Structured Oral Hip Examination Question 7

Structured Oral Hip Examination Question 7

EXAMINER: This is a radiograph of a 68-year-old woman who has been referred up to the orthopaedic clinic by the physiotherapist-led musculoskeletal clinic with an 18-month history of left hip pain and difficulty walking. (Figure 2.12.)

CANDIDATE: This is an anteroposterior (AP) radiograph of the pelvis demonstrating a coarsened trabecular pattern of the left hip, a thickened left cortex compared with the opposite hip, and increased density of the left hip compared with the right side. Both iliopectineal (Brim sign) and ilioischiatic lines are thickened. There is sclerosis involving the left pelvis (ileum, ischium and pubic rami), left femur and lower lumbar spine. The radiograph is highly suspicious of Paget’s disease.

Differential diagnosis would include other causes of increased and disorganized bone turnover such as sclerotic bony metastasis (prostatic carcinoma), renal osteodystrophy, fibrous dysplasia, multiple myeloma, lymphoma, osteopetrosis and hyperparathyroidism.

EXAMINER: What is Paget’s disease?

CANDIDATE: Paget’s disease is a metabolic bone disorder of unknown aetiology characterized by a disorganized increase in osteoclastic bone resorption and compensatory osteoblastic new bone formation. There is accelerated but chaotic bone remodelling in which the bone is biomechanically weak and prone to deformity and fracture.

The disease can be divided into three major phases, lytic, mixed lytic/sclerotic and sclerotic, each of which is

Figure 2.12 Anteroposterior (AP) radiograph demonstrating Paget’s disease of the left hemipelvis.

associated with distinctive clinical, radiological and pathological features.

EXAMINER: What causes Paget’s disease? What is the pathophysiology of Paget’s disease?

CANDIDATE: The primary abnormality of Paget’s disease is an intense focal resorption of normal bone by abnormal osteoclasts. These osteoclasts are abnormal in size, activity and quantity. The abnormal osteoclasts make large resorption cavities in the bone matrix. In response to the osteoclast resorption, osteoblasts are recruited, resulting in bone formation. The osteoblast activity is rapid such that the newly formed bone is not organized and remains irregular and woven in nature, less resistant and more elastic than typical lamellar bone; prone to deformity and fracture.

EXAMINER: What are the other radiographic features of Paget’s disease?

CANDIDATE: Radiographic features of Paget’s include:  Advanced disease in the long bones is characterized by coarsened trabecula, bony sclerosis, bony enlargement and deformity. A ‘candle flame’ or ‘blade of grass’ sign represents a wedge- or V-shaped pattern of advancing lysis in the diaphysis of long bones. The femur develops a lateral curvature whilst the tibia develops an anterior curvature that may result in fracture. Fine cracks may appear (stress fractures) which resemble Looser zones but occur on the convex bone surface.

 Lateral radiographs of the lumbar spine demonstrate a ‘picture-frame’ vertebral body that is secondary to severe osteoporosis centrally and a thickened, sclerotic cortex.

 The skull is involved in 29–65% of cases. Inner and outer table involvement leads to diploic widening. Osteoporosis circumscripta is a well-defined lysis, most commonly involving the frontal bone, producing well-defined geographic lytic lesions in the skull. It is seen in the early or lytic phase, when osteoclastic resorption overwhelms bone production. At a later stage a ‘cotton wool appearance’ represents mixed lytic and blastic pattern of thickened calvarium.

 Protrusio deformity of the pelvis is a common occurrence with advanced Paget’s disease.

EXAMINER: What are the current theories regarding the aetiology of Paget’s disease?

CANDIDATE: The aetiology of Paget’s disease is still unknown. Proposed theories include viral, genetic and environmental causes. Paramyxoviruses such as measles virus, respiratory syncytial virus, and canine distemper virus have been implicated. Electron microscopy has shown virus-like structures that resemble the paramyxovirus in osteoclast nuclei and cytoplasm of cells affected by Paget’s disease. However, more recent studies have been unable to confirm the presence of specific viral antibodies in patients with Paget’s disease. Environmental factors implicated include high levels of arsenic and an uncertain association with cats and dogs. Genetically 5–40% of patients have first-degree relatives with the disease.

