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Up to 20% of patients are dissatisfied following total knee arthroplasty (TKA), most often due to pain and/or stiffness. The differential diagnosis includes immune reaction to the prosthesis. However, there is no consensus on diagnostic criteria for immune failure, an allergic reaction, to a TKA. Histologic evaluation could provide evidence as to whether an allergic reaction caused TKA failure. A recent study showed an increase in CD4+ lymphocytes compared to CD8+ lymphocytes in patients lymphocyte transformation testing (LTT) + for Ni. This finding is consistent with Ni sensitization, but can lymphocyte subsets be used to diagnose immune failure on a case-by-case basis?Periprosthetic tissues from 18 revision cases of well-fixed, aseptic, but painful and/or stiff primary TKAs were analyzed. Six patients LTT- for Ni were matched as a cohort for age, sex, and body mass index (BMI), to 12 patients LTT + for Ni. Periprosthetic tissue biopsies underwent immunohistochemical IHC staining for CD4+ and CD8+ lymphocyte subsets and were compared by LTT status. The immunohistochemicalIHC results were also compared with periprosthetic histology.There was no relationship between LTT status and mean CD4+ cells/hpf or CD4+:CD8+ lymphocyte ratio. No relationship was found between LTT stimulation index (continuous or categorical) and CD4+:CD8+ ratio or aseptic lymphocyte-dominant vasculitis-associated lesion ALVAL score.Lymphocytes in periprosthetic tissue are highly variable in number, subtype ratio, and location, and have no relationship to LTT result or ALVAL score on a case-by-case basis. Based on these results, lymphocyte subsets cannot diagnose immune failure. Further work is needed to determine criteria for the diagnosis of immune failure of a TKA.

Background An allergic reaction may rarely cause a painful or stiff total knee arthroplasty (TKA). However, no consensus diagnostic criteria for TKA immune failure exist. Lymphocyte transformation testing (LTT) measures immune sensitivity to various materials, but its role in diagnosing an allergic reaction to a TKA has not been established. This study compares TKA periprosthetic tissues in a) LTT-positive versus -negative patients and b) patients with conventional CoCrNi versus hypoallergenic implants. Methods Periprosthetic tissues from 26 revision cases of well-fixed, aseptic, but painful or stiff TKAs were analyzed. Twelve patients LTT positive for nickel (Ni) were matched as a cohort to 6 LTT-negative patients. In 4 patients LTT positive for Ni, tissue from first revision of CoCrNi implants was compared with tissue from subsequent revision of hypoallergenic implants. Histology was evaluated using the aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL) score. Results No correlation was found between LTT and any ALVAL score component. The mean total ALVAL score was 3.8 ± 1.5 for LTT-negative patients and 3.3 ± 1.2 for LTT-positive patients (P = .44). The mean total ALVAL score at revision of CoCrNi implants was 3.0 ± 1.8 compared with 5.8 ± 0.5 at rerevision of hypoallergenic implants (P = .053). Conclusion Periprosthetic TKA tissue reactions were indistinguishable between LTT-positive and -negative patients. LTT does not predict the periprosthetic tissue response. ALVAL scores of hypoallergenic revision implant tissue trended higher than primary CoCrNi implant tissue. A positive LTT may not indicate that a periprosthetic immune reaction is the cause of pain and stiffness after TKA. Level of Evidence 3, retrospective cohort study.

Aims Loosening of the tibial component after total knee arthroplasty (TKA) is a common indication for revision. Increasing the strength of the initial tibial implant/cement interface is desirable. There is little information about the surgical techniques that lead to the highest strength. We investigated the effects of eight variables on the strength of the initial tibial baseplate/cement interface. Materials and Methods A total of 48 tibial trays were cemented into acrylic holders using cement from two manufacturers, at three different times (early, normal, and late) using two techniques: cementing the tibial plateau or the plateau and the keel; and involving two conditions of contamination with marrow fat (at the metal/cement and cement/cement interfaces). Push-out tests were performed with load continuously recorded. Results Compared with normal conditions, early cementing increased the mean strength of the interface when using the two cements, Simplex and Palacos, by 48% and 72%, respectively. Late cementing reduced the strength by 47% and 73%, respectively. Cementing the keel increased the mean strength by 153% and 147%, respectively, for the two cements. Contamination of the metal/cement interface with fat reduced the mean strength by 99% and 94% for the two cements but adding cement to the underside of the tibial tray prior to insertion resulted in the mean strength being lowered by only 65% and 43%, respectively. Conclusion In order to maximize the strength of the tibial tray/cement interface, cement should be applied to the component soon after mixing, contamination of the interface should be avoided, and the keel and the plateau should be cemented.

