The External Obturator Footprint as a Landmark for Stem Depth in Direct Anterior Total Hip Arthroplasty - Clinical Validation

Study Overview
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Brief Summary
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One of the goals of Total Hip Arthroplasty (THA) is to reconstruct leg length as adequately as possible. In order to achieve this one needs landmarks that are visible both on the templating X ray as well as during surgery. The classical posterior and lateral approaches often rely on the distance from the greater trochanter (GT) to the shoulder of the femoral stem or the distance from the lesser trochanter (LT) to the side of the neck osteotomy. If the surgeon finds out on the digital template that the distance from the GT to the shoulder of the implant should be X mm to achieve equal leg length, than the surgeon can try to reconstruct this during surgery. During the Direct Anterior Approach (DAA) these landmarks usually are not visible or require additional dissection injuring important soft tissue structures along the way. One anatomical structure that appears to be always visible during the DAA is the External Obturator tendon (EO). It was recently confirmed that the level of insertion of the EO onto the proximal femur can also always be determined on pre-operative X rays. It therefore represents one of the few landmarks that is visible both on the templating X ray as well as during DAA THA. Indeed, many hip surgeons, including ourselves, believe that if the shoulder of the femoral stem is near the insertion of the EO leg length cannot be far off. However, there is no clinical data to support this. The investigators would therefore like to the correlate the distance observed intra-operatively to the actual established distance on the post-operative X ray.

Official Title
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The External Obturator Footprint as a Landmark for Stem Depth in Direct Anterior Total Hip Arthroplasty - Clinical Validation

Conditions
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Coxarthrosis

Intervention / Treatment
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* Procedure: Total Hip arthroplasty via a Direct Anterior Approach


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: All patient who underwent THA via DAA by a single surgeon who routinely documents the distance from the shoulder of the stem to the upper border of the EO tendon Exclusion Criteria: Distance not noted No radiographs available
Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Patients who underwent DAA THA<br>Patients who underwent DAA THA by a single surgeon who routinely documents the distance from the should of the stem to the upper end of the EO footprint | Procedure: Total Hip arthroplasty via a Direct Anterior Approach<br>* Total Hip arthroplasty via a Direct Anterior Approach<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Correlation between the distance measured intra-operatively and presumed distance on the pelvic radiographs |  | 2 days | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Visibility of the EO tendon intra-operatively |  | 2 days | 
| Inter and intra-rater reliability |  | 2 days | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Total hip Arthroplasty, leg length, templating, direct anterior approach, external obturator footprint