High Yield Overview

MINIMALLY INVASIVE POSTERIOR THA

Mini-posterior approach | Arthroplasty

ArthroplastySubspecialty

15Key Steps

5Danger Zones

60-90minDuration

Critical Must-Knows

Primary THA through shortened posterior incision (6-10cm)
POSTERIOR REPAIR of capsule + rotators ESSENTIAL - reduces dislocation to 1-2%
Sciatic nerve posterior to short external rotators - knee flexion protects
Test stability in posterior dislocation position (flexion/adduction/IR)

Examiner's Pearls

"
POSTERIOR REPAIR (capsule + rotators) reduces dislocation from 4-5% to 1-2%
"
SCIATIC NERVE: posterior to short external rotators, knee flexion relaxes it
"
SHORT EXTERNAL ROTATORS: piriformis, gemelli, obturator internus, quadratus femoris - TAG and REPAIR
"
POSTERIOR DISLOCATION POSITION: flexion, adduction, internal rotation - test stability here
"
MIS = 6-10cm incision vs 15-20cm standard - same principles, better visualization technology

Mnemonic

POGO-Q

Piriformis - most superior, key landmark for sciatic nerve

Obturator internus (between gemelli)

Gemelli (superior and inferior)

Obturator externus (deep, below quadratus)

Quadratus femoris - most inferior, protect MCFA deep to it

Mnemonic

REPAIR

Release rotators close to femoral insertion (tag with sutures)

Expose capsule and perform T or L capsulotomy (tag edges)

Prepare bone tunnels in greater trochanter posterior facet

Approximate capsule first with transosseous sutures

Incorporate short external rotators into repair

Reattach to bone through tunnels - creates tension band

Critical Danger Structures

Sciatic Nerve

Posterior to short external rotators. Location: Exits pelvis below piriformis, runs over gemelli and obturator internus, then over quadratus femoris. Protection: KNEE FLEXION relaxes nerve; release rotators at femoral insertion (not proximally); avoid aggressive posterior retraction; maintain awareness during all steps.

Superior Gluteal Neurovascular Bundle

Above piriformis. Location: Exits greater sciatic notch superior to piriformis, courses between gluteus medius and minimus. Protection: Do NOT extend gluteus maximus split more than 5cm above greater trochanter; avoid forceful proximal retraction.

Inferior Gluteal Nerve and Vessels

Below piriformis. Location: Exits below piriformis, supplies gluteus maximus. Protection: Careful dissection near piriformis; avoid blind dissection posterior to rotators; preserve to maintain gluteus maximus function.

Medial Circumflex Femoral Artery

Deep to quadratus femoris. Location: Branch of profunda femoris, passes between quadratus femoris and adductor magnus, supplies femoral head. Protection: Avoid aggressive deep retraction below quadratus femoris; gentle quadratus release if needed.

Femoral Nerve and Vessels

Anterior to hip capsule. Location: Femoral nerve, artery, vein in femoral triangle anteriorly. Protection: Avoid overly anterior acetabular retractor placement; check retractor position during cup insertion; protect with anterior labrum.

Comparison: Minimally Invasive vs Standard Posterior Approach

Feature	MIS Posterior	Standard Posterior
Incision length	6-10cm	15-20cm
Muscle approach	Gluteus maximus split	Same
Rotator management	Tag and repair	Same (essential)
Visualization	Specialized retractors, lighting	Direct
Learning curve	Steeper	Established
Complications	Same when done well	Same
Recovery	Possibly faster early	Standard

Key Points:

Same surgical principles apply to both
Posterior repair ESSENTIAL in both
MIS requires specialized instrumentation
Cosmetic benefit but no proven long-term advantage
Surgeon experience more important than incision length

Evidence:

No significant difference in long-term outcomes
Early recovery advantages debated
Learning curve associated with higher early complication rates

Positioning and Preparation

Patient Position: Lateral decubitus on standard operating table

Setup:

Bean bag or pelvic posts for stable pelvic positioning
Operative leg freely draped for full mobility
Ensure pelvis is truly vertical - affects cup orientation
Arm support and all pressure points padded

Key Considerations:

Pelvic tilt DIRECTLY affects cup orientation measurements
Tilted pelvis causes malpositioned cup if not recognized
Mark bony landmarks before draping (ASIS, GT, posterior iliac spine)
Confirm leg length markers before incision

Operative Technique

Step 1: POSITIONING AND LANDMARKS

POSITIONING: Lateral decubitus with pelvis stabilized by anterior and posterior posts or bean bag. Confirm pelvis is vertical - any tilt affects cup orientation. Operative leg freely mobile for dislocation and manipulation. Mark greater trochanter and intended incision line.

