1 Introduction

Disruption of anterior cruciate ligament (ACL) is a common ligamentous injury of the knee that causes significant disabilities, especially among athletes.^1,2 The exact prevalence of anterior cruciate ligament injuries remains unclear; however, “It has been estimated that 200,000 ligaments are torn each year, and 100,000 anterior cruciate ligament reconstructions are performed each year in the United States”.³ Considering all strategies that are used for managing this situation, ACL reconstruction surgery is one of the most common orthopedic surgeries, principally in the field of sport medicine; however, despite its popularity, there is no ideal surgical technique and graft, which can be constantly used.^1–5 Ideally, graft context must mostly mimic the natural ACL. Apart from the graft type, mechanical and biological features of the graft must also prepare a reliable feature following operation. Moreover, in this regard, a reliable fixation and least morbidity originality from the graft origin are considered as two other important factors.^4,5 In the last decade, bone–patella tendon–bone autograft anterior cruciate ligament (BPTB-ACL) reconstruction has been considered as the gold standard technique for ACL reconstruction. This method seems to have certain benefits such as strength of the tissue, convenient harvesting of the graft, and bone to bone healing in addition to providing a reliable fixation.^5,6 Nevertheless, several concerns still exist such as interference in extensor mechanism of knee and morbidities related to the harvesting of graft including the anterior knee pain and patellar fracture. These concerns lead to lesser use of this technique in comparison with hamstring auto grafts and allografts.^5,6 Herein, we introduce a modified patellar side harvest technique, as a revised method for BPTB-ACL reconstruction surgery, and discuss the outcomes of patients who underwent this surgery.

2 Material and methods

2.4

2.4 Surgical technique

After primary arthroscopy, in order to harvest the graft, a single longitudinal incision of 4–7 cm in length was made from the distal pole of patella to the tibial tuberosity. By cutting through the prepatellar bursa, patellar bone and patellar tendon were exposed. Furthermore, patellar tendon was assessed for its length and width. In all cases, the patellar tendon was detached by making two parallel incisions in the middle-third of patellar tendon. The tendon was first stabbed once by a scalpel, and then isolated by a blunt device such as handle of scalpels, proximal to distal, in the direction of tendon fibers. This technique provides an intact graft with no tattering. Harvested tendon measured 10 mm in width and was variable in length depending on each patient. To harvest the patellar side of graft, we made two convergent incisions measuring 25–30 mm in length, forming an isosceles triangle with 10 mm at the base. Osteotomy was executed through specified points on patellar bone by 45° angle; during osteotomy, the deepest part placed in the triangles base measured 5 mm and decreased in depth further from the base to head of the triangle. Moreover, in order to do an osteotomy on a tibia bone, a harvest of 20–30 mm in length, 5–10 mm in depth, and 10 mm in width was considered (Fig. 1). Before isolation, one hole is made on the boney parts of both sides for threads, followed by isolation of both boney parts as a full thickness. All these steps were performed keeping the knee in a flexion position hanging beside the bed. After collecting the graft, a 1.0 vicryl thread is added into the ringers or normal saline fluid without any antibiotics. There was not any forced tension to the tendon. These threads were later used to pass the graft from the tunnels. Furthermore, intracondylar notch was assessed by arthroscopy and, if necessary, notchplasty was performed. Moreover, the femoral tunnel was placed by the following procedure: initially, resident ridge was found on the posterior edge of femoral condyle, almost between 9 and 9:30 o'clock on right and between 2 and 2:30 o'clock on left, following which a tunnel was dug to a depth of 1–2 mm less than the part of the patellar bone, connected to the graft. Usually measuring 8–9 mm in diameter, the femoral tunnels edge is about 5 mm away from the subchondral bone; moreover, the exit sites of the guide pins are about 3–4 cm proximal to lateral epicondyle of the femur. The tibial tunnel is drilled further by using a tibial jig reference from the anterior part of PCL insertion or by using a tibial eminence in a position, which makes the biggest angle with the articular surface to create a 10 mm diameter tunnel.

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Fig. 1 An example of harvested bone–patellar bone–tendon graft.

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Furthermore, a nylon thread was passed through the femoral canal by a guide pin and the tip of the nylon thread was inserted into the tibial canal and was then pulled out of the joint from the tibial canal by a grasper. Thus, the two ends of the thread were passed through the femoral and tibial canals and then the graft was attached to the nylon thread from its distal part and was dragged from the femoral side so that the boney part of the graft was placed in the femoral canal. Length of femoral canal's rim was almost between 25 and 30 mm. The boney part of the graft was then pushed (hammered) to the edge of the condyle bone in order to create a satisfying pressfit. On unsatisfaction by the pressfit, an Orthomed® (Arthrex®, USA) bio screw of 30 mm length and a diameter equal to the canal's diameter was used on the bone. Moreover, while the knee was flexed by 10–15° and the graft was tensed, the tibial part of the graft was fixed on this point by two possible methods: 1) the bony part of the graft is placed in the tibial canal or 2) it is left out of the canal because of its length and only the tendon part is placed in the canal. In the former circumstance, Orthomed® (Arthrex®, USA) bio screw of 30 mm length and a diameter equal to that of the canal was used, whereas in the latter circumstance, the end of the tibial part was fixed by a staple. If, for instance 2/3 of the canal is filled by the boney part and the rest by the tendon, then simultaneously bio screw and staple are used for tibial end's fixation. The aforementioned steps are visualized and checked by arthroscopy and later the stability of the graft is assessed by arthroscopy and physical examination. Eventually, by bony tissues created from rimming the femoral and tibial canal and also the bony parts of the graft, osteotomy holes of tibia and patella are filled.

