Total Knee Arthroplasty With 4.4 mm of Tibial Polyethylene : An Update

Three hundred eighty-seven one-piece, 8-mm tibial components were implanted in 313 patients. All tibial prostheses were manufactured with 4.4 mm of polyethylene. From this group, 116 patients underwent simultaneous bilateral total knee arthroplasty with an 8-mm tibial component on one side and a tibial component with at least 6.4 mm of polyethylene on the other side. Follow-up averaged 11.8 years. The average Knee Society knee score was 81, and the average pain score was 46. No polyethylene wear or osteolysis was identified radiographically. There were 7 knees with tibial radiolucencies, 5 knees with polyethylene failure of metal-backed patellae, and 1 tibial component failure. Survival rates for loosening or revision of any component for any reason were 98.9%, 97.5%, 95.1%, and 93.2% at 5-, 10-, 15-, and 18-years, respectively.     

Highly Crosslinked Polyethylene Does Not Reduce the Wear in Total Knee Arthroplasty : In Vivo Study of Particles in Synovial Fluid

The aim was to assess if the reduction in polyethylene wear with highly crosslinked polyethylene suggested by studies with knee simulators is confirmed in patients with a knee arthroplasty. The use of a conventional or a highly crosslinked polyethylene was randomly assigned intraoperatively. Twelve months after surgery a knee arthrocentesis was performed and the synovial fluid of 17 patients in each group was studied analysing the number, size and shape of the polyethylene particles by scanning electron microscope. We found no significant differences in the concentration, size or morphology of polyethylene particles between groups. The great variability in the number of particles between individuals suggests that in vivo polyethylene wear depends on many factors and probably the type of polyethylene is not the most significant.     

Posterior Cruciate-Retaining Versus Posterior-Stabilized Total Knee Arthroplasty : A Meta-Analysis

The objective of this meta-analysis was to compare outcomes of posterior cruciate-retaining and posterior stabilized prostheses. A computerized literature search was conducted to identify randomized controlled trials comparing the clinical outcomes of cruciate-retaining and posterior-stabilized designs. The table of contents of four major Orthopaedic journals and the references section of two arthroplasty text books were reviewed to identify other relevant studies. Ultimately, 1114 patients (1265 knees) were compared. Statistical analysis revealed a significant difference in flexion and range of motion in favor of posterior-stabilized knees, but no difference in complication rates. The clinical importance of this remains unknown. The decision to use one design versus the other should rest with the surgeon's preference and comfort with a particular design.     

Retrieval Analysis of Femoral Zirconium Components in Total Knee Arthroplasty : Preliminary Results

Safety of oxidized zirconium (OxZr) in total knee arthroplasty (TKA) has been supported by biomechanical, clinical, and radiologic data. Retrieved OxZr femoral components and corresponding polyethylene (PE) inserts were examined to rule out patterns leading to early failure. Sixteen retrieved TKA with an OxZr femoral component were included. The PE inlays were analyzed applying an established scoring system for wear and surface damage. Femoral components were screened for scratching, pitting, delamination, and striations. The prostheses were in situ for 16.4 ± 11.9 months. The average wear and damage score for the tibial PE inserts was 36.0 ± 12.7. The average score in the visual analysis of the OxZr femoral components was 1.3 ± 1.3. The data presented in this study did not show major wear of the PE in TKA using OxZr components. In this cohort, there were no failures directly related to this implant.     

Total Knee Arthroplasty with an Uncemented Trabecular Metal Tibial Component : A Registry-Based Analysis

Previous poor results have kept the appeal of uncemented total knee arthroplasties (TKAs) minimal. We analyzed the mid-term survivorship and reasons for failures of a contemporary uncemented porous tantalum monoblock tibial component nation-wide. During the study period (2003–2010), such tibial components were used in 1143 primary TKAs recorded in the Finnish Arthroplasty Registry. Seven-year survivorship of these TKAs was 100% (95% CI 99–100) with revision for aseptic loosening of the tibial component, and 97% (95% CI 96–98) with revision for any reason as the respective end points. The most common reasons for revisions were instability and prosthetic joint infections. In conclusion, TKAs using an uncemented porous tantalum monoblock tibial component showed excellent mid-term survivorship in a population-based setting.     

