Orthopaedics Flashcards
1
Q
How does compartment syndrome present? Which signs occur late?
A
Pain - out of proportion, on passive stretch
Parasthesia
Pallor
Swelling
Late - pulseless, perishingly cold, paralysis
2
Q
Describe the pathophysiology of compartment syndrome
A
Pressure within a muscle compartment rises, due to fracture and swelling. Osseofascial pressure rises to more than venous pressure, forcing the veins to close and restricting venous drainage. This causes stasis of blood within the compartment and aviscious cycle of increased pressure.
Ischaemia occurs because the oxygen and metabolites are used up and the pressure is too high for arterial blood to perfuse the tissue.
3
Q
Which 2 fractures most commonly cause compartment syndrome?
A
Tibial shaft
Supracondylar
4
Q
What is the treatment for compartment syndrome?
A
Fasciotomy.
2 incisions either side of the tibia to reach all 4 compartments.
5
Q
Which structures are at risk during a fasciotomy for tibial compartment syndrome?
A
Superficial peroneal nerve
Saphenous vein and nerve
6
Q
What are the red flag symptoms of cauda equina?
A
Bilateral pain Saddle anaesthesia Bowel incontinence and bladder retention Reduced reflexes - anal wink, bulbocavernosus Reduced anal tone
7
Q
What causes cauda equina?
A
Space occupying lesion eg tumour or disc prolapse compresses nerve root L1 or below. This affects all of the nerve roots below this point
8
Q
What would you order if you suspected cauda equina?
A
Urgent MRI
Discectomy within 48 hours
9
Q
What is the differential for a single acute painful joint?
A
Septic arthritis
Gout
Malignancy
Pseudogout Bursitis Transient synovitis (child)
10
Q
What is the work up for a single acute painful joint?
A
FBC
CRP
Blood culture
Aspirate - culture, histology and crystal analysis
(For septic arthritis, malignancy and gout/pseudogout)
11
Q
Which bacteria are associated with septic arthritis
A
Staph aureus
Neisseria gonorrhoea
Pseudomonas aeruginosa (immunocompromised)
12
Q
Which bacteria are associated with an infected animal bite?
A
Pasturella multocida
13
Q
What bacteria are associated with an infected human bite?
A
Staph aureus
Eikenella corrodens
14
Q
What is the treatment for a bite wound?
A
Allow to heal by secondary intention.
7 days co amox or metro+doxy
15
Q
Which nerve is at risk following a supracondylar fracture? How is it tested?
A
Anterior interosseous.
Can’t make ok sign because radial half of flexor digitorum profundus and flexor pollicis longus
16
Q
What artery is at risk following a supracondylar fracture?What sign would you look for to check it?
A
Brachial artery
Check pulses
17
Q
What is a major complication of a supracondylar fracture? What signs would you look for?
A
Volkmann’s ischaemic contracture.
Skin puckering - indicates puncture of brachialis
Signs of compartment syndrome: Pain out of proportion, passive stretch, swelling, parasthesia (pulse, cold, paralysis)
18
Q
What is the difference between a buckle fracture and a greenstick fracture?
A
(Both are partial thickness breaks due to the pliability of paediatric bones)
Buckle - break is a crush on opposite side to the tension
Greenstick - break is a snap on the side of the tension
19
Q
What is the difference between a Smith’s and Colle’s fracture?
A
Both - low energy (think elderly women) extra articular distal radius fracture
Colles - dorsally displaced
Smiths - volarly displaced
20
Q
How would you manage a minimally displaced distal radial fracture?
A
Surgical fix because risk to pronation and supination even if slightly displaced.
21
Q
How would you assess whether a distal radial fracture was displaced?
A
Volar tilt >11 degrees
Dorsal tilt >22 degrees
22
Q
Which nerve is at risk in a distal radial fracture?
A
Median nerve - acute carpal tunnel syndrome
23
Q
Which tendon is at risk in a distal radial fracture?
A
Extensor pollicis longus
24
Q
How does a SUFE present?
A
11-14 years
Overweight
Hip pain (can present as knee pain)
FABER position - flexed, abducted and in external rotation
25
What complications are associated with a SUFE?
Avascular necrosis of the femoral head
| Arthritis
26
How is a SUFE treated?
Single percutaneous screw
27
What is the blood supply to the femoral head?
| Which is most likely to be occluded in avascular necrosis?
