Periprosthetic Tissue Reaction Independent of LTT Result and Implanted Materials in Total Knee Arthroplasty

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.

Lymphocyte Transformation Testing (LTT) in Cases of Pain Following Total Knee Arthroplasty: Little Relationship to Histopathologic Findings and Revision Outcomes

BACKGROUND

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.

METHODS

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.

RESULTS

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 p < 0.01). 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 (0.015 < r < 0.30, 0.13 < p < 0.95). In addition, the ALVAL score did not correlate significantly with either pre-revision or post-revision KSS or range of motion (0.061 < r < 0.365, 0.09 < p < 0.88).

CONCLUSIONS

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.

LEVEL OF EVIDENCE

Diagnostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Femoral-Acetabular Mating: The Effect of Femoral and Combined Anteversion on Cross-Linked Polyethylene Wear

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Wear Rates of Larger-Diameter Cross-Linked Polyethylene at 5 to 13 Years: Does Liner Thickness or Component Position Matter?

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 (<6.5 mm vs ≥6.5 mm) 40.69 mm³/y vs 24.47 mm³/y, respectively (P = .315); acetabular component abduction angle (<45° vs ≥45°): 38.68 mm³/y vs 27.8 mm³/y, respectively (P = .522); acetabular anteversion (<20° vs ≥20°): 41.32 mm³/y vs 31.79 mm³/y, respectively (P = .521). There were no dislocations, mechanical failures, or revisions. There were 7 hips with volumetric wear rates ≥80 mm³/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.

Defining high activity in arthroplasty patients

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.

What is the upper limit of cement penetration for different femoral hip resurfacing components?

We used a validated femoral resurfacing model to obtain measurements of pressure and temperature and quantify cement distribution as a function of inner geometry and cementing technique of five different femoral hip resurfacing components. The purpose was to investigate if manufacture cementing recommendations are reliable. ASR showed only with the recommended manual cementing technique low cement pressures of 58.0±50.2kPa and low interface temperatures of 33.3±4.1°C. BHR had large cement defects of 10.4±1.1mm. Conserve Plus caused the smallest cement penetration depths of 2.9±0.6mm. Durom was tolerant against changes of the cementing technique but showed the widest spread of temperature data 42.8±7.0°C. ReCap showed the highest risk for incomplete seating with a cement mantle thickness of 4.3±0.9mm. Polymerization heat did not exceed the threshold of 45°C with a cement penetration depth of less than 4.2mm in any circumstances of this study.

The Hip Society: algorithmic approach to diagnosis and management of metal-on-metal arthroplasty

Since 1996 more than one million metal-on-metal articulations have been implanted worldwide. Adverse reactions to metal debris are escalating. Here we present an algorithmic approach to patient management. The general approach to all arthroplasty patients returning for follow-up begins with a detailed history, querying for pain, discomfort or compromise of function. Symptomatic patients should be evaluated for intra-articular and extra-articular causes of pain. In large head MoM arthroplasty, aseptic loosening may be the source of pain and is frequently difficult to diagnose. Sepsis should be ruled out as a source of pain. Plain radiographs are evaluated to rule out loosening and osteolysis, and assess component position. Laboratory evaluation commences with erythrocyte sedimentation rate and C-reactive protein, which may be elevated. Serum metal ions should be assessed by an approved facility. Aspiration, with manual cell count and culture/sensitivity should be performed, with cloudy to creamy fluid with predominance of monocytes often indicative of failure. Imaging should include ultrasound or metal artifact reduction sequence MRI, specifically evaluating for fluid collections and/or masses about the hip. If adverse reaction to metal debris is suspected then revision to metal or ceramic-on-polyethylene is indicated and can be successful. Delay may be associated with extensive soft-tissue damage and hence poor clinical outcome.

The Hip Society: algorithmic approach to diagnosis and management of metal-on-metal arthroplasty

Since 1996 more than one million metal-on-metal articulations have been implanted worldwide. Adverse reactions to metal debris are escalating. Here we present an algorithmic approach to patient management. The general approach to all arthroplasty patients returning for follow-up begins with a detailed history, querying for pain, discomfort or compromise of function. Symptomatic patients should be evaluated for intra-articular and extra-articular causes of pain. In large head MoM arthroplasty, aseptic loosening may be the source of pain and is frequently difficult to diagnose. Sepsis should be ruled out as a source of pain. Plain radiographs are evaluated to rule out loosening and osteolysis, and assess component position. Laboratory evaluation commences with erythrocyte sedimentation rate and C-reactive protein, which may be elevated. Serum metal ions should be assessed by an approved facility. Aspiration, with manual cell count and culture/sensitivity should be performed, with cloudy to creamy fluid with predominance of monocytes often indicative of failure. Imaging should include ultrasound or metal artifact reduction sequence MRI, specifically evaluating for fluid collections and/or masses about the hip. If adverse reaction to metal debris is suspected then revision to metal or ceramic-on-polyethylene is indicated and can be successful. Delay may be associated with extensive soft-tissue damage and hence poor clinical outcome.

The 2012 Frank Stinchfield Award: Decreasing patient activity with aging: implications for crosslinked polyethylene wear

BACKGROUND

Patient activity influences polyethylene wear. However, it is unclear how individual activity changes with patient aging after THA.

