Opening-Wedge Distal Femoral Osteotomy With Concomitant Medial Meniscal Root Repair

Abstract

Background:

Valgus malalignment leads to excessive loading of the lateral compartment and has been associated with lateral compartment meniscal injuries and early-onset knee osteoarthritis. Distal femoral osteotomy (DFO) is a treatment option that allows correction of the mechanical access to offload the lateral compartment. Lateral opening-wedge distal femoral osteotomy and medial meniscal root repairs are both aimed to address the pathologic biomechanics of the tibiofemoral joint and when successful can delay or even prevent progression to end-stage osteoarthritic changes in the lateral and medial compartment, respectively.

Indications:

Distal femoral osteotomy is indicated for patients with normal metabolic bone health and valgus malalignment who may present with concurrent lateral meniscal injury, symptomatic lateral compartment arthritis, or a chronic medial collateral ligament tear/laxity.

Technique Description:

Long-leg alignment radiographs and preoperative magnetic resonance images are required to evaluate the degree of mechanical access deviation and to evaluate for soft tissue injury, as there is often concomitant lateral meniscal or cartilage pathology present. This technique demonstrates the optimal order of surgical steps for DFO with a concurrent medial meniscal root repair. The senior author’s preferred order is to first perform the open lateral approach and expose the lateral cortex for the placement of plate prior to arthroscopic work and excess fluid extravasation. Intra-articular work is then performed with a diagnostic arthroscopy followed by medial meniscal root repair. Finally, the osteotomy and subsequent internal fixation are performed.

Results:

The literature on opening-wedge DFO outcomes is heterogeneous, with variable rates of successful outcomes and complications. Saithna et al reported that International Knee Documentation Committee and the pain subdomain of Knee injury and Osteoarthritis Outcome Scores significantly improved postoperatively following lateral opening-wedge DFOs in patients with lateral compartment osteoarthritis. The 10-year success rate of varus-producing DFO has been reported to be 64% to 85%.

Discussion:

We describe a technique for correction of a valgus deformity with opening-wedge DFO and concurrent meniscal root repair. This surgical technique effectively restores the native femoral and tibial axis with appropriate load distribution and also concurrently restores the appropriate function of the medial meniscus which allows axial force dispersion via hoop stresses for the medial compartment.

Patient Consent Disclosure Statement:

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.

Graphical Abstract

This is a visual representation of the abstract.

Video Transcript

This is a video presentation depicting a monoplanar distal femoral osteotomy and a medial meniscal root repair for the treatment of valgus alignment in the setting of lateral meniscal deficiency and early lateral compartment osteoarthritis (OA) and a medial meniscal root tear.

Shown here are the disclosures for the authors involved.

Valgus mechanical malalignment is associated with an increased risk of degenerative changes after a lateral meniscectomy, namely of the lateral and patellofemoral compartments.^2,3 Furthermore, valgus malalignment carries a high risk of instability in both the coronal and sagittal planes. Meniscal root pathology carries similar consequences in the tibiofemoral joint as complete meniscal deficiency. ⁵ Both meniscal root repair and distal femoral osteotomy are complex procedures in their own right, each of which is not without its own risks as well. When addressed in concert, many factors must be considered. Most notably to the operating surgeon, the order of operations for the surgical procedure to be carried out must be carefully and strategically planned. But, when executed appropriately, these patients can achieve good to excellent postoperative outcomes.^1,6 In addition, while there is an abundance of literature to suggest similar outcomes between the medial closing-wedge distal femoral osteotomy and lateral opening-wedge osteotomy, the senior author prefers a lateral opening wedge due to the safety of the surgical approach and the relative ease of achieving a precise correction via an opening-wedge technique. ⁷

This operation was performed on a 28-year-old woman with a medical history pertinent for complex knee injury 10 years ago sustained while longboarding. At that time, she underwent an anterior cruciate ligament (ACL) reconstruction with a hamstring autograft, as well as a subtotal lateral meniscectomy. She endorsed having never felt like her stability had been restored post-surgery, but she was able to return to activities, albeit in a restricted fashion. Six weeks prior to her presentation, she collapsed following significant valgus force event which resulted in significant pain. From that point until presenting, she endorsed having experienced recurrent effusions and difficulty negotiating stairs.

Examination of the patient’s right knee was notable for a mild-to-moderate effusion, pain to palpation across the medial joint line and over the medial collateral ligament (MCL), a grade 2B Lachman with a grade 3 pivot shift, and increased gapping to valgus stress test. Overall, physical examination findings were consistent with a retear of her ACL, obvious valgus malalignment, and a complete MCL injury.

