In this prospective study a total of 80 consecutive
Chinese patients with Crowe type I or II developmental dysplasia of
the hip were randomly assigned for hip resurfacing arthroplasty
(HRA) or total hip replacement (THR). Three patients assigned to HRA were converted to THR, and three
HRA patients and two THR patients were lost to follow-up. This left
a total of 34 patients (37 hips) who underwent HRA and 38 (39 hips)
who underwent THR. The mean follow-up was 59.4 months (52 to 70)
in the HRA group and 60.6 months (50 to 72) in the THR group. There was
no failure of the prosthesis in either group. Flexion of the hip
was significantly better after HRA, but there was no difference
in the mean post-operative Harris hip scores between the groups.
The mean size of the acetabular component in the HRA group was significantly
larger than in the THR group (49.5 mm vs 46.1 mm, p = 0.001). There was
no difference in the mean abduction angle of the acetabular component
between the two groups. Although the patients in this series had risk factors for failure
after HRA, such as low body weight, small femoral heads and dysplasia,
the clinical results of resurfacing in those with Crowe type I or
II hip dysplasia were satisfactory. Patients in the HRA group had
a better range of movement, although neck-cup impingement was observed.
However, more acetabular bone was sacrificed in HRA patients, and
it is unclear whether this will have an adverse effect in the long
term.
Reports of improved functional outcome of Metal on Metal Hip
Purpose. This study was performed to evaluate clinical and radiographic outcomes of Hip
Few independent studies have reported the outcome of resurfacing arthroplasty of the hip. The aim of this study was to report the five-year clinical outcome and seven-year survival of an independent series. A total of 610 Birmingham Hip
Humeral resurfacing arthroplasty has been advocated as an alternative to stemmed humeral component designs given its ability to preserve proximal bone stock. Further, these implants have become more attractive given the possibility of stem-related complications including humeral fracture, stress shielding, and osteolysis; complications that may necessitate fixation, revision to long stem components, or reverse total shoulder arthroplasty. As more total shoulder arthroplasties are performed in younger patient populations, the likelihood of increased revision procedures is inevitable. Maintaining proximal bone stock in these cases with use of a resurfacing arthroplasty not only facilitates explant during revision arthroplasty, but preservation of proximal metaphyseal bone facilitates reimplantation of components. Clinical results of these resurfacing components have demonstrated favorable results similar to stemmed designs. Unfortunately, resurfacing arthroplasty may not be as ideal as was hoped with regard to recreating native humeral anatomy. Further, resurfacing arthroplasty may increase the risk of peri-prosthetic humeral fracture, and lack of a formal humeral head cut makes glenoid exposure more difficult, which may be associated with a higher degree of neurovascular injury. Stemless humeral components are designed for strong metaphyseal fixation and avoid the difficulty with glenoid exposure seen in resurfacing designs, as these components require a formal humeral head cut. Early clinical outcomes of a single stemless design demonstrated significant improvements in clinical outcome scores, without evidence of component migration, subsidence or loosening. The only mid-term clinical results of stemless design implants are seen with the Arthrex Eclipse system (Arthrex, Naples, FL). In a prospective study involving 78 patients at 5-year follow-up, significant improvements were observed in clinical outcome scores. While there was evidence of proximal stress shielding in an older population, this did not influence shoulder function. The overall revision rate was 9% at 5 years, with no component necessitating revision as a result of humeral component loosening.
Aim: The aim of this study was to assess the role of Hip Arthroscopy in the patient with a symptomatic
Introduction: The suitability of third generation metal-on-metal hip resurfacing for patients with a primary diagnosis of osteonecrosis (ON) has been debated. The preservation of femoral head bone stock for femoral prosthetic support is essential for long term stability of the implant. We hypothesized that the Kaplan-Meier survival estimates for resurfacing patients with a primary diagnosis of ON would be significantly lower than the survival estimates for resurfacing patients with a primary diagnosis of osteoarthritis (OA). Methods: One thousand one hundred and forty-eight patients were implanted with a modern hip resurfacing system as part of a United States multi-center investigational device exemption (IDE) study. Of these, 116 subjects had a preoperative diagnosis of ON. A multivariate analysis of variance was performed to identify risk factors for component revision for any reason. Results: A diagnosis other than OA was found to be one significant risk factor for revision. However, the survival estimates were not significantly different (95.9% and 95.8% at 24 months for OA and ON, respectively, p=0.46) when comparing the OA group to the ON group. Comparing only the Ficat stage III and IV to the OA population also did not show a significant difference in implant survival (95.9% OA and 96.1% ON III/IV at 24 months, p=0.57). Discussion:
The Birmingham
Introduction:
Purpose: A multicenter prospective evaluation of the Conserve Plus resurfacing implant (Wright Medical Technology) was undertaken to assess clinical and radiographic outcomes as well as ion levels. This study focuses on the serum, erythrocyte and urinary levels of cobalt and chromium in those patients undergoing hip resurfacing arthroplasty. Methods: A subset of patients enrolled in a multicenter trial to assess hip resurfacing arthroplasty had serum, erythrocyte and urinary cobalt and chromium levels measured. Levels were assessed preoperatively, then at three months, six months then yearly thereafter. Clinical outcome measurements were performed with WOMAC and Rand questionnaires. Results: Fifty-four out of 124 patients enrolled in the overall study had cobalt and chromium ion assessments performed. During the first year there was an increase in serum cobalt levels from 1.4 ug/l at 3 months to 2.4 ug/l at one year. Serum chromium levels increased from 1.4 ug/l at 3 months to 3.5 ug/l at one year. Erythrocyte cobalt levels increased from 0.8 ug/l at 3 months to 1.4 ug/l at one year. Erythrocyte chromium levels decreased from 1.5 ug/l at 3 months to 1.4 ug/l at one year. Urinary levels for cobalt increased from 12.7 ug/l at 3 months to 13.8 ug/l at one year. Urinary chromium levels rose from 4.0 ug/l at 3 months to 5.1 ug/l at one year. Conclusions: Increasing ion levels were seen during the first year post hip resurfacing arthroplasty. Clinical outcomes demonstrate predictable improvements in pain and function consistent with hip replacement surgery.
The early designs of hip resurfacing implants suffered high rates of early failure, making it impossible to obtain valuable mid-term radiostereophotogrammetric (RSA) results. The metal-on-metal Birmingham Hip
Purpose of study: We report the results of a prospective case series of 10 patients who developed tumour-like masses following resurfacing arthroplasty. Method: Ten subjects were referred to the tumour service at the Nuffield Orthopaedic Centre with symptomatic masses around the hip, all had previously received a resurfacing arthroplasty. We report the clinical, radiographic and histologic features of these cases. Results: MRI and ultrasound scanning was preformed, which demonstrated masses with solid and cystic components. Biopsy was performed and subsequent histological examination revealed a profound plasma-cell lymphocytic response associated with metal wear debris. There were no infections in this series. Three subjects required revision surgery. Conclusion: Over 50,000 resurfacing arthroplasties have been implanted worldwide over the past ten years. Although the early clinical results are encouraging little is known about the long term consequences of large head metal on metal bearing surfaces. Despite this, these devices are being widely marketed and are often implanted in younger patients.
Aim: We present the outcome of Birmingham Hip
Introduction. Hip
Introduction. There is no consensus on the ideal management of young, active patients with disabling coxarthrosis. Within this group, patients with femoral head defects secondary to cysts or avascular necrosis pose particular challenges.
Aims:
Purpose:
A ceramic-on-ceramic hip resurfacing implant (cHRA) was developed and introduced in an MHRA-approved clinical investigation to provide a non metallic alternative hip resurfacing product. This study aimed to examine function and physical activity levels of patients with a cHRA implant using subjective and objective measures both before and 12 months following surgery in comparison with age and gender matched healthy controls. Eighty-two unilateral cHRA patients consented to this study as part of a larger prospective, non-randomised, clinical investigation. In addition to their patient reported outcome measures (PROMs), self- reported measures of physical activity levels and gait analysis were undertaken both pre- operatively (1.5 weeks) and post operatively (52 weeks). This data was then compared to data from a group of 43 age gender and BMI matched group of healthy controls. Kinetics and kinematics were recorded using an instrumented treadmill and 3D Motion Capture. Statistical parametric mapping was used for analysis. cHRA improved the median Harris Hip Score from 63 to 100, Oxford Hip score from 27 to 48 and the MET from 5.7 to 10.3. cHRA improved top walking speed (5.75km vs 7.27km/hr), achieved a more symmetrical ground reaction force profile, (Symmetry Index value: 10.6% vs 0.9%) and increased hip range of motion (ROM) (31.7° vs 45.9°). Postoperative data was not statistically distinguishable from the healthy controls in any domain. This gait study sought to document the function of a novel ceramic hip resurfacing, using those features of gait commonly used to describe the shortcomings of hip arthroplasty. These features were captured before and 12 months following surgery. Preoperatively the gait patterns were typical for OA patients, while at 1 year postoperatively, this selected group of patients had gait patterns that were hard to distinguish from healthy controls despite an extended posterior approach. Applications for regulatory approval have been submitted.
Introduction: Preliminary results of the Birmingham Hip
In 1997 the Birmingham Hip Resurfacing was introduced to address the needs of young active patients. Alternative designs were introduced to try and improve wear performance. The aim of this study was a comparative cohort study of two types of metal-on-metal bearing to determine the mechanism of failure at 15 years. The study reviewed 91 Brimingham Hip Resurfacings (BHR) (Smith and Nephew) and 715 DUROM hip resurfacing (Zimmer) procedures in prior to 2009. Failure was defined as revision of either component for any reason. Kaplan-Meyer survivorship analysis performed. Routine follow-up with serum metal ion levels and radiographs. Mean follow-up was 17.9 years (range 15.2 – 25.1). The mean age at operation was 51.6 years (SD 8.6, range 20.7 to 70.2), including 299 women (37.1%). The Birmingham resurfacing demonstrated 92.3% survivorship at 15 years (SE 2.8, 95% CI 3.9 – 7.8) and 90.0% at latest follow-up (SE 3.5, 95% CI 4.9 to 9.4). By comparison, the DUROM survivorship at 15 years was 89.1% at 15 years (SE 1.2, 95% CI 2.0 to 2.5) and 87.4% (SE 1.3, 95% CI 2.5 to 2.3) at latest follow-up. There was no statistically significant difference in survivorship between groups (p= 0.32). Survival in male patients was 92.7% compared to 80.0% in females. The reported failures occurred from Adverse Reaction to Metal Debris (32 patients), periprosthetic femoral neck fracture (6) and aseptic loosening (41), PJI (12) and undiagnosed pain (6). The mean cobalt and chromium levels at last follow-up were 33.4 nmol/L and 36.5 nmol/L respectively. This study demonstrates two differently designed metal-on-metal hip resurfacing provided a durable alternative to total hip replacement, particularly in younger male patients with osteoarthritis. Differences in design did determine the reason for revision with acetabular fixation being one of the principal failure mechanisms for the DUROM compared to elevated ion levels.
