- Email: [email protected]
(iii) Posterolateral instability of the knee
Current Orthopaedics (2000) 14, 337–341 © 2000 Harcourt Publishers Ltd doi: 10.1054/ cuor.2000.0129, available online at http://www.idealibrary.com on
Mini-Symposium—Soft tissue knee surgery
(iii) Posterolateral instability of the knee
A. J. Kumar, D. Bickerstaff
ments and the lateral head of the gastrocnemius on the femoral condyle. Layer 3. The deepest layer divides into two laminae just posterior to the overlying iliotibial tract. These laminae encompass three ligaments: The lateral collateral ligament, the fabello-fibular (popliteo-fibular) ligament and the arcuate-popliteal ligament complex (Fig. 1 and 2). The lateral collateral ligament and popliteus complex are considered to be the primary stabilizing structures.3,4,5 The popliteus complex consists of a dynamic component, the popliteus muscle-tendon unit, as well as a static component, which consists of
INTRODUCTION Posterolateral rotatory instability (PLRI) is a complex problem frequently missed in the acute stage of knee injury and has challenged orthopaedic surgeons over the years. Even today, when surgical treatment for most ligamentous injuries to the knee have a reliable and reproducible outcome, PLRI remains underdiagnozed and poorly treated. Although PLRI can present as an isolated injury, this is rarity and in the majority of cases, it will form part of some type of multiplanar instability.
SURGICAL ANATOMY The lateral structures of the knee may be assigned to three distinct layers.1 Layer 1. The most superficial layer, has two parts; the iliotibial tract and its expansion anteriorly, and the superficial portion of the biceps and its expansion posteriorly. It is continuous from the prepatellar bursa to the filmy covering over the popliteal fossa. The peroneal nerve lies on the deep side of layer 1, just posterior to the biceps tendon. Layer 2. Anteriorly it is formed by the retinaculum of the quadriceps, most of which descends anterolaterally and adjacent to the patella. Posteriorly, layer 2 is incomplete and is represented by the two patellofemoral ligaments. The proximal ligament joins the terminal fibres of the lateral intermuscular septum, the distal one ends posteriorly at the fibula or at the insertions of the posterolateral capsular reinforce-
A. J. Kumar FRCSEd Orth, SpR Orthopaedics, The Freeman Hospital, Newcastle-upon-Tyne, UK, Former Clinical Knee Fellow, Sheffield; D. Bickerstaff FRCS, Consultant Orthopaedic Surgeon, Northern General Hospital, Herries Road, Sheffield S5 7AU, UK
Fig. 1 Lateral dissection, right knee. 1: lateral collateral ligament, cut; 2: popliteus tendon; 3: inferior popliteo-meniscal fascicle; 4: lateral meniscus; 5: superior popliteo-meniscal fascicle; 6: popliteo-fibular fascicle (anterior limb); 7: popliteo-fibular fascicle (posterior limb).
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338
Current Orthopaedics Physical signs Varus thrust or hyperextension during gait. Anteroposterior translation. Varus stress External rotation. Arcuate popliteal ligament complex Politeofibular ligament
Antero-posterior translation test. This should be tested at 30 and 90 degrees of knee flexion. An increase in posterior translation at 30° but not at 90° is suggestive of a PLRI injury whereas an increase at 30° as well as at 90° indicates an injury to the posterior cruciate ligament.
Fig. 2 Postero-lateral dissection.
Varus stress. several ligamentous structures. These ligamentous structures branch from the popliteus tendon and insert onto the fibula, the tibia, and the lateral meniscus and are referred to as the popliteo-fibular ligament, the popliteo-tibial ligament and the popliteo-meniscal fascicle, respectively.
Performing a varus stress on the affected knee at 20° flexion will cause a slight increase in lateral joint line opening when compared with the uninjured knee. External rotation.
Hughston2 looked at 140 patients with chronic posterolateral instability but in only 68 patients could the accurate mechanism of injury be determined. Twentytwo had a direct blow to the tibia with the knee extended, which is a characteristic athletic injury. Eight had sustained a direct blow to the tibia with the knee flexed, such as in an automobile accident. Thirty-eight patients had sustained a twisting injury to the knee.
