Metallosis due to impingement between the socket and the femoral neck in a metal-on-metal bearing total hip prosthesis. A case report

Notching of the Neck After Acetabular Constraint Necessitating Femoral Component Revision

A 75-year-old woman who had previously undergone a left revision total hip arthroplasty with the use of a constrained acetabular liner presented with recurrent dislocation of the hip. Intraoperatively, there was metallic staining of the hip capsule and significant notching of the femoral neck, consistent with impingement of the intact locking ring, necessitating stem revision. Constrained acetabular liners have high failure rates due to intraprosthetic impingement, but to our knowledge, failure due to notching of the femoral component and metallosis from repeated impingement has not been described. Surgeons should be aware of this potential mode of failure.

Impingement Resulting in Femoral Notching and Elevated Metal-Ion Levels After Dual-Mobility Total Hip Arthroplasty

A 60-year-old woman underwent revision total hip arthroplasty with a modular dual-mobility articulation for recurrent dislocation. At 1-year follow-up, the patient reported no dislocations but had occasional clicking and discomfort with extreme motion. A Dunn radiograph identified notching of the femoral stem, attributed to impingement. Metal ions were elevated without adverse local-tissue reaction. After 4.5 years of observation, the notch size remained stable. She denied pain. Neither stem fracture nor prosthetic dislocation occurred. Impingement against cobalt-chromium acetabular bearing surfaces can result in notching of titanium femoral components after total hip arthroplasty. Increased anteversion intended to protect against posterior dislocation may be a risk factor. Posterior notching is best visualized on Dunn views, so incidence may be underestimated. No associated femoral implant fractures were identified on literature review.

Increased Serum Ion Levels After Ceramic-on-Metal Bearing Total Hip Arthroplasty: Influence of an Asian Lifestyle

BACKGROUND

Recent clinical studies have suggested that systemic metal ion levels are significantly elevated at midterm follow-up in patients with ceramic-on-metal (COM) bearing. However, it is not clear whether there is a correlation between patient-related factors including the lifestyle and elevated levels of serum metal ions following COM total hip arthroplasty (THA).

METHODS

Serum metal levels were measured in 201 patients (234 hips) including 121 COM patients (140 hips) and 80 non-COM patients (94 hips). The Harris Hip Score, University of California, Los Angeles activity scale score, and Western Ontario and McMaster Universities Osteoarthritis Index score were measured and radiographs were obtained for the analysis.

RESULTS

Significantly higher levels of cobalt (Co) and chromium (Cr) were detected in the serum of the COM THA group (Co: 1.86 ± 4.0 μg/L; Cr: 1.81 ± 2.87 μg/L) than those of the non-COM THA group (Co: 0.27 ± 0.14 μg/L; Cr: 0.19 ± 0.25 μg/L; P < .001). The serum metal levels of patients who achieved the squatting position and the kneeling position were significantly higher than those of patients who could not squat (Co: P = .033; Cr: P = .074) and kneel (Co: P = .049; Cr: P = .031). The metal ion levels of the COM THA group correlated with the total range of motion (Co: P = .0293; Cr: P = .0399).

CONCLUSION

Patients who underwent a 36-mm COM THA showed high serum metal levels although good clinical outcomes at the midterm follow-up. We found that COM THA patients who were capable of greater range of motion, squatting, and kneeling are at risk of metal ion-related problems.

Does Pelvic Sagittal Inclination in the Supine and Standing Positions Change Over 10 Years of Follow-Up After Total Hip Arthroplasty?

BACKGROUND

Functional anteversion and inclination of the cup change as the pelvic sagittal inclination (PSI) changes. The purposes of this study were to investigate the chronological changes of PSI during a 10-year follow-up period after total hip arthroplasty (THA) and to report the characteristics of patients who showed a greater than 10° change in the PSI from the supine to the standing position.

METHODS

The subjects were 70 patients who were followed up for 10 years after THA. PSI values in the supine and standing positions were measured by 2D-3D matching using computed tomography images and pelvic radiographs. PSI values before THA and 1, 5, and 10 years after THA were compared in both the supine and standing positions.

RESULTS

Supine PSI showed less than 5° of change, whereas standing PSI showed a significant decrease with time over the 10-year period. Although 43% of patients with less than 10° of difference in the PSI between the supine and standing positions before THA increased PSI posteriorly (reclining) more than 10° in standing from the supine position at 10 years, no late dislocation was observed.

CONCLUSION

Supine PSI showed no significant change, but standing PSI showed a significant increase posteriorly with time over a 10-year period. However, this PSI change did not reach the level that it caused negative consequences such as late dislocation. The pelvic position in the supine position might still be a good functional reference position of the pelvis for aiming to achieve proper cup alignment at 10 years.

Orthogonal Double Plating and Autologous Bone Grafting of Postoperative Humeral Shaft Nonunion - A Rare Case Report and Review of Literature

Introduction:

Nonunion following surgical stabilization of humeral shaft fractures, although infrequent, remains a challenge as limited surgical options are available. The difficulties in re-fixation are due to osteolysis produced by the loose implant components and disuse osteopenia of the entire bone segment. We share our experience in the management of a long standing diaphyseal nonunion of humerus following titanium LCP fixation.

Case Report:

A 58 years old woman presented with 20 months old nonunion following titanium LCP fixation of her closed humeral shaft fracture, done elsewhere. The interesting intraoperative findings, noteworthy, are about the extensive metallosis and the gross cortical defect measuring 10cm x 1cm x 1cm, corresponding to the foot print of the previous plate with exposed medullary canal. It was managed by debridement, dual plate fixation using 9 holed and 12 holed stainless steel LCPs in an orthogonal fashion and autologous bone grafting. The nonunion healed in 5 months and she regained all the movements except for terminal 10° of elbow extension and 15° of shoulder abduction at her final follow up of 30 months. According to Stewart and Hundley classification the final result was found to be good.

Conclusion:

We recommend the judicious use of long and short plates in 90-90 orientation along with autogenous bone grafting in the management of a long standing humeral shaft nonunion having extensive cortical resorption following surgical stabilization by plating.

