Important Differences Exist in Posterior Condylar Offsets in an Osteological Collection of 1,058 Femurs.

Posterior condylar offset (PCO) has important implications in total knee arthroplasty (TKA) function and design. In an osteological study of 1,058 femurs, we measured PCO using two separate techniques with a 3D digitizer. Measurements were standardized for the size of the femur. The medial PCO was greater than lateral PCO (32.6mm vs. 31.2mm, P<0.0001). In 53% of individuals, the medial PCO differed between sides by more than 2mm. Age did not affect standardized medial or lateral PCO. Compared with African-Americans, Caucasians had a larger standardized medial (1.3mm vs. 1.2mm, P=0.006) and lateral (1.1mm vs. 1.0mm, P=0.004) PCOs. The standardized medial (1.2mm vs. 1.3mm, P=0.073), and lateral (1.1mm vs. 1.1mm, P=0.098), PCO did not differ between men and women, respectively.

Predictors of range of motion in patients undergoing manipulation after TKA.

BACKGROUND: Knee stiffness or limited range of motion (ROM) after total knee arthroplasty (TKA) may compromise patient function. Patients with stiffness are usually managed with manipulation under anesthesia (MUA) to improve ROM. However, the final ROM obtained is multifactorial and may depend on factors such as comorbidities, implant type, or the timing of MUA. QUESTIONS/PURPOSES: We asked whether diabetes mellitus, implant type, and the interval between TKA and MUA influenced post-MUA ROM. METHODS: From a group of 2462 patients with 3224 TKAs performed between 1999 and 2007 we retrospectively reviewed 96 patients with 119 TKAs (4.3%) who underwent MUA. We determined the presence of diabetes mellitus, implant type, and the interval between TKA and MUA. RESULTS: The average increase in ROM after MUA was 34°. Patients with diabetes mellitus experienced lower final ROM after MUA (87.5° versus 100.3°) as did patients with cruciate-retaining (CR) prostheses versus posterior-stabilized (92.3° versus 101.6°). The interval between TKA and MUA inversely correlated with final ROM with a decrease after 75 days. CONCLUSIONS: Most patients experience improvements in ROM after MUA. Patients with diabetes mellitus or CR prostheses are at risk for lower final ROM after MUA. Manipulation within 75 days of TKA is associated with better ROM.

Retrieval analysis of Harris-Galante I and II acetabular liners in situ for more than 10 years.

BACKGROUND AND PURPOSE: There have been few reports documenting the wear and oxidation performance of the polyethylene bearing surface of HGPI and HGPII THA devices. We evaluated retrieved HGPI and HGPII acetabular liners that had been in situ for more than 10 years and determined whether there was a relationship between clinical and radiographic factors, surface damage, wear, and oxidation. MATERIALS AND METHODS: 129 HGPI and II acetabular liners with implantation times of > 10 years were retrieved at 4 institutions between 1997 and 2010. The liners were made from a single resin and were gamma radiation-sterilized in air. Surface damage, linear wear, and oxidation index (OI) were assessed. Differences in clinical and radiographic factors, surface damage, linear wear, and OI for the 2 designs were statistically evaluated separately and together. RESULTS: Articular surface damage and backside damage was similar in the 2 designs. The linear penetration rate was 0.14 (SD 0.07) mm/year for the HGPI liners and 0.12 (SD 0.08) mm/year for the HGPII liners. For both cohorts, the rim had a higher OI than the articular surface. 74% of the liners had subsurface cracking and 24% had a complete fracture through the acetabular rim. INTERPRETATION: Despite modification of the HGP locking mechanism in the HGPII design, dissociation of the liner from the acetabular shell can still occur if fracture of the rim of the liner develops due to oxidative degradation.

Bacterial pathogen-associated molecular patterns stimulate biological activity of orthopaedic wear particles by activating cognate Toll-like receptors.

