Hip structured oral questions
Structured Hip oral examination question 1
EXAMINER: This is a radiograph of a 77-year-old woman who sustained a displaced intracapsular fractured neck of femur 3 years earlier managed with a hemiarthroplasty of the hip (see Figure 2.1). She was admitted onto the orthopaedic ward last night because of increasing left hip pain and difficulty mobilizing.
CANDIDATE: This is an anteroposterior (AP) radiograph of the pelvis taken on the 11/5/11 demonstrating a cemented Thompson’s hemiarthroplasty of the left hip. The neck cut is straight down on to the lesser trochanter. The prosthesis seems to have sunk below the lesser trochanter and there are radiolucencies in Gruen zones 1, 4, 5 and 7. There appears to be a faint rim of calcification in the soft tissues, adjacent to the lateral cortex of the femur. The femoral head size would seem to match the acetabulum so it is not under or oversized and the femoral stem orientation appears neutral, neither excessively anteverted nor retroverted. I would like to see immediate postoperative radiographs to confirm whether there has been a change in stem position from the time of the original surgery and would also like to see an up-to-date lateral radiograph of the hip.
EXAMINER: Here is a lateral radiograph of the left hip that was taken on admission. (Figure 2.2.)
Figure 2.1 Anteroposterior (AP) radiograph of loose left cemented Thompson’s hemiarthroplasty hip.
Figure 2.2 Lateral radiograph of loose left cemented Thompson’s hemiarthroplasty hip.
CANDIDATE: The lateral radiograph demonstrates loosening of the Thompson’s prosthesis with a large cortical lytic lesion surrounding the stem. There appears be reactive bone formation along the posteromedial diaphysis of the femur and a suggestion of a possible soft tissue mass. There is lateral cortical destruction at the tip of the stem.
EXAMINER: What do you think is going on?
CANDIDATE: The stem appears loose. The prosthesis has only been inserted for 3 years. I think the radiographs are highly suggestive of infection until proven otherwise.
EXAMINER: How would you investigate this patient?
CANDIDATE: I would perform routine blood tests including CRP and ESR to see if there are raised inflammatory markers.1 EXAMINER: How helpful are these?
CANDIDATE: They have relatively low sensitivity and low specificity as markers of prosthetic joint infection. Berbari et al. (Level II) published a systematic review in the JBJS American edition in 2010 on the use of inflammatory markers for diagnosis of prosthetic joint infection.2 They concluded that IL-6 is a much more sensitive test for infection.
EXAMINER: What do you mean by sensitivity and specificity?3
CANDIDATE: Sensitivity is the ability of a test to pick up truly infected cases and specificity the ability of the test to exclude appropriately those cases which are not infected.
Or in more general terms sensitivity is the proportion of individuals with the disease (or condition) who are correctly identified by the test. Specificity is the proportion of individuals without the disease who are correctly identified by the test.
Positive predictive value is the probability that a patient with a positive result genuinely has infection and the negative predictive value is the probability that a patient with a negative result has genuinely avoided infection.4
EXAMINER. The paper actually reported that IL-6 was more accurate than CRP or ESR rather than sensitive. What do we mean by accuracy?
CANDIDATE: The accuracy of a test is defined as the proportion of tests that have given the correct result (true positives and true negatives).
EXAMINER: So how are you going to proceed with this patient?
CANDIDATE: I would want to take the patient to theatre and perform an aspiration of the hip to rule out infection.
EXAMINER: You are jumping in a bit fast. Is there anything else you might want find out beforehand?
CANDIDATE: I would want to take a full history from the patient. A number of patients who develop infection have early wound problems such as prolonged redness, induration, swelling or discharge. There may be a history of repeated courses of antibiotics. The wound may have become frankly infected requiring washout in theatre.
Onset of hip pain following a problem-free interval and an episode of sepsis is suggestive of haematogenous seeding of infective organisms from elsewhere. I would enquire if there was a history of bacteraemia from a UTI, chest infection or dental extraction.
Pain from an infected prosthesis is typically non-mechanical and unrelated to physical activity and not relieved by rest.
EXAMINER: The wound was oozy postoperatively but settled down. A large part of picking up periprosthetic infection is obtaining a good history and examination along with a high index of clinical suspicion.
How useful is a hip aspiration in diagnosing infection?