Although hip replacement and resurfacing procedures both aim to restore mobility, improve joint function, and relieve pain, it is unclear how each differ in terms of gait mechanics and if they are affected by varying walking speeds. We compared limb symmetry and ground reaction force (GRF) profiles between bilateral total hip arthroplasty patients (THA), bilateral hip resurfacing arthroplasty patients (HRA), and healthy control participants (CON) during level-treadmill walking at different speeds. Bilateral THA and bilateral HRA patients (nTHA = 15; nHRA = 15; postoperative 12–18 months), and age-, mass-, and height-matched CON participants (nCON = 20) underwent gait analysis on an instrumented treadmill. Walking trials started at 4 km/h and increased in 0.5 km/h increments until top walking speed (TWS) was achieved. Gait symmetry index (SI = 0% for symmetry) was assessed between limbs during weight-acceptance, mid-stance and push-off phases of gait; and vertical GRFs were captured for the normalised stance phase using statistical parametric mapping (SPM; CI = 95%).Abstract
Objectives
Methods
Iliopsoas tendonitis occurs in up to 30% of patients after hip resurfacing arthroplasty (HRA) and is a common reason for revision. The primary purpose of this study was to validate our novel computational model for quantifying iliopsoas impingement in HRA patients using a case-controlled investigation. Secondary purpose was to compare these results with previously measured THA patients. We conducted a retrospective search in an experienced surgeon's database for HRA patients with iliopsoas tendonitis, confirmed via the active hip flexion test in supine, and control patients without iliopsoas tendonitis, resulting in two cohorts of 12 patients. The CT scans were segmented, landmarked, and used to simulate the iliopsoas impingement in supine and standing pelvic positions. Three discrete impingement values were output for each pelvic position, and the mean and maximum of these values were reported. Cup prominence was measured using a novel, nearest-neighbour algorithm. The mean cup prominence for the symptomatic cohort was 10.7mm and 5.1mm for the asymptomatic cohort (p << 0.01). The average standing mean impingement for the symptomatic cohort was 0.1mm and 0.0mm for the asymptomatic cohort (p << 0.01). The average standing maximum impingement for the symptomatic cohort was 0.2mm and 0.0mm for the asymptomatic cohort (p << 0.01). Impingement significantly predicted the probability of pain in logistic regression models and the simulation had a sensitivity of 92%, specificity of 91%, and an AUC ROC curve of 0.95. Using a case-controlled investigation, we demonstrated that our novel simulation could detect iliopsoas impingement and differentiate between the symptomatic and asymptomatic cohorts. Interestingly, the HRA patients demonstrated less impingement than the THA patients, despite greater cup prominence. In conclusion, this tool has the potential to be used preoperatively, to guide decisions about optimal cup placement, and postoperatively, to assist in the diagnosis of iliopsoas tendonitis.
Hip resurfacing arthoplasty (HRA) showed promising early and mid-terms results at the beginning of the new millennium. Adverse local tissue reactions associated with metal debris considerably slowed down the implantation of HRA which use is now limited to a few specialized centers. The long term success of this procedure, however, is still largely unknown. This study aimed to provide the clinical results of a series of 400 consecutive HRA with a minimum follow-up of 20 years. All patients treated with Conserve®Plus HRA between November 1996 and November 2000 were retrospectively selected and 355 patients (400 hips) were included. The clinical results of this series was previously reported in 2004 at a follow up of 2 to 6 years[1]. There were 96 women (27%) and 259 men (73%). Mean age at surgery was 48.2 ± 10.9 years. Long-term survivorship was assessed with Kaplan-Meier survival estimates. UCLA hip scores and SF-12 quality of life scores were collected at follow-up visits. Radiographic positioning of the acetabular component was assessed with the computation of the contact patch to rim (CPR) distance. Radiolucencies about the metaphyseal stem and around the acetabular component were recorded to assess the quality of the component fixation.Background
Methods
A 34-year-old woman with a benign form of osteopetrosis developed osteoarthritis of the hip. In order to avoid the difficulties associated with inserting the femoral component of a conventional total hip arthroplasty, a hybrid metal-on-metal resurfacing was performed. There were several technical challenges associated with the procedure, including the sizing of the component, press-fit fixation of the acetabular component and femoral head preparation, as well as trying to avoid a fracture. No surgical complication occurred. After more than a year following surgery, the patient showed excellent clinical function and remained satisfied with the outcome. We conclude that the hybrid metal-on-metal resurfacing arthroplasty represents a valuable option for the treatment of patients with osteopetrosis and secondary hip osteoarthritis.
We performed 96 Birmingham resurfacing arthroplasties of the hip in 71 consecutive patients with avascular necrosis of the femoral head. A modified neck-capsule-preserving approach was used which is described in detail. The University of California, Los Angeles outcome score, the radiological parameters and survival rates were assessed. The mean follow-up was for 5.4 years (4.0 to 8.1). All the patients remained active with a mean University of California, Los Angeles activity score of 6.86 (6 to 9). Three hips failed, giving a cumulative survival rate of 95.4%. With failure of the femoral component as the endpoint, the cumulative survival rate was 98.0%. We also describe the combined abduction-valgus angle of the bearing couple, which is the sum of the inclination angle of the acetabular component and the stem-shaft angle, as an index of the optimum positioning of the components in the coronal plane. Using a modified surgical technique, it is possible to preserve the femoral head in avascular necrosis by performing hip resurfacing in patients with good results.
Patients undergoing hip resurfacing arthroplasty (HRA) is typically reserved for highly active patients. Patient Reported Outcome Measures (PROMs) such as the Oxford Hip Score (OHS) are reported to have ceiling effects, which may limit physicians' ability to measure health gain in these patients. The Metabolic Equivalent of Task (MET) index is a validated compendium assigning energy expenditure to a wide range of activities; for example, a slow walk expends 2.9 kcal/kg/hour, golf expends 4.0 kcal/kg/hour, while moderate lacrosse typically expends 8.1 kcal/kg/hour. We hypothesized that for patients with high OHS (47–48) after HRA, the MET index could better discriminate between high-performing individuals. We evaluated 97 consecutive HRA patients performed by a single surgeon. They prospectively completed an online Oxford Hip Score. They also listed three activities which they had performed independently in the preceding 2 weeks with a Likert-scale slider denoting intensity of effort. Matched data-sets were obtained from 51 patients, from which 23 had OHS of 47–48 at 6-months. Their activity with the highest MET index was selected for analysis. The 23 patients' OHS improved from 29.3 ± 7.0 preoperatively to 47.6 ± 0.5 after 6-months, while their MET indices improved from 8.5 ± 3.7 to 12.9 ± 3.5 kcal/kg/hr. The activities performed by these high-performance individuals ranged from the lowest, pilates (8.05 kcal/kg/hour), to highest, running at 22km/hr (23 kcal/kg/hour). 45% of patients undergoing HRA in this cohort had OHS of 47 and 48 at 6-months after surgery. Unlike the OHS, the MET index described variation in physical activity in these high-performance individuals, and did so on an objective measurable scale.
Hip resurfacing arthroplasty (HRA) lost its popularity because of excessive wear of the ASR M/M design. Now that causes of wear have been identified, it remains an attractive treatment option for young patients because of its bone-conserving nature, the preservation of bone mineral density, a low dislocation rate, and its biomechanical precision. We assessed the long-term clinical outcomes of 1074 patients (1321 hips) who were implanted with hybrid Conserve®Plus HRA, with 556 surgeries performed in patients younger than 50 years of age (average, 41.6 years) compared to 765 surgeries performed in patients 50 years or older (average, 58.1 years). 74% of the patients were male. There were no exclusion criteria. The <50 group had a larger proportion of dysplasia and hips operated during the first generation of surgical technique.Introduction
Methods
Hip resurfacing remains a safe and effective option according to registry data. Results in women were less reliable, in part owing to soft tissue impingement. Biolox Delta ceramic bearing couples are now in widespread use with very low complication rates. We set about merging these three elements to develop a novel hip resurfacing arthroplasty. Contours of both acetabular and femoral components were generated from biometric data, adapted to the constraints of ceramic machining, to ensure that radii blended from the bearing surface avoiding any sharp boundaries. Plasma spray coating with titanium and hydroxyapatite direct onto ceramic was developed and tested using shear, tensile and taber abrasion testing. Wear testing was carried out to 5 million cycles according to the ASTM. Destructive testing was carried out in a variety of test conditions and angles. Cadaveric testing demonstrated stability using a single use disposable instruments for both conventional and patient specific procedures. Very low dose CT enabled the entire interface to be observed as the Ceramic is radiolucent, enhancing migration analysis, which will be undertaken at 4 intervals to confirm stability. Functional scores and gait analysis will be used in the safety study. The CE study recruitment is underway, with first in human trials starting in summer 2017. PMA submission will follow the safety study. Commercial release of the device in Europe is unlikely before 2019, and in the USA may not be until 2027. The path to novel device development in 2017 is very costly in time and money.
We aimed to demonstrate the clinical safety of a novel anatomic cementless ceramic hip resurfacing device. Concerns around the safety of metal on metal arthroplasty have made resurfacing less attractive, while long term function continues to make the concept appealing. Biolox Delta ceramic is now used in more than 50% of all hip arthroplasties, suggesting that it's safety profile is acceptable. We wondered if a combination of these concepts might work? The preclinical testing of anatomic hip resurfacing device developed by our group was presented last year. A twenty patient safety study was designed. Patients had to be between the ages of 18 and 70. The initial size range was restricted to femoral heads between 46 and 54, representing the common sizes of hip resurfacing. The primary outcomes were clinical safety, PROMs and radiological control. Secondary outcomes include CTRSA and metal ion levels. 20 patients were recruited, aged 30–69. 7 were women and 13 were men. There were no operative adverse events in their operations undertaken between September 2017 and February 2018. One patient had a short episode of atrial fibrillation on the second postoperative day, and no other complications. At three months the median oxford hip score had risen from 27 (range 14–38) to 46 (31–48). Cobalt and chromium levels were almost undetectable at 3 months. Fixation appeared satisfactory in all patients, with no migration detected in either component. CTRSA is in process. The initial safety of a novel cementless ceramic resurfacing device is demonstrated by this data. The 10 year, 250 case efficacy study will continue in 5 other European centres.