Aseptic loosening of orthopaedic implants is induced by wear particles generated from the polymeric and metallic components of the implants. Substantial evidence suggests that activation of Toll-like receptors (TLRs) may contribute to the biological activity of the wear particles. Although pathogen-associated molecular patterns (PAMPs) produced by Gram-positive bacteria are likely to be more common in patients with aseptic loosening, prior studies have focused on LPS, a TLR4-specific PAMP produced by Gram-negative bacteria. Here we show that both TLR2 and TLR4 contribute to the biological activity of titanium particles with adherent bacterial debris. In addition, lipoteichoic acid, a PAMP produced by Gram-positive bacteria that activates TLR2, can, like LPS, adhere to the particles and increase their biological activity, and the increased biological activity requires the presence of the cognate TLR. Moreover, three lines of evidence support the conclusion that TLR activation requires bacterially derived PAMPs and that endogenously produced alarmins are not sufficient. First, neither TLR2 nor TLR4 contribute to the activity of "endotoxin-free" particles as would be expected if alarmins are sufficient to activate the TLRs. Second, noncognate TLRs do not contribute to the activity of particles with adherent LPS or lipoteichoic acid as would be expected if alarmins are sufficient to activate the TLRs. Third, polymyxin B, which inactivates LPS, blocks the activity of particles with adherent LPS. These results support the hypothesis that PAMPs produced by low levels of bacterial colonization may contribute to aseptic loosening of orthopaedic implants.

Incidence of postthrombotic syndrome in patients undergoing primary total hip arthroplasty for osteoarthritis.

BACKGROUND: Postthrombotic syndrome (PTS) is a chronic condition in the lower extremity that develops after deep vein thrombosis (DVT). The incidence of PTS after total hip arthroplasty (THA) is not well established. QUESTIONS/PURPOSES: We (1) determined the incidence of PTS after DVT in patients undergoing primary THA for osteoarthritis; and (2) determined whether the incidence of PTS was greater in patients with DVT than without. METHODS: We retrospectively reviewed records of all 1037 patients who underwent primary THA for osteoarthritis during a 4-year period. All patients underwent postoperative screening ultrasound. We identified 21 (2%) patients with a DVT by ultrasound of whom 14 had a minimum 1-year followup (mean, 3.4 years; range, 1.0-6.0 years). PTS was diagnosed if any two of the six clinical signs were documented. RESULTS: Three of 14 patients with DVT had at least two signs consistent with PTS; two of these had a DVT proximal to the soleal arch. Three of 91 randomly matched patients undergoing THA without DVT had at least two signs of PTS. The incidence of developing PTS after THA appeared higher in patients with DVT than in patients without DVT. CONCLUSIONS: While we observed a difference between the incidence of PTS after THA in patients with and without DVT, that incidence was based on only three of 1037 patients with DVT after THA. PTS does not appear to be a major complication after DVT in patients undergoing THA. LEVEL OF EVIDENCE: Level III, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.

Post damage in contemporary posterior-stabilized tibial inserts: influence of implant design and clinical relevance.

The mechanisms of damage at the polyethylene post in 3 contemporary tibial insert designs were evaluated and compared with a historical standard (Insall-Burstein II; Zimmer, Warsaw, Ind). One hundred five gamma sterilized posterior-stabilized tibial inserts were revised after an average of 4.7 years (0.05-13.6 years). Retrievals were classified according to their designs: Insall-Burstein II (n = 28); PFC (Johnson & Johnson, Raynham, Mass; n = 30); NexGen (Zimmer; n = 32); and Scorpio (Stryker Orthopaedics, Mahwah, NJ; n = 15). Reasons for revision and patient details were available. Surface damage scoring and photogrammetry were performed on all the retrieved tibial inserts. Oxidation analysis was carried out for traceable historical, gamma air-sterilized and conventional, gamma inert-sterilized tibial inserts (n = 61) with the use of infrared spectroscopy. The posts for all 3 contemporary designs exhibited damage similar to the historical controls. Articular, post, and backside damage scores significantly increased with implantation time. Post damage was insensitive to design and patient factors but was exacerbated by oxidation. An association between damage at the post and articular surface was also confirmed. Logistic models suggested an interaction between post damage, backside surface damage, and implant loosening.