Standing alignment radiographs were used to approximate the weight-bearing axis and confirmed significant valgus malalignment. The mechanical medial proximal tibial angle was 87.1°, the mechanical lateral distal femoral angle was 80.9°, and the mechanical tibiofemoral angle was 5°. The senior author found that the long-leg mechanical axis is accurately determined through the deviation from midline and through the mechanical tibiofemoral angle. The authors found the mechanical axis to be deviated approximately 17.5 mm from midline, thereby falling through the central portion of the lateral tibial plateau. This corresponded with a mechanical tibiofemoral angle of approximately 5°. Therefore, our aim was to correct the patient to near-neutral mechanical alignment with a 5° correction.

Stress radiographs were performed at 20° of flexion and confirmed increased valgus gapping of 3.6 mm of the right knee, which was high compared with the left knee.

Select sagittal and coronal magnetic resonance imaging (MRI) findings are displayed. The sagittal cut demonstrates obvious mispositioned prior ACL tunnels, most notably the tibial tunnel being significantly too posterior. It also demonstrates signal disruption of the ACL, indicating graft rupture. The coronal MRI cut demonstrates evidence of areas of grade 2-4 chondral wear in the lateral compartment as well as ghosting of the medial meniscal root with associated extrusion.

In summary, the findings on physical examination of this patient correlated well with her imaging findings, and the diagnoses of complete ACL retear, complete MCL tear, medial meniscal root tear, valgus malalignment, and lateral meniscal deficiency with early lateral compartmental OA were made. A plan was made for a staged surgery, which would involve a staged approach, with the first operation including a varus-producing lateral distal femoral osteotomy (DFO) and medial meniscal root repair. A second operation would be required to address the patient’s ACL revision reconstruction, a lateral extra-articular tenodesis, and an MCL reconstruction. This pathology was chosen to be treated in a staged fashion, both due to anatomical constraints of the necessary surgical treatment and due to overall complexity. The MCL was to be treated during the second stage due to the close proximity of the anatomical site for MCL femoral tunnel placement with the medial hinge of the DFO. The ACL and possible lateral extra-articular tenodesis were also chosen to be addressed during the second stage largely due to the complexities of the procedures already involved in this case, especially involving the lateral aspect of the distal femur.

Examination under general anesthesia begins with the pivot shift test. Here, the patient displays an explosive pivot shift of her right knee, that is, 3+. Next, valgus stress testing revealed increased valgus gapping of her right knee to around 2 mm. Finally, her dial test is normal, along with her posterior drawer test.

After sterile prepping and draping of the knee in the standard fashion, a high-thigh tourniquet is placed. The approach for osteotomy is initiated first with an incision over the lateral aspect of her distal thigh. This is done first to allow for effective structure identification before fluid extravasation occurs during arthroscopy. The posterior aspect of the superficial iliotibial band is then incised in a similar manner at its posterior third. An elevator is then used to elevate the vastus lateralis in effort to identify the distal femur. The dissection then proceeds anteriorly, subperiosteally, and posteriorly.

Next, arthroscopic assessment of the medial meniscal root tear is performed by probing the meniscus and noting a posterior horn root tear. A curette is used to decorticate the root attachment site and the surrounding area in preparation for repair of the meniscal root tear. A curved shaver is used in combination with the curette to accomplish this task.

Next, using arthroscopic scissors, the extruded meniscus is released from periarticular and capsular adhesions to mobilize the posterior horn so that the root could be reattached at the appropriate anatomical site. The posterior horn was also released from the previous all-inside devices that had been used to fix the meniscus during her last operation. Upon completion of this release, the extrusion was addressed and the meniscus root could be restored to its proper insertional site.

An incision over the anteromedial tibia is made, and subperiosteal dissection allows for placement of a drill guide directly against the tibia. Arthroscopic confirmation of proper placement of the root aiming arm of the guide is made. The drill guide is used to drill 2 cannulas, one at a time, into the area that was previously the decorticated tibial attachment site. The first suture tape is then placed in the meniscus, with the suture tape being passed from inferior to superior. The curved suture passer is then flipped and the suture tape is passed through the meniscus in the opposite direction, and a vertical mattress suture has been created.

Using a passing wire, the ends of the suture tape in the meniscus are then passed down through one of the tibial tunnels. The second suture tape is then placed in the meniscus in the same fashion as the previous suture; thus, another vertical mattress suture is placed in the medial meniscus root tear. Once again, a passing wire is used to shuttle the second suture through the other tibial tunnel. Then, the sutures can be tied over a cortical button on the anterior cortex of the tibia under arthroscopic visualization to ensure proper tensioning and to ensure final fixation is sufficient.

Turning attention back to the osteotomy site, retractors are placed to increase visualization of the lateral thigh exposure. Furthermore, these retractors are integral to providing safety as well; care should be made such that they are along the posterior and far medial cortex to protect the neurovascular structures.

A guide pin is now placed from lateral to medial, aiming toward the adductor tubercle at a 45° angle. A guide is used to direct a second pin in relation to the position of the first pin—this pin also driven parallel to the adductor tubercle at a 45° angle. The cutting guide orientation is set by these 2 pins, and so it is paramount for the guide to be perpendicular to the femoral shaft; otherwise, the plate will not fit well.

