Osteosarcoma

• These are spindle cell neoplasms that produce Osteoid
• It is the second most common primary malignancy of bone behind multiple myeloma.

OSTEOSARCOMA CLASSIFICATION
• High grade Intramedullary Osteosarcoma
• Low Grade “ “
• Telengiectatic Osteosarcoma
• Surface Osteosarcoma
1. Paraosteal
2. Periosteal
3. High Grade Surface Osteosarcoma
• Osteosarcoma of the Jaw
• Multicentric osteosarcoma
• Secondary osteosarcoma
• Irradiation induced Osteosarcoma
• Dedifferentiated Chondrosarcoma
• Osteosarcoma derived from benign precursors

Osteosarcoma may be also classified based on prognostic importance

Low Grade
• Parosteal
• Low-grade central
Intermediate Grade
• Periosteal
High Grade
• Conventional
• Telangiectatic
• Small cell
• Postradiation
• Pagetoid
• High-grade surface


Aetiology:
‣ Genetic abnormalities: p53 suppressor genes, Rb gene, F33 isoform, ErbB-2 (Her – 2neu), transforming growth factor beta, isoform 3 expression
‣ Associations: Retinoblastoma (Rb gene), Rothmund-Thomson syndrome, and Li-Fraumeni syndrome (p53 gene)
‣ Li-Fraumeni syndrome: sarcomas in young patients and pre-menopausal breast cancer in the mothers of the young patients
‣ Rothmund Thomson syndrome: rare genodermatosis that features a progressive, early-onset poikiloderma, a high incidence of juvenile cataracts, stunted growth, and a wide range of skeletal abnormalities.

‣ Osteosarcoma is the most common type of bone sarcoma(The most common primary bone malignancy is multiple myeloma, and the most common malignancy affecting bone is metastatic carcinoma)
‣ Bimodal peak age incidence
‣ Majority occur within the second decade (~60%)
‣ Second peak age >55; often secondary osteosarcomas
‣ Incidence: 0.3 per 100,000 per year

Local Growth:
 Osteosarcomas usually arise within the metaphyseal region of long bones.
 They may be located within the bone or on the surface of the bone.
 If untreated, osteosarcomas will continue to grow, with local destruction of bone and extension outside the bone into the surrounding soft tissues.
 The physis and articular cartilage may act as a relative barrier to tumor extension, but epiphyseal or intra-articular extension is still seen frequently.
Metastases
 Osteosarcomas, as with all sarcomas, usually metastasize hematogenously.
 Lymph node metastases are not common and usually present only very late in the course of metastatic disease.
 15% to 20% of patients present with metastases at time of diagnosis.
 Most common site of metastasis: lungs
 Second most common: bone
 Skip lesions: distinct smaller areas apart from primary tumor within same bone
 Prognosis: same as or worse than distant metastases (lung or bone)


a) Classic Osteosarcoma (High Grade Intramedullary osteosarcoma)

 Most common in second or third decade.
 Fifty percent of lesions seen about the knee joint.
 Histological cell types are osteoblastic, chondroblastic, fibroblastic and small cell
 Arises from the medullary canal
 MC location: distal femur > proximal tibia >proximal humerus
 Can occur in any bone

CF:
 Pain before a tumour mass is noticeable.
 Pain is due to microinfarctions occurring in the bone.
 Night pain is an important symptom but is seen in only 25% of patients.
 Pain gradually worsening, though may be intermittent or increase with activity
 Pain is usually present for weeks to months, not acutely
 Dilated veins over swelling.
 Fusiform swelling, fixed to bone, firm and immobile
 Tenderness is usually present to palpation, with range of motion, and with weight bearing
 About 10- 20% patients have pulmonary metastasis at presentation
 Metastasize in 80% patients treated by surgery alone

Investigations:
• X-ray:
 Permeated lytic destruction of metaphyseal bone
 “Codman’s reactive triangle”
 Sunburst pattern or hair on end appearance.
 Areas of bone formation maybe present
 Occasionally the lesion is pure sclerotic or lytic.
 There is usually some cortical destruction with extension of a soft tissue mass
 Associated higher-level lesion in the femur- “skip” lesion

MRI: identifies
 Extent of soft tissue involvement
 Intramedullary spread
 Neurovascular involvement
At least one sequence of entire bone (preferably coronal T1 images) to rule out skip lesion in same bone (metastasis) is essential

Whole-body bone scan: Uptake on scan of primary lesion is almost always present, but scan is to rule out other sites of disease.
 May detect other sites of disease
 May also show skip lesion in same bone

• Biopsy:
Periphery of the tumour is the best tissue for a biopsy because
• It is easy to reach.
• Soft enough for a diagnostic frozen section, and
• Representative of the most aggressive portion.