Metal on metal hip resurfacing (MMHR) has been advocated for the younger patient for several reasons including for the preservation of bone stock and ease of revision to total hip replacement (THR), thus ‘buying an additional operation’ for the patient. This rationale however assumes a good functional outcome after the revision to a THR and that the results of the ‘revision primary’ will not be compromised by the resurfacing which preceded it. We present our data on a consecutive series of 68 revised MMHRs. Between September 1997 and September 2009, 927 consecutive patients underwent a hip resurfacing procedure performed by one of three senior surgeons at our institution. The Cormet resurfacing system was used for all patients. Sixty-eight of these patients had their resurfacing revised. Oxford hip score (OHS) obtained at a minimum of 12 months follow-up was used as the primary outcome measure.Introduction
Methods
Because of concerns regarding excessive wear and short-term failures attributed to the metal-on-metal bearings, the use of metal-on-metal hip resurfacing arthroplasty (MOMHRA) has been greatly reduced since 2008, despite great mid-term results for well-designed implants and in certain patient populations. The true cause of excessive wear was then unknown. Therefore, identification of true risk factors for the procedure became paramount to refine indications and improve survivorship outcomes. Over the last 10 years, a systematic search of the US national library of Medicine and National institutes of health with the key words “metal-on-metal” and hip resurfacing” was conducted and returned 2186 items. Of these items, 862 were deemed relevant to our research purposes and entered in our center's reference database from which this review was performed.Introduction
Methods
As an alternative to total hip arthroplasty (THA), hip resurfacing arthroplasty (HRA) provides the advantage of retaining bone stock. However, femoral component loosening and femoral neck fracture continue to be leading causes of revision in HRA. Surgical technique including cementation method and bone preparation, and patient selection are known to be important for fixation. This study was designed to understand if and to what extent compromise in bone quality and the presence of cysts in the proximal femur contribute to resurfacing component loosening. A finite element (FE) model of a proximal femur was used to calculate the stress in the cement layer. Bone density to Young's modulus relationship was used to calibrate the bone stiffness in the model using computed tomography. A contemporary resurfacing implant (BHR, Smith & Nephew) was used in the FE model. The effect of reduced bone quality (35% reduction relative to normal baseline; osteoporosis threshold) and presence of cysts on stress in the bone cement layer was then assessed using the same FE model. The center of the cyst (a localized spherical cavity 1 cm in diameter) was located directly under the contact patch. Simulations were run with two locations of the center of the cyst, on the surface of the resected bone and 1 cm below it. The surface cyst was filled with bone cement, but the inner cyst was empty. The contact force and location for the model were obtained from instrumented implant studies. Simulations were run representing the peak loads during two activities, jogging and stand-up from seated position. While density reduction of the bone reduced the stress in the CoCr femoral head, the Von-Mises stress in the cement layer was amplified. The peak Von-Mises stress in the cement layer under the contact patch increased more than six times for the jogging activity, and more than ten times for the stand-up activity, relative to values for normal bone density. The impact of cysts on the cement layer stress or the strain distributions in the bone were minimal. The results show a greater risk of failure of the cement layer under conditions of reduced bone density. In contrast cement stresses and bone strains appeared to be relatively immune to a surface cyst filled with bone cement or an empty inner cyst. Contraindications of hip resurfacing include severe osteopenia and multiple cysts of the femoral head, however no strict or quantitative criteria exist to guide patient selection. Research similar to the one presented herein, maybe key to developing better patient selection criteria to reduce risk associated with compromised femoral head fixation.
In a study of 76 consecutive hip resurfacing arthroplasty procedures, the reasons for choosing this procedure rather than total hip arthroplasty (THA) were reviewed. Patient age, preoperative diagnosis, presence of bone deficiency and other technical factors were considered. The mean age of patients, 79% of whom were men, was 44 years (20 to 76). The preoperative diagnosis in 59% of patients was osteoarthritis and in 37% avascular necrosis. The decision to resurface the hip rather than to perform THA was influenced primarily by the patient’s choice. In 43 cases (57%), the patient had prior knowledge of the procedure and specifically that it be considered. Other important considerations were the patient’s level of physical activity, the expectation of non-compliance with mobilisation and rehabilitation, the expectation of instability of the hip, the quality of bone and the surgeon’s experience with the surgical technique. As experience of the procedure grew, the mean age of patients who underwent resurfacing arthroplasty increased. The early clinical results of resurfacing indicate that the range of motion is less than in hip replacement, that the resurfaced hip demands less care against dislocation or wear, and that the patient mobilises and rehabilitates more rapidly and reaches a higher level of physical ability than with THA. As mid-term and long-term results become available, the indications for and prevalence of hip resurfacing arthroplasty are likely to increase.
There is only a paucity of information on the outcome of resurfacing arthroplasty in patients suffering from hip osteoarthritis secondary to developmental dysplasia (DDH). When performing arthroplasty in dysplastic hips, the anatomic abnormalities offer reconstructive challenges, in particular in resurfacing. The present study was therefore conducted to address the following questions: Can hip resurfacing arthroplasty provide satisfactory clinical results in patients with DDH? Can the patients return to sports and recreational activities? Can the hip biomechanics be restored? And finally, can surface arthroplasty reestablish a normal, symmetric gait pattern? The study comprised 24 consecutive patients (32 hips) with a mean age of 44.2 years who underwent surface replacement due to hip osteoarthritis secondary to DDH. Surgery was performed by two senior surgeons using either the Durom implant or the Birmingham Hip Resurfacing prosthesis, dependent on the surgeon’s preference. At a mean follow-up of 43 months, all patients were evaluated cross-sectionally. We assessed clinical and radiographical data and investigated spatiotemporal gait parameters using an electronic mat. The Harris Hip Score improved from 54.7 +/−13.3 to 97.3 +/−5.2 (p<
0.001) and University of California at Los Angeles (UCLA) activity levels increased from 5.3 +/−2.0 to 8.6 +/−1.6 (p<
0.001), respectively. Hip flexion improved from 95.7° +/−16.5° to 106.7° +/−10.6° (p<
0.001). At a mean of 11.2 +/−4.8 weeks after surgery, all patients returned to sports activity. They participated in a mean of 6.0 +/−2.6 different disciplines, 2.8 +/−1.3 times and 4.1 +/−3.6 hours per week. The most common disciplines were cycling, swimming, exercise walking and downhill-skiing. Spatiotemporal parameters of gait demonstrated a symmetrical gait pattern without major differences to normative data. Both, the hip lever arm ratio and the femoral offset increased significantly (p<
0.001) from 0.48 +/−0.07 to 0.57 +/−0.08 and from 39.3 +/−8.2 mm to 45.6 +/−6.2 mm, respectively. Grade I heterotopic ossifications were seen in two hips, there were no Grade II or III ossifications. Two surface replacements failed, both failures could be attributed to surgical errors. The surface arthroplasty risk index was 3.2 +/−1.4 for the entire cohort and 4.5 for the revision cases. Femoral radiolucencies were detected in ten of the remaining 30 hips. The present study demonstrated that hip resurfacing achieved satisfactory clinical results in patients with hip osteoarthritis secondary to DDH. The failure rate of 6.3% did not reach our expectations, however, both failures could be attributed to surgical errors. Further follow-up is nevertheless of utmost importance to assess the significance of femoral stem radiolucencies in this young and active group of patients.
The modern humeral head resurfacing was developed by Stephen Copeland, M.D. and introduced in 1986 as an alternative to stemmed humeral implants. At the time, first and second generation monoblock and modular stems with non-offset humeral heads posed many challenges to the surgeon to recreate the pre-morbid humeral head anatomy during anatomic TSA. The consequences of non-anatomic humeral head replacement were poor range of motion, increased native glenoid or glenoid component wear and premature rotator cuff failure. Additionally, the early generation humeral stems were very difficult to extract when revision was needed. The original stemless devices were cup resurfacing implants that were designed based on the early hip experience. The Copeland resurfacing device offered the ability to better match native humeral head anatomy and was considered less invasive and easier to revise. Glenoid exposure required more extensive dissection but TSA could be successfully completed. Clinical results for motion, function and outcome scores are similar to stemmed implants. The survivorship of the implants is also on par with other available implants and loosening has not been an issue. Stress shielding is not reported. Multiple manufacturers offered similar products all designed to try to predictably recreate the pre-morbid anatomy and to make insertion easier. Critical review of resurfacing arthroplasty radiographs has raised concern about the challenges of placing the implant with proper sizing and position. Most surgeons have implanted resurfacing implants as hemiarthroplasties. The development of anatomic TSA implants has allowed surgeons to better recreate the normal pre-morbid anatomy of the humerus. Newer stem designs are convertible or easily removable. This counters many of the original design benefits of resurfacing. The primary reason for revision of resurfacing implants is malposition followed by glenoid arthrosis and rotator cuff failure. Revision surgery after resurfacing has had mixed results. Stemless implants were introduced in Europe 13 years ago. Stemless devices share the benefits of resurfacing as minimally invasive and easier to revise. The added benefit of better glenoid access allows the surgeon to implant a glenoid. Most available implants have minimal follow-up. Mid-term follow-up of one design has demonstrated good fixation and loosening is uncommon. No studies are available that critically evaluate the surgeon's ability to recreate normal pre-morbid anatomy, whether revision arthroplasty is bone preserving and if results of revision will improve.
Stemless shoulder arthroplasty implants for the proximal humerus provide cementless metaphyseal prosthetic fixation. A near-perfect anatomic restoration of the proximal humeral articular surface is possible with this canal-sparing design—avoiding the risks associated with humeral stems and preserving bone for later revision. When compared with proximal humeral resurfacing, stemless arthroplasty avoids the potential technical errors that may lead to oversized implants, abnormal shift of the glenohumeral joint center of rotation, and excessive strain on the native rotator cuff. While canal-sparing stemless implants represent a new concept in shoulder arthroplasty without mid- and long-term results, the failures associated with resurfacing humeral arthroplasty have been documented in the literature. Unlike a stemless component, use of a resurfacing technique (and hence preservation of the humeral head) makes glenoid prosthetic implantation challenging and often impossible.
Metal-on-metal hip arthroplasty is nowadays a well spread technique for hip replacement. It is a technically demanding procedure with sine qua non steps. Most of the large Australian, British and north-American clinical outcomes found about 20% early failure, within 3 months, during the steep part of the learning curve. In a biomechanical study on cadaver we showed that valgus and version placements should be appropriate in order to get the most effective strength in compression. But valgus placement is drastically limited by lateral neck notching which leads to early fracture. Anteversion also should be manage to address the cam-type shape of the ventro-lateral femoral neck, since most of the young patient with hip arthritis present retroverted misalignment of the head along the neck axis. The size of the femoral head is another issue because big head component needs a big acetabular cup. Sparing large amount of bone on the femoral side might lead to bone lost on the pelvic side. In order to enhance the placement of the femoral component – smallest one, in valgus, without retroversion and without neck notching – manufacturers propose mechanical device based on neck intraoperative palpation. Digitalized versions of this principle are also available. These systems still demand experienced surgeon to make slight adjustment on entry point and trajectory of the guide-wire. Imageless computer navigation based on proximal femur palpation and atlas is interesting on almost normal bone but could be inaccurate on altered bone, especially cam-type shape. Navigation based on CT scan gives exact 3D information and accurate planning but is still time consuming. Navigation on 2D fluoroscopic view shows good clinical results with only about 20 minutes more than a standard procedure. We proposed a bone morphing® procedure with emphasis of surface palpation on head-neck junction to get accurately the personal shape of each femur. Preliminary results on pathological bones showed safe reaming of the head without notching.
