Reproducibility and accuracy of templating uncemented THA with digital radiographic and digital TraumaCad templating software

Does two dimensional templating allow for the use of reduced-size ancillaries in total hip arthroplasty?

PURPOSE

Rising costs in healthcare for total hip arthroplasty (THA) mean that new solutions must be considered, such as the use of single-use ancillaries (SUA). The goal of this study was to assess the accuracy of 2D templating in primary THA for the use of reduced-size SUA. Our hypothesis was that the accuracy of 2D templating in primary THA would be higher than 95%, give or take two sizes.

METHOD

This single-centre prospective study included all primary THAs performed over two years. Templating was carried out using 2D templating on anteroposterior pelvic X-rays. The template sizes were compared to the implant sizes. The primary endpoint was the rate of coincidence between digitally templated estimates and the actual implant sizes. The secondary endpoint was the difference of accuracy based on patient parameters.

RESULTS

We analysed 512 cases of THA. Accuracy within two sizes was 96.9% for acetabular implants and 98.5% for femoral implants. Accuracy was below the 95% threshold only in patients under 55 and over 85 years old. A BMI above 30.0 kg/m2 significantly reduced accuracy but did not fall below the 95% threshold. The operated hip, the type of implant, and the operative indication did not significantly influence templating accuracy.

CONCLUSION

Using reduced-size SUA with five rasps and five reamers depending on template sizes means that THA can be performed in more than 95% of cases allowing the use of compact single use ancillaries.

Trabecular Metal Augments During Complex Primary Total Hip Arthroplasty

Background

Trabecular metal augments (TMAs) have been extensively used in revision total hip arthroplasty (THA) to address acetabular bone defects. However, limited data exists regarding TMA utilization during primary THA. This study aims to assess the clinical and radiographic outcomes of TMAs used during primary THA.

Methods

A single-institution retrospective case series of primary THA patients treated with TMA between 2010 and 2019 was performed. Patient demographics, complications, and revisions were recorded. Cup position, center of rotation, leg length, and radiolucent lines were assessed radiographically. The Kaplan-Meier method was used to compute implant survivorship.

Results

Twenty-six patients (30 hips) were included with average age of 52.6 ± 15.3 years (range: 22-78) and mean follow-up of 4.1 ± 2.1 years (range: 2.0-8.9). Most TMAs were indicated for developmental dysplasia of the hip (n = 18; 60.0%). On average, hip center of rotation was lowered 1.5 ± 1.3 cm and lateralized 1.2 ± 1.5 cm, while leg length and global offset were increased by 2.4 ± 1.2 cm and 0.4 ± 1.0 cm, respectively. At final follow-up, 3 hips (10.0%) required revision: one (3.3%) for aseptic loosening and 2 (6.7%) for instability. No patients had progressive radiolucent lines at final follow-up. Five-year survival with aseptic loosening and all-cause revision as endpoints was 100% (95% confidence interval: 90.0%-100.0%) and 92.1% (95% confidence interval: 81.3%-100.0%), respectively. One patient required revision for aseptic loosening after the 5-year mark.

Conclusions

Trabecular metal augmentation during primary THA demonstrates satisfactory early to mid-term outcomes. TMA is a viable option for complex primary THA when bone loss is encountered or secondary support is required.

Level of Evidence

Level IV.

Surgeon's Experience and Accuracy of Preoperative Digital Templating in Primary Total Hip Arthroplasty

Purpose

Preoperative planning has become essential in performance of total hip arthroplasty (THA). However, data regarding the effect of the planner's experience on the accuracy of digital preoperative planning is limited. The objective of this study was to assess the accuracy of digital templating in THA based on the surgeon's experience.

Materials and Methods

A retrospective study was conducted. An analysis of 98 anteroposterior pelvic radiographs, which were individually templated by four surgeons (two hip surgeons and two orthopaedic residents) using TraumaCad® digital planning, was performed. A comparison of preoperatively planned sizes with implanted sizes was performed to evaluate the accuracy of predicting component size. The results of preoperative planning performed by hip surgeons and orthopaedic residents were compared for testing of the planner's experience.

Results

Femoral stem was precisely predicted in 32.4% of cases, acetabular component in 40.3%, and femoral offset in 76.7%. Prediction of cup size showed greater accuracy than femoral size among all observers. No differences in any variable were observed among the four groups (acetabular cup P=0.07, femoral stem P=0.82, femoral offset P=0.06). All measurements showed good reliability (intraclass correlation coefficient [ICC] acetabular cup: 0.76, ICC femoral stem: 0.79).

Conclusion

The results of this study might suggest that even though a surgeon's experience supports improved precision during the planning stage, it should not be restricted only to surgeons with a high level of experience. We consider preoperative planning an essential part of the surgery, which should be included in training for orthopaedics residents.

Development and validation of multiple linear regression models for predicting total hip arthroplasty acetabular prosthesis

PURPOSE

To establish a multivariate linear equation to predict the diameter (outer diameter) of the acetabular prosthesis used in total hip arthroplasty.

