Fractures of the Tibial Plateau

                   Fractures of the Tibial Plateau

                                      Dr KS Dhillon

Anatomy

The tibial plateau consists of a medial and a lateral plateau which articulates with the medial and lateral femoral condyles respectively.

The medial plateau is oval in shape and is slightly concave from side to as well as front to back. The lateral plateau is nearly circular in shape and is concave from side to side and slightly convex from front to back, especially at the posterior part.The medial plateau bone is harder and less likely to fracture. The cartilage of the lateral plateau is about 4 mm as compared to that of the medial plateau which is about 3 mm.

The lateral meniscus is larger than the medial meniscus and it covers a large portion of the lateral tibial plateau. The medial meniscus is C- shaped and covers the peripheral portions of anterior, medial and posterior aspect of the medial tibial plateau.

Between the the two tibial articular facets is the intercondyloid eminence (spine of tibia). The eminence is surmounted on either side by a prominent tubercle, on to the sides of which the articular facets are prolonged. At the back and front of intercondyloid eminence are depressions which give  attachment to the anterior and posterior cruciate ligaments and the menisci. Anteriorly the tibial condyles are continuous with one another, forming a large flattened area. This area is triangular in shape. It is broad above and narrow below where it ends forming a large oblong elevation known as the tibial tuberosity which gives attachment to the patella tendon.

At the posteriorly aspect the condyles are separated by a shallow depression called the posterior intercondyloid fossa. This fossa gives attachment to part of the posterior cruciate ligament .
The medial condyle has a deep groove on the posterior aspect which gives attachment to the Semimembranosus tendon. On medial convex surface the medial condyle gives attachment to the tibial collateral ligament.

On the posterior aspect of the lateral tibial condyle there is flat, nearly circular facet for articulation with the fibular head. On the anterior aspect of the lateral surface of the lateral condyle is a bony prominence called the Gerdy’s tubercle which gives attachment to the iliotibial band.
The tibial plateau slopes posteroinferiorly at about 10 degrees.

Epidemiology and burden to society 

Tibial plateau fractures with or without metaphyseal/diaphyseal extension account for about 1.2% of all fractures. The lateral plateau fractures account for 55-70% of tibial plateau fractures. Ten to twenty percent of the fractures involve the medial tibial plateau and 10-30% of the fractures are
bicondylar.

There is a bimodal distribution of mechanism of injury for tibial plateau fractures. High energy causing fractures is seen in young adults especially in the 5th decade. This mechanism is more common among the males. Low energy mechanism of injury is seen in the elderly with osteoporotic bones and this mechanism of injury is usually seen in females.
Significant functional impairment can result from joint incongruity, instability, malalignment and post-traumatic arthritis.

Classification of tibial plateau fractures

The AO/ASIF classification for tibial plateau fractures is detailed and comprehensive. It divides the fractures into extraarticular, partial articular and completely articular. The fractures are further subdivided based upon the severity and comminution of the fractures. The classification is long and is most often used for research purposes.

The AO foundation classifies the proximal tibia fractures into 3:

Extra-articular
A1 – Avulsion fractures
A2 – Metaphyseal simple fracture
A3 – Metaphyseal multifragmentary fracture

Partial articular
B1 – Pure split of condyle without depression
B2 – Pure depression of condyle
B3 – Split with depression

Complete articular
C1 – Simple split with simple Metaphyseal fracture
C2 – Simple split with multifragmentary Metaphyseal fracture
C3 – Multifragmentary condyle and Metaphyseal fracture.

The most commonly used classification for tibial plateau fractures is the one by Schatzker because of its ease of communication, although it is not as comprehensive as the AO classification [1].

Schatzker classification of tibial plateau fractures [2].

• Type I   --Pure split fracture of lateral tibial plateau
• Type II  --Split-depression fracture of lateral tibial plateau
• Type III --Pure central depression fracture of lateral tibial plateau
• Type IV --Medial tibial plateau fracture
• Type V  --Bicondylar tibial plateau fracture
• Type VI --Bicondylar tibial plateau fracture with metaphyseal and    diaphyseal dissociation

Mechanism of Injury

Lateral plateau fractures are produced by valgus producing force and medial plateau fractures are produced by varus producing force. Axial  compressive forces produce bicondylar plateau fractures.
Low energy fractures are more common among older people with poor quality bone. Low energy forces produce split fractures with depression. High energy forces as seen in motor vehicle accidents and falls from a height result in axial loads which produce bicondylar fractures with associated injuries.

