All-Inside Bone–Patellar Tendon–Bone Anterior Cruciate Ligament Reconstruction

Abstract

Anterior cruciate ligament reconstruction (ACLR) with bone–patellar tendon–bone (BPTB) graft is commonly performed. Fixation is traditionally performed with interference screws, which has certain disadvantages as the tendon can be damaged or cut during insertion or tension can be lost when inserting the tibial screw. For soft-tissue grafts, all-inside ACLR with blind sockets has gained increased interest over the past 2 decades and has several advantages over the use of full tunnels. Randomized trials have shown better patient-reported outcomes, less pain, and less tunnel widening with all-inside ACLR. Generally, all-inside ACLR is not considered with BPTB grafts because there is a fear of graft-tunnel mismatch, but this can be avoided by paying attention to patellar tendon length and patient height. In this article, we present an all-inside technique for BPTB ACLR using standard equipment that is reproducible with a low risk of graft-tunnel mismatch.

Anterior cruciate ligament (ACL) injuries are common orthopaedic injuries, and ACL reconstruction (ACLR) is commonly performed in younger or more active patients.1, 2, 3 Hamstring tendon and bone–patellar tendon–bone (BPTB) autografts are the most used grafts in younger patients.² Fixation for BPTB ACLR generally consists of screw fixation for both the femoral and tibial tunnels.² This fixation method is reliable but has some risks, including stripping or damaging the tendon with femoral screw fixation and loosening of the graft or rupture of sutures in the tibial bone block with tibial fixation.⁴

All-inside reconstruction with tunnel sockets has been increasingly used for soft-tissue grafts and has been shown to have several advantages. In a meta-analysis of randomized controlled trials, all-inside ACLR has been shown to lead to improved patient-reported outcomes, less tunnel widening, and improved laxity.⁵ Furthermore, Lubowitz et al.⁶ showed in a randomized controlled trial that all-inside reconstruction led to reduced pain compared with full tibial tunnel drilling, even up to 2 years. However, all-inside ACLR is traditionally not considered with BPTB because of the fear of graft-tunnel mismatch. One technique was published 15 years ago using a retrograde screw, but it was not widely used and the screw is not available anymore.⁷ The goal of this article is therefore to report on all-inside ACLR with BPTB autograft using a safe and reproducible technique with standard instrumentation (Video 1).

Surgical Technique

Indications

Preoperative imaging using magnetic resonance imaging (MRI) is important to avoid graft-tunnel mismatch. The sagittal images from the MRI study are reviewed, and the middle-third patellar tendon length is measured (Fig 1). Using the graft metrics table created at The Ohio State University (OSU), one can calculate whether all-inside reconstruction is possible (Table 1). At our institution, a total length of 25 mm is used for the tibial and femoral bone plugs combined. In the case of this patient with a height of 1.88 m, a 50-mm patellar tendon is not too long for all-inside ACLR.

Fig 1.

A sagittal T2 magnetic resonance image shows the measurement of the patellar tendon length (yellow line), which is approximately 50 mm in this case. This turned out to match the intraoperative measurement of 50 mm. The asterisk indicates the patella, and the hashtag indicates the patellar tendon.

Table 1.

OSU Graft Metrics

Height		Graft Length, mm
Imperial Units	Metrics
<5 ft 5 in	<1.65 m	60-65
5 ft 5 in to 5 ft 11 in	1.65-1.80 m	65-70
≥6 ft 0 in	>1.80 m	70-75

OSU, The Ohio State University.

Graft Harvest

A standard midline incision is used, and dissection is carried down to the paratenon. The paratenon is incised and preserved for later closure, and the patellar tendon is exposed. By use of a 10-mm dual blade, the middle third of the patellar tendon is incised. Then, a 10-mm-wide and 13-mm-long patellar bone block is harvested using a 10-mm saw and a small osteotome; a mallet should not be used to avoid the risk of patellar fracture. For the tibial bone block, a 15- to 20-mm-long and 10-mm-wide bone block is harvested using the saw and osteotome. The graft is released from its adhesions and brought back to the back table for preparation (Fig 2).

Fig 2.

Anterior view of a left knee after harvesting of the patellar tendon autograft (case shown in Fig 1). The aimed dimensions of harvesting for this technique are a 10-mm-wide and 13-mm-long patellar bone block (hashtag) and a 10-mm-wide and 20-mm-long tibial bone block (asterisk). The short patellar bone block decreases the risk of patellar fracture and enables easy passage into the tibial tunnel.

