Publications by authors named "Shiraz A Sabah"

15 Publications

  • Page 1 of 1

Patient-Reported Function and Quality of Life After Revision Total Knee Arthroplasty: An Analysis of 10,727 Patients from the NHS PROMs Program.

J Arthroplasty 2021 Mar 19. Epub 2021 Mar 19.

Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences (NDORMS), University of Oxford, Oxford, UK; Nuffield Orthopaedic Centre, Oxford, UK.

Background: The aim of the study was to investigate changes in patient-reported outcome measures (PROMs) after revision total knee arthroplasty (rTKA).

Methods: A total of 10,727 patients undergoing elective rTKA were recruited from the UK National Health Service PROMs data set from 2013 to 2019. PROMs were collected at baseline and six months to assess joint function (Oxford Knee Score, OKS) and quality of life (EQ-5D). Associations with a change in the OKS (COKS) were investigated through multiple linear regression.

Results: The mean COKS was 12.4 (standard deviation 10.7) points. A total of 6776 of 10,329 (65.6%) patients demonstrated increase in the OKS above the minimal important change of 7.5 points. The median change in the EQ-5D utility was 0.227 (interquartile range 0.000 to 0.554). A total of 4917 of 9279 (53.0%) patients achieved a composite endpoint of improvement greater than the minimal important change for joint function and 'better' QoL as per the Paretian analysis. A total of 7477 of 10,727 (69.7%) patients reported satisfaction with rTKA. A total of 7947 of 10,727 (74.1%) patients felt surgery was a success. A total of 4888 of 10,632 (46.0%) patients reported one or more adverse events. A higher preoperative OKS was associated with a lower COKS (coefficient -0.63 [95% confidence interval -0.67 to -0.60]). Other factors associated with a lower COKS were postoperative complication(s), age under 60 years, longer duration of knee problems, patients who identified as disabled, problems in EQ-5D dimensions of anxiety/depression and self-care, comorbid conditions (circulatory problems, diabetes, and depression), and earlier year of procedure in the data set.

Conclusion: Two-thirds of patients experienced a meaningful improvement in joint function after rTKA. However, there was a high frequency of patient-reported complications. These findings may enable better informed discussion of the risks and benefits of discretionary rTKA.
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http://dx.doi.org/10.1016/j.arth.2021.03.037DOI Listing
March 2021

Evidence for the validity of a patient-based instrument for assessment of outcome after revision knee arthroplasty.

Bone Joint J 2021 Apr;103-B(4):627-634

Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Oxford, UK.

Aims: To estimate the measurement properties for the Oxford Knee Score (OKS) in patients undergoing revision knee arthroplasty (responsiveness, minimal detectable change (MDC-90), minimal important change (MIC), minimal important difference (MID), internal consistency, construct validity, and interpretability).

Methods: Secondary data analysis was performed for 10,727 patients undergoing revision knee arthroplasty between 2013 to 2019 using a UK national patient-reported outcome measure (PROM) dataset. Outcome data were collected before revision and at six months postoperatively, using the OKS and EuroQol five-dimension score (EQ-5D). Measurement properties were assessed according to COnsensus-based Standards for the selection of health status Measurement Instruments (COSMIN) guidelines.

Results: A total of 9,219 patients had complete outcome data. Mean preoperative OKS was 16.7 points (SD 8.1), mean postoperative OKS 29.1 (SD 11.4), and mean change in OKS + 12.5 (SD 10.7). Median preoperative EQ-5D index was 0.260 (interquartile range (IQR) 0.055 to 0.691), median postoperative EQ-5D index 0.691 (IQR 0.516 to 0.796), and median change in EQ-5D index + 0.240 (IQR 0.000 to 0.567). Internal consistency was good with Cronbach's α 0.88 (baseline) and 0.94 (post-revision). Construct validity found a high correlation of OKS total score with EQ-5D index ( = 0.76 (baseline), = 0.83 (post-revision), p < 0.001). The OKS was responsive with standardized effect size (SES) 1.54 (95% confidence interval (CI) 1.51 to 1.57), compared to SES 0.83 (0.81 to 0.86) for the EQ-5D index. The MIC for the OKS was 7.5 points (95% CI 5.5 to 8.5) based on the optimal cut-off with specificity 0.72, sensitivity 0.60, and area under the curve 0.66. The MID for the OKS was 5.2 points. The MDC-90 was 3.9 points. The OKS did not demonstrate significant floor or ceiling effects.

