The Accuracy of Digital Templating for Primary Total Hip Arthroplasty: Is There a Difference Between Direct Anterior and Posterior Approaches?

Accepted Manuscript The Accuracy of Digital Templating for Primary Total Hip Arthroplasty: Is there a Difference between Direct Anterior and Posterior approaches? Shai S. Shemesh, MD, Jonathan Robinson, MD, Aakash Keswani, Michael Bronson, MD, Calin S. Moucha, MD, Darwin Chen, MD PII:

S0883-5403(16)30917-2

DOI:

10.1016/j.arth.2016.12.032

Reference:

YARTH 55563

To appear in:

The Journal of Arthroplasty

Received Date: 1 September 2016 Revised Date:

29 November 2016

Accepted Date: 17 December 2016

Please cite this article as: Shemesh SS, Robinson J, Keswani A, Bronson M, Moucha CS, Chen D, The Accuracy of Digital Templating for Primary Total Hip Arthroplasty: Is there a Difference between Direct Anterior and Posterior approaches?, The Journal of Arthroplasty (2017), doi: 10.1016/j.arth.2016.12.032. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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The Accuracy of Digital Templating for Primary Total Hip Arthroplasty: Is there a

Shai S Shemesh, MD1 Jonathan Robinson, MD1 Aakash Keswani1

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Michael Bronson, MD1

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Difference between Direct Anterior and Posterior approaches?

Calin S Moucha, MD1

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Darwin Chen, MD 1

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Department of Orthopaedic Surgery, Icahn School of Medicine at Mount Sinai - New York, NY

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Author Contributions Statement: All authors have demonstrated[1] substantial contributions to research design, or the acquisition, analysis or interpretation of data; [2] drafting the paper or revising it critically; [3] approval of the submitted and final versions.

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Address for Correspondence: Darwin Chen, MD Assistant Professor Department of Orthopaedic Surgery Icahn School of Medicine at Mount Sinai 5 E 98 St New York, NY 10029 Phone: (212) 241-1461 FAX: (212) 241-9710 E-mail: [email protected]

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The Accuracy of Digital Templating for Primary Total Hip Arthroplasty: Is there a

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Difference between Direct Anterior and Posterior approaches?

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Abstract

2 Background: The direct anterior approach (DAA) has gained recent popularity for total hip

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arthroplasty (THA), as it provides immediate feedback on cup position and limb length using

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fluoroscopy. The purpose of this study was to evaluate any differences in the accuracy of digital

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templating for preoperative planning of THA, performed with two different surgical approaches:

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DAA using a radiolucent table with intraoperative fluoroscopy and the posterior approach (PA).

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Methods: 131 consecutive patients (148 hips) underwent a THA by a single surgeon, using the

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same cup and stem designs. 75 hips were performed using the DAA using a fracture table and

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fluoroscopy. 73 hips were performed using the PA with the patient positioned in lateral decubitus

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using standard positioners without fluoroscopy. Preoperative radiographs were digitally

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templated by the same surgeon.

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Results: The PA patients had a higher mean BMI and were more likely to have a preoperative

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diagnosis of AVN. The accuracy of templating for predicting the cup size to within 2mm was

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91% for DAA vs. 88% for PA (p=0.61). For stem size, the accuracy was 85% (to within 1 size)

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for the DAA vs. 77% for the PA (p=0.71). Likewise, there was no significant difference in

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predicting the final stem’s neck angle or femoral offset.

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Conclusions: Digital templating was found to be a reliable and highly accurate method for

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predicting component sizes and offset for THA, regardless of using either the PA or the DAA

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with fluoroscopy.

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Keywords: THA, direct anterior approach, digital templating, fluoroscopy

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Introduction

26 A successful total hip arthroplasty is predicated upon restoring the biomechanics of the

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hip as well as selecting implants of appropriate size to avoid intraoperative or postoperative

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complications and to ensure long-lasting function[1] . By using a digital templating algorithm,

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the surgeon can employ a stepwise method to determine the size and position of the proposed

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prosthesis within the bone to ensure optimal function of the joint following surgery. The

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accuracy of digital templating have been shown in several studies to be between 78-98% to

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within 1 size for the femoral stem, and between 80-91% to within 2mm for the acetabular

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component[2-5].

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The direct anterior approach (DAA) using a specialized orthopaedic fracture table and intraoperative image intensifier has become increasing popular over the past decade. The

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intraoperative use of fluoroscopy allows enhanced accuracy of the cup placement and restoration

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of leg length and offset compared to standard techniques[6-8]. The image intensifier can be

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utilized as a confirmatory measure at several different points during surgery, including femoral

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neck resection, acetabular preparation/cup insertion, femoral broaching, and component trialling.

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Use of fluoroscopy during DAA THA in the supine position has been shown to decrease the

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variability of acetabular cup anteversion and inclination[9].

