Avascular necrosis

Avascular necrosis, bones affected, etiology, femoral head blood supply, pathology of AVN, clinical features, clinical signs, radiology and MRI findings, classification, management and complications.

1. Avascular Necrosis Dr. Anshu Sharma Assistant Prof. Dept. of Orthopaedics , GMC&H.

2. Introduction Avascular Necrosis (AVN) of the bone is a pathological process that results from interruption of the blood supply to the bone, either temporary or permanently.

3. Bones commonly Affected: FEMORAL HEAD SCAPHOID TALUS HUMERAL HEAD RADIAL HEAD HUMERAL CAPITELLUM LATERAL FEMORAL CONDYLE

4. AVN OF THE HEAD OF THE FEMUR Death of the bone & bone cells from interruption of blood supply that leads to structural changes in the femoral head ,consequent collapse and secondary Osteoarthritis Also known as Chandler’s Disease/ Coronary disease of Hip. Young Adults 30-50 years. Male : Female--- 4:1 60% => B/L

5. M/c site => Anterolateral aspect (Being principal Wt. bearing portion) Incidence increases with Steroid usage, Alcohol & Trauma. AVN only occurs in FATTY MARROW, which contains a Sparse vascular supply. In contrast to Hematopoietic marrow which has a rich blood supply.

6. Etiology Idiopathic Trauma Alcohol consumption Corticosteroid intake Cushing disease Hemoglobinopathies (SCD; Polycythemia ) Caisson disease ( Dysbaric osteonecrosis ) Cigarette smoking Gout and hyperuricemia Collagen Vascular dis. SLE Hypercoagulable states Hyperlipidemia Organ transplantation Pregnancy Gaucher disease Pancreatitis Neoplasms CRF Hemodialysis HIV

7. VARIATION OF VASCULAR PATTERN WITH THE ADVANCING AGE… Phase 1: at birth Lateral epiphyseal Metaphyseal . Phase 2: infantile(4 month – 4 years) Metaphyseal supply goes on decreasing (as the epiphyseal ossification center becomes enlarged and prominent ) Lateral epiphyseal artery assumes major role. Phase 3: intermediate (4-7 years) Growth plate becomes completely developed and as a “firm barrier” Lateral epiphyseal is the only source of blood supply Phase 4: pre-adolescent(9-10 years) Lateral epiphyseal along with Artery of Ligamentum T eres (that becomes prominent now ) as ….medial epiphyseal artery

8. VARIATION OF VASCULAR PATTERN WITH THE ADVANCING AGE… Phase 5: In adolescent and adults Lateral epiphyseal artery…& Artery of Ligamentum T eres becomes the major source of blood supply WHY PREDILECTION FOR OCCURRENCE OF AVN ENDARTRIOLAR SUPPLY AND LACK OF COLLATERALS RETROGADE BLOOD SUPPLY SMALL DIAMETER VESSELS AT SUB-CHONDRAL REGION MOST OF PART IS COVERED BY ARTICULAR CARTILAGE VASCULAR SINUSOIDS OF MARROW DON’T HAVE ANY ADVENTITIAL LAYER SO EASILY COMPRESSED BY MARROW EDEMA

9. CLINICAL FEATURES: No distinguishing Clinical Features/ High index of suspicion Asymptomatic Pain gradual & insidious in nature Range Of Motion (ROM) ; patient may walk with a limp. Radiographic findings may appear after a delay of several months to years following the onset of symptoms.

10. PAIN OF AVN : Focal over the groin / hip or it may radiate to the buttocks, anteromedial thigh or knee. Induced mechanically by standing & walking & may be eased by rest. May be very intense, throbbing, deep & often intermittent. Worsened by coughing & at night. 40% of patients have night pain asso . with morning stiffness.

11. Characteristics of Pain: ROM may be diminished, especially after collapse of the femoral head. ROM may be limited, especially in flexion, abduction & internal rotation. Gait :- Patients may walk with a limp. The Trendelenburg sign may be Positive. To be diagnosed at an early stage, high index of suspicion, especially true with U/L involvement because of the high risk of the dev. of AVN in the C/L Hip

12. PATHOPHYSIOLOGY: Intravascular Extraosseous : Arterial Intraosseous : Arterial Venous Extravascular Extraosseous factor ( Capsular factors) Intraosseous factors

13. Extraosseous Vascular Factors Arterial Factors Most important Femoral Head blood supply is an End-Organ System with poor collateral development. Trauma to the hip may l/t contusion or mechanical interruption to the Lateral Retinacular Vessels (main blood supply of the femoral head & neck ). Trauma , vasculitis ( Raynauds ds), vasospasm (decompression sickness ).