Conclusion: This study found that the OKS was a useful and valid instrument for assessment of outcome following revision knee arthroplasty. The OKS was responsive to change and demonstrated good measurement properties. Cite this article:  2021;103-B(4):627-634.
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http://dx.doi.org/10.1302/0301-620X.103B4.BJJ-2020-1560.R1DOI Listing
April 2021

Revision knee replacement for prosthetic joint infection: Epidemiology, clinical outcomes and health-economic considerations.

Knee 2021 Jan 23;28:417-421. Epub 2021 Jan 23.

Nuffield Orthopaedic Centre, Windmill Road, Oxford OX2 9JA, UK. Electronic address:

Prosthetic joint infection (PJI) is a devastating complication of knee replacement surgery. Recent evidence has shown that the burden of disease is increasing as more and more knee replacement procedures are performed. The current incidence of revision total knee replacement (TKR) for PJI is estimated at 7.5 cases per 1000 primary joint replacement procedures at 10 years. Revision TKR for PJI is complex surgery, and is associated to a high rate of post-operative complications. The 5-year patient mortality is comparable to some common cancer diagnoses, and more than 15% of patients require re-revision by 10 years. Patient-reported outcome measures (PROMs) including joint function may be worse following revision TKR for PJI than for aseptic indications. The complexity and extended length of the treatment pathway for PJI places a significant burden on the healthcare system, highlighting it as an area for future research to identify the most clinically and cost-effective interventions.
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http://dx.doi.org/10.1016/j.knee.2020.12.024DOI Listing
January 2021

Management of aseptic failure of the mobile-bearing Oxford unicompartmental knee arthroplasty.

Knee 2020 Dec 13;27(6):1721-1728. Epub 2020 Nov 13.

Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UK; Nuffield Orthopaedic Centre, Oxford, UK.

Background: Unicompartmental knee arthroplasty (UKA) accounts for 9.1% of primary knee arthroplasties (KAs) in the UK. However, wider uptake is limited by higher revision rates compared with total knee arthroplasties (TKA) and concerns over subsequent poor function. The aim of this study was to understand the revision strategies and clinical outcomes for aseptic, failed UKAs at a high-volume centre.

Methods: This was a retrospective, single-centre cohort study of 48 patients (31 female, 17 male) with 52 revision UKAs from 2006 to 2018. Median time to revision was 67 (range 4-180) months. Indications for revision were progression of osteoarthritis (n = 31 knees, 59.6%), unexplained pain (n = 10 knees, 19.2%), aseptic loosening (n = 6 knees, 11.5%), medial collateral ligament incompetence (n = 3 knees, 5.8%) and recurrent bearing dislocation (n = 2 knees, 3.8%). Technical details of surgery, complications and functional outcome were recorded.

Results: Failed UKAs were revised to primary TKAs (n = 29 knees, 55.8%), revision TKAs (n = 9 knees, 17.3%), bicompartmental KAs (n = 11 knees, 21.2%), or unicompartmental-to-unicompartmental KAs (n = 3 knees, 5.8%). Median follow up was 81 (range 24-164) months. Four patients (7.7%) died from unrelated causes. No re-revisions were identified. Surgical complications required re-operation in five knees (9.6%). Median Oxford Knee Score at latest follow up was 38 (range 9-48) points and median EQ5D3L index 0.707 (range -0.247 to 1.000).

