Biplanar Proximal Tibial Opening-Wedge Osteotomy for a Chronic PCL Tear With Medial Compartment Arthritis

Abstract

Background:

Chronic posterior cruciate ligament (PCL) insufficiency leads to instability of the knee, resulting in increased loading of the medial and patellofemoral compartments. Chronic PCL insufficiency progressively damages the menisci and chondral surfaces and can accentuate and worsen varus malalignment. Biplanar proximal tibial opening-wedge osteotomy (BPTO) is a treatment option for chronic PCL tears with medial compartment arthritis which concurrently treats sagittal (flat slope) and varus coronal alignment.

Indications:

Opening-wedge BPTO is indicated in active patients who present with varus malalignment and flat slope with concomitant degenerative medial compartment osteoarthritis and PCL insufficiency. In general, BPTO is contraindicated in patients with a significantly elevated body mass index (BMI), smokers, or in those who have advanced tricompartmental osteoarthritis.

Technique Description:

Preoperative long-leg radiographs are essential to preoperative evaluation. Ideal coronal alignment following correction would have the mechanical axis pass through the apex of the lateral tibial eminence to properly off-load the medial compartment. Magnetic resonance imaging (MRI) studies are also useful for determining the presence and extent of concomitant soft tissue and chondral injury, especially in the lateral compartment. This video demonstrates the senior author’s preferred technique for a biplanar proximal tibial opening (PTO) with concomitant chondroplasty and partial medial meniscectomy (PMM). The senior author’s preferred order of operations is also displayed and involves first performing an arthroscopy, then proceeding with the open portions of the case, including the medial approach and subsequent osteotomy.

Results:

Past studies have supported PTO as a reliable treatment option for varus malalignment. Bode et al reported a 5-year survival rate of 96% of patients with an overall complication rate of 8.6%. The authors also reported that Lysholm scores were also significantly improved at 60-month follow-up compared with preoperative scores.

Discussion:

This is a technique for the correction of a varus malalignment with concomitant flat slope and PCL insufficiency with biplanar open-wedge PTO. This operation corrects the mechanical axis and sagittal slope of the knee and restores proper load distribution across the tibiofemoral articulation. In conclusion, a biplanar open-wedge PTO is a useful alternative to joint arthroplasty for active patients with a chronic PCL tear, medial compartment arthritis, and varus malalignment.

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 the technique for performing an opening wedge biplanar proximal tibial osteotomy for posterior cruciate ligament (PCL) insufficiency, medial compartment arthritis, and varus alignment.

Shown here are the disclosures for the listed authors.

Chronic varus malalignment with medial compartment arthritis leads to increased load distribution across the medial compartment of the tibiofemoral articulation. A proximal tibial opening-wedge biplanar osteotomy modifies the geometry of force transmission across the knee joint to restore load distribution to a state that more closely resembles that of the native knee.

A flat tibial slope may result in an increased risk for a PCL tear and has been identified as a cause of postoperative graft laxity and failed PCL reconstructions.^1,2 In the setting of PCL insufficiency a flat tibial slope can worsen instability, namely posterior tibial translation and the corresponding pathologic tibiofemoral biomechanics. The objective of this surgery is to concomitantly correct the varus malalignment and to also increase the sagittal plane posterior tibial slope, thereby increasing anteroposterior plane stability.

The case featured in this video involves a 62-year-old very active man who presented with a chief complaint of right knee pain of 4 years duration. The patient initially presented to clinic in the prior year with a torn PCL, medial compartment osteoarthritis, and varus malalignment. At that time, he was trialed on a medial unloader brace, which was found to improve his symptoms. He now returned to clinic with worsening right knee instability and medial joint line pain.

Physical examination revealed a 3+ posterior drawer sign. The patient also had tenderness along the medial point line and crepitation to palpation. His knee was otherwise stable to anterior, medial, and lateral loads. Altogether, these exam findings were consistent with a medial compartment arthritis and a chronic PCL tear.

