Nonoperative management Surgery
Lateral retinacular release
Arthroscopic proximal realignment
Medial patellofemoral ligament (MPFL) reconstruction
Medial tibial tubercle transfer
• Finally, the role of proximal and distal realignment for treatment of patients with patellofemoral malalignment and/or instability is explored. The decision-making process in assessing malalignment/instability of the patellofemoral articulation, the criteria for tibial tubercle transfer in both the medial and anteromedial direction versus proximal realignment, and details of the surgical techniques are addressed.
• Patellofemoral instability encompasses a continuum of abnormal patellofemoral joint mechanics, ranging from subluxation to dislocation, the cause of which can be either traumatic or atraumatic.
• Patellofemoral instability is defined as abnormal, clinically symptomatic, lateral, or, in rare cases, medial translation of the patella out of the trochlear groove. In cases of recurrent subluxation, there is lateral translation of the patella early in the flexion range.
• Patients may experience a sense of giving way, slipping, or abnormal motion of the patella, unless the patient has permanent lateral tracking of the patella, which is most often secondary to malalignment.
• Recurrent subluxation encompasses a spectrum from minor subtle translation of the patella that is not associated with a clinically evident relocation to episodes of major recurrent subluxation when the patella nearly dislocates in the early stages of flexion and then reduces with a clinically apparent snap or shift.
• Permanent lateral subluxation is often defined under the category of malalignment and is characterized by a persistent laterally displaced patella through the range of motion (ROM) of the knee, with little or no tendency to recenter in the trochlea. It is often associated with patellar tilt.
• The usual mechanism of traumatic patellar dislocation is external rotation of the tibia with concomitant contracture of the quadriceps.
• Relevant anatomy, history, physical examination, and imaging modalities that would aid in diagnosis are discussed.
• Conservative therapy for the treatment of the various instabilities is briefly discussed.
The anatomy of the entire lower extremity is paramount in the discussion of patellofemoral instability. Starting proximally at the hip, femoral version (anterior or posterior) can affect patellofemoral mechanics. With femoral anteversion, the distal femoral trochlea is internally rotated with a neutral hip alignment. Conversely, with femoral retroversion, the distal femoral trochlea is externally rotated with a neutral hip alignment. Normal femoral anteversion is approximately 14 degrees. Excessive hip anteversion causes the patella to displace laterally. Varying degrees of femoral torsion may also be present, which affects the position of the trochlea. Excessive femoral antever-sion with or without internal femoral torsion is usually accompanied by tibial external rotation, which has the effect of further displacing the patella laterally. Dysplasia of the medial or lateral femoral condyle also affects patellofemoral mechanics. If the lateral condyle is hypoplastic, the bony constraint to lateral subluxation is not present in flexion at 20 degrees and beyond.
The patella is a sesamoid bone contained within the extensor mechanism. It is made up of a medial and lateral facet separated by a median ridge. Usually the lateral facet is longer and more sloped to match the corresponding condyle. The rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius all send fibers to the extensor mechanism at the proximal aspect of the patella and respective retinaculum. All muscles originate from the proximal femur except for the rectus femoris, which originates on the anterior inferior iliac spine (reflected head) and superior acetabulum (direct head). The orientation of the quadriceps muscle fibers is important in patellofemoral mechanics because they create varying vectors of force on the patella during contraction. The vastus medialis obliquus originates on the medial intermuscular septum and the adductor tubercle and inserts on the medial proximal third of the patella. The vastus medialis obliquus is the most obliquely oriented muscle and therefore provides a medially directed force vector to the patella during extension, which decreases lateral subluxation. All the quadriceps muscles are innervated by the femoral nerve.
At the distal aspect of the patella is the patellar tendon, which inserts on the tibial tubercle. The tendon is separated from the anterior tibia by the deep infrapatellar bursa. Further posterior to this is the infrapatellar fat pad. Other static restraints to the patella are the medial and lateral patellofemoral ligament and the medial and lateral patellotibial ligament. The MPFL has an almost 90-degree orientation to the patella and therefore is one of the main static restraints to lateral subluxation. The MPFL has been found to be the primary restraint to lateral patellar translation at 20 degrees of flexion, contributing 60% of the total restraining force.1
CLINICAL FEATURES AND EVALUATION
The events surrounding the onset of the knee instability often point to a diagnosis. If the patient's instability is a result of trauma, most often a ruptured MPFL with or without underlying malalignment may be suspected. In the acute setting, the patient may present with a large hemarthrosis and tenderness over the medial femoral epicondyle and medial border of the patella, in addition to pain or apprehension with lateral translation of the patella. If the patient's instability is indolent in nature and has occurred over years, most likely the patient has some component of malalignment. In the chronic setting, the patient may give a history of the knee "giving way" with increasing activity. These patients also may complain of an intermittent effusion and pain over the lateral retinaculum and lateral patellar facet. By history, it is important to determine whether the patient has symptomatic instability, either subluxation or dislocation, or purely patellofemoral pain secondary to chondrosis or arthrosis associated with malalignment.
After an appropriate history is taken, the patient is examined standing. Overall varus or valgus alignment of the lower extremity, which can affect patellofemoral mechanics, can be evaluated. A valgus knee tends to increase the quadriceps angle (Q angle) and loading of the lateral facet of the patella. The position of the patella can also be assessed. If the patellae are facing each other when the feet are parallel there may be some degree of femoral anteversion or femoral internal torsion. This is usually accompanied by some degree of tibial external rotation, which can be assessed by palpating the tibial tubercle. The position of the plantigrade foot also can give some insight to overall alignment. With excessive external rotation of the tibia, there is usually a compensatory foot pronation with heel valgus. Leg length discrepancy may also be evaluated at this time by noting any pelvic obliquity. Finally, the patient's gait may be evaluated for any asymmetry. With proper mechanics, the hip and ankle center should line up so that the overall mechanical axis passes through the center of the knee. Any noticeable pelvic obliquity could be attributed to abductor deficiency. Last, a loaded flexion squat can be performed. Pain and crepitus referable to the patellofemoral articulation is often accentuated by this maneuver.
