Femoral fit in ABG-II hip stems, influence on clinical outcome and bone remodeling: a radiographic study

Excellent survival of two anatomically adapted hydroxyapatite coated cementless Total Hip Arthroplasties. A mean follow-up of 11.3 years

There are many different types of cementless anatomically adapted Total Hip Arthroplasties (THAs) on the market, the Anatomic Benoist Gerard (ABG) I and II are such types of cementless THAs. In this retrospective single-centre study we evaluated the overall survival with revision for any reason and aseptic loosening as endpoint at more than 11 years follow-up. Between 2000 and 2004, 244 cementless THAs were performed in 230 patients in a primary care hospital. At a mean of 11.3 years follow-up (range 9.8 - 12.8 years) clinical examination, plain radiography and Patient Reported Outcome Measures (PROMs) were obtained and analysed. The PROMs consisted of the Oxford Hip Score (OHS) and the Western Ontario and McMaster University Index (WOMAC). At a mean of 11.3 years follow-up 32 patients (13.1%) had died of unrelated causes. Of the remaining cohort all 198 patients (212 THAs) have been reached for evaluation. There were no patients considered as lost to follow-up. At a mean of 11.3 years 11 patients (11 THAs) have had a revision of either the femoral implant or acetabular component resulting in an overall survival of 95.5%. There was no statistically significant difference (p=0.564) in survival between the ABG I and II THAs. Radiographic there were no changes between the ABG I and II last follow up. The ABG II performed statistically significant better in PROMs. We concluded that both anatomically adapted hydroxyapatite coated cementless THAs show excellent survival at more than 11 years follow-up.

Retrospective clinical and X-ray-based outcome analysis of a short-stem hip arthroplasty taking into account the operative learning curve over 7 years in the 3-year control course

INTRODUCTION

Self-monitoring is crucial to work progressively with a high-quality standard. A retrospective analysis is a valuable tool for studying the postoperative outcome of a prosthesis and for evaluating the learning process for the surgeon.

MATERIALS AND METHODS

The learning process of one surgeon was analysed in 133 cases of hip arthroplasty. These were divided into seven groups representing the surgical years 2008-2014. Over the course of 3 postoperative years, a total of 655 radiographs were analysed at regarding three radiological quality parameters (centrum-collum-diaphyseal angle (CCD angle), intramedullary fit&fill ratio (FFR), and migration) and ancillary outcome parameters (Harris Hip Score (HHS), blood loss, operating time, and complications). This period was divided into five times: 1st-day post-op, 6 M, 12 M, 24 M, and 36 M. Bivariate Spearman's correlation analysis and pairwise comparisons were performed.

RESULTS

The total collective achieved a proximal FFR of over 0.8. The distal prosthesis tip migrated and was located on the lateral cortex within the first months. The CCD angle initially showed a variation with a subsequent constant course. The HHS showed a significant increase (p < 0.001) to over 90 points postoperatively. Over time, the operating time and blood loss decreased. Intraoperative complications existed only at the beginning of the learning phase. A learning curve effect can be determined for almost all parameters by comparing the subject groups.

CONCLUSIONS

Operative expertise was shown to gain through a learning curve, whereby postoperative results corresponded to the system philosophy of the short hip stem prosthesis. The distal FFR and the distal lateral distance could represent the principle of the prosthesis, which overall could be an interesting approach for verification of a new parameter.

Surgeon-Stratified Periprosthetic Fracture Risk in a Single-Hospital Cohort of 1531 Uncemented ABG-II Femoral Stems at Primary Total Hip Arthroplasty

Purpose

Late periprosthetic fracture risk with uncemented ABG-II femoral stems at primary total hip arthroplasty (THA) has been reported before, but single-hospital surgeon-stratified reports of this implant have never been published. We asked whether periprosthetic fracture rates of ABG-II femoral stems implanted at a single tertiary hospital depended on patients' age, gender and the operating surgeon.

Methods

The study included 1531 consecutive primary ABG-II femoral stems implanted at a single tertiary hospital between January 1, 2012 and December 31, 2018. The Kaplan-Meier and Cox regression analyses were performed after 3.6-10.6 years of follow-up.