QUESTIONS/PURPOSES

We quantified changes in individual gait cycles and gait speed, assessed age-related differences in these parameters, and determined their relationship to polyethylene wear.

METHODS

A microprocessor was worn on the ankle to quantify the activity of 14 healthy patients with a well-functioning THA at two time periods: early (within 3.5 years of implantation) and late (10-13 postoperative years). Wear was measured on serial radiographs using edge detection-based software.

RESULTS

Mean activity decreased by 16% from the early to the late period: 2.04 million gait cycles/year to 1.71 million gait cycles/year. Mean gait speed decreased by 9%: 15.4 cycles/minute to 14.0 cycles/minute. The activity of the 10 patients who were younger than 65 years at surgery decreased by 14% (2.34 million gait cycles/year to 2.02 million gait cycles/year), while the four patients 65 years or older at surgery decreased by 28% (1.29 million gait cycles/year to 0.94 million gait cycles/year). Gait speed was 26% slower for patients 65 years or older than for patients younger than 65 years. The mean linear penetration rate decreased by 42% from the first 5 years (early wear rate) to the next 8 years (late wear rate, 5-13 years): 0.043 mm/year to 0.025 mm/year.

CONCLUSIONS

The greatest patient activity and wear occurred during the first 5 years. Walking speed and gait cycles both decreased with aging, resulting in deceasing wear over time.

State of the art in hard-on-hard bearings: how did we get here and what have we achieved?

Total hip arthroplasty has shown excellent results in decreasing pain and improving function in patients with degenerative disease of the hip. Improvements in prosthetic materials, designs and implant fixation have now resulted in wear of the bearing surface being the limitation of this technology, and a number of hard-on-hard couples have been introduced to address this concern. The purpose of this article is to review the origins, development, survival rates and potential advantages and disadvantages of the following hard-on-hard bearings for total hip arthroplasty: metal-on-metal standard total hip arthroplasty; metal-on-metal hip resurfacing arthroplasty, ceramic-on-ceramic total hip arthroplasty; and ceramic-on-metal bearings. Improvements in the manufacturing of metal-on-metal bearings over the past 50 years have resulted in implants that provide low wear rates and allow for the use of large femoral heads. However, concerns remain regarding elevated serum metal ion levels, potential teratogenic effects and potentially devastating adverse local tissue reactions, whose incidence and pathogenesis remains unclear. Modern total hip resurfacing has shown excellent outcomes over 10 years in the hands of experienced surgeons. Current ceramic-on-ceramic bearings have demonstrated excellent survival with exceptionally low wear rates and virtually no local adverse effects. Concerns remain for insertional chipping, in vivo fracture and the variable incidence of squeaking. Contemporary ceramic-on-metal interfaces are in the early stages of clinical use, with little data reported to date. Hard-on-hard bearings for total hip arthroplasty have improved dramatically over the past 50 years. As bearing designs continue to improve with new and modified materials and improved manufacturing techniques, it is likely that the use of hard-on-hard bearings will continue to increase, especially in young and active patients.

Survival of hard-on-hard bearings in total hip arthroplasty: a systematic review

BACKGROUND

Improvements in prosthetic materials, designs, and implant fixation for THA have led to bearing surface wear being the limitation of this technology. Hard-on-hard bearings promise decreased wear rates and increased survival. However, there may be different survival rates based on bearing materials, manufacturing technologies, and femoral component designs. Additionally, survival rate variability may be based on study design.

QUESTIONS/PURPOSES

We determined survival rates and study levels of evidence and quality for the following bearings: stemmed metal-on-metal THA, metal-on-metal hip resurfacing, ceramic-on-ceramic THA, and ceramic-on-metal THA.

METHODS

We performed a systematic review of the peer-reviewed literature addressing THA hard-on-hard bearings. Quality for Level I and II studies was assessed.

RESULTS

The four Level I or II second-generation stemmed metal-on-metal THA studies reported between 96% and 100% mean survival at 38 to 60 months. The two Level I hip resurfacing studies reported 94% and 98% mean survival at 56 and 33 months. The four Level I studies of ceramic-on-ceramic THA reported survival from 100% at mean 51 months to 96% at 8 years.

CONCLUSIONS

While hard-on-hard bearing survival rates have generally been variable with earlier designs, contemporary implants have demonstrated survival of 95% or greater at followup of between 3 and 10 years. Some variability in survival may be due to differences in surgical technique, component positioning, and implant designs. As bearing designs continue to improve with modified materials and manufacturing techniques, use will increase, especially in young and active patients, though concerns remain about the increased reports of adverse events after metal-on-metal bearings.

Fracture of a cross-linked polyethylene liner: a multifactorial issue

A limited number of reports have detailed the cause of fracture of a highly cross-linked polyethylene liner. Typically, the fractures have occurred in a region of thin and/or unsupported polyethylene, in association with superiorly directed edge loading conditions secondary to an excessively inclinated acetabular component. This case report details an unusual fracture mechanism of a 5-mrad cross-linked liner caused by horizontal loading conditions. The report details several factors that were felt to be etiologic including the specific liner locking mechanism. The treatment options are discussed.

