Short cementless femoral stems are increasingly popular as they allow for less dissection for insertion. Use of such stems with the anterior approach (AA) may be associated with considerable per-operative fracture risk. This study's primary aim was to evaluate whether patient-specific femoral- and pelvic- morphology and surgical technique, influence per-operative fracture risk. In doing so, we aimed to describe important anatomical thresholds alerting surgeons. This is a single-center, multi-surgeon retrospective, case-control matched study. Of 1145 primary THAs with a short, cementless stem inserted via the AA, 39 periprosthetic fractures (3.4%) were identified. These were matched for factors known to increase fracture risk (age, gender, BMI, side, Dorr classification, stem offset and indication for surgery) with 78 THAs that did not sustain a fracture. Radiographic analysis was performed using validated software to measure femoral- (canal flare index [CFI], morphological cortical index [MCI], calcar-calcar ratio [CCR]) and pelvic- (Ilium-ischial ratio [IIR], ilium overhang, and ASIS to greater trochanter distance) morphologies and surgical technique (% canal fill). Multivariate and Receiver-Operator Curve (ROC) analysis was performed to identify predictors of fracture. Femoral factors that differed included CFI (3.7±0.6 vs 2.9±0.4, p3.17 and II ratio>3 (OR:29.2 95%CI: 9.5–89.9, p<0.001). Patient-specific anatomical parameters are important predictors of fracture-risk. When considering the use of short stems via the AA, careful radiographic analysis would help identify those at risk in order to consider alternative stem options

Short cementless femoral stems are increasingly popular as they allow for less dissection for insertion. Use of such stems with the anterior approach (AA) may be associated with considerable per-operative fracture risk. This study's primary aim was to evaluate whether patient-specific femoral- and pelvic- morphology and surgical technique, influence per-operative fracture risk. In doing so, we aimed to describe important anatomical thresholds alerting surgeons. This is a single-centre, multi-surgeon retrospective, case-control matched study. Of 1145 primary THAs with a short, cementless stem inserted via the AA, 39 periprosthetic fractures (3.4%) were identified. These were matched for factors known to increase fracture risk (age, gender, BMI, side, Dorr classification, stem offset and indication for surgery) with 78 THAs that did not sustain a fracture. Radiographic analysis was performed using validated software to measure femoral- (canal flare index [CFI], morphological cortical index [MCI], calcar-calcar ratio [CCR]) and pelvic- (Ilium-ischial ratio [IIR], ilium overhang, and ASIS to greater trochanter distance) morphologies and surgical technique (% canal fill). Multivariate and Receiver-Operator Curve (ROC) analysis was performed to identify predictors of fracture. Femoral factors that differed included CFI (3.7±0.6 vs 2.9±0.4, p<0.001) and CCR (0.5±0.1 vs 0.4±0.1, p=0.006). The mean IIR was higher in fracture cases (3.3±0.6 vs 3.0±0.5, p<0.001). % Canal fill was reduced in fracture cases (82.8±7.6 vs 86.7±6.8, p=0.007). Multivariate analysis and ROC analyses revealed a threshold CFI of 3.17 was predictive of fracture (sensitivity:84.6% / specificity:75.6%). Fracture risk was 29 times higher when patients had CFI>3.17 and II ratio>3 (OR:29.2 95%CI: 9.5–89.9, p<0.001). Patient-specific anatomical parameters are important predictors of fracture-risk. When considering the use of short stems via the AA, careful radiographic analysis would help identify those at risk in order to consider alternative stem options

Aims. Femoral bone preparation using compaction technique has been shown to preserve bone and improve implant fixation in animal models. No long-term clinical outcomes are available. There are no significant long-term differences between compaction and broaching techniques for primary total hip arthroplasty (THA) in terms of migration, clinical, and radiological outcomes. Methods. A total of 28 patients received one-stage bilateral primary THA with cementless femoral stems (56 hips). They were randomized to compaction on one femur and broaching on the contralateral femur. Overall, 13 patients were lost to the ten-year follow-up leaving 30 hips to be evaluated in terms of stem migration (using radiostereometry), radiological changes, Harris Hip Score, Oxford Hip Score, and complications. Results. Over a mean follow-up period of 10.6 years, the mean stem subsidence was similar between groups, with a mean of -1.20 mm (95% confidence interval (CI) -2.28 to -0.12) in the broaching group and a mean of -0.73 mm (95% CI -1.65 to 0.20) in the compaction group (p = 0.07). The long-term migration patterns of all stems were similar. The clinical and radiological outcomes were similar between groups. There were two intraoperative fractures in the compaction group that were fixed with cable wire and healed without complications. No stems were revised. Conclusion. Similar stem subsidence and radiological and clinical outcomes were identified after the use of compaction and broaching techniques of the femur at long-term follow-up. Only the compaction group had intraoperative periprosthetic femur fractures, but there were no long-term consequences of these. Cite this article: Bone Jt Open 2021;2(12):1035–1042

