Alignment and Balance Methods in Total Knee Arthroplasty.

Total knee arthroplasty is one of the most commonly performed orthopaedic surgical procedures in the United States. Primary concepts in the surgical technique include restoring limb alignment and soft-tissue balance about the knee. Currently, traditional mechanical alignment concepts that focus on restoring neutral limb alignment have been challenged by the principle of kinematic alignment. In addition to these recent philosophical challenges, new technologies have been introduced to help the surgeon more accurately achieve optimal limb alignment and soft-tissue balance.

Case report: analysis of an ultra-high-molecular-weight polyethylene acetabular cup retrieval at 41 years.

A polyethylene cup explanted after 41 years was examined using several analytical techniques to determine whether there was a material cause for the extremely low wear observed. Neither the amount of polyethylene oxidation nor crystallinity appeared to be a factor.

Simultaneous bilateral total hip arthroplasty with hydroxyapatite-coated implants: a 20-year follow-up.

Bilateral hip arthroplasty has been reported to be a safe and effective way to treat bilateral hip arthritis in a selective group of patients. We report a follow-up of 30 patients who underwent simultaneous bilateral total hip arthroplasty with hydroxyapatite implants and were followed for an average of 19.4 years. Patients had an average Harris Hip Score of 90 at the latest follow-up (range, 78-99). The average Western Ontario and McMaster Universities Arthritis Index questionnaire index score was 12 (range, 0-41), with high functional results on the 12-Item Short Form Health Survey (SF-12) and Oxford 12 questioners. Using the Kaplan-Meier survivorship analysis, with revision for any reason as an end point, survivorship was 94% at 12 years, 88% at 15 years, 74% at 18 years, and 61% at 23 years. All revisions were for the acetabular component, and the survivorship for the femoral component was 100% throughout the 23-year period. We conclude that bilateral uncemented total hip arthroplasty can provide satisfactory long-term clinical, radiological, and functional outcomes in patients even with older-generation polyethylene liners and stem designs.

Acoustic emission studies of posterior stabilized and cruciate retaining knee arthroplasties.

Different acoustic frequencies have been used to diagnose progression of osteoarthritis, gross pathology, and wear in knee prostheses. It is possible that detailed analysis of higher frequencies could detect and quantify the smaller geometric changes (asperities) that develop in articular prosthetic wear. In this study we evaluated the feasibility of using ultrasonic emission to determine total knee arthroplasty (TKA) type and time from implantation using a simple, handheld measurement system. We examined the ultrasound emission generated by similar designs of posterior stabilized (PS) and cruciate retaining (CR) total knee prostheses and native knees of 58 patients and 10 controls. The subjects were asked to sit, rise, sit again, and take five steps while recording the acoustic data from both knees. Acoustic emission analysis examined frequency distributions and power spectrums of the recorded signals, and their relations to prosthesis type and time from implantation. We screened 44 CR and 48 PS TKAs, as well as 24 native knees. Analysis of this data suggested a possibility of differentiating between type of implants, and a relation to time since implantation. Our data suggest that we might be able to assess the status and time from implantation of a TKA by acoustic emission signals. Further in vitro analysis of the relationship of wear to ultrasonic emission data are needed for accurate quantification of arthroplasty wear. A simple, in-office screening tool for TKA patients could indicate which patients require closer follow-up and monitoring due to risk of potential problems.

Feasibility of using ultrasonic emission for clinical evaluation of prosthetic hips.

BACKGROUND: Previous acoustic emission (AE) studies of the hip have proposed using AE for the diagnosis of musculoskeletal conditions and assessing the clinical status (loosening, wear, etc.) of prostheses. However, these investigations have had problems with spurious signal noises or complicated measurement techniques, or both. PURPOSE: We performed a study on 98 patients to evaluate the feasibility of employing ultrasonic emission (UE) to determine total hip arthroplasty (THA) status, using a simple, hand-held measurement system that has addressed some of the prior problems with hip AE studies. METHODS: UE was recorded from both hips of study patients during walking and sitting activities. The patients had 79 metal-on-polyethylene implants, and at least 15 each with ceramic-on-polyethylene, ceramic-on-ceramic and metal-on-metal articulations; 10 young subjects without THA were similarly recorded as controls. Data were obtained from waveform analysis and standard UE signal parameters. Patient radiographs were evaluated for THA status, and wear measurements were made for metal-on-polyethylene articulations. RESULTS: There were distinct types of UE waveforms produced; one was typical of the control subjects as well as some patients. We did not find an apparent relationship among these waveform types and type of THA bearing, length of implantation or wear measurements in the metal on polyethylene bearings. CONCLUSIONS: Our results suggest that it may be possible to assess the status of THA by UE signals, but further studies are necessary to quantify this finding. The clinical relevance of this investigation is that a simple, in-office screening means for THA patients could indicate those patients who require closer follow-up and monitoring.

