Early Post-operative Periprosthetic Femur Fracture in the Presence of a Non-cemented Tapered Wedge Femoral Stem

Effects of Cerclage Cabling on Preventing Periprosthetic Femoral Fractures When Using Cementless Stems for Unstable Femoral Neck Fractures

BACKGROUND

Periprosthetic femoral fractures (PFFs) are serious complications in hip arthroplasty for femoral neck fractures. The rates of intraoperative (iPFFs) and postoperative PFFs (pPFFs) are higher in cementless stem cases than in cemented cases. This study aimed to investigate the effects of cerclage cabling on PFF prevention in cementless arthroplasty for femoral neck fractures.

METHODS

This retrospective study included 329 consecutive patients who underwent hip arthroplasty using a cementless stem for femoral neck fractures. A total of 159 and 170 patients were in the non-cabling and cabling groups, respectively. Patient characteristics were comparable in both groups. The PFF occurrence (iPFF and pPFF) rates, reoperation rates, operative time, and blood loss volume were compared between the groups.

RESULTS

The iPFF rate was significantly higher in the noncabling group (6.3%) than in the cabling group (0%, P < .001). The rate of pPFF was significantly higher in the non-cabling group (5.1%) than in the cabling group (0.6%; P = .016). All patients in the non-cabling group required reoperation (5.1%), whereas the patient in the cabling group was an ambulatory case and required no reoperation (0%, P = .003). No significant difference in either operative time or blood loss volume was observed between the non-cabling (50 minutes, 133 mL) and cabling (52 minutes, P = .244; 149 mL, P = .212, respectively) groups.

CONCLUSIONS

When a cementless stem is used to treat unstable femoral neck fractures, cerclage cabling effectively prevents iPPF and pPPF without increasing surgical time or blood loss volume.

Weak hammering sounds are associated with postoperative subsidence in cementless total hip arthroplasty

PURPOSE

The aim of this study was to investigate the relationship between the hammering sound level and the presence of postoperative subsidence.

METHODS

The last five hammering sounds during the final-size broaching procedure and during the real stem insertion were recorded and analysed in 95 patients who were operated on by one of seven surgeons using two implants (Trident cup, Accolade II, Stryker; G7 cup, Taperloc Complete Microplasty Stem, Zimmer Biomet). The maximum peak was semi-automatically identified and analysed to determine the maximum C-weighted sound pressure level (LCpeak) of each of the five hammering sounds and the equivalent continuous A-weighted sound pressure (LAeq) of the entire five-sound hammering procedure.

RESULTS

Among the 95 hips, 25 (26.3%) had ≥ 3 mm of postoperative subsidence. Therefore, 125 of 475 hammering sounds (LCpeak) and 25 of 95 hammering procedures (LAeq) in both the broaching procedure and stem insertion procedure were associated with postoperative subsidence. The hammering sound level in both the broaching and stem insertion procedures were significantly weaker in patients with postoperative subsidence than in those without subsidence. Among the seven surgeons, there was intra-surgeon and inter-surgeon heterogeneity with large variance regarding the sound levels. With univariate and multivariate analyses, the hammering sound level was independently associated with postoperative subsidence in the two models.

CONCLUSION

A weak hammering sound level was associated with postoperative subsidence in THA with a cementless stem. An objective evaluation of the hammering procedure might be useful to decrease the incidence of postoperative subsidence.

Risk Factors for Periprosthetic Femoral Fractures After Cementless Total Hip Arthroplasty

BACKGROUND

The present study aimed to identify the risk factors of periprosthetic femoral fracture (PFF) after cementless total hip arthroplasty and rank them based on importance.

METHODS

The age, sex, body mass index (BMI), osteoporosis, canal flare index (CFI), canal bone ratio (CBR), canal calcar ratio (CCR), stem design, and stem canal fill ratio (P1, P2, P3, and P4) of the proximal femoral medullary cavity of 111 total hip arthroplasty patients who had PFF and 388 who did not have PFF were analyzed. Independent-samples student t-tests were used for continuous variables, and Chi-square tests were used for categorical variables. The importance rankings of influencing factors were assessed using a random forest algorithm. Dimensionally reduced variables were then incorporated into a binary logistic regression model to determine the PFF-related risk factors.

RESULTS

The mean age, BMI, CBR, CCR, and incidence of osteoporosis were higher in cases of PFF (all P < .001), while the mean CFI, P1, P2, P3, and P4 were lower in cases of PFF (P < .001, P = .033, P = .008, P < .001, and P < .001, respectively). Additionally, the stem design was also statistically associated with PFF (P < .001). Multivariate logistic regression revealed that advanced age, higher BMI, osteoporosis, stem design, lower CFI, higher CBR, higher CCR, lower P1, lower P2, lower P3, and lower P4 were the risk factors of PFF (P < .001, P < .001, P < .001, P < .001, P < .001, P = .010, P < .001, P = .002, P < .001, P < .001, and P = .007, respectively). The ranked importance of the risk factors for PFF was P3, CFI, osteoporosis, CBR, age, P4, P1, stem design, CCR, BMI, and P2.