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Whether fluoroscopy is used or not, the direct anterior approach and posterior approach

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are quite different in many regards, including patient positioning (supine vs. lateral decubitus),

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the use of different tools/instruments, as well as the soft tissue releases required to fully mobilize

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the femur [10]. Compared to DAA, the PA arguably permits the surgeon a wider intraoperative

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view to expose both acetabulum and femur, and allows easy manipulation of the leg owing to the

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lateral decubitus position[11]. The PA can be used in a range of cases, from standard primary

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cases to challenging cases such as revision surgeries with massive bone loss.

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The choice of surgical approach was shown in previous studies to affect component size and position. A recent study by Rivera et al. shows an increased frequency of femoral stems at

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least 2 sizes smaller than expected of more than 6-times higher with DAA without fluoroscopy

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compared with PA[12] . This difference was attributed to the technical difficulty of femoral

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preparation and the surgeon's knowledge of possible related complications such as fracture.

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Another recent study by Hirohito et al. compared femoral stem position and anteversion of DAA

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to PA [13]. They observed that more femoral components were implanted in more than 3 degrees

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of flexed alignment with the DAA, and that the postoperative femoral anteversion change from

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native anteversion was larger in the DAA group. Kobayashi et al. found a higher degree of

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accuracy in regards to cup inclination and anteversion and a significantly higher incidence of

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stem in flexion in the DAA group[11]

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To the authors' knowledge, there is only a single published study that compared the accuracy of digital templating for THA performed through the DAA versus PA [12]. This may

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be of particular importance to surgeons who are skilled in both techniques and routinely perform

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THA with both approaches. We therefore sought to evaluate the accuracy of digital templating

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for preoperative planning of THA performed with two different surgical approaches: the DAA

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using a radiolucent fracture table with intraoperative fluoroscopy and the PA on a standard

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operating table with no fluoroscopy. Secondly, we aimed to determine which preoperative and

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intraoperative factors might be associated with reduced digital templating accuracy. We

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hypothesized that the intraoperative use of fluoroscopy would increase the accuracy in favor of

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the DAA for both acetabular and femoral components.

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Materials and Methods

73 74 Following institutional review board approval, we retrospectively reviewed inpatient

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charts, surgical records, and radiographs of patients who underwent a primary total hip

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arthroplasty by the senior author (DC) at a single arthroplasty center, from December 2013 until

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January 2016. The senior author (DC) performs posterior THA as well as DAA THA and has

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extensive clinical experience in both approaches.

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Our data included 131 consecutive patients who received 148 primary cementless THA

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surgeries. We included patients who were operated for either severe, end stage osteoarthiris or

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end stage avascular necrosis of the femoral head (AVN). Exclusion criteria were a history of

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prior surgery on the affected hip, THA for femoral neck fractures, post-traumatic osteoarthritis

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and complex deformities (i.e. severe hip dysplasia, Legg- Calve-Perthes) for their possible

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negative effect on the accuracy of the preoperative templating.

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All operative notes were reviewed, and any patient with an intraoperative complication that may have affected the size of the prosthesis implanted was excluded. Two nondisplaced

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calcar fractures occurred intraoperatively, one in each group (a 29-year-old male who underwent

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posterior THA for AVN and a 65-year-old female who underwent a DAA THA for end-stage

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osteoarthritis). Both fractures occurred during broach preparation and were treated with a single

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cerclage cable prior to final stem insertion. Good initial stability was achieved in both cases.

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However, these cases were excluded due to our concern that a periprosthetic fracture may affect

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the final femoral component chosen, regardless of the degree of displacement. The severity of

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osteoarthritis on the preoperative radiographs was graded using the Kellgren and Lawrence

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grading scale [14]. All patients received a Tritanium cup and Accolade II stem (Stryker-

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Howmedica-Osteonics, Rutherford, NJ). The Tritanium cup is a cementless hemispheric

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acetabular design which has a 2-mm increase with each size. The Accolade II is a second-

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generation proximally-coated, tapered cementless stem with a morphometric wedge shape and a

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size-specific medial curvature [15] .

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100 Templating

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All patients had a standardized plain pelvic radiograph (film-focus distance 115 cm)

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taken at the preoperative screening in supine position with both feet in 10° to 15° of internal

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rotation. A calibration marker (25-mm metallic sphere, XEMarc, Farmingdale, NY) was

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positioned between the legs of the patient at the anteroposterior level of the greater trochanter.

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All preoperative digital radiographs were calibrated with a 25-mm marker included on the

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anteroposterior (AP) pelvic radiograph. Care was taken to ensure the radiographs were well

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centered with the coccyx pointing just above the symphysis pubis as well as symmetrical

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obturator foramina. Radiographs were templated preoperatively by the senior author using

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OrthoView Software (OrthoView LLC, Jacksonville, FL) (Image 1). A step-by-step digital

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templating algorithm for digital preoperative planning was used, as described by Bono[1].

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This method consists of 3 steps: magnification calibration, planning phase (femoral canal

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diameter, acetabulum diameter and leg length discrepancy are measured and the recommended

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sizes are determined) and final templating stage (selection and position of the cup and stem with

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correction of LLD).

