Revision rate after short-stem total hip arthroplasty: a systematic review of 49 studies

Do all short stem types restore biomechanical parameters of the hip? Comparison according to femoral neck osteotomy levels

PURPOSE

There is no consensus on ideal short femoral stem design. A classification system proposed by Feyen and Shimmin divides short stems in two types according to femoral neck osteotomy levels: subcapital (IIIA) and standard (IIIB). The study aims to determine which design type is more successful in restoring native biomechanical parameters and whether stem type has an impact on clinical results.

METHODS

In this retrospective comparative study, patients that have undergone short stem hip arthroplasty were evaluated according to stem types: type IIIA (n = 52, 66.7%) (Mathys Optimys) and IIIB (n = 26, 33.3%) (Implantcast Aida and Smith & Nephew SMF). Pelvis X-rays were assessed in terms of femoral neck length, horizontal and vertical hip centres of rotation, horizontal and vertical femoral offsets, abductor lever arm lengths, leg lengths, and stem-shaft angles. Improvement in Harris hip scores, differences between post-operative and pre-operative measurements, and stem-shaft angles were evaluated and compared between two groups.

RESULTS

Mean femoral neck resection (8.27 ± 6.68 mm in IIIA and 15 ± 6.33 mm in IIIB) was significantly different between both groups (p < 0.001). Harris hip scores were increased at post-operative six months in both groups with no difference (84.4 ± 6.4 and 84.6 ± 5.5, p = 0.4). The absolute values of differences between pre-operative and post-operative horizontal centres of rotation (p = 0.63), vertical centers of rotation (p = 0.75), horizontal femoral offsets (p = 0.78), vertical femoral offsets (p = 0.83), abductor lever arm distances (p = 0.63), and leg length (p = 0.21) measurements were not different between both groups. Stem positions were both varus with no statistically significant difference between groups (p = 0.14).

CONCLUSION

We found no difference regarding restoration of biomechanical parameters between short stem designs with different levels of neck osteotomy. Additionally, short stem can mostly result in varus component positioning regardless of the level of neck osteotomy.

Long-term outcomes of the mayo conservative hip system in patients aged 30 years or less with osteonecrosis of the femoral head: mean follow-up of more than 10 years

INTRODUCTION

Historically, total hip arthroplasty (THA) in very young patients has been associated with lower survivorship. However, the long-term outcomes of THA using short stems for osteonecrosis of the femoral head (ONFH) in very young patients remain unclear. Therefore, this study aimed to investigate the long-term outcomes of the Mayo conservative hip system, a short metaphyseal stabilised stem, in patients with ONFH aged ≦30 years.

MATERIALS AND METHODS

We retrospectively reviewed 104 joints in 76 patients with ONFH who underwent THA using the Mayo conservative hip system with a minimum follow-up of 8 years. The mean follow-up period was 12.5 (range, 8-19) years. Patients were categorised into two age groups (≦30 years, n = 21 and > 30 years, n = 83). Radiographic evaluation was used to assess stem sinking, stress shielding, and spot welds. The clinical evaluations were performed using the Japanese Orthopedic Association (JOA) hip score. Postoperative major complication and revision surgery rates were also assessed.

RESULTS

The patient characteristics were similar between the two groups, except for the age. Revision surgeries were performed in five cases, with similar implant survival rates between the groups. Dislocations occurred in the older age group alone (four joints). One case of intra-operative periprosthetic femoral fracture was found in the younger age group. Stem sinking of > 3 mm occurred in one and seven joints in the younger and older age groups, respectively. Spot welds were observed in most joints (93.2%) in modified Gruen zones 2 and 6 without significant differences between the groups. Stress shielding showed no significant differences in the frequency of occurrence or location between the two groups. Furthermore,the JOA score showed no significant difference between the two groups.

CONCLUSION

The use of short stems in patients aged ≤ 30 years with ONFH showed favourable long-term outcomes.

Total Hip Replacement with a Fully Hydroxyapatite-Coated Shortened Stem: Five- to Thirteen-Year Follow-Up Results

Background: Shortened femoral stems aim to mimic the biomechanical performance of traditional stems while preserving more bone and minimizing soft tissue damage. Our objective is to assess the outcomes of patients treated with a shortened stem (Furlong Evolution, JRI Orthopaedics, Sheffield, UK) to analyze the implant's efficacy and survivorship. Methods: This retrospective observational study included all patients aged 18 to 70 undergoing uncemented shortened stem total hip replacement at Hospital del Mar between 2010 and 2018. Hip function and pain were assessed with the Merle d'Aubigné-Postel scale and visual analog scale, respectively. A radiographic analysis measured stem and cup orientation, leg length discrepancy, stem subsidence, and radiolucencies around the cup. Perioperative complications, prosthetic failures, and reoperations were documented. Results: A total of 109 patients (74 male, 35 female) of a mean age of 51.8 ± 8.8 years were included. The average follow-up was 91 ± 17.4 months. Radiographically, 71 (65.1%) of the stems had been inserted at the appropriate angulation (±3°), and 102 (93.6%) of the cups had been placed in the Lewinnek safety zone. Leg length discrepancy was observed in 19 (17.4%) cases. The mean Merle d'Aubigné-Postel score improved from 13.1 ± 1.39 preoperatively to 17.8 ± 0.49 at 6 months postoperatively (p < 0.001). Merle d'Aubigné-Postel subscales also reflected a statistically significant improvement (p < 0.001). The mean pain score 12 months postoperatively was 0.52 ± 1.22, with 95.4% of patients declaring themselves satisfied or highly satisfied. The expected 13-year survival according to a Kaplan-Meier analysis was 100% in the absence of infection and 91.3% if revision for any cause is taken as a survival endpoint. Conclusions: The shortened stem under analysis provides excellent functional results and long-term survival rates.

Long stem revision versus short stem revision with plate osteosynthesis for Vancouver type B2 periprosthetic femoral fracture: a comparative study of eighty five cases

PURPOSE

Periprosthetic femoral fractures (PPFs) around the hip are challenging complications in orthopaedic surgery, particularly Vancouver type B2 (VTB2) fractures. The surgical management of these fractures is crucial and depends on various factors. Cementless short taper stem with plate osteosynthesis is an alternative surgical technique. This study aims to compare the outcomes of this surgical technique with revision arthroplasty (RA) with long stem in the treatment of VTB2 PPFs.

METHODS

This retrospective study was conducted in a single medical institute from February 2010 to May 2019. Patients who had received either total hip arthroplasty or bipolar hemiarthroplasty and subsequently developed a VTB2 PPF were included; patients who sustained intra-operative fractures or received a cemented stem previously were excluded from the analysis. The patients were divided into two groups: group I received RA with cementless long stem, while group II underwent RA with cementless short taper stem with plate osteosynthesis. Demographic data, radiographic and functional outcomes, and complications were analyzed between the two groups.

RESULTS

A total of 85 patients diagnosed with VTB2 PPFs were included in the study. There were no significant differences between the two groups in terms of demographic data, including age, gender, mean follow-up times, estimated blood loss, and operative times. The radiographic results showed that there was no significant difference in the incidence of subsidence and implant stability between the two groups. However, group II tended to have less subsidence and periprosthetic osteolysis. Patients in group II had significantly better functional scores (mean Harris hip score: post-operative: 60.2 in group I and 66.7 in group ii; last follow-up: 77.4 in group 1 and 83.2 in group II (both p < 0.05)). There were no significant differences in the overall complication rate, including infection, dislocation, re-fracture, and revision surgery, between the two groups.

CONCLUSIONS

Both surgical techniques, cementless long stem and cementless short taper stem with plate osteosynthesis, are effective in the treatment of Vancouver B2 PPFs, with no significant differences in outcomes or complications. However, patients in cementless short taper stem with plate osteosynthesis had better functional scores at both post-operative and the last follow-up.

Midterm Comparative Analysis of Short Femoral Stem Survivorship in Dorr Type A Femurs

Background

Proximal-distal mismatch has emerged as a prominent concern in Dorr type A femoral morphology, prompting the exploration of short stems as promising alternatives to conventional stems. This study aimed to evaluate clinical and radiographic outcomes of total hip arthroplasty (THA) using short femoral stems in Dorr type A proximal femoral morphology with a minimum follow-up of 5 years.

Methods

Patients with short femoral stems in Dorr type A between 2011 and 2017 were included. Patients with the Short Modular Femoral (SMF) stem and Metha stem were recruited and patients with a shortened tapered stem (Tri-Lock BPS) were matched by propensity score matching based on age, sex, body mass index, calcar to canal ratio, and diagnosis. Patient-reported outcomes and the presence of thigh pain were assessed at 5 years postoperatively. Revision rate, complication rate, and radiographic outcomes were also assessed and compared.

Results

Twenty-two cases (81%) in the SMF stem and 43 cases (65%) in the Metha stem had more than 5 years of follow-up data available. The SMF stem showed a higher failure rate than the other 2 groups, with 18% requiring revision surgery in the SMF stem compared to 4.6% in the Metha stem, and 2.3% in the Tri-Lock BPS. The SMF stem showed considerable complications such as stem position change and lateral cortical hypertrophy with inferior clinical outcomes than the other 2 stem groups. When the Metha stem and the Tri-Lock BPS groups were compared, more intraoperative fractures were observed in the Metha stem, whereas stress shielding and anterior thigh pain were significantly more prevalent in the Tri-Lock BPS.

Conclusions

The SMF stem might be less reliable than previously reported, showing a high failure rate and increased radiologic complications. Thus, its use for THA in Dorr Type A femurs needs caution. On the other hand, the Metha stem showed comparable outcomes to the shortened tapered Tri-Lock BPS.

Mid-term survival of the Optimys short stem: A prospective case series of 500 patients

BACKGROUND

In recent years, there has been an increase in the number of total hip arthroplasty procedures in the younger patient population. This active group has higher expectations of their prosthesis in comparison to the older population, and there is a greater physical demand for the prosthesis. Short femoral stems were introduced to retain proximal bone stock and joint biomechanics and became more common to implant in this specific population. Currently, the long-term survival and functional outcomes of various short stems are still being investigated in different clinics.

AIM

To determine the 5-year survival of the Optimys hip stem.

METHODS

This was a prospective multicenter cohort study of 500 patients conducted in two hospitals in the Netherlands. All patients received the Optimys short stem (Mathys Ltd, Bettlach, Switzerland). The primary outcome measure was survival of the hip stem, with revision as the endpoint. The secondary outcome measurements included patient-reported outcome measures (PROMs). Kaplan-Meier analysis was used to calculate the 5-year survival rate. Log-minus-log transformation was performed to calculate the 95% confidence interval (95%CI). Mixed model analyses were performed to assess the course of the PROMs during the 1st 2 years after surgery. Analyses were modeled separately for the 1st and 2nd years to calculate the yearly change in PROMs during both follow-up periods with accompanying 95%CIs.