Fixed versus rotating platform total knee arthroplasty: a prospective, randomized, single-blind study

The purpose of this randomized, single-blind clinical trial was to compare a rotating platform (RP) total knee arthroplasty to a fixed-bearing (FB) total knee arthroplasty. Ninety-five knees in 69 patients were implanted by 2 surgeons. There were no significant differences in the preoperative demographics. At a minimum of 2-year follow-up, clinical outcomes and complication rates were similar, with the exception that the RP group had significantly better stair-climbing scores (P = .04). Postoperative range of motion was equally good in both groups (FB knees, 1°-125°; RP knees, 1-126°). There were no bearing dislocations in the RP group. In conclusion, this RP design performs at least as well as the FB version, and the RP patients reported better stair-climbing ability. Enthusiasm for this finding should be tempered by the relatively small sample size.

The influence of cementing technique in hip resurfacing arthroplasty on the initial stability of the femoral component

PURPOSE

In clinical and retrieval analyses, over-penetration of cement, incomplete seating of the prosthesis with a resultant polar cement mass, or both, have been associated with early femoral failures of resurfacing arthroplasties. We used human bone specimens to experimentally compare the initial stability of different cementing techniques.

METHODS

Twenty-six pairs of fresh frozen femora were prepared for resurfacing using original instruments (DePuy ASR). ASR femoral resurfacing prostheses were implanted using two different cementing techniques: (1) component filling and (2) cement applicator. Real-time measurements of pressure and temperature during implantation, analyses of cement penetration and micro motions under torque application were performed.

RESULTS

Applicator use reduced significantly the cement penetration depth (9.2 mm vs 5.3 mm with the applicator, p = 0.001), polar mantle (8.1 mm vs 2.6 mm, p = 0.008), cement defects (3.7 mm vs 0.1 mm, p = 0.008) and interface temperatures (40.3°C vs 33.1°C, p < 0.001 ). Initial rotational stability showed statistically significant less extreme values with the cement applicator technique (range 3.4-51.7 m°/Nm, 11.0-29.7 m°/Nm, p = 0.024).

CONCLUSIONS

The cement applicator technique significantly reduces cement defects, incomplete seating, over-penetration and interface temperatures with a more consistent initial stability of the ASR femoral resurfacing prostheses.

Measuring acetabular component position on lateral radiographs - ischio-lateral method

The standard method for the evaluation of arthritis and postoperative assessment of arthroplasty treatment is observation and measurement from plain films, using the flm edge for orientation. A more recent employment of an anatomical landmark, the ischial tuberosity, has come into use as orientation for evaluation and is called the ischio-lateral method. In this study, the use of this method was evaluated as a first report to the literature on acetabular component measurement using a skeletal reference with lateral radiographs. Postoperative radiographs of 52 hips, with at least three true lateral radiographs taken at different time periods, were analyzed. Component position was measured with the historical method (using the flm edge for orientation) and with the new method using the ischio-lateral method. The mean standard deviation (SD) for the historical approach was 3.7° and for the ischio-lateral method, 2.2° (p < 0.001). With the historical method, 19 (36.5%) hips had a SD greater than ± 4°, compared to six hips (11.5%) with the ischio-lateral method. By using a skeletal reference, the ischio-lateral method provides a more consistent measurement of acetabular component position. The high intra-class correlation coefficients for both intra- and inter-observer reliability indicate that the angle measured with this simple method, which employs no further technology, increased time, or cost, is consistent and reproducible for multiple observers.

Cementing techniques for hip resurfacing arthroplasty: in vitro study of pressure and temperature

Cementing irregularities have been associated with femoral failures of resurfacing arthroplasties in retrieval studies. We used an in vitro model to measure pressure, temperatures, and cement penetration as a function of 6 different cementing techniques. Filling the component with cement can lead to overpenetration or increase the resistance to component seating with resultant polar cement mass. Both conditions result in high and long-lasting cement pressures, cement defects, as well as peak temperatures higher than 50°C. Manual application of cement provides complete penetration of the available fixation area with the lowest cement pressures, the smallest total cement mass, and a peak temperature of 36.0°C ± 4.1°C. Application of the principles elucidated by this study may reduce the risk of cement overpenetration and incomplete seating.

Metal-metal reactivity: Houston, we have a problem!

In this single-surgeon series, both resurfaced hips in 1 woman and a total hip arthroplasty in another were revised for symptomatic pseudotumor (3 of 588 hips; 0.51% overall incidence; 2.2% in women). All 3 hips had 50-mm acetabular components. There was no difference in mean lateral opening angle (mean 38.7° vs 42.8° for the others) but these 3 hips all had increased acetabular anteversion (mean 27.1° vs 16.4° for the others; P<.05). Increased combined anteversion is a mechanical common denominator in pseudotumor formation. Female sex and small component size are variables associated with congenital dysplasia, which typically has a small, shallow socket and high combined anteversion. Thus, native anatomy may predispose to the joint mechanics that lead to pseudotumor formation, and not sex or size. The aggregate results indicate that the determination of satisfactory component position includes (1) assessment of the acetabular component lateral opening, (2) acetabular component version, and (3) femoral version. A mechanical problem suggests a mechanical solution. To insure capture of the femoral head by the socket and the intended bearing tribology, acetabular lateral opening angles should be <50°, assuming a femoral neck-shaft angle of 130° to 135°. Combined anteversion should not exceed 40°. In resurfacing of dysplastic cases where the neck-shaft angle exceeds 140°, the acetabular lateral opening angle needs to be correspondingly lower to achieve equivalent head capture and bearing contact.