Conclusions: Aseptic, revision UKA at a high-volume centre had good clinical outcomes. Bicompartmental KA demonstrated excellent function and should be considered an alternative to TKA for progression of osteoarthritis for appropriately trained surgeons.
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http://dx.doi.org/10.1016/j.knee.2020.10.003DOI Listing
December 2020

Manipulation Under Anesthetic After Primary Knee Arthroplasty Is Associated With a Higher Rate of Subsequent Revision Surgery.

J Arthroplasty 2020 09 11;35(9):2640-2645.e2. Epub 2020 Apr 11.

Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UK; NIHR Biomedical Research Unit, University of Oxford, Oxford, UK; Nuffield Orthopaedic Centre, Oxford, UK.

Aim: To determine the association between manipulation under anesthetic (MUA) after primary knee arthroplasty and subsequent revision surgery.

Methods: Patients undergoing primary knee arthroplasty from April 2011 to April 2016 with minimum 1-year follow-up to April 2017 were identified from the national hospital episode statistics for England. The first arthroplasty per patient, per side, was included; cases with a record of subsequent infection or periprosthetic fracture were excluded. Patients undergoing MUA within 1 year to the same knee were identified, defining the populations for the MUA and non-MUA cohorts. Mortality-adjusted Kaplan-Meier survival analysis (revision arthroplasty) was performed to a maximum of 6 years. A Cox proportional hazards model was used to determine the hazard for revision, adjusting for type of primary arthroplasty, gender, age group, year, comorbidity index, obesity, regional deprivation, rurality, and ethnicity.

Results: A total of 309,650 primary arthroplasty cases (309,650 patients) were included. MUA within 1 year was recorded in 6882 patients (2.22%; 95% confidence interval [95% CI], 2.17-2.28) defining the MUA cohort; all others were included in the parallel non-MUA cohort. At 6 years, the mortality-adjusted estimated implant survival rate in the MUA cohort was 91.2% (95% CI, 90.0-92.2) in comparison to 98.1% (95% CI, 98.0-98.2) in the non-MUA cohort. In the fully adjusted model, this corresponded to an adjusted hazard for revision of 5.03 (hazard ratio; 95% CI, 4.55-5.57).

Conclusion: Patients who underwent MUA within 1 year of primary arthroplasty were at a 5-fold increased risk of subsequent revision even after excluding cases of infection or fracture. Further investigation of the etiology of stiffness after primary knee arthroplasty and the optimal treatment options to improve outcomes is justified.
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http://dx.doi.org/10.1016/j.arth.2020.04.015DOI Listing
September 2020

Self-Reported Neurotoxic Symptoms in Hip Arthroplasty Patients With Highly Elevated Blood Cobalt: A Case-Control Study.

J Patient Saf 2020 Mar 23. Epub 2020 Mar 23.

From the Institute of Orthopaedics and Musculoskeletal Science, University College London.

Objectives: This study aimed to investigate the prevalence of self-reported neurotoxicity and cognitive defects in hip replacement patients with markedly raised blood cobalt.

Methods: Case group comprised 53 patients with metal-on-metal (MoM) implants and a history of blood Co ≥20 μg/L for a median of 3 years (interquartile range, 2-5 years). The control group comprised 53 patients with ceramic-on-ceramic prostheses and blood Co <1 μg/L. Median age was 67 years (interquartile range, 60-74 years). The participants completed the Neurotoxic Symptom Checklist-60, Diabetic Neuropathy Score, Douleur Neuropathique-10, and Systemic Symptom Checklist, and underwent the Mini-Mental State Examination.

