Fixation, polyethylene wear, and pelvic osteolysis in primary total hip replacement

Femoral bone is preserved using cemented polished stems in young patients

BACKGROUND

Techniques that ensure femoral bone preservation after primary THA are important in younger patients who are likely to undergo revision surgery.

QUESTIONS/PURPOSES

We examined femoral stem survival, bone deficiency at revision arthroplasty, and radiographic bone loss in hips implanted with a cemented polished double-taper stem in a cohort of patients younger than 55 years.

METHODS

We reviewed 197 hips (median patient age, 47 years; range, 16-54 years) after a minimum followup of 2 years (median, 7 years; range, 2-19 years) since primary THA. Clinically, we determined survival to major and minor stem revision and cases of bone deficiency requiring a long stem or impaction bone grafting or created by the need for femoral osteotomy at revision arthroplasty. Radiographically, we assessed stem loosening, femoral osteolysis, and femoral bone deficiency.

RESULTS

Stem survival to major revision for aseptic loosening was 100% at 13 years and for any reason was 97% (95% CI, 93-100%). At revision of seven stems, a long stem was used in one hip, a total femoral replacement in one hip and impaction bone grafting in one hip. No femoral osteotomies were required. Bone was preserved in four hips by cement-within-cement stem exchange. No stems were radiographically loose. Proximal osteolysis was present in 11% of femurs. Femoral bone deficiency was graded as Paprosky Type I (97%) or II (3%) and Endo-Klinik Grade 0 (79%) or I (21%).

CONCLUSIONS

Cemented polished taper stems have high survival at 13 years in young patients and enable femoral bone preservation for subsequent revision.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Osteolysis in the well-fixed socket

Osteolysis remains a common reason for revision after total hip arthroplasty (THA). For osteolysis associated with loose cups, revision is indicated. For osteolysis around a well-fixed cup, the decision is more controversial. The data available data support retention of the cupwith lesional treatment, working through screw holes and access channels for debridement and grafting. The choice of graft material to fill defects, if any, remains controversial. Several studies demonstrate good survivorship with cup retention strategies. Complete revision allows more complete debridement of the lesion and better graft fill, and allows implantation of a modern cup, typically with a full line of liners and bearing surfaces available. Additionally, revision allows fine tuning of the orientation of the cup, which may be advantageous for optimising hip stability. The author prefers to retain a well-fixed cup if it meets the following criteria: it is well-fixed to intra-operative testing, it is well-positioned, it is of sufficient size to allow insertion of a new liner with a reasonable head size, new liners are available, and the hip is stable to intra-operative trialing after liner insertion.

Progression of periacetabular osteolytic lesions

BACKGROUND

The development of three-dimensional computed tomography (CT) imaging techniques has enabled the detection, accurate measurement, and monitoring of periprosthetic osteolytic lesions. The aim of this study was to track the progression in size of osteolytic lesions and to determine those factors that are associated with the risk of progression. A secondary aim was to investigate whether progression in size of osteolytic lesions could be monitored with use of radiographs.

METHODS

We retrospectively determined, with use of sequential CT scans, the progression of periacetabular osteolysis over a period of as much as nine years in a cohort of twenty-six patients (thirty acetabular components) in whom the cementless acetabular component or components had been in place for longer than ten years at the time of the initial CT scan. High-resolution CT scans with metal-artifact suppression were used to determine the volume of osteolytic lesions. Progression in the size of osteolytic lesions per year was calculated as the change in the volume of osteolytic lesions between serial CT scans. Associations were determined between the progression in size of osteolytic lesions, osteolysis rate at the initial CT, patient age, sex, walking limitations, and activity level. Progression in size of osteolytic lesions as determined with use of CT was compared with that determined with use of radiographs.

RESULTS

Mean progression in the size of osteolytic lesions, as determined with use of CT, was 1.5 cm(3)/yr (range, 0 to 7.5 cm(3)/yr). The amount of osteolysis at the initial CT scan and patient activity were good predictors of osteolytic lesion progression. The strongest predictor of osteolytic lesion progression occurred when these two risk factors were combined (p = 0.0019). The value of radiographs was limited to monitoring of larger lesions identified by CT.

CONCLUSIONS

This is the first study to report on the progression of osteolysis adjacent to cementless acetabular components from medium to long-term follow-up. The data suggest that the osteolysis rate at the initial CT and patient activity can be useful factors in predicting the progression in size of periacetabular osteolytic lesions.

Squeaking in third- and fourth-generation ceramic-on-ceramic total hip arthroplasty: meta-analysis and systematic review

Postoperative squeaking in ceramic-on-ceramic total hip arthroplasty is a recently emerging phenomenon. We performed a meta-analysis of published data to examine patient and procedural risk factors. Twelve studies (6137 patients, total) were analyzed, with 150 patients (2.4%) complaining of squeaking. The only significant patient risk factor was increasing body mass index (P = .03, n = 2957). There was no significance found with patient age, sex, height, weight, or procedural laterality for squeak incidence. For implant type, the presence of a Stryker Accolade femoral stem (beta-titanium; Stryker Orthopedics, Mahwah, NJ) was significantly found to increase squeak (P < .0001, n = 4654). The presence of a raised metallic lip on the acetabular component was not found to be associated with squeak. Acetabular cup position was also not found to have a significant bearing on the incidence of squeaking.

Gait symmetry: a comparison of hip resurfacing and jumbo head total hip arthroplasty patients

Proponents of large femoral head total hip arthroplasty (THA) and hip resurfacing arthroplasty (HRA) have touted the potential for restoration of more normal hip kinematics. This study examined 20 patients (10 THA and 10 HRA patients) approximately 18 months after surgery. Subjects were evaluated at a self-selected pace, while bilateral spatial-temporal gait variables, hip flexion/extension kinematics, and ground reaction forces were collected. For both groups, swing time was increased on the surgical side, whereas peak hip flexion, peak extension, and flexion at heel strike were decreased. Peak hip extension and peak vertical ground reaction forces were decreased in THA subjects compared with HRA subjects. After a large-diameter THA or HRA, subjects do not display symmetric gait approximately 18 months postoperatively. Total hip arthroplasty subjects demonstrated restricted hip extension and reduced limb loading when compared with HRA subjects.