Hip resurfacing arthroplasty has been surgical options in younger and more active patients with osteoarthritis (OA) and osteonecrosis (ON) of the femoral head. Although excellent midterm results of this procedure have been reported, there is a concern about postoperative impingement between the preserved femoral neck and the acetabular component. There were few reports about kinematics after hip resurfacing. Therefore, the purpose of this study was to investigate the postoperative motion analysis after hip resurfacing using a noble dynamic flat-panel detector (FPD) system by which clear sequential images were obtained with low dose radiation exposure. 11 patients (mean age: 47.8 ± 7.4), 15 hips were included in this study. There were ten men and one woman. The preoperative diagnoses were ON of the femoral head in 10 hips, OA in 3 hips, and others in 2 hips. Mean postoperative follow-up period was 25.1 ± 21.6 months. Femoral anteversion, cup inclination and cup anteversion were measured on computed tomography and plain radiograph. Impingement signs such as the reactive osteophyte formation and divot around the femoral neck were also investigated on the anteroposterior (AP) and lateral radiographs. Sequential images of active and passive flexion motion in 45-degrees semilateral position, and active abduction motion in a supine position were obtained using a noble dynamic FPD system.Introduction
Materials and methods
The Copeland shoulder resurfacing arthroplasty (CSRA) (Figure1) is a cementless, pegged humeral head surface replacement which has been in clinical use since 1986. The indications for CSRA are more or less the same as conventional stemmed arthroplasty. This procedure can be considered for all patients who require shoulder replacement due to GHJ arthritis resulted from primary or secondary OA, RA, and other variations of inflammatory arthritis. It is also suggested as the first choice option for relatively young patients with post-traumatic arthritis, avascular necrosis (AVN), and instability arthropathy. This observational study reports functional and radiological outcome in CSRA during 4 years follow-up. 109 consecutive patients with primary osteoarthritis (45.9%), rheumatoid arthritis (39.4%), rotator cuff arthropathy (9.2%), and avascular necrosis (5.5%) underwent CSRA. Patients including 68 females (63%) and 41 males (37%) underwent this procedure (63 right-sided and 46 left-sided including 9 bilateral shoulders). The outcome assessment included pain and satisfaction, Oxford Shoulder Score (OSS), Constant Score (CS), and SF-12. Imaging was reviewed for glenoid morphology (Walch classification) (Figure2) and humeral head migration. The average follow-up period was 4 years, (range: 1 to 10 years).Background
Methods
The Birmingham hip resurfacing (Smith & Nephew, Tennessee) (BHR) has been used in younger more active patients. We report on our experience of 206 BHR procedures in patients aged 50 years or less with a minimum ten year follow-up. Clinical outcome scores, body mass index (BMI), gender and age were analysed to investigate resurfacing outcomes. 200 patients (158 males and 42 females) with an average operation age of 43.33 years (SD ±5.66) were investigated. There were 6 bilateral procedures The mean follow-up period was 12.44 years (SD ±1.71). The arthroplasties were completed between April 1999 and December 2002 by one surgeon. Data and outcome measurements were collected prospectively and analysed retrospectively. We evaluated Harris Hip Scores, Short Form-36 (SF-36v2) Scores, Tegner Activity Score Scores and McMaster Universities Osteoarthritis Index Scores (WOMAC) comparatively at preoperative, six month and yearly intervals.Aim
Methods
There has been renewed interest in metal-on-metal bearings as hip resurfacing components for treatment in young, active patients. This study examines the effects of fixation (cemented or uncemented heads) and bone-implant interface conditions (stem-bone and head-bone) on the biomechanics of the Birmingham hip resurfacing (BHR) arthroplasty, using high resolution, 3-d computational models of the bilateral pelvis from a 45-year-old donor. Femoral bone stress and strain in the natural and BHR hips were compared. Bone remodelling stimuli were also determined for the BHR hips using changes in strain energy. Proximal femoral bone stress and strain were non-physiological when the BHR femoral component was fixed to bone. The reduction of strain energy within the femoral head was of sufficient magnitude to invoke early bone resorption. Less reduction of stress was demonstrated when the BHR femoral component was completely debonded from bone. Bone apposition around the distal stem was predicted based on the stress and strain transfer through the stem. Femoral stress or strain patterns were not affected by the type of fixation medium used (cemented vs. Uncemented). Analysis of proximal stress and strain shielding in the BHR arthroplasty provides a plausible mechanism for overall structural weakening due to loss of bony support. It is postulated that the proximal bone resorption and distal bone formation may progress to neck thinning as increasing stress and strain transfer occurs through the stem. This may be further exacerbated by additional proximal bone loss through avascular necrosis. Medium term retrieval specimens have shown bone remodelling that is consistent with our results. It is unclear if the clinical consequences of neck thinning will become more evident in longer-term follow-ups of the BHR.
Female gender, old age (men >60y and women > 55y), severe acetabular dysplasia, poor proximal femoral bone geometry, large (>1cm) femoral head cysts, limb-length discrepancy (> 2cm) and small prosthetic head size (less than 50mm for men and less than 46mm for women) are risk factors for hip resurfacing arthroplasty (HRA). To present clinical and radiographic results of HRA in patients having risk factors. Patients and methods: A total of 39 HRA was inserted in 33 patients (11 men and 22 women). Birmingham hip resurfacing (Smith & Nephew, UK) was used in 9 hips and Adept (Finsbury, UK) was used in 30 hips. Among the 30 hips inserted Adept, 11 cups were fixed with rim screws. The mean age of the patients at the time of operation was 52 years. The mean weight and height of the male and female patients were 70.4kg and 167cm, 58.5kg and 154.4cm, respectively. The median head size of the male and female patients was 50mm and 42mm, respectively. Preoperative diagnosis was primary osteoarthritis in 6 hips and secondary osteoarthritis due to aceatbular dysplasia (DDH) in 33 hips. Risk factors of HRA were listed for each patient. The Harris hip score and visual analogue pain scale (VAS) were measures of clinical outcome. Radiographic review was performed retrospectively. MRI and CT images were acquired in 29 hips and 2 hips, respectively, at a mean of 4.8 years after HRA to find periprosthetic soft tissue abnormality such as a psedotumor. Kaplan-Meier method was used to calculate implant survivorship.Introduction
Purpose
More and more metal-on-metal hip resurfacing arthroplasty (HRA) implants have been used for active younger patients because of its higher success rate and better function outcomes for this group of patients compared to the traditional total hip arthroplasty (THA). One of the advantages of HRA is femoral neck preservation, which provides better bone structure in case a revision is necessary in the future. However, some believe that the outcomes after revision of hip resurfacing were not as good as the traditional THA. The purpose of this study was to provide our outcomes of the revisions, due to various causes, from over 3000 HRAs. Between May 2001 and April 2013, a single surgeon performed 3180 HRA. During that same period, 88 required revision (2.8%). Among them, the primary causes of the revision were acetabular component loosening in 22 cases; femoral component loosening in 21; femoral neck fracture in 19; adverse wear in eight; deep infection in four; and other causes for the rest. 68 of these revisions were performed by the same surgeon, while the remainder were revised elsewhere. 53 among these 68 cases had reached a minimum follow-up of two years and were included in this report. In 96%(51/53) of cases, the revision bearing was a large metal type including in 6/8 cases of adverse wear failure. There were eight cases of adverse wear with ion levels elevated above 10 μg/L, metalosis and inflammatory reaction seen at the time of revision. All of these cases had acetabular inclination angles larger than 50°. 7/8 of these cases were revised to another large metal bearing with improved acetabular component position. We analyzed the clinical scores, complications and radiographic results and compared them between these groups.Introduction:
Method:
The incidence of cancer needs to be interpreted with caution and can only be ascertained by a prospective study.
The Birmingham Hip Resurfacing (BHR) has been used in the younger more active patient for the treatment of advanced osteoarthritis. Long-term follow-up of the BHR is limited. The Australian national joint replacement registry shows that failure rates vary greatly, depending on implant types. 77 consecutive BHR procedures with a minimum ten year follow-up are reported. There were 70 patients (44 males and 26 females) with an average operation age of 57.4 years (SD ±12.6). All patients were evaluated, including the “learning curve” patients. The mean follow-up period was 11.42 years (SD ±0.50). The arthroplasties were performed between April 1999 and December 2000 by one surgeon, with a standardised patient selection set of criteria. Data and outcome measurements were collected prospectively and analysed retrospectively. We evaluated Harris Hip Scores, Short Form-36 (SF-36v2) Scores, Tegner Activity Score Scores and McMaster Universities Osteoarthritis Index Scores (WOMAC) comparatively at preoperative, six month and yearly intervals In 8 patients (10 procedures) the implant was The BHR prosthesis, in this series, has been shown to be effective, reliable, and durable in this group of highly active, relatively young patients. Problems with metallic debris, sensitivity reactions, and osteolysis have not been seen. However, we believe that with better selection criteria, improved understanding of component positioning and surgical techniques, results can be improved.
To evaluate the radiological changes after metal on metal resurfacing arthroplasty. Between December 1998 and August 2004, 166 hips in 150 patients who underwent metal resurfacing arthroplasty and followed up more than 4 years. Their mean age at the time of operation was 37.3 years(range, 15–68 years) and mean period of follow-up was 6.1 years(range, 48–95 months). The cause of arthroplasty included 115 avascular necrosis, 43 osteoarthritis, 7 ankylosing spondylitis, 1 haemophilic arthropathy. All patients had anteroposterior, translateral radiographs of the hip made preoperatively and each follow-up visit, and we analyzed radiographic findings such as radiolucencies or impingement signs around implant, neck narrowing and heterotopic ossification.Purpose
Materials and Methods
The aim of this study is to analysis the ability of these patients, treated with MOMHR, to resume sport activities by gait analysis and clinical evaluations. Metal on metal hip resurfacing (MOMHR) is indicated to treat symptomatic hip osteoarthritis in young active patients. These patients require a high level of function and desire to resume sport activities after surgery. 30 consecutive male patients playing high impact sports with unilateral hip osteoarthritis and normal contralateral hip were included in the study, they were treated with MOMHR by the same surgeon. No patients were lost to follow. The mean age at operation was 39.1 years (range 31 to 46). Primary diagnosis was osteoarthritis. OHS, HHS, UCLA activity score were completed at pre-operative time, six months and one year after surgery. Functionally, gait analysis was performed in all patients 6 months and one year after surgery. A stereophotogrammetric system (Smart-DX, BTS, Milano, Italy, 10 cameras, 250Hz) and two platforms (9286BA Kistler Instrumente AG, Switzerland) were used. Cluster of 4 markers were attached on the skin of each bone segment, a number of anatomical landmarks were calibrated and segment anatomical frames defined, markers were positioned by the same operator. Walking, running and squat jump were analyzed and strength and range of movement of the hips and knees were calculated.Background
Study Design & Methods
The advantages are preservation of bone stock, non violation of the proximal femur, reduction of stress shielding in the proximal femur and it is quite physiological. The one important thing is to avoid notching the neck to prevent disastrous fractures. The implant is less forgiving and the learning curve is steep. The ultimate usefulness can only be gauged once longer follow-ups are available.
