Distal femoral cortical hypertrophy after hip arthroplasty using a cementless doubletapered femoral stem

Exploring the optimal mechanical properties of triply periodic minimal surface structures for biomedical applications: A Numerical analysis

Currently, cutting-edge Additive Manufacturing techniques, such as Selective Laser Melting (SLM) and Electron Beam Melting (EBM), offer manufacturers a valuable avenue, especially in biomedical devices. These techniques produce intricate porous structures that draw inspiration from nature, boast biocompatibility, and effectively counter the adverse issues tied to solid implants, including stress shielding, cortical hypertrophy, and micromotions. Within the domain of such porous structures, Triply Periodic Minimal Surface (TPMS) configurations, specifically the Gyroid, Diamond, and Primitive designs, exhibit exceptional performance due to their bioinspired forms and remarkable mechanical and fatigue properties, outshining other porous counterparts. Consequently, they emerge as strong contenders for biomedical implants. However, assessing the mechanical properties and manufacturability of TPMS structures within the appropriate ranges of pore size, unit cell size, and porosity tailored for biomedical applications remains paramount. This study aims to scrutinize the mechanical behavior of Gyroid, Diamond, and Primitive structures in solid and sheet network iterations within the morphological parameter ranges suitable for tasks like cell seeding, vascularization, and osseointegration. A comparison with the mechanical characteristics of host bones is also undertaken. The methodology revolves around Finite Element Method (FEM) analysis. The six structures are originally modeled with unit cell sizes of 1, 1.5, 2, and 2.5 mm, and porosity levels ranging from 50% to 85%. Subsequently, mechanical properties, such as elasticity modulus and yield strength, are quantified through numerical analysis. The results underscore that implementing TPMS designs enables unit cell sizes between 1 and 2.5 mm, facilitating pore sizes within the suitable range of approximately 300-1500 μm for biomedical implants. Elasticity modulus spans from 1.5 to 33.8 GPa, while yield strength ranges around 20-304.5 MPa across the 50%-85% porosity spectrum. Generally, altering the unit cell size exhibits minimal impact on mechanical properties within the range above; however, it's noteworthy that smaller porosities correspond to heightened defects in additively manufactured structures. Thus, for an acceptable pore size range of 500-1000 μm and a minimum wall thickness of 150 μm, a prudent choice would involve adopting a 2.5 mm unit cell size.

Advanced porous hip implants: A comprehensive review

The field of orthopaedic implants has experienced significant advancements in recent years, transforming the approach to orthopaedic treatments. Amongst these advancements, porous structures have emerged as a promising solution to address the limitations of traditional solid implants. This comprehensive review paper offers a thorough overview of the importance of advanced porous hip implants, focusing on three key areas bone morphology and biomechanical parameters, complications associated with solid implants, and the benefits of porous structures and porous implants. Understanding the intricate interplay between bone morphology and biomechanical parameters is crucial when designing orthopaedic implants. Mimicking the native bone structure ensures optimal osseointegration, load distribution, and long-term success. Porous implants closely resemble natural bone structures, facilitating improved integration and biomechanical compatibility. Complications with solid implants are a significant concern in orthopaedic procedures. Stress shielding, cortical hypertrophy, and micromotion can lead to implant failure or revision surgeries. By contrast, porous structures promise to mitigate these issues by promoting bone ingrowth, reducing stress concentrations, and providing stability at the bone-implant interface. The benefits of porous structures and porous implants go beyond addressing solid implant complications. These structures enhance bone in-growth potential, strengthening integration and long-term stability. The interconnected porosity promotes nutrient diffusion and new blood vessel formation, supporting healing and minimizing infection risk. Furthermore, porous implants exhibit improved mechanical properties, such as lower elastic modulus and higher energy absorption, that better match those of bone. This feature helps alleviate stress shielding and enhances the overall performance and longevity of the implant. In conclusion, advanced porous implants have tremendous potential in orthopaedics. By closely mimicking native bone structure and reducing complications associated with solid implants, they can revolutionize orthopaedic treatments. Further research and development are warranted to fully exploit the potential of these innovative solutions and improve patient outcomes.

Comparison of Short Curved Stems and Standard-length Single Wedged Stems for Cementless Total Hip Arthroplasty

Purpose

The purpose of this study was to compare the clinical and radiographic outcomes with use of short-curved stems versus standard-length single wedged stems over a minimum follow-up period of five years.