Severe Periprosthetic Metallosis and Polyethylene Liner Failure Complicating Total Hip Replacement: The Cloud Sign

We present a case of an 85-year-old woman with extensive metallosis of the left hip joint secondary to prosthetic polyethelene liner dislocation and wear. Radiographs demonstrated amorphous cloudy radiodensities surrounding the prosthesis, a feature we have called the “cloud sign.” The presence of amorphous cloudy radiodensities as a radiographic sign of metallosis has not been previously described to our knowledge.

Effects of coordinate-system construction methods on postoperative computed tomography evaluation of implant orientation after total hip arthroplasty

OBJECTIVE

In total hip arthroplasty, it is important to assess postoperative implant orientation. The computed tomography-based (CT-based) three-dimensional (3D) templating method using 3D preoperative planning software is generally recommended. In this method, postoperative implant orientation within a bony coordinate system can be measured by overlaying a 3D computerized model of the implant on a real postoperative CT image of the implant. The bony coordinate system consists of several reference points (RPs) marked on a CT image of the bone surface. Therefore, preoperative and postoperative coordinate systems do not always match. We investigated how the difference between coordinate systems constructed from RPs chosen by manual methods (M1 and M2) and those constructed by the computer matching method influences the results of measurement validation.

METHODS

In M1, postoperative RPs were chosen without a specific tool in a single planning module. In M2, postoperative RPs were chosen with as little deviation as possible from preoperative RPs, verifying preoperative RPs on another monitor.

RESULTS

M1 and M2 produced mean errors in acetabular cup inclination of 0.7° ± 0.5° and 0.5° ± 0.3°, respectively, and mean errors in cup anteversion of 1.3° ± 1.2° and 0.5° ± 0.4°, respectively, which were statistically significant differences. M1 and M2 produced mean errors in femoral stem anteversion of 2.4° ± 2.0° and 2.7° ± 2.1°, respectively, not a significant difference, but these errors were larger than errors in cup orientation.

DISCUSSION

We recommend referring to preoperative RPs when choosing postoperative RPs. Surgeons must be aware that for evaluation of postoperative stem anteversion, manual methods may produce considerable error.

[Possibilities and limits of modern polyethylenes. With respect to the application profile]

BACKGROUND

Polyethylene is still one of the most important materials in the field of hip and knee arthroplasty. The clinical results of the last decades have helped to further develop polyethylene into a high-tech material. Progress in the development of new materials must be compared with the tried and tested ones to provide optimal and most individual patient care.

OBJECTIVES

This article gives an overview of the history and current application profile of the material ultra-high molecular weight polyethylene (UHMWPE) in hip and knee arthroplasty.

MATERIAL AND METHODS

With the aid of the current literature, new developments in the field of the material UHMWPE, also with respect to the biological activity of wear, the particular biomechanics of the knee joint as well as alternative hard-hard bearing surfaces in the hip, are represented in terms of implant safety.

RESULTS

The problems concerning polyethylene are now well recognized. The disadvantages of the material UHMWPE could be consistently reduced based on material research so that modern polyethylenes have gradually been shown in clinical trials that they can be reliably used.

CONCLUSION

Despite this the potential for improvement has still not yet been fully exploited. Any further development must be extensively tested both biomechanically and biologically before the material can be used in vivo. Long-term results are still necessary before a material can be accepted as being clinically safe.

Risk of edge-loading and prosthesis impingement due to posterior pelvic tilting after total hip arthroplasty

BACKGROUND

Proper implant orientation is essential for avoiding edge-loading and prosthesis impingement in total hip arthroplasty. Although cup orientation is affected by a change in pelvic tilt after surgery, it has been unclear whether surgeons can prevent impingement and edge-loading by proper positioning by taking into account any change in pelvic alignment associated with alteration of hip range of motion.

METHODS

We simulated implant orientation without edge-loading and prosthesis impingement, even with a change in pelvic tilt and associated change in hip range of motion after surgery, by collision detection using implant models created with computer-aided design.

FINDINGS

If posterior pelvic tilting with a corresponding hyperextension change in hip range of motion after surgery remains within 10°, as occurs in 90% of cases, surgeons can avoid edge-loading and impingement by correctly orienting the implant, even when using a conventional prosthesis. However, if a 20° change occurs after surgery, it may be difficult to avoid those risks.

INTERPRETATION

Although edge-loading and impingement can be prevented by performing appropriate surgery in most cases, even when taking into account postoperative changes in pelvic tilt, it may also be important to pay attention to spinal conditions to ensure that pelvic tilting is not extreme because of increasing kyphosis.

Risk of impingement and third-body abrasion with 28-mm metal-on-metal bearings

BACKGROUND

Concerns have been raised about the sequelae of metal-on-metal (MoM) bearings in total hip arthroplasty (THA). However, retrieval studies, which offer the best insight into the clinically relevant mechanisms of MoM wear, have followed predictable trends to date such as indicting cobalt-chromium (CoCr) metallurgy, cup design, high conformity between the head and cup, "steep cups," "microseparation," and "edge wear."

QUESTIONS/PURPOSES

We wished to evaluate a set of retrieved 28-mm MoM THA for signs of (1) cup-to-stem impingement; (2) normal wear pattern and concomitant stripe damage on femoral heads that would signify adverse wear mechanics; and (3) well-defined evidence of third-body scratches on bearings that would indicate large abrasive particles had circulated the joint space.

METHODS

Ten 28-mm MOM retrievals were selected on the basis that femoral stems were included. Revision surgeries at 3 to 8 years were for pain, osteolysis, and cup loosening. CoCr stems and the MoM bearings were produced by one vendor and Ti6Al4V stems by a second vendor. All but two cases had been fixed with bone cement. We looked for patterns of normal wear and impingement signs on femoral necks and cup rims. We looked for adverse wear defined as stripe damage that was visually apparent on each bearing. Wear patterns were examined microscopically to determine the nature of abrasions and signs of metal transfer. Graphical models recreated femoral neck and cup designs to precisely correlate impingement sites on femoral necks to cup positions and head stripe patterns.