Incidence of postthrombotic syndrome in patients undergoing primary total knee arthroplasty for osteoarthritis.

UNLABELLED: Postthrombotic syndrome (PTS) is characterized by edema, venous ectasia, hyperpigmentation, varicose veins, venous ulceration, and pain with calf compression after deep venous thrombosis (DVT). We determined the incidence of PTS after DVT diagnosed on screening ultrasound in patients undergoing primary total knee arthroplasty (TKA) for osteoarthritis (OA). We retrospectively reviewed the records of 1406 patients who underwent primary TKA for osteoarthritis and compared the incidence of PTS in patients without and with DVT. All patients had postoperative screening ultrasound. From these 1406 patients we identified 66 (4.7%) who had DVT, 50 of whom had a minimum of 1 year followup (mean, 4.97 years; range, 1.00-7.53 years). PTS was diagnosed if any two of six signs were documented in the medical record. Three of 50 patients with DVT (6%) had signs consistent with PTS; two of these three had a DVT proximal to the soleal arch. Seven (8%) of 88 patients randomly chosen for primary TKA because of OA with similar mean age and gender, but without DVT, had signs of PTS. PTS does not seem to be a major sequela of DVT in patients undergoing primary TKA for OA. LEVEL OF EVIDENCE: Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Revision total knee arthroplasty for aseptic and septic causes in patients with rheumatoid arthritis.

UNLABELLED: Revision total knee arthroplasty in patients with rheumatoid arthritis can be challenging. We asked whether we could confirm previously reported high failure rates following revision total knee arthroplasty in patients with rheumatoid arthritis. We therefore determined the Knee Society knee score and function scores, radiographic evidence of failure, and overall survival of the revision procedure in these patients. We retrospectively reviewed 39 patients with rheumatoid arthritis who underwent 45 TKA revisions from 1994 to 2006. Twenty-seven of the 45 TKA revisions were for mechanical failure of the prosthetic components and 18 for infection. Five of the 27 knees (19%) revised for mechanical failure subsequently failed a second time. Five of the 18 patients who underwent revision for infection died within 6 months and three of the remaining knees failed secondary to reinfection. Excluding the knees that failed, the average Knee Society knee score and function score improved in both subgroups. Two knees had radiographic evidence of nonprogressive tibial radiolucencies. The probability of survival for all knees (revision as the end point) was 76% +/- 9% at 5 years. We confirmed the previously reported high mortality and subsequent failure rates following revision total knee arthroplasty for both mechanical issues and infection in patients with rheumatoid arthritis and emphasize the potential difficulties in treating these patients. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Survivorship of a low-stiffness extensively porous-coated femoral stem at 10 years.

UNLABELLED: A novel low-stiffness extensively porous-coated total hip femoral component was designed to achieve stable skeletal fixation, structural durability, and reduced periprosthetic femoral stress shielding. In short- to intermediate-term clinical review, this implant achieved secure biologic fixation and preserved periprosthetic bone. We retrospectively reviewed all 102 prospectively followed patients (106 implants) with this implant to document the longer-term implant survivorship, clinical function, fixation quality, and periprosthetic bone preservation. Ninety-seven patients with 101 implants had current followup or were followed to patient death (range, 1-14 years; average, 10 years). Eighty-six living patients were followed for an average implant survivorship of 10 years. There were no known femoral implant removals. The average Harris hip score at 10-year followup was 98. Radiographs demonstrated secure implant fixation and maintenance of periprosthetic bone. These data suggest this implant design provided long-term function characterized by extensive fixation, structural durability, and radiographic appearance of maintained periprosthetic cortical thickness and density. LEVEL OF EVIDENCE: Level I, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Isolated resurfacing of the previously unresurfaced patella total knee arthroplasty.

