Arthroscopic popliteus bypass graft for posterolateral instabilities of the knee

Objective An arthroscopic technique for the reconstruction of the posterolateral corner combined with posterior cruciate ligament (PCL) reconstruction was developed. Indications Posterolateral rotational instabilities of the knee. Combined lesions of the PCL, the popliteus complex (PLT) and the posterolateral corner. Isolated PLT lesions lacking static stabilizing function. Contraindications Neuromuscular disorders; knee deformities or fractures; severe posterolateral soft tissue damage. Surgical technique Six arthroscopic portals are necessary. Using the posteromedial portal, resect dorsal septum with a shaver. Visualize the PCL, the lateral femoral condyle and the posterolateral recessus with the PLT. Dissect the popliteomeniscal fibers; retract PLT until sulcus popliteus is visualized. Drill a 6-mm tunnel anteriorly into the distal third of the sulcus popliteus. Visualize femoral footprint of the PLT and place an anatomical drill tunnel. Pull the popliteus bypass graft into the knee and fix with bioscrews. Fix the reconstructed PCL. In cases of additional LCL injury, reconstruct LCL with autologous graft. Postoperative management Partial weight-bearing for 6 weeks, range of motion exercises, quadriceps-strengthening exercises on postoperative day 1. Full extension allowed immediately with flexion limited to 20° for 2 weeks, to 45° for up to week 4, and to 60° up to week 6. Use a PCL brace for 3 months, running and squatting exercises allowed after 3 months. Results In the 35 patients treated, no technique-related complications. After 1 year, 12 patients had a mean Lysholm Score of 88.6 (± 8.7) points and a side-to-side difference in the posterior drawer test of 2.9 (± 2.2) mm (preoperative 13.3 [± 1.9] mm). Conclusion Low complication risk and good and excellent clinical results after arthroscopic posterolateral corner reconstruction.

8 Dorsal anatomy of the right knee of a human cadaver with the posterolateral corner, consisting out of the lateral collateral ligament (LCL), the popliteus complex, and the posterolateral capsule. The popliteus complexiscreatedby the popliteus tendon and the arcuate complex (AC). The most prominent structure of the AC is the popliteofibular ligament.This ligament mainly secures the static stabilizing function of the popliteus muscle-tendon complex (PLT) standing [14]. The static biomechanical function of resistance against passive external rotation of the tibia is achieved in combination with the arcuate complex (AC; [11]). The AC mainly comprises the popliteofibular ligament, the fabellofibular ligament, popliteomeniscal fibers, and multiple extensions of the popliteus tendon to the tibia and to the posterior capsule (. Fig. 1). Thereby, the AC represents the primary static stabilizer to external rotation [10,15,21]. The most prominent structure of the AC is the popliteofibular ligament (. Fig. 1, 2a, b). 2 8 Lateral anatomy of the right knee of a human cadaver in a extension and b 90°of flexion. The femoral footprint of the popliteus muscle-tendon is on average 1.2 cm distal of the femoral footprint of the lateral collateral ligament (distance center to center) [2] The great importance of the AC for stabilization of the tibia against external rotation especially in flexion has been described previously [10,15,17]. If the AC is injured, primary posterior translation and coupled external rotation [13,21] increases. With an isolated injury of the posterior cruciate ligament (PCL), a posterior instability of up to 10 mm in 90°of flexionresults [16]. Additional dissection of the PLT results in a dorsal instability of up to 15 mm in the posterior drawer test in 90°of flexion. These biomechanical results indicate that a dorsal instability of more than 10 mm in 90°of flexion results in a combined posterolateral rotational instability [16]. Up to 70 % of all PCL injuries are combined injuries with additional lesions of the posterolateral corner [8,16].
For an exact analysis of the kind of instability(dorsal, lateral, rotational, posterolateral, or combined), it has to be considered that the main constraint against tibial external rotation from 0 to 30°is the LCL, while the arcuate complex becomes dominant towards increasing flexion, exhibiting its main function at 90°of flexion [3,5,9]. In addition, the LCL is the main stabilizer against varus stress in 0-30°extension. In this study, patients with a posterolateral rotational instability including a posterior drawer of more than 10 mm underwent reconstruction of the popliteus complex with a popliteus bypass graft in combination with PCL reconstruction. LCL was additionally reconstructed only if a lateral instability in 10°of flexion was evident.
The first anatomical reconstruction of the popliteus complex with an anatomical popliteus bypass graft was described by Werner Müller in 1982 [12]. Thereafter, numerous surgical techniques to reconstruct the static stabilizing function of the PLT have been described [1,4,6,7,18,20,22,23]. Most of these are extraanatomical techniques with lim-ited capacity to stabilize the posterolateral corner. With anatomical techniques for the reconstruction of the posterolateral corner, good and excellent results have been described [9,19]. However, the described techniques are basically open surgical procedures, without the advantages of an arthroscopic technique.
We therefore developed a novel arthroscopic procedure for anatomic reconstruction of the popliteus complex with a popliteus bypass graft [2]. In this paper, the operative technique is presented in detail.

