 The plantar plates are fibro-cartilaginous condensations underneath the metatarsophalangeal (MTP) joints that stabilize the joints particularly preventing dorsal dislocation of the proximal phalanx (P1). During propulsion, the toes themselves play an important role in weight transfer as well as stability. It follows that any functional deficiency of the toes may lead to overload of the MTP joints leading to pain at the metatarsal heads. Any dysfunction of the hallux and sesamoid complex with its associated muscles and tendons may also lead to pain under the lesser metatarsal heads. The first ray plays an important role in both static and dynamic stability of the foot particularly at the propulsion (third rocker) phase of gait.
Gurdip S Chahal Mark B Davies Chris M Blundell
Abstract The objective of this paper is to describe the anatomical and biomechanical considerations for treating metatarsalgia. We describe a method of classification incorporating the causes and lead onto a comprehensive description of the treatment of metatarsalgia. Important clinical findings and investigations are discussed in treating this common pathology and a case study used as an example to illustrate the above. This paper highlights the complex nature of metatarsalgia and describes the factors a surgeon needs to consider prior to embarking on treatment.
Biomechanical considerations
Keywords forefoot; metatarsalgia; pain; treatment
The rocker concept of gait analysis is well described5 and is a useful way of understanding and describing pathology leading to metatarsalgia. The two most important factors concerning the metatarsal heads with respect to normal function are their position relative to the ground and their relative length. During the second rocker of gait the foot is flat to the ground and the tibia passes over the ankle controlled by eccentric contraction of the posterior calf muscles. It follows that if any of the metatarsal heads are closer to the ground during this phase this will lead to increased load and pressures over this area. This is sometimes termed ‘static metatarsalgia’. The position of the metatarsal heads relative to the ground are governed by two factors; the slope of the metatarsals in the sagittal plane and motion at the tarso-metatarsal (TMT) joints. TMT joint function varies across the foot leading to altered biomechanics at the metatarsal heads when ground reaction forces are applied. The lateral column (fourth and fifth rays) undergoes mainly dorsiflexion and is relatively mobile. It aids lateral deceleration during gait. The central column (second and third rays) have relatively limited motion at the TMT joints which is a factor in the increased incidence of central metatarsalgia.6 The medial column (first ray), provides plantar flexion and the pronation required for the propulsive action of the hallux during the third rocker. Any disruption in this function leads to transfer metatarsalgia. TMT joint degenerative disease leads to overloading of the metatarsal heads with the central column particular vulnerable for the reasons stated above during propulsion. Relatively long metatarsal length also leads to overloading at the metatarsal heads with the plantar plate being at risk from repetitive overloading.
Introduction Metatarsalgia is defined as pain in the forefoot under one or more metatarsal heads. It is a common forefoot symptom seen within the foot and ankle sub-speciality clinics but it is not a diagnosis. Metatarsophalangeal pathology may be secondary to a variety of problems including trauma, structural deformity and systemic disease amongst others. The prevalence of foot problems in the general population is 10%, whilst in the elderly it ranges from 50% to 95%.1 It has been estimated that 90% of foot disorders affect the forefoot. Metatarsalgia is probably the most common cause of foot pain among middle-aged women.2 There have been many attempts to classify the pathologies causing metatarsalgia such as osseous or soft tissue, congenital, acquired and/or iatrogenic. Previous authors have divided metatarsalgia into primary or secondary.1 With the addition of iatrogenic causes, this latter classification is perhaps the most useful in guiding management strategies.3 Treatment strategies are guided by the multi-factorial nature of metatarsalgia. It is therefore imperative for the surgeon to have a clear understanding of the biomechanical and anatomical causes of metatarsalgia in order to select the optimal management.
Gurdip S Chahal BSc (Hons) FRCS (Tr & Orth), Consultant Surgeon, Warwick Hospital, UK. Conflicts of interest: none declared. Mark B Davies FRCS (Tr & Orth), Consultant Surgeon, Sheffield Foot & Ankle Unit, Northern General Hospital, UK. Conflicts of interest: none declared.
Primary metatarsalgia
Chris M Blundell BMedSci (Hons) MB ChB MD FRCS (Tr&Orth), Consultant Surgeon, Sheffield Foot & Ankle Unit, Northern General Hospital, UK. Conflicts of interest: none declared.
ORTHOPAEDICS AND TRAUMA xxx:xxx
This is probably best considered as due to causes originating within the foot or related structures. Commonly this is due to
1
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Please cite this article as: Chahal GS et al., Treating metatarsalgia: current concepts, Orthopaedics and Trauma, https://doi.org/10.1016/ j.mporth.2019.11.005
FOOT AND ANKLE
anatomical characteristics of the metatarsals (M) that affect their relationships to one another and to the rest of the foot. For example, forces through the second metatarsal [M2] may be increased in patients with a congenitally short M1 or in the presence of hallux valgus which is a very common cause. Clinical effects of this often lead to plantar plate disruption with metatarsophalangeal joint deformity and dislocation, secondary toe interphalangeal deformity such as claw or hammer toes. Inter-digital neuroma formation is also a result of increased pressures across the lesser metatarsals as are stress fractures. Other causes include disproportionate length of M2 or M3, congenital deformities of the metatarsal heads such as brachymetatarsia (Figure 1), tightness of the triceps surae muscles, fixed equinus of the foot, pes cavus (Figure 2), and any hindfoot abnormality that results in over-loading of the forefoot.
Figure 2 A pes cavus deformity displaying a high calcaneal pitch leading to a rigid foot type often predisposed to a tight Achilles tendon and metatarsalgia.
