A comparison of conventional guidewire alignment jigs with imageless computer navigation in hip resurfacing arthroplasty

Augmented Reality Based Navigation for Computer Assisted Hip Resurfacing: A Proof of Concept Study

Implantation accuracy has a great impact on the outcomes of hip resurfacing such as recovery of hip function. Computer assisted orthopedic surgery has demonstrated clear advantages for the patients, with improved placement accuracy and fewer outliers, but the intrusiveness, cost, and added complexity have limited its widespread adoption. To provide seamless computer assistance with improved immersion and a more natural surgical workflow, we propose an augmented-reality (AR) based navigation system for hip resurfacing. The operative femur is registered by processing depth information from the surgical site with a commercial depth camera. By coupling depth data with robotic assistance, obstacles that may obstruct the femur can be tracked and avoided automatically to reduce the chance of disruption to the surgical workflow. Using the registration result and the pre-operative plan, intra-operative surgical guidance is provided through a commercial AR headset so that the user can perform the operation without additional physical guides. To assess the accuracy of the navigation system, experiments of guide hole drilling were performed on femur phantoms. The position and orientation of the drilled holes were compared with the pre-operative plan, and the mean errors were found to be approximately 2 mm and 2°, results which are in line with commercial computer assisted orthopedic systems today.

Accuracy of Computer-Aided Techniques in Orthopaedic Surgery: How Can It Be Defined, Measured Experimentally, and Analyzed from a Clinical Perspective?

Surgical accuracy is multifactorial. Therefore, it is crucial to consider all influencing factors when investigating the accuracy of a surgical procedure, such as the surgeon's experience, the assistive technologies that may be used by the surgeon, and the patient factors associated with the specific anatomical site. For in vitro preclinical investigations, accuracy should be linked to the concepts of trueness (e.g., distance from the surgical target) and precision (e.g., variability in relation to the surgical target) to gather preclinical, quantitative, objective data on the accuracy of completed surgical procedures that have been performed with assistive technologies. The clinical relevance of improvements in accuracy that have been observed experimentally may be evaluated by analyzing the impact on the risk of failure and by taking into account the level of tolerance in relation to the surgical target (e.g., the extent of the safety zone). The International Organization for Standardization (ISO) methodology enables preclinical testing of new assistive technologies to quantify improvements in accuracy and assess the benefits in terms of reducing the risk of failure and achieving surgical targets with tighter tolerances before the testing of clinical outcomes.

Validating a Modified Circle Theorem Method for the Measurement of Acetabular Cup Anteversion on Plain Radiography with Intra-Operative Data from Robotic Assisted Total Hip Arthroplasty

This study aims to validate a modified circle theorem method for the calculation of true version of the acetabular component on anteroposterior x-rays with intra-operative version data derived from robotic assisted total hip arthroplasty (THA). Planar anteversion measurements recorded intraoperatively in 80 THAs were correlated to measurements on anteroposterior radiographs. The mean anteversion of the cohort measured by the robotic system and on plain radiography was 21.2° ± 2.0° and 19.9° ± 3.4° respectively and 97.5% of cases were in a 30% relative error. The correlation between the true and planar measurements of anteversion on plain radiographs was strong (Pearson correlation coefficient of 0.9422). We conclude that the circle theorem method can be validated with data from robotic guided THA.

The impact of proximal femoral morphology on failure strength with a mid-head resection short-stem hip arthroplasty

Mid-head resection short-stem hip arthroplasty is a conservative alternative to conventional total hip replacement and addresses proximal fixation challenges in patients not suitable for hip resurfacing. It is unclear whether proximal femoral morphology impacts the ultimate failure load of mid-head resection implanted femurs, thus the aim of this study was to investigate the effect of native neck-shaft angle (NSA) and coronal implant alignment on proximal femoral strength. In total, 36 synthetic femurs with two different proximal femoral morphologies were utilized in this study. Of them, 18 femurs with a varus NSA of 120° and 18 femurs with a valgus NSA of 135° were each implanted with a mid-head resection prosthesis. Femurs within the two different femoral morphology groups were divided into three equal coronal implant alignment groups: 10° valgus, 10° varus or neutral alignment. Prepared femurs were tested for stiffness and to failure in axial compression. There was no significant difference in stiffness nor failure load between femurs implanted with valgus-, varus- or neutrally aligned implants in femurs with a NSA of 120° (p = 0.396, p = 0.111, respectively). Femurs implanted in valgus orientation were significantly stiffer and failed at significantly higher loads than those implanted in varus alignment in femurs with a NSA of 135° (p = 0.001, p = 0.007, respectively). A mid-head resection short-stem hip arthroplasty seems less sensitive to clinically relevant variations of coronal implant alignment and may be more forgiving upon implantation in some femoral morphologies, however, a relative valgus component alignment is recommended.

Evaluation of a patient specific femoral alignment guide for hip resurfacing

A novel alternative to conventional instrumentation for femoral component insertion in hip resurfacing is a patient specific, computed tomography based femoral alignment guide. A benchside study using cadaveric femora was performed comparing a custom alignment guide to conventional instrumentation and computer navigation. A clinical series of twenty-five hip resurfacings utilizing a custom alignment guide was conducted by three surgeons experienced in hip resurfacing. Using cadaveric femora, the custom guide was comparable to conventional instrumentation with computer navigation proving superior to both. Clinical femoral component alignment accuracy was 3.7° and measured within ± 5° of plan in 20 of 24 cases. Patient specific femoral alignment guides provide a satisfactory level of accuracy and may be a better alternative to conventional instrumentation for initial femoral guidewire placement in hip resurfacing.

