Knee Arthroscopy

Portals

 

1.  Anterolateral

 

Viewing portal

- 1cm lateral to patella tendon

- 1cm above joint line

- 1 cm below inferior pole patella

 

Problems

- too medial, in fat pad

- too high, limitation by patella, difficult to see posterior horns

- too low, damage anterior horn meniscus

 

Limitations

- PCL

- anterior horn LM

- posterior horn MM in tight knees

 

2.  Anteromedial

 

Instrumentation portal

- also used for viewing posterior horn MM, anterior horn LM

- 1 cm above joint line

- 1 cm lateral to patella tendon

- 1 cm below inferior pole patella

 

Can be useul to insert needle first

 

3.  Superolateral portal

 

Landmarks

- just lateral to quadriceps tendon

- 2.5 cm above SL corner of patella

 

Uses

- evaluate PFJ

- drainage portal

- resection plicae

- removal loose bodies

 

4.  Posteromedial portal 

 

Must

1.  Have distended the knee with saline so the soft spot bulges

2.  Flex the knee to 90o so NV bundle falls posteriorly

3.  Marked the bony landmarks prior

 

Landmarks

- 1 cm above joint line

- 1 cm posterior to MFC

- flex knee slightly

- introduce needle & then skin incision and blunt dissect to post capsule

- pass switching stick / insert cannula over it

 

Anatomical

- anterior to medial head gastrocnemius

- posterior to MCL / MFC

- superior to pes

 

Uses

- posterior horn tears MM

- loose bodies

- PCL reconstruction / posterior tibial joint line debridement

 

Risks

- saphenous nerve

 

5.  Posterolateral Portal

 

Technique

- distend joint with fluid

- knee at 90o

 

Landmarks

- where posterior margin of femoral cortex intersects posterior aspect of fibula

- 2cm above joint line

- behind LFC

 

Knee Posterolateral Portal

 

Anatomy

- behind LCL

- anterior to lateral head gastrocnemius

- between ITB and biceps

 

Uses

- repair posterior lateral meniscus

 

Risks

- CPN

 

6.  Accessory far medial and lateral portals

 

2.5 cm medial and lateral to standard anterior portals

 

Uses

 

Far medial portal

- gives good access to body of lateral meniscu

- angle is above the tibial spines

 

7.  Central trans-patella portal

 

Landmarks

- midline

- 1cm below inferior pole patella

 

Uses 

- ACL

- OCD

 

Incisions for Inside / Out Sutures or Removal of Loose Bodies

 

Posteromedial incision

 

Placed at the posterior aspect of MFC

- knee in 90° flexion

- 3-4 cm long

- 1/3 of incision above joint line & 2/3 below

- medial head gastrocnemius posterior

- MCL anterior

- infrapatellar branch of saphenous nerve 1 cm above joint line

- avoid saphenous nerve which runs in fat above the sartorius

- open sartorius fascia, retract to protect nerve

- expose capsule

 

Posterolateral incision

 

Centred on joint line

- knee at 90o

- LCL

- biceps inferiorly to protect CPN

- must dissect lateral gastronemius off capsule and retract

- protects posterior neurovascular bundle

 

Complications

 

Incidence

 

Uncommon

- overall < 1%

- NV complications rare

- incidence 0.1%

 

Nerve Injury

 

From incorrect placement of portals

 

Risk reduced by

- correct placement

- use of blunt trocar

 

1.  Infrapatellar branch saphenous nerve

- anteromedial portal

 

2.  Saphenous Nerve

- most commonly injured

- usually from posteromedial portal

- needles during arthroscopic in-out meniscal repair

 

3.  Common Peroneal Nerve

- second most commonly injured

- direct puncture for posterolateral portal

- passage of needles for arthroscopic meniscal repair

- entrapment by sutures of meniscal repair

 

Can be avoided by

- flexion of knee

- direct dissection & identification

- use retractor to deflect needles

 

Tourniquet related Neuropraxia

 

Risk reduced by

 

1.  Minimal duration 

- < 90 min UL 

- < 120 min LL

 

2. Minimal pressure

- < 250 UL

- < 350 LL 

 

3. Adequate cuff width

- > 1.2 limb diameter

 

4. Positioning

- direct pressure on nerve from inappropriate positioning

 

RSD 

 

Uncommon

 

Considered when

- prolonged pain > than expected

- vasomotor disturbance

- stiffness

- trophic changes

 

Compartment Syndrome

 

From extravasation of fluid for distension of joint

- fluid may enter through rupture of synovial pouch

- into thigh through suprapatellar pouch

- into calf through semimembranosus bursa

 

Risk reduced by

- minimise water pressure used

- minimise duration of procedure

- absorbable solution

- minimise number of capsular punctures

- avoid 6/52 post injury

- palpate leg at end of procedure

 

Compartment Syndrome Post ACL Reconstruction

 

Management

- usually will resolve

 

1.  Keep patient asleep

- elevate foot

- compress with eshmarc bandage to remove water

 

2.  Mini incision in fascia

- allows water to escape

- will see muscle is very oedematous

 

3.  Ensure patient has not had vascular injury