Iatrogenic metatarsalgia Iatrogenic metatarsalgia is really a variant of primary metatarsalgia and occurs from forefoot surgery. Hallux valgus surgery may cause excessive shortening and/or elevation of M1, thereby overloading of the mid-foot rays is not uncommon. Metatarsal osteotomies may result in this excessive shortening, elevation, or depression; delayed union or nonunion; or restriction of the range of extension of the MTP joints. Although thought of as a ‘cardinal sin’ of forefoot surgery, isolated excision of a metatarsal head is occasionally seen and causes overloading of the adjacent head. Resection of the proximal phalanges may also be a causative factor in the overloading of metatarsal heads (Figure 6). A summary of the causes of metatarsalgia is given in Table 1.
Secondary metatarsalgia Secondary metatarsalgia is caused by general conditions that affect metatarsal loading via indirect mechanisms. One such mechanism is inflammatory synovitis and pannus formation, which may lead to subluxation or dislocation of the metatarsophalangeal joints with atrophy and distal migration of the plantar fat pad. This is a causative mechanism in patients with rheumatoid arthritis, gout, or psoriasis (Figures 3 and 4). Secondary metatarsalgia can also be due to neurological disorders (e.g. hereditary sensory motor neuropathy) metatarsal malunions, or sequelae of Freiberg disease (Figure 5).
Figure 3 Forefoot of patient with rheumatoid arthritis.
Figure 1 The fourth metatarsal brachymetatarsia (hypoplasia of a metatarsal), which is an example of a congenital cause of metatarsalgia due to overloading of adjacent metatarsal heads. This deformity may be associated with Down’s, Larsen or Turner syndromes and not infrequently with parathyroid hormone abnormalities.
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Figure 4 A rheumatoid foot with associated severe deformities including dislocation of metatarsophalangeal joints leading to metatarsalgia due to increased pressures.
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Clinical examination Patients will localize pain to the forefoot pointing out any deformity. A common expression is a feeling of ‘walking on pebbles’. The clinical examination will include an assessment of the €ld test along with any gastro-soleus complex with the Silfverskio hindfoot deformity. It is important to build a picture of what the cause of metatarsalgia maybe. So first ray deformities, hallux valgus and rigidus need specifically looking for along with testing for medial column stability. The MTP joints should be examined for pain over the metatarsal heads as well as testing for plantar plate stability with the draw test. The interspaces also should be palpated for the presence of Morton neuromata. A wider general examination should be conducted if one finds for example a cavus foot or evidence of an inflammatory arthropathy.
Investigations
Figure 5 Freiberg disease of the second metatarsal head with infarction and secondary collapse, which can often be a cause of intraarticular forefoot pain.
Laboratory investigations may be appropriate if systemic disease such as diabetes or rheumatoid arthritis is suspected. Plain radiographs are an essential part of primary investigations in metatarsalgia. The standing dorso-plantar and lateral views are necessary to evaluate the metatarsal parabola (relative lengths), metatarsal declination as well as digital bony deformities. Sesamoid axial views may also be utilised to evaluate their contribution to increased plantar loading or degenerative disease. Static pedobarographic studies can provide crucial information about the pressures and loads under the foot in the weightbearing position. A dynamic system can give information about the pressure changes occurring during gait, which can be of value in decision-making, planning surgery and orthotic design. It has also been advocated as a screening tool to predict areas at risk of developing pressure ulceration in diabetic feet with neuropathy.7 This patient group may have the underlying risk factors described above but not necessarily complain of pain. Ultrasonography is a useful modality in diagnosing Morton’s neuroma and plantar plate pathology. It has the advantage of being a dynamic source of imaging which is particular useful in assessing instability but is very dependent upon the ability of the operator. Magnetic resonance imaging may also aid the diagnosis of Morton’s neuroma, stress fractures, bone oedema, bursitis, flexor tenosynovitis, plantar plate pathology or other miscellaneous space-occupying lesions within the forefoot.
Illustrative case study An 18-year-old female underwent Weil osteotomies of both feet third and fourth metatarsals. She presented a number of months later to a tertiary referral centre complaining of metatarsalgia under the left fourth MTP joint and the right third MTP joint. Examination revealed: Left foot second and third toes were elevated, clinically not engaging the ground.
Figure 6 Iatrogenic overloading of the metatarsal stumps secondary to metatarsal head resection. This type of surgery is sometimes used in the management of low-demand patients with rheumatoid disease. The parabola has been disrupted with the third metatarsal being overshortened with increased plantar pressures over the distal aspects of the adjacent metatarsal remnants.