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The center of rotation of the native acetabulum was determined by importing a digital cup template, corrected for magnification, and placing it within the osseous margins of the

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acetabulum. The cup was placed at a 45° angle to the inter-teardrop axis with the medial border

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of the prosthesis placed within the inner and outer walls of the pelvis. The femoral stem was

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chosen to achieve appropriate medio-lateral cortical engagement in the femoral metaphysis. With

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the appropriate stem size, the level of the femoral neck osteotomy level was measured from a

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point at the most proximal tip of the lesser trochanter. The femoral stem neck cut, seating height,

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offset, and neck length were chosen to restore hip anatomy to the contralateral hip. If there was

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significant radiographic malpositioning of the operative hip, such as from an external rotation

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contracture, the contralateral hip was templated. Patients undergoing a subsequent contralateral

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THA (17 patients) were templated as if undergoing a first THA.

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Surgical technique

A total number of 148 hips (131 patients) met inclusion criteria. 73 hips underwent THA

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using a posterior approach, and 75 were performed with a direct anterior approach. All posterior

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THAs were performed with a uniform technique. The patients were placed in a lateral decubitus

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position on a standard operating table with pelvic positioners placed posteriorly (sacrum) and

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anteriorly (pubic symphysis and rami). The posterior approach to the hip was performed, taking

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down the short external rotators and capsule as 1 continuous L shaped flap. The hip was then

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dislocated posteriorly. The proximal femur was fully exposed and the femoral neck osteotomy

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level was identified, as per the preoperative plan, using a ruler. The acetabulum was then

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exposed with retractors placed around the anterior, posteroinferior and superior borders. We

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sequentially reamed using hemispherical reamers, obtaining a healthy bony bed for a press fit

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socket. We then impacted a cup into the acetabulum in approximately 40 ± 10 degrees of

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abduction and 15 ± 10 degrees of anteversion[16] . It was affixed with screws in the superior

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acetabular dome for adjunctive fixation. The femur was exposed and sequentially broached up to

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the appropriate size. We then performed a trial reduction and the hip is brought through a range

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of motion and checked for stability. The combination of components providing the best fit,

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stability, restoration of offset, and equalization of leg lengths was finally chosen. Following that,

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the final components were placed and a posterior repair was performed.

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Direct anterior THAs were performed with the patient in the supine position according to

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the technique described by Matta et al. [7, 8]. The patients were placed in the supine position on

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the Hana table (OSI Inc., Union City, CA), with a perineal post and the boots attached to the

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table. Image intensifier was used to: identify the neck osteotomy, assess acetabular reaming

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position and depth, confirm final position of the cup and following femoral broaching to confirm

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the femoral component size, canal fill, hip offset, and limb length as compared with the opposite

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hip.

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Post-operative radiographic evaluation

Postoperative radiographs at the 6-week review were used to analyze the leg length discrepancy

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(LLD) and femoral offset. LLD was determined by first drawing a horizontal line connecting the

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caudal margins of the two ischial tuberosities as a pelvic reference. The perpendicular distances

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from the bi-ischial line to the tips of each of the lesser trochanters (the femoral reference) were

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then measured [17] . LLD was expressed as the difference in measurements between the two

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hips. To eliminate bias the study had 2 observers (SS, JR) collect the LLD and femoral offset

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data, other than the surgeon. The actual cup, head and stem implant sizes were retrieved from

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operating room implant records, and compared to the templated results recovered from the

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Orthoview software report. The femoral offset was determined by measuring the perpendicular

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distance between the center of the femoral head and a line drawn down the center of the femoral

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shaft [18], on both postoperative radiograph and preoperative templated radiograph. Neck length

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and stem length were retrieved from the manufacturer’s implant information table, that indicates

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the specific lengths for each stem size.

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Statistical analysis was conducted using SAS (version 9.3) with a 2 tailed alpha of 0.05. Continuous variables were analyzed using paired Student t test after testing for normality and

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equal variance. Categorical analysis was conducted with chi-square and Fisher’s exact test where

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appropriate. Percentage analysis of planning accuracy was performed using three different

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accuracy thresholds: 1) 100% accuracy, 2) accuracy within 2mm or 1 size, and 3) accuracy

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within 4 mm or 2 sizes (as shown in Tables 2 and 3).

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In multivariate logistic regression analysis to detect factors associated with reduced digital templating accuracy, all predictors were included in the model regardless of p-value from

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bivariate analysis. All variables were assessed for confounding and interaction where

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appropriate. A p value of less than 0.05 was regarded as significant. Final models were assessed

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for goodness of fit using the Hosmer-Lemeshow test.

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Results

131 patients who underwent 148 primary THAs fulfilled our criteria for inclusion. All

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interventions were primary THA for osteoarthritis or hip AVN. The characteristics of the

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patients in the PA and DAA groups are summarized in Table 1.The two groups deferred with

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regards to the etiology, with the PA group having a significantly larger percentage of patients

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diagnosed with AVN (25% vs. 9.3%, p<0.001). The PA patients had a significantly higher BMI

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when compared to DA patients (29.8 vs. 26.6, p=0.02). Analysis of preoperative radiographs

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showed no significant differences in Kellgren-Lawrence classification. DAA patients were found

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to have a greater mean preoperative LLD (4.9 ± 4.0 mmvs. 3.7 ± 3.0 mm, p=0.05), with the

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affected leg being shorter.