The seven-year wear of highly cross-linked polyethylene in total hip arthroplasty: a double-blind, randomized controlled trial using radiostereometric analysis

BACKGROUND

The use of highly cross-linked polyethylene is now commonplace in total hip arthroplasty. Hip simulator studies and short-term in vivo measurements have suggested that the wear rate of highly cross-linked polyethylene is significantly less than that of conventional ultra-high molecular weight polyethylene. However, long-term data to support its use are limited. The aim of this study was to compare the intermediate-term steady-state wear of highly cross-linked polyethylene compared with that of conventional ultra-high molecular weight polyethylene acetabular liners in a prospective, double-blind, randomized controlled trial with use of radiostereometric analysis.

METHODS

Fifty-four patients were randomized to receive hip replacements with either conventional ultra-high molecular weight polyethylene acetabular liners (Zimmer) or highly cross-linked polyethylene liners (Longevity; Zimmer). All patients received a cemented, collarless, polished, tapered femoral component (CPT; Zimmer) and an uncemented acetabular component (Trilogy; Zimmer). Clinical outcomes were assessed and the three-dimensional penetration of the head into the socket was determined for a minimum of seven years. Linear regression was used to calculate the steady-state wear rate following the creep-dominated penetration seen during the first year.

RESULTS

At a minimum of seven years postoperatively, the mean total femoral head penetration was significantly lower in the highly cross-linked polyethylene group (0.33 mm; 95% confidence interval [CI], ±0.10 mm) than it was in the ultra-high molecular weight polyethylene group (0.55 mm; 95% CI, ±0.10 mm) (p = 0.005). The mean steady-state wear rate of highly cross-linked polyethylene was 0.005 mm/yr (95% CI, ±0.015 mm/yr), compared with 0.037 mm/yr (95% CI, ±0.019 mm/yr) for conventional ultra-high molecular weight polyethylene (p = 0.007). No patient in the highly cross-linked polyethylene group had a wear rate above the osteolysis threshold of 0.1 mm/yr, compared with 9% of patients in the ultra-high molecular weight polyethylene group.

CONCLUSIONS

This study demonstrates that highly cross-linked polyethylene has a significantly lower steady-state wear rate compared with that of conventional ultra-high molecular weight polyethylene. Longer-term follow-up is required to determine if this will translate into improved clinical performance and longevity of these implants.

Highly crosslinked polyethylene reduces wear in total hip arthroplasty at 5 years

BACKGROUND

Although hip arthroplasty reliably relieves pain and improves function, problems have arisen with wear and osteolysis. Highly crosslinked polyethylene has been developed to address this problem although at present there is limited clinical evidence it does so longer term.

QUESTIONS/PURPOSES

We compared the in vivo wear of standard versus highly crosslinked polyethylene (HXLP) in primary total hip arthroplasty at a minimum of 5-year followup.

METHODS

We enrolled 122 patients in a prospective, double-blinded, randomized trial and followed them annually to assess their progress. Annual radiographs were analyzed using previously validated edge detection software to assess for two-dimensional, three-dimensional, and volumetric wear. The mean follow up was 5.5 years (range, 4.1 to 7 years).

RESULTS

The two-dimensional wear measurements for HXLP showed lower wear compared to the conventional group (0.05 mm/year versus 0.26 mm/year, respectively). Three-dimensional and volumetric wear were similarly lower in the HXLP group.

CONCLUSIONS

Highly crosslinked polyethylene undergoes substantially less wear than conventional polyethylene at medium term. The effect of hip arthroplasty longevity will need to be assessed with longer-term studies, but this may lead to a decreased need for revision as a result of less wear and osteolysis.

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.

Direct comparison of polyethylene wear in cemented and uncemented acetabular cups

Background

It has been indicated that, in the long term, the rate of wear and the degree of osteolysis observed with uncemented acetabular components are greater than those associated with cemented cups, but most studies which compare the wear characteristics of cementless with cemented cups have used historical controls. We report a direct comparison of wear of a cemented and an uncemented cup with similar design, polyethylene, and sterilization method.

Materials and methods

The study cohort includes 92 patients who were operated in 1997 with primary total hip replacement and have been followed for a period of 9–10 years. All patients were operated by posterolateral approach. In patients 70 years or older we used a cemented cup, in those 60 years or younger we used an uncemented cup, and in patients between 60 and 70 years we used either a cemented or uncemented cup as decided by the surgeon. At follow-up, radiographic imaging was obtained as standard anterioposterior view of the pelvis, and mean wear was determined as described by Livermore et al.

Results

The overall wear of the cemented acetabular components was 1.07 ± 0.78 mm, and that of the uncemented cups was 1.18 ± 0.61 mm (P = 0.529). Wear was significantly associated with male sex (P = 0.003), younger age (P = 0.003), and degree of inclination (P < 0.001), but wear was not significantly associated with cemented versus uncemented cup (P = 0.437).

Conclusion

Our findings in this 9–10-year follow-up study suggest that cementless cups wear no more than cemented cups of similar design.

Distribution of periacetabular osteolytic lesions varies according to component design

Using computed tomography, the volume, location, and number of osteolytic lesions were determined adjacent to 38 Harris-Galante 1 (HG-1) acetabular components fixed with screws and 19 porous-coated anatomic (PCA) acetabular components press-fitted without screws. The median implantation times were 16 and 15 years, respectively. The mean total lesion volumes were similar: 11.1 cm(3) (range, 0.7-49 cm(3)) and 9.8 cm(3) (range, 0.4-52 cm(3)), respectively, for hips with HG-1 and PCA components (P = .32). There was a significant difference in the proportion of rim-related, screw or screw hole-related, and combined lesions between the 2 component designs (P < .0001). HG-1 components had more screw and screw hole-related lesions, and PCA components had more rim-related lesions. Although there are concerns regarding screw and screw hole-associated osteolysis, these findings suggest that peripheral fixation may be well maintained in the long term with the use of multiple-hole acetabular components with screw fixation.