Medial and lateral circumflex arteries (from the deep femoral)
Obturator artery through the ligament to the head of the femur
MEDIAL circumflex
28
How would you investigate a possible SUFE?
Frog leg lateral hip xray
| Easily missed on AP
29
Describe the Salter Harris classification.
I - Slip through the growth plate
II - Above. Through growth plate and up through metaphysis
III - Lower. Through the growth plate and down through the epiphysis
IV - Through both metaphysis, growth plate and epiphysis
V - Crush
30
What is the most common type of Salter Harris fracture?
II
31
What is the differential for a child with a limp?
Infection - osteomyelitis, septic arthritis, transient synovitis
Malignancy
Trauma/fracture
SUFE (11-14)
Perthes (3-11)
DDH (0-3)
32
How does most hip pathology present?
FABER position and shortened
Flexed, abducted, externally rotated
(Except dislocation which is internally rotated)
33
How does Perthes disease present?
Scrawny, chav child (3-11 years)
| Decreased ROM, pain, Faber position
34
What is Perthes disease?
Idiopathic avn of femoral head in a child
35
How does AVN of femoral head look on an x ray?
Decreased epipyseal height
| Increased density
36
How does developmental hip dysplasia occur?
Lax joint and shallow acetabulum causes the femoral head to develop outside the acetabulum in utero.
37
What is the treatment for DDH?
Developmental dysplasia of the hip.
| Pavlik harness
38
Describe the tests performed on neonates to screen fro DDH
Ortolani - Out. Flex to 90 and abduct legs out. Push thigh up to reduce. Click is positive
Barlow - Back. Flex to 90 and legs together. Push back to dislocate. Click is positive.
39
What are the 4 defects involved with clubfoot?
C - midfoot cavus
A - forefoot adductus
V - hindfoot varus
E - hindfoot equinus
Not passively correctable
40
Where do the nerve roots emerge in relation to the vertebral disc in
a) The cervical spine
b) The rest of the spine
a) nerve root emerges above
b) nerve root emerges below
This is because there are 7 cervical vertebrae and 8 cervical nerve roots.
41
Which nerve root is being tested by the biceps reflex?
C5
42
Which nerve root is being tested by the supinator reflex?
C6
43
Which nerve root is being tested by the triceps reflex?
C7
44
How would you test the sensation and movement of C5?
Sensation - lateral shoulder
| Movement - elbow flexion
45
How would you test the sensation and movement of C6?
Sensation - lateral forearm
| Movement - wrist extension
46
How would you test the sensation and movement of C7?
Sensation - middle finger
| Movement - elbow extension
47
How would you test the sensation and movement of C8?
Sensation - little finger
| Movement - finger flexion
48
How would you test the sensation and movement of T1?
Sensation - medial forearm
| Movement - finger abduction
49
How would you test the sensation and movement of L2?
Sensation - medial thigh/ groin
| Movement - hip flexion
50
How would you test the sensation and movement of L3?
Sensation - medial and anterior thigh
| Movement - knee extension
51
How would you test the sensation and movement of L4?
Sensation - medial calf
| Movement - dorsiflexion (foot drop)
52
How would you test the sensation and movement of L5?
Sensation - Big toe round to lateral calf
| Movement - toe extension
53
How would you test the sensation and movement of S1?
Sensation - Posterior calf
| Movement - plantarflexion
54
Which nerve root is being tested by the knee reflex?
L3/4
55
Which nerve root is being tested by the ankle reflex?
S1
56
How would you test the sensation and movement of S4?
Sensation - Perineum
| Movement - Anal tone, incontinence
57
What nerve might be damaged by axillary node clearance? What effect would it have?
Long thoracic
Serratus anterior
Winged scapula
Press hands on wall and it pokes out
58
What nerve might be damaged by fracture of the neck of the humerus or dislocation of the shoulder? What effect would it have?
Axillary
Deltoid
Arm abduction 15-90 degrees
Numbness in regimental badge area
59
What are the signs of damage to the long thoracic nerve?
Serratus anterior - winged scapula
60
What are the signs of damage to the axillary nerve?
Weakness in arm abduction 15-90 degrees
| Numbness in regimental badge area
61
What are the signs of damage to the thoracodorsal nerve?