One reason that young and active patients choose hip resurfacing arthroplasty (HRA) rather than stemmed total hip arthroplasty (THA) is that they wish to return to high impact sports after their operation. Few studies have addressed the outcome in hip arthroplasty patients who choose to participate in high impact sports post-operatively. We therefore wanted to determine if the durability of HRA in highly active patients was decreased. From 5/2001 to 5/2011, a single surgeon performed 2434 HRA cases in 2013 patients. The study group consists of all patients that had a UCLA Activity score of 9 or 10 at any point after surgery in our prospective database. There were 936 (38%) cases in 776 patients who reported participating in high impact sports at some point after surgery. This group was compared to the entire database. The mean age of the study group was 50 ± 8 years, which was significantly younger than the entire group (Introduction:
Methods:
The use of hip resurfacing arthroplasty (HRA) has largely regressed due to the fear of metal-on-metal bearings. However committed HRA users continue to assert the functional advantages that a geometry retaining implant would have on a patient”s hip. Currently worldwide, HRA is only recommended to men who demand an active lifestyle. Despite this precarious indication, it is not clear to what extent HRA has on higher activity function. The aim of this study was to determine the functional extent to which could be achieved with HRA. The primary objective is to assess the loading pattern change for patients implanted with HRA at high walking speeds and inclinations. The second objective is to compare their loading features to a healthy group to determine if a normal gait pattern could be achieved. Between 2012 and 2016, a total of 28 prospective unilateral HRA patients were analysed on an instrumented treadmill from a single centre. All 28 patient patients had a uniform implant type and had no other lower limb operations or disease. Perioperative plain orthogonal radiographs were used to measure hip length and global hip offset change. A healthy control group (n=35) were analysed to compare. All HRA patients gait characteristics were assessed at incrementally higher speeds and inclinations to determine the extent of improvement HRA has on a challenging activity. A Student t-test along with a multivariate analysis was done with significance set at α=0.05. Weight and height variance was accounted with Hof normalisation. The HRA and control group were reasonably matched for age (57 vs 55yrs), BMI (27 vs 25) and height (175 vs 170cm) respectively. Hip measurements revealed less than 5mm change for all cases. The mean time from initial preoperative gait assessment to postoperative assessment was 30 months (24–48months). The mean top walking speed for controls was 1.97m/s and postoperatively 2.1 m/sec for the HRA group. The significant (p<0.001) loading change during flat walking can be seen with restoration of symmetry. Walking at an inclination demonstrated a marked change during weight acceptance (p<0.001) and a loading pattern returning to near normal. This prospective study found HRA patients walking faster than age matched controls. They demonstrated a significant change in their loading pattern, by significantly shifting load from the unaffected side to the implanted side. Uphill walking, an activity which requires more hip flexion, demonstrated a change in stance phase which was near normal. This small comparative study confirms near physiological function can be achieved with HRA at higher activity levels.
Femoral neck fracture is a serious complication in hip resurfacing arthroplasty and reducing its risk is a major challenge. From a biomechanical point of view changing the geometrical characteristics in surgery could affect the stresses in the femoral neck. We analysed standing AP X-rays of 85 randomly selected patients having pain in the pelvic region in order to gain better understanding of the geometrical influences. Patients were selected on age, weight, pelvis visibility and no deformations of the proximal femur. A variety of geometrical characteristics has been measured and analysed using the two-sided t-test. A significant difference was found between men and women, which was compared to previous publications in order to verify the measurement method. Statistical indication could not be found for leg-dominancy influencing geometrical dimensions. This is not mentioned in literature, but it is mentioned that the BMC and BMD differs between the legs. Several linear relations have been found between geometrical characteristics and demographics. The average head-neck ratio for both left and right was about 1.4 and the ratio of the abductor moment arm and body moment arm was about 2.1. The linear relation between femoral head diameter and femoral neck diameter indicates that the femoral component should be chosen according to the natural head diameter. The ratio between the abductor arm and body arm in combination with the bodyweight determines the static stresses in the femoral neck and can be changed in surgery by altering the hip axis length and neck shaft angle.
Metal on metal hip articulations are associated with the release of cobalt and chromium ions. There are few published reports of these levels following hip resurfacing arthroplasty. This study was undertaken to determine cobalt and chromium ion levels following hip resurfacing arthroplasty. Ninety-one patients were prospectively entered in a study assessing ion levels following hip resurfacing arthroplasty. Serum, erythrocyte and urine cobalt and chromium levels were measured. Samples were collected preoperatively then at three months, six months and yearly thereafter. Each sample was analyzed with an ICPMS assay machine. Preoperatively the median values for serum, erythrocyte and urine cobalt and chromium levels were all within the normal range. Median serum cobalt levels increased from baseline (0.1 ug/l) to 1.1 ug/l at one year and 1.6 ug/l at two years. Median serum chromium levels increased from baseline (0.2 ug/l) to 1.9 ug/l at one year and 3.3 ug/l at two years. Median erythrocyte cobalt levels increased from baseline (0.1 ug/l) to 1.0 ug/l at one year and 1.3 ug/l at two years. Median erythrocyte chromium levels increased slightly from baseline (1.0 ug/l) to 1.2 ug/l at both one and two year follow-up. No correlation was seen between ion levels and patient activity, implant position, clinical scores or BMI. No clinical effects of elevated ions were observed. Outliers of either cobalt or chromium were seen in twelve patients (13%) in the series. Hip resurfacing arthroplasty is associated with significant elevations of cobalt and chromium ions. An increase in serum levels of both cobalt and chromium has been noted at two years. This trend also occurs with erythrocyte cobalt but not with erythrocyte chromium. There is a close correlation between serum and erythrocyte cobalt levels but not between serum and erythrocyte chromium levels. We recommend using serum cobalt and serum chromium measurements as a standardised method of ion analysis following metal on metal hip replacement. This allows for capture of maximal levels of both ions in vivo. Further study is required to determine if any clinical effect will be seen as a result of these elevated ions.
Metal-on-metal hip resurfacing is increasingly common. Patients suitable for hip resurfacing are often young, more active, may be in employment and may have bilateral disease. One-stage bilateral total hip replacement has been demonstrated to be as safe as a two-stage procedure and more cost effective. The aim of this study was to compare the in-patient events, outcome and survival in patients undergoing one-stage resurfacing with a two-stage procedure less than one-year apart.
No patients have undergone a revision procedure during the study period and no patient is awaiting revision surgery.
Pre-existing hip pathology such as femoroacetabular impingement is believed by some, to have a direct causal relationship with osteoarthritis of the hip. The strength of this relationship remains unknown. We investigate the prevalence of abnormal bone morphology in the symptomatic hip on the pre-operative anteroposterior pelvic radiograph of consecutive patients undergoing hip resurfacing. Rotated radiographs were excluded. One hundred patients, of mean age 53.5 years were included (range 33.4–71.4 years, 32% female). We examined the films for evidence of a cam-type impingement lesion (alpha angle >50.5°, a pistol grip, Pitt's pits, a medial hook, an os acetabuli and rim ossification), signs of acetabular retroversion or a pincer-type impingement lesion (crossover sign, posterior wall sign, ischial sign, coxa profunda, protrusio, coxa vara, Tonnis angle < 5°), and hip dysplasia (a Tonnis acetabular angle >14° and a lateral centre-edge angle of Wiberg <20°). Pre-existing radiographic signs of pathology were present in a large proportion of hips with low grade (Tonnis grade 1–2) arthritis. There is a group of patients who presented with more advanced osteoarthritis in which we suspect abnormal bone morphology to be a causative factor but, for example, neck osteophytes obscure the diagnosis of a primary cam lesion. Our findings corroborate those of Harris and Ganz. Impingement is radiographically detectable in a large proportion of patients who present with early arthritis of the hip, and therefore we agree that it is a likely pre-cursor for osteoarthritis. Treatments directed at reducing hip impingement may stifle the progression of osteoarthritis.
Hip resurfacing arthroplasty (HRA) in patients with a varus deformity of the femoral neck-shaft angle (NSA) is associated with poorer outcomes. Our experience has not reflected this. We examined the Oxford Hip Scores (OHS), Harris Hip Scores (HHS) and outcomes of patients with varus hips against a normal cohort to ascertain any significant difference. We identified 179 patients. Measurement of the femoral neck-shaft angle was undertaken from antero-posterior radiographs pre-operatively. The mean NSA was 128.5 degrees (SD 6.3). Patients with a NSA of less than 122.2 were deemed varus and those above 134.8 valgus. These parameters were consistent with published anatomical studies. The varus cohort consisted of 23 patients, mean NSA 118.7 (range 113.6-121.5), mean follow-up 49 months (range 13-74). Mean OHS and HHS were 16 and 93.5 respectively. Complications included 2 cases of trochanteric non-union; no femoral neck fractures, early failures or revisions. Normal cohort consisted of 125 patients, mean NSA 128 degrees, mean follow-up 41 months (range 6-76). The OHS and HSS were 18.8, 88.9 respectively. Complications included 5 trochanteric non-unions and 1 revision due to an acetabular fracture following a fall. Statistical analysis demonstrated no statistical difference between the cohorts OHS (p=0.583) or HHS (p=0.139). Our experience in patients with a varus femoral neck has been positive. Our analysis has demonstrated no statistical difference in hip scores between the cohorts. We have not yet experienced any femoral neck fractures, which we believe is due to the use of the Ganz trochanteric flip and preservation of blood supply.
Hip resurfacing arthroplasty (HRA) in patients with a varus deformity of the femoral neck-shaft angle (NSA) has been cited in the literature as contributory factor towards a poorer outcome. Our experience has not reflected this. We examined the outcomes of patients with varus hips against a normal cohort. Measurement of the femoral neck-shaft angle was undertaken from standard antero-posterior radiographs pre-operatively. The mean NSA was 128.5 degrees (SD 6.3). Patients less than 122.2 were deemed varus and those above 134.8 valgus. These parameters were consistent with the published literature. The varus cohort consisted of 23 patients, mean NSA 118.7 (range 113.6-121.5), mean follow-up 49 months (range 13-74), mean OHS & HHS, 16 & 93.5 respectively. Complications included 2 cases of trochanteric non-union; no femoral neck fractures or revisions. The normal cohort consisted of 125 patients, mean NSA 128 degrees, mean follow-up 41 months (range 6-76), mean OHS & HSS, 18.8 & 88.9 respectively. Complications included 5 cases of trochanteric non-union and 1 revision. Statistical analysis demonstrated no difference between the cohorts OHS (p=0.583) or HHS (p=0.139). Our experience in patients with a varus femoral neck has been positive. Our analysis has demonstrated no difference in outcomes between the cohorts.
