Using MRI To Detect Soft Tissue Reactions And Implant Integration As Related To Implant Modularity

All enrolled arthroplasty designs will be evaluated utilizing the input of:

• Evaluation of MR images: Presence, location, type and volume of synovitis, Synovial thickness, Impression of synovium, Presence and location of decompression of synovitis, Presence and location of low signal intensity deposits, Presence of soft tissue edema, Presence and location of dehiscence, Presence, location and volume of osteolysis, Assessment of implant loosening, Presence of and location of neurovascular compression, Disruption of abductors due to distended pseudocapsule, Presence of enlarged lymph nodes and presence and grading of adverse local tissue reaction.
• Pre-operative blood metal ion levels
• Pre-operative Hip disability and Osteoarthritis Outcome Score
• Pathologic evaluation of tissue obtained intra-operatively
• Intra-operative grade of soft tissues around the primary total hip replacement
• Implant wear analysis

All enrolled arthroplasty designs will be evaluated utilizing the input of:

• The formation a fibrous membrane and/or osteolysis around the implants
• Individual risk factors from subjects (gender, BMI, primary diagnosis, and level of activity)
• Individual risk factors based on implant characteristics (stem length, head size, and modular stem connections).

Patients will be classified as symptomatic with mechanical symptoms and symptomatic with unexplained pain. These groups are based on the categories used by the National Joint Registry of England and Wales. Patients presenting with loosening, instability, or malalignment will be classified as "mechanical" failure. In cases of loosening, patients will be categorized as having acetabular or femoral loosening, only when documented intra-operatively by the surgeon. Patients presenting with pain not attributable to implant loosening, instability, or component malposition will be classified as "unexplained" failure. No specific unit of measure will be used for this outcome measure.

Blood samples will be drawn into lithium-heparin containing tubes with non-contamination precautions, and analyzed with high resolution inductively coupled mass spectrometry for the most accurate assessment of Cobalt and Chromium metal ion levels, to be measured in parts per million (ppm) or microgram per liter (ug/L)

The assessment of hip replacement acetabular component position will be performed using the Einzel-Bild-Roentgen-Analysis (EBRA) software. The femoral stem-shaft angle will be measured in the frontal plane. The acetabular inclination angle will be measured in the frontal plane. The acetabular anteversion angle will be measured in the lateral plane. All measurements will be expressed in units of degrees.

Evaluation of MR images: Presence, location, type and volume (measurement units of mm^3) of synovitis, Synovial thickness (measurement units of mm), Impression of synovium, Decompression of synovitis, Decompression into Trochanteric Bursa, Decompression into Iliopsoas, Presence and location of low signal intensity deposits, Presence of soft tissue edema, Presence and location of dehiscence, Presence, location and volume (measurement units of mm^3) of osteolysis, Assessment of implant loosening, Presence of and location of neurovascular compression, Disruption of abductors due to distended pseudocapsule, Presence of enlarged lymph nodes and presence and grading of adverse local tissue reaction. All quantitative values have the units of measurement indicated.

A subjective scoring system will be used for intraoperative damage assessment of the hip joint. The system is based on a 0 to 3 scale denoting the level of involvement of the soft tissues surrounding the joint (capsule, synovium, and muscle): 0 = Normal tissue; 1 = Fluid collection ± mild synovial reaction with or capsular dehiscence; 2 = the same findings as a score of 1, but with moderate synovial reaction; and 3 = the same findings as a score of 2, but with the addition of damage to the abductor muscle and/or osteolysis. No specific unit of measure will be used for this outcome measure.

Histological evaluation will be using a 10 point aseptic lymphocytic vasculitis associated lesion (ALVAL) score to assess tissue reaction to a total hip replacement. The ALVAL score is a summation of individual grades assigned to the integrity of the synovial lining, presence and extent of inflammatory cell infiltrates, necrosis and tissue organization.

We will use a supplemental grading system intended for metal-on-poly and ceramic implants since ALVAL grading is used primarily for metal-on-metal (MOM) articulations and may not detect similar features of wear debris in non-MOM articulations, polyethylene, metal or corrosion products. The presence of ceramic and polyethylene particles and the relative number of macrophages, giant cells, histiocytes, acute or chronic inflammatory cells, and presence of necrotic tissue will be graded using the scale of: 1) absent (-), little (+), moderate (++), extensive (+++). No specific unit of measure will be used for this outcome measure.

The bearing surfaces of the femoral heads and acetabular components, the neck trunnion of the total hip replacement femoral stems, and the matching female tapers of the total hip replacement heads retrieved at surgery will be scanned with a technique that utilizes a non-contact measurement method to calculate volumetric wear (measurement units of mm^3) and linear wear (measurement units of mm).

Quantitative imaging, specifically T2 mapping of soft tissues near the implant, specifically, the synovium and synovial volume.