Clinical Surgery

830 Pages·2008·98.26 MB·English

by  Alfred Cuschieri

694 Part 5 Specialist Surgery
Once a sore has developed it is graded according to
Pressure sores
depth as follows:
Pressure sores (decubitus ulcers or bed sores) are a erythema;
common source of referral to the plastic surgical team. blister;
They are due to prolonged unrelieved pressure over bony full-thickness skin loss into subcutaneous tissue;
prominences and are common in patients who are bed- muscle breakdown;
ridden or have restrictive casts or appliances and in those bone/joint involvement.
who have large insensate areas.
Sites
Aetiology
The site of the sore depends on the position the patient has
If tissue pressure is greater than perfusion pressure, then been lying in.
the blood supply to the tissue will be compromised and
ischaemia with eventual necrosis occurs. Muscle is more Common
susceptible to ischaemia than skin. A cone-shaped area of Sacral: from lying supine.
tissue breakdown results, with its apex at the skin surface Ischial: from sitting, particularly in wheelchair-bound
and its base overlying the bony prominence. The size of patients.
the resultant pressure sore is proportional to the pressure Trochanteric: from lying on one side.
exerted and its duration. Malleolar: from tight-fitting lower-limb plaster casts.
Predisposing factors include the following. Heel: from lying supine.
• Infection of the pressure sore can increase its depth.
• Shearing forces lead to degloving of the subcutaneous Rare
tissues, impairing their blood supply. • Occipital: lying supine, particularly in neurosurgical
• Excessive moisture worsens the situation by macerat- patients.
ing or eroding the skin. If this is due to faecal or urinary • Ears: lying on one side or tight-fitting bandages.
incontinence, there is the added risk of infection. • Elbow.
• Malnutrition, anaemia and immunosuppression, from • Scapula.
concomitant illness or pharmacotherapy, not only predis-
pose to pressure sores but also impair healing once the
Management
ulcer is established. Unfortunately, these factors are com-
mon in debilitated individuals. Prevention is the best treatment and so Waterlow
• Insensitivity, caused by peripheral or central nervous scores should be recorded in debilitated or bedridden
system damage, allows sores to develop unnoticed from patients and appropriate preventive measures instituted
minor trauma. Infection can also go undetected until the in those deemed at risk. Once a pressure sore is estab-
sore reaches a considerable size. lished, treatment first addresses general factors, then
relieves pressure and then involves specific management
of the ulcer.
Risk assessment and grading
The Waterlow score was established to predict those pati-
General factors
ents most likely to develop pressure sores so that prevent-
ive measures can be taken. It involves scoring the patient • Nutrition: malnutrition and hypoproteinaemia should
on the following factors: be addressed. The patient should be considered for naso-
body mass index; gastric or parenteral feeding if oral intake is insufficient or
age; not possible.
sex; • Anaemia should be assessed and corrected with dietary
continence; supplements or transfusion according to severity.
mobility; • Incontinence: catheterization is necessary for urinary
nutrition; incontinence. If faecal incontinence is causing recurrent
skin changes; infection or considerable deterioration of the pressure
adverse wound healing factors; sore, faecal diversion should be considered.
neurological deficit; • Infection should be assessed with regular swabs or
surgical interventions; tissue biopsy. Appropriate antibiotic therapy should be
drugs. instituted and surgical debridement may be necessary.
Plastic and Reconstructive Surgery Chapter 42 695
Examples include gluteus maximus flap for sacral or
Relief of pressure
ischial pressure sores and tensor fascia lata flap for
• Turning is vital to eliminate prolonged pressure. trochanteric sores. Occasionally, it is possible to provide
• Specific beds are available to eliminate continued local- sensation by the use of innervated flaps, e.g. tensor fascia
ized pressure and decrease shearing forces. These include lata flap incorporating the lateral femoral cutaneous
low air loss mattresses, Clinitron bed (fluidized by warm nerve. Postoperatively, it is important to avoid pressure
air), Pegasus bed (alternating pressure) and Nimbus bed on the flap for 3-4 weeks.
(dynamic floatation). Since recurrence of pressure sores is common and pro-
• Padding of pressure areas with specific appliances can gressively more difficult to treat, prevention is vital in
prevent sores developing and progressing. These include these patients.
heel pads, horseshoe head rings and a variety of pressure-
relieving cushions for wheelchairs.