Graft Preparation

The patellar tendon length is measured, and the final decision for all-inside versus standard tibial full-tunnel ACLR is now made based on the OSU graft metrics table (Table 1). The patellar side is used for the tibial socket, and the tibial side is used for the femoral socket. The femoral bone block is prepared for a 9.5-mm diameter with a 13-mm length and the tibial bone block is prepared for a 10-mm diameter with a 12-mm length in this case. Two drill holes are made in the femoral tunnel, with one at the proximal-third and one at the distal 10% of the bone block. The distal hole is used for a rescue suture that consists of a 1.3-mm SutureTape (Arthrex, Naples, FL), which is first passed through the distal hole and then from medial to lateral through the proximal part of the tendon. The bone block is prepared for adjustable-loop fixation with a cortical button using the TightRope (Arthrex). For the distal bone block, 1 hole is drilled slightly distal to the midline. Then, the FiberTag TightRope system (Arthrex) is used to connect the adjustable loop with the bone block. This has the advantage of not only relying on bone block fixation but also applying fixation to the distal part of the patellar tendon and reducing the risk of stripping or cutting out. Finally, the bone-tendon junctions are marked (Fig 3).

Fig 3.

View of the prepared graft on the back table, with the femoral bone block on the right and the prepared tibial bone block on the left. The bone-tendon junctions are marked. The asterisk indicates the bone block for the tibial tunnel, and the hashtag indicates the bone block for the femoral tunnel.

Tunnel Creation

Standard anteromedial and anterolateral portals are created, and a diagnostic arthroscopy is performed, along with treatment of other pathologies. The torn ACL is identified, and the remnant is debrided using a shaver. A small notchplasty is performed to improve visualization of the footprint. A small dimple is created for the location of the femoral footprint using a curette, a Femoral ACL Marking Hook (Arthrex) is placed in this dimple, and a FlipCutter drill (Arthrex) is drilled to the femoral insertion. The location is checked, and the femoral socket is then drilled until the 7-mm step of the drill sleeve is reached. Bone debris is removed, and a FiberSnare (Arthrex) is inserted through the drill sleeve and retrieved through the anteromedial portal (Fig 4). A similar procedure is then performed for creation of the tibial tunnel, the location of which is between the posterior border of the anterior horn of the lateral meniscus and the medial eminence. The minimal length of the tunnel should be 30 mm. If it is short, the tibial tunnel inclination angle can be adjusted. A looped FiberSnare suture is inserted, and both the femoral shuttle suture and the tibial shuttle suture are retrieved together from within the joint to avoid a soft-tissue bridge (Fig 5).

Fig 4.

Arthroscopic view of a left knee from the anteromedial portal showing a deep femoral tunnel position with the shuttle suture (black suture, asterisk) passed through. The hashtag indicates the posterior position with only 1 to 2 mm of back wall. It should be noted that it is not a problem if the posterior wall is very thin because there is suspensory fixation and no compression with a screw is performed.

Fig 5.

Arthroscopic view of a left knee from the anterolateral portal showing grasping of both the femoral shuttle suture (black suture, asterisk) and tibial shuttle suture (white and blue suture, hashtag) to avoid a soft-tissue bridge as the graft is introduced in the knee from the anteromedial portal.

Graft Insertion and Fixation

The medial portal is enlarged to enable graft passage. The sutures of the prepared graft are passed through the loop of the femoral shuttle suture, and the sutures and femoral side of the graft are pulled into the joint. The button is pulled through the femoral tunnel and flipped on the femoral cortex, and the white tensioning sutures are used to pull the bone block into the femoral tunnel. The tibial sutures are then loaded into the tibial shuttle suture and are pulled through the tibial tunnel. The tibial bone block and remainder of the graft are pulled into the joint and into the tibial tunnel. The Attachable Button System (ABS; Arthrex) is attached to the white tibial tensioning sutures and the graft is tensioned on the tibial side. With the use of a probe, it is confirmed that there is good tension of the graft and no impingement (Fig 6). Incisions are closed in layers (Fig 7).

Fig 6.

