Optimizing indications and technique in osteotomies around the knee

Indications

The ideal candidate for PTO is a young patient (<65 years), moderately active, with medial isolated osteoarthritis, malalignment <15°, tibial bone varus angle >5° and a minimum range of motion >90° of flexion on the affected knee. Relative contraindications are age >65 years, impaired range of motion with <90° of flexion and ≥15° of flexion contracture, ≥20° of correction and rheumatoid or inflammatory arthritis. PTO should be considered on an individual basis. Non-suitable patients are obese (BMI >30) and patients with bicompartmental arthritis or with previous lateral meniscectomy (2). Smoking plays a negative role especially as it may interfere with bone healing in open-wedge PTO and may cause nonunion.

Instability used to be a contraindication in PTO, but nowadays sagittal and coronal alignment modification through this surgical technique may represent a useful solution in a patient with anterior cruciate ligament (ACL) rupture and posterolateral corner injuries (PLC). Varus deformity results in the tensile force on ACL to increase, and a varus alignment >5° is recognized as a risk factor for failure of ACL reconstruction. Nowadays, PTO might be performed, if degenerative changes occur, in patients with varus knee plus ACL rupture in the absence of dynamic instability on weight-bearing lateral radiographs. ACL reconstruction may be combined with PTO or performed as a second surgical stage, usually in patients with painful instability combined with medial degenerative changes in a varus knee (3).

Chronic PLC laxity leads to a decreased ability for withstanding a loading stress applied to the knee and varus alignment worsens this situation. Therefore, according to Arthur et al. (4), correction of the varus alignment through PTO alone can result in better knee stability and good clinical outcomes, while only 38% of their cohort needed a second stage procedure consisting of ligament reconstruction.

Techniques

Many PTO techniques have been developed and used in history, but today, opening- and closing-wedge osteotomy are the most commonly used (see Table 2). In the lateral closing-wedge technique, correction is achieved by removing a bone wedge from the lateral tibia, retaining the hinge and closing the gap. It has been widely used in the past for its high rate of consolidation, but progressively lost part of its popularity due to some disadvantages, such as shortening of the leg, the need for fibular osteotomy, the interruption of proximal tibiofibular joint and the risk of peroneal nerve injury. On the other hand, in the medial open-wedge technique, a single line osteotomy is performed respecting a lateral hinge and a progressive opening is realized until the planned wedge and degree of correction are reached. The site is then fixed with a plate and might be filled with a bone graft. This technique preserves the bone stock, but it affects the position of the patella and it carries the disadvantage of a possible nonunion. Besides, the open-wedge technique might be performed in multiple planes: biplanar osteotomies are performed when an additional cut is made at the anterior third of the tibia behind the anterior tibial tubercle (ATT) at about 110° of the horizontal osteotomy. With this method, the tibia is prevented from rotating around the vertical axis and it creates an anterior buttress against sagittal movements. Moreover, this results in a higher surface of bone contact, enhancing the possibility of a good and rapid consolidation.

In the planning of a PTO, patellar height and eventual leg length discrepancy should be critically determined, since the biplanar open-wedge technique results in a distalization of the patella and an increase in the leg length. We know that the patella height will decrease approximately 2 mm per 10° of valgus correction (2). One solution would be to orient the oblique osteotomy cut distally to the ATT, and fix it with one or two bicortical screws. This may be indicated in patients requiring a correction of more than 10° and/or in patients with a preexisting patella infera. Regarding leg length discrepancy, a close-wedge osteotomy may be better indicated in patients with a discrepancy of more than 1.5 cm in favor of the operated leg.

Triplanar osteotomy might be suitable for patients with a posterior cruciate ligament (PCL) injury associated with a varus knee, with a tibial slope of less than 9° (5). Indeed, an increase of the tibial slope may easily be performed concomitantly to an open-wedge PTO. Likewise, an ACL-deficient knee with a varus deformity and high tibial slope (9–12°) may benefit from a close-wedge osteotomy since the tibial slope tends to decrease in this technique (6). In case of a combined ACL + PTO procedure, the osteotomy must be performed first, positioning of the anterior proximal screws should be done after drilling of the tibial tunnel and passage of the graft. However, it’s still unclear if an advantage in a combined HTO + ACL reconstruction exists, compared to HTO alone (7).

