PCL Paper

Correction of Chronic Irreducible Posterior Knee Subluxation in multiple ligament patients using External fixation Distraction: A Novel technique.

Suriyapong Saowaprut, MD. , Tavit Charoensopa, MD. , Apisan Chinanuvathana, MD.

Institute of orthopedics, Lerdsin General Hospital, Bangkok, Thailand.

Neglected traumatic knee dislocation is an uncommon but complex and difficult to treat problem. Especially, when multiple ligament injury was left untreated for months before seeking a medical service. This may cause a significant and permanent disability.

The ideal goal of treatment for patient with knee dislocation is to obtain painless, stable and full range of motion knee. Unfortunately, to achieve all the goals can be very difficult because when the treating knee is stable, usually will reveal limited knee range-of-motion.

Posterior sag of tibia is one of the most common problem after prolong neglected knee dislocation. This posterior sag will eventually become irreducible with time in some cases. If the knee is in irreducible position before we perform further ligament reconstruction, the reconstructed graft will receive too much stress leading to failure of reconstruction and poor outcome.

We proposed novel technique to correct irreducible posterior knee subluxation using distraction external fixator. In this present paper, we report 2 cases of chronic irreducible posterolateral knee dislocation and 1 case of neglect ipsilateral fracture of femoral shaft and proximal tibia with posterolateral knee dislocation.

We had treated irreducible knee joint by external fixation distraction technique before we performed posterior cruciate ligament (PCL) and posterolateral complex reconstruction in 2 patients with chronic irreducible posterolateral knee dislocation. While the third patient with neglected floating knee with chronic irreducible posterolateral knee dislocation had used same technique to correct irreducible knee before performing high tibial corrective osteotomy to correct malunion of proximal tibia.

After recovery period, all the three patients’ knees were stable and achieved functional range-of-motion. Furthermore, our patients satisfied the results and their quality of life was improved.



To treat patient with multiple knee ligament injury, we have to balance two opposing goal of treatments which are obtaining a stable knee and obtaining a full range of motion. Unfortunately, achieving all the goals is very difficult because when the treating knee is stable, the knee will usually reveal limited range of motion. Especially, when multiple knee ligament injury was left untreated for months before seeking a medical service. The chance to obtain all the goals is rare and the patient may eventually has significant and permanent disability.

Posterior sag of tibia is one of the most common problem after posterior knee dislocation. Especially, when appropriate knee reduction was not performed and maintained at the first place, the posterior knee subluxation almost always occurred.  Furthermore, this posterior subluxation of the tibia may become irreducible with time in some case.

We purposed technique to correct the irreducible knee using distractive external fixator. With this technique, extensive surgical exposure during release of contracture structures is not required and surgical complications can be avoided.


Case 1

A 28 years old male was injured by a motor vehicle accident 8 months ago. He presented to primary hospital with an open wound at his right knee. The wound was cleaned and sutured. His leg was immobilized with cast and treated nonopetatively. He refused further treatment at primary hospital and continued nonoperative treatment with a traditional medicine.

Unfortunately, 6 months later, the knee and leg pain still persisted and his knee was stiffed, then he decided to go to the second hospital. A doctor informed that he had PCL avulsion which operation required. His knee was manipulated and lysis adhesion was done, however avulsed PCL fragment could not been fixed due to bone fragment union.

At our hospital, he had continually knee pain and instability. Physical examination revealed old scar at his right knee, irreducible posterior knee sagging. Range of motion was 30- 90 degree both in active and passive motion. Lachman’s test, Valgus and varus stress test could not evaluate. Lower limb neurovascular appeared normal. Knee radiographs demonstrated a large avulsed PCL fragment, joint space narrowing and posterior sag of the tibia (Figure 1). Range of motion exam under anesthesia was 30- 90 degree both in active and passive motion.

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Figure 1. Right knee radiographs show posterior subluxation of tibia and a large bony fragment of PCL avulsion and joint space narrowing.

After discussion of options with the patient, we planned to restore stable functional knee by performed ligament reconstruction. However the patient’s knee is in the subluxate position, thus we have to restore knee position first.

To avoid the risk of circulation disruption caused by extensive surgical intervention, we performed reduction of the dislocated knee by gradually soft tissue distraction using the external fixator technique. Two steinmann pins and parallel tube frames were applied at both femur and tibia. Then parallel tube frame of femur and tibia were connected to each other with two distractor rods (Figure2).

