Varus malalignment of short femoral stem not associated with post-hip arthroplasty fracture

An Uncommon Deformity of the Collarless, Polished, Double-Taper (CPT) Stem After a Periprosthetic Fracture in Total Hip Arthroplasty

We present an uncommon case of a Collarless, Polished, Double-Taper (CPT) stem deformity (irreversible stem bending) occurring due to a Periprosthetic Fracture (PPF) in Total Hip Arthroplasty (THA). The entire course of the case, including treatment, risk factors, and failure analysis of the deformed CPT by its manufacturer, Zimmer Biomet (Warsaw, USA),is described. The discussion considers in detail the (risk) factors that led to this particular stem deformity, incorporating current literature. We conclude with learning points on how to prevent stem abnormalities in PPFs in the future.  In our case, there were some case-specific risk factors associated with bending of the CPT stem. These factors are a relative varus angle, relative under-sizing of the stem, and a potentially inadequate cement mantle around the primary stem. No material or manufacture failure of the stem could be found. Still, it is very unusual that the femoral stem deforms without fracturing. Taken together, we present a unique case of a Periprosthetic Fracture with CPT stem deformity following Total Hip Arthroplasty.

Influence of stem length on sagittal alignment in total hip arthroplasty: a comparison between short and standard stems

BACKGROUND

Total hip arthroplasty (THA), a critical surgery for hip joint pain relief and mobility restoration, involves careful consideration of various factors, including stem length. Short stems are often chosen for their potential to reduce tissue damage and thigh pain. Precise alignment is necessary to alleviate complications such as stem loosening and fractures. We aimed to compare intramedullary insertion freedom and alignment changes between short and standard stems in THA. This study is based on preoperative planning simulations, highlighting the potential clinical implications.

METHODS

This retrospective study involved 102 hip joints (34 each from Dorr A, B, and C) undergoing initial THA between 2015 and 2017. A preoperative computed tomography scan was used to create three-dimensional bone models for planning virtual surgery, assessing stem insertion in flexion/extension, and measuring the anterior femoral offset. One-way repeated-measures analysis of variance was conducted to compare intramedullary insertion freedom and anterior femoral offset across the three Dorr classifications (A, B, and C). A paired t-test was used to compare intramedullary insertion freedom and anterior femoral offset between short and standard stems for each Dorr classification and between different medullary shapes.

RESULTS

Statistically significant differences were observed between the stem types (p < 0.05). Short stems demonstrated significantly greater intramedullary insertion freedom, with averages of 7.5°, 8.2°, and 9.1° for Dorr A, B, and C, respectively, compared with 4.3°, 5.0°, and 5.8° for standard stems. Additionally, the anterior femoral offset was significantly higher in short stems, with an average increase of 2.5 mm across classifications, compared to 1.2 mm in standard stems (p < 0.05).

CONCLUSION

Short stems offer enhanced intramedullary insertion freedom and improved anterior femoral offset, potentially leading to better alignment outcomes in THA. However, their increased freedom necessitates precise surgical planning, particularly in patients with wider medullary morphologies. These findings emphasize the importance of simulation-based planning in understanding the impact of stem length, while clinical studies are needed to validate these results.

Impact of femoral stem alignment on periprosthetic bone density in THA: a study of the Avenir Complete stem

INTRODUCTION

Thigh pain, aseptic loosening, and failure after total hip arthroplasty has been reported. Therefore, this study examines the impact of femoral stem alignment on periprosthetic bone mineral density (BMD) in THA using the Avenir Complete cementless stem, focusing on the role of precise stem alignment in maintaining proximal femoral BMD.

MATERIALS AND METHODS

Consecutive patients who received the Avenir Complete stem via mini anterolateral approach in the supine position between March 2019 and March 2022 were included. Dual-energy X-ray absorptiometry was used to assess BMD changes, and computed tomography scans were used to evaluate stem alignment.

RESULTS

BMD was maintained in the distal femur, but showed a slight decrease in the proximal femur. A negative correlation was observed among varus malalignment, anteversion errors, and changes in BMD in the proximal femur.

CONCLUSIONS

The findings underscore the importance of accurate stem positioning in THA, particularly in avoiding varus malalignment and anteversion errors, as misalignment can adversely affect proximal femoral BMD and potentially lead to early stem loosening. This study enhances the understanding of the influence of the Avenir Complete stem on postoperative BMD, highlighting the need for precise alignment to optimize outcomes.

Finite element analysis of mechanical stress in a cementless tapered-wedge short stem in the varus position

BACKGROUND

In recent years, the use of tapered-wedge short stems has increased due to their ability to preserve bones and tendons. Surgical techniques occasionally result in a varus position of the stem, which is particularly pronounced in short stems. Although the varus position is not clinically problematic, there are reports of an increased incidence of stress shielding and cortical hypertrophy. Thus, we evaluated and examined the acceptable range of varus angles using finite element analysis.

