Technology and Health Care 22 (2014) 263–272 DOI 10.3233/THC-140820 IOS Press
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Outcomes with cementless total hip resurfacing: 5 year follow-up Kerstin Radtke∗ , Max Ettinger, Henrik Heidgen, Thilo Floerkemeier, Yvonne Noll, Christina Stukenborg-Colsman, Henning Windhagen and Gabriela von Lewinski Department of Orthopedic Surgery, Hannover Medical School, Hannover, Germany Received 21 January 2014 Accepted 18 April 2014 Abstract. BACKGROUND: Resurfacing Arthroplasty (RA) of the hip has undergone resurgence with initially mainly good clinical results in young patients. It was mainly performed in younger more active patients with severe symptomatic arthritis of the hip including pelvic deformity. Furthermore the proximal femoral anatomy was preserved for surgical procedures in the future. OBJECTIVE: The aim of the study was to perform a prospective review of the very first 85 hips that had implantation of one cementless resurfacing system and a mean follow up of 5 years. METHODS: 85 cementless Total Hip Resurfacing devices have been performed in 75 patients in our orthopaedic department. The mean age of the study group was 49.8 years. Harries Hip Score, clinical examination data and radiographic parameters including the neck shaft angle (NSA), stem shaft angle (SSA) and detection of radiolucencies were analyzed. RESULTS: Estimated implant survival at five years of follow-up was 88.2% using revision for all causes as the end point. Mean HHS was 92.5 (range 80–100) five years after Resurfacing Arthroplasty. CONCLUSIONS: In conclusion we have to admit, that there was a high proportion of failed hip resurfacings but in the proportion that succeeded we saw good clinical results. Keywords: Total hip resurfacing, Resurfacing Arthroplasty (RA), clinical results
1. Background Resurfacing Arthroplasty (RA) was undergoing a resurgence with actually mainly good clinical results-up to 97% survivorship at three years follow up and good results with regard to function [1– 15] (Table 1). Especially patients with early primary or secondary osteoarthritis of the femoral head often require hip resurfacing arthroplasty [5–12,16,17]. In the younger past mechanisms of failure and success in total hip resurfacing have been identified [4,5,8,10,16,18–26]. After experiences procedure and resurfacing design have been changed and complications as femoral component loosening, notching, bone fractures and stress-shielding decreased. It was shown that bone preparation and cementing the stem when cysts in the femoral head are taller than 1 cm prevents loosening, but in general results in patients with cystic diseases are worse than in patients without femoral bone cysts. According to thinner femoral component design, notching and resulting bone fractures have decreased. In hip resurfacing by ∗
Corresponding author: Kerstin Radtke, Hannover Medical School (MHH), Department of Orthopedic Surgery, Anna-vonBorries-Str. 1-7, D-30625 Hannover, Germany. Tel.: +49 511 5354 847; Fax: +49 511 5354 682; E-mail: [email protected]. c 2014 – IOS Press and the authors. All rights reserved 0928-7329/14/$27.50
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K. Radtke et al. / Outcomes with cementless total hip resurfacing: 5 year follow-up Table 1 Results after hip resurfacing arthroplasty in the literature [1–5;31]
Author (Journal) Amstutz et al. (JBJS Am)
Year
n
Prosthesis
Follow-up
Results in Harris Hip Score 90
Revisions 11
Revision rate 11%
2010
100
Converse plus
11.7 years (10.8–12.9)
Rahman et al. (CORR)
2010
329
Birmingham hip resurfacing
6.6 years (5–9.2)
94.3
10
3.4%
Costi et al. (J Arthroplasty)
2010
270
Wagner resurfacing arthroplasty
5 years/ 10 years/ 16 years
82/ 79/ 49
−
26% 65% 83%
Klein et al. (Z Orthop Unfall)
2008
115
ASR Depuy
12.5 months 6–23 months
97
13
15.6%
Steffen et al. (JBJS Br)
2008
610
Birmingham hip resurfacing
4.2 years
93.1
23
3.8%
Mont et al. (CORR)
2007
724
Converse plus
33 months
93.3
15
2%
Present study
2011
85
ESKA implants, Type BS, Lübeck
60 months
94.2
10
11.7%
Table 2 Inclusion and exclusion criteria for Hip Resurfacing Arthroplasty in this study Inclusion criteria Patients with severe osteoarthritis of the hip Age 18–65 years
Exclusion criteria Patients refusing follow-up Revision hip arthroplasty
onlay technique the stress-shielding and loosening is reduced and trabecular bone will adapt to the fixation surface [4–8,12,15,20,21,27–31]. It was also shown that indices such as the surface arthroplasty risk index can be used to identify suitable patients [32]. It was additionally shown that success increases with the number of performed RAs by an orthopedic surgeon [14,32,33].
