MEDIAL PATELLOFEMORAL LIGAMENT RECONSTRUCTION Dr.T.K.Byakika Orthopaedic consultant & Adjunct Professor JKUAT COHES

Introduction The medial Patellofemoral ligament(MPFL) is the primary ligamentous restraint against lateral patella displacement It is the primary soft issue restraint to lateral patella displacement in early flexion The MPFL provides 50-60% of the medial soft tissue resistance to lateral dislocation of the patella Patella dislocations therefore usually result in injury to the medial retinacular ligaments Competence of the MPFL is necessary and sufficient to restore lateral patellar mobility to a normal range

ANATOMY 3 layers of the capsuloligamentous structures on medial aspect of the knee MPFL and superficial medial collateral ligament in layer 2 The MPFL runs transversely from the proximal half of the medial patella border to the femur near the medial epicondyle(saddle between the epicondyle and the adductor tubercle) Patella attachment is wider than the femoral attachment, approximates upper 1/3 MPFL acts as a check rein restraint from lateral deviation of the patella

ANATOMY As knee progresses into flexion, patellofemoral congruence and trochlear geometry,especially the slope angle of the lateral trochlear facet, provide the major restraints to lateral patellar displacement

Indications Non-operative treatment is indicated for acute first time dislocators without associated osteochondral fractureS or loose body Surgical intervention Recurrent patella instability(x2) Ostechondral fracture or a loose body Smaller isolated chondral injuries(mechanical symptoms)

IDEAL CANDIDATE Trochlear morphology normal or type A dysplasia Tibial tuberosity-trochlear sulcus angle of 0 to5 degrees valgus or a tibial tuberosity trochlear groove distance less than 20mm with the knee at 0 degrees flexion No excessive increase in the patellar height ratio(Caton-Deschamps index <1.2, or Insall-Salvati index < 1.4 Patellar tilt < 20degrees

Pertinent Imaging Plain X-rays, identify avulsion #s, loose bodies, patella alta &trochlea dysplasia Computed tomography(CT) Stress radiography MRI, location and extent of medial soft tissue injury, can also identify osteochondral injuries on the patella and femur plus loose bodies that may be missed on plain xrays

Important Imaging considerations for preop planning Patellar height Caton and Deschamps, 1.2 or > patella alta > 1.2 consider Tibial tubercle osteotomy and distalisation as additional procedure Tibial tubercle-trochlear groove(TT-TG) distance When latersl offset measures 20mm or more, nedialistion of the TT can be considerd Trochlea morphology Assessed on true lateral x-ray

Pertinent physical findings Patellar translation: Knee flexed to 30 degrees, lateral patella translation greater than 10mm = laxity Patella apprehension

Basic principles Numerous techniques Free tendon autografts , gracilis, semitendinosus Attachment sites selected on basis of the anatomy of the native MPFL Open repair techniques outperform arthroscopic ones Proper tensioning of the MPFL critical. Intraoperatively the knee should easily flex to 90 degrees, avoid overtightening

Basic principles Graft should have similar stiffness but greater strength than the native MPFL= GRACILIS Incisions, single or 2 separate ones, oblique, transverse or longitudinal Fixation to the patella with bone anchors, bone tunnels 2 strands upper is at superomedial corner of the patella and at or just distal to the junction of the upper and medial 1/3 of the medial border of the patella If bone tunnels then be careful to avoid fractures

Basics The femoral attachment site can be referenced from the medial femoral epicondyle, 10mm proximal and 2mm posterior or from the adductor tubercle 4mm distal and 2mm anterior. Or use fluoroscopy/true lateral view KEY POINT IS TO REPRODUCE THE NORMAL TIGHTENING OF THE LIGAMENT IN EXTENSION AND RELAXATION IN FLEXION. It acts as a check rein in early flexion(0-30 degrees) so under greatest tension so can lead to painful restriction of knee flexion and articular cartliage overload on the medial half of the patellofemoral compartment

Basics Practical point is to insert a k wire, tie the ends of the graft Then cycle knee through flexion and extension as assess movement of the graft Fix the graft with knee at 30-40 degrees Don’t pull patella medially but prevent lateral translation beyond the lateral margin of the trochlear Fixation to femur, suture anchor, interference screw, endobuttons.

Procedure A gracilis autograft, whip stitched 1cm at each end Make a 2cm incision on the medial patella aspect Drill 2.4mmtip guide to 25mm, 2nd one 15-20mm below, overdrill guide pins with 4.5mm drill to 25mm Pass the tails through the eyelet of a 4.75mm swivel lock and push into proximal hole until eyelet is fully seated, screw swivel lock anchor into patella. Put in the 2nd distal swivel lock The femoral insertion is very important to maintain proper biomechanics through out the entire ROM.

Procedure Examination under anaesthesia to confirm excessive lateral patellar mobility,>10mm lateral translation and the absence of an endpoint with knee at 30begrees of flexion Harvest tendon graft and prepare it

Postoperative management Active quadriceps exercises between 0 and 90 degrees of flexion at postoperative day one Knee brace 6/52 PWB with crutches FROM after 6/52 Full activity at 12 weeks

results 3 patients with new technique 2 female and one male Age range 29-34 History of trauma Initial satisfactory outcomes( preliminary) One with symptomatic hardware

TOP TECHNICAL PEARLS FOR THE PROCEDURE Surgical management for at least 2 documented patellar instability events and a confirmatory physical examination demonstrating excessive lateral patella laxity Femoral tunnel placement is one of the most critical steps in the operation Adjust the tunnel placement to ensure appropriate graft behaviour during flexion and extension recreating isometry Check for accurate tunnel placement using flouroscopy Set the MFFL graft length without tension Avoid excessive medial constraint by ensuring the graft is not tight Post op motion preservation is key after MPFL reconstruction

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