CT chest to detect any pulmonary metastasis

Pathology:
 Osteosarcoma produces high-grade spindle cell sarcomatous stroma with malignant osteoblasts that produce malignant osteoid or bone.
 Tumor cells are typically anaplastic (less differentiated), may show marked atypia and pleomorphic (widely variable) nuclei, and may show many and/or bizarre mitoses.
 There may be areas of osteoblastic (osseous), fibroblastic (fibrous), or chondroblastic (cartilage) appearance, but if there is the presence of malignant osteoid (wavy, lace-like, uncalcified bone matrix produced by malignant osteoblasts), the diagnosis of osteosarcoma is made regardless of the associated areas.

Grading:
 Helps to assess prognosis
 Low grade tumours do not require chemotherapy and are less likely to develop metastasis
 Most osteosarcomas are high-grade tumors( mostly IIB Enneking)


• Poor prognostic factors in osteosarcoma are:-
a. Metastases to lung, bone and lymph nodes
b. Expression of P glycoprotein in the cells
c. High Alkaline phosphatase
d. High Lactate dehydrogenase
e. Vascular Invasion
f. Large tumour size
g. No alteration in DNA ploidy after chemotherapy
h. Absence of anti heat shock protein 90 antibody after chemotherapy

Treatment:
Neoadjuvant chemotherapy, Surgery
In extremity osteosarcoma, limb-sparing surgery, with wide resection of the tumour, is the standard approach.
Chemo for osteosarcoma: Methotrexate, Adriamycin, cisplatin, and ifosfomide. Neoadjuvant chemotherapy is delivered for 8- 12 weeks followed by resection of the tumour. Maintenance chemotherapy is given for 6- 12 months.

Neoadjuvant chemotherapy:
 Neoadjuvant chemotherapy may shrink the primary tumor and sterilize microscopic tumor foci in the reactive zone around it, facilitating resection and increasing the chance for limb-sparing surgery.
 Neoadjuvant chemotherapy also allows time for surgical planning, the fabrication of a custom tumor prosthesis, or the procurement of allograft tissue for implantation.
 Finally, neoadjuvant chemotherapy induces necrosis in the primary tumor, and the amount of this necrosis serves as an extremely important prognostic indicator for long-term survival
 Thallium 201 is used to assess tumour response after chemotherapy
Side effects of these medications can be severe, and toxicities can occur.
These include mucositis, cardiomyopathy (doxorubicin), alopecia, myelosuppression, nausea/vomiting, and relative immunocompromise, sepsis, and rarely even death.

Medications used during chemotherapy treatment to minimize side effects
 Granulocyte colony-stimulating factor (G-CSF;):Improves neutropenia by stimulating neutrophil production by marrow, decreases infections and febrile neutropenias
 Erythropoietin stimulates red blood cell production.
 Dexrazoxane protects against cardiomyopathy of doxorubicin.
 Leucovorin rescues normal cells from effects of high-dose methotrexate and decreases myelosuppression and mucositis

Limb sparing Surgery

Limb-sparing surgery is indicated for patients in whom wide margins can be obtained without sacrificing so much tissue that the remaining limb is nonfunctional.
 Usually, the determining factor is the ability to spare major nerves. Major vessels need to be preserved or reconstructed.

Role of radiation therapy:
 Mainly for palliation
 may be the safest oncologic treatment following initial resection with positive margins(margins containing malignant cells)

b) HAEMORRHAGIC or Telengiectatic Osteosarcoma
 High-grade, purely lytic tumour, incidence of pathologic fracture is high.
 0.4% to 12% of all osteosarcomas
 Histology: Bag of blood with few cellular elements, cellular elements have highly malignant appearance
 X ray: Permeative or ballooned out appearance resembling aneurysmal bone cyst with little bone production
 A pathologic fracture may necessitate amputation rather than limb salvage.
 Impending lesions should be either immobilized to prevent pathological fracture or treated with early surgery.
 Treatment is by multi agent chemotherapy and surgery

c) PARAOSTEAL OSTEOSARCOMA
 More common in females, slightly older age group(2nd and 3rd decades)
 Most common surface osteosarcoma. Other surface osteosarcomas include periosteal osteosarcoma and high grade surface osteosarcoma
 5% of osteosarcomas
 MC sites: distal femur>proximal humerus
 Patients usually complain of a painless mass, dull aching type of pain may also be a presenting complaint
 Slow growing low-grade tumour usually appearing in posterior aspect (surface) of the distal femur (over the external aspect of bone)

X-rays reveal dense mineral deposits within the tumour
• DD on X-ray: Myositis ossificans. The ossification in myositis ossificans is more mature at the periphery of the lesion, whereas the center of a periosteal osteosarcoma is more heavily ossified and lobulated.
• Differentiated from osteochondroma that it lacks the corticomedullary trabecular continuity
• ‘Cleavage plane’ or a radiolucent line between tumour and cortex
• Has a ‘stuck on’ appearance. It may wrap around cortex, with invasion into bone later

Histology:
• The osseous trabeculae are regularly arranged. Between the normal trabeculae are atypical spindle cells. Cartilage is frequently present and is arranged as a cap over the lesion
• In around 1/6th of the lesions that appear in X-rays as Paraosteal osteosarcoma there is a high grade element. In this circumstance the lesion is termed a “Dedifferentiated Osteosarcoma”, for which the prognosis is worse.