PLRI causes posterior subluxation of the lateral tibial plateau. This can be demonstrated with the patient prone and the knees bent to 90°. The lower leg is then externally rotated and increased rotation is detected on comparing the angle of the feet with the neutral plane. The test is repeated at 30°. External rotation can also be demonstrated by a posterior pivot shift. In more severe cases, external rotation and recurvatum can be demonstrated in a test described by Hughston and Norwood.6 This is performed with the patient supine by holding both big toes at the same time and lifting both lower limbs from the examining couch. If there is PLRI then the knee hyperextends and externally rotates.
DIAGNOSIS
INVESTIGATIONS
Posterolateral instability of the knee has been frequently underdiagnozed which explains the number of chronic presentations. An index of suspicion as well as familiarity performing a number of clinical tests and a carefully recorded history are essential for an accurate diagnosis. The patient with an injury to the posterolateral corner will present with the variety of symptoms usually resulting from a combination of ligamentous injuries. However, pain in the posterolateral aspect of the knee and instability with the knee in extension have been more specifically associated with posterolateral injuries. Careful observation of the gait may demonstrate a varus thrust or hyperextension during the weight-bearing phase. Over the years a number of tests have been described and although the majority of them are nonspecific for PLRI, they certainly have a role in providing additional information to the orthopaedic surgeon confronted with this complex ligamentous injury.
These include stress radiography, MRI, examination under anaesthesia and arthroscopic assessment. Plain radiography offers little help and MRI, although usually capable of determining popliteal tendon injuries, does not offer information regarding other structures. Stress radiography can offer evidence of PRLI and also serve as a tool to assess the success of reconstruction. If there is any doubt as to the diagnosis, an examination under anaesthesia should be performed. Occasionally arthroscopy can show evidence of damage to the popliteal tendon or the popliteal-fibular ligament.
MECHANISM OF INJURY
TREATMENT An isolated PRLI is rare and can be treated conservatively with adequate rehabilitation if there is minimal rotation. However most of the patients presenting
Posterolateral instability of the knee with PRLI will have associated ligamentous injuries, and in these, surgical reconstruction is the preferred treatment. Acute injuries The treatment of the acute injuries is different from that of the chronic ones and should be performed as soon as the extent of the injuries has been assessed and other required investigations such as angiography have been performed. Any associated ligamentous injuries, usually to the ACL and/or PCL should, be repaired or reconstructed at the same sitting. These should be performed by open surgery as arthroscopicy increases the risk of compartment syndrome due to extravasation of fluid. For posterolateral reconstruction, we like to expose the lateral and posterolateral aspect through hockey stick incision and carefully inspect the lateral collateral ligament, popliteus tendon, popliteo-fibular ligament, arcuate ligament, biceps tendon, common peroneal nerve and posterior capsule. The aim of the surgery is the repair or reconstruction of the three key structures in the posterolateral complex, the lateral collateral ligament, popliteofibular ligament and popliteus muscle unit. If the former two are avulsed from their origin or insertion, they can be repaired. If they rupture mid-substance we perform a Larson-type reconstruction using hamstring tendons as described later. The popliteus muscle unit often avulses at the musculo-tendon junction, which is difficult to repair, or reconstruct. If avulsed from its insertion it can be re-attached. All other structures are primarily repaired using direct sutures or bone anchors.
