COMPLICATION AFTER THE RECONSTRUCTION OF THE OLD PATELLAR TENDON RUPTURE KOMPLIKACIJA NAKON REKONSTRUKCIJE ZASTARELE RUPTURE LIGAMENTA ČAŠICE

Introduction. Chronic patellar tendon rupture (PTR) occurs rarely, its frequency and prevalence are unknown. There are very little data on the late patellar tendon reconstruction in rheumatoid arthritis and its complications. Case report. Here we present a surgical repair of a PTR with early postoperative rupture of contralateral patellar tendon, for a 21-year old woman with past medical history of juvenile rheumatoid arthritis (treated with corticosteroids) who sustained initial injury 11 months prior to the presentation. The contralateral side was used for autograft harvesting. We used BTB (bone-tendo-bone) autograft and allografts followed by double-wire loop reinforcement and with immediate postoperative mobilization. The patient was followed for 2 years and the function of both knees was restored completely, with a full active range of motion. In this case, reconstruction of an 11-month-old chronic PTR (with complete resorption of the tendon and completely separated infrapatellar pads, complicated by the contralateral PTR) with BTB autograft and allografts, and double wire loop reinforcement gave an excellent functional result. Conclusion. Two years after the surgical treatment, the extensor function of both knees was completely restored with a full range of movements. The patient reported satisfying outcomes and was able to return to all pre-injury activities without assistance of orthopaedic devices.


Introduction
Chronic PTR (patellar tendon rupture) is a rare injury and its frequency and prevalence are not determined yet 1 . There is no consensual decision about criteria that defines PTR as chronic condition, but daily activities of patients with this lesion are significantly limited 2,3 . Diagnosis is based on clinical findings, with the palpation of a tendon defect at the point of rupture and proximal migration of a patellar bone. Ultrasound and MR imaging are useful in recognizing this lesion, preoperative preparation and establishing the associated injuries 4 .
The operative treatment of the unrecognized PTRs is a surgically challenging procedure with unpredictable postoperative results based on many studies that tried to describe surgical technique for this type of injury. There is no gold standard in the surgical treatment of these injuries 5 . Described techniques include the use of autografts 6,7,8,9 or allografts 10,11,12,13 and synthetic materials such as Dacron or Ligament Augmentation and Reconstruction System (LARS) 14,15,16,17 . The literature regarding chronic PTR in patients with rheumatoid arthritis is scarce 18,19,20 and common postoperative complications are infections, patellar fractures and quadriceps muscle atrophy 5 .
The aim of this paper is to present a rare form of injury and early postoperative complication. To our knowledge, such postoperative complication and its surgical treatment are not reported in the treatment of chronic PTR in patients with juvenile rheumatoid arthritis. We present an operative technique of the reconstruction of chronic PTR with the postoperative rupture of the contralateral patellar tendon from which bonepatellar tendon-bone autograft was harvested. BTB autograft and allografts from the bone bank was used with immediate postoperative mobilization. This case report highlights the importance of the early diagnosis, describes operative techniques used in chronic PTR repair and treatments of the early postoperative complications such as rupture of the contralateral tendon.

Case report
A 21-year-old female suffered a left knee injury after she fell from the staircases.
She felt a severe knee pain, as if something "snapped" in her joint, and noticed that knee was swollen. She has been suffering from juvenile rheumatoid arthritis for many years and has been treated with oral corticosteroids. The patient went to the ER, where the knee Xray was taken ( Figure 1) and she was diagnosed with a knee distortion and contusion. As a result, her knee was put in a cast immobilization. Afterward, she underwent a course of physical therapy for 11 months. Passive range of motion was 0 to 130 degrees, with a knee extensor lag. The Lachman, McMurray and Apley, valgus and varus stress tests were all negative. The left knee MRI showed a complete PTR with a tendon almost completely resorbed by the surrounding tissue and infrapatellar pads completely separated ( Figure 2).
