Patellofemoral Syndrome a Paradigm for Current Surgical Strategies
Section snippets
Literature review
If we search for a specific answer in the literature to “anterior knee pain,” we often end up confused by conflicting or incomplete data and little direction. Such a search will likely uncover a number of overlapping and imprecise diagnoses, including anterior knee pain, patellofemoral syndrome, chondromalacia patella, patellar instability, patellofemoral arthritis, and patellar malalignment.
No fewer than 56 factors are cited in the literature as having an association with these diagnoses (Box 1
What does current scientific knowledge tell us?
Is there a consensus in literature-based evidence regarding prevalent surgical-based dogma? Current belief suggests that a medial tibial tubercle transfer with or without lateral release is somewhat of a panacea. Many clinical studies, but few laboratory studies, support medial tubercle transfer. The natural history of medial tibial tubercle transfer is often medial patellofemoral joint arthrosis (Fig. 4) and then later medial compartment arthrosis (Fig. 5). Biomechanical studies would predict
Patellar tracking
Van Kampen and Huiskes [18] noted that the three-dimensional motion of the patella consisted of flexion, wavering tilt, medial rotation, and lateral shift as the knee flexes, and that this tracking was controlled by the geometry of the trochlea and greatly influenced by the rotation of the tibia. He concluded that patellar tracking is highly susceptible to tibial rotations, which have a greater effect than either lateral retinacular release or tubercle elevation. He said that, to be valid, all
A framework for patient analysis: the basis for a better surgical strategy
A thorough literature review suggests that a new approach is needed to reduce and compartmentalize these multiple variables into some rational way. It would be helpful if there were a framework upon which to integrate and relate these many detailed observations. Searching a catalog of surgical techniques for the right solution is prone to lead to failure. On the contrary, the surgeon should “think biomechanics, think anatomy” and make this the basis of understanding pathomechanics. Such an
Biomechanics
The factors that increase patellofemoral articular pressure can be defined: (1) the total body weight, (2) the total muscle force needed to transmit the body weight to the ground, (3) the orientation of the skeleton beneath the muscle layer, (4) the length of the lever arms (height), and (5) the surface area that accepts the muscle force. Subluxation of the patella, for example, decreases the surface area for contact.
Paul Maquet's book Biomechanics of the Knee[20] is a masterly introduction to
Anatomy
This paradigm assumes that anatomy is normal because its design is the most optimal for function. Hence an abnormal anatomy does not function as well. Anatomically there are only four major tissues to take into consideration: the skeleton, the muscles, the ligaments, and the cartilage. The skeleton creates the geometry that dictates the vector direction. Its length dictates how far the body mass is from the knee joint and the ground. The force provided by muscles and body weight dictate the
Evaluate the skeleton
The skeleton is considered to have failed if it has an abnormal geometry. Brattström [21] showed in his series of patients with recurrent dislocation of the patella that a shallow sulcus was nearly always present. Dejour and colleagues [9] pointed out that this elevated shallow sulcus is best seen on a true lateral radiograph and he described three grades of dysplasia (Fig. 11A–D). The reshaping of the trochlear geometry requires bending or fracturing the subchondral plate, potentially damaging
Evaluate patellofemoral ligaments
The primary stabilizer of the patellofemoral joint preventing lateral dislocation is the medial patellofemoral ligament as Conlon [37] first demonstrated biomechanically that the MPFL was the primary stabilizer (Fig. 18A, B). There are three stabilizers resisting lateral patellar displacement. These are most importantly the medial retinacular ligaments, next in importance the trochlear geometry and lastly the lateral retinaculum. The medial patellofemoral ligament part of the medial retinaculum
Evaluate articular cartilage
To evaluate articular cartilage, the author prefers the double-contrast CT-arthrogram. Ultimately, of course, MRI will supplant it, but to date, at Michigan Orthopaedic Specialty Hospital, the resolution has been better with CT than with magnetic resonance (Fig. 23A–D). Some lesions of course are seen better with arthroscopy, but there is difficulty determining a precise location of the lesion, the surface area measurement, and especially the depth on the lesion when subchondral bone is not
Evaluate the muscle and tendon
The understanding of the pathophysiology of tendonopathy remains unknown. What is recognized is the lack of an inflammatory response in the diseased tendon. It has been stated that all successful treatments have as a common denominator the stimulation of an inflammatory response necessary for healing. Kannus and Jozsa [39], in a review of the pathology of ruptured tendons, found anoxic mitochondria to be the common feature in all. Quadriceps muscle atrophy may be quite severe in cases of
Summary for evaluation of the patellofemoral joint
As stated in Box 3, an evaluation of the patellofemoral joint begins with a look at the skeleton, then the ligaments, then the articular cartilage, and finally the muscle and tendon.
Changing the skeleton changes the ligament stress and the cartilage loading. Addressing the ligaments or the cartilage does not change the skeleton. If the knee joint is moving sideways (pointing inward) (Fig. 24) while the body is moving forward, a shear force is created, straining the medial retinaculum and
Surgical strategy: putting it all together
The goal of operative treatment is to normalize the biomechanics through restitution of normal anatomy. The morbidity of surgery may dictate otherwise. When multiple anatomic abnormalities are present, it is not known which may be more important. If a patient has patellofemoral cartilage damage, recurrent lateral patellar subluxation, trochlear dysplasia, a femoral anteversion of 45°, an external tibial torsion of 45°, a genu valgum of 10°, a patella alta, and a contracture of the Achilles, is
Case study analysis
Case 1: (see Fig. 1, Fig. 2) A 42-year-old law-enforcement officer presented 20 years after he dislocated patella playing college football, and was treated with a medial tibial tubercle transfer and lateral retinacular release (Fig. 33A–C). He has pain with all walking and riding in a car. Before considering a prosthesis, evaluate the skeletal alignment. The ligaments and cartilage condition is obviously poor (Fig. 33D). Coronal alignment (full standing lower limb) shows 5° genu valgum.
Summary
This article made five main points:
Bone architecture dictates where the force vectors acting on the patella will be directed.
Abnormal skeletal alignment may alter the displacement forces acting on the patellofemoral joint, causing ligament failure with subsequent instability.
Skeletal malalignment may also increase patellar facet loading leading to arthrosis.
Increased joint loading with the addition of subluxation may further increase unit loading. Pain results from this excess load and tension
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