Exam Pearl

Technical Tip: EXAM KEY: LATERAL DECUBITUS is standard for posterior approach. PELVIC TILT directly affects cup position - if tilted anteriorly, measured anteversion will be LESS than actual. Ensure true vertical pelvis positioning.

Dangers at this step

Pelvic tilt causing cup malposition (unrecognized tilt = maloriented cup)
Inadequate stabilization allowing pelvic movement
Pressure injuries from prolonged positioning

Step 2: INCISION AND SUPERFICIAL DISSECTION

INCISION: MIS posterior = 6-10cm (vs 15-20cm standard). Centered over or slightly posterior to greater trochanter. Oblique direction from posterosuperior to anteroinferior, following gluteus maximus fibers. Incise skin and subcutaneous tissue. Identify fascia lata and gluteus maximus fascia.

Exam Pearl

Technical Tip: EXAM KEY: MINI-POSTERIOR = 6-10cm incision. Same surgical principles as standard posterior - just smaller window. Requires specialized retraction and lighting. Do NOT compromise on safety for incision size.

Dangers at this step

Incision too small limiting visualization and increasing tissue trauma
Excessive skin retraction causing edge necrosis
Wrong incision placement compromising exposure

Step 3: GLUTEUS MAXIMUS SPLIT

GLUTEUS MAXIMUS: Incise gluteus maximus fascia in line with muscle fibers. Split gluteus maximus BLUNTLY between fibers - this is muscle-splitting, NOT detachment. Limit split to 5cm above greater trochanter to protect SUPERIOR GLUTEAL NEUROVASCULAR BUNDLE. Insert self-retaining or specialized MIS retractors.

Exam Pearl

Technical Tip: EXAM KEY: GLUTEUS MAXIMUS SPLIT - blunt dissection in line with fibers. Do NOT extend more than 5cm proximal to GT - superior gluteal nerve exits above piriformis and courses between glut med/min. Injury causes Trendelenburg gait.

Dangers at this step

Superior gluteal nerve injury from excessive proximal split
Excessive muscle damage from forceful retraction
Gluteus maximus denervation from inferior gluteal nerve injury

Step 4: IDENTIFY SHORT EXTERNAL ROTATORS

IDENTIFY SHORT EXTERNAL ROTATORS: Expose posterior hip capsule and overlying short external rotators. From superior to inferior: piriformis (key landmark), gemelli with obturator internus between, quadratus femoris. Sciatic nerve exits BELOW piriformis and runs posterior to these muscles.

Exam Pearl

Technical Tip: EXAM KEY: POGO-Q mnemonic for rotators (Piriformis, Obturator internus, Gemelli, Obturator externus, Quadratus). SCIATIC NERVE exits inferior to piriformis in 90% (may split piriformis in 10%). Always know its location.

Dangers at this step

Sciatic nerve injury from blind dissection
Failure to identify correct anatomy
Damage to inferior gluteal nerve and vessels

Step 5: TAG AND RELEASE SHORT EXTERNAL ROTATORS

TAG AND RELEASE ROTATORS: Place tagging sutures in piriformis and conjoined tendon (superior gemellus, obturator internus, inferior gemellus) BEFORE release. Incise rotators close to their femoral insertion (away from sciatic nerve). Protect quadratus femoris if possible (MCFA runs deep to it). Maintain knee flexed to relax sciatic nerve.

Exam Pearl

Technical Tip: EXAM KEY: TAG rotators with sutures BEFORE cutting - this is CRITICAL for repair. Release at femoral insertion, NOT proximally near nerve. Piriformis + conjoined tendon most important for repair. Knee flexion protects sciatic nerve.

Dangers at this step

Inadequate tagging preventing later repair (increases dislocation)
Sciatic nerve injury during rotator release (release close to femur)
MCFA injury with aggressive quadratus release

Step 6: CAPSULOTOMY

CAPSULOTOMY: Expose posterior capsule. Perform T-shaped or L-shaped capsulotomy. TAG capsule edges for repair. Clear capsule from acetabular rim as needed for exposure. The capsule is an important stabilizer - preserve for repair.

Exam Pearl

Technical Tip: EXAM KEY: TAG CAPSULE for repair - capsular repair + rotator repair together reduce dislocation to less than 1-2%. T-capsulotomy: vertical along margin, horizontal at neck. Both capsule AND rotators must be repaired.

Dangers at this step

Failure to tag capsule preventing repair
Excessive capsule excision compromising repair
Injury to labrum affecting press-fit stability

Step 7: HIP DISLOCATION

HIP DISLOCATION: Dislocate hip posteriorly with flexion, adduction, internal rotation. May use corkscrew device in femoral head to control dislocation. Controlled dislocation prevents fracture. Remove femoral head after neck osteotomy if preferred.

