Current Concepts in Anterior Tibial Closing Wedge Osteotomies for Anterior Cruciate Ligament Deficient Knees

Abstract

Purpose of Review

Anterior closing wedge osteotomies (ACWO) are utilized to better restore knee stability and in situ forces on anterior cruciate ligament (ACL) grafts during ACL revision reconstruction while reducing the risk of retearing and subsequent revision procedures. However, clinical outcomes following ACWO for patients undergoing ACL reconstruction remains largely limited. The purpose of this review was to provide a concise overview of the current literature on indication, techniques, and outcomes following ACWO in ACL-deficient patients undergoing primary or revision ACL reconstruction while discussing the authors’ preferred technique to ACWO during a staged ACL revision reconstruction.

Recent Findings

Currently available clinical studies and case reports have demonstrated ACWO to improve knee stability and outcomes for patients with an increased posterior tibial slope undergoing primary or revision ACL reconstruction with low complication rates.

Summary

The ACWO provides an adjunct surgical option to decrease graft failure while improving knee stability and post-surgical outcomes for patients with an increased posterior tibial slope undergoing primary or revision ACL reconstruction. Further investigations are warranted to validate currently reported outcomes following ACWO in higher-level clinical studies with longer-term follow-up.

Introduction

Anterior cruciate ligament (ACL) injuries are prevalent in athletic patients sustaining knee injuries [1], with a reported incidence of 36.9 per 100,000 person-years [2]. The ACL plays a key role in stabilizing the knee, protecting it against excessive anterior translation and internal rotation. Resultant instability following ACL rupture is associated with an increased risk of meniscus injuries, cartilage lesions, and development of early-onset osteoarthritis with associated functional limitations [3, 4]. ACL reconstruction is performed to restore knee stability and prevent complications inherent within the ACL-deficient knee. However, ACL re-ruptures are not infrequent, reported to occur in up to 11% of patients [5]. Risk factors for ACL graft failure include an increased posterior tibial slope (PTS greater than 12°), a narrow inter-condylar notch, and excessive anterior tibial translation (ATT; > 6mm) [6•, 7–9, 10••]. During primary ACL reconstruction and more commonly revision ACL reconstruction, a tibial osteotomy may be utilized to provide a more favorable ACL biomechanical environment by reducing the forces experienced across the ACL, decreasing the risk for re-ruptures [6•, 7, 9, 11••, 12••].

High tibial osteotomies (HTO), including medial opening or lateral closing wedge osteotomies, are most commonly indicated to correct malalignment in patients with sagittal plane deformities about the knee [4, 13, 14]. Meanwhile, anterior closing wedge osteotomies (ACWO) have been reported to reduce ATT and the associated in situ forces placed across the ACL graft by allowing for correction of increased PTS during primary or revision ACL reconstruction [12••, 15, 16], decreasing the risk of graft re-rupture [4, 12••, 14, 15]. ACWO are infrequently performed in patients undergoing primary ACL rupture, being indicated primarily in patients with excessive PTS [12••]. Despite the increased popularity of ACWO [6, 17••], limited data is available on the outcomes of ACWO during primary and revision ACL reconstruction. As such, the purpose of this review article was to provide a concise overview of the current indications, techniques, and outcomes of ACWO in ACL-deficient knees while presenting our preferred technique.

Indications

The most commonly reported indication for an ACWO is presentation with sagittal plane malalignment from an increased PTS (generally accepted as greater than 12°) in patients undergoing revision or re-revision ACL reconstruction [6•, 12••, 17••] (Table 1). As overall knee joint stability is dependent on the slope of the tibial plateau in the sagittal plane, a high PTS leads to increased translational forces on the ACL as the tibia translates anteriorly, placing the ACL at higher risk of failure [12••, 15, 16]. The use of an ACWO has also been reported for the treatment of symptomatic knee instability secondary to an increased PTS above 15° following a previously failed open wedge HTO with primary injury of the ACL [11••]. However, ACWO are primarily utilized during revision ACL reconstruction, as the ACWO might add significant morbidity in the treatment of patients during primary ACL reconstruction with a PTS below 15° [12••, 17••].