Arthroscopic view of a left knee from the anterolateral portal showing that the bone blocks are passed into the femoral and tibial bone tunnels and the graft is tensioned, indicating no graft-tunnel mismatch. The asterisk indicates the graft in the femoral tunnel, and the hashtag indicates the graft in the tibial tunnel. Excellent tension is shown.

Fig 7.

Arthroscopic view of a left knee from the anterolateral portal showing no impingement of the graft at full extension. The asterisk indicates the notch, and the hashtag indicates the graft.

Rehabilitation

Standard protocols for ACLR are used after this technique. Early weight bearing and range of motion are allowed as tolerated, except in cases of concomitant radial meniscal repair or root repair, in which weight bearing is limited. An early focus should be placed on patellar mobility and extension because these can be difficult with BPTB ACLR. Patellofemoral resistance training should be avoided in the first 8 weeks to decrease the risk of anterior knee pain.

Discussion

The BPTB graft is the most used graft by surgeons in the United States, and fixation has been reported to occur with screw fixation in the femur in 83% of cases and in the tibia in 95% of cases.² Cortical button fixation is only reported to be used in 14% of femoral cases and 2% of tibial cases. The described technique with double cortical fixation avoids the pitfalls of screw fixation, which mainly consist of tendon stripping or damage by inserting the femoral screw and loosening of the graft or rupture of sutures when inserting the tibial screw.

The most important element for this technique is the consideration of patient height and tendon length, and preoperative correlation with patellar tendon length on MRI and patient's height is recommended. A recent study by Janani et al.⁸ assessed the patellar tendon length on MRI in 1,002 patients and reported a mean length of 45.2 mm with a small standard deviation of 1.3 mm, indicating only minor spread. Campbell et al.⁹ assessed the patellar length on MRI in 100 male and 100 female individuals and found a longer patellar length in female individuals (47.4 ± 5.4 mm vs 43.9 ± 5.2 mm). They also found that patient height was predictive of patellar length. In our OSU graft metrics table, there is no consideration of sex because sex is mostly predictive of patellar length and not intra-articular distance.⁹

At our institution, this technique has been shown to be reliable using the described methods. The risk of complications with screw fixation is avoided, and graft-tunnel mismatch has not occurred. This technique is limited by the lack of outcome studies in the literature.⁷ Studies assessing the incidence of graft-tunnel mismatch should be performed, and the OSU graft metrics table should be validated for this purpose, although it has been used for over 10 years at our institution for soft-tissue graft, and tendon length has been shown to correlate with patient height.⁹ Pearls and pitfalls of our technique are presented in Table 2.

Table 2.

Pearls and Pitfalls of All-Inside Bone–Patellar Tendon–Bone ACL Reconstruction

Pearls

The surgeon should assess the preoperative patellar length on MRI and review the patient’s height.

The surgeon should review the OSU graft metrics table for ideal total length and adjust bone blocks accordingly.

Only limited bone block harvest is required at the patella, which decreases the risk of fracture.

The surgeon should prepare the tibial (patellar) bone block with fixation on the tendon itself for extra fixation given the smaller bone block.

The surgeon should ensure that a posterior (deep) femoral tunnel is created.

The surgeon should ensure that a small tibial bone block is used to ease passage into the tibial tunnel (given the more acute angle).

Pitfalls

Femoral and/or tibial bone blocks that are too long will make tunnel entry difficult.

Failure to re-measure the final tendon length might increase the risk of mismatch.

A button extender or screw fixation should be available as a backup option.

The knee should be kept extended when tensioning the tibial tensioning sutures with an adjustable loop to not capture the knee in flexion.

ACL, anterior cruciate ligament; MRI, magnetic resonance imaging; OSU, The Ohio State University.

In conclusion, all-inside BPTB ACLR is a straightforward and safe technique that has the benefits of all-inside reconstruction and avoids the pitfalls of screw fixation. Patient height and tendon length should be considered to avoid graft-tunnel mismatch.

Disclosures

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: J.P.v.d.L. receives fellowship (non-personal) funding grants from Arthrex and Smith & Nephew and is an editorial board member of Arthroscopy. C.C.K. reports a consulting or advisory relationship with Arthrex.

Supplementary Data

Video 1

Open harvesting and arthroscopy are shown in a left knee, with the arthroscope in the anterolateral portal and instrumentation from the anteromedial portal, unless specified otherwise.