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Figure 2. Distractive external fixator apparatus.


Because of knee joint space narrowing, we distracted to open joint space first. Distraction was gradually started at a rate of 1 mm/day under careful observation to avoid overdistraction and the patient’s discomfort. When the joint space had opened to 2 cm wide, the tibia was distracted anteriorly to reduce posterior tibial subluxation. Reduction of the knee dislocation was achieved 7 weeks after the distractor external fixator application (Figure 3). We performed manipulation after removed the external fixator and found patient’s knee range of motion was 10-110 degree, Valgus and varus stress test were negative. Finally, we decided to perform arthroscopic examination, lysis adhesion and arthroscopic PCL reconstruction with bone-quadriceps tendon (Figure 4).

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Figure 3. After longitudinal distraction was satisfied, the distraction device was turn into the AP direction and gradually traction. Knee radiographs show a satisfied distraction.


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Figure 4. Arthroscopic view shows completely torn of ACL, Osteophyte at intercondylar notch were removed & PCL reconstruction was done.


After 6 weeks of long leg cast application, the cast was removed and intensive rehabilitation was began with passive and active exercise, and progressive weight bearing was allowed after 12 weeks. Range of motion at 12 weeks post operative was 20 to 90 degree.

At 1 year Follow-up, the patient had no pain in either knee joint and the patient could walk without walking aid. Active right knee motion ranged from 10 to 110 degrees. Radiographs demonstrated good right knee alignment with slightly posterior tibial subluxation (Figure 5, 6).


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Figure 5. One-year follow-up, range of motion in extension (A) and flexion (B) position

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Figure 6. One-year follow up, X-ray AP (A), lateral (B) show a reduction with a slightly posterior sagging.

Case 2

A 17 years old female sustained twisted knee injury from a motorcycle accident. After a few days of neurovascular observation of lower extremities, the knee was immobilized with long leg cast for 6 weeks. On examination after cast removal, her knee range of motion was 0-45 degree. Passive range of motion was started and progressive weight bearing was allowed since then. However as the knee range of motion was gradually improved, the knee was progressively unstable especially during gait.


Four months after injury, the patient was referred to our institute. Examination at this time revealed posterior tibial sag 3+ with incomplete reduction under anterior drawer force without end point. Knee range of motion was 0-110 degree. Varus stress examination found opening of lateral joint line more than 10 mm both in 0 and 30 degree of flexion. The dial test, prone external rotation test and reverse pivot shift test were positive. 


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Figure7. Preoperative knee radiographs show old avulsion of fibular head and posterolateral knee subluxation.


We decided to reduce subluxate knee using our distraction external fixator technique. The patient’s knee reduction was achieved within 2 weeks (Figure 8).

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Figure 8. Lateral knee radiograph shows satisfied knee reduction.

In same admission, the patient was taken to operative room to remove external fixator and underwent transtibial PCL reconstruction with semitendinosus tendon autograft and Posterolateral complex, LCL reconstruction with gracilis tendon autograft using Larson’s technique. Long leg cast was applied immediately after surgery (Figure 9). 

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Figure 9. Knee radiographs after PCL reconstruction.

Six weeks later, the long leg cast was removed and progressive weight bearing was begun. Intensive rehabilitation program was started to gain knee motion. Twelve weeks following surgery, knee range of motion was 10-70 degree, the patient was able to bear full weight. At 80 degree of knee flexion, anterior edge of tibial plateau flushes with distal femoral condyle.

At 6 months after reconstruction, knee range of motion was increased to 0-100 degree with posterior drawer test 1+; she was weaned from knee brace and walked independently without gait aids (Figure 10). 


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Figure 10. Six months follow up range of motion. (A) Extension (B) flexion left knee (C) flexion right knee.

Case 3

A 31 years old man presented to our orthopedics clinic with gross right knee deformity, knee pain and giving way during walk. Twenty years ago, he stated that he had car accident but unable to recognize the exact details of accident mechanism. At that time, He had fracture shaft of right femur and proximal tibial fracture treated with skeletal traction for 3 months. After traction was removed, He was taken to local practitioner for further treatment. The right knee deformity developed overtime however he was able to return to moderate activity without knee pain. 2 years ago, anterior knee pain was gradually recognized and he was experienced an episode of giving way during gait.

