SRI SIDDHARTHA MEDICAL COLLEGE,TUMKUR DEPARTMENT OF ORTHOPAEDICS

SRI SIDDHARTHA MEDICAL COLLEGE,TUMKUR DEPARTMENT OF ORTHOPAEDICSTopic:DYNAMIC MEDIAL PATELLOFEMORAL LIGAMENT RECONSTRUCTION IN RECURRENT PATELLAR INSTABILITY:A surgical technique

Moderator:Prof. Dr. J.K ReddyDept. of Orthopaedics

Presenter:Dr. Jaipalsinh MahidaJr. Resident M.S Ortho Dept. of Orthopaedics

Introduction:Recurrent patellar instability is common after a primary episode of traumatic patellofemoral dislocation. There is damage to the MPFL in almost all cases of traumatic patellofemoral dislocationDislocation is a result of anatomical abnormalities and/or insufficient soft tissue restraints. Medial patellofemoral ligament (MPFL) is the main soft tissue restraint to lateral patellar translation.Non-surgical approaches have been advocated to treat acute patellar dislocation , while many operative procedures proximal realignment, distal realignment, combined realignment, lateral retinacular release and MPFL reconstruction are designed to treat chronic / recurrent patellar dislocations.

Graft anchorage, viability and anisometry of reconstruct play an important role in outcomes of the procedure.MPFL reconstruction has been recommended in adults over the past decade after recurrent patellar instability.In present study MPFL reconstruction using hamstring graft in a dynamic pattern performed successfully in four patients. Kujala score and Crosby and Insall outcome rating scale used to evaluate outcome with follow up upto 24 months.

Anatomy:Static stabilizers: Are primary stabilizers of patella shape of patella, femoral sulcus, patellar tendon of appropriate length, and normally tensioned medial capsule reinforced byMedial patellofemoral ligament and patellotibial ligaments. Dynamic stabilizer vastus medialis obliquus stabilizes the patella against lateral pull of vastus lateralis.

Biomechanics:Stability and normal tracking of the patella with knee flexion requires a complex coordination of static and dynamic stabilizers. From 0 to 30 of the knee flexion, medial patellofemoral ligament and other soft tissue are primary restraints to lateral patellofemoral dislocation. With the greater knee flexion, the bony confines of the lateral femoral condoyle and trochlear groove captures the patella and patellar stability.

PathoAnatomy: H. dejour classification

These underlying pathologies predispose to an acute over load of soft tissue stabilizers and rupture of MPFL with patellar dislocation following minimal trauma. Primary instability factorsTrochlear dysplasiaPatella alta Patella tilt TT-TG distance(q angle quantification by CT scan)Secondary instability factorsExcessive external femoral rotation / Excessive femoral ante versionExcessive external tibial rotationGenu valgumGenu recurvatum

Evaluation:

We evaluate the following features:-Integrity of medial patello femoral ligamentHeight of patella on physical and radiographic examinationLength of patellar tendonPosition of patella in relationship to trochlea

Physical examination:

gaitstanding alignmentQ angle:- for males : mean Q angle is 10 - for females : mean Q angle is 155 - q angle leads to relative lateral shift of patella Q angle results from - femoral external rotation - external rotation - genu valgum - tibia vara

J sign: Observe the movement of the patella during active knee extension, lateral subluxation of the patella as the knee approaches full extension is indicative of j sign positive. Positive j sign indicates Increase lateral force or Increase Qangle.

Apprehension test : Patella pushed laterally in 200 - 300 of flexion

Laxity: patellar translation is assessed by passively moving patella medially and laterally with knee at 0 and 30 of flexion, the amount of translation is quantified in quadrants. Normal glide is one but more than two quadrants indicates laxity.

Patellar tilt: it is done with knee in full extension normally patella can be tilted so that the lateral edge is well anterior to the medial edge.Inability to do this indicates lateral retinacular tightness.

rotational malalignment:Measured by the relationship of the transmalleolar axis to the Coronal axis of the proximal tibia, is typically neutraltibial torsion also may be assessed through measurement of the thigh-foot angle, average values are 5internalIt leads to Increase Q angle and Increase TT-TG distance

excessive femoral ante version:measured by hip rotations with the patient in prone position with hips extended and knees at 90of flexionNormal range of hip rotations are about 45. With femoral antevertion range of internal rotation increases and range of External Rotation reduced.It leads to Increase Q angle and Increase TT-TG distance

Radiographic evaluation:long standing weight bearing hip-to-ankle, A.P view: helps in assessing the angular deformity of knee i.e. genu varum and genu valgum

Lateral view with 30 of knee flexion:Insall-salvati ratio: normal value: 1.0 to 1.2value indicates: patella alta: When patella alta is present, the patella becomes engaged with greater degrees of knee flexion, where the patella is not captured and it is at increased risk for instability.