Third-generation ceramic-on-ceramic bearing surfaces in revision total hip arthroplasty

With an increase of revision total hip arthroplasty (THA), the choice of bearing surface becomes more important. Wear debris by conventional metal-on-polyethylene articulations may cause extensive osteolysis, especially in young patients. We analyzed the clinical and radiographic outcomes after revision THA using third-generation ceramic-on-ceramic bearing surfaces in 42 hips. The mean age of the patients was 48.8 years (32-59 years), and the mean duration of follow-up monitoring was 5.4 years (3.2-8.0 years). At final follow-up examination, the average Harris Hip Score was 91.3. Although minor complications were observed in 6 hips (14.3%), no hips required additional revision surgery. No hip showed radiolucent lines, acetabular cup migration, or osteolysis. Our data show that clinical and radiographic outcomes after revision THA using third-generation ceramic-on-ceramic bearing surfaces are favorable. Ceramic-on-ceramic bearing surfaces can be preferentially considered for revision THA, especially in young patients. Further studies with long-term follow-up data are warranted.

THA with highly cross-linked polyethylene in patients 50 years or younger

Highly cross-linked polyethylene has been associated with low in vitro wear, but also has decreased in vitro ultimate yield strength. We therefore asked whether highly cross-linked polyethylene would result in lower outcome scores, wear, or early failure in a young patient population. Seventy THAs in 64 patients were performed using a highly cross-linked (electron beam-irradiated to 9 Mrads) acetabular liner and a cobalt-chrome femoral head. The average age of the patients at surgery was 41 years (range, 19-50 years). The minimum followup was 2.4 years (average, 4 years; range, 2.4-6.5 years). We recorded demographic and clinical data, including Harris hip score. Polyethylene wear measurements were analyzed with a validated, computer-assisted, edge detection method. The average Harris hip score improved from 53 to 92 at last followup. There was no evidence of acetabular or femoral loss of fixation, subsidence, or loosening. Linear wear was undetectable at this followup interval. No patient experienced catastrophic failure or underwent revision surgery. These data show low polyethylene wear rates and no catastrophic failures at early followup in a young patient cohort.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Eight- to ten-year clinical and radiographic outcome of a porous tantalum monoblock acetabular component

In a prospective study, the authors used a porous tantalum monoblock acetabular component for primary total hip arthroplasty between November 1997 and June 1999. A total of 156 consecutive primary total hip arthroplasty were done in 143 patients younger than 75 years. A total of 151 hips had a follow-up time from 8 to 10 years. The average preoperative total Harris hip score of 44.0 +/- 13.8 increased to 97.0 +/- 6.2 at the latest follow-up. The average preoperative Oxford hip score of 43.3 +/- 6.5 improved to 13.9 +/- 2.3 at the latest follow-up. Radiographic evaluation including the Ein-Bild-Röntgen-Analyse (EBRA) digital system showed no radiographic evidence of gross polyethylene wear, progressive radiolucencies, osteolytic lesions, acetabular fracture, or component subsidence. There were 7 (4.5%) postoperative complications all unrelated to the acetabular component.

Wear is reduced in THA performed with highly cross-linked polyethylene

Highly cross-linked polyethylene (HCLPE) has been used extensively to decrease osteolysis and related implant failure in THA. We compared the wear rate of HCLPE and noncross-linked conventional PE (CPE) liners and the rate of radiographic calcar resorption and osteolysis in young patients (35-60 years of age) who underwent THA by one surgeon. Thirty-four patients (41 THAs) who received a hybrid THA using a HCLPE liner were match-paired for age, gender, body mass index, and diagnosis with a group of patients who underwent THA with identical implants but with a CPE liner. The minimum followup was 4 years (average, 5.3; range, 4-8 years). Using the Livermore measurement technique, the averages of total wear of the HCLPE and CPE liners were 0.01 mm (range, -0.23-0.4) and 0.64 mm (range, 0-1.7), respectively. The average annual wear was less for the HCLPE than the noncross-linked PE (0.002 mm, range, -0.05-0.1 versus 0.12 mm, range, 0-0.29, respectively). Four hips in the HCLPE group and 23 in the CPE group had calcar resorption measuring averages of 2.5 mm (range, 2-3) and 7.5 mm (range, 1.8-23.8), respectively. Periprosthetic osteolysis occurred in two and eight hips in the HCLPE and CPE groups, respectively. Longer followup is needed to determine if these findings will result in improved implant survivorship.

LEVEL OF EVIDENCE

Level III, therapeutic study.

A double-blind, prospective, randomized controlled trial comparing highly cross-linked and conventional polyethylene in primary total hip arthroplasty

Highly cross-linked polyethylene was developed to reduce articular bearing wear in total hip arthroplasty. In vitro studies have shown reduced wear in comparison with conventional polyethylene. A double-blind, prospective, randomized trial was performed comparing highly cross-linked and conventional polyethylene in 119 patients. The primary outcome variables were linear, 3-dimensional, and volumetric wear as determined by analysis of digitized radiographs using validated wear measurement software. Linear, 3-dimensional, and volumetric wear rates were significantly less in the highly cross-linked polyethylene group between 6 months and 4 years postoperatively (P < .05). The data presented here show that highly cross-linked polyethylene reduces short-term polyethylene wear. The intermediate and long-term clinical results of highly cross-linked polyethylene remain unknown pending further follow-up.

A comparison of the outcome of cemented all-polyethylene and cementless metal-backed acetabular sockets in primary total hip arthroplasty

We compared, after a 10-year-minimum follow-up, the outcome of 50 cemented all-polyethylene Charnley acetabular sockets with that of 51 cementless metal-backed sockets in 2 comparable cohorts of young patients. Although the revision rate for the cemented and cementless group was 28% and 35%, respectively, the revision rate for aseptic loosening was 28% for the cemented and 12% for the cementless group. The mean polyethylene wear was 0.112 and 0.114 mm/y, respectively, for the 2 groups. Linear osteolysis was observed in 18 of 50 cemented sockets. Expansile osteolysis presented in 10 of 51 cementless sockets and only in one of the cemented sockets. In conclusion, cementless components had more durable fixation than cemented components. However, they presented more aggressive expansile osteolysis caused by the coexistence of polyethylene and metal debris.

