What are the predictors and prevalence of pseudotumor and elevated metal ions after large-diameter metal-on-metal THA?

BACKGROUND: Soft tissue masses, or "pseudotumors," around metal-on-metal total hip arthroplasty (MoM THA) have been reported frequently; however, their prevalence remains unknown. Several risk factors, including elevated metal ion levels, have been associated with the presence of pseudotumor, although this remains controversial. QUESTIONS/PURPOSES: The goals of this study were to (1) determine the prevalence of pseudotumors after large-diameter head MoM THA; (2) identify risk factors associated with pseudotumor formation and elevated metal ion levels; and (3) determine the early failure rate of large-diameter MoM THA. METHODS: Between December 2005 and November 2012, 258 hips (215 patients) underwent large-diameter head primary MoM THA at our institution. Clinical followup was obtained in 235 hips (91%). Using an inclusion criteria of a minimum followup of 1 year, a subset of 191 hips (mean followup, 4 years; range, 1-7 years) was recruited for high-resolution ultrasound screening for the presence of pseudotumor. Whole blood cobalt and chromium ion levels, UCLA activity level, WOMAC score, patient demographics as well as surgical, implant, and radiographic data were collected. Bivariate correlations and multivariate log-linear regression models were used to compare the presence of pseudotumor and elevated metal ions with all other factors. RESULTS: Ultrasound detected a solid, cystic, or mixed mass in 20% hips (38 of 191). No correlation was found between the presence of pseudotumor and any risk factor that we examined. After controlling for confounding variables, elevated cobalt ions were correlated (p<0.001, R=0.50, R2=0.25) with smaller femoral head size, the presence of bilateral MoM THA, and female sex. Elevated chromium ions were correlated (p<0.001, R=0.59, R2=0.34) with smaller femoral head size, presence of bilateral MoM THA, and lower body mass index. The overall survival of MoM THA was 96% at a mean followup of 4.5 years (range, 2-8 years). CONCLUSIONS: With the numbers available, we found no associations between the presence of pseudotumor and the potential risk factors we analyzed, including elevated metal ion levels. Further work is needed to explain why larger femoral head sizes resulted in lower metal ion levels despite being associated with higher early failure rates in joint registry data. LEVEL OF EVIDENCE: Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Unnecessary ordering of magnetic resonance imaging of the knee: A retrospective chart review of referrals to orthopedic surgeons.

There is a noticeable increase in the unnecessary ordering of Magnetic Resonance Imaging (MRI) of the knee in older patients. This quality improvement study assessed the frequency of unnecessary pre-consultation knee MRIs and investigated the effect on the outcome of the patients' consultation with the orthopedic surgeon. 650 medical charts of patients aged 55 years or older referred to an orthopedic clinic with knee complaints were reviewed. Patients arriving with a pre-consultation MRI were identified, and the usefulness of the MRI was evaluated using the appropriateness criteria developed to support this study. Of the 650 patient charts reviewed, 225 patients presented with a pre-consultation MRI, 76% of which were not useful for the orthopedic surgeon. The ordered knee MRI scans were considered not useful because they were requested for confirmed meniscal tear for patients ≥55 years, suspected degenerative disorder and ligament/tendon injury, or for patients with severe osteoarthritis without locking or extension. These MRI scans were done despite the absence of signs of effusion, tenderness, soft tissue swelling, decreased range of motion, or difficulty of weight-bearing, a lack of persistent knee joint pain at the time of assessment, or with no x-ray before ordering MRI. Half of the patients with a pre-consult MRI did not present with plain radiographs of their knee, however, 35% of those still required an x-ray to be ordered at the time of the surgical consult. A logistic regression analysis on post-consult disposition found that patients with pre-consult MRI were less likely to be considered for total knee arthroplasty (TKA) (OR 0.424, CI 0.258-0.698, p = 0.001). Patients assessed by an advanced practice physiotherapist prior to referral for surgical consult were 4.47 more likely to have TKA (CI 2.844-7.039, p< 0.000). Most of the pre-consult knee MRIs were deemed as unnecessary for the orthopedic surgeon's clinical decision-making. This study highlights the potential benefits of following a comprehensive model of care within the referral process to reduce the unnecessary high orders of pre-consult MRI scans.

