Anatomy
3 Sesamoids may be present in great toe
- 2 almost always present on plantar aspect of MTPJ
- 1 may be present on plantar aspect of IPJ
MTPJ sesamoids most important
- embedded in FHB tendons
- held together by intersesamoid ligament & plantar plate
- each side of crista / inter-sesamoid ridge
- articulate with plantar facets of 1st MT
Tibial usually larger than fibula
Tibial more impacted in weight bearing than fibula
- higher incidence traumatic injury to tibial
Insertions
- FHB
- Adductor hallucis
- Abductor hallucis
- Plantar plate
- Intersesamoid Ligament
- Plantar aponeurosis
Orientation
- Proximal to MT head in stance
- Pulled under MT head with DF / toe off
Ossification
- between 7-10 years
- often multiple centers
- may result in bipartite / tripartite appearance
Bipartite
- fibular rare
- tibial bipartite in ~ 10%
- bilateral in ~ 25% of these
- congenital absence - one or both
Blood Supply
Type A 50% medial plantar artery and plantar arch
Type B 25% plantar arch
Type C 25% medial plantar artery
Increased risk of AVN if only single vessel into sesamoid
- which is seen in Type C more commonly than B
Functions
- absorb weight bearing pressure
- reduce friction
- protect tendons
- act as fulcrum to inc mechanical force of FHB
- Sesamoids and Collats provide medial / lateral stability of 1st MTPJ
History
Do not always present with symptoms directly referable to sesamoids
- generalized pain around Hallux
- pain after sudden pop or snap after running
Pain as hallux extends in terminal part of stance phase
Neuralgic symptoms or numbness if digital nerve compressed
Examination
Local tenderness
Decreased strength on PF
Pain on passive DF
Loss of active & passive DF
Cavus foot
- plantar flexed 1st ray
- excess axial load on sesamoid
Imaging
Standard lateral not very useful
- AP, medial oblique, lat oblique, axial
Bone scan
Projection important to differentiate sesamoids from MTPJ
- may be obscured by AP scan
- PA or oblique with Collimation useful for DDx
- caution with increased uptake in ~25% of asymptomatic patients
- marked difference to contralateral side significant
MRI
Useful for Osteomyelitis
CT
Useful for post-traumatic changes
- compared with contralateral side
Conditions
1. Fracture
Difficult to differentiate from symptomatic multipartite sesamoid
- especially if fracture through bipartite
- comparison X-ray with contralateral foot
- MRI & bone scan with pin hole collimation useful
Non operative management
- initial treatment
- orthosis / dancer's pad / cast / MT bar
- especially stress fracture
Surgery
- excision of most comminuted fragment or entire sesamoid
- preferred over bone graft in most cases
- consider graft for athletes
2. Osteochondritis
Infrequent
- osteonecrosis with regeneration & calcification may be present
- may be enlarged / deformed / sclerotic with mottling / fragmentation
3. Infection
Rare except diabetic neuropathy
- Pseudomonas relatively common
4. Sesamoiditis
Repetitive trauma especially teens / young adults
- Inflammation & bursal thickening may be present
5. Osteoarthritis
May be in conjunction with MTPJ OA / RA / Gout
Management
Stiff soled or rocker bottom shoe + MT pad
Sesamoidectomy
- may decreases pain
- Don't remove both
- leads to clawing of hallux
6. Intractable Plantar Keratoses
Usually caused by
- sesamoid with plantar located osseous prominence
- plantarflexed first metatarsus / cavus
Management
Intractable lesions
- sesamoid shaving or resection
- avoid shaving if 1st MT is plantarflexed
- consider basilar dorsiflexion osteotomy
7. Nerve Impingement
Impingement of medial branch plantar digital nerve on medial sesamoid
Sesamoidectomy
Principles
1. Never excise both
- high incidence of Hallux Valgus or Cock Up deformity
2. Never make incision directly over sesamoid
3. Always repair adductor if excising lateral sesamoid
Produce mechanical defect in FHB unit
- can excise up to 2/3 of either without disturbing ligamentous attachments
- may relieve pain without disrupting FHB mechanism
Tibial
Tibial sesamoid excision
- 3cm plantar medial incision
- Medial branch plantar digital nerve identified & retracted
- Locate sesamoid by palpation
- Flex hallux 20-30o & retract FHL
- Incise inter-sesamoid ligament & pull sesamoid medial
- Shell out from capsule & plantar plate with knife
- Imbricate capsule
Tibial sesamoid shaving
- Plantar medial approach
- Excise plantar 1/2 with microsagittal saw
- Smooth with rongeur
Fibular
Approach
- either dorsal or plantar approach
- dorsal demanding due to depth
- plantar - NV bundle & FHL to negotiate
Dorsal incision
- from 2-3 cm proximal to web space
- Identify & protect branch SPN
- Interval between Adductor Hallucis & joint capsule opened
- Tendon of Add Hallucis reflected from lateral sesamoid
- Grasp sesamoid & divide inter-sesamoid ligament
- Release proximal & distal & excise
- repair adductor
- Close skin
Plantar incision
- Flex hallux
- 4cm incision between MT 1 & 2
- Retract NV bundle either lateral or medial
- Locate FHL & open pulley over it
- Flex hallux to relax FHL & retract medially
- Divide inter-sesamoid ligament
- Excise proximally & distally
- Reattach cuff of FHB
- Consider oblique wire across MTPJ
Complications
Cock up toe
Hallux valgus or varus
Nerve injury
Fat pad disruption
Painful plantar scar if plantar incision