Minimum ten-year results of a porous acetabular component for Crowe I to III hip dysplasia using an elevated hip center

We conducted a retrospective study of the placement of porous-coated acetabular components using screws at more than 20 mm above the teardrop without structural bone graft for dysplastic hips to determine long-term outcome. Thirty hips (29 patients) were monitored for a mean of 15.2 years (range, 10.4-18.3 years) after surgery. Compared with 12 contralateral normal hips, the distance of the hip center from the teardrop was significantly high (26.8 +/- 4.8 and 13.4 +/- 2.7 mm P < .001); however, it was not laterally different (31. 5 +/- 5.1 and 31.7 +/- 5.0 mm). No acetabular components showed loosening. One metal shell was revised for wear and osteolysis. Morselized bone grafted in 25 hips was incorporated in all cases. Slight elevation of the hip center without lateralization in cementless cups fixed with screws was well tolerated for dysplastic hips.

Metal-on-metal hip resurfacing arthroplasty: a review of periprosthetic biological reactions

Metal-on-metal hip resurfacing arthroplasty has undergone a recent resurgence as an alternative treatment option for young and active patients with significant osteoarthritis. The claimed advantages of metal-on-metal hip resurfacing arthroplasty include lower wear rate, preservation of bone stock for subsequent revision procedures, restoration of anatomic hip mechanics, and enhanced stability due to the larger diameter of articulation. A disadvantage, however, is that the metal-on-metal resurfacing releases large amounts of very small wear particles and metal ions. The long-term biological consequences of the exposure to these Co-Cr particles and ions remain largely unknown. The purpose of this review is to provide an overview of the current literature on the adverse periprosthetic biological reactions associated with metal-on-metal hip resurfacing arthroplasty.

The Harris-Galante porous-coated, hemispherical, polyethylene-lined acetabular component in patients under 50 years of age

We have reviewed 70 Harris-Galante uncemented acetabular components implanted as hybrid hip replacements with cemented stems between 1991 and 1995 in 53 patients whose mean age was 40 years (19 to 49). The mean follow-up was for 13.6 years (12 to 16) with no loss to follow-up. We assessed the patients both clinically and radiologically.

The mean Oxford hip score was 20 (12 to 46) and the mean Harris hip score 81 (37 to 100) at the final review. Radiologically, 27 hips (39%) had femoral osteolysis, 13 (19%) acetabular osteolysis, and 31 (44%) radiolucent lines around the acetabular component. Kaplan-Meier survival curves were constructed for the outcomes of revision of the acetabular component, revision of the component and polyethylene liner, and impending revision for progressive osteolysis.

The cumulative survival for revision of the acetabular component was 94% (95% confidence interval 88.4 to 99.7), for the component and liner 84% (95% confidence interval 74.5 to 93.5) and for impending revision 55.3% (95% confidence interval 40.6 to 70) at 16 years.

Uncemented acetabular components with polyethylene liners undergo silent lysis and merit regular long-term radiological review.

The creep and wear of highly cross-linked polyethylene: a three-year randomised, controlled trial using radiostereometric analysis

The creep and wear behaviour of highly cross-linked polyethylene and standard polyethylene liners were examined in a prospective, double-blind randomised, controlled trial using radiostereometric analysis. We randomised 54 patients to receive hip replacements with either highly cross-linked polyethylene or standard liners and determined the three-dimensional penetration of the liners over three years. After three years the mean total penetration was 0.35 mm (SD 0.14) for the highly cross-linked polyethylene group and 0.45 mm (SD 0.19) for the standard group. The difference was statistically significant (p = 0.0184). From the pattern of penetration it was possible to discriminate creep from wear. Most (95%) of the creep occurred within six months of implantation and nearly all within the first year. There was no difference in the mean degree of creep between the two types of polyethylene (highly cross-linked polyethylene 0.26 mm, SD 0.17; standard 0.27 mm, SD 0.2; p = 0.83). There was, however, a significant difference (p = 0.012) in the mean wear rate (highly cross-linked polyethylene 0.03 mm/yr, SD 0.06; standard 0.07 mm/yr, SD 0.05). Creep and wear occurred in significantly different directions (p = 0.01); creep was predominantly proximal whereas wear was anterior, proximal and medial. We conclude that penetration in the first six months is creep-dominated, but after one year virtually all penetration is due to wear. Highly cross-linked polyethylene has a 60% lower rate of wear than standard polyethylene and therefore will probably perform better in the long term.

Similar wear in total hip arthroplasties with metallic or zirconia femoral heads

Ceramic femoral heads have been used in an attempt at reducing polyethylene wear of total hip arthroplasties. Clinical results with zirconia femoral heads have been mixed. This study was undertaken to compare the polyethylene wear and incidence of periprosthetic osteolysis in total hip replacements performed using a 28-mm zirconia versus a 28-mm cobalt chromium femoral head. Thirty-five hips with a 28-mm cobalt chromium head and 68 hips with a 28-mm zirconia head were evaluated after a minimum follow-up of 2 years (average, 4.0 years; range, 2.0 to 9.1 years). A monoblock acetabular component was used in all patients. Polyethylene wear was measured in serial radiographs from 58 of the hips utilizing a computer-assisted vector wear technique. Periacetabular osteolysis developed in three patients (two with a zirconia head and one with a cobalt chromium head). The total wear and the annual wear rate were 0.48 mm and 0.11 mm/year for the cobalt chromium heads and 0.53 mm and 0.14 mm/year for the zirconia heads, respectively. We found no benefit with respect to the rate of polyethylene wear or incidence of osteolysis with the use of zirconia femoral heads.

Patient compliance with clinical follow-up after total joint arthroplasty

BACKGROUND

Periodic clinical and radiographic evaluation is commonly recommended by orthopaedic surgeons to monitor patients following total joint arthroplasty, yet the compliance with and efficacy of patient follow-up protocols have not been well defined. The purpose of this study was to evaluate patient compliance with early clinical follow-up after total hip arthroplasty or total knee arthroplasty.

METHODS

We performed a retrospective review of clinical follow-up compliance for 776 patients who had undergone a total joint arthroplasty in the lower extremity. This cohort included 505 total hip arthroplasties (372 primary and 133 revision procedures) and 271 total knee arthroplasties (195 primary and seventy-six revision procedures). The patients were given one-time verbal instructions by the treating surgeon at the three-month postoperative visit to return for the one-year follow-up evaluation. At the one-year follow-up evaluation, those who returned were once again verbally instructed to return a year later. Demographic factors, functional hip and knee scores, and follow-up compliance at one and two years after surgery were assessed.

