Trochleoplasty in major trochlear dysplasia: current concepts
© Beaufils et al; licensee BioMed Central Ltd. 2012
Received: 30 March 2011
Accepted: 21 February 2012
Published: 21 February 2012
Trochleoplasty is the theoretical solution to persistent symptoms (pain and/or instability) related to trochlear dysplasia where there is not only a trochlear flatness but also a trochlear prominence. The threshold of prominence indicating surgical intervention has as yet not been determined. A bump of 5 mm is generally accepted as the inferior limit. Given the interventional nature of this demanding procedure, it should be proposed in selected cases after considerable discussion with the patient. Trochleoplasty is indicated as a primary procedure for major trochlear dysplasia with a prominence > 5 mm. Stabilization is obtained in most of the cases with the risk of residual mild anterior knee pain. It is also indicated as a salvage procedure when a previous surgery failed. Despite the reputation of the procedure, the published results are encouraging in terms of prevention of re-dislocation, satisfaction index, and radiological outcomes. Post-operative stiffness is the main complication, which may require manipulation under anaesthesia or arthroscopic arthrolysis. There are few other complications reported and to date secondary necrosis of the trochlea has not been reported. Technically speaking, the deepening trochleoplasty is a difficult procedure without reliable landmarks. We propose a recession wedge trochleoplasty which is an easier procedure. It is never undertaken as an isolated procedure, but always in conjunction with other realignment procedures of the extensor apparatus according to the "a la carte" surgery concept.
KeywordsTrochlea Patello femoral dysplasia Patellar instability Trochleoplasty
The importance of a dysplastic trochlea as a component of patellar instability (especially recurrent dislocation or habitual dislocation) has been recognized for many years. It is usually combined with other static or dynamic abnormalities such as genu recurvatum, patella alta, patellar tilt, increased Q angle and bone torsional abnormalities.
Major trochlear dysplasia is characterized by the combination of a flat and/or prominent trochlea proud of the anterior femoral cortex which offer inadequate tracking during flexion and lead to patella subluxation respetively [1, 2].
Many surgical techniques have been proposed for the treatment of patellar instability. Trochleoplasty has been described as corrective treatment for bony abnormalities for many years with the goal of restoring normal anatomy. Correcting the trochlear depth abnormality plays a major role to stabilising the patella because it facilitates proper entrance of the patella into the groove of the trochlea. In our experience the restoration of the trochlea groove by trochleoplasty prevents future patellar dislocation and is effective in reducing anterior knee pain.
Elevation of the lateral trochlear facet was first described by Albee  in 1915, followed by deepening trochleoplasty [2, 4–12] which tries to create a new sulcus by removing subchondral bone. Recently Goutallier  proposed an easier concept, termed Recession Trochleoplasty, in which the bump is solely corrected with the trochlea remaining flat. This has now been adopted as our preferred technique .
Trochleoplasty is considered as a demanding technique and frequently may be avoided due to a lack of familiarity. However it can be a useful addition to the surgical armamentarium of the patellofemoral surgeon and has precise indications.
Trochleoplasty can be proposed as a primary procedure for primary trochlea dysplasia or as a salvage procedure  in case of failure after previous patellar alignment surgery, principally Anterior Tibial Tubercle Transfer (ATTT).
In the large majority of the cases, trochleoplasty is performed in association with other procedures (bony procedures such as ATTT transfer, or soft tissue procedure such as medial patello femoral ligament (MPFL) reconstruction). This combined procedures follow the concept of "à la carte" surgery described by Henri and David Dejour [1, 7], which tries to address all the abnormalities during one surgical intervention.
What about the congruency between a flat dysplastic patella on a deepened trochlea? (Figure 2)
What is the morbidity of this demanding technique, particularly bone healing and the risk of subchondral bone or cartilaginous necrosis?
Pre-operative imaging forms the key to determine when trochleoplasty is indicated. We have established a standard protocol of plain radiographs for visualisation of the patello-femoral joint. These consist of AP view, lateral view at 20° of flexion, lateral view in full extension with quadriceps contraction, skyline views at 30° in neutral rotation of the leg  and in external rotation (in order to demonstrate an eventual lateral subluxation). Additional bone imaging is provided by computed tomography .
the Crossing Sign described by Walch characterizes the trochlea flatness.
the trochlear bump or prominence is measured by the distance between a line tangential to the anterior femoral cortex, and a line parallel to this through the trochlear groove. A bump > 5 mm characterizes a major dysplasia (Figure 4)
Patellar height may also be determined to consider an ATTT distalization procedure. We prefer to use the Caton Deschamps  index > 1.2
The procedure is performed supine. A tourniquet minimises bleeding from the exposed areas of cancellous bone. Arthroscopy may be performed to confirm the absence of cartilage defect prior to trochleoplasty surgery. The differing techniques are described as follows:
1 Deepening Trochleoplasty
2 Recession trochleoplasty
Post operatively the knee is placed in an extension brace for the initial three weeks. Full weight bearing is allowed. Knee flexion is restricted to 0 to 60 degrees for the first three postoperative weeks, and then slowly increased to reach 90 degrees on the sixth week. Return to sports is allowed at 6 months.
