S

sabre tibia anterior (sagittal-plane) bowing of tibia; characteristic of Paget’s disease

sac cyst; capsule

sacral plexus nerve fibre plexus (originating from spinal nerves L2–S2) that gives rise to all lower-limb nerves

sacroiliac joint articulation between spine and pelvis; fibrous joint between sacrum and iliac bones

SAD ulcer classification system see Table U2

sagittal plane see cardinal planes of the body

sagittal-plane anomalies lower-limb/foot sagittal-plane positional variants, i.e. ankle equinus, functional hallux limitus, hallux rigidus, sagittal-plane blockade, first-ray hypermobility and longitudinal-arch anomalies (pes planus, pes cavus and medial midtarsal joint neuroarthropathy)

sagittal-plane blockade loss/reduction of sagittal-plane motion at first metatarsophaloangeal joint; occurs during gait in an overpronated foot with functional hallux limitus

St Vincent’s declaration, 1990 internationally agreed statement of intent that a 50% reduction in lower-limb amputation would be achieved by 2000 by proactive approaches to diabetic foot disease

St Vitus’ dance see chorea

salicylic acid; SA topical agent that is caustic/keratolytic in high strengths (i.e. 40–70%, applied topically as ointment/paste; used to treat verrucae and heloma dura – see Table C2), and antifungal (see Table A13), antiseptic and astringent (Table S1) in lower strengths (i.e. 3–5% applied topically as an ointment/lotion/cream/powder); it is incompatible with iodine, iron salts and oxidizing agents

Table S1 Treatment of dyshidrosis

saline see normal saline

salt chemical compound formed by interaction of an acid with a base

salt solution see hypertonic saline

sampling harvesting small amounts of tissue to allow laboratory microbiological culture and determine antimicrobial sensitivity; clinical samples should be taken before application of antiseptics/antimicrobial therapies; skin and nail scrapings are sealed in a labelled paper sachet; wound exudate samples (taken from the deepest part of wound) are transported in a sterile container; adequate amounts of the sample must be harvested, and include full clinical details (e.g. nature of sample, location, date of collection, patient biographical details, information of health status and current medications regime)

sandals see Table F7

sand flea see chigoe

saphenous nerve major branch of femoral nerve, branches of which subserve medial thigh, leg and foot sensation; proximally, the saphenous nerve courses with the femoral artery through the femoral triangle and into the subsartorial canal (deep to sartorius muscle); distally, the saphenous nerve courses with the great saphenous vein

saphenous-nerve entrapment saphenous-nerve impingement at its exit point from the subsartorial canal, just proximal to knee joint; characterized by sensory dysfunction (e.g. paraesthesia) over medial aspect of lower leg and foot

saphenous veins; SV main superficial veins draining the leg and foot

sarcoidosis systemic granulomatous disease of unknown cause, causing pulmonary fibrosis and generalized granuloma formation

sarcolemma muscle fibre plasma membrane

Sarcopetes scabiei mite, causing scabies

sartorius thin, long, diagonal, strap-like anterior thigh muscle; forms lateral boundary of femoral triangle and roof of adductor canal

saturated solution solution in which no more solute will dissolve; characterized by undissolved crystals within the liquid

saucerization; revivication wound (ulcer) edge debridement back to healthy bleeding tissue, to remove devitalized tissue, and promote drainage, epithelialization and healing (see Table U1)

sausage toe see toes sausage

scab wound surface crust/eschar; formed of dried exudate and blood

scabicide topical agent that kills scabies mites

scabies highly contagious, very pruritic, vesicular skin reaction caused by host acute inflammatory response to female scabies mite faeces within the epidermis; typical skin sites affected include finger webbing, volar aspect of wrist; patient and all contacts should be treated with topical scabicides (e.g. permethrin (Lyclear) or 25% benzyl benzoate BP preparations) and antipruritic preparations (e.g. 10% crotamiton cream [Eurax])