Lateral view with 30 of knee flexion: For trochlear dysplasia:Crossing sign: When anterior cortical outline of condyle intersects trochlear outline, indicates dysplastic sulcus. Double contour(Trochlear bump) : When trochlear line extends anterior to femoral cortex.

Merchants view: tangential axial view of patellofemoral joint obtained with knee in 45 of flexion.Sulcus angle: normal angle : 140, if > 140 : trochlear dysplasia

Congruence Angle: normal : -8 to +14, if >14 indicates lateral subluxation.

Lateral Patello Femoral Angle(Laurin Angle): normal: angle opens laterally, abnormal: angle opens medially or lines become parallel.

CT scan evaluation: Helps in assessing the bony anatomy and architecture of patellofemoral joint at different angles of knee flexion. The protocol includes mid-axial images obtained from 0to60 of flexion in 10 of increments. Is quantification of Q angle. TT-TG distance : normal measures are 2to 9 mm , borderline measures are 10to 19 mm, pathological > 20Sulcus angleCongruence angleTrochlear depth

MANAGEMENT OF PATELLO FEMORAL INSTABILITY:

Types of patellar dislocationsAcute patellar dislocations: Results from high energy transfer, where anatomy of joint is normal. Results from internal rotation of femur on a fixed externally rotated tibia. Major sequelae of acute patellar dislocation is tear of medial patellofemoral ligament (MPFL). most acute dislocations are treated non-operatively unless associated with an osteochondral injury. When surgery is needed MPFL is repaired / reconstructed

Chronic / recurrent patellar dislocations: condition where patellar dislocation had occurred at least twice, or where patellar instability following initial dislocation had persisted for more than three months. A large number of procedures have been described to treat recurrent patellar dislocations. No single surgery is universally successful in correcting the chronic patellar instability. We need to customize surgery based on the knee problem. Our approach is to identify the underlying problem that cause the patellofemoral instability and systemically correct them.

The surgical procedures are classified into:Proximal Realignment Of Extensor Mechanism:Lateral retinacular releaseMedial plication/ reefingVastus Medialis Obliquus advancementMedial PatelloFemoral Ligament reconstructionDistal Realignment Of Extensor Mechanism:Medial or antero medial displacement of tibial tuberosity

MEDIAL PATELLO FEMORAL LIGAMENT RECONSTRUCTION:

The procedures like medial plication, vastus medialis obliquus advancement, and lateral retinacular release are non anatomic procedures. They dont address the principle of pathology in recurrent patellar dislocation. MPFL is the primary soft tissue passive restraint to pathologic lateral patellar dislocation, and MPFL is torn when patella dislocates, hence reconstruction of MPFL is done in an attempt to restore its function.Anatomy of medial patellofemoral ligament

MPFL arises from medial surface upper two thirds of patella above equator and inserts into a groove between adductor tubercle and medial epicondyle

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Indication: skeletally mature patient, excessive lateral laxity normal trochlea, Q angle is normal, TT-TG distance is < 20mm, low grade trochlear dysplasia.Contraindications: skeletally immature patients.Scottle radiographic landmark:for femoral tunnel placement on MPFL reconstruction.

2 perpendicular lines drawn to line 1. Line 2 is medial condyleLine 3 is blumensaat line.26

PostOperative Care: knee joint is immobilized in extension with a simple knee brace for 3 days after surgery. Range-of-motion exercises and gait with weight bearing on two crutches are started and gradually progressed. Weight bearing is allowed as tolerated immediately after surgery. Walking with full weight bearing usually is possible 2 or 3 weeks after surgery. Extension during walking is maintained with a knee brace for 6 weeks. Achieving at least 90 degrees knee flexion by the end of postoperative week 3 is encouraged. Jogging is allowed after 3 months, and participation in the original sporting activity is allowed 6 months after surgery, depending on the patient.

Present study:based on the fixation techniques MPFL reconstruction procedures can be broadly classified into: Static:on either side graft is fixed rigidly at isometric points of parent MPFL with staples or interference screws or anchors in bony tunnelsDynamic:graft is secured to soft tissue at isometric points either on one or both sides with sutures.Advantage of dynamic reconstructs over static greater chances of accommodation in length all through the range of motion of knee thus bringing down the peak pressure on patellofemoral joint during flexion.The drawbacks of dynamic reconstruction: weak anchorage leading to chances of failure and other complications of their own depending on the procedure.