CANDIDATE: Spangehl et al. (level I) demonstrated a sensitivity of 0.86, a specificity of 0.94, a positive predictive value of 0.67 and a negative predictive value of 0.98 with initial imageguided aspiration in 180 patients undergoing revision hip arthroplasties.5 They reported that aspiration alone is not sufficient for the diagnosis because of the risk of false-positive and false-negative results. They suggested in low-probability cases with a normal ESR and CRP that aspiration was not necessary. Aspiration would be indicated if pretest probability for infection was high (acute onset of pain, systemic illness, sinus formation) particularly if the CRP/ESR was normal or in all cases where the CRP or ESR was high.
EXAMINER: Joint aspiration was negative. How are you going to manage this patient?
CANDIDATE: I would need to get more history from the patient, most importantly what her symptomatic complaints are and also fully assess her fitness for anaesthesia and surgery.
EXAMINER: She has a 2-year history of intermittent progressively worsening hip pain worse with activities such as walking or rising from a chair. She is not the fittest patient for surgery; she developed pseudo-bowel obstruction and aspiration pneumonia postoperatively after the hemiarthroplasty requiring HDU admission.
CANDIDATE: I would need to sit down with the patient and fully discuss what her expectations from surgery were. We would need to reach an agreement on whether she would wish to proceed with revision hip surgery taking on board/ taking into account/accepting the potential risks and complications of the surgery weighed against the probable benefits of the procedure.6
EXAMINER: She can’t live with her pain – she wants you to do something!
CANDIDATE: I would still be very suspicious that the hemiarthroplasty has a low-grade infection and perform a twostage hip revision operation for her.
EXAMINER: Are there any other tests you might want to perform that could diagnose infection before going ahead with surgery?
CANDIDATE: The use of nuclear imaging (technetium-99 triplephase bone scan, gallium imaging, labelled-leukocyte scans or FDG-PET imaging) for the detection of periprosthetic joint infection is worth considering but controversial. The recent AAOS clinical practice guidelines summary from 2010 reported a weak recommendation for their use.7
EXAMINER: How do you classify periprosthetic hip infection?
CANDIDATE: Tsukayama et al. proposed a 4-stage system consisting of early postoperative, late chronic and acute haematogenous infections, and positive intraoperative cultures of specimens obtained during revision of a presumed aseptically loose THA.8,9
Early postoperative infection presents less than 1 month after surgery with a febrile patient and a red swollen discharging wound. With late postoperative infection the patient is well, the wound has healed well, there is a worsening of hip pain and a never pain-free interval. Acute haematogenous infection can occur several years after surgery with a history of bacteraemia (UTI or other source of infection) and severe hip pain in a previously well-functioning hip. Positive intraoperative culture (at least three samples from different locations taken with clean instruments) occurs when a preoperative presumptive diagnosis of aseptic loosening was made.
McPherson et al. have also developed a staging system for periprosthetic hip infections that included three categories: infection type (acute versus chronic), the overall medical and immune health status of the patient, and the local extremity
(wound) grade.10
EXAMINER: Why are you discounting a one-stage procedure?
CANDIDATE: Although there are advantages to performing a one-stage procedure such as low treatment cost and preservation of patient function it is a controversial option as the success rate is less than a two-stage procedure. The procedure involves removal of the prosthesis, thorough debridement and re-implantation at a single sitting.
EXAMINER: What are the prerequisites for a one-stage procedure?
CANDIDATE: There may be a case for performing a single-stage revision in a specialist centre with a large experience in dealing with infected hips.
EXAMINER: That’s not quite the question I asked.
CANDIDATE: Prerequisites include a known organism sensitive to antibiotics, no pus present, elderly patients or patients with multiple medical problems. It is also indicated in healthy individuals devoid of re-infection risk who have adequate bone and soft tissue for reconstruction and a low virulence pathogen.
EXAMINER: What are the reported success rates for a single-stage revision?
CANDIDATE: Buchholz et al. who pioneered one-stage revisions at the Endo-Klinic in Hamburg reported a success rate of 77% in 583 revisions, but only after extensive bone and soft-tissue resection, which compromised long-term function.11 These results were published in 1981 and can be viewed as somewhat historic now. Raut et al. from Wrightington reported a success rate of 86% in 57 cases at average follow-up of 7 years despite many discharging sinuses.12,13 Hanssen and Rand summarized the results of single-stage exchange and found a cumulative success rate of 83% when antibiotic-loaded cement was used but only 60% when it was not.14
EXAMINER: What are the advantages to performing a two-stage procedure?