scald tissue damage caused by applied wet heat (e.g. hot water, steam); unconscious scalding of feet and subsequent blistering/ulceration are associated with marked distal sensory neuropathy

scalded-skin syndrome see syndrome, scalded-skin

scale device marked at regular intervals, used for measuring;

scalpel fine, sharp knife; used for surgical division of soft tissues

scan visual image produced by magnetic resonance imaging (MRI), computed tomography (CT), ultrasound (US) or radionucleotide investigation

scar avascular fibrous tissue overlain by thin epidermis; characteristic of healing by secondary intention, e.g. at site of surgical incision, healed ulcer or other traumatic episode affecting skin/deeper tissues

scarf osteotomy Z osteotomy first metatarsal distal osteotomy used to correct hallux abductovalgus deformity; Z-shaped cut made through first metatarsal shaft (to realign the longitudinal axis along sagittal and horizontal planes; careful angulation of short arms of Z allows frontal-plane rotation of first metatarsal head) and resection of medial eminence at first metatarsal head (Figure S1); the osteotomy is normally fixated internally using wires or bone screws, allowing early postoperative ambulation

Figure S1 (A) Scarf osteotomy to 1st metatarsal, and Akin procedure to proximal phalanx hallux; (B) Scarf osteotomy, medial view. This article was published in Neale’s Disorders of the Foot, Lorimer, French, O’Donnell, Burrow, Wall, Copyright Elsevier, (2006).

scarification roughening of an eschar surface

schizophrenia relatively common group of psychoses, characterized by delusions and hallucinations, and marked withdrawal from social contact

Schwartz osteotomy dorsal, oblique, closing-wedge osteotomy, maintaining a plantar hinge of bone, e.g. to correct plantarflexed metatarsal

sciatica pain originating in lower-back/buttock area and radiating down posterior thigh; often caused by pressure on the sacral plexus from a herniated intravertebral disc (in L4–S2 spinal segment); may also present as isolated heel pain, i.e. referred pain from S1/2 segment of nerve

sciatic nerve largest mixed nerve in the body; innervates the majority of the lower limb; originates from the sacral plexus (L4, 5; S1, 2, 3); courses deep to gluteus maximus, entering the thigh on posterior surface of adductor magnus; descends between it and hamstrings; it divides approximately halfway along thigh, forming the common peroneal and tibial nerves

scintiphotography photographic image of the distribution of an intravenous-administered radiopharmaceutical (X- or gamma-ray-emitting) agent

scissored gait gait typifying spastic cerebral palsy (i.e. hip flexed and internally rotated; knee flexed; ankle plantarflexed); the patient takes small steps, walking stiffly on tiptoe with bent knees and no heel contact

scleroderma skin changes characteristic of systemic sclerosis

sclerosing agent agent injected into varicosed veins to cause segmental lumen collapse, to improve venous return/minimized venous incompetence

sclerosing haemangioma see dermatofibroma

sclerosis tissue induration and fibrosis; associated with long-term chronic inflammation

sclerotome area of skeleton innervated by a single spinal nerve

scoliosis S-shaped spinal curvature in frontal plane, causing muscle/soft-tissue compensation, e.g. flexible (soft-tissue contracture) or fixed (bony ankylosis) deformity; causes apparent leg length inequality (due to pelvic tilt imposed by lumbar scoliosis), and apparent arm length inequality (thoracic spine scoliosis imposes shoulder tilt)

scorbutic relating to chronic vitamin C deficiency

screening testing of an asymptomatic population to identify those who are susceptible to a given disease; identified/at-risk subjects may be offered disease treatment/preventive measures

screw arthrodesis surgical fixation of a joint by insertion of an indwelling bone screw, after abrading opposing capital cartilages

Scropulariopsis brevicaulis mould causing proximal subungual onychomycosis

scurvy; vitamin C deficiency severe, long-term, chronic lack of dietary vitamin C; characterized by chronic tiredness, debility, anaemia, dependent oedema, gum ulceration, skin and mucous membrane haemorrhages, and the tendency for healed wounds to break open