339
Hughston’s posterolateral reconstruction consists of anterior and superior advancement of the lateral gastrocnemius tendon, superior posterolateral capsule, fibular collateral ligament and popliteus tendon. They also highlighted that the anterior cruciate ligament is doomed to fail if associated posterolateral instability is missed and left untreated. Clancy’s7 technique utilizes the biceps femoris tendon. The entire tendon and muscle is transferred to the lateral epicondyle while the insertion is left attached to the fibula. This procedure creates a new fibular collateral ligament and may tighten up the arcuate complex (Fig. 3). Insall8 used a semitendinosus graft to reconstruct just the lateral collateral ligament. An inverted ‘Y’ tunnel is fashioned in the fibular head and the graft is fixed proximally at the epicondyle with barbed staples in a belt-buckle fashion or with a screw and soft tissue washer. The popliteus bypass procedure described by Muller4 reconstructs the popliteus muscle not as an active constraint but as a tenodesis. A strip of biceps tendon or ilio-tibial tract left attached distally is passed along the line of the popliteus tendon (Fig. 4). Sidles and Larson9 used the tendon of semitendinosus as a graft for reconstruction. If the lateral collateral ligament is intact but the posterolateral complex is disrupted in isolation, they then routed the semitendinosus graft from the femoral epicondyle to the posterior aspect of the fibula through a drill hole to its anterior aspect and fixed it to the tibia. However, if the lateral collateral ligament was also damaged then they would swing the same graft round from the anterior aspect of the fibula back to the femoral epicondyle in a figure of eight fashion to reconstruct
Chronic injuries Unfortunately this is the commonest presentation of PLRI and in most cases there is an accompanying lesion of the PCL and sometimes the ACL, therefore treatment requires a careful assessment of the degree of instability and the number of structures affected. The natural history of the chronic posterolateral injury leads to progressive varus deformity, compression of the medial compartment and increased stretching of the lateral structures. This is why a valgus upper tibial osteotomy should be considered as the first step in the management of those patients presenting with a varus knee and lateral thrust when walking. This can be done at the same time of the reconstruction or as the first part of a two-stage procedure. Reconstruction of the lateral structures of the knee is more challenging. In the chronic setting one needs to address the three key structures; the lateral collateral ligament, popliteo-fibular ligament and popliteus muscle unit. Hughston and Jacobson1 in 1985 published the long-term results of surgical treatment for chronic posterolateral instability of the knee.
Fig. 3 Postero-lateral reconstruction using biceps femoris tendon (Clancy).
340
Current Orthopaedics
Fig. 4 Popliteus bypass using iliotobial tract (Muller).
the lateral collateral ligament. Sidles believes that there is slightly more isometry from the posterior aspect of the fibula to the anterior aspect of epicondyle and from the anterior aspect of the fibula to the posterior aspect of epicondyle and thus recommends a figure of eight loop. We10 have also used Larson technique to reconstruct both lateral collateral ligament and popliteo-fibular ligaments using semitendinosus and gracilis graft. We believe that the entire fibula head is relatively isometric to the lateral epicondyle throughout the range of knee motion and instead of fixing the graft at two points at its femoral site we use one large tunnel (usually 8 or 9 mm). Tendon-healing in the bone tunnel11 has been shown in animal studies to occur at a relatively early stage, between 8 and 12 weeks. The force to failure of the popliteofibular ligament approaches 425 N (range 204–778) and that of the lateral collateral ligament is 750 N(range 317–1203).3 Based on Noyes’ data,12 the combined graft of semitendinosus and gracilis would have a strength of 2054 N. Graft fixation has received a lot of attention of late, since fixing soft tissue to bone always provides more of a challenge than fixing bone to bone. We used a bioabsorbable interference screw for fixation and it has been shown that biodegradable interference fixation exhibits the same pull-out force and stiffness as titanium interference screws.13
limb is prepared and draped. The semitendinosus and gracilis tendons are harvested by Pagnani’s technique.14 The semitendinosus and gracilis tendons are trimmed to length (the length of tendon required to pass through the fibula head and with both ends lying 30 mm into the femoral tunnel) and stitched together with a whipstitch method at both ends using No. 5 ethibond. With the knee flexed 60–70 degrees, a lateral curved skin incision is centred distally between Gerdy’s tubercle on the tibia and the anterior aspect of the fibular head. The incision crosses the lateral epicondyle at its proximal boundary and is extended parallel to the femur. The skin and subcutaneous tissue are reflected from the fascia as a posteriorly based flap. The iliotibial band is then spilt in the line of its fibres at the level of the lateral femoral epicondyle along the length of the skin incision. The common peroneal nerve is then exposed at the inferior portion of the biceps tendon and is dissected free of its fascial attachments and protected. The fibular head is exposed; a transverse tunnel is made from anterior to posterior at the base of the fibular head using a cannulated reamer (usually 7 or 8 mm). The lateral epicondyle is identified and dissected, a guide wire is passed from the lateral to medial side at the site of insertion of the lateral collateral ligament and popliteus tendon. A tunnel of about 40 mm is made using a cannulated reamer (usually 8 or 9 mm) depending on the thickness of the graft and inferior and anterior edges of the tunnel is rasped to prevent tendon abrasion. The graft is pulled through the fibular tunnel, and then the posterior limb of the graft is passed underneath the iliotibial band. The anterior limb of the graft is used to reconstruct the lateral collateral ligament and the posterior limb the popliteo-fibular
Surgical technique: tunnel technique After the induction of general anaesthesia, a complete examination of the knee ligaments is repeated and is compared with the preoperative evaluation. With the patient supine, a tourniquet is inflated, and the lower
Fig. 5A
Tunnel technique, sagittal view.