RESULTS

Patient compliance with clinical follow-up after all arthroplasties was 61% at one year and 36% at two years. With use of a multivariate model for patients who had total hip arthroplasty, the analyses showed that a revision hip procedure (p = 0.006), younger patient age (p = 0.04), and a higher preoperative Harris hip score for gait (p = 0.04) were associated with follow-up compliance at two years. Of the factors analyzed for patients who had total knee arthroplasty, only nonwhite race (p = 0.03) was found to be a positive predictor of follow-up compliance at the two-year follow-up interval.

CONCLUSIONS

Patient compliance with clinical follow-up after total joint arthroplasty in response to a verbal request made by the surgeon once at three months and once at one year postoperatively was poor in this series. These data indicate that this method (one-time verbal instruction) is insufficient to ensure compliance for follow-up after total joint arthroplasty.

Evaluation of two surgical techniques for acetabular reconstruction in total hip replacement for congenital hip disease: results after a minimum ten-year follow-up

We have evaluated the results of total hip replacement in patients with congenital hip disease using 46 cemented all-polyethylene Charnley acetabular components implanted with the cotyloplasty technique in 34 patients (group A), and compared them with 47 metal-backed cementless acetabular components implanted without bone grafting in 33 patients (group B). Patients in group A were treated between 1988 and 1993 and those in group B between 1990 and 1995. The mean follow-up for group A was 16.6 years (12 to 18) and the mean follow-up for group B was 13.4 years (10 to 16). Revision for aseptic loosening was undertaken in 15 hips (32.6%) in group A and in four hips (8.5%) in group B. When liner exchange was included, a total of 13 hips were revised in group B (27.7%). The mean polyethylene wear was 0.11 mm/yr (0.002 to 0.43) and 0.107 mm/yr (0 to 0.62) for groups A and B, respectively. Polyethylene wear in group A was associated with linear osteolysis, and in group B with expansile osteolysis. In patients with congenital hip disease, when 80% cover of the implant can be obtained, a cementless acetabular component appears to be acceptable and provides durable fixation. However, because of the type of osteolysis arising with these devices, early exchange of a worn liner is recommended before extensive bone loss makes revision surgery more complicated.

Does highly cross-linked polyethylene wear less than conventional polyethylene in total hip arthroplasty? A double-blind, randomized, and controlled trial using roentgen stereophotogrammetric analysis

A prospective double-blind, randomized, and controlled trial was conducted using roentgen stereophotogrammetric analysis; 54 total hip arthroplasty patients were randomized to receive either highly cross-linked polyethylene (HXLPE) or standard ultra-high-molecular-weight polyethylene (UHMWPE) liners. The 3-dimensional penetration of the liner was determined over 2 years. For the first 3 months, both polyethylene types had a rapid penetration rate (HXLPE: 0.22 mm, SD = 0.17 mm; UHMWPE: 0.21 mm, SD = 0.15 mm; P = .78). After 3 months, the HXLPE penetration rate (0.06 mm/y, SD = 0.06 mm/y) was significantly lower than the UHMWPE penetration rate (0.10 mm/y, SD = 0.07 mm/y; P = .04). The penetration in the first 3 months was probably caused by creep or bedding in; from 3 months onward, much of the penetration was probably caused by wear. We conclude that HXLPE has a 40% lower wear rate as compared with UHMWPE, suggesting that it will perform better in the long term.

Temporal radiographic texture analysis in the detection of periprosthetic osteolysis

Periprosthetic osteolysis is one of the most serious long-term problems in total hip arthroplasty. It has been primarily attributed to the body's inflammatory response to submicron polyethylene particles worn from the hip implant, and it leads to bone loss and structural deterioration in the surrounding bone. It was previously demonstrated that radiographic texture analysis (RTA) has the ability to distinguish between osteolysis and normal cases at the time of clinical detection of the disease; however, that analysis did not take into account the changes in texture over time. The goal of this preliminary analysis, however, is to assess the ability of temporal radiographic texture analysis (tRTA) to distinguish between patients who develop osteolysis and normal cases. Two tRTA methods were used in the study: the RTA feature change from baseline at various follow-up intervals and the slope of the best-fit line to the RTA data series. These tRTA methods included Fourier-based and fractal-based features calculated from digitized images of 202 total hip replacement cases, including 70 that developed osteolysis. Results show that separation between the osteolysis and normal groups increased over time for the feature difference method, as the disease progressed, with area under the curve (AUC) values from receiver operating characteristic analysis of 0.65 to 0.72 at 15 years postsurgery. Separation for the slope method was also evident, with AUC values ranging from 0.65 to 0.76 for the task of distinguishing between osteolysis and normal cases. The results suggest that tRTA methods have the ability to measure changes in trabecular structure, and may be useful in the early detection of periprosthetic osteolysis.

Radiographic texture analysis in the characterization of trabecular patterns in periprosthetic osteolysis

RATIONALE AND OBJECTIVES

Periprosthetic osteolysis is a disease attributed to the body's reaction to fine polyethylene wear debris shed from total hip replacements. The purpose of this preliminary study was to investigate the ability of radiographic texture analysis (RTA) to characterize the trabecular texture patterns on pelvic images for osteolysis and normal total hip arthroplasty (THA) cases.

MATERIALS AND METHODS

Fourier-based and fractal-based texture features were calculated for a database of digitized radiographs from 202 THA cases, 70 of which developed osteolysis. The features were calculated from regions of interest selected at two time points: less than 1 month after surgery, and at the first clinical indication of osteolysis (or randomly selected follow-up time for normal cases). Receiver operating characteristic (ROC) analysis was used to compare feature performance at baseline and follow-up for osteolysis and normal cases.

RESULTS

Separation between the RTA features for osteolysis and normal cases was negligible at baseline and increased substantially for the follow-up images. The directional Fourier-based feature provided the best separation with an A(z) value from ROC analysis of 0.75 for the follow-up images, in the task of distinguishing between normal and osteolytic cases.

CONCLUSIONS

The results from this preliminary analysis indicate that qualitative changes in trabecular patterns from immediately after surgery to the eventual detection of osteolysis correspond to quantitative changes in RTA features. It therefore appears that RTA provides information that could potentially be useful to aid in the detection of this disease.