CONCLUSIONS

Lower P3, lower CFI, osteoporosis, higher CBR, advanced age, lower P4, lower P1, stem design, higher CCR, higher BMI, and lower P2 increased the risk of PFF.

[Risk factors and prevention strategies for periprosthetic femoral fractures in hip arthroplasty]

BACKGROUND

Periprosthetic fractures represent a major complication following joint replacement surgery, particularly total hip arthroplasty (THA). Due to demographic changes, a rising number of THAs is expected to lead to an increase in periprosthetic femoral fractures (PPF) in the coming decades. Despite the resulting high clinical relevance, there is as yet no comprehensive overview of risk factors and possible preventive approaches to PPF.

OBJECTIVES

The aim of this review is to present current findings and data from various studies and to derive evidence-based recommendations for clinical practice.

METHODS

Narrative review.

RESULTS

Various factors, such as advanced age, female sex, and rheumatic conditions, can increase the risk of PPF. In the presence of risk factors, a comprehensive assessment of bone health, including DXA osteodensitometry, should be considered prior to surgery.

CONCLUSIONS

An individualized approach is essential in the planning and execution of THAs to minimize the risk of PPF. In cases of confirmed osteoporosis or for women aged ≥ 70 years and men aged ≥ 75 years, cemented stem fixation should be chosen, as uncemented stems are associated with an increased risk of PPF. Overall, the clinical risk profile should be considered in preoperative planning and postoperative care to reduce this complication and improve patient care.

Deep-Learning Automation of Preoperative Radiographic Parameters Associated With Early Periprosthetic Femur Fracture After Total Hip Arthroplasty

BACKGROUND

The radiographic assessment of bone morphology impacts implant selection and fixation type in total hip arthroplasty (THA) and is important to minimize the risk of periprosthetic femur fracture (PFF). We utilized a deep-learning algorithm to automate femoral radiographic parameters and determined which automated parameters were associated with early PFF.

METHODS

Radiographs from a publicly available database and from patients undergoing primary cementless THA at a high-volume institution (2016 to 2020) were obtained. A U-Net algorithm was trained to segment femoral landmarks for bone morphology parameter automation. Automated parameters were compared against that of a fellowship-trained surgeon and compared in an independent cohort of 100 patients who underwent THA (50 with early PFF and 50 controls matched by femoral component, age, sex, body mass index, and surgical approach).

RESULTS

On the independent cohort, the algorithm generated 1,710 unique measurements for 95 images (5% lesser trochanter identification failure) in 22 minutes. Medullary canal width, femoral cortex width, canal flare index, morphological cortical index, canal bone ratio, and canal calcar ratio had good-to-excellent correlation with surgeon measurements (Pearson's correlation coefficient: 0.76 to 0.96). Canal calcar ratios (0.43 ± 0.08 versus 0.40 ± 0.07) and canal bone ratios (0.39 ± 0.06 versus 0.36 ± 0.06) were higher (P < .05) in the PFF cohort when comparing the automated parameters.

CONCLUSIONS

Deep-learning automated parameters demonstrated differences in patients who had and did not have early PFF after cementless primary THA. This algorithm has the potential to complement and improve patient-specific PFF risk-prediction tools.

Perioperative periprosthetic femur fracture associated with direct anterior total hip arthroplasty using metaphyseal fit and fill stem

INTRODUCTION

This study aims to identify radiographic and clinical risk factors of perioperative periprosthetic femur fracture associated with the direct anterior approach (DAA) using a metaphyseal fit and fill stem. We hypothesize stem malalignment with this femoral implant places increased stress on the medial calcar region, which leads to an increased risk of periprosthetic fracture.

METHODS

We compared patients with periprosthetic femur fractures following DAA total hip arthroplasty (THA) utilizing the Echo Bi-Metric Microplasty Stem (Zimmer Biomet, Warsaw, IN) to a cohort of patients who did not sustain a periprosthetic fracture from five orthopedic surgeons over four years. Postoperative radiographs were evaluated for stem alignment, neck cut level, Dorr classification, and the presence of radiographic pannus. Univariate and logistic regression analyses were performed. Demographic and categorical variables were also analyzed.

RESULTS

Fourteen hips sustained femur fractures, including nine Vancouver B2 and five AG fractures. Valgus stem malalignment, proud stems, extended offset, and patients with enlarged radiographic pannus reached statistical significance for increased fracture risk. Low femoral neck cut showed a trend toward statistical significance.

CONCLUSION

Patients undergoing DAA THA using a metaphyseal fit and fill stem may be at increased risk of perioperative periprosthetic fracture when the femoral stem sits proudly in valgus malalignment with extended offset and when an enlarged pannus is seen radiographically. This study identifies a specific pattern in the Vancouver B2 fracture cohort with regard to injury mechanism, time of injury, and fracture pattern, which may be attributed to coronal malalignment of the implant.

Highly accurate acoustical prediction using support vector machine algorithm for post-operative subsidence after cementless total hip arthroplasty

PURPOSE

Acoustic analysis has recently been applied to cementless total hip arthroplasty (THA). The aim of this study was to develop a machine learning algorithm to predict post-operative subsidence with high accuracy.