The sitting examination is then performed with the legs flexed 90 degrees over the examination table. Again, the orientation of the patella can be observed. Laterally facing patellae can indicate extensor mechanism malalignment. The tuberosul-cus angle can also be measured while the knee is flexed to 90 degrees (Fig. 57-1). It represents the angle between a perpendicular to the transepicondylar axis and a line drawn from the
midpoint of the patella to the tuberosity. Normally this measures 0 degrees, and greater than 10 degrees is considered abnor-mal.2 Tibial torsion can also be evaluated by palpating the tibial tubercle. In normal alignment, the tibial tubercle should lie lateral to the midline of the femur, although this is highly variable in the population. Vastus medialis obliquus atrophy can also be appreciated at this point. With flexion and extension of the knee, crepitus can be palpated and patellar tracking observed. The flexion arc in which the patient has pain is sometimes a tipoff as to the location of the patient's disease. Early range flexion pain and crepitus indicate a more distal lesion, a painful arc and crepitus between 30 and 70 degrees indicate a mid-patellar lesion, and a painful crepitus in greater degrees of flexion indicates a more proximal lesion on the patella. The soft tissues are responsible for stability of the patellofemoral articulation in the first 30 degrees of flexion, whereas the bony anatomy becomes more critical beyond 30 degrees of flexion. At approximately 20 degrees of flexion, the patella should seat fully in the femoral trochlea. A pathologic J sign can be observed as the patella seated in the trochlea subluxates laterally with terminal extension. ROM and muscle strength of the knee and ankle should be documented.
From the sitting position, the patient is then placed supine. With the extensor mechanism relaxed, any effusion can be noted and the entire knee should be palpated to include the medial and lateral facets, retinaculum, common extensor tendon, tibial tubercle, and patella tendon. Next the patella should be compressed against the trochlea and moved medially and laterally. Pain during this maneuver implicates the patellofemoral articulation. Lateral glide of more than 50% of the width of the patella is considered abnormal unless there is symmetrical patellar hypermobility associated with generalized ligamentous laxity. A patellar apprehension sign may be encountered when the patient has a sense of dislocation or subluxation with a laterally directed force. Several measurements can now be taken. Leg length can be measured by taking the distance from the anterior superior iliac spine to the tip of the medial malleolus. The Q angle can also be measured (Fig. 57-2). This is measured from the anterior superior iliac spine to the center of the patella to the tibial tubercle. Normal values are up to 15 degrees in the male and up to 18 degrees in the female. The larger Q angles in females are due to the wider pelvis and increase in genu valgum as com-
pared to males. The author believes that the most accurate Q-angle measurement is made at 30 degrees of flexion because the patella should be well centered in the trochlear groove by 20 to 25 degrees of flexion. If the Q angle is measured in extension, an inaccurate low value may be obtained since the patella lies laterally in terminal extension from lack of bony constraint. Excessive femoral anteversion, internal femoral torsion, genu valgum, and external tibial torsion all increase the Q angle. A thorough examination would not be complete without a liga-mentous examination. Last hamstring tightness should be evaluated by measuring the popliteal angle. The angle can be measured by flexing the hip to 90 degrees, extending the knee to the maximum, and then measuring the angle between the femur and tibia. Values greater than 25 degrees indicate hamstring tightness.
From the supine position, the patient should then be placed prone. In this position, hip ROM can be assessed by internally and externally rotating the flexed knees. With the knees flexed in this position, femoral and tibial lengths can be assessed. Finally, quadriceps tightness can be assessed by flexing the knees. With the pelvis level, the heel should come toward the buttocks in a symmetrical level and increased tightness in the anterior thigh, as compared to the contralateral side, could be an indication of quadriceps tightness.
ures the ratio of the length of the patellar tendon to the largest diagonal measurement of the patella on the lateral projection. Normal ratios are 0.8 to 1.2. Ratios less than 0.8 indicate patella baja and ratios greater then 1.2 indicate patella alta. Another similar method is that of Blackburn and Peel,4 who measure the distance from the tibial plateau to the inferior articular surface of the patella as compared to the length of the patella articular surface. A ratio from between 0.54 to 1.06 is normal. Values greater than 1.06 indicate patella alta. This measurement has been found to be more accurate in the evaluation of patella alta and baja. The lateral view can also give an indication to the amount of patellofemoral arthritis by the amount of joint space that is present.
The last view obtained is the axial view (Fig. 57-3). Traditional sunrise views are taken with the knee in various degrees of flexion depending on institutional guidelines. Typically they are taken at greater degrees of flexion (i.e., greater than 45 degrees). At these degrees of flexion, almost all patellae are well seated in the trochlea and mild patellofemoral malalignment may be missed. Two standardized views are typically used. The Merchant view5 is taken with the knee flexed to 45 degrees. The x-ray source is placed proximal to the knee with the plate distal to the knee. The congruence angle, described by Merchant, can be measured from this radiograph. On the axial view, the angle between the medial and lateral condyle is bisected. Then a line is drawn from the femoral trochlea to the lowest point on the median ridge of the patella. The angle between these two lines represents the congruence angle. If the line falls medial to the bisector, it is a negative value and if it falls to the lateral side, it is a positive value. Merchant found the average congruence angle in 100 normal subjects was -6 degrees with a standard deviation of 11 degrees. In a normal knee, the median ridge of the patella lies on the medial condyle. The Laurin view6 is another axial view, taken at 20 to 30 degrees of knee flexion. The x-ray tube is placed between the ankles and the x-ray plate is held proximal to the knees. On this view, the lateral patellofemoral angle can be measured. This angle is measured from a line drawn across the most anterior portions of the medial and lateral femoral condyles in the axial view to a line that follows the slope of the lateral patella facet. Normally this angle should increase laterally. In patients with patellar tilt or lateral patellar subluxation, the angle is parallel or increased medially.
Evaluation of patellofemoral pain starts with a standard bilateral standing anteroposterior view of the knees. This probably has the least amount of information as it pertains to patellofemoral disease but may give insight into degenerative joint disease and accessory ossification centers of the patella as possible sources of pain. A modification of this radiograph is a flexed knee antero-posterior view called the tunnel view. This gives insight into disease of the femoral condyles and can diagnose an osteochon-dral defect.