Scytilidium dimidiatum mould; a cause of distal and lateral subungual onychomycosis characteristically causing black/dark brown discoloration of affected nail plates

sea-borne conditions foot problems contracted from sea bathing, commonly in tropical waters, e.g. jellyfish/coral/sea anemone stings, traumatic injury from sea urchins/venomous fish

sea urchin injury fragmentation of sea urchin spines within e.g. plantar skin, causing ongoing pain and possible ulcer formation

sebaceous gland gland (opening into hair follicle) secreting sebum

seborrhoeic dermatitis see dermatitis, seborrhoeic

seborrhoeic keratosis; seborrhoeic wart; senile wart; basal cell papilloma; stucco keratosis common, pigmented, entirely benign skin tumours with rough, warty, dull surface; of unknown cause; occur in any skin area; characterized by homogeneous colour throughout (most on limbs/feet are white-grey in colour and <4 mm diameter), and a distinct (sometimes overhanging) edge; incidence increases with advancing age; treated by cryotherapy

sebum oily secretion from sebaceous glands

‘second-class travel’ syndrome see syndrome, ‘second-class travel’

second-degree nerve injury see Table N3

second messengers intracellular biochemicals that trigger intracellular reactions; released in response to cell membrane receptor stimulation

second pain see pathophysiological pain

Second Skin adhesive plastic film; used to prevent blister formation in skin areas subject to friction and shear

secondary hyperalgesia long-term tissue hypersensitivity beyond area of original injury; due to excitation of dorsal horn N-methyl-d-aspartate (NMDA) receptors (see syndrome, complex regional pain)

secondary infection subsequent infection, by different microorganism

secretion substance produced by a gland

secretomotor autonomic stimulation of a gland

section (1) to cut or divide tissue

section (2) tissue specimen prepared for microscopic examination

sediment insoluble material within a liquid that separates and sinks on standing

seed corns see heloma, miliare; Table C14

seizure attack/fit

selective amputation elective amputation of supernumerary digits

selective serotonin reuptake inhibitors; SSRIs class of major antidepressant drugs, better tolerated and with fewer side-effects than monoamine oxidase inhibitors (MAOIs); SSRIs antagonize ropivacaine metabolism (i.e. increase risk of ropivacaine toxicity); e.g. fluoxetine (Prozac), paroxetine (Seroxat)

self-aspirating syringe dental pattern syringe with spring-loaded plunger mechanism; blood shows within the cartridge (on cessation of plunger pressure) if needle tip is within a blood vessel

self-limiting therapeutic agent/disease whose effects cease in a predictable manner

semi demi/half/partly

semibespoke footwear shoes/boots made on a last that has been adapted to match the patient’s foot (contrast with bespoke footwear)

semibespoke last see last, semibespoke; Table C22

semicurved last see last, semicurved; Table C22

semilunar half-moon-shaped, e.g. lunula

semimembranosus posterior thigh muscle

semipermeable membrane permeable to water, ions and small molecules, but normally impermeable to larger molecules/colloids, e.g. tunica intima

semipermeable adhesive film dressings see Table D10

semipermeable hydrogels see Table D10

semistraight last see last, semistraight; Table C22

semitendinosus posterior thigh muscle

Semmes–Weinstein aesthesiometer a range of graded and calibrated nylon monofilaments which bend at predetermined forces, individually mounted in plastic handles; used to deliver a range of touch pressure stimuli to skin (see monofilament)