Activity monitoring has important applications in orthopaedic and medical research. There is a paucity of information on device accuracy. Thirty adults tested the accuracy of 10 devices in 5 activities: walk 400-M, run 400-M, walk 10-M, ascend and descend 10 steps. A second protocol tested slow walking speeds at 1.0, 1.5, 1.8, and 2.0MPH. The waist-based devices FitBit One and Omron HJ-321 were >90% accurate for all activities. The wristband devices and Smartphone Apps were 95% accurate at lower cadence activities, but undercounted running by ~25%. Waist-based, dedicated activity monitors are highly accurate in a variety of activities.

Background Cross-linked polyethylene (XLPE) has demonstrated significantly reduced wear and osteolysis into the second decade for total hip arthroplasty. There is a relative paucity of data with ≥36-mm bearings. Issues include potential effects of reduced liner thickness and component position on wear, osteolysis, and mechanical failure of the bearing. Methods Radiographs of 48 primary total hip arthroplasties with ≥36-mm modular XLPE bearings were analyzed at a minimum 5 years postoperative on serial radiographs using a validated, edge-detection-based algorithm. Subgroups were examined to assess the effect of bearing diameter, liner thickness, acetabular abduction angle, and acetabular anteversion on XLPE wear. Results There was no significant difference in volumetric wear when subgroups were stratified by component factors: liner thickness ( 3 /y vs 24.47 mm 3 /y, respectively ( P = .315); acetabular component abduction angle ( 3 /y vs 27.8 mm 3 /y, respectively ( P = .522); acetabular anteversion ( 3 /y vs 31.79 mm 3 /y, respectively ( P = .521). There were no dislocations, mechanical failures, or revisions. There were 7 hips with volumetric wear rates ≥80 mm 3 /y; 1 had possible osteolysis. Conclusion Larger-diameter XLPE wear was not measurably affected by liner thickness, acetabular abduction angle, or acetabular anteversion. However, there is a trend for increasing volumetric wear with increasing bearing size. Wear outliers do occur, and continued follow-up of larger-diameter XLPE bearings is warranted.

Patients, and their femurs, come in all shapes, sizes, and types. Fortunately, so do cementless femoral stems. Each surgeon should have a "go to" cementless femoral component that can address over 90% of cases. A simple approach is to separately consider (A) the part inside the bone and (B) the part outside the bone. The inner-cortical geometry (Dorr type) and bone density influence stem size (the part inside the bone) and influence femoral canal preparation. Femoral deformity or old hardware can occasionally necessitate the use of a short stem or a modular stem. Restoration of limb length and offset is a function of the neck angle and length (the part outside the bone). Undersizing of cementless stems increases the risk of aseptic loosening while restoration of limb length and offset favorably affects patient satisfaction and function.

With improvements in implant modularity and polyethylene, it is important to assess the contemporary performance of cement vs. cementless fixation in total knee arthroplasty (TKA). Aseptic loosening is the most common indication for revision. Registry data indicates that the type of fixation (cemented, cementless, or hybrid) makes little difference in revision rates for younger patients (

The utilization of lymphocyte transformation testing (LTT) has increased for diagnosing metal sensitivity associated with total knee arthroplasty (TKA), but its validity for the diagnosis of TKA failure due to an immune reaction has not been established. In this study, we sought to characterize the relationship of a positive LTT result to histopathologic findings and clinical and functional outcomes.This was a retrospective study of 27 well-fixed, aseptic, primary TKA cases in which the patient had persistent pain and/or stiffness and underwent revision due to a suspected metal allergy to nickel, as determined on the basis of positive LTT. Revision procedures were performed by a single experienced arthroplasty surgeon. Periprosthetic tissue samples obtained at the time of revision surgery were scored using the aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL) scoring system.Eight patients were categorized as mildly reactive; 8 patients, moderately reactive; and 11 patients, highly reactive to nickel by LTT. The predominant findings on routine histopathologic analysis were fibrosis and varying degrees of lymphocytic infiltration in 17 (63%) of the 27 cases. The average ALVAL score of the cohort was 3.1 ± 1.9, of a maximum score of 10. Average Knee Society Score (KSS) values improved post-revision, as did range of motion (all p0.01). Neither LTT stimulation index as a continuous variable nor as a categorical variable (mildly reactive, moderately reactive, highly reactive) was correlated with ALVAL score, pre-revision function (as assessed by KSS-clinical, KSS-functional, and range of motion), or change in function at the most recent follow-up (0.015r0.30, 0.13p0.95). In addition, the ALVAL score did not correlate significantly with either pre-revision or post-revision KSS or range of motion (0.061r0.365, 0.09p0.88).On the basis of this analysis, including histopathologic assessment, LTT results alone were insufficient for the diagnosis of TKA failure due to an immune reaction. A positive LTT may not indicate that an immune reaction is the cause of pain and stiffness post-TKA. The role of LTT in assessing TKA failure from an immune reaction needs further investigation. Diagnostic criteria for such TKA failure need to be established.Diagnostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Cross-linked polyethylene (XLPE) has generally low rates of wear and osteolysis at 10 years, but component position may become important with longer follow-up. At 5-13 years, neither acetabular component lateral opening angle nor version were significantly correlated to wear. In the present study, we analyzed the effects of femoral anteversion and combined anteversion on XLPE wear.Forty-two well-functioning primary total hip arthroplasties in 36 patients, performed by a single surgeon via a posterior approach, were followed for a minimum of 5 years (mean, 7.1 years; range, 5.0-10.3). All hips had a modular, XLPE liner with a ≥36-mm bearing. Femoral anteversion was measured on the modified Budin view. Wear was measured on radiographs using a validated, computer-assisted, edge-detection-based algorithm. The mean lateral opening angle was 40.4° (range, 22.6°-50.3°). The mean acetabular version was 19.1° (range, 11.3°-27.5°). Neither of these variables was significantly correlated to wear. Effects of femoral anteversion and combined anteversion on XLPE wear were assessed using linear and polynomial regression analysis.Femoral anteversion (mean, 18.4°; range, 6.8°-30.7°) was significantly correlated to linear wear (mean, 0.06 mm/y; range, 0-0.16), showing an inverse parabolic relationship with the least wear occurring at 18.2° (P = .02). Combined anteversion (mean, 37.2°; range, 21.8°-54.3°) showed a similar significant relationship with the least wear at 38.1° (P.001). Based on regression, combined anteversion between 24.6° and 50.4° resulted in linear wear rates less than 0.1 mm/y.To the authors' knowledge, this is the first study to identify femoral anteversion as an independent factor influencing XLPE wear, with least wear occurring around 18°. At 5-10 years, average linear wear of XLPE is below 0.1 mm/y over a 25°-50° range of combined anteversion, with the least wear around 38°. Femoral-acetabular mating is a product of both components. Femoral component version and combined anteversion had a greater effect on wear than acetabular component lateral opening angle. Additional studies are warranted, but these results indicate that the sensitivity of wear studies is increased with version assessments.