With the lateral view of the knee, patella alta (high) or patella baja (low) can be evaluated. The Insall Salvati technique3 meas-
Standing mechanical axis view can be taken to assess lower extremity limb alignment. Normally the mechanical axis, a line from the femoral head to the middle of the tibial plafond, should fall just medial to the center of the knee joint. The Q angle, as described before, can also be measured on the radiograph. Varus or valgus angulation at the knees can be measured and an appreciation of femoral anteversion/torsion and tibial torsion can be visualized.
A computed tomography (CT) of the knee at various angles of flexion can give insight to the patellofemoral dynamics (Fig. 57-4). Axial images through the midpoint of the patella are taken at 10-degree increments from 0 to 60 degrees of flexion. Congruence angle and lateral patellofemoral angle can be measured from these images at varying degrees of flexion.
Another use of CT is the measurement of the anterior tibial tubercle to trochlear groove distance (Fig. 57-5).7 Axial images are taken from the proximal trochlea through the tibial tubercle on the same sequence, with the extremity fixed in extension. It is thought that more than a 2-cm distance is highly abnormal, representing excessive lateralization of the tibial tubercle with a high valgus vector on the knee. Although one study suggests that the normal range is 2 to 9 mm and greater than 10mm is abnormal,7,8 the exact cutoff between "normal" and "abnormal" would be very difficult to ascertain because of the very wide range of anatomic variations.
A final use of CT is in the evaluation of the rotational alignment of the lower extremity. Femoral anteversion/torsion can be evaluated by measuring the angle between the line bisecting the femoral neck and a line drawn across the posterior condyles of the femur on subsequent cuts. In the same way, tibial torsion can be evaluated by measuring the angle between the line across the posterior tibial plateau superimposed on the transmalleolar axis. If excessive femoral anteversion results in patellofemoral malalignment, a femoral derotational osteotomy may be in order.
Magnetic resonance imaging can also be helpful in diagnosis. Although CT is better for visualization of bone detail, magnetic
Figure 57-5 The anterior tibial tubercle to trochlear groove distance. A computed tomography measurement of the distance between the center of the trochlear groove and the attachment of the patella tendon to the anterior tibial tubercle. Axial images are taken from the proximal trochlea through the tibial tubercle on the same sequence with the extremity fixed in extension. A, A line is drawn along the posterior femoral condyles on the cut through the deepest portion of the trochlear groove. A perpendicular (x) is drawn from the center of the groove to this line and measured. The distance (a) is measured from this intersection to a fixed point; in this case, the edge of the frame. B, The same parallel line is transposed with a parallel rule to the cut through the midportion of the tendon attachment on the tubercle at the same perpendicular distance (x). The distance (b) is measured to the same fixed point. The anterior tibial tubercle to trochlear groove distance is a - b. In this instance, it was 5 mm, well within normal range.
resonance imaging is more sensitive for osteochondral, ligament, and meniscal injuries that may be caused by a traumatic patellar dislocation. These findings include disruption of the MPFL and osteochondral bone bruises or fractures involving the infer-omedial patella and lateral femoral condyle.9-11
Last, in some cases, a bone scan may be useful. With patellar instability, the biomechanical and metabolic processes that maintain homeostasis of the cartilage and soft-tissue structures are affected. The loss of this homeostasis is typically undetectable with radiographs or magnetic resonance imaging. The bone scan, on the other hand, can demonstrate a persistently abnormal technetium scintigram of the involved area prior to the development and progression of irreversible degenerative changes that would be evident on radiograph or magnetic resonance imaging.12 In the arena of patellar instability, an area of uptake on the lateral patella facet could mean abnormal articular loading in the face of other normal imaging modalities.
Nonsurgical treatment of patellofemoral instability is the cornerstone of treatment. Henry13 reported an approximately 80% success rate in the literature for the conservative treatment of patellofemoral instability. The mainstay of treatment involves the selective strengthening of the vastus medialis obliquus with de-emphasis on strengthening the vastus lateralis. This focus has changed from general quadriceps strengthening that was previously prescribed for patellofemoral pain. McConnell14 has developed a treatment plan for patellofemoral pain that has a reported success rate of 96%. Her method consists of muscle re-education focusing on the vastus medialis obliquus and taping of the patella to modify tilt or subluxation. The use of a patella-stabilizing brace is another treatment modality that may have some benefit. Closed-chain exercises, stationary bike, elliptical runner, and other core strengthening exercises help strengthen and stabilize the knee joint without excessive loading of the joint. Prone quadriceps stretching, iliotibial band stretching, and lateral retinacular stretching are paramount. Lower extremity strengthening, patellar stabilization, lower extremity flexibility, and proprioception are important treatment modalities. Correction of excessive foot pronation or supination with orthotics can have a positive effect on alignment in that this limits compensatory external and internal rotation of the tibia, respectively. Nonsteroidal anti-inflammatory drugs may be used as an adjunct to treatment, and a level of activity modification to limit loading of the patellofemoral joint can be beneficial.
In the realm of patella dislocations, there are numerous retrospective studies in the literature that detail the success of nonoperative and operative treatment of first-time patella dislocators. Consensus between the studies is problematic due to the varying sample sizes, differing follow-up, varied surgical techniques, and heterogeneity between populations. One prospective, randomized study demonstrated equivalent results between operative and nonoperative treatment for first-time patella dislocation.15 Conservative treatment, which includes immobilization of the knee in extension for 2 to 3 weeks, followed by strength and ROM exercises, has therefore become the author's treatment of first-time dislocators. The author's only indications for acute surgical intervention for first-time dis-locators include unstable osteochondral fractures and asymmetrical unreduced lateral subluxation of the patella.