RESULTS

The mean age of the total 500 patients was 62.3 years (standard deviation: 10.6) and 202 were male (40%). At a median follow-up of 5.5 years (interquartile range: 4.5-6.7), 7 patients were deceased and 6 revisions were registered, for infection (n = 3), subsidence (n = 2) and malposition (n = 1). This resulted in an overall 5-year survival of 98.8% (95%CI: 97.3-99.5). If infection was left out as reason for revision, a stem survival of 99.4% (95%CI: 98.1-99.8) was seen. Baseline questionnaires were completed by 471 patients (94%), 317 patients (63%) completed the 1-year follow-up questionnaires and 233 patients (47%) completed the 2-year follow-up. Both outcome measures significantly improved across all domains in the 1st year after the operation (P < 0.03 for all domains). In the 2nd year after surgery, no significant changes were observed in any domain in comparison to the 1-year follow-up.

CONCLUSION

The Optimys stem has a 5-year survival of 98.8%. Patient-reported outcome measures increased significantly in the 1st postoperative year with stabilization at the 2-year follow-up.

Short stem hip arthroplasty with the optimys prosthesis is a safe and effective option for obese patients: a mid-term follow-up multicenter study

INTRODUCTION

Short stems are a valuable option in young patients undergoing total hip arthroplasty (THA) because of their bone stock preserving properties facilitating revision hip arthroplasty. Although the effect of obesity on conventional THA is well studied, data about short stem THA in obese patients are lacking. Therefore, this study aimed to investigate the influence of obesity on complications, revisions, and outcome after short stem THA.

MATERIALS AND METHODS

This multicenter, observational cohort study included patients undergoing short stem THA with the optimys prosthesis. Follow-up examinations were performed at specific intervals up to 7 years postoperatively. Operation characteristics, general and specific complications, revisions, VAS rest pain, VAS load pain, VAS patient satisfaction, and Harris Hip Score (HHS) were recorded and statistically compared between obese (BMI ≥ 30 kg/m2) and non-obese (BMI < 30 kg/m2) patients.

RESULTS

Of the 224 patients included with a mean follow-up of 87.2 months (range 81.9-104.0), 69 were assigned to the OB group and 155 to the non-OB group. A minimally invasive approach was significantly less often selected in obese patients (p = 0.049), whereas operating time and length of hospital stay were not significantly different. The rate of general and specific complications did not significantly differ between both groups. Survival of the optimys prosthesis was 99.1% at 7-year follow-up and one patient per group had to undergo revision surgery. VAS rest pain, load pain, and satisfaction improved from preoperatively to postoperatively in both groups without a significant difference between both groups. While the HHS was improved from preoperatively to postoperatively, obese patients showed a significantly lower HHS at the 7-year follow-up (p = 0.01) but still exhibited an excellent scoring above the PASS threshold.

CONCLUSION

Short stem THA with the optimys prosthesis is a safe and effective option also in obese patients with an excellent clinical outcome and a low complication rate.

Ten-year follow-up and clinical outcome of a metaphyseal anchoring short hip stem prosthesis: a retrospective single-centre analysis

PURPOSE

Short stems for total hip arthroplasty are an alternative to traditional conventional long stems. Short stems are designed to facilitate minimal-invasive surgery, improve bone-stock preservation, and mimic a physiological load distribution. However, there is little evidence of the long-term outcome of short stems. This study aims to analyze the ten year survival rates and clinical outcome of one specific metaphyseal short hip stem implant.

METHODS

We retrospectively analyzed the patient records of the patients who underwent a total hip arthroplasty with a monoblock partial collum sparing metaphyseal short hip stem prosthesis in 2008 and 2009 in our clinic. Patients were contacted, and clinical follow-up was recorded using the German version of the modified Harris Hip Score. Furthermore, complications, revision surgery, and post-operative radiographs were analyzed.

RESULTS

Data from 339 primary implantations in 322 patients were retrieved. The mean follow-up was 10.6 years. Seven patients underwent a revision. The ten year survival rate with any revision surgery as the endpoint was 97.5%. The mean modified Harris Hip Score was 86 points (range 30 to 91 points). Five patients had an intraoperative fracture of the femur (1.6%). Two patients (0.6%) had a dislocation of the hip. The stem tip-to-cortex distance, measured in the anterior posterior view, was 2.6 mm (range 0 to 8.3 mm).

CONCLUSION

The ten year survival rate of our used monoblock partial collum sparing metaphyseal short hip stem implant is comparable to traditional stems for total hip arthroplasty.

A neck-sparing short stem shows significantly lower blood loss in total hip arthroplasty compared to a neck-resecting short stem

Short stems are associated with a significantly lower blood loss (BL) compared to straight stems in total hip arthroplasty (THA). Different types of stems differ in design, fixation and level of femoral neck osteotomy. Therefore, we sought to evaluate the difference regarding the perioperative BL between two short stems with different designs in direct anterior approach (DAA). A total of 187 THA performed by a single surgeon were analysed. 107 patients received a neck-resecting (Group A) and 80 patients a neck-sparing short stem (Group B). Blood counts of the day before surgery and of two days after surgery were evaluated. Total blood volume and BL were calculated. Additionally, duration of surgery was analysed. The perioperative BL was significantly lower in Group B (451.4 ± 188.4 ml) compared to Group A (546.6 ± 232.7 ml; p = 0.002). The postoperative haematocrit (31.6 ± 3.7% vs. 30.4 ± 4.4%; p = 0.049) and haemoglobin-level (11.0 ± 1.3 g/dL vs. 10.4 ± 1.5 g/dL; p = 0.002) were significantly higher in Group B. Duration of surgery was significantly shorter in Group B (62.0 ± 11.4 min vs. 72.6 ± 21.8 min; p < 0.001). The use of a neck-sparing short stem leads to a significantly decreased BL compared to a neck-resecting short stem in DAA THA. A less extensively conducted capsular release necessary for optimal femoral exposition might lead to a lower perioperative BL and shorter durations of surgery.

Short-stem hip arthroplasty in Australia and the Netherlands: a comparison of 12,680 cases between the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) and the Dutch Arthroplasty Register (LROI)

BACKGROUND AND PURPOSE

We compared the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) and the Dutch Arthroplasty Register (LROI) regarding patient, prosthesis, and procedure characteristics as well as revision rates for uncemented short-stem total hip arthroplasties (THAs).

PATIENTS AND METHODS

All THAs with an uncemented short-stemmed femoral component performed between 2009 and 2021 were included from the AOANJRR (n = 9,328) and the LROI (n = 3,352). Kaplan-Meier survival analyses and multivariable Schemper's weighted Cox regression analyses with data from 2009-2021 and 2015-2021 were performed with overall revision as endpoint.

RESULTS

In Australia, the proportion of male patients (51% vs. 40%), patients with ASA III-IV score (30% vs. 3.7%), BMI ≥ 30.0 (39% vs. 19%), and femoral heads of 36 mm (58% vs. 20%) were higher than in the Netherlands. Short-stem THAs in Australia and the Netherlands had comparable 10-year revision rates (3.4%, 95% confidence interval [CI] 2.9-4.0 vs. 4.8%, CI 3.7-6.3). Multivariable Cox regression analyses with data from 2009-2021 showed a higher risk for revision of short-stem THAs performed in the Netherlands (HR 1.8, CI 1.1-2.8), whereas the risk for revision was comparable (HR 0.9, CI 0.5-1.7) when adjusted for more potential confounders using data from 2015-2021.

CONCLUSION

Short-stem THAs in Australia and the Netherlands have similar crude and adjusted revision rates, which are acceptable at 10 years of follow-up.

A comparison of uncemented short versus standard stem length in total hip arthroplasty: results from the Dutch Arthroplasty Register

BACKGROUND AND PURPOSE

We aimed to compare revision rates between uncemented short and standard stems in total hip arthroplasties (THAs) and the corresponding patient-reported outcome measures (PROMs).

PATIENTS AND METHODS

We included all short (C.F.P., Fitmore, GTS, Metha, Nanos, Optimys, Pulchra, and Taperloc Microplasty) and standard stems in uncemented THAs registered between 2009 and 2021 in the Dutch Arthroplasty Register. Kaplan-Meier survival and multivariable Cox regression analyses were performed with overall and femoral stem revision as endpoints.

RESULTS

Short stems were used in 3,352 and standard stems in 228,917 hips. 10-year overall revision rates (4.8%, 95% confidence interval [CI] 3.7-6.3 vs. 4.5%, CI 4.4-4.6) and femoral stem revision rates (3.0%, CI 2.2-4.2 vs. 2.3%, CI 2.2-2.4) were comparable for short- and standard-stem THAs. Today's predominant short stems (Fitmore and Optimys) showed short-term revision rates similar to that of standard-stem THAs. Other, less frequently used short stems had higher 10-year overall (6.3%, CI 4.7-8.5) and femoral stem (4.5%, CI 3.1-6.3) revision rates. Multivariable Cox regression also showed a higher risk for overall (HR 1.7, CI 1.0-2.9) and femoral stem revision (HR 2.0, CI 1.1-3.5) using the latter short stems compared with standard stems. An exploratory analysis of PROMs showed no difference.

CONCLUSION

There was no overall difference in revision rates but a tendency toward increased revision of short stems both for the whole THA and for the stem itself. The less frequently used short stems had increased revision risk. No difference in PROMs was shown.

Femoral Anteversion in Total Hip Arthroplasty: Retrospective Comparison of Short- and Straight-Stem Models Using CT Scans

Data on reconstruction of the femoral anteversion (FA) and the center of rotation after total hip arthroplasty (THA) are rare. We aimed to answer whether a short-stem fixation enables improved anatomical reconstruction of the FA compared to a straight-stem. Methods: One hundred and thirty patients who underwent short- (n = 89, group A, prospective) or straight-stem THA (n = 41, group B, retrospective) were included. CT scans of the hip, knee, and ankle were performed pre- and postoperatively in group A and in group B during the last follow-up. Femoral torsion was determined using three-dimensional models. Results: The mean preoperative FA was 22.4° ± 11.0°, and the mean postoperative FA was 23.4° ± 10.1°. The relative difference was −0.8° ± 8°, and the absolute difference was 6.4° ± 4.9°. Gender analysis revealed significant differences in preoperative FA between female (f) and male (m) patients (28.1° ± 11.2° (f) vs. 18.4° ± 8.3° (m); p > 0.001) as well as in postoperative FA (26.7° ± 23.5° (f) vs. 21.0° ± 9.7° (m); p < 0.007) in group A. Postoperative FA was higher in group A (mean 6.8°; 23.9° ± 10.1° (f) vs. 16.6° ± 8.6° (m); p < 0.001). Conclusions: The study’s findings suggest that short-stem THA leads to improved anatomical FA reconstruction; however, a substantial postoperative gender-related FA difference was detectable, which may warrant consideration by surgeons when determining the final stem anteversion. It should be noted that the impact of the postoperative gender-related FA difference on clinical outcomes is not entirely clear, and further research is warranted to elucidate this relationship.

