Saturday, January 30, 2010

Pigmented villonodular synovitis


• Pigmented villonodular synovitis (PVNS) is a slow growing lesion of uncertain etiology arising from the synovial membrane, characterized by villous and nodular overgrowths of the synovial membrane of the bursa or the tendon sheath.
• The appendicular skeleton, especially large joints such as the knee and hip joints are frequently involved.
Synonyms: Until Jaffe in 1941 proposed the term pigmented villonodular synovitis this condition has been known as synovial xanthoma, synovial endothelioma/ fibroendothelioma, Benign fibrous histiocytoma, xanthomatous GCT, Myeloplaxoma, fibrohemosideric sarcoma , Sarcoma fusigigantocellulare.

• 1852: 1st described as neoplastic process due to unrelenting growth pattern, by Chassaignac, eroding surrounding bone and joint tissue, & high recurrence rate post-resection.
• 1865: Simon described a focal form of PVNS
• 1909: Moser described a diffuse PVNS
• 1941: 1st reported & coined by Jaffe et al. as synovitis, shifting from neoplastic to inflammatory foci.

• Age: 3rd-4th decades of life, rare in children
• Sex: no sex based predilection
• Incidence: 1.8 per million population
• no predilection for any laterality

• repetitive trauma (50%) causing recurrent local hemorrhage to affected joint (cf:hemophilics show progressive erosive arthropathies).
• proliferation of the synovium of joints, tendon sheaths or bursae.
• It is a reactive condition, and not a true neoplasm.
• PVNS classically presents as a monoarticular disease, mimicking arthritis.
• Recurrent atraumatic haemarthrosis is a characteristic feature.
• Often aggressive, with marked extra-articular extension.


Monoarticular involvement (most common), occurs in two forms: localized and diffuse.
Two variants as described by Granowitz -

a. Localized form (LPVNS): focal involvement of the synovium
- Nodular / Sessile or Pedunculated masses.
- Hands & feet
b. Diffuse form (DPVNS) (more common): affects virtually the entire synovium, eg.
- Intra-articular PVNS tends to be of the diffuse form.
- Tendon sheath PVNS (Giant cell tumour of tendon sheath[GCCTS]), the nodular form.

• MC site: knee joint, followed by the hip and shoulder.
• Knee:
- anterior compartment common
- mostly at meniscocapsular junction
- synovium in the region of the anterior horn of the medial meniscus is the most common site
- infrapatellar fat pad, suprapatellar pouch, intercondylar notch, anterior horn of the lateral meniscus, and the medial and lateral recesses of the knee have been reported.
• Uncommon : elbow, ankle, shoulder, foot, wrist
• Rare : spine, cervical involvement commoner than thoracic and lumbar

Clinical features:
o Pain (80%)
o Swelling(76%)
o Reduced range of movement(52%)
o Locking(16%)
o Instability/palpable mass(12%)

Type specific features:
- if untreated, causes continuous pain and discomfort, limiting ADLs
- at knee often present with signs and symptoms of meniscal pathology (locking, catching, and instability)
- episodic character of joint effusion—the patient may have completely symptom-free periods between exacerbations

- Slow, insidious onset of pain, swelling, and
- stiffness in the involved joint
- most or all joints involved
- swelling and pain more pronounced
- decreased range of motion of the affected joint
- poorly localized
- with sometimes extra-articular extension, either primary or recurrent.
- may encroach on major neurovascular structures.
- Osteoarthritis- continued inflammation and joint erosions lead to articular cartilage destruction, may finally need total joint arthroplasty.

Aspiration of joint: characteristically reveals a blood tinged brownish-stained aspirate.

• Soft tissue swelling will be marked due to haemorrhage and lobulated synovial tissue.
• May reveal cysts or erosions in the joint mimicking gout.
• Bony erosions are usually from without, especially in the hip
• periarticular erosions, with a thin rim of reactive bone
• Osteoporosis is characteristically absent
• Can affect the epiphysis
• Reciprocal bony lesions on opposite sides of the joint, despite articular preservation, are highly suggestive of PVNS
• Late feature of joint space narrowing indicates articular cartilage loss, is difficult to distinguish from primary OA.