Associate injuries

Soft tissue injuries associated with plateau fractures include injuries to the ligaments, menisci, popliteal vessels and the peroneal nerve. These fractures can also lead to a compartment syndrome of the leg.

Lateral plateau fractures are often associated with tear of meniscus and tears of the medial collateral and anterior cruciate ligaments. Lateral meniscus tear is likely if the articular depression is more than 5 mm and when the condylar widening is more than 6 mm.

Medial plateau fractures are caused by much higher-energy forces than
their counterparts in the lateral plateau. Here the medial plateau piece remains in its anatomic position while the lateral fragment and entire lower leg displaces. Some refer to such injuries as a ‘‘fracture dislocation’’ of the knee. These fractures are associated with a higher incidence of lateral collateral ligament, anterior cruciate ligament, popliteal artery, and peroneal nerve injury as compared to other subtype.

Bicondylar fractures are often open injuries with varying degree of comminution and are often associated with a compartment syndrome.

Clinical evaluation

Patients with high-energy injuries require a thorough trauma evaluation, according the Advanced Trauma Life Support (ATLS) protocol, typically by a multidisciplinary team. Life threatening injuries are attended to initially and once the patient is stable, the orthopaedic injuries are attended to.
The neurologic and vascular status is first accessed followed by inspection of the skin around the knee and proximal as well as distal to the knee.

Open fractures are classified as per Gustilo and Anderson classification [3], where Grade I injuries have a laceration of less than 1 cm; Grade II injuries have a larger laceration (1–10 cm) and Grade III injuries are more severe. Grade III injuries are further subclassified into III A injuries with more than 10 cm laceration and increased comminution, contamination and or stripping of bone, III B injuries which require a soft-tissue coverage procedure to cover the exposed bone, and III C injuries which require vascular repair to salvage the limb.

Closed injuries are also closely examined for the presence of contusions, blisters, and swelling. The Tscherne and Goetzen [4] classification is useful in classifying the status of the soft tissue in patients with close fractures.

Tscherne and Goetzen classification consist of 4 grades of injury

• Grade 0 injury results from low energy, indirect force. The fracture pattern is usually spiral and soft  tissue damage is none to minimal.
• Grade 1 injuries result from mild to moderate rotational forces and soft tissue injury is often in the form of superficial abrasions or contusions.
• Grade 2 injuries result from high energy forces which produce transverse segmental and complex fracture patterns. The soft tissue injury is usually in form of deep, contaminated abrasions with localised skin/muscle contusion and an impending compartment syndrome. 
• Grade 3 injuries result from high energy forces and the fracture pattern is always complex with extensive skin contusion,  myonecrosis; degloving; vascular injury and compartment syndrome.

Neurovascular injuries are common when high-energy forces are involved. The common peroneal nerve is commonly involved but the tibial nerve is also in the vicinity and should be examined.
Vascular injury usually involves the popliteal artery and this injury is more commonly associated with medial plateau fractures. Posteriorly displaced fracture fragments can compress on the neurovascular bundle and produce vascular injury. Ankle-brachial index (ABI) should  be measured if there is any suspicion of vascular injury. If the ABI is less than 0.9 and the physical  findings are suggestive of an arterial injury, an arteriogram must be done and surgical intervention would be indicated if there is vascular injury.

Knee instability to varus and valgus stress in full extension should be assessed because a knee dislocation can pose as a tibial plateau fracture.
Knee dislocation is a known risk factor for vascular injury and that makes assessment of vascular status mandatory.

Compartment syndrome of the leg can be a serious complication of tibial plateau fractures. Prompt diagnosis with early intervention can prevent devastating consequences. A compartment syndrome must be ruled out in all patients with tibial plateau fractures.
There are six clinical findings which are useful in the diagnosis of a compartment syndrome:

• Pain in the affected extremity which is disproportionate to the injury
• Pain in leg with passive stretching of leg muscles
• Paresis of the muscles of the compartment
• Hypoesthesia or paresthesia in the distribution of the nerves that run through the affected compartment
• Tense and firm compartment with hardening or inflammation, or both.
• Weak or absent distal pulses. 

Clinical finding of a tense compartment, pain on stretching of muscles, swelling, decreased sensitivity and difficulty in moving the limb points to a highly likely diagnosis of compartment syndrome.