Results: The MoM and ceramic-on-ceramic groups were compared, the results were as follows: Neurotoxic Symptom Checklist-60 (median): cognitive defects (2.0 versus 1.9; P = 0.002), chest complaints (1.3 versus 1.3; P = 0.042), balance disturbances (1.3 versus 1.0; P < 0.001), sleep disturbances (2.7 versus 2.0; P = 0.004), mood disorders (2.0 versus 1.5; P = 0.001), sensorimotor disorders (1.6 versus 1.2; P < 0.001), physical complaints (2.0 versus 1.4; P = 0.009), fatigue (2.0 versus 1.6; P = 0.001), and total score (108 versus 90; P < 0.001); abnormal Diabetic Neuropathy Score/Douleur Neuropathique-10 (%): 60.3/13.2 versus 24.5/1.9 (P < 0.001/P = 0.028). Systemic Symptom Checklist (in percent): feeling cold (37.7 versus 17; P = 0.01), weight gain (18.9 versus 1.9; P = 0.008), metallic taste (26.4 versus 3.8; P = 0.002), worsening eyesight (37.7 versus 15.1; P = 0.008) and hearing (24.5 versus 7.5; 0.032), ankle swelling (32.1 versus 7.5; P = 0.002), shortness of breath on exertion (9.4 versus 5.7; P = 0.015), and generalized rash (28.3 versus 7.5; P = 0.01); and Mini-Mental State Examination (median): 29 versus 30 (P = 0.017). Patients in the MoM group were aware of their high cobalt levels and displayed a higher tendency to overreport symptoms (P < 0.001), which could have contributed to the higher scores.

Conclusions: Frequency of reporting a number of symptoms was markedly higher in MoM patients, but clinically significant neurotoxicity was not observed (possibly due to the short exposure to elevated cobalt). Patients with repeated blood Co ≥20 μg/L measurements should be questioned about possible systemic health complaints at follow-up.
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http://dx.doi.org/10.1097/PTS.0000000000000687DOI Listing
March 2020

The silhouette technique: improving post-operative radiographs for planning of correction with a hexapod external fixator.

Strategies Trauma Limb Reconstr 2017 Aug 12;12(2):127-131. Epub 2017 May 12.

Consultant Paediatric Orthopaedic Surgeon, Great Ormond Street Hospital for Children, London, WC1N 3JH, UK.

Correction of deformity of a bone through use of a hexapod external fixator requires clear definition of the relationship between the bone and the frame. Achieving adequate orthogonal calibrated radiographs for this aim, with minimum X-ray exposure, can prove a challenge in the radiography suite. We describe a simple technique for obtaining adequate imaging, without the use of additional equipment. Introduction of the technique to our department has demonstrated an improvement in the adequacy of planning radiographs and a reduction in the requirement for repeat imaging.
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http://dx.doi.org/10.1007/s11751-017-0287-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5505883PMC
August 2017

Cervical dural calcification and cervical myelopathy in X-linked hypophosphataemic rickets: a case report and review of the literature.

Br J Neurosurg 2019 Apr 25;33(2):222-223. Epub 2017 Apr 25.

a Spinal Surgery Unit , Royal National Orthopaedic Hospital , Stanmore , UK.

X-linked hypophosphataemic rickets (XLHR) is a genetic disorder resulting from a genetic mutation in the PHEX gene. This may cause ossification of soft tissue structures risking spinal cord compression. We present the first known case of cervical dural calcification secondary to XLHR to cause myelopathic symptoms due to cord compression.
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http://dx.doi.org/10.1080/02688697.2017.1319908DOI Listing
April 2019

Higher Blood Cobalt and Chromium Levels in Patients With Unilateral Metal-on-Metal Total Hip Arthroplasties Compared to Hip Resurfacings.

J Arthroplasty 2016 06 17;31(6):1261-1266. Epub 2015 Dec 17.

Coxa Hospital for Joint Replacement, Tampere, Finland.

Background: Adverse soft tissue reactions in metal-on-metal (MoM) hip replacements are associated with cobalt (Co) and chromium (Cr) ions in blood. We report the prevalence and risk factors for elevated blood Co and Cr levels in patients with a unilateral MoM hip.

Methods: From a single institution, blood Co and Cr levels were analyzed in 1748 patients (692 hip resurfacings and 1056 total hip arthroplasties [THAs]). Concentrations exceeding 7 ppb were considered elevated, and the risk factors for elevated levels were calculated with binary logistic regression.