Exam Pearl

Technical Tip: EXAM KEY: POSTERIOR DISLOCATION = FLEXION, ADDUCTION, INTERNAL ROTATION. Controlled technique prevents fracture. Some surgeons prefer neck cut in situ then extraction. Corkscrew provides control during dislocation.

Dangers at this step

Uncontrolled dislocation causing soft tissue damage
Femoral neck fracture with forceful dislocation
Acetabular rim fracture with leveraging

Step 8: FEMORAL NECK OSTEOTOMY AND HEAD REMOVAL

FEMORAL NECK OSTEOTOMY: Neck cut with oscillating saw per template. Standard 45° angle from lesser trochanter. Remove femoral head. Excellent visualization of femoral canal is a KEY ADVANTAGE of posterior approach.

Exam Pearl

Technical Tip: EXAM KEY: FEMORAL EXPOSURE is EXCELLENT in posterior approach - major advantage over anterior approaches. Direct visualization of canal for accurate broaching and stem placement. Version typically 10-15° anteversion.

Dangers at this step

Incorrect neck cut level affecting leg length/offset
Femoral calcar fracture during head removal
Inadequate bone removal causing femoral fracture during broaching

Step 9: FEMORAL PREPARATION

FEMORAL PREPARATION: Box osteotome to open canal. Sequential broaching with trial stems. Ensure appropriate version (10-15° anteversion typically). Posterior approach allows direct visualization of canal and version. Confirm stable broach seating before final implant.

Exam Pearl

Technical Tip: EXAM KEY: Femoral version is DIRECTLY visualized in posterior approach - align with posterior femoral condyles as reference. Canal preparation straightforward with direct visualization. Avoid varus or retroversion.

Dangers at this step

Incorrect version (excessive anteversion increases anterior dislocation risk)
Femoral fracture from aggressive broaching
Varus stem positioning from inadequate lateralization

Step 10: ACETABULAR EXPOSURE AND PREPARATION

ACETABULAR EXPOSURE: Retractors around acetabulum - anterior (inferior to ASIS), inferior (in obturator foramen), posterior as needed. Retract femur anteriorly with bone hook or dedicated retractor. Sequential reaming to bleeding subchondral bone. Maintain peripheral rim for press-fit.

Exam Pearl

Technical Tip: EXAM KEY: Femur must be retracted ANTERIORLY for acetabular visualization. Target cup position: 40° ± 10° inclination, 15° ± 10° anteversion (Lewinnek). Combined anteversion (cup + stem) = 25-45° for stability.

Dangers at this step

Cup malposition (most common technical error in THA)
Anterior wall perforation with over-medialization
Femoral nerve injury from aggressive anterior retraction

Step 11: ACETABULAR COMPONENT IMPLANTATION

ACETABULAR IMPLANTATION: Press-fit cup with 1-2mm under-ream. Confirm position before final impaction. Supplemental screws if questionable fixation. Insert liner (polyethylene, ceramic, or dual mobility per plan).

Exam Pearl

Technical Tip: EXAM KEY: Cup orientation by direct visualization or with guides. In lateral decubitus, account for pelvic position. Navigation can improve accuracy if available. Confirm rigid fixation before liner insertion.

Dangers at this step

Cup malposition causing impingement or dislocation
Inadequate press-fit (consider screws if any movement)
Liner malseating

Step 12: FEMORAL COMPONENT IMPLANTATION

FEMORAL IMPLANTATION: Insert final femoral stem (cemented or press-fit per plan). Confirm version and stable seating. Trial head for stability and leg length assessment.

Exam Pearl

Technical Tip: EXAM KEY: Posterior approach allows excellent femoral component insertion. Confirm appropriate version by aligning with posterior condyles. Trial extensively before final head placement.

Dangers at this step

Incorrect version (critical for stability)
Periprosthetic fracture during insertion
Cement extravasation (if cemented technique)

Step 13: TRIAL REDUCTION AND STABILITY TESTING

TRIAL REDUCTION: Reduce hip with trial head. Test stability in ALL positions, especially the POSTERIOR DISLOCATION POSITION - flexion, adduction, internal rotation. This is the position of risk with posterior approach. Assess leg length with contralateral comparison. Confirm adequate soft tissue tension.

Exam Pearl

Technical Tip: EXAM KEY: CRITICAL to test stability in POSTERIOR DISLOCATION POSITION - flexion past 90°, adduction, internal rotation. If unstable: larger head, higher offset, constrained liner, or adjust components. Document stable ROM achieved.

Dangers at this step

Unrecognized instability (will dislocate postoperatively)
Leg length discrepancy (measure carefully)
Over-lengthening (sciatic nerve risk if more than 4cm)

Step 14: FINAL COMPONENTS AND REDUCTION

FINAL COMPONENTS: Insert definitive head. Reduce hip. Final stability check. Confirm leg length and offset acceptable. Irrigate joint thoroughly.