When conservative treatment fails to provide satisfactory results, surgery may be indicated. Surgical techniques can be grouped into proximal and distal realignment procedures. Proximal alignment procedures include a lateral release (open or arthroscopic), lateral release and medial plication (open or arthroscopic), and MPFL reconstruction. Distal realignment procedures include the medialization of the tibial tubercle and anteromedialization of the tibial tubercle. The Maquet technique, anteriorization of the tibial tubercle, has been used mainly to unload the patellofemoral joint in patients with patellofemoral arthritis without malalignment. The Hauser technique is a tibial tubercle osteotomy and moves the tibial tubercle medial, distal, and posterior due to the triangular cross-section of the proximal tibia. This technique has been abandoned because it increases the patellofemoral joint reactive forces, resulting in the subsequent development of patellofemoral arthritis. In this chapter, lateral retinacular release, arthroscopic proximal realignment, MPFL reconstruction, medial tibial tubercle transfer, and anteromedialization of the tibial tubercle are discussed in detail.
Abnormal patellar tilt increases loading of the lateral patella facet, causes contracture of the lateral retinaculum, and increases the incidence of patellofemoral arthritis on the lateral side. Current indications for lateral release consist of (1) patellofemoral pain with lateral tilt, (2) lateral retinacular pain with lateral tilt or lateral patella position, and (3) tight lateral retinaculum/excessive lateral pressure syndrome.16 This operation is done for pain and is not indicated as a stand-alone procedure for instability. If lateral release is done for instability, the results deteriorate with time. Lateral release is contraindicated with a hypermobile patella. In addition, the authors do not perform lateral release as an isolated procedure for the treatment of recurrent lateral patellar dislocation. Lateral retinacu-lar release can be performed either arthroscopically or open. During knee arthroscopy, the patellar tracking is best observed through a superomedial or superolateral portal. Selective femoral nerve stimulation can be used under general anesthesia to allow active quadriceps contraction and thus evaluate dynamic tracking. If at this point, lateral retinacular release is appropriate, the lateral retinaculum should be divided within 1 cm of the patella starting approximately 2 cm proximal to the proximal pole and extending 2 cm distal to the distal pole. Elec-trocautery can be used and care must be taken to cauterize the lateral superior geniculate vessels. The tendon fibers of the vastus lateralis should be avoided as this could cause relative weakness of the lateral compartment and a medial patella subluxation. The most common complication of a lateral release is hemarthrosis from laceration of the superolateral geniculate vessels. An open technique can also be employed, which entails an approximately 3-cm longitudinal incision, about 1 cm lateral to the patella. Skin and subcutaneous tissue are divided with a scalpel down to the retinaculum. A Z-plasty is then performed on the transverse fibers of the retinaculum. Once adequate correction is obtained, sutures can be used to prevent further lengthening of the lateral retinaculum. As in the arthroscopic procedure, care is taken to identify and coagulate the supero-lateral geniculate vessels.
Medial reefing is often indicated with a lateral release in proximal realignment. This can be done open, arthroscopically assisted (mini-open), or done all arthroscopically. The author's ideal indications for proximal realignment include traumatic onset, recurrent episodes associated with an abnormal lateral patellar glide indicating insufficiency of the MPFL and medial soft-tissue restraints, no significant arthrosis of the medial facet, and normal alignment and quadriceps angle. The author uses this arthroscopic technique only in cases of mild instability and uses a formal MPFL reconstruction for cases of moderate to severe instability.
Using a thigh holder and standard arthroscopy portals, an epidural needle is introduced through the medial retinaculum next to the proximal medial border of the patella. A no. 1 poly-diaxone monofilament suture is introduced through the spinal needle into the joint and withdrawn through an accessory portal with a grasper. The spinal needle is then withdrawn from the retinaculum only, into the subcutaneous tissue, and then reinserted into the joint after moving it posterior to the first needle tract. This loop of suture is then withdrawn through the accessory portal and the process is repeated. This procedure can be repeated until the amount of medial imbrication is deemed adequate. An arthroscopic lateral release, if necessary, can then be performed as described previously. The sutures in the medial capsule can then be tied using standard arthroscopic knot-tying techniques.
Postoperative Rehabilitation Postoperatively the patient is placed in a hinged knee brace in extension for 1 week followed by ROM exercises with physical therapy. ROM is gradually increased to a maximum of 90 degrees over a 4-week period. Bracing is continued until quadriceps strength returns. The patient is weight bearing as tolerated postoperatively.
Results The all-inside technique of proximal realignment has been successful. In Halbrecht's review17 of 5-year results, 93% of patients who underwent the procedure reported significant improvement. The average Lysholm score improved from 41.5 to 79.3 (P < 0.05). There were no complications or redislocations. Patients in the study reported significant improvement in pain, swelling, stair climbing, crepitus, and ability to return to sports (P < 0.05).
The author prefers to use formal MPFL in cases of moderate to severe instability. His other indications include traumatic onset, recurrent episodes associated with an abnormal lateral patellar glide (indicating insufficiency of the MPFL and medial soft-tissue restraints), no significant arthrosis of the medial facet, and normal alignment and quadriceps angle.
Technique First, make an incision the length of the patella, located over the junction of the medial and middle thirds of the patella (in line with the medial border of the expansion of the patellar tendon at the distal patellar pole). If a tibial tubercle realignment procedure is indicated, this should be performed first before MPFL reconstruction. The goal of MPFL surgery is to provide a checkrein to lateral displacement of the patella; this surgery is not performed to pull the patella into the trochlea. Perform a subperiosteal dissection, extending medially deep to layers 1 and 2, exposing layer 3 (the capsular layer) at the medial border of the patella. Deeper dissection, between layers 2 and 3, is preferable to dissection superficial to layer 2 because it allows incorporation with advancement of the MPFL (layer 2) superficial to the graft during wound closure. Using a curved clamp to develop the selected tissue interval, bluntly dissect medial retinacular layers between the patella and medial femoral epicondyle.
A single-strand semitendinous allograft or autograft approximately 5 to 7 mm in diameter is prepared for the MPFL substitute. If the graft is small in diameter, it may be doubled to achieve the 5- to 7-mm diameter. A running baseball stitch with no. 2 FiberWire is placed for approximately 15 mm from one end of the graft to help in seating the graft in the femoral tunnel. If the graft is doubled, it should be run from the two free ends.
