High complication rates and poor outcomes have been widely reported in patients undergoing revision of large head metal-on-metal arthroplasty. A previous study from our centre showed high rates of dislocation, nerve injury, early cup loosening and pseudotumor recurrence. After noting these issues, we implemented the following changes in surgical protocol in all large head MOM revisions: One: Use of highly porous shells in all cases. Two: Use of largest femoral head possible. Three: Low threshold for use of dual mobility and constrained liners when abductors affected or absent posterior capsule. Four: Use of ceramic head with titanium sleeve in all cases. Five: Partial resection of pseudotumor adjacent to sciatic and femoral nerves.

The purpose of the present study is to compare the new surgical protocol above to our previously reported early complications in this group of patients

We specifically looked at (1) complications including reoperations, (2) radiologic outcomes, and (3) functional outcomes. Complication rates after (Group 1), and before (Group 2) modified surgical protocol were compared using Chi-square test, assuming statistical significance p < 0 .05.

Major complications occurred in 4 (8.3%) of 48 patients who had modified surgical technique, compared to 12 (38%) of 32 revisions prior to modification (p < 0 .05). Two hips of 48 (4.17%) endured dislocations in Group 1, compared to 9 of 32 (28%) in Group 2 (p < 0 .05). Four patients of 48 had repeat revision in Group 1: 2 for recurrence of pseudotumor, 1 for dislocation, and 1 for infection, compared to 6 patients who had 7 repeat revisions of 32 patients in Group 2: 3 for acetabular loosening, 3 for dislocation, and 1 for recurrence of pseudotumor (p=0.1). None of 48 revisions in Group 1 had acetabular loosening, compared to 4 of 32 in Group 2 (p=0.02). Two patients had nerve injury in Group 2, compared to none in Group 1 (p=0.16). The mean WOMAC pain score was 87.1 of 100 and the function score was 88.4 of 100 in Group 1, compared to a mean WOMAC pain score of 78 of 100 (p=0.6) and a function score of 83 of 100 in Group 2 (p=0.8).

Modification of the surgical techniques described in the introduction has resulted in a significant decrease in complications in revision of large head MOM total hips. We continue to use this protocol and recommend it for these difficult cases.

The prevalence of pseudotumours in patients with large-head metal-on-metal (MOM) THA has been the subject of implant recalls and warnings from various regulatory agencies. To date, there is no consensus on whether ultrasound or MRI is superior for the detection and following the progression of pseudotumours. Ultrasound is relatively cheap but can be operator dependent. MARS MRI has the advantage of excellent visibility of the soft tissue. However, MRI comes at a marked increase cost and takes about twice as long to perform. At our institution, we prospectively compared ultrasound to MRI for pseudotumour detection in an asymptomatic cohort of patients with MOM THAs. We enrolled 40 patients with large-head MOM THAs in the study. The mean age was 54 years (range, 34–76 years). The mean time from surgery was 54 months (range, 40–81 months). There were 28 men and 12 women. All patients underwent ultrasound and MRI using slice encoding for metal artifact correction. The gold standard was defined as follows: if both ultrasound and MRI agreed, this was interpreted as concordant and the result was considered accurate. Ultrasound and MRI agreed in 37 of 40 patients (93%). The prevalence of pseudotumours was 31% (12 of 39) in our cohort. Twenty-three of 39 patients (59%) had completely normal tests and four (10%) had simple fluid collections. Ultrasound had a sensitivity of 100% and specificity of 96% while MRI had a sensitivity of 92% and specificity of 100%. Conclusions: A negative ultrasound rules out pseudotumour in asymptomatic patients as this test is 100% sensitive. Given its lower cost, we recommend ultrasound as the initial screening tool for pseudotumours. More recently, Kwon et al have compared ultrasound to MARS MRI for following the progression of pseudotumours. They found a strong agreement between the 2 modalities for assessing change in size and consistency of pseudotumours

The prevalence of pseudotumours in patients with large-head metal-on-metal (MOM) THA has been the subject of implant recalls and warnings from various regulatory agencies. To date, there is no consensus on whether ultrasound or MRI is superior for the detection of pseudotumours. Ultrasound is relatively cheap but can be operator dependent. MARS MRI has the advantage of excellent visibility of the soft tissue. However MRI comes at a marked increase cost and takes about twice as long to perform. At our institution we prospectively compared ultrasound to MRI for pseudotumour detection in an asymptomatic cohort of patients with MOM THAs. Methods. We enrolled 40 patients with large-head MOM THAs in the study. The mean age was 54 years (range, 34–76 years). The mean time from surgery was 54 months (range, 40–81 months). There were 28 men and 12 women. All patients underwent ultrasound and MRI using slice encoding for metal artifact correction. The gold standard was defined as follows: if both ultrasound and MRI agreed, this was interpreted as concordant and the result was considered accurate. Results. Ultrasound and MRI agreed in 37 of 40 patients (93%). The prevalence of pseudotumours was 31% (12 of 39) in our cohort. Twenty-three of 39 patients (59%) had completely normal tests and four (10%) had simple fluid collections. Ultrasound had a sensitivity of 100% and specificity of 96% while MRI had a sensitivity of 92% and specificity of 100%

Background. Previous studies have indicated poor outcomes and high complication rate in patients having revision of metal-on-metal (MoM) hip implants resulting from adverse local tissue reactions. Metal ions released by MoM bearings may potentially increase infection occurrence in patients with failed implants. Questions/purposes. We reviewed all patients at our institution who sustained revision of a failed large-head metal-on-metal hip implant to determine if infection-related complications are associated with the elevation of serum metal ions concentration. Methods. From December 2005 to April 2013, we performed 44 revisions of large-head MoM total hip arthroplasty (THA) and resurfacing in 44 patients. In all revision procedures MoM couplings (ASR XL Acetabular System and DePuy ASR Hip Resurfacing System) were explanted. Preoperative diagnosis were: aseptic loosening in 21 hips, hip pain with high serum metal ions levels in 7 hips, high serum metal ions levels without hip pain in 9 hips, deep infections in 4 hips, unexplained hip pain in 2 hips and periprosthetic fracture in 1 hip. Serum cobalt and chromium analysis were preoperatively conducted in 25 patients. Intraoperative fluid aspiration was performed in all cases to determine the presence or absence of periprosthetic joint infection. Results. Fluid analysis for bacteria reported that 35 of 45 cases were culture negative and 10 of 45 cases (22%) were culture positive to Staphylococcus (St) Aureus (4), St Capitis (2), St Epidermidis (2), St Hominis (1), Streptococcus Mitis (1). All preoperative diagnoses of deep infection were confirmed. Within patients evaluated with serum metal ions analysis (mean Co and Cr, 78 μg/l and 39 μg/l, respectively), five cultures resulted positive (20%). The infection rate within patients with higher (> 20 μg/l) metal ions levels (4 positive cultures of 18, 22%) was not significantly higher than infection rate within patients with lower (≤ 20 μg/l) metal ions levels (1 positive culture of 7, 14%). Conclusions. We observed a high rate of periprosthetic joint infection among our revision cases. High metal ions concentrations released by MoM bearings might promote bacterial infections in patients with MoM THA and resurfacing. When evaluating patients with failed MoM hip devices, there may be an increased incidence of co-infection in these patients