Influence of bone density on the cement fixation of femoral hip resurfacing components

In clinical outcome studies, small component sizes, female gender, femoral shape, focal bone defects, bad bone quality, and biomechanics have been associated with failures of resurfacing arthroplasties. We used a well-established experimental setup and human bone specimens to analyze the effects of bone density on cement fixation of femoral hip resurfacing components. Thirty-one fresh frozen femora were prepared for resurfacing using the original instruments. ASR resurfacing prostheses were implanted after dual-energy X-ray densitometer scans. Real-time measurements of pressure and temperature during implantation, analyses of cement penetration, and measurements of micro motions under torque application were performed. The associations of bone density and measurement data were examined calculating regression lines and multiple correlation coefficients; acceptability was tested with ANOVA. We found significant relations between bone density and micro motion, cement penetration, cement mantle thickness, cement pressure, and interface temperature. Mean bone density of the femora was 0.82 +/- 0.13 g/cm(2), t-score was -0.7 +/- 1.0, and mean micro motion between bone and femoral resurfacing component was 17.5 +/- 9.1 microm/Nm. The regression line between bone density and micro motion was equal to -56.7 x bone density + 63.8, R = 0.815 (p < 0.001). Bone density scans are most helpful for patient selection in hip resurfacing, and a better bone quality leads to higher initial component stability. A sophisticated cementing technique is recommended to avoid vigorous impaction and incomplete seating, since increasing bone density also results in higher cement pressures, lower cement penetration, lower interface temperatures, and thicker cement mantles.

Changes in whole blood metal ion levels following resurfacing: serial measurements in a multi-centre study

Seventy-seven patients implanted with unilateral resurfacing prosthesis were recruited from four centres. Serial whole blood samples were collected and ion levels were analysed. In most cases, the ion levels stabilized by 3 months. The 24 month median ion levels were 1.49ug/l for chromium and cobalt. In approximately 50% of patients the increase in chromium and cobalt level was less than 1ug/l. There were 6 patients with abnormally high metal ion levels. Of these 4 were significant outliers, had high ion levels that became apparent between 12 and 24 months after implantation, and had a high cup abduction angle. Not all patients with high cup abduction angles demonstrated high levels. There were differences in ion levels between the four centres that correlated with variation in acetabular component placement. Variability in ion levels was seen with the same prosthesis, underscoring the importance of surgical technique, longitudinal analysis, and multi-centre trials.

Decolonization of drug-resistant organisms before total joint arthroplasty

Periprosthetic joint infection is now the leading cause of failure after a total knee arthroplasty, and Staphylococcus aureus, most commonly from the patient's own flora, typically is the infective agent. Several preoperative screening tests have been developed to identify patients who are carrying methicillin-resistant S aureus. Testing and decolonization programs have generally been effective in decreasing the incidence of surgical site infections, but the role of such programs in total joint arthroplasty has not been thoroughly investigated. Although recent studies found a tendency toward fewer methicillin-resistant S aureus infections after total joint arthroplasty when a testing and decolonization program was used, most of these studies were underpowered. Larger, randomized, controlled studies are needed.

Metal-metal bearing surfaces in hip arthroplasty

There is no mystery regarding the allure of metal-metal bearings: high stability and low wear potential. The special risks associated with these bearings are coming into focus and include a macrophage response to excessive metal particles (metal reactivity) and a lymphocyte-dominated reaction (metal sensitivity). The most common presentation of an adverse local tissue reaction (ALTR) is persistent pain. The incidence of ALTR has not been completely defined, but the risk appears to be increased in resurfacing, in women, and in bilateral cases. The differential diagnosis includes septic and aseptic loosening, and the evaluation should include aspiration. The diagnosis is confirmed by histological examination.

Posterior femoroacetabular impingement (PFAI) - after hip resurfacing arthroplasty

INTRODUCTION

The recent, encouraging outcome literature on hip resurfacing arthroplasty (HRA) has not sufficiently examined the potential occurrence of postoperative femoroacetabular impingement (PFAI) and sequelae. The current study asks the questions, "Does femoroacetabular impingement occur after hip resurfacing arthroplasty (HRA) and, if so, what are the clinical outcomes?"

METHODS

Sixty-nine consecutive hips in 57 patients with a minimum of 2 years clinical and radiographic follow-up were evaluated. Both acetabular and femoral component positions and postsurgical changes in the femoral neck and acetabulum were recorded.

RESULTS

Fourteen hips in 13 patients (20%) developed a small scalloped, corticated erosion in the posterior neck, just distal to the femoral component and adjacent to the acetabular component rim. These erosions were between 5 and 10 mm in depth and became apparent at an average of 15 months (range, 6 to 24 months) following surgery. After 2 years, they showed no further progression. The location and shape of the erosions indicate PFAI as the etiology. One hip also demonstrated similar changes in the anterior neck. The Harris Hip Score and UCLA (University of California at Los Angeles) Activity Scores were higher in patients with such erosions (97.5 and 9.2, respectively), compared to those patients without (93.5 and 8.4, respectively). Additionally, patients with erosions reported slightly better pain relief on average than patients with no radiographic evidence of impingement. No significant differences in range of motion or component position were found between the two groups.