3 Results

A total of 1024 patients including 154 females (23.8%) and 870 males (76.2%) with mean age of 30.6 ± 3.6 years (Ranged from 21 to 46 years) were enrolled in this study. Table 1 shows the demographics and baseline characteristics. Left knee was assessed in 492 patients (48%) and right knee in 532 patients (52%), however, almost 36% of patients suffered from coexisting meniscal injury.

Results for Lachman's tests and pivot shift tests are shown in Table 2. Based on the findings, 81% of patients had results of 2 + for Lachman's test and 58% showed 3 + for pivot shift test, preoperatively. Considering the pivot shift and Lachman's test at 36 months of follow up, patients showed significant improvement in the integrity of ACL (p < 0.05).

Functional activity score measurement using IKDC at 6-month follow up showed good to excellent (grades A and B) results in 768 (75%) patients, moderate (grade C) in 184 (18%) patients, and poor results (grade D) in 72 (7%) patients.

Results of Tegner activity level scale showed a mean score of 6 (ranged from 3 to 9) after 36-month follow up. The mean laxity assessed using a KT-1000 arthrometer improved from 6.4 ± 2.2 mm preoperatively to 2.1 ± 1.1 mm at the end of 3-year follow-up period (p = 0.031).

Table 3 reports the different complication rates among the studied patients. There was only one case of patellar fracture during surgery, which was fixed with the cannulated screw and tension band wiring technique and remained intact until six months of follow up. Moreover, deep infection and superficial infection were documented in 3 patients (0.2%) and 22 patients (2.1%), respectively. Based on VAS for assessment of anterior knee pain, only 56 patients (5.5%) at third month and 23 patients (2.3%) at sixth-month follow-up experienced pain with scale of more than 7.

Revision during three years follow-up period was needed only in 3.3% of cases. The statistics of return to work was provided up to six months. The filler graft was conducted due to various reasons such as new traumatic event.

4 Discussion

However, the modified patellar side harvest technique is a revised method for BPTB-ACL reconstruction surgery, to our knowledge, it has been described here for the first time. Resizing the bony part of patella and proximal tibia and harvesting the patellar bone deformation in the form of a pyramid are the most applied modifications in our study.

In the last two decades, there have been controversies regarding the management of ACL injuries, which recently “centers more on the choice of graft selection for reconstruction instead of whether surgery is necessary”.³ Several studies considered life threatening complications of the anterior knee pain and occurrence of patellar fracture during BPTB and assessed the midterm and long-term outcomes of each of these methods.^3,7–9 The rate of graft failure and tendon fixation stability which is higher according to the biomechanical and biological features of patellar tendon has been already reported.^5,7–9 Generally, BPTB grafting compared with soft tissue grafts, was shown to be more likely the result of reconstructions with normal Lachman score, normal pivot shift, maximal-manual KT-1000 side-to-side difference of less than 3 mm, and less flexion loss.^7,10,11 While, the choice of graft should be individualized, the graft type might not be the primary determinant for successful outcomes after the ACL surgery.³ Current evidence gives credit to the BPTB method, for example, this graft's attractive features include its high ultimate tensile load (approximately 2300 N), its stiffness (approximately 620 N/mm), and the possibility of rigid fixation with its attached bony ends.³ Additionally, one advantage of using BPTP method is a lowered fracture risk due to removal of bony graft by a lower depth. Although it is rare, complication related to the harvest site of graft has been already reported. In accordance with our study, a case of proximal tibial fractures following BPTB_ACL reconstruction surgery has been reported.¹² A case of patellar fracture three years after ACL reconstruction with BPTB graft which was presented with patellofemoral instability and treated with patellar osteotomy has been also reported.¹³

Another valued feature of this method is the use of bony tissues yielded from rimming of the femoral and tibial canal and trimming the bony tissues in fixation points. It may cause faster healing process; however, lower graft failure rate was revealed at midterm outcome of this study with 5.9% graft failure cases. It was determined by pivot shift test results of >3 + indicating the need for revision procedures. Some reports have shown that healing process of donor sites of BPTB graft may last 12 months to get similar to contralateral knee and rarely complicated with patellar tendon ossification.^14,15 The type of chosen graft and the used fixation have not shown any significant influence on the incidence of complications.^5,7–9

Postoperative anterior knee pain, specially kneeling pain, has been pointed out as one of major drawbacks of the BPTB-ACL reconstruction surgery.^3,16 In particular, in the Asian and Middle Eastern population, kneeling is a common position during daily activities such as praying or other religious ceremonies, eating, and socializing; therefore, kneeling pain is a major concern regarding ACL reconstruction.¹⁷ A comparative study Kim et al. also showed more significant anterior knee pain in patients who underwent BPTB.³ Some studies revealed that such complications occurred due to injury to the infrapatellar branch of saphenous nerve, whereas several other studies showed that this nerve branch cross over to the tibial tubercle could be potentially injured during skin incision. Some controversies still exist in this regard.^7,8,18–20 In a recent survey, the anterior knee pain has been reported in only 2.3% of cases, which is less than the previously reported score.^21,22 Considerably, few investigators and orthopedic surgeons suggested various techniques to lower the harvest site morbidity; of these, Koh et al.‘s technique is highly recommended.^23,24

We claim that using our modified patellar side harvest technique for BPTB-ACL reconstruction surgery could result in fewer complications such as anterior knee pain or fracture during or after the surgery. The advantages of this modified method include better knee stability, greater graft strengths, bone to bone fixation, less pain, rapid rehabilitation, and sooner access to work. Further prospective cohort studies are still needed to generalize the results of current study.

5 Conclusion

Experienced acceptable clinical outcomes in our study were reported in most of the patients who underwent BPTB-ACL reconstruction surgery with modified patellar side harvest technique.

Funding

The authors received no funding for this work.