2. Objective Purpose of the present study is to evaluate the long-term results of a cementless hip resurfacing system.
3. Methods Between June 2004 and April 2006, 85 cementless Total Hip Resurfacing devices have been performed by 6 senior surgeons in 75 patients in our orthopaedic department. The hips were treated with a cementless metal-on-metal hip resurfacing system (Type Bionic System, ESKA Implants AG, Lübeck). Before starting the follow-up approval of the local ethical board was obtained. The study was performed with informed consent and following all the guidelines for experimental investigation in human subjects required by the Institutional Review Board (IRB)/Ethics Committee of Hannover Medical School of which all authors are affiliated. The mean age was 49.8 years (range 20 to 65 years). Mean age of the
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Fig. 1. Evaluated radiographic parameters: B = Femoral Offset, C = Offset of the Cup, D = Neck Shaft Angle, D’ = Stem Shaft Angle. (Colours are visible in the online version of the article; http://dx.doi.org/10.3233/THC-140820)
women in this study was 49.98 years, mean age of the men was 49.48 years. Mean body-mass-index (bmi) in this study was 26.59 kg/m2 . Mean bmi of the female study participants was 26.35 kg/m2 . Mean bmi of the male study participants was 27.01 kg/m2 . The mean duration of follow up was 60.1 months (range 48 to 62 months). All patients received operation due to severe osteoarthritis of the hip (definition Kellgren and Lawrence grade IV or more) (Table 2). 40% of the patients developed osteoarthritis because of hip dysplasia and in one patient an osteonecrosis of the femoral head was seen. The majority of the operated patients were female (64%). At the completion of the study no patient had died. All the data on these patients were collected: Harris Hip Score, clinical examination data and radiographic parameters including the neck shaft angle (NSA), stem shaft angle (SSA), detection of radiolucencies. 3.1. Surgical procedure In the initial period the devices have been performed by 6 senior surgeons. In the following we have reduced the number of surgeons to 3. We used an antero-lateral approach in all cases. A metal-on-metal bearing total hip resurfacing system (Type Bionic System, ESKA Implants AG, Lübeck) was performed in each case. The acetabular shell is hemispherical, the acetabular and the femoral component are with a porous coating for cementless fixation. The femoral component has a fixation stem that is available in 30, 40 and 50 mm lengths. Eleven sizes are available from 38 mm diameter to 58 mm, with increments in 2 mm. The components are made of Cobalt-Chrome-Molybdaen. 3.2. Postoperative procedure Postoperative management included full weight bearing mobilization. The patients received antiembolism stocking and pharmaceutical thrombo-embolism-prevention (s.c. injections of 40 mg Enoxaparin-Natrium). For outcome measurements we used the Harris Hip Score (HHS) to evaluate the disease-specific progress of the patients. We evaluated the range-of-motion at each follow-up visit. At each visit we evaluated radiographic parameters: We evaluated the neck shaft angle, the stem-shaft angle, the femoral offset and the offset of the cup according to radiographic analysis in the literature (demonstrated in Fig. 1) [9,29,34,35]. The difference between neck shaft angle and stem-shaft angle
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K. Radtke et al. / Outcomes with cementless total hip resurfacing: 5 year follow-up Table 3 Causes of failure for the revised hip resurfacing arthroplasties and time to revision Reason for revision Aseptic loosening Acetabular component only Femoral component only Inlay only Both femoral and acetabular component Fracture of femoral neck Femoral impingement Infection Total
No. of hips
Time to revision [months]
1 4 1 0 1 1 2 10
15 6.25 5 − 2 2 26 13.1
was calculated. All evaluated parameters were related to the point of implantation during the study. 48 of 75 patients had a minimum follow up of 48 months. 3.3. Statistical analysis We compared the means of the HHS with a one-way ANOVA combined with a post hoc Tukey Test (Prism 5, GraphPad Software Inc.). For all analyses, a statistical confidence level of 95% was selected. For demographic data, bmi, HHS and for radiographic parameters mean average and range was determined for the whole study population and for subgroups. For subgroups survivorship was analyzed and the results were compared. Time to revision and rate of failure were calculated.
4. Results The average duration of follow-up for this series was 60.15 months (range 48–62 months after the implantation). Rate of follow-up was 75% at five years after the resurfacing. Ten of 85 hips underwent revision of the resurfacing implants after a mean time of 13.1 months. Mean time to revision was 13.1 months (range 1–34 months), four were in men, six in women, giving a 1.1 times higher revision rate in male patients. Mean bmi in the group that underwent revision was 25.36 kg/m2 , what is lower than mean bmi in the whole study population. In this study we did not see an increased failure rate in overweight patients. The causes of failure for the 10 revised hips are listed in Table 3. Aseptic loosening occurred in six resurfaced hips, in four cases it concerned only the femoral component. Mean time to revision due to femoral component loosening was 6.25 months. Fracture of the femoral neck occurred in one single case with a time to revision of two months after the implantation. Two cases of deep wound infection were reported which required a debridement, antibiotics and were changed into a total hip arthroplasty after a period of 6 weeks after debridement. Time to revision was 24 and 28 months in these cases. We saw one single case of postoperative femoral impingement. In this case postoperative pain augmented. We did not see a benefit from postoperative conservative therapy and the hip was revised to short stem hip arthroplasty. Mean acetabular component diameter in revised hips was 53.1 mm (range 50–56 mm), mean head component diameter was 45.7 mm (range 42–50). The mean Harries Hip Score (HHS) was 94.2 points (range 80–100 points) five years postoperatively. Patient satisfaction was evaluated to be good or best in 93% of all cases five years after the implantation. Relating the results to the point of implantation during the study, it was seen that the mean HHS of the
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Table 4 Radiographic results and the Harris Hip Score related to the point of the operation during the study 2004 Mean Range 2005 Mean Range 2006 Mean Range
NSA [◦ ]
SSA [◦ ]
I NSA-SSA I [◦ ]
HHS [points]
135.6 128–138
129.6 92–147
10.6
85
134.94 128–136
133.75 120–149
5.69
96
130.15 127–134
129.4 127–130
3.06
100
Fig. 2. Lifetable demonstrating survival times of the implanted prosthesis.