In present study they performed MPFL reconstruction procedure in four consecutive patients with chronic patellar instability following trauma. MPFL reconstruction was done with hamstring tendons detached distally and secured to patellar periosteum after being passed through a bony tunnel in the patella without an implant and using the medial collateral ligament as a pulley. In all 4 knees, the MPFL reconstruction was isolated and was not associated with any other realignment procedures.

Operative procedure:

A diagnostic arthroscopy was performed in all patients before starting reconstruction. The ipsilateral gracilis and semitendinosus tendon is freed from its attachment distallyCare must be taken not to detach the tendon from its muscle and not to strip the periosteum of the proximal tibial tubercle. The distal ends of tendons are to be reefed for control to redirect the tendons. The coupled tendon diameter is to be measured with a graft sizer.

Medial collateral ligament pulley: In 30-45 of knee flexion, a 2-3 cm longitudinal skin incision was made in the area of the medial epicondyle and the adductor tubercle. The proximal attachment of the medial collateral ligament (MCL) was identified and its posterior one-third of the superficial layer was elevated without disturbing its attachment distally or proximally. The free ends of both the tendons were passed subcutaneously beneath the fascia but superficial to the joint capsule and then redirected from underneath this MCL sling gaining a pulley effect [Figure 6(a)].

Fixation of graft to patella: 2 cm anterior skin incision was made over the central part of the medial border of the patella. A small periosteal flap was cut to expose the medial border of the patella. A guide wire was passed through the patella directing superolaterally under fluoroscopic control. Approximate reamer size of graft diameter was passed over the guidewire to drill a tunnel through the thickness of the patella. The two free ends were passed subcutaneously beneath the fascia and into the patellar tunnel medio-laterally with the patella reduced into the trochlea at 30 of knee flexion.The appropriate tension in graft was gained in this position; the grafts were then sutured to the fascia and periosteum over the patella [Figure 6(b)]. Before completing the procedure, the patellar tracking and stability was judged clinically and arthroscopically through the range of motion of the knee.

Postoperatively:knee brace locked in extension and weight bearing as tolerated with crutches until pain and swelling had resolved. Use of the brace was continued until the quadriceps strength returned to Grade 4 (usually first 2 weeks postoperatively). From 2nd - 5th week, early range of motion by use of physical therapy and continuous passive motion was prescribed. During this period full weight bearing with a hinged bracelocked between 0 and 90 was advised. After 6 weeks, free activity was allowed without brace. Controlled sports activities after 3 months and contact sports after 6 months were allowed.

Discussion:

In this series, gracialis and semitendinosis are used in a dynamic fashion. By preserving the proximal attachments other major issues such as viability, anisomery and optimal tension in various positions through the range of motion can be achieved which finally judge the final outcome.

Deie et al in his series used single hamstring graft without disturbing its distal attachment for reconstruction by passing it through posterior one-third of superficial part of MCL at its proximal attachment, patellar attachment was secured by fixing the graft into the tunnel at level of superiomedial pole of the patella with a biotenodesis screw.

Fink et alzl used quadriceps tendon after stripping its proximal attachment at desirable length, the graft is then fixed on femoral isometric point with an interference screw after dissecting the tendon distally over the patella keeping it attached to the patella and rotating it 90 medially underneath the medial prepatellar tissue.

Panagopoulos et al in his series used similar technique used by Deie et al. but used medial intermuscular septum at the adductor magnus insertion at pulley on the femoral side instead of MCL.

Rehabilitation protocol was designed keeping in mind tendon to bone tunnel healing. The initial graft to fascia suturing heals in 2-3 weeks hence knee range of motion exercises are started. The bone to tendon incorporation starts at 2 weeks, takes reasonable good loads at 12 weeks and is completed by 26 weeks. In present cases, sports activities were allowed at 3 months and activities resembling contact sports causing greater loads on patellofemoral joint were started at 6 months so as not to compromise graft anchorage.

Conclusion:Preliminary results indicate that MPFL reconstruction using an autologous hamstring graft is a simple, implant free, cost effective procedure with little associated donor site morbidity and good preliminary outcomes; it greatly helps in preventing further episodes of patellar subluxations or dislocations and in improving quality of life. Further clinical studies are needed to confirm these early results

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