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Comparison of the implant sizes that were finally chosen intraoperatively showed no statistically

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significant difference between the two groups in the following parameters: cup size, stem size,

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head size, neck length and offset (Table 1).

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Before comparing the accuracy between the two groups of patients, we first established the accuracy of templating for the entire cohort (n=148) regardless of the surgical approach

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(Table 2). Eighty nine percent of cups were templated to within 1 size (2mm), and 99%, to

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within 2 size (4mm). Eighty four percent of stems were templated to within 1 size, neck angle

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was accurately predicted in 87%. Stem neck length and offset were recreated to within 4mm of

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the template in 91% and 86%, respectively.

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Prediction of Cup Size

Digital templating predicted the exact acetabular cup size in 49% of DAA cases and

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41% of PA cases (p=0.33) (table 3) . For DAA hips, a total of 91% of cup sizes were predicted

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within ±2 mm (1 size), and 99% were predicted to within ±4 mm (2 sizes), compared with 88%

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and 99% for PA hip, respectively.

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Prediction of Stem Size and Offset

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The increments of the manufactured Accolade 2 stem are within 1 sizes, reflecting a 3mm change in stem length. The exact femoral stem size was predicted in 43% of DAA hips and 41%

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of PA hips (p=0.37) (table 3). Templated stem were within ±1 size of the actual stems in 85% of

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DAA hips and 77% of PA hips (p=0.71). Prediction of stem neck length and offset were also

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highly accurate in both groups, with no statistically significant difference. The Accolade II stem

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has two neck angle options: the standard 132° neck angle and the 127° neck angle. For each neck

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angle option, the femoral offset increases as the stem size increases. Neck angle was predicted

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accurately in 87% of DAA hips and 88% of PA hips. Most cases where neck angle varied from

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the template, were converted from 132 to 127 intraoperatively (8 out of 9 PA hips, 7 out of 10

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DAA hips).

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Leg Length Discrepancy and Neck osteotomy level

Preoperatively, the mean LLD was - 4.9mm in the DAA groups and - 3.7mm in the PA

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group (p=0.05). The accuracy of femoral neck cut was precise in 15% of cases in both groups,

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within 1 mm in 35% of DAA and 40% PA (p=0.52). Neck cut was within 2mm in 55% of DAA

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and 62% of PA (p=0.39). Postoperatively, the mean LLD was +1.3 mm (SD, 1.3 mm) in DAA

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hips and +2.5mm(SD, 1.7mm) in PA hips (p=0.01). Analysis of the delta between the

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preoperative and postoperative LLD reflecting the total lengthening achieved, revealed similar

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mean lengthening of 6.2mm (SD, 3.3mm) in PA patients and 6.2mm (SD, 4.3mm) in DAA

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patients (p=0.94). Comparison of postoperative radiographs demonstrated that the osteotomy

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level was 1mm higher in average for the DAA hips compared with PA hips (12+/-2.2mm vs.

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11+/-2.4mm, p=0.01)

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Multivariate analysis To detect factors associated with reduced digital templating accuracy, we applied a Multivariate analysis (Table 4). The posterior approach was not found to be a risk factor for

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reduced accuracy. The patients’ age, BMI, severity of arthritis and the preoperative diagnosis of

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osteonecrosis were not associated with reduced accuracy. Male gender was found to significantly

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affect the accuracy of templating, specifically for predicting stem size (OR 2.74, 95% CI 1.02-

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7.47). The existence of preoperative LLD, was found to have a negative effect on the accuracy,

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for predicting the cup size (OR 0.74, 95% CI 0.58-0.96).

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Discussion

The direct anterior approach (DAA) for THA has grown steadily and rapidly in the United States over the past 10 years [19]. An AAHKS survey in 2014 indicated 26 % of US

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surgeons utilize the DAA for THA, while only 1% utilized this approach back in 2003[20].

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However, it is still not clear what is the volume of surgeons who have transitioned to DAA

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exclusively, and how many alternate between different approaches depending on the case.

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With more surgeons opting to use the DAA for total hip arthroplasty, we saw the importance of

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proving the validity of digital templating and establishing its’ accuracy specifically for DAA-

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THA. Despite its well-documented use in total hip arthroplasty, little has been described on its

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use in DAA THA[11, 12].