Exam Pearl

Technical Tip: EXAM KEY: Final components should replicate trial findings. Head size affects stability - larger heads (32mm, 36mm) more stable. Adequate offset restores abductor tension and posterior soft tissue tension.

Dangers at this step

Component mismatch from trial
Inadequate irrigation leaving debris
Failure to confirm final stability

Step 15: POSTERIOR REPAIR - CRITICAL STEP

POSTERIOR REPAIR: THE KEY TO MODERN POSTERIOR APPROACH SUCCESS. Create 2-3 drill holes in posterior facet of greater trochanter. Pass transosseous sutures. First repair posterior capsule to bone. Then repair short external rotators (piriformis + conjoined tendon) over capsule as second layer. Creates posterior soft tissue tension band preventing posterior dislocation.

Exam Pearl

Technical Tip: EXAM KEY: POSTERIOR REPAIR = CAPSULE + ROTATORS through bone tunnels. Reduces dislocation from 4-5% to 1-2%. This is THE difference in modern posterior approach. Both layers important - capsule first, then rotators over top.

Dangers at this step

Inadequate repair strength (use transosseous, not soft tissue only)
Failure to repair one or both layers
Trochanter fracture from aggressive drilling

Closure and Post-operative

Closure:

Irrigate wound thoroughly (minimum 3L)
Gluteus maximus fascia reapproximated
Subcutaneous closure with absorbable sutures
Skin closure (staples or subcuticular)
Sterile dressing

Post-operative Care:

Weight bearing as tolerated immediately
Hip precautions 6-12 weeks:
- Avoid flexion more than 90°
- Avoid adduction past midline
- Avoid internal rotation
VTE prophylaxis per institutional protocol
Standard THA rehabilitation pathway

Complications

Minimally Invasive Posterior THA Complications

Complication	Recognition	Prevention	Management
Posterior dislocation (1-2% with repair)	Hip pain, shortened leg, external rotation; X-ray confirms; occurs with flexion/adduction/IR activities	POSTERIOR REPAIR (capsule + rotators); appropriate component position; larger head size (32-36mm); patient education on precautions	Closed reduction under sedation; if recurrent: constrained liner, larger head, revise malpositioned components, or augment with dual mobility
Sciatic nerve injury (0.5-1%)	Foot drop, numbness in sciatic distribution; weak plantarflexion and dorsiflexion; EMG abnormal at 3-4 weeks	Knee flexion during surgery; release rotators at femoral insertion; avoid aggressive posterior retraction; limit lengthening to less than 4cm	Immediate post-op assessment; remove any hematoma if suspected; EMG at 3-4 weeks; most recover with time; foot drop AFO if needed
Superior gluteal nerve injury	Trendelenburg gait; abductor weakness; hip abductor atrophy over time	Limit gluteus maximus split to 5cm above GT; avoid forceful proximal retraction	Physical therapy for abductor strengthening; may be permanent if nerve transected
Femoral fracture (intraoperative)	Sudden give during broaching or stem insertion; visible crack on femur	Appropriate canal preparation; sequential broaching; avoid excessive force; consider cerclage prophylactically in osteoporotic bone	Cerclage wiring; may need longer stem; ORIF if displaced; protected weight bearing
Component malposition	Impingement, instability, limping, leg length discrepancy; abnormal position on X-ray	Careful attention to cup inclination/anteversion; femoral version verification; use navigation if available; intraoperative imaging	Revision of malpositioned component if symptomatic; may require cup and/or stem revision
Infection (1-2%)	Wound drainage, fever, elevated inflammatory markers (CRP, ESR); positive aspiration	Prophylactic antibiotics; laminar flow; minimize traffic; meticulous technique; screen and eradicate S. aureus carriers	Aspiration and culture; DAIR if early; two-stage revision if chronic; antibiotic suppression if not surgical candidate

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

EXAMINER

"You are performing a posterior approach THA. Describe the importance of posterior repair and your technique for performing it."

EXCEPTIONAL ANSWER

Posterior repair of the capsule and short external rotators is THE critical step that has transformed the posterior approach from a high dislocation rate (4-5%) to comparable rates with other approaches (1-2%). My technique: First, I TAG the piriformis and conjoined tendon with sutures BEFORE releasing them at their femoral insertion. After completing the arthroplasty, I create 2-3 drill holes in the posterior facet of the greater trochanter. I then repair in TWO layers - first the posterior capsule is sutured through the bone tunnels, then the short external rotators are repaired OVER the capsule as a second layer. This creates a posterior soft tissue tension band that resists the posterior dislocation vector of flexion, adduction, and internal rotation.