Lower limb trauma surgery
Dressings Lower limb trauma encompasses a wide range of injuries.
It has been famously quoted that you can put anything on As well as fracture management the integrity of vessels,
a pressure sore, except the patient. A variety of dressings nerves and soft tissues must be addressed. In most plastic
are available. These range from antisloughing dressings surgery units a lower limb trauma team exists. This
(to remove cellular debris) to foam-padded dressings (to includes orthopaedic and plastic surgeons, occupational
protect areas at risk). In a clean pressure sore or following therapists and physiotherapists, as well as pain manage-
surgical debridement, the vacuum-assisted closure (VAC) ment and prosthetic services.
system can be used. This is a sponge dressing which is
made to measure and placed snugly into the cavity of the
Anatomy
sore. Via a sealed tubing system it is connected to a free-
standing vacuum device. An airtight seal is created with an
Compartments and muscles (Table 42.4)
occlusive dressing and negative pressure is then exerted
over the wound. This removes oedema and wound The tibia and fibula are the bones of the lower leg. The
effluent, which delays healing, as well as reducing the tibia bears 85% of the weight and lies medially. It is bound
bacterial load. It is thought to actually increase local blood to the laterally lying fibula by the interosseous membrane.
flow to the wound, although the exact mechanisms of this The lower leg is enclosed in deep fascia like a stocking.
are unclear. Its main use in pressure sore management is This is a continuation of the popliteal fascia. It encloses
to reduce the size of the wound, which it does by encour- the calf and lateral lower leg, attaching to the anterior and
aging granulation and wound contraction. posterior borders of the tibia. Anterior and posterior
Specific management Table 42.4 Compartments and muscles of the lower limb.
Firstly, the pressure sore needs to be accurately assessed. Anterior compartment (dorsiflexes the foot)
Microbiological evaluation should be obtained with Extensor hallucis longus
wound swabs or tissue biopsies. The presence of more Extensor digitorum longus
than 100,000 organisms per gram of tissue is usually Tibialis anterior
indicative of infection and appropriate antibiotics should Peroneus tertius
be instituted. The size and extent of the wound should be
Lateral compartment (everts the foot)
examined. This involves probing any cavity and obtaining
Peroneus longus
radiographs of the underlying bone to detect osteomyel-
Peroneus brevis
itis. Contrast studies are useful to delineate sinus tracts
leading away from the ulcer. Posterior compartment (plantar flexes the foot)
Superficial
The aims of surgical intervention are:
Gastrocnemius
• thorough debridement of the ulcer, all necrotic tissue
Soleus
and the underlying bursa;
Planaris
• resection of the underlying bone, which is often
Deep
unhealthy or frankly osteomyelitic;
Flexor hallucis longus
• coverage of the defect with well-vascularized tissue.
Flexor digitorum longus
In general, large regional skin or myocutaneous flaps are
Tibialis posterior
used as rotation or advancement flaps to cover the defect.
696 Part 5 Specialist Surgery
Definition Rare
• Occipital: tying supine, particularly in neurosurgical
Pressure sores: ulcers over bony prominences caused
patients
by prolonged unrelieved pressure leading to ischaemic
• Ears: lying on one side or tight-fitting bandages
necrosis
• Elbow
• Scapula
Local predisposing factors
• Infection
Management
• Shearing forces
Preventive measures instituted in those deemed at risk based
• Excessive moisture
on Waterlow score
• Malnutrition, anaemia and immunosuppression
• Insensitivity
General
• Nutrition: make sure patient is fed (enterally or
Risk assessment and grading parenteralfy)
Waterlow score • Anaemia: correct
Risk assessment score based on following: • Incontinence: catheter for urine, consider diversion for
• Body mass index faeces
• Age • Infection: treat appropriately
• Sex
• Continence
Pressure
• Mobility • Turn patient frequently
• Nutrition • Use special beds:
• Skin changes (a) Clinitron (fluidized by warm air)
• Adverse wound healing factors (b) Pegasus (alternating pressure)
• Neurological deficit (c) Nimbus (dynamic floatation).
