Achieving a Spherical Femoroplasty During Hip Arthroscopy with Computer Assisted Visualization Software: A Prospective Single-Blinded Randomized Controlled Multi-Surgeon Study

Benjamin D Kuhns¹, Elizabeth G Walsh¹, Ajay C Lall^1,2, Benjamin G Domb^1,2*

¹American Hip Institute Research Foundation, Chicago, IL 60018, USA
²American Hip Institute, Chicago, IL 60018, USA

*Correspondence author: Benjamin G Domb, MD, American Hip Institute Research Foundation, Chicago, IL 60018, USA and American Hip Institute, Chicago, IL 60018, USA; Email: [email protected]  

Citation: Kuhns BD, et al. Achieving a Spherical Femoroplasty During Hip Arthroscopy with Computer Assisted Visualization Software: A Prospective Single-Blinded Randomized Controlled Multi-Surgeon Study. J Ortho Sci Res. 2025;6(2):1-10.

Copyright^© 2025 by Kuhns BD, et al. All rights reserved. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Table 1: Operative Hip and C-arm Positions with Cam deformity location.

Figure 1: Operating room setup for computer-assisted visualization software.

Figure 2: Intraoperative templating for cam resection by computer-assisted visualization software.

Figure 3: Computer-assisted guidance for measuring appropriate resection depth. Computer display demonstrating a pre-resection 75-degree alpha angle and post-resection 41-degree alpha angle at the 1:00 position in the left hip of a 25-year-old male with a large Cam deformity.

Statistical Analysis

A priori power analysis was performed to determine the minimum number of patients required to achieve at least 80% power. Assuming a mean 9-minute difference ( ±  10) in total femoroplasty time between groups, it was determined that 14 patients in each group would be needed for appropriate power. All statistical analyses were performed using Microsoft Excel (Microsoft Corp, Redmond, Washington) with the Real Statistics Add-in. Mean and standard deviation were calculated for all continuous variables. To assess normality and variance, the Shapiro-Wilk test and F-test were employed, respectively. Comparisons between the two groups were made using a student’s t-test or its non-parametric equivalent, the Mann-Whitney test. In the case of non-parametric data with unequal variances, the Welch test was performed. Categorical data was analyzed using a chi-squared test. Subgroup analyses comparing femoroplasty time between surgeons was performed in a similar manner. Significance was set at p < .05.

Results

Patient Demographics

Following randomization, 27 patients were allocated into the conventional fluoroscopy cohort while 24 patients were allocated to the CAV arm of the study. Secondary to technical complications with the C-Arm, intraoperative fluoroscopy time and radiation exposure was obtained on 18 and 19 patients for the conventional fluoroscopy and CAV groups respectively (Fig. 4). Demographic data is outlined in Table 2. The senior surgeon completed 74% of the cases in the CAV cohort compared to 78% in the conventional fluoroscopy group (p=0.95).

Figure 4: Patient selection flow chart. CAV: Computer-Assisted Visualization.

Table 2: Preoperative demographic data for the computer assisted visualization and conventional fluoroscopy cohorts.

Intraoperative Femoroplasty and Fluoroscopy Data

The median femoroplasty time for the conventional fluoroscopy group was 14 minutes (IQR 9-23.75) while the median femoroplasty time for the assisted visualization cohort was 15 minutes (IQR: 11-37). There were no statistical differences between the two groups for average femoroplasty time or fluoroscopy exposure (Table 3). There was a significant reduction in alpha angle between both groups (p<0.001) with no differences between groups (p=0.30). There were no intraoperative femoroplasty complications, unintended effects or harms identified between groups related to the study.

Table 3: Intraoperative femoroplasty and fluoroscopic exposure data.

Surgeon Comparison

The senior surgeon had a significantly shorter femoroplasty time with less radiation exposure in the conventional fluoroscopy cohort compared to the less experienced surgeon (p<0.05; Table 4). For the senior surgeon, there was a non-significant increase in femoroplasty time and radiation exposure for the patients in the CAV group while there was a non-significant decrease in radiation exposure for the less experienced surgeon. There were no differences in femoroplasty time or radiation exposure between the senior and junior surgeons for CAV patients. For the junior surgeon, there was similar femoroplasty time between the conventional and CAV cohorts (31.0min vs. 29.4min; p=0.83) with lower radiation exposure time (91.0s vs. 44.1s; p=0.11) and dose (13.3 mGy vs. 8.9 mGy; p=0.36).  For the junior surgeon there was no significant difference in postoperative alpha angle between the CAV and the conventional fluoroscopy groups (44.8° ± 4.3° vs. 47.4° ± 4.0°; p=0.85).

Table 4: Surgeon comparison by experience.

Discussion

The present study demonstrates that in a randomized controlled trial, the use of computer assisted visualization software does not significantly increase femoroplasty time or radiation exposure. For the senior surgeon there was a non-significant increase in both femoroplasty time and radiation exposure, while the junior surgeon had no change in femoroplasty time and decreased radiation exposure and fluoroscopic exposure time in the CAV arm of the study. Femoroplasty accuracy, as defined by postoperative alpha angle, was comparable between the conventional fluoroscopy and CAV groups. 