If clinical examination is inconclusive compartment pressures should be measured. The difference between the diastolic pressure and the intracompartmental pressure is a sensitive indicator of tissue perfusion pressure, and a value of 30 mm Hg or less has been recommended as the threshold for fasciotomies [5,6]. The threshold for compartment measurement and fasciotomy can be kept low since consequences of a missed or delayed diagnosis can be disastrous. The incidence of compartment syndrome is high in Schatzker V and VI fractures.

The incidence of compartment syndrome can be upto 17% in closed and 18.7% of open complex pattern proximal tibia fractures [7].

Radiological assessment

Traditionally, plain anteroposterior (AP), oblique views and lateral view x-rays of the proximal tibia are taken for diagnosis of the tibial plateau fractures. A tibial plateau view can be useful for evaluation of these fracture. For a tibial plateau view an anterior-posterior X-ray is taken with the tube tilted 10 degrees posteriorly.

Fracture morphology can be best delineated with fine (2–2.5 mm) cut computed tomography (CT) images. The CT images can be very useful for operative planning. The CT scan is most useful if the scan is done after traction via an external fixator. The scan will show the degree of comminution and the extent of depression of the bone fragments [8].

Although an MRI can detect ligamentous and meniscal injuries which are often associated with tibial plateau fractures, the role of MRI of the knee in patients with plateau fractures has yet to be defined. There is scant evidence that routine use of an MRI in patients with plateau fractures impacts clinical outcome. Often the presences of external fixators precludes the use of MRI in these patients [8].

Treatment

Initial treatment
High-energy tibial plateau fractures usually have concomitant soft tissue injury, with extensive swelling and fracture blisters around the proximal leg. The fracture has to be stabilized early to allow for soft tissue healing. The fracture stabilization can be achieved by temporary external fixation and this will allow the soft tissue to heal, reduce pain and allow early mobilization of the patient. A CT scan should be carried out after external fixation to further define the fracture pattern. Definitive surgical treatment is usually delayed till the soft tissues are healthy enough to withstand surgical
trauma. The time between injury and definitive surgical treatment can vary from a few days to 3 weeks or more.

Treatment Principles

Anatomic reduction of articular surface should be obtained and maintained. The condylar width and the mechanical axis should be restored. Injuries to the menisci should be addressed. The bone fixation must be stable enough to allow for early mobilization of the joint and the patient.

Nonsurgical treatment 

Nonsurgical treatment can be considered in the elderly patients who are non ambulatory and in those patients with pre-existing arthritis of the knee. Elderly patients involved in sedentary activities, who have articular incongruity of less than 5 mm and varus / valgus instability of less than 5 to 10 degrees can be treated nonsurgically.

In nonsurgical management of tibial plateau fractures the knee is immobilized for 1-2 weeks in a knee immobilizer or knee brace which is locked in extension. After 2 weeks controlled knee motion is started from 0 to 30 degrees, and gradually increasing the range of motion to 90 degrees at 4 weeks. Non weight bearing on affected limb is maintained for 6 to 8 weeks.

Surgical treatment

The absolute indications for surgery includes, open tibial plateau fractures, presences of compartment syndrome and the presences of vascular injury.

The relative indications for surgery include axial malalignment, instability in full extension, articular incongruity of more than 3 mm in young active individuals and the presences of condyle widening. Displaced bicondylar and invariably all medial plateau fractures would require surgical treatment.
Currently most authors recommend surgical treatment for lateral tibial plateau fractures when there is articular surface depression of more than 2–3 mm, condylar widening of more than 5 mm, or valgus deformity of more than 5 degrees [9,10,11]. All patients with unstable knee need to be treated operatively.

Most authors agree that all medial plateau fractures should be operatively reduced and fixed in their anatomic position [12,13]. Fracture dislocation of the knee which is often associated with medial plateau fracture has to be treated by surgery.

Fixation technique will depend on the fracture type. Type I, II, and III  fractures can be stabilized with buttress plates with raft screws. Type IV fractures are usually fixed with a medial buttress plate. Type V and VI fractures can be stabilized with a single lateral base fixed angle implant or by dual plating, one lateral and the other posteromedial.

Post operative care includes elevation of the leg, use of brace till the patient is able to straight leg raising exercise, early knee mobilization and non-weight bearing ambulation for 10 to 12 weeks.