• ideal investigation
• nodular mass (periarticular or synovial) with bone erosion
• MRI is invaluable in early diagnosis and evaluating extent. Nodular synovial masses -low signal on T1/T2 sequences
• “dark on dark” on T1- and T2-weighted images

• Loculated joint effusions, Complex heterogeneous echogenic masses and markedly thickened synovium

• direct visualisation of synovium
• Has both diagnostic and therapeutic value in resection of tumours
• Normal arthroscopic findings however does not exclude PVNS (Klompmaker et al)

• Synovium looks like a “shaggy carpet”.
• LPVNS is pedunculated, lobular lesion localized to one area of the synovium.
• On microscopy, Histiocytes, lipid laden macrophages, hemosiderin containing cells and frequent giant cells are seen.
• Subsynovial nodular proliferation of large round, polyhedral or spindle cells with prominent cytoplasm and pale nuclei.

Differential diagnosis
• Hemophiliac lobular synovitis (↑hemosiderin deposition, lacks lipidladen histiocytes and giant cells, which is classic indications of PVNS)
• Osteoarthritis
• Rheumatoid arthritis,
• Meniscal tear, or other ligamentous injury

• Synovectomy:
o Total synovectomy (open or arthroscopic):
- Open (anterior approach midline incision or medial parapatellar arthrotomy) for the diffuse form for the intraarticular component
- Arthroscopic synovectomy, has gained popularity, has several advantages over the open technique, preferred for LPVNS, shows higher recurrence in DPVNS.
- The standard anterior portals are not effective, whereas the accessory posterior portals are necessary
to accomplish total posterior synovectomy
o Vascular or neurologic injury may occur during this procedure, especially if there is posterior extra-articular
extension of the lesion or fibrosis after irradiation. Open synovectomy should be preferred in such cases
o Open posterior synovectomy (“lazy S-shaped” incision): done subsequently for extensions into the popliteal fossa.
• Local excision: for the nodular form (recurrence rare).
• Radiotherapy (3500- 4000 cGy) (Radiation induced synovectomy/ intra-articular radiation synovectomy using yttrium Y-90) has been used in the management of recurrences with varying success; side effect is soft tissue radionecrosis
• Advanced cases with secondary arthritis should be addressed with arthroplasty plus extensive synovectomy to decrease recurrence.

• LPVNS: excellent prognosis, low recurrence rate if managed surgically, recurrence 8%.
• DPVNS: surgical excision difficult, recurrence rate of up to 46%.
• The debate continutes: malignant or inflammatory-
- Rare reports describe malignant transformation and metastasis, (presence of trisomy 7 and clonal DNA rearrangements reported).
- Bertoni et al reported eight patients with malignant PVNS; mortality rate was 50%.
- Oehler et al found strong support for its being a chronic inflammatory process and not noeplastic.
- Currently, data are inconclusive to prove PVNS as either malignant or inflammatory process.
- It shows neither cellular atypia nor abnormal mitosis, recent cytogenetic studies say that pathogenesis remains unresolved.

1. Jaffe HL, Lichtenstein L, Sutro CJ. Pigmented villonodular synovitis, bursitis and tenosynovitis. Arch Pathol 1941;31:731–65.
2. Granowitz SP, D’Antonio J, Mankin HL. The pathogenesis and long-term end results of pigmented villonodular synovitis. Clin Orthop Relat Res 1976;114:335–51.
3. Oehler S, Fassbender HG, Neureiter D, Meyer-Scholten C, Kirchner T, Aigner T: Cell populations involved in pigmented villonodular synovitis of the knee. J Rheumatol 2000;27: 463-470.
4. Bertoni F, Unni KK, Beabout JW, Sim FH: Malignant giant cell tumor of the tendon sheaths and joints (malignant
pigmented villonodular synovitis). Am J Surg Pathol 1997;21:153-163.

Sunday, January 17, 2010

Osteoid Osteoma

Osteoid Osteoma

 Most commonly involves the diaphysis of long bones especially femur and tibia, and the proximal femur is the most common site.
 50% of tumours involve the lower extremity
 Osteoid osteoma may have a unique ‘pathogenic’ nerve supply
 Three types have been described: Intracortical (80%), cancellous and subperiosteal
 The pain may be referred to an adjacent joint and when the lesion is intracapsular it may simulate arthritis with effusions ,spasms and contractures
 Occasionally pain precedes the appearance of radiographic changes, and leads to multiple incorrect diagnoses including neurosis
 In the spine, posterior elements of the lumbar spine is most commonly involved (next common thoracic spine). An associated scoliosis is often present
 If the nidus is in proximity to a nerve root, root irritation can develop.
 In the lumbar spine, this pain can present as sciatica and suggest the diagnosis of a herniated intervertebral disc
 Torticollis may be seen if the cervical spine is involved.
 Aspirin or nonsteroidal anti-inflammatory agents relieves pain secondary to a high concentration of prostaglandins in the nidus