On examination, the right knee was revealed fixed gross S shaped deformity with tibial dislocate posterior to femoral condyle (Figure 11) and had 10 mm of total anteroposterior translation without end point.


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Figure 11. Gross knee deformity at time of surgery


His knee range of motion was 0-110 with knee dislocated throughout range of motion. Varus stress test was positive, prone external rotation test and posterolateral drawer test were positive.

Total length of lower limbs were 75 on the left and 76 cm on the right and mechanical axis deviation were 10 mm lateral on the right and 8 mm medial to the left. Radiographs revealed union right femoral shaft fracture, mLDFA and mPTA on both knees appeared within normal limits with minimal discrepancy (Figure 12).

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Figure 12. Preoperative scanogram; mDFA mechanical distal femoral angle,mPTA mechanical proximal tibial angle, PPTA posterior proximal tibial angle.


However the lateral knee radiographs demonstrated anterior slope of right proximal tibia which exacerbated the knee deformity during weight bearing. Fluoroscopic evaluation demonstrated 20 mm posterior subluxation of tibia and with stress test subluxation was reduced to 6 mm. (Figure 13) 

After having discussion about treatment options, the patient was taken to operative room and distraction external fixator was applied (Figure 14).  Following two weeks of gradual joint distraction, the desired joint position was obtained. The patient was brought to operative room to remove the external fixator and corrective osteotomy was performed to correct total limb alignment and proximal tibial slope.

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Figure 13. Preoperative assessment of knee joint subluxation under fluoroscope.

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Figure 14. Right knee with distractive external fixator application.


Postoperative radiographs shown mPTA was 88 degrees and restoration of tibial posterior slope. (Figure 15)

Six months after surgery, bone union was obtained at osteotomy site and the patient was reported no knee pain and range of motion was 10-120 degree. The patient was able to walk independent without gait aids. (Figure 16)

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Figure 15. Postoperative radiographs 


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Figure 16. Six months follow up range of motion and radiographs.



Because of rarity of this injury in developed country and the variety of mechanism, character and clinical presentation of this injury, there is very little data available in literature about multiple ligament injury treatment. Especially, the patient with irreducible knee subluxation patients, minimal data exist and most of them are case reports or case series.


Nevertheless, treatment preference is different among discrete surgeon. Therefore, there is no consensus on appropriate treatment which ranged from conservative treatment with cast immobilization to extensive sophisticated surgical treatment.

Henshaw et al 1 described a 17-year-old case report regarding a chronic traumatically dislocated knee with fixed posterior dislocation with S shaped gross deformity and inability to ambulate. The patient was treated with open reduction and malunion tibial plateau correction without cruciate ligament reconstruction 31 weeks after injury. The reduction was maintained by placing crossed steinmann pin across joint for 6 weeks and a cylindrical cast was applied for 12 weeks after open reduction. The final result yielded a range of motion of knee joint from 5 to 40 degrees.

The two 17-year-old patients were reported by Simonian et al.2 They were treated with open joint reduction followed by anterior cruciate ligament and posterior cruciate ligament reconstruction 4 months and 8 months after injury, respectively. External fixator compass hinges were applied for the first 6 weeks, and the final results yielded ranges of motion of knee joints of 5 to 105 degrees and 0 to 120 degrees, respectively.

Nurzat et al.3 reported a 65-year-old man with an unreduced posterolateral knee dislocation with laterally dislocated patella was seen 3 weeks after injured. Medial femoral condyle was found buttonholed through the medial capsule together with the medial collateral ligament and lying in the medial joint space that allowed posterior rotary dislocation of the joint. Both cruciate ligaments and medial meniscus were torn. There was no evidence of any vascular or nerve injury. Reduction was accomplished by removal of the capsuloligamentous structures which were incarcerated in the trochea and intercondylar notch and by excised irreparable torn meniscus. Following posterior cruciate ligament reconstruction with patellar tendon autograft, lateral patellar release, vastus medialis advancement and gracilis transfer were done. Then the hinge external fixator was applied to maintain the reduction. Range of motion was 5-90 degrees without instability and pain.