Treatment:
• It does not respond well to either chemotherapy or radiation therapy.
• Wide surgical resection is the treatment of choice.
• Dedifferentiated form: responds to multiagent chemotherapy.

d) PERIOSTEAL OSTEOSARCOMA
 More common in females in the second decade of life.
 1-2% of all osteosarcomas
 Common in the diaphysis of femur and tibia(anterior surface)
 X rays:
 Radiographically, a fusiform mass with lucency and ossification
 A sunburst appearance is seen resting on a saucerised cortical depression.
 Cortical depression can mimic a periosteal chondroma, but periosteal osteosarcoma is associated with a larger size (>4 cm) and irregular margins
 Histologically the lesion is more chondroblastic.
 Wide surgical resection is the modality of choice. This is combined with chemotherapy.
 The prognosis is intermediate between High grade intramedullary osteosarcoma and paraosteal osteosarcoma

e) SECONDARY OSTEOSARCOMA
 May arise in Paget’s disease, osteoblastoma, fibrous dysplasia, benign giant cell tumour, osteochondroma, Melorheostosis, osteogenesis imperfecta, bone infarction, and chronic osteomyelitis.
 Most common of the “secondary osteosarcomas”-Pagetic osteosarcoma
 The most frequent location for pagetic osteosarcoma is the humerus, followed next by the pelvis and femur.
 Several thousand-fold increased risk of osteosarcoma in patients with Paget's disease compared to the general population
 Occur in an older population (55 to 85 years old)
 Increasingly painful mass is most common presentation.
 Occur in Flat bones, unlike conventional osteosarcoma due to frequent involvement of pelvis and scapula with Paget's disease
 X-rays: reveal destructive mass, usually with soft tissue extension in bone with Paget's disease.
 The prognosis for patients with pagetic osteosarcoma is extremely poor.
 Occur in 5% of patients with polyostotic Paget’s disease

f) LOWGRADE INTRAMEDULLARY OSTEOSARCOMA
 1 to 2% of all osteosarcomas
 Older, typically third decade
 Radiographically, sclerotic density in metaphyseal bone.
 Often confused with fibrous dysplasia or by progression or recurrence after treatment for suspected benign disease
 Prognosis is similar to paraosteal sarcoma
 Wide resection is the treatment of choice.

g) IRRADIATION INDUCED OSTEOSARCOMA
• Usually with >4000 cGy radiation dosage
• Usually appears after 3- 15 years from the time of radiation insult.
• Common in flat bones like scapula, pelvis and rib

h) MULTICENTRIC OSTEOSARCOMA
a. Synchronous–occurring in childhood and adolescents and
b. Metachronous – occurring in adults.
Prognosis is poor for both types.
i) Soft -Tissue Osteosarcoma (extra osseous osteosarcoma)
• Can occur in muscle tissue (4% of all osteosarcomas)
• Tumour is usually seen in large muscle groups of the pelvis, thigh areas or the shoulder.
• DD: Myositis ossificans.
Myositis ossificans has a zonal pattern of ossification (Ackermann zone phenomenon) with the mature dense ossification concentrating at the periphery of the lesion.
Treatment: Wide resection, +/- adjuvant chemotherapy and radiotherapy

j) HIGH GRADE SURFACE OSTEOSARCOMA
 Up to 1% of osteosarcomas
 Located on surface of bone
 Otherwise identical to conventional osteosarcoma in histology, treatment, and prognosis

k) SMALL CELL OSTEOSARCOMA
 Rare; about 1% to 4% of all osteosarcomas
 Controversy: Are these “atypical Ewing sarcoma”?
 Age, location, and radiographic picture similar to conventional osteosarcoma
 Typically has a destructive, permeative pattern, sometimes extends into diaphysis
 Histology: there is often difficulty in distinguishing this tumor from Ewing sarcoma and other small round cell tumors if no osteoid is seen on biopsy.
 Usually has areas of osteoblastic activity, which helps distinguish it from Ewing sarcoma

Perthes DIsease Current Concepts

Perthe's disease- aetiology:
G. C. Perthes in Germany, J. Calvé in France and A.T. Legg in America described the disease almost simultaneously, in 1910.

Synonyms: Coxa Plana; osteochondritis deformans juvenilis

Aetiology:

Theories and Supporting Evidence
1. Compromised Vascular supply: Angiograms and laser Doppler flow studies showing that the medial circumflex artery is missing or obliterated in many cases and that the obturator artery or the lateral epiphyseal artery are also affected in some cases.