KEY POINTS TO SCORE

Posterior repair reduces dislocation from 4-5% to 1-2%

TAG rotators BEFORE release - piriformis and conjoined tendon

Create bone tunnels in posterior facet of greater trochanter

Repair in TWO layers - capsule first, then rotators over top

Creates tension band resisting posterior dislocation vector

Both layers essential for maximum stability

COMMON TRAPS

✗Failing to tag rotators before release (prevents adequate repair)

✗Only repairing one layer (both capsule AND rotators needed)

✗Soft tissue to soft tissue repair (through-bone is stronger)

✗Skipping repair due to time pressure (this is THE critical step)

LIKELY FOLLOW-UPS

"How do you test stability before closure?"

VIVA SCENARIOStandard

EXAMINER

"How do you protect the sciatic nerve during the posterior approach to the hip?"

EXCEPTIONAL ANSWER

The sciatic nerve is the main neurological structure at risk in the posterior approach. It lies posterior to the short external rotators and exits the greater sciatic notch below the piriformis in 90% of patients. My protection strategies include: First, I keep the KNEE FLEXED throughout the procedure - this relaxes the nerve and reduces stretch injury risk. Second, I release the short external rotators CLOSE TO THEIR FEMORAL INSERTION, keeping the dissection away from the nerve proximally. Third, I avoid aggressive posterior retraction, as the nerve is immediately posterior to the rotators. Fourth, I limit lengthening to less than 4cm, as excessive lengthening significantly increases neuropraxia risk. Finally, I maintain constant awareness of the nerve's location even though I don't formally identify it in every case.

KEY POINTS TO SCORE

Sciatic nerve exits BELOW piriformis (90%) - key anatomical landmark

KNEE FLEXION relaxes the nerve - maintain throughout surgery

Release rotators at FEMORAL INSERTION (away from nerve)

Avoid aggressive POSTERIOR RETRACTION (nerve immediately posterior)

Limit lengthening to less than 4cm (excessive stretch causes neuropraxia)

Injury rate 0.5-1% in primary THA

COMMON TRAPS

✗Stating sciatic nerve exits above piriformis (it exits BELOW)

✗Releasing rotators proximally near the nerve

✗Keeping knee extended (increases nerve tension)

✗Excessive lengthening without considering nerve risk

LIKELY FOLLOW-UPS

"A patient wakes up with foot drop after posterior THA. What is your management?"

VIVA SCENARIOStandard

EXAMINER

"Compare the posterior approach to the direct anterior approach for primary THA. When would you choose each?"

EXCEPTIONAL ANSWER

Both are excellent approaches when performed well. POSTERIOR advantages: Excellent femoral exposure (best of any approach), familiar to most surgeons, versatile for complex anatomy, easier in obese patients. Disadvantages: Requires hip precautions, historically higher dislocation (though with repair now 1-2%). DIRECT ANTERIOR advantages: No muscles cut (internervous interval), lowest dislocation rate (0.5-1%), often no precautions, supine positioning allows intraoperative imaging. Disadvantages: LFCN injury 10-15%, challenging femoral exposure especially in muscular patients, significant learning curve. I would choose POSTERIOR for: revision surgery, dysplastic hips, obese patients, or when I need excellent femoral exposure. I would choose ANTERIOR for: standard primary THA in appropriate body habitus where minimal restrictions are prioritized.

KEY POINTS TO SCORE

Posterior: Excellent femoral exposure, familiar, versatile, works in obesity

Posterior with repair: Dislocation 1-2% (comparable to DAA)

DAA: No muscles cut, lowest dislocation 0.5-1%, no precautions typically

DAA: LFCN injury 10-15%, challenging femoral exposure, steep learning curve

Surgeon experience most important factor in outcomes

Choose approach based on patient factors and surgeon expertise

COMMON TRAPS

✗Claiming one approach is universally superior (both excellent when done well)

✗Ignoring LFCN injury rate with DAA (10-15%)

✗Using old dislocation data for posterior (without repair)

✗Not acknowledging learning curve for DAA

LIKELY FOLLOW-UPS

"A patient specifically requests the anterior approach but you primarily do posterior. What do you discuss?"