Table 1.

Summary of indications and contraindications of anterior closing wedge osteotomy

Potential indications	Contraindications
Revision ACL reconstruction with sagittal plane posterior slope ≥12°	Genu recurvatum with knee hyperextension >10°
Primary ACL injury with a posterior tibial slope of more than 15°	Posterior cruciate ligament deficiency
	Genu varus malalignment >10°
	Grade IV tibiofemoral osteoarthritis *
	Body mass index >30 kg/m2
	Smoking history (>20 cigarettes per day)
	Patella alta (when the osteotomy is performed above the TT)†

Legends:*, based on Kellgren-Lawrence grading scale; †, indicates a relative contraindication; ACL anterior cruciate ligament, TT tibial tubercle

Contraindications to ACWO include patients with severe malalignment of the lower limb (>10° genu recurvatum; >10° varus), greater than 10° knee hyperextension, or evidence of grade IV osteoarthritic changes according to Kellgren and Lawrence classification [14, 17••] (Table 1). Body mass index >30 and patients smoking > 20 cigarettes per day have been reported as relative contraindications [12••].

Biomechanical Background

Multiple biomechanical studies have reported the ACWO to successfully reduce forces placed across the ACL during various loading conditions. In their biomechanical study, Imhoff et al. reported on the effect of PTS correction on ATT and in situ ACL graft force by measuring these variables under axial loading (200 N and 400 N) before and after ACWO in ten ACL-deficient (and subsequently reconstructed) cadaveric knees [19]. ACL graft force was measured using a load cell that was attached to the tibial sutures of the ACL graft. Following PTS correction with a 10° ACWO, the authors reported significant a decrease in ATT in ACL-deficient knees during loading when compared to measurements made prior to PTS correction [19]. The force across the ACL grafts following PTS correction was noted to decrease by up to 33% of axial load when compared to those in the intact state [19]. Similarly, Yamaguchi et al. reported that PTS correction decreased force across the ACL while also reducing ATT when an anteriorly directed force was applied to the knee between 5° and 45° of flexion and throughout full knee range of motion when a valgus force was applied. Additionally, there was no significant change in ACL graft force or ATT under tibiofemoral compression with an internal torque following PTS correction beyond 5° of knee flexion [20^••].

Surgical Technique

ACWOs can be performed using different techniques and osteotomy locations. Techniques can be broadly categorized based on osteotomy location in relation to the tibial tubercle (TT) (Fig. 1). Sonnery-Cottet et al. first described performing the ACWO at the level of the TT, detaching 6 cm of the TT bone segment. Two staples were utilized to secure the osteotomy, and two lag screws were used to fix the TT, yielding an average posterior slope correction of 5.2° [6•]. The Hees and Petersen described removal of the anterior wedge below the TT without detaching the TT, resulting in an average PTS correction of 7° [12••]. This technique was similarly performed in a case report by Nishino et al. resulting in an 8° PTS correction in an ACL-deficient knee [11••]. Meanwhile, Dejour et al. reported performing the osteotomy above the TT, starting from the superior margin of the patellar tendon insertion on the tibia and continuing inferiorly [21•]. The osteotomy was then secured using two anterior staples on both sides of the patellar tendon [21•]. Similarly, Walker et al. described an ACWO technique performed above the TT [22]. When performing the osteotomy above the TT in patients with existing patella alta, surgeons must exercise caution as the ACWO has been reported to exacerbate existing patella alta [23]. As such, careful patient selection based on presentation and previous surgical history is essential when indicating patients for an ACWO.

Fig. 1.