Results: Elevated blood metal ion levels were more common in MoM THA than in resurfacing patients (17.4% vs 5.9%, P < .001), and in 5 of the 7 THA brands, more than 20% of patients had elevated metal ion concentrations, whereas the proportion was less than 10% in all hip resurfacings. In resurfacings, small femoral head (odds ratio [OR] 1.30 per millimeter decrease [CI, 1.12-1.49]), high acetabular inclination (OR 1.15 per degree increase [CI 1.09-1.22]), and young age (OR 1.05 per year decrease [1.02-1.10]) were independent risk factors for elevated ions. In the THA group, female gender (OR 2.04 [CI 1.35-3.06]), longer time between surgery and ion measurement (OR 1.19 per year increase [CI 1.05-1.34]), and large headsize (OR 1.07 per millimeter increase [CI 1.01-1.13]) were risk factors for elevated ions.

Conclusion: Given the high percentage of elevated levels, the systematic surveillance of especially large diameter MoM THAs seems justified.
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http://dx.doi.org/10.1016/j.arth.2015.11.045DOI Listing
June 2016

Lessons learnt from metal-on-metal hip arthroplasties will lead to safer innovation for all medical devices.

Hip Int 2015 Jul-Aug;25(4):347-54. Epub 2015 Jul 13.

Royal National Orthopaedic Hospital, Stanmore - UK.

Metal-on-metal bearings were re-popularised in the late 1990s with the introduction of modern hip resurfacing. Large diameter (LD) metal-on-metal (MoM) hips became more prevalent and have been the least successful group of hip implants ever used. They were rapidly adopted from 2004 until the British Hip Society stopped their use in 2012. Well functioning MoM hip results (including the BHR and Metasul) are hidden in the mire of poor results from the group of all MoM bearings.We have reviewed what happened and we make 3 observations. Firstly, collaboration between surgeons and then between surgeons and other disciplines, first identified and then solved the clinical management problems. Secondly, the problems with MoM hips occurred because hip simulation was inadequate at predicting performance in patients. They gave no indications of the biological effects of wear in the human environment. Lastly, retrieval of failed implants was essential to understanding why failure occurred.These lessons must never be forgotten and must form the basis by which new or altered implants are introduced and how they should be monitored. This will enable safer innovation for patients, surgeons and manufacturers. The problems with MoM hips will not have been in vain.
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http://dx.doi.org/10.5301/hipint.5000275DOI Listing
June 2016

Changes in blood ion levels after removal of metal-on-metal hip replacements: 16 patients followed for 0-12 months.

Acta Orthop 2014 Jun 23;85(3):259-65. Epub 2014 Apr 23.

Institute of Orthopedic Research and Education.

Background And Purpose: In patients with metal-on-metal (MoM) hip prostheses, pain and joint effusions may be associated with elevated blood levels of cobalt and chromium ions. Since little is known about the kinetics of metal ion clearance from the body and the rate of resolution of elevated blood ion levels, we examined the time course of cobalt and chromium ion levels after revision of MoM hip replacements.

Patients And Methods: We included 16 patients (13 female) who underwent revision of a painful MoM hip (large diameter, modern bearing) without fracture or infection, and who had a minimum of 4 blood metal ion measurements over an average period of 6.1 (0-12) months after revision.

Results: Average blood ion concentrations at the time of revision were 22 ppb for chromium and 43 ppb for cobalt. The change in ion levels after revision surgery varied extensively between patients. In many cases, over the second and third months after revision surgery ion levels decreased to 50% of the values measured at revision. Decay of chromium levels occurred more slowly than decay of cobalt levels, with a 9% lag in return to normal levels. The rate of decay of both metals followed second-order (exponential) kinetics more closely than first-order (linear) kinetics.

Interpretation: The elimination of cobalt and chromium from the blood of patients who have undergone revision of painful MoM hip arthroplasties follows an exponential decay curve with a half-life of approximately 50 days. Elevated blood levels of cobalt and chromium ions can persist for at least 1 year after revision, especially in patients with high levels of exposure.
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http://dx.doi.org/10.3109/17453674.2014.913223DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4062792PMC
June 2014

A comparison of the diagnostic accuracy of MARS MRI and ultrasound of the painful metal-on-metal hip arthroplasty.

