Anterior Opening-Wedge Proximal Tibial Osteotomy for Slope Correction of Genu Recurvatum

Abstract

Background:

Symptomatic genu recurvatum is defined as greater than 5° of knee hyperextension and can be caused by osseous deformity, soft tissue laxity, or a combination. Common symptoms include pain, weakness, instability, decreased range of motion, leg length discrepancy, and stretching of the posterior capsuloligamentous structures of the knee. In instances where the genu recurvatum is caused by reverse tibial slope, literature supports the use of anterior opening-wedge proximal tibial osteotomy (OW PTO) to treat genu recurvatum by increasing tibial slope. Correction of anterior slope to a more anatomic, posterior orientation allows any stressed ligaments to return to their normal tension and restores the native biomechanics of the knee.

Indications:

The primary indication for OW PTO is genu recurvatum that is nonresponsive to physical therapy or genu recurvatum with concurrent ligamentous injury. The heel-height test provides an objective assessment for the identification and measurement of knee hyperextension.

Technique Description:

2 guide pins are placed parallel to the tibial plateau, engaging the posterior cortex. A small micro sagittal saw is used to cut the anterior cortex. Osteotomes are used to complete the osteotomy, preserving a posterior hinge. An opening spreader device is placed and opened slowly while keeping the posterior cortex intact. The new slope is maintained by use of an opening wedge osteotomy plate and screws. Allograft bone graft is packed thoroughly into the osteotomy site. Fluoroscopy is used throughout the case to assess appropriate orientation and depth of the osteotomy, as well as the final opening width.

Results:

A review of 5 studies demonstrated adequate reduction in hyperextension, with a mean knee hyperextension ranging from 17° to 32° preoperatively and 0° to 7° postoperatively. Patients had significantly improved postoperative clinical outcomes compared with the preoperative state.

Discussion/Conclusion:

Anterior OW PTO has been shown to be a safe method of accurately correcting tibial plateau slope for the treatment of genu recurvatum. Patients can expect correction of knee hyperextension, restoration of anatomic posterior tibial slope, decreased posterior tibial translation, and increased subjective outcome scores.

Patient Consent Disclosure Statement:

The author(s) attest 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 presentation is entitled Anterior Opening-Wedge Proximal Tibial Osteotomy for Slope Correction of Genu Recurvatum.

The authors’ disclosures are listed on this slide.

Genu recurvatum is defined as hyperextension of the knee that is greater than 5°. It can be the result of numerous etiologies including ligamentous injury, congenital deformities, previous growth plate injury, polio and/or other muscle diseases that involves weakness and atrophy of the quadriceps muscles and subsequent hyperextension of the knee.

When recurvatum is caused by anterior tibial slope, diagnosis can be difficult as many clinicians are misled to believe there is a posterior tibial sag and/or ligamentous injury. Anterior tibial slope causes increased stress on the posterior cruciate ligament (PCL) and other posterior structures of the knee during axial loading, which subsequently increases the risk of ligamentous and meniscal injuries. ² For this very reason, clinicians must carefully examine patients for concurrent ligamentous or structural injury especially in the posterior knee. In the case of isolated genu recurvatum, initial treatment typically includes rehabilitation programs focusing on quadriceps strengthening to help patients compensate for symptomatic knee hyperextension. ¹ If rehabilitation does not provide symptomatic relief, proximal tibial osteotomy should be performed to produce a more native, posterior tibial slope and decrease knee hyperextension.^1,3-5

The patient presented is a 38-year-old male who presented with gross knee deformity, chronic pain, stiffness, swelling and mechanical symptoms, as well as functional limitations. Two months prior, he had been playing in the yard with his son when he experienced pain in his posterior knee and had subsequent episodes of instability and popping which was worse in flexion. He was examined by an outside provider and magnetic resonance imaging (MRI) indicated the presence of a posterior horn medial meniscal tear. He was ultimately referred to our practice when a physical therapist had concerns for laxity of the PCL.

Our physical examination revealed 7 cm of heel height to 130° of flexion compared with the 1 cm of heel height and 140° of flexion of the contralateral knee. Pain prevented him from achieving end flexion of the right knee and the tibial plateau was less prominent than the femoral condyles when compared with the left knee. Lachman's test and posterior drawer revealed stable endpoints, and there was no varus or valgus laxity. Overall, the examination was suggestive of a medial meniscal posterior horn tear and anterior tibial slope.

Plain films of the knee including anteroposterior (AP), Rosenburg, lateral, sunrise, and full-length standing revealed an anterior tibial slope of 11° as well as visible deformity of the right tibial tubercle.

An MRI from an outside provider was reviewed and revealed a stable-appearing horizontal tear of the posterior horn of the medial meniscus as well as an anterior tibial slope.

We concluded that physeal arrest of the right proximal anterior tibia during maturation led to malunion of the tibial tubercle and an anterior tibial slope. His resultant anterior tibial slope was severe enough to be defined as genu recurvatum, and his altered tibiofemoral biomechanics led to posterior subluxation of the tibia. This resulted in PCL pseudolaxity, increased stress on the posterior horn of the medial meniscus, and early degenerative changes of the medial, lateral, and patellofemoral compartments. We explained the pathology to the patient, and after discussion of the risks and benefits the patient elected to undergo anterior opening-wedge proximal tibial osteotomy with a concurrent medial meniscus repair.