Total hip arthroplasty following failure of free vascularized fibular graft.

BACKGROUND: Many treatments for osteonecrosis of the femoral head, including the use of a free vascularized fibular graft, have been advocated in an attempt to delay the need for hip arthroplasty. The purpose of this study was to document the clinical and radiographic results of total hip arthroplasty performed following failure of a free vascularized fibular grafting procedure. METHODS: Twenty total hip arthroplasties in eighteen patients who had previously undergone a free vascularized fibular grafting procedure for the treatment of osteonecrosis were retrospectively reviewed. A straight-stem femoral component was used in twelve hips, a tapered femoral component with removal of residual fibular graft was used in five hips, and a tapered stem without graft removal was used in three hips. The twelve hips with a straight-stem femoral component and previous vascularized fibular grafting were compared with thirty-six osteonecrotic hips in thirty other patients who had undergone total hip arthroplasty but had not had previous free vascularized fibular grafting. The radiographic outcomes with respect to initial femoral component alignment and subsequent migration and the clinical outcomes were compared. RESULTS: Analysis of the immediate postoperative radiographs demonstrated significantly improved alignment of the femoral component when a high-speed burr had been used to remove residual fibular graft (p = 0.001), although doing so did significantly increase both the intraoperative blood loss (p = 0.017) and the operative time (p = 0.0002). There was no significant difference in the amount of migration of either the acetabular or the femoral component between the control and study groups at the time of the most recent follow-up. When comparing patients with or without a previous free vascularized fibular graft, the mean postoperative scores at three years were significantly worse in patients who had undergone a previous free vascularized fibular graft (p = 0.03). One revision occurred in the study group at seventy-two months due to acetabular wear, and one revision occurred in the control group at 108 months due to aseptic loosening. CONCLUSIONS: This study raises concern that the outcome of total hip arthroplasty in patients who previously underwent a free vascularized fibular graft for the treatment of osteonecrosis of the femoral head may be worse than that in patients without previous free vascularized fibular grafting. The intraoperative use of a high-speed burr can improve the alignment of the femoral component by removing more of the residual graft. However, this technique does increase intraoperative blood loss and operative time. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions to Authors on jbjs.org for a complete description of levels of evidence.

The effect of muscle contusion on cortical bone and muscle perfusion following reamed, intramedullary nailing: a novel canine tibia fracture model.

BACKGROUND: Management of tibial fractures associated with soft tissue injury remains controversial. Previous studies have assessed perfusion of the fractured tibia and surrounding soft tissues in the setting of a normal soft tissue envelope. The purpose of this study was to determine the effects of muscle contusion on blood flow to the tibial cortex and muscle during reamed, intramedullary nailing of a tibial fracture. METHODS: Eleven adult canines were distributed into two groups, Contusion or No-Contusion. The left tibia of each canine underwent segmental osteotomy followed by limited reaming and locked intramedullary nailing. Six of the 11 canines had the anterior muscle compartment contused in a standardized fashion. Laser doppler flowmetry was used to measure cortical bone and muscle perfusion during the index procedure and at 11 weeks post-operatively. RESULTS: Following a standardized contusion, muscle perfusion in the Contusion group was higher compared to the No-Contusion group at post-osteotomy and post-reaming (p < 0.05). Bone perfusion decreased to a larger extent in the Contusion group compared to the No-Contusion group following osteotomy (p < 0.05), and the difference in bone perfusion between the two groups remained significant throughout the entire procedure (p < 0.05). At 11 weeks, muscle perfusion was similar in both groups (p > 0.05). There was a sustained decrease in overall bone perfusion in the Contusion group at 11 weeks, compared to the No-Contusion group (p < 0.05). CONCLUSIONS: Injury to the soft tissue envelope may have some deleterious effects on intraosseous circulation. This could have some influence on the fixation method for tibia fractures linked with significant soft tissue injury.