Wear and acetabular component orientation in third generation alumina-on-alumina ceramic bearings: an analysis of 33 retrievals [corrected]

We studied 33 third generation, alumina ceramic-on-ceramic bearings retrieved from cementless total hip replacements after more than six months in situ. Wear volume was measured with a Roundtest machine, and acetabular orientation from the anteroposterior pelvic radiograph. The overall median early wear rate was 0.1 mm(3)/yr for the femoral heads, and 0.04 mm(3)/yr for the acetabular liners. We then excluded hips where the components had migrated. In this stable subgroup of 22 bearings, those with an acetabular anteversion of < 15 degrees (seven femoral heads) had a median femoral head wear rate of 1.2 mm(3)/yr, compared with 0 mm(3)/yr for those with an anteversion of > or =15 degrees (15 femoral heads, p < 0.001). Even under edge loading, wear volumes with ceramic-on-ceramic bearings are small in comparison to other bearing materials. Low acetabular anteversion is associated with greater wear.

Minimum 6-year followup of highly cross-linked polyethylene in THA

To reduce wear rates and particulate debris, highly cross-linked polyethylene has been in use in total hip arthroplasty for 8 years. We designed this followup study to primarily determine the total penetration rate of the femoral head and the steady-state wear rate of cross-linked polyethylene in patients undergoing primary total hip arthroplasty. We retrospectively reviewed data from 182 patients (200 hips) with a minimum 6-year followup (mean, 6.9 years; range, 6-8 years) and an average age of 60.2 years at surgery. The average Harris hip score, University of California-Los Angeles activity score, and WOMAC score were 91.1, 6.3, and 11.3, respectively. Radiographic evaluation showed no evidence of loosening or osteolytic lesions around the cup or stem. No revisions were performed for polyethylene wear or liner fracture. The average steady-state wear rate was -0.002 +/- 0.01 mm per year and -0.026 +/- 0.13 mm per year for 28-mm and 32-mm head sizes, respectively. We observed no correlation between the total wear rate and femoral head size, brand of polyethylene, age, gender, primary diagnosis, mode of fixation, surgical approach, University of California-Los Angeles activity score, Harris hip score, or WOMAC. Highly cross-linked polyethylene liners are associated with excellent midterm clinical, radiographic, and wear results in this group of patients.

Third-generation alumina-on-alumina ceramic bearings in cementless total hip arthroplasty

BACKGROUND

Wear debris has been implicated in the pathogenesis of osteolysis. Alumina-on-alumina ceramic bearings have a low wear rate, which may reduce the prevalence of osteolysis. The purpose of this study was to determine the rates of wear and osteolysis associated with modern cementless hip arthroplasty with alumina-on-alumina bearings at five years.

METHODS

We analyzed a series of 301 third-generation alumina-on-alumina cementless primary total hip replacements in 283 patients. The average age of the patients at the time of the arthroplasty was fifty-eight years. All procedures were performed with use of the same surgical technique and the same implant at a single center. At a minimum of five years postoperatively, ten patients had died and twenty-two patients were lost to follow-up. We assessed patients clinically and radiographically, and all retrieved bearings were analyzed for wear.

RESULTS

At the time of the latest follow-up, the mean Harris hip score was 95 points. All surviving implants had radiographic evidence of stable bone ingrowth. There were nine revisions of one or both components. Four stems were revised following periprosthetic fracture, one stem was revised because of aseptic loosening at two months, and one stem was revised to facilitate a femoral shortening osteotomy. Two cups were revised because of psoas tendinitis, and both components of one arthroplasty were revised because of impingement and osteolysis. The rate of survival of both components, with revision because of aseptic loosening or osteolysis as the end point, was 99% at seven years. The retrieved femoral heads showed an early median wear rate of 0.2 mm(3) per year.

CONCLUSIONS

Cementless primary total hip prostheses with a third-generation alumina-on-alumina bearing showed very low wear and were associated with minimal osteolysis at the time of follow-up, at a minimum of five years.

Revision total hip replacement using cemented collarless double-taper femoral components

We investigated 219 revisions of total hip replacement (THR) in 211 patients using a collarless double-taper cemented femoral component. The mean age of the patients was 72 years (30 to 90). The 137 long and 82 standard length stems were analysed separately. The mean follow-up was six years (2 to 18), and no patient was lost to follow-up. Survival of the long stems to re-revision for aseptic loosening at nine years was 98% (95% confidence interval (CI) 94 to 100), and for the standard stems was 93% (95% CI 85 to 100). At five years, one long stem was definitely loose radiologically and one standard stem was probably loose. Pre-operative femoral bone deficiency did not influence the results for the long stems, and corrective femoral osteotomy was avoided, as were significant subsidence, major stress shielding and persistent thigh pain. Because of these reliable results, cemented long collarless double-taper femoral components are recommended for routine revision THR in older patients.

Progression of acetabular periprosthetic osteolytic lesions measured with computed tomography

BACKGROUND

A better understanding of the factors associated with the size and/or progression of osteolytic lesions has been hampered by a lack of sensitivity of radiographic measurement techniques.

METHODS

We retrospectively analyzed quantitative computed tomography scans that had been made with use of a high-resolution multi-slice scanner with a metal artifact-suppression protocol. The scans had been made to determine the volume of osteolytic lesions around thirty-five cementless Harris-Galante acetabular components that had been in situ for at least ten years. Repeat scans of thirty hips allowed for the measurement of progression in the size of osteolytic lesions over a one-year period. Associations between the volume of osteolytic lesions, progression in the size of the lesions, polyethylene wear since the time of implantation, change in component position, and patient-related variables (age, gender, body mass index, activity level, walking limitations, joint pain, and function) were determined.

RESULTS

In sixteen of the thirty hips that had repeat computed tomography scans, the lesions progressed in size during the study period. The median size of the lesions in these sixteen hips was 10.3 cm(3) at the time of the initial scan, compared with 13.3 cm(3) at a median of fifteen months later (p = 0.001). Osteolytic lesions measuring >10 cm(3) in volume on the initial scan were 2.5 times (95% confidence interval 1.3 to 4.8 times) more likely to progress in size over one year than smaller lesions were. Patients with greater polyethylene wear rates, higher activity levels, no walking limitations, and larger prosthetic femoral head dimensions (26 or 28 mm) had significantly larger osteolytic lesions (p < 0.0001, p = 0.009, p = 0.006, and p = 0.028, respectively). Progression in the size of the osteolytic lesions over one year was significantly associated with larger initial osteolytic lesions (p = 0.002), greater polyethylene wear rates (p = 0.009), and larger (26 or 28-mm) prosthetic femoral head dimensions (p = 0.019).