METHODS

The acoustic parameters of the hammering sounds during a broaching procedure for 62 hips in 55 patients who underwent THAs with cementless taper-wedged stem were analysed. The patient's basic background such as age, sex, height, weight and body mass index, the femoral morphological parameters and the hammering sound characteristics of 24 features of normalised sound pressure (nSP) in 24 frequency ranges were applied to binary classification using a support vector machine using the following models with different features: model A, nSP only; model B, nSP + patients' basic background features; model C, nSP + patients' basic background features + femoral morphological parameters.

RESULTS

In 62 hips with 310 hammering sounds, 12 hips (19.4%) showed ≥ 3 mm of post-operative subsidence; hence, 60 hammering sounds were set as positive examples and 250 hammering sounds were set as negative examples. The AUC was very high in all models. The accuracy (AUC/sensitivity/specificity/positive predictive value/negative predictive value/accuracy rate) of each model was as follows: model A, 0.963/0.656/0.996/0.980/0.925/0.934; model B, 0.9866/0.675/1.000/1.000/0.928/0.937 and model C, 0.998/0.750/1.000/1.000/0.950/0.957.

CONCLUSION

In this study, we developed a high-accuracy machine learning algorithm for post-operative subsidence using acoustic parameters and additional pre-operative features. Our results represent a step toward the realisation of acoustic monitoring to avoid the complication in cementless THA.

Cemented Femoral Fixation in a High-Risk Cohort Diminishes Risk of Early Postoperative Periprosthetic Fracture

BACKGROUND

Early periprosthetic fractures (PPFx) following primary total hip arthroplasty (THA) create significant morbidity. Established risk factors for early PPFx include age, gender, body mass index, surgical approach, and implant fixation. We investigated the role of femoral fixation on early PPFx (<90 days postoperatively) in a high-risk cohort undergoing direct anterior approach (DAA) THA.

METHODS

The final cohort comprised 344 consecutive patients (390 hips) with risk factors for PPFx (age >68 years and body mass index <25 kg/m2) who underwent primary DAA THA between May 4, 2009 and December 31, 2019 and had 90-day follow-up. Noncemented fixation was used in 229-hips, while cemented fixation was used in 161 hips. The primary outcome was early PPFx. Fisher's exact test was used for categorical variables, while t-tests were used to compare continuous variables.

RESULTS

We observed 8 early PPFx (2.1%), all fractures occurring in the noncemented group. Baseline demographics were similar but not equal, with the cemented group being older (78.0 versus 76.3 years; P = .004) with a greater proportion of females (91.9% versus 69.4%; P < .001). The rate of early PPFx was significantly higher with noncemented fixation compared to cemented fixation (3.5% versus 0.0%; P = .023). A post hoc power analysis confirmed sufficient power (1-β = 0.81).

CONCLUSION

Although baseline risk factors for early PPFx are not easily modifiable, surgical factors can be modified. Cemented fixation has the potential to markedly reduce the risk of early PPFx in high-risk patients undergoing DAA THA.

Femoral Component Undersizing and Alignment are Risk Factors for Early Periprosthetic Femur Fracture

BACKGROUND

Known risk factors for early periprosthetic femur fracture (PFF) following total hip arthroplasty (THA) include poor bone quality and the use of cementless implants. The association between femoral component size and alignment and the risk of early PFF is not well described. We evaluated radiographic parameters of femoral component sizing and alignment as risk factors for early PFF.

METHODS

From 16,065 primary cementless THAs, we identified 66 cases (0.41%) of early PFFs (<90 days from index THA) at a single institution between 2016 and 2020. Sixty early PFFs were (1:2) matched to 120 controls based on the femoral component model, offset, surgical approach, age, body mass index (BMI), and gender. Radiographic assessment of preoperative bone morphology and postoperative femoral component orientation included stem alignment, metaphyseal fill, and implant congruence with medial cortical bone. A multivariable logistic regression was built to identify radiographic risk factors associated with early PFF.

RESULTS

Markers of preoperative bone quality including canal calcar ratio (P = .003), canal flare index (P < .001), anteroposterior canal bone ratio (CBR) (P < .001), and lateral CBR (P < .001) were statistically associated with PFF. Distance between the medial cortical bone and implant was greater in cases of PFF (2.5 mm vs 1.4 mm) (P < .001). A multivariate analysis demonstrated that a larger lateral metaphyseal CBR (Odds Ratio [OR] 5), valgus implant alignment (OR 5), and medial implant-bone incongruity (OR 2) increased the risk of early PFF.

CONCLUSION

A larger lateral metaphyseal CBR, valgus component alignment, and implant incongruity with medial cortical bone posed the greatest radiographic risk for early PFF following cementless THA.

Periprosthetic fracture as a late mode of failure of the Anatomique Benoist Girard II femoral prosthesis

Aim

The Anatomique Benoist Girard (ABG) II femoral implant was a commonly used stem for primary total hip replacement (THR) at our institution (Launceston, Tasmania Australia). We identified peri‐prosthetic fracture as the main cause of late failure.

Methods

The late periprosthetic fracture rate for ABG II implants was reviewed with national statistics, using Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) data. National revision rates for periprosthetic fracture were used to compare ABG II with all other cementless femoral stems.