The anterior closing wedge osteotomy can be performed at (A), below (B), or above (C) the tibial tubercle (red) and aimed at the posterior cortex

Preoperative Planning

Prior to surgery, a detailed clinical examination and radiographic imaging must be obtained to ensure proper indications for posterior slope correction. The goal of an ACWO is to reduce the PTS to less than 10° [12••]. The posterior tibial slope should be measured from short lateral radiographs to determine the precise amount of correction necessary to reach a final PTS of around 6°–8° [17••]. The tibial slope can be measured by calculating the angle between the proximal anatomical tibial axis the line defining the posterior inclination of the tibial plateau (Fig. 2) [24, 25]. Additionally, the angle created by the preoperative extension of the knee should be accounted for during measurement to avoid postoperative genu recurvatum [12••]. DePhillipo et al. estimated that 1° of slope correction equated to approximately 1.67 mm of anterior resection of the tibia [17••]; however, this correlation can vary depending on the level and angle of the osteotomy. By utilizing this estimate and appropriate preoperative planning, surgeons can perform the ACWO and avoid slope overcorrection. It is important to maintain a PTS between 5° and 10° and avoid overcorrection to avoid increased strain on and risk of tearing the posterior cruciate ligament [17••].

Fig. 2.

Posterior tibial slope is measured by calculating the angle between the proximal anatomic tibial axis the line defining the posterior inclination of the tibial plateau (red). The planned osteotomy is visualized (blue), and the tibial tubercle is noted (brown)

Intraoperative Technique: Author’s Preferred Technique

The patient is placed in a supine position, and physical examination under anesthesia is performed. The foot of the operating table is lowered to allow for arthroscopic manipulation. A diagnostic arthroscopy is performed with evaluation of the menisci and concomitant repair when appropriate. Most commonly, the previous ACLR graft remnants and soft tissues from the established femoral tunnel were debrided followed by bone grafting. The foot of the table should be raised to flex the knee to approximately 45° to protect the neurovascular structures, and the anterior aspect of the tibia can be exposed by making a 6cm incision beginning 1 cm distal from the tibial joint line, approximately 1 to 2 cm medial to the tibial tuberosity. At this stage, it is important to protect the patellar tendon by passing a Cushing elevator proximal to the tendon insertion, isolating the distal extent of the tendon (Fig. 3) [17••]. The lateral extensor muscles are detached from the tibia to isolate the tibial tubercle in preparation for the osteotomy. The periosteum is elevated away from both sides of the osteotomy site in a proximal to distal fashion. Next, the superficial portion of the medial collateral ligament to the posterior aspect of the tibia is separated from the bone to expose the tibial tuberosity. Retractors are then placed behind the tibial plateau anterior to the fibular head. The osteotomy site is marked with 4 converging 2.0-mm distal Kirschner wires (K-wires) perpendicular to the shaft of the tibia using fluoroscopic guidance (Fig. 4), ensuring a perfect lateral image. These are drilled on the sides of the patellar tendon obliquely in the proximal tibia and aimed at the tibial insertion site of the posterior cruciate ligament. The height between the K-wires is predetermined based on the planned degree of posterior tibial slope correction assessed preoperatively. The osteotomy is then performed using an oscillating saw at the position of the K-wires at the level of the TT without violating the posterior cortex to protect the popliteal vasculature (Fig. 5). Irrigation should be used to avoid heat necrosis and healing complications [12••]. To correct the varus alignment, the osteotomy plane can be planned and cut with medial sloping. The length of the narrow blade is marked to guide bone cutting and avoid damaging the popliteal structures. The anterior-based bone wedge is removed, and K-wires can be noted to sit parallel to the tibial joint surface prior to removal. The osteotomy is then closed by gentle knee hyperextension and manual pressure over 5 to 7 min, controlling for the amount of desired correction and preventing fracture of the posterior tibial cortex. This allows for the ACWO to be visualized and confirmed fluoroscopically so that adjustments can be made if necessary. Richards staples are placed to hold the osteotomy closed (Fig. 6). Staples should be placed strategically in cases of staged ACL reconstruction to avoid the entrance of a new ACL tibial tunnel in the future. Two K-wires distal to the proximal tibial joint line were inserted for final inspection of the slope correction and the posterior cortex. Following the osteotomy, previous tibial tunnels can be bone grafted. Instrumentation is then removed, and the skin is closed in standard fashion. Postoperative radiographs demonstrate a reduction in PTS and hardware following both stages of the ACL reconstruction (Fig. 7).

Fig. 3.