RESULTS

The evidence revealed that all CoCr cup liners had impinged on either anterior or posterior facets of femoral necks. Liner impingement at the most proximal neck notch occurred with the head well located and impingement at the distal notch occurred with the head rotated 5 mm out of the cup. The hip gained 20° motion by such a subluxation maneuver with this THA design. All heads had stripe wear, the basal and polar stripes coinciding with cup impingement sites. Analysis of stripe damage revealed 40 to 100-μm wide scratches created by large particles ploughing across bearing surfaces. The association of stripe wear with evidence of neck notching implicated impingement as the root cause, the outcome being the aggressive third-body wear.

CONCLUSIONS

We found consistent evidence of impingement, abnormal stripe damage, and evidence of third-body abrasive wear in a small sample of one type of 28-mm MoM design. Impingement models demonstrated that 28-mm heads could lever 20° out of the liners. Although other studies continue to show good success with 28-mm MoM bearings, their use has been discontinued at La Pitie Hospital.

Histologic, serologic, and tribologic findings in failed metal-on-metal total hip arthroplasty: AAOS exhibit selection

Despite multiple changes in second-generation metal-on-metal hip implants, greater-than-expected revision rates have led to alarm. We hypothesized that the finding of intraoperative metallosis would be associated with a high metal load on histologic analysis and that both would be associated with increased wear, greater serum metal ion levels, and predictable biologic responses in the histologic sections. We evaluated the implant positioning, serum ion levels, intraoperative findings of metallosis, wear characteristics of retrieved implants (tribology), histology, and outcomes in a series of eighteen large-diameter metal-on-metal total hip arthroplasties. The arthroplasties were divided into two groups on the basis of the intraoperative finding of metallosis and into two groups on the basis of the metal load score. Intraoperative metallosis was not associated with a high metal load score (p = 0.15). The finding of intraoperative metallosis was associated with greater serum metal ion levels, greater wear rates, and greater complication rates. Aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL) scores were similar between the metallosis and non-metallosis groups (p = 0.49) as well as between the high and low-metal-load groups (p = 0.56).

Notching of the femoral stem neck in metal-on-metal total hip replacement: a case report

We report a case of impingement in a metal-on-metal total hip replacement causing both notching of the femoral stem neck and aseptic loosening of the acetabular component. The acetabular component was inserted in excessive anteversion. The femoral stem and acetabular components were retrieved. A larger femoral head was used, and an acetabular component was placed in a less anteverted position. Intra-operative testing through different ranges of movement is recommended to identify potential impingement.

Anatomical hip range of motion after implantation during total hip arthroplasty with a large change in pelvic inclination

The supine functional pelvic plane is the recommended reference pelvic plane for acetabular cup planning in navigation-assisted total hip arthroplasty. However, it is unclear whether it can be used in patients with a large preoperative positional change in pelvic inclination (PC) from the supine to the standing position because it is unknown whether these patients have a different hip range of motion (ROM). We measured the anatomical hip ROM after implantation by computed tomography-based navigation in 91 patients and found it to be similar between those with a small PC (<10°) and those with a large PC (≥10°). There was no significant correlation between ROM and preoperative PC. The supine functional pelvic plane is adequate for cup planning whether the PC is small or large.

Cutaneous manifestation of metallosis in a metal-on-metal total hip arthroplasty after acetabular liner dissociation

In this case report, we describe a cutaneous manifestation of extensive metallosis in a patient 4 months post-metal-on-metal total hip arthroplasty with a Pinnacle cup with dissociation of the liner from the shell and resultant stripe burnishing of the shell and notch wear of the femoral neck. Dissociation of a metal liner has not been previously reported with this implant. Cutaneous metallosis has only been reported once in the literature. Clinicians should heighten their suspicion for metallosis secondary to hardware failure when encountering patients with skin discoloration in the setting of a painful and poorly functioning hip arthroplasty. In patients with failure of a metal-on-metal prosthesis with a modular metal liner in the acetabular component, liner dissociation must be considered.

Minocycline-induced periarticular black bones in inflamed joints which underwent arthroplastic reconstruction

Background

Minocycline-induced pigmentation of bone (black bone) is well described in tooth-bearing intra-oral bone, but is less known in periarticular bone in patients who have undergone total joint arthroplasty. On a retrospective basis, we investigated the short-term clinico-radiological results of total joint arthroplasties in which the patient developed minocycline-induced periarticular black bone.

Methods

We found 5 cases (0.08%), in 4 patients, of periarticular bone pigmentation revealed during total joint arthroplasties (2 hips, 2 knees, and 1 ankle) in our series of total joint surgeries (6,548 cases) over a 10-year time period in our 3 institutes. Their mean age was 56 years at surgery. All patients had received long-term minocycline treatment. Mean dosage and duration of minocycline was 160 mg/day and 2.2 years, respectively. Minocycline had been prescribed for reactive arthritis (one), rheumatoid arthritis (two) and late infection after total joint arthroplasty (two patients). Mean follow-up period was 3.4 years after the surgeries.

Results

All cases had black or brown pigmentation in the periarticular bones during the surgery. There was no pigmentation in the cartilage or soft tissues of the joints. The mean Japanese Orthopaedic Association (JOA) score or Japanese Society for Surgery of the Foot (JSSF) scale for rheumatoid arthritis foot and ankle joints at latest follow-up (case 1, 66; case 2, 87; case 3, 77; case 4, 77; case 5, 80) improved compared to those of pre-surgery (case 1, 47; case 2, 45; case 3, 55; case 4, 34; case 5, 55). No implant loosening was noted on radiographic examination during the follow-up period. No abnormal bone formation, bone necrosis, hemosiderin deposition, malignancy or metallic debris was found on histological examination.

Conclusions

No clinico-radiological symptoms of total joint arthroplasties showed in the patients with minocycline-induced periariticular black bone in the short-term. Systemic minocycline treatment has the potential to induce significant black pigmentation of many tissues. In particular, minocycline-induced pigmentation of periarticular bone may be accelerated by inflammation due to rheumatic or pyogenic arthritis. Surgeons should recognize the risk of bone pigmentation in inflamed joints due to the systemic treatment of minocycline and explore its influence on periarticular bone and total joint arthroplasty in the long-term.

Survivorship of second-generation metal-on-metal primary total hip replacement

BACKGROUND

Second generation metal-on-metal total hip replacements (THR) were introduced in the late 1980s and various studies reported conflicting data on their outcome.