CANDIDATE: It is particularly important to perform a two-stage revision with more severe infections or virulent organisms, as the success rate of a single-stage procedure is much less in these situations.
EXAMINER: That’s not what I asked.
CANDIDATE: It is more versatile for reconstruction allowing the use of either cemented or cementless components and bone allograft in patients with severe bone loss. It allows clinical assessment of the response to antibiotics prior to re-implantation.
EXAMINER: What are the disadvantages of a two-stage procedure?
CANDIDATE: It can be difficult to nurse patients between stages and the second-stage surgery can be difficult due to soft tissue scarring, limb shortening, disuse atrophy, loss of bone density and distortion of anatomy. If a PROSTALAC spacer is used it can dislocate or fracture and it is more costly to perform a twostage procedure.
EXAMINER: So you perform the first-stage revision, how long will you keep the patient on antibiotics? (Figure 2.3.)
CANDIDATE: Duration of antibiotic treatment and timing between stages remains controversial. Current practice suggests delaying the second stage for at least 6 weeks pending good clinical progress with antibiotics and wound healing. A number of surgeons re-implant at 3 months treating the patient with 6 weeks of antibiotics and then further 6 weeks without antibiotics regularly monitoring the CRP/ESR for any signs of elevation and checking clinical progress for any signs of reoccurrence of infection such as sinus discharge or increasing hip pain. Some surgeons would routinely re-aspirate the hip to exclude any residue infection before going ahead with the second stage.
EXAMINER: Five of my last six THAs have become infected – what should I do?
CANDIDATE: Stop operating and investigate.
EXAMINER: Go on.
CANDIDATE: I would want to know if the same organism had
been identified in the five cases particularly if the organism was
Staphylococcus aureus as this may suggest a nasal carrier in theatre. Nasal swab cultures would need to be taken of relevant theatre staff and appropriate treatment started.
We would want to investigate for a breakdown in theatre sterility. I would involve microbiology and investigate the laminar flow system to see if it was working correctly.
There may be issues with the preparation of the instruments set such as packaging integrity and expiry date. A sterilization indicator should be present and the packaging must be dry.
There may be a breakdown in the precautions that must be taken by the scrub practitioner during the procedure such as Figure 2.3
Anteroposterior (AP) radiograph of first stage PROSTALAC spacer.
the sterile field not being constantly observed and too much movement around the sterile field, including the opening and closing of doors and a wide space not being observed between scrubbed staff.
Taylor and Bannister showed that sets opened outside the confines of the laminar hood have significantly higher colony forming unit (CFU) counts during and after surgery.15 Very few centres follow Sir John Chamley’s technique of opening the instrument sets under the canopy at each stage of the operation.
Madhavan et al.’s paper from Bristol in the Annals of the
Royal College of Surgeons England specifically looked at breakdown in theatre discipline during total joint replacement.16 They noted a slackness had crept into theatre protocol such as corridor from changing room to theatre and theatre personnel attire.
EXAMINER: Do you know any papers that have looked at theatre sterility?
CANDIDATE: The classic paper on theatre sterility was published by Lidwell et al. in 1982.17 This was an MRC randomized study which showed a decrease in infection rates following joint replacements carried out in ultra-clean theatres.
The deep infection rate was 3.4% in conventional theatres, 1.7% with ultraclean air and body exhaust and 0.2% when this was combined with prophylactic antibiotics.
EXAMINER: That’s fine. Let’s move on.
Alternative scenario
Differential diagnosis of the lesion would be granulomatous reaction to wear debris from Thompson’s hemiarthroplasty. This is much more likely with a metal-on-polyethylene bearing THA interface. Other important differentials include metastatic disease and soft tissue sarcoma.
The examiner could lead you down the path of investigation of a possible tumour mass. A bone scan and MRI would need to be ordered for further investigation. A computed tomography-guided fineneedle aspiration of the mass could be performed. See references 18 and 19 for a similar type of scenario.
Endnotes
1. The candidate has got out of sync with the examiner and flow of the question. Not a disaster. The candidate should have answered how they would manage the patient with the standard default answer of history, examination and investigations etc.