METHODS

A cohort of 258 individuals who underwent THA at our medical facility were included in this study. The independent variables encompassed the patients' height, weight, foot length, gender, age, and surgical access. The dependent variable in this study was the diameter of the acetabular prosthesis utilized during the surgical procedure. The entire cohort dataset was randomly partitioned into a training cohort and a validation cohort, with a ratio of 7:3, employing the SPSS 26.0 software. Pearson correlation analysis was conducted to examine the relationships between the patients' height, weight, foot length, gender, age, surgical access, and the diameter of the acetabular prosthesis in the training cohort. Additionally, a multiple linear regression equation was developed using the independent variables from the training cohort and the diameter of the acetabular prosthesis as the dependent variable. This equation aimed to predict the diameter of the acetabular prosthesis based on the patients' characteristics. The accuracy of the equation was evaluated by substituting the data of the validation cohort into the multiple linear equation. The predicted acetabular prosthesis diameters were then compared with the actual diameters used in the operation.

RESULTS

The correlation analysis conducted on the training cohort revealed that surgical access (r = 0.054) and age (r = -0.120) exhibited no significant correlation with the diameter of the acetabular prosthesis utilized during the intraoperative procedure. Conversely, height (r = 0.687), weight (r = 0.654), foot length (r = 0.687), and sex (r = 0.354) demonstrated a significant correlation with the diameter of the acetabular prosthesis used intraoperatively. Furthermore, a predictive equation, denoted as Y (acetabular prosthesis diameter in mm) = 20.592 + 0.548 × foot length (cm) + 0.083 × height (cm) + 0.077 × weight (kg), was derived. This equation accurately predicted the diameter within one size with an accuracy rate of 64.94% and within two sizes with an accuracy rate of 94.81%.

CONCLUSION

Anthropometric data can accurately predict the diameter of acetabular prosthesis during total hip arthroplasty.

KingMark's dual-marker versus a conventional single-marker templating system: is there a difference in accuracy of predicting final implant sizes and leg lengths?

AIMS

Pre-operative templating for total hip replacement (THR) surgery leads to more accurate implant sizing and positioning. This study aimed to compare the KingMark™ dual-marker system for magnification calibration to the current gold standard single-marker system in accuracy of predicting implant size and restoration of leg length post-operatively.

METHODS

This is a retrospective analysis of patients who had primary THR surgery from 2013 to 2019 by a single surgeon. Patients were in two cohorts whose operations were completed at separate healthcare facilities. Patients in the first cohort had pre-operative templating using the KingMark system; patients in the second cohort had templating using a single-marker. For all patients, pre-operative radiographs were reviewed; predicted implants noted; and leg length discrepancies calculated. These were compared to post-operative data. We then tested the null hypothesis that there was no difference between the templating methods for prediction accuracy of implant size and achieving restoration of leg length.

RESULTS

A total of 121 patients were included in the KingMark cohort, and 104 were included in the single-marker cohort. In the KingMark cohort, 83.5% of patients had implantation of a cup within one size of that predicted, compared to 71.2% of the single-marker cohort. This superiority was statistically significant. There was a greater proportion of exact cup size predictions in the KingMark cohort, but this was not statistically significant. We did not find any significant difference between the cohorts for stem size, or stem placement, or reduction of leg length discrepancy.

CONCLUSION

We have demonstrated statistically significant superiority of the KingMark over a single-marker templating system for predicting cup size in primary THR surgery. For post-operative restoration of leg length, our study did not show any advantage of KingMark templating compared to single-marker templating.

Outcomes Following Primary Total Hip Arthroplasty With Concomitant Gluteus Medius Repair Using the Direct Anterior Approach

Outcomes following total hip arthroplasty (THA) with concomitant gluteus medius (GM) repair using the direct anterior approach (DAA) are scarce. The primary purpose of this study was to report patient-reported outcome measures (PROMs) with 2-year follow-up of patients with osteoarthritis and GM tear who underwent primary THA and GM repair through the DAA. The secondary purpose was to compare these outcomes with a benchmark propensity-matched control group who underwent a DAA THA without GM tear. Patients were eligible if they received a primary THA and GM repair via the DAA between January 2015 and October 2018 and had baseline PROMs with 2-year follow-up. Patients were excluded if they had workers' compensation or were unwilling to participate. PROM subanalysis was performed between patients and a propensity-matched control group with DAA THA without GM tear. Fourteen patients were included in the study, all of whom were female. Significant improvement for all PROMs and high rate of achieving the minimal clinically important difference (MCID) at 2-year follow-up were reported. All patients were propensity-matched to 28 patients for sex, age, and body mass index. Preoperative PROMs between groups were similar, and both groups reported comparable improvement, satisfaction, and MCID achievement at 2-year follow-up. Primary THA with concomitant GM repair using the DAA yielded good functional outcomes and a high rate of MCID achievement at 2-year follow-up. Based on these results, the DAA can be used safely to address symptomatic GM tears during THA. Furthermore, these outcomes were comparable to a propensity-matched control group without GM tear. [Orthopedics. 2023;46(1):39-46.].

Trabecular titanium cups in acetabular revision arthroplasty: analysis of 10-year survivorship, restoration of center of rotation and osteointegration

AIMS

In case of severe bone loss, acetabular revision can be challenged using extra porous pure trabecular titanium (TT) revision cups designed to ensure enhanced iliac and ischiatic purchase. Aim of the study is to report on the clinical and radiological results of a TT acetabular component, evaluating functional outcome, restoration of the hip center of rotation and osteointegration.