patients who were operated in 2004 was 85, in 2005 it increased to 96, in 2006 it was 100 points (p < 0.05). Radiographic analysis showed that the mean preoperative neck-shaft angle (NSA) was 135.19◦ (range 128–139◦), the postoperative stem-shaft angle (SSA) was measured 132.15◦ (range 92–160◦). The difference between these two angles was measured 7.57◦ (range 0–46◦). In the patients who were operated in 2004 the mean NSA was measured 135.6◦ (range 128–138◦), the mean SSA was measured 129.6◦ (range 92–147◦). The mean difference between the two angles was calculated to be 10.6◦. For the patients, who were operated in 2005 the mean NSA was measured 134.94◦ (range 128–136◦), the mean SSA was measured to be 133.75◦ (range 120–149◦) and the difference between the two angles was calculated to be 5.69◦ . For the operated patients in 2006, the difference between NSA and SSA was calculated to be 3.06◦ with a mean NSA measured 130.15◦ (range 127–134◦) and a SSA measured 129.4◦ (range 127–130◦). The radiographic results and the Harris Hip Score related to the point of operation during the study are shown in Table 4 and Figs 3–4. No radiolucencies around the acetabular component or around the femoral component were detected in any of the radiographs. Risk factor groups were evaluated and are shown in Table 5. The rate of failure was 12.5% in male and 11.3% in female patients, it was calculated to be 1.13 times higher in male patients, what is only a trend. A significant higher revision rate in the presented study is shown for hip pathologies such as hip dysplasia (revision rate 33.3%) and for patients younger than 55 years (14.28%).
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K. Radtke et al. / Outcomes with cementless total hip resurfacing: 5 year follow-up Table 5 Risk factor group analysis risk factor groups Sex Male Female Age < 55 > 55 Pathologies Dysplasia Necrosis of the femoral head
rate of failure [◦ ]
time to failure [months]
12.5 11.3
18.5 5.0
11.53 14.28
23.33 8.71
33.3 1.3
12.3 2.0
Fig. 3. Results of the comparison of the means of the HHS.
Fig. 4. Radiographic results related to the point of the operation during the study.
Estimated implant survival was 88.2% at 5 years follow-up using revision for all causes as the end point. Lifetables were constructed on the basis of the survival times of the arthroplasties (shown in Fig. 2). 5. Conclusions Resurfacing Arthroplasty of the hip had become a common option as an alternative to Total Hip Arthroplasty in young patients with high physical demand. Preserving bone stock, including the femoral neck, part of the femoral head and the femoral canal is possible in RA, what is important for revision arthroplasties in very young patients. Patient interest and surgical demand increased during the last years [4–7,14,35–38]. This study shows good clinical results in the group that was followed up with a mean HHS of 92.5% (range 80–100%) five years after Total Hip Resurfacing. Ten of 85 resurfaced hips underwent revision operation, eight due to implant-associated complications, two due to deep infection. The survival analysis showed a cumulative implant survival of 88.5% at five years using revision for all causes as the end point. Rate of follow-up was 75% at five years after the Hip Resurfacing. We acknowledge some limitations of our study: First, we only performed and analyzed a small number of RAs (n = 85). Second, we prospectively analyzed only the clinical follow-up of these cases,
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including reasons for revision and risk factor analysis. Other studies evaluated metal-on-metal bearing THRs and the effects of metal ion levels. It was shown in a high number of published studies that a high acetabular component inclination correlates with high metal ion levels, pseudotumors, and component loosening [3,6–10]. Ion level analysis was additionally performed for all symptomatic resurfaced hips in the department, independent of participation in any study. The collected data does not lead to statistical results due to absence of preoperative data and data on asymptomatic patients. In this study, loosening was found in 2 cases, bone fracture was complication in 4 cases. No neurological complication was seen, no luxation is described. The number of eight RAs has been transformed into Total Hip Arthroplasty with a standard stem and six of eight have been transformed into Total Hip Arthroplasty with a short stem. A mainly big acetabular component diameter was found in the revised hips. Other studies described a contrary correlation between acetabular diameter and implant failure. Prosser et al. and Corten et al. described a statistically significant rate of revisions in head sizes less than 50 mm. Contrarian results were found by Buergi et al. Component oversizing could lead to an impingement of the psoas tendon [11–14]. We tried to track several predictive factors that are associated with implant failure. These included factors as gender, age and radiographic factors such as preoperative diagnosis, implant shaft angle, neck shaft angle and preoperative pathologies. Preoperative pathologies (with corresponding radiographic pathologies), such as hip dysplasia and avascular necrosis led to higher revision rates [11]. Schmalzried et al. reported lower Harris Hip Score in patients with preoperative lower bone density. We hypothesized female gender would be a negative factor in implant survival due to little implant sizes. Nunley et al. found a revision rate of 10% at 4 years for females over 65 years [15]. Comparable results were found by Prosser et al. and Amstutz et al. However, regarding other publications reveals mixed results [3,15–23]. In the presented study the rate of failure was 12.5% in male and 11.3% in female patients, it was calculated to be 1.13 times higher in male patients, what is only a