METHODS

Implant survival of 1,270 second-generation 28 mm metal-on-metal primary THR in 1,121 patients followed prospectively at a mean of 6.8 years postoperatively was evaluated retrospectively. The probability of survival at 10 years was estimated using the method of Kaplan and Meier, and relative risk factors including age, gender, BMI, type of implant fixation and component size were calculated using the Cox proportional-hazards model.

RESULTS

Sixty-three (5%) THRs were revised, these being 28 hips for aseptic loosening and 35 for reasons other than aseptic loosening. The probability of survival at 10 years, with revision for any reason as the endpoint, was 0.90 (95% confidence interval (CI) 0.86-0.94) for the THR as a whole, 0.91 (95% CI 0.87-0.95) for the cup, and 0.96 (95% CI 0.94-0.98) for the stem. No demographic factors or covariates were found to significantly affect the implant survivorship.

DISCUSSION

As there was no superior probability of survival, and there have been concerns on putative local and systemic toxicity of metal debris, the use of second-generation metal-on-metal articulations for primary THR remains moot.

Severe corrosion after malpositioning of a metallic head over the Morse taper of a cementless hip arthroplasty. A case report

Morse tapers are frequently used in total hip replacement to achieve precise adjustment of lengths and femoral offset. Mechanically, they do not raise any specific problems so long as strict positioning requirements are observed and elements from different manufacturers are not mixed together. We report a case in which the implant induced unexplained pain at 2 years, in relation to a defective fit between the metallic head and the Morse taper. Asymmetric partial fit of the head onto the taper was detected on control X-ray and was implicated as causing metallosis due to excessive release of metal debris from the Morse taper. Revision required femoral stem exchange because of the damage to the Morse taper as well as replacing the cup with new metal-metal bearings. Evolution was favorable at 3 years' follow-up. Most hip replacements include a Morse taper; the present clinical case is a reminder that strict positioning rules are to be respected, without which corrosion and wear may lead to mechanical failure.

Femoroacetabular cup impingement after resurfacing arthroplasty of the hip

Femoroacetabular cup impingement (FACI), defined as the presence of a bony spur or indentation at the femoral neck corresponding to the abutment site of metallic cup, was observed in 9 (11%) of the 84 hips with contemporary resurfacing arthroplasty of the hip. All FACIs occurred in men after a mean of 14 months (range, 8-24 months) postoperatively. Five patients had persistent groin pain if the hip was moved into flexion, abduction, and external rotation. One patient sustained a late-onset fracture through the femoral neck already weakened by postoperative change of osteonecrosis. Mean postoperative Harris hip score in the FACI group was poorer than that in the non-FACI group (P = .003). Multiple logistic regression analysis showed a significant association of FACI with a low acetabular cup inclination (odds ratio, 1.42; 95% confidence interval, 1.01-1.99; P = .046) and a high cup uncoverage ratio (odds ratio, 1.36; 95% confidence interval, 1.01-1.84; P = .045).

Modular neck for prevention of prosthetic impingement in cases with excessively anteverted femur

BACKGROUND

It is important to adjust stem anteversion in cases of excessive femoral version to avoid prosthetic impingement-related complications in total hip arthroplasty. Although modular necks are considered an effective solution, their application in cases with wide variations in femoral anteversion remains to be elucidated. This study aimed to simulate the effects of different modular necks on prevention of prosthetic impingement due to excessive femoral anteversion.

METHODS

We investigated range of motion without prosthetic impingement by collision detection using implant computer-aided design models of the ANCA-Fit system.

FINDINGS

Modular necks could provide an adequate range of motion in cases with up to 60° of femoral anteversion. However, few alternative necks were available in cases with excessive femoral anteversion, while many options could be used for femoral offset and version control in cases with average amounts of femoral anteversion without prosthetic impingement.

INTERPRETATION

We conclude that modular necks might provide a marginal advantage over other options such as cemented, conical or modular stems for cases with an excessively anteverted femur, although they could help to maintain the femoral offset in some cases with average femoral anteversion.

Catastrophic failure of a metal-on-metal total hip arthroplasty secondary to metal inlay dissociation

Metal-on-metal bearing surfaces in total hip arthroplasty have been recently shown to have acceptable survivorship properties (J Bone Joint Surg Am. 2006;88:1183; J Bone Joint Surg Am. 2006;88:1173), and they have certain advantages and disadvantages when compared to conventional metal-on-polyethylene bearing surfaces. Like traditional metal-on-polyethylene bearings, these metal-on-metal implants may also suffer from catastrophic failure. This case report represents an unusual situation in a 57-year-old man in which dissociation of a metal inlay in a metal-on-metal total hip arthroplasty resulted in articulation of the inferior aspect of the inlay with the femoral neck, leading to femoral neck notching, extensive periprosthetic soft tissue metallosis, osteolysis, and subsequent prosthetic catastrophic failure.

Metal-on-metal bearings: the evidence so far

Lately, concerns have arisen following the use of large metal-on-metal bearings in hip replacements owing to reports of catastrophic soft-tissue reactions resulting in implant failure and associated complications. This review examines the literature and contemporary presentations on current clinical dilemmas in metal-on-metal hip replacement.

Femoral head size does not affect ion values in metal-on-metal total hips

BACKGROUND

Metal-on-metal articulations can release substantial amounts of particles containing cobalt and chromium into the surrounding milieu, causing concern for cellular toxicity and adverse local soft tissue reactions. The diameter of the femoral head has been one of the variables that inversely affects wear of metal-on-metal total hip arthroplasty (THA). The oxidative stress of increased metal ions can be measured with serum markers. It is still controversial if larger femoral head diameters decrease wear rates in patients with metal-on-metal THA and if the increased metal ions alter the body's antioxidant status.

QUESTIONS/PURPOSES

We therefore (1) determined whole blood metal ions in patients with small (28 mm and 36 mm) and large (40 mm and 44 mm) diameter femoral heads; (2) measured oxidative stress markers (total antioxidants, nitrotyrosine, and peroxides); and (3) determined whether acetabular version or inclination influenced ion levels.

METHODS

One hundred four patients were retrospectively studied. We recorded Harris hip scores and UCLA activity scores. All patients were followed at 1 year.

