Abstract
Background:
Patellofemoral anatomy allows for substantial freedom of motion. Medial patellofemoral ligament (MPFL) tears occur in up to 96% of lateral patellar dislocations. Risk factors for subsequent instability include maltracking and increased tibial tubercle to trochlear groove (TT-TG) distance.
Indication:
Medial patellofemoral ligament reconstruction (MPFLR) with concurrent tibial tubercle osteotomy (TTO) is indicated in patients with recurrent dislocation or unresolved apprehension. Concurrent TTO should be considered for TT-TGs 15-20 mm depending on overall clinical picture and risk factors. We strongly consider TTO for TT-TGs ≥20 mm and for revision procedures.
Technique Description:
Following diagnostic arthroscopy, a midline incision is made from the inferior patellar pole to 3 cm beyond the tibial tubercle. The anterior compartment is incised and retracted laterally. An osteotomy guide is affixed to the tibia and an osteotomy cut is made with a saw, leaving a small bridge of periosteum distally. The osteotomy is competed proximally with osteotomes, then medialized and held in place with two 4.5-mm screws. An incision is made on the superomedial patella and two 0.045 inch guidewires are placed at the MPFL insertion and overdrilled with a 3.5-mm drill. A 22-cm semitendinosus allograft is prepared and fixed to the patella using two 3.5-mm anchors. An incision is made over the medial epicondyle and a 2.4-mm beath pin is placed at Schöttle point. Isometry is confirmed and the pin is overdrilled with a 6-mm reamer. The allograft is passed just superficial to capsule from the peripatellar incision to the medial incision, docked into the femur, and secured with a 6-mm interference screw at 30° of flexion after confirmation of appropriate graft length.
Results:
Studies have demonstrated improved outcomes for patients undergoing MPFLR + TTO compared with isolated MPFL in the setting of maltracking and increased TT-TG distance. In addition, a recent meta-analysis demonstrated no negative effect of concurrent TTO on return to sport timeline.
Discussion/Conclusion:
MPFLR with concurrent TTO is effective, with surgical correction of underlying maltracking and satisfactory return to sport. Consideration to MPFL + TTO should be given to patients with recurrent instability and pathologically increased TT-TG.
The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.
This is a visual representation of the abstract.
Keywords
Video Transcript
The following is a video on tibial tubercle osteotomy with concomitant medial patellofemoral ligament reconstruction (MPFLR).
The authors have nothing to disclose.
Patellofemoral anatomy is such that it allows for substantial freedom of motion. Patellar instability is common, and this occurs particularly among young and athletic women with a reported incidence of 33 per 100,000 persons. Patellofemoral instability accounts for 2%-3% of knee cases presenting to clinic. Risk factors for patellar instability and its recurrence are well established and include young age, maltracking, and trochlear dysplasia.
The following is a case of a 24-year-old woman presenting with 12 years of progressive anterior right knee pain and patellar instability. She reports over 100 instances of lateral patellar subluxation and no previous knee surgery. She has failed conservative treatment including extensive physical therapy (PT) and is limited in her activities of daily living (ADLs) due to apprehension and pain.
On physical examination, she had 140° range of motion, 2 quadrants of medial translation, and 3 quadrants of lateral translation with a soft endpoint. She has significant patellar apprehension in full extension and mild crepitation. Her pathologic lateral translation and associated apprehension resolved at and beyond 30° of knee flexion. She has 5/5 strength of her quads and hamstrings, and her knee is otherwise stable.
Preoperative imaging demonstrated a Caton-Deschamps Index (CDI) of 1.15 and lateral patellar subluxation on Merchant views. She was noted to have a tibial tubercle to trochlear groove (TT-TG) distance of 24-mm and Dejour D dysplasia, with the presence of a cliff sign and a supratrochlear spur.
In terms of surgical indications, pathologic tibial tubercle malalignment has been implicated as underlying cause of patellar instability. Classically, a TT-TG distance of 17-20-mm or greater has been suggestive of the role of a tibial tubercle osteotomy (TTO). In addition, the MPFL is the primary lateral stabilizer of the patella during early flexion and also plays a large role in patellar instability. Rupture of the MPFL is present in 90%-95% of patients after first time lateral dislocation and represents a loss of the primary soft tissue restraints.