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The senior author of this study (DC) is a fellowship-trained arthroplasty surgeon that has

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significant experience in both surgical approaches, and chooses the approach based on various

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patient characteristics. We refrain from performing DAA THA in obese patients with an

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immobile abdominal pannus. This is reflected by the lower mean BMI in the DAA group in the

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current study. The direct anterior approach can be performed with or without the use of a

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specialized table and/or fluoroscopy. We favor the use of a radiolucent orthopaedic table, a table-

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mounted femoral hook, selective soft tissue releases (posterosuperior hip capsule over the saddle

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of the femoral neck, conjoined and piriformis tendons as needed) based on mobility of the femur,

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and the routine use of fluoroscopy throughout the case. The DAA provides a direct view of the

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acetabulum with visualization of all bony and soft tissue landmarks to allow reference for

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appropriate cup positioning [21]. A major advantage of DAA THA is that it facilitates the use of

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fluoroscopy during surgery due to the supine position of the patient. This position provides less

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alteration of pelvic orientation during the case [22]. The proper use of fluoroscopy during DAA

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THA helps to mimic preoperative pelvic tilt and provides feedback of pelvic orientation and cup

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positioning.

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One of the major technical challenges with the DAA is femoral exposure and canal

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preparation [11-13, 23]. Several recent studies comparing variability in size and position between

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the DAA and PA for primary THA, indicate a difference in stem position, with or without a

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concomitant difference in stem size [11-13]. Rivera et al. studied the adherence of surgical

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sizing to preoperative templating in 112 THAs, of which 59 were implanted through PA and 53

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through DAA without intraoperative fluoroscopy, by a single surgeon. They demonstrated a

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higher prevalence of undersized as well as severely undersized stems in their DAA group when

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compared with their PA group. 54.72% of their DAA THAs had an undersized stem of 1 size or

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more, and 24.5% were undersized to more than 2 sizes (compared with 16.95% and 3.39% in the

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PA group, respectively). Postoperative radiographs showed that canal fill was significantly

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higher in PA THAs than in DAA THAs. The authors concluded that such a systematic mistake

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may be explained by the technical difficulty of adequate canal preparation in DAA, and

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suggested that the intraoperative use of fluoroscopy may have prevented that mistake from

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occurring. We have demonstrated a higher accuracy than previously reported in predicting

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femoral stem size during DAA THA, with only 5.3% of stems undersized to 2 sizes or more, and

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14.6% undersized to 1 size or more. This may be due to the use of a uniquely anatomically

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designed tapered wedge stem (Accolade 2 as opposed to a Zimmer Fitmore in Rivera et al.) as

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well as the our consistent use of fluoroscopy.

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Comparison of templating accuracy yielded similar results in both PA and DAA groups,

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with numbers comparable to previous studies [2, 4, 5, 24]. In multivariate analysis, the posterior

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approach was not associated with increased risk of inaccurately selecting component sizes. This

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is reassuring for surgeons who use both approaches in their everyday practice and routinely

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perform digital templating preoperatively. Male gender was associated with a 2.74 times odds of

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inaccurately selecting the stem size, compared with female patients. A recent study by

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Pourmoghaddam et al. aimed to further improve the accuracy of templating by applying a

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predictive model that included BMI, age, gender, height, and weight [25]. They have

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successfully achieved a 99% accuracy within ± 2 of templated size. Their finding perhaps might

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explain our gender related observation. We also found a correlation between preoperative LLD

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and inaccuracy of templated cup size. This may possibly be explained by an effort to minimize

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the effect of LLD through the choice of cup size during templating.

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For DAA THA, the supine position (with direct comparison of leg lengths) and the use of

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fluoroscopy have been described as advantageous in minimizing LLD [8, 26]. We did not find a

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significant difference in accuracy of the templated osteotomy level between the two approaches,

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although we did find a statistically significant difference in postoperative LLD (1.3 mm in the

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DAA group and 2.5mm in the PA group). However, the clinical importance of this finding

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remains questionable, since LLD is usually perceived only when shortening exceeds 10 mm and

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lengthening 6 mm [27]. Additionally, even though the postoperative measurement gave a longer

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operative side in the posterior approach group, our analysis shows that the actual delta was

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similar in both groups.

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This study had several notable strengths. All our patients were operated on by a single

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surgeon, using the exact same implants, same basic technique and same templating algorithm.

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We do have several limitations. First, the two groups differed in their mean BMI and there was a

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higher incidence of AVN in the PA group. These differences may also account for the

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significantly higher preoperative LLD, which is a common finding in patients with osteonecrosis

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due to the collapse of the femoral head and secondary degenerative arthritis [28, 29]. Second, we

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did not assess intraobserver and interobserver reliability for the different component

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measurements. Third, our analysis did not include component position, which has been shown to

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vary between different approaches. Fourth, the fact our analysis compared only a single implant

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design can be considered a limitation although we believe our conclusions can be generalized to

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other designs. Finally, we did not compare our DAA with fluoroscopy to DAA without it, to

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isolate the effect of fluoroscopy on accuracy.

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Conclusion

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sizes, offset and the level of femoral neck osteotomy, regardless of using either the PA or the

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DAA with fluoroscopy, and has proven effective, reliable and essential technique

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for preoperative planning.