14. Intraosseous Vascular Factors Arterial Factors Circulating micro-emboli that block the microcirculation of the femoral head In Conditions like- Fat emboli (hyperlipidemia associated with alcoholism) S teroid therapy SCD N itrogen bubbles in decompression sickness

15. Intraosseous Vascular Factors Venous Factors Enlargement of intramedullary fat cells or fat-loading osteocytes causes the cells to expand; this may be the most significant factor l/t obstruction of venous drainage. Reducing venous outflow & causing stasis Caisson disease & SCD .

16. Extravascular Factors Intraosseous Factors Steroid Hypertrophy of Fat cells Gaucher cells & Inflammatory cells Encroach on intraosseous capillaries Intramedullary circulation Compartment syndrome Alcohol & Steroid Direct toxic metabolic effect on osteogenic cells

17. Extravascular Factors Capsular Factors Trauma, Infection & Arthritis Effusions within the Hip joint

18. IMAGING MODALITIES : X- RAY Normal Demineralization, osteopenia & osteoporosis Mottling & sclerosis..cystic changes Crescent sign ….sub- chondral fractures…..collapse Flattening of the femoral head Joint space narrowing Osteophytes formation with acetabular involvement Secondary osteoarthritis of the hip joint

19. RADIOLOGICAL IMAGES

20. CT SCAN IN AVN : LOSS OF ASTERIK SIGN & SUBCHONDRAL FRACTURE

21. IMAGING MODALITIES: SCINTIGRAPHY Focal increase in the uptake

22. IMAGING MODALITIES : MRI MRI is most sensitive modality in detection of AVN. It is also useful in differentiating AVN from non-AVN disease of femoral head. MRI also effective in assessing joint effusion, marrow conversion , marrow edema, articular cartilage congruity. Classic Findings :- look for focal lesion in the antero -superior portion of femoral head that is well demarcated but is inhomogeneous. T1 images => low signal intensity. T2 images => double line sign => classic sign of AVN, made up of 2 concentric low and high signal bands.

23. T1 shows hypointense signals in bilateral femoral heads (Right>Left ) T2 shows hyperintense ring like areas

24. CLASSIFICATION AND STAGING 1960s –3 stage staging system 1970s – 4 th stage added Hungerford and lennox : – added stage 0 Most widely used…… PAUL FICAT & ARLET

25. FICAT & ARLET CLASSIFICATION

26. STERNBERG ET.AL(1995) Modified Ficat & Arlet Classification STAGE 0: NORMAL X-RAY ; NORMAL BONE SCAN ; NORMAL MRI STAGE 1: NORMAL X RAY ; ABNORMAL –BONE SCAN & MRI A : <15% B : 15-30% C :>30% STAGE 2: ABNORMAL X-RAY; BONE SCAN & MRI A : <15% B : 15-30% C :>30% STAGE 3: SUBCHONDRAL COLLAPSE PRODUCING CRESCENT SIGN A : <15% B : 15-30% C :>30%

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28. Crescent sign(shown with arrow) is the earliest indicator of mechanical failure from accumulated stress fractures of non repaired trabeculae .

29. ARCO SYSTEM (ASSOCIATION REASERCH CIRCULATION OSSEOUS) .

30. TREATMENT AIM TO KEEP THE JOINT FROM BREAKING DOWN. Preserve rather than Replacing Femoral Head & Cartilage. Early Intervention has favorable impact on the disease prognosis irrespective of T/t modality used.

31. PROTECTED WEIGHT BEARING Protect the involved area from excessive stress by using some form of limited weight bearing. Canes or even crutches are frequently prescribed Don’t alter the natural course of the disorder INDICATIONS:-  Alternative to surgical management  Small, Asymptomatic lesions  Low weight bearing area, such as the medial aspect of the femoral head  Poor medical condition  Following certain types of surgical procedures, such as core decompression, grafting, and osteotomies (used as an adjunct)  Most important role : relatively advanced stages of osteonecrosis . Cane or Crutches can diminish symptoms and improve function considerably until such time as a reconstructive procedure is indicated

32. Non Surgical management

33. Hyperbaric oxygen (HBO ) HBO improves oxygenation, reduces oedema & induces angioneogenesis , a reduction in intra osseous pressure & improvement in microcirculation Reis et al, 24 involving 16 hips in 12 patients, all with Steinberg Stage 1 disease, gave each patient 100 consecutive days of HBO, which involved breathing 100 % oxygen via a maskat 2-2.4 atmospheres pressure for 90 minutes They reported that 13 of the 16 femoral heads subsequently appeared normal on MRI after this T/t

34. Electric, Electromagnetic & Acoustic T/t Pulsed Electromagnetic Field stimulation, is reported to be useful for treatment of osteonecrosis in 4 reports. Mechanisms Of Action:- -Local control of inflammation -Enhances repair activity & healing process by stimulating neovascularisation & new bone formation.