An oscillating saw is then used to cut down to a depth of 5 mm of the lateral femoral cortex in relation to the 2 guide pins that were previously driven. Using a small osteotome, the osteotomy is completed through the anterior cortex, leaving a 1-cm medial bone hinge.

Using this same small osteotome, osteotomy is completed posteriorly with a finger against the posterior cortex to protect the posterior neurovascular structures while the osteotome is advanced. This should be done in a purposeful and controlled manner as this is arguably the most important and most dangerous step of the case. Using a medium-sized osteotome, the midportion of the osteotomy was performed through the cortical bone.

An opening spreader device is now positioned with a mallet and left in place for 5 minutes to allow for stress relaxation of the patient’s medial cortex hinge. In the meantime, this is a good time to bend the flanges on the distal aspect of the distal femoral fixation plate to ensure that they will cause minimal postoperative irritation in the patient.

With the distal femoral plate in place, opening of the device is initiated. One screw is placed proximal to the osteotomy site and one screw is placed distally to establish provisional fixation. Then, the spreader device can be removed and the remainder of the screws can be placed. In total, four 4.5-mm cortical screws are placed proximally and three 6.5-mm cancellous screws are placed distally, providing for a solid and secure fixation of the patient’s distal femoral osteotomy. Final fluoroscopic views should confirm adequate placement of the plate and screws.

Fluoroscopy is of vital importance to the success of this case and should be used when necessary throughout the case to ensure both a safety and appropriate technique.

This procedure is not without significant potential complications. Therefore, strategies and techniques aimed at avoidance of these complications are integral to performing this operation safely and successfully. While there are numerous possible complications, there are 3 worth mentioning due to both their relative potential and magnitude.

The first is iatrogenic fracture of the far medial cortex. Steps taken to avoid this include very slow and meticulous opening of the osteotomy site. The correction should be obtained gradually either with sequential wedges increasing in size or with a spreader device that can slowly be enlarged until desired correction is met. This desired correction should then be maintained for 3 to 5 minutes to allow for stress relaxation of the medial cortex; the spreader can then be removed. Relatively immediately following this step, the appropriately sized wedged should be inserted and the corresponding plate be applied. Of note, in the case of far medial cortex fracture, a small open approach should be used to the medial femur. Taking care to avoid the neurovascular bundle, a small plate or staple should be used to stabilize the fracture.

The second complication is neurovascular injury. Given the proximity of the neurovascular bundle to the supracondylar femur, mainly posteromedial, the dissection and retractor placement are of upmost importance. Following exposure of the lateral cortex of the femur, slow, meticulous subperiosteal dissection should be carried out and retractors can then be placed along the anterior and posterior cortex. The osteotomy itself should be made starting with an oscillating saw for approximately 5 mm. Then the osteotomy is continued with osteotomes and done in a controlled manner using fluoroscopy as needed for confirmation. Using this technique allows for greater control and therefore less risk of plunging, causing iatrogenic neurovascular damage.

The last possible complication worth mentioning is incorrect mechanical axis correction, either too much or too little. Starting with preoperative planning, long-leg radiographs can be used to determine the optimal amount of correction needed to obtain neutral mechanical alignment. Fluoroscopy can and should be used to confirm appropriate correction, both throughout the case and at its conclusion.

Postoperative rehabilitation guidelines for this operation involve range of motion restriction for the first 2 weeks to be advanced as tolerated, weight-bearing restrictions for the first 8 weeks until radiographs can be obtained for evidence of healing, and then advanced to partial protected weight-bearing. Radiographic evidence is crucial to guiding the progression of postoperative therapy and rehabilitation guidelines. At 6 months, repeat radiographs will be a determinant of timing for proceeding with the second-stage operation to address the ACL graft and MCL tears.

While there is an abundance of prior literature assessing outcomes of similar surgical techniques, there are 2 specific works worth mentioning. The first is an article by Shivji et al ⁹ published in KSSTA in 2020, which assessed 10-year outcomes of lateral opening DFO. They assessed 86 DFOs and looked at postoperative correction accuracy, complications, reoperations, and failures defined as progress to total knee arthroplasty or revision. They reported a 10-year survival rate of 89% with a mean survival of 113 months. They also found the average correction was 8.2% overcorrection. Overall, they demonstrated DFO was a safe, replicable, and successful surgery for joint preservation in patients with valgus alignment.

Another article to mention was the work by LaPrade et al ⁴ which assessed outcomes in 45 knees undergoing transtibial pullout repair for meniscal root tears. They reported significant improvements in Western Ontario and McMaster Universities Arthritis Index and Lysholm scores for all subgroups assessed, with only 3 of 45 repairs failing. Furthermore, they found no differences in outcomes scores or failure rate when comparing by age (<50 years vs >50 years) or by laterality (medial vs lateral). They showed their described transtibial technique provided statistical improvements regarding reported outcome scores with a very low failure rate.