Complications

Complications that can occur after tibial plateau fractures include:

• Infection which can result from delay in treating open fractures, not carefully handling soft tissues and when the operating time is prolonged. Infection rates of up to 24% have been reported especially after bicondylar fractures [14].
• Compartment syndrome. The incidence of compartment syndrome varies between 7 to 27% [15].
• Nonunion can be aseptic which is usually seen at the metadiaphyseal tibial junction or the nonunion can be septic which is seen in patients with open fractures. Non union rates of 2 to 10% have been reported [15].
• Contractures can result from arthrofibrosis which may require knee manipulation or arthroscopic lysis of intra-articular adhesions. Early mobilization of the knee can reduced the incidence or arthrofibrosis.
• Post-traumatic osteoarthritis. Post traumatic OA rates of between 9 and 44% have been reported [15].

Outcome of treatment of tibial plateau fractures and risk of OA

Most of the published studies on the outcome of treatment of tibial plateau fractures include small patient groups or a short term follow-up. However, in 2007 Rademakers et al [16] published a retrospective study which analysed the long term functional and radiological outcome of surgically treated tibial plateau fractures. The study involved 202 consecutive patients with tibial plateau fracture who were treated surgically, of whom 112 were males and 90 females, with an average age of 46 years. One hundred and nine patients had a long term follow-up ranging from 5 to 27 years (mean 14 years). The mean range of knee motion was 135 degrees, a mean Neers score was 88.6 points and a mean HSS score was 84.4 points.

In 31% of the patients secondary osteoarthritis (OA) developed but was well tolerated in 64% of the patients. Sixty-nine percent of the patients on long term follow-up had no OA, 21% had mild OA, 7% moderate OA and 3% had severe OA. Sixty four percent of the patients with moderate to severe OA had good to excellent Neers scores and 46% had good to excellent HSS scores. Malalignment of more 5 degrees was more often associated with moderate to severe OA as compared to normal alignment of the knee. Age apparently had no influence on the outcome in this study. Two of the 202 (1%) patients developed severe progressive OA which was treated with a knee replacement.
Manidakis et al [17] in 2010 published a retrospective study which evaluated the functional outcome and incidence of post-traumatic OA in 125 patients with tibial plateau fractures. One hundred and one patients were treated surgically and 24 patients were treated conservatively. The mean follow-up was 20 months (12- 70 months). Residual varus was seen in 9.6%, residual valgus in 8.8% of the patients and in 5% there was limb length inequality of 2 cm or less. The American Knee Society (AKSS) score was good in 68.8%, fair in 24% and poor in 7.2% of the patients. OA was seen in 26.4% of the patients. Five patients (4%) had a total knee replacement.

Mehin et al [18] studied the incidence of endstage OA in patients with tibial plateau fractures. They obtained their data from the administrative data base of a level I trauma centre with a higher than average number of patients with complex tibial plateau fractures. Furthermore they were unaware if any of the patients had pre-existing OA when they sustained a fracture of the proximal tibia. They were able to obtain data for 311 patients who were treated for tibial plateau fractures and were followed up in the hospital for 11 years. A 10 years survival analysis for end stage OA was done. The 10 years survival for endstage OA was 96% in this group of patients. For those treated surgically the survival was 97% and for those treated conservatively the 10 years survival was 93%. Endstage OA which required a reconstructive procedure such as a joint replacement, tibial osteotomy or arthrodesis was seen in 4.5% of the patients. A knee replacement (partial or total) was carried out in 2.8% of the patients.

From these scarce reports in literature the incidence of post-traumatic OA following tibial plateau appears to vary from 26 to 31% with about 10% developing moderate to severe OA. The incidence of endstage OA is about 3% in patients who are surgical treated and 7% in conservatively treated tibial plateau fractures. The functional outcome appears to be good in most patients.

Risk and outcome of total knee replacement

Wasserstein et al [19] did a matched population based cohort study on the risk of total knee replacement after surgical treatment of tibial plateau fractures. They used administrative health data base in the province of Ontario, Canada to identify patients who had surgical treatment of tibial plateau fractures. They matched the patients with individuals from the general population. They identified 8,426 patients with a median age of 48.9 years who had surgical treatment of tibial plateau fractures and compared them with a matched control of 33,698 individuals from the general population.

The risk factors for higher rates of total knee replacement were increased age (after 48 years), bicondylar fractures and greater comorbidities. The risk of knee replacement was 5.3 higher for patients with surgically treated tibial plateau fractures as compared to individuals in the general population. Older patients with more severe fractures were more likely to need a knee replacement. At 10 years 7.35% of the patients with surgically treated tibial plateau fractures had a knee replacement.