Materials and Methods

A retrospective study of primary total hip arthroplasties performed using the Fitmore® stem (127 hips, 122 patients) and the M/L taper® stem (195 hips, 187 patients) between October 2012 and June 2014 was conducted. The clinical and radiographic outcomes were obtained for evaluation over a minimum follow-up period of five years.

Results

In both the Fitmore® and M/L taper® groups, the mean Harris hip score improved from 52.4 and 48.9 preoperatively to 93.3 and 94.5 at the final follow-up, respectively (P=0.980). The mean Western Ontario and McMaster Universities Osteoarthritis Index scores also improved from 73.3 and 76.8 preoperatively to 22.9 and 25.6 at the final follow-up, respectively (P=0.465). Fifteen hips (Fitmore®: 14 hips; M/L taper®: one hip, P<0.001) developed intraoperative cracks and were treated simultaneously with cerclage wiring. Radiography showed a radiolucent line in 24 hips in the Fitmore® group and 12 hips in the M/L taper® group (P=0.125). Cortical hypertrophy was detected in 29 hips (Fitmore® group: 28 hips; M/L taper® group: one hip, P<0.001).

Conclusion

Similarly favorable clinical and radiographic outcomes were achieved with use of both short-curved stems and standard-length single wedged stems. However, higher cortical hypertrophy and a higher rate of femoral crack were observed with use of Fitmore® stems.

Unexpected early loosening of rectangular straight femoral Zweymüller stems with an alumina-reduced surface after total hip arthroplasty-a prospective, double-blind, randomized controlled trial

BACKGROUND

Alumina particles from the grit blasting of Ti-alloy stems are suspected to contribute to aseptic loosening. An alumina-reduced stem surface was hypothesized to improve osseointegration and show comparable short-term outcomes to those of a standard stem.

METHODS

In this prospective, double-blind, randomized trial, 26 standard (STD) and 27 experimental new technology (NT) stems were implanted. The latter were additionally treated by acid etching and ice blasting to remove alumina particles from the grit-blasting process. Follow-up occurred at 12 and 24 months. Bone mineral density (BMD) around the stem was measured by a dual-energy x-ray absorptiometry device (DEXA). Radiographs were reviewed for alterations. Clinical scoring comprised the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the Harris Hip Score (HHS). Survival rates were calculated up to 50 months.

RESULTS

Lower mean BMD and more severe cortical hypertrophies were found in the NT group. At 12 months, radiolucent lines were observed mostly in the metaphyseal zone for both groups, with a progression tendency in the NT group at 24 months. At 12 months, pain scores and the WOMAC total and physical activity scores were significantly lower in the NT group, without any differences thereafter. The number of NT stem revisions amounted to 6 (24%) and 11 (41%) at 24 and 50 months, respectively.

CONCLUSION

In the NT group, unexpected catastrophic failure rates of 41% caused by early aseptic loosening were noted within 50 months. Compared with the STD stems, NT stems lead to poor clinical and radiographic results.

LEVEL OF EVIDENCE

II.

TRIAL REGISTRATION

NCT05053048.

Bone remodeling and cortical thinning distal to the femoral stem: a retrospective review

INTRODUCTION

There is a paucity of information on the bone remodeling that occurs distal to the femoral stem following total hip arthroplasty as most previous studies have focused on proximal changes. In this study, we report the cortical thinning that occur distal to the femoral stem after primary total hip arthroplasty.

METHODS

A retrospective review was performed at one institution over a 5-year period. 156 primary total hip arthroplasty procedures were included. The Cortical Thickness Index (CTI) was measured on both operative and non-operative hips at 1 cm, 3 cm and 5 cm below the prosthetic stem tip on anteroposterior radiographic images pre-operatively as well as at 6 months, 12 months and 24 months post-operatively. The difference in average CTI was measured using paired t-tests.

RESULTS

There were statistically significant decreases in CTI distal to the femoral stem at 12 months and 24 months (-1.3% and -2.8%, respectively). Greater losses were seen in female patients, patients older than 75, and patients with BMI less than 35 at 6 months postoperative. There were no differences in CTI at any time point on the non-operative side.

CONCLUSION

The current study demonstrates that patients undergo bone loss as measured by CTI distal to the stem in the first 2 years following total hip arthroplasty. Comparison to the contralateral non-operative side confirms that this change is greater than expected for the natural aging process. A greater understanding of these changes will help optimize post-operative management and direct future innovations in implant design.