Latissimus dorsi weakness
| Can't use a crutch
62
What are the signs of damage to the median nerve?
| movement and sensation
```
Thenar wasting
Weakness in thumb adduction - palm on table and raise up
Ok sign (anterior interosseous branch)
```
Carpal tunnel
63
What are the signs of damage to the ulnar nerve?
| movement and sensation
1st webspace wasting
Weakness in abduction of fingers together
Ulnar claw - from damaged lumbricals
Pain/numbness in medial hand
64
What are the signs of damage to the radial nerve?
| movement and sensation
Wrist drop
Pain/numbness on back of hand
65
What are the signs of damage to the anterior interosseous nerve?
Weakness in ok sign
66
What are the signs of damage to the superior gluteal nerve? (movement and sensation)
Trendelenberg gait
Pain over buttock
67
What are the signs of damage to the ilioinguinal nerve?
Pain from abdomen to groin
| Illicited by pressing inguinal ligament
68
What are the signs of damage to the obturator nerve?
| movement and sensation
Weakness in leg adduction
| Pain in groin
69
What are the signs of damage to the common peroneal nerve?
| movement and sensation
Foot drop
Pain around knee (common)
Circle between big and second toe (deep)
70
What are the signs of damage to the tibial nerve?
Weakness in plantarflexion
71
What are the signs of damage to the saphenous nerve?
Pain on medial/posterior calf
72
What are the signs of damage to the long cutaneous nerve of the thigh?
Pain on lateral and anterior thigh
73
What are the signs of damage to the superficial peroneal nerve?
Pain on anterior calf
74
What are the signs of damage to the sural nerve?
Pain on lateral/posterior calf
75
What are the signs of damage to the musculocutaneous nerve? (movement and sensation)
Pain/numbness on lateral forearm
| Weakness in BBC muscles (brachialis, bicep brachii and coracobrachialis)
76
What nerve might be damaged by fracture of the shaft of the humerus? What effect would it have?
Radian nerve in the spiral groove
Wrist drop
Weakness in finger extension
77
What are the nerve roots of the long thoracic nerve?
C5 C6 and C7 (raise your hands up to heaven)
78
What are the nerve roots of the pudendal nerve
S2 S3 and S4 (poo and wee off the floor)
79
What are the nerve roots of the musculocutaneous, axillary, median, radial and ulnar nerves?
```
Musculocutaneous - C5, 6, 7
Axillary - C5, C6
Radial - C5, C6, C7, C8, T1
Median - C5, C6, C7, C8, T1
Ulnar - C8, T1
```
80
What are the signs of damage to the femoral nerve?
Weakness in knee extension, hip flexion
Pain/ numbness in anterior and medial aspect of the thigh and lower leg
81
What are the nerve roots of the femoral nerve?
L2-4
82
What are the nerve roots of the sciatic nerve?
L4 to S3
83
Which drug is useful in back pain, to reduce muscle spasm?
Baclofen
84
What are the causes of pathological fractures?
```
Osteoporosis
Malignancy - primary or mets
Paget's disease of the bone
Metabolic bone disease
Hyperparathyroid
Osteogenesis imperfecta
Infection - osteomyelitis
```
85
Name and describe some fracture patterns.
```
Transverse - straight across
Oblique - diagonal
Spiral
Intra articular
Segmental - 2 breaks leave a flail segment
Comminuted - crushed into lots of pieces
```
86
How would you work up a suspected fracture?
2 planes x ray - AP and lateral usually
CT if comminuted
```
If repeated fractures/elderly
Calcium
Vitamin D
PTH
?Biopsy
MRI for nerve compromise
```
87
What are the contraindications for reducing a fracture
Undisplaced
| Vertebral
88
Give some immediate fracture complications.
Nerve palsy
Ischaemia
Haemorrhage
89
Give some early (but not immediate) fracture complications.
Compartment syndrome
Infection
DVT
Fat embolus
90
Give some late fracture complications.
```
Non union
Malunion
Stiffness
AVN
CRPS - complex regional pain syndrome
```
91
How do you describe an x ray of a fracture?
Name age and date of x ray
This is a (lateral, AP, PA ..) of the ...
The most obvious abnormality is..
Which bone
Where (epiphysis, metaphysis, diaphysis)
Pattern (transverse, oblique, spiral, segment, comminuted)
Displacement?