METHODS

85 patients, who underwent acetabular revision with a TT revision cup system between October 2009 and December 2018, were included in a retrospective study. Clinical outcome were assessed with Harris Hip Score (HHS). The hip rotation center was measured using the Pierchon method on the AP pelvis film. Loosening of the cup was determined according to the Kosashvili modification of Gill's criteria. Kaplan- Meier survivorship curve was performed. Results The mean follow-up was 6.12 years. The average HHS improved from 54.7 points to 89.7 points (p < 0.05). Two acetabular components (2.3%) were re-revised after a mean of 5.6 years, for aseptic loosening and for infection, with a progressive radiolucency and a > 5 mm vertical migration, respectively. The radiographic evaluation of the position of the hip rotation center revealed a statistically significant difference (p < 0.05) between the pre- and post-operative values. The hip rotation center was correctly restored within 5% of the reference Pierchon values in a percentage of 85.4% relative to horizontal parameters and within 8% in a percentage of 66.7% relative to vertical parameters. 5-year and 10-year survivorships were, respectively, 100% and 88%.

CONCLUSIONS

In case of severe bone loss, TT revision cup system allows for good restoration of center of rotation and osteointegration showing good 10-year survival rate.

Pre-Operative Digital Templating Aids Restoration of Leg-Length Discrepancy and Femoral Offset in Patients Undergoing Total Hip Arthroplasty for Primary Osteoarthritis

Background

Pre-operative planning and templating is a crucial pre-requisite for total hip arthroplasty (THA). Recently, the use of digital radiography has allowed templating to be digitalised instead of traditional methods involving the use of radiograph transparencies. The primary aim of this study was to compare the accuracy in correction of leg length discrepancy (LLD) and restoring femoral offset in patients undergoing THA for primary osteoarthritis with pre-operative digital templating (PDT) versus conventionalplanning without digital templating.

Methods

This retrospective cohort study compared two groups of patients who underwent THA for primary osteoarthritis. During the period of the year 2020, 56 patients underwent THA with pre-operative digital templating and 50 patients without digital templating. Two independent blinded observers recorded all radiological data.

Results

The digital templated and non-digital templated cohorts were matched for variables including age (mean = 71.8 years vs 70.9 years), pre-operative LLD (-4.9mm vs -5.2mm) and pre-operative offset (41.2mm vs 43.7mm). PDT resulted in correction of LLD to <5mm compared to the contralateral hip in 76.8% of cases, 5-10mm in 21.4% and >10mm in one case (1.8%). The non-digital templated cohort had a LLD of <5mm in 50% of cases, 5-10mm in 28% and >10mm in 22%. Chi-square testing demonstrated these results to be statistically significant (p = 0.002). The mean pre-operative offset in the digital templated group was 40mm and 46mm post-operatively. The non-digital templated cohort had a mean pre-operative offset of 42mm and 36mm post-operatively. Independent t-testing revealed statistical significance of these results (p = 0.05).

Conclusion

PDT leads to an increased likelihood of restoring LLD to <5mm and a significantly increased likelihood of preventing lengthening >10mm. PDT also significantly increases the chance of restoring femoral offset to match the pre-operative native hip. Decreased offset is seen predominantly in the non-digitally templated patients.

Digital templating for the implantation of a curved short hip stem with an anterolateral MIS approach shows gender differences in digital templating

PURPOSE

Digital templating shows reliable accuracy for straight stem systems. In recent years, the implantation of short stems through minimally invasive approaches has gained more popularity. Minimally invasive approaches (MIS) show the risk of undersizing femoral components. Therefore, we questioned the planning adherence for a curved short stem and a bi-hemispherical acetabular cup implanted through an anterolateral MIS approach.

METHODS

A consecutive series of 964 hips (index surgery between 2014 and 2019) with Fitmore^® curved short stem and Allofit/-S^® acetabular cup (both ZimmerBiomet Inc, Warsaw, IN) were included. Preoperative digital templating was conducted anterior-posterior (AP) digital radiographs of the hip using mediCAD^® version 5.1 (Hectec GmbH, Altdorf, Germany). The templates of acetabular and femoral components (offset option and stem size) were retrospectively evaluated for general adherence, and according to sex, BMI and planner's experience.

RESULTS

Planning adherence for the exact offset option was 70.6 and 21.6% for exact offset option and stem size. Adherence for acetabular cup  ± 1 size was 74.8%. A significant difference between male and female patients for the offset option could be found (p = 0.03, z = -2983). In 22.5% of male patients, an offset option one size higher and in 12.3% of female patients an offset option one size smaller than templated was used intraoperatively CONCLUSION: Digital templating for the Fitmore^® stem in cementless THA with a minimally invasive anterolateral approach shows comparable planning adherence to the existing literature for this cementless short stem. However, a lower planning adherence was detected compared to conventional straight stem systems. In male patients, the femoral offset is frequently undersized and in female patients frequently oversized compared to the preoperative plan. Surgeons should be aware of this difficulty in digital templating for Fitmore^® hip stem.

The accuracy and reliability of preoperative digital 2D templating in prosthesis size prediction in uncemented versus cemented total hip arthroplasty: a systematic review and meta-analysis

The purpose of this study was to compare the accuracy and the inter- and intra-observer reliability of preoperative digital 2D templating in prosthesis size prediction for the planning of cemented or uncemented THA.