Minimally Invasive Posterior THA - Exam Summary

High-Yield Exam Summary

Key Indications

•Primary THA - surgeon preference/expertise
•Revision surgery (excellent femoral exposure)
•Complex anatomy (dysplasia, prior surgery)
•Obese patients (better access than anterior)
•When excellent femoral visualization needed

MIS Posterior Specifics

•Incision: 6-10cm (vs 15-20cm standard)
•Same surgical principles as standard posterior
•Requires specialized retraction and lighting
•Learning curve - don't compromise safety for incision size
•Cosmetic advantage but no proven long-term outcome difference

Short External Rotators - POGO-Q

•Piriformis - most superior, sciatic nerve exits BELOW
•Obturator internus - between gemelli
•Gemelli - superior and inferior
•Obturator externus - deep, below quadratus
•Quadratus femoris - most inferior, MCFA deep to it

5 Danger Zones

•Sciatic nerve - posterior to rotators, knee flexion protects, release at femoral insertion
•Superior gluteal NV bundle - above piriformis, limit split to 5cm above GT
•Inferior gluteal nerve/vessels - below piriformis, supplies gluteus maximus
•MCFA - deep to quadratus femoris, supplies femoral head
•Femoral nerve/vessels - anterior, avoid aggressive anterior retraction

POSTERIOR REPAIR - Critical Step

•Reduces dislocation from 4-5% to 1-2%
•TAG rotators BEFORE release
•Create bone tunnels in GT posterior facet
•Repair capsule FIRST layer
•Repair rotators OVER capsule as second layer
•Creates posterior tension band resisting dislocation

Stability Testing

•Test in POSTERIOR DISLOCATION POSITION
•Position of risk: Flexion, Adduction, Internal Rotation
•Document stable ROM achieved
•If unstable: larger head, higher offset, constrained liner

Sciatic Nerve Protection

•Exits below piriformis in 90%
•KNEE FLEXION relaxes nerve
•Release rotators at femoral insertion (away from nerve)
•Avoid aggressive posterior retraction
•Limit lengthening to less than 4cm

Exam Tips

•POSTERIOR REPAIR = capsule + rotators (both essential)
•Dislocation rate with repair: 1-2% (comparable to DAA)
•Excellent femoral exposure is KEY advantage
•Sciatic nerve injury: 0.5-1% (knee flexion protects)
•Hip precautions: 6-12 weeks (avoid flex/add/IR)
•Pelvic tilt in lateral decubitus affects cup orientation

References:

Pellicci PM, et al. Posterior approach to total hip replacement: results of 526 consecutive cases. J Bone Joint Surg Am. 1998;80(4):519-525.
Kwon MS, et al. Does surgical approach affect total hip arthroplasty dislocation rates? Clin Orthop Relat Res. 2006;447:34-38.
Goldstein WM, et al. Posterior soft-tissue repair in primary total hip replacement. J Bone Joint Surg Am. 2001;83(10):1496-1500.
Berry DJ, et al. Posterior approach THA: comparison with and without soft tissue repair. J Arthroplasty. 2011;26(6 Suppl):132-137.
Chechik O, et al. Surgical approach and prosthesis fixation in hip arthroplasty: a meta-analysis. Hip Int. 2009;19(1):44-48.
Weeden SH, Paprosky WG. Minimal incision total hip arthroplasty: posterior approach. Clin Orthop Relat Res. 2004;429:227-234.
Ogonda L, et al. A minimal-incision technique in total hip arthroplasty does not improve early postoperative outcomes. J Bone Joint Surg Am. 2005;87(4):701-710.
Demos HA, et al. Surgical approach and dislocation rate in primary total hip replacement. J Arthroplasty. 2001;16(2):139-146.
Masonis JL, Bourne RB. Surgical approach, abductor function, and total hip arthroplasty dislocation. Clin Orthop Relat Res. 2002;405:46-53.
Sibia US, et al. Incidence and risk factors for sciatic nerve injury in primary total hip arthroplasty. J Arthroplasty. 2017;32(8):2431-2434.

Comparison: Minimally Invasive vs Standard Posterior Approach

Feature	MIS Posterior	Standard Posterior
Incision length	6-10cm	15-20cm
Muscle approach	Gluteus maximus split	Same
Rotator management	Tag and repair	Same (essential)
Visualization	Specialized retractors, lighting	Direct
Learning curve	Steeper	Established
Complications	Same when done well	Same
Recovery	Possibly faster early	Standard

Key Points:

Same surgical principles apply to both

Posterior repair ESSENTIAL in both

MIS requires specialized instrumentation

Cosmetic benefit but no proven long-term advantage

Surgeon experience more important than incision length

Evidence:

No significant difference in long-term outcomes

Early recovery advantages debated

Learning curve associated with higher early complication rates

Step 1: POSITIONING AND LANDMARKS

Exam Pearl

Dangers at this step

Pelvic tilt causing cup malposition (unrecognized tilt = maloriented cup)
Inadequate stabilization allowing pelvic movement
Pressure injuries from prolonged positioning

Step 2: INCISION AND SUPERFICIAL DISSECTION

Exam Pearl

Dangers at this step

Incision too small limiting visualization and increasing tissue trauma
Excessive skin retraction causing edge necrosis
Wrong incision placement compromising exposure