Incidence of Osteolysis in Total Knee Arthroplasty : Comparison Between Radiographic and Retrieval Analysis

Detection of polyethylene wear and osteolysis in total knee arthroplasty using radiographs is imprecise. To correlate radiographic findings with retrieved tibial component analysis, we reviewed knee revision cases. A joint registry was used to identify all knee revisions. Radiographic scoring systems were developed. Radiographs were analyzed for osteolysis and implant alignment. Polyethylene liner retrievals were visually and optically graded for surface damage. Statistical analyses that included correlation analysis and Mann-Whitney U test were used. When osteolysis was found, radiographic scores and delamination score were significantly higher (P = .047 and P = .014, respectively). Delamination is a good indicator for polyethylene wear and osteolysis. There is a need to develop in vivo methods to identify polyethylene changes and thereby prevent severe clinical outcomes.     

Double-Concave Deformity of the Polyethylene Tibial Post in Posterior Stabilized Total Knee Arthroplasty

This report describes a unique case of bilateral total knee arthroplasty necessitating revision of the polyethylene insert, which showed prominent marks on the tibial post resulting from repeated seiza-style sitting. The patient presented 7 years postoperatively with knee pain and flexion disturbance due to continuous joint effusion persisting for more than 4 months. Proliferating synovia throughout the joint revealed reactive synovitis to polyethylene particles. The retrieved polyethylene inserts displayed double-concave deformity of the tibial post with burnishing and creep in tibiofemoral articulation. The damage pattern of retrieved polyethylene inserts reflected the data from tibiofemoral contact location obtained using a shape-matching technique in the early postoperative phase. This case provides an example of damage to the polyethylene tibial post caused by a floor-sitting lifestyle and the potential clinical sequelae.     

Clinical Results of the Wear Performance of Cross-Linked Polyethylene in Total Hip Arthroplasty : Prospective Randomized Trial

To investigate the clinical results of cross-linked polyethylene (CLPE) and to compare the CLPE wear against zirconia and stainless steel heads, we studied the radiographic wear after a minimum 3-year follow-up in total hip arthroplasty (THA). Ninety-four hips were randomly implanted with a 22.225-mm head cemented THA—the group of non-CLPE against zirconia and CLPE against 2 different zirconias and stainless steel. The linear wear rate was significantly lower in the group of CLPE against zirconia (0.067, 0.059 mm/y) and against stainless steel (0.068 mm/y) compared with non-CLPE against zirconia (0.170 mm/y). In the short-term results, the wear performance of CLPE against zirconia was superior to that of non-CLPE; however, it did not show a better wear rate than CLPE against stainless steel. Furthermore, long-term investigations will be necessary for understanding CLPE wear in vivo.     

Total Knee Arthroplasty for Arthritic Knees with Tibiofibular Stress Fractures : Classification and Treatment Guidelines

Forty-two tibial and 5 fibular stress fractures in 34 patients with knee arthritis were radiologically classified into intraarticular malunited and ununited fractures, and extraarticular impending, acute, united, malunited, and ununited fractures. Depending on fracture type, total knee arthroplasty was performed using long-stem tibial component, metal augments, corrective osteotomy, or in routine fashion. At a mean follow-up of 36 months, the mean Knee Society knee score improved from 36.7 points preoperatively to 90.3 points; function score improved from 24 to 86.2 points. All fractures had united at the last follow-up with no complications of infection, joint instability, and patellar problems. Total knee arthroplasty for knee arthritis in the presence of tibiofibular stress fractures restores limb alignment and facilitates fracture healing with excellent functional outcome.     

Fixation,Survival and Osteolysis with a Modern Posterior-Stabilized Total Knee Arthroplasty

Early failure of the NexGen prosthesis with a 3° fluted, 4 hole tibial component has been reported. We evaluated fixation, survival and osteolysis with the NexGen LPS prosthesis with a 7° fluted, solid tibial component at a mean of 10 years. Knees were evaluated using Knee Society and LEAS scores, survival analysis, and univariable modeling. No knee had tibial loosening or debonding. With the endpoint mechanical failure (132 knees), the 12 year survival was 88.8% (CI 61.5–97.1).With failure defined as any reoperation (132 knees), the 12 year survival was 88.1% (CI 62.3–96.7). Osteolysis occurred in 16 knees, associated with male gender and LEAS score > 10. Loosening was not seen with this tibial component.     