Shown here are plain radiographs that were obtained for this patient preoperatively. The Rosenberg view radiograph demonstrates significant medial compartment narrowing of the right knee compared with the contralateral side. The long leg standing view demonstrates significant varus malalignment (approximately 8°) of the right knee compared with the left. Lastly, standard lateral view radiographs revealed a flat tibial slope of approximately 4° and posterior stress radiographs demonstrated approximately 17 mm of increased posterior tibial translation on the symptomatic knee.

Sagittal magnetic resonance imaging (MRI) images demonstrated moderate degenerative changes of the medial femoral condyle, and also a complete PCL tear with attenuation, in the images on the left and right respectively.

Altogether, findings from physical exam and pertinent imaging were consistent with the diagnoses of a chronic PCL tear, medial compartment osteoarthritis, and varus malalignment of the right knee. The plan was made for a right knee arthroscopy to address any intra-articular pathology and a proximal tibial opening wedge bi-planar osteotomy with the goal of increasing the posterior tibial slope and correcting the coronal plane malalignment.^4-6

Examination under anesthesia included a bilateral posterior drawer test, which was 3+ on the right knee and 0 on the left knee.

The arthroscopic portion of the case was performed first, beginning with medial and lateral parapatellar incisions. Some mild synovitis was noted in the patient’s suprapatellar pouch and rather diffuse areas of grade 3 to grade 4 chondromalacia were noted in the trochlear groove. The patient’s medial compartment had areas of grade 4 chondromalacia as well as a complex radial flap tear of the mid to posterior third junction aspect of his medial meniscus. A partial medial meniscectomy was performed with a shaver and a basket punch. This concluded the arthroscopic portion of the case.

A 6- to 7-cm incision was next made from the medial joint line extending distally and down to bone between the anterior crest of the tibia and its posteromedial aspect. Next, an elevator was used to elevate subperiosteally under the medial collateral ligament (MCL) and popliteus musculature posteriorly and anteriorly under the deep infrapatellar bursa and patellar tendon. Tissue retractors were then placed, and fluoroscopy was used to drill 2 guide pins at the level of the proximal tibial metaphyseal flare and parallel to the joint line that aimed toward the fibular head.

An oscillating saw was then used to create a cut in the medial tibia to a depth of 5 mm under direct visualization. The anterior extent of the osteotomy was then completed using a small osteotome under direct visualization using a Z-retractor to keep the patellar tendon protected. The midportion of the osteotomy was completed using a medium osteotome under fluoroscopic guidance. The posterior extent of the osteotomy was completed once again using a small osteotome. A 1-cm lateral hinge was preserved. During advancement of the osteotome during this portion of the procedure, a finger was used to palpate the edge of the osteotome at the posterior cortex and to protect the neurovascular structures posteriorly.

The opening spreader device was then advanced with a mallet to the desired depth under direct visualization. The depth of each arm of the device was confirmed radiographically following advancement. The device was then opened to the desired osteotomy correction and left in place for 5 minutes to allow for stress relaxation of the 1 cm lateral cortical hinge. Once open, position of the device was confirmed radiographically. Next, an opening tine device was then placed as anteriorly as possible through which the posteriorly sloped osteotomy plate was positioned. With the device in place, a posterior drawer was performed, and posterior tibial translation was noted to be markedly reduced from the preoperative state.

Acceptable anatomic tibial slopes fall between 5° and 10° in the sagittal plane, and are ideally neutral in the coronal plane. The final resultant slope of a biplanar opening-wedge osteotomy should fall into this range without putting excessive force on the extensor mechanism and while planning for a comfortable slope that will reduce stress on the PCL without shifting an excessive amount of stress on to the anterior cruciate ligament (ACL). Biomechanical studies suggest that between 8° and 11° of posterior tibial slope results in the optimal balance between ACL and PCL stress forces. Given that this patient was malaligned in both the coronal and sagittal planes, we aimed to have a final correction that would result in neutral coronal alignment and approximately 8° of tibial slope. Upon completing our osteotomy cut, we opened our medial based wedge slowly and meticulously. During this step, we preferentially placed our spreading device toward the anterior aspect of our osteotomy in order to open the anterior portion of our osteotomy more than the posterior portion.