Individuals learn to master new motor skills (such as learning a new surgical technique) by evaluating available feedback to alter future performance. Continuous concurrent augmented feedback is supplementary information presented to the learner throughout the performance of a task. An example of this type of feedback is the visual information provided by computer navigation during arthroplasty surgery. This type of feedback is a potentially powerful tool for learning because it theoretically guides the learner to the correct response, reduces errors, and reinforces correct actions. However, motor learning theory suggests that this type of feedback may impair learning because of development of dependence on the additional feedback or distraction from intrinsic feedback. In the current era of reduced number of training hours it is essential to assess the role of computer navigation on trainees. Our objective was to determine whether computer navigation influences the learning curve of novices performing hip resurfacing arthroplasty. We conducted a systematic review and critical appraisal of the literature. There is some evidence from randomised controlled trials that navigation use by trainees facilitates accurate placement of arthroplasty components compared to conventional instrumentation. There is no evidence that training with computer navigation impairs performance in retention tests (re-testing on same task after an interval of time) or transfer tests (re-testing in different conditions i.e. without concurrent feedback). We conclude that although there are significant limitations of the published literature on this topic there is no available evidence that supports concerns regarding the theoretical detrimental effects of computer navigation on the learning curve of arthroplasty trainees.
Adverse bone remodeling in the proximal femur may be detrimental to the long term survival of resurfacing prosthesis. Bone resorption beneath the femoral shell and thinning of the femoral neck have been observed. We present a radiological analysis of the incidence, rate, site of neck thinning and changes observed within the femoral neck, in 100 cases, with a minimum of five years follow-up. Femoral neck diameter was measured at zero, two and five years post-operatively, at the head neck junction and five mm distally. Pre and post-operative head to neck ratios, natural and reconstructed offset, femoral neck-shaft and stem-shaft angles and cup inclination angle were measured. Two distinct patterns of neck thinning were observed. In 76 cases (slow thinning group), we observed a reduction of <
5% of original neck diameter at two years and <
10 % at five years (mean 1.5%, sd+/− 1.5). In 24 cases (rapid thinning group), a reduction of >
5% of original neck diameter at two years and >
10% at five years (mean 10.4%, sd+/− 4.8) was observed. The difference in the percentage reduction in neck diameter was significantly different between the two groups at both time points (p<
0.01). Larger head-neck ratios were observed in the rapid thinning group, both pre and post operatively (p<
0.01). The viability of bone underneath the femoral head may be compromised as a consequence of a non-physiological bone loading mechanism. FEA has predicted stress shielding underneath the femoral head and loading of the mini stem. Compromised blood supply of the retained epiphyseal remnant may play a part in femoral head resorption. Femoral neck thinning is a phenomenon of unproven aetiology which affects almost 25% of our resurfacing cases.
Potential benefits of resurfacing include improved abductor muscle function, resulting from preservation of the femoral neck offset, and greater range of hip motion, resulting from the larger diameter bearings. Mont et al (2007) compared biomechanical outcomes during gait for individuals with unilateral resurfacing and standard arthroplasty and concluded that hip resurfacing yielded superior function, as defined by faster walking speeds. However, comprehensive data of 3-dimensional moments and hip kinematics was not presented and functional assessment was limited to gait analysis only.
Analyses of six different cementing techniques (cemtech) were performed using high viscosity (HVC) (Smart Set GHV, DePuy, Blackpool, England) and low viscosity cement (LVC) (Endurance, DePuy, Blackpool, England):
Manual application HVC ¼filling of the component with LVC and manual appl. ¼filling HVC and manual appl. ½filling LVC ½filling HVC Complete filling with LVC A force of 150N was used to press five shells in each cemtech group on foam specimens. During seating cement pressures and polymerization heat 5 mm under the foam surface were measured. Specimens were cut into quarters, surfaces were digitalized and cement penetration areas and depths were quantified using a pixel-analysis-software. The effects of the cemtech were examined by Kruscal-Wallis and Mann-Whitney-U-tests (two-sided, p-value<
0.05, SPSS)
Maximum temperatures were A) 36.0± 4.1°C, B) 45.0±5.7°C, C) 36.2±4.2°C, D) 53.5±2.5°C, E) 48.3±6.5°C and F) 53.2±12.6°C. D, E and F exceeded 50°C. A provided even cement penetration over the available fixation area without involvement of the internal area and the stem. Cemtech that used LVC cement (B, D and F) showed higher interior area cement contents than HVC (A, E and C). The cement content in the interior area was A) 39.3±26.4mm2, B) 72.1±16.9mm2, C) 37.7±10.5mm2, D) 99.0±24.6mm2, E) 67.5±15.6mm2 and F) 121.0±29.0mm2. A showed mainly complete seating with a cement mantle thickness of 0.5±0.7 mm. All other cemtech had incomplete seating in all specimens with significantly thicker polar cement mantles (p=0.032) up to a maximum of 4.6±1.2mm for E.
Risk of impingement after total hip resurfacing arthroplasty may be great because femoral head-neck unit is preserved and there is little flexibility to adjust limb length and femoral offset, but this potentially worrisome phenomenon has been rarely reported. Impingement between femoral neck and acetabular cup was observed in a cohort of patients who underwent contemporary total hip resurfacing arthroplasty. We then questioned whether patient demographics, component features or suboptimal position of components would be risk factors for impingement. We reviewed a consecutive series of 51 patients (61 hips) who underwent contemporary total hip resurfacing arthroplasty. The mean age at the time of the index arthroplasty was 38 years (18 to 64). The most common diagnosis leading to the total hip resurfacing arthroplasty was osteonecrosis of the femoral head in 41 hips (67%). All the procedures were performed by single surgeon through an anterolateral approach. All the patients were assessed clinically and radiographically at a mean of 32 months (24 to 53) postoperatively. Femoro-acetabular cup impingement, defined as the presence of bony spur at the femoral neck corresponding to abutment site of the metallic cup, was observed in seven of the 61 hips (11.5%). Of these, five patients reported limitation of activities due to groin pain. The average postoperative Harris hip score of impingement hips was inferior to those of non-impingement hips (p = 0.004). No significant difference was detected between the impingement hips and non-impingement hips with regard to of patient demographics, component features and radiographic measurements including cup inclination, cup version, femoral component version, anterior femoral offset, stem-shaft angle, femoral offset and limb length discrepancy. Our multivariate analysis revealed that only acetabular cup uncoverage ratio had a significant association with femoro-acetabular cup impingement (p = 0.04, odds ratio 1.385 [95% CI, 1.014 – 1.891]). There was no aseptic loosening of components or femoral neck fracture. We found a high incidence of impingement between retained femoral neck and metallic acetabular cup after contemporary total hip resurfacing arthroplasty in association with an increased acetabular cup uncoverage ratio. As patients with femoro-acetabular cup impingement showed inferior clinical results, it is crucial to avoid excessive protrusion of acetabular cup beyond bony margin by proper selection of acetabular component size and appropriate positioning.
Although total hip arthroplasty (THA) is quite predictable and durable in older patients, young and active patients have higher rates of revision and these rates are especially increased when the etiology is osteonecrosis. Recent advancement of hip resurfacing technology, HRA has been revived again. Numerous advantages and promising results of HRA have been published. But patient selection and techniques etc still remain issues for HRA in general and especially for patients with osteonecrosis. In the case of HRA in patients with osteoarthritis, the bone quality is stronger and there is no head necrosis and surgical techniques are fundamentally different when compared to osteonecrosis. In osteonecrosis, there is a higher risk and greater concern of the neck fracture due to necrosis and osteoporosis, insecure fixations as well as a progression of necrosis in the subchondral bone. These factors should be considered when assessing hips with osteonecrosis. The ultimate assessment is the condition of the prepared femoral head. This makes resurfacing arthroplasty for osteonecrosis a challenging procedure. This study was performed to assess the overall clinical and radiological results of the total resurfacing arthroplasty for the patients with osteonecrosis of the femoral head(ONFH) after a minimum 5 year-follow-up. 444 hips of ONFH received resurfacing arthroplasty from Sep 1998 to Mar.2008. 88 hips which were followed up minimally 5 years were included in this study. Among 88 hips(79 patients) of ONFH that have underwent hip resurfacing arthroplasties from Dec 1998 to Apr 2003, 85 hips(76 patients) were available for the complete study. The mean age at the time of operation was 37 (16–67) years old. The average follow-up period was 80 (60–112) months. The patients were clinically evaluated with the Harris hip score, hip or thigh pain, limb length discrepancy and range of motion. As a radiological evaluation, we observed the changes of implant position, patterns of bone remodeling in the neck and complications such as femoral neck fracture, loosening and osteolysis. Metal ion in the serum was also analysed. The Harris hip score increased from 77.8 preoperatively to 98.4 at the final visit. Hip abduction/adduction and rotations significantly improved after the operation. Flexion contracture disappeared and further flexion also returned to almost normal. No patient complained of limb length discrepancy and pain on the hip or thigh at the last visit. Although they are not related to the clinical result, some cases showed various types of radiographic changes in the neck of the proximal femur. Neck narrowing was observed in 3 hips. There was no detectable wear or change of position of the acetabular cup and femoral stem. Our experience with resurfacing arthroplasty in osteonecrosis of the femoral head indicates that the overall results are superior to conventional THA in the aspect of pain relief, the range of hip motion, earlier rehabilitation and earlier return to preoperative activity. This procedure of his resurfacing arthroplasty could be an alternative between joint preserving procedures and THA in the case of early-to-mid staged osteonecrosis of the femoral head especially in younger patients who need arthroplasty. Extent and location of necrosis, and bone quality are the most important factors in resurfacing arthroplasty in osteonecrosis. Precise preoperative planning and meticulous surgical technique is needed to perform resurfacing arthroplasty. But long-term studies are needed to determine the survivorship and to evaluate the metal toxicity after resurfacing arthroplasty.
High early failure rates have been reported with certain metal-metal surface arthroplasties and good results have been reported with others. This is a minimum 10-year review of the first 1000 consecutive resurfacings including all ages and diagnoses from one centre. The first 1000 surface arthroplasties (892 patients) were followed-up with postal questionnaires. Of these the first 402 hips (350 patients) were also invited for a clinico-radiological review. 54 patients (63 hips) died 6.7 years (0.7–12.6) later due to unrelated causes. Mean follow-up is 12.2 years (range 10.8–13.7). Radiographs were assessed independently by a senior musculoskeletal radiologist.Introduction
Methods
761 cases in 613 patients with minimal two years follow-up had both metal ion levels and quality pelvis X-ray identified in our database and are included in this study. The UCLA activity score, femoral shaft angle, body mass index, weight, American Society of Anesthesiologists (ASA) score, combined range of motion (CROM), diagnosis, age, implant brand, gender, AIA, bearing size, and duration of implantation were analyzed to determine the potential risk factors for elevated metal ion levels with use of uni- and multi-variable logistic regression models. A safe zone for hip resurfacing (RAIL: Relative Acetabular Inclination Limit) was calculated based on implant size and AIA on AP pelvis X-ray. For AIA below the RAIL, there were no adverse wear failures or dislocations, and only 1% of cases with ion levels above 10 μg/L. We have not found a lower limit of AIA where failures occurred. Other than high inclination angle and small bearing size, female gender was the only other factor that correlated with high ion levels in the multivariate analysis. We have described the robust “safe zone” for acetabular component position based on metal ion levels in a large patient cohort for metal-on-metal hip resurfacing arthroplasty. Our study suggests that adverse wear failures with hip resurfacing may be highly predictable and avoidable. If the AIA is below the RAIL, rare dislocations are also prevented.