trend. In the literature a contrarian result is reported. Reviews and the Analysis of the Australian Joint Registries show in general better results in men [11–14]. A significant higher revision rate in the presented study is shown for hip pathologies such as hip dysplasia (revision rate 33.3%). Higher revision rates are shown in this study for patients younger than 55 years (14.28%), what is also contrarian to the results in the literature, where best results were seen in patients under 55 and an increasing complication rate in patients older than 65 years. In the presented study the majority of young patients were operated due to deformities, older patients were exclusively operated due to arthrosis, what might explain this particular result. However, regarding 25% loss to follow up with mainly unclear results, failure rate is unacceptably high. We suggested an association between the experience of the surgeon and implant survivorship. Initial 6 hip surgery experienced senior surgeons performed THR and revision rate in the first year was 25.7%. After the reduction of the number of performing surgeons and with increasing experience the revision rate decreased to 6.25% in year two and three of using this implant. Analyzing radiographic patterns dependent on the time of implantation in the study shows that in the first year performing this study, there has been a high difference between NSA und SSA correlating with bad results in the HHS. Initial positioning of the femoral component was more in a varus position. Malpositioning of the acetabular component with a high inclination can lead to higher shear force what leads to component loosening [17]. In year two and three this difference decreased, revision rate decreased and the results in the HHS increased. A high number of studies have already analyzed this effect. It was shown that component mal-positioning is strongly associated with complication rate [15]. Other studies have already described high complication rates in early cases. Nunley et al. have seen higher complication rates for the surgeon’s first 25 cases compared to the second and they reported 26% of the first operated hips in a relative varus position [15,24]. This is in accordance to our results.
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High variation in revision rate is reported. Evaluating published literature in English language with more than 30 cases and a follow-up of more than five years shows revision rates between 3.4% and 26% at five years of follow-up [3,5,16,19,25–30]. Our revision rate for all reasons for revision (implantassociated failure and infections) was 11.7% at five years. Rahman et al. had a revision rate of 3.4% at 6.6 years follow-up [5], Steffen et al. reported a revision rate of 3.8% at 4.2 years of follow-up [31]. Both worked with the Birmingham Hip Resurfacing system what might not be comparable based on a different design and a cementing technique. Costi et al. reported a much higher revision rate and longer period of follow-up [4], what is not comparable to our time of follow-up. Allover, RA shows high revision rate that is much higher than revision rate in Total Hip Arthroplasty. However, the RAs that were followed up had indeed good clinical outcome with high results in functional scores. Additionally, in up-to-date literature, a prevalence of THR related pseudo-tumors (soft-tissue mass), soft tissue necrosis, vasculitis and hypersensitivity is described, even in asymptomatic patients. No correlation was reported between serum ion levels and the dimension of the tumor mass. Renal elimination of nickel, chromium, cobalt was much higher in patients with loose implants, same as concentration in adjacent tissues [32–34]. In conclusion we have to admit, that failure rate is unacceptably high. There is a high proportion of loss to follow up with unclear result. In the proportion that succeeded we saw good clinical results with a mean Harris Hip Score of 92.5 points. In accordance to the present literature of RA we also could show that correct positioning is mandatory for the long term results. However, regarding up-to-date-literature reporting complications as RA related pseudo-tumors, softtissue necrosis, vasculitis and hypertensitivity in high quantity at long-term follow-up, we have to resume that many effects and complications were unexpected and not to calculate. If possible, in young patients other surgical options should always be utilized. Diagnostics should be extended to visualize e.g. femoroacetabular impingement, initial osteonecrosis of the femoral head, acetabular labral lesions or other bordered defects. According to diagnostic findings, alternative treatment (e.g. arthroscopy, mini-open operation) should be executed [35,36]. In young patients without severe osteoarthritis, causes of osteoarthritis should always be treated to prevent of arthroplasty. In young patients with severe osteoarthritis of the hip as in the presented study, arthroscopy same as cartilage repair are no surgical options anymore. Actually, we see good clinical results in short stem hip arthroplasty. This type of implant also preserves bone stock, what is important for revision arthroplasties. Smith et al. had shown in a meta-analysis better functional outcomes following RA than after THA. But they had also shown greater incidences of complications and revision operations after RA [37]. Gulow et al. reported encouraging results for the short stem arthroplasty [38]. Regarding high revision rates and complications after RA, we see short stem THA as a good alternative to RA [37]. Even though the results of the present study demonstrate quite good long-term results in patients who reached this long-term follow-up we stopped the implantation of every implant system of RAs at the moment due to critical ethical situation of the current metal ion discussion on RAs.