Posterolateral instability of the knee
341
association with cruciate ligament injuries. Diagnosis is usually made by careful examination and investigation. MRI may be useful in identifying a structural problem but not in assessing rotational instability. Surgical treatment in the acute stage is mandatory, as chronic reconstruction is less successful in restoring normal knee function. In both scenarios the success of the surgery depends upon repairing or reconstructing the three key structures; the lateral collateral ligament, popliteofibular ligament and popliteus muscle unit.
REFERENCES
Fig. 5B Tunnel technique, coronal view.
ligament After threading the ends of the ethibond suture from the graft through the eye of the guide wire, the guide wire is pulled out of the femur from the medial side along with the suture. Whilst maintaining the tension on the suture the graft is moved in the tunnel in such a way that the posterior limb of the graft is anterior and the anterior limb is posterior. Maintaining tension on the suture the knee joint is moved a few times through the full range of movement. The graft is fixed using a Bio-fix interference screw one size bigger than the size of the tunnel with the knee in extension and the tibia internally rotated (Fig 5A and B). The iliotibial band is closed with No.0 vicryl and the skin is closed with a subcuticular stitch over a Redivac suction drain. Postoperatively, those injuries associated with ACL or PCL disruption treated by concomitant anterior cruciate ligament reconstruction are immobilized in an ACL brace for 6 weeks and weight bearing as tolerated on crutches. If performed along with posterior cruciate ligament reconstruction then the knee is kept in extension in a splint for 2 weeks and for another 4 weeks in a PCL brace, weight bearing as tolerated with crutches. CONCLUSION Injury to the posterolateral corner of the knee is becoming increasingly recognised, particularly in
1. Sebbacher J R, Inglis A E, Marshall J L, Warren R F. The structure of the posterolateral aspect of the knee. J Bone Joint Surg 1982; 64-A(4) 536–541. 2. Hughston J C, Jocobsen K E. Chronic posterolateral rotatory instability of the knee. J Bone Joint Surg 1985; 67A: 351. 3. Maynard M J, Deng X, Wickiewicz T L, Warreen R F. The poplitedfibular ligament: rediscovery of a key element in the posteroateral stability. Am J Sports Med 1996; 24: 311–316. 4. Muller W. Form, function, and ligament reconstruction. In: The Knee. Berlin: Springer-Verlag, 1983. 5. Staubli H U. Posteromedial and posterolateral capsular injuries associated with posterior cruciate ligament insufficiency. Sports Med Arthrosc Rev 1994; 2: 146–164. 6. Hughston J C, Norwood L A. The Posterolateral drawer test and external rotational recurvatum test for posterolateral instability of the knee. Clin Orthop 1980; 147: 82–87. 7. Clancy W G, Meister K, Craythorne C B. Posterolateral cornor collateral ligament reconstruction. Master Techniques in Orthopeadic Surgery. Reconstructive Knee Surgery. Raven Press, 1995; 143–156. 8. Insall N J, Windsor R E, Scott W N, Kelly M A, Aglietti P. Surgery of the Knee. Volume 1, 2nd edn. Churchill Livingstone, 1993; 462–464. 9. Larson R V, Sidlles J, Beals T. Isometry of the lateral collateral and popliteofibular ligaments and a technique for reconstruction. International Teaching Meeting; The Wellington Hospital, London NW89LE 21–22 March 1996: 92–96. 10. Kumar A, Jones S, Bickerstaff D R. Posterolateral reconstruction of the knee: a tunnel technique for proximal fixation. The Knee 1999; 6: 257–260. 