Aims. BoneMaster is a thin electrochemically applied hydroxyapatite (HA) coating for orthopaedic implants that is quickly resorbed during osseointegration. Early stabilization is a surrogacy marker of good survival of femoral stems. The hypothesis of this study was that a BoneMaster coating yields a fast early and lasting fixation of stems. Methods. A total of 53 patients were randomized to be treated using Bi-Metric cementless femoral stems with either only a porous titanium plasma-sprayed coating (P group) or a porous titanium plasma-sprayed coating with an additional BoneMaster coating (PBM group). The patients were examined with radiostereometry until five years after surgery. Results. At three months, the mean total translation (TT) was 0.95 mm (95% confidence interval (CI) 0.68 to 1.22) in the P group and 0.57 mm (95% CI 0.31 to 0.83) in the PBM group (p = 0.047). From two to five years, the TT increased by a mean of 0.14 mm (95% CI 0.03 to 0.25) more in the P group than in the PBM group (p = 0.021). In osteopenic patients (n = 20), the mean TT after three months was 1.61 mm (95% CI 1.03 to 2.20) in the P group and 0.73 mm (95% CI 0.25 to 1.21) in the PBM group (p = 0.023). After 60 months, the mean TT in osteopenic patients was 1.87 mm (95% CI 1.24 to 2.50) in the P group and 0.82 mm (95% CI 0.30 to 1.33) in the PBM group (p = 0.011). Conclusion. There was less early and midterm migration of cementless stems with BoneMaster coating compared with those with only a porous titanium plasma-sprayed coating. Although a BoneMaster coating seems to be important for stem fixation, especially in osteopenic patients, further research is warranted. Cite this article: Bone Joint J 2022;104-B(6):647–656

We examined 108 uncemented femoral stems with modular femoral heads which had been retrieved for reasons other than loosening. There were detectable amounts of wear and corrosion in 10 of 29 (34.5%) mixed-alloy components and 7 of 79 (9%) single-alloy components after a mean implantation time of 25 months. We found no correlation between the presence or extent of corrosion or surface damage and any of time in situ, initial diagnosis, reason for removal, age, or weight. Stems with wear and corrosion were less likely to show histological bony ingrowth. The interface between the head and stem of modular total hip components is a possible source of ion release and wear debris, but wear and corrosion were totally absent in most specimens. This suggests that this problem could be avoided, and that further research is required to develop manufacturing methods which would minimise such changes

Six porous-coated, uncemented femoral components were revised at a mean of 34.5 months for persistent thigh pain. At operation the stems were rigidly stable, difficult to extract, and showed good bony ingrowth. The four men and two women, with an average age of 59 years, all had thigh pain starting within the first year, progressive over time and unresponsive to conservative measures. These cases show that rigid fixation with good bony ingrowth does not guarantee the clinical success of a porous-coated uncemented femoral stem

Purpose. The purpose of this study is to evaluate the midterm results of cementless revision total hip arthroplasty (THA) using Wagner Cone Prosthesis. Material and Methods. Between 1996 and 2007, 36 hips in 36 consecutive patients underwent femoral revision THA using Wagner Cone Prosthesis. Among them 28 hips were followed for more than 5 years. The mean age at revision surgery was 57 years and a mean follow-up was 7.6 years. The Paprosky classification system was used for preoperative bone loss evaluation. Clinical results were evaluated using Harris hip scores. For evaluation of the femoral component, radiolucent lines at bone-implant interfaces were evaluated and femoral component vertical subsidence was measured. Heterotopic bone formation and complications were also evaluated. Results. The mean period from 1. st. operation to revision THA was 8.0 years. For the femoral bone loss, in eleven hips bone grafting was done. For the prevention of femoral stem fracture, femoral wiring was done in 12 hips. In eighteen hips acetabular cup revision was done simultaneously and in 5 hips isolated stem revision was done. The mean Harris hip score improved from 52 to 83 at final follow-up. With respect to radiological results all femoral stems showed bone ingrowths, 3 out of 28 (10.7%) femoral stems showed subsidence more than 5 mm. Two patients needed acetabular revision for acetabular loosening during follow up period. There was one patient who complained of anterior thigh pain. One patient had recurrent dislocation and required revision surgery for soft tissue augmentation. Conclusions. We achieved favorable midterm clinical and radiological results for femoral stem revisions using Wagner cone prosthesis. This cementless femoral stem can be a good option for femoral stem revision