• Surgical interventions • Padding: heel pads, horseshoe head rings, pressure-
• Drugs relieving cushions
• Dressings: antisloughing dressings, foam padded
Grading (according to depth) dressings, VAC system
• Erythema
• Blister
Specific management
• Full-thickness skin loss into subcutaneous tissue Accurate assessment
• Muscle breakdown • Swabs/tissue biopsies for microbiology (> 100,000
• Bone/joint involvement
organisms/g of tissue means infection is present)
• Measure size and extent of wound by probing any cavity
and obtaining radiographs
CCoommmonmon
lying supine Aims of surgery
particularly in wheelchair-bound • Debridement of the ulcer
• Resection of the underlying bone
lying on-one side • Cover defect with well-vascularized tissue: probably a
tight-fitting lower-limb plaster casts myocutaneous flap
• Recurrence is common
intermuscular septa are attached to the peroneal surface ment lies between the anterior and posterior intermuscu-
of the fibula and these, with the tibia and interosseous lar septa. The posterior flexor compartment is commonly
membrane, divide the lower leg into three compartments called the calf. It is separated from the peroneal compart-
(Fig. 42.18). The anterior extensor compartment is bounded ment by the posterior intermuscular septum and from the
medially by the subcutaneous border of the tibia, laterally anterior compartment by the interosseous membrane. Its
by the anterior intermuscular septum and behind by the muscles lie in two groups, superficial and deep, subdivid-
interosseous membrane. The lateral peroneal compart- ing it into two compartments.
Plastic and Reconstructive Surgery Chapter 42 697
Figure 42.18 Cross-section of the right
lower leg.
The course and functions of these nerves are shown in
Arteries
Figs 42.19 & 42.20.
• Anterior tibial artery: supplies the anterior (extensor)
compartment of the lower leg. It starts at the bifurcation of
Lower limb injuries
the popliteal artery under the fibrous arch of the soleus
muscle. It lies medial to the neck of the fibula. It passes
Pretibial lacerations
forwards above the upper border of the interosseous
membrane and then descends in front of it. It lies between These are flap lacerations of the thin skin overlying the
the malleoli at the ankle joint and there becomes the subcutaneous tibial border. They are common in the
dorsalis pedis artery, which can be easily palpated. It elderly population, who tend to have thin fragile skin, and
passes under the extensor retinacula with the deep per- are often the result of minimal trauma.
oneal nerve lying laterally. Any haematoma should be evacuated to avoid pressure
• Posterior tibial artery: supplies the posterior (flexor) necrosis of the overlying skin. Broad-based skin flaps with
compartment of the lower leg. It also starts at the bifurca- a proximally based pedicle may be viable and can be relaid
tion of the popliteal artery under the fibrous arch of and secured with Steri-strips. Thin distally based flaps will
soleus. It runs deep to gastrocnemius and soleus on the have unreliable blood flow and are often not viable. This
tibialis posterior, flexor digitorum longus and tibia. At the type of injury should be debrided and resurfaced with a
ankle joint it lies behind the medial malleolus where it can split-thickness skin graft. This may be feasible under local
be easily palpated. Here it is between the tendon of flexor anaesthetic.
digitorum longus and the tibial nerve.
• Peroneal artery: supplies the lateral compartment of the
Open fractures
lower leg. It is a branch of the posterior tibial artery arising
just after it commences. It runs medial to the fibula These injuries are often the result of high-velocity trauma.
between tibialis posterior and flexor hallucis longus. Concomitant injury to other sites, including the head,
chest and abdomen, are common. Therefore the initial
management of these patients should be thorough assess-
Nerves
ment as per the ATLS protocol. The lower limb should
About a hand's breadth above the knee the sciatic nerve then be carefully evaluated once the patient is stable.
divides into the tibial and common peroneal nerves. The
common peroneal nerve divides under peroneus longus Evaluation
into the deep and superficial peroneal nerves. The nerve • Vascularity: palpate the posterior tibial and dorsalis
of the anterior compartment of the lower leg is the deep pedis arteries. If they cannot be felt manually, use hand-
peroneal. The nerve to the lateral compartment is the held Doppler ultrasound. If there is any uncertainty or if
superficial peroneal and the nerve to the posterior com- revascularization may be needed, then angiography of the
partment is the tibial nerve. lower limb is indicated.
698 Part 5 Specialist Surgery
Figure 42.19 Course and distribution of the tibial nerve.
• Bony injury. X-ray of the fracture should provide a clear structures have been damaged and determine how the
description of fracture site, displacement and stability. soft-tissue defect can be reconstructed.