Angulated?
Shortened?
Rotated?
92
How do you describe an x ray of a bone lesion?
Name age and date of x ray
This is a (lateral, AP, PA ..) of the ...
The most obvious abnormality is..
```
Which bone
Where (epiphysis, metaphysis, diaphysis)
Lytic or sclerotic
Cortex or medulla
Through the periosteum?
Well defined border?
Periosteal thickening?
```
93
What is the name for a radiculopathy of the lateral cutaneous nerve of the thigh?
Meralgia paraesthetica
94
What are the risk factors for dupuytrens contracture?
```
Manual labour
Phenytoin
Alcoholic liver disease
Trauma
FHx
```
95
What is the treatment for an intracapsular NOF?
Mobile - total hip replacement
| Not mobile - hemiarthroplasty (cement)
96
What is the treatment for an intertrochanteric NOF?
Dynamic hip screw
97
What is the treatment for a subtrochanteric NOF?
Intramedullary nail
98
How does De Quervains tenosynovitis present?
Swollen side of wrist
| Pain over ther radial styloid on forced abduction/flexion of the thumb.
99
Describe the parts of an intervertebral disc. What type of collagen makes up each part?
```
Annulus fibrosus (outside) - type 1 collagen
Nucleus pulposus (inside) - type 2 collagen
```
100
Which direction does an intervertebral disc normally herniate? Why?
Posterolaterally
| Because the posterior longitudinal ligament is the weakest
101
Describe the layers of the back that the needle of a spinal anaesthetic must pass through.
```
Supraspinous ligament
Interspinous ligament
Ligamentum flavum
(Epidural here)
Dura mater
Arachnoid mater
(Spinal here)
```
```
(Then
Pia mater
The cord
Other sides of the meninges
Posterior longitudinal ligament
Vertebral body/disc
Anterior longitudinal ligament)
```
102
At what spinal level do most episodes of cauda equina occur?
L4/5
Pressing on L5 nerve root (toe extension)
L5/S1
Pressing on S1 nerve root (plantarflexion)
103
What are the main causes of radiculopathy?
Disc herniation
Degenerative - spondylosis
Arthritic osteophytes
Diabetes (microvascular damage to nerves)
104
Describe the first 2 vertebrae
Atlas - C1. A ring shape
| Axis - C2 Has the dens which slots into C1 to allow rotation of the head
105
Describe the femoral and sciatic stretch tests. What do they identify?
Sciatic - passive straight leg raise in dorsiflexion
Femoral - passive hip extension with knee in flexion
Stretch the nerves to illicit radiculopathy pain
106
Describe some special x ray views
Frog leg lateral - for SUFE
| Scaphoid view - scaphoid fracture
107
Give a differential for back pain
Mechanical - muscular, disc herniation, arthritic changes (spondylosis), inflammatory (spondylitis), compression fracture
Systemic - discitis, malignancy, connective tissue disease
Referred - renal colic, AAA, pancreatitis
108
What are the borders of the anatomical snuff box?
Extensor pollicis longus
Extensor pollicis brevis
Abductor pollicis longus (b for thumB)
109
What complications are associated with a scaphoid fracture? Why?
Non union
AVN
Blood supply travels distal to proximal
110
What are the risk factors for a NOF?
Female
Age
Osteopenia/osteoporosis
111
Why do we measure lactate in trauma/sepsis?
Marker of uncompensated hypoperfusion.
Therefore marker of morbidity/AVN in fractures/ischaemia risk
Associated with poor outcomes
112
The consultant asks you to prep a patient for theatre for a total hip replacement. What do you do?
Fbc, u and e, group and save 2 units, lactate
Fluid
Nil by mouth
Reverse Warfarin and place on Rivaroxaban (for knee and hip surgery, all others use LMWH)
Place on sliding scale if insulin dependent
Bactoban and hibiscrub for MRSA prophylaxis
113
Describe Gardner's classification for NOFs.
I - Incomplete
II - Complete, undisplaced
III - Complete, partially displaced
IV - Complete fully displaced
114
Describe the Nottingham Hip fracture score.
Risk of 30 day mortality high if 7/10
```
Age - 66-85 3 points, over 85 4 points
Sex M more likely to die even though F more likely to fracture
Mental state
Hb
In a home
Comorbidities
Cancer
```
115
What is the 1 year mortality following a NOF?