11. Rodeo S A, Arnoczky S P, Torzilli P A, Hidaka C, Warren R F. Tendon-healing in a bone tunnel. A biomechanical and histological study in the dog. J Bone Joint Surg 1993; 75A: 1795–1803 12. Noyes F R, Butler D L, Grood E S, Zernicke R F, Hefzy MS. Biomechanical analysis of human ligament grafts used in knee-ligament repair and reconstructions. J Bone Joint Surg 1984; 66A: 344–352. 13. Weiler A, Windhagen H J, Raschke M J, Laumeyer A, Hoffmann R F. Biodegradable interference screw fixaton exhibits pull-out force and stiffness similar to titanium screws. Am J Sports Med 1998; 26: 119–126. 14. Pagnani M J, Warner Jon J P, O’Brien S J, Warren R F. Anatomic considerations in harvesting the semitendinosus and gracilis tendons and a technique of harvest. Am J Sports Med 1993; 21: 565–571.
Mini-Symposium—Soft tissue knee surgery
(iii) Posterolateral instability of the knee
A. J. Kumar, D. Bickerstaff
ments and the lateral head of the gastrocnemius on the femoral condyle. Layer 3. The deepest layer divides into two laminae just posterior to the overlying iliotibial tract. These laminae encompass three ligaments: The lateral collateral ligament, the fabello-fibular (popliteo-fibular) ligament and the arcuate-popliteal ligament complex (Fig. 1 and 2). The lateral collateral ligament and popliteus complex are considered to be the primary stabilizing structures.3,4,5 The popliteus complex consists of a dynamic component, the popliteus muscle-tendon unit, as well as a static component, which consists of
INTRODUCTION Posterolateral rotatory instability (PLRI) is a complex problem frequently missed in the acute stage of knee injury and has challenged orthopaedic surgeons over the years. Even today, when surgical treatment for most ligamentous injuries to the knee have a reliable and reproducible outcome, PLRI remains underdiagnozed and poorly treated. Although PLRI can present as an isolated injury, this is rarity and in the majority of cases, it will form part of some type of multiplanar instability.
SURGICAL ANATOMY The lateral structures of the knee may be assigned to three distinct layers.1 Layer 1. The most superficial layer, has two parts; the iliotibial tract and its expansion anteriorly, and the superficial portion of the biceps and its expansion posteriorly. It is continuous from the prepatellar bursa to the filmy covering over the popliteal fossa. The peroneal nerve lies on the deep side of layer 1, just posterior to the biceps tendon. Layer 2. Anteriorly it is formed by the retinaculum of the quadriceps, most of which descends anterolaterally and adjacent to the patella. Posteriorly, layer 2 is incomplete and is represented by the two patellofemoral ligaments. The proximal ligament joins the terminal fibres of the lateral intermuscular septum, the distal one ends posteriorly at the fibula or at the insertions of the posterolateral capsular reinforce-
A. J. Kumar FRCSEd Orth, SpR Orthopaedics, The Freeman Hospital, Newcastle-upon-Tyne, UK, Former Clinical Knee Fellow, Sheffield; D. Bickerstaff FRCS, Consultant Orthopaedic Surgeon, Northern General Hospital, Herries Road, Sheffield S5 7AU, UK
Fig. 1 Lateral dissection, right knee. 1: lateral collateral ligament, cut; 2: popliteus tendon; 3: inferior popliteo-meniscal fascicle; 4: lateral meniscus; 5: superior popliteo-meniscal fascicle; 6: popliteo-fibular fascicle (anterior limb); 7: popliteo-fibular fascicle (posterior limb).