The origin of the MPFL is now identified on the distal femur. The adductor tubercle and medial epicondyle should be identified. The saddle between these two structures is the femoral origin of the MPFL. A 2.4-mm drill pin is then placed in the center of the saddle. A suture is then wrapped around the drill pin and then attached to the insertion of the MPFL on the patella. The insertion of the MPFL lies on the medial proximal one half of the patella. The knee is placed in 30 degrees of flexion, and the suture is tensioned slightly. The knee is taken through a ROM to evaluate the length change of the suture. Maximum tension should be seen between 0 degrees and 30 degrees, with progressive laxity between 30 degrees and full flexican. The femoral origin point is adjusted to minimize length change of the suture with knee flexion. If lengthening occurs in flexion, replace the pin more distally toward the medial femoral epicondyle. If lengthening occurs in extension, move the pin more proximally toward the adductor tubercle. Slight lengthening will not affect the overall results. Adjustment of the femoral origin of the MPFL is complete when the isometric point is established.
Now with the MPFL femoral origin identified, the femoral tunnel can be made with the appropriately sized reamer over the guide pin to a depth of 20 mm. The graft is then fixed in the femoral pilot hole with the appropriately sized Bio-Tenodesis screw. The sutures previously placed in the end of the graft can be brought in through the cannulated Bio-Tenodesis screwdriver to facilitate seating of the graft. The screw should be placed on the medial aspect of the femoral tunnel with the graft exiting laterally. The Bio-Tenodesis screw should be advanced until it is flush with cortical bone. Security of the graft then can be evaluated.
Next, a 2.4-mm Beath pin is placed at the insertion of the MPFL on the medial patella, as previously identified. The pin is advanced transversely across the patella until it exits laterally. Isometry should be again tested by provisionally fixating the free end of the graft to the patella. The tendon should be marked at the cortical edge of the patella and cut an additional 15 mm distal to this point. After confirming correct placement of the insertion of the graft, an appropriately sized reamer is placed over the pin and a patella tunnel of 20mm in depth is made. Usually a 6-mm reamer is used with a 5.5-mm Bio-Tenodesis screw. A no. 2 fiber wire (FiberWire; Artherex, Naples, FL) then is run as a baseball stitch at the distal aspect of the graft for approximately 15 mm. The free ends of the suture are then placed through the eyelet of the Beath pin and pulled into the patellar tunnel to the previously marked depth and fixated with another Bio-Tenodesis screw. The Bio-Tenodesis screw is advanced over the superior portion of the graft until flush with the patellar cortex. A medial imbrication can now be performed if there is redundant medial tissue. The wound is then closed in the standard fashion.
Alternatively, a suture anchor technique can be used for patellar fixation. A cancellous bone trough is created in the medial edge of the patella, anterior to the articular surface, from the midwaist superiorly. Two Bio-Suture Taks (Arthrex, Naples, FL) are placed in this trough and the free end of the graft is fixed with suture.
Postoperative Rehabilitation Postoperatively the patient is placed in a hinged knee brace in extension for 1 week followed
Box 57-1 Principal Indications for Medial Tibial Tubercle Transfer
1. Patients with lateral patellar instability and/or patellar malalignment with moderate to severe static malalignment, with radiographic or computed tomography evidence of tilt and/or subluxation
2. Tibial tubercle malalignment with normal or only mild insufficiency of the medial patellofemoral ligament
3. Lateral patellar instability with patella alta
5. When there is concern about tethering the medial facet by proximal realignment in the presence of advanced medial arthrosis by ROM exercises with physical therapy. ROM is gradually increased to a maximum of 90 degrees over a 4-week period. Bracing is continued until quadriceps strength returns. The patient is weight bearing as tolerated postoperatively. Return to sports is allowed at 6 months postoperatively if there is full motion, no pain or swelling, and strength at least 80% of the unoperated side.
Results Various techniques of anatomic reconstruction of the MPFL have been described and have met with success. At 2-year follow-up, Drez et al18 found that 93% of their patients had good to excellent results after MPFL reconstruction. In another study by Gomes et al,19 94% of patients had good to excellent results at over 5 years of follow-up after MPFL reconstruction.
The author's principal indications for medial tibial tubercle transfer are given in Box 57-1. If significant patella alta is present, tightening the proximal medial restraints will not correct the problem and will create abnormal forces. In these cases, the patellar centers into the groove in higher degrees of flexion. Some of the best results of distal realignment or medial tubercle transfers occur in patients with patella alta and lateral patellar instability. Likewise, J tracking, where the patella "jumps" out laterally in terminal extension, is an indicator of a "valgus vector" from bony malalignment, which starts at the hip from internal femoral torsion. The more practical solution would be to make the correction at the tibial tubercle, although on a theoretical basis, a femoral derotation osteotomy would correct the problem at its source.
The advantages of distal realignment are listed in Box 57-2. Numerous studies have looked at the effects of medialization and anteromedialization on patellofemoral mechanics. The effect of anterior displacement of the tuberosity on patello-femoral contact forces is discussed in a later section. However, there are numerous publications in the literature that show that medial tubercle transfer corrects tilt as well as subluxation and transfers force at the patellofemoral joint from a lateral to a medial direction.
In a recent study by Ramappa et al20 it was shown that increasing the Q angle increases patellofemoral contact pressures and transfers forces to the lateral facet of the patella. An increased Q angle also tilts and subluxates the patella laterally. It was further established that medialization corrects the mal-tracking and partially corrects the increased contact pressures in the patellofemoral articulation.
Medial tubercle transfer, however, is contraindicated in patients with a normal Q angle or no clinical or radiographic evidence of tubercle malalignment. In a cadaver study by Kuroda et al,21 medialization in the presence of a normal Q angle increased patellofemoral contact pressures, along with increasing the contact pressures in the medial tibiofemoral compartment. These authors also concluded that overmedialization should be avoided in the varus knee, the knee with medial compartment arthrosis, and the knee with previous total or subtotal medial meniscectomy.