EXAMINER: That’s fine. I am however a bit sceptical about the cats and dogs theory. Moving on – what are the complications of Paget’s disease?

CANDIDATE: Complications of Paget’s disease include:  Compression fractures of the vertebral body (commonest complication of spinal Paget’s).

 Pagetic spinal stenosis, defined as compression of the spinal cord, cauda equina or spinal nerves by expanded pagetic bony tissue of the spine. Most common in the lumbar region and typically single level causing cord or nerve root compression.

 An enlarged and deformed skull can lead to increased intracranial pressure, hydrocephalus or cranial nerve deficits such as facial palsy (narrowing of neural foramina), hearing loss or blindness (pressure on optic nerve).

 High cardiac output secondary to increased bone vascularity

(rare).

 Insufficiency fractures.

 Osteosarcoma, chondrosarcoma, malignant fibrous histiocytoma and giant cell tumours all have been reported with Paget’s disease.

EXAMINER: What are the indications for THA in Paget’s disease?

CANDIDATE: The indications are similar to non-Pagetoid disease. It is important to make sure that the pain is arising from the joint surface and not the bone. Bone pain with active Paget’s is suggested by an increased alkaline phosphatase value. It is also important to exclude insufficiency fractures, neurological compression in the spine or Paget’s sarcoma as a cause of pain.

EXAMINER: How do you assess disease activity?

CANDIDATE: Patients with active Paget’s disease have a raised alkaline phosphatase (AlkPhos) and urine hydroxyproline values. The higher the level the more active the disease is. Patients with very high AlkPhos levels are thought to be at higher risk of bleeding and heterotrophic ossification formation.

EXAMINER: If the Paget’s disease is active what will you do?

CANDIDATE: I would make a referral to one of my rheumatoid colleagues for a Pamidronate (Aredia) injection. This is a bisphosphonate, which is a potent inhibitor of osteoclastic activity, and hence bone resorption. This reduces bone vascularity and bleeding and possibly the incidence of heterotopic ossification.

EXAMINER: What are the technical issues of performing THA in

Paget’s disease?

CANDIDATE: There is tendency for excessive bleeding at surgery due to increased vascularity. Blood should ideally be crossmatched or at the least available from a group and save within 10 minutes. Bone can be very hard and sclerotic making it difficult to ream and broach. Burrs may be needed to enter the bone prior to reaming and/or broaching. Varus deformity of the proximal end of the femur predisposes to varus placement of the femoral component.

Protrusio as we have mentioned is a common finding and I would consider using bone graft medially to compensate. Some surgeons use lateral offset liners and antiprotrusio cages although this complicates surgery.

As Paget’s bone is brittle there is a higher risk of both intraoperative and postoperative fracture.

There is some controversy as to whether there is an increased risk of heterotopic ossification occurring from the abnormalities of osteogenic differentiation in Paget’s disease patients. Some surgeons routinely give prophylaxis to reduce

the risk of HO. [Candidate score 6]

EXAMINER: There is a bit more than that when planning THA.

CANDIDATE: As bone pain is common in Paget’s disease and does not necessarily improve with THA a diagnostic local anaesthetic injection to rule out concurrent bone pathology may be indicated. It is also important to exclude referred pain from spinal stenosis or radiculopathy and other causes of musculoskeletal pain.

Good quality, full-length radiographs to assess the degree of deformity and the extent of bone involvement.

Radiographs should be scrutinized for the presence of a stress fracture that could account for hip pain. The fractures may be in the region of the femoral neck, intertrochanteric area or femoral shaft. They usually present as incomplete or fissure fractures on the tension side of the bone. Unrelenting hip pain and radiographic bone destruction suggest sarcomatous change.