Result

ABG II stems accounted for 1% (2719 implants) of all femoral stem implants in Australia during the 12‐year review period, compared to 23% (587 implants) in Launceston Hospitals. Although the Launceston cumulative percent revision rate for the ABG II stem was lower than the National rate at all time points, the reasons for revision were similar. The most common reason for revision of ABG II was fracture (56.8%), followed by loosening (15.3%). This differs from the reasons for revision in other cementless prostheses (loosening 23.9%, fracture 20.8%, dislocation 18.7%). Cumulative percent revision rates from late periprosthetic fracture, were higher for the ABG II stem than other cementless femoral prostheses.

Conclusion

This review of the AOANJRR has confirmed a local and national higher revision rate of the ABG II stem due to late periprosthetic fracture compared with other cementless stems. Stem design must be considered to reduce the risk of late periprosthetic fracture.

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.

Inadequate Metadiaphyseal Fill of a Modern Taper-Wedge Stem Increases Subsidence and Risk of Aseptic Loosening: Technique and Distal Canal Fill Matter!

BACKGROUND

Adequate interference fit and mechanical stability through optimal surgical technique are essential to prevent subsidence and loosening in cementless total hip arthroplasty. The purpose of this study is to determine the effect of surgical technique on radiographic subsidence and subsequent stability of a modern taper-wedge cementless stem.

METHODS

A retrospective review of 250 consecutive cementless primary total hip arthroplasties performed by 2 surgeons was completed. Surgeon A vigorously broached, maximizing the mediolateral stem dimension and confirmed final broach stability with a torsional test, whereas Surgeon B did not. All patients received identical taper-wedge stems. Preoperative bone morphology (canal flare index), postoperative subsidence, and canal fill were radiographically assessed.

RESULTS

Canal flare index was not different between groups (P = .747). There was significantly less subsidence at 1 month for Surgeon A (0.3 vs 1.3 mm, P < .001). Additional subsidence at 1 year occurred in only 0.8% of Surgeon A (1/119) compared to 51.6% of Surgeon B stems (33/64, P < .001). Surgeon technique and canal fill measured at 60 mm below the lesser trochanter were the only variables predictive for subsidence, where Surgeon A and B had a mean canal fill of 95% and 86%, respectively. Surgeon B had 2 cases of aseptic loosening (2%) at 2 and 3 years postoperatively.

CONCLUSION

These observations support that maximizing mediolateral canal fill and avoiding under-sizing the femoral implant with meticulous broaching technique minimizes subsidence and optimizes stability of modern cementless taper-wedge stems. Failure to optimize canal fill with appropriate broaching and surgical technique may predispose femoral components to failure from aseptic loosening.

Clinical Practice Guidelines in Action: Differences in Femoral Neck Fracture Management by Trauma and Arthroplasty Training

INTRODUCTION

The purpose of this study was to survey trauma and arthroplasty surgeons to investigate associations between subspecialty training and management of geriatric femoral neck fractures and to compare treatments with the American Academy of Orthopaedic Surgeons clinical practice guidelines.

METHODS

Five hundred fifty-six surgeons completed the online survey consisting of two sections: (1) surgeon demographics and (2) two geriatric hip fracture cases with questions regarding treatment decisions.

RESULTS

In both clinical scenarios, arthroplasty surgeons were more likely than trauma surgeons to recommend total hip arthroplasty (THA) (case 1: 96% versus 84%; case 2: 29% versus 10%; P ≤ 0.02) and spinal anesthesia (case 1: 70% versus 40%; case 2: 62% versus 38%; P < 0.01). Surgeons who have made changes based on clinical practice guidelines (n = 96; 21% of surveyed) cited more use of THA (n = 56; 58% of respondents) and cemented stems (n = 28; 29% of respondents).

CONCLUSION

Arthroplasty surgeons are more likely to recommend THA over hemiarthroplasty and have a higher expectation for spinal anesthesia for the management of geriatric femoral neck fractures.

Comparison of the Incidence of Intra-operative Fractures in Hip Hemi-arthroplasty Performed in Supine and Lateral Positions

Purpose

The difficulty of femoral preparation with supine-position hip hemi-arthroplasty (HA) often leads to intra-operative fractures (IOFs). We aimed to clarify the incidence and types of IOFs in HA for hip fractures performed in the supine and lateral positions.

Materials and Methods

We retrospectively investigated cases of HA for acute femoral neck fractures from June 2013 to May 2018. We examined the incidence and types of IOFs according to different approaches. We defined supine-position in HA as the supine and hip-hyperextended (over-range) femoral preparation position, and lateral position as the lateral and hip-flexed femoral preparation position. We used a short tapered wedged stem.

Results

Supine-position HA was used in 46 patients (23.7%) and lateral-position HA in 148 patients (76.3%). IOFs in supine-position HA occurred in 8 patients (17.4%) and included five Vancouver A_GT and three Vancouver B2 fractures. IOFs in lateral-position HA occurred in 3 patients (2.0%) and included one Vancouver A_GT and two Vancouver B fractures. Supine-position HA was a risk factor for IOFs (adjusted odds ratio, 9.71; 95% confidence interval, 2.37-39.8; P<0.01).