Results

In the cohort, we recorded 8 intraoperative, 22 early postoperative (within 90 days of implantation) and 26 late periprosthetic fractures (over 90 days postoperatively). The revision rate of ABG-II femoral stems was 5.1/100 component-years for early and 0.3/100 component-years for late periprosthetic fractures. The Kaplan-Meier cumulative probability of periprosthetic fracture was 2.1% at one, 2.3% at 2, 3.2% at 5, and 6.5% at 10 years after the implantation. Higher patient's age at operation was an independent risk factor of subsequent periprosthetic fracture (hazard ratio 1.07, 95% confidence interval 1.03-1.10; p < 0.01), regardless of the operating surgeon. Most of the fractured femora were Dorr type C (stovepipe).

Conclusion

The study presents the largest published ABG-II femoral stem cohort from a single hospital so far with 9291 component-years of observation. Periprosthetic fracture risk of ABG-II increased with patients' age, had no variability between different surgeons, and was considerably higher from other uncemented femoral stems used at the same hospital.

Level of Evidence

III.

Early Radiographic Fit and Fill Analysis of a New Metaphyseal-Filling Triple Taper Stem Designed Using a Large Computed Tomography Scan Database

Background

Numerous cementless stems are available to maximize implant stability, fit, and survivorship in total hip arthroplasty. Recently, a new metaphyseal-filling triple-taper collared stem was designed using femoral morphology data obtained from over 1300 computed tomography scans. The purpose of this study was to evaluate the radiographic fit and fill of this new stem in the coronal and sagittal dimensions.

Methods

In this retrospective review, postoperative radiographs of patients receiving this new stem were analyzed in accordance with previously published fit and fill analyses. All radiographs were taken 6 weeks postoperatively. Means and standard deviations were reported for all fit and fill parameters.

Results

Fifty-nine hips were analyzed from 55 patients undergoing total hip arthroplasty. The coronal proximal fill was 85.02 ± 8.06%, and coronal distal fill was 75.21 ± 9.71%. The sagittal proximal fill was 86.51 ± 8.77%, and sagittal distal fill was 59.17 ± 8.66%. Mean calcar collar coverage was 80.64 ± 19.6% and all patients had full seating of the collar. Six cases (10.2%) had a collar length greater than the calcar length, with a mean collar overhang of 0.7 ± 0.4 mm.

Conclusions

This new stem demonstrated significant proximal fill in both the coronal and sagittal planes and validates the design intent of this implant. This is the first study to evaluate sagittal fit and fill of a femoral stem. Long-term follow-up is required to understand the clinical impact these fit and fill characteristics may have on patients' long-term outcomes.

Varus stem positioning does not affect long-term functional outcome in cementless anatomical total hip arthroplasty

INTRODUCTION

Varus positioning is the most common femoral malposition in total hip arthroplasty (THA). We compared the long-term outcomes of an anatomical cementless femoral stem positioned in varus versus neutral alignment.

MATERIALS AND METHODS

Data were retrospectively reviewed for all patients receiving a cementless anatomical femoral stem in THA for osteoarthritis between 1998 and 2008. Exclusion criteria were complex cases, incomplete data or follow-up < 1 year. Primary outcome was survival rate with complications and secondary outcomes were clinical scores, thigh pain, radiological score, cortical hypertrophy and filling rate.

RESULTS

Of the 283 included patients, 127 stems were classified as varus and 156 neutral. Mean follow-up was 10 years. Femoral stem size was smaller in the varus group (4.1 vs. 4.4, p = 0.047). A stem-filling rate < 80% was more frequent in the varus group (p < 0.001). The long-term survival rate without any revision procedure was 94.8% ± 2.3% (95%CI 88.4-98.7) in the varus group and 94.1% ± 2.0% (95%CI 91.3-99.1) in the neutral group (p = 0.55). There was no difference in clinical scores, thigh pain or complication occurrence between groups. The Engh-Massin score was lower in the varus group (p < 0.01) and cortical hypertrophy was higher (p < 0.001).

CONCLUSIONS

A varus alignment of a cementless anatomic femoral stem does not affect survivorship, clinical outcomes or complication rate on an average follow-up of 10 years, despite increasing stress-shielding rates.

A Surgeon's handedness in direct anterior approach-hip replacement

BACKGROUND

The impact of handedness on clinical outcomes was easily overlooked in hip replacement. This study aimed to find whether the component positioning and hip function were affected by the handedness in total hip arthroplasty (THA) through direct anterior approach (DAA).