35. Extracorporeal Shockwave Therapy There are only 2 papers in Pubmed . The only study is by Wang et al who compared the results of such therapy in 23 patients (29 hips) with the results in a group treated with non- vascularized fibular grafting. At a mean of 25 months, 79% of the shock-wave group had improved Harris Hip Scores compared with 29% of the group treated with non- vascularized fibular grafting.

36. OPERATIVE MANAGEMENT JOINT PRESERVING PROCEDURES A) CORE DECOMPRESSION B ) BONE GRAFTING C) OSTEOTOMIES JOINT REPLACING PROCEDURES A) HIP RESURFACING PROCEDURE B ) HIP REPLACEMENT OTHERS A ) POROUS TANTALUM ROD B) ENDOPROSTHESIS C) RESECTION ARTHROPLASTY D) ARTHRODESIS

37. CORE DECOMPRESSION (FORAGE) A) AS ISOLATED PROCEDURE B) WITH ADJUVENTS : PEMF : BMP : DBM C) WITH BONE GRAFTING( Originally by PHEMISTER) : CANCELLOUS( BY FICAT) : CORTICAL( cortical strut/ vascularised fibula) :MPBG :OSTEOCHONDRAL

38. Indications Core decompression is effective for symptomatic relief in nearly all stages in all patients who present with a painful hip secondary to ON d/t decrease of intramedullary pressure done by it. Transient symptomatic relief in an advanced stage & in already collapsing or when collapse is impending. It is Most Effective in Stage I & II lesions that are size A (15% of head affected) & B (15%–30% of head affected ). The larger the lesion, the less likely the patient is to have a successful outcome.

39. Rationally…..for CD BIOLOGICAL CHANGES : 1. Decreases intra- ossous pressure 2. Revascularization through channel l 3. Prevention of additional ischaemic events MECHANICAL CHANGES: 1. Removal of the necrotic bone & thus removing obstruction to revascularisation

40. Standard Technique & its Variations Ficat & Arlet proposed creating an 8 to 10 mm diameter core track & this became a “standard” . Recently some authors have suggested that the same effect of standard core can be achieved by producing Multiple Smaller Core Tracks of 3-mm dia range. This can be done percutaneously & theoretically # risk & shortens the operative time & morbidity. Steinberg et al proposed making Smaller Angled Core Tracks into the Necrotic Segment from the Central Core Canal.

41. Postoperative Management:- The lateral cortical window produces a stress riser in the proximal femur So Protect the patient from unprotected weightbearing for the first 6 weeks. Reported incidence of # with core decompression is <1% & has almost always been associated with either a fall or failure to use protective devices (crutches or a walker) in the first 6 week.

42. BONE GRAFTING (TECHNIQUES) Bone grafting procedures are a group of joint preserving techniques that involve the removal of the diseased femoral head segment, f/b its replacement with 1 or more of a variety of bone graft options. M ost valuable in treating patients with Stage I & II disease.

43. Techniques 1.Grafting Through Lateral Core Track 2.Grafting Through Femoral Neck Window 3.Grafting Through Articular Surface Window

44. LATERAL CORE TRACK TECHNIQUE PEARLS: - Simple technique -Minimal Invasiveness -Avoidance of surgical dislocation of the hip. PITFALLS: Inability to directly visualize the joint surfaces - Inexact nature of removing diseased bone & replacing it with bone graft under fluoroscopic guidance - Risk of postoperative #

45. FEMORAL NECK WINDOW ( LIGHTBULB TECHNIQUE) - Watson-Jones or Smith-Peterson approach is used -A window is created to expose the anterio femoral neck , at the level of the junction of the femoral head & neck - When Combined with a Bone Grafting procedure, refered as the “ light bulb” procedure. - Advantage is the improved access to the necrotic femoral head segment & the avoidance of direct iatrogenic cartilage damage. - Disadvantage is the creation of a cortical defect in the femoral neck, which raises the risk of fracture

46. ARTICULAR SURFACE WINDOW (TRAPDOOR TECHNIQUE) With this method, the hip is surgically dislocated using a technique aimed at preserving the blood supply to the femoral head & neck. Once exposed, a “trapdoor” window is made in the femoral head cartilage to access the diseased subchondral bone. When combined with a bone grafting procedure, refered as the “Trapdoor” Procedure. Advantage : Exposure allows a direct evaluation of the cartilage surface & underlying diseased femoral head segment & allows for precise bone graft placement. Disadvantage : Demanding technique, Iatrogenic cartilage damage & osteonecrosis Surgical dislocation