2. Berbari E, Mabry T, Tsaras G et al. Inflammatory blood laboratory levels as markers of prosthetic joint infection: a systematic review and meta-analysis. J Bone Joint Surg Am 2010;92-A:2102–2109.
3. These are double-bullet questions fired at the candidate from a high-powered rifle and the candidate has to give a precise, correct answer back and then the oral continues on.
4. In the oral exam it is better to explain these terms to the examiners by drawing a table but in this particular question it doesn’t quite fit together with the interactions to do this.
5. Spangehl MJ, Masri BA, O’Connell JX et al. Prospective analysis of preoperative and intraoperative investigations for the diagnosis of infection at the sites of two hundred and two revision total hip arthroplasties. J Bone Joint Surg Am 1999;81-A:672–682.
6. Waffly answer but can’t be helped – it is what needs to be said by the candidate to the examiners. A standard, safe, nondescript response.
7. It may be enough just to mention the uncertainties with nuclear imaging or one may have to quantify your answer a bit more fully. It is a judgement decision but don’t persist with your answer if the examiners want to move on. 99mTechnetium bone scans are sensitive but not specific. Some investigators have found that a negative scan rules out infection while others have reported that a scan can occasionally be negative in the presence of infection if there is inadequate blood supply to the bone. A 99m-technetium bone scan identifies areas of increased bone activity through preferential uptake of the diphosphonate by metabolically active bone. Increased uptake occurs with loosening, infection, heterotopic bone formation, Paget’s disease, stress fractures, modulus mismatch of a large uncemented stem, neoplasm, reflex sympathetic dystrophy, and other metabolic conditions. In the uncomplicated THA, uptake around
the lesser trichinae and shaft is usually insignificant by 6 months, but in 10% of cases, uptake may persist at the greater trochanter, prosthesis tip and acetabulum for more than 2 years. The pattern of uptake has not been found to consistently reflect the presence or absence of infection. Gallium imaging likewise has a poor sensitivity and accuracy. The use of leukocyte scans is generally preferred, having a higher sensitivity (88–92%) and specificity (73–100%), but their usefulness for the diagnosis of infection continues to be debated. FDG-PET is expensive, limited to a few institutions and although very sensitive does not allow differentiation between an inflamed aseptically loosened prosthesis and an infected one.
8. Tsukayama DT, Estrada R, Gustilo RB. Infection after total hip arthroplasty. A study of one hundred and six infections. J Bone Joint Surg Am 1996;78-A:512–523.
9. This is sometimes referred to as Gustilo’s classification. With due respect to the first author Gustilo is easier to remember.
10. McPherson EJ, Woodson C, Holtom P et al. Periprosthetic total hip infection. Outcomes using a staging system. Clin Orthop Relat Res 2002;403:8–15.
11. Buchholz HW, Elson RA, Engelbrecht E et al. Management of deep infection of total hip replacement. J Bone Joint Surg Br 1981;63-B:342–353.
12. Raut VV, Siney PD, Wroblewski BM. One-stage revision of infected total hip replacements with discharging sinuses. J Bone Joint Surg Br 1994;76-B:721–724.
13. With due respect although Raut is the first author I think ‘Wroblewski from Wrightington has shown’ is easier to remember. There is enough to learn already without making things difficult for yourself!
14. Hanssen AD, Rand JA. Evaluation and treatment of infection at the site of a total hip or knee arthroplasty. J Bone Joint Surg Am 1998;80-A:910–922.
15. Taylor GJS, Bannister GC. Infection and interposition between ultraclean air source and wound. J Bone Joint Surg Br
1993;75-B:503–504.
16. Madhavan P, Blom A, Karagkevrakis B et al. Deterioration of theatre discipline during total joint replacement – have theatre protocols been abandoned? Ann R Coll Surg Engl
1999;81:262–265.
17. Lidwell OM, Lowbury EJ, Whyte W et al. Effect of ultraclean air in operating rooms on deep sepsis in the joint after total hip or knee replacement: a randomised study. Br Med J
1982;285:10–14.
18. Hanna MW, Thornhill TS. Thigh mass and lytic diaphyseal femoral lesion associated with polyethylene wear after hybrid total knee arthroplasty. A case report. J Bone Joint Surg Am 2006;88-A:2473–2478.
19. Patterson P, Grigoris P, Raby N et al. A thigh mass associated with a total hip replacement in a 69-year-old woman. Clin Orthopaed Related Res 2002;404:373–377.