Risk Factors Associated With Femorotomy or Fracture During Cementless Stem Removal and Generation of an Individual Predictive Risk Score

BACKGROUND

Femorotomy is a commonly used technique during cementless stem removal but should be preferred in selective revision cases to prevent intraoperative femoral fracture associated with deteriorated clinical outcome. Our aim was to assess the risk factors for fracture or femorotomy and develop a predictive risk stratification score.

METHODS

A monocentric retrospective cohort including 202 patients was analyzed. Thirty six candidate prognostic factors were assessed.

RESULTS

The following independent predictors of fracture or femorotomy were identified: presence of a "bracket sign" (Odds Ratio [OR]: 10.857; 95% Confidence interval [CI]: 2.613-45.115; P = .001) defined as a distal spot weld between the surface of the implant and closest endosteum, bone contact in zone 2 (OR: 4.700; 95% CI: 1.827-12.089; P = .001), 6 (OR: 4.966; 95% CI: 1.823-13.530; P = .002), 12 (OR: 9.660; 95% CI: 3.715-25.116; P < .0001), 13 (OR: 2.958; 95% CI: 1.009-8.021; P = .033), and global hypertrophy (OR: 0.170; 95% CI: 0.036-0.806; P = .026). The prognostic score, named Femorotomy INcidence Numeric scoring system, had good performance and discriminability; the area under the curve of the model was 0.924 (95% CI: 0.878-0.969).

CONCLUSION

The only independent risk factors were those assessed on X-ray (eg, bracket sign, bone contact in zones 2, 6, 12, and 13), while global hypertrophy was protective. We noticed the importance of differentiating pedestals and "bracket signs"; the latter is an indicator of fixation of the stem. We developed a risk prediction score (Femorotomy INcidence Numeric score) of fracture or femorotomy that can be used as a companion tool to assess the risk for doing an early osteotomy of the femur.

Taper-wedge stem suitable for anterior approach total hip arthroplasty: Adequate biomechanical reconstruction parameters and excellent clinical outcome at mid-term follow-up

BACKGROUND

The direct anterior approach (DAA) for total hip arthroplasty (THA) is a less invasive and muscle-sparing approach that seems to improve early function and patient satisfaction. Several studies, however, have reported high complication and revision rates due to the technical difficulties related to the femoral preparation.

AIM

To evaluate the usefulness and safety of a new stem equipped with a morphometric design and a size-specific medial curvature in DAA for THA.

METHODS

This retrospective study was based on 130 patients that underwent mini-invasive DAA procedures for THA using the Accolade II stem. A total of 144 procedures were included in the assessment, which was based on postoperative complications, survival rates, functional parameters, and patient related outcomes.

RESULTS

Overall complications were recorded in 6 procedures (4.2%). There were no complications related to the stem implantation and no intraoperative fractures. Only one patient was revised for deep infection. On radiographs, biomechanical hip reconstruction was satisfactory and no stem showed any subsidence greater than 2 mm. Full osseointegration based on Engh scores was seen in all of the implanted stems. Median Harris hip score at final follow-up was 99 points (range 44-100 points), which resulted excellent in 91.3% of patients. The median values of the osteaorthritis outcome score ranged from 87.5 to 95.

CONCLUSION

The mid-term positive outcomes and low complication rate in our consecutive series of patients support the safety and suitability of this new stem design in DAA for THA.

Long term results of the Bicontact D stem in dysplastic osteoarthritis: a 10-15 year follow-up study

PURPOSE

The purpose of the present study was to investigate the results of total hip arthroplasty (THA) using the Bicontact D stem with a minimum 10 year follow-up that focused on patients with developmental dysplasia of the hip (DDH).

METHODS

One hundred five patients with osteoarthritis due to DDH who underwent primary THA were included in this study. The mean final follow-up period was 12.7 ± 1.2 years (range 10-15 years). All cases were evaluated both clinically and radiographically, and Kaplan-Meier survivorship was determined as stem revision for any reason as the end point.

RESULTS

Modified Harris hip score averaged 89.0 ± 1.1 (range 60-98) at the final follow-up. The survivorship was 99.0% (95% confidence interval 93.4-99.9%) at 15.0 years, and only one hip with a well-fixed stem required stem revision due to recurrent dislocations. Cortical hypertrophy (CH) was observed in 40 of 105 hips (38.1%), and stress shielding (SS) progressed to grade 3 or 4 in six hips (6 of 105 hips: 5.7%) during the study period. Among the six hips with progressed SS, Dorr type C proximal femoral geometry was seen in five hips.