Therefore, our surgical plan was for a diagnostic knee arthroscopy, MPFLR with hamstring allograft, and TTO.
In terms of surgical technique, the patient is placed supine on an operating table. The superomedial border of the patella is marked out for a 2-3-cm incision. Similarly, an approximately 6-cm incision is marked out from the inferior border of the patella and down over the tibial tubercle.
Standard anteromedial and anterolateral portals are marked. Diagnostic arthroscopy demonstrated medial hypoplasia, Dejour D dysplasia, and overall preservation of the patellofemoral articular surface. We then proceeded with our open MPFLR and TTO.
A midline incision is made from the inferior patellar pole, down to 3-cm beyond the tibial tubercle. Medial and lateral flaps are raised and the medial border of the anterior compartment is incised, with the musculature mobilized gently laterally with a Cobb elevator, so that, this can be retracted with a malleable soft tissue retractor.
A tuberosity pin is placed with a pin guide, such that, it is perpendicular to the tibia. A cutting guide, in this case with a 45° angle, is placed over the tuberosity pin. The cutting block is positioned medial to the tuberosity, and at this point, a saw exit indicator can be used to ensure an appropriate lateral exit point which leaves at least the posterolateral 1/3 of cortex intact. The guide is then held in place with 2 breakaway pins and a center collared pin.
The distal aspect of the breakaway pins is snapped off and soft tissue retractors are placed. The osteotomy cut is then made with a large sagittal saw using the top slot of the cut guide. It is important to avoid detaching the tuberosity distally and leaving a small bridge of periosteum if possible. The central collared breakaway pin is removed and the cutting guide slid off the remaining pin remnants.
Subsequently, the osteotomy is completed proximally using an osteotomy and a mallet. The tibial tubercle is slid anteromedially along the osteotomy according to the preoperative plan. Subsequently, a 3.2-mm drill bit is used to drill bicortically in a manner perpendicular to the osteotomy cut itself in the location of the proximal screw hole. We leave this drill bit in situ to hold our reduction and subsequently drill our second screw hole with another 3.2-mm drill bit. This second drill bit is removed and the near cortex overdrilled with a 4.5mm drill to allow for lagging by technique.
The hole is measured, then countersunk, and an appropriately sized, fully-threaded 4.5-mm screw placed in the distal screw hole. Subsequently, the process is repeated for the proximal screw, first overdrilling, then measuring, then countersinking, then finally placing a 4.5-mm screw. Each screw is then hand tightened to ensure satisfactory osteotomy compression.
Graft preparation can be started immediately at the beginning of the case provided that graft length is set after osteotomy fixation. Graft preparation is performed using a semitendinosus allograft that is at least 22-cm in length. Frayed edges are cleared off and the first 3-cm of the graft is marked. Subsequently, this is whipstitched with a #2 ultra-high molecular weight polyethylene jacketed suture. We ensure that the tendon fits through a 5-mm sizer, then the other end of the graft is cut at 22-cm and tubularized. Whipstitching is performed at the other end. Finally, both suture ends are passed through the eyelets of 3.5 by 15.8-mm polyetheretherketone anchors in preparation for docking into the patella.
Patellar preparation is begun by making an incision on the superomedial aspect of the patella and carrying this through the layers of the medial knee until just superficial to the capsule. The superomedial border of the patella is exposed and two 0.045-inch guidewires are placed under direct visualization in the patella, one at the 50 yard line and the other at the superomedial border of the patella. If desired, fluoroscopy can be used for secondary confirmation of pin placement.
The pins are overdrilled with a 3.5-mm drill to a depth of 20 mm. Each tail of the prepared semitendinosus allograft is subsequently docked to the 2 prepared patellar tunnels and secured using two 3.5-mm anchors, resulting in a U-shaped construct. We subsequently loop a suture around the middle of the graft to assist in passing. A 2-cm incision is then made over the palpable medial epicondyle and adductor tubercle. The plane just superficial to the capsule is bluntly dissected between the two incisions. The graft is pulled into the medial incision using the previously placed passing suture. We are now ready for femoral tunnel preparation.