337
338
Current Orthopaedics Physical signs Varus thrust or hyperextension during gait. Anteroposterior translation. Varus stress External rotation. Arcuate popliteal ligament complex Politeofibular ligament
Antero-posterior translation test. This should be tested at 30 and 90 degrees of knee flexion. An increase in posterior translation at 30° but not at 90° is suggestive of a PLRI injury whereas an increase at 30° as well as at 90° indicates an injury to the posterior cruciate ligament.
Fig. 2 Postero-lateral dissection.
Varus stress. several ligamentous structures. These ligamentous structures branch from the popliteus tendon and insert onto the fibula, the tibia, and the lateral meniscus and are referred to as the popliteo-fibular ligament, the popliteo-tibial ligament and the popliteo-meniscal fascicle, respectively.
Performing a varus stress on the affected knee at 20° flexion will cause a slight increase in lateral joint line opening when compared with the uninjured knee. External rotation.
Hughston2 looked at 140 patients with chronic posterolateral instability but in only 68 patients could the accurate mechanism of injury be determined. Twentytwo had a direct blow to the tibia with the knee extended, which is a characteristic athletic injury. Eight had sustained a direct blow to the tibia with the knee flexed, such as in an automobile accident. Thirty-eight patients had sustained a twisting injury to the knee.
PLRI causes posterior subluxation of the lateral tibial plateau. This can be demonstrated with the patient prone and the knees bent to 90°. The lower leg is then externally rotated and increased rotation is detected on comparing the angle of the feet with the neutral plane. The test is repeated at 30°. External rotation can also be demonstrated by a posterior pivot shift. In more severe cases, external rotation and recurvatum can be demonstrated in a test described by Hughston and Norwood.6 This is performed with the patient supine by holding both big toes at the same time and lifting both lower limbs from the examining couch. If there is PLRI then the knee hyperextends and externally rotates.
DIAGNOSIS
INVESTIGATIONS
Posterolateral instability of the knee has been frequently underdiagnozed which explains the number of chronic presentations. An index of suspicion as well as familiarity performing a number of clinical tests and a carefully recorded history are essential for an accurate diagnosis. The patient with an injury to the posterolateral corner will present with the variety of symptoms usually resulting from a combination of ligamentous injuries. However, pain in the posterolateral aspect of the knee and instability with the knee in extension have been more specifically associated with posterolateral injuries. Careful observation of the gait may demonstrate a varus thrust or hyperextension during the weight-bearing phase. Over the years a number of tests have been described and although the majority of them are nonspecific for PLRI, they certainly have a role in providing additional information to the orthopaedic surgeon confronted with this complex ligamentous injury.
These include stress radiography, MRI, examination under anaesthesia and arthroscopic assessment. Plain radiography offers little help and MRI, although usually capable of determining popliteal tendon injuries, does not offer information regarding other structures. Stress radiography can offer evidence of PRLI and also serve as a tool to assess the success of reconstruction. If there is any doubt as to the diagnosis, an examination under anaesthesia should be performed. Occasionally arthroscopy can show evidence of damage to the popliteal tendon or the popliteal-fibular ligament.
MECHANISM OF INJURY
TREATMENT An isolated PRLI is rare and can be treated conservatively with adequate rehabilitation if there is minimal rotation. However most of the patients presenting
Posterolateral instability of the knee with PRLI will have associated ligamentous injuries, and in these, surgical reconstruction is the preferred treatment. Acute injuries The treatment of the acute injuries is different from that of the chronic ones and should be performed as soon as the extent of the injuries has been assessed and other required investigations such as angiography have been performed. Any associated ligamentous injuries, usually to the ACL and/or PCL should, be repaired or reconstructed at the same sitting. These should be performed by open surgery as arthroscopicy increases the risk of compartment syndrome due to extravasation of fluid. For posterolateral reconstruction, we like to expose the lateral and posterolateral aspect through hockey stick incision and carefully inspect the lateral collateral ligament, popliteus tendon, popliteo-fibular ligament, arcuate ligament, biceps tendon, common peroneal nerve and posterior capsule. The aim of the surgery is the repair or reconstruction of the three key structures in the posterolateral complex, the lateral collateral ligament, popliteofibular ligament and popliteus muscle unit. If the former two are avulsed from their origin or insertion, they can be repaired. If they rupture mid-substance we perform a Larson-type reconstruction using hamstring tendons as described later. The popliteus muscle unit often avulses at the musculo-tendon junction, which is difficult to repair, or reconstruct. If avulsed from its insertion it can be re-attached. All other structures are primarily repaired using direct sutures or bone anchors.