Consider using cell salvage, hypotensive anaesthesia and predonation of autologous blood if intraoperative blood loss is anticipated to be high with active disease. Concurrent osteotomy may be needed if component alignment is difficult. Marked protrusio can make hip dislocation very difficult.

EXAMINER: You mentioned osteotomy, how often do you perform osteotomy when you perform THA for Paget’s disease?

CANDIDATE: In the majority of patients with Paget’s THA can be performed without need for osteotomy. However, if deformity is severe, precluding implantation with a standard stem, then planning for reduction osteotomy to correct the deformity and/or the use of modular stems must be made preoperatively.

EXAMINER: What type of hip replacement would you use?

CANDIDATE: Although there has been a trend in recent years to use uncemented components in Paget’s disease in this patient I would use a cemented THA. She is 68 and has Paget’s disease and I think it is a reasonable option in this situation. If the patient is younger then the choice becomes more controversial. Although previous studies have recommended the use of cement in the last 20 years there has been a trend to use uncemented components. The worry that the altered morphology of pagetoid bone adversely influences ingrowth into cementless implants has not been borne out in practice. The biology of bone ingrowth for initial fixation of uncemented components depends, in part, on the ability of bone to proceed through the early phase of fracture healing.

Patients with Paget’s disease are not known to have compromised ability for fracture healing and these patients progress through the biological process of fracture healing at normal speed.

Parvizi et al. reported on 21 cementless THA implanted against pagetoid bone; all were stable and demonstrated radiographic evidence of ingrowth at 7-year follow-up.¹ Lusty et al. from Sydney, Australia reported medium-term results of 23 uncemented THA at 6.7-year follow-up.² There were three revisions, one stem for aseptic loosening and two stems after periprosthetic fracture.

Some surgeons prefer cementless components especially when bone is very sclerotic or a concurrent osteotomy is done. Extremely sclerotic bleeding bone will make interdigitation of cement difficult and cement extravasation into the fracture gaps may occur after osteotomy. If using a cementless cup the use of adjuvant acetabular screws is recommended.

EXAMINER: Any special complications that can occur postoperatively?

CANDIDATE: There is a reported greater incidence of heterotopic ossification.

EXAMINER: Anything else?

CANDIDATE: Dislocation.

EXAMINER: No, I am not aware of an increased risk of dislocation. However, several studies have documented osteolysis following THA in patients with Paget’s disease.³ This is thought to be related to the increased metabolic turnover of the pathological bone. Other authors have reported that osteolysis is not a problem following THA in Paget’s disease.⁴

Other complications include periprosthetic fracture around total hip implants, and the continuation of bone pain following arthroplasty, microfractures and malignant transformation to osteosarcoma.

Gold medal

EXAMINER: What causes have been identified for the increased number and activity of pagetic osteoclasts?

CANDIDATE: Causes identified include:

1.      Osteoclastic precursors are hypersensitive to calcitriol (1,25 (OH) 2D3).

2.      Osteoclasts are hyper-responsive to RANK ligand (RANKL), the osteoclast stimulatory factor that mediates the effects of most osteotropic factors on osteoclast formation.

Endnotes

1.        Parvizi J, Schall DM, Lewallen DG, Sim FH. Outcome of uncemented hip arthroplasty components in patients with Paget’s disease. Clin Orthop Relat Res 2002;403:127–134.

2.        Lusty PJ, Walter WL, Walter WK, Zicat B. Cementless hip arthroplasty in Paget’s disease at medium-term follow-up (average of 6.7 years). J Arthroplasty 2007;22(5):692–696.

3.        Alexakis PG, Brown BA, Howl WM. Porous hip replacement in Paget’s disease: an 8–2/3-year follow-up. Clin Orthop Relat Res 1998;350:138–142.

4.        LudkowskiP, Wilson-MacDonald J.Total arthroplastyinPaget’s disease of the hip: a clinical review and review of the literature. Clin Orthop Relat Res 1990;255:160–167.