Hatem et al.4 reported 14 years old with chronic posterolateral dislocation for 14 months associated with anterior cruciate ligament and posterior cruciate ligament (ACL, PCL) and medial collateral ligament (MCL) rupture. A two staged approach was done; the first stage included arthroscopic debridement of the intervening tissues, which were thickened and resembled meniscal tissue, followed by reduction of the knee and open MCL repair to maintain the reduction. The second stage was done for ACL and PCL reconstruction.

A 47 year old man reported by Kota et al.5 was chronic fracture dislocation, patella tendon insufficiency and Peroneal nerve injured, treated by IIizalov distraction followed by osteosynthesis and patella tendon reconstruction for 11 weeks. Final passive motion of the left knee ranged from 0 to 110 degrees, and there was an extension lag of 15 degrees with slight posterior sagging. Peroneal nerve palsy did not improve.

The crucial steps in surgical management of the fixed, chronically subluxated or dislocated knee consists of (1) knee reduction, (2) achieve stability through a reconstruction, and (3) protect the reconstruction while maintaining a functional knee range of motion. Among these steps, if knee joint is in irreducible position before performing ligament reconstruction, the graft will receive too much stress which may lead to failure of the reconstruction and poor outcomes. Therefore, the patient with irreducible knee subluxation or dislocation usually undergoes open reduction by performing extensive surgical release of scar and contracture structures before reconstruction procedure.

However, the extensive surgical procedure may cause iatrogenic damage of the neurovascular or residual knee stabilizing structure. Because of in chronic knee subluxation, the knee deformity and scar formation usually distort the normal knee anatomy and plane of knee approach. Furthermore, after extensive surgical release through scar tissue, it may result in further scar formation especially in patient who cannot follow early range of motion rehabilitation protocol.


In most literature about treatment of multiple knee ligament injury, the external fixator is usually used to stabilize the dislocated knee in acute setting. However as mentioned above, treatment of patient with chronic multiple knee ligament injury, the external fixator is frequently used to maintain the knee joint reduction after reconstruction procedure.

Strobel 6 suggested treatment of fixed posterior knee subluxation in PCL deficient knee with continuous posterior knee brace with inlay support. In 59.3% of the patients, the irreducible knee subluxation could be reduced completely within treatment period of 180 days. With this success, it supports his theory about a continuous anterior tibial force is necessary to reduce the posterior subluxation against soft tissue resistance.

According to strobel’s theory, we purposed distractive external fixator technique for gradually reduce posterior knee subluxation before performing other steps of knee reconstruction. We achieved knee reduction within 7 weeks for the first case and 2 weeks for other cases. After knee reconstructive procedure, we also acquired good results both in knee stability and functional knee motion without using a hinge knee external fixator in all three distinct cases of irreducible knee subluxation. All of our patients satisfied with  their    surgical results. They obtained painless knee and were able to walk without gait aids. Moreover, they also attended moderate activity with comfort.

From the results of this study, we conclude that the use of the distractive external fixator technique is effective for the treatment of chronic irreducible posterior knee subluxation. In addition,using this technique, the patient could avoid risk of the extensive surgical complications.








1. Henshaw RM, Shapiro MS, Oppenheim WL.  Delayed reduction of traumatic knee dislocation. Clin Orthop. 1996; 330:152–156.

2. Simonian PT, Wickiewicz TL, Hotchkiss RN, Warren RF. Chronic knee dislocation: reduction, reconstruction, and application of a skeletally fixed knee hinge. Am J Sports Med. 1998;26:591–595.

3. Nurzat E, Nevzat E, Irfan E , Ahmet H. Delayed reduction of irreducible chronic posterolateral dislocation of the knee with buttonholing of the medial femoral condyle. European Journal of Trauma. 2005; 6:586-589.

4. Hatem GS, Duncan JAL. Chronic Irreducible Posterolateral Knee Dislocation: Two-Stage Surgical Approach. Arthroscopy.2007; 23: 564-564.

5. Kota W, Yasuharu Y, Hideji K, Masaaki I, Yoshihiko T, Toshihiko Y, Seijchi I. Chronic Knee Fracture Dislocation Treated by the Ilizarov Technique: Case Report. J Trauma. 2001; 50:151–154.

6. Strobel MJ, Weiler A, Schulz MS, Russe K, Eichhorn HJ. Fixed posterior subluxation in posterior cruciate ligament-deficient knees: diagnosis and treatment of a new clinical sign. Am J Sports Med. 2002 Jan-Feb; 30(1):32-8.





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