Finally, the postoperative degree of correction is still a matter of debate. In the recent literature, an individualized postoperative correction is suggested, rather than a correction to the Fujisawa area (62–68% of the lateral tibia width). For example, some authors proposed a correction to 55% tibial width (1.7–2° mechanical valgus) (8) to balance medial and lateral loading stress, while others suggest a hypercorrection to a mechanical axis of 4.5° in valgus, to better distribute stress among the two compartments (9). The authors usually pursue a tailor-made correction, in patients with osteoarthrosis, the postoperative axis should be in the Fujisawa area, while for PTO associated with cartilage or meniscus procedures, we usually plan for a mechanical axis of 0–3° valgus.

There is still a large opportunity for improvement in osteotomies including further development in navigation systems, especially to navigate the tibial slope, control the joint line obliquity and the precision of the correction in double level osteotomies. Preoperative 3D-CT scan planning resulting in individualized cutting blocks and customized plates may improve the reliability and the precision of the osteotomy, as well as facilitate its realization. Those techniques are still in development and their performances are still under investigation.

Indications

Ideal candidate for a DFO procedure should be younger than 65 years, active, with a valgus deformity, affected by isolated lateral compartment osteoarthritis. Candidates should have a preoperative extension/flexion 0–120° range of motion with a normal BMI. Poor postoperative outcomes are related to BMI >30, nicotine abuse and severe patellofemoral osteoarthritis, which some authors consider a relative contraindication for the DFO procedure. Other contraindications to this procedure are severe lateral compartment involvement (Ahlback >III), medial compartment or tricompartimental osteoarthritis, as well as poorly controlled chronic inflammatory arthritis and osteoporosis. Valgus deformity greater than 20° are considered a contraindication to DFO as it can be associated with severe ligamentous instability (11).

DFO can be indicated in patients affected by chondral lesions of the lateral compartment in a valgus knee, in order to achieve correction of the malalignment and protection of the chondral repair. Cartilage treatment can be combined at the same time as the correction of the deformity, whereas deformities due to growth disorders or post-traumatic must be addressed, if possible, before the onset of the arthrosis. DFO might also be beneficial in young, sportive patients, even with initial stage of osteoarthrosis, who need a concomitant lateral meniscus allograft transplantation, in order to offload the lateral compartment and the freshly implanted allograft.

In case of ligamentous instability, DFO can be performed as a standalone procedure or combined with a concomitant or staged ligament reconstruction. For example, some studies have analyzed the outcomes after lateral open-wedge DFO alone performed on valgus knee with MCL deficiency, showing a decrease of the medial opening at 30° of flexion. This could be considered in low-demand patients (12).

Techniques

DFO can be performed as a lateral open-wedge technique or as a medial close-wedge one (Fig. 2). In the first one, osteotomy is performed with an inclination of 20° from two to three fingers proximal to lateral epicondyle aiming at a point few millimeters proximal to the medial epicondyle, in order to remove a bony wedge of predefined dimension and gently opening the site in varus until the desired degree of correction is reached. The site is then fixed with plates and might be filled with bone graft. The medial hinge should be preserved by advancing the oscillating saw no more than 1 cm away from the medial cortex, as it is more fragile and prone to fracture, resulting in collapsing of the osteotomy site and great difficulty in controlling the rotational stability (13). This procedure is technically more demanding, but allows an accurate correction and the restoration of the femoral height, especially in those patients requiring mild to large correction. On the other hand, the disadvantages of this procedure are represented by the danger of hinge fracture and the incidence of delayed union or nonunion of the osteotomy site. A study analyzed the biomechanics result of the femoral osteotomies, highlighting how the lateral open-wedge technique resulted in inferior stability and in lower stiffness compared to the close-wedge one. Therefore, a bone graft or substitute should be mandatory in order to enhance the biological healing. In the close-wedge technique, parallel pins are then driven in the cortex from the medial supracondylar area to the lateral condyle and the proximal part of the osteotomy is performed through the antero-posterior cortex, preserving the lateral one. The bone wedge is removed and the osteotomy site is closed and fixed, compressing the medial cortex. The conventional single plan osteotomy has been replaced by the biplanar technique, in which the osteotomies are performed in the posterior three-quarters of the femur and completed with an ascending cut performed on the anterior surface of the femur. This technique allows for a more distal positioning of the lateral hinge point, a wider contact of surface and more accurate control of the rotational stability. Finally, it enhances biological bone healing. Furthermore, studies reported no loss of correction in the follow-up examination and low incidence of nonunion. However, there is still an active debate about the indication to open- versus close-wedge surgical techniques. A recent systematic review (14) showed similar outcomes for the two procedures, with no difference in radiographic correction, bony healing or patient-reported outcomes.