Jumbo cups can be used to address many acetabular revision cases with bone loss. The technique of implantation is relatively straight forward, and there is the potential to maximize bone-to-cup surface area, approximate the natural hip center, and to obtain a construct that allows immediate weight bearing. Experience from multiple sources has demonstrated survivorship up to 83% at 20 years, limited mostly by the wear of conventional polyethylene. A contraindication to this method is irradiated bone and a limitation is restoration of peripheral acetabular bone stock, which could compromise further revision surgery.

There are practical and fiscal benefits of head–neck modularity. Taper corrosion occurs with all head sizes and rarely necessitates revision. The role of design and manufacturing variables continues to be investigated and debated. The utilization of ceramic heads has increased but the cost–utility ratio needs scrutiny. Changes in surgical practice, including smaller incisions and the increased use of cementless, tapered titanium stems are challenges to consistent and adequate taper assembly. Surgical taper assembly is variable and important regardless of the head material. Standardization of surgical taper assembly is desirable for all head materials: taper assembly has been implicated in ceramic head fracture as well as in fretting and corrosion.

In the Registry Era, in the Information Age, and with a competitive and expanding marketplace, the focus has been on the prosthetic joint devices. However, a distinction should be made between mechanical failure of a device, failure of an arthroplasty, and the limitations of technology. The patient and the surgeon play central roles in the majority of revisions (failure of an arthroplasty). Analysis of a large United States database indicates that the most common causes of revision are instability/dislocation (22.5%), mechanical loosening (19.7%), and infection (14.8%). Acetabular component position has been linked to higher wear and instability. Increased odds of component mal-position were found with lower-volume surgeons and patients with a higher body mass index. Medical co-morbidities significantly increase the risk for revision within 12 months of surgery. Patient demographics and pre-operative status have been shown to be more important than implant factors in predicting the presence of thigh pain, dissatisfaction, and a low hip score. The most predictive factors were ethnicity, educational level, poverty level, income, and a low pre-operative WOMAC score or pre-operative SF-12 mental component score.

There is evidence that high levels of physical activity following arthroplasty of the hip or knee can lead to early revision. However, the term ‘highly active’ is not well defined. A validated ankle accelerometer was used to quantify activity in 13 patients, who had undergone a total of 20 arthroplasties of the lower limbs and who had active lifestyles. The assessments were taken at a mean of 8.7 years post-operatively (1.8 to 15.8). The mean gait cycles per day was 8273 (5964 to 12 557), which extrapolates to 3.0 million cycles per year (cpy) (2.2 to 4.6). The mean percentage of time spent in high activity mode was 4.3%, or about one hour per day. The mean percentage of cycles in high activity was 40%. Based on these data, we propose the following definitions of high activity: > 3 million cpy; one hour per day in high activity mode; 40% of cycles in high activity mode. Extrapolating the sample of activity over the time since operation, the mean cycles per arthroplasty was 25.2 million, with a maximum of 44.1 million. No joint has been revised, or shows evidence of impending failure. Cite this article: Bone Joint J 2016;98-B(1 Suppl A):95–7.