The potential for bone remodeling in the proximal femur may be detrimental to the long term survival of resurfacing prosthesis. A retrospective analysis of radiological changes in the femoral neck was undertaken for 96 patients (100 hips, 76 males and 24 females), with a minimum of 5 years following hip resurfacing. The mean age at surgery was 53.8 years. Femoral neck diameter was measured post-operatively, at 2 and 5 years. Pre and post-operative head to neck ratios, femoral head-shaft offset, femoral neck and implant stem-shaft angles were also measured. Two groups of patients were identified with differing rates of reduction in their femoral neck diameter. Over the first 2 years, Group A (24%) mean reduction was 2.02mm/year while Group B (76%) mean reduction was 0.33 mm/year. At 5 years, the Group A mean reduction was 5.64mm (sd±2.03mm) while Group B reduction was 1.16mm, (sd±0.97mm). The difference was significant at both time points (p<
0.01). Larger head-neck ratios were observed in the group A, both pre and post operatively (p<
0.01). Finite Element Analysis has predicted stress shielding underneath the femoral head and loading of the mini stem. This may explain bone resorption underneath the shell and remodeling around the mini stem. Compromised blood supply of the retained epiphyseal remnant may also play a part in femoral head resorption. Group A with a larger proportion of females and femoral heads will potentially have a larger proportion of epiphyseal remnant retained. A further mechanism that could be influential in the development of neck thinning and bone resorption may be due to fluid pumping mechanism causing osteolytic erosion at the bone cement interface. In conclusion, femoral neck thinning is a phenomenon of unproven aetiology which is affecting almost 25% of our resurfacing cases. Further investigations are needed to determine its aetiology and remedy.
This study evaluates metal ion levels in patients enrolled in a prospective evaluation of hip resurfacing arthroplasty utilizing the Conserve Plus implant (Wright Medical Technology). Serum, urine and erythrocyte metal ion levels were assessed preoperatively and postoperatively. Average levels at three months were 24 nmol/l for cobalt and 40 nmol/l for chromium. These increased to 40 nmol/l for cobalt and 80 nmol/l for chromium at the six-month mark. The clinical significance of increased metal ion levels is yet to be determined. To evaluate the clinical, functional and radiographic outcome of hip resurfacing arthroplasty utilizing the Conserve Plus implant (Wright Medical Technology). Serum, urine and erythrocyte metal ion levels were evaluated both pre and postoperatively. Ion levels for both cobalt and chromium increased from the three-month to the six-month mark postoperatively and were significantly elevated relative to preoperative values. This study helps to establish a baseline for metal ion levels following hip resurfacing arthroplasty. Serum, urine and erythrocyte metal ion levels were assessed preoperatively and postoperatively. All levels were within normal range preoperatively. Average serum levels at three months were 24 nmol/l for cobalt and 40 nmol/l for chromium. These increased to 40 nmol/l for cobalt and 80 nmol/l for chromium at the six-month mark. Average erythrocyte metal ion levels at three months were 0.92 ug/l for cobalt and 1.8 ug/l for chromium. The average erythrocyte levels at six months were 1.3 ug/l for cobalt and 2.0 ug/l for chromium. A prospective multi-center study to evaluate the outcome of hip resurfacing arthroplasty was initiated in July 2003. Each patient was evaluated preoperatively and postoperatively with outcome scores, radiographs as well as serum, urine and erythrocyte metal ion levels. The results of this prospective evaluation show a rise in ion levels from three to six months postoperatively. Further follow-up is necessary to assess future trends with respect to the ion levels as well as the clinical significance. Funding: This study has been sponsored in part by Wright Medical Technology.
Alignment of the initial femoral guidewire is critical in avoiding technical errors that may increase the risk of failure of the femoral component. A novel alternative to conventional instrumentation for femoral guidewire insertion is a computed tomography (CT) based alignment guide. The aim of this study was to assess the accuracy of femoral component alignment using a CT-based, patient specific femoral alignment guide. Between March 2010 and January 2011, 25 hip resurfacings utilizing a CT-based femoral alignment guide were performed by three surgeons experienced in hip resurfacing. Stem-shaft angle (SSA) accuracy was assessed using minimum 6 week post-operative digital radiographs. A benchside study was also conducted utilizing six pairs of cadaveric femora. Each pair was divided randomly between a group utilizing firstly a conventional lateral pin jig followed by computer navigation and a group utilizing a CT-based custom jig. Guidewire placement accuracy for each alignment method was assessed using AP and lateral radiographs.Introduction:
Methods:
This study was designed to determine the risk of femoral neck fracture after anterior or posterior notching of the femoral neck. The anterior femoral neck is under tensile forces during gait similarly to the superior neck [6].
We tested the femora flexed at 25° flexion to simulate loading as seen during stair ascent. [3] The posterior 5mm notched femoral necks were tested in extension to simulate sporting activities like running. The results were compared to the control group in neutral alignment using a one- way ANOVA:
Neutral (Control) 4303.09 ± 911.04N Superior 5mm 2423.07 ± 424.16N p=0.003 Anterior 5mm in 25° flexion 3048.11 ±509.24N p=0.087 Posterior 5mm in 25° extension3104.61±592.67N p=0.117 The anterior 5mm notch tested in single-leg stance and anterior notch in flexion displayed lower compressive loads to failure (3374.64N and 3048.11N). The mean load to failure value for the posterior 5mm notches in extension was 3104.62N compared to 4303.09N for the control group. Our data suggests that anterior and posterior 2mm notches are not significantly weaker in axial compression. The anterior 5mm notches was not significant in axial compression (p=0.38), but trended towards significance in flexion (p=0.087). A 5mm posterior notch was not significant. (p=0.995, p=0.117). The 5mm superior notch group was significantly weaker with axial compression supporting previous published data (p=0.003).
The purpose of this study is to evaluate short to mid-term clinical and radiological results of metal on metal resurfacing arthroplasty in osteonecrosis of the femoral head (ONFH). 185 hips of 169 patients who underwent metal on metal resurfacing arthroplasty using Birmingham Hip Resurfacing system (Midland Medical Technololgies, Birmingham, UK) between December 1998 and May 2005 were available for this study and all cases were followed up over 3 years. All preoperative diagnoses were ONFH. The extents of necrotic area were analyzed by preoperative MRI scanning. Their mean age at the time of operation was 37.7(range, 16–67) years old and mean period of follow-up was 88(range, 36–113) months. For the clinical assessments, Harris hip scores, UCLA activity scores, pain and ROM were evaluated. Radiological changes such as radiolucencies around the stem, impingement sign, neck narrowing, osteolysis around head and neck junction, loosening of implants, heterotopic ossifications were evaluated in the serial antero-posterior, translateral radiographs of the hip joint. Preoperative necrotic area was average 42.7(range, 11.5–60) %. Clinically, the average Harris hip score was improved from 85.2 points to 97.1 points at final follow-up. Average UCLA activity scores at the last follow-up was 8.8 and almost of the patients showed high activity and returned to their original job. ROM were very satisfactory. Radiologically, the mean inclination of acetabular component was 48.0°. There were no radiolucent lines around the acetabular components, but 3 cases showed radiolucent lines around the stem of femoral components. Osteolytic lesions were noticed in 10 cases around head-neck junction. Nine hips had impingement signs around the head-neck junction. There was no case which showed evidence of stress shielding. Moderate neck narrowing were shown in 3 cases. There were 6 cases of heterotopic ossification. One hip had a revision surgery to a total hip arthroplasty using big metal ball because of loosening of acetabular component. There was no patient complained limb length discrepancy and no infection, dislocation, thigh pain. The midterm performance of metal on metal resurfacing arthroplasty in ONFH was very excellent in the aspects of pain relief, ROM of hip joints, rehabilitation and return to preoperative activity and minimization of common complications of conventional total hip arthroplasty. There was no mechanical failure related to the osteonecrosis and we can conclude that performing resurfacing arthorplasty in osteonecrosis less than 50% of extent can be justified. However, performing resurfacing arthroplasties in osteonecrosis of femoral heads needs meticulous surgical techniques and longer learning curve to prevent early failure. Even though our midterm follow-up study revealed excellent results, more long-term follow-up studies are mandatory to determine the survivorship and to verify the problems related to the increased serum metal ion and metal ion toxicity after resurfacing arthroplasty.
Variability in femoral head preparation and high cement pressures may be associated with failure to seat femoral components during hip resurfacing. Furthermore, excessive pressures may lead to over penetration of bone by cement with resulting necrosis of the underlying bone. We designed an experimental model to test the hypothesis that partial-length pressure-relief slots made longitudinally in the proximal bone of the femoral head, without extending to the head neck junction, would allow controlled leakage of cement during initial insertion of a femoral head resurfacing component, but would then become sealed during final insertion to prevent excessive loss of cement while still allowing accurate seating of the component. Thirty-one resurfacing femoral components were cemented onto foam femoral head models. The clearance between foam model and implant was measured to determine the minimum space available for cement. Eleven components were inserted using hand pressure alone, 20 were hammered. Pressure relief slots were prepared in 10 femoral heads. The slots, 4mm deep grooves, were made in the proximal bone only, without extending to the head-neck junction. Cement pressure inside the component was measured during insertion. Implants were sectioned after implantation in order to determine whether they had been fully seated or not. The clinical relevance of the measures taken was tested by measuring the diameter of prepared femoral heads during 20 hip resurfacing operations in order to determine the extent of variability in intra-operative femoral head preparation. Mean intraoperative clearance between bone and implant was −0.19mm (0.11 to −0.93mm). Mean clearance between foam model and implant was −0.30mm (0.35 to −0.94mm). Full seating was obtained in 22/31 components. Of those not fully seated, all had clearance less than −0.74mm. Full seating with a clearance of less than −0.35mm was only possible when pressure relief slots had been made in the femur. The use of a pressure relief slot longer than half the femoral head length allowed full seating in 9/9 cases, compared to 13/22 without. Cement pressure obtained with a hand pressure technique was less than half that observed with hammering (20.8vs56.0psi, p=0.0009) but was not associated with failure to seat the implant if a slot was used. Variability of the actual diameter of the femoral head prepared may be associated with difficulty in fully seating resurfacing components. The same degree of variability in the space available for cement was observed in both intra-operative and test specimens. The use of a pressure-relief slot allows full seating of resurfacing implants with hand pressure alone, thereby halving cement pressure, in an experimental model, even when clearance between implant and bone is less than optimal.