Femoral component positioning in resurfacing arthroplasty--effects on cortical strains.

Previous studies have suggested that femoral component positioning in resurfacing arthroplasty may affect strains in the femoral neck that could lead to decreased implant longevity. A strain gaged, Sawbones model was used to determine the femoral neck strains for a variety of resurfacing head translations and angulations. We found that head positions affected strain distributions, most positions leading to increased neck strains, often over 100%, with the exception being a varus head position where the superior neck strains decreased over 50%. Although the clinical meaning of these findings is unclear, it could be of concern for stress-shielding or fatigue fracture of the femoral neck.

Obturator dislocation of total hip arthroplasty--a case report.

This study consists of a single case report of a patient who had an irreducible obturator dislocation of a total hip arthroplasty after a motor vehicle accident, not previously described in the English literature. In particular, the focus will be on offering an educated opinion on the risk factors for dislocation and difficulties encountered with this type of dislocation. The aim is to offer valuable insight based on the operative experience with this patient and to supplement the literature with the management of such a complication following total hip arthroplasty.

Pilates training for use in rehabilitation after total hip and knee arthroplasty: a preliminary report.

UNLABELLED: Recently, a strong emphasis has been placed on establishing rehabilitation protocols after primary total hip and knee arthroplasty in an attempt to shorten, improve, and standardize the postoperative period of recovery. Less invasive surgical techniques, patient demands, and the pressure of insurance regulations have forced postoperative rehabilitation to be placed on an expedited scale. With these concerns in mind, we introduce a pre- and postarthroplasty program involving the Pilates method. Modified exercises have been developed to account for the postoperative precautions and needs of total hip and knee arthroplasty patients. A patient-driven interest in the use of Pilates for postoperative rehabilitation has led to the development of our programs following total hip or knee arthroplasty. In reviewing our early observations of a small series of patients, it appears this technique can be utilized without early complications; however, further studies are necessary to confirm its utility and safety. LEVEL OF EVIDENCE: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Surface oxidized zirconium total hip arthroplasty head damage due to closed reduction effects on polyethylene wear.

Recent case studies of surface oxidized zirconium THA heads removed after attempted, closed reduction have shown significant surface damage that has been suggested as potentially deleterious to polyethylene wear. We obtained 4 clinically retrieved specimens, produced well-characterized surface damage on additional heads, and tested them on a hip simulator. After 1 million cycles, the amount of polyethylene wear was related to the extent of surface damage, the most damaged clinical specimen showing more than 50 times more wear than a new head. Although all heads after failed attempted closed reduction(s) should be replaced, surface oxidized zirconium heads are of particular concern; those patients with a successful, simple closed reduction should be monitored for excessive wear.

Metal-on-metal hip resurfacing radiographic evaluation techniques.

Hip resurfacing devices require a new radiographic evaluation technique owing to femoral components with short or no stems. Fourteen US surgeons implanted 1148 metal-on-metal hip resurfacing (HR) devices in a US-FDA-IDE clinical trial, which began in 2001. In this multi-center, prospective study, 337 patients (mean age, 50.1 years) were enrolled as a study group of unilateral HR arthroplasties. Radiographs of 292 HR arthroplasties at a minimum 2-year follow-up (maximum 3 years) were reviewed. There were 10 patients with radiographic evidence of femoral component instability beyond 2 years, as evidenced by subsidence > or = 5mm. Of these, 7 did not have clinical symptoms associated with femoral component instability. In the study group, 24 revisions were reported, of which 8 were due to femoral neck fractures, 4 were due to acetabular component loosening, 11 were due to femoral component loosening, and 1 due to dislocation.

Kinematics of the stiff total knee arthroplasty.