Surgical principles and objectives
The goal of the surgical procedure is to regain the static stabilizing function of the popliteus complex. The dynamic stabilizing function of the popliteus complex should thereby be preserved. These goals should be achieved by an arthroscopic procedure with exact and anatomic tunnel placement [ x-ray views (in clinically suspected cases of axis deviation) 4 Stress x-rays with anterior and posterior drawer of both knees (. Fig. 3) 4 Preoperative management to assure good range of motion (> 0-0-100°) 4 Intensive quadriceps strengthening preoperatively 4 Side which is planned for operation should be marked prior to surgery 4 Arthroscopic instruments: hook, grasper, shaver (4 mm blade, not too sharp), radiofrequency electrode, guide wires, tendon harvester, drill bits in different sizes (6-10   Care should be taken not to injure the popliteus tendon. If a radiofrequency electrode is used for dissection of the popliteomeniscal fibers, care should be taken not to injure the cartilage at the posterolateral tibial plateau. Customarily, only the lateral popliteomeniscal fibers must be dissected along a length of 1-2 cm Fig. 10a, b 9 The popliteus tendon (green arrow) is retracted with a hook and the sulcus popliteus (red arrow) can be visualized. The arthroscope enters from posteromedial (right knee). The arcuate complex is observed to be wrapped onto the tendon, leading to a loss of the static stabilizing function of the popliteus tendon. In such cases, the popliteus tendon may be easily retracted to expose the sulcus c A useful technique to ensure correct tibial tunnel placement is to palpate the fibular head with the tip of the drill guide and to position the center of the tip of the drill guide 5-7 mm below the cranial edge of the popliteus tendon. A guide wire is positioned in the distal part of the sulcus popliteus. The anterior start point of the drill guide is positioned between the lateral edge of the tibial tuberosity and the medial edge of Gerdy's tubercle.The tibial tunnel was drilled with a 6-mm cannulated drill. It has been shown that the presented arthroscopic technique is highly accurate and reliable [2].Therefore, intraoperative fluoroscopy to check the location of the tunnel is optional Operative Orthopädie und Traumatologie 3 · 2016 199   Postoperative management 4 Wound dressing until postoperative day 2 4 Partial weight-bearing (10-20 kg) for 6 weeks 4 PCL brace for 3 months (i. e., Jack PCL, Albrecht, Unterschleißheim, Germany) with limited range of motion 0-0-20°for 2 weeks, 0-0-45°f or 2 weeks and 0-0-60°for further 2 weeks. 0-0-90°until week 8 and then free range of motion. 4 Range-of-motion exercises in the prone position and passive flexion against quadriceps contraction up to 60°allowed from postoperative day 1 4 Quadriceps strengthening exercises are allowed from postoperative day 1 4 Active knee flexion is not allowed for the first 6 weeks postoperatively 4 Proprioception loading exercises should be included 4 Running and squatting exercises are begun after 3 months from the index procedure

Results
To date, 35 patients have received a popliteus bypass graft due to a posterolateral rotational instability in combination with a PCL reconstruction. No intra-or postoperative complications have been observed so far. After 1 year, 12 patients (6 women) were examined (study still continuing). The mean age was 35.3 (± 13.6) years with a mean body mass index of 27.1 (± 3.6). The mean time from trauma to surgery was 11  weeks. Among all patients who underwent surgery as described above, 3 patients received an additional LCL reconstruction, 1 patient underwent an additional ACL reconstruction, 1 patient had an additional high tibial osteotomy due to 7°of varus deformity (one-stage procedure), and 1 patient had an additional torsional osteotomy of the femur due to torsional deformity after femoral shaft fracture (two-stage procedure). The mean postoperative Lysholm Score was 88.4 (± 8.7) points, whereas the mean Tegner Score was preoperatively 5.6 (± 1.8) and 4.9 (± 1.0) points during follow-up. The Visual Analog Scale function was 2.8 (± 1.5; 0 complete function, 10 no function) and the Visual Analog Scale pain was 1.9 (± 1.8; 0 no pain, 10 maximal pain). In the preoperative stress x-rays with the Telos device, the mean side-to-side difference in the posterior drawer test in 90°of flexion was -13.3 (± 1.9) mm and postoperatively the mean side-to-side difference was -2.9 (± 2.2) mm. The Dial Test was negative in 10 of 12 patients. The arthroscopic technique of posterolateral corner reconstructions has a low complication rate and leads to good and excellent clinical results.