Conclusion

Supine-position in HA is an IOF risk factor and significantly increases the incidence of great trochanter fractures of Vancouver type A.

Does Proximally Coated Single-Wedge Cementless Stem Work Well in Dorr Type C Femurs? Minimum 10-year Followup

BACKGROUND

Total hip arthroplasty (THA) with a proximally coated single-wedge (PSW) cementless stem had been generally considered not to be suitable for Dorr Type C femurs. This study compares the long term outcomes of PSW stem according to the type of proximal femoral geometry.

MATERIALS AND METHODS

307 primary THAs in 247 patients were performed with PSW cementless stem and followed up for over 10 years in this retrospective study. According to Dorr's criteria, 89 femurs were classified as Type A, 156 as Type B, and 62 as Type C. They were followed up for an average of 13.2 years (range 10.0-17.3 years). All the hips were evaluated clinically and radiologically.

RESULTS

There was no significant difference in stem survivorship and clinical outcomes including the incidence of thigh pain and the mean postoperative Harris hip score (HHS) in all three groups. No significant differences were observed in osteolysis, pedestal formation, or cortical hypertrophy among the groups. Radiolucent lines <2 mm in thickness in Gruen zone 4 and 7 (P = 0.003 and P = 0.044, respectively), spot-weld (P < 0.001), and stress shielding (P = 0.010) of proximal femur were more pronounced in Dorr C type femora than in Type A or B. Fifty-six intraoperative fractures were identified among 307 hips with PSW stems. The incidence of intraoperative or postoperative femoral fractures was not significantly different among the groups.

CONCLUSIONS

From over a 10-year followup, the PSW stem provided a recommendable option with satisfactory outcomes and excellent stem survivorship regardless of the Dorr type.

Polished, Collarless, Tapered, Cemented Stems for Primary Hip Arthroplasty May Exhibit High Rate of Periprosthetic Fracture at Short-Term Follow-Up

BACKGROUND

Cemented stems are designed to follow 1 of 2 principles of fixation: composite beams or slide taper. Stems in the latter category have a collarless, polished, tapered (CPT) design and subside into the cement mantle, creating hoop stresses. We compared the rate of periprosthetic fracture (PPF) of stem designed with these 2 principles of fixation. In addition, we examined radiographic factors that may predispose to the development of PPF.

METHODS

We retrospectively reviewed all patients who underwent primary THA by a single surgeon using highly polished cemented stems. PPF rates were compared between CPT stems (follow-up, 21 months; standard deviation [SD], 22) and composite beam stems (follow-up, 21.7 months; SD, 26). Demographic data were compared between patients with and without a PPF. Three preoperative radiographic parameters (canal bone ratio [CBR], canal-calcar ratio, and canal flare index), stem alignment, and cement mantle were compared in match-paired patients with and without a PPF (1:34).

RESULTS

Seven of 1460 THA patients developed a PPF (0.479%); 4 hips of 185 with a CPT stem (2.2%); and 3 of 1275 hips with a composite beam stem (0.23%; P = .0064). Three of the 4 PPFs in the CPT group and none in the composite beam group were classified as Vancouver B2. The CBR in patients with a PPF was 0.50 (SD, 0.07) and 0.43 (SD, 0.07) in the match cohort of hips without PPF (P = .013).

CONCLUSION

CPT stems may be associated with a higher risk of PPF that often require reoperation. An increased CBR may be a risk factor for postoperative PPF.

Cementless Tapered Wedge Femoral Stems Decrease Subsidence in Obese Patients Compared to Traditional Fit-and-Fill Stems

BACKGROUND

Femoral component stability and resistance to subsidence is critical for osseointegration and clinical success in cementless total hip arthroplasty. The purpose of this study was to radiographically evaluate the anatomic fit and subsidence of 2 different proximally tapered, porous-coated modern cementless femoral component designs.

METHODS

A retrospective cohort study of 126 consecutive cementless total hip arthroplasties was performed. Traditional fit-and-fill stems were implanted in the first 61 hips with the remaining 65 receiving morphometric tapered wedge stems. Preoperative bone morphology was radiographically assessed by the canal flare index. Canal fill in the coronal plane, subsidence, and the sagittal alignment of stems was measured digitally on immediate and 1-month postoperative radiographs.

RESULTS

Demographics and canal flare indices were similar between groups. The percentage of femoral canal fill was greater in the tapered wedge compared to the fit-and-fill stem (P = .001). There was significantly less subsidence in the tapered wedge design (0.3 mm) compared to the fit-and-fill design (1.1 mm) (P = .001). Subsidence significantly increased as body mass index (BMI) increased in the fit-and-fill stems, a finding not observed in the tapered wedge design (P = .013).

CONCLUSION

An anatomically designed morphometric tapered wedge femoral stem demonstrated greater axial stability and decreased subsidence with increasing BMI than a traditional fit-and-fill stem. The resistance to subsidence, irrespective of BMI, is likely due to the inherent axial stability of a tapered wedge design and may be the optimal stem design for obese patients.

