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Patella stabilisation – Tibial tubercle osteotomy and Medial patellofemoral ligament reconstruction

    Overview

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    In cases of recurrent patella instability, and once maximal non-operative management has been exhausted, a surgical stabilisation is indicated.
    The non operative interventions to be explored are covered in the indications section. There are a number of operations for patella stabilization which have been used over the years, although more recently realignment of the patella with a tibial tubercle osteotomy (TTO) most commonly to distalise and medalise associated with reconstruction of the medial patellofemoral ligament (MPFL) have become the most popular. Sometimes these are used together and occasionally there is a need for Vastus Medialis advancement (as described by Insall) in addition.
    Combining the TTO and the MPFL reconstruction poses potential problems for incision placement, but my strategy is to use a single anterior longitudinal incision allowing for both the TTO and the hamstring harvest, but with a longer incision than normally used for performing a TTO.

    Indications

    INDICATIONS
    The indication for surgery is recurrent patella dislocation, with failure of non-operative treatment. Non-operative treatment includes using a patella wrap splint and formal physiotherapy.
    This is the case of a 23 year old female with recurrent patella dislocation and hypermobility
    Following MRI scanning a diagnosis of patella alta and lateral patella tracking was made.
    SYMPTOMS & EXAMINATION
    Evidence of generalised hyper mobility with a Beighten score of 7/9
    This patient was a chronic dislocator so there we no manifestations of acute or sub-acute patella dislocation such as superomedial bruising and tenderness, at the origin and insertion of the MPFL. However there was apprehension to lateral translation, with >50% translatability of the patella laterally.
    The patella was very high clinically, with 3 finger breaths from inferior pole to tubercle; consequently the patellae were very prominent.
    Assessment of overall stance, gait and musculature revealed good core stability, reasonable gluteus control (negative Trendelenburg), reasonable quads musculature and hamstrings not tight (popliteal angle of 5 degrees)
    IMAGING
    The imaging should start simply with plain Xrays, ideally including alignment views, as excessive valgus particularly may play a role in lateral patella dislocation.
    MRI scan – Ideally this should be on a standard MRI coil, not a dedicated knee coil as this flexes the knee slightly which alters the measurement of patella indices. The most important findings were minimal patella-trochlea overlap in full extension, evidence of recent bone marrow oedema in keeping with recent recurrent patella dislocation and a tibial tubercle trochlea groove (TTTG) of 20mm. This indicates that the patella needs to travel from medial to lateral during a flexion arc as the trochlea is more medial than the tibial tubercle. Caution must be made however during measurement of the TTTG with trochlea dysplasia. Dysplasia of the trochlea is manifest by lateral dominance (relative to the length of the medial trochlea) absence of a trochlea groove (DeJour grading) and a short trochlea cranio-caudally.
    ALTERNATIVE OPERATIVE TREATMENT
    Isolated TTO
    There are many variations on this technique with eponymous names such as the Elmslie-Trillat where there is an isolated sliding of the tibial tubercle medially, or modifications such as the Roux-Goldthwaite where half to the patella tendon and tibial tubercle are rotated around the remaining half insertion of the tubercle. However like many eponymous techniques it is safer to think in terms of a generic procedure of tubercle osteotomy and to realign the patella in the direction to correct the anatomical abnormalities measured from the imaging.
    Isolated MPFL reconstruction
    This is a very useful technique when there has been a traumatic dislocation which becomes recurrent and the anatomy is relatively normal.

    NON-OPERATIVE MANAGEMENT
    This must be completed:
    Physiotherapy assessment and rehabilitation with gluteus and core control, quads strengthening. Consideration of taping.
    Patella wrap splints in acute dislocations to encourage early mobility of the knee , by providing a lateral patella bolster to aid patient confidence.
    Avoid knee extension splints in view of loss of quads.

    CONTRAINDICATIONS
    Poor compliance with physiotherapy
    Active infection
    Concern over poor patient compliance with rehabilitation.