METHODS

Total 102 patients who underwent bilateral DAA-THAs simultaneously between May 2016 and November 2018 in our institute were reviewed. All surgeries were operated by one right-handed surgeon. Their demographic, cup positioning, stem alignment, femoral stem fit, Harris hip score (HHS), intraoperative and postoperative complications were used to evaluate the role of handedness in DAA.

RESULTS

The inclination of left cups was significantly larger than that of right cups (42.61 ± 7.32 vs 39.42 ± 7.19, p = 0.000). The stem fit of left femur was significantly larger than that of right femur (84.34 ± 4.83 vs 82.81 ± 6.07, p = 0.043). No significant differences in safe zone ratio, HHS and complications between bilateral hips were found.

CONCLUSIONS

A surgeon's handedness had significant impact on cup's inclination and femoral stem fit in DAA-THA. However, there were no significant differences of cup malpositioning, stem alignment, hip function scores and complications between bilateral DAA-THAs.

Variation in greater trochanteric lateroversion: a risk factor for femoral stem varus in total hip arthroplasty

INTRODUCTION

Correct implant positioning is required to achieve adequate biomechanics. The greater trochanter is more medially or laterally positioned in some patients, known as trochanteric lateroversion. However, studies have not identified correlations between postoperative coronal alignment and variation in greater trochanteric lateroversion. The purpose of this study was to identify the effects of variation in greater trochanteric lateroversion on postoperative stem coronal alignment and to investigate other factors related to stem coronal alignment.

METHODS

A total of 213 hips in 149 patients who underwent total hip arthroplasty were included in this prospective study. The greater trochanters were categorised into 5 groups according to the degree of variation in greater trochanteric lateroversion, and the stem coronal alignment angle and stem fit were measured on anteroposterior radiographs.

RESULTS

Postoperative stem varus was positively correlated with greater trochanteric lateroversion (r = 0.26065, p = 0.0001) and negatively correlated with the stem fit (r = -0.16568, p = 0.0155).

DISCUSSION

Excessive variation in greater trochanteric lateroversion was a risk factor for femoral stem varus, and the stem varus position was always accompanied by inadequate canal filling. When the tip of the trochanteric overhang exceeded the centreline of the femoral canal, the influence of lateroversion of the greater trochanter on the femoral stem remarkably increased. Appropriate measures should be implemented to avoid a stem varus position and inappropriate stem fit.

Is there any difference between tapered titanium stems with similar geometry and hydroxyapatite coating?

PURPOSE

Several tapered stems with similar geometry and extensive hydroxyapatite coating have recently been introduced. It is not clear, however, whether they share the same design or whether they exhibit any difference that might affect their clinical performances. In this study, we analysed five tapered stems fully coated with hydroxyapatite to establish whether they exhibit similar geometric features and may therefore be used indifferently when a cementless stem is indicated.

METHODS

The length of the stem, the coronal and sagittal diameters, the length of the stem shoulder and the metadiaphyseal angle were measured. The ratio between the proximal and distal coronal diameters of the stem and that between the proximal and distal cross-sectional areas were calculated as a flare index and tapered index, respectively.

RESULTS

The proximal coronal diameter ranged between 24.9 and 28 mm in the smaller size and between 34 and 38.4 mm in the largest sizes. The proximal sagittal diameter ranged between 10.2 and 11.8 in the smallest size and between 14.4 and 17.2 in the largest. A significant difference was found between stems of different brands in the flare index, tapered index, length of stem shoulder and metadiaphyseal angle.

CONCLUSIONS

Lookalike tapered stems with extensive HA coating actually exhibit significant differences in several geometric features potentially affecting their clinical performances. As a result, these stems should not be used indifferently, but rather they should be selected on the basis of the femoral morphology of the operated patient.

Total Hip Intraoperative Femur Fracture: Do the Design Enhancements of a Second-Generation Tapered-Wedge Stem Reduce the Incidence?

BACKGROUND

Intraoperative femur fracture (IFF) is a well-known complication in primary uncemented total hip arthroplasty (THA). Variations in implant instrumentation design and operative technique may influence the risk of IFF. This study investigates IFF between a standard uncemented tapered-wedge femoral stem and its second-generation successor with the following design changes: size-specific medial curvature, proportional incremental stem growth, modest reduction in stem length, and distal lateral relief.

METHODS

A single experienced surgeon's patient database was retrospectively queried for IFF occurring during primary uncemented THA using a standard tapered-wedge femoral stem system or a second-generation stem. All procedures were performed using soft tissue preserving anatomic capsule repair and posterior approach. The primary outcome measure was IFF. A z-test of proportions was performed to determine significant difference between the 2 stems with respect to IFF. Patient demographics, Dorr classification, and implant characteristics were also examined.