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Surgical treatment
Examples of causes of the three types of metatarsalgia Primary metatarsalgia Secondary metatarsalgia
Other causes
Functional pathology Inflammatory pathology 1. Short ipsilateral 1. Rheumatoid limb arthritis 2. Footwear related 2. Osteoarthritis
Nerve entrapment
Structural pathology 1. Sesamoid pathology 2. Stress fractures 3. MTP instability 4. Freiberg disease 5. Hallux rigidus 6. Hallux valgus 7. Hindfoot pathology 8. Cavus foot 9. First ray instability 10. Plantarflexed MT 11. MT length abnormality
3. Gout 4. SLE 5. Seronegative arthritides Infective causes 1. Leprosy
Surgical management of metatarsalgia is complex and may involve a considerable variety of surgical procedures, best divided into soft tissue and bony procedures. Soft tissue procedures Gastrocnemius muscle recession is a procedure that targets the ankle equinus due to gastrocnemius contracture leading to metatarsalgia. The Strayer procedure involves incision of the gastrocnemius aponeurosis and proximal release of the medial head of the gastrocnemius. The Strayer procedure was first devised as a treatment for spasticity but is commonly used for muscle tightness.9 Tendon transfers in patients with claw toe deformity may require MTP joint release, extensor apparatus lengthening, or flexor tenotomy (of the longus and/or brevis flexors). A transfer of the flexor digitorum longus tendon to the dorsum of the P1 extensor hood of the same toe has been described as the GirdlestoneeTaylor procedure10 as a treatment for a flexible claw toe. Plantar plate repair can be performed where plantar plate tears are sutured. Studies have evaluated the outcomes of this procedure.11 This technique may be useful in selected patients with acute MTP joint instability but no dislocation. Plantar plate repair by suturing or tenodesis to the base of P1 can be combined with a shortening metatarsal osteotomy via a dorsal approach. The limited exposure makes this procedure technically challenging, however, contemporary suture-passing instruments have been designed specifically to aid this procedure. Morton neuromas can be excised through either a plantar or dorsal incision. Dorsal incisions are favoured due to problems associated with plantar scarring.
1. Morton’s neuroma 2. Tarsal tunnel syndrome Vascular 1. Intermittent claudication 2. Buerger’s disease Spinal 1. Nerve root pathology
Neurological causes 1. Diabetes mellitus 2. Charcot Marie-Tooth 3. Freidreich’s ataxia 4. Polio
MT, metatarsal; MTPJ, metatarsophalangeal joint; SLE, systemic lupus erythematosus.
Table 1
Bony procedures Should first ray pathology be identified as the cause of the metatarsalgia this is usually addressed with corrective surgery thus reducing pathological loading of the lesser metatarsal heads. Many different techniques have been used to treat malalignment of the lesser metatarsals. They can be classified based on either the site of the cut (proximal basal, diaphyseal or distal) or the biomechanical effect (elevation and/or shortening).5 The Helal osteotomy of the metatarsal diaphysis described an oblique osteotomy of the metatarsal diaphysis with a long cut starting proximally at the dorsal, and ending distally at the volar, aspect of the bone. Fixation is not performed and weight bearing is used to allow the metatarsal head to heal at the correct level. This procedure has been shown to have a high complication rate, principally that of transfer metatarsalgia,12 and as a result the procedure has fallen out of favour.
Right foot third metatarsal head was malrotated into the sole of the foot. Pedobarographic studies were performed. Pedobarograph studies of the left foot (Figure 7) showed there was an area of high localized pressure under the fourth metatarsal head. Studies of the right foot showed high localized pressure under the third metatarsal head (Figure 8). The investigations show an iatrogenic transfer metatarsalgia of the left fourth MTP joint and right third MTP joint. The patient was successfully treated with a left fourth Weil osteotomy and a right third corrective dorsal closing wedge de-rotation osteotomy.
Non-surgical treatment Once the history, examination and investigations are complete, the aetiological factors should be corrected and local measures taken to relieve the symptoms. The first-line treatment is nonoperative management with consideration of surgery with the failure of conservative treatment. Nevertheless, there is little Level 1 evidence to support the efficacy of conservative treatments for metatarsalgia.8 Treatments may include stretching exercises particularly of the posterior calf muscle group, footwear modifications (e.g. a rocker bottom shoe) and orthotic management and injection therapy particularly for neuromas.
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Basal metatarsal osteotomy: basal metatarsal osteotomy was described by Barouk in 2003 (BRT, BaroukeRippsteineToullec).13 This is useful in treating metatarsalgia with sagittal plane malalignment without significant MTP joint pathology. This is a powerful corrective osteotomy with good results if care is taken not to excessively elevate the metatarsal. This osteotomy is useful to correct excessive metatarsal pitch, which is contributing to the
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Figure 7 Pedobarograph studies of the left foot. MTPJ, metatarsophalangeal joint.
metatarsalgia (i.e. a cavus type foot) and is usually part of a wider procedure.
Weil osteotomy: Weil osteotomy described by Weil in 1991 has been the most widely used metatarsal osteotomy in Europe. A dorsal longitudinal or transverse incision is performed. A minimally invasive method is used to expose each MTP joint between the extensor digitorum longus and brevis tendons, without lengthening the tendons or cutting the collateral ligaments, except in patients with fixed or axial dislocation requiring joint release. The osteotomy is made in a horizontal fashion. A double-layer cut may be needed to remove a slice of bone when length is decreased by more than 4 mm, to avoid plantarization of the head and to improve intrinsic muscle function.4 Under/ overcorrection may lead to transfer metatarsalgia therefore meticulous preoperative planning is necessary and intraoperative
Distal metatarsal osteotomy: distal metatarsal osteotomy is performed at the neck or head of the metatarsal. There are three main types of distal osteotomies. These are the main workhorse osteotomies used in metatarsalgia. Gauthier osteotomy: gauthier osteotomy is a distal wedge with the acute angle at the plantar aspect is removed to produce limited shortening and elevation of the head.14 Both the osteotomy and its fixation are technically challenging but produce excellent outcomes in Freiberg disease.