This study was registered in the NIHR PROSPERO database (ID: CRD42020216649) and conducted according to the PRISMA guidelines. A search of electronic databases in March 2021 found 29 papers overall. The quality of evidence was assessed using the IHE Quality Appraisal of Case Series Studies Checklist and the CASP Randomised Controlled Trials Checklist. A meta-analysis was conducted, and the accuracy was presented as proportions and the inter- and intra-observer reliability were measured using intraclass correlation coefficients (ICC).

Accuracy within one prosthesis size (±1) for cemented stems was 0.89 (95% confidence interval (CI) 0.83–0.95), cemented cups 0.78 (95% CI 0.67–0.89), uncemented stems 0.74 (95% CI 0.66–0.82) and uncemented cups 0.73 (95% CI 0.67–0.79) (test of group differences: p = 0.010). Inter-observer reliability (ICC) for uncemented cups was 0.88 (95% CI 0.85–0.91), uncemented stems 0.86 (95% CI 0.81–0.91), cemented stems 0.69 (95% CI 0.54–0.84) and cemented cups 0.68 (95% CI 0.55–0.81) (test of group differences: p = 0.004). Due to lack of data, intra-observer reliability (ICC) could only be calculated for uncemented prostheses, which for the stems was 0.90 (95% CI 0.88–0.92) and for the cups was 0.87 (95% CI 0.83–0.90) (test of group differences: p = 0.124).

The accuracy of preoperative digital templating is greater for cemented prostheses, but the inter-observer reliability is greater for uncemented prostheses. The intra-observer reliability showed a high level of agreement for uncemented prostheses.

Cite this article: EFORT Open Rev 2021;6:1020-1039. DOI: 10.1302/2058-5241.6.210048

Anthropometric method for estimating component sizes in total hip arthroplasty

BACKGROUND

Preoperative templating is essential in total hip arthroplasty (THA) as it not only helps to facilitate the correct implant type and size but also determines the post-operative biomechanics. Templating is also increasingly important from a medico-legal perspective and recommended in the British Orthopaedic Association Guide to Good Practice. Although templating has become increasingly digitised, there are no simple anthropometric models to predict implant sizes in the absence of digital methods.

AIM

To assess the accuracy of using an easily obtainable measurement (shoe size) to predict component sizes in THA compared with digital templating.

METHODS

Digital radiographs from a cohort of 102 patients (40 male, 62 female) who had undergone uncemented or hybrid THA at a single centre were retrospectively templated to desired cup and stem sizes using TraumaCad^®. We compared the templated size to the actual size of the implant and assessed if there was any correlation with the patient’s shoe size.

RESULTS

Statistically significant positive correlations were observed between: shoe size and templated cup size (ρ = 0.92, P < 0.001); shoe size with implanted cup size (ρ = 0.71, P < 0.001); shoe size and templated stem size (ρ = 0.87, P < 0.001); and shoe size with implanted stem size (ρ = 0.57, P < 0.001). Templated and implanted acetabular cup sizes were positively correlated (ρ = 0.76, P < 0.001) and were exact in 43.1% cases; 80.4% of implanted cup sizes were within 1 size (+/- 2 mm) of the template and 100% within 2 sizes (+/- 4 mm). Positive correlation was also demonstrated between templated and implanted femoral stem sizes (ρ = 0.69, P < 0.001) and were exact in 52.6% cases; 92.6% were within 1 size of the template and 98% within 2 sizes.

CONCLUSION

This study has shown there to be a significant positive correlation between shoe size and templated size. Anthropometric measurements are easily obtainable and can be used to predict uncemented component sizes in the absence of digital methods.

Value of preoperative three-dimensional planning software (AI-HIP) in primary total hip arthroplasty: a retrospective study

Objective

We performed a retrospective study to compare the accuracy of preoperative planning using three-dimensional AI-HIP software and traditional two-dimensional manual templating to predict the size and position of prostheses. The purpose of this study was to evaluate the accuracy of AI-HIP in preoperative planning for primary total hip arthroplasty.

Methods

In total, 316 hips treated from April 2019 to June 2020 were retrospectively reviewed. A typical preoperative planning process for patients was implemented to compare the accuracy of the two preoperative planning methods with respect to prosthetic size and position. Intraclass correlation coefficients (ICCs) were used to evaluate the homogeneity between the actual prosthetic size and position and the preoperative planning method.

Results

When AI-HIP software and manual templating were used for preoperative planning, the stem agreement was 87.7% and 58.9%, respectively, and the cup agreement was 94.0% and 65.2%, respectively. The results showed that when AI-HIP software was used, an extremely high level of consistency (ICC > 0.95) was achieved for the femoral stem size, cup size, and femoral osteotomy level (ICC = 0.972, 0.962, and 0.961, respectively).

Conclusion

AI-HIP software showed excellent reliability for predicting the component size and implant position in primary total hip arthroplasty.

Two year follow up of supercapsular percutaneously assisted total hip arthroplasty

BACKGROUND

Dislocation after primary total hip arthroplasty (THA) has an incidence of 2-3%. Approximately 77% of dislocations occur within the first year after surgery. The SuperPATH technique is a minimally invasive approach for THA that preserves soft tissue attachments. The purpose of this study is to describe the dislocation rate at 1 year after SuperPATH primary THA.