RESULTS

Forty-one of 1510 patients (2.72%) who received a standard tapered-wedge femoral stem sustained an IFF, whereas 5 of 800 patients (0.63%) using the second-generation stem incurred an IFF. No other significant associations were found.

CONCLUSION

A standard tapered-wedge femoral stem instrumentation system resulted in greater than 4 times higher incidence of IFF than its second-generation successor used for primary uncemented THA. Identifying risk factors for IFF is necessary to facilitate implant system improvements and thus maximize patient outcomes.

Comparison of anatomic vs. straight femoral stem design in total hip replacement - femoral canal fill in vivo

INTRODUCTION

The femoral canal fill between an anatomic and a straight prosthesis design in cementless total hip arthroplasty (THA) was compared. We hypothesised that the anatomic SPS stem has higher proximal fill and lesser distal fill than the straight stem.

MATERIAL AND METHODS

The femoral canal fill was measured on 3 months routine postoperative x-rays at 5 levels of the stem in 50 consecutive patients, aged 35-83 years, who underwent 56 THA procedures by a single surgeon in this hospital. 22 patients received a straight design Ceramconcept Global stem, 34 patients received an anatomic design Symbios SPS stem. Both anteroposterior (AP) and lateral x-rays were combined to suggest a 3-D measurement.

RESULTS

On the AP x-rays, the canal fill was significantly higher using the anatomic design stem at the proximal measurement levels, and was significantly higher at the distal levels using the straight stem. With the AP and lateral x-rays combined, the canal fill at the proximal levels was also significantly higher in the anatomic groups, nonsignificantly lower at the central level and significantly lower at the distal levels.

DISCUSSION

In THA surgery, achieving high fill at the metaphysis of the femur and less fill at the diaphysis has been suggested to result in satisfactory outcome and high stability of the prosthesis. This study demonstrated that, compared to straight stem design, an anatomically designed stem has a significantly higher metaphyseal femoral canal fill.

Results of Cemented Anatomically Adapted Total Hip Arthroplasty: A Follow-Up Longer Than 10 years

This retrospective single-center study evaluated the >10-year follow-up (FU) and survival of 2 anatomically adapted cemented total hip arthroplasties (THAs) in a series of 308 patients (323 THAs) with a mean age of 76.2 years at operation. At a mean of 11 years of FU, patient-reported outcome measures, clinical examination, and plain radiography were analyzed. In 6 THAs, the femoral and/or acetabular component was revised. Reasons for revision were aseptic loosening and infection. At >10 years of FU, there was an overall survival for both THAs of 98.1%. Radiographic radiolucent lines were seen in 15 THAs affecting Gruen zone 4 and Delee and Charnley zone II. We conclude that both anatomically adapted cemented THAs have an excellent survival at 11 years of FU.

Influences of fit and fill following hip arthroplasty using a cementless short-stem prosthesis

INTRODUCTION

The purpose of this study consisted in examining the effects of fit and fill ratio of the Metha prosthesis (BBraun, Aesculap, Tuttlingen, Germany) on radiological and clinical outcomes at a follow-up of 1 year.

METHODS

40 patients were included. Fit and fill ratio measurements, radiological and clinical examinations were performed preoperatively and postoperatively. Correlations were established between fit and fill ratio, and potential factors like sex, age, body mass index, Harris Hip Score and changes of radiological signs.

RESULTS

The whole cohort (100%) had a tight fit and fill ratio (>0.8) at the proximal level and at each follow-up. "Champagne-flute" configuration provoked high distal tight-fit and fill ratio. Poor distal fit and fill ratio compared to the proximal and the mid-stem level was measurable at each follow-up (p < 0.05). Correlations between fit and fill ratio and preoperative femur configurations were detectable.

CONCLUSIONS

Implanting the Metha prosthesis induces tight fit and fill ratio at the proximal and coated sections. Preoperative femur configuration should be considered to achieve best fit and fill situation and therefore excellent primary stability. In most cases "normal" and "stove-pipe" configurations provide good proximal fit and fill. Since "champagne-flute" configuration induces undesirable tight distal fit and fill ratio the size of the Metha (®) stem should be adequately increased to achieve a more proximal load transmission.