Biomechanical Properties of Bionic Collum Femoris Preserving Hip Prosthesis: A Finite Element Analysis

OBJECTIVE

Compared with total hip replacement, conventional collum femoris preserving prosthesis has a better bone retention effect. However, damage to the trabecular bone of the proximal femur leads to inevitable abnormal stress distribution, which leads to increased risks of femoral neck bone absorption, periprosthetic fracture, prosthesis loosening, rotation, and sinking. Thus, we compare the biomechanical properties of collum femoris preserving (CFP) and bionic collum femoris preserving (BCFP) hip prostheses.

METHODS

The Sawbone digital model (#3503, left, medium) was selected as the research object. We used the Mimics 21.0 software to reconstruct the digital model of the femur and the SolidWorks 2019 software to build and assemble the three-dimensional models of CFP and BCFP prostheses. With the ANSYS Workbench 2021R1 software, the models were meshed and assigned values to simulate the load of a single foot under slow walking. We measured the mechanical distribution of the whole model and obtained the stress nephogram.

RESULTS

For CFP prosthesis, the peak stresses of the medial interface of the stem neck, the lateral interface of the stem neck, and the end of the stem were 64.894, 32.199, and 8.578 MPa, respectively; the peak stresses of the medial surface of the femoral shaft, the lateral surface of femoral shaft, the medial femoral neck bone-prosthesis interface (osteotomy interface), the lateral femoral neck bone-prosthesis interface (basal area), the lateral femoral neck bone-prosthesis interface (osteotomy interface), and the greater trochanter area were 28.093, 24.790, 14.388, 5.118, 4.179, and 8.245 MPa, respectively; the valley stress of the greater trochanter area was 1.134 MPa. For BCFP prosthesis, the peak stresses of the medial interface of the stem neck, the lateral interface of the stem neck, and the end of the stem were 47.015, 26.771, and 47.593 MPa, respectively; the peak stress of tension screw was 15.739 MPa; the peak stresses of the medial surface of the femoral shaft, the lateral surface of femoral shaft, the medial femoral neck bone-prosthesis interface (osteotomy interface), the lateral femoral neck bone-prosthesis interface (basal area), the lateral femoral neck bone-prosthesis interface (osteotomy interface) and the greater trochanter area were 28.581, 25.364, 15.624, 6.434, 4.986, and 8.796 MPa, respectively; the valley stress of the greater trochanter area was 1.419 MPa; the peak stress of bone-metal interface between the tension screw and the lateral surface of the femur was 5.858 MPa.

CONCLUSION

Compared with the CFP prosthesis, the design of the BCFP prosthesis is based on the lever balance theory. With the bionic reconstruction of tension trabeculae, BCFP prosthesis makes up for the defects of CFP prosthesis design, optimizes the stress distribution, and reduces the stress shelter effect of the proximal femur, which has better biomechanical properties.

Bionic reconstruction of tension trabeculae in short-stem hip arthroplasty: a finite element analysis

BACKGROUND

Short-stem hip arthroplasty (SHA) is characterized by metaphyseal load transfer that effectively preserves the bone stock, but still suffers from stress shielding in the proximal femur. We designed a tension screw to mimic tension trabeculae in the new bionic collum femoris preserving (BCFP) short stem for bionic reconstruction, aiming to restore the biomechanics of hip joint.

METHODS

Native femur finite element model was constructed to investigate the biomechanics of hip joint based on computed tomography (CT) data. The maximum absolute principal stress/strain cloud chart allowed the direction of stress/strain to be assessed. Six BCFP models with different screw angles (5°, 10°, 15°, 20°, 25°, and 30°) and the Corail model were created. The stress/strain distribution and overall stiffness were compared between each of the BCFP and Corail implanted models.

RESULTS

The native model visualized the transfer pathways of tensile and compressive stress. The BCFP stems showed significantly higher stress and strain distribution in the greater trochanteric region compared to conventional total hip arthroplasty (THA). In particular, the BCFP-5° stem demonstrated the highest average strain in both medial and lateral regions and the overall stiffness was closest to the intact femur.

CONCLUSIONS

Stress transfer pathways of trabecular architecture provide biomechanical insight that serves as the basis for bionic reconstruction. The tension screw improves load transfer pattern in the proximal femur and prevents stress reduction in the greater trochanteric region. The BCFP-5° stem minimizes the stress shielding effect and presents a more bionic mechanical performance.

Survival and radioclinical evaluation of the Optimys™ short stem at more than 6years' mean follow-up: A retrospective study of 108 cases

INTRODUCTION

The short stems developed in recent years offer an interesting alternative to standard long stems. The Optimys™ short stem has been widely studied, but not according to the National Institute for Health and Care Excellence (NICE) criteria. We therefore conducted a retrospective study of Optimys™ at a minimum 5years' follow-up, to assess: (1) survival on NICE criteria, (2) complications, (3) functional results, and (4) subsidence, restoration of offset and bone remodeling.

HYPOTHESIS

Optimys™ shows survival comparable to that of other non-cemented standard and short stems, with a<0.5% per year revision rate or<2.5% at 5years on NICE criteria.

MATERIAL AND METHODS

A single-center retrospective study included 108 Optimys™ stems at a mean 76.5months' follow-up (range: 60-112months). Clinical [Harris, Oxford-12 and forgotten hip (French version: SHO-12) scores] and radiologic data were collected pre- and postoperatively. Analysis focused on implant survival, complications, functional results and radiological results (restoration of offset, bone remodeling, subsidence and osseointegration) and risk factors for stem migration.

RESULTS

At a mean 76.5months' follow-up (range: 60-112months), Optimys™ survival was 97.7% (95% CI: 0.945-1). Oxford and Harris scores improved significantly: respectively, 16.1 vs. 44.7 [Δ=28.598; 95% CI: 27.410-29.785 (p<0.001)] and 45.3 vs. 95 [Δ=49.662; 95% CI: 47.442-51.882 (p<0.001)]. Mean forgotten hip score (SHO-12) at last follow-up was 82.7±19.6 (range: 35.4-100.0). There was 1 case of aseptic revision at 11months for femoral osseointegration defect. Mean subsidence was 1.64mm (range: 0-20.63mm); no predisposing factors could be identified. Femoral offset increased by a mean 2.41±4.53mm (range: -10.10 to 14.70mm).

CONCLUSION

The present study reports good survival for the Optimys™ stem, which meets NICE criteria. Radiologic and clinical results were encouraging, with a low rate of subsidence, comparable to other series, but with increased femoral offset.

LEVEL OF EVIDENCE

IV; retrospective cohort study.

Simultaneous Bilateral Total Hip Arthroplasty with Straight-Stems and Short-Stems: Does the Short One Do a Better Job?

BACKGROUND

Total hip arthroplasty (THA) is known to be the most successful orthopaedic surgery of the last century, but it is still struggling with controversies concerning one-stage bilateral THA. The current study aimed to compare the clinical outcome of patients with unilateral or simultaneous bilateral THA by using short-stem and straight-stem designs and focusing on operation time, blood loss, and length of hospital stay (LOS).

MATERIAL AND METHODS

Between 2006 and 2018, 92 patients were enrolled in this study. Forty-six patients underwent a bilateral THA in one session, and forty-six matched patients underwent a unilateral THA. In each of the two groups (unilateral vs. bilateral), 23 patients received either a straight (unilateral: 10 females, 13 males, mean age 63; bilateral: 12 females, 11 males, mean age 53 years) or short stem (unilateral: 11 females, 12 males, mean age 60 years; bilateral: 12 females, 11 males, 53 mean age 62 years). The blood count was checked preoperatively as well as one and three days after surgery. Furthermore, the operation time and LOS were investigated.

RESULTS

Compared to THA with straight-stems, short-stem THA showed significantly less blood loss; there was no difference in the LOS of both groups. A significantly shorter operative time was only observed in the bilateral THA.

CONCLUSION

The current study showed that simultaneous bilateral THA appears to be safe and reliable in patients without multiple comorbidities. In addition, short-stem THA appears to be beneficial in terms of clinical performance and outcome, and it appears to be superior to straight-stem THA, regardless of whether the patient underwent unilateral or simultaneous bilateral THA.

Survivorship, complications and patient-reported outcomes in calcar-guided short-stem THA: prospective mid-term multicenter data of the first 879 hips

INTRODUCTION

Short stems are a bone and soft-tissue preserving alternative to conventional stems. The aim of this multicenter study is to present the mid-term outcomes of a calcar-guided short stem.

MATERIALS AND METHODS

This is a prospective case series of the first 879 total hip arthroplasties performed on 782 patients across 5 centers using identical calcar-guided short stems. In a mid-term follow-up (6 years), rates and reasons for complications and revisions were documented. The Harris Hip Score (HHS) was obtained; patients reported pain and satisfaction using a visual analog scale.

RESULTS

A total of 43 patients died in the study cohort for non-related reasons; 26 patients (3.0%) required at least 1 revision after the index procedure. The survival rate for endpoint stem revision at mid-term was 98.4%. The main reasons for stem revision were aseptic loosening and early periprosthetic fractures. Sex had no influence on stem survival. Older patients or those with a high body mass index showed increased risk for stem revision during follow-up. Dorr type A morphology revealed a significantly lower risk of stem revision than Dorr type B or C (p = 0.0465). The HHS, satisfaction, and load pain at mid-term were 96.5 (SD 8.0), 9.7 (SD 0.9), and 0.5 (SD 1.9), respectively.

CONCLUSIONS

This short stem produced highly satisfactory outcomes at mid-term, with 98.4% implant survival for any cause of stem revision and low complication rates. Long-term results are required to further evaluate these promising mid-term results.

[The challenge of revising a well-fixed curved calcar-guided short stem in total hip arthroplasty: Introduction of a new curved extraction chisel system]

OBJECTIVE

Safe and bone-conserving extraction of a well-fixed curved short stem without the necessity of a transfemoral approach.

INDICATIONS

The revision of a well-fixed curved short stem, for example, due to periprosthetic infection or malposition. Meticulous preparation of the cone and the lateral shoulder of the stem.

CONTRAINDICATIONS

Correct placement of the chuck not possible.