The kinematics of 10 total knee replacements with poor flexion (<90 degrees ) were compared with 11 replacements with good flexion (>110 degrees ) at a mean of 3 years from surgery using optical calibration with implant shape-matching techniques from radiographs taken in standing, early-lunge, and late-lunge positions. There were no significant differences between groups in anteroposterior translation of the medial and lateral femoral condyles or tibial rotation during standing and early lunge. Groups differed in amount of posterior translation of the femoral condyles during late lunge because of the poor-flexion group's inability to achieve the same amount of flexion as the good-flexion group. Poor flexion after total knee arthroplasty, we conclude, is not associated with abnormal kinematics in the setting of well-aligned, well-fixed implants.

Integrity of the stem-cement interface in THA: effects of stem surface finish and cement porosity.

No consensus exists for the optimal surface finish on cemented total hip prosthesis stems. The purpose of this study was to determine the effects of stem finish and interfacial cement porosity on the integrity of the stem-cement interface. Simulated stems made of Co-Cr, having polished or matte surfaces, at room temperature or heated to 37 degrees C, were cemented into Sawbones simulated femurs. Push out testing of the stem-cement interface was performed immediately after cement polymerization and after two aging periods in 37 degrees C saline or 37 degrees C air, and the extent of interfacial porosity at the stem-cement interface was determined. Polished stems exhibited an average 60% greater interfacial strength than that of matte stems initially and up to 240% after aging treatments. Cement porosity at the stem-cement interface and incomplete cement interdigitation into surface asperities on matte stems likely allowed saline penetration into the stem-cement interface during wet aging, resulting in a rapid decrease of shear strength. Stem preheating to 37 degrees C virtually eliminated interfacial pores and resulted in greater shear strengths regardless of surface finish. Polished stem surfaces with stem preheating provided the best interfacial shear strength and sealing ability against saline penetration into the stem-cement interface and could result in increased longevity of stem fixation.

Psoriatic arthritis and arthroplasty: a review of the literature.

Psoriatic arthritis is an inflammatory arthropathy as- sociated with the characteristic dermatologic lesions of psoriasis. The diagnosis of psoriatic arthritis is quite difficult, due to the overlap of patients with osteoarthritis (OA) or rheumatoid arthritis (RA) with concomitant non-associated psoriasis. A nonspecific elevation in inflammatory markers (erythrocyte sedimentation rate, ESR; antinuclear antibodies, ANA; or rheumatoid factor, RF) and characteristic radiographic features are often present in these patients. The mainstay of treatment is medical management, using NSAIDs, various immunosuppressants, and anti-TNF agents, for both pain control and possibly as disease modifying agents. Only a minority of patients require surgical intervention, leading to the limited amount of literature concerning total joint arthroplasty and psoriatic arthritis. While past literature has yielded high infection rates post-arthroplasty, newer studies have found more promising results. Alternative surgical options for treating destructive arthritis include open or arthroscopic synovectomy. While early results are promising, recurrence rates and long-term outcomes are not yet available.

Effect of anesthesia type on limb length discrepancy after total hip arthroplasty.

A retrospective study of 132 patients (63 spinal anesthesia and 69 general anesthesia) undergoing total hip arthroplasty was performed by 4 fellowship-trained adult reconstructive surgeons to determine the influence of anesthesia type on postoperative limb length and medial offset. Limb length discrepancy occurred in 87.0% of patients who received regional anesthesia as opposed to 47.6% patients who had general anesthesia (P<.001). Differences in postoperative medial offset measurements between the 2 groups were not statistically significant. It was concluded that surgeons operating on patients who receive regional anesthesia should supplement intraoperative tests for assessing hip stability with meticulous preoperative templating to avoid overlengthening the operative limb.

Hydroxylapatite-coated acetabular shells with arc deposited titanium surface roughening and dual radius design.