CONCLUSIONS

There is considerable variation in the rates of progression of the size of osteolytic lesions around stable acetabular components. Lesion size and the progression of lesion size are generally related to polyethylene wear rates, higher patient activity levels, and larger-diameter femoral heads. Osteolytic lesions measuring >10 cm(3) in volume are associated with a high rate of progression.

Estimation of the wear volume after total hip replacement. A simple access to geometrical concepts

Various formulas have been proposed to calculate the volume of prosthetic wear from the penetration depth of the head as assessed on plain radiographs, based on idealized, three-dimensional geometrical models of a prosthetic hip. However, for most published formulas no (or no simple) derivation is available and not all of them are correct. We describe a simple geometrical model that allows for transparent derivation of equations for various components of prosthetic wear volume and compare the calculated volumes with those obtained from published equations. These components are: (1) a right generalized cylinder resulting from a linear shift of a half spherical part of the prosthetic head into the hemispherical cup, (2) an additional wedge that is "cut" from the cup and (3) the wear from an optional additional cylindrical portion of the cup. We emphasize that calculation of a three-dimensional wear volume from linear penetration depth should be based on a geometrical concept that is transparent and simple enough for clinical research, such as the one presented. The incorrect formula of Kabo et al. should be completely abandoned.

Acetabular fixation options: first-generation modular cup curtain calls and caveats

This study reviewed the outcome of a single institution's experience with 910 primary total hip arthroplasties using 3 different types of modular, first-generation, hemispheric porous-coated cups. The population included 433 Arthopor, 394 ACS Triloc+, and 83 Harris-Galante components. Among 168 total hip arthroplasties that have undergone acetabular revision, aseptic loosening has occurred in 20 cases. Using liner or cup revision for any reason as an end point, we found that 15-year survivorship was 74.9% +/- 6.2% (95% confidence interval) for the Arthopor cups, 70.1% +/- 7.0% for the ACS Triloc+ components, and 89.3% +/- 10.3% for the Harris-Galante cups (P = .02, log rank). Despite a high incidence of revision for polyethylene wear-related complications and occasional late porous-coating delamination, survivorship using revision for aseptic loosening as an end point exceeded 95% at 15 years for all 3 cup designs.

The value of anteroposterior pelvic radiographs for evaluating pelvic osteolysis

We investigated the role of conventional radiographs and computed tomography scans for the routine followup of total hip arthroplasty patients. Among 92 total hip arthroplasties with a mean followup of 8.5 years, 94 acetabular lesions were detected among 63 hips using computed tomography and 42 of these hips had osteolysis diagnosed on radiograph. Using computed tomography as a gold standard, the sensitivity of anteroposterior pelvic radiographs for the detection of acetabular osteolysis was 67% and the specificity was 72%. Although smaller lesions were more frequently missed, osteolysis was diagnosed on radiograph in 20 of 22 total hip arthroplasties with lesion volumes of at least 10 mL. Because larger osteolytic lesions were generally detected on radiograph, two-dimensional and three-dimensional lesion sizes correlated. However, the limits of agreement for the volume estimates based on the radiograph area were -14.6 to 18.7 mL. Although radiographs can be useful to screen for clinically important pelvic osteolysis, computed tomography images are necessary to accurately measure lesion volumes.

Sports activity after total hip and knee arthroplasty : specific recommendations concerning tennis

Lower extremity total joint arthroplasties are among the most successful operations in orthopaedics. Presently, it appears that some patients wish to not only have general functions restored, but also desire the opportunity to return or continue on a high level of activity. This review summarises the literature concerning athletic activity, and tennis in particular, in relation to lower extremity total joint arthroplasties. Orthopaedic surgeons frequently recommend participation in low-impact sports such as swimming, walking, bicycling, bowling and golf. The patient's return to these recreational activities appears to be without problems. In contrast, there has been a general consensus from surgeons to avoid high-impact sports such as tennis and jogging after total joint arthroplasty, but there have been numerous studies that reported functional results being compatible with these activity levels. Conflicts emerge with some studies that describe lower survival rates for hip and knee arthroplasty in patients participating in high-impact sports. Most of these studies report that participation in sporting activities following total joint arthroplasty refers to increased polyethylene wear and debris, which could eventually result in implant failure. With recent advances in implant technology and surgical technique, the survival rates for modern prosthetic designs and patients with these high demands are promising. Various studies assessing the association between clinical outcome and participation in tennis did not demonstrate a harmful effect on implant survival rates. Although the majority of these studies do not reflect a true representation of the average patient undergoing total joint arthroplasty, more surgeons are confronted with the patients' desire to continue with sports activity. To optimise results, patients who demand higher levels of activity must be carefully selected, and must have the motivation and drive to optimise their results. In general, all patients should be encouraged to remain physically active to improve general health, maintain good bone quality, and improve implant fixation. There is still a need for prospective, randomised controlled studies concerning high activity and its impact on total joint arthroplasty.

Early clinical and radiographic analysis of the Fitmore cup

The Fitmore titanium mesh cementless acetabular component in 115 hip arthroplasties was reviewed at an average of 33 months of follow-up. None were revised nor had infection. One hip dislocated 4 years postoperatively. Two femoral components were revised. The average Harris Hip Score at the last follow-up was 90 points. In the 96 sets of radiographs available, there was no loosening or new radiolucency. One hip had nonprogressive osteolysis adjacent to a screw. This press-fit cup has its polar region flattened and is rim loading. Noncontact (gaps) at the acetabular floor is expected and is not critical for fixation. In all but 6 hips, these gaps filled. In 5 hips, a minimal gap (<or=0.5 mm) remained in part of the equatorial region. The Fitmore cup osseointegrates successfully.