METHODS

Patients diagnosed with osteoarthritis of the hip joint who had undergone arthroplasty were selected and classified into three types [champagne-flute (type A), intermediate (type B), and stovepipe (type C)]. Finite element analysis was performed using Mechanical Finder. The model was created using a Taperloc microplasty stem with the varus angle increased by 1° from 0° to 5° from the bone axis and classified into seven zones based on Gruen's zone classification under loading conditions in a one-leg standing position. The volume of interest was set, the mean equivalent stress for each zone was calculated.

RESULTS

A significant decrease in stress was observed in zone 2, and increased stress was observed in zones 3 and 4, suggesting the emergence of a distal periosteal reaction, similar to the results of previous studies. In zone 2, there was a significant decrease in stress in all groups at a varus angle ≥ 3°. In zone 3, stress increased from ≥ 3° in type B and ≥ 4° in type C. In zone 4, there was a significant increase in stress at varus angles of ≥ 2° in types A and B and at ≥ 3° in type C.

CONCLUSION

In zone 2, the varus angle at which stress shielding above Engh classification grade 3 may appear is expected to be ≥ 3°. Distal cortical hypertrophy may appear in zones 3 and 4; the narrower the medullary cavity shape, the smaller the allowable angle of internal recession, and the wider the medullary cavity shape, the wider the allowable range. Long-term follow-up is required in patients with varus angles > 3°.

The influence of mental health on early outcomes following total hip arthroplasty

BACKGROUND

Poor mental health is difficult to recognize and as a result, its association with recovery from total joint arthroplasty is difficult to assess. The purpose of this study was to investigate the relationship between overall mental health scores and outcomes in the early postoperative period following unilateral total hip arthroplasty (THA).

METHODS

This is a retrospective review of prospectively collected data involving 142 patients who underwent primary unilateral THA. Independent variables included patient demographics and preoperative Patient-Reported Outcomes Measurement Information System (PROMIS), Global Physical Health (GPH) and Global Mental Health (GMH) and Hip Disability and Osteoarthritis Outcome Score, Joint Replacement (HOOS JR) scores as well as diagnoses of depression or anxiety. Dependent variables included length of stay (LOS), disposition at discharge, narcotic consumption until discharge, 6-week postoperative GPH, GMH and HOOS JR scores and magnitude of change compared to preoperative scores. Preoperative GMH and postoperative outcomes were compared using Pearson correlation coefficient, independent t-tests, Pearson's Chi-Square test, and univariate logistic regression.

RESULTS

Patients with preoperative GMH scores below the 25% quartile were less likely to be discharged home and resulted in lower GPH, GMH and HOOS JR scores at 6-week follow-up compared to patients with preoperative GMH scores in the top 25% quartile. However, patients with low preoperative GMH scores demonstrated a greater magnitude of improvement in both the GPH and GMH scores compared to patients in the top 25% quartile. There was no difference in opioid consumption or LOS between either groups. When comparing patients with and without depression/anxiety, no difference was seen in any of the outcomes measured.

CONCLUSION

Unilateral THA offers significant improvements in both physical and mental function to patients with hip osteoarthritis and poor mental health, though overall scores remain lower than in those with better mental health.

Clinical and radiological outcomes of an uncemented metaphyseal short stem at minimum 10 years of follow-up: a prospective observational study

PURPOSE

There is growing interest around short stems as they provide a less invasive approach for total hip arthroplasty preserving bone stock for a possible revision surgery if required. The main purpose of this work was to assess the long-term performance of an uncemented metaphyseal short stem in terms of survival rate and in addition its clinical and radiological outcomes.

MATERIALS AND METHODS

From January to December 2010, we prospectively enrolled all consecutive patients undergoing primary total hip arthroplasty with an uncemented metaphyseal short stem in our institution with a minimum follow-up of 10 years. The radiographic features investigated were the varus-valgus stem orientation, areas of osteolysis and radiolucencies, stress shielding, and heterotopic calcifications. The clinical outcomes were measured using the HHS.

RESULTS

A total of 163 patients (172 hips) were finally included and the measured survival rate at 10 years was 99.6%. The average HHS increased from 55.0 preoperatively to 97.8 at the last follow-up (p < 0.0001). Among them, 137 patients (164 hips) were also available for radiographic assessment. Mild varus malalignment was observed in 40% of cases and remained stable in the serial X-rays and was not associated with step loosening. Mild stress shielding was observed around 13 stems (9%) and moderate only around 3 implants.

CONCLUSION

In conclusion, the uncemented metaphyseal short stems showed excellent survival and clinical results at 10 years and at a radiographical level very low stress shielding was observed; moreover, besides the high frequency of varus alignment the implanted stems was not associated with revision surgery or with worse clinical outcomes.

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

INTRODUCTION

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Standard versus short stem cemented Exeter® when used for primary total hip arthroplasty: a survivorship analysis

AIMS

The aims were to compare the survival of the cemented standard (150 mm) with the short (DDH [35.5 mm offset or less], number 1 short stem [125 mm options of 37.5 mm, 44 mm, 50 mm offset] and revision [44/00/125]) Exeter® V40 femoral stems when used for primary total hip arthroplasty (THA).