• Soft-tissue damage: the size and site of soft-tissue dam- • Nerves: motor and sensory function of each nerve must
age are important. They give a clue as to what underlying be assessed and documented (Table 42.5).
Plastic and Reconstructive Surgery Chapter 42 699
Figure 42.20 Course and distribution of the superficial and deep peroneal nerves.
Classification only is it useful for aiding management plans but it can also
There are a variety of classifications available for describing be a rough guide to prognosis. For example, approximately
open fractures of the lower limb. The Gustillo classification 4% of grade IIIC injuries often proceed to amputation and
is commonly used for open tibial injuries (Table 42.6). Not approximately 70% of grade IIIB injuries require flap cover.
700 Part 5 Specialist Surgery
Table 42.5 Assessment of motor and sensory function of The patient is then transferred to theatre and further
lower limb nerves. assessment of the injury is performed under general
anaesthesia. The specific management is then dictated by
Tibial nerve the nature of the injury. As a rule all grossly contaminated
Motor and devitalized skin, muscle and free bone fragments are
Inability to plantar flex the foot at the ankle indicates removed during this procedure and copious irrigation is
proximal lesions and paralysis of the gastrocnemius and performed. If possible the fracture is also stabilized at this
soleus muscles
time, with external or internal fixation as appropriate. If
Sensory vascular injury is present it must be repaired as a priority.
Loss of sensation over the lower posterior calf, lateral foot and Often no attempt is made to close the wound at this stage
little toe (sural nerve) and it is left open and packed with suitable dressings.
Quite often the zone of injury in these wounds is not
Deep peroneal nerve demarcated on presentation. Tissues of marginal viability
Motor may become non-viable. Therefore re-exploration and
The patient has footdrop with inability to dorsiflex the foot further debridement may be necessary 48-72 h later.
and great toe due to paralysis of the extensor hallucis Once the viability of the remaining tissue is beyond doubt
longus and tibialis anterior and the fracture has been appropriately fixed, the method
Sensory of soft-tissue reconstruction can be addressed.
Loss of sensation over the first web space
Soft-tissue reconstruction
Superficial peroneal nerve This is dictated by the site and extent of the soft-tissue loss.
Motor • Split skin grafting. This is appropriate for defects with a
Inability to evert the foot at the ankle due to paralysis of suitably clean and graftable bed. Therefore it is usually
peroneus longus and peroneus brevis precluded if the fracture is exposed, as the periosteum will
have been stripped.
Sensory
• Local muscle flaps. These are ideal to cover small areas of
Loss of sensation over anterolateral calf and second and third
exposed fracture site. The medial head of gastrocnemius
web spaces
is most commonly used. The muscle can be split in its
midline through a longitudinal posterior calf incision.
The medial half is then detached from its insertion into
Table 42.6 Gustillo classification of open tibial fractures.
the Achilles tendon and tunnelled through to fill the
defect. A split skin graft is then placed over the exposed
Grade Tissue injury
muscle.
• Local fasciocutaneous flaps. Again these are useful for
I Clean wound < 1 cm
smaller defects. They can also be used to cover fracture
II Wound 1 -5 cm but no significant tissue disruption
sites. The donor site can be closed directly if small or split
MIA Wound > 5 cm but adequate soft-tissue coverage
skin grafted.
with local tissues
IIIB Extensive soft-tissue loss, contamination, periosteal • Free tissue transfer. This is necessary for larger defects
stripping and a variety of muscles can be employed. Microvascular
IIIC Arterial injury requiring repair anastomosis is necessary usually to the posterior or anter-
ior tibial vessels.
Bone reconstruction
Management The problem of bony loss can also be addressed.
Once the patient has been appropriately resuscitated, • Small defects can be bridged with cancellous bone
wound swabs should be taken and broad-spectrum anti- grafts as long as there is a well-vascularized bed. It is
biotics started. Tetanus prophylaxis should be assessed advisable to wait 6-8 weeks after injury before doing this,
and immunoglobulin given if required. The wound as non-vascularized bone is susceptible to infection.
should be dressed with a non-absorbent dressing and • Larger defects require vascularized bone as free tissue
Betadine-soaked gauze and then wrapped and splinted. transfer.
Manipulation of fractures at this stage should only be • Intermediate-sized defects can be treated using the
performed if they are impinging on the vascularity of the Ilizarov technique. An external fixator is used that encour-
lower lee. ages distraction osteogenesis.