    Setup

    General anaesthesisa
    Preoperative IV Antiobiotics
    My personal preference is to avoid a tourniquet, but this certainly may be used according to surgeon preference.
    Side support relatively high allowing for the superolateral portal
    Foot roll at approximately 70 degrees knee flexion, heels over the end of the bed.
    Foot pump on the contra-lateral foot.
    Social wash and then 2% chlorhexidine in alcohol preparation and standard arthroscopic draping with an exclusion U-drape, additional large drape around the end of the operating table and then a pouched knee arthroscopic drape – caution on large pouches which can drag down low and risk de-sterilisation.

    Operation – 1

    Free draping of the operative limb, with the knee flexed to approximately 70 degrees by using a thigh support and foot holder.
    Arthroscope, suction, coblator available. Some surgeons like to use a shaver rather than radio-frequency coblation.

    Arthroscopic drape for collecting fluid. Note there is 360 degree access to the knee, which is free to flex passively through a full range, but is held with a side support and foot roll so that ‘at rest’ the knee is held in approximately 70 degrees.

    The patella, tubercle and tibi0-femoral joint line have been drawn.
    The standard incisions for an arthroscopically-guided TTO or MPFL have been drawn.
    TTO scar – paralateral longitudinal
    Hamstring harvest scar
    Superomedial incision marked for patella tunnel drilling of MPFL
    The dotted line represents the centre of the planned incision for this combined TTO and MPFL to avoid 2 incisions and leaving a ‘future-proof’ incision for this knee.

    Superolateral scoping provides the best assessment of patella tracking.
    This starts ‘wet’, but once good views obtained, the irrigation fluid should be turned off drained and an assessment made of :
    1 Patella height – relative to the trochlea
    2. Patella engagement within the trochlea – where in the knee flexion arc does this occur?

    Evidence of patella dislocation with chondral scuffing.

    Laterally tilted and high patella relative to the trochlea – minimal overlap of the patella and the trochlea in full extension

    Again the patella is laterally tilted and high with chondral damage from recurrent patella dislocation

    From the superolateral portal, the patella is assessed in full extension. This is the position of most instability as can be appreciated by the approximately 50% overlap of the patella width to the lateral side of the trochlea.

    From the superolateral portal, the patella is assessed in 30-40 degrees. As the knee flexes the patella starts to locate in the trochlea groove, but here in mid-flexion there is still lateral tracking.

    From the superolateral portal, the patella is assessed in 90 degrees, initially with fluid and then ‘dry’ as the arthroscopic fluid has a significant effect on the tracking. Here at 90 degrees the patella is congruent.

    Operative setup to observe the patella during its tracking cycle in the trochlea.
    Using the patella-trochlea overlap as a guide, a plan is made to distalise and in this case also medialise the tibial tubercle to improve the patella tracking. Using the arthroscopic probe or a notch ruler, the number of millimetres of distalisation is assessed.

    The central incision is made over the tibial tubercle to allow access to both the lateral side of the Tubercle (for the TTO) and the medial side of the tubercle (for the hamstring harvest).

    Sharp dissection with knife down to the tibial tubercle and then haemostasis.

    The lateral edge of the patella tendon is identified and then an incision continued distally in line with the tendon, overlying tibialis anterior and the tibial tubercle.

    Prior to performing the osteotomy, it is sensible to find the hamstring insertion on the medial side of the tubercle adjacent to the superficial MCL insertion. The sartorius, gracilis and semitendonosus tendons insert together as the “pes anserinus” or ‘goose’s foot’.
    The pes is approximately 5cm distal from the joint line on the medial side of the tibial tubercle.

    A transverse incision can be made in the sartorial fascia and a curved arterial haemostat then used to hook out the tendons individually.
    The Gracilis tendon is the central tendon of the three and is sufficiently strong for an MPFL reconstruction.
    The Gracilis tendon is then carefully freed from any vinculae ( the additional insertions which supply tendon nutrition). Vinculae are much rarer around Gracilis than semi-Tendonosus, but it is wise to check before inserting the tendon stripper to reduce the risk of tendon amputation.

    The tendon stripper is inserted and locked on the Gracilis tendon before being pushed towards the hamstring origin, into the posterior compartment around the Gracilis tendon. Should the Gracilis tendon be particularly thin or short then semi-tendonosus should be harvested instead.
    We use the Linvatec Hamstring stripper which has an option to cut the tendon proximally, but usually the tendon will separate itself from the muscle belly.
    A finger or swab should always be kept around the Gracilis insertion to protect against excess force which might avulse the tendon from its insertion, consequently losing the tendon inside the posterior compartment of the thigh.