SURGICAL TECHNIQUE

Choice of a standard approach to the hip joint. Luxation. Removal of the implanted head. Preparation of the proximal femur and removal of bone at the stem shoulder. Attachment of the chuck to the cone. Insertion of the "prestarter" chisels through the guided slots of the chuck, starting with the lateral chisel, followed by the ventral and dorsal chisel. The cut must point outwards away from the implant. Repetition of this procedure using the "starter" chisels in the same order. Removal of the chuck. Careful insertion of the "final" chisels in the same order. Trial of a stem extraction using an extraction tool. Optional repetition of the whole procedure. In order to avoid fractures, opening of the medial interface only after preparation laterally, ventrally and dorsally, by careful insertion of the medial chisels in the respective order alongside the calcar. Finally, extraction of the stem.

POSTOPERATIVE MANAGEMENT

Postoperative protocol according to the respective revision implants and fixation technique used.

RESULTS

The described procedure has proven successful in clinical practice in the three author affiliations in a total of 14 cases. In 3 (21.4%) cases, despite the use of the extraction chisel system, an additional transfemoral approach or fenestration had to be performed to remove the short stem. Primary straight stems were used in over half of the cases (57.8%) as revision implants, whereas in 4 cases (36.4%) a cementless short stem could again be used.

Does an Ultra-Short Anatomic Cementless Femoral Stem Improve Long-Term (Up to 17 Years) Results in Patients Younger Than 30 Years?

BACKGROUND

The purpose of this long-term (up to 17 years) follow-up study was to determine: (1) clinical results and evidence of clicking or squeaking sounds; (2) radiographic results, including rates of osseointegration, bone remodeling, and osteolysis; (3) rates of complications including thigh pain, periprosthetic fracture, and ceramic fracture; (4) rates of revision; and (5) survival rates of implants in patients younger than 30 years.

METHODS

We analyzed the results of 240 consecutive primary total hip arthroplasty in 180 patients (118 men and 62 women who had a mean age of 27 years (range, 21 to 30 years)). The mean follow-up was 16 years (range, 14 to 17 years).

RESULTS

Mean Harris hip score, Western Ontario and McMaster Universities score, and University of California, Los Angeles activity score were 93 points, 18 points, and 7 points, respectively, at final follow-up. Radiographically, all of the acetabular components and all but two femoral components were well-fixed at the final follow-up. No hip had osteolysis or exhibited Grade 3 stress shielding. All but two patients had no groin or thigh pain. No hip had a periprosthetic or ceramic fracture. Eight hips (3%) exhibited squeaking sounds. Two acetabular components and two femoral stems were revised. The survival of the acetabular and femoral component was 99.2% (95% confidence interval, 94 to 100%).

CONCLUSION

The results of the present long-term study of ultra-short anatomic cementless femoral stems suggest excellent clinical and radiographic results in patients younger than 30 years.

Three-year migration analysis of a new metaphyseal anchoring short femoral stem in THA using EBRA-FCA

Cementless calcar-guided femoral short stems in total hip arthroplasty (THA) have become increasingly popular over the years. Early distal migration of femoral stems measured by Einzel-Bild-Roentgen Analyse, Femoral Component Analyse (EBRA-FCA) has been reported to be a risk factor for aseptic loosening. The aim of this study was to analyse axial migration behavior and subsidence of a new short stem (launched in 2015) over a follow-up period of 3 years. According to the study protocol, 100 hip osteoarthritis patients who consecutively received an unilateral cementless calcar-guided short stem (ANA.NOVA proxy) at a single department were prospectively included in this mid-term follow-up study. Thirteen patients were lost to follow-up, resulting in 87 patients with unilateral THA who fulfilled the criteria for migration analysis with EBRA-FCA. The cohort comprised 41 males (mean age: 60 ± 16.5; mean BMI (Body Mass Index): 30 ± 13) and 46 females (mean age: 61 ± 15.5; mean BMI: 27 ± 10). Seven standardized radiographs per patient were analyzed with EBRA-FCA. An average migration of 2.0 mm (0.95-3.35) was observed within the first 3 years. The median increase during the first year was higher than in the second and third year (1.2 mm [IQR: 0.5-2.15] vs. 0.3 mm [IQR: 0.1-0.6 mm] vs. 0.25 mm [IQR: 0.1-0.5 mm]. Detected migration did not lead to stem loosening, instability, dislocation, or revision surgery in any patient. A higher risk for subsidence was observed in male and heavyweight patients, whereas the female gender was associated with a lower risk. No correlation between migration and revision could be observed. Although moderate subsidence was detectable, the performance of the short stem ANA.NOVA proxy is encouraging. Yet, its use may be re-considered in overweight and male patients due to more pronounced subsidence.

Medial malleolar osteotomy for the correction of tibiotalar varus deformity during total ankle arthroplasty: Results in 95 ankles

BACKGROUND

The importance of deformity correction before or during total ankle replacement (TAR) has been recognized for a long time. Our results of TAR, combined with medial malleolar lengthening osteotomy, for the reconstruction of osteoarthritic ankles with varus deformity are hereby reported.

METHODS

All ankles in which a medial malleolar osteotomy was performed during implantation of an ankle prosthesis during the period 1998-2018 were filtered out of our database. Preoperative coronal talar alignment was evaluated by measuring the angle between the tibial shaft and talar dome on the weightbearing mortise ankle radiograph. Patient-reported outcomes were measured with the Foot and Ankle Outcome Score (FAOS) and the Foot and Ankle Ability Measure (FAAM). A Kaplan-Meier survival curve was constructed and the number of revisions per 100 observed component years was calculated for interprosthetic comparison.

RESULTS

A total of 95 TARs were included, consisting of the Alpha Ankle Arthroplasty (n = 22); Buechel-Pappas (n = 14) and the Ceramic Coated Implant Evolution (n = 59) prostheses. The preoperative average talar angle in these ankles was 12.4 degrees varus. In 33% (31/95) corrective procedures, in addition to the medial malleolar osteotomy, were performed. A reoperation rate of 44% (42/95) was found, including 28 revisions (revision rate 29% (4% septic; 25% aseptic) at an average follow-up of 5.9 years, resulting in a survival of 0.69 for the total cohort at 10 years of follow-up. At an average follow-up of 6.6 years the average FAOS scores were: FAOS_symptoms 66, FAOS_pain 73, FAOS_function 78, FAOS_sport 45 and FAOS_{quality of life} 56 respectively. The FAAM_adl score averaged 64.

CONCLUSION

This is the largest cohort of TAR combined with medial malleolar osteotomy to date. A 29% revision rate at 5.9 years of average follow-up compares unfavorably with regular cohort studies and with most other results in varus-deformed ankles. Scores on the FAOS and FAAM are comparable to those obtained in regular cohorts with similar length of follow-up. TAR in varus-deformed ankles necessitating medial malleolar osteotomy has an even higher failure rate than regular TAR. Obtaining a stable prosthesis with a neutrally-aligned hindfoot at the end of the procedure is of paramount importance.

LEVEL OF EVIDENCE

IV.

Can We Predict Fracture When Using a Short Cementless Femoral Stem in the Anterior Approach?

BACKGROUND

Short cementless femoral stems may allow for easier insertion with less dissection. The use of short stems with the anterior approach (AA) may be associated with a considerable perioperative fracture risk. Our aim was to evaluate whether patient-specific femoral and pelvic morphology and surgical technique, influence the perioperative fracture risk. Furthermore, we sought to describe important anatomical thresholds alerting surgeons.

METHODS

A single-center, multi-surgeon retrospective, case-control matched study was performed. Thirty nine periprosthetic fractures (3.4%) in 1,145 primary AA THAs using short cementless stems were identified. These were matched with 78 THA nonfracture controls for factors known to increase the fracture risk. A radiographic analysis using validated software measured femoral (canal flare index [CFI], morphological cortical index [MCI], and calcar-calcar ratio [CCR]) and pelvic (Ilium-ischial ratio [IIR], ilium overhang, and anterior superior iliac spine [ASIS] to greater trochanter distance) morphologies and surgical techniques (% canal fill). A multivariate and Receiver-Operator Curve (ROC) analysis was used to identify fracture predictors.

RESULTS

CFI (3.7 ± 0.6 vs 2.9 ± 0.4, P < .001) and CCR (0.5 ± 0.1 vs 0.4 ± 0.1, P = .006) differed. The mean IIR was higher in fracture cases (3.3 ± 0.6 vs 3.0 ± 0.5, P < .001). Percent canal fill was reduced in fracture cases (82.8 ± 7.6 vs 86.7 ± 6.8, P = .007). Multivariate and ROC analyses revealed a threshold CFI of 3.17 which was predictive of fracture (sensitivity: 84.6%/specificity: 75.6%). The fracture risk was 29 times higher when patients had CFI >3.17 and II ratio >3 (OR: 29.2 95% CI: 9.5-89.9, P < .001).

CONCLUSION

Patient-specific anatomical parameters are important predictors of a fracture-risk. A careful radiographic analysis would help identify those at a risk of early fracture using short stems, and alternative stem options should be considered.

Survivorship and Outcomes of Femoral Neck Preserving Stems in Primary Total Hip Arthroplasty

BACKGROUND

Short-stem femoral implants (SSFIs) promote the preservation of bone in the femoral neck, reduce soft tissue disruption, and facilitate minimally invasive surgical techniques. The purpose of this study was to report the revision rate, complication rate, patient satisfaction, patient-reported outcomes, and radiographic outcomes of patients who underwent total hip arthroplasty (THA) with the Alteon Neck Preserving Femoral Stem (ANPS).

METHODS

A prospectively maintained database was reviewed which analyzed 92 THAs between the years 2016 and 2018. Patient-reported outcomes, patient satisfaction, complication rates, and radiographic outcomes were assessed at 2-5 years postoperatively.

RESULTS

The final cohort consisted of 63 hips. Five patients (7.9%) underwent revision surgery and 2 (3.2%) had other complications not requiring revision. Survivorship when considering only the femoral component was 93.7% at an average of 41.4 months of follow-up. The average postoperative Oxford Hip Score (41.5 ± 8.3) and Harris Hip Score (77.9 ± 16.6) demonstrated significant improvement among our nonrevised patients, respectively (P < .001). Radiographs demonstrated spot welding in 56% of arthroplasties most commonly in Gruen Zones 2, 3, and 13 and that femur radiolucencies were visualized in 58% predominantly along the distal aspect of the stem. Radiographic femoral component subsidence was present in 9.7% of patients.

CONCLUSION

The ANPS may be less reliable than previously reported. Our cohort's revision rate was unacceptably high with 6.3% requiring revision surgery for femoral component loosening in less than 5 years. Surgeons should consider the challenges and prohibitive failure rate associated with SSFIs before routine usage in THA.

Short neck-preserving femoral stem for total hip arthroplasty: medium-term results of a 68-case series

INTRODUCTION

Short stems seem to be a good alternative for young patients as they offer promising results, rapid recovery and preservation of metaphyseal bone stock. This is one of the few studies in the literature to report medium-term clinical-radiological results for short hip stems.