METHODS

All elective primary THAs performed by the senior author using the SuperPATH approach. Exclusion criteria were acute femoral neck fracture, revision surgery, or malignancy. There were 214 of 279 eligible patients available for telephone interviews (76.7%). Medical records were reviewed for secondary outcomes including early and late complications, cup positioning, distance ambulated on postoperative day one, discharge destination, and blood transfusions.

RESULTS

Mean age at surgery was 64 ± 10.8 years and mean time to telephone follow up was 773 ± 269.7 days. There were 104 female and 110 male patients. There were zero dislocations reported. Blood transfusions were performed in 3.7% of patients, and 75.7% were discharged to home at an average of 2.3 ± 1.0 days. Cup position averaged 43.6 ± 5.2° abduction and 20.9 ± 6.2° anteversion, with an average leg length discrepancy of 3.6 ± 3.32 mm. Complications included three intraoperative calcar fractures, one periprosthetic femur fracture, one early femoral revision, three superficial infections, and one instance of wound necrosis.

CONCLUSION

SuperPATH approach is safe for use in primary THA resulting in a low dislocation rate.

Use of Acetate Templates Over Digital Radiographs for Templating in Total Hip Arthroplasty: Technique and Its Validation

PURPOSE

Acetate templates were commonly used for templating for total hip arthroplasty. With digital radiographs having replaced conventional analogue radiographs, newer techniques are required. We describe a method for templating images of digital radiographs using conventional acetate templates, which is independent of a magnification marker or PACS system.

METHODS

Fifty-one patients (64 hips) who were treated with primary THA were prospectively evaluated. Templating was done by keeping the acetate template directly over the digital image of the radiograph on a liquid crystal display (LCD) monitor, after calibrating the linear scale generated by the digital radiography machine. The size of prosthesis predicted on this templating technique was compared with the actual sizes used during the surgery. Inter-observer and intra-observer reliabilities were assessed. Our calibration method was further validated by comparing the size of the cup calculated on postoperative radiograph using digital templating software (mediCAD Hectec GmbH) and the actual size used during surgery.

RESULTS

Accurate size was predicted for 36.7% of the acetabular cup and 35.9% of femoral stems. The accuracy within ± one size was 89.9% for acetabular cups and 91.4% for femoral stems. Excellent inter-observer and intra-observer reliability were seen for both femoral and acetabular components.

CONCLUSION

The method described provides an accurate, reproducible, convenient and low-cost technique of preoperative templating. It combines the ease of using acetate templates with the convenience of being able to use digital images, without the need for expensive software.

Can 3D surgical planning and patient specific instrumentation reduce hip implant inventory? A prospective study

BACKGROUND

Modern designs of joint replacements require a large inventory of components to be available during surgery. Pre-operative CT imaging aids 3D surgical planning and implant sizing, which should reduce the inventory size and enhance clinical outcome. We aimed to better understand the impact of the use of 3D surgical planning and Patient Specific Instrumentation (PSI) on hip implant inventory.

METHODS

An initial feasibility study of 25 consecutive cases was undertaken to assess the discrepancy between the planned component sizes and those implanted to determine whether it was possible to reduce the inventory for future cases. Following this, we performed a pilot study to investigate the effect of an optimized inventory stock on the surgical outcome: we compared a group of 20 consecutive cases (experimental) with the 25 cases in the feasibility study (control). We assessed: (1) accuracy of the 3D planning system in predicting size (%); (2) inventory size changes (%); (3) intra and post-operative complications.

RESULTS

The feasibility study showed variability within 1 size range, enabling us to safely optimize inventory stock for the pilot study. (1) 3D surgical planning correctly predicted sizes in 93% of the femoral and 89% of the acetabular cup components; (2) there was a 61% reduction in the implant inventory size; (3) we recorded good surgical outcomes with no difference between the 2 groups, and all patients had appropriately sized implants.

CONCLUSIONS

3D planning is accurate in up to 95% of the cases. CT-based planning can reduce inventory size in the hospital setting potentially leading to a reduction in costs.

Pre-operative templating in THA. Part II: a CT-based strategy to correct architectural hip deformities

INTRODUCTION

Pre-operative templating for total hip arthroplasty (THA) remains inaccurate due to improper magnification and alignment. We aimed to describe an improved templating strategy using computed tomography (CT) to predict component sizes and offsets with greater accuracy.

MATERIALS AND METHODS

We analysed 184 CT images acquired for pre-operative templating of primary THA. We aimed to restore native (pre-arthritic) femoral offset and limb length, by raising the head center to the level of the templated cup center cranio-caudally, but maintaining the pathologic (pre-operative) head center medio-laterally (except in medialized hips). Acetabular offset (AO) and femoral offset (FO) were measured on pre-operative CT scans, during acetate templating, and on post-operative true antero-posterior radiographs.

RESULTS

The post-operative offsets were within ± 5 mm from templated estimates in 174 hips (91%) for AO, in 116 hips (61%) for FO, in 111 hips (58%) for GO, and in 134 hips (70%) for neck cut level. The post-operative hip architecture reproduced the templated hip architecture within ±5 mm in 77 hips (40%). The agreement between planned and post-operative parameters was moderate for stem size (0.57), cup size (0.62), AO (0.50), but fair for FO (0.45). The AO decreased in most arthritic types, notably in lateralized hips (6.6 mm), but remained unchanged in medialized hips. The FO increased in most arthritic types (1.8-3.1 mm) but remained unchanged in medialized and lateralized hips.