    Once the Gracilis tendon is harvested, the end is whipstitched with 2 Vicryl and tucked safely back inside the wound to prevent graft loss or damage during the tubercle osteotomy.

    Two 2.5mm drill holes are made from lateral to medial at the proximal and distal extents of the tubercle bone block. This will define the extent of the osteotomy.

    Proximally the osteotomy should be at the level of the patella tendon insertion.
    The Hohman retractor is underneath the patella tendon insertion to expose this for the drill hole.

    Distally this depends on the size of the patient, but for a ‘standard’ 70Kg patient about 5-6cm will suffice.
    Two pairs of fine forceps are inserted into the drill holes to ‘mark’ the extent of the osteotomy prior to the next step…..

    The proximal forceps are removed and using a microsaggital saw the osteotomy is ‘scored’ along its length.
    Proximally a slight biplane osteotomy is used cutting underneath the patella tendon to the proximal drill hole. This is performed with the microsaggital saw.
    If a tourniquet is used or there is little bleeding then saline irrigation should be used.
    Note a swab beneath the saw protecting the lateral skin edge. This is particularly important when using a central incision to allow TTO and hamstring harvest.

    The microsaggital saw is replaced for the Precision Stryker saw and the main line of the osteotomy is the completed front the lateral side up to the medial cortex.

    The medial cortical osteotomy is completed with osteotomes.
    The tibial tubercle (TT) is then mobilised to allow sufficient translation. There is often a tight band like structure proximally and medially which needs dividing to allow mobilisation of the TT bone block
    Depending on the amount of distalisation required and the relative size of the bone block, resection of the distal TT bone block (8mm in this case) or the more distal tibial anterior crest is then performed.

    The tibial tubercle bone block has been distalised 8mm and medicalised slightly, then secured with there hex head small fragment screws.

    Operation – 2

    Attention is then turned to the MPFL again and the superomedial incision made to allow drilling of the patella tunnel.

    A 4.5mm solid, tipped drill is then used to drill transversely from superomedially at the origin of the MPFL across the patella.
    Note the osteotome placed posterior to the drill to protect the soft tissue.

    A 2.5mm Beath pin is then used to pass a Nylon pull through suture across the patella and throughout the skin laterally.

    The Nylon looped pull through suture is then shuttled across the patella with the loop medially.

    A small incision is made over the medial epicondyle and slightly proximal. A mini medial subvastus approach is made.
    A pilot drill hole is made with the Beath pin. The insertion of the MPFL is slightly proximal and anterior to the medial epicondyle – approximately half way to the adductor tubercle.

    The angle of the femoral tunnel is identified by the Beath pin.

    The Gracilis tendon is folded over a 15mm Endobutton and the double strand graft whipstitched at its free end with 1 vicryl.
    The graft is then passed though the patella

    Graft passed across the patella and the endpbutton toggled on the lateral surface of the patella.

    The graft is then passed underneath Vastus Medialis Obliquus (VMO), but extra-articular. This is easily achieved by passing a Arterial clamp underneath the VMO and then placing the whipstitches into the jaws of the clamp and pulling back into the medial window.

    It is sensible to place a loop under the graft in the superomedial window so that the graft can be pulled back to allow insertion of the wire into the femoral tunnel.
    Here the wire is already placed in the femoral tunnel

    Using a pointed bone reduction forceps the tibial tubercle bone block is held in its new postion, distalised and medicalised.

    A single 2.5mm drill is then inserted into the centre of the tibial tubercle bone block, securing the TT to the tibia.

    The driver is disconnected, leaving the 2.5mm drill holding the TT bone block in place as a temporary fixation.

    With the temporary fixation in position, a further arthroscopy from the superolateral portal is made to reassess the patella height relative to the trochlea and looking at patella tilt and the angle at which patella engagement occurs within the trochlea. This should be compared to the original patella tracking.

    Good patella engagement and tracking has beed achieved

    Three small fragment 3.5mm screws are inserted, ideally at slightly different angles, all countersunk.
    The pattern I favour is proximally a partially threaded cancellous screw and then two cortical screws distally.