Hip structured oral questions
Structured oral examination question 1
EXAMINER: This is a radiograph of a 77-year-old woman who sustained a displaced intracapsular fractured neck of femur 3 years earlier managed with a hemiarthroplasty of the hip (see Figure 2.1). She was admitted onto the orthopaedic ward last night because of increasing left hip pain and difficulty mobilizing.
CANDIDATE: This is an anteroposterior (AP) radiograph of the pelvis taken on the 11/5/11 demonstrating a cemented Thompson’s hemiarthroplasty of the left hip. The neck cut is straight down on to the lesser trochanter. The prosthesis seems to have sunk below the lesser trochanter and there are radiolucencies in Gruen zones 1, 4, 5 and 7. There appears to be a faint rim of calcification in the soft tissues, adjacent to the lateral cortex of the femur. The femoral head size would seem to match the acetabulum so it is not under or oversized and the femoral stem orientation appears neutral, neither excessively anteverted
nor retroverted. I would like to see immediate postoperative radiographs to confirm whether there has been a change in stem position from the time of the original surgery and would also like to see an up-to-date lateral radiograph of the hip.
EXAMINER: Here is a lateral radiograph of the left hip that was taken on admission. (Figure 2.2.)
Figure 2.1 Anteroposterior (AP) radiograph of loose left cemented Thompson’s hemiarthroplasty hip.
Figure 2.2 Lateral radiograph of loose left cemented Thompson’s hemiarthroplasty hip.
CANDIDATE: The lateral radiograph demonstrates loosening of the Thompson’s prosthesis with a large cortical lytic lesion surrounding the stem. There appears be reactive bone formation along the posteromedial diaphysis of the femur and a suggestion of a possible soft tissue mass. There is lateral cortical destruction at the tip of the stem.
EXAMINER: What do you think is going on?
CANDIDATE: The stem appears loose. The prosthesis has only been inserted for 3 years. I think the radiographs are highly suggestive of infection until proven otherwise.
EXAMINER: How would you investigate this patient?
CANDIDATE: I would perform routine blood tests including CRP and ESR to see if there are raised inflammatory markers.1 EXAMINER: How helpful are these?
CANDIDATE: They have relatively low sensitivity and low specificity as markers of prosthetic joint infection. Berbari et al. (Level II) published a systematic review in the JBJS American edition in 2010 on the use of inflammatory markers for diagnosis of prosthetic joint infection.2 They concluded that IL-6 is a much more sensitive test for infection.
EXAMINER: What do you mean by sensitivity and specificity?3
CANDIDATE: Sensitivity is the ability of a test to pick up truly infected cases and specificity the ability of the test to exclude appropriately those cases which are not infected.
Or in more general terms sensitivity is the proportion of individuals with the disease (or condition) who are correctly identified by the test. Specificity is the proportion of individuals without the disease who are correctly identified by the test.
Positive predictive value is the probability that a patient with a positive result genuinely has infection and the negative predictive value is the probability that a patient with a negative result has genuinely avoided infection.4
EXAMINER. The paper actually reported that IL-6 was more accurate than CRP or ESR rather than sensitive. What do we mean by accuracy?
CANDIDATE: The accuracy of a test is defined as the proportion of tests that have given the correct result (true positives and true negatives).
EXAMINER: So how are you going to proceed with this patient?
CANDIDATE: I would want to take the patient to theatre and perform an aspiration of the hip to rule out infection.
EXAMINER: You are jumping in a bit fast. Is there anything else you might want find out beforehand?
CANDIDATE: I would want to take a full history from the patient. A number of patients who develop infection have early wound problems such as prolonged redness, induration, swelling or discharge. There may be a history of repeated courses of antibiotics. The wound may have become frankly infected requiring washout in theatre.
Onset of hip pain following a problem-free interval and an episode of sepsis is suggestive of haematogenous seeding of infective organisms from elsewhere. I would enquire if there was a history of bacteraemia from a UTI, chest infection or dental extraction.
Pain from an infected prosthesis is typically non-mechanical and unrelated to physical activity and not relieved by rest.
EXAMINER: The wound was oozy postoperatively but settled down. A large part of picking up periprosthetic infection is obtaining a good history and examination along with a high index of clinical suspicion.
How useful is a hip aspiration in diagnosing infection?