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Figure 8 Pedobarograph studies of the right foot. MTPJ, metatarsophalangeal joint.
metatarsalgia and uncontrolled elevation leading to mal-union. However, there is good evidence that DMMO surgery at a specialized foot and ankle unit produced good patient satisfaction, functional improvement, and low complication rates.16 Lesser MTP joint silicone implants have shown good outcomes for the lesser MTP joints.17 Silastic implants may offer an alternative to the metatarsal osteotomy in certain conditions affecting the middle metatarsals (e.g. degenerative disease and fixed MTP joint dislocation) with care taken to ensure adjacent ray is not susceptible to transfer metatarsalgia.
fluoroscopy is recommended. It is a useful osteotomy on overlong metatarsals. Complications include stiffness and a floating toe due to the change in intrinsic muscle action. Distal metatarsal metaphyseal osteotomy: distal metatarsal metaphyseal osteotomy (DMMO) has increased in popularity with the introduction of minimally invasive surgery. A low-speed burr is used (<8000 rpm) in conjunction with a stab incision at the after the soft tissues are stripped off the neck. The burr is held at 45 to the bone. No internal fixation is used and toe strapping is often utilised as well as a stiff-soled shoe. There is evidence to show DMMOs are equivalent to Weil osteotomies when comparing functional outcome measures.15 Complications include delayed healing particularly radiographically, transfer
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Excisional arthroplasty procedures: excisional arthroplasty surgery of the metatarsal head or the proximal phalanx (partial of complete) are used particularly in low-demand patients with
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FOOT AND ANKLE
severe deformity such as rheumatoid or psoriatic arthropathy. The Stainsby procedure as described by Stainsby and Briggs in 200118 describes resection of most of the proximal phalanx, which in theory repositions the plantar plate under the metatarsal head. Excision of the metatarsal head again has been used in the rheumatoid foot but is at risk of causing iatrogenic metatarsalgia form often due to excessive resection as described in the iatrogenic section above.
7 Duckworth T, Boulton AJM, Betts RP, Franks CI, Ward D. Plantar pressure measurements and the prevention of ulceration in the diabetic foot. J Bone Joint Surg 1985; 67-B: 79e85. 8 Espinosa N, Maceira E, Myerson MS. Current concept review: metatarsalgia. Foot Ankle Int 2008; 29: 871e9. 9 Maskill JD, Bohay DR, Anderson JG. Gastrocnemius recession to treat isolated foot pain. Foot Ankle Int 2010; 31: 19e23. 10 Haddad SL, Sabbagh RC, Resch S, Myerson B, Myerson MS. Results of flexor-to-extensor and extensor brevis tendon transfer for correction of the crossoversecond toe deformity. Foot Ankle Int 1999; 20: 781e8. 11 Weil Jr L, Sung W, Weil Sr LS, Malinoski K. Anatomic plantar plate repair usingthe Weil metatarsal osteotomy approach. Foot Ankle Spec 2011; 4: 145e50. 12 Winson IG, Rawlinson J, Broughton NS. Treatment of metatarsalgia by slidingdistal metatarsal osteotomy. Foot Ankle 1988; 9: 2e6. 13 Barouk LS. The BRT new proximal metatarsal osteotomy. Forefoot reconstruc-tion. France. Springer-Verlag, 2003; 133e48. 14 Gauthier G, Elbaz R. Freiberg’s infraction: a subchondral bone fatigue fracture.A new surgical treatment. Clin Orthop Relat Res 1979; 142: 93e5. 15 Henry J, Besse JL, Fessy MH, AFCP. Distal osteotomy of the lateral metatarsals: aseries of 72 cases comparing the Weil osteotomy and the DMMO percutaneous osteotomy. Orthop Traumatol Surg Res 2011; 97(suppl. 6): S57e65. 16 Haque S, Kakwani R, Chadwick C, Davies MB, Blundell CM. Outcome of minimally invasive distal metatarsal metaphyseal osteotomy (DMMO) for lesser toe metatarsalgia. Foot Ankle Int 2016; 37: 58e63. 17 Maestro M. Implants en silicone monobloc dans le remplacement rales. In: des articu-lations metatarsophalangiennes late Leemrijse TH, Valtin B, eds. Pathologie du pied et de la cheville. Paris: Elsevier Masson ed, 2009; 216e21. 18 Briggs PJ, Stainsby GD. Metatarsal head preservation in forefoot arthroplasty. Foot Ankle Surg 2001; 7: 93e101.
Conclusion The treatment of metatarsalgia must involve seeking out the underlying cause(s) of the pain taking into account the anatomical and biomechanical contributive factors as well as assessing first ray function and proximal deformity. Management of metatarsalgia may be conservative or surgical, soft tissue or bony. Newer surgical procedures have a reliable outcome but care must be taken as they are often technically challenging. A REFERENCES 1 Fadel GE, Rowley DI. (iv) Metatarsalgia. Curr Orthop 2002; 16: 193e204. https://doi.org/10.1054/cuor.2002.0269. 2 Dockery GL. Evaluation and treatment of metatarsalgia and keratic disorders.In: Myerson MS, editor. 3 DuVries HL. Surgery of the foot. 2nd edn. St Louis: C V Mosby Co, 1965; 204. 4 Besse J-L. Metatarsalgia. Orthop Traumatol: Surg Res 2017; 103: S29e39. 5 Kirtley C. Clinical gait analysis/theory and practice. Oxford: Churchill-Livingstone, Elsevier, 2006. 6 Clinical Practice Guideline Forefoot Disorders Panel, Thomas JL, Blitch IV EL, et al. Diagnosis and treatment of forefoot, disorders. Section 2. Central metatarsalgia. J Foot Ankle Surg 2009; 48: 239e50.