Postoperative anterior knee pain can be challenging after primary total knee arthroplasty. Isolated patellar resurfacing may provide symptomatic improvement in those patients with an unresurfaced patella. Seventeen isolated patellar resurfacing procedures were performed. Patient outcomes were evaluated using the Knee Society clinical and roentgenographic evaluation systems. Continued symptomatology and overall patient satisfaction were also analyzed. No revisions have been necessary at 47 months of follow-up. Overall, Knee Society knee scores and knee function scores significantly improved. Eight patients (53%) are asymptomatic and were satisfied with the procedure, whereas 7 patients (47%) continue to have anterior knee pain and are unsatisfied. Isolated patellar resurfacing for anterior knee pain in total knee arthroplasty with an unresurfaced patella has a low morbidity and revision rate but may not provide patients with predictable symptomatic improvement.

Analysis of retrieved ultra-high-molecular-weight polyethylene tibial components from rotating-platform total knee arthroplasty.

Mobile-bearing total knee Arthroplasties (TKAs) were designed to increase conformity, decrease contact stresses, and decrease polyethylene damage. Our objective was to evaluate the performance of retrieved mobile-bearing TKAs with respect to wear damage of the polyethylene in a series of components obtained at revision surgery. Tibial component polyethylene superior and inferior surface damage and radiographic radiolucency analysis was conducted on 40 retrieved mobile-bearing TKAs. Higher levels of superior articulating surface damage were found to be associated with higher levels of inferior surface damage in this retrieval study. Greater levels of damage were present on both surfaces in components with greater radiographic radiolucency scores and mechanically loose components. The mobile-bearing TKA remains vulnerable to polyethylene wear damage at the superior surface and introduces an independent inferior surface also vulnerable to wear damage.

Stimulation of macrophage TNFalpha production by orthopaedic wear particles requires activation of the ERK1/2/Egr-1 and NF-kappaB pathways but is independent of p38 and JNK.

Bone loss that causes aseptic loosening of orthopedic implants is initiated by pro-inflammatory cytokines produced by macrophages in response to implant-derived wear particles. MAPK and NF-kappaB signaling pathways are activated by the particles; however, it is not clear which of the signaling pathways are important for the initial response to the wear particles and which are only involved at later steps in the process, such as osteoclast differentiation. Here, we show that the ERK1/2, p38, JNK, and NF-kappaB pathways are rapidly activated by the wear particles but that only the ERK1/2 and NF-kappaB pathways are required for the initial response to the wear particles, which include increases in TNFalpha promoter activity, TNFalpha mRNA expression, and secretion of TNFalpha protein. Moreover, ERK1/2 activation by wear particles is also required for increased expression of the transcription factor Egr-1 as well as Egr-1's ability to bind to and activate the TNFalpha promoter. These results, together with our previous studies of the PI3K/Akt pathway, demonstrate that wear particles coordinately activate multiple signaling pathways and multiple transcription factors to stimulate production of pro-inflammatory cytokines, such as TNFalpha. The current study also demonstrates that the signaling pathways are activated to a much greater extent by wear particles with adherent endotoxin than by "endotoxin-free" wear particles. These results, together with those demonstrating the requirement for ERK1/2/Egr-1 and NF-kappaB, show that activation of these signaling pathways is responsible for the ability of adherent endotoxin to potentiate cytokine production, osteoclast differentiation, and bone loss induced by wear particles.

Isolated all-polyethylene patellar revisions for metal-backed patellar failure.

UNLABELLED: The outcome of isolated patellar component revisions after metal-backed patellar failure is variable with satisfactory results reported from 78% to 100%. To supplement information in the literature we determined the failure rate and the functional outcome based on the Knee Society clinical and roentgenographic evaluation systems of isolated patellar component revisions after metal-backed patellar component failure. We retrospectively reviewed 27 patients with 28 isolated patellar component revisions for metal-backed patellar component failure performed between 1988 and 2005. Twenty-five knees in 24 patients were available for review with a minimum followup of 24 months (mean, 90 months; range, 24-210 months). All knees were revised with a cemented all-polyethylene patellar component and all tibial polyethylene components were routinely exchanged. One failure (4%) occurred 122.6 months after the isolated patellar component revision secondary to femoral and tibial component loosening. The average Knee Society knee score improved from 73 to 89 points, whereas the average Knee Society function score improved from 56 to 65. Our data confirm those in the literature suggesting a successful outcome can be achieved with an isolated patellar component revision for metal-backed patellar component failure. LEVEL OF EVIDENCE: Level IV, retrospective case series. See the Guidelines for Authors for a complete description of levels of evidence.

