Faculty Bibliography

Rehabilitation after total hip and knee arthroplasty is a rapidly expanding discipline. With the introduction of minimally invasive techniques and the pressure of insurance regulations, postoperative rehabilitation has been placed on an accelerated track. As surgeons turn to more aggressive postoperative protocols and early entry into outpatient therapies, we introduce a pre- and postoperative program involving the Pilates method. Renewed patient interest in the use of Pilates for postoperative rehabilitation has led to the development of safe and modified exercises for patients undergoing total hip or knee arthroplasty. While this technique appears safe and effective anecdotally, further controlled trials are necessary to prove its validity

Hydroxyapatite-coated femoral components were introduced to enhance fixation, but concerns were raised about whether the coating would be maintained over time. We therefore determined the long-term clinical and radiographic results of a proximally hydroxyapatite-coated femoral component and compared the mechanical failure rate to other fixation methods at similar lengths of followup. The study group, culled from a large, multicenter prospective study population, consisted of 146 patients (166 hips) with followup of 15 to 18 years. Average age at time of the index procedure was 51 years, and the most common diagnoses were osteoarthritis (71%) and osteonecrosis (11%). Average Harris hip scores were 42.7 preoperatively and 91.5 at most recent followup. Radiographically, one stem showed stable fibrous fixation, and all other unrevised stems were bony stable. Of 13 stem revisions in the study population, only one stem has been revised for aseptic loosening. Forty-nine percent of hips have an osteolytic lesion in proximal areas of Gruen Zones 1, 7, 8, or 14 only. Both the femoral aseptic revision and mechanical failure rates are 0.6% at 15-year minimum followup. The data demonstrate excellent long-term survivorship of this hydroxyapatite-coated femoral component used in a relatively young patient group

Use of a dished polyethylene insert in 114 total knee arthroplasties, all with the posterior cruciate ligament resected or recessed, was retrospectively studied. Patients were evaluated at a mean follow-up of 8.3 years. Mean range of motion increased from 92 degrees to 111 degrees . Mean Knee Society pain and function scores increased from 35.2 and 39.7 to 91.3 and 74.7, respectively. WOMAC scores improved significantly in each category evaluated, including pain, stiffness, and physical function. Kaplan-Meier survivorship was 95% at 10 years (95% confidence interval, 82%-99%). The use of a dished polyethylene insert in primary total knee arthroplasty provides good to excellent midterm results regardless of whether the posterior cruciate ligament is recessed or sacrificed

Total hip arthroplasty has evolved in regard to surgical technique, implant design, and long-term survivorship over the last several decades with excellent clinical results. Owing to these improvements, indications for surgery have expanded to include a greater variety of patients. We present the case of a 62-year-old man who underwent total hip arthroplasty 39 years after contralateral hemipelvectomy. The importance of an appropriate preoperative plan in regard to patient positioning and postoperative protocol is addressed. Our patient was informed that data concerning his case would be submitted for publication

We have investigated the role of the penetration of saline on the shear strength of the cement-stem interface for stems inserted at room temperature and those preheated to 37 degrees C using a variety of commercial bone cements. Immersion in saline for two weeks at 37 degrees C reduced interfacial strength by 56% to 88% after insertion at room temperature and by 28% to 49% after preheating of the stem. The reduction in porosity as a result of preheating ranged from 71% to 100%. Increased porosity correlated with a reduction in shear strength after immersion in saline (r = 0.839, p < 0.01) indicating that interfacial porosity may act as a fluid conduit

Advances in medical treatment have led to improved life expectancy in patients with sickle cell hemoglobinopathies. Improved life expectancy has, in turn, led to an increasing number of patients with osteonecrosis requiring total hip arthroplasty. Patient evaluation begins with understanding the extent of the disease process and the patient's musculoskeletal manifestations (ie, pyogenic infection, marrow hyperplasia, osteonecrosis). A multidisciplinary approach to implementing effective preoperative treatment strategies increases the likelihood of a successful surgical outcome. Intraoperatively, consideration of bone stock, bone quality, and method of component fixation may help minimize the risk of eccentric reaming, perforation or fracture of either the acetabulum or the femur, and loosening. The optimal mode of acetabular and femoral fixation in these patients has not been conclusively determined, but recent results of cementless total hip arthroplasty have been encouraging. Although patients with sickle cell disease are at increased risk of medical and surgical complications, total hip arthroplasty in the appropriately selected patient can provide significant pain relief, restoration of function, and patient satisfaction

To address the clinical problems of joint stiffness, acetabular pain, and component wear, recent bipolar heads have been designed to achieve increased inner bearing range of motion. We tested four designs to determine if this compromises component integrity. Inner bearing ranges of motion were determined and the components then mechanically tested to determine inner bearing pull-out disassociation strengths as well as static and dynamic impingement forces for disassociation. Inner bearing ranges of motion with a 22 mm head were between 65 degrees to 84 degrees for the four prostheses. Pull-out forces for disassociation ranged between 700 N to 1475 N; static impingement forces were 20 Nm to 49 Nm and dynamic impingement forces were 5 Nm to 24 Nm. There was no relation between bipolar head inner bearing range of motion and the potential for component disassociation; however, one design modification produced a lowered disassociation strength. Design modifications must be evaluated by a variety of test methods to adequately determine their effects on bipolar head integrity

Long-term survival of uncemented hip components is dependent upon successful biological fixation. This study examined a new prosthetic surface treatment consisting of a highly porous open structure of commercially pure titanium, Tritanium Dimensionalized Metal; its overall porosity is approximately 65-70%. With the use of an implantable chamber in dogs, the effects of this treatment on bone ingrowth and strength of attachment were compared to both titanium (overall porosity of 30-35%) and cobalt chrome beads (overall porosity of 35-40%), with and without hydroxyapatite coating. At 6 and 12 weeks, chambers were explanted and specimens underwent high-resolution radiographic imaging and mechanical testing. At 12 weeks, Tritanium surfaces had greater bone penetration and tensile strength than remaining surface types. Over 40% of the Tritanium specimens had a tensile strength greater than 500 N, exceeding the testing capability of the servohydraulic equipment. The highly porous Tritanium surfaces allow for a far greater amount of bone ingrowth than beaded surfaces, and may create a geometry that enhances mechanical strength. Tritanium Dimensionalized Metal surface treatment may result in a clinically valuable implant fixation surface to induce rapid ingrowth and a strong bone-implant interface, contributing to increased implant survivorship

It has been shown that preheating the femoral stem prior to insertion minimizes interfacial porosity at the stem-cement interface. In this study, the effects of methylmethacrylate monomer temperature prior to mixing on the properties of stem-cement interface and cement polymerization were evaluated for 4 degrees C, room temperature, and 37 degrees C using a test model and cementing techniques that simulated a clinical situation. The nature and extent of interfacial porosity of stem-cement interface was quantified, the static shear strength of the stem-cement interface determined, and the time and temperature of polymerization at the cement-bone interface were measured. Compared to RT monomer, preheating monomer to 37 degrees C produced higher polymerization temperatures and greater initial interfacial shear strength with an unchanged amount of interfacial porosity. Precooling monomer to 4 degrees C produced lower polymerization temperatures and decreased initial interfacial shear strength, with the amount of interfacial porosity unchanged compared to the RT group. Although clinical techniques of preheating or precooling bone cement have some effects on the properties of the stem-cement interface and cement polymerization, they do not appear to enhance implant fixation