CONCLUSION

This study of 105 THAs using the Bicontact D stem that focused on DDH patients with a minimum 10 year follow-up period achieved satisfactory clinical and radiological outcomes. Dorr type C proximal femoral geometry could be considered a risk factor for progressed SS.

Comparison of the 5-Year Outcomes Between Standard and Short Fit-and-Fill Stems in Japanese Populations

Background

Fit-and-fill stems are known to have excellent outcomes; however, severe stress shielding has been reported in Japanese populations. Short fit-and-fill stems were modified for Asians; however, there have been no previous reports of its outcome. In this study, we compared the 5-year (mean 68-month) outcomes of 2 fit-and-fill stems with different lengths (standard or short).

Material and methods

We reviewed 100 total hip arthroplasties in each standard- or short-stem group. Radiographs were evaluated for femoral morphology, stress shielding, bone remodeling, and fixation. Clinical evaluation was performed using the Japanese Orthopaedic Association (JOA) scores.

Results

There was no difference in the degree of stress shielding between the 2 groups. Significant differences were observed in radiolucent lines in zone 4 (P = .005) and cortical hypertrophy in zone 3 (P < .0001) and 5 (P = .048) between the 2 groups. The canal flare index (P < .0003), cortical index (P < .0003), height (P < .0345), and stem size (P < .0081) individually affected stress shielding in the standard-stem group. In contrast, the cortical index (P < .0107) was the only relative factor in the short-stem group. All stems were judged to have bone ingrowth. The JOA score improved significantly (P < .0001); however, there were no significant differences between the 2 groups.

Conclusion

The outcomes of both standard and short fit-and-fill stems were favorable. There were no significant differences in the stress shielding or JOA scores. Although there were a few differences in bone remodeling and factors affecting stress shielding, stem length reduction has been achieved without adverse effects with the Japanese femur.

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

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.

Distal femoral cortical hypertrophy not associated with thigh pain using a short stem femoral implant

BACKGROUND

Thigh pain following a well-fixed total hip arthroplasty (THA) remains problematic and a source of patient dissatisfaction. The purpose of this study is to evaluate if the development of distal femoral cortical hypertrophy (DFCH) is associated with postoperative thigh pain after THA.

METHODS

All patients who underwent an uncomplicated primary THA via a direct anterior approach with the Taperloc Microplasty (Zimmer Biomet, Warsaw, IN, USA) implant between 2011 and 2015 were mailed a pain drawing questionnaire. Radiographs were reviewed at 1 year minimum to determine cortical thickness change from immediate post-op. Thigh pain was compared to DFCH. 293 patients were included in the study.

RESULTS

Mean follow-up was 3.2 years. A total of 218 hips (74%) had cortical hypertrophy in Gruen zone 3 and 165 hips (56%) had cortical hypertrophy in Gruen zone 5. 52 hips (18%) had ⩾25% cortical hypertrophy in zone 3 and 91 hips (31%) had ⩾25% cortical hypertrophy in zone 5. A total of 44 patients (15%) reported anterior thigh pain and 43 patients (15%) reported lateral thigh pain. Development of DFCH in either Gruen zone 3 or 5 was not associated with anterior or lateral thigh pain. Stem size was positively correlated with zone 3 hypertrophy and inversely related to zone 5 hypertrophy. Thigh pain was not associated with patient age, gender, activity level or stem size.

CONCLUSIONS

The development of distal femoral cortical hypertrophy after THA with a short stem implant was high, but not associated with patient-reported anterior or lateral thigh pain.

No Clinically Important Differences in Thigh Pain or Bone Loss Between Short Stems and Conventional-length Stems in THA: A Randomized Clinical Trial

BACKGROUND

Short-length stems were developed to reduce bone loss of the proximal femur and potentially decrease the incidence of thigh pain after cementless THA. However, it remains unknown whether short stems indeed reduce bone loss or the frequency of thigh pain.

QUESTIONS/PURPOSES

Is there a difference between short- and standard-length stems in terms of: (1) the frequency or severity of thigh pain, (2) modified Harris hip scores, (3) implant loosening, or (4) bone mineral density as measured by dual-energy x-ray absorptiometry?