Semmes–Weinstein monofilament see monofilament

senescence process of ageing

senile dementia progressive mental deterioration associated with ageing/old age; characterized by marked short-term memory loss, stubbornness, difficulty with novel experiences, self-centredness and childish behaviour

senile lentigo see lentigo

senile wart see seborrhoeic keratosis

senility physiological and psychological processes characteristic of old age

sensation central nervous system translation of incoming sensory stimuli into conscious awareness

sense stimulus perception

sensitive capable of perceiving sensation/responsive to stimuli

sensitivity measure of accuracy of a clinical test, i.e. how well false-positive results are highlighted; calculated as ratio of true-positive results and the sum of the number of true-positive plus false-negative results, expressed as a percentage; i.e. sensitivity = (true-positive/[true-positive + false-negative]) × 100 (see specificity)

sensitization induction of allergy (i.e. acquired sensitivity)

sensorimotor mixed nerve with both afferent sensory and efferent motor fibres

sensorimotor examination examination of lower-limb sensory and motor function; i.e. assessment of light touch, pinprick awareness, blunt–sharp discrimination, vibration awareness, monofilament tests, muscle power, Babinski and deep tendon reflexes (see Tables M14 and N4)

sensors pressure-sensitive electronic cells embedded within a foot plate, allowing within-gait plantar pressure analysis

sensory relating to sensation (Table S2)

Table S2 Afferent sensory impulses from the skin and superficial tissues

sensory assessment see Table M13

sensory deprivation diminution/loss of appreciation of external stimuli

sensory neuropathy dysfunction of some/all sensory functions (see distal sensory polyneuropathy)

sepsis presence of pus/pus-forming pathogenic organisms/their toxins in blood or tissue; characterized by a portal of entry (e.g. break in skin integrity) and increasing symptoms as sepsis worsens, i.e. marked inflammation, acute tenderness (patient ‘guards’ infected area, unless there is sensory neuropathy), lymphangitis (of lymphatic vessels draining infected tissues), regional lymphadenopathy (see lymphadenitis), suppuration, pus and abscess formation, general malaise and pyrexia; treatment depends on the degree of infection, local and limb tissue status, host response to infection, and nature of infecting organism; resolution of infection due to e.g. presence of a foreign body/ingrowing toe nail/paronychia/corn is usually achieved by removal of the artefact (allowing free drainage of any pus) together with appropriate dressing, and review (Table S3); more extensive infection (e.g. cellulitis; lymphangitis; lymphadenitis) or localized infection in an ‘at-risk’ patient should be considered for systemic antibiosis

Table S3 Treatment of local sepsis

septate compartmented

septicaemia life-threatening systemic disease due to pus-forming pathogenic organisms (e.g. bacteria) within circulating blood, characterized by generalized toxaemia, marked pyrexia and severe hypotension leading to toxic shock, general organ failure and death unless appropriate antibiosis and fluid replacement are initiated urgently

septic arthritis arthritis due to joint infection

sequela outcome of disease

sequestrum piece of diseased/non-viable bone, separated from surrounding healthy bone; characteristic of chronic osteomyelitis; sequestrum may exfoliate through overlying soft tissues

Serie One type of silicone putty; used to fashion orthodigita

sero-negative (sero −ve) arthritis arthritides not characterized by expression of specific immune-related plasma proteins, although other markers of inflammation will be present (e.g. raised erythrocyte sedimentation rate, C-reactive protein); (see Table A11)

sero-positive (sero +ve) arthritis arthritides characterized by expression of specific immune-related plasma proteins, e.g. rheumatoid factor

serotonin; 5-hydroxytryptamine; 5-HT vasoconstrictor phospholipid; liberated by platelets, and present in high concentrations in central nervous system and peripheral tissues; also inhibits gastric secretions