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49. BONE GRAFT (TYPES) 1. NONVASCULARISED (FIBULA STRUT) Nonvascularized cortical bone grafts are typically prepared as several struts that provide structural support under the articular surface within the evacuated segment This construct is often augmented with cancellous bone graft in an effort to improve its osteoconductive and/or osteoinductive properties

50. 2 . VASCULARISED Grafts: ( MPBG) 1.Local pedicled grafts, which do not require microvascular reanastomosis . E g:Muscle P edicle B one G rafts Vascularized Pedicle Bone G rafts 2. Free vascularized grafts, which require a microvascular reanastomosis . E g : Free Vascularized F ibula G raft

51. PROXIMAL FEMORAL OSTEOTOMIES The main rationale proposed for the efficacy of osteotomies is the biomechanical effect of moving the collapsed/necrotic segment of the femoral head from the principal weight-bearing area of the hip to an area that bears less/no direct weight and to allow weight-bearing contact to now happen in an area of relatively normal bone and cartilage. Categories:- VALGUS or VARUS osteotomies usually combined with FLEXION or EXTENSION. Trans-trochanteric rotational osteotomies– ANTERIOR or POSTERIOR.

52. VALGUS OSTEOTOMY WITH FLEXION W hen the necrotic segment is located in the anterosuperior part of the femoral head with less than 20% posterior involvement. Optimal patient population would be those that are less than 45 years of age and are not on steroids or chemotherapy.

53. VARUS OSTEOTOMY WITH FLEXION (OR EXTENSION) 1. CURVED: ( Merle D’ Aubigne type) 2. MEDIAL DISPLACEMENT : ( Mc Murray type) 3 . ANGULATION ( Pauwel’s ‘1’ type)

54. TRANSTROCHANTERIC ROTATIONAL OSTEOTOMY ( SUGIOKA ) ANTERIOR Transposition of the necrotic focus to the ant. & inf. part of the femoral head away from the weight-bearing area as a result of the ant. rotation of the head. -PREVENTS PROGRESSIVE COLLAPSE OF ARTICULAR SURFACE -TO IMPROVE CONGRUITY OF JOINT REPOSITION THE NECROTIC ANT,SUP PART OF HEAD TO ANON- WT BEARING AREA -HEAD AND NECK SEGMENT ROTATED ANT.LY AROUND ITS LONG AXIS WT BEARING IS TRANSMITTED TO THE POST ARTICULAR SURFACE.

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56. Arthroplasty Resurfacing Arthroplasty Unipolar and Bipolar Arthroplasty Total hip replacement

57. Resurfacing Arthroplasty Femoral & Acetabular Surface Replacement & Hemi-Surface Replacement for Osteonecrosis of the Hip. > 30% femoral head involvement Little Bone sacrifice

58. TOTAL HIP ARTHROPLASTY F or advanced osteonecrosis of the hip. Excellent pain relief & functional improvements.

59. POROUS TANTALUM ROD A novel approach in T/t of stage I & II P recollapse osteonecrosis . This rod functions analogously to a Cortical Strut Graft allowing structural & osteoconductive properties.

60. Acrylic Cement Injection Debriding the necrotic zone then elevating & supporting the collapsed segment by the injection of cement. Wood and coworkers reported on very preliminary results 21 of 20 cases. All patients realized immediate pain relief with improved hip scores , with 3 patients undergoing early conversion to total hip arthroplasty . Relatively invasive but may have the advantage of maintaining femoral head congruity. Long-term results with perhaps a randomized controlled series will be necessary if this is a viable alternative to reconstructive surgery.

61. Arthrodesis Mostly a salvage procedure in contemporary orthopedics. In the patient with significant pain & disability & in whom nonsurgical T/t has failed with contraindication to prosthetic replacement. Clinical success can be achieved as it may relieve hip pain. The recommended position is 0° to 5° of adduction, 25° to 30 ° of flexion & 0° to 15° of external rotation.

62. Resection Arthroplasty T/t of last resort Provides pain free mobile but unstable hip. Complete resection of the head & neck of the femur Can achieve a good range of pain-free motion & will be able to function reasonably well for most activities of daily living. The use of a shoe lift is generally necessary as a result of the shortening of the extremity, which averages approximately 1.5 inches. There will be a noticeable abductor lurch & patients will require some form of assistive device for ambulation. Indication :- patient with severe pain and disability who is not a suitable candidate for reconstruction.

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