CANDIDATE: Spangehl et al. (level I) demonstrated a sensitivity of 0.86, a specificity of 0.94, a positive predictive value of 0.67 and a negative predictive value of 0.98 with initial imageguided aspiration in 180 patients undergoing revision hip arthroplasties.5 They reported that aspiration alone is not sufficient for the diagnosis because of the risk of false-positive and false-negative results. They suggested in low-probability cases with a normal ESR and CRP that aspiration was not necessary. Aspiration would be indicated if pretest probability for infection was high (acute onset of pain, systemic illness, sinus formation) particularly if the CRP/ESR was normal or in all cases where the CRP or ESR was high.
EXAMINER: Joint aspiration was negative. How are you going to manage this patient?
CANDIDATE: I would need to get more history from the patient, most importantly what her symptomatic complaints are and also fully assess her fitness for anaesthesia and surgery.
EXAMINER: She has a 2-year history of intermittent progressively worsening hip pain worse with activities such as walking or rising from a chair. She is not the fittest patient for surgery; she developed pseudo-bowel obstruction and aspiration pneumonia postoperatively after the hemiarthroplasty requiring HDU admission.
CANDIDATE: I would need to sit down with the patient and fully discuss what her expectations from surgery were. We would need to reach an agreement on whether she would wish to proceed with revision hip surgery taking on board/ taking into account/accepting the potential risks and complications of the surgery weighed against the probable benefits of the procedure.6
EXAMINER: She can’t live with her pain – she wants you to do something!
CANDIDATE: I would still be very suspicious that the hemiarthroplasty has a low-grade infection and perform a twostage hip revision operation for her.
EXAMINER: Are there any other tests you might want to perform that could diagnose infection before going ahead with surgery?
CANDIDATE: The use of nuclear imaging (technetium-99 triplephase bone scan, gallium imaging, labelled-leukocyte scans or FDG-PET imaging) for the detection of periprosthetic joint infection is worth considering but controversial. The recent AAOS clinical practice guidelines summary from 2010 reported a weak recommendation for their use.7
EXAMINER: How do you classify periprosthetic hip infection?
CANDIDATE: Tsukayama et al. proposed a 4-stage system consisting of early postoperative, late chronic and acute haematogenous infections, and positive intraoperative cultures of specimens obtained during revision of a presumed aseptically loose THA.8,9
Early postoperative infection presents less than 1 month after surgery with a febrile patient and a red swollen discharging wound. With late postoperative infection the patient is well, the wound has healed well, there is a worsening of hip pain and a never pain-free interval. Acute haematogenous infection can occur several years after surgery with a history of bacteraemia (UTI or other source of infection) and severe hip pain in a previously well-functioning hip. Positive intraoperative culture (at least three samples from different locations taken with clean instruments) occurs when a preoperative presumptive diagnosis of aseptic loosening was made.
McPherson et al. have also developed a staging system for periprosthetic hip infections that included three categories: infection type (acute versus chronic), the overall medical and immune health status of the patient, and the local extremity
(wound) grade.10
EXAMINER: Why are you discounting a one-stage procedure?
CANDIDATE: Although there are advantages to performing a one-stage procedure such as low treatment cost and preservation of patient function it is a controversial option as the success rate is less than a two-stage procedure. The procedure involves removal of the prosthesis, thorough debridement and re-implantation at a single sitting.
EXAMINER: What are the prerequisites for a one-stage procedure?
CANDIDATE: There may be a case for performing a single-stage revision in a specialist centre with a large experience in dealing with infected hips.
EXAMINER: That’s not quite the question I asked.
CANDIDATE: Prerequisites include a known organism sensitive to antibiotics, no pus present, elderly patients or patients with multiple medical problems. It is also indicated in healthy individuals devoid of re-infection risk who have adequate bone and soft tissue for reconstruction and a low virulence pathogen.
EXAMINER: What are the reported success rates for a single-stage revision?
CANDIDATE: Buchholz et al. who pioneered one-stage revisions at the Endo-Klinic in Hamburg reported a success rate of 77% in 583 revisions, but only after extensive bone and soft-tissue resection, which compromised long-term function.11 These results were published in 1981 and can be viewed as somewhat historic now. Raut et al. from Wrightington reported a success rate of 86% in 57 cases at average follow-up of 7 years despite many discharging sinuses.12,13 Hanssen and Rand summarized the results of single-stage exchange and found a cumulative success rate of 83% when antibiotic-loaded cement was used but only 60% when it was not.14
EXAMINER: What are the advantages to performing a two-stage procedure?