Periprosthetic femoral fractures and trying to avoid them: what is the contribution of femoral component design to the increased risk of periprosthetic femoral fracture?

AIMS

Periprosthetic femoral fractures (PFF) following total hip arthroplasty (THA) are devastating complications that are associated with functional limitations and increased overall mortality. Although cementless implants have been associated with an increased risk of PFF, the precise contribution of implant geometry and design on the risk of both intra-operative and post-operative PFF remains poorly investigated. A systematic review was performed to aggregate all of the PFF literature with specific attention to the femoral implant used.

PATIENTS AND METHODS

A systematic search strategy of several journal databases and recent proceedings from the American Academy of Orthopaedic Surgeons was performed. Clinical articles were included for analysis if sufficient implant description was provided. All articles were reviewed by two reviewers. A review of fundamental investigations of implant load-to-failure was performed, with the intent of identifying similar conclusions from the clinical and fundamental literature.

RESULTS

In total 596 articles were initially identified, with 34 being eligible for analysis. Aggregate analysis of 1691 PFFs in 342 719 primary THAs revealed a significantly higher number of PFFs with cementless femoral implants (p < 0.001). Single-wedge and double-wedge (fit-and-fill) femoral implants were associated with a threefold increase in PFF rates (p < 0.001) compared with anatomical, fully coated and tapered/rounded stems. Within cemented stems, loaded-taper (Exeter) stems were associated with more PFFs than composite-beam (Charnley) stems (p = 0.004). Review of the fundamental literature revealed very few studies comparing cementless component designs.

CONCLUSION

Very few studies within the PFF literature provide detailed implant information. Cementless implants, specifically those of single-wedge and double-wedge, have the highest PFF rates in the literature, with most investigations recommending against their use in older patients with osteoporotic bone. This review illustrates the need for registries and future PFF studies to record implant name and information for future analysis. Furthermore, future biomechanical investigations comparing modern implants are needed to clarify the precise contribution of implant design to PFF risk. Cite this article: Bone Joint J 2017;99-B(1 Supple A):50-9.

The influence of cemented femoral stem choice on the incidence of revision for periprosthetic fracture after primary total hip arthroplasty

Aims

Periprosthetic fracture (PF) after primary total hip arthroplasty (THA) is an uncommon but potentially devastating complication. This study aims to investigate the influence of cemented stem designs on the risk of needing a revision for a PF.

Patients and Methods

We analysed data on 257 202 primary THAs with cemented stems and 390 linked first revisions for PF recorded in the National Joint Registry (NJR) of England, Wales and Northern Ireland to determine if a cemented femoral stem brand was associated with the risk of having revision for a PF after primary THA. All cemented femoral stem brands with more than 10 000 primary operations recorded in the NJR were identified. The four most commonly used cemented femoral stems were the Exeter V40 (n = 146 409), CPT (n = 24 300), C-Stem (n = 15 113) and Charnley (n = 20 182). We compared the revision risk ratios due to PF amongst the stems using a Poisson regression model adjusting for patient factors. Compared with the Exeter V40, the age, gender and ASA grade adjusted revision rate ratio was 3.89 for the cemented CPT stem (95% confidence interval (CI) 3.07 to 4.93), 0.89 for the C-Stem (95% CI 0.57 to 1.41) and 0.41 for the Charnley stem (95% CI 0.24 to 0.70).

Conclusions

The limitations of the study include incomplete data capture, analysis of only PF requiring revision and that observation does not imply causality. Nevertheless, this study demonstrates that the choice of a cemented stem may influence the risk of revision for PF. Cite this article: Bone Joint J 2016;98-B:1347–54.

New Approach and Stem Increased Femoral Revision Rate in Total Hip Arthroplasty

This study compared the femoral stem revision and loosening rates in primary total hip arthroplasty between 2 different approaches and stem designs. Recent reports comparing the direct anterior approach with either the posterior or lateral approach showed that patients undergoing the direct anterior approach have less pain and an accelerated functional recovery in the early postoperative period. After converting to an anterior approach, the authors observed an increased rate of femoral stem revision. From 2003 to 2009, a posterior or lateral approach was used to insert 514 stems of 2 designs. These cases included the use of an extensively coated cobalt-chrome stem (n=232) or a straight, dual-tapered, proximally porous-coated titanium stem (n=282). In the following years, from 2009 to 2012, 594 short, proximally coated, titanium tapered-wedge stems were inserted through a direct anterior approach. The revision rates of femoral stems inserted through a posterior approach or a lateral approach were compared with those inserted via a direct anterior approach. No stem revisions occurred in the posterior approach group or the lateral approach group, and 5 stems were revised in the anterior approach group for periprosthetic fracture or aseptic loosening (0.8%). Significantly more stem revisions occurred after the use of the new stem design and a direct anterior approach (P=.04).

Outcomes of Surgical Treatment of Periprosthetic Femoral Fractures in Cementless Hip Arthroplasty

Purpose

We aimed to evaluate the results of surgical treatment of periprosthetic femoral fractures in cementless total hip arthroplasty (THA).