Acta Orthop 2014 Aug 3;85(4):375-82. Epub 2014 Apr 3.

Institute of Orthopedic and Musculoskeletal Science , University College London, the Royal National Orthopedic Hospital, Brockley Hill , Stanmore.

Background And Purpose: Metal artifact reduction sequence (MARS) MRI and ultrasound scanning (USS) can both be used to detect pseudotumors, abductor muscle atrophy, and tendinous pathology in patients with painful metal-on-metal (MOM) hip arthroplasty. We wanted to determine the diagnostic test characteristics of USS using MARS MRI as a reference for detection of pseudotumors and muscle atrophy. PatienTS AND METHODS: We performed a prospective cohort study to compare MARS MRI and USS findings in 19 consecutive patients with unilateral MOM hips. Protocolized USS was performed by consultant musculoskeletal radiologists who were blinded regarding clinical details. Reports were independently compared with MARS MRI, the imaging gold standard, to calculate predictive values.

Results: The prevalence of pseudotumors on MARS MRI was 68% (95% CI: 43-87) and on USS it was 53% (CI: 29-76). The sensitivity of USS in detecting pseudotumors was 69% (CI 39-91) and the specificity was 83% (CI: 36-97). The sensitivity of detection of abductor muscle atrophy was 47% (CI: 24-71). In addition, joint effusion was detected in 10 cases by USS and none were seen by MARS MRI.

Interpretation: We found a poor agreement between USS and MARS MRI. USS was inferior to MARS MRI for detection of pseudotumors and muscle atrophy, but it was superior for detection of joint effusion and tendinous pathologies. MARS MRI is more advantageous than USS for practical reasons, including preoperative planning and longitudinal comparison.
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http://dx.doi.org/10.3109/17453674.2014.908345DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4105768PMC
August 2014

Revision of metal-on-metal hip arthroplasty in a tertiary center: a prospective study of 39 hips with between 1 and 4 years of follow-up.

Acta Orthop 2013 Jun 28;84(3):237-45. Epub 2013 Apr 28.

Department of Orthopaedic Surgery, Imperial College, Charing Cross Hospital, London, UK.

Background And Purpose: Operative findings during revision of metal-on-metal hip arthroplasty (MOMHA) vary widely and can involve massive soft tissue and bone disruption. As a result, planning of theater time and resources is difficult, surgery is challenging, and outcomes are often poor. We describe our experience with revision of MOMHA and provide recommendations for management.

Patients And Methods: We present the findings and outcomes of 39 consecutive MOMHAs (in 35 patients) revised in a tertiary unit (median follow-up time 30 (12-54) months). The patients underwent a preoperative work-up including CT, metal artifact reduction sequence (MARS) MRI, and blood metal ion levels.

Results: We determined 5 categories of failure. 8 of 39 hips had conventional failure mechanisms including infection and impingement. Of the other 31 hips, 14 showed synovitis without significant disruption of soft tissue; 6 had a cystic pseudotumor with significant soft tissue disruption; 7 had significant osteolysis; and 4 had a solid pseudotumor. Each category of failure had specific surgical hazards that could be addressed preoperatively. There were 2 reoperations and 1 patient (2 hips) died of an unrelated cause. Median Oxford hip score (OHS) was 37 (9-48); median change (ΔOHS) was 17 (-10 to 41) points. ΔOHS was similar in all groups-except those patients with solid pseudotumors and those revised to metal-on-metal bearings, who fared worse.

Interpretation: Planning in revision MOMHA is aided by knowledge of the different categories of failure to enable choice of appropriate personnel, theater time, and equipment. With this knowledge, satisfactory outcomes can be achieved in revision of metal-on-metal hip arthroplasty.
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http://dx.doi.org/10.3109/17453674.2013.797313DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3715818PMC
June 2013

Pseudotumors in association with well-functioning metal-on-metal hip prostheses: a case-control study using three-dimensional computed tomography and magnetic resonance imaging.