Structured Oral Hip Examination Question 7

EXAMINER: This is a radiograph of a 68-year-old woman who has been referred up to the orthopaedic clinic by the physiotherapist-led musculoskeletal clinic with an 18-month history of left hip pain and difficulty walking. (Figure 2.12.)

CANDIDATE: This is an anteroposterior (AP) radiograph of the pelvis demonstrating a coarsened trabecular pattern of the left hip, a thickened left cortex compared with the opposite hip, and increased density of the left hip compared with the right side. Both iliopectineal (Brim sign) and ilioischiatic lines are thickened. There is sclerosis involving the left pelvis (ileum, ischium and pubic rami), left femur and lower lumbar spine. The radiograph is highly suspicious of Paget’s disease.

Differential diagnosis would include other causes of increased and disorganized bone turnover such as sclerotic bony metastasis (prostatic carcinoma), renal osteodystrophy, fibrous dysplasia, multiple myeloma, lymphoma, osteopetrosis and hyperparathyroidism.

EXAMINER: What is Paget’s disease?

CANDIDATE: Paget’s disease is a metabolic bone disorder of unknown aetiology characterized by a disorganized increase in osteoclastic bone resorption and compensatory osteoblastic new bone formation. There is accelerated but chaotic bone remodelling in which the bone is biomechanically weak and prone to deformity and fracture.

The disease can be divided into three major phases, lytic, mixed lytic/sclerotic and sclerotic, each of which is

 

Figure 2.12 Anteroposterior (AP) radiograph demonstrating Paget’s disease of the left hemipelvis.

associated with distinctive clinical, radiological and pathological features.

EXAMINER: What causes Paget’s disease? What is the pathophysiology of Paget’s disease?

CANDIDATE: The primary abnormality of Paget’s disease is an intense focal resorption of normal bone by abnormal osteoclasts. These osteoclasts are abnormal in size, activity and quantity. The abnormal osteoclasts make large resorption cavities in the bone matrix. In response to the osteoclast resorption, osteoblasts are recruited, resulting in bone formation. The osteoblast activity is rapid such that the newly formed bone is not organized and remains irregular and woven in nature, less resistant and more elastic than typical lamellar bone; prone to deformity and fracture.

EXAMINER: What are the other radiographic features of Paget’s disease?

CANDIDATE: Radiographic features of Paget’s include:  Advanced disease in the long bones is characterized by coarsened trabecula, bony sclerosis, bony enlargement and deformity. A ‘candle flame’ or ‘blade of grass’ sign represents a wedge- or V-shaped pattern of advancing lysis in the diaphysis of long bones. The femur develops a lateral curvature whilst the tibia develops an anterior curvature that may result in fracture. Fine cracks may appear (stress fractures) which resemble Looser zones but occur on the convex bone surface.

 Lateral radiographs of the lumbar spine demonstrate a ‘picture-frame’ vertebral body that is secondary to severe osteoporosis centrally and a thickened, sclerotic cortex.

 The skull is involved in 29–65% of cases. Inner and outer table involvement leads to diploic widening. Osteoporosis circumscripta is a well-defined lysis, most commonly involving the frontal bone, producing well-defined geographic lytic lesions in the skull. It is seen in the early or lytic phase, when osteoclastic resorption overwhelms bone production. At a later stage a ‘cotton wool appearance’ represents mixed lytic and blastic pattern of thickened calvarium.

 Protrusio deformity of the pelvis is a common occurrence with advanced Paget’s disease.

EXAMINER: What are the current theories regarding the aetiology of Paget’s disease?

CANDIDATE: The aetiology of Paget’s disease is still unknown. Proposed theories include viral, genetic and environmental causes. Paramyxoviruses such as measles virus, respiratory syncytial virus, and canine distemper virus have been implicated. Electron microscopy has shown virus-like structures that resemble the paramyxovirus in osteoclast nuclei and cytoplasm of cells affected by Paget’s disease. However, more recent studies have been unable to confirm the presence of specific viral antibodies in patients with Paget’s disease. Environmental factors implicated include high levels of arsenic and an uncertain association with cats and dogs. Genetically 5–40% of patients have first-degree relatives with the disease.