A Cushing elevator (arrow) is passed proximal to the tendon insertion onto the tibial tubercle (TT), protecting the patellar tendon (PT) by isolating the distal extent of the tendon. Standard patient orientation: bottom of the image is distal (D), top of the image is proximal (P), left side of image is lateral (L), and right is medial (M)

Fig. 4.

The osteotomy site was marked with 4 converging 2.0-mm distal Kirschner wires (A) perpendicular to the shaft of the tibia using fluoroscopic guidance (B)

Fig. 5.

The osteotomy is performed at the proximal (A) and distal (B) aspects of the tibial tubercle using an oscillating saw at the position of the Kirschner wires without violating the posterior cortex to protect the popliteal vasculature

Fig. 6.

View of the final construct fixated with three staples, two inserted medial and one lateral to the tibial tubercle

Fig. 7.

Postoperative anteroposterior (AP) and lateral radiographs demonstrate a decrease in posterior along with three Richard staples, interference screw, and endobutton

Postoperative Protocol

Previous technical notes have described different postoperative protocols with regard to weight bearing status and range of motion following ACWO. Hees et al. reported partial weight bearing for 2 weeks and unrestricted range of motion following surgery [12••]. Meanwhile, Dephillipo et al. recommended non-weight bearing for a total of 8 weeks with restricted passive range of motion from 0° to 90° for the first 2 weeks following surgery [17••]. In our practice, patients are instructed to remain toe-touch weight bearing in a knee immobilizer brace utilizing crutches for 6 weeks to protect the integrity of the osteotomy, with weight bearing gradually increased over the subsequent weeks. The brace is locked in full extension to prevent postoperative recurvatum during the first 2 weeks postoperatively. Physical therapy should begin immediately following surgery to reduce edema, while the brace is gradually unlocked to allow for increased knee range of motion beginning at 2 weeks. Lateral radiographs of the knee are obtained 6 weeks following surgery to confirm maintained slope correction and assessment healing at the osteotomy site. When a two-staged procedure is planned, postoperative lateral radiographs can also be used to establish baseline imaging of bone tunnels in regard to bony incorporation following tunnel grafting for subsequent ACL reconstruction.

Outcomes

Outcomes following ACWO have only been reported during single-stage ACL revision reconstruction. The case series study by Sonnery-Cottet et al. analyzed outcomes in 5 patients with a minimum of two prior ACL reconstructions and a PTS of 12° or greater (Table 2). At a mean follow-up of 31.6 months, a significant improvement in knee stability was reported, with a decrease in side-to-side anterior laxity from 10.4 to 2.8 mm (p=0.002) as measured using the Telos stress device (Telos GmbH, Marburg, Germany) [6•]. A significant increase in subjective outcomes (Lysholm, International Knee Documentation Committee Subjective Knee Form (IKDC-SKF), and Tegner activity scale scores) were appreciated when compared to preoperative evaluation (all p<0.05) [6•]. Return to the preinjury level of sport was observed in 80% of patients, and no complications were reported with a mean PTS correction of 4.4° [6•]. Dejour et al. similarly reported an increase in patient-reported outcome scores (Lysholm and IKDC-SKF) when compared to preoperative scores, with no reported graft ruptures or recurrent instability in nine patients undergoing a second revision ACL surgery with ACWO and a minimum of 2-year follow-up [21•]. The case report by Walker et al. similarly reported positive outcomes following ACWO in the setting of ACL reconstruction [22], while Nishino et al. documented improvements in subjective outcomes in a single patient undergoing ACWO following a failed medial opening wedge HTO [12••].

Table 2.