CONCLUSIONS

Small, corticated, non-progressive erosions can occur from femoroacetabular impingement following HRA. The erosions were more commonly posterior in this series, and they tended to occur in active patients. There is no adverse effect on clinical outcomes, and more specifically, there is no association of PFAI with pain.

Resistant organisms in infected total knee arthroplasty: occurrence, prevention, and treatment regimens

Infection of a primary joint arthroplasty can be a life-changing event for a patient. When the infecting organism demonstrates antibiotic resistance, treatment can be prolonged, and the chances for a successful outcome may be decreased. Antibiotic resistance has been an evolutionary process since the introduction of pharmacologic treatment and until recently has been more problematic with nosocomial types of infections. Methicillin-resistant Staphylococcus aureus skin infections within the community among school or sports teams has been a recent cause for concern. Hospitals have implemented screening and/or isolation procedures to reduce the risk of spreading these resistant organisms and identify patients colonized with resistant organisms. These measures have been successful in patients undergoing total joint arthroplasty. It is important for the orthopaedic surgeon to be knowledgeable about the emergence of resistant bacteria, preoperative and intraoperative screening guidelines, and postoperative considerations to prevent resistant organism infections in total joint arthroplasty patients.

A comparison of total hip resurfacing and total hip arthroplasty - patients and outcomes

A comparison of pertinent preoperative and postoperative data relative to total hip resurfacing versus total hip arthroplasty (THA) would assist in evaluating current perceptions in outcome. We compared 50 consecutive metal-metal resurfacing replacements in 50 patients with 44 consecutive conventional total hip arthroplasties in 35 patients, who were implanted during the same time period, by the same surgeon, and followed prospectively for 2 to 4 years. The patients undergoing hip resurfacing were 62% male, 9 years younger, and 3.2 inches taller, with a lower mean body mass index and American Society of Anesthesiologists (ASA) grade than patients undergoing total hip arthroplasty. Preoperatively, patients undergoing resurfacing had a lower Harris hip score (46 vs 52 points), more pain, higher UCLA (University of California at Los Angeles) activity scores (4.2 vs 3.6), and better range of motion. Surgical time for resurfacing was 18% longer, but there was less total blood loss and fewer transfusions. Postoperatively, there was no difference in Harris hip score (97 vs 96). Patients undergoing resurfacing had higher function, Short Form-12 physical activity scores, and UCLA activity scores, but also a higher incidence of slight or mild pain. There were no differences in postoperative range of motion or dislocation (one each). The preoperative characteristics and general health status of the average patient undergoing resurfacing are more favorable than that of the average patient undergoing conventional total hip arthroplasty. Caution should be applied in attributing differences in outcomes directly to the arthroplasty technology.

Perceptions concerning hip resurfacing from attendees at the Second Annual U.S. Comprehensive Course on Total Hip Resurfacing Arthroplasty

Resurfacing hip arthroplasty represents a new, alternative technology to standard total hip arthroplasty. We examined the perceptions about resurfacing after the Second Annual United States Comprehensive Course on Total Hip Resurfacing Arthroplasty, which was a multi-company sponsored educational event to advance general knowledge, basic science, and surgical skills relevant to this field. The course led to a substantial increase in knowledge concerning resurfacing as evaluated from pre- and post-tests. The perceptions concerning indications, patient selection, and beliefs of the course attendees are reported.

Cementing techniques for hip resurfacing arthroplasty: development of a laboratory model

BACKGROUND

Hip resurfacing is extremely technique-sensitive, yet scientific investigations into cementing techniques are lacking. In this study, we tested open-cell, reticulated, carbon-foam materials in comparison with paired human femoral heads to validate a laboratory cementing model for resurfacing arthroplasty.

METHODS

Paired human femoral heads prepared for resurfacing were compared with thirty and sixty-pore-per-inch fat-filled foam specimens. Two different cementing techniques were analyzed: manual application of high-viscosity cement, and half component-filling with low-viscosity cement. Real-time measurements were made of cement pressure and temperature. Cement penetration areas and depths were quantified.

RESULTS

We found no significant differences between the human femoral heads and the fat-filled thirty-pore-per-inch foam models in all measured variables (pressures at the top, chamfer and outer wall, temperature at the 5-mm and 15-mm subsurface). There was no significant difference in the cement penetration of the human femoral heads and the fat-filled thirty-pore-per-inch foam models. There were a number of significant differences between the human femoral heads and the sixty-pore-per-inch foam models with use of the low-viscosity cement technique. The differences between the cementing techniques were greater than those between the three materials for most of the measurements.

CONCLUSIONS

Fat-filling (to emulate bone marrow) of lower-density carbon foam more closely simulates the cement penetration resistance and thermal properties of human femoral heads than does the denser (unfilled) material. This model is sensitive to differences in cementing technique.

Reduction of osteolysis with use of Marathon cross-linked polyethylene. A concise follow-up, at a minimum of five years, of a previous report

We previously reported wear data at a minimum of two years following thirty-four total hip replacements with a Marathon cross-linked polyethylene liner and twenty-four replacements with a conventional (gamma-sterilized-in-air) Enduron polyethylene liner. In this current study, with sequential five-year radiographs, wear rates were determined with use of linear regression analysis. The Marathon polyethylene had average wear rates of 15.4 mm(3)/yr and 8.0 mm(3)/million cycles. The Enduron polyethylene had average wear rates of 55.5 mm(3)/yr and 29.9 mm(3)/million cycles. The adjusted volumetric wear rate of the Marathon polyethylene was 73% lower than that of the Enduron polyethylene (p = 0.001). Osteolysis developed in eight of the twenty-four hips with an Enduron liner but was not apparent in any hip with a Marathon liner.