CANDIDATE: It is particularly important to perform a two-stage revision with more severe infections or virulent organisms, as the success rate of a single-stage procedure is much less in these situations.
EXAMINER: That’s not what I asked.
CANDIDATE: It is more versatile for reconstruction allowing the use of either cemented or cementless components and bone allograft in patients with severe bone loss. It allows clinical assessment of the response to antibiotics prior to re-implantation.
EXAMINER: What are the disadvantages of a two-stage procedure?
CANDIDATE: It can be difficult to nurse patients between stages and the second-stage surgery can be difficult due to soft tissue scarring, limb shortening, disuse atrophy, loss of bone density and distortion of anatomy. If a PROSTALAC spacer is used it can dislocate or fracture and it is more costly to perform a twostage procedure.
EXAMINER: So you perform the first-stage revision, how long will you keep the patient on antibiotics? (Figure 2.3.)
CANDIDATE: Duration of antibiotic treatment and timing between stages remains controversial. Current practice suggests delaying the second stage for at least 6 weeks pending good clinical progress with antibiotics and wound healing. A number of surgeons re-implant at 3 months treating the patient with 6 weeks of antibiotics and then further 6 weeks without antibiotics regularly monitoring the CRP/ESR for any signs of elevation and checking clinical progress for any signs of reoccurrence of infection such as sinus discharge or increasing hip pain. Some surgeons would routinely re-aspirate the hip to exclude any residue infection before going ahead with the second stage.
EXAMINER: Five of my last six THAs have become infected – what should I do?
CANDIDATE: Stop operating and investigate.
EXAMINER: Go on.
CANDIDATE: I would want to know if the same organism had
been identified in the five cases particularly if the organism was
Staphylococcus aureus as this may suggest a nasal carrier in theatre. Nasal swab cultures would need to be taken of relevant theatre staff and appropriate treatment started.
We would want to investigate for a breakdown in theatre sterility. I would involve microbiology and investigate the laminar flow system to see if it was working correctly.
There may be issues with the preparation of the instruments set such as packaging integrity and expiry date. A sterilization indicator should be present and the packaging must be dry.
There may be a breakdown in the precautions that must be taken by the scrub practitioner during the procedure such as Figure 2.3
Anteroposterior (AP) radiograph of first stage PROSTALAC spacer.
the sterile field not being constantly observed and too much movement around the sterile field, including the opening and closing of doors and a wide space not being observed between scrubbed staff.
Taylor and Bannister showed that sets opened outside the confines of the laminar hood have significantly higher colony forming unit (CFU) counts during and after surgery.15 Very few centres follow Sir John Chamley’s technique of opening the instrument sets under the canopy at each stage of the operation.
Madhavan et al.’s paper from Bristol in the Annals of the
Royal College of Surgeons England specifically looked at breakdown in theatre discipline during total joint replacement.16 They noted a slackness had crept into theatre protocol such as corridor from changing room to theatre and theatre personnel attire.
EXAMINER: Do you know any papers that have looked at theatre sterility?
CANDIDATE: The classic paper on theatre sterility was published by Lidwell et al. in 1982.17 This was an MRC randomized study which showed a decrease in infection rates following joint replacements carried out in ultra-clean theatres.
The deep infection rate was 3.4% in conventional theatres, 1.7% with ultraclean air and body exhaust and 0.2% when this was combined with prophylactic antibiotics.
EXAMINER: That’s fine. Let’s move on.
Alternative scenario
Differential diagnosis of the lesion would be granulomatous reaction to wear debris from Thompson’s hemiarthroplasty. This is much more likely with a metal-on-polyethylene bearing THA interface. Other important differentials include metastatic disease and soft tissue sarcoma.
The examiner could lead you down the path of investigation of a possible tumour mass. A bone scan and MRI would need to be ordered for further investigation. A computed tomography-guided fineneedle aspiration of the mass could be performed. See references 18 and 19 for a similar type of scenario.
Endnotes
1. The candidate has got out of sync with the examiner and flow of the question. Not a disaster. The candidate should have answered how they would manage the patient with the standard default answer of history, examination and investigations etc.