MATERIALS AND METHODS

This prospective study evaluated 68 short femoral stems in 63 patients treated with total hip replacement. Clinical, functional and quality-of-life outcomes were measured at 6 and 12 months, and annually thereafter until the end of follow-up. The radiological analysis included measurements of potential leg length discrepancies, stem alignment and signs compatible with stress shielding.

RESULTS

Fifty-four males (59 hips) and nine females (9 hips) of an average age of 44.3 years (range, 25-68) were studied. The most common diagnosis was osteoarthritis (51.5%). Mean overall follow-up was 7.8 years (range, 5.8-9.8). The overall survival rate was 97.1% (95% CI 88.7-99.7%). Surgery resulted in an increase of 42.3 ± 1.1 points in the modified Harris Hip Score and 21.9 ± 0.6 points in the Oxford Hip Score (p < 0.001, respectively). Moreover, the pain score as measured on a numerical rating scale (NRS) improved from 95.8 to 36.3. As regards function, an improvement was observed from 3.2 ± 0.8 points to 6.8 ± 1.14 points on the University of California at Los Angeles activity score (p < 0.001, respectively). The radiological analysis showed an absence of radiolucencies or stress-shielding throughout the series. The complications rate at the end of follow-up was 5.7%.

CONCLUSIONS

The use of ultra-short cylindrical stems with complete anchorage in the femoral neck was shown to offer promising medium-term results. Such stems appear to be a good option for young patients, who are likely to require several revisions over their lifetime.

Ten-year revision rates of contemporary total ankle arthroplasties equal 22%. A meta-analysis

BACKGROUND

The National Institute for Health and Care Excellence criterion for hip replacements is a (projected) revision rate of less than 5% after 10 years. No such criterion is available for ankle prostheses. The objective of the current study is to compare survival rates of contemporary primary ankle prostheses to the hip-benchmark.

METHODS

The PRISMA methodology was used. Eligible for inclusion were clinical studies reporting revision rates of currently available primary total ankle prostheses. Data was extracted using preconstructed forms. The total and prosthesis-specific annual revision rate was calculated.

RESULTS

Fifty-seven articles of eight different ankle prostheses were included (n = 5371), totaling 513 revisions at an average 4.6 years of follow-up. An annual revision rate of 2.2 was found (i.e. an expected revision rate of 22% at 10 years).

CONCLUSIONS

The expected 10-year revision rate of contemporary ankle prostheses is lower than the current benchmark for hip prostheses.

A neck-preserving short stem better reconstructs the centre of rotation than straight stems: a computed tomography-based cadaver study

INTRODUCTION

Short femoral hip stems with a metaphyseal anchoring concept have been designed to treat younger patients with good bone quality. The aim of this study was to reconstruct the centre of rotation and soft tissue balancing and preserve bone in the long-term perspective.

MATERIALS AND METHODS

Eighteen human femurs were randomised into three groups: (1) metaphyseal anchoring short stem, (2) shortened straight stem, (3) straight stem). Prior to the implantation of the hip stems, a computed tomography (CT) of the bones was performed and the femoral ante-torsion and ante-tilt was measured and compared to the results of the post-implantation CT. This could be calculated based on the 3D coordinates taken from the pre- and post-op CT scans, which were transformed into the same coordinate systems.

RESULTS

The mean preoperative caput-collum-diaphyseal (CCD) angle for the three groups was 126.87° ± 3.50° (Group 3: 129.64° ± 3.53°, Group 1: 123.76° ± 5.56°, Group 2: 127.53° ± 1.42°) and was consistent with published reports. The postoperative CCD angles with 126.85° ± 3.43° were within a very good reconstruction range for all three groups. The anterior offset comparison among these three groups showed significant difference in reconstruction. The smallest difference between the anatomical (preoperative) and postoperative condition was seen in Group 1 (1.47° ± 0.60°), followed by Group 2 (3.60° ± 0.23°) and Group 3 (8.00° ± 0.70°) groups. The horizontal offset showed no significant difference among the groups and was within the window of ± 5 mm.

CONCLUSION

In this cadaver study, we found that the metaphyseal anchoring, partially neck-preserving short hip stem best reconstructs the ante-torsion and the ante-tilt of the femoral neck. Therefore, it can be a useful stem in younger or active middle-aged patients.

A 24-year single-centre experience with Collum Femoris Preserving stem: clinical and radiological results in young and elderly population

OBJECTIVE

The primary aim was to evaluate the long-term follow-up of Collum Femoris Preserving (CFP) stem, specifically focusing on stem survivorship, complications, as well as on clinical and radiological results. The secondary study objective is an age-based sub-analysis (<65 years vs. ⩾65 years) of long-term results.

MATERIALS AND METHODS

We performed a retrospective analysis of patients who underwent CFP implantation between 1997 and 2009. A total of 311 patients (342 hips) were included with a mean follow-up of 15.8 ± 2.2 (range 11-24) years. 2 age groups were analysed: Group-Y (age <65) and Group-E (age ⩾65). Group-Y included 182 hips (mean follow-up 16.3 ± 4.2 years), whereas Group-E included 160 hips (mean follow-up 15.5 ± 3.7 years). Clinical (HHS, OHS and VAS) and radiological data were obtained at final follow-up. Any complications, reoperations, prosthetic components revisions and stem revisions were analysed.

RESULTS

According to HSS score, 95% of patients reported excellent/good results (95.6% Group-Y vs. 94.4% Group-E) with an overall stem survival rate of 93.3% (94% Group-Y vs. 92.5% Group-E; p = 0.37). Overall, 87% of stem revisions were performed with primary stems. The rate of prosthetic components revision was 9.9 % (9.9% in Group-Y vs. 10% in Group-E; p = 1). The reoperation rate was 10.8% (11.5% in Group-Y vs. 10.0% in Group-E; p = 0.73).

CONCLUSIONS

The CFP stem provides good clinical and radiological long-term results with low rate of complications in both young and elderly patients. No significant difference in stem revision and reoperation rates was observed between the 2 groups. Both in elderly and young patients, CFP stem allows revisions to be performed with primary stems.

Medium-term outcomes of short stems in total hip arthroplasty

Background

Prosthetic surgery has shown good short-term results with the use of short stems, results comparable with the experience of conventional stems. The aim of this study was to investigate and describe the characteristics and clinical course of patients operated on with the short stem GTS in the medium term.

Methods

Between November 2010 and September 2014, 152 primary hip prostheses were operated on in 142 patients with a mean follow-up of 95.49 months (range 75–120). We analyzed the intraoperative and postoperative complications and the reviews performed during the follow-up.

Results

One intraoperative complications occurred; case in which a femoral calcar fracture occurred and a screw was required during the operation. The clinical evaluation at the end of the follow-up, according to the Merle D’Aubigne Scale, showed the mean value was 17.3684 (SD 0,79472), with a survival at the end of the follow-up of 99.3% of the placed GTS stems.

Conclusions

GTS short stems have shown good results after more than 6 years of follow-up, with comparable results to conventional uncemented stems. Short-stem hip arthroplasty is an advanced way to preserve bone stock while protecting soft tissue

MINIMA Short Stem Versus Standard Profemur (TL) Stem in Primary Total Hip Replacement: A Comparative Study

Background: The objective of our study was to compare a novel squared section, tapered design - with four conicity - short stem, the MINIMA® short stem with the cementless Profemur® TL standard femoral stem in primary total hip arthroplasty (THA) in terms of functional outcomes, radiologic evaluation and other peri-operative and post-operative data.

Material and methods: This is a comparative study including 46 patients undergoing primary THA. In 23 patients, the MINIMA® short stem was used. These patients were matched with another 23 patients in whom a cementless Profemur® TL standard femoral stem was used. The levels of the pain were evaluated according to the Visual Analog Scale/Numerical Rating Scale (VAS/NRS). The functional and clinical evaluation of the patients was performed with Harris Hip Score (HHS), Charnley’s Hip score, EuroQol (EQ-5D)-(EQ-100), Patient Health Questionnaire (PHQ-9), and neuropathic pain questionnaire (DN-4). The rest of the comparison data included demographic data, the American Society of Anesthesiologists score (ASA), Charlson Index score, the pre-operative diagnosis, radiographic evaluation, the days of hospitalization, the operating time, incision length, blood loss, and blood transfusion requirements and complication rates.

Results: The two cohorts had comparable results regarding all patients’ peri-operative data. The radiographic assessment revealed considerable higher levels of femoral offset and femoral subsidence for the MINIMA group, but within acceptable limits for both cohorts. The majority of the functional and other scores did not give strong prominence to one specific femoral stem.

Conclusion: Our comparative study underlined the efficacy of the MINIMA® short stem, due to the fact that it revealed comparable and, in some cases, relatively better short-term outcomes compared with the TL standard femoral stem. Yet, more well-designed long-term research is required in order to further establish its effectiveness.

French Hip & Knee Society classification of short-stem hip prostheses: Inter- and intra-observer reproducibility

INTRODUCTION

In total hip replacement (THR), a short stem theoretically provides more physiological force transfer to the proximal femur, conserves bone stock and facilitates minimally invasive surgery. On the other hand, such implants involve a learning curve and incur risk of malpositioning or fracture and of secondary mobilization. There are several types of short stem, and classification is needed. Classifications exist, but are based more on implant length than on anchorage zone, and most have not been tested for reproducibility. The French Hip & Knee Society (SFHG) developed a short-stem classification based on anchorage zone inside the femur. The objectives of the present study were: (1) to present the classification, (2) to apply it to the short-stem models available in France and those widely used worldwide, and (3) to assess reproducibility.

HYPOTHESIS

The SFHG short-stem classification enables reproducible comparison.

MATERIAL AND METHOD

A short-stem classification according to anchorage zone was drawn up by an expert group. The stems and the classification were presented to 12 surgeons performing THR, who classified the stems according to the classification; a retest was performed 2 months later.

RESULTS

The classification is based on femoral stem anchorage site, in 5 types: type 1, cephalic; type 2, isolated cervical; type 3, Calcar femorale; type 4, metaphyseal; and type 5, conventional metaphyseal-diaphyseal, with shortened stems. Inter-observer reproducibility was 92.7% [95%CI: 91.7%-93.6%], with kappa 0.785 [95%CI: 0.755-0.814], and Lin test-rest concordance correlation coefficient 0.852 [95%CI: 0.836-0.869]. Intra-observer reproducibility was 94.0% [95%CI: 91.9%-96.1%], with kappa 0.820 [95%CI: 0.759-0.882], and Lin test-retest concordance correlation coefficient 0.820 [95%CI: 0.792-0.849].

DISCUSSION

This new classification enables femoral implants to be reproducibly compared according to anchorage zone.

LEVEL OF EVIDENCE

IV; retrospective study without control group.