A customised, uncemented femoral stem was introduced clinically in 1995 after several years of development and pre-clinical testing. All the patients operated in our hospital have entered a prospective clinical study. The aim of this study is to present the short-term clinical data. Furthermore, the measurement of implant migration and the periprosthetic bone remodelling at two years is also reported. Materials and methods: The femoral stem is designed from preoperative CT-scans, machined in Ti-alloy and circumferentially coated with a 50μm hydroxyapatite (HA) layer in the proximal 50-70%. Fifty-one patients (median age 52 years) have been followed clinically for a minimum of 3 years using the Merle-d’Aubignè score. Migration of the femoral stem has been measured with radiostereometry (RSA), the precision of the measurements is better than 0.080 mm for translations and 0.30° for rotations. Periprosthetic bone remodelling is expressed as the change in bone mineral density (BMD) in seven zones (Gruen) relative to the postoperative values. RSA- and DEXA measurements have been performed postoperatively and then after 3, 6, 12 and 24 months. Results: One stem had to be revised after 3 months due to a periprosthetic fracture. The clinical scores were as follows (preop/3 years): Pain 2.6/5.5, ROM 3.7/5.7, function 2.7/5.9, total score 9.1/17.1. Six patients complained of thigh pain during the first two years, however, this complication resolved spontaneously in five patients within the three years follow-up. The mean subsidence after two years was 0.055 mm (SE ±0.045 mm) and the mean axial rotation was 0.29° (SE ± 0.12°). The mean bone loss in zone 7 was 34%; in the other zones the bone loss was less than 14%. The mean overall bone loss was 8%. Discussion: The short-term clinical experiences with this patient-specific, cementless femoral stem are encouraging. The stem seems to be very stable during the first two postoperative years indicating that biological fixation of the femoral stems has been achieved. The change in the BMD was less than 14% in all Gruen zones, except for the proximal medial area where the bone loss was 34%

We compared the clinical and radiological outcomes of two cementless femoral stems in the treatment of patients with a Garden III or IV fracture of the femoral neck. A total of 70 patients (70 hips) in each group were enrolled into a prospective randomised study. One group received a short anatomical cementless stem and the other received a conventional cementless stem. Their mean age was 74.9 years (50 to 94) and 76.0 years (55 to 96), respectively (p = 0.328). The mean follow-up was 4.1 years (2 to 5) and 4.8 years (2 to 6), respectively. Perfusion lung scans and high resolution chest CTs were performed to detect pulmonary microemboli. At final follow-up there were no statistically significant differences between the short anatomical and the conventional stems with regard to the mean Harris hip score (85.7 (66 to 100) versus 86.5 (55 to 100); p = 0.791), the mean Western Ontario and McMaster Universities Osteoarthritis Index (17 (6 to 34) versus 16 (5 to 35); p = 0.13) or the mean University of California, Los Angeles activity score (5 (3 to 6) versus 4 (3 to 6); p = 0.032). No patient with a short stem had thigh pain, but 11 patients (16%) with a conventional stem had thigh pain. No patients with a short stem had symptomatic pulmonary microemboli, but 11 patients with a conventional stem had pulmonary microemboli (symptomatic in three patients and asymptomatic in eight patients). One hip (1.4%) in the short stem group and eight (11.4%) in the conventional group had an intra-operative undisplaced fracture of the calcar. No component was revised for aseptic loosening in either group. One acetabular component in the short stem group and two acetabular components in the conventional stem group were revised for recurrent dislocation. Our study demonstrated that despite the poor bone quality in these elderly patients with a fracture of the femoral neck, osseo-integration was obtained in all hips in both groups. However, the incidence of thigh pain, pulmonary microemboli and peri-prosthetic fracture was significantly higher in the conventional stem group than in the short stem group