2. Increased intra-articular pressure:
Animal experiments have shown that an ischemia similar to that in Legg-
Calvé-Perthes disease can be generated by increasing the intra-articular pressure

3. Raised Intraosseous pressure The venous drainage in the femoral head is impaired, causing an increase in intraosseous pressure

4. Coagulation disorder
Association with Protein C or S deficiency. These factors normally inhibit coagulation

5. A maturation disorder Legg- Calvé- Perthe’s disease patients are shorter, on average, than their peers of the same age and show a retarded skeletal age

6. Social conditions: Studies in the UK have shown that Legg- Calvé- Perthes disease is more common in the lower social strata

7.Genetic factors: Genetic studies have shown that first degree relatives of children with Perthe’s disease are 35 times more likely to suffer from the condition than
the normal population.

Classifications
Catterall’s Head-at-risk Signs
1. Lateral subluxation of the femoral head from the acetabulum.
2. Speckled calcification lateral to the capital epiphysis.
3. Diffuse metaphyseal reaction (metaphyseal cysts).
4. A horizontal physis, and
5. Gage sign: A radiolucent V-shaped defect in the lateral epiphysis and adjacent metaphysis.

Salter Thompson Classification
• Type A: Extent of the fracture is less than 50% of the superior dome of the femoral head. Good results.
• Type B: Extent of the fracture is more than 50% of the dome. Fair or poor results.

Herring Lateral Pillar Classification
• Group A: No involvement of the lateral pillar.
• Group B: At least 50% of lateral pillar height maintained.
• Group C: Less than 50% of lateral pillar height maintained.

The lateral pillar consists of the lateral most 30% of the femoral head in an AP projection. To designate borderline groups between B and C the B/C border group was included.
B/C1: lateral pillar more than 50% width, but < 2 to 3 mm width
B/C2: lateral pillar more than 50% width, but little ossification
B/C3: lateral pillar more than 50% width, but depressed relative to central column.

Catterall Classification
• Group I: Anterior part of head involved.
• Group II: Anterior and partial lateral involvement.
Sequestrum+ Mild metaphyseal changes
• Group III: Anterior and lateral head involvement
Sequestrum + Diffuse metaphyseal changes + Coxa
magna
• Group IV: Complete head involvement
Collapse of head


stages
Stages of Perthe’s Disease (Waldenström Staging)

Stage and Characteristics
1. Avascular stage. The femoral head appears slightly denser than normal on the x-ray and is slightly flattened; the joint space is widened (Waldenström sign).
Lateralisation of the femoral head.

2. Stage of resorption (Fragmentation). Femoral head breaks up into fragments
Lucent areas appear in the femoral head
Increased density resolves
Acetabular contour is more irregular

3. Stage of reossification. The femoral head is rebuilt
New bone formation occurs in the femoral head

4. Healing stage. End stage with or without defect healing (normal hip, coxa magna, coxa parva, flattened head etc.)


Clinical Features:

• Limp and mild to moderate hip pain
• The ROM of the hip is restricted, in particular abduction and internal rotation.

Prognostic Features:
• Deformity of femoral head, Age, subluxation, lateral calcification, mobility and sex in decreasing order of significance
• Herring lateral pillar classification has the best prognostic significance
• Gage sign and Horizontal growth plate as originally described by Caterall have no prognostic significance

Differential Diagnosis:
1. Epiphyseal dysplasia: The following are features
Bilateral involvement
Largely symmetrical findings
Possible involvement of other joints or the spine
Possible involvement of the acetabulum
Few sclerotic or cystic changes in the femoral head
Little tendency toward lateral calcification or subluxation
Typical stages of LCPD like sclerosis, collapse, fragmentation and reossification are not apparent

2. Osteochondritis dissecans of the femoral head
3. Chondroblastoma of the femoral head
• The height of the femoral head is not initially reduced, nor is the
cartilage thickened.
• The presence of non-load-related pain

Stages of radiological changes in Perthe's disease:
Early
• Joint space widening(waldenstrom's sign)
• Increased density of femoral epiphysis
• Subchondral fracture, or “crescent sign,” seen on lateral radiograph
Midstage
• Fragmentation and flattening of head
• Widening of the physis
• Femoral neck cysts
• Extrusion of the femoral head
Late
• Coxa magna
• High-riding trochanter
• Flattened femoral head
• Irregular articular surface

Perthe’s disease features:
Unilateral involvement,
If bilateral involvement is present: pronounced asymmetry, disease in differing stages, possibly also of differing severity,
No involvement of other joints or the spine,
No involvement of the acetabulum,
Sclerotic and cystic changes in the femoral head,
Cystic changes in the metaphysis,
Tendency toward lateral calcification and subluxation


DD
Other disorders associated with Avascular Necrosis of the femoral head in children:

Sickle cell anemia
Thalassemia ((high incidence (25%) of avascular femoral head necrosis ))
Trichorhinophalangeal syndrome
Klinefelter syndrome
Morquio’s syndrome
Down syndrome (trisomy 21)
Achondroplasia
Gaucher’s disease
 Myelomeningocoele
Hemophilia (the incidence in hemophilia is 7%)
 Congenital tibial pseudoarthrosis


Treatment
Treatment is guided my dividing the patient into three groups.