Distal realignment is sometimes indicated in combination with proximal realignment when there is both traumatic insufficiency of the MPFL as well as tubercle malalignment. In these cases, both abnormalities need to be corrected.
There are a number of disadvantages of distal realignment that should be recognized before performing this procedure. They are listed in Box 57-3.
Technique Medial tubercle transfer was first described by Trillat et al22 in 1964. It was then popularized by Cox as the Elmslie-Trillat procedure.
Arthroscopy is first performed to address any associated lesions, chondroplasty is performed if necessary, and patellar tracking assessed. At this time, a decision must be made as to whether to perform anteromedialization rather than straight medialization. In general, even in the presence of significant chondral changes at the time of arthroscopy, if the patient is not symptomatic from the chondrosis or arthrosis, straight medial-ization to correct patellar instability and/or malalignment would be indicated. If the patient has symptomatic arthrosis or chon-drosis, the location and severity of the lesion should be noted before deciding which direction to move the tibial tubercle. Furthermore, in some patients with very severe grade IV disease in both the patella and trochlea in diffusely, no further surgery may
Box 57-2 Advantages of Distal Realignment
1. It addresses one of the more common predisposing factors, namely, tubercle malalignment.
2. It allows an aggressive rehabilitation program.
3. These patients are less likely to have range-of-motion problems in comparison with open proximal reconstructions or imbrications.
4. Although pressure transfers go from lateral to medial on the patella when transposing the tubercle medially, one is less likely to tether the medial facet of the patella with an overconstrained proximal realignment.
5. There is less violation of the extensor mechanism.
6. It is well established that medial tuberosity transfer corrects lateral subluxation (congruence angle) as well as lateral patellar tilt (lateral patellofemoral angle).
Box 57-3 Disadvantages of Distal Realignment
1. It does not address an incompetent medial patellofemoral ligament.
2. It cannot be performed properly before skeletal maturity.
3. There is internal fixation that often requires later removal.
4. There is a potential for posterior neurovascular complications when using anterior to posterior-directed bicortical screws in the proximal tibia.
5. There is the potential for osseous delayed union or nonunion.
6. As mentioned previously, increased loading of the medial tibiofemoral compartment occurs, contraindicating its use in the varus knee or knee with medial compartment arthrosis.
Figure 57-7 Exposing the patellar tendon. Both sides of the tendon must be freed up to prevent tethering when the tubercle is shifted.
Figure 57-6 Lateral incision for tibial tubercle medialization (Elmslie-Trillat). The tibial tubercle (circle) and Q angle are marked.
Figure 57-7 Exposing the patellar tendon. Both sides of the tendon must be freed up to prevent tethering when the tubercle is shifted.
be indicated at this time and the patient may be a better candidate for other procedures.
The decision as to whether to perform a lateral retinacular release, either arthroscopic or open, should be made next. Lateral retinacular release is performed in those cases where there is excessive tightness of the lateral retinaculum secondary to a passive patellar tilt, in patients with symptomatic arthrosis or chondrosis in the lateral compartment of the patellofemoral joint, and radiographic or CT imaging evidence of a decreased lateral patellofemoral angle. Lateral release alone, in these cases, is only indicated for excessive lateral pressure syndrome, with lateral facet pain, a tight lateral retinaculum, minimal or only grade 1 to 2 lateral facet changes, and no subluxation or clinical instability symptoms.
The medial tubercle transfer is performed through a small 3-to 4-cm longitudinal incision just lateral to the tibial tubercle (Fig. 57-6). A 1 to 1.5 cm thick, 5 to 6cm long osteoperiosteal shingle with hand osteotomes is created. The patellar tendon is mobilized so that the undersurface of its attachment can be well visualized with retraction (Fig. 57-7). The first cut is performed from lateral to medial with a 1- to 1.5-inch wide hand osteotome 1 cm thick at the level of the tibial tubercle (Fig. 57-8). Care should be made to make this osteotomy directly in the coronal plane. However, if one is to err, err on the side of going from posterior to anterior when going from the lateral to the medial direction so that when the tubercle is transferred, it will move slightly anteriorly and never posteriorly, which would increase patellofemoral contact pressures. A mark is made on the skin distally, 5 to 6 cm distal to the tubercle, and a curved osteotome is used to aim for this point to angle quickly toward the anterior cortex. A small osteotome is used to complete the osteotomy transversely just on the proximal side of the tibial tubercle to prevent propagation into the tibial plateau. Osteo-clasis is performed, leaving the distal soft tissues intact, and the tibial tubercle is gently rotated medially (Fig. 57-9). The parameters used by the author are that the patella is fully engaged and congruent by 20 degrees of flexion and that the Q angle is corrected to below 10 degrees as measured intraoperatively. Temporary fixation is achieved with a 3.2-mm drill bit to, but not through, the posterior cortex, at which time a final assessment of tracking is made (Fig. 57-10). In general, the transfer ranges from a 1- to 1.5-cm shift. If the surgeon is satisfied with the degree of tubercle transfer and the tracking is satisfactory, fixation is performed with a fully threaded 4.5-mm bicortical screw with metal washer (Fig. 57-11). Since this osteotomy is a short, thin osteoperiosteal shingle, the author routinely uses only one bicortical screw, allowing rigid fixation and an aggressive postoperative rehabilitation program. However, if the osteotomy is on the larger side, one can consider fixation with two screws. Care must be taken when drilling through the posterior cortex of the tibia in this area. Drilling should be performed with the knee in at least 90 degrees of flexion and taking care not to plunge through the posterior cortex (Fig. 57-12). In
Figure 57-8 For medialization, a 1 to 1.5cm thick, 5 to 6cm long shingle is adequate. It is left attached by periosteum distally at the anterior cortex. The osteotomy is performed with hand osteotomes laterally to medially. The osteotomy must be made directly in the coronal plane for true medialization. Care must be taken not to angle posteriorly or else posteromedialization will occur. This could lead to overloading.