339
Hughston’s posterolateral reconstruction consists of anterior and superior advancement of the lateral gastrocnemius tendon, superior posterolateral capsule, fibular collateral ligament and popliteus tendon. They also highlighted that the anterior cruciate ligament is doomed to fail if associated posterolateral instability is missed and left untreated. Clancy’s7 technique utilizes the biceps femoris tendon. The entire tendon and muscle is transferred to the lateral epicondyle while the insertion is left attached to the fibula. This procedure creates a new fibular collateral ligament and may tighten up the arcuate complex (Fig. 3). Insall8 used a semitendinosus graft to reconstruct just the lateral collateral ligament. An inverted ‘Y’ tunnel is fashioned in the fibular head and the graft is fixed proximally at the epicondyle with barbed staples in a belt-buckle fashion or with a screw and soft tissue washer. The popliteus bypass procedure described by Muller4 reconstructs the popliteus muscle not as an active constraint but as a tenodesis. A strip of biceps tendon or ilio-tibial tract left attached distally is passed along the line of the popliteus tendon (Fig. 4). Sidles and Larson9 used the tendon of semitendinosus as a graft for reconstruction. If the lateral collateral ligament is intact but the posterolateral complex is disrupted in isolation, they then routed the semitendinosus graft from the femoral epicondyle to the posterior aspect of the fibula through a drill hole to its anterior aspect and fixed it to the tibia. However, if the lateral collateral ligament was also damaged then they would swing the same graft round from the anterior aspect of the fibula back to the femoral epicondyle in a figure of eight fashion to reconstruct
Chronic injuries Unfortunately this is the commonest presentation of PLRI and in most cases there is an accompanying lesion of the PCL and sometimes the ACL, therefore treatment requires a careful assessment of the degree of instability and the number of structures affected. The natural history of the chronic posterolateral injury leads to progressive varus deformity, compression of the medial compartment and increased stretching of the lateral structures. This is why a valgus upper tibial osteotomy should be considered as the first step in the management of those patients presenting with a varus knee and lateral thrust when walking. This can be done at the same time of the reconstruction or as the first part of a two-stage procedure. Reconstruction of the lateral structures of the knee is more challenging. In the chronic setting one needs to address the three key structures; the lateral collateral ligament, popliteo-fibular ligament and popliteus muscle unit. Hughston and Jacobson1 in 1985 published the long-term results of surgical treatment for chronic posterolateral instability of the knee.
Fig. 3 Postero-lateral reconstruction using biceps femoris tendon (Clancy).
340
Current Orthopaedics
Fig. 4 Popliteus bypass using iliotobial tract (Muller).