Plastic and Reconstructive Surgery Chapter 42 701
compromise and the enclosed muscles become ischaemic.
Degloving injury
Prolonged ischaemia will result in necrosis and, ultim-
This is an avulsion of the skin, with or without underlying ately, fibrosis of the muscles and surrounding soft-tissue
tissues from deeper planes. Degloving injuries are com- structures. Compartment syndrome in the lower limb
monly the result of road traffic accidents. Those that result is defined as intercompartmental pressures exceeding
from being run over by a bus or truck are most serious, as 35 mmHg. These can be measured at the bedside using a
the broad tyres of these vehicles distribute the shearing special manometer.
forces over a wide area, which can result in circumferential Clinically, the patient complains of pain out of propor-
degloving of the entire skin and subcutaneous tissue of the tion to the injury and this is exacerbated by stretching of
leg. the involved compartment muscles. As pressure increases
The plane through which the skin is detached can be there is loss of sensation in the distribution of the involved
superficial, involving just skin and subcutaneous fat. nerves and ultimately the local pulses are lost, although
However it can also incorporate the deep fascia. The skin the latter is not necessary to make the diagnosis. The
may tear, creating a flap, or there may be no detectable 'four Ps' of compartment syndrome that aid diagnosis
skin breach, just bruising and swelling. The perforator comprise:
blood supply from the muscles to the skin and subcutan- • pain;
eous fat is destroyed. So too is the vascular network in the • paraesthesia;
superficial fascia. This results in ischaemic necrosis of the • paralysis;
detached skin. There are two types of degloving injury. • pulselessness.
• Type I: open wound due to degloving of the skin and Treatment involves immediate decompression. This is
subcutaneous fat with a narrow zone of undermined performed under general anaesthesia by incising all four
tissue around the periphery of the wound. muscle compartments (fasciotomy). The wounds are
• Type II: extensive undermining of soft tissues with no left open, allowing swelling to occur unrestricted, and
or a relatively small open wound. The initial assessment of dressed with appropriate sterile dressings. The wounds are
these wounds frequently underestimates the extent of closed at a later time once the acute episode has resolved.
damage, as most of the leg appears normal, apart from the Sometimes this is not possible directly and split skin grafts
presence of tyre marks and patches of ecchymosis. Unless are used.
treated early, the full extent of soft-tissue loss is apparent
only a few days later, and gives rise to systemic sepsis due
Surgery for congenital deformities
to necrosis of large areas of subcutaneous fat underneath
the normal-looking skin. Fluoroscein injected intra-
Congenital head and neck problems
venously circulates only to viable tissue and is a method
of defining all non-viable tissue (that which does not
Embryology
fluoresce) at an early stage.
The clinical picture initially is less dramatic than The embryology of the head and neck is complicated. The
expected, but the skin does not show blanching on pres- normal skull develops from a membranous capsule that
sure or capillary refill and skin edges do not bleed. All non- encloses a growing brain and then ossifies, whereas the
viable skin and underlying fat should be excised and the base undergoes mainly cartilaginous ossification. In the
defect resurfaced with a split-thickness skin graft. There third week of embryonic life these processes develop
can be a delay in graft application, allowing a 'second look' around the primitive mouth (Fig. 42.21).
at 48 h and further debridement if necessary. The non- • The frontonasal process projects down from the skull.
viable areas excised can be used as donor sites if the defect The nostrils develop from two olfactory pits within it. This
requiring grafting is extensive. This should be performed projection finally forms the nose, nasal septum, nostrils,
early. philtrum (central upper lip depression) and the premaxilla.
• The two maxillary processes, one on each side, come to
the midline and fuse with the frontonasal process. These
Compartment syndrome
form the cheeks, upper lip (excluding the philtrum),
Oedema is a sequela of trauma. If this occurs in a limited upper jaw and palate (excluding the premaxilla).
anatomical space, such as one of the four compartments • The two mandibular processes meet in the midline to
of the lower limb, tissue pressure will rise. As tissue pres- form the mandible.
sure rises, the pressure on and within the local venous sys- Abnormalities of this complex fusion process result in
tem also rises. Arterial resistance subsequently increases one of the most common congenital deformities, cleft lip
and inflow is reduced. If left untreated there is vascular and palate.