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Treating metatarsalgia: current concepts
Anatomical considerations The normal distal parabola created by the metatarsal heads plays an important role on the loaded foot mechanics. During weightbearing, the five metatarsal heads are at the same distance from the ground. The angle between the bone and the ground decreases from the M1 (20 ) to M5 (5 ). The metatarsals are connected by the transverse inter-metatarsal ligament and, therefore, act together as a single functional unit.4 The plantar plates are fibro-cartilaginous condensations underneath the metatarsophalangeal (MTP) joints that stabilize the joints particularly preventing dorsal dislocation of the proximal phalanx (P1). During propulsion, the toes themselves play an important role in weight transfer as well as stability. It follows that any functional deficiency of the toes may lead to overload of the MTP joints leading to pain at the metatarsal heads. Any dysfunction of the hallux and sesamoid complex with its associated muscles and tendons may also lead to pain under the lesser metatarsal heads. The first ray plays an important role in both static and dynamic stability of the foot particularly at the propulsion (third rocker) phase of gait.
Gurdip S Chahal Mark B Davies Chris M Blundell
Abstract The objective of this paper is to describe the anatomical and biomechanical considerations for treating metatarsalgia. We describe a method of classification incorporating the causes and lead onto a comprehensive description of the treatment of metatarsalgia. Important clinical findings and investigations are discussed in treating this common pathology and a case study used as an example to illustrate the above. This paper highlights the complex nature of metatarsalgia and describes the factors a surgeon needs to consider prior to embarking on treatment.
Biomechanical considerations
Keywords forefoot; metatarsalgia; pain; treatment
The rocker concept of gait analysis is well described5 and is a useful way of understanding and describing pathology leading to metatarsalgia. The two most important factors concerning the metatarsal heads with respect to normal function are their position relative to the ground and their relative length. During the second rocker of gait the foot is flat to the ground and the tibia passes over the ankle controlled by eccentric contraction of the posterior calf muscles. It follows that if any of the metatarsal heads are closer to the ground during this phase this will lead to increased load and pressures over this area. This is sometimes termed ‘static metatarsalgia’. The position of the metatarsal heads relative to the ground are governed by two factors; the slope of the metatarsals in the sagittal plane and motion at the tarso-metatarsal (TMT) joints. TMT joint function varies across the foot leading to altered biomechanics at the metatarsal heads when ground reaction forces are applied. The lateral column (fourth and fifth rays) undergoes mainly dorsiflexion and is relatively mobile. It aids lateral deceleration during gait. The central column (second and third rays) have relatively limited motion at the TMT joints which is a factor in the increased incidence of central metatarsalgia.6 The medial column (first ray), provides plantar flexion and the pronation required for the propulsive action of the hallux during the third rocker. Any disruption in this function leads to transfer metatarsalgia. TMT joint degenerative disease leads to overloading of the metatarsal heads with the central column particular vulnerable for the reasons stated above during propulsion. Relatively long metatarsal length also leads to overloading at the metatarsal heads with the plantar plate being at risk from repetitive overloading.
Introduction Metatarsalgia is defined as pain in the forefoot under one or more metatarsal heads. It is a common forefoot symptom seen within the foot and ankle sub-speciality clinics but it is not a diagnosis. Metatarsophalangeal pathology may be secondary to a variety of problems including trauma, structural deformity and systemic disease amongst others. The prevalence of foot problems in the general population is 10%, whilst in the elderly it ranges from 50% to 95%.1 It has been estimated that 90% of foot disorders affect the forefoot. Metatarsalgia is probably the most common cause of foot pain among middle-aged women.2 There have been many attempts to classify the pathologies causing metatarsalgia such as osseous or soft tissue, congenital, acquired and/or iatrogenic. Previous authors have divided metatarsalgia into primary or secondary.1 With the addition of iatrogenic causes, this latter classification is perhaps the most useful in guiding management strategies.3 Treatment strategies are guided by the multi-factorial nature of metatarsalgia. It is therefore imperative for the surgeon to have a clear understanding of the biomechanical and anatomical causes of metatarsalgia in order to select the optimal management.
Gurdip S Chahal BSc (Hons) FRCS (Tr & Orth), Consultant Surgeon, Warwick Hospital, UK. Conflicts of interest: none declared. Mark B Davies FRCS (Tr & Orth), Consultant Surgeon, Sheffield Foot & Ankle Unit, Northern General Hospital, UK. Conflicts of interest: none declared.
Primary metatarsalgia
Chris M Blundell BMedSci (Hons) MB ChB MD FRCS (Tr&Orth), Consultant Surgeon, Sheffield Foot & Ankle Unit, Northern General Hospital, UK. Conflicts of interest: none declared.
ORTHOPAEDICS AND TRAUMA xxx:xxx
This is probably best considered as due to causes originating within the foot or related structures. Commonly this is due to
1
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Please cite this article as: Chahal GS et al., Treating metatarsalgia: current concepts, Orthopaedics and Trauma, https://doi.org/10.1016/ j.mporth.2019.11.005
FOOT AND ANKLE
anatomical characteristics of the metatarsals (M) that affect their relationships to one another and to the rest of the foot. For example, forces through the second metatarsal [M2] may be increased in patients with a congenitally short M1 or in the presence of hallux valgus which is a very common cause. Clinical effects of this often lead to plantar plate disruption with metatarsophalangeal joint deformity and dislocation, secondary toe interphalangeal deformity such as claw or hammer toes. Inter-digital neuroma formation is also a result of increased pressures across the lesser metatarsals as are stress fractures. Other causes include disproportionate length of M2 or M3, congenital deformities of the metatarsal heads such as brachymetatarsia (Figure 1), tightness of the triceps surae muscles, fixed equinus of the foot, pes cavus (Figure 2), and any hindfoot abnormality that results in over-loading of the forefoot.
