Sequential Steps for Femoral Release Before Progressive Broaching in Direct Anterior Approach THA
The sequential femoral releases prior to broaching in direct anterior approach total hip arthroplasty should proceed as follows: (1) removal of the superolateral capsule, (2) release of the transverse iliofemoral ligament, (3) release of the descending iliofemoral ligament, (4) release of the ischiofemoral ligament, (5) release of the conjoint tendon if needed, and (6) release of the obturator externus if additional mobility is required 1, 2.
Understanding the Biomechanical Rationale
The direct anterior approach requires the femur to be positioned in approximately 20° of adduction and 20° of extension to allow broach passage 1. The primary anatomical obstacles are impingement between the broach handle and the anterior superior iliac spine (ASIS) and anterior inferior iliac spine (AIIS) 1. Each sequential release progressively increases femoral external rotation and distraction, which are critical for adequate exposure.
Step-by-Step Release Sequence
1. Superolateral Capsule Removal
- This is performed immediately after acetabular preparation and cup implantation
- Removes the initial constraint to femoral elevation 2
- Allows initial access to the proximal femur
2. Transverse Iliofemoral Ligament Release
- Provides the most significant initial gain in external rotation (average 14.1° ± 6.1°) 1
- Reduces impingement volume from 4.8 cm³ to 1.8 cm³ 1
- This is often the most impactful single release
3. Descending Iliofemoral Ligament Release
- Adds an additional 13.8° ± 5.3° of external rotation 1
- Further reduces impingement volume to 1.2 cm³ 1
- After these first two ligament releases, approximately 71% (10/14) of femurs become accessible for broaching 1
4. Posterior Capsule Release
- Releases the posterior aspect of the capsule to further elevate the femur 2
- Critical for achieving adequate femoral exposure in standard cases
5. Ischiofemoral Ligament Release (if needed)
- Required in cases with limited mobility after the above releases
- Most femurs (10/14) become accessible by this point 1
6. Conjoint Tendon Release (if needed)
- Reserved for cases requiring additional mobility
- Incremental benefit decreases with each subsequent release 1
7. Obturator Externus Release (rarely needed)
- Final release option for particularly challenging exposures
- Provides minimal additional benefit in most cases 1
Critical Technical Points
Variability Between Patients: The number of releases needed varies extensively between specimens—some femurs require only iliofemoral ligament releases while others need more extensive soft tissue work 1. Assess mobility after each release rather than performing all releases routinely.
Avoid Over-Release: Progressive assessment prevents unnecessary soft tissue disruption. After each release, test femoral mobility with external rotation and distraction before proceeding to the next step 1.
Extended Exposure Options: If adequate exposure cannot be achieved with capsular releases alone, consider:
- Distal extension of the incision 3
- Proximal extension of the incision 3
- Extended trochanteric osteotomy for revision cases 3
Common Pitfalls
Premature Broaching: Attempting to broach before adequate releases increases the risk of periprosthetic femoral fracture, which is already elevated with anterior approaches 4. Sequential releases with mobility testing prevent this complication.
Inadequate Posterior Capsule Release: Failure to adequately release the posterior capsule is a common cause of difficult femoral exposure 2. This structure must be released to allow proper femoral elevation.
Nerve Injury Risk: The lateral femoral cutaneous nerve is at risk during the approach, with injury rates of approximately 30% 5. The sequential release technique itself does not significantly increase this risk, but awareness is essential.