Infection in primary total knee arthroplasty: contributing factors

Infection after a total knee arthroplasty is an infrequent but serious complication that can have devastating consequences. Infection carries a risk of significant morbidity, and the cost of treatment can be a substantial burden to the health care system. Eradication of infection can be very difficult. Prevention of infection remains the ultimate goal. Identification of host risk factors, careful patient selection, and optimization of the wound environment and the operating room remain some of the core fundamental steps that help minimize the overall incidence of infection. Although the exact role of each of these risk factors in a clinical setting can be debatable, a multidisciplinary approach incorporating all known and established methods of infection control can help to minimize the incidence of infection following total knee arthroplasty.

Diagnosis and treatment of the infected primary total knee arthroplasty

A diagnosis of infection in the painful primary total knee replacement is not always a straightforward endeavor. No single, fail-proof diagnostic study for infection exists. Often multiple diagnostic studies that include imaging, blood work, and joint aspiration as well as history and physical examination need to be considered. Infection may not always be determined before surgery, in which case intraoperative frozen sections can help to confirm infection or refute a negative workup. Treatment options vary, depending on the timing in the infection process and the source of the infection and may consist of simpler treatment courses, such as irrigation, débridement, and polyethylene exchange, to more complex treatment courses, such as two-stage revision with an antibiotic spacer to fusion or amputation. The orthopaedic surgeon uses an essential armamentarium of diagnostic and treatment options to determine the presence of infection and tailor the individual treatment of each patient.

Effect of changing indications and techniques on total hip resurfacing

Recently, improved metal-on-metal bearing technology has led to the reemergence of resurfacing as a reasonable option for total hip arthroplasty. During the course of a prospective multicenter FDA-IDE evaluation of metal-on-metal total hip resurfacings, we modified our indications and emphasized surgical technique where the femoral surface area was small due to femoral cysts and small component size. We assessed the influence of these changes on complication rates in the first cohort of 292 patients and the second of 724, and then compared these outcomes in the second cohort with historical reports of resurfacing. We had a minimum followup of 24 months (mean, 33 months; range, 24-60 months). After changes were made in the indications and technique, the overall complication rate decreased from 13.4% to 2.1% with the femoral neck fracture rate reduced from 7.2% to 0.8%. The outcomes of the second cohort compare with modern-day resurfacing devices and appear superior to historical results. The data suggest patients should be carefully selected and technique optimized to reduce complications. Long-term followup is required to see if these promising results will be maintained.

Why total hip resurfacing

Improvements in materials and fixation have addressed many of the limitations of resurfacing total hip arthroplasty (THA). The functional demands and the longevity of arthroplasty patients are increasing. Many patients have embraced the functional capacity, bone conservation, and revision options of hip resurfacing. Young men have historically been at increased risk for failure of total THA. In this patient subgroup, the survivorship of hybrid metal-metal resurfacing THA has been demonstrated to exceed that of THA, but patient selection is critical. The procedure is now also conservative on the acetabular side, and revision of the cementless acetabular component is rare. The operative parameters of femoral resurfacing revisions (conversion to a THA) are similar to that of a primary THA. Bearing technology will continue to evolve.

Extended travel after hip arthroplasty surgery. Is it safe?

Hip arthroplasty and extended travel are each recognized as risk factors for venous thromboembolism (VTE). The safety of travel after hip arthroplasty is currently unknown. Patients who had traveled more than 200 miles within 6 weeks of a hip arthroplasty or hip resurfacing were identified and contacted. All patients received VTE chemoprophylaxis with enoxaparin, dalteparin, fondaparinox, or warfarin. A total of 608 patients traveled an average of 1377 miles at an average of 6.5 days after surgery. Among these patients, 462 traveled by airplane, 143 by car, and 3 by train. There were no deaths, no symptomatic pulmonary embolisms, and only 5 (0.82%) symptomatic deep venous thromboses. Nine (1.5%) patients experienced bleeding complications. With chemical VTE prophylaxis, extended travel within 6 weeks of hip arthroplasty surgery is associated with a low rate of symptomatic deep venous thrombosis, with no known pulmonary embolisms and no deaths.

What would you do? Challenges in hip surgery

The following are 5 case presentations of interesting and challenging patients with hip pathology.