RESULTS

The activity scores were similar in the two groups. There was no difference in metal ion levels or oxidative stress markers between patients with small- or large-diameter femoral heads. Acetabular inclination and anteversion had no effect on the metal ion levels.

CONCLUSIONS

The data suggest there is no difference in ion values in patients with large or small metal-on-metal THA and the increased metal ions do not alter the oxidant status of the patient.

Metal neck and liner impingement in ceramic bearing total hip arthroplasty

Although impingement between the neck of the metallic stem and the ceramic liner has been suspected to be the cause of ceramic liner failure in ceramic-on-ceramic total hip arthroplasty (THA), no report has directly demonstrated microscopic damage on ceramic liner. We performed 18 reoperations on 18 patients who had undergone third generation ceramic-on-ceramic THA. Considering impingement, 16 patients, who were reoperated more than 1 year after previous ceramic bearing THA, were evaluated. Retrieved alumina liners, showing evidence of impingement, were examined by means of visual inspection and scanning electron microscopy (SEM). Four of the 16 hips showed neck notching and black stained liners, evidence of metallic neck to ceramic impingement. Impinged alumina bearings had been implanted for an average of 62.5 months (range: 35-99 months) before reoperation. SEM of the black stained area demonstrated disruptive wear and loss of surface integrity. Furthermore, one liner had multiple microcracks, and its cross-sectional SEM analysis revealed one microcrack propagating into the deep portion of the ceramic liner. Our observations suggest that metal neck-to-ceramic impingement in ceramic-on-ceramic THA can cause microcrack formation in ceramic liner.

Metal Ion release with large-diameter metal-on-metal hip arthroplasty

Preoperative and postoperative ion concentrations were measured in 29 metal-on-metal, large-diameter head total hip arthroplasty (LDH-THA) patients. Mean chromium, cobalt (Co), and titanium levels from LDH-THA were 1.3, 2.2, and 2.7 μg/L at 12 months. The open femoral head design showed significantly higher Co concentrations than the closed design (3.0 vs 1.8 μg/L, P = .037). Compared with previously published ion levels from a hip resurfacing system presenting the same bearing characteristics, Co levels were significantly higher in LDH-THA (2.2 vs 0.7 μg/L, P < .001). This study has demonstrated that the addition of a sleeve with modular junctions and an open femoral head design of LDH-THA causes more Co release than bearing surface wear (157% and 67%, respectively). Even if no pathologic metal ion threshold level has been determined, efforts should be made to minimize its release. We recommend modification or abandonment of the modular junction and femoral head open design for this specific LDH-THA system.

Is alumina-on-alumina ceramic bearings total hip replacement the right choice in patients younger than 50 years of age? A 7- to 15-year follow-up study

INTRODUCTION

The alumina-on-alumina bearing couple in total hip replacement seems to be well adapted for young and active patients because of the absence of wear and the rarity of osteolysis. Over the long term, doubts persist as to the cementless cup fixation and on the functioning of this bearing system because of possible acoustic emissions during use.

HYPOTHESIS

In young subjects, the ceramic-on-ceramic bearing system limits wear and osteolysis occurrences, without exposing patients to serious side effects. MATERIAL AND MEHTODS: We report the results, with between 7 and 15 years of follow-up, for 32mm-diameter alumina-on-alumina implants in 76 patients younger than 50 years of age (83 hips), combining cementless press-fit hemispheric cups with titanium stems, [either cemented (63 Osteal™ stems) or cementless (20 Multicône™ stems)], with particular attention paid to cup fixation and noise emissions during implant function. First-generation or Cerafit trellis™ acetabular components had a riveted titanium mesh (31 cases), whereas the most recent (Cerafit hydroxyapatite [HA]™) cups had a porous surface coated with hydroxyapatite (52 cases).

RESULTS

Three cases of aseptic loosening of the cemented stems were observed as well as late migration of a Cerafit trellis™ cup in the 12th postoperative year. One ceramic insert broke in the eighth postoperative year. With the exception of one case, the patients, questioned retrospectively, reported no audible noise. With aseptic loosening (revised or not), the criterion for failure, the 12-year survival rate was 91±11% for the Cerafit trellis™ acetabular components and 91±16% for the cemented Osteal™ stems. The 9- and 7-year survival rates for the Cerafit HA™ cups and the Multicône™ stems, respectively, were 100%. Including all revisions for any cause, the 10-year survival rate of the entire series was 92%±11%.

DISCUSSION

Despite the absence of wear and osteolysis, the long-term survival of these implants in young subjects should be improved. Although longer follow-up is necessary to formulate a definitive opinion, we tend to prefer cementless stem and cup fixation in ceramic-on-ceramic bearing systems.

LEVEL OF EVIDENCE

Level 4 retrospective study.

The John Charnley Award: Metal-on-metal hip resurfacing versus large-diameter head metal-on-metal total hip arthroplasty: a randomized clinical trial

Resurfacing arthroplasty has become an attractive option for young patients who want to maintain a high activity level. One recent study reported modestly increased activity levels for patients with resurfacing compared to standard total hip arthroplasty (THA). We conducted a prospective randomized clinical trial to compare clinical outcomes of resurfacing versus large-head metal-on-metal total hip arthroplasty. We randomized 107 patients deemed eligible for resurfacing arthroplasty to have either resurfacing or standard THA. Patients were assessed for quality-of-life outcomes using the PAT-5D index, WOMAC, SF-36, and UCLA activity score. The minimum followup was 0.8 years (mean, 1.1 years; range, 0.8-2.2 years). Of the 73 patients followed at least one year, both groups reported improvement in quality of life on all outcome measures. There was no difference in quality of life between the two arms in the study. Serum levels of cobalt and chromium were measured in a subset of 30 patients. In both groups cobalt and chromium was elevated compared to baseline. Patients receiving a large-head metal-on-metal total hip had elevated ion levels compared to the resurfacing arm of the study. At 1 year, the median serum cobalt increased 46-fold from baseline in patients in the large-head total hip group, while the median serum chromium increased 10-fold. At 1 year, serum cobalt was 10-fold higher and serum chromium 2.6-fold higher than in the resurfacing arm. Due to these excessively high metal ion levels, the authors recommend against further use of this particular large-head total hip arthroplasty.

LEVEL OF EVIDENCE

Level I, randomized clinical trial. See Guidelines for Authors for a complete description of levels of evidence.