Other authors have reported a lower incidence of knee replacement in patients with prior tibial plateau fractures. Rademakers et al [16] reported an incidence of 1%, Manidakis et al [17] reported an incidence of 4% and Mehin et al [18] reported an incidence of 2.8%. From the reported series in literature the incidence therefore appears to vary between 1 to 7%.

There is no clear consensus on the indications for a total knee replacement (TKR) in patients with endstage OA [20]. The decision to do a TKR is usually made by the surgeon in consultation with the patient. The surgeon is usually less like to do a TKR in patients with cardiovascular and psychosocial comorbidities and is more likely to do a joint replacement in patients with severe pain and in those with advanced radiological OA [20]. Zeni et al [20] were able to identify some of the factors which can predict the probability of a patient opting for a knee replacement. They found that patients who were older, those with slower Time Up and Go (TUG) and Stair Climbing Task (SCT) times and those with weak quadriceps, lower self-reported function and less knee extension were more likely to undergo a knee replacement when they have endstage knee OA. Studies show that the severity of radiological OA and reported levels of disability do not correlate and factors other than severity of radiological OA are important determinants for a joint replacement [20]. Patients with less than moderate amount of OA who undergo knee replacement are known to be at risk of a poorer pain and functional outcome [21].

In making a decision to do a knee replacement for patients with post-traumatic OA one has to be mindful that the results of total knee replacement for post traumatic OA are not as good as that for primary OA.

Weiss et al [22] evaluated the outcome of total knee arthroplasty in patients with a prior fracture of the tibial plateau. Their study included 62 patients with prior tibial plateau fracture who had a cemented condylar total knee arthroplasty. The mean age of the 62 patients was 63 years. Forty of the patients were females and 22 were males. The average follow-up was 4.7 years. There were postoperative complications in 26% of the knee replacements and 10 % had intraoperative complications. Thirteen patients had reoperations, 5 had manipulation, 3 had wound revision, and 5 had component revision. There were 2 deep infections (3.2%). The mean increase in range of motion was 3.3 degrees. Fifty patients had no pain, 5 had mild pain, 5 had moderate pain and 3 had severe pain on follow-up.

Other authors have also reported poor outcome and higher rate of complications after knee replacement in patients with prior tibial plateau fractures. Roffi and Merritt [23] reported a 38.5% rate of major intraoperative and/or postoperative complications in patients who knee replacement for OA following fractures around the knee. Lonner et al [24]  reported a 57% complication rate for knee replacement in patients with post-traumatic OA of the knee.

Saleh et al [25] reported a 33% failure rate and a 20% infection rate in patients who had a knee replacement after open reduction and internal fixation of tibial plateau fractures.
Though it is well known that the results of total knee replacement for primary OA are excellent, unfortunate the outcome of knee replacement for post-traumatic OA following fractures around the knee are not so promising. Hence the decision to undertake a knee replacement for post-traumatic OA of knee has to be taken with diligence after informing the patient of the risks involved.

Conclusion

Tibial plateau fractures are serious injuries which are usually associated with soft-tissue complications. The high-energy tibial plateau fractures are often associated with high complication rates. Staged treatment is recommended in severe cases.

Good functional outcome can be achieved if the surgeon strives to achieve joint congruity, axial alignment, stability, and a satisfactory range of knee motion.

Open fractures and fractures with joint instability and significant joint incongruity are definitive indications for surgical treatment, provided that the patient is fit for surgery.

Early motion must instituted even in patients who are treated conservative because prolonged immobilization is associated with arthrofibrosis and joint stiffness.

The functional outcome of tibial plateau fractures is good. Long term follow up (mean 14 years) of patients with tibial plateau fractures can have average functional scores between 84 to 88 and an average flexion of 135 degrees. The incidence of posttraumatic OA ranges from between 26.4 to 31% with about 10% developing moderate to severe OA. The incidence of severe OA is between 3 to 4 % and endstage OA is seen in about 2.8% of the patients. The incidence of patients undergoing knee replacement for endstage OA is between 1 to 4% although one study from Canada reported a higher incidence of 7%. This high rate may be due to the fact that there is no clear consensus on the indications for knee replacement and some surgeon may extend the indication depending on the their personal preferences and the type of patients they treat. However the outcome of knee replacement in patients with post-traumatic OA is not as good as in patients with primary OA.

References

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