Aims: The aim of this study was to measure implant migration and bone remodelling of the proximal femur two years after insertion of a customized or a standard femoral stem. Materials and methods: In a prospective, randomized study 26 hips (26 patients) have been examined postoperatively and after 3, 6, 12 and 24 months using radiostereometry (RSA) and DEXA. Thirteen hips received a customized femoral stem (Unique, SCP as) and 13 hips received a standard uncemented femoral stem (ABG¨, Stryker-Howmedica). An uncemented acetabular cup (Duraloc¨, DePuy) was used in all hips. The mean age of the patients was 55 (24–67) years. Results: The median displacement of the custom/ standard femoral stems was 0.04/0.01 mm along the - medial-lateral axis, 0.08/0.02 mm along the proximal-distal axis and 0.03/0.08 mm along the anterior-posterior axis, respectively. Statistically, there was no difference between the two groups. One custom stem subsided 5.2 mm at one year, but showed no further migration at two years. The mean decrease in bone mineral density (BMD) in all Gruen zones was 6% in the Custom-group and 7% in the ABG-group. The most pronounced bone loss was seen in Zone 7 and was 21% and 25% for the two groups, respectively. Discussion: We found no statistically signiþcant difference in short-term stem migration comparing a customized and a standard, uncemented femoral stem. Furthermore, the changes in bone mineral density were almost equal in femurs with either type of prosthesis

Background: Over the past decade, several modifications have been introduced to uncemented femoral stems. The design of the stems, however, still classically fall under two categories: anatomical and straight. The purpose of this paper is to report the first clinical, radiographic and periprosthetic densitometry results of a cementless total hip arthroplasty performed with an off-the-shelf extended metaphyseal loading device. Fifty-eight consecutive patients who received aproximally loading non-cemented hip prosthesis were followed for an average of 4.4 years. Patients were clinically and radiographically followed at 3 weeks, 3 months, 6 months, 1 year and yearly thereafter. In addition, a group of 8 consecutive patients were studied with Dual X-Ray Absorptiometry Scans(DEXA) at the same intervals during the first year and at 18 months after surgery. The extended proximal geometry of the device allowed for initial and secondary stability reflected by the low subsidence values over time. The maintenance of periprosthetic bone stock over time and the absence of stress shielding can be explained by the proximal loading pattern of the stem

Purpose:. In order to acquire good stability of an arthroplasty hip, the proper placement of the implants, which prevents impingement between the stem neck and the socket, is important. In general, the anteversion of the uncemented femoral stem depends on the relationship between the three-dimensional structure of the proximal femoral canal and the proximal stem geometry. The exact degree of the anteversion will be known just after broaching during the operation. If the stem anteversion could be forecasted, preoperative planning of the socket placement would be relatively easy. Furthermore, when a high degree of anteversion is forecasted, a special femoral stem to reduce it, such as a modular stem, could be prepared. However, we experienced that the preoperatively measured anteversion of the femoral neck using computer tomography (CT) was sometimes different from that of the stem measured during the operation. The purpose of this study was to investigate whether the preoperative measurement would be helpful to predict the stem anteversion by examining the relationship between the anteversion of the femoral neck and the stem. Patients and methods:. A total of 57 primary THAs by one senior surgeon from April 2011 until March 2012 were carried out. Two THAs using a modular stem and one for the hip after previous proximal femoral osteotomy were excluded. The remaining 54 THAs were examined. The used uncemented stems were designed for proximal metaphyseal fixation. CT scans, including the distal femoral condyles as well as the hips, were carried out in all cases preoperatively. The anteversion of the femoral neck was measured as the angle of the maximum longitudinal line of the cross section of the femoral neck to the line connecting the posterior surfaces of both of the distal femoral condyles (Fig. 1). The femoral neck anteversion was measured at three levels (Fig. 1). The stem anteversion was measured just after the femoral broaching during the THA. The relationship between the anteversion angles of the femoral neck and of the stem was examined by using a regression analysis. The institutional review board approved this study. Results:. The anteversion angles of the femoral neck varied widely when they were measured at all of the levels (Table 1). The anteversion angle of the femoral neck was not always identical to that of the stem. There were 32–46% of cases in which the difference between the stem anteversion and the femoral neck anteversion was within 5 degrees. There was a significant relationship between the anteversion of the stem and that of the femoral neck measured at all three levels (Fig. 2). When it was measured just below the femoral head, it was the closest to one, and the p-value was the lowest. Discusssion and Conclusions:. The anteversion of the uncemented stem could be calculated by using the formula to show the relationship between the stem anteversion and the femoral neck antevesion measured preoperatively. The values appeared to be sufficiently correct for making clinical decisions, although a prospective study may be necessary to confirm this