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Digital templating for primary cementless THA can be expected to accurately predict implant

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Figure legends:

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Table I. Comparison of patient demographic characteristics between direct anterior (DAA) and

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posterior approach (PA) patients

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Table III. Bivariate analysis comparing digital templating accuracy for direct anterior versus

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posterior approach THA patients

346

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Table IV. Multivariate analyses of factors associated with reduced digital templating accuracy

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Image 1. A. preoperative planning for a left primary cementless DAA THA, templated sizes

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appear in a textbox on the bottom of the radiograph (NC =neck cut) B. Postoperative radiographs

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with the exact same cup and stem sizes used.

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352 353 354 355 356 357 358 359 360 361

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References

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Bono, J.V., Digital templating in total hip arthroplasty. J Bone Joint Surg Am, 2004. 86-A Suppl 2: p. 118-22. Gamble, P., et al., The accuracy of digital templating in uncemented total hip arthroplasty. J Arthroplasty, 2010. 25(4): p. 529-32. Kumar, P.G., et al., Reproducibility and accuracy of templating uncemented THA with digital radiographic and digital TraumaCad templating software. Orthopedics, 2009. 32(11): p. 815. Shaarani, S.R., G. McHugh, and D.A. Collins, Accuracy of digital preoperative templating in 100 consecutive uncemented total hip arthroplasties: a single surgeon series. J Arthroplasty, 2013. 28(2): p. 331-7. Steinberg, E.L., et al., Preoperative planning of total hip replacement using the TraumaCad system. Arch Orthop Trauma Surg, 2010. 130(12): p. 1429-32. Bhandari, M., et al., Outcomes following the single-incision anterior approach to total hip arthroplasty: a multicenter observational study. Orthop Clin North Am, 2009. 40(3): p. 329-42. Matta, J.M. and T.A. Ferguson, The anterior approach for hip replacement. Orthopedics, 2005. 28(9): p. 927-8. Matta, J.M., C. Shahrdar, and T. Ferguson, Single-incision anterior approach for total hip arthroplasty on an orthopaedic table. Clinical orthopaedics and related research, 2005. 441: p. 115-124. Rathod, P.A., et al., Does fluoroscopy with anterior hip arthoplasty decrease acetabular cup variability compared with a nonguided posterior approach? Clinical Orthopaedics and Related Research®, 2014. 472(6): p. 1877-1885. Rodriguez, J.A., H.J. Cooper, and J. Robinson, Direct anterior approach to THR: what it is and what it is not. Current reviews in musculoskeletal medicine, 2013. 6(4): p. 276. Kobayashi, H., et al., Surgeons changing the approach for total hip arthroplasty from posterior to direct anterior with fluoroscopy should consider potential excessive cup anteversion and flexion implantation of the stem in their early experience. Int Orthop, 2015. Rivera, F., et al., Risk of stem undersizing with direct anterior approach for total hip arthroplasty. Hip Int, 2016. 26(3): p. 249-53. Abe, H., et al., Difference in stem alignment between the direct anterior approach and the posterolateral approach in total hip arthroplasty. The Journal of arthroplasty, 2015. 30(10): p. 1761-1766. Kellegren, J. and J. Lawrence, Radiological assessment of osteoarthritis. Ann Rheum Dis, 1957. 16: p. 494-501. Issa, K., et al., Radiographic fit and fill analysis of a new second-generation proximally coated cementless stem compared to its predicate design. The Journal of arthroplasty, 2014. 29(1): p. 192-198. Lewinnek, G.E., et al., Dislocations after total hip-replacement arthroplasties. J Bone Joint Surg Am, 1978. 60(2): p. 217-20. Marcucci, M., et al., A multimodal approach in total hip arthroplasty preoperative templating. Skeletal radiology, 2013. 42(9): p. 1287-1294. Charles, M.N., et al., Soft-tissue balancing of the hip: the role of femoral offset restoration. Instr Course Lect, 2005. 54: p. 131-41.

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Ziran, N.M. and J.M. Matta, Anterior Approach Total Hip Arthroplasty with an Orthopedic Table, in Minimally Invasive Surgery in Orthopedics, R.G. Scuderi and J.A. Tria, Editors. 2016, Springer International Publishing: Cham. p. 1-20. Matta, J.M., Symposium I: Surgical Approach for Primary Total Hip Arthroplasty; Direct Anterior Approach: Safe and Effective, in The 20th Combined Open Meeting of The Hip Society and the American Association of Hip and Knee Surgeons (AAHKS). 2014. Horne, P.H. and S.A. Olson, Direct anterior approach for total hip arthroplasty using the fracture table. Curr Rev Musculoskelet Med, 2011. 4(3): p. 139-45. Slotkin, E.M., P.D. Patel, and J.C. Suarez, Accuracy of fluoroscopic guided acetabular component positioning during direct anterior total hip arthroplasty. The Journal of arthroplasty, 2015. 30(9): p. 102-106. Hartford, J.M. and S.B. Knowles, Risk Factors for Perioperative Femoral Fractures: Cementless Femoral Implants and the Direct Anterior Approach Using a Fracture Table. J Arthroplasty, 2016. The, B., et al., Digital versus analogue preoperative planning of total hip arthroplasties: a randomized clinical trial of 210 total hip arthroplasties. J Arthroplasty, 2007. 22(6): p. 866-70. Pourmoghaddam, A., et al., A patient-specific predictive model increases preoperative templating accuracy in hip arthroplasty. J Arthroplasty, 2015. 30(4): p. 622-6. Yi, C., et al., Early complications of anterior supine intermuscular total hip arthroplasty. Orthopedics, 2013. 36(3): p. e276-81. Konyves, A. and G.C. Bannister, The importance of leg length discrepancy after total hip arthroplasty. J Bone Joint Surg Br, 2005. 87(2): p. 155-7. Dong, N., et al., Effect of Preoperative Leg Length Discrepancy on Functional Outcome and Patient Satisfaction After Total Hip Arthroplasty in Cases of Osteonecrosis of the Femoral Head. J Arthroplasty, 2016. Zhang, H., et al., Cementless total hip arthroplasty in Chinese patients with osteonecrosis of the femoral head. J Arthroplasty, 2008. 23(1): p. 102-11.