The John Charnley Award: Metal-on-metal hip resurfacing versus large-diameter head metal-on-metal total hip arthroplasty: a randomized clinical trial

Resurfacing arthroplasty has become an attractive option for young patients who want to maintain a high activity level. One recent study reported modestly increased activity levels for patients with resurfacing compared to standard total hip arthroplasty (THA). We conducted a prospective randomized clinical trial to compare clinical outcomes of resurfacing versus large-head metal-on-metal total hip arthroplasty. We randomized 107 patients deemed eligible for resurfacing arthroplasty to have either resurfacing or standard THA. Patients were assessed for quality-of-life outcomes using the PAT-5D index, WOMAC, SF-36, and UCLA activity score. The minimum followup was 0.8 years (mean, 1.1 years; range, 0.8-2.2 years). Of the 73 patients followed at least one year, both groups reported improvement in quality of life on all outcome measures. There was no difference in quality of life between the two arms in the study. Serum levels of cobalt and chromium were measured in a subset of 30 patients. In both groups cobalt and chromium was elevated compared to baseline. Patients receiving a large-head metal-on-metal total hip had elevated ion levels compared to the resurfacing arm of the study. At 1 year, the median serum cobalt increased 46-fold from baseline in patients in the large-head total hip group, while the median serum chromium increased 10-fold. At 1 year, serum cobalt was 10-fold higher and serum chromium 2.6-fold higher than in the resurfacing arm. Due to these excessively high metal ion levels, the authors recommend against further use of this particular large-head total hip arthroplasty.

LEVEL OF EVIDENCE

Level I, randomized clinical trial. See Guidelines for Authors for a complete description of levels of evidence.

Impingement as a mechanism of dissociation of a metasul metal-on-metal liner

This case report is of a patient with disassociation of the acetabular cup liner caused by impingement. The cup inclination (39 degrees) and anteversion (24 degrees) were good as measured by computer navigation. Impingement occurred because the head-neck ratio was 2.0, and the hip length and offset were short by one head length. Successful revision without intraoperative impingement was accomplished with one size head larger (32 mm; head-neck ratio, 2.3) and one size longer to correct hip length and offset.

Is patient selection important for hip resurfacing?

The optimal implant option for hip arthroplasty in the young, active patient remains controversial. There has been renewed interest for metal-on-metal hip resurfacing due to improved design and manufacturing of implants, better materials, enhanced implant fixation, theoretical advantages over conventional total hip arthroplasty, and recent Food and Drug Administration approval of two devices. Recent studies indicate satisfactory short- and midterm clinical results (1- to 10-year followup) with low complication rates, but there is a learning curve associated with this procedure, a more extensive surgical approach is necessary, and long-term results have yet to be determined. Proper patient selection may help avoid complications and improve patient outcomes. Patient selection criteria in the literature appear based predominantly on theoretical considerations without any consensus on stratifying patient risk. The most commonly reported complications encountered with hip resurfacing include femoral neck fracture, acetabular component loosening, metal hypersensitivity, dislocation, and nerve injury. At the time of clinical evaluation, patient age; gender; diagnosis; bone density, quality, and morphology; activity level; leg lengths; renal function; and metal hypersensitivity are important factors when considering a patient for hip resurfacing. Based on our review, we believe the best candidates for hip resurfacing are men under age 65 with osteoarthritis and relatively normal bony morphology.

LEVEL OF EVIDENCE

Level V, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Characterization of a highly cross-linked ultrahigh molecular-weight polyethylene in clinical use in total hip arthroplasty

This article reports on a commercially available extensively cross-linked ultrahigh molecular-weight polyethylene (HXPE) produced by subjecting molded GUR 1050 ultrahigh molecular-weight polyethylene (UHMWPE) to 100 +/- 10 kGy of electron beam radiation followed by melt annealing and sterilization by gas plasma. When compared to contemporary conventional molded GUR 1050 UHMWPE sterilized by 37 kGy of gamma radiation, the HXPE material has enhanced wear properties, has no detectable free radicals, and is resistant to oxidation and oxidative-related material property changes. The relative wear improvement of the HXPE is maintained in the presence of bone cement or alumina particles. The HXPE produced greater than 90% fewer wear particles in all size ranges and statistically significantly (P < .0001) smaller average-size particles than did the conventional UHMWPE.

Cup-neck impingement due to the malposition of the implant as a possible mechanism for metallosis in metal-on-metal total hip arthroplasty

The metal-on-metal bearing total hip prosthesis is expected to reduce the risk of debris-related osteolysis. However, several reports demonstrated that the socket-stem impingement in the metal-on-metal prosthesis due to the implant malposition results in titanium wear debris and secondary metallosis. In this article, we presented a case of massive metallosis due to metal-on-metal impingement. A 60-year woman had severe hip pain due to fracture of the greater trochanter. We planned a revision of the metal-on-metal inlay. Intraoperatively, the trochanteric bursa and joint space were found to be stained black. Black stained granulation tissue was observed between the femoral stem and the great trochanter. Intraoperatively, notching was noticed on both the posteroinferior aspect of the neck of the femoral component and the anterior aspect of the metal liner and polyethylene core. The notch corresponded to the position of impingement between the socket and the femoral neck during the maximum extension of the hip. To clarify the mechanism of cup-neck impingement, the alignment of the prosthesis and pelvic tilt were evaluated. The cup was placed in too much anteverted position. In addition, increased posterior tilt of pelvis in the standing position made the anteversion of the acetabular cup more significant, which enhanced the cup-neck impingement during the gait. Careful attention is necessary for implant alignment and pelvic tilt especially in metal-on-metal-bearing total hip arthroplasty.

Metal-on-metal hip resurfacing arthroplasty

The main advantage of hip resurfacing is bone conservation for patients likely to outlive a primary conventional hip replacement. Previous attempts at hip resurfacing failed predominantly because of the consequences of a high amount of wear of thin polyethylene acetabular components and poor femoral component fixation. With correct patient selection, surgeon education, and operative technique, survivorship at five years is comparable with that of traditional hip replacements. Hip resurfacing has its own unique set of complications, including a fractured neck of the femur. It is necessary to understand the risk factors prior to performing the procedure.