Aging performance of a compliant layer bearing acetabular prosthesis in an ovine hip arthroplasty model

The wear performance of a polyurethane compliant layer (CL) material formed into an acetabular component and implanted into a sheep model of cemented total hip arthroplasty was assessed at 6, 12, 24, and 48 months. Four (11%) of 36 acetabular components debonded from the cement and one component was slightly loose at the cement-bone interface. There was no macroscopic evidence of fracture, wear, or deformation of the CL material on the articular surface of the acetabular components. Small numbers of polymeric wear particles was found in the hip synovial tissues of 10 sheep, most commonly in the early time groups, and were likely associated with initial wear of surface asperities. The wear performance of the CL was unchanged during a 48-month implantation period.

Hip and Knee Arthroplasty in the Geriatric Population

Osteoarthritis is the leading cause of hip and knee pathology in the geriatric population. Hip and knee arthroplasty are the definitive interventions to alleviate pain and restore physical functioning. Complications related to these procedures do occur: the most com-mon of these are infection, thromboembolism, dislocations, and periprosthetic fractures. New improvements related to minimally invasive and computer-assisted navigation surgery techniques are promising and already have shown excellent outcomes in patients exposed to joint arthroplasty.

Porous-coated cups fixed with screws: a 12-year clinical and radiostereometric follow-up study of 50 hips

BACKGROUND

Excellent mid-term results have stimulated the use of hemispherical porous-coated cups in hip replacement. With longer follow-up, there have been problems related to polyethylene wear and liner fixation, and osteolysis has been documented in reports of selected cases. We evaluated the clinical and radiographic results of 50 patients followed for 12 years.

PATIENTS AND METHODS

58 consecutive patients (58 hips), mean age 55 years, were operated with Harris-Galante (HG) I or II cups using line-to-line fit and additional screw fixation. Polyethylene linersgamma-sterilized in air and 32-mm ceramic heads were used. 8 patients died within 12 years, leaving 50 patients with a complete 12 year follow-up. 23 of the cups were also evaluated with radiostereometry (RSA) for migration, liner stability, and wear.

RESULTS

All metal shells were still in situ after 12 years. 4 hips had been revised due to femoral loosening. In these revisions, the liner had been exchanged due to wear and/or instability, resulting in a cup survival rate of 89%. 28 cups displayed osteolytic lesions, mainly in relation to screws. RSA revealed minimum translations, but in many cases there were pronounced liner rotations suggesting unstable liners within the metal shell. The annual proximal wear was 0.09 mm and the three-dimensional wear was 0.16 mm.

INTERPRETATION

RSA can predict the long-term performance of cup fixation. Low migration during the initial years after implantation indicates excellent long-term results regarding fixation of the metal shell. The main problem with this design appears to be liner instability and osteolysis, factors that are probably interrelated. Because these phenomena are clinically silent, we recommend regular follow-up of patients with HG cups to avoid sudden loosening and complicated revisions.

13-Jahres-Ergebnisse der CLS-Spreizpfanne in der primären Hüftendoprothetik

BACKGROUND

Clinical studies of the CLS expansion cup in hybrid hip arthroplasty generally show good results. However, follow-up times are limited to between 5 and 10 years. The aim of our study was to assess the clinical and radiological outcome of the CLS cup after more than 10 years.

MATERIAL AND METHOD

After a follow-up of 13 years (10-15 years), 41 of 186 patients with a total of 41 CLS cups were available for clinical and radiological evaluation. In addition, a digital analysis of all radiographs was done. This included measurement of the migration, inclination, polyethylene wear, shaft subsidence, and osteolytic lesions.

RESULTS

The average preoperative Harris hip score was 48, which increased to 81 at final follow-up. No acetabular loosening was found. Two cups (5%) showed osteolytic lesions not exceeding 50% of the specific zone according to DeLee and Charnley and were considered stable. There was no migration or inclination of the cups. The average polyethylene wear corresponded to 0.1 mm/year. Sixteen patients (39%) showed osteolyses around the stem and were considered loose.

CONCLUSION

The CLS expansion cup provides excellent clinical results after 13 years in hybrid total hip arthroplasty. Time-correlative polyethylene wear and the extremely high rate of stem loosening have no consequences for the cup stability in our patient group. Acetabular osteolysis is rare.

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.

Revisability of the CHARITE artificial disc replacement: analysis of 688 patients enrolled in the U.S. IDE study of the CHARITE Artificial Disc

STUDY DESIGN

A prospective, randomized, multicenter, FDA-regulated Investigational Device Exemption clinical trial.

OBJECTIVES

To analyze the incidence of, and reasons for, reoperation in all patients (treatment and control) enrolled in the IDE study.

SUMMARY OF BACKGROUND DATA

This is the first report of the incidence and nature of reoperations following lumbar TDR as part of a controlled, prospective, multicenter trial.

METHODS

A total of 688 patients meeting the inclusion and exclusion criteria were enrolled in one of three arms of the study at 14 centers across the United States. This cohort includes 71 nonrandomized cases, 205 randomized cases, and 313 continued access cases, all receiving the CHARITE Artificial Disc, as well as 99 randomized cases in the control group (ALIF with threaded fusion cages and autograft). A detailed analysis was performed of clinical chart notes, operative notes, and adverse event reports for all patients requiring reoperation following their index surgery.

RESULTS

Of the 589 patients with TDR, 52 (8.8%) required reoperation. Of the 99 patients with lumbar fusion, 10 (10.1%) required reoperation, and an additional 2 required surgery for adjacent level disease (P = 0.7401). There were 24 TDR patients who underwent a repeated anterior retroperitoneal approach, with 22 (91.7%) having had a successful removal of the prosthesis. Seven of the 24 TDR prostheses requiring removal were revised to another CHARITE Artificial Disc. The mean time to reoperation in all patients was 9.7 months. A total of 29 patients (4.9%) in the TDR group required posterior instrumentation and fusion as did 10 (10.1%) in the control group (P = 0.0562). At 2 years or more follow-up, 93.9%(553/589 = 93.9%) of patients receiving TDR with the CHARITE Artificial Disc had a successfully functioning prosthesis with a mean of over 7 degrees of flexion-extension mobility.

CONCLUSIONS

Lumbar TDR with the CHARITE Artificial Disc did not preclude any further procedures at the index level during primary insertion, with nearly one third being revisable to a new motion-preserving prosthesis and just over two thirds being successfully converted to ALIF and/ or posterior pedicle screw arthrodesis, the original alternative procedure.