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Outcomes with cementless total hip resurfacing: 5 year follow-up Kerstin Radtke∗ , Max Ettinger, Henrik Heidgen, Thilo Floerkemeier, Yvonne Noll, Christina Stukenborg-Colsman, Henning Windhagen and Gabriela von Lewinski Department of Orthopedic Surgery, Hannover Medical School, Hannover, Germany Received 21 January 2014 Accepted 18 April 2014 Abstract. BACKGROUND: Resurfacing Arthroplasty (RA) of the hip has undergone resurgence with initially mainly good clinical results in young patients. It was mainly performed in younger more active patients with severe symptomatic arthritis of the hip including pelvic deformity. Furthermore the proximal femoral anatomy was preserved for surgical procedures in the future. OBJECTIVE: The aim of the study was to perform a prospective review of the very first 85 hips that had implantation of one cementless resurfacing system and a mean follow up of 5 years. METHODS: 85 cementless Total Hip Resurfacing devices have been performed in 75 patients in our orthopaedic department. The mean age of the study group was 49.8 years. Harries Hip Score, clinical examination data and radiographic parameters including the neck shaft angle (NSA), stem shaft angle (SSA) and detection of radiolucencies were analyzed. RESULTS: Estimated implant survival at five years of follow-up was 88.2% using revision for all causes as the end point. Mean HHS was 92.5 (range 80–100) five years after Resurfacing Arthroplasty. CONCLUSIONS: In conclusion we have to admit, that there was a high proportion of failed hip resurfacings but in the proportion that succeeded we saw good clinical results. Keywords: Total hip resurfacing, Resurfacing Arthroplasty (RA), clinical results
1. Background Resurfacing Arthroplasty (RA) was undergoing a resurgence with actually mainly good clinical results-up to 97% survivorship at three years follow up and good results with regard to function [1– 15] (Table 1). Especially patients with early primary or secondary osteoarthritis of the femoral head often require hip resurfacing arthroplasty [5–12,16,17]. In the younger past mechanisms of failure and success in total hip resurfacing have been identified [4,5,8,10,16,18–26]. After experiences procedure and resurfacing design have been changed and complications as femoral component loosening, notching, bone fractures and stress-shielding decreased. It was shown that bone preparation and cementing the stem when cysts in the femoral head are taller than 1 cm prevents loosening, but in general results in patients with cystic diseases are worse than in patients without femoral bone cysts. According to thinner femoral component design, notching and resulting bone fractures have decreased. In hip resurfacing by ∗
Corresponding author: Kerstin Radtke, Hannover Medical School (MHH), Department of Orthopedic Surgery, Anna-vonBorries-Str. 1-7, D-30625 Hannover, Germany. Tel.: +49 511 5354 847; Fax: +49 511 5354 682; E-mail: [email protected]. c 2014 – IOS Press and the authors. All rights reserved 0928-7329/14/$27.50
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K. Radtke et al. / Outcomes with cementless total hip resurfacing: 5 year follow-up Table 1 Results after hip resurfacing arthroplasty in the literature [1–5;31]
Author (Journal) Amstutz et al. (JBJS Am)
Year
n
Prosthesis
Follow-up
Results in Harris Hip Score 90
Revisions 11
Revision rate 11%
2010
100
Converse plus
11.7 years (10.8–12.9)
Rahman et al. (CORR)
2010
329
Birmingham hip resurfacing
6.6 years (5–9.2)
94.3
10
3.4%
Costi et al. (J Arthroplasty)
2010
270
Wagner resurfacing arthroplasty
5 years/ 10 years/ 16 years
82/ 79/ 49
−
26% 65% 83%
Klein et al. (Z Orthop Unfall)
2008
115
ASR Depuy
12.5 months 6–23 months
97
13
15.6%
Steffen et al. (JBJS Br)
2008
610
Birmingham hip resurfacing
4.2 years
93.1
23
3.8%
Mont et al. (CORR)
2007
724
Converse plus
33 months
93.3
15
2%
Present study
2011
85
ESKA implants, Type BS, Lübeck
60 months
94.2
10
11.7%
Table 2 Inclusion and exclusion criteria for Hip Resurfacing Arthroplasty in this study Inclusion criteria Patients with severe osteoarthritis of the hip Age 18–65 years
Exclusion criteria Patients refusing follow-up Revision hip arthroplasty
onlay technique the stress-shielding and loosening is reduced and trabecular bone will adapt to the fixation surface [4–8,12,15,20,21,27–31]. It was also shown that indices such as the surface arthroplasty risk index can be used to identify suitable patients [32]. It was additionally shown that success increases with the number of performed RAs by an orthopedic surgeon [14,32,33].
