This article is more than 5 years old. Information may no longer be current.
Surgical correction of recurrent patella instability: Proximal, distal or both
Aim for balanced patella tracking in the central trochlea and avoid undue patellar cartilage loads.
Making a decision regarding proximal or distal realignment in a patient with recurrent patella instability is challenging. Some surgeons favor performing proximal realignment exclusively by medial patellofemoral ligament tendon graft reconstruction or full medial imbrication after lateral release. Other orthopedic surgeons almost always move the tibial tubercle medially in the patient with recurrent patella instability.
The goal must be to identify the best surgical intervention that will minimize risk of future problems while controlling the disability permanently. Decision-making in patients with patella instability involves many factors. With careful analysis of each patient’s patellofemoral anatomy, location of articular lesions, alignment and lower extremity kinematic function, it is possible to make an optimal surgical plan for each patient.
The goal is to create a balanced patellofemoral relationship, throughout full range of motion, without adding abnormal load, particularly to any area of articular breakdown.
Important considerations
The following guidelines should be helpful:
- If the medial patellofemoral ligament is elongated but intact, it may be advanced to restore tension and prevent recurrent instability in many patients, as long as the patella is appropriately balanced in a satisfactory trochlea with little abnormal alignment.
- If the relationship between the patella tendon insertion (tibial tubercle) and the trochlear groove (TT-TG relationship) is such that the Q angle is abnormally high (over 20 is a common guideline), the surgeon should determine if there is a lateralizing force vector. He/she should also consider that a medial tibial tubercle transfer will add to the likelihood of permanent correction and balanced tracking of the patella in the central trochlea without adding undue load to patellar cartilage (Bicos, Dejour).
- If the trochlea is very flat or the lateral edge of the trochlea is dysplastic, the bony architecture will not resist laterally directed forces on the extensor mechanism. Also, optimizing the “tracking vector” by moving the tibial tubercle medially will reduce tension in a reconstructed medial patellofemoral ligament.
- Medial patellofemoral ligament reconstruction (MPFL) is technically demanding and generally utilizes a tendon graft, which is far stronger than the native medial patellofemoral ligament. The surgeon needs to carefully weigh the risks as well as the benefits of this technique. Restoration of normal MPFL function (ie, gentle guiding of the patella into a balanced relationship with the trochlea in the first 20° of knee flexion by a native 208 N ligament) should be the goal (Amis).
|
Image with permission: Fulkerson JP, Disorders of the Patellofemoral Joint, Lippincott, Williams and Wilkins, 2004 |
|
Technique
In all patients, a good preoperative evaluation should include axial radiographs at 30°-45° knee flexion (Merchant view) and if necessary, computerized tomography or MRI to evaluate cartilage and trochlea anatomy. By putting these studies together with a very careful clinical exam, the surgeon can identify a distorting lateral force vector applied to the patella clinically and determine if medialization of the tibial tubercle will be necessary to achieve a long-term, balanced, stable result without adding undue pressure to injured articular cartilage.
By the same token, the surgeon should not move the tibial tubercle unless there is evidence of “chronic” extensor mechanism lateralization that is structural in nature (ie, not secondary only to disruption of the medial patellofemoral ligament).
If a patient has recurrent lateral patella instability related solely or predominately to a rupture of the MPFL, then restoration of this ligament alone should be sufficient, particularly if the trochlea is normal or near normal. In other words, you should address underlying structural problems at the time of surgery to avoid future instability related to congenitally aberrant anatomic structures and/or function that cannot be corrected otherwise.
Putting all the information together, the surgeon should proceed to arthroscopy, placing the patient supine on the operating table. We use distal portals applied medially and laterally, and will use a proximal medial approach about 3-cm above the medial/proximal pole of the patella in selected patients. Arthroscopy establishes the exact nature and location of articular lesions as well as the degree of patella lateral tracking and tilt related to lateral tightness.
An arthroscopic lateral release is appropriate only for abnormal tilt, or tension, in the lateral retinaculum. This will sometimes improve the tracking, but it does nothing for a patulous, stretched-out or completely deficient MPFL. If the patella is easily maintained in the trochlea and the trochlea is well developed, you may only have to restore MPFL function. You must take into account any medial articular lesion and avoid overloading it. If the medial patella has been substantially injured related to recurrent dislocation, particularly on the distal aspect of the patella, an anteromedial tibial tubercle transfer may be needed for unloading of the distal medial facet.
Evaluation
|
|
Arthroscopic and open evaluation of the medial patellofemoral ligament is possible. Following arthroscopic assessment of MPFL integrity, we use a short incision, about 3-cm long, at the proximal medial border of the patella, incise the vastus medialis obliquus (VMO) from the patella, leaving a cuff of tendon on both sides, and then grasp the tendon of the VMO with a Kocher clamp such that tension may be applied to the underlying MPFL.
As you apply tension to the ligament, pass a finger to the deep aspect of the medial patellofemoral ligament all the way to the adductor tubercle. In this manner, you can establish the presence of an intact, albeit stretched-out medial patellofemoral ligament.
At this point, when the ligament is found to be intact and inserted appropriately at the adductor tubercle, you can place it onto the dorsum of the patella anatomically to re-establish appropriate medial support tension. This is essentially what Nam and Karzel advocate. It is important to note that the ligament has adequate tensile strength to provide needed medial support.
In this manner, the MPFL may be sutured in place using #2 Ethibond (Johnson & Johnson) while checking arthroscopically to assure that the patella is repositioned appropriately in the trochlea during motion without disruption of the repair and without focal overload.