Small and similar amounts of micromotion in an anatomical stem and a customized cementless femoral stem in regular-shaped femurs. A 5-year follow-up randomized RSA study

BACKGROUND AND PURPOSE

High primary stability is important for long-term survival of uncemented femoral stems. Different stem designs are currently in use. The ABG-I is a well-documented anatomical stem with a press-fit design. The Unique stem is designed for a tight customized fit to the cortical bone of the upper femur. This implant was initially developed for patients with abnormal anatomy, but the concept can also be used in patients with normal femoral anatomy. We present 5-year radiostereometric analysis (RSA) results from a randomized study comparing the ABG-I anatomical stem with the Unique femoral stem.

PATIENTS AND METHODS

100 hips with regular upper femur anatomy were randomized to either the ABG-I stem or the Unique femoral stem. RSA measurements were performed postoperatively and after 3, 6, 12, 24, and 60 months.

RESULTS

RSA measurements from 80 hips were available for analysis at the 5-year follow-up. Small amounts of movement were observed for both stems, with no statistically significant differences between the 2 types.

INTERPRETATION

No improvement in long-term stability was found from using a customized stem design. However, no patients with abnormal geometry of the upper femur were included in this study.

Radiographic fit and fill analysis of a new second-generation proximally coated cementless stem compared to its predicate design

The purpose of this study was to compare in vivo fit and fill analysis of a new second-generation proximally coated cementless stem compared to its predicate design. This prospective trial of 100 total hip arthroplasties compared specific radiographic "Fit and Fill" parameters between the two designs. Fit type was assessed by comparing the type of canal fill. Post-operative fill parameters such as mean stem-to-canal ratios and mean minimum and maximum gaps between the stems to the cortical bone in different sections and areas were compared. A significantly higher proportion of the second-generation stems had Type I fit (82% vs. 54%), had better stem to canal fill ratio in the middle (90.6% vs. 85.3%) and distal sections (88.1% vs. 78.6%) compared to the older design. The new second-generation stem design had a significantly better canal fit and distal canal fill in the medial and lateral portions.

Shortening of an anatomical stem, how short is short enough? An in vitro study of load transfer and primary stability

An anatomical stem should be short enough to avoid distal locking and distal load transfer but long enough to ensure adequate primary stability of the stem. In this in vitro study, the cortical strains in the femur and the primary stability of the stem were measured after insertion of Anatomic Benoist Girard-I anatomical stems with gradually reduced stem length in six human cadaver femurs in order to find the optimal stem length. A shortening of 40–50 mm, corresponding to a stem extending 30–40 mm below the lesser trochanter, did not affect stem stability but nearly normalized the load distribution in the lower metaphysis and upper diaphysis. The large strain shielding observed in the calcar region was not influenced by shortening of the stem.

[Implant position of total hip arthroplasty shafts. Establishment of a new method for comparison between planned and achieved shaft positions]

BACKGROUND

One of the main goals of the preoperative planning of hip prostheses is adequate shaft positioning with reconstruction of leg length and offset. The purpose of this study was to compare the planned and achieved shaft positions using a modified program for migration measurement.

METHODS

In 60 cases of total hip replacement the preoperative planning was compared with the postoperative radiograph using a modified version of the well-established EBRA-FCA program. The results of this new measurement were compared to conventional measurements. In 25 cases the intraobserver and interobserver reliability was determined.

RESULTS

The novel measurements correlated best with the measured distance between the greater trochanter and the center of rotation and yielded the best intraobserver and interobserver reliability. In general, cementless stems had a slightly more proximal position (0.65 mm) compared to cemented stems.

CONCLUSIONS

The modified program for migration measurement facilitates a reproducible and fast comparison of the planned and achieved shaft positions thus implementing an early and objective control of postoperative shaft position.

Low BMD affects initial stability and delays stem osseointegration in cementless total hip arthroplasty in women: a 2-year RSA study of 39 patients

BACKGROUND AND PURPOSE

Immediate implant stability is a key factor for success in cementless total hip arthroplasty (THA). Low bone mineral density (BMD) and age-related geometric changes of the proximal femur may jeopardize initial stability and osseointegration. We compared migration of hydroxyapatite-coated femoral stems in women with or without low systemic BMD.