METHODS

Between March 2013 and January 2014, three surgeons performed 205 primary THAs. To be eligible, patients needed to be at least 20 years of age, have not undergone previous history of hip surgery, and have no metabolic bone disease. A total of 100 patients were randomized to receive THA either with a short stem (n = 56) or with a standard-length stem (n = 44). Both stems were proximally coated, tapered, cementless stems. Compared with standard stems, short stems typically were 30- to 35-mm shorter. A total of 73% (41 of 56) and 77% (34 of 44) of those groups, respectively, were accounted for at a minimum of 5 years and were analyzed. The presence of thigh pain during activity was evaluated using a 10-point VAS, and the modified Harris hip score was calculated by research assistants who were blinded to the treatment groups. Plain radiographs were taken at 6 weeks, 6 months, and 12 months postoperatively, and every 1 year thereafter; loosening was defined as subsidence > 3 mm or a position change > 3° on serial radiographs. Radiological assessment was performed by two researchers who did not participate in the surgery and follow-up evaluations. Bone mineral density of the proximal femur was measured using dual-energy x-ray absorptiometry at 4 days, 1 year, 2 years, and 5 years postoperatively. The primary endpoint of our study was the incidence of thigh pain during 5-year follow-up. Our study was powered at 80% to detect a 10% difference in the proportion of patients reporting thigh pain at the level of 0.05.

RESULTS

With the numbers available, we found no difference between the groups in the proportion of patients with thigh pain; 16% (9 of 56) of patients in the short-stem group and 14% (6 of 44) of patients in the standard-stem group experienced thigh pain during the follow-up period (p = 0.79). In all patients, the pain was mild or moderate (VAS score of 4 or 6 points). Among the 15 available patients who reported thigh pain, there was no difference between the implant groups in mean severity of thigh pain (4.3 ± 0.8 versus 4.2 ± 0.7; p = 0.78). There were no between-group differences in the short versus standard-length stem groups in terms of mean modified Harris hip score by 5 years after surgery (89 ± 13 versus 95 ± 7 points; p = 0.06). No implant was loose and no hip underwent revision in either group. Patients in the short-stem group showed a slightly smaller decrease in bone mineral density in Gruen Zones 2, 3, and 5 than those in the standard-stem group did; the magnitude of the difference seems unlikely to be clinically important.

CONCLUSION

We found no clinically important differences (and few differences overall) between short and standard-length THA stems 5 years after surgery in a randomized trial. Consequently, we recommend that clinicians use standard-length stems in general practice because standard-length stems have a much longer published track record in other studies, and short stems can expose patients to the uncertainty associated with novelty, without any apparent offsetting benefit.

LEVEL OF EVIDENCE

Level I, therapeutic study.

Does increased diameter of metal femoral head associated with highly cross-linked polyethylene augment stress on the femoral stem and cortical hypertrophy?

PURPOSE

Cortical hypertrophy (CH) after total hip arthroplasty (THA) is thought as a process of femoral cortical functional adaptation against the stem. However, no study has been performed to investigate the association between CH and femoral head size. The purpose of this study is to investigate the factors related to femoral CH around the cementless stem after THA.

METHODS

THAs in 31 patients using 36-mm metal head and as a control, age-matched 62 THAs with 32-mm metal head have been analyzed. Radiographs were reviewed at four years to determine cortical thickness change from immediate post-operative one. Pre-operative and immediate post-operative radiographs were used to calculate the femoral morphology, canal fill ratio, stem alignment, and femoral and acetabular offset. Univariate and multivariate logistic regression analyses were performed to identify the risk factors for CH.

RESULTS

Patients with a 36-mm metal head had a significantly higher rate of severe CH (P = 0.001) than those with a 32-mm metal head. The multivariate logistic regression analysis with dependent variables of CH showed that the use of a 36-mm metal head had a significantly positive effect on CH. The odds ratio of a 36-mm metal head in mild CH was 2.517 (95% confidence interval, 1.032-6.143; P = 0.043), and that in severe CH was 8.273 (95% confidence interval, 2.679-25.551; P = 0.000). Age and the canal flare index were weakly and negatively influenced by mild CH.

CONCLUSIONS

The use of a 36-mm metal head was the dominant risk factor for CH.

The use of density mapping in the analysis of thigh pain after total hip arthroplasty in patients with well-fixed tapered wedge stems

PURPOSE

The mechanisms underlying thigh pain in patients with well-fixed cementless femoral components after total hip arthroplasty (THA) remains unclear. We hypothesized that the thigh pain is correlated with the initial contact state of the stem and aimed to investigate the relation between thigh pain and the initial contact state.

MATERIALS AND METHODS

A total of 209 hips of 184 patients were analysed in this retrospective case-control study. The patients were divided into a thigh pain group (n = 13 hips) and a control group (without thigh pain, n = 196). Post-operative stem contact images were three-dimensionally visualized by a density mapping function using computed tomography data, which quantified the stem contact area according to Gruen zones. Thigh pain was defined as anterior or anterolateral pain upon loading at 3-month post-operatively.