30%
116
What are the complications associated with an untreated intracapsular NOF?
AVN
Non union because no periosteum in femoral neck therefore no callus
Pain
Disability
Mortality 30%
117
What are the complications associated with a hip arthroplasty?
```
Any op -
Infection
Bleeding
NV damage
Chronic pain
Anaesthetic reaction
```
Specific-
Leg length discrepancy
Stiffness
Dislocation
118
What are the complications associated with an untreated extracapsular NOF?
Pain
Disability
Mortality 30%
119
How does ankylosing spondylitis present?
Lower back pain and stiffness of insidious onset
Stiffness worse in the morning and improves with exercise
Night pain
```
Reduced lateral flexion
Reduced forward flexion - Schober's test - a line is drawn 10 cm above and 5 cm below the back dimples. The distance between the two lines should increase by more than 5 cm when the patient bends as far forward as possible
Reduced chest expansion
Bamboo spine
Sacroilitis
```
120
What are the risk factors for an spond?
Male
| HLA-B27
121
How is ank spond treated?
Regular exercise such as swimming
Physiotherapy
NSAIDs are the first-line treatment
'Anti-TNF therapy should be given to patients with persistently high disease activity despite conventional treatments' (etanercept and adalimumab)
122
How does osteoarthritis present?
```
Gradual onset
Assymetric joint pain
Knee, hip, pip and dip
Less than 1 hour morning stiffness
Relieved by rest
```
123
What are the radiological features of osteoarthritis?
L - loss of joint space
O - osteophytes
S - subchondral cysts
S - sclerosis
124
What is the treatment of osteoarthritis?
```
Weight loss
Physio
Paracetamol
NSAIDs
Steroid injections
Joint replacement
```
125
What complications of osteoarthritis?
```
Gout
Pseudogout
Chondrolysis and loose bodies
Stress fractures
Radiculopathy
```
126
What are the risk factors for osteoarthritis?
```
Obesity
Varus/valgus deformities
Repetitive microtrauma (pneumatic drill)
Gout
Pseudogout
Menopause
```
127
What are the indications for a joint replacement for osteoarthritis?
```
Pain -
Steroid injections no longer effective
Night pain
Pain when resting
Startup pain
```
Affecting activities of daily living
128
What are Heberdens and Bouchards nodes?
Heberden - at the end - DIP joint
Bouchard - PIP joint
Both associated with osteoarthritis
Hard bony outgrowths caused by osteophytes
129
Which type of bone is most affected by osteoporosis?
Cancellous spongy bone
130
What is the difference between normal and osteoporotic bone?
Decreased density, especially in the cancellous bone. Thin trabeculae and increased numbers of Haversian canals (parallel to the length of the bone)
131
What are the main risk factors for osteoporosis?
FRAX factors:
```
Female
Fractured hip
Rheumatoid arthritis
Alcohol
Age
Smoking
Steroids
Low BMI
```
Endocrine - hyperthyroid, parathyroid, premature menopause, acromegaly
Early menopause
CKD
132
What is the FRAX score?
FFRAASSL
```
Female
Fractured hip
Rheumatoid arthritis
Alcohol
Age
Smoking
Steroids
Low BMI
```
Risk of fracture in osteporosis
133
When is a DEXA scan indicated?
Fracture plus
```
Minor trauma
Steroids
Rheumatoid arthritis
Early menopause
Post menopause and low BMI
```
134
What is the treatment for osteoporosis?
Bisphosphonates (alendronic acid)
| Adcal
135
What is the mechanism of action of bisphosphonates?
Cause apoptosis of osteoclasts
136
What are the side effects of bisphosphonates?
GORD (acidic)
Hypocalcaemia
Osteonecrosis of the jaw
137
What is the bone profile blood result likely to show in osteoporosis?
Normal
138
What is the difference between the pain presentation of osteoporosis and osteomalacia?
OsteoPorosis hurts part of the time, osteoMalacia hurts most of the time.
139
Which types of bone are at most at risk of fracture in osteomalacia?
Flat bones - pubic rami, scapula, ribs
140
What is the bone profile blood result likely to show in osteomalacia?
Low vit D
Thererfore Low Ca
Therefore High PTH and High Alk phos
141
What is the pathophysiology of Paget's disease of the bone?