Serotulle medicated tulle gras (see Table D10)

serpiginous denoting an ulcer/other skin lesion with an irregular border

serum fluid portion of blood, i.e. remainder, after all cells and plasma proteins have been removed; forms inflammatory exudate

sesamoid bones; sesamoids small bones, developed as a centre of ossification within a tendon at the point of maximal force, e.g. overlying a joint or bony prominence; articular aspect of sesamoid is covered with cartilage; sesamoids are prone to the same range of bone pathologies as any skeletal element

sesamoid complex position see Table H6

sesamoid drift apparent movement of FHB sesamoids at plantar aspect of 1 MTPJ in a foot with hallux abductovalgus; in fact, the sesamoids maintain their normal relationship with FHB tendon, but medial drift of head of first metatarsal gives the impression that the sesamoids have drifted into a more lateral position

sesamoid evaluation evaluation of the health and position of FHB sesamoids in relation to first metatarsal head, from anteroposterior and ‘skyline’ view radiographs; sesamoid fracture is identified (preferentially) from technetium bone scan

sesamoid fracture traumatic/stress fracture of one or both FHB sesamoids at 1 MTPJ, characterized by 1 MTPJ plantar pain, tenderness, bruising and soft-tissue swelling, typically following sports-induced trauma; differential diagnosis should exclude bipartite sesamoid

sesamoid ligaments within 1 MTPJ medial (tibial) and lateral (fibular) sesamoid ligaments insert into medial and lateral collateral ligaments of 1 MTPJ, respectively; also give fibrous attachments to deep transverse ligament

sesamoid planing procedure surgical reduction of dorsiplantar dimension of the FHB sesamoids at 1 MTPJ, by removal of transverse section of their non-articular surface, to reduce dimension of an overlarge sesamoid whilst preserving its articulation with first metatarsal head

sesamoid position location of FHB sesamoids in relation to the plantar of the first metatarsal head and/or the first intermetatarsal space, as part of assessment of hallux abductovalgus (see sesamoid drift)

sesamoid projection; skyline projection see Table R1

sesamoid view radiograph see Table R1

sesamoiditis plantar pain and inflammation in area of FHB sesamoids, e.g. in association with FHB tendinitis at 1 MTPJ, sesamoid bursitis, 1 MTPJ synovitis, sesamoid chondromalacia, hypertrophy of tibial FHB sesamoid secondary to pathomechanical trauma in an overpronating foot; characterized by pain during toe walking (e.g. in high-heeled shoes, dancing or sport)

sessile flat, broad-based and non-pedunculated (e.g. skin lesion)

set realignment of apposing ends of a fractured bone and maintenance of this relationship during healing

Sever’s disease see disease, Sever’s

Sever’s sign see sign, Sever’s

sex biological quality distinguishing male and female, expressed by the presence of two X (i.e. female) or X + Y (i.e. male) chromosomes

sex-linked disorders see single-gene disorders

shaft midsection of a long bone

shaft pad see Table P1

Shagreen patches see disease, Bourneville’s

shank reinforcing tempered metal strip, approximately 1 cm wide, inserted between mid- and outsoles, from heel to forepart of a shoe (see Table F6)

shank stiffener firm splinting material (e.g. stiff leather, glass fibre) lying between the heel seat and forefoot tread of a shoe during construction, to prevent buckling of the waist, often used in conjunction with a Thomas heel (see Table F7)

Sharpey’s fibres fibres continuous with ligament or fascia, inserting into bone, anchoring soft tissue to bone

sharps disposal safe disposal of sharp, single-use instruments into rigid, non-openable ‘hazard’ containers (e.g. complying with BS 7320 [1997]), and its subsequent certified incineration

shear imposed load, delivering equal (in magnitude) and opposite (in direction) parallel forces, that tends to displace the object along a plane parallel to and between lines of force, causing adjacent structures to slide past one another; tissues are subjected to shear load during movement

shear load during movement, see also strain (3) and Stress (1)

sheet hydrogels see Table D10

shin anterior lower-leg area, inferior to the knee (see tibia)

shingles herpes zoster (see herpes zoster)

shin splint tenderness and pain, induration and swelling of muscles within the lower-leg anterior compartment; caused by chronic overuse; associated with pathomechanical adaptation for compensated wholefoot or forefoot varus, and poor training regimes

shock profound physical depression characterized by low blood pressure, circulatory collapse and coma