Poor prognosis group: Treatment indicated:
• Catterall 3 and 4
• Salter-Thompson
• Lateral pillar C
• At risk clinically
• At risk radiographically, regardless of the disease extent
• Age<8yrwithdeformity
• Age >8 yr (Catterall group 2, 3, and 4, with or without at-risk signs; lateral pillar B and C; Salter-Thompson B), with or without head deformity

Good prognosis group: no treatment necessary:
• Catterall 1 and 2(generally good prognosis in 90% of cases)
• Salter-Thompson A
• Lateral pillar A
• If disease is in reossification stage

Indeterminate prognosis group: may require treatment if head at risk signs is present. Otherwise no treatment is indicated.
• Catterall 2
• Lateral pillar B

Principles of treatment• The first principle regardless of the method of treatment is restoration of motion.
• Restoration of motion can be accomplished by bed rest alone, or with skin traction and progressive abduction to relieve the muscle spasms
• Reassessment is done in 1 week to assure that range of motion has considerably improved (to at least 45 degrees of abduction
• The cornerstone of treatment for Legg-Calve-Perthes syndrome is referred to as containment
• The essence of containment is that, in order to prevent deformities of the diseased epiphysis, the femoral head must be contained within the depths of the acetabulum
• Arthrography is a useful adjunct in determining whether the femoral head actually can be contained and, if so, in what position this is best accomplished.
• It is essential to regain range of motion before instituting containment treatment
• Hinged abduction: This is a condition in which the head levers out of the acetabulum with abduction instead of moving within the socket
• Demonstration of the hinge abduction phenomenon is a contraindication to any type of containment treatment
• Surgical containment (Varus Derotational Osteotomy / Innominate Osteotomy/ Lateral Shelf acetabuloplasty) is the most popular method of treatment
• Abduction brace like the Atlanta Scottish Rite orthosis are used by surgeons who prefer nonsurgical containment

• The requisites for an varus derotation intertrochanteric osteotomy are:
1. Epiphyseal plate not too steep,
2. No major leg shortening,
3. Congruency between the femoral head and the acetabulum,
4. Ability to contain the femoral head in the acetabulum in abduction and internal rotation
5. Only slight restriction of abduction


• Pre requisites for an innominate osteotomy (Salter’s osteotomy) include:
1. Restoration of a full range of motion,
2. A round or almost round femoral head, and congruency of the joint, demonstrated arthrographically.
3. The head must be well seated in flexion, abduction.
• Combined varus derotation and innominate osteotomies are being evaluated for Caterall 3 and 4 stage disease

• Shelf Arthroplasty: is becoming popular as a method of containment
Prerequisites-
1. Children older than 8 years with Catterall group 2, 3, or 4 disease with or without at-risk signs,
2. Lateral pillar type B or C disease, and
3. Salter-Thompson type B disease;
4. If subluxation is present, it must be reducible on a dynamic arthrogram

Risk factors for poor results with this technique are age older than 11 years, female gender, and Catterall group 4 disease.
• Triple Innominate osteotomy as a method of containment is being investigated
• Arthrodiastasis: the use of hip distraction for periods of 4 to 5 months, with or without soft tissue release, in older children with Perthes disease is also being investigated


Management of the Noncontainable Hip
Management of the Noncontainable Hip and the Late-presenting Patient with Deformity:

• These include patients in later stages (reossification) of the disease, those with noncontainable deformities, and those who have lost containment after undergoing either surgical or nonsurgical containment
• These patients usually demonstrate hinge abduction on arthrography.
• The salvage procedures to be considered at this point include abduction extension osteotomy, lateral shelf arthroplasty, Chiari osteotomy, and cheilectomy
• These salvage procedures are done with limited aims of pain relief, correction of limb length inequality and improvement of movement and abductor weakness
• Cheilectomy removes the anterolateral part of the head that impinges on the acetabulum in abduction
Cheilectomy does not correct any residual shortening or abductor weakness
This procedure should only be done after the physis has closed, otherwise an
SCFE may ensue.
• Chiari Osteotomy improves the lateral coverage of the head, but does not give coverage to the deformed head in abduction and it may exacerbate abductor weakness
• Abduction extension osteotomy is indicated when arthrography demonstrates joint congruency in extended and adducted position
This osteotomy improves the limb length, decreases limp and improves function and range of motion