Appropriate management of proximal femoral asphericity as a part of FAIS surgical treatment impacts postoperative outcomes. Inadequate femoroplasty either through over-or under resection leads to inferior outcomes and increases rates of revision hip arthroscopy as well as early conversion to total hip arthroplasty [6]. Challenges to appropriate Cam resection include limited intraoperative visualization or an incomplete understanding of the three-dimensional geography of the cam deformity in relation to the femoral head-neck junction [19]. Historically, proximal femoral under-resection was a leading cause for patients requiring revision hip arthroscopy with Cvetanovich, et al., reporting residual FAI as an intraoperative finding in 81% of revision hip surgeries in a systematic review of 348 patients [10]. However, possibly in response to higher rates of under-resection, proximal femoral over-resection has been increasing in incidence and may be more common than under-resection in revision surgeries.8 Further, femoral over-resection is potentially more devastating with limited treatment options and higher rates of conversion to total hip arthroplasty [21,27]. In a 2018 study on 120 patients undergoing revision hip arthroscopy, Mansor and colleagues report inferior rates of achieving the MCID and PASS for patients who had an over-resection compared to patients with an under-resection or no proximal femoral deformity [21]. Further, the authors identified an increased rate of early conversion to arthroplasty in the over-resection group compared to the under-resection cohort (30% vs. 0%; p=0.02). These findings demonstrate that it can be particularly challenging to identify the true extent of a cam lesion solely through arthroscopic means and while fluoroscopy free techniques have been described, the majority of arthroscopic hip surgeons rely on intraoperative imaging to confirm satisfactory cam resection.  Technological advances allowing for three-dimensional deformity visualization as well as intraoperative resection guidance are designed to reduce the rates of inaccurate femoroplasty [22]. From a preoperative standpoint, Tannast, et al., reported on the early utilization of a CT-based three dimensional modeling tool (HipMotion) to evaluate patient specific impingement positions through virtual range of motion analyses [31]. Three dimensional modeling software has been particularly valuable when considering torsional deformities and the decision making process for when to pursue a osteotomies in addition to hip arthroscopy [17,29]. Recently, an automated three dimensional hip modeling system was constructed using T1 VIBE sequencing on a 3T MRA which demonstrated high correlations to CT based models, demonstrating promising results for radiation free modeling [32]. Additionally, software such as HipMotion and MIMICs based modeling systems have also been employed to evaluate the effects of virtual osteoplasty on range of motion to aid in preoperative planning [5,17]. Commercially available comprehensive preoperative modeling platforms have been developed to assist surgeons with preoperative planning. The Smith and Nephew Dyonics PLAN (Smith and Nephew; Andover, MA) has been shown to accurately model the entirety of the cam deformity as well as prevent under-resection [1,13]. Similarly, the Stryker HipMap (Stryker Kalamazoo, MI, USA) is a commercially available three-dimensional modeling software platform which employs a low-dose radiation CT protocol to develop femoral and acetabular models. Advantages of HipMap include comprehensive measures of intra-and extra-articular impingement as well as deformity analyses incorporating anticipated resection depths and expected radiographic changes following a planned resection. Preoperative knowledge of the Cam deformity’s geographic location and extent, coupled with the ability to conceive a virtual osteoplasty, may aid the surgical approach and decision-making, particularly for developing hip preservation surgeons [3,13].

Intraoperative technology designed to increase femoroplasty accuracy and efficiency may particularly benefit surgeons earlier in the learning curve for hip arthroscopy. Dumont, et al., reported a significantly increased operative time for the first 75 cases, while Smith and colleagues found that radiation dose and fluoroscopy time decreased significantly over a single surgeon’s first 100 cases [12,30]. Integrating CT data with the Brainlab surgical navigation platform, Almoussa, et al., found that inexperienced surgeons were able to perform similar resections to experienced surgeons using a sawbones model [2]. However, when the platform was applied clinically by a senior surgeon, there was no difference in resection quality between the navigated and non-navigated groups [7]. Using the Orthomap 3D navigation software (Stryker; Mahwah, NJ, USA) integrated with a preoperative CT scan, Van Houcke, et al., found that postoperative alpha angle was significantly decreased in the navigated compared to the non-navigated cohort in a randomized control trial [15]. While navigation proved successful in decreasing the maximum alpha angle, the authors report that there remained a 13% rate of incomplete cam resection compared to a 29% rate of incomplete Cam resection in the non-navigated group (p>0.05). Using the computer assisted visualization software, the present study found a significant reduction in intraoperative alpha angle compared to preoperative radiographs. Further, for the experienced surgeon the CAV platform had a nonsignificant increase in femoroplasty time and radiation exposure while for the junior surgeon radiation exposure and femoroplasty time were non-significantly decreased. This was an improvement compared to the conventional fluoroscopy cohort where the less experienced surgeon had significantly longer femoroplasty time with increased radiation exposure compared to the experienced surgeon. This finding demonstrates a potential benefit of computer assisted deformity visualization even outside of the traditional learning curve, as the less experienced surgeon still had over one hundred arthroscopic cases in 2 years of experience prior to the onset of the study. It is possible that for surgeons in the traditional learning cuver (<100 cases), the benefits of CAV software would be even more apparent, however this requires additional study. The results of the present study compare well to a prior study comparing a senior and junior surgeon with the CAV softare where the authors found assisted visualization increased the accuracy of the femoroplasty without significantly affecting femoroplasty time in a cadaveric study [4]. Taken together, in the hands of a less experienced surgeon, computer assisted visualization may aid in achieving a highly accurate femoroplasty while potentially decreasing femoroplasty time and radiation exposure during the learning curve [25].