CONCLUSIONS

We described a strategy for pre-operative templating in THA. Despite the accuracy of CT, the authors found significant variations between planned and post-operative reconstructions, which suggest that pre-operative templating should only be used as an approximate guide.

Pre-operative planning in THA. Part III: do implant size prediction and offset restoration influence functional outcomes after THA?

INTRODUCTION

Few studies evaluated clinical benefits of pre-operative templating in total hip arthroplasty (THA). We investigated whether mismatch between planned and real implant sizes and medio-lateral offsets compromises THA outcomes.

MATERIALS AND METHODS

We reviewed records of 184 primary THAs with pre-operative CT scans used for templating. Acetabular offset (AO), femoral offset (FO) and global offset (GO) were measured on pre-operative CT scans, during acetate templating, and post-operative antero-posterior radiographs. Multivariable analyses were performed to determine if Forgotten Joint Score (FJS) and Oxford Hip Score (OHS) at > 2 years were associated with differences between post-operative and planned parameters.

RESULTS

The FJS and OHS were not influenced by mismatch of component sizes nor of FO and GO. The FJS was better when the post-operative AO was greater than planned (p = 0.050). The FJS differed among arthritic types (p = 0.015). Multivariable analyses confirmed that older patients had better OHS (beta - 0.16; p = 0.033) and FJS (beta 0.74; p = 0.002), medialized hips had worse FJS (beta - 20.1; p = 0.041) and hips with greater AO than planned had better FJS (beta 1.71; p = 0.024) CONCLUSIONS: Implanting a component of different size than planned did not compromise THA outcomes, but medialized hips had worse scores, and conservative acetabular reaming improved scores.

Templating in uncemented total hip arthroplasty-on intra- and interobserver reliability and professional experience

BACKGROUND

This study examines the intra-, and interobserver reliability of digital templating in uncemented total hip arthroplasty (THA), and assesses whether these values are dependent on professional experience.

METHODS

Three independent observers retrospectively examined digital X-rays of 34 consecutive hips scheduled for uncemented THA. These were templated using templating software. Evaluations were carried out on two occasions at least 6 weeks apart. Findings were compared to each surgeon's own findings, and then to the other surgeons' findings. Data underwent statistical analysis to assess and describe reliability.

RESULTS

The intraobserver reliability of the method was found to be good. The intra-class correlation coefficient (ICC) for individual surgeons ranged from 0.81 to 0.87 for acetabular components and 0.74 to 0.91 for femoral components. However, it was somewhat lower for neck length with kappa statistics (κ) from 0.41 to 0.51 with agreement in about 70% of the cases. Interobserver reliability was similar, with an ICC of 0.87 for the acetabular component and 0.79 for the femoral component, but somewhat lower for neck length with κ of 0.27 and agreement in 41% of the cases. We found no association between increasing experience and increasing precision, as the least experienced observer showed the highest intraobserver reliability.

CONCLUSIONS

The reliability of digital templating of uncemented THA is good for acetabular and femoral components, but inferior for neck length. Precision does not rely on professional experience. Digital templating provides surgeons with a valuable tool for preoperative planning, but cannot supersede the intraoperative assessment and final decision.

Accuracy and Reliability of Preoperative On-screen Templating Using Digital Radiographs for Total Hip Arthroplasty

PURPOSE

Preoperative on-screen templating is a method of using acetate templates on digital images. The aim of the present study was to evaluate the accuracy, intra- and interobserver reliabilities of preoperative on-screen templating using digital radiographs for total hip arthroplasty (THA).

MATERIALS AND METHODS

Two hundred patients with hip disease who were treated with primary cementless THA were retrospectively evaluated. The accuracy of on-screen templating was assessed by comparing the predicted prosthesis sizes with the actual sizes used operatively. The inter- and intraobserver reliabilities of the templating results were also evaluated.

RESULTS

The prosthesis prediction accuracy within ±one size was 96.6% for the cup size and 97.8% for the stem size. The inter- and intraobserver reliabilities for the implant size were substantial (kappa>0.70). The intra- and interobserver reliabilities for the leg length discrepancy and femoral offset difference using the intraclass correlation coefficient ranged from 0.89 to 0.97.

CONCLUSION

Preoperative on-screen templating using digital radiographs showed substantial accuracy and reliability for implant prediction. It is an effective method for predicting the size of implant, correcting the leg length discrepancy and restoring the femoral offset.

How to best measure femoral length and lateralisation after total hip arthroplasty on antero-posterior pelvic radiographs

PURPOSE

Various methods exist for measuring limb length and lateralisation after total hip arthroplasty. Most of them utilise standard anteroposterior (AP) pelvic radiographs, but their results can be affected by patient position during imaging and thus the position of the lower limb on the coronal plane. The aim of this study is to evaluate how commonly used measuring methods of limb lengthening and femoral offset are affected by the position of the lower limb in the coronal plane.