• There is a distinct demarcation between the nidus and the reactive bone
• The nidus consists of an interlacing network of osteoid trabeculae with variable mineralisation.
• The trabecular organization is haphazard and the greatest degree of mineralisation is in the centre of the lesion

• X rays: Central lytic nidus with extensive reactive sclerosis. The nidus is always less than 1.5 cm although the area of the reactive bone sclerosis may be larger.
• The radiolucent nidus may be obscured by dense sclerotic bone
• When the lesion is intramedullary there is less sclerotic bone
• CT scan is the investigation of choice
• Double density sign on bone scan (Focal areas of increased uptake with a second smaller area of increased uptake)
• MRI scans will show extensive edema, which may be confused with a marrow-replacing neoplasm and is therefore not recommended if osteoid osteoma is the suspected lesion

Bone island (enostoses):
‣ Mimic osteoid osteoma on X-rays but MRI changes are different from an Osteoid osteoma.

Treatment: If surgery is undertaken, it is important to eradicate the entire symptomatic nidus.
 Removal of a large amount of the surrounding sclerotic bone should be avoided because it can severely weaken the bone and may result in a pathologic fracture
 Intralesional resection by simple curettage of the nidus followed by high-speed burring is done often (Burr down technique).
 Intraoperative localization of the lesion may be done by technetium labeled methylene diphosphonate and detection by a Geiger counter
 If block excision is performed, intraoperative roentgenograms of the specimen are advised to document complete removal of the nidus
 CT-guided percutaneous resection for small tumours is becoming popular.
 Percutaneous Radiofrequency ablation is being tried. Under CT Guidance a radiofrequency probe is placed into the lesion and the nidus is heated upto 80degree C. This induces ionic agitation and frictional heat to cause tumor necrosis
 The patient may be also treated nonoperatively using NSAIDS. About 50% of the patients treated with NSAIDs will have their lesions burnt out with no further medical or surgical treatment necessary

1. Cantwell CP et al: Current trends in treatment of osteoid osteoma with an emphasis on radiofrequency ablation. Eur Radiol 2004; 14(4):607.

Wednesday, January 6, 2010

Metal on Metal Bearing in Hip Arthroplasty

Metal on Metal (MoM)

- Are associated with decreased wear rate compared to conventional polyethylene
- Mixed film lubrication appears to be the operative mechanism in most metal-on-metal hip joints
- With metal-on-metal bearings, in contrast to polyethylene bearings, a larger-diameter bearing actually produces lower wear rates than does a smaller-diameter bearing
- Larger-diameter bearings have a greater arc of motion(and thus better ROM), which decreases the risk of impingement and also lessens the incidence of dislocation
- Alloys of cobalt (Co) and chromium (Cr) have been preferred for MOM bearings in THR because of their hardness.
- High chromium content provides good corrosion resistance
- There are two types of wear particles with MoM bearings: Co-Cr-Mo particles and chromium oxide particles
- It has been hypothesized that the Co-Cr-Mo particles are produced by the wear of the carbides on the bearing surfaces and the prosthesis matrix, and that the chromium oxide particles come from the passivation layer on the implant surface and possibly from oxidized chromium carbides

Metal hypersensitivity:
- all metals in a biological environment corrode; the ions released can combine with proteins and activate the immune system as antigens and elicit hypersensitivity responses
- the incidence of hypersensitivity is approximately 2 per 10,000
- are generally delayed cell-mediated responses
- ALVAL: are Lymphocytic infiltrations in the subsurface layer of the lining tissues, which were either diffuse or aggregated around small postcapillary vessels
- delayed type hypersensitivity should be considered when a patient with a well-fixed implant experiences chronic, aching pain with evidence of synovitis (an irritable range of motion) but has no objective evidence of infection
- If a modular MOM bearing is being considered, the use of substrates without Co-Cr (e.g., titanium) will allow revision of only the bearings in cases were hypersensitivity develops

What is New in Hip Resurfacing(Metal on Metal)?

-S. Glyn-Jones and H. Pandit reported in Dec 2009 JBJS B that incidence of ALVAL is higher in women especially if performed under 40 years of age.

-Factors significantly associated with an increase in revision rate were female gender, age under 40, dysplasia and small components.

-the higher revision rates in women could be due to increased prevalence of allergy in women because of wearing jewellery, increased ROM, which would be more likely to cause impingement, edge loading or different gait patterns