Femoroacetabular Impingement

Femoroacetabular impingement
aetiology

▪ The presence of aberrant morphology involving the proximal femur and/or the acetabulum results in abnormal contact between the femoral neck and the acetabular rim during terminal motion of the hip.
▪ Ganz described two types of FAI: cam impingement and pincer impingement.
▪ Cam impingement: Cam impingement occurs when an abnormally shaped (ie, nonspherical) femoral head with increased radius is jammed into the acetabulum during normal motion, especially flexion. The prominence on the femoral neck is forced into the acetabulum and results in tearing of the labrum and/or its avulsion from the rim.
▪ The pincer impingement: is the result of abnormal contact between the acetabular rim and the femoral neck. The femoral head in this situation may be normal, and the abutment is mostly a result of overcoverage of the femoral head in conditions such as coxa profunda or acetabular retroversion.
▪ Both mechanisms lead to cartilage wear and eventually osteoarthritis

clinical features

▪ Presents in active young adults with slow onset of groin pain that may start after a minor trauma
▪ Hip or groin pain on prolonged standing or sitting or athletic activities.
▪ Anteroposterior impingement test(fig a). The patient is placed supine with the hip in 90° of flexion. Internal rotation of the hip and adduction recreates the symptoms.
▪ Posteroinferior impingement test(fig b) is performed by having the patient lie supine on the edge of the bed and having the legs hang free from the end of the bed in order to produce maximum hip extension. External rotation with the hip in extension that gives rise to severe, deep-seated groin pain is indicative of posteroinferior impingement



x-rays:


Following X-rays are required ,

1. True AP view of pelvis- A true X-ray is one in which the coccyx points toward the symphysis pubis with a distance of 1 to 2 cm between them
2. Cross table lateral view with hip in 10 deg of Internal Rotation.
3. Dunn View- An anteroposterior radiograph of the hip in neutral rotation, 20deg of abduction, and 90deg of flexion.

Differentiating b/n Cam and Pincer type impingement is important as the treatment varies.

Common Features-Pitt’s pit - Fibrocystic changes at the femoral head-neck junction
seen on X-ray but more clear in CT/MRI scan - 91% specific & positive predictive value of 71%

Features of Pincer Impingement- True AP View of Pelvis , ,
a Retroverted Acetabulum,
1.The Crossover sign- Anterior wall of the acetabulum crossing the posterior
wall.

2. The Posterior Wall sign- Center of the femoral head lying lateral to the
posterior wall.

3. The Ischial Sign- Ischial spine projecting into the pelvic cavity on
the AP pelvic radiograph.

b. Coxa Profunda:

1. The medial wall of the acetabulum lies on or medial to the ilioischial line.

2. Protrusio, which represents the more severe form of coxa profunda, is
diagnosed when the femoral head crosses the ilioischial line.

Features of Cam type Impingement- Cross Table Lateral/ Dunn View,
1. Asphericity of femoral head.

2. Alpha Angle > 50.5 degrees ( The angle between the axis of the neck and
the point where the bone of the head-neck junction crosses outside the
radius of curvature of the head)

3. The Head-Neck Offset Ratio measured by dividing the anterior offset by the femoral head diameter)


Treatment
Non operative Treatment:
▪ NSAIDs, activity modification, restriction of athletic activities

Operative:
Surgical Dislocation of the Hip (Ganz et al)
▪ Involves dislocation of the hip, with preservation of the blood supply to the femoral head, and femoroacetabular osteoplasty
▪ After crossing the obturator externus muscle posteriorly, the MFCA runs anteriorly toward the short rotators and crosses the femoral neck anteriorly to become the retinacular vessels penetrating the femoral neck
▪ Preservation of the short posterior rotators of the hip ensures that the MFCA is not damaged during surgical dislocation of the hip.
▪ Involves a trochanteric flip osteotomy through a lateral incision and a lazy S–shaped capsulotomy
▪ Osteoplasty of the femoral neck is then carried out.
▪ The torn labrum is débrided, and osteotomy is performed of the acetabular rim to remove the chondral lesion
▪ The remaining labrum is reattached using nonabsorbable anchor sutures.


Hip arthroscopy:
▪ Is both diagnostic as well as therapeutic
▪ Maybe useful for simple cam type impingement.
▪ The disadvantage of hip arthroscopy is in the fact that, it is difficult to address posterior labral lesions, inability to guide the extent of resection of the femoral neck prominence and inadequate treatment of an associated chondral lesion