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ACCEPTED MANUSCRIPT Table I. Comparison of patient demographic characteristics between direct anterior (DAA) and posterior approach (PA) patients

75 (100%)

73 (100%)

62.4 (SD 13.1)

60.9 (SD 15.8)

31 (41%) 44 (59%)

28 (38%) 45 (62%)

EP

BMI = Body mass index

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1 Only applies to osteoarthritis etiology patients

P -Value 0.52 0.71

RI PT

Posterior

0.02*

55 (75%) 18 (25%) 29.8 (SD 5.8)

34 (45%) 41 (55%)

44 (60%) 29 (40%)

0 (0%) 0 (0%) 28 (37%) 40 (53%)

0 (0%) 0 (0%) 15 (21%) 44 (60%)

4.9 (SD 4.0) 1.3 (SD 1.3) 6.2 (SD 4.3) 51 (SD 3.6) 33 (SD 2.7) 5.3 (SD 1.6) 109 (SD 4.9) 35 (SD 2.1) 43 (SD 4.9) 12 (SD 2.2)

3.7 (SD 3.0) 2.5 (SD 1.7) 6.2 (SD 3.3) 51 (SD 2.8) 33 (SD 3.0) 5.6 (SD 1.7) 110 (SD 5.2) 34.8 (SD 2.1) 43.6 (SD 4.5) 11 (SD 2.4)

M AN U

SC

68 (91%) 7 (9.3%) 26.6 (SD 3.3)

TE D

Age (mean) Gender Male Female Etiology Osteoarthritis Avascular necrosis BMI (mean) Side Left Right Kellgren Lawrence Classification1 '1 '2 '3 '4 Leg-length discrepancy (mean, mm) Pre-op Post-op Delta Cup size (mean, mm) Head size (mean, mm) Stem size (mean) Stem length (mean, mm) Neck length (mean, mm) Offset (mean, mm) Neck cut (mean, mm)

Direct Anterior

<0.001* 0.51

0.15

0.05* 0.01* 0.94 0.84 0.42 0.36 0.36 0.74 0.26 0.01*

ACCEPTED MANUSCRIPT Table II. Digital templating accuracy for all THA patients

67 (45%) 39 (26%) 62 (42%) 62 (42%) 115 (78%) 57 (39%) 129 (87%) 22 (15%)

Cup size (mm) Head neck length (mm) Stem size Stem length (mm) Stem neck length (mm) Offset (mm) Neck angle (degrees) Neck cut (mm)

1 +/- 2mm for all categories except stem size (+/- 1 sizes), and neck cut (+/- 1 mm)

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2 +/- 4mm for all categories except stem size (+/- 2 sizes), and neck cut (+/- 2 mm)

Accurate within 4 mm or 2 sizes n(%)2 146 (99%) 111 (75%) 124 (84%) 124 (84%) 135 (91%) 127 (86%) 86 (58%)

RI PT

100 % accuracy n (%)

Full cohorts (n=148) Accurate within 2 mm or 1 sizes n (%)1 132 (89%) 45 (30%) 62 (42%) 62 (42%) 131 (89%) 105 (71%) 55 (37%)

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1 +/- 2mm for all categories except stem size (+/- 1 sizes), and neck cut (+/- 1 mm)

AC C

EP

TE D

Accurate within 4 mm or 2 sizes n(%)2 72 (99%) 56 (77%) 56 (77%) 60 (82%) 68 (93%) 63 (86%) 45 (62%)

RI PT

M AN U

2 +/- 4mm for all categories except stem size (+/- 2 sizes), and neck cut (+/- 2 mm)

Posterior (n=73) Accurate within 2 mm or 1 sizes n (%)1 64 (88%) 25 (34%) 30 (41%) 30 (41%) 65 (89%) 54 (74%) 29 (40%)