RESULTS

Thirteen hips (6.2%) had thigh pain; however, all the hips demonstrated stable bony ingrowth radiographically. The thigh pain group had a significantly lower contact area in zone 2 (p = 0.014). The multivariate logistic regression analysis showed that the contact area of zone 2 was negatively correlated with thigh pain [odds ratio (OR): 0.858, p = 0.018], and the canal flare index was negatively correlated with the development of thigh pain (OR: 0.336, p = 0.026).

CONCLUSIONS

We identified an association between the initial contact state and post-operative thigh pain. Our data demonstrated that proper lateral contact prevents the occurrence of thigh pain in THA using a tapered wedge stem.

Malalignment and distal contact of short tapered stems could be associated with postoperative thigh pain in primary total hip arthroplasty

PURPOSE

Short tapered stem placement has been extensively employed in total hip arthroplasty (THA). Suboptimal fixation tends to cause postoperative complications, such as thigh pain. However, it remains unclear whether poor seating/alignment of short tapered stems contributes to thigh pain. In this study, we retrospectively examined the factors that might be associated with thigh pain.

METHODS

Medical records of 230 patients who had undergone THAs at our hospital were reviewed retrospectively. All patients received the same mediolateral (ML) short tapered femoral stems. The association between thigh pain and patients' demographics, radiographic findings, or the type of fitting of the femoral stems was investigated.

RESULTS

In our cohort, 68 patients (27.8%) presented with thigh pain. Among 203 type I fit patients, 62 (30.5%) developed thigh pain, while only 6 out of 43 (12.2%) type II fit patients had thigh pain, with the differences being statistically significant (x² = 6.706, p = 0.01). In addition, hip anteroposterior radiographs exhibited that the stem angulation (mean 2.52°), the variation in angulation (mean 1.32°), and the extent of femoral stem subsidence (mean 0.29 cm) were greater in patients with thigh pain than in their counterparts without thigh pain (all p < 0.05).

CONCLUSION

Malalignment and improper seating of short tapered stems could be at least one of the reasons for post-THA thigh pain. The distal contact between the stem tip and the medial femoral cortex might result in thigh pain. Our study suggested that distal implant contact should be avoided, and stem alignment should be meticulously performed in the placement of ML short tapered femoral stems for THA.

Radiological Evaluation of the Relationship Between Cortical Hypertrophy and Stress Shielding After Total Hip Arthroplasty Using a Cementless Stem

Background

Unloading of the proximal medial femoral cortex is usually associated with an increased bone strain at the distal part of the prosthesis, which may cause distal femoral cortical hypertrophy (CH). The objective of this study was to determine the factors that may be considered a predisposition to distal femoral CH and its effect on the stress shielding (SS) or durability of the fixation of the stem.

Methods

A total of 240 total hip arthroplasties were performed between January 2006 and December 2016, with all hips implanted with a Bicontact stem. The minimum follow-up period was more than 2 years, and the mean follow-up period was 7.2 years. The radiographic outcome was assessed on an anteroposterior hip radiograph. CH and SS were assessed on postoperative radiographs in the Gruen zone. We defined CH that appeared in zone 3 or 5 as ‘the focal type’ and defined CH that appeared in zones 2, 3, 4, 5, and 6 as ‘the diffuse type.’ SS followed the procedures from the Engh classification.

Results

CH was found in 72 hips (30% of the 240 hips), the focal type was found in 23 hips (9.6% of the 240 hips), and the diffuse type was found in 49 hips (20.4% of the 240 hips). SS was found in 41 hips (17.1% of 240 hips), including 32 hips with SS, which was found after the development of CH. One hip was from the focal-type CH and 31 hips were from the diffuse-type CH. SS, which is typically found in Engh classification types 1 and 2 developed in 13 hips, and SS, which is widely seen in Engh classification types 3 and 4 developed in 19 hips. All 19 hips with progressed SS were found after the diffuse-type CH had developed. In addition, among the 19 hips with progressed SS, Dorr type A was found in 0 hips, Dorr type B in 8 hips, and Dorr type C in 11 hips.

Conclusions

According to the results of our radiological evaluation, development of the diffuse-type CH after total hip arthroplasty using Bicontact stems is one of the critical causes of the later development of SS and could be predicted to progress to SS. To prevent the development of the diffuse-type CH, the indication to choose a Bicontact stem for a Dorr type C with osteoporotic bone should be considered.