Management of the deficient patella in revision total knee arthroplasty.

UNLABELLED: There are a number of options available to manage the patella when revising a failed total knee arthroplasty. If the previous patellar component is well-fixed, undamaged, not worn, and compatible with the femoral revision component, then it can be retained. When a patellar component necessitates revision and is removed with adequate remaining patellar bone stock, an onlay-type all-polyethylene cemented implant can be used. Management of the patella with severe bony deficiency remains controversial. Treatment options for the severely deficient patella include the use of a cemented all-polyethylene biconvex patellar prosthesis, patellar bone grafting and augmentation, patellar resection arthroplasty (patelloplasty), performing a gull-wing osteotomy, patellectomy, or the use of newer technology such as a tantalum (trabecular metal) patellar prosthesis. Severe patellar bone deficiency is a challenging situation because restoration of the extensor mechanism, proper patellar tracking, and satisfactory anatomic relationships with the femoral and tibial components are critical for an optimal clinical outcome. LEVEL OF EVIDENCE: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Retention of superficially damaged femoral components after metal-backed patella component failure.

Metal-backed patellar components have been associated with high rates of failure often causing surface damage to the femoral component. Retention of a superficially damaged femoral component may be an alternative to a more extensive patellar and femoral component revision. Twenty-three metal-backed patellar components were revised. Superficially damaged femoral components were retained when a described set of criteria were met. At an average follow-up of 80.3 months, evidence of only 1 failure (4%) was observed. The Knee Society knee score improved from 69 to 88 (P < .001), whereas the Knee Society knee function score improved from 52 to 63 (P < .003). The findings from this study indicate that retaining a superficially damaged femoral component after metal-backed patella revision is a reasonable surgical option.

Comparison of the roles of IL-1, IL-6, and TNFalpha in cell culture and murine models of aseptic loosening.

Pro-inflammatory cytokines, such as IL-1, IL-6, and TNF, are considered to be major mediators of osteolysis and ultimately aseptic loosening. This study demonstrated that synergistic interactions among these cytokines are required for the in vitro stimulation of osteoclast differentiation by titanium particles. In contrast, genetic knock out of these cytokines or their receptors does not protect murine calvaria from osteolysis induced by titanium particles. Thus, the extent of osteolysis was not substantially altered in single knock out mice lacking either the IL-1 receptor or IL-6. Osteolysis also was not substantially altered in double knock out mice lacking both the IL-1 receptor and IL-6 or in double knock out mice lacking both TNF receptor-1 and TNF receptor-2. The differences between the in vivo and the cell culture results make it difficult to conclude whether the pro-inflammatory cytokines contribute to aseptic loosening. One alternative is that in vivo experiments are more physiological and that therefore the current results do not support a role for the pro-inflammatory cytokines in aseptic loosening. We however favor the alternative that, in this case, the cell culture experiments can be more informative. We favor this alternative because the role of the pro-inflammatory cytokines may be obscured in vivo by compensation by other cytokines or by the low signal to noise ratio found in measurements of particle-induced osteolysis.

The balance between endotoxin accumulation and clearance during particle-induced osteolysis in murine calvaria.