shoe fit appropriateness of length (i.e. heel to ball, heel to toe), width (i.e. across metatarsal heads and throat), depth (i.e. of toe box and midfoot) and flare (i.e. in-flare or out-flare) of a shoe/boot in relation to the dimensions of the wearer’s foot, together with any other item, e.g. in-shoe orthoses that the shoe must accommodate (see Table F9)

shoe modification shoe upper/sole adaptations, to accommodate foot deformity (see Table F10); see footwear modifications

shoe parts see footwear

shoe sizes Table S4

Table S4 Comparison of UK, US and continental adult shoe sizes

shoe stretcher see stretching machine

shoe trauma excess mechanical forces (compression; friction) imposed on foot tissues by ill-fitting shoewear, leading to a wide range of skin, soft-tissue and nail pathologies; shoe trauma does not cause foot deformity per se, but exacerbates existing problems or tendency to deformity

shoe type see Table F6

shoe wear marks areas of increased wear on the upper, insole and outsole of a shoe, reflecting foot-imposed forces throughout gait, and characterizing foot deformities; they form part of forensic podiatry, as the shoe mirrors the foot that habitually wears it (Table S5; see Figure W1); wearer characteristics may be deduced from shoe condition, e.g. white spots (dried splashes of sugary urine) on leather upper in a patient with poorly controlled diabetes mellitus

Table S5 Diagnosis of foot function from shoe wear marks

short first metatarsal predisposes to hallux abductovalgus, focal plantar hyperkeratosis or heloma durum of plantar skin overlying second metatarsophalangeal joint

short fourth metatarsal imposes overload at third and fifth MTPJs, with deformity of adjacent third and fifth toes; may be diagnostic of pseudohypoparathyroidism or pseudopseudohypoparathyroidism

short plantar ligament short, thick, wide ligament uniting the calcaneum and cuboid, deep to the long plantar ligament (see Table A7)

short saphenous vein; small saphenous vein see saphenous vein

short T1 inverse recovery imaging; STIR magnetic resonance imaging (MRI) modality, visualizing bone matrix (which appears white); fat is selectively suppressed (appears black)

short-wavelength light violet and ultraviolet parts of light spectrum

shoulder drop pectoral girdle asymmetry; shoulders (from frontal plane) do not lie parallel to transverse plane/ground surface, and one arm appears longer

shuffling gait see festinant gait

sibling one of two or more children of the same parentage

sicca syndrome see syndrome, Sjögren’s

sickle-cell trait heterozygous expression of haemoglobin S (HbS) gene (i.e. individual carries both HbS [sickle haemoglobin] and HbA [normal] genes, but does not express characteristics of sickle-cell anaemia); HbS-containing erythrocytes tend to deform (sickle) when tissue oxygen tension is low (e.g. when tourniquet is applied); see anaemia, sickle-cell

side-effect adverse/unexpected/undesirable effect of a drug/treatment

siderosis see haemosiderosis

sign objective features of disease, and noted by examining clinician (contrast with symptoms); note: eponymous signs are denoted as ‘positive’ when their characteristics are present

signature see prescription

Silastic joint implant; Silastic prosthetic joint silicone hinge implanted following joint debridement, to create an arthroplasty

silent nociceptor see sleeping nociceptors

silicone liquid/gel/solid oxides of silicon (depending on their degree of polymerization)

silicone gel padding (e.g. Silipos) silicone gel incorporated on to/within a fixing medium, e.g. elasticated stockinette; used to protect areas of skin from excess pressure/friction, and prevent hyperkeratosis formation

silicone implant injection of silicone gel e.g. into plantar tissues of a patient with fibrofatty pad atrophy) to reduce local pain and prevent hyperkeratosis formation; effective short-term technique

silicone putties mouldable siliconized pastes which set after mixing with a hardener; used to fashion silicone orthodigital splints

silver-impregnated dressings wound dressings incorporating silver (1 part per million); used to treat meticillin-resistant Staphylococcus aureus (MRSA)-infected ulcers (see Table D10)