2. Berbari E, Mabry T, Tsaras G et al. Inflammatory blood laboratory levels as markers of prosthetic joint infection: a systematic review and meta-analysis. J Bone Joint Surg Am 2010;92-A:2102–2109.
3. These are double-bullet questions fired at the candidate from a high-powered rifle and the candidate has to give a precise, correct answer back and then the oral continues on.
4. In the oral exam it is better to explain these terms to the examiners by drawing a table but in this particular question it doesn’t quite fit together with the interactions to do this.
5. Spangehl MJ, Masri BA, O’Connell JX et al. Prospective analysis of preoperative and intraoperative investigations for the diagnosis of infection at the sites of two hundred and two revision total hip arthroplasties. J Bone Joint Surg Am 1999;81-A:672–682.
6. Waffly answer but can’t be helped – it is what needs to be said by the candidate to the examiners. A standard, safe, nondescript response.
7. It may be enough just to mention the uncertainties with nuclear imaging or one may have to quantify your answer a bit more fully. It is a judgement decision but don’t persist with your answer if the examiners want to move on. 99mTechnetium bone scans are sensitive but not specific. Some investigators have found that a negative scan rules out infection while others have reported that a scan can occasionally be negative in the presence of infection if there is inadequate blood supply to the bone. A 99m-technetium bone scan identifies areas of increased bone activity through preferential uptake of the diphosphonate by metabolically active bone. Increased uptake occurs with loosening, infection, heterotopic bone formation, Paget’s disease, stress fractures, modulus mismatch of a large uncemented stem, neoplasm, reflex sympathetic dystrophy, and other metabolic conditions. In the uncomplicated THA, uptake around
the lesser trichinae and shaft is usually insignificant by 6 months, but in 10% of cases, uptake may persist at the greater trochanter, prosthesis tip and acetabulum for more than 2 years. The pattern of uptake has not been found to consistently reflect the presence or absence of infection. Gallium imaging likewise has a poor sensitivity and accuracy. The use of leukocyte scans is generally preferred, having a higher sensitivity (88–92%) and specificity (73–100%), but their usefulness for the diagnosis of infection continues to be debated. FDG-PET is expensive, limited to a few institutions and although very sensitive does not allow differentiation between an inflamed aseptically loosened prosthesis and an infected one.
8. Tsukayama DT, Estrada R, Gustilo RB. Infection after total hip arthroplasty. A study of one hundred and six infections. J Bone Joint Surg Am 1996;78-A:512–523.
9. This is sometimes referred to as Gustilo’s classification. With due respect to the first author Gustilo is easier to remember.
10. McPherson EJ, Woodson C, Holtom P et al. Periprosthetic total hip infection. Outcomes using a staging system. Clin Orthop Relat Res 2002;403:8–15.
11. Buchholz HW, Elson RA, Engelbrecht E et al. Management of deep infection of total hip replacement. J Bone Joint Surg Br 1981;63-B:342–353.
12. Raut VV, Siney PD, Wroblewski BM. One-stage revision of infected total hip replacements with discharging sinuses. J Bone Joint Surg Br 1994;76-B:721–724.
13. With due respect although Raut is the first author I think ‘Wroblewski from Wrightington has shown’ is easier to remember. There is enough to learn already without making things difficult for yourself!
14. Hanssen AD, Rand JA. Evaluation and treatment of infection at the site of a total hip or knee arthroplasty. J Bone Joint Surg Am 1998;80-A:910–922.
15. Taylor GJS, Bannister GC. Infection and interposition between ultraclean air source and wound. J Bone Joint Surg Br
1993;75-B:503–504.
16. Madhavan P, Blom A, Karagkevrakis B et al. Deterioration of theatre discipline during total joint replacement – have theatre protocols been abandoned? Ann R Coll Surg Engl
1999;81:262–265.
17. Lidwell OM, Lowbury EJ, Whyte W et al. Effect of ultraclean air in operating rooms on deep sepsis in the joint after total hip or knee replacement: a randomised study. Br Med J
1982;285:10–14.
18. Hanna MW, Thornhill TS. Thigh mass and lytic diaphyseal femoral lesion associated with polyethylene wear after hybrid total knee arthroplasty. A case report. J Bone Joint Surg Am 2006;88-A:2473–2478.
19. Patterson P, Grigoris P, Raby N et al. A thigh mass associated with a total hip replacement in a 69-year-old woman. Clin Orthopaed Related Res 2002;404:373–377.