Femoral cementing technique for hip resurfacing arthroplasty

The resurgence of metal-metal bearings has renewed interest in hip resurfacing, but a paucity of information exists regarding femoral cementing technique. We developed a laboratory model in which 72 open-cell foam specimens were used to simulate bone. Analyses of two cement viscosities, two foam porosities, and six cementing techniques were performed: manual cement application only, manual application and filling of one quarter of the component with cement, filling of half of the component, manual application and half component filling, full component filling, and manual application and full component filling. For manual application, cement was pressurized into the foam by rolling the finger tips. For component filling, a defined quantity of cement was poured into the component before pressing it onto the foam. Specimens were cut into quarters, and cement penetration was quantified in seven areas: top, chamfer, wall, interior area, and proximal, medial, and distal stem. The manual technique showed a 3-mm thick, even cement penetration of the outer fixation surface (top = 26 +/- 0 mm(2), chamfer = 14.9 +/- 0.2 mm(2), wall = 55.6 +/- 5.2 mm(2)). None of the other techniques showed a significantly higher penetration in these areas. Large differences were found between all techniques at the medial stem (27.7 +/- 17.5 mm(2), p < 0.001) and the interior area (128.5 +/- 69.6 mm(2), p = 0.013). An increasing degree of penetration occurred from manual cement application to manual application and full component filling. Sixteen specimens showed incomplete seating, which occurred with all techniques except the manual technique. The manual technique consistently gave an approximately 3-mm thick even cement penetration over the outer fixation area. Pouring any cement into the shell resulted in variable degrees of deeper penetration and a risk of incomplete seating, which have been associated with bone necrosis and early fracture.

Hip resurfacing arthroplasty

Hip resurfacing arthroplasty is a type of hip replacement that involves capping the femoral head and preserving bone of the proximal femur. Metal-on-metal surface replacements have been manufactured since the early 1990s. Recent studies indicate excellent clinical results with low failure rates at 1- to 5-year follow-up. Although these early results are encouraging, resurfacing devices must be used with caution because less is known about their long-term safety and efficacy. The best candidates for resurfacing are patients younger than age 60 years with good bone stock. The surgical approach is similar to that for standard total hip replacements, but with slightly more dissection because the femoral head must be preserved and displaced to visualize the acetabulum. To reduce complications, resurfacing arthroplasty should be performed by surgeons who have received training specifically in this technique.

The infected hip: telltale signs and treatment options

The diagnosis of deep infection after total hip arthroplasty may not be obvious. Mild pain may be the only symptom. Normal radiographs do not exclude infection. Screening blood tests include the erythrocyte sedimentation rate and the C-reactive protein. If either test is elevated with a painful total hip, aspiration of the joint is efficacious. Aspiration remains the cornerstone for the diagnosis and treatment of infection. Intraoperative frozen sections can also be of value in the diagnosis of infection; however, this method is dependent on tissue sampling. A 2-stage revision remains the criterion standard for treatment. An antibiotic-impregnated cement spacer can deliver a high concentration of antibiotic to the infected space, maintain soft tissue tension, and provide better function than a resection arthroplasty. Direct exchange is rarely indicated today.

The optimal metal-metal arthroplasty is still a total hip arthroplasty: in opposition

The longevity of any hip arthroplasty in an individual patient cannot be predicted with certainty so revisability of the arthroplasty remains an issue. As the occurrence of loosening and osteolysis decreases, then fatigue failure of femoral stems, complications of modular connections, and infection will become relatively more common modes of failure. Metal-metal hip resurfacing conserves bone stock, which provides better options for revision surgery. Hip resurfacing favors early intervention and has demonstrated excellent outcomes in young active males, the group historically at increased risk for failure of a conventional total hip arthroplasty. The best balance of the benefit-risk ratio for hip resurfacing is in those patients at increased risk for failure of a conventional total hip arthroplasty.

Development rationale for an articular surface replacement: a science-based evolution

Hip resurfacing has an enduring appeal because of the advantages of bone conservation and maximal joint stability. However, a far from satisfactory experience with earlier resurfacing designs led to its virtual disappearance in the 1980s. The concept was reintroduced in the late 1990s. The current generation of resurfacing devices generally consisted of a large-diameter metal-on-metal articulation, the femoral components being cemented and the acetabular components utilizing various forms of cementless fixation. The encouraging medium-term results, with a follow-up of up to 8 years using the current generation of surface replacement joints, combined with favourable reports related to long-term performance of some metal bearings have led to a rapid increase in the use of such components with these devices. This trend is most marked in younger, more active patients who have expectations of restoration of lifestyle in addition to improved mobility and pain relief and in whom failure with conventional total hip replacement is much higher than previously reported with more sedentary patients. The aim of this paper is, firstly, to highlight a number of areas of improvement and, secondly, to explain how these may be addressed by making modifications to the design of both implants and instrumentation and to the surgical technique. The areas identified for improvement were tissue preservation (thinner components, and reduced steps between sizes), acetabular cup issues (fixation, insertion, and positioning), femoral component issues (design, loading, and cementation), improved bearing surface characteristics, and simplified precise instrumentation with a low-trauma surgical technique.

Optimizing patient selection and outcomes with total hip resurfacing

Short-term failures of total hip resurfacing have been related to specific characteristics of the proximal femur. A radiographic arthritic hip grading scale was used to assess four characteristics of the proximal femur: bone density, shape, biomechanics, and focal bone defects. Hips with no unfavorable characteristics were Grade A, hips with one unfavorable characteristic were Grade B, hips with two unfavorable characteristics were Grade C, hips with three unfavorable characteristics were Grade D, and hips with four unfavorable characteristics were Grade F. One hundred forty-seven consecutive hips were treated with metal-on-metal resurfacing by a single surgeon. There were no femoral neck fractures. Of the 91 hips eligible for a minimum 2 year followup, 90% were Grades A or B, 10% were Grade C, and none were Grades D or F. With a minimum 2-year followup, arthritic hip grading was associated with preoperative Harris hip score, occurrence of mild to moderate postoperative pain, preoperative and postoperative range of motion, preoperative and postoperative hip center of rotation, preoperative and postoperative horizontal femoral offset, preoperative and postoperative limb length discrepancy, and acetabular radiolucencies. Hips with a lesser degree of secondary arthritic changes have a higher arthritic hip grade and better outcomes with total hip resurfacing. Relatively strict selection criteria for resurfacing were associated with a low occurrence of short-term failures.