Can cobalt levels estimate in-vivo wear of metal-on-metal bearings used in hip arthroplasty?

High levels of cobalt and chromium ions are detected in the blood and urine of patients with metal-on-metal (MoM) hip replacement. These elements are released as a result of wear at the bearing surfaces. Wear rates depend on a multitude of factors, which include the bearing geometry, carbon content, manufacturing processes, lubrication, speed and direction of sliding of the surfaces, pattern of loading, and orientation of the components. In-vivo wear of MoM bearings cannot be reliably measured on X-rays because no distinction can be made between the bearing surfaces. Hip simulator studies have shown that wear rates are higher during the initial bedding-in phase and subsequently drop to very low levels. Accordingly, metal ion levels would be expected to decrease with the use of the bearing, measured as implantation time following surgery. However, several clinical studies have found that metal ion levels either gradually rise or fluctuate instead of decreasing to lower levels. Moreover, hip simulator studies predict that large-diameter bearings have lower wear rates than small-diameter bearings. In clinical studies, however, metal levels in patients with large-diameter bearings are unexpectedly higher than those in patients with small-diameter bearings.

As a consequence, high cobalt ion levels in patients do not necessarily imply that their MoM bearings produce much wear debris at the time that their levels were measured; it may simply be due to accumulation of wear debris from the preceding time. Exercise-related cobalt rise may overcome this limitation and give a better assessment of the current wear status of a MoM bearing surface than a measure of cobalt levels only.

Anatomic hip range of motion after implantation during total hip arthroplasty as measured by a navigation system

Simulation of prosthetic impingement is important for preventing complications after total hip arthroplasty (THA). Although the anatomical hip range of motion (ROM) in patients after THA is an essential parameter for these simulations, previous simulation studies substituted various clinical hip ROMs for the anatomical hip ROM. Using a navigation system, anatomical hip ROM was accurately assessed after implantation during primary THA in 30 patients. We found that the hip could be passively moved to 113 degrees of flexion, 34 degrees of extension, 46 degrees of abduction, 75 degrees of internal rotation, and 36 degrees of external rotation. Almost all reference hip ROMs used in previous simulations were smaller than these values. Therefore, wider hip ROM values should be used as parameters for such simulations.

Impingement with total hip replacement

Impingement is a cause of poor outcomes of prosthetic hip arthroplasty; it can lead to instability, accelerated wear, and unexplained pain. Impingement is influenced by prosthetic design, component position, biomechanical factors, and patient variables. Evidence linking impingement to dislocation and accelerated wear comes from implant retrieval studies. Operative principles that maximize an impingement-free range of motion include correct combined acetabular and femoral anteversion and an optimal head-neck ratio. Operative techniques for preventing impingement include medialization of the cup to avoid component impingement and restoration of hip offset and length to avoid osseous impingement.

Acetabular labral tears of the hip: examination and diagnostic challenges

The purpose of this clinical commentary is to provide an evidence-based review of the examination process and diagnostic challenges associated with acetabular labral tears of the hip. Once considered an uncommon entity, labral tears have recently received wider recognition as a source of symptoms and functional limitation. Information regarding acetabular labral tears and their association to capsular laxity, femoral acetabular impingement (FAI), dysplasia of the acetabulum, and chondral lesions is emerging. Physical therapists should understand the anatomical structures of the hip and recognize how the clinical presentation of labral tears is difficult to view isolated from other hip articular pathologies. Clinical examination should consider lumbopelvic and extra-articular pathologies in addition to intra-articular pathologies when assessing for the source of symptoms and functional limitation. If a labral tear is suspected, further diagnostic testing may be indicated. Although up-and-coming evidence suggests that information obtained from patient history and clinical examination can be useful, continued research is warranted to determine the diagnostic accuracy of our examination techniques.

Contact mechanics analysis of metal-on-metal hip resurfacing prostheses

Finite-element method was employed to study the contact mechanics in metal-on-metal hip resurfacing prostheses, with particular reference to the effects of bone quality, the fixation condition between the acetabular cup and bone, and the clearance between the femoral head and the acetabular cup. Simple finite-element bone models were developed to simulate the contact between the articulating surfaces of the femoral head and the acetabular cup. The stresses within the bone structure were also studied. It was shown that a decrease in the clearance between the acetabular cup and femoral head had the largest effect on reducing the predicted contact-pressure distribution among all the factors considered in this study. It was found that as the clearance was reduced, the influence of the underlying materials, such as bone and cement, became increasingly important. Stress shielding was determined to occur in the bone tissue surrounding the hip resurfacing prosthesis considered in this study. However, the stress-shielding effects predicted were less than those observed in conventional total hip replacements. Both the effects of bone quality (reduction in elastic modulus) and the fixation condition between the cup and the bone were found to have a negligible effect on the predicted contact mechanics at the bearing surface. The loading was found to have a relatively small effect on the predicted maximum contact pressure at the bearing surface; this was attributed to an increase in contact area as the load was increased.

The S-ROM stem and its use with alternative bearings

Many long-term studies of total hip arthroplasty (THA) show excellent results. This long-term success depends on many factors, including implant fixation and bearing surface wear. As THA is commonly performed on patients with a steadily increasing life span and activity level, the issue of wear has become critical. Advances in the wear properties of polyethylene have been significant, but, in the search for low long-term wear rates, hard bearing surfaces are frequently used.

Intraspinal metalloma resulting in late paraparesis

The metal-related complications caused by orthopedic implants have long been a concern, but these problems have been considered mostly in the field of arthroplasty or internal fixation of fractures. The recent prevalence of spinal instrumentation has evoked a similar concern among spine surgeons. Here, we present a case of intraspinal metallosis adjacent to the pedicular hook occurring after treatment of vertebral fracture by posterior spinal instrumentation and fusion, and causing paraparesis at the 3rd postoperative year. Metallic granulomas can appear around the pedicular hooks as in the reported case. Crevice and fretting corrosion are results at the junctions of rod-screw, rod-hook, transverse connector rod and other connector rods in modular spinal implants. Adequate usage of transpedicular screws may inhibit the occurrence of such a complication. For this reason, further studies are necessary to increase metallic corrosive resistance to inhibit crevice and fretting corrosion.