PATIENTS AND METHODS

61 female patients with hip osteoarthritis were treated with cementless THA with anatomically designed hydroxyapatite-coated femoral stems and ceramic-ceramic bearing surfaces (ABG-II). Of the 39 eligible patients between the ages of 41 and 78 years, 12 had normal systemic BMD and 27 had osteopenia or osteoporosis. According to the Dorr classification, 21 had type A bone and 18 had type B. Translational and rotational migration of the stems was evaluated with radiostereometric analysis (RSA) up to 2 years after surgery.

RESULTS

Patients with low systemic BMD showed higher subsidence of the femoral stem during the first 3 months after surgery than did those with normal BMD (difference = 0.6, 95% CI: 0.1-1.1; p = 0.03). Low systemic BMD (odds ratio (OR) = 0.1, CI: 0.006-1.0; p = 0.02), low local hip BMD (OR = 0.3, CI: 0.1-0.7; p = 0.005) and ageing (OR = 1.1, CI: 1.0-1.2; p = 0.02) were risk factors for delayed translational stability. Ageing and low canal flare index were risk factors for delayed rotational stabilization (OR = 3, CI: 1.1-9; p = 0.04 and OR = 1.1, CI: 1.0-1.2; p = 0.02, respectively). Harris hip score and WOMAC score were similar in patients with normal systemic BMD and low systemic BMD.

INTERPRETATION

Low BMD, changes in intraosseous dimensions of the proximal femur, and ageing adversely affected initial stability and delayed osseointegration of cementless stems in women.

Retrospective and consecutive analysis of the long-term outcomes of the SBG stem: a 15-year follow-up study

BACKGROUND

In 1991, 230 cementless total hip arthroplasties (THAs) with anatomical Stolzalpe-Buchner-Graf (SBG) stems were implanted in 230 patients at our hospital. Patients were examined retrospectively and consecutively 15 years after the operations.

METHODS

In total, 118 patients were available for follow-up (average 12.8 +/- 3.8 years postoperatively), with 44 examined clinically/radiologically at our hospital and 74 interviewed by telephone. Five THAs needed revision (stem explantation), three for aseptic loosening. Average patient age at the time of surgery was 61 years (27-91 years). For all THAs, we implanted ceramic-to-metal heads in combination with ultra-high molecular weight polyethylene inlay (ceramic/polyethylene and metal/polyethylene articulating components).

RESULTS

The survival rate of the SBG stem was 98.13% (CI 94.32-99.39%) with aseptic loosening as the endpoint and 96.98% (CI 92.85-98.74%) with revision and stem explantation for any other reason as the endpoint. The average Harris Hip Score was 36.0 +/- 6.9 (range 22-45) preoperatively, increasing to 88.2 +/- 15.3 (30-100) for clinically evaluated patients and 80.3 +/- 11.3 (27-91) for telephone-interviewed patients at 15 years postoperatively. Osteolysis and radiolucent lines around the prosthetic stem were rarely observed (mainly at the proximal diaphysis).

CONCLUSION

These follow-up results emphasize the excellent long-term outcomes associated with the SBG stem.

Cementless total hip replacement: a prospective clinical study of the early functional and radiological outcomes of three different hip stems

INTRODUCTION

Optimal fixation of cementless total hip stems is essential for long-term survival rates.

AIM

The purpose of this prospective study was to evaluate the early clinical and radiological outcomes of two new total hip stems with metaphyseal (Symax®) and predominantly diaphyseal (Hipstar®) anchoring principles in comparison to the well-established straight Zweymueller (SL-Plus®) stem.

METHOD

Clinical and radiological evaluations of 74 patients were undertaken preoperatively as well as at 6 and 12 months postoperatively using the Harris Hip Score (HHS) and Western Ontario and McMaster Universities-Score.

RESULTS

During follow-up no stem had to be revised. The mean preoperative HHS of the three study groups amounted to 54.6 ± 15.7 points. At the 12 months follow-up the mean HHS in the SL-Plus group (n = 22) was 88.3 ± 10.5 points, in the Hipstar group (n = 25) 83.3 ± 15.0 and the in Symax group (n = 27) 83.6 ± 15.1. Due to stress shielding the straight Hipstar stem revealed radiolucent lines in the proximal Gruen zones of about 60%, whereas the SL-Plus stem showed significantly more radiolucent lines (87%). However, subsequent long-term studies must be carried out in order to clarify if the progression of radiolucent lines may influence the clinical result and implant longevity.