EXAMINER: That’s fine. I am however a bit sceptical about the cats and dogs theory. Moving on – what are the complications of Paget’s disease?

CANDIDATE: Complications of Paget’s disease include:  Compression fractures of the vertebral body (commonest complication of spinal Paget’s).

 Pagetic spinal stenosis, defined as compression of the spinal cord, cauda equina or spinal nerves by expanded pagetic bony tissue of the spine. Most common in the lumbar region and typically single level causing cord or nerve root compression.

 An enlarged and deformed skull can lead to increased intracranial pressure, hydrocephalus or cranial nerve deficits such as facial palsy (narrowing of neural foramina), hearing loss or blindness (pressure on optic nerve).

 High cardiac output secondary to increased bone vascularity

(rare).

 Insufficiency fractures.

 Osteosarcoma, chondrosarcoma, malignant fibrous histiocytoma and giant cell tumours all have been reported with Paget’s disease.

EXAMINER: What are the indications for THA in Paget’s disease?

CANDIDATE: The indications are similar to non-Pagetoid disease. It is important to make sure that the pain is arising from the joint surface and not the bone. Bone pain with active Paget’s is suggested by an increased alkaline phosphatase value. It is also important to exclude insufficiency fractures, neurological compression in the spine or Paget’s sarcoma as a cause of pain.

EXAMINER: How do you assess disease activity?

CANDIDATE: Patients with active Paget’s disease have a raised alkaline phosphatase (AlkPhos) and urine hydroxyproline values. The higher the level the more active the disease is. Patients with very high AlkPhos levels are thought to be at higher risk of bleeding and heterotrophic ossification formation.

EXAMINER: If the Paget’s disease is active what will you do?

CANDIDATE: I would make a referral to one of my rheumatoid colleagues for a Pamidronate (Aredia) injection. This is a bisphosphonate, which is a potent inhibitor of osteoclastic activity, and hence bone resorption. This reduces bone vascularity and bleeding and possibly the incidence of heterotopic ossification.

EXAMINER: What are the technical issues of performing THA in

Paget’s disease?

CANDIDATE: There is tendency for excessive bleeding at surgery due to increased vascularity. Blood should ideally be crossmatched or at the least available from a group and save within 10 minutes. Bone can be very hard and sclerotic making it difficult to ream and broach. Burrs may be needed to enter the bone prior to reaming and/or broaching. Varus deformity of the proximal end of the femur predisposes to varus placement of the femoral component.

Protrusio as we have mentioned is a common finding and I would consider using bone graft medially to compensate. Some surgeons use lateral offset liners and antiprotrusio cages although this complicates surgery.

As Paget’s bone is brittle there is a higher risk of both intraoperative and postoperative fracture.

There is some controversy as to whether there is an increased risk of heterotopic ossification occurring from the abnormalities of osteogenic differentiation in Paget’s disease patients. Some surgeons routinely give prophylaxis to reduce

the risk of HO. [Candidate score 6]

EXAMINER: There is a bit more than that when planning THA.

CANDIDATE: As bone pain is common in Paget’s disease and does not necessarily improve with THA a diagnostic local anaesthetic injection to rule out concurrent bone pathology may be indicated. It is also important to exclude referred pain from spinal stenosis or radiculopathy and other causes of musculoskeletal pain.

Good quality, full-length radiographs to assess the degree of deformity and the extent of bone involvement.

Radiographs should be scrutinized for the presence of a stress fracture that could account for hip pain. The fractures may be in the region of the femoral neck, intertrochanteric area or femoral shaft. They usually present as incomplete or fissure fractures on the tension side of the bone. Unrelenting hip pain and radiographic bone destruction suggest sarcomatous change.