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Medial open-wedge distal femoral osteotomy.

Citation: EFORT Open Reviews 7, 6; 10.1530/EOR-22-0057

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Finally, postoperative correction is still a matter of debate, as many authors recommend a correction to the neutral alignment (50% WBL), but recent biomechanics studies (15) showed that a 5° of overcorrection restores near-normal contact pressure and contact area in the lateral compartment. In our experience, in single DFO, we usually favor biplanar medial closing-wedge osteotomy, unless there is a hypoplasia of the lateral condyle. In this situation, we rather go for a lateral opening-wedge osteotomy. Both osteotomies are fixed with a rigid plate and locked screws.

Indications

The ideal candidates for a DLO are patients affected by a varus axial deformity, which correction at one level, would create a non-physiological deviation of the joint line. If during preoperative PTO planning the Mechanical medial proximal tibial angle (mMPTA) is more than 95°, lateral distal femoral angle >90° and the planned bone wedge size is >15 mm, then DLO should be considered. Those indications come from studies that highlighted how a postoperative mMPTA greater than 95° leads to inferior clinical outcomes, increased medial joint stress and higher failure rates. Other good candidates are patients with deformity both in the femur and in the tibia with mMPTA <85° and mechanical lateral distal femoral angle >90°, affected by medial compartment osteoarthritis (16). Furthermore, patients with pre-existent joint line obliquity, such as a patient who underwent epiphysiodesis or previous osteotomy, could be addressed with this procedure.

Techniques

In order to treat a varus deformity with a DLO, a lateral close-wedge femoral osteotomy has to be combined with a medial open-wedge tibial osteotomy. The surgical techniques performed are the same as aforementioned for open-wedge PTO and closed-wedge DFO. Surgery should start from the DFO close-wedge procedure, in order to save a bony wedge that could be used as a filling graft in the PTO open-wedge procedure, and thus enhance bone healing. A further potential advantage of performing the open-wedge as a second step is that surgeons can perform a refined intraoperative adjustment of the leg axis (17). This is possible by correcting the deformity on the femoral side in order to reach a horizontal JLO and then addressing the varus deformity with the tibial osteotomy. The combination of close-wedge femoral osteotomy and open-wedge tibial osteotomy prevents leg length discrepancy as well. Nowadays, no consensus has been reached over the ideal postoperative alignment and joint line orientation. Some authors perform a slight overcorrection with a mean mTFA postoperative of 0.8°, while others aim for a 2–3° of mTFA (18). In our experience, we suggest correcting the deformity present on the distal femur, followed by the correction of the constitutional varus +3 to 5° according to the global correction to be planned.

Indications

Anterior closed-wedge osteotomy (ACWO) can be performed in patients with recurrent ACL reconstruction failures associated with a PTS greater than 12°. Contraindications to this procedure are severe malalignment of more than 10° varus, more than 10° knee hyperextension and evidence of grade IV Kellgren–Lawrence osteoarthritis. Relative contraindications involve obese patients and heavy smokers.

Anterior open-wedge osteotomy (AOWO) can be performed in patients with symptomatic PCL deficiency and an evident sagittal tibial malalignment caused by decreased PTS. A recent article (20) suggests considering AOWO in patients undergoing PCL reconstruction with a PTS <5° and a PTS <7° in patients undergoing PCL revision. In the case of genu recurvatum, Dejour et al. (21) stated that an absolute indication is represented by the combination of bony and soft tissue recurvatum which might be addressed by osteotomy alone or by soft tissue reconstructive procedures. AOWO might be indicated if the recurvatum is due to a decreased PTS and if the patient complains of pain or instability, and it can only be performed in skeletally mature individuals. AOWO is contraindicated in patients with deformity secondary to poliomyelitis, as this would create more knee instability, and in patients with pure soft tissue recurvatum.