A 11-mm posteriorly sloped Puddu plate was placed to correct his malalignment in the coronal plane. The posteriorly sloped plate was positioned on the anteromedial tibia to increase his posterior tibial slope. The osteotomy was fixed placing two 4.5-mm cortical screws distally and two 6.5-mm fully threaded cancellous screws proximally.

After fixation of the plate, a lateral incision was made, and a staple was placed along Gerdy tubercle in order to ensure that the osteotomy would not open further laterally given the patient’s older age.

Finally, the osteotomy site was packed with allograft bone graft and the incisions were closed with suture ensuring adequate hemostasis.

This is a complex procedure, and it is not without potential complications. Fracture through the lateral hinge is one that can slow down healing or affect coronal plane alignment correction. While performing the opening of the osteotomy with the spreading device, or upon placement of wedge, the osteotomy can propagate a fracture through the lateral hinge. This is more common in larger corrections, particularly those >10 mm. This can be minimized by optimization of the osteotomy level and angle, aiming to have a trajectory directed toward the proximal aspect of fibular head, which coincides with the metaphyseal flare of the tibia. Second, slowly achieving correction and pausing incrementally to allow for gradual opening of the spreader device helps to minimize the risk of a lateral hinge fracture. If there is concern that a fracture may have occurred, then a staple should be placed on the lateral aspect of the tibia to help stabilize the fracture.

Inadequate correction is a second complication that can occur. Inadequate preoperative planning can lead to inadequate correction, leaving the patient in malalignment. Therefore, thorough preparation of the planned correction is crucial to ensure the desired correction.

Neurovascular injury is also a concern during this procedure. Excessive penetration posteriorly can risk injury to the neurovascular bundle. This can be minimized with a thorough and meticulous subperiosteal dissection posteriorly. Then, placement of a posterior retractor can protect the posterior knee structures. Finally, by utilizing the oscillating saw to a depth of 5 mm and finishing the osteotomy in a controlled fashion with osteotomes can allow for performance of the osteotomy in a more controlled fashion.

Postoperative rehabilitation for this procedure consists of range of motion restriction to 90° of knee flexion in the first 2 weeks, and then is advanced as tolerated. The patient remains nonweightbearing for the first 8 weeks postoperatively until 8-week postoperative films can be obtained. If at this point, there is radiographic evidence of healing, partial protected weight bearing may be initiated. Weight bearing is to be advanced at one-quarter body weight percentage per week until full weight bearing as tolerated can be achieved at 3-months postoperatively, at which point, repeat radiographs are obtained.

Prior literature has reported proximal tibial opening (PTO) to be a reliable treatment option for patients with osteoarthritis, cartilage defects, and symptomatic malalignment.^1-3,7 A systematic review and meta-analysis completed by Kunze et al ⁷ demonstrated good to excellent return to sport and return to work rates with relatively low rates of complications and progression to total knee arthroplasty. In addition, an advantage of the biplanar PTO technique is the capacity to increase posterior tibial slope, thereby decreasing force on the native or reconstructed PCL and decreasing posterior tibial translation.^1-3 While there is biomechanical literature supporting the role of biplanar osteotomy in addressing flat slope in the setting of PCL insufficiency or concurrent PCL reconstruction, there is a relative sparsity of data regarding outcomes in this patient cohort. Future work should examine clinical outcomes within this unique cohort.

Final postoperative day 1 films show a restoration of neutral coronal alignment with increased posterior tibial slope and reveal the hardware to be in good position.