Study characteristics and outcomes following anterior closing wedge osteotomy

Author (year)	Study design (level of evidence)	Mean follow-up (m) (mean [range])	Osteotomy level according to TT	Patient-reported outcome scores (mean change)	Mean posterior slope correction	Other reported outcomes
Sonnery-Cottet et al. (2014) [6•]	Case series (IV)	31.6 [23–45]	NR	Lysholm: 41.6* IKDC-SKF: 39.6* Tegner activity: 0.2	4.4°	Mean decrease in anterior laxity: 7.6mm* % return to preinjury level: 80 Graded IKDC, K-L classification
Dejour et al. (2015) [21•]	Retrospective cohort (III)	48 [12–91.2]	Above	Mean change Lysholm: 35.4* IKDC-SKF: 27.1*	8.8°	Negative Lachman and pivot shift in all patients. No change in patellar height
Nishino et al. (2020) [11••]	Case report (IV)	12	NR	Lysholm: 95	8.0°
Walker et al. (2015) [22]	Case report (IV)	18	Above	Lysholm: 90.0 IKDC-SKF: 73.6 (objective score: A) KSS: 97.5	12.0°	Preoperative VAS pain: 0/10. Negative Lachman and pivot shift in all patients. RTS achieved

* indicates a significant difference between preoperative and postoperative values

Legends: M months, NR not reported, IKDC-SKF International Knee Documentation Committee Subjective Knee Evaluation Form, KSS Knee Society Score, TT tibial tubercle, IKDC International Knee Documentation Committee, K-L Kellgren-Lawrence, VAS visual analogue scale, RTS return to sport

Complications

Despite early results suggesting the utility of the ACWO procedure in correcting PTS and reducing ACL graft strain, ACWO share comparable risks and complication associated with other tibial osteotomies. Without careful preoperative planning and intraoperative control of the osteotomy, incorrect degrees of PTS correction and nonparallel cuts can occur leading to further malalignment in both the coronal and sagittal planes [12••, 17••, 18]. Fractures beyond the desired osteotomy site have also been reported to occur both through the far cortex with intra-articular involvement [17, 23, 26]. To reduce the risk for intra-articular fractures, weakening the opposite cortex by inducing greenstick fractures via the insertion of drill holes has been recommended [27].

Due to its proximity in the posterior aspect of the knee, the popliteal artery is at risk during ACWO. To help reduce the risk of iatrogenic popliteal artery injury, the osteotomy should be performed in 45° to 90° of knee flexion and the posterior hinge of the osteotomy be left intact [12••]. Additional neurovascular complications following ACWO may occur as a result of indirect compression from elevated compartment pressures following surgery due to swelling or in the event of vascular injury [28]. The risk of pseudoarthrosis and healing complications have also been reported [12••]. To mitigate this pitfall, the posterior hinge should be left intact, and the osteotomy saw should be cooled during the procedure [12••]. Additionally, infections have been reported to occur in up to 4% of tibial osteotomies cases [29–31]. As such, to effectively minimize the risk for associated complications, careful patient selection, as well as thorough preoperative planning, is essential.

Conclusion

In the ACL-deficient patient with elevated PTS, early studies suggest that ACWO improve knee stability and reduce graft strain following primary and revision ACL reconstruction. Further studies evaluating the efficacy of ACWO with long-term patient follow-up and prospective studies comparing ACL-deficient patients with elevated PTS undergoing ACL reconstruction with or without ACWO are warranted.

Declarations

Human and Animal Rights and Informed Consent

This article does not contain any studies with human or animal subjects performed by any of the authors.

Conflict of Interest

Amar Vadhera, Derrick Knapik, Safa Gursoy, Daniel Farivar, and Allison Perry declare that they have no conflict of interest.

Jorge Chahla is a paid consultant of Arthrex, Inc, CONMED Linvatec, Ossur, and Smith & Nephew, outside of the submitted work. He is a board or committee member of American Orthopaedic Society for Sports Medicine, Arthroscopy Association of North America, and International Society of Arthroscopy, Knee Surgery, and Orthopaedic Sports Medicine.

Brian Cole is Dr. Cole reports receiving research support or royalties, serves as a paid consultant, or other financial support from Aesculap, NIH, Operative Techniques in Sports Medicine, Ossio, Regentis, Smith and Nephew, Arthrex Inc, Elsevier publishing, Bandgrip Inc, Acumed LLC, Encore Medical, LP, GE Healthcare, Merck Sharp & Dohme Corporation, SportsTek Medical, Inc, and Vericel Corporation, outside of the submitted work.