Do radiological findings around the Fitmore stem change over time?

Aims

Although the short stem concept in hip arthroplasty procedure shows acceptable clinical performance, we sometimes get unexplainable radiological findings. The aim of this retrospective study was to evaluate changes of radiological findings up to three years postoperatively, and to assess any potential contributing factors on such radiological change in a Japanese population.

Methods

This is a retrospective radiological study conducted in Japan. Radiological assessment was done in accordance with predetermined radiological review protocol. A total of 241 hips were included in the study and 118 hips (49.0%) revealed radiological change from immediately after surgery to one year postoperatively; these 118 hips were eligible for further analyses. Each investigator screened whether either radiolucent lines (RLLs), cortical hypertrophy (CH), or atrophy (AT) appeared or not on the one-year radiograph. Further, three-year radiographs of eligible cases were reviewed to determine changes such as, disappeared (D), improved (I), stable (S), and progression (P). Additionally, bone condensation (BC) was assessed on the three-year radiograph.

Results

CH was observed in 49 hips (21.1%), AT was observed in 63 hips (27.2%), and RLLs were observed in 34 hips (14.7%) at one year postoperatively. Among 34 hips with RLLs, 70.6% showed change of either D or I on the three-year radiograph. BC was observed in younger patients more frequently.

Conclusion

The Fitmore stem works well in a Japanese population with favourable radiological change on hips with RLLs. Longer-term follow-up is required to determine clinical relevance.

Cite this article: Bone Jt Open 2022;3(1):20–28.

Ultra-Short Bone Conserving Cementless Femoral Stem

Excellent long-term results have been reported with conventional length cementless femoral stems in total hip arthroplasty; however, proximal stress shielding and thigh pain are still a concern. Metaphyseal engaging bone conserving short stems provide theoretical benefits compared with conventional length cementless stems, including avoiding proximal-distal mismatch, decreasing proximal stress shielding, and limiting perioperative fractures. The purpose of the ultra-short bone conserving cementless stem was to reproduce natural load transfer with an ultra-short stem obtaining optimal stability using the morphology of the proximal femur. Loss of stability of the stem and failure of osseous ingrowth is a potential concern with the use of ultra-short proximal loading cementless femoral stems. Ultra-short, metaphyseal-fitting anatomic or non-anatomic cementless femoral stems provided stable fixation without relying on diaphyseal fixation in young and elderly patients, suggesting that metaphyseal-fitting alone is sufficient in young and elderly patients who have good bone quality.

Short-term success of proximal bone stock preservation in short hip stems: a systematic review of the literature

Total hip arthroplasty is performed more frequently in younger patients nowadays, making long-term bone stock preservation an important topic. A mechanism for late implant failure is periprosthetic bone loss, caused by stress shielding around the hip stem due to different load distribution. Short stems are designed to keep the physical loading in the proximal part of the femur to reduce stress shielding. The aim of this review is to give more insight into how short and anatomic stems behave and whether they succeed in preservation of proximal bone stock.

A systematic literature search was performed to find all published studies on bone mineral density in short and anatomic hip stems. Results on periprosthetic femoral bone mineral density, measured with dual-energy X-ray absorptiometry (DEXA), were compiled and analysed per Gruen zone in percentual change.

A total of 29 studies were included. In short stems, Gruen 1 showed bone loss of 5% after one year (n = 855) and 5% after two years (n = 266). Gruen 7 showed bone loss of 10% after one year and –11% after two years. In anatomic stems, Gruen 1 showed bone loss of 8% after one year (n = 731) and 11% after two years (n = 227). Gruen 7 showed bone loss of 14% after one year and 15% after two years.

Short stems are capable of preserving proximal bone stock and have slightly less proximal bone loss in the first years, compared to anatomic stems.

Cite this article: EFORT Open Rev 2021;6:1040-1051. DOI: 10.1302/2058-5241.6.210030

Cemented short-stem total hip arthroplasty: Characteristics of line-to-line versus undersized cementing techniques using a validated CT-based finite element analysis

Short stems are becoming increasingly popular in total hip arthroplasty as they preserve the bone stock and simplify the implantation process. Short stems are advised mainly for patients with good bone stock. The clinical use of short stems could be enlarged to patients with poor bone stock if a cemented alternative would be available. Therefore, this study aimed to quantify the mechanical performance of a cemented short stem and to compare the "undersized" cementing strategy (stem one size smaller than the rasp) with the "line-to-line" technique (stem and rasp with identical size). A prototype cemented short stem was implanted in eight pairs of human cadaveric femora using the two cementing strategies. Four pairs were experimentally tested in a single-legged stance condition; stiffness, strength, and bone surface displacements were measured. Subject-specific nonlinear finite element models of all the implanted femora were developed, validated against the experimental data, and used to evaluate the behavior of cemented short stems under physiological loading conditions resembling level walking. The two cementing techniques resulted in nonsignificant differences in stiffness and strength. Strength and stiffness as calculated from finite element were 8.7 ± 16% and 9.9 ± 15.0% higher than experimentally measured. Displacements as calculated from finite element analyses corresponded strongly (R ²  ≥ .97) with those measured by digital image correlation. Stresses during level walking were far below the fatigue limit for bone and bone cement. The present study suggests that cemented short stems are a promising solution in osteoporotic bone, and that the line-to-line and undersized cementing techniques provide similar outcomes.

Short versus conventional stem in cementless total hip arthroplasty : An evidence-based approach with registry data of mid-term survival

Background

Short-stemmed total hip arthroplasty (THA) is well established and gaining popularity in Germany. The perception that short stems may predispose to primary instability in the femur has resulted in a more thorough follow-up of younger patient cohorts than the typical uncemented THA population. To address this issue, an evidence-based approach is presented for a retrospective mid-term survival analysis of a large registry-based cohort in primary cementless THA comparing short stems with a matched group of conventional stems.

Material and methods

Propensity score matching (PSM, see Infobox 1) was used on 131,580 primary cementless THAs fulfilling the inclusion criteria performed between November 2012 and September 2019 and the cumulative probability of revision (CPR) of short and conventional stems for any reason, for reasons excluding prosthetic joint infection (PJI), and due to PJI were compared.

Results

After PSM at 1:1 balanced groups of 17,526 short stems and of 17,526 conventional stems were achieved demonstrating no significant difference for CPR for any reason and for reasons excluding PJI. Matched CPR for any reason was 2.9% (95% confidence interval, CI, 2.4–3.5%) 5 years after primary THA in the short stem and 3.1% (95% CI 2.7–3.4%) in the conventional stem group. The CPR excluding PJI was 2.2% (95% CI 1.7–2.7%) vs. 2.1% (95% CI 1.8–2.4%). In contrast, the incidence of PJI was statistically significant lower for short stems.

Conclusion

For the considered period, there was no statistically significant survival difference in uncemented THA between comparison groups but a lower incidence for PJI in short-stem THA. Further analyses of registry data are required to rule out range of indications and late mechanical failure of short stems.

Three-dimensional analysis of the cortical contact state of short and conventional stems in different stem positions in total hip arthroplasty

BACKGROUND

Despite the increasing use of short cementless stems in total hip arthroplasty, their potential benefits have yet to be confirmed. We evaluated the cortical contact state of short and conventional stems in different femoral canal types and stem positions using a CT-based 3-dimensional templating software.

METHODS

We reviewed 153 hips in 153 patients, grouped according to femoral canal type-normal (68), champagne-flute (41), and stove-pipe canal (44). We investigated the influence of stem position on the contact state by evaluating three situations of stem anteversion (original anteversion, +5°anteverted, and +5°retroverted), three stem positions, neutral +2°extended, and +2°flexed positions using Taperloc Complete Microplasty^Ⓡ stem.

FINDINGS

The contact values of all zones between both stems in all canal types exhibited no significant differences. The values in zones 1, 2, 6, and 7 of both stems in 5° retroverted and anteverted, 2° extended and flexed positions were not significantly different compared to those of the neutral position. However, the values in zones 3, 4, and 5 of both stems were significantly greater compared to those of the neutral position in 2° extended and flexed positions; these values were also significantly larger in all canal types for the conventional stem.

INTERPRETATION

We demonstrated that the short and conventional stems can achieve the same proximal cortical contact in any femoral canal, regardless of the stem position. However, extended and flexed stem positions increase the distal contact, especially in conventional stems. Furthermore, the distal contact increases for the retroverted stem insertions.

Biomechanical Behavior of an Hydroxyapatite-Coated Traditional Hip Stem and a Short One of Similar Design: Comparative Study Using Finite Element Analysis

Background

The objective is to compare, by the means of finite elements analysis, the biomechanical behavior of a conventional stem of proven performance with a short stem based on the same fixation principles.

Methods

A 3D femur was modeled from CT scan data, and real bone density measures were incorporated into it. Load stresses were applied to that bone in 3 different scenarios: without prosthesis, with the conventional stem, and with the short stem. Different bone loading patterns were compared by Gruen’s zones both visually and statistically using Welch’s test.

Results

The implantation of a stem generates a certain degree of stress shielding in the surrounding bone, but the pattern of the change is very similar in the compared stem models. Although there is statistical significance (P < 0.01) in the mean stress variation in most of the Gruen’s zones, the magnitude of the difference is always under 2 MPa (range: 0.01 – 1.74 MPa).

Conclusions

The bone loading patterns of the traditional stem and the short stem are very similar. Although there is no evidence of a link between biomechanics and clinical outcomes, our results may suggest that theoretical advantages of short stems can be exploited without the fear of altering bone loading patterns.

The experience of an indipendent center with the MINIHIP® femoral stem

The implantation of short femoral stems has significantly increased over the past decade, thanks to their preservation of bone stock, allowing for easier potential revision of components and physiological joint reconstruction. Their main features are metaphyseal fixation and partial retention of the femoral neck which lead to biomechanical advantages and high stability. They also guarantee the preservation of bone stock and insertion through minimally invasive approaches. Fifty-one non-consecutive patients with osteoarthritis or avascular necrosis were treated by two senior surgeons with total hip arthroplasty (THA) with anterior or anterolateral approach between April 2013 and October 2016. Cementless short femoral stem monobloc (Minihip, Corin, Cirencester, UK) was implanted in all patients who were studied retrospectively. Radiographic outcome was analyzed and clinical outcomes were assessed with Harris Hip Score (HHS), Hip handicap and Osteaorthritis Outcome Score (HOOS) and Oxford Hip Score (OHS). Based on radiological results we did not find periprosthetic osteolysis while bone resorption was evaluated in 5 implants which were classified according to Gruen. The MiniHip stem demonstrates adequate metaphyseal grip, excellent implant stability to ensure implant survival.