The aim of this study is the presentation of the results in 48 cases of revision THA with excessive proximal bone loss with the use of the Wagner cementless femoral stem. The bone loss classified with the AAOS system for proximal femoral bone deficiency in type I (17 patients), II (27 patients), and III (4 patients). We used the titanium alloy Wagner stem trying to achieve primary distal stabilisation because of its conical shape and its longitudinal ridges while we expected secondary proximal stabilization due to the osseointegration properties of the material. We didn’t use grafts. The mean follow- up is 9, 6 years. The results are very satisfactory to excellent with marked pain relief, improvement of the walking ability and excessive bone restoration in the proximal part of the femur. 7 of the patients had a symptomless stem subsidence up to 16mm the first year with subsequent stabilization thereafter. One of the patients required a new revision the 7th postoperative year due to stem’s fracture in its distal part. We conclude that the Wagner stem in these difficult THA revisions offers firm primary distal fixation, impressive proximal bone regeneration and satisfactory clinical outcomes without using grafts

Background

Uncemented dual-tapered stems are a popular choice for primary total hip arthroplasty (THA). The purpose of this study was to examine long-term outcomes after primary THA utilizing a single dual-tapered stem.

Aims

The aim of this study was to compare the survivorship and radiographic outcomes at ten-year follow-up of three prospective consecutive series of patients each of which received a different design of cementless femoral components for total hip arthroplasty (THA).

We have evaluated the difference in the migration patterns over two years of two cementless stems in a randomised, controlled trial using radiostereophotogrammetric analysis (RSA). The implants studied were the Furlong HAC stem, which has good long-term results and the Furlong Active stem, which is a modified version of the former designed to minimise stress concentrations between the implant and bone, and thus to improve fixation.

A total of 23 Furlong HAC and 20 Furlong Active stems were implanted in 43 patients. RSA examinations were carried out immediately post-operatively and at six, 12 and 24 months post-operatively.

The subsidence during the first year in the Furlong HAC stem, was approximately one-third that of the Furlong Active stem, the measured mean subsidence of the femoral head at six months being 0.27 mm (95% confidence interval (CI) 0.03 to 0.51) and 0.99 mm (95% CI 0.38 to 1.60), respectively (p = 0.03). One Active stem continued to subside during the second year. All hips, regardless of the type of stem were clinically successful as judged by the Oxford hip score and a derived pain score without any distinction between the two types of stem.

The initial stability of the Furlong Active stem was not as good as the established stem which might compromise osseo-integration to the detriment of long-term success. The changes in the geometry of the stem, to minimise stress have affected the attainment of initial stability.

Introduction and Aims: With interest in minimally invasive surgery, and smaller incisions for total hip arthroplasty (THA), ways to ensure appropriate alignment are critical. Femoral stem varus has been associated with poorer results. We report the incidence of varus placement of a tapered, proximally plasma-sprayed, titanium femoral component and describe the outcomes of varus at minimum five-year follow-up.

Method: Between 1986 and 1997, 1080 tapered, proximally plasma-sprayed femoral components were implanted in primary cementless THA at one institution. Twenty-six components in 25 patients were placed in five degrees or more of varus. Two patients were lost to follow-up. The need for further surgery was assessed and Harris hip scores evaluated.

Results: Harris hip scores improved an average of 44 points. All femoral components were judged to be osteo-integrated. There was no displacement or progression into further varus, or impending failures. One well-fixed stem was revised at an outside institution for unexplained pain at 2.5 years. Survival with aseptic loosening as an end-point is 100 percent. Overall survival of the femoral component is 96 percent at 10 years average follow-up.