Materials and Methods

From June 2002 to May 2012, 40 patients who could be followed-up for more than 1 year after surgery were enrolled in this study. The mean duration of follow-up was 28.5 months (range, 15-97 months) and the average age at the time of surgery was 71.5 years (range, 38-89 years). The fracture types were determined by using the Vancouver classification. Among intraoperative fractures, there were type A in 3 hips, type B2 in 2 hips and type B3 in one. Among postoperative fractures, type AG was present in 5 hips, type AL in 2 hips, type B1 in 15 hips, type B2 in 6 hips, type B3 in 3 hips, and type C in 3 hips. Evaluation of the results was based on bony union, stability of the prosthesis, postoperative complications, and Harris hip score at the final follow-up.

Results

Bony union was achieved in all but one case and the average time for bony union was 21 weeks. The mean Harris hip score was 86 at the final follow-up. Clinical results were above good in 34 of 40 hips (85.0%). Stem loosening occurred in one patient with a type B1 fracture treated with open reduction and plate fixation. Nonunion was observed in 1 patient with an AG type fracture.

Conclusion

Open reduction and fixation using a plate with a screw and cerclage wiring provided good results for periprosthetic fractures in patients who had a stable femoral stem without bone defects. Revision surgery with a cementless long stem should be considered in patients with an unstable stem or suspected stability in B1 type of THA using a proximal fixation type.

Clinical characteristics and risk factors of periprosthetic femoral fractures associated with hip arthroplasty: A retrospective study

Periprosthetic femoral fracture (PFF) is a complicated complication of both primary and revision hip arthroplasty with an increasing incidence. The present study aimed to summarize the clinical characteristics and identify the risk factors for PFF which would be potentially helpful in the prevention and treatment of PFF.We retrospectively analyzed the clinical data of 89 cases of PFF, and a case-control study was designed to identify the potential risk for intraoperative and postoperative PFF in both primary and revision hip arthroplasty.The overall incidence of PFF was 2.08% (intraoperative: 1.77%, postoperative: 0.30%, revision: 13.60%, and primary: 0.97%). The most commonly used treatment strategy was fixation with cerclage wire or band for intraoperative PFF, whereas long stem revision with plate or cortical allograft strut fixation was the main treatment strategy for postoperative PFF. The risk factors for intraoperative PFF in primary total hip arthroplasty (THA) included the diagnosis of development dysplasia of the hip (DDH) (odds ratio [OR] = 5.01, 95%CI, 1.218-20.563, P=0.03) and CBR ≥ 0.49 (OR = 3.34, 95%CI, 1.138-9.784, P = 0.03). The increased age was associated with increased incidence of postoperative PFF in primary THA (OR = 1.09, 95%CI, 1.001-1.194, P = 0.04). As for the intraoperative PFF in revision THA, we found that receiving multiple operations before revision (OR = 2.45, 95%CI, 1.06-5.66, P = 0.04), revisions due to prosthetic joint infection (OR = 6.72, 95%CI, 1.007-44.832, P = 0.04), the presence of cementless implant before revision (OR = 13.54, 95%CI, 3.103-59.08, P = 0.001), and femoral deformity (OR = 8.03, 95%CI, 1.656-38.966, P = 0.01) were all risk factors.Screening for high-risk patients, preoperative templating, and detailed discharge instructions may be the potential strategies to reduce the incidence of PFF. The treatment of PFFs should take into account Vancouver classification system, patient's characteristics as well as the experience of the operating surgeon.

Peri-prosthetic fractures around tumor endoprostheses: a retrospective analysis of eighteen cases

PURPOSE

Tumour hip and knee endoprostheses have become the mainstay for reconstruction of patients with bone tumours. Fixation into host bone has improved over time. However, some patients present with a peri-prosthetic fracture over follow-up. The objective of this study was to analyse the mode of presentation and survival of implant after a peri-prosthetic fracture around a tumour endoprosthesis.

METHODS

Eighteen peri-prosthetic fractures (17 patients) were included. All patients were treated at a tertiary care center. There were 11 (65%) women; the median age at the time of fracture was 38 years old. All implants were cemented and all knee endoprostheses were fixed-hinge. Twelve (67%) fractures occurred after femoral resection and six (33%) fractures after proximal tibial resection.

RESULTS

There were three femoral neck fractures (UCS C), three femoral shaft type C fractures, two femoral shaft type B1, one tibial shaft type B2, three tibial shaft type C, three ankle fractures (UCS C) and three patella fractures (UCS F). Two fractures were treated conservatively and 16 were operated on. Only one patient had the implant revised. There were eight (44%) failures over follow-up; none of the conservative treatment failed. The cumulative probability of failure for any reason was 27% (8-52) and 55% (22-79) at five and ten years, respectively.

CONCLUSIONS

Peri-prosthetic fractures around massive endoprostheses are different from that of standard implants. There are more type C fractures; internal fixation is an attractive option at the time of presentation but the risk of revision over follow-up is high and patients should be informed accordingly.