Figure 57-8 For medialization, a 1 to 1.5cm thick, 5 to 6cm long shingle is adequate. It is left attached by periosteum distally at the anterior cortex. The osteotomy is performed with hand osteotomes laterally to medially. The osteotomy must be made directly in the coronal plane for true medialization. Care must be taken not to angle posteriorly or else posteromedialization will occur. This could lead to overloading.
Figure 57-12 Lateral radiograph of a completed tibial tubercle medialization. The screw should be placed with the knee in flexion to avoid injury to posterior neurovascular structures.
those cases in which MPFL deficiency is a problem and instability and tracking are not fully corrected, it can be addressed, either arthroscopically or open at this time.
We use the tourniquet for the open part of this case and then release it prior to closure and achieve hemostasis. A drain is not usually necessary as it is for anteromedialization. The subcutaneous tissues and skin are closed carefully, and the patient is placed in a long-leg brace locked in extension.
Postoperative Rehabilitation The biomechanics of a flat versus oblique osteotomy have been described by Cosgarea et al.23 In cases of straight medial tubercle transfer with a small thin flat osteotomy, weight bearing can be allowed right away, whereas in a patient with an anteromedialized tubercle, with a larger oblique osteotomy, weight bearing should be prohibited for the first 4 to 6 weeks postoperatively.
In general, full ROM is allowed immediately and usually these patients regain full ROM within a couple of weeks after surgical intervention. Protected weight bearing for the first 3 to 4 weeks with the brace locked in extension is encouraged until the patient has good quadriceps control. Since the quadriceps and extensor mechanism are not violated, early quadriceps isometrics are allowed with resisted quadriceps strengthening allowed at 6 to 8 weeks, at which point there is some early bony healing.
Results Multiple large series have reported a very high success rate with a low rate of complications.24-26 In summary, the major conclusions of these clinical studies of medial tubercle transfer are the following:
1. It is best in young patients without evidence of severe systematic chondrosis or arthrosis.
2. Medial tubercle transfer corrects subluxation (congruence angle) as well as tilt (lateral patellofemoral angle).
3. Adequate postoperative Q-angle correction (<10 degrees) correlates with a good outcome.
4. Patella alta patients do well with this procedure.
5. Screw removal is common.
The indications for a combined procedure are a combination of tubercle malalignment and traumatic incompetence of the medial restraints, particularly the MPFL. Usually this occurs in a patient with recurrent (traumatic onset) lateral instability leading to proximal insufficiency and a static lateral position of the patella from distal malalignment, with an increased Q angle and radiographic evidence of tilt and/or subluxation. The author's approach in these cases is to correct the tubercle malalignment first and then reassess patellar tracking. This is to eliminate the valgus vector pulling the patella laterally. In this instance, if only proximal realignment is performed, the Q angle and the valgus vector forces would be increased even more and create abnormal stresses on the patellofemoral joint. With this approach, after the tubercle malalignment correction is performed, if it is thought that patellar tracking is still not corrected and there is still lateral instability of the patella, the additional proximal realignment necessary to correct the problem is then performed. In the author's practice, an arthroscopic medial imbrication has been sufficient to correct the problem in the majority of patients. Open reconstruction of the MPFL, which is performed in cases of severe insufficiency of this ligament, has been only rarely necessary. If tibial tubercle malalignment is borderline and the patella is very lax, the author chooses to do the proximal realignment first followed by evaluation of patellar tracking and possible tubercle transfer.
If pain is a significant component of the patient's symptom complex, in combination with malalignment, a decision must be made as to whether to move the tubercle straight medially or anteromedially. In general, if the patient has symptomatic chon-drosis or arthrosis that is lateral or distal, anteriorization is considered in addition to the medialization. One must ask when is it appropriate to move the tubercle anteromedially instead of just medially and when should a tubercle transfer be avoided altogether?
When considering tibial tubercle osteotomy for patel-lofemoral arthrosis with malalignment, it is important to define which patients will benefit most from anteromedialization. In general, these are patients with pain secondary to symptomatic arthrosis of the patellofemoral articulation with malalignment, with or without symptoms of lateral patellar instability. The role of medialization has already been discussed. The goal in these patients is to unload and relieve the pain of symptomatic lesions as well as to realign by anteriorization of the tibial tubercle. At the same time, one must be wary of loading other areas of diseased cartilage and causing more pain by performing this procedure.
Anteriorization of the tibial tubercle dates back to 1963 with the so-called Maquet principle (which may have actually first been described by Bandi in 1962).27-31 The Maquet principle stated that elevation of the tibial tubercle reduces patellar tendon forces and decreases the vector angle between the quadriceps and the patellar tendon force and thus reduces the resultant patellofemoral joint reaction vector force. In Maquet's initial biomechanical studies,28-31 he concluded that 2 cm of advancement of the tibial tubercle reduced the compressive patellar forces by about 50% and also decreased the tibiofemoral forces. By his theory, the greater the elevation of the tubercle is, the greater the benefit of decreasing the patellofemoral contact forces. In the 1970s and 1980s, in both Europe and the United States, this procedure was commonly used for patients with symptomatic patellofemoral arthrosis. Unfortunately, elevation of the tibial tubercle up to 2 cm led to many complications, such as skin necrosis, wound breakdown, infection, fracture, and nonunion. Furthermore, in Maquet's biomechani-cal studies, he did not account properly for rotational or horizontal vectors in his calculations and he assumed that the vector force of the quadriceps pole was equal to the vector force of the patellar tendon pole, which is erroneous.
Subsequently, between the hallmark study of Ferguson et al32 in 1979 to the present, numerous authors have studied tibial tubercle transfer extensively.32-60 A summary of the conclusions of these biomechanical studies on anteriorization are listed in Box 57-4.
Clinical confirmation of these biomechanical findings has been further demonstrated by the excellent clinical studies by Fulkerson et al.35,44,51,52 They demonstrated that the patients who gained the most benefit from anteromedialization of the tibial tubercle were those with chondrosis or arthrosis in the lateral or distal portion of the patella.