silver nitrate; AgNO₃ topical agent causing brown staining and precipitation of a keratin-based eschar when applied to skin; antiseptic and astringent (i.e. <5% concentration); escharotic (i.e. >5% to < 20% concentration) and caustic (i.e. >25% concentration); action on skin mitigated by immersion in saline solution; used to treat mosaic verruca (see trichloroacetic acid) Table C2

silver sulfasalazine antiseptic agent; 1% cream used topically to treat infected lesions and burns

simple bone cyst; solitary bone cyst asymptomatic fluid-filled cavities with sclerotic margins, lined with connective tissue or osteoid membrane, in bone, e.g. calcaneum or metatarsal in children; may form the site of pathological fracture

simple fracture see Table C18

simple insole see insole

simple interrupted suture Table S6

Table S6 Types of suturing techniques (see also Figure H4)

Sinding–Larsen–Johansson disease see disease, Sinding–Larsen–Johansson

sine wave continuous, oscillating stream of energy, generated by an electrosurgery unit; used during surgery to section/separate soft tissues (see Table E2)

single-digit padding clinical pad applied to an individual digit to cushion tissues or deflect forces (see Table P1, Figure P1)

single-gene disorders genetic disorders caused by DNA mutation within a single gene; single-gene sex-linked disorders occur when an affected gene forms part of either X or Y chromosomes

single-leg heel-raise test see test, single-leg heel-raise

single-limb support phase within the gait cycle during which the body mass is carried by a single limb; approximately 80% of gait cycle (see Table D9)

single-photon emission computed tomography; SPECT computed tomography scanning modality that detects energy emitted from injected technetium (⁹⁹Tc), producing an anatomic image/scintogram

single-winged plantar metatarsal pad; SWPMP pad clinical pad (usually made of semicompressed felt), as a modification to a standard plantar metatarsophalangeal pad; cutouts deflect pressure away from first/fifth metatarsophalangeal joints (MTPJs) to central MTPJs/metatarsal shafts; cutout (wing) may be infilled by cushioning material; also manufactured from appliance materials and incorporated into insoles Table P1, Figure P1

sinister left

sinoatrial node; atriculoventricular node; AV node area of muscle (within right atrial wall of heart) that contracts spontaneously; links to all other areas of heart muscle (via Purkinje fibres) allowing all areas of heart muscle to contract synchronously and regularly

sinus fistula/tract leading from one body cavity to another or from a body cavity to the exterior, e.g. tract connecting an infected area of osteomyelitis to the skin surface

sinus formation route through overlying tissues and skin, allowing escape of pus or bursal fluid (note: bursal fluid may solidify to plug sinus exit, resembling a corn)

sinus tarsi osseous canal formed by sulcus calcanei (at superior aspect of calcaneum) and sulcus tali (at inferior aspect of talus); visible on lateral radiograph of foot – obscured in overpronated foot/pes planus, and very marked in supinated foot/pes cavus; contains interosseous talocalcaneal ligament (see syndrome, sinus tarsi)

sinusoid terminal blood vessel with an irregular and larger calibre than that of a normal capillary

Sjögren’s syndrome see syndrome, Sjögren’s

skeletal muscle relaxants central nervous system-acting agents (e.g. baclofen, diazepam) used to reduce chronic muscle spasm/spasticity associated with multiple sclerosis

skeletal traction bone pin insertion, together with application of sustained tension via an external apparatus, to promote bone growth (see Ilizarov frame)

skeleton bony framework; collective term for the bones of the body

skewfoot generalized foot hypermobility, excessive foot pronation and abduction

ski jump view see skyline projection

skin; cutis tissue investing the entire body, and in modified form lining the gut and respiratory systems; largest organ of the body; formed of four layered structures: epidermis, basement membranous zone, dermis, subcutaneous layer (Figure S2; Tables S7 and S8)

Figure S2 Structure of the skin.

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