Second-generation uncemented stems: excellent 5-13-year results

INTRODUCTION

The purpose of this study was to prospectively evaluate the 5-13-year results of a cementless total hip arthroplasty with a special focus on the survivorship,occurrence of osteolysis, incidence of intraoperative femoral fractures, thigh pain, and cortical hypertrophy of the femoral stem. The femoral component used in this study was titanium fluted, slotted, symmetrical component that was prepared with intraoperative machining. The proximal third of the stem had hydroxyl-apatite coating and horizontal steps.

METHODS

The clinical and radiographical results of a consecutive series of 157 total hip arthroplasties (124 patients)with this stem were investigated. Minimum follow-up was 5 years. The average age of the patients at the time of surgery was 47 years. Three patients died and ten patients were lost to follow-up, leaving 142 hips for evaluation. The clinical result was evaluated on the basis of the Merled’Aubigné score, complications and thigh pain. A detailed radiographic analysis was performed at each follow-up visit. Kaplan–Meier survivorship analysis was performed to evaluate stem, cup, and bearing survivorship.

RESULTS

The mean follow-up was 8.5 years (range 5-13 years). The average Merle d’Aubigné score improved from 10.5 points preoperatively to 17.4 points postoperatively.The cumulative 10-year survival rate was 99% for the femoral component, 99% for the acetabular component,and 69% for the bearing. Thigh pain was identified in three patients (2%). There was no distal femoral osteolysis.Seventy-nine percent of all the hips had endosteal spot welds around the coated, proximal one-third of the prosthesis.51% had radio dense lines around the distal tip of the prosthesis,and 3% had cortical hypertrophy. One undersized stem and one cup were revised for aseptic loosening, and 25 bearings were exchanged.

CONCLUSIONS

Uncemented, machined, fluted titanium canal-filling femoral components achieve reliable fixation in this young patient population. They have a decreased incidence of activity-related thigh pain, lower rate of intraoperative femur fractures and cortical hypertrophy with comparable bone-ingrowth in comparison to other second generation uncemented femoral components described in literature. Bearing wear and the need for bearing exchange was the only limitation of these constructs.

Cemented versus non-cemented hemiarthroplasty of the hip as a treatment for a displaced femoral neck fracture: design of a randomised controlled trial

BACKGROUND

A discussion is ongoing whether displaced femoral neck fractures in elderly patients should be treated with a non-cemented or a cemented hemiarthroplasty. A recent Cochrane analysis stresses the importance of further research into the relative merits of these techniques. We hypothesise that non-cemented hemiarthroplasty will result in at least the same technical-functional outcome and complication rate, with a shorter operation time.

METHODS AND DESIGN

A randomised controlled multicentre trial will be performed.The study population consists of 200 patients of 70 years and older. Patients with a displaced femoral neck fracture will be allocated randomly to have a cemented or a non-cemented hemiarthroplasty. Data will be collected preoperatively, immediately postoperatively, and 6 weeks, 3 months and 1 year postoperatively.The main outcome measures of this study are technical-functional results of the hemiarthroplasty, duration of surgery, complications, and mid-thigh pain. Secondary outcome measures are living conditions at final follow up, self-reported health-related quality of life, and radiological evaluation of the hemiarthroplasty.

CONCLUSION

A recent Cochrane analysis did not find arguments in favour of either non-cemented or cemented hemiarthroplasty. The forthcoming trial will compare treatment for a displaced femoral neck fracture by cemented versus non-cemented hemiarthroplasty. Our results will be published as soon as they become available.

TRIAL REGISTRATION

Trial Registration Number NTR1508.

An in vitro study of the strain distribution in human femora with anatomical and customised femoral stems

Hydroxyapatite-coated standard anatomical and customised femoral stems are designed to transmit load to the metaphyseal part of the proximal femur in order to avoid stress shielding and to reduce resorption of bone. In a randomised in vitro study, we compared the changes in the pattern of cortical strain after the insertion of hydroxyapatite-coated standard anatomical and customised stems in 12 pairs of human cadaver femora. A hip simulator reproduced the physiological loads on the proximal femur in single-leg stance and stair-climbing. The cortical strains were measured before and after the insertion of the stems.

Significantly higher strain shielding was seen in Gruen zones 7, 6, 5, 3 and 2 after the insertion of the anatomical stem compared with the customised stem. For the anatomical stem, the hoop strains on the femur also indicated that the load was transferred to the cortical bone at the lower metaphyseal or upper diaphyseal part of the proximal femur.

The customised stem induced a strain pattern more similar to that of the intact femur than the standard, anatomical stem.