2. Objective Purpose of the present study is to evaluate the long-term results of a cementless hip resurfacing system.
3. Methods Between June 2004 and April 2006, 85 cementless Total Hip Resurfacing devices have been performed by 6 senior surgeons in 75 patients in our orthopaedic department. The hips were treated with a cementless metal-on-metal hip resurfacing system (Type Bionic System, ESKA Implants AG, Lübeck). Before starting the follow-up approval of the local ethical board was obtained. The study was performed with informed consent and following all the guidelines for experimental investigation in human subjects required by the Institutional Review Board (IRB)/Ethics Committee of Hannover Medical School of which all authors are affiliated. The mean age was 49.8 years (range 20 to 65 years). Mean age of the
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265
Fig. 1. Evaluated radiographic parameters: B = Femoral Offset, C = Offset of the Cup, D = Neck Shaft Angle, D’ = Stem Shaft Angle. (Colours are visible in the online version of the article; http://dx.doi.org/10.3233/THC-140820)
women in this study was 49.98 years, mean age of the men was 49.48 years. Mean body-mass-index (bmi) in this study was 26.59 kg/m2 . Mean bmi of the female study participants was 26.35 kg/m2 . Mean bmi of the male study participants was 27.01 kg/m2 . The mean duration of follow up was 60.1 months (range 48 to 62 months). All patients received operation due to severe osteoarthritis of the hip (definition Kellgren and Lawrence grade IV or more) (Table 2). 40% of the patients developed osteoarthritis because of hip dysplasia and in one patient an osteonecrosis of the femoral head was seen. The majority of the operated patients were female (64%). At the completion of the study no patient had died. All the data on these patients were collected: Harris Hip Score, clinical examination data and radiographic parameters including the neck shaft angle (NSA), stem shaft angle (SSA), detection of radiolucencies. 3.1. Surgical procedure In the initial period the devices have been performed by 6 senior surgeons. In the following we have reduced the number of surgeons to 3. We used an antero-lateral approach in all cases. A metal-on-metal bearing total hip resurfacing system (Type Bionic System, ESKA Implants AG, Lübeck) was performed in each case. The acetabular shell is hemispherical, the acetabular and the femoral component are with a porous coating for cementless fixation. The femoral component has a fixation stem that is available in 30, 40 and 50 mm lengths. Eleven sizes are available from 38 mm diameter to 58 mm, with increments in 2 mm. The components are made of Cobalt-Chrome-Molybdaen. 3.2. Postoperative procedure Postoperative management included full weight bearing mobilization. The patients received antiembolism stocking and pharmaceutical thrombo-embolism-prevention (s.c. injections of 40 mg Enoxaparin-Natrium). For outcome measurements we used the Harris Hip Score (HHS) to evaluate the disease-specific progress of the patients. We evaluated the range-of-motion at each follow-up visit. At each visit we evaluated radiographic parameters: We evaluated the neck shaft angle, the stem-shaft angle, the femoral offset and the offset of the cup according to radiographic analysis in the literature (demonstrated in Fig. 1) [9,29,34,35]. The difference between neck shaft angle and stem-shaft angle
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K. Radtke et al. / Outcomes with cementless total hip resurfacing: 5 year follow-up Table 3 Causes of failure for the revised hip resurfacing arthroplasties and time to revision Reason for revision Aseptic loosening Acetabular component only Femoral component only Inlay only Both femoral and acetabular component Fracture of femoral neck Femoral impingement Infection Total
No. of hips
Time to revision [months]
1 4 1 0 1 1 2 10
15 6.25 5 − 2 2 26 13.1
was calculated. All evaluated parameters were related to the point of implantation during the study. 48 of 75 patients had a minimum follow up of 48 months. 3.3. Statistical analysis We compared the means of the HHS with a one-way ANOVA combined with a post hoc Tukey Test (Prism 5, GraphPad Software Inc.). For all analyses, a statistical confidence level of 95% was selected. For demographic data, bmi, HHS and for radiographic parameters mean average and range was determined for the whole study population and for subgroups. For subgroups survivorship was analyzed and the results were compared. Time to revision and rate of failure were calculated.
4. Results The average duration of follow-up for this series was 60.15 months (range 48–62 months after the implantation). Rate of follow-up was 75% at five years after the resurfacing. Ten of 85 hips underwent revision of the resurfacing implants after a mean time of 13.1 months. Mean time to revision was 13.1 months (range 1–34 months), four were in men, six in women, giving a 1.1 times higher revision rate in male patients. Mean bmi in the group that underwent revision was 25.36 kg/m2 , what is lower than mean bmi in the whole study population. In this study we did not see an increased failure rate in overweight patients. The causes of failure for the 10 revised hips are listed in Table 3. Aseptic loosening occurred in six resurfaced hips, in four cases it concerned only the femoral component. Mean time to revision due to femoral component loosening was 6.25 months. Fracture of the femoral neck occurred in one single case with a time to revision of two months after the implantation. Two cases of deep wound infection were reported which required a debridement, antibiotics and were changed into a total hip arthroplasty after a period of 6 weeks after debridement. Time to revision was 24 and 28 months in these cases. We saw one single case of postoperative femoral impingement. In this case postoperative pain augmented. We did not see a benefit from postoperative conservative therapy and the hip was revised to short stem hip arthroplasty. Mean acetabular component diameter in revised hips was 53.1 mm (range 50–56 mm), mean head component diameter was 45.7 mm (range 42–50). The mean Harries Hip Score (HHS) was 94.2 points (range 80–100 points) five years postoperatively. Patient satisfaction was evaluated to be good or best in 93% of all cases five years after the implantation. Relating the results to the point of implantation during the study, it was seen that the mean HHS of the
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267
Table 4 Radiographic results and the Harris Hip Score related to the point of the operation during the study 2004 Mean Range 2005 Mean Range 2006 Mean Range
NSA [◦ ]
SSA [◦ ]
I NSA-SSA I [◦ ]
HHS [points]
135.6 128–138
129.6 92–147
10.6
85
134.94 128–136
133.75 120–149
5.69
96
130.15 127–134
129.4 127–130
3.06
100
Fig. 2. Lifetable demonstrating survival times of the implanted prosthesis.