Bacterial endotoxin may contribute to aseptic loosening of orthopedic implants even in the absence of clinical or microbiological evidence of infection. One potential source of endotoxin during aseptic loosening is systemically circulating endotoxin, derived from intestinal flora, minor infections, or dental procedures, that may bind to wear particles. The current study demonstrates that systemically derived endotoxin accumulates when 'endotoxin-free' titanium and polyethylene particles are implanted on murine calvaria. Time-course experiments and experiments using germ-free mice rule out the possibility that the observed endotoxin accumulation may be due to bacterial contamination. In contrast, endotoxin is cleared from titanium particles that originally carry high amounts of adherent endotoxin. The mechanism of endotoxin clearance is not dependent on induction of a respiratory burst. Taken together, these results indicate that a balance between endotoxin accumulation and endotoxin clearance controls the steady-state level of endotoxin surrounding orthopedic wear particles implanted on murine calvaria. This balance may regulate the rate of osteolysis in the murine calvaria model as well as in patients with aseptic loosening.

Inhibition of the PI3K-Akt signaling pathway reduces tumor necrosis factor-alpha production in response to titanium particles in vitro.

BACKGROUND: Wear debris contributes to implant loosening after total joint arthroplasty, and few advances have been made in our ability to inhibit the biological response to wear particles. Bacterial endotoxins augment the effects of wear particles in vitro and in vivo. The cytokine, tumor necrosis factor-alpha (TNF-alpha), is produced by macrophages in response to bacterial endotoxins and wear particles, and it increases osteoclast activity resulting in bone resorption and implant loosening. The phosphoinositol-3-kinase (PI3K)-Akt intracellular signal transduction pathway contributes to cytokine production in response to soluble endotoxin. We investigated the role of the PI3K-Akt pathway in the production of TNF-alpha in response to wear particles with adherent endotoxin and so-called endotoxin-free wear particles. METHODS: Cultured RAW264.7 murine macrophages were incubated with titanium particles with adherent endotoxin or with endotoxin-free titanium particles in the presence and absence of specific inhibitors of PI3K (LY294002) or Akt (SH-5). Akt activation was assessed with use of Western blot. TNF-alpha production was measured with use of enzyme-linked immunosorbent assay. Cytotoxicity was determined by measuring lactic dehydrogenase release. RESULTS: Titanium particles with adherent endotoxin increased Akt activation, whereas endotoxin-free titanium particles did not. The PI3K inhibitor reduced TNF-alpha production by 70% in response to titanium with adherent endotoxin without increasing cytotoxicity. Similarly, the Akt inhibitor reduced TNF-alpha production by 83% in response to titanium particles with adherent endotoxin without increasing cytotoxicity. High concentrations of endotoxin-free titanium particles resulted in a small delayed increase in TNF-alpha production that was completely blocked by the PI3K inhibitor. CONCLUSIONS: Inhibition of the PI3K-Akt pathway reduces macrophage TNF-alpha production in response to titanium particles with adherent endotoxin and endotoxin-free particles in vitro.

Evaluation of machining methods for trabecular metal implants in a rabbit intramedullary osseointegration model.

Implant success is dependent in part on the interaction of the implant with the surrounding tissues. Porous tantalum implants (Trabecular Metal, TM) have been shown to have excellent osseointegration. Machining this material to complex shapes with close tolerances is difficult because of its open structure and the ductile nature of metallic tantalum. Conventional machining results in occlusion of most of the surface porosity by the smearing of soft metal. This study compared TM samples finished by three processing techniques: conventional machining, electrical discharge machining, and nonmachined, "as-prepared." The TM samples were studied in a rabbit distal femoral intramedullary osseointegration model and in cell culture. We assessed the effects of these machining methods at 4, 8, and 12 weeks after implant placement. The finishing technique had a profound effect on the physical presentation of the implant interface: conventional machining reduced surface porosity to 30% compared to bulk porosities in the 70% range. Bone ongrowth was similar in all groups, while bone ingrowth was significantly greater in the nonmachined samples. The resulting mechanical properties of the bone implant-interface were similar in all three groups, with only interface stiffness and interface shear modulus being significantly higher in the machined samples.

Contemporary total joint arthroplasty.

Total joint arthroplasty is a highly successful procedure for end-stage lower extremity arthritis. Excellent pain relief and significantly improved function is usual after surgery when used for appropriate indications by highly skilled surgeons using contemporary designed components. Future improvement in design and materials to reduce wear will further enhance clinical outcomes and long-term implant survival.