METHODS

A standing pelvic AP radiograph post implantation of a right total hip prosthesis was digitised. The right femur and its femoral stem were digitally segmented, such that they could be positioned orthogonal to the pelvis horizontal reference, with 10° of adduction, and with 10° of abduction, with respect to the centre of rotation. Various limb lengths and implant lateralisation were also digitised. We obtained nine x-rays differing one to three variables. Twice four independent surgeons performed three femoral length measurement methods and femoral offset measurement methods. Intra and inter-observer error as well as the effect of the femoral position on the measurements were studied.

RESULTS

With respect to length measurements, the distance between the centre of rotation (C) and the tip of the lesser trochanter (LT) increased by 3 mm per cm of lateralisation. This measurement was not affected by the hip position in abduction or adduction. The distance between the tip of the lesser or greater trochanter (GT) and the horizontal passing through the centre of rotation was strongly affected by the hip position in abduction or adduction. With respect to offset, the distance between the centre of rotation and the greater trochanter (C-GT) was the most consistent and was not affected by variations in lengths or femoral axis. At the level of the lesser trochanter, the distance of the femoral anatomical axis and to Perkin's line was heavily influenced by the femoral position.

CONCLUSION

The C-LT distance was consistent in measuring limb length and the C-GT distance was reliable in determining femoral offset regardless of the relative position of the femur.

Acetate templating on digital images is more accurate than computer-based templating for total hip arthroplasty

BACKGROUND

Templating is an important aspect of preoperative planning for total hip arthroplasty and can help determine the size and positioning of the prosthesis. Historically, templating has been performed using acetate templates over printed radiographs. As a result of the increasing use of digital imaging, surgeons now either obtain additional printed radiographs solely for templating purposes or use specialized digital templating software, both of which carry additional cost.

QUESTIONS/PURPOSES

The purposes of this study was to compare acetate templating of digitally calibrated images on an LCD monitor to digital templating in terms of (1) accuracy; (2) reproducibility; and (3) time efficiency.

METHODS

Acetate onlay templating was performed directly over digital radiographs on an LCD monitor and was compared with digital templating. Five separate observers participated in this study templating on 52 total hip arthroplasties. For the acetate templating, the digital images were magnified to the scaled reference on the templates provided by the manufacturer (ratio 1.2:1) before templating using a 25-mm marker as a reference. Both the acetate and digital templating results were then compared with the actual implanted components to determine accuracy. Interobserver and intraobserver variability was determined by an intraclass correlation coefficient. Observers recorded time to complete templating from the time of complete upload of patients' imaging onto the system to completion of templating.

RESULTS

Both acetate and digital templates demonstrated moderate accuracy in predicting within one size of the eventual implanted acetabular cup (77% [199 of 260]; 70% [181 of 260], respectively; p = 0.050; 95% confidence interval [CI], 0.058-0.32), whereas acetate templating was better at predicting the femoral stem compared to digital templating (75% [195 of 260]; 60% [155 of 260], respectively; p < 0.001; 95% CI, 0.084-0.32). Acetate templating showed moderate to substantial interobserver agreement (cup intraclass correlation coefficient [ICC] = 0.55; 95% CI, 0.14-0.86; femoral ICC = 0.75; 95% CI, 0.39-0.95) and both methods showed almost perfect intraobserver agreement in reproducibility (acetate cup ICC = 0.82; 95% CI, 0.66-0.97; acetate femoral ICC = 0.86; 95% CI, 0.74-0.97; digital cup ICC = 0.82; 95% CI, 0.68-0.97; digital femoral ICC = 0.88; 95% CI, 0.77-1.0). Acetate templating could be performed more quickly (acetate mean 119 seconds; range, 37-220 seconds versus 154 seconds; range, 73-343 seconds; p < 0.001).

CONCLUSIONS

Acetate onlay templating on digitally calibrated images can be a reliable substitute for digital templating using specialized software. It is quicker to perform and much less expensive. Hospitals and practices need not purchase expensive software, particularly at lower volume centers.

LEVEL OF EVIDENCE

Level III, diagnostic study.

Comparison of robotic-assisted and conventional acetabular cup placement in THA: a matched-pair controlled study

BACKGROUND

Improper acetabular component orientation in THA has been associated with increased dislocation rates, component impingement, bearing surface wear, and a greater likelihood of revision. Therefore, any reasonable steps to improve acetabular component orientation should be considered and explored.

QUESTIONS/PURPOSES

We therefore sought to compare THA with a robotic-assisted posterior approach with manual alignment techniques through a posterior approach, using a matched-pair controlled study design, to assess whether the use of the robot made it more likely for the acetabular cup to be positioned in the safe zones described by Lewinnek et al. and Callanan et al.

METHODS

Between September 2008 and September 2012, 160 THAs were performed by the senior surgeon. Sixty-two patients (38.8%) underwent THA using a conventional posterior approach, 69 (43.1%) underwent robotic-assisted THA using the posterior approach, and 29 (18.1%) underwent radiographic-guided anterior-approach THAs. From September 2008 to June 2011, all patients were offered anterior or posterior approaches regardless of BMI and anatomy. Since introduction of the robot in June 2011, all THAs were performed using the robotic technique through the posterior approach, unless a patient specifically requested otherwise. The radiographic cup positioning of the robotic-assisted THAs was compared with a matched-pair control group of conventional THAs performed by the same surgeon through the same posterior approach. The safe zone (inclination, 30°-50°; anteversion, 5°-25°) described by Lewinnek et al. and the modified safe zone (inclination, 30°-45°; anteversion, 5°-25°) of Callanan et al. were used for cup placement assessment. Matching criteria were gender, age ± 5 years, and (BMI) ± 7 units. After exclusions, a total of 50 THAs were included in each group. Strong interobserver and intraobserver correlations were found for all radiographic measurements (r > 0.82; p < 0.001).