LEVEL OF EVIDENCE

Prognostic study, Level II (retrospective study). See the Guidelines for Authors for a complete description of levels of evidence.

In vivo wear of bilateral total hip replacements: conventional versus crosslinked polyethylene

Crosslinked polyethylene (PE) was developed to reduce volumetric wear in prosthetic joints. Hip simulator studies have shown promising results but there is as yet limited clinical data. We identified three patients with bilateral total hip replacements who received a crosslinked PE liner (Marathon, DePuy, Warsaw, IN, USA) on one side and a conventional PE insert (Enduron, DePuy) on the contralateral side. As an assessment of in vivo PE wear, linear head penetration was measured on standardized radiographs using a validated computer-assisted technique. In all the three cases, a marked reduction of more than 70% in volumetric wear was found in association with Marathon crosslinked PE. These case reports support the efficacy of this type of crosslinked PE in a selected group that allows direct comparison of the two different materials without the influence of patient-related factors such as activity, gender, weight, or others.

Preoperative templating and biomechanics in total hip arthroplasty

Preoperative templating is an essential ingredient of a successful hip arthroplasty. The socket template is positioned first to establish the center of rotation of the reconstruction. For femoral templating, a surgeon should not only consider the part inside the bone (the size of the component), but should also consider the part outside the bone, which determines limb length and biomechanical parameters such as theabductor muscle and joint reaction forces. Medializing the hip center of rotation and increasing the horizontal femoral offset can improve clinical outcomes and reduce polyethylene wear. Modern modular systems allow limb length adjustment and biomechanical improvement for a range of patients.

Metal-on-metal resurfacing arthroplasty: no way under the sun!--in opposition

The functional demands and the longevity of hip arthroplasty patients are increasing. High volumetric wear and osteolysis limit the durability of metal-ultra high molecular weight polyethylene resurfacing. Cemented femoral hemiresurfacing components (no acetabular component) do not develop osteolysis and rarely loosen. Consistent long-term fixation has been demonstrated with hemispherical cementless acetabular components. Metal-metal bearings have demonstrated low wear and rare osteolysis over 3 decades of use. These facts form foundation for total hip resurfacing with metal-metal bearings.

Activity sampling in the assessment of patients with total joint arthroplasty

Quantitative assessment of patient activity is important in evaluating the outcomes of joint prostheses, and such methods are gaining popularity. The single greatest impediment to quantitative activity assessment is patient compliance. How many days of sampling are necessary to provide reliable and accurate estimates of walking activity? The current study analyzes how well sampling for 4 consecutive days of activity compares to assessing activity for 7 or more days with the same pedometer in 131 patients with either a total hip or total knee prosthesis. The mean steps per day obtained throughout the full-length sampling (7-123 days) was strongly correlated to the one obtained from the random consecutive 4-day sample (r2 = 0.94, P < .001) with only 5 outliers. The 4-day activity assessment gave an underestimation of 4.7% (P = .5). The number of outliers increased with fewer days of sampling. Monitoring activity for 4 consecutive days yields a quantitative assessment that is within 5% of a sampling of 7 or more days.

The relationship between activity and ions in patients with metal-on-metal bearing hip prostheses

BACKGROUND

Total hip replacements with metal-on-metal bearings are frequently implanted in young, active patients. The relationship between patient activity and cobalt and chromium ion levels has not been investigated, to our knowledge.

METHODS

Seven patients with well-functioning metal-on-metal bearing hip prostheses and one control subject (no implants), all with normal renal function, were monitored during a two-week-long activity protocol. Lower-extremity activity was continuously assessed with use of a computerized, two-dimensional accelerometer. During the first week, the subjects were requested to limit physical activity. The subjects then completed an hour-long treadmill test followed by a week in which they were encouraged to be as physically active as practically possible. Serum levels of cobalt and chromium ions and urine levels of chromium were assessed at ten time-points during these two weeks.

RESULTS

Regardless of activity, the serum ion levels for a given patient were essentially constant and no correlation was found between patient activity and serum levels of cobalt or chromium, or urine levels of chromium. A mean increase in activity of 28% during the week of high-intensity activity was associated with a mean decrease of 2.7% in the serum cobalt level and a mean increase of 2.0% in the serum chromium level. During the treadmill test, a mean increase in activity of 1621% was associated with a mean increase of 3.0% in the serum cobalt level and a mean increase of 0.8% in the serum chromium level. These results fall within the variability for the measurement accuracy of these tests.

CONCLUSIONS

For these patients, serum cobalt and chromium ion levels were not acutely affected by patient activity. Periodic measurements of serum ion levels could be used to monitor the tribologic (lubrication, friction, and wear) performance of a metal-on-metal bearing without adjusting for patient activity. Additional research is needed into the kinetics of ion production, transport, and excretion.