What are the layers of muscles exposed during a posterior approach for bipolar hemiarthroplasty in an elderly patient with an intracapsular neck of femur fracture?

Muscle Layers Exposed During Posterior Approach for Bipolar Hemiarthroplasty

The posterior approach for bipolar hemiarthroplasty exposes muscles in the following sequence: gluteus maximus (split along fiber direction), short external rotators (piriformis, superior and inferior gemelli, obturator internus), and finally the hip capsule which is incised in a T-shaped fashion. 1

Step-by-Step Anatomical Dissection

1. Superficial Layer: Gluteus Maximus

• The gluteus maximus is split along its fiber direction rather than being detached, which preserves muscle integrity and facilitates closure 1
• This muscle splitting technique minimizes tissue trauma and bleeding during the approach 1

2. Deep Layer: Short External Rotators

• The short external rotators are encountered next and include the piriformis, superior gemellus, obturator internus, and inferior gemellus muscles 2, 3
• Traditional technique involves detaching these muscles from their femoral insertion 2
• Modified approaches preserve these short external rotators to reduce dislocation risk, which is particularly important given that posterior approach historically carried higher dislocation rates 2, 3

3. Hip Capsule

• The hip capsule is incised in a T-shaped fashion to expose the fracture site 3
• This capsular incision provides adequate visualization for femoral neck osteotomy and prosthesis insertion 1

Critical Technical Considerations for Dislocation Prevention

Meticulous capsular repair is essential to minimize dislocation risk, as the posterior approach has been associated with higher dislocation rates in elderly patients, particularly those with neurological or cognitive impairment 1, 4, 5

Enhanced Repair Technique

• Capsular-enhanced repair using suture anchors significantly reduces postoperative dislocation rates 3
• The posterior hip capsule and short external rotators should be meticulously repaired after prosthesis implantation 3
• Studies demonstrate 0% dislocation rates with modified short external rotator-sparing approaches compared to 7.7% with standard techniques 2

Important Caveats

• While the 2022 AAOS guidelines state that current evidence does not show outcome differences between surgical approaches (anterior, lateral, or posterior), this applies to the general population 6
• In high-risk patients with neurological or cognitive impairment, surgeons should strongly consider avoiding the posterior approach due to documented increased dislocation risk in this specific subgroup 4, 5
• The posterior approach was associated with all cases of dislocation in neurologically or cognitively impaired patients in case series 4

Closure Sequence

Closure proceeds in reverse order: capsule repair first (with or without suture anchors), then short external rotator reattachment, and finally gluteus maximus approximation 3