Strengths

The strengths of this study include the design as a randomized controlled trial as well as the standardized surgical technique for obtaining a spherical femoroplasty. Both surgeons had extensive experience in complex hip arthroscopy with the junior surgeon training under the senior surgeon prior to starting practice.

Limitations

This study has multiple limitations. While the study was initially powered to detect an 8-minute difference between conventional fluoroscopy and CAV arms, detecting a lesser difference may require a larger sample size in future studies. Further, the power analysis was not designed to detect differences between the senior and junior surgeon and the number of patients treated by the senior and junior surgeon were not identical. Additionally, patient-reported outcomes and postoperative variables were not included in the analysis, as this data is focused on intraoperative time and radiation exposure and postoperative outcomes are currently being collected in a prospective fashion. Despite these limitations, we believe that this study contributes valuable data regarding the value of intraoperative femoroplasty visualization software, particularly for junior hip preservation surgeons.

Conclusion

The image-based computer assisted visualization software does not significantly lengthen femoroplasty or fluoroscopy time during cam resection. Additionally, computer assisted visualization may decrease femoroplasty time and radiation exposure for less experienced surgeons, supporting this technology as a promising tool in achieving accurate and reliable cam resection during hip arthroscopy.

Conflict of Interests

The authors declare no conflict of interest. Dr. Kuhns serves on the editorial board for Arthroscopy.

Ms. Walsh has nothing to disclose.  Dr. Lall has received consulting fees from Arthrex, Inc., Stryker Corp.; has received research support from Arthrex Inc., Medwest, Smith and Nephew, Stryker Corp., Vericel, Zimmer Biomet; has received any other financial or material support Arthrex Inc., Iroko, Medwest, Smith and Nephew, Stryker Corp., Vericel, Zimmer Biomet. Dr. Lall serves as the Medical Director of Hip Preservation at St. Alexius Medical Center and as a Clinical Instructor at the University of Illinois College of Medicine.

Dr. Domb has had ownership interests in the American Hip Institute and affiliates, North Shore Surgical Suites, and Munster Specialty Surgery Center; research support from Arthrex, Stryker, Smith and Nephew, and Ossur; consulting fees from Arthrex, Medacta, Stryker, and SI-Bone Inc; has received educational support from Arthrex, Stryker; speaking fees from Arthrex; travel and lodging from Arthrex and Stryker; food and beverage from Arthrex, DJO Global, Medacta, Stryker, Zimmer Biomet, DePuy Synthes Sales, Medtronic, Trice Medical, Medwest Associates, SI-Bone Inc, Xiros Inc, Intellijoint Surgical Inc, Electronic Waveform Lab Inc; royalties from Arthrex, DJO Global, Medacta, Orthomerica; patents with Arthrex, Orthomerica, and DJO Global. Dr. Domb is Director of Hip Preservation at St. Alexius Medical Center and a board member for the American Hip Institute Research Foundation, AANA Learning Center Committee, the Journal of Hip Preservation Surgery, Journal of Arthroscopy, AOSSM Research Committee, and ISHA Executive Board. The American Hip Institute Research Foundation (American Orthopedic Foundation) funds research and is where our study was performed.

Ethical Statement

This study was performed in accordance with the ethical standards in the 1964 Declaration of Helsinki. This study was carried out in accordance with relevant regulations of the US Health Insurance Portability and Accountability Act (HIPAA). Details that might disclose the identity of the subjects under study have been omitted. This study was approved by the IRB. (IRB Tracking Number: 20200279). This study is registered on ClinicalTrails.gov, with an ID number of: NCT04265222.

Consent of Publication

This study was performed at the American Hip Institute Research Foundation. 

Authorship Contribution Statement

Benjamin D. Kuhns, MD, MS.-Data collection/analysis, writing, and revision of the manuscript.

Elizabeth G. Walsh, BS.-Data collection/analysis, writing, and revision of the manuscript.

Ajay C. Lall, MD, MS.-Data interpretation, writing, and revision of the manuscript. 

Benjamin G. Domb, MD-Data interpretation, writing, and revision of the manuscript.  

Funding/Sponsorship

Funding for the study was provided through a research grant by the Stryker Corporation (Kalamazoo, MI, USA).

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