the lateral collateral ligament. Sidles believes that there is slightly more isometry from the posterior aspect of the fibula to the anterior aspect of epicondyle and from the anterior aspect of the fibula to the posterior aspect of epicondyle and thus recommends a figure of eight loop. We10 have also used Larson technique to reconstruct both lateral collateral ligament and popliteo-fibular ligaments using semitendinosus and gracilis graft. We believe that the entire fibula head is relatively isometric to the lateral epicondyle throughout the range of knee motion and instead of fixing the graft at two points at its femoral site we use one large tunnel (usually 8 or 9 mm). Tendon-healing in the bone tunnel11 has been shown in animal studies to occur at a relatively early stage, between 8 and 12 weeks. The force to failure of the popliteofibular ligament approaches 425 N (range 204–778) and that of the lateral collateral ligament is 750 N(range 317–1203).3 Based on Noyes’ data,12 the combined graft of semitendinosus and gracilis would have a strength of 2054 N. Graft fixation has received a lot of attention of late, since fixing soft tissue to bone always provides more of a challenge than fixing bone to bone. We used a bioabsorbable interference screw for fixation and it has been shown that biodegradable interference fixation exhibits the same pull-out force and stiffness as titanium interference screws.13
limb is prepared and draped. The semitendinosus and gracilis tendons are harvested by Pagnani’s technique.14 The semitendinosus and gracilis tendons are trimmed to length (the length of tendon required to pass through the fibula head and with both ends lying 30 mm into the femoral tunnel) and stitched together with a whipstitch method at both ends using No. 5 ethibond. With the knee flexed 60–70 degrees, a lateral curved skin incision is centred distally between Gerdy’s tubercle on the tibia and the anterior aspect of the fibular head. The incision crosses the lateral epicondyle at its proximal boundary and is extended parallel to the femur. The skin and subcutaneous tissue are reflected from the fascia as a posteriorly based flap. The iliotibial band is then spilt in the line of its fibres at the level of the lateral femoral epicondyle along the length of the skin incision. The common peroneal nerve is then exposed at the inferior portion of the biceps tendon and is dissected free of its fascial attachments and protected. The fibular head is exposed; a transverse tunnel is made from anterior to posterior at the base of the fibular head using a cannulated reamer (usually 7 or 8 mm). The lateral epicondyle is identified and dissected, a guide wire is passed from the lateral to medial side at the site of insertion of the lateral collateral ligament and popliteus tendon. A tunnel of about 40 mm is made using a cannulated reamer (usually 8 or 9 mm) depending on the thickness of the graft and inferior and anterior edges of the tunnel is rasped to prevent tendon abrasion. The graft is pulled through the fibular tunnel, and then the posterior limb of the graft is passed underneath the iliotibial band. The anterior limb of the graft is used to reconstruct the lateral collateral ligament and the posterior limb the popliteo-fibular
Surgical technique: tunnel technique After the induction of general anaesthesia, a complete examination of the knee ligaments is repeated and is compared with the preoperative evaluation. With the patient supine, a tourniquet is inflated, and the lower
Fig. 5A
Tunnel technique, sagittal view.
Posterolateral instability of the knee
341
association with cruciate ligament injuries. Diagnosis is usually made by careful examination and investigation. MRI may be useful in identifying a structural problem but not in assessing rotational instability. Surgical treatment in the acute stage is mandatory, as chronic reconstruction is less successful in restoring normal knee function. In both scenarios the success of the surgery depends upon repairing or reconstructing the three key structures; the lateral collateral ligament, popliteofibular ligament and popliteus muscle unit.
REFERENCES
Fig. 5B Tunnel technique, coronal view.
ligament After threading the ends of the ethibond suture from the graft through the eye of the guide wire, the guide wire is pulled out of the femur from the medial side along with the suture. Whilst maintaining the tension on the suture the graft is moved in the tunnel in such a way that the posterior limb of the graft is anterior and the anterior limb is posterior. Maintaining tension on the suture the knee joint is moved a few times through the full range of movement. The graft is fixed using a Bio-fix interference screw one size bigger than the size of the tunnel with the knee in extension and the tibia internally rotated (Fig 5A and B). The iliotibial band is closed with No.0 vicryl and the skin is closed with a subcuticular stitch over a Redivac suction drain. Postoperatively, those injuries associated with ACL or PCL disruption treated by concomitant anterior cruciate ligament reconstruction are immobilized in an ACL brace for 6 weeks and weight bearing as tolerated on crutches. If performed along with posterior cruciate ligament reconstruction then the knee is kept in extension in a splint for 2 weeks and for another 4 weeks in a PCL brace, weight bearing as tolerated with crutches. CONCLUSION Injury to the posterolateral corner of the knee is becoming increasingly recognised, particularly in
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