Wear Comparison Between a Highly Cross-Linked Polyethylene and Conventional Polyethylene Against a Zirconia Femoral Head : Minimum 5-Year Follow-Up

Highly cross-linked polyethylene (HXLPE) was developed to reduce wear of articular bearing surface in total hip arthroplasty patients. Several studies have shown reduced wear of HXLPE compared with conventional polyethylene; however, these studies had used HXLPE in combination with a Co-Cr metal head. The purpose of this study was to compare the 5-year in vivo wear of HXLPE with that of conventional PE using a zirconia femoral head. Forty-five hips with a Trilogy HXLPE (Zimmer, Warsaw, Ind) were matched and compared with a control group of 20 conventional Trilogy PE hips. The 2-dimensional linear wear rate was significantly less in the HXLPE group between 1 and 5 years postoperation (P < .001). The results show that HXLPE reduces short-term polyethylene wear against not only a Co-Cr head but also a zirconia head.     

Peroneal Nerve Dysfunction After Total Knee Arthroplasty : Characterization and Treatment

The purpose of this study was to report on the presentation, evaluation, treatment, and outcome of patients who had a peroneal nerve dysfunction after total knee arthroplasty. Six patients were unable to achieve adequate range of motion after physical therapy, and the remaining 5 patients had sensory symptoms that interfered with daily activities despite adequate range of motion. All 11 patients had abnormal electrodiagnostic testing but had intact motor strength and were treated with surgical decompression of the nerve. The patients with motion problems had a mean increase in range of motion of 40° (range, 20°-70°) at final follow-up. All patients with dominant sensory symptoms had a resolution of leg and foot pain after treatment. Orthopedic surgeons should be aware of peroneal nerve dysfunction as a possible cause of unsatisfactory rehabilitation and/or persistent atypical lateral leg pain after total knee arthroplasty.     

Mobile vs Fixed-Bearing Total Knee Arthroplasty Performed by a Single Surgeon : A 4- to 6.5-Year Randomized,Prospective, Controlled,Double-Blinded Study

The superiority between posterior-stabilized mobile-bearing and fixed-bearing designs still remains controversial. Fifty-six consecutive patients undergoing primary, unilateral knee arthroplasty for osteoarthritis were randomly assigned to receive either a mobile-bearing (29 patients) or fixed-bearing (27 patients) prosthesis. We report the results at 4 to 6.5 years (mean, 5.5) follow-up. The Knee Society knee scores, pain scores, functional scores and Oxford knee scores were not statistically different (P > 0.05) between the two groups. Mean postoperative range-of-motion of mobile-bearing knees was significantly greater than that of fixed-bearing knees (127º versus 111º, P = 0.011). 72% of patients could sit cross legged, 48% could sit on the floor, and 17% could squat. Kaplan–Meier survival rate was 100%. No spin-out of mobile bearing was observed. The radiological analysis showed no osteolysis or implant loosening.     

Clinical Outcomes After Simultaneous Bilateral Total Knee Arthroplasty : Comparison to Unilateral Total Knee Arthroplasty and Healthy Controls

The purpose of this study was to evaluate the functional outcomes of persons who underwent simultaneous bilateral total knee arthroplasty (TKA) compared to subjects who underwent unilateral TKA and a healthy control group. Fifteen subjects who underwent primary bilateral TKA and 15 sex, age, and body mass index-matched subjects who underwent primary unilateral TKA were observed prospectively for 2 years. Subjects in both surgical groups showed significant improvement in Knee Outcome Scores, Short Form 36 physical component scores, Timed Up and Go, and stair-climbing tasks (P ≤ .004). No differences in final outcomes were found between surgical groups. In addition, most 2-year clinical measures were no different between the surgical and control groups. Subjects medically appropriate for bilateral TKA should be afforded this option.     