Conclusion: As visualisation decreases with decreasing incision length, a component that is reliably placed into appropriate position is required. Implant position with this component is forgiving. It may be an excellent choice for less-invasive techniques with compromised visualisation. In varus, the stem performs well, with no revisions for aseptic loosening and a 96 percent survival at up to 16 years.

A clinical and radiographic study was conducted on 97 total hip arthroplasties (79 patients) performed for congenital hip dislocation using three-dimensional custom cementless stem. The mean age was 48 years (17 to 72). The mean follow up was 123 months (83 to 182).

According to Crowe, there were 37 class 1, 28 class 2, 13 class 3 and 19 class 4. The average lengthening was 25 mm (5 to 58 mm), the mean femoral anteversion 38.6° (2° to 86°) and the correction in the prosthetic neck −23.6° (71° to 13°). The average Harris hip score improved from 58 to 93 points. Six hips (6.2%) required a revision. The survival rate was 97.7% ± 0.3% at 13 years.

Custom cementless stem allows anatomical reconstruction and good functional results in a young and active population with disturbed anatomy, while avoiding a femoral osteotomy.

A clinical and radiological study was conducted on 97 total hip replacements performed for congenital hip dislocation in 79 patients between 1989 and 1998 using a three-dimensional custom-made cementless stem. The mean age at operation was 48 years (17 to 72) and the mean follow-up was for 123 months (83 to 182).

According to the Crowe classification, there were 37 class I, 28 class II, 13 class III and 19 class IV hips. The mean leg lengthening was 25 mm (5 to 58), the mean pre-operative femoral anteversion was 38.6° (2° to 86°) and the mean correction in the prosthetic neck was −23.6° (−71° to 13°). The mean Harris hip score improved from 58 (15 to 84) to 93 (40 to 100) points. A revision was required in six hips (6.2%). The overall survival rate was 89.5% (95% confidence interval 89.2 to 89.8) at 13 years when two hips were at risk.

This custom-made cementless femoral component, which can be accommodated in the abnormal proximal femur and will correct the anteversion and frontal offset, provided good results without recourse to proximal femoral corrective osteotomy.

We report the results of cementless total hip arthroplasty using the Bi-metric titanium femoral stem at a minimum follow up of 10 years and a mean of 12.2 years (range 10–17).

64 hips (43 male/21 female) were implanted consecutively into 54 patients between 1988 and 1995. The mean age at operation was 54.3 years (range 42–65). All patients had a Bi-metric uncemented stem (Biomet UK). The first 13 patients received a metal backed screw in acetabular cup (TTAP-ST, Biomet UK) with the remainder receiving metal backed pressfit cups (Universal, Biomet UK).

All patients were followed up annually and assessed using the Hip Society Score (HSS; max 40 points) to record pain, function and mobility. Survivorship was calculated using the Kaplan-Meier method.

57 hips were followed up for a minimum of ten years. There were 4 deaths (6 hips) before completion of follow up and 1 patient was lost to follow up.

Using revision for any reason as the end point of the study; survivorship for the total hips at 10 years was 89.5% (95% confidence interval: 78.1–96.1%) with a mean Hip Society Score of 34.9 (range 20–40) compared to 14.5 (range 8–24) pre-operatively (p< 0.01 student t test).

Survivorship for the femoral stem in isolation was 100% at 10 years (95% CI 93.7–100%) and there continues to be no revisions to date at a mean follow up of 12.2 years.

The screw fix cup performed poorly with 3 acetabular revisions (including 1 liner change) before the 10 year follow up, a failure rate of 23.1%. There has sub-sequently been a further 4 acetabular revisions.

Ten year survivorship for the pressfit cup is 93.5% (95% CI 82.0–98.8%) with 3 revisions (including 2 liner changes) at ten years. There has subsequently been one further acetabular revision and 9 further liner changes (29.5% failure rate).

There have been no recorded infections and no instances of thigh pain.

Radiographs at ten years showed all the femoral stems were stable with no evidence of migration. Two stems had small radiolucent lines at the bone-implant interface but no signs of loosening. One stem had an area of osteolysis in Gruen zone 7 but didn’t require revision. Rates of osteolysis were extremely low given the large amounts of particulate debris in the hip from the worn acetabular liners.

In conclusion, although neither cup has proved to be particularly successful the Bi-metric stem has performed well at 10 year follow up and continues to do so. This is inspite of the fact they were implanted into a young and active group of patients.