Subsequently, a C-arm is brought in and a 2.4-mm beath pin is used to localize Schöttle point. This is driven in bicortically, aiming proximally to avoid the trochlea, and anteriorly to avoid exiting the posterior metadiaphysis. At this point, our graft is draped around the base of the beath pin and the knee is cycled while directly visualizing the graft. Motion about the pin suggests anisometry and potential utility of pin readjustment. When pin position and isometry are satisfactory, the pin is overdrilled with a 6-mm reamer. We are now ready to pass our graft.
The passing suture from the graft is loaded into the beath pin and pulled through the femur, docking the graft. The suture is gently tightened and patellar mobility is examined in extension, aiming for 2 quadrants of lateral translation. The knee is cycled to ensure that full flexion is maintained, and the knee is not captured. Patellar mobility is rechecked in extension. Finally, the graft is fixed at 30° of flexion using a 6-mm interference screw. A final patellar mobility check is performed.
A free needle is used in conjunction with the ultra-high-molecular-weight polyethylene jacketed suture in the anchor islet to double back on the graft and reinforce fixation.
Closure is performed in standard fashion, using 0 vicryl for the deep structures, followed by interrupted 2-0 monocryl and running 3-0 monocryl in a running subcuticular fashion. The patient is placed in a sterile dressing and placed in a hinged knee brace locked in full extension.
Comparison of pre- and postoperative radiographs demonstrates improvement in patellar tracking. In this case, we corrected the patient from a TT-TG of 24-14 mm.
In terms of tips and tricks, efficient arthroscopy will minimize subsequent soft tissue edema. One should make the incision directly over the tubercle, as the tubercle will medialize, thus offloading closure. One should aim for a TT-TG correction to <15-17 mm, ensuring not to over correct to <10 mm. Also ensure sufficient patellar anchor spread to avoid convergence and aim the femoral tunnel proximal and anterior to avoid the trochlea.
Surgeons should also cycle the knee prior to final graft fixation to ensure unimpeded knee range of motion. Perhaps most notably, setting the length of the MPFL should be performed after osteotomy fixation.
Selection of osteotomy and its angle also merits discussion. We generally consider adding an osteotomy for TT-TGs 15-20-mm depending on overall clinical picture and risk factors. We strongly consider osteotomy for TT-TGs greater than or equal to 20-mm and for revision procedures. Of note, anteriorization offloads the patellofemoral joint and should be considered for concurrent chondral pathology. Osteotomy guides are classically available at 45, 60, and 90°, with 90° corresponding to pure anteriorization. In patients with isolated maltracking, consideration is given to a 45° osteotomy or a flatter freehand cut. In patients with combined maltracking and patellofemoral chondral pathology, we generally employ a 60° guide.
Postoperative rehabilitation begins with heel touch weight bearing for the first 6 weeks postoperatively. Patients are allowed to work on unloaded motion from 0 to 90°. Weight bearing is advanced between weeks 6-8 and biking is initiated at week 12, with sports specific drills beginning at 16-24 weeks postoperatively based on clinical examination and radiographic osteotomy healing.
In terms of published outcomes, Franciozi et al, performed a Level 2 study of 24 isolated MPFLRs compared with 18 combined cases with TTO in patients with a TT-TG of 17-20 mm. They found that outcomes were significantly improved with the addition of an osteotomy in this population.
Platt et al in their 2021 meta-analysis compared isolated MPFLR to MPFLR with TTO with or without trochleoplasty. The authors found that average time to return to sport was 6.7 months and that return to sport was not affected by the addition of an osteotomy.
The following are our references.
Thank you for your time and attention.
Footnotes
Submitted May 26, 2022; accepted August 22, 2022.
The authors declared that they have no conflicts of interest in the authorship and publication of this contribution. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.