Techniques

ACWO is a surgical procedure in which an anterior bony wedge is removed by the tibia in order to decrease the PTS by closing the osteotomy site. It might be performed with different techniques and different osteotomy positions, below, above or at the same level of the ATT. Dejour et al. and Walker et al. (22) described an osteotomy technique above the ATT, starting from the superior margin of patellar tendon and securing the osteotomy site with two staples. This technique should not be performed in a patient with patella alta, as it might worsen the patella tracking biomechanics. Sonnery-Cottet et al. first described an osteotomy technique below the ATT, involving a 6-cm ATT osteotomy and subsequent synthesis with two cortical screws (23), while Hees and Petersen modified the technique, avoiding the ATT detachment (24). All techniques require a good exposure on both sides of the tibia and perfect symmetry in the closing-wedge osteotomy, which may be checked by ensuring that two guide wires lie parallel to the joint line. The two converging guide wires, which define the osteotomy limits, should be driven aiming at the posterior cortex, just 1 cm below the PCL tibial insertion, without violating the posterior hinge. If a combination of ACWO and ACL revision is planned, the autograft harvesting must be performed as a first step and the fixation system should not interfere with the creation of the tibial tunnel. Studies (24) demonstrated good outcomes with postoperative PTS less than <10°, authors suggest that postoperative correction should be ideally in the 6–8° range.

In AOWO, an anterior tibial bony line is cut and progressively opened in order to achieve an increased PTS. As ACWO, osteotomies might be performed above, below or at the same level as the ATT (25). The most used surgical technique is the one described by Lecuire et al. (26) in which a prior 6–8 cm tangential ATT osteotomy is performed, followed by the cut of the osteotomy line under the ATT, then the opening of the wedge at the planned correction is made. The guide pins must be positioned at the tibial insertion of the PCL and the posterior hinge should not be damaged. Surgeons must pay attention to be perfectly symmetrical in the opening of the wedge, the osteotomy site can be filled with bony graft and the ATT should be proximalized based on the correction achieved to avoid a patella infera. Posterior knee laxity should be then reassessed after the fixation in order to address the need for PCL reconstruction or not.

Indications

In the case of patella instability, surgical procedures are indicated when the instability becomes persistent and the patient has suffered from two to three episodes of dislocation. In this setting, the surgeons must assess and recognize all the potential factors that caused or facilitated the dislocation. Amongst the four risk factors described by Dejour et al. (27), abnormal tibial tubercle -trochlear groove index (TT-TG) should be systematically appreciated and corrected through an osteotomy of the ATT. Increase TT-TG might also be caused by excessive tibial rotation, femoral anteversion, valgus and recurvatum deformity. It is therefore important to define the greater TT-TG in a reliable manner to prevent the creation of an iatrogenic painful overload of the medial compartment consecutive to the osteotomy. Osteotomy of the ATT might also be helpful in asymmetrical patellofemoral osteoarthritis with an abnormal TT-TG. This osteotomy is usually associated with a facetectomy of the lateral portion of the patella.

Techniques

If the TT-TG value is >20 mm measured on CT or >13 mm on MRI, a tibial tubercle medialization is suggested, as it decreases the valgus force exerted by the extensor mechanism. The aim should be the restoration of a TT-TG between 10 and 15 mm. In the case of patella alta (Caton-Deschamps >1.2) with a short patellar tendon, a tibial tubercle distalization is advised, aiming to restore the normal value and to obtain a better patellar tracking. In the case of a hypoplastic medial facet of the trochlea (type C), a tibial tubercle distalization of 5 mm and an optional medialization could be performed to enhance the patellar tracking. Surgeons must take into account that during ATT distalization of 1 cm, a subsequent 4 mm medialization will occur. Lateral retinaculum lengthening should be performed only if the tightness of lateral restraints causes a negative patellar tilt test. Medial patellofemoral ligament (MPFL) reconstruction should be frequently added to reduce the failure rate of the aforementioned procedures.