An excellent 5-year survival rate despite a high incidence of distal femoral cortical hypertrophy in a short hip stem

BACKGROUND

Although reported results on short stems sound very promising, the occurrence of distal femoral cortical hypertrophy is often observed. The aim of the present study was to report 5-year survival data of a commercially available trochanter sparing short stem and investigate the clinical impact of distal femoral cortical hypertrophy on the outcome.

METHODS

123 total hip arthroplasties were performed on 120 patients from April 2008 to May 2010 (mean age 62, range 29-89 years; 71 hips from male patients, 58%). Clinical and radiological data were collected preoperative, at 6 weeks, 1, 2, 3, and 5 years postoperative to assess the outcome. Radiographs taken immediately postoperative as well as 1 and 5 years postoperative were used to identify and assess cortical hypertrophy.

RESULTS

1 stem had to be revised due to aseptic loosening, resulting in a Kaplan-Meier survival analysis with endpoint for stem revision of 99.2% (95% Confidence Interval 94.1-99.9) at 5 years. 96 radiological and 95 clinical follow-ups were analysed 5 years postoperative. 68 (71%) hips showed distal femoral cortical hypertrophy after 5 years. The average Harris Hip Score and Oxford Hip Score improved 33 (standard deviation (SD) 15.1, range 2-70), 18 (SD 12.1, range -10-43) points, respectively. Overall 16% of the patients reported thigh pain, unrelated to the presence of cortical hypertrophy.

DISCUSSION

This short stem shows an excellent 5-year survival rate and good clinical outcome despite a high incidence of cortical hypertrophy. However, the question of the mechanism of load transfer arises.

Use of Bone Health Evaluation in Orthopedic Surgery: 2019 ISCD Official Position

This position development conference (PDC) Task Force examined the assessment of bone status in orthopedic surgery patients. Key questions included which orthopedic surgery patients should be evaluated for poor bone health prior to surgery and which subsets of patients are at high risk for poor bone health and adverse outcomes. Second, the reliability and validity of using bone densitometry techniques and measurement of specific geometries around the hip and knee before and after arthroplasty was determined. Finally, the use of computed tomography (CT) attenuation coefficients (Hounsfield units) to estimate bone quality at anatomic locations where orthopedic surgery is performed including femur, tibia, shoulder, wrist, and ankle were reviewed. The literature review identified 665 articles of which 198 met inclusion exclusion criteria and were selected based on reporting of methodology, reliability, or validity results. We recommend that the orthopedic surgeon be aware of established ISCD guidelines for determining who should have additional screening for osteoporosis. Patients with inflammatory arthritis, chronic corticosteroid use, chronic renal disease, and those with history of fracture after age 50 are at high risk of osteoporosis and adverse events from surgery and should have dual energy X-ray absorptiometry (DXA) screening before surgery. In addition to standard DXA, bone mineral density (BMD) measurement along the femur and proximal tibia is reliable and valid around implants and can provide valuable information regarding bone remodeling and identification of loosening. Attention to positioning, selection of regions of interest, and use of special techniques and software is required. Plain radiographs and CT provide simple, reliable methods to classify the shape of the proximal femur and to predict osteoporosis; these include the Dorr Classification, Cortical Index, and critical thickness. Correlation of these indices to central BMD is moderate to good. Many patients undergoing orthopedic surgery have had preoperative CT which can be utilized to assess regional quality of bone. The simplest method available on most picture archiving and communications systems is to simply measure a regions of interest and determine the mean Hounsfield units. This method has excellent reliability throughout the skeleton and has moderate correlation to DXA based on BMD. The prediction of outcome and correlation to mechanical strength of fixation of a screw or implant is unknown.

Prospective 5-year study with 96 short curved Fitmore™ hip stems shows a high incidence of cortical hypertrophy with no clinical relevance

Background

An increased occurrence of cortical hypertrophy (CH) was observed 1–2 years after implanting short curved Fitmore hip stems. There are no published data about either the clinical relevance or the progression of CH over the long term.

Methods

Ninety-six primary total hip arthroplasties were performed between 2008 and 2010 using the Fitmore hip stem. Clinical and radiological parameters were recorded preoperatively and at 1, 2, 3, and 5 year follow-up.