Table 42.7 Embryology of the branchial arches.
Cartilage/bone Soft tissue (endoderm
Arch structure Cranial nerve Muscles (mesoderm) and ectoderm) Artery Abnormality
First Mandible, maxilla, V, including Muscles of mastication, mylohyoid, Anterior two-thirds Maxillary Cleft lip and palate,
incus, malleus chorda anterior belly digastric, tensor tongue glands and preauricular skin tags,
tympani palati and tensor tympani mucous membranes Treacher-Collins syndrome,
Pierre Robin syndrome
Second* Stapes, styloid process, VII Muscles of facial expression,
stylohyoid ligament, buccinator, platysma,
lesser horn and superior stapedius, stylohyoid,
part hyoid bone posterior belly of digastric
Third Greater horn and caudal IX Stylopharyngeus, upper pharyngeal Carotid
part of hyoid constrictors
Fourth Thyroid cartilage X: superior Lower pharyngeal constrictors, Right: subclavian
laryngeal levator paliti Left: aortic arch
Sixth Cricoid, epiglottic and X: recurrent Intrinsic laryngeal/pharyngeal muscles Pulmonary arteries This explains why the
arytenoid cartilages laryngeal and ductus recurrent laryngeal nerve
arteriosus on left is looped under the ductus
arteriosus on the left
* The second arch grows down over the other arches, leaving a space known as a cervical sinus. This normally disappears but if it persists it may form a branchial cyst or sinus
(filled with glairy fluid saturated with cholesterol crystals) or a branchial fistula. The fistula extends from the anterior border of the junction of lower and middle thirds of the
sternocleidomastoid to between the external and internal carotid arteries and then opens into the tonsillar fossa.
Plastic and Reconstructive Surgery Chapter 42 703
Cleft lip and palate
Cleft lip and/or palate is one of the most common
congenital abnormalities, occurring in approximately 1 in
700 live births. There is a definite genetic influence.
Subsequent siblings of an affected child have a risk of
developing a cleft of between 1 in 10 and 1 in 50. When
both parents have a cleft the risk of involvement of their
offspring is 1 in 2 to 1 in 3.
Cleft lip and palate may occur separately or together
and may be unilateral or bilateral:
• cleft lip and palate (50%) (Fig. 42.23a);
• cleft lip alone (25%) (Fig. 42.23b);
• cleft palate alone (25%).
Submucous cleft palate is one of the mildest forms. The
Figure 42.21 Fetal head (ventral aspect) showing the embry-
palatal mucosa is intact but the muscular layers are not; it
ological development of the face.
should be suspected in a child with a bifid uvula. It may not
become apparent until the child has difficulty in phonation.
Around the same time a series of branchial arches
(or pharyngeal arches) develop, eventually fusing in the Management
midline (Table 42.7). The external depressions between • Multidisciplinary teams are necessary to treat this
these arches are known as the ectodermal branchial clefts, complex problem. Members include plastic, ENT and
whereas the internal grooves are known as the endoder- maxillofacial or orthodontic surgeons, speech therapists,
mal branchial pouches (Table 42.8). nutritionists, paediatricians and psychologists.
• Feeding can be difficult with cleft palates and the
baby will have difficulty in suckling but not swallowing.
Breast-feeding may not be possible. Special teats have
been developed to help bottle-feeding.
• Surgical repair is carried out in stages. Timing varies
greatly between surgeons but the trend is now towards
early (neonatal) repair of the lip and repair of the palate at
6 months.
• Orthodontic treatment is carried out in parallel with
other procedures. Emphasis is placed on the early phase of
permanent dentition. Bone grafting to the alveolar cleft
defect at 10-12 years of age will allow teeth to migrate into
the correct position.
Table 42.8 Embryology of the branchial clefts and branchial pouches.
Pouch Structure (endoderm + mesoderm) Cleft Structure (endoderm)
First Middle ear, mastoid antrum, tympanic membrane First External auditory meatus, tympanic membrane
Second Tympanic cavity, palatine tonsils Second
Third Thymus gland, inferior parathyroid (III) Third Thymus gland descends, pulling parathyroid III
below parathyroid IV
Fourth Superior parathyroid (IV) Fourth Attached to the thyroid gland, therefore prevents
parathyroid IV going below parathyroid III
Fifth Ultimobranchial body, which develops into
parafollicular (C) cells of thyroid gland