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Table III. Bivariate analysis comparing digital templating accuracy for direct anterior versus posterior approach THA patients Direct Anterior (n=75) Accurate within 2 mm Accurate within 4 mm 100 % accuracy 100 % accuracy or 2 sizes or 1 sizes n (%) n (%) 1 2 n (%) n(%) 37 (49%) 68 (91%) 74 (99%) 30 (41%) Cup size (mm) 20 (27%) 20 (27%) 55 (73%) 19 (26%) Head neck length (mm) 32 (43%) 32 (43%) 64 (85%) 30 (41%) Stem size 32 (43%) 32 (43%) 64 (85%) 30 (41%) Stem length (mm) 62 (81%) 66 (88%) 67 (89%) 54 (74%) Stem neck length (mm) 27 (36%) 51 (68%) 64 (85%) 30 (41%) Offset (mm) 65 (87%) 64 (88%) Neck angle (degrees) 11 (15%) 26 (35%) 41 (55%) 11 (15%) Neck cut (mm)

100 % accuracy 0.33 0.99 0.99 0.87 0.33 0.61 0.99 0.99

P-value Accurate within 2 mm or 1 sizes n (%)1 0.61 0.37 0.37 0.85 0.99 0.47 0.52

Accurate within 4 mm or 2 sizes n(%)2 0.99 0.71 0.71 0.66 0.33 0.99 0.39

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Stem size accuracy (+/- 1 size) Odds ratio (95% CI) P Value

Stem neck length accuracy (+/- 2 mm) Odds ratio (95% CI) P Value

Offset (+/- 2 mm) Odds ratio (95% CI)

P Value

Neck angle accuracy (+/- 5 degrees) Odds ratio (95% CI) P Value

Neck cut accuracy (+/- 2 mm) Odds ratio (95% CI)

P Value

Posterior approach1 Age

1.80 (0.83-3.89) 2.59 (0.78-8.57)

0.12 0.36

0.70 (0.32-1.52) 0.99 (0.96-1.02)

0.36 0.42

1.22 (0.45-3.29) 0.99 (0.96-1.03)

0.70 0.70

0.81 (0.26-2.51) 0.97 (0.93-1.01)

0.71 0.14

0.84 (0.40-1.77) 1.00 (0.97-1.03)

0.75 0.83

1.23 (0.43-3.52) 1.00 (0.96-1.05)

0.70 0.84

0.83 (0.40-1.72) 1.01 (0.98-1.04)

0.50 0.41

Male gender2

2.52 (0.68-9.44)

0.17

1.27 (0.58-2.79)

0.55

2.74 (1.02-7.47)

0.05

0.86 (0.29-2.52)

0.78

1.97 (0.89-4.36)

0.10

1.73 (0.59-5.11)

0.32

0.84 (0.41-1.73)

0.65

Avascular necrosis etiology3 BMI

2.35 (0.20-27.79) 1.02 (0.90-1.14)

0.50 0.79

1.06 (0.36-3.16) 1.01 (0.93-1.09)

0.91 0.89

2.21 (0.67-7.37) 1.02 (0.92-1.12)

0.20 0.72

0.57 (0.04-7.20) 1.01 (0.90-1.13)

0.66 0.88

1.37 (0.46-4.07) 0.94 (0.86-1.02)

0.57 0.12

0.52 (0.09-2.85) 0.97 (0.87-1.08)

0.45 0.56

0.88 (0.32-2.47) 0.96 (0.89-1.04)

0.80 0.30

0.55 0.02

0.79 (0.33-1.88) 0.97 (0.88-1.08)

0.86 0.61

0.78 (0.36-1.69) 0.85 (0.71-1.02)

0.73 0.08

0.74 (0.44-1.35) 1.07 (0.92-1.25)

0.82 0.36

1.06 (0.48-2.36) 0.97 (0.86-1.09)

0.95 (0.31-2.88) 0.93 (0.78-1.10)

0.57 0.37

0.72 (0.34-1.26) 1.03 (0.93-1.14)

0.79 0.54

SC M AN U TE D EP

Kellgren Lawrence Classification 1.87 (0.61-5.78) Pre-op leg-length discrepancy 0.74 (0.58-0.96) 1 Relative to anterior total hip replacement approach reference 2 Relative to female gender 3 Relative to osteoarthritis etiology reference 4 Relative to KL Classification 4

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Table IV. Multivariate analyses of factors associated with reduced digital templating accuracy Cup size accuracy (+/- 2mm) Head neck length accuracy (+/- 2 mm) Risk Factor Odds ratio (95% CI) P Value Odds ratio (95% CI) P Value

0.85 0.55

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Figure legends:

Table I. Comparison of patient demographic characteristics between direct anterior (DAA) and

SC

Table II. Digital templating accuracy for all THA patients

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posterior approach (PA) patients

Table III. Bivariate analysis comparing digital templating accuracy for direct anterior versus

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posterior approach THA patients

Table IV. Multivariate analyses of factors associated with reduced digital templating accuracy

Image 1. A. preoperative planning for a left primary cementless DAA THA, templated sizes

TE D

appear in a textbox on the bottom of the radiograph (NC =neck cut) B. Postoperative radiographs

AC C

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with the exact same cup and stem sizes used.

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