Step 3: GLUTEUS MAXIMUS SPLIT

Exam Pearl

Dangers at this step

Superior gluteal nerve injury from excessive proximal split
Excessive muscle damage from forceful retraction
Gluteus maximus denervation from inferior gluteal nerve injury

Step 4: IDENTIFY SHORT EXTERNAL ROTATORS

Exam Pearl

Dangers at this step

Sciatic nerve injury from blind dissection
Failure to identify correct anatomy
Damage to inferior gluteal nerve and vessels

Step 5: TAG AND RELEASE SHORT EXTERNAL ROTATORS

Exam Pearl

Dangers at this step

Inadequate tagging preventing later repair (increases dislocation)
Sciatic nerve injury during rotator release (release close to femur)
MCFA injury with aggressive quadratus release

Step 6: CAPSULOTOMY

Exam Pearl

Dangers at this step

Failure to tag capsule preventing repair
Excessive capsule excision compromising repair
Injury to labrum affecting press-fit stability

Step 7: HIP DISLOCATION

Exam Pearl

Dangers at this step

Uncontrolled dislocation causing soft tissue damage
Femoral neck fracture with forceful dislocation
Acetabular rim fracture with leveraging

Step 8: FEMORAL NECK OSTEOTOMY AND HEAD REMOVAL

Exam Pearl

Dangers at this step

Incorrect neck cut level affecting leg length/offset
Femoral calcar fracture during head removal
Inadequate bone removal causing femoral fracture during broaching

Step 9: FEMORAL PREPARATION

Exam Pearl

Dangers at this step

Incorrect version (excessive anteversion increases anterior dislocation risk)
Femoral fracture from aggressive broaching
Varus stem positioning from inadequate lateralization

Step 10: ACETABULAR EXPOSURE AND PREPARATION

Exam Pearl

Dangers at this step

Cup malposition (most common technical error in THA)
Anterior wall perforation with over-medialization
Femoral nerve injury from aggressive anterior retraction

Step 11: ACETABULAR COMPONENT IMPLANTATION

Exam Pearl

Dangers at this step

Cup malposition causing impingement or dislocation
Inadequate press-fit (consider screws if any movement)
Liner malseating

Step 12: FEMORAL COMPONENT IMPLANTATION

FEMORAL IMPLANTATION: Insert final femoral stem (cemented or press-fit per plan). Confirm version and stable seating. Trial head for stability and leg length assessment.

Exam Pearl

Dangers at this step

Incorrect version (critical for stability)
Periprosthetic fracture during insertion
Cement extravasation (if cemented technique)

Step 13: TRIAL REDUCTION AND STABILITY TESTING

Exam Pearl

Dangers at this step

Unrecognized instability (will dislocate postoperatively)
Leg length discrepancy (measure carefully)
Over-lengthening (sciatic nerve risk if more than 4cm)

Step 14: FINAL COMPONENTS AND REDUCTION

FINAL COMPONENTS: Insert definitive head. Reduce hip. Final stability check. Confirm leg length and offset acceptable. Irrigate joint thoroughly.

Exam Pearl

Dangers at this step

Component mismatch from trial
Inadequate irrigation leaving debris
Failure to confirm final stability

Step 15: POSTERIOR REPAIR - CRITICAL STEP

Exam Pearl

Dangers at this step

Inadequate repair strength (use transosseous, not soft tissue only)
Failure to repair one or both layers
Trochanter fracture from aggressive drilling

Complication

Recognition

Prevention

Management

Posterior dislocation (1-2% with repair)

Hip pain, shortened leg, external rotation; X-ray confirms; occurs with flexion/adduction/IR activities

POSTERIOR REPAIR (capsule + rotators); appropriate component position; larger head size (32-36mm); patient education on precautions

Closed reduction under sedation; if recurrent: constrained liner, larger head, revise malpositioned components, or augment with dual mobility

Sciatic nerve injury (0.5-1%)

Foot drop, numbness in sciatic distribution; weak plantarflexion and dorsiflexion; EMG abnormal at 3-4 weeks

Knee flexion during surgery; release rotators at femoral insertion; avoid aggressive posterior retraction; limit lengthening to less than 4cm

Immediate post-op assessment; remove any hematoma if suspected; EMG at 3-4 weeks; most recover with time; foot drop AFO if needed

Superior gluteal nerve injury

Trendelenburg gait; abductor weakness; hip abductor atrophy over time

Limit gluteus maximus split to 5cm above GT; avoid forceful proximal retraction

Physical therapy for abductor strengthening; may be permanent if nerve transected

Femoral fracture (intraoperative)

Sudden give during broaching or stem insertion; visible crack on femur

Appropriate canal preparation; sequential broaching; avoid excessive force; consider cerclage prophylactically in osteoporotic bone