patients who were operated in 2004 was 85, in 2005 it increased to 96, in 2006 it was 100 points (p < 0.05). Radiographic analysis showed that the mean preoperative neck-shaft angle (NSA) was 135.19◦ (range 128–139◦), the postoperative stem-shaft angle (SSA) was measured 132.15◦ (range 92–160◦). The difference between these two angles was measured 7.57◦ (range 0–46◦). In the patients who were operated in 2004 the mean NSA was measured 135.6◦ (range 128–138◦), the mean SSA was measured 129.6◦ (range 92–147◦). The mean difference between the two angles was calculated to be 10.6◦. For the patients, who were operated in 2005 the mean NSA was measured 134.94◦ (range 128–136◦), the mean SSA was measured to be 133.75◦ (range 120–149◦) and the difference between the two angles was calculated to be 5.69◦ . For the operated patients in 2006, the difference between NSA and SSA was calculated to be 3.06◦ with a mean NSA measured 130.15◦ (range 127–134◦) and a SSA measured 129.4◦ (range 127–130◦). The radiographic results and the Harris Hip Score related to the point of operation during the study are shown in Table 4 and Figs 3–4. No radiolucencies around the acetabular component or around the femoral component were detected in any of the radiographs. Risk factor groups were evaluated and are shown in Table 5. The rate of failure was 12.5% in male and 11.3% in female patients, it was calculated to be 1.13 times higher in male patients, what is only a trend. A significant higher revision rate in the presented study is shown for hip pathologies such as hip dysplasia (revision rate 33.3%) and for patients younger than 55 years (14.28%).
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K. Radtke et al. / Outcomes with cementless total hip resurfacing: 5 year follow-up Table 5 Risk factor group analysis risk factor groups Sex Male Female Age < 55 > 55 Pathologies Dysplasia Necrosis of the femoral head
rate of failure [◦ ]
time to failure [months]
12.5 11.3
18.5 5.0
11.53 14.28
23.33 8.71
33.3 1.3
12.3 2.0
Fig. 3. Results of the comparison of the means of the HHS.
Fig. 4. Radiographic results related to the point of the operation during the study.
Estimated implant survival was 88.2% at 5 years follow-up using revision for all causes as the end point. Lifetables were constructed on the basis of the survival times of the arthroplasties (shown in Fig. 2). 5. Conclusions Resurfacing Arthroplasty of the hip had become a common option as an alternative to Total Hip Arthroplasty in young patients with high physical demand. Preserving bone stock, including the femoral neck, part of the femoral head and the femoral canal is possible in RA, what is important for revision arthroplasties in very young patients. Patient interest and surgical demand increased during the last years [4–7,14,35–38]. This study shows good clinical results in the group that was followed up with a mean HHS of 92.5% (range 80–100%) five years after Total Hip Resurfacing. Ten of 85 resurfaced hips underwent revision operation, eight due to implant-associated complications, two due to deep infection. The survival analysis showed a cumulative implant survival of 88.5% at five years using revision for all causes as the end point. Rate of follow-up was 75% at five years after the Hip Resurfacing. We acknowledge some limitations of our study: First, we only performed and analyzed a small number of RAs (n = 85). Second, we prospectively analyzed only the clinical follow-up of these cases,
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including reasons for revision and risk factor analysis. Other studies evaluated metal-on-metal bearing THRs and the effects of metal ion levels. It was shown in a high number of published studies that a high acetabular component inclination correlates with high metal ion levels, pseudotumors, and component loosening [3,6–10]. Ion level analysis was additionally performed for all symptomatic resurfaced hips in the department, independent of participation in any study. The collected data does not lead to statistical results due to absence of preoperative data and data on asymptomatic patients. In this study, loosening was found in 2 cases, bone fracture was complication in 4 cases. No neurological complication was seen, no luxation is described. The number of eight RAs has been transformed into Total Hip Arthroplasty with a standard stem and six of eight have been transformed into Total Hip Arthroplasty with a short stem. A mainly big acetabular component diameter was found in the revised hips. Other studies described a contrary correlation between acetabular diameter and implant failure. Prosser et al. and Corten et al. described a statistically significant rate of revisions in head sizes less than 50 mm. Contrarian results were found by Buergi et al. Component oversizing could lead to an impingement of the psoas tendon [11–14]. We tried to track several predictive factors that are associated with implant failure. These included factors as gender, age and radiographic factors such as preoperative diagnosis, implant shaft angle, neck shaft angle and preoperative pathologies. Preoperative pathologies (with corresponding radiographic pathologies), such as hip dysplasia and avascular necrosis led to higher revision rates [11]. Schmalzried et al. reported lower Harris Hip Score in patients with preoperative lower bone density. We hypothesized female gender would be a negative factor in implant survival due to little implant sizes. Nunley et al. found a revision rate of 10% at 4 years for females over 65 years [15]. Comparable results were found by Prosser et al. and Amstutz et al. However, regarding other publications reveals mixed results [3,15–23]. In the presented study the rate of failure was 12.5% in male and 11.3% in female patients, it was calculated to be 1.13 times higher in male patients, what is only a trend. In the literature a contrarian result is reported. Reviews and