Biomechanics of a cemented short stem: a comparative in vitro study regarding primary stability and maximum fracture load

PURPOSE

In total hip arthroplasty, uncemented short stems have been used more and more frequently in recent years. Especially for short and curved femoral implants, bone-preserving and soft tissue-sparing properties are postulated. However, indication is limited to sufficient bone quality. At present, there are no curved short stems available which are based on cemented fixation.

METHODS

In this in vitro study, primary stability and maximum fracture load of a newly developed cemented short-stem implant was evaluated in comparison to an already well-established cemented conventional straight stem using six pairs of human cadaver femurs with minor bone quality. Primary stability, including reversible micromotion and irreversible migration, was assessed in a dynamic material-testing machine. Furthermore, a subsequent load-to-failure test revealed the periprosthetic fracture characteristics.

RESULTS

Reversible and irreversible micromotions showed no statistical difference between the two investigated stems. All short stems fractured under maximum load according to Vancouver type B3, whereas 4 out of 6 conventional stems suffered a periprosthetic fracture according to Vancouver type C. Mean fracture load of the short stems was 3062 N versus 3160 N for the conventional stems (p = 0.84).

CONCLUSION

Primary stability of the cemented short stem was not negatively influenced compared to the cemented conventional stem and no significant difference in fracture load was observed. However, a clear difference in the fracture pattern has been identified.

4- to 8-year complication analysis of 2 'partial collum' femoral stems in primary THA

OBJECTIVES

Compare the clinical and radiological outcome of CFP stem with the MiniHip design in a prospective series, with special interest in intraoperative periprosthetic fracture (IPPF).

METHODS

We prospectively followed 101 cases treated with the MiniHip stem (Group 1) and 89 with the CFP stem (Group 2) operated between 2010 and 2014. No significant demographic differences were observed between both groups. Median follow-up was 72 months. Average stem length was 41% shorter in the MiniHip group (p < 0.001). Radiological parameters were measured and a logistcic regression model was created to evaluate factors associated with IPPF.

RESULTS

Mean mHHS improved from 54 to 95 in the MiniHip group (p < 0.001) and from 64 to 98 in the CFP group (p < 0.001). No significant differences were observed in terms of loosening, infection or instability. We observed 7 IPPFs (3.68%), 3 in group 1 and 4 in group 2. After adjusting for confounders, CFP was not associated with a greater risk of IPPF (OR 3.23; 95% CI, 0.250-42.034, p = 0.368), however, a more complex fracture pattern was observed with this stem design. Prior acetabular fractures were associated with IPPF (OR 66.85; 95% CI, 1.142-3911, p = 0.043). Compared to Dorr A femurs, type Dorr B appeared protective against IPPF (OR 0.039; 95% CI, 0.001-1.109, p = 0.058). Valgus alignment tended to increase the risk of IPPF (OR 20.59; 95% CI 0.870-487.221, p = 0.061).

CONCLUSIONS

MiniHip showed similar radiological outcomes to CFP at short- to mid-term follow-up without increasing IPPFs with a shorter stem length. Given that CFP produced a more complex IPPF pattern, surgeons should be cautious with alignment of this particular design, especially in Dorr A femur.

Mid-term gender-specific differences in periprosthetic bone remodelling after implantation of a curved bone-preserving hip stem

BACKGROUND

The implant-specific periprosthetic bone remodelling in the proximal femur is considered to be an important factor influencing the long-term survival of cementless hip stems. Particularly data of gender-specific differences regarding bone-preserving stems are very rare in literature and mainly limited to short-term investigations. Therefore, we investigated at mid-term one arm of a prospective randomised study to evaluate if there is an influence of gender on implant-specific stress shielding after implantation of a curved bone preserving hip stem (Fitmore) 5 years postoperatively.

HYPOTHESIS

We hypothesised there will be no gender-specific differences in periprosthetic bone remodelling.

PATIENTS AND METHODS

A total of 20 female and 37 male patients underwent total hip arthroplasty using the Fitmore stem. Clinical, radiological as well as osteodensitometric examinations were performed preoperatively, 7 days and 3, 12 and 60 months postoperatively. Clinical data collection included the Western Ontario and McMaster Universities Arthritis Index (WOMAC) and the Harris Hip Score (HHS). Periprosthetic bone mineral density (BMD) was measured using Dual Energy X-ray Absorptiometry (DXA) and the periprosthetic bone was divided into 7 regions of interest (ROI) for analysis. The results at 3, 12 and 60 months were compared with the first postoperative measurement after 7 days to obtain a percentage change.

RESULTS

Periprosthetic BMD showed a decrease in all 7 ROIs for both groups 5 years postoperatively referred to the baseline value, except ROI 3 (0.8%, p=0.761), representing the distal lateral part of the stem, and ROI 5 (0.3%, p=0.688), representing the distal medial part of the stem in the male cohort. Significant gender differences were found in ROI 1 (-16.0% vs. -3.5%, p=0.016) and ROI 6 (-9.9% vs. -2.1%, p=0.04) in favour of the male patients. Clinical results showed no significant gender differences 5 years postoperatively with regard to WOMAC (mean 0.4 (±0.8, 0-3.3) in women vs. 0.3 (±0.8, 0-4.2) in men, p=0.76) and HHS (mean 93.0 (±9.7, 66.0-100.0) in women vs. 93.9 (±11.5, 53.0-100.0) in men, p=0.36).

CONCLUSION

Proximal stress shielding was observed independent of gender 5 years postoperatively. However, there was a significantly lower bone loss proximal lateral and medial below the calcar in male patients, indicating a more physiological load transfer. [ClinicalTrials.gov identifier: NCT03147131 (Study ID D.3067-244/10). Registered 10 May 2017 - retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT03147131?term=Bieger&draw=2&rank=1] LEVEL OF EVIDENCE: IV; prospective study without control group.

Neck-sparing short femoral stems: A meta-analysis

BACKGROUND

Neck sparing short femoral stems are supposed to ease restoration of the proximal femoral anatomy and physiological hip biomechanics. This stem design is of particular interest as they have the potential to generate prosthetic hips that have higher functional performance with an improved lifespan, and revise more easily. Unlike previously published meta-analysis, this meta-analysis was initiated to determine if neck sparing short femoral stems compared to conventional stems: (1) resulted in improved functional performance; (2) reduced risk of thigh pain; (3) reduced risk of reoperation/revision, and 4) reduced stress shielding related bone loss in the proximal femur.

MATERIAL AND METHODS

Literature databases were searched between 1st January 2005 and 30th March 2019. The primary search was conducted using the electronic databases MEDLINE, EMBASE, PubMed, Open Grey, Trip Pro, Evidence Search, and Cochrane. Eligible studies were assessed for homogeneity, with continuous outcomes expressed as standardized mean difference with 95% confidence interval and dichotomous data as odds-ratio with 95% confidence interval.

RESULTS

Ten randomised clinical trials were eligible; these trials included 1259 total hip arthroplasty procedures, inclusive of 616 neck sparing short stems and 643 conventional stems. We were not able to find a significant functional advantage of using neck sparing short stems based on Harris Hip scores (0.0850; 95% CI: -0.03 to 0.20 [p=0.40]) and WOMAC scores (-0.0605; 95% CI: -0.03 to 0.15 [p=0.87]). We found a trend in favour of neck sparing short stems to reduce the risk of thigh pain but this was non significant (odds ratio of 0.11; 95% CI: 0.03 to 0.43 [p=0.178]). Neck sparing short stems were associated with similar early- to mid-term dislocation and revision rates compared to conventional stems with odds ratio of 1.435 (95% CI: 0.545 to 3.780 [p=0.968]) and of 0.581 (95% CI: 0.220 to 1.532 [p=0.972]), respectively. Neck sparing short stems were found to have less bone loss in both Gruen zones 1 and 7 (3.324; 95% CI: -7.683 to 1.036 [p<0.001], and of -4.632; 95% CI: -9682 to 0.418 [p<0.001], respectively).

DISCUSSION/CONCLUSION

Neck sparing short femoral stems achieve excellent early to mid-term outcomes in both clinical and radiological outcome scores that are in keeping with conventional stems functionally. Hitherto, results from this meta-analysis suggest that neck-sparing stems may achieve better maintenance of bone mineral density than their conventional counterparts, in addition to fewer cases of thigh pain.

LEVEL OF EVIDENCE

I; meta-analysis.

Straight stem and threaded cup in patients under 60 years of age: 28.8-30.2 years of follow-up

Purpose

The aim of this retrospective observational study of one cohort was to evaluate the long-term outcome in patients younger than 60 years after total hip arthroplasty using a straight uncemented stem and an uncemented threaded cup.

Methods

Between 1986 and 1987, 75 hips of 75 patients (mean age, 53.35 ± 6.17 years) were consecutively implanted with an Alloclassic Zweymüller/Alloclassic SL stem and an Alloclassic CSF cup. Forty-four patients had died over the last 30 years. The remaining 31 patients (mean age, 82.9 ± 6.4 years) were reinvited for follow-up examinations. Clinical and radiographic evaluations were carried out.

Results

At a mean follow-up of 29.5 (28.8–30.2), 4 patients (5.3%) were lost to follow-up.

For the endpoint aseptic loosening (defined as the removal of stem or the cup for 2 cases), the overall survival rate is 97.3%. For the endpoint revision for any reason (22 patients), the survival rate is 70.6%. Eleven patients needed an exchange of head and liner, caused by wear. The average time from implantation until change of head and liner was 21.44 years (SD 5.92). Other reasons for revision surgery were septic loosening (3 cases), aseptic loosening of stem and cup (1 case), aseptic loosening of stem (1 case), periprosthetic calcification (2 cases), implant fracture (1 case), periprosthetic fracture (1 case), intraoperative fissure of stem (1 case), and total wear of liner including cup (1 case).

Conclusion

The combination of a straight stem (Alloclassic) and a screw cup (CSF) shows excellent results in young patients under the age of 60 at ultra-long-term follow-up at 30 years. Revisions due to wear of the polyethylene liner are more likely than in the older patients.

Mid-term migration pattern of a calcar-guided short stem: A five-year EBRA-FCA-study

BACKGROUND

Short-term results of several short-stem designs have indicated early axial migration. Mid- and long-term results for most designs are lacking. The objective of this study was to evaluate the mid-term migration pattern of a calcar-guided short stem five years postoperative.

METHODS

Implant migration of 191 calcar-guided short stems was assessed by Ein-Bild-Roentgen-Analysis Femoral-Component- Analysis (EBRA-FCA) 5 years after surgery. Migration pattern of the whole group was analyzed and compared to the migration pattern of implants potentially being "at hazard" with a subsidence of more than 1.5 mm at 2 years postoperatively. Influence of preoperative Dorr types (A vs. B vs. C), age (<70 vs. >70 years), gender (female vs. male), weight (<90 kg vs. >90 kg), BMI (<30 vs. >30) and uni-vs. bilateral procedures on mid-term migration pattern was analyzed. Additionally outcome of varus- and valgus stem alignment was assessed.