Consider using cell salvage, hypotensive anaesthesia and predonation of autologous blood if intraoperative blood loss is anticipated to be high with active disease. Concurrent osteotomy may be needed if component alignment is difficult. Marked protrusio can make hip dislocation very difficult.

EXAMINER: You mentioned osteotomy, how often do you perform osteotomy when you perform THA for Paget’s disease?

CANDIDATE: In the majority of patients with Paget’s THA can be performed without need for osteotomy. However, if deformity is severe, precluding implantation with a standard stem, then planning for reduction osteotomy to correct the deformity and/or the use of modular stems must be made preoperatively.

EXAMINER: What type of hip replacement would you use?

CANDIDATE: Although there has been a trend in recent years to use uncemented components in Paget’s disease in this patient I would use a cemented THA. She is 68 and has Paget’s disease and I think it is a reasonable option in this situation. If the patient is younger then the choice becomes more controversial. Although previous studies have recommended the use of cement in the last 20 years there has been a trend to use uncemented components. The worry that the altered morphology of pagetoid bone adversely influences ingrowth into cementless implants has not been borne out in practice. The biology of bone ingrowth for initial fixation of uncemented components depends, in part, on the ability of bone to proceed through the early phase of fracture healing.

Patients with Paget’s disease are not known to have compromised ability for fracture healing and these patients progress through the biological process of fracture healing at normal speed.

Parvizi et al. reported on 21 cementless THA implanted against pagetoid bone; all were stable and demonstrated radiographic evidence of ingrowth at 7-year follow-up.¹ Lusty et al. from Sydney, Australia reported medium-term results of 23 uncemented THA at 6.7-year follow-up.² There were three revisions, one stem for aseptic loosening and two stems after periprosthetic fracture.

Some surgeons prefer cementless components especially when bone is very sclerotic or a concurrent osteotomy is done. Extremely sclerotic bleeding bone will make interdigitation of cement difficult and cement extravasation into the fracture gaps may occur after osteotomy. If using a cementless cup the use of adjuvant acetabular screws is recommended.

EXAMINER: Any special complications that can occur postoperatively?

CANDIDATE: There is a reported greater incidence of heterotopic ossification.

EXAMINER: Anything else?

CANDIDATE: Dislocation.

EXAMINER: No, I am not aware of an increased risk of dislocation. However, several studies have documented osteolysis following THA in patients with Paget’s disease.³ This is thought to be related to the increased metabolic turnover of the pathological bone. Other authors have reported that osteolysis is not a problem following THA in Paget’s disease.⁴

Other complications include periprosthetic fracture around total hip implants, and the continuation of bone pain following arthroplasty, microfractures and malignant transformation to osteosarcoma.

Gold medal

EXAMINER: What causes have been identified for the increased number and activity of pagetic osteoclasts?

CANDIDATE: Causes identified include:

1.      Osteoclastic precursors are hypersensitive to calcitriol (1,25 (OH) 2D3).

2.      Osteoclasts are hyper-responsive to RANK ligand (RANKL), the osteoclast stimulatory factor that mediates the effects of most osteotropic factors on osteoclast formation.

Endnotes

1.        Parvizi J, Schall DM, Lewallen DG, Sim FH. Outcome of uncemented hip arthroplasty components in patients with Paget’s disease. Clin Orthop Relat Res 2002;403:127–134.

2.        Lusty PJ, Walter WL, Walter WK, Zicat B. Cementless hip arthroplasty in Paget’s disease at medium-term follow-up (average of 6.7 years). J Arthroplasty 2007;22(5):692–696.

3.        Alexakis PG, Brown BA, Howl WM. Porous hip replacement in Paget’s disease: an 8–2/3-year follow-up. Clin Orthop Relat Res 1998;350:138–142.

4.        LudkowskiP, Wilson-MacDonald J.Total arthroplastyinPaget’s disease of the hip: a clinical review and review of the literature. Clin Orthop Relat Res 1990;255:160–167.