    The tracking should be checked again and recorded.

    The graft is pulled through the femur and tensioned laterally with a Kocher.
    Fixation should be after checking of patella position arthroscopically and by fixation at 90 degrees to prevent over tightening of the MPFL which can over tighten the patellofemoral joint.

    Wide view of the operative setup at fixation as the graft is tensioned and secured with an interference screw medially in the femur.
    I normally use a 7 x 25mm screw in a 7mm socket as the bone is strong and the margins ‘sharp’. Oversizing the femoral screw can lead to graft amputation.

    Ensuring that the PFJ is not over constrained by an MPFL that is too tight – check in deep flexion.

    Washout the TTO site and photograph to document the position and screw heads.

    Closure in a standard manner with interrupted 0 Vicryl, 2-0 vicryl deep dermal and 3-0 monocryl subcuticular, glue and steristrips

    Padded occlusive dressing
    Wool / crepe

    Postoperative radiograph at 12 weeks showing 3 small fragment screws in the tubercle, an Endobutton on the lateral patella and an interference screw in the medial femoral graft tunnel for the MPFL

    Lateral 12 week radiograph showing good union of the TTO

    The Skyline view demonstrating well centralised patella sitting in the trochlear groove.

    Operation – 3
    Post Operative

    Day case procedure. The advise for physiotherapy is as below:
    Fully weight bear with brace locked in extension
    When sitting unlock brace 0-60 for first 4 weeks and the 0-90 between 4 and 6 weeks
    The brace can be removed at night in bed.

    The patient removes the bulky bandage at 48 hours and maintains the clear occlusive dressing in place, but can shower.
    Review in clinic at 2 weeks for wound check and X-ray.
    Further Xray at 6 and 12 weeks to confirm union.
    Sometimes the screws are tender and require removal

    Recommended Reading

    Isolated MPFL reconstruction
    At 16 months post operatively in 219 MPFL procedures Howells et al showed no recurrent dislocations:
    Howells NR, Barnett AJ, Ahearn N, Ansari A, Eldridge JD.
    Medial patellofemoral ligament reconstruction: a prospective outcome assessment of a large single centre series. J Bone Joint Surg Br. 2012 Sep;94(9):1202-8.
    However there was a statistically different functional outcome in hyper mobile patients, but without true discloation:
    Howells NR, Eldridge JD. Medial patellofemoral ligament reconstruction for patellar instability in patients with hypermobility: a case control study. J Bone Joint Surg Br. 2012 Dec;94(12):1655-9
    Isolated TTO
    Out of 1182 knees, Longo et al found through systematic review of a variety of TTO technique results papers, a recurrence rate of 7% short-term and 8.3% long-term was identified, demonstrating the effectiveness of TTO as a treatment for recurrent patella instability
    Longo UG, Rizzello G, Ciuffreda M, Loppini M, Baldari A, Maffulli N, Denaro V. Elmslie-Trillat, Maquet, Fulkerson, Roux Goldthwait, and Other Distal Realignment Procedures for the Management of Patellar Dislocation: Systematic Review and Quantitative Synthesis of the Literature. Arthroscopy. 2016 May;32(5):929-43.
    A good recent review article impressing the importance of treating the anatomical abnormality is Grimm NL, Lazarides AL, Amendola A.
    Tibial Tubercle Osteotomies: a Review of a Treatment for Recurrent Patellar Instability. Curr Rev Musculoskelet Med. 2018 Jun;11(2):266-271.

    Combined TTO and MPFL reconstruction
    At a mean 48 months postoperatively in a level 4 case-controlled series of extreme anatomical risk patients including severe trochlea dysplasia, Allen et al reported only 1 dislocation and 1 subluxation episode out of 48 knees in 31 patients.
    Allen MM, Krych AJ, Johnson NR, Mohan R, Stuart MJ, Dahm DL.
    Combined Tibial Tubercle Osteotomy and Medial Patellofemoral Ligament Reconstruction for Recurrent Lateral Patellar Instability in Patients With Multiple Anatomic Risk Factors. Arthroscopy. 2018 May 19.
    A

    Reference

    • orthoracle.com

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