Figure 2 A pes cavus deformity displaying a high calcaneal pitch leading to a rigid foot type often predisposed to a tight Achilles tendon and metatarsalgia.
Iatrogenic metatarsalgia Iatrogenic metatarsalgia is really a variant of primary metatarsalgia and occurs from forefoot surgery. Hallux valgus surgery may cause excessive shortening and/or elevation of M1, thereby overloading of the mid-foot rays is not uncommon. Metatarsal osteotomies may result in this excessive shortening, elevation, or depression; delayed union or nonunion; or restriction of the range of extension of the MTP joints. Although thought of as a ‘cardinal sin’ of forefoot surgery, isolated excision of a metatarsal head is occasionally seen and causes overloading of the adjacent head. Resection of the proximal phalanges may also be a causative factor in the overloading of metatarsal heads (Figure 6). A summary of the causes of metatarsalgia is given in Table 1.
Secondary metatarsalgia Secondary metatarsalgia is caused by general conditions that affect metatarsal loading via indirect mechanisms. One such mechanism is inflammatory synovitis and pannus formation, which may lead to subluxation or dislocation of the metatarsophalangeal joints with atrophy and distal migration of the plantar fat pad. This is a causative mechanism in patients with rheumatoid arthritis, gout, or psoriasis (Figures 3 and 4). Secondary metatarsalgia can also be due to neurological disorders (e.g. hereditary sensory motor neuropathy) metatarsal malunions, or sequelae of Freiberg disease (Figure 5).
Figure 3 Forefoot of patient with rheumatoid arthritis.
Figure 1 The fourth metatarsal brachymetatarsia (hypoplasia of a metatarsal), which is an example of a congenital cause of metatarsalgia due to overloading of adjacent metatarsal heads. This deformity may be associated with Down’s, Larsen or Turner syndromes and not infrequently with parathyroid hormone abnormalities.
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Figure 4 A rheumatoid foot with associated severe deformities including dislocation of metatarsophalangeal joints leading to metatarsalgia due to increased pressures.
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Clinical examination Patients will localize pain to the forefoot pointing out any deformity. A common expression is a feeling of ‘walking on pebbles’. The clinical examination will include an assessment of the €ld test along with any gastro-soleus complex with the Silfverskio hindfoot deformity. It is important to build a picture of what the cause of metatarsalgia maybe. So first ray deformities, hallux valgus and rigidus need specifically looking for along with testing for medial column stability. The MTP joints should be examined for pain over the metatarsal heads as well as testing for plantar plate stability with the draw test. The interspaces also should be palpated for the presence of Morton neuromata. A wider general examination should be conducted if one finds for example a cavus foot or evidence of an inflammatory arthropathy.
Investigations
Figure 5 Freiberg disease of the second metatarsal head with infarction and secondary collapse, which can often be a cause of intraarticular forefoot pain.
Laboratory investigations may be appropriate if systemic disease such as diabetes or rheumatoid arthritis is suspected. Plain radiographs are an essential part of primary investigations in metatarsalgia. The standing dorso-plantar and lateral views are necessary to evaluate the metatarsal parabola (relative lengths), metatarsal declination as well as digital bony deformities. Sesamoid axial views may also be utilised to evaluate their contribution to increased plantar loading or degenerative disease. Static pedobarographic studies can provide crucial information about the pressures and loads under the foot in the weightbearing position. A dynamic system can give information about the pressure changes occurring during gait, which can be of value in decision-making, planning surgery and orthotic design. It has also been advocated as a screening tool to predict areas at risk of developing pressure ulceration in diabetic feet with neuropathy.7 This patient group may have the underlying risk factors described above but not necessarily complain of pain. Ultrasonography is a useful modality in diagnosing Morton’s neuroma and plantar plate pathology. It has the advantage of being a dynamic source of imaging which is particular useful in assessing instability but is very dependent upon the ability of the operator. Magnetic resonance imaging may also aid the diagnosis of Morton’s neuroma, stress fractures, bone oedema, bursitis, flexor tenosynovitis, plantar plate pathology or other miscellaneous space-occupying lesions within the forefoot.
Illustrative case study An 18-year-old female underwent Weil osteotomies of both feet third and fourth metatarsals. She presented a number of months later to a tertiary referral centre complaining of metatarsalgia under the left fourth MTP joint and the right third MTP joint. Examination revealed: Left foot second and third toes were elevated, clinically not engaging the ground.
Figure 6 Iatrogenic overloading of the metatarsal stumps secondary to metatarsal head resection. This type of surgery is sometimes used in the management of low-demand patients with rheumatoid disease. The parabola has been disrupted with the third metatarsal being overshortened with increased plantar pressures over the distal aspects of the adjacent metatarsal remnants.