METHODS

Patients were retrospectively identified from an arthroplasty database. A total of 664 short stem Exeter® variants were identified, of which 229 were DDH stems, 208 number 1 stems and 227 revision stems were implanted between 2011 and 2020. A control group of 698 standard Exeter® stems used for THA was set up, and were followed up for a minimum of 10 years follow-up (implanted 2011). All-cause survival was assessed for THA and for the stem only. Adjusted analysis was undertaken for age, sex and ASA grade.

RESULTS

The median survival time for the short stems varied according to design: DDH had a survival time of 6.7 years, number 1 stems 4.1 years, and revision stems 7.2 years. Subjects in the short stem group (n = 664) were significantly younger (mean difference 5.1, P < 0.001) and were more likely to be female (odds ratio 1.89, 95% CI 1.50 to 2.39, P < 0.001), compared to the standard group. There were no differences in THA (P = 0.26) or stem (P = 0.35) survival at 5 years (adjusted THA: 98.3% vs. 97.2%; stem 98.7% vs. 97.8%) or 10 years (adjusted THA 97.0% vs. 96.0 %; stem 96.7% vs. 96.2%) between standard and short stem groups, respectively. At 5 years no differences were found in THA (DDH: 96.7%, number 1 97.5%, revision 97.3%, standard 98.6%) or stem (DDH: 97.6%, number 1 99.0%, revision 97.3%, standard 98.2%) survival between/among the different short stems or when compared to the standard group.

CONCLUSION

The Exeter® short stems offer equivocal survival when compared to the standard stem at 5- to 10-year follow-up, which does not seem to be influenced by the short stem design.

Can Arthroplasty Stem Influence Outcome: A Randomized Controlled Trial of Stem Length in Cemented Total Hip Arthroplasty

BACKGROUND

The primary aim was to assess whether a short (125 millimeter (mm)) stem offered an equivalent hip-specific function compared to the standard (150 mm) stem when used for cemented total hip arthroplasty. Secondary aims were to evaluate health-related quality of life, patient satisfaction, stem height and alignment, as well as radiographic loosenings and complications between the two stems.

METHODS

A prospective twin-center double-blind randomized control trial was conducted. During a 15-month period, 220 patients undergoing total hip arthroplasty were randomized to either a standard (n = 110) or a short (n = 110) stem. There were no significant (P ≥ .065) differences in preoperative variables between the groups. Functional outcomes and radiographic assessment were undertaken at a mean of 1 and 2 years.

RESULTS

There were no differences (P = .428) in hip-specific function according to the mean Oxford hip scores at 1 year (primary endpoint) or at 2 years (P = .622) between the groups. The short stem group had greater varus angulation (0.9 degrees, P = .003) when compared to the standard group and were more likely (odds ratio 2.42, P = .002) to have varus stem alignment beyond one standard deviation from the mean. There were no significant (P ≥ .083) differences in the forgotten joint scores, EuroQol-5-Dimension, EuroQol-visual analogue scale, short form 12, patient satisfaction, complications, stem height, or radiolucent zones at 1 or 2 years between the groups.

CONCLUSION

The cemented short stem used in this study had equivalent hip-specific function, health-related quality of life, and patient satisfaction when compared to the standard stem at mean 2 years post operation. However, the short stem was associated with a greater rate of varus malalignment, which may influence future implant survival.

The 'critical trochanter angle' does not show superiority over the CCD angle in predicting varus stem alignment in cementless short-stem total hip arthroplasty

PURPOSE

Varus positioning of the femoral stem can affect the hip offset (HO). The critical trochanter angle (CTA) was introduced in 2019 as a novel geometric angle, to predict varus stem alignment in cementless straight stem THA. The aim of this study was to evaluate the applicability of the CTA as a predictor for stem alignment in THA with a cementless neck resecting short stem.

PATIENTS AND METHODS

In this retrospective study, 106 patients (index surgery 2014-2019) with unilateral THA and a morphologically healthy contralateral hip as a reference (Kellgren-Lawrence ≤ 1) were included. A cementless short stem with meta-diaphyseal fixation and press-fit cup was implanted in all cases. Stem alignment, CCD angle, CTA and offset reconstruction were measured on preoperative and 3 months postoperative AP radiographs of the pelvis.

RESULTS

Preoperative lower CTA and lower CCD angle were positively correlated (r = 0.472; p < 0.001). Higher varus stem alignment is correlated with lower CTA (r = - 0.384; p < 0.001) and lower CCD angle (r = - 0.474; p < 0.001). A CTA of 23.1° or lower showed a sensitivity of 59.1% and a specificity of 87.1% (AUC: 0.733) and a CCD angle of 132.75° or lower a sensitivity of 68.2% and a specificity of 80.6% (AUC: 0.77) for a varus stem alignment > 3°.

CONCLUSION

The CTA is also applicable in cementless THA with a neck resecting short stem to evaluate risk of intraoperative varus stem positioning. The CCD angle shows higher sensitivity with marginally lower specificity. Therefore, the CTA is not superior in predicting varus stem alignment in short-stem THA.

LEVEL OF EVIDENCE

IV.