Tibial Stem Tip Pain in Stemmed Revision Total Knee Arthroplasty : Treatment with Tension Band Plating

The use of stemmed modular components in revision total knee arthroplasty has led to increasingly described pain located at the tip of the stem of the implant. This has been described in the literature as being due to the elastic modulus mismatch between the stem tip and the host bone. Current management is re-revision total knee arthroplasty in an attempt to alleviate the mismatch. This case report describes a novel technique using a dynamic compression plate acting as a tension band at the stem tip to successfully treat this condition.     

Comparison of High Tibial Osteotomy and Unicompartmental Knee Arthroplasty in the Treatment of Unicompartmental Osteoarthritis : A Meta-Analysis

We conducted a systematic review of comparative clinical trials assessing the results of high tibial osteotomy (HTO) and unicompartmental knee arthroplasty (UKA) in patients with strictly unilateral osteoarthritis of the knee. A literature search was conducted through Medline, Embase and Cochrane library. A total of 11 comparative studies were included. Pooled results showed: UKA showed significantly better results compared to HTO in terms of function results, however, no difference in specific knee score was observed; HTO got slightly better results of the range of motion; a trend towards an increased velocity was found in UKA without significant difference. Postoperative rate of revision and complications did not differ significantly between two groups. With the correct patient selection, both HTO and UKA show effective and reliable results.     

Revision Total Knee Arthroplasty for Component Malrotation is Highly Beneficial : A Case Control Study

Component malrotation is a recognized cause of post total knee arthroplasty (TKA) pain. We reviewed 24 patients who had TKA revision due to component malrotation as the only objective abnormality. Mean combined component rotation was 6.8° excessive internal rotation, as documented by computed tomography. Twenty-four matched control patients had TKA revision due to aseptic loosening. Mean follow-up was 37 months. Preoperative Knee Society Score improved by 49 points at 6 months postoperatively for the malrotation patients and by 39 for the loosening patients. At last follow-up, Knee Society Score was 80 for the malrotation group and 75 for the loosening group. We recommend the use of computed tomography scans in evaluation of all patients with early painful TKAs and no objective evidence of infection. When component malrotation is demonstrated, early revision should be considered.     

Assessment of Reactive Synovitis in Rotating-Platform Posterior-Stabilized Design : A 10-Year Prospective Matched-Pair MRI Study

This is the first long-term (mean 11.6 years), prospective, matched-pair study (based on age, gender, BMI and UCLA scores) using MAVRIC (multi-acquisition variable-resonance image combination) magnetic resonance imaging to analyze reactive synovitis and osteolysis between rotating-platform posterior-stabilized (RP-PS), fixed-bearing metal-back (FB-MB), and all-polyethylene tibial (APT) in active patients (24 total, 8 in each group, mean age of 64 years, mean UCLA of 8.5) with identical femoral component and polyethylene. Reactive synovitis was observed in 6 RP-PS (75%), all 8 FB-MB (100%), and 6 APT (75%). There was a significant difference between the RP-PS and FB-MB knees in volumetric synovitis (P = 0.023). Osteolysis with bone loss more than 4 mm was seen in 3 FB-MB, 2 APT and none for RP-PS. These were not statistically significant.     

Osteotomy and Unicompartmental Knee Arthroplasty Converted to Total Knee Arthroplasty : Data From the New Zealand Joint Registry

We reviewed the revision rate and functional outcome of all patients who had a total knee arthroplasty (TKA) after an osteotomy or unicompartmental knee arthroplasty (UKA) on the New Zealand Joint Registry. We used these data to compare the results with primary TKA scores, including comparison of age-matched subgroups. There were 711 patients who had undergone TKA as salvage for a failed osteotomy with a revision rate of 1.33 per 100 component years and a mean 6-month Oxford Knee Score (OKS) of 36.9. There were 205 patients who had a failed UKA converted to TKA with a revision rate of 1.97 per 100 component years and a mean OKS of 29.1. The revision rates of TKA for both failed osteotomy and failed UKA were significantly poorer than after primary TKA (0.48 per 100 component years). The mean OKS after revision of a UKA was significantly poorer than both primary TKA and TKA for a failed osteotomy. There was no significant difference in mean OKS between primary TKA and TKA for a failed osteotomy, even among patients younger than 65 years. Revision of a failed osteotomy to a TKA has improved functional results compared with revision of a failed UKA. However, both yield poorer survivorship rates compared with primary TKA.