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Surgical treatment
Examples of causes of the three types of metatarsalgia Primary metatarsalgia Secondary metatarsalgia
Other causes
Functional pathology Inflammatory pathology 1. Short ipsilateral 1. Rheumatoid limb arthritis 2. Footwear related 2. Osteoarthritis
Nerve entrapment
Structural pathology 1. Sesamoid pathology 2. Stress fractures 3. MTP instability 4. Freiberg disease 5. Hallux rigidus 6. Hallux valgus 7. Hindfoot pathology 8. Cavus foot 9. First ray instability 10. Plantarflexed MT 11. MT length abnormality
3. Gout 4. SLE 5. Seronegative arthritides Infective causes 1. Leprosy
Surgical management of metatarsalgia is complex and may involve a considerable variety of surgical procedures, best divided into soft tissue and bony procedures. Soft tissue procedures Gastrocnemius muscle recession is a procedure that targets the ankle equinus due to gastrocnemius contracture leading to metatarsalgia. The Strayer procedure involves incision of the gastrocnemius aponeurosis and proximal release of the medial head of the gastrocnemius. The Strayer procedure was first devised as a treatment for spasticity but is commonly used for muscle tightness.9 Tendon transfers in patients with claw toe deformity may require MTP joint release, extensor apparatus lengthening, or flexor tenotomy (of the longus and/or brevis flexors). A transfer of the flexor digitorum longus tendon to the dorsum of the P1 extensor hood of the same toe has been described as the GirdlestoneeTaylor procedure10 as a treatment for a flexible claw toe. Plantar plate repair can be performed where plantar plate tears are sutured. Studies have evaluated the outcomes of this procedure.11 This technique may be useful in selected patients with acute MTP joint instability but no dislocation. Plantar plate repair by suturing or tenodesis to the base of P1 can be combined with a shortening metatarsal osteotomy via a dorsal approach. The limited exposure makes this procedure technically challenging, however, contemporary suture-passing instruments have been designed specifically to aid this procedure. Morton neuromas can be excised through either a plantar or dorsal incision. Dorsal incisions are favoured due to problems associated with plantar scarring.
1. Morton’s neuroma 2. Tarsal tunnel syndrome Vascular 1. Intermittent claudication 2. Buerger’s disease Spinal 1. Nerve root pathology
Neurological causes 1. Diabetes mellitus 2. Charcot Marie-Tooth 3. Freidreich’s ataxia 4. Polio
MT, metatarsal; MTPJ, metatarsophalangeal joint; SLE, systemic lupus erythematosus.
Table 1
Bony procedures Should first ray pathology be identified as the cause of the metatarsalgia this is usually addressed with corrective surgery thus reducing pathological loading of the lesser metatarsal heads. Many different techniques have been used to treat malalignment of the lesser metatarsals. They can be classified based on either the site of the cut (proximal basal, diaphyseal or distal) or the biomechanical effect (elevation and/or shortening).5 The Helal osteotomy of the metatarsal diaphysis described an oblique osteotomy of the metatarsal diaphysis with a long cut starting proximally at the dorsal, and ending distally at the volar, aspect of the bone. Fixation is not performed and weight bearing is used to allow the metatarsal head to heal at the correct level. This procedure has been shown to have a high complication rate, principally that of transfer metatarsalgia,12 and as a result the procedure has fallen out of favour.
Right foot third metatarsal head was malrotated into the sole of the foot. Pedobarographic studies were performed. Pedobarograph studies of the left foot (Figure 7) showed there was an area of high localized pressure under the fourth metatarsal head. Studies of the right foot showed high localized pressure under the third metatarsal head (Figure 8). The investigations show an iatrogenic transfer metatarsalgia of the left fourth MTP joint and right third MTP joint. The patient was successfully treated with a left fourth Weil osteotomy and a right third corrective dorsal closing wedge de-rotation osteotomy.
Non-surgical treatment Once the history, examination and investigations are complete, the aetiological factors should be corrected and local measures taken to relieve the symptoms. The first-line treatment is nonoperative management with consideration of surgery with the failure of conservative treatment. Nevertheless, there is little Level 1 evidence to support the efficacy of conservative treatments for metatarsalgia.8 Treatments may include stretching exercises particularly of the posterior calf muscle group, footwear modifications (e.g. a rocker bottom shoe) and orthotic management and injection therapy particularly for neuromas.
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Basal metatarsal osteotomy: basal metatarsal osteotomy was described by Barouk in 2003 (BRT, BaroukeRippsteineToullec).13 This is useful in treating metatarsalgia with sagittal plane malalignment without significant MTP joint pathology. This is a powerful corrective osteotomy with good results if care is taken not to excessively elevate the metatarsal. This osteotomy is useful to correct excessive metatarsal pitch, which is contributing to the
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Figure 7 Pedobarograph studies of the left foot. MTPJ, metatarsophalangeal joint.
metatarsalgia (i.e. a cavus type foot) and is usually part of a wider procedure.
Weil osteotomy: Weil osteotomy described by Weil in 1991 has been the most widely used metatarsal osteotomy in Europe. A dorsal longitudinal or transverse incision is performed. A minimally invasive method is used to expose each MTP joint between the extensor digitorum longus and brevis tendons, without lengthening the tendons or cutting the collateral ligaments, except in patients with fixed or axial dislocation requiring joint release. The osteotomy is made in a horizontal fashion. A double-layer cut may be needed to remove a slice of bone when length is decreased by more than 4 mm, to avoid plantarization of the head and to improve intrinsic muscle function.4 Under/ overcorrection may lead to transfer metatarsalgia therefore meticulous preoperative planning is necessary and intraoperative
Distal metatarsal osteotomy: distal metatarsal osteotomy is performed at the neck or head of the metatarsal. There are three main types of distal osteotomies. These are the main workhorse osteotomies used in metatarsalgia. Gauthier osteotomy: gauthier osteotomy is a distal wedge with the acute angle at the plantar aspect is removed to produce limited shortening and elevation of the head.14 Both the osteotomy and its fixation are technically challenging but produce excellent outcomes in Freiberg disease.