Periprosthetic femur fractures

Successful treatment of periprosthetic femur fractures, like all fractures, requires careful attention to understand the fracture pattern nuances, identifying and executing a rational treatment approach, and providing an appropriate postoperative recovery protocol. Unlike most other fractures, modification of standard techniques is often required to obtain a stable fixation construct, and there is a greater role for revision arthroplasty in the treatment of periprosthetic fractures. Optimal indications for surgical repair versus revision arthroplasty and optimal postoperative weight-bearing protocols remain uncertain. Reported outcomes for patients with periprosthetic femoral shaft fractures are generally good and are relatively consistent. Results for periprosthetic distal femur fractures, however, are less good and more inconsistent. Both periprosthetic femoral shaft and distal femur fractures are associated with relatively high mortality rates, approaching that of patients with hip fractures. This review should provide insight into the current solutions and challenges for the treatment of patients with periprosthetic femur fractures.

High incidence of stem loosening in association with periprosthetic femur fractures in previously well-fixed cementless grit-blasted tapered-wedge stems

PURPOSE

Periprosthetic femur fracture is a potentially worrisome phenomenon for cementless stem fixation. The aim of this study was to document the incidence of stem loosening following periprosthetic femur fracture in previously well-fixed cementless grit-blasted tapered-wedge stems.

METHODS

We identified 36 periprosthetic femur fractures of either Vancouver B1 or B2 following hip arthroplasties using cementless grit-blasted tapered-wedge titanium stems at three participating institutions (GB group). The control group consisted of 21 periprosthetic femur fractures of either Vancouver B1 or B2 following hip arthroplasties using cementless proximal porous-coated stems at the same institutions during the same period of study (PC group). All femoral stems had been in a well-fixed state before occurrence of fracture. All patients were treated surgically and femoral stem stability was assessed using preoperative radiographs and confirmed by intraoperative scrutinization.

RESULTS

Seven (19.4%) of 36 fractures were Vancouver B1 and 29 (80.6%) were Vancouver B2 in the GB group, whereas 18 (85.7%) of 21 fractures were Vancouver B1 and 3 (14.3%) were Vancouver B2 in the PC group (P < 0.0001). The odds ratio for stem loosening was 24.86 (95% CI, 5.69-108.63) in the GB group versus the PC group.

CONCLUSIONS

Hip arthroplasty using cementless grit-blasted tapered-wedge titanium stems showed higher incidence of stem loosening in association with periprosthetic femur fracture than hip arthroplasty conducted using proximal porous-coated stems. A high index of suspicion of stem loosening might be necessary in periprosthetic femur fracture following hip arthroplasty using this type of stems.

Loosely implanted cementless stems may become rotationally stable after loading

BACKGROUND

Experimental studies have suggested that initial micromotion of cementless components may lead to failure of osteointegration. Roentgen stereophotogrammetric analyses have shown durable implant fixation can be achieved long-term even when initial instability exists, as evidenced by subsidence. However improved implant stability as a result of subsidence, before osteointegration, has not been shown biomechanically.

QUESTIONS/PURPOSES

We asked whether insertionally loose cementless tapered femoral stems show (1) less rotational stability (more toggle); (2) more subsidence; and (3) reduced ability to resist torsion (lower initial construct stiffness), lower torque at failure, and greater rotation to failure in comparison to well-fixed cementless tapered femoral stems.

METHODS

Ten matched pairs of cadaveric femurs were implanted with well-fixed and loose cementless tapered stems. The loose stem construct was obtained by appropriately broaching the femur but afterwards inserting a stem one size smaller than that broached. Femoral stem rotational stability of implanted femurs was tested by measuring the angular rotation (ie, toggle) required to produce a torque of 2 N-m at 0 N, 250 N, and 500 N vertical load in 25° adduction simulating single-legged stance. Subsidence was measured as vertical movement during the toggle tests. Then at 500 N initial vertical load, femoral stems were externally rotated to failure. The construct stiffness between 5 and 40 N-m was determined to assess ability to resist torsion. The torque and rotation to failure were recorded to compare failure characteristics. Groups were compared using mixed model ANOVA followed by Tukey-Kramer post hoc pairwise comparison for toggle and subsidence tests and by Student's paired t-tests for stiffness, torque at failure, and rotation to failure tests.

RESULTS

Loose tapered cementless stems were less stable (ie, more toggle) than well-fixed at 0 N of load (p < 0.0001), but no difference was detectable in toggle between loose and well-fixed stems at 250 N (p = 0.7019) and 500 N (p = 0.9970). Loose tapered cementless stems showed significant subsidence at 250 N (p < 0.0001) and 500 N (p < 0.0001), which was not found in the well-fixed stems at 250 N (p = 0.8813) and 500 N (p = 0.1621). Torsional stiffness was lower for loose stems as compared with well-fixed stems (p = 0.0033). No difference in torque at failure (p = 0.7568) or rotation to failure (p = 0.2629) was detected between loose and well-fixed stems.

CONCLUSIONS

In this study, we observed that insertionally loose cementless stems have the ability to subside and become rotationally stable with loading. They did not exhibit a lower torque or rotation to failure in comparison to well-fixed stems when under simulated single-legged stance.

CLINICAL RELEVANCE

Secondary rotational stabilization may prevent insertionally loose tapered stems from producing a stress pattern that predisposes to early postoperative periprosthetic fracture around loose cemented stems.