RESULTS

One hundred percent (50/50) of the robotic-assisted THAs were within the safe zone described by Lewinnek et al. compared with 80% (40/50) of the conventional THAs (p = 0.001). Ninety-two percent (46/50) of robotic-assisted THAs were within the modified safe zone described by Callanan et al. compared with 62% (31/50) of conventional THAs p (p = 0.001). The odds ratios for an implanted cup out of the safe zones of Lewinnek et al. and Callanan et al. were zero and 0.142, respectively (95% CI, 0.044, 0.457).

CONCLUSIONS

Use of the robot allowed for improvement in placement of the cup in both safe zones, an important parameter that plays a significant role in long-term success of THA. However, whether the radiographic improvements we observed will translate into clinical benefits for patients-such as reductions in component impingement, acetabular wear, and prosthetic dislocations, or in terms of improved longevity-remains unproven.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Effect of training level on accuracy of digital templating in primary total hip and knee arthroplasty

The use of digital radiography and templating software continues to become more prevalent in orthopedics as the number of total hip arthroplasty (THA) and total knee arthroplasty (TKA) procedures increases every year. The purpose of this study was to evaluate the effect of training level on the accuracy of digital templating for primary THA and TKA. Digital radiographs of 97 patients undergoing primary THA (49 cases) and TKA (48 cases) were retrospectively templated using OrthoView digital planning software (OrthoView LLC, Jacksonville, Florida). Anteroposterior hip and lateral knee radiographs were digitally templated and compared with the actual size of the implants used intraoperatively. An implant sales representative, physician assistant, medical student (J.D.K.), resident (A.R.H.), and fellowship-trained arthroplasty surgeon (B.R.L.) templated all cases independently after a standardized orientation and were blinded to the actual component sizes used for surgery. The medical student, resident, and arthroplasty surgeon retemplated the same 97 cases 1 month later to determine intraobserver reliability. Digital templating was accurate in predicting the correct implant size in 33% of THAs and 54% of TKAs. In 73% of THAs and 92% of TKAs, digital templating was within 1 size of the actual implant used, and in 88% of THAs and 99% of TKAs, templating was within 2 sizes of the final components. In no cases did the templated implant size vary by >3 sizes from the final components. Interobserver reliability for templating THAs and TKAs showed good reliability as measured by intraclass correlation coefficient (ICC) (ICC(THA)=.70; ICC(TKA)=.86). Intraobserver reliability for templating THAs had excellent reliability for the resident and arthroplasty surgeon, with a kappa coefficient (κ) of 0.92, and good reliability for the medical student (κ=0.78). Intraobserver reliability for templating TKAs showed excellent reliability among all examiners (κ=0.90).

Predictive value of preoperative digital templating in THA depends on the surgical experience of the performing physician

Digital preoperative templating is increasingly used to predict the correct component size in total hip arthroplasty (THA). Experienced surgeons could avoid the new technique and rely on a digital template done by a younger colleague. We compared the accuracy of preoperative templating between orthopedic residents (group A) and an experienced orthopedic surgeon (group B). In 106 cases, the software-predicted component sizes of both groups were compared with component sizes placed surgically. An accurate prediction of the acetabular component was achieved in 63% of cases in group A compared with 88% of cases in group B (P=.001). Concerning the femoral component, accurate prediction was achieved in 89% in group A and 97% in group B (P=.021). If performed by an experienced orthopedic surgeon, digital templating is an accurate method to predict the prosthetic component size in THA.

Ceramic-on-ceramic total hip arthroplasty: incidence of instability and noise

BACKGROUND

Alternative bearing materials in THA have been developed to reduce the incidence of osteolysis. Alumina-on-alumina bearings exhibit extremely low wear rates in vitro, but concerns exist regarding component impingement with the potential for dislocation and the occurrence of noise.

QUESTIONS/PURPOSES

We determined generation of squeaking and the relationship between squeaking and component position.

METHODS

We prospectively entered 436 alumina-on-alumina, cementless, primary THAs in 364 patients into our institutional database. All procedures were performed with the same surgical technique and the same implant. We obtained Harris Hip scores and a noise questionnaire and assessed radiographic component position and loosening. We determined the difference in abduction angle between squeakers and nonsqueakers. Minimum followup was 2 years (average, 3.5 years; range, 2.0-6.2 years).

RESULTS

The mean Harris hip score increased from 51.9 preoperatively to 94.4 at latest followup. Six hips underwent reoperation: four hips (1.1%) for dislocation and two (0.53%) for periprosthetic fracture after trauma. The incidence of noise of any type was 11%, with the most common type of noise being clicking or snapping. Squeaking was reported by 1.9% of patients, with no patient being revised for this phenomenon. We found no association between component position and squeaking.

CONCLUSIONS

At average 3 years followup, 98% of ceramic-on-ceramic THAs did not require a revision, with 1.1% of hips having been revised for dislocation. Fewer than 2% of patients reported hearing an audible squeak, with no association found between component position and squeaking.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.