The risks of the deepening trochleoplasty include breaking of the osteochondral flap, distal detachment, and creating a too thin flap decreasing its blood supply. There are still concerns about the viability of the articular cartilage after trochleoplasty. The recession wedge trochleoplasty has a decreased the risk of chondral damage and necrosis. Since the dysplastic segment of trochlea is lifted as a single osteochondral block and there is no need to fashion a new groove by cutting the osteochondral flap, it is possible to preserve a greater amount of subchondral bone. This makes this the recession arthroplasty a more attractive option for older patients with less pliable cartilage with decreased risk of possible serious and irreversible articular and subchondral injury. In our series, we reported no cases of chondrolysis, subchondral necrosis or non-union of the osteochondral block.
It is worthy of note that in cases of recession trochleoplasty the wedge and the trochlear recess are flat and complementary, whereas in the deepening trochleoplasty, the osteochondral flap might not tally perfectly with the V shaped recipient bone bed. Any small areas of separation between the two surfaces could slow down the osteointegration process. Similarly the use of screw to stabilise osteotomy rather than sutures may increase compressions between the two surfaces. Surprisingly chondrolysis has never been reported with the deepening trochleoplasty.
Schottle  studied the cartilage viability after the Bereiter trochleoplasty He found that tissue in the trochlear groove remained viable, with retention of distinctive hyaline architecture and composition and only a few minor changes in the calcified layers.
Literature review: trochleoplasty for major dysplastic trochlea
Masse et al 
Reynaud et al 
Gougeon et al 
Albee(75%) deepening (25%)
Goutallier et al 
Recession wedge trochleoplasty
Verdonk et al. 
Von Knoch et al. 
Donell et al. 
Modified Dejour trochleoplasty
Utting et al.
Thaunat et al 
Recession wedge trochleoplasty
To date published outcomes of both deepening and recession trochleoplasty are similar with improved subjective outcome scores reported in the short term [4, 8–14, 18] (Table 1). Comparisons between series are difficult since the surgical procedures and follow-up are variable, the number of patients is often small and patients have been operated for mixed indications of pain rather than dislocation [12, 13]. Moreover, it is not possible to assess the participation of trochleoplasty in the patellofemoral stability, because it is rarely solely performed and other abnormalities are corrected as part of the surgical procedure. As a result of this, there is a lack of high level studies reported in the literature.
Goutallier has reported a case series with 67% of patients reporting that they were either satisfied or very satisfied with the outcome of surgery where trochleoplasty was performed as a salvage procedure. Other series show 100% satisfaction rates (Table 1).
In our series, the operation failed to stabilize the patellofemoral joint in only two cases. The average objective knee score at last follow up was 80 (+/-17) for the Kujala score , 70 (+/-18) for the KOOS and 67 (+/-17) for the IKDC. Patients who had a previous surgery, and those with patellofemoral chondral lesions noted during the surgery or degenerative changes on the preoperative radiographs were noted to have a lower Kujala score at last follow up.
Interestingly all the patients operated for painfree instability (n = 7) reported have slight pain. This was located at the site of screws to reattach the tibial tubercle and so was not directly related to the trochleoplasty itself. All the patients with pre-operative pain bar one (n = 11) report significant pain improvement at last follow up.
Both deepening or recession trochleoplasty are able to reduce the trochlea bump. In our series, the trochlear groove height changed from an average of 4.8 mm pre-operatively to an average of -0.8 mm post-operatively (Figure 7, 8, 10). Patellar tilt changed from an average of 14° (6° to 26°) preoperatively to an average of 6° (range -1° to 24°). It is interesting to note there was no significant difference in the correction of the patellar tilt angle when comparing the groups who had or not the adjunction of a MPFL reconstruction. Thus our series suggests that MPFL reconstruction is not be necessary when a recession wedge trochleoplasty is performed. The reduction of the boss height allows the avoidance of lateral misdirection and facilitates the sliding of the patellar into the trochlea recess.
Although the deepening or recessing trochleoplasty is effective in reducing anterior knee pain, it does not halt the progression of patellofemoral arthritis, although the follow up of the above studies is too short to draw any definitive conclusions. In our series , at the time of the latest follow-up, six knees had osteoarthritic changes in the patellofemoral compartment according to the classifcation by Iwano et al . These are similar to the results obtained with deepening trochleoplasty . Trochleoplasty cannot be proposed as a prevention of late osteoarthritis.
Trochleoplasty is indicated as a primary procedure for major trochlear dysplasia with a prominence > 5 mm. Stabilization is obtained in most of the cases with the risk of residual mild anterior knee pain. Trochleoplasty can be also proposed as a salvage procedure when a previous surgery failed. In these cases, one can expect a stabilization of the knee and improvement of anterior knee pain.
Reported results are encouraging in terms the prevention of re-dislocation, satisfaction index, The rate of complications is low. Long terms outcomes have not been reported and there are no consistent data on the capacity to prevent secondary arthritis
Technically speaking, the deepening trochleoplasty is a difficult procedure. Recession wedge trochleoplasty is an easier procedure. It is never an isolated procedure but always in conjunction with other realignment procedures according to the "a la carte" surgery concept.
Anterior tibial tubercle transfer
Medial patello femoral ligament
distance between tibial tubercle and trochlear groove on CTscan.
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