Current concepts of metal-on-metal hip resurfacing

The second-generation, metal-on-metal (MOM) bearing for total hip replacements was launched in the 1980s, and resurfacing followed in the mid-1990s. Remaining challenges include long-term bone remodeling of the femoral resurfacing and consideration of adverse MOM wear conditions. Precise understanding of manufacturing variables such as alloy types, bearing diameters, design tolerances, and surface finish is imperative in obtaining clinical consistency and safety in the patient. This review examines femoral fixation, bone remodeling, and wear studies of MOM implants and provides a brief overview of the latest outcome and retrieval data and how these data integrate with the in vitro wear studies.

Dissociation of the metal inlay from the polyethylene liner in an uncemented threaded cup

We describe a case of spontaneous dissociation of the metal inlay from the polyethylene cup of a sandwiched metal-on-metal total hip prosthesis manufactured from Co-28Cr-6Mo SM 21 alloy. The patient, a 51-year-old active woman, started to feel groin pain 50 months postoperatively. The pain progressed after a slight trauma and led to final revision after 66 months in situ. No signs of impingement were observed. The polyethylene cup showed an approximately 2 mm-deep groove in the superior wall, and the head was heavily worn on the lateral side. In addition to the typically observed abrasive wear patterns, several types of severe wear defects were noticed. Extensive metallosis and necrosis were observed histologically. This unusual case of substantial deformation of the head and the cup was presumed to have occurred as a result of the increased friction and consequent high wear of the metal head.

Metal-on-metal total hip replacement

Metal-on-metal bearings have wear rates that are 20 to 100 times lower than metal-on-conventional polyethylene. The amount of wear generally is the same order of magnitude for the head and the cup. There is an initial run-in period of higher wear followed by lower, steady-state wear. Wear rate is a function of the interplay of material(s), macrogeometry, microgeometry, and the resultant type and amount of lubrication. The wear resistance and clinical performance of a metal-on-metal bearing are more sensitive to macrogeometry and lubrication than a metal-on-polyethylene bearing. Metal wear particles are nanometers in linear dimension. They are much smaller and more numerous than the submicron polyethylene wear particles, but the volume of periprosthetic inflammatory tissue is less. Osteolysis seems to be relatively rare. Little is known about the systemic distribution of metal particles and ions. The significance of systemic distribution also is not known. The levels of serum and urine Co and Cr ions are elevated in patients with metal-on-metal bearings, but the long-term, steady-state levels are not much higher than those from corrosion of modular femoral components. Because of the elevated levels of Co and Cr ions, there is a greater risk of delayed type hypersensitivity. There also is concern about the potential for malignant degeneration secondary to prolonged exposure to these elements. The available data are insufficient to address this concern. Rigorous long-term studies are needed. It will take decades of close clinical observation to determine if the benefits of metal-on-metal bearings outweigh the associated risks.

Cementless Metasul metal-on-metal total hip arthroplasty in patients less than fifty years old

BACKGROUND

Durable results of total hip arthroplasty have been difficult to achieve in young patients. We reviewed the intermediate-term clinical and radiographic results in a series of active, higher-demand patients who were less than fifty years old when they underwent cementless total hip arthroplasty with the use of the Metasul metal-on-metal articulation.

METHODS

Seventy total hip arthroplasties were performed in sixty-two patients who were younger than fifty years of age (average age, thirty-seven years). Two patients (two hips) had had a resection arthroplasty because of deep infection less than five years postoperatively and were excluded. Sixty patients (sixty-eight hips) were available for complete clinical and radiographic analysis after a mean duration of follow-up of seven years.

RESULTS

The mean preoperative Harris hip score of 49 points improved to 95 points at the time of final follow-up; fifty-six patients (93%) had an excellent result. No component was seen to be loose radiographically at the time of final follow-up. Only one focal area of pelvic osteolysis in one patient and two small focal areas of femoral osteolysis in another patient were identified. The hip with focal pelvic osteolysis underwent revision surgery with a liner change and bone-grafting of the osteolytic lesion around a stable component.

CONCLUSIONS

At a mean of seven years after arthroplasties with a Metasul metal-on-metal articulation, there was a low rate of osteolysis and aseptic loosening in this group of young patients. However, additional follow-up is necessary to determine any possible long-term deleterious effects associated with this metal-on-metal articulation.

Mechanical performance of ceramic acetabular liners under impact conditions

Although new generation alumina ceramics have exhibited a reduced incidence of fracture, concern still persists about the behavior of ceramic acetabular liners under impact conditions. The objective of this study was to explore whether fracture of a new generation alumina ceramic liner was likely to occur in vivo. Ceramic liners were impacted with forces of 23, 21, 15, and 12 kN (n = 3 at each force). At 23 kN, all 3 ceramic liners fractured on the first impact; at 12 kN none of the ceramic liners fractured after 20 impacts. The threshold force of 12 kN is large in comparison with estimated physiologic forces on the hip during falls or stumbling, suggesting that ceramic liner fracture is not a definite consequence of liner impact.

Clinical and simulator wear study of alumina ceramic THR to 17 years and beyond

Three THAs with cementless monolithic alumina ceramic sockets and cementless Co-alloy stems were retrieved because of aseptic loosening after 17 and 24 years. At revision heads and cups were marked for orientation. Maps were drawn of wear patterns with the use of light microscopy and surveyed by SEM. In a simulator experiment 28-mm-diameter alumina heads and liners were used. The cups were mounted inverted in a hip simulator and run with calf serum as the lubricant. The hip loads were 2 kN maximum and a 1-Hz frequency for 20 million cycles. Wear severity was classified into five grades. In retrieved implants, SEM analysis showed that the main wear zones (MWZ) had Grade 4 wear. The peripheral wear zones (PWZ) showed grain pull-out regions (Grade 5 wear). These corresponded to neck-socket impingement and head-acetabular cup separation. Gray was due to transferred CoCr particles from the stem. In the simulator study, the MWZ had only localized areas of grain pull out surrounded by polished surface regions (Grade 4 wear) at 20 million cycles; stripe wear was not seen. The alumina ceramic bearings proved excellent up to 22 years in simulator studies and clinical studies. However, microseparation kinematics would be necessary in the simulator to duplicate the more peripheral wear zones.