the Analysis of the Australian Joint Registries show in general better results in men [11–14]. A significant higher revision rate in the presented study is shown for hip pathologies such as hip dysplasia (revision rate 33.3%). Higher revision rates are shown in this study for patients younger than 55 years (14.28%), what is also contrarian to the results in the literature, where best results were seen in patients under 55 and an increasing complication rate in patients older than 65 years. In the presented study the majority of young patients were operated due to deformities, older patients were exclusively operated due to arthrosis, what might explain this particular result. However, regarding 25% loss to follow up with mainly unclear results, failure rate is unacceptably high. We suggested an association between the experience of the surgeon and implant survivorship. Initial 6 hip surgery experienced senior surgeons performed THR and revision rate in the first year was 25.7%. After the reduction of the number of performing surgeons and with increasing experience the revision rate decreased to 6.25% in year two and three of using this implant. Analyzing radiographic patterns dependent on the time of implantation in the study shows that in the first year performing this study, there has been a high difference between NSA und SSA correlating with bad results in the HHS. Initial positioning of the femoral component was more in a varus position. Malpositioning of the acetabular component with a high inclination can lead to higher shear force what leads to component loosening [17]. In year two and three this difference decreased, revision rate decreased and the results in the HHS increased. A high number of studies have already analyzed this effect. It was shown that component mal-positioning is strongly associated with complication rate [15]. Other studies have already described high complication rates in early cases. Nunley et al. have seen higher complication rates for the surgeon’s first 25 cases compared to the second and they reported 26% of the first operated hips in a relative varus position [15,24]. This is in accordance to our results.
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K. Radtke et al. / Outcomes with cementless total hip resurfacing: 5 year follow-up
High variation in revision rate is reported. Evaluating published literature in English language with more than 30 cases and a follow-up of more than five years shows revision rates between 3.4% and 26% at five years of follow-up [3,5,16,19,25–30]. Our revision rate for all reasons for revision (implantassociated failure and infections) was 11.7% at five years. Rahman et al. had a revision rate of 3.4% at 6.6 years follow-up [5], Steffen et al. reported a revision rate of 3.8% at 4.2 years of follow-up [31]. Both worked with the Birmingham Hip Resurfacing system what might not be comparable based on a different design and a cementing technique. Costi et al. reported a much higher revision rate and longer period of follow-up [4], what is not comparable to our time of follow-up. Allover, RA shows high revision rate that is much higher than revision rate in Total Hip Arthroplasty. However, the RAs that were followed up had indeed good clinical outcome with high results in functional scores. Additionally, in up-to-date literature, a prevalence of THR related pseudo-tumors (soft-tissue mass), soft tissue necrosis, vasculitis and hypersensitivity is described, even in asymptomatic patients. No correlation was reported between serum ion levels and the dimension of the tumor mass. Renal elimination of nickel, chromium, cobalt was much higher in patients with loose implants, same as concentration in adjacent tissues [32–34]. In conclusion we have to admit, that failure rate is unacceptably high. There is a high proportion of loss to follow up with unclear result. In the proportion that succeeded we saw good clinical results with a mean Harris Hip Score of 92.5 points. In accordance to the present literature of RA we also could show that correct positioning is mandatory for the long term results. However, regarding up-to-date-literature reporting complications as RA related pseudo-tumors, softtissue necrosis, vasculitis and hypertensitivity in high quantity at long-term follow-up, we have to resume that many effects and complications were unexpected and not to calculate. If possible, in young patients other surgical options should always be utilized. Diagnostics should be extended to visualize e.g. femoroacetabular impingement, initial osteonecrosis of the femoral head, acetabular labral lesions or other bordered defects. According to diagnostic findings, alternative treatment (e.g. arthroscopy, mini-open operation) should be executed [35,36]. In young patients without severe osteoarthritis, causes of osteoarthritis should always be treated to prevent of arthroplasty. In young patients with severe osteoarthritis of the hip as in the presented study, arthroscopy same as cartilage repair are no surgical options anymore. Actually, we see good clinical results in short stem hip arthroplasty. This type of implant also preserves bone stock, what is important for revision arthroplasties. Smith et al. had shown in a meta-analysis better functional outcomes following RA than after THA. But they had also shown greater incidences of complications and revision operations after RA [37]. Gulow et al. reported encouraging results for the short stem arthroplasty [38]. Regarding high revision rates and complications after RA, we see short stem THA as a good alternative to RA [37]. Even though the results of the present study demonstrate quite good long-term results in patients who reached this long-term follow-up we stopped the implantation of every implant system of RAs at the moment due to critical ethical situation of the current metal ion discussion on RAs.
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