Learning curve of acetabular cup positioning in total hip arthroplasty using a cumulative summation test for learning curve (LC-CUSUM)

Despite advances in surgical techniques and instrumentation, optimal cup positioning in total hip arthroplasty (THA) is challenging with a limited accuracy. We evaluated whether a learning curve exists for the optimal cup positioning, using the LC-CUSUM test (Learning curve cumulative summation test). We evaluated the first 100 consecutive THA performed by two surgeons, who had a year of fellowship training in the same teaching hospital. A learning curve of cup positioning was plotted in each series using the LC-CUSUM score. There was no significant difference of numbers of outlier between two surgeons (P = 0.079). Both surgeons completed the learning curve of optimal cup positioning before 50 procedures, and maintained competence. A substantial learning period is necessary in the optimal positioning of an acetabular cup.

Computer navigation experience in hip resurfacing improves femoral component alignment using a conventional jig

BACKGROUND

The use of computer navigation has been shown to improve the accuracy of femoral component placement compared to conventional instrumentation in hip resurfacing. Whether exposure to computer navigation improves accuracy when the procedure is subsequently performed with conventional instrumentation without navigation has not been explored. We examined whether femoral component alignment utilizing a conventional jig improves following experience with the use of imageless computer navigation for hip resurfacing.

MATERIALS AND METHODS

Between December 2004 and December 2008, 213 consecutive hip resurfacings were performed by a single surgeon. The first 17 (Cohort 1) and the last 9 (Cohort 2) hip resurfacings were performed using a conventional guidewire alignment jig. In 187 cases, the femoral component was implanted using the imageless computer navigation. Cohorts 1 and 2 were compared for femoral component alignment accuracy.

RESULTS

All components in Cohort 2 achieved the position determined by the preoperative plan. The mean deviation of the stem-shaft angle (SSA) from the preoperatively planned target position was 2.2° in Cohort 2 and 5.6° in Cohort 1 (P = 0.01). Four implants in Cohort 1 were positioned at least 10° varus compared to the target SSA position and another four were retroverted.

CONCLUSIONS

Femoral component placement utilizing conventional instrumentation may be more accurate following experience using imageless computer navigation.

Computer navigation vs conventional mechanical jig technique in hip resurfacing arthroplasty: a meta-analysis based on 7 studies

The studies on the accuracy of femoral component in hip resurfacing arthroplasty with the help of computer-assisted navigation were not consistent. This study aims to assess at the functional outcomes after computer navigation in hip resurfacing arthroplasty by systematically reviewing and meta-analyzing the data, which were searched up to December 2011 in PubMed, MEDLINE, EMBASE, MetaMed, EBSCO HOST, and the Web site of Google scholar. Totally, 197 articles about hip resurfacing arthroplasty were collected; finally, 7 articles met the inclusion criteria and were included in this meta-analysis (520 patients with 555 hip resurfacing arthroplasty). The odds ratio for the number of outliers was 0.155 (95% confidence interval, 0.048-0.498; P < .003). In conclusion, this meta-analysis suggests that the computer-assisted navigation system makes the femoral component positioning in hip resurfacing arthroplasty easier and more precise.

Avoiding short-term femoral neck fracture with imageless computer navigation for hip resurfacing

BACKGROUND

Femoral neck fracture in hip resurfacing has been attributed to technical error during femoral head preparation. In the absence of fracture, several radiographic findings have been speculated to increase the risk of femoral component failure.

QUESTIONS/PURPOSES

We examined whether (1) the use of navigation to reduce technical errors during femoral head preparation reduces the incidence of femoral neck fractures in the short-term followup period; and (2) alignment of the femoral component with the use of computer navigation reduces the incidence of femoral neck thinning, femoral stem radiolucencies, and stem migration.

METHODS

We retrospectively reviewed the first 100 Birmingham Hip Resurfacings performed in 94 prospectively followed patients between October 2005 and November 2007. We examined all radiographs on last followup. Eighty-six patients of the 94 patients had a minimum followup of 2 years (mean, 2.5 years; range, 2-4.1 years).

RESULTS

There were no cases of femoral neck notching, varus femoral component alignment, or femoral neck fractures in the series. Neck thinning of greater than 10% was observed in three patients and perimetaphyseal stem lucencies were noted in 10 patients. In three patients, the metaphyseal stem showed varus migration relative to the postoperative stem-shaft angle at latest followup. There was one revision to a total hip arthroplasty for deep sepsis. The overall survivorship at 4 years was 99%.

CONCLUSIONS

The use of imageless computer navigation to reduce technical errors in hip resurfacing may reduce the incidence of femoral neck fracture in the short-term. However, neck thinning, stem radiolucencies, and stem migration remain radiographic sequelae of hip resurfacing despite the use of navigation for placement of the femoral component.

The future of hip resurfacing

With experience in metal-metal resurfacing, several opportunities to improve resurfacing technology have been identified. There is a need for better education on hip resurfacing in residency training programs. The majority of short-term complications associated with resurfacing are related to surgical technique or component position. Innovations to improve acetabular component position and femoral-acetabular mating are needed. Although the majority of high wear and adverse local tissue reactions (ALTR) can be prevented by proper component positioning, the variable exposure to metal particles and ions associated with metal-metal resurfacing components continues to be a concern and bearing surface technology will evolve.