Cerclage wiring; may need longer stem; ORIF if displaced; protected weight bearing

Component malposition

Impingement, instability, limping, leg length discrepancy; abnormal position on X-ray

Careful attention to cup inclination/anteversion; femoral version verification; use navigation if available; intraoperative imaging

Revision of malpositioned component if symptomatic; may require cup and/or stem revision

Infection (1-2%)

Wound drainage, fever, elevated inflammatory markers (CRP, ESR); positive aspiration

Prophylactic antibiotics; laminar flow; minimize traffic; meticulous technique; screen and eradicate S. aureus carriers

Aspiration and culture; DAIR if early; two-stage revision if chronic; antibiotic suppression if not surgical candidate

Feature	Posterior	DAA
Dislocation rate	1-2% (with repair)	0.5-1%
Muscle cut	Short external rotators	None (internervous)
Femoral exposure	Excellent	Challenging
Acetabular exposure	Good	Good
Learning curve	Established	Significant
LFCN injury	Rare	10-15%
Fluoroscopy	Optional	Commonly used
Hip precautions	6-12 weeks	Often none
Surgeon positioning	Lateral decubitus	Supine
Obese patients	Feasible	Challenging

Feature	Posterior	DAA
Dislocation rate	1-2% (with repair)	0.5-1%
Muscle cut	Short external rotators	None (internervous)
Femoral exposure	Excellent	Challenging
Acetabular exposure	Good	Good
Learning curve	Established	Significant
LFCN injury	Rare	10-15%
Fluoroscopy	Optional	Commonly used
Hip precautions	6-12 weeks	Often none
Surgeon positioning	Lateral decubitus	Supine
Obese patients	Feasible	Challenging

Minimally Invasive Posterior THA

MINIMALLY INVASIVE POSTERIOR THA

Critical Must-Knows

Examiner's Pearls

POGO-Q

REPAIR

Critical Danger Structures

Sciatic Nerve

Superior Gluteal Neurovascular Bundle

Inferior Gluteal Nerve and Vessels

Medial Circumflex Femoral Artery

Femoral Nerve and Vessels

Comparison: Minimally Invasive vs Standard Posterior Approach

Posterior Soft Tissue Repair - The Key to Modern Success

Posterior vs Direct Anterior Approach

Preventing Posterior Dislocation

Protecting the Sciatic Nerve

Positioning and Preparation

Operative Technique

Step 1: POSITIONING AND LANDMARKS

Dangers at this step

Step 2: INCISION AND SUPERFICIAL DISSECTION

Dangers at this step

Step 3: GLUTEUS MAXIMUS SPLIT

Dangers at this step

Step 4: IDENTIFY SHORT EXTERNAL ROTATORS

Dangers at this step

Step 5: TAG AND RELEASE SHORT EXTERNAL ROTATORS

Dangers at this step

Step 6: CAPSULOTOMY

Dangers at this step

Step 7: HIP DISLOCATION

Dangers at this step

Step 8: FEMORAL NECK OSTEOTOMY AND HEAD REMOVAL

Dangers at this step

Step 9: FEMORAL PREPARATION

Dangers at this step

Step 10: ACETABULAR EXPOSURE AND PREPARATION

Dangers at this step

Step 11: ACETABULAR COMPONENT IMPLANTATION

Dangers at this step

Step 12: FEMORAL COMPONENT IMPLANTATION

Dangers at this step

Step 13: TRIAL REDUCTION AND STABILITY TESTING

Dangers at this step

Step 14: FINAL COMPONENTS AND REDUCTION

Dangers at this step

Step 15: POSTERIOR REPAIR - CRITICAL STEP

Dangers at this step

Closure and Post-operative

Complications

Minimally Invasive Posterior THA Complications

Exam Viva Scenarios

Minimally Invasive Posterior THA - Exam Summary

Key Indications

MIS Posterior Specifics

Short External Rotators - POGO-Q

5 Danger Zones

POSTERIOR REPAIR - Critical Step

Stability Testing

Sciatic Nerve Protection

Exam Tips

Minimally Invasive Posterior THA

MINIMALLY INVASIVE POSTERIOR THA

Critical Must-Knows

Examiner's Pearls

POGO-Q

REPAIR

Critical Danger Structures

Sciatic Nerve

Superior Gluteal Neurovascular Bundle

Inferior Gluteal Nerve and Vessels

Medial Circumflex Femoral Artery

Femoral Nerve and Vessels

Comparison: Minimally Invasive vs Standard Posterior Approach

Posterior Soft Tissue Repair - The Key to Modern Success

Posterior vs Direct Anterior Approach

Preventing Posterior Dislocation

Protecting the Sciatic Nerve

Positioning and Preparation