Aneurysmal Bone Cyst

Aneurysmal Bone Cyst
• Nonneoplastic vasocystic tumour
• Age group: 10-20 years old(peak age: 11 years)
• Can occur in any decade of adult life, but nearly 80% occur in the 2nd decade
• Represent 1.5% of all primary bone tumors
• Maybe primary or secondary( arising in other tumours)
• Frequency: distal femur> proximal tibia> proximal humerus> distal radius.
• The vertebrae are involved in 12% to 27% of patients
• Primary ABC maybe neoplastic. Chromosomal rearrangements suggestive of cancer like the USP6 and CDH11 are seen.
• Spontaneous regression may be seen in active primary ABCs. But rare in aggressive or secondary lesions
• May be of hydraulic pressure origin, secondary to haemorrhage and could be traumatically induced.
• Are not true cysts but rather sponge-like collections of interconnected fibrous tissue and blood-filled spaces
• Are destructive lesions and replace bone and thin the cortices of the host bone.
• In the spine, two-thirds of aneurysmal bone cysts will arise from posterior elements and one-third will arise from the vertebral body and present as an aggressive osteolytic lesion with extensive permeative cortical destruction.
• Children with open physes are much more prone to local recurrence (up to 50%)
• Pathological fractures are common and more frequent in humerus and femur


histology and classification

Campanacci’s classification of ABC (1)
1. Aggressive cyst: signs of reparative osteogenesis with ill-defined margins and no periosteal shell.
2. Active cyst: has an incomplete periosteal shell and a defined margin between the lesion and the host bone.
3. Inactive cyst: has a complete periosteal shell and a sclerotic margin between the cyst and the long bone.


Histology:

• Composed of blood filled spaces with intervening fibrous septae. True endothelial cells are not found.
• The tissue is sponge like with cavernous spaces filled with blood.
• Cavities surrounded by gray or brownish tissue with an osseous component
• At the periphery of the lesion is an eggshell-like layer of periosteal bone around the lesion
• Solid variant of ABC consist of fibrous or granular tissue with local haemorrhages and a layer of reactive bone.
• There are skeletal tumours that may demonstrate an aneurysmal component: Giant cell tumour, chondroblastoma, osteoblastoma, chondromyxoid fibroma, fibrous dysplasia, and malignant haemorrhagic osteosarcoma

Imaging
X rays:
– Eccentrically (maybe central also) located lytic lesion, expansile with septations.
– Classically, blown out cortex with egg-shell thin rim of reactive bone
– Sites: metaphysis of long bone, posterior elements of spine, distal phalanx of fingers
– Fluid levels can be seen on MRI /CT scans, which may also be seen with telengiectatic osteosarcoma

CT:
Useful to assess lesions of the pelvis or vertebral column more precisely than radiography
Helps to assess carefully the presence of the periosteal rim of bone around a lesion

MRI
‣ can evaluate soft tissue involvement
‣ On T2-weighted images, the lesions have high signal levels, and layering in the blood (fluid-fluid levels) often can be seen
‣ more accurate assessment than CT or radiography of the extent of an aneurysmal bone cyst

DD
Differential Diagnosis for Holes in Bone: (Mnemonic: FOGMACHINE)
Fibrous dysplasia
Osteoid osteoma, Osteoblastoma,Osteosarcoma, Osteofibrous dysplasia
Giant cell tumor
Myeloma
Aneurysmal bone cyst, adamantinoma
Chondromyxoid fibroma, chondroblastoma, chondrosarcoma
Histiocytosis
Infection
Nonossifying fibroma
Enchondroma, Ewing sarcoma


Treatment
– Augmented curettage and bone grafting.
– Repeated embolisation to reduce the rate of haemorrhagic expansion especially in difficult areas like the pelvis
– Pathologic fractures: require curettage , bone grafting +/- stabilisation
– Pelvic ABCs: spontaneous regression after biopsy has been noted. Consider observation after biopsy. If regression occurs no need for further surgery. If progression occurs, perform curettage
– Spinal ABCs: preoperative selective arterial embolisation, extended intralesional curettage with grafting +/- limited fusion. Embolisation though poses risk of cerebral emboli and also ischemic damage to the cord
– Incompletely resectable, recurrent or aggressive ABCs: low dose radiation(26 to 30 cGy)
– If a patient does have a local recurrence, repeat surgical excision can be performed.
– Selective arterial embolisation as a definitive procedure can be used in locations where a tourniquet cannot be used and control of bleeding can become difficult (e.g., spine, pelvis, and the proximal portions of the extremities)(2)


Ref:
1. Campanacci M, Capanna R, Picci P. Unicameral and aneurysmal bone cysts. Clin Orthop 1986; 204:25-36.
2. Green JA, Bellemore MC, Marsden FW. Embolization in the treatment of aneurysmal bone cysts. J Pediatr Orthop 1997;17(4):440-443.