An examination under anesthesia revealed range of motion in the right knee to be from 8 cm of heel height to 135° of flexion compared with 1 cm to 140° on the left. His femoral condyles were palpably anterior to the tibia, indicating posterior tibial subluxation. There was no gapping on varus or valgus stress, and his posterior drawer test was negative. He had a negative pivot-shift exam and exhibited a pseudo Lachman's test.

A vertical incision is made from the midportion of the patella extending downward to 6 cm distal to the joint line, raising full-thickness subcutaneous flaps. The patellar tendon is isolated, and the tibial tuberosity is exposed. Medial dissection is performed and the periosteum under the medial collateral ligament (MCL) is elevated to the posteromedial corner of the tibia. Laterally, the anterior compartment musculature is elevated 1 cm distal to Gerdy's tubercle and lateral dissection is performed to expose the anterior aspect of the proximal tibiofibular joint.

Anteromedial and lateral portals for the arthroscopy are created within the osteotomy incision. Arthroscopy revealed an incidental partial type 1 lateral meniscal root tear posteriorly, and a partial lateral meniscectomy was performed. Chondroplasty was performed for grade 2 chondromalacia of the distal patella, trochlear groove, and lateral and medial femoral condyles.

Inspection of the medial compartment revealed a complete longitudinal meniscal tear of the posterior horn that propagated obliquely from the red-white junction superiorly to the meniscocapsular junction of the inferior surface. Three Smith and Nephew all-inside devices were used to repair the posterior horn of the medial meniscus.

Attention is then turned to the osteotomy. A retractor is used to protect the extensor mechanism while 2 guide pins are placed parallel to the tibial plateau between the tibial articular margin and patellar tendon insertion until they engage the posterior cortex, and their position is confirmed by fluoroscopy.

A small micro sagittal saw is then used to cut the anterior cortex, making anterior, anteromedial, and anterolateral cuts in plane with the guidepins. Osteotomes are then used to finish the osteotomy in a controlled fashion around the deep lateral and medial aspects of the cut until it is fluoroscopically confirmed to be within 1 cm of the posterior cortex bilaterally. An opening spreader device is then placed and slowly and carefully opened to ensure the posterior hinge of cortex remains intact. The spreader and an osteotomy trial wedge are used to maneuver the gap until the tibial slope is in the desired anatomic position on fluoroscopy and that clinically the heel heights are symmetric to the normal contralateral knee, and the implements are left in place for 5 minutes to permit stress relaxation of the posterior cortex. A 12.5 mm posteriorly sloped Puddu plate (Arthrex, Naples) is then placed and fixed proximally with two 6.5 mm fully threaded cancellous screws and distally with two 4.5-mm cortical screws. In this patient, 1 distal cancellous screw was used as the cortical screws were not biting well due to soft bone.

Examination revealed the patient's posterior sag and PCL pseudolaxity were eliminated and his medial and lateral femoral condyles were 5 and 7 mm posterior to his anterior tibial margin, respectively.

Allogenic bone graft is then packed in tightly into the osteotomy site until the opening wedge is filled.

The deep and superficial incisions are closed with suture and dressed in sterile fashion.

Anterior opening-wedge osteotomy is a technically challenging procedure and potential complications can result in devastating long-term effects. As such it is important to take care to implement safe technique aimed at minimizing risk for these complications. The first complication to consider is iatrogenic neurovascular injury. The popliteal neurovascular bundle lies in close proximity to the posterior tibial cortex. Therefore, ensuring proper depth of guide pins for osteotomy is crucial to ensure they remain unicortical. Further when utilizing the small microsagittal saw blade, care must be taken to avoid breaching the posterior cortex. Iatrogenic patellar tendon injury is also a risk with this procedure. Ensuring proper placement of retractors throughout the procedure is key, namely, placing a z retractor deep to the patellar tendon. Further care must be taken to avoid pulling excess force through that retractor as this could lead to peeling of the patellar insertion. A third complication to be avoided is iatrogenic fracture of the posterior cortex. This can be avoided with ensuring proper location of the guide pins and proper depth and trajectory of the tibial cut. Again, the anterior cortex should be gradually opened in a controlled fashion.

Rehabilitation recommendations for anterior opening-wedge proximal tibial osteotomies include 8 weeks of nonweightbearing followed by partial protected weightbearing with crutches until the patient can ambulate without a limp. Range of motion is restricted to 0° to 90° of passive knee flexion for the first 2 weeks, after which flexion may be advanced as tolerated.

Current literature by Kim et al ³ including objective measurements of tibial plateau angle correction and subjective anatomical and functional scoring by patients who underwent anterior opening-wedge proximal tibial osteotomy supports the chosen method for correction of genu recurvatum secondary to bony abnormalities such as anterior tibial slope.

Final postoperative plain films reveal a corrected tibial slope with the hardware on the anterolateral tibia to be in good position.