Modern metal-on-metal bearing resurfacings have been in use for nearly two decades. Local and systemic metal ion exposure continues to cause concern. We could not find a prospective metal ion study in such patients with a 10-year follow-up. This is the first ten year prospective study of metal ion levels in blood and their release in urine following hybrid fixed metal-on-metal surface arthroplasty. Twenty six patients were included in an ongoing longitudinal metal ion study of patients with unilateral metal-on-metal hip resurfacings. Three of them were excluded due to subsequent contralateral resurfacing and one has relocated abroad. Cobalt and chromium levels were assessed in 12 hour urine collections before and periodically after operation (5 days to 10 years) using high resolution plasma mass spectrometry. Mean age at operation was 53 years and mean BMI 27.9.Introduction
Methods
The Birmingham mid-head hip resurfacing arthroplasty (Smith & Nephew, Tennessee) (BMHR) is designed for use in patients with avascular necrosis of the femoral head. The BMHR has limited short-mid term follow-up results. We report the experience of 27 consecutive BMHR procedures with a minimum two year follow-up. 23 patients (20 males and 3 females) with an average operation age of 49.8 years (SD ±10.9) (22–65) were investigated. The mean follow-up period was 3.0 years (SD ±0.77). The operations were between April 2008 and November 2011 by one surgeon. Data and outcome measurements were collected prospectively and analysed retrospectively. Procedures were reviewed to determine function. We evaluated Harris Hip Scores, Short Form-36 (SF-36v2) Scores, Tegner Activity Score Scores and McMaster Universities Osteoarthritis Index Scores (WOMAC) comparatively at preoperative, six month and yearly intervals. Paired samples t-tests were applied to determine improvements where p<0.05 was deemed as significant. There were no patient deaths. There were no revisions. Harris Hip scores for pre-operative 6, 12, 24 and 36 month intervals were: 52.30, 84.14, 83.07, 87.50 and 89.50. Average pre-operative 6, 12, 24 and 36 month SF36v2 Total scores were: 116.54, 124.32, 130.44, 135.97 and 133.18. Tegner scores for pre-operative 2.75, 3.29, 3.00, 3.67 and 3.01. WOMAC Total scores for aforementioned intervals for the posterior approach were: 59.51, 84.22, 90.30, 86.86 and 92.25. The mean Harris Hip scores improved significantly between preoperative and 6, 12, 24 and 36 months (p<0.001). The mean SF-36v2 physical scores improved significantly between preoperative and 6, 12, 24 and 36 months (p<0.016). WOMAC scores improved significantly between preoperative and 6, 12, 24 and 36 months (p<0.017). The presence of avascular necrosis significantly increases the revision rate for hip resurfacing surgery. The BMHR prosthesis, in this short term follow-up, appears to avoid the main cause of failure, femoral component loosening. Longer term efficacy remains to be seen. We plan to continue close supervision of these patients.
There is much research on metal on metal hip resurfacing arthroplasty (HRA) but few studies have reported the outcome with respect to implant characteristics from non-specialist centres. To report the survival, clinical and radiological outcomes of a single surgeon series of HRA with an average follow-up of 5 years.Background
Aim
It was the purpose to evaluate the biomechanical changes that occur after optimal and non-optimal component placement of a hip resurfacing (SRA) by using a subject specific musculoskeletal model based on CT-scan data. Nineteen hips from 11 cadavers were resurfaced with a BHR using a femoral navigation system. CT images were acquired before and after surgery. Grey-value segmentation in Mimics produced contours representing the bone geometry and identifying the outlines of the 3 parts of the gluteus medius. The anatomical changes induced by the procedure were characterised by the translation of the hip joint center (HJCR) with respect to the pelvic and femoral bone. The contact forces during normal gait with ‘optimal’ component placement were calculated for a cement mantle of 3 mm, a socket inclination of 45° and anteversion of 15°. The biomechanical effect of ‘non-optimal placement’ was simulated by varying the positioning of the components.Introduction
Materials and Methods
Hip resurfacing arthroplasty (HRA) is increasingly carried out as an alternative to total hip arthroplasty (THA) in young patients. During the procedure, a metal stem on the retrosurface of the HRA is inserted into the femoral head to ensure the implant is located centrally with respect to the femoral neck. It has been suggested that the stem may interfere with bone loading. In light of this, the current study employed finite element (FE) models to investigate the change in the HRA-implanted bone mechanics as a result of removing the stem. FE models of a cadaveric femur pre- and post-HRA surgery were analysed to determine changes in bone stress/ strain. The implanted models simulated geometry for a cemented HRA with and without a non-cemented stem (HRA-Stem and HRA-NoStem, respectively) and included more accurate multiple material parameters to simulate the non-homogeneous material distribution in the femoral bone. The models included loading conditions simulating an instant at 10% of the gait cycle. Bone stresses/strains in the femoral head and neck of the implanted models were compared with the intact condition to assess the change in bone mechanics. Changes in cement mantle stresses between the HRA-Stem and HRA-NoStem models were also compared. When comparing similar volumes of bone in the femoral neck, both HRA models showed a similar variation in stress from the intact condition and bone stresses were low in comparison to the ultimate strength of cortical bone. There was less change in peak strain energy in the femoral head of the HRA-NoStem model than the HRA-Stem model. Cement mantle stresses in the HRA-NoStem model were slightly higher than for the HRA-Stem model and the peak compressive stress was close to the fatigue limit for bone cement. These preliminary results suggest that the bone loading is more normal without the stem. However, there are increased cement mantle stresses.
Hip resurfacing arthroplasty has gained popularity as an alternative for total hip arthroplasty. Usually, cemented fixation is used for the femoral component. However, each type of resurfacing design has its own recommended cementing technique. In a recent investigation the effect of various cementing techniques on cement mantle properties was studied. This study showed distinct differences in cement mantle volume, filling index and morphology. In this study, we investigated the effect of these cement mantle variations on the heat generation during polymerization, and its consequences in terms of thermal bone necrosis. Two FEA models of resurfacing reconstructions were created based on CT-data of Thermal analyses were performed of the polymerization process, simulating three different types of bone cement: Simplex P (Stryker), CMW3 (DePuy J&J) and Osteobond (Zimmer), with distinct differences in polymerization characteristics. The polymerization kinematics were based on data reported previously. During the polymerization simulations the cement and bone temperature were monitored. Based on the local temperature and time of exposure, the occurrence of thermal bone necrosis was predicted. The total volume of necrotic bone was calculated for each case.Introduction
Materials and methods
Lesion location and volume are critical factors to select patients with osteonecrosis for whom resurfacing arthroplasty is appropriate. However, no reliable surgical planning system which can assess relationship between necrotic lesions and the femoral component has been established. We have developed a 3D-MRI-based planning system for resurfacing arthroplasty. The purpose of the present study was to evaluate its feasibility. The subjects included five patients with osteonecrosis of ARCO stage 3 or 4 who had undergone resurfacing THA at our institute. All patients had an MRI before surgery using 3D-SPGR sequences and fat suppression 3D-SPGR sequencea. In cases where it was difficult to distinguish bone marrow edema and reparative zone on 3D-SPGR images, fat suppression 3D-SPGR sequences were used. Simulation of resurfacing arthroplasty was performed on image analysis software where multidirectional oblique views could be reconstructed. The femoral neck axis was determined by drawing line through centers of two spheres which were fitted to the normal portion of the femoral head and the mid-portion of femoral neck. A femoral component was virtually implanted to align the femoral neck axis and match the implant center and femoral head center.Introduction
Methods
Uncemented acetabular component fixation has been considered the most reliable fixation method in contemporary metal-on-metal hip resurfacing arthroplasty (HRA). During prospective long-term follow-up of a HRA device, we have encountered a surprisingly high incidence of this complication and wish to alert surgeons and manufacturers of this problem. The study group was comprised of all 373 HRAs performed by a single surgeon using this hybrid hip resurfacing implant from May 2001 to March 2005. The acetabular component features a dual-coated bone ingrowth surface of plasma-sprayed titanium plus hydroxylappatite. There were a total of 34 revisions identified at the time of this study.Introduction:
Methods:
The modern generation of hip resurfacing arthroplasties was developed in the early 1990’s with one of the original designs being the McMinn Resurfacing Total Hip System. This was a hybrid metal on metal prosthesis, with a smooth hydroxyapetite coated press fit mono block cobalt chrome shell with a cemented femoral component. Although no longer produced in this form, lessons may be learned from this original series of components. With metal on metal resurfacing arthroplasty now facing criticisms and concerns with regard function, bone preservation capability and soft tissue issues such as ‘pseudotumors’, it is the aim of this long-term study to assess the outcome and survival of an original series of resurfacing arthroplasties. 27 resurfacing arthroplasties were performed in 25 consecutive patients between June 1994 and November 1996. 16 right hips and 11 left were performed in 14 female patients and 11 male patients. The average age at the time of surgery was 50.5 years (SD 7.9, range 30–63). All surgeries were performed by a single surgeon using a posterior lateral approach. Following the initial early care, each patient received bi-annual follow up along with open access to the clinic with any concerns or complications. A retrospective review of the case notes was conducted and outcome scores retrieved from a prospectively updated database. Radiographs were analyzed and a Kaplan Meier survival chart was constructed for the group. At latest review 3 patients have died (5yrs, 8yrs and 13.8yrs) and 1 patient has been lost to follow up (5yrs). 7 resurfacings have required revision, all due to acetabular loosening, at a mean follow up of 7 years 11months (SD 2.03years, range 4–10). Metallosis was documented in 4 of the revision cases, however no extensive soft tissue inflammation or ‘pseudotumor’ identified. The mean follow up of the remaining 16 hips is 12years and 10months (SD 12.8months, Range 10.4yrs–14.0 years). The Kaplan Meier survival at a minimum follow up of 10 years is 75.8% (95% CI 0.67–0.95). Mean Oxford hip scores at latest follow up was 20.6 (SD 8.8, range 12–38). There was no significant difference between cup inclination angles for the surviving cohort and those who required a revision procedure with mean cup inclinations of 52.5 (SD 5.5, range 45–60) and 58 degrees respectively (SD 9.1, range 50–70)(p=0.255). This original series of hip resurfacings, with up to 14 years follow up, shows a survival of 76% at the minimum follow up of 10 years. All failures were due to loosening of the smooth backed acetabulum, which with a modern porous coating, failure may have been avoided or delayed. Despite high inclinations angles no soft tissue reactions were identified within this series. No femoral failures were identified suggesting unlike much literature focus, long-term failure may not be related to the femoral head or neck.