PROTRUSIO ACETABULI (OTTO PELVIS)

The German pathologist Otto first described Protrusio acetabuli, (also known as ‘arthrokatadysis’,) in 1824. Hence also known as Otto Pelvis

Aetiology:

Idiopathic, or primary protrusio acetabuli: no causative factors are found in this group
· Secondary protrusio acetabuli: The causes are as follows

Infectious
ü Gonococcus
ü Echinococcus
ü Staphylococcus
ü Streptococcus
ü Mycobacterium tuberculosis

Neoplastic
ü Hemangioma
ü Metastatic carcinoma (breast, prostate most common)
ü Neurofibromatosis
ü Radiation-induced osteonecrosis

Inflammatory
ü Rheumatoid arthritis
ü Ankylosing spondylitis
ü Juvenile rheumatoid arthritis
ü Psoriatic arthritis
ü Acute idiopathic chondrolysis
ü Reiter’s syndrome
ü Osteolysis following hip Replacement

Metabolic
ü Paget’s disease
ü Osteogenesis imperfecta
ü Ochronosis
ü Acrodysostosis
ü Osteomalacia (very high incidence –50%)
ü Hyperparathyroidism

Traumatic
ü Sequalae of acetabular fracture
ü Surgical error during hip Replacement

Genetic
ü Trichorhinophalangeal syndrome
ü Stickler syndrome
ü Trisomy 18
ü Ehler-Danlos syndrome
ü Marfan’s syndrome
ü Sickle cell disease

Pathomechanics
.
The typical orientation for the joint reaction force is 69 degrees from horizontal during the stance phase of gait.
.
McCollum et al.. found that protrusio acetabuli occurs at 65 degrees from the horizontal and concluded that the axis of migration was nearly the same as that of the joint-reaction force during stance(1)
.
Eppinger’s theory: the condition is secondary to a chondrodystrophy wherein the three plates of the triradiate cartilage remain unfused, allowing protrusion of the femoral head medially into the pelvis
.
Inflammatory causes lead to destruction and weakening of the bone surrounding the hip with resultant migration along the joint-reaction vector

The deformity may progress until the greater trochanter impinges on the side of the pelvis

An associated varus deformity of the femoral neck is often seen

CF:
-Idiopathic protrusio presents in early adolescence, hence should be kept in the differential diagnosis of hip pain in a teenager
-Common in younger women
-Present with pain and stiffness, rarely with knee pain
-Arising from a seated position is a frequent cause of exacerbation

X-Rays:
.
-The Wiberg’s center-edge angle over 40 degrees is diagnostic of protrusio acetabuli
-Normally on an AP radiograph the medial wall of the acetabulum lies 2 mm lateral to the ilioischial line in a male and 1 mm medial to this line in a female.
-If the medial wall of the acetabulum protruded medial to the ilioischial line (Kohler’s line) by 3 mm in males or 6 mm in females it favours the diagnosis of protrusio.
-May be graded as mild (1 to 5 mm), moderate (6 to 15 mm), or severe (>15 mm), with reference from the ilioischial line.

Treatment:
· In skeletally immature patients, with an open triradiate cartilage: surgical closure of the triradiate cartilage is done. A valgus intertrochanteric osteotomy may be combined

· In adolescent or skeletally mature patients: Valgus intertrochanteric osteotomy (VITO). This lateralises the mechanical axis of the limb. Soft tissue releases of the psoas tendon may be done.

· VITO procedure should not be performed on patients who are over age 40 years or whom have significant degenerative changes visualized on plain radiographs.

Older Adult Patients:
· Total hip Arthroplasty is the treatment of choice

The principles of THA in protrusio acetabuli are:
-Restoration of hip center at its anatomical location for proper joint biomechanics
-The intact peripheral rim of the acetabulum should be used to support the acetabular component
-Cavitary and segmental defects in the medial wall must be reconstructed with bone grafting

Surgical pearls:
-The sciatic nerve will lie near the joint compared to normal patients, and should be routinely identified and protected.
-Trochanteric osteotomy may be required for exposure
-When dislocation is difficult, removal of portion of the posterior acetabular wall maybe required.
-In severe cases, the head is incarcerated into the acetabulum, such cases require osteotomy of the neck at the desired level and removal of the head is facilitated by a corkscrew or rarely as piecemeal.
-The medial wall of the acetabulum is thin or may be partly membranous, and it should not be perforated.
-Medial reaming should be avoided
-Only peripheral reaming should be done to make the acetabular dome to converge
-A protrusio cup is available which avoids medial bone grafting
-If the pelvis is osteoporotic it is better to fix an antiprotrusio cage rather than attempting to press-fit the acetabular component and causing a fracture.


Ref:
1. McCollum DE, Nunley JA, Harrelson JM: Bone-grafting in total hip replacement for acetabular protrusion. J Bone Joint Surg Am 1980;62:1065-1073.
2. Ranawat CS, Zahn MG: Role of bone grafting in correction of protrusion acetabuli by total hip arthroplasty. J Arthroplasty 1986;1:131-137.
3. Van de Velde S, Fillman R, Yandow S. Protrusio acetabuli in Marfan syndrome: indication for surgery in skeletally immature Marfan patients. J Pediatr Orthop. 2005; 25:603-6.
4. Van De Velde S, Fillman R, Yandow S: The aetiology of protrusio acetabuli: literature review from 1824 to 2006. Acta Orthop Belg 2002; 72:524.
6. Dunlop CC, Jones CW, Maffulli N: Protrusio acetabuli. Bull Hosp Jt Dis 2005; 62:105