Large multi nucleated osteoclasts
Increased breakdown of bone, stimulates increased osteoblastic activity.
Lots of thick bone - sabre tibia and skull
Due to high demand, the bone produced is low quality, weak, vascular.
142
What complications are associated with Paget's disease of the bone?
Fractures
Arthritis
Osteosarcoma (high bone turnover)
Deformity
143
What is the bone profile blood result likely to show in Paget's disease of the bone?
High Alk Phos (high bone turnover)
144
What is the bone profile blood result likely to show in bone mets?
High alk phos (high turnover)
| Enough to increase Ca
145
What is the bone profile blood result likely to show in primary hyper PTH?
High PTH
| Therefore high Ca
146
What is the bone profile blood result likely to show in secondary hyper PTH?
Low Ca
| Therefore high PTH
147
What are the most common cancers to metastasise to the bone?
Prostate
Breast
Lung/bronchial
(and the rest of the hexagon)
Thyroid
Kidney
148
Which bone mets are more likely to be lytic and which are more likely to be sclerotic?
Lytic - thyroid, bronchial, renal
| Sclerotic - Prostate, breast
149
How do bone mets develop?
1. Cancerous cells have less e-cadherin on the membrane. This leads to reduced adhesion between cells.
2. Cancer cells recruit niche cells to release lots of protease to lyse the surrounding stroma.
3. Cancer cells enter the blood/lymph/coelom
4. Cancer cells release integrins to aid adhesion to the endothelium in the bone.
5. Cancer cells release VEG-F to increase angiogenesis at the bone.
6. Lytic cancer releases GF to stimulate blasts to stimulate clasts.
7. Sclerotic cancer releases ET-1 to increase blasts.
150
Which bones do malignant lesions commonly develop in?
Thoracic spine
| Proximal femur
151
What are the red flag signs and symptoms for a bone met?
```
Night pain
Progressive pain
Pathological fracture
Neurological deficit - spinal cord compression
Hypercalcaemia
```
Weight loss
Appetite loss
Smoker
152
What are the early symptoms of hypercalcaemia?
Stones...
Polyuria
Renal stones
Moans...
Pancreatitis
Constipation
Vomiting
Groans....
Depression
Fatigue
153
What are the late symptoms of hypercalcaemia?
Cardiovascular
Short QT -> arrhythmia
Renal tubular damage - electrolyte disturbance, AKI
154
What is the differential for causes of hypercalcaemia?
Malignancy
Paget's disease of the bone
HyperPTH
Sarcoid
TB
CKD
Lithium
155
How is hypercalcaemia treated?
Loop diuresis + fluid
| Bisphosphonates
156
What tests would you order if you suspected a bone met?
Fbc - anaemia of chronic disease, polycythaemia from EPO secreting renal cell cancer, neutrophilia
LFT - Alk phos
Bone profile - PTH, serum calcium
PSA, U&E, serum thyroxine - to hunt the primary
CXR
X ray limb in 2 planes
CT chest abdo pelvis
Technitium bone scan
MRI if neuro compromise
Biopsy - carried out by resecting surgeon
157
What test can most sensitively identify bone mets?
Technitium bone scan
| Identifies hotspots
158
What is the most common primary bone tumour?
Osteoid osteosarcoma
159
How does osteoid osteosarcoma present?
Young adult
Distal femur
On xray
Sclerotic
Elevation of periosteum
Sunray spicules
160
How does Ewings' sarcoma present?
Child
Flat or long bones
On x ray
Lytic
161
What are the causes of duypeytren's contracture?
Thickening of the palmar fascia
```
Idiopathic (FHx)
Cirrhosis
Phenytoin
Trauma
Manual labour
```
162
How does tenosynovitis present?
Pain over radial styloid on forced flexion of the thumb
| Finkelstein test
163
How does tennis elbow present?
Lateral epicondylitis
| Pain on wrist extension when elbow flexed
164
How does golfer's elbow present?
Medial epicondylitis
| Pain on wrist flexion when elbow flexed
165
Which bursa is affected by Housemaid's knee?
Prepatellar
166
Which bursa is affected by Clergyman's knee?
Infrapatellar
167
Why does damage to the radial nerve in the spiral groove only cause mild weakness of elbow extension?
The branches to the long and medial heads arise proximal to the radial groove