Keep in mind that restoration of the MPFL in this way may fail if there are uncorrected, laterally directed forces (ie, deficient lateral trochlea, a high TT-TG relationship) pulling against it.
Also, patients with hyperlax connective tissues will be particularly prone to failure of a retinacular reconstruction alone if surgery fails to compensate for or correct abnormal laterally directed forces and trochlea dysplasia
Tibial tubercle transfer
At this point, if tibial tubercle transfer is necessary because of trochlea dysplasia or an excessively high Q angle (TT-TG index >20), the tibial tubercle may be medialized or anteromedialized (adding some anteriorization is important when there is a distal patella articular lesion) and secured with two cortical screws, using lag technique in the posterior cortex.
|
|
|
In most cases, 1 cm of medialization is very helpful in balancing load on the patella. It should be noted that we do not advocate medialization of the tibial tubercle unless unloading of an articular lesion or balancing of the tracking vector is necessary.
In a patient with lateral trochlea dysplasia, symptomatic articular lesion, or an excessive lateral tracking vector, failure to medialize the tibial tubercle will increase the risk of failure.
In particular, adding load to a patella articular lesion by pulling the patella medially without balancing the tracking vector increases the likelihood of postoperative pain or failure of the reconstruction.
Moving the tibial tubercle provides an important opportunity to balance “tracking forces,” restoring soft tissue/retinacular restraints to a normal configuration.
A medial patellofemoral ligament reconstruction should not force the patella into an unbalanced, albeit centralized, position against laterally directed forces that will either undo the repair or produce excessive articular load.
Tendon graft
Nonetheless, an MPFL reconstruction using tendon graft will be necessary in some cases.
We find that this is not often necessary, as a healed MPFL may be advanced to re-establish normal medial support similar to the native 208 N medial patellofemoral ligament.
When the MPFL has been completely disrupted and there is no healing of the residual ligament — or if the surgeon feels there is inadequate medial tissue to restore normal balance medially — a tendon graft may be placed at the proximal third of the patella and extended to the adductor tubercle region anatomically.
We favor an endobutton to secure the tendon on the patella side and a biotenodesis screw [Arthrex or Smith & Nephew] to maintain fixation on the MPFL femoral anatomic origin in such patients.
Conclusion
In conclusion, decision making with regard to proximal, distal or combined surgery in the patient with PF instability is somewhat complex, and a critical evaluation of each patient’s underlying structure and function is necessary to design the best possible plan for each patient.
The goal should be a balanced extensor mechanism, without adding abnormal articular load to the patella, tracking centrally in the trochlear groove. The best approach will be both restorative and compensatory for underlying, predisposing factors.
|
|
|
For more information:
- Amis AA, Firer P, Mountney J, et al. Anatomy and biomechanics of the medial patellofemoral ligament. Knee. Sept. 2003;10(3):215-220.
- Arendt EA, Fithian D and Cohen E. Current concepts of lateral patella dislocation. Clin Sports Med. 2002; 21(3):499-519.
- Bicos J, Amis A, Fulkerson JP. The medial patellofemoral ligament: current concepts. Am J Sports Medicine. 2007;35;484-492.
- Dejour H, Walch G, Nove-Josserand L, Guier C. Factors of patellar instability: an anatomic radiographic study. Knee Surg Sports Traumatol Arthrosc. 1994;2(1):19-26.
- Elias JJ, Cech JA, Weinstein DM, Cosgrea AJ. Reducing the lateral force acting on the patella does not consistently decrease patellofemoral pressures. Am J Sports Med. 2004;32(5):1202-1208.
- Farr J. Anteromedialization of the tibial tubercle for treatment of patellofemoral malpositioning and concomitant isolated patellofemoral arthrosis. Tech Orthop. 1997;12:151-164
- Ficat P, Ficat C, Bailleux. Syndrome d’hyperpression externe de la rotule. Rev Chir Orthop Rep Appar Mot. 1975;61:39-59.
- Fulkerson JP. Anteromedialization of the tibial tuberosity for patellofemoral malalignment. Clin Orthop. 1983;177:176-181.
- Fulkerson JP, Becker G, Meaney J, et al. Anteromedial tibial tubercle transfer without bone graft. Am J Sports Med. 1990;18: 490-497.
- Fulkerson JP. Disorders of the Patellofemoral Joint. Philadelphia: Lippincott Williams & Wilkins, 2004.
- Fulkerson JP. Common patellofemoral disorders. AAOS Monograph, 2005.
- Merchant AC, Mercer RL, Jacobsen RH, et al: Radiographic analysis of patellofemoral congruence. J Bone Joint Surg. 1974;56A:1391-1396,
- Nam E and Karzel R. Mini open medial reefing and arthroscopic lateral release for the treatment of recurrent patella dislocation. Am J Sports Med. 2005;33(2):220-230.
- Pidoriano AJ, Weinstein RN, Buuck DA, et al. Correlation of patellar articular lesions with results from anteromedial Tibial Tubercle transfer. Am J Sports Med. 1997;25:533-7.
- Post W. Clinical evaluation of patients with patellofemoral disorders. Arthroscopy. 1999;15(8): 841-851.
- Schutzer SF, Ramsby GR, Fulkerson JP. Computed tomographic classification of patellofemoral pain patients. Orthop Clin North Am. 1986;17:235-248.
- John P. Fulkerson, MD, Orthopedic Associates of Hartford PC, clinical professor and sports medicine fellowship director, University of Connecticut School of Medicine, Hartford. 499 Farmington Ave., Suite 300, Farmington, CT 06032; 860-549-8269; jpfulkersonmd@aol.com.