A retrospective review of two multicenter prospective stud- ies was performed of a dual radius design acetabular shell, one with a titanium arc deposited surface roughening and hydroxylapatite coating (AD HA) designed to optimize initial component stability and enhance biological ixation and the other grit-blasted and HA (GB HA) coated. The purpose of the study was to evaluate intermediate clinical and radiographic success of this device, as compared to a grit-blasted HA (GB HA) coated shell of the same design. Eighty-nine hips (83 patients) with a diagnosis of noninlam- matory degenerative joint disease (NIDJD) were implanted with the AD HA shells (Group 1) by three surgeons at three sites. Patients were evaluated clinically and radiographi- cally for 5 to 8 years postoperatively (mean, 5.5 years). Clinical and radiographic data for 179 cases with GB HA shells and a diagnosis of NIDJD (Group 2) were reviewed retrospectively at an equivalent time frame. Fifty-eight hips in each group with a minimum 5-year follow-up were identiied through patient matching, based on age, gender, and preoperative body mass index, to provide the cohorts for this study. Radiographically, all patients in Group 1 were stable, and there were no cases of acetabular loosening or revision of the acetabular shell. Three patients in Group 2 had radiographic evidence of acetabular shell migration and eight shells (three dislocations, ive acetabular loosenings) had been revised by 60 months postoperatively. Intermediate results with the AD HA shells are encouraging, as evidenced by clinical success, radiographic stability, and 100% survi- vorship at 5 to 8 years (mean, 66 months).

Ceramic-on-ceramic total hip arthroplasty early dislocation rate.

Wear debris from metal-on-polyethylene articulation in conventional total hip arthroplasty can limit the implant's longevity. Modern ceramic material with high wear resistance and low fracture risk has the potential to extend the lifetime of total hip arthroplasty, which makes the procedure potentially more suitable for young, active patients. Concerns with brittle ceramic material include fracture risk, the "squeak" phenomenon, and potentially a higher dislocation rate secondary to limited neck lengths and liner options. We therefore determined the early dislocation rate in modern ceramic-on-ceramic total hip arthroplasty. In 1635 total hip arthroplasties performed over the 9-year period (1996-2005), we observed three anterior and 15 posterior dislocations (1.1%). All were treated successfully, one with a revision and 17 with closed reduction under general anesthesia. Ceramic-on-ceramic total hip arthroplasty can be a good alternative bearing surface with a low dislocation rate.

Evaluation of an expandable stem total hip replacement system.

The expandable nail concept uses high-pressure saline to inflate the diameter of a cylindrical implant to achieve fixation within the medullary canal of bone. Expandable nails are used clinically in a number of fracture management applications and have been more recently developed as a femoral component for total hip replacement. In this study, the expandable total hip replacement stem design was evaluated, specifically testing to determine if acrylic cement can be used in place of saline for permanent expansion, to observe the amount of stem subsidence after cyclic loading, and to document if stem expansion creates untoward stresses in the femur. The results included that the expandable femoral component could be expanded with cement if careful control of cement viscosity is used with a modified filling technique. Neither untoward hoop strains nor stem subsidence was found in tests with the cadaveric femurs. Bench testing has confirmed the stability of these stems. In addition, the substitution of cement for saline would make the construct permanent, avoiding the risk of deflation and loosening. The concept of an expandable femoral prosthesis is appealing and would have many potential clinical applications. The need for cemented stems or the more difficult and costly "Ling technique" could be avoided with their use in tumor surgery, hip fracture management, and total hip replacements associated with osteoporosis or a patulous femora in both primary and revision settings.

Rehabilitation after total hip and knee arthroplasty: a new regimen using Pilates training.

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.

Clinical outcome of total hip arthroplasty using the normalized and proportionalized femoral stem with a minimum 20-year follow-up.

Currently, there are several femoral stem designs available for use, but few have an extended track record. We have previously reported on 10- and 15-year outcome studies of total hip arthroplasty (THA) using a cemented normalized and proportionalized femoral stem from a single surgeon series. This is a follow-up study reporting the minimum 20-year outcome of this femoral stem design. The study began with THA performed in a consecutive series of 184 patients; stem fixation was achieved using first-generation cementing techniques. The overall early complication rate was 10%. There were 23 patients (31 hips) who had been followed-up for a minimum 20-year period (average 21.3 years). Mean d'Aubigne and Postel scores improved from 5.9 to 11.3; mean Harris hip scores improved from 43.8 to 92.8. Kaplan-Meier survivorship was 93% at 20 years (95% confidence interval); there were no stem failures. The use of a cemented normalized and proportionalized femoral stem in primary THA provides satisfactory long-term clinical and radiological outcomes in patients.