Synovial cells inappropriately release cytokines that recruit immune cells and fibroblasts and create a toxic environment to cartilage . The synovial cells are a primary source of the inflammation, and therefore, complete synovectomy is needed to minimize the risk of continued pain and disability .
Young Age. On average Rheumatoid Arthritis (RA) patients are 10 years younger than typical OA patient requiring THA . Greater functional demands, increased longevity requirements for the implant and higher expectations all contribute to making younger patients more challenging to treat successfully (see Patient Risk Factors – Age).
Polyarticular Involvement. Inflammatory Arthritis rarely affects an isolated joint. A broader view of functional goals must be addressed before a joint surgeon puts on the blinders as says “Your knee looks terrible, I can fix that and you will feel better.” The ipsilateral hip and knee are affected in up to 50% of cases, and the upper extremity (especially MCP, PIP, and also wrist joint) are involved in most cases . A plan that addresses the multiple sources of disability will maximize rehab/recovery and minimize risk of complication. Should a wrist be fused before TKA to maximize postop recovery or will TKA rehab overstress a fused wrist leading to higher risk of complication? Can an ipsilateral hip and knee be addressed in the same hospitalization? If not, which should undergo surgery first? It is generally recommended that THA preceed TKA, as rehab from THA is less affected by a painful ipsilateral knee than vise versa. Obtaining deep knee flexion after TKA requires adequate hip ROM, which can be compromised by a severely arthritic hip.
RA patients commonly have c-spine instability (90%) and therefore a lateral c-spine flexion/extension x-ray are important to evaluate canal diameter (< 14 mm is risk for cord compression, and ADI >10 mm is risk for instability). Patients with ankylosing spondylitis similarly have spine issues, notably loss of lumbar spine lordosis, which can lead to pelvic hyperextension and increased anteversion.
Severe Deformity. Standard implants assume that a given patient will fall within a range of anatomic “normal”, whereby variations in femoral neck angle, canal diameters, etc can be addressed by the variety of implant sizes in a normal tray. Yet in inflammatory arthritis, its not uncommon for these patients to fall outside is “normal”. JRA for example may present with excessive femoral anteversion, anterior bowing. Its therefore, important to obtain anatomic measurements, and consider custom implants when necessary. These patients have higher risk of acetabluar protrusion (which complicates the surgical approach and may require in situ femoral neck cut, or troch osteotomy. it also brings the sciatic nerve closer to the surgical field). Juvenile Rheumatoid arthritis patients commonly present with excessive femoral anteversion and anterior bowing.
Bone Quality. Many patients have poor bone quality secondary to disease and chronic medication (such as steroids). There is a higher risk of acetabular protrusion in THA for RA patients (10% vs. < 2% for primary OA) and even higher risk in ankylosing spondylitis (30%).
Cementless femoral stems in THA show lower rates of loosening in RA patients , and yet cemented stems may be considered to reduce the higher rates of periprosthetic fracture intraop and postop. Furthermore, there is a high incidence of large cystic areas that may require bone grafting. Postoperative subsidence, particularly along the medial tibia following TKA is a concern. Aseptic loosening remains a concern for TKA and thus cemented components are recommended.
Soft Tissue Quality. Ligament attenuation may require greater implant constraint (which has the unfortunate effect of translating greater force to the bone implant interface, where the bone is also less strong, thus risking premature loosening). However, the opposite is also seen, whereby chronic deformity leads to rigid contractures (particularly knee flexion contractures after long-term wheelchair use), which can be refractory to intraoperative correction (with approximately 30% residual deformity postop). There are reports on preoperative serial casting to address the contracture.
Patients with ankylosing spondylitis have a high risk for developing hetertopic ossification post-op (consider giving 700 cGy within 72 hours to minimize risk). In psoriatic patients avoid any incision that includes a plaque as they are colonized by bacteria.
Systemic Disease: Higher rate of dermatitis, fragile skin, and vasculitis can lead to wound complications. Osteopenia is common, and may lead to implant loosening, periprosthetic fractures, and implant subsidence.
Medications (immune-modulating agents) .
-NSAIDS. Associated with a higher risk of bleeding, and while some recommended holding one week before surgery , other sources demonstrate no correlation between nsaids and increased transfusion risk .
-STEROIDS. Are used as maintenance medication or episodic dosing for flair ups. This is an important distinction, as patients on chronic steroids may have adrenal insufficiency and will thus require a stress dose of 50-100 mg hydrocortisone (or 10-15 mg methylprednisone IV) with postoperative taper to the preoperative dose to prevent an Addison’s Crisis . Chronic steroids are associated with poor bone quality, poor wound healing and immunocompromise (with 3x increased risk of joint infection ).
-DMARDS. These medications have been hugely successful in slowing the progression of disease and delaying the need for TJA, decreasing the incidence of THA in RA patients by 50% since the advent of TNF-alpha inhibitors. In patients that do require arthroplasty, these medications exhibit immunomulatory effects and thus dosing must be considered individually with regards to timing of surgery . In contrast to most DMARDS, Methotrexate should not be held in the perioperative period, as studies demonstrate a higher infection rate when held (with the exception of renal impaired patients, whereby it should be held 1 weeks before and after surgery). Examining the chart indicates that joint surgeons should not simply stop all medications before surgery, but rather discuss timing with a patient’s rheumatologist, to minimize the risk of a flair in other joints after surgery, thus delaying rehab from surgery.
Outcomes: Despite the additional complexity associated with TJA for inflammatory arthritis, the outcomes are positive. Survivorship at 10 years is about 90% (and comparable to standard OA patients) . Functional scores were inferior to OA patients, however, this is hardly surprising considering the polyarticular involvement in these patients.
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