Results

CH appeared mainly on antero-posterior radiographs in Gruen Zones 2, 3, 5, and 6. After 1 year, the diameter was 10 ± 2 mm and remained constant thereafter. The CH rate after 1 year was 69% and after 5 years 71%. Subsidence after 1 year was 1.6 ± 1.55 mm and 1.93 ± 1.72 mm after 5 years. Cortical thinning was 46% after 1 year and 56% after 5 years, mainly in Gruen Zones 7 and 8. In the first year radiolucencies were found in 51% in all Gruen Zones, and in 20% after 5 years. Patient, implant, and surgical factors did not correlate with radiological outcomes except that larger stems had more CH. After 5 years, the Harris Hip Score had improved from 59 to 94 and the Oxford Hip Score from 22 to 41. Radiographic parameters, notably CH, were not associated with clinical outcomes except that cortical thinning correlated with lower outcome scores.

Conclusions

CH correlated neither with clinical outcome nor with patient, surgical or implant factors, except for a positive correlation with stem size. The Fitmore hip stems settled within the first year to a stable fixation and then remained almost unchanged. However, cortical thinning is common in Gruen Zone 7 and 8 meaning that there is stress-shielding.

Stemless hip arthroplasty versus traditional implants: a comparative observational study at 30 months follow-up

INTRODUCTION:

The aim of this retrospective case-control study is to evaluate clinical and radiographic results of short stems compared with traditional hip prostheses.

METHODS:

46 short stems (SS) and 50 traditional stems (TS) were selected. All the stems were implanted by the same surgeon using posterior approach because of primary osteoarthritis, post-traumatic osteoarthritis and avascular necrosis. All the patients were compared clinically by Harris Hip Score (HHS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), visual analogue scale (VAS), 12-item Short Form Health Survey (SF-12F/M) and radiographically (offset, CD angle, limb length discrepancy, cup inclination, subsidence, osseointegration, heterotopic ossification). Radiographic evaluations were carried out by 3 different blinded surgeons. A statistical analysis was performed (chi-square, t-test, Mann-Whitney).

RESULTS:

At a mean follow-up of 30 months all the implanted stems were well-positioned and osseointegrated. In both groups there was a marked improvement in pain ( p < 0.001) with a statistically significant advantage in the SS group for WOMAC (90.8 vs. 87.5; p = 0.02) and in part for HHS (93 vs. 91.7; p = 0.18). The radiographic evaluations, with high concordance correlation between the 3 blinded surgeons (ICC consistently >0.80), showed no significant differences in the restoration of the articular geometry, with a reduction of cortical hypertrophy (2% SS vs. 7% TS) and periprosthetic stress-shielding ( p < 0.05) in the SS group. On the other hand, SS were more related to limb length discrepancy (61% vs. 33%; p < 0.05). No major complications were recorded in the 2 groups.

CONCLUSION:

Short stems were shown to be comparable or better than traditional implants at short-term follow-up.

Long-term results of total hip arthroplasty using Charnley Elite-Plus stem and the effect of stem geometry on radiographic distal femoral cortical hypertrophy

BACKGROUND

The Elite-Plus stem has two shape variations: roundback and flanged. The correlation between the radiographic results and stem geometry has not been previously investigated. The objective of this study was to evaluate the long-term primary total hip arthroplasty results using Elite-Plus stems, and the effect of stem geometry on radiographic distal femoral cortical hypertrophy.

METHODS

We retrospectively evaluated, radiographically, 156 patients (173 hips) who underwent total hip arthroplasty between April 1998 and November 2005, and were followed up for >5 years, postoperatively. Radiographic factors affecting distal femoral cortical hypertrophy were analysed using multivariable logistic regression analysis.

RESULTS

The mean follow-up period was 11.6 (5-17.8) years. During follow-up, femoral components were revised in 7 hips; one was revised due to aseptic loosening. Another femoral component was loosened and waiting for revision. The 10- and 15-year survival rates for aseptic stem loosening were 100% and 98.1% (95% CI: 92.5-99.5), respectively. Distal femoral cortical hypertrophy occurred in 23 hips (14.8%), and more often with roundback type (34.1%) than with flanged type (7.2%). Distal femoral cortical hypertrophy was observed in 34.8% of hips with valgus alignment, 11.3% with neutral alignment, and 12.5% with varus alignment. Multivariable logistic regression analysis showed that roundback stem shape and valgus stem alignment significantly affected the occurrence of distal femoral cortical hypertrophy.

CONCLUSIONS

The Elite-Plus stem has excellent long-term clinical and radiographic results in Japanese patients. The occurrence of distal femoral cortical hypertrophy significantly depends on the shape and alignment of Elite-Plus stems.