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Figure 8 Pedobarograph studies of the right foot. MTPJ, metatarsophalangeal joint.
metatarsalgia and uncontrolled elevation leading to mal-union. However, there is good evidence that DMMO surgery at a specialized foot and ankle unit produced good patient satisfaction, functional improvement, and low complication rates.16 Lesser MTP joint silicone implants have shown good outcomes for the lesser MTP joints.17 Silastic implants may offer an alternative to the metatarsal osteotomy in certain conditions affecting the middle metatarsals (e.g. degenerative disease and fixed MTP joint dislocation) with care taken to ensure adjacent ray is not susceptible to transfer metatarsalgia.
fluoroscopy is recommended. It is a useful osteotomy on overlong metatarsals. Complications include stiffness and a floating toe due to the change in intrinsic muscle action. Distal metatarsal metaphyseal osteotomy: distal metatarsal metaphyseal osteotomy (DMMO) has increased in popularity with the introduction of minimally invasive surgery. A low-speed burr is used (<8000 rpm) in conjunction with a stab incision at the after the soft tissues are stripped off the neck. The burr is held at 45 to the bone. No internal fixation is used and toe strapping is often utilised as well as a stiff-soled shoe. There is evidence to show DMMOs are equivalent to Weil osteotomies when comparing functional outcome measures.15 Complications include delayed healing particularly radiographically, transfer
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Excisional arthroplasty procedures: excisional arthroplasty surgery of the metatarsal head or the proximal phalanx (partial of complete) are used particularly in low-demand patients with
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severe deformity such as rheumatoid or psoriatic arthropathy. The Stainsby procedure as described by Stainsby and Briggs in 200118 describes resection of most of the proximal phalanx, which in theory repositions the plantar plate under the metatarsal head. Excision of the metatarsal head again has been used in the rheumatoid foot but is at risk of causing iatrogenic metatarsalgia form often due to excessive resection as described in the iatrogenic section above.
7 Duckworth T, Boulton AJM, Betts RP, Franks CI, Ward D. Plantar pressure measurements and the prevention of ulceration in the diabetic foot. J Bone Joint Surg 1985; 67-B: 79e85. 8 Espinosa N, Maceira E, Myerson MS. Current concept review: metatarsalgia. Foot Ankle Int 2008; 29: 871e9. 9 Maskill JD, Bohay DR, Anderson JG. Gastrocnemius recession to treat isolated foot pain. Foot Ankle Int 2010; 31: 19e23. 10 Haddad SL, Sabbagh RC, Resch S, Myerson B, Myerson MS. Results of flexor-to-extensor and extensor brevis tendon transfer for correction of the crossoversecond toe deformity. Foot Ankle Int 1999; 20: 781e8. 11 Weil Jr L, Sung W, Weil Sr LS, Malinoski K. Anatomic plantar plate repair usingthe Weil metatarsal osteotomy approach. Foot Ankle Spec 2011; 4: 145e50. 12 Winson IG, Rawlinson J, Broughton NS. Treatment of metatarsalgia by slidingdistal metatarsal osteotomy. Foot Ankle 1988; 9: 2e6. 13 Barouk LS. The BRT new proximal metatarsal osteotomy. Forefoot reconstruc-tion. France. Springer-Verlag, 2003; 133e48. 14 Gauthier G, Elbaz R. Freiberg’s infraction: a subchondral bone fatigue fracture.A new surgical treatment. Clin Orthop Relat Res 1979; 142: 93e5. 15 Henry J, Besse JL, Fessy MH, AFCP. Distal osteotomy of the lateral metatarsals: aseries of 72 cases comparing the Weil osteotomy and the DMMO percutaneous osteotomy. Orthop Traumatol Surg Res 2011; 97(suppl. 6): S57e65. 16 Haque S, Kakwani R, Chadwick C, Davies MB, Blundell CM. Outcome of minimally invasive distal metatarsal metaphyseal osteotomy (DMMO) for lesser toe metatarsalgia. Foot Ankle Int 2016; 37: 58e63. 17 Maestro M. Implants en silicone monobloc dans le remplacement rales. In: des articu-lations metatarsophalangiennes late Leemrijse TH, Valtin B, eds. Pathologie du pied et de la cheville. Paris: Elsevier Masson ed, 2009; 216e21. 18 Briggs PJ, Stainsby GD. Metatarsal head preservation in forefoot arthroplasty. Foot Ankle Surg 2001; 7: 93e101.
Conclusion The treatment of metatarsalgia must involve seeking out the underlying cause(s) of the pain taking into account the anatomical and biomechanical contributive factors as well as assessing first ray function and proximal deformity. Management of metatarsalgia may be conservative or surgical, soft tissue or bony. Newer surgical procedures have a reliable outcome but care must be taken as they are often technically challenging. A REFERENCES 1 Fadel GE, Rowley DI. (iv) Metatarsalgia. Curr Orthop 2002; 16: 193e204. https://doi.org/10.1054/cuor.2002.0269. 2 Dockery GL. Evaluation and treatment of metatarsalgia and keratic disorders.In: Myerson MS, editor. 3 DuVries HL. Surgery of the foot. 2nd edn. St Louis: C V Mosby Co, 1965; 204. 4 Besse J-L. Metatarsalgia. Orthop Traumatol: Surg Res 2017; 103: S29e39. 5 Kirtley C. Clinical gait analysis/theory and practice. Oxford: Churchill-Livingstone, Elsevier, 2006. 6 Clinical Practice Guideline Forefoot Disorders Panel, Thomas JL, Blitch IV EL, et al. Diagnosis and treatment of forefoot, disorders. Section 2. Central metatarsalgia. J Foot Ankle Surg 2009; 48: 239e50.
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Please cite this article as: Chahal GS et al., Treating metatarsalgia: current concepts, Orthopaedics and Trauma, https://doi.org/10.1016/ j.mporth.2019.11.005