Anteromedialization of the tibial tubercle was first described by Fulkerson44 in 1983 with a subsequent follow-up in 1990.35 It is indicated for patients with patellar malalignment consisting of tilt and/or subluxation in association with arthrosis, preferably in the areas described. Fulkerson's biomechanical studies were in concert with others showing that anteriorization of 12 to 15 mm and medialization of 9 to 10 mm of the tibial tubercle results in decreased lateral facet pressures and a shifting of the contact pressures of the patella proximally and medially.20,32-34,36,37,47,61,62
The obliquity of the cut can be varied so that a maximal obliquity (which is limited by the lateral intermuscular septum to approximately 60 degrees) is indicated for patients with arthrosis, more pronounced than malalignment, to maximize anteriorization and minimize medialization. On the other hand, an osteotomy with less obliquity can be created for more medi-alization when malalignment is more of an issue than arthrosis.
Box 57-4 Conclusions of Biomechanical Studies on Anteriorization
1. Anteriorization of the tibial tubercle more than 12 to 15mm is never necessary because further elevation has minimal biomechanical effect (it may, in fact, have a deleterious effect by loading the proximal portion of the patella) and increases the risk of complications. In particular, wound complications increase dramatically with an elevation of more than 15 mm.
2. Anteromedialization of the tibial tubercle decreases contact pressures, mostly on the distal and lateral portions of the patella, and transfers the load proximally and medially.
3. Anteriorization of the tibial tubercle rotates the patella on its horizontal axis and relieves pressure on the distal portion of the patella, but loads the proximal portion of the patella. This is particularly evident at elevations of more than 15 mm.
4. Anteromedialization of the tibial tubercle shifts contact forces from the distal lateral portion of the patella to the proximal medial portion of the patella.
5. There is an extremely variable effect of anterior or anteromedial tibial tubercle transfer from patient to patient because every tracking pattern is different and the problem is multifactorial. There is a wide range of changes and shifting of contact pressures with anteromedialization and anteriorization.61
In summary, most biomechanical and clinical studies suggest that the location of the arthrosis is a much more important factor than the extent of disease.
Ideal Indications: Anteromedialization
1. A patient has symptomatic arthrosis of the patellofemoral joint that is located in the lateral or distal portion of the patella associated with clinical and radiographic evidence of malalignment consisting of tilt and/or subluxation.
2. The patient has failed an extensive nonoperative rehabilitation program.
3. In combination with cartilage restoration procedures of the patella or trochlea to unload and protect the concomitant procedures unless the primary symptomatic and treated lesion is located on the proximal one-third of the patella. These patients may have undergone a microfracture, autolo-gous chondrocyte implantation, or patellar or trochlear OATS procedure. Anteromedialization is often combined with these procedures to correct malalignment and unload the treated areas of the articular cartilage.
In most patients with symptomatic arthrosis, unless secondary to direct trauma, a degree of malalignment is frequently present. Oftentimes this is subtle and can only be identified by the CT studies described previously. Careful assessment of the tubercle alignment is mandatory.
Technique After arthroscopic evaluation and treatment, if a final decision to perform the anteromedialization has been made, this procedure is performed through a laterally based incision (Fig. 57-13), and, if necessary, a lateral retinacular release is performed (Fig. 57-14). If there are pre-existing incisions, a skin bridge of at least 5 cm is mandatory and the incision can be modified if necessary. It is important to free up the patellar tendon on both sides to allow proper transfer of shift in forces to the patella (Fig. 57-15). The tibialis anterior is carefully dissected off the lateral tibial crest, subperiosteally, back to the limit of the lateral intermuscular septum. The osteotomy should be approximately 8 cm in length, so the incision should allow adequate exposure of the tibia to this extent (Fig. 57-16).
The author prefers to use an AMZ Guide (DePuy-Mitek, Norwood, MA; Fig. 57-17). This is helpful to predetermine the exact obliquity of the cut and to ensure a flat cut so that there are no incongruities in the contact areas between the two surfaces when shifting the tubercle anteriorly and medially. As an alternative, a flat pin block from a commercially available external fixation system can be used.
The AMZ Guide is placed in the proposed spot and a specially designed caliper can be placed inside the holes of the guide to determine where the osteotomy will exit on the lateral side. The more proximal part of the osteotomy will exit the tibia more posteriorly and taper more anteriorly as it courses distally. As mentioned previously, the maximum obliquity possible is approximately 60 degrees, so that the osteotomy exits just anterior to the lateral intermuscular septum. This is a tapering cut from the medial border of the patellar tendon insertion to the tibial crest approximately 8 cm distally. A specially designed retractor is used to protect the lateral soft tissues and the vital neurovascular structures posterior to the lateral intermuscular septum. A power saw is used to make the initial oblique cut, and the final cuts are performed using hand osteotomes (Figs. 57-18 and 57-19). A transverse cut is made just proximal to the patellar tendon with a 0.5-inch straight osteotome (Fig. 57-20) with a connecting cut between the transverse cut and the longitudinal osteotomy posterior to the tibial tubercle at its proximal extent to prevent propagation into the tibial plateau
The osteotomy is carefully completed from proximal to distal using a small hand osteotome, attempting to leave the distal soft tissues intact. Once the osteoclasis is complete, the tubercle is rotated anteriorly and medially the desired amount (Figs. 57-22 and 57-23). The two proposed screw sites are marked on the anterior tibial cortex and the osteotomy is fixed temporarily with a 3.2-mm drill bit at the planned distal screw site, going through the osteotomy and the anterior cortex of the tibia but not the posterior cortex (Fig. 57-24). At this point, the patellar tracking is assessed clinically and the amount of anteriorization and medialization is determined as well as the correction of the
Figure 57-18 The osteotomy is initiated with an oscillating saw. A special retractor is used to protect the anterolateral musculature, which has been elevated off the lateral tibial slope subperiosteally.Was this article helpful?
Did You Know That Herbs and Spices Have Been Used to Treat Rheumatoid Arthritis Successfully for Thousands of Years Do you suffer with rheumatoid arthritis Would you like to know which herbs and spices naturally reduce inflammation and pain 'Treating Rheumatoid Arthritis with Herbs, Spices and Roots' is a short report which shows you where to start.