RESULTS

Mean axial subsidence was 1.5 mm (SD 1.48 mm) at final follow-up. Two years after surgery 73 short stems were classified "at hazard". Of these stems, 69 cases showed secondary stabilisation in the following period, whereas 4 cases presented unstable with more than 1 mm of further subsidence. Stem revision was not required neither in the group of implants with early stabilisation nor the group with pronounced early onset migration. Male gender and heavy-weight patients had a significant higher risk for axial migration, as well as extensive valgus stem alignment, whereas for Dorr type B, compared to A, no statistical difference could be observed.

CONCLUSIONS

In most cases, even in the group of stems being "at hazard", settling could be documented. While different Dorr types did not show a statistically significant impact on axial migration, particularly in male and heavy-weight patients the risk of continuous subsidence is increased. In those 4 cases with further migration, undersizing of the stem could be recognized. At present, clinical consequences are still uncertain.

Metaphyseal anchoring short stem hip arthroplasty provides a more physiological load transfer: a comparative finite element analysis study

BACKGROUND

Short stem total hip arthroplasty (SHA) preserves femoral bone stock and is supposed to provide a more natural load transfer compared to standard stem total hip arthroplasty (THA). As comparative biomechanical reference data are rare we used a finite element analysis (FEA) approach to compare cortical load transfer after implantations of a metaphyseal anchoring short and standard stem in native biomechanical femora.

METHODS

The subject specific finite element models of biomechanical femora, one native and two with implanted metaphyseal anchoring SHA (Metha, B. Braun Aesculap) and standard THA (CLS, Zimmer-Biomet), were generated from computed tomography datasets. The loading configuration was performed with an axial force of 1400 N. Von Mises stress was used to investigate the change of cortical stress distribution.

RESULTS

Compared to the native femur, a considerable reduction of cortical stress was recorded after implantation of SHA and standard THA. The SHA showed less reduction proximally with a significant higher metaphyseal cortical stress compared to standard THA. Moreover, the highest peak stresses were observed metaphyseal for the SHA stem while for the standard THA high stress pattern was observed more distally.

CONCLUSIONS

Both, short and standard THA, cause unloading of the proximal femur. However, the metaphyseal anchoring SHA features a clearly favorable pattern in terms of a lower reduction proximally and improved metaphyseal loading, while standard THA shows a higher proximal unloading and more distal load transfer. These load patterns implicate a reduced stress shielding proximally for metaphyseal anchoring SHA stems and might be able to translate in a better bone preservation.

Biomechanical Analysis to Probe Role of Bone Condition and Subject Weight in Stiffness Customization of Femoral Stem for Improved Periprosthetic Biomechanical Response

Stress shielding due to difference in stiffness of bone and implant material is one among the foremost causes of loosening and failure of load-bearing implants. Thus far, femoral geometry has been given priority for the customization of total hip joint replacement (THR) implant design. This study, for the first time, demonstrates the key role of bone condition and subject-weight on the customization of stiffness and design of the femoral stem. In particular, internal hollowness was incorporated to reduce the implant stiffness and such designed structure has been customized based on subject parameters, including bone condition and bodyweight. The primary aim was to tailor these parameters to achieve close to natural strain distribution at periprosthetic bone and to reduce interfacial bone loss over time. The maintenance of interfacial bone density over time has been studied here through analysis of bone remodeling (BR). For normal bodyweight, the highest hollowness exhibited clinically relevant biomechanical response, for all bone conditions. However, for heavier subjects, consideration of bone quality was found to be essential as higher hollowness induced bone failure in weaker bones and implant failure in stronger bones. Moreover, for stronger bone, thinner medial wall was found to reduce bone resorption over time on the proximo-lateral zone of stress shielding, while lateral thinning was found advantageous for weaker bones. The findings of this study are likely to facilitate designing of femoral stems for achieving better physiological outcomes and enhancement of the quality of life of patients undergoing THR surgery.

Fixation of the short global tissue-sparing hip stem

AIMS

Short, bone-conserving femoral components are increasingly used in total hip arthroplasty (THA). They are expected to allow tissue-conserving implantation and to render future revision surgery more straightforward but the long-term data on such components is limited. One such component is the global tissue-sparing (GTS) stem. Following the model for stepwise introduction of new orthopaedic implants, we evaluated early implant fixation and clinical outcome of this novel short-stem THA and compared it to that of a component with established good long-term clinical outcome.

METHODS

In total, 50 consecutive patients ≤ 70 years old with end-stage symptomatic osteo-arthritis were randomized to receive THA with the GTS stem or the conventional Taperloc stem using the anterior supine intermuscular approach by two experienced hip surgeons in two hospitals in the Netherlands. Primary outcome was implant migration. Patients were followed using routine clinical examination, patient reported outcome using Harris Hip Score (HHS), Hip Disability And Osteoarthritis Outcome Score (HOOS), EuroQol five-dimension questionnaire (EQ5D), and Roentgen Stereophotogrammetric Analysis (RSA) at three, six, 12, and 24 months. This study evaluated the two-year follow-up results.

RESULTS

In addition to the initial migration pattern of distal migration (subsidence, Y-translation) and retroversion (Y-rotation) also exhibited by the Taperloc stem, the GTS stem showed an initial migration pattern of varization (X-translation combined with Z-rotation) and posterior translation (Z-translation). However, all components stabilized aside from one Taperloc stem which became loose secondary to malposition and was later revised. Clinical outcomes and complications were not statistically significantly different with the numbers available.

CONCLUSION

A substantially different and more extensive initial migration pattern was seen for the GTS stem compared to the Taperloc stem. Although implant stabilization was achieved, excellent long-term survival similar to that of the Taperloc stem should not be inferred. Especially in the absence of clinically proven relevant improvement, widespread usage should be postponed until long-term safety has been established. Cite this article: Bone Joint J 2020;102-B(6):699-708.

Calcar-Guided Short Stems in Total Hip Arthroplasty: A Two-Year Prospective Multicentre Study

Background:

Calcar-guided short-stem Total Hip Arthroplasty (THA) is increasingly being used to preserve proximal femoral bone stock for potential later revision surgery.

Objective:

In this study, we aimed to expand the clinical evidence on calcar-guided short-stem THA used in daily clinical practice, focusing on clinical outcomes as well as radiographic signs of stress shielding and femoral bone loss.

Methods:

In a prospective multicentre study, we enrolled 213 patients with a total of 224 THAs for mainly degenerative indications. The patients were examined clinically and radiographically 6 to 12 weeks, 12 months, and 24 months postoperatively.

Results:

All clinical outcomes improved significantly over the first 6 to 12 weeks compared to preoperative values (P < 0.001). At 24 months, the mean Harris hip score was 95.3 ± 6.7, and the mean visual analogue scale for pain was 1.0 ± 1.7 under load and 0.5 ± 1.3 at rest. We observed early distal stem migration in six patients and late migration in one patient. Additionally, we found 16 cases of radiographic signs indicative of stress shielding. Four patients required stem revision surgery: two for stem migration, one for periprosthetic fracture, and one for deep infection.

Conclusion:

Overall, calcar-guided short-stem THA resulted in excellent clinical outcomes after two years of follow-up, and the radiographs revealed few signs of stress shielding. We, therefore, regard calcar-guided short-stem THA as a safe and effective treatment alternative in daily clinical practice.

Total hip replacement using MINIMA® short stem: A short-term follow-up study

BACKGROUND

Total hip replacement has become one of the most successful orthopaedic procedures. The length of the femoral stem constitutes one of the most important geometrical and mechanical features of the prosthesis. Several different implants are currently available but data are limited concerning the clinical results for some of these implants.

AIM

To report the short-term clinical and radiological results of a novel squared section, tapered design – with four conicity - short stem in total hip replacement.

METHODS

This is a retrospective study of a prospectively collected data using of MINIMA^® short stem in 61 consecutive patients with at least 1 year follow-up. The collected data included patients’ demographics, type of arthritis, bone morphology, perioperative data, clinical results using Harris Hip Score, EuroQol (EQ-5D), pain score and satisfaction rate, complications and radiological results.

RESULTS

Total 61 patients were included in our study with a mean age of 56 years of age (range 25-73 years). The majority of them (68.6%) were women, thirty seven patients (56.9%) were less than 60 years of age and almost half of patients (45.1%) suffered from secondary osteoarthritis (hip dysplasia, osteonecrosis, etc.). The mean time of follow-up examination was 33.4 mo (2.8 years) with a range of 12-57 months (1-4.8 years). In 35 patients (56.9%) the follow-up examination was more than 3 years. No major complications such as revision, periprosthetic fracture, dislocation or infection were presented. Re-admission 90 d postoperatively or laterwas deemed unnecessary for any reason regarding the operation. Respectively, the mean pain score, mean Harris hip score, and mean EQ-5D were improved from 6.3, 58.7 and 77.3 preoperatively to 0.1, 95.1, and 79.8 postoperatively. The Satisfaction rate at the final follow-up was 9.9 (SD 0.3, range 8.0-10.0). All stems were classified as stable bone ingrowth and no radiolucent lineswere revealed in any of the modified Gruens’ zone at the postoperative X-rays. Stem subsidence was within acceptable limits and the incidence of distal cortical hypertrophy was relatively low.

CONCLUSION

The clinical and radiological results concerning the MINIMA^® short stem are excellent according to this first report of this specific design of the short femoral stems. Because of the small number of cases and short-term follow-up of this study, a longer follow up time and more patients’ enrollment is required.

Bone remodelling and integration of two different types of short stem: a dual-energy X-ray - absorptiometry study

PURPOSE

Different kinds of bone preserving hip stems have been created to assure a more physiological distribution of the strengths on the femur. The aim of this research is to evaluate the density reaction of the periprosthetic bone while changing the conformation of the prosthetic implant on dual-energy X-ray - absorptiometry (DXA).

METHODS

This is a prospective, single-centre study assessing bone remodelling changes after implantation of two short hip stems, dividing the patients in two groups according to the implant used: 20 in group A, Metha (B-Braun), and 16 in group B, SMF (Smith and Nephew). All participants had a pre-operative and a post-operative (24 months) DXA evaluating the changes in bone mass density (BMD) occurred in the five Gruen's zones.

RESULTS

Compared to the pre-operative value, differences in BMD percentage were statistically significant only in ROI 4 (p < 0.05), with an increase in both groups (9 and 18%, respectively). The average increase in BMD was of 7.3% and 7.2% in the 2 groups.

CONCLUSION

According to our study, both stems have proved able to provide good load distribution across the metaphyseal region favouring proper system integration. Nonetheless, is certainly needed to perform other studies with longer follow-up and bigger populations to give strength to these conclusions.