J Bone Joint Surg Am 2012 Feb;94(4):317-25

Department of Orthopaedic Surgery, Charing Cross Hospital (Imperial College Healthcare NHS Trust and Imperial College London), Fulham Palace Road, London W6 8RF, United Kingdom.

Introduction: Many papers have been published recently on the subject of pseudotumors surrounding metal-on-metal hip resurfacing and replacement prostheses. These pseudotumors are sterile, inflammatory lesions within the periprosthetic tissues and have been variously termed masses, cysts, bursae, collections, or aseptic lymphocyte-dominated vasculitis-associated lesions (ALVAL). The prevalence of pseudotumors in patients with a well-functioning metal-on-metal hip prosthesis is not well known. The purpose of this study was to quantify the prevalence of pseudotumors adjacent to well-functioning and painful metal-on-metal hip prostheses, to characterize these lesions with use of magnetic resonance imaging, and to assess the relationship between their presence and acetabular cup position with use of three-dimensional computed tomography.

Methods: We performed a case-control study to compare the magnetic resonance imaging findings of patients with a well-functioning unilateral metal-on-metal hip prosthesis and patients with a painful prosthesis (defined by either revision arthroplasty performed because of unexplained pain or an Oxford hip score of <30 of 48 possible points). Thirty patients with a painful hip prosthesis and twenty-eight controls with a well-functioning prosthesis were recruited consecutively. All patients also underwent computed tomography to assess the position of the acetabular component.

Results: Thirty-four patients were diagnosed with a pseudotumor. However, the prevalence of pseudotumors in patients with a painful hip (seventeen of thirty, 57%) was not significantly different from the prevalence in the control group (seventeen of twenty-eight, 61%). No objective differences in pseudotumor characteristics between the groups were identified. No clear association between the presence of a pseudotumor and acetabular component position was identified. The Oxford hip score in the group with a painful hip (mean, 20.2; 95% confidence interval [CI], 12.7 to 45.8) was poorer than that in the control group (mean, 41.2; 95% CI, 18.5 to 45.8; p ≤ 0.0001).

Conclusions: A periprosthetic cystic pseudotumor was diagnosed commonly (in thirty-four [59%] of the entire study cohort) with use of metal artifact reduction sequence (MARS) magnetic resonance imaging in this series of patients with a metal-on-metal hip prosthesis. The prevalence of pseudotumors was similar in patients with a well-functioning hip prosthesis and patients with a painful hip. Pseudotumors were also diagnosed commonly in patients with a well-positioned acetabular component. Although magnetic resonance imaging is useful for surgical planning, the presence of a cystic pseudotumor may not necessarily indicate the need for revision arthroplasty. Further correlation of clinical and imaging data is needed to determine the natural history of pseudotumors to guide clinical practice.
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http://dx.doi.org/10.2106/JBJS.J.01508DOI Listing
February 2012

Magnetic resonance imaging findings in painful metal-on-metal hips: a prospective study.

J Arthroplasty 2011 Jan 9;26(1):71-6, 76.e1-2. Epub 2010 Feb 9.

Imperial College London, London, UK.

Metal artifact reduction sequence magnetic resonance imaging findings are reported in a prospective series of 31 patients with unexplained painful metal-on-metal (MOM) hips. The abnormalities identified were fluid collection (20 patients), solid mass (2 patients), moderate to severe muscle atrophy (23 patients), and muscle edema (8 patients). In conclusion, soft tissue lesions and muscle atrophy appear to be prevalent in unexplained painful MOM hips. Metal artifact reduction sequence magnetic resonance imaging may be useful to diagnose and monitor at-risk hips but requires validation in well-functioning MOM hips before it can guide clinical decision making.
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http://dx.doi.org/10.1016/j.arth.2009.11.008DOI Listing
January 2011