The patient underwent surgery under spinal anesthesia with a tourniquet applied. Firstly, a bone-patellar tendon-bone autograft was taken from the contralateral knee, similar to the graft in ACL (anterior cruciate ligament) reconstruction. Simultaneously, two cadaveric BTB allografts of appropriate dimensions were taken from the bone bank of the Ortopaedic Clinic in Novi Sad. A 15-cm-long skin incision was made on the anterior side of the left knee. After the surgical debridement, a 25-mm-long and 8-mm-wide bone trough was created in the tibial tubercle. Then, using a tibial ACL guide, a bone tunnel was made (also 25-mm-long and 8-mm-wide) in the central part of patella, from its superior to its inferior pole ( Figure 3). Afterwards, tibial and patellar bone tunnels of the same dimensions were made on the both sides of the initially made tunnel. BTB autograft was set on the central position, press fit into the tibial trough and stabilized with a 3.5 mm cortical screw, and then a prepared patellar graft was inserted into the centrally bored patellar tunnel and also stabilized with a 3.5 mm cortical screw. Two cadaveric BTB allografts were set and stabilized using the same procedure, which were prepared to have dimensions identical to those of the contralateral knee autograft. Two metal wires were fastened around the patellar basis with a screw secured to the tibial tubercle to protect the patellar grafts ( Figure 4).
After tightening the wire loop, the passive knee range of motion was evaluated. A drain was inserted in the knee and the wound was closed in layers.
Postoperatively, a CPM (continuous passive motion) machine was used from the day 1, and the patient was placed in passive flexion of 90 degrees for 6 weeks. On postoperative day 5, the patient slipped on her way to the bathroom and felt as if something "snapped" in her right knee, which was considerably swollen. A diagnosis of PTR of the right knee was made immediately, from which the BTB autograft was taken during the first procedure. Patella alta was found on the X-ray of the right knee, which was an indication for the urgent surgical treatment.
The patient underwent new procedure the day after this complication. The surgery was performed under spinal anesthesia with the use of tourniquet. The same skin incision made for the BTB autograft was used expose the point of rupture of the right patellar tendon. After the surgical debridement, the bone incisions on tibia and patella (25-mm-long and 8-mm-wide), from which the autograft were taken, were covered with press fit of the prepared cadaveric allograft of the same dimensions and stabilized with two cortical 3.5 mm screws on patella and tibia, respectively. The degenerated remnants of the patellar tendon were sutured using Krakow stitches ( Figure 5). Two metal wires were fastened around the patellar base with a cortical screw secured to the tibial tubercle to protect the patellar graft and newly sutured patellar tendon. After tightening the wire loop, the passive right knee range of motion was evaluated. A drain was inserted in the knee and the wound was closed in layers.
A CPM machine was used from the first postoperative day the patient was placed in passive flexion of 90 degrees for the first 6 weeks. Simultaneous quadriceps strengthening and active extension exercises were performed during the physical treatment. While walking in the postoperative period, the patient had tutor orthosis on both knees in the full extension and she was able to fully regain the appropriate footing. At three months follow up, the active range of motion on both knees was 0 to 130 degrees. Osteosynthetic materials were removed from her knees after a year and a half.
At two years follow up, the patient had a full range of motion on both knees, including both flexion and extension with the restored quadriceps strength and good results of isokinetic muscle testings (PrimaDOC multi-joint isokinetic dynamometer, Easytech, Italy), was able to perform knee bends and was walking normally without any external support.

Discussion
Among all injuries of the knee extensor mechanism, approximately 3-6% are related to the PTR. Between 1.5% and 2% of all tendon injuries are related to the PTR 21,22 .
They are most common in young men under 40 (M/F ratio is 6:1), while the most frequent mechanism of the PTR is an eccentric overload of the knee extensor mechanism with a planted foot and flexed knee 23  The use of the artificial synthetic materials in the reconstruction of the patellar tendon started in 1980s, but it was accompanied by complications, such as reactive synovitis and ruptures 27,28 . The application of LARS was not adequately and timely tested and due to the small number of randomized studies with LARS, its effects on the process of regeneration of patellar tendon are still not known. In literature, only midterm studies about LARS augmentation could be found and are usually related to the older patients, so we decided to use a combination of autograft and BTB allografts 5,17 .
The use of BTB allografts is the gold standard which has been successfully applied in the treatment of knee ligaments injuries. Milankov et al reported the use of contralateral BTB autograft for chronic patellar tendon rupture reconstruction, which resulted in an excellent knee extensor mechanism reconstruction 29 .
Due to the long period between the injury and the surgical treatment of about 11 months, our patient had radiographic findings of a patellar tendon completely resorbed by the surrounding tissue and infrapatellar pads completely separated and partially resorbed.
Therefore, it was necessary to use both an allograft and a contralateral BTB autograft which is used as a benchmark to correctly prepare allografts (in order to have correct dimension of the graft and match it to the contralateral side). Burks and Edelson 11 were the first to use BTB allografts in the patellar tendon reconstruction. One bone plug was secured to the tendon insertion at the tibial tubercle with screws, while the other was secured to the patella using "zuggurtung" technique.
Thus, using a contralateral BTB autograft, we were able to accurately reconstruct the extensor mechanism of the injured knee, which proved to be almost identical to the contralateral knee, with a strong autograft fixation. The main disadvantage of this technique is taking a graft from the non-injured knee, although Shelbourne and Urch 30 proved that taking BTB autografts from the non-injured knee does not affect its function.
Long-term treatment with steroids in patients with rheumatoid arthritis may have a role in the weakening of the patellar tendon. However, due to the lack of the studies dealing with complications after taking the autografts from the uninjured knee from patients with history of corticosteroid treatment, we had a conversation with the patient in order to weight out risk and benefits of this procedure. As a result, we decided to procced with this procedure in order to anatomically reconstruct the injured knee as it was described previously 19,20,26 .
The adequate length and tension of the grafts are very important; if these parameters are not correct, too tensed graft would cause a defect in the knee flexion, while insufficient tension of the graft would cause a defect in its extension. Palencia et al 18  PTR of the "donor" knee was also treated with the application of BTB allografts, double fire loops and suturing the ruptured tendon because it was an acute lesion. Double fire loop technique reduces tension on the repaired patellar tendon and contributes to the better regeneration and early mobilization of the injured knee, while the osteosynthetic material is removed after the complete functional restoration of the joint 31 . Our patient was on the long-term corticosteroid therapy with degenerative alterations on her tendon and our opinion was that end-to-end suture with no allografts would not be sufficient.
Postoperative immobilization is applied from 6 to 8 weeks 10, 16 , or even longer in some cases 32 which may lead to the consecutive knee contractures and the need for manipulation under anesthesia 8 . In literature, different types of postoperative external fixation are described, such as reinforced tendon repairs 24,33,34,35 , mostly with a single wire 6,8,13,14,36 , with immediate CPR treatment in order to avoid quadriceps muscle atrophy and knee contractures. In our case, we used multiple wires described by Casey and Tietjens 31 , which are mechanically stronger than a single circumferential loop and allow immediate mobilization without the use of postoperative casting or any other type of postoperative immobilization.
At eighteen months postoperatively, we removed the wires due to their breaking. Some authors 8,13,14 suggest the wire removal 6 to 10 weeks after the operation, but Casey and Tietjens 31 recommend the wire removal to be postponed at least six weeks after the surgery. It allows a patient to regain the full range of motion in the injured knee, so that repaired tendon could strengthen sufficiently before the wire removal.
In this case, reconstruction of an 11-month-old chronic PTR (with complete resorption of the tendon and completely separated infrapatellar pads, complicated by the contralateral PTR) with BTB autograft and allografts, and double wire loop reinforcement gave an excellent functional result. Two years after the surgical treatment, the extensor function of both knees was completely restored with a full range of movements. The patient reported satisfying outcomes and was able to return to all pre-injury activities without assistance of orthopaedic devices. Although additional surgery was needed to remove double wire loop reinforcement, it enabled an early mobilization and more secure healing of the repaired patellar tendons.        the autograft was taken, were covered with press fit of the prepared cadaveric allograft of the same dimensions and stabilized with two cortical 3.5 mm screws on patella and tibia, respectively. Then, the degenerated remains of the patellar tendon were sutured using Krakow stitches